Three key factors affecting treatment results of low-intensity pulsed ultrasound for delayed unions and nonunions: instability, gap size, and atrophic nonunion

If some predictable factors that affect the treatment results of low-intensity pulsed ultrasound (LIPUS) for delayed union or nonunion could be determined, these might provide us with suggestions for whether LIPUS should be used as an alternative treatment for surgery or an adjuvant therapy after surgery. Therefore, the objective of the present study was to determine what factors affected failure of fracture healing after LIPUS for delayed unions and nonunions. A one-year observational retrospective cohort study was conducted with a consecutive cohort of 101 delayed unions and 50 nonunions after long bone fractures that were treated with LIPUS between May 1998 and April 2007. The main outcome measure was radiographic determination of osseous bone union status within one year after start of LIPUS therapy. Statistical evaluation was used to recognize predictable factors that affect treatment results of LIPUS for delayed union and nonunion. Delayed union group (n = 101): Seventy-five delayed unions (74.3 %) united without an additional major surgical intervention. Failure of LIPUS therapy was associated with types of nonunion (atrophic/oligotrophic vs. hypertrophic, relative risk 23.72 [95 % CI 1.20-11.5], p < 0.01), instability at fracture site (unstable vs. stable, relative risk 3.03 [95 % CI 1.67-5.49], p < 0.001), and maximum fracture gap size not less than 9 mm (relative risk 3.30 [95 % CI 1.68-6.45]). Nonunion group (n = 50): Thirty-four nonunions (68.0 %) united without an additional major surgical intervention. Failure of LIPUS therapy was associated with method of fixation (intramedullary nail vs. others, relative risk 4.50 [95 % CI 1.69-12.00], p < 0.001), instability at fracture site (unstable vs. stable, relative risk 4.56 [95 % CI 2.20-9.43], p < 0.0001), and maximum fracture gap size not less than 8 mm (relative risk 5.09 [95 % CI 1.65-15.67]). LIPUS should be applied as an adjuvant therapy in combination with surgical intervention for an established atrophic nonunion with instability and/or with larger fracture gap.