Stem-bone contact patterns of a long straight tapered uncemented stem for primary THA

Subsidence of the Corail stem in total hip arthroplasty: no influence of bony contact

INTRODUCTION

This study investigated stem subsidence following primary total hip arthroplasty (THA) with a Corail stem in patients who underwent two-staged bilateral THA. The second outcome of interest was to investigate whether a specific single cortical bone contact point might reduce postoperative stem subsidence.

METHODS

The present study was conducted following the STROBE guidelines. The records of patients who underwent THA between 2016 and 2023 were accessed. All patients who underwent two-staged bilateral THA were retrieved. The direct contact between the stem and the cortical bone was assessed at various points in the metaphysis and the distal portion of the stem (diaphysis) in both anteroposterior radiographs of the pelvis (medial and lateral bone contact) and a Lauenstein view of the hip (anterior and posterior bone contact). The following parameters were measured and compared to assess stem subsidence: distance from the proximal femur at the stem bone interface and the tip of the lesser trochanter (distance A); distance from the tip of the lesser trochanter and the tip of the femoral stem (distance B).

RESULTS

In total, 250 patients were included, 45% (149 of 250 patients) were women and 61% (153 of 250 THAs) were implanted primarily on the right side. The mean age of patients at the time of the first THA was 64.3 ± 10.0 years and the mean body mass index (BMI) was 28.0 ± 4.9 kg/m2. The mean length of the follow-up was 14.1 ± 10.8 months. The overall stem subsidence following THA was 2.8 ± 0.7 mm (P < 0.006). A direct cortical bone-implant contact did not exert a statistically significant difference in subsidence of the THA stem at the metaphysis and diaphysis (P > 0.5). Stem subsidence following THA with a collarless cementless Corail stem was approximately 2.8 mm at 14 months.

CONCLUSIONS

Direct cortical bone contact of the stem at diaphysis and metaphysis seems not to influence stem subsidence following THA using the Corail stem.

Three-Dimensional Osseointegration Patterns of Cementless Femoral Stems: An ex Vivo Study with High-Resolution Imaging and Histological Evaluation

BACKGROUND

Osseointegration is essential for the long-term survival of cementless femoral stems and is dependent on periprosthetic bone quality and correct implantation technique. The aim of this study was to evaluate the 3-dimensional long-term fixation patterns of, and bone microarchitecture around, cementless hip stems.

METHODS

Four specimens with varying degrees of bone quality and fixation characteristics from body donors who had received Alloclassic Zweymüller hip stems during their lifetime (mean time in situ at the time of death: 12.73 years) were evaluated with use of radiographs, high-resolution computed tomography (CT) scans, and hard-tissue histology. The CT voxel size was 85 µm, and the following parameters were calculated: total bone volume, total bone volume fraction, trabecular bone volume, trabecular bone volume fraction, cortical bone volume, cortical bone volume fraction, and cortical thickness. Bone-implant contact and canal fill index values for each Gruen zone of the specimens were calculated with use of histological samples.

RESULTS

Femoral stems with apparently good cortical contact on clinical radiographs showed higher values for cortical bone volume, trabecular bone volume, and cortical thickness in the high-resolution CT analysis than femoral stems with apparently weak cortical contact on clinical radiographs. Based on the histological evaluation, the mean bone-implant contact ranged from 22.94% to 57.24% and the mean canal fill index ranged from 52.33% to 69.67% among the specimens.

CONCLUSIONS

This study demonstrated different osseointegration patterns of cementless femoral stems on the basis of radiographs, high-resolution CT scans, and histological evaluation. Femora with high cortical bone volume and cortical thickness were associated with higher canal fill indices, whereas femora with low cortical bone volume and cortical thickness had lower canal fill indices and showed a characteristic corner-anchorage pattern.

CLINICAL RELEVANCE

Osseointegration patterns and thus the long-term survival of cementless femoral stems are dependent on cortical bone volume and cortical thickness.