Open reduction and internal fixation is the treatment of choice for patients with displaced fractures of the lateral and medial malleoli. Ideally, operative treatment restores sufficient stability to allow full mobility at the ankle joint. However, because of the necessity to protect the ankle from weight-bearing and other forces, we routinely immobilise the ankle in a below-knee cast because of our concerns about patient compliance. We carried out a prospective study to assess patient compliance with instructions on non-weight bearing following ORIF of ankle fractures.

All 30 patients at our hospital who were treated for an ankle fracture over a 14 month period were included in our study. 22 of these underwent ORIF. A below knee cast was applied in all cases, and patients were instructed not to put any weight on the injured limb. A pressure sensitive film (Fuji Prescale Film, Sensor Products Inc., NJ, USA) was incorporated into the cast beneath the heel pad. Patients were informed that this was being done to measure the pressure within the cast, for the purposes of a trial. The cast was changed (including the pressure sensitive film) at two-week intervals over a six week period, providing three separate measurements of pressure on the heel. The sole of the cast was also examined, to complement the findings on the pressure film. At each visit, the patients level of pain was assessed using a visual analogue score, and the wound (if present) was examined.

There was a remarkable variation in the amount of weight bearing performed by the patients in this study, but several trends could be observed. In most cases, patient compliance was greatest in the first four weeks following cast application, but patients tended to put significant weight on the limb in the 4–6 week period. Female patients tended to comply better than males. Patients with a history of alcohol or drug abuse complied poorly. Compliance was lower in those individuals with lower pain scores. Of interest, the degree of weight bearing did not significantly affect the radiological or clinical outcome at the 6-week mark in any case. We conclude that patient compliance with non-weight bearing is generally poor, although the effect of this poor compliance on the long-term outcome requires further study.