Reliability And Accuracy Of The Radiographic Measurement Method With Crowe Type ? DDH In The Assessment Of Leg Length Discrepancy With Total Hip Arthroplasty

Objective: To compare the measurements based on different anatomical references for the measurement of the lower leg length in adults with Crowe IV developmental dislocation of the hip(DDH)before and after primary total hip arthroplasty(THA).We validated the different methods for preoperative and postoperative radiographic measurement of LLDs and evaluated their reliability and accuracy.Methods : LLDs were measured on full-leg radiographs for 10 patients(11 hips,2 men,8 women)with Crowe IV DDH who were of proposed for primary THA in Sichuan Provincial People's Hospital from January 2013 to July 2016.Four lines were constructed on each of the radiographs,bisecting the acetabular teardrops(T),ischial spines(TI),inferior sacroiliac joint(SIJ)and inferior obturator foramen(O).Measurements were taken from these lines to the most prominent medial point on the lesser trochanter(LT),to the tip of the greater trochanter(GT),to corner point between the femoral neck and head(Y)and to the center of the femoral head(CH).The true LLD was determined the distance from the umbilicus to the medial malleolus as well as the top of the femoral head to the center of the tibial plafond for each lower limb.Using the intraclass correlation coefficient(ICC)evaluates the reliability of the different measurements.The intra-observer and inter-observer variability were calculated.Using a 2-sample paired t test,the P value for each of the categories was determined and found to be <0.01 for each of the LLD measurements when compared to the evaluated true LLD.Results: Measurements including the inferior aspect of the ischial tuberosities(Transischial line)to the most prominent medial point on the lesser trochanter(TI-LT),the inferior aspect of the ischial tuberosities to the tip of the greater trochanter(TI-GT),the inferior obturator foramen to the tip of thegreater trochanter(O-GT),the inferior obturator foramen to the most prominent medial point on the lesser trochanter(O-LT)and inferior sacroiliac joint to the most prominent medial point on the lesser trochanter(SIJ-LT)are not significantly different from the evaluated true LLD.The distances from TI to GT and TI to LT appear to almost prefect(ICC>0.9)in intraobserver agreement and interobserver agreement when using TI-GT and TI-LT for preoperative and postoperative radiographic measurement of LLD.