Sternal Anomalies with Supernumerary and Subnumerary Vertebrae and Ribs – Case Reports

Background: Variations in the number of ribs and vertebrae have been noted in other wise normal looking people with some having supernumerary while others subnumerary. Sternal variations and anomalies though have not been as widely documented. These are two cases with one having a combination of sternal anomalies, supernumerary thoracic vertebrae and ribs and subnumerary lumbar vertebrae while the other had subnumerary thoracic vertebrae and ribs.
Findings: Case 1: A 38year old female who had eleven thoracic vertebrae and corresponding pairs of ribs, nine pairs attached and two floating. The other skeletal components were normal.
Case 2: Adult male had 13 thoracic vertebrae and thirteen corresponding pairs of ribs. Ten pairs of ribs attached to the cage and three floating. There were four lumber vertebrae. The manubrium of the sternum was much longer, ended at the third coastal cartilage attachment and there was an oval defect in the body of the sternum at the level of 5th costal cartilage. The rest of the skeleton was normal.
Conclusions: Osteological variations in the rib cage and vertebrae are clinically important because they can mislead an unsuspecting clinician during diagnostic and therapeutic lumbar punctures, counting of ribs during heart examinations, drainage of the thorax and the 12th rib is important in citing of the incision for nephrectomy and other medical procedures. Radiological diagnosis, Forensic and medical legal pathological identifications need to put into consideration such variations.