Radiological and survival comparison of four methods of fixation of a proximal femoral stem

Discrepancy of Trial Rasp and Femoral Stem Relative Position Within the Femoral Canal of a Coated Tapered System: An Intraoperative, Intrapatient Controlled Study

Background

For a successful total hip arthroplasty, the final position of the trial rasp should be adopted by the femoral stem to achieve correct positioning. This study aimed to characterize the discrepancy of the stem and rasp position in vivo of a widely used dual-tapered straight stem with rectangular cross section that is known to have an oversized stem with respect to the rasp.

Methods

The distances between the tip of the greater trochanter and the shoulder of the implant and rasp were measured on 39 intraoperatively acquired fluoroscopic image pairs. Leg-length discrepancy was also measured clinically before and after surgery.

Results

A paired t-test showed a significant average protrusion of the femoral stem with respect to the final rasp position of 2.63 mm (standard deviation = 2.3 mm, P < .001), while 88% of the cases had no leg-length discrepancy after surgery. The quantified stem protrusion was statistically significant but did not reach clinical relevance and was easily mitigated in our study.

Conclusions

The quantified stem protrusion appears to be clinically manageable, as only 2 cases required attenuation of stem positioning: in one case by the use of a femoral head with a shorter neck and in the other case by rerasping the femoral bed. Neither case was associated with the most extreme differences in position of the stem with respect to the final rasp. In addition, the used stem shows good overall outcomes in other studies. It appears that factors other than stem and rasp position play a critical role to the surgeon and for total hip arthroplasty success.

Results of a hydroxyapatite-coated femoral stem (Corail) in Chinese: a minimum 10-year follow-up

Background

Due to the adverse effects of cemented hip arthroplasty, uncemented stems with hydroxyapatite (HA) coating reduces these risks and enhanced integration. The concept of an extensive HA coating for the fixation of a tapered femoral stem (Corail^®) was introduced, which can achieve durable biological fixation and preserve normal periprosthetic bone activity. Here we describe the clinical and radiological outcome in patients with the Corail^® stem.

Methods

92 total hip replacements in 81 patients using the Corail^® stem were followed-up. 47 patients were women, and the mean age at surgery was 62.9 ± 8.7 (34–71) years. The indications included: osteoarthritis of the hip (71.1%), avascular necrosis (13.6%), femur neck fractures in elderly (9.7%) and post-traumatic osteoarthritis (6.8%).

Findings

Eight patients died during follow-up. The revision was only found in two patients due to line wear and resulted in an 10-year Kaplan–Meier estimated overall survival rate of 97.83%. The clinical results were good, with a mean Harris hip score of 92.3 ± 5.6 (72–100). The mean total Merle d’Aubigné and Postel score was 6.8 ± 0.5 pre-operatively and 16.1 ± 1.4 at latest follow-up. All unrevised implants were radiographically stable, with a mean liner wear of 0.07 mm/year.

Conclusion

This long-term analysis confirmed the durability of the functional and radiographic results. Our findings suggest the long-term results of Corail^® HA-coated stem are more satisfactory which is preferable to any other system.

Fully hydroxyapatite-coated total hip replacement: ten-year results

We assess 254 consecutive primary total hip replacements (THRs) using a fully hydroxyapatite (HA)-coated stem and socket (Furlong; JRI, London, UK). Minimum follow-up was 10 years. Harris hip score (HHS) increased from 49.8 preoperatively to 86.2 at follow-up. The most remarkable clinical finding was the near absence of thigh pain. After 10 years of follow-up, all stems met stability criteria and none needed revision for aseptic loosening. Three cups (1.2%) were revised for aseptic loosening. Two more cups were revised for recidivant dislocation. Varus placement of the femoral stem was present in 63 hips (24.8%) and valgus in 13 hips (5%). None of these technical defects showed radiologic progression, and there was no measurable correlation between them and the clinical score. Intraoperative femoral fractures occurred in 25 cases (9.8%) with no further influence on implant evolution. These findings strongly support the use of the JRI Furlong system for primary THR because it provides excellent clinical and radiologic results, with 0% and 1.2% cup and stem aseptic loosening, respectively, at 10 years. In addition, its tolerance to technical implantation defects makes it suitable even for less experienced hip surgeons.

Neck-preserving femoral stems

BACKGROUND

Surgeons undertaking total hip arthroplasty (THA) routinely perform a distal femoral neck resection. It has been argued that retaining the femoral neck during THA can provide mechanical and biological advantages.

PURPOSES

The objectives of this study were to review: (1) the current evidence on the advantages of femoral neck preservation during THA and (2) the clinical and radiological outcome of neck-preserving femoral stems.

METHODS

A search of the English-language literature on neck-preserving THA and on the individual neck-preserving implants was performed using PubMed, Ovid SP and Science Direct.

RESULTS

Studies have indicated that neck preservation offers superior tri-planar implant stability and allows more accurate restoration of the hip geometry and biomechanics. The trend towards tissue sparing surgery has contributed to the development of bone-conserving short-stem implants that offer variable levels of neck preservation. Despite an initial learning curve, these implants have generated promising early clinical results, with low revision rates and high outcome scores. However, radiological evaluation of some neck-preserving implants has detected a characteristic pattern of proximal femoral bone loss with distal cortical hypertrophy. The long-term implications of this finding are not yet known.

CONCLUSIONS

Preserving the femoral neck during THA has biomechanical advantages. However, long-term outcome data are needed on neck-preserving femoral stems to evaluate on-going bone remodelling and assess implant performance and survival.

High incidence of migration with poor initial fixation of the Accolade stem

BACKGROUND

Numerous cementless femoral stem design variations are in clinical use. Because initial implant instability and micromotion are associated with aseptic loosening of the femoral component, migration analysis provides an early assessment of implant survivorship.

QUESTIONS/PURPOSES

We determined the (1) migration pattern of the Accolade cementless femoral stem; (2) clinical factors predisposing to stem migration; (3) self-reported patient outcomes; and (4) our current rate of aseptic stem loosening.

METHODS

We retrospectively analyzed 81 femoral stems for aseptic migration using Ein-Bild-Roentgen-Analyse-femoral component analysis. Postoperatively, patients completed the WOMAC and SF-12 questionnaires. We assessed radiographic factors potentially associated with subsidence: indices of bone shape and quality, canal fill of the implant, and radiographic signs of loosening. Minimum followup was 24 months (mean, 29 months; range, 24-48 months).

RESULTS

The average subsidence at 24 months was 1.3 mm (range, 0-1.5 mm). In the first 2 years, 36% of stems subsided more than 1.5 mm. Large stem size was associated with subsidence. Radiolucent lines (> 1.5 mm in three zones) were present in 10% of stems and associated with lower questionnaire scores. The 5-year survivorship for aseptic loosening of the 367 stems was 97% with revision as end point and 95% for radiographic failure.

CONCLUSIONS

The high incidence of migration and stems with radiographic failure raises concerns about patient clinical function and long-term survivorship of this stem design. This migration pattern may be due to poor initial stability with a subsequent lack of osseointegration. Our results differ from radiographic findings and clinical durability of other similar cementless stem designs.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

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.

A histological study of retrieved Cambridge acetabular components

A new uncemented acetabular component, the Cambridge cup, has been designed to mimic the anatomy and physiology of subchondral bone in order to minimise stress shielding and enhance long-term component stability. Cambridge cups were implanted in a cohort of 50 women who presented with displaced sub-capital fracture of the femoral neck. The cups were manufactured with an hydroxyapatite (HA) coating. Twenty six cups were implanted after removal of the HA. Twelve Cambridge cups were retrieved post-mortem between two and 84 months after implantation. Histological and histomorphometric testing was undertaken to analyse the residual HA coating thickness, bone apposition to the implant surface and particulate wear debris in the surrounding tissues. The HA-coated implants showed significantly greater bone apposition to the implant surface with significantly less fibrous tissue formation than the uncoated implants. Where HA resorption occurred, bone and bone marrow was seen adjacent to the implant. Excessive wear of the ultra high molecular weight polyethylene liner was not seen. The HA-coated components demonstrated good initial bone implant bonding and the flexible carbon polymer appeared to maintain stability following HA resorption. The uncoated implants showed little or no bony apposition but had a fibrous membrane apposed to the implant surface. This may be explained by a combination of micro-motion at the bone implant interface and having a component surface finish that was poorly suited to osseous attachment. Hydroxyapatite coated acetabular components can provide reliable osseous attachment. Subsequent HA resorption need not compromise medium-term osseous fixation to an appropriate implant surface.

High survival rate of hydroxyapatite-coated hip prostheses100 consecutive hips followed for 10 years

We followed 100 consecutive primary total hip replacements with a proximal hydroxyapatite coating for 10 years. No patient was lost to follow-up. 29 patients (32 hips) died before the 10-year follow-up was done; none of their hips had been revised. Thigh pain on activity occurred in 3 hips. We found no radiographic signs of loosening of the femoral components. In course of time the location of dense bone around the femoral stem, which would suggest implant/bone stress transfer, moved distally in 51 of 67 stems after 10 years. No linear or distal osteolysis occurred around the stem. Revision of 1 stem was performed because of thigh pain, but it was found fixed to bone proximally, while 3 cups were revised because of acetabular osteolysis. The 10-year survival of the stem and cup, using revision or pending revision as endpoint, was 100% (95% CI: 99-100) and 97% (95% CI: 94-99), respectively.

Uncemented stems in hip replacement--hydroxyapatite or plain porous: does it matter? Based on a prospective study of HA Omnifit stems at 15-years minimum follow-up

For many years, acrylic cement has been regarded as the unique available means for a long term and secure fixation of components in hip arthroplasty. A new generation of uncemented implants coated in hydroxyapatite (HA) has arisen since the mid-1980s, aiming to provide a 'biological interface' between metal and surrounding bone, and thus the hydroxyapatite interface was defined some years ago as a distinct entity from both cemented and 'plain porous' fixation. Based upon our 20-year experience with the HA Omnifit stem, this paper aims to discuss the efficiency of hydroxyapatite as a means of fixation for femoral components in hip arthroplasty, then examine whether the addition of a calcium phosphate layer induces any adverse effects, and finally make comparisons between HA-coated versus porous hip stems reported in the literature. With respect to fixation of femoral components in hip arthroplasty we report excellent results from the partially coated HA Omnifit stem in our series, with 99.20% of survival rate at 17-year follow-up, these results being consistent and similar to other HA series in the literature. HA 'uncemented' fixation can therefore be considered reliable and efficient. Furthermore, two decades of hydroxyapatite coatings have resulted in the identification of no major adverse effects. In fact calcium phosphate ions participate in the physiological turn-over of bone remodelling, and the HA coating is replaced by new bone formation without any fibrous tissue layer. Since HA particles are biodegradable and do not produce any inflammatory reaction in the surrounding bone, fears of osteolysis or third body wear due to HA debris have not been confirmed. Finally, comparison between HA versus plain porous femoral components through the literature has demonstrated better results with HA than porous alone both in terms of the quantity and quality of bone remodelling, and the potential migration and subsidence of the stem.

Effect of hydroxyapatite coating on risk of revision after primary total hip arthroplasty in younger patients: findings from the Danish Hip Arthroplasty Registry

BACKGROUND

The effect of hydroxyapatite (HA) on implant survival in the medium and long term is uncertain. We studied the effect of HA coating of uncemented implants on the risk of cup and stem revision in primary total hip arthroplasty (THA).

PATIENTS AND METHODS

Using the Danish Hip Arthroplasty Registry (DHR), we identified patients less than 70 years old who had undergone uncemented primary THA during 1997-2005. 4,125 HA-coated and 7,737 non-HA-coated cups and 3,158 HA-coated and 4,749 non-HA-coated stems were available for analysis. The mean follow-up time was 3.4 years for cups and 3.2 years for stems. We estimated the relative risk (RR) of revision due to aseptic loosening or any cause, and adjusted for possible confounders (age, sex, fixation of opposite implant part, and diagnosis for primary THA) using multivariate Cox regression analysis.

RESULTS

The adjusted RRs for revision of HA-coated cups and stems due to aseptic loosening were 0.89 (95%CI: 0.37-2.2) and 0.71 (95%CI: 0.27-1.9) with up to 9 years of follow-up, compared to non-HA-coated implants. When taking all causes of revision into consideration, the risk estimates were 0.85 (95%CI: 0.68-1.1) and 0.81 (95%CI: 0.61-1.1) for HA-coated cups and stems, respectively.

INTERPRETATION

In this medium-term follow-up study, the use of HA-coated implants was not associated with any clearly reduced overall risk of revision compared to non-HA-coated implants.

Genetic susceptibility to total hip arthroplasty failure: a preliminary study on the influence of matrix metalloproteinase 1, interleukin 6 polymorphisms and vitamin D receptor

BACKGROUND

Matrix metalloproteinase (MMP)1, interleukin(IL)6 and vitamin D receptor (VDR) have been implicated in the biological cascade of events initiated by particulate wear debris and bacterial infection, resulting in periprosthetic bone loss around loosened total hip replacements (THRs). The individual responses to such stimuli may be dictated by genetic variation.

OBJECTIVE

To study the effect of single-nucleotide polymorphisms (SNPs) within these candidate genes.

METHODS

A case-control study of the MMP1, IL6 and VDR genes was performed for possible association with deep sepsis or aseptic loosening. All cases included in the study were Caucasian patients with osteoarthritis who had received a cemented Charnley total hip arthroplasty (THA) and polyethylene acetabular cup. Cases consisted of 91 patients with early aseptic loosening and 71 patients with microbiological evidence of deep infection on surgery. Controls consisted of 150 patients with THAs that were clinically asymptomatic for over 10 years and showed no radiographic features of aseptic loosening. DNA samples from all individuals were genotyped using Taqman allelic discrimination.

RESULTS

The C allele (p = 0.001; OR = 3.27; 95% CI 2.21 to 4.83) and C/C genotype (p = 0.001) for the MMP1 SNP were highly associated with aseptic failure when compared with controls. No statistically significant relationships were found between aseptic loosening and the MMP2, MMP4, IL6 -174 or VDRL SNPs. The T allele (p = 0.007; OR = 1.76; 95% CI 1.16 to 2.66) and T/T genotype (p = 0.028) for VDR-T were statistically associated with osteolysis owing to deep infection as compared with controls. No statistically significant relationship was found between septic failure and any of the other SNPs examined in this study.

CONCLUSIONS

Aseptic loosening and possibly deep infection of THR may be due to the genetic influence of candidate susceptibility genes. SNP markers may serve as predictors of implant survival and aid in pharmacogenomic prevention of THR failure.

Hip arthroplasty with proximal transmission of force: first clinical results with a new partially cemented femoral stem

BACKGROUND

Proximal stem fixation by partial cementing is a new concept in hip arthroplasty. We conducted a prospective clinical and radiological analysis to evaluate the preliminary outcome of this new technique with the Option 3000 stem (Mathys Orthopaedics, Bettlach, Switzerland).

METHODS AND FOCUS

One hundred and thirty-three hip replacements in 123 patients have been performed between 1996 and 2003: All of them were followed up regularly both clinically and radiological and 53 were analysed with the EBRA-FCA method. Eighty-six patients with 95 hips could be seen in August 2004. At this point of time, the mean follow-up time was 61 months (5.08 years) with a maximum of 100 months (8.33 years)

RESULTS

The clinical data reported an average Harris Hip Score of 85.5. Nine stems had to be exchanged over the period of study. The EBRA-FCA analysis reported a mean subsidence less than 1.5 mm after 2 years, then an average stable subsidence of 2.4 mm. So the results are similar to the early results obtained with other fixation concepts and the long-term results appear promising.

Proximal cement fixation in total hip arthroplasty--first results with a new stem design

Stem loosening and stress-shielding are problems encountered in cemented hip arthroplasty. Could proximal stem fixation by partial cementing solve the problem? More physiological transmission of forces with only proximal cement fixation seems to be possible with this recent development (Z-stem, Option 3000, Mathys Orthopaedics, Bettlach, Switzerland). In a prospective clinical trial, this new implant was used for total hip arthroplasty in human patients. One hundred and thirty-three (133) total hip replacements in 123 patients were performed between April 1996 and January 2003. All of them were followed up regularly; 53 were analysed with the EBRA-FCA method (Einzel Bild Röntgen Analyse--femoral component analysis), whereas the rest were analysed using conventional follow-up X-rays. Eighty-six (86) patients with 95 hips could be examined in August 2004 to obtain mid-term results. At this stage, the mean follow-up time was 61 months (5.08 years), with a maximum of 100 months (8.33 years). Up to October 2004, nine cases needed a revision. The clinical data collected reported an average Harris Hip Score of 89.3 (good). The EBRA-FCA analysis reported a mean subsidence of less than 1.5 mm after the first two years, under the EBRA threshold of predicted loosening. At the latest follow-up (at an average of 61 months), there was an average stable subsidence of 2.4 mm in general. Eight (8) patients presented with subsidence of more than 5 mm. The results of the new implant seem to be encouraging. Finally, comparing our results to other fixation concepts will require longer follow-up periods.

Genetic susceptibility to total hip arthroplasty failure--positive association with mannose-binding lectin

Mannose-binding lectin (MBL) may be involved in the biologic cascade of events initiated by wear debris and bacterial infection around loosened total hip arthroplasties (THAs). Individual responses to such stimuli may be dictated by genetic variation caused by single nucleotide polymorphisms (SNPs). We performed a case-control study on 4 MBL SNPs using case patients (n = 91) with aseptic loosening or deep infection (n = 71). Control subjects (n = 150) had clinically and radiologically well-fixed THAs for more than 10 years. Frequency of the C allele (P = .001) and that of the genotype C/C (P = .004) for the -550 SNP were associated with aseptic failure. The codon 54 SNP G allele (P = .012) and G/G genotype (P = .027) frequencies were associated with aseptic failure as well. In the septic group, the frequency of the C allele (P = .01) and that of the genotype C/C (P = .05) for the -550 SNP were significant. Failure of THAs may be under genetic influence to candidate susceptibility genes such as MBL.

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.

Continuous bone loss around a tapered uncemented femoral stem: a long-term evaluation with DEXA

BACKGROUND

Periprosthetic bone loss is a well-documented phenomenon after uncemented total hip arthroplasty (THA); however, little is known about how bone mineral density (BMD) changes after 2 years.

PATIENTS AND METHODS

14 patients with hip arthrosis (group A) were operated with a proximally porous- and hydroxyapatite-coated stem and followed for 10 years with DEXA, radiographs and Harris hip score (HHS). Another group of 14 patients (group B) was evaluated at 6 and 14 years using the same prosthesis and protocol.

RESULTS

No stem was revised and all stems were well-Fixed. At final follow-up, HHS was 97 points in group A after 10 years and 94 points in group B after 14 years. Bone mineral changes in group A were greatest in Gruen zones 1 and 7, where the losses were 31% and 26%, respectively, after 2 years on the operated side. The decrease in BMD continued after 2 years and in Gruen zone 7 it was faster than the rate of bone loss on the control side. In group B, the annual change in BMD on the operated side was not significantly different from the bone loss in group A.

INTERPRETATION

Up to 14 years after implantation of a tapered uncemented stem, the BMD in the calcar region continues to decrease faster than would be expected from normal ageing.

Migration and cyclic motion of a new short-stemmed hip prosthesis--a biomechanical in vitro study

BACKGROUND

Uncemented, short-stemmed hip prostheses have been developed to reduce the risk of stress shielding and to preserve femural bone stock. The long-term success of these implants is yet uncertain. Prerequisite for osseointegration is sufficient primary stability. In this study the cyclic motion and migration patterns of a new short-stemmed hip implant were compared with those for two clinically successful shaft prostheses.

METHODS

The prostheses were implanted in paired fresh human femura and loaded dynamically (gait cycle) with increasing load (max 2,100 N) up to 15,000 cycles. Relative displacements between prosthesis and bone were recorded using a 3D-video analysis system.

FINDINGS

The short stem displayed a biphasic migration pattern with stabilisation at maximum load. Initial migration was predominantly into varus and was greater than that for the shaft prostheses. Failure occurred in cases of poor bone quality and malpositioning. Cyclic motion of the short prosthesis was less than that for the shaft prostheses. Surface finish showed no effect. System stiffness for the new stem was lower than for the shaft prostheses.

INTERPRETATION

The new stem tended to migrate initially more than the shaft prostheses, but stabilised when cortical contact was achieved or the cancellous bone was compacted sufficiently. Bone quality and correct positioning were important factors for the short stem. The lower cyclic motion of the new stem should be favourable for bony ingrowth. The lower system bending stiffness with the new implant indicated a more physiological loading of the bone and should thereby reduce the effects of stress shielding.

15-year follow-up results of the hydroxyapatite ceramic-coated femoral stem

PURPOSE

To evaluate the clinical and radiological outcomes following implantation of the Furlong hydroxyapatite ceramic-coated femoral stem in total hip arthroplasty.

METHODS

A longitudinal cohort of 116 consecutive patients (134 hips) was followed up prospectively. The follow-up period was at least 13 years (range, 13- 15 years). Clinical and radiological assessments were made using the Merle d'Aubigne and Postel score and Engh score for fixation and stability, respectively. Osteointegration was assessed radiographically by examining the bone implant interface using the method described by Gruen.

RESULTS

22 patients died during the study period and 6 were lost to follow-up. The respective mean Merle d'Aubigne and Postel scores for pain, range of movement, and ability to walk were 2.2, 2.8, and 2.4 preoperatively and 5.8, 4.8, and 5.4 postoperatively. Engh described satisfactory bony ongrowth as 10 points or more; the mean Engh score for fixation and stability was 24.7 (fixation=10, stability=14.7). One femoral stem was revised for a periprosthetic fracture caused by a fall, but none was revised for loosening. This gave a 99% survival at 13 years (95% confidence interval 94-100).

CONCLUSION

The long-term results of this hydroxyapatite ceramic-coated femoral prosthesis are very satisfactory.

Long-term follow-up (11 years plus) results of JRI (Furlong) total hip arthroplasty in young patients: cause for concern regarding acetabular cup?

We describe the clinical and radiological long-term outcomes of 77 primary total hip replacements in 69 patients using the fully hydroxyapatite-coated JRI (Furlong) total hip replacement. The total cases followed up were 77 hips, performed at a mean duration of 11 years and 2 months. Twelve hips could not be followed up for various reasons, which are discussed in the results section. The mean Harris hip score was 89. Seventeen acetabular cups were revised for aseptic loosening. Only one femoral stem was revised, for fracture. By Engh's criteria there were a further two unstable cups with no symptoms, and all femoral stems were stable. Kaplan-Meier survivorship analysis revealed a survival of 98.8% for the femoral stem, 78.7% for the acetabular cup, and a combined survival of 77.8% for both components. Our findings suggest that the JRI (Furlong) hip gives a durable femoral stem implant fixation, whereas the prosthesis-bone interface achieved with the acetabular component is questionable.

Total hip arthroplasty with an uncemented hydroxyapatite-coated tapered titanium stem: results at a minimum of 10 years' follow-up in 104 hips

BACKGROUND

The purpose of this study was to evaluate the minimum 10-year results of primary total hip arthroplasty using an uncemented, hydroxyapatite-coated tapered stem. Radiological signs of bone remodeling are also presented.

METHODS

We followed a consecutive series of 105 patients (115 hips), who had had an uncemented, proximally hydroxyapatite-coated Bi-Metric femoral component for a mean of 12.2 years (range 10.0-14.9 years). The average age at operation was 52 years. Detailed clinical and radiological analyses were performed after a minimum of 5 and 10 years. Eight patients (10 hips) had died, and one patient was lost to follow-up, leaving 104 hips for final evaluation. The clinical result was evaluated by the Harris Hip Score, complications, and thigh pain.

RESULTS

All patients still had their femoral components in place at the final follow-up. The average Harris Hip Score after 10 years was 92 (range 50-100) with no deterioration over time. Radiologically, several signs of progressive remodeling were identified, but no stem showed signs of loosening.

CONCLUSIONS

The intermediate clinical and radiological results with this stem are encouraging. In the hands of various surgeons, the stem has performed well in a young, high-risk population.

Osteointegration of femoral stem prostheses with a bilayered calcium phosphate coating

Our purpose was to evaluate the osteointegration of bilayered calcium phosphate (CaP)-coated femoral hip stems in a canine model. A first layer of hydroxyapatite (HA) 20 microm thick and a superficial layer of Biphasic Calcium Phosphate (BCP) 30 microm thick were plasma-sprayed on to the proximal region of sandblasted Ti6Al4V prostheses. Bilayered CaP-coated and non-coated canine femoral stems were implanted bilaterally under general anesthesia in 6 adult female Beagle dogs. After 6 and 12 months, a significant degradation of the bilayered coating occurred with a remainder of 33.1+/-12.4 and 23.6+/-9.2 microm in thickness, respectively. Lamellar bone apposition was observed on bilayered coated implants while fibrous tissue encapsulation was observed on non-coated femoral stems. The bone-implant contacts (BIC) were 91+/-3% and 81+/-8% for coated and 7+/-8% and 8+/-12% for non-coated implants, at 6 and 12 months, respectively. Our study supports the concept of a direct relationship between the biodegradation of CaP coating and the enhanced osteointegration of titanium prostheses. A bilayered CaP coating might therefore enhance bone apposition in the early stages because of the superior bioactivity of the BCP layer while the more stable HA layer might sustain bone bonding over long periods.

Stair climbing is more critical than walking in pre-clinical assessment of primary stability in cementless THA in vitro

Pre-clinical testing of hip endoprostheses is a mandatory requirement before clinical release. Inadequate loading conditions may lead to lower elastic and plastic interface movements than those occurring post-operatively in vivo. This study investigated the influence of patient activity on the primary stability of cementless prostheses with a special emphasis on active simulation of muscle forces. A loading setup, based on validated musculo-skeletal analyses, was used to generate the hip contact force during walking and stair climbing by transmitting muscle forces through the femur. In addition, a loading configuration which only generated the hip contact force occurring during stair climbing at the prosthesis head was simulated. CLS prostheses were implanted in 18 composite femora and subjected to cyclical loading. The relative micro-movements at the bone-prosthesis interface were determined and appeared to be extremely sensitive to the specific patient activity. Compared to walking, stair climbing generated higher micro-movements, with pronounced axial and rotational components. Stair climbing with the femur loaded by the resultant hip contact force only exhibited a characteristic valgus tilt of the stem with significantly lower interface micro-movements than under active simulation of muscle forces. The analyses suggest that stair climbing induced the highest mechanical instability at the bone-prosthesis interface, a level which may compromise the necessary osseointegration process. Active simulation of muscle forces considerably affects the primary stability of cementless hip endoprostheses. Pre-clinical in vitro tests should therefore simulate stair climbing and include muscle activity in the assessment of initial implant stability, otherwise micro-movements may be underestimated and the primary stability overestimated.

Hydroxyapatite-Coated Femoral Stem Survivorship at 10 Years

The Omnifit-HA femoral stem component has shown excellent results in early clinical studies. This is an independent prospective study of the outcome of a ydroxyapatite-coated femoral component implanted by one surgeon with an intermediate-term follow up. The senior author performed 103 consecutive uncemented total hip arthroplasties in 96 patients from July 1991 to December 1996. The components implanted were the Omnifit-HA femoral stem and the Omnifit PSL porous-coated acetabular shell. The mean age at the time of the index procedure was 52 years old (range, 27–78) and male:female ratio was 54:42. Three patients were deceased and four patients were lost to follow-up. The mean follow up was 10.3 years (range, 7.3–12.7 years). Clinical and radiographic evaluations were performed by an independent observer. The average preoperative and postoperative Harris Hip Scores were 55 and 92, respectively. The overall survivorship of the Omnifit-HA stem was 100% with no femoral revisions. The survivorship of the Omnifit PSL cup was 89.7% with 4 acetabular revisions for aseptic loosening and 6 polyethelene liner exchanges for osteolysis or late instability. The mean polyethylene wear rate was 0.24 mm per year. This long-term follow up shows that the use of circumferentially coated hydroxyapatite stems can protect against the migration of wear debris along the femoral stem.

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.

Grit-blasted and hydroxyapatite-coated total hip arthroplasty: an 11- to 14-year follow-up study

We report long-term results of the first clinical trial of hydroxyapatite-coated total hip arthroplasty conducted in Japan. The hemispherical cup and the straight-tapered stem were made of titanium alloy with a grit-blasted, hydroxyapatite-coated surface. The surface roughness before and after hydroxyapatite coating was 1.4 microm and 3.4 microm, respectively. Thirty-three patients (35 hips) were followed prospectively; of these, 1 patient was lost to follow-up, 5 were deceased at the latest follow-up, and 27 were followed for 11 to 14 years. Two cups and one stem (two patients) were revised. Survivorship, with radiological acetabular loosening as the endpoint, was 62.3% at 14 years. At the latest radiological follow-up, stable fixation with bone ongrowth was achieved in 46% of the acetabular cups and 89% of the femoral stems. Acetabular cups with host bone coverage of less than 60% had a high rate of failure. The suboptimal result of the hydroxyapatite-coated smooth cup indicates that porous coatings under the hydroxyapatite coating would be beneficial for hydroxyapatite-coated total hip implants, especially for the acetabular components.

Hydroxyapatite: catalyst or conjuror?

A prospective, randomized, intermediate-term study of 174 patients (199 hips) comparing proximally hydroxyapatite (HA)-coated and non-HA-coated surfaces of identical stem design is presented. Clinical and radiographic data from 152 patients (174 hips) confirmed comparable outcomes in both groups according to the Hospital for Special Surgery modification of the Postel--d'Aubigne Hip Rating System. The non-HA group showed significantly higher (P=.03) activity-related thigh pain, however. There were no significant radiographic differences, with all stems showing bone ongrowth. The use of HA-coated stems resulted in early recovery of function and reduced activity-related trochanteric and thigh pain. A possible explanation for the difference is most likely early superior osseointegration. HA as a biologic adjuvant should gain widespread acceptance because of rapid recovery of function and lesser trochanteric and thigh pain.

Early failure of a press-fit carbon fiber hip prosthesis with a smooth surface

We investigated a press-fit anatomically shaped hip stem made of carbon fiber-reinforced composite material in a prospective clinical study. The intention of the design was that a surface of interlaced carbon fibers in the proximal part would achieve metaphyseal fixation. A total of 51 carbon stems were implanted in 48 patients (30 women and 22 men). Mean age at operation was 59 years. The patients were followed clinically, radiologically, and with computed tomography. At 6-year follow-up, aseptic loosening was observed in 47 hips (92%). Forty stems were revised on average 30 months (range, 9-58 months) postoperatively. All revised carbon stems showed fibrous fixation without any bony on-growth. No osteolysis was seen. Histologically, no carbon wear or inflammatory reactions were observed. Only 4 cases had a good clinical result with bony fixation on computed tomography scan. The carbon fiber prosthesis without effective ingrowth or on-growth irregularities showed a high rate of early loosening.

Hydroxyapatite coating improves 8- to 10-year performance of the link RS cementless femoral stem

In a prospective randomized clinical study, 12 hydroxyapatite (HA)-coated and 8 identical but non-coated stems were implanted in 20 patients. At 8- to 10-year follow-up, the HA-coated stems displayed excellent clinical and radiographic results in 11 out of 12 patients, whereas 7 out of 8 non-coated stems were failures and had been subject to revision. Despite the small number of patients in this series, HA coating seems to improve the long-term stable fixation of uncemented femoral implants.

Total hip arthroplasty with a modified cementing technique using hydroxyapatite granules

Results of total hip arthroplasties with a modified cementing technique using hydroxyapatite were evaluated. Femoral and acetabular components were inserted with cement after hydroxyapatite granules (phi = 100-300 microm). The study group comprised 268 hips in 232 patients. The diagnosis was osteoarthritis in 197 patients. After a mean follow-up of 10.3 years, 5 patients died and 30 patients were lost to follow-up, leaving 218 hips (197 patients; mean age, 58.2 years) for evaluation. Three hips were revised because aseptic (1) and septic (2) loosening of acetabular components. Six other sockets were defined as radiologically loose, and no femoral component was loose. Osteolysis was identified in 2 femora and 0 acetabula. The overall loosening rate was 3.2% for acetabular components and 0% for femoral components. These results show that the loosening rate of cemented total hip arthroplasty components, especially the acetabulum, is reduced markedly with this modified cementing technique.

Grit-blasted titanium femoral stem in cementless primary total hip arthroplasty: a 5- to 10-year multicenter study

A total of 133 cementless primary total hip arthroplasties using the Zweymuller-Alloclassic grit-blasted titanium tapered stem were performed in 3 institutions. The patient cohort was divided into 2 subgroups, nonselected and selected, on the basis of excellent bone stock and age (<65 years old at surgery). Acetabular components were all cementless, and bearing surfaces were all alumina-ceramic on polyethylene. After a 7.3-year average follow-up period (range, 5-10 years), 118 primary femoral replacements in 109 patients could be reviewed fully. Mean age at surgery was 55.7 years (range, 27-84 years). According to the Merle d'Aubigne and Charnley rating system, clinical results were graded excellent and good in 89% of hips and fair in 11%. Radiologically, early subsidence >2 mm could be detected in 4 hips (3.4%). Calcar atrophy and spot welds were noted in 77% and 82% of hips. Femoral osteolysis granuloma was noted in 4 hips (3.4%). There has been no stem fracture and no ceramic head breakage. The survivorship at 10 years with definite femoral aseptic loosening (radiographic failure) as the endpoint was 100% (95% Wilson confidence interval, 78.4%-100%; worst scenario, 95.4%). A significant difference between the nonselected and selected patient subgroups was observed only for early reoperation (P =.03) and proximal stress shielding (P =.01). Press-fitting but not filling the femoral canal with a rough titanium, straight, tapered femoral component represents, at intermediate follow-up, a promising cementless option in primary total hip arthroplasty.

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.

Diversity of proximal femoral medullary canal

To analyze the endosteal dimensions of the proximal femoral medullary canal, we studied 50 cadaver femora using computed tomography and a border detection method from 20 mm above the lesser trochanter, the osteotomy level, down to the isthmus. We documented the presence of a dense calcar septum in 96% of femora studied. In addition to mediolateral, anteroposterior, and neck-oriented dimensions, we calculated canal flare indices (CFIs) between the osteotomy level and the isthmus and metaphyseal canal flare indices (MCFIs) between the osteotomy level and the level 20 mm below the lesser trochanter midpoint to describe the shape of the endosteal cavity. With respect to the canal opening, the anteroposterior and mediolateral planes parallelled each other over the entire region as indicated by the high correlation (r = .7, P < .001) between the CFIs in these directions. The prediction of one dimension from another was unreliable in the metaphyseal region, where bone ingrowth is supposed to occur in a femoral prosthesis. The MCFI seemed to be the best parameter to distinguish the various types of proximal femoral canal shapes. We have described the variability of the proximal femoral endosteal dimensions in detail and find that the wide variation in the shape and size of the proximal femoral medullary canal means that it is almost impossible to achieve 100% cortical contact with the stem, especially in the metaphysis.

5- to 8-year results of the Freeman press-fit hip arthroplasty without HA coating: a clinicoradiologic study

Sixty-one consecutive patients (68 hips) with an average age of 49.7 years (range, 21-72 years) had the Freeman uncemented hip arthroplasty without HA coating performed in the Southern General Hospital between 1987 and 1990. These patients were reviewed retrospectively for a mean duration of 66 months (range, 3-103 months). A high incidence of significant thigh pain (40.4%) at 5 to 8 years was noted in this series. The average 5- to 8-year femoral subsidence was 5.4 mm (range, 0-16.1 mm) in 45 hips. Seventeen hips (29.3%) required revision at the time of analysis. Nine hips (15.5%) were revised for aseptic loosening at an average duration of 54 months after the index operation. The conclusion drawn from this series is that the Freeman press-fit hip produced unsatisfactory medium-term results.

Nonlinear three-dimensional finite element analysis of newly designed cementless total hip stems

We designed 2 new types of proximally coated stems (the FMS and FMS-anatomic) based on the endosteal geometry of femora with congenital dislocation or dysplastic hip. The FMS was symmetric while the FMS-anatomic was asymmetric. We compared the proximal fit and fill to the femoral canal, contact stress, relative motion, and load transfer to the femur of 5 stems (FMS, FMS-anatomic, Omnifit, Omniflex, and individual stem) using three-dimensional computer simulation and finite element analysis. The FMS and FMS-anatomic showed a significantly greater fit and fill than conventional stems. The dispersion of the contact stresses and reduction of relative motions in the proximal area were the best in the FMS-anatomic compared to other stems with the exception of the individual stem. In addition, the FMS-anatomic stem transferred most of the load to the proximal femur. Our results suggest that the FMS-anatomic should provide better biomechanical stability at least in the early postoperative period.

Cost-utility analysis of total hip arthroplasties. Technology assessment of surgical procedures by mailed questionnaires

A retrospective study comparing 700 consecutive total hip arthroplasties, utilizing four types of implants, was performed. Questionnaires based on hip scores were sent to 593 living patients. Useful responses were received from 363 (61%) patients. Hip scores and quality-adjusted life-years were calculated. Multiple regression analysis, controlling for all possible biases, demonstrated one cementless implant as superior to all others. We believe that the use of mailed questionnaires is a simple and convenient system of follow-up, saving patients the need for outpatient clinic visits. The validity of such replies, however, has yet to be established.