The anterior band of the inferior glenohumeral ligament: biomechanical properties from tensile testing in the position of apprehension.

The shoulder is the most commonly dislocated joint in the body. The primary restraint to anterior instability is the anterior band of the inferior glenohumeral ligament, where lesions are found after dislocation. The amount of surgical plication required to eliminate instability and maintain full range of shoulder motion remains unclear. We performed tensile testing with the shoulder in abduction and external rotation in 11 human, fresh-frozen, cadaveric glenohumeral joints to improve understanding of the glenoid origin of the anterior band of the inferior glenohumeral ligament and to quantify midsubstance irrecoverable elongation. After measuring the length, width, and thickness of the anterior bands with digital micrometry, biomechanical properties were obtained on bone-ligament-labrum-bone (b-l-l-b) complexes. The complexes were aligned for tensile testing with the humerus abducted 60 degrees and externally rotated. The b-l-l-b complexes were then loaded to failure at a strain rate of 100%/sec. Seven of the complexes failed at the glenoid insertion site (representing the Bankart lesion), 2 at the humeral insertion site, and 2 at the anterior band midsubstance. The ultimate load for the b-l-l-b complexes was 353+/-32 N (mean+/-SE), and tensile stress at failure of the glenoid insertion site averaged 9.6+/-2.1 MPa. When the complex failed at the glenoid insertion site, total elongation of the b-l-l-b complex was 9.1+/-0.5 mm, and the ligament midsubstance strain was 13.0%+/-1.8%. Irrecoverable elongation was only 0.8 mm when failure occurred at the glenoid insertion site. Our results indicate patients with initial anterior glenohumeral instability have small irrecoverable capsuloligamentous elongation so that meaningful plication in addition to repair of the Bankart lesion may be unnecessary.

Evaluation of a proprioception pathway in patients with stable and unstable shoulders with somatosensory cortical evoked potentials.

Histologic studies have documented the presence of mechanoreceptors in the glenohumeral ligaments, capsule, and labrum; however, direct evidence of an intact afferent electrical pathway originating in structures in the shoulder is lacking. Because somatosensory cortical evoked potentials are transmitted by way of the dorsal columns of the spinal cord and carry proprioceptive information, this technique can be easily applied to evaluate the potential proprioceptive function of various intraarticular structures for shoulder stability. Patients have somatosensory cortical evoked potentials monitored while undergoing shoulder arthroscopy. The inferior glenohumeral ligament, middle glenohumeral ligament, subscapularis tendon, biceps tendon, supraspinatus rotator cuff capsule, glenoid labrum, and humeral head were evaluated. The intraarticular structures were stimulated with a monopolar electrode probe inserted through the anterior portal, and the evoked potentials were recorded with scalp electrodes. Generated wave forms were recorded and evaluated by measuring the peak-to-peak amplitude and latency. Three groups of patients with shoulder complications were studied: (1) no intraarticular pathologic condition and stable, (2) anterior instability with a Bankart lesion, and (3) anterior instability with a loose capsule. The articular cartilage of the humeral head generated no wave form in any subject. All other intraarticular structures generated consistent wave forms. No statistically significant difference was seen among the three groups when both amplitude and latency for the intraarticular structures were compared.

Excision and disassembly of sperm tail microtubules during sea urchin fertilization: requirements for microtubule dynamics.

To determine the fate of the sperm tail during fertilization, the microtubules of the incorporated axoneme are measured using a monoclonal antibody against acetylated alpha-tubulin in zygotes from the sea urchin Strongylocentrotus purpuratus. This antibody recognizes axonemal microtubules, but does not recognize egg cytoplasmic tubulin or microtubules. The detachment of the axoneme from the male pronucleus occurs as early as 15 min post-insemination. Following excision, the axoneme is often found in close association with the female pronucleus during its migration to the male pronucleus. Fragmentation of the sperm tail, detected at 25 min, continues with only a few micrometers remaining at 85 min post-insemination. The fluorescence intensity of the axonemal fragments diminishes over time as compared to intact axonemes. At 100 min post-insemination, the sperm axoneme is no longer detected. Alternative imaging approaches using brief cold or elevated calcium extraction to disrupt the labile cytoplasmic, but not axonemal, microtubules, indicate that these observations are not due to changes in the post-translational modifications of alpha-tubulin. In the presence of nocodazole, a microtubule assembly inhibitor, a large portion of the tail remains visible at 100 min post-insemination; this suggests that microtubule dynamics are required for the disassembly of the sperm tail. Furthermore, the detachment of the axoneme from the male pronucleus requires the formation of the sperm aster. This suggests that the sperm aster microtubules both detach the axoneme from the male pronucleus, and also cause the translocation of the tail towards the female pronucleus after pronuclear union. In summary, the sperm tail is excised from the male pronucleus and the tail microtubules disassembled during the first cell cycle of sea urchin fertilization, and these events require new microtubule assembly within the zygote.

Imaging and graphics in medicine: concept of an object-oriented platform for clinical research.

We present a workstation-based research platform with two major components. A turnkey application system provides a functionality kernel for a broad community of clinical users with an interest in digital imaging. A development toolbox allows efficient implementation of research ideas and consistent integration of new applications with the common framework of the turnkey system. The platform is based on an elaborate object class structure describing objects for image processing, computer graphics, study handling and user interface control. Thus expertise of computer scientists familiar with this application domain is brought into the hospital and can be readily used by clinical researchers.

The thoracic outlet syndrome.

The thoracic outlet syndrome is a compressive neurovascular condition of the upper extremity. The neurologic, arterial, and venous structures may be affected individually or in combination in any given patient. Multiple surgical and medical subspecialists may be involved in the care of these patients, including orthopedic, vascular, and thoracic surgeons, neurosurgeons, and neurologists. The topic is extremely controversial; some authors believe that this is a very common condition, while others question the existence of the syndrome. There is disagreement concerning the diagnosis, workup, and proper therapeutic management. The purpose of this article is to critically review and analyze the literature on this subject.

Old displaced fracture of the scaphoid. An unusual cause of carpal tunnel syndrome.

The case of a 37-year-old man with carpal tunnel syndrome and a palpable mass in the proximal wrist is reported. Roentgenograms revealed an old middle-third scaphoid fracture with the proximal pole displaced into the proximal carpal tunnel. Excision of this mass led to a complete resolution of the patient's carpal tunnel problem.