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

Biomechanical Performance of the Cemented Hip Stem with Different Surface Finish

The integrity of the cemented fixation interface is responsible for the long-term longevity of artificial hip prostheses. Metallic stems with roughened surfaces are considered to provide stronger adhesion with cement. However, clinical studies have reported that roughened stems show a lower survival rate than polished stems. These studies clearly reveal that the causes of artificial stem loosening are very complicated and multifaceted. Therefore, this study was conducted to investigate the mechanical effect of stem surface finish in cemented hip replacement. To accomplish this, a series of cement–metal specimens were tested configurations to assess the mechanical characteristics of the cement–metal interface specimens. A finite elemental model of cemented femoral prostheses was then created, in which the cement–stem interface was assumed to be in different bonding states according to the experimentally measured interface properties. The failure probabilities of the cement mantle and cemented interface under physiological loadings were evaluated. Experimental results indicate that the polished metal produced higher interfacial tensile and lower shearing strengths than the roughened metal. The polished stems were predicted to induce a lower failure probability of cement mantle and higher integrity of the cement–stem interface when compared to the roughened stem. Overall, current results provide significant evidence to support the clinical outcomes of cemented hip prostheses with different stem surface finishes.

Polished Cemented Femoral Stems Have a Lower Rate of Revision Than Matt Finished Cemented Stems in Total Hip Arthroplasty: An Analysis of 96,315 Cemented Femoral Stems

BACKGROUND

Matt and polished femoral stems have been historically grouped together in registry assessment of the outcome of cemented femoral stems in total hip arthroplasty. This is despite differences in the mode of fixation and biomechanics of loading. The aims of this study are to compare the survivorship of polished tapered stems with matt finished cemented stems.

METHODS

Data on primary total hip arthroplasty undertaken for a diagnosis of osteoarthritis from September 1999 to December 2014 were included from a National Joint Registry. Revision rates of the 2 different types of femoral components were compared.

RESULTS

There were 96,315 cemented femoral stems included, of which 82,972 were polished tapered and 13,343 matt finish. The cumulative percent revision at 14 years of polished stems was 3.6% (3.0-4.2) compared to 4.9% (4.1-5.7) for matt finish stems. Polished tapered stems had a significantly lower revision rate of femoral revision (hazard ratio 0.56, P < .001). This difference is evident in patients aged <75, and becomes apparent in the mid-term and continues to increase with time. Aseptic loosening accounts for 75% of revisions of matt finish stems compared to 20% for polished tapered stems.

CONCLUSION

Although both polished and matt finish stems have excellent early to mid-term results, the long-term survivorship of polished stems is significantly better, with aseptic loosening becoming an issue with matt finish stems. In the future reports of cement fixation for femoral stems may benefit from separate analysis of polished and matt finish.

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.

Total hip replacement and surface replacement for the treatment of pain and disability resulting from end-stage arthritis of the hip (review of technology appraisal guidance 2 and 44): systematic review and economic evaluation

BACKGROUND

Total hip replacement (THR) involves the replacement of a damaged hip joint with an artificial hip prosthesis. Resurfacing arthroplasty (RS) involves replacement of the joint surface of the femoral head with a metal surface covering.

OBJECTIVES

To undertake clinical effectiveness and cost-effectiveness analysis of different types of THR and RS for the treatment of pain and disability in people with end-stage arthritis of the hip, in particular to compare the clinical effectiveness and cost-effectiveness of (1) different types of primary THR and RS for people in whom both procedures are suitable and (2) different types of primary THR for people who are not suitable for hip RS.

DATA SOURCES

Electronic databases including MEDLINE, EMBASE, The Cochrane Library, Current Controlled Trials and UK Clinical Research Network (UKCRN) Portfolio Database were searched in December 2012, with searches limited to publications from 2008 and sample sizes of ≥ 100 participants. Reference lists and websites of manufacturers and professional organisations were also screened.

REVIEW METHODS

Systematic reviews of the literature were undertaken to appraise the clinical effectiveness and cost-effectiveness of different types of THR and RS for people with end-stage arthritis of the hip. Included randomised controlled trials (RCTs) and systematic reviews were data extracted and risk of bias and methodological quality were independently assessed by two reviewers using the Cochrane Collaboration risk of bias tool and the Assessment of Multiple Systematic Reviews (AMSTAR) tool. A Markov multistate model was developed for the economic evaluation of the technologies. Sensitivity analyses stratified by sex and controlled for age were carried out to assess the robustness of the results.

RESULTS

A total of 2469 records were screened of which 37 were included, representing 16 RCTs and eight systematic reviews. The mean post-THR Harris Hip Score measured at different follow-up times (from 6 months to 10 years) did not differ between THR groups, including between cross-linked polyethylene and traditional polyethylene cup liners (pooled mean difference 2.29, 95% confidence interval -0.88 to 5.45). Five systematic reviews reported evidence on different types of THR (cemented vs. cementless cup fixation and implant articulation materials) but these reviews were inconclusive. Eleven cost-effectiveness studies were included; four provided relevant cost and utility data for the model. Thirty registry studies were included, with no studies reporting better implant survival for RS than for all types of THR. For all analyses, mean costs for RS were higher than those for THR and mean quality-adjusted life-years (QALYs) were lower. The incremental cost-effectiveness ratio for RS was dominated by THR, that is, THR was cheaper and more effective than RS (for a lifetime horizon in the base-case analysis, the incremental cost of RS was £11,284 and the incremental QALYs were -0.0879). For all age and sex groups RS remained clearly dominated by THR. Cost-effectiveness acceptability curves showed that, for all patients, THR was almost 100% cost-effective at any willingness-to-pay level. There were age and sex differences in the populations with different types of THR and variations in revision rates (from 1.6% to 3.5% at 9 years). For the base-case analysis, for all age and sex groups and a lifetime horizon, mean costs for category E (cemented components with a polyethylene-on-ceramic articulation) were slightly lower and mean QALYs for category E were slightly higher than those for all other THR categories in both deterministic and probabilistic analyses. Hence, category E dominated the other four categories. Sensitivity analysis using an age- and sex-adjusted log-normal model demonstrated that, over a lifetime horizon and at a willingness-to-pay threshold of £20,000 per QALY, categories A and E were equally likely (50%) to be cost-effective.

LIMITATIONS

A large proportion of the included studies were inconclusive because of poor reporting, missing data, inconsistent results and/or great uncertainty in the treatment effect estimates. This warrants cautious interpretation of the findings. The evidence on complications was scarce, which may be because of the absence or rarity of these events or because of under-reporting. The poor reporting meant that it was not possible to explore contextual factors that might have influenced study results and also reduced the applicability of the findings to routine clinical practice in the UK. The scope of the review was limited to evidence published in English in 2008 or later, which could be interpreted as a weakness; however, systematic reviews would provide summary evidence for studies published before 2008.

CONCLUSIONS

Compared with THR, revision rates for RS were higher, mean costs for RS were higher and mean QALYs gained were lower; RS was dominated by THR. Similar results were obtained in the deterministic and probabilistic analyses and for all age and sex groups THR was almost 100% cost-effective at any willingness-to-pay level. Revision rates for all types of THR were low. Category A THR (cemented components with a polyethylene-on-metal articulation) was more cost-effective for older age groups. However, across all age-sex groups combined, the mean cost for category E THR (cemented components with a polyethylene-on-ceramic articulation) was slightly lower and the mean QALYs gained were slightly higher. Category E therefore dominated the other four categories. Certain types of THR appeared to confer some benefit, including larger femoral head sizes, use of a cemented cup, use of a cross-linked polyethylene cup liner and a ceramic-on-ceramic as opposed to a metal-on-polyethylene articulation. Further RCTs with long-term follow-up are needed.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42013003924.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

The effect of a collar and surface finish on cemented femoral stems: a prospective randomised trial of four stem designs

PURPOSE

The optimal design for a cemented femoral stem remains a matter of debate. Over time, the shape, surface finish and collar have all been modified in various ways. A clear consensus has not yet emerged regarding the relative merits of even the most basic design features of the stem. We undertook a prospective randomised trial comparing surface finish and the effect of a collar on cemented femoral component subsidence, survivorship and clinical function.

METHODS

One hundred and sixty three primary total hip replacement patients were recruited prospectively and randomised to one of four groups to receive a cemented femoral stem with either a matt or polished finish, and with or without a collar.

RESULTS

At two years, although there was a trend for increased subsidence in the matt collarless group, this was not statistically significant (p = 0.18). At a mean of 10.1 years follow-up, WOMAC scores for the surviving implants were good, (Range of means 89-93) without significant differences. Using revision or radiographic loosening as the endpoint, survivorship of the entire cohort was 93 % at 11 yrs, (CI 87-97 %). There were no significant differences in survivorship between the two groups with polished stems or the two groups with matt stems. A comparison of the two collarless stems demonstrated a statistically significant difference in survivorship between polished (100 %) and matt (88 %) finishes (p = 0.02).

CONCLUSIONS

In the presence of a collar, surface finish did not significantly affect survivorship or function. Between the two collarless groups a polished surface conferred an improved survivorship.

The Basis CL cemented femoral stem: results after 8.9 years follow-up

This prospective study was conducted to demonstrate that the matte-finish Basis CL cemented endoprosthetic stem delivers good qualitative results after 10 years. Between January and December 1999, 205 consecutive hips (201 patients; 74.5 ± 6.8 years at surgery) underwent primary total hip arthroplasty with the Basis CL and the same acetabular cup (RM Classic cup) at a single institution. Follow-up data at 10 years was available for 120 hips (average follow-up of 8.9 years, ±2.9). Mean Harris Hip Score improved from 39.5 ± 16.8 at baseline to 75.9 ± 16.7 at 10-year follow-up (p<0.001). Four hips required revision during the study: three for infection and one for pain. There were no cases of aseptic loosening, implant migration, or stem fracture. Cumulative survival at 10 years was 97.4% with the endpoint of revision for any reason. In conclusion, results with the matte-finish cemented Basis CL indicated that it was safe and effective after medium-term follow-up.

Displacement of a cemented femoral stem during attempted closed reduction of a dislocated total hip arthroplasty

Displacement of a cemented femoral stem during attempted closed reduction of a dislocated total hip arthroplasty has been anecdotally described in the literature. All these reports involved use of cemented, highly polished, tapered stems. We report, the first to our knowledge, a case of displacement of a cemented, textured femoral stem, during attempted closed reduction. The case is being reported not only for its rarity but also to alert treating surgeons of this devastating complication which can expose the patient to the risks of open surgery. Gentle reduction, using the gravity method of Stimpson, under fluoroscopy control, may be safer and prevent this complication from occurring. If the cement mantle is intact, cement-within-cement is a reliable, quick, and simple technique to overcome this difficult problem.

Eleven-year follow-up of second-generation metal-on-metal total hip arthroplasty

PURPOSE

To investigate the cause of failure in matte-surface cemented stems in second-generation metal-on- metal total hip arthroplasty (THA).

METHODS

Records of 26 men and 11 women (39 hips) aged 29 to 72 years who underwent primary cementless THAs by a single surgeon using second-generation metal-on-metal prostheses and were followed up for a mean of 122 (range, 120-141) months were reviewed. Two types of femoral stems were used: a cementless Ti-alloy stem (n=21) and a matte-surface, iron-based alloy, cemented stem (n=18). Clinical outcomes were measured using the Harris hip score. Radiographs were assessed for stem loosening and osteolysis. Patient activity levels were graded. Surfaces of the retrieved femoral stems and periprosthetic tissue samples were examined. Metallic and cement particles were studied. Hypersensitivity to metal was tested.

RESULTS

None of the cementless stems were revised; no osteolysis or stem loosening occurred. In contrast, 7 of 18 matte-surface cemented stems were revised owing to stem loosening or osteolysis. Periprosthetic tissues revealed abundant cement-related particles; 90% were zirconium oxides but a few were iron particles. Histological examination of periprosthetic tissues showed perivascular infiltration of lymphocytes and macrophages containing tiny foreign materials. Metal hypersensitivity was not associated with aseptic loosening.

CONCLUSION

Metal-on-metal THA with cementless components could be recommended for young, active patients to prevent wear and osteolysis. The matte-surface cemented stem is more likely to fail owing to friction during the earlier stage and cement-related biological processes during the later stage.

Random damage and characteristics of debris particles are two important and yet ignored factors in the mechanical integrity of the stem-cement interface of a total hip replacement: influence of the surface finish of the metal stem

The importance of the conditions at the stem-cement interface in cemented total joint replacements (THRs) with regard to the in vivo longevity of the implant is well recognized. In the present study, we used a simplified model of one part of a cemented THR (alloy rectangular beam bonded to rectangular cement plate) to study the influence of surface finish of the alloy beam (stem) on two measures of the evolution of random damage at the alloy beam-cement plate interface (stem-cement interface), under quasi-static direct shear load. Three surface finishes of the beams were used: satin-finish, grit-blasted, and plasma-sprayed. The random damage events were monitored from the emitted acoustic signals, with the two measures computed from these signals being the intensity of random damage events (IRDE) and the mean damage event energy (MDEE). Large number of random damage events (higher values of IRDE and low value of MDEE) occurred with grit blasted specimens, suggesting a high probability for the generation of debris particles at the interface. These findings, in conjunction with details on the size and shape of the debris particles, obtained using scanning electron microscopy, lead to the suggestion that satin-finish stems are desirable for use in cemented THRs.

In vitro measurement of interface micromotion and crack in cemented total hip arthroplasty systems with different surface roughness

BACKGROUND

Cemented stems with various surface roughnesses are used in total hip arthroplasty. However, it is not clear how the surface roughness of the stem affects the longevity of the implant. In this study, we investigated the effect of the stem roughness on the micromotion at the bone-cement and cement-implant interface and investigated cracks in the cement layer through in vitro measurement.

METHODS

Stems with the same shape and material but with different surface roughness (polished with Ra=0.05 microm and matte-finished with Ra=0.83 microm) were tested to measure the interface micromotion using custom-made sensors. The stems were implanted in five paired cadaver femurs and cyclic loading was applied to the femoral head to measure the interface micromotion. After loading, we measured the crack length and calculated the crack length density at the cement layer.

FINDINGS

The difference in the interface micromotion between the polished stem and the rough stem was not significant except at the distal region of the cement-bone interface. More cracks were found at the distal region of the polished stem than at the rough stem. The magnitude of the cement crack length density did not correlate with the interface micromotion.

INTERPRETATION

The results showed that the difference in the roughness between the polished and matte finishes did not significantly affect the micromotion and crack of the interface. However, more cement wear particles were expected in the matte-finished stem.

Mechanical aspects of degree of cement bonding and implant wedge effect

BACKGROUND

The degree of bonding between the femoral stem and cement in total hip replacement remains controversial. Our objective was to determine the wedge effect by debonding and stem taper angle on the structural behavior of axisymmetric stem-cement-bone cylinder models.

METHODS

Stainless steel tapered plugs with a rough (i.e. bonded) or smooth (i.e. debonded) surface finish were used to emulate the femoral stem. Three different stem taper angles (5 degrees , 7.5 degrees , 10 degrees ) were used for the debonded constructs. Non-tapered and tapered (7.5 degrees ) aluminum cylindrical shells were used to emulate the diaphyseal and metaphyseal segments of the femur. The cement-aluminum cylinder interface was designed to have a shear strength that simulated bone-cement interfaces ( approximately 8MPa). The test involved applying axial compression at a rate of 0.02mm/s until failure. Six specimens were tested for each combination of the variables. Finite element analysis was used to enhance the understanding of the wedge effect.

FINDINGS

The debonded stems sustained about twice as much load as the bonded stem, regardless of taper angle. The metaphyseal model carried 35-50% greater loads than the diaphyseal models and the stem taper produced significant differences. Based on the finite element analysis, failure was most probably by shear at the cement-bone interface.

INTERPRETATION

Our results in this simplified model suggest that smooth (i.e. debonded) stems have greater failure loads and will incur less slippage or shear failure at the cement-bone interface than rough (i.e. bonded) stems.

Minimum 10-year survival of Kerboull cemented stems according to surface finish

The optimal surface finish for a cemented THA stem is still debated. We hypothesized surface finish would influence survival of Kerboull cemented hip arthroplasties and a matte finish would have lower survival. We reviewed survival of 433 total hip arthroplasties in 395 patients: 284 consecutive patients (310 hips) were enrolled in a prospective, randomized study of polished (165 hips) or matte finish stems (145 hips) and compared to a historical series of satin stems (123 hips) in 111 patients. The satin and matte finish implants had similar geometry but the polished was quadrangular rather than oval. Finish roughnesses were: polished (radius, 0.04 microm), satin (radius, 0.9 microm), and matte (radius, 1.7 microm). The mean age of the patients at the time of the index arthroplasty was 63.6 years. The survival rate at 13 years, using radiographic loosening as the end point, was 97.3%+/-2.6% for polished stems, 97.1%+/-2.1% for satin stems, and 78.9%+/-5.8% for matte stems. The data suggest survival of Kerboull stems was higher with a polished or satin surface finish than with a matte finish.

LEVEL OF EVIDENCE

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

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.

Ten-year survivorship of rough-surfaced femoral stem with geometry similar to Charnley femoral stem

The aim of this study is to review the 10-year results of 269 cemented total hip arthroplasties performed using the Harvard femoral stem with matte surface finish and Charnley stem-like geometry. This is a retrospective cross-sectional survivorship study. We retrospectively reviewed the results of 269 cemented total hip arthroplasties performed using the Harvard femoral stem in 257 patients (men/women 93:164, mean age 71.2 years) between 1990 and 1994. The median duration of follow-up for the surviving implants was 118 (range 60-129) months. Radiographs were reviewed to evaluate the type of osteoarthritis, cement mantle thickness, alignment of the components, presence of aseptic loosening, and radiolucent lines. Kaplan-Meier survival analysis and Cox proportional hazards analysis were performed to evaluate 10-year survival and the impact of various radiological parameters on the prosthesis survival respectively. Of the 248 eligible patients (260 hips), 6 patients (7 hips) were lost to follow-up, and 67 patients had died at the time of the study; 36 hips (35 patients) underwent revision surgery for aseptic failure (median duration 60 months, range 12-125 months), and 11 hips were revised for septic failure (median duration 24 months, range 10-53 months from the index procedure). The femoral component was revised in all patients, whereas the acetabular component was revised in 27 patients. Ten-year survival for the femoral and acetabular components using aseptic loosening (with and without revision surgery) as an end point was 77.5% (71.5%-83.5%) and 91.1% (87.2%-95%), respectively. Cox regression analysis did not reveal a statistically significant (P > 0.05) effect of various radiological parameters on survival rate. Our results demonstrate that the matte surface finish femoral component (with geometry similar to Charnley femoral component) has less satisfactory long-term survival rate.

Staged bilateral total hip arthroplasty using rough and smooth surface femoral stems with similar design: 10-year survivorship of 48 cases

BACKGROUND

Various studies have reported good long-term results using femoral stems with either smooth or rough surfaces. In this retrospective cross-sectional survivorship study, we reviewed the 10-year results of 51 bilateral staged cemented total hip arthroplasties using the Harvard or the Charnley femoral stems-which have almost similar geometry but a different surface finish.

METHODS

51 patients were reviewed at median interval of 10 (Harvard group) and 11 years (Charnley group) after the primary operation. We evaluated cement mantle thickness, alignment of the components, presence of radiolucent lines, and aseptic loosening. Kaplan-Meier analysis was performed to calculate the survival rate using various endpoints.

RESULTS

8 hips in the Harvard group were revised for aseptic loosening of the femoral component at a median interval of 6.3 years after the primary procedure. 3 hips in the Charnley group were revised for aseptic loosening of the femoral and acetabular components between 10 and 11 years after the primary procedure. The 10-year survival rate for the femoral component using revision surgery for aseptic loosening as an endpoint was 80% (95% CI: 31-42) and 95% (95% CI: 44-47) in the Harvard and the Charnley group, respectively. Cox regression analysis did not reveal any statistically significant effect of various radiographical parameters on the survival rate (p < 0.05).

INTERPRETATION

Our results demonstrate that in the group of patients studied, the femoral stem component with the matt surface finish had less satisfactory 10-year survival than the femoral stem of similar design which had a smooth surface finish.

Fatigue debonding of the roughened stem-cement interface: effects of surface roughness and stem heating conditions

The aim of this study was to determine the effects of cyclic loading on the debond process of a roughened stem-cement interface used in total hip arthroplasty. The specific goals were to assess the effects of two surgeon-controlled variables (stem heating and degree of stem surface roughness) and to determine if an independent finite element-based fracture mechanics model could be used to predict the debond response. A clamped cantilever beam geometry was used to determine the fatigue debond response of the stem-cement interface and was created using an experimental mold that simulated in vivo cementing conditions. A second experiment was performed using a torsion-loading model representative of the stem-cement-bone composite. For both experiments, two stem heating (room temperature and 50 degrees C) and surface roughness conditions (grit blasted: Ra = 2.3 and 5.1 microm) were used. Finally, a finite element model of the torsion experiment with provision for crack growth was developed and compared with the experimental results. Results from both experiments revealed that neither stem preheating nor use of a stem with a greater surface roughness had a marked effect on the fatigue debond response. There was substantial variability in the debond response for all cases; this may be due to microscopic gaps at the interface for all interface conditions. The debond rate from the finite element simulation (10(-7.31) m/cycle) had a magnitude similar to the experimental torsion model (10(-(6.77 +/- 1.25)) m/cycle). This suggests that within the context of the experimental conditions studied here that the debond response could be assessed using a linear elastic fracture mechanics-type approach.

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.