Correlation of radiographic muscle cross-sectional area with glenohumeral deformity in children with brachial plexus birth palsy

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.

Advancing glenohumeral dysplasia treatment in brachial plexus birth injury: the end-to-side spinal accessory to suprascapular nerve transfer technique

PURPOSE

Brachial plexus birth injury (BPBI) is a common injury with the spectrum of disease prognosis ranging from spontaneous recovery to lifelong debilitating disability. A common sequela of BPBI is glenohumeral dysplasia (GHD) which, if not addressed early on, can lead to shoulder dysfunction as the child matures. However, there are no clear criteria for when to employ various surgical procedures for the correction of GHD.

METHODS

We describe our approach to correcting GDH in infants with BPBIs using a reverse end-to-side (ETS) transfer from the spinal accessory to the suprascapular nerve. This technique is employed in infants that present with GHD with poor external rotation (ER) function who would not necessitate a complete end-to-end transfer and are still too young for a tendon transfer. In this study, we present our outcomes in seven patients.

RESULTS

At presentation, all patients had persistent weakness of the upper trunk and functional limitations of the shoulder. Point-of-care ultrasounds confirmed GHD in each case. Five patients were male, and two patients were female, with a mean age of 3.3 months age (4 days-7 months) at presentation. Surgery was performed on average at 5.8 months of age (3-8.6 months). All seven patients treated with a reverse ETS approach had full recovery of ER according to active movement scores at the latest follow-up. Additionally, ultrasounds at the latest follow-up showed a complete resolution of GHD.

CONCLUSION

In infants with BPBI and evidence of GHD with poor ER, end-to-end nerve transfers, which initially downgrade function, or tendon transfers, that are not age-appropriate for the patient, are not recommended. Instead, we report seven successful cases of infants who underwent ETS spinal accessory to suprascapular nerve transfer for the treatment of GHD following BPBI.

Early Elbow Flexion Contracture Predicts Shoulder Contracture in Infants with Brachial Plexus Birth Injury

OBJECTIVE

To determine if children who present with an elbow flexion contracture (EFC) from brachial plexus birth injury (BPBI) are more likely to develop shoulder contracture and undergo surgical treatment.

STUDY DESIGN

Retrospective review of children <2 years of age with BPBI who presented to a single children's hospital from 1993 to 2020. Age, elbow and shoulder range of motion (ROM), imaging measurements, and surgical treatment and outcome were analyzed. Patients with an EFC of ≥10° were included in the study sample. Data from 2445 clinical evaluations (1190 patients) were assessed. The final study cohort included 72 EFC cases matched with 230 non-EFC controls. Three patients lacked sufficient follow-up data.

RESULTS

There were 299 included patients who showed no differences between study and control groups with respect to age, sex, race, ethnicity, or functional score. Patients with EFC had 12° less shoulder range of motion (95% CI, 5°-20°; P < .001) and had 2.5 times the odds of shoulder contracture (OR, 2.5; 95% CI, 1.3-4.7; P = .006). For each additional 5° of EFC, the odds of shoulder contracture increased by 50% (OR, 1.5; 95% CI, 1.2-1.8; P < .001) and odds of shoulder procedure increased by 62% (OR, 1.62; 95% CI, 1.04-2.53; P = .03). Sensitivity of EFC for predicting shoulder contracture was 49% and specificity was 82%.

CONCLUSIONS

In patients with BPBI <2 years of age, presence of EFC can be used as a screening tool in identifying shoulder contractures that may otherwise be difficult to assess. Prompt referral should be arranged for evaluation at a BPBI specialty clinic, because delayed presentation risks worsening shoulder contracture and potentially more complicated surgery.

Age Influence Upon Glenohumeral Remodeling After Shoulder Axial Rebalancing Surgery in Brachial Plexus Birth Injury

BACKGROUND

Shoulder rebalancing procedures have been proven to provide satisfactory functional improvements in patients with shoulder external rotation (ER) deficit due to brachial plexus birth injury (BPBI). However, the influence of age at the time of surgery on osteoarticular remodeling remains uncertain. The purposes of this retrospective case series were (1) to assess the age impact on glenohumeral remodeling and (2) to determine an age limit after which significant changes can no longer be expected.

METHODS

We reviewed preoperative and postoperative magnetic resonance imaging data of 49 children with BPBI who underwent a tendon transfer to reanimate active shoulder ER, with (n=41) or without (n=8) concomitant anterior shoulder release to restore passive shoulder ER, at a mean age of 72 ± 40 months (19;172). Mean radiographic follow-up was 35 ± 20 months (12;95). Univariate linear regressions were used to assess the influence of age at the time of surgery upon changes of glenoid version, glenoid shape, percentage of the humeral head anterior to the glenoid midline, and glenohumeral deformity. Beta coefficients with 95% CI were calculated.

RESULTS

Improvements of glenoid version, glenoid shape, percentage of the humeral head anterior and glenohumeral deformity significantly decreased by 0.19 degrees [CI=(-0.31; -0.06), P =0.0046], 0.02 grade [CI=(-0.04; -0.01), P =0.002], 0.12% [CI=(-0.21; -0.04), P =0.0076], and 0.01 grade [CI=(-0.02; -0.01), P =0.0078] per additional month of age at the time of surgery, respectively. The threshold of 5 years was identified as the age at the time of surgery after which significant remodeling no longer occurred. No significant postoperative changes were observed in patients without glenohumeral dysplasia on preoperative magnetic resonance imaging.

CONCLUSION

In the setting of BPBI-related glenohumeral dysplasia, the younger the surgical axial rebalancing of the shoulder, the greater the glenohumeral remodeling seems to be. Such procedure seems to be safe in patients without significant joint deformity on preoperative imaging.

LEVEL OF EVIDENCE

Therapeutic-Level IV.

Assessment of the relationship between Brachial Plexus Profile activity short form scores and modified Mallet scores

INTRODUCTION

This study aims to assess the relationship between the modified Mallet classification and the Brachial Plexus Profile activity short form (BP-PRO activity SF). The therapist or surgeon classifies upper extremity movement for the modified Mallet classification, while the BP-PRO assesses parents' perceptions of difficulty performing activities.

PURPOSE

To provide a deeper understanding of the relationship of functional and perceived outcome measurements.

STUDY DESIGN

Prospective, correlational design.

METHODS

Eighty children with brachial plexus birth injuries were evaluated using the modified Mallet classification, while parents simultaneously answered the BP-PRO activity SF questions. All patients had undergone one of three surgical interventions to improve shoulder function. The relationship between the two measures, patient injury levels, and surgical histories were assessed.

RESULTS

The average modified Mallet scores and BP-PRO activity SF scores weakly correlated (r = 0.312, P = .005) and both measures differentiated between C5-6 and C5-7 injury levels (P = .03 and P = .02, respectively). Conversely, the modified Mallet scores could differentiate between the three surgical groups (F = 8.2, P < .001), while the BP-PRO activity SF could not (P = .54).

CONCLUSION

The results suggest that these tools measure different aspects of patient outcomes. The Mallet classification may be more focused on shoulder motion than the BP-PRO activity SF. Additional questions that specifically require shoulder function could be incorporated into the BP-PRO activity SF to improve understanding of patient/parent perceptions of shoulder function for children with brachial plexus injuries. Clinicians should be aware of the strengths, weaknesses, and limitations of each outcome assessment tool for appropriate use and interpretation of results.

A protocol-based treatment plan to improve shoulder function in children with brachial plexus birth injury: a comparative study

Children with permanent brachial plexus birth injury have a high risk of developing posterior shoulder subluxation. In 2010, we implemented a protocol to reduce the incidence of this deformity, including early passive exercises, ultrasound screening, botulinum toxin-A injections, shoulder splinting and targeted surgeries. Two-hundred and thirty-seven consecutive children treated at our institution, with a mean follow-up of 11 years (range 1 to 17) were compared in three groups: children born from 1995 to 1999 (n = 53), 2000-2009 (n = 109) and 2010-2019 (n = 75). Posterior shoulder subluxation developed in 48% of all patients but the mean age at detection of shoulder subluxation decreased from 5 years to 4.9 months. Need for shoulder relocation surgery also decreased from 28% to 7%. Mean active shoulder external rotation in adduction improved from 2° to 46°. In conclusion, our established protocol has the potential to reduce the incidence of posterior shoulder subluxation in children with brachial plexus birth injury.Level of evidence: II.

The outcome of soft-tissue release and tendon transfer in shoulders with brachial plexus birth palsy

Background

Shoulder involvement in brachial plexus birth palsy is common, and the adduction, internal rotation contracture deformity often requires some form of surgical treatment. There are very few long-term reports on release of contracted muscles and tendon transfers, especially in older children. We are reporting the single-center results of such a surgery with detailed outcome analysis.

Methods

The prospectively collected data from brachial plexus birth palsy cases who had undergone contracture release and tendon transfer were retrospectively studied and examined. The new Mallet and functional scores were compared with the original data forms and then analyzed. The radiographic evidence of glenoid dysplasia and its correlation with age and functional outcome was assessed.

Results

A total of 82 cases with surgery at mean age of 9.5 ± 5.09 years and a follow-up of 8 ± 3.8 (3-20) years entered the study. Of these, 56% of cases had 7 to 20 years of age at surgery. Fifty-four (66%) patients had only shoulder surgery, and 28 (34%) required additional reconstructive surgeries for hand and wrist. Moderate to severe glenohumeral dysplasia was present in 38%. The preoperative Mallet score of 10.6 ± 2.97 improved to 19.3 ± 3.39 (P < .001). Eighty-one percent of patients showed improvement in “reaching face” functions, 71% in “above head” functions, and 74% in “midline functions.” The cases with lack of improvement in midline function mostly belonged to pan-plexus injuries. Noticeable subjective and objective improvement was also observed in cases with glenohumeral dysplasia in their Mallet and functional scores (P < .001). The improvement in function and subjective satisfaction of 92% was observed irrespective of age at surgery.

Conclusion

Soft-tissue release and tendon transfer for brachial plexus birth palsy shoulder can improve function and limb appearance even in older children and young adults and even in the presence of glenohumeral dysplasia.

Effect of Glenohumeral Reduction Type Combined With Tendon Transfer for Brachial Plexus Injury on Objective, Functional, and Patient-Reported Outcomes

PURPOSE

Glenohumeral (GH) joint reductions are frequently performed during tendon transfer surgery for brachial plexus birth injuries (BPBI); however, the effect of reduction method (none required, closed, surgical) has not been assessed. This study compared objective, functional, and patient-reported outcomes between children who underwent a tendon transfer and (1) did not require GH reduction, (2) required concomitant closed GH reduction, or (3) required concomitant surgical GH reduction.

METHODS

Fifty-four children with BPBI who previously underwent teres major and/or latissimus dorsi transfer with or without concomitant GH reduction participated. Joint reduction method was classified as none required (n = 21), closed (n = 9), or surgical (n = 24). Motion capture was collected in a neutral position, abduction, external rotation, and internal rotation. Glenohumeral joint angles and displacements were calculated. Joint angular displacements represented the differences between the joint angles in each terminal position and the joint angles of the arm at rest in the neutral position. A hand surgeon determined modified Mallet scores. Participants' parents completed the Brachial Plexus Profile Activity Short Form (BP-PRO-SF) to assess physical activity performance.

RESULTS

The no-reduction group had significantly less GH elevation than the surgical-reduction group for all positions and significantly less GH elevation than the closed-reduction group for the neutral, external rotation, and internal rotation positions. There were no differences in GH rotation angles. Glenohumeral joint displacements from neutral and modified Mallet scores were similar. The no-reduction group demonstrated significantly greater BP-PRO-SF scores than the surgical-reduction group.

CONCLUSIONS

Patients who underwent a closed or surgical GH joint reduction consistently displayed more GH elevation. Clinically, this corresponds to an abduction contracture. Whereas increased abduction contracture provided a benefit of greater overhead motion, modified Mallet scores were similar between groups. The surgical-reduction group demonstrated lower BP-PRO-SF outcomes.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Influence of Brachial Plexus Birth Injury Location on Glenohumeral Joint Morphology

PURPOSE

Patient presentation after brachial plexus birth injury (BPBI) is influenced by nerve injury location; more contracture and bone deformity occur at the shoulder in postganglionic injuries. Although bone deformity after postganglionic injury is well-characterized, the extent of glenohumeral deformity after preganglionic BPBI is unclear.

METHODS

Twenty Sprague-Dawley rat pups received preganglionic or postganglionic neurectomy on a single forelimb at postnatal days 3 to 4. Glenohumeral joints on affected and unaffected sides were analyzed using micro-computed tomography scans after death at 8 weeks after birth. Glenoid version, glenoid inclination, glenoid and humeral head radius of curvature, and humeral head thickness and width were measured bilaterally.

RESULTS

The glenoid was significantly more declined in affected compared with unaffected shoulders after postganglionic (-17.7° ± 16.9°) but not preganglionic injury. Compared with the preganglionic group, the affected shoulder in the postganglionic group exhibited significantly greater declination and increased glenoid radius of curvature. In contrast, the humeral head was only affected after preganglionic but not postganglionic injury, with a significantly smaller humeral head radius of curvature (-0.2 ± 0.2 mm), thickness (-0.2 ± 0.3 mm), and width (-0.3 ± 0.4 mm) on the affected side compared with the unaffected side; changes in these metrics were significantly associated with each other.

CONCLUSIONS

These findings suggest that glenoid deformities occur after postganglionic BPBI but not after preganglionic BPBI, whereas the humeral head is smaller after preganglionic injury, possibly suggesting an overall decreased biological growth rate in this group.

CLINICAL RELEVANCE

This study expands understanding of the altered glenoid and humeral head morphologies after preganglionic BPBI and its comparisons with morphologies after postganglionic BPBI.

Shoulder internal rotation contracture in brachial plexus birth injury: proximal or distal subscapularis release?

BACKGROUND

In cases of brachial plexus birth injury with internal rotation contracture of the shoulder, the subscapularis muscle may be released proximally, from the subscapular fossa, or distally, along with periarticular soft tissues arthroscopic to the glenohumeral joint. We hypothesized that the indication for each procedure would rely primarily on patients' bone remodeling potential and periarticular soft-tissue contractures, performing proximal releases in patients aged < 4 years and periarticular distal releases in older patients. The purpose of this study was to analyze the outcomes such a strategy could provide.

METHODS

All patients presenting with brachial plexus birth injury-related shoulder internal rotation contractures who underwent a subscapularis release were included; in addition, to restore the joint axial balance, the infraspinatus was systematically reanimated with a tendon transfer (ie, latissimus dorsi or lower trapezius) during the same operating time. Chart review yielded preoperative and postoperative clinical and radiographic measurements, including active and passive range of motion of the shoulder in external rotation (ER) with the arm at the side of the body, the modified Mallet score, glenoid version, and the percentage of the humeral head arthroscopic to the middle of the glenoid process.

RESULTS

Between July 2012 and January 2018, 28 children were operated on at our institution. In patients who underwent proximal subscapularis release (n = 13), significant improvements were observed regarding active shoulder ER, passive shoulder ER, the modified Mallet score, glenoid version, and the percentage of the humeral head arthroscopic to the middle of the glenoid process, averaging 58° ± 32° (P < .0001), 56° ± 20° (P < .0001), 9.7 ± 3.1 points (P = .0006), 15° ± 10° (P = .0034), and 24% ± 20% (P = .0113), respectively, after a mean follow-up period of 4 years. Following distal release procedures (n = 15), these improvements averaged 26° ± 29° (P = .0024), 27° ± 28° (P = .0011), 3.3 ± 4.1 points (P = .0049), 2° ± 17° (P = .4086), and 4% ± 18% (P = .215), respectively, after a mean follow-up period of 3 years.

CONCLUSION

When combined with axial rebalancing of the joint, the proximal release of the subscapularis muscle appears to be sufficient to provide satisfactory functional outcomes in patients with great bone remodeling potential and supple periarticular soft tissues. In older patients, a more comprehensive release of the glenohumeral joint's arthroscopic aspect seems to provide lower but still significant clinical improvements.

Characterization of Infraspinatus Tendon Anatomy: The Soft-Tissue Portion of Remplissage

Purpose

To characterize the morphology of the infraspinatus (IS) tendon and evaluate the bony anatomy of the humeral head (HH) to determine if there is a correlation between HH measurements and the amount of available IS tendon.

Methods

The superior-inferior width as well as the medial-lateral (M-L) length of the inferior and superior portions of the IS tendon were measured in 15 human cadaveric shoulders. Three measurements were then obtained for each corresponding humeral head: (1) anterior to posterior (A-P) distance, (2) midcoronal humeral head distance (MCHH), and (3) M-L distance. Pearson correlation coefficients (R) of tendon measurements relative to HH measurements were determined.

Results

The mean ± SD HH measurements were 44.3 ± 3.3 mm for A-P, 49.3 ± 3.4 mm at the MCHH, and 52.2 ± 3.4 mm in the M-L plane. The mean M-L length of the superior portion of the IS tendon was significantly different from the inferior portion (42.4 vs 31.0 mm, P < .0001). The mean ± SD width of the IS tendon was 19.4 ± 3.0mm. There was a statistically significant correlation (R = 0.58) between the M-L length of the superior IS tendon relative to the M-L HH distance (P < .05) and the A-P HH distance (P < .05).

Conclusions

The superior M-L IS tendon length was significantly greater than the inferior M-L length. The M-L HH and the AP HH distances were significantly correlated to the M-L length of the superior portion of the IS tendon. These relationships may provide an estimation of the length of available IS tendon to help guide the management of Hill-Sachs lesions (HSLs).

Clinical Relevance

Knowledge of the available IS length can help optimize the management of HSLs following anterior shoulder dislocation. If IS tendon M-L length is less than HSL M-L length, then remplissage may result in capsulomyodesis rather than tenodesis. Placement of the superior anchor in a position that is as superior as possible within the HSL defect will maximize the opportunity for IS tenodesis.

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.

Healthy versus pathological learning transferability in shoulder muscle MRI segmentation using deep convolutional encoder-decoders

Fully-automated segmentation of pathological shoulder muscles in patients with musculo-skeletal diseases is a challenging task due to the huge variability in muscle shape, size, location, texture and injury. A reliable automatic segmentation method from magnetic resonance images could greatly help clinicians to diagnose pathologies, plan therapeutic interventions and predict interventional outcomes while eliminating time consuming manual segmentation. The purpose of this work is three-fold. First, we investigate the feasibility of automatic pathological shoulder muscle segmentation using deep learning techniques, given a very limited amount of available annotated pediatric data. Second, we address the learning transferability from healthy to pathological data by comparing different learning schemes in terms of model generalizability. Third, extended versions of deep convolutional encoder-decoder architectures using encoders pre-trained on non-medical data are proposed to improve the segmentation accuracy. Methodological aspects are evaluated in a leave-one-out fashion on a dataset of 24 shoulder examinations from patients with unilateral obstetrical brachial plexus palsy and focus on 4 rotator cuff muscles (deltoid, infraspinatus, supraspinatus and subscapularis). The most accurate segmentation model is partially pre-trained on the large-scale ImageNet dataset and jointly exploits inter-patient healthy and pathological annotated data. Its performance reaches Dice scores of 82.4%, 82.0%, 71.0% and 82.8% for deltoid, infraspinatus, supraspinatus and subscapularis muscles. Absolute surface estimation errors are all below 83 mm² except for supraspinatus with 134.6 mm². The contributions of our work offer new avenues for inferring force from muscle volume in the context of musculo-skeletal disorder management.

Integrated iterative musculoskeletal modeling predicts bone morphology following brachial plexus birth injury (BPBI)

Brachial plexus birth injury (BPBI) is the most common nerve injury among children. The glenohumeral joint of affected children can undergo severe osseous deformation and altered muscle properties, depending on location of the injury relative to the dorsal root ganglion (preganglionic or postganglionic). Preganglionic injury results in lower muscle mass and shorter optimal muscle length compared to postganglionic injury. We investigated whether these changes to muscle properties over time following BPBI provide a mechanically-driven explanation for observed differences in bone deformity between preganglionic and postganglionic BPBI. We developed a computational framework integrating musculoskeletal modeling to represent muscle changes over time and finite element modeling to simulate bone growth in response to mechanical and biological stimuli. The simulations predicted that the net glenohumeral joint loads in the postganglionic injury case were nearly 10.5% greater than in preganglionic. Predicted bone deformations were more severe in the postganglionic case, with the glenoid more declined (pre: -43.8°, post: -51.0°), flatter with higher radius of curvature (pre: 3.0 mm, post: 3.7 mm), and anteverted (pre: 2.53°, post: 4.93°) than in the preganglionic case. These simulated glenoid deformations were consistent with previous experimental studies. Thus, we concluded that the differences in muscle mass and length between the preganglionic and postganglionic injuries are critical mechanical drivers of the altered glenohumeral joint shape.

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.

Isolated open anterior shoulder release in brachial plexus birth palsy

BACKGROUND

In children with brachial plexus birth palsy (BPBP), a shoulder joint internal contracture is commonly observed, which may result in glenohumeral osseous deformities and posterior joint subluxation. The purpose of this retrospective study was to evaluate the impact of an isolated anterior shoulder release on osteoarticular disorders and assess the subsequent clinical improvements.

METHODS

Forty consecutive BPBP patients with glenohumeral dysplasia underwent an open anterior shoulder release. Shoulder scans (ie, magnetic resonance imaging preoperatively and computed tomography postoperatively) were conducted to assess glenoid version and the percentage of the humeral head anterior to the middle of the glenoid fossa. Clinical data including analytical shoulder range of motion and modified Mallet scores were collected.

RESULTS

After a mean follow-up period of 23 months, glenoid version and the percentage of the humeral head anterior to the middle of the glenoid fossa significantly improved from -32° and 18%, respectively, to mean postoperative values of -12° (P < .001) and 45% (P < .001), respectively. Passive and active external rotation increased from -2° and -43°, respectively, to 76° (P < .001) and 54° (P < .001), respectively. The mean modified Mallet score significantly improved from 14.2 to 21.4 points (P < .001). In 8 children with satisfactory passive motion, a latissimus dorsi transfer was performed secondarily to obtain satisfactory active motion.

CONCLUSION

In BPBP patients with glenohumeral deformities, isolated open anterior release of the shoulder induces significant remodeling of the joint, reducing posterior joint subluxation and improving both passive and active shoulder ranges of motion. Additional latissimus transfer remains mandatory in selected cases to achieve satisfactory function.

Computational analysis of glenohumeral joint growth and morphology following a brachial plexus birth injury

Children affected with brachial plexus birth injury (BPBI) undergo muscle paralysis. About 33% of affected children experience permanent osseous deformities of the glenohumeral joint. Recent evidence suggests that some cases experience restricted muscle longitudinal growth in addition to paralysis and reduced range of motion at the shoulder and elbow. It is unknown whether altered loading due to paralysis, muscle growth restriction and contracture, or static loading due to disuse is the primary driver of joint deformity after BPBI. This study uses a computational framework integrating finite element analysis and musculoskeletal modeling to examine the mechanical factors contributing to changes in bone growth and morphometry following BPBI. Simulations of 8 weeks of glenohumeral growth in a rat model of BPBI predicted that static loading of the joint is primarily responsible for joint deformation consistent with experimental measures of bone morphology, whereas dynamic loads resulted in normal bone growth. Under dynamic loading, glenoid version angle (GVA), glenoid inclination angle (GIA), and glenoid radius of curvature (GRC) (-1.3°, 38.2°, 2.5 mm respectively) were similar to the baseline values (-1.8°, -38°, 2.1 mm respectively). In the static case with unrestricted muscle growth, these measures increased in magnitude (5.2°, -48°, 3.5 mm respectively). More severe joint deformations were observed in GIA and GRC when muscle growth was restricted (GVA: 3.6°, GIA: -55°, GRC: 4.0 mm). Predicted morphology was consistent with literature reports of in vivo glenoid morphology following postganglionic BPBI. This growth model provides a framework for understanding the most influential mechanical factors driving glenohumeral deformity following BPBI.

Motion Necessary to Achieve Mallet Internal Rotation Positions in Children With Brachial Plexus Birth Palsy

BACKGROUND

Upper extremity function in children with brachial plexus birth palsy (BPBP) is assessed with clinical tests such as the Mallet classification, which uses a hand to spine position to assess shoulder internal rotation, or the modified Mallet classification, which adds an additional internal rotation task (hand to belly). Children with BPBP frequently have difficulty performing the hand to spine task. This study compared scapulothoracic and glenohumeral (GH) parameters associated with successful completion of the hand to spine and hand to belly modified Mallet positions.

METHODS

Motion capture measurement of 32 children with BPBP was performed in hand on spine, internal rotation (hand to belly), hand to mouth, and maximal humerothoracic extension positions. Modified Mallet scores were determined by a hand surgeon.

RESULTS

Children with better hand to spine performance demonstrated significantly greater GH extension and a nonsignificant trend toward increased GH internal rotation compared with children with scores <3. Children with better internal rotation position performance demonstrated significantly greater GH internal rotation and no significant difference in GH extension. Hand on spine and internal rotation Mallet scores moderately correlated (Pearson r=0.469); however, 54% of children who could place their palms flat on their bellies could not reach behind their backs.

CONCLUSIONS

Successfully reaching behind one's back requires both internal rotation and extension, representing a multiplanar motion. The hand to belly performance is less affected by extension and should be considered for internal rotation assessment, particularly for children undergoing surgical intervention that may affect internal rotation.

LEVEL OF EVIDENCE

Level II.

Surgical Technique and Anatomical Considerations for the Modified L'Episcopo Tendon Transfer

BACKGROUND

Birth brachial plexus injury usually affects the upper trunks of the brachial plexus and can cause substantial loss of active shoulder external rotation and abduction. Due to the unbalanced rotational forces acting at the glenohumeral joint, the natural history of the condition involves progressive glenohumeral joint dysplasia with associated upper limb dysfunction. Surgical reconstruction methods have been described previously by Sever and L'Episcopo, and modified by Hoffer and Roper to release the adduction contracture and to restore external rotation and shoulder abduction.

METHODS

The authors describe their preferred technique for contracture release and tendon transfer to improve external rotation and shoulder abduction. Pertinent anatomy and highlights of surgical exposure are reviewed.

RESULTS

The senior author has utilized this technique with consistent clinical outcomes to improve shoulder function for patients with persisting nerve palsy associated with birth brachial plexus injury. A review of the literature supports utilization of this technique.

CONCLUSIONS

Transfer of the latissimus dorsi and teres major to the posterior rotator cuff for reanimation of shoulder abduction and external rotation deficits associated with birth brachial plexus injury is a safe and reliable technique. Careful patient selection and attention to surgical detail are critical for optimal outcomes.

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.

The Effect of Scapular Position on Magnetic Resonance Imaging Measurements of Glenohumeral Dysplasia Caused by Neonatal Brachial Plexus Palsy

PURPOSE

Neonatal brachial plexus palsy (NBPP) frequently causes glenohumeral dysplasia. Quantification of this dysplasia on magnetic resonance imaging can determine the need for and the success of nonsurgical or surgical intervention. However, we hypothesize that the variable position of the scapula on the thorax between affected and unaffected shoulders affects dysplasia measurements.

METHODS

Magnetic resonance imaging studies were analyzed from 19 NBPP patients (ages 0.8-18 years; median, 2.4 years) without prior shoulder surgery. Three reviewers measured the glenoid version angle (GVA) and percentage of humeral head anterior to the midscapular line (PHHA) on standard axial images ("thoracic axial") and on reformatted axial images aligned perpendicular to the scapular plane ("scapular axial"), which corrects for scapulothoracic position. Scapular tilt and protraction were measured to assess their impact on the difference between thoracic and scapular GVA and PHHA measurements. Intra- and interrater reliability were calculated for GVA and PHHA on both views.

RESULTS

The GVA of the affected shoulder was significantly greater on thoracic than on scapular images, by an average of 5° and as much as 34°. The PHHA was significantly less in the affected shoulders on thoracic than on scapular images, by an average of 5% and as much as 33% of humeral head width. The difference in GVA, but not PHHA, between thoracic and scapular axial images in the affected shoulder correlated with scapular tilt. Unaffected shoulders showed no significant difference in GVA or PHHA between thoracic and scapular axial images. Interrater reliability ranged from fair to substantial and did not differ between thoracic and scapular images.

CONCLUSIONS

Thoracic axial images overestimate the severity of glenohumeral dysplasia in NBPP, owing at least in part to the variable position of the scapula on the thorax. This confounding effect must be considered in interpretation of axial quantitative measures of glenohumeral dysplasia in NBPP.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic III.

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.

Botulinum Toxin Injection for Internal Rotation Contractures in Brachial Plexus Birth Palsy. A Minimum 5-Year Prospective Observational Study

BACKGROUND

Brachial plexus birth palsy is frequently associated with internal rotation contractures of the shoulder as a result of muscle imbalance. The purpose of this study is to assess the effect of botulinum toxin A (BTX-A) injection in the subscapular (SC) muscle on external rotation and the need for tendon transfer for external rotation of the shoulder.

METHODS

A prospective comparative study was performed including 15 consecutive patients treated with BTX-A and a historic control group of 67 patients with mean age 30 months (SD 10). The BTX-A injection (2 IU/kg body weight) was performed immediately following MRI under general anesthesia in the SC muscle. Passive external rotation, the need for tendon transfer surgery, glenohumeral deformity, and muscle degeneration were evaluated. The hazard ratio for no relapse of internal rotation contracture after BTX-A injection compared with no BTX-A injection was calculated.

RESULTS

In the BTX-A group, the passive external rotation in adduction increased from -1 degree (95% CI, -10 to 8) to 32 degrees (95% CI, 17-46) at 3 months and 6 patients were indicated for surgery compared with a decline from -2 degrees (95% CI, -7 to 3) to -11 degrees (95% CI, -17 to -6) in the control group with 66 indications for surgery. At 5 years of follow-up, 10 patients in the BTX-A group were indicated for surgery with a hazard ratio of 4.0 (95% CI, 1.9 to 8.4).

CONCLUSIONS

BTX-A injection in the SC muscle of brachial plexus birth palsy patients can reduce internal rotation contractures and subsequently the need for tendon transfer surgery. At 5 years of follow-up a relapse was seen in 67% of the patients treated with BTX-A. Because at MRI less SC degeneration was found in the good responders on BTX-A treatment, this group seems to be the best target group. Further research is needed on patient selection for BTX-A injection including glenohumeral deformity, SC degeneration, as well as doses of BTX-A to be used.

LEVEL OF EVIDENCE

Level II-prospective comparative study.

Open Glenohumeral Joint Reduction and Latissimus Dorsi and Teres Major Tendon Transfers for Infants and Children Following Brachial Plexus Birth Palsy

Glenohumeral dysplasia can occur in brachial plexus birth palsy due to an imbalance of muscle forces. Most commonly this occurs in C5-C6 injuries where the shoulder external rotators are weak compared with the shoulder internal rotators. Treatment of the dysplasia with open reduction of the glenohumeral joint in combination with rebalancing the muscles can improve the development of the joint. Furthermore, the tendon transfer can improve shoulder function by decreasing the internal rotation forces about the shoulder while increasing the external rotation forces. This paper describes the indications, contraindications, and technique of performing an open glenohumeral joint reduction and latissimus dorsi and teres major tendon transfers for brachial plexus birth palsy.

Analysis of normal and dysplastic glenohumeral morphology at magnetic resonance imaging in children with neonatal brachial plexus palsy

BACKGROUND

Glenoid version and percentage of the humeral head anterior to the scapular line are commonly used 2-D measures to assess deformity of the glenohumeral joint of children with neonatal brachial plexus palsy.

OBJECTIVE

To assess whether glenoid version and percentage of the humeral head anterior to the scapular line would be altered by standardizing the measurements to the orientation of the scapula.

MATERIALS AND METHODS

Twenty-one bilateral magnetic resonance imaging (MRI) scans were evaluated by four reviewers. Measurements were performed on the axial image slices and again after applying 3-D reformatting.

RESULTS

Three-dimensional reformatting led to intrapatient corrections up to 25° for version and -30% for percentage of the humeral head anterior to the scapular line. The mean difference on the involved side between clinical and anatomical version across all subjects from all reviewers was 2.2° ± 3.9° (range: -4.5° to 11.5°). The mean difference in the percentage of the humeral head anterior to the scapular line after reformatting was -1.8% (range: -15.9% to 5.2%).

CONCLUSION

Measurements can differ greatly for the same child depending on technical factors of image acquisition and presentation in the clinical setting. With this study, we present a clinically accessible protocol to correct for scapular orientation from MRI data of children with neonatal brachial plexus palsy.

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.

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.

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.

"Popeye muscle" morphology in OBPI elbow flexion contracture

BACKGROUND

The pathophysiology of elbow flexion contracture (EFC) in obstetrical brachial plexus injury (OBPI) is not established. In basic science models, neonatal denervation leads to impaired muscle growth. In clinical studies, diminished growth is correlated with extent of denervation, and improved with surgical repair. In EFC, the biceps are clinically short and round vs the contralateral size, termed the "Popeye muscle". The objective of this study was to determine if the biceps morphology (muscle belly and tendon length) in arms with EFC secondary to OBPI is different vs the contralateral.

METHODS

This is a retrospective matched-cohort study. Patients with unilateral EFC (>20°) secondary to OBPI were identified (median = 6.6 years, range = 4.7-16.8). A blinded radiologist used computed tomography to measure length of the biceps short head muscle belly, and tendon bilaterally using standardised anatomical landmarks.

RESULTS

Twelve patients were analyzed. The biceps muscle belly in the injured arm was shorter in all patients vs contralateral, mean difference = 3.6 cm (80%), p < 0.001. The biceps tendon in the injured arm was longer in all patients vs contralateral, mean difference = 1.13 cm (127%), p < 0.001. The total biceps length in the injured arm was shorter in all patients vs contralateral, mean difference = 2.5 cm (89%), p < 0.001.

CONCLUSIONS

This is the first human study confirming growth discrepancy of an elbow flexor in EFC. Distinct biceps morphology is demonstrated, with a significantly shorter muscle belly and overall length, but longer tendon vs normal. This is termed the "Popeye muscle" for its irregular morphology. Findings are consistent with impaired limb growth in denervation.

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.

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.

Scapulothoracic and glenohumeral contributions to motion in children with brachial plexus birth palsy

BACKGROUND

Brachial plexus birth palsy occurs in 0.4 to 4.6 of every 1000 live births, with residual shoulder dysfunction in approximately one third of cases. Clinical measures, such as the Mallet classification, provide no insight into the scapulothoracic and glenohumeral contributions to tested global shoulder movements. This study describes the scapulothoracic and glenohumeral components of shoulder motion during the modified Mallet test.

METHODS

Twelve children with Erb's palsy (C5-6) and 8 children with extended Erb's palsy (C5-7) were recruited. The unaffected limbs of 6 subjects were also tested. Locations of markers placed on the thorax, humerus, and scapula were recorded in a neutral position and each of the modified Mallet positions. Scapulothoracic, glenohumeral, and humerothoracic helical displacements and acromion process linear displacements were compared between groups.

RESULTS

The brachial plexus birth palsy groups exhibited significantly smaller glenohumeral displacements in all modified Mallet positions and significantly larger scapulothoracic displacements in the global external rotation and hand to mouth positions. Discriminant function analysis using only humerothoracic variables correctly classified 76.9% of subjects. Discriminant function analysis incorporating scapulothoracic, glenohumeral, and acromion process displacement variables produced accuracy of 92.6%.

CONCLUSIONS

Children with brachial plexus birth palsy demonstrated decreased glenohumeral contributions to achieve every modified Mallet position and increased scapulothoracic contribution in two positions compared with the unaffected group. Different scapulothoracic and glenohumeral strategies were identified between groups. Finally, scapulothoracic and glenohumeral components of shoulder motion are more specific than humerothoracic measures to diagnostic classification.

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.

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.

Meta-analysis of function after secondary shoulder surgery in neonatal brachial plexus palsy

BACKGROUND

Shoulder internal rotation contracture, active abduction, and external rotation deficits are common secondary problems in neonatal brachial plexus palsy (NBPP). Soft tissue shoulder operations are often utilized for treatment. The objective was to conduct a meta-analysis and systematic review analyzing the clinical outcomes of NBPP treated with a secondary soft-tissue shoulder operation.

METHODS

A literature search identified studies of NBPP treated with a soft-tissue shoulder operation. A meta-analysis evaluated success rates for the aggregate Mallet score (≥ 4 point increase), global abduction score (≥ 1 point increase), and external rotation score (≥ 1 point increase) using the Mallet scale. Subgroup analysis was performed to assess these success rates when the author chose arthroscopic release technique versus open release technique with or without tendon transfer.

RESULTS

Data from 17 studies and 405 patients were pooled for meta-analysis. The success rate for the global abduction score was significantly higher for the open technique (67.4%) relative to the arthroscopic technique (27.7%, P<0.0001). The success rates for the global abduction score were significantly different among sexes (P=0.01). The success rate for external rotation was not significantly different between the open (71.4%) and arthroscopic techniques (74.1%, P=0.86). No other variable was found to have significant impact on the external rotation outcomes. The success rate for the aggregate Mallet score was 57.9% for the open technique, a nonsignificant increase relative to the arthroscopic technique (53.5%, P=0.63). Data suggest a correlation between increasing age at the time of surgery and a decreasing likelihood of success with regards to aggregate Mallet with an odds ratio of 0.98 (P=0.04).

CONCLUSIONS

Overall, the secondary soft-tissue shoulder operation is an effective treatment for improving shoulder function in NBPP in appropriately selected patients. The open technique had significantly higher success rates in improving global abduction. There were no significant differences in the success rates for improvement in the external rotation or aggregate Mallet score among these surgical techniques.

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.

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.