Background: Low-intensity pulsed ultrasound (LIPUS) was shown to accelerate fracture healing with delayed unions and non-unions as well as fresh fractures.

Objective: To know the factors which affected clinical results of LIPUS treatment for delayed unions and non-unions.

Design: Prospective Cohort Study

Setting: University Hospital

Intervention: 192 delayed or non-unions of long bone or clavicle were treated by LIPUS from May 1998 to April 2007. Background factors (age and gender of patient, history of smoking, personality of each fracture, intervals from injury to application of LIPUS treatment) were prospectively investigated. All patients were followed up at the outpatient clinic and AP and lateral view of radiographs were taken usually every 4 weeks. Main outcome of this study was set as “bone union” and it was defined as cortical continuity in a minimum of three cortices on two views on radiographs and without pain at the fracture site on palpation.

Main Outcome Measurement: The overall success rate was 75%, and the success rate of subcutaneous bones were higher (tibia: 81%, radius and ulna: 80%)than that of deeper bone (femur: 64%, humerus 58%). Logistic multi-variant regression showed that the greatest gap size between the main bone fragments (p< 0.0001), instability of a fracture site (p< 0.0001), and the intervals between injury to the application of LIPUS (p< 0.05) were independent predictors for the success of LIPUS treatment for delayed and non-unions.

Conclusion: We believe that the greatest gap size of main fragments, instability of a fracture site, and the age of non-union are the factors that affected LIPUS clinical results.

Objective: The purpose of the present study was to assess whether clinicians are actually able to evaluate the mechanical status of lengthening callus from plain radiographs.

Materials and Methods: 36 rats were employed in this study. Their left femurs were lengthened by 6 mm as a bone lengthening model. Rats were euthanized at 4 8 12 and 16 weeks after lengthening. Both femora were X-rayed and then bone density parameters (bone mineral content, bone mineral density and bone area) of lengthening callus were measured using pQCT. Three-point bending test was performed to determine the mechanical strength of the both bones. We defined the ratio of the strength of lengthening side to control side as estimated strength recovery rate (%). Then 20 orthopaedic surgeons evaluated only the X-ray photographs and tried to estimate the relative mechanical strength (%) of the affected side compared to the control side.

Results: Between the recovery percentage of mechanical strength and bone mineral content, a positive simple correlation (R2=0.11, p< 0.05) was seen. No significant correlation was seen between the recovery percentage of mechanical strength estimated by orthopaedists and the mechanical strength measured by three-point bending test (qualified doctors: R2=0.0793 p=0.291 unqualified doctors: R2=0.0523 p=0.394).

Discussion and conclusion: It became obvious that to estimate the strength of lengthening callus from plain radiographs alone is quite difficult as compared with the studies of the simple fracture model that have been reported until now.