Hydrogen Peroxide May Reduce the Risk for Revision Surgery and Infection in Primary Shoulder Arthroplasty: Two-year Follow-up From a Prospective, Blinded, Controlled Trial.

BACKGROUND: The purpose of this study was to determine whether the addition of hydrogen peroxide to the preoperative skin preparation for primary total shoulder arthroplasty is associated with a difference in patient-reported outcomes, risk for postoperative infection, and risk for revision surgery at a minimum of 2-year follow-up. METHODS: This was a prospective, blinded, and controlled trial, which included a consecutive series of patients undergoing primary shoulder arthroplasty. The control group underwent standard sterile skin preparation using ethyl alcohol and ChloraPrep applicators, and the peroxide group had the same preparation with the addition of hydrogen peroxide between the alcohol and ChloraPrep applications. We then compared patient-reported outcome scores (American Shoulder and Elbow Surgeons Shoulder Score [ASES], simple shoulder test [SST], visual analog scale [VAS]), infections, and revision surgeries between the two groups at 2-year follow-up. RESULTS: Of the 61 patients included in the original study, 52 of 58 (85%) living patients agreed to participate in this study. No preoperative differences were observed between groups. No difference was observed in ASES, SST, or VAS scores at 2 years. More revision surgeries were done in the control group (7 versus 2, P = 0.268) and Cutibacterium acnes infections (2 versus 0, P = 0.168). CONCLUSION: The addition of hydrogen peroxide to the preoperative skin preparation before primary shoulder arthroplasty is safe, and additional research is warranted to investigate whether it may decrease the risk for revision surgery and postoperative C acnes infection. LEVEL OF EVIDENCE: III.

The Effect of Lateralization and Distalization After Grammont-Style Reverse Total Shoulder Arthroplasty.

BACKGROUND: The purpose of this study is to evaluate the relationship between multiple radiographic measures of lateralization and distalization and clinical outcome scores after reverse total shoulder arthroplasty (RTSA). METHODS: We retrospectively evaluated all RTSAs performed by the senior author between January 1, 2007, and November 1, 2017. We then evaluated the visual analog scale for pain (VAS pain), Simple Shoulder Test (SST), and American Shoulder and Elbow Surgeons (ASES) scores and complication and reoperation rates at a minimum of 2-year follow-up. We measured preoperative and postoperative (2-week) radiographs for the lateralization shoulder angle (LSA), the distalization shoulder angle (DSA), lateral humeral offset (LHO), and distance from glenoid to lateral aspect of the greater tuberosity (GLAGT). A multivariable analysis was performed evaluating the effect of the postoperative radiographic measurements on final patient reported outcomes (ASES scores, SST, VAS pain). RESULTS: The cohort included 216 shoulders from unique patients who had patient reported outcome scores available at a minimum of 2-year follow-up (average, 4.0±1.9 years) for a total follow-up rate of 70%. In the multivariable models, more lateralization (LSA) was associated with worse final ASES scores -0.52 (95% CI: -0.88 to -0.17; p=0.004), and more distalization (DSA) was associated with better final ASES scores 0.40 (95% CI: 0.11, 0.69; p=0.007). More lateralization (LSA) was associated with worse final SST scores -0.06 (95% CI: -0.11, -0.003; p=0.039). Finally, greater distalization (DSA) was associated with lower final VAS pain scores, Ratio = 0.98 (95% CI: 0.96, 1.00; p=0.021). CONCLUSION: Greater distalization and less lateralization are associated with better function and less pain after Grammont-style RTSA. If utilizing a Grammont-style implant, remaining consistent with Grammont's principles of implant placement will afford better final clinical outcomes.

Three-month Delay in Rotator Cuff Repair: 2-year Follow-up.

INTRODUCTION: This study examined 2-year outcomes of patients who underwent delayed rotator cuff repair (RCR) compared with those who underwent RCR without delay. METHODS: In this prospective comparative study, two groups were formed: (1) patients planning RCR during a 6-week elective surgery ban and (2) patients undergoing RCR at least 6 weeks after the ban. The Simple Shoulder Test, American Shoulder and Elbow Surgeon score, and visual analog scale for pain were collected preoperatively and at 2 years postoperatively. Magnetic resonance imaging assessed healing 6 months postoperatively. RESULTS: With a 93.3% 2-year follow-up (13/15 delay group, 15/15 control), there was an 87-day difference in presentation to surgery (P = 0.001), with no significant preoperative demographic or tear characteristic differences between groups. Intraoperatively, there were no differences between groups in repair characteristics. Preoperative versus postoperative differences in American Shoulder and Elbow Surgeon score (P < 0.001), visual analog scale (P < 0.001), and Simple Shoulder Test scores (P < 0.001) were significant but not between groups (P = 0.650, 0.586, 0.525). On MRI, 58% in the delay group and 85% in the control group had healed (P = 0.202). DISCUSSION: Although a 3-month delay showed no statistically significant effect on outcomes, the delay group had an approximately 27% higher failure rate. Thus, although a 3-month period of nonsurgical treatment before RCR may be reasonable, larger studies are warranted for definitive conclusions.

Estrogen and testosterone supplementation improves tendon healing and functional recovery after rotator cuff repair.

Failure of healing after rotator cuff repair (RCR) is common. The purpose of the current study was to evaluate the effect of systemic estrogen or testosterone supplementation on tendon healing after RCR. Seventy-two adult male mice were utilized for all experiments. The supraspinatus tendon was transected and repaired with 6-0 Prolene suture on the left shoulder of 51 animals. Mice were segregated into three groups postoperative: (1) vehicle group (VG; n = 18), (2) estrogen group (EST; n = 17), and (3) testosterone group (TST; n = 16). An unrepaired control group (unrepaired, n = 21) did not have surgery. Utilizing these animals, histological analysis, activity testing, biomechanical testing and RNA sequencing (RNA-seq) was performed. At 8 weeks post-RCR, TST, and EST supplementation improved the overall histologic structure of the repaired enthesis site. No differences in ultimate failure loads or stiffness were detected between VG, EST, and TST groups after biomechanical testing. RCR caused a reduction in wheel activity compared to unrepaired controls and supplementation with TST restored wheel activity. RNA-seq analysis indicated that estrogen and testosterone regulated different pathways associated with enthesis healing, including a suppression of inflammatory signaling. Supplementation with sex hormones improved the structure of the repaired tendon enthesis and significantly regulated expression of diverse pathways regulating multiple biological processes. Testosterone administration following RCR restored wheel activity without having a detrimental impact on biomechanical strength. Future human studies of sex hormone supplementation after RCR are warranted as supplementation in an animal model may improve tendon enthesis healing.

Biomechanical comparison of suture bridge rotator cuff repair with and without dermal allograft pledgets.

BACKGROUND: One method to augment rotator cuff repair is to pass dermal allograft pledgets along the sutures that bridge from the medial to the lateral row. It remains unclear whether this augmentation method alters repair biomechanics. METHODS: This was a controlled laboratory study. After an a priori power analysis, 9 pairs of rotator cuffs underwent double-row suture bridge rotator cuff repair, half randomized to augmentation with dermal allograft pledgets passed along the suture bridge sutures. Repairs were then mounted on a material testing system and loaded cyclically 500 cycles to measure applied force and displacement. Repairs then underwent ultimate failure testing, and stiffness, ultimate failure force, and ultimate failure displacement were measured. Paired t tests were performed to compare between groups. RESULTS: There were no differences between groups in construct gapping with cyclic loading after 500 cycles (P = .885). There were no differences between the augmented and control groups in yield force (103.5 ± 5.0 vs. 101.4 ± 5.9 N, respectively, P = .183), stiffness (94.2 ± 13.9 vs. 90.9 ± 13.8, P = .585), or ultimate failure force (255.3 ± 65.8 vs. 285.3 ± 83.2, P = .315). There were no differences between groups in failure modes, with most specimens failing by cuff tissue tearing within or medial to the construct. CONCLUSION: The addition of dermal allograft pledgets does not positively or negatively influence the time-zero biomechanical characteristics of double-row suture bridge rotator cuff repair.

Common Complication From Routine Shoulder Surgery: Postoperative Stiffness After Rotator Cuff Repair.

Rotator cuff repair is commonly performed, and stiffness represents one of the most common complications. Unique characteristics of postoperative stiffness, including its natural history and pathoanatomy, differentiate it from other etiologies of shoulder stiffness. Patient risk factors that have been associated with postoperative stiffness should be reviewed to better help clinicians tailor their presurgical risk assessment. Although stiffness in this setting has clinical consequences for patients' postoperative shoulder function, it is important to discuss the important implications of stiffness as it relates to rotator cuff healing. Multiple strategies have been proposed to decrease the incidence of postoperative stiffness. There is evidence to support these preventive strategies, and it has led to author recommendations for treatment of refractory cases and prevention.

Inlay vs. onlay humeral components in reverse total shoulder arthroplasty: a biorobotic shoulder simulator study.

BACKGROUND: Both inlay and onlay humeral implants are available for reverse total shoulder arthroplasty (rTSA), but biomechanical data comparing these components remain limited. This study investigated the effects of inlay and onlay rTSA humeral components on shoulder biomechanics using a biorobotic shoulder simulator. METHODS: Twenty fresh-frozen cadaveric shoulders were tested before and after rTSA with either an inlay or onlay humeral implant. Comparisons were performed between the most commonly implanted configurations for each implant (baseline) and with a modification to provide equivalent neck-shaft angles (NSAs) for the inlay and onlay configurations. Specimens underwent passive range-of-motion (ROM) assessment with the scapula held static, and scapular-plane abduction was performed, driven by previously collected human-subject scapulothoracic and glenohumeral kinematics. Passive ROM glenohumeral joint angles were compared using t tests, whereas muscle force and excursion data during scapular-plane elevation were evaluated with statistical parametric mapping and t tests. RESULTS: Maximum passive elevation was reduced for the inlay vs. onlay humeral components, although both implants caused reduced passive elevation vs. the native joint. Inlay rTSA also demonstrated reduced passive internal rotation at rest and increased external rotation at 90° of humerothoracic elevation vs. the native joint. All preoperative planning estimates of ROM differed from experiments. Rotator cuff forces were elevated with an onlay vs. inlay humeral implant, but simulated muscle excursions did not differ between systems. Compared with the native joint, rotator cuff forces were increased for both inlay and onlay implants and deltoid forces were reduced for inlay implants. Muscle excursions were dramatically altered by rTSA vs. the native joint. Comparisons of inlay and onlay humeral implants with equivalent NSAs were consistent with the baseline comparisons. CONCLUSIONS: Rotator cuff forces required to perform scapular-plane abduction increase following rTSA using both inlay and onlay implants. Rotator cuff forces are lower with inlay implants compared with onlay implants, although inlay implants also result in reduced passive-elevation ROM. Deltoid forces are lower with inlay implants in comparison to the native joint but not with onlay implants. The differences between inlay and onlay components are largely unaffected by NSA, indicating that these differences are inherent to the inlay and onlay designs. In those patients with an intact rotator cuff, decreased rotator cuff forces to perform abduction with an inlay humeral implant compared with an onlay implant may promote improved long-term outcomes owing to reduced deltoid muscle fatigue when using an inlay implant.

Arthroscopic scapulothoracic bursectomy with and without superomedial angle scapuloplasty: a comparison of patient-reported outcomes.

BACKGROUND: Operative treatment of scapulothoracic bursitis most commonly comprises arthroscopic scapulothoracic bursectomy with or without partial superomedial angle scapuloplasty. There is currently no consensus regarding whether or when scapuloplasty should be performed. Prior studies are limited to small case series, and optimal surgical indications are not yet established. The purposes of this study were (1) to retrospectively review patient-reported outcomes of arthroscopic treatment of scapulothoracic bursitis and (2) to compare outcomes between scapulothoracic bursectomy alone and bursectomy with scapuloplasty. We hypothesized that bursectomy with scapuloplasty would provide superior pain relief and functional improvement. MATERIALS AND METHODS: All cases of scapulothoracic débridement with or without scapuloplasty completed at a single academic center from 2007 through August 2020 were reviewed. Patient demographic characteristics, symptomatology data, physical examination findings, and corticosteroid injection response data were collected from the electronic medical record. Visual analog scale pain, American Shoulder and Elbow Surgeons, Simple Shoulder Test, and Single Assessment Numeric Evaluation scores were collected. Comparisons between the group undergoing bursectomy alone and the group undergoing bursectomy with scapuloplasty were made using the Student t test for continuous variables and the Fisher exact test for categorical variables. RESULTS: Thirty patients underwent scapulothoracic bursectomy alone, and 38 patients underwent bursectomy with scapuloplasty. Final follow-up data were available for 56 of 68 cases (82%). Final postoperative visual analog scale pain scores (3.4 ± 2.2 and 2.8 ± 2.2, respectively; P = .351), American Shoulder and Elbow Surgeons scores (75.8 ± 17.7 and 76.5 ± 22.5, respectively; P = .895), and Simple Shoulder Test scores (8.8 ± 2.3 and 9.5 ± 2.8, respectively; P = .340) were similar between the bursectomy-alone and bursectomy-with-scapuloplasty groups. CONCLUSION: Both arthroscopic scapulothoracic bursectomy alone and bursectomy with scapuloplasty are effective treatments for scapulothoracic bursitis. Operative time is shorter without scapuloplasty. In this retrospective series, these procedures showed similar outcomes regarding shoulder function, pain, surgical complications, and rates of subsequent shoulder surgery. Further studies with a focus on 3-dimensional scapular morphology may help optimize patient selection for each of these procedures.

Active physical therapy does not improve outcomes after reverse total shoulder arthroplasty: a multi-center, randomized clinical trial.

OBJECTIVE: To compare range of motion (ROM) and patient-reported outcomes (PROs) between a structured home exercise program (HEP) and active, supervised physiotherapy (PT) after primary Reverse total shoulder arthroplasty (RTSA) by performing a multicenter randomized clinical trial. METHODS: Patients undergoing primary RTSA at 2 centers were randomized to either a HEP group, in which they were given a handout and a rope pulley, or a PT group, in which they were given a standardized prescription. Surgical technique and implants were standardized. At baseline, 6 weeks, 3 months, and 1 year postoperatively, we obtained American Shoulder and Elbow Surgeons scores, Western Ontario Osteoarthritis Scores, visual analogue scale for pain scores, and measured ROM via videotape. On video, ROM was then measured by blinded observers. At all study visits, patients were asked how many days per week they were in PT and how many days a week they completed HEP to determine compliance and crossover. An a priori power analysis suggested 29 patients per group, 56 patients total to detect a difference of 30° in active forward elevation with a power of 0.8 at a 2-sided alpha of 0.05. RESULTS: 89 patients were randomized, 43 to PT, and 46 to HEP. We obtained 1-year PRO follow-up on 83 patients (93%) and ROM follow-up on 73 patients (82%). Nine patients (20%) crossed over from HEP to PT and 2 patients (4%) crossed over from PT to HEP. Complications occurred in 13% of HEP and 17% of PT patients (P = .629). Using mixed models that account for baseline values, there were no significant differences between groups in PROs or ROM at final follow-up. CONCLUSION: In this 2-center, randomized clinical trial, there were no significant differences in patient outcomes or ROM between HEP and PT after RTSA. These findings suggest that it may not be necessary to recommend PT as a protocol for all patients after RTSA.

A stabilizing role of the glenoid labrum: the suction cup effect.

BACKGROUND: The glenoid labrum acts as a bumper, deepening glenoid concavity and amplifying the concavity-compression mechanism, and serves as the scapular attachment for glenohumeral ligaments. The role of the posterosuperior labrum in anteroinferior glenohumeral stability, and the role of the anterior labrum in posterior stability has been debated. The purpose of this study was to quantify the contribution of anteroinferior and posterosuperior labral tears to loss of glenohumeral stability in multiple directions. METHODS: Fourteen fresh-frozen cadaveric shoulders were tested on a custom stability ratio measurement apparatus. The peak force that was required to translate the humeral head in anterior, anteroinferior, posterior, and posteroinferior directions was measured under 5 conditions: intact labrum (n = 14), anteroinferior labral tear (n = 7), posterosuperior labral tear (n = 7), combined labral tear (n = 14), and no labrum (n = 14). The stability ratio was defined as the peak translational force divided by the compressive force. Within force-translation curves, we defined the suction cup effect as the force required to release the negative pressure created by an intact labrum. RESULTS: The suction cup effect was usually present with the intact labrum and always disappeared after removal of the labrum for anterior (100% vs. 0%) and posterior (86% vs. 0%) translations (P < .001). After creation of an anteroinferior labral tear, the stability ratio for posterior direction decreased (P < .001) and the suction cup effect disappeared (P < .001). After creation of a posterosuperior labral tear, stability ratios in the anterior and anteroinferior directions decreased (P ≤ .006) and the suction cup effect disappeared (P ≤ .015). The stability ratio for anterior and anteroinferior testing was more diminished by posterosuperior labral tears than anteroinferior labral tears, and the stability ratio for posterior testing was more diminished by anteroinferior labral tears than posterosuperior labral tears. CONCLUSION: Anteroinferior labral tears decreased posterior stability and posterosuperior labral tears decreased anterior and anteroinferior stability, largely because of loss of the suction cup effect.

High and low performers in internal rotation after reverse total shoulder arthroplasty: a biplane fluoroscopic study.

BACKGROUND: Internal rotation in adduction is often limited after reverse total shoulder arthroplasty (rTSA), but the origins of this functional deficit are unclear. Few studies have directly compared individuals who can and cannot perform internal rotation in adduction. Little data on underlying 3D humerothoracic, scapulothoracic, and glenohumeral joint relationships in these patients are available. METHODS: Individuals >1-year postoperative to rTSA were imaged with biplane fluoroscopy in resting neutral and internal rotation in adduction poses. Subjects could either perform internal rotation in adduction with their hand at T12 or higher (high, N = 7), or below the hip pocket (low, N = 8). Demographics, the American Shoulder and Elbow Surgeons score, Simple Shoulder Test, and scapular notching grade were recorded. Joint orientation angles were derived from model-based markerless tracking of the scapula and humerus relative to the torso. The 3D implant models were aligned to preoperative computed tomography models to evaluate bone-implant impingement. RESULTS: The Simple Shoulder Test was highest in the high group (11 ± 1 vs. 9 ± 2, P = .019). Two subjects per group had scapular notching (grades 1 and 2), and 3 high group and 4 low group subjects had impingement below the glenoid. In the neutral pose, the scapula had 7° more upward rotation in the high group (P = .100), and the low group demonstrated 9° more posterior tilt (P = .017) and 14° more glenohumeral elevation (P = .047). In the internal rotation pose, axial rotation was >45° higher in the high group (P ≤ .008) and the low group again had 11° more glenohumeral elevation (P = .058). Large rotational differences within subject groups arose from a combination of differences in the resting neutral and maximum internal rotation in adduction poses, not only the terminal arm position. CONCLUSIONS: Individuals who were able to perform high internal rotation in adduction after rTSA demonstrated differences in joint orientation and anatomic biases versus patients with low internal rotation. The high rotation group had 7° more resting scapular upward rotation and used a 15°-30° change in scapular tilt to perform internal rotation in adduction versus patients in the low group. The combination of altered resting scapular posture and restricted scapulothoracic range of motion could prohibit glenohumeral rotation required to reach internal rotation in adduction. In addition, inter-patient variation in humeral torsion may contribute substantially to postoperative internal rotation differences. These data point toward modifiable implant design and placement factors, as well as foci for physical therapy to strengthen and mobilize the scapula and glenohumeral joint in response to rTSA surgery.

A shared genetic architecture between adhesive capsulitis and Dupuytren disease.

BACKGROUND: The etiology of adhesive capsulitis involves inflammation, thickening, and fibrosis of the shoulder capsule. The underlying genetic factors are poorly understood. The purpose of this study was to identify genetic variants associated with adhesive capsulitis using the UK Biobank (UKB) cohort and compare them with variants associated with Dupuytren disease investigating a common etiology between the 2 fibrotic disorders. METHODS: A genome-wide association study (GWAS) was performed using data from UKB with 10,773 cases of adhesive capsulitis, and a second GWAS was performed with 8891 cases of Dupuytren disease. Next, a comparison of association statistics was performed between adhesive capsulitis and Dupuytren disease using the data from both GWAS. Finally, single-nucleotide polymorphisms (SNPs) previously reported from candidate gene studies for adhesive capsulitis and Dupuytren disease were tested for association with adhesive capsulitis and Dupuytren disease using the summary statistics from their respective GWAS. RESULTS: The UKB GWAS for adhesive capsulitis identified 6 loci that reached genome-wide statistical significance: a cluster of 11 closely linked SNPs on chromosome 1; a single SNP on chromosome 2; a single SNP on chromosome 14; 2 closely linked SNPs on chromosome 21; 33 closely linked SNPs on chromosome 22; and 3 closely linked SNPs on the X chromosome. These SNPs were associated with 8 different genes including TSPAN2/NGF, SATB2, MRPL52/MMP14, ERG, WNT7B, and FGF13. A GWAS for Dupuytren disease was performed and a comparison to the adhesive capsulitis GWAS showed 13 loci significantly associated with both phenotypes. A validation attempt of 6 previously reported SNPs associated with adhesive capsulitis using UKB summary statistics was unable to confirm any of the previously reported SNPs (all P > .19). All 23 previously reported SNPs associated with Dupuytren disease were confirmed using the UKB summary statistics (P < 2.1 × 10-3) CONCLUSION: This GWAS investigating adhesive capsulitis has identified 6 novel loci involving 8 different genes to be associated with adhesive capsulitis. A GWAS investigating Dupuytren disease was performed and compared to the adhesive capsulitis GWAS, and 13 common loci were identified between the 2 disorders with genes involved in pathologic fibrosis. We were unable to validate the SNPs in candidate genes previously reported to be associated with adhesive capsulitis although we were able to confirm all previously reported SNPs associated with Dupuytren disease. The strong genetic overlap between the adhesive capsulitis and Dupuytren disease loci suggests a similar etiology between the 2 diseases.

Rotator cuff muscle imbalance associates with shoulder instability direction.

BACKGROUND: Although muscle weakness and/or imbalance of the rotator cuff are thought to contribute to the development of shoulder instability, the association between muscular dysfunction and shoulder instability is not completely understood. The purpose of this study was to evaluate rotator cuff and deltoid muscle cross-sectional areas in different types of shoulder instability (anterior, posterior, and multidirectional instability [MDI]) and to determine the associations between muscular imbalance and shoulder instability direction. METHODS: Preoperative magnetic resonance images of patients with shoulder instability who subsequently underwent arthroscopic glenohumeral labral repair or capsular plication were evaluated. Shoulder instability was classified into 3 categories by direction: (1) anterior, (2) posterior, and (3) MDI. The rotator cuff (supraspinatus, subscapularis, and infraspinatus + teres minor) and deltoid (anterior and posterior portions, and total) muscle areas were measured on T1 sagittal and axial slices, respectively. The ratios of the subscapularis to infraspinatus + teres minor area and the anterior deltoid to posterior deltoid area were calculated to quantify the transverse force couple imbalance. RESULTS: A total of 189 patients were included, where each group consisted of 63 patients. The infraspinatus + teres minor muscle area was smaller than the subscapularis muscle area in the anterior instability group (P = .007). The subscapularis muscle area was smaller than the infraspinatus + teres minor muscle area in the posterior instability and MDI groups (P ≤ .003). The anterior deltoid muscle area was smaller than the posterior deltoid muscle area in all groups (P ≤ .001). The subscapularis-to-infraspinatus + teres minor area ratio in the anterior instability group (1.18 ± 0.40) was higher than that in the posterior instability and MDI groups (0.79 ± 0.31 and 0.93 ± 0.33, respectively; P < .001). There was no difference in the anterior deltoid-to-posterior deltoid area ratio among the 3 groups. CONCLUSION: Patients with anterior instability have smaller muscle area of the posterior rotator cuff as compared with the anterior rotator cuff. In contrast, patients with posterior instability and MDI have smaller muscle area of the anterior rotator cuff as compared with the posterior rotator cuff. Thus, the direction of shoulder instability is associated with rotator cuff muscle area.

Revision Reverse Total Shoulder Arthroplasty With Pectoralis Major Transfer for Anterior Deltoid Deficiency: A Case Report.

CASE: A 70-year-old male patient presented with anterior deltoid weakness from Parsonage-Turner neuropathy status post failed nerve transfer and a failed total shoulder arthroplasty with pseudoparalysis. The patient underwent revision to a reverse total shoulder arthroplasty with concomitant pectoralis major transfer to substitute for the anterior deltoid. An excellent functional result was attained as early as 6 weeks after surgery. CONCLUSION: Pectoralis major transfer can be an effective treatment option for isolated anterior deltoid insufficiency, even in the setting of a reverse total shoulder arthroplasty.

Reverse total shoulder glenoid component inclination affects glenohumeral kinetics during abduction: a cadaveric study.

BACKGROUND: Optimal implant placement in reverse total shoulder arthroplasty (rTSA) remains controversial. Specifically, the optimal glenoid inclination is unknown. Therefore, a cadaveric shoulder simulator with 3-dimentional human motion specific to rTSA was used to study joint contact and muscle forces as a function of glenoid component inclination. METHODS: Eight human cadaver shoulders were tested before and after rTSA implantation. Scapular plane abduction kinematics from control subjects and those with rTSA drove a cadaveric shoulder simulator with 3-dimentional scapulothoracic and glenohumeral motion. Glenoid inclination varied from -20° to +20°. Outputs included compression, superior-inferior (S/I) shear, and anterior-posterior shear forces from a 6° of freedom load cell in the joint, and deltoid and rotator cuff muscle forces. Data were evaluated with statistical parametric mapping and t-tests. RESULTS: Inferior glenoid inclination (-) reduced S/I shear by up to 125% relative to superior inclination, with similar compression to the neutral condition (0°). Superior inclinations (+) increased the S/I shear force by approximately the same magnitude, yet decreased compression by 25% in the most superior inclination (+20°). There were few differences in deltoid or rotator cuff forces due to inclination. Only the middle deltoid decreased by approximately 7% for the most inferior inclination (-20°). Compared with native shoulders, the neutral (0°) rTSA inclination showed reduced forces of 30%-75% in the anterior deltoid and a trend toward decreased forces in the middle deltoid. Force demands on the rotator cuff varied as a function of elevation, with a trend toward increased forces in rTSA at peak glenohumeral elevation. CONCLUSIONS: Inferior inclination reduces superior shear forces, without influencing compression. Superior inclination increased S/I shear, while decreasing compression, which may be a source of component loosening and joint instability after rTSA. Inferior inclination of the rTSA glenoid may reduce the likelihood of glenoid loosening by reducing the magnitude of cyclic shear and compressive loading during arm elevation activities, although this may be altered by specific-subject body habitus and motion. These factors are especially important in revision rTSA or glenoid bone grafting where there is already a 3-fold increase in glenoid baseplate loosening vs. primary rTSA.

Reverse Total Shoulder Arthroplasty Alters Humerothoracic, Scapulothoracic, and Glenohumeral Motion During Weighted Scaption.

BACKGROUND: Reverse total shoulder arthroplasty (rTSA) typically restores active arm elevation. Prior studies in patients with rTSA during tasks that load the arm had limitations that obscured underlying three-dimensional (3D) kinematic changes and the origins of motion restrictions. Understanding the scapulothoracic and glenohumeral contributions to loaded arm elevation will uncover where functional deficits arise and inform strategies to improve rTSA outcomes. QUESTIONS/PURPOSES: In a cohort of patients who had undergone rTSA and a control cohort, we asked: (1) Is there a difference in maximum humerothoracic elevation when scapular plane elevation (scaption) is performed with and without a handheld weight? (2) Is maximum humerothoracic elevation related to factors like demographics, patient-reported outcome scores, isometric strength, and scapular notching (in the rTSA group only)? (3) Are there differences in underlying 3D scapulothoracic and glenohumeral motion during scaption with and without a handheld weight? METHODS: Ten participants who underwent rTSA (six males, four females; age 73 ± 8 years) were recruited at follow-up visits if they were more than 1 year postoperative (24 ± 11 months), had a BMI less than 35 kg/m 2 (29 ± 4 kg/m 2 ), had a preoperative CT scan, and could perform pain-free scaption. Data from 10 participants with a nonpathologic shoulder, collected previously (five males, five females; age 58 ± 7 years; BMI 26 ± 3 kg/m 2 ), were a control group with the same high-resolution quantitative metrics available for comparison. Participants in both groups performed scaption with and without a 2.2-kg handheld weight while being imaged with biplane fluoroscopy. Maximum humerothoracic elevation and 3D scapulothoracic and glenohumeral kinematics across their achievable ROM were collected via dynamic imaging. In the same session the American Shoulder and Elbow Surgeons (ASES) score, the Simple Shoulder Test (SST), and isometric strength were collected. Data were compared between weighted and unweighted scaption using paired t-tests and linear mixed-effects models. RESULTS: When compared with unweighted scaption, maximum humerothoracic elevation decreased during weighted scaption for patients who underwent rTSA (-25° ± 30°; p = 0.03) but not for the control group (-2° ± 5°; p = 0.35). In the rTSA group, maximum elevation correlated with the ASES score (r = 0.72; p = 0.02), and weighted scaption correlated with BMI (r = 0.72; p = 0.02) and the SST (r = 0.76; p = 0.01). Scapular notching was observed in three patients after rTSA (Grades 1 and 2). Four of 10 patients who underwent rTSA performed weighted scaption to less than 90° humerothoracic elevation using almost exclusively scapulothoracic motion, with little glenohumeral contribution. This manifested as changes in the estimated coefficient representing mean differences in slopes in the humerothoracic plane of elevation (-12° ± 2°; p < 0.001) and true axial rotation (-16° ± 2°; p < 0.001), scapulothoracic upward rotation (7° ± 1°; p < 0.001), and glenohumeral elevation (-12° ± 1°; p < 0.001), plane of elevation (-8° ± 3°; p = 0.002), and true axial rotation (-11° ± 2°; p < 0.001). The control group demonstrated small differences between scaption activities (< |2°|), but a 10° increase in humerothoracic and glenohumeral axial rotation (both p < 0.001). CONCLUSION: After rTSA surgery, maximum humerothoracic elevation decreased during weighted scaption by up to 88° compared with unweighted scaption, whereas 4 of 10 patients could not achieve more than 90° of elevation. These patients exhibited appreciable changes in nearly all scapulothoracic and glenohumeral degrees of freedom, most notably a near absence of glenohumeral elevation during weighted scaption. Patients with rTSA have unique strategies to elevate their arms, often with decreased glenohumeral motion and resultant compensation in scapulothoracic motion. In contrast, the control group showed few differences when lifting a handheld weight. CLINICAL RELEVANCE: Functional deficiency in activities that load the shoulder after rTSA surgery can affect patient independence, and they may be prevalent but not captured in clinical studies. Pre- or postoperative rehabilitation to strengthen scapular stabilizers and the deltoid should be evaluated against postoperative shoulder function. Further study is required to determine the etiology of deficient glenohumeral motion after rTSA, and the most effective surgical and/or rehabilitative strategies to restore deficient glenohumeral motion after rTSA.

Anatomic total shoulder glenoid component inclination affects glenohumeral kinetics during abduction: a cadaveric study.

BACKGROUND: Although typically favorable in outcome, anatomic total shoulder arthroplasty (aTSA) can require long-term revision. The most common cause for revision is glenoid loosening, which may result from eccentric cyclic forces and joint translations. "Rocking" of the glenoid component may be exacerbated by the joint geometry, such as glenoid inclination and version. Restoration of premorbid glenoid inclination may be preferable, although laboratory and computational models indicate that both superior inclination and inferior inclination have benefits. This discrepancy may arise because previous studies were limited by a lack of physiological conditions to test inclination. Therefore, a cadaveric shoulder simulator with 3-dimensional human motion was used to study joint contact and muscle forces with isolated changes in glenoid inclination. METHODS: Eight human cadaveric shoulders were tested before and after aTSA. Scapular-plane abduction kinematics from human subjects were used to drive a cadaveric shoulder simulator with 3-dimensional scapulothoracic and glenohumeral motion. Glenoid inclination was varied from -10° to +20°, whereas compressive, superior-inferior shear, and anterior-posterior shear forces were collected with a 6-df load cell during motion. Outputs also included muscle forces of the deltoid and rotator cuff. Data were evaluated with statistical parametric mapping repeated-measures analysis of variance and t tests. RESULTS: Inferior glenoid inclination (-10°) reduced both compressive and superior-inferior shear forces vs. neutral 0° inclination by up to 40%, and even more when compared with superior inclination (P < .001). Superior inclinations (+10° and +20°) tended to increase deltoid and rotator cuff forces vs. neutral 0° inclination or inferior inclination, on the order of 20%-40% (P ≤ .045). All force metrics except anterior-posterior shear were lowest for inferior inclination. Most aTSA muscle forces for neutral 0° inclination were not significantly different from native shoulders and decreased 45% and 15% in the posterior deltoid and supraspinatus, respectively (P ≤ .003). Joint translations were similar to prior reports in aTSA patients and did not differ between any inclinations or compared with native shoulders. Joint reaction forces were similar to those observed in human subjects with instrumented aTSA implants, providing confidence in the relative magnitude of our results. CONCLUSIONS: Inferior inclination reduces overall forces in the shoulder. Superior inclinations increase the muscle effort required for the shoulder to achieve similar motion, thus increasing the forces exerted on the glenoid component. These results suggest that a preference toward aTSA glenoid components in inferior inclination may reduce the likelihood of glenoid loosening by reducing excessive muscle and joint contact forces.

The Effect of Sex Hormone Deficiency on the Incidence of Rotator Cuff Repair: Analysis of a Large Insurance Database.

BACKGROUND: The purpose of the present study was to analyze the association between sex hormone deficiency and rotator cuff repair (RCR) with use of data from a large United States insurance database. METHODS: A retrospective analysis of insured subjects from the Truven Health MarketScan database was conducted, collecting data for RCR cases as well as controls matched for age, sex, and years in the database. Multivariable logistic regression models adjusted for matching variables were utilized to compare RCR status with estrogen deficiency status and testosterone deficiency status. These associations were confirmed with use of data from the Veterans Genealogy Project database, with which the relative risk of RCR was estimated for patients with and without sex hormone deficiency. RESULTS: The odds of RCR for female patients with estrogen deficiency were 48% higher (odds ratio, 1.48; 95% confidence interval, 1.44 to 1.51; p < 0.001) than for those without estrogen deficiency. The odds of RCR for males with testosterone deficiency were 89% higher (odds ratio, 1.89; 95% confidence interval, 1.82 to 1.96; p < 0.001) than for those without testosterone deficiency. Within the Veterans Genealogy Project database, the relative risk of estrogen deficiency among RCR patients was 2.58 (95% confidence interval, 2.15 to 3.06; p < 0.001) and the relative risk of testosterone deficiency was 3.05 (95% confidence interval, 2.67 to 3.47; p < 0.001). CONCLUSIONS: Sex hormone deficiency was significantly associated with RCR. Future prospective studies will be necessary to understand the pathophysiology of rotator cuff disease as it relates to sex hormones. LEVEL OF EVIDENCE: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Restoration of the native humeral anatomy during stemless anatomic total shoulder arthroplasty: a radiographic comparison of intramedullary versus freehand resection.

BACKGROUND: During anatomic total shoulder arthroplasty (aTSA), the humeral head can be resected with or without the use of an intramedullary cutting guide, the former referred to as intramedullary (IM) resection and the latter referred to as freehand (FH) resection. Outcomes following aTSA are predicated upon the restoration of the native humeral anatomy, which can be more challenging with stemless implants. To date, no studies have determined which method of humeral head resection is superior in restoring native anatomy. Our purpose was to determine whether FH or IM resection was superior in restoring native anatomy during aTSA with stemless implants. METHODS: A review of all patients who underwent aTSA using the stemless Tornier Simpliciti Shoulder System at two academic institutions by two separate surgeons between January 2017 and June 2020 was performed. One surgeon at one institution performed stemless aTSA using the IM resection technique, while the second surgeon utilized the FH resection technique. Patients were excluded if they underwent surgery for an indication other than glenohumeral osteoarthritis, if they received a short-stem or standard-stem implant, or if they lacked adequate preoperative and postoperative Grashey radiographs. One hundred eleven patients across both institutions (51 IM, 60 FH) were included for the final radiographic assessment. The humeral head height (HH) and neck-shaft angle (NSA) were measured on preoperative and postoperative Grashey radiographs. The centers of rotation (CORs) were measured on postoperative Grashey radiographs. Patients were classified as having acceptable restoration of their native anatomy if the change (Δ) in COR or HH was ≤3 mm and ≤ 5 mm, respectively, or if the postoperative NSA was ≥130°. RESULTS: IM resection had the greatest acceptable restoration of COR (90.2% IM versus 70% FH, P = .009), HH (96.1% IM vs. 63.3% FH, P < .001), and NSA (96.1% IM vs. 78.3% FH, P = .006) relative to FH resection. The mean postoperative NSAs for the IM and FH cohorts were 134.4° (±2.1°) and 133.8° (±5.4°), respectively (P = .208). The mean ΔCORs for the IM and FH groups were 1.2 (±1.5) and 2.3 (±1.2) mm, respectively (P < .001). Finally, the mean ΔHHs for the IM and FH cohorts were 1.7 (±1.4) and 4.4 (±2.9) mm, respectively (P < .001). CONCLUSIONS: Restoration of the native humeral anatomy following stemless aTSA occurred at a significantly higher rate when using IM vs. FH resection.