To ascertain whether the tip–apex distance (TAD), calcar referenced TAD (CalTAD), and the sum of both (TADcalTAD) are predictive measurements of mobilisation of the cephalic screw in patients with trochanteric hip fractures.
Between 2014 and 2015, 68 patients (mean age 86 years, 45 females, 23 males) with a trochanteric hip fracture underwent intramedullary nailing. The TAD and CalTAD were measured, and for each parameter, we calculated sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV).
There is evidence of a statistically significant association between a TAD and CalTAD greater than 25 mm and a TADcalTAD greater than 50 mm and mobilisation of the cephalic screw. All measurements have similar sensitivity, but the TAD presents the highest specificity (p < 0.01).
To avoid the risk of mobilisation of the cephalic screw and possible subsequent failure of the construct, surgeons should strive for a TAD and CalTAD less than 25 mm and a TADcalTAD less than 50 mm when using intramedullary fixation.