Objectives: Atypical femoral fractures (AFFs) are a rare but important complication of anti-resorptive therapy (ART). The pathophysiology of these fractures remains poorly understood. AFFs are associated with low serum alkaline phosphatase (ALP) and other bone turnover markers, but the diagnosis is established on radiological grounds. This study investigated differences in serum biochemistry at time of hospitalisation AFFs and ‘typical’ femoral shaft fractures (TFFs).
Study design: Retrospective observational study across two centrs in Queensland, Australia between 2012 - 2022
Methods: All femoral shaft fractures presenting across two hospitals between 2012 – 2022 were screened for inclusion. Two groups comprising AFFs and TFFs were identified for comparison. Blood results at the time of hospital admission were reviewed from the electronic medical record.
Results: 143 fractures were included, with 41 patients in the AFF group and 102 in the TFF group. Significant differences were observed between AFF and TFF groups in median serum ALP (56IU/L vs 83IU/L, p=<0.001), vitamin D level (86.8nmol/L vs 69.5nmol/L, p = 0.01), albumin (38g/L vs 36g/L, p = 0.015), globulin (27g/L vs 29g/, p = 0.02), creatinine (68 vs 77, p = 0.05) and B12 (360pg/ml vs 250pg/ml, p = 0.03). In the AFF group, 22.5% patients had a serum ALP <40IU/L compared with 3.9% in the TFF group. There was no significant difference observed in the remaining markers of liver function, electrolytes, blood group or coagulation profile.
Conclusion:
Most datapoints were similar between groups. These data suggest that AFFs are associated with low serum ALP levels on presentation. Lower creatinine levels in the AFF group may reflect reduced muscle mass, an important marker of frailty.