The Canine Unicompartmental Elbow (CUE) Arthroplasty System

Medial compartment disease (MCD) of the elbow is the typical end-stage situation of many elbow disorders, such as fragmented medial coronoid process (FCP). But it might also be a primary disease, inducing accelerated medial joint arthritis, probably as a consequence of elbow mechanical axis deviation. Predominant characteristics of MCD are loss of cartilage at the medial coronoid process and the opposing humeral trochlea resulting into bone-on-bone contact, together with the collapse of the medial joint compartment. At arthroscopy, the situation is red and white, with a clearly visible sagittal demarcation line from no cartilage at the medial compartment to visible normal cartilage at the lateral joint compartment (see fig. 1).

The Canine Unicompartmental Elbow (CUE) Arthroplasty System (Arthrex Vet Systems, Naples, Fla.) is thought as an alternative to other treatment modalities dealing with severe degenerative joint diseases, such as total elbow replacement or osteotomies of the humerus or the ulna. Designed as a resurfacing procedure with the aim to eliminate bone-on-bone contact at the medial joint compartment, the principle is similar to unicompartmental knee arthroplasty in humans (see fig. 2). The technique consists of the completion of an open arthrotomy of the elbow, most typically via osteotomy of the medial epicondyle (alternatively by tenotomy) (see fig. 3). Fragments at the medial coronoid process are removed and a high molecular weight polyethylene domed cylinder of 4-6 mm in diameter is implanted in the centre of the eburnated coronoid. The corresponding lesion at the humeral trochlea is resurfaced with a double-cylinder metallic implant. The technique of implantation is similar to osteochondral transplantation, in which the transplants are press-fitted into place. While the implantation is straight forward, osteotomy of the medial epicondyle with reflection of the flexor muscles and the medial collateral ligament has turned out to be the most challenging part of the procedure. Complications associated with the operative technique are mostly related to the osteotomy rather than to the implantation, but it is the preferred approach, as carpal hyperflexion was relatively common with the tenotomy.  [...]