The influence of implant design on periprosthetic bone remodelling of two types of uncemented HA-coated hip stems. A two-year follow-up study using DEXA.

UNLABELLED: Proximal bone resorption and an increased fracture rate in the ABG-I stem has been shown. For these reasons the ABG-I stem design was changed to the ABG-II. In this study periprosthetic bone loss around the ABG-I vs ABG-II is compared to verify if the design changes resulted in improved proximal bone preservation. METHODS: 51 patients were randomised to either the ABG-I or ABG-II hip prosthesis. Periprosthetic BMD change at various time points was measured using DEXA. Between the two groups (age, gender, weight etc.) no statistical difference was encountered. Compared to the baseline at two years the ABG-II preserved bone better proximally (e.g. zone 7: ABG-II: -3.7%, ABG-I: -11.9%, p=0.05) than the ABG-I. Distally, the trend was opposite and less bone loss was measured for the ABG-I than the ABG-II in zones 3, 4 and 5 (n.s.). CONCLUSION: this study confirms the philosophy behind the design changes from the ABG-I to ABG-II stem where increased elasticity, more proximal HA-coating, a shorter and distally polished stem, were meant to reduce proximal bone resorption. In future this may lead to fewer periprosthetic fractures and to less complicated revision surgery.

Periprosthetic bone remodelling of two types of uncemented femoral implant with proximal hydroxyapatite coating: a 3-year follow-up study addressing the influence of prosthesis design and preoperative bone density on periprosthetic bone loss.

Periprosthetic bone loss is a major cause of concern in patients undergoing total hip arthroplasty (THA). Further studies are required to identify the factors determining the pattern of bone remodelling following THA and obtain improvements in the design and durability of prostheses. In this study, we monitored periprosthetic bone loss around two different types of hydroxyapatite coated femoral implant over a 3-year period to evaluate their design and investigate the relationship with the preoperative bone mineral density (BMD) at the spine, hip and forearm. Sixty patients (35 F, 25 M, mean age 63 years, range 46-75 years) undergoing THA were randomised to either the Anatomic Benoist Girard (ABG) or Mallory-Head (MH) femoral stem. Preoperative dual-energy X-ray absorptiometry (DXA) scans were acquired of the posteroanterior (PA) and lateral lumbar spine, the contralateral hip and the non-dominant forearm. Postoperative DXA scans were performed to measure periprosthetic BMD at 10 days (treated as baseline), 6 weeks, and 3, 6, 12, 24 and 36 months after THA using a standard Gruen zone analysis. Results were expressed as the percentage change from baseline and the data examined for the differences in bone loss between the different Gruen zones, between the ABG and MH stems, and the relationship with preoperative BMD. A total of 50 patients (24 ABG, 26 MH) completed the study. Three months after THA there was a statistically significant BMD decrease in every Gruen zone that varied between 5.6% and 13.8% for the ABG prosthesis and between 3.8% and 8.7% for the MH prosthesis. Subsequently, in most zones BMD reached a plateau or showed a small recovery. However, BMD continued to fall in Gruen zones 1 and 7 in ABG patients and Gruen zone 1 in MH patients. Bone loss was less in every Gruen zone in MH patients compared with ABG with the largest difference (10%, P=0.018) in Gruen zone 7. Highly significant relationships were found between periprosthetic bone loss and preoperative BMD measured at the PA spine ( P<0.001), total hip ( P=0.004) and total distal radius ( P<0.001). This study showed differences between two different designs of hydroxyapatite-coated implant that confirmed that prosthesis design influences periprosthetic bone loss. The study also showed that patients' bone density measured at the spine, hip or forearm at the time of operation was a major factor influencing bone loss around the femoral stem.

Hydroxyapatite coated hip prosthesis followed up for 5 years.

We prospectively studied 250 patients with a proximal hydroxyapatite coated hip prosthesis. The follow-up period was 5 years. All components showed osseointegration except for one deep infection. The morphology of bone remodeling with either endosteal bone formation or periosteal bone formation was dependent on the way the stem filled the medullary canal. No linear or distal osteolysis around the stems was observed.

The hydroxyapatite-ABG hip system: 5- to 7-year results from an international multicentre study. The International ABG Study Group.

A proximally hydroxyapatite (HA)-coated hip prosthesis designed for proximal stem bonding and stress transfer was studied in a consecutive series of 398 patients in an ongoing, prospective multicenter study. Follow-up was 5 to 7 years. The clinical results were excellent with a mean preoperative Merle d'Aubigné score of 8.5 and 17.3 at 5 years. Only mild thigh pain not necessitating analgesics or a walking stick was reported in 3.6% at 5 years. Three cups and 3 stems had to be revised, all before the 2-year assessment and mainly for technical reasons. No components needed revision after 2 years. The 5-year HA-coated component survival was 99.2%. Serial radiographs showed excellent osseointegration, which was independent of pre-existing bone stock. The rate of radiographic bone remodeling was highest during the first 3 years, and positive bone remodeling (bone formation) preceded negative bone remodeling (bone resorption). The concept of transitional load transfer from proximal to distal could be acknowledged, with proximal load transfer highest in 77%. The combination of anatomic stem design with distal overreaming and proximal HA coating was thought to be the reason for these excellent results. Proximal circumferential osseointegration seems to be real because no linear or distal osteolysis was observed.

Quantitative analysis of technetium-99m-methylene diphosphonate uptake in unilateral hydroxyapatite-coated total hip prostheses: first year of follow-up.

UNLABELLED: A prospective study was performed on 80 patients who had undergone a unilateral hydroxyapatite (HA)-coated total hip arthroplasty to establish the normal periprosthetic uptake of methylenediphosphonate (MDP) as a function of implant age. METHODS: Patients were imaged periodically while they were asymptomatic at 1, 3, 6 and 12 mo postoperatively. Quantitative measurements were performed with a region of interest (ROI) technique. The HA-coated and uncoated areas were marked in comparison with the normal contralateral femur. The uptake ratios of the MDP were determined postoperatively in the following 12 mo. RESULTS: It was found that a decrease of the uptake ratios occurred in all ROIs. However, for the HA-coated areas, the uptake ratios still remained raised as a result of bony ingrowth. CONCLUSION: The results of the first year of follow-up were considered to be a normal database that will be used as a reference when the same group of patients are followed up to 5 yr postoperatively to detect any potential modes of failure of the implant.