Safe corridors for external skeletal fixator pin placement in feline long bones.

Abstract

External skeletal fixation is an established technique in cats for biological fixation of long bone fractures, stabilisation of the joints, and treatment of shearing injuries and angular deformities. As appropriate and accurate pin insertion is imperative for a successful outcome, knowledge of topographic anatomy and areas that are safe (safe corridors) for pin placement is integral to successful surgery. At present, however, safe corridors have not been determined fully in feline orthopaedics, with surgeons having to rely on knowledge based on canine orthopaedics. This study was performed to determine safe corridors for pin placement in feline long bones. The limbs of six feline cadavers were frozen. Only limbs with no history of orthopaedic conditions were used. Transverse sections through the limbs were examined, and anatomical structures were determined in relation to the bone. These structures were compared with those of the contralateral limbs, which were dissected for topographic assessment. Safe corridors were defined as topographic areas where no vital structures, muscles or joints were present. Examination of the humerus revealed safe corridors at its proximal craniolateral aspect and on the medial and lateral humeral condyles. Safe corridors of the antebrachium were identified on the lateral aspect of the olecranon, the distal two-thirds of the medial antebrachium and the distal third of the lateral antebrachium. Safe corridors in the femur consisted of a small area lateral to and just below the major trochanter, and on the medial and lateral femoral condyles. Evaluation of the tibia revealed safe corridors on the medial aspect of the entire tibia, the cranial aspect of the proximal tibia on the tibial crest and the area just proximal to the lateral malleolus. Safe corridors for pin placement during external skeletal fixation in feline limbs differed from those in canine limbs. Knowledge of canine anatomy may be inapplicable to pin placement in feline limbs undergoing external skeletal fixation.