Effect of glenoid component inclination on its fixation and humeral head subluxation in total shoulder arthroplasty

Objective. To investigate the effect of glenoid component inclination angle on the fixation of cemented glenoid-bone structures and humeral head subluxation.

Background. Results of shoulder replacements, in terms of glenoid component fixation and joint functionality, are bad and must be improved. Repeated glenoid component tilting, a result of eccentric contact forces harms glenoid component fixation. However, the effect of glenoid component inclination is unknown.

Methods. Keeled glenoid components are cemented into bone substitutes and positioned under inclination angles varying between −4.5° and +4.5°. For each inclination angle 5 glenoid specimens are loaded by a horizontal, constant joint compression force (725 (SD 10) N) and a vertical, superior directed subluxation force (shear force), cyclically varying between 0 and 350 (SD 1) N. After 200,000 load cycles, the upper and lower glenoid component rim-displacements are measured during 1500 additional load cycles by custom made displacement sensors.

Results. The maximal superior rim-displacement significantly increased and the minimal inferior rim-displacement dramatically decreased for increasing glenoid component inclination angles up to +4.5°. Maximal ratio of subluxation force over compression force significantly decreased for increasing glenoid component inclination.

Conclusions. According to this study, decreasing glenoid component inclination angle decreases glenoid component tilting and humeral head subluxation and the results can be used to improve total shoulder replacements.

Relevance Better understanding of the effect of glenoid component inclination on glenoid component tilting and humeral head subluxation may be useful information for the surgeon to improve results of the total shoulder arthroplasty, when replacing the glenoid surface.     

Iliac crest allograft glenoid reconstruction for recurrent anterior shoulder instability in athletes: Surgical technique and results

Performing a labral repair alone in patients with recurrent anterior instability and a large glenoid defect has led to poor outcomes. We present a technique involving the use of the iliac crest allograft inserted into the glenoid defect in athletes with recurrent anterior shoulder instability and large bony defects of the glenoid (>25% of glenoid diameter). All athletes with recurrent anterior shoulder instability and a large glenoid defect that underwent open anterior shoulder stabilization and glenoid reconstruction with the iliac crest allograft were followed over a 4-year period. Preoperatively, a detailed history and physical exam were obtained along with standard radiographs and magnetic resonance imaging of the affected shoulder. All patients also completed the Simple Shoulder Test (SST) and American Shoulder and Elbow Surgeons (ASES) evaluation forms preoperatively. A computed tomography scan was obtained postoperatively to assess osseous union of the graft and the patient again went through a physical exam in addition to completing the SST, ASES, and Western Ontario Shoulder Instability Index (WOSI) forms. 10 patients (9 males, 1 female) were followed for an average of 16 months (4–36 months) and had a mean age of 24.4 years. All patients exhibited a negative apprehension/relocation test and full shoulder strength at final follow-up. Eight of 10 patients had achieved osseous union at 6 months (80.0%). ASES scores improved from 64.3 to 97.8, and SST scores improved from 66.7 to 100. Average postoperative WOSI scores were 93.8%. The use of the iliac crest allograft provides a safe and clinically useful alternative compared to previously described procedures for recurrent shoulder instability in the face of glenoid deficiency.     

关节窝植骨增加标准型人工颞下颌关节窝假体稳定性的效果评价

目的: 为提高标准型人工颞下颌关节窝假体植入的稳定性,进行关节窝植骨并评价其应用效果。方法: 2013年11月—2014年2月间收治的经计算机辅助测量设计并进行人工关节置换的8例患者,采用关节窝植骨代替关节窝骨磨削的方法进行手术技术改进,通过计算假体的骨接触面积,评价植骨法对提高关节窝假体植入稳定性的作用。植骨术后CT模拟测量评价假体骨接触面积变化,评价其稳定性,并利用SPSS 19.0软件包中的配对t检验评价是否有统计学差异。结果: 采用关节窝植骨法假体术中就位稳定,术后CT测量显示,关节窝假体的骨接触面积比磨骨法增加34.85%（P<0.05）。结论: 关节窝植骨可以显著提高人工关节窝假体的稳定性。     

Periarticular fiber system of the shoulder joint

The structure and attachment of the glenoid labrum were examined from the functional point of view in 42 shoulder-joint cavities using a combination of macroscopic and microscopic techniques. The labrum continues the long tendon of the biceps as far as the ventral glenoid notch and is supplemented by a connecting band between the superior and inferior glenohumeral ligaments. In the upper quadrants, the periarticular fibers are broadly attached to the neck of the scapula and separated by a gap from the articular cartilage. In the lower quadrants, they are attached to both the neck of the scapula and the joint surface. The periarticular structures consist of bundles of parallel collagen fibers that run round the entire circumference of the cavity. The labrum, glenohumeral ligaments, and inserting tendons form a basket of fibers around the neck of the scapula, which constitutes a functional unit: the periarticular fiber system (PAFS). This acts as a tension-brace for the joint cavity and takes part in the local transmission of pressure through the cavity. Detachment of the labrum, or the labral-biceps anchor, should only be diagnosed when it can be shown that the tissue between the PAFS and the upper part of the neck of the scapula has been torn, and that the extent of the gap formation reaches laterally and caudally beyond the peripheral edge of the cartilage.     

Bilateral glenoid hypoplasia

A case of bilateral glenoid hypoplasia in a boy afflicted with posterior fossa medulloblastoma is described. Glenoid hypoplasia is a rarely reported bilateral finding either in subjects complaining of shoulder pain or abduction/adduction movements reduction as well as shoulder recurrent dislocations. In this patient as in most of those reported in the literature the finding was incidental and could have been easily overlooked. It consists of shallow, irregular glenoid fossae which are hypoplastic, whereas the humeral heads are normal in size and shape. At the present time there is no explanation for this anomaly. Received 21 April 1997; Revision received 12 November 1997; Accepted 17 November 1997     

Glenoid hypoplasia and its relationship to instability

 Glenoid hypoplasia, or dysplasia of the scapular neck, is usually a bilateral and symmetric finding. Associated findings include hypoplasia of the humeral head, elongation of the glenoid cavity, and alterations in the shape of the coracoid or clavicle. Glenoid hypoplasia has been reported sporadically in the radiologic literature, but the condition may be more frequent than previously thought. In this paper, we discuss the radiographic findings of glenoid hypoplasia and explore the possibility of an association between glenoid hypoplasia and shoulder instability.