Update on humeral condylar fracture treatment in dogs

Fractures of the humeral condyle are common in dogs – particularly breeds such as springer spaniels, cocker spaniels, Labrador retrievers and Yorkshire terriers.

The most common configuration is a fracture of the lateral portion of the condyle and this type accounts for approximately 90% of humeral condylar fractures. Fractures of the medial humeral condyle account for approximately 5% and the remainder are double condylar fractures with a “Y” or “T” configuration (Figure 1).

Factors that contribute to this are thought to be the anatomical structure of the lateral portion with a relatively narrow epicondylar ridge of bone compared to the medial side (Figure 1) and incomplete ossification of the humeral condyle (IOHC) or humeral intercondylar fissure. IOHC was first reported in cocker spaniels in the United States by Marcellin-Little et al¹, and the first UK report was by Butterworth and Innes², suggesting a predisposition in springer spaniels in the UK.

Other breeds reported to have this condition include the Labrador retriever³, German pointer⁴, English pointer⁵, German Wachtel⁶ and Rottweiler⁷.

Incomplete ossification of the humeral condyle

The humeral condyle develops as two secondary centres of ossification – medial and lateral. At between eight and 12 weeks of age the cartilaginous plate that separates these two centres should ossify. IOHC refers to the assumed failure of this process and the persistence of a cartilaginous plate, although other authors have suggested it may represent a condylar stress fracture² and hence the term humeral condylar fissure has been proposed.

Some support for the latter argument comes from reported cases of dogs that have had normal humeral condyle on a CT scan and subsequently developed humeral intracondylar fissure at a later date. In addition, one report documented propagation of a limited IOHC to a fracture line that extended through the humeral condyle⁸. Furthermore, a report in a cocker spaniel documented complete ossification on a CT scan, but 22 months later a lesion typical of IOHC was identified on repeat CT.

Such cases suggest so-called IOHC lesions can develop in the mature skeleton and are not always a result of failed ossification of the cartilaginous plate during skeletal maturation. Thus IOHC lesions can be partial (not extending from articular surface to the supracondylar foramen) to complete.

Complete lesions are associated with minor instability and therefore cause pain and lameness, whereas partial IOHC lesions are clinically silent.

The prevalence of IOHC in springer spaniels in the UK has been estimated using CT scanning of dogs presented for reasons unrelated to elbow lameness⁹. The prevalence of IOHC was estimated at 14% although these were all partial IOHC lesions.

Interestingly, in the same population CT scans showed abnormalities on the medial coronoid process in 50% of subjects, although the two conditions did not show a significant association. IOHC lesions are often surrounded by dense sclerotic bone as noted on CT scanning (Figure 2).

Diagnosis of IOHC can be challenging in the absence of cross-sectional imaging modalities. Pain on elbow extension in an at-risk breed should raise suspicion of IOHC. A craniocaudal elbow radiograph may show the fissure line in the humeral condyle (Figure 3) as long as the x-ray beam is parallel to the plane of the fissure. It can sometimes be useful to take several craniocaudal projections at slightly differing and mild angles of obliquity. Radiographs may also show periosteal reaction on the lateral epicondylar ridge (Figure 3) as a result of the increased stress on this area and the resultant response of bone.

Management of IOHC is controversial and evolving. The initial approach in the 1990s was to treat the fissure fracture as a standard intra-articular fracture and apply the traditional principles of accurate reduction and rigid internal fixation with a lag screw technique to compress the fracture line. Compression produces friction and provides stability. However, it became apparent that while such an approach provided pain relief from the resultant stability, the fracture line tended not to heal. There is an argument to consider painful IOHC lesions as a non-union fracture scenario.

Occasionally, dogs would re-present acutely months or years later with a broken screw at the fissure line; a screw broken through fatigue because of cyclic loading and a failure of the surrounding bone to heal. Because of this, most surgeons would place a large screw diameter (for example, 4.5mm cortical screw) to maximise the core diameter and the area moment of inertia with a resultant increased resistance to bending forces.

Some surgeons also suggested a position screw was preferred over a lag screw because purchase of threads in both portions of the condyle provided less likelihood of screw loosening and loss of stability. Given the fact compression of the fracture line did not seem to help fracture healing, there was some logic to this argument and it also avoided the risk of over compression of the fracture, which can occasionally occur with the relatively uncontrolled compression of a standard lag screw.

Given the risk of fracture non-union and implant fatigue, an alternative approach using a shaft screw was also reported¹⁰. A shaft screw has a large unthreaded section with a negative profile thread to engage in the transcortex. Such an approach appears to provide good long-term survival of the implant, but again, fracture healing of the IOHC fissure was inconsistent.

Traditional approaches to IOHC have been of limited success and with high complication rates¹¹. Of 79 elbows with IOHC treated at six UK referral centres, the overall complication rate was 59.5%. Seroma (n=25) and surgical site infection (n=24) were the most commonly encountered complications and implant failure occurred in two dogs.

Interestingly, placement of the transcondylar screw in lag fashion rather than as a positional screw significantly reduced the incidence of postoperative surgical site infection, suggesting compression of the fissure is advantageous.

Quite why the infection rate is so high with this clinical scenario is not certain, but candidate reasons include the site of the lateral surgical approach and the superficial nature of the operative site. Some surgeons suggest placing the transcondylar implant from medial to lateral to avoid the lateral incision and there is a suggestion this might reduce postoperative infection rates.

The usefulness of bone grafting in IOHC was demonstrated in a series of nine dogs¹². Using either autogenous cancellous bone graft or corticocancellous dowel in combination with a self-compressing screw to provide stability, seven of eight elbows assessed by CT had bridging bone across the intracondylar fissure. A novel cannulated and fenestrated implant – the F2T2 – has been investigated as a potential implant to provide stability and accommodate bone graft within the internal structure¹³.

More recently, a self-compressing titanium screw placed in a bone void created using a customised step drill bit and filled with canine demineralised bone matrix has been reported and is commercially available (Veterinary Instrumentation, Sheffield; Figures 4a and 4b). These latter approaches are based on the assumption clinical IOHC cases are atrophic non-unions and require debridement, bone grafting and rigid internal fixation to achieve union and long-term success.

In summary, the literature to date would suggest:

• Complete IOHC lesions cause chronic pain and lameness because of instability. The lesion should be considered an articular non-union fracture.
• As such, accurate reduction, rigid internal fixation, compression and grafting are recommended.

Displaced fractures of the humeral condyle

Displaced fractures of the humeral condyle involve a sagittal plane fracture through the condyle together with a fracture through one or both of the epicondylar ridges. A fracture through the lateral epicondylar ridge is much more common and this results in the lateral portion of the humeral condyle becoming unstable. Often, such fractures occur during normal activity – suggesting these fractures result from acute propagation of IOHC. Indeed, some animals will have a prodromal lameness, presumably caused by IOHC, and then a sudden onset displaced fracture.

Lateral condylar fractures are common in immature patients at three to four months of age in breeds such as the springer spaniel, Labrador retriever, Staffordshire bull terrier and Yorkshire terrier. Medial condylar fractures also tend to occur in this age group, although the breed distribution appears somewhat different with German shepherd dog and pointer breeds being represented. Double condylar fractures (“Y” or “T” configuration) tend to occur in skeletally mature dogs and common breeds are springer spaniels, Staffordshire bull terriers and German shepherd dogs.

The traditional approach to fractures involving the lateral portion of the humeral condyle has been to place a transcondylar screw in lagged fashion and to combine this with an anti-rotational device (Kirschner wire, screw or epicondylar plate). However, evidence suggests the anti-rotational device used can have a significant association with the observed complication rate¹⁴ and the author would recommend the use of an epicondylar plate (Figure 5), particularly in breeds predisposed to IOHC.

It might also be logical to apply the principles of IOHC treatment outlined above to the treatment of the humeral intracondylar fracture line in these cases – debridement, compression and grafting, at least in adult dogs with this injury.

Fractures of the medial portion of the humeral condyle typically have a more oblique proximal fracture line, resulting in a relatively larger displaced condylar fragment. This provides more opportunity for implant placement and the author would recommend a medial plate in combination with a transcondylar screw.

Double condylar fractures are among the most challenging fractures to occur in dogs. A variety of options is available for repair, but it is recommended surgery is undertaken by those experienced with methods of internal fixation. The principles of accurate reduction and rigid internal fixation apply to the articular portion of this fracture configuration and this is combined with plate and screw fixation, which typically involves the use of a medial and lateral plate in combination (Figure 6).

Whether these plates are applied though a caudal approach via olecranon osteotomy, or through a combined medial then lateral approach¹⁵, is a matter for consideration with each individual case – as well as surgeon preference.

Summary

Humeral condylar fractures are common in dogs and there is now a greater awareness of the predisposing factors and the need to reduce the risk of potential complications. IOHC is a challenging clinical scenario, but newer treatment methods involving a self-compressing screw in combination with bone grafting show promising results in comparison to traditional techniques.

Clinical evidence suggests fractures of the lateral portion of the humeral condyle are best treated with a transcondylar compression implant in combination with an epicondylar screw or plate.