Small Animal Orthopaedics and Arthroscopy

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Canine Unicompartmental Elbow resurfacing for dogs with medial compartment disease

Fragmentation of the medial coronoid process (FCP) is a complex disease of the canine elbow which typically affects young dogs of medium and large breeds. The specific pathology of the condition is not clearly understood but focal overloading of the medial coronoid by the humeral condyle caused by assynchronous growth of the radius and ulna or some other abnormality occurs at a young age leading to subchondral bone fissuring of the medial coronoid. The extent of the subchondral bone fissuring then leads to fragmentation of the medial coronoid and variable degrees of articular cartilage destruction of the medial coronoid and humeral condyle.

The degree of fragmentation and cartilage destruction can be very variable with some dogs presenting with just coronoid disease and no overt fragment, some with visible fissures of the coronoid, some with unstable fragments and some with unstable fragments and wide areas of cartilage destruction (termed medial compartment disease).

Arthroscopic pictures of the medial coronoid showing just coronoid disease with no fragments, a coronoid fragment with little cartilage injury and a coronoid fragment with extensive cartilage disease

Treatment depends very heavily on how extensive the condition is and determining how extensive the damage is from plain radiographs is very difficult. Arthroscopy of the elbow provides a huge amount of information, in particular how widespread the cartilage damage is and in many cases simple fragment removal and lesion bed debridement is all that is needed at the time of arthroscopy. However cases that have medial compartment disease often respond poorly to simple lesion debridement as this does nothing to relieve the impingement of the exposed subchondral bone of the medial coronoid with the exposed subchondral bone of the humeral condyle with persistent lameness and a poor long term prognosis.

Treatment options for Medial compartment disease

More radical subtotal medial coronoid ostectomy will often provide some temporary improvement but does nothing to improve long term outcomes, however as this can be performed arthroscopically it is our favoured technique in a small subset of dogs where the presentation is in older age where it can prove beneficial as a palliative treatment, often in conjunction with some other less invasive strategies.

Arthroscopic image after extensive subtotal medial coronoid ostectomy

Sliding humeral osteotomy (SHO) was proposed as a technique to shift the weight bearing axis away from medial side and onto the healthy lateral side and studies have shown this to be effective, however there is a relatively high complication rate with this technique and so it has been slow to become accepted.

Craniocaudal radiograph of a dog with profound medial compartment disease. There is extensive osteophyte formation in the medial aspect of the coronoid and humeral condyle and the outline of the medial coronoid is irregular.

Canine unicompartmental elbow (CUE) resurfacing addresses the condition in a different way. The theory behind CUE is that the impinging subchondral bones are resurfaced with a metallic implant in the humerus running on an Ultra High Molecular Weight Polyurethane implant in the coronoid. The procedure requires an extensive arthrotomy via osteotomy of the medial epicondyle in order to accurately place the implants but results are very encouraging and the complication rate is acceptably low. This surgery is certainly not the panacea for treatment but we do feel that it provides a better treatment option in young dogs with extensive elbow disease where the long term outcomes with traditional techniques are not good. It should not be confused with Total Elbow Replacement which has a significantly high complication rate and is really only an option for end stage elbow disease where both the medial and lateral compartments are destroyed.

Craniocaudal radiograph of a dog that has had CUE, the metallic humeral implant is in good alignment with the ulna implant and the medial epicondylar osteotomy has been repaired with a 3.5mm screw. Adjacent are the implants with a small haemostat to demonstrate their size.