Is There a Relation Between Muscle Mass Surrounding Fractures and Acute Compartment Syndrome Incidence? A Retrospective Cohort Study Examining Extra-articular Tibial Fractures

Background Acute compartment syndrome (ACS) following tibial fractures is a frequent and potentially catastrophic complication when not promptly identified. Aims The aim of this study was to compare muscle mass and ACS incidence rate around extra-articular tibial fracture sites. This could potentially highlight muscle mass as an ACS risk factor. Methods This retrospective cohort study was performed in a level I trauma center and included 614 extraarticular tibial fractures occurring between 01/01/2005 and 12/31/2019 in 559 patients older than 16. Fractures classified as AO/OTA 41-A, 42-A, 42-B, 42-C and 43-A were eligible. The tibia was arbitrarily divided into 8 equally long bony segments, and each fracture was allocated to one of these segments depending on the localization of its center. For each tibial segment, an ACS incidence rate was determined. Alternatively, muscle mass surrounding the same 8 equally long tibial segments was measured on a series of 31 patients having undergone bilateral fine cut computed tomography scans of the legs. These measurements were obtained from healthy limbs (no past surgery, no ancient or recent trauma, no active or sequelar infection, no tumoral condition, no systemic disease with muscular involvement) using a semi-automatic tool in Osirix (ROI volume/compute volume) with manual drawing and automatic propagation of measurements of muscle volume. Results Figure 1 shows ACS incidence rates using a LOESS (locally estimated scatterplot smoothing) curve and mean muscle volumes associated to each of the 8 tibial segments. Conclusion When comparing ACS incidence rate and muscle volume curves, a similarity is visible as both curves increase initially and then slope down. Because both cohorts of patients were different and heterogenous, a purely mathematical or statistical comparison is not possible. However, descriptive comparison of both curves may lead to the conclusion that the more muscle mass is around a fracture site, the more chances there are of developing ACS.