Kazuya Tamai

Different scapular kinematics in healthy subjects during arm elevation and lowering: Glenohumeral and scapulothoracic patterns

HYPOTHESIS The scapulothoracic (ST) joint affects glenohumeral (GH) joint function. We observed 3-dimensional scapular motions during arm elevation and lowering to identify the scapulohumeral rhythm in healthy subjects and to compare it between the dominant and nondominant arms. MATERIALS AND METHODS Twenty-one healthy subjects participated in this study. Participants randomly elevated and lowered the arms in the scapular plane, and data were recorded by a computerized 3-dimensional motion analyzer at each 10 degrees increment. RESULTS Of the 42 shoulders, 21 showed a greater ratio of GH motion relative to ST motion whereas the other 21 showed a smaller ratio of GH motion relative to ST motion. The angle of upward rotation of the scapula showed a statistically significant difference between both types. The mean maximum angles of upward rotation, posterior tilting, and internal rotation were 36.2 degrees +/- 7.0 degrees , 38.7 degrees +/- 5.7 degrees , and 36.8 degrees +/- 12.2 degrees , respectively. No significant difference was found in angles of 3 scapular rotations between the dominant and nondominant arms. DISCUSSION These results indicate that there are 2 distinctly different scapulohumeral rhythms in healthy subjects but without a significant difference between dominant and nondominant arms. These findings should be referred to when one is interpreting kinematics in a variety of shoulder disorders.

Primary frozen shoulder: brief review of pathology and imaging abnormalities

BackgroundPrimary frozen shoulder (FS) is a painful contracture of the glenohumeral joint that arises spontaneously without an obvious preceding event. Investigation of the intra-articular and periarticular pathology would contribute to the treatment of primary FS.Review of literatureMany studies indicate that the main pathology is an inflammatory contracture of the shoulder joint capsule. This is associated with an increased amount of collagen, fibrotic growth factors such as transforming growth factor-beta, and inflammatory cytokines such as tumor necrosis factor-alpha and interleukins. Immune system cells such as B-lymphocytes, T-lymphocytes and macrophages are also noted. Active fibroblastic proliferation similar to that of Dupuytren’s contracture is documented. Presence of inflammation in the FS synovium is supported by the synovial enhancement with dynamic magnetic resonance study in the clinical setting.ConclusionPrimary FS shows fibrosis of the joint capsule, associated with preceding synovitis. The initiator of synovitis, however, still remains unclear. Future studies should be directed to give light to the pathogenesis of inflammation to better treat or prevent primary FS.

Stability of volar locking plate systems for AO type C3 fractures of the distal radius: biomechanical study in a cadaveric model

BackgroundThe purpose of the present study was to compare the relative stability of five volar locking plates (all of which are available for the treatment of intraarticular fractures of the distal radius) under loading conditions simulating the physiological forces that occur during early active mobilization.MethodsFive plating techniques were applied to surgically simulated AO type C3.2 distal radius fractures in formalin-fixed cadavers. The specimens were tested with a servohydraulic materials testing machine with 250 N of axial compression load for 3000 cycles. After cyclic loading, the specimens were loaded until they demonstrated failure in axial compression. The five fixation systems studied included a DRV locking plate (group 1), a Stellar plate (group 2), an Acu-Loc plate (group 3), AO Locking Distal Radius System 2.4 (group 4); and a Matrix SmartLock plate (group 5).ResultsNone of the plate fixations tested failed during the cyclic loading. Group 2 had a higher elastic limit than groups 4 and 5. There were no significant differences among the five groups for the failure load. Failure occurred at the distal portion of the fixation system, at the ulnar side locking pin, or the locking screw was bent (groups 1, 2, 3); the ulnar side locking screw was broken (groups 3, 4); the locking screw became loose (group 4); and the ulnar side locking screw was uncoupled from the screw hole (group 5).ConclusionsAll of the five volar plate fixation systems provided sufficient stability to permit 3000 repeated motions of the digits after surgery for AO type C3 distal radius fractures.

Rapid destruction of the humeral head due to bone fragility: report of two cases

Rapid destruction of the femoral head has been well understood since Postel’s report in 1970 [1]. This condition occurs mostly in elderly women, and considerable concern has been directed to the subchondral insufficiency fracture as a cause of femoral head collapse [2]. In contrast, rapid destruction of the humeral head is rare; only one case of nonnecrotic humeral head collapse is reported in the literature [3]. We treated two patients whose humeral head collapse was most possibly due to an insufficiency fracture. The patients and/or their families were informed that data from the case would be submitted for publication and gave their consent.

Proximal Humeral Fractures: Classification and Treatment

Proximal humeral fractures account for 4–5 % of all fractures, with the higher incidence in women. The AO/ASIF system and the Neer’s four-segment classification are used to record the fracture anatomy. The Neer’s classification is more appropriate to provide an anatomic basis for guiding treatment regimens.