Effectiveness of a Superelastic Nitinol Device for Fixation of Syndesmosis in Ankle Fracture

CATEGORY: Ankle; Trauma INTRODUCTION/PURPOSE: Syndesmosis injuries are increasingly common. Available fixation options are not yet optimal. The PUMA System (Panther Orthopedics, Sunnyvale, CA) is an FDA-cleared superelastic, nitinol-based fixation device for the ankle syndesmosis which provides stabilization without over-compression or loosening during cyclical loading. The spring-like design of the PUMA System allows physiological micro-motion while maintaining continuous compression and resisting syndesmosis widening, without material creep. The objective of this prospective study is to assess the effectiveness and complication rate of the PUMA device for treatment of fracture-associated syndesmosis injuries. METHODS: We prospectively collected radiographic and clinical data on 32 consecutive patients treated for fracture-associated syndesmotic disruption with the PUMA System(TM) at 8 centers. Primary outcome measures included adverse event rates, radiographic evaluations for syndesmosis integrity and implant failure, and rates of revision surgery. RESULTS: All 32 patients had successful repair of their ankle syndesmosis (Figure 1). The mean age of patients at time of operation was 42 years (range 16- 68). There were 13 females (13/32, 40.6%) and 19 (19/32, 59.4%) males. Postoperative radiographic evaluations confirmed satisfactory syndesmosis healing with maintained reduction in the ankle mortise in 33/33 (100%) ankles. There was no evidence of lysis, device migration or syndesmotic or medial clear space widening. There were no infections or soft tissue complications. All fractures healed. No devices required removal and there were no revision surgeries. CONCLUSION: The PUMA System(TM) provides physiologic stabilization of the syndesmosis due to the design features that allow for continuous compression without creep. We found no device-related complications nor construct failures in our series. The superelastic implant design allows physiologic motion at the syndesmosis but does not creep or stretch following displacement. This flexibility obviates the need for routine removal. The implant's low-profile buttons without suture and knot tying requirements eliminate the concern for subcutaneous knot irritation and slippage. Additional biomechanical and clinical outcomes study of this device may further optimize rehabilitation protocols for patients treated for syndesmotic injury.