An MRI study on the relations between muscle atrophy, shoulder function and glenohumeral deformity in shoulders of children with obstetric brachial plexus injury

Qualitative and quantitative analysis of glenoid bone stock and glenoid version: inter-reader analysis and correlation with rotator cuff tendinopathy and atrophy in patients with shoulder osteoarthritis

PURPOSE

Glenoid bone stock and morphology and rotator cuff muscle quality and tendon integrity affect the outcome of total shoulder arthroplasty. We hypothesized that glenoid bone loss correlates with rotator cuff muscle fatty infiltration (FI), tendinopathy, and atrophy.

DESIGN

Forty-three 3D CT scans and MRIs of 43 patients (mean age 62 years; SD 13 years; range 22-77 years) referred for primary shoulder pain were evaluated. Measurements of glenoid bone stock, version, and posterior humeral subluxation index (HSI) were assessed on an axial CT image reconstructed in the true scapular plane. Measurements utilized the Friedman line to approximate the pre-pathologic surface. Glenoid morphology was assigned by modified Walch classification. Rotator cuff FI, atrophy, and tendon integrity were assessed on corresponding MRIs.

RESULTS

There was a very strong negative correlation between increasing glenoid version and HSI (r = - 0.908; p < 0.0001). There was a moderately negative correlation between anterior bone loss and HSI (r = - 0.562; p < 0.0001) and a moderately positive correlation between posterior bone loss and HSI (r = 0.555; p < 0.0001). Subscapularis muscle FI correlated moderately with increased anterior and central bone loss and increased humeral head medialization (r = 0.512, p = 0.0294; r = 0.479, p = 0.033; r = 0.494, p = 0.0294; respectively). Inter-observer reliability (intra-class correlation coefficient [ICC] and kappa) was good to excellent for all measurements and grading.

CONCLUSION

Glenoid anteversion and anterior and posterior bone loss are associated with varying HSI. Subscapularis muscle FI, not tendon integrity, correlates to anterior and central glenoid erosion. The study adds evidence that neither rotator cuff tendinopathy nor muscle atrophy exhibits a significant relationship to HSI.

Correction to: Qualitative and quantitative analysis of glenoid bone stock and glenoid version: inter-reader analysis and correlation with rotator cuff tendinopathy and atrophy in patients with shoulder osteoarthritis

Purpose Glenoid bone stock and morphology and rotator cuff muscle quality and tendon integrity affect the outcome of total shoulder arthroplasty. We hypothesized that glenoid bone loss correlates with rotator cuff muscle fatty infiltration (FI), tendinopathy, and atrophy.Design Forty-three 3-D CT scans and MRIs of 43 patients (mean age 62 years; SD 13 years; range 22-77 years) referred for primary shoulder pain were evaluated. Measurements of glenoid bone stock, version, and posterior humeral subluxation index (HSI) were assessed on an axial CT image reconstructed in the true scapular plane. Measurements utilized the Friedman line to approximate the pre-pathologic surface. Glenoid morphology was assigned by modified Walch classification. Rotator cuff FI, atrophy, and tendon integrity were assessed on corresponding MRIs.Results There was a very strong negative correlation between increasing glenoid version and HSI (r = - 0.908; p < 0.0001). There was a moderately negative correlation between anterior bone loss and HSI (r = - 0.562; p < 0.0001) and a moderately positive correlation between posterior bone loss and HSI (r = 0.555; p < 0.0001). Subscapularis muscle FI correlated moderately with increased anterior and central bone loss and increased humeral head medialization (r = 0.512, p = 0.0294; r = 0.479, p = 0.033; r = 0.494, p = 0.0294, respectively). Inter-observer reliability (intra-class correlation coefficient [ICC] and kappa) was good to excellent for all measurements and grading.Conclusion Glenoid anteversion and anterior and posterior bone loss are associated with varying HSI. Subscapularis muscle FI, not tendon integrity, correlates to anterior and central glenoid erosion. The study adds evidence that neither rotator cuff tendinopathy nor muscle atrophy exhibits a significant relationship to HSI.

A New Surgical Technique for Internal Shoulder Contractures Secondary to Obstetric Brachial Plexus Injury: An Anterior Coracohumeral Ligament Release

Background  Obstetric brachial plexus injuries result from traction injury during delivery; 30% of these children sustain persisting functional limitations related to an external rotation deficit of the shoulder. The aim of this study was to compare the intraoperative gain in external rotation after a posterior subscapular release and an anterior coracohumeral ligament release.

Methods  This is a prospective study on 102 children with an internal rotation contracture of the shoulder who received either a posterior subscapular release (posterior skin incision along the medial border of the scapula of 3–5 cm) or an anterior (5-mm skin incision) coracohumeral ligament release between 1996 and 2010. After general anesthesia, internal and external rotations in both adduction and abduction were measured before and after the surgical release.

Results  After a posterior subscapular release, the intraoperative external rotation improved with a mean of 64 degrees (95% confidence interval [CI]: 54–74; p  < 0.001) in adduction and with a mean of 41 degrees (95% CI: 32–49; p  < 0.001) in abduction. After an anterior coracohumeral ligament release, external rotation increased with a mean of 61 degrees (95% CI: 56–66; p  < 0.001) in adduction and a mean of 42 degrees in abduction (95%CI: 39–45, p  < 0.001). Differences between these two groups were not statistically different.

Conclusion  The anterior release technique shows comparable results with the posterior subscapular release. And since it is performed through a smaller incision of 5 mm, this is our preferred method to increase passive external rotation.

Level of evidence  II.

The Pathogenesis of Glenohumeral Deformity and Contracture Formation in Obstetric Brachial Plexus Palsy-A Review

Contractures of the shoulder joint and glenohumeral joint dysplasia are well known complications to obstetrical brachial plexus palsy. Despite extensive description of these sequelae, the exact pathogenesis remains unknown. The prevailing theory to explain the contractures and glenohumeral joint dysplasia states that upper trunk injury leads to nonuniform muscle recovery and thus imbalance between internal and external rotators of the shoulder. More recently, another explanation has been proposed, hypothesizing that denervation leads to reduced growth of developing muscles and that reinnervation might suppress contracture formation. An understanding of the pathogenesis is desirable for development of effective prophylactic treatment. This article aims to describe the current state of knowledge regarding these important complications.

The Surgical Strategy to Correct the Rotational Imbalance of the Glenohumeral Joint after Brachial Plexus Birth Injury

In upper brachial plexus birth injury, rotational balance of the glenohumeral joint is frequently affected and contracture in medial rotation of the arm develops, due to a severe palsy or insufficient recovery of the lateral rotators. Some of these children present with a severe glenohumeral joint contracture in the first months, although regular physiotherapy has been provided, a condition associated with a posteriorly subdislocated or dislocated humeral head. These conditions should be screened early by a pediatrician or specialized physiotherapist. Both aspects of muscular weakness affecting the lateral rotators and the initial or progressive glenohumeral deformity and/or subdislocation must be identified and treated accordingly, focusing on the reestablishment of joint congruence and strengthening of the lateral rotators to improve rotational balance, thus working against joint dysplasia and loss of motor function of the shoulder in a growing child. Our treatment strategy adapted over the last 20 years to results from retrospective studies, including biomechanical aspects on muscular imbalance and tendon transfers. With this review, we confront our actual concept to recent literature.

Three dimensionality of gleno-humeral deformities in obstetrical brachial plexus palsy

The primary objective of this study was to test the hypothesis that gleno-humeral deformity in children and adolescent with obstetrical brachial plexus palsy is three-dimensional (3D). The study also compared the metrological properties of typical two-dimensional gleno-humeral measures to the newly developed 3D measures. Thirteen individuals (age = 11.8 ± 3.3 years) with obstetrical brachial plexus palsy participated in this IRB-approved study. 3D axial magnetic resonance images were acquired for both shoulders. Glenoid and humeral models were created in order to quantify 3D glenoid version, humeral head migration, and glenoid concavity. Two-dimensional (2D) measures were acquired as recommended in the literature. All measures were completed by two observers in this observer-blind study. Compared to the non-involved side, the glenoid was more retroverted (7.91°, p = 0.003) and inferiorly oriented (7.28°, p = 0.009). The humeral head was migrated more posteriorly (5.54 mm, p = 0.007), inferiorly (-3.96 mm, p = 0.013), and medially (-3.63 mm,p = 0.002). Eleven of the 13 glenoids were concave, based on the 3D glenoid models. The concurrent validity between three- and 2D measures were highly dependent of the parameter measured, the slice level used for the 2D analysis, and the presence/absence of pathology (0.63 < r < 0.91). The standard error of measurement for the 2D anterior-posterior version (>3°) was larger than that for the 3D measure of version (<1°) on the involved side. This study clearly demonstrated that the gleno-humeral deformation in obstetrical brachial plexus palsy is 3D, emphasizing the need for 3D subject specific gleno-humeral shape analysis for follow-up and treatment plans in children with obstetrical brachial plexus palsy.

Degree of Contracture Related to Residual Muscle Shoulder Strength in Children with Obstetric Brachial Plexus Lesions

BACKGROUND AND OBJECTIVES

 Little is known about the relation between residual muscle strength and joint contracture formation in neuromuscular disorders. This study aimed to investigate the relation between residual muscle strength and shoulder joint contractures in children with sequelae of obstetric brachial plexus lesion (OBPL). In OBPL a shoulder joint contracture is a frequent finding. We hypothesize that residual internal and external rotator strength and their balance are related to the extent of shoulder joint contracture.

METHODS

 Clinical assessment was performed in 34 children (mean 10.0 years) with unilateral OBPL and Narakas classes I-III. External and internal rotation strengths were measured with the shoulder in neutral position using a handheld dynamometer. Strength on the affected side was given as percentage of the normal side. Contracture was assessed by passive internal and external rotations in degrees (in 0° abduction). Mallet classification was used for active shoulder function.

RESULTS

 External and internal rotation strengths on the affected side were approximately 50% of the normal side and on average both equally affected: 56% (SD 18%) respectively 51% (SD 27%); r = 0.600, p = 0.000. Residual strengths were not related to passive internal or external rotation (p > 0.200). Internal rotation strength (r =  - 0.425, p <0.05) was related to Narakas class. Mallet score was related to external and internal rotation strengths (r = 0.451 and r = 0.515, respectively; p < 0.01).

CONCLUSION

 The intuitive notion that imbalances in residual muscle strength influence contracture formation cannot be confirmed in this study. Our results are of interest for the understanding of contracture formation in OBPL.

Shoulder strength profiles in children with and without brachial PLEXUS PALSY

INTRODUCTION

We characterized bilateral shoulder strength and the balance of antagonist/agonist muscle pairs in children with brachial plexus palsy (BPP) and with typical development (TD).

METHODS

In 15 children with unilateral BPP and 11 with TD, bilateral maximal isometric shoulder strength in flexion/extension, internal/external rotation, and abduction/adduction was recorded using a hand-held dynamometer. Correlation between strength and active range of motion were evaluated using the Mallet score.

RESULTS

Children with BPP had strength asymmetry in all muscles, whereas children with TD had significant strength asymmetry for flexors and abductors. In children with BPP, extensors and external rotators were the weakest muscles, leading to sagittal and transverse plane muscle imbalances. Higher strength values were related to better active range of motion.

CONCLUSIONS

This study highlights the importance of documenting shoulder strength profiles in children with BPP which may help predict deformity development.

Computational sensitivity analysis to identify muscles that can mechanically contribute to shoulder deformity following brachial plexus birth palsy

PURPOSE

Two mechanisms, strength imbalance or impaired longitudinal muscle growth, potentially cause osseous and postural shoulder deformity in children with brachial plexus birth palsy. Our objective was to determine which muscles, via either deformity mechanism, were mechanically capable of producing forces that could promote shoulder deformity.

METHODS

In an upper limb computational musculoskeletal model, we simulated strength imbalance by allowing each muscle crossing the shoulder to produce 30% of its maximum force. To simulate impaired longitudinal muscle growth, the functional length of each muscle crossing the shoulder was reduced by 30%. We performed a sensitivity analysis to identify muscles that, through either simulated deformity mechanism, increased the posteriorly directed, compressive glenohumeral joint force consistent with osseous deformity or reduced the shoulder external rotation or abduction range of motion consistent with postural deformity.

RESULTS

Most of the increase in the posterior glenohumeral joint force by the strength imbalance mechanism was caused by the subscapularis, latissimus dorsi, and infraspinatus. Posterior glenohumeral joint force increased the most owing to impaired growth of the infraspinatus, subscapularis, and long head of biceps. Through the strength imbalance mechanism, the subscapularis, anterior deltoid, and pectoralis major muscles reduced external shoulder rotation by 28°, 17°, and 10°, respectively. Shoulder motion was reduced by 40° to 56° owing to impaired growth of the anterior deltoid, subscapularis, and long head of triceps.

CONCLUSIONS

The infraspinatus, subscapularis, latissimus dorsi, long head of biceps, anterior deltoid, pectoralis major, and long head of triceps were identified in this computational study as being the most capable of producing shoulder forces that may contribute to shoulder deformity following brachial plexus birth palsy.

CLINICAL RELEVANCE

The muscles mechanically capable of producing deforming shoulder forces should be the focus of experimental studies investigating the musculoskeletal consequences of brachial plexus birth palsy and are potentially critical targets for treating shoulder deformity.

Assessing shoulder motion in children: age limitations to Mallet and ABC Loops

BACKGROUND

Shoulder ROM and function of the shoulder are difficult to evaluate in young children. There has been no determination of the age at which children can comply with the current assessment tools in use, but doing so would be important, because it gives us more accurate insight into the development and assessment of shoulder functional ROM in young children.

QUESTIONS/PURPOSES

We (1) determined whether age would limit the use of two different observational scales used to assess shoulder ROM and function in young children (the Mallet scale and the ABC Loops protocol); and (2) compared the two scales in terms of intra- and interobserver reliabilities.

METHODS

Sixty-five able-bodied children (32 boys, 33 girls; mean age, 3.9 years; range, 0.5-7.0 years) were recruited from local preschools and evaluated using the Mallet scale and ABC Loops protocol. Children were assessed on their ability to complete the examinations and time to completion for each measurement protocol. Intra- and interobserver reliability was tested by percentage agreement. Forty-eight children (mean age, 4.4 years; SD, 1.3 years) were able to complete the Mallet and ABC Loops measurement protocols; 17 children (mean age, 2.3 years; SD, 1.1 years) failed to complete either test.

RESULTS

Younger children had more difficulty completing the examinations; there was a strong negative correlation between age and failure: probability of failure increased with decreasing age (Pearson r = -0.601, p < 0.001). Children who were able to complete one test were able to complete the other. Interobserver and intraobserver agreement was very high for both scales (in excess of 95% for all comparisons), and with the numbers available, there were no differences between the scales.

CONCLUSIONS

The Mallet scale and ABC Loops protocol have high reliability metrics in children younger than 6 years, but very young children (those younger than 3 years) generally will not be able to complete the examinations. The ABC Loops test took longer to perform than the Mallet scale but may more comprehensively evaluate a child's functional capabilities. We therefore state that both assessment tools can be reliably used in children older than 3 years; we believe the ABC Loops gives a more accurate assessment of shoulder ROM.

Shoulder strength profiles in children with and without brachial PLEXUS PALSY

INTRODUCTION

We characterized bilateral shoulder strength and the balance of antagonist/agonist muscle pairs in children with brachial plexus palsy (BPP) and with typical development (TD).

METHODS

In 15 children with unilateral BPP and 11 with TD, bilateral maximal isometric shoulder strength in flexion/extension, internal/external rotation, and abduction/adduction was recorded using a hand-held dynamometer. Correlation between strength and active range of motion were evaluated using the Mallet score.

RESULTS

Children with BPP had strength asymmetry in all muscles, whereas children with TD had significant strength asymmetry for flexors and abductors. In children with BPP, extensors and external rotators were the weakest muscles, leading to sagittal and transverse plane muscle imbalances. Higher strength values were related to better active range of motion.

CONCLUSIONS

This study highlights the importance of documenting shoulder strength profiles in children with BPP which may help predict deformity development.

Developing core sets for patients with obstetricbrachial plexus injury based on the International Classificationof Functioning, Disability and Health

Background

Symptoms of obstetric brachial plexus injury (OBPI) vary widely over the course of time and from individual to individual and can include various degrees of denervation, muscle weakness, contractures, bone deformities and functional limitations. To date, no universally accepted overall framework is available to assess the outcome of patients with OBPI. The objective of this paper is to outline the proposed process for the development of International Classification of Functioning, Disability and Health (ICF) Core Sets for patients with an OBPI.

Methods

The first step is to conduct four preparatory studies to identify ICF categories important for OBPI: a) a systematic literature review to identify outcome measures, b) a qualitative study using focus groups, c) an expert survey and d) a cross-sectional, multicentre study. A first version of ICF Core Sets will be defined at a consensus conference, which will integrate the evidence from the preparatory studies. In a second step, field-testing among patients will validate this first version of Core Sets for OBPI.

Discussion

The proposed method to develop ICF Core Sets for OBPI yields a practical tool for multiple purposes: for clinicians to systematically assess and evaluate the individual’s functioning, for researchers to design and compare studies, and for patients to get more insight into their health problems and their management.

Muscular and glenohumeral changes in the shoulder after brachial plexus birth palsy: an MRI study in a rat model

Background

Shoulder abnormalities are the major cause of morbidity in upper brachial plexus birth palsy (BPBP). We developed a rat model of upper trunk BPBP and compared our findings to previously reported animal models and to clinical findings in humans.

Methods

Forty-three 5-day-old newborn rats underwent selective upper trunk neurectomy of the right brachial plexus and were studied 3 to 20 weeks after surgery. The passive shoulder external rotation was measured and the shoulder joint was assessed bilaterally by a 7.2T MRI bilaterally.

Results

We found a marked decrease in passive shoulder external rotation, associated with a severe subscapularis muscle atrophy and contracture. None however developed the typical pattern of glenohumeral dysplasia.

Conclusions

In contradiction with previous reports, our study shows that the rat model is not adequate for preclinical studies of shoulder dysplasia. However, it might serve as a useful model for studies analyzing shoulder contracture occurring after upper BPBP.

Musculoskeletal growth in the upper arm in infants after obstetric brachial plexus lesions and its relation with residual muscle function

AIM

Denervation after obstetric brachial plexus lesion (OBPL) is associated with reduced musculoskeletal growth in the upper arm. The aim of this study was to investigate whether reduced growth of upper arm flexor and extensor muscles is related to active elbow function and humeral length.

METHOD

In this study, 31 infants age less than 6 months (mean age 4.3mo; range 2.1-5.9mo; 17 males; 14 females;) with unilateral OBPL (Narakas class I, 19; II, 3; III, 2; and IV, 7) treated at the VU medical centre, in whom neurosurgical reconstruction was considered were prospectively studied using magnetic resonance imaging of both arms at a mean age of 4.3 months. Humeral length and the cross-sectional area (CSA) of elbow flexor and extensor muscles were measured in both upper arms. Paresis of elbow function was estimated when the infants were a mean age of 4.5 months using the Gilbert score.

RESULTS

Both flexor and extensor CSAs were significantly smaller on the affected side than on the unaffected side (88% [SD 32%], p=0.020, and 88% [SD 24%], p=0.001 respectively), as was humeral length (96% [SD 7%], p=0.005) (unaffected side 100% in all cases). There was no relation between the reduction in flexor and extensor CSA and residual muscle function. In 17 out of 31 patients, hypertrophy of flexor and/or extensor muscles was observed. Humeral length was not related to muscle parameters.

INTERPRETATION

Denervation has different effects on muscle growth and function as well as bone growth. In young infants with an OBPL, muscle size is not a predictor of muscle function. Flexion contractures of the elbow later in childhood may not be explained by a dominance of flexor muscle mass in infants.

Early effects of muscle atrophy on shoulder joint development in infants with unilateral birth brachial plexus injury

AIM

Shoulder deformities in children with a birth brachial plexus injury (BBPI) are caused by muscle imbalances; however, the underlying mechanisms are unclear. The aim of this study was to assess the early interactions between shoulder muscles and shoulder joint development.

METHOD

In a retrospective magnetic resonance imaging (MRI) study of 36 infants (21 males, 15 females) younger than 12 months (mean 4.8 mo) with unilateral BBPI, volumes and thicknesses of standardized segments of the infraspinatus, subscapularis, and deltoid muscles were measured in both shoulders and expressed as ratios of pathological/unaffected side. The relation between muscle ratios and humeral head subluxation, passive external rotation, glenoid version, and deformity was analysed.

RESULTS

Compared with the unaffected side, the muscles of the affected side were of significantly smaller volume and thickness. The subscapularis was the most severely affected muscle, its volume being only 64% (SD 21%) and its thickness only 79% (SD 23%) of the corresponding values on the unaffected side (p < 0.001). Severe subluxation was predicted by the combination of low infraspinatus and subscapularis volume ratios (r(2) = 0.223; p = 0.014), but not by muscle thickness ratios. Subluxation was related to passive external rotation (p < 0.05), glenoid version (p < 0.01), and deformity (p < 0.01).

INTERPRETATION

In infants with BBPI, muscle size is decreased during in the first months of life by both atrophy and, possibly, by a reduction in the number of sarcomeres in series. These effects are strongly related to shoulder joint subluxation.