Morphology of the tibialis anterior muscle and its implications in minimally invasive plate osteosynthesis of tibial fractures.

We examined the variation in the origin of the tibialis anterior muscle from the lateral aspect of the tibial shaft and interosseous membrane as well as the variation in the morphology of its musculotendinous junction. Forty cadaveric lower leg specimens (20 right and 20 left) were dissected to reveal the anterior compartment. The origin of the tibialis anterior muscle and its relation to the lateral tibial shaft and interosseous membrane were determined. The position of the musculotendinous junction relative to the medial malleolus was also measured. Tibial length ranged from 29.5 to 45 cm (mean, 36.5+/-3.1 cm). The distal limit of the muscle origin was 5.9 to 20.5 cm (mean, 12.1+/-3.3 cm) from the tip of the medial malleolus. The distance between the musculotendinous junction and the medial malleolus ranged from 1.4 to 10.8 cm (mean, 6.1+/-1.9 cm). The attachment of the muscle belly ends between 15.3 and 31.8 cm (mean, 24.4+/-4.1 cm) distally from the joint line at the knee. There was no statistical correlation between tibial length and muscle morphology.This variation warrants consideration in the percutaneous insertion of screws in the distal end of long plates, as the neurovascular bundle may be injured in patients with a shorter muscle belly. We advocate an open distal approach to protect the neurovascular bundle during insertion of the plate and distal screws.