Measuring limb length discrepancy using pelvic radiographs: Most appropriate method

Author(s): Dr. Sunil Kumar PC, Dr. Deepak MK, Dr. Mohan Kumar and Dr. Jyothish K

Abstract: Introduction: Leg length inequality following total hip replacement its still common. In order to reduce limb length inequality, surgeons undertake pre-operative measurements, by preoperative templating and use various forms of intraoperative measurements, including computer navigation. We studied to compare and find out which measurement technique for assessing limb length discrepancy using two different pelvic reference has excellent inter-observer variability using standard antero-posterior radiograph.
Material and Methods: 40 patients (40 hips) had their measurement of limb length discrepancy on standard AP radiographs. The measurement was done by two observers one is orthopedic surgeon, and other one is radiologist. Two lines were constructed on each of the radiographs, bisecting the acetabular teardrops, ischial spines. Measurements were taken from these lines to the most conspicuous medial point on the lesser trochanter.
Results: For measuring limb length using teardrop as a pelvic reference and lesser trochanter as femoral reference inter-observer agreement for radiological measurments kappa=0.893 (good aggrement) for pre-operative radiographic measurements and kappa=0.813 (good aggrement) for post-operative radiographic measurements. By using ischial tuberosity as a pelvic reference and lesser trochanter as femoral reference inter-observer agreement for radiological measurments kappa=0.723 (Substantial aggrement) for pre-operative radiographic measurements and kappa=0.752 (Substantial aggrement) for post-operative radiographic measurements.
Conclusions: Measurement of limb length on radiographs has excellent interobserver reliability with the use of the inter teardrop as a pelvic landmark was a better with measurements to the lesser trochanter. Interobserver variability testing showed less agreement when the ischial tuberosity was used as a pelvic landmark compared with the teardrop.

DOI: https://doi.org/10.22271/ortho.2022.v8.i1f.3048