A randomized trial of hydroxyapatite coated prostheses in total hip arthroplasty

Hydroxyapatite-Coated Femoral Stems in Primary Total Hip Arthroplasty: An Updated Meta-Analysis

BACKGROUND

Most primary total hip arthroplasties (THAs) performed in the United States utilize cementless fixation with porous or hydroxyapatite (HA) coating. A previous meta-analysis comparing HA-coated versus non-HA-coated stems in primary THA published in 2013 found no significant difference between the 2. However, an updated analysis of the current literature is needed to assess the potential benefit of HA-coated stems in primary THA.

METHODS

Various libraries were searched through May 2022 according to Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines. Studies included were randomized controlled trials comparing HA-coated femoral stems to non-HA-coated stems in primary THA. Outcomes included Harris Hip Score (HHS), endosteal bone formation, radiolucent lines, linear wear rate, revision for aseptic loosening, thigh pain, and heterotopic ossification.

RESULTS

There were significantly fewer revisions for aseptic loosening (P = .004) and decreased postoperative thigh pain (P = .03) for patients who have with HA-coated stems. There was no significant difference in HHS (P = .20), endosteal bone formation (P = .96), radiolucent lines (P = .75), linear wear rate (P = .41), or heterotopic ossification (P = .71) between HA-coated and non-HA-coated stems.

CONCLUSION

We found that HA-coated femoral stems in primary THA led to significantly fewer stem revisions for aseptic loosening and less postoperative thigh pain compared to non-HA-coated stems. These findings suggest HA-coated femoral stems should be preferred over non-HA-coated femoral stems in primary THA.

Does preclinical analysis based on static loading underestimate post-surgery stem micromotion in THA as opposed to dynamic gait loading?

The success of cementless hip stems depends on the primary stability of the implant quantified by the amount of micromotion at the bone-stem interface. Most finite element (FE)-based preclinical studies on post-surgery stem stability rely on static analysis. Hence, the effect of dynamic gait loading on bone-stem relative micromotion remains virtually unexplored. Furthermore, there is a paucity of research on the primary stability of grooved stems as opposed to plain stem design. The primary aim of this FE study was to understand whether transient dynamic gait had any incremental effect on the net micromotion results and to further draw insights into the effects of grooved texture vis-à-vis a plain model on micromotion and proximal load transfer in host bone. Two musculoskeletal loading regimes corresponding to normal walking (NW) and stair climbing (SC) were considered. Although marginally improved load transfer was predicted proximally for the grooved construct under static loading, the micromotion values (max: NW ~ 7 μm; SC ~ 10 μm) were found to be considerably less in comparison to plain stem (max: NW ~ 50 μm; SC ~ 20 μm). For both physiological load cases, a significant surge in micromotion values was predicted in dynamic analyses as opposed to static analyses for the grooved stem (~ 390% greater). For the plain model, the increase in these values from static to dynamic loading is relatively moderate yet clinically significant (~ 230% greater). This suggests that the qualitative similarities notwithstanding, there were significant dissimilarities in the quantitative trends of micromotion for different cases under both analyses.

High Subsidence Rate After Primary Total Hip Arthroplasty Using a Zweymüller-type Noncemented Implant With a Matte Surface

Introduction:

The surface topography is one key factor that affects the initial fixation of prosthesis in total hip arthroplasty (THA). We aimed to evaluate the mid-term results of a Zweymüller-type noncemented femoral implant (Elance stem) that had a matte surface with a target average roughness of 1.0 to 2.5 μm. The prosthesis was subjected to alkali and heat treatments to enhance its bone-bonding property.

Methods:

In this retrospective study, 30 THAs (27 patients) done using an Elance stem from September 2012 to October 2014 were evaluated clinically and radiographically for a mean follow-up of 6.3 ± 1.7 years after the index THA.

Results:

Stem revision was indicated for six hips (20%). The survival rate with stem revision for any reason was 86.4% (95% confidence interval, 68.9%-94.8%) at 5 years. Stem subsidence >5 mm was noted in 17 hips (56.7%). The survival rate with stem subsidence >5 mm as the end point was 46.6% (95% confidence interval, 29.9%-64.2%) at 5 years.

Conclusion:

The Zweymüller-type noncemented stem with a low-roughness matte surface demonstrated a high subsidence rate, although the bone-bonding property was potentially enhanced by the alkali and heat treatments. Surgeons should be aware that an insufficient surface roughness could lead to poor mechanical fixation of the noncemented stem, even with an appropriate stem geometry and surface chemistry.

What Is the Risk of Revision Surgery in Hydroxyapatite-coated Femoral Hip Stems? Findings From a Large National Registry

BACKGROUND

Despite wide adoption of hydroxyapatite (HA)-coated femoral stems in THA, no studies have found differences in the risk of revision surgery with its use or investigated the interaction of different prosthesis designs with stem coating.

QUESTIONS/PURPOSES

The purpose of this study was to evaluate the risk of revision in THAs with HA-coated stems compared with non-HA-coated. To achieve this purpose, we asked: (1) What is the difference in risk of revision of THAs with HA-coated femoral stems compared with non-HA-coated using an aggregate analysis? (2) What is the difference in risk of revision of THAs with HA-coated femoral stems compared with non-HA-coated for five prosthesis types that used the same femoral and acetabular component combination but where the femoral stem had both a HA and non-HA coating option?

METHODS

The Australian Orthopaedic Association National Joint Replacement Registry analyzed cementless primary THA registered between September 1, 1999, and December 31, 2014. Of the 147,645 cases that fit our selection criteria, 81.1% (N = 119,673) had HA-coated stems. Overall (that is, all procedures with any prostheses in the registry) and five prosthesis designs where both an HA-coated stem and non-HA-coated stem exist (Zimmer's VerSys®/Trilogy® [N = 3924], Biomet's Mallory-Head®/Mallory-Head [N = 2538], Smith & Nephew's SL-Plus/EP Fit-Plus [N = 2028], Biomet's Taperloc®/Exceed [N = 1668], and Biomet's Taperloc/Mallory-Head [N = 1240]) were evaluated. Revision surgery was the outcome of interest. Survival analyses were conducted and hazard ratios (HRs) were adjusted for age, sex, bearing surface, femoral head size, and acetabular component HA coating.

RESULTS

In the overall cohort, HA stems had a lower any-cause revision risk after 6 months (HR, 0.83; 95% confidence interval [CI], 0.72-0.95; p = 0.007). However, the risk of revision varied when we evaluated the effect of HA on revision for specific prothesis combinations that had both HA and non-HA options for the femoral stem. VerSys/Trilogy, Mallory-Head/Mallory-Head, Taperloc/Exceed, and Taperloc/Mallory-Head did not have a lower risk of any-cause revision with HA-coated stems compared with non-HA-coated. Only the SL-Plus/EP Fit-Plus subgroup showed a lower risk of revision for loosening (HR, 0.17; 95% CI, 0.06-0.44 between 0 and 7 years; p < 0.001) with HA- compared with non-HA-coated stems, but this was observed after an early (< 6 months) higher risk of revision for any reason (HR, 2.88; 95% CI, 1.15-7.21; p = 0.024).

CONCLUSIONS

Overall, HA coating of femoral stems was found to be associated with a 17% lower risk of revision for any reason. However, the lower risk of revision associated with HA was not consistent for all prosthesis designs where both HA- and non-HA-coated femoral stem versions were available. Some HA-coated stems have higher revision rates compared with their non-HA-coated versions. Our findings suggest that the effect of HA coating on revision risk varies depending on prosthesis design.

LEVEL OF EVIDENCE

Level II, therapeutic study.

Comparison of an Uncemented Tapered Stem Design in Cobalt-Chrome vs Titanium at 15-Year Follow-Up

BACKGROUND

Cobalt-chromium (Co-Cr) and titanium (Ti) have been the most popular materials employed for cementless implants. The purpose of this study was to compare clinical and radiological results of a single stem design with both alloys at long-term follow-up.

METHODS

Two hundred consecutive uncemented stems implanted in 171 patients (100 Co-Cr and 100 Ti implants) between 1999 and 2002 were studied. Mean age of the patients was 60.9 years (range, 20-84). Clinical results were evaluated using the Harris hip score. The presence of thigh pain was also analyzed. Stem fixation was graded according to Engh criteria. Radiolucent lines, osteolysis, and stem subsidence were also analyzed.

RESULTS

At 15-year follow-up, no stems had been revised. Both groups showed similar clinical results with mean Harris hip score of 93.4 (Co-Cr) vs 93.9 (Ti). There was no difference in the rate of thigh pain (11 vs 8.3, respectively, P = .507). Radiolucent lines were more frequent in the Co-Cr group (63.6% vs 35.6%, P < .001).

CONCLUSION

Ti stems showed better osteointegration than Co-Cr stems, with a significantly lower incidence of radiolucent lines. However, this did not affect the clinical results or the appearance of thigh pain.

Survival of hydroxyapatite-coated cups: acetabular screws involve a lower rate of revision surgery due to aseptic loosening

BACKGROUND

It is believed that the path of acetabular screws may represent a shuttle between hydroxyapatite (HA) particles and the liner. The aim was to assess the relationship between acetabular screws and revision surgery for aseptic loosening in total hip arthroplasties (THAs).

MATERIAL AND METHODS

A retrospective multicentric study was performed. Patients older than 18 years and patients who underwent THA with both the stem and cup HA-coated were included. The rate of revision-surgery considering only aseptic loosening was calculated. The proportion of cases in which acetabular screws were used was registered, as well as the proportion of cups that showed osteolysis. The statistical relationship between acetabular screws and osteolysis, as well as acetabular screws and revision-surgery for aseptic loosening were assessed.

RESULTS

There were 749 cases. Mean age 62.1 (45-84) years. Mean follow-up 14.19 (8.9-16.7) years. Revision surgery was performed in 12.8% (96/749) of the cups. 73.95% (71/96) of the revised cups showed aseptic loosening. The overall 15-year survival of the cups considering only aseptic loosening was 84.4%. Acetabular screws were used in 47.5% (356/749) of the cups. Acetabular screws were used in 40.44% (55/136) of the cups that showed osteolysis. The use of acetabular screws was associated with less osteolysis (p = 0.006). Acetabular screws were used in 35.21% (25/71) of the cups that were revised for aseptic loosening. The use of acetabular screws was associated with a lower rate of revision surgery (p = 0.020).

CONCLUSIONS

In THA with the stem and cup HA-coated, the use of acetabular screws is associated with a lower rate of revision surgery.

Direct silanization of zirconia for increased biointegration

High-performance bioinert ceramics such as zirconia have been used for biomedical devices since the early seventies. In order to promote osseointegration, the historical solution has been to increase the specific surface of the implant through roughness. Nevertheless these treatments on ceramics may create defects at the surface, exposing the material to higher chances of early failure. In zirconia, such treatments may also affect the stability of the surface. More recently, the interest of improving osseointegration of implants has moved the research focus towards the actual chemistry of the surface. Inspired by this, we have adapted the current knowledge and techniques of silica functionalization and applied it to successfully introduce 3-aminopropyldimethylethoxy silane (APDMES) directly on the surface of zirconia (3Y-TZP). We used plasma of oxygen to clean the surface and promote hydroxylation of the surface to increase silane density. The samples were extensively characterized by means of X-ray photoelectron spectroscopy (XPS) and contact angle, mechanically tested and its cytotoxicity was evaluated through cell adhesion and proliferation tests. Additionally, aging was studied to discard negative effects of the treatment on the stability of the tetragonal phase. No adverse effect was found on the mechanical response of treated samples. In addition, plasma-treated samples exhibited an unexpectedly higher resistance to aging. Finally, silane density was 35% lower than the one reported in literature for silica. However cells displayed a qualitatively higher spreading in opposition to the rounder appearance of cells on untreated zirconia. These results lay the foundations for the next generation of zirconia implants with biologically friendlier surfaces.

STATEMENT OF SIGNIFICANCE

The use of zirconia-based ceramics in biomedical devices is broad and well accepted, especially in dental implants. However, they do not bond naturally to bone, therefore to ensure fixation surgeons typically rely on roughness at different scales, or on cements. Alternatively in this work we present a new perspective of surface modification through chemistry to enhance the interaction between surface and biological environment, without the downsides of roughness. This surface treatment is proposed for zirconia, which allowed a direct silanization of its surface and a higher cell attachment. The results of this research may open the possibility for the next generation of bioinert ceramic implants with more advanced tailored surfaces for increased osseointegration.

The Absence of Hydroxyapatite Coating on Cementless Acetabular Components Does Not Affect Long-Term Survivorship in Total Hip Arthroplasty

BACKGROUND

Hydroxyapatite (HA) has been applied to joint prostheses as a bioactive coating to prolong their durability. However, HA benefits for cup survival in total hip arthroplasty (THA) remain controversial. In this study, we compared the survival of cups with and without HA coating during a minimum follow-up of 18 years.

METHODS

In total, 183 THA cases in 163 patients were analyzed, including 73 cups with HA coating (HA(+) group) and 110 without HA coating (HA(-) group); otherwise, the cups had identical titanium-sprayed rough surfaces and were fixed with screws. In both groups, the same conventional polyethylene liners were applied. Zirconia and alumina ceramic heads were used in the HA(+) and HA(-) groups, respectively. We retrospectively analyzed cup survival based on cup revision for any reason or aseptic loosening as end points.

RESULTS

In total, 7 and 8 revisions were performed in the HA(-) and HA(+) groups with survival rates of 86.3% and 90.1%, respectively. Among them, 3 cups in the HA(-) group and 1 cup in the HA(+) group were revised for aseptic loosening in 20 years (survival rates 94.1% and 98.7%, respectively). No significant difference was detected in cup survival rates between the groups based on both end points. There were no stem revisions during the observation period.

CONCLUSION

The results suggested that HA coating did not have either beneficial or adverse effects on the long-term cup survival in primary cementless THA.

A short-term follow-up study of a surgeon-customised fully-coated hydroxyapatite femoral stem using a nation-wide joint registry

OBJECTIVE

To compare revision rates between otherwise-identical fully-coated and proximally-coated hydroxyapatite (HA) femoral stems using a nation-wide registry.

METHODS

249 proximally-coated stems (50 μm HA) and 225 fully-coated stems (100 μm HA and 50 μm titanium) were followed over a mean of 34.9 and 23.2 months respectively.

RESULTS

Four proximally-coated (rate: 1.61%) and five fully-coated stem revisions (rate: 2.20%) were reported, with no statistical difference between groups (p = 1.0, OR 0.90, 95% CI 0.20-3.97). Registry data showed no difference in performance between fully-coated and proximally-coated stems nationwide (rate: 2.22%, p = 0.82).

CONCLUSION

There is no statistical difference in survival between fully-coated and proximally-coated HA prostheses in the short-term.

Long-Term Comparison of Porous Versus Hydroxyapatite Coated Sleeve of a Modular Cementless Femoral Stem (SROM) in Primary Total Hip Arthroplasty

Hydroxyapatite (HA) is commonly used on femoral stems to assist in osseous integration but there is limited evidence of the benefit it provides. We report a prospective comparison of 117 and 102 patients receiving either porous or HA coated sleeves respectively. Patients were evaluated at mean of 12.5 years in the porous and 13.7 years in the HA groups. The mean Harris Hip Score was 94.7 and 94.5 in the porous and HA groups respectively. One porous and 2 HA stems required revision. This study demonstrates that there is no long-term advantage to using an HA coating on the sleeve of this modular stem and confirms excellent long-term results for the SROM stem in a primary arthroplasty setting.

LEVEL OF EVIDENCE

II (prospective cohort study).

Does hydroxyapatite coating have no advantage over porous coating in primary total hip arthroplasty? A meta-analysis

There are some arguments between the use of hydroxyapatite and porous coating. Some studies have shown that there is no difference between these two coatings in total hip arthroplasty (THA), while several other studies have shown that hydroxyapatite has advantages over the porous one. We have collected the studies in Pubmed, MEDLINE, EMBASE, and the Cochrane library from the earliest possible years to present, with the search strategy of “(HA OR hydroxyapatite) AND ((total hip arthroplasty) OR (total hip replacement)) AND (RCT* OR randomiz* OR control* OR compar* OR trial*)”. The randomized controlled trials and comparative observation trials that evaluated the clinical and radiographic effects between hydroxyapatite coating and porous coating were included. Our main outcome measurements were Harris hip score (HHS) and survival, while the secondary outcome measurements were osteolysis, radiolucent lines, and polyethylene wear. Twelve RCTs and 9 comparative observation trials were included. Hydroxyapatite coating could improve the HHS (p < 0.01), reduce the incidence of thigh pain (p = 0.01), and reduce the incidence of femoral osteolysis (p = 0.01), but hydroxyapatite coating had no advantages on survival (p = 0.32), polyethylene wear (p = 0.08), and radiolucent lines (p = 0.78). Hydroxyapatite coating has shown to have an advantage over porous coating. The HHS and survival was duration-dependent—if given the sufficient duration of follow-up, hydroxyapatite coating would be better than porous coating for the survival. The properties of hydroxyapatite and the implant design had influence on thigh pain incidence, femoral osteolysis, and polyethylene wear. Thickness of 50 to 80 μm and purity larger than 90% increased the thigh pain incidence. Anatomic design had less polyethylene wear.

The Effect of Hydroxyapatite Coating on Long-term Results of Total Hip Arthroplasty with Hydroxyapatite-coated Anatomic Femoral Stem

Purpose

To evaluate the clinical and radiological results, as well as the survival rate, associated with total hip arthroplasty using a hydroxyapatite (HA)-coated anatomical femoral stem at a follow-up of ≥12 years.

Materials and Methods

From April 1992 to May 1997, 86 patients (102 hips) underwent total hip arthroplasty with a HA-coated ABG I (Anatomical Benoist Giraud; Howmedica) hip prosthesis. The average age at the time of surgery was 53.4 years and the mean duration of follow-up was 17.1 years (range, 12.1-21.0 years). The Harris hip score (HHS) and radiographic assessments of thigh pain were used to evaluate the clinical results. We observed osteointegration, cortical hypertrophy, reactive line, calcar resorption and osteolysis around the femoral stems. The survival rate of the femoral stems was evaluated by using the span of time to a revision operation for any reasons was defined as the end point.

Results

The mean HHS was 50.5 preoperatively and 84.2 at the time of last follow-up. Osteolysis only around the HA-coated proximal portion of the femoral stem was observed in 72 hips, cortical hypertrophy all around the distal portion of the femoral stem was observed in 38 hips, and calcar resorption was observed in 44 hips. A reactive line was observed in 13 hips, but was unrelated to component loosening. Stem revision operations were performed in 24 (23%) hips due to osteolysis (14 hips), fracture (5 hips) and infection (5 hips). The femoral stem survival rate was 75% over the mean duration of follow-up.

Conclusion

Total hip arthroplasty using a HA-coated anatomical femoral stem showed necessitated a high rate of revision operations due to osteolysis around the femoral stem in this long term follow-up study.

Results at a minimum of 10 years of follow-up for AMS and PerFix HA-coated cementless total hip arthroplasty: impact of cross-linked polyethylene on implant longevity

PURPOSE

The purpose of this study was to report results at a minimum of 10 years for hydroxyapatite (HA) coating on the titanium arc-sprayed cementless total hip arthroplasty (THA) and to evaluate the impact of cross-linked polyethylene (XLPE) on implant longevity.

METHODS

A total of 131 consecutive primary THAs in 123 patients using an AMS acetabular cup and a PerFix HA stem were retrospectively reviewed. Conventional PE was used for 62 hips (CPE group) and cross-linked PE for 69 hips (XLPE group), with mean follow-up periods of 13 and 11.5 years, respectively. These patients were reviewed using the Japanese Orthopaedic Association (JOA) Hip Score and evaluated in terms of PE wear, osteolysis, and implant survival.

RESULTS

The JOA score improved from 42.6 to 83.9 points at the final follow-up. The mean wear rate of 0.12 mm/year in the CPE group was significantly greater than that of XLPE at 0.007 mm/year. In the CPE group, ten (16.1 %) and two (3.2 %) hips, respectively, underwent PE exchange due to severe wear and acetabular revision due to loosening associated with osteolysis. Three patients had revision in the XLPE group: one cup for aseptic loosening, one PE for recurrent dislocation, and one stem for neck fracture. No evident osteolysis was seen in the XLPE group. Kaplan-Meier survivorship with any revision as the end point shows that the 12-year survival rate was 97.7 % for cups, 93.8 % for PE liners, and 99.2 % for stems. Multivariate analysis revealed that the use of XLPE significantly reduced the risk of revision, with the odds ratio (OR) of 4.3.

CONCLUSIONS

AMS and PerFix HA components in this series show excellent implant fixation; however, high rates of PE wear and subsequent osteolysis were limiting factors in long-term success. Low wear rates with XLPE suggest improved implant longevity.

Minimum 10 year survivorship analysis of a partially coated hydroxyapatite tapered femoral stem in elderly patients with an average age over 75

This is a retrospective, non-comparative study of 212 consecutive patients who underwent Total Hip Arthroplasty with an uncemented hydroxyapatite (HA) coated stem system from November 1997 to March 2000. The objective of the study was to analyze the performance of the implant at a minimum of 10 years in older patients (mean age 79.6 years). The Kaplan-Meier survivorship of the femoral stem at 10 years was 100%, and 97.5% for the whole prosthesis. The mean Merle d'Aubigné clinical score improved from 4.4 ± 2.1 points pre-operatively to 13.39 ± 3.77 points at final follow-up (p<0.05), and the mean VAS score for thigh pain was 1.25. The radiographic analysis showed that there were no significant radiolucent lines or osteolysis compromising the fixation of the implant.

Hydroxyapatite-coated femoral stems in primary total hip arthroplasty: a meta-analysis of randomized controlled trials

BACKGROUND

Controversy exists over the use of hydroxyapatite (HA)-coated femoral stems in primary total hip arthroplasty (THA). We conducted a meta-analysis of randomized controlled trials (RCT) to compare the clinical and radiologic outcomes of primary THA using HA-coated versus non-HA-coated femoral stems.

METHODS

Databases including MEDLINE, EMBASE and the Cochrane Library were searched to find relevant RCTs comparing HA-coated versus non-HA-coated femoral stems in primary THA. Data analyses were performed using RevMan 5.0 (The Cochrane Collaboration).

RESULTS

Seven studies (792 hips) met the inclusion criteria. The pooled weighted mean difference (WMD) for the postoperative Harris hip score was 3.04 (95% CI: -4.47 to 10.54, P = 0.43). The cumulative risk ratios (RR) for the presence of endosteal condensation and radioactive lines were 1.02 (95% CI: 0.93 to 1.12, P = 0.64) and 1.01 (95% CI: 0.90 to 1.14, P = 0.81), respectively.

CONCLUSIONS

This meta-analysis demonstrates that the use of HA-coated femoral stems in primary THA has no clinical or radiological benefits.

Bone-bonding properties of Ti metal subjected to acid and heat treatments

The effects of surface treatment on the bone-bonding properties of Ti metal were examined by both mechanical detaching test and histological observation after implantation into rabbit tibiae for various periods ranging from 4 to 26 weeks. The bone-bonding ability of Ti metal, which is extremely low as it is abraded, was hardly increased by simple heat treatment at 600 °C or treatment with H(2)SO(4)/HCl mixed acid alone, but was markedly increased by the heat treatment after the acid treatment. Even Ti metal that had been previously subjected to NaOH treatment showed considerably high bone-bonding ability after acid and heat treatments. Such high bonding abilities were attributed to their high apatite-forming ability in the body environment. Their high apatite-forming abilities were attributed to a high positive surface charge, and not to the type of crystalline phase or specific roughness of their surfaces. The present study has demonstrated that acid and subsequent heat treatments are effective for conferring stable fixation properties on Ti metal implants.

Juvenile arthritis patients report favorable subjective outcomes of hip arthroplasty despite poor standard outcome scores

We evaluated midterm patient-reported outcomes and satisfaction with total hip arthroplasty in patients who had severe juvenile idiopathic arthritis. Thirty-one patients (49 hips), with a mean age of 29 years (range, 16-43 years), reported low hip pain and stiffness at follow-up (mean, 7 years; range, 3-17 years). Up to 92% were satisfied with their ability to perform various activities; 96% were satisfied with pain relief. A mean postoperative flexion arc of 96° was observed. Final 36-Item Short Form Health Survey, EuroQol in 5 dimensions, Western Ontario and McMaster Universities Arthritis Index, and Harris Hip scores were lower than reference populations, particularly for mobility, physical functioning, and social functioning subscores. Young adults with end-stage hip involvement and severe longstanding juvenile idiopathic arthritis expressed high satisfaction with total hip arthroplasty, which improved range of motion, pain, and stiffness, despite poor performance on widely used outcome measures.

Is hydroxyapatite coating necessary to improve survivorship of porous-coated titanium femoral stem?

We compared the clinical and radiologic results in 55 patients (110 hips) associated with proximally porous-coated titanium stems that were identical in geometry but differed with regard to proximal surface treatment (with or without hydroxyapatite coating). The mean age at the time of the operation was 46.3 years (27-63 years), and mean length of follow-up was 15.6 years (15-16 years). The mean Harris hip score in both groups improved from 39 points and 41 points, respectively, to 93 and 91 points, respectively, at the last follow-up. After 16 years, the cumulative survival for the stem was 100% in both groups and for the cup was 89% in both groups. After long-term follow-up, hydroxyapatite coating on the porous surfaces did not improve or diminish the results of total hip arthroplasty.

Distal fixation of proximally coated tapered stems may predispose to a failure of osteointegration

Despite excellent long-term results of proximally coated tapered wedge femoral stems in noncemented total hip arthroplasty, we have consistently observed a minority fail to achieve osteointegration. We retrospectively reviewed 320 consecutive total hip arthroplasties performed by a single surgeon using a single stem over a 4-year period. Clinical and radiographic parameters were analyzed for risk factors predisposing to a failure of osteointegration, defined as a progressive circumferential radiolucency around the proximal porous coating on both anteroposterior and lateral radiographs. Fifteen stems (4.7%) failed to osteointegrate; 3 underwent femoral revision for persistent thigh pain, whereas the remainder expressed varying degrees of symptomatology. Risk factors associated with failure of osteointegration were male sex, a smaller canal-flare index, larger stem size, and greater canal fill at the mid- and distal-thirds of the stem. Awareness of variability in proximal femoral morphology and problems caused by distal fixation with a proximally coated implant may help avoid this uncommon but potentially serious complication.

Seven-year results of a tapered, titanium, hydroxyapatite-coated cementless femoral stem in primary total hip arthroplasty

Background

Aseptic loosening of cemented hip prostheses is recognized as a long-term problem, and especially in males and younger patients. Much energy has been focused on developing new prostheses that are designed for cementless fixation. We evaluated the performance of and periprosthetic bone response to a tapered, titanium, hydroxyapatite (HA)-coated femoral hip prosthesis at a minimum of 7 years of follow-up after treatment with primary total hip arthroplasty.

Methods

Seventy-eight patients and 86 hips were included in the study. There were 35 men and 43 women; the mean age at the time of the operation was 59 years (range, 41 to 81 years). We used a tapered, titanium (Ti6Al4V), HA-coated femoral implant. We evaluated the patients at a minimum of 7 years of follow-up after treatment with primary total hip arthroplasty. Clinical evaluation was performed using the scoring system and the hip scores were assigned according to the level of pain, the functional status and the range of motion. The patients who refused to return, but who did forward X-rays for review after being contacted were questioned by phone about the functional status of their hip. Radiographic follow-up was performed at six weeks, at three, six and twelve months and yearly thereafter. All the available radiographs were collected and assessed for implant stability, subsidence, osseointegration, osteolysis, stress shielding and evidence of periprosthetic lucency.

Results

Eighty-six hips (78 patients) were available for review at follow-up of greater than 7 years. In 11 of the 86 cases, acetabular failure required revision of the acetabular component, but the femoral stem survived and it was available for long-term evaluation. The radiographs were obtained at 7-year follow-up for another 20 hips, but the patients would not come in for the 7-year clinical evaluation. Therefore, a phone interview was conducted to assess any change in the functional status at a minimum of 7 years.

Conclusions

The mechanical fixation of a tapered, titanium, HA-coated femoral implant was excellent in this study. This femoral design provided reliable osseointegration that was durable at a mean of 7 years follow-up.

Bone remodeling in proximal HA-coated versus uncoated cementless SL-Plus((R)) femoral components: a 5-year follow-up study

BACKGROUND AND PURPOSE

Bone resorption at the femoral stem due to stress shielding has been particularly observed secondary to cementless hip replacement. This prospective study of 126 total-hip replacements was performed to examine clinical outcomes and changes in peri-prosthetic bone density after implantation of a double-tapered cementless femoral component manufactured with versus without hydroxyapatite (HA) coating.

METHODS

Sixty-seven femoral components with and 59 femoral components without proximal HA coating were implanted and examined after a mean follow-up of 5.8 (SD 1.1, 2.8-7.8) years. The Harris hip score (HHS) and plain radiographs were used for clinical and radiological follow-up evaluations. Possible changes in peri-prosthetic bone mineral density (BMD) were measured by dual-energy X-ray absorptiometry (DEXA).

RESULTS

Clinical outcome, measured by HHS, was similar in both groups. On plain radiographs, significantly less radiolucent lines were observed for the coated implants. DEXA revealed a significant increase in BMD at the proximal zones, along the medial side, and at the stem tips in the coated compared with the non-coated implants.

INTERPRETATION

Hydroxyapatite-coated implants yield favorable radiographic characteristics, but no greater clinical benefit after 5 years' implantation.

Porous-coated femoral components with or without hydroxyapatite in primary uncemented total hip arthroplasty: a systematic review of randomized controlled trials

The purpose of this systematic review was to determine the clinical and radiologic benefit of hydroxyapatite coating in uncemented primary total hip arthroplasty. A database of Medline articles published up to September 2007 was compiled and screened. Eight studies involving 857 patients were included in the review. Pooled analysis for Harris hip score as a clinical outcome measure demonstrated no advantage of the hydroxyapatite coating (WMD: 1.49, P = 0.44). Radiologically, both groups showed equal presence of endosteal bone ingrowth (RR: 1.04, P = 0.66) and radioactive lines (RR: 1.02, P = 0.74) in the surface area of the prosthesis. This meta-analysis demonstrates neither clinical nor radiologic benefits on the application of a hydroxyapatite coating on a femoral component in uncemented primary total hip arthroplasty.

A randomized trial of hydroxyapatite-coated femoral stems in total hip arthroplasty: a 13-year follow-up

A prospective randomized trial comparing hydroxyapatite (HA)-coated and non-HA-coated femoral total hip arthroplasty components was conducted. Sixty-one consecutive patients undergoing primary hip arthroplasty were randomized to receive an identical femoral component with or without HA. Forty-eight hips were available for review at an average of 13 years and 5 months after surgery. The only femoral stem revised was secondary to femoral fracture after mitral valve area. All femoral stems were well fixed on x-ray with no evidence of loosening. There was no statistically significant difference in the revision rates or in the Harris hip score between the HA vs non-HA-coated groups. This study suggests there is no clinical advantage to the use of a hydroxyapatite coating on the femoral component of this design for primary total hip arthroplasty.

Hydroxyapatite coated femoral stems in primary total hip arthroplasty: a meta-analysis

We conducted meta-analysis of clinical studies of HA coated femoral stems in hip arthroplasty. After an exhaustive literature search, we abstracted relevant data on the outcomes of stem survival from aseptic loosening and Harris Hip scores. The risk ratios and mean differences with 95% confidence intervals (CI) are reported. 9 studies met our inclusion criteria for the analysis. The cumulative risk ratio for femoral stem survival from aseptic loosening was 1.0 (95% CI: 0.995 to 1.005) P = .98. The pooled mean difference for the Harris Hip scores (HHS) was 0.072 (95% CI: -0.062 to 0.206), P = .293. The results of this study demonstrate that there are no clinical benefits in the use of HA/porous coating over porous coating alone in primary hip arthroplasty.

The use of hydroxyapatite on press-fit tapered femoral stems

The advantage of an HA coating includes superior proximal femoral osteointegration and reduced thigh pain, reduced subsidence risk, reduced distal wear particle migration, and better preservation of periprosthetic bone quality. Furthermore, the survivorship and clinical outcomes are at least comparable to cemented and uncoated uncemented systems without any substantial deleterious effect of the HA coating like third-body wear or late failures. In our opinion, these advantages justify the increased cost. With over 20 years of favorable cumulative data, the continued use of HA can be recommended as an effective and reliable adjunct to cementless tapered femoral fixation in primary THA.

Failure of dual radius hydroxyapatite-coated acetabular cups

Introduction

Many kind of hydroxyapatite-coated cups were used, with favorable results in short term studies; it was supposed that its use could improve osteointegration of the cup, enhancing thus stability and survivorship. The purpose of this study is to analyze the long term behavior of the hemispheric HA coated, Dual Radius Osteonics cup and to discuss the way of failure through the exam of the revised components and of both periacetabular and osteolysis tissue.

Materials and Methods

Between 1994 and 1997, at the Department of Orthopedic Sciences of the Insubria University, using the posterolateral approach, were implanted 276 Dual Radius Osteonics^® in 256 patients, with mean age of 63 years.

Results

At a mean follow-up of 10 years (range 8–12 years), 183 cups in 165 patients, were available for clinical and radiographical evaluation. 22 Cups among the 183 were revised (11%). The cause of revision was aseptic loosening in 17 cases, septic loosening in one case, periprosthetic fracture in another case, osteolysis and polyethylene wear in two cases and, finally, recurrent dislocations in the last one. In the remaining patients, mean HHS increased from a preoperative value of 50,15 to a postoperative value of 92,69. The mean polyethylene wear was 1,25 mm (min. 0,08, max. 3,9 mm), with a mean annual wear of 0,17 mm. The mean acetabular migration on the two axis was 1,6 mm and 1,8 mm. Peri-acetabular osteolysis were recorded in 89% of the implants (163 cases). The cumulative survivorship (revision as endpoint) at the time was 88,9%.

Conclusion

Our study confirms the bad behavior of this type of cup probably related to the design, to the method of HA fixation. The observations carried out on the revised cup confirm these hypotheses but did not clarify if the third body wear could be a further problem. Another interesting aspect is the high incidence of osteolysis, which are often asymptomatic becoming a problem for the surgeon as the patient refuses the possibility of a revision.

Hydroxyapatite-coated tapered cementless femoral components in total hip arthroplasty

Tapered cementless femoral fixation provides a reliable option for routine primary total hip arthroplasty (THA). The use of hydroxyapatite (HA)-coated stems is increasing as a result of mounting evidence that HA may improve the reliability of bone osseointegration and improve overall THA outcomes. These trends are based on a growing body of literature that supports both the theoretical and clinical rationale of this approach. There is solid clinical evidence that the combination of tapered geometry with an HA coating increases the likelihood of reliable femoral fixation. A comprehensive review of this literature evaluating the clinical use of cementless femoral components that use an HA coating is presented, and reveals that HA-coated stems have significantly improved proximal femoral fixation with less stress shielding and superior osseous remodeling. Although these advantages have not been shown to significantly increase long-term durability, there is sufficient data to support the routine use of HA-coated, tapered cementless femoral stems in THA.

A randomized clinical trial of cementless femoral stems with and without hydroxyapatite/tricalcium-phosphate coating: an 8- to 12-year follow-up study

To evaluate the effect of hydroxyapatite coating on cementless femoral stem, a prospective randomized clinical trial was conducted. A total of 84 hips from 69 patients were assigned to a hydroxyapatite/tricalcium-phosphate-coated group or a noncoated group. Thirty-two patients (37 hips) who received hydroxyapatite/tricalcium-phosphate-coated stems and 31 patients (38 hips) who received noncoated stems were followed for an average of 127 months. Forty-nine patients (78%) were men, and the average age was 45.5 years. Preoperative diagnosis was osteonecrosis in 62 hips (83%). The mean Harris hip score at the time of final follow-up was 91 points in the coated group and 90 points in the noncoated group. Six acetabular components (3 in each group) were revised. One femoral stem in the noncoated group was loose. There was no statistical difference in the survival distributions of the implants between the 2 groups.

Minimum 10-year results of a tapered, titanium, hydroxyapatite-coated hip stem: an independent review

The performance of, and periprosthetic bone response to, a tapered, titanium (Ti6Al4V), hydroxyapatite-coated femoral hip prosthesis was evaluated at minimum of 10 years of follow-up. Data were prospectively collected on 147 consecutive primary hip arthroplasties performed in 133 patients by a single surgeon during a 2-year interval. Clinical and radiographic analyses of 96 hips in 86 patients were independently performed by 2 surgeons who were not involved in the care of these patients. There were no cases of aseptic loosening of the femoral component. Subsidence and stress shielding occurred in 5% and 2% of cases, respectively, and was not clinically significant. In all 15 hips that required revision of the acetabular component, the femoral component was found to be well fixed, without any occurrence of distal osteolysis. This femoral design provided reliable osseointegration that was durable at a mean of 11.5 years of follow-up.

New femoral designs: do they influence stress shielding?

Virtually all contemporary cementless femoral hip stems are designed with the goals of achieving immediate and long-term stability, restoring hip mechanics, and minimizing thigh pain. However, the incorporation of features specifically intended to minimize stress-mediated bone resorption (stress shielding) has been variable. Attempts to reduce bone loss through stem design have yielded inconsistent results and, in certain instances, early and catastrophic failure. Prior beliefs regarding the determinants of stress shielding were based upon the qualitative assessment of bone loss using plain radiographs. These are being challenged, particularly with regard to the role of porous coating level. This is in large part due to the refinement and widespread availability of dual-energy xray absorptiometry (DEXA), which allows quantitative assessment of bone mineral density both pre- and postoperatively. The available evidence indicates stem stiffness plays a dominant role. Progressive bone loss through stress shielding has potentially dire consequences. While such problems have not manifested as severe or widespread clinical issues, the preservation of femoral bone stock is an important and desirable goal.

Hydroxyapatite-coated titanium porous plasma spray tapered stem: experience at 15 to 18 years

Advocates of hydroxyapatite in primary total hip arthroplasty report enhanced fixation and early improvements in pain and function. Others report no difference in long-term outcomes with hydroxyapatite application to an already proven fixation surface. We previously reported more rapid clinical improvement with a proximally porous, plasma-sprayed titanium, tapered geometry stem. We now report the long-term followup data on 191 consecutive total hip arthroplasties in which a standard (130 hips) or the hydroxyapatite-coated stem (61 hips) was implanted. At average 12.7 years followup, one stem (noncoated) was revised for aseptic loosening. The Harris hip total and pain scores were similar. Survivorship of the femoral component with aseptic loosening as the endpoint was 99.2% for noncoated stems and 100% for hydroxyapatite stems. The long-term survivorship of plasma-sprayed titanium tapered stems was excellent regardless of hydroxyapatite application, with neither benefit nor detriment observed.

Failure of the uncoated titanium ProxiLock femoral hip prosthesis

New prostheses should be evaluated for stability and clinical performance. In a prospective randomized clinical trial, we implanted 22 titanium (Ti) and 20 hydroxyapatite-coated (HA) ProxiLock femoral hip prostheses during total hip arthroplasty in 42 patients. The patients were followed for 24 months with clinical, radiographic and radiostereometric analysis. Full weightbearing was allowed immediately postoperatively. One patient with a titanium stem was lost to followup. During the first two months, 34 of the 41 stems subsided and/or rotated towards retroversion, regardless of stem type. At the 24-month followup 35 of the 41 prostheses were either fully stabilized (16 HA and 11 Ti stems) or had clinical irrelevant migration (four HA and four Ti stems). Six Ti prostheses showed continuous migrations with maximums of 4.7 mm translation and 12.2 degrees retroversion; four of these were revised, the other two had no clinical complaints.

CLINICAL RELEVANCE

The migration pattern we found indicates insufficient primary fixation of the ProxiLock stem in an immediate full weightbearing protocol. The HA coating improves the secondary stability of the prosthesis compared to the uncoated stem. Early migration is associated with an increased risk of possible future loosening and revision, and therefore we discontinued the use of this prosthesis.

LEVEL OF EVIDENCE

Therapeutic Level I. See Guidelines for Authors for a complete description of levels of evidence.

Clinical and radiological outcome of hydroxyapatite-coated femoral stem in revision hip arthroplasty

We used a proximally hydroxyapatite-coated femoral stem in revision arthroplasty of 48 cases with aseptic loosening and Paprosky defect class 1 or 2. We reviewed the outcome after 6.1 (4--9.3) years. The clinical outcome was good, with a mean postoperative HHS of 90 (51--100) points. There were five reoperations all on the acetabular side and none for the femoral stem. At follow-up, we observed cancellous sclerosis radiographically in 19 cases-especially in non-tightly fitted stems and mainly in Gruen zones 2 and 6. In 13 cases, cortical thickening was seen, mainly in Gruen zones 3 and 5 and especially in tightly fitted stems. These bony changes were significant and not related to any clinical parameter. They started to appear from 6 months onward, with increasing frequency with longer follow-up. We find that the standard Mallory-Head hydroxyapatite-coated femoral stem is suitable for revision in cases with lower-class femoral defects.

Excellent results from proximally HA-coated femoral stems with a minimum of 6 years follow-up: a prospective evaluation of 100 patients

BACKGROUND

There have been few reports on the mid- and long-term follow-up results of the proximally HA-coated femoral stem. We evaluated this type of stem prospectively, with 6-12 years of follow-up.

METHODS

The survival rate, Harris hip score and radiographic features of 106 hips in 100 consecutive patients were evaluated. The mean age at operation was 51 years (SD 8.2).

RESULTS

The mean Harris hip score at the time of the latest follow-up was 95 points. Spot welds occurred in 95% of the patients and were first observed at a mean follow-up of 1.4 years in one or more of the Gruen regions, corresponding to the coated part of the femoral stem. A higher grade of stress shielding correlated with a less favorable Harris hip score and pain subscore. According to the criteria of Engh, all stems were graded as stable and durable bone-ingrown. No femoral component was revised.

INTERPRETATION

At an average follow-up of 8 years, this proximally HA-coated femoral component showed favorable clinical and radiological outcome and excellent survivorship.

Femoral fit predicts radiologic changes, but not clinical results, in Mallory-head total hip arthroplasties

We prospectively studied the clinical and radiologic results of three groups of patients: 89 patients who had standard primary total hip replacements; 63 patients with hip dysplasia who had primary total hip replacements; and 48 patients who had revision total hip replacements. We studied the differences in clinical and radiologic behaviors of a titanium hydroxyapatite-coated stem with variations in the tightness of fit of the prosthesis in the femoral canal, operative group, stem size, grade of osteoporosis, and morphometric features of the femur. The clinical results in all three groups are slightly favorable for the standard primary group. Pain relief and stem survival in the three groups were similar to those reported in other studies regarding cementless prostheses. Nontight femoral fit significantly positively influenced the development of cancellous densification; however, the presence of osteoporosis also contributed to the formation of cancellous densification. Only tight femoral canal fit significantly positively influenced the development of cortical thickening independent of other parameters. There was no correlation between clinical parameters and the radiologic phenomena in either of the groups.

Physical characterization of different-roughness titanium surfaces, with and without hydroxyapatite coating, and their effect on human osteoblast-like cells

The aim of this study was to characterize and compare various titanium (Ti) and hydroxyapatite (HA) coatings on Ti6Al4V, in view of their application on noncemented orthopedic implants. Two innovative vacuum plasma sprayed (VPS) coatings, the first of ultrahigh rough and dense Ti (PG60, Ra=74 microm) and the second of ultrahigh rough and dense Ti coated with HA (HPG60, Ra=52 microm), have been developed, and the response of osteoblast-like cells (MG-63) seeded on these new coatings was evaluated in comparison to: a low roughness and sandblasted (Ti/SA, Ra=4 microm) Ti6Al4V surface; Ti medium (TI01, Ra=18 microm), and high (TI60, Ra=40 microm) roughness VPS coatings; and the relative Ti plus HA duplex coatings (HT01, Ra=12 microm and HT60, Ra=36 microm respectively), also obtained by VPS. PG60 coating presented no open porosity, making it dense and potentially intrinsically stronger. Cell adhesion and proliferation on PG60 was similar to those of the smoothest one (Ti/SA) and adhesion on ultrahigh roughness was lower than the medium- and high-roughness coatings, whereas cell proliferation on PG60 was lower than TI60. The HA coating determined significant increases in cell proliferation at medium and high roughness levels when compared to the relative Ti coating, but not compared to the ultrahigh one; all HA-coated surfaces showed a decrease in alkaline phosphatase activity and collagen I production. Surface morphology and the HA coating strongly affected cell behavior. However, ultrahigh values of roughness are not correctly seen by cells, and the presence of HA has no improving effects.

No effect of hydroxyapatite particles in phagocytosable sizes on implant fixation: An experimental study in dogs

The influence of wear debris on bone healing around orthopedic implants is debated. Hydroxyapatite (HA) particles and polyethylene (PE) particles have been shown to have a negative effect on osteoblast cultures in vitro. The present study investigated the in vivo effects of HA and PE particles on the mechanical fixation and gap healing around experimental HA implants. Nonloaded implants (n = 30) were inserted bilaterally into the proximal tibia of 15 dogs with a 2-mm gap to the bone. The peri-implant gap was either (1) empty (n = 6) or filled with (2) hyaluronic acid (n = 8), (3) hyaluronic acid and HA particles (n = 8), or (4) hyaluronic acid and PE particles (n = 8). After 4 weeks, the animals were killed. The implant interface was evaluated by pushout testing until failure and by histomorphometry. Both HA and PE particles were found to be phagocytosed by macrophage-like cells in the interfacial tissue. HA particles were also integrated in newly formed bone. We found no negative effect of the particulate material on mechanical fixation of the implants or on bone formation around the implants.

The effect of adjuvant calcium phosphate coating on a porous-coated femoral stem

A prospective, randomized, double-blind, multicenter trial was done to determine if the addition of hydroxyapatite and tricalcium phosphate to the porous coating of a cementless femoral component would result in improved clinical and radiographic outcomes. Patients were randomized to receive identical porous-coated stems with (n = 159 hips) or without (n = 159 hips) hydroxyapatite and tricalcium phosphate coating. At 2 to 5 years followup (mean, 37 months), no implants were revised for aseptic loosening. There was no difference in clinical function between the two groups with respect to the Harris hip score or Western Ontario and McMaster Universities Osteoarthritis Index scores. Bony ingrowth occurred frequently in both groups with 99% of the hydroxyapatite and tricalcium phosphate group and 98% of the control group showing radiographic evidence of osseointegration. Implants coated with hydroxyapatite and tricalcium phosphate had significantly fewer radiolucencies adjacent to the porous coating, indicative of improved osseointegration. Radiolucencies were present in Gruen Zones 1, 7, 8, or 14 in 25% of the control group and in 7% of the hydroxyapatite and tricalcium phosphate group. This improved osseointegration could serve as an added barrier to particulate debris migration and increase the long-term survivorship of the implant.

Comparison of porous-coated titanium femoral stems with and without hydroxyapatite coating

BACKGROUND

The purpose of this prospective, randomized study was to evaluate the clinical and radiographic results associated with proximally porous-coated titanium stems that were identical in geometry but differed with regard to proximal surface treatment (with or without hydroxyapatite coating).

METHODS

A prospective, randomized study was performed to evaluate fifty patients (100 hips) who had undergone sequential bilateral primary total hip replacement. A proximally porous-coated titanium stem with hydroxyapatite coating was implanted on one side and a proximally porous-coated titanium stem without hydroxyapatite coating was implanted on the other side during the same operative setting in all fifty patients. A cementless acetabular component made of titanium was used in all hips. There were thirty-six men and fourteen women; the mean age at the time of the operation was 45.3 years. The mean duration of follow-up was 6.6 years. Clinical and radiographic evaluations were performed preoperatively; at six weeks; at three, six, and twelve months; and yearly thereafter.

RESULTS

The Harris hip scores in the hydroxyapatite-coated group (mean, 94 points) and non-hydroxyapatite-coated group (mean, 92 points) were similar at the final follow-up examination. The prevalence of transient pain in the thigh was 4% in each group. No acetabular or femoral component demonstrated aseptic loosening. Bone-remodeling patterns, including calcar atrophy, were similar in the two groups. No acetabular or femoral osteolysis was seen.

CONCLUSIONS

At a mean of 6.6 years postoperatively, the clinical and radiographic results associated with proximally porous-coated femoral prostheses with identical geometries that differed only with regard to the presence or absence of hydroxyapatite coating were similar.

Cementless mallory-head HA-coated hip arthroplasty for osteoarthritis in hip dysplasia

Sixty-three cementless Mallory-Head HA-coated femoral prostheses (Biomet, Warsaw, IN) were used in primary total hip arthroplasty in 50 patients with osteoarthritic hips because of congenital hip dysplasia. The implanted cup was also cementless (41 Harris Galante and 22 Ringlock). The patients were followed up for a mean period of 75.1 months (range, 44-110). Clinical and radiologic analysis were performed. Harris Hip Score increased from 42 to 90 points; 97% of the patients had no or only mild pain, and limping decreased from 90% to 20%. Complications were marginal: no infections, one habitual dislocation, one peroperative fracture of the femur, and one transient ischiadic nerve palsy. Two HG cups were revised for augmented polyethylene wear. Radiographically, no subsidence of the prosthesis or bone atrophy of the proximal femur could be detected. No correlations were found between the radiologic phenomena and the clinical outcome, but the tightness of the prosthesis fit had a definitive influence on the radiographic bone remodeling pattern. The cementless Mallory-Head HA-coated femoral prosthesis shows excellent clinical and radiological mid-term results in osteoarthritic hip dysplasia patients. There was no need for the use of a specially designed dysplasia femoral prosthesis.

Cementless Mallory Head HA-coated femoral prosthesis in primary total hip arthroplasty: Clinical and radiological results of a four to nine year prospective study

We prospectively studied 152 hips in 126 patients with a proximally porous and hydroxyapatite coated double tapered straight femoral prosthesis. The follow-up period was 4.2 to 9.6 years. All but two prostheses showed osseo-integration. The mean Harris hip score (HHS) increased from 40 to 92 points and 97% of the patients had no or only mild pain. Limping and the use of walking aids decreased substantially after the operation. The morphology of positive bone remodelling with either endosteal bone formation or periosteal bone formation was correlated with the stem fit in the medullary canal (p=0.0001). Negative bone remodelling features could not be demonstrated. There was no correlation between the clinical parameters and the radiological phenomena. (Hip International 2002; 4: 345-56).