Numerous closed and open reduction techniques have been described for the treatment and salvage of dogs with hip joint luxation. However, open reduction techniques may be beyond the financial reach of many owners and may be unnecessary if the hip joint can be reduced and reduction maintained without surgical intervention. Consequently, attempted closed reduction with or without some form of external coaptation is the most frequent initial approach to management.1 The most frequently used method of maintaining hip joint reduction following successful initial closed reduction of a craniodorsal luxation is placement of an Ehmer sling. This bandage is purported to internally rotate, flex, and abduct the hip joint while holding the pelvic limb in a non–weight-bearing position.1–3 Traditional Ehmer slings are composed of cast padding to protect the metatarsal region and porous adhesive tape to create the frame encircling the metatarsal region, thigh, and body.3
The success rate of closed reduction in achieving a reduced and functional hip joint has been previously reported as 19 of 36 (52.8%)1; however, to the authors’ knowledge, the success rate of closed reduction in conjunction with a traditional Ehmer sling has not been reported. Complications associated with Ehmer sling application for canine patients have been anecdotally described,4 and the incidence and complications of soft tissue injuries following cast application for fracture stabilization have also been reported.5 However, the equivalent information is not available for Ehmer slings. The purpose of the study reported here was to determine the incidence of reluxation in dogs with craniodorsally luxated hip joints following primary management with closed reduction and Ehmer sling placement and the incidence of soft tissue injury associated with sling use. We also wished to test for associations between potential risk factors for hip reluxation or sling-associated soft tissue injury and outcome for these patients.
Materials and Methods
Case selection criteria
Medical records of dogs with craniodorsal hip joint luxation managed with closed reduction and Ehmer sling placement between August 1, 2007, and August 1, 2017, were included in the study. Centers that contributed cases were solicited by email contact to a convenience sample of department service chiefs known personally to the first and second authors and by placing a call for center recruitment through the American College of Veterinary Emergency and Critical Care email list management software. Case records were subsequently received from 10 veterinary medical centers: Animal Medical Center (New York, NY), Cornell University College of Veterinary Medicine (Ithaca, NY), Cornell University Veterinary Specialists (Stamford, Conn), Garden State Veterinary Specialists (Tinton Falls, NJ), University of Illinois College of Veterinary Medicine (Urbana, Ill), University of Minnesota College of Veterinary Medicine (Saint Paul, Minn), Oklahoma State University Center for Veterinary Health Sciences (Stillwater, Okla), University of Guelph Veterinary College (Guelph, ON, Canada), Tufts University Cummings School of Veterinary Medicine (North Grafton, Mass), and Texas A&M University College of Veterinary Medicine and Biomedical Sciences (College Station, Tex). Cases were identified by computerized record searches at each institution, and data pertaining to each case were derived from the medical records. Dogs were excluded if minimum patient follow-up information (including information on hip position, patient status, and treatment plan at the time of Ehmer sling removal) was unavailable, if the Ehmer sling was placed as an adjunct to any open reduction and fixation method, if the Ehmer sling was custom made rather than of a traditional type created with bandage materials, or if successful closed reduction was not documented by radiography or fluoroscopy at the time of Ehmer sling placement.
Medical records review
Medical records were reviewed independently at each facility, and collected information was collated by the authors. At each institution, medical records were reviewed by an individual who was provided with a standardized spreadsheet with written definitions of all variables.1 Data recorded included the admitting hospital; age, breed, sex, body weight, and body condition score (on a scale of 1 to 9) of the dog; cause of luxation and whether it resulted from trauma (as reported by the owner); radiographic findings at admission and throughout management of the case; and concurrent injuries (presence and type). Polytrauma was classified as severe if any injuries other than cutaneous wounds were present in addition to the luxated hip joint. Other information recorded included experience level of the clinician placing the sling (intern, resident, or board-certified surgeon) and whether financial constraints played a role in selecting the Ehmer sling as a management technique (yes or no). Details regarding closed reduction were obtained, including procedure and timing relative to injury; instructions for home care and owner compliance; sling management; financial costs of Ehmer sling placement and management interventions; incidence, severity, and management protocol for any sling-associated soft tissue injuries; and outcome for the hip joint (as determined by radiographic examination) and patient at the time of sling removal. If > 1 type of soft tissue injury was recorded for a patient, the injury considered to be most severe was used for purposes of analysis. Injuries that comprised ≥ 1 open wound or that necessitated amputation of the limb were classified as severe. Radiographs were reviewed by board-certified radiologists or surgeons at each institution as part of case management and were not reevaluated retrospectively.
Statistical analysis
Data were assessed for normality with the Shapiro-Wilk test and were summarized as frequency (percentage with 95% CI) and mean ± SD for normally distributed data or as median and IQR for nonnormally distributed data. Differences between group means were assessed with a Student t test when data were normally distributed and with a Mann-Whitney U test when data were not normally distributed. Differences between group proportions were assessed by use of the z test or univariable logistic regression to obtain odds ratios. Postestimation model checking was performed with the Hosmer-Lemeshow test together with examination of Pearson and deviance residuals. Commercially available softwarea was used for all analyses. Values of P < 0.05 were considered significant.
Results
Ninety-two dogs met the study inclusion criteria, with records for 2 to 24 dogs submitted by each facility. Median age of included dogs was 6 years (IQR, 2.9 to 9 years). Forty-seven dogs were female (38 spayed and 9 sexually intact), and 44 were male (34 castrated and 10 sexually intact). Sex was not recorded for 1 dog. Mixed-breed dogs were most commonly represented (n = 15). Seventy-seven dogs were purebred, with Labrador Retrievers (n = 11), Yorkshire Terriers (7), German Shepherd Dogs (6), and Pomeranians (6) most frequently identified. Median body weight was 18.1 kg (39.8 lb; IQR, 6 to 33.5 kg [13.2 to 73.7 lb]), and median body condition score was 5 (IQR, 4 to 6).
Hip joint luxation occurred in the absence of owner-reported trauma in 18 of 92 (19.6%; 95% CI, 12% to 29.1%) dogs. Traumatic causes of luxation consisted of vehicular trauma (n = 46), jump or fall (21), owner-induced injury (4), dogfight injury (2), and leash injury (1). The body weight of dogs that sustained owner-induced injury ranged from 1.6 to 6.4 kg (3.5 to 14.1 lb). Evidence of preexisting abnormalities was detected on pelvic radiographs of 12 (13.0%; 95% CI, 6.9% to 21.7%) dogs. Findings consisted of hip dysplasia (with or without osteoarthritis; n = 11) and a hip implant (1). The left hip joint was luxated in 51 (55.4%) dogs, and the right hip joint was luxated in 41 (44.6%), with no significant (P = 0.30) difference in frequency; no dogs had bilateral luxations. Of the 74 dogs with hip joint luxation reported secondary to trauma, 34 (45.9%; 95% CI, 34.3% to 57.9%) had polytrauma; 20 dogs had a head injury or blunt trauma to the thorax or abdomen, and the remaining 14 dogs had soft tissue wounds or limb fractures. Twenty-eight of 92 (30.4%; 95% CI, 21.3% to 40.9%) dogs were classified as having severe polytrauma according to the study definition. Five (5.4%; 95% CI, 1.8% to 12.2%) dogs had chip fractures of the acetabulum or femoral head of the luxated joint, and 8 (8.7%; 95% CI, 3.8% to 16.4%) dogs had fractures involving the weight-bearing axis elsewhere in the pelvis. Five (5.4%; 95% CI, 2.4% to 1.8%) dogs had a fracture along the pelvic weight-bearing axis on the side contralateral to the luxation.
Intervention
Closed reduction with Ehmer sling placement was performed ≤ 24 hours after injury for 67 dogs and between 1 and 4 days after injury in the remaining 25 dogs. The procedure was performed for 73 of 92 (79.3%; 95% CI, 69.6% to 87.1%) dogs under general anesthesia, and the other 19 (20.7%; 95% CI, 12.9% to 30.4%) dogs underwent the procedure with sedation. One dog had epidural anesthesia. The records of 7 dogs indicated that the sling was placed after open reduction and fixation techniques were recommended to the owner but declined because of financial constraints. Slings were placed by board-certified surgeons (n = 61 dogs), residents (19), or interns (12). For all dogs, slings were maintained for a median of 10 days (IQR, 5 to 15 days). Thirteen of the 92 (14.1%; 95% CI, 7.7% to 23%) dogs were kept in the hospital for the duration of sling use. Of the 79 dogs that were discharged for home care after sling placement, crate rest restriction was not clearly recommended or was not documented in the medical records for 16 (20.3%; 95% CI, 12% to 30.8%), and written bandage care instructions were not provided for 7 (8.9%; 95% CI, 3.6% to 17.4%). Lack of owner compliance with aspects of recommended home care of bandages was reported in the records of 7 of 72 (9.7%; 95% CI, 4.0% to 19%) dogs for which bandage instructions were provided.
Bandages were changed a median of every 5.5 days (IQR, 3.1 to 9.0 days). The sling was reported as wet or soiled at the time of ≥ 1 bandage change for 22 of 92 (23.9%; 95% CI, 15.6% to 33.9%) dogs. A wet or soiled sling was more common for males (17/44 [39%]; 95% CI, 24.2% to 53.0%) than for females (8/47 [17%]; 95% CI, 6.3% to 27.8%; P = 0.01).
The cost of care for closed reduction of the luxated hip joint from the time of diagnosis until sling removal was available for 60 dogs. The median total cost was $1,521.89 (IQR, $1,046.04 to $2,498.44) after adjustment for inflation.
Outcomes
Following Ehmer sling placement and management, 40 of 92 (43.5%; 95% CI, 33.2% to 54.2%) dogs had reluxation of the same hip joint before or shortly after sling removal. Seventeen of 40 (43%; 95% CI, 27% to 59.1%) subsequently underwent femoral head and neck ostectomy, and 13 (33%; 95% CI, 18.6% to 49.1%) underwent successful open reduction and fixation. Of the remaining 10 dogs, 8 were discharged from the hospital with a luxated hip joint, 1 was euthanized, and 1 underwent pelvic limb amputation because of severe soft tissue injuries from the sling.
Forty-six of 92 (50%; 95% CI, 39.4% to 60.6%) dogs experienced some type of soft tissue injury secondary to sling use, including superficial pyoderma (n = 19), pressure necrosis wounds (15), urine scald (5), edema at the distal aspect of the affected limb (3), self-trauma to the affected foot (2), and vascular compromise to the distal part of the affected limb resulting in tissue loss (2). When superficial pyoderma was not considered as a complication, the proportion of dogs that had a soft tissue injury decreased to 27 of 92 (29.3%; 95% CI, 20.3% to 39.8%). Of the 46 dogs with soft tissue injury, 17 (37%; 95% CI, 23.2% to 52.5%) had injuries classified as severe. These included open wounds that required ongoing management to allow second-intention healing (n = 12), open wounds that were ultimately closed surgically (4), or vascular injury requiring amputation (1). Severe soft tissue injuries developed in 8 of 61 (13%; 95% CI, 5.8% to 24.2%), 4 of 19 (21%; 95% CI, 6.1% to 45.6%), and 5 of 12 (42%; 95% CI, 15.2% to 72.3%) dogs that had slings placed by board-certified surgeons, residents, and interns, respectively. Seventeen of 79 (21.5%; 95% CI, 13.1% to 32.2%) dogs managed at home had severe soft tissue injuries caused by the sling, compared with 0 of 13 (0%) dogs that were hospitalized for the duration of sling use; however, the apparent difference in incidence was nonsignificant (P = 0.09). Five of 7 (71%; 95% CI, 29.0% to 96.3%) dogs for which owner compliance with instructions was reported as lacking developed severe soft tissue injuries, compared with 12 of 72 (16.7%; 95% CI, 8.9% to 27.3%) dogs that did not have poor compliance documented (P = 0.004). Dogs that experienced a severe soft tissue injury wore the sling for a median of 12 days (IQR, 9 to 17 days), compared with a median of 7 days (IQR, 3 to 14 days) for dogs that did not have this outcome (P = 0.01).
The frequency of hip joint reluxation for dogs with and without a reported traumatic cause for initial luxation was 37 of 74 (50%; IQR, 38.1% to 61.9%) and 3 of 18 (17%; IQR, 3.6% to 41.4%), respectively (P = 0.02). Slings were maintained for a median of 14 days (IQR, 10 to 17 days) for hip joints that remained reduced and a median of 7 days (IQR, 3 to 12 days) for those that reluxated at or near the time of sling removal (P = 0.003). Bandage changes were performed a median of every 7 days (IQR, 4.5 to 9.5 days) for hip joints that remained reduced and a median of every 4.3 days (IQR, 2 to 7 days) for those that subsequently reluxated (P = 0.01).
Risk factor analysis for hip joint reluxation
For dogs that had trauma reported as the cause for hip joint luxation, the odds of reluxation following management with an Ehmer sling were significantly (P = 0.02) greater than those for dogs without known trauma (OR, 5.0; 95% CI, 1.3 to 18.7). Similarly, the odds of reluxation were significantly (P = 0.03) higher (OR, 2.8; 95% CI, 1.1 to 6.9) for dogs with serious polytrauma than for dogs without this finding. No associations were identified between age, body weight, breed, or body condition score and the odds of reluxation. The presence of radiographic evidence of preexisting pelvic abnormalities, intra-articular fractures of the affected joint, and fractures affecting the weight-bearing axis of the contralateral pelvic limb were not significantly associated with increased or decreased odds of reluxation. Similarly, the experience level of the clinician who placed the sling was not significantly associated with increased or decreased odds of reluxation.
Risk factor analysis for severe soft tissue injury
Among the 79 dogs that were managed at home, the odds severe soft tissue injury was caused by the sling were significantly (P < 0.01) greater for dogs with poor owner compliance noted in the record (OR, 12.5; 95% CI, 2.2 to 72.2) than for those without this finding. For all dogs, the odds of severe injury of this type were significantly (P = 0.03) greater when the original sling was placed by an intern than when it was placed by a board-certified surgeon or resident (OR, 4.0; 95% CI, 1.1 to 14.9). For dogs with slings that became wet or soiled during the period of use, the odds of severe soft tissue injury were significantly (P = 0.005) higher (OR, 5.7; 95% CI, 1.7 to 18.8).
Discussion
In the present study, the incidence of reluxation in dogs with a craniodorsal hip joint luxation treated by closed reduction and application of an Ehmer sling was 40 of 92 (43.5%) and severe soft tissue injuries consisting of open wounds or severe tissue ischemia secondary to sling use developed in 17 of 92 (18.5%) patients. The incidence of hip joint reluxation in our study was similar to that in previous reports. One study1 found that reluxation occurred in 3 of 10 dogs, and another6 identified reluxation in 35 of 74 (47%) dogs following closed reduction. The present study was restricted to craniodorsal hip joint luxations managed with closed reduction and an Ehmer sling, whereas previous investigations reported on all patients managed with closed reduction and did not specify whether an Ehmer sling, another form of external coaptation, or exercise restriction had been implemented as adjunctive treatment. A control group was not included in our study; therefore, assessment of whether sling application was associated with a reduced risk of reluxation, compared with closed reduction and exercise restriction alone, was beyond the scope of the investigation. However, we speculated that the similarity in reluxation rates between the present study and studies1,6 that included closed reductions managed with other methods could suggest that an Ehmer sling does not have therapeutic benefit over those other methods
The incidence of soft tissue injury of any type associated with Ehmer sling application was 46 of 92 (50%), including the previously mentioned 17 (18.5%) dogs that developed severe injuries. These findings were similar to the incidence of soft tissue injury in association with cast application in a previous study,5 in which 3 of 6 cats and 38 of 60 dogs (63%) had injuries and 8 of 41 (20%) animals experienced severe injuries. A notable difference, however, was that the casts in that study5 were maintained for a mean of 23 days before the resultant injury was identified, whereas when severe soft tissue injury was found in our population, the sling was in place for a median of only 12 days. This suggested that an Ehmer sling should be treated with more caution and monitored more closely than a cast.
In accordance with the results of previous studies,1,6 German Shepherd Dog and Labrador Retriever were among the most commonly represented breeds in our study population, and vehicular trauma was the most commonly reported cause of luxation. We found that a known traumatic event and injuries consistent with serious polytrauma were associated with increased odds of reluxation following management with an Ehmer sling. We speculated that these associations reflected increased soft tissue injury around the hip joint, compromising joint stability in these patients after closed reduction. We did not find that preexisting pelvic abnormalities identified by radiography, intra-articular fractures of the affected joint, or fractures of the contralateral weight-bearing axis of the pelvis were associated with increased odds of reluxation. This may have been the result of a type II error or clinician case selection, considering that closed reduction was performed in the presence of the specific fractures or other abnormalities identified.
This study revealed an association between reluxation and a shorter duration of Ehmer sling use; slings were maintained for a median of 14 days for hips that remained reduced and a median of 7 days for those that reluxated. Owing to the retrospective nature of the study, the timing of sling removal relative to the identification of reluxation was unclear for each case, and this prevented an assessment of whether early sling removal could have promoted reluxation or was performed because a reluxation had been identified by the supervising clinician.
Increased risk of developing severe soft tissue injuries was associated with poor owner compliance with instructions, the sling becoming wet or soiled, and placement of the sling by an intern rather than a resident or board-certified surgeon; the frequency of these injuries was also associated with maintaining the sling for a longer period of time (median of 12 vs 7 days for dogs that did and did not develop injuries, respectively). None of the patients kept hospitalized for the duration of sling use sustained severe soft tissue injuries, although the number of hospitalized dogs was small and the difference between the hospitalized and outpatient populations was not found to be significant. The development of severe injuries in dogs cared for at home suggested that an emphasis on owner education at the time of sling placement and frequent reassessment by medical personnel might help to improve outcomes for these patients. An Ehmer sling is one of the more technically challenging bandages used in veterinary medicine,7,8 and the increased risk of soft tissue injury when the sling was applied by an intern was presumably attributable to a lack of experience leading to incorrect tension or placement. Custom-made neoprene slings are available, and we speculate that these may achieve a similar limb position with a lower complication rate.
The present study had a number of limitations. Data may not have been uniformly or accurately recorded at the time care was provided. In particular, information on complications associated with the Ehmer sling might have been underreported, and there might have been a bias toward overreporting of owner compliance or bandage care issues following identification of a soft tissue injury. The technique of sling placement was not standardized among the facilities that participated in the study. We also limited the timing of our assessment of joint outcome to that reported at the time of Ehmer sling removal; there was no attempt at uniform long-term follow-up, and some hip joints found to be reduced on recheck radiographs at the time of sling removal may have subsequently reluxated. Furthermore, the study was likely underpowered for exploration of some biologically plausible associations between preexisting pelvic abnormalities or concurrent injuries such as intra-articular fractures and reluxation. Finally, all of the participating facilities were veterinary teaching hospitals, and the findings may not be generalizable to hospitals where cases are managed only by experienced clinicians.
Additional research evaluating whether placement and appropriate maintenance of an Ehmer sling might reduce hip joint reluxation rates, compared with closed reduction without external coaptation, would be valuable. However, the information obtained in the present study may be of assistance to veterinarians and clients attempting to decide whether closed reduction with Ehmer sling placement is a reasonable treatment option for a dog with a craniodorsal hip joint luxation. Owners electing primary management of craniodorsal hip joint luxation with closed reduction and Ehmer sling application, rather than open surgical stabilization, should be made aware of the risks of reluxation and severe soft tissue injury, despite the costs of care.
Acknowledgments
No third-party funding was received in connection with this study. The authors declare that there were no conflicts of interest.
The authors thank Drs. Elizabeth Rozanski, Cummings School of Veterinary Medicine at Tufts University; Adrienne Bentley, Cornell University Veterinary Specialists; Leah Park, Garden State Veterinary Specialists; and Wendy S. Greathouse, College of Veterinary Medicine at Texas A&M University for assistance with case recruitment.
ABBREVIATIONS
| CI | Confidence interval |
| IQR | Interquartile (25th to 75th percentile) range |
Footnotes
Stata, version 13, StataCorp, College Station, Tex.
References
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