Introduction. For anatomical reconstruction in shoulder arthroplasty, it is important to understand normal glenohumeral geometry. Unfortunately, however, the details of the glenohumeral joint in Asian populations have not been sufficiently evaluated. There is a racial difference in body size, and this difference probably results in a difference in glenohumeral size. The purpose of this study was to evaluate three-dimensional geometry of the glenohumeral joint in the normal Asian population and to clarify its morphologic features. Methods. Anthropometric analysis of the glenohumeral joint was performed using computed tomography scans of 160 normal shoulders from healthy volunteers in age from 20 to 40 years. Using OsiriX MD, Geomagic Studio, and AVIZO software, the dimensions of humeral head width, humeral head diameter, glenoid height, glenoid width, and glenoid diameter were analyzed three-dimensionally (Figure 1). In diameter analyses, the humeral head was assumed to be a sphere and the glenoid was to fit a sphere (Figure 2–3). Sex differences in height, humeral length, humeral head width, humeral head diameter, glenoid height, glenoid width, and glenoid diameter were compared using Mann-Whitney U tests. The correlations between sides and among the respective parameters in the glenohumeral dimensions were evaluated with Spearman rank correlation tests. The significance level was set at 0.05 for all analyses. Results. Average height and humeral length of the volunteers were 164.7 ± 9.7 cm and 29.1 ± 1.8 cm respectively. The normal Asian glenohumeral joint has average humeral head width of 41.4 ± 3.7 mm, humeral head diameter of 42.9 ± 3.6 mm, glenoid height of 31.5 ± 2.8 mm, glenoid width of 23.1 ± 2.4 mm, and glenoid diameter of 62.0 ± 6.8 mm. The humeral head and glenoid were significantly larger in males than in females (p<0.001 in all analyses). The average radius difference between the glenoid and the humeral head was 9.6 ± 2.8 mm, and there was no sex difference (p=0.359). The average ratio of the glenoid radius to the humeral head radius was 144.9% ± 12.2%, and the ratio was significantly larger in females than in males (p=0.026). The glenohumeral size was well correlated between the two sides, and there were direct correlations among the heights, humeral length, humeral head size, and glenoid size (p<0.001 in all analyses). Conclusions. The present study revealed that the values of glenohumeral dimensions were uniform in both males and females with a strong correlation between the dominant shoulder and the nondominant shoulder. Since there are direct correlations among height, humeral length, and the size of the glenohumeral joint, we can also predict the glenohumeral size of patients from their respective heights. The present results would be useful to determine the size of implants and to improve clinical outcomes of shoulder arthroplasty for glenohumeral joints of Asian patients. The size of the Asian glenohumeral joint was obviously smaller than that reported in the past literature including black and Caucasian populations. Some shoulder prostheses that are designed in Europe or America and are widely used worldwide could be oversized for small females

Purpose. There is minimal information on outcome of glenohumeral debridement for treatment of shoulder osteoarthritis (OA). The purpose of this study was to examine the outcome of this procedure with or without acromioplasty /resection of clavicle in subjective perception of disability and functional range of motion and strength at one year following surgery. Method. Prospectively collected data of patients with advanced OA of the glenohumeral joint who were not good candidates for shoulder arthroplasty due to young age, high activity level, or desire to avoid major surgery at the time of assessment were included. Arthroscopic debridement included removal of loose bodies, chondral flaps, and degenerative tissue. Resection of the lateral end of the clavicle or acromioplasty was performed as clinically indicated for management of osteoarthritis of the Acromioclavicular (AC) joint or subacromial impingement respectively. Disability at 12 months following surgery was measured by the American Shoulder and Elbow Surgeons (ASES) assessment form, Constant-Murley score (CMS), strength, and painfree range of motion in four directions. Results. Sixty-seven patients (mean age= 57, SD: 15 (range: 25–87), range: 35–86, 35 females, 32 males) were included in analysis. The average symptom duration was 5 years. Fifteen (22%) patients had left shoulder involvement with 37 (55%) having right shoulder problem and 15(22%) reporting bilateral complaints. The right shoulder was operated on in 41 (61%) patients. Fifty two (78%) patients had an associated subacromial decompression [49 (73%) had acromioplasty and 27 (40%) had resection of the lateral end of the clavicle with some procedures overlapping]. Paired student t-tests showed a statistically significant improvement in scores of ASES and CMS (p<0.001) and painfree range of motion (p=0.02) at 1 year follow-up. However, no change was observed in strength (p>0.05). Conclusion. Arthroscopic debridement with or without acromioplasty /resection of the lateral end of the clavicle improves disability and painfree range of motion in patients suffering from osteoarthritis of glenohumeral joint at one year following surgery

Aim. Biomechanical models of the shoulder have been used to measure forces and glenohumeral pressures. Their results have been found to vary. The aim of this study was to produce a biomechanical model to replicate the biomechanical principles of the glenohumeral joint and to measure the centre of pressure on the glenoid through a mid-range of arm movement with an intact and a compromised rotator cuff. Method. The model consisted of anatomic saw-bones of a scapula and proximal humerus with calibrated extension springs to mimic rotator cuff muscles. Glenoid pressures were measured using pressure sensitive film. The joint was examined through a mid-range of movement with an intact rotator cuff and a supraspinatus deficiency. Results. In the normal cuff model, in neutral, the centre of pressure was in the centre of the glenoid and migrated inferiorly on abduction, rotation and 45° of flexion. The only exception to this was 90° flexion and 35° extension. Concavity compression force rose in internal/external rotation, was steady on flexion/extension but dropped on abduction. In the supraspinatus-deficient model, the centre of pressure dropped to the inferior lip in neutral and rose on any movement with extremes of flexion and abduction, resulting in subacromial impingement. Concavity compression force rose slightly on flexion and extension. On abduction, the force rose as much as three times that of the normal cuff. Discussion. The results suggest that the humeral joint reaction force rests in the centre of the glenoid and is driven inferiorly on arm movement. Loss of supraspinatus reverses this pattern and leads to impingement. These results would be in keeping with osteoarthritic patterns in vivo and may have a bearing on glenoid prosthesis design. Conclusion. The glenohumeral joint demonstrated inferior migration of the humeral reaction force on elevation of the arm. Cuff pathology leads to breakdown of this mechanism

Abstract. Objective. Radial to axillary nerve and spinal accessory (XI) to suprascapular nerve (SSN) transfers are standard procedures to restore function after C5 brachial plexus dysfunction. The anterior approach to the SSN may miss concomitant pathology at the suprascapular notch and sacrifices lateral trapezius function, resulting in poor restoration of shoulder external rotation. A posterior approach allows decompression and visualisation of the SSN at the notch and distal coaptation of the medial XI branch. The medial triceps has a double fascicle structure that may be coapted to both the anterior and posterior division of the axillary nerve, whilst preserving the stabilising effect of the long head of triceps at the glenohumeral joint. Reinnervation of two shoulder abductors and two external rotators may confer advantages over previous approaches with improved external rotation range of motion and strength. Methods. Review of the clinical outcomes of 22 patients who underwent a double nerve transfer from XI and radial nerves. Motor strength was evaluated using the MRC scale and grade 4 was defined as the threshold for success. Results. 18/22 patients had adequate follow-up (Mean: 29.5 months). Of these, 72.2% achieved ≥grade 4 power of shoulder abduction and a mean range of motion of 103°. 64.7% achieved ≥grade 4 external rotation with a mean range of motion of 99.6°. Conclusions. The results suggest the use of the combined nerve transfer for restoration of shoulder function via a posterior approach, involving the medial head branch of triceps to the axillary nerve and the XI to SSN

Aim. Clavicular osteotomy was described as an adjunct to deltopectoral approach for improved exposure of the glenohumeral joint. This study aims to present contemporary outcomes and complications associated with the routine use of clavicular osteotomy by a single surgeon in a regional setting within New Zealand. Methods. A retrospective case series of patients who have undergone any shoulder arthroplasty for any indication between March 2017 to August 2022. This time period includes all patients who had clavicular osteotomy(OS) and patients over an equal time period prior to the routine use of osteotomy as a reference group (N-OS). Oxford Shoulder Score (OSS) and a Simple Shoulder Test (STT) were used to assess functional outcomes and were compared with the reported literature. Operative times and Complications were reviewed. Results. 66 patients were included in the study. 33 patients in the OS group and 33 in the N-OS group. No difference in age, sex, indications for operative intervention and the surgery provided was identified. No significant difference in operative time between groups (N-OS 121 minutes; OS 128 minutes). No clinically significant difference was identified in the OSS (N-OS; mean 38 vs OS 39) or the STT (N-OS 8.3 vs OS 9). The outcomes scores of both groups are in keeping with published literature. Two post operative clavicle fractures, one prominent surgical knot occurred in the OS that required further surgical intervention. Two cases of localized pain over the clavicle and one case of the prominent lateral clavicle were reported in the OS group. Two cases of localized pain over clavicle reported in the N-OS group. Conclusion. Use of clavicular osteotomy is not associated with inferior patient reported. The osteotomy introduces specific risks, however, the study provides evidence that these complications are infrequent and avoidable. Surgeons should feel confident in using this adjunct when exposure to the shoulder is difficult

Aim. Deadspace is the tissue and bony defect in a surgical wound after closure. This space is presumably poorly perfused favouring bacterial proliferation and biofilm formation. In arthroplasty surgery, an obligate deadspace surrounding the prosthesis is introduced and deadspace management, in combination with obtaining therapeutic prophylactic antibiotic concentrations, is important for limiting the risk of acquiring a periprosthetic joint infection (PJI). This study aimed to investigate cefuroxime distribution to an orthopaedic surgical deadspace in comparison with plasma and bone concentrations during two dosing intervals (8 h × 2). Method. In a setup imitating shoulder arthroplasty surgery, but without insertion of a prosthesis, microdialysis catheters were placed for cefuroxime sampling in a deadspace in the glenohumeral joint and in cancellous bone of the scapular neck in eighteen pigs. Blood samples were collected from a central venous catheter as a reference. Cefuroxime was administered according to weight (20 mg/kg). The primary endpoint was time above the cefuroxime minimal inhibitory concentration of the free fraction of cefuroxime for Staphylococcus aureus (fT > MIC (4 µg/mL)). Results. During the two dosing intervals, mean fT > MIC (4 µg/mL) was significantly longer in deadspace (605 min) compared with plasma (284 min) and bone (334 min). For deadspace, the mean time to reach 4 µg/mL was prolonged from the first dosing interval (8 min) to the second dosing interval (21 min), while the peak drug concentration was lower and half-life was longer in the second dosing interval. Conclusions. In conclusion, weight-adjusted cefuroxime fT > MIC (4 µg/mL) and elimination from the deadspace was longer in comparison to plasma and bone. Our results suggest a deadspace consolidation and a longer diffusions distance, resulting in a low cefuroxime turn-over. Based on theoretical targets, cefuroxime appears to be an appropriate prophylactic drug for the prevention of PJI. Acknowledgments. We would like to thank Department of Clinical Medicine, the surgical research laboratories, Aarhus University Hospital and Department of Clinical Biochemistry, Lillebaelt Hospital, Vejle, Denmark, for supporting this study. This research was funded by Novo Nordisk Foundation, grant number [NNF20OC0062032, 2020]

Analyzing shoulder kinematics is challenging as the shoulder is comprised of a complex group of multiple highly mobile joints. Unlike at the elbow or knee which has a primary flexion/extension axis, both primary shoulder joints (glenohumeral and scapulothoracic) have a large range of motion (ROM) in all three directions. As such, there are six degrees of freedom (DoF) in the shoulder joints (three translations and three rotations), and all these parameters need to be defined to fully describe shoulder motion. Despite the importance of glenohumeral and scapulothoracic coordination, it's the glenohumeral joint that is most studied in the shoulder. Additionally, the limited research on the scapulothoracic primarily focuses on planar motion such as abduction or flexion. However, more complex motions, such as internally rotating to the back, are rarely studied despite the importance for activities of daily living. A technique for analyzing shoulder kinematics which uses 4DCT has been developed and validated and will be used to conduct analysis. The objective of this study is to characterize glenohumeral and scapulothoracic motion during active internal rotation to the back, in a healthy young population, using a novel 4DCT approach. Eight male participants over 18 with a healthy shoulder ROM were recruited. For the dynamic scan, participants performed internal rotation to the back. For this motion, the hand starts on the abdomen and is moved around the torso up the back as far as possible, unconstrained to examine variability in motion pathway. Bone models were made from the dynamic scans and registered to neutral models, from a static scan, to calculate six DoF kinematics. The resultant kinematic pathways measured over the entire motion were used to calculate the ROM for each DoF. Results indicate that anterior tilting is the most important DoF of the scapula, the participants all followed similar paths with low variation. Conversely, it appears that protraction/retraction of the scapula is not as important for internally rotating to the back; not only was the ROM the lowest, but the pathways had the highest variation between participants. Regarding glenohumeral motion, internal rotation was by far the DoF with the highest ROM, but there was also high variation in the pathways. Summation of ROM values revealed an average glenohumeral to scapulothoracic ratio of 1.8:1, closely matching the common 2:1 ratio other studies have measured during abduction. Due to the unconstrained nature of the motion, the complex relationship between the glenohumeral and scapulothoracic joints leads to high variation in kinematic pathways. The shoulder has redundant degrees of freedom, the same end position can result from different joint angles and positions. Therefore, some individuals might rely more on scapular motion while others might utilize primarily humeral motion to achieve a specific movement. More analysis needs to be done to identify if any direct correlations can be drawn between scapulothoracic and glenohumeral DoF. Analyzing the kinematics of the glenohumeral and scapulothoracic joint throughout motion will further improve understanding of shoulder mechanics and future work plans to examine differences with age

Purpose. To examine measurement properties of four disability outcomes in patients with advanced osteoarthritis of the glenohumeral joint. Methods. This was a prospective longitudinal study of patients with advanced osteoarthritis of the glenohumeral joint who underwent a Total Shoulder Arthroplasty (TSA) and were followed for 6 months. Four measures [Western Ontario Osteoarthritis Shoulder (WOOS) Index, the American Shoulder and Elbow Surgeons (ASES) assessment, Constant-Murley score (CMS), and Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH)] were completed 2-3 weeks before surgery and at 6 months after surgery. Results. Seventy-seven patients (average age: 66, range 35 to 86, 60% women, 40% men) participated in the study. The Cronbach's Coefficient Alpha of subjective measures was high at 0.91, 0.86, and 0.83 for WOOS, ASES, and QuickDASH respectively. All measures were able to discriminate between men and women's levels of disability at p< 0.05. Correlations between pre-operative scores were moderate (0.59 to -0.79) and slightly increased post-operatively (0.61 to -0.87). All measures were sensitive in detecting change in the disability status over a period of 6 months. Conclusion. All four disability measures were reliable and valid for use in patients with advanced osteoarthritis of the glenohumeral joint. Outcome measurement in busy clinics can be facilitated by choosing valid and reliable measures that have the advantage of simplicity for use by patients and clinicians. The consensus-based standards for selection of outcome measures have been developed for hip and knee arthritis and need to take place for the shoulder joint. Developing consensus by an international group of experts will improve consistency in using outcome measures in patients with shoulder problems

The Hill-Sachs lesion is a bony defect of the humeral head that occurs in association with anterior instability of the glenohumeral joint. Hill-Sachs lesions are common, with an incidence approaching nearly 100% in the setting of recurrent anterior glenohumeral instability. However, the indications for surgical management are very limited, with less than 10% of anterior instability patients considered for treatment of the Hill-Sachs lesion. Of utmost importance is addressing bone loss on the anterior-inferior glenoid, which is highly successful at preventing recurrence of instability even with humeral bone loss. In the rare situation where the Hill-Sachs lesion may continue to engage the glenoid, surgical management is indicated. Surgical strategies are variable, including debridement, arthroscopic remplissage, allograft transplantation, surface replacement, and arthroplasty. Given that the population with these defects is typically comprised of young and athletic patients, biologic solutions are most likely to be associated with decades of sustainable joint preservation, function, and stability. The first priority is maximizing the treatment of anterior instability on the glenoid side. Then, small lesions of less than 10% are ignored without consequence. Lesions involving 10–20% of the humeral head are treated with arthroscopic remplissage (defect filled with repair of capsule and infraspinatus). Lesions greater than 20% that extend beyond the glenoid tract are managed with fresh osteochondral allografts to biologically restore the humeral head. Lesions great than 40% are most commonly associated with advanced arthritis and deformity of the humeral articular surface and are therefore treated with a humeral head replacement. This treatment algorithm maximises our ability to stabilise and preserve the glenohumeral joint

INTRODUCTION. Total shoulder arthroplasty (TSA) implants are used to restore function to individuals whose shoulder motions are impaired by osteoarthritis. To improve TSA implant designs, it is crucial to understand the kinematics of healthy, osteoarthritic (OA), and post-TSA shoulders. Hence, this study will determine in vivo kinematic trends of the glenohumeral joints of healthy, OA, and post-TSA shoulders. Methods. In vivo shoulder kinematics were determined pre and post-operatively for five unilateral TSA subjects with one healthy and a contralateral OA glenohumeral joint. Fluoroscopic examinations were performed for all three shoulder categories (healthy, OA, and post-TSA) for each subject shoulder abduction and external rotation. Then, three-dimensional (3D) models of the left and right scapula and humerus were constructed using CT scans. For post-operative shoulders, 3D computer-aided design models of the implants were obtained. Next, the 3D glenohumeral joint kinematics were determined using a previously published 3D to 2D registration technique. After determining kinematics, relative Euler rotation angles between the humerus and scapula were calculated in MATLAB® to determine range of motion (ROM) and kinematic profiles for all three shoulder categories. The ROMs for each category were compared using paired t-tests for each exercise. Also, the location of the contact point of the humerus on the glenoid was found. This allowed the vertical translation from the most superior to most inferior contact point (SI contact range) to be calculated as well as the horizontal translation from the most anterior to most posterior contact point (AP contact range). The SI and AP contact ranges for all shoulder categories were compared using paired t-tests for each exercise. Results. Abduction. According to preliminary results, the averages range of abduction for healthy, OA, and post-TSA shoulders was 51.5 °, 19.4°, and 56.7°, respectively. The average SI contact range of abduction for healthy, OA, and post-TSA shoulders was 14.1 mm, 16.4 mm, and 14.1 mm, respectively while the AP contact range was 10.0, 14., and 14.3, respectively. The ranges of abduction between healthy and OA and between OA and post-TSA shoulders, and the AP contact range for healthy and OA shoulders displayed statistically significant differences at the α=0.05 level. External Rotation. The averages range of External Rotation for healthy, OA, and post-TSA shoulders was 63.6°, 31.1°, and 44.5°, respectively. The averages SI contact range of External Rotation for healthy, OA, and post-TSA shoulders was 20.7, 12.7, and 15.9 mm, respectively while the averages AP contact range was 8.5,12.9 mm, and 13.8 mm, respectively. The ranges of abduction for healthy and OA as well as AP contact range for healthy and OA shoulders were statistically different at the α=0.05 level. Conclusions. This study's preliminary results indicate that healthy, OA, and post-TSA shoulders show statistically significant difference in kinematic trends including ROM and contact point translation. These differences may result from the varying geometries of each condition or from subjects altering kinematic trends to reduce pain in OA shoulders. In addition, this study may provide a reference for future studies analyzing the kinematics of post TSA shoulders

The Hill-Sachs lesion is a bony defect of the humeral head that occurs in association with anterior instability of the glenohumeral joint. Hill-Sachs lesions are common, with an incidence approaching nearly 100% in the setting of recurrent anterior glenohumeral instability. However, the indications for surgical management are very limited, with less than 10% of anterior instability patients considered for treatment of the Hill-Sachs lesion. Of utmost importance is addressing bone loss on the anterior-inferior glenoid, which is highly successful at preventing recurrence of instability even with humeral bone loss. In the rare situation where the Hill-Sachs lesion may continue to engage the glenoid, surgical management is indicated. Surgical strategies are variable, including debridement, arthroscopic remplissage, allograft transplantation, surface replacement, and arthroplasty. Given that the population with these defects is typically comprised of young and athletic patients, biologic solutions are most likely to be associated with decades of sustainable joint preservation, function, and stability. The first priority is maximising the treatment of anterior instability on the glenoid side. Then, small lesions of less than 10% are ignored without consequence. Lesions involving 10–20% of the humeral head are treated with arthroscopic remplissage (defect filled with repair of capsule and infraspinatus). Lesions greater than 20% that extend beyond the glenoid tract are managed with fresh osteochondral allografts to biologically restore the humeral head. Lesions great than 40% are most commonly associated with advanced arthritis and deformity of the humeral articular surface and are therefore treated with a humeral head replacement. This treatment algorithm maximises our ability to stabilise and preserve the glenohumeral joint

Biologic supplementation and augmentation techniques have become popular in recent years. There has been considerable media attention regarding professional athletes and celebrities who have traveled around the world to receive treatments using proprietary cocktails of platelet rich plasma, bone marrow aspirate concentrates, extracellular matrix, adipose-derived stem cells, human as well as xenograft derived collagen implants and protein supplements among other components. Unfortunately, the medical evidence regarding these treatments has often been inconsistent, inadequate with respect to levels of evidence with a dearth of mid- and long-term data to guide our treatments. This presentation will review the data available regarding the treatment of rotator cuff tendinosis, partial thickness rotator cuff tears, full thickness rotator cuff tears and osteoarthritis of the glenohumeral joint. Unfortunately, there are more questions than answers regarding the use of biologics

Chronic massive irreparable rotator cuff tears represent a treatment challenge and the optimal surgical technique remains controversial. Superior capsular reconstruction (SCR) has been proposed as a means to provide superior stability to the glenohumeral joint, thus facilitating restoration of shoulder function. However, despite the growing use of SCR there is a paucity of data evaluating the outcomes when performed using a dermal allograft. The purpose of this study was to (1) report the overall survival rate (reoperation and clinical failure) of SCR (2) evaluate for pre-operative factors predicting reoperation and clinical failure. From January 1, 2015 to November 31, 2017, 65 patients were diagnosed with irreparable rotator cuff tears and consented for a superior capsular reconstruction. These surgeries were performed by 6 surgeons, all fellowship trained in either sports or shoulder and elbow fellowships. Outcomes were graded as excellent, satisfactory, or unsatisfactory using the modified Neer scale. An unsatisfactory result was defined as a clinical “failure”. The Kaplan-Meier survival models were created to analyze reoperation-free and failure-free survival for the entire group. The reconstruction was performed using a dermal allograft. There were 31 patients excluded due to insufficient follow-up (< 6 months), leaving 34 included in this study. The mean follow-up was 12 months (range, 6–23). The average number of prior surgeries was 0.91 (range, 0–5), with 52.9% of patients receiving a prior rotator cuff repair and 38.2% of patients with a prior non-rotator cuff arthroscopy procedure. The one and two-year survival-free of surgery was 64% and 44% and the one and two-year survival free of failure was 34% and 16% following SCR, respectively. For the patients that underwent a reoperation, 62.5% (n= 5/8) underwent reverse shoulder replacements, 25% (n= 2/8) latissimus dorsi tendon transfers, and 12.5% (n= 1/8) a diagnostic arthroscopy. The average period between the primary and revision surgery was 10.2 months (range, 2.1–18.5). All but two patients (75%, n= 6/8) had at least one surgery prior to the SCR. There were 14/34 (41.2%) patients who experienced pain, weakness, and restricted range of motion. These patients were defined as clinical failures with an unsatisfactory grading on Neer's criteria. Previous surgery predicted reoperation (80% vs 43%, p = 0.03). Female gender predicted clinical failure (100% vs 43%, p < 0 .01). Superior Capsule Reconstruction performed for large to massive rotator cuff tears has a high rate of persistent pain and limited function leading to clinical failure in 65% (n= 22/34) of patients. The rate of failure is increased in revision cases, female gender and increased Goutallier fatty infiltration of the infraspinatus. Narrowed indications are recommended given the surgical complexity and high rate of early failure

Introduction. Resurfacing of the glenohumeral joint has gained popularity since its first introduction in 1958. Advantages of resurfacing over conventional shoulder arthroplasty include preservation of humeral bone stock, closer replication of individual anatomy, reduction of periprosthetic fracture risk, non-violation of medullary canal, and ease of revision to a stemmed component if needed. Materials and Methods. We reviewed a group of patients with arthrosis of the glenohumeral joint who underwent humeral resurfacing, and who were at a minimum of two years post surgery. From January 2000 to March 2011, 51 humeral resurfacing procedures were performed in 49 patients. Patients were contacted for review, and assessed using patient reported outcome measures. An Oxford Shoulder score as well as a subjective satisfaction and outcome questionnaire was completed, as well as details regarding further surgery or revision. 2 patients had died, 11 patients were not contactable, and in 4 the medical files had been lost. In the remaining 32 shoulders, the average follow-up was 5.9 years. The mean age at time of surgery was 62.3 years (range 36 to 84). Results. Complications included 7 revisions (average 2.4 years post surgery), a further 2 patients await revision. There were 2 subscapularis tendon ruptures managed operatively. A further 2 patients required surgery – one for impingement and acromioclavicular joint arthrosis, and the other for instability. The mean Oxford Shoulder score in the unrevised shoulders was 35.4 (range 10 to 47). Conclusion. We have encountered a high rate of revision in patients undergoing humeral resurfacing for glenohumeral arthrosis. In those who have not been revised, there is a wide spread of patient satisfaction as evidenced by the subjective outcome scores. NO DISCLOSURES

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. Reverse shoulder arthroplasty (RSA) provides an effective alternative to anatomic shoulder replacements for individuals with cuff tear arthropathy, but certain osteoarthritic glenoid deformities make it challenging to achieve sufficient long term fixation. To compensate for bone loss, increase available bone stock, and lateralize the glenohumeral joint center of rotation, bony increased offset RSA (BIO-RSA) uses a cancellous autograft for baseplate augmentation that is harvested prior to humeral head resection. The motivations for this computational study are twofold: finite element (FE) studies of BIO-RSA are absent from the literature, and guidance in the literature on screw orientations that achieve optimal fixation varies. This study computationally evaluates how screw configuration affects BIO-RSA graft micromotion relative to the implant baseplate and glenoid. METHODS. A senior shoulder specialist (GSA) selected a scapula with a Walch Type B2 deformity from patient CT scans. DICOM images were converted to a 3D model, which underwent simulated BIO-RSA with three screw configurations: 2 divergent superior & inferior locking screws with 2 convergent anterior & posterior compression screws (SILS); 2 convergent anterior & posterior locking screws and 2 superior & inferior compression screws parallel to the baseplate central peg (APLS); and 2 divergent superior & inferior locking screws and 2 divergent anterior & posterior compression screws (AD). The scapula was assigned heterogeneous bone material properties based on the DICOM images’ Hounsfield unit (HU) values, and other components were assigned homogenous properties. Models were then imported into an FE program for analysis. Anterior-posterior and superior-inferior point loads and a lateral-medial distributed load simulated physiologic loading. Micromotion data between the RSA baseplate and bone graft as well as between the bone graft and glenoid were sub-divided into four quadrants. RESULTS. In all but 1 quadrant, APLS performed the worst with the graft having an average micromotion of 347.1µm & 355.9 µm relative to the glenoid and baseplate, respectively. The SILS configuration ranked second, having 211.2 µm & 274.4 µm relative to the glenoid and baseplate. AD performed best, allowing 247.4 µm & 225.4 µm of graft micromotion relative to the glenoid and baseplate. DISCUSSION. Both APLS and SILS techniques are described in the literature for BIO-RSA fixation; however, the data indicate that AD is superior in its ability to reduce graft micromotion, and thus some revision to common practices may be necessary. While these micromotion data are larger than data in the extant RSA literature, there are several factors that account for this. First, to properly model the difference between locking and compression screws, we simulated friction between the compression screw heads and baseplate rather than a tied constraint as done in other studies, resulting in larger micromotion. Second, the trabecular bone graft is at greater risk of deforming than metallic spacers used when studying micromotion with glenosphere lateralization, increasing graft deflection magnitude. Future work will investigate the effects of various BIO-RSA variables. For any figures or tables, please contact authors directly

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

The treatment of proximal humerus fractures remains controversial. The literature is full of articles and commentary supporting one method over another. Options include open reduction and internal fixation, hemiarthroplasty, and reverse shoulder arthroplasty. Treatment options in an active 65-year-old are exceptionally controversial given the fact that people in this middle-aged group still wished to remain active and athletic in many circumstances. A hemiarthroplasty offers the advantage of a greater range of motion, however, this has a high incidence of tuberosity malunion or nonunion and this is a very common reason for revision of that hemiarthroplasty for fracture to a reverse shoulder replacement. One recent study showed a 73% incidence of tuberosity malunion or nonunion in shoulders that had a revised hemiarthroplasty to a reverse shoulder replacement. Progressive glenoid wear and erosion is also a risk after a hemiarthroplasty in the younger patient, especially someone who is young and active. In addition, studies show shorter operative time in hemiarthroplasty. The range of motion is highly dependent on proper tuberosity healing and this is often one of the most challenging aspects of the surgical procedure as well as the healing process. A reverse shoulder replacement in general has less range of motion compared to a hemiarthroplasty with anatomically healed tuberosities, however, the revision rate is lower compared to a hemiarthroplasty. (This is likely related to few were options for revision). The results after a reverse shoulder replacement may not be as dependent on tuberosity healing, however, importantly the tuberosities do need to be repaired and the results are significantly better if there is healing of the greater tuberosity, giving some infraspinatus and/or teres minor function to the shoulder. Complete lack of tuberosity healing forces the shoulder into obligate internal rotation with attempted elevation and this can be functionally disabling. Academic discussion is beginning surrounding the use of a reverse shoulder replacement in the setting of glenohumeral joint arthritis in a primary setting as it is believed that the glenosphere and baseplate may have greater longevity than a polyethylene glenoid. Along with this discussion, we will likely see greater application of the use of a reverse shoulder replacement in the setting of fracture for younger patients. In general, open reduction internal fixation should still remain the treatment of choice in the setting of a fracture that can be fixed. However, a strong argument can be made that if an arthroplasty is necessary, a reverse shoulder replacement is the implant of choice

Modern total shoulder arthroplasty seeks to produce a construct that reproduces the kinematics and stability of the native glenohumeral joint. The latest 4th generation implants are modular, adaptable, and capable of use as either anatomic or reverse shoulder arthroplasty components. During surgery, these implants are “universal”; post-operatively, they are “convertible”. Recent work has demonstrated that reverse shoulder arthroplasty components may indeed be the emerging standard of care for most (if not all) shoulder arthroplasty indications. As this new frontier develops, the use of a convertible/universal implant creates the flexibility to individually choose the best surgical option for each patient

Introduction. Shoulder motion results from a complex interaction between the interconnected segments of the shoulder girdle. Coordination is necessary for normal shoulder function and is achieved by synchronous and coordinated muscle activity. During rotational movements, the humeral head translates on the glenoid fossa in the anterior-posterior plane. Tension developed by the rotator cuff muscles compresses the humeral head into the glenoid fossa. This acts to limit the degree of humeral head translation and establishes a stable GH fulcrum about which the arm can be moved. Previous studies have been limited by the use of contrived movement protocols and muscular coordination has not been previously considered with regard to shoulder rotation movements. This study reports the activation profile and coordination of 13 muscles and 4 muscle groups during a dynamic rotational movement task based on activities of daily living. Methods. Eleven healthy male volunteers were included in the study. Electromyography (EMG) was recorded from 13 muscles (10 surface and 3 fine-wire intramuscular electrodes) using a wireless EMG system. EMG was recorded during a movement task in which the shoulder was consecutively rotated internally (phase 1) and externally (phase 2) with a weight in the hand. Muscle group data was calculated by ensemble averaging the activity of the individual component muscles. Mean signal amplitude and Pearson correlation coefficient (PCC) analysed muscle activation and coordination, respectively. Results. The mean length of phase 1 (internal rotation) and phase 2 (external rotation) was 1.1s (SD+0.15) and 1.09s (SD+0.18), respectively with no significant difference between them. Mean signal amplitude was significantly higher during external rotation for the anterior, middle and posterior deltoid, teres major and the rotator cuff muscles (Table 1). Significant positive correlations were identified between the activation patterns of the deltoid and rotator cuff groups (PCC=0.95, p=<0.001), the deltoid and latissimus dorsi-teres major groups (PCC=0.74, p=<0.001) and the latissimus dorsi-teres major and rotator cuff groups (PCC=0.87, p=<0.001) (Figure1). Discussion. The subscapularis is extensively described as an internal rotator of the glenohumeral joint; however, during this study it was primarily active during external rotation. During activities of daily living the subscapularis balances the force generated by the supraspinatus and infraspinatus by contracting eccentrically as external rotation progresses. This balance between the anterior and posterior rotator cuff maintains anterior-posterior stability of the humeral head on the glenoid fossa. There is a highly coordinated and synchronous relationship between all the major muscle groups of the shoulder during rotational activities, which ensures glenohumeral joint stability. The function of the shoulder muscles is task specific. This has important implications when considering the impact of muscle pathology on shoulder dysfunction and the treatment strategies employed