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Managing incomplete ossification of the humeral condyle

A guide to diagnosing and managing the condition commonly seen in dogs

Fractures of the humeral condyle are common in the dog. The lateral side is fractured most often (in 34 to 67 percent of cases), with intracondylar fractures (often referred to as “Y” or “T” fractures) less common (26 to 35 percent of cases). Lateral condylar fractures are most prevalent in skeletally immature dogs, whereas medial and intracondylar fractures are usually seen in skeletally mature dogs and are often, but not exclusively, associated with more severe trauma, such as a road traffic accident.

TURLOUGH O’NEILL NORTHWEST VETERINARY SPECIALISTS
TURLOUGH O’NEILL NORTHWEST VETERINARY SPECIALISTS

Turlough O’Neill, MVB, MACVSc, MVS, CertSAS, ECVS, MRCVS, holds the RCVS Certificate and European Diploma in Small Animal Surgery. He is an RCVS Specialist in Small Animal Surgery (Orthopaedics) and an EBVS European Specialist in Small Animal Surgery.

It has been recognised that Spaniel breeds have a high incidence of humeral condylar fractures (Marcellin-Little et al., 1994; Butterworth and Innes, 2001). Often these injuries are in skeletally mature dogs, with unexpectedly low levels of trauma. It is now recognised that some dogs have a sagittal, radiolucent fissure present at the intracondylar isthmus, which separates the medial and lateral parts of the condyle and may extend from the articular surface to, or towards, the supratrochlear foramen (Figure 1). Initial reports revealed these fissures in the contralateral limb of dogs with humeral condylar fractures, but further investigations have shown fissures unilaterally or bilaterally in lame or clinically sound dogs (Marcellin-Little et al., 1994; Butterworth and Innes, 2001).

The exact pathogenesis of this fissure is unclear. Theories suggest failure of fusion of the separate centre of ossification of the distal humerus, gives rise to the condition (incomplete ossification of the humeral condyle; IOHC). It is proposed that normal physiological loading on this weakened condyle may cause the fissure to progress across the physis to the supratrochlear foramen. Recently it has been suggested that in some dogs, the fissure represents a stress fracture developing after ossification is complete, and therefore should be called humeral intracondylar fissure (HIF) (Butterworth and Innes, 2001). This is supported by reports of the appearance of fissures in previously normal condyles. The presence of joint incongruency has been implicated in the development of these stress fractures (Moores and Moores, 2017).

FIGURE (1) A craniocaudal view showing a radiolucency line between the condyles
FIGURE (1) A craniocaudal view showing a radiolucency line between the condyles

Diagnosis 

Diagnosis is based on demonstration of a fissure. To see them, the X-ray beam must be directed parallel to the fissure. Several different craniocaudal projections may be required. An artefactual line may be created by the superimposition of the ulna on the condyle (a “mach line”) (Butterworth and Innes, 2001). Occasionally the fissure may extend only partway across the condyle (a partial fissure). New bone formation can be seen on the lateral epicondylar ridge in response to instability. Normal radiographs do not exclude the presence of a fissure.

FIGURE (2) CT scans reveal a complete fissure
FIGURE (2) CT scans reveal a complete fissure
FIGURE (3) CT scans reveal a partial fissure with sclerosis on either side of the defect
FIGURE (3) CT scans reveal a partial fissure with sclerosis on either side of the defect

Computed tomography (CT) is the gold standard. CT scans reveal the presence of a complete (Figure 2) or incomplete (Figure 3) hypoattenuating area of the condyle. Importantly, CT allows assessment of the elbow joint for other lesions, such as elbow dysplasia and incongruency. In one study, 95 percent of affected dogs had bilateral fissures, with medial coronoid disease in 26 percent and degenerative joint disease in 79 percent of elbows (Marcellin-Little et al., 1994; Butterworth and Innes, 2001). 

Dogs with IOHC may present with lameness, condylar fractures secondary to IOHC or as an incidental finding in non-lame dogs. Dogs with fractured condyles are treated with appropriate internal fixation. While the epicondylar ridges tend to heal if stability is provided, the intracondylar region may never heal. In the case of a juvenile with a lateral condylar fracture, we often use a small pin as an antirotation device. In cases of IOHC, we recommend a more robust form of fixation, typically a bone plate spanning the fracture site (Figure 4). As the condylar fissure frequently fails to unite, there is an increased risk of fatigue failure of the transcondylar screw (Figure 5) with subsequent condylar fracture, recurrence of lameness or loss of fracture reduction. For this reason, the largest transcondylar screw that can be safely placed should be used.

FIGURE (4) A lateral condylar fracture repair with a plate supporting the epicondylar ramus and a 4.5mm shaft screw across the condyles
FIGURE (4) A lateral condylar fracture repair with a plate supporting the epicondylar ramus and a 4.5mm shaft screw across the condyles

Management 

Management of IOHC must balance the benefits of the procedure against the risk of complications. Surgical stabilisation by transcondylar screw placement aims to resolve lameness and reduce risk of fracture or of developing lameness. In cases of lameness with pain associated with the elbow and the presence of a fissure, screw placement is recommended. Complication rates as high as 59.5 percent have been recorded, with seroma formation and post-operative infection (30.4 percent) (Hattersley et al., 2011).

FIGURE (5) Fracture repair failure; broken screws with displacement necessitating a repair review
FIGURE (5) Fracture repair failure; broken screws with displacement necessitating a repair review

The use of positional rather than lag screws increased the likelihood of post-operative sepsis (Hattersley et al., 2011). Implant failure is minimised by increasing the screw size. It is recommended that the transcondylar screw protrude 2mm to 3mm from the transcortex to aid easier removal should screw failure occur. The use of a shaft screw has been advocated, as this has a thicker shaft or core, increasing the radius of the screw at the fissure line and dramatically reducing the risk of failure by breakage. It is reported that screws placed from lateral to medial, as is the most common practice, had a 50 percent complication rate, whereas screws placed from medial to lateral (Figure 6) did not have any major complications (Moores and Moores, 2017).

Conservative management is associated with high rates of fracture of the humeral condyle; 43 percent of partial fissures and 8 percent of complete fissures fracture within 18 months of diagnosis (Marcellin-Little et al., 1994). In a second study that followed 30 dogs with IOHC diagnosed in 34 elbows, only five dogs (six elbows) (18 percent) progressed to fracture in 24 months; a further two dogs had persistent lameness and had transcondylar screws placed. Twelve other dogs were reported to never be lame, eight were occasionally lame but did not require medication, one was persistently mildly lame and did not require medication and two were persistently lame and required medication (Moores and Moores, 2017). Interestingly, the fissure size does not relate to fracture risk, suggesting that stress of repetitive loading can cause the fissure to develop and fail (Moores and Moores, 2017).

FIGURE (6) A transcondylar screw placed from medial to lateral
FIGURE (6) A transcondylar screw placed from medial to lateral

In summary, IOHC is commonly seen in Spaniels and investigations should be performed if there is an increased index of suspicion. Fractures need to be repaired robustly and owners warned of likely failure to achieve bone union at the fissure site and the possibility of implant failure. Partial fissures and complete fissures can progress to fracture or lameness. Transcondylar prophylactic screw placement can help treat lameness and prevent failure, but have high complication rates. Use of as large a screw as possible is recommended, and placing the screw from medial to lateral may decrease the number of complications. Conservative management may be considered in clinically unaffected dogs; however, this may need reviewing should signs appear.

Turlough O’Neill

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