Aims

The aim of this study was to describe a quantitative 3D CT method to measure rotator cuff muscle volume, atrophy, and balance in healthy controls and in three pathological shoulder cohorts.

The use of shorter humeral stems in reverse shoulder arthroplasty has been reported as safe and effective. Shorter stems are purported to be bone preserving, easy to revise, and have reduced surgical time. However, a frequent radiographic finding with the use of uncemented short stems is stress shielding. Smaller stem diameters reduce stress shielding, however, carry the risk of varus or valgus malalignment in the metadiaphyseal region of the proximal humerus. The aim of this retrospective radiographic study was to measure the true post-operative neck-shaft (N-S) angle of a curved short stem with a recommended implantation angle of 145°.

True anteroposterior radiographs of patients who received RTSA using an Ascend Flex short stem at three specialized shoulder centres (London, ON, Canada, Lyon, France, Munich, Germany) were reviewed. Radiographs that showed the uncemented stem and humeral tray in orthogonal view without rotation were included. Sixteen patients with proximal humeral fractures or revision surgeries were excluded. This yielded a cohort of 124 implant cases for analysis (122 patients, 42 male, 80 female) at a mean age of 74 years (range, 48 – 91 years). The indications for RTSA were rotator cuff deficient shoulders (cuff tear arthropathy, massive cuff tears, osteoarthritis with cuff insufficiency) in 78 patients (63%), primary osteoarthritis in 41 (33%), and rheumatoid arthritis in 5 (4%).

The humeral component longitudinal axis was measured in degrees and defined as neutral if the value fell within ±5° of the humeral axis. Angle values >5° and < 5 ° were defined as valgus and varus, respectively. The filling-ratio of the implant within the humeral shaft was measured at the level of the metaphysis (FRmet) and diaphysis (FRdia). Measurements were conducted by two independent examiners (SA and TW). To test for conformity of observers, the intraclass correlation coefficient (ICC) was calculated.

The inter- and intra-observer reliability was excellent (ICC = 0.965, 95% confidence interval [CI], 0.911– 0.986). The average difference between the humeral shaft axis and the humeral component longitudinal axis was 3.8° ± 2.8° (range, 0.2° – 13.2°) corresponding to a true mean N-S angle of 149° ± 3° in valgus. Stem axis was neutral in 70% (n=90) of implants. Of the 34 malaligned implants, 82% (n=28) were in valgus (mean N-S angle 153° ± 2°) and 18% (n=6) in varus position (mean N-S angle 139° ± 1°). The average FRmet and FRdiawere 0.68 ± 0.11 and 0.72 ± 0.11, respectively. No association was found between stem diameter and filling ratios (FRmet, FRdia) or cortical contact with the stem (r = 0.39).

Operative technique and implant design affect the ultimate positioning of the implant in the proximal humerus. This study has shown, that in uncemented short stem implants, neutral axial alignment was achieved in 70% of cases, while the majority of malaligned humeral components (86%) were implanted in valgus, corresponding to a greater than 145° neck shaft angle of the implant. It is important for surgeons to understand that axial malalignment of a short stem implant does influence the true neck shaft angle.

This study examined the regional variations of cortical and cancellous bone density present in superiorly eroded glenoids. It is hypothesized that eroded regions will contain denser bone in response to localized stress. The shift in natural joint articulation may also cause bone resorption in areas opposite the erosion site.

Clinical CT scans were obtained for 32 shoulders (10m/22f, mean age 72.9yrs, 56–88yrs) classified as having E2-type glenoid erosion. The glenoid was divided into four measurement regions - anterior, inferior, posterior, and superior - as well as five depth regions. Depth regions were segmented in two-millimeter increments from zero to 10 millimeters, beginning at the center of the glenoid surface. A repeated-measures multiple analysis of variance (RM-MANOVA) was performed using SPSS statistical software to look for differences and interactions between mean densities in each depth, quadrant, and between genders. A second RM-MANOVA was performed to examine effects of gender and quadrant on cortical to cancellous bone volume ratios. Significance was set at p < 0 .05.

Quadrant and depth variables showed significant multivariate main effects (p 0.147 respectively). Quadrant, depth, and their interaction showed significant univariate main effects for cortical bone (p≤0.001) and cancellous bone (p < 0 .001). The lowest bone density was found to be in the inferior quadrant for cancellous bone (307±50 HU, p < 0 .001). The superior quadrant contained the highest mean density for cortical bone (895±97 HU), however it was only significantly different than in the posterior quadrant (865±97 HU, p=0.022). As for depth, it was found that cortical bone is most dense at the glenoid surface (zero to two millimeters, 892±91 HU) when compared to bone at two to eight millimeters in depth (p < 0 .02). Cancellous bone was also most dense at the surface (352±51 HU), but only compared to the eight to 10 millimeters depth (p=0.005). Cancellous bone density was found to decrease with increasing depth. For cortical-to-cancellous bone volume ratios, the inferior quadrant (0.37±0.28) had a significantly lower ratio than all other quadrants (p < 0 .001)

The superoposterior region of the glenoid was found to have denser cancellous bone and a high ratio of cortical to cancellous bone, likely due to decreased formation of cancellous bone and increased formation of cortical bone, in response to localized stresses. The inferior quadrant was found to have the least dense cortical and cancellous bone, and the lowest volume of cortical bone relative to cancellous bone. Once again, this is likely due to reduction in microstrain responsible for bone adaptation via Wolff's law. The density values found in this study generally agree with the range of values found in previous studies of normal and arthritic glenoids. An important limitation of this study is the sizing of measurement regions. For a patient with a smaller glenoid, a depth measurement of two millimeters may represent a larger portion of the overall glenoid vault. Segments could be scaled for each patient based on a percentage of each individual's glenoid size.

Superiorly eroded glenoids in cuff tear arthropathy represent a surgical challenge for reconstruction. The bone loss orientation and severity may influence glenoid component fixation. This computed-tomography study quantifies both the degree of erosion and orientation in superiorly eroded Favard E2 glenoids. We hypothesized that the erosion in E2 glenoids does not occur purely superiorly, rather, it is oriented in a predictable posterosuperior orientation with a largely semicircular line of erosion.

Three-dimensional reconstructions of 40 shoulders with E2 glenoids (28 female, 12 male patients) at a mean age of 74 years (range, 56–88 years) were created from computed-tomography images. Point coordinates were extracted from each construct to analyze the morphologic structure. The anatomical location of the supra- and infraglenoid tubercle guided the creation of a superoinferior axis, against which the orientation angle of the erosion was measured. The direction and, thus, orientation of erosion was calculated as a vector. By placing ten point coordinates along the line of erosion and creating a circle of best fit, the radius of the circle was placed orthogonally against a chord that resulted by connecting the two outermost points along the line of erosion. To quantify the extent of curvature of the line of erosion between the paleo- and neoglenoid, the length of the radius of the circle of best fit was calculated. Individual values were compared against the mean of circle radii. The area of bony erosion (neoglenoid), was calculated as a percentage of the total glenoid area (neoglenoid + paleoglenoid). The severity of the erosion was categorized as mild (0% to 33%), moderate (34% to 66%), and severe erosion (>66%).

The mean orientation angle between the vector of bony erosion and the superoinferior axis of the glenoid was 47° ± 17° (range, 14° – 74°) located in the posterosuperior quadrant of the glenoid, resulting in the average erosion being directed between the 10 and 11 o'clock position (right shoulder).

In 63% of E2 cases, the line of erosion separating the paleo- and neoglenoids was more curved than the average of all bony erosions in the cohort. The mean surface area of the neoglenoid was 636 ± 247 mm2(range, 233 – 1,333 mm2) and of the paleoglenoid 311 ± 165 mm2(range, 123 – 820 mm2), revealing that, on average, the neoglenoids consume 67% of the total glenoid surface. The extent of erosion of the total cohort was subdivided into one mild (2%), 14 moderate (35%) and 25 severe (62%) cases.

Using a clock-face for orientation, the average orientation of type E2 glenoid defects was directed between the 10 and 11 o'clock position in a right shoulder, corresponding to the posterosuperior glenoid quadrant. Surgeons managing patients with E2 type glenoids should be aware that a superiorly described glenoid erosion is oriented in the posterosuperior quadrant on the glenoid clock-face when viewed intra-operatively. Additionally, the line of erosion in 63% of E2 glenoids is substantially curved, having a significant effect on bone removal techniques when using commercially available augments for defect reconstruction.

Aims

The aim of this study was to report the outcomes of different treatment options for glenoid loosening following reverse shoulder arthroplasty (RSA) at a minimum follow-up of two years.

Aims

Controversy about the use of an anatomical total shoulder arthroplasty (aTSA) in young arthritic patients relates to which is the ideal form of fixation for the glenoid component: cemented or cementless. This study aimed to evaluate implant survival of aTSA when used in patients aged < 60 years with primary glenohumeral osteoarthritis (OA), and to compare the survival of cemented all-polyethylene and cementless metal-backed glenoid components.

Introduction

Reverse Total Shoulder Arthroplasty (rTSA) is an efficient treatment, to relieve from pain and to increase function. However, scapular notching remains a serious issue and post-operative range of motion (ROM) presents many variations. No study compared implant positioning, different implant combinations, different implant sizes on different types of patient representative to undergo for rTSA, on glenohumeral ROM in every degree of freedom.

INTRODUCTION

The glenoid version assessment is crucial step for any Total Shoulder Arthroplasty (TSA) procedure. New methods to compute 3D version angle of the glenoid have been proposed. These methods proposed different definitions of the glenoid plane and only used 3 points to define each plane on the 3D model of the scapula. In practice, patients often come to consultation with their CT-scans. In order to reduce the x-ray dose, the scapulae are often truncated on the inferior part. In these cases, the traditional scapula plane cannot be calculated. We hypothesised that a new plane definition, of the scapula and the glenoid, that takes into account all the 3D points, would have the least variation and provide more reliable measures whatever the scapula is truncated or not. The purpose of the study is to introduce new fully automatic method to compute 3D glenoid version for TSA preoperating planning and test its results on artificially truncated scapulae.

PURPOSE

We performed an anatomical study to clarify humeral insertions of coracohumeral ligament (CHL) and superior glenohumeral ligament (SGHL) and their relationship with subscapularis tendon. The purpose of our study was to explain the « Comma Sign » observed in retracted subscapularis tears treated by arthroscopy.

Purpose

to analyze the survivorship of the RSA with a minimum 10 years follow up.

Introduction

the aim of this study was to analyse the long-term radiological changes following tsa in order to better understand the mechanisms responsible for loosening.

Purpose of the study: Data concerning the teres minor in the context of rotator cuff tears is scarce despite the fact that this muscle plays a crucial role in the event of an infraspinaus tear. The purpose of this study was to analyse the computed tomography and magnetic resonance images of the teres minor muscle in rotator cuff tears.

Material and method: The aspect of the teres minor muscle was studied in 1624 shoulders with rotator cuff tears. The axial and sagittal CT or MRI aspect was noted as normal, hypertrophic, atrophic or absent (Walch classification). We searched for correlations with the tendon torn, tear mechanism (trauma, degeneration, mixed), gender, dominance, time to imaging, age at imaging, and fatty infiltration of the supraspinatus, infraspinatus and subscapularis.

Results: The teres minor was noted normal in 90.9% of the shoulder, hypertrophic in 5.2%, atrophic in 3.2% and absent in 0.2%. The type of cuff tear had a significant impact (p< 0.0005). Regarding the aspect of the teres minor muscle, the highest percentages were as follows: normal for isolated supraspinatus tears, hypertrophic for supraspinatus and subscapularis tears, atrophic for posterosuperior (supraspinatus, infraspinatus ± teres minor) tears and absent for massive tears involving the supraspinatus, the infraspinatus ± the subscapularis (p< 0.0005). The correlation was statistically significant between the aspect of the teres minor and the grade of fatty infiltration of the infraspinatus (p< 0.0005) and the subscapularis (p< 0.0005).

Discussion: The aspect of an atrophic or absent teres minor, which correlates with the trumpet sign in massive tears, was only found in 3.5% of the tears. There would thus be few indications for latissimus dorsi transfer to restore active external rotation.

Purpose of the study: Many rotator cuff tears occur in the context of a work accident or an occupational disease (schedule 57-A in the French occupational disease nomenclature). This context is a negative factor for outcome although diverse opinions are expressed in the literature. We wanted to study the occupational outcome of operated patients after rotator cuff repairs and to determine what factors affect this outcome.

Material and method: From 2000 to 2005, 1155 patients underwent rotator cuff repair performed by the same operator. The context was an occupational context (schedule 57-A) in one quarter of these patients (n=290, 25.1%). Among these, 87.6% (n=254) responded to a mail questionnaire. In all 262 shoulders were included in this series (8 bilateral cases). Male gender predominated (72%) and 69% of the tears were in the right shoulder. Mean patient age was 50.53±6.4 years. In this series, 67% of the tears were related to a work accident and 33% to an occupational disease. The patients were salaried workers (75.2%), independent craftsmen (12.6%), and civil servants (11.8%). The occupational category was heavy manual labour (68.3%), light manual labour (25.5%), non manual occupation (6.1%). The injury involved one tendon in 64.1%, two tendons in 28.2% and three tendons in 7.6%. Classical open repair was performed for 70.6%), mini-open repair for 9.2%, and arthroscopic repair for 20.2%.

Results: Patients resumed their occupational activity in 59.64% of the cases (mean age 48±0.8 years); 40.45% did not resume their occupational activity (mean age 54±5.3 years). Excepting cases of retirement or interruption related to another medical condition, the shoulder was the reason for not resuming work in 16% of patients. Young age (p=0.0005) and type of surgery (open procedure p=0.0004) were factors favouring resumption of occupational activity while gender, occupational category and type of injury had no effect. The duration of sick leave (full time) depended on the occupational category (p=0.004) and somewhat on gender, age, occupational situation, work accident or occupational disease, and type of surgery/

Conclusion: Work accidents or occupational disease were not synonymous with failure of rotator cuff repair. Age was the leading prognostic factor.

Purpose of the study: The purpose of this study was to report the clinical and radiographic outcomes a minimum five years after Latarjet-Patte treatment for recurrent traumatic anterior instability of the shoulder in rugby players. It was hypothesised that the Latarjet-Patte procedure fulfils the needs for shoulder stability in rugby players with anterior instability.

Material and methods: Thirty-four players (37 shoulders) were included. Mean age was 23.4 years (17–33). A bone lesion of the glenoid was noted in 73% of the shoulders, a humeral defect in 68%.

Results: Mean follow-up was 144 months (range 68–237). There was no recurrence (dislocation or subluxation). Apprehension persisted in five patients (14%). Sixty-five percent of the patients resumed playing rugby. Only one patient interrupted his sports activities because of the operated shoulder. The Walch-Duplay and Rowe scores were 86 and 93 points on average. The satisfaction rate was 94%. The block healed in 89% of shoulders (3 fractures, 1 nonunion). Twenty-six shoulders (70%) were free of degenerative disease, 11 shoulders (30%) presented stage 1 lesions.

Discussion: In rugby players, anterior instability exhibits characteristic bone lesions of the humerus and glenoid which can be identified as risk factors for recurrent instability. The Latarjet-Patte procedure provides a stable shoulder allowing resumption of rugby player for most patients with no long-term degradation of the shoulder joint. These results are in favour of our strategy to propose the coracoids block systematically for recurrent anterior instability in rugby players.

Purpose of the study: Reversed prostheses provide improved active anterior elevation in shoulders free of cuff tears by lengthening the deltoid and increasing is lever arm. The purpose of this work was to search for a correlation between arm lengthening and postoperative active anterior elevation.

Material and methods: One hundred eighty-three reversed prostheses were reviewed with minimum one year follow-up for a complete clinical and radiographic work-up. Using a previously validated protocol, arm lengthening was assessed either in comparison with the contralateral side or with preoperative measurements. A statistical analysis was performed to search for a correlation between lengthening of the humerus and the arm with active anterior elevation.

Results: Considering the entire series, mean lengthening of the humerus was 0.2±1.4 cm (range −4.7 to +5.4). Postoperative active anterior elevation was 141±27 (range 30–180). There was no correlation between humerus lengthening or shortening and active anterior elevation (p=0.169). A shorter arm produced an active anterior elevation at 121 and 0 – 1 cm lengthening an active anterior elevation at 140; lengthening 1 – 2.5 cm gave active anterior elevation at 144 and beyond 2.5 cm 147. The difference in active anterior elevation was statistically significant (p< 0.001) between patients with a shortening and those with a lengthening.

Discussion: Arm lengthening corresponds to a lengthening of the humerus plus a lengthening of the infra-acromial space. We found a statistically negative correlation between arm shortening (and thus deltoid shortening) and active anterior elevation and a positive trend between lengthening and active anterior elevation. Our measurement did not take into account the increased lever arm of the deltoid and thus only partially expresses the improvement in deltoid function. Nevertheless, our study shows that objective evaluation of deltoid lengthening is possible pre- intra- and postoperatively and that this measurement can be correlated with postoperative functional outcome.

Purpose: Recognition of the glenoid version is important for evaluation of different pathologies. There is no consensus on method to use to evaluate version. The purpose of this study was to compare different measurement strategies in one hundred-sixteen (116) patients with shoulder CT-scans.

Method: Scapula CT-scan axial images were revised and the cut below the base of the coracoid was selected. The glenoid version was measured according to the Friedman method (FM) and the “scapula body” methods (BM). In case of B2 glenoid three different reference lines have been measure: the neo-glenoid NG (posterior erosion surface), paleo-glenoid PG (original glenoid surface) and the intermediate-glenoid IG (line from anterior and posterior edge). Three orthopaedic surgeons independently examined the images two times and intra/inter-observer reliability was calculated using Intra-Class Correlation (ICC). The objective of this paper is to define which method shows best reliability.

Results: Group 1 (B2 excluded n=53): The average glenoid version was significantly different between two measurement techniques for all three observers, with an average of – 7.29° for BM technique and – 10.43° for FM. Intra-observer reliability was excellent for both methods (ICC: 0.958–0.979 for FM; 0.940–0.970 for BM). Inter-observer reliability was excellent for both methods (FM: ICC= 0.977; BM: ICC= 0.962). The light superiority of the first method was not significant. For group 2 – B2 glenoid (n=63): six different measures of version were taken resulting by two scapula reference line (FM and BM) and three glenoid reference line (PG, IG, NG). The average glenoid versions were significantly different (p0.82). The inter-observer reliability were also very-good or excellent for all methods (ICC > 0.79). The most reliable method for measurement of B2 glenoid version was the association of the Friedman line for the scapula axis and the intermediate glenoid line with excellent intra observer reliability (ICC > 0.957) and inter-observer reliability (ICC=0.954).

Conclusion: Measurement of glenoid version on axial cut of a Ct-scan is highly reliable. Significant differences exist between measures depending which method is used, underlying the importance of a consensus for research and clinical purpose. Despite very good performance of all methods, authors recommend the use of the Friedman method for the scapula axis reference and an intermediate glenoid line in case of B2 glenoid.

Purpose: The glenoid status is a crucial aspect of planning for shoulder replacements. This study revisits the classification proposed by Walch et al and discusses its value to orthopedic surgeons in terms of reproducibility and reliability.

Method: Three evaluators viewed one hundred-sixteen (116) shoulder CT-scans with primary glenohumeral arthritis and classified glenoid wear according to Walch classification two times. The validation study was done for three sets of data: Set I: the complete classification: A1, A2, B1, B2, C. Set II: regrouping with main categories: A,B,C. Set III: regrouping categories according to glenoid facet morphology; Normal concavity: A1, A2, B1; Biconcave glenoid: B2; Retroverted glenoid: C.

Results: Intra-observer Kappa values for Observer 1, 2, and 3 averaged 0.866 (0.899, 0.927, 0.773) for Set I; for Set II, the values averaged 0.915 (0.955, 0.975, 0.814); and for Set III, the values averaged 0.874 (0.897, 0.948, 0.777), all excellent values. Inter-observer reliability values for Set I averaged 0.621 (0.776, 0.512, 0.574), indicating good agreement; for Set II, the values averaged 0.759 (0.880, 0.713, 0.685), indicating excellent inter-observer agreement; and for Set III, the average was 0.642 (0.825, 0.519, 0.581), indicating good inter-observer agreement.

Conclusion: A clarification of the Walch et al classification of the osteoarthritic glenoid was necessary, especially with regards to the wordings of categories B2 and C. When used properly, it is a reliable and valuable tool for orthopedic surgeons of all levels of experience in the evaluation of the osteoarthritic glenohumeral joint.

Purpose of the study: Fatty infiltration and atrophy of rotator cuff muscles is an important prognostic factor for anatomic healing and function after repair. The purpose of this study was to analyse factors influencing the development and progression of the supraspinatus muscle and to search for correlation between infiltration and atrophy.

Material and method: Preoperative arthroscans and MRI series for 1688 patients with rotator cuff tears were reviewed. We searched for correlations between fatty infiltration of the supraspinatus muscle and gender, age at imaging, size of the tear, onset (trauma or not), and time from symptom onset to imaging. Fatty infiltration was noted according to the Goutallier classification and on the MRI using the classification adapted by Fuchs. For the statistical analysis, fatty infiltration was considered minor for grades 0 and 1, moderate for grade 2 and severe for grades 3 and 4. Muscle atrophy was assessed using the tangent sign.

Results: Fatty infiltration of the supraspinatus increased significantly with the size of the tendon tear (p< 0.0005), time from symptom onset to imaging (lp< 0.0005) and patient age (p< 0.0005). Atrophy increased with number of torn tendons, positive tangent sign was correlated with the grade of fatty infiltration of the supraspinatus (p< 0.0005) and the infraspinatus (p< 0.0005). Moderate and severe fatty infiltration developed a mean 3 and 5 years, respectively, after symptom onset.

Discussion: Surgical treatment should be undertaken before the appearance of moderate (grade 2) fatty infiltration and atrophy (positive tangent sign).

Conclusion: Moderate fatty infiltration of the supraspinatus develops on average three years after onset of symptoms.

Purpose of the study: Four elements differentiate myotendinous tears of the infraspinatus from other rotator cuff tears: the tendon insertion on the trochiter and the joint capsule are spared; the onset in characterized by intense muscle oedema followed at 6 to 12 months by severe and definitive fatty degeneration.

Material and method: Fifty-nine myotendinous tears of the infraspinatus were collected prospectively from 1993 to 2007. Female gender predominated (58%); trauma was noted at onset in 22% of the shoulders and the mean age of discovery was 48.9 years. Twenty-nine shoulders were seen at the acute phase with significant muscle oedema recognized on the MRI T2 Fat Sat sequence. A second group of 30 patients had grade 4 fatty infiltration of the infraspinatus without full thickness cuff tears. The EMG was available for 23 shoulders and was normal in all, ruling out a neurological cause. Associated lesions of the supraspinatus and infraspinatus tendons were: tendon calcification (61%) and partial tears at the acute phase (21%) and chronic phase (70%) suggesting a degenerative cause.

Results: Twenty-four patients underwent surgery and 35 had a medical treatment. At mean 46 months follow-up (range 12–125) the Constant score improved from 51.7 to 69.4 points (p< 0.0001). There was no different statistically between the operated and non-operated patients (p=0.325). All patients seen at the acute phase of the oedema progressed to complete grade 4 fatty degeneration of the muscle, irrespective of the treatment delivered.

Discussion: Early diagnosis of this lesion can be achieved with T2 Fat Sat MRI sequences. Arthroscopic repair to tighten the infraspinatus muscle could avoid the irremediable degeneration with total loss of muscle function.

Introduction: Clinically evident neurological injury of the operated limb after total shoulder arthroplasty is not uncommon. The purpose of this prospective study was to determine the incidence of subclinical neurological lesions after reverse shoulder arthroplasty and anatomic shoulder arthroplasty (group control), and to correlate its occurrence to postoperative lengthening of the arm.

Method: We included all patients needing a total shoulder arthroplasty either anatomic or reversed. Each patient underwent a pre- and postoperative electromyography (EMG). This study focused on the clinical, radiological and EMG evaluation, with a measure of the lengthening of the arm in case of reversed shoulder arthroplasty according to a protocol previously validated.

Result: Between November 2007 and February 2009, we collected 41 patients (42 prostheses), including 23 anatomic (group 1) and 19 reverse (group 2) primary shoulder arthroplasties. The 2 groups were similar according to mean age, comorbidity, male/female ratio and nerve conduction abnormalities on EMG performed on an average of 10 days before surgery. Control EMG realized at an average of 3.6 weeks postoperatively showed in group 1, a plexus lesion due to an intra-operative complication. In group 2, we noticed 9 recent neurological damages (45% of cases) involving mainly the axillary nerve; 8 were rapidly regressive. The incidence of recent injury was significantly more frequent in group 2 (p=0.003) with a risk 10.4 times higher (95% CI 1.4, 74.8). Mean lengthening of the arm after a reverse was 3.1 cm ± 1.8 (range 0.2 to 5.9) compared to preoperative measurement and 2.4 cm ± 2.1 (range −0.5 to 5.8) compared with the normal contra-lateral side.

Discussion: The occurrence of peripheral neurological lesion following a reverse shoulder arthroplasty is common but usually transient. These lesions may cause postoperative pain, alter rehabilitation and can theoretically induce prosthetic instability. Lengthening of the arm is considered as one of the major factors responsible for this neurologic damage. Indeed, surgical dissection, compression phenomena by use of retractors or presence of hematoma, vascular injury, mobilization of the upper limb and possibly interscalene block are similar for the two types of prosthesis. Arm lengthening is thus a compromise between necessary retensionning of the deltoid for good mobility and instability avoidance, and lengthening which may be responsible for neurological lesions, acromial fractures and permanent arm abduction.