Randomized comparison between the cemented Scientific Hip Prosthesis and Omnifit: 2-year DEXA and minimum 10-year clinical follow-up.

Radiostereometry (RSA) of the cemented Scientific Hip Prosthesis (SHP) reported excessive migration and predicted high failure rates. In a prospective randomized clinical trial we compared minimum 10 years results of the SHP (n=38) with the Omnifit-stem (n=37). Two-year bone remodelling, compared with dual energy x-ray absorptiometry and assessed in regions of interest A-D based on the 7 Gruen zones, showed better periprosthetic bone preservation around the SHP in all but one regions (P<.05). At 10 years Harris Hip Score was better for the SHP (P=.0001) but Oxford Hip Score was the same (P=.79). There were no revisions in either group, but radiographic loosening was definite in 1 SHP and 1 Omnifit. Based on earlier RSA studies, the rough surface finish of the SHP was expected to cause cement abrasion, osteolysis and inferior survival. However our clinical and remodelling results could not confirm these expectations, suggesting that the link of early migration and mid-term clinical results is not sufficiently clear for the SHP.

International survey of primary and revision total knee replacement.

PURPOSE: Total knee arthroplasty (TKA) is currently the international standard of care for treating degenerative and rheumatologic knee joint disease, as well as certain knee joint fractures. We sought to answer the following three research questions: (1) What is the international variance in primary and revision TKA rates around the world? (2) How do patient demographics (e.g., age, gender) vary internationally? (3) How have the rates of TKA utilization changed over time? METHODS: The survey included 18 countries with a total population of 755 million, and an estimated 1,324,000 annual primary and revision total knee procedures. Ten national inpatient databases were queried for this study from Canada, the United States, Finland, France, Germany, Italy, the Netherlands, Portugal, Spain, and Switzerland. Inpatient data were also compared with published registry data for eight countries with operating arthroplasty registers (Denmark, England & Wales, Norway, Romania, Scotland, Sweden, Australia, and New Zealand). RESULTS: The average and median rate of primary and revision (combined) total knee replacement was 175 and 149 procedures/100,000 population, respectively, and ranged between 8.8 and 234 procedures/100,000 population. We observed that the procedure rate significantly increased over time for the countries in which historical data were available. The compound annual growth in the incidence of TKA ranged by country from 5.3% (France) to 17% (Portugal). We observed a nearly 27-fold range of TKA utilization rates between the 18 different countries included in the survey. CONCLUSION: It is apparent from the results of this study that the demand for TKA has risen substantially over the past decade in countries around the world.

A retrospective analysis of two independent prospective cartilage repair studies: autogenous perichondrial grafting versus subchondral drilling 10 years post-surgery.

BACKGROUND: Experimental data indicate that perichondrial grafting to restore articular cartilage defects will result in repair with hyaline-like cartilage. In contrast. debridement and drilling results in repair with fibro-cartilage. In this retrospective study the long-term clinical results of both procedures were compared to evaluate the theoretical benefit of repair with hyaline-like tissue. METHODS: From two independent studies patients were selected with a cartilage defect in their knee. The selection was performed using strict inclusion criteria published elsewhere [Bouwmeester et al. Int. Orthop. 21 (1997) 313]. The patients were treated with either a perichondrium transplantation (PT group, n = 14) or with an 'open' debridement and drilling procedure (DD group, n = 11). The results of both procedures after 10-11 years were evaluated using the Hospital for Special Surgery Knee Score (HSSS), X-ray examination, clinical examination and visual analogue scales (VAS) for pain during walking and at rest. RESULTS: Both procedures resulted in a general improvement compared to the situation before the operation. After an average of 10 years in the PT group there were three failures, in the DD group none, success rates were 78% and 100%, respectively. When comparing the successful PT patients with the DD patients, there were no differences in HSSS and VAS data. Both groups showed an equal number of irregular operation surface sites on X-ray (PT 9/11 versus DD 8/10). CONCLUSIONS: This study shows that clinically at 10 years follow-up no difference was observed between debridement and drilling and perichondrium transplantation for treatment of an isolated cartilage defect. This raises questions about ongoing research to develop methods in order to improve the results of debridement and drilling as therapy for an isolated cartilage defect in a young patient (< or = 40 years).

Improving peri-prosthetic bone adaptation around cementless hip stems: a clinical and finite element study.

This study assessed whether the Symax™ implant, a modification of the Omnifit(®) stem (in terms of shape, proximal coating and distal surface treatment), would yield improved bone remodelling in a clinical DEXA study, and if these results could be predicted in a finite element (FE) simulation study. In a randomized clinical trial, 2 year DEXA measurements between the uncemented Symax™ and Omnifit(®) stem (both n=25) showed bone mineral density (BMD) loss in Gruen zone 7 of 14% and 20%, respectively (p<0.05). In contrast, the FE models predicted a 28% (Symax™) and 26% (Omnifit(®)) bone loss. When the distal treatment to the Symax™ was not modelled in the simulation, bone loss of 35% was predicted, suggesting the benefit of this surface treatment for proximal bone maintenance. The theoretical concept for enhanced proximal bone loading by the Symax™, and the predicted remodelling pattern were confirmed by DEXA-results, but there was no quantitative match between clinical and FE findings. This was due to a simulation based on incomplete assumptions concerning the yet unknown biological and mechanical effects of the new coating and surface treatment. Study listed under ClinicalTrials.gov with number NCT01695213.

Randomised trial comparing bone remodelling around two uncemented stems using modified Gruen zones.

For assessment of bone remodelling around total hip arthroplasty using dual-emission X-ray absorptiometry (DEXA), a variety of different systems to identify regions of interest (ROI) have been used, making comparisons between stem designs difficult. The Gruen zones are now widely used for this purpose. We present the results of a randomised clinical trial comparing 2 uncemented stem designs with proximal coating, using a modification of the Gruen zones to allow improved representation of the effect of the implant on bone mineral density (BMD) over time. DEXA-data were used in a randomised trial with 2 years follow up, comparing the uncemented Symax(TM) (n=25) and Omnifit(®) (n=24) stems. The effect on BMD was determined using the 'standard' adapted Gruen zones, and a modification which studied an equal length and position for zones 1 and 7 around both stems, assuring that the same regions in terms of cancellous and cortical bone were compared. The 'modified' regions of interest give lower BMD values around the Omnifit(®) than using the 'standard' Gruen zones (3.6 % in zone 7, p<0.05). The difference with the Symax(TM) BMD values, which had been concealed using the standard Gruen zones, became statistically significant in favour of the Symax(TM) implant. This adaptation can detect a statistically significant difference in bone preservation in zone 7 between stems that would otherwise not have been revealed. We recommend the use of 'modified' Gruen zones for more valid comparison of remodelling caused by different implant designs.

Results of total hip arthroplasties in the young patient; further evidence for a barrier against articular wear debris by hydroxyapatite coatings.

We examined the hypothesis that the circumferential osseous apposition around HA-coated implants forms a protective barrier against articular wear debris. Sixty-five hydroxyapatite-coated total hip arthroplasties in 57 patients (age <50years) with polyethylene-metal articulation were evaluated regarding PE-wear, osteolysis, and clinical outcome at a minimum of 10 years follow-up. There was no correlation between PE-wear and osteolysis of the femoral zones or cup zones I and III. A strong Pearson correlation was found between polyethylene wear and osteolysis around cup zone II, where the cup only consisted of polyethylene (p<0,01). The aseptic failure rate was 1.5% for the femoral component and 4.5% for the cup after 10 years of follow-up. The average Harris Hip Score was 90 and the average Engh score for fixation was 23 after 10 years . Around HA-coated parts of the prosthesis bone formation remained stable, regardless of the degree of polyethylene wear. The average linear polyethylene wear was 0,16 mm/year. The circumferential osseous apposition of the HA-coated implants possibly formed a protective barrier against articular wear debris. The use of cups with a backside gap resulted in PE-wear associated osteolysis in cup zone II and may be considered to be best avoided.

Comparison of two hydroxyapatite-coated femoral stems: clinical, functional, and bone densitometry evaluation of patients randomized to a regular or modified hydroxyapatite-coated stem aimed at proximal fixation.

Clinical function, bone mineral density (BMD), and radiographs of 80 randomly allocated, hydroxyapatite-coated femoral stems of two differing lengths were studied for 2 years. The short stem was optimized for proximal fixation. The predictive value of bone densitometry was also studied. After 2 years, significantly more bone apposition and a higher BMD percentage were observed in Gruen zone 7 of the short stem. We conclude that stem design can be enhanced to achieve more proximal fixation. However, we found a higher incidence of pain with the short stem, indicating a trade-off between increased proximal fixation and diminished overall mechanical stability. No strong correlations between clinical function and radiographic evaluation of remodeling were found with BMD, suggesting that dual-energy x-ray absorptiometry has no predictive value for short-term clinical outcome.

Osteoconductive coatings for total joint arthroplasty.

Osteoconductive calcium phosphate coatings for total joint arthroplasty have been in clinical use since the mid1980s. The basic principles involved and basic science evidence for the efficacy of osteoconductive coatings were examined. Hydroxyapatite coatings provide consistent and better filling with bone of the gaps and spaces around cementless joint components after surgery as compared with porous-coated implant surfaces, resulting in better implant stability. Of all the calcium phosphate coatings, hydroxyapatite coatings have had the most widespread application in hip arthroplasty. Their clinical advantages over more conventional implant surfaces are evident in primary and revision hip arthroplasties. A clinical survival rate in the author's series of 97% at a minimum of 11 years followup for the femoral component in a young active patient population (average age, 53 years) was obtained with no mechanical failures. The average polyethylene wear rate in this group was 0.129 mm/year. In a similar group of young patients with revision arthroplasty using hydroxyapatite-coated femoral components, an 11-year survival rate of 93% was obtained. Histologic analysis of specimens retrieved at autopsy confirmed the excellent bony fixation of components. Advantages of the more recent biomimetic hydroxyapatite coatings were examined.