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

A fracture of the tuberosity is associated with 16% of anterior glenohumeral dislocations. Manipulation of these injuries in the emergency department is safe with less than 1% risk of fracture propagation. However, there is a risk of associated neurological injury, recurrent instability and displacement of the greater tuberosity fragment. The risks and outcomes of these complications have not previously been reported. The purpose of this study was to establish the incidence and outcome of complications associated with this pattern of injury. We reviewed 339 consecutive glenohumeral dislocations with associated greater tuberosity fractures from a prospective trauma database. Documentation and radiographs were studied and the incidence of neurovascular compromise, greater tuberosity fragment migration and intervention and recurrent instability recorded. The mean age was 61 years (range, 18–96) with a female preponderance (140:199 male:female). At presentation 24% (n=78) patients had a nerve injury, with axillary nerve being most common (n=43, 55%). Of those patients with nerve injuries 15 (19%) did not resolve. Greater tuberosity displacement >5mm was observed in 36% (n=123) of patients with 40 undergoing acute surgery, the remainder did not due to comorbidities or patient choice. Persistent displacement after reduction accounted for 60 cases, later displacement within 6 weeks occurred in 63 patients. Recurrent instability occurred in 4 (1%) patients. Patient reported outcomes were poor with average EQ5D being 0.73, QDASH score of 16 and Oxford Shoulder Score of 41. Anterior glenohumeral dislocation with associated greater tuberosity fracture is common with poor long term patient reported outcomes. Our results demonstrate there is a high rate of neurological deficits at presentation with the majority resolving spontaneously. Recurrent instability is rare. Late tuberosity fragment displacement occurs in 18% of patients and regular follow-up for 6 weeks is recommended to detect this

Knowledge of the premorbid glenoid shape and the morphological changes the bone undergoes in patients with glenohumeral arthritis can improve surgical outcomes in total and reverse shoulder arthroplasty. Several studies have previously used scapular statistical shape models (SSMs) to predict premorbid glenoid shape and evaluate glenoid erosion properties. However, current literature suggests no studies have used scapular SSMs to examine the changes in glenoid surface area in patients with glenohumeral arthritis. Therefore, the purpose of this study was to compare the glenoid articular surface area between pathologic glenoid cavities from patients with glenohumeral arthritis and their predicted premorbid shape using a scapular SSM. Furthermore, this study compared pathologic glenoid surface area with that from virtually eroded glenoid models created without influence from internal bone remodelling activity and osteophyte formation. It was hypothesized that the pathologic glenoid cavities would exhibit the greatest glenoid surface area despite the eroded nature of the glenoid and the medialization, which in a vault shape, should logically result in less surface area. Computer tomography (CT) scans from 20 patients exhibiting type A2 glenoid erosion according to the Walch classification [Walch et al., 1999] were obtained. A scapular SSM was used to predict the premorbid glenoid shape for each scapula. The scapula and humerus from each patient were automatically segmented and exported as 3D object files along with the scapular SSM from a pre-operative planning software. Each scapula and a copy of its corresponding SSM were aligned using the coracoid, lateral edge of the acromion, inferior glenoid tubercule, scapular notch, and the trigonum spinae. Points were then digitized on both the pathologic humeral and glenoid surfaces and were used in an iterative closest point (ICP) algorithm in MATLAB (MathWorks, Natick, MA, USA) to align the humerus with the glenoid surface. A Boolean subtraction was then performed between the scapular SSM and the humerus to create a virtual erosion in the scapular SSM that matched the erosion orientation of the pathologic glenoid. This led to the development of three distinct glenoid models for each patient: premorbid, pathologic, and virtually eroded (Fig. 1). The glenoid surface area from each model was then determined using 3-Matic (Materialise, Leuven, Belgium). Figure 1. (A) Premorbid glenoid model, (B) pathologic glenoid model, and (C) virtually eroded glenoid model. The average glenoid surface area for the pathologic scapular models was 70% greater compared to the premorbid glenoid models (P < 0 .001). Furthermore, the surface area of the virtual glenoid erosions was 6.4% lower on average compared to the premorbid glenoid surface area (P=0.361). The larger surface area values observed in the pathologic glenoid cavities suggests that sufficient bone remodelling exists at the periphery of the glenoid bone in patients exhibiting A2 type glenohumeral arthritis. This is further supported by the large difference in glenoid surface area between the pathologic and virtually eroded glenoid cavities as the virtually eroded models only considered humeral anatomy when creating the erosion. For any figures or tables, please contact the authors directly

Massive irreparable rotator cuff tears often lead to superior migration of the humeral head, which can markedly impair glenohumeral kinematics and function. Although treatments currently exist for treating such pathology, no clear choice exists for the middle-aged patient demographic. Therefore, a metallic subacromial implant was developed for the purpose of restoring normal glenohumeral kinematics and function. The objective of this study was to determine this implant's ability in restoring normal humeral head position. It was hypothesized that (1) the implant would restore near normal humeral head position and (2) the implant shape could be optimized to improve restoration of the normal humeral head position. A titanium implant was designed and 3D printed. It consisted of four design variables that varied in both implant thickness (5mm and 8mm) and curvature of the humeral articulating surface (high constraint and low constraint. To assess these different designs, these implants were sequentially assessed in a cadaver-based biomechanical testing protocol. Eight cadaver specimens (64 ± 13 years old) were loaded at 0, 30, and 60 degrees of glenohumeral abduction using a previously developed shoulder simulator. An 80N load was equally distributed across all three deltoid heads while a 10N load was applied to each rotator cuff muscle. Testing states included a fully intact rotator cuff state, a posterosuperior massive rotator cuff tear state (cuff deficient state), and the four implant designs. An optical tracking system (Northern Digital, Ontario, Canada) was used to record the translation of the humeral head relative to the glenoid in both superior-inferior and anterior-posterior directions. Superior-Inferior Translation. The creation of a posterosuperior massive rotator cuff tear resulted in significant superior translation of the humeral head relative to the intact cuff state (P=0.016). No significant differences were observed between each implant design and the intact cuff state as all implants decreased the superior migration of the humeral head that was observed in the cuff deficient state. On average, the 5mm low and high constraint implant models were most effective at restoring normal humeral head position to that of the intact cuff state (-1.3 ± 2.0mm, P=0.223; and −1.5 ± 2.3mm, P=0.928 respectively). Anterior-Posterior Translation. No significant differences were observed across all test states for anterior-posterior translation of the humeral head. The cuff deficient on average resulted in posterior translation of the humeral head, however, this was not statistically significant (P=0.128). Both low and high constraint implant designs were found to be most effective at restoring humeral head position to that of the intact cuff state, on average resulting in a small anterior offset (5mm high constraint: 2.0 ± 4.7mm, P=1.000; 8mm high constraint: 1.6 ± 4.9mm, P=1.000). The 5mm high constraint implant was most effective in restoring normal humeral head position in both the superior-inferior and anterior-posterior directions. The results from this study suggest the implant may be an effective treatment for restoring normal glenohumeral kinematics and function in patients with massive irreparable rotator cuff tears. Future studies are needed to address the mechanical efficiency related to arm abduction which is a significant issue related to patient outcomes

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

Background. Rotator cuff atrophy evaluated with computed tomography scans has been associated with asymmetric glenoid wear and humeral head subluxation in glenohumeral arthritis. Magnetic resonance imaging has increased sensitivity for identifying rotator cuff pathology and has not been used to investigate this relationship. The purpose of this study was to use MRI to assess the association of rotator cuff muscle atrophy and glenoid morphology in primary glenohumeral arthritis. Methods. 132 shoulders from 129 patients with primary GHOA were retrospectively reviewed and basic demographic information was collected. All patients had MRIs that included appropriate orthogonal imaging to assess glenoid morphology and rotator cuff pathology and were reviewed by two senior surgeons. All patients had intact rotator cuff tendons. Glenoid morphology was assigned using the modified-Walch classification system (types A1, A2, B1, B2, B3, C, and D) and rotator cuff fatty infiltration was assigned using Goutallier scores. Results. 46 (35%) of the shoulders had posterior wear patterns (23 type B2s, 23 type B3s). Both the infraspinatus and teres minor independently had significantly more fatty infiltration in B2 and B3 type glenoids compared to type A glenoids (p<0.001). There was a greater imbalance in posterior rotator cuff muscle fatty atrophy in B2 and B3 type glenoids compared to type A glenoids (p<0.001). However, there was no difference in axial plane imbalance between B2 and B3 glenoids (p=1.00). There was increased amount fatty infiltration of the infraspinatus among B2 and B3-type glenoids compared to type A glenoids on multivariate analysis controlling for age and gender (p<0.001). Conclusions. These results identify significant axial plane rotator cuff muscle imbalances in B2 and B3-type glenoids compared to concentrically worn glenoids, favoring a relative increase in fatty infiltration of the infraspinatus and teres minor compared to the subscapularis in glenoids with patterns of posterior wear. For any figures or tables, please contact authors directly

Glenohumeral chondrolysis is a devastating condition characterized by the rapid dissolution of glenohumeral cartilage and resultant joint destruction. Excessive intra-articular use of thermal heat, suture anchors that are prominent or loose, and the use of an intra-articular pain pump (IAPP) delivering local anesthetics have all been implicated as causative factors. Between November 2007 and February 2010, 29 patients presented with glenohumeral chondrolysis related to one or more of the causative factors noted above. Seventeen patients have been followed since their initial presentation, with the remainder presenting for evaluation only, at the suggestion of their attorneys. Of those 17 patients, 7 were male and mean age at the time of their index surgery was 28.6 years (range 15-55 years). Two patients developed chondrolysis as a result of prominent suture anchors and 15 as a result of an IAPP delivering bupivacaine. Two patients underwent placement of an IAPP following closed manipulation for adhesive capsulitis and 13 underwent IAPP placement following arthroscopic labrum repair or capsular plication using one to seven suture anchors. Onset of symptoms related to chondrolysis, such as increased pain, stiffness and crepitation, occurred at a mean 8 months (range 1-32 months) following the index procedure. Twelve of the 17 patients underwent one or more additional arthroscopic procedure, typically for debridement and chondroplasty, and in some cases, capsular release. A loose suture anchor was found in one joint at arthroscopy, which was removed. Eleven patients had radiographs documenting joint space obliteration at most recent follow-up or at the time of prosthetic shoulder arthroplasty. At most recent follow-up, 7 patients had undergone 3 total shoulder replacements and 4 humeral head resurfacing procedures. Four other patients were contemplating prosthetic shoulder arthroplasty. For those undergoing shoulder replacement, range of motion recovered modestly so that active forward elevation improved from 111° to 137° (p<0.05) and active abduction improved from 99° to 123° (p<0.05). Seven of the 12 patients presenting for evaluation only had also undergone prosthetic shoulder arthroplasty elsewhere by the time of their presentation, so that overall, 14 of 29 patients had undergone their first prosthetic shoulder replacement for chondrolysis within 25 months (range 9-54 months) of their index procedure. The onset of chondrolysis in two patients following the use of an IAPP after closed manipulation has not been reported previously. Post-arthroscopic glenohumeral chondrolysis (PAGCL) is a devastating condition that strikes young patients and frequently requires shoulder replacement surgery. The use of an intra-articular pain pump delivering local anesthetics is the principal causative factor for glenohumeral chondrolysis in most patients and should be abandoned

Cementless surface replacement arthroplasty (CSRA) is an established treatment for glenohumeral osteoarthritis. Few studies however, evaluate its role in cuff tear arthopathy. The purpose of this study is to compare the outcomes of CSRA for both glenohumeral osteoarthritis and cuff tear arthopathy. 42 CSRA with the Mark IV Copeland prosthesis were performed for glenohumeral osteoarthritis (n=21) or cuff tear arthopathy (n=21). Patients were assessed with Oxford and Constant scores, patient satisfaction, range of motion and radiologically with plain radiographs. Mean follow-up and age was 5.2 years and 74 years in both groups. Functional outcomes were significantly higher in OA compared with CTA with OSS improving from 18 to 37.5 and 15 to 26 in both groups respectively. Forward flexion improved from 60° to 126° and 42° to 74° in both groups. Three patients in the CTA group had a deficient subscapularis tendon, two of whom dislocated anteriorly. Humeral head resurfacing arthroplasty is a viable treatment option for glenohumeral osteoarthritis. In patients with CTA, functional gains are limited. We suggest CSRA should be considered in low demand patients where pain is the primary problem. Caution should be taken in patients with a deficient subscapularis due to the high risk of dislocation

Purpose:. The optimal degree of conformity between the glenoid and humeral components in cemented total shoulder arthroplasty (TSA) has not been established. Glenoid component stability is thought to be at risk due to the “rocking-horse” phenomenom, which, can lead to increased micromotion and loosening in response to humeral head edge loading. The goal of this biomechanical study is to investigate the influence of glenohumeral mismatch on bone-implant interface micromotion in a cemented glenoid implant model. Methods:. Twenty-Five cemented glenoid components (Affiniti, Tornier, Inc., Bloomington, MN, USA) were implanted in polyurethane foam biomechanics testing blocks. Five glenoid sizes, 40 mm, 44 mm, 48 mm, 52 mm and 55 mm (n = 5 per glenoid size), were cyclically tested according to ASTM Standard F-2028-08. A 44 mm humeral head (Affiniti, Tornier, Inc., Bloomington, MN, USA) was positioned centrally within the glenoid fixed to a materials testing frame (MTS Mini-Bionix II, Eden Prairie, MN, USA). Phase I testing (n = 3 per glenoid size) involved a subluxation test for determination of the humeral head translation distance which would be used for phase II cyclic testing. During cyclic loading, the humeral head was translated ± distance for 50,000 cycles at a frequency of 2 Hz, simulating approximately 5 years of device use. Glenoid compression, distraction, and superior-inferior glenoid translation were measured throughout testing via two differential variable reluctance transducers. Results:. Humeral head translation distance was identified as 0.55 mm, 1.09 mm, 2.32 mm, 3.82 mm, and 4.73 mm for each glenoid size, respectively (Figure 1). No significant difference was noted in 40 mm glenoids between cycle 1 and 50,000 for all parameters evaluated during testing (p > 0.05) (Figure 2). Conversely, a significant decrease in superior-inferior translation was present for 44 mm between cycle 1 and 50,000 (p = 0.010) (Figure 3). When analyzing all data from the first two smallest glenoid sizes, glenoid compression and translation both showed significantly increased micromotion with 40 mm glenoid sizes compared with the 44 mm glenoid size (p = 0.010 and p = 0.002, respectively). No significant difference was found with respect to glenoid distraction (p = 0.136). Conclusion:. The first phase of mechanical testing established the subluxation displacement of the humeral head against the glenoid for each prosthetic mismatch couple, which was larger for couples with greater glenohumeral mismatch. During cyclic testing, this displacement distance was covered in the same amount of time leading to differences in humeral head velocity and resultant stresses seen at the implant-cement-foam interfaces. A smaller mismatch in glenohumeral radius may lead to greater stress with shorter humeral translation compared to greater mismatch allowing for larger translations with lower resultant stresses. Data from our study will provide further clarification on the importance of glenohumeral mismatch on implant stability. Further studies are warranted to fully evaluate the impact and optimal amount radial mismatch for a clinical setting

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

Background:. Currently, there are a variety of different reverse shoulder implant designs but few anatomic studies to support the optimal selection of prosthetic size. This study analyzed the glenohumeral relationships of patients who underwent reverse shoulder arthroplasty (RSA). Methods:. Ninety-two shoulders of patients undergoing primary RSA for a massive rotator cuff tear without bony deformity or deficiency and 10 shoulders of healthy volunteers (controls) were evaluated using three-dimensional CT reconstructions and computer aided design (CAD) software. Anatomic landmarks were used to define scapular and humeral planes in addition to articular centers. After aligning the humeral center of rotation with the glenoid center, multiple glenohumeral relationships were measured and evaluated for linearity and size stratification. The correction required to transform the shoulder from its existing state (CT scan) to a realigned image (CAD model) was compared between the RSA and control groups. Size stratification was verified for statistical significance between groups. Generalized linear modeling was used to investigate if glenoid height, coronal humeral head diameter and gender were predictive of greater tuberosity positions. Results:. All 92 shoulders were grouped into three different categories based on glenoid height. The humeral head size, glenoid size, lateral offset, and inferior offset all increased linearly (r. 2. > 0.95), but the rate of increase varied (slopes range from 0.59 to 1.9). Translations required to normalize the shoulder joint were similar between healthy and pathologic cases except for superior migration. Glenoid height, coronal humeral head diameter and gender predicted the greater tuberosity position within 1.09 ± 0.84 mm of actual position in ninety percent of the patient population. Morphometric measurements for each stratified group were all found to be statistically significant between groups (p ≥ 0.05). Conclusion:. Patients who undergo RSA with minimal bony deformity have superior subluxation of the glenohumeral joint. Predicting the anatomic position of the greater tuberosity is dependent on gender, glenoid height and coronal humeral head diameter. This anatomic data provides a guide to avoid inadvertent mismatch of prosthetic and patient shoulder size. If the surgeon is able to measure glenoid height and coronal humeral head diameter preoperatively, accurate planning of the position of the greater tuberosity can be accomplished

Introduction. Augmented glenoid implants provide a new avenue to correct glenoid bone loss and can possibly reconcile current prosthetic failures and improve long-term performance. Biomechanical implant studies have suggested benefits from augmented glenoid components but limited evidence exists on optimal design of these augmented glenoid components. The aim of this study was to use integrated kinematic finite element analysis (FEA) model to evaluate the optimal augmented glenoid design based on biomechanical performance in extreme conditions for failure. Materials and Methods. Computer aided design software (CAD) models of two different commercially available augmented glenoid designs - wedge (Equinox®, Exactech, Inc.) and step (Steptech®, Depuy Synthes) were created per precise manufacturer's dimensions and sizes of the implants. Using FE modeling, these implants were virtually implanted to correct 20° of glenoid retroversion. Two glenohumeral radial mismatches (RM) (3.5/4mm and 10 mm) were evaluated for joint stability and implant fixation to simulate high risk conditions for failure. The following variables were recorded: glenohumeral force ratio, relative micromotion (distraction, translation and compression), and stress on the implant and at the cement mantle interface. Results. The wedged and step designs showed similar force ratio measurements with both RM [(wedge (3.5 mm: 0.69; 10 mm: 0.7) and step (4 mm: 0.72; 10 mm: 0.75)]. Surrogate for micromotion was a combination of distraction, translation and compression. As radial mismatch increased, both implants showed less distraction [wedge design (3.5 mm: 0.042 mm; 10mm: 0.030 mm); step design (4 mm: 0.04 mm; 10 mm: 0.027 mm)]. As radial mismatch increased, both implants showed more translation [wedge design (3.5 mm: 0.058 mm; 10mm: 0.062 mm); step design (4 mm: 0.023 mm; 10 mm: 0.063 mm)]. During compression measurements, the different designs did not follow the same pattern as their conformity setting changed. The wedge one decreased as radial mismatch increased, (at 3.5mm: 0.18 mm; at 10 mm: 0.10 mm) and the step design increased as its radial mismatch increased (at 3.5 mm: 0.19 mm; at 10 mm: 0.25 mm). Quantitatively, the step design showed higher risk of implant instability and loosening. As radial mismatch increased, the stress level on the backside of the implant increased as opposed to the stress levels on the cement mantle which decreased for both designs as the radial mismatch increased [wedged (3.5 mm: 2.9 MPa; 10mm: 2.6 MPa); step (3.5 mm: 4.4 MPa; 10 mm: 4.1 MPa)]. In this situation, the risk of loosening was higher for the step designwhich exceeded the endurance limit of the cement material (4 MPa). Discussion. Implant loosening and wear are associated with increased micromotion and high stress levels. Based on our FEA model, overall increased radial mismatch has an advantage of providing higher glenohumeral stability but not without tradeoffs, such as higher implant and cement mantle stress levels, and micromotion increasing the risk of implant loosening, failure or fracture over time, leading to poorer clinical outcomes and higher revision rates, especially when considering a step augmented glenoid design

Background. A challenge to obtaining proper glenoid placement in total shoulder arthroplasty is eccentric posterior bone loss and associated glenoid retroversion. This bone loss can lead to poor stability and perforation of the glenoid during arthroplasty. The purpose of this study was to evaluate the three dimensional morphology of the glenoid with associated bone loss for a spectrum of osteoarthritis patients using 3-D computed tomography imaging and simulation software. Methods. This study included 29 patients with advanced glenohumeral osteoarthritis treated with shoulder arthroplasty. Three-dimensional (3D) reconstruction of preoperative CT images was performed using image analysis software. Glenoid bone loss was measured at ten, vertically equidistant axial planes along the glenoid surface at four distinct anterior-posterior points on each plane for a total of 40 measurements per glenoid. The glenoid images were also fitted with a modeled pegged glenoid implant to predict glenoid perforation. Results. The average bone loss was greatest posteriorly in the AP plane at the central axis of the glenoid in the SI plane. Walch A2 and B1 shoulders had bone loss more centrally located, while Walch B2 shoulders displayed more posterior and inferior bone loss. There was a significant difference in the overall average bone loss for patients with no predicted peg perforation compared to patients predicted to have peg perforation (p=0.37). Peg perforation was most common in Walch B2 shoulders, in the posterior direction, and involved the central and posterior-inferior peg. Discussion. These data demonstrate a clear, anatomical pattern of glenoid bone loss for different classes of glenohumeral arthritis. These findings can be used to develop various models of glenoid bone loss to guide surgeons, predict failures, and help develop better glenoid implant

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

Introduction. The treatment of glenohumeral arthritis in a young patient poses a significant challenge. Factors that affect decision making include higher activity levels, greater expectations, and concerns of implant longevity. Conflicting results have been reported in the literature. The purpose of this study is to report on our results for resurfacing of the humeral head combined with a biologic glenoid resurfacing using a soft tissue allograft for the treatment of glenohumeral osteoarthritis. Methods. From 2003 to 2009 a retrospective multi-center review of 15 humeral and biologic glenoid resurfacing procedures with a mean age of 36.5 yrs. was performed. Indications for surgery included a diagnosis of glenohumeral arthritis non-responsive to conservative treatment. Exclusion criteria included major glenoid osseous deficiency, advanced rheumatoid arthritis, and chronic infection. Results. Mean follow-up of 57.1 months showed that on average active forward elevation improved from 126.8° to 136° and external rotation improved from 27.1° to 35.3°. The mean pre-operative and post-operative VAS score only improved from 7.9 to 5.1. Five (29%) patients were converted a total shoulder arthroplasty (TSA) at an average of 24 months with no complications in the remaining patients. Discussion. The clinical outcome of humeral head resurfacing with soft tissue resurfacing of the glenoid has not yielded encouraging results, as both pain and function are not significantly improved. Due to the disappointing results of this procedure and high revision rate, it is no longer these authors primary treatment option for OA in the young. Determining the optimal treatment for osteoarthritis in the young patient is still being investigated

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

Introduction. The reliability of currently available proximal humeral fracture classi?cation systems has been shown to be poor, giving rise to the question whether a more objective measure entails improved predictability of surgical outcome. This study aims to apply a novel software system to predict the functional range of motion of the glenohumeral joint after proximal humeral fracture. Method. Using a validated system that simulates bone-determined range of motion of spheroidal joints such as the shoulder joint, we categorically analysed a consecutive series of 79 proximal humeral fractures. Morphological properties of the proximal humerus fractures were related to simulated bone-determined range of motion. Results. The interobserver variability of range of motion assessment using our system showed excellent agreement (0.798). Maximal glenohumeral abduction and forward ?exion of intra-articular fractures were 34.3±6.6 SE and 60.7±12.4 SE degrees. For fractures with a displaced greater tuberosity abduction was 75.0±5.9 SE and forward flexion was 118.2±4.9 SE degrees, whilst for fractures where both tuberosities had been displaced they were 60.0±10.9 SE and 69.6±13.4 SE degrees respectively. For non-intra articular fractures without displaced tuberosities movements were 89.3±3.3 SE and 122.6±3.4 SE degrees respectively. The head inclination angle was positively correlated with maximum abduction (0.362, p = 0.014). Offset was negatively correlated with maximum abduction, but not statistically signi?cant (0.834, p = 0.087). Conclusion. This study has demonstrated a novel and effective tool allowing the prediction of functional motion after proximal humeral fracture based on bone anatomy. The study demonstrates that intra-articular fractures generally have the worst prognosis with regards to bone-determined ROM. Fractures with displaced tuberosities show more motion limitations for abduction than for forward ?exion. A reduced head inclination angle is a strong predictor of limited bone-determined range of motion for all types of proximal humerus fractures

Introduction. Reverse total shoulder arthroplasty (RTSA) is a commonly performed operation for a variety of pathologies. Despite excellent short-term outcomes, complications are commonly encountered. Recurrent instability occurs in up to 31% of cases, often due to components placed with too little tension. Acromial stress fractures can occur in up to 7% of cases, often due to components placed in too much tension. Despite these concerns, there is little evidence evaluating the intraoperative tension and glenohumeral contact forces (GHCF) during RTSA. The purpose of this study was to measure the intraoperative GHCF during RTSA. Methods. 26 patients were enrolled after obtaining IRB approval. Inclusion criteria were patients undergoing primary RTSA. An instrumented strain gauge implant was designed to attach to an Exactech Equinoxe (Gainesville, FL) baseplate during RTSA. A specially designed trial glenosphere was then attached to the instrumented baseplate. Wires from the strain gauges were connected to a 24-bit analog input and placed outside the operative field to a computer that measure the forces. After joint reduction, GHCF were measured in neutral, passive flexion, passive abduction, passive scaption and passive external rotation (ER). Five patients were excluded due to wire calibration issues. Results. 21 patients were enrolled. The average age was 70 (range 54–84). The average height was 169.5cm (range 154.9–182.9), and average weight was 82.7 kg (range 45.4–129.3) There were 11 females and 10 males. There were thirteen 42mm glenospheres and eight 38mm glenospheres used. The mean GHCF values were 135N at neutral, 123N at ER, 165N in flexion, 110N in scaption, and 205N in abduction. The mean force values were significantly affected by joint position (p=0.002). The mean force at terminal abduction is significantly greater than the mean force at terminal ER and terminal scaption (p<0.05). Conclusion. This study demonstrates that an intraoperative measurement of GHCF can be successfully performed during RTSA using strain gauges. GHCF during RTSA are at their lowest in scaption and ER. They are at their maximum in abduction. Surgeons should keep these findings in mind during trialing to potentially reduce complications associated with inappropriate intraoperative tensioning

Introduction. Advanced medical imaging techniques have allowed the understanding of the patterns of relative bone motions at human joints. 1. However, poor imaging contrasts of soft tissues have not allowed the full understanding of various glenohumeral ligaments (GHL) functions during glenohumeral joint (GHJ) manoeuvres. This is presently a significant limitation to research as these structures are said to be responsible for the passive stability of the GHJ. 2. Furthermore, the repairs of GHJ instability often take recourse to these structures. 3. Earlier studies have presented a model that numerically reconstructs or simulates GHJ motions. 4. and how the locus of bony attachment points of the GHLs on a dynamic GHJ could be numerically tagged and trailed. 5. The aim of this study was to advance these previous findings by developing an algorithm that allows the quantification of GHL lengths at any instantaneous position of the GHJ. Materials and Method. CT scan of a set of humerus and scapula was reconstructed into two individual surface meshes of interconnected nodes, each node having a unique vectorial identification in space. The two attachment nodes (a and b) of a GHL were identified on the bones. 5. Least squares geometric sphere was fitted upon the humeral head (HH) and its centre (c) and radius (r) quantified. 6. Vectors a, b and c were applied to represent the ‘dominant ligament plane’ concomitant with the 2D ‘dominant plane’ of Runciman (1993). 7. This plane defined the path through which the ligament wrapped on the HH. The point of initial or end of contact of GHL on the HH was defined as the point on HH where a line from c intercepts the ligament at 90°. Total GHL length was calculated as the sum of its three segments, namely: (1) Proximal segment – a straight line from its glenoid attachment node to the point of initial contact (2) Wrap segment – an arc of (r) radius of curvature from initial to end contact points (3) Distal segment – a straight line from end contact point to the humeral node of attachment. The wrap segment was further refined by adjusting ligament contacts along this path to the actual surface contour of the HH by integrating all the surface nodes along the path. The algorithm was tested for short incremental steps of GHJ abduction, flexion, rotation and translations on the Amadi et al's kinematics simulation model. 4. . Results. From plotted graphs of 5 simulated GHL, lengths increased or decreased smoothly as the rotations and translations were increased or decreased at a constant rate, respectively. Some GHJ motion directions resulted in contrasting stretching or folding effects on different ligaments in a mathematically reasonable manner. Conclusion. This numerical application would allow the quantification of functional loading of each GHL during simulated or reconstructed GHJ motion and hence provide understanding of how the various GHL may be treated during surgical repairs

Total shoulder arthroplasty has gone through several generations, as instruments and implant designs have given surgeons both more options in the alignment of the components and more guidance in the best choices to make. However, while the measurement of alignment has become more sophisticated, the importance of particular aspects of alignment to actual patient comfort and function has been less completely characterised.

Overstuffing of the joint and proud humeral heads have been most associated with clinical failure. The efforts to avoid this can be divided into two camps: 1.) The anatomic school, who believe an experienced surgeon can divine the correct anatomy that existed before the distortions of arthritis began, and that the surgeon should make free-hand cuts and alignments to restore the normal anatomy. 2.) The cutting-guide school, who believe that average versions and positions avoid error and that soft-tissue balancing requires occasional deviations from “normal” anatomy.

Reverse total shoulder replacement in contrast is a semi-constrained implant, with built-in “internal impingement” at the extremes of motion, which can cause notching and/or instability (levering out). Initial European experience favored placing the humeral component in 0 degrees, but most surgeons have gravitated toward 15–20 degrees of retroversion to allow easy conversion from/to a hemiarthroplasty as needed. Increased retroversion may block internal rotation, and increased anteversion limits external rotation.