Is Atrophic Nonunion a Misnomer - A Hospital-based Prospective Cross-Sectional Study

Objective  The present study was conducted to estimate histologically the proportion of avascularity of fracture ends in case of nonunion of long bones. Methods  A total of 15 cases of established quiescent nonunion were operated according to the standard protocol and the fracture ends were evaluated histologically. The biopsied tissue was briefly fixed with formalin, embedded with paraffin (FFPE), and 5-micron sections were stained with hematoxylin and eosin according to standard protocols. Immunohistochemistry with anti-CD31 antibody (JC70A clone, DBS) was performed manually using standard protocols. Results  All cases of quiescent nonunion were included; radiologically, 2 cases were oligotrophic, and 13 cases were of atrophic nonunion. A total of 20% of the patients were females, 40% were in the age group between 31and 40 years old, and, radiologically, all cases were of atrophic nonunion. All cases showed positivity for CD-31 on immunohistochemistry. The blood vessel density was category I in 13.33% of the cases and category II in 86.67% of the cases. Four cases presented with mild inflammation and two presented with moderate inflammation. The average vessel count was 10 per high power field in the age groups between 20 and 30, 31 and 40, and 41and 50 years old. The age group between 61 and 70 years old showed an average vessel count of 4 per high power field. The difference in the vessel counts of oligotrophic and atrophic nonunion was not significant. No correlation was observed in the density of vessel count and duration of nonunion Conclusion  The nomenclature for the classification of nonunion into atrophic, oligotrophic, and hypertrophic needs revision. Our findings do not support that atrophic and oligotrophic nonunion are histologically different.