MRI of rotator cuff muscle atrophy in relation to glenohumeral joint incongruence in brachial plexus birth injury

Glenohumeral Dysplasia Following Brachial Plexus Birth Injuries: A Review

BACKGROUND AND OBJECTIVES

Despite the high morbidity associated with glenohumeral dysplasia (GHD) in children with brachial plexus birth injuries, the progression of this condition often remains unnoticed, even after correcting for the underlying brachial plexus birth injuries. GHD, driven by a multifactorial process involving disruptions in both direct and indirect neural regulation of bony and muscular structures, can lead to intermittent or permanent shoulder mobility imbalances, significantly impacting the quality of life of those affected. Recent research efforts are increasingly directed toward identifying the root causes, managing the deformity, and determining effective treatment options for correcting GHD.

METHODS

A comprehensive search strategy was used by the authors to identify relevant literature relating to the progression, pathoanatomy, clinical presentation, and management of GHD following brachial plexus birth injuries across various search engines, such as PubMed, Scopus, and Embase. Considering the topic's interdisciplinary nature, articles were retrieved from both neurosurgical and orthopaedic journals to enrich the review.

RESULTS

Given the challenges in managing patients with brachial plexus birth injuries, a multidisciplinary care team consisting of certified occupational hand therapists, neurosurgeons, plastic surgeons, and orthopedic surgeons, specializing in brachial plexus injuries should be advocated for. The aim of this collaborative effort is to correct brachial plexus birth injuries and prevent the persistence of GHD.

CONCLUSION

As research continues to focus on understanding the complexities of this condition, the aim of this review article is to summarize the current literature on the course of brachial plexus birth injury and the development of GHD. By doing so, we hope to provide neurosurgeons with the necessary knowledge and essential tools needed to identify and effectively treat GHD during management of brachial plexus birth injuries.

Subscapularis impairment on magnetic resonance imaging is correlated with functional limitations in neonatal brachial plexus palsy

PURPOSE

The relationship between functional shoulder deficits in children with neonatal brachial plexus palsy (NBPP) and magnetic resonance imaging (MRI) shoulder abnormalities was evaluated.

METHODS

Shoulder function was assessed in 16 children (mean age: 5.8 years; range: 3-12 years) with NBPP based on shoulder rotator muscle strength, as measured using an isokinetic dynamometer and the modified Mallet score. The thickness and fatty infiltration of the subscapularis and infraspinatus muscles, and the morphology of the glenoid on MRI, were also determined.

RESULTS

The highest subscapularis fatty infiltration subgroup of NBPP patients promoted the highest alteration muscle thickness and modified Mallet score.

CONCLUSIONS

In NBPP children, subscapularis impairments play a major role in the functional limitations. This study of pediatric NBPP patients highlighted the value of adding an examination of the muscles to routine MRI assessment of bone parameters in the shoulders of NBPP children.

TRIAL REGISTRATION

NCT03440658.

Shoulder Internal Rotation Contracture Formation in Surgically Managed C5, C6 Brachial Plexus Birth Injuries: Neurotmetic Lesions Fare Worse Than Avulsions

BACKGROUND

A typical feature in infants with severe C5-C6 brachial plexus birth injury (BPBI) requiring nerve repair is the formation of shoulder internal rotation contracture (IRC). The underlying pathophysiological mechanism is unknown, and the sequelae can be difficult to treat. The severity of the IRC differs among children. C5-C6 lesions are heterogeneous at the root level. Our null hypothesis was that the type of root-level lesion (axonotmesis or neurotmesis versus avulsion) was not associated with the extent of IRC formation over time in children with upper-trunk BPBI.

METHODS

We performed a retrospective analysis of all patients with upper-trunk BPBI who underwent primary surgery of the C5 and/or C6 spinal nerves between 1990 and 2020 and had follow-up of at least 2 years. The primary outcome was passive shoulder external rotation (ER) in adduction at 1, 3, 5, 7, and 15 years of age. The secondary outcome was whether additional shoulder surgery was performed. The relationship between the nature of the C5-C6 lesion and IRC formation was analyzed using linear mixed models. The Kaplan-Meier method was used to estimate the cumulative risk of secondary shoulder procedures.

RESULTS

In total, 322 patients were analyzed; mean follow-up was 7.2 ± 4.6 years. The C5-C6 root lesion type was significantly related to the passive range of ER (overall test in linear mixed model, p = 0.007). Children with avulsion of C5 and C6 (n = 21) had, on average, 18° (95% confidence interval [CI], 6.3° to 30°) less IRC formation than those with neurotmesis of C5 and C6 (n = 175) and 17° (2.9° to 31°) less than those with neurotmesis of C5 and avulsion of C6 (n = 34). IRC formation did not differ between the neurotmesis C5-C6 and neurotmesis C5-avulsion C6 groups. Secondary shoulder procedures were performed in 77 patients (10-year risk, 28% [95%CI, 23% to 34%]).

CONCLUSIONS

Shoulder IRC formation in infants with BPBI with surgically treated C5-C6 lesions occurs to a lesser degree if the C5 root is avulsed than when C5 is neurotmetic. This finding provides insight into the possible causative pathoanatomy and may ultimately lead to strategies to mitigate IRC.

LEVEL OF EVIDENCE

Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Ultrasound assessment of glenohumeral dysplasia in infants

Brachial plexus birth injury can lead to irreversible neuromuscular dysfunction and skeletal deformity of the upper extremity and shoulder girdle, ultimately resulting in glenohumeral dysplasia. Diagnosis and treatment of affected infants requires a multi-disciplinary approach in which imaging plays a vital role. While MRI is excellent for assessing both the shoulder and spine of these children, it is costly and requires sedation and is thus typically reserved for preoperative planning. US, however, is inexpensive, dynamic and readily available and provides excellent visualization of the largely cartilaginous glenohumeral joint. As such, it has become a highly useful modality during early diagnosis and follow-up of children with brachial plexus birth injuries. In this review, we describe the relevant anatomy of the glenohumeral joint, outlining the normal sonographic appearance as well as providing tips and tricks for identifying and characterizing pathology.

Value of shoulder US compared to MRI in infants with obstetric brachial plexus paralysis

PURPOSE

Children with brachial plexus birth injury (BPBI) may eventually develop glenohumeral instability due to development of unbalanced muscular strength. Our major goal in this study is to compare the accuracy of physical examination and ultrasonography (US) in determination of glenohumeral instability in infants with BPBI compared with magnetic resonance imaging (MRI) as a gold standard, and to investigate the role and value of US as a screening modality for assessing glenohumeral instability.

METHODS

Forty-two consecutive patients (mean age, 2.3±0.8 months) with BPBI were enrolled into this prospective study. Patients were followed up with physical examination and US with dynamic evaluation in 4-6 weeks intervals. Patients who developed glenohumeral instability based on physical examination and/or US (n=21) underwent MRI. Glenohumeral instability was defined as alpha angle >30° and percentage of posterior humeral head displacement >50%. Diagnostic accuracy of physical examination and US was calculated and quantitative parameters were compared with Wilcoxon test.

RESULTS

Glenohumeral instability was confirmed with MRI in 15 of 21 patients. Accuracy and sensitivity of physical examination and US were 47%, 66% and 100%, 100%, respectively in determination of glenohumeral instability. No significant difference was found for the alpha angle (p = 0.173) but the percentage of posterior humeral head displacement was statistically significant between US and MRI (p = 0.028).

CONCLUSION

Our results indicate that US with dynamic evaluation is a good alternative for MRI in assessment of glenohumeral instability in infants with BPBI, since it is highly accurate and specific, and quantitative measurements used for glenohumeral instability were comparable to MRI. US can be used as a screening method to assess glenohumeral instability in infants with BPBI.

Glenoid vault and humeral head alignment in relation to the scapular blade axis in young patients with pre-osteoarthritic static posterior subluxation of the humeral head

BACKGROUND

Static posterior subluxation of the humeral head is a pre-osteoarthritic deformity preceding posterior erosion in young patients. Its etiology remains unknown. The aim of this study was to analyze the differences in scapular morphology between young patients with pre-osteoarthritic static posterior subluxation of the humeral head and healthy controls with a centered humeral head.

METHODS

We performed a retrospective analysis of all patients with pre-osteoarthritic static posterior subluxation of the humeral head who were treated in our institution between January 2018 and November 2019. Fourteen shoulders in 12 patients were included in this study and then matched according their age, sex, and affected side with controls. Computed tomography images of both groups were compared in the standardized axial imaging plane for differences in scapular morphology. The following parameters were measured: glenoid version relative to the Friedman line and scapular blade axis, scapulohumeral and glenohumeral subluxation index, and neck angle, as well as glenoid and humeral offset.

RESULTS

The patients in the subluxation group showed significantly higher scapulohumeral and glenohumeral subluxation indexes than controls (0.76 vs. 0.55 [P < .0001] and 0.58 vs. 0.51 [P = .016], respectively). The mean measurements of glenoid version according to the Friedman line and relative to the scapular blade axis were significantly higher in the subluxation group than in controls (19° vs. 4° [P < .0001]and 14° vs. 2° [P = .0002], respectively). The glenoid vault was significantly more anteriorly positioned with respect to the scapular blade axis in the subluxation group than in controls (neck angle, 166° vs. 173° [P = .0003]; glenoid offset, 9.2 mm vs. 4.6 mm [P = .0005]). The midpoint of the humeral head showed a posterior offset with respect to the scapular blade axis in the subluxation group, whereas controls had an anteriorly placed midpoint of the humeral head (-2 mm vs. 3.1 mm, P = .01). A higher scapulohumeral subluxation index showed significant correlations with an increased anterior offset of the glenoid vault (increased glenoid offset: r = 0.493, P = .008 and decreased neck angle: r = -0.554, P = .002), a posterior humeral offset (r = -0.775, P < .0001), and excessive glenoid retroversion measured by both methods (Friedman line: r = 0.852, P < .0001; scapular blade axis: r = 0.803, P < .0001). A higher glenohumeral subluxation index also correlated significantly with an increased anterior offset of the glenoid vault (increased glenoid offset: r = 0.403, P = .034; decreased neck angle: r = -0.406, P = .032) and posterior humeral offset (r = -0.502, P = .006).

CONCLUSION

Young patients with pre-osteoarthritic static posterior subluxation of the humeral head have significant constitutional differences in scapular morphology in terms of an increased anterior glenoid offset, excessive glenoid retroversion, and increased posterior humeral offset in relation to the scapular blade compared with healthy matched controls.

Contemporary imaging of the pediatric shoulder: pearls and pitfalls

In skeletally immature patients, the presence of growth plates and articular cartilage of the shoulder can create a predisposition for unique injuries not observed in adults. Furthermore, increasing participation in sports by children and adolescents appears to be leading to a corresponding increase in the number of sports-related injuries. The importance of radiologists being familiar with pediatric shoulder imaging and its associated injuries is therefore growing. In this article, we review the normal development and maturation pattern of ossification centers of the shoulder from the early gestational period through adolescence. Brachial plexus birth palsy, physeal injuries, shoulder dislocation, and internal impingement are discussed within the context of the child's age and the mechanism of injury to guide radiologists to a correct diagnosis.

Effects of Increased Retroversion Angle on Glenoid Baseplate Fixation in Reverse Total Shoulder Arthroplasty: A Finite Element Analysis

Background

Increased glenoid retroversion occurs in patients with severe arthritis but its effect on baseplate fixation of a reverse total shoulder arthroplasty (rTSA) is not clear. The purpose of this study is to determine the effects of increasing glenoid retroversion on baseplate fixation in rTSA using finite element analysis (FEA) modelling.

Methods

Five sets of computerized tomographic (CT) images of healthy normal shoulders were selected and segmented with Amira (Thermo Fisher Scientific) to obtain the solid geometries. Scapula FEA models with 5°, 10°, 15°, 20° and 25° retroversion angles were generated for each healthy scapula geometry and a rTSA glenoid baseplate was implanted on each model. Maximum stress at the anterior and posterior portions of the glenoid and the micromotion between the bone and baseplate were recorded. After simulation with normal scapular bone material properties (Young's modulus 4GPa and Poisson's ratio 0.3), another set of simulations was run on each subject with a 25° retroversion angle and poor bone quality (Young's modulus 500 MPa and Poisson's ratio 0.3) to study a worst-case scenario. Micromotions in each model were also recorded. All statistical analysis was done with SPSS.

Results

Simulation results of models generated from the same subject but with different retroversion angles showed a clear pattern: as retroversion angle increased, the stresses increased posteriorly and decreased anteriorly. Also, micromotion between the bone and the baseplate increased with the increase of retroversion angle. With analysis of variance (ANOVA), we found that all three values change significantly as the retroversion angle increases (p < 0.001). The simulation results also showed that micromotion was large in shoulders with small glenoid size and poor bone quality. However, even in the model with the worst-case scenario (smallest glenoid size, poorest bone quality and 25° retroversion angle), the maximum micromotion and the maximum stresses are still within the safe range.

Discussion

In all cases with both normal and poor bone quality, the stresses and micromotion stayed below the threshold to allow for bone ingrowth of the glenoid baseplate to occur. Based on these results, for glenoid baseplates with a central peg/post and 4 screws for fixation, rTSA baseplate retroversion does not need to be corrected to less than 10° to provide good initial fixation as has been recommended for a cemented glenoid component and can withstand the initial stresses and micromotion up to 25° of retroversion.

Level of evidence

Basic Science Study; Computer Modeling.

Follow-up Study on the Effects of Tendon Transfers and Open Reduction on Moderate Glenohumeral Joint Deformity in Brachial Plexus Birth Injury

BACKGROUND

Soft-tissue contractures about the shoulder in patients with brachial plexus birth injury are common and can lead to progressive shoulder displacement and glenohumeral dysplasia. Open or arthroscopic reduction with musculotendinous lengthening and tendon transfers have become the standard of care. The clinical function and radiographic joint remodeling beyond the first 2 years after surgery are not well understood.

METHODS

We performed a follow-up study of 20 patients with preexisting mild to moderate glenohumeral joint deformity who had undergone open glenohumeral joint reduction with latissimus dorsi and teres major tendon transfers and concomitant musculotendinous lengthening of the pectoralis major and/or subscapularis. Prospective collection of Modified Mallet and Active Movement Scale (AMS) scores and radiographic analysis of cross-sectional imaging for glenoid version, humeral head subluxation, and glenohumeral joint deformity classification were analyzed for changes over time.

RESULTS

The average duration of radiographic follow-up was 4.2 years (range, 2 to 6 years). The mean glenoid version improved from -31.8° to -15.4° (p < 0.0001). The mean percentage of the humeral head anterior to the middle of the glenoid (PHHA) improved from 9.6% to 30.4% (p < 0.0001). The mean glenohumeral joint deformity score improved from 3.7 to 2.1 (p < 0.0001).

CONCLUSIONS

All parameters showed the greatest magnitude of improvement between preoperative measurements and 1 year of follow-up. There were no significant changes beyond the 1-year time point in the Mallet scores, AMS scores, or radiographic outcome measures, possibly because of insufficient power, although trends of improvement were noted for some outcomes. No decline in outcome measures was found during the study period.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Effectiveness and safety of early intramuscular botulinum toxin injections to prevent shoulder deformity in babies with brachial plexus birth injury (POPB-TOX), a randomised controlled trial: study protocol

INTRODUCTION

In children with brachial plexus birth injury (BPBI), denervation of the shoulder muscles leads to bony deformity in the first months of life, reducing active and passive range of motion (ROM) and causing activity limitation. The aim of this multicentre randomised controlled trial is to evaluate the effectiveness of botulinum toxin injections (BTI) in the shoulder internal rotator muscles of 12-month-old babies in limiting the progression of posterior subluxation of the glenohumeral joint, compared with a sham procedure mimicking BTI. The secondary aims are to evaluate the effectiveness of BTI in (1) limiting the progression of glenoid retroversion and three-dimensional (3D) deformity and (2) improving shoulder ROM and upper limb function, as well as to confirm the tolerance of BTI.

METHODS AND ANALYSIS

Sixty-two babies with unilateral BPBI and a risk of posterior humeral head subluxation will be included. Only those with at least 7% posterior subluxation of the humeral head compared with the contralateral shoulder on the MRI will be randomised to one of two groups: 'BTI' and 'Sham'. The BTI group will receive BOTOX injections at the age of 12 months in the internal shoulder rotator muscles (8 UI/kg). The sham group will undergo a sham BTI procedure. Both groups will undergo repeated shoulder MRI at 18 months of age to quantify changes in the percentage of posterior migration of the humeral head (primary outcome), glenoid version and 3D bone deformity. Clinical evaluations (passive shoulder ROM, active movement scale) will be carried out at baseline and 15 and 18 months of age. The mini-assisting hand assessment will be rated between 10 and 11 months and at 18 months of age. Adverse events will be recorded at least monthly for each child.

ETHICS AND DISSEMINATION

Full ethical approval for this study has been obtained. The findings will be disseminated in peer-reviewed publications.

TRIAL REGISTRATION NUMBER

EudraCT: 2015-001402-34 in European Clinical Trial database; NCT03198702 in Clinical Trial database; Pre-results.

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.

Humeral retroversion and shoulder muscle changes in infants with internal rotation contractures following brachial plexus birth palsy

AIM

To examine humeral retroversion in infants who sustained brachial plexus birth palsy (BPBI) and suffered from an internal rotation contracture. Additionally, the role of the infraspinatus (IS) and subscapularis (SSc) muscles in the genesis of this bony deformation is explored.

METHODS

Bilateral magnetic resonance imaging (MRI) scans of 35 infants (age range: 2-7 mo old) with BPBI were retrospectively analyzed. Retroversion was measured according to two proximal axes and one distal axis (transepicondylar axis). The proximal axes were: (1) the perpendicular line to the borders of the articular surface (humeral centerline); and (2) the longest diameter through the humeral head. Muscle cross-sectional areas of the IS and SSc muscles were measured on the MRI-slides representing the largest muscle belly. The difference in retroversion was correlated with the ratio of muscle-sizes and passive external rotation measurements.

RESULTS

Retroversion on the involved side was significantly decreased, 1.0° vs 27.6° (1) and 8.5° vs 27.2° (2), (P < 0.01), as compared to the uninvolved side. The size of the SSc and IS muscles on the involved side was significantly decreased, 2.26 cm² vs 2.79 cm² and 1.53 cm² vs 2.19 cm², respectively (P < 0.05). Furthermore, the muscle ratio (SSc/IS) at the involved side was significantly smaller compared to the uninvolved side (P = 0.007).

CONCLUSION

Even in our youngest patient population, humeral retroversion has a high likelihood of being decreased. Altered humeral retroversion warrants attention as a structural change in any child being evaluated for the treatment of an internal rotation contracture.

Deltoid muscle morphometry as an index of impaired skeletal muscularity in neonatal intensive care

We hypothesised that extremely premature infants would have decreased muscle mass at term-corrected age compared to term-born infants and that the degree of reduced muscle mass acquisition would correlate with the duration of invasive mechanical ventilation. The MRI brain scans of infants admitted in the neonatal unit at King's College Hospital between 1 January 2010 and 1 June 2016 were retrospectively reviewed. The coronal cross-sectional area of the left deltoid muscle (DCSA) was measured in 17 infants born < 28 weeks of gestation and in 20 infants born at term. The prematurely born infants had a median (IQR) gestation age of 25 weeks (24-27) and the term infants 40 weeks (38-41). The duration of invasive mechanical ventilation for the prematurely born infants was 39 days (14-62) and that for the term infants 4 days (2-5), p < 0.001. DCSA was smaller in prematurely born infants (median 189, IQR 176-223 mm²) compared to term-born infants (median 302, IQR 236-389 mm²), p < 0.001. DCSA was related to gestation age (r = 0.545, p = 0.001), weight z-score at MRI (r = 0.658, p < 0.001) and days of invasive mechanical ventilation (r = - 0.583, p < 0.001). In conclusion, extremely premature infants studied at term had a lower muscle mass compared to term-born infants.

CONCLUSION

Our results suggest that prolonged mechanical ventilation in infants admitted in neonatal intensive care is associated with reduced skeletal muscle mass acquisition. What is Known: • Prolonged mechanical ventilation in adult intensive care patients has been associated with skeletal muscle dysfunction and atrophy. • The cross-sectional area of the deltoid muscle has been used to evaluate muscle atrophy in infants with a previous branchial plexus birth injury. What is New: • Premature infants studied at term exhibit lower cross-sectional area of the deltoid muscle than their term counterparts. • Prolonged mechanical ventilation could be associated with skeletal muscle impairment.

Shoulder muscle atrophy and its relation to strength loss in obstetrical brachial plexus palsy

BACKGROUND

Treatment/prevention of shoulder muscle strength imbalances are major therapeutic goals for children with obstetrical brachial plexus palsy. The study aims were to characterize muscle atrophy in children/adolescents with unilateral obstetrical brachial plexus palsy, to quantify the agonist-antagonist muscle volume balance and the association between muscle volume and strength.

METHODS

Eight boys and four girls (age=12.1, standard deviation=3.3) participated in this case-control study. Three-dimensional magnetic resonance images of both shoulders were acquired. The unimpaired shoulder served as a reference. Volumes of deltoid, pectoralis major, supraspinatus, infraspinatus, teres major, subscapularis were calculated based on 3D models, derived through image segmentation. Maximal isometric torques were collected in six directions.

FINDINGS

All the major muscles studied were significantly atrophied. The teres major demonstrated the biggest difference in atrophy between groups (51 percentage points), the pectoralis major was the least atrophied (23 percentage points). The muscle volume distribution was significantly different between shoulders. Muscle volume could predict maximal voluntary isometric torques, but the regression coefficients were weaker on the impaired side (72% to 91% of the strength could be predicted in the uninvolved side and 24% to 90% in the involved side and external rotation strength could not be predicted).

INTERPRETATION

This study demonstrates muscle atrophy varied across all the main shoulder muscles of the glenohumeral joint, leading to significant muscle volume imbalances. The weaker coefficients of determination on the impaired side suggest that other variables may contribute to the loss of strength in addition to atrophy.

Inter-joint coordination analysis of reach-to-grasp kinematics in children and adolescents with obstetrical brachial plexus palsy

BACKGROUND

Obstetrical brachial plexus palsy is a common birth injury to nerves passing through the brachial plexus that may result in structural and functional abnormalities. Individual joint trajectories from kinematic analyses have been used to evaluate the source and extent of abnormalities. Here, two summary measures of limb kinematics were utilized: 1) the Arm Profile Score summarizing upper limb joint kinematic abnormalities from a typical pattern across a task, and 2) the recently developed Multi-joint Coordination Measure using principal component analysis to characterize typical coordination of multiple joints throughout a task and compute deviations in time and space. Our aim was to compare these kinematic measures in persons with and without injury and relate these to clinical and functional scales.

METHODS

3D kinematic data from 10 upper limb joints were collected on 15 children and adolescents with obstetrical brachial plexus palsy and 21 controls during a reach-to-grasp task in both limbs. The two kinematic measures were computed and correlated with each other and the Mallet and ABILIHAND-Kids.

FINDINGS

Both measures revealed that joint angles primarily contributing to shoulder and wrist motion were most prominently affected in the non-dominant limb in obstetrical brachial plexus palsy, with the Multi-joint Coordination Measure additionally indicating when in the motion coordination worsens. These were moderately interrelated but neither correlated with other scales.

INTERPRETATION

The Multi-joint Coordination Measure, while related to the Arm Profile Score, may have additional utility for individualized treatment planning and evaluation of any motor task due to the unique spatial-temporal information provided.

Quantitative Dixon MRI sequences to relate muscle atrophy and fatty degeneration with range of motion and muscle force in brachial plexus injury

BACKGROUND

Assessment of muscle atrophy and fatty degeneration in brachial plexus injury (BPI) could yield valuable insight into pathophysiology and could be used to predict clinical outcome. The objective of this study was to quantify and relate fat percentage and cross-sectional area (CSA) of the biceps to range of motion and muscle force of traumatic brachial plexus injury (BPI) patients.

METHODS

T1-weighted TSE sequence and three-point Dixon images of the affected and non-affected biceps brachii were acquired on a 3 Tesla magnetic resonance scanner to determine the fat percentage, total and contractile CSA of 20 adult BPI patients. Regions of interest were drawn by two independent investigators to determine the inter-observer reliability. Paired Students' t-test and multivariate analysis were used to relate fat percentage, total and contractile CSA to active flexion and biceps muscle force.

RESULTS

The mean fat percentage 12±5.1% of affected biceps was higher than 6±1.0% of the non-affected biceps (p<0.001). The mean contractile CSA 8.1±5.1cm² of the affected biceps was lower than 19.4±4.9cm² of the non-affected biceps (p<0.001). The inter-observer reliability was excellent (ICC 0.82 to 0.96). The contractile CSA contributed most to the reduction in active flexion and muscle force.

CONCLUSION

Quantitative measurement of fat percentage, total and contractile CSA using three-point Dixon sequences provides an excellent reliability and relates with active flexion and muscle force in BPI.

Boston Children's Hospital approach to brachial plexus birth palsy

The treatment of infants with brachial plexus birth palsy (BPBP) continues to be a focus at Boston Children's Hospital. Over the last 15 years, there have been many developments in the treatment of infants with BPBP. Some of the greatest changes have emerged through technical advances such as the advent of distal nerve transfers to allow targeted reinnervation as well as through research to understand the pathoanatomical changes that lead to glenohumeral dysplasia and how this dysplasia can be remodeled. This review will discuss our current practice of evaluation of the infant with BPBP, techniques for microsurgical reconstruction, and prevention and treatment of secondary glenohumeral dysplasia.

Perspectives on glenohumeral joint contractures and shoulder dysfunction in children with perinatal brachial plexus palsy

Shoulder joint deformities continue to be a challenging aspect of treating upper plexus lesions in children with perinatal brachial plexus palsy (PBPP). It is increasingly recognized that PBPP affects the glenohumeral joint specifically, and that abnormal scapulothoracic movements are a compensatory development. The pathophysiology and assessment of glenohumeral joint contractures, the progression of scapular dyskinesia and skeletal dysplasia, and current shoulder imaging techniques are reviewed.

Glenohumeral Dysplasia Following Neonatal Brachial Plexus Palsy: Presentation and Predictive Features During Infancy

PURPOSE

To evaluate the presence and degree of glenohumeral dysplasia (GHD) in infants undergoing surgical exploration for neonatal brachial plexus palsy (NBPP) and to identify potential predictive factors of early maladaptive shoulder morphology.

METHODS

We included all consecutive patients with NBPP who underwent surgical exploration of their brachial plexus and who had a preoperative magnetic resonance imaging scan at our institution over a 3-year period. Demographic, therapy, and surgical data were collected. Imaging was reviewed for glenoid morphology, glenoid version, percent humeral head anterior to the scapula, and alpha angle.

RESULTS

Of 116 infants who presented to our institution during this 3-year period, 19 (16%) underwent surgical exploration and were included in the study. Median age at the time of the scan was 16 weeks (interquartile range, 14-46 weeks). Fourteen of 19 (74%) had GHD of Waters class 2 or increased malformation. Babies who had more severe palsies underwent earlier surgery and had less severe GHD at the time of surgery than did those with less severe palsies who had surgery later. Less severe GHD was associated with more severe palsies, as indicated by Narakas classification and number of root avulsions. Active external rotation was almost universally absent whereas other shoulder movements were present to varying degrees. More severe GHD was associated with greater total shoulder active range of motion and greater pectoralis major muscle mass.

CONCLUSIONS

Glenohumeral dysplasia occurs often and early in NBPP and may occur in the absence of restricted range of motion. Predictors include increasing age and factors related to muscular imbalance. As such, GHD likely affects the functional outcome that may be achieved with reinnervation, and early screening may improve outcomes.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic IV.

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.

Biomechanical Basis of Shoulder Osseous Deformity and Contracture in a Rat Model of Brachial Plexus Birth Palsy

BACKGROUND

The purpose of this study was to investigate the relative contributions of two proposed mechanisms, strength imbalance and impaired longitudinal muscle growth, to osseous and postural deformity in a rat model of brachial plexus birth palsy (BPBP).

METHODS

Thirty-two Sprague-Dawley rat pups were divided into four groups on the basis of surgical interventions to induce a strength imbalance, impaired growth, both a strength imbalance and impaired growth (a combined mechanism), and a sham condition in the left forelimb. Maximum passive external shoulder rotation angle (ERmax) was measured bilaterally at four and eight weeks postoperatively. After the rats were killed at eight weeks, the glenohumeral geometry (on microcomputed tomography) and shoulder muscle architecture properties were measured bilaterally.

RESULTS

Bilateral muscle mass and optimal length differences were greatest in the impaired growth and combined mechanism groups, which also exhibited >15° lower ERmax (p < 0.05; four weeks postoperatively), 14° to 18° more glenoid declination (p < 0.10), and 0.76 to 0.94 mm more inferior humeral head translation (p < 0.10) on the affected side. Across all four groups, optimal muscle length was significantly correlated with at least one osseous deformity measure for six of fourteen muscle compartments crossing the shoulder on the affected side (p < 0.05). In the strength imbalance group, the glenoid was 5° more inclined and the humeral head was translated 7.5% more posteriorly on the affected side (p < 0.05).

CONCLUSIONS

Impaired longitudinal muscle growth and shoulder deformity were most pronounced in the impaired growth and combined mechanism groups, which underwent neurectomy. Strength imbalance was associated with osseous deformity to a lesser extent.

CLINICAL RELEVANCE

Treatments to alleviate shoulder deformity should address mechanical effects of both strength imbalance and impaired longitudinal muscle growth, with an emphasis on developing new treatments to promote growth in muscles affected by BPBP.

Contributions of muscle imbalance and impaired growth to postural and osseous shoulder deformity following brachial plexus birth palsy: a computational simulation analysis

PURPOSE

Two potential mechanisms leading to postural and osseous shoulder deformity after brachial plexus birth palsy are muscle imbalance between functioning internal rotators and paralyzed external rotators and impaired longitudinal growth of paralyzed muscles. Our goal was to evaluate the combined and isolated effects of these 2 mechanisms on transverse plane shoulder forces using a computational model of C5-6 brachial plexus injury.

METHODS

We modeled a C5-6 injury using a computational musculoskeletal upper limb model. Muscles expected to be denervated by C5-6 injury were classified as affected, with the remaining shoulder muscles classified as unaffected. To model muscle imbalance, affected muscles were given no resting tone whereas unaffected muscles were given resting tone at 30% of maximal activation. To model impaired growth, affected muscles were reduced in length by 30% compared with normal whereas unaffected muscles remained normal in length. Four scenarios were simulated: normal, muscle imbalance only, impaired growth only, and both muscle imbalance and impaired growth. Passive shoulder rotation range of motion and glenohumeral joint reaction forces were evaluated to assess postural and osseous deformity.

RESULTS

All impaired scenarios exhibited restricted range of motion and increased and posteriorly directed compressive glenohumeral joint forces. Individually, impaired muscle growth caused worse restriction in range of motion and higher and more posteriorly directed glenohumeral forces than did muscle imbalance. Combined muscle imbalance and impaired growth caused the most restricted joint range of motion and the highest joint reaction force of all scenarios.

CONCLUSIONS

Both muscle imbalance and impaired longitudinal growth contributed to range of motion and force changes consistent with clinically observed deformity, although the most substantial effects resulted from impaired muscle growth.

CLINICAL RELEVANCE

Simulations suggest that treatment strategies emphasizing treatment of impaired longitudinal growth are warranted for reducing deformity after brachial plexus birth palsy.

Prevalence of Posterior Shoulder Subluxation in Children With Neonatal Brachial Plexus Palsy After Early Full Passive Range of Motion Exercises

BACKGROUND

Children with neonatal brachial plexus palsy (NBPP) are often prescribed shoulder range of motion (ROM) exercises; however, the extent and timing of exercise implementation remains controversial in the context of shoulder joint integrity. The association of ROM exercises to delayed posterior shoulder subluxation (PSS) is unknown.

OBJECTIVE

To determine prevalence of PSS in children with NBPP who began full passive ROM exercises before 6 months of age, and characteristics associated with development or absence of PSS in children.

DESIGN

Cross-sectional study.

SETTING

Tertiary care NBPP referral center.

PARTICIPANTS

Forty-six children with NBPP, aged 24-57 months, who began full ROM exercises before 6 months of age.

METHODS

One radiologist conducted bilateral shoulder ultrasound (US) on each child to evaluate for PSS. One occupational therapist evaluated each child clinically for PSS using defined parameters without knowledge of US results.

MAIN OUTCOME MEASURES

By US, 20% of children had PSS; 46% had PSS by clinical examination. Shoulder active ROM limitations and history of shoulder surgery were associated with presence of PSS. Extent of NBPP was not associated with PSS.

RESULTS

Nine of 46 children (20%) met US criteria for PSS; α angle was 58° ± 21° (mean ± standard deviation [SD]). Twenty-one children (46%) met clinical criteria. Mean age at examination was 35 ± 10 months. Shoulder active ROM (P ≤ .004) was associated with PSS, whereas passive ROM was not (P ≥ .08). History of secondary shoulder surgery and primary nerve graft repair were associated with PSS (P = .04). Extent of NBPP by Narakas classification was not associated with PSS (P = .48).

CONCLUSIONS

Early use of full-arc passive ROM home exercise program is not associated with increased prevalence of PSS in children with NBPP compared to prevalence of PSS in published literature. We suggest careful clinical examination, based on defined criteria, provides a reasonable screening examination for evaluating PSS that can be confirmed by noninvasive US.

Late reconstruction of brachial plexus birth palsy

Brachial plexus birth palsy (BPBP) presents to the physician on a clinical spectrum, and may substantially impair the child. Potential interventions to improve function for the child with BPBP include physical therapy, microsurgical nerve reconstruction and nerve transfers, soft-tissue balancing and reconstruction with musculotendinous transfers, and osteotomies. Some interventions, such as nerve reconstruction, are best performed in infancy; others, such as muscle transfers and osteotomies, are performed to treat manifestations of this condition that appear later in childhood. Although controversy continues to exist regarding the natural history and surgical management of these patients, recent literature has improved our understanding of surgical indications, anticipated outcomes, and potential complications. On the basis of current evidence, we present here the recommendations for surgical intervention in the upper extremity of children with BPBP, and encourage early referral to a brachial plexus specialist to establish care.

Elbow Flexion Contractures in Childhood in Obstetric Brachial Plexus Lesions: A Longitudinal Study of 20 Neurosurgically Reconstructed Infants with 8-Year Follow-up

OBJECTIVE

 Little knowledge exists on the development of elbow flexion contractures in children with obstetrical brachial plexus lesion (OBPL). This study aims to evaluate the prognostic significance of several neuromuscular parameters in infants with OBPL regarding the later development of elbow flexion contractures.

METHODS

 Twenty infants with OBPL with insufficient signs of recovery in the first months of life who were neurosurgically reconstructed were included. At a mean age of 4.6 months, the following neuromuscular parameters were assessed: existence of flexion contractures, cross-sectional area (CSA) of upper arm muscles on MRI, Narakas classification, EMG results, and elbow muscle function using the Gilbert score. In childhood at follow-up at mean age of 7.7 years, we measured the amount of flexion contractures and the upper arm peak force (Newton). Statistical analysis is used to assess relations between these parameters.

RESULTS

 Flexion contractures of greater than 10 degrees occurred in 55% of our patient group. The relation between the parameters in infancy and the flexion contractures in childhood is almost nonexistent. Only the Narakas classification was related to the development of flexion contractures in childhood (p = 0.006). Infant muscle CSA is related to childhood peak muscle force.

CONCLUSION

 The role of infancy upper arm muscle hypotrophy/hypertrophy, reinnervation, and early elbow muscle function in the development of childhood elbow contractures remains unclear. In this cohort prediction of childhood flexion, contractures were not possible using infancy neuromuscular parameters. We suggest that contractures might be an adaptive process to optimize residual muscle function.

Glenohumeral abduction contracture in children with unresolved neonatal brachial plexus palsy

BACKGROUND

Following neonatal brachial plexus palsy, the Putti sign-obligatory tilt of the scapula with brachiothoracic adduction-suggests the presence of glenohumeral abduction contracture. In the present study, we utilized magnetic resonance imaging (MRI) to quantify this glenohumeral abduction contracture and evaluate its relationship to shoulder joint deformity, muscle atrophy, and function.

METHODS

We retrospectively reviewed MRIs of the thorax and shoulders obtained before and after shoulder rebalancing surgery (internal rotation contracture release and external rotation tendon transfer) for twenty-eight children with unresolved neonatal brachial plexus palsy. Two raters measured the coronal positions of the scapula, thoracic spine, and humeral shaft bilaterally on coronal images, correcting trigonometrically for scapular protraction on axial images. Supraspinatus, deltoid, and latissimus dorsi muscle atrophy was assessed, blinded to other measures. Correlations between glenohumeral abduction contracture and glenoid version, humeral head subluxation, passive external rotation, and Mallet shoulder function before and after surgery were performed.

RESULTS

MRI measurements were highly reliable between raters. Glenohumeral abduction contractures were present in twenty-five of twenty-eight patients, averaging 33° (range, 10° to 65°). Among those patients, abductor atrophy was present in twenty-three of twenty-five, with adductor atrophy in twelve of twenty-five. Preoperatively, greater abduction contracture severity correlated with greater Mallet global abduction and hand-to-neck function. Abduction contracture severity did not correlate preoperatively with axial measurements of glenohumeral dysplasia, but greater glenoid retroversion was associated with worse abduction contractures postoperatively. Surgery improved passive external rotation, active abduction, and hand-to-neck function, but did not change the abduction contracture.

CONCLUSIONS

A majority of patients with persistent shoulder weakness following neonatal brachial plexus palsy have glenohumeral abduction deformities, with contractures as severe as 65°. The abduction contracture occurs with abductor atrophy, with or without associated adductor atrophy. This contracture may improve global shoulder abduction by positioning the glenohumeral joint in abduction. Glenohumeral and scapulothoracic kinematics and muscle pathology must be further elucidated to advance an understanding of the etiology and the prevention and treatment of the complex shoulder deformity following neonatal brachial plexus palsy.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

The role of subscapularis muscle denervation in the pathogenesis of shoulder internal rotation contracture after neonatal brachial plexus palsy: a study in a rat model

We assessed the role of subscapularis muscle denervation in the development of shoulder internal rotation contracture in neonatal brachial plexus injury. Seventeen newborn rats underwent selective denervation of the subscapular muscle. The rats were evaluated at weekly intervals to measure passive shoulder external rotation. After 4 weeks, the animals were euthanized. The subscapularis thickness was measured using 7.2T MRI axial images. The subscapularis muscle was then studied grossly, and its mass was registered. The fiber area and the area of fibrosis were measured using collagen-I inmunostained muscle sections. Significant progressive decrease in passive shoulder external rotation was noted with a mean loss of 58° at four weeks. A significant decrease in thickness and mass of the subscapularis muscles in the involved shoulders was also found with a mean loss of 69%. Subscapularis muscle fiber size decreased significantly, while the area of fibrosis remained unchanged. Our study shows that subscapularis denervation, per se, could explain shoulder contracture after neonatal brachial plexus injury, though its relevance compared to other pathogenic factors needs further investigation.

The role of muscle imbalance in the pathogenesis of shoulder contracture after neonatal brachial plexus palsy: a study in a rat model

BACKGROUND

An internal rotation contracture of the shoulder is common after neonatal brachial plexus injuries due to subscapularis shortening and atrophy. It has been explained by 2 theories: muscle denervation and muscle imbalance between the internal and external rotators of the shoulder. The goal of this study was to test the hypothesis that muscle imbalance alone could cause subscapularis changes and shoulder contracture.

MATERIALS AND METHODS

We performed selective neurectomy of the suprascapular nerve in 15 newborn rats to denervate only the supraspinatus and the infraspinatus muscles, leaving the subscapularis muscle intact. After 4 weeks, passive shoulder external rotation was measured and a 7.2-T magnetic resonance imaging scan of the shoulders was used to determine changes in the infraspinatus and subscapularis muscles. The subscapularis muscle was weighed to determine the degree of mass loss. An additional group of 10 newborn rats was evaluated to determine the sectional muscle fiber size and muscle area of fibrosis by use of images from type I collagen immunostaining.

RESULTS

There was a significant decrease in passive shoulder external rotation, with a mean loss of 66°; in the thickness of the denervated infraspinatus, with a mean loss of 40%; and in the thickness and weight of the non-denervated subscapularis, with mean losses of 28% and 25%, respectively. No differences were found in subscapularis muscle fiber size and area of fibrosis between shoulders after suprascapular nerve injury.

CONCLUSIONS

Our study supports the theory that shoulder muscle imbalance is a cause of shoulder contracture in patients with neonatal brachial plexus palsy.

In vivo pediatric shoulder muscle volumes and their relationship to 3D strength

In the pediatric shoulder, injury and pathology can disrupt the muscle force balance, resulting in severe functional losses. As little data exists pertaining to in vivo pediatric shoulder muscle function, musculoskeletal data are crucially needed to advance the treatment of pediatric shoulder pathology/injury. Therefore, the purpose of this study was to develop a pediatric database of in vivo volumes for the major shoulder muscles and correlate these volumes with maximum isometric flexion/extension, internal/external rotation, and abduction/adduction joint moments. A methodology was developed to derive 3D shoulder muscle volumes and to divide the deltoid into sub-units with unique torque producing capabilities, based on segmentation of three-dimensional magnetic resonance images. Eleven typically developing children/adolescents (4F/7M, 12.0 ± 3.2 years, 150.8 ± 16.7 cm, 49.2 ± 16.4 kg) participated. Correlation and regression analyses were used to evaluate the relationship between volume and maximum, voluntary, isometric joint torques. The deltoid demonstrated the largest (30.4 ± 1.2%) and the supraspinatus the smallest (4.8 ± 0.5%) percent of the total summed volume of all six muscles evaluated. The anterior and posterior deltoid sections were 43.4 ± 3.9% and 56.6 ± 3.9% of the total deltoid volume. The percent volumes were highly consistent across subjects. Individual muscle volumes demonstrated moderate-high correlations with torque values (0.70-0.94, p<0.001). This study presents a comprehensive database documenting normative pediatric shoulder muscle volume. Using these data a clear relationship between shoulder volume and the torques they produce was established in all three rotational degrees-of-freedom. This study furthers the understanding of shoulder muscle function and serves as a foundation for evaluating shoulder injury/pathology in the pediatric/adolescent population.

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.

Reoperation for failed shoulder reconstruction following brachial plexus birth injury

BACKGROUND

Various approaches have been developed to treat the progressive shoulder deformity in patients with brachial plexus birth palsy. Reconstructive surgery for this condition consists of complex procedures with a risk for failure.

CASE PRESENTATIONS

This is a retrospective case review of the outcome in eight cases referred to us for reoperation for failed shoulder reconstructions. In each case, we describe the initial attempt(s) at surgical correction, the underlying causes of failure, and the procedures performed to rectify the problem. Results were assessed using pre- and post-operative Mallet shoulder scores. All eight patients realized improvement in shoulder function from reoperation.

CONCLUSIONS

This case review identifies several aspects of reconstructive shoulder surgery for brachial plexus birth injury that may cause failure of the index procedure(s) and outlines critical steps in the evaluation and execution of shoulder reconstruction.

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.

Biceps brachii long head overactivity associated with elbow flexion contracture in brachial plexus birth palsy

BACKGROUND

The etiology of elbow flexion contracture in children with brachial plexus birth palsy remains unclear. We hypothesized that the long head of the biceps brachii muscle assists with shoulder stabilization in children with brachial plexus birth palsy and that overactivity of the long head during elbow and shoulder activity is associated with an elbow flexion contracture.

METHODS

Twenty-one patients with brachial plexus birth palsy-associated elbow flexion contracture underwent testing with surface electromyography. Twelve patients underwent repeat testing with fine-wire electromyography. Surface electrodes were placed on the muscle belly, and fine-wire electrodes were inserted bilaterally into the long and short heads of the biceps brachii. Patients were asked to perform four upper extremity tasks: elbow flexion-extension, hand to head, high reach, and overhead ball throw. The mean duration of muscle activity in the affected limb was compared with that in the contralateral, unaffected limb, which was used as a control. Three-dimensional motion analysis, surface dynamometry, and validated function measures were used to evaluate upper extremity kinematics, elbow flexor-extensor muscle imbalance, and function.

RESULTS

The mean activity duration of the long head of the biceps brachii muscle was significantly higher in the affected limb as compared with the contralateral, unaffected limb during hand-to-head tasks (p = 0.02) and high-reach tasks (p = 0.03). No significant differences in mean activity duration were observed for the short head of the biceps brachii muscle between the affected and unaffected limbs. Isometric strength of elbow flexion was not significantly higher than that of elbow extension in the affected limb (p = 0.11).

CONCLUSIONS

Overactivity of the long head of the biceps brachii muscle is associated with and may contribute to the development of elbow flexion contracture in children with brachial plexus birth palsy. Elbow flexion contracture may not be associated with an elbow flexor-extensor muscle imbalance, as previously hypothesized. The negative impact of elbow flexion contracture on upper extremity function warrants future research in the development of preventive and therapeutic techniques to address elbow flexion contractures in children with brachial plexus birth palsy.

Treatment of shoulder sequelae in brachial plexus birth injury

BACKGROUND

Many children with permanent brachial plexus birth injury (BPBI) develop shoulder problems, with subsequent joint deformity without treatment. We assessed the indications and outcome of shoulder operations for BPBI.

PATIENTS AND METHODS

31 BPBI patients who had undergone a shoulder operation in our hospital between March 2002 and December 2005 were included in the study. Relocation of the humeral head had been performed in 13 patients, external rotation osteotomy of the humerus in 5 patients, subscapular tendon lengthening in 5 patients, and teres major transposition in 8 patients. Subjective results were registered. Shoulder range of motion was measured, and function assessed according to the Mallet scale. Magnetic resonance imaging (MRI) was performed pre- and postoperatively. Glenoscapular angle (GSA) and percentage of humeral head anterior to the middle of the glenoid fossa (PHHA) were measured. Congruency of the glenohumeral joint (GHJ) was estimated. The mean follow-up time was 3.8 (1.7-6.8) years.

RESULTS

At follow-up, the subjective result was satisfactory in 30 of the 31 patients. There were 4 failures, which in retrospect were due to wrong choice of surgical method in 3 of these 4 patients. Mean increase in Mallet score was 5.5 after successful relocation, 1.4 after rotation osteotomy, 2.2 after subscapular tendon lengthening, and 3.1 after teres major transposition. Congruency of the shoulder joint improved in 10 of 13 patients who had undergone a relocation operation, with mean improvement in GSA of 33º and mean increase in PHHA of 25%. There were no substantial changes in congruency of the glenohumeral joint in patients treated with other operation types.

INTERPRETATION

Restriction of the range of motion and malposition of the glenohumeral joint can be improved surgically in brachial plexus birth injury. Remodeling of the joint takes place after successful relocation of the humeral head in young patients.

Impaired growth of denervated muscle contributes to contracture formation following neonatal brachial plexus injury

BACKGROUND

The etiology of shoulder and elbow contractures following neonatal brachial plexus injury is incompletely understood. With use of a mouse model, the current study tests the novel hypothesis that reduced growth of denervated muscle contributes to contractures following neonatal brachial plexus injury.

METHODS

Unilateral brachial plexus injuries were created in neonatal mice by supraclavicular C5-C6 nerve root excision. Shoulder and elbow range of motion was measured four weeks after injury. Fibrosis, cross-sectional area, and functional length of the biceps, brachialis, and subscapularis muscles were measured over four weeks following injury. Muscle satellite cells were cultured from denervated and control biceps muscles to assess myogenic capability. In a comparison group, shoulder motion and subscapularis length were assessed following surgical excision of external rotator muscles.

RESULTS

Shoulder internal rotation and elbow flexion contractures developed on the involved side within four weeks following brachial plexus injury. Excision of the biceps and brachialis muscles relieved the elbow flexion contractures. The biceps muscles were histologically fibrotic, whereas fatty infiltration predominated in the brachialis and rotator cuff muscles. The biceps and brachialis muscles displayed reduced cross-sectional and longitudinal growth compared with the contralateral muscles. The upper subscapularis muscle similarly displayed reduced longitudinal growth, with the subscapularis shortening correlating with internal rotation contracture. However, excision of the external rotators without brachial plexus injury caused no contractures or subscapularis shortening. Myogenically capable satellite cells were present in denervated biceps muscles despite impaired muscle growth in vivo.

CONCLUSIONS

Injury of the upper trunk of the brachial plexus leads to impaired growth of the biceps and brachialis muscles, which are responsible for elbow flexion contractures, and impaired growth of the subscapularis muscle, which correlates with internal rotation contracture of the shoulder. Shoulder muscle imbalance alone causes neither subscapularis shortening nor internal rotation contracture. Impaired muscle growth cannot be explained solely by absence of functioning satellite cells.

Effects of botulinum toxin-induced paralysis on postnatal development of the supraspinatus muscle

The mechanical environment plays an important role in musculoskeletal tissue development. The present study characterized changes in supraspinatus muscle due to removal of mechanical cues during postnatal development. An intramuscular injection of botulinum toxin type A (BTX) was used to induce and maintain paralysis in the left shoulders of mice since birth while the right shoulders received saline and served as contralateral controls. A separate group of animals was allowed to develop normally without any injections. Muscles were examined postnatally at various time points. The maximum isometric tetanic force generated by the muscle was significantly reduced in the BTX group compared to saline and normal groups. The paralyzed muscles were smaller and showed significant muscle atrophy and fat accumulation on histologic evaluation. Myogenic genes myogenin, myoD1, myf5, myf6, and fast type II myosin heavy chain (MHC) isoform were significantly upregulated while slow type I MHC isoform was significantly downregulated in the BTX group. Adipogenic genes C/EBPα, PPARγ2, leptin, and lipoprotein lipase were significantly upregulated in the BTX group. Results indicate that reduced muscle loading secondary to BTX-induced paralysis leads to fat accumulation and muscle degeneration in the developing muscle. Understanding the molecular and compositional changes in developing supraspinatus muscles may be useful for identifying and addressing the pathological changes that occur in shoulder injuries such as neonatal brachial plexus palsy.

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.

Musculoskeletal deformities secondary to neurotomy of the superior trunk of the brachial plexus in neonatal mice

The developmental course of musculoskeletal deformities in neonatal brachial plexus palsy (NBPP) has not been studied extensively. The goals of this study were to: (1) evaluate a new animal model of NBPP, (2) characterize the development of musculoskeletal abnormalities in paralyzed shoulders, and (3) investigate the expression of myogenic and adipogenic genes in paralyzed rotator cuff muscles. Neonatal mice were divided into neurotomy and sham groups. The neurotomy group underwent surgical transection of the superior trunk of the brachial plexus within 24 h of birth. The sham group underwent the same surgical exposure, but the brachial plexus was left intact. Musculoskeletal deformities were evaluated with radiological and histological assays at 2, 4, 8, 12, and 30 weeks after birth. The supraspinatus muscles of a separate group of mice were used to examine expression of myogenic and adipogenic genes at 8 weeks. The neurotomized forelimbs developed deformities similar to those seen in human NBPP. The deformities progressed with age. The denervated supraspinatus muscles showed intramuscular fat accumulation and upregulation of both myogenic and adipogenic genes compared to the normal. The current study presents a useful animal model for future research examining musculoskeletal changes secondary to neonatal nerve injury.

Structural changes in muscle and glenohumeral joint deformity in neonatal brachial plexus palsy

BACKGROUND

Internal rotation contracture of the shoulder is common in children with neonatal brachial plexus palsy. A long-standing contracture may cause osseous deformities in the developing shoulder. The purpose of the study was to evaluate the relationship between osseous deformities of the glenohumeral joint and structural differences due to muscle denervation in the rotator cuff muscles.

METHODS

One hundred and two children with residual neonatal brachial plexus palsy underwent magnetic resonance imaging of both shoulders. The glenoid version and posterior, medial, and superior subluxation of the humeral head were measured. The shapes of the glenoid and the humeral head were categorized, and the infraspinatus, supraspinatus, subscapularis, and deltoid muscles were scored as being normal, atrophic, or atrophic with fatty degeneration.

RESULTS

Muscle degeneration was most prominent in the subscapularis muscle. Glenoid version correlated with the structural differences in the subscapularis muscle. Posterior subluxation of the humeral head and the shape of the glenoid correlated with all abnormal rotator cuff muscles. Superior humeral subluxation correlated only with changes in the supraspinatus muscle. Medialization and the shape of the humeral head were not associated with atrophic changes of the rotator cuff. Regeneration of the rotator cuff muscles was not significantly different in patients with a C5-C6 (C7) or a complete brachial plexus lesion. However, the changes in glenoid version, the degree of posterior humeral subluxation, and the degree of medial humeral subluxation were significantly more severe in patients with a C5-C6 (C7) lesion compared with those in patients with a complete lesion of the brachial plexus.

CONCLUSIONS

Structural differences in the rotator cuff muscles alter the direction of the humeral head forces on the developing glenoid fossa and can lead to osseous deformities. Glenohumeral deformities are significantly greater with a C5-C6 (C7) lesion than with a complete brachial plexus lesion in which the large internal rotators are also affected. Reducing the muscular imbalance that occurs with a C5-C6 (C7) lesion could diminish glenohumeral joint incongruency and may improve the outcome of subsequent soft-tissue release or tendon transfer surgery.

Ossification of the proximal humerus in children with residual brachial plexus birth palsy: a magnetic resonance imaging study

BACKGROUND

Children with residual brachial plexus birth palsy may develop deformities of the humeral head and the glenoid. Surgical treatment has been described to maximize function and to lessen deformity by means of glenohumeral remodeling. The timing and technique of surgical intervention have not been resolved. The timing of the appearance on magnetic resonance imaging of the ossific nuclei in patients with brachial plexus birth palsy has not been described. We examined the timing of ossification about the proximal humerus. Our hypothesis was that the timing of ossification of the proximal humerus differs between the side involved in brachial plexus palsy and the uninvolved side.

METHODS

A retrospective study was performed of 117 children with residual brachial plexus birth palsy (aged 5 mo to 10 y) who had magnetic resonance imaging scans of the bilateral shoulders performed at our institution between 2000 and 2007. All axial slices were reviewed by a single observer for evidence of ossification of the humeral head epiphysis, the greater tuberosity, and the lesser tuberosity, as well as for evidence that the 3 were coalesced. Statistical analysis was performed to compare the involved and uninvolved sides.

RESULTS

The appearance of the greater tuberosity ossific nucleus on the involved side was significantly delayed. There was a trend towards delay in the appearance of the lesser tuberosity ossific nucleus and the coalescence of the 3 ossific nuclei on the involved side. The duration during which ossification of the involved brachial plexus side occurred was generally shorter compared with the uninvolved side.

CONCLUSION

There is delay in the ossification of the involved side in brachial plexus birth palsy, and a shorter duration of ossification.

Current concepts in the management of brachial plexus birth palsy

Brachial plexus birth palsy, although rare, may result in substantial and chronic impairment. Physiotherapy, microsurgical nerve reconstruction, secondary joint corrections, and muscle transpositions are employed to help the child maximize function in the affected upper extremity. Many present controversies regarding natural history, microsurgical treatment, and secondary shoulder reconstructive surgery remain unresolved in infants with brachial plexus birth palsies. Recent literature has enhanced our understanding of the pathoanatomy and natural history of the injury as well as the surgical indications, expected outcomes, and complications; this literature has led to improved care of these patients. Based on the present evidence, recommendations for both microsurgery and shoulder reconstruction with tendon transfer and arthroscopic and open reductions are presented.

Brachial plexus birth injury: US screening for glenohumeral joint instability

PURPOSE

To prospectively evaluate the use and optimal timing of ultrasonographic (US) screening for posterior shoulder subluxation in infantswith brachial plexus birth injury (BPBI).

MATERIALS AND METHODS

Approval of the ethics committee and informed consent of guardians was obtained. This population-based prospective study included neonates with BPBI who were born in Helsinki from January 1, 2003 through December 31, 2006, and in whom BPBI was verified with sequential clinical examinations. US was performed at 1, 3, 6, and 12 months. Size (width and height) of the humeral head and its ossification center and congruency of the shoulder (alpha angle) were measured. Frequency of BPBI and permanent changes were evaluated. This study also included patients who were referred from the tertiary catchment area. For statistical analysis, 95% confidence intervals were calculated, and analysis of variance was performed.

RESULTS

BPBI was seen in 132 of 41980 neonates (3.1 per 1000). In 27 cases (0.64 per 1000), BPBI did not heal during the 1st year of life and was considered permanent. The humeral head and its ossification center were smaller on the affected side in permanent BPBI. Nine patients with permanent palsy had posterior subluxation of the humeral head depicted with US (alpha angle, >30 degrees ). In five patients, posterior subluxation [corrected] was detected at 3 months. Nineteen of 21 patients with BPBI from the tertiary catchment area had permanent palsy. Ten of 19 patients developed posterior subluxation of the shoulder, which was verified with US. Altogether, three of these cases were not detected by surgeons. Posterior subluxation of the humeral head developed during the 1st year of life in one-third of patients with permanent BPBI. In more than one-half (55% [five of nine]) of the patients, posterior subluxation [corrected] was detected with US at 3 months, and in 89% (eight of nine), it was detected at 6 months.

CONCLUSION

US is a fast and useful tool for diagnosis of posterior subluxation of the humeral head, and examination of the glenohumeral joint should be performed at 3 and 6 months of age in infants with BPBI if symptoms persist.

The biceps tendon as a measure of rotational deformity in residual brachial plexus birth palsy

BACKGROUND

Children with residual brachial plexus birth palsy often develop internal rotation contractures with subsequent glenohumeral dysplasia seen on axial imaging. Coronal deformity (characterized by humeral head subluxation), and angular deformity (characterized by glenoid retroversion) have been defined. We hypothesize that the location of the biceps tendon characterizes rotational deformity.

METHODS

A retrospective study was performed on 91 children (average age 3.2+/-2.2 y) who lacked external rotation beyond neutral and had magnetic resonance imaging (MRI) scans of bilateral shoulders performed at our institution between 2000 and 2007. The charts were reviewed for the measurement of the external rotation of the involved shoulder with the arm adducted and the scapula stabilized. The glenoscapular angle (glenoid version), the percentage of the humeral head anterior to the middle of the glenoid fossa (PHHA), and the angle of rotation of the biceps tendon (biceps angle) were measured on MRI scans of both shoulders. Statistical analysis was performed to compare these MRI measurements for the involved and uninvolved sides, and to identify the correlations between them and the external rotation.

RESULTS

The average biceps angle was 47.9+/-15.2 degrees on the uninvolved side and 26.2+/-15.0 degrees on the involved side. The average differences between the 2 shoulders in the biceps angle (21.7+/-20.5 degrees), the version (18.9+/-15.0 degrees), and the PHHA (19.8+/-13.6%) were all significant (P<0.001). Only the biceps angle correlated significantly with external rotation (P<0.001). This correlation remained significant even when the version and the PHHA were held constant (P=0.004).

CONCLUSION

The biceps angle is a measure of rotational deformity in patients with residual brachial plexus birth palsy, and correlates better with external rotation than either the glenoid version or the PHHA. The biceps angle may be a useful measure of rotational glenohumeral deformity before and after surgery.

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

Background

A substantial number of children with an obstetric brachial plexus lesion (OBPL) will develop internal rotation adduction contractures of the shoulder, posterior humeral head subluxations and glenohumeral deformities. Their active shoulder function is generally limited and a recent study showed that their shoulder muscles were atrophic. This study focuses on the role of shoulder muscles in glenohumeral deformation and function.

Methods

This is a prospective study on 24 children with unilateral OBPL, who had internal rotation contractures of the shoulder (mean age 3.3 years, range 14.7 months to 7.3 years). Using MR imaging from both shoulders the following parameters were assessed: glenoid form, glenoscapular angle, subluxation of the humeral head, thickness and segmental volume of the subscapularis, infraspinatus and deltoid muscles. Shoulder function was assessed measuring passive external rotation of the shoulder and using the Mallet score for active function. Statistical tests used are t-tests, Spearman's rho, Pearsons r and logistic regression.

Results

The affected shoulders showed significantly reduced muscle sizes, increased glenoid retroversion and posterior subluxation. Mean muscle size compared to the normal side was: subscapularis 51%, infraspinatus 61% and deltoid 76%. Glenoid form was related to infraspinatus muscle atrophy. Subluxation was related to both infraspinatus and subscapularis atrophy. There was no relation between atrophy of muscles and passive external rotation. Muscle atrophy was not related to the Mallet score or its dimensions.

Conclusion

Muscle atrophy was more severe in the subscapularis muscle than in infraspinatus and deltoid. As the muscle ratios are not related to passive external rotation nor to active function of the shoulder, there must be other muscle properties influencing shoulder function.

Shoulder problems in children with brachial plexus birth palsy: evaluation and management

Traction injury to the brachial plexus sustained during the birth process that results in impaired neuromuscular function of the upper extremity continues to occur despite advances in modern obstetric care. The most common pattern of injury usually results in motor weakness of shoulder external rotation, leading to internal rotation contractures and subsequent deformity of the skeletally immature glenohumeral joint. Understanding of these deformities and effective surgical intervention have advanced greatly over the past decade. Restoration of balance between internal and external rotation forces around the shoulder has great potential for remodeling of the glenohumeral joint in the young child. Arthroscopic-directed release of the contracture, with select use of latissimus dorsi transfer to provide external rotation power, has proved to be effective for many children with these contractures.