To Cement or Not? Five-Year Results of a Prospective, Randomized Study Comparing Cemented vs Cementless Total Knee Arthroplasty.

BACKGROUND: The optimal mode of fixation in total knee arthroplasty is a continuing subject of debate. METHODS: Previously, we reported 2-year results for this prospective, randomized trial. Knee Society Scores, Oxford scores, and pain visual analog scales were collected pre-operatively and post-operatively. Minimum 5-year follow-up has been obtained with radiographic analysis for 85 patients. RESULTS: Mean Knee Society Scores and Oxford scores and patient-reported outcomes were similar in both groups. Each group had 1 additional revision, but neither was related to implant fixation. Survivorship with revision as an endpoint was equivalent (95.9% and 95.3%, P = .98). There was no significant difference in radiolucencies observed between groups (P = .10), all were non-progressive. CONCLUSION: Cementless and cemented total knee arthroplasty had equivalent patient-reported outcomes and survivorship at midterm follow-up. Updates are planned at 10 and 15-year intervals to observe long-term modes of failure between these 2 methods of fixation.

Otto Aufranc Award: Crosslinking Reduces THA Wear, Osteolysis, and Revision Rates at 15-year Followup Compared With Noncrosslinked Polyethylene.

BACKGROUND: Crosslinked polyethylene (XLPE) liners used for primary THA have demonstrated lower wear rates than noncrosslinked, conventional polyethylene (CPE) liners through the first decade of clinical service. However, little high-quality evidence is currently available regarding the second decade performance of these implants and it remains uncertain whether the onset of osteolysis has simply been delayed or if the wear associated with XLPE liners will remain low enough that osteolysis will not occur. It is also unknown how the potential reductions in wear and osteolysis will influence long-term revision rates. QUESTIONS/PURPOSES: Do patients who underwent THA with XLPE liners demonstrate (1) a lower rate of revision for wear-related complications; (2) a reduced wear rate; and (3) a lower frequency of osteolysis compared with those with CPE liners? METHODS: Over an 18-month period from 1999 to 2000, 226 patients who had 236 primary THAs consented to participate in a randomized controlled trial conducted at one institution. To be eligible for intraoperative randomization, patients had to be implanted with a 28-mm cobalt-chrome alloy femoral head, a 4-mm lateralized liner, and the same cup and stem design. Six patients with six THAs were excluded intraoperatively because they did not receive study components for reasons unrelated to the liner material. The remaining 230 THAs among 220 patients were randomized to XLPE liners or CPE liners. The mean age at surgery was 62 ± 11 years and there were no differences in age, gender, or body mass index among the groups. There was no differential loss to followup between the study groups; among patients not known to be deceased or having undergone revision, minimum 14-year radiographic followup is available for 85 THAs including 46 with XLPE and 39 with CPE liners. Polyethylene wear was measured radiographically using Martell's Hip Analysis Suite and areas of osteolysis were evaluated before revision or at most recent followup. Revision rates at 15 years using reoperation for any reason and revision for wear or osteolysis were calculated using cumulative incidence considering patient death as a competing risk. RESULTS: The cumulative incidence of revision at 15 years using reoperation for wear-related complications as an endpoint was lower in the XLPE group than the CPE group (0%, 95% confidence interval [CI], 0%-0% versus 12%, 95% CI, 7%-19%; p < 0.001). Among unrevised THAs with minimum 14-year radiographic followup, the mean steady-state linear wear rate for THAs with XLPE liners was lower than the mean linear wear rate for the THAs with CPE liners (0.03 ± 0.05 versus 0.17 ± 0.09 mm/year; mean difference, 0.14; 95% CI, 0.11-0.17; p < 0.001). Osteolysis of any size was noted among 9% (four of 46) of the hips in the XLPE group and 46% (18 of 39) of the hips in the CPE group (odds ratio, 0.19; 95% CI, 0.07-0.51; p < 0.001). CONCLUSIONS: This randomized study with followup into the second decade demonstrated reductions in revision, wear, and osteolysis associated with the use of XLPE. The low wear rates and absence of any mechanical failures among the XLPE liners at long-term followup affirm the durability of these components that did not incorporate antioxidants. Although osteolysis has not been eliminated, it occurs infrequently and has not caused any clinical problems to date. LEVEL OF EVIDENCE: Level I, therapeutic study.

No Difference in Reoperations at 2 Years Between Ceramic-on-metal and Metal-on-metal THA: A Randomized Trial.

BACKGROUND: Hard-on-hard bearings for total hip arthroplasty continue to warrant analysis even though crosslinked polyethylene is performing very well. Ceramic-on-metal (CoM) has low in vitro wear and did well in an early clinical trial. We report on a prospective, randomized, multicenter investigational device trial comparing CoM with metal-on-metal (MoM). QUESTIONS/PURPOSES: (1) Is there a difference in the number or type of revisions comparing CoM with MoM? (2) Are cobalt and chromium metal levels different for CoM and MoM THA? METHODS: Between August 2005 and October 2006, of 1015 patients screened, 390 patients were enrolled at 11 centers and randomized to 194 CoM and 196 MoM bearings. There was no difference in the preoperative patient demographics between the study groups. Mean followup was 50 months (range, 22-75 months). Seventy-two patients from two centers had metal level analysis. RESULTS: With the numbers available, there was no difference in the proportion of patients undergoing revisions between the MoM and the CoM cohorts (MOM: 3% [six of 196]; COM: 1.5% [three of 194]; p = 0.50). Four MoM revisions were unrelated to the bearing surface. Two had bearing surface-related reoperations, one for an aseptic lymphocyte-dominated vasculitis-associated lesion and one for elevated metal levels with acetabular malposition. None of the CoM revisions were related to the bearing surface. The metal level analysis revealed that in contrast to the CoM, the MoM bearing group had increasing values of erythrocyte and serum cobalt from 1 to 5 years (CoM erythrocyte 0.45-0.55 ppb, p = 0.11 and CoM serum 0.88-0.85, p = 0.55, and MoM erythrocyte 0.32-0.51 ppb, p < 0.01 and MoM serum 0.65-1.01 ppb, p < 0.01). In addition, the MoM cobalt levels in erythrocytes and serum at 5 years were more variable than at 1 year (erythrocyte interquartile range [IQR], 0.26-0.44 to 0.31-1.21 ppb and serum IQR, 0.42-0.80 to 0.64-2.20 ppb, p < 0.02 for both). CONCLUSIONS: Although both bearings performed well at short-term followup, the CoM bearing group had no wear-related revisions and maintained consistently low metal levels. The MoM cobalt elevations may be important considering recent reports of taper corrosion. This CoM bearing was approved by the FDA but withdrawn from the market because of low sales. If it were available, the authors would not use CoM until long-term data were available. The bearing would have to outperform crosslinked polyethylene because it is unlikely that CoM metal levels will return to normal. LEVEL OF EVIDENCE: Level I, therapeutic study.

To Cement or Not? Two-Year Results of a Prospective, Randomized Study Comparing Cemented Vs. Cementless Total Knee Arthroplasty (TKA).

The optimal mode of fixation in total knee arthroplasty (TKA) is a subject of debate. We enrolled 100 TKA patients randomized to cemented or cementless fixation. Knee Society Scores (KSS), Oxford scores and pain visual analog scales (VAS) were collected pre-operatively and post-operatively. Two-year follow-up was obtained for 93 patients. The mean VAS trended higher for the cementless group at 4 months (P=0.06). At 2 years, the KSS functional scores, Oxford scores, and self-reported questions for satisfaction, less pain and better function were similar but the cemented group had higher KSS clinical scores (96.4 vs. 92.3, P=0.03). More radiolucencies were seen in cementless knees (P<0.001). The cementless group had one revision for instability and one cemented knee was revised for infection. Cementless TKA showed equivalent survivorship (revision for any reason as the endpoint) compared to cemented TKA at this early follow-up. Close monitoring of radiolucencies is important with continued follow-up.

A prospective, randomized study of cross-linked and non-cross-linked polyethylene for total hip arthroplasty at 10-year follow-up.

In 1999, our institution initiated a prospective study to compare the outcome of total hip arthroplasty patients randomized to either non-cross-linked liners or polyethylene liners that were cross-linked with 5.0 Mrad of gamma-irradiation and heat treated to eliminate free radicals. Among 230 randomized THAs, 13 have had reoperations, and 31 patients with 32 THAs died with less than 9-year follow-up. Follow-up for the remaining 185 THAs averaged 10.0 ± 1.8 years. There have been 9 wear-related liner exchanges among the non-cross-linked group and none among the cross-linked group. Using revision for wear-related complications as an endpoint, survivorship at 10-years was 94.7 ± 4.6% for non-cross-linked and 100% for cross-linked (P = .003). Among unrevised hips, the mean linear wear rate was 0.22 mm/yr for non-cross-linked and 0.04 mm/yr for cross-linked (P < .001). The incidence of clinically important osteolysis with an area of at least 1.5 square centimeters among unrevised hips was 22% for non-cross-linked and 0% for cross-linked (P < .001).

Results of prospective, randomized clinical trials comparing standard and high-flexion posterior-stabilized TKA: a focused review.

High-flexion total knee arthroplasty (TKA) designs have been available for several years for patients desiring a greater postoperative flexion. We conducted a focused review on published results of prospective, randomized clinical trials that compared a standard posterior-stabilized TKA with a high-flexion posterior-stabilized TKA design. Follow-up ranged from 1 to 2.7 years. None of the articles included in the review showed a statistical difference between the standard and high-flexion designs in clinical flexion or range of motion. Mean postoperative flexion ranged from 106° to 130° for the standard design and 110° to 128° for the high-flexion design. Based on currently available literature, high-flexion cruciate-substituting TKAs do not appear to provide increased flexion in the short term. The downsides of these designs, such as increased cost, increased bone resection, and early femoral loosening, need to be weighed against the potential long-term improvement in polyethylene wear due to increased conformity in high flexion. Continued follow-up to document these findings will be important.

Prospective randomized comparison of high-flex and standard rotating platform total knee arthroplasty.

We sought to determine if the rotating platform (RP) high-flex design provides improved flexion compared with the standard RP total knee. A total of 142 patients were randomized to receive an RP flex (RP-F) or RP TKA. Supine flexion was measured with a goniometer and lateral x-ray. There was no difference in flexion measured at any interval between groups (1-year clinical flexion RP, 124.0°; RP-F, 124.2°; P = .949; 1-year x-ray flexion RP, 117.9°; RP-F, 117.6°; P = .985). There was no difference between groups comparing the improvement from preoperative to 1-year postoperative flexion (RP-F, 5.2°; RP, 4.1°; P = .580). There were 13 patients with postoperative patellar crepitus, with more in the RP-F group (RP-F, 11 patients [16.7%]; RP, 2 patients [3.2%]; P = .017). Owing to these results, coupled with the increased bone resection and higher cost, we no longer routinely use the RP-F design.

Detection of periprosthetic infections with use of ribosomal RNA-based polymerase chain reaction.

BACKGROUND: Previously described molecular biology techniques used to detect periprosthetic infections have been complicated by false-positive results. We have reported the development of a messenger RNA (mRNA)-based procedure to reduce these false-positive results. The limitations of this procedure are the lack of a universal target and reduced sensitivity due to a low concentration of bacterial mRNAs in test samples. The objective of the present study was to determine whether reverse transcription-quantitative polymerase chain reaction (RT-qPCR) using universal primers can be used to detect the more abundant bacterial ribosomal RNA (rRNA) as an indicator of periprosthetic infection. METHODS: Serial dilutions of simulated synovial fluid infections were analyzed with rRNA RT-qPCR to determine the detection limit of this assay. Escherichia coli cultures treated with gentamicin were analyzed with RT-qPCR over a twenty-day time course to determine the degradation of rRNA as compared with the decrease in the viable cell count as determined by means of cell plating. As a proof of concept, group-specific polymerase chain reaction primers were developed for Streptococcus species and were tested against fifteen orthopaedically relevant organisms to show the potential for speciation with this assay. Sixty-four patients with a symptomatic effusion at the site of a total knee arthroplasty were enrolled, and complete patient information was documented in a prospective manner. Synovial fluid analysis with rRNA RT-qPCR was performed in a blind fashion. RESULTS: The rRNA RT-qPCR assay was able to detect as few as 590 colony forming units/mL of Staphylococcus aureus and 2900 colony forming units/mL of Escherichia coli. The rRNA RT-qPCR signal closely followed cell death, pointing to its potential use as a viability marker. Three group-specific primer sets correctly identified their intended targets without amplifying closely related species. Clinically, the test correctly identified all six patients with a confirmed infection and all fifty patients who clearly did not have an infection. Eight patients had some laboratory or clinical signs of infection, but their status could not be confirmed. Infection was indicated by rRNA RT-qPCR in three of these patients who had elevated synovial fluid white blood-cell counts but negative results on culture. For statistical purposes, all patients who were categorized as indeterminate were considered to have an infection for the purpose of analysis, for a prevalence of 22% in this cohort. CONCLUSIONS: With respect to current diagnostic tests, rRNA-based RT-qPCR demonstrated 100% specificity and positive predictive value with a sensitivity equivalent to that of intraoperative culture. The RT-qPCR signal followed bacterial culture trends but exhibited detectable level for seven days after sterilization, allowing for the detection of infection after the antibiotic administration. These findings indicate that rRNA RT-qPCR is a sensitive and reliable test that retains the universal detection and speciation of DNA-based methods while functioning as a viability indicator.

2008 John Charnley award: metal ion levels after metal-on-metal total hip arthroplasty: a randomized trial.

UNLABELLED: Metal-on-metal bearing total hip arthroplasty is performed more commonly than in the past. There may be manufacturing differences such as clearance, roughness, metallurgy, and head size that affect performance. In a prospective, randomized trial, we compared 2-year postoperative ion levels for a 28-mm metal-on-polyethylene bearing with 28-mm and 36-mm metal-on-metal bearings. We measured serum, erythrocyte, and urine ion levels. We observed no difference in the ion levels for the 28-mm and 36-mm metal-on-metal bearings. The ion levels in these patients were lower than reported for most other metal-on-metal bearings. Although both erythrocyte and serum cobalt increased, erythrocyte chromium and erythrocyte titanium did not increase despite a four- to sixfold serum chromium and a three- to fourfold serum titanium increase. This may represent a threshold level for serum chromium and serum titanium below which erythrocytes are not affected. LEVEL OF EVIDENCE: Level I, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.