Functional and morphological divergence in the forelimb musculoskeletal system of scratch-digging subterranean mammals (Rodentia: Bathyergidae).

Whether the forelimb-digging apparatus of tooth-digging subterranean mammals has similar levels of specialization as compared to scratch-diggers is still unknown. We assessed the scapular morphology and forelimb musculature of all four solitary African mole rats (Bathyergidae): two scratch-diggers, Bathyergus suillus and Bathyergus janetta, and two chisel-tooth diggers, Heliophobius argenteocinereus and Georychus capensis. Remarkable differences were detected: Bathyergus have more robust neck, shoulder, and forearm muscles as compared to the other genera. Some muscles in Bathyergus were also fused and often showing wider attachment areas to bones, which correlate well with its more robust and larger scapula, and its wider and medially oriented olecranon. This suggests that shoulder, elbow, and wrist work in synergy in Bathyergus for generating greater out-forces and that the scapula and proximal ulna play fundamental roles as pivots to maximize and accommodate specialized muscles for better (i) glenohumeral and scapular stabilization, (ii) powerful shoulder flexion, (iii) extension of the elbow and (iv) flexion of the manus and digits. Moreover, although all bathyergids showed a similar set of muscles, Heliophobius lacked the m. tensor fasciae antebrachii (aiding with elbow extension and humeral retraction), and Heliophobius and Georychus lacked the m. articularis humeri (aiding with humeral adduction), indicating deeper morphogenetic differences among digging groups and suggesting a relatively less specialized scratch-digging ability. Nevertheless, Heliophobius and Bathyergus shared some similar adaptations allowing scratch-digging. Our results provide new information about the morphological divergence within this family associated with the specialization to distinct functions and digging behaviors, thus contributing to understand the mosaic of adaptations emerging in phylogenetically and ecologically closer subterranean taxa. This and previous anatomical studies on the Bathyergidae will provide researchers with a substantial basis on the form and function of the musculoskeletal system for future kinematic investigations of digging behavior, as well as to define potential indicators of scratch-digging ability.

Sexual dimorphism and allometry in human scapula shape.

Scapula shape is highly variable across humans and appears to be sexually dimorphic-differing significantly between biological males and females. However, previous investigations of sexual dimorphism in scapula shape have not considered the effects of allometry (the relationship between size and shape). Disentangling allometry from sexual dimorphism is necessary because apparent sex-based differences in shape could be due to inherent differences in body size. This study aimed to investigate sexual dimorphism in scapula shape and examine the role of allometry in sex-based variation. We used three-dimensional geometric morphometrics with Procrustes ANOVA to quantify scapula shape variation associated with sex and size in 125 scapulae. Scapula shape significantly differed between males and females, and males tended to have larger scapulae than females for the same body height. We found that males and females exhibited distinct allometric relationships, and sexually dimorphic shape changes did not align with male- or female-specific allometry. A secondary test revealed that sexual dimorphism in scapula shape persisted between males and females of similar body heights. Overall, our findings indicate that there are sex-based differences in scapula shape that cannot be attributed to size-shape relationships. Our results shed light on the potential role of sexual selection in human shoulder evolution, present new hypotheses for biomechanical differences in shoulder function between sexes, and identify relevant traits for improving sex classification accuracy in forensic analyses.

Ultrasound-guided rhomboid intercostal block (RIB) for acute scapula fracture in the emergency department.

INTRODUCTION: Proper pain in acute scapular fractures can be challenging to achieve due to their anatomy and location. While the current mainstay of treatment relies on opioids, the Rhomboid Intercostal Block (RIB) has been utilized for anesthesia to effectively treat pain for scapular fractures. However, it has not yet been utilized in the emergency department (ED). CASE REPORT: In this case report, we present the first documented use of RIB to treat pain safely and effectively in a 69-year-old male with a scapula fracture following a ground-level fall in the ED. The RIB was performed under ultrasound guidance, providing precise localization and administration of the nerve block. CONCLUSION: The RIB demonstrated successful pain management in the ED. Although hopeful, further research is needed to understand limitations, potential side effects, length of pain control, and overall clinical outcomes of the RIB in the ED.

Ultrasound Evaluation and Guided Injection of the Subscapularis and Serratus Anterior Muscles Between the Scapula and the Thoracic Cage: A Technical Note.

Most subscapularis and serratus anterior muscles lie between the scapula and the thoracic cage. Evaluation of this area in patients with scapulothoracic dyskinesis, snapping scapular syndrome, or interscapular pain can provide valuable information to clinicians. However, ultrasound scanning of pathologies in this area is hindered by anatomical limitations. In this study, we described a simple patient setup position and scanning method for ultrasound evaluation and guided intervention of the subscapularis and serratus anterior muscles between the scapula and thoracic cage.

Verification of acromion marker cluster and scapula spinal marker cluster methods for tracking shoulder kinematics: a comparative study with upright four-dimensional computed tomography.

BACKGROUND: This study validated the accuracy of the acromion marker cluster (AMC) and scapula spinal marker cluster (SSMC) methods compared with upright four-dimensional computed tomography (4DCT) analysis. METHODS: Sixteen shoulders of eight healthy males underwent AMC and SSMC assessments. Active shoulder elevation was tracked using upright 4DCT and optical motion capture system. The scapulothoracic and glenohumeral rotation angles calculated from AMC and SSMC were compared with 4DCT. Additionally, the motion of these marker clusters on the skin with shoulder elevation was evaluated. RESULTS: The average differences between AMC and 4DCT during 10°-140° of humerothoracic elevation were - 2.2° ± 7.5° in scapulothoracic upward rotation, 14.0° ± 7.4° in internal rotation, 6.5° ± 7.5° in posterior tilting, 3.7° ± 8.1° in glenohumeral elevation, - 8.3° ± 10.7° in external rotation, and - 8.6° ± 8.9° in anterior plane of elevation. The difference between AMC and 4DCT was significant at 120° of humerothoracic elevation in scapulothoracic upward rotation, 50° in internal rotation, 90° in posterior tilting, 120° in glenohumeral elevation, 100° in external rotation, and 100° in anterior plane of elevation. However, the average differences between SSMC and 4DCT were - 7.5 ± 7.7° in scapulothoracic upward rotation, 2.0° ± 7.0° in internal rotation, 2.3° ± 7.2° in posterior tilting, 8.8° ± 7.9° in glenohumeral elevation, 2.0° ± 9.1° in external rotation, and 1.9° ± 10.1° in anterior plane of elevation. The difference between SSMC and 4DCT was significant at 50° of humerothoracic elevation in scapulothoracic upward rotation and 60° in glenohumeral elevation, with no significant differences observed in other rotations. Skin motion was significantly smaller in AMC (28.7 ± 4.0 mm) than SSMC (38.6 ± 5.8 mm). Although there was smaller skin motion in AMC, SSMC exhibited smaller differences in scapulothoracic internal rotation, posterior tilting, glenohumeral external rotation, and anterior plane of elevation compared to 4DCT. CONCLUSION: This study demonstrates that AMC is more accurate for assessing scapulothoracic upward rotation and glenohumeral elevation, while SSMC is preferable for evaluating scapulothoracic internal rotation, posterior tilting, glenohumeral external rotation, and anterior plane of elevation, with smaller differences compared to 4DCT.

Bizarre parosteal osteocondromatous proliferation (BPOP) of the acromion with soft tissue recurrence.

Bizarre parosteal osteochondromatous proliferation (BPOP) is a benign but rare periosteal-originating chondrogenic tumor. It commonly arises from the hands and feet. It is slow-growing and often presents as a painless lump. On imaging, the mass is well-marginated and almost always remains contiguous with the cortical bone. Histologically, the lesion is composed of a disorganized admixture of fibrous tissue, bone, and cartilage with bizarre features. Treatment is surgical and local recurrence is common contiguous with bone. This case report demonstrates an uncommon acromial BPOP with the first reported recurrence not contiguous with the underlying cortex.

Sling and forget it? A systematic review of operative versus nonoperative outcomes for scapula fractures.

BACKGROUND: The majority of scapula fractures have historically been treated nonoperatively. The current literature describing patient outcomes following scapula fractures is limited. Our objective was to determine differences in outcomes between operatively and nonoperatively treated scapular fractures. The goal of our study was to provide an updated and comprehensive systematic review for scapula body, neck, and glenoid fractures focusing on several outcomes including union rate, return to work, pain, shoulder active range of motion, strength, functional scores, and any recorded complication. METHODS: The PRISMA methodology was followed for this systematic review. Articles were obtained from the PubMed/Medline database using the following search terms: scapula body OR scapula neck OR intra-articular glenoid AND fracture. Additional articles were obtained by searching the bibliographies of included references. Studies were included if they contained clinical data on one or more of our study objectives and contained participants with a scapular body, neck, and/or glenoid fracture who were at least 16 year old. A total of 35 papers, with 822 total cases were included. Studies chosen were assessed for level of evidence and reviewed for data pertaining to the current study objectives. All cases of scapula fractures found throughout the literature were analyzed for outcome data. Outcomes studied included union rate, return to work, pain, shoulder active range of motion, strength, functional scores, and recorded complications. RESULTS: The overwhelming majority of scapula fractures go on to union. The majority of patients will eventually return to work. Persistent postinjury pain is unfortunately common. Shoulder range of motion and strength are decreased when compared to the contralateral shoulder. Nonoperative glenoid fractures have the lowest reported functional scores. Malunion, need for additional surgeries, and post-traumatic arthritis were the most common complications. CONCLUSION: When treating scapula fractures, orthopedic surgeons must consider the specific fracture pattern, as well as patient specific goals. Risks and benefits of both operative and nonoperative management should be discussed with the patient including the exceptionally low nonunion rate regardless of treatment option and that persistent pain following injury is unfortunately common.

The shoulder joint complex in the throwing motion.

The shoulder joint complex in the overhead athlete is organized to effectively transfer the proximally generated forces distally into the arm. The organization also protects the joints and anatomic structures against the repetitive high velocities, large ranges of motions, and compressive, shear, translational, and distraction loads in the overhead motion while placing the hand in the "launch window." Coupling of the movements of the scapula, clavicle, and humerus results in scapulohumeral rhythm (SHR). Effective SHR requires the clavicle and scapula-and, at times, the mechanically linked claviscapular segment-to move the arm into the task-specific position and motion and requires the humerus to move through the ranges of motion to achieve the specific task in the throwing motion. Alterations in SHR can negatively affect effective shoulder joint complex function in the overhead throwing motion and increase injury risk. There are 4 phases of clavicular, scapular, and claviscapular motion that are coupled with arm motion in SHR. The first 3 phases occur in arm elevation motions from 0°-90° and result in the claviscapula and humerus being placed in task-specific positions. The fourth phase is coupling of claviscapular motion with humeral motion to maintain ball-and-socket kinematics throughout the throwing motion. Alterations in this composite motion are termed "scapular dyskinesis." The dyskinesis is considered an impairment of the efficient mobility of the claviscapular segment of the shoulder complex. The most prevalent problem with scapular dyskinesis is the association of scapular protraction and consequent glenoid antetilt with alterations in humeral rotation and posterior humeral head translation to produce shoulder joint internal impingement. Task effectiveness in overhead throwing is also based on and determined by humeral range of motion, precision of humeral motion, and velocity of humeral motion, as well as humeral and arm position in 3-dimensional space. This activity requires maximum ball-and-socket kinematics to create the highest amount of concavity-compression that creates stability for the joint. There are bony and soft-tissue contributions to this stability. Injuries to the glenoid labrum are among the most common deficits that alter concavity-compression. Clinical evaluation of the shoulder joint complex in the injured throwing athlete should be comprehensive and systematic, following an evaluation pathway for proximal and distal causative factors and including observation of humeral motion. This type of evaluation can result in intervention protocols that address the pathoanatomic, pathophysiological, and pathomechanical deficits identified.

Rehabilitation of the painful shoulder.

Managing the painful shoulder in overhead athletes can be difficult because of a lack of time-loss injuries in overhead sports and focusing primarily on either pathoanatomic causes or movement impairments. Although managing the painful shoulder can be challenging, the combination of identifying pathoanatomic causes with movement impairments can provide a more focused rehabilitation approach directed at the causes of shoulder pain. Understanding the potential influence of scapular positioning as well as mobility and/or strength impairments on shoulder pain can help clinicians develop more directed rehabilitation programs. Furthermore, sports-specific methods such as long toss or the use of weighted balls for achieving physiological or performance-based gains have limited empirical evidence regarding their clinical and performance-based benefits, which may impede the rehabilitation process. Applying a comprehensive evaluation approach prior to and throughout the treatment process can assist clinicians with selecting the most appropriate treatment based on patient need. Reconsidering traditional treatments based on existing evidence may help refine the treatment process for overhead athletes with shoulder pain.

Epidemiology, treatment, and mortality of 3973 scapula fractures from the Swedish fracture register.

BACKGROUND: Scapula fractures are relatively uncommon, accounting for <1% of all fractures and approximately 3%-5% of shoulder girdle fractures. This study comprehensively describes the epidemiology, fracture classification, treatment, and mortality associated with scapula fractures within a large adult Swedish population. METHODS: This observational study included all patients ≥ 18 years old at the time of injury with a scapula fracture (ICD S42.1) registered in the Swedish Fracture Register between March 2011 and June 2020. Variables studied were age, sex, and injury mechanism, including energy level, fracture classification, associated fractures, treatment, and mortality. RESULTS: We included 3930 patients (mean age 58 years, standard deviation 18, 64% men) with 3973 scapula fractures. Some 22% of the fractures were caused by high-energy trauma and 21% had at least 1 associated fracture. High energy-injuries were most common in glenoid neck (44%) and scapular body (35%) fractures. However, same-level falls were the most common cause of glenoid rim (62%) and intra-articular glenoid (55%) fractures. Clavicle fractures (9%) and proximal humerus fractures (5%) were the most commonly associated fractures. The most common fracture types were the glenoid rim (n = 1289, 32%) and scapular body (n = 1098, 28%) fractures. Nonoperative treatment was performed in 81% of patients. Glenoid rim and intra-articular glenoid fractures were treated operatively in over 30% of cases. The mortality rate for the whole cohort was 4% at 1 year. CONCLUSIONS: Scapula fractures are predominately sustained by men. High energetic injuries and associated fractures are present in 1 in five patients. Nonoperative treatment is chosen in 4 of five patients, but for some fracture types 1 in 3 undergo surgery.

The scapula spine may not be a suitable source of bone graft for glenoid reconstruction in critical bone loss.

AIMS: The hypothesis is that the scapula spine can provide a graft of suitable dimensions for use in cases of shoulder instability with critical bone loss. We aimed to investigate its utility with grafts of differing sizes. METHODS: The scapula spine was measured on CT scans of 50 patients who had undergone anterior stabilization. The theoretical ability to harvest a graft of either 2x1x1cm or 2x0.8x0.8cm was analyzed. RESULTS: Using the 2 x 1 x 1cm threshold, 36% of the scapulae had at least one zone from which a suitable graft could be obtained. 61% had only one zone from which a suitable graft could be obtained. Using the 2 x 0.8 x 0.8cm threshold, 72% had at least one zone from which a graft could be obtained. 47% met the threshold in one zone only. CONCLUSION: The scapula spine can be used as a source of autograft. Grafts up to 2 x 1 x 1cm can be harvested in some individuals, however the anatomy is very variable. TAKE HOME MESSAGE: The scapula spine can be used but we recommend that individualized preoperative planning is undertaken to ensure that a suitable graft can be harvested from the spine and to identify the exact location.

Defining shoulder function and dysplasia in patients with longitudinal deficiencies of the upper limb.

BACKGROUND: Phenotypic differences and functional limitations in children with congenital radial and ulnar longitudinal deficiencies (RLD/ULD) are well understood for the forearm and hand. However, anatomical features of shoulder elements in these pathologies have only been scarcely reported. Moreover, shoulder function has not been assessed in this patient population. Therefore, we aimed to define radiologic features and shoulder function of these patients at a large tertiary referral center. METHODS: We prospectively enrolled all patients with RLD and ULD (minimum age: 7 years) for this study. Eighteen patients (12 RLD, 6 ULD) with a mean age of 17.9 years (range, 8.5-32.5) were evaluated using clinical examination (shoulder motion and stability), patient-reported outcome measures (Visual Analog Scale, Pediatric/Adolescent Shoulder Survey, Pediatric Outcomes Data Collection Instrument), and radiologic grading of shoulder dysplasia (including length and width discrepancy of the humerus, glenoid dysplasia in the anteroposterior and axial view [Waters classification], and scapular and acromioclavicular dysplasia assessment). Descriptive statistics and Spearman correlation analyses were performed. RESULTS: Despite five (28%) cases having anterioposterior shoulder instability and five (28%) cases with decreased motion, outcome scores indicated an overall excellent function of the shoulder girdle, with mean Visual Analog Scale of 0.3 (range, 0-5), mean Pediatric/Adolescent Shoulder Survey of 97 (range, 75-100), and mean Pediatric Outcomes Data Collection Instrument Global Functioning Scale of 93 (range, 76-100). The humerus was, on average, 15 mm shorter (range, 0-75), and metaphyseal and diaphyseal diameters both reached 94% of the contralateral side. Glenoid dysplasia was detected in nine (50%) cases, with increased retroversion evident in 10 (56%) cases. However, scapular (n = 2) and acromioclavicular (n = 1) dysplasia were rare. Based on radiographic findings, a radiologic classification system for dysplasia types IA, IB, and II was developed. CONCLUSIONS: Adolescent and adult patients with longitudinal deficiencies exhibit various mild-to-severe radiologic abnormalities around the shoulder girdle. Nevertheless, these findings did not seem to negatively affect shoulder function as the overall outcome scores were excellent.

Medial scapular body (MSB) Goutallier classification: MRI-based reliability and validity of evaluation of the Goutallier classification for grading fatty infiltration of the rotator cuff.

BACKGROUND: The degree of atrophy and fatty infiltration of rotator cuff muscle belly is a key predictor for cuff repairability. Traditionally, Goutallier grading of fatty infiltration is assessed at sagittal scapular Y-view. Massive rotator cuff tears are associated with tendon retraction and medial retraction of cuff musculature, resulting in medialization of the muscle bulk. Thus, standard Y-view can misrepresent the region of interest and may misguide clinicians when assessing repairability. It is hypothesized that by assessing the muscle belly with multiple medial sagittal magnetic resonance imaging (MRI) sections at the medial scapular body, the Medial Scapular Body-Goutallier Classification (MSB-GC) will improve reliability and repeatability, giving a more representative approximation to the degree of fatty infiltration, as compared with the original Y-view. METHODS: Fatty infiltration of the rotator cuff muscles were classified based on the Goutallier grade (0-4) at 3 defined sections: section 1, original Y-view; section 2, level of suprascapular notch; and section 3, 3 cm medial to the suprascapular notch on MRI scans. Six subspecialist fellowship-trained shoulder surgeons and 3 musculoskeletal radiologists independently evaluated deidentified MRI scans of included patients. RESULTS: Of 80 scans, 78% (n = 62) were massive cuff tears involving the supraspinatus, infraspinatus, and subscapularis tendons. Interobserver reliability (consistency between observers) for Goutallier grade was excellent for all 3 predefined sections (range: 0.87-0.95). Intraobserver reliability (repeatability) for Goutallier grade was excellent for all 3 sections and 4 rotator cuff muscles (range: 0.83-0.97). There was a moderate to strong positive correlation of Goutallier grades between sections 1 and 3 and between sections 2 and 3 and these were statistically significant (P < .001). There was a reduction in the severity of fatty infiltration on the Goutallier classification from sections 1 to 3 across all muscles: 42.5% of both supraspinatus and infraspinatus were downgraded by 1, 20% of supraspinatus and 3.8% of infraspinatus were downgraded by 2, and 2.5% of supraspinatus were downgraded by 3. CONCLUSION: This study found that applying the Goutallier classification to more medial MRI sections (MSB-GC) resulted in assignment of lower grades for all rotator cuff muscles. Additionally, this method demonstrated excellent test-retest reliability and repeatability. Inclusion of a more medial view or whole scapula on MRI, especially in advanced levels of tear retraction, could be more reliable and representative for assessment of the degree of fatty infiltration within the muscle bulk that could help predict tear repairability and therefore improve clinical decision making, which should be studied further in clinical studies.

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

BACKGROUND: Fractures 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 describes our evolution of fixation techniques. METHODS: Between 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. RESULTS: Of 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 1 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°-91.3° pre and postoperatively, respectively). CONCLUSIONS: ORIF 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 1 of the plates, (3) use of hook features under the acromion or os trigonum if possible, and (4) liberal use of bone graft.

Premorbid glenoid anatomy reconstruction from contralateral shoulder 3-dimensional measurements: a computed tomography scan analysis of 260 shoulders.

BACKGROUND: Total shoulder arthroplasty (TSA) aims to reconstruct the premorbid anatomy of a pathologic shoulder. A healthy contralateral shoulder could be useful as a template in planning TSA. The symmetry between the left and right shoulders in healthy patients remains to be proved. The purpose of this study was to compare the 3-dimensional anatomy of the glenoid between sides in a healthy population. METHODS: A multinational computed tomography scan database was retrospectively reviewed for all healthy bilateral shoulders in patients aged between 18 and 50 years. One hundred thirty pairs of healthy shoulder computed tomography scans were analyzed, and glenoid version, inclination, width, and height, as well as glenoid lateral offset and scapula lateral offset, were measured. All anatomic measures were computed with Blueprint, validated 3-dimensional planning software. The intraclass correlation coefficient was determined for each measure between left and right shoulders. The minimal detectable change (MDC) was calculated using the following formula: MDC=2×1.96×Standarderrorofmeasurement. RESULTS: The comparison between 130 pairs of healthy scapulae showed statistically significant differences in absolute values between right and left glenoid version (-5.3° vs. -4.6°, P < .01), inclination (8.4° vs. 9.3°, P < .01), and width (25.6 mm vs. 25.4 mm, P < .01), as well as scapula offset (105.8 mm vs. 106.2 mm, P < .01). Glenoid height was comparable between right and left shoulders (33.3 mm vs. 33.3 mm, P = .9). The differences between the means were always inferior to the MDC regarding glenoid version, inclination, height, and width, as well as scapula offset. Very strong intraclass correlation coefficients between the left and right shoulders were found for all evaluated paired measures. CONCLUSION: Healthy contralateral scapulae are highly reliable to predict inclination, height, width, and scapula offset and are reliable to predict version of a given scapula. Paired right and left scapulae were not statistically symmetrical regarding mean glenoid version, inclination, and width, as well as scapula offset. Nevertheless, the reported differences were not higher than the MDC for this cohort, confirming that healthy contralateral shoulders can be a useful template in TSA preoperative planning.

High delta angle after reverse total shoulder arthroplasty increases stresses of the acromion: biomechanical study of different implant positions.

BACKGROUND: Acromial fractures after reverse total shoulder arthroplasty (RTSA) are a common complication. Nevertheless, only a few studies have identified risk factors for acromial fractures after RTSA. High delta angle (combination of inferiorization and medialization of the center of rotation [COR]) after RTSA was identified as a risk factor in recent studies. The aim of this study was the biomechanical exploration of different delta angles and implant configurations with regard to the acromial stress. METHODS: In a rigid body model of the upper extremity muscle, forces of the deltoid muscle were calculated before and after implanting RTSA in different arm and implant positions. The deltoid muscle was divided into an anterior, middle, and posterior part. Implant positions of the glenoid components were changed in the medialization, lateralization, and inferiorization of the COR as well as lateralization of the humeral component. Further, in a finite element model of the upper extremity, the stresses of the acromion in the same implant design configurations were measured. RESULTS: Differences in acromial stress between different delta angle model configurations were observed. Lateralization (5 and 10 mm) of the glenosphere reduced the maximal acromial stress by 21% (1.5 MPa) and 31% (1.3 MPa), respectively. Inferiorization (5 and 10 mm) of the glenosphere increased the maximal acromial stress by 5% (2.0 MPa) and 15% (2.2 MPa), respectively. Changes in positioning the humeral component was found to have the highest impact in this model configuration. A 10-mm-lateralized humeral component reduced acromial stress by 37% (1.2 MPa), whereas in the 6-mm-medialized configuration, an increase in acromial stress by 83% (3.48 MPa) was observed. There was a high correlation between the delta angle and acromial stress (R2 = 0.967). CONCLUSION: Implant design configuration has an impact on the acromial stress. High delta angles correlate with an increase in acromial stress. Both lateralization of the COR and the humerus decreased the acromial stress in our study. The lateralization of the humerus has the highest impact in influencing acromial stress. Because of contrary results in the current literature, further studies with focus on the acromial stress influenced by different anatomic variants of the shoulder and the acromion are needed before a clinical recommendation can be made.

Preoperative patient factors that predict achieving the minimal clinically important difference following arthroscopic treatment of snapping scapula syndrome.

BACKGROUND: The aim of this study was to define the minimal clinically important difference (MCID) values for patient-reported outcomes (PROs) after arthroscopic treatment of snapping scapula syndrome (SSS) using a distribution-based method, and to identify demographic, clinical, and intraoperative factors significantly associated with the achievement of MCID. It was hypothesized that subjective satisfaction scores after the procedure would be strongly associated with the achievement of MCID thresholds for the PROs and that pain, preoperative response to injection, and a scapulectomy in addition to bursal resection would be predictive of clinically relevant improvement. METHODS: Patients who underwent arthroscopic treatment of SSS between October 2005 and September 2020 with a minimum of 2-year short-term postoperative follow-up were enrolled in this retrospective single-center study. The MCID was calculated using a distribution-based approach for the following PROs: 12-Item Short Form Health Survey (SF-12), American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES), Quick Disabilities of the Arm, Shoulder, and Hand questionnaire (QuickDASH), Single Assessment Numeric Evaluation (SANE), and visual analog scale (VAS) pain "today" and "at worst." The association between achievement of the MCID and postoperative subjective satisfaction was investigated, and factors associated with achievement of MCID were determined using bivariate analysis. RESULTS: Of a total of 190 patients assessed for eligibility, 77 patients (38.1 ± 14.3 years; 36 females) were included. Within the study population, statistically significant improvements in postoperative SF-12 physical component summary (PCS) (P < .001) and mental component summary (MCS) (P < 0.034), ASES (P < .001), QuickDASH (P < .001), SANE (P < .001), and VAS pain (P < .001) scores were observed at the minimum 2-year follow-up. The calculated MCID threshold values based on the study population were 5.0 for SF-12 PCS, 5.8 for SF-12 MCS, 11.3 for ASES, -10.5 for QuickDASH, 14.7 for SANE, 1.5 for VAS pain, and 1.7 for VAS pain at worst. Reaching the MCID was strongly associated with postoperative satisfaction (rated on a scale of 1-10). Across the PROs, younger age, favorable preoperative response to injection, partial scapuloplasty or scapulectomy, no prior surgery, and pain and function at baseline were significantly associated with attaining MCID. CONCLUSIONS: Patients who underwent arthroscopic treatment for SSS experienced clinically significant improvements in functional scores, pain, and quality of life. This study demonstrated predictive roles for certain patient-specific factors and diagnostic variables for achieving MCID in PROs, which may help surgeons preoperatively assess the probability of success and manage patient expectations.

Free Vascularized Scapula tip Flap to L5-S1 Vertebral Defect After Chronic Infection Related to Interbody Fusion Cage: A Case Report.

Septic nonunion after vertebral fusion can lead to significant patient disability. The management of septic nonunions usually involves surgical debridement, bone fixation, and antibiotic therapy. Particularly challenging is lumbosacral vertebral nonunions, which necessitate a difficult surgical approach. We present a novel approach using a scapula tip free flap through an intra-abdominal approach to reconstruct a L5-S1 vertebral defect after a septic nonunion. Our patient, 31-year-old man, with no medical conditions, had a fusion of L5-S1 due to severe lower back pain secondary to isthmic spondylolysis and spondylolisthesis. Despite multiple attempts of surgical fusion, postoperatively the patient developed a septic nonunion. Following a modified DAIR, the nonunion was reconstructed with a scapula tip bone flap 4 × 3 × 2 cm. The subscapular vessels were anastomosed to the deep inferior epigastric vessels after an intra-abdominal inset. The patient was discharged at 15 days postoperatively without any complications. At 1-year follow-up the patient is pain-free, off opiate analgesia with radiological evidence of fusion between the scapula tip, L5 and the S1 vertebral body. This case report describes the use, for the first time, of a free scapula tip, to a lumbosacral spinal defect. The use of the free scapula tip flap may be considered for reconstruction of osseous spinal defects due to its long pedicle and the unique bone shape.

Regarding a human costoscapular joint by Prof. Dr. H. von Luschka (1870): A translation.

Knowledge of variant anatomy was important during the time of Dr. Hubert von Luschka (1820-1875) and continues to be of relevance in current practice to prevent medical and surgical errors and to improve patient outcomes. Dr. H. von Luschka described an anatomical variant observed in the left scapula of a 40-year-old male: a connection between the medial superior angle of the scapula, piercing through the serratus posterior muscle to connect via a synovial capsule to the articular surface of the thoracic wall. The clinical relevance of this so-called "Luschka's tubercle" of the shoulder continues to be discussed. This translation is intended to broaden access to this hallmark manuscript to a wide audience of English readers. The introduction places the manuscript in the context of historical and current discussions. Three authors, all proficient in the German and English languages and educated in the anatomy of the shoulder, conducted the translation. The skeletal process that is part of the described joint structure appears similar to what is now called Luschka's tubercle. The full structure, including its connecting parts, are not currently included in anatomical nomenclature. In conclusion, Luschka's text and named tubercle continue to contribute to the discussion of scapulothoracic joint disorders.

Prevalence of positive modified scapular assistance test in patients with shoulder pain with and without scapular dyskinesis: a cross-sectional study.

BACKGROUND: Scapular dyskinesis (SD) is defined as an altered position of the scapula or altered motion patterns and their relationship with shoulder pain (SP) is still under debate. The modified scapular assistance test (mSAT) modifies scapular kinematics and is used to determine the impact of scapular dyskinesis in shoulder pain. However, data about the relationship between SD and the result of mSAT is scarce. PURPOSE: The aim of this study is to establish the frequency of positive mSAT in patients with SP and compare the prevalence in those with and without SD. As a secondary objective, we compare changes in pain intensity during the mSAT in patients with a positive test between those with and without SD. STUDY DESIGN: Cross-sectional study. METHODS: Adult patients with a diagnosis of SP and with pain ≥2 during anterior flexion were included. The mSAT, scapular dyskinesis test (SDT), and shoulder function were assessed. RESULTS: The study was conducted between August 2018 and May 2022 and included 70 patients. The prevalence of SDT was 54.29%. No statistically significant associations were detected when assessing the relation between the presence of mSAT and SDT (p-value 0.83). When comparing pain response during the mSAT in patients with a positive test, no differences were seen between patients with SD and patients without SD (p-value 0.26). CONCLUSIONS: The prevalence of positive mSAT results was equal between individuals with and without SD. These findings suggest that the presence or absence of SD in individuals with SP was independent of the mSAT result. The mSAT should not be used solely for the assessment of SD in clinical practice nor be influenced by the SDT result. More research is needed to determine if the result of this test could inform prognosis and guide treatment choices.