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III–2 Porosis on the Side Treated With Low-Intensity Pulsed Ultrasound (LIPUS) After Intramedullary Nailing of Femoral Shaft Fractures

Objective: We previously reported that low-intensity pulsed ultrasound (LIPUS) treatment after intramedullary nailing of femoral shaft fractures effectively promotes early bone healing. In this study, we examined whether porosis occurs on the side treated with LIPUS by prospectively comparing the treatment and non-treatment groups. Methods: After we performed intramedullary nailing in 17 patients (12 men and 5 women) with AO type A femoral shaft fracture, the patients were divided into the LIPUS treatment group (n = 8) and non-treatment group (n = 9) for examination. Using front and side postoperative plain radiography, we examined whether porosis occurred significantly on the treated side by evaluating the appearance order of anterior, posterior, lateral, and medial calluses and days required for bridging callus formation. Results: In the treatment group, the mean appearance order of the anterior callus was 1.5 months, earlier than those of the posterior and medial calluses (3.5 and 2.9, respectively), whereas the order of the lateral callus was 2.2, earlier than that of posterior callus (P < 0.05). Meanwhile, no significant differences were observed in the appearance orders of the calluses in the non-treatment group. When the 2 groups were compared, only the appearance order of the anterior callus was earlier in the treatment group (1.5 vs. 2.7; P = 0.02). The days required for bridging callus formation was shorter in the anterior side (44 days in average) than in the posterior side (93 days in average) only in the treatment group (P = 0.02). When the 2 groups were compared, the bridging callus of the only anterior side was formed earlier (P = 0.03) in the treatment group (44 vs. 78 days). Conclusions: Induction of porosis occurred from the anterior and lateral sides, which were treated with LIPUS after intramedullary nailing of the femoral shaft fractures.