Detection of bony defects around cementless acetabular components in total hip arthroplasty: a DEXA study on 10 human cadavers

Does a Monoblock Acetabular Component With a Ceramic Liner Cause More Pelvic Bone Loss Than a Conventional Modular Cementless Acetabular Component? A 2-Year Randomized Clinical Trial

BACKGROUND

Ceramic-on-ceramic bearings permit the use of large femoral head size while maintaining a favorable effect on wear rates. However, because of increased device rigidity, periprosthetic bone quality could be negatively affected due to stress shielding. The purpose of this study is to assess pelvic periprosthetic bone remodeling around a monoblock ceramic-on-ceramic acetabular component compared to that around a conventional modular metal-on-polyethylene device.

METHODS

Participants were randomized to receive hip replacement using either a porous-coated, modular metal-on-polyethylene acetabular component (n = 46) or a hydroxyapatite and titanium-coated monoblock shell with an integrated ceramic-on-ceramic bearing (n = 40). Radiographic assessments were completed preoperatively and postoperatively, and measurements of bone mineral density (BMD) using dual-energy X-ray absorptiometry with region free analysis were performed postoperatively and over 2-years of follow-up.

RESULTS

There was no significant difference in BMD between the 2 groups at baseline or over the following 2 years. At follow-up, complete shell-to-bone contact without a radiolucent line was observed in 26 (67%) of the modular devices and in 37 (93%) of monoblock (P < .001). The modular device was an independent predictor of radiolucent lines (odds ratio 19.1, P = .007). No cases underwent revision surgery for acetabular loosening.

CONCLUSION

Both the porous-coated modular and hydroxyapatite-coated monoblock acetabular components showed successful clinical results at short-term follow-up with no difference in pixel-level BMD. Using a large head monoblock device does not appear to be associated with an adverse effect on the local bone environment when compared to a modular device. NCT: NCT01558752.

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.

Large head metal-on-metal cementless total hip arthroplasty versus 28 mm metal-on-polyethylene cementless total hip arthroplasty: design of a randomized controlled trial

Background

Osteoarthritis of the hip is successfully treated by total hip arthroplasty with metal-on-polyethylene articulation. Polyethylene wear debris can however lead to osteolysis, aseptic loosening and failure of the implant. Large head metal-on-metal total hip arthroplasty may overcome polyethylene wear induced prosthetic failure, but can increase systemic cobalt and chromium ion concentrations. The objective of this study is to compare two cementless total hip arthroplasties: a conventional 28 mm metal-on-polyethylene articulation and a large head metal-on-metal articulation. We hypothesize that the latter arthroplasties show less bone density loss and higher serum metal ion concentrations. We expect equal functional scores, greater range of motion, fewer dislocations, fewer periprosthetic radiolucencies and increased prosthetic survival with the metal-on-metal articulation.

Methods

A randomized controlled trial will be conducted. Patients to be included suffer from non-inflammatory degenerative joint disease of the hip, are aged between 18 and 80 and are admitted for primary cementless unilateral total hip arthroplasty. Patients in the metal-on-metal group will receive a cementless titanium alloy acetabular component with a cobalt-chromium liner and a cobalt-chromium femoral head varying from 38 to 60 mm. Patients in the metal-on-polyethylene group will receive a cementless titanium alloy acetabular component with a polyethylene liner and a 28 mm cobalt-chromium femoral head. We will assess acetabular bone mineral density by dual energy x-ray absorptiometry (DEXA), serum ion concentrations of cobalt, chromium and titanium, self reported functional status (Oxford hip score), physician reported functional status and range of motion (Harris hip score), number of dislocations and prosthetic survival. Measurements will take place preoperatively, perioperatively, and postoperatively (6 weeks, 1 year, 5 years and 10 years).

Discussion

Superior results of large head metal-on-metal total hip arthroplasty over conventional hip arthroplasty have been put forward by experts, case series and the industry, but to our knowledge there is no randomized controlled evidence.

Conclusion

This randomized controlled study has been designed to test whether large head metal-on-metal cementless total hip arthroplasty leads to less periprosthetic bone density loss and higher serum metal ion concentrations compared to 28 mm metal-on-polyethylene cementless total hip arthroplasty.

Trial registration

Netherlands Trial Registry NTR1399

Bone remodelling around HA-coated acetabular cups : a DEXA study with a 3-year follow-up in a randomised trial

This study was designed to investigate bone remodelling around the cup in cementless THA. Previous studies indicate an advantage of better sealing of the bone-prosthesis interface by HA/TCP coating of implants, inhibiting polyethylene-induced osteolysis. One hundred patients gave informed consent to participate in a controlled randomized study between porous coated Trilogy versus Trilogy Calcicoat (HA/TCP coated). The cup was inserted in press-fit fixation. The femoral component was a cementless porous coated titanium alloy stem (Bi-Metric), with a modular 28-mm CrCo head. The Harris Hip Score (HHS) and bone mineral density (BMD) determined by DEXA scanning were used to study the effect. Measurements revealed no difference between the two groups after 3 years either in the clinical outcome or in terms of periprosthetic bone density. Patients with a body mass index above normal regained more bone mineral than patients with normal weight. This finding supports the assumption that load is beneficial to bone remodelling.