Variability in amount of weight-bearing while performing weight-bearing radiographs for assessing stability of ankle fractures

Purpose Weight-bearing (WB) radiographs are commonly used to judge stability of type B fibula fractures and guide the choice of treatment. Stable fractures can be treated conservatively, and unstable fractures surgically. The question is raised how much weight patients actually put on their broken ankle while making a WB radiograph. The current study will give insight in the actual amount of WB in WB radiographs. Methods In this retrospective cohort study, 57 patients with a type B fibula fracture with a medial clear space (MCS) < 6 mm on regular mortise (RM) view who underwent a WB radiograph were included. We designed a ramp with a scale in the plateau where the radiographs were taken. Total body weight (TBW) and amount of WB on the fractured limb were measured. Results The mean WB on the fractured limb was 49 (13-110) kg and the mean TBW was 79 (45-128) kg, calculating a mean percentage of WB of 63. The mean MCS on the RM radiograph was 3.0 mm, compared to 2.9 mm on the WB radiograph. The mean superior clear space (SCS) was 3.2 mm on the RM view, compared to 3.2 mm on the WB radiograph as well. The average fibular dislocation was 1.5 mm on the RM radiograph, compared to 1.6 mm on the WB radiograph. Conclusion There is a big variability in the amount of weight-bearing on the ankle when a WB radiograph is made. This is important to keep in mind when assessing the radiographs and deciding on the treatment course.