4DCT Imaging for Improved Diagnosis and Treatment of Wrist Ligament Injuries

Aim 1:

40 cadaveric forearm/hand specimens will be obtained from the Mayo Clinic Anatomical Bequest program. 10 will be used to refine the ligament injury model and 30 will be used as follows. The specimens will undergo radiographic screening and will be excluded from the study if they have evidence of fracture, bony trauma, significant arthritic changes, or previous surgeries. The tendons will be loaded. The remaining soft tissues will be dissected from the proximal ulna and radius. Polymethylmethacrylate (PMMA) resin will be used to affix the proximal radius and ulna in a circular acrylic fixture. The custom wrist motion simulator was designed to generate muscle-assisted flexion-extension and radial-ulnar deviation movements and is CT-compatible. Each tendon will be dynamically loaded with a constant 10 N, maintained throughout the movement in the following conditions: wrist flexion-extension and radial-ulnar deviation. The hand will be fixed in a grip that is connected to a programmable linear actuator. The linear actuator drives the grip back-and-forth along the x-axis with free-motion along the z-axis. The linear actuator will be programmed to allow the wrist to perform a full radial-ulnar or flexion-extension motion at 30 deg/sec which simulates in vivo wrist motion speeds. A motion cycle is approximately 2 seconds. The wrist will be cycled 100 times in flexion-extension prior to each testing condition. A static CT image will be acquired in the neutral posture. Then, each wrist will be imaged using 4DCT during flexion-extension and radial-ulnar deviation, in the following conditions: intact (control), volar SLIL cut, membranous SLIL cut, dorsal SLIL cut, radioscaphocapitate ligament cut, and long radiolunate ligament cut.

Aim 2:

4DCT scanning will be performed bilaterally on 60 patients (30 males, 30 females) with unilateral SLIL injury who are scheduled to undergo a surgical intervention. In addition, patients will have pre-surgical volar and dorsal arthroscopic confirmation of ligament injury, categorized by Geissler and European Wrist Arthroscopy Society (EWAS) classifications; video recording of the arthroscopy will be obtained for later analysis. PRWE and VAS questionnaires will be completed at the 4DCT visit for the injured wrist and the Total Patient Rated Wrist Evaluation (PRWE) score (sum of pain and function subscales) and composite change in Visual Analog Pain Scale (VAS) score used in the analysis. 4DCT wrist data will be obtained while the subjects perform flexion-extension and radial-ulnar deviation. The dynamic image sequence will be processed with existing software tools to obtain metrics describing the interosseous distances between the articular surfaces of the scaphoid, lunate, and radius, during the movement cycles. Given the difficulty of diagnosing SLIL injury, the uninjured contralateral wrist is often used as a "control" for comparison by physicians; therefore, the difference in right/left metrics will be used in the study.

Aim 3:

The same 60 patients ( see Aim 2) will be evaluated. Surgeons will assess pre-surgical scapholunate interosseus distances (quantified using 4DCT in Aim 2) and document a treatment plan to address the particular injury. Subsequently, 4DCT-based treatment plans will be compared with arthroscopic evaluation (obtained in Aim 2); any existing wrist x-rays (e.g. AP, lateral, stress views) and MRIs may be used in this comparison as well. The surgeon will then select and perform the targeted surgical intervention based on both 4DCT and arthroscopic findings. 4DCT will be performed, and the PRWE and VAS completed by patients at 1 year postoperatively; quantification of radioscaphoid contact patterns will be assessed during bilateral wrist flexion-extension and radial-ulnar deviation to determine if normal patterns of motion are restored.