A predictive model for the critical shoulder angle based on a three-dimensional analysis of scapular angular and linear morphometrics.

BACKGROUND: The purpose of this study was to define the features of scapular morphology that are associated with changes in the critical shoulder angle (CSA) by developing the best predictive model for the CSA based on multiple potential explanatory variables, using a completely 3D assessment. METHODS: 3D meshes were created from CT DICOMs using InVesalius (Vers 3.1.1, RTI [Renato Archer Information Technology Centre], Brazil) and Meshmixer (3.4.35, Autodesk Inc., San Rafael, CA). The analysis included 17 potential angular, weighted linear and area measurements. The correlation of the explanatory variables with the CSA was investigated with the Pearson's correlation coefficient. Using multivariable linear regression, the approach for predictive model-building was leave-one-out cross-validation and best subset selection. RESULTS: Fifty-three meshes were analysed. Glenoid inclination (GI) and coronal plane angulation of the acromion (CPAA) [Pearson's r: 0.535; -0.502] correlated best with CSA. The best model (adjusted R-squared value 0.67) for CSA prediction contained 10 explanatory variables including glenoid, scapular spine and acromial factors. CPAA and GI were the most important based on their distribution, estimate of coefficients and loss in predictive power if removed. CONCLUSIONS: The relationship between scapular morphology and CSA is more complex than the concept of it being dictated solely by GI and acromial horizontal offset and includes glenoid, scapular spine and acromial factors of which CPAA and GI are most important. A further investigation in a closely defined cohort with rotator cuff tears is required before drawing any clinical conclusions about the role of surgical modification of scapular morphology. LEVEL OF EVIDENCE: Level 4 retrospective observational cohort study with no comparison group.

High Critical Shoulder Angle Values Are Associated With Full-Thickness Posterosuperior Cuff Tears and Low Values With Primary Glenohumeral Osteoarthritis.

PURPOSE: To compare critical shoulder angle (CSA) measurements using high-quality radiographs in the following groups: Group 1: symptomatic atraumatic full-thickness rotator cuff (RC) tears; Group 2: symptomatic primary glenohumeral osteoarthritis (GHOA); and Group 3: no RC tear or primary GHOA being treated for glenohumeral instability or symptomatic labral pathology (control group). METHODS: A prospective observational case control study with 10 shoulders in each group was performed GHOA and full-thickness RC tears were diagnosed by radiographs and magnetic resonance imaging (MRI). For these three groups, the exclusion criteria were the following: Group 1) partial thickness RC tears, traumatic RC tears, isolated subscapularis tears, and advanced cuff tear arthropathy with erosion of the superior glenoid; Group 2) secondary causes of glenohumeral arthritis; coexistent full-thickness RC tear; and Group 3) glenoid bone lesions that may affect the CSA measurement. Only shoulders with adequate radiographic quality (Suter-Henninger type A and C) were eligible. A one-way ANOVA, followed by Tukey multiple pairwise-comparisons test, was performed to compare the groups. Interobserver and intraobserver reliability was assessed using Intraclass Correlation Coefficients (ICC). RESULTS: Mean CSA values were 37.4° ± 4.7 (RC tear group), 28.9° ± 2.4 (GHOA group), and 32.8° ± 1.1 (control group). The CSA of the RC group was higher than the control group (P = .006) and the GHOA group (P = .000). The CSA of the GHOA group was lower than the control group (P = .027). Intraobserver and interobserver reliabilities for the CSA measurement were excellent (Observer 1 [ICC]: .986 [95% CI .970-.993]; Observer 2 [ICC]: .976[95% CI .951-.989]; and Observer 1v2: 0.968[95% CI .933-.985]). CONCLUSIONS: There is a difference in the CSA between patients with symptomatic atraumatic full-thickness RC tears (4.6° higher than the control group), symptomatic GHOA (3.8° lower than the control group), and glenohumeral instability or labral pathology with no RC tear or GHOA. LEVEL OF EVIDENCE: Level 2, prospective observational case control diagnostic study.

A prospective observational case control study investigating the coronal plane scapular morphological differences in full-thickness posterosuperior cuff tears and primary glenohumeral osteoarthritis.

INTRODUCTION: The critical shoulder angle (CSA) is a surrogate marker of the coronal plane morphology of the scapula. CSA differences between scapulae could be due to differences in glenoid inclination (GI) or the location of the most lateral part of the acromion relative to the inferior glenoid, or both. An understanding of the hierarchy of the scapular morphological changes associated with glenohumeral osteoarthritis (GHOA) and rotator cuff (RC) tears would allow accurate biomechanical modeling. METHODS: A prospective observational case control study was undertaken in which the GI, "nonglenoid"-CSA, acromial vertical offset index, acromial horizontal offset index, acromial horizontal-vertical offset index, and coronal plane angulation of the acromion (CPAA-m) were measured on high-quality radiographs to compare coronal plane scapular anatomy in: (1) patients with asymptomatic atraumatic full-thickness RC tears, (2) patients with symptomatic primary GHOA, and (3) a control group with no RC tear or GHOA treated for glenohumeral instability or symptomatic labral pathology. Intraobserver reliability of the measurements was performed. RESULTS: In the GHOA group, the GI was lower (less superiorly inclined) than the RC tear group (difference between the means: -4.8°, 95% confidence interval [CI] [-8.8°, -0.9°], P = .014) and the control group (difference between the means: -7.9°, 95% CI [-11.8°, -3.9°], P = .000); there was no difference in the acromial measurements. In the RC tear group, the nonglenoid-CSA was higher (difference between the means: 7.7°, 95% CI [3.0°, 12.3°], P = .001), the acromial vertical offset index was lower (difference between the means: -0.13, 95% CI [-0.24, -0.01], P = .026), and the acromial horizontal-vertical offset index was higher (difference between the means: 0.15, 95% CI [0.01, 0.28], P = .030) than the control group; there was no difference in the acromial horizontal offset index or the GI. The CPAA-m was lower (greater coronal plane downslope of the acromion) in both GHOA (difference between the means: -9.6°, 95% CI [-18.6°, -0.5°], P = .036) and RC tears (difference between the means: -9.9°, 95% CI [-19.0°, -0.9°], P = .029) compared with the control group. The intraclass correlation coefficients for intraobserver reliability demonstrated excellent reliability for the measurements (all >0.900). DISCUSSION: Scapulae associated with GHOA have lower GI, but no spatial differences in the location of the lateral acromion compared with a normal population. Scapulae associated with RC tears have a lower vertical offset of the lateral acromion, but no difference in horizontal offset or GI compared with a normal population. The downslope of the acromion in the coronal plane is greater (lower CPAA-m) in both RC tears and GHOA than the normal population.

The Critical Shoulder Angle Shows a Reciprocal Change in Magnitude When Evaluating Symptomatic Full-Thickness Rotator Cuff Tears Versus Primary Glenohumeral Osteoarthritis as Compared With Control Subjects: A Systematic Review and Meta-analysis.

PURPOSE: To determine whether a high critical shoulder angle (CSA) is associated with symptomatic full-thickness rotator cuff (RC) tears and/or whether a low CSA is associated with primary glenohumeral osteoarthritis (GHOA). METHODS: A systematic review was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. All observational studies that examined an association between CSA and full-thickness RC tears and/or primary GHOA were included. A primary meta-analysis was performed including all studies that met the inclusion criteria regardless of radiographic quality. A secondary meta-analysis was performed to explore the hypothesis that radiographic quality was a source of heterogeneity, which excluded those studies in which radiograph quality was not strictly defined and controlled. RESULTS: For the primary meta-analysis, 11 studies met the inclusion criteria for RC tears and 5 for primary GHOA. The CSA was greater in the RC tear group than the control group (mean difference 4.03°, 95% confidence interval 2.95°-5.11, 95% prediction interval 0.0487°-8.01°; P < .001). The CSA was lower in the GHOA group than the control group (mean difference -3.98°, 95% confidence interval -5.66° to -2.31°, 95% prediction interval -10.2° to -2.19°; P < .001).A high level of heterogeneity was observed in the RC tear analysis (I2 = 88.4), which decreased after the exclusion of 5 studies based on radiographic quality (I2 = 75.3). A high level of heterogeneity also was observed in the primary GHOA analysis (I2 = 87.3), which decreased after the exclusion of 2 studies based on the radiographic quality (I2 = 48.2). CONCLUSIONS: There is a reciprocal change in magnitude of the CSA when evaluating symptomatic full-thickness RC tears versus primary GHOA as compared with control subjects. Radiographic quality is a source of heterogeneity in studies that investigate a link between CSA and RC tears and primary GHOA. LEVEL OF EVIDENCE: Level III, systematic review and meta-analysis of Level III studies.

Biomechanical comparison of knotless wide suture double-row SutureBridge rotator cuff repair to double-row standard suture repair.

BACKGROUND: A comparison of self-reinforcement and footprint compression between standard- and wide-diameter suture material in double-row SutureBridge repair techniques has not been performed. The aim of this study was to compare the self-reinforcement and footprint contact pressure generated under progressive tensile loads between 2 double-row SutureBridge rotator cuff repair techniques: 1 performed with FiberWire and 1 performed with FiberTape in a knotless technique. MATERIALS AND METHODS: Rotator cuff repairs were performed in 10 pairs of ovine shoulders. One group underwent a double-row SutureBridge repair using FiberWire. The other group underwent an identical repair with FiberTape. Footprint contact pressure was measured from 0° to 60° of abduction under loads of 0-60 N. Pull-to-failure tests were then performed. RESULTS: In both repair constructs at 0° of abduction, each 10-N increase in rotator cuff tensile load led to a significant increase in footprint contact pressure (P < .05). The rate of increase in footprint contact pressure was greater in the FiberTape construct (ratio, 1.68; P = .00035). In both repair constructs, the highest values for footprint contact pressure were seen at 0° of abduction. No difference in pull to failure, peak load, or total energy was found between the groups. CONCLUSION: Self-reinforcement was seen in both double-row SutureBridge repairs with standard- and wide-diameter suture material but was greater in the repair with the wide-diameter suture material construct. Footprint compression is greater in a knotless double-row SutureBridge repair with wide-diameter suture material than in a knotted double-row SutureBridge repair with standard-diameter suture material at 20° of abduction.

Image intensifier distortion influences a surgeon's ability to aim guidewires during orthopaedic procedures.

OBJECTIVE: Accurate insertion of a guidewire under image intensifier guidance is a fundamental skill required by orthopaedic surgeons. This study investigated how image intensifier distortion, which is composed of pin-cushion and sigmoidal components, changed the apparent trajectory of a guidewire, and the resulting deviation between the intended and actual guidewire tip position. MATERIALS AND METHODS: Intraoperative image intensifier images for 220 consecutive patients with hip fractures were retrospectively corrected for distortion using a global polynomial method. The deviation between the intended and actual guidewire tip positions was calculated. Additional distortion parameters were tested using an image intensifier produced by a different manufacturer, and a flat-panel c-arm. RESULTS: Deviation was approximately 1 cm if the guidewire was aimed from the extremity of the image and almost 0 if the entry point was only 20% from the centre (p < 0.001). The direction of deviation was different for left and right hips, with average deviations measuring 3 mm proximal and 5 mm distal respectively (p < 0.001). The flat-panel c-arm almost completely eliminated distortion. CONCLUSIONS: Image intensifier distortion significantly altered the intended trajectory of a guidewire, with guidewires aimed from the image periphery more affected than guidewires aimed from the centre. Furthermore, for right hips, guidewires should be aimed distal to their intended position, and for left hips they should be aimed proximal to achieve their desired position. The flat-panel c-arm eliminated the effect of distortion; hence, it may be preferable if precision in guidewire positioning is vital.

Shoulder abduction diminishes self-reinforcement in transosseous-equivalent rotator cuff repair in both knotted and knotless techniques.

PURPOSE: The self-reinforcement mechanism after double row suturebridge rotator cuff repair generates increasing compressive forces at the tendon footprint with increasing tendon load. Passive range of motion is usually allowed after rotator cuff repair. The mechanism of self-reinforcement could be adversely affected by shoulder abduction. METHODS: Rotator cuff tears were created ex vivo in nine pairs of ovine shoulders. Two different repair techniques were used. One group was repaired using a double row 'suturebridge' construct with tied horizontal medial row mattress sutures (Knotted repair group). The other group was repaired identically except that medial row knots were not tied (Knotless repair group). Footprint compression was measured at varying amounts of abduction and under tendon loads of 0, 10, 20, 30, 40, 50 and 60N. The rate of increase of contact pressure (degree of self-reinforcement) was calculated for each abduction angle. RESULTS: Abduction diminishes footprint contact pressure in both knotted and knotless double row suturebridge constructs. Progressive abduction from 0 to 40 abduction in the knotless group and 0-30 in the knotted group results in a decrease in self-reinforcement. Abduction beyond this does not cause a further decrease in self-reinforcement. There was no difference in the rate of increase of footprint contact pressure at each angle of abduction when comparing the knotted and knotless groups. CONCLUSION: In the post-operative period, high tendon load combined with minimal abduction would be expected to generate the greatest amount of footprint compression which may improve tendon healing. Therefore, to maximize footprint compression the use of abduction pillows should be avoided while early isometric strengthening should be used.

Knotless double-row SutureBridge rotator cuff repairs have improved self-reinforcement compared with double-row SutureBridge repairs with tied medial knots: a biomechanical study using an ovine model.

BACKGROUND: In double-row SutureBridge (Arthrex, Naples, FL, USA) rotator cuff repairs, increasing tendon load may generate progressively greater compression forces at the repair footprint (self-reinforcement). SutureBridge rotator cuff repairs using tied horizontal mattress sutures medially may limit this effect compared with a knotless construct. MATERIALS AND METHODS: Rotator cuff repairs were performed in 9 pairs of ovine shoulders. One group underwent repair with a double-row SutureBridge construct with tied horizontal medial-row mattress sutures. The other group underwent repair in an identical fashion except that medial-row knots were not tied. Footprint contact pressure was measured at 0° and 20° of abduction under loads of 0 to 60 N. Pull-to-failure tests were then performed. RESULTS: In both repair constructs, each 10-N increase in rotator cuff tensile load led to a significant increase in footprint contact pressure (P < .0001). The rate of increase in footprint contact pressure was greater in the knotless construct (P < .00022; ratio, 1.69). The yield point approached the ultimate load to failure more closely in the knotless model than in the knotted construct (P = .00094). There was no difference in stiffness, ultimate failure load, or total energy to failure between the knotless and knotted techniques. CONCLUSION: In rotator cuff repair with a double-row SutureBridge configuration, self-reinforcement is seen in repairs with and without medial-row knots. Self-reinforcement is greater with the knotless technique.

The effect of using a cement gun with a narrow nozzle on cement penetration for total elbow arthroplasty: a cadaveric study.

PURPOSE: To compare the cement mantle characteristics associated with use of a narrow nozzle cement gun versus the use of a 60-mL catheter tip syringe. METHODS: Twelve cadaveric distal humeri were cemented with either a cement gun or a syringe without canal occlusion. The humeri were sectioned and photographed. The corticocancellous junction and the outer margin of the cement mantle were analyzed digitally. The corticocancellous junction defined the available area for cement penetration. The outline of the cement mantle defined the actual area of penetration. The ratio of penetration to the available area was recorded for each slice. The mean ratio for each humerus was multiplied by the number of slices in that sample containing cement to calculate a cement index. RESULTS: The cement penetration ratios observed in cross-sections at the same level and the cement index were significantly greater with the use of the cement gun than with the use of the syringe. There was no difference in the number of slices that contained cement. CONCLUSIONS: The use of a cement gun with a narrow nozzle improved cement mantle characteristics compared with the use of a syringe when measured in a cadaveric model in the absence of canal occlusion. CLINICAL RELEVANCE: Improving cement mantle characteristics may decrease the incidence of aseptic loosening after total elbow arythroplasty.

Unreconstructable acute distal humeral fractures and their sequelae treated with distal humeral hemiarthroplasty: a two-year to eleven-year follow-up.

BACKGROUND: The aim of this study was to describe for the first time the medium to long-term outcome after distal humeral hemiarthroplasty (DHH). METHODS: Twenty-six patients (mean age, 62; range, 29-92 years) treated with DHH for intra-articular distal humeral fractures and its sequelae were studied retrospectively. RESULTS: Four patients had died and 4 had been revised to total elbow arthroplasty: 2 for periprosthetic fractures and 2 for primary component loosening (all in prostheses without an anterior flange). Six other complications had occurred: ulnar neuritis, 4; stiffness, 1; and wound necrosis, 1. Seventeen patients underwent assessment at a mean of 80 months after surgery. The mean values of the American Shoulder and Elbow Surgeons (ASES) elbow score (pain, 9.93; function, 25; satisfaction, 9.06); Mayo Elbow Performance Score (90); Quick Disabilities of Arm, Shoulder and Hand (19), and EuroQol EQ5D (Index, 0.84; Visual Analog Scale, 80) outcome measures demonstrated good function and satisfaction with little pain. The mean flexion extension arc was 116°. There was no evidence of instability. Radiologic evidence of ulnar wear was seen in 13 patients and may be related to prosthetic design to some extent. Worse wear was associated with a higher ASES pain score, lower satisfaction score, and lower EuroQoL Visual Analog Scale of quality of life. Degree of wear correlates with time after surgery but not with age at the time of surgery. CONCLUSION: DHH offers a treatment option for unreconstructable distal humeral fractures and is associated with a good long-term outcome. LEVEL OF EVIDENCE: Level IV, case series, treatment study.

Lateral Acromioplasty With the Aim of Reducing the Critical Shoulder Angle Using Techniques Based on the Lateral Acromial Border Result in Larger-Than-Necessary Resections.

Purpose: To compare the axial plane orientation and width and length of the acromial resections required to reduce the critical shoulder angle (CSA) using lateral acromioplasty (LA) techniques that are based on the lateral acromial border with an ideal resection that is oriented parallel to the glenoid. Methods: This was a retrospective observational cohort study of symptomatic patients that were investigated for shoulder pain, instability, or fracture with high-quality computed tomography (CT). The CT scan data were used to create 3-dimensional meshes, and a series of LA resection planes were mapped. The orientation, width, and length of each resection based on the lateral acromial border (lateral, anterolateral, posterolateral, and image guided) to reduce the measured CSA to 35° or 30° was compared with an ideal resection that was oriented parallel to the glenoid. Results: 23 models had CSA 30.1° to 35°, and 13 had CSA >35°. In the models with CSA >35°, there was no angular difference between the resection planes of the lateral, anterolateral, or image-guided resections compared with the ideal technique; there were differences in the required width and length of the resections to reduce the CSA to 35° (additional width/length: lateral, 3.2/14.8 mm; anterolateral, 2.8/10.6 mm; posterolateral, 6.9/19.2 mm; image guided, 2.4/10.3 mm). Width and length differences were also present in the models with CSA >30° when the resections aimed to reduce the CSA to 30° (additional width/length: lateral, 2.5/12.5 mm; anterolateral, 1.9/8.8 mm; posterolateral, 7.4/19.0 mm; image guided, 1.6/8.8 mm). Conclusions: LA techniques based on the lateral acromial border did not replicate the ideal resection and may lead to excessive deltoid release which could adversely affect clinical results. Clinical relevance: Our findings do not support LA techniques based on the lateral acromial border.

The Lateral Deltoid Originates From the Entire Lateral Wall of the Acromion: MRI and Histologic Cadaveric Analysis Regarding Vertical Lateral Acromioplasty.

PURPOSE: The aim of this study was to assess the nature of the middle deltoid muscle insertion onto the lateral acromion by macroscopic, MRI and histologic examination and to, therefore, assess the potential impact of a vertical lateral acromioplasty on the deltoid origin. METHODS: We assessed the acromial origin of the deltoid in 6 cadaver shoulders by macroscopic, MRI and histologic examination. The cadavers were scanned with T1 and proton density-weighted sequences. H&E- and Masson trichrome-stained histologic sections through the acromion were taken and visualized under polarized microscopy. RESULTS: The enthesis of the deltoid muscle consisted of dense birefringent bundles of collagen that blended with the bony endplate of the acromion at all points on its lateral wall. A prominent band of collagen was seen on both MRI and histologic slices, traversing the superior surface of the acromion. It was continuous with the deltoid origin and blended with the superficial fascia of the deltoid laterally. CONCLUSIONS: The middle deltoid muscle occupies the entire lateral acromion. CLINICAL RELEVANCE: A high critical shoulder angle is associated with rotator cuff tears. A lateral acromioplasty resects the lateral acromion and aims to normalize the critical shoulder angle. However, a vertical lateral acromioplasty may release the middle deltoid origin from the lateral acromion. The superior band of collagen may anchor the middle deltoid to the superior acromion and prevent retraction.

Reverse Shoulder Arthroplasty for the treatment of Proximal humeral fractures in the Elderly (ReShAPE trial) : study protocol for a multicentre combined randomised controlled and observational trial.

BACKGROUND: Proximal humeral fractures are common in older patients. The majority are minimally displaced and are associated with good outcomes after nonoperative treatment. Poorer outcomes are associated with displaced, multipart fractures. There is no clear benefit from surgical fracture fixation compared to nonoperative treatment. Replacement of the fractured humeral head with a hemiarthroplasty is another treatment option, but has not been shown to be clearly superior to nonoperative treatment or internal fixation. Recently, reverse total shoulder arthroplasty has been used to treat these fractures, particularly in the older population with several case series demonstrating good outcomes. No comparative trial has been performed to test the effectiveness of reverse total shoulder arthroplasty against nonoperative treatment. METHODS/DESIGN: ReShAPE (Reverse Shoulder Arthroplasty for the treatment of Proximal humeral fractures in the Elderly) is a multicenter combined randomized and observational study. The primary objective is to compare pain and function 12 months post fracture using the American Shoulder and Elbow Society (ASES) score in patients aged 70 years or older with three- and four-part proximal humeral fractures treated by either reverse shoulder arthroplasty or nonoperative treatment. Secondary outcome measures will include the DASH (Disability of the Arm, Shoulder and Hand) score, the EQ-5D (EuroQol Health Survey), the EQ-VAS, pain, radiological parameters and complications. DISCUSSION: The study will assess the effectiveness of reverse shoulder arthroplasty for complex proximal humeral fractures and thereby guide treatment of a common injury in the older population. TRIAL REGISTRATION: World Health Organization Universal Trial Number (WHO UTN): U1111-1180-5452 . Registered on 10 March 2016. Australian and New Zealand Clinical Trials Registry (ANZCTR): 12616000345482 . Registered on 16 March 2016.

The clinical outcome and activity levels of patients under 55 years treated with distal humeral hemiarthroplasty for distal humeral fractures: minimum 2-year follow-up.

BACKGROUND: The aim of the present study was to describe the clinical outcomes and activity levels of young patients after distal humeral hemiarthroplasty (DHH). METHODS: Six patients under 55 years (mean 44 years; range 29 years to 52 years) treated with DHH at a mean postoperative time of 81 months (range 24 months to 133 months) were studied retrospectively. Two other patients had been revised for aseptic loosening and were excluded. RESULTS: The mean Mayo Elbow Score (MEPS) (88), Subjective Elbow Value (SEV) (89), Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) (12) and American Shoulder and Elbow Surgeons (ASES) elbow pain (6), function (23) and satisfaction scores (9) were satisfactory. The mean University of California, Los Angeles (UCLA) activity score was 7.2. CONCLUSIONS: Although only rarely indicated, DHH has satisfactory clinical outcomes in young patients and allows a higher level of function than is generally advised after total elbow arthroplasty.