Posterior Acromion Research Articles

Reliable technique for acromion density assessment on CT.

Acromial stress fracture (ASF) is an uncommon but acknowledged complication of reverse total shoulder arthroplasty (RTSA). There is no standardised method to directly measure the bone mineral density of the acromion to allow a detailed analysis of the potential mechanism of ASF. The aim is to establish a reliable and reproducible technique for measurement of acromial density on computer tomography (CT). A retrospective review on CT scans obtained for three groups of patients: those planned for RTSA (n = 26); age and gender-matched non-operative (n = 26); and young non-operative patients (n = 28) were performed. Standardised axial images of 1 mm thickness at 1 mm increments were created following horizontal straightening on the coronal and sagittal views. To assess inter-rater reliability, two senior CT radiographers performed density measurements using standard region of interest (ROI) tool on the CTs with the ROI placed on the mid (ROI 1) and posterior (ROI 2) acromion. ROIs were selected as the most common locations for acromion fracture post RTSA. Measurements were repeated at least 6 weeks apart. Intra-class coefficients (ICC) were used to determine intra- and inter-rater reliability. ICCs demonstrated good to high intra-rater and inter-rater reliability for both ROI 1 and ROI 2 across all three groups. The lower margin of 95% confidence intervals was more than 0 for all intra-class coefficients. This study demonstrates a reliable method of measuring acromion density on CT. This method can be used to assess bone mineral density in the clinical setting and in future studies investigating ASF following RTSA.

Posteroinferior glenosphere positioning is associated with improved range of motion following reverse shoulder arthroplasty with a 135° inlay humeral component and lateralized glenoid

BackgroundOptimal glenosphere positioning in a lateralized reverse shoulder arthroplasty (RSA) to maximize functional outcomes has yet to be clearly defined. Center of rotation (COR) measurements have largely relied on AP radiographs which allow assessment of lateralization and inferior position, but ignore scapular Y radiographs which may provide an assessment of posterior and inferior position relative to the acromion. The purpose of this study was to evaluate the COR in the sagittal plane and assess the effect of glenosphere positioning with functional outcomes utilizing a 135° inlay stem with a lateralized glenoid. MethodsA retrospective review was performed on a prospectively maintained multicenter database on patients who underwent primary RSA from 2015-2021 with a 135° inlay stem. The COR was measured on minimum 2-year postoperative sagittal plain radiographs using a perfect-circle fit method. A perfect circle was made on the glenosphere and the center was marked. From there, four measurements were made: 1) center to the inner cortex of the coracoid, 2) center to the inner cortex of the anterior acromion, 3) center to the inner cortex of the middle acromion, 4) center to the inner cortex of the posterior acromion. Regression analysis was performed to evaluate any association between the position of the COR relative to bony landmarks with functional outcomes. ResultsA total of 136 RSAs met the study criteria. There was no relation with any of the distances with outcome scores (ASES, VAS). In regards to range of motion (ROM), each distance had an effect on at least one parameter. The COR to coracoid distance had the broadest association with ROM with improvements in forward flexion (FF), external rotation (ER0), and internal rotation with arm at 90° (IR90) (p = <0.001, 0.031, <0.001; respectively). The COR to coracoid distance was also the only distance to affect the final FF and IR90. For every 1 mm increase in this distance, there was a 1.8° increase in FF and 1.5° increase in IR90 (ß = 1.78; 95% CI 0.85 – 2.72, p = <0.001, ß = 1.53; 95% CI 0.65 – 2.41, p = <0.001; respectively). ConclusionEvaluating the COR following RSA in the sagittal plane suggests that posteroinferior glenosphere position may improve ROM when using a 135° inlay humeral component and a lateralized glenoid.

Correlation of Acromial Morphology With Risk and Direction of Shoulder Instability: An MRI Study

Background: The influence of bony morphology on the development of posterior shoulder instability is not well known. Purpose: To determine if acromial morphology, as measured on magnetic resonance imaging (MRI), is associated with posterior or anterior shoulder instability. Design: Cross-sectional study; Level of evidence, 3. Methods: MRI measurements of posterior acromial coverage (PAC), posterior acromial height (PAH), posterior acromial tilt (PAT), and anterior acromial coverage (AAC) were completed for 3 separate matched groups who underwent surgical intervention: posterior instability, anterior instability, and a comparison group of patients who underwent arthroscopic surgery for snapping scapula. Inclusion criteria were patients with recurrent instability <40 years of age without multidirectional instability, glenoid bone loss >13.5%, or glenoid retroversion >10%. Results: Overall, 37 patients were included in each group. PAC was significantly less in the posterior instability group than in the anterior instability and comparison groups (68.3° vs 88.7° vs 81.7°; P < .001). PAH was significantly greater in the posterior group than in the anterior instability group (11.0 mm vs −0.1 mm; P < .001) and comparison group (0.7 mm; P < .001). There was no difference between the posterior and anterior groups in terms of PAT or AAC (P = .45 and P = .05, respectively). PAT was significantly smaller in the posterior instability group than the comparison group (55.2° vs 62.2°; P = .026). The anterior and comparison groups were not significantly different in PAH or PAT (P = .874 and P = .067, respectively) but were significantly different in AAC (P = .026). Conclusion: A higher and flatter posterior acromion, as measured on preoperative MRI, appears to be associated with patients who require arthroscopic capsulolabral repair due to posterior shoulder instability. This information may help clinicians to both diagnose and predict the need for operative intervention for patients with posterior labral tears.

Poster 182: Acromial Morphology Influences Instability Risk and Direction: An MRI Study

Objectives: To determine if acromial morphology is associated with posterior or anterior shoulder instability as measured on MRI. Methods: MRI measurements of posterior acromial coverage (PAC), posterior acromial height (PAH), posterior acromial tilt (PAT), and anterior acromial coverage (AAC) were completed for three separate matched groups who underwent surgical intervention: posterior instability, anterior instability, and a comparison group of patients with who underwent arthroscopic surgery for snapping scapula. Inclusion criteria were patients with recurrent instability younger than 40 years of age without multidirectional instability, glenoid bone loss greater than 13.5% or glenoid retroversion greater than 10%. Results: Thirty-seven patients were included in each group. PAC was significantly less in the posterior instability group when compared to anterior and the comparison groups (68.3° vs. 88.7° vs. 81.7°, p&lt;.001). PAH was significantly greater in the posterior group than compared to the anterior instability patients (11.0 mm vs -0.1 mm, p&lt;.001) as well as the comparison patients (0.7 mm, p&lt;.001). There was no difference between the posterior and anterior groups in terms of PAT or AAC (p=0.45, p=0.05). PAT was significantly smaller in the posterior instability group than the comparison group (55.2 degrees vs 62.2 degrees, p=0.026). The anterior and comparison groups were not significantly different in PAH or PAT (p=8.74, p=0.067) but were significantly different with AAC (p=0.26). Conclusions: The posterior acromion is significantly higher and flatter in patients with posterior shoulder instability who require arthroscopic capsulolabral repair when measured on pre-operative MRI. This information may help clinicians to both diagnose and predict the need for operative intervention for patients with posterior labral tears.

Effectiveness of Ankle Stretching and Strengthening Exercises to Improve Rounded Shoulder Posture: A Pilot Study

Introduction: Incorrect posture habits and reduced physical activity can predispose individuals to various changes in the muscular and skeletal structures. Rounded Shoulder Posture (RSP) is one such clinical manifestation that deforms the normal relationship of various structures. Different treatment protocols have been devised for correcting RSP; however, postural changes in the musculoskeletal system can also be addressed by focusing on muscular imbalances elsewhere in the biomechanical kinetic chain. Aim: To analyse and investigate the efficacy of ankle muscle stretching and strengthening exercises in enhancing the correction of RSP in young adults. Materials and Methods: The present pilot study was conducted at Amity Institute of Physiotherapy in Noida, Uttar Pradesh, and Prime Hospital and Ortho Centre in Faridabad, Haryana, India, from January 2021 to July 2021. A total of 30 young adults with RSP were randomly allocated into two groups of 15 each. Group 1 (control group) received six weeks of conventional exercises consisting of scapular stabilisation and stretching of the pectoralis minor muscle. Group 2 (experimental group) received ankle plantar flexor stretching and ankle dorsiflexor strengthening in addition to the conventional exercises, three times per week for six weeks, with each session lasting between 30 to 45 minutes. RSP and ankle Dorsi-Flexion (DF) were assessed using the posterior Acromion to Table Distance (ATD) in a supine lying position and a universal goniometer, respectively, pre-intervention and post-intervention for the dominant and non-dominant sides. For statistical analysis, after determining the normality of the data, either a Paired-test or Wilcoxon rank sum test was used to compare the data within each group. Further, either a two-sample Independent t-test or WilcoxonMann-Whitney U test was used to find statistical differences between the two groups at a 5% level of significance. Results: The subjects had an average age of 24.8±4.07 years and a Body Mass Index (BMI) of 24.10±4.39 kg/m2 , with 11 male and 19 female participants (p-value=0.70), with the right side being the dominant side for all. At baseline, there was no significant difference in the variables between the two groups (p-value&gt;0.05). After the six-week intervention, a significant difference was found in the ATD (dominant pre: 6.17±1.02, dominant post: 3.47±1.05, p-value&lt;0.0001; non-dominant pre: 6.07±1.05, non-dominant post: 3.32±0.92, MD=-2.75; p-value&lt;0.0001) and DF (dominant pre: 16.23±1.37, dominant post: 19.27±1.33, MD=3.03; non-dominant pre: 15.67±1.05, non-dominant post: 19.53±0.74, MD=3.87; p-value&lt;0.0001) in the experimental group. However, the control group revealed a significant difference only for ATD (dominant pre: 6.51±0.89, dominant post: 4.47±0.84, MD=-2.05; non-dominant pre: 6.23±1.00, non-dominant post: 4.41±0.90, MD=-1.82; p-value&lt;0.0001). Additionally, when compared to the control group, the experimental group showed statistically significant results for ATD and DF (p-value&lt;0.05). Conclusion: The incorporation of ankle muscle strengthening and stretching exercises was found to be more effective compared to the conventional treatment used for correcting RSP.

Association of the Posterior Acromion Extension with Glenoid Retroversion: A CT Study in Normal and Osteoarthritic Shoulders.

Posterior eccentric glenoid wear is associated with higher complication rates after shoulder arthroplasty. The recently reported association between the acromion shape and glenoid retroversion in both normal and osteoarthritic shoulders remains controversial. The three-dimensional coordinates of the angulus acromialis (AA) and acromioclavicular joint were examined in the scapular coordinate system. Four acromion angles were defined from these two acromion landmarks: the acromion posterior angle (APA), acromion tilt angle (ATA), acromion length angle (ALA), and acromion axial tilt angle (AXA). Shoulder computed tomography scans of 112 normal scapulae and 125 patients with primary glenohumeral osteoarthritis were analyzed with simple and stepwise multiple linear regressions between all morphological acromion parameters and glenoid retroversion. In normal scapulae, the glenoid retroversion angle was most strongly correlated with the posterior extension of the AA (R2 = 0.48, p < 0.0001), which can be conveniently characterized by the APA. Combining the APA with the ALA and ATA helped slightly improve the correlation (R2 = 0.55, p < 0.0001), but adding the AXA did not. In osteoarthritic scapulae, a critical APA > 15 degrees was found to best identify glenoids with a critical retroversion angle > 8 degrees. The APA is more strongly associated with the glenoid retroversion angle in normal than primary osteoarthritic scapulae.

Biomechanical Analysis of Clavicle Hook Plates with a Range of Posterior Hook Offsets Implanted at Different Acromion Positions in the Acromioclavicular Joint: A Finite Element Analysis Study

The clavicle hook plate is commonly used in acromioclavicular injuries; however, the biomechanical effect of the posterior hook offset and hook position is unclear. This study applied a finite element analysis (FEA) to evaluate these parameters to improve the clinical strategy. Nine FEA models with 0-mm, 5-mm, and 10-mm posterior hook offsets implanted in the anterior, middle, and posterior acromion were established to evaluate the stress distribution and the reaction force on the acromion. The 5-mm and 10-mm posterior hook offsets at all acromion positions reduced the reaction force on the acromion but slightly increased the stress on the clavicle. The 0-mm offset increased the reaction force at all acromion positions and was relatively lower at the middle acromion. The clavicle hook plate with a posterior hook offset reduces the reaction force on the acromion, providing a flexibility of the hook position. These results provide surgeons with the biomechanical basis for the hook offset and position and engineers with the mechanical basis for the implant design.

Determination of predisposing scapular anatomy with a statistical shape model-Part II: shoulder osteoarthritis.

Shoulder osteoarthritis can be divided into different glenoid types (A, B, C, and D) and subtypes. The aim of this study was to investigate if there is an association between the prearthropathy scapular anatomy, shoulder osteoarthritis, and different glenoid types and subtypes. Using principal components analysis, a statistical shape model (SSM) of the scapula was constructed from a data set of 110 computed tomographic (CT) scans. These subjects formed the control group. Next, CT scan images of 117 patients with osteoarthritis were classified according to the modified Walch classification. A complete 3-dimensional (3D) scapular bone model was created for every patient, and using the SSM, a reconstruction of their prearthropathy scapular anatomy was performed. Automated 3D measurements were performed in both the patient and control group to obtain glenoid version and inclination, critical shoulder angle (CSA), posterior acromial slope (PAS), lateral acromion angle, scapular offset, and the rotational alignment of the coracoacromial complex. These parameters were compared between controls, patients with osteoarthritis, and glenoid types and subtypes. Mean version and inclination for the control group was 6° retroversion and 8° superior inclination (both SD 4°). The mean CSA, PAS, coracoid-posterior acromion angle, posterior acromion-scapular plane angle, and fulcrum axis ratio were 30° (SD 4°), 64° (SD 8°), 116° (SD 9°), 55° (SD 7°), and 46% (SD 4%), respectively. Patients with osteoarthritis had a significant lower CSA, posterior acromion-scapular plane angle, coracoid-posterior acromion angle, and fulcrum axis ratio (27°, 50°, 111°, and 44%, all P < .001). We found a significant difference between the control group and the respective glenoid types for the following parameters: mean CSA and coracoid-posterior acromion angle for A glenoids (27°, P = .001, and 111°, P = .007); mean version, CSA, PAS, coracoid-posterior acromion angle, posterior acromion-scapular plane angle, and fulcrum axis ratio for B glenoids (11°, 27°, 71°, 111°, 49°, and 43%, all P< .001); and mean version, CSA, and posterior acromion-scapular plane angle for D glenoids (2°, P = .002, 26°, P = .003, and 48°, P= .007). There seems to be an association between prearthropathy scapular anatomy and shoulder osteoarthritis. A small lateral extension and less posterior rotation of the acromion is associated with shoulder osteoarthritis and is present in almost all types and subtypes of glenoid morphology. Furthermore, B and D glenoids are associated with, respectively, a more and less pronounced prearthropathy glenoid retroversion.

The critical shoulder angle does not change over time: a radiographic study.

The anatomy of the scapula may predispose individuals to develop shoulder pathologies. The purpose of this study was to determine if the scapular anatomy, in particular the critical shoulder angle (CSA), changes over a long-term follow-up, or if it is a stable parameter. We hypothesized that increasing age would not influence the scapular morphology. We analyzed shoulder radiographs in our database from 2002 to 2019 to extract radiographs at an interval of at least 10 years. Radiographic analysis included measuring the CSA and assessing the acromion type according to Bigliani and Morrison, the posterior acromial height and the posterior acromial tilt. A total of 41 patients (47 shoulders) with a mean age of 53 years (range, 15-76; standard deviation [SD], ±14) fulfilled the inclusion criteria. The mean interval between the 2 sets of radiographs was 12 years (range, 10-16; SD ±2).The mean CSA did not change significantly with 34° (range, 20-41; SD ±4) at the first and 34° (range, 19-44; SD ±5) (P = .597) at the second assessment. On the initial lateral radiographs ("Neer view"), there were 11 type 1 (24%), 32 type 2 (70%), and 3 type 3 (6%) acromia according to Bigliani and Morrison. At the second assessment, there were 16 type 1 (34%), 28 type 2 (60%), and 3 type 3 (7%). Between both sets of radiographs, 11 were different (23%), without a trend in the type of change being discernible. The posterior acromial height was stable with 19 mm (range, 2-36; SD ±8) at the first and 18 mm (range, 5-38; SD ±8) at the second assessment (P = .186). The posterior acromion tilt changed from 59° (range, 34-81; SD ±10) to 62° (range, 30-81; SD ±10) (P < .001). Among 6 cases with rotator cuff tears (RCTs) already at the first assessment, the CSA did not change significantly at 10 years' follow-up (P = .414). Among the 10 cases with new RCTs at the second assessment, the CSA did not change significantly at 10 years' follow-up from 34° (range, 25-41; SD ±5) to 35° (range, 24-44; SD ±6) (P = .510). In the group of 31 shoulders without RCT, the mean CSA at the first assessment of 34° (range, 28-41; SD ±3) stayed also stable with 34° (range, 28-40; SD ±3) (P = .796). The CSA is an anatomical parameter of the scapula that does not change in size after closure of the physes.

Safe Needle Insertion Locations for Motor Point Injection of the Triceps Brachii Muscle: A Pilot Cadaveric and Ultrasonography Study.

Objective To determine the location of the motor endplate zones (MoEPs) for the three heads of the triceps brachii muscles during cadaveric dissection and estimate the safe injection zone using ultrasonography.MethodsWe studied 12 upper limbs of 6 fresh cadavers obtained from body donations to the medical school anatomy institution in Seoul, Korea. The locations of MoEPs were expressed as the percentage ratio of the vertical distance from the posterior acromion angle to the midpoint of the olecranon process. By using the same reference line as that used for cadaveric dissection, the safe injection zone away from the neurovascular bundle was identified in 6 healthy volunteers via ultrasonography. We identified the neurovascular bundle and its location with respect to the distal end of the humerus and measured its depth from the skin surface.ResultsThe MoEPs for the long, lateral, and medial heads were located at a median of 43.8%, 54.8%, and 60.4% of the length of the reference line in cadaver dissection. The safe injection zone of the medial head MoEPs corresponded to a depth of approximately 3.5 cm from the skin surface and 1.4 cm away from the humerus, as determined by sonography.ConclusionCorrect identification of the motor points for each head of the triceps brachii would increase the precision and efficacy of motor point injections to manage elbow extensor spasticity.

Posterosuperior shoulder dislocation due to the rupture of deltoid posterior fibers: a case report

BackgroundSuperior shoulder dislocation is a rare type of shoulder dislocation. Its occurrence is thought to be associated with rupture of the deltoid; however, few reports are available on the mechanism of onset and the treatment of a superior shoulder dislocation. Here we describe a case of dislocation in the direction of the posterior acromion, referred to as posterosuperior shoulder dislocation, caused by the traumatic rupture of deltoid posterior fibers.Case presentationAn 83-year-old woman who fell on her right elbow in the hospital presented to our department with complaints of right shoulder pain. She had been undergoing conservative treatment for a massive rotator cuff tear and a rupture of the long head of biceps tendon 5 years previously. X-ray radiography images at the time of the trauma revealed that the right humeral head was dislocated upwards and in the direction of the posterior acromion. Magnetic resonance imaging (MRI) revealed newly ruptured deltoid posterior fibers, in addition to the massive rotator cuff tear. Closed reduction was performed and the shoulder joint was held in external rotation at 30 degrees for 6 weeks. However, re-dislocation was observed at an early stage after the removal of the orthosis and marked instability remained.ConclusionsThis is the first case of posterosuperior shoulder dislocation. It suggests that rupture of the deltoid posterior fibers contributes to the onset of posterosuperior shoulder dislocation in patients with a massive rotator cuff tear. Moreover, in superior shoulder dislocation, conservative treatment may result in continuing instability which requires surgical treatment.

Effect of breast cancer surgery on chest tightness and upper limb dysfunction.

This study aimed to investigate the possible changes in anterior chest tightness after breast cancer surgery. We also try to investigate whether anterior chest tightness is associated with upper-limb dysfunction after breast cancer surgery. Eighty-three women who underwent breast cancer surgery were evaluated before and 2 weeks, 3 months, and 9 months after surgery. Anterior chest tightness was measured using the length of the pectoralis minor muscle through 2 methods (length from the coracoid process to the fourth rib and linear distance from the table to the posterior acromion with supine position). Shoulder range of motion and the K-DASH (Korean version of Disability Arm and Shoulder Questionnaire) score were measured to quantify functional performance of upper limb. Anterior chest tightness of patients with breast cancer significantly increased after surgery. Upper limb dysfunction was observed such as reduced shoulder range-of-motion and increased K-DASH score over time. Increase in chest tightness was correlated with shoulder range-of-motion reduction. Chest tightness was not correlated with K-DASH score directly. However, shoulder range-of-motion reduction was significantly correlated with K-DASH score. Chest tightness and upper limb dysfunction increased in breast cancer survivor. Increase in chest tightness after surgery is associated with upper limb dysfunction and careful attention is required.

Acromial J-bone graft on the acromion for surgical treatment of glenohumeral instability: an anatomical study.

Anterior glenohumeral instability is frequently associated with anteroinferior glenoid bone defects. One original technique has been described in the literature that incorporates a J-shaped graft from the iliac crest into the anterior glenoid rim. The main goal of the present study was to evaluate the feasibility of harvesting a J-shaped graft from the acromion that corresponds to previously described dimensions. The secondary goal was to determine the ideal harvesting site. Forty shoulders from 20 cadavers were included. Twenty grafts were harvested from the posterior acromion and 20 from the lateral acromion. The length, width and thickness of the grafts were measured. The incision was then enlarged to confirm the absence of an acromial fracture by fluoroscopic control. Harvesting a graft whose size was similar to a J-graft was successfully performed in all cases (100%) with a mean (SD) incision of 4.2 (0.3) cm. Mean (SD) harvesting time was 4.5 (0.5) minutes. Two acromial fractures were identified during lateral harvesting (10%) and none during posterior harvesting (p = 0.49). It is always possible to harvest a J-graft on the acromion. The posterior side of the acromion is the best site to harvest a graft that has the necessary size to treat glenoid bone defects.

Arthroscopic lateral acromion resection (ALAR) optimizes rotator cuff tear relevant scapula parameters

The acromion index (AI), critical shoulder angle (CSA) and lateral acromion angle (LAA) are predictive for degenerative rotatory cuff tears. Their unfavorable values are associated with a suboptimal deltoid force vector. The aim of this study was to evaluate whether an optimization of the radiological parameters could be achieved through a specific arthroscopic lateral acromion resection (ALAR). The procedure was performed in eight fresh frozen cadaver shoulders. True a.p. and axial radiographs were taken before and after the intervention for radiological evaluation. The anterior and posterior acromion edges were marked with a spinal needle. Then 1cm of the lateral acromion was resected with a 5.0 acromionizer (Arthrex Inc., Naples, FL, USA) beginning from the anterior aspect. The resection was completed over the total width of 1cm from anterior to posterior. Finally the deltoid insertion was dissected via an open approach to ensure its integrity. The fluoroscopy images were evaluated regarding the pre- and postinterventional parameters AI, CSA and LAA. After the intervention, the mean AI could be significantly reduced from 0.62±0.11 to 0.40±0.15 (p=0.012). Also the mean CSA was significantly reduced from 35.0°±7.65° to 25.12°±8.29° (p=0.018). The LAA could not be significantly changed (76.5°±14.02° vs. 82.13±8.93; p=0.107). There was no injury to the deltoid insertion. The radiographic parameters AI und CSA can be optimized significantly by ALAR without macroscopic discontinuity of the deltoid insertion. Level IV, case series without comparison group.

Measurement of dynamic scapular kinematics using an acromion marker cluster to minimize skin movement artifact.

The measurement of dynamic scapular kinematics is complex due to the sliding nature of the scapula beneath the skin surface. The aim of the study was to clearly describe the acromion marker cluster (AMC) method of determining scapular kinematics when using a passive marker motion capture system, with consideration for the sources of error which could affect the validity and reliability of measurements. The AMC method involves placing a cluster of markers over the posterior acromion, and through calibration of anatomical landmarks with respect to the marker cluster it is possible to obtain valid measurements of scapular kinematics. The reliability of the method was examined between two days in a group of 15 healthy individuals (aged 19-38 years, eight males) as they performed arm elevation, to 120°, and lowering in the frontal, scapular and sagittal planes. Results showed that between-day reliability was good for upward scapular rotation (Coefficient of Multiple Correlation; CMC = 0.92) and posterior tilt (CMC = 0.70) but fair for internal rotation (CMC = 0.53) during the arm elevation phase. The waveform error was lower for upward rotation (2.7° to 4.4°) and posterior tilt (1.3° to 2.8°), compared to internal rotation (5.4° to 7.3°). The reliability during the lowering phase was comparable to results observed during the elevation phase. If the protocol outlined in this study is adhered to, the AMC provides a reliable measurement of upward rotation and posterior tilt during the elevation and lowering phases of arm movement.

Spontaneous Healing of Acromial Stress Fracture Caused by Clavicle Hook Plate in Acromioclavicular Joint Dislocation: A Case Report

Clavicular hook plate is known to be an effective treatment on acromioclavicular (AC) joint injury, but there have been some reports of complications, like osteolysis and bony erosion of the undersurface of acromion. Fifty-five year old male underwent open reduction and hook plate insertion on Rockwood type 5 acromioclavicular joint dislocation. He complained of protrusion of posterior acromion at 1 month after the surgery, and acromial fracture was noted in simple radiographs. The hook plate was removed and any other treatment for osteosynthesis was refused by the patient. At the 18 months after the surgery, the patient had no pain and a full range of motion with no tenderness around the shoulder joint. After two years, plain radiographs revealed complete bony union of the acromion fracture.

Measurement of subacromial impingement of the rotator cuff

Objective: Recent evidence suggests that shoulder impingement syndrome arises from primary rotator cuff pathology and may be related to the inability of the rotator cuff to prevent superior humeral head migration in shoulder elevation. Impingement involves compression of subacromial structures, including the rotator cuff. Previously, clinical tests have been shown to be inaccurate in diagnosing rotator cuff impingement. A lack of anatomical validity might explain the inaccuracy of these tests. This study aimed to clarify the anatomical basis of subacromial compression of the rotator cuff by analysing the compression forces generated and observing the structures impinged in a variety of shoulder positions. Design: This observational case series involved the dissection of nine embalmed cadaveric shoulders. Method: Pressure transducers were placed deep to the coracoid process, coracoacromial ligament, the anterior acromion and the posterior acromion. Shoulders were moved into internal and external rotation from the positions of flexion, abduction and extension. At each position, pressure readings were recorded and structures being compressed observed visually. Results: Highest pressures were recorded in flexion/internal rotation at the coracoacromial ligament, in abduction/internal rotation at the coracoid process (both involving the rotator interval) and in abduction/internal rotation at the coracoacromial ligament (involving supraspinatus). Supraspinatus was also observed to be compressed in extension/external rotation (against the anterior acromion). Infraspinatus was compressed in extension/external rotation (against the posterior acromion), while subscapularis was compressed in flexion/internal rotation and flexion/external rotation (both against the coracoid process). Conclusion: This study identifies shoulder positions likely to impinge particular rotator cuff tendons.

Anatomical validity of the Hawkins–Kennedy test – A pilot study

Purpose Despite routine use, clinical tests used to diagnose subacromial impingement often display poor diagnostic accuracy. A lack of anatomical validity may contribute to the poor diagnostic accuracy. The current study aimed to examine the anatomical validity of measuring subacromial pressure in the Hawkins–Kennedy impingement test in a cadaveric shoulder. Methods Subacromial pressures were measured using pressure transducers in non-provocative and provocative Hawkins–Kennedy test positions using an ABA research design with 25 repeated measures in one cadaver. Data collected included pressure at four subacromial locations (coracoid process, coraco-acromial ligament, anterior acromion and posterior acromion), and observation of anatomical structures impinging on transducers. The split-middle method of visual analysis and the Reliable Change Index (RCI) were applied to examine any differences between provocative and non-provocative positions. Results There was increased pressure in the provocative position at the coraco-acromial ligament, which impinged biceps brachii, and at the anterior acromion, which impinged the rotator interval. Conclusion Findings of the current study provide evidence that suggest that structures other than the rotator cuff tendons may be impinged during the Hawkins–Kennedy test.

Propionibacterium acnes colonization of the human shoulder

Propionibacterium acnes (P. acnes) is frequently cultured in patients with wound infections after shoulder surgery. The purpose of this study was to characterize the colonization of various anatomic locations with P. acnes in order to explain this clinical observation. Culture samples were collected from the skin overlying the shoulder, hip, and knee of 20 subjects (10 male, 10 female). Semi-quantitative cultures of P. acnes and Staphylococcus species were performed to define bacterial prevalence and burden at each site. The participants completed a questionnaire that assessed skin health, hygiene, and co-morbid medical conditions. Physical examination was performed to define local skin characteristics. Anterior and posterior acromial sites had a greater prevalence of P. acnes than the hip (anterior p=0.018; posterior p= 0.038) and knee (anterior p=0.0014; posterior p= 0.035) sites. The axilla had a greater prevalence of P. acnes than the knee (p=0.008). Males had a greater prevalence of P. acnes than females at the anterior (p=0.007) and posterior acromion sites (p=0.025). The burden of P. acnes at the anterior acromion (p=0.024), posterior acromion (p=0.035), and axilla (p=0.03) was greater than the mean burden at the hip. The burden of P. acnes at the anterior acromion (p=0.004), posterior acromion (p=0.007), and axilla (p=0.008) was greater than the mean burden at the knee. Males had a greater burden of P. acnes than females at the acromial sites (anterior p=0.0049; posterior p=0.0131). Propionibacterium acnes colonizes the shoulder at increased rates compared to the knee and hip, and men have a higher bacterial burden than females. These findings are consistent with clinical observations of postoperative shoulder infections. Basic science study.

Effects of shoulder position on axillary nerve positions during the split lateral deltoid approach

The axillary nerve may be injured during percutaneous fixation of proximal humerus fractures. This study investigated the kinematic behavior of the superior and inferior borders of the axillary nerve under varying shoulder positions. This information may reduce iatrogenic neurologic injury during fracture reduction and hardware placement. The lateral deltoid approach was performed on 7 fresh frozen shoulders. The inferior and superior borders of the axillary nerve were tagged. Screws were placed in the anterior, middle, and posterior acromion as landmarks. Three-dimensional distances of the inferior and superior border of the nerve were measured to the mid-acromion while the shoulder was placed in combinations of forward flexion, vertical abduction, and humeral rotation. The distances were compared by repeated measures ANOVA statistical analysis. The distance from the mid-acromion to the superior border of the axillary nerve was 66.6 mm (+/-5.7), and to the inferior axillary nerve was 75.7 mm (+/-5.8) with the shoulder in neutral position. Vertical abduction to 60 degrees significantly moved the superior and inferior borders of the axillary nerve to a distance of 53.9 (+/-7.7) and 61.6 mm (+/-8.1), respectively (P < 0.005). Forward flexion had no significant effect on the position of the axillary nerve (P > 0.5). The longest distance from the mid-acromion to the inferior border of the axillary nerve was 86 mm with the arm forward flexed. The main determinant of axillary nerve position with respect to the acromion is vertical abduction. Axillary nerve position is essentially unaffected by varying degrees of humeral rotation and forward flexion. Vertical glenohumeral abduction to 60 degrees is required to move the nerve significantly closer to the acromion.