Objectives

Small animal models of fracture repair primarily investigate indirect fracture healing via external callus formation. We present the first described rat model of direct fracture healing.

Percutaneous stabilisation of tibial fractures by locking plates has become an accepted form of osteosynthesis. A potential disadvantage of this technique is the risk of damage to the neurovascular bundles in the anterior and peroneal compartments. Our aim in this anatomical study was to examine the relationship of the deep peroneal nerve to a percutaneously-inserted Less Invasive Stabilisation System tibial plate in the lower limbs of 18 cadavers. Screws were inserted through stab incisions. The neurovascular bundle was dissected to reveal its relationship to the plate and screws.

In all cases, the deep peroneal nerve was in direct contact with the plate between the 11th and the 13th holes. In ten specimens the nerve crossed superficial to the plate, in six it was interposed between the plate and the bone and in the remaining two specimens it coursed at the edge of the plate.

Percutaneous insertion of plates with more than ten holes is not recommended because of the risk of injury to the neurovascular structures. When longer plates are required we suggest distal exposure so that the neurovascular bundle may be displayed and protected.

Intramedullary tibial nailing was performed in ten paired cadavers and the insertion of a medial-to-lateral proximal oblique locking screw was simulated in each specimen. Anatomical dissection was undertaken to determine the relationship of the common peroneal nerve to the cross-screw.

The common peroneal nerve was contacted directly in four tibiae and the cross-screw was a mean of 2.6 mm (1.0 to 10.7) away from the nerve in the remaining 16. Iatrogenic injury to the common peroneal nerve by medial-to-lateral proximal oblique locking screws is therefore a significant risk during tibial nailing.

We made a prospective study of 208 patients with tibial fractures treated by reamed intramedullary nailing. Of these, 11 (5.3%) developed dysfunction of the peroneal nerve with no evidence of a compartment syndrome. The patients with this complication were significantly younger (mean age 25.6 years) and most had closed fractures of the forced-varus type with relatively minor soft-tissue damage. The fibula was intact in three, fractured in the distal or middle third in seven, with only one fracture in the proximal third. Eight of the 11 patients showed a ‘dropped hallux’ syndrome, with weakness of extensor hallucis longus and numbness in the first web space, but no clinical involvement of extensor digitorum longus or tibialis anterior. This was confirmed by nerve-conduction studies in three of the eight patients. There was good recovery of muscle function within three to four months in all cases, but after one year three patients still had some residual tightness of extensor hallucis longus, and two some numbness in the first web space. No patient required further treatment