ORIGINAL ARTICLE A. Nehme Æ J.-L. Tricoire Æ G. Giordano Æ D. Rouge P. Chiron Æ J. Puget Coracoclavicular joints. Reflections upon incidence, pathophysiology and etiology of the different forms Received: 13 February 2003 / Accepted: 12 July 2003 / Published online: 22 October 2003 Ó Springer-Verlag 2003 Abstract Since the first description of the coracoclavic- ular joint in 1861, many papers have been published reporting its occurrence, anatomical description, and geographical distribution. However, there are as yet no published articles with a convincing explanation for the rather variable forms of this variant. In this study, we investigated the occurrence of the coracoclavicular joint in the current and medieval population of Toulouse city and propose, through biometric measures, an explana- tion for the different forms of this anatomical variant. A total of 2192 chest X-rays taken for various conditions at a receiving hospital and 392 specimens (784 scapulae and an equal number of clavicles) of the L’Isle-Jourdain Series were examined with this aim. When present in the osteologic collection, the sizes of the articular conoid process as well as the height of the corresponding cor- acoid and acromial processes were noted. A coracocla- vicular joint was noted in 0.82% and in 1.78% of the individuals examined in the radiological and osteologic series, respectively. The conoid process varied in size and correlated with the disposition of each correspondent coracoacromial arch. Osteoarthritis was noted in some of these joints when there was discordance between the conoid process size and the architecture of the corre- spondent coracoacromial arch, suggesting impingement. Our findings support a genetic origin for this variant, and suggest that its occurrence is also probably influenced by environmental factors. Osteoarthritis of this joint may be responsible for shoulder pain. Keywords Coracoclavicular joints Æ Anatomical forms Æ Arthritis Introduction The presence of a diarthrodial joint between the clavicle and the coracoid process of the scapula (i.e. coracocla- vicular joint) (Fig. 1) is a rare condition according to most authors [3, 5, 6, 7, 9, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23], and its real incidence varies between the different continents [3, 4]. Some inevitable confusion occurs in the definition of what constitutes a coracoclavicular joint, because false joints can occur in this region by close apposition of the bony regions, such as the so-called bursal joints, and joints formed by fibrocartilaginous metaplasia of the trapezoid ligament [7, 13, 20]. Part of the problem lies in the fact that anatomists have de- scribed many forms of this variant, and have identified real joints without a long process [11, 13]. Our interest in this subject followed the incidental discovery of a bilateral coracoclavicular joint on a chest X-ray (Fig. 1). Shaded 3D images were obtained after helical CT scan (Fig. 2). The condition was also present on another chest X-ray from the same patient, obtained 24 years earlier (Fig. 1). We then undertook further radiological and osteologic exploration of this condi- tion, in order to detect its incidence in Southwest France populations (Toulouse). The aim of this study was to assess the incidence of this condition in the medieval and current population of Toulouse, and to suggest an explanation for the different forms of the coracoclavicular joints. Materials and methods Radiological study The radiological study was carried out over a period of 14 months. A total of 2192 unselected chest X-rays taken for various Surg Radiol Anat (2004) 26: 33–38 DOI 10.1007/s00276-003-0178-y A. Nehme (&) Æ J.-L. Tricoire Æ G. Giordano Æ P. Chiron Æ J. Puget Department of Orthopedic Surgery and Traumatology, Rangueil University Hospital, Avenue du Professeur Jean Poulhe`s, 31054 Toulouse Cedex 4, France E-mail: inehme@club-internet.fr Tel.: +33-6-61405856 Fax: +33-5-61322232 D. Rouge Department of Anthropology, Faculty of Medicine Toulouse-Rangueil, University of Paul Sabatier, Alle´e Jules Guesdes, 31000 Toulouse, France