Failure of total hip arthroplasty with a precoated prosthesis. 4- to 11-year results

Excellent Long-Term Survival Rate of Polished, Tapered, Cemented Stems in Patients Aged 35 Years or Younger With Avascular Necrosis or Inflammatory Arthritis of the Hip

BACKGROUND

Total hip arthroplasty (THA) for avascular necrosis (AVN) or inflammatory arthritis (IA) comes with a relatively high risk of aseptic stem loosening, especially in young patients. There are limited long-term data on the survivorship of polished, tapered, cemented stems in this population. We therefore performed a single-center retrospective study investigating the survival of this particular stem type in young patients with AVN or IA.

METHODS

All patients aged ≤35 years who had received a THA for AVN or IA operated on by the senior author between 1990 and 2010 at the University Hospitals Leuven were identified. In total, 85 THAs in 62 patients were included. Primary endpoint was revision of the femoral component for aseptic loosening. Secondary endpoints were revision of the acetabular component for aseptic loosening, revision for other reasons, and the presence of radiolucencies around the components.

RESULTS

The mean follow-up for the entire cohort was 18.0 ± 5.3 years (range 8.0-28.9). Taking revision for aseptic loosening as endpoint, the survival of cemented stems was 100% after 15 years and 95.1% after 20 years. Survival of uncemented cups (91.3%) was significantly better than survival of cemented cups (50.3%) after 20 years of follow-up for aseptic loosening. Taking revision for any reason as endpoint, the survival of THAs with uncemented and cemented cups was 90% and 43.1% at 20 years respectively. Radiolucencies developed in the cement mantles around 11 of the 81 nonrevised stems, mainly in zones 1 and 7.

CONCLUSION

In this cohort of young patients with high-risk profiles for aseptic stem loosening, polished, tapered, cemented stems showed excellent long-term survival rates and they therefore remain a viable alternative to uncemented stem designs.

Primary hybrid THA using a polymethyl methacrylate-precoated stem: A single-center experience with a 10-year minimum follow-up

The high failure rate of cemented femoral components in the 1970s facilitated the improvement of the cementing technique and surface finishes such as polymethylmethacrylate (PMMA)-precoated stems, reporting a survival rate of >95% at 10 years from some studies. However, controversy persists regarding whether precoated femoral stems are associated with a longer revision-free prosthesis survival. The purpose of this study was to evaluate the clinical and radiological outcomes of PMMA-precoated femoral stems, and analyze factors associated with implant survival. We retrospectively reviewed 73 primary hybrid total hip arthroplasties performed using PMMA-precoated femoral stems. The mean age of the patients was 61 years. During the mean follow-up period of 13 years, 18 hips (24.7%) underwent aseptic loosening, and all of the loosened stems were subjected to revision surgery 8.8 years (range 4.6-15.5 years) from the index surgery. Younger age and poor cementing were significantly associated with aseptic loosening (P = 0.013 and P < 0.001, respectively). However, the aseptic loosening rate was also high at 13.1% even with a good cementing technique. In conclusion, the PMMA-precoated stem failed to show expected advantages and needs to be replaced with other surface finish stem designs. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1300-1306, 2017.

Massive femoral osteolysis secondary to loosening of a cemented roughened long stem: a case report

The surface finish of a femoral stem plays an important role in the longevity of cemented total hip arthroplasty. In efforts to decrease the rate of aseptic loosening, some prostheses have been designed to have a roughened surface that enhances bonding between the prosthesis and cement, but clinical outcomes remain controversial. We present a rare case of massive osteolysis with extreme femoral expansion that developed after cemented revision total hip arthroplasty. The destructive changes in the femur were attributable to abnormal motion of the stem and were aggravated by the roughened precoated surface of the long femoral component. Revision surgery using a total femur prosthesis was performed because there was insufficient remaining bone to fix the new prosthesis. The surgical technique involved wrapping polypropylene meshes around the prosthesis to create an insertion for the soft tissue, which proved useful for preventing muscular weakness and subsequent dislocation of the hip.

Fifteen-year results of precoated femoral stem in primary hybrid total hip arthroplasty

Background

There has been controversy whether methylmethacrylate precoating of the cemented femoral stem is a solution for aseptic loosening or rather contributes to increased failure rates in cemented total hip arthroplasties.

Methods

On a retrospective basis, we analyzed 76 primary hybrid total hip arthroplasties from 63 patients with precoated, cemented femoral stems between October 1990 and December 1995. The mean age of the patients was 46.8 years (range, 22 to 77 years) with a minimum follow-up of 14 years (mean, 15.5 years; range, 14 to 19.5 years). Third generation cementing techniques were employed in all cases.

Results

Twenty-four out of 76 cases (31.6%) showed aseptic loosening of the femoral stems, of which 23 stems were revised at an average revision time of 8 years (range, 3 to 14.8 years). The main mode of loosening was cement-stem interface failure in 22 hips (91.7%). Twenty-one out of 24 failed hips (87.5%) demonstrated C2 cementing grades (p < 0.001). Kaplan-Meier survivorship analysis using radiographic aseptic loosening of the femoral stem as the endpoint for failure showed survival rates of 76.5% at 10 years (95% confidence interval [CI], 71.4 to 81.6) and 63.2% at 19 years (95% CI, 57.3 to 69.1).

Conclusions

An early failure of the precoated femoral stem in this study was mainly due to an insufficient cementing technique. Achievement of good cement mantle may improve the survival rates.

If hip implant retrievals could speak, what would they tell us?

Hip implant retrieval analysis is the most important source of insight into the performance of new materials and designs of hip arthroplasties. Even the most rigorous in vitro testing will not accurately simulate the behavior of implant materials and new designs of prosthetic arthroplasties. Retrieval analysis has revealed such factors as the effects of gamma-in-air sterilisation of polyethylene, fatigue failure mechanisms of polymethylmethacrylate bone cement, fretting corrosion of Morse taper junctions, third body wear effects of both hard-on-hard and hard-on-soft bearing couples, and the effects of impingement of components on the full spectrum of bearing surfaces, none of which was predicted by pre-implantation in vitro testing of these materials and combinations. The temporal sequence of the retrieval process is approximately six years from first implantation through retrieval analysis, laboratory investigation, and publication of results, and thus, in addition to rigorous clinical evaluation, represents the true development and insight cycle for new designs and materials.

Ulnar component surface finish influenced the outcome of primary Coonrad-Morrey total elbow arthroplasty

BACKGROUND

Controversy remains regarding the mechanisms leading to ulnar loosening after elbow replacement. We therefore assessed the loosening rate of the ulnar component as a function of the surface finish of a commonly used implant design.

MATERIALS AND METHODS

This study included 3 groups who received implants with 3 different surface finishes: sintered beads (278 components), polymethylmethacrylate precoating (219 components), and plasma-sprayed beads (205 components).

RESULTS

The 3 groups who received the implants did not differ statistically in age, sex, or underlying diagnosis. The rates of mechanical failure for the sintered, precoated, and plasma-sprayed ulnar components were 6.8%, 12.8%, and 0%, respectively. The 7-year Kaplan-Meier survival rates free of mechanical failure were 93.1% for the sintered-beads group, 83.1% for the precoated group, and 100% for the plasma-sprayed group. Failed precoated ulnar components often failed early and exhibited typical features, including proximal debonding and severe focal or global osteolysis, sometimes leading to periprosthetic insufficiency fractures.

CONCLUSION

Precoating the ulnar component with polymethylmethacrylate can lead to an increased rate of loosening and severe osteolysis. A plasma-sprayed ulnar component is associated with a very low mechanical failure rate with surveillance of less than 10 years.

Functional interface micromechanics of 11 en-bloc retrieved cemented femoral hip replacements

BACKGROUND AND PURPOSE

Despite the longstanding use of micromotion as a measure of implant stability, direct measurement of the micromechanics of implant/bone interfaces from en bloc human retrievals has not been performed. The purpose of this study was to determine the stem-cement and cement-bone micromechanics of functionally loaded, en-bloc retrieved, cemented femoral hip components.

METHODS

11 fresh frozen proximal femurs with cemented implants were retrieved at autopsy. Specimens were sectioned transversely into 10-mm slabs and fixed to a loading device where functional torsional loads were applied to the stem. A digital image correlation technique was used to document micromotions at stem-cement and cement-bone interfaces during loading.

RESULTS

There was a wide range of responses with stem-cement micromotions ranging from 0.0006 mm to 0.83 mm (mean 0.17 mm, SD 0.29) and cement-bone micromotions ranging from 0.0022 mm to 0.73 mm (mean 0.092 mm, SD 0.22). There was a strong (linear-log) inverse correlation between apposition fraction and micromotion at the stem-cement interface (r(2) = 0.71, p < 0.001). There was a strong inverse log-log correlation between apposition fraction at the cement-bone interface and micromotion (r(2) = 0.85, p < 0.001). Components that were radiographically well-fixed had a relatively narrow range of micromotions at the stem-cement (0.0006-0.057 mm) and cement-bone (0.0022-0.029 mm) interfaces.

INTERPRETATION

Minimizing gaps at the stem-cement interface and encouraging bony apposition at the cement-bone interface would be clinically desirable. The cement-bone interface does not act as a bonded interface in actual use, even in radiographically well-fixed components. Rather, the interface is quite compliant, with sliding and opening motions between the cement and bone surfaces.

The condition of the cement mantle in femoral hip prosthesis implantations--a post mortem retrieval study

Despite numerous studies demonstrating the characteristics of the optimal cement mantle in joint replacement, the clinical state of the cement mantle is rarely assessed. A random sample of 214 cemented implanted femoral hip components was retrieved post mortem from Hamburg, Germany, and sectioned to investigate the quality of the cement mantle. The most common observation made in at least one measured region per retrieval was debonding (82% of stems), followed by a thin cement mantle (74%), stem-bone contact (48%), soft tissue at the stem interface (44%), no cement-bone interdigitation (30%), a gap at the stem interface (28%), voids in the cement (22%) and cracks and blood in the cement mantle (<10%). 21% of stems demonstrated complete debonding of the interface. However, distributions of all other defects were local, with less than 10% of stems demonstrating any imperfection in more than 21% of the regions assessed. No progressive damage was observed with implantation duration. The results suggest that current implantation technique may be adequate for proper implant function over the service life in the older patient population. However, for younger and more active patients, perfection of the cementation technique is crucial, particularly in modern implant systems such as resurfacing. The frequency of almost all defects could be further reduced by careful implantation technique, providing the increased service life necessary for the ever younger, more physically demanding, patient population.

The design features of cemented femoral hip implants

We undertook a review of the literature relating to the two basic stem designs in use in cemented hip replacement, namely loaded tapers or force-closed femoral stems, and the composite beam or shape-closed designs. The associated stem fixation theory as understood from in vitro studies and finite element modelling were examined with reference to the survivorship results for each of the concepts of fixation.

It is clear that both design principles are capable of producing successful long-term results, providing that their specific requirements of stem metallurgy, shape and surface finish, preparation of the bone and handling of the cement are observed.

Pin-on-disc evaluation of self-reinforced composite poly(methyl methacrylate) for total joint replacements

Femoral components of hip replacements are commonly anchored in the femur with bone cement or poly(methyl methacrylate) (PMMA). Wear or fracture of bone cement can lead to loosening of the femoral component, which drastically affects the success and longevity of hip replacements. Self-reinforced composite PMMA (SRC-PMMA) has been previously developed for potential use, as a precoat material for hip replacements. The composite consists of high strength fibers that have been shown to have greatly improved mechanical properties over bulk PMMA. The goal of this work was to examine SRC-PMMA for improved wear properties, as a function of processing temperature. Pin-on-disc tests were used to characterize and rank the wear rates of SRC-PMMA and PMMA. Composites made with higher processing temperatures had significantly lower wear rates than do PMMA at a significance level of p < or = 0.05. The lowest wear rate was 8.2 microg/m, at a processing temperature of 136 degrees C, compared to a wear rate for PMMA of 13.3 microg/m. At the lowest processing temperature (105 degrees C), a wear rate higher than PMMA was found, and failure was dominated by fiber delamination. In the more completely processed samples (122 degrees C < or = T < or = 150 degrees C), wear rates were equivalent to or better than PMMA, and smoother and more homogenous wear was noted in wear tracks. Fatigue cracks were prominent at higher processing temperatures or when the wear pin was riding orthogonal to fibers. Wear particles were collected and examined. Wear particle diameter and aspect ratio showed no correlation to processing temperature, but were similar to particles retrieved from human tissue samples.

Polished vs rough femoral components in grade A and grade C-2 cement mantles

The ideal surface for cemented femoral components remains controversial. Six polished stems were compared with 6 rough stems both with good cement mantle and also with poor cement mantles in a stair-climbing model. With good cement mantles, both the polished and the rough stems were loose by 6 million cycles. However, none were loose by radiographic criteria. With the poor cement mantle, both stems became loose earlier and developed more micromotion, the polished stems having significantly higher and earlier motion than the rough. Radiographic evidence of debonding was not visible until the stems had motion of more than 2,000 microm. In the presence of a good cement mantle in this laboratory model there was no significant difference in the development of micromotion under fatigue stair-climbing conditions between a polished or grit-blasted femoral component. However, in the presence of a poor cement mantle, the polished components had earlier and higher micromotion. This study reinforces the importance of centralization and cement technique, particularly if using a polished surface finish.

Precooling of the femoral canal enhances shear strength at the cement-prosthesis interface and reduces the polymerization temperature

Preheating of the femoral stem in total hip arthroplasty improves the cement-prosthesis bond by decreasing the interfacial porosity. The main concern, however, is the potential thermal osteonecrosis because of an increased polymerization temperature. In this study, the effects of femoral canal precooling on the characteristics of the cement-stem interface were evaluated in an experimental model for three test conditions: precooling of the femoral canal, preheating of the stem (44 degrees C), and a control in which stems were inserted at room temperature without thermal manipulation of the implant, cement, or bone. Compared to the control group, precooling of the femoral canal and preheating of the stem had similar effects on the cement-stem interface, with greater interfacial shear strength and a reduced porosity. Femoral canal precooling also produced a lower temperature at the cement-bone interface. No difference was found in the ultimate compressive strength of bone cement for the three preparation conditions. Based on this laboratory model, precooling of the femoral canal could improve shear strength and porosity at the stem-cement interface, minimize thermal injury, and maintain the mechanical strength of the cement.

High failure rate of a modern, proximally roughened, cemented stem for total hip arthroplasty

The role of surface finish on the survivorship of cemented femoral stems continues to be debated. A total of 34 proximally roughened cemented stems were implanted in 33 consecutive patients undergoing total hip arthroplasty by a single surgeon. An alarmingly high failure rate was observed, prompting a retrospective chart review, analysis of radiographs, and evaluation of retrieved stems and pathological specimens. Nineteen patients were available with more than two years follow-up. Of these 19 patients, nine stems had failed (47%) due to severe osteolysis and stem loosening. Failures were significantly more common in the male gender (p<0.005), and young (p=0.05), tall (p<0.002), and heavy patients (p<0.004). All failed revised hips showed severe metallosis, with both gross and microscopic evidence of metallic shedding from the stems. Our findings suggest that this proximally roughened stem is susceptible to early failure. Failure is characterized by stem debonding, subsidence within the cement mantle, shedding of metallic and cement particles due to fretting, and rapidly progressive osteolysis. These findings have been observed with other rough surface finish cemented stems.

Favourable mid-term results of the VerSys CT polished cemented femoral stem for total hip arthroplasty

We evaluated the mid-term clinical and radiographical performance of a cohort of patients who underwent primary total hip replacement with a modern, forged cobalt-chrome, polished cemented femoral stem with proximal and distal centralisation. Sixty-seven patients with 73 hybrid total hip replacements were followed up clinically and radiographically for an average of 6.1 years (4-8.5). No patient was lost. No hips required revision, and all stems are radiographically well-fixed. Four hips developed localised osteolysis: one at the site of a proximal periprosthetic fracture, another at the level of a lateral femoral window of a previous core decompression, the third at the mid third of the femoral component, and the fourth on the greater trochanter, associated with accelerated polyethylene wear. This modern polished stem yielded excellent, predictable clinical and radiographic results at an intermediate follow-up.

The effect of surface finish and of vertical ribs on the stability of a cemented femoral stem: an in vitro stair climbing test

The search for improved femoral fixation in cemented total hip arthroplasty is ongoing. Two design variables, surface finish and stem contour, were evaluated. Sixteen titanium femoral stems of one design were cemented into fiberglass femora. One half of the components had a polished surface and the rest had a roughened finish. Within each group, 4 stems had vertically oriented ribs on the proximal portion and 4 did not. Micromotion was measured in a stair climbing simulator with loading to a joint reaction force of 200 kg for 6 million cycles. Micromotion increased throughout the course of the experiment. Stems with a polished surface had significantly higher micromotion. Although stems with ribs had less micromotion compared with those without ribs, this difference was not statistically significant.

Metallic shedding, surface finish changes, and extensive femoral osteolysis in the loose Spectron EF stem

The addition of a proximal rough surface finish in the satin finish Spectron stem (Spectron EF) reportedly does not alter its clinical performance. However, we have revised 15 Spectron EF stems because of aseptic loosening and extensive femoral osteolysis at early and intermediate-term followup, raising a question as to its safety. We sought to determine which interface has aseptic failure, the presence of massive femoral osteolysis, and the consequences of loosening at the implant-cement interface in the implant's surface finish. Fifteen patients with aseptic loosening of a proximal rough surface-finished Spectron EF stem at intermediate-term followup (Group A) were compared with seven patients having revisions of the same stem for infection or recurrent dislocation but without loosening (Group B). Radiographs for Group A showed debonding at the cement-implant interface and stem subsidence in 13 hips, and severe femoral osteolysis in seven, including two pathologic periprosthetic fractures. During revision surgery, all 13 subsided stems showed a metallic stained pseudomembrane and metallic shedding with polishing of the stem surface. None of the patients in Group B who had revision surgery had these changes. Aseptic failure of the Spectron EF stem was characterized by debonding, subsidence, and metallic shedding with concomitant massive femoral osteolysis and metallosis, which is similar to conditions reported for loose, rough cemented stems, but has not been reported for the satin finish Spectron stem.

LEVEL OF EVIDENCE

Therapeutic study, Level III (retrospective comparative study). See the Guidelines for Authors for a complete description of levels of evidence.

The cemented femoral stem: selecting the ideal patient

A woman who is elderly, lightweight, and low demand has traditionally been considered an ideal candidate for a cemented femoral stem. Patients who are young, heavy, and high demand have been considered higher risk for failure and, therefore, better suited for cementless femoral stems. However, modern cement techniques and implants have improved outcomes in high-risk cohorts, and stress shielding, thigh pain, and osteolysis have emerged as long-term challenges for cementless femoral stems. Recently reported positive bone remodeling around a cemented, triple-tapered, polished, collarless stem behaving according to the taper-slip philosophy of femoral stem fixation may widen the traditional indications for cemented femoral stems. Paradoxically, patients initially thought to be poor candidates for cemented fixation may benefit most from the long-term bone preservation and positive loading characteristics of this new generation of cemented stem technology.

A rough surface finish adversely affects the survivorship of a cemented femoral stem

To assess the role of surface finish in the survivorship of a cemented femoral stem, we evaluated the midterm clinical and radiographic performances of a cohort of patients who had total hip arthroplasties with two cemented femoral stems that differed only in surface finish. One hundred seventy-five patients [64 total hip arthroplasties with rough, textured stems (radius, 1.75-2.5 microm) and 138 total hip arthroplasties with satin finish, textured stems (radius, 0.5 microm)] were followed up clinically and radiographically for 4-8 years. All surgeries were done by one surgeon using the same surgical technique, acetabular cup, cement type, and cementing technique. The groups had similar demographics, diagnoses, preoperative clinical scores, cement mantle qualities, alignments, and lengths of followup. Seven hips in the rough surface group and none in the satin surface group had aseptic loosening. The femoral bone-cement interface showed progressive radiolucent lines or osteolysis in eight of 64 rough stems and in three of 138 satin stems. A rough, textured stem of this design is more likely to fail at intermediate followup than a satin surface stem. We recommend that the surface of cemented stems should be satin or polished with a radius less than 0.5 microm.

LEVEL OF EVIDENCE

Therapeutic study, Level III-1 (case-control study). See the Guidelines for Authors for a complete description of levels of evidence.

Pre-coated femoral components in hybrid total hip arthroplasty

We present the medium-term results of hybrid total hip arthroplasties using pre-coated stems with a second-generation cementing technique. The 128 hips in 111 patients (18 men and 93 women) were followed up at a mean of 11 years after surgery. The mean age at the time of surgery was 61 years. Both components of one hip were removed at ten months after surgery for infection. None of the other 127 femoral components showed possible, probable, or definite loosening at the most recent follow-up. Five acetabular components were revised for aseptic loosening, recurrent dislocation, or displacement of the polyethylene liner from the metal shell. The mean Harris hip score at follow-up was 84 points. A pre-coated femoral component with a second-generation cementing technique provides good clinical function and survival in the medium term.

Analysis of 16 retrieved proximally cemented femoral stems

Sixteen proximally cemented, collared, and distally splined, Bridge Hip femoral stems with a matte proximal surface and smooth distal surface were retrieved because of loosening. Electron microscopy, with correlated elemental analysis, identified titanium particulate embedded in the internal surface of the cement mantle. Data supported the observations that loosening of the femoral stems was related to proximal debonding at the cement-implant interface, loosening at the proximal cement-bone interface, and inherent rotational instability. Cement-implant interface debonding resulted in the proximally matte femoral stem surface abrading with the opposing cement mantle, resulting in particulate and osteolysis in some cases. Careful consideration of implant design and clinically relevant biomechanical testing protocols should be considered before the clinical introduction of future proximally cemented femoral stems.

Revision total hip arthroplasty with use of a cemented femoral component. Results at a mean of ten years

BACKGROUND

Revision of the femoral component of a total hip replacement with use of cement has been associated with early mechanical failure due to aseptic loosening. The purpose of the present study was to determine the long-term survival after revision of the femoral component with cement and to identify factors that were predictive of failure.

METHODS

The results of 129 revision total hip arthroplasties that had been performed with use of a cemented femoral stem were reviewed to determine component survival. Ninety-seven hips that had been followed for a minimum of five years were included in survival analysis and tests of significance. Harris hip scores were used to quantify clinical outcomes. Clinical and surgical factors were analyzed to determine whether they were predictive of failure.

RESULTS

The mean Harris hip score improved from 52 points preoperatively to 71 points at the time of the most recent follow-up (p < 0.001). The ten-year survival rate was 91% with rerevision of the femoral component because of aseptic loosening as the end point and 71% with mechanical failure as the end point. Patients who were more than sixty years old had greater long-term component survival and less pain than younger patients did (p < 0.05). A good-quality postoperative cement mantle was associated with better long-term radiographic signs of fixation (p < 0.001). Poor femoral bone quality was associated with an increased rate of rerevision for aseptic loosening (p = 0.021).

CONCLUSIONS

Revision with use of a cemented femoral component remains an option for selected patients, with an acceptable ten-year survival rate and fair radiographic evidence of fixation. Our patients had acceptable clinical outcomes at ten years, and few had notable pain. The best results may be achieved in older patients (those who are sixty years old or more) with adequate bone stock who are managed with modern cementing techniques.

Mastering the art of cemented femoral stem fixation

Cemented femoral stem fixation is reproducible and provides excellent early recovery of hip function in patients 60 to 80 years old. The durability of fixation has been evaluated up to 20 years with 90% survivorship. Achieving a uniform cement mantle and minimizing polyethylene wear has been shown to reduce the incidence of fixation failure. This article describes the senior author's (C.S.R.) technique for cemented total hip arthroplasty with particular emphasis on the art of cemented femoral stem fixation and his experience with 3 different cemented stem designs over 30 years. The results of using this cement technique with a modern stem design with a surface roughness of 30 to 40 microinches have produced a 95% survivorship at 10- to 20-year follow-up in patients 60 to 80 years old.

Durability of the cemented femoral stem in patients 60 to 80 years old

The importance of surface roughness and durability of fixation of the cemented femoral stem were examined. Three cohorts of patients approximately 60 to 80 years old, had cemented total hip replacements: Charnley (1978-1983) with first-generation cement technique consisting of canal-plugging and digital packing; Omnifit (1986-1991), and Ranawat-Burstein (R-B) Interlok (1992-1994) with modified third-generation cement technique. Kaplan-Meier survivorships, using failure for all causes (best case) were 90% +/- 5.1% at 20 years for the Charnley 95.1%+/- 3.4% at 15 years for the Omnifit and 99.5% +/- 0.5% at 9 years for the R-B Interlok prosthesis. Log rank test with paired data showed no significant differences between the groups for mechanical failure as an end point. Comparisons of survivorship curves for failure from all causes showed significant differences between the Charnley compared with the Omnifit and Interlok series respectively, with no significant differences between the Omnifit and R-B Interlok series. The cemented femoral stem, with a good cement mantle and surface roughness ranging from 30 to 150 microinches, did not show any significant differences in mechanical failure. Other variables such as stem centralization and low polyethylene wear need additional evaluation in survivorship of cemented total hip replacements.

Fifteen-year survivorship of a collarless, cemented, normalized femoral stem in primary hybrid total hip arthroplasty with a modified third-generation cement technique

This prospective review aimed to evaluate 15-year survivorship of the collarless, third-generation cemented, normalized, Omnifit (Osteonics, Allendale, NJ) femoral stem in hybrid total hip arthroplasty (THA). Between January 1986 and June 1990, a single surgeon prospectively implanted 250 consecutive hybrid THAs (215 patients) using a modified third-generation cement technique in selected patients. A Harris-Galante (I or II) (Zimmer, Warsaw, IN) cementless shell with modular polyethylene (4150 resin) liners gamma-sterilized in air were implanted. Kaplan-Meier survivorship of the femoral or acetabular component with mechanical failure (revision for aseptic loosening) as the end-point was 100% +/- 0% at 15 years. Wear couple exchange and bone grafting was performed in 1 case (0.4%) for progressive acetabular osteolysis. This report supports femoral component centralization and good cement mantle to ensure durability of the collarless, cemented, normalized femoral stem with a surface roughness of 30-40 microinches.

Effect of bone porosity on the mechanical integrity of the bone-cement interface

BACKGROUND

Osteopenia is one factor that may influence the decision about the type of implant fixation to use in total hip arthroplasty. However, clinical studies generally do not associate the outcome of an arthroplasty with the degree of osteopenia. The mechanical integrity of the cement fixation of an implant may be affected by the relative degree of osteopenia, which could account for some of the variable long-term results after total hip arthroplasty performed with cement. The purpose of this study was to determine the effects of bone porosity, trabecular orientation, cement pressure, and cement penetration depth on fracture toughness at the bone-cement interface.

METHODS

Trabecular bone from the proximal part of bovine femora was used with a single brand of commercial acrylic bone cement to form compact-tension interface specimens representing a range of bone porosities, orientations, and cement pressures within a clinically achievable range. All specimens were loaded to failure with use of a servohydraulic testing machine, and fracture toughness at the interface was calculated. After testing, images of a representative sample of specimens were made with use of computed tomography to measure the penetration depth of the cement into the bone.

RESULTS

Significant correlations were found between fracture toughness and bone porosity, trabecular orientation, and cement pressure, with bone porosity having the strongest effect (p < 0.000015). Examination of the computed tomographic images also showed a significant correlation between fracture toughness and maximum cement penetration depth (p < 0.033), as well as significant partial correlations between maximum and mean penetration depth and bone porosity (p < 0.0037 and p < 0.0028).

CONCLUSION

The fracture resistance of the bone-cement interface is greatly improved when the ability of the cement to flow into the intertrabecular spaces is enhanced.

A prospective randomized trial of cemented femoral components with polished versus grit-blasted surface finish and identical stem geometry

This randomized, prospective study compared 2 cemented hip stems that differed only in the surface finish, which was polished or grit blasted. A total of 226 hybrid total hips were evaluated at an average of 4.8 years postoperatively. No stem in either group was loose or revised for aseptic loosening. There was one case of significant distal lysis in the grit-blasted group. There was no statistical difference between polished and grit-blasted stems in incidence of lysis or bone-cement radiolucency. Harris Hip score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and SF-36 analysis showed no difference between groups. In conclusion, when adequate cement mantles are achieved around the femoral component, little difference in construct durability between polished and grit-blasted surface finish components can be detected at 4.8-year follow-up for this stem design.

Use of prepolymerized cement spacers to augment the femoral component in revision total knee arthroplasty: a clinical outcome report and laboratory experiment

A technique for revision total knee arthroplasty managing posterior femoral condylar bone loss with prepolymerized polymethyl methacrylate cement spacers as augments to the femoral component is described in 10 consecutive cases. The maximum follow-up time is 63 months. This method allows for maintenance of the posterior joint line, which in turn facilitates appropriate flexion-extension gap balancing. The cement spacers are inexpensive compared with metal augments. An experimental study confirms that the cement spacers produce a chemical and physical bond with fresh cement. This eliminates the risk of particulate debris production between the cement augment and the fixation cement. Although the cement spacers have been produced to match one manufacturer's implants, they could be applied to other knee systems.

Primary hybrid total hip arthroplasty with a roughened femoral stem: integrity of the stem-cement interface

One hundred and two consecutive cemented femoral stems were evaluated in 92 patients at an average 9-year follow-up and a minimum 5-year follow-up (range, 5-14 years). The stem used was cobalt chromium with a collar, normalization steps, and a roughened surface (Ra 40); the stem was inserted using contemporary cementing techniques. This series demonstrated a femoral component aseptic loosening rate of 2.0% and a femoral component survivorship of 97.2 +/- 2.0% at 10 years. One of 2 failed stems was revised at 95 months for failure at the cement-bone interface. The second failed stem showed failure at the cement-bone interface with incomplete debonding radiographically at 65 months. The remaining femoral components did not demonstrate any evidence of debonding at the stem-cement interface. These results compare favorably with other series of cemented femoral stems, as well as with those with a polished surface.

Precoated femoral component in primary hybrid total hip arthroplasty: results at a mean 10-year follow-up

This is a mid-term report at 10 years' mean follow-up of a study of a precoated femoral component used in primary hybrid total hip arthroplasty (THA). Of an original cohort of 98 hips undergoing THA performed by one surgeon, 75 hips in 65 patients (mean age, 67 years) were prospectively followed up for 7 to 12 years (mean, 10 years). All hips had the same porous coated acetabular component and a precoated femoral component (with an oval cross-section) implanted using Simplex bone cement (Howmedica, Rutherford, NJ). There was no femoral component loosening or revision. Two acetabular components in patients with rheumatoid arthritis and protrusio acetabulae had radiographic loosening; however, only 1 was symptomatic and was revised. Acetabular osteolysis was seen in 4 hips (5.3%), and minor femoral osteolysis was seen in 3 hips (4%). Used in this manner in this patient population, precoating is not detrimental to successful fixation at 10 years' mean follow-up of primary hybrid THA.

Early failure of precoated femoral components in primary total hip arthroplasty

BACKGROUND

In an effort to decrease the rate of aseptic loosening, certain cemented femoral components were designed to have a roughened or textured surface with a methylmethacrylate precoating. Reports differ as to whether this step has increased or decreased the rate of failure. This study was designed to evaluate this issue.

METHODS

Five hundred and fourteen hips treated with a cemented Harris Precoat stem (Zimmer, Warsaw, Indiana) were evaluated clinically and radiographically and compared with 254 hips treated with an uncoated Harris Design-2 stem (Howmedica, East Rutherford, New Jersey). Prostheses that had been removed at revision were examined. The cementing and surgical techniques were identical and the population demographics were similar for these two groups.

RESULTS

The mean durations of follow-up were 8.4 and 13.5 years for the Precoat and uncoated Design-2 stems, respectively. At those times, at least forty-nine (9.5%) of the 514 Precoat components and at least ten (3.9%) of the 254 uncoated Design-2 stems had failed (p = 0.006). Five Precoat stems fractured, and no uncoated Design-2 stems fractured. Component failure was associated with use in young, active, heavy men with a diagnosis of avascular necrosis and generally with the use of smaller components. The cementing technique was satisfactory in the majority of the patients, and there were no qualitative differences in cementing technique between the hips that failed and those that did not. The mechanisms of failure of the Precoat prostheses included bone-cement loosening, focal osteolysis, stem fracture, and prosthesis-cement debonding. Fractures of smaller components occurred as a result of fatigue failure and were associated with good distal fixation but proximal stem loosening.

CONCLUSIONS

The rate of failure of roughened, precoated, cemented femoral components was considerably higher and occurred earlier than that of femoral components that were neither textured nor precoated with methylmethacrylate. Younger patients with avascular necrosis had a higher risk of failure; however, this factor alone did not completely explain the differences in outcome between these two components. The causes of aseptic loosening are multifactorial and may be related to component design and size as well as to precoating and surface finish.

A critical assessment of proximal macrotexturing on cemented femoral components

We analyzed the cement-metal interface of 3 different types of femoral components that had proximal macrotexturing after in vitro insertion and after fatigue testing designed to produce debonding and micromotion. These components were compared with clinical retrieval specimens. The cement did not flow into the macrotexturing; rather, hollow, brittle volcanoes or calderas were formed. These fragile protrusions of cement become worn down or abraded by debonded components. This abrasion of cement may contribute to the early and aggressive osteolysis seen in some of these early failures with proximal macrotextured components. The formation of these volcanos and calderas can be aborted by placing bone-cement onto the macrotexturing before stem insertion. This simple technique allows the macrotexturing to be filled with cement.

The Frank Stinchfield Award. Influence of cement technique on the interface strength of femoral components

The optimal surface finish for polymethylmethacrylate cemented femoral components remains controversial. Concerns about early debonding of the prosthesis-cement interface have led surgeons to use roughened surfaces to enhance the cement-prosthesis bond. However, loosening of roughened stems is associated with the generation of excessive wear debris. The purpose of the current study was to determine whether the time to cementation influenced the cement-prosthesis bond of four roughened cobalt chrome surfaces (60 grit-blasted, 10 grit-blasted, 10 grit-blasted with polymethylmethacrylate precoating, glass bead-blasted) and one polished cobalt chrome surface. Fixation strength was assessed using mechanical pushout and tensile testing. Roughened and polymethylmethacrylate precoated surfaces had significantly greater tensile and shear strengths at early cementation times compared with polished surfaces. However, roughened components had significant decreases in tensile and shear strengths as cementation time increased from 2 to 4 minutes and 2 to 6 minutes. In contrast, tensile and shear strengths for the polished surface were significantly lower than for the roughened surfaces and did not change with longer cementation times. When using a roughened or precoated cemented femoral component, the surgeon should consider cementing earlier with wetter cement to maximize the cement-prosthesis bond. When implanting a polished femoral component, it is preferable that the cement is doughy, because the cement-prosthesis bond is not influenced by the wetness of the cement and it is easier to maintain the orientation of the femoral component.

Early failure of modern cemented stems

In the late 1970s, improved cement technique was introduced in an attempt to address the problem of early cemented stem loosening. Subsequently, numerous centers reported stem survival rates of >95% beyond 10 years. Long-term cemented stem fixation was believed widely to be consistently obtainable in most patients. Despite the widespread clinical success of these early cemented stems, numerous changes were introduced in stem design and cement technique. In more recent years, a surprising number of series of early failures of cemented stems have been reported. Some designs consistently have had a high early failure rate. Others have failed infrequently, but the failures have occurred early and with extensive osteolysis. Numerous causes have been proposed, including poor cement technique, undersized broaches, increased stem offset, decreased stem length, rough surface finish, and circular stem cross-section. Failures often are multifactorial and defy a simple explanation based on a single parameter. Results of cemented stems are more variable than previously appreciated. There are nuances of cemented stem design, cement technique, and patient selection that can lead to early failure and that are not understood completely at present. Given the availability of many cemented designs with proven records of clinical success, new design features should be introduced prudently with extensive premarket testing, limited clinical release, and careful postmarket surveillance.

The significance of stem-cement loosening of grit-blasted femoral components

This study analyzed 15 patients who underwent revision for loosening at the stem-cement interface. The femoral components were from the same manufacturer and had grit-blast roughened surfaces. An apparent radiographic deficiency in the cement mantle was present in at least one zone in 1 3 patients. In 9 of 12 patients with localized osteolysis, the osteolysis developed in a zone with an apparent radiographic cement mantle defect. Loosening occurred due to tension failure of the stem-cement interface followed by axial subsidence and movement into relative retroversion. Motion between the stem and the cement mantle fueled an abrasive wear mechanism between the roughened metal surface and the cement mantle, generating excessive metal and cement particles that gained access to endosteal bone via defects in the cement mantle and resulting in localized osteolysis. Although the roughened surface played a central role in these failures, it is unlikely the layer of polymethylmethacrylate (precoat) played a role in the mechanism of failure. In some cases, debonding occurred as a result of tension failure of the metal-precoat interface. In others, tension failure occurred within the cement mantle, leaving the precoat and some cement from the mantle on the stems. There was no difference in the mechanism of failure of stems with precoat proximally compared to stems with precoat proximally and distally. One stem had no precoat; findings in this patient were indistinguishable from the others. The significance of debonding depends on the surface roughness of the stem. Debonding carries a poorer prognosis with a rougher stem surface because of abrasive wear with the generation of numerous metal and cement particulates, which can lead to rapid osteolysis if there are cement mantle defects. Stems with a higher metal-cement bond strength may require a higher quality cement mantle for long-term success.

Hybrid total hip arthroplasty with a precoated offset stem. Four to nine-year results

BACKGROUND

Use of modern cementing techniques for fixation of femoral components in total hip arthroplasty has had excellent clinical and radiographic results in most patients. However, several authors have described early loosening of femoral components with roughened and precoated finishes. The purpose of this study was to examine the performance of the precoated Iowa stem, which has increased offset, and to compare the results with those of another cemented precoated femoral component with standard offset used at our institution.

METHODS

We carried out a prospective analysis of 102 primary hybrid total hip arthroplasties (a cementless acetabular component and a cemented femoral component) performed with use of the Iowa femoral component in ninety-five patients at our institution. The Iowa stem was used in hips that required greater offset than is available with standard stems as determined by preoperative templating. The average age of the patients at the time of the index procedure was sixty-nine years. Sixteen patients (seventeen hips) died before the forty-eight-month minimum follow-up period had elapsed. Two patients were lost to follow-up, and radiographic follow-up was incomplete for one. The mean duration of clinical and radiographic follow-up of the remaining eighty-two hips in the seventy-six surviving patients was sixty-five months (range, forty-eight to 104 months).

RESULTS

The average preoperative Harris hip score of 47 points (range, 16 to 69 points) improved to an average of 87 points (range, 24 to 100 points) at the time of the review. Two hips underwent femoral component revision. Four femoral stems were radiographically loose at an average of thirty-four months. Femoral osteolysis was seen in five hips (6 percent) at an average of fifty-four months postoperatively. No acetabular component was revised because of aseptic loosening. According to Kaplan-Meier analysis, the seven-year survival rate, with an end point of femoral revision, osteolysis, or stem debonding, was 90.6 percent (95 percent confidence interval, 0.87 to 0.94).

CONCLUSIONS

The prevalence of revision, osteolysis, and loosening after total hip arthroplasty with the Iowa femoral component at our institution was higher than that seen in our series of Harris Precoat stems, which had a survival rate of 98.4 percent (95 percent confidence interval, 0.97 to 1.00) at ten years with the same end points. The design of the Iowa stem may make it difficult to achieve a good cement mantle, and, in combination with the geometry and increased offset of the stem, may compromise the long-term survival of this cemented femoral component.

A stem design change to reduce peak cement strains at the tip of cemented total hip arthroplasty

A series of 3-dimensional finite element models was created to assess different designs of the tip of the stems of cemented femoral components of total hip arthroplasty that would decrease the peak axial tensile cement strains developed near the tip. Features of stem design that would facilitate positioning the femoral component in a neutral position centered in uniform cement mantle of adequate thickness also were evaluated. These studies showed that a stem that had a narrow tip profile that would accept an externally applied polymethyl methacrylate centralizer shaped similar to a napkin ring and had a gradual transition zone to join the body of the implant achieved these objectives. Such a combination resulted in the reduction of the peak axial strains to less than half the magnitude of the peak strains around a conventional tip (830 vs 1,868 microstrain). The reduction in peak axial strains was to one third the magnitude of the strains developed adjacent to a stem with a hole drilled into the tip to accept the commonly used fin-type polymethyl methacrylate centralizer (830 vs 2,466 microstrain). These goals were achieved because a stem that is designed to accept a napkin ring-style centralizer i) has a lower bending stiffness at the tip of the implant, ii) allows room for a thicker cement mantle, and iii) avoids creating a stress riser adjacent to the edge of the drill hole. The peak cement strains adjacent to a stem of this design are well below the endurance limit of cement as long as the transition zone where the narrow tip meets the body of the implant is gradual.

Thin cement mantle and osteolysis with a precoated stem

The radiographic and clinical results of 55 hips (52 patients) implanted with the Harris precoat hip prosthesis using second generation cementing technique were investigated in this study. All metal backed sockets were fixed with cement. The preoperative diagnoses were osteoarthritis secondary to dysplastic hips in 42 patients, primary osteoarthritis in six, rapidly destructive coxarthrosis in five, and osteonecrosis of the femoral head in two. The average age of patients at the time of surgery was 67 years. The average duration of followup was 8 years. The rates of aseptic loosening and osteolysis in the femoral side were 5.5% (three hips) and 12.7% (seven hips), respectively. Three sockets were loosened, and no osteolysis was detected in the acetabular side. The mantle of cement in the femur was graded using the criteria described by Mulroy et al. Twenty-seven of 55 (49%) hips had regions with a thin cement mantle less than 1 mm in thickness or a defect in the cement mantle. Osteolysis was detected in seven of the 27 (26%) hips. Locations of osteolysis were coincidental with those of thin cement mantle or defect with the exception of one hip. This study clearly shows that a thin cement mantle less than 1 mm in thickness and a defect in the cement mantle lead to osteolysis.

Long-term results of cemented femoral stems with roughened precoated surfaces

Several recent articles have raised the question that rough surfaces with or without precoating may contribute to the loosening of cemented femoral stems. In this article the author collates selected reports of several different cemented femoral stem designs that have rough surfaces which have shown excellent long term results. Femoral stem loosening is generally multifactorial. It often is difficult to separate the effect of stem design or other changes from the effect of surface finish. Many rough surfaced cemented femoral stems have served well for decades. It is important to analyze all the pertinent factors in cases of early loosening.