Incomplete ossification of the canine humeral condyle - Veterinary Practice
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Incomplete ossification of the canine humeral condyle

‚ÄčIncomplete ossification of the humeral condyle (IOHC) has been reported as an uncommon cause of forelimb lameness in dogs but may be an important risk factor for humeral condylar fractures (Denny, 1983; Anderson et al, 1990; Marcellin- Little, et al, 1994).

Incomplete ossification of the humeral condyle (IOHC) has been reported as an uncommon cause of forelimb lameness in dogs but may be an important risk factor for humeral condylar fractures (Denny, 1983; Anderson et al, 1990; Marcellin- Little, et al, 1994).

IOHC is recognised in a number of breeds, including Springer spaniels, Cocker spaniels, Labrador retrievers and Rottweilers. Both Springer spaniels and Cocker spaniels appear to be over-represented for this condition.

Normal ossification of the humeral condyle starts at two weeks of age in the dog and is normally complete between eight and 12 weeks of age. There are three centres of ossification which develop in the humeral condyle. One ossification centre develops into the capitulum and the lateral part of the condyle, one into the trochlea and the medial part of the condyle, and a smaller ossification centre forms the medial epicondyle.

Failure of the lateral and medial condyle ossification centres to completely fuse in the juvenile dog leads to the presence of a fibrous fissure in the intercondylar region which is an area of inherent weakness. It is commonly, but not always, a bilateral condition.

The aetiology of IOHC is unknown although it is suspected to have a hereditary component (Marcellin-Little et al, 1994).

Dogs with IOHC can present in one of three ways:

  • varying degrees of forelimb lameness;
  • humeral condylar fractures; and
  • as an incidental finding.

1. Forelimb lameness

Dogs with IOHC can present with unilateral or bilateral forelimb lameness which may vary from mild and intermittent to severe. The degree of lameness is often reported to be worse after exercise and there is often limited response to anti-inflammatory medication.

Elbow pain is most consistently found on extension of the joint especially if pressure is applied to lateral condyle. Unless there is concurrent joint pathology such as medial coronoid disease or osteoarthritis, there is generally no reduction in the range of motion of the joint and there is usually no palpable joint effusion (Butterworth and Innes, 2001).

Diagnosis of IOHC is based on confirmation of an intercondylar fissure. This is often achieved using craniocaudal radiographs of the elbow (Marcellin-Little et al, 1994; Butterworth and Innes, 2001). However, as the x-ray beam must pass along the line of the fibrous fissure for it to be observed (Figure 1a), several views are often required and failure to see a fissure on plain radiography does not rule out a diagnosis of IOHC (Marcellin-Little et al, 1994; Butterworth and Innes, 2001; Carrera et al, 2008).

It is also important to take views of the contralateral elbow joint. The intercondylar fissure is easily detected using computed tomography (CT) which has significantly improved the diagnosis of this condition (Figure 1b) (Carrera et al, 2008).

Reported treatment of patients with lameness secondary to IOHC has involved placement of a transcondylar cortical lag screw (Butterworth and Innes, 2001). A 3.5mm or 4.5 mm cortical screw is preferred because it is stiffer in bending compared to a 4.0mm cancellous screw.

Some surgeons have recommended a positional screw over a lag screw on the basis of improved stability but others argue that the compression provided by the lag screw is more likely to result in union.

The screw size should be as large as possible for the individual patient. For example, a 4.5mm cortical screw is used in the majority of Springer spaniels (Figure 2). This is because the screw may continue to be loaded in the long term due to persistence of the fissure line post-operatively, which is not an uncommon finding.

Post-operative care includes exercise restriction over a six-week period and suitable analgesia, usually non-steroidal anti-inflammatory drugs (NSAIDs). Possible post-operative complications include failure of the transcondylar screw secondary to withstand long-term cyclical loading and septic arthritis.

Prognosis for patients undergoing prophylactic screw placement of the treatment of prodromal lameness is reported to be good for those that have an uncomplicated recovery, with resolution or at least significant improvement in the degree of lameness in the majority of cases (Butterworth and Innes, 2001; Meyer- Lindenberg et al, 2002). Owners should be warned that even if a fissure has not been identified radiographically on pre-operative radiographs of the contralateral elbow, clinical signs associated with IOHC may become apparent at a later date.

2. Humeral condylar fractures

Patients with IOHC can also present with humeral condylar fracture. Owners will often report that the fracture occurred during normal activity with little or no history of trauma. Prodromal lameness can also be reported. Humeral condylar fractures are divided into three categories, of which lateral humeral condylar fractures are the most common:

  • lateral humeral condylar fractures (Figure 3a);
  • medial humeral condylar fractures;
  • intercondylar fractures – classified as either a Y or T fracture depending on where the fracture lines cross the epicondylar ridges (Figure 3b).

Dogs with humeral condylar fractures present with non weightbearing lameness of the affected forelimb with marked soft tissue swelling. Pain and crepitus are noted if the elbow is manipulated.

A definitive diagnosis is achieved by obtaining orthogonal radiographic views (mediolateral and craniocaudal) of the affected elbow. Again, it is important to radiograph the contralateral elbow to assess for the presence of IOHC.

The majority of patients presenting with fracture secondary to IOHC do not have a significant history of trauma. However, full patient assessment is still a vital part of the management of these animals to ensure concurrent issues are not missed.

Patients must receive suitable analgesia, most commonly a combination of a NSAID and an injectable opioid. Bandaging of the affected limb is not usually required and indeed the weight of the dressing can act as a fulcrum if the dressing does not extend far enough proximal to the fracture. Cage confinement prior to surgical management of these fractures is also essential.

Humeral condylar fractures have an articular portion and therefore exact anatomical reduction and rigid internal fixation of these fractures is essential.

(a) Lateral condylar fractures

These fractures are approached via a lateral incision passing just cranial to the point of the lateral epicondyle. A transcondylar lag screw is used to achieve interfragmentary compression across the condyle.

This is most commonly placed using an inside-out approach where the condylar fragment is externally rotated to allow placement of the glide hole for the lag screw. This ensures placement of the lag screw in the centre of the condyle.

Some surgeons use a partially threaded cancellous screw in immature animals rather than a cortical screw which provides greater purchase in soft epiphyseal and metaphyseal bone. However, cancellous screws have a much lower bending strength than their cortical equivalents so a cortical screw is often combined with a washer in these immature patients.

A second point of fixation is required in the epicondylar ridge to prevent rotation of the condylar fragment around the transcondylar screw. This is usually achieved using a Kirschner wire placed from distal at the base of the epicondylar ridge proximally across the fracture line in to the diaphysis.

This implant should engage the medial cortex of the humeral diaphysis to provide stability and the pin should be bent to prevent migration (Figure 4a).

(b) Medial condylar fractures

The principles of fixation for these uncommon fractures are the same as those for the management of lateral condylar fractures although the approach is medial rather than lateral. The medial condyle of the humerus is larger than its lateral equivalent and therefore a lag screw can be used to reduce the medial epicondylar fracture in place of a Kirschner wire.

(c) Intercondylar fractures

Intercondylar fractures are technically challenging and should only be attempted by an experienced surgeon. More recently, a bilateral approach has been advocated for internal reduction and fixation of these fractures although a caudal approach via an olecranon osteotomy or triceps tenotomy can also be used. The intercondylar fissure is reduced using a transcondylar lag screw which can be placed using either a lateral or medial approach. Medial and lateral bone plates are then applied (Figure 4b).

Post-operative care

Post-operative care for these patients is similar and includes the provision of adequate analgesia including opioids in the initial post-operative period. NSAIDs should be continued for a minimum of 2-3 weeks postoperatively depending on the individual patient and fracture type.

Exercise restriction is essential in the post-operative period and this should be stressed to the owner. Confinement to a single small room with non-slip flooring or a cage is required in the initial post-operative period with lead exercise for toileting purposes only.

The post-operative radiographs are repeated at four to six weeks depending on the age of the patient and the fracture type and the exercise regime altered accordingly.

Prognosis

The prognosis for lateral and medial condylar fractures is generally good if early and adequate reduction is achieved (Denny 1983). However, failure of fusion of the intercondylar fissure in IOHC fracture fixation means that implant failure is a more significant risk for these patients. There is a high incidence of radiographic osteoarthritis following these fractures and this should be discussed with the owner prior to surgery (Gordon et al, 2003). The prognosis for intercondylar fractures is somewhat more guarded although one study reported a good or excellent outcome in the majority of cases in the hands of an experienced surgeon (McKee et al, 2005).

3. IOHC as an incidental finding

IOHC can be recognised in asymptomatic patients, usually when the “normal” elbow joint is imaged. Currently opinion varies on the management of these patients as they are at higher risk of fracture but this must be balanced with the possible post-operative complications associated with prophylactic transcondylar screw placement. This should be discussed with the individual owner when this situation arises to allow an informed decision to be made.

Acknowledgements

I would like to thank Dr Eithne Comerford and Professor John Innes for the help regarding the research and writing of this article and for the use of the images.

References

Butterworth, S. J. and Innes J. F. (2001) Incomplete humeral condylar fractures in the dog. Journal of Small Animal Practice 42: 394-398. Denny, H. R. (1983) Condylar fractures of the humerus in the dog; a review of 133 cases. Journal of Small Animal Practice 24: 185-197. Gordon, W. J., Besancon, M. F. et al. (2003). Frequency of post-traumatic osteoarthritis in dogs after repair of a humeral condylar fracture. Veterinary and Comparative Orthopaedics and Traumatology 16 (1): 1-5. Marcellin-Little, D. J, DeYoung, D. J., Ferris, K. K. and Berry, C.M. (1994) Incomplete ossification of the humeral condyle in spaniels. Veterinary Surgery 23: 475-487. McKee, W. M., Macias, C. and Innes, J. F. (2005) Bilateral fixation of Y-T humeral condyle fractures via medial and lateral approaches in 29 dogs. Journal of Small Animal Practice 46: 217-226.

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