Carpal tunnel expansion by palmarly directed forces to the transverse carpal ligament.

This study investigated the expansion of the carpal tunnel resulting from the application of palmarly directed forces to the transverse carpal ligament (TCL) from inside the carpal tunnel. Ten fresh-frozen cadaveric hands were dissected to evacuate the carpal tunnel, and thus to expose the TCL. A custom lever device was built to apply forces, ranging from 10 N to 200 N, to the TCL. Without force application, the carpal tunnel area was 148.4+/-36.8 mm2. The force application caused the TCL to form arches with an increase in cross-sectional areas of 33.3+/-5.6 mm2 at 10 N and 48.7+/-11.4 mm2 at 200 N, representing respective increases of 22.4% and 32.8% relative to the initial carpal tunnel area. The TCL length remained constant under the applied forces. It was found that the TCL arch formation was due to the narrowing of the arch width, which resulted from the migration of the bony insertion sites of the TCL. A geometrical model of the carpal tunnel was then developed to elucidate the relationships among the arch width, TCL length, arch height, and arch area. The model illustrated the effectiveness of carpal tunnel expansion by TCL elongation or arch width narrowing.

Finger joint motion generated by individual extrinsic muscles: a cadaveric study.

BACKGROUND: Our understanding of finger functionality associated with the specific muscle is mostly based on the functional anatomy, and the exact motion effect associated with an individual muscle is still unknown. The purpose of this study was to examine phalangeal joints motion of the index finger generated by each extrinsic muscle. METHODS: Ten (6 female and 4 male) fresh-frozen cadaveric hands (age 55.2 +/- 5.6 years) were minimally dissected to establish baseball sutures at the musculotendinous junctions of the index finger extrinsic muscles. Each tendon was loaded to 10% of its force potential and the motion generated at the metacarpophalangeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints was simultaneously recorded using a marker-based motion capture system. RESULTS: The flexor digitorum profundus (FDP) generated average flexion of 19.7, 41.8, and 29.4 degrees at the MCP, PIP, and DIP joints, respectively. The flexor digitorum superficialis (FDS) generated average flexion of 24.8 and 47.9 degrees at the MCP and PIP joints, respectively, and no motion at the DIP joints. The extensor digitorum communis (EDC) and extensor indicis proprius (EIP) generated average extension of 18.3, 15.2, 4.0 degrees and 15.4, 13.2, 3.7 degrees at the MCP, PIP and DIP joints, respectively. The FDP generated simultaneous motion at the PIP and DIP joints. However, the motion generated by the FDP and FDS, at the MCP joint lagged the motion generated at the PIP joint. The EDC and EIP generated simultaneous motion at the MCP and PIP joints. CONCLUSION: The results of this study provide novel insights into the kinematic role of individual extrinsic muscles.

Complex, multidimensional thumb movements generated by individual extrinsic muscles.

The objective of this study was to investigate three-dimensional thumb joint movements produced by individual extrinsic thumb muscles. Ten cadaveric arms were dissected to expose the musculotendinous junctions of the flexor pollicis longus (FPL), abductor pollicis longus (APL), extensor pollicis brevis (EPB), and extensor pollicis longus (EPL). Each muscle/tendon was loaded to 10% of its maximal force capability whereas three-dimensional angular movements of the carpometacarpal (CMC), metacarpophalangeal (MCP), and interphalangeal (IP) joints were obtained simultaneously. We found that each extrinsic muscle produced unique joint angular trajectories in multiple directions. The FPL, APL, EBP, and EPL generated two, two, three, and six movements, respectively. The extrinsic muscles all together generated eight movements among the multiple thumb joints. High interjoint coordination was shown between the MCP joint flexion and IP joint flexion by FPL loading, as well as between the MCP joint extension and IP joint extension by EPL loading. High intrajoint coordination was observed between extension and supination at the CMC joint by the APL, EPL, and EPB. We concluded that each muscle produces movements in multiple joints and/or in multiple anatomical directions. The findings provide a novel insight into the biomechanical roles of the extrinsic muscles of the thumb.

Anatomic double-bundle anterior cruciate ligament reconstruction revision surgery.

With the increasing number of double-bundle anterior cruciate ligament (ACL) reconstructions being performed, revision cases are expected. This report describes the first 3 cases of revision double-bundle ACL surgeries performed at our institution. In 3 athletes in whom the ACL was previously reconstructed with an anatomic double-bundle technique, new traumatic events occurred and an ACL retear was diagnosed. In cases 1 and 2 the anteromedial (AM) bundle was completely torn and the posterolateral (PL) bundle was stretched and nonfunctional. In case 1 both bundles were reconstructed via the previous tunnels, and the AM and PL grafts were tensioned at 60 degrees of flexion and full extension, respectively. In case 2 the PL femoral tunnel was posterosuperior to the PL anatomic position. Therefore we drilled a third femoral tunnel and used the previous PL tunnel as our new AM tunnel. In case 3 the rupture pattern presented an intact and functional PL bundle and a midsubstance AM tear. We decided to revise only the AM bundle using the previous AM tunnels, which were anatomically positioned. This report shows that revision of anatomic double-bundle ACL reconstruction is reasonable to accomplish and that the principles of anatomy are essential as a guide to approaching each case.