Coracoid abnormalities and their relationship with glenohumeral deformities in children with obstetric brachial plexus injury

Open Anterior Subscapularis Release for Adduction and Medial Rotation Shoulder Contracture in Neonatal Brachial Plexus Palsy

INTRODUCTION

Adduction and medial rotation shoulder contracture are prevalent in unresolved neonatal brachial plexus palsy (NBPP). Various surgical options exist, including open anterior subscapularis release, to address this condition. This study assessed the outcomes of this procedure.

MATERIALS AND METHODS

This cross-sectional, observational study focused on a cohort of children aged over 12 months who underwent open anterior subscapularis release to remedy residual shoulder contracture from upper or global NBPP over 11 years. The Mallet score was utilised to appraise deficits in shoulder function.

RESULTS

The study included 32 patients. The sex ratio was 0.78. The median age at surgery was 36 months (25; 56). The right side was affected in 75% of cases. The median improvement in the Mallet score after subscapularis release was 4 (2; 6). This enhancement was statistically significant (P < 0.001), with a median follow-up duration of 78 months (72; 82). There was a substantial increase in shoulder abduction (P < 0.001) and lateral rotation (P < 0.001). Hand-to-mouth (P < 0.001) and hand-to-head (P < 0.001) manoeuvres exhibited significant enhancement. The hand-to-spine manoeuvre did not show a substantial alteration. A significant correlation was found between the injury severity and the enhancement of the Mallet score post-surgery (P = 0.009).

CONCLUSION

Open anterior subscapularis release yielded significant mid-term functional enhancements in shoulder motion, with no modification in medial rotation. Improvements were observed even in children beyond 4 years of age, with those having more severe injuries showing greater functional recovery.

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.

A lower critical coracoid process angle is associated with type-B osteoarthritis: a radiological study of normal and diseased shoulders

Background

Degenerative rotator cuff tears and osteoarthritis (OA) are associated with differences in coronal plane scapular morphology, with particular focus on the effect of the critical shoulder angle (CSA) on shoulder biomechanics. The effect, if any, of axial plane scapular morphology is less well established. We have noticed wide disparity of axial coracoid tip position in relation to the face of the glenoid and sought to investigate the significance of this through measurement of the critical coracoid process angle (CCPA), which incorporates coracoid tip position and glenoid version.

Methods

CCPA, CSA, and glenoid retroversion were measured by three independent reviewers from the cross-sectional two-dimensional computed tomography (CT) and magnetic resonance imaging of 160 patients in four equal and matched case-control groups: (1) a control group of patients with a radiologically normal shoulder and no history of shoulder symptoms who had a CT thorax for another reason, (2) patients with primary OA with Walch type-A glenoid wear pattern on CT scan, (3) patients with type-B glenoid primary OA, and (4) patients with magnetic resonance imaging–proven atraumatic tears of the posterosuperior rotator cuff.

Results

Interobserver agreement was excellent for all measured parameters. The median CCPA was significantly lower in the type-B OA group (9.3˚) than that in controls (18.7˚), but not significantly different in the other study groups. There was a trend toward greater glenoid retroversion in the type-B OA group, but receiver operating characteristic curve analysis demonstrated the CCPA to be by far the most powerful discriminator for type-B OA. The optimal cutoff value was calculated for the CCPA at 14.3˚ with a sensitivity of 93% and specificity of 90% for type-B OA. Compared with controls, the CSA was significantly higher in the rotator cuff tear group and lower in both OA groups, but did not differentiate between type-A and type-B OA.

Conclusion

Combined with a lower CSA, a lower CCPA (<14.3˚) is strongly predictive of type-B glenoid OA. The authors propose a simple model of pectoralis major biomechanics to explain the effect of this axial plane anatomical variation, which requires further investigation.

Isolated open anterior shoulder release in brachial plexus birth palsy

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Anatomical study of the coracoid process in Mongolian male cadavers using the Latarjet procedure

Background

The Latarjet procedure addresses recurrent anterior shoulder instability in the context of a significant bony defect. However, the bony and soft tissue anatomy of the coracoid in coracoid transfer procedures has not yet been defined in Mongolian men. The aims of this study were to describe the soft tissue attachments of the coracoid regarding the bony anatomy, define the average amount of bone available for coracoid transfer, analyze the characteristics of the pectoralis minor and coracoid, and study the relationship between the bony dimensions of the coracoid and body length in Mongolian men.

Methods

We dissected 30 shoulders from 15 male Mongolian cadavers, exposing the coracoid process and attached anatomical structures including the lateral clavicle and acromion, then measured the bony dimensions of the coracoid and the locations and sizes of the coracoid soft tissue footprints.

Results

The mean length of the coracoid available for transfer was 23.93 ± 2.32 mm. The mean length of the coracoid was 42.10 ± 2.3 mm, and the mean width and height of the coracoid midpoint were 15.29 ± 1.70 mm and 11.61 ± 1.98 mm, respectively. The pectoralis minor was part of the joint capsule and passed over the coracoid in some samples. The mutation rate of the pectoralis minor footprint, which was asymmetrical and irregular, was 23.33 %. Statistical analysis involved a multiple linear regression equation.

Conclusions

The average amount of bone available for use in coracoid transfer in Mongolian men was less than that of other populations. Mutation of the pectoralis minor may induce intraoperative capsule injury because this muscle passes over the coracoid deep to the joint capsule of the glenohumeral joint and constitutes part of the shoulder joint, strengthening the joint. Statistically, higher coracoids appeared in shorter patients and longer coracoids appeared in taller patients. Surgically, great care should be taken to consider a patient’s height to precisely implement the congruent-arc Latarjet technique.

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.

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.