Introduction. Reverse total shoulder arthroplasty continues to have a high complication rate, specifically with component instability and scapular notching. Therefore, the purpose of this study was to quantify the effects of humeral component neck angle and version on impingement free range of motion. Methods. A total of 13 cadaveric shoulders (4 males and 9 females, average age = 69 years, range 46 to 96 years) were randomly assigned to two studies. Study 1 investigated the effects of humeral component neck angle (n=6) and Study 2 investigated the effects of humeral component version (n=7). For all shoulders, Tornier Aequalis® Reversed Shoulder implants (Edina, MN) were used. For study 1, the implants were modified to 135, 145 and 155 degree humeral neck shaft angles and for Study 2 a custom implant that allowed control of humeral head version were used. For biomechanical testing, a custom shoulder testing system that permits independent loading of all shoulder muscles with six degree of freedom positioning was used. (Figure 1) Internal control experimental design was used where all conditions were tested on the same specimen. Study 1. The adduction angle and internal/external humeral rotation angle at which impingement occurred were measured. Glenohumeral abduction moment was measured at 0 and 30 degrees of abduction, and anterior dislocation forces were measured at 30 degrees of internal rotation, 0 and 30 degrees of external rotation with and without subscapularis loading. Study 2. The degree of internal and external rotation when impingement occurred was measured at 0, 30 and 60 degrees of glenohumeral abduction in the scapular plane with the humeral component placed in 20 degrees of anteversion, neutral version, 20 degrees of retroversion, and 40 degrees of retroversion. Statistical analysis was performed with a repeated measures analysis of variance with a Tukey post-hoc test with a significance level of 0.05. Results. Study 1. Adduction deficit angles for 155, 145, and 135 degree neck-shaft angle were 2 ± 5 degrees of abduction, 7 ± 4 degrees of adduction, and 12 ± 2 degrees of adduction (P <0.05), respectively. Impingement-free angles of humeral rotation and abduction moments were not statistically different between the neck-shaft angles. The anterior dislocation force was significantly higher for the 135degree neck-shaft angle at 30 degrees of external rotation and significantly higher for the 155 degree neck shaft angle at 30 degrees of internal rotation (P<.01). The anterior dislocation forces were significantly higher when the subscapularis was loaded (P <0.01). Study 2. Maximum external rotation was the limiting position for impingement particularly at 0 degrees of abduction. Maximum external rotation before impingement occurred increased significantly with increasing humeral retroversion (p < 0.05) (Figure 2). No impingement or subluxation occurred at any humeral version in 60 degrees of glenohumeral abduction. Conclusion. In reverse shoulder arthroplasty, 155 degree neck-shaft angle was more prone to impingement with adduction but had the advantage of being more stable. In addition, 40 degrees of retroversion has the largest range of humeral rotation without impingement

Background:. The purpose of this study was to compare the biomechanical effects of the trapezius transfer and the latissimus dorsi transfer in a cadaveric model of a massive posterosuperior rotator cuff tear. Methods:. Eight cadaveric shoulders were tested at 0°, 30°, and 60° of abduction in the scapular plane with anatomically based muscle loading. Humeral rotational range of motion and the amount of humeral rotation due to muscle loading were measured. Glenohumeral kinematics and joint reaction forces were measured throughout the range of motion. After testing in the intact condition, the supraspinatus and infraspinatus were resected, simulating a massive rotator cuff tear. The lower trapezius transfer was then performed. Three muscle loading conditions for the trapezius (12N, 24N, 36N) were applied to simulate a lengthened graph as a result of excessive creep, a properly tensioned graph exerting a force proportional to the cross-sectional area of the inferior trapezius, and an over-constrained graph respectively. Next the latissimus dorsi transfer was performed and tested with one muscle loading condition 24N. A repeated-measures analysis of variance was used for statistical analysis. Results:. The amount of internal rotation due to muscle loading increased with massive cuff tear at 0°, 30°, 60° abduction (p < 0.05), and was restored with the latissimus transfer at 0° abduction and the trapezius transfer at all abduction angles. (Figure 1) The cuff tear decreased glenohumeral joint compressive force, which was restored with the trapezius transfer at all positions; however, the latissimus transfer failed to restore the intact compressive force (p < 0.05). (Figure 2) At neutral rotation and 0° abduction, there was an increase in the anteriorly directed force for the rotator cuff tear and latissimus transfer conditions, that was restored to intact values by the trapezius transfer (p < 0.05). (Figure 3) At maximum internal rotation and 0° of abduction, the apex of humeral head shifted superiorly and laterally after massive cuff tear (p < 0.05); this abnormal shift was more closely restored to intact values by the trapezius transfer than the latissimus transfer in directions (p < 0.05). Conclusion:. The trapezius transfer for massive cuff tear restores native glenohumeral forces better than the latissimus transfer by recruiting an exogenous force across the glenohumeral joint. However, the increase in compressive force seen with the trapezius transfer may be problematic in patients with osteoarthritis. Clinical studies to evaluate the results of the trapezius transfer are warranted

Introduction & Aims. Over the last decade, sensor technology has proven its benefits in total knee arthroplasty, allowing the quantitative assessment of tension in the medial and lateral compartment of the tibiofemoral joint through the range of motion (VERASENSE, OrthoSensor Inc, FL, USA). In reversal total shoulder arthroplasty, it is well understood that stability is primarily controlled by the active and passive structures surrounding the articulating surfaces. At current, assessing the tension in these stabilizing structures remains however highly subjective and relies on the surgeons’ feel and experience. In an attempt to quantify this feel and address instability as a dominant cause for revision surgery, this paper introduces an intra-articular load sensor for reverse total shoulder arthroplasty (RTSA). Method. Using the capacitive load sensing technology embedded in instrumented tibial trays, a wireless, instrumented humeral trial has been developed. The wireless communication enables real-time display of the three-dimensional load vector and load magnitude in the glenohumeral joint during component trialing in RTSA. In an in-vitro setting, this sensor was used in two reverse total shoulder arthroplasties. The resulting load vectors were captured through the range of motion while the joint was artificially tightened by adding shims to the humeral tray. Results. For both shoulder specimens, the newly developed sensor provided insight in the load magnitude and characteristics through the range of motion. In neutral rotation and under a condition assessed as neither too tight nor too loose, glenohumeral loads in the range of 10–30lbs were observed. As expected, with increasing shim thickness these intra- articular load magnitudes increased. Assessing the load variations through the range of motion, high peak forces of up to 120 lbs were observed near the limits of the range of motion, most pronounced during external humeral rotation. Conclusions. In conclusion, this paper presents an intra-articular load sensor that can be used during the trialing phase in reverse total shoulder arthroplasty. A first series of cadaveric experiments provided evidence of realistic load ranges and load characteristics with respect to the end of the range of motion. Currently, effort is undertaken to develop a biomechanically validated load range that can serve as a target in surgery

Glenoid exposure is the name of the game in total shoulder arthroplasty. I can honestly say that it took me more than 5 years but less than 10 to feel confident exposing any glenoid, regardless of the degree of bone deformity and the severity of soft-tissue contracture. This lecture represents the synthesis of my experience exposing some of the most difficult glenoids. The basic principles are performing extensive soft-tissue release, minimizing the anteroposterior dimension of the humerus by osteophyte excision, making an accurate humeral neck cut, having a plethora of glenoid retractors, and knowing where to place them. The ten tips, in reverse order of importance are: 10.) Tilt the table away from operative side—this helps face the surface of the glenoid, especially in cases of posterior wear, toward the surgeon. 9.) Have multiple glenoid retractors—these include a large Darrach, a reverse double-pronged Bankart, one or two blunt Homans, small and large Fukudas. 8.) Remove all humeral osteophytes before attempting to retract the humerus posteriorly to expose the glenoid—this helps to decrease the overall anteroposterior dimension of the humerus and allows for maximum posterior displacement of the humerus. 7.) Make an accurate humeral neck cut—even 5mm of extra humeral bone will make glenoid exposure difficult. 6.) Optimal humeral position—it has been taught that abduction, external rotation, and extension is the optimal position. It may vary with each case. Therefore, experiment with humeral rotation to find the position that allows maximum visualization. This is often the position that makes the cut surface of the humerus parallel to the surface of the glenoid. 5.) Optimal retractor placement—my typical retractor placement is a Fukuda on the posterior lip of the glenoid, a reverse double-pronged Bankart on the anterior neck of the scapula, and a blunt Homan posterosuperiorly. Occasionally, a second blunt Homan anteroinferiorly is helpful, particularly in muscular males with a large pectoralis major. 4.) Laminar spreader for lateral humeral displacement—this can be helpful for posterior capsulorrhaphy or for posterior glenoid bone grafting. 3.) Maximal humeral capsular release—the release of the anterior capsule from the humerus must go well past the 6 o'clock position and up the posterior surface of the humerus. This aides in humeral exposure but also allows for more posterior displacement of the humerus during glenoid exposure. 2.) Anteroinferior capsular release or excision—extensive anteroinferior release or excision (my preference), allows for maximal posterior humeral displacement and also restores external rotation. 1.) Posterior or posteroinferior capsular release—release of the posteroinferior corner of the capsule from the glenoid results in a noticeable increase in posterior humeral retractability. In cases without substantial posterior subluxation, extensive release of the entire posterior capsule is performed

Glenoid exposure is the name of the game in total shoulder arthroplasty. I can honestly say that it took me more than 5 years but less than 10 to feel confident exposing any glenoid, regardless of the degree of bone deformity and the severity of soft-tissue contracture. This lecture represents the synthesis of my experience exposing some of the most difficult glenoids. The basic principles are performing extensive soft-tissue release, minimizing the anteroposterior dimension of the humerus by osteophyte excision, making an accurate humeral neck cut, having a plethora of glenoid retractors, and knowing where to place them. The ten tips, in reverse order of importance are: 10.) Tilt the table away from operative side—this helps face the surface of the glenoid, especially in cases of posterior wear, toward the surgeon. 9.) Have multiple glenoid retractors—these include a large Darrach, a reverse double-pronged Bankart, one or two blunt Homans, small and large Fukudas. 8.) Remove all humeral osteophytes before attempting to retract the humerus posteriorly to expose the glenoid—this helps to decrease the overall anteroposterior dimension of the humerus and allows for maximum posterior displacement of the humerus. 7.) Make an accurate humeral neck cut—even 5mm of extra humeral bone will make glenoid exposure difficult. 6.) Optimal humeral position—it has been taught that abduction, external rotation, and extension is the optimal position. It may vary with each case. Therefore, experiment with humeral rotation to find the position that allows maximum visualization. This is often the position that makes the cut surface of the humerus parallel to the surface of the glenoid. 5.) Optimal retractor placement—my typical retractor placement is a Fukuda on the posterior lip of the glenoid, a reverse double-pronged Bankart on the anterior neck of the scapula, and a blunt Homan posterosuperiorly. Occasionally, a second blunt Homan anteroinferiorly is helpful, particularly in muscular males with a large pectoralis major. 4.) Laminar spreader for lateral humeral displacement—this can be helpful for posterior capsulorrhaphy or for posterior glenoid bone grafting. 3.) Maximal humeral capsular release—the release of the anterior capsule from the humerus must go well past the 6 o'clock position and up the posterior surface of the humerus. This aides in humeral exposure but also allows for more posterior displacement of the humerus during glenoid exposure. 2.) Anteroinferior capsular release or excision—extensive anteroinferior release or excision (my preference), allows for maximal posterior humeral displacement and also restores external rotation. 1.) Posterior or posteroinferior capsular release—release of the posteroinferior corner of the capsule from the glenoid results in a noticeable increase in posterior humeral retractability. In cases without substantial posterior subluxation, extensive release of the entire posterior capsule is performed. Following these steps will help the surgeon to gain adequate glenoid exposure, even in the most difficult cases

Introduction:. Reverse total shoulder arthroplasty (RTSA) has become instrumental in relieving pain and returning function to patients with end-stage rotator cuff disease. A distalized and medialized center of rotation in addition to a semi-constrained implant design allows the deltoid to substitute for the non-functioning rotator cuff. The purpose of this study was to examine the relationship between specific deltoid and rotator cuff muscle parameters and functional outcomes following RTSA. Methods:. Patients undergoing RTSA by a single surgeon were enrolled in a prospective, IRB approved RTSA outcomes registry. Inclusion criteria were diagnosis of cuff tear arthropathy or massive rotator cuff tear, a minimum 2-year follow-up, and a preoperative shoulder MRI. We excluded patients undergoing revision arthroplasty, fracture, and a history of previous open shoulder surgery. For the 28 patients meeting our criteria, the cross-sectional area (CSA) of the anterior, middle, and posterior deltoid were measured on an axial MRI (Figure 1). Fatty infiltration (FI) of the deltoid, supraspinatus (SS), infraspinatus (IS), teres minor, and subscapularis were assessed on sagittal T1-MRI quantitatively via image processing and qualitatively on the 5-point Fuchs scale by a fellowship-trained musculoskeletal radiologist. Outcome measures included active forward elevation (aFE), active external rotation (aER), active internal rotation (aIR), strength in abduction, Constant-Murley score (CMS), Subjective Shoulder Value (SSV), Visual Analogue Scale (VAS) pain, and American Shoulder and Elbow Surgeons (ASES) total and ASES activities of daily living (ADL) scores as assessed by a trained, clinical research nurse. Correlation of deltoid CSA and FI with outcomes measures was analyzed with a Spearman rank correlation coefficient (ρ) with significance at P < .05. Results:. The correlations between preoperative deltoid size and quantitative deltoid FI to postoperative function are shown in Table 1. The total deltoid CSA showed the most significant, positive correlations with outcome measures. The anterior deltoid CSA showed the strongest correlation to postoperative strength in abduction. Quantitative FI of the deltoid was negatively associated with several outcome measures (Table 1). Quantitative FI of the SS and IS demonstrated a significant negative correlation with aER (ρ = −.732, P = .039 and ρ = −.790, P = .004, respectively). The grade of FI, as assessed using the Fuchs scale, did not correlate to any clinical outcome data. Discussion and Conclusion:. Preoperative deltoid size and FI of the deltoid and the rotator cuff muscles correlate to 2-year functional outcomes following RTSA. The anterior, posterior, and total CSA of the deltoid had significant, positive associations with several outcome measures, whereas FI of the deltoid, SS, and IS had significant, negative associations, particularly with humeral rotation. In the future, optimization of deltoid and rotator cuff muscle function preoperatively may improve functional outcomes in RTSA

Background:. An upper extremity model of the shoulder was developed from the Stanford upper extremity model (Holzbaur 2005) in this study to assess the muscle lengthening changes that occur as a function of kinematics for reverse total shoulder athroplasty (RTSA). This study assesses muscle moment arm changes as a function of scapulohumeral rhythm (SHR) during abduction for RTSA subjects. The purpose of the study was to calculate the effect of RTSA SHR on the deltoid moment arm over the abduction activity. Methods:. The model was parameterized as a six degree of freedom model in which the scapula and humeral rotational degrees of freedom were prescribed from fluoroscopy. The model had 15 muscle actuators representing the muscles that span the shoulder girdle. The model was then uniformly scaled according to reflective markers from motion capture studies. An average SHR was calculated for the normal and RTSA cohort set. The SHR averages were then used to drive the motion of the scapula and the humerus. Lastly 3-dimensional kinematics for the scapula and humerus from 3d-2d fluoroscopic image registration techniques were used to drive the motion of model. Deltoid muscle moment arm was calculated. Results:. Muscle moment arms were calculated for the anterior, lateral and posterior heads of the deltoid. Significant changes (>1 mm) were only found in comparing the anterior deltoid muscle moment arm predictions between the normal and RTSA group. The anterior deltoid for RTSA had a moment arm range from −12.5–20.6 mm over the max abduction arc. The anterior deltoid for normal group had a moment arm range from −14.5–22.6 mm over the max abduction arc. There is a difference of 2 mm between the normal and RTSA anterior deltoid moment arm that converges to 0 at 45° of elevation. The 2 mm difference is also seen again as the difference diverges again (Figure 1). There were no significant differences found between normal and RTSA groups for the lateral and posterior deltoid. The most significant difference between moment arm calculations for the RTSA and normal group was found in the Anterior deltoid. (Figure 1). Conclusion:. It was found that the muscle moment arms in the RTSA group were significantly different than in the normal group for the anterior deltoid. No other significant differences were found. In the initial 40° of elevation there is a 2 mm difference in anterior deltoid muscle moment arm between the normal and RTSA group. This difference is also found is seen from 60°–90° of elevation. From 35° −55° there is no difference between RTSA and normal groups. SHR for the RTSA (1.8: 1) is significantly lower than in the normal (2.5: 1) group. Differences found in muscle moment arms over the abduction arc between RTSA and normal groups point to the significant change of the anterior deltoid after RTSA. This study primary objective was to assess the differences in muscle moment arms as a function of SHR (Kinematic differences). Significant differences found may improve implant design, surgical technique, and rehabilitative strategies for reverse shoulder surgery

Introduction:. Reverse total shoulder arthroplasty (RTSA) has become an accepted surgical treatment for patients with severe deficiency of the rotator cuff. Despite the utility of RTSA in managing difficult shoulder problems, humeral rotation does not reliably improve and may even worsen following RTSA. Several approaches to increase active external rotation (aER) postoperatively have been proposed including the use of concomitant latissimus dorsi tendon transfer (LDTT) or the use of an increased lateral-offset glenosphere (LG). We hypothesized that clinical outcome and range of motion after RTSA with a +4 mm or +6 mm LG would be comparable to RTSA with LDTT in patients with a lack of aER preoperatively. Methods:. An IRB-approved, prospective, single surgeon RTSA registry was reviewed for patients treated with LDTT or LG for preoperative aER deficiency with minimum 1-year follow-up. Patients qualified for aER deficiency if they had a positive ER lag sign or less than or equal to 10 degrees of aER preoperatively. Matched control groups with patients that did not have preoperative lack of aER and were not treated with LDTT or LG were included for comparison. Outcomes measures included Constant-Murley score (CMS), American Shoulder and Elbow Surgeons (ASES) score, Subjective Shoulder Value (SSV), ASES Activities of Daily Living (ADL) score, Visual Analogue pain Scale (VAS), active forward elevation (aFE), active internal rotation (aIR), and aER. An independent, institutional biostatistician performed statistical analyses. Results:. The LDTT group had 21 patients (10 male, 11 female) and the LG group had 16 patients (5 male, 11 female). CMS, ASES, SSV, ADL, VAS, and aFE were significantly improved in case and control groups following RTSA (P < .05). There was no significant difference in the degree of improvement of CMS, ASES, SSV, ADL, VAS or aFE between the LDTT group and its control group or the LG group and its control group (P > .05). aER was significantly improved in the LDTT and LG groups (P < .001), but did not improve significantly in either control group (P > .05) (Figure 1). The LDTT group had a significantly lower postoperative aER than its control group (P = .001), whereas the LG group had similar postoperative aER to its control group (P = .376) (Figure 1). The LG group had significantly greater aER preoperatively and postoperatively than the LDTT group (P < .001 and P = .013). There was no significant difference in degree of improvement of aER between the LDTT and LG groups (P = .212). The LDTT group had a significantly lower postoperative aIR than its control group (P=.025), whereas the LG group had similar postoperative aIR to its control group (P = .234). The LG group had significantly greater improvement in aIR than the LDTT group (P=.009). Conclusion:. To our knowledge, this is the first series to compare outcomes of two common techniques used to improve aER following RTSA. In this series, we found overall similar improvements in outcomes between the groups. These results suggest that use of a LG may be preferable to LDTT given the relatively simplified surgical technique, similar improvement in aER, comparable clinical outcome scores, and the added benefit of improved aIR

Background:. Individuals with large Hill-Sachs lesions may be prone to failure and reoccurrence following standard arthroscopic Bankart repair. Here, the Remplissage procedure may promote shoulder stability through infraspinatus capsulo-tenodesis directly into the lesion. Little biomechanicaldata about the Remplissage procedure on glenohumeral kinematics, stability, and range of motion (ROM) currently exists. Questions/purposes:. What are the biomechanical effects of Bankart and Remplissage repair for large Hill-Sachs lesions?. Methods:. Six cadaveric shoulders were tested using a custom shoulder testing system. ROM and glenohumeral translation with applied loads in anterior-posterior (AP) and superior-inferior (SI) directions were quantified at 0° and 60° gleno-humeral abduction. Six conditions were tested: intact, Bankart lesion, Bankart with 40% Hill-Sachs lesion, Bankart repair, Bankart repair with Remplissage, and Remplissage repair alone. Results:. Humeral external rotation (ER) and total range of motion (TR) increased significantly from intact after the creation of the Bankart lesion at both 0° abduction (ER +27.0°, TR +35.8°, p < 0.05) [Fig 1] and 60° abduction (ER +9.5°, TR +30.7°, p < 0.05) [Fig 2], but did not increase further with the addition of the Hill-Sachs lesion. The Bankart repair restored range of motion to intact values 0° abduction at addition of the Remplissage repair did not significantly alter range of motion from the Bankart repair alone. There were no significant changes in AP or SI translation between Bankart repair with and without Remplissage compared to the intact specimen. Conclusions:. The addition of the Remplissage procedure for treatment of large Hill-Sachs lesions had no statistically significant effect on ROM or translation for treatment for large Hill-Sachs lesions. Clinical Relevance: The Remplissage technique may be a suitable option for engaging Hill-Sachs lesions. Further clinical studies are warranted