OPEN REDUCTION AND STABILIZATION OF A LUXATED COXOFEMORAL JOINT IN A DOMESTIC RABBIT (ORYCTOLAGUS CUNICULUS) USING A TOGGLE-PIN FIXATION

Ligamentum teres reconstruction using autogenous semitendinosus tendon with toggle technique in rabbits

Background

Ligamentum teres (LT) has traditionally been considered a vestigial or redundant structure in humans; however, based on new studies and the evolution of hip arthroscopy, the LT injury has been viewed as a source of hip pain. Therefore, LT reconstruction can be beneficial in some cases. Rabbits have been frequently used as a model for cranial cruciate ligament reconstruction but few studies are available for ligamentum teres reconstruction.

Objective

To evaluate the semitendinosus tendon to replace ligamentum teres with the toggle technique, using rabbits as an experimental model.

Methods

Twenty-six female Norfolk rabbits with approximately 3 months of age were divided into two equal groups after excision of ligamentum teres (LT) from the right hip joint: G1-no reconstruction of LT and capsulorrhaphy; G2-double-bundle reconstruction of the LT using semitendinosus tendon autograft. In both groups, the LT was removed from the right hip joint. In G2 the autograft was harvested from the left hind limb of the same rabbit. The rabbits were evaluated clinically at different time intervals; before surgery (M1), 48 h (M2), 15 days (M3), 30 days (M4) and 90 days (M5) after surgery.

Results

The rabbits supported their limbs on the ground in both the groups. As complications of the procedure, four hip joints showed subluxations in the radiographic evaluation of G1; three at M4 and one at M5. In G2; two luxations of hip joints at M3 and one subluxation at M4 were seen. On ultrasound, irregular articular surface was seen in 30.8% of the rabbits that had subluxation of hip joints. Gross evaluation identified tendon graft integrity in 76.92% of the rabbits. Histological analysis revealed graft adhesion to the bone in the early phase comprised of sharpey-like collagen fibers.

Conclusion

The double-bundle reconstruction of the LT using autologous semitendinosus tendon associated with the toggle rod shows an early phase of tendon graft ligamentization at 90 days post-operatively in young rabbits, but biomechanical bias suffered by the tendon during gait must be considered.

Exotic Mammal Orthopedics

Orthopedic disorders are a common clinical presentation for the exotic clinician. Before treating the fracture it is vital to stabilize the patient. Small exotic mammals are characterized by relatively thinner bones, adding to the difficulty the small size already represents. A combination of conservative and surgical treatment options are available. The principles of orthopedic surgery and ideas behind the treatment options remain the same as for small mammals, but not all techniques can be directly extrapolated. Historically, the tie-in fixator has been the preferred surgical choice whenever feasible, but further development in bone plates represents a promising advancement.