Immediate effects of paraffin therapy on finger range of motion: A replicated N-of-1 study

Background Paraffin therapy and hydrotherapy are widely used thermal modalities in hand rehabilitation; however, limited evidence directly compares their immediate effects on finger joint contractures. Purpose To compare the immediate effects of paraffin therapy and hydrotherapy on finger contractures. Methods Three patients with postoperative or post-traumatic contractures participated. An AB single-case design evaluated the additional effects of paraffin therapy administered after hydrotherapy. Phase A involved hydrotherapy combined with manual therapy, followed by Phase B, comprising paraffin therapy with the same manual therapy. Active flexion and extension angles were measured using a standard goniometer immediately after each session. Participants completed 8 sessions (4 per phase). Time-series data were analyzed using a Bayesian local linear trend (LLT) model. A PND of ≥70% indicated a clinically significant intervention effect. Results Improvements in total joint range of motion (ROM) occurred in both phases for all participants. Bayesian analysis revealed that during the paraffin phase (Phase B), additional ROM improvements were noted in two participants compared to Phase A (hydrotherapy). PND values indicated a clinically significant intervention effect (≥70%) for most joints in all participants. Conclusion Administering paraffin therapy as a subsequent intervention to hydrotherapy yielded significant additional improvements in active ROM, demonstrating its effectiveness for finger contractures. Additionally, although the fixed-order design limits causal attribution, this study highlights the value of N-of-1 designs combined with Bayesian analysis for data-driven, individualized clinical decision-making in hand rehabilitation.