Study on Sustentaculum Tali Fragment Constancy in Intraarticular Calcaneus Fracture.

Objectives: To establish reproducible measurements of the sustentaculum tali (ST) fragment regarding fracture classification and patient-related factors.

Design: Retrospective.

Setting: Trauma center, University Hospital.

Patients: A retrospective analysis of the 142 fractured calcanei of 122 patients (101 men and 21 women) treated at our institution between 2012 and 2020 was performed. As control, 62 unaffected calcanei were used.

Intervention: Radiographic images were evaluated twice within 2 weeks by 2 orthopaedic surgeons and 1 postgraduate student. Angulation and diastasis were used to distinguish ST fragment constancy based on computed tomography. Using these parameters, the prevalence of inconstant ST fragments was assessed. We also analyzed factors related to ST fragment inconstancy. Patient factors included age, body mass index, smoking, and diabetes. Radiographic factors included the Sanders classification, location of the outermost fracture line of the posterior facet, presence of an intraarticular fracture of the ST, and ST fragment width.

Main Outcome Measurements: Angulation and diastasis were used to confirm the ST fragment constancy. Potential risks for inconstant ST fragment subsequently defined.

Results: According to the criteria, ST fragment inconstancy was observed in 34.5%. ST fragment width was significantly smaller in the inconstant group ( P < 0.001). Severe comminution of the posterior facet ( P < 0.05), intraarticular fracture of the ST ( P < 0.001), and diabetes ( P < 0.05) were significantly higher in the inconstant group. The cut-off value of the ST fragment width was 20.5 mm.

Conclusions: In intraarticular calcaneus fractures, small ST fragment width, comminuted fracture, intraarticular fracture of the ST, and diabetes were associated with the inconstant group. The ST fragment was expected to be inconstant when the width was less than 20.5 mm.