Calculation method to predict postoperative limb length in patients undergoing THA following developmental dysplasia of hips

Abstract

BackgroundLimb length discrepancy (LLD) is one of the main cause of dissatisfaction after total hip arthroplasty (THA). The teardrop-lesser trochanter method can accurately predict and analyze LLD for healthy people. However, for patients with preoperative LLD, no method for predicting postoperative LLD is currently available, and these patients are highly susceptible to more severe LLD after THA. Accordingly, this study proposed a calculation method to predict postoperative limb length for these patients.MethodsEighty patients who underwent THA between May 2016 and October 2018 due to unilateral developmental dysplasia of the hip (DDH) were evaluated. Relevant parameters were measured from radiographs of full-length lower limbs, e.g. the distance between the rotation center of the hip and the midpoint of the tibial plafond and the distance between the point which was marked at the same height as the lesser trochanter on the anatomical long axis of the femur and the midpoint of the tibial plafond. Then, a mathematical model was established by simplifying the structure from the hip to the ankle. The relationship between the placement position of the prosthesis and the LLD value was calculated by Law of Sines and Iterative Calculation.ResultsThe preoperatively predicted LLD values and the postoperatively measured LLD values were compared, yielding a mean absolute difference of 3.7 (range, 0.1 to 8.6) mm. The intraclass correlation coefficient (ICC) of the two parameters exhibited strong reliability (ICC = 0.911, 95%CI, 0.795 to 0.955). The Bland-Altman plot also showed good conformity between the two parameters.ConclusionsThe proposed calculation method effectively predicted the postoperative LLD using preoperative parameters. Despite the complexity of the method, it can go a long way towards reducing the occurrence of severe postoperative LLD in DDH-THA.

An Intraoperative Method to Minimize Leg Length Discrepancy in Anterior Minimally Invasive Total Hip Arthroplasty—A Prospective Study

“…In the methods described by Williamson and Reckling [ 41 ], the distance between the most inferior point of the ischia and the lesser trochanter is measured, while in the method described by Woolson et al, the distance between inferior point of the acetabular teardrop and the lesser trochanter is measured [ 22 ]. Meermans et al demonstrated that the teardrop method was more reliable than the bi-ischial line [ 42 ], although neither method accounts for hip flexion or abduction deformity at the time of the X-ray, which tends to underestimate the measured LLD, or any causes of LLD that do not involve the hip [ 43 ]. Therefore, the use of templates should be complemented with a reliable intra-operative method to achieve better control of leg length.…”

“…Additionally, each dataset, calculated by two independent observers, was evaluated to assess the agreement between the two measurements, utilizing the Bland–Altman plot [ 23 ]. Moreover, any cause of LLD involving the contralateral hip or ipsilateral other joints was excluded to minimize the unreliability of the trans-teardrop method [ 43 ].…”

Stress-specific differences in Distal Femoral Epiphysis of Leg Length Discrepancy and Pelvic Tilt. A Finite-Element Analysis

“…True LLD refers to the unequal length of the bones of the lower extremities on both sides, and is usually caused by abnormal development of the affected limb caused by a variety of pathological factors. Common associated conditions include developmental dislocation (dysplasia) of the hip (DDH), trauma, Perthes disease, and septic arthritis of the hip (Guo et al 2019). The normal progression of the lower extremity from varum to valgum is well studied.…”

“…Li et al research show knee radiographic changes in patients with unilateral DDH were not associated with LLD(Li et al 2014). In our research, through 3D reconstruction, the pelvis, femur, cartilage structures are completely simulated, and the measurement is performed directly on the model without measuring the image.Guo et al(Guo et al 2019) studied the LLD after total hip arthroplasty in adults with DDH and suggested that changes in lower extremity length may not only lead to LLD but also change the angle of the pelvis. In 1983, Friberg et al(Friberg 1983) demonstrated that LLD can cause changes in coronal and crosssectional angles of the pelvis and spine.…”