Poor outcome of the PCA and Harris-Galante hip prostheses. Randomized study of 171 arthroplasties with 9-year follow-up

Long-term follow-up of bone density changes in total hip arthroplasty: comparative analysis from a randomized controlled trial of a porous titanium construct shell vs. a porous coated shell

PURPOSE

Periacetabular bone loss poses a considerable challenge in the longevity and stability of acetabular implants used in total hip arthroplasty (THA). Innovations in implant design, specifically the introduction of three-dimensional (3D) porous titanium constructs, might reduce bone resorption. The purpose of this study was to build upon our previous randomized controlled trial, which found no change in periacetabular bone loss between a 3D porous none-hydroxyapatite coated titanium cup and a standard porous hydroxyapatite coated cup over a two year follow-up period by extending the follow-up duration to ten years post-surgery.

METHODS

This was a single-centre, long-term follow-up study conducted over a ten year period in patients who had previously participated in a randomized controlled trial comparing a 3D porous titanium construct shell (PTC group) with a standard porous hydroxyapatite coated titanium shell (PC-group). The primary outcome measured was the change in bone mineral density (BMD) within four specific periacetabular zones, alongside overall bone loss, which was assessed through BMD in the lumbar spine at two, six and ten years postoperatively. Secondary outcomes included clinical outcome measures.

RESULTS

In total, 18 in the PTC and 20 in the PC group were analysed for the primary endpoint up to ten years. The mean bone mineral density in zones 1-4 was 3.7% higher in the PTC group than in the PC group at six years postoperatively and 12.0% higher at ten years. Clinical outcomes, and the frequency of adverse events did not differ between the groups.

CONCLUSIONS

The PTC group displayed superior long-term bone preservation compared to the PC group while maintaining similar clinical outcomes up to ten years postoperatively. Although with a small sample size, our findings suggest that porous titanium cups have the potential to minimize BMD loss around the cup which could contribute to improving THA outcomes and implant durability.

Uncemented Cups and Impaction Bone Grafting for Acetabular Bone Loss in Revision Hip Arthroplasty: A Review of Rationale, Indications, and Outcomes

Total hip arthroplasty (THA) is increasingly performed in young patients and the number of revisions is estimated to rise over time. Acetabular osteolysis and bone loss are frequently encountered during revision and may be classified and treated in different ways. Impaction bone grafting (IBG) with morselized allograft offers a viable option. IBG was introduced over 40 years ago in combination with cemented cups, and is also used with uncemented cups. The impacted bone chips act as a void filler to restore bone stock; once incorporated they are substituted by host bone. Surgery entails assessment of the defect, acetabular preparation, preparation of the morselized graft, impaction of the graft, and cup implantation. Satisfactory medium- and long-term results have now been reported in most studies. With the advent of high-porosity cups, indications have been extended, enhancing the potential of IBG, in which primary stability of the cup to the host bone is essential for a successful procedure. Synthetic bone substitutes have also been used in combination with allogenic grafts and may extend the original technique for which long-term studies are warranted.

Vitamin E highly cross-linked polyethylene reduces mid-term wear in primary total hip replacement: a meta-analysis and systematic review of randomized clinical trials using radiostereometric analysis

Vitamin E incorporation into highly cross-linked polyethylene (HXLPE) has been introduced to improve wear resistance, and vitamin E incorporated HXLPE (VEPE) has been used in total hip arthroplasty.

The aim of this meta-analysis was to investigate the wear properties of VEPE in clinical practice by synthesizing the data provided in randomized clinical trials.

The effects on implant stability, functional outcomes and revision rate of VEPE were also compared with those of HXPLE or ultra-high molecular weight polyethylene (UHMWPE).

Literature searches were conducted on 1 January 2020 using MEDLINE, EMBASE, Cochrane and ClinicalTrials.gov databases. Randomized controlled trials (RCTs) comparing the aforementioned parameters between VEPE and standard HXPLE/UHMWPE liners were included.

Methodological quality and the bias of the included studies were analysed. Meta-analyses were performed using the Review Manager software.

Nine RCTs met the eligibility criteria and were included. At early and mid-term follow-up, the vertical penetration and the total penetration of the femoral head were both significantly reduced in the VEPE group. The steady state wear rate of the VEPE group was also remarkably lower.

However, at two-year follow-up, significantly increased cup migration was observed in the VEPE group. Moreover, the mid-term clinical outcomes of the VEPE group were worse, while the total revision rates between the two groups were not significantly different.

The limited number of included studies may compromise our conclusion regarding clinical outcomes of the VEPE bearing surface. More RCTs with longer follow-up periods are needed to further investigate the effects of VEPE in total hip arthroplasty.

Cite this article: EFORT Open Rev 2021;6:759-770. DOI: 10.1302/2058-5241.6.200072

The fate of sagittal alignment in tapered uncemented femoral components in total hip arthroplasty: 889 hips followed for a minimum of 10 years

PURPOSE

Aseptic loosening is rare after primary total hip arthroplasty (THA) with mostly uncemented tapered stems; however, different factors can modify the results. We question whether 3 different current femoral components and/or the surgical technique affect the clinical and radiological outcome after a minimum follow-up of 10 years.

METHODS

889 uncemented tapered stems implanted from 1999 to 2007 were evaluated for a minimum follow-up of 10 years. Group 1 (273 hips) shared a conical shape and a porous-coated surface, group 2 (286 hips) a conical splined shape and group 3 (330 hips) a rectangular grit-blasted stem. Groups 1 and 2 were implanted through a posterolateral approach and group 3 using an anterolateral approach. Clinical outcomes and anteroposterior and sagittal radiographic analyses were compared.

RESULTS

No thigh pain was reported in unrevised patients. Mean Harris Hip score was lower for patients in group 3 for pain and function at all intervals. 14-year implant survival for aseptic loosening was 98.2% (95% confidence interval [CI] 96.2-100) in group 3. No revision for aseptic loosening was found with the other designs. A stem position outside neutral limits in the sagittal alignment (p = 0.001, hazard ratio: 6.17, 95% CI, 2.05-18.61) was associated with aseptic loosening in group 3.

CONCLUSIONS

Most current uncemented straight tapered femoral components can provide adequate bone fixation in primary THA after 10 years. Conical stems inserted through a posterolateral approach are more reliable than rectangular ones inserted through an anterolateral approach.

Early Polyethylene Failure in a Modern Total Hip Prosthesis: A Note of Caution

BACKGROUND

Historically, there has been excellent survivorship of total hip arthroplasty with newer implants expected to outperform prior generations. Review of our institutional database identified problems with one particular cross-linked polyethylene liner in mid-term follow-up, which has not been reported in the literature. We report on the technical aspects of this liner, as well as the clinical and radiographic factors associated with early failure of this bearing in our practice.

METHODS

A retrospective review of our institutional database was performed from January 2009 to June 2019 of patients who presented with significant osteolysis in the setting of prior total hip arthroplasty with a contemporary polyethylene liner. Demographic and radiographic measures were collected for all patients.

RESULTS

Twelve patients were identified, with nine undergoing revision surgery. All patients demonstrated radiographic osteolysis at the time of revision surgery. The average time to diagnosis of failure was 55.9 months (range: 12-120 months). Average cup position preoperatively was 44 degrees inclination (range: 36-53 degrees) and 21 degrees anteversion (range: 10-34 degrees). Nine patients underwent revision of the acetabular component, with two also undergoing femoral component revision. The Manufacturer and User Facility Device Experience database revealed 22 reported cases of wear-related failure from 2009 to 2019.

CONCLUSIONS

Considering that no identifiable risk factors related to patient demographics or implant position were identified, the Exactech Connexion GXL liner may be prone to a high rate of early failure from wear and severe secondary osteolysis. We recommend close surveillance of patients with this bearing surface.

Good implant survival after acetabular revision with extensive impaction bone grafting and uncemented components

Aims

This single-centre observational study aimed to describe the results of extensive bone impaction grafting of the whole acetabular cavity in combination with an uncemented component in acetabular revisions performed in a standardized manner since 1993.

Methods

Between 1993 and 2013, 370 patients with a median age of 72 years (interquartile range (IQR) 63 to 79 years) underwent acetabular revision surgery. Of these, 229 were more than ten years following surgery and 137 were more than 15 years. All revisions were performed with extensive use of morcellized allograft firmly impacted into the entire acetabular cavity, followed by insertion of an uncemented component with supplementary screw fixation. All types of reoperation were captured using review of radiographs and medical charts, combined with data from the local surgical register and the Swedish Hip Arthroplasty Register.

Results

Among patients with possible follow-up of ten and 15 years, 152 and 72 patients remained alive without revision of the acetabular component. The number of deaths was 61 and 50, respectively. Of those who died, six patients in each group had a reoperation performed before death. The number of patients with a reoperation was 22 for those with ten-year follow-up and 21 for those with 15 years of follow-up. The Kaplan-Meier implant survival rate for aseptic loosening among all 370 patients in the cohort was 96.3% (95% confidence interval (CI) 94.1 to 98.5) after ten years and 92.8% (95% CI 89.2 to 96.6) after 15 years.

Conclusion

Extensive bone impaction grafting combined with uncemented revision components appears to be a reliable method with favourable long-term survival. This technique offers the advantage of bone stock restoration and disputes the long-standing perception that uncemented components require > 50% of host bone contact for successful implant survival. Cite this article: Bone Joint J 2020;102-B(2):198–204.

Patient-specific hip geometry has greater effect on THA wear than femoral head size

In vivo linear penetration in total hip arthroplasty (THA) exhibits similar values for 28mm and 32mm femoral head diameter with considerable variations between and within the studies. It indicates factors other than femoral head diameter influence polyethylene wear. This study is intended to test the effect of patient׳s individual geometry of musculoskeletal system, acetabular cup orientation, and radius of femoral head on wear. Variation in patient׳s musculoskeletal geometry and acetabular cup placement is evaluated in two groups of patients implanted with 28mm and 32mm THA heads. Linear wear rate estimated by mathematical model is 0.165-0.185mm/year and 0.157-0.205mm/year for 28 and 32mm THA heads, respectively. Simulations show little influence femoral head size has on the estimated annual wear rate. Predicted annual linear wear depends mostly on the abduction angle of the acetabular cup and individual geometry of the musculoskeletal system of the hip, with the latter having the greatest affect on variation in linear wear rate.

Porous titanium construct cup compared to porous coated titanium cup in total hip arthroplasty. A randomised controlled trial

PURPOSE

The purpose of this study was to determine if a new titanium cup with increased porosity resulted in different periacetabular bone loss and migration compared to a porous coated cup.

METHODS

Fifty-one patients with primary hip osteoarthritis were randomized to either a cup with porous titanium construct backside (porous titanium group, n = 25) or a conventional porous coated titanium cup (control group, n = 26). The primary outcome variable was change in periacetabular bone mineral density two years after surgery measured with dual energy X-ray absorptiometry (DXA). Secondary outcomes were implant fixation measured with radiostereometry (RSA) and clinical outcome scores.

RESULTS

The pattern of bone remodelling was similar in the two groups with almost complete restoration to baseline values. BMD diminished in the two proximal zones and increased in the two distal zones. After minimal migration up to six months all implants in both groups became stable. We found no difference between the two groups in clinical outcome scores.

CONCLUSIONS

In this prospective, randomized, controlled trial on a new porous titanium cup we found, compared to the control group, no clinically relevant differences regarding periacetabular bone preservation, implant fixation or clinical outcome up to two years postoperatively.

Method of fixation does not influence the overall risk of rerevision in first-time cup revisions

BACKGROUND

During the last two decades, uncemented fixation has been increasingly preferred worldwide during cup revision surgery. In Sweden, the number of uncemented cup revisions has been increasing during the last decade. However, it is unclear whether the risk of rerevision differs between cemented and uncemented cups.

QUESTION/PURPOSES

We determined (1) the risk of rerevision after cemented and uncemented fixation; (2) the influence of concomitant stem revision on the risk of rerevision of the cup; (3) the difference in risk of rerevision of an uncemented cup revision compared with liner revision only; and (4) whether the surgical incision influenced the risk of rerevision.

METHODS

Between 1979 and 2010, 19,342 first-time cup revisions were reported to the Swedish Hip Arthroplasty Register. From these, 749 were excluded (hip resurfacing, cases with tumor diagnoses, and missing data) leaving 18,593 (73% cemented) for further analysis. We used a Cox regression model adjusted for age, sex, primary diagnosis, method of fixation, concomitant stem revision, and cemented/uncemented fixation to assess risk of rerevision.

RESULTS

The relative risk for rerevision for any reason did not differ between cemented and uncemented fixation (relative risk [RR], 0.94). If the stem was not revised at index revision, the risk of further cup revision increased twofold (RR, 1.91). Liner revisions were associated with a 70% increased risk for rerevision of the cup as a result of any reason and especially because of dislocation (RR, 2.94). The surgical incision did not influence the overall risk for rerevision (direct lateral/posterolateral: RR, 1.02) or the risk of rerevision resulting from dislocation (RR, 0.91).

CONCLUSIONS

We found no difference in the overall risk of rerevision between cemented and uncemented fixation. Liner exchange had a higher risk for rerevision when compared with cases being rerevised with a new uncemented cup.

Characterisation of a metallic foam-cement composite under selected loading conditions

An open-cell metallic foam was employed as an analogue material for human trabecular bone to interface with polymethyl methacrylate (PMMA) bone cement to produce composite foam-cement interface specimens. The stress-displacement curves of the specimens were obtained experimentally under tension, shear, mixed tension and shear (mixed-mode), and step-wise compression loadings. In addition, under step-wise compression, an image-guided failure assessment (IGFA) was used to monitor the evolution of micro-damage of the interface. Microcomputed tomography (µCT) images were used to build a subject-specific model, which was then used to perform finite element (FE) analysis under tension, shear and compression. For tension-shear loading conditions, the strengths of the interface specimens were found to increase with the increase of the loading angle reaching the maximum under shear loading condition, and the results compare reasonably well with those from bone-cement interface. Under compression, however, the mechanical strength measured from the foam-cement interface is much lower than that from bone-cement interface. Furthermore, load transfer between the foam and the cement appears to be poor under both tension and compression, hence the use of the foam should be discouraged as a bone analogue material for cement fixation studies in joint replacements.

New polyethylenes in total hip replacement: A ten- to 12-year follow-up study

Between 1999 and 2001, 90 patients underwent total hip replacement using the same uncemented acetabular and femoral components with a 28 mm metallic femoral head but with prospective randomisation of the acetabular liner to either Durasul highly cross-linked polyethylene or nitrogen-sterilised Sulene polyethylene. We assessed 83 patients at a minimum follow-up of ten years. Linear penetration of the femoral head was estimated at six weeks, six and 12 months and annually thereafter, using the Dorr method, given the non-spherical shape of the acetabular component. There was no loosening of any component; only one hip in the Sulene group showed proximal femoral osteolysis. The mean penetration of the femoral head at six weeks was 0.08 mm (0.02 to 0.15) for the Durasul group and 0.16 mm (0.05 to 0.28) for the Sulene group (p = 0.001). The mean yearly linear penetration was 64.8% lower for the Durasul group at 0.05 mm/year (sd 0.035) for the Sulene group and 0.02 mm/year (sd 0.016) for the Durasul (p < 0.001). Mean linear femoral head penetration at ten years was 61% less in the Durasul than Sulene group. Highly cross-linked polyethylene gives excellent results at ten years.

Excellent fixation achieved with cementless posteriorly stabilized total knee arthroplasty

Cementless posteriorly stabilized (PS) total knee arthroplasty has not been widely accepted primarily because of prior unpredictable results and concern about micromotion at the tibial fixation interface caused by the cam/post interaction. A prospective consecutive series of 114 cementless, tricompartmental periapatite-coated single-radius PS implants in 110 patients with a mean age 62 years was performed to determine if initial stability and biologic fixation could be achieved. At a mean follow-up of 36 months, all implants demonstrated radiographic evidence of stable biologic fixation with no evidence of loosening, osteolysis, stress shielding, or progressive radiolucent lines. Based on these early results, cementless, periapatite-coated single-radius PS total knee arthroplasty offers marked promise.

Early proximal migration of cups is associated with late revision in THA: a systematic review and meta-analysis of 26 RSA studies and 49 survivalstudies

BACKGROUND AND PURPOSE

The association between excessive early migration of acetabular cups and late aseptic revision has been scantily reported. We therefore performed 2 parallel systematic reviews and meta-analyses to determine the association between early migration of acetabular cups and late aseptic revision.

METHODS

One review covered early migration data from radiostereometric analysis (RSA) studies, while the other focused on revision rates for aseptic loosening from long-term survival studies. Thresholds for acceptable and unacceptable migration were classified according the Swedish Hip Arthroplasty Register and the Australian National Joint Replacement Registry: < 5% revision at 10 years.

RESULTS

Following an elaborate literature search, 26 studies (involving 700 cups) were included in the RSA review and 49 studies (involving 38,013 cups) were included in the survival review. For every mm increase in 2-year proximal migration, there was a 10% increase in revision rate, which remained after correction for age, sex, diagnosis, hospital type, continent, and study quality. Consequently, proximal migration of up to 0.2 mm was considered acceptable and proximal migration of 1.0 mm or more was considered unacceptable. Cups with proximal migration of between 0.2 and 1.0 mm were considered to be at risk of having revision rates higher than 5% at 10 years.

INTERPRETATION

There was a clinically relevant association between early migration of acetabular cups and late revision due to loosening. The proposed migration thresholds can be implemented in a phased evidence-based introduction, since they allow early detection of high-risk cups while exposing a small number of patients.

Cost savings of using a cemented total hip replacement: an analysis of the National Joint Registry data

The debate whether to use cemented or uncemented components in primary total hip replacement (THR) has not yet been considered with reference to the cost implications to the National Health Service. We obtained the number of cemented and uncemented components implanted in 2009 from the National Joint Registry for England and Wales. The cost of each component was established. The initial financial saving if all were cemented was then calculated. Subsequently the five-year rates of revision for each type of component were reviewed and the predicted number of revisions at five years for the actual components used was compared with the predicted number of revisions for a cemented THR. This was then multiplied by the mean cost of revision surgery to provide an indication of the savings over the first five years if all primary THRs were cemented. The saving at primary THR was calculated to be £10 million with an additional saving during the first five years of between £5 million and £8.5 million. The use of cemented components in routine primary THR in the NHS as a whole can be justified on a financial level but we recognise individual patient factors must be considered when deciding which components to use.

Does a collar improve the immediate stability of uncemented femoral hip stems in total hip arthroplasty? A bilateral comparative cadaver study

The aim of this study was to compare the immediate stability of collared vs collarless uncemented femoral stems in total hip arthroplasty. A bilateral comparative study of 20 cadavers (40 hips: 20 collarless, 20 collared) was performed. Forces in the vertical and horizontal planes required to initiate subsidence of femoral stem and subsequent femoral fracture were measured. In vertical plane, subsidence began at an average force of 3129 ± 494 N for collarless stems and 6283 ± 3584 N for collared stems (P = .02). Fracture occurred at a significantly higher force for collared stems (P = <.001). In horizontal plane, subsidence began at an average force of 540 ± 170 N for collarless stems and 678 ± 206 N for collared stems (P = .01). Fracture occurred at a significantly higher force for collared stems (P = .005). Collared uncemented stems have significantly greater immediate stability than collarless. They are able to withstand greater vertical and horizontal forces before the initiation of subsidence and subsequent fracture.

Distribution of periacetabular osteolytic lesions varies according to component design

Using computed tomography, the volume, location, and number of osteolytic lesions were determined adjacent to 38 Harris-Galante 1 (HG-1) acetabular components fixed with screws and 19 porous-coated anatomic (PCA) acetabular components press-fitted without screws. The median implantation times were 16 and 15 years, respectively. The mean total lesion volumes were similar: 11.1 cm(3) (range, 0.7-49 cm(3)) and 9.8 cm(3) (range, 0.4-52 cm(3)), respectively, for hips with HG-1 and PCA components (P = .32). There was a significant difference in the proportion of rim-related, screw or screw hole-related, and combined lesions between the 2 component designs (P < .0001). HG-1 components had more screw and screw hole-related lesions, and PCA components had more rim-related lesions. Although there are concerns regarding screw and screw hole-associated osteolysis, these findings suggest that peripheral fixation may be well maintained in the long term with the use of multiple-hole acetabular components with screw fixation.

Fifteen-year to twenty-year results of cementless Harris-Galante porous femoral and Harris-Galante porous I and II acetabular components

This study examined long-term survivorship of primary total hip arthroplasty (THA) using cementless Harris-Galante porous femoral and Harris-Galante porous I or II acetabular components. Of 113 hips (101 patients) studied, 60 hips (53 patients) were available for follow-up at a mean of 17.2 years after surgery. A total of 10 hips had documented revision, and 2 hips had failed radiographically. The average Harris hip score was 82. Radiographically, 12 hips demonstrated eccentric wear, 8 had osteolysis, and 1 had a broken tine. The overall survival rate was 87.7%; the mean volumetric wear rate was 74.96 mm(3); and the mean polyethylene linear penetration rate was 0.153 mm/y, similar to that of well-cemented THA in other series. This long-term outcome for an early-generation cementless THA is promising and provides a standard by which to judge the newer generation of cementless implants.

Increased risk of revision of acetabular cups coated with hydroxyapatite

BACKGROUND

Hydroxyapatite (HA) is the main inorganic component of bone, and HA coating is widely used on acetabular cups in hip arthroplasty. It has been suggested that this surface finish improves cup survival.

METHODS

All patients registered in the Swedish Hip Arthroplasty Register between 1992 and 2007 with an uncemented acetabular implant that was available either with or without HA coating were identified. 8,043 total hip arthroplasties (THAs) with the most common cup types (Harris-Galante, Romanus, and Trilogy) were investigated. A Cox regression model including type of coating, age, sex, primary diagnosis, cup type, and type of stem fixation was used to calculate adjusted risk ratios (RRs) for the risk of revision.

RESULTS

HA coating was a risk factor for cup revision due to aseptic loosening (adjusted RR 1.7; 95% CI: 1.3-2). Age at primary arthroplasty of < 50 years, a diagnosis of pediatric hip disease, the use of a cemented stem, and the Romanus and Harris-Galante cup types were also associated with statistically significantly increased risk of cup revision due to aseptic loosening.

INTERPRETATION

Our findings question the routine use of HA-coated cups in primary total hip arthroplasty. With some designs, this practice may even increase the risk of loosening-resulting in revision surgery.

Uncemented and cemented primary total hip arthroplasty in the Swedish Hip Arthroplasty Register

BACKGROUND AND PURPOSE

Since the introduction of total hip arthroplasty (THA) in Sweden, both components have most commonly been cemented. A decade ago the frequency of uncemented fixation started to increase, and this change in practice has continued. We therefore analyzed implant survival of cemented and uncemented THA, and whether the modes of failure differ between the two methods of fixation.

PATIENTS AND METHODS

All patients registered in the Swedish Hip Arthroplasty Register between 1992 and 2007 who received either totally cemented or totally uncemented THA were identified (n = 170,413). Kaplan-Meier survival analysis with revision of any component, and for any reason, as the endpoints was performed. Cox regression models were used to calculate risk ratios (RRs) for revision for various reasons, adjusted for sex, age, and primary diagnosis.

RESULTS

Revision-free 10-year survival of uncemented THA was lower than that of cemented THA (85% vs. 94%, p < 0.001). No age or diagnosis groups benefited from the use of uncemented fixation. Cox regression analysis confirmed that uncemented THA had a higher risk of revision for any reason (RR = 1.5, 95% CI: 1.4-1.6) and for aseptic loosening (RR = 1.5, CI: 1.3-1.6). Uncemented cup components had a higher risk of cup revision due to aseptic loosening (RR = 1.8, CI: 1.6-2.0), whereas uncemented stem components had a lower risk of stem revision due to aseptic loosening (RR = 0.4, CI: 0.3-0.5) when compared to cemented components. Uncemented stems were more frequently revised due to periprosthetic fracture during the first 2 postoperative years than cemented stems (RR = 8, CI: 5-14). The 5 most common uncemented cups had no increased risk of revision for any reason when compared with the 5 most commonly used cemented cups (RR = 0.9, CI: 0.6-1.1). There was no significant difference in the risk of revision due to infection between cemented and uncemented THA.

INTERPRETATION

Survival of uncemented THA is inferior to that of cemented THA, and this appears to be mainly related to poorer performance of uncemented cups. Uncemented stems perform better than cemented stems; however, unrecognized intraoperative femoral fractures may be an important reason for early failure of uncemented stems. The risk of revision of the most common uncemented cup designs is similar to that of cemented cups, indicating that some of the problems with uncemented cup fixation may have been solved.

Cementless total hip arthroplasty for primary osteoarthritis in patients aged 55 years and older

BACKGROUND

Cemented total hip arthroplasty has been the treatment of choice for elderly patients with osteoarthritis. We analyzed survival rates of the most common cementless designs used in this age group in Finland.

PATIENTS AND METHODS

Inclusion criteria permitted 10,310 replacements (8 designs) performed in patients aged 55 years or older to be selected for evaluation. The risk of revision of each of the 8 implants was compared with that of a group comprising 3 cemented designs as the reference (9,549 replacements). Survival analyses were performed overall and separately for 3 age cohorts: 55-64 years (6,781 replacements), 65-74 years (8,821 replacements), and 75 years or older (4,257 replacements).

RESULTS

In all patients aged 55 years or more, the Bi-Metric stem had a higher survival rate for aseptic loosening at 15 years than the cemented reference group: 96% (95% CI: 94-98) vs. 91% (CI: 90-92). However, the 15-year survival rates of the Bi-Metric/Press-Fit Universal (71% (CI: 67-75)) and the Anatomic Mesh/Harris-Galante II (72% (CI: 67-78)) total hip replacements were lower than that of the reference group (86% (CI: 84-87)). Information was scarce for patients aged 75 years or more.

INTERPRETATION

Cementless proximal porous-coated stems are a good option for elderly patients. Even though biological fixation is a reliable fixation method in THA, polyethylene wear and osteolysis remain a serious problem for cementless cup designs with unplugged screw holes and low-quality liners.

In vitro fatigue failure of cemented acetabular replacements: a hip simulator study

Although hip simulators for in vitro wear testing of prosthetic materials used in total hip arthroplasty (THA) have been available for a number of years, similar equipment has yet to appear for endurance testing of fixation in cemented THA, despite considerable evidence of late aseptic loosening as one of the most significant failure mechanisms in this type of replacements. An in vitro study of fatigue behavior in cemented acetabular replacements has been carried out, utilizing a newly developed hip simulator. The machine was designed to simulate the direction and the magnitude of the hip contact force under typical physiological loading conditions, including normal walking and stair climbing, as reported by Bergmann et al. (2001, Hip 98, Freie Universitaet, Berlin). A 3D finite element analysis has been carried out to validate the function of the hip simulator and to evaluate the effects of boundary conditions and geometry of the specimen on the stress distribution in the cement mantle. Bovine pelvic bones were implanted with a Charnley cup, using standard manual cementing techniques. Experiments were carried out under normal walking and descending stairs loading conditions with selected load levels from a body weight of 75-125 kg. Periodically, the samples were removed from the test rigs to allow CT scanning for the purpose of monitoring damage development in the cement fixation. The hip simulator was found to be satisfactory in reproducing the hip contact force during normal walking and stair climbing, as reported by Bergmann et al. Finite element analysis shows that the stress distributions in the cement mantle and at the bone-cement interface are largely unaffected by the geometry and the boundary conditions of the model. Three samples were tested up to 17 x 10(6) cycles and sectioned post-testing for microscopic studies. Debonding at the bone-cement interface of various degrees in the posterior-superior quadrant was revealed in these samples, and the location of the failures corresponds to the highest stressed region from the finite-element analysis. Preliminary experimental results from a newly developed hip simulator seem to suggest that debonding at the bone-cement interface is the main failure mechanism in cemented acetabular replacements, and descending stairs seem to be more detrimental than normal walking or ascending stairs with regard to fatigue integrity of cement fixation.

New polyethylenes in total hip replacement: a prospective, comparative clinical study of two types of liner

Ultra-high-molecular-weight polyethylene sterilised in the absence of air and highly cross-linked polyethylene have been used to avoid osteolysis and loosening in total hip replacement. Our prospective randomised study has assessed the results using two different polyethylenes associated with the same prosthetic design. We assessed 45 Allofit acetabular components with a Sulene-polyethylene liner of conventional polyethylene gamma sterilised with nitrogen and 45 Allofit acetabular components with a Durasul-polyethylene liner sterilised in ethylene oxide, both matched with an Alloclassic stem with a 28 mm modular femoral head. The prostheses were implanted between May 1999 and December 2001. The mean follow-up was for 66.3 months (60 to 92). The linear penetration of the femoral head was estimated at 6 weeks, at 6 and 12 months and annually thereafter from standardised digitised radiographs using image-analysis software. There was no loosening of any prosthetic component. There were no radiolucent lines or osteolysis. The mean rate of penetration calculated from regression analysis during the first five years was 38 microm/year (SD 2) for the Sulene group and 6 microm/year (SD 1) for the Durasul group (p = 0.00002). The rate of penetration of the Durasul group was 15.7% of that of the Sulene group.

Fatigue failure in the cement mantle of a simplified acetabular replacement model

Although the role of fatigue failure in aseptic loosening of cemented total hip replacements has been extensively studied in femoral components, studies of fatigue failure in cement mantle of acetabular replacements have yet to be reported, despite that the long-term failure rate in the latter is about three times that of femoral components. Part of the reason may be that a complex pelvic bone structure does not land itself readily for a 2D representation as that of a femur.In this work, a simple multilayer model has been developed to reproduce the stress distributions in the cement mantle of an acetabular replacement from a plane strain finite element pelvic bone model. The experimental multilayer model was subjected to cyclic loading up to peak hip contact force during normal walking. Radial fatigue cracks were observed in the vicinity of the maximum tangential and compressive stresses, as predicted by the FE models. Typical fatigue striations were also observed on the fracture surfaces post cyclic testing. The results were examined in the context of retrieval studies, 3D FE analysis and in vitro experimental results using full-sized hemi-pelvic bone models.

A radiostereometric analysis of the Bryan Cervical Disc prosthesis

STUDY DESIGN

Prospective, radiostereometric study of the Bryan Cervical Disc prosthesis (Medtronic Sofamor Danek, Memphis, TN) for the treatment of a single-level disc disease of the cervical spine.

OBJECTIVE

To study the stability of the titanium endplates of the disc prosthesis at the interface between the bone and prosthesis.

SUMMARY OF BACKGROUND DATA

Cervical disc prosthesis is a motion-sparing technology in which the longevity is dependent on initial fixation as well as secondary fixation with bone ingrowth into the surface of the device. Little is known regarding the stability of this fixation with the currently studied prosthesis.

METHODS

Eleven patients with symptomatic cervical radiculopathy underwent implantation of a radiostereometry modified Bryan prosthesis after a standard anterior cervical discectomy. The adjacent vertebrae were perioperatively marked with tantalum markers. The patients were then frequently studied with radiostereometric radiographs and evaluated for pain, and neurologic and physical function for 2 years.

RESULTS

Both titanium endplates of the device were immediately stable in 5 patients. Small but measurable changes (micromotions) were recorded in 4 patients until the 3-month examination and in 2 patients at the 3-6-month time period. All prostheses continued to be stable after 6 months until the final assessment at 2 years after surgery. The recorded micromotions did not influence the clinical results.

CONCLUSIONS

The Bryan prosthesis is immediately stable in many patients and is securely fixed to the bone within 3-6 months in all patients. The result of this study suggests that there is sufficient bone ingrowth on the coated surface of the Bryan prosthesis endplates to stabilize securely the prosthesis.

Ten-year results of ALIZE acetabular cup with hydroxyapatite coating and AURA hydroxyapatite-coated stem in total hip arthroplasty

One hundred seven total hip arthroplasties were done between 1991 and 1992 with ALIZE acetabular cup with hydroxyapatite coating (Biomet France, Valence, France) and AURA hydroxyapatite-coated stem (Biomet France) in 107 patients. The articulation was ceramic on polyethylene for 102 patients and metal on polyethylene for the remaining 5 patients. The mean follow-up of the series was 8.4 +/- 2.5 years. The mean preoperative Merle d'Aubigné hip functional score was 10.6 +/- 3 vs 15.8 +/- 1.8 at the latest follow-up. Sixty-three patients were alive for the long-term follow-up at a mean of 9.67 +/- 0.25 years. Of the patients, 98.5% were satisfied or very satisfied at the latest follow-up. Five revisions were documented in these series: 1 for acetabular loosening, 2 for traumatic ceramic head fracture, 1 for polyethylene replacement, and 1 for stem replacement due to bone fracture. The mean wear rate was 0.076 +/- 0.043 mm/y (<0.1 mm/y considered as the normal wear rate). The overall survival rate at 10 years was 95.6% +/- 2.1% using revision of either component as the end point.

High wear rates and extensive osteolysis in 3 types of uncemented total hip arthroplasty: a review of the PCA, the Harris Galante and the Profile/Tri-Lock Plus arthroplasties with a minimum of 12 years median follow-up in 96 hips

BACKGROUND

High wear rates and femoral and acetabular osteolysis have been-and still are-the main problems in uncemented total hip replacement. We reviewed 96 consecutive cementless total hip replacements of 4 different designs.

PATIENTS AND METHODS

21 PCA, 25 Harris Galante Porous/Harris Galante I (stem/cup), 25 Profile pressfit/ Tri-Lock Plus (stem/cup) and 25 Profile HA-coated/Tri-Lock Plus (stem/cup) prostheses were included. The operations were performed in the period 1984-1991. Median follow-up ranged from 12-16 years. Wear and osteolysis were measured.

RESULTS

Mean linear wear rates ranged from 0.17 to 0.21 mm/year in the 4 groups, and there were no statistically significant differences between the groups (p = 0.9, ANOVA). Moderate or extensive osteolysis was found in 46 of the 96 hips included. The association between high and low wear rates (more or less than 0.20 mm/ year) and extent of osteolysis was statistically significant (p < 0.001, t-test). We found poor 12-year survival of the primary prostheses in all 4 groups (50-70%), mainly due to revisions because of wear of the polyethylene liner and/or osteolysis. The infrequently documented Profile/Tri-Lock Plus systems did not perform differently from the PCA and the HG.

INTERPRETATION

The poor long-term results with these uncemented total hip arthroplasties illustrate the necessity of regular radiographic evaluation in order to detect osteolysis and liner failure, which are both generally asymptomatic until catastrophic failure appears.

Porous-coated cups fixed with screws: a 12-year clinical and radiostereometric follow-up study of 50 hips

BACKGROUND

Excellent mid-term results have stimulated the use of hemispherical porous-coated cups in hip replacement. With longer follow-up, there have been problems related to polyethylene wear and liner fixation, and osteolysis has been documented in reports of selected cases. We evaluated the clinical and radiographic results of 50 patients followed for 12 years.

PATIENTS AND METHODS

58 consecutive patients (58 hips), mean age 55 years, were operated with Harris-Galante (HG) I or II cups using line-to-line fit and additional screw fixation. Polyethylene linersgamma-sterilized in air and 32-mm ceramic heads were used. 8 patients died within 12 years, leaving 50 patients with a complete 12 year follow-up. 23 of the cups were also evaluated with radiostereometry (RSA) for migration, liner stability, and wear.

RESULTS

All metal shells were still in situ after 12 years. 4 hips had been revised due to femoral loosening. In these revisions, the liner had been exchanged due to wear and/or instability, resulting in a cup survival rate of 89%. 28 cups displayed osteolytic lesions, mainly in relation to screws. RSA revealed minimum translations, but in many cases there were pronounced liner rotations suggesting unstable liners within the metal shell. The annual proximal wear was 0.09 mm and the three-dimensional wear was 0.16 mm.

INTERPRETATION

RSA can predict the long-term performance of cup fixation. Low migration during the initial years after implantation indicates excellent long-term results regarding fixation of the metal shell. The main problem with this design appears to be liner instability and osteolysis, factors that are probably interrelated. Because these phenomena are clinically silent, we recommend regular follow-up of patients with HG cups to avoid sudden loosening and complicated revisions.

Long-term results of uncemented acetabular cups with an ACS polyethylene liner. a 14-16-year follow-up study

We assessed the clinical and radiographic results of 40 porous-coated acetabular cups with an Acetabular Cup System polyethylene liner over a minimum 14-year follow-up. Femoral head penetration was estimated using a software package. Fifteen cups were revised, 11 due to polyethylene liner rupture. All cups but two were radiographically stable, and 11 hips showed acetabular osteolysis. The overall femoral head penetration rate in hips without liner fracture with reference to the early penetration point was 0.1188+/-0.070 mm per year. Polyethylene liner fractures were associated with higher early femoral head penetration (P<0.0001) and a vertical cup position (P=0.0016). The 14-year survival without cup revision for any reason was 63.9%, 71.8% with no ACS polyethylene liner fracture and 65.3% with no acetabular osteolysis. Most cups showed a good clinical outcome in general, but major Acetabular Cup System liner failure and osteolysis were frequent. Patients with the ACS cups still in place should be monitored closely.

Development and problems of metal-on-metal hip arthroplasty

For over 40 years, the metal-on-polyethylene bearing has dominated the field of total hip replacement. Problems of wear, osteolysis (dissolution of bone), and ultimately failure of prostheses have led to the development of alternative bearing surfaces. Metal-on-metal hip resurfacing has taken current orthopaedic surgery almost by storm. However, metal ion release following metal-on-metal hip resurfacing remains a major cause for concern. This article looks into the development and examines problems and issues surrounding metal-on-metal resurfacing arthroplasty.

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

BACKGROUND

We studied the ability of DEXA to detect bony defects around cementless acetabular components in total hip arthroplasty. The aim of our study was to provide a tool for detection and quantification of osteolytic lesions for the planning of revision cases.

METHODS

We measured BMC in 10 human pelvis specimens retrieved from post mortem. We created standardized defects behind inserted acetabular components and compared the ash weights of the removed bone to the corresponding BMC measurements.

RESULTS

We found a good correlation between the BMC differences measured and the corresponding ash weights.

INTERPRETATION

We conclude that DEXA can detect even small defects in the bone adjacent to the cup.

Uncemented total hip arthroplasty for primary osteoarthritis in young patients: a mid-to long-term follow-up study from the Finnish Arthroplasty Register

INTRODUCTION

The survival of total hip arthroplasties (THAs) has been considered to be poor in young patients. We evaluated the population-based survival of uncemented THA for primary osteoarthritis (OA) in patients under 55 years of age and the factors affecting survival.

METHODS

The Finnish Arthroplasty Register was established in 1980. Between that year and 2003, 92,083 primary THAs were entered in the register, 5,607 of which were performed for primary OA in patients under 55 years of age. Using records from these 5,607 THAs, we selected uncemented femoral and acetabular components that had been used in more than 100 operations during the study period. Survival of both components (cup/stem) and their combinations were analyzed separately with the Kaplan-Meier analysis and the Cox regression model.

RESULTS

All uncemented stems studied showed a survival rate of over 90% at 10 years. The Biomet Bi-Metric stem had a 95% (95% CI 93- 97) survival rate even at 15 years. Overall survival of the extendedly porous-coated Lord Madréporique stem (p = 0.003) and the proximally porous-coated Anatomic Mesh stem (p = 0.0008) were poorer than that of the Biomet Bi-Metric stem. When endpoint was defined as stem revision for any reason, results were generally similar; there was no difference, however, between the survival rates of the Lord Madréporique stem and the Bi-Metric stem. Of the acetabular components, the Biomet Universal, the ABG Il and the Harris-Galante II cups showed < 90% survival rates at 10 years with aseptic loosening as endpoint; at 13 years the corresponding survival rates were 94% (95% CI 91-97) for the Biomet Universal and 95% (95% CI 91-98) for the Harris-Galante II cups with aseptic loosening as endpoint. The PCA Pegged porous-coated uncemented cup showed a poor 13-year survival rate of 68% (95% CI 59-78) with aseptic loosening as endpoint. However, when endpoint was defined as any revision (including exchange of liner), the 10-year survival rates of all brands of cup except Harris-Galante II declined to under 80%.

INTERPRETATION

Modern second-generation uncemented stems, with proximal circumferential porous- or HA-coating, seem to be a good choice for young patients with primary OA. Similarly, modern press-fit porous- and HA-coated cups appear to have good endurance against aseptic loosening in these young patients. However, liner revisions were common; thus, survival rates of uncemented cups were unsatisfactorily low. Polyethylene wear and unfavorable locking mechanisms between the metal shell and the polyethylene liner and their sequelae remain matters of concern in this young and active group of patients.

Comparison of the uncemented Cone and the cemented Bimetric hip prosthesis in young patients with osteoarthritis: an RSA, clinical and radiographic study

BACKGROUND

There is no consensus as to whether uncemented or cemented femoral stems should be used in younger patients. We compared the uncemented Cone stem to the cemented Bimetric stem in young patients with osteoarthritis.

PATIENTS AND METHODS

We randomized 45 relatively young patients (< 65 years old, mean age 54 years) with osteoarthritis to either an uncemented Cone stem or a cemented Bimetric stem. All patients were followed for 2 years. Outcome was assessed by the Merle d'Aubigné score, conventional radiography and repeated radio-stereometric analysis (RSA). We also followed 81 Cone stems for 8 (7-12) years with revision as endpoint.

RESULTS

The clinical outcome was excellent. No patient had postoperative thigh pain. The migration was small. The Bimetric stem was stable during the whole observation period, while the Cone stem subsided and rotated to retroversion during the first 3 months post-operatively, and then remained stable. In the follow-up study of 81 Cone stems, 1 stem was revised.

INTERPRETATION

We conclude that both the cemented Bimetric stem and the uncemented Cone stem are stable and give excellent clinical results after 2 years in relatively young patients with osteoarthritis. Although designed for CDH hips, the Cone stem appears to be suitable also for patients with osteoarthitis.

In vitro fatigue behaviour of a cemented acetabular reconstruction

In this study, a hemi-pelvis of composite sawbone was implanted with a Charnley cup using a conventional bone cement and the acetabular replacement was tested under constant amplitude cyclic loads, simulating the maximum hip contact force during normal walking. The damage development in the reconstruction was detected and monitored using CT scanning at regular test intervals, verified by microscopy post testing. Three identical experimental results showed that extensive debonding at the bone-cement interface occurred around the dome region after 20 million cycles.

Outcome of an acetabular design with hydroxyapatite coating on a rough substrate

Outcomes of hydroxyapatite-coated cups have not been as consistently successful as outcomes of hydroxyapatite-coated stems; therefore, we studied a newer generation acetabular design with a plasma-sprayed hydroxyapatite coating on an arc-deposited rough titanium substrate. Our objective was to determine whether clinical and radiographic outcomes would be better than reported for earlier-generation designs. Ninety consecutive hips in 85 patients implanted with this design were followed up prospectively for 2 to 5 years after surgery. Hip scores improved from a preoperative mean of 59 (+/- 12) to final followup mean of 91 (+/- 12). One hip was revised for recurrent dislocation. No hips were revised for aseptic loosening. No cup had complete continuous radiolucent lines. Incomplete lucent lines were noted on early postoperative radiographs. With followup, radiolucent line length decreased by a mean 32% and radiolucent line density increased by 9%. Mean polyethylene linear and volumetric head penetration rates were 0.17 (+/- 0.16) mm/year and 73 (+/- 70) mm/year, respectively. Head penetration rates were higher in men. No other factor (age, body weight, cup abduction, or anteversion angle) correlated with head penetration rate. Our study presents encouraging short-term results. Improvement in radiolucent lines suggests a beneficial effect of hydroxyapatite coating on osseointegration of the cup.

LEVEL OF EVIDENCE

Therapeutic study, Level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.

Porous-coated anatomic uncemented total hip arthroplasty. A 10-17-year follow-up

A total of 91 PCA total hip arthroplasties were analysed with a mean follow-up of 13.5 years. Thirty-one cups and six stems were revised. If the patients excluded from the follow-up study are included (113 hips), the cumulative probability of having revision of any prosthetic component for any cause was 16.0% (0.1%-31.9%) at 14 years in the "best case" scenario. Thigh pain (17 hips) was correlated with unstable fixation. Radiographic loosening occurred in 21 cups and 12 stems. Cup loosening was related to acetabular polyethylene wear equal to or more than 2mm per year and also to cup size and thereby polyethylene thickness. Stem loosening was related to poor femoral canal filling. Fifty hips had femoral osteolysis which was related to polyethylene wear of more than 2 mm, poor femoral filling and unstable fixation. (Hip International 2005; 15: 78-84).

Clinical and radiological results of hydroxyapatite-coated acetabular cups

We prospectively studied a consecutive series of 60 primary total hip arthroplasties in 52 patients. All patients had a hydroxyapatite-coated hemispherical acetabular cup (OCTOFIT). Mean patient age was 52.5 (34-73) years. In 38 hips, a 28-mm and in 22 hips a 32-mm diameter cobalt-chrome femoral head was used. We could follow 53 hips for a mean of 81 (28-125) months. Four cups were revised because of osteolysis, and in another six cups, slight osteolysis without migration was seen. The average annual linear wear rate was 0.05 mm (+/-0.05) for 28-mm heads and 0.16 mm (+/-0.09) for 32-mm heads (p<0.0001). Survivorship analysis predicted a survival rate of 86+/-6.7% at 10 years.

Investigation of interfacial strength and its structure on the development of a new design of UHMWPE acetabular component

Previous studies associated with the development of a new ultra-high-molecular-weight polyethylene (UHMWPE) acetabular component have shown high interfacial tensile strengths through chemical and mechanical bonds between virgin UHMWPE or polymethylmethacrylate (PMMA) and PMMA/methylmethacrylate (MMA) monomer treated UHMWPE. Along with the interfacial strength, the mechanism of interfacial strength development has been investigated, correlating the interfacial strength to its structure, with the different molding temperatures or amount of PMMA in the treated UHMWPE. Of three different fracture patterns-adhesive, mixed, and cohesive-most fractures occurred in the mixed or cohesive mode, indicating either a strong interface or a weak bulk phase. Load-displacement plots from the interfacial tensile tests represented two distinct fracture patterns, suggesting the nature of interfacial structure. Comparison of theoretical and real interfacial strength showed a close match between the two strengths for the interface between PMMA and treated UHMWPE, but a large difference for the interface between UHMWPE and treated UHMWPE. This result hints that although the PMMA/treated UHMWPE interface develops its interfacial strength in a relatively simple mechanism of direct chemical bonds, the UHMWPE/treated-UHMWPE interface builds its strength in a complex way.

Measurement of bone defects adjacent to acetabular components of hip replacement

Computed tomography can assist in the detection of periprosthetic osteolysis, but it has not been used to measure the actual volume of bone defects adjacent to hip replacement components because of the scanning artifact caused by metal. The aim of the current study was to develop a spiral computed tomography technique that provides precise and reliable volumetric measurement of bone defects adjacent to uncemented metal-backed acetabular components. Computed tomography scans were taken of small and large defects of known volume created in the ilium in a bovine hemipelvis and a pelvis from a cadaver. Scans were analyzed by two independent observers. The computed tomography operating conditions were determined that enabled volumetric measurements and that were accurate to within 96% for small and large defects and precise to greater than 98% for small and large defects. This computed tomography technique has the capability to measure accurately and precisely the volume of bone defects in the ilium adjacent to metal-backed acetabular components. This technique has clear advantages over plain radiographs. It will allow investigation of the natural history of osteolytic lesions, enhance preoperative planning, and improve monitoring of the outcomes of treatments of osteolysis.

Two different cementless femoral components in primary total hip arthroplasty

The results of first (51 Harris-Galante stems with an average follow-up of 12.3 years) and second generation (53 MultiLock stems with an average of 6.4 years) cementless femoral stems in total hip replacement were analysed. Ten Harris-Galante stems were revised (9.8% at 8 years and 22.8% at 13 years) and one unstable MultiLock stem (2.6% at 8 years). Thirty-seven Harris-Galante and 45 MultiLock stems were osseo-integrated. Femoral osteolysis was seen in 21 Harris-Galante (26.6% at 8 years and 43.7% at 13 years) and in 3 MultiLock stems (8.0% at 8 years). At intermediate follow-up, second generation stems show less bone remodelling changes than first generation stems at the same interval. Distal osteolysis and pronounced stress-shielding have not been encountered in second generation stems. (Hip International 2002; 12: 289-302).

The fate of revised uncemented acetabular components in patients with rheumatoid arthritis

The results of patients with rheumatoid arthritis who had revision hip arthroplasty have been studied infrequently. The purpose of this study was to review the authors' clinical and radiographic experiences and outcomes with revision hip arthroplasty. Revision total hip arthroplasties were done on 28 patients (30 hips). All hips had morselized bone grafting and four hips had bulk allografts for segmental defects. The mean age of the patients at the time of surgery was 50 years (range, 20-74 years). Patients were followed up for 4 to 15 years (mean, 7 years). At the latest followup, 14 hips (13 patients) of the 30 hips (47%) had good and excellent Harris hip score ratings. Mechanical failures included six hips (five patients) that had revision arthroplasty and two hips (two patients) that had resection arthroplasty. Six other hips (five patients) had poor Harris hip score ratings. The Kaplan-Meier survivorship curve for failure of the acetabular component revealed an 89% chance of survivorship curve for failure of the acetabular component revealed an 89% chance of survival at 60 months and a 44% chance of survival at 108 months. Based on the results of this study, revision hip arthroplasty for acetabular loosening with a cementless acetabular prosthesis has a low rate of success in patients with rheumatoid arthritis.

Locking mechanism failure in the Harris-Galante porous acetabular component associated with recurrent hip dislocation

In this review of longitudinal studies of the Harris-Galante porous acetabular component, 20% of all revisions were caused by failure of the polyethylene liner locking mechanism. We report 2 cases of locking mechanism failure in the Harris-Galante porous acetabular component presenting with recurrent dislocation. Broken tines from the acetabular locking mechanism were found embedded into the polyethylene liners in both cases. In a 79-year-old woman with recurrent dislocation, the polyethylene liner and femoral head were replaced, and the acetabular component was revised. In a 74-year-old man with chronic recurrent dislocation, the polyethylene liner and femoral head were replaced, but the acetabular component was preserved. Appropriate treatment for locking mechanism failure with a well-fixed acetabular component depends on many factors, and further long-term data are needed.

Primary total hip arthroplasty using a grit-blasted, press-fit femoral prosthesis.Long-term results with survivorship analysis

BACKGROUND

This report presents the initial experience with the use of a grit-blasted, press-fit femoral prosthesis.

METHODS

The first 300 consecutive primary total hip arthroplasty procedures using a collarless, three-dimensional tapered, straight, titanium alloy stem with a grit-blasted surface (performed in 299 patients) were evaluated with independent clinical and radiographic follow-up examinations up to sixteen years. Eight different types of acetabular components, including a cementless all-polyethylene socket in 80 percent of the cases, were used. Radiographic evaluation, performed by an independent observer using a zonal analysis method, included assessment of component migration, Enghs implant-bone femoral fixation score, implant-bone demarcations, and periprosthetic osteolysis. The average duration of long-term radiographic follow-up was 12.6 years (range; 10 to 16 years).

RESULTS

At last examination only five hips were lost to follow-up and 69 patients were deceased. The overall mechanical failure rate (i.e. unstable with or without revision) of the femoral component was 2 percent. The femoral revision rate was 7 percent (two hips for aseptic loosening, five hips for septic loosening, and twelve hips with osseointegrated stems for severe progressive femoral osteolysis) and the acetabular revision rate was 27 percent (revised for either socket migration or progressive peri-acetabular osteolysis or both). Survivorship, based on any revision (femoral or acetabular) was 89 percent at ten years and 62 percent at fourteen years; survivorship of the femoral component was 95 percent at ten years and 90 percent at fourteen years. The incidence of femoral periprosthetic osteolysis, by radiographic examination at ten years or more was 47 percent, including 12 hips (5 percent) with distal endosteal osteolysis. Femoral implant-bone fixation was stable, bone-ongrowth in 97 percent; stable, fibrous-fixation in 1 percent, and unstable, fibrous-fixation in 2 percent of the cases.

CONCLUSIONS

The grit-blasted, press-fit, collarless, tapered femoral component continued to per-form well clinically and radiographically up to sixteen years of follow-up despite the challenging environment of periprosthetic osteolysis associated with the acetabular component design. The high incidence of failure among the cementless all-polyethylene sockets was not unexpected and the use of this acetabular implant was discontinued in 1985. While considered a "first-generation" cementless stem, this implant is still in use virtually without design modifications. This study demonstrates the durability of the results of the grit-blasted femoral component and indicates that such an implant offers a viable alternative for fixation without bone cement. (Hip International 2002; 2: 55-72).

Surgical approaches for osteoarthritis

Patients with osteoarthritis (OA) often benefit from properly performed surgical procedures. However, the scientific database from studies investigating appropriate timing of surgery, patient morbidity, quality of life before and after the intervention, and cost utility of different procedures is insufficient. In order to allow a fair allocation of resources in future health care systems, randomized controlled trials (RCTs) with defined entry criteria, sufficient number of patients, and valid outcome measures should be performed for different surgical approaches. They should especially include control groups with conservative treatment in order to allow an evidence based comparison between different therapeutic approaches. At present, however, optimal management of OA as a dynamic disease process must include a combination of conservative as well as operative treatment modalities. In case of malalignment, instability and intra-articular causes of mechanical dysfunction, correction of these abnormalities and relief of symptoms can be achieved with properly indicated and performed osteotomies. Debridement by arthroscopy and arthotomy probably does not alter the natural history of OA and true clinical outcomes are difficult to determine, but it can provide transient relief of symptoms. Joint replacement has to be considered for refractory pain associated with disability and radiological deterioration. As the pre-operative functional status seems to influence the outcome not only in joint replacement but also in joint-preserving osteotomies, the indication for these procedures might be expanded in the future.

The Harris-Galante total hip arthroplasty: a minimum 8-year follow-up study

A total of 93 Harris-Galante Porous I (HGP- I) prostheses were analyzed with a mean follow-up of 10.2 years. Thigh pain (28 hips) correlated with unstable fixation (P<.005), female gender (P<.045), young age (P<.05), poor distal femoral fill (P<.002), subsidence (P<.0001), and osteolysis (P<.05). Thirteen stems and 6 metallic shell cups were revised. Kaplan-Meier analysis showed 13-year survival rates of 92.5% +/- 5.8% for the metallic shell cup, 79.7% +/- 13% for the HGP-I cup, and 76.3% +/- 14.0% for the stem. Five polyethylene liners were changed because of wear >1 mm. Radiographic loosening occurred in 8 cups. Radiographic bone ingrowth was present in 54 stems, stable fibrous fixation was present in 24 stems, and unstable fixation was present in 15 stems. The mean polyethylene wear was 0.17 mm/y. Eleven hips (11.8%) had acetabular osteolysis, and 24 (25.8%) had femoral osteolysis, the latter being more frequent in unstable stems (P<.007). The HGP-I metallic cup shows better clinical and radiographic results than the stem, which frequently is associated with pain, unstable fixation, and osteolysis. Excessive polyethylene wear is frequent.

Correlation of wear debris-induced osteolysis and revision with volumetric wear-rates of polyethylene: a survey of 8 reports in the literature

This survey focused on clinical reports of polyethylene wear and osteolysis in total hip replacements. With regard to documentation of clinical wear-rates, 57 publications were reduced to an analysis of 8 reports of THR series, including the incidence of osteolysis. A direct correlation was found among volumetric wear-rates, incidence of osteolysis and revision rates in THR concepts of the 1983-1987 era. As volumetric wear rate increased, the incidence of osteolysis and revision rates increased. With regard to our grading system for volumetric wear, with follow-up in the 4-15 year range, osteolysis was rare in group A (wear = 0-80 mm3/year), ranging from 6% to 31% in group B (wear 40-80 mm3/year) and from 21% to 100% in group C (wear > 140 mm3/year). With regard to cup design, the optimal low-wear group had mainly cemented polyethylene cups with 22 and 28 mm head sizes. The mid-wear group B had metal-backed cemented and uncemented cups, with 28 mm head size, and the high-risk group C had only uncemented, metal-backed cups, with the highest wear in the 32 mm head size. Less than 10 years of follow-up did not distinguish adequately between different designs of THR, except in a few cases which had early failures due to material or design deficiencies. Overall, the cemented all-polyethylene cup combined with the smaller ball head proved to be better.