An anthropometric analysis to derive formulae for calculating the dimensions of anatomically shaped humeral heads.

BACKGROUND: The elliptical shape of the humeral head has been vaguely described, but a more detailed mathematical description is lacking. The primary goal of this study was to create formulae to describe the mathematical relationships between the various dimensions of anatomically shaped humeral heads. METHODS: Three-dimensional computer models of 79 proximal humeri derived from computed tomography scans (white subjects, 47 male and 32 female; ages, 17-87 years) were studied. Linear regression analysis of the obtained humeral measurements was performed, and Pearson correlation coefficient (R) values were calculated. To substantiate the results of the linear regression analysis, Welch t-test was used to compare various parameters of small, medium, and large humeral heads. RESULTS: Formulae for calculating humeral head height, diameters of the base of the humeral head in the frontal and sagittal planes, and radii of curvature in the frontal and sagittal planes were derived from the linear regression plots that were found to have strong (1 ≥ R ≥ 0.50) correlations. By Welch t-test, differences between the 3 head sizes were statistically significant in each case (P ≤ .022). The elliptical shape of the base of the humeral head was found to elongate with increasing humeral head size. CONCLUSIONS: Mathematical formulae relating various humeral head dimensional measurements are presented. The formulae derived in this study may be useful for the design of future prosthetic shoulder systems in which the goal is to replicate normal anatomy. This is the first study to describe that the elliptical shape of the base of the humeral head elongates as head size increases.

Anterior cruciate ligament reconstruction in skeletally immature knees: an anatomical study.

The purpose of this study was to anatomically evaluate anterior cruciate ligament (AL) reconstruction ate anterior cruciate ligament (ACL) reconstruction techniques in skeletally immature knees. Four cadav-techniques in skeletally immature knees. Four cadaveric knees from 2 skeletally immature children were used. After preoperative magnetic resonance imaging (MRI), various ACL reconstruction techniques were performed. On the tibial side, 30 degrees, 45 degrees, and 60 degrees tunnels were made; on the femoral side, a transtibial femoral tunnel was made, and over-the-top placement was used. After reconstruction, specimens underwent MRI imaging and were sectioned for descriptive analysis. The 30 degrees epiphyseal tunnel is feasible in older children, the standard 45 degrees tibial tunnel threatens the anteromedial proximal tibial physis and the tibial tubercle apophysis, and the 60 degrees vertical tunnel violates centrally in the proximal tibial physis. Both the transtibial femoral tunnel and the over-the-top placement are near the posterior distal femoral physis and perichondrial ring. When an interference screw is used for fixation, the physis is difficult to avoid. We recommend giving careful attention to technical details during ACL reconstruction in skeletally immature knees.

Glenohumeral muscle activation during provocative tests designed to diagnose superior labrum anterior-posterior lesions.

BACKGROUND: Despite considerable medical advances, arthroscopy remains the only definitive means of superior labrum anterior-posterior (SLAP) lesion diagnosis. Natural shoulder anatomic variants limit the reliability of radiographic findings and clinical evaluations are not consistent. Accurate clinical diagnostic techniques would be advantageous because of the invasiveness, patient risk, and financial cost associated with arthroscopy. PURPOSE: The purpose of this study was to examine the behavior of the joint-stabilizing muscles in provocative tests for SLAP lesions. Electromyography was used to characterize the muscle behavior, with particular interest in the long head of the biceps brachii (LHBB), as activation of the long head and subsequent tension in the biceps tendon should, based on related research, elicit labral symptoms in SLAP lesion patients. STUDY DESIGN: Controlled laboratory study. METHODS: Volunteers (N = 21) without a history of shoulder injury were recruited. The tests analyzed were active compression, Speed's, pronated load, biceps load I, biceps load II, resisted supination external rotation, and Yergason's. Tests were performed with a dynamometer to improve reproducibility. Muscle activity was recorded for the long and short heads of the biceps brachii, anterior deltoid, pectoralis major, latissimus dorsi, infraspinatus, and supraspinatus. Muscle behavior for each test was characterized by peak activation and proportion of muscle activity. RESULTS: Speed's, active compression palm-up, bicep I, and bicep II produced higher long head activations. Resisted supination external rotation, bicep I, bicep II, and Yergason's produced a higher LHBB proportion. CONCLUSION: Biceps load I and biceps load II elicited promising long head behavior (high activation and selectivity). Speed's and active compression palm up elicited higher activation of the LHBB, and resisted supination and Yergason's elicited selective LHBB activity. These top performing tests utilize a unique range of test variables that may prove valuable for optimal SLAP test design and performance. CLINICAL RELEVANCE: This study examines several provocative tests that are frequently used in the clinical setting as a means of evaluating a potential SLAP lesion.