The influence of casting techniques on the redisplacement risk of reduced distal radius fractures in adults

Introduction: Successfully reduced distal radius fractures (DRFs) often redisplace while casted. Poor cast moulding might be a risk factor for redisplacement of DRFs. This study aims to assess whether cast moulding quality, as determined by casting indices, impact the risk of redisplacement. Also, we assessed the influence of the cast applicant and the material used on the redisplacement risk. Materials and methods: We retrospectively reviewed cases from a prospective cohort (trial registration NL8311). We included 172 adequately reduced and circumferentially casted DRFs with a complete two-week radiographic follow-up. Fracture alignment was measured on all radiographs (trauma, post-reduction and follow-up) in accordance with the Dutch guideline for DRFs. When unacceptably aligned after 2 weeks, the DRF was labelled as redisplaced. Cast moulding quality was measured using the Three Point Index (TPI), Cast Index (CI) and Gap Index (GI). A TPI > 0.8, CI > 0.7 and GI > 0.15 implicates poor cast moulding. Multivariable logistic regression was used to examine the influence of cast moulding quality, cast applicant and casting material on the redisplacement risk. We corrected for patient age, intra-articular involvement, the degree of radial inclination and radial shortening. Results: Redisplacement occurred in 40% of DRFs. The mean index scores were poor (TPI 0.94, CI 0.85, GI 0.22), indicating generally suboptimal cast moulding quality. None of the cast indices were significantly associated to redisplacement (OR [95% CI]: TPI 1.2 [0.6 to 2.5], CI 2.4 [0.7 to 15.7], GI 1.6 [0.7 to 4.0]). DRFs casted by nurse practitioners had significantly lower odds of redisplacement compared to those casted by emergency room nurses. Type of casting (synthetic versus plaster of Paris) was not associated with redisplacement. Conclusions: Cast moulding quality, measured using cast indices, is not associated with redisplacement of reduced DRFs. Casts applied by nurse practitioners redisplaced significantly less often.