Factors Influencing Acromial and Scapular Spine Strain after Reverse Total Shoulder Arthroplasty: A Systematic Review of Biomechanical Studies

Background: Acromial and scapular spine fractures after reverse total shoulder arthroplasty (RTSA) can be devastating complications leading to substantial functional impairments. The purpose of this study was to review factors associated with increased acromial and scapular spine strain after RTSA from a biomechanical standpoint. Methods: A systematic review of the literature was conducted based on PRISMA guidelines. PubMed, Embase, OVID Medline, and CENTRAL databases were searched and strict inclusion and exclusion criteria were applied. Each article was assessed using the modified Downs and Black checklist to appraise the quality of included studies. Study selection, extraction of data, and assessment of methodological quality were carried out independently by two of the authors. Only biomechanical studies were considered. Results: Six biomechanical studies evaluated factors associated with increased acromial and scapular spine strain and stress. Significant increases in acromial and scapular spine strain were found with increasing lateralization of the glenosphere in four of the included studies. In two studies, glenosphere inferiorization consistently reduced acromial strain. The results concerning humeral lateralization were variable between four studies. Humeral component neck-shaft angle had no significant effect on acromial strain as analysed in one study. One study showed that scapular spine strain was significantly increased with a more posteriorly oriented acromion (55° vs. 43°; p < 0.001). Another study showed that the transection of the coracoacromial ligament increased scapular spine strain in all abduction angles (p < 0.05). Conclusions: Glenoid lateralization was consistently associated with increased acromial and scapular spine strain, whereas inferiorization of the glenosphere reduced strain in the biomechanical studies analysed in this systematic review. Humeral-sided lateralization may increase or decrease acromial or scapular spine strain. Independent of different design parameters, the transection of the coracoacromial ligament resulted in significantly increased strains and scapular spine strains were also increased when the acromion was more posteriorly oriented. The results found in this systematic review of biomechanical in-silico and in-vitro studies may help in the surgical planning of RTSA to mitigate complications associated with acromion and scapular spine fracture.

Rotator cuff irreparability or failure of repair (re-tear): technical note on middle trapezius tendon transfer for reproduction of supraspinatus function

Purpose Based on its close anatomic features and nearly-collinear force vector to those of supraspinatus muscle, the current article describes a technique of middle trapezius tendon transfer for reproduction of supraspinatus function in the context of rotator cuff irreparability/re-tear management. Methods While seating the patient in beach-chair position, arthroscopic gleno-humeral examination and sub-acromial decompression are initially performed. Hamstring tendons are harvested and fashioned as flattened quadruple sheet. Through McKenzie approach, infraspinatus and subscapularis tendons are repaired. Then, medial half of middle trapezius insertion tendon is harvested from most medial 5-6 cm of the scapular spine. Through McKenzie approach, hamstring sheet is retrieved via a sub-trapezius/sub-acromial corridor from the scapular wound. Hamstring sheet is re-attached to cuff footprint by double row/suture bridge repair configuration. While retracting the scapula and placing gleno-humeral joint in 45O-abduction/45O-external rotation, hamstring sheet is re-attached to released middle trapezius tendon by non-absorbable sutures. Finally, tendon reconstruct is dynamically-tested in different positions of range of motion. Results Transfer of medial portion of middle trapezius insertion tendon (lengthened by interposition hamstring tendon sheet) to cuff footprint was technically feasible. Dynamic testing showed smooth sub-acromial gliding motion of the tendon reconstruct. Conclusion For reproduction of supraspinatus function, hamstring tendon augmented-middle trapezius tendon transfer to cuff footprint heralds a number of technical and biomechanical advantages; thus offering a potential effective modality of cuff irreparability/re-tear management in relatively young patients of high functional demands. However, current description should be investigated in further biomechanical and clinical studies to validate its long-term outcomes.

Reverse Shoulder Arthroplasty, Deltopectoral Approach vs. Anterosuperior Approach: An Overview of the Literature

Reverse shoulder arthroplasty (RSA) has become an optimal treatment for numerous orthopedic entities, such as rotator cuff tear arthropathies, pseudoparalysis, fracture sequelae, acute fractures, failed arthroplasties, osteoarthritis, and rheumatoid arthritis, and is linked with relief of topical pain and regaining of functionality. Presently, RSA has been conducted through anterosuperior (AS) or deltopectoral (DP) approach. The aim of the study was to discuss both approaches and to examine broadly their features to render a comparison in terms of clinical effectiveness. An electronic search in PubMed, EMBASE, and Google Scholar databases was performed, using combinations of the following keywords: RSA, DP approach, AS approach, notching, and cuff tear arthropathy. A total of 61 studies were found, and 16 relevant articles were eventually included. Currently published literature has not shown significant diversities in the clinical course due to approach preference; risk of instability seems to be greater in DP approach, while regarding scapular notching and fracture rates the findings were conflicted. In addition, the AS approach has been associated with decreased risk of acromial and scapular spine fractures. In conclusion, both surgical approaches have shown similar clinical outcomes and effectiveness concerning pain and restoring range of motion (ROM) in rotator cuff tear arthropathies. In the future, further investigations based on large-scale well-designed studies are required to address clinical gaps allowing in-depth comparison of both approaches.

Relationship Between Rotator Cuff Tears and Scapular Morphology

Background The purpose of this study was to identify differences in the morphology of the scapula according to the presence or absence of a rotator cuff tear (RCT). Methods One hundred and three shoulders with and 87 shoulders without RCTs were included in this study. The critical shoulder angle (CSA) and lateral acromion angle in the frontal view and the acromial coverage angle (ACA) and coracoid and scapular spine angle (CSSA) in the lateral view were evaluated using three-dimensional computed tomography. The glenoid anterior tilt, anterior acromial projection angle (AAPA), coracoid process angle, scapular spine angle (SSA) and inferior angle angle (IAA) with respect to the scapular plane were measured in the lateral view. The morphological parameters of the scapula associated with RCT were statistically analysed using a multivariate logistic regression analysis. Results In univariate logistic regression analysis, CSA, ACA, CSSA, AAPA, SSA and IAA were significantly different between shoulders with and without RCTs. In multivariate logistic regression analysis, CSA and IAA were greater in shoulders with RCT and were significantly associated with this condition. Conclusion To the best of our knowledge, this is the first study to focus on the relationship between RCT and the scapular body. RCT cases were characterised by a greater curvature of the scapular body in addition to CSA.

Treatment strategies for scapular spine fractures: a scoping review

Fractures of the scapular spine are relatively rare and can occur without (1) or with (2) association to a reverse shoulder arthroplasty (RSA). To date there are only limited data on the topic. The aim of this scoping review was to identify all available literature and report current treatment concepts. A scoping review was conducted by searching PubMed for relevant studies between 2000 and October 2020. All studies were included which gave detailed descriptions of the treatment strategy. A total of 21 studies with 81 patients were included for the analysis. The mean age over all patients was 62 years (range: 24 to 89 years) and 77% of the patients were female. In 19.8% of cases, the fracture occurred after a traumatic fall from standing height. Eighty-six per cent of the patients had an RSA-associated scapular spine fracture (2). These patients were older compared to group (1) (47 ± 19.6 vs. 76 ± 5.6 years, p = 0.0001) and the majority were female (85%). The majority from group (1) underwent operative treatment with plate fixation. Most patients regained full function and range of motion. RSA-associated fractures (2) were mainly treated non-operatively, with moderate clinical outcome. A high rate of nonunions was reported. Scapular spine fractures without RSA are mainly treated operatively with good clinical results. In association with RSA, scapular spine fractures are mainly treated non-operatively and lead to inferior clinical and radiological results. This scenario seems to be problematic and further research is required to sharpen treatment concepts in this group. Cite this article: EFORT Open Rev 2021;6:788-796. DOI: 10.1302/2058-5241.6.200153

Scapular spine base fracture with long outside-in superior or posterior screws with reverse shoulder arthroplasty

Background: The purpose of the present study was to determine how long superior screws alone or in combination with posterior placement of metaglene screws protruding and penetrating into the scapular spine in reverse total shoulder arthroplasty affect the strength of the scapular spine in a fresh cadaveric scapular model.Methods: Seven fresh cadaver scapulas were allocated to the control group (short posterior and superior screws) and seven scapulas to the study group (spine base fixation with a 4-inch-long superior screw, three with both long superior and long posterior screws).Results: The failure load was lower in the spine fixation group (long screw [869 N] vs. short screw [1,123 N]); however, this difference did not reach statistical significance (p>0.05). All outside-in long superior or superior plus posterior screws failed due to scapular spine base fracture; failures in the short screw group were due to acromion fracture. An additional posterior outside-in screw failed to significantly decrease the failure load of the acromion spine.Conclusions: The present study highlights the significance of preventing a cortical breach or an outside-in configuration when a superior or posterior screw is inserted into the scapular spine base.

Surgical Treatment of Concomitant Scapular Spine Pseudoarthrosis and Rotator Cuff Impingement: A Case Report

Background: Nonunion and pseudoarthrosis formation following scapular spine fracture is a rare condition and is limited only to case reports. Some authors reported its association with rotator cuff impingement. Standard treatment is not defined well as the condition is rare. Case Report: Our patient was a 61-year-old man with painful nonunion in addition to cuff impingement. Surgical treatment by open reduction, internal fixation with reconstruction plate and tension band wiring, along with bone grafting led to fracture union, as well as complete resolution of the rotator cuff tendinopathy. Conclusion: Surgical fixation seems to be the best choice in treating scapular spine pseudoarthrosis. The first attempt should be the best, so we took an aggressive approach by the use of plating, tension band wiring, and bone grafting altogether.

Double plating is associated with higher fixation strength than single plating in osteoporotic fractures of the scapular spine: a biomechanical study

Introduction The number of atraumatic stress fractures of the scapular spine associated with reverse shoulder arthroplasty is increasing. At present, there is no consensus regarding the optimal treatment strategy. Due to the already weakened bone, fractures of the scapular spine require a high fixation stability. Higher fixation strength may be achieved by double plating. The aim of this study was to evaluate the biomechanical principles of double plating in comparison to single plating for scapular spine fractures. Methods In this study, eight pairs (n = 16) of human shoulders were randomised pairwise into two groups. After an osteotomy at the level of the spinoglenoid notch, one side of each pair received fracture fixation with a single 3.5 LCP (Locking Compression Plate) plate. The contralateral scapular spine was fixed with a 3.5 LCP and an additional 2.7 LCP plate in 90–90 configuration. The biomechanical test protocol consisted of 700 cycles of dynamic loading and a load-to-failure test with a servohydraulic testing machine. Failure was defined as macroscopic catastrophic failure (screw cut-out, plate breakage). The focus was set on the results of specimens with osteoporotic bone quality. Results In specimens with an osteoporotic bone mineral density (BMD; n = 12), the mean failure load was significantly higher for the double plate group compared to single plating (471 N vs. 328 N; p = 0.029). Analysis of all specimens (n = 16) including four specimens without osteoporotic BMD revealed no significant differences regarding stiffness and failure load (p > 0.05). Conclusion Double plating may provide higher fixation strength in osteoporotic bone in comparison to a single plate alone. This finding is of particular relevance for fixation of scapular spine fractures following reverse shoulder arthroplasty. Level of evidence Controlled laboratory study.