Coracoclavicular joint in italians: prevalence and effects on neighbouring joints

Introduction; lt is well known that a bar of bone may rarely exist between the lateral as- pect of the clavicle and the coracoid process; however, the occurrence of the joint is iden- tified by a definite articular facet on the conoid tubercle of the clavicle. Usually, coraco- clavicular joint (CCJ) is discovered in routine chest radiography. However x-ray evaluation furnished wrong data because the CCl may not be seen as consequence of bony super- imposition or because it is mistaken for an ossification of the coracociavicular ligaments. At present, we know that CCJ is more frequent in Asian people. However its prevalence in Europeans and whether it may predispose to degenerative changes of neighbouring joints (AC and sternoclavicular joint) or whether it is a congenital or acquired, asymptomatic or symptomatic anomaly is still a matter for discussion. Material and methods; 738 dry clavicles which belonged to Italian people and were part of the skeletal collection of four human anatomical museums were analyzed in order to reveal an articularfacet on the conoid tubercle and degenerative changes of the AC and sternoclavicular joints. Only three of these collections were documented for the individual's age and gender, therefore we know that 578 were specimens from adult males, 106 from adult females and 28 from children. Of theremaining 26 adult dry clav- icles we have no information. Three major patterns of degenerative changes of the AC and sternoclavicular joints were seen. Type I: slight unevenness of the eburneated articu- lar surface; Type Il: modest osteophytes with moderate unevenness of the articular sur- face; Type lll; prominent osteophytes forming a beard-like excrescence around the deformed articular surface. Statistical analysis was performed on the data. Results: Of the 738 clavicles, 5 (0.67%) (p<0.05) (bilaterally in only 1 case) showed an articular facet on the conoid tubercle. In all 3 cases, specimens belonged to adult males. No macroscopic degenerative changes have been observed on the clavicular facet of the CCJ. One of the 5 specimens showed no degenerative changes of the AC or sternoclav- icular joint, while 3 and 1, respectively, had modest osteophytes with moderate uneven- ness or prominent osteophytes of both neighbouring joints. Of the remaining 705 dry clav- icles of adult subjects, 28.7%, 44.3 %, 21.2% and 5.81 % had, respectively, no signs of degenerative changes of the AC joint or belonged to Type l, ll and lll; while the corresponding proportions for the sternociavicular joint were 35.3%, 47.4%, 14.2% and 3.1%. Conclusions; in the only two studies that have been carried out on southern European specimens, the prevalence of the CCJ was 0.3% and 2.8%. Howevec these data have been extracted from too small a number of specimens; 358 and 180, respectively. We have found 5 clavicles (0,67 %) in a sample of 738 with an articular facet on the conoid tubercle. This percentage is notably lower than that revealed in Asian specimens (9,9%), therefore the theory stating that CCJ is trasmitted in a dominant fashion rather than to be consequent upon particular mechanical loads, appears more plausible. Although our data are not sig- nificant, no CCJ was observed on skeletal immature clavicles. None of the 5 specimens with CC\} had degenerative changes of the anomalous joint or a significative correlation with osteorthritis of the AC or sternoclavicular joints with respect specimens without CCJ. Therefore, except for rare cases in which CCJ might cause a neu- rovascular compression, anatomical and physiological significance of this joint seems to be only academic.