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

Background

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

Methods

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

Results

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

Conclusion

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

Residual-limb quality and functional mobility 1 year after transtibial amputation caused by vascular insufficiency

This study identified which residual-limb quality factors are related to functional mobility 1 year after transtibial (TT) amputation. A group of 28 TT amputees were evaluated with respect to their functional mobility (Prosthesis Evaluation Questionnaire [PEQ], Locomotor Index, Timed Up and Go test). The general (Chakrabarty score) and bony (tibial length, relative fibular length) residual-limb quality factors were assessed. An increase in general residual-limb quality (Chakrabarty >60) was correlated with greater functional mobility in one of the outcome measures (PEQ). For bony residual-limb quality, a tibial length of 12-15 cm distal from the knee joint line was correlated with greater functional outcome for all three outcome measures and the relative fibular length was not correlated with functional mobility for any of the outcome measures. This study showed that specific aspects of residual-limb quality are related to increased functional mobility. The amputation technique and resulting residual-limb factors may be important for patients to achieve functional prosthetic use.

Interobserver reliability of the Mallet score

The interobserver reliability of the Mallet score for active shoulder function was assessed by three experienced observers in a group of 30 children with an obstetric brachial plexus lesion (mean age 7.1 years, range 4.5-10 years). Interobserver reliability, measured using weighted kappa, was good. Kappa varied between 0.37 and 0.84 and differed between the different aspects of the Mallet score and different pairs of observers. In decreasing order, mean weighted kappa was 0.75 for abduction, 0.73 for hand to neck, 0.67 for hand to spine, 0.6 for external rotation and 0.53 for hand to mouth.