Prospective comparison of differences in bone mineral density adjacent to two biomechanically different types of cementless femoral stems

No difference for changes in BMD between two different cementless hip stem designs 2 years after THA

This study evaluates how 2 different total hip arthroplasty (THA) stems compares regarding adaptive bone remodelling. The stems are both proximally porous coated, aiming for proximal fixation, but with different dispersal of the coating. They are also differently designed regarding the distal tip of the stem. We aimed to investigate if there is a difference in periprosthetic adaptive bone remodelling between two different designs. From February 2016 to September 2017, we randomised 62 patients, 1:1 (mean age = 64 years, Female/Male = 28/34), scheduled for an uncemented THA to receive either an EBM or a BM THA stem. We performed dual-energy x-ray absorptiometry (DEXA) scans within a week after surgery and at 3, 6, 12 and 24 months with measurements of bone mineral density (BMD) in the 7 Gruen zones (region of interest (ROI) 1–7). Additionally, Oxford Hip Score and Harris Hip Score were collected at 6, 12 and 24 months. We found a decrease in BMD between the postoperative and the 24-months values in all ROIs for both stems. The greatest decrease over time was seen for both groups in the ROI1 (BM = − 8.4%, p = 0.044, and EBM = − 6.5%, p = 0.001) and ROI7 (BM = − 7%, p = 0.005, and EBM = − 8.6%, p < 0.0005). We found a tendency in ROI2–4 of a higher degree of bone loss in the EBM group. However, this difference only continued beyond 6 months in ROI4 (24 months: BM = − 1.2% and EBM = − 2.8%, p = 0.001). The stems show similar adaptive bone remodelling and are clinically performing well.

An Ultra-Short Femoral Neck-Preserving Hip Prosthesis: A 2-Year Follow-up Study with Radiostereometric Analysis and Dual X-Ray Absorptiometry in a Stepwise Introduction

BACKGROUND

Total hip arthroplasty (THA) with a diaphyseal stem may risk bone loss. In order to save proximal bone stock in young patients with a high activity level and a long life expectancy, the interest in short stems has evolved. The purpose of this prospective observational cohort study was to evaluate the fixation of, and bone remodeling around, the Primoris femoral neck-preserving hip implant.

METHODS

Fifty younger patients with end-stage osteoarthritis were managed with the Primoris hip implant. We evaluated bone mineral density (BMD) using dual x-ray absorptiometry (DXA) and implant migration using radiostereometric analysis (RSA). A region-of-interest (ROI) protocol for 4 ROIs was applied to assess BMD. The association between BMD and migration was evaluated to determine the fixation of the Primoris implant and bone remodeling in the proximal part of the femur. Follow-up evaluation was performed at regular intervals from day 1 (baseline) until 24 months after surgery.

RESULTS

The major stem migrations were subsidence (Y axis; mean, 0.38 mm) at 6 weeks and varus tilt (rotation) (Z axis; mean, 0.93°) at 6 to 12 months. In ROI4 (the calcar area), a significant gain in bone was found with a mean difference of 4.1% (95% confidence interval [CI], 0.8% to 7.4%; p < 0.02) at 24 months postoperatively. Significant bone loss was found in ROI1 and ROI2, with a mean difference of -4.9% (95% CI, -7.4% to -2.4%; p = 0.0003) and -8.9% (95% CI, -11.5% to -6.2%; p = 0.0001), respectively. Linear regression and multivariate regression analysis showed a significant negative association between maximal total point motion and BMD (p = 0.02, R = 15%; and p < 0.05, R = 26%, respectively).

CONCLUSIONS

The Primoris component showed satisfactory primary stability with promising results at the 24-month follow-up. DXA scans showed limited stress-shielding with the proximal loading pattern of the Primoris. Better bone quality was associated with less implant migration.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Periprosthetic femoral bone loss in total hip arthroplasty: systematic analysis of the effect of stem design

INTRODUCTION

Periprosthetic bone loss may lead to major complications in total hip arthroplasty (THA), including loosening, migration, and even fracture. This study analysed the influence of femoral implant designs on periprosthetic bone mineral density (BMD) after THA.

METHODS

The results of all previous published studies reporting periprosthetic femoral BMD following THA were compiled. Using these results, we compared percent changes in bone loss as a function of: femoral stem fixation, material, and geometry.

RESULTS

The greatest bone loss was in the calcar region (Gruen Zone 7). Overall, cemented stems had more bone loss distally than noncemented stems, while noncemented stems had more proximal bone loss than cemented stems. Within noncemented stems, cobalt-chromium (CoCr) stems had nearly double the proximal bone loss compared to titanium (Ti) alloy stems. Finally, within noncemented titanium alloy group, straight stems had less bone loss than anatomical, tapered, and press-fit designs.

DISCUSSION

The findings from the present study quantified percent changes in periprosthetic BMD as a function of fixation method, alloy, and stem design. While no one stem type was identified as ideal, we now have a clearer understanding of the influence of stem design on load transfer to the surrounding bone.

Pooled outcome of total hip arthroplasty with the CementLess Spotorno (CLS) system: a comparative analysis of clinical studies and worldwide arthroplasty register data

PURPOSE

Our aim was to elucidate the pooled outcome of the CementLess Spotorno (CLS) system in total hip arthroplasty (THA).

METHODS

We compared the outcome of clinical inventor studies, independent clinical studies, and worldwide register data. The main endpoints for analysis were revision rates.

RESULTS

Twenty clinical studies were evaluated and, with one exception, overall found revision rates largely in line with register data. Revision rates (revisions per 100 observed component years) range from 0.15 (inventor study) to 0.28 (independent studies) and 0.43 (register datasets).

CONCLUSION

Data of journal publications and register datasets using the CLS system do not differ significantly with respect to revision rates. Only the initial inventor study reports a revision rate three times lower than in pooled worldwide register datasets.

Femoral bone density changes after total hip arthroplasty with uncemented taper-design stem: a five year follow-up study

We measured bone density (BD) changes to assess adaptive bone remodelling five years after uncemented total hip arthroplasty with taper-design femoral component using quantitative computed-tomography-assisted osteodensitometry (qCT). Nineteen consecutive patients (21 hips) with degenerative joint disease were enrolled in the study. A press-fit cup and a tapered uncemented stem ceramic-ceramic pairing were used in all patients. Serial clinical, radiological and qCT osteodensitometry assessments were performed after the index operation and at the one, two and five year follow-ups. At the latest follow-up, the clinical outcome was rated satisfactory in all hips. The radiological assessment showed signs of osteointegration with stable fixation of all cups and stems. Overall, there was evidence of a BD loss at year five (p = 0.004). We estimate that BD loss was between 2.2% and 12.1% in comparison with baseline postoperative values. Progressive loss of BD in the metaphyseal region was observed in all hips. We found unremarkable BD changes of diaphyseal cortical BD throughout the five year follow-up period. qCT osteodensitometry technology allows differentiation of cortical and cancellous BD changes over time. Periprosthetic BD changes at the five year follow-up are suggestive of stable stem osteointegration with proximal femoral diaphysis load transfer and metaphyseal stress shielding.

TOTAL HIP ARTHROPLASTY WITH BIOMEC PROSTHESIS: 20-YEAR FOLLOW-UP

OBJECTIVE

To analyze the clinical and radiological outcomes from total hip arthroplasty using the Biomec prosthesis over a 20-year period (1988 to 2009).

METHODS

The patients were evaluated clinically in accordance with the Merle d'Aubigné and Postel functional classification, and underwent anteroposterior (AP) radiography of the pelvis and the operated joint in lateral view. The variables evaluated were acetabular and femoral osteolysis, polyethylene wear, nail migration, follow-up and clinical outcomes.

RESULTS

The mean follow-up was 10.6 years (range 4 to 21 years). The sample consisted of 84 patients (32 men and 52 women) and the mean preoperative age was 47 years. We found that 88% of the results from the clinical evaluation were good or excellent. In relation to the radiological findings, 92.5% of the results were good. The mean wear on the polyethylene was 1.4 mm.

CONCLUSION

The use of the Biomec prosthesis in this cohort showed good clinical and radiographic results.

Five-year DEXA study of 88 hips with cemented femoral stem

We performed repeated dual-energy X-ray absorptiometry (DEXA) measurements over five years in a homogeneous patient population to study the effect of a cemented stem on proximal femoral bone remodelling. Data from 88 patients (88 hips) implanted with total hip arthroplasty (THA) prostheses were extracted from three randomised studies. Femoral bone mineral density (BMD) was measured using a Lunar DPX-IQ densitometer for five years postoperatively. At one year the BMD changes had decreased between -2.0% [region of interest (ROI) 1] and -11.5% (ROI 7). During the follow-up period the BMD initially increased during the second year and thereafter decreased again in ROIs 5, 6 and 7. The loss of BMD at five years was more pronounced in region 7 (12.9%) and decreased with increasing age, total hip replacement (THR) on the right side and decreasing weight of the patient. We found that after the initial phase of early bone loss a period of recovery follows. Thereafter the BMD decreases again, which probably reflects the normal ageing of bone after uncomplicated cemented THA.

Quantitative CT-assisted osteodensitometry of femoral adaptive bone remodelling after uncemented total hip arthroplasty

The aim of this prospective study was to measure bone density changes and to assess adaptive bone remodelling after uncemented total hip arthroplasty with a taper-design femoral component using quantitative computer-tomography-assisted osteodensitometry. This method is able to differentiate cortical and cancellous bone structures. Twenty-seven consecutive patients (29 hips) with degenerative joint disease were enrolled in the study. Serial clinical, radiological and CT-osteodensitometry assessments were performed after the index operation. At the 2-year follow-up, the clinical outcome was rated satisfactory in all hips. The radiological assessment showed signs of osteointegration and stable fixation of all cups and stems. We observed a -17% decrease of cortical bone density and -22% decrease of cancellous bone density in the greater trochanter and femoral neck region. Cortical and cancellous bone density decrease at the level of the lesser trochanter was -9% and respectively -4%. We observed small changes of cortical bone density in the diaphyseal regions; in contrast, cancellous bone density increased (range 6% to 27%) in the diaphyseal regions. Overall, a trend of bone density recovery was observed throughout the follow-up period. Periprosthetic bone density changes at the 2-year follow-up are suggestive of stable osteointegration with proximal femoral diaphysis load transfer and moderate metaphyseal stress-shielding.

Quantitative computer-assisted osteodensitometry in total hip arthroplasty

Several factors can cause bone loss and fixation failure following total hip arthroplasty (THA), including polyethylene wear debris, implant micromotion and stress shielding. Various techniques have been used in an effort to detect bone density loss in vivo, all with varying success. Quantitative computed tomography (qCT)-assisted osteodensitometry has been shown to be useful in assessing the in vivo structural bone changes after THA. It has a high resolution, accuracy and reproducibility, thereby making it a useful tool for research purposes, and it is able to differentiate between cortical and cancellous bone structures and assess the bone/implant interface. This technique also provides valuable information about the pattern of stress shielding which occurs around the prosthesis and can show early bony changes, which may prove informative about the quality of implant fixation and surrounding bone adaptation. In conjunction with finite-element analysis, qCT is able to generate accurate patient-specific meshes on which to model implants and their effect on bone remodelling. This technology can be useful to predict bone remodelling and the quality of implant fixation using prostheses with different design and/or biomaterials. In the future, this tool could be used for pre-clinical validation of new implants before their introduction in the market-place.