H.6 Surgical implant to treat a common wrist injury
There are 8 bones in the human wrist. Painless, full range of motion of the wrist demands that these bones move together in concert. (Kamal et al., 2016) Coordinated movement of the bones is made possible by ligaments connecting them. Two wrist bones, the scaphoid and the lunate, and the scapholunate (SL) ligament between them, form a clinically relevant complex. The SL ligament is frequently ruptured during falls on an outstretched hand. The resulting injury results in pathologic, independent motion of the scaphoid and lunate. This is acutely limiting and may precipitate painful arthritis if left untreated.
There is no routinely effective treatment for SL ligament injuries. Attempts to repair the SL ligament with sutures frequently fail. (Rohman et al., 2014) Attempts to replace (“reconstruct” to hand surgeons) the torn ligament are similarly unpredictable. Until a repaired or reconstructed ligament heals, the SL interval needs to be immobilized. Orthopedic hardware currently used to immobilize the SL interval is inadequate. This shortcoming is likely responsible for the frequent failure of SL ligament repair or reconstruction.
The intact SL ligament resists distracting and rotational forces. (Dimitris et al., 2015) Any implant used to support a healing SL ligament would, ideally, do the same. Wires, and less commonly screws, are currently used to immobilize the SL interval. These implants resist distraction (screws) or torque (wires) but not both.
An implant at the SL interval would have to be specially designed to avoid impingement on the surrounding bones.
Any implant used at the SL interval would ideally immobilize the SL interval only temporarily or be easily removable. This would allow for restoration of natural motion once a repaired or reconstructed ligament healed.
The goal is to develop an orthopedic implant to effectively support SL ligament repair or reconstruction. Such an implant would make SL repair or reconstruction predictable.
I have clinical experience with SL injuries and with several different surgical strategies. I have studied different implants in cadavers, and I have used a novel implant clinically. I have access to patients with this injury, access to a cadaver lab, and access to biomechanical testing equipment.
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