SLR - December 2020 - Gabrielle Lee
Biomechanical Testing of a Transmetatarsal Base Screw in Lisfranc Injuries
Reference: Fitzpatrick S, Bologna M, Reynolds A, Schimoler P, Smolinski A, Kharlamov A, Westrick E, Miller M. Biomechanical Testing of a Transmetatarsal Base Screw in Lisfranc Injuries. J Orthop Trauma. 2020 Nov; 34 (11), 420-423.
Level of Evidence: V
Scientific Literature Review
Reviewed By: Gabrielle Lee, DPM
Residency Program: Montefiore Medical Center – Bronx, NY
Podiatric Relevance: Lisfranc injuries are one of the more common podiatric injuries missed in the acute care setting. Untreated lisfranc injuries can lead to chronic pain, progressive deformity, and dysfunction of the foot. Lisfranc injuries can be osseous, purely ligamentous, or both. Open reduction internal fixation or primary arthrodesis are the most commonly employed techniques for surgical management. Studies have shown that primary arthrodesis of purely ligamentous Lisfranc injuries have resulted in better outcomes. The authors of this article investigated the differences between the traditional “homerun” screw and the transmetatarsal screw in providing stability across the Lisfranc joint in cadaveric models.
Methods: Eight pairs of cadaveric feet had the dorsal and interosseous Lisfranc ligaments transected at the medial cuneiform (C1) and first metatarsal (M1), at the medial cuneiform to second metatarsal (M2), and at the middle cuneiform (C2) and second metatarsal. All feet underwent standard fixation with 3.5mm fully cannulated screws between C1 and M1 and between C2 and M2. One foot from each pair was randomly fixated with Lisfranc “homerun” screw (LIS) from the C1 to M2, or the transmetatarsal screw (TMT) between the bases of M1 and M2. Markers were placed on the dorsum of M1/M2 and C1/C2 to measure displacements at four locations (C1-M1, C2-M2, M1-M2, and C1-M2). All feet were loaded on the plantar forefoot to 100N, 400N, 800N, and 1100N, representing non weight-bearing, partial weight-bearing, full weight-bearing, and overload of active movement, respectively.
Results: There was a statistically significant difference between the two repair types in the displacement at the Lisfranc joint between medial cuneiform and second metatarsal base. No statistical significance was found in the other three articulations. Less displacement was seen in the samples with the transmetatarsal screw than that of the “homerun” screw with the most significant reduction in displacements at 1100 N.
Conclusions: The authors concluded that a transmetatarsal screw construct provides better stability across the Lisfranc joint and prevents displacement between C1 and M2 more effectively. The displacement of the Lisfranc joint is along the same axis as the “homerun” screw which is only resisted by the screw threads. However, a transmetatarsal screw can provide a resistant force that is closer to the perpendicular axis of the Lisfranc joint which, in turn, increases the rigidity and stability of the C1-M1-M2-C2 construct. The transmetatarsal screw can also be utilized in injuries with significant medial cuneiform comminution or constructs with heavy screw traffic preventing placement in the medial cuneiform. However, it is unclear how this fixation technique will be tolerated in patients which is a limitation of this cadaveric study. Primary arthrodesis of the tarsometatarsal joints would still be the technique of choice in purely ligamentous Lisfranc injuries in my practice as it was shown to have better outcome, patient satisfaction, and less instances of second procedure for hardware removal. However, I may consider incorporating a transmetatarsal screw technique in primary arthrodesis to further strengthen the construct which may reduce the incidences of nonunion.