Proximal Abducting Ulnar Osteotomy (PAUL)

Elbow dysplasia is a major cause of front limb lameness in medium to large dog breeds. In the majority of cases, it starts in, or is limited to, the medial compartment, with fragmentation of the medial coronoid process (FCP) and/or osteochondritis dissecans of the medial humeral condyle (OCD), usually associated with different degrees of joint incongruity.

Conventional surgical treatment with joint debridement and removal of loose osteo-cartilaginous bodies is not rewarding if joint incongruity persists; the result is overloading and subchondral bone exposure with erosion of the cartilage of the medial humeral condyle and medial coronoid area of the ulna. Medial collapse of the joint attributable to friction and resultant loss of the osteocartilaginous layer is intensified leading to a vicious circle. Consequently, the paw moves medially during weight-bearing, which increases the load on the medial compartment. Friction from bone-on-bone contact produces heat and necrotic debris, exacerbating the biochemical cascade in osteoarthritis (OA).

Rationale for PAAL osteotomy
A number of different osteotomies have been proposed and implemented for the treatment of medial compartment syndrome, mostly based on the assessment of incongruities within the joint, or more recently, on the forces exerted by the muscles proximal to the joint. Consideration of the overall loading of the limb offers another viewpoint and may identify the actual cause of the condition and thus generate a more rational treatment approach.  [...]