Session II - Foot and Ankle

Lag Screw Fixation of the Lateral Malleolus

Paul Tornetta, III, MD, Boston University Medical Center, Boston, MA; Steve Nguyen, MD; Claude Scott, MD, State University of New York Health Science Center at Brooklyn, Brooklyn, NY

Purpose: Fixation of the lateral malleolus is typically performed with plate osteosynthesis. However, laterally placed plates are frequently palpable and cause irritation in many patients. Minimal fixation of the lateral malleolus through a smaller incision, if stable, would be an advantage. The purpose of this study was to evaluate the efficacy of lag-screw-only fixation of the lateral malleolus in unstable ankle fractures.

Methods: A series of 47 ankle fractures meeting specific inclusion criteria were treated with lag-screw-only fixation of the lateral malleolus. This represented 34% of the ankle fractures fixed during the study period. To be included, the fracture had to be a simple oblique pattern without significant comminution that was long enough to accept at least two lag screws placed with 1 cm between them. Patients older than 50 were excluded. All screws were placed from anterior to posterior. There were 24 isolated lateral malleolar fractures with deltoid incompetence, 23 ligamentous SE4 (OTA 44-B2.1), 18 bimalleolar SE4 fractures (OTA 44-B2.2), and 6 PE4 (OTA 44-C1.1). Medial malleolar fractures were treated with ORIF using lag screws, and deltoid incompetence was treated closed. Postoperative management included a short leg cast for 3 - 6 weeks followed by ankle mobilization in an aircast. Weight-bearing was initiated at 6 weeks if the syndesmosis was intact and at 10 - 12 weeks if it was fixed. A comparison group by fracture type in which a plate was used laterally was chosen at random from those who had complete followup.

Results: All fractures in the study group had an anatomically reduced mortise. Thirty-five fractures were fixed with 2 lag screws, 10 with 3 lag screws, and 2 with 4 lag screws. The incision used for lag screw placement was shorter (average 30%) and more anterior than in the comparison group. The curvilinear anterior incision enabled easier lag screw placement without tension on the anterior soft tissues. The average time required for fixation of the lateral malleolus was 13 minutes. All fractures united without loss of reduction and there were no soft tissue complications. Followup averaged 1.6 years for 42 patients (4 lost). Upon questioning, only one patient (2 %) had any complaints of lateral pain as compared with 17% the plate group. No patient had palpable hardware as compared to 56 % of the plate group, and none had any restriction in shoe wear due to irritation over hardware as compared with 15% of the plate group.

Discussion: Operative fixation of the oblique lateral malleolus fractures is most commonly performed with a combination of lag screws and a lateral plate. These plates are often palpable and can cause irritation over the hardware, sometimes requiring removal to allow for freedom of shoe wear. The use of screw-only fixation allowed for a smaller incision and decreased patient complaints compared to a similar group of patients fixed with a lateral plate. No modification of the standard rehabilitation protocol was required. All fractures in this series healed without loss of reduction and lateral complaints were virtually eliminated.

Conclusion: Lag screw-only fixation of oblique distal fibular fractures that are a component of an unstable ankle injury is safe and effective. Patient complaints of lateral pain after treatment of unstable ankle injury can be diminished by the use of this technique.