Bone loss around failed femoral implant measured by dual-energy X-ray absorptiometry

Assessing Periprosthetic Bone in Total Wrist Arthroplasty: The Validity of DXA

INTRODUCTION

Dual-energy X-ray absorptiometry (DXA) can measure bone mineral density (BMD) around joint arthroplasties. DXA has never been used in total wrist arthroplasties (TWA). We investigated (1) whether BMD differs between 2 TWAs implanted in the same cadaver forearm, (2) the effect of forearm rotation and wrist extension on measured BMD around TWA in a cadaver, and (3) the precision of DXA in a cadaver and patients.

METHODOLOGY

One ROI around the distal and 1 and 3 ROIs (ROI1-3) around the proximal component were used. Ten DXA scans were performed on forearm and femur mode convertible to orthopedic knee mode without arthroplasty, with ReMotion, and with Motec TWA in one cadaver forearm. Ten scans with 5° increments from 90°-70° pronation and 0°-20° extension, were performed with Motec. Precision was calculated as coefficient of variation (CV%) and least significant change (LSC%) from cadaver scans and double examinations with femur mode converted to orthopedic knee mode in 40 patients (20 ReMotion, 20 Motec).

RESULTS

BMD was higher in all Motec than corresponding ReMotion ROIs (p < 0.05). BMD changed with 10° supination in the distal ROI and ROI1, and with 5° extension in the distal ROI (p < 0.05). In the cadaver the orthopedic knee mode was more precise than the forearm mode in 3 Motec ROIs (p < 0.05). In patients CV was 2.21%-3.08% in the distal ROI, 1.66%-2.01% in the proximal ROI, and 1.98%-2.87% with 3 ROIs.

CONCLUSIONS

DXA is feasible for BMD measurement around the proximal component using the orthopedic knee mode, but not the distal component of TWA.

Short to Midterm Follow-Up of Periprosthetic Bone Mineral Density after Total Hip Arthroplasty with the Ribbed Anatomic Stem

Background

Femoral bone remodeling around hip prosthesis after total hip arthroplasty (THA) is definite but unpredictable in time and place. This study aimed to investigate the implant-specific remodeling and periprosthetic bone mineral density (BMD) changes after implantation of the Ribbed anatomic cementless femoral stem.

Methods

After power analysis, 41 patients who had undergone primary unilateral THA with the Ribbed anatomic cementless stem were included. BMD of the seven Gruen zones was measured by dual-energy X-ray absorptiometry, and the contact, fitness, and fixation of the femoral stem and proximal femur were analyzed by X-ray. Additional clinical outcome parameters were also recorded.

Results

Compared with the contralateral unoperated side, significant reductions of BMD were detected in the distal zone (Gruen zone 4: 1.665±0.198 versus 1.568±0.242 g/cm², P=0.001) and middle distal zone (Gruen zone 5: 1.660±0.209 versus 1.608±0.215 g/cm², P=0.026) on the prosthetic side, but no significant differences in BMD were detected in other zones (Gruen zones 1, 2, 3, 6, and 7). Subgroups analyses indicated no significant correlation between periprosthetic BMD changes and clinical factors including primary disease and body mass index. Visible areas of bone ingrowth indicated solid fixation of the femoral stem and there was no case of loosening. Clinical and functional outcome scores were excellent with mean HHS of 93.13 points and mean WOMAC score of 5.20 points, and three patients described intermittent mild thigh pain at the final follow-up.

Conclusions

For the Ribbed femoral stem, the periprosthetic BMD was well maintained in the proximal femur, while periprosthetic BMD was significantly reduced in the distal and middle distal zones of the femur. Further clinical investigations are required to examine the efficacy of the Ribbed stem, particularly with regard to long-term survival. This trial is registered with ChiCTR1800017750.

Larger femoral periprosthetic bone mineral density decrease following total hip arthroplasty for femoral neck fracture than for osteoarthritis: a prospective, observational cohort study

Studies on patients with degenerative joint disease of the hip show that femoral periprosthetic bone mineral decreases following total hip arthroplasty. Scarcely any osteodensitometric data exist on femoral neck fracture (FNF) patients and periprosthetic bone remodelling. In two parallel cohorts we enrolled 87 patients (mean age, 72 ± 12 years; male:female ratio, 30:57) undergoing total hip arthroplasty for either primary osteoarthritis (OA) of the hip (n = 37) or for an acute FNF (n = 50) and followed them for a mean of 5.4 years. Outcomes were bone mineral density (BMD) changes in the periprosthetic Gruen zones 1-7, the incidence of periprosthetic fractures and clinical outcome. The bone mineral loss in the fracture group was more than twice that of the osteoarthritis group, -16.9% versus -6.8% (p = 0.004). The incidence of periprosthetic fractures was 12% (6/50) in the fracture cohort compared with none (0%) in the OA cohort (p = 0.03). Periprosthetic bone mineral loss following total hip arthroplasty is significantly greater in patients who are treated for acute FNF than in OA patients. This decrease of BMD follows a different pattern with the FNF patients losing larger proportions of bone in Gruen zones 1, 2, 6, and 7 while the OA patients tend to have larger losses only in zones 1 and 7.

Changes in bone mineral density of the acetabulum, femoral neck and femoral shaft, after hip resurfacing and total hip replacement

It is accepted that resurfacing hip replacement preserves the bone mineral density (BMD) of the femur better than total hip replacement (THR). However, no studies have investigated any possible difference on the acetabular side.

Between April 2007 and March 2009, 39 patients were randomised into two groups to receive either a resurfacing or a THR and were followed for two years. One patient’s resurfacing subsequently failed, leaving 19 patients in each group.

Resurfaced replacements maintained proximal femoral BMD and, compared with THR, had an increased bone mineral density in Gruen zones 2, 3, 6, and particularly zone 7, with a gain of 7.5% (95% confidence interval (CI) 2.6 to 12.5) compared with a loss of 14.6% (95% CI 7.6 to 21.6). Resurfacing replacements maintained the BMD of the medial femoral neck and increased that in the lateral zones between 12.8% (95% CI 4.3 to 21.4) and 25.9% (95% CI 7.1 to 44.6).

On the acetabular side, BMD was similar in every zone at each point in time. The mean BMD of all acetabular regions in the resurfaced group was reduced to 96.2% (95% CI 93.7 to 98.6) and for the total hip replacement group to 97.6% (95% CI 93.7 to 101.5) (p = 0.4863). A mean total loss of 3.7% (95% CI 1.0 to 6.5) and 4.9% (95% CI 0.8 to 9.0) of BMD was found above the acetabular component in W1 and 10.2% (95% CI 0.9 to 19.4) and 9.1% (95% CI 3.8 to 14.4) medial to the implant in W2 for resurfaced replacements and THRs respectively. Resurfacing resulted in a mean loss of BMD of 6.7% (95% CI 0.7 to 12.7) in W3 but the BMD inferior to the acetabular component was maintained in both groups.

These results suggest that the ability of a resurfacing hip replacement to preserve BMD only applies to the femoral side.

Early bone growth on the surface of titanium implants in rat femur is enhanced by an amorphous diamond coating

BACKGROUND AND PURPOSE

Amorphous diamond (AD) is a durable and compatible biomaterial for joint prostheses. Knowledge regarding bone growth on AD-coated implants and their early-stage osseointegration is poor. We investigated bone growth on AD-coated cementless intramedullary implants implanted in rats. Titanium was chosen as a reference due to its well-known performance.

MATERIALS AND METHODS

We placed AD-coated and non-coated titanium implants (R(a) ≈ 0.2 μm) into the femoral bone marrow of 25 rats. The animals were divided in 2 groups according to implant coating and they were killed after 4 or 12 weeks. The osseointegration of the implants was examined from hard tissue specimens by measuring the new bone formation on their surface.

RESULTS

4 weeks after the operation, the thickness of new bone in the AD-coated group was greater than that in the non-coated group (15.3 (SD 7.1) μm vs. 7.6 (SD 6.0) μm). 12 weeks after the operation, the thickness of new bone was similar in the non-coated group and in the AD-coated group.

INTERPRETATION

We conclude that AD coating of femoral implants can enhance bone ongrowth in rats in the acute, early stage after the operation and might be an improvement over earlier coatings.

Quantification of bone density of the proximal femur after hip resurfacing arthroplasty--comparison of different DXA acquisition modes

Total hip arthroplasty (THA) is a traditional operative procedure in the treatment of osteoarthritis. The hip resurfacing arthroplasty (HRA) provides an alternative to the THA for young active patients. HRA is a bone-preserving procedure eliminating the problem of proximal femoral stress shielding and osteolysis associated to THA. Unfortunately, there is no standardized methodology to monitor the quality of bone after HRA. In this study, areal bone mineral density (BMD) in the operated hip (10 regions of interests [ROIs] of 34 volunteered HRA patients) was measured using Lunar Prodigy dual-energy X-ray absorptiometry, and the agreement of a standard (dual femur) and an orthopedic (orthopedic hip) acquisition modes was compared. Furthermore, reproducibility of the patient-specific analysis procedures was tested. The analysis procedures were reproducible with both acquisition modes (1.18%-1.37%). The mean (± standard deviation) difference between the acquisition modes was 1.46 ± 0.93%. At ROIs, a strong linear relationship was found between the results from 2 acquisition modes (R(2)=0.801-0.966, p<0.01). In conclusion, both acquisition modes were reproducible, and it is suggested that the error induced by the different acquisition modes does not affect interpretation of BMD changes after HRA surgery.

[Application possibilities of osteodensitometry in detecting and preventing periprosthetic bone resorption following cementless total hip artheroplasty]

<zakljucak> Najcesca komplikacija ugradnje bescementne endoproteze kuka kod bolesnika sa koksartrozom jeste periproteticna osteoresorpcija koja se javlja u toku prvih nedelja i meseci posle ugradnje implantata i koja dovodi do njegovog labavljenja ili periproteticnog preloma butne kosti. Osteodenzitometrijskim merenjem BMD pre ugradnje endoproteze, a zatim kontinuiranim pracenjem promena BMD posle operacije, moguce je otkriti bolesnike koji imaju povecan rizik od razvoja masivne periproteticne osteoresorpcije i pravovremeno preduzeti neophodne mere za obezbedjenje dugotrajne stabilnosti endoproteze, a time i kvaliteta zivota bolesnika sa koksartrozom.

Tartrate-resistant acid phosphatase 5b (TRAP 5b) as a marker of osteoclast activity in the early phase after cementless total hip replacement

BACKGROUND

After total hip replacement, increased bone metabolism is seen. A local periprosthetic osteopenia can be measured by dual-energy X-ray absorptiometry (DXA), but it is still unkown whether biochemical markers can be used to monitor the local remodeling at an earlier stage.

PATIENTS AND METHODS

In this prospective study we compared the biochemical markers tartrate-resistant acid phosphatase 5b (TRAP 5b), bone ALP, osteocalcin and CrossLaps with periprosthetic DXA in 17 consecutive patients after uncemented total hip replacement.

RESULTS

We found a highly significant early increase in TRAP 5b after 2 weeks and 6 weeks, which was followed by a densitometrically detectable decrease in bone mineral density after 26 weeks, especially in periprosthetic section Gruen zone 7. Bone ALP and osteocalcin levels as markers of osteoblast activity, and also Cross-Laps as a further marker of osteoclast activity, did not appear to allow any significant prediction of local bone remodeling.

DISCUSSION

Our findings show that TRAP 5b is a sensitive parameter for monitoring of osteoclast activity after cementless total hip replacement, and may predict local osteopenia.

Differences in stability and bone remodeling between a customized uncemented hydroxyapatite coated and a standard cemented femoral stem A randomized study with use of radiostereometry and bone densitometry

The custom made Unique stem is designed to fit closely to the metaphyseal region of the femur in order to obtain maximum mechanical stability and optimal load transfer. Thirty-seven patients (38 hips) with non-inflammatory arthritis were randomized to the uncemented custom made Unique stem or the Elite Plus stem inserted with cement. The patients have been followed clinically as well as with radiostereometry (RSA) and Dual-energy X-ray Absorptiometry (DXA) for 2 years. After 2 years the RSA result showed minimal translation and rotation for the Unique stem while the Elite Plus rotated slightly (mean 1.05 degrees) into retroversion. Compared to previous studies the Elite Plus was as stable as the Charnley prosthesis. The DXA results showed a significantly higher proximal and total (10% for the Unique versus 5% for Elite) bone loss for the Unique stem compared to the Elite Plus. Thus the optimal proximal press-fit of the custom made stem did secure a stable fixation, but did not decrease the proximal bone loss.

Medium-term dexa analysis of an uncemented femoral component

We investigated the bone remodelling around the AML uncemented femoral component using DEXA analysis and plain radiography in 19 patients at a mean of 89 months from operation. All patients had previously been analysed at a mean of 32 months after surgery. We found a decrease in bone mineral density around the AML implant between the two scans in Gruen zones 1,2 and 6 of up to 8%, but an increase in zones 4,5 and 7 of up to 36%. The increase in zones 4 and 5 were statistically significant (P>0.05). The relative difference between the operated and unoperated hips also showed a reduction in the bone density ratio with time, except in zones 4 and 5 where an increase was seen. We confirm the results of previous studies of proximal stress shielding and distal loading around the AML implant and demonstrate that bone remodelling continues in the medium term. (Hip International 2004; 14: 182-8).

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

We compared the differences in bone mineral density (BMD) adjacent to two biomechanically different cementless femoral stems (Spotorno and Evolution-K). Measurements were performed within the first week after surgery and 3, 6, 12, and 24 months postoperatively in a prospective study of 31 patients with 37 total hip arthroplasties. A modified Harris hip score and a visual analogue score for patient satisfaction was used to evaluate the clinical outcome. For both stems, dual X-ray absorptiometry measurements revealed a decrease in BMD in Gruen zone 7. Patients with a Spotorno stem also had a significant decrease in BMD in zones 1 and 2. In patients with an Evolution-K stem, there was a positive correlation between the clinical outcome and BMD in Gruen zones 1 and 4. Our data suggest that periprosthetic bone loss is equal to if not less pronounced adjacent to the Evolution-K stem as compared to the Spotorno stem.