gms | German Medical Science

Objectives: Osteoarthritis (OA) is the most common disorder of the Sternoclavicular Joint (SCJ) affecting about half of the adult population. When symptomatic, it manifests with pain and swelling over the joint. Although strongly correlated with age, the influence of biomechanical factors such as the length of the clavicle have not yet been studied in relation to the osteoarthritis. This question becomes relevant in cases of clavicular fractures where shortening as a result of conservative management is often considered as an acceptable outcome. Therefore, in this study we analysed the relation between clavicular length and the presence of OA at the SCJ.

Methods: In this case-control study, CT scans of adult patients with polytrauma presenting to the Emergency Department of our hospital were analysed. Patients with clavicular injury were excluded and SCJs of the remaining patients were evaluated to detect OA, which was defined as radiologically confirmed presence of osteophytes, subchondral cysts, or cortical sclerosis. Medial-most and lateral-most points of the clavicle were marked on the slices passing through the SC and AC joints respectively. The x-, y-, and z-axis coordinates of these two points were determined from the DICOM meta-data and clavicular length was calculated as the distance between these two points using 3D geometry.

Results and conclusion: Preliminary data of 334 SCJs from 167 patients (64% males, 36% females) with a mean age of 48.5 ± 20.5 years were analysed. Multivariate logistic regression models revealed that age and clavicular length were independent risk factors for OA while gender did not reach statistical significance. The final logistic model showed good discriminative ability, the results of which have been summarised in the table below. According to this model, 1 mm increase in clavicular length was associated with 9% and 7% reduction in the odds of developing OA on the left and the right sides respectively. Comparing the mean clavicular length using t-test showed a significantly shorter clavicle in the group with OA (145.8 vs 152.7 mm, p = 0.0001, left and 144.2 vs 150.3 mm, p = 0.0007, right). Average of chest breadth, defined as the horizontal distance between the two AC joints was significantly less in patients with OA on at least one of the sides compared to those without OA (283.6 vs 298.1mm, p = 0.001, t-test).

Table 1 [Tab. 1]

Our data suggests that the risk of developing OA at the SCJ is higher for individuals with a shorter clavicle. This is of clinical relevance in cases of clavicular fractures where the shortening of the clavicle might lead to a higher risk of developing SCJ OA in the future. More biomechanical studies are needed to find out the mechanism of this effect.