Itoi, Eiji

Background An anteroinferior osseous defect of the glenoid rim is sometimes encountered in patients with recurrent anterior dislocations of the shoulder. A defect of more than 21% of the glenoid length is reported to cause instability after Bankart repair. Hypothesis We can estimate the critical size of glenoid defects by using radiography or computed tomography. Study Design A controlled laboratory study. Methods Osseous defects of 0%, 9%, 21%, 34%, and 46% of the glenoid length were created stepwise in 12 cadaveric scapulae, and plain radiographs simulating the axillary and West Point views and computed tomographic images were obtained. The maximum width of the remnant glenoid was measured under each condition and expressed as a percentage of the width of the intact glenoid. Results A 21% defect appeared to be 18.6% of the intact glenoid on the West Point view. With computed tomography, a 21% defect resulted in loss of 50% of the width on a single slice across the lower one-fourth of the glenoid. Conclusions We can estimate the size of a glenoid defect by using the West Point radiographic view or computed tomogram. Clinical Relevance These images gave decisive information as to whether an osseous glenoid defect required bone grafting to achieve stability after Bankart repair.

Pre‐surgical measurement of supraspinatus muscle extensibility is important for rotator cuff repair. The purpose of the present study was to explore the potential feasibility of a shear wave ultrasound elastography (SWE)‐based method, combined with B‐mode ultrasound, to measure the in vivo stiffness of the supraspinatus muscle non‐invasively and thus obtain key information about supraspinatus muscle extensibility. Our investigation comprised two steps. First, we determined the orientation of the supraspinatus muscle fibers in cadaveric shoulders without rotator cuff tear in order to optimize the ultrasound probe positions for SWE imaging. Second, we investigated the feasibility of quantifying the stiffness of the normal supraspinatus muscle by SWE in vivo. The supraspinatus muscle was divided into four anatomical regions: anterior superficial (AS), posterior superficial (PS), anterior deep (AD), and posterior deep (PD). Each region was examined by SWE. The SWE stiffnesses of AD, AS, PD, and PS were 40.0 ± 12.4, 34.0 ± 9.9, 32.7 ± 12.7, 39.1 ± 15.7 kPa, respectively. SWE combined with B‐Mode ultrasound imaging could be a feasible method for quantifying the local stiffness of the rotator cuff muscles. Clin. Anat. 28:213–218, 2015. © 2014 Wiley Periodicals, Inc.

Purpose The purpose of this in vitro biomechanical study was to assess the effects of the remplissage procedure for small‐ and large‐sized Hill‐Sachs lesions (HSLs) on shoulder range of motion (ROM) with a special interest in the apprehension position. Methods HSLs of 50% and 100% of the glenoid width were simulated in 7 cadaveric shoulders as small and large lesions, respectively, and the postoperative condition was reproduced by placing suture anchors on the articular surface and tying down the infraspinatus at the medial edge of the would‐be lesion site. ROMs were measured in abduction, internal rotation, and external rotation with the humerus in the adducted and abducted position. In addition, the ROM was measured in the anterior apprehension position, in which 2 torques of external rotation and extension were applied simultaneously, and external rotation and horizontal extension ROMs were measured with the humerus in different abduction angles (20°, 40°, and 60°). Results For standard ROMs, the procedure for the 50% HSL maintained complete ROMs, whereas the procedure for the 100% HSL significantly decreased external rotation ROM with the humerus in both the adducted and abducted positions, as well as abduction ROM. In the apprehension position, remplissage for the 50% HSL decreased extension ROM with the humerus abducted to 40° and 60°. Remplissage for the 100% HSL significantly decreased both external and extension ROMs regardless of the humeral abduction angle. Conclusions In the cadaveric model with an intact humeral head and the simulated postoperative condition, the remplissage procedure for a large HSL caused significant restrictions in ROM of abduction in the scapular plane and external rotation with the humerus in both adduction and abduction. It also caused significant restrictions in both external rotation and extension ROMs in the apprehension position. Clinical Relevance The indication for the remplissage procedure for the larger HSL should be considered carefully, especially for the competitive throwing athlete who needs exceptional external rotation ROM for optimal overhead throwing performance.

Background There have been few biomechanical studies to clarify which size of a glenoid defect is critical. However, those studies have assumed that the defect occurred anteroinferiorly. Recent studies have reported that the defect is located anteriorly rather than anteroinferiorly. Therefore, the effect of the anterior, not anteroinferior, glenoid defect on shoulder stability needs to be investigated. Hypothesis The anterior glenoid defect would have a similar effect on anterior shoulder stability as that of the anteroinferior glenoid defect. Study Design Controlled laboratory study. Methods Eight fresh-frozen cadaveric shoulders were used (mean age, 74 years). The specimen was attached to a shoulder-testing device with the arm in abduction and external rotation. An osseous defect was created stepwise with a 2-mm increment of the defect width. The stability ratio was used to evaluate joint stability. With a 50-N axial force, the translational force applied to the humeral head was measured by a force transducer. Results The stability ratio without a defect (32% ± 6%) significantly decreased after creating a 6-mm defect (17% ± 5%; P = .0001), which was equivalent to 20% of the glenoid length. Conclusion An osseous defect at 3 o'clock with a width that was equal to or greater than 20% of the glenoid length significantly decreased anterior stability. Clinical Relevance The results suggest that reconstruction of the glenoid concavity might be necessary in shoulders with an anterior glenoid defect of at least 20% of the glenoid length.

The contribution of axial arm rotation to translation of the humeral head with the arm in the hanging position was examined using nine fresh-frozen cadaveric shoulders. Three standard clinical tests were simulated: anterior and posterior translation and sulcus tests. In both the anterior translation and sulcus tests, anterior and infe rior displacements were significantly restricted in inter nal rotation but not in neutral and external rotation. In the posterior translation test, no significant differences in displacement could be observed in internal, neutral, or external rotation. Since anterior and inferior translations of the humeral head were significantly affected by the rotation of the arm, we recommend that the anterior translation and sulcus tests be performed in various rotations.

Summary Nine fresh frozen cadaveric shoulders were used to examine the changes in intraarticular pressure (IAP) of the shoulder joint and the position of the humeral head under various loads to determine the relationship between these parameters. All the soft tissues superficial to the rotator cuff were removed. The position of the humerus relative to the scapula was monitored using an electromagnetic tracking system before and after venting the capsule with 0, 0.5, and 1.0 kg of load applied to the humerus inferiorly in addition to the weight of the arm. Simultaneously, the IAP was monitored using a pressure transducer before venting the capsule. Venting had a significant effect on the position of the humeral head: the positions of the head after venting were significantly lowered in all loading conditions. The average IAP was −76 cm H 2 O without load, and the value decreased in a linear fashion with increased load; the correlations were significant in four of six shoulders without dislocation. The correlations were less significant between the pressure and the position, and there were no significant correlations between the load and the position. IAP, which is determined primarily by the load applied, is important to stabilize the shoulder inferiorly. Because IAP is intimately related to the external load and the response is specific to individuals, examination of IAP response to external load may be helpful in characterizing various instabilities of the shoulder.

Abstract Purpose: The purpose of this study was to investigate the difference in contact geometry at the undersurface of acromion in shoulders with and without a rotator cuff (RC) tear. Type of Study: Case‐control study. Methods: Forty fresh cadaveric shoulders (average age at death, 61 years) without gross osteoarthritic changes were divided into the intact RC group (n = 20) and the RC tear group (n = 20). Clinical impingement was simulated by compressing the humeral head and the intact portion of the RC against the coracoacromial arch with an axial compressive force of 25 kg while the humerus was held abducted 20° in the scapular plane. The contact pattern between the acromion and the RC was measured with Fuji Prescale super low‐pressure–sensitive film (Fuji Photo Film Co, Ltd, Tokyo, Japan). The imprint image was analyzed using Global Lab image software (Automatix, Marlboro, MA). Results: The percentage of the maximum anteroposterior dimension of the imprint on Fuji film to the anteroposterior diameter of the acromial undersurface was 29% ± 9% in intact RC shoulders, and 39% ± 13% in shoulders with an RC tear ( P >.05). The percentage of the maximum mediolateral dimension of the imprint to the mediolateral diameter of the corresponding part of the acromial undersurface was 27% ± 12% in intact RC shoulders, and 48% ± 11% in shoulders with an RC tear. This difference was statistically significant ( P <.005). Conclusions: The contact geometry of the acromial undersurface with the underlying RC in the anteroposterior dimension, which might be related to the appearance in supraspinatus outlet view, was not significantly different between shoulders with and without an RC tear. These findings suggest that factors other than acromial shape play a significant role in the pathogenesis of RC tears. The implication regarding the role of acromioplasty remains to be clarified.