Effect of humeral component version on impingement in reverse total shoulder arthroplasty.

Reverse shoulder arthroplasty is growing in popularity for patients with deficient rotator cuffs; however, the phenomenon of scapular notching continues to be a concern. This study examined the effects of humeral component version in the Aequalis Reversed Shoulder Prosthesis (Tornier, Edina, MN) on impingement of the humeral prosthesis against the scapula to test the hypothesis that the mechanical contact of the humeral component with the scapular neck is influenced by the version of the humeral component. Seven shoulders from deceased donors were tested after the Aequalis Reversed Shoulder was implanted. The deltoid, pectoralis major, and latissimus dorsi were loaded based on physiologic cross-sectional area. The degree of internal and external rotation when impingement, subluxation, or dislocation occurred was measured at 0°, 30°, and 60° glenohumeral abduction in the scapular plane. Testing was performed with the humeral component placed in 20° of anteversion, neutral version, 20° of retroversion, and 40° of retroversion. Maximum external rotation at 0° abduction was -1° ± 4° at 20° anteversion, 15° ± 3° at neutral, 28° ± 4° at 20° retroversion, and 44° ± 5° at 40° retroversion (P < .05). Maximum internal rotation at 0° abduction was 128° ± 9° at 20° anteversion, 112° ± 9° at neutral, 99° ± 8° at 20° retroversion, and 83° ± 8° at 40° retroversion (P < .05). Maximum external rotation at 30° abduction was 70° ± 6° at 20° anteversion, 84° ± 7° at neutral, 97° ± 6° at 20° retroversion, and 110° ± 5° at 40° retroversion (P < .05). There was no limitation to internal rotation at 30° abduction. No impingement occurred at 60° abduction. Version of the humeral component plays a role in range of motion and impingement in reverse total shoulder arthroplasty. Anteversion can significantly decrease the amount of external rotation achievable after reverse total shoulder surgery. Placing the Aequalis Reversed Shoulder humeral component at between 20° and 40° of retroversion more closely restores a functional arc of motion without impingement.

Stephenson DR ，Oh JH ，McGarry MH ，Rick Hatch GF 3rd ，Lee TQ ... -  《-》

Influence of glenoid component design and humeral component retroversion on internal and external rotation in reverse shoulder arthroplasty: a cadaver study.

A common disadvantage of reverse shoulder arthroplasty is limitation of the range of arm rotation. Several changes to the prosthesis design and implantation technique have been suggested to improve rotation range of motion (ROM). Glenoid component design and degree of humeral component retroversion influence rotation ROM after reverse shoulder arthroplasty. The Aequalis Reversed™ shoulder prosthesis (Tornier Inc., Edina, MN, USA) was implanted into 40 cadaver shoulders. Eight glenoid component combinations were tested, five with the 36-mm sphere (centred seating, eccentric seating, inferior tilt, centred with a 5-mm thick lateralised spacer, and centred with a 7-mm thick lateralised spacer) and three with the 42-mm sphere (centred with no spacer or with a 7-mm or 10-mm spacer). Humeral component position was evaluated with 0°, 10°, 20°, 30°, and 40° of retroversion. External and internal rotation ROMs to posterior and anterior impingement on the scapular neck were measured with the arm in 20° of abduction. The large glenosphere (42 mm) was associated with significantly (P<0.05) greater rotation ROMs, particularly when combined with a lateralised spacer (46° internal and 66° external rotation). Rotation ROMs were smallest with the 36-mm sphere. Greater humeral component retroversion was associated with a decrease in internal rotation and a significant increase (P<0.05) in external rotation. The best balance between rotation ROMs was obtained with the native retroversion, which was estimated at 17.5° on average in this study. Our anatomic study in a large number of cadavers involved a detailed and reproducible experimental protocol. However, we did not evaluate the variability in scapular anatomy. Earlier studies of the influence of technical parameters did not take humeral component retroversion into account. In addition, no previous studies assessed rotation ROMs. Rotation ROM should be improved by the use of a large-diameter glenosphere with a spacer to lateralise the centre of rotation of the gleno-humeral joint, as well as by positioning the humeral component at the patient's native retroversion value.

Berhouet J ，Garaud P ，Favard L 《Orthopaedics & Traumatology-Surgery & Research》

Evaluation of the role of glenosphere design and humeral component retroversion in avoiding scapular notching during reverse shoulder arthroplasty.

Scapular notching is a common observation during radiological follow-up of reverse shoulder arthroplasty. The purpose of this study was to evaluate the effect of glenosphere design and humeral component retroversion on movement amplitude in the scapular plane and inferior scapular impingement. The Aequalis Reversed Shoulder Prosthesis (Tornier) was implanted into 40 cadaver shoulders. On the glenoid side, 8 different combinations were tested: 36-mm glenosphere: centered (standard), eccentric, with an inferior tilt, or with the center of rotation (COR) lateralized by 5 or 7 mm; and 42-mm centered glenosphere: used alone or with the COR lateralized by 7 or 10 mm. The humeral component was positioned in 0°, 10°, 20°, 30°, and 40° of retroversion. Maximum adduction and abduction were measured when inferior impingement and superior impingement, respectively, were detected. The average increase in abduction amplitude was 10° and inferior impingement occurred 18° later with a 42-mm glenosphere, especially when it was lateralized by 10 mm, relative to a 36-mm centered glenosphere (P < .05). These 2 combinations provided a 28° increase in the movement amplitude in the scapular plane. Positioning of the humeral component in 10° or 20° of retroversion or in anatomical retroversion was most effective at avoiding inferior impingement but had less effect on abduction range of motion (except with the 42-mm glenosphere). Our study confirmed published results with various glenosphere designs but was unique in describing the effect of humeral retroversion on scapular impingement. Inferior scapular notching can be most effectively prevented by using large-diameter glenospheres with lateralized COR and by making sure to replicate the patient's native humeral retroversion.

Berhouet J ，Garaud P ，Favard L 《-》

Combined effect of change in humeral neck-shaft angle and retroversion on shoulder range of motion in reverse total shoulder arthroplasty - A simulation study.

We studied combined effect of change in humeral neck shaft angle and retroversion on shoulder ROM in reverse total shoulder arthroplasty using 3-dimensional simulations. Using a 3D model construct based on the CT scans of 3 males and a 3-dimensional analysis program, a humeral component of reverse total shoulder arthroplasty was implanted in 0°, 10°, 20°, 30°,40° retroversion and 135°, 145°, and 155° neck shaft angle. Total horizontal range of motion (sum of horizontal adduction and abduction) at 30° and 60° scaption, adduction in the scapular plane and IR behind the back were measured for various combinations of neck shaft angle and retroversion. Change in retroversion didn't show any effect on total horizontal range of motion. Total horizontal range of motion at both 30° and 60° scaption, showed maximum values at 135° neck shaft angle and minimum values at 155° neck shaft angle. With any combination of retroversion angles, adduction deficit was maximum at 155° neck shaft angle and no adduction deficit at 135° neck shaft angle. Every 10° decrease in neck shaft angle resulted in an average 10.4° increase in adduction. For every 10° increase in retroversion, there was loss of internal rotation behind the back up to at least one vertebral level. 135° neck shaft angle resulted in maximum total horizontal range of motion both at 30° and 60° scaption regardless of retroversion angles. 135° neck shaft angle also reduced the chances of scapular impingement. Decrease in retroversion angle resulted in more amount of internal rotation behind the back.

Jeon BK ，Panchal KA ，Ji JH ，Xin YZ ，Park SR ，Kim JH ，Yang SJ ... -  《-》

Humeral version in reverse shoulder arthroplasty affects impingement in activities of daily living.

Impingement after reverse shoulder arthroplasty (RSA) has been correlated with implant design and surgical techniques. Previous studies suggested that humeral retroversion can reduce impingement and increase external rotation range of motion (ROM). The purpose of this study was to determine how humeral version affects impingement in activities of daily living (ADLs). A single surgeon performed virtual RSA on 30 arthritic shoulders that were reconstructed from preoperative computed tomography scans. For each subject, the humeral component was placed into 5 versions: -40°,-20°, 0°, +20°, and +40° (- indicates retroversion, + indicates anteversion). Intra-articular and extra-articular impingement was calculated for 10 ADLs. Impingement-free ROM was also calculated for abduction, forward flexion, scapula plane elevation, and internal/external rotation (standardized tests). Risk of impingement for ADLs was assessed as the collective duration and frequency of impingement across all motions. Frequent impingement sites were identified. For the ADLs, 0° version showed the least amount of impingement. In contrast, 40° retroversion resulted in the largest ROM for the standardized tests (118° ± 19° abduction, 109° ± 16° forward flexion, 111° ± 10° scapula plane elevation, 140° ± 15° internal/external rotation). The site of impingement changed with version: retroversion increased the extra-articular impingement, and anteversion increased the contact between the inferior glenoid and the humeral cup. Humeral version can significantly affect impingement in RSA. Maximizing ROM in standardized tests may not reduce the risk of impingement during ADLs. Our results showed that an average 0° of version should be preferred, but the large variability among subjects suggested that optimum version may vary among individuals.

Kontaxis A ，Chen X ，Berhouet J ，Choi D ，Wright T ，Dines DM ，Warren RF ，Gulotta LV ... -  《-》