Healing indices are poorly standardized in distraction osteogenesis literature

Distraction osteogenesis is the process by which tissue is created through gradual distraction at a regular rate and rhythm. It is commonly used for bone lengthening due to congenital limb differences, malunion, and bone defects. As the timing and complexity of this procedure are necessarily dependent on the length gained or transported, surgeons have utilized various healing indices to describe their results including bone healing index (BHI), lengthening index (LI), consolidation index (CI), and external fixation index (EFI). Accurate and consistent definitions are therefore needed to compare outcomes across studies to eliminate the variability in the reporting of these important indices. This review seeks to evaluate the current literature on the accuracy and consistency of how these indices are defined.

Studies using the terms BHI, LI, CI, or EFI published prior to December 31, 2025 were searched and screened using the Pubmed/Medline and Web of Science databases. Separate searches were performed for each healing index; 62 articles reporting BHI, 41 for LI, 63 for CI, and 145 for EFI, met inclusion criteria.

Across the studies reporting on BHI, 29.0% did not explicitly define BHI and another 22.6% defined the parameter incorrectly, mostly confusing the term with EFI (78.6%). In 29.3% of the articles that included LI, a definition was not provided. Among the articles that did provide an LI definition, 55.2% were incorrect. Of these, 68.8% mistakenly equate LI with EFI. For CI, 28.6% of articles mentioning the term did not provide a definition. When CI was defined, it was frequently described in terms more consistent with BHI (66.7%). 24.4% of CI definitions were incomplete and only 4.4% were complete and correct. Conversely, EFI was accurately described in 96.7% of its studies.

Significant inconsistencies exist in the definitions for healing indices across studies on distraction osteogenesis. The use of the terms BHI, and LI remains inconsistent and inaccurate across studies. The use of CI is consistently and incorrectly used interchangeably with BHI. EFI definitions were consistent. This investigation demonstrates the lack of standardized healing indices and underscores the urgent need to establish a common measure for assessing healing.