Scapular deformity in obstetric brachial plexus palsy and the Hueter-Volkmann law; a retrospective study.

BACKGROUND: The Hueter-Volkmann law describes growth principles around joints and joint deformation. It states that decreased stress leads to increased growth and that excessive stress leads to growth retardation. Aim of this study was to test the possible results of this principle by measuring the effect of dorsal humeral head subluxation on scapular growth in children with Obstetrical Brachial Plexus Lesions (OBPL). According to the Hueter-Volkmann law, subluxation should result in decrease of growth of the dorsal length of the scapula (by increased dorsal pressure) and increase of the ventral length (decreased pressure).

METHODS: 58 children (mean age 20 months, range 1-88 month) with unilateral OBPL and good quality MRI of both shoulders were included. On MRI, humeral head subluxation, joint deformation, and ventral and dorsal scapular lengths were measured. Data were expressed as a ratio of the normal side.

RESULTS: In affected scapulas both ventral and dorsal side were smaller compared to the normal side. Reduction of growth on the affected side was more marked on the dorsal side than on the ventral side (6.5 mm respectively 4.5 mm, p < 0.001). The balance of growth reduction as expressed by the ratio of ventral and dorsal length was strongly related to subluxation (R(2) = 0.33, p < 0.001) and age (R(2) = 0.19, p < 0.001).

CONCLUSIONS: The Hueter-Volkmann law is incompletely active in subluxated shoulders in OBPL. Dorsal subluxation indeed leads to decrease of growth of the dorsal length of the scapula. However, decreased stress did not lead to increased growth of the ventral length of the scapula.