The effects of denervation, reinnervation, and muscle imbalance on functional muscle length and elbow flexion contracture following neonatal brachial plexus injury

Surgical Treatment of Infantile Shoulder Dislocation Following Brachial Plexus Birth Injury

BACKGROUND

Glenohumeral dysplasia following brachial plexus birth injury (BPBI) can present as dislocation of the glenohumeral joint in infancy. Multiple nonoperative treatment strategies have been reported for these early dislocations, yet none are universally successful; thus, surgical treatment may be required. However, reports of surgical treatment in infancy are scarce. The present study retrospectively reviews the outcomes of patients with BPBI treated surgically for glenohumeral dislocation under 1 year of age.

METHODS

Medical records were retrospectively reviewed for patients treated surgically for glenohumeral dislocation under 1 year of age. Dislocation was defined on magnetic resonance imaging (MRI) as a percentage of the humeral head anterior to the scapular line (PHHA) <10%, or on ultrasound, as the humeral head ossific nucleus entirely posterior to the posterior scapular line. The primary outcome was defined as the need for reoperation. Additional outcomes included Mallet scores for global shoulder function and PHHA and glenoid version measurements on follow-up MRI. Patients with <1 year follow-up were excluded.

RESULTS

Thirty-two patients underwent surgical intervention for shoulder dislocation at ages 5 months to <1 year with average follow-up of 4.6 years. Of these 32 patients, 25 underwent internal rotation contracture release and external rotation tendon transfer (ERTT), with 3 (12.0%) requiring revision surgery; 7 underwent release alone, with 6 (85.7%) requiring revision surgery. Across all groups, patients ultimately had improved passive and active external rotation (20.0 to 80.0 degrees, -90.0 to 30.0 degrees, respectively, P<0.0001) and global Mallet scores (14.5/30 to 19.5/30, P<0.001) without worsened internal rotation function. The indications for requiring further surgical intervention for the 9 patients were recurrent IR contracture, redislocation, persistent ER weakness, and weak abduction.

CONCLUSIONS

Surgical treatment of infantile shoulder dislocation following BPBI can improve glenohumeral alignment and global shoulder function. The inclusion of external rotation tendon transfers at the index procedure lowers the risk of reoperation, whereas not sacrificing internal rotation function when combined with partial subscapularis release.

LEVEL OF EVIDENCE

Level IV.

Impact of tendon transfer on scapulothoracic and glenohumeral motion in children with brachial plexus birth injuries

BACKGROUND

Tendon transfers are often utilized to improve shoulder external rotation and abduction in children with brachial plexus birth injuries and are designed to improve glenohumeral (GH) joint motion. However, changes in scapulothoracic (ST) and GH joint function after tendon transfer are not well defined. The purpose of this study was to quantify changes in GH, ST, and humerothoracic (HT) joint function before and after tendon transfer, and we hypothesized that tendon transfers would reorient the arc of motion into more external rotation and abduction, but not increase GH motion.

METHODS

Motion analysis was performed in 15 children (ages 3-16) before and after transfer of teres major and/or latissimus dorsi. ST, GH, and HT joint angles were measured in a neutral, resting position and each of the modified Mallet positions. Joint angular displacements from the neutral position and the total arc of internal-external rotation for each joint were also calculated. Relevant joint angles, joint angular displacements, and internal-external rotation arcs were compared using multivariate analyses of variance with repeated measures and univariate posthoc analyses.

RESULTS

Glenohumeral and HT external rotation were significantly increased in all positions postoperatively. The arc of GH internal-external rotation was unchanged, but oriented in more external rotation after surgery. Only 6 patients gained active external rotation. Glenohumeral and HT internal rotation were significantly decreased after surgery, but ST internal rotation was significantly increased. Two patients had loss of midline function. In the abduction position, GH elevation joint angles were unchanged, but ST and HT elevation increased.

DISCUSSION

Only 4 patients gained active GH external rotation and maintained their internal rotation. Each of those patients underwent isolated tendon transfer without concomitant joint release. Seven patients maintained their preoperative internal rotation, which was attributed to increased ST internal rotation. The other half of patients lost internal rotation and gained external rotation through reorientation of the arc of rotation. Nine patients gained HT elevation, with 3 attributed to increased ST upward rotation, 5 attributed to a combination of increased ST upward rotation, and increased GH elevation, and 1 attributed to increased GH abduction contracture. These findings challenge the dogma that teres major/latissimus dorsi tendon transfers augment GH motion and highlight the importance of ST function for outcome determination.

Shoulder external rotation contracture following neonatal brachial plexus injury

BACKGROUND

Glenohumeral posterior external rotation contractures and scapular winging are frequently overlooked problems in residual neonatal brachial plexus injury (NBPI). Recent attention has emphasized their impact on vital functions such as feeding and hygiene. This study aims to present the epidemiology of posterior glenohumeral contractures in a significant pediatric NBPI population and explore contributing factors.

METHODS

We conducted a retrospective analysis of data collected from January 2019 to November 2022, involving a case series of 262 children with residual NBPI. The data included demographics, palsy level, prior surgical history, and the modified Mallet scale. Glenohumeral passive internal rotation in abduction and cross-body adduction angles were measured bilaterally. Subjects were categorized into "Belly-" (Mallet hand-to-belly <3) and "Belly+" (Mallet hand-to-belly ≥3) groups.

RESULTS

The median participant age was 7.9 years (range: 3.5-21 years). Extension injury patterns included Erb's palsy (56.5%), extended Erb's palsy (28.6%), and global palsy (14.9%). Contractures exceeding 10°, 20°, and 30° were prevalent in both internal rotation in abduction and cross-body adduction angles. The "Belly-" group (9.5%) demonstrated a significant reduction in both angles compared to the "Belly+" group. Weak correlations were found between internal rotation in abduction (r = 0.390, P < .0001) or cross-body adduction (r = 0.163, P = .0083) angles and Mallet hand-to-abdomen item. Glenohumeral reduction and Hoffer procedures led to a notable decrease in cross-body adduction angle, without affecting "Belly-" prevalence. Global injuries exhibited decreased angles compared to Erb's group.

CONCLUSIONS

External rotation glenohumeral contractures are prevalent in residual NBPI, impacting midline access. Surprisingly, the history of glenohumeral procedures or extensive injuries did not increase the likelihood of losing the ability to reach the belly. Receiver operating characteristic analysis suggests specific thresholds for maintaining this ability.

The Putti Sign Following Residual Brachial Plexus Birth Injury: Prevalence and Significance

BACKGROUND

The Putti sign, a common deformity and complaint in children with brachial plexus birth injury (BPBI), stems from a glenohumeral (GH) abduction contracture. Despite recent clinical studies offering insights into this deformity, none have explored the prevalence of the Putti sign or its correlation with GH abduction contractures.

METHODS

We conducted a prospective analysis of 238 patients (median age 7.5 years; range, 4.1-16.2) with residual BPBI seen in the clinic from December 2019 to December 2022. Epidemiological data, including demographics, palsy levels, modified Mallet scale sum, surgical history, and presence/absence of the Putti sign and glenohumeral adduction angle (GHADD), were collected. Patients were categorized into 4 age groups: 0 to 5 years (n=67), 6 to 10 years (n=102), 11 to 15 years (n=53), and 16 years and older (n=16). Results were expressed as medians (minimum-maximum), with frequency comparisons done using Pearson's chi-square analysis. Mann-Whitney U and Kruskal-Wallis tests were used for quantitative variable comparison, and receiver operating characteristic (ROC) analysis determined the threshold GHADD angle for Putti sign appearance.

RESULTS

Main findings included: (1) 27% of patients with residual BPBI exhibited the Putti sign, (2) confirmed correlation between the Putti sign and GH adduction contractures, (3) Putti sign manifestation with GHADD angle measuring less than -5° because to abduction contracture, and (4) association between this deformity and reduced activities requiring external rotation. No significant differences in Putti sign prevalence were found across age groups.

CONCLUSIONS

Our study underscores the common occurrence of the Putti sign in children with residual BPBI. It is important to note that we highlight its functional significance beyond cosmetic concerns. Contrary to prior literature, our analysis reveals functional impairment associated with the Putti sign. Although no age-based differences in Putti sign prevalence were observed, patients aged 0 to 5 years and 11 to 15 years showed more severe glenohumeral abduction contractures, possibly due to growth spurts.

LEVEL OF EVIDENCE

Diagnosis IV.

Sexual dimorphisms in skeletal muscle: current concepts and research horizons

The complex compositional and functional nature of skeletal muscle makes this organ an essential topic of study for biomedical researchers and clinicians. An additional layer of complexity is added with the consideration of sex as a biological variable. Recent research advances have revealed sexual dimorphisms in developmental biology, muscle homeostasis, adaptive responses, and disorders relating to skeletal muscle. Many of the observed sex differences have hormonal and molecular mechanistic underpinnings, whereas others have yet to be elucidated. Future research is needed to investigate the mechanisms dictating sex-based differences in the various aspects of skeletal muscle. As such, it is necessary that skeletal muscle biologists ensure that both female and male subjects are represented in biomedical and clinical studies to facilitate the successful testing and development of therapeutics for all patients.

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.

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.

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.

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.

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.

Transient neonatal shoulder paralysis causes early osteoarthritis in a mouse model

Neonatal brachial plexus palsy (NBPP) occurs in approximately 1.5 of every 1,000 live births. The majority of children with NBPP recover function of the shoulder. However, the long-term risk of osteoarthritis (OA) in this population is unknown. The purpose of this study was to investigate the development of OA in a mouse model of transient neonatal shoulder paralysis. Neonatal mice were injected twice per week for 4 weeks with saline in the right supraspinatus muscle (Saline, control) and botulinum toxin A (BtxA, transient paralysis) in the left supraspinatus muscle, and then allowed to recover for 20 or 36 weeks. Control mice received no injections, and all mice were sacrificed at 24 or 40 weeks. BtxA mice exhibited abnormalities in gait compared to controls through 10 weeks of age, but these differences did not persist into adulthood. BtxA shoulders had decreased bone volume (-9%) and abnormal trabecular microstructure compared to controls. Histomorphometry analysis demonstrated that BtxA shoulders had higher murine shoulder arthritis scale scores (+30%), and therefore more shoulder OA compared to controls. Articular cartilage of BtxA shoulders demonstrated stiffening of the tissue. Compared with controls, articular cartilage from BtxA shoulders had 2-fold and 10-fold decreases in Dkk1 and BMP2 expression, respectively, and 3-fold and 14-fold increases in Col10A1 and BGLAP expression, respectively, consistent with established models of OA. In summary, a brief period of paralysis of the neonatal mouse shoulder was sufficient to generate early signs of OA in adult cartilage and bone.

Clinical and psychosocial outcomes following correction of supination deformity in obstetrical brachial plexus palsy patients: A retrospective study

Background

Forearm supination contracture is the mostAQ common deformity of the forearm following obstetric brachial plexus palsy (OBPP). Supination deformities in OBPP may be corrected by performing forearm osteotomy; however, the high recurrence rate limits patient satisfaction. Apart from the cosmetic impairment of this deformity, there are no previous reports on the clinical and psychosocial outcomes of forearm osteotomy in patients with supination deformities secondary to OBPP. Therefore, our study aimed to assess the clinical, functional, and psychosocial outcomes following forearm pronation osteotomy in OBPP patients with supination deformity.

Methods

This retrospective study was conducted after a chart review of all OBPP sequelae with supination forearm deformity in patients who underwent forearm pronating osteotomy from 2006 to 2018. Data relating to OBPP were gathered, and functional and psychosocial outcomes were assessed using the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire through interviews

Results

This study included 60 patients with a mean age of 8.7 years at the time of surgery. A total of 46 patients had lesions involving C5-T1 (76.7%). The mean preoperative supination deformity position was 68.5°, the mean amount of correction was 98.9°, and the mean forearm position was 30.5°, postoperatively. In the DASH assessment scale used postoperatively, 24 patients (42.9%) reported no restrictions on their daily activities, 25 patients (44.6%) believed that their social activities were unaffected, and 20 patients (35.7%) strongly disagreed with feeling less capable or less confident due to arm, shoulder, or hand problems. The factors significantly affecting position at the final follow-up were the amount of correction (p = 0.011), postoperative position (p = 0.005), and degree of pronation achieved (p = 0.02). The amount of correction significantly affected both self-confidence (p = 0.049) and activities of daily living (p = 0.033).

Conclusion

In conclusion, our study showed that the position at the final follow-up, the degree of pronation achieved intraoperatively, and the postoperative position significantly affected the position at follow-up and the outcome assessment. The amount of intraoperative correction was significantly associated with higher self-confidence and normal activities of daily living.

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.

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.

Glenohumeral abduction contractures after residual neonatal brachial plexus injury

Glenohumeral abduction contractures are common in patients with neonatal brachial plexus injury, but little has been previously published about them. We conducted a retrospective analysis of data prospectively collected from 205 consecutive children (108 female) of mean age 9.6 years with neonatal brachial plexus injury (C5-C6, 58%; C5-C7, 29%; C5-T1, 14%). Most children (69%) showed a glenohumeral abduction contracture, it being more common in those with upper neonatal brachial plexus injury.Level of evidence: III.

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.

Experimental nerve transfer model in the neonatal rat

Clinically, peripheral nerve reconstructions in neonates are most frequently applied in brachial plexus birth injuries. Most surgical concepts, however, have investigated nerve reconstructions in adult animal models. The immature neuromuscular system reacts differently to the effects of nerve lesion and surgery and is poorly investigated due to the lack of reliable experimental models. Here, we describe an experimental forelimb model in the neonatal rat, to study these effects on both the peripheral and central nervous systems. Within 24 hours after birth, three groups were prepared: In the nerve transfer group, a lesion of the musculocutaneous nerve was reconstructed by selectively transferring the ulnar nerve. In the negative control group, the musculocutaneous nerve was divided and not reconstructed and in the positive control group, a sham surgery was performed. The animal´s ability to adapt to nerve lesions and progressive improvement over time were depict by the Bertelli test, which observes the development of grooming. Twelve weeks postoperatively, animals were fully matured and the nerve transfer successfully reinnervated their target muscles, which was indicated by muscle force, muscle weight, and cross sectional area evaluation. On the contrary, no spontaneous regeneration was found in the negative control group. In the positive control group, reference values were established. Retrograde labeling indicated that the motoneuron pool of the ulnar nerve was reduced following nerve transfer. Due to this post-axotomy motoneuron death, a diminished amount of motoneurons reinnervated the biceps muscle in the nerve transfer group, when compared to the native motoneuron pool of the musculocutaneous nerve. These findings indicate that the immature neuromuscular system behaves profoundly different than similar lesions in adult rats and explains reduced muscle force. Ultimately, pathophysiologic adaptations are inevitable. The maturing neuromuscular system, however, utilizes neonatal capacity of regeneration and seizes a variety of compensation mechanism to restore a functional extremity. The above described neonatal rat model demonstrates a constant anatomy, suitable for nerve transfers and allows all standard neuromuscular analyses. Hence, detailed investigations on the pathophysiological changes and subsequent effects of trauma on the various levels within the neuromuscular system as well as neural reorganization of the neonatal rat may be elucidated. This study was approved by the Ethics Committee of the Medical University of Vienna and the Austrian Ministry for Research and Science (BMWF-66.009/0187-WF/V/3b/2015) on March 20, 2015.

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.

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.

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.

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.

Nerve lengthening and subsequent end-to-end repair yield more favourable outcomes compared with autograft repair of rat sciatic nerve defects

Outcomes of end-to-end nerve repairs are more successful compared with outcomes of repairs bridged by nerve grafts. However, end-to-end repairs are not always possible for large nerve gaps, as excessive tension may cause catastrophic failure. In this study, we built on previous nerve-lengthening studies to test the hypotheses that gradual lengthening of the proximal stump across a large nerve gap enables an end-to-end repair and such a repair results in more favourable regenerative outcomes than autografts, which represent the gold standard in bridging nerve gaps. To test these, we compared structural and functional outcomes in Lewis rats after repair of sciatic nerve gaps using either autografts or a novel compact internal fixator device, which was used to lengthen proximal nerve stumps towards the distal stump over 2 weeks, prior to end-to-end repair. Twelve weeks after the initial injury, outcomes following nerve lengthening/end-to-end repair were either comparable or superior in every measure compared with repair by autografting. The sciatic functional index was not significantly different between groups at 12 weeks. However, we observed a reduced rate of contracture and corresponding significant increase in paw length in the lengthening group. This functional improvement was consistent with structural regeneration; axonal growth distal to the injury was denser and more evenly distributed compared with the autograft group, suggesting substantial regeneration into both tibial and peroneal branches of the sciatic nerve. Our findings show that end-to-end repairs following nerve lengthening are possible for large gaps and that this strategy may be superior to graft-based repairs.

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.

Assessment of Spinal Curvatures in Children With Upper Trunk Obstetrical Brachial Plexus Palsy

PURPOSE

Effects of upper trunk obstetrical brachial plexus palsy (OBPP) on the spinal curvature and relationship between the curvature degrees and upper limb movements have not been reported.

METHODS

Spinal Mouse was used to assess spinal curvature characteristics in the sagittal and frontal planes. Upper limb movements were assessed with using the Active Movement Scale in only study group.

RESULTS

The degree of frontal plane curvatures was higher in the study group. In the OBPP group, 11 of 25 (44%) children had thoracal C-shaped scoliosis. Nine of these children had contralateral side scoliosis. Shoulder external rotation was inversely correlated with scoliosis angle. Moreover, shoulder external rotation and elbow flexion were lower in children with scoliosis in the OBPP group.

CONCLUSIONS

Upper trunk OBPP may affect frontal plane alignment. Especially insufficient shoulder external rotation scores may lead to constitute thoracal scoliosis as a result of trunk compensation.

Prevalence and etiology of elbow flexion contractures in brachial plexus birth injury: A scoping review

PURPOSE

To synthesize the evidence on the prevalence and etiology of elbow flexion contractures secondary to brachial plexus birth injury (BPBI).

METHODS

Using Arksey and O'Malley's scoping review framework, MEDLINE, EMBASE, PsycINFO, and CINAHL databases were searched, followed by a comprehensive grey literature search. Articles and abstracts of studies of all level of evidence on the prevalence, natural history, clinical presentation, etiology, and treatment of elbow flexion contractures in BPBI were included.

RESULTS

Of the 884 records found, 130 full text articles were reviewed, and 57 records were included. The median prevalence of elbow flexion contracture in BPBI was 48%. The magnitude of the contractures was between 5 and 90 degrees. Contractures > 30 degrees were found in 21% to 36% of children. With recent clinical and lab studies, there is stronger evidence that the contractures are largely due to the effects of denervation causing failure in the growth of the affected flexor muscles, while muscle imbalance, splint positioning, and postural preferences play a smaller role.

CONCLUSION

The etiology of elbow flexion contractures is multifaceted. The contribution of growth impairment in the affected muscles offers greater understanding as to why maintaining passive range of motion in these contractures can be difficult.

Scapular Stabilization Limits Glenohumeral Stretching in Children With Brachial Plexus Injuries

PURPOSE

To quantify the effects of scapular stabilization on scapulothoracic and glenohumeral (GH) stretching.

METHODS

Motion capture data during external rotation and abduction with and without scapular stabilization were collected and analyzed for 26 children with brachial plexus birth palsy. These positions were performed by an experienced occupational therapist and by the child's caretaker. Scapulothoracic and GH joint angular displacements were compared between stretches with no stabilization, stabilization performed by the therapist, and stabilization performed by the caretaker. The relationship between the age and ability of the therapist and caretaker to perform the stretches with scapular stabilization was also assessed.

RESULTS

During external rotation there were no significant differences in either the scapulothoracic or GH joint during stabilization by either the therapist or the caretaker. During abduction, both scapulothoracic and GH joint angular displacements were statistically different. Scapulothoracic upward rotation angular displacement significantly decreased with scapular stabilization by the therapist and caretaker. Glenohumeral elevation angular displacement significantly decreased with scapular stabilization performed by the therapist and caretaker. There were only weak correlations between age and the differences in scapulothoracic and GH joint angular displacement performed by both the therapist and the caretaker.

CONCLUSIONS

The findings of this study indicate that scapular stabilization may be detrimental to passive stretching of the GH joint in children, as demonstrated by a reduced stretch. Based on the findings of this study, we have changed our practice to recommend passive stretches without scapular stabilization for children aged 5 years and older with brachial plexus birth palsy. In infants and children aged less than 5 years, we now recommend stretching with and without scapular stabilization until the effect of scapular stabilization is objectively assessed in these age groups.

LEVEL OF EVIDENCE/TYPE OF STUDY

Therapeutic IV.

Natural History of the Elbow Bony Architecture in Patients With Obstetric Brachial Plexus Injury and the Association With Flexion Contractures

PURPOSE

The purposes of this study were to evaluate the radiographic anatomy of the elbow and try to determine its possible relation to elbow flexion contracture in patients with obstetric brachial plexus injury (OBPI).

METHODS

All patients with a history of OBPI with elbow flexion contracture who were evaluated clinically and radiographically were included in the study. A review was performed to include serial elbow examinations and previous treatment. Radiographs of the elbow were examined for the presence of bony abnormalities as a potential cause of elbow flexion contracture or the presence of progressive arthritic changes over time.

RESULTS

Fifty-nine patients with a history of OBPI with elbow flexion contracture were included in the study. Of them, 53 had normal bony architecture, 2 had mild radial head subluxation, and 4 had chronic anterior radial head dislocations. At a mean age at final clinical follow-up of 21 years (range, 7 to 83 years), only 7% of patients had pain localized to their elbow. There were only three patients with elbow arthritis, including two of the four with radial head dislocations.

CONCLUSIONS

In the absence of a radial head dislocation, most elbow joints do not seem to undergo abnormal anatomic bony changes in patients with OBPI and flexion contractures.

LEVEL OF EVIDENCE

Level IV (retrospective case series).

What influences contracture formation in lower motor neuron disorders, severity of denervation or residual muscle function? An analysis of the elbow contracture in 100 children with unilateral Brachial Plexus Birth Injury

PURPOSE

As in other neuromuscular disorders, both denervation and muscle paresis/imbalance are implicated as aetiological factors for contractures in children with a Brachial Plexus Birth Injury (BPBI). Although both factors are related, it is unclear which factor is dominant. The aim of this study is to assess whether contracture formation in children is predominantly related to denervation or to residual muscle function/imbalance. This might be relevant for understanding contracture formation in other neuromuscular disorders.

METHODS

A total of 100 children (61 boys; mean age 10.4 years, 4 to 18) with unilateral BPBI were included in this cross-sectional study. Severity of the denervation was classified according to Narakas. Muscle function of flexors and extensors of both elbows was measured (in Newtons) using a hand-held dynamometer and flexion contractures were measured with a goniometer. The relation between denervation, muscle function/muscle balance and flexion contracture was assessed using univariate and multivariate analysis.

RESULTS

Of the children, 57 were Narakas class I, 13 class II and 30 class III. Mean flexion contracture was 25° (90° to -5°). At the affected side the forearm flexion force was 47% and extension force was 67% of the force of the unaffected side. Contractures were more severe in children with higher Narakas classifications (p = 0.001), after neurosurgery (Mann-Whitney U test, p = 0.009) and were related to age (Spearman's Rho = -0.3, p = 0.008) and to paresis of the extensors (Rho = 0.4, p = 0.000). Flexor paresis as a percentage of unaffected side (Rho = 0.06, p = 0.6) and muscle balance had no influence.

CONCLUSION

In BPBI, elbow contractures are related to the severity of the neurological lesion, not to residual muscle function.

LEVEL OF EVIDENCE

Level II - prognostic study.

One-bone forearm osteodesis and biceps re-routing to correct severe supination contracture in a paediatric patient with late obstetric brachial plexus palsy

PURPOSE

The one-bone forearm arthrodesis has been performed to change the position of the forearm in children with fixed supination deformity due to upper extremity neurologic deficit. In this article, we present a retrospective review of children with late obstetric brachial plexus palsy who underwent palliative surgery to correct severe supination contracture by one-bone forearm osteodesis and biceps re-routing. This technique has not been described previously.

MATERIALS AND METHODS

In this retrospective study, four consecutive patients with upper extremity weakness and severe supination contracture who underwent forearm osteodesis in neutral or slight pronation and biceps re-routing. The average age of patients at the time of surgery was 12 years six months (range, 7-14 years).

RESULTS

The average follow-up was one year ten months (range, 1 year 6 months to 2 years 7 months). The rotation of the forearm set in neutral (3 patients) and 15° pronation (1 patient). No patients noted adverse effects on the shoulder, elbow or wrist, and none missed having forearm rotation.

CONCLUSIONS

One-bone forearm osteodesis and biceps re-routing technique should be considered in some patients with fixed forearm supination deformity and concomitant severe pronation deficit. In this group of patients, repositioning the forearm in a more pronated (or less supinated) position may improve the use of that extremity in activities of daily living. The surgical technique is fairly simple and can be done in a single procedure.

Supination Contractures in Brachial Plexus Birth Palsy: Long-Term Upper Limb Function and Recurrence After Forearm Osteotomy or Nonsurgical Treatment

PURPOSE

Forearm osteotomy for supination deformity in brachial plexus birth palsy (BPBP) may lead to improved function of the upper limb. However, recurrence rates are high and limit satisfactory results.

METHODS

We reviewed the long-term outcome of the entire upper limb of 22 BPBP patients with a supination contracture who were treated by forearm osteotomy and compared them with an age-matched group that was treated nonsurgically (n = 28). Recurrence was defined as a passive pronation below 30°.

RESULTS

The median follow-up was 5.0 years (range, 1.5-14 years). The mean passive pronation after forearm osteotomy, including patients with recurrence at follow-up, improved from -1° (SD, 9°) to 33° (SD, 48°) at final follow-up, mean active wrist extension improved from 23° (SD, 40°) to 41° (SD, 38°). An overall improvement of wrist and hand strength was present. In patients without recurrence, pronation improved to a mean of 66° (SD, 23°) at final follow-up. Recurrence of the supination contracture was present in 9 cases (41%) and was only present in patients with a single bone osteotomy. Recurrence was associated with lower age at surgery (recurrence mean, 4 [SD, 1.2] and no recurrence 8 [SD 4.5]), lower shoulder external rotation (recurrence mean, 28 [SD, 17] and no recurrence 49 [SD, 23]), and overall lower hand function at baseline.

CONCLUSIONS

Forearm osteotomy improves forearm pronation and hand function. Recurrence should be considered as a potential complication after forearm osteotomy and is associated with young age and lower function of shoulder and hand. Single-bone osteotomy might also be a risk factor for recurrence.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Biceps Rerouting after Forearm Osteotomy: An Effective Treatment Strategy for Severe Supination Deformity in Obstetric Plexus Palsy

Study Design Retrospective cohort study. Objective Supination deformity in obstetric brachial plexus injury can have debilitating consequences for the functionality of the hand. Surgical treatment by a forearm osteotomy has a recurrence rate of 20 to 42%. As a complement to forearm osteotomy, a biceps rerouting may improve outcome. Methods Children with residual brachial plexus injury, who had a forearm osteotomy for a supination contracture and had a postoperative decrease of pronation to 50 degrees or less, were indicated for a biceps rerouting. Shoulder, elbow and hand function, biceps strength, Mallet score, and Raimondi score were assessed with a minimum follow-up of 2 years. Results Five patients (median age: 8 years; range: 4-10) underwent biceps rerouting between 2008 and 2012. Median follow-up time was 6.8 years (range: 3.2-7.0 years). Passive pronation increased in all cases (median 0 degree at baseline to 80 degrees at final follow-up). Active pronation also increased. Active median wrist extension was -30 degrees at baseline and 45 degrees at follow-up. Biceps strength and grip strength improved in two cases. No recurrences were present. Conclusion The sequentially planned surgical treatment of forearm osteotomy and biceps rerouting should be considered in the treatment of severe supination deformity, as it is effective in improving pronation of the forearm and hand function, without recurrence at follow-up. Level of Evidence/Type of Study Level III, case series, therapeutic study.

The natural history and management of brachial plexus birth palsy

Brachial plexus birth palsy (BPBP) is an upper extremity paralysis that occurs due to traction injury of the brachial plexus during childbirth. Approximately 20 % of children with brachial plexus birth palsy will have residual neurologic deficits. These permanent and significant impacts on upper limb function continue to spur interest in optimizing the management of a problem with a highly variable natural history. BPBP is generally diagnosed on clinical examination and does not typically require cross-sectional imaging. Physical examination is also the best modality to determine candidates for microsurgical reconstruction of the brachial plexus. The key finding on physical examination that determines need for microsurgery is recovery of antigravity elbow flexion by 3-6 months of age. When indicated, both microsurgery and secondary shoulder and elbow procedures are effective and can substantially improve functional outcomes. These procedures include nerve transfers and nerve grafting in infants and secondary procedures in children, such as botulinum toxin injection, shoulder tendon transfers, and humeral derotational osteotomy.

Afferent Innervation, Muscle Spindles, and Contractures Following Neonatal Brachial Plexus Injury in a Mouse Model

PURPOSE

We used an established mouse model of elbow flexion contracture after neonatal brachial plexus injury (NBPI) to test the hypothesis that preservation of afferent innervation protects against contractures and is associated with preservation of muscle spindles and ErbB signaling.

METHODS

A model of preganglionic C5 through C7 NBPI was first tested in mice with fluorescent axons using confocal imaging to confirm preserved afferent innervation of spindles despite motor end plate denervation. Preganglionic and postganglionic injuries were then created in wild-type mice. Four weeks later, we assessed total and afferent denervation of the elbow flexors by musculocutaneous nerve immunohistochemistry. Biceps muscle volume and cross-sectional area were measured by micro computed tomography. An observer who was blinded to the study protocol measured elbow flexion contractures. Biceps spindle and muscle fiber morphology and ErbB signaling pathway activity were assessed histologically and immunohistochemically.

RESULTS

Preganglionic and postganglionic injuries caused similar total denervation and biceps muscle atrophy. However, after preganglionic injuries, afferent innervation was partially preserved and elbow flexion contractures were significantly less severe. Spindles degenerated after postganglionic injury but were preserved after preganglionic injury. ErbB signaling was inactivated in denervated spindles after postganglionic injury but ErbB signaling activity was preserved in spindles after preganglionic injury with retained afferent innervation. Preganglionic and postganglionic injuries were associated with upregulation of ErbB signaling in extrafusal muscle fibers.

CONCLUSIONS

Contractures after NBPI are associated with muscle spindle degeneration and loss of spindle ErbB signaling activity. Preservation of afferent innervation maintained spindle development and ErbB signaling activity, and protected against contractures.

CLINICAL RELEVANCE

Pharmacologic modulation of ErbB signaling, which is being investigated as a therapy for congestive heart failure, may be able to recapitulate the protective effects of afferent innervation in spindle development and contracture prevention. Muscle spindle preservation may also have implications in proprioception and motor learning, both of which are impaired in NBPI.

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.

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.

Treatment of supination deformity for obstetric brachial plexus injury: a systematic review and meta-analysis

PURPOSE

To conduct a systematic review and meta-analysis of the literature evaluating treatment outcome for supination deformity in obstetric brachial plexus injury.

METHODS

We included studies on brachial plexus and supination deformity with follow-up of at least one year and quantitative measurements of forearm mean passive pronation and position at rest. Meta-analysis was used to explore modifying factors.

RESULTS

An elaborate search strategy resulted in 366 studies, of which 13 were included totaling 238 patients (157 osteotomies and 71 biceps rerouting). There was a 75° gain in position at rest and a 65° gain in passive pronation for the osteotomy group, compared to a 79° gain in position at rest for the biceps rerouting group. More severe deformities had greater gains. No influence of age was found. Important adverse effects were hardware failure and a biceps rupture. Recurrence in the osteotomy group was 20% to 40%, versus none in the soft-tissue group.

CONCLUSIONS

This review showed an overall benefit for forearm osteotomies and for biceps rerouting for supination deformity with the gain proportionate to the severity of the deformity.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic III.

The developing shoulder has a limited capacity to recover after a short duration of neonatal paralysis

Mechanical stimuli are required for the proper development of the musculoskeletal system. Removal of muscle forces during fetal or early post-natal timepoints impairs the formation of bone, tendon, and their attachment (the enthesis). The goal of the current study was to examine the capacity of the shoulder to recover after a short duration of neonatal rotator cuff paralysis, a condition mimicking the clinical condition neonatal brachial plexus palsy. We asked if reapplication of muscle load to a transiently paralyzed muscle would allow for full recovery of tissue properties. CD-1 mice were injected with botulinum toxin A to paralyze the supraspinatus muscle from birth through 2 weeks and subsequently allowed to recover. The biomechanics of the enthesis was determined using tensile testing and the morphology of the shoulder joint was determined using microcomputed tomography and histology. A recovery period of at least 10 weeks was required to achieve control properties, demonstrating a limited capacity of the shoulder to recover after only two weeks of muscle paralysis. Although care must be taken when extrapolating results from an animal model to the human condition, the results of the current study imply that treatment of neonatal brachial plexus palsy should be aggressive, as even short periods of paralysis could lead to long-term deficiencies in enthesis biomechanics and shoulder morphology.

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.

Contribution of denervated muscle to contractures after neonatal brachial plexus injury: not just muscle fibrosis

INTRODUCTION

We investigated the contribution of muscle fibrosis to elbow flexion contractures in a murine model of neonatal brachial plexus injury (NBPI).

METHODS

Four weeks after NBPI, biceps and brachialis fibrosis were assessed histologically and compared with the timing of contracture development and the relative contribution of each muscle to contractures. Modulus of elasticity and hydroxyproline (collagen) content were measured and correlated with contracture severity. The effect of halofuginone antifibrotic therapy on fibrosis and contractures was investigated.

RESULTS

Elbow contractures preceded muscle fibrosis development. The brachialis was less fibrotic than the biceps, yet contributed more to contractures. Modulus and hydroxyproline content increased in both elbow flexors, but neither correlated with contracture severity. Halofuginone reduced biceps fibrosis but did not reduce contracture severity.

CONCLUSIONS

Contractures after NBPI cannot be explained solely by muscle fibrosis, arguing for investigation of alternate pathophysiologic targets for contracture prevention and treatment.

Surgical correction of a rotational deformity of the shoulder in patients with obstetric brachial plexus palsy

We evaluated results at one year after surgical correction of internal rotation deformities in the shoulders of 270 patients with obstetric brachial plexus palsy. The mean age at surgery was 6.2 years (0.6 to 35). Two techniques were used: open subscapularis elongation and latissimus dorsi to infraspinatus transfer. In addition, open relocation was performed or attempted in all patients with subluxed or dislocated joints. A mixed effects model approach was used to evaluate the effects of surgery on internal and external rotation, abduction, flexion and Mallet score. Independent factors included operative status (pre- or post-operative), gender, age, the condition of the joint, and whether or not transfer was performed. The overall mean improvement in external rotation following surgery was 84.6° (95% confidence interval (CI) 80.2 to 89.1) and the mean Mallet score improved by 4.0 (95% CI 3.7 to 4.2). There was a mean decrease in internal rotation of between 27.6° and 34.4° in the relocated joint groups and 8.6° (95% CI 5.2 to 12.0) in the normal joint group. Abduction and flexion were unchanged following surgery. Adding a latissimus dorsi transfer did not result in greater improvement in the mean external rotation compared with elongation of the subscapularis alone.

Cite this article: Bone Joint J 2013;95-B:1432–8.