Evaluation of the clinical effects of diet and physical rehabilitation in dogs following tibial plateau leveling osteotomy

Wendy I. Baltzer Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis OR 97331.

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Sarah Smith-Ostrin Department of Lois Bates Acheson Veterinary Teaching Hospital, College of Veterinary Medicine, Oregon State University, Corvallis OR 97331.

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Jennifer J. Warnock Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis OR 97331.

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Craig G. Ruaux Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis OR 97331.

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Abstract

OBJECTIVE To assess clinical effects of an omega-3 fatty acid and protein-enriched diet, physical rehabilitation, or both in dogs following tibial plateau leveling osteotomy (TPLO) and arthroscopic surgery for cranial cruciate ligament (CCL) disease.

DESIGN Randomized, prospective clinical trial.

ANIMALS 48 dogs with unilateral CCL disease.

PROCEDURES Dogs were randomly assigned to receive a dry omega-3 fatty acid and protein-enriched dog food formulated to support joint health (test food [TF]), a dry food formulated for maintenance of adult dogs (control food [CF]), TF plus rehabilitation (TF-R), or CF plus rehabilitation (CF-R). Data collected over 6 months included body weight, body condition score, ground reaction force data, tibial plateau angle, limb circumference measurements, subjective pain and lameness scores assigned by surgeons and dog owners, and daily activity measured by accelerometry.

RESULTS Peak vertical force and vertical impulse were greater after surgery for dogs in the TF groups than in the CF groups; peak vertical force was greater after surgery in dogs that underwent rehabilitation than in those that did not. Owner scores indicated lower frequencies of lameness and signs of pain during some activities for the TF group, compared with other groups, and for the TF-R and CF-R groups, compared with the CF group. Sedentary time decreased and time spent in light-to-moderate or vigorous activity increased in all groups over time. Rehabilitation was significantly associated with greater time spent in light-to-moderate activity, regardless of diet.

CONCLUSIONS AND CLINICAL RELEVANCE Feeding the TF and providing physical rehabilitation during the first 6 months after TPLO were associated with improvements in some indices of clinical outcome and function in dogs. Significant interactions between time and some outcome variables were observed, indicating further research is warranted.

Abstract

OBJECTIVE To assess clinical effects of an omega-3 fatty acid and protein-enriched diet, physical rehabilitation, or both in dogs following tibial plateau leveling osteotomy (TPLO) and arthroscopic surgery for cranial cruciate ligament (CCL) disease.

DESIGN Randomized, prospective clinical trial.

ANIMALS 48 dogs with unilateral CCL disease.

PROCEDURES Dogs were randomly assigned to receive a dry omega-3 fatty acid and protein-enriched dog food formulated to support joint health (test food [TF]), a dry food formulated for maintenance of adult dogs (control food [CF]), TF plus rehabilitation (TF-R), or CF plus rehabilitation (CF-R). Data collected over 6 months included body weight, body condition score, ground reaction force data, tibial plateau angle, limb circumference measurements, subjective pain and lameness scores assigned by surgeons and dog owners, and daily activity measured by accelerometry.

RESULTS Peak vertical force and vertical impulse were greater after surgery for dogs in the TF groups than in the CF groups; peak vertical force was greater after surgery in dogs that underwent rehabilitation than in those that did not. Owner scores indicated lower frequencies of lameness and signs of pain during some activities for the TF group, compared with other groups, and for the TF-R and CF-R groups, compared with the CF group. Sedentary time decreased and time spent in light-to-moderate or vigorous activity increased in all groups over time. Rehabilitation was significantly associated with greater time spent in light-to-moderate activity, regardless of diet.

CONCLUSIONS AND CLINICAL RELEVANCE Feeding the TF and providing physical rehabilitation during the first 6 months after TPLO were associated with improvements in some indices of clinical outcome and function in dogs. Significant interactions between time and some outcome variables were observed, indicating further research is warranted.

Current methods of postoperative treatment for human patients following anterior cruciate ligament injury include supportive care and the use of physical rehabilitation to improve muscle mass and speed the return to preinjury function.1–3 Many protocols exist, and selection is dependent on the surgical technique used. Following surgery for treatment of CCL deficiency in dogs, postoperative rehabilitation protocols have been reported to improve outcome, maintain muscle mass in the thigh region, reduce lameness, and reduce radiographic evidence of progressive osteoarthritis.4–9 Physical rehabilitation after TPLO has been reported to improve range of motion and increase thigh muscle mass, but may not improve lameness or weight bearing in dogs, at least in the short term.6,9

Many surgical techniques are available for the treatment of CCL injury in dogs. Proponents of the TPLO technique cite early return to function and reduced progression of osteoarthritis in the stifle joint; however, reports10–13 in the literature have not always supported these claims. Regardless, TPLO is presently the most commonly recommended surgical technique in small-breed and large-breed dogs.14–16 Methods to improve outcome and reduce the time to return to preinjury function after TPLO have resulted in limited success, and progression of osteoarthritis in the stifle joint following surgery is common.6,8–11,17,18

The management of osteoarthritis has been investigated in many species, with recent findings indicating that a multimodal approach to treatment is most likely to yield improvement in clinical signs.19–23 Therapeutic diets have been advocated as 1 method of managing osteoarthritis in dogs. Results of blinded, placebo-controlled clinical trials investigating therapeutic diets with high omega-3 fatty acid content indicate that dogs with osteoarthritis have greater PVF and improved case-specific outcome measures beginning 7 to 13 weeks after initiation of the diet, compared with those of control dogs fed a diet without added omega-3 fatty acids.24–26 For dogs with chronic osteoarthritis, a diet rich in omega-3 fatty acids was associated with a more rapid decrease in carprofen dosage (determined on the basis of clinical signs), compared with that for dogs fed a diet containing low amounts of these products.27 Omega-3 fatty acids were also shown to reduce expression and activity of proteoglycan-degrading enzymes and expression of various inflammation-inducible cytokines by bovine chondrocytes in vitro, supporting that administration of such products might have a role in alleviation of factors associated with arthritis.28

Recommendations for management of dogs following TPLO vary with surgeon preference, and to the authors' knowledge, no prospective studies have been published in which outcomes were compared among dogs treated with and without a specific rehabilitation protocol and dietary management program after the procedure. The objective of the study reported here was to determine the clinical effects of an omega-3 fatty acid and protein-enriched diet, physical rehabilitation, or both in dogs over a 6-month period following TPLO and arthroscopic surgery for the treatment of CCL disease. We hypothesized that a diet rich in omega-3 fatty acids and protein and a physical rehabilitation program would each be associated with a lower frequency and severity of lameness (as assessed by gait analysis and subjective evaluations by surgeons and dog owners) as well as increased physical activity, compared with results for dogs not receiving these treatments.

Materials and Methods

Dogs

Client-owned dogs > 1 year of age undergoing TPLO and stifle joint arthroscopy for treatment of acutely occurring, arthroscopically confirmed CCL disease were prospectively recruited for the study between August 1, 2010, and February 1, 2014. Dogs with signs of systemic illness, CBC or serum biochemical results outside of the laboratory reference ranges, CCL disease of the contralateral hind limb, or signs of joint disease in 1 or both forelimbs were excluded, as were dogs with concurrent or previous history of immune-mediated joint disease or osteochondrosis dissecans affecting a pelvic limb, patellar luxation, or fractures of the distal aspect of a femur or proximal aspect of a tibia. Dogs were also excluded if the CCL injury had occurred > 2 months prior to surgery or if they had received corticosteroids or NSAIDs ≤ 2 weeks or ≤ 24 hours prior to surgery, respectively.

An investigation of radiographic outcomes (including osteotomy healing time and evidence of osteoarthritis and patellar desmitis) and markers of synovial joint inflammation in the same dogs was performed concurrently, and the results are reported elsewhere.29 The studies were approved by the Institutional Animal Care and Use Committee of Oregon State University. Informed owner consent was obtained prior to enrollment of dogs.

Group assignments and blinding

Dogs were randomly assigned to 1 of 4 postoperative treatment groups. Dogs received a dry omega-3 fatty acid and protein-enriched dog food formulated to support joint healtha (TF), a dry food formulated for maintenance of adult dogsb (CF), TF-R, or CF-R. On the basis of previous clinical studies4–9 reported in the literature involving dogs undergoing surgery for CCL disease, 12 dogs were assigned to each treatment group for a total of 48 dogs. Assignment of dogs to these treatment groups was performed with conventional spreadsheet software.c Briefly, a spreadsheet was generated containing columns for dog accession number, treatment designator, and 48 random numbers generated with a randomization function. The random number column was then used to sort the column containing treatment group designators against the dog number column in ascending order. This action randomized the treatment group designators against the dog accession number.

Veterinarians, researchers, and owners of dogs involved in the study were blinded to the food that was fed to the dogs. Radiologists who obtained radiographs were blinded to all treatment group assignments (foods fed and whether physical rehabilitation was performed).

Surgical procedures and radiologic evaluation

Arthroscopic and TPLO procedures were performed in dogs under general anesthesia by board-certified surgeons or by surgical residents under the direct supervision of a board-certified surgeon. Arthroscopy was performed immediately prior to the TPLO with a 30° fore-oblique 2.7- to 4.0-mm arthroscope; arthroscopic and instrument portals were placed at the midpoint along the length of the patellar ligament between the patella and tibia and 2 to 4 mm lateral and medial to the patellar ligament.30 The medial meniscus of the affected stifle joint was evaluated arthroscopically and probed with manual instruments and then categorized as intact (with no arthroscopic signs of disease) or as having radial tears, a longitudinal (ie, nondisplaced bucket-handle) tear, or severe disease (double or triple bucket-handle tears or displacement or loss of meniscal tissue).30 Dogs with bucket-handle tears had a partial caudal meniscectomy performed, and those with severe disease underwent caudal medial meniscectomy.30 The TPLO was performed as described elsewhere.31 Meniscal release was not performed. The plate type was selected according to the surgeon's discretion; however, all dogs that weighed ≥ 50 kg (110 lb) had a locking TPLO plated placed following the osteotomy.

Dogs of the present study received carprofene (4.4 mg/kg [2 mg/lb], once, SC) at the time of surgery but at no other time afterwards. Postoperative analgesic treatment consisted of hydromorphone hydrochloridef (0.1 mg/kg [0.045 mg/lb], IV, q 4 to 6 h) for 24 to 48 hours, followed by treatment with sustained-release morphine sulfateg (1 mg/kg [0.45 mg/lb], PO, q 12 h) for 7 days. Perioperative antimicrobial treatment consisted of cefazolinh (22 mg/kg [10 mg/lb], IV) 30 minutes prior to surgery and every 90 minutes during the procedure. The day of surgery was considered day 0, and preoperative values on day 0 represented the baseline values for all time-dependent procedures.

Radiologic examination was performed prior to, immediately after, and at 8 and 24 weeks after surgery. Dogs were sedated for radiography with a combination of dexmedetomidinei (5 μg/kg [2.27 μg/lb], IV) and butorphanolj (0.1 mg/kg, IV), except for immediate postoperative imaging. The tibial plateau angle was measured preoperatively and postoperatively by board-certified surgeons (WIB and JJW) using previously described techniques32; all radiographic images were obtained by radiologists.

Diets and physical rehabilitation

Beginning with the first meal after surgery, dogs were fed the assigned foods, which were supplied to owners for 6 months (Appendix). The foods were supplied in plain white bags to the Veterinary Teaching Hospital and labeled by the supplier only as either diet A or B. Owners were instructed to refrain from administration of any NSAIDs; nutraceuticals, vitamins, or other supplements; or homeopathic treatments to their dogs during the 6-month study period. Owners were also instructed that the supplied food was to be given at all meals, with ≥ 90% of the diet consisting of the food supplied. Dog treats were allowed but had to comprise < 10% of the dog's food intake as estimated by the owner. The amount fed was to be at least the same volume of dry food that the dog was receiving before the study, but no other guidelines were given to maintain blinding because caloric content of the 2 foods differed. Any dog that developed lameness as reported by the owner during the study period was brought to the researchers and assessed. Such dogs were removed from data analysis and further participation in the study.

Beginning 3 days after surgery, owners of all dogs, regardless of group, were instructed to perform passive range-of-motion exercises of the affected limb for a total of 15 repetitions/session, 2 times/d until 3 months after surgery. Walking of all dogs was allowed on a leash only, twice daily for 5 to 10 minutes beginning 2 weeks after surgery. Beginning 8 weeks after surgery, the duration of the walks was increased by 10 min/walk/wk until 3 months after surgery, when dogs were allowed any activity without restrictions.

In addition, beginning 2 weeks after surgery, owners of dogs in the TF-R and CF-R groups were instructed to have their dogs perform sit-to-stand exercises for a total of 10 repetitions/session, 3 times/d until 3 months after surgery. Beginning 3 to 4 weeks after surgery, underwater treadmill exercise was provided to dogs in the TF-R and CF-R groups according to the following schedule: once weekly for 3 weeks, then twice weekly for 2 weeks, then 3 times weekly for 3 weeks (total duration, 8 weeks). The first underwater treadmill treatment was completed with the water height at the approximate level of the middle to distal regions of the tibiae. The treadmill speed was set to allow the dog to walk smoothly but not to trot or pace (speeds ranged from 1.3 to 1.6 km/h [0.8 to 1.0 mile/h]), and the duration of treatment was 5 minutes. For the second underwater treadmill treatment, the water level was increased so that the stifle joints were submerged in the standing position but raised above the water surface during the upward swing phase of the gait when walking. For the remaining treatments, the water level was sequentially increased by 2 to 4 inches at the start of each session (until a maximum level was reached at the height of the shoulder (ie, at the level of the scapulohumeral joint) and kept stable during the session. Time in the water was increased at each session by 5 minutes (as deemed appropriate according to the discretion of a certified canine rehabilitation practitioner) until the dog was walking on the treadmill for 30 minutes, and this duration of treatment was then maintained for the remaining sessions. All dogs progressed to walking for 30 minutes with the water at shoulder height, but progress was dependent on the perceived comfort level and ability of the dog, and the goal was achieved faster for some dogs than for others. The gait speed was not faster than a smooth walk at any time; dogs were walked on the treadmill at a speed that allowed them to continue at a steady pace without labored breathing or stumbling and while still using the affected limb (similar to perceived exertion in children33), and this speed typically resulted in panting and signs of effort from the dog. No other treatments were performed during underwater treadmill sessions.

Owner compliance regarding diet, exercise, and use of the activity monitor was recorded by 1 author (SSO) at each time point, therapy session, or both for each dog. These results were recorded in the dogs' medical records. Any dog that missed evaluation at an assigned time point or missed an assigned therapy session was removed from the study, and another dog was recruited to take its place.

Outcome measures

Objective assessments included analysis of ground reaction forces measured by use of a pressure-sensitive walkway systemk (ie, platform) on day 0 (just prior to surgery) and at 2, 8, 16, and 24 weeks after surgery. The platform was used to determine PVF and VI from 5 footfalls/dog/time point during a walk with a velocity of 1.1 to 1.5 m/s and an acceleration-deceleration variation of 0.5 m/s2. A trial was considered valid for analysis if the velocity and acceleration-deceleration were within the described parameters. Multiple acceptable trials were used in analysis of the data.

Thigh and proximal tibial region circumference were determined by 1 of 2 researchers (WIB or JJW). With the dog in lateral recumbency, thigh circumference was measured with a tensile tape measure.l The long axis of the femur was measured from the greater trochanter to the lateral femoral condyle, and thigh circumference was determined at a point calculated as 70% of that distance in the proximal-distal direction. The circumference of the proximal tibial region was measured at the level of its greatest width, where the cranial tibial muscle was judged largest in diameter. Circumference measurements were reported as a ratio of the affected limb to the contralateral hind limb.8,34

Each dog wore an activity monitorm at the time of discharge from the hospital and at 2, 8, 12, 16, and 24 weeks after surgery, for 1 wk/time point. The accelerometry monitor was placed in a small pouch attached to a harness at the dorsal midline between the shoulders of the dog. Owners were instructed to have their dog wear the harness with the monitor at all times during each evaluation period and that the monitor could get wet but was not to be submerged in water; thus, the dog was not allowed to swim during these intervals, and the monitors were not worn during the treadmill exercise. Activity data were recorded as the amount of time spent each week in sedentary, light-to-moderate, and vigorous activity as defined previously.35 Accelerometer counts were recorded with commercial softwaren to determine the daily time spent in sedentary, light-to-moderate, or vigorous physical activity by dividing the weekly counts by 7 for daily counts. The specific count thresholds corresponding to these intensity levels were derived from the Freedson equation36 (also termed MET [metabolic equivalent of 1 kcal/kg/h] prediction equation) as described elsewhere.37

Body weight was assessed prior to surgery and 8 and 24 weeks after surgery by use of a single digital walk-on scale that was calibrated weekly throughout the study. The BCS was determined at the same time points by the board-certified surgeons (WIB and JJW) or surgery residents in training under supervision of the surgeons using a previously described scale of 1 (extremely thin) to 9 (obese).38

Subjective scoring of signs related to pain and lameness was performed independently by veterinarians and dog owners at baseline (just prior to surgery) and at 2, 8, 16, and 24 weeks after surgery. Veterinarians assessed signs of pain and lameness using modified scoring systems (Supplementary Appendix S1, available at avmajournals.avma.org/doi/suppl/10.2460/javma.252.6.686)39,40 Briefly, pain assessment included scoring of vocalization (0 to 2), movement (0 to 2), behavior (0 to 3), and response to manipulation (0 to 3), where the lowest and highest scores represented no signs and greatest signs of pain or discomfort, respectively.39 Lameness was scored from 0 (stands and walks normally) to 4 (non-weight-bearing lameness).40 Owner evaluations were performed with a scoring system that comprised 15 variables (Supplementary Appendix S2, available at avmajournals.avma.org/doi/suppl/10.2460/javma.252.6.686). This included scoring of the dog's overall activity for the month and week preceding the evaluation (each from 1 [unable to walk] to 10 [normal activity]); degree of difficulty in sitting, rising from recumbency, and squatting to urinate or defecate (each from 1 [difficult] to 10 [easy]); mood and attitude for the month and week preceding the evaluation (each from 1 [depressed or withdrawn] to 10 [happy or attention seeking]); changes in the amount of daily activity (from 1 [no change] to 10 [large change]) and willingness to play (from 1 [not willing] to 10 [very willing]); and lameness when walking, trotting, or running, and signs of pain when turning suddenly (each from 1 [never] to 10 [always]).

Statistical analysis

Before the start of the study, potential confounders were identified. Confounders assessed included breed, age, sex, body weight, BCS, whether meniscal surgery was performed, presurgical and postsurgical tibial plateau angle, development of CCL disease in the contralateral limb, and subjectively assessed owner-reported compliance with management instructions. Owner-reported compliance was not controlled for in the study. Continuous variables were tested for normal distribution with the Shapiro-Wilk test. Identified potential confounders were assessed by comparison among groups by means of 1-way ANOVA when data were normally distributed (age, body weight, and tibial plateau angle) or a Kruskal-Wallis test when data were not normally distributed (BCS). Intergroup comparisons for sex and neuter status were performed with contingency table analysis (χ2 tests). Data for ground reaction forces (PVF and VI), accelerometry data (daily activity), and owner questionnaire responses (frequencies of lameness in various scenarios) were analyzed by means of stepwise multivariate linear regression followed by multi-way ANOVA or the Kruskal-Wallis test when data were or were not were consistent with a normal distribution, respectively. The minimal adequate model for each response variable assessed was determined by stepwise regression, starting from a model incorporating all of the potential confounders identified, with serial removal of potential confounders that failed to show explanatory power. The resulting models, applied for both the ANOVA and Kruskal-Wallis tests, incorporated the variation in each variable accounted for by time (in weeks after surgery), individual dog variability, physical rehabilitation (yes vs no), diet (TF vs CF), and treatment-by-time interaction (ie, whether the effect of treatment varied with time). False discovery rate was controlled by the Benjamini-Hochberg method to derive adjusted P values, with the threshold for significance set at an adjusted value of P < 0.05. Posttest analysis of intergroup differences (ie, assessment of the effects of time after surgery, diet type, rehabilitation, and interactions among time, diet, and rehabilitation treatment) was performed with the Tukey honest significant difference test following multi-way ANOVA and by the Dunn test following the Kruskal-Wallis test. Statistical analyses were performed with an open-source statistical program.41,o

Results

Of 48 dogs enrolled in the study, 28 were females (all spayed) and 20 were males (18 neutered and 2 sexually intact). The proportions of spayed females and neutered males in the TF (6/6 and 6/6, respectively), CF (6/6 and 4/5, respectively), TF-R (8/8 and 3/4, respectively), and CF-R (8/8 and 4/4, respectively) groups were similar (P > 0.05). The 2 sexually intact males were in the CF and TF-R groups. Mean ± SD age did not differ significantly among the TF (4.7 ± 2.2 years), CF (5.8 ± 2.1 years), TF-R (4.9 ± 3.2 years), and CF-R (5.1 ± 2.2 years) groups.

The most commonly represented breeds of dogs were Labrador Retriever (n = 9; 5 in the CF group, 2 in the TF group, and 1 each in the other 2 groups), Golden Retriever (6; 3 in the CF-R group and 1 each in the other 3 groups), and American Staffordshire Terrier (3; 2 and 1 in the CF and CF-R groups, respectively). There were 2 Rottweilers (1 each in the TF and CF-R groups) and 2 Australian Shepherds (both in the TF-R group). The following breeds were represented by 1 dog each: German Shorthaired Pointer, German Shepherd Dog, and Blue Heeler (all in the CF group); Boxer and Saint Bernard (both in the TF-R group); Samoyed and Mastiff (both in the CF-R group); and Great Dane (CF group). The remaining dogs were of mixed breeds (3 in the CF group and 5 each in the other 3 groups).

Owners reported that they followed exercise, activity, feeding, and postoperative care instructions adequately when asked verbally at each assessment time point or physical rehabilitation session; however, the owners of 3 of 48 (6%) dogs (1 each in the TF, CF, and TF-R groups) indicated that their dogs would not eat the assigned food or did not seem to find it palatable. These 3 dogs were removed from the study and were not included in any subsequent data analysis. Six of 48 (13%) dogs developed complications during the study. One dog in the CF group developed erythema, swelling, and serosanguinous discharge at the TPLO incision site 1 month after surgery. The site was aseptically prepared with chlorhexidine solution and saline (0.9% NaCl) solution, and a sample was obtained for aerobic and anaerobic microbial culture but results were negative, and the discharge, swelling, and erythema resolved uneventfully in ≤ 1 week. Three (6%) dogs (1 each in the TF, CF, and CF-R groups) developed contralateral CCL disease between 20 and 24 weeks after surgery. Two (4%) dogs (1 each in the CF and TF-R groups) developed medial meniscal disease in the affected limb during the study; both of these dogs developed substantial lameness with an audible clicking or popping sound when walking between 16 and 20 weeks after surgery, and both underwent a second arthroscopic procedure in which a bucket-handle tear of the medial meniscus was identified and resected. The 5 dogs that developed CCL disease of the contralateral limb or postoperative medial meniscal disease or injury were removed from the remaining data analyses starting on the date when the complication was first observed. The dog that developed a serosanguinous discharge from the incision was not removed from the study, but a 5-day delay prior to the start of increasing exercise off leash was implemented while the wound healed.

Body weight varied among treatment groups and over time (P < 0.001 for both comparisons), and there were significant time-by-treatment interactions for body weight 8 and 24 weeks after surgery (P < 0.005). Mean body weight at both postoperative time points differed significantly (P < 0.001) from the baseline value for all 4 treatment groups (Table 1). There was no significant difference in body weight between dogs of the TF and CF groups over time. There was a significant (P < 0.001) effect of time on body weight for dogs in the TF-R group, compared with those in the TF and CF-R groups, with dogs in the TF-R group maintaining weight and those in TF and CF-R groups losing weight (P < 0.001). None of the dogs in the CF or CF-R groups gained weight after surgery; however, some dogs in the TF and TF-R groups lost or gained weight during the 6 months after surgery (P < 0.001). The proportions of dogs in each treatment group that lost weight and gained weight at each time point, compared with that measured at baseline, were summarized (Table 2).

Table 1—

Summary data (mean ± SD) for 48 client-owned dogs in a study to evaluate the effects of diet and physical rehabilitation on various outcome measures following TPLO and arthroscopic surgery for treatment of unilateral CCL disease.

VariableTFCFTF-RCF-R
Body weight (kg)
  Baseline38.5 ± 10.639.2 ± 8.234 ± 10.537.4 ± 12.6
  8 wk38 ± 10.736 ± 7.533 ± 11.234.3 ± 12.5
  24 wk37.7 ± 11.236.4 ± 9.434.7 ± 12.934.1 ± 12.4
BCS*
  Baseline5.8 ± 1.26.4 ± 1.15.5 ± 0.36.6 ± 1.4
  2 wk5.7 ± 1.56.0 ± 0.95.0 ± 0.55.6 ± 0.3
  8 wk5.8 ± 1.45.8 ± 0.35.1 ± 1.15.8 ± 1.2
  24 wk5.6 ± 1.46.0 ± 1.45.8 ± 15.5 ± 1.3
Tibial plateau angle (°)
  Baseline25.7 ± 3.725.5 ± 3.424.8 ± 3.326.8 ± 4.5
  Immediately after surgery8.0 ± 3.46.2 ± 2.99.5 ± 5.57.4 ± 3.2
  8 wk7.8 ± 3.96.2 ± 2.48.9 ± 2.97.3 ± 3.3
  24 wk7.4 ± 3.06.4 ± 2.69.1 ± 3.38.7 ± 6.0
PVF (% body weight)
  Baseline28.0 ± 19.620.9 ± 10.634.0 ± 14.831.2 ± 13.1
  8 wk42.8 ± 18.934.6 ± 8.940.9 ± 11.230.4 ± 10.2
  16 wk40.0 ± 14.732.8 ± 9.141.7 ± 7.336.3 ± 10.1
  24 wk41.7 ± 19.738.3 ± 13.645.6 ± 14.639.1 ± 11.4
VI (% body weight × s)
  Baseline8.0 ± 7.26.0 ± 3.110.3 ± 4.47.5 ± 4.3
  8 wk13.2 ± 6.010.8 ± 3.512.4 ± 5.27.9 ± 2.7
  16 wk12.7 ± 6.511.7 ± 5.113.1 ± 3.68.9 ± 2.1
  24 wk13.9 ± 6.812.9 ± 5.414.0 ± 6.711.3 ± 2.6
Thigh circumference ratio
  Baseline0.97 ± 0.061.0 ± 0.060.97 ± 0.140.95 ± 0.06
  8 wk0.97 ± 0.080.99 ± 0.090.90 ± 0.060.97 ± 0.07
  16 wk0.95 ± 0.120.98 ± 0.061.02 ± 0.060.98 ± 0.06
  24 wk1.01 ± 0.090.99 ± 0.031.0 ± 0.090.97 ± 0.09
Proximal tibial region circumference ratio
  Baseline0.95 ± 0.090.95 ± 0.071.0 ± 0.160.98 ± 0.08
  8 wk1.0 ± 0.120.97 ± 0.060.95 ± 0.081.0 ± 0.12
  16 wk0.98 ± 0.030.99 ± 0.070.98 ± 0.051.01 ± 0.06
  24 wk0.99 ± 0.061.0 ± 0.111.01 ± 0.081.01 ± 0.12

Dogs were randomly assigned to receive a dry omega-3 fatty acid and protein–enriched dog food formulated to support joint health (TF), a dry food formulated for maintenance of adult dogs (CF), TF-R, or CF-R after surgery. Baseline values were determined prior to surgery on day 0. At baseline and 2 weeks, there were 12 dogs/group. At 8 weeks, there were 11 dogs in the TF, CF, and TF-R groups and 12 in the CF-R group. From 16 to 24 weeks, there were 10 dogs in the TF and TF-R groups, 9 in the CF group, and 11 in the CF-R group.

Assessed on a scale of 1 (extremely thin) to 9 (obese).

Values determined radiographically by board-certified surgeons (WB and JW).

Calculated as measurement of the affected limb divided by measurement of the unaffected limb at predetermined sites.

Table 2—

Descriptive summary of changes in body weight or BCS after TPLO for the same 48 dogs as in Table 1.

 Weight lossWeight gainBCS decreasedBCS increased
Time and groupProportion of dogsMean change (kg)*Proportion of dogsMean change (kg)*Proportion of dogsMean change*Proportion of dogsMean change*
8 wk
  TF5/122.15/121.23/121.14/120.9
  CF9/112.00/11NA9/110.710/11NA
  TF-R10/112.10/11NA8/110.83/110.7
  CF-R12/123.10/12NA10/121.10/12NA
24 wk
  TF5/113.34/111.54/111.12/111.6
  CF8/114.40/11NA9/110.710/11NA
  TF-R4/111.67/112.73/110.87/110.9
  CF-R9/124.40/12NA8/121.80/12NA

Differences were calculated by comparison with the baseline value for the same dogs.

Mean change was calculated only for dogs that had the specified change in the variable.

NA = Not applicable.

See Table 1 for remainder of key.

Dogs in the CF and CF-R groups had significantly (P < 0.01) higher mean BCS at baseline on day 0, compared with the other 2 groups; however, this difference was not noted from week 2 onward (Table 1). There was a significant (P < 0.001) effect of time on BCS and a significant (P < 0.001) interaction between treatment and time for this variable. The TF-R group dogs had significantly (P < 0.01 and P < 0.05, respectively) lower mean BCS at weeks 2 and 8, compared with that for dogs in the TF and CF groups; however, differences among groups were not noted after 8 weeks. The proportions of dogs in each treatment group that had subjectively lower and higher BCS at 8 and 24 weeks, compared with that measured at day 0, were tabulated (Table 2).

Arthroscopy at the time of TPLO revealed that the medial meniscus was intact in 9 dogs (5 in the TF-R group, 2 TF group, and 1 each in the CF and CF-R groups). Radial tears of the medial meniscus were identified in 21 dogs (7 in the CF-R group, 6 in the CF group, 5 in the TF group, and 3 in the TF-R group). There were bucket-handle tears of the medial meniscus identified in 11 dogs (4 in the TF group, 3 in the TF-R group, and 2 each in the CF and CF-R groups). Severe disease of the medial meniscus requiring caudal hemimenisectomy was identified in the remaining 7 dogs (3 in the CF group, 2 in the CF-R group, and 1 each in the TF and TF-R groups). There was no significant (P > 0.05) difference among groups in the incidence or severity of meniscal disease at surgery.

Mean tibial plateau angle did not differ significantly (P > 0.05) among the 4 treatment groups at baseline (Table 1). There was no significant (P > 0.05) difference in tibial plateau angle among groups over time after surgery.

Stepwise linear regression modeling identified significant (P < 0.001 for both comparisons) effects of time following surgery for PVF and VI in all groups. The TF diet was associated with significantly greater (P < 0.001 for both comparisons) postoperative PVF and VI, compared with results for dogs receiving the CF diet. Rehabilitation treatment was associated with significantly (P < 0.01) greater postoperative PVF, compared with that of dogs that did not undergo rehabilitation, but did not have a significant effect on VI. Significant (P < 0.05) interaction effects were observed between time and treatment (both diet and rehabilitation) for PVF and VI and between diet and time for VI (P < 0.05). At baseline, mean PVF was greater in the TF-R group than in the CF group (P < 0.01) and in the CF-R group than in the CF group (P < 0.05; Table 1; Figure 1). Mean VI at baseline was significantly greater in the TF-R group than in the CF-R (P < 0.05), CF (P < 0.01), and TF groups (P < 0.01; Figure 2). Both ground reaction forces improved significantly (P < 0.01 for both variables) over time in all groups. At 8 weeks after surgery, dogs fed the TF diet, but not the CF diet, had significantly (P < 0.01) improved PVF and VI, compared with those recorded at baseline. The PVF was significantly (P < 0.05) greater in the TF-R group than in the CF-R group at week 8 and was significantly (P < 0.01 and P < 0.05 respectively) greater in the TF-R group than in the CF group at weeks 16 and 24. The VI was also significantly (P < 0.01) greater in the TF-R group than in the CF-R group at week 16.

Figure 1—
Figure 1—

Results of analysis for PVF over time in 48 dogs that underwent TPLO and arthroscopic surgery for unilateral CCL disease and were randomly assigned to receive a dry omega-3 fatty acid and protein-enriched dog food formulated to support joint health alone (TF) or with physical rehabilitation (TF-R) or a dry food formulated for maintenance of adult dogs alone (CF) or with physical rehabilitation (CF-R) after surgery. Results are presented by food type (TF and TF-R [A] vs CF and CF-R [B]) to aid interpretation. Data were obtained immediately prior to surgery (0 weeks) and 2 to 24 weeks later. Curves show local least squares regression lines fit to the data; gray margins represent the 95% confidence intervals for regression lines. Mean PVF at baseline was greater for the TF-R group, compared with the CF group (P < 0.01), and for the CF-R group, compared with the CF (P < 0.05) group. Values improved significantly (P < 0.01) over time for all groups; PVF was greater for the TF-R group than the CF-R group at week 8 (P < 0.05) and greater for the TF-R group than the CF group at weeks 16 and 24 (P < 0.01 and P < 0.05, respectively). At baseline and 2 weeks, there were 12 dogs/group. At 8 weeks, there were 11 dogs in the TF, CF, and TF-R groups and 12 in the CF-R group. From 16 to 24 weeks, there were 10 dogs in the TF and TF-R groups, 9 in the CF group, and 11 in the CF-R group.

Citation: Journal of the American Veterinary Medical Association 252, 6; 10.2460/javma.252.6.686

Figure 2—
Figure 2—

Results of analysis for VI over time for the same 48 dogs as in Figure 1 (TF and TF-R groups [A] and CF and CF-R groups [B]). The VI improved significantly (P < 0.01) over time in all groups. The TF-R group had significantly greater baseline VI, compared with the CF-R (P < 0.05), TF (P < 0.01), and CF (P < 0.01) groups and had significantly (P < 0.01) greater VI than the CF-R group at week 16. See Figure 1 for remainder of key.

Citation: Journal of the American Veterinary Medical Association 252, 6; 10.2460/javma.252.6.686

There was no significant association of rehabilitation status (P = 0.242), diet (P = 0.396), or time (P = 0.380) with thigh circumference measurement ratios (Table 1). There was also no significant association of rehabilitation status (P = 0.296), diet (P = 0.920), or time (P = 0.083) with the tibial circumference measurement ratio.

Weekly recordings of activity monitor data revealed that the sedentary time per day decreased significantly (P = 0.031) over time in all groups (Table 3). There was no significant association of rehabilitation status (P = 0.64) or diet (P = 0.47) with this variable. There were no significant (P > 0.05 for all groups) interactions among rehabilitation status, diet, and time with respect to sedentary time per day.

Table 3—

Mean ± SD daily activity data measured by use of accelerometry following TPLO for the same 48 dogs as in Table 1.

VariableTFCFTF-RCF-R
Sedentary time (min)
  1 wk872 ± 85885 ± 60890 ± 60874 ± 62
  8 wk818 ± 120872 ± 43874 ± 74853 ± 30
  16 wk865 ± 265690 ± 281759 ±187755 ±129
  24 wk833 ± 76790 ± 233767 ± 228831 ± 56
Time in light-to-moderate activity (min)
  1 wk52.6 ± 19.551.5 ± 21.042.1 ± 46.361.7 ± 44.1
  8 wk44.9 ±14.072.9 ± 29.481.1 ± 41.169.1 ± 20.4
  16 wk64.6 ± 25.368.4 ± 30.279.6 ± 39.882.2 ± 50.8
  24 wk71.8 ± 7.056.5 ± 33.280.8 ± 44.080.1 ± 28.6
Time in vigorous activity (min)
  1 wk1.9 ± 2.01.1 ± 2.60.4 ± 1.91.8 ± 3.3
  8 wk0.9 ± 0.81.3 ± 1.62.6 ± 3.12.0 ± 1.4
  16 wk4.2 ± 4.42.8 ± 3.95.5 ± 6.13.7 ± 5.2
  24 wk6.6 ± 7.01.6 ± 1.85.2 ± 5.73.7 ± 6.1

Each dog was fitted with a harness, and activity data were recorded with an accelerometry device placed in a pouch attached to the harness at the dorsal midline between the shoulders. Accelerometer counts were recorded weekly at predetermined time points and used to determine the amount of time per day that dogs were sedentary or engaged in light-to-moderate or vigorous activity.35–37 The first week for activity monitoring began with discharge from the hospital after TPLO.

See Table 1 for remainder of key.

There was a significant (P = 0.013) increase in the duration that dogs of all groups spent in light-to-moderate activity per day over time (Table 3). Rehabilitation was significantly (P = 0.001) associated with this variable, with dogs that underwent rehabilitation spending more time in light-to-moderate activity than dogs that did not (Figure 3). Time spent in light-to-moderate activity by dogs in the TF-R group during week 24 was nearly twice that recorded during week 1. For dogs in the CF-R and TF groups, the daily time spent in light-to-moderate activity during week 24 was 1.3 and 1.4 times that in week 1, respectively. In contrast, the dogs of the CF group had 1.1 times the measured activity of week 1 during week 24. There was no significant (P = 0.39) association of diet and no significant (P = 0.59) interaction between diet and rehabilitation status in the analysis of time spent in light-to-moderate activity daily.

Figure 3—
Figure 3—

Results of analysis for time spent in light-to-moderate activity for the same 48 dogs as in Figure 1 (TF and TF-R groups [A] and CF and CF-R groups [B]). Data were obtained by use of an accelerometry device placed in a pouch at the dorsal midline between the shoulders by attachment to a harness. Activity data were recorded weekly and used to determine the amount of time that dogs were sedentary or engaged in light-to-moderate or vigorous activity35–37; results were divided by 7 to attain mean daily time spent in each type of activity. The first week for activity monitoring began with discharge from the hospital after TPLO. Mean time spent in light-to-moderate activity increased (P = 0.013) for all groups over time. Rehabilitation was significantly (P = 0.001) associated with greater time spent in this level of activity after surgery. See Figure 1 for remainder of key.

Citation: Journal of the American Veterinary Medical Association 252, 6; 10.2460/javma.252.6.686

Time spent in vigorous activity per day also increased significantly (P = 0.006) over time in all groups (Table 3). There was no significant association of rehabilitation status (P = 0.075) or diet (P = 0.12) with this variable. There were no significant (P > 0.05) interactions among treatment, diet, and time with respect to time spent in vigorous activity per day.

Veterinarian assessment for signs of pain and lameness in dogs before and after surgery did not reveal any significant differences among the 4 treatment groups for vocalization, movement, behavior, response to manipulation, or lameness scores; however, all groups improved in all areas of assessment over time after surgery (P < 0.05; data not shown). There were also no significant differences in mean owner scores for signs related to pain and lameness among treatment groups prior to surgery, and after surgery, these scores improved for all groups over time (P < 0.05; data not shown). Although owners were advised to comply with exercise restrictions, and activity at home was to be increased gradually from 8 to 12 weeks after surgery, owner scoring reflected that dogs had been observed trotting, running, or turning sharply prior to the 12-week cutoff. No significant differences were identified among the 4 treatment groups in this analysis except for owner-assessed frequency of lameness when dogs were trotting or running and signs of pain when turning suddenly while walking (Figures 4–6). Dogs in the TF group had a more rapid decline in frequency and lower overall frequency for these variables over time than did dogs in the CF, TF-R, or CF-R groups (P < 0.01). In addition, dogs in the TF-R and CF-R groups had significantly (P < 0.05) lower frequencies of lameness when running and signs of pain when turning suddenly, compared with results for dogs in the CF group.

Figure 4—
Figure 4—

Results of analysis for subjective owner scoring of lameness for the same 48 dogs as in Figure 1 (TF and TF-R groups [A] and CF and CF-R groups [B]) when observed trotting. The frequency of signs was scored from 1 (never) to 10 (always lame). Dogs in the TF group had a more rapid decline in mean frequency of lameness during trotting over time, compared with results for dogs in the CF, TF-R, or CF-R groups (P < 0.01). Breaks in the 95% confidence interval lines at some time points resulted from low variability within groups and thus very narrow confidence intervals at those points. See Figure 1 for remainder of key.

Citation: Journal of the American Veterinary Medical Association 252, 6; 10.2460/javma.252.6.686

Figure 5—
Figure 5—

Results of analysis for subjective owner scoring of lameness for the same 48 dogs as in Figure 1 (TF and TF-R groups [A] and CF and CF-R groups [B]) when observed running. The frequency of signs was scored from 1 (never) to 10 (always lame). Dogs in the TF group had a more rapid decline in the mean frequency of lameness during running over time, compared with results for dogs in the CF, TF-R, or CF-R groups (P < 0.01). Dogs in the TF-R and CF-R groups had significantly (P < 0.05) lower frequencies of lameness when running than did dogs in the CF group. Breaks in the 95% confidence interval lines at some time points resulted from low variability within groups and thus very narrow confidence intervals at those points. See Figure 1 for remainder of key.

Citation: Journal of the American Veterinary Medical Association 252, 6; 10.2460/javma.252.6.686

Figure 6—
Figure 6—

Results of analysis for subjective owner scoring of signs of pain for the same 48 dogs as in Figure 1 (TF and TF-R groups [A] and CF and CF-R groups [B]) when observed to turn sharply at a walk. The frequency of signs was scored from 1 (never) to 10 (always painful when turning). Dogs in the TF group had a more rapid decline in the mean frequency of signs of pain under these conditions than did dogs in the CF, TF-R, or CF-R groups (P < 0.01 for all comparisons). Dogs in the TF-R and CF-R groups had lower frequencies of signs of pain under these conditions than did dogs in the CF group (P < 0.05 for both comparisons). See Figures 1 and 4 for remainder of key.

Citation: Journal of the American Veterinary Medical Association 252, 6; 10.2460/javma.252.6.686

Discussion

Management of dogs in the postoperative period following TPLO for CCL disease has been controversial. Proponents of physical rehabilitation following surgery argue that development of balance and proprioception enables a faster recovery, while others report no improvement in lameness with rehabilitation, although improvements in muscle mass and range of motion have been observed.6,8,9,42,43

The TF with added omega-3 fatty acids was associated with improved PVF and VI following TPLO surgery, compared with the CF in this study. This effect was significant (P < 0.001) for both ground reaction forces, with greater weight bearing in TF-fed groups than in CF-fed groups beginning at 8 weeks after surgery. To the author's knowledge, the present study was the first in which findings indicated a more rapid recovery of weight bearing in dogs fed an omega-3 fatty acid-enriched diet after surgery for CCL disease than in dogs fed a maintenance diet. In other studies,24–26 dogs fed omega-3 fatty acid-enriched diets for management of osteoarthritis had improvements in ground reaction forces, and we considered it possible that omega-3 fatty acid-mediated reduction of proinflammatory mediators contributed to the results seen in dogs of the present study. Although all groups had gradual improvement in PVF and VI over time, which was consistent with other reports9,39,44–46 of outcome for dogs following TPLO with or without rehabilitation, rehabilitation was significantly associated with improved PVF in the present study. No effect of rehabilitation on VI was observed following surgery; however, PVF has been shown to be the single most accurate ground reaction force for kinetic pelvic limb lameness evaluation in dogs.9,47,48

Significant interaction effects were observed between time and treatment for PVF and VI and between diet and time for VI. The presence of significant interactions indicates that the effect of one factor (eg, treatment) varies with the value of another factor (eg, time). In the presence of significant interactions, the intergroup differences identified must be interpreted cautiously. Further studies with larger groups of dogs are warranted to confirm the associations of diet and rehabilitation with these outcomes.

To the authors' knowledge, this was the first report in which significant improvement in ground reaction forces following TPLO was identified by 8 weeks after surgery in dogs, whereas other reports9,46,49 have indicated a mean of 5 to 7 months is needed for significant improvement to be detected. Ground reaction forces, determined by use of a force platform, have been found to be consistent and accurate for determining temporal changes in lameness in dogs.50 It has been suggested that measurements of PVF and VI are accurate means of gait assessment, and both are used for research involving dogs.47–53 Although the pressure-sensitive walkway used in the present study may record significantly lower measures of PVF and VI than a force plate measurement system for any 1 limb, data derived from the system used were found to be consistent; therefore, the pressure-sensitive walkway system is considered a valid method for evaluating kinetic variables over time in dogs.53 Analysis of these variables in the present study indicated that both the TF and the rehabilitation protocol used were associated with a more rapid return of function to the affected limb.

Unlike the findings in a previous study6 of dogs undergoing physical rehabilitation following TPLO, dogs in the present study had no significant differences in thigh or proximal tibial region circumference measurements over time after surgery. The dogs in our study had minimal to no muscle atrophy in the affected hind limb prior to surgery (with mean ratios of affected-to-unaffected limb circumferences ranging from 0.95 to 1.0), which could explain why there was little change seen in limb circumference ratios over time.

To the authors' knowledge, this was the first study in which accelerometry was used to assess dogs' activity as an outcome measure following TPLO for CCL disease. No activity monitors were worn by the dogs during any physical rehabilitation session. The amount of sedentary time per day decreased significantly and time spent in light-to-moderate or vigorous activity increased significantly over time for dogs of all groups, with exercise restrictions being lifted incrementally and increased activity allowed starting at 8 weeks following surgery. The most striking findings regarding activity were in the amount of time dogs spent in light-to-moderate activity; rehabilitation (regardless of diet) was significantly associated with activity at this level, and dogs undergoing rehabilitation had greater amounts of light-to-moderate activity than dogs that did not, even at 6 months after surgery (when dogs were no longer participating in a prescribed rehabilitation program). The accelerometer used in the present study has been reported elsewhere as a valid and reliable device for objective measurement of habitual physical activity and at-home activity monitoring of dogs.35,54,55 It has been used to effectively discriminate standardized activity levels and was validated as an objective means of quantifying posttreatment activity in dogs in a previous study.55 An increase in vigorous or light-to-moderate activity might be an indicator of increased comfort, whereas an increase in sedentary time might be related to discomfort during movement. Although activity increased over time for all groups in the present study, our results corresponded with those of a previously reported study,35 in which dogs were sedentary most of the time.

For dogs in the present study, most recorded activity was in the light-to-moderate intensity category, reflecting the likelihood that most dogs in the study were companions rather than performance or working animals; therefore, their activity was likely not as intense as that of canine athletes or working dogs. Our results suggested that a rehabilitation program such as that used in the present study has the potential to increase light-to-moderate activity in companion dogs over that achieved with surgery alone in the first 6 months following TPLO for CCL. Rehabilitation focusing specifically on muscle strengthening, functional exercise, and knee joint range of motion results in the greatest improvement and return to function in people following anterior cruciate ligament surgery.1,2 The results of the study reported here suggested that this might be the case for dogs following TPLO as well; unfortunately, 1 limitation of the study was that activity levels of the dogs prior to injury could not be determined, and it was unknown whether their postoperative activity levels were higher than, lower than, or similar to the preinjury levels. As mentioned, the authors believe this is the first report to describe the effects of rehabilitation on activity following TPLO; because this objective outcome measure is relatively new, understanding its long-term implications is difficult. Increasing muscle mass and remaining physically active both have the potential to reduce the signs of osteoarthritis21,44,56 and would therefore likely be beneficial in dogs after TPLO as well.

The prevalence of medial meniscal disease (39/48 [81%]) at the time of surgery in dogs of the present study was similar to findings in previous reports57–62 of dogs with signs of meniscal disease present at arthroscopy. In the present study, 21 of 48 (44%) dogs had radial tears and 18 of 48 (38%) had bucket-handle tears or meniscal disease requiring hemimenisectomy in the caudal horn of the medial meniscus. During the 6-month postoperative period, 2 of 48 (4%) dogs in the present study developed meniscal injury in the affected joint, and both dogs had bucket-handle tears, similar to findings in previous reports.59–62 One of these dogs was in the TF-R group and one was in the CF group, but no conclusions could be drawn regarding associations with treatment. The incidence of surgical site inflammation and signs of potential postoperative infection (serosanguinous to purulent incisional discharge) have been reported to range from 6 of 193 (3.1%) to 66 of 1,000 (6.6%).58,60,62 Among the 48 dogs of our study, only 1 dog (in the CF group) had this complication, and microbial culture yielded negative results. No dogs required implant removal during the 6-month study period, indicating that implementation of rehabilitation with an underwater treadmill according to the described protocol beginning 3 to 4 weeks after surgery did not influence this variable.

The TF in this study had added omega-3 fatty acids and had 31% crude protein content on an as-fed basis, whereas the CF did not have omega-3 fatty acids added or measured and contained 21% crude protein. Omega-3 fatty acids, particularly EPA and DHA as present in the TF, have been shown to reduce signs of lameness, increase PVF, and improve physical activity in dogs with osteoarthritis.24–27,63 These products have been shown to reduce production of arachidonic acid and prostaglandin E2 and various proinflammatory mediators25,26,64 while increasing production of less proinflammatory factors.26,65,66 Omega-3 fatty acids were also shown to modulate several catabolic factors associated with degradation of articular cartilage in vitro.28 Despite these findings, differences in the effects of supplementation on clinical signs and changes in PVF in dogs with osteoarthritis have been described in various reports.25,26,63 Variability in the diet and overall content of omega-3 fatty acids (α-linoleic acid vs EPA and DHA) from fish oil may be responsible for these variations in outcome measures. Both EPA and DHA have been found to be important inhibitors of inflammation in dogs. Omega-3 fatty acids also include α-linoleic acid, which is not efficiently converted to EPA or DHA in dogs.67 Therefore, the total amount of omega-3 fatty acid content in a diet or a supplement might be misleading, because content of the important components (EPA and DHA) may be low. Veterinarians and dog owners should be educated about the importance of achieving a combined dosage of EPA and DHA that is between 230 and 370 mg/kg of body weight0.75 per day, regardless of the total omega-3 fatty acid content68 (note that body weight in pounds must be converted to kilograms [ie, divided by 2.2] for use in this equation). The TF in the present study contained 0.18 g of EPA and DHA combined/100 kcal, so that a dog consuming 1,000 kcal/d would consume 1,800 mg of EPA and DHA combined. At 230 mg/kg of body weight0.75, the amount expected to achieve a therapeutic effect for a 10-kg (22-lb) dog would be 1,293 mg/d. A 10-kg dog would have a maintenance energy requirement69 of 742 kcal/d (132 χ [body weight in kg]0.75) and would thus consume a minimum of 1,336 mg of EPA plus DHA/d, which is greater than the minimum amount required, when fed the TF evaluated in this study.

The authors speculated that improvement in specific outcome variables for dogs in the TF-R group, compared with other groups, following TPLO might have been attributable to a combination of reduction in proinflammatory mediators and pain after surgery along with improvements in proprioception, limb function, and muscle strength with rehabilitation. Rehabilitation can improve muscle mass and strength, increase stifle joint range of motion, and improve limb use and has been associated with reduced administration of NSAIDS in studies of dogs during the postoperative period.5,6,8,46,70

The high protein-to-calorie ratio of the TF (31% protein as fed), compared with that of the CF (21% protein as fed), may have supported muscle mass and strength development in the dogs in the TF-R group. A limitation of the study was our inability to assess possible changes in lean tissue mass. Substantial loss of lean tissue mass and muscle atrophy develops in the affected limb of dogs with CCL injury.71,72 Body weight was variable among dogs in this study but did not significantly increase over time in any group, and limb circumference measurements did not change in any group during the 6 months after TPLO. However, without objective measures of the percentage of body fat or lean tissue mass (eg, by use of dual-energy x-ray absorptiometry), the potential changes in muscle mass that might have occurred remained unknown. In human patients undergoing rehabilitation after surgery for cruciate ligament injury, dietary protein supplementation was associated with greater quadriceps muscle hypertrophy and strength, compared with that of patients undergoing rehabilitation after surgery without supplemental protein intake.73 Thus, increased protein intake during the recovery period, especially during rehabilitation, could contribute to a faster recovery in dogs and could at least partially explain why dogs in the TF-R group had higher ground reaction forces by 8 weeks after TPLO, compared with the baseline value, whereas the other groups (including the CF-R group) did not.

Analysis of subjective owner assessments for signs related to pain and lameness indicated that dogs in the TF group had a significantly lower frequency of lameness over time when trotting or running and a more rapid decrease in the frequency of signs of pain when turning suddenly while walking, compared with dogs in the CF, TF-R, and CF-R groups (P < 0.01). We considered that a reduction in proinflammatory mediators in the joint with oral omega-3 fatty acid supplementation might partly account for this finding, and similar observations have been identified in dogs with osteoarthritis fed a diet rich in omega-3 fatty acids.24,26,27 Dogs in the TF-R and CF-R groups also had significantly (P < 0.05) lower frequencies of these owner-reported findings than did dogs in the CF group. Unfortunately, dog owners could not be blinded to the rehabilitation component of treatment, and a placebo effect could have influenced this finding. In 1 study74 of dogs with osteoarthritis, caregiver placebo effects were found to influence subjective owner evaluation of lameness up to 40% of the time. A food similar to the TF in the present study has previously been investigated for its effects on dogs with osteoarthritis in a blinded, placebo-controlled study.24 In that investigation,24 improvements in gait (PVF) as well as case-specific (owner-reported) outcome measures were found for dogs with osteoarthritis fed the omega-3 fatty acid-rich diet, compared with results for dogs fed a control diet without omega-3 fatty acids. Results of the present study supported that feeding the TF was associated with a more rapid decline in frequency of owner-reported signs of lameness and pain when their dogs were engaged in active behaviors such as running, trotting, or turning suddenly.

Limitations of the present study included the small group size (9 to 12 dogs/group). A variety of breeds was included, and this could be expected to influence some results. Because the investigators and owners were blinded only to the dietary component of treatment, the subjective evaluations might have been influenced by perceptions regarding physical rehabilitation. Owners were directed to feed at least the same volume of dry food they were feeding their dogs previously, with no other restriction on the minimum or maximum amount to be fed. Caloric content differed between the 2 foods, and to maintain blinding, researchers remained unaware of this variable and thus were unable to prescribe exact amounts to feed each dog. This allowed owners to determine the amount of food needed to maintain the dogs' body weight, and weight varied within groups during the study. Another limitation was that owners were also allowed to provide up to 10% of the diet as dog treats, which would have introduced variability in the proportion of diets comprised by the prescribed food. It is also possible that treats included supplements such as omega-3 fatty acids that could have influenced the results, although all owners were asked not to give treats that included such supplements. The TF also contained glucosamine (28 mg/100 kcal, or 21 mg/kg/d [9.54 mg/lb/d] for a 10-kg dog), which might have affected the results of the study and contributed to improved outcome measures in groups that received the TF; however, the amount of glucosamine given was likely less than a therapeutic dose because results of studies19,69,75,76 in dogs have indicated that ≤ 55 mg/kg/d (25 mg/lb/d) was needed to improve signs of lameness.

An additional limitation of the present study was that the content of omega-3 fatty acids and glucosamine in the CF was not known. A representative for the manufacturer of the CF stated (in verbal communication with one of the authors [WIB]) that no omega-3 fatty acids (including EPA and DHA) or glucosamine was added to the food (nor were they listed as ingredients) and that content of these nutrients was not analyzed.p Although the specific amounts of these nutrients in the CF were not known, none of the listed ingredients was known to contain substantial amounts of omega-3 fatty acids or glucosamine, and we considered it unlikely that any trace amounts of these products in the food had any clinical effect.

Results of the present study indicated that, if tolerated by the dog, feeding of an omega-3 fatty acid and protein-enriched food such as the TF investigated in this study and implementing a rehabilitation program including underwater treadmill exercises as described herein can reduce recovery time for function of the affected limb and that rehabilitation can increase light-to-moderate physical activity in dogs in the 6 months following TPLO and arthroscopic surgery. Further research into the mechanisms by which these treatments influence recovery variables is warranted.

Acknowledgments

Supported by a grant from the Nestlé Purina PetCare Co, which had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Presented in abstract form as an oral presentation at the 2015 American College of Veterinary Surgeons Summit, Nashville, Tenn, October 2015.

ABBREVIATIONS

BCS

Body condition score

CCL

Cranial cruciate ligament

CF

Control food

CF-R

Control food plus rehabilitation

DHA

Docosahexaenoic acid

EPA

Eicosapentaenoic acid

PVF

Peak vertical force

TF

Test food

TF-R

Test food plus rehabilitation

TPLO

Tibial plateau leveling osteotomy

VI

Vertical mpulse

Footnotes

a.

Purina JM Joint Mobility Diet, Nestlé Purina PetCare Co, St Louis, Mo.

b.

Pedigree Adult Complete Nutrition, MARS Inc, McKean, Va.

c.

EXCEL 2010 for Macintosh, Microsoft Corp, Redmond, Wash.

d.

DePuy Synthes Vet, West Chester, Pa.

e.

Rimadyl, Zoetis Inc, Kalamazoo, Mich.

f.

Hydromorphone hydrochloride injection, West-Ward Pharmaceutical Corp, Eatontown, NJ.

g.

Morphine sulfate extended release, Mallinckrodt Inc, Hazelwood, Mo.

h.

Cefazolin for injection, HIKMA Farmaceutica SS, Portugal, distributed by West-Ward Pharmaceutical Corp, West Eatontown, NJ.

i.

Dexdomitor, Orion Pharma, Orion Corp (Finland), distributed by Pfizer Animal Health, New York, NY.

j.

Torbugesic, Pfizer Inc, New York, NY.

k.

High-resolution mat, Tekscan Systems Inc, South Boston, Mass.

l.

Gulick II tape measure, Country Technology Inc, Gay Mills, Wis.

m.

Actical monitor, Minimitter Inc, Bend, Ore.

m.

ActiLife Software, version 4.4.0, ActiGraph, Pensacola, Fla.

o.

R, version 3.3.3, R Foundation for Statistical Computing, Vienna, Austria. Available at: www.R-project.org. Accessed Nov 30, 2014.

p.

Mars Inc. McLean, Va: Personal communication, 2015.

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Appendix

Nutrient and moisture contents of 2 foods fed to client-owned dogs in a study to evaluate the effects of diet and physical rehabilitation on clinical variables of interest following TPLO and arthroscopic surgery for treatment of CCL disease.

 TFCF
VariableAs fedAmount/100 kcal MEAs fedAmount/100 kcal ME
Crude protein31.0%8.07 g21.0%6.32 g
Crude fat13.0%3.40 g10.0%3.01 g
Crude fiber1.69%0.44 g4.0%1.2 g
Moisture12.0%NA12.0%NA
Linoleic acid (omega-6 fatty acid)2.08%0.54 g2.5%
Omega-3 fatty acid1.03%0.25 g
EPA and DHA0.69%0.18 g
Glucosamine1,100 mg/kg28 mg
Calcium1.53%0.40 g1.0%
Phosphorus1.12%0.29 g0.8%
Copper15.4 mg/kg0.40 mg10 mg/kg
Zinc240 mg/kg6.25 mg200 mg/kg
Vitamin E900 IU/kg23.43 IU200 IU/kg

The TF was a dry omega-3 fatty acid and protein-enriched dog food formulated to support joint health (caloric density, 3,324 kcal ME/kg).a The CF was a dry food formulated for maintenance of adult dogs (caloric density, 3,842 kcal ME/kg).b Crude fiber and moisture are reported as maximum content. All other variables are reported as minimum content.

— = Information not available from the manufacturer. NA = Not applicable.

  • Figure 1—

    Results of analysis for PVF over time in 48 dogs that underwent TPLO and arthroscopic surgery for unilateral CCL disease and were randomly assigned to receive a dry omega-3 fatty acid and protein-enriched dog food formulated to support joint health alone (TF) or with physical rehabilitation (TF-R) or a dry food formulated for maintenance of adult dogs alone (CF) or with physical rehabilitation (CF-R) after surgery. Results are presented by food type (TF and TF-R [A] vs CF and CF-R [B]) to aid interpretation. Data were obtained immediately prior to surgery (0 weeks) and 2 to 24 weeks later. Curves show local least squares regression lines fit to the data; gray margins represent the 95% confidence intervals for regression lines. Mean PVF at baseline was greater for the TF-R group, compared with the CF group (P < 0.01), and for the CF-R group, compared with the CF (P < 0.05) group. Values improved significantly (P < 0.01) over time for all groups; PVF was greater for the TF-R group than the CF-R group at week 8 (P < 0.05) and greater for the TF-R group than the CF group at weeks 16 and 24 (P < 0.01 and P < 0.05, respectively). At baseline and 2 weeks, there were 12 dogs/group. At 8 weeks, there were 11 dogs in the TF, CF, and TF-R groups and 12 in the CF-R group. From 16 to 24 weeks, there were 10 dogs in the TF and TF-R groups, 9 in the CF group, and 11 in the CF-R group.

  • Figure 2—

    Results of analysis for VI over time for the same 48 dogs as in Figure 1 (TF and TF-R groups [A] and CF and CF-R groups [B]). The VI improved significantly (P < 0.01) over time in all groups. The TF-R group had significantly greater baseline VI, compared with the CF-R (P < 0.05), TF (P < 0.01), and CF (P < 0.01) groups and had significantly (P < 0.01) greater VI than the CF-R group at week 16. See Figure 1 for remainder of key.

  • Figure 3—

    Results of analysis for time spent in light-to-moderate activity for the same 48 dogs as in Figure 1 (TF and TF-R groups [A] and CF and CF-R groups [B]). Data were obtained by use of an accelerometry device placed in a pouch at the dorsal midline between the shoulders by attachment to a harness. Activity data were recorded weekly and used to determine the amount of time that dogs were sedentary or engaged in light-to-moderate or vigorous activity35–37; results were divided by 7 to attain mean daily time spent in each type of activity. The first week for activity monitoring began with discharge from the hospital after TPLO. Mean time spent in light-to-moderate activity increased (P = 0.013) for all groups over time. Rehabilitation was significantly (P = 0.001) associated with greater time spent in this level of activity after surgery. See Figure 1 for remainder of key.

  • Figure 4—

    Results of analysis for subjective owner scoring of lameness for the same 48 dogs as in Figure 1 (TF and TF-R groups [A] and CF and CF-R groups [B]) when observed trotting. The frequency of signs was scored from 1 (never) to 10 (always lame). Dogs in the TF group had a more rapid decline in mean frequency of lameness during trotting over time, compared with results for dogs in the CF, TF-R, or CF-R groups (P < 0.01). Breaks in the 95% confidence interval lines at some time points resulted from low variability within groups and thus very narrow confidence intervals at those points. See Figure 1 for remainder of key.

  • Figure 5—

    Results of analysis for subjective owner scoring of lameness for the same 48 dogs as in Figure 1 (TF and TF-R groups [A] and CF and CF-R groups [B]) when observed running. The frequency of signs was scored from 1 (never) to 10 (always lame). Dogs in the TF group had a more rapid decline in the mean frequency of lameness during running over time, compared with results for dogs in the CF, TF-R, or CF-R groups (P < 0.01). Dogs in the TF-R and CF-R groups had significantly (P < 0.05) lower frequencies of lameness when running than did dogs in the CF group. Breaks in the 95% confidence interval lines at some time points resulted from low variability within groups and thus very narrow confidence intervals at those points. See Figure 1 for remainder of key.

  • Figure 6—

    Results of analysis for subjective owner scoring of signs of pain for the same 48 dogs as in Figure 1 (TF and TF-R groups [A] and CF and CF-R groups [B]) when observed to turn sharply at a walk. The frequency of signs was scored from 1 (never) to 10 (always painful when turning). Dogs in the TF group had a more rapid decline in the mean frequency of signs of pain under these conditions than did dogs in the CF, TF-R, or CF-R groups (P < 0.01 for all comparisons). Dogs in the TF-R and CF-R groups had lower frequencies of signs of pain under these conditions than did dogs in the CF group (P < 0.05 for both comparisons). See Figures 1 and 4 for remainder of key.

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