Management of Canine Y-T Humeral Fractures Using Titanium Polyaxial Locking Plates in 17 Dogs
ABSTRACT
The objective of this study was to document the short- and medium-to-long-term outcomes and complication rates of Y-T humeral condylar fractures fixed using titanium polyaxial locking plate (T-PLP). A retrospective review was performed of the medical records and radiographs of dogs with a Y-T humeral condylar fracture treated with T-PLP at a single veterinary referral center (2012–2018). Seventeen cases met the inclusion criteria. Medium- to long-term follow-up (.6 mo) information was derived using the Liverpool Osteoarthritis in Dogs (LOAD) questionnaire. Recorded complications were catastrophic (1/17) and minor (2/17). Gait at 10–12 wk following surgery was subjectively assessed as good or excellent for 13 cases. Radiographic bone union was achieved in 7/12 cases at 4–6 wk. LOAD scores obtained a mean of 15 mo (range 6–29 mo) following surgery and indicated no or mild impairment in 15/16 and moderate functional impairment in 1. The application of T-PLP for the treatment of Y-T humeral condylar fractures resulted in adequate stabilization allowing successful fracture healing and medium- to long-term outcomes comparable to previous reports. According to results of LOAD testing, the medium- to long-term follow-up suggests that clients were aware of mild to moderate functional impairment in all cases.
Introduction
Humeral condylar fractures are common in dogs.1,2 Humeral intracondylar fissures may predispose to humeral condylar fracture.3–5 Fractures involving both portions of the humeral condyle and an intracondylar fracture are termed Y-T fractures.4 Reports of treatment of Y-T fractures have involved internal fixation with medial or combined medial and lateral plating using conventional or locking plates.4,6–8 Fixation including a transcondylar screw with bilateral plates was associated with a lower complication rate than transcondylar screw and multiple Kirschner wires.6 Minimally invasive Y-T fracture fixation has been reported in a single case.9
The irregular contours of the distal humerus and local neurovascular and musculotendinous structures complicate plate application.10 Additionally, the supratrochlear foramen and narrow epicondylar ridges, the potential for comminution, the proximity to articular surfaces, and the fact that fracture fragments are often small add further difficulty. Nonlocking plates require accurate contouring to maximize bone–plate apposition, and although they have the advantage of permitting screw angulation, screws must be placed bicortically to minimize the risk of implant loosening.7,10,11 In contrast, where locking plates are employed, construct stiffness does not require accurate anatomical contouring of the plate,12–15 and monocortical screws may be utilized.16 Some locking plate systems require screw placement at a specific angle to achieve locking.17–19 A titanium polyaxial locking plate (T-PLP) is available for veterinary patients and has been featured in a number of published biomechanical studies.20–23 Theorized benefits of T-PLP include lower susceptibility to infection,24 screw insertion angles of up to 10°, and the ability to contour in multiple planes (reconstruction–style plate).
The purpose of this study was to retrospectively evaluate short- and medium-to-long-term outcomes and complications associated with stabilization of Y-T humeral fractures using bilaterally applied T-PLP.a
Materials and Methods
Case records of dogs with Y-T fractures treated at a single veterinary referral center (Southern Counties Veterinary Specialists, Ringwood, Hampshire, United Kingdom) between January 2012 and January 2018 were reviewed. Criteria for inclusion in this study were canine nonchronic Y-T fractures and index treatment fixation involving bilateral T-PLP (excluding revision surgeries), complete medical records (until at least 6 wk following surgery) and preoperative and immediate postoperative radiographs of the humerus with appropriate positioning to allow evaluation of the fracture reduction and implants. Information collected included signalment, cause of the injury, presence of comorbidities, presence of comminution, presence of suspected humeral intracondylar fissure (HIF), size and location (medial and lateral plate and screw sizes and number of screws proximal or distal to the fracture for screws) of implants, use of adjunctive implants, and use and type of bone graft.
Assessment of Imaging
Preoperative imaging (orthogonal radiography or computed tomography [CT]) was reviewed to record comminution (absent: 3 fragments, moderate: 4–5 fragments, severe: >5 fragments25). When CT imaging of the contralateral humerus was available, the presence of a contralateral HIF was recorded.26 Postoperative and follow-up radiographs were assessed for visible articular step defects (ASDs; 0: no step, 1: <1 mm step, 2: 1–3 mm step, or 3: >3 mm step), and visible intracondylar gap defects (IGDs; measured at the level of the articular surface).
Follow-up radiographs were assessed for fracture healing, adapting a previously described radiographic grading system used for assessment of tibial fractures27 (Table 1), and incidence of implant-associated complications. All images were assessed digitally.b
Surgical Treatment
All dogs underwent preanesthetic assessment, and dedicated anesthetic protocols were prepared for each patient. Cefuroximec (20 mg/kg) was administered IV 30 min before commencing surgery and every 90 min during surgery.
Perioperative medication was not standardized but was based on anesthetists’ preferences. Oral nonsteroidal anti-inflammatory drugs were administered unless contraindicated. Perioperative analgesia (methadone,d 0.1–0.4 mg/kg) was administered according to requirements assessed through pain scoring.
Surgery involved positioning in dorsal recumbency. Medial and lateral approaches were made in all cases.8,28,29 The medial part of the condyle was reduced first, giving attention to accurate reduction of the supracondylar portion of the fracture. Fixation of the supracondylar fracture was achieved with a T-PLP (reconstruction or straight). Next the lateral part of the condyle was reduced, and fixation was performed with a transcondylar screw and T-PLP. Occasionally, additional fixation elements (lag screws and intramedullary Kirshner wires) were employed. When indicated, based on the presence of HIF, a transcondylar screw was placed in the contralateral humeral condyle under the same general anesthetic.
Diagnostic Imaging: Postoperation Assessment
Veterinary examination was performed by the operating surgeon, 4–6 wk postoperatively and, for some dogs, at 10–12 wk postoperatively. Function was subjectively graded by the examining surgeon as excellent (no lameness), good (mild lameness), fair (mild to moderate lameness), or poor (moderate to severe lameness).29 The reduction of range of motion (ROM) of the affected elbow was assessed via goniometric examination and graded as normal ROM (>125°),30 mild reduction (a loss of <20°), moderate reduction (a loss of 20–40°), and severe reduction (a loss of >40°). Medium- to long-term follow-up data (> 6 mo after surgery)31 were obtained in all cases by owner telephone interview using the Liverpool Osteoarthritis in Dogs (LOAD) questionnaire at the time of the writing of this study. Cases were grouped for functional disability as previously described according to their aggregate LOAD score (mild disability 0–10, moderate disability 11–20, severe disability 21–30, extreme disability >30).32
Complications were categorized as catastrophic (amputation/euthanasia), major (surgical or medical management required), or minor (no further management required).31
Results
Animals
Twenty-five Y-T humeral fractures were treated during the study period. Of these, 17 cases, operated by five different surgeons, satisfied the inclusion criteria. Breeds consisted of cocker spaniel (n = 7), English springer spaniel (n = 4), French bulldog (n = 3), and one of each of the following breeds: Jack Russell terrier, Hungarian vizsla, and Staffordshire bull terrier. The mean body weight was 16.1 kg (range 4.5–25.1 kg). Eleven patients were male, and six were female. The mean age was 43 mo (range 5–96 mo). Eight fractures occurred during light exercise, and the rest were associated with a trauma. No relevant comorbidities or preexisting diseases were present in the patients in the study.
Preoperative Imaging
All cases had preoperative radiography. CT was performed in 10 cases and declined in 7. One case had a prior contralateral condylar fracture. Comminution was absent in 13, moderate in 2, and severe in 2 cases. Contralateral HIF was diagnosed in 8/10 cases in which CT was performed; 6/8 patients with concomitant contralateral HIF had sustained the Y-T fracture during light exercise, whereas the remaining two had fractured during a fall. HIF was suspected from sclerosis of the fracture surface in all 10 cases that had CT.
Surgery
Surgery in all cases involved reduction and T-PLP fixation of the medial epicondyle as the first stage of the procedure, followed by reduction of the lateral part and transcondylar screw placement, finishing with application of lateral epicondyle T-PLP fixation. Fixation of the medial supracondylar portion of the fracture was achieved with 16/17 reconstruction and 1/17 straight T-PLP plates, compared with the lateral portion of the fracture where reconstruction plates were used in every case. Transcondylar screws were placed medial to lateral in 5 cases and lateral to medial in 12 cases. Five transcondylar screws were positional, six were in lag fashion, and the mode of placement was not recorded for six transcondylar screws. Additional fixation was placed in 10 cases. Details of the implants are given in Table 2, and an example of a repair is shown in Figure 1. In two cases, autogenous cancellous bone graft was placed (acquired from the ipsilateral proximal humerus).
Citation: Journal of the American Animal Hospital Association 58, 1; 10.5326/JAAHA-MS-7155
Postoperative Imaging
Evaluation of immediate postoperative radiographs recorded articular steps defects of grade 0 in nine cases, grade 1 in seven cases, and grade 2 in one case. Mean IGD was 0.25 mm (range 0.2–1.2 mm).
Results of Contralateral HIF Management
In 6/8 cases diagnosed with contralateral HIF, a transcondylar screw was placed in the contralateral humerus under the same anesthetic as the Y-T fracture repair.
Complications
One catastrophic (case 11) and two minor complications were recorded (cases 1 and 14). Failure of the medial plate and loss of screw bone purchase and failure of plate–screw coupling in the lateral plate were observed in addition to migration of the transcondylar screw in case 11 (Figure 2). Revision surgery was performed; however, repeat implant failure was observed and the clients elected amputation at that stage. Suspected superficial incisional surgical site infection involving mild serous discharge was noticed in case 14 four days following surgery, which resolved with no intervention. Migration of a medial epicondylar Kirschner wire out of the bone and into the surrounding soft tissues was noted on follow-up radiography (case 1), with no associated clinical signs and no treatment performed. Table 3 correlates the presence of perioperative comminution, ASD, IGD, and postoperative complications.
Citation: Journal of the American Animal Hospital Association 58, 1; 10.5326/JAAHA-MS-7155
Clinical, Radiographic, and Owner-Assessed Follow-Up
Veterinary re-examination was performed in all cases at 4–6 wk. Gait was subjectively assessed as excellent in 2 (11.7%), good in 10 (58.8%), fair in 4 (23.5%), and poor in 1 (5.8%) (the case with the catastrophic complication). The elbow ROM was considered subjectively normal in three cases, with mild reduction reported in eight, moderate reduction in five, and no recorded assessment in one (the case with the catastrophic complication) (106 ± 11.7). Radiographic bone healing at 4–6 wk was graded for 12 cases as 1 (n = 1), 2 (n = 6), 3 (n = 2), 4 (n = 2), and 5 (n = 1), with bone union achieved in 7/12 at this stage.
There was further veterinary examination at 10–12 wk in three cases. Between the examinations at 4–6 wk and at 10–12 wk, gait score improved in two cases and remained good in one case. The ROM improved in two cases from moderate to mild reduction (115.1 ± 10.3). Radiographs were acquired in all three cases, and bone healing scores remained stable at grade 2 in two cases and progressed from grade 4 to grade 3 in one case.
LOAD scores were obtained for 16 cases (excluding case 11) with a mean of 15 mo (range 6–29 mo) following surgery with a mean value of 4.3/52 (range 2–13). Midterm (>6–12 mo) mean aggregate LOAD score was 3 (n = 6, range 1–5). Long-term (12 mo) mean aggregate LOAD score was 5.6 (n = 10, range 3–10) with one dog scoring over 8 and therefore classified as showing moderate functional impairment.
Discussion
Spaniels have previously been recognized as being overrepresented for condylar fractures,33 and this was also the case in the current study (11/17 cases). The reason for the overrepresentation of spaniel breeds is the condition HIF. This condition was previously termed incomplete ossification of the humeral condyle (IOHC).33 Recently, HIF has been recognized as a propagating intracondylar fissure extending proximally from the articular surface,34,35 which predisposes to condylar fracture.36 A relatively high proportion of Y-T fractures in this study occurred during light exercise or while running (16/17), potentially indicating a predisposing weakness in the humeral condyle.
In this study of 17 consecutive Y-T fractures addressed with bilateral T-PLP, the authors report two (11.2%) minor complications and one (5.6%) catastrophic outcome resulting from implant failure. Additional fixation was used in most cases in this study as temporary stabilisation following fracture reduction. The authors are aware these implants were unlikely to add to the stiffness of the overall construct. However, they also felt it was not necessary to remove them. In this study, no complications involving Y-T fracture fixation occurred in cases with a contralateral transcondylar screw. In three previous reports of plated fixation of Y-T fractures, implant-related complications were documented in 2/29 (7%);8 1/13 (7.7%),9 6/30 (20%),4 and 4/13 (30.8%).6
The outcome at 4–6 wk following surgery was considered good or excellent by subjective lameness score in 12/17 patients in this study (70.5%). Subjective medium- to long-term outcome by aggregate LOAD score was indicative of mild functional impairment in 15/16 patients. Subjective scales for assessment of outcome were reported in four other studies following Y-T fracture repair. Limb function was “good” or “excellent” in 27/30 (90%) 6–14 wk following surgery;4 in 12/13 (92.3%) 5–11 wk following surgery,6 limb function was recorded as “fully functional” in 9/13 (69%) 6–8 wk following surgery9 and as “lameness resolution” in 27/28 (96.4%) in a recent study.8 In the current series, three dogs were re-examined at 10–12 wk, revealing improvements in clinical function in two, which may indicate that examination at 4–6 wk may not represent the final functional outcome. The authors suggest that the difference in timing of the re-examinations, in addition to the subjectivity of the grading scales, may offer an explanation for the poorer lameness scores following surgery in the current series. Timing of short term re-examination for recent studies (6–8 wk postoperatively and 6 wk postoperatively)8,9 were similar for the current study (4–6 wk and 10–12 wk), and short-term subjective outcomes were similar. Previously reported outcomes for humeral condylar fracture in which assessment was by veterinary examination showed that less than half of the patients regained full limb function in the long term.2 Superior outcomes were reported in a more recent study of eight working dogs,37 in which all dogs returned to normal (2/8) or near-normal (6/8) preinjury activity. Long-term follow-up was available for 9/18 cases in the most recent study on Y-T fractures, with the outcome measured by a validated owner questionnaire (canine brief pain inventory).38 Of nine owners, three reported some degree of ongoing pain. More objective measures of clinical long-term outcome, possibly evaluating longer-term radiographic signs of osteoarthritis, are needed in order to generate further information on long-term expectation after Y-T humeral fracture.
Anatomical reduction and rigid fixation are accepted principles of articular fracture surgery.39 In terms of biomechanics, perfect reduction of the intracondylar portion with interdigitation of the fracture surfaces is also likely to improve construct stability overall. This is often achieved in condylar fracture management using a transcondylar screw in lag fashion. However, the surgeons involved subscribed a theory demonstrated in a recent study, showing that positional screw fixation following forceps-applied interfragmentary compression may achieve greater and more durable interfragmentary compressive force compared with a lag screw.40 Intracondylar fracture gaps have been shown to increase the rate of progression of radiographically apparent osteoarthritis41 and may increase the risk of fracture fixation failure. However, in the current study and in a previous study reporting intracondylar fracture gaps,29 reduction was challenging to assess on plain radiography. Also, if cases with incorrectly positioned radiographs were excluded in this study, CT would be a more sensitive modality for assessment of condylar reduction. Functional outcomes were adequate in the majority of cases with IGDs <1 mm in 16/17 cases and 2 mm in a single case. The latter case did not demonstrate more lameness on follow-up in comparison with the other cases. However, thorough evaluation of the long-term impact of such a defect would require histological evaluation of the adjacent articular cartilage.
ASDs ≤1.5 mm were reported in one study of lateral humeral condylar fractures to have no influence on outcome or osteoarthritis progression.42 Similarly, articular margin reconstruction was found to have no correlation with follow-up osteoarthritis score in a study of 15 fractures in 13 dogs.3 In the current study, a single case had a defect >1 mm, and implant failure was observed in this case. An increased step defect may indicate failure to achieve anatomical reduction, such that supracondylar implants acted in bridging mode (rather than neutralization mode), potentially increasing the risk of implant failure. Intracondylar gap defects and ASDs may also influence the rate of progression of osteoarthritis. Sufficiently long-term radiographic follow-up was not available to record meaningful data in this respect; however, future studies should aim to provide such information.
Implant selection has relevance to the minimization of IGDs and ASDs. Where nonlocking plates are used and imperfectly contoured, tightening of the screws may draw bone fragments to the plate, disrupting fracture reduction, particularly at the articular surface.43 The authors propose that use of a locking plate and screw system minimizes time spent contouring and abolishes the risk of loss of fracture reduction during screw tightening. Although perfect anatomical fit of the plate to the bone is not a requirement for achieving stability in a locking plate, contouring remains of some importance to reduce the screw working distance and therefore reduce the risk of screw failure.14
The use of the string-of-pearls plate has been reported for Y-T fracture fixation.6,44 The string-of-pearls plate acts as a locking plate, with an angle-stable screw–plate interface with three rotational degrees of freedom that may be of benefit in the context of the irregular contour of the humeral condyle. However, angulation of the screws in the plate holes is not possible; thus contouring must be relied upon to direct screws into the bone. This is also the case for the locking compression plates fixation reported recently;9 however, this plate is less versatile when contouring in multiple planes. The T-PLP system used in the current series demonstrates significant versatility in contouring (particularly the reconstruction plate) but in addition allows angling of screws up to 10° within the plate hole with no loss of stiffness or push-out resistance (where push-out refers to failure of screw–plate interface).20 This allows the surgeon to direct screws to maximize bone purchase and increase screw density where fragments are small and screws are placed adjacent to critical anatomy (e.g., supratrochlear foramen).
The push-out resistance of the T-PLP has been investigated by Bufkin and others.20 In this plating system, push-out resistance is correlated with screw insertion torque and screw angulation.22 Therefore, recommendations are to maintain the screw insertion angle under 10° and to apply screws into bone of sufficient strength to permit application of appropriate insertional torque (3.5 Nm). Boudreau and others showed insertion torque increased resistance to failure under shear force for the T-PLP system (and not for other systems in which locking involves a thread-in-thread mechanism),22 because T-PLP failed mostly by screw–plate decoupling (push-out). Screw bending was another mode of failure for the T-PLP system under shear force. The surgeon using T-PLP should aim to maximize screw length within bone and place bicortical screws where possible, and, to avoid screw bending, the screw working distance should be minimized by meticulous contouring of the plate.
In a study of 30 Y-T fractures comparing fixation with biaxial plating versus unilateral plate and Kirschner wire fixation, complication rates were not found to differ.4 However, the authors of that study emphasized that the two populations of dogs were not comparable in terms of their signalment, with younger and lighter dogs having undergone fixation with a unilateral plate and Kirschner wire (mean age 9.8 versus 59.3 mo and mean body weight 9.8 versus 22.6 kg). Thus the recommendation was to perform biaxial plating in heavier dogs (in which increased construct stiffness is required) and older dogs (in which healing may be expected to be slower).4 In the current study, T-PLP fixation was employed in dogs ranging in body weight from 4.5 to 25.1 kg and in age from 5 to 96 mo. Fractures associated with HIFs are likely to result in incomplete healing at the intracondylar fracture site,45 and therefore, strong fixation—plating—is critical.
Assessment of the single case with a catastrophic outcome in this study reveals a few concerns that might predict implant failure. The medial supracondylar plate was a 2.4 mm reconstruction plate. Other dogs of a similar body weight received two 2.7 mm plates or a combination of a 2.7 mm plate and a 3.5 mm plate. The 2.4 mm plate may have been insufficiently strong. Titanium plates (ALPS 10 and PAX reconstruction) have been shown to have reduced bending strength compared with other locking-plate systems.46 This is potentially important when the implant is used in a bridging mode. Push-out of screws was apparent on the distal-most screws of the lateral plate. This may indicate a failure to follow the manufacturer’s guidelines (screw angle >10°), compromising the locking mechanism, although this is not clearly apparent in the immediate postoperative imaging. It is possible that failure of the medial plate resulted in overload of the lateral plate, increasing strain on the screw–plate interfaces. Particular caution should be applied to the selection of the size and type (reconstruction versus straight). It seems likely that use of undersized plates and the reduced strength of reconstruction versus straight plates23 contributed to inadequate stiffness in this non-load-sharing fracture. Following review of the case with catastrophic outcome, the authors are now commonly placing a T-PLP straight plate on the medial supracondylar portion of the fracture because the straight T-PLP has been shown to have a higher bending stiffness compared with the reconstruction plate,23 and the requirement for a lot of plate contouring (which is more easily performed with a reconstruction plate) is not as great on the relatively straight portion of the medial epicondylar region. Further studies are required in order to provide definitive implant selection recommendations; the data in Figure 3 represent the implants used for the different weight ranges in this case series and may be used for preliminary future reference.
Citation: Journal of the American Animal Hospital Association 58, 1; 10.5326/JAAHA-MS-7155
The LOAD metrology instrument was devised for owner-assessed measurement of the clinical impact of osteoarthritis,32 accepting that this instrument is not strictly validated for assessment of function in this scenario. Factors other than postoperative osteoarthritis may have influenced the medium- to long-term clinical function. The authors would suggest that, in the situation of long-term assessment following articular fracture, it is reasonable to assume that the limiting factor will be degenerative joint disease. Thus, LOAD was used in an attempt to increase the objectivity of the published data. LOAD results for this study reveal that clients were aware of a degree of ongoing functional disability (mild in 15/16 cases and moderate in 1) following Y-T fracture surgery at a mean follow-up of 15 mo. Veterinary surgeons should make clients aware before embarking on surgical management of Y-T fractures that some clinical features of joint disease may remain apparent in the medium- to long-term.
There are several limitations of this study. Medium- to long-term outcome reporting was limited to client assessment of clinical function, with no direct objective assessment of implant stability and cartilage health. Radiographic assessments were performed by only one observer, with the potential for skewing of results as a result of unaccounted intraobserver variation. Furthermore, also because of the retrospective nature of the study, the limited number of cases and patients available for radiographic follow-up examination, and the lack of a comparator, only descriptive statistics were presented. Additionally, different surgeons were involved in the cases reported here, and the size of the implants selected was a subjective decision made by the operating surgeon. Finally, there was no objective outcome measure specifically of joint function. Goniometry is an informative test of elbow ROM30 and was only used in the short-term assessment in this study. The LOAD instrument measures overall function rather than specific function, and force plate analysis instead of subjective gait evaluation would have provided a more objective method, whereas activity monitoring might have given data regarding exercise capacity. Future studies should aim to provide more objective data.
Conclusion
The application of bilaterally applied T-PLP with TC screw was employed for the stabilization of Y-T humeral fractures. Short-term radiographic evidence of bone union was confirmed in 7/12 patients. Medium- to long-term outcome was comparable to previous reports of treatment of this injury in 16/17 cases, and there was one case with a catastrophic outcome. Information regarding adequate implant selection and safe use of these implants in particular with heavier patients and comminuted fractures should be clarified with further studies.
Caudocranial (A) and mediolateral (B) projections immediately before and after (C, D) surgery of case 15.
Caudocranial (A) and mediolateral (B) projections immediately after surgery and at the time of implant failure (C, D) of case 11.
Number of different-sized T-PLPs (2 mm, 2.4 mm, 2.7 mm, and 3.5 mm) used in different weight ranges (0–9 kg, 10–19 kg, and >20 kg). T-PLP, titanium polyaxial locking plate.
Contributor Notes
From Southern Counties Veterinary Specialists, Hampshire, United Kingdom.
