Implantation Of Reverse Shoulder Arthroplasty Research Articles

A gender and size specific evaluation of Grammont-type inlay versus lateralizing onlay stem designs in achieving lateralization and distalization in reverse shoulder arthroplasty

IntroductionIn reverse shoulder arthroplasty (RSA) new designs enable greater amounts of lateralization to prevent instability and scapular notching and increase range of motion, however, excessive lateralization leads to stress upon the acromion that can result in scapular spine fatigue fractures. Aim of this study was to gender- and size-specifically assess the influence of glenosphere size and different humeral designs on lateralization, distalization, and bony impingement-free range of motion (ROM) in patients undergoing RSA.MethodsComputed tomography scans from 30 osteoarthritic patients (f:15, m:15) and 20 cuff tear arthropathy patients (f:10, m:10) were used to virtually simulate RSA implantation. The efficacy of an inlay Grammont-type system vs. an onlay lateralizing system combined with different glenosphere sizes (36 mm vs. 42 mm) in achieving ROM, lateralization, and distalization was evaluated. Moreover, gender and patient’s constitution were correlated to humeral size by radiologically measuring the best-fit circle of the humeral head.ResultsA different amount of relative lateralization was achieved in both genders using large glenospheres and onlay designs. Latter yielded a higher ROM in all planes for men and women with a 42 mm glenosphere; with the 36 mm glenosphere, an increased ROM was observed only in men. The 155° inlay design led to joint medialization only in men, whereas all designs led to lateralization in women. When adjusting the absolute amount of lateralization to humerus’ size (or patient’s height), regardless of implant type, women received greater relative lateralization using 36 mm glenosphere (inlay: 1%; onlay 12%) than men with 42 mm glenosphere (inlay: -3%; onlay: 8%).ConclusionThe relative lateralization achieved using onlay design is much higher in women than men. Small glenospheres yield greater relative lateralization in women compared to large glenospheres in men. Humeral lateralization using onlay designs should be used cautiously in women, as they lead to great relative lateralization increasing stress onto the acromion.Level of evidenceBasic Science Study, Computer Modeling.

Operative treatment of acromial and scapular spine fracture nonunions complicating reverse total shoulder arthroplasty

BackgroundFractures of the acromion and spine can have a major impact on the outcome of reverse shoulder arthroplasty (RSA) with respect to pain, motion, and function. Reports on internal fixation for these fractures are isolated to small series or case reports with variable outcomes. The purpose of this study was to report on the outcome of open reduction and internal fixation (ORIF) of acromion or spine fractures encountered before or after RSA and describe our evolution of fixation techniques. MethodsBetween 2011 and 2023, 22 fractures or nonunions of the acromion or spine of the scapula underwent ORIF at a single institution and were followed for a minimum of 1 year. In 16 shoulders, fractures occurred after RSA, whereas 5 shoulders underwent ORIF prior to RSA. One shoulder had undergone prior failed ORIF elsewhere and revision ORIF was performed at our institution. There were 10 males and 12 females with a mean age of 67 (SD=15.1) years. Fixation strategies included single (n=11) and double plate fixation (n=11). Kruskal-Wallis one-way analyses of variance were used to analyze continuous variables and Chi-square tests employed for categorical variables. ResultsOf the 5 fractures treated with ORIF pre-RSA, 1 shoulder suffered an additional fracture medial to the hardware and 1 required additional bone grafting for incomplete union at the time of RSA. These 5 shoulders all underwent RSA uneventfully, but one fracture experienced late displacement of the scapular spine nonunion, leading to plate removal. Of the 16 post-RSA ORIF shoulders, radiographic union was confirmed in 14 and substantial residual inferior angulation identified in 3. New fractures occurred after ORIF in 5 shoulders. For patients who underwent ORIF after RSA, pain scores improved from a mean of 8 to 1.9 points, with more modest elevation gains (58.2° to 91.3° pre- and postoperatively, respectively). ConclusionsORIF of acromion and scapular spine fractures or nonunions in the setting of RSA have the potential to lead to union. When these fractures and nonunions are encountered prior to RSA, ORIF allows for uneventful RSA implantation, but secondary displacement may occur. ORIF seems to lead to improvements in pain, but more modest improvements in motion and function. Our fixation strategy has evolved to (1) dual plating, (2) spanning the whole length of the spine with one of the plates, (3) use of hook features under the acromion or os trigonum if possible, and (4) liberal use of bone graft.

Stemless RSA shows good short-term radiological stability and clinical outcomes in elderly patients

BackgroundThe main goal of this study was to investigate the influence of patient age on humeral implant fixation in stemless reverse shoulder arthroplasty (RSA). The secondary goals were to investigate the influence on the occurrence of complications and on clinical outcomes. MethodsWe performed a retrospective multicenter study, including a series of patients operated on for stemless RSA. All patients were reviewed at a minimum of 2 years, with clinical and radiographic evaluation. The primary endpoint was the occurrence of migration of the humeral implant at the final follow-up. Secondary endpoints were clinical scores, occurrence of postoperative complications, need for revision surgery, and radiographic changes. Each patient ≥70 year old was matched on gender and body mass index,with a patient < 70 year old on a 1:1 basis. ResultsForty-five patients aged ≥70 years were included and matched, with 45 patients aged <70 years, giving a total of 90 patients (54.4% men) with the mean age being 68.5 ± 7.9 years. There was no difference between the 2 groups in terms of surgical modalities. There was no correlation between age and clinical outcomes. Three migrations of the humeral implant occurred, none leading to a revision, without any influence of age (P = 1.0). We found no correlation between patient age and the occurrence of a postoperative complication (P = 1.0), reoperation (P = 1.0) or any of the other radiographic parameters assessed. ConclusionThis study reported the stability of stemless RSA implants in elderly patients. Clinical outcomes, complication, and revision rates were not affected by age either.

Is there a role for acromioplasty and tuberoplasty in reverse shoulder arthroplasty to improve impingement-free range of motion?

Hypothesis and BackgroundLateralizing the center of rotation in reverse shoulder arthroplasty (RSA) decreases the risk of scapular notching due to inferior impingement but may limit range of motion (ROM) in abduction and forward flexion related to superior acromial impingement. Our primary hypothesis was that, using a 3-dimensional (3D) computer model, a virtual acromioplasty (with or without tuberoplasty) could improve abduction and forward flexion following RSA for cuff tear arthritis (CTA) or massive cuff tear. Our secondary hypothesis was that, based on the virtual planning, a surgical acromioplasty could be performed safely during RSA, without increasing the risk of postoperative acromial fracture. MethodsEighty seven patients with CTA scheduled for RSA were analyzed with a 3D software and impingement-free ROM was measured. After virtual prosthesis implantation, early acromio-humeral impingement (abduction ≤ 80° or forward flexion ≤ 120°) was observed in 25% of the cases (22/87). A virtual acromioplasty (with or without tuberoplasty) was then performed and glenohumeral ROM was measured again. Based on this 3D planning, a surgical acromioplasty (with or without tuberoplasty) was performed to improve ROM in the vertical plane in these 22 patients with early acromial impingement. Patients were followed with minimum 24 months of follow-up to assess final shoulder ROM and complications. ResultsAfter virtual acromioplasty alone (n = 11) or acromioplasty with tuberoplasty (n = 11), glenohumeral abduction significantly increased from 75° ± 6.9 before to 89.5° ± 23.4, and forward flexion from 119.3° ± 12 to 135.2° ± 10 (P < .001). After surgical acromioplasty/tuberoplasty, the final mean global forward flexion was 148° ± 5 and mean global abduction 150° ± 8 in these patients. At last follow-up, no acromial fracture was observed. ConclusionIn a 3D model, early acromial impingement may limit abduction (≤80°) or forward flexion (≤120°) after virtual RSA implantation for CTA or massive cuff tear. Virtual acromioplasty (with or without tuberoplasty) shows improved ROM in abduction and flexion. In patients with early impingement, a surgical acromioplasty can be performed safely during RSA, through a deltopectoral approach, without increasing the risk of postoperative acromial fracture.

Stemless Reverse Shoulder Arthroplasty.

Since the Food and Drug Administration (FDA) approval nearly two decades ago, the indications for and utilization of reverse shoulder arthroplasty (RSA) have expanded considerably. Stemless RSA designs have been used in Europe since 2005, but have only recently been introduced in domestic Investigational Device Exemption trials. Potential advantages of stemless RSA are similar to those of stemless anatomic total shoulder arthroplasty, which may include fewer shaft-related complications, avoidance of stress shielding, bone preservation, and easier revision surgery. European data support similar outcomes between certain stemless RSA prostheses compared with that of stemmed RSA implants at early and mid-term follow-up. However, long-term outcomes remain to be seen and differences exist between the stemless RSA designs used in Europe and those being studied in domestic clinical trials. An understanding of the potential advantages and disadvantages of stemless RSA, differences between existing designs, and reported clinical outcomes is prudent for the safe and meaningful implementation of this new technology in the United States.

Tailored modular spacers and handmade spacers in periprosthetic shoulder infection: clinical and functional results after 2-year follow-up

BackgroundThe diagnosis and treatment of periprosthetic shoulder infections are challenging; two-stage procedure using antibiotic-loaded spacers offers appropriate infection resolution and satisfactory clinical results. The main purpose of this study was to compare functional results in patients who keep different type of spacers as definitive treatment after first-stage procedure for periprosthetic shoulder infections. Secondary aim was to evaluate clinical and functional scores comparing patients who still hold the spacers with patients who already underwent prosthesis reimplantation. Materials and MethodsForty eight patients treated with tailored modular (TM) or handmade (HM) spacer for shoulder chronic infection were enrolled. Twenty five patients (52.1%) underwent reverse shoulder arthroplasty implantation; 23 patients (47.9%) decided to hold the spacer and to continue to use it as a functional prosthesis (17 TM spacers, 6 HM spacers). Clinical data were recorded and functional scores were calculated at 35.2-month follow-up after last shoulder surgical procedure. Visual analog pain scale was used to measure pain; Constant Score, Simple Shoulder Test, Disabilities of the Arm, Shoulder and Hand Score, and American Shoulder and Elbow Surgeons score were calculated to assess shoulder function. ResultsWe found no significant score differences in patients treated with different kind of antibiotic spacers after first-stage and second-stage procedure. Prosthesis reimplantation seems to be the best option for patients who are motivated, active, and medically stable, achieving better functional results compared to spacer retention, although we found no statistically significant improvement in pain reduction before and after prosthesis reimplantation. ConclusionsTwo-stage exchange procedures with antibiotic spacer are highly effective in infections eradication. No superiority was found in TM spacers over HM ones when the spacer was retained and when the second-stage procedure took place. Second-stage procedure appears to be effective only in improving shoulder function and not in reducing pain regardless of the kind of antibiotic-loaded spacer used. We suggest to avoid second-stage procedure in low-demanding patients with reasonable shoulder function and acceptable pain control (visual analog scale <3).

Greater Tuberosity Fractures after RTSA: A Matched Group Analysis.

Periprosthetic fractures, such as acromial and spine fractures, are known complications following implantation of reverse shoulder arthroplasty (RTSA). The entity of greater tuberosity fractures (GTF) has rarely been studied in the literature. The purpose of this study was to analyze the outcome of postoperative greater tuberosity fractures after RTSA compared to a matched control group. The main findings of this study are that a GTF after RTSA is associated with worse clinical outcome scores (mean absolute CS 50 ± 19 (p = 0.032); SSV 63% ± 26 (p = 0.022); mean force 1 kg ± 2 kg (p = 0.044)) compared with the control group (mean absolute CS 62 ± 21; SSV 77% ± 29; mean force 2 kg ± 2 kg). In terms of postoperative range of motion, the fracture group was significantly worse in terms of external rotation (17° ± 19° vs. 30° ± 19° (p = 0.029)). Internal rotation, flexion, as well as abduction of the shoulder appear to be unaffected (internal rotation GTF 4 ± 2, control group 5 ± 3 (p = 0.138); flexion GTF 102° ± 28°, control group 114° ± 27° (p = 0.160); abduction GTF 109° ± 42°, control group 120° ± 39° (p = 0.317)).

Development of a machine learning algorithm to identify total and reverse shoulder arthroplasty implants from X-ray images

IntroductionDemand for total shoulder arthroplasty (TSA) has risen significantly and is projected to continue growing. From 2012 to 2017, the incidence of reverse total shoulder arthroplasty (rTSA) rose from 7.3 cases per 100,000 to 19.3 per 100,000. Anatomical TSA saw a growth from 9.5 cases per 100,000 to 12.5 per 100,000. Failure to identify implants in a timely manner can increase operative time, cost and risk of complications. Several machine learning models have been developed to perform medical image analysis. However, they have not been widely applied in shoulder surgery. The authors developed a machine learning model to identify shoulder implant manufacturers and type from anterior-posterior X-ray images. MethodsThe model deployed was a convolutional neural network (CNN), which has been widely used in computer vision tasks. 696 radiographs were obtained from a single institution. 70% were used to train the model, while evaluation was done on 30%. ResultsOn the evaluation set, the model performed with an overall accuracy of 93.9% with positive predictive value, sensitivity and F-1 scores of 94% across 10 different implant types (4 reverse, 6 anatomical). Average identification time was 0.110 s per implant. ConclusionThis proof of concept study demonstrates that machine learning can assist with preoperative planning and improve cost-efficiency in shoulder surgery.

Elongation of the brachial plexus after reverse shoulder arthroplasty: an anatomical study.

The use of reverse shoulder arthroplasty (RSA) is becoming more extended and its clinical results are good or excellent according to the literature. The main biomechanical characteristic of RSA is that it lowers and medializes the centre of rotation of the shoulder causing an arm lengthening. Although the number of neurological complications is low (5%), there are more neurophysiological changes in the brachial plexus with RSA than with the anatomic shoulder arthroplasty. The main goal of this study was to quantify the lengthening of the terminal branches of the brachial plexus suffered after RSA implantation. 20 Embalmed cadavers were analysed. Four distances using bone references were employed to measure the lengthening of the arm and subacromial space. The brachial plexus and its terminal branches (radial, axillary, ulnar, musculocutaneous and median nerves) and the axillary artery, were identified and marked. Measurements were made to determine the change of position of the neurovascular structures, the arm lengthening and the lengthening of each nerve before and after the implantation of RSA. Two models of RSA were used: SMR®(Lima) and Delta Xtend®(DePuy-Synthes). The mean arm elongation was 10.5mm. The subacromial space suffers an elongation of 20.5-29.8%. All the neurovascular structures suffered elongation: median nerve 23.1%, musculocutaneous nerve 22.1%, ulnar nerve 19%, radial nerve 17%, axillary nerve 12-14.5%, axillary artery 24.8%. There were no differences in the results between the types of prosthesis. Due to its design, the RSA causes an arm lengthening which is reflected by the elongation of the neurovascular structures of the arm.

Reverse shoulder arthroplasty after failed tendon transfer for irreparable posterosuperior rotator cuff tears.

Tendon transfers (TTs) can be successful for the management of selected posterosuperior functionally irreparable rotator cuff tears. However, when these procedures fail to provide adequate pain relief or functional improvement, reverse shoulder arthroplasty (RSA) is commonly considered the next treatment option. The effect of prior TT on RSA remains largely unknown. The purposes of this investigation were to evaluate the outcomes of RSA after previous TT performed for posterosuperior functionally irreparable rotator cuff tears and to determine the effect of various TT types on RSA. A retrospective review of 2 institutional databases identified 33 patients who underwent RSA implantation between 2006 and 2019 with a previous failed tendon transfer (FTT) of the shoulder and at least 2 years of clinical follow-up. FTTs included 21 latissimus dorsi transfers, 6 latissimus dorsi and teres major (LD-TM) transfers, and 6 lower trapezius transfers. RSAs were performed at an average of 5.5 years (range, 0.3-28 years) after FTT, with a mean follow-up period of 4.1 ± 2.0 years. Outcomes evaluated included the visual analog scale pain score, range of motion, absolute Constant-Murley score (CS) and relative CS, American Shoulder and Elbow Surgeons score, Subjective Shoulder Value, complications, and implant survivorship free of reoperation or revision. RSA significantly improved pain and function, with improvements in the visual analog scale pain score (6.2 preoperatively vs. 2.2 at most recent follow-up, P < .001), active elevation (85° vs. 111°, P < .001), American Shoulder and Elbow Surgeons score (51 vs. 74, P = .001), absolute CS (34 vs. 48, P = .003), and relative CS (42% vs. 59%, P = .002), exceeding the minimal clinically important difference threshold. There were 7 complications (21%) across the entire cohort, with dislocation (n = 3, 9.1%) as the most common complication. Comparison across TT groups showed that LD-TM transfer had the highest complication rate (3 shoulders, 50%), followed by lower trapezius transfer (1 shoulder, 16.7%); latissimus dorsi transfer had the lowest rate (3 shoulders, 14.3%; P = .037). Survivorship free of revision or reoperation was estimated to be 90.1% at 1 year, 84.9% at 2 years, and 71.2% at 5 years, with no difference among TT groups (P = .654). RSA can serve as a viable salvage option for FTT procedures. At mid-term follow-up, RSA led to significant improvements in pain, range of motion, and patient-reported outcomes. Patients with prior LD-TM transfers may have a higher complication rate, but no other differences were found between TT groups.

Backside polyethylene wear in reverse shoulder arthroplasty.

Aseptic loosening from implant-associated osteolysis in reverse shoulder arthroplasty (RSA) may contribute to premature implant failure. Although articular side polyethylene (PE) damage has been well documented in the literature, no studies to date have investigated backside wear in RSA. The aims of this investigation were to (1) document and compare the damage between the backside and articular surface in explanted RSA components, (2) assess whether certain quadrants have a greater propensity for damage, and (3) report the most common mode(s) of backside PE damage. Twenty-one RSA humeral liners retrieved during revision procedures between 2005 and 2014 were included for analysis. The mean time between implantation and extraction was 16 months (10 days-88 months). Diagnoses at the time of revision included dislocation (10), infection (4), mechanical failure (3), loosening (2), and unknown (2). Liners were examined under light microscopy (×10-30 magnification) and damage on the articular and backside of the liner surface was graded using the modified Hood score. The location and damage modality were compared between the articular side and backside of the implant. Damage was noted on the articular surfaces of all 21 liners and on the backside surface of 20 liners. The total damage in all the quadrants was higher on the articular surface than on the backside of the component, with a mean difference in total quadrant damage scores of 11.74 ± 3.53 (P < .001). There was no difference in damage among the quadrants on the backside (P = .44) or the articular surface (P = .08). The articular side exhibited greater scratching, abrasion, and surface deformation than the backside (P < .001). This short-term retrieval study demonstrated that backside PE damage occurs on the humeral component of RSA implants. There was greater damage to the articular side of the liner but wear to the backside was present in almost all liners. The clinical importance of backside wear in RSA and its overall contribution to PE particulate disease and osteolysis needs further investigation.

Conjoint tendon lengthening for recalcitrant anterior shoulder pain after reverse shoulder arthroplasty: a technique article

The incidence of reverse shoulder arthroplasty (RSA) has increased since the Food and Drug Administration approved its use in the United States in 2004. With the current RSA implants available for surgeon use within the United States of America, each design, regardless of humeral inlay vs. onlay, distalizes the shoulder's center of rotation. This new center of rotation purposely increases tension to the deltoid, which is the main working muscle in RSA, but also retensions the adjacent tendons. Some patients after RSA experience continued anterior shoulder discomfort that limits their active range of motion and overall patient satisfaction. It has been isolated with physical examination that there is tenderness to palpation at the coracoid process and throughout the conjoint tendon. We have completed conjoint tendon lengthening procedures on this subset of patients with excellent clinical results. This article describes the technique for patients who underwent conjoint tendon lengthening after RSA for recalcitrant anterior shoulder pain.

Reverse Shoulder Arthroplasty Humeral Lateralisation: A Systematic Review.

Different studies on reverse shoulder arthroplasty (RSA) have proposed changes to the humeral design to lateralise the humeral centre of rotation (COR), with humeral inclination to 135 or 145 from 155 degrees or to switch to onlay humeral trays from inlay design; with both having also been used in combination. There have been many studies and systematic reviews to show the difference in outcomes and complications to the variations in glenoid design but to date, there have been no systematic studies to compare different humeral inclinations for RSA implants.Searches using keywords were used in common medical search engines in a systematic fashion. The article was reviewed for the class of evidence and bias, summarised and compared in meta-analysis. Inclusion criteria included studies on adults with RSA that compared lateralised humeral implants to medialised.The search produced 349 articles; of these, we identified nine studies that met the inclusion criteria. Our review identified a total of 562 patients who had been included in studies directly comparing lateralised humerus to a more medial design. Meta-analysis showed a significantly reduced risk of scapular notching in lateralised humerus compared to the standard medialised component. The external rotation range of motion in the lateralised group was statistically significant.The improvement in scapular notching and gain in the range of motion without any apparent downside in the form of reduced patient-reported outcome measures or complications suggest a lateralised humeral component is superior to the more medialised design in RSA. A large RCT with a longer-term follow-up is needed to confirm whether there is clinically significant benefit from the lateralisation of the humerus.

Changes in deltoid muscle tension after reverse shoulder arthroplasty as quantified by shear wave elastography: relationship with radiographic parameters and functional outcomes

IntroductionImplantation of a reverse shoulder arthroplasty (RSA) impacts deltoid length, shape and tension. Quantification of changes in deltoid muscle tension with implantation of RSA has remained elusive. The purpose of this study was to use shear wave elastography (SWE) to quantify deltoid muscle stiffness preoperatively, intraoperatively and postoperatively in patients undergoing RSA. MethodsTwenty patients scheduled to undergo RSA (ReUnion, Stryker) were prospectively enrolled in this study. A single observer trained in SWE quantified deltoid stiffness preoperatively, intraoperatively, and postoperatively. Clinical evaluation included pain, motion, quickDASH, ASES, Oxford, and subjective shoulder value scores. Preoperative and postoperative radiographs were measured by an independent observer to determine the lateralization and distalization shoulder angles (LSA and DSA). A statistical analysis was then performed to determine whether changes in deltoid muscle stiffness correlated with any of these parameters. ResultsImplantation of a RSA lead to an increase SWE deltoid stiffness value from 22.4 ± 4.2 kPa preoperatively to 29.9 ± 5.23 kPa (P˂ .0001) immediately after surgery, and 26.6 ± 6.6kPa (P= .03) at most recent follow-up. Preoperative SWE deltoid stiffness values did not differ when measured in the office or under anesthesia. Reverse arthroplasty did not significantly change the LSA (P= .051), but did increase the DSA (P< .0001). Greater SWE deltoid stiffness values correlated with better active elevation (P= .0128) better external rotation (P= .0247), and larger DSA (P= .0026). Elevation and external rotation showed a positive correlation with the DSA and a negative correlation with the LSA. ConclusionAfter implantation of one RSA design incorporating glenoid and humeral lateralization, deltoid stiffness as measured with SWE increased significantly. Deltoid stiffness seems to correlate with joint distalization, elevation and external rotation. SWE seems to be reliable to quantify deltoid stiffness after reverse shoulder arthroplasty. Level of EvidenceLevel IV; Diagnostic Study

Infection control and outcome of staged reverse shoulder arthroplasty for the management of shoulder infections.

BackgroundThe treatment of septic arthritis, caused by either hematogenous seeding, injections, or surgery, can be challenging. Staged reverse shoulder arthroplasty (RSA) with temporary implantation of an antibiotic-loaded spacer is widely accepted but still discussed controversially. This study investigated the shoulder-specific bacterial spectrum, infection control rate, functional outcome, and infection-free survival rate after staged RSA in the mid- to long-term follow-up. It was hypothesized that staged RSA would show a high infection-free survival rate.MethodsA total of 39 patients treated with staged RSA for primary septic arthritis (n = 8), secondary infection (n = 8), or periprosthetic infection (n = 23) were retrospectively included. The infection control rate was calculated based on cultures taken intraoperatively at spacer removal and RSA implantation. Infection-free survival was defined as no revision due to infection. The minimum follow-up period for functional outcome assessment was 2 years (n = 14; mean, 76 months; range, 31-128 months).ResultsCutibacterium (26%) and coagulase-negative staphylococci (23%) were the predominant pathogens. The infection control rate was 90%. The cumulative infection-free survival rate was 91% after 128 months. Follow-up examinations showed a mean Constant score of 48 (range, 7-85), a mean QuickDASH (short version of Disabilities of the Arm, Shoulder and Hand questionnaire) score of 40.0 (range, 11.4-93.3), and a mean pain score of 1.6 (range, 0-7).ConclusionStaged RSA implantation was confirmed to be a reliable treatment option for primary, secondary, and periprosthetic infections of the shoulder. The infection control rate and infection-free survival rate are satisfactory. However, patients and surgeons must be aware of functional impairment even after successful treatment of infections.

Automated muscle elongation measurement during reverse shoulder arthroplasty planning

Adequate deltoid and rotator cuff elongation in reverse shoulder arthroplastyis crucial to maximize postoperative functional outcomes and to avoid complications. Measurements of deltoid and rotator cuff elongation during preoperative planning can support surgeons in selecting a suitable implant design and position. Therefore, this study presented and evaluated a fully automated method for measuring deltoid and rotator cuff elongation. Complete scapular and humeral models were extracted from computed tomography scans of 40 subjects. First, a statistical shape model of the complete humerus was created and evaluated to identify the muscle attachment points. Next, a muscle wrapping algorithm was developed to identify the muscle paths and to compute muscle lengths and elongations after reverse shoulder arthroplasty implantation. The accuracy of the muscle attachment points and the muscle elongation measurements was evaluated for the 40 subjects by use of both complete and artificially created partial humeral models. Additionally, the muscle elongation measurements were evaluated for a set of 50 arthritic shoulder joints. Finally, a sensitivity analysis was performed to evaluate the impact of implant positioning on deltoid and rotator cuff elongation. For the complete humeral models, all muscle attachment points were identified with a median error < 3.5 mm. For the partial humeral models, the errors on the deltoid attachment point largely increased. Furthermore, all muscle elongation measurements showed an error < 1 mm for 75% of the subjects for both the complete and partial humeral models. For the arthritic shoulder joints, the errors on the muscle elongation measurements were <2 mm for 75% of the subjects. Finally, the sensitivity analysis showed that muscle elongations were affected by implant positioning. This study presents an automated method for accurately measuring muscle elongations during preoperative planning of shoulder arthroplasty. The results show that the accuracy in measuring muscle elongations is higher than the accuracy in indicating the muscle attachment points. Hence, muscle elongation measurements are insensitive to the observed errors on the muscle attachment points. Related to this finding, muscle elongations can be accurately measured for both a complete humeral model and a partial humeral model. Because the presented method also showed accurate results for arthritic shoulder joints, it can be used during preoperative shoulder arthroplasty planning, in which typically only the proximal humerus is present in the scan and in which bone arthropathy can be present. As the muscle elongations are sensitive to implant positioning, surgeons can use the muscle elongation measurements to refine their surgical plan.

The influence of reverse arthroplasty humeral component design features on scapular spine strain

Reverse shoulder arthroplasty (RSA) humeral implant parameters have been previously studied with respect to range of motion, deltoid function, and stability. However, limited literature exists on the influence of humeral design features on scapular spine strain. The purpose of this cadaveric biomechanical simulator study was to evaluate the role of humeral component lateralization and neck-shaft angle (NSA) on scapular spine strain. Eight fresh-frozen cadaveric shoulders were tested using an invitro shoulder simulator. A custom-designed modular RSA system was implanted that allowed for the in situ adjustment of humeral lateralization and NSA. Scapular spine strain was measured by strain gauges placed along the acromion and scapular spine in clinically relevant positions representative of the Levy fracture zones. All testing was conducted in both abduction and forward elevation. In Levy zones 2 and 3, increasing humeral lateralization caused significant incremental decreases in scapular spine strain at 0° and 90° abduction (P < .042). Strain decreases as high as 34% were noted with increases in humeral lateralization from -5 to 15 mm (P = .042). Changing NSA had no statistically significant effect on scapular spine strain (P > .14). Some humeral implant design features in RSA have effects on scapular spine strain. Humeral component lateralization had significant effects, whereas adjusting NSA resulted in no substantial differences in scapular spine strain. Understanding humeral component variables is important to allow for design optimization of future RSA implants.

Anatomic versus reverse shoulder arthroplasty: a mid-term follow-up comparison.

Anatomic total shoulder arthroplasty improves pain and function with a reported reoperation rate of approximately 1% per year. With improved glenoid fixation, reverse shoulder arthroplasty implants may outperform anatomic total shoulder arthroplasty. We evaluate the functional outcomes and reoperation rate of anatomic total shoulder arthroplasty versus reverse shoulder arthroplasty at a minimum eight-year follow-up or revision. Between 2005 and 2010, 187 shoulders (137 anatomic total shoulder arthroplasty, 50 reverse shoulder arthroplasty) were retrospectively reviewed at a mean of 8.8 years. The mean age at surgery was 67 years. Females were more commonly treated with reverse shoulder arthroplasty. Both groups had similar body mass index and comorbidities. Outcome measures evaluated included abduction, forward elevation, external rotation, internal rotation, Simple Shoulder Test, Constant score, American Shoulder and Elbow Score, University of California Los Angeles Shoulder score, and Shoulder Pain and Disability Index. At follow-up, anatomic total shoulder arthroplasty demonstrated greater overhead range of motion and external rotation. All patient-reported outcomes remained similar between groups. Reverse shoulder arthroplasty patients were more likely to rate shoulders as much better or better after surgery (90% versus 67%, p = 0.004). Complications were observed in 24% of anatomic total shoulder arthroplasties and 8% of reverse shoulder arthroplasties (p = 0.02). Reoperation was more common in anatomic total shoulder arthroplasties (23% versus 4%, p = 0.003). At mid-to-long-term follow-up, reverse shoulder arthroplasties demonstrated significantly fewer complications and reoperations than anatomic total shoulder arthroplasties. Despite similar patient-reported outcomes, reverse shoulder arthroplasty patients were more likely to be satisfied with their shoulder.

Risk factors for instability after reverse shoulder arthroplasty.

This study aims to identify risk factors related to postoperative instability after reverse shoulder arthroplasty and evaluate the modalities and results of treatments in a large series of patients, with medium to long-term follow-up. Retrospective multicenter series of 1035 consecutive Grammont type reverse shoulder arthroplasties implanted between 1992 and 2010. 19.9% had a reverse shoulder arthroplasty with bony lateralization on the glenoid side. Patients were reviewed and radiographed with minimum five years' follow-up. At a mean follow-up of eight years, the overall rate of postoperative instability was 3.0%. Instability was more frequent in case of reverse shoulder arthroplasty for revision surgery, in younger patients, in case of scapular notching, and tuberosity resorption. Lateralized reverse shoulder arthroplasties were associated with a lower instability rate. A reoperation to restore stability was needed in 70% of cases. The improvement in Constant Score was lower in patients with unstable reverse shoulder arthroplasties when compared to stable reverse shoulder arthroplasties. Younger patients are at higher risk for instability after Grammont type reverse shoulder arthroplasty implantation. Conversely, lateralized reverse shoulder arthroplasties resulted protective. When conservative treatment had failed, shoulder stability can be obtained with reoperation or prosthetic revision (needed in 70% of the cases), but to the price of lower functional results.

Early Debris Formation with a Porous Tantalum Glenoid Component: Radiographic Analysis with 2-Year Minimum Follow-up.

Porous tantalum has been used effectively in hip, knee, and reverse shoulder arthroplasty implants. However, a first-generation porous tantalum glenoid component for use in anatomic shoulder arthroplasty previously demonstrated failure, with failure usually preceded by the appearance of intra-articular metallic debris. After redesign, the component was reintroduced in 2009. The purpose of the current study was to evaluate the radiographic and clinical outcomes of the redesigned glenoid component. Sixty-eight patients undergoing total shoulder arthroplasty received a Trabecular Metal porous tantalum glenoid component (73 components; 5 patients underwent staged bilateral procedures). No polymethylmethacrylate cement was used (off-label usage in the U.S.). A grading system to assess metallic debris formation was developed using radiographs of the previous generation of porous tantalum glenoid components that failed. Radiographs from the current series were independently reviewed by 2 shoulder arthroplasty specialists, and their results were compared. Glenoid components were evaluated for signs of bone ingrowth and metallic debris formation. Sixty-six (90%) of the 73 components were evaluated at a minimum of 2 years of follow-up (mean radiographic follow-up of 50.8 months; range, 24 to 68 months). Of these, 92.4% demonstrated minimal or no glenoid radiolucency. Overall, the prevalence of metallic tantalum debris formation was 44% (29 of 66). Sequential radiograph review demonstrated that the incidence of metallic debris formation increased for each year of follow-up, with radiographs from 2, 3, 4, and ≥5 years of follow-up demonstrating a metallic debris incidence of 23%, 36%, 49%, and 52%, respectively. Additionally, the severity of metallic debris formation increased with follow-up duration. There was no component dissociation or revision due to implant breakage in this series. The porous tantalum glenoid component studied had excellent short-term component fixation. However, the development of metallic debris, increasing in both overall incidence and degree of severity over time, raises concern for potential failure of this glenoid component. Longer follow-up is required. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.