Rotator Cuff Repair and Overlay Augmentation by Direct Interlocking of a Nonwoven Polyethylene Terephthalate Patch Into the Tendon: Evaluation in an Ovine Model.

BACKGROUND: Arthroscopic repair of large rotator cuff tendon tears is associated with high rates of retear. Construct failure often occurs at the suture-tendon interface. Patch augmentation can improve mechanical strength and healing at this interface. PURPOSE: To introduce a novel technique for suture-free attachment of an overlaid patch and evaluate its biomechanical strength and biological performance. STUDY DESIGN: Descriptive and controlled laboratory studies. METHODS: An established ovine model of partial infraspinatus tendon resection and immediate repair was used. After a nonwoven polyethylene terephthalate patch was overlaid to the resected tendon, a barbed microblade was used to draw fibers of the patch directly into the underlying tissue. In vivo histological assessment of healing was performed at 6 and 13 weeks after implantation. Ex vivo models were used to characterize primary repair strength of the suture-free patch fixation to tendon. Additional ex vivo testing assessed the potential of the technique for patch overlay augmentation of suture-based repair. RESULTS: The in vivo study revealed no macroscopic evidence of adverse tissue reactions to the interlocked patch fibers. Histological testing indicated a normal host healing response with minimal fibrosis. Uniform and aligned tissue ingrowth to the core of the patch was observed from both the tendon and the bone interfaces to the patch. There was no evident retraction of the infraspinatus muscle, lengthening of the tendon, or tendon gap formation over 13 weeks. Ex vivo testing revealed that direct patch interlocking yielded tendon purchase equivalent to a Mason-Allen suture (150 ± 58 vs 154 ± 49 N, respectively; P = .25). In an overlay configuration, fiber interlocked patch augmentation increased Mason-Allen suture retention strength by 88% (from 221 ± 43 N to 417 ± 86 N; P < .01) with no detectable difference in repair stiffness. CONCLUSION: Testing in an ovine model of rotator cuff tendon repair suggested that surgical interlocking of a nonwoven medical textile can provide effective biomechanical performance, support functional tissue ingrowth, and help avoid musculotendinous retraction after surgical tendon repair. CLINICAL RELEVANCE: The novel technique may facilitate patch augmentation of rotator cuff repairs.

Prospective multicentre mid-term clinical and radiological outcomes of 159 reverse total shoulder replacements and assessment of the influence of post-operative complications.

Background: The aim of our prospective multicentre study is to evaluate the five-year follow-up outcomes of primary reverse shoulder replacement utilizing two different designs of glenoid baseplates. Methods: There were 159 reverse shoulder replacements (91 cemented and 68 uncemented stems, 67 Trabecular Metal baseplates and 92 Anatomical Shoulder baseplates in 152 patients (99 women) with a mean age of 74.5 (58-90) years. The principal diagnosis was rotator cuff arthropathy in 108 shoulders. Results: Clinical and functional results improved significantly overall; the adjusted Constant Murley score improved from 28.2 ± 13.3 pre-operatively to 75.5 ± 22.8 (p < 0.0001) and the mean Subjective Shoulder Value improved from 27.5 ± 20 to 73.8 ± 21.3 points (p < 0.0001). Radiologically, there was good bony stability in 88% and 86% of cemented and uncemented stems without significant impact on the Constant Murley score and Subjective Shoulder Value at one, two and five years post-surgery. There were no significant clinical differences between Trabecular Metal and Anatomical Shoulder baseplates at five years. There were four cases of intraoperative shaft fractures that were managed with cables. Although the Trabecular Metal baseplates showed better integration radiologically, there was no significant difference in the mean of Constant Murley, Subjective Shoulder Value and the range of motion depending on the grade of inferior scapular notching at one-, two- and five-year intervals. Conclusions: Reverse total shoulder arthroplasty restores the function in shoulder with significant improvements in function and moderate complications with minor differences between both designs of baseplates that were not reflected clinically.

Transplant of Autologous Mesenchymal Stem Cells Halts Fatty Atrophy of Detached Rotator Cuff Muscle After Tendon Repair: Molecular, Microscopic, and Macroscopic Results From an Ovine Model.

BACKGROUND: The injection of mesenchymal stem cells (MSCs) mitigates fat accumulation in released rotator cuff muscle after tendon repair in rodents. PURPOSE: To investigate whether the injection of autologous MSCs halts muscle-to-fat conversion after tendon repair in a large animal model for rotator cuff tendon release via regional effects on extracellular fat tissue and muscle fiber regeneration. STUDY DESIGN: Controlled laboratory study. METHODS: Infraspinatus (ISP) muscles of the right shoulder of Swiss Alpine sheep (n = 14) were released by osteotomy and reattached 16 weeks later without (group T; n = 6) or with (group T-MSC; n = 8) electropulse-assisted injection of 0.9 Mio fluorescently labeled MSCs as microtissues with media in demarcated regions; animals were allowed 6 weeks of recovery. ISP volume and composition were documented with computed tomography and magnetic resonance imaging. Area percentages of muscle fiber types, fat, extracellular ground substance, and fluorescence-positive tissue; mean cross-sectional area (MCSA) of muscle fibers; and expression of myogenic (myogenin), regeneration (tenascin-C), and adipogenic markers (peroxisome proliferator-activated receptor gamma [PPARG2]) were quantified in injected and noninjected regions after recovery. RESULTS: At 16 weeks after tendon release, the ISP volume was reduced and the fat fraction of ISP muscle was increased in group T (137 vs 185 mL; 49% vs 7%) and group T-MSC (130 vs 166 mL; 53% vs 10%). In group T-MSC versus group T, changes during recovery after tendon reattachment were abrogated for fat-free mass (-5% vs -29%, respectively; P = .018) and fat fraction (+1% vs +24%, respectively; P = .009%). The area percentage of fat was lower (9% vs 20%; P = .018) and the percentage of the extracellular ground substance was higher (26% vs 20%; P = .007) in the noninjected ISP region for group T-MSC versus group T, respectively. Regionally, MCS injection increased tenascin-C levels (+59%) and the water fraction, maintaining the reduced PPARG2 levels but not the 29% increased fiber MCSA, with media injection. CONCLUSION: In a sheep model, injection of autologous MSCs in degenerated rotator cuff muscle halted muscle-to-fat conversion during recovery from tendon repair by preserving fat-free mass in association with extracellular reactions and stopping adjuvant-induced muscle fiber hypertrophy. CLINICAL RELEVANCE: A relatively small dose of MSCs is therapeutically effective to halt fatty atrophy in a large animal model.

Indirect markers for length adjustment in distal biceps tendon allograft reconstruction.

Chronic musculotendinous retraction, shortening and fibrosis after distal biceps tendon tears makes a primary reconstruction often difficult or even impossible. Interposition reconstruction with allograft provides a solution, however there is no consensus about appropriate intraoperative graft length adjustment. Therefore, the purpose of this study was to find a practical reference value for distal biceps tendon length adjustment. Three-dimensional surface models of healthy distal biceps tendons were created based on 85 MRI scans. The tendon length was measured from the myotendinous junction to the insertion on the bicipital tuberosity. Inter-epicondylar distance (IED) and radial head diameter (RHD) were measured on antero-posterior radiographs as a surrogate for patient size. Correlations between the tendon length and IED, RHD and patient's height (PH) were calculated. Mean length of the external part of the distal biceps tendon was 69mm (female 64mm, male 71mm). The tendon length in mm was on average 1.1 times of the IED (mm), 3 times of the RHD (mm) and 0.4 times of PH (cm). Herewith, the tendon length could be predicted within a narrow range of +/-1cm in 84% by using IED, 82% by using RHD and 80% by using PH. Intra- and inter-reader reliabililty of IED and RHD was excellent (R2 = 0.938-0.981). The distal biceps tendon length can be best predicted within 1cm with an accuracy of 82-84% using the IED and RHD with an excellent intra- and inter-reader reliability.

Sternoclavicular joint injections and their predictive value for the outcome of surgery.

BACKGROUND: Sternoclavicular joint injections are one of the first-line treatment options for painful non-infectious pathologies of the sternoclavicular joint; however, their long-term effects and predictive value in decision-making for surgery are yet to be defined. METHODS: 27/32 Patients who received in total 36 computed tomography-guided sternoclavicular joint injections in 2012-2017 replied the questionnaire with a mean follow-up of 38 months after the first sternoclavicular joint injection. Of those patients, seven underwent subsequent surgery. We evaluated pain response after sternoclavicular joint injection and American Shoulder and Elbow Surgeons-score at later follow-up. RESULTS: Directly after sternoclavicular joint injection, pain decreased from Visual Analog Scale 5.3 ± 2.4 to 3.8 ± 3 (p = 0.001). In the seven patients who underwent surgery for degenerative changes, definitive outcome correlated with pain relief after the last infiltration (r = 0.86, p = 0.012). Also, the final American Shoulder and Elbow Surgeons-score was lower in patients with multiple injections compared to those who were satisfied after the first injection (p = 0.019). DISCUSSION: Sternoclavicular injections are a useful tool in the context of degenerative sternoclavicular joint disorders as the amount of pain reduction is, in case the short-term effect is not long-lasting, at least a strong indicator for the future success of operative treatment.

Stand-alone coracoclavicular suture repair achieves very good results in unstable distal clavicle fractures at a minimum follow-up of 1 year.

BACKGROUND: The treatment of unstable (Neer type IIB and V) extra-articular distal clavicle fractures remains challenging, especially when encountering a small lateral fragment which does not allow for sufficient screw purchase. It was the purpose of this study to present the clinical and radiologic outcome of a consecutive series of patients treated by a stand-alone coracoclavicular stabilization using a so-called cow-hitch technique with a suture anchor. METHODS: Nineteen patients were treated with a specific surgical technique for distal clavicle fractures (11 left, 8 right) with either rupture or bony avulsion of the coracoclavicular ligaments. Fourteen patients were examined in our outpatient clinic for the purpose of this study after a mean follow-up of 5 years (1-12.2 years). The examination included scoring according to Constant Murley score (CMS), the American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES), the Subjective Shoulder Value (SSV), and follow-up radiographs. Two additional patients were amenable to a telephone interview. RESULTS: All patients reported very good subjective results, with a mean SSV of 92% and a mean ASES score of 96%. The CMS resulted in average absolute values of 92 points. Fractures consolidated in 95% of cases. One patient developed an asymptomatic pseudarthrosis. The coracoclavicular distance was restored from 21 mm preoperatively to 11 mm at the final follow-up and finally showed an average side-to-side difference of +1.8 mm. Sports activities were fully resumed after an average of 4.7 months. CONCLUSION: The coracoclavicular stand-alone cow-hitch suture repair for unstable distal clavicle fractures is a minimally invasive fixation technique without prominent hardware that allows for an anatomic reduction and stable fixation with a low complication and high bony union rate. Both radiographic and clinical long-term results are very satisfactory.

Planning tool for first metatarsal length in hallux valgus surgery.

BACKGROUND: The precise planning of metatarsal (MT) I length in hallux valgus surgery is important. However, currently no tool exists which allows the surgeon to reliably predict this parameter. METHODS: 30 virtual 3-dimensional hallux valgus surgeries were performed on varied deformation models based on cadaveric feet scans. The shortening of the first ray during distal metatarsal I osteotomy for different osteotomy angles were measured. An algebraic 2-dimensional calculation was done and compared to the results obtained from the 3-dimensional models. RESULTS: Inadvertent shortening of the first metatarsal bone can be as much as 8 mm depending on the amount of intermetatarsal angle (IMA) correction and osteotomy angle. Comparison of the 3 dimensional simulations and the 2 dimensional model resulted in a very strong correlation (R > 0.99 p < 0.00001). Based on our findings an anterior pointing osteotomy of approximately 10° is necessary to restore the length in distal metatarsal I hallux valgus surgery. CONCLUSION: A slight misdirection of the osteotomy plane in distal hallux valgus surgery may result in relevant unwanted alterations in first metatarsal bone length and triangulation by eye is insufficient in this complex geometrical situation without appropriate planning. The present study provides surgeons a practical tool to plan and control the change of first metatarsal length during hallux valgus procedure through exact orientation of the osteotomy angle. If no alteration of length is intended, it may be generalized that an anterior direction of the cut relative to the second metatarsal bone will preserve the length of the first metatarsal bone.

Biomechanical and Clinical Evaluation of the Optimal Arm Position After Rotator Cuff Surgery With an Adjustable Abduction Brace.

Abduction braces are used with the intention of relieving tension on the supraspinatus, thereby protecting an operative repair. It is not known, however, whether patients wearing a brace do deposit the weight of the arm on the brace effectively or actively stabilize the arm despite the brace. It is further unknown what position of the arm is most effective to relax the shoulder and is considered most comfortable. Twenty-two patients who had undergone an arthroscopic supraspinatus repair were postoperatively fitted with a standard abduction brace equipped with a torque sensor to measure the weight of the arm on the brace on the first and second postoperative days. The most comfortable arm position, tear size, and degenerative muscular changes on magnetic resonance imaging were assessed. Most patients (15 vs 5) preferred a low angle of abduction with the brace in the scapular rather than the true frontal plane irrespective of tear location or size. While loads applied to the brace were slightly higher at high abduction angles (70° and 90°) under regional anesthesia (day 1), they were significantly higher at low abduction angles (30° and 50°) with the arm fully awake (day 2). The most comfortable brace position-which is at low angles of abduction (30° to 50°) in the scapular plane-is associated with the highest load transfer to the brace in the unanesthetized arm. The authors therefore conclude that if an abduction brace is used, it should be fitted in the scapular plane with an abduction angle between 30° and 50°. [Orthopedics. 2021;44(1):e1-e6.].

Systematic Biomechanical Analysis of Prerequisites for Reliable Intraoperative Bonding of Polymethylmethacrylate Bone Cement in Preexisting Cement in Revision Arthroplasty.

Removal of a stable cement mantle may be invasive and time consuming and may result in unnecessary damage to bone and surrounding soft tissue. The goal of this study was to investigate the feasibility of the use of polymethylmethacrylate cement on preexisting cement as well as to explore the prerequisites for practical clinical use under standardized laboratory conditions. The strength of the cement-cement interface was evaluated with a 4-point bending to failure test, according to International Organization for Standardization 5833, as well as standardized shear strength, according to American Society for Testing and Materials D732. Various intraoperative cleaning agents were tested to remove simulated contamination with bone marrow. Contamination of the cement-cement interface with bone marrow decreases bending strength, modulus, and shear strength. Removal of the bone marrow with a degreasing agent significantly increases bending strength as well as bending modulus and can increase shear strength up to 9% compared with use of a nondegreasing agent. The cement-cement interface may reach up to 85% of bending strength, 92% of bending modulus, and comparable shear strength compared with a uniform cement block. Meticulous removal of fatty contaminant is important. Use of a degreasing agent further increases the stability of the cement-cement interface. With these precautions, it is safe to assume that the combined molecular and mechanical interlock is sufficient for most clinical applications and will not represent the weakest link in prosthetic revision. [Orthopedics. 2021;44(1):e55-e60.].

Bankart Repair Versus Latarjet Procedure for Recurrent Anterior Shoulder Instability: A Systematic Review and Meta-analysis of 3275 Shoulders.

BACKGROUND: Little consensus is available regarding the standard treatment for recurrent anterior instability of the shoulder. Typically, treatment selection has been based on training and tradition rather than the available evidence. PURPOSE: This study aimed to compare the clinical outcomes between arthroscopic Bankart procedure and the Latarjet procedure in the treatment of recurrent anterior shoulder instability with emphasis on follow-up time. STUDY DESIGN: Systematic review and meta-analysis. METHODS: We searched PubMed, Cochrane Central Register of Controlled Trials, Scopus, Ovid, and Web of Science up to January 2018 and included studies that compared arthroscopic Bankart versus Latarjet for treatment of anterior shoulder instability. Continuous data, such as operative time and patient-reported outcomes, were pooled as mean differences (MDs), whereas dichotomous data, such as recurrence, revision, redislocation, arthropathy, infection, and hematoma, were pooled as risk ratios (RRs), with 95% CIs. RESULTS: Pooling data from 7 cohort studies (3275 patients) showed that arthroscopic Bankart was associated with a higher risk of redislocation (RR, 2.74; 95% CI, 1.48-5.06; P = .03), a higher risk of recurrence (RR, 2.87; 95% CI, 1.91-4.30; P < .0001), and a lower risk of infection (RR, 0.16; 95% CI, 0.06-0.43; P = .0002) compared with Latarjet, while the effect size did not favor arthroscopic Bankart or Latarjet in terms of Rowe score (MD, 0.22; 95% CI, -5.64 to 6.08; P = .94), revision (RR, 0.34; 95% CI, 0.08-1.39; P = .13), and hematoma (RR, 0.20; 95% CI, 0.03-1.19; P = .07). The effect estimate showed a pronounced advantage for Latarjet from 6 to 10 years postoperatively in terms of recurrence and redislocation (RR, 3.00; 95% CI, 1.98-4.56 and RR, 2.85; 95% CI, 1.51-5.38, respectively). CONCLUSION: Our results showed that Latarjet had less risk of recurrence and redislocation with longer follow-up time. Both procedures were comparable in terms of Rowe score, the need for revision, and postoperative hematoma formation, whereas Bankart repair was associated with a lower risk of infection.

Os Acromiale in Reverse Total Shoulder Arthroplasty: A Cohort Study.

BACKGROUND: Increased passive deltoid tension after reverse total shoulder arthroplasty (RTSA) potentially leads to displacement or tilting of a preexisting os acromiale. PURPOSE: To analyze patients with an os acromiale who underwent RTSA and compare their outcomes and complications with a matched control group without an os acromiale. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: In this study, 45 shoulders in 42 patients with an os acromiale (cases) were matched to 133 patients without os acromiale (controls) who underwent RTSA between 2005 and 2016. The mean follow-up was 52 ± 32 months. Matching criteria included sex, type of surgery, duration of follow-up, and age. The Constant score (CS), Subjective Shoulder Value (SSV), and radiological outcomes were assessed postoperatively at 1-year, 2-year, and final follow-up visits. RESULTS: The mean CS, SSV, and range of motion improved from preoperative levels to the final follow-up in both groups (P < .01). Patients with an os acromiale had a relative CS of 70 ± 23 versus 76 ± 21 points (P = .15) and an SSV of 70 ± 30 versus 73 ± 24 (P = .52) compared with controls at the final follow-up visit. Patients with an os acromiale had significantly decreased active flexion of 104° ± 33° versus 114° ± 33° (P = .03) at 1 year and active abduction of 103° ± 37° versus 121° ± 38° at 2 years postoperatively (P = .02). A postoperatively painful os acromiale was found in 12 cases (27%) and spontaneously resolved in 8 cases after a mean of 33 months (range, 12-47 months; P = .04). CONCLUSION: RTSA reliably restores patient satisfaction despite the presence of an os acromiale, with a slightly impaired range of motion. Postoperative local tenderness at the os acromiale can be expected in 1 out of 4 patients, but this resolves spontaneously over time in the majority of patients.

Suprascapular nerve decompression in addition to rotator cuff repair: a prospective, randomized observational trial.

BACKGROUND: Tear and retraction of the supraspinatus (SS) and infraspinatus (IS) musculotendinous units and/or their repair may be associated with traction damage to the suprascapular nerve, potentially responsible for pain or weakness of the rotator cuff (RC). Arthroscopic release of the transverse scapular ligament at the suprascapular notch has been advocated to prevent or treat suprascapular nerve impairment associated with RC retraction and/or repair. The effect of this procedure on preoperative normal nerve function is, however, not well studied.We hypothesize that (1) decompression of the suprascapular nerve without preoperative pathologic neurophysiological findings will not improve clinical or imaging outcome and (2) suprascapular decompression will not measurably change suprascapular nerve function. METHODS: Nineteen consecutive patients with a magnetic resonance arthrography documented RC tear involving SS and IS but normal preoperative electromyography (EMG)/nerve conduction studies of the SS and IS were enrolled in a prospective, controlled trial involving RC repair with or without suprascapular nerve decompression at the suprascapular notch. Nine patients were randomized to undergo, and 10 not to undergo, a decompression of the suprascapular nerve. Patients were assessed clinically (Constant score, mobility, pain, strength, subjective shoulder value), with magnetic resonance imaging and neurophysiology preoperatively and at 3- and 12-month follow-up. RESULTS: There was no clinically relevant difference between the release and the non-release group in any clinical parameter at any time point. At magnetic resonance imaging, there was a slightly greater increase of fatty infiltration of the IS in the release group without any other differences between the 2 groups. Electromyographically, there were no pathologic findings in the non-release group at any time point. Conversely, 3 of the 9 patients of the release group showed pathologic EMG findings at 3 months, of whom 2 had recovered fully and 1 only partially at 12 months. CONCLUSION: In the presence of normal EMG findings, suprascapular nerve release added to arthroscopic RC repair is not associated with any clinical benefit, but with electromyographically documented, postoperative impairment of nerve function in 1 of 3 cases. Suprascapular nerve release does not therefore seem to be justified as an adjunct to RC repair if preoperative EMG findings document normal suprascapular nerve function. Based on these findings, the ongoing prospective randomized trial was terminated.

Radiographic performance depends on the radial glenohumeral mismatch in total shoulder arthroplasty.

BACKGROUND: Optimal radii of curvature of the articulating surfaces of the prosthetic components are factors associated with the longevity of cemented glenoid components in anatomical total shoulder arthroplasty. It was the purpose of this study, to evaluate the radiographic and clinical performance of an anatomical glenoid component of a total shoulder arthroplasty (TSA) with respect to radial mismatch of the glenoid and humeral component. METHODS: In a retrospective study 75 TSA were analyzed for their clinical and radiographic performance with computed tomography by independent examiners using an established methodology. The study group was divided in two groups, one with mismatch < 4.5 mm (n:52) the others with mismatch ≥4.5 mm (n:23) and analyzed for confounding variables as indication, primary or revision surgery, age, gender, glenoid morphology and implant characteristics. RESULTS: The mean glenohumeral radial mismatch was 3.4 mm (range 0.5-6.9). At median follow-up of 41 months (range 19-113) radiographic loosening (defined as modified Molé scores ≥6) was present in 7 cases (9.3%). Lucencies around the glenoid pegs (defined as modified Molé score ≥ 1) were present in 34 cases (45%). Radiolucencies were significantly associated with a radial mismatch < 4.5 mm (p = 0.000). The pre- to postoperative improvements in Subjective Shoulder Value and absolute Constant Score were significantly better in the group with a mismatch ≥4.5 mm (p = 0.018, p = 0.014). CONCLUSION: A lower conformity of the radii of humerus and glenoid seems to improve the loosening performance in TSA. Perhaps cut-off values regarding the recommended mismatch need to be revalued in the future.

Little benefit of surgical anchor and suture removal and of antibiotic therapy beyond 6 weeks in infected rotator cuff repair.

BACKGROUND: The purpose of this study was to investigate the benefit of surgical anchor and/or suture removal and prolonged antibiotic therapy in acute and chronic infections of rotator cuff repair (RCIs). METHODS: A single-center cohort and case-control study (Cox regression) was performed. Outcome variables were remission of infection and postinfection reoperations due to failed tendon healing for mechanical causes. All analyses were performed with an emphasis on anchor and suture retention or removal. RESULTS: We identified 54 primary RCIs (44 men; median age 54 years) that were surgically revised (10 by open débridement and 44 by arthroscopy). Twenty-eight (52%) were not intact on revision surgery (débridement) - 10 were partially and 18 totally re-ruptured. The median number of surgical revisions was 1 (range, 1-3), and the median duration of postsurgical antibiotic therapy was 75 days. After a minimal follow-up of 2 years, 8 infections (8/54, 15%) recurred. Twenty patients needed a revision surgery; in all of those 20 patients, intraoperative samples were negative for infection. By multivariate analysis, anchor removal at the first revision influenced neither remission (hazard ratio [HR] 0.9, 95% confidence interval [CI] 0.4-2.0) nor the need for later revision surgery due to mechanical sequelae (HR 0.6, 95% CI 0.1-1.4). The corresponding HRs for suture removal were 0.9 (95% CI 0.4-1.7) and 0.4 (95% CI 0.1-1.2). Likewise, the numbers of revision surgery (HR 0.5, 95% CI 0.2-1.3) and antibiotics beyond 6 weeks failed to influence remission (HR 1.1, 95% CI 0.4-3.1). CONCLUSIONS: In our RCI cohort, the removal of anchors or sutures, repeated revision surgery, or an antibiotic therapy beyond 6 weeks failed to improve remission or to reduce sequelae.

Acromial Fractures Following Reverse Total Shoulder Arthroplasty: A Cohort Controlled Analysis.

Fractures of the acromion can develop after reverse total shoulder arthroplasty (RTSA). This study sought to identify risk factors for acromial fractures in patients with RTSA. A total of 1146 RTSAs were performed at the authors' institution between 1999 and 2016. In 21 patients (1.8%), the authors identified an acromial fracture during the postoperative course. These patients were compared with a matched cohort of 84 patients who had not developed an acromial fracture postoperatively. As an indicator of changes in pre- to postoperative deltoid loading, the authors created an angle called the "delta angle." There was an elevated risk for acromial fractures with lower lateralization of the humerus from pre- to postoperatively (4.1±7.1 mm vs 8.4±6.1 mm; P=.006), lower preoperative anteroposterior acromial slope (117.3°±11.2° vs 121.7°±17.0°; P=.044), and higher glenoid inclination (beta angle, 72.0°±5.5° vs 76.5°±6.8°; P=.005). Pre- to postoperative changes in the beta angle (9.2°±8.0° vs 4.4°±9.4°; P=.022) and the delta angle (29.4°±8.1° vs 19.5°±9.7°; P<.001) were larger in the fracture group. In addition, diagnosed and treated osteoporosis appeared to be a risk factor for acromial fractures (33% vs 13%; P=.047). The delta angle after RTSA seems to correlate with the risk of developing an acromial fracture. Patients with a high glenoid inclination and/or osteoporosis should be informed that they are at risk. Further, surgeons should be aware that lower distalization together with greater medialization of the center of rotation was associated with more acromial fractures in this study. [Orthopedics. 2020; 43(1):15-22.].

Angle of approach to the superior rotator cuff of arthroscopic instruments depends on the acromial morphology: an experimental study in 3D printed human shoulders.

BACKGROUND: Portal placement is a key factor for the success of arthroscopic procedures, particularly in rotator cuff repair. We hypothesize that the acromial anatomy may strongly determine the position of the shoulder bony landmarks and limit the surgeon's freedom to position the arthroscopic approaches in direction towards the acromion. The purpose of this study was to analyze the relation between different acromial shapes and the freedom of movement of arthroscopic instruments relative to the rotator cuff from standardized arthroscopic portals in a laboratory study on 3D shoulder models. METHODS: 3D models of shoulders with a broad range of different acromial shapes were printed using CT and MRI scans. Angles from the portals to defined points on the rotator cuff and the supraglenoid tubercle were measured. In conventional radiographs, the critical shoulder angle, the scapular body acromial angle, and the glenoid acromial angle were measured and compared with the measured angles to the rotator cuff. RESULTS: There was a large variation of angles of approach of instruments to the rotator cuff between the seven shoulders for each portal. From the joint line portal and the posterior edge portal, the biggest angles were measured to the posterior cuff. From the intermediate portal, the angles were largest to the intermediate rotator cuff and from the anterior portals to the anterior cuff. To the supraglenoid tubercle, best access was from anterior. For all portals, there was a big correlation between the glenoid acromial angle and the scapular body acromial angle with the angles of approach to the tendon and especially to the supraglenoid tubercle. CONCLUSION: The access to the rotator cuff from almost every portal is influenced by the acromial shape. As hypothesized, a small (small GAA) and flat (big SBAA) acromion provide an easier approach to the rotator cuff from almost every portal. Therefore, it may severely influence the instruments maneuverability.

Changes of Supraspinatus Muscle Volume and Fat Fraction After Successful or Failed Arthroscopic Rotator Cuff Repair.

BACKGROUND: Muscle atrophy and fatty infiltration are limiting factors for successful rotator cuff (RC) repair. Quantitative data regarding these hallmarks of degenerative muscle changes after RC repair in humans are scarce. By utilizing a new application of the 6-point Dixon magnetic resonance imaging technology, 3-dimensional volume and fat fraction analysis of the whole RC muscle have become possible. PURPOSE: Quantitative analysis of atrophy and fatty infiltration of the supraspinatus muscle after healed and failed RC tendon-to-bone repair. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Muscle volume and fat fraction were measured preoperatively and at 3 and 12 months postoperatively in 19 failed and 21 healed arthroscopic supraspinatus tendon repairs, with full muscle volume segmentation and magnetic resonance Dixon sequences. RESULTS: In both groups, the muscle volume initially decreased 3 months after RC repair by -3% in intact (P = .140) and -10% in failed repair (P = .004) but recovered between 3 and 12 months to 103% (P = .274) in intact and 92% (P = .040) in failed repairs when compared with the preoperative volume (difference of change between groups, preoperative to 12 month: P = .013). The supraspinatus muscle's fat fraction did not significantly change after successful repair (6.5% preoperative, 6.6% after 3 months, and 6.7% after 12 months; all nonsignificant). There was, however, a significant increase from 7.8% to 10.8% at 3 months (P = .014) and 11.4% at 12 months (P = .020) after failed repair (difference between groups at 3- and 12-month follow-up: P = .018 and P = .001, respectively). CONCLUSION: After successful arthroscopic repair, RC tendon tear-induced fatty infiltration can be almost stopped, and muscle atrophy can even be slightly reversed. In case of a failed repair, however, these changes are further pronounced during the first 3 postoperative months but seem to stabilize thereafter.

Posterior Acromial Morphology Is Significantly Associated with Posterior Shoulder Instability.

BACKGROUND: The purpose of this paper was to determine whether acromial morphology influences anteroposterior shoulder stability. We hypothesized that a more horizontal and higher position of the acromion in the sagittal plane would be associated with posterior instability. METHODS: In this retrospective study, patients with unidirectional posterior instability were age and sex-matched to a cohort of patients with unidirectional anterior instability. Both cohorts were compared with a control group of patients with no instability and no degenerative glenohumeral (rotator cuff and/or joint surface) or acromial changes. Measurements on radiographs included posterior acromial tilt, anterior and posterior acromial coverage (AAC and PAC), posterior acromial height (PAH), and the critical shoulder angle (CSA). RESULTS: The number of patients enrolled in each instability group was 41, based on a priori power analysis. The control group consisted of 53 shoulders. Of the measured anatomic factors, PAH showed the most significant association with posterior instability (odds ratio [OR] = 1.8; p < 0.001) in the logistic regression model. PAH was significantly greater in the posterior instability group compared with the anterior instability group (30.9 versus 19.5 mm; p < 0.001). With a cutoff value of PAH of 23 mm, the OR for posterior instability was 39. Shoulders with posterior instability were also significantly different from normal shoulders with regard to PAH (p < 0.001), AAC (p < 0.001), and PAC (p < 0.001) whereas, in the shoulders with anterior instability, all of these values except the AAC (p = 0.011) did not differ from those of normal shoulders. CONCLUSIONS: Specific acromial morphology is significantly associated with the direction of glenohumeral instability. In shoulders with posterior instability, the acromion is situated higher and is oriented more horizontally in the sagittal plane than in normal shoulders and those with anterior instability; this acromial position may provide less osseous restraint against posterior humeral head translation. A steep "Swiss chalet roof-type" acromion virtually excluded recurrent posterior instability in an albeit relatively small cohort of patients. Additional investigation is needed to determine the relevance of these findings for future treatment. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Early Recognition of a Transient Ischemic Attack Utilizing Cerebral Oxygenation Monitoring During Shoulder Surgery in the Beach Chair Position: A Case Report.

Shoulder surgery in the beach chair position is routinely performed, and central neurological events are rare but potentially devastating. We present a patient with transient neurological deficits after a sudden blood pressure drop with a simultaneous decrease of regional cerebral saturation values registered by cerebral oximetry. We reviewed published cases and proposed possible strategies to prevent the occurrence of similar complications in this context.

Mechanisms of Suture Integration in Living Tissue: Biomechanical and Histological In Vivo Analysis in Sheep.

The potential of nonabsorbable suture material to augment tissue strength in the long-term is by far not exploited by most of the currently used sutures. The authors hypothesized that different sutures yield specific histological tissue reactions associated with specific mechanical shear resistance of the suture against the tissue. Four different suture types (Orthocord, Ethibond, FiberTape, and FiberWire) were implanted in 36 sheep shoulders (supraspinatus/greater tuberosity). One thread at each time point (6, 16, and 22 weeks) was used for histology, and 11 threads at each time point (0, 6, 16, and 22 weeks) were used for biomechanical longitudinal pullout testing. Histology included tissue maturity, activity of tissue reaction, and invasion of cells and tissue into the suture material. Fiber-Tape had the highest mean pullout strength at 6, 16, and 22 weeks of 4.4 N/cm (SD, 2.1 N/cm), 10.1 N/cm (SD, 5.1 N/cm), and 12.8 N/cm (SD, 6.0 N/cm), respectively. However, general pullout strength at 22 weeks was surprisingly low, particularly for Ethibond, Orthocord and FiberWire. The overall maturity of the surrounding tissue correlated (r=0.84, P=.001) with mechanical performance. Interestingly, in all 4 suture types, an intimate in- and on-growth of fibrous tissue to the filaments and into the space between suture fibers could be shown. However, for Ethibond, Orthocord, and FiberWire, the authors found an unexpected circumferential space around the sutures, often forming an inner and outer capsule, separating the sutures from the surrounding tissue with a shifting layer. [Orthopedics. 2019; 42(3):168-175.].