Vascular anatomy of the clavicle: an aid to midshaft clavicle fracture management

Introduction: Clavicle fractures are common across both adults and paediatric populations. Furthermore, gender differences in clavicular anatomy are well-documented, with male clavicles often measuring longer and thicker than their female counterparts. We aimed to elucidate disparities in surrounding vasculature, between genders, as well as within the same patient. The greatest proportion of these fractures occurs within the middle third of the clavicle. These fractures are often treated conservatively and, in some cases, can lead to complications of malunion and more rarely non-union, which may require surgical intervention. However, these surgeries present the risk of iatrogenic complications which include but are not limited to neurovascular deficit, hardware failure and scarring. The aim of this study is to better understand the relationship between major vascular structures surrounding the middle third of the clavicle, to improve patient outcomes following mid-shaft clavicle fracture management.

Methods: Upper-limb 3D CT angiograms were retrospectively retrieved from the PACS Royal Free database. Our search timeframe was set between January to December of 2022. Inclusion criteria comprised of non-orthopaedic referrals and patients of skeletally mature age. Exclusion criteria included any fracture cases or subclavian pathologies which would disrupt normal anatomy. As a result of our search requirements, thirty patient CTAs of the upper limb were retrieved; we noted age, gender, and reason for the scan request for all patients, as well as the number of slices on each of the scans. We measured clavicle length, thickness, distance, and angle with respect to the subclavian artery and vein. Measurements were collated and analysed using Microsoft Excel 2022, to calculate the mean and range; the means were then compared using an unpaired two-tailed t-test. A linear regression analysis was also conducted on age and clavicle thickness to inform whether these values would prove important to consider pre-operatively.

Results: Thirty patients’ upper limb CTAs were retrieved, 15 of which were female and 15 were male. The mean age of all patients was 54 years (ranging from 25 to 85) with males averaging 59 years and females averaging 50 years. Twenty-seven measurements were obtained for the right clavicle and 28 for the left clavicle, due to some CTs only visualising the right or left clavicles. The mean clavicle length and thickness were 14.7 cm (95% CI: 14.3 to 15) and 11.8 mm (95% CI: 11.1 to 12.5) respectively. Statistically significant gender differences were observed with respect to these parameters, with male clavicles measuring longer (p-value<0.00001) and thicker along the mid-section (p-value<0.00001) when compared with the female mean. No statistically significant right and left differences were observed in length (p-value > 0.05) or thickness (p-value > 0.05 0.685). The mean distances between the clavicle and subclavian artery and the subclavian vein were 14.2 mm and 15.1 mm respectively. The female clavicle exhibited closer proximity to the subclavian vein at a mean of 13.3 mm (95% CI: 11.5 to 15) which was significantly lower than the male mean of 17.4 (95% CI: 13.8 to 21.1) (p-value < 0.05). Statistically significant gender differences were observed with respect to the subclavian vein (p-value < 0.05). The mean distance between the right clavicle and the right subclavian artery was 14.5 mm (95% CI: 12.4 to 16.6), compared to the left subclavian artery which was more proximal at 13.9 mm (95% CI: 11.9 to 15.9). This was not a statistically significant difference (p-value > 0.05). No statistically significant differences were observed between right and left clavicles, concerning the angle of the artery (p-value > 0.05), or in the angle of the vein (p-value > 0.05). No statistically significant differences in angles were observed between female (p-value > 0.05) and male clavicles (p-value > 0.05).

Conclusion: Our study found significant gender differences in the parameters of clavicle length, thickness and proximity of the subclavian artery and vein. However, no significant differences were found in vascular angularity or between the right and left clavicular anatomy. Our findings suggested that male clavicles tend to have greater thickness and length, and are therefore less likely to pose a risk of iatrogenic injury during operative intervention when compared with female patients.