Dynamic stability of the glenohumeral joint

Ultrasonographic Measurement of Torsional Side Difference in Proximal Humerus Fractures and Humeral Shaft Fractures: Theoretical Background with Technical Notes for Clinical Implementation

Both nonoperative and operative treatment of proximal humerus fractures (PHF) and humeral shaft fractures can result in torsional side differences. Several measurement methods are available to determine torsional malalignment. While conventional X-ray or computed tomography would entail additional radiation exposure for the patient, and while magnetic resonance imaging might be associated with higher costs and is not suitable in cases of surgically treated fractures due to metal-induced artifacts, the sonographic measurement of humeral torsion represents a readily available and quickly performable measurement method without radiation exposure. Both fully sonographic procedures and sonographically assisted procedures have been described in the literature for this purpose. To date, however, its application in the case of trauma patients, for example those with healed PHF and humeral shaft fractures, is not reported. This viewpoint article aims to provide a concise summary of the literature concerning ultrasonographic indirect measurements of humeral torsional side differences, with technical notes for clinical implementation in case of healed proximal humerus fractures and humeral shaft fractures.

Humeral head coverage in arthroscopic partial repair of massive rotator cuff tears improves functional outcomes: an analysis of influential factors

BACKGROUND

Although partial rotator cuff repair has shown good outcomes, differences in clinical outcomes remain concerns. This study was performed to determine whether patients with humeral head coverage would show better functional outcomes than patients without humeral head coverage and to identify the factors for humeral head coverage after arthroscopic partial repair of massive tears.

METHODS

We performed a retrospective study of 63 patients with massive rotator cuff tears who underwent arthroscopic partial repair between 2012 and 2018. Two to four margin convergences were first performed; then, the Mason-Allen technique was performed. The patients were divided into 2 groups: those with humeral head coverage (38 cases) and those without humeral head coverage (25 cases). The following factors were evaluated: age; sex; hypertension; diabetes; osteoporosis; preoperative and postoperative pseudoparalysis, visual analog scale (VAS) pain score, Constant score, acromiohumeral distance, and subacromial bony spur; and subscapularis tear and repair. Muscle atrophy and fatty degeneration were evaluated by magnetic resonance imaging preoperatively, and the integrity of the repaired cuff was evaluated by ultrasonography at a minimum of 2 years after surgery.

RESULTS

Compared with preoperative values, significant improvements in VAS pain scores (from 6.27 to 2.32 in patients with humeral head coverage and from 7.00 to 2.81 in those without humeral head coverage) and Constant scores (from 51.35 to 75.95 and from 44.62 to 69.81, respectively) were observed in both groups (P < .001). Statistical analysis revealed that postoperative VAS pain scores (2.32 vs. 2.81) and Constant scores (75.95 vs. 69.81) in patients with humeral head coverage were superior to those in patients without humeral head coverage (P = .044 and P = .003, respectively). The integrity of the repaired cuff was evaluated by ultrasonography, and partial tears were found in 4 of 37 patients with humeral head coverage and 2 of 26 patients without humeral head coverage (P = .816). Univariable logistic regression analysis revealed that age (P < .001), comorbidity (P = .005), symptom duration (P = .023), preoperative shoulder mobility (P < .001), maintained acromiohumeral distance (P = .006), subscapularis tear (P = .026), and less preoperative supraspinatus and infraspinatus muscle atrophy (P = .001 and P = .010, respectively) had significant correlations with humeral head coverage.

CONCLUSIONS

Overall satisfactory results were achieved in most patients regardless of high retear rates, but patients with partial repair covering the humeral head were associated with better outcomes than patients without humeral head coverage. Multivariable regression analysis revealed that age (<70 years, P = .003), capability of shoulder mobility (P = .005), maintenance of the acromiohumeral space (>7 mm, P = .016), and less atrophy of the rotator cuff muscles (P = .021) were favorable factors to achieve humeral head coverage during surgical partial repair of massive rotator cuff tears.

Computer-Assisted Preoperative Planning and Patient-Specific Instrumentation for Glenoid Implants in Shoulder Arthroplasty

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Glenoid component positioning affects implant survival after total shoulder arthroplasty, and accurate glenoid-component positioning is an important technical aspect.

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The use of virtual planning and patient-specific instrumentation has been shown to produce reliable implant placement in the laboratory and in some clinical studies.

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Currently available preoperative planning software programs employ different techniques to generate 3-dimensional models and produce anatomic measurements potentially affecting clinical decisions.

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There are no published data, to our knowledge, on the effect of preoperative computer planning and patient-specific instrumentation on long-term clinical outcomes.

Management of rotator cuff tears - Key historical landmarks

The management of rotator cuff pathology has developed over hundreds of years. In this article, we take a journey from the early days, in order to understand how we have reached our modern-day practice. Initially our understanding of rotator cuff pathology was based on cadaveric anatomical findings and this has enhanced over the years by the development of radiological and surgical techniques. We discuss the historical debates over the pathogenesis of cuff dysfunction. This work describes the landmark publications by several clinicians who have made important contributions to our understanding of rotator cuff pathology and its management. We follow the trends of surgical management of rotator cuff tears, traditionally performed via an open technique, to an exponential rise in arthroscopic surgery in recent years. As new techniques emerge, a review of the historical rise and fall of techniques is a reminder for us to remain vigilant of surgical indications and rigorous outcome analysis.

Investigation of the range of motion of the shoulder joint in subjects with rotator cuff arthropathy while performing daily activities

Background

Patients who have rotator cuff arthropathy experience a limited range of motion (ROM) of the shoulder joint and experience problems in performing their daily activities; however, no evidence is available to suggest the exact ROM of the shoulder joint in this population. Therefore, this study sought to determine the degree of motion of the shoulder joint in three planes during different activities.

Methods

Five subjects with rotator cuff injuries participated in this study. The motion of the shoulder joints on both the involved and normal sides was assessed by a motion analysis system while performing forward abduction (task 1), flexion (task 2), and forward flexion (task 3). The OpenSIM software program was used to determine the ROM of the shoulder joints on both sides. The difference between the ranges of motion was determined using a two-sample t-test.

Results

The ROMs of the shoulder joint in task 1 were 93.5°±16.5°, 72.1°±2.6°, and 103.9°±25.7° for flexion, abduction, and rotation, respectively, on the normal side and 28°±19.8°, 31°±31.56°, and 48°±33.5° on the involved side (p<0.05). There was no significant difference between the flexion/extension and rotation movements of the shoulder joint when performing task 1. However, the difference between flexion and rotation movements of the shoulder joints for the second task was significant (p>0.05).

Conclusions

Those with rotator cuff arthropathy have functional limitations due to muscle weakness and paralysis, especially during the vertical reaching task. However, although these individuals have decreased ROM for transverse reaching tasks, the reduction was not significant.

The biomechanics of the rotator cuff in health and disease - A narrative review

The rotator cuff has an important role in the stability and function of the glenohumeral joint. It is a complex anatomic structure commonly affected by injury such as tendinopathy and cuff tears. The rotator cuff helps to provide a stabilising effect to the shoulder joint by compressing the humeral head against the glenoid cavity via the concavity compression mechanism. To appreciate the function of the cuff it is imperative to understand the normal biomechanics of the cuff as well as the mechanisms involved in the pathogenesis of cuff disease. The shoulder joint offers a wide range of motion due to the variety of rotational moments the cuff muscles are able to provide. In order for the joint to remain stable, the cuff creates a force couple around the glenohumeral joint with coordinated activation of adjacent muscles, which work together to contain the otherwise intrinsically unstable glenohumeral joint and prevent proximal migration of the humerus. Once this muscular balance is lost, increased translations or subluxation of the humeral head may result, leading to changes in the magnitude and direction of the joint reaction forces at the glenohumeral joint. These mechanical changes may then result in a number of clinical presentations of shoulder dysfunction, disease and pain. This narrative review aims to highlight the importance of functional rotator cuff biomechanics whilst assessing the kinetics and kinematics of the shoulder joint, as well as exploring the various factors involved in cuff disease.

Does the posterior glenoid osteotomy reduce the rate of recurrence in patients with posterior shoulder instability - A systematic review

BACKGROUND

Posterior shoulder instability (PSI) is becoming an increasingly recognised condition. A number of different treatment modalities exist to treat PSI including arthroscopic or open surgeries when non-operative treatment has failed. The primary aim of this systematic review was to analyse the rate of recurrent instability after posterior glenoid osteotomy (PGO) for recurrent PSI, while secondary aim was to identify complication rate and the amount of retroversion correction.

PATIENTS AND METHODS

A review of the online databases MEDLINE and Embase was conducted on 1 November 2019 according to PRISMA guidelines. The review was registered prospectively in the PROSPERO database (Registration No. CRD42020161984). Clinical studies reporting either the recurrence rate, complications or amount of retroversion correction after PGO for PSI were included. The studies were appraised using the Methodological Index for Non-Randomized Studies (MINORS) tool.

RESULTS

The search strategy identified 9 studies eligible for inclusion. Of the 9 studies, 4 showed an improvement in retroversion with a mean change in retroversion of 10^o. All 9 studies reported on recurrence rate with an overall rate of 22%. Complications were discussed in only 7 of the studies with overall rate of 18.3%. The most common complication reported in the studies were degenerative changes of the glenohumeral joint (7.3%) and iatrogenic fractures (5.5%).

CONCLUSION

PGO is a viable option in patients with recurrent PSI that have increased retroversion and have failed non-operative or arthroscopic treatment. It does however carry a significant risk of complications.

LEVEL OF EVIDENCE

IV; Systematic review.

Isokinetic evaluation of the shoulder and elbow after Latarjet procedure

BACKGROUND/HYPOTHESIS

The Latarjet procedure changes the anatomy of the shoulder, moving the coracoid process distally through an incision in the subscapularis muscle. Some authors have studied the effect of this surgery on shoulder rotator strength. Our hypothesis is that the Latarjet procedure decreases elbow supination and flexion strength.

METHODS

A retrospective case series, evaluating patients submitted to the Latarjet procedure between May 2013 and June 2017. Movements of the elbow (supination, pronation, flexion and extension) and shoulder (internal and external rotation) were evaluated bilaterally using a Biodex System 3 isokinetic dynamometer (Biodex Medical Systems, New York) in concentric/concentric mode.

RESULTS

We evaluated 20 patients with an average follow-up of 36 months. In the elbow, we observed a 9.1% decrease in supination strength at a speed of 60°/s (p=0.044), without statistical difference at 120°/s (p=0.570). In the shoulder, there was a 13.5% decrease in external rotation strength at 60°/s and 4.5% at 180°/s (p=0.009 and p=0.040, respectively). The other movements did not demonstrate any statistically significant differences.

CONCLUSION

After the Latarjet procedure, the supination strength at 60°/s was decreased, as was the external rotation strength of the shoulder at 60°/s and 180°/s. We did not observe any reduction in strength for shoulder flexion or internal shoulder rotation.

LEVEL OF EVIDENCE

IV, case series.

Influence of Shoulder Position on Functional Control Ratio During Isokinetic Assessment

CONTEXT

One of the possible mechanisms leading to secondary impingement syndrome may be the strength imbalance of shoulder rotators which is known as functional control ratio (FCR). The FCR is a ratio dividing the eccentric peak torque of the external rotators by the concentric peak torque of the internal rotators. Previous studies have focused on the reproducibility and reliability of isokinetic assessment, but there is little information on the influence of variable shoulder positions on FCR.

OBJECTIVE

To compare shoulder FCR across 3 different shoulder abduction positions during isokinetic assessment.

DESIGN

Cross-sectional study.

SETTING

Biomechanics laboratory.

PARTICIPANTS

Thirty-one healthy young university students (age 22.35 [0.95] y, weight 60.52 [9.31] kg, height 168.23 [9.47] cm).

INTERVENTIONS

The concentric peak torque of internal rotators and eccentric peak torque of external rotators of right shoulder were measured on an isokinetic dynamometer.

MAIN OUTCOME MEASURES

Concentric peak torque of the internal rotators and eccentric peak torque of the external rotators, measured using an isokinetic dynamometer.

RESULTS

The concentric peak torque of internal rotators was significantly lower at 120° shoulder abduction compared with other positions (P < .001). The FCR was significantly higher at 120° shoulder abduction than 90° (P = .002) or 60° (P < .001) shoulder abduction because of the lower concentric peak torque. No significant difference was found in the FCR between the other 2 shoulder positions (P = .14).

CONCLUSIONS

Shoulder position variations may influence FCR because of weakness of the internal rotators. Rehabilitation and injury prevention training programs should specifically focus on strengthening the internal rotators at more elevated angles of shoulder abduction.

Posterior Shoulder Instability: What to Look for

Posterior shoulder instability is often hard to diagnose with clinical examination. Patients generally present with vague pain, weakness, and/or joint clicking but less frequently complaining of frank sensation of instability. Imaging examinations, especially MR imaging and magnetic resonance arthrography, have a pivotal role in the identification and management of this condition. This review describes the pathologic micro/macrotraumatic magnetic resonance features of posterior shoulder instability as well as the underlying joint abnormalities predisposing to this condition, including developmental anomalies of the glenoid fossa, humeral head, posterior labrum, and capsular and ligamentous structures.

Magnetic Resonance Imaging Correlates With Computed Tomography for Glenoid Version Calculation Despite Lack of Visibility of Medial Scapula

PURPOSE

To assess the accuracy of measuring glenoid version on magnetic resonance imaging (MRI) in the presence of varying amounts of the medial scapula body as compared with the gold standard of glenoid version measured on computed tomography (CT) imaging, including the entire scapula in a cohort of young patients with shoulder instability and without glenohumeral arthritis.

METHODS

A retrospective review was performed on instability patients with preoperative MRI and CT imaging. Measurements of available scapular width and glenoid version were performed using the Cobb angle method to measure the angle between the plane of the glenoid fossa to Friedman's line on axial images. Intra- and interrater reliability analysis was performed using intraclass correlation coefficients to assess agreement between MRI and CT measurements. Paired t tests were used to compare measurement differences between MRI and CT.

RESULTS

Thirty-two patients with both MRI and CT scans were assessed. Intra- and inter-rater assessment revealed strong agreement for scapular width measurement. For glenoid version measurement, intra-rater agreement was excellent and inter-rater agreement was moderate on CT and good on MRI. The mean available scapular body width was 24.7 mm longer on CT as compared with MRI (95% confidence interval 17.5-31.9, P < .0001; 109.8 ± 8.2 mm vs 85.1 ± 16.9 mm, respectively), with MRI having an average of 78.2% (±17.6%) of the CT scapular width shown on CT. No significant difference in glenoid version was found between MRI and CT (95% confidence interval -0.87 to 1.75, P = .499; MRI -2.57° vs CT -2.13°).

CONCLUSION

MRI provided significantly shorter available scapular widths when compared with CT imaging in a cohort of patients with glenohumeral instability and without arthritis. However, this failed to produce a significant difference of ≥5° in measured glenoid version compared with CT measurements when 75% (8 cm) of the scapular width was present on MRI. Measuring glenoid version on MRI does not appear to be significantly affected when the entirety of the medial border of the scapula is not included in the imaging field.

LEVEL OF EVIDENCE

Level III; study of diagnostic test.

Bone defect-induced alteration in glenoid articular surface geometry and restoration with coracoid transfer procedures: a cadaveric study

BACKGROUND

This study analyzed the alteration in glenoid articular geometry with increasing anterior bone loss, as well as its subsequent correction with 2 modifications of the Latarjet procedure.

METHODS

Anterior defects were simulated by creating glenoid osteotomies (10%, 20%, 30%, and 40%), and defects were reconstructed using 2 Latarjet modifications (classic and congruent arc). A total of 108 computed tomography scans were performed (1) on intact scapulae (n = 12), (2) after each bone defect (n = 48), and (3) after each reconstruction (n = 48). Glenoid parameters (width, area, arc length, and version) were analyzed on computed tomography scans. Statistical analysis was used to determine significant differences between intact, deficient, and reconstructed glenoids.

RESULTS

All parameters were reduced with every 10% defect increment (mean change in width, 2.5 mm; area, 64 mm²; version, 2.2°; and arc length, 2.2 mm). Width correction with the classic Latarjet procedure was not statistically significant in 30% and 40% defects. Area correction in 30% defects was not significant with the classic Latarjet procedure and was significantly undercorrected in 40% defects. Version correction was not significant after the classic Latarjet procedure in 20%, 30%, and 40% defects. Arc-length correction was not significant in 20% and 30% defects with the classic Latarjet procedure and was significantly undercorrected in 40% defects. The congruent-arc Latarjet procedure overcorrected glenoid parameters in all defects; however, area and arc length were not significantly different from intact glenoids in 40% defects (P < .05).

CONCLUSION

Glenoid articular geometry is progressively altered with a sequential increase in anterior bone defects from 0% to 40%. The classic Latarjet procedure provided significant correction in bone defects of 10% and 20%. The congruent-arc Latarjet procedure restored and overcorrected most parameters even in 40% glenoid defects.

[Torsional malalignment of the humerus]

The torsion of the humerus describes the physiological rotation of the humerus around its longitudinal axis. Various clinical and radiological methods for measurement have been described. The computed tomography method is currently the gold standard. The angle between the humeral head axis and the transepicondylar axis is measured. This angle is called retroversion. Values of retroversion vary between 10° and 40°. For the treatment of many humeral pathologies, a precise reconstruction of the anatomical retroversion is required. The retroversion of the humerus has to be considered in shoulder arthroplasty, in fracture situations and also in planning correction of posttraumatic deformities. If an orientation to the original anatomical landmarks of the humerus is no longer possible, an orientation to the contralateral side is recommended.

The Walch type B humerus: glenoid retroversion is associated with torsional differences in the humerus

BACKGROUND

The Walch type B glenoid has the hallmark features of retroversion, joint subluxation, and bony erosion. Although the type B glenoid has been well described, the morphology of the corresponding type B humerus is poorly understood. As such, the aim of this imaging-based anthropometric study was to investigate humeral torsion in Walch type B shoulders.

METHODS

Three-dimensional models of the full-length humerus were generated from computed tomography data for the Walch type B group (n = 59) and for a control group of normal nonarthritic shoulders (n = 59). An anatomic humeral head-neck plane was created and used to determine humeral torsion relative to the epicondylar axis. Measurements were repeated, and intraclass correlation coefficients were calculated.

RESULTS

The type B humeri had significantly (P < .001) less retrotorsion (14° ± 9°) than the control group (36° ± 12°) relative to the epicondylar axis. Male and female individuals within the control group showed statistically significant differences in humeral torsion (P = .043), which were not found in the type B group. Inter-rater reliability showed excellent agreement for humeral torsion (intraclass correlation coefficient, 0.962). A subgroup analysis between Walch type B2 and B3 shoulders showed no significant differences in any of the humeral or glenoid parameters.

CONCLUSION

The Walch type B humerus has significantly less retrotorsion than non-osteoarthritic shoulders. At present, it is unknown whether the altered humeral retrotorsion is a cause or effect of the type B glenoid. In addition, it is unknown whether surgeons should be reconstructing type B2 humeral component version to pathologic torsion or to nonpathologic population means to optimize arthroplasty survivorship.

Seasonal changes in glenohumeral joint isokinetic strength in professional rugby league players

OBJECTIVE

To assess glenohumeral joint (GHJ) rotation strength across a rugby league season, since strength of rotator cuff musculature may protect against contact injuries to the shoulder.

DESIGN

A prospective cohort study was used to compare GHJ rotation pre-, in-, and post-season.

SETTING

Laboratory.

PARTICIPANTS

Twenty-nine players from a professional European Super League club.

MAIN OUTCOME MEASURES

Isokinetic dynamometry for concentric and eccentric muscle actions for shoulder internal and external rotation at 240°/s. Peak torque, traditional strength ratios, and dynamic control ratios were compared.

RESULTS

There were no significant differences between peak torque strength parameters at any time point. Similarly, differences in strength ratios failed to reach statistical significance across the season. Ipsilateral strength ratios were indicative of selective strengthening of internal rotators for concentric and eccentric muscle actions.

CONCLUSIONS

The findings suggest that rugby league players are no more likely to sustain a shoulder injury in the latter stages of the season as a result of decreased GHJ rotation strength. Players were able to maintain strength across the season which is valuable to practitioners developing conditioning programmes to optimise performance and minimise the risk of injury. This may afford protection, particularly during forced external rotation following physical contact.

Return to play after arthroscopic treatment for shoulder instability in elite and professional baseball players

BACKGROUND

This study evaluated the clinical outcome of arthroscopic treatment for anterior shoulder dislocation in elite and professional baseball players.

METHODS

This study included 51 baseball players who underwent arthroscopic Bankart repair between 2008 and 2015. The follow-up duration was set at 24 months or longer, based on clinic visit or telephone survey. After surgery, players who played in 1 or more official games were considered to have returned to play (RTP), and those who participated in more than 10 official games were considered to have solidly returned to play (sRTP). The RTP and sRTP rates were analyzed by player position (pitcher, catcher, and in-fielder), and the period of RTP after surgery (rehabilitation period) was investigated.

RESULTS

Of 51 baseball players (mean age, 20.9 years), 14 were pitchers, 6 were catchers, and 31 were in-fielders. Pitchers showed 64% RTP and 57% sRTP, catchers, 83% RTP and 83% sRTP, and in-fielders, 90% RTP and 90% sRTP. The overall RTP and sRTP rates were 82% and 80%, respectively. The average RTP period after surgery (rehabilitation period) was 8.4 months, with 9.6, 9.1, and 7.4 months for pitchers, catchers, and in-fielders, respectively.

CONCLUSIONS

The RTP after arthroscopic Bankart repair shows favorable results, with the nonthrowing shoulder and in-field position yielding the best results. Players undergoing arthroscopic Bankart repair and the surgeon should be aware of the possible outcomes based on the throwing/nonthrowing arm and various positions.

Biomechanics of posterior shoulder instability - current knowledge and literature review

Posterior instability of the shoulder is a rare condition and represents about 10% of shoulder instability. It has become more frequently recognized in the last year, even though it is more difficult to diagnose than anterior shoulder instability. As this form of shoulder pathology is somewhat rare, biomechanical knowledge is limited. The purpose of our study was to perform an extensive literature search, including PubMed and Medline, and to give an overview of the current knowledge on the biomechanics of posterior shoulder instability. The PubMed/Medline databases were utilized, and all articles related to posterior shoulder instability and biomechanics were included to form a comprehensive compilation of current knowledge. A total of 93 articles were deemed relevant according to our inclusion and exclusion criteria. As expected with any newly acknowledged pathology, biomechanical studies on posterior shoulder instability remain limited in the literature. Current biomechanical models are performed in a static manner, which limits their translation for explaining a dynamic pathology. Newer models should incorporate dynamic stabilization of both the rotator cuff and scapulothoracic joint. There is a current lack of knowledge with regards to the pathomechanism of posterior shoulder instability, with no consensus on appropriate treatment regimens. Further investigation is therefore required at both basic science and clinical levels.

Does Anchor Placement on the Glenoid Affect Functional Outcome After Arthroscopic Bankart Repair?

BACKGROUND

In arthroscopic Bankart repair, anchor positions can affect glenoid labral height and functional outcomes.

PURPOSE

To evaluate anchor placement on the glenoid during Bankart lesion repair and determine which placement would lead to better functional outcomes.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHOD

This study included 90 patients (74 males, 16 females; average age, 23.7 years; range, 18-47 years) who underwent surgery for Bankart lesions between December 2009 and March 2014. The mean follow-up duration was 32.7 months (range, 26-48 months). We divided anchor positions into 2 groups: on the glenoid face and at the glenoid edge. The anchor position on the glenoid and the labral height were examined with computed tomography (CT) arthrography at 4.5-month follow-up, and Rowe scores were calculated at 2-year follow-up.

RESULTS

The group with the anchor placed on the glenoid face contained 63 patients, and the group with the anchor placed at the glenoid edge or rim contained 27 patients. Mean labral heights at 4.5 months postoperatively in the 2 groups were 5.4 ± 0.22 mm and 3.2 ± 0.16 mm, respectively ( P < .01), and mean Rowe scores at 2 years were 94.7 and 79.5, respectively ( P < .01). Rowe scores calculated at 2-year follow-up were significantly related to anchor position ( P < .01).

CONCLUSION

Anchors positioned on the glenoid face resulted in the greatest restored labral height and better functional outcome (Rowe score). Thus, anchor placement on the glenoid face should be considered, as it may yield better functional outcome in arthroscopic Bankart repair.

Differences in Glenohumeral Joint Rotation and Peak Power Output Between Super League and Championship Rugby League Players

Haines, MR. Differences in glenohumeral joint rotation and peak power output between Super League and Championship Rugby League players. J Strength Cond Res 32(6): 1685-1691, 2018-Rugby league is a high-intensity sport with large impact forces sustained during play, resulting in high prevalence of shoulder injury. Consequently, shoulder strength and player power are important considerations for injury prevention and performance. Additionally, professional teams regularly compete against semiprofessional teams, where differences in physical conditioning could be marked. The aim of this study was to test for differences in glenohumeral joint rotation and peak power between a professional Super League (SL) and semiprofessional Rugby League Championship (RLC) teams. A cross-sectional analysis was used to test 25 SL and 24 RLC players during preseason training. Isokinetic dynamometry, at 240°·s for concentric and eccentric actions was used to assess glenohumeral rotation. Peak power was determined using a maximal 30-second cycle ergometer test. Selective muscular development of the internal rotators without concomitant external rotator strength was evident in the SL team but not the RLC team. Internal rotation peak torque was higher for the SL club for concentric (∼24%) and eccentric (∼16%) muscle actions (p ≤ 0.05), and this contributed to a lower ipsilateral reciprocal muscle group ratio (external to internal concentric) for the SL team compared with the RLC team (∼47% and ∼60% respectively; p ≤ 0.05). Peak power output was also higher for the SL team (1,409 ± 153 vs. 1,273 ± 159 W; p ≤ 0.05). The results highlight a mismatch in the physical conditioning of SL and RLC players with implications for practitioners to design strength and conditioning programs that minimize the risk of injury while optimizing performance.

Shoulder function in patients with deltoid paralysis and intact rotator cuff

INTRODUCTION/HYPOTHESIS

The purpose of this study is to determine the mid/long term shoulder function in patients with complete deltoid paralysis and intact rotator cuff. 27 patients with at least 2-years FU were included.

MATERIALS AND METHODS

Outcome measures included pain, range of motion (including the swallowtail test STT), deltoid extension lag test DELT and Bertelli test), subjective fatigability using the injured shoulder and postoperative modified Neer ratings.

RESULTS

At an average 68 months FU, mean shoulder abduction was 131°, flexion 153°, external rotation with the arm at the side 58° and 58° with the arm abducted. All patients reported quick fatiguability with repetitive use of the injured arm which did not change over time. Average pain score was 2. Eighteen patients had positive STT and DELT tests and all patients had positive Bertelli test.

DISCUSSION

This study demonstrates that patients with deltoid paralysis and intact rotator cuff do maintain most of their shoulder function and this is sustained over time.

LEVEL OF EVIDENCE

Level IV; prognostic Study: case series.

Anatomy and Biomechanics of the Unstable Shoulder

PURPOSE

To review the anatomy of the shoulder joint and of the physiology of glenohumeral stability is essential to manage correctly shoulder instability.

METHODS

It was reviewed a large number of recently published research studies related to the shoulder instability that received a higher Level of Evidence grade.

RESULTS

It is reviewed the bony anatomy, the anatomy and function of the ligaments that act on this joint, the physiology and physiopathology of glenohumeral instability and the therapeutic implications of the injured structures.

CONCLUSION

This knowledge allows the surgeon to evaluate the possible causes of instability, to assess which are the structures that must be reconstructed and to decide which surgical technique must be performed.

Influence of the Labrum on Version and Diameter of the Glenoid: A Morphometric Study Using Magnetic Resonance Images

PURPOSE

To use magnetic resonance imaging to determine the influence of the labrum on both the osseous version and effective diameter of the glenoid.

METHODS

This was a retrospective, cross-sectional study of patients with shoulder pain who underwent MRI between February 2014 and February 2015. The morphology of the glenoid labrum and glenoid was scanned with a 3-T magnetic resonance imaging scanner, and variables were measured by use of IntelliSpace PACS Enterprise. Patients were included if they were aged between 18 and 40 years and the radiologist reported a normal glenohumeral joint or if they were young patients aged less than 30 years with acute traumatic isolated partial- or full-thickness tears of the rotator cuff with a history of symptoms of less than 3 months. A pilot study was conducted with 3 observers and 3 repeated measurements at intervals to determine the interobserver and intraobserver reliability. Data analysis included descriptive statistics of measured variables, as well as paired Student t tests to determine the relative difference between labral and osseous morphometric variables.

RESULTS

Excellent inter-rater reliability (0.95-0.96) and intrarater reliability (0.93-0.98) were obtained in the pilot study of 20 patients. The study population was composed of 100 patients with a mean age of 37.3 years (standard deviation [SD], 11.8 years), having a gender distribution of 56 male and 44 female patients; there were 53 right and 47 left shoulders. The glenoid osseous version measured -5.7° (SD, 5.3°), and the labral version measured -10° (SD, 5.5°); the glenoid osseous diameter measured 28.0 mm (SD, 3.3 mm), and the labral diameter measured 31.9 mm (SD, 3.2 mm). The labrum significantly increased the version by 4.3° (P = .001) and significantly increased the diameter by 3.9 mm (P = .001).

CONCLUSIONS

The results of this study showed that the labrum increased the effective glenoid version by 75% (4.3° of retroversion) and the effective glenoid diameter by 14% (3.9 mm).

LEVEL OF EVIDENCE

Level IV, prognostic case series.

Comparison of Magnetic Resonance Imaging and Computed Tomography Scans of the Glenoid Version in Anterior Dislocation of the Shoulder

The glenoid version is an important factor in the etiology of anterior dislocation of the shoulder and the planning of shoulder surgery. Few reports compare the magnetic resonance imaging (MRI) measurements of the glenoid version with those of computed tomography (CT). This study aimed to show that it is possible to use MRI instead of CT, which is accepted as the gold standard today for the evaluation of the glenoid version. A total of 55 patients with a history of 1 nonsurgically treated unilateral anterior dislocation of the shoulder who had both MRI and CT records for the dislocated shoulders constituted the study group. The glenoid version was measured in the axial plane on MRI and CT. Mean glenoid version measured by the observers was -1.6°±4.7° (95% confidence interval, -2.3° to -0.8°) and -1.8°±4.3° (95% confidence interval, -2.5° to -1.2°) by CT and MRI, respectively (P=.126). The evaluation of the CT and MRI measurements made by the 3 observers (X, Y, and Z) revealed no significant difference, as the P values of X CT - X MRI, Y CT - Y MRI, and Z CT - Z MRI were .550, .406, and .238, respectively. Interclass correlation among the 3 observers for CT and MRI was 0.996 and 0.981, respectively. The imaging methods of MRI and CT can be interchangeably used in the evaluation of the glenoid version in cases of anterior dislocation of the shoulder. [Orthopedics. 2017; 40(4):e687-e692.].

The importance of glenoid version in patients with anterior dislocation of the shoulder

BACKGROUND

Although increased retroversion of the glenoid has been shown to be an important factor in posterior instability of the shoulder, there are few studies reporting glenoid bone structure as a risk factor in anterior dislocation of the shoulder. This study aimed to compare glenoid version in patients with anterior dislocation of the shoulder and individuals in a control group with no shoulder problems before undergoing computed tomography and to assess a possible relationship between demographic characteristics and glenoid version angle.

METHODS

The study group comprised 63 patients (12 women and 51 men; mean age, 35.71 years) with 1 or multiple unilateral anterior dislocations of the shoulder (dislocated group), whereas 63 individuals (11 women and 52 men; mean age, 35.38 years) with no history of shoulder complaints and no signs of instability constituted the control group. The glenoid version angle was measured on an axial cut of the computed tomography scan.

RESULTS

The glenoid version angles on the dislocated side in the study group were significantly more anteverted than those of the dominant (P < .001) and nondominant (P = .023) shoulders of the control group. The version angles of dislocated shoulders significantly differed from those of nondislocated shoulders of both men (P = .041) and women (P = .049). There was no significant relationship between the glenoid version angle on the dislocated side and dislocation mechanism (P = .883), age group (P = .356), or number of dislocations (P = .971).

CONCLUSIONS

Glenoid version is an important factor for the development of anterior dislocation of the shoulder.

Accuracy of sagittal oblique view in preoperative indirect magnetic resonance arthrography for diagnosis of tears involving the upper third of the subscapularis tendon

BACKGROUND

The purpose of this study was to investigate the accuracy of sagittal oblique view (SOV) magnetic resonance imaging grading for tears involving the upper third of the subscapularis tendons in correlation with arthroscopic findings. We also propose a schematic classification in the SOV for upper-third subscapularis tears.

METHODS

The study analyzed 364 patients with an average age of 56.0 years. All patients underwent indirect magnetic resonance arthrography (MRA) before surgery. A slightly different magnetic resonance grading was introduced with SOV by musculoskeletal radiologists (Y.C.Y. and J.Y.Y.) and an orthopedic shoulder surgeon (H.Y.R.) who had no information about the clinical data. Subscapularis tendon tear classifications were all prospectively analyzed. Magnetic resonance grading was compared with the arthroscopic findings.

RESULTS

The sensitivity, specificity, and accuracy of subscapularis tendon tear detection were 0.72, 0.77, and 0.75, respectively, for the radiologists. For the orthopedic surgeon, the corresponding values were 0.73, 0.83, and 0.79, respectively. The κ coefficients for interobserver agreement comparing magnetic resonance grade of the musculoskeletal radiologists with the arthroscopic grading showed fair values (κ value, 0.301). Interobserver agreement between the magnetic resonance grade of the orthopedic surgeon and arthroscopic grades was fair (κ value, 0.377). Interobserver agreement between the musculoskeletal radiologists and the orthopedic surgeon was moderate (κ value, 0.591).

CONCLUSIONS

The accuracy of SOV indirect MRA for detecting tears was 0.75 to 0.79. Although the correlation between magnetic resonance and arthroscopic grading was only fair, for most of the magnetic resonancegrading on SOV, the first facet view showed similar results compared with arthroscopy. The accuracy of determining whether subscapularis repair is indicated was 0.82 to 0.83 with SOV indirect MRA.

Biomechanical Evaluation of Glenoid Version and Dislocation Direction on the Influence of Anterior Shoulder Instability and Development of Hill-Sachs Lesions

BACKGROUND

Abnormal glenoid version is a risk factor for shoulder instability. However, the degree to which the variance in version (both anteversion and retroversion) affects one's predisposition for instability is not well understood.

PURPOSE

To determine the influence of glenoid version on anterior shoulder joint stability and to determine if the direction of the humeral head dislocation is a stimulus for the development of Hill-Sachs lesions.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten human cadaveric shoulders (mean age, 59.4 ± 4.3 years) were tested using a custom shoulder dislocation device placed in a position of apprehension (90° of abduction with 90° of external rotation). Glenoid version was adjusted in 5° increments for a total of 6 version angles tested: +10°, +5°, 0°, -5°, -10°, and -15° (anteversion angles are positive, and retroversion angles are negative). Two humeral dislocation directions were tested. The first direction was true anterior through the anterior-posterior glenoid axis. The second dislocation direction was 35° inferior from the anterior-posterior glenoid axis based on the deforming force role of the pectoralis major. The force and energy to dislocate were recorded.

RESULTS

Changes in glenoid version manifested a linear effect on the dislocation force. The energy to dislocate increased as a second-order polynomial as a function of increasing glenoid retroversion. Glenoid version of +10° anteversion and -15° retroversion was highly unstable, resulting in spontaneous dislocation in one-quarter (10/40) and one-half (25/40) of the specimens anteriorly and posteriorly, respectively, in the absence of an applied dislocation force. The greater tuberosity was observed to engage with the anterior glenoid rim, consistent with Hill-Sachs lesions, 40% more frequently when the dislocation direction was true anterior compared with 35° inferior from the anterior-posterior glenoid axis. The engagement of the greater tuberosity caused an increase in the energy required to dislocate.

CONCLUSION

Glenoid version has a direct effect on the force required for a dislocation. An anterior-inferior dislocation direction requires less energy for a dislocation and results in a lower risk of the development of a Hill-Sachs lesion than a direct anterior dislocation direction.

CLINICAL RELEVANCE

Consideration should be given to glenoid version when choosing a surgical treatment option for anterior shoulder instability.

Assessment of Rotation in Proximal Humeral Osteotomy

The correlation between the shift measured on bone surface in rotatory osteotomy and the radiologic change of the retroversion angle was analyzed. The humeral head retroversion was measured radiographically in 7 isolated humeri by means of a semiaxial projection. All bones were then osteotomized and the humeral head rotated in order to increase and decrease the retroversion. The retroversion was measured radiographically for each new rotational position of the head. The relationship between the measured shift in rotatory osteotomy and the change of retroversion was found to be linear. Twelve patients with recurrent anterior shoulder joint dislocations and a small humeral head retroversion were operated on in order to increase the retroversion. In all patients the increase of retroversion angle was smaller (57%) than expected on the basis of the shift in osteotomy and humeral diameter. The mean increase of retroversion was 2°/mm shift (range 1.3–3.0°/mm).

Glenoid version and its relationship to glenohumeral instability and labral tears

BACKGROUND

Evidence suggests a relationship between glenoid retroversion and posterior instability, but no literature exists comparing glenoid version referencing the scapular body versus the endosteal vault. This study evaluated glenoid version and its relationship to unidirectional instability and labral tears.

METHODS

Glenoid version in patients with unidirectional instability or labral tears was measured with magnetic resonance imaging by either the Friedman method or the Poon and Ting method. Analyses of variance followed by independent t tests were used to compare 3 groups: anterior instability or labral tears (anterior pathology group, n = 33); posterior instability or labral tears (posterior pathology group, n = 34); and stable controls (n = 30). The referencing error for 2-dimensional axial images was evaluated for variance by imaging facility. Interobserver and intraobserver reliability scores were calculated.

RESULTS

With the Friedman method, the posterior pathology group (-9°) was more retroverted than the control group (-4°) (P = .0005) and the anterior pathology group (-5°) (P = .0104) but there was no difference between the control group and anterior pathology group (P = .38). The referencing error in the sagittal plane averaged 23° and varied by facility (P = .0365). The coronal-plane error averaged 1° and did not vary by facility (P = .7180). Intraclass correlation coefficient scores showed good to excellent intrarater and inter-rater reliability.

CONCLUSION

The posterior pathology group had 5° more retroversion than controls using the Friedman method. Glenoid version using the Poon and Ting method or the Friedman method did not predict anterior instability or labral tears. Axial magnetic resonance images were constructed with a referencing error in the sagittal plane that varied by magnetic resonance imaging facility and has implications for improving 2-dimensional axial imaging protocols.

Analysis of scapular kinematics during active and passive arm elevation

[Purpose] Early postoperative passive motion exercise after arthroscopic rotator cuff repair remains controversial. To better understand this issue, this study was aimed at evaluating scapular kinematics and muscle activities during passive arm elevation in healthy subjects. [Subjects and Methods] The dominant shoulders of 27 healthy subjects were examined. Electromagnetic sensors attached to the scapula, thorax, and humerus were used to determine three-dimensional scapular kinematics during active arm elevation with or without external loads and passive arm elevation. Simultaneously, the activities of seven shoulder muscles were recorded with surface and intramuscular fine-wire electrodes. [Results] Compared with active arm elevation, passive elevation between 30° and 100° significantly decreased the scapular upward rotation and increased the glenohumeral elevation angle. However, no significant differences in scapular posterior tilt and external rotation were observed between active and passive arm elevation, and scapular plane kinematics were not affected by muscle activity. [Conclusion] Unlike active motion with or without an external load, passive arm elevation significantly decreased the scapular upward rotation and significantly increased the mid-range glenohumeral elevation. These data, which suggest that passive arm elevation should be avoided during the early postoperative period, may expand the understanding of rehabilitation after arthroscopic rotator cuff repair.

Glenoid Dysplasia: Pathophysiology, Diagnosis, and Management

➤Subtle forms of glenoid dysplasia may be more common than previously thought and likely predispose some patients to symptomatic posterior shoulder instability. Severe glenoid dysplasia is a rare condition with characteristic radiographic findings involving the posteroinferior aspect of the glenoid that often remains asymptomatic.➤Instability symptoms related to glenoid dysplasia may develop over time with increased activities or trauma. Physical therapy focusing on rotator cuff strengthening and proprioceptive control should be the initial management.➤Magnetic resonance imaging and computed tomographic arthrograms are useful for detecting subtle glenoid dysplasia by revealing the presence of an abnormally thickened or hypertrophic posterior part of the labrum, increased capsular volume, glenoid retroversion, and posteroinferior glenoid deficiency.➤Open and arthroscopic labral repair and capsulorrhaphy procedures have been described for symptomatic posterior shoulder instability. Glenoid retroversion of >10° may be a risk factor for failure following soft-tissue-only procedures for symptomatic glenoid dysplasia.➤Osseous procedures are categorized as either glenoid reorientation (osteotomy) or glenoid augmentation (bone graft), and no predictable results have been demonstrated for any surgical strategy. Glenoid osteotomies have been described for increased retroversion, with successful results, although others have noted substantial complications and poor outcomes.➤In severe glenoid dysplasia, the combination of bone deficiency and retroversion makes glenoid osteotomy extremely challenging. Bone grafts placed in a lateralized position to create a blocking effect may increase the risk of the development of arthritis, while newer techniques that place the graft in a congruent position may decrease this risk.

History of surgical intervention of anterior shoulder instability

BACKGROUND

Anterior glenohumeral instability most commonly affects younger patients and has shown high recurrence rates with nonoperative management. The treatment of anterior glenohumeral instability has undergone significant evolution over the 20th and 21 centuries.

METHODS

This article presents a retrospective comprehensive review of the history of different operative techniques for shoulder stabilization.

RESULTS

Bankart first described an anatomic suture repair of the inferior glenohumeral ligament and anteroinferior labrum in 1923. Multiple surgeons have since described anatomic and nonanatomic repairs, and many of the early principles of shoulder stabilization have remained even as the techniques have changed. Some methods, such as the Magnusson-Stack procedure, Putti-Platt procedure, arthroscopic stapling, and transosseous suture fixation, have been almost completely abandoned. Other strategies, such as the Bankart repair, capsular shift, and remplissage, have persisted for decades and have been adapted for arthroscopic use.

DISCUSSION

The future of anterior shoulder stabilization will continue to evolve with even newer practices, such as the arthroscopic Latarjet transfer. Further research and clinical experience will dictate which future innovations are ultimately embraced.

In vivo measurements of humeral movement during posterior glenohumeral mobilizations

OBJECTIVES

The purpose of this study was to quantify in vivo posterior translational movements occurring in the glenohumeral joint during posterior mobilizations and to determine the intratester reliability of those posterior translational movements.

METHODS

Twenty-eight individuals (17 females, 11 males) participated in this study. One physical therapist utilized a Kaltenborn approach to apply three grades of posterior humeral mobilization. A hand held dynamometer was used to quantify the force used during each grade of mobilization. Ultrasound imaging was used to visualize and measure posterior humeral movement. Statistical analysis included descriptive statistics for force and posterior movement, intraclass correlation coefficient (ICC) for intrarater reliability of force and posterior movement during each grade of mobilization and paired t-tests to compare movement and force between grades of mobilization.

RESULTS

Mean posterior movement (mm) measurements were 3.0, 8.2 and 10.7 for grade I, grade II and grade III mobilizations, respectively. Mean force (Newtons) measurements used during mobilization were 41.7, 121.5 and 209.4 for grade I, grade II and grade III mobilizations, respectively. The ICCs ranged from 0.849 to 0.905 for movement and from 0.717 to 0.889 for force. Force and measurement values were significantly different between grades of mobilization and between dominant and non-dominant arms. Gender was found to be significantly associated with force.

DISCUSSION

Mean movements and mean forces occurring during posterior mobilization increased with increasing grades. Intratester reliability was high for all grades of manual mobilization supporting the use of subjective feedback to determine appropriate force application. Quantification of forces and movements helps to clarify parameters that can serve as a reference for clinical practice.

The effect of glenoid cavity depth on rotator cuff tendinitis

INTRODUCTION

Some of the most important causes of shoulder pain are inflammation and degenerative changes in the rotator cuff (RC). Magnetic resonance imaging (MRI) is a noninvasive and safe imaging modality. MRI can be used for the evaluation of cuff tendinopathy. In this study, we evaluated the relationship between glenoid cavity depth and cuff tendinopathy and we investigated glenoid cavity depth on the pathogenesis of cuff tendinopathy.

MATERIALS AND METHODS

We retrospectively evaluated 215 patients who underwent MRI. Of these, 60 patients showed cuff tendinopathy (group A) and 54 patients showed no pathology (group B). Glenoid cavity depth was calculated in the coronal and transverse planes.

RESULTS

The mean axial depth was 1.7 ± 0.9 and the mean coronal depth 3.8 ± 0.9, for group A. The mean axial depth was 3.5 ± 0.7 and the mean coronal depth 1.5 ± 0.8, for group B. There were significant differences in the axial and coronal depths between the two groups.

CONCLUSION

High coronal and low axial depth of the glenoid cavity can be used to diagnose RC tendinitis.

Biomechanical Effect of Thickness and Tension of Fascia Lata Graft on Glenohumeral Stability for Superior Capsule Reconstruction in Irreparable Supraspinatus Tears

PURPOSE

To investigate the effects of graft length and thickness on shoulder biomechanics after superior capsule reconstruction.

METHODS

Subacromial peak contact pressure and glenohumeral superior translation were measured at 0°, 30°, and 60° of glenohumeral abduction in 8 fresh-frozen cadaveric shoulders under 5 conditions: (1) intact shoulder; (2) irreparable supraspinatus tendon tear, (3) superior capsule reconstruction with a fascia lata allograft 4-mm thick and 15 mm longer than the distance from the superior glenoid to the lateral edge of the greater tuberosity, as determined during placement at 30° of glenohumeral abduction; (4) superior capsule reconstruction with a fascia lata allograft 8-mm thick and with the same 15 mm relative length determined at 10° of glenohumeral abduction, and (5) superior capsule reconstruction with a fascia lata allograft 8-mm thick and with the 15-mm relative length determined at 30° of glenohumeral abduction. To investigate the effect of graft thickness, we compared the data from conditions 1, 2, 3, and 5. To assess the effect of graft length, we compared conditions 1, 2, 4, and 5.

RESULTS

With superior capsule reconstruction using a 4-mm graft, subacromial peak contact pressure (but not superior translation) was significantly lower than with irreparable supraspinatus tears (at 0° abduction: 259% decrease; P = .0002; at 30° abduction: 113% decrease; P = .01). The superior capsule reconstruction using an 8-mm graft significantly decreased both subacromial peak contact pressure (at 0° abduction: 246% decrease, P = .0002; at 30° abduction: 158% decrease; P = .0008; at 60° abduction: 57% decrease; P = .04) and superior translation (at 0° abduction: 135% decrease; P = .02; at 30° abduction; 130% decrease; P = .004). Graft length with placement at 10° glenohumeral abduction was 5 mm greater than that at 30° abduction. The 8-mm superior capsule reconstruction performed at 10° or 30° of glenohumeral abduction significantly decreased subacromial peak contact pressure (placement at 10° and 30°: 0° abduction, P = .0002 and .0002, respectively; 30° abduction, P = .0004 and .0005, respectively; 60° abduction, P = .04 and .04, respectively) and superior translation (placement at 10° and 30°; 0° abduction, P =.04 and .02, respectively; 30° abduction, P = .02 and .004, respectively) compared with irreparable supraspinatus tears.

CONCLUSIONS

Superior capsule reconstruction normalized the superior stability of the shoulder joint when the graft was attached at 10° or 30° of glenohumeral abduction. An 8-mm-thick graft of fascia lata had greater stability than did a 4-mm-thick graft.

CLINICAL RELEVANCE

Grafts 8-mm thick and attached at 15° to 45° of shoulder abduction (equal to 10° to 30° of glenohumeral abduction) biomechanically restore shoulder stability during superior capsule reconstruction using fascia lata.

Is arthroscopic remplissage a tenodesis or capsulomyodesis? An anatomic study

PURPOSE

Arthroscopic remplissage of a Hill-Sachs lesion is classically described as a capsulotenodesis of the infraspinatus within the posterolateral humeral head. The aim of this cadaveric study was to evaluate the anatomic relationship between the position of anchors and sutures placed for remplissage and the infraspinatus and teres minor. The hypothesis was that remplissage actually corresponds to a capsulomyodesis of the infraspinatus and teres minor muscles.

METHODS

A two-anchor arthroscopic remplissage was performed followed by open dissection of ten fresh-frozen human cadaveric shoulders. The exit point of sutures related to muscle-tendon unit as well as the distance between the anchors and the rotator cuff was measured.

RESULTS

The superior sutures were localized generally in the infraspinatus, near the musculotendinous junction. The inferior sutures passed through the teres minor muscle in seven of ten cases. The distance between the superior and inferior anchors and the posterolateral greater tuberosity was 14 ± 2 and 12 ± 3 mm, respectively.

CONCLUSIONS

Arthroscopic remplissage is a capsulomyodesis of infraspinatus and teres minor rather than a capsulotenodesis of the infraspinatus alone as previously believed. Muscular damage may explain posterosuperior pain observed in patients who underwent remplissage.

Electromyographic Analysis of the Shoulder Girdle Musculature During External Rotation Exercises

Background:

Implementation of overhead activity, a key component of many professional sports, requires an effective and balanced activation of the shoulder girdle muscles, particularly during forceful external rotation (ER) motions.

Purpose:

To identify activation strategies of 16 shoulder girdle muscles/muscle segments during common shoulder ER exercises.

Study Design:

Descriptive laboratory study.

Method:

Thirty healthy subjects were included in this study, and 16 shoulder girdle muscles/muscle segments were investigated (surface electrode: anterior, middle, and posterior deltoid; upper, middle, and lower trapezius; serratus anterior; teres major; upper and lower latissimus dorsi; and upper and lower pectoralis major; fine wire electrodes: supraspinatus, infraspinatus, subscapularis, and rhomboid major) using a telemetric electromyography (EMG) system. Five ER exercises (standing ER at 0° and 90° of abduction, with underarm towel roll, prone ER at 90° of abduction, side-lying ER with underarm towel) were studied. Exercise EMG amplitudes were normalized to EMG at maximum ER force in a standard position. Univariate analysis of variance and post hoc analysis applied on EMG activity of each muscle were used to assess the main effect of the exercise condition.

Results:

Muscular activity differed significantly among the ER exercises (P < .05 to P < .001). The greatest activation for anterior and middle deltoid, supraspinatus, upper trapezius, and serratus anterior occurred during standing ER at 90° of abduction; for posterior deltoid, middle trapezius, and rhomboid during side-lying ER with underarm towel; for lower trapezius, upper and lower latissimus dorsi, subscapularis, and teres major during prone ER at 90° of abduction; and for the clavicular and sternal part of the pectoralis major during standing ER with underarm towel.

Conclusion:

Key glenohumeral and scapular muscles can be optimally activated during specific ER exercises, particularly in positions that stimulate athletic overhead motions.

Clinical Relevance:

These results enable sports medicine professionals to target specific muscles during shoulder rehabilitation protocols while minimizing the effect of others, providing a foundation for optimal evidence-based exercise prescription. They also provide information for tailored muscle training and injury prevention in overhead sports.

Trunk kinematics and muscle activities during arm elevation

BACKGROUND

While trunk movement accompanies arm elevation, trunk muscle activities during arm elevation at different speeds are unclear. The purpose of this study was to examine the trunk muscle activities at various speeds of arm elevation and then to evaluate their roles in trunk kinematics.

METHODS

Twenty-two healthy subjects participated. The participants performed right shoulder flexion at three different speeds. Surface electromyography was used to measure the activities of bilateral external oblique muscles (EO), internal oblique muscles (IO), rectus abdominis muscles (RA) and lumber erector spinae muscles (ES). A three-dimensional motion analyzer was used to measure arm and trunk movements.

RESULTS

In natural and slow movements, the muscle activities of left ES, right EO and left IO were significantly augmented compared with those of the contralateral muscles, in the relatively late phase. In fast movement, the muscle activities of both ES were significantly augmented during the early phase compared with later in the action. The muscle activities of the left ES and the right EO were significantly augmented compared with those of the contralateral muscles. There was a consistent pattern of trunk extension, lateral flexion and rotation during arm elevation, irrespective of the speed.

CONCLUSIONS

Bilateral ES activity may be required for back-extension torques, especially for the early phase of rapid elevating motion. The anterior muscles' activity may contribute to the production of anterior force against the backward movement of the center of mass of the upper limb in the late phase. Trunk rotation, controlled by the trunk muscles in harmony, may assist the scapular movement to align the scapular plane in the arm elevating plane.

Sensitivity of physical examination versus arthroscopy in diagnosing subscapularis tendon injury

The purpose of this study was to examine the accuracy of physical examination in the detection of subscapularis tendon tears and compare it with the gold standard of arthroscopy to determine whether clinical examination can reliably predict the presence of subscapularis tendon tears. This was a retrospective analysis of 52 patients (52 shoulders) who underwent arthroscopic subscapularis tendon repairs between September 2008 and April 2012. Positive findings on any combination of the belly press, lift-off, and bear hug tests constituted a positive physical examination result. There was a positive finding on physical examination in 42 of 52 patients. The sensitivity of the physical examination as a whole was 81%. The literature has shown that the belly press, bear hug, and lift-off tests are specific to the subscapularis tendon. To the authors’ knowledge, this is the first study to evaluate the sensitivity of these 3 separate clinical tests as a composite. Knowledge regarding the sensitivity of the subscapularis-specific physical examination as a composite can lead practitioners to implement all 3 components, even when 1 test has a negative finding, thus promoting a more thorough physical examination. Because unrepaired subscapularis tendon tears can result in poor outcomes in the repair of other rotator cuff tendons, a complete physical examination would be beneficial to patients with shoulder pathology. The authors conclude that physical examination, when performed consistently by an experienced practitioner, can reliably predict the presence of subscapularis tendon tears.

Addressing glenoid bone deficiency and asymmetric posterior erosion in shoulder arthroplasty

Glenoid bone deficiency and eccentric posterior wear are difficult problems faced by shoulder arthroplasty surgeons. Numerous options and techniques exist for addressing these issues. Hemiarthroplasty with concentric glenoid reaming may be a viable alternative in motivated patients in whom glenoid component failure is a concern. Total shoulder arthroplasty has been shown to provide durable pain relief and excellent function in patients, and numerous methods and techniques can assist in addressing bone loss and eccentric wear. However, the ideal amount of version correction in cases of severe retroversion has not yet been established. Asymmetric reaming is a commonly used technique to address glenoid version, but correction of severe retroversion may compromise bone stock and component fixation. Bone grafting is a technically demanding alternative for uncontained defects and has mixed clinical results. Specialized glenoid implants with posterior augmentation have been created to assist the surgeon in correcting glenoid version without compromising bone stock, but clinical data on these implants are still pending. Custom implants or instruments based on each patient's unique glenoid anatomy may hold promise. In elderly, sedentary patients in whom bone stock and soft-tissue balance are concerns, reverse total shoulder arthroplasty may be less technically demanding while still providing satisfactory pain relief and functional improvements.

Obtaining glenoid positioning data from scapular palpable points in vitro

Both clinical and biomechanical problems affecting the shoulder joint suggest that investigators should study force transmission into and out from the scapula. To analyze force transmission between the humeral head and the glenoid, one must know the position of the glenoid. Studies have analyzed the position of the scapula from the positions of three palpable points, but the position of the glenoid relative to three palpable points has not been studied. Dry scapulae (N = 13) were subjected to X-rays and a critical angle, Θ (which relates the plane determined by the three palpable points on the scapula to a plane containing the glenoid center and the first two palpable points) was calculated. The mean value for Θ was 28.5 ± 5.60 degrees. The obtained Θ allows us to determine the position of the glenoid from three palpable points. This information could be used in calculation of forces across the shoulder joint, which in turn would allow optimizing the choice of strengthening exercises.

Morphology of the normal and arthritic glenoid

The normal glenoid has a pear-shape aspect and is slightly retroverted. It has a variable orientation in the sagittal plane. The cartilage surface area corresponds to 28 % of the area of the humeral head with a radius of curvature greater than the humeral head. Mechanical properties are significantly higher at the center and posterior edge of the glenoid. With osteoarthritis, the glenoid becomes larger with a greater width and an increasing of the retroversion angle. The wear can be centric or excentric. Mechanical properties are significantly higher at the center and posterior edge of the glenoid.

Effect of glenoid implant design on glenohumeral stability: an experimental study

BACKGROUND

Though several glenoid implants were developed over the past years, a high rate of glenoid loosening remains. This complication is linked to the glenohumeral stability, defined as humeral head translation. In an intact shoulder, this concept is ensured by all active and passive elements, particularly the labrum. Two features of a glenoid implant can be adjusted to improve the stability, or, in other words, to decrease the translations: the first is the mismatch, defined as the difference of curvature between the prosthetic head and glenoid; the second is the shape of the glenoid component. Therefore, the objective of this study was to compare the performance of 2 glenoid components (Ceraver, Roissy, France): (1) a standard design and (2) a design named "labrum design" with a superior part simulating the anatomic labrum.

METHODS

An experimental device was developed to evaluate forces and kinematics. The device simulated active, dynamic and continuous abduction of an entire arm. It reproduced the Scapulo-Humeral Rhythm. The labrum design was installed first. To evaluate the effect of mismatch on the glenohumeral stability, 3 humeral heads were tested, corresponding to the ones recommended by the company. The experiment was repeated for the standard design.

FINDINGS

The results obtained show a general decrease of the prosthetic head translation with the labrum design compared to the standard design. No noticeable effect of mismatch was found.

INTERPRETATION

A proof of concept of the interest of the artificial labrum was provided since it improved the glenohumeral stability.

Anatomic and biomechanical fundamentals of the thrower shoulder

The act of throwing requires proper functioning and timing of the entire kinetic chain musculature to generate a coordinated movement pattern for ball delivery. The role of the shoulder complex is vital in the transmission of force from the lower extremities and trunk to the arm and hand. A review of the anatomic and biomechanical factors of the shoulder girdle will be discussed as it pertains to the thrower. An understanding of the relationship of the muscles, ligaments, and osseous structures is essential to the successful diagnosis and treatment of shoulder pathology and dysfunction.