Title: Morphological Study on the Synostosis of First and Second Rib
Authors: Dr K. Pushpakala, Dr G.B. Lakshmi Gayathri
DOI: https://dx.doi.org/10.18535/jmscr/v8i1.79
Abstract
Introduction
A rib is a highly vascular cancellous bone enclosed in a thin layer of compact bone, which are thicker on its surfaces and thinner in its borders. There are twelve pairs of bony arches which form the osseous framework of thorax, and articulates with the vertebral column posteriorly(15). The twelve pairs of ribs develops in the ninth week of intrauterine life, from the costal processes of the thoracic vertebrae(11). Congenital anomalies of the ribs are very rare. An unusual anamoly of the fusion of first and second ribs i.e., Synostosis or the bicipital ribs had been said to have an incidence of 0.3%, as reported from a study based on chest radiographs(7).
Synostosis of the first rib is a rare anatomical peculiarity which occurs due to fusion of the shafts of these distinct ribs, mostly happening in relation to first rib as, fusion of the first rib with the cervical rib or as its fusion with the second rib(18). Rib anomalies like forked ribs or fused ribs involving first rib mainly result from the misexpression of specific Hox 3 genes(5).
The synostosis of the first and second ribs is usually asymptomatic, but may also cause musculoskeletal pain, intercostal nerve entrapment or any significant vascular pathology. Since the first rib is involved, the bicipital rib may be a rare cause of thoracic outlet syndrome. Such an anomaly may be associated with many syndromes like Klippell-Feil syndrome, Poland syndrome, Neurofibromatosis, Spondylocostal dysostosis etc(21).
In this paper we report a case of bicipital rib, and by presenting this, we attempt to highlight on the evolution, morphological implications and clinical significance of the bicipital rib. The knowledge of its prevalence is essential for the Anatomists from academic point of view and also important for Clinicians, Surgeons and Radiologists for early diagnosis and surgical intervention.
Materials and Methods
The morphological pattern of the fusion of first and second ribs were studied in about 100 thoracic cage skeletons, from the osteology lab of the Institute of Anatomy of Madurai Medical college. The anamoly of the synostosis of the first and second rib, was obtained on the right side of only one thoracic cage skeleton, where the other side revealed normal first and second ribs. The line of fusion in the observed specimen was very obvious and prominent. The specimen was well examined, photographed and relevant anatomic features and measurements were recorded.
