Outcome following surgical stabilization of distal diaphyseal and supracondylar femoral fractures in dogs

Abstract

Signalment, clinical features, fixation techniques, complications, and outcome for dogs presenting with distal diaphyseal and supracondylar femoral fractures were retrospectively reviewed. A total of 45 dogs with unilateral femoral fractures were included. Supracondylar femoral plates were the most popular method of fixation. However, various fixation techniques resulted in favorable outcomes in most dogs with 19/45 cases achieving full function and 22/45 achieving acceptable function. Degree of fracture comminution did not appear to affect complication rate or be a surrogate for worse clinical outcome.

Introduction

Canine femoral fractures are the most common appendicular fracture, comprising 45% of all long-bone fractures and 20% to 25% of all fractures seen in small animals (1,2). Of these, distal femoral extra-articular fractures can be described as either supracondylar (6% of femoral fractures) (i.e., non-physeal fractures of the distal metaphyseal region) or distal physeal (18% to 21% of femoral fractures) (2,3). Supracondylar femoral fractures are most commonly reported in skeletally mature dogs (4,5). The topography of the canine femur with distal femoral procurvatum in concert with a naturally occurring isthmus at the level of the distal femoral metaphysis in chondrodystrophic breeds appears to predispose these breeds to this type of fracture (2,4). Limited bone stock of the distal femur, proximity of a high motion joint (i.e., stifle), fracture comminution and procurvatum offsetting the distal femur caudal to the diaphysis may cumulatively present challenges for internal fixation (2,4,5).

Canine distal femoral diaphyseal and supracondylar fractures have a low incidence of occurrence (3). Multiple fixation strategies are suggested for these fractures (2,6) including the use of bone plates (7), interlocking nails (8), Kirschner wires, Rush pinning, lag screw fixation, intramedullary rods (9), and external skeletal fixation (10). However, a distinction is not made between supracondylar or physeal (i.e., Salter-Harris) fractures in some reports, making interpretation of the outcome and any complications as a function of exact fracture configuration challenging (9). Furthermore, a case series reviewing the use of supracondylar femoral plates (Veterinary instrumentation, Sheffield, UK) in the context of distal femoral fracture stabilization is lacking. Roch and Gemmill (11) reported use of these plates for stabilization after distal femoral wedge ostectomy, in the context of medial patellar luxation. Supracondylar plates have been designed with the assistance of finite element analysis to be used as bridging plates across comminuted fractures, with the aim of minimal contouring and maximizing the number of cortices engaged within the distal femoral fragment, which is offset caudally relative to the distal femoral shaft (12). Two plate designs have evolved (Veterinary instrumentation, Sheffield, UK); the supra-condylar plate (SCP), which has screw holes distributed throughout the whole length of the plate (Figure 1a), and the supra-condylar osteotomy plate (SCOP), which incorporates a bridging plate segment without screw holes (to be laid over the fracture/osteotomy site), increasing the area moment of inertia of the implant in that segment (Figure 1b).

Figure 1.

a — Supra-condylar plate (SCP). Plate designs from top to bottom: 3.5-mm broad long left plate, 3.5-mm narrow long left plate, 2.7-mm left plate, 2.4-mm left plate, 2.0-mm long left plate, 2.0-mm left plate. b — Supra-condylar osteotomy plate (SCOP). Plate designs from top to bottom: 3.5-mm left plate, 2.7-mm left plate, 2.4-mm left plate, 2.0-mm left plate.

The purpose of this retrospective multicenter case series was to describe the signalment, clinical features, fixation techniques, complications, and outcomes for dogs presenting with distal diaphyseal or supracondylar femoral fractures.

Materials and methods

Medical records of dogs presented between 2007 and 2018 for surgical treatment of distal femoral and supracondylar fractures at 12 referral centers in the UK and 2 referral centers in Australia were obtained for review. Cases were included in the study if complete clinical records, pre-operative and postoperative radiographic imaging, and clinical and radiographic follow-up were available for review. The term supracondylar has been used previously to define the distal metaphyseal region of the femur (2). The authors are unaware of a methodology that can be used to confidently identify the boundaries of the distal femoral metaphysis, which cannot be outlined using anatomic landmarks. In our study, fractures were first classified as distal femoral (1). Of these, fractures were defined as supracondylar if they were found to be proximal to the distal femoral physis (in skeletally immature animals) and/or extra-articular (in skeletally mature animals) but still within the distal femoral segment. The quadrate method as described by Unger et al (1) whereby a square representing the widest portion of the distal femur was templated onto each radiograph, was used to define the distal femoral segment. Fractures were classified as distal diaphyseal if proximal to the distal femoral segment but still within the distal third of the femur, according to the measurements made on pre-operative radiographs (Figure 2). The middle of oblique and transverse fractures, the broadest part of the wedge for wedge fractures and the center of the area of comminution for comminuted fractures were used to define fractures as either supracondylar or distal diaphyseal (1). Physeal (Salter-Harris) fractures were not included in the study.

Figure 2.

Illustration of fracture classification scheme used. Fractures of the distal third of the femur (x/3) were considered for analysis. Fractures were classified as supracondylar using the quadrate method described by Unger et al (1). The width of the widest point of the distal femoral epiphysis (y) was used to draw a square over the distal epiphysis, within which non-physeal, nonarticular fractures were classified as supracondylar. Fractures were classified as distal diaphyseal when proximal to the square drawn using the quadrate method but still within the distal third of the femur.

Complications were classified using Cook et al (13) proposed criteria in terms of the timescale of their occurrence as perioperative (before surgery, during surgery, and up to 3 mo after surgery), short-term (between 3 and 6 mo after surgery), midterm (6 to 12 mo after surgery), or long-term (more than 12 mo after surgery). Complications were further classified as either catastrophic (when a complication or associated morbidity had caused permanent unacceptable function, was directly related to death, or was the cause for euthanasia), major (when a complication or associated morbidity required further surgical or medical treatment, based on current standards of care, to resolve), or minor (when not requiring additional surgical or medical treatment to resolve). Clinical outcome was evaluated based on the data recorded by the attending surgeon at the last revisit or based on information gathered from the owners at the time of data collection. Clinical outcome was classified in terms of time frame as perioperative (pre-, intra- and up to 3 mo post-surgery), short-term (> 3 to 6 mo post-surgery), midterm (> 6 to 12 mo post-surgery), and long-term (> 12 mo post-surgery). Clinical outcome was subsequently subjectively classified as dogs having achieved full function (restoration to, or maintenance of, full intended level and duration of activities and performance from pre-injury or pre-disease status, without medication), acceptable function (restoration to, or maintenance of, intended activities and performance from pre-injury or pre-disease status that is limited in level or duration and/or requires medication to achieve) or unacceptable function (all other outcomes) (13).

Results

Forty-five dogs with unilateral femoral fractures were eligible for inclusion in the study. A median number of 4 cases (range: 1 to 6) was collected from each referral center. The median age of the study population at the time of surgery was 2 y 3 mo (range 0 y 3 mo to 9 y 10 mo). Median body weight (BW) was 9.1 kg (range: 2.15 to 50 kg). Twenty-nine dogs were male (13 of which were neutered) and 16 were female (7 of which were neutered). Breeds represented in the study population were: cross-breed (n = 6), cocker spaniel (n = 4), 3 each of Staffordshire bull terrier, Jack Russell terrier, Chihuahua, border terrier, bichon frise, 2 each of pug, Maltese terrier, border collie, and 1 each of the shih tzu cross Maltese, Rottweiler, Pomeranian cross, lhasa apso, Labrador retriever, Jack Russell terrier cross, husky, greyhound, dachshund, cockapoo, boxer, Belgian shepherd, working cocker, and beagle. Fracture etiologies were recorded in 39/45 cases (Appendix 1, available from the corresponding author) and included road-traffic accident (20/45), fall from height (11/45), and leg entrapment (3/45). Thirty-two dogs had right femoral fractures and 13 had left femoral fractures.

Eighteen dogs were diagnosed with supracondylar femoral fractures and 27 with distal diaphyseal fractures. Fracture configuration comprised 15 comminuted, 15 transverse, and 15 oblique. Twenty-one of the 45 dogs suffered adjunctive orthopedic and/or soft tissue injuries (Table 1).

Table 1.

Concurrent injuries listed by dog.

Age	Sex	Breed	Trauma type	Other injuries	Fracture location and configuration
1 y 5 mo	FN	Springer spaniel	RTA	Pneumothorax	Left, distal diaphyseal, comminuted
1 y 11 mo	FN	Beagle	RTA	Vertebral subluxation of T8–T9, with suspected compression fracture of the body of T9. Damage to the articular facets and dorsal spinous process was not seen and no neurological deficits were apparent. Subluxation of the 9th right rib head.	Right, distal diaphyseal, transverse
11 mo	MN	Jack Russell terrier	Hit by falling log	Fracture of left acetabulum, left ischium, and left pubis.	Left distal, diaphyseal, comminuted
1 y 1 mo	F	Cockapoo	RTA	Right coxofemoral luxation, bilateral sacroiliac luxation, right ilial body fracture, left ischiatic fracture, and pubic symphysis separation.	Right, distal diaphyseal, comminuted
3 y 4 mo	M	Chihuahua	RTA	Comminuted fracture/avulsion of the right calcaneus, loss of viability of skin over dorsal aspect of the right pes.	Right, distal diaphyseal, transverse
9 mo	MN	Crossbreed	RTA	Laceration between digits IV and V.	Right, distal diaphyseal, oblique
3 mo	M	Boxer	Fall from height	Fracture of the right femoral head capital physis with minimal displacement or apparent instability.	Right, supracondylar, oblique
1 y	M	Pomeranian-cross	RTA	Bladder rupture. Right ischial fracture, multiple pubic fractures, right ilial body fracture.	Left, distal diaphyseal, transverse
2 y 11 mo	FN	Crossbreed	RTA	Left sacroiliac luxation, bilateral pubic fractures, left ischial fracture.	Right, supracondylar, transverse
4 mo	F	Pug	Mild unknown trauma	Suspected Salter-Harris type V of the ipsilateral distal femoral physis.	Right, supracondylar, oblique
9 mo	M	Bichon frise	RTA	Mid-diaphyseal, oblique, right tibial fracture, right coxofemoral luxation, bilateral right sacroiliac luxation and multiple pelvic floor fractures.	Right, supracondylar, transverse
3 y 1 mo	MN	Crossbreed	Fell from height	Pulmonary contusions and mild pneumothorax.	Right, supracondylar, oblique
4 y 1 mo	MN	Border terrier	Hit by metal rod	Small puncture wound on the right hock.	Right, distal diaphyseal, comminuted
4 y 1 mo	MN	Dachshund	RTA	Multiple pelvic floor fractures, right ischiatic tuberosity fracture, left cranial ischiatic fracture.	Right, supracondylar, oblique
3 y	M	Crossbreed	RTA	Right ischial fracture, pelvic floor fractures, left ilial body fracture.	Right, supracondylar, oblique
3 y 10 mo	FN	Maltese terrier	RTA	Right coxofemoral luxation, right sacroiliac luxation, bilateral pubic fractures and right ischiatic fracture.	Left, distal diaphyseal, oblique
7 y	MN	Maltese	RTA	Left trochanteric fracture, laceration left inguinal region.	Right, supracondylar, comminuted
3 y 6 mo	MN	Rottweiler	Fell out of moving vehicle	Non-displaced right ischial fracture, incidental OCD lesion of medial femoral condyle seen at surgery.	Right, distal diaphyseal, comminuted
8 mo	MN	Border terrier	RTA	Laceration lateral aspect of the right thigh.	Right, distal diaphyseal, comminuted

M — male; MN — male neutered; F — female; FN — female neutered; RTA — road-traffic accident; OCD — osteochondritis dissecans.

Fixation methods employed for fracture stabilization comprised a predominance of lateral plating, used in 27 dogs. Of those, femoral supracondylar plates were used in 18/27 dogs, locking-compression plates (LCP; Synthes, West Chester, Pennsylvania, USA) in 4/27 dogs, dynamic-compression plates (DCP) in 2/27 dogs, a locking reconstruction plate (VetLOX Titanium plate; Freelance Veterinary, Somerset, UK) in 1/27 dogs, a notched locking T-plate (Synthes) in 1/27 dogs and a broad locking TPLO plate (Synthes) in 1/27 dogs. Plate-rod fixation was used in 9 dogs, with LCP plates used in 4/9 dogs, DCP plates in 3/9 dogs, a supracondylar plate in 1/9 dogs, and a string-of-pearls plate (Orthomed UK, Halifax, West Yorkshire, UK) in 1/9 dogs. Crossed-arthrodesis wires were employed as the main method of fixation in 4/45 dogs, external skeletal fixation was employed in 3/45 dogs, and bilateral plating (with either 2 string-of-pearls plates in 1 dog or with an LCP medially and supracondylar plate laterally in another dog) in 2/45 dogs (Figure 3). Further details are presented in Appendix 1.

Figure 3.

Post-operative cranio-caudal and mediolateral radiographic views of multiple fixation methods employed. a — Crossed arthrodesis wires with intramedullary pin countersunk at intercondylar notch. b — Intramedullary pin used in combination with supracondylar 3.5-mm plate. c — Intramedullary pin used in combination with 9-hole SOP 3.5-mm plate. d — Type IIb modified ‘tie-in’ configuration external skeletal fixator. e) Bilateral 2.7-mm SOP plates. f — Supracondylar plate.

In the 20 dogs in which a supracondylar plate was employed (either in isolation or in combination with other implants), 2.0-, 2.7-, or 3.5-mm plates were used. In 12 cases a supracondylar plate (SCP) and in 8 cases a supra-condylar osteotomy plate (SCOP) were used. Supracondylar plates were used as the primary method of fixation in 18/45 dogs (excluding a case in which a supracondylar plate was combined with an IM pin, and a case in which a contralateral LCP plate was added). Of these 18 cases, 3 comminuted fractures, 6 oblique fractures, and 9 transverse fractures were recorded; 10 being supracondylar and 8 distal diaphyseal. In 3 of these 18 cases, a single intra-fragmentary arthrodesis wire was also placed, and in 1 case crossed arthrodesis wires were also placed, either to maintain fracture reduction during surgery or as adjunctive fixation (Appendix 1). Supracondylar femoral plates were used without any adjunctive fixation in 14 cases (Figure 3a).

Outcome

All cases had at least 1 post-operative consultation and radiographs with a veterinary surgeon. Radiographic follow-up had a median duration of 7 wk (range: 2 to 28 wk) and clinical follow-up for a median duration of 8 wk (range: 4 to 208 wk). Clinical and radiographic follow-up data allowed for attribution of a perioperative outcome in all cases, short-term outcome in 9 cases, medium-term in 3 cases, and long-term in 1 case. Nineteen of the 45 cases were deemed to have achieved full function at their last recorded follow-up, 22 had achieved acceptable function, and 4 unacceptable function. Of those dogs in which SCP/SCOP was employed, 9/20 cases were deemed to have achieved full function, 10 had achieved acceptable function, and 1 had unacceptable function at their last recorded follow-up. Among cases in which supracondylar plates were used as the primary method of fixation, 9/18 dogs achieved full and 9/18 achieved acceptable function.

A total of 16 postoperative complications were recorded in 14 dogs. Catastrophic complications were recorded in 4 dogs, 2 of which were diagnosed with quadriceps contracture, defined as an inability to flex the stifle with concurrent tarsal extension and flexed digits on the operated limb. The third dog with a recorded catastrophic complication suffered failure of the initial fixation with 4 crossed arthrodesis wires (later revised with a supracondylar plate). A fourth dog had proximal migration of the intramedullary pin, inserted as part of a plate-rod construct and was still severely lame at the last recorded follow-up (19 wk after surgery). Major complications were recorded in 6 cases. These included worsening of pre-existing medial patellar luxation requiring corrective surgery (in 2 cases), surgical site infection with ipsilateral septic arthritis of the stifle (in 1 case), external skeletal fixator pin discharge (in 1 case), patellar desmitis (in 1 case) and screw loosening requiring removal (in 1 case). Minor complications were recorded in 6 cases and included pin tract discharge without the need for any intervention (in 3 cases), edema in the operated limb (in 1 case), limb shortening due to premature closure of the distal femoral physis without associated lameness (in 1 case) and screw loosening that did not require surgical removal (in 1 case). All recorded complications were classified as “perioperative” with regard to the time frame of their occurrence, with the exception of the case in which screw migration requiring screw removal was detected. The latter was classed as “long-term,” having occurred 13 mo after surgery.

Of the 20 dogs in which SCP/SCOP was employed, 4 postoperative complications occurred; 1 catastrophic (quadriceps contracture and IM pin migration), 2 major (patella luxation and screw loosening requiring removal), and 1 minor (screw loosening as an incidental finding not requiring removal). An SCP plate was used in both cases in which screw loosening occurred. In total, 2 of the 14 dogs that had a SCP/SCOP plate applied as sole method of fixation had recorded complications, accounting for a rate of complications of 2/14 (14.3%).

Discussion

To the authors’ knowledge, this multicenter study describes the largest case series of canine distal diaphyseal/supracondylar fractures to date and the only series evaluating the use of the SCP/SCOP in the context of femoral fracture repair. No complications were recorded in the 3 cases of comminuted fractures in which SCPs were used in bridging mode, suggesting the implant performs adequately in a scenario of comminution, as did other fixation strategies reported in this manuscript. Single screw loosening was recorded in 2 cases and although both fractures healed uneventfully, 1 screw did require surgical removal. A recent ex vivo biomechanical study on the effect of bicortical or monocortical locking screws on a mid-diaphyseal femoral fracture gap model (14), reported no screw loosening or screw pull-out with locking screws compared to a 70% incidence of screw pull out when cortical screws were used (15). Distal femoral locking plates are also available (New Generation Devices, Glen Rock, New Jersey, USA) and it is plausible that the use of a locking plate and screws could have reduced the risk of screw loosening.

Our case series has an overall rate of complications of 31.1%. Previously published case series documenting the use of internal fixation for non-articular fractures in dogs reported complication rates that varied between 5% and 37% (16–20). Pin migration occurred in 2/9 plate-rod cases in our series, in both instances necessitating pin removal. Pin associated complications (with pin migration being the most frequently reported), requiring a form of intervention have been reported in 9% to 19% of plate-rod repairs (16–18).

Quadriceps contracture was reported in 2 cases in this case series. Young dogs with distal femoral fractures appear to be predisposed (21). However, both cases reported herein were adult dogs with comminuted fractures. The presence of comminution, and as such, due to a higher energy injury, more adjunctive soft tissue damage and more callus formation rather than age could have been a predisposing facture to contracture development in our cases.

Linear LCP or DCP plates were used to repair 13 fractures. Given the limited 3-dimensional contouring that such plates can tolerate, the use of this fixation strategy may involve either over-reducing the distal fracture to increase the bone stock available for screw placement distally (2) or helical plating (22). Over-reduction of the distal fragment could predispose to misalignment of the patellar and quadriceps mechanism (2,5). Interestingly, in our series, iatrogenic de novo patellar luxation was not a recorded complication. However, worsening of preexisting medial patellar luxation, requiring surgical intervention, was recorded in 2 cases. Possible etiologies to explain this complication could include lateral distal femoral soft tissue dissection at the time of fracture repair, malreduction of the distal femoral fragment, or postoperative quadriceps muscle atrophy affecting either the magnitude or direction of force through the patellofemoral joint.

Our study has limitations inherent in its retrospective nature. When assessing outcome, we opted for the “last observation carried forward” method, which has limitations in interpretation of outcome (23,24). Given the short duration of follow-up in some of the cases it is plausible that some could have developed undocumented mid- to long-term complications that could have significantly affected outcome (25,26). It is equally plausible that, should there have been short-, mid- and long-term follow-up available for all cases, some of the cases with “acceptable” outcome could have been allowed the necessary time to recover full function and as such, outcome in our series could be negatively biased. Similarly, the presence of adjunctive polytrauma in our case series (21/45) makes it difficult to discern the precise contribution of each individual injury to the final outcome recorded. The short duration of follow-up also precluded a radiological analysis of the time to complete fracture healing in all cases. Contribution of case material from multiple referral hospitals treated by multiple surgeons also introduced variation in surgeon experience and postoperative management between cases.

In summary, this case series documents the use of multiple fixation strategies for the management of supracondylar and distal diaphyseal femoral fractures in dogs. Comminution was often present, but this did not appear to result in a poorer outcome, neither did whether the fracture was distal diaphyseal or supracondylar. Complication rates when SCP/SCOP plate fixation was used were comparable to those for other fixation strategies.