Introduction
Cranial cruciate ligament (CCL) disease is one of the most common etiologies of pelvic limb lameness in canines.1 Cranial cruciate ligament disease can be surgically managed in a variety of ways; however, a recent survey2 of veterinary surgeons suggests tibial plateau leveling osteotomy (TPLO) to be the favored technique.2 This procedure, as first outlined by Slocum and Slocum,3 has the goal of neutralizing cranial tibial thrust experienced during pelvic limb weight bearing by leveling the tibial plateau via a radial osteotomy. The segments are subsequently stabilized to maintain the new tibial plateau angle (TPA) via a TPLO plate and screws.
Correlation between increasing patient body weight and increased complication rates of TPLOs has been reported.4,5 One report4 described that for every 4.5-kg increase in body weight, the OR of postoperative complications increased by 1.10. The mean weight of the 9 dogs in the cited study that experienced implant failure or tibial fracture was greater than the cohort as a whole. Correlation between patient body weight and the risk of surgical site infection (SSI) following TPLO has also been investigated in numerous retrospective studies5–7 with conflicting results; however, a prospective study8 comparing postoperative antibiotic use with use of a placebo showed a significant association between risk of SSI and increasing patient size.
Change in TPA during the convalescent period following TPLO has been reported in dogs.9 The clinical consequences of change in TPA during convalescence following TPLO have not been rigorously described in the literature; however, an increase in TPA at recheck evaluation has been associated with an increased risk of tibial tuberosity fracture following TPLO.10 Different stabilization systems for management of TPLO patients > 50 kg have been described in the literature, including double plating. Double plating involves the addition of a second plate on the proximal tibia, caudal to the TPLO plate, to promote rigid fixation of the osteotomy and decrease the risks of increasing TPA and micromotion at the osteotomy.4,11,12 An abstract13 on the use of a single locking 3.5-mm jumbo TPLO plate for stabilization following TPLO reports a major complication rate of 20% (approx 3/14) and minor complication rate of 6% (1/14). There was no statistical change in TPA when comparing immediate postoperative and 6 week postoperative values.
Kowaleski et al14 evaluated the short-term clinical performance of an anatomically precontoured locking plate in dogs undergoing TPLO. In that case series, intraoperative complications were reported in 4 of 56 (7.1%) patients, minor postoperative complications were reported in 3 of 56 (5.4%) patients, and no major or catastrophic postoperative complications were noted. Their patient population additionally showed a median bone healing score of 4/4 (a qualification of 4 describing excellent union with > 75% healing). The mean change in TPA throughout the convalescent period within the series was 0.15 ± 1.32°. This led the authors to conclude that the investigated plate revealed reliably excellent bone union, minimal change in TPA, and a relatively lower complication rate than previously reported.14
The objective of the present study was to evaluate the effectiveness of a single locking 3.5/4.0-mm jumbo TPLO plate in maintaining the postoperative TPA in dogs weighing > 50 kg. A secondary objective was to evaluate the postoperative bone healing scores and complication rates associated with the use of this implant in comparison with the recent literature.4,14,15 It was hypothesized that the implementation of this system in TPLO patients > 50 kg would prevent secondary loss of reduction and therefore preserve postoperative TPA. It was additionally hypothesized that the bone healing scores and complication rates would be comparable to those of the published literature on TPLO.
Methods
Selection criteria and collected data
The medical records of all canine patients from a single referral practice that had a TPLO performed by a board-certified surgeon stabilized with a locking 3.5/4.0-mm jumbo TPLO plate from a single manufacturer (New Generations Devices) between January 2017 and May 2022 were retrospectively reviewed. Suspected diagnosis of CCL disease was based on physical examination and was confirmed with intra-articular evaluation. Patients that had incomplete medical records or lacked radiographic follow-up at the approximately 8-week postoperative period were excluded.
Data collected from the medical records included signalment, physical examination findings, perioperative management, preoperative TPA, intraoperative joint evaluation findings, implantation chosen, and surgical technique. Lameness was scored from 0 to 5 based on physical examination findings of clinically sound, barely detectable, mild, moderate, severe, or non–weight bearing, respectively.
Stifle joint evaluation
Intraoperative stifle joint evaluation was performed via arthroscopy (n = 22) or craniomedial arthrotomy (2) allowing confirmation of a complete (17) or partial (7) CCL rupture. Meniscal pathology was diagnosed in 10 of 24 (41.6%) cases, including axial fraying of the medial meniscus (n = 1) managed via radiofrequency collagen shrinkage, partial meniscal tear managed via radiofrequency collagen shrinkage and meniscal release (1), or bucket handle tears or maceration of the medial meniscus (8) managed with partial meniscectomy. Menisci without pathology were either left intact (n = 10) or released via transection of the caudal meniscotibial ligament using radiofrequency ablation (4) according to the operating surgeon’s preference.
Surgical technique
Following a standard medial approach to the proximal tibia, all TPLOs were completed as first described by Slocum and Slocum3 with minor variation. A TPLO jig was used in 13 of 24 (61.9%) cases. A TPLO saw blade with a radius of 27 mm (n = 1), 30 mm (5), or 33 mm (18) was used to produce a high tibial osteotomy with a rapidly widening cranial strut and perpendicular caudal cut within the proximal tibia. The proximal segment was rotated by a mean of 12.8 mm (range, 9.5 to 17.5 mm) aiming to produce a postoperative TPA of 5°. Initial stabilization of the proximal segment was achieved using one or two 1.58-mm (1/16 inch) threaded k-wires placed at, or proximal to, the point of insertion of the patellar tendon on the cranial tibia and directed caudally. The k-wires were cut to the level of the tibial tuberosity and left in situ. All tibial osteotomies were stabilized with 8-hole locking 3.5/4.0-mm jumbo TPLO plates secured using locking self-tapping screws (Figure 1). Screw sizes were 3.5 mm only (n = 7), 4.0 mm only (8), or a combination of both (9). An incisional block of liposomal bupivacaine (Nocita; Elanco Animal Health) was infused in 10 of 24 cases (41.6%). The surgical site was closed routinely in 3 layers.
A photograph displaying the various sizes of plates used to stabilize the proximal tibial segment following tibial plateau leveling osteotomy (TPLO) to demonstrate the relative increase in size of the 3.5/4.0-mm jumbo TPLO plate used within the patients described in this report. From left to right: 3.5-mm mini TPLO plate, 3.5-mm standard TPLO plate, 3.5-mm broad TPLO plate, 3.5/4.0-mm jumbo TPLO plate.
Citation: Journal of the American Veterinary Medical Association 261, 12; 10.2460/javma.23.07.0379
Postoperative management
Patients were administered a combination of nonsteroidal anti-inflammatories (n = 24) with gabapentin (21), tramadol (4), or both (1). Dogs received postoperative antibiotics (n = 9) at the discretion of the primary clinician or in a randomized fashion when concurrently enrolled in a prospective clinical study evaluating the impact of postoperative antibiotic administration on the incidence of SSI.
Rechecks and complications
Outcome and complications were recorded from the medical records of both the institution where surgery was performed and from records of the primary care veterinarian associated with the patient. Complications were classified as previously outlined into categories of catastrophic, type I major, type II major, or minor.16 Catastrophic complications included those that led to permanent unacceptable function or mortality, major complications being those that required surgical treatment (type I) or medical treatment (type II) for resolution, and minor complications resolving without intervention.16 The diagnosis of SSI was performed as previously described.8,17 Suspected infections were confirmed and treated on the basis of culture and susceptibility results when consented to or via empirical therapy when culture and susceptibility testing was declined. Follow-up time frames were defined as previously outlined into categories of perioperative, short term, mid term, and long term corresponding to 0 to 3 months, > 3 to 6 months, > 6 to 12 months, and > 12 months, respectively.16
Radiographic evaluation
The radiographic projections obtained were mediolateral tibial radiographs centered on the stifle joint with 90° stifle joint flexion and 90° tarsocrural joint flexion. Immediate postoperative radiographs were performed under general anesthesia. Recheck radiographs were taken approximately 8 weeks postoperatively and were performed awake or under sedation when the appropriate views could not be obtained without. TPA was measured on the immediate postoperative radiographs and on the follow-up radiographs using a digital radiographic viewing software by 2 individuals (1 resident in small animal surgery and 1 board-certified small animal surgeon). To calculate TPA, 1 line was drawn along the tibial axis delineated by a proximal landmark of the tibial intercondylar eminences and distal landmark of the center of the talus. A second line was drawn along the tibial plateau. Finally, the angle between a line perpendicular to the tibial axis and the tibial plateau was calculated and defined as the TPA.18 Change in TPA for each individual was calculated by subtracting the follow-up TPA from the immediate postoperative TPA. Osteotomy healing was additionally assessed on the follow-up radiographs including an orthogonal cranial-caudal tibial projection. Scores of 0 through 4 correlating to 0%, 1% to 25%, 26% to 50%, 51% to 75%, and 76% to 100% osseous bridging of the osteotomy on follow-up radiographs were assigned.19 The authors were blinded to patient identity by removing any patient identifiers from the digital radiographic file. The radiographs were evaluated in a randomized order to prevent influence of initial postoperative TPA value on follow-up TPA value obtained.
Owner-perceived outcomes
Owners of the included patients were contacted via email and telephone for participation in a questionnaire. The Canine Brief Pain Inventory20 (CBPI) was performed regarding their pet’s surgical limb. Owners were asked to evaluate their overall satisfaction with their pet’s outcome and whether they would pursue the surgical intervention again in the future. Owners were questioned to ensure no further complications had been encountered that were not documented in the medical records.
Statistical analysis
Descriptive statistics were used to evaluate the basic properties of the data. Continuous variables were summarized by use of the mean and compared via the Student t test. Statistical software (R, version 4.3.1, The R Foundation) was used to perform statistical analysis. Paired t tests were used to compare interobserver TPA. Statistical significance was set at P < .05 for all analysis.
Results
Demographics and preoperative findings
Twenty-eight stifles in 25 dogs > 50 kg underwent a TPLO stabilized with a locking 3.5/4.0-mm jumbo TPLO plate between January 2017 and May 2022. Three dogs underwent staged bilateral TPLOs. Four cases were not presented for an 8-week radiographic recheck (inclusive of 1 stifle of a bilaterally operated patient) and therefore excluded from analysis, leaving 24 stifles available to assess. The breeds of the included patients were Mastiff (n = 4), Great Dane (3), Saint Bernard (3), Old English Mastiff (3), Cane Corso (2), Great Pyrenees (2) and one each of Newfoundland, Alaskan Malamute, Irish Wolfhound, Mastiff mix, and Boerboel. Mean age at time of surgery was 50 months (range, 12 to 91 months). Fourteen dogs were neutered males, 8 dogs were spayed females, and 2 dogs were intact males. Mean body weight at the time of surgery was 73.2 kg (range, 52 to 93 kg) with a mean body condition score of 6.8/9 (range, 5 to 8). All dogs were noted to be lame on preoperative evaluation, with accompanying tibial thrust, stifle effusion, and medial buttress. Five patients were bilaterally lame. Lameness grades at presentation were a mean of 2.9/5 (range, 1 to 4), with a median of 3. The mean preoperative TPA was 27.38° (range, 24° to 34°).
Postoperative lameness
Mean immediate postoperative lameness as assessed the morning following surgery was 3.5/5 (range, 2 to 5), with a median of 4. Incisional recheck was performed at a mean of 14.3 days (range, 10 to 23 days) postoperatively, with mean lameness scores of 2.5/5 (range, 1 to 4), with a median of 3. Radiographic recheck was performed at a mean of 65 days (range, 51 to 96 days) postoperatively. Mean lameness score at radiographic recheck was 0.75/5 (range, 0 to 2), with a median of 1. Further recheck examinations were documented in 20 patients, with final rechecks occurring 597 days (range, 214 to 1,552) postoperatively. Thirteen patients were noted to have no lameness on the surgical leg at the final documented evaluation. Two patients were noted to be non–weight-bearing lame at the final documented examination, one experiencing a catastrophic complication and the other experiencing a major complication. The remaining 5 patients had no description regarding ambulation within their final documented examination.
Questionnaire follow-up
Seven patients were known to be deceased at the time of writing, with 1 patient euthanized as the result of a catastrophic complication. The remaining 6 patients were euthanized or passed away at a mean of 709 days (range, 214 to 1,552) postoperatively due to unrelated causes. Of the surviving patients, questionnaire data were retrieved in 12 cases at a mean of 1,012 days (range, 388 to 2,098 days) postoperatively. The remaining 5 patients were lost to follow-up. Canine Brief Pain Inventory20 results related to the patient’s surgical limb revealed mean pain severity scores of 1.2/10 (range, 1 to 2.75), with a median of 1. Mean pain interference scores were 1.4/10 (range, 1 to 3.5), with a median of 1.08. Owners rated the patient’s quality of life as very good in 2 cases and as excellent in the remaining 10. Owner satisfaction with the surgical procedure was rated as satisfied in 1 case and as very satisfied in 11. Of respondents, 11 indicated they would pursue the procedure again, while the remaining respondent indicated they might consider it.
Radiographic evaluation
Twenty-four cases were presented for repeat radiographs at a mean of 65 days postoperatively (range, 51 to 96 days). Immediate postoperative TPA measurement obtained mean values of 5.04° (range, 3° to 8°) for observer 1 and 6.42° (range, 3° to 11°) for observer 2. Mean recheck TPAs of 5.88° (range, 4° to 8°) by observer 1 and 7.58° (range, 3° to 12°) for observer 2 were calculated. The mean change in TPA was calculated as 0.83° (range, –2° to 3°) for observer 1 and 1.17° (range, –1° to 4°) for observer 2. This increase in TPAs over time was found to be statistically significant (P < .05) for both observers, with a P value of .02 for observer 1 and < .01 for observer 2. Data sets for observer 1 and observer 2 were statistically different, with an interobserver P value of < .01. Assessment of osteotomy healing at the radiographic recheck revealed grade 4 healing in 18 of 24 stifles (75%) and grade 3 healing in the remaining 6 of 24 (25%; Figure 2). Mean healing grade was 3.75, with a median value of 4.
Immediate postoperative lateromedial (A) and craniocaudal (B) and recheck lateromedial (C) and craniocaudal (D) radiographs from a 1-year-old, male neutered Saint Bernard displaying the use of the 3.5/4.0-mm jumbo TPLO plate. The recheck radiographs were taken 96 days postoperatively. This radiograph was scored as grade 4 healing. Scores of 0 through 4 were assigned correlating to 0%, 1 to 25%, 26 to 50%, 51% to 75%, and 76% to 100% osseous bridging of the osteotomy. *Two antirotation k-wires were used in this patient to provide initial stabilization of the proximal segment and were left in situ.
Citation: Journal of the American Veterinary Medical Association 261, 12; 10.2460/javma.23.07.0379
Complications
No intraoperative complications were recorded. The postoperative complication rate was 45.8% (n = 11/24). Perioperative complications were recorded in 7 of 24 (29%) cases and classified as minor in 1 of 24 (4.2%) cases and major in 6 of 24 (20.8%). The minor perioperative complication was diagnosis of pivot shift that resolved without intervention. Major perioperative complications were further classified into type I (n = 2/24 [8.3%]) or type II (5/24 [20.8%]). One type I major complication was a seroma overlying the antirotation pin treated with a sedated pin-pull procedure, which resolved clinical signs. The second type I major complication was a persistent ulcerative lesion overlying the surgical site. Conservative management of a suspected lick granuloma was recommended with no improvement. Implant removal with concurrent resection of the lesion was performed 145 days postoperatively. Concurrent culture was negative. This complication occurred in one of the patients that underwent bilateral TPLO, and the contralateral implant was prophylactically removed under the same anesthetic event 201 days postoperatively. All type II major perioperative complications were classified as SSIs that were resolved with medical therapy.
Follow-up beyond the 8-week radiographic recheck via questionnaire or clinical examination was obtained in 23 patients at a mean of 553 days (range, 145 to 2,098 days). No short-term complications were encountered. One midterm type I major complication (1/24 [4.2%]) was documented 314 days postoperatively following presentation for an intermittent lameness and a draining tract. Implant removal was performed under general anesthesia, and concurrent culture confirmed Staphylococcus pseudintermedius infection. Subsequent medical management guided by susceptibility resulted in resolution of clinical signs.
Three long-term complications (3/24 [12.5%]) were noted that were classified as a type I major complication, a type II major complication, and a catastrophic complication. The type I major complication was diagnosed 529 days postoperatively on presentation for intermittent hind limb lameness, which was unsuccessfully managed conservatively until 610 days postoperatively. Removal of the TPLO implants was then performed. The implantation was noted to be loose with moderate discharge present at the site. Cultures performed at surgery and thereafter were persistently negative. Physiotherapy and medical management of osteoarthritis were recommended, and at recheck evaluation 979 days postoperatively, the operated-upon limb had no observable lameness.
The long-term type II major complication occurred in the same patient that experienced a perioperative type I major complication of a suspected lick granuloma requiring surgical excision for resolution. This patient had concurrent prophylactic TPLO plate construct removal of the contralateral limb and subsequently developed a new suspected lick granuloma on the prophylactically operated-upon limb. This was documented at the time of questionnaire 444 days postoperatively. This complication was undergoing medical management under guidance of the primary care veterinarian at the time of writing with improvement described by the owner, but without resolution.
The single catastrophic complication was documented 1,071 days postoperatively. The patient presented for severe swelling and non–weight-bearing lameness of the operated-upon limb. Removal of the TPLO implants was performed and a closed-suction drain was placed. Culture and sensitivity returned β-hemolytic Streptococcus with predictable susceptibility to cephalosporins, and the patient was managed in the hospital with IV antimicrobials. The patient was released from the hospital due to overall improvement in limb function, appetite, and demeanor but returned 1,078 days postoperatively for general decline. Blood work revealed a severe, moderately regenerative anemia, azotemia, hypoalbuminemia, severe hyperbilirubinemia, and elevation in creatine kinase. Euthanasia was elected due to overall patient condition and financial limitation.
Discussion
The primary hypothesis, that the implementation of a locking 3.5/4.0-mm jumbo TPLO plate in dogs > 50 kg would effectively prevent loss of reduction resulting in a change in TPA, was rejected. This was based on the statistically significant increase in measured TPA (0.83° to 1.17°) during convalescence measured by both observers. No intraoperative complications were recorded during the use of the aforementioned implant; however, a postoperative complication rate of 11 of 24 (45.8%), inclusive of 1 minor, 1 catastrophic, and 9 major complications, was described. This led to rejection of a portion of the secondary hypothesis of comparable complication rates to the recent published literature on TPLO.4,14,15 In the face of high complication rates, a mean healing grade of 3.75 with a median of 4 was comparable to that published in the literature,14 providing agreement to the portion of the hypothesis that bone healing scores would be comparable to the published literature on TPLO.
A difference in calculated TPA at recheck following TPLO has previously been reported.9,10,21 Only a poster abstract13 has described the use of a single locking 3.5/4.0-mm jumbo TPLO plate for stabilization following TPLO, reporting no statistical change in TPA at 6-week postoperative follow-up. This is in contrast to the statistical increase in TPA of 0.83° to 1.17° depending on observer found in the present series. This implies secondary loss of reduction resulting in a change in TPA of the proximal tibial segment throughout the convalescent period, entering into question whether the investigated implant provides adequate stability in patients > 50 kg. Previous investigations of the influence of various plating styles on TPA changes have shown that fixation using locking screws resulted in significantly less change in postoperative TPA when compared with nonlocking screws.21 Despite the use of a locking implant in this case series, secondary loss of reduction resulting in a change in TPA was described. An implant from a single manufacturer was used in all patients included in this study. Statistics from a previous publication22 discussing changes in TPA in dogs following TPLO indicate that implant type was the only variable associated with changes in TPA postoperatively. It is possible that the use of a similarly large implant of a different design may prevent postoperative TPA change; however, this cannot be determined in the present report. In our cohort, 3.5-mm screws were used initially due to inability to source 4.0-mm screws in all screw lengths necessary to complete the procedure for patients of this size. Due to the sample size of this cohort, the impact of screw size used on postoperative TPA change could not be evaluated. Further evaluation of screw size in prevention of secondary loss of reduction resulting in a change in TPA is warranted in this patient population to ensure that the use of 3.5-mm screws in some patients did not influence the results in this study.
The clinical significance of losing rotation during convalescence has not been rigorously investigated, nor has an acceptable change in TPA been reported. One report10 evaluating risk factors for postoperative tibial tuberosity fracture in TPLO patients shows that an increase in TPA over time was associated with tibial tuberosity fracture. No patients experienced tibial tuberosity fractures throughout the follow-up period of this study; however, this may be due to type II statistical error. The lack of tibial tuberosity fractures observed in our patients may also be explained by the decision to leave antirotational k-wires in situ, as a recent report23 outlined a 92% reduction in the risk of tibial tuberosity fractures when k-wires were left in situ compared with when they were removed at the time of surgery. A change in TPA is a secondary loss of reduction, which indicates that instability at the osteotomy site is present and some degree of bone and/or implant failure has occurred. Despite a lack of significant evidence that changes in TPA are detrimental to the patient’s clinical status, stability of the osteotomy with minimization of interfragmentary strain is essential for direct bone healing to occur.24 Radiographic healing scores with a calculated mean and median of 3.75 and 4 respectively demonstrates high percentages of healing in the majority of patients; however, grade 3 healing was described in 6 of 24 (25%) patients. This stratification in healing may partially be explained by the statistical increase in TPA calculated in this report. A secondary loss of reduction implies an unstable environment for osteotomy healing, and a more stable environment may have increased the healing scores of our patient population.
A postoperative complication rate of 11 of 24 (45.8%) was described in our report, leading to the rejection of a portion of the secondary hypothesis of comparable complication rates to the published literature on TPLO.4,14,15 These previous reports within the recent literature display postoperative complication rates of 5.4% to 11.4% (3/56 to 173/1,519); however, mean weights of the 3 cited studies varied from 35.7 to 37.3 kg and therefore were lower than the lightest patient within the cohort of this report.4,14,15 One of these cited studies4 displayed a correlation between increasing patient body weight and increased complication rates of TPLOs. The increased incidence of complications was described by an OR of 1.10 for every 4.5-kg increase in body weight. The literature on patient populations with similar patient weights in their inclusion criteria as the studied cohort reveals comparably higher complication rates of 18.4% to 27.8% (63/342 to 15/54).11,13,25 The reason for this increased rate of complication in heavier patients is unknown; however, the statistically increased TPA during convalescence of 0.83° to 1.17° in our patient population displays movement at the level of the osteotomy. This indicates instability and that some degree of bone and/or implant failure has occurred, which may predispose to postoperative complications.
A total perioperative SSI rate of 5 of 24 (20.8%) was recorded in this case series and is comparable to some other reports12,23,26 of similar cohorts. A prospective study8 comparing postoperative antibiotic use with a placebo reported an OR of 1.047 to describe increasing risk of SSI for each kilogram increase in body weight. Using this reported value, one can calculate an increased risk of 193% when comparing a 52-kg patient (the lightest patient from the studied cohort) with a 37.3-kg patient (the mean patient weight from a cohort of 1,231 TPLO patients).4 Two retrospective studies5,6 also noted an increased risk of SSI with increasing body weight. One study,11 however, reported an SSI rate of 11.4% (39/342) in patients > 45 kg. In that report, 80% (274/342) of patients received postoperative antimicrobials in comparison with 37.5% (9/24) in the present study. It is unclear whether the different rates of postoperative antimicrobial use are sufficient to account for the lower SSI rate, as studies attempting to evaluate this correlation have shown conflicting results.27 A retrospective study26 specific to patients > 50 kg revealed a lower incidence of SSI in patients receiving postoperative antibiotics. A prospective study evaluating the effect of postoperative antimicrobial use in giant-breed dogs following orthopedic surgery has not been performed to date and may be warranted to further investigate whether this particular population may benefit from their use. Despite the noted difference in antibiotic use, the SSI rate of 11.4% (39/342) in patients > 45 kg11 is more similar to the range of 2.9% to 11% (14/476 to 71/659) reported in the recent literature on complications following TPLO.5,7,15 These lower incidences of SSI should be considered the goal when developing and investigating further implantation systems in giant breeds.
Four complications encountered within the study period were TPLO implant removal for suspected latent implant infections. Culture and sensitivity were performed at the time of implant removal in all 4 cases; however, 2 cases had negative culture results. A recent publication28 evaluating risk factors and timing of deep SSI found an incidence of 3.0% (144/4,813) at a median of 279 days (49 to 2,394 days) postoperatively. This highlights the importance of including long-term follow-up following TPLO, as latent infections may develop many months to years following surgery. In acknowledgment of this statement, the present case series may underestimate the already high incidence (4/24 [16.7%]) of implant removal when using the locking jumbo 3.5/4.0-mm TPLO implant, as follow-up did not extend through the life span of all patients.
Instability at the osteotomy site has been discussed in association with SSI rate and implant-associated infection.26,29 This association has been implicated as a possible explanation for a difference in SSI rates when locking, and nonlocking plates are used following TPLO in dogs > 50 kg, as the use of nonlocking plates in the cited case series was statistically associated with a higher incidence of infection.26 Despite micromotion being discussed as a possible reason for resultant infection, little experimental data are available in the literature associating these 2 events. A recent experimental study30 in a murine femoral fracture model revealed that stable fixation allowed a higher proportion of 1 murine strain to clear an inoculation of Staphylococcus epidermidis in comparison with those mice of the same strain with an unstable fixation.30 This possible association is supported by the high SSI and implant removal rate noted in our patient population with concurrent statistical difference in TPA over convalescence; however, causation cannot be determined in this report.
Despite high complication rates encountered within the present case series, owner-perceived outcomes were noted to be high, with the majority of respondents seeing their pet’s quality of life as excellent and their pain severity and pain interference scores related to their surgical leg as low. While the overall low pain severity and interference scores collected on the postoperative CBPI are encouraging, it must be noted that no CBPI data were collected prior to surgery, preventing comparative analysis following intervention. Canine Brief Pain Inventory data were obtained in extant patients due to the nature of the questionnaire reflecting current status of the patient. While this avoided recall bias, the lack of CBPI data on deceased patients may introduce selection bias in the reported pain severity and pain interference scores. This is particularly evident because the patient experiencing a catastrophic complication of euthanasia was not included in CBPI data, which may have displayed comparatively very different values due to the patient’s condition at the time of euthanasia. The majority of respondents were very satisfied with the outcome of the procedure and would consider the procedure again in the future. This satisfaction rate aligns with the majority of patients having no detectable lameness at final documented evaluation. The majority of complications encountered from the procedure were SSIs, and nearly all resolved with medical or surgical treatment, which may explain the ultimate satisfaction and appropriate limb use encountered in follow-up.
Limitations of the present study include the retrospective design, which relies on complete medical records and prevents procedural standardization. The retrospective nature additionally prevents standardization of medical management of patients postoperatively, including how SSIs were managed. The small sample size limits the ability to thoroughly investigate the influence that various confounding factors may have on the outcome measures. These factors include, but are not limited to, varied histories, comorbidities, degrees of orthopedic disease, surgical techniques, and postoperative medication prescriptions. A further limitation is the lack of a case control group. Additionally, while a standard lameness scale was used to report lameness among patients, multiple observers of various experience levels documented lameness over time during recheck examination, which may introduce some inconsistency in lameness reporting between patients and visits within the same patient. To truly investigate the influence a stabilization system has on outcome for dogs > 50 kg undergoing TPLO, a randomized controlled clinical trial would be necessary. Due to the infrequency in which giant-breed dogs are presented to this hospital for management of CCL disease, this would require a long collection period to accumulate adequate case numbers. Alternatively, a multi-institutional study may be best to investigate this question.
In acknowledgment of the limitations outlined above, we conclude that the use of a locking 3.5/4.0-mm jumbo TPLO plate for canine patients > 50 kg undergoing a TPLO did not prevent secondary loss of reduction resulting in a change in TPA. Additionally, use of the aforementioned implant yielded unacceptable postoperative outcomes in the described population when compared with the recent literature on postoperative outcome following TPLO. The majority of these complications were incisional in nature and resolved with appropriate medical or surgical management. In the face of a high rate of complications and loss of reduction resulting in change in TPA postoperatively, comparable bone healing scores were described, and owner-perceived outcomes were high. Further investigation may include prospective cohort studies, studies utilizing gait analysis as an outcome measure, studies investigating the nature of incisional infections in giant-breed patients, and prospective studies comparing the outcomes of patients > 50 kg stabilized with various implantation systems and screw sizes.
Acknowledgments
The authors would like to recognize Mr. Brady Henderson for volunteering his valuable time to aid in data collection.
Disclosures
The authors have nothing to disclose. No AI-assisted technologies were used in the generation of this manuscript.
Funding
The authors have nothing to disclose.
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