Intramedullary Screws for Metatarsal Fractures May Injure the Flexor Tendons: A Cadaveric Study

Research Type: Level 4 – Case series Introduction/Purpose: Intramedullary screws are becoming a fixation option for management of metatarsal fractures, though there has been limited literature to date on their use. One potential complication associated with their use is the possibility of flexor tendon injury. The purpose of this study is to determine the frequency and amount of flexor tendon disruption associated with intramedullary screw fixation for metatarsal fractures. Methods: Seven left and right lower extremity cadaver specimens were procured. The 2nd through 5th metatarsals (MT) were pinned with a guidewire, and drilled retrograde with a 2.7 millimeter (mm) drill. A 3.6 mm metatarsal screw was then inserted. The plantar surface of the specimens was then exposed to visualize the flexor tendons. The tendon location relative to the drill hole, incidence of tendon disruption, percentage of tendon disruption, and the distance between the tendon and the drill hole were measured. Results: Overall, 21/56 (37.5%) flexor tendons were damaged, 5 in the 2nd MT, 7 in the 3rd, 9 in the 4th, and 0 in the 5th. The hit rates for the 2nd, 3rd, 4th, and 5th MT were 35.7%, 50%, 64.3%, and 0%, and the percentage of tendon disruption was 15%, 11%, 11%, and 0%, respectively. The mean distance from uninjured tendons to the drill hole was 1.07 mm, 0.94 mm, 0.9 mm, and 2.03 mm in the 2nd-5th MT, respectively. The majority of flexor tendons were found medial to the drill hole across all metatarsals. Conclusion: The insertion of intramedullary screws for fixation of metatarsal fractures is associated with a high rate of flexor tendon injury (37.5%), most commonly in the 4th metatarsal. No flexor tendon injuries were observed in the 5th MT. The percentage of flexor tendon injury involves roughly 10-20% of the width of the tendon. Adjusting the start point to a slightly more lateral position if possible may minimize the risk of flexor tendon injury, and patients should be counseled on the possibility of flexor tendon rupture postoperatively. Flexor Tendon Disruption and Location Relative to Screw Hole