Uncemented femoral stem orientation and position in total hip arthroplasty: A CT study

Abstract

In total hip arthroplasty (THA), accurate positioning of components is important for the functionality and long life of the implant. Femoral component version has been underinvestigated when compared with the acetabular cup. Accurate prediction of the femoral version on the preoperative plan is particularly important because a well‐fitting uncemented stem will, by definition, press‐fit into a version that is dictated by the anatomy of the proximal femur. A better understanding of this has recently become an unmet need because of the increased use of uncemented stems and of preoperative image‐based planning. We present the first, three‐dimensional (3D) comparison between the planned and achieved orientation and position of the femoral components in THA. We propose a comparison method that uses the 3D models of a, computed tomography‐generated (CT‐generated), preoperative plan and a postoperative CT to obtain the discrepancy in the six possible degrees of freedom. We ran a prospective study (level 2 evidence) of 30 patients undergoing uncemented THA to quantify the discrepancy between planned and achieved femoral stem orientation and position. The discrepancy was low for femoral stem vertical position and leg length, and varus‐valgus and anterior‐posterior orientation. The discrepancy was higher for femoral version with a mean (±SD) of −1.5 ± 7.8 deg. Surgeons should be aware of the variability of the eventual position of uncemented stems in THA and acknowledge the risk of achieving a less‐than‐optimal femoral version, different from the preoperative 3D CT plan.

The Accuracy of Patient-Specific Instrumentation with Laser Guidance in a Dynamic Total Hip Arthroplasty: A Radiological Evaluation

“…While numerous studies on the cup position in a THA are available, there are limited data on the femoral stem position [ 18 , 31 , 32 ]. Recent literature has reported the importance of planning the femoral osteotomy for a successful THA as the femoral neck resection influences the leg length, offset and the tracking of the implant [ 17 , 33 ].…”

“…On the femoral side, due to the complex morphology and variability of the proximal medullary canal, the level and angle of the femoral neck osteotomy can influence the leg length and stem anteversion especially in cementless implants. A femoral osteotomy and stem placement should be performed to optimize the leg length discrepancy and to reproduce the femoral offset [ 3 , 17 , 18 ].…”

The Patient-Specific Combined Target Zone for Morpho-Functional Planning of Total Hip Arthroplasty

“…The cup orientation is calculated according to Murray’s radiographic definition [ 72 ] relative to the pelvic coordinate system. Two landmarks were manually selected on the proximal and distal end of the surface model of the stem to define the stem axis (similar to [ 73 ]). The neck and stem axis were used to calculate the stem orientation, stem position, CCD angle and neck length using homogenous matrix operations [ 74 ].…”

Imaging in Hip Arthroplasty Management Part 2: Postoperative Diagnostic Imaging Strategy

“…Radiographs are the first imaging modality used for routine follow-up in asymptomatic and painful cases [ 7 ]. CT and MRI used to suffer from metallic artifacts, but are nowadays central in HA complications diagnosis [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ]. Nuclear medicine studies are helpful when CT and MRI are inconclusive when a complication is suspected [ 40 ] but are beyond the scope of this paper.…”