Radiographic acetabulotrochanteric distance measurement as a novel method for determining leg length discrepancy in patients with hemiarthroplasty.

Objectives: This study aims to evaluate the interobserver reliability and interobserver reproducibility of radiographic acetabulotrochanteric distance (ATD) measurement and to investigate its accuracy by comparing it with conventional radiographic methods used in leg length discrepancy (LLD) measurement.

Patients and methods: Between January 2017 and January 2022, a total of 97 patients (39 males, 58 females; mean age: 77.8±7.1 years; range, 61 to 91 years) who underwent pelvic radiographic evaluation and hemiarthroplasty (HA) due to femoral neck fracture were retrospectively analyzed. For ATD measurement, the distance between the line connecting the upper cartilage of the acetabulum (AC) and the extreme point of the greater trochanter (GT) was used. The AC-GT measurement on both sides was compared with bottom of the ischial tuberosities-lesser trochanter (BI-LT), center of the femoral head-BI (CH-BI), inferior acetabular teardrops-LT (IT-LT) measurements. The agreement between the methods was examined with the intraclass correlation coefficient (CCI).

Results: According to the AC-GT & BI-LT, AC-GT & BI-CH methods, there were very strong (ICC: 0.75), moderate (ICC: 0.69) and acceptable (ICC: 0.33) agreements, respectively. Significant agreement was found between all measurements (p<0.001). A positive correlation was detected in the correlation analysis of all measurements (p<0.001). Intra- and interobserver agreement for ATD measurement (AC-GT) was excellent (ICC: >0.8).

Conclusion: The ATD measurement correlates well with known measurement techniques on pelvic radiography and can be used as an alternative to this method. It has excellent intra- and interobserver agreements. This method can predict LLD after HA, but does not consider other length differences in the lower limbs.