The Prevalence of Cam Morphology: A Cross-Sectional Evaluation of 3,558 Cadaveric Femora.

Purpose: We sought to determine (1) the prevalence of cam deformity in the population and that of bilateral cam deformity, (2) the typical location of a cam lesion, and (3) the typical size of a cam lesion by direct visualization in cadaveric femora. Methods: Two observers inspected 3,558 human cadaveric femora from the Hamann-Todd Osteological Collection from the Cleveland Museum of Natural History. Any asphericity >2 mm from the anterior femoral neck line was classified as a cam lesion. Once lesions had been inspected, the prevalence in the population, prevalence by gender, and prevalence of bilateral deformity were determined. Additionally, each lesion was measured and localized to a specific quadrant on the femoral neck based upon location of maximal deformity. Results: Cam lesions were noted in 33% of males and 20% of females. Eighty percent of patients with a cam lesion had bilateral lesions. When stratified by location of maximal deformity, 90.9% of lesions were in the anterosuperior quadrant and 9.1% were in the anteroinferior quadrants. The average lesion measured 17 mm long × 24 mm wide × 6 mm thick in men and 14 mm × 22 mm × 4 mm in women (p < 0.05). Conclusions: The population prevalence of cam deformity determined by direct visualization in cadavers may be higher than has been suggested in studies utilizing imaging modalities. Level of Evidence : Level II, diagnostic study.

Biomechanical comparison of the modified Bristow procedure with and without capsular repair.

PURPOSE: The Bristow procedure has become an effective surgical option for recurrent anterior instability of the shoulder; however, there is no consensus on whether a capsule repair following a Bristow procedure is necessary to restore glenohumeral stability. The purpose of this study was to evaluate whether capsular repair with a modified Bristow procedure affects rotational range of motion and glenohumeral stability. METHODS: Rotational range of motion, glenohumeral translation and kinematics were measured in eight cadaveric shoulders in 90° shoulder abduction in the scapular and coronal planes for four conditions: intact, 20 % bony Bankart lesion, modified Bristow without capsular repair and modified Bristow with capsular repair. RESULTS: Creation of the bony Bankart led to a significant increase in total range of motion and anterior-inferior translation compared to the intact shoulder. The modified Bristow procedure significantly decreased anterior-inferior translation compared to the bony Bankart but did not decrease total range of motion. Capsular repair decreased total range of motion in the scapular and coronal planes and altered normal glenohumeral kinematics in external rotation positions. CONCLUSION: Repairing the capsule in a Bristow procedure decreases rotational range of motion yet does not offer any added anterior-inferior translational stability. Capsular repair also significantly alters normal glenohumeral kinematics. Capsule repair with a Bristow procedure may not add additional glenohumeral stability in positions of apprehension and may potentially over constrain the joint and cause altered kinematics.

Biomechanical analysis of the modified Bristow procedure for anterior shoulder instability: is the bone block necessary?

BACKGROUND: Anterior shoulder instability with bone loss can be treated successfully with the modified Bristow procedure. Opinions vary regarding the role of the soft-tissue sling created by the conjoined tendon after transfer. Therefore, the aim of this study was to determine the effect of the modified Bristow procedure and conjoined tendon transfer on glenohumeral translation and kinematics after creating anterior instability. METHODS: Eight cadaveric shoulders were tested with a custom shoulder testing system. Range-of-motion, translation, and kinematic testing was performed in 60° of glenohumeral abduction in the scapular and coronal planes under the following conditions: intact joint, Bankart lesion with 20% glenoid bone loss, modified Bristow procedure, and soft tissue-only conjoined tendon transfer. RESULTS: A Bankart lesion with 20% bone loss resulted in significantly increased external rotation and translation compared with the intact condition (P < .05), as well as an anterior shift of the humeral head apex at all points of external rotation. Both the modified Bristow procedure and soft-tissue Bristow procedure maintained the increase in external rotation but resulted in significantly decreased translation (P < .05). There was no difference in translation between the 2 reconstructions. CONCLUSIONS: The increase in external rotation suggests that the modified Bristow procedure does not initially restrict joint motion. Translational stability can be restored in a 20% bone loss model without a bone block, suggesting the importance of the soft-tissue sling.

Double rib penetration of the spinal canal in a patient with neurofibromatosis.

BACKGROUND: Rib head penetration into the spinal canal in patients with severe kyphoscoliosis secondary to neurofibromatosis type-1 (NF-1) is extremely rare. Double rib head penetration has only been reported once earlier. METHODS: We are reporting on an adolescent male with NF-1 and severe thoracic kyphoscoliosis with adjacent double rib head penetration into the spinal canal without neurological deficits. Only one was recognized on the initial radiographic imaging. RESULTS: A 14-year-old with NF-1 and 74 degrees left thoracic scoliosis and 75 degrees kyphosis was treated at our institution. Preoperative computed tomography (CT) demonstrated protrusion of the left T6 rib head into the spinal canal on the convexity of the curve, compressing the spinal cord. Staged surgical procedures for resection of the rib head and correction of the spinal deformity were planned. After presumed successful resection of the penetrated rib head, a postoperative CT revealed the presence of a second adjacent left T7 rib head in the spinal canal. This was not initially recognized owing to the severe deformity and image obliquity of the CT gantry. Another procedure was performed to remove this rib head. He was then placed in halo traction until anterior and posterior spinal fusion and segmental spinal instrumentation were performed. He achieved good deformity correction and had no neurological deficits throughout his treatment. CONCLUSIONS: Rib head protrusion into the spinal canal can occur with spine deformity in NF-1. If present, the imaging should be carefully reviewed for the possibility of an adjacent rib head penetration that may have been obscured by the limitations of CT in the context of a dysplastic spinal deformity. LEVEL OF EVIDENCE: Level V. Case study.