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

Changes in Shoulder Rotation Based on Elevation in Children With Brachial Plexus Birth Injury

PURPOSE

Lack of shoulder external rotation is common in children with brachial plexus birth injuries. Development of glenohumeral (GH) dysplasia is associated with progressive loss of passive external rotation. Some authors recommend measuring external rotation with the arm adducted, whereas others recommend measurement with the arm in 90° of abduction. The purpose of this study was to compare active and passive external rotation and internal rotation measured in adduction versus abduction.

METHODS

Fifteen children with brachial plexus birth injuries held their affected arms in maximal external and internal rotation with the arm adducted and the arm at approximately 90° of abduction. Active and passive rotations were measured with three-dimensional motion capture. Scapulothoracic (ST) internal/external rotation and GH internal/external rotation joint angles were calculated and compared using multivariable, one-way repeated measures analyses of variance.

RESULTS

There were no significant differences for active or passive ST rotation in external rotation in adduction versus abduction. Glenohumeral external rotation was significantly increased with the arm in abduction compared with adduction both actively and passively. There were no differences in ST rotation in active versus passive conditions, but all GH rotations were significantly greater passively.

CONCLUSIONS

Shoulder internal/external rotation in abduction and adduction is not interchangeable. Comprehensive assessment of shoulder external and internal rotation should include both adduction and abduction.

CLINICAL RELEVANCE

For children with brachial plexus birth injuries, both active and passive GH external rotations were greater in abduction. Therefore, early GH joint dysplasia may be missed if GH external rotation is measured in abduction. Additionally, consistency in arm position is important for comparison over time. The entire ST rotation capacity was used to perform maximal internal and external rotation, but the entire passive GH range of motion was not actively used. This highlights an area for potential surgical intervention to improve motion.

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.

Brachial plexus birth injury: advances and controversies

While there is considerable spontaneous recovery in most cases of brachial plexus birth injury, many children are left with significant problems that may lead to lifelong functional limitations, loss of work and social isolation. Detailed treatment with the right strategy can provide very valuable improvement in function. Over the past few years, the clinical approach to brachial plexus birth palsy has entered a new era in both diagnostic and surgical treatment methods. This article reviews four areas of management, the role of imaging in defining the severity of the injury, the optimal timing of for nerve exploration and reconstruction in appropriate cases, the advantages and potential complications of nerve transfers, and the role of physiotherapy. Available evidence is considered. Although it is difficult to make clear and precise inferences on a subject where there are many variables and considerable uncertainties, some currently accepted views will be summarized.Level of evidence: V.

The Relative Efficacy of Available Proteasome Inhibitors in Preventing Muscle Contractures Following Neonatal Brachial Plexus Injury

BACKGROUND

Contractures following neonatal brachial plexus injury (NBPI) are associated with growth deficits in denervated muscles. This impairment is mediated by an increase in muscle protein degradation, as contractures can be prevented in an NBPI mouse model with bortezomib (BTZ), a proteasome inhibitor (PI). However, BTZ treatment causes substantial toxicity (0% to 80% mortality). The current study tested the hypothesis that newer-generation PIs can prevent contractures with less severe toxicity than BTZ.

METHODS

Unilateral brachial plexus injuries were surgically created in postnatal (5-day-old) mice. Following NBPI, mice were treated with either saline solution or various doses of 1 of 3 different PIs: ixazomib (IXZ), carfilzomib (CFZ), or marizomib (MRZ). Four weeks post-NBPI, mice were assessed for bilateral passive range of motion at the shoulder and elbow joints, with blinding to the treatment group, through an established digital photography technique to determine contracture severity. Drug toxicity was assessed with survival curves.

RESULTS

All PIs prevented contractures at both the elbow and shoulder (p < 0.05 versus saline solution controls), with the exception of IXZ, which did not prevent shoulder contractures. However, their efficacies and toxicity profiles differed. At lower doses, CFZ was limited by toxicity (30% to 40% mortality), whereas MRZ was limited by efficacy. At higher doses, CFZ was limited by loss of efficacy, MRZ was limited by toxicity (50% to 60% mortality), and IXZ was limited by toxicity (80% to 100% mortality) and loss of efficacy. Comparisons of the data on these drugs as well as data on BTZ generated in prior studies revealed BTZ to be optimal for preventing contractures, although it, too, was limited by toxicity.

CONCLUSIONS

All of the tested second-generation PIs were able to reduce NBPI-induced contractures, offering further proof of concept for a regulatory role of the proteasome in contracture formation. However, the narrow dose ranges of efficacy for all PIs highlight the necessity of precise proteasome regulation for preventing contractures. Finally, the substantial toxicity stemming from proteasome inhibition underscores the importance of identifying muscle-targeted strategies to suppress protein degradation and prevent contractures safely.

CLINICAL RELEVANCE

Although PIs offer unique opportunities to establish critical mechanistic insights into contracture pathophysiology, their clinical use is contraindicated in patients with NPBI at this time.

The Relationship Between Elbow Flexion Postures and Overhead Reaching in Birth Brachial Plexus Injuries

PURPOSE

The aim of this study was to investigate the effect of alterations in muscle length of the biceps in various elbow postures during shoulder elevation and muscle activation.

METHODS

Participants aged 5 years and older with a birth brachial plexus injury were asked to perform elevation shoulder (abduction and flexion) in 7 elbow conditions. Surface electromyography was applied to bilateral biceps and triceps.

RESULTS

Peak shoulder elevation was present in the immobilized 20° elbow posture. Muscle activity of the triceps and biceps was impacted by the elbow posture via immobilization.

CONCLUSIONS

Elbow postures in elongated postures, via immobilization, may result in higher shoulder elevation due to increased passive forces when there is an altered muscle state of the biceps in this population. Clinicians should consider the optimal elbow joint posture (<30°) to improve overhead reaching in this population.

Long-Term Results of Isolated Latissimus Dorsi to Rotator Cuff Transfer in Brachial Plexus Birth Injury

Background  Brachial plexus birth injury results in deficits in strength and motion, occasionally requiring surgery to restore power to the deficient external rotators of the shoulder in these patients. This is a retrospective analysis of the long-term results of an isolated latissimus dorsi transfer to the rotator cuff in patients with brachial plexus birth injury. Methods  This is a retrospective review of prospectively collected data for patients undergoing isolated latissimus dorsi transfer into the infraspinatus in addition to release of the internal rotation contracture of the shoulder with greater than 5 years' follow-up. Preoperative and postoperative shoulder elevation and external rotation were documented. Failure of surgery was defined as a return of the internal rotation contracture and a clinically apparent clarion sign. Results  A total of 22 patients satisfied the inclusion criteria: 9 global palsies and 13 upper trunk palsies. The average follow-up was 11 years, ranging from 7.5 to 15.9 years. There was a trend for improved external rotation in the global palsy cohort at final follow-up ( p  = 0.084). All nine global palsies maintained adequate external rotation without a clarion sign. Five of the 13 upper trunk palsies failed the latissimus dorsi transfer and subsequently required either teres major transfer and/or rotational osteotomy. In these five failures, the period from initial transfer to failure averaged 6.6 years, ranging from 3.4 to 9.5 years. Conclusion  The results of this study indicate that patients with global palsy have sustained long-term improved outcomes with isolated latissimus dorsi transfer while patients with upper trunk palsy have a high rate of failure. Based on these results, we recommend isolated latissimus dorsi transfer for global palsy patients who have isolated infraspinatus weakness. Level of Evidence:  Case series - Level IV.

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.

The role of sympathetic innervation in neonatal muscle growth and neuromuscular contractures

Neonatal brachial plexus injury (NBPI), a leading cause of pediatric upper limb paralysis, results in disabling and incurable muscle contractures that are driven by impaired longitudinal growth of denervated muscles. A rare form of NBPI, which maintains both afferent and sympathetic muscle innervation despite motor denervation, protects against contractures. We have previously ruled out a role for NRG/ErbB signaling, the predominant pathway governing antegrade afferent neuromuscular transmission, in modulating the formation of contractures. Our current study therefore investigated the contributions of sympathetic innervation of skeletal muscle in modulating NBPI-induced contractures. Through chemical sympathectomy and pharmacologic modification with a β2 -adrenergic agonist, we discovered that sympathetic innervation alone is neither required nor sufficient to modulate contracture formation in neonatal mice. Despite this, sympathetic innervation plays an intriguing sex-specific role in mediating neonatal muscle growth, as the cross-sectional area (CSA) and volume of normally innervated male muscles were diminished by ablation of sympathetic neurons and increased by β-adrenergic stimulation. Intriguingly, the robust alterations in CSA occurred with minimal changes to normal longitudinal muscle growth as determined by sarcomere length. Instead, β-adrenergic stimulation exacerbated sarcomere overstretch in denervated male muscles, indicating potentially discrete regulation of muscle width and length. Future investigations into the mechanistic underpinnings of these distinct aspects of muscle growth are thus essential for improving clinical outcomes in patients affected by muscle disorders in which both length and width are affected.

Shoulder extension impairment with residual neonatal brachial plexus injury

BACKGROUND

Impairment of both shoulder extension and behind-the-back function are common in patients with residual neonatal brachial plexus injury (NBPI), but have scarcely been studied or reported in the literature. Behind-the-back function is classically evaluated using the hand-to-spine task used for the Mallet score. Angular measurements of shoulder extension with residual NBPI have generally been studied utilizing kinematic motion laboratories. To date, no validated clinical examination method for this has been described.

METHODS

Intraobserver and interobserver reliability analyses of 2 shoulder extension angles-passive glenohumeral extension (PGE) and active shoulder extension (ASE)-were performed. Afterwards, a retrospective clinical study was conducted on prospectively collected data on 245 children with residual BPI treated from January 2019 through August 2022. Demographic characteristics, level of palsy, previous surgical procedures, modified Mallet score, and bilateral PGE and ASE data were analyzed.

RESULTS

All inter- and intraobserver agreements were excellent, ranging from 0.82 to 0.86. The median patient age was 8.1 years (3.5-21). Among the 245 children, 57.6% had Erb's palsy, 28.6% extended Erb's palsy, and 13.9% global palsy. One hundred sixty-eight (66%) of the children could not touch their lumbar spine, among whom 26.2% (n = 44) had to swing the arm to reach it. Both the degrees of ASE and PGE achieved correlation significantly with the hand-to-spine score, the ASE strongly (r = 0.705) and the PGE weakly (r = 0.372) (both P < .0001). Significant correlations also were found between lesion level and the hand-to-spine Mallet score (r = -0.339; P < .0001) and ASE (r = -0.299; P < .0001), and between patient age and the PGE (P = .0416, r = -0.130). A statistically significant decrease in PGE and incapacity to reach the spine were found in patients who underwent glenohumeral reduction, shoulder tendon transfer, or humeral osteotomy, relative to those who had microsurgery or no surgery. Receiver operating curves showed that, for both PGE and ASE, the minimum extension angle required to successfully perform the hand-to-spine task was 10°, with sensitivity levels of 69.9 and 82.2, and specificity levels of 69.5 and 87.8 (both P < .0001), respectively.

CONCLUSIONS

Glenohumeral flexion contracture and lost ASE are extremely common in children with residual NBPI. Both the PGE and ASE angles can be measured reliably with a clinical exam, with at least 10° of PGE and ASE necessary to perform the hand-to-spine Mallet task.

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.

The Philadelphia Shriners Hospital Approach to Brachial Plexus Birth Injury

The care of children with brachial plexus birth injuries (BPBI) is a complex multidisciplinary endeavor. At the Shriners Hospital for Children in Philadelphia, we have sought to elevate the quality of care delivered to patients through outcomes research and collaboration with colleagues around the world. Our approach to the management of this challenging pathology has evolved time and again. Here, we describe our current approach to patient assessment and operative management in patients with BPBI and its many sequelae.

Permanent Brachial Plexus Birth Injury: Helsinki Shoulder Protocol

Passive shoulder exercises from birth and ultrasound screening from 3 to 12 months. Botox is given to shoulder internal rotators and a bracing commenced, if alpha-angle exceeds 30°, or passive shoulder external rotation is below 70 degrees. Plexus reconstruction is recommended to children with root avulsion(s) on magnetic resonance imaging or 3-month Toronto Test Score < 3.5. Specific neurotization is recommended to children without avulsions, but lack of progress in healing. Shoulder dysplasia was diagnosed in 49% of 270 patients with permanent brachial plexus birth injury in our catchment area from 1995 to 2021. The age at detection of shoulder dysplasia dropped from mean 5.4 years in children born before 2000 to mean 3.9 months in children born after 2009. Botox was given to 57% of the patients born after 2009. Rate of shoulder relocation decreased from 28 to 7% while mean active shoulder external rotation in adduction increased from 2 to 46°.

Clinical Diagnosis of the Infantile Shoulder Subluxation in Residual Brachial Plexus Birth Injury and Its Correlation With Ultrasound Diagnosis

INTRODUCTION AND AIMS OF STUDY

Timely detection of shoulder subluxation in infants with brachial plexus birth injury (BPBI) is essential to prevent the progression of glenohumeral deformity. Shoulder ultrasonography (USG) is routinely used to detect an infantile subluxation/dislocation, but its use is limited because of the paucity of expert radiologists in developing countries. The aim of this study was to determine the clinical examination predictors to determine shoulder subluxation in patients with BPBI correlating with ultrasound confirmation.

METHODS

We prospectively studied children who presented to our hospital between 2017 and 2021 diagnosed as brachial plexus birth injury. In patients developing internal rotation contracture of the shoulder, we looked for 3 standard clinical signs: reduced passive external rotation <60 degrees, deep anterior crease (DAC) and relatively short arm segment. Shoulder subluxation was defined as USG measurement of alpha angle>30 degrees and ossific nuclei of the humerus lying behind the dorsal scapular line. Sensitivity and specificity were used to assess their efficacy in clinical diagnosis of shoulder subluxation in different groups. The predicted probability of shoulder subluxation from each prediction rule was compared with actual distributions based on USG confirmation.

RESULTS

Of the 58 BPBI infants who developed PER<60 degrees at the shoulder, 41 had USG confirmed shoulder subluxation. The 2 independent predictors of shoulder subluxation (PER<45 degrees and DAC) were identified in the current patient population based on data analysis. The presence of short arm segment is a very specific marker of shoulder subluxation but not sensitive. The predicted probability of shoulder subluxation from the prediction rule combining all the 3 markers were similar to the actual distributions in the current patient population.

CONCLUSIONS

PER<45 degrees and presence of deep anterior crease are clinical markers indicating shoulder dislocation in patients with BPBI developing reduced external rotation at the shoulder. On the basis of the proposed clinical diagnosis algorithm, the above markers along with the selective use of USG can help in early detection and treatment of infantile shoulder dislocation.

Glenoid osteotomy with various tendon transfers for brachial plexus birth palsy: clinical outcomes

BACKGROUND

Posterior shoulder dislocation is one of the disabling complications of brachial plexus birth injury (BPBI), and various treatment options including capsule and surrounding muscles release for open reduction, humeral derotational osteotomy, and tendon transfers have been recommended to manage it. In the present study, we aimed to determine the clinical outcome of open reduction with soft tissue release, tendon transfer, and glenoid osteotomy in patients with BPBI and posterior shoulder dislocation or subluxation.

METHODS

From 2018 to 2020, 33 patients who underwent open reduction, glenoid osteotomy, and tendon transfer were included. The glenohumeral deformity was classified according to the Waters radiographic classification. Functional assessment was performed using the Mallet grading system before and at least 2 years after the surgery.

RESULTS

The patients were monitored for 26.88 ± 5.47 months. Their average age was 27.5 ± 14 months. Significant improvement was seen in the overall Mallet score (from 13.5 to 18.91 points) and its segments including hand-to-mouth, hand-to-neck, global abduction, global external rotation, abduction range of motion (ROM), and external rotation ROM. Hand-to-back score and the presence of a Trumpet sign were significantly decreased in the postoperation phase (all P values < .001). The above-mentioned variables significantly changed for both infantile and noninfantile dislocations.

CONCLUSION

Our study demonstrated that open reduction along with glenoid osteotomy improves retroversion, and muscle strengthening with different muscle transfers is an effective technique for BPBI.

Can the Sup-ER Protocol Decrease the Prevalence and Severity of Elbow Flexion Deformity in Brachial Plexus Birth Injuries?

BACKGROUND

Brachial plexus birth injuries (BPBIs) can often result in functional and cosmetic deficits including, according to a recent scoping review, elbow flexion contractures in up to 48%. A treatment algorithm that includes a custom long-arm orthosis to optimize early glenohumeral joint positioning (Sup-ER protocol) has been shown to improve shoulder range of motion. Although the protocol was not intentionally designed to affect the elbow, this study investigates the prevalence and severity of elbow flexion contractures in children treated with that protocol.

METHODS

This prospective cross-sectional cohort study examined 16 children aged 4 and older with BPBI severe enough to be treated with the Sup-ER protocol. Passive and active elbow flexion and extension range of motion (ROM) were assessed in both arms. Elbow flexion contractures were defined as > 5^o from neutral.

RESULTS

Within the cohort of 16 patients (mean age: 7.0 years, range: 4.5-11.6 years), the mean maximal passive elbow extension was -6.2° in the affected arm and + 5.1° (hyperextension) in the unaffected arm. Zero patients had a severe elbow flexion contracture (>30^o) and only 6/16 met the lowest threshold definition of elbow flexion contracture (>5^o), with a mean onset at 22 months of age.

CONCLUSIONS

This study suggests an unintended decreased prevalence and severity of elbow flexion contractures in children with more severe BPBI treated with the Sup-ER protocol, relative to published values.

Long-Term Outcomes of Biceps Rerouting for Flexible Supination Contractures in Children With Brachial Plexus Birth Injuries

PURPOSE

Forearm supination contractures occur in 7% of children with brachial plexus birth injuries (BPBI). Biceps rerouting is proposed when pronation has deteriorated but is passively correctable to at least 0° (neutral). The purpose of this investigation was to evaluate long-term outcomes of biceps rerouting for this indication, including magnitude and maintenance of correction, complications, and subsequent osteotomy.

METHODS

We conducted a retrospective review of all children with BPBI and forearm supination contractures treated with biceps rerouting alone, for the above indications, from 1993 to 2017 with at least 2 years follow-up. Demographic information, BPBI characteristics, surgical details, and ranges of motion were obtained from medical records. Pre- and postoperative active pronation (AP) and supination (AS), elbow flexion contracture, and arc of forearm rotation (Arc) were analyzed using linear mixed-effect models.

RESULTS

Twenty-five children (13 females; 13 left forearms; 15 global BPBI) underwent biceps rerouting at age 7 ± 3 years and were followed for 6 ± 3 years. Before surgery, the mean AP and AS were 6° ± 29° and 62° ± 27°, respectively. At the final follow-up, the mean AP, AS, and Arc were 39° ± 36°, 18° ± 34°, and 57° ± 42°, respectively. AP was significantly improved and AS was significantly decreased by 2 years after surgery and at the final follow-up. Neither Arc nor elbow flexion contracture changed significantly. Two of 25 (8%) children underwent subsequent forearm osteotomy.

CONCLUSIONS

Biceps rerouting in children with BPBI improves the forearm position when pronation is deteriorating by shifting the arc from supination to pronation without decreasing the arc of motion or worsening elbow flexion contractures. There is a low risk of complications and a limited need for subsequent forearm osteotomy. These results are maintained over time. When performed before passive pronation is reduced beyond neutral, this procedure may prevent severe supination contractures and reduce the need for forearm osteotomy.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

RNA-Seq analysis reveals sex-dependent transcriptomic profiles of human subacromial bursa stratified by tear etiology

Rotator cuff tendinopathy, a major cause of shoulder disability, occurs due to trauma or degeneration. Our molecular understanding of traumatic and degenerative tears remains elusive. Here, we probed transcript level differences between traumatic and degenerative tears. Subacromial bursa tissues were collected from patients with traumatic or degenerative tears during arthroscopy (N = 32). Transcripts differentially expressed by tear etiology were detected by RNA-seq. RNA-seq results were validated by real-time quantitative polymerase chain reaction. We identified 334 protein-coding transcripts differentially expressed between traumatic and degenerative tears in females and 167 in males at a fold-change greater than 2. In females, XIRP2, MYL1, MYBPC1, TNNT1, and LMOD2, were highly expressed in traumatic tears whereas TPSD1, CDSN, RCVRN, LTBP4, and PTGS1 were elevated in degen tears. Transcripts elevated in traumatic tears represented muscle cell differentiation and development, and muscle contraction whereas those elevated in degenerative tears represented cell activation and immune response. In males, AZGP1, CNTFR, COL9A1, ZNF98, and EREG were highly elevated in traumatic tears whereas MYL2, HOXD11, SLC6A7, CADM1, and MMP17 were highly expressed in degenerative tears. Transcripts elevated in traumatic tears represented metabolic/catabolic processes, and transmembrane protein transport while processes related to cell cycle were mainly enriched in degenerative tears. Numerous long noncoding RNAs were differentially expressed between traumatic and degenerative tears in both sexes. In summary, this study provides insights into molecular biology of bursa in patients with rotator cuff tendon disease based on tear acuity and novel sex-based transcript differences that could inform clinical decision making in treating patients with traumatic or degenerative shoulder injuries.

Natural history of elbow flexion and forearm rotation contractures in obstetric brachial plexus injury

A prospective database study was undertaken to investigate the severity and progression of elbow and forearm contractures in patients with obstetric brachial plexus injury. One-hundred and fifty-nine patients, who had not undergone nerve repair (mean age 12 years at last follow-up) (56 Narakas Group 1, 66 Group 2, 27 Group 3, 10 Group 4) were studied. Mean fixed flexion of the elbow at last follow-up was 13° for Group 1, 15° for Group 2, 19° for Group 3 and 24° for Group 4. Severe contracture of 30° or more developed in 31 children (mean age 118 months), with poorer active shoulder abduction being a significant risk factor. Onset of contracture was before the age of 5 years but did not increase substantially beyond 12 years. Active and passive pronation and supination tended to decrease with increasing injury severity. Seventeen children developed severe restriction of passive pronation (supination contracture) (mean age 69 months), and 12 developed severe restriction of passive supination at a mean of 137 months.Level of evidence: III.

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.

Clavicle lengthening, a novel operation technique to reduce pain in brachial plexus birth injury patients

BACKGROUND

Brachial plexus birth injury (BPBI) can lead to an imbalance of shoulder musculature that can lead to glenohumeral contractures, and joint and osseous deformities. Glenoid hypoplasia, lengthening of coracoid and acromion, protraction, lateral rotation and elevation of the scapula, and shortening of the clavicle can be observed. As a consequence, the trapezius, levator scapulae, rhomboid, and supraspinatus muscles are overloaded in daily activities causing pain, which can be difficult to treat conservatively. It is hypothesized that operative lengthening of the clavicle may lead to a more anatomic position of the scapula and periscapular muscles, which, as a consequence, may lead to less overloading pain. This study presents the results of this new technique in patients with BPBI.

MATERIALS AND METHODS

Seven patients (median age 20 years) were included and underwent a lengthening osteotomy of the clavicle at the affective side. Preoperatively, the osseous deformities were confirmed with a computed tomography scan. Patient-reported outcome measures, Disabilities of Arm, Shoulder and Hand score, and Mallet score were evaluated pre- and postoperatively.

RESULTS

After a median of 42 (interquartile range [IQR]: 8.0) months' follow-up, all patients were satisfied with the result. The median numeric rating scale for satisfaction was 8.0 (IQR: 2). Pain decreased from a median numeric rating scale of 7.0 (IQR: 2) preoperatively to 2.0 (IQR: 3) at the final follow-up. The median Mallet score was 14.5 (IQR: 1) preoperatively and 14 (IQR: 0) at the final follow-up. The median Disabilities of Arm, Shoulder and Hand score was 36.7 (IQR: 24.1) at the final follow-up. All patients returned to their normal work without changes in working conditions.

CONCLUSION

Short-term follow-up shows that in patients with BPBI with a short clavicle at the affected side and malposition of the scapula, a lengthening osteotomy of the clavicle is a safe and promising technique to reduce pain based on overloading, without deterioration of shoulder function.

Brachial plexus birth injury and cerebral palsy lead to a common contracture phenotype characterized by reduced functional muscle length and strength

Introduction

Brachial plexus birth injury (BPBI) and cerebral palsy (CP) both cause disabling contractures for which no curative treatments exist, largely because contracture pathophysiology is incompletely understood. The distinct neurologic nature of BPBI and CP suggest different potential contracture etiologies, although imbalanced muscle strength and insufficient muscle length have been variably implicated. The current study directly compares the muscle phenotype of elbow flexion contractures in human subjects with BPBI and CP to test the hypothesis that both conditions cause contractures characterized by a deficit in muscle length rather than an excess in muscle strength.

Methods

Subjects over 6 years of age with unilateral BPBI or hemiplegic CP, and with elbow flexion contractures greater than 10 degrees on the affected side, underwent bilateral elbow flexion isokinetic strength testing to identify peak torque and impulse, or area under the torque-angle curve. Subjects then underwent needle microendoscopic sarcomere length measurement of bilateral biceps brachii muscles at symmetric joint angles.

Results

In five subjects with unilateral BPBI and five with hemiplegic CP, peak torque and impulse were significantly lower on the affected versus unaffected sides, with no differences between BPBI and CP subjects in the percent reduction of either strength measurement. In both BPBI and CP, the percent reduction of impulse was significantly greater than that of peak torque, consistent with functionally shorter muscles. Similarly, in both conditions, affected muscles had significantly longer sarcomeres than unaffected muscles at symmetric joint angles, indicating fewer sarcomeres in series, with no differences between BPBI and CP subjects in relative sarcomere overstretch.

Discussion

The current study reveals a common phenotype of muscle contracture in BPBI and CP, with contractures in both conditions characterized by a similar deficit in muscle length rather than an excess in muscle strength. These findings support contracture treatments that lengthen rather than weaken affected muscles. Moreover, the discovery of a common contracture phenotype between CP and BPBI challenges the presumed dichotomy between upper and lower motor neuron lesions in contracture pathogenesis, instead revealing the broader concept of “myobrevopathy”, or disorder of short muscle, warranting increased investigation into the poorly understood mechanisms regulating muscle length.

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.

Location of brachial plexus birth injury affects functional outcomes in a rat model

Brachial plexus birth injury (BPBI) results in shoulder and elbow paralysis with shoulder internal rotation and elbow flexion contracture as frequent sequelae. The purpose of this study was to develop a technique for measuring functional movement and examine the effect of brachial plexus injury location (preganglionic and postganglionic) on functional movement outcomes in a rat model of BPBI, which we achieved through integration of gait analysis with musculoskeletal modeling and simulation. Eight weeks following unilateral brachial plexus injury, sagittal plane shoulder and elbow angles were extracted from gait recordings of young rats (n = 18), after which rats were sacrificed for bilateral muscle architecture measurements. Musculoskeletal models reflecting animal-specific muscle architecture parameters were used to simulate gait and extract muscle fiber lengths. The preganglionic neurectomy group spent significantly less (p = 0.00116) time in stance and walked with significantly less (p < 0.05) elbow flexion and shoulder protraction in the affected limb than postganglionic neurectomy or control groups. Linear regression revealed no significant linear relationship between passive shoulder external rotation and functional shoulder protraction range of motion. Despite significant restriction in longitudinal muscle growth, normalized functional fiber excursions did not differ significantly between groups. In fact, when superimposed on a normalized force-length curve, neurectomy-impaired muscle fibers (except subscapularis) accessed regions of the curve that overlapped with the control group. Our results suggest the presence of compensatory motor control strategies during locomotion following BPBI. The clinical implications of our findings support emphasis on functional movement analysis in treatment of BPBI, as functional and passive outcomes may differ substantially.

Muscle architecture, growth, and biological Remodelling in cerebral palsy: a narrative review

Cerebral palsy (CP) is caused by a static lesion to the brain occurring in utero or up to the first 2 years of life; it often manifests as musculoskeletal impairments and movement disorders including spasticity and contractures. Variable manifestation of the pathology across individuals, coupled with differing mechanics and treatments, leads to a heterogeneous collection of clinical phenotypes that affect muscles and individuals differently. Growth of muscles in CP deviates from typical development, evident as early as 15 months of age. Muscles in CP may be reduced in volume by as much as 40%, may be shorter in length, present longer tendons, and may have fewer sarcomeres in series that are overstretched compared to typical. Macroscale and functional deficits are likely mediated by dysfunction at the cellular level, which manifests as impaired growth. Within muscle fibres, satellite cells are decreased by as much as 40–70% and the regenerative capacity of remaining satellite cells appears compromised. Impaired muscle regeneration in CP is coupled with extracellular matrix expansion and increased pro-inflammatory gene expression; resultant muscles are smaller, stiffer, and weaker than typical muscle. These differences may contribute to individuals with CP participating in less physical activity, thus decreasing opportunities for mechanical loading, commencing a vicious cycle of muscle disuse and secondary sarcopenia. This narrative review describes the effects of CP on skeletal muscles encompassing substantive changes from whole muscle function to cell-level effects and the effects of common treatments. We discuss growth and mechanics of skeletal muscles in CP and propose areas where future work is needed to understand these interactions, particularly the link between neural insult and cell-level manifestation of CP.

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.

Structures contributing to the shoulder contracture in brachial plexus birth palsy. An intraoperative biomechanical study

Internal rotation contracture of the shoulder is a common sequel of the brachial plexus birth palsy. The purpose of this study is to describe the surgical method used in our centre and to measure the effect of sequentially releasing several anatomical structures that have been ascribed as the cause of the contracture. Twenty-four consecutive patients were operated on with an open release. We documented the increase in passive external rotation after each surgical step. We found small gains in passive external rotation when performing coracoidectomy and division of the upper part of the subscapularis tendon; 4° (95% confidence interval [CI] 2°-6° p < 0.01) and 6° (95% CI 4°-8° p < 0.01), respectively. A substantial gain in external rotation occurred when dividing the entire subscapularis tendon, 43° (95% CI 38°-48°, p < 0.01). Our findings indicate that a clinically relevant surgical release of the contracture requires lengthening of the entire subscapularis musculo-tendinous unit.Level of evidence: IV.

Sex-specific role of myostatin signaling in neonatal muscle growth, denervation atrophy, and neuromuscular contractures

Neonatal brachial plexus injury (NBPI) causes disabling and incurable muscle contractures that result from impaired longitudinal growth of denervated muscles. This deficit in muscle growth is driven by increased proteasome-mediated protein degradation, suggesting a dysregulation of muscle proteostasis. The myostatin (MSTN) pathway, a prominent muscle-specific regulator of proteostasis, is a putative signaling mechanism by which neonatal denervation could impair longitudinal muscle growth, and thus a potential target to prevent NBPI-induced contractures. Through a mouse model of NBPI, our present study revealed that pharmacologic inhibition of MSTN signaling induces hypertrophy, restores longitudinal growth, and prevents contractures in denervated muscles of female but not male mice, despite inducing hypertrophy of normally innervated muscles in both sexes. Additionally, the MSTN-dependent impairment of longitudinal muscle growth after NBPI in female mice is associated with perturbation of 20S proteasome activity, but not through alterations in canonical MSTN signaling pathways. These findings reveal a sex dimorphism in the regulation of neonatal longitudinal muscle growth and contractures, thereby providing insights into contracture pathophysiology, identifying a potential muscle-specific therapeutic target for contracture prevention, and underscoring the importance of sex as a biological variable in the pathophysiology of neuromuscular disorders.

Effect of arthroscopic shoulder release on shoulder mobility and bone deformity following brachial plexus birth injury: a systematic review and meta-analysis

BACKGROUND

Specific information to guide clinical practice is lacking for the effects of arthroscopic release on bone and joint deformities, as well as the additional benefits of tendon transfer, in children with brachial plexus birth injury. The aims of this study were (1) to evaluate changes in shoulder mobility and bone and joint deformity, (2) to evaluate the effect of release with and without tendon transfer on the same outcomes, and (3) to evaluate the perioperative and long-term complications.

METHODS

We conducted a systematic review and meta-analysis. Four databases were searched using relevant inclusion and exclusion criteria from inception until May 2020. The quality of articles was evaluated using the Methodological Index for Non-randomized Studies (MINORS) scale. Data regarding patients, interventions, and clinical and radiologic outcomes were reported.

RESULTS

Thirteen articles were included: 6 of low quality and 7 of moderate quality separated into 17 studies (266 children). The mean follow-up duration was 32.4 months (standard deviation, 15.2 months). Arthroscopic release significantly improved the Mallet score (standardized mean difference [SMD], 3.1 [95% confidence interval (CI), 1.5-4.7]; P < .001) and passive external rotation (SMD, 3.6 [95% CI, 2.3-4.9]; P = .02). The percentage of humeral head anterior (SMD, 1.3 [95% CI, 0.7-1.9]; P = .003) and glenoid retroversion (SMD, 1.4 [95% CI, 0.9-2]; P = .01) also improved. Descriptive analysis of the data suggested that concomitant tendon transfer further improved mobility. Recurrence of internal-rotation contracture was reported in 8 of 157 children.

DISCUSSION

This systematic review showed that arthroscopic release effectively improves both shoulder mobility and bone deformity, with few complications in young children with brachial plexus birth injury. As such, it seems reasonable to propose a stepwise approach starting with a release without transfer.

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.

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.

The Relationship between Trunk Control and Upper Extremity Function in Children with Obstetric Brachial Plexus Palsy

PURPOSE

This study aimed to assess sitting skills and trunk control in children with obstetric brachial plexus palsy (OBPP) and investigate the effect of these skills on upper extremity function.

METHODS

A total of 106 children with OBPP aged 10-18 months were included in this study. Injury severity was determined with Narakas Classification. The Gross Motor Function Measurement Sitting Sub-scale was used to assess sitting skills, while the Sitting Assessment Scale was used to evaluate the trunk control. The upper extremity functions were assessed with using the Active Movement Scale and the Modified Mallet Score.

RESULTS

As the severity of injury increased, sitting skills and trunk control values decreased (p = .0001). In addition, upper extremity function decreased with the decreasing sitting skills and trunk control (p = .0001).

CONCLUSION

Rehabilitation approaches should involve approaches that aim to increase trunk control in addition to programs targeting the extremity function in children with OBPP.

Corrective Procedure for Flexion Contracture of the Elbow in Neonatal Palsy Sequelae: Long-term Follow-up

BACKGROUND

Aim of this paper is to validate a procedure for correcting elbow flexion contracture in patients suffering from brachial plexus neonatal palsy sequelae during their teens. Elbow flexion contracture represents an unsolved problem in the natural history of obstetric brachial plexus palsy (OBPP) because of the consistent deformity recurrence. Following a previous paper, in which an original technique was proposed in a small sample of patients, the authors show the possible correction of the deformity in a larger group of patients.

METHODS

The procedure includes a combination of a posterior approach to the elbow with olecranon tip section and an anterior one with capsulotomy and soft tissue release to improve elbow range of motion. A series of 26 patients, who underwent the procedure, were checked out in medium and long term. Collected data were age, type of brachial plexus palsy, length of hospitalization, duration of surgery, preoperative and postoperative elbow range of motion, preoperative and postoperative DASH scores and satisfaction scores. Explaining further details about the procedure, the Authors report their results, including a statistical analysis.

RESULTS

At the final follow-up, the mean increase of elbow extension was about 22°. Functional outcomes were successful as well, with a mean increase of 10 points of DASH score. Over 75% of patients were fully satisfied with their outcome.

CONCLUSIONS

The outcome has confirmed the good efficacy of the procedure in increasing elbow extension but also in improving cosmetic appearance in adolescents suffering from flexed elbow in OBPP sequelae.

Relative importance of factors affecting activity and upper extremity function in children with Narakas Group 2 brachial plexus birth palsy

The aim of the study was to determine the differences in upper limb function and activity/participation levels between preschool children with Narakas Groups 2a and 2b obstetric brachial plexus injury; and to determine the significance level of the factors affecting upper limb functions in these patients. Sixty-seven children, aged 3 to 7, who had not had surgical intervention, were evaluated in terms of joint movements, modified Mallet classification, Raimondi hand classification, brachial plexus outcome measure, paediatric outcome data collection instrument and stereognosis. There were significant functional differences between the groups, in favour of Group 2a. The movements affecting total function of the upper limb were: hand to spine (p < 0.001), global abduction (p < 0.001) and hand to mouth (p < 0.001), in descending order of significance. Passive internal rotation was the most important passive joint movement affecting shoulder function (p < 0.001). The results of this study suggest that more emphasis should be placed on the shoulder internal rotation in treatment strategies.Level of evidence: III.

Preganglionic and Postganglionic Brachial Plexus Birth Injury Effects on Shoulder Muscle Growth

PURPOSE

Brachial plexus birth injury can differ in presentation, depending on whether the nerve ruptures distal to, or avulses proximal to, the dorsal root ganglion. More substantial contracture and bone deformity at the shoulder is typical in postganglionic injuries. However, changes to the underlying muscle structure that drive these differences in presentation are unclear.

METHODS

Seventeen Sprague-Dawley rats received preganglionic or postganglionic neurectomy on a single limb on postnatal days 3 and 4. Muscles crossing the shoulder were retrieved once the rats were sacrificed at 8 weeks after birth. External rotation range of motion, muscle mass, muscle length, muscle sarcomere length, and calculated optimal muscle length were measured bilaterally.

RESULTS

Average shoulder range of motion in the postganglionic group was 61.8% and 56.2% more restricted at 4 and 8 weeks, respectively, compared with that in the preganglionic group, but affected muscles after preganglionic injury were altered more severely (compared with the unaffected limb) than after postganglionic injury. Optimal muscle length in preganglionic injury was shorter in the affected limb (compared with the unaffected limb: -18.2% ± 9.2%) and to a greater extent than in postganglionic injury (-5.1% ± 6.2%). Muscle mass in preganglionic injury was lower in the affected limb (relative to the unaffected limb: -57.2% ± 24.1%) and to a greater extent than in postganglionic injury (-28.1% ± 17.7%).

CONCLUSIONS

The findings suggest that the presence of contracture does not derive from restricted longitudinal muscle growth alone, but also depends on the extent of muscle mass loss occurring simultaneously after the injury.

CLINICAL RELEVANCE

This study expands our understanding of differences in muscle architecture and the role of muscle structure in contracture formation for preganglionic and postganglionic brachial plexus birth injury.

NRG/ErbB signaling regulates neonatal muscle growth but not neuromuscular contractures in neonatal brachial plexus injury

Neonatal brachial plexus injury (NBPI) causes disabling and incurable muscle contractures that are driven by impaired growth of denervated muscles. A rare form of NBPI, which maintains afferent muscle innervation despite motor denervation, does not cause contractures. As afferent innervation regulates various aspects of skeletal muscle homeostasis through NRG/ErbB signaling, our current study investigated the role of this pathway in modulating contracture development. Through pharmacologic modification with an ErbB antagonist and NRG1 isoforms, we discovered that NRG/ErbB signaling does not modulate the development of contractures in neonatal mice. Instead, ErbB inhibition impeded growth in nondenervated skeletal muscles, whereas increased ErbB activation exacerbated denervation‐induced skeletal muscle atrophy. This potential regulatory effect of NRG/ErbB signaling on neonatal muscle growth warrants deeper investigation.

Radiographic and Clinical Outcomes of the Shoulder in Long-Term Follow-Up of Brachial Plexus Birth Injury

PURPOSE

The purpose of this study was to examine radiographic and functional outcomes of the shoulder in brachial plexus birth injury (BPBI) patients at long-term follow-up.

METHODS

Medical records were reviewed at the Shriners Hospital in St. Louis to identify patients older than 18 years with a diagnosis of BPBI. Twenty-five patients were included in this study. Evaluations included radiographic examination, clinical examination, and outcome measures including the Mallet classification, visual analog scale (VAS) for shoulder pain, American Shoulder and Elbow Shoulder score (ASES), quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH), Simple Shoulder Test (SST), and Patient-Reported Outcomes Measurement Information System (PROMIS) domain measures.

RESULTS

The mean age of the patients included was 44 years. Average follow-up was 37 years. No patient had primary nerve reconstruction surgery. Thirteen patients had a history of shoulder surgery at an average age of 6 years. There was a wide spectrum of deformity seen radiographically. Fifty-five percent of patients had evidence of glenoid retroversion, posterior humeral translation, or a biconcave glenoid. An additional 20% of patients had complete posterior dislocation of the humeral head. Despite the degenerative changes seen on radiographs, the mean VAS for pain was low, at 2. The mean ASES shoulder score was 54. The mean QuickDASH score was 30. Mean PROMIS Physical Function, Pain Interference, Depression, and Anxiety scores were near the means for the general population, with similar outcomes in patients treated with shoulder surgery compared with those treated without surgery.

CONCLUSIONS

Adult BPBI patients experience minimal shoulder pain despite deformity and degenerative changes on shoulder radiographs. Whereas there are significant deficits in range of motion and function, PROMIS scores in adult BPBI patients are normal.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Outcomes of Botulinum Toxin Injection for Shoulder Internal Rotation Contractures in Infants with Brachial Plexus Birth Injury

PURPOSE

Shoulder internal rotation contractures (IRC) are common sequela of brachial plexus birth injuries (BPBI). Botulinum toxin A (BTX-A) injection into targeted muscles has been described to facilitate functional improvement at the shoulder joint and prevent glenohumeral dysplasia. The purpose of this study was to assess the outcomes of BTX-A injections on shoulder IRC in children with BPBI.

METHODS

We conducted a retrospective analysis of 47 children with shoulder IRC due to BPBI, who were treated with BTX-A. Shoulder passive external rotation in adduction and Active Movement Scale external rotation scores were recorded before and after BTX-A injection. We also recorded the number of children who underwent secondary surgical balancing procedures to improve shoulder motion after BTX-A injection.

RESULTS

Mean age at the time of injection was 12 months (range, 5-23 months). Subjects demonstrated a significant increase in passive external rotation of 46° (range, 10° to 90) at 4 months; an average improvement of 18° (range, -30° to 80°) persisted at 11 months after injection. A total of 28 patients (60%) underwent subsequent external rotation tendon transfer. At 5-year follow-up, 7 patients (15%) had adequate functional shoulder range of motion and did not undergo external rotation tendon transfer.

CONCLUSIONS

Botulinum toxin A injections result in improvement in IRC due to BPBI, which is sustained beyond the expected half-life of 3 months. As many as 15% of patients who have this treatment avoid external rotation tendon transfer.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic IV.

Timing of proteasome inhibition as a pharmacologic strategy for prevention of muscle contractures in neonatal brachial plexus injury

Neonatal brachial plexus injury (NBPI) causes disabling and incurable contractures, or limb stiffness, which result from proteasome‐mediated protein degradation impairing the longitudinal growth of neonatally denervated muscles. We recently showed in a mouse model that the 20S proteasome inhibitor, bortezomib, prevents contractures after NBPI. Given that contractures uniquely follow neonatal denervation, the current study tests the hypothesis that proteasome inhibition during a finite window of neonatal development can prevent long‐term contracture development. Following neonatal forelimb denervation in P5 mice, we first outlined the minimum period for proteasome inhibition to prevent contractures 4 weeks post‐NBPI by treating mice with saline or bortezomib for varying durations between P8 and P32. We then compared the ability of varying durations of longer‐term proteasome inhibition to prevent contractures at 8 and 12 weeks post‐NBPI. Our findings revealed that proteasome inhibition can be delayed 3‐4 days after denervation but is required throughout skeletal growth to prevent contractures long term. Furthermore, proteasome inhibition becomes less effective in preventing contractures beyond the neonatal period. These therapeutic effects are primarily associated with bortezomib‐induced attenuation of 20S proteasome β1 subunit activity. Our collective results, therefore, demonstrate that temporary neonatal proteasome inhibition is not a viable strategy for preventing contractures long term. Instead, neonatal denervation causes a permanent longitudinal growth deficiency that must be continuously ameliorated during skeletal growth. Additional mechanisms must be explored to minimize the necessary period of proteasome inhibition and reduce the risk of toxicity from long‐term treatment.

The results of decompression of the musculocutaneous nerve entrapment in children with obstetric brachial plexus palsy

PURPOSE

Elbow flexion is a key indicator of functional recovery in obstetric brachial plexus palsy (OBPP). However, lack of flexion could be a result of an entrapped musculocutaneous nerve during the healing period. The purpose of this study was to investigate the possible compression of the musculocutaneous nerve and outcomes of decompression.

METHODS

The study included 11 children aged with a mean age of 10.9 ± 2.7 months (range, 8-16 months) with Narakas 2 involvement OBPP, who had insufficient elbow flexion but had satisfactory shoulder abduction. Prior to surgery, magnetic resonance imaging (MRI) was performed to identify the entrapment. The children were evaluated pre-operatively and at 3 and 12 months postoperatively using the Active Movement Scale and Faradic Excitability Test. The musculocutaneous nerve was explored and decompressed in all the children. Regular physiotherapy and a home exercise programme were prescribed after surgery.

RESULTS

The MRI findings were consistent with the surgical exploration in all the infants. Statistical analyses showed that decompression of the musculoskeletal nerve improved active movement scale scores on elbow flexion and faradic excitability test values of biceps brachii within 3 months after surgery.

CONCLUSION

Children with delayed elbow flexion and satisfactory shoulder abduction may have an entrapped musculocutaneous nerve in the proximal arm and decompression of the nerve improves elbow function.

Nerve graft versus nerve transfer for neonatal brachial plexus: shoulder outcomes

OBJECTIVE

The decision-making in neonatal brachial plexus palsy (NBPP) treatment continues to have many areas in need of clarification. Graft repair was the gold standard until the introduction of nerve transfer strategies. Currently, there is conflicting evidence regarding outcomes in patients with nerve grafts versus nerve transfers in relation to shoulder function. The objective of this study was to further define the outcomes for reconstruction strategies in NBPP with a specific focus on the shoulder.

METHODS

A cohort of patients with NBPP and surgical repairs from a single center were reviewed. Demographic and standard clinical data, including imaging and electrodiagnostics, were gathered from a clinical database. Clinical data from physical therapy evaluations, including active and passive range of motion, were examined. Statistical analysis was performed on the available data.

RESULTS

Forty-five patients met the inclusion criteria for this study, 19 with graft repair and 26 with nerve transfers. There were no significant differences in demographics between the two groups. Understandably, there were no patients in the nerve grafting group with preganglionic lesions, resulting in a difference in lesion type between the cohorts. There were no differences in preoperative shoulder function between the cohorts. Both groups reached statistically significant improvements in shoulder flexion and shoulder abduction. The nerve transfer group experienced a significant improvement in shoulder external rotation, from -78° to -28° (p = 0.0001), whereas a significant difference was not reached in the graft group. When compared between groups, there appeared to be a trend favoring nerve transfer in shoulder external rotation, with the graft patients improving by 17° and the transfer patients improving by 49° (p = 0.07).

CONCLUSIONS

In NBPP, patients with shoulder weakness experience statistically significant improvements in shoulder flexion and abduction after graft repair or nerve transfer, and patients with nerve transfers additionally experience significant improvement in external rotation. With regard to shoulder external rotation, there appear to be some data supporting the use of nerve transfers.

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.

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.

Reconstruction of the Suprascapular Nerve in Brachial Plexus Birth Injury: A Comparison of Nerve Grafting and Nerve Transfers

BACKGROUND

Shoulder external rotation recovery in brachial plexus birth injury is often limited. Nerve grafting to the suprascapular nerve and transfer of the spinal accessory nerve to the suprascapular nerve are commonly performed to restore shoulder external rotation, but the optimal surgical technique has not been clearly demonstrated. We investigated whether there was a difference between nerve grafting and nerve transfer in terms of shoulder external rotation recovery or secondary shoulder procedures.

METHODS

This is a multicenter, retrospective cohort study of 145 infants with brachial plexus birth injury who underwent reconstruction with nerve grafting to the suprascapular nerve (n = 59) or spinal accessory nerve to suprascapular nerve transfer (n = 86) with a minimum follow-up of 18 months (median, 25.7 months [interquartile range, 22.0, 31.2 months]). The primary outcome was the Active Movement Scale (AMS) score for shoulder external rotation at 18 to 36 months. The secondary outcome was secondary shoulder surgery. Two-sample Wilcoxon and t tests were used to analyze continuous variables, and the Fisher exact test was used to analyze categorical variables. The Kaplan-Meier method was used to estimate the cumulative risk of subsequent shoulder procedures, and the proportional hazards model was used to estimate hazard ratios (HRs).

RESULTS

The grafting and transfer groups were similar in Narakas type, preoperative AMS scores, and shoulder subluxation. The mean postoperative shoulder external rotation AMS scores were 2.70 in the grafting group and 3.21 in the transfer group, with no difference in shoulder external rotation recovery between the groups (difference, 0.51 [95% confidence interval (CI), -0.31 to 1.33]). A greater proportion of the transfer group (24%) achieved an AMS score of >5 for shoulder external rotation compared with the grafting group (5%) (odds ratio, 5.9 [95% CI, 1.3 to 27.4]). Forty percent of the transfer group underwent a secondary shoulder surgical procedure compared with 53% of the grafting group; this was a significantly lower subsequent surgery rate (HR, 0.58 [95% CI, 0.35 to 0.95]).

CONCLUSIONS

Shoulder external rotation recovery in brachial plexus birth injury remains disappointing regardless of surgical technique, with a mean postoperative AMS score of 3, 17% of infants achieving an AMS score of >5, and a high frequency of secondary shoulder procedures in this study. Spinal accessory nerve to suprascapular nerve transfers were associated with a higher proportion of infants achieving functional shoulder external rotation (AMS score of >5) and fewer secondary shoulder procedures.

LEVEL OF EVIDENCE

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

Proteasome inhibition preserves longitudinal growth of denervated muscle and prevents neonatal neuromuscular contractures

Muscle contractures are a prominent and disabling feature of many neuromuscular disorders, including the 2 most common forms of childhood neurologic dysfunction: neonatal brachial plexus injury (NBPI) and cerebral palsy. There are currently no treatment strategies to directly alter the contracture pathology, as the pathogenesis of these contractures is unknown. We previously showed in a mouse model of NBPI that contractures result from impaired longitudinal muscle growth. Current presumed explanations for growth impairment in contractures focus on the dysregulation of muscle stem cells, which differentiate and fuse to existing myofibers during growth, as this process has classically been thought to control muscle growth during the neonatal period. Here, we demonstrate in a mouse model of NBPI that denervation does not prevent myonuclear accretion and that reduction in myonuclear number has no effect on functional muscle length or contracture development, providing definitive evidence that altered myonuclear accretion is not a driver of neuromuscular contractures. In contrast, we observed elevated levels of protein degradation in NBPI muscle, and we demonstrate that contractures can be pharmacologically prevented with the proteasome inhibitor bortezomib. These studies provide what we believe is the first strategy to prevent neuromuscular contractures by correcting the underlying deficit in longitudinal muscle growth.

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.