Collateral Ligament – Repair or Not?

Collateral ligaments are found on the medial and lateral aspects of the major joints. Those of the stifle, hock and elbow are of most interest in veterinary clinical practice. The function of the collateral ligaments is to control valgus and varus motion at the joint. The ligaments are robust, easily identifiable structures that originate close to the joint and typically coincident with the location of the screw-axis of the joint. Collateral ligaments tend to be somewhat flattened, rather than circular in cross-section, with a more extensive ‘fan-shaped’ insertion often made over a relatively larger area of bone and this reflects a complex structure and mechanical function. In dogs, being quadrupeds, the centre of gravity is eccentric to the axis of the limbs and consequently, there is a net tendency for the lateral aspect of stifle, hock and elbow joints to be under tension while the opposite is true of the medial aspects. This observation suggests that the stabilisation of a lateral- collateral deficient joint might be more challenging than stabilising a joint with a medial collateral injury.

Ligaments are essentially collagenous structures with a complex hierarchical structure of fascicles, fibrils, sub- fibrils and microfibrils. Cells, predominantly fibroblasts are sparse and there is a meager blood supply via the origin and insertion, however, it is likely that blood supply recruited from adjacent soft tissues becomes important following injury. Ligaments have the potential to recover functionality following injury, even complete section. The process essentially involves the formation of a fibrous scar, which, over time and in the presence of a suitable biological and mechanical environment, has the potential to ‘remodel’ back to indistinguishable ligamentous tissue. The role of the clinician faced with a collateral ligament injury can be defined in terms of managing the patient to provide the optimum biological and mechanical environment to permit ligamentous healing and remodeling.  [...]