Biomechanical analysis of the subscapularis,infraspinatus and teres minor length and moment arm after reverse shoulder arthroplasty: a cadaveric study

BackgroundReverse shoulder arthroplasty (RSA) affects the length and moment arm of the deltoid and rotator cuff. Currently, RSA is commonly considered for cuff-intact conditions, such as primary glenohumeral osteoarthritis. As such, understanding the effect of contemporary lateralized designs on the rotator cuff is paramount. The purpose of this study was to determine changes in length and moment arm of the subscapularis, infraspinatus and teres minor with implantation of one of 3 RSA designs.MethodsA previously validated model was used in 6 hemi-toraces with the shoulder attached. Suture lines were run through pneumatic cylinders from the insertion to the origin of 10 muscles to apply a constant, stabilizing load. Electromagnetic tracking sensors were fixed to the thorax, scapula, and humerus to record 3-dimensional kinematics. Coordinate systems were established according to ISB recommendations. The origin and insertion of the subscapularis, infraspinatus and teres minor were digitized and tracked. Testing consisted of manually rotating the humerus through 5 cycles of its internal-external rotation arc. Kinematic data was collected at 120 Hz. Testing was performed in 3 positions of abduction: 0°, 30°, and 60°. After testing the intact shoulder, RSA was performed using 3 different configurations: an onlay 135-degree humeral component matched with a 2-mm lateralized glenosphere, the same humeral component with a 6-mm lateralized glenosphere, and an inlay 135-degree humeral component matched with a 10 mm lateralized glenosphere. Minimal muscle operative lengths, maximal muscle operative lengths, and muscle moment arms were computed.ResultsWhen compared with the native shoulder, all 3 configurations of RSA resulted in statistically significant increases in both the minimal and maximal operative lengths of the subscapularis in all abduction positions. The teres minor only showed a statistically significant increase in minimal and maximal length at 60° of abduction. The infraspinatus showed a statistically significant increase in tendon excursion at 0° and 30° of abduction. In 40° of abduction and 40° of internal rotation, all RSA configurations translated in a decreased subscapularis internal rotation moment arm. On the contrary, RSA increased the external rotation moment arm of the infraspinatus in neutral rotation and 0° of abduction.ConclusionImplantation of contemporary lateralized RSA implants led to increased length of the subscapularis to a greater extent than the increased length experienced by the infraspinatus and teres minor. The moment arm of the subscapularis decreased, whereas the moment arm of the teres minor in neutral rotation with the arm in abduction increased.Level of EvidenceLevel III; Basic Science, Biomechanics Study     

Postimpingement instability following reverse shoulder arthroplasty: a parametric finite element analysis

BackgroundInstability following reverse shoulder arthroplasty is influenced by various factors such as component design, component positioning, and soft tissue tensioning. Patients may achieve glenohumeral motion beyond initial scapular impingement during activities of daily living which could further compound instability. However, instability/subluxation risk postscapular impingement is not well documented. Conventional range of motion analysis tools cannot account for the restraining effect of soft tissues or subluxation risk after impingement. Using a previously validated finite element analysis approach, the purpose of this study was to investigate the effects of glenoid component lateralization and humeral component angle of inclination (AOI), with or without simulated subscapularis repair, on postimpingement subluxation. We hypothesized that lack of subscapularis repair, a valgus humeral component AOI, and glenoid medialization would all result in greater postimpingement instability.MethodsA FE model of the shoulder including the subscapularis tendon and middle deltoid was created, incorporating a general representation of a commercial reverse shoulder arthroplasty implant placed under the direction of a fellowship-trained shoulder surgeon. The deltoid and subscapularis were tensioned and wrapped around the reconstructed glenohumeral joint prior to simulating motion. Humeral rotations were then prescribed to simulate external rotation (neutral to 50°), extension (neutral to 50°), adduction (neutral to 30°), and abduction (neutral to 90°). The effects of three glenosphere lateralization offsets (2, 4, and 10 mm) and 2 humeral liner angles of inclination (varus-150° and valgus-155°) on subluxation propensities were investigated with and without the subscapularis tendon present.ResultsSimulated subscapularis repair resulted in 21%-34% less postimpingement subluxation. Presence of the subscapularis provided stability over a greater range of abduction. Impingement-free range of motion was similar regardless of the presence or absence of the subscapularis. The valgus AOI resulted in 23% less subluxation during abduction. During other motions however, the valgus AOI resulted in 67%-110% greater postimpingement subluxation (subscapularis present), which further worsened without the subscapularis.ConclusionImplant design modifications to improve stability may not be beneficial for all motions, highlighting the importance of directionality when investigating instability. Liner-bone impingement appears to compound instability/subluxation and the subscapularis appears to restrain postimpingement instability.Level of evidenceBasic Science Study; Computer Modeling     

Effect of reverse total shoulder arthroplasty humeral inclination on glenohumeral range of motion,deltoid force,and glenoid strain: a biomechanical study

BackgroundReverse total shoulder arthroplasty (RSA) primarily varies between 2 implant design options: a 135 humeral stem inclination that closely resembles anatomic orientation, versus the Grammont-style 155 humeral stem inclination that further medializes and distalizes the center of rotation (COR). The purpose of this study was to compare deltoid force, glenoid strain, and simulated glenohumeral range of motion (ROM) between RSA 135 and RSA 155 designs, with a series of standardized permutations of glenosphere offset and rotator cuff pathology.MethodsTwelve fresh-frozen cadaveric shoulder specimens were studied using a shoulder simulator. Native shoulder motion profiles for reproducible abduction range of motion were established using a customized testing device. Optical 3-dimensional tracking and pressure sensors were used to accurately record glenohumeral range of motion (ROM), deltoid force, and glenoid strain for RSA 135 and RSA 155 designs. For each cohort, all combinations of glenosphere offsets and rotator cuff tendon involvement were evaluated.ResultsThere was no significant difference in the overall abduction ROM between the 155 and the 135 humeral stem implants (P = .75). Resting abduction angle and maximum abduction angle were significantly greater with a 155 + STD (standard offset) construct than with a 135 + STD construct (P < .001 and P = .01, respectively). Both stem inclinations decreased combined deltoid force requirements as compared the native shoulder with a massive cuff tear. Effective glenoid strain did not vary significantly between 135 + STD and 155 + STD constructs (P = .66).ConclusionOverall, range of motion between the 135 and the 155 humeral stem inclinations was not significantly different. The cumulative deltoid force was lower in RSA shoulders when compared to native shoulders with massive rotator cuff tears, highlighting the utility of both implant designs. The Grammont-style 155 stem coupled with a 2.5 mm inferior offset glenosphere required less deltoid force to reach maximum abduction than did the more anatomic, lateralized 135 stem coupled with a 4 mm lateral offset glenosphere.Level of EvidenceBasic Science, Biomechanics Controlled Laboratory Study     

The impact of subscapularis integrity on functional outcome in reverse total shoulder arthroplasty utilizing a 135˚ stem

BackgroundReverse shoulder arthroplasty (RSA) predictably restores overhead function and provides pain relief in patients with glenohumeral arthritis and rotator cuff deficiency. Implant design with an anatomic inclination angle of 135˚ may provide an advantage in the healing rates of subscapularis tendon (SST) repairs. The purpose of this study was to use ultrasound to evaluate the subscapularis repair healing rate, and secondarily, to compare outcomes between healed and non-healed SSTs, in patients undergoing RSA with a 135˚ inclination angle.MethodsA prospectively collected, multicenter shoulder arthroplasty registry was queried to identify patients undergoing RSA with a 135˚ inclination stem with a minimum of 1 year follow-up. Ultrasound analysis was performed at final follow-up to assess subscapularis integrity. Exclusion criteria included RSA for fracture, fracture sequelae or failed prior arthroplasty. Outcome measures included American Shoulder and Elbow Surgeons score (ASES), Western Ontario Osteoarthritis of the Shoulder (WOOS), Single Anatomic Numeric Evaluation (SANE), and Constant scores. Additionally, subscapularis functional assessments included range of motion, belly-press and shirt-tuck tests. Statistical analysis was performed using ANOVA, Chi-square, and student t-tests with SPSS. Results were considered significant at P < .05.ResultsSeventy-eight patients meeting the inclusion criteria were identified from the registry, however, only seventy-five patients had ultrasound and healing data. The subscapularis was repaired in 60 patients and healing via ultrasound was noted in 56.7% (34/60). In most cases, a subscapularis peel was performed, with lesser tuberosity osteotomy performed in 9.38% of cases. Patients whose subscapularis was repaired were found to be older (72.2 vs. 64.9, P < .001) and the majority of patients with an unrepaired subscapularis were male (13/15, 86.7% unrepaired vs. 27/60, 45.0% repaired). Both healed and non-healed patient cohorts showed statistical improvement in all pain and functional outcome scores from their baselines. However, there were no significant differences in outcome scores between healed and non-healed SST. With regards to SST repair, only overall WOOS (Δ+15.62, P = .049) and physical component of the WOOS score (Δ+15.97, P = .040) were higher in patients with nonrepaired SST. There was no correlation between the ability to perform a belly-press or shirt-tuck test and subscapularis repair or evidence of radiographic healing. Patients who did not have their subscapularis repaired demonstrated greater passive external rotation at the side from 31° to 51° (P = .044). A significant increase in passive forward flexion was noted in patients with healed subscapularis from 117° to 135° (P = .042). There was no statistical difference in active range of motion between either the repaired/nonrepaired or healed/non-healed cohorts.ConclusionOur study demonstrates a healing rate of 57% following repair in patients undergoing RSA with a 135˚ angle. Standardized outcome measures overall demonstrated no difference between patients with a healed subscapularis compared to those with a non-healed or unrepaired subscapularis.Level of EvidenceIV, case series, treatment study.     

Clinical results of humeral stem lateralization in reverse shoulder arthroplasty: Comparative study of 145° onlay curved stem vs 155° inlay straight stem

BackgroundThe main limits of Grammont's reverse shoulder arthroplasty (RSA) design are loss of external rotation and scapular notching. These limits can be addressed with glenoid and/or humeral lateralization. Currently, there is no uniformity in the literature regarding the best option to improves these outcomes. Lateralization of the humeral side should be an option. The aim of the present study was to compare outcomes of a 145 degree onlay curved stem vs a 155 degree inlay straight stem.MethodsA retrospective analysis of 96 consecutive patients undergoing RSA (98 shoulders) was performed. Of these, 47 patients (48 shoulders) underwent RSA with a Aequalis Reversed II Stem (Group A) and 49 (50 shoulders) with a lateralized humeral stem (Ascend Flex©) (Group B). The exclusion criteria included any relevant glenoid bone loss in the horizontal plane or vertical plane and patients with post-traumatic conditions including humeral head necrosis. Patient with teres minor fatty infiltration superior to grade 2 according to Goutallier's classification were also excluded. Constant score, muscular strength and range of motion (ROM), were evaluated preoperatively and for 2 years postoperatively. Radiographs were examined for scapular notching.ResultsComparing clinical outcomes, there were significant improvements with active ROM using lateralized shoulder stem (Group B) in flexion, abduction and external rotation (P > .05). However, while evaluating the Constant score and muscular strength, no important difference emerged between the two groups. Scapular notching was observed in 29.17% of cases (24 shoulders) of Group A and in 12% of cases (6 shoulders) of Group B. Moreover, the average degree of notching was reduced in Group B in which the grade 1 was observed in 4 shoulders out of 50. Grade 2 was observed in 7 shoulders in Group A and in 2 shoulders in Group B. Grade 3 and grade 4 were observed only in 1 patient in Group A, and no one in Group B.ConclusionsThe lateralized humeral stem (145°, onlay, curved stem) in RSA improves ROM, particularly external rotation and abduction compared to Aequalis Reversed II Stem. No significant difference was found between the two groups regarding muscular strength. Both designs provide an overall improvement on function and pain relief. Moreover, the incidence of scapular notching is lower in a lateralized humeral stem implant (12% of cases) compared to traditional reverse prostheses with an Aequalis Reversed II Stem (29.17% of cases).Level of EvidenceIII     

Does critical shoulder angle predict abduction motion and acromion-tuberosity impingement in reverse shoulder arthroplasty?

BackgroundVirtual planning software for reverse shoulder arthroplasty (RSA) has introduced the ability to optimize implant position in an effort to maximize bony impingement–free motion. Abduction impingement typically occurs between the glenoid and polyethylene or between the tuberosities and the acromion or coracoid. Acromion-tuberosity impingement has been considered less desirable, as it may create additional stress on the acromion. Patients with a large acromion overhang may have higher rates of acromion-tuberosity impingement. As the critical shoulder angle (CSA) represents a larger distance from the glenoid face to the acromion, the purpose of this study was to evaluate the impact of implant selection and position on abduction motion and acromion-tuberosity impingement, with a focus on the association to CSA. We hypothesize that a larger CSA will be associated with less abduction motion and an increase in acromion-tuberosity impingement.MethodsThis is a retrospective cohort case series of 85 consecutive patients who underwent RSA from June 2020 to January 2021. Humeral and glenoid components were implanted virtually (SurgiCase) using a standard protocol for a single implant system (DJO AltiVate Short Stem Reverse) with an inset humeral component. Implant variables analyzed included baseplate location (central vs. inferior glenoid), glenosphere lateralization (10 mm vs. 6 mm), and humeral shell (standard vs. semiconstrained). The maximal degree of abduction and location of impingement were recorded at external rotation of 0°, 45°, and 90°. Implant combinations that resulted in no impingement and no motion were recorded.ResultsIncrease in CSA was associated with acromion-tuberosity impingement for nearly every combination at 0° and 45° external rotation; however, there were no significant associations between CSA and maximum abduction motion. Acromion-tuberosity impingement was associated with central glenosphere placement in all degrees of external rotation (P < .001), use of a 10 mm lateralized glenosphere for 0° (P < .001) and 45° (P = .076), and using a standard polyethylene shell for 0° (P = .032) and 45° external rotation (P = .007). Maximal abduction motion was associated with inferior placement (P < .001), and use of a 10 mm lateralized glenosphere (P < .001) in all positions of external rotation but was not influenced by the polyethylene type.ConclusionIncreased CSA is associated with acromion-tuberosity impingement and can be used to screen for patients at risk for bony impingement in abduction. Placement of the glenosphere centrally and use of a 10 mm lateralized glenosphere were associated with higher rates of acromion-tuberosity impingement. Maximal abduction can be achieved using a 10 mm lateralized glenosphere and inferior placement.     

Effect of tuberosity repair on functional outcome of reverse shoulder arthroplasty in proximal humerus fractures

PurposeUnsatisfactory results of hemiarthroplasty in Neer's 3- and 4-part proximal humerus fractures in elderly, have led to the shift towards reverse shoulder arthroplasty (RSA). The objective of our study was to repair the tuberosities that are generally overlooked during RSA and observe its impact on the functional outcome and shoulder scores.MethodsWe include elderly patients with acutely displaced or dislocated 3- or 4-part proximal humerus fractures from July 2013 to November 2019 who were treated with RSA along with tuberosity repair by non-absorbable sutures and bone grafting harvested from the humeral head. Open injuries and cases with neuro-muscular involvement of the deltoid muscle were excluded. According to the tuberosity healing on radiographs of the shoulder at 9th postoperative month, the patients were divided into 2 groups, as the group with successful tuberosity repair and the other with failed tuberosity repair. Statistical analysis of the functional outcome and shoulder scores between the 2 groups were done by independent t-test for normally distributed parameters and Mann-Whitney test for the parameters, where data was not normally distributed.ResultsOf 41 patients, tuberosity healing was achieved in 28 (68.3%) and failed in 13 (31.7%) cases. Lysis of the tuberosity occurred in 5 patients, tuberosity displacement in 2, and nonunion in 2. Mean age was 70.4 years (range 65 – 79 years) and mean follow-up was 58.7 months (range 18 – 93 months). There were no major complications. Group with successful tuberosity repair showed improvement in mean active range of movements, like anterior elevation (165.1° ± 4.9° vs. 144.6° ± 9.4°, p < 0.000), lateral elevation (158.9° ± 7.2° vs. 138.4° ± 9.6°, p < 0.000), external rotation (30.5° ± 6.9° vs. 35.0° ± 6.3°, p = 0.367), internal rotation (33.7° ± 7.5° vs. 32.6° ± 6.9°, p = 0.671) and in mean shoulder scores including Constant score (70.7 ± 4.1 vs. 55.5 ± 5.7, p < 0.000), American shoulder and elbow surgeons score (90.3 ± 2.4 vs. 69.0 ± 5.7, p < 0.000), disability of arm shoulder and hand score (22.1 ± 2.3 vs. 37.6 ± 2.6, p < 0.000).ConclusionSuccessful repair and tuberosity healing around the RSA prosthesis is associated with statistically significant improvement in postoperative range of motion, strength and shoulder scores. Standardized repair technique and interposition of cancellous bone grafts, harvested from the humeral head can improve the rate of tuberosity healing.     

Patterns of strain and the determination of the safe arc of motion after subscapularis repair—A biomechanical study

This study characterizes the strain patterns and safe arcs for passive range of motion (ROM) in the superior and inferior subscapularis tendon in seven cadaveric shoulders, mounted for controlled ROM, after deltopectoral approach to the glenohumeral joint, including tenotomy of the subscapularis tendon 1 cm medial to its insertion on the lesser tuberosity. The tenotomy was repaired with end‐to‐end suture in neutral rotation. Strain patterns were measured during passive ROM in external rotation (ER), ER with 30° abduction (ER+30), abduction, and forward flexion in the scapular plane (SP) before and after surgery. Percentages were calculated from 35 trials corresponding to five trials of each motion across seven specimens. With ER of 0?30°, 89% of trials of superior subscapularis tendon and 100% of trials of inferior subscapularis tendon achieved strains >3%, with very similar patterns noted in ER+30. In abduction of 0?90°, 5.8% of trials of superior and 85.3% of trials of inferior tendon achieved >3% strain. With passive ROM in SP, 26.5% of trials reached 3% strain in superior tendon compared to 100% in inferior tendon. Strain patterns in abduction and SP differed significantly (p < 0.001). Selective tenotomy and repair of the superior subscapularis tendon with open reparative or reconstructive shoulder procedures, when feasible, may be favorable for protected early passive ROM and rehabilitation postoperatively. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:518–524, 2016.

     

Locked posterior shoulder dislocation treated by arthroscopic tenodesis of the subscapularis in the reversed Hill-Sachs lesion

Report of a case of locked posterior shoulder dislocation, diagnosed after 3 weeks with an impression fracture involving almost 30% of the humeral head. Closed reduction was not stable. Shoulder arthroscopy confirmed the fracture and the unstable character of the dislocation. The subscapularis tendon was attached in this lesion using two suture anchors. Immediate shoulder stability was obtained. The 6-month follow-up was good, and the shoulder became stable and pain free. Arthroscopic tenodesis of the subscapularis may be an alternative to the McLaughlin technique in locked posterior shoulder dislocations involving 20–40% of the humeral head in cases presenting within 6 months after the initial episode.     

Adjusting Implant Size and Position Can Improve Internal Rotation After Reverse Total Shoulder Arthroplasty in a Three-dimensional Computational Model

BackgroundEfforts during reverse total shoulder arthroplasty (RSA) have typically focused on maximizing ROM in elevation and external rotation and avoiding scapular notching. Improving internal rotation (IR) is often overlooked, despite its importance for functional outcomes in terms of patient self-care and hygiene. Although determinants of IR are multifactorial, it is unable to surpass limits of bony impingement of the implant. Identifying implant configurations that can reduce bony impingement in a computer model will help surgeons during preoperative planning and also direct implant design and clinical research going forward.Questions/purposesIn a CT-modeling study, we asked: What reverse total shoulder arthroplasty implant position improves the range of impingement free internal rotation without compromising other motions (external rotation and extension)?MethodsCT images stored in a deidentified teaching database from 25 consecutive patients with Walch A1 glenoids underwent three-dimensional templating for RSA. Each template used the same implant and configuration, which consisted of an onlay humeral design and a 36-mm standard glenosphere. The resulting constructs were virtually taken through ROM until bony impingement was found. Variations were made in the RSA parameters of baseplate lateralization, glenosphere size, glenosphere overhang, humeral version, and humeral neck-shaft angle. Simulated ROM was repeated after each parameter was changed individually and then again after combining multiple changes into a single configuration. The impingement-free IR was calculated and compared between groups. We also evaluated the effect on other ROM including external rotation and extension to ensure that configurations with improvements in IR were not associated with losses in other areas.ResultsCombining lateralization, inferiorization, varus neck-shaft angle, increased glenosphere size, and increased humeral anteversion resulted in a greater improvement in internal rotation than any single parameter change did (median baseline IR: 85° [interquartile range 73° to 90°]; combined changes: 119° [IQR 113° to 121°], median difference: 37° [IQR 32° to 43°]; p < 0.001).ConclusionIncreased glenosphere overhang, varus neck-shaft angle, and humeral anteversion improved internal rotation in a computational model, while glenoid lateralization alone did not. Combining these techniques led to the greatest improvement in IR.Clinical RelevanceThis computer model study showed that various implant changes including inferiorization, varus neck-shaft angle, increased glenosphere size, and increased humeral anteversion can be combined to increase impingement-free IR. Surgeons can employ these currently available implant configurations to improve IR when planning and performing RSA. These findings support the need for further clinical studies validating the effect of implant configuration on resultant IR.     

Referencing the pectoralis major tendon for humeral stem height placement in reverse shoulder arthroplasty for fracture

BackgroundProximal humerus fractures remain a challenging problem, and reverse total shoulder arthroplasty (RSA) has demonstrated reliable outcomes in fracture applications. Despite this, guidelines for placement of the humeral component are lacking.MethodsTwelve cadaveric shoulders (6 cadaveric torsos) were utilized. An onlay RSA stem was placed with the lateral potion of the humeral cup positioned at the level of the greater tuberosity. Measurements were taken from the top of the pectoralis major tendon to the top of the humeral stem. A separate computer-aided analysis was conducted analyzing the height of an RSA humeral stem and an RSA humeral stem with a cup using values extrapolated from prior data.ResultsThe average distance from the top of the pectoralis to the top of the humeral stem was 4.0 cm (3.4 cm to 4.8 cm) with a standard deviation of 4.1. The humeral cup added an average of 9.1 mm. Computer-aided design data demonstrated the average height of the humeral stem was 3.9 cm above the superior aspect of the pectoralis tendon, and the average height with the humeral cup added was 4.8 cm.ConclusionBoth the cadaveric and computer-aided design data demonstrated a similar height for both the distances from the superior portion of the pectoralis to the superior aspect of an onlay RSA stem and the humeral cup. The measurement from the humeral cup may allow for translational use with inlay RSA humeral stems. This study demonstrates the superior border of the pectoralis major tendon to be a reliable landmark in RSA humeral stem placement.Level of evidenceLevel IV; Cadaveric Study     

Management of the subscapularis contracture during shoulder arthroplasty for primary glenohumeral arthritis

Aim To evaluate the safety and effectiveness of a particular subscapularis release in shoulder arthroplasty for primary glenohumeral arthritis. Materials and methods Twenty-eight patients (19F, 9M) underwent shoulder arthroplasty for primary glenohumeral arthritis. Preoperative average Constant Score (CS) was 31.2 points (range 14–52), active anterior elevation (AAE) 92° (30–100°) and active external rotation (AER) 11° (−40 to 20°). During arthroplasty for subscapularis contracture, patients underwent subscapularis release freeing the superior tubular tendon (STT) with a section of the coracohumeral ligament (CHL) and the superior glenohumeral ligament (SGHL) and a deep release consisting of a section of the middle glenohumeral ligament (MGHL), very close to the glenoid labrum, and the inferior glenohumeral ligament (IGHL). An anatomic study was performed on 13 cadavers, verifying the structure of subscapularis tendon and its relationship with the capsule, the surrounding ligaments and the axillary nerve. Moreover, after having placed traction sutures on the subscapularis tendon, its lengthening was measured after STT release alone and after STT and deep release. The complete absence of neurological and vascular lesions was also verified. Results Average follow-up: 2.9 years. Postoperative mean CS was 70.5 (p〈0.005), with an absolute gain of 39.1. AAE increased from 92° to 142° (p=0.001) while AER increased from 8° to 48° (p=0.002). At the last follow-up, 19 patients (67.8%) were very satisfied, 5 patients (17.8%) were satisfied, 3 patients (10.7%) partially satisfied and 1 patient (3.5%) unsatisfied. In the anatomic control, the average lengthening of subscapularis tendon was 0.9 cm after STT release alone and 2.5 cm after STT and deep release. No vascular and neurological lesions were observed. Conclusions The subscapularis release during shoulder arthroplasty is extremely important to obtain the proper balance between anterior and posterior soft tissues and to achieve an optimal range of motion and joint stability. An adequate anatomical dissection could give good tendon mobilisation and lengthening, necessary for a good repair, and lead to a recovery of the range of motion, particularly for external rotation.     

Radiographic outcomes of patients undergoing reverse shoulder arthroplasty using inlay versus onlay components: is there really a difference?

IntroductionAchieving soft tissue tension in RSA occurs by displacement of the humerus from the glenoid. We compared the lateral and inferior humeral displacement of two RSA systems radiographically. Each system utilized a humeral implant with a 135-degree neck-shaft angle and offered lateralized glenospheres. One had an onlay component and the other an inlay. Our primary hypothesis was that an alteration of surgical technique would negate the differences in their geometries radiographically. Secondarily, we sought to determine if a difference in complications or revisions occurred with these different designs.MethodsTwo hundred and eleven patients underwent RSA by a single surgeon with either an inlay or onlay prosthesis over a 2-year period. A true AP Grashey radiograph was utilized to measure: 1) Glenohumeral offset (GHO); 2) Acromiohumeral distance (AHD); 3) Pivot point (PP); 4) Humeral head cut surrogate (HHC) and 5) Humeral Socket Depth (HSD). Complications recorded included postoperative acromial fractures, revision for any reason, instability, and infections.ResultsThere was no significant difference in GHO or AHD between the two groups. There was a difference in PP and HHC between the groups (P < .001). The onlay group had an HHC 1.8 mm larger than inlay. Of the inlay group patients, 66% had their humeral tray placed above the level of the humeral osteotomy.DiscussionA larger HHC in the onlay group and implanting the inlay above the humeral osteotomy negates differences in AHD and GHO.Level of evidenceLevel III; Retrospective Comparative Study     

The effect of subscapularis management technique on outcomes and complication rates following reverse total shoulder arthroplasty

BackgroundRepair of the subscapularis tendon following rTSA has been shown to decrease postoperative dislocations in some studies, but the effect of repair on other outcomes has not been defined. We proposed to assess differences in postoperative pain, function, range of motion, strength, complications, and reoperations after three types of management of the subscapularis tendon—primary repair (tendon-to-tendon), transosseous repair, and no repair—at a minimum of two years of follow-up after rTSA.MethodsReview of an institutional database identified patients with primary rTSA treated by a single surgeon using the same operative technique and implant (medial glenoid with lateral humeral implant) except for subscapularis repair (tendon-to-tendon repair, transosseous repair, no repair). Patients with revision rTSA, anatomic TSA, hemiarthroplasty, or surgery for proximal humeral fracture, nonunion, or malunion were excluded.ResultsOf 210 patients meeting inclusion criteria, 82 (39%) had primary tendon repair of the subscapularis (PTR), 88 (41.9%) had transosseous repair (TOR), and 40 (19%) did not have the subscapularis repaired (NR). Of all demographics and comorbidities measured, the only significant differences among treatments groups were in gender (54.9% female in PTR, 43.2% in TOR, and 72.5% in NR, p = 0.008) and subscapularis status before surgery (89% intact in PTR, 80.7% in TOR, and 38.5% in NR, p < 0.001). There were significantly more patients in the NR group whose operative indication was massive rotator cuff tear compared to the TO and PR groups. Similarly, there were significantly more patients whose operative indication was primary osteoarthritis in the TR group over the PR group, and the PR group over the NR group. There were no significant differences in complication rates (11% PTR, 13.6% TOR, 15% NR, p = 0.79) or reoperation rates (PTR 2.4%, TOR 2.3%, NR 5.0%, p = 0.66) or associations between subscapularis management technique and reoperation or complication rates.ConclusionSubscapularis management technique in rTSA did not affect complication or reoperation rates, and the procedure led to improvements in pain, function, range of motion, and strength in all three treatment groups. Repair of the subscapularis, regardless of technique, led to greater improvements in pain compared to no repair, although this may be partially attributable to better preoperative subscapularis status in the repair groups. Both repair techniques led to equal improvements in all measured outcomes, with the exception of primary tendon repair producing more improvement in ER strength compared to transosseous repair.Level of evidenceLevel III; Case Control Study     

The glenohumeral micromotion and influence of the glenohumeral ligaments during axial rotation in varying abduction angle

BackgroundThe patients with shoulder instability or disorders in overhead athletes have been considered to have an abnormal micromotion at the glenohumeral joint. However, the normal range of the micromotion has not been available during axial rotation with various abduction angles, especially above 90° abduction. This study aimed to investigate the glenohumeral translation and influence of the glenohumeral ligaments during axial rotation with up to maximum abduction.MethodsFourteen healthy volunteers performed active axial rotations at 0°, 90°, 135°, and maximal abduction angles. The positions of the humeral head center relative to the glenoid at maximally external, neutral, and maximally internal rotations (ER, NR, IR, respectively) for each abduction angle were evaluated using two- (2D) and three-dimensional (3D) shape matching registration techniques. The shortest pathway and its length between the origin and insertion of the superior, middle, and inferior glenohumeral ligaments (SGHL, MGHL, and IGHL, respectively) were calculated for each position.ResultsThe glenohumeral joint showed 3.1 mm of superoinferior translation during axial rotation at 0° abduction (P < 0.0001), and 2.6 mm and 4.5 mm anteroposterior translation at 135° and maximal abduction (P < 0.0001), respectively. The SGHL and MGHL reached a maximum length at ER with 0° abduction, and the anterior and posterior bands of the IGHL reached a maximum at ER with 90° abduction and IR with 0° abduction.ConclusionsThese findings indicated that the SGHL played a role as an inferior suppressor at 0° abduction, while the anterior band of IGHL played a role as an anterior stabilizer at 90° abduction. Every glenohumeral ligament did not get taut and the anteroposterior translation became greater with increasing abduction angle, above 90°. These results could be used as a reference when comparing with the pathological shoulders in the future study.     

Pressure between the humeral head and the subscapularis tendon after the modified Boytchev procedure

The pressure between the humeral head and the subscapularis tendon was determined in 32 patients who had recurrent anterior shoulder dislocations. These patients' pressures were measured during a modified Boytchev procedure both before and after transposition of the conjoined tendon, and they were remeasured at the time of screw removal, performed at a mean of 13 months after the initial surgery. The mean clinical follow-up period was 31 months. A micro-tip catheter transducer was inserted into the glenohumeral joint between the humeral head and the subscapularis tendon. Pressures were measured at particular degrees of motion for two positions: passive external rotation of the arm at the side at 0 degrees, 15 degrees, 30 degrees, 45 degrees, and 60 degrees and passive external rotation at the 90 degrees abducted position at 0 degrees, 30 degrees, 60 degrees, and 90 degrees. The pressures were statistically significantly higher after the conjoined tendon transfer at all measured degrees of motion in the two positions. The pressures at the time of screw removal were not statistically significantly different from those seen after the tendon transfer during external rotation at 90 degrees of abduction. The modified Boytchev procedure increases the pressure between the humeral head and the subscapularis tendon. We suspect that this increased pressure increases proprioceptive stimuli in the subscapularis tendon and thus accelerates the protective reflex needed to prevent shoulder dislocation.     

The coracoid impingement of the subscapularis tendon: a cadaver study

To study the anatomic relationships and varieties of anterior impingement of the rotator cuff, an examination of 124 shoulder joints from 62 embalmed cadavers was performed. The distance between the lesser tuberosity and the coracoid was measured at different degrees of humeral rotation in the shoulder joint. Neither lateral differences nor differences with respect to donor gender were found in the distance measurements between the coracoid process and the lesser tuberosity for any rotational angle. In addition, no significant differences were found between shoulders with and without rupture of the subscapularis tendon. No lateral dominance was found for the subscapularis tunnel area.     

Computer tomography assessment of the subscapularis after reverse shoulder arthroplasty and subscapularis repair: reduction in subscapularis size do not affect clinical outcomes

BackgroundExcellent Clinical and patient-reported outcome have been reported following Reverse Shoulder Arthroplasty (RTSA). However, outcomes in range of motion (ROM) remain variable. The role and importance of subscapularis repair during RTSA is a topic of intense debate and the long term-integrity of the subscapularis after repair remains poorly studied. Aims of this study were to radiologically evaluate pre- and postoperative condition of the subscapularis muscle in RTSA with concurrent subscapularis tendon repair using transosseous suture, and to investigate the correlation between clinical and radiological results.MethodsPatients who had undergone RTSA with subscapularis repair in our Institute between January 2010 and November 2016 were included. Constant, UCLA, Simple Shoulder Test and Visual Analog Scale (VAS) pain questionnaires were administered pre- and postoperatively. Internal rotation ability was recorded on a 6-point scale. Pre - and postoperatively shoulder CT scans were performed by a blinded examiner from which subscapularis muscle cross-sectional area (SMCSA) and supraspinatus fossa cross-sectional area (SFCSA) were measured in square millimeters. The SMCSA/SFCSA ratio was employed to standardize values for individual anatomical differences between patients.ResultsThe study included 32 patients (32 shoulders). Mean follow-up was 74.6 months ± 15.2 months (range 35–117 months). Statistically significant differences were found between pre- and postoperative VAS score, Constant Score, UCLA and Simple Shoulder Test scales (P < .0001). A postoperative SMCSA reduction of >35% was found in 38% of patients. Only 21% of patients maintained their preoperative SMCSA/SFCSA ratio. Overall, a statistically significant difference in pre and postoperative SMCSA/SFCSA ratios was found (P < .001). A correlation between radiological findings and clinical outcomes was not found.ConclusionPostoperative subscapularis size expressed as SMCSA and SMCSA/SFCSA ratio, was significantly reduced in the majority of patients treated with non-lateralized RTSA design and concurrent subscapularis tendon repair at final follow-up. A correlation between radiological findings and clinical outcomes was not found. RTSA with subscapularis tendon repair provides a high degree of patient satisfaction, as well as statistically significant improvements in clinical outcomes and internal rotation ROM. Being associated with several advantages, subscapularis repair may be routinely recommended.Level of evidenceLevel II; Prospective Cohort Design; Prognosis Study     

Modified load sharing rip-stop technique in patients with traumatic transtendinous rotator cuff tear: Surgical technique and clinical outcomes

BackgroundTranstendinous rotator cuff tear is likely to occur due to trauma in sports activities, with a frequency of <2% of total rotator cuff tears. These tears are difficult to treat because of limited tendon tissue in the proximal stump, and standard repair techniques are sometimes ineffective. Few studies have reported on the repair technique and clinical outcomes for transtendinous rotator cuff tear, and an appropriate repair technique has, therefore, not been established. The purpose of this study was to use our modified load sharing rip-stop technique to repair transtendinous rotator cuff tear and to clarify the clinical effectiveness of this technique.MethodsThis was a retrospective case series review of eight patients who underwent the modified load sharing rip-stop technique for repairing traumatic transtendinous rotator cuff tear between January 2013 and June 2017. The eight patients were followed up for at least 2 years (range: 24–41 months). Cuff integrity was evaluated using magnetic resonance imaging at 12 months after surgery using the Sugaya classification. We evaluated the pre- and postoperative ranges of motion, American Shoulder and Elbow Surgeons score, Constant Shoulder Score, and muscle strength at 90° abduction. Data were analyzed using the Mann–Whitney U test and Fisher's exact tests. P < .05 was considered to indicate statistical significance.ResultsSix patients were classified as Sugaya I and two as Sugaya II. ASES score (38.5–90.2, P = .0008), Constant shoulder score (36.5–79, P = .002), flexion (85°–158.1°, P = .002), abduction (85°–157.5°, P = .001), external rotation (38.8°–55°, P = .024), and muscle strength at 90° abduction (2.95–5.39 kg, P = .028) improved significantly. Six patients were able to return to their previous sports activity.ConclusionUsing our modified load sharing rip-stop technique for repair of transtendinous rotator cuff tear, patients obtained good clinical outcomes and could return to sports activities.     

Influence of humeral prosthesis height on biomechanics of glenohumeral abduction. An in vitro study

BACKGROUND: During shoulder replacement surgery, the normal height of the proximal part of the humerus relative to the tuberosities frequently is not restored because of differences in prosthetic geometry or problems with surgical technique. The purpose of the present study was to determine the effect of humeral prosthesis height on range of motion and on the moment arms of the rotator cuff muscles during glenohumeral abduction. METHODS: Tendon excursions and abduction angles were recorded simultaneously in six cadaveric specimens during passive glenohumeral abduction in the scapular plane. Moment arms were calculated for each muscle by computing the slope of the tendon excursion-versus-glenohumeral abduction angle relationship. The experiments were carried out with the intact joint and after replacement of the humeral head with a prosthesis that was inserted in an anatomically correct position as well as 5 and 10 mm too high. RESULTS: Insertion of the prosthesis in positions that were 5 and 10 mm too high resulted in significant and marked reductions of the maximum abduction angle of 10 degrees (range, 5 degrees to 18 degrees ) and 16 degrees (range, 12 degrees to 20 degrees ), respectively. In addition, the moment arms of the infraspinatus and subscapularis decreased by 4 to 10 mm. This corresponded to a 20% to 50% decrease of the abduction moment arms of the infraspinatus and an approximately 50% to 100% decrease of the abduction moment arms of the subscapularis, depending on the abduction angle and the part of the muscle being considered. CONCLUSIONS: If a humeral head prosthesis is placed too high relative to the tuberosities, shoulder function is impaired by two potential mechanisms: (1) the inferior capsule becomes tight at lower abduction angles and limits abduction, and (2) the center of rotation is displaced upward in relation to the line of action of the rotator cuff muscles, resulting in smaller moment arms and decreased abduction moments of the respective muscles. Clinical Relevance: In patients managed with shoulder replacement surgery, limitation of range of motion, loss of abduction strength, and overload with long-term failure of the supraspinatus tendon are potential consequences of positioning the humeral head of the prosthesis proximal to the anatomic position.