Kory D Charron

Wear rate of highly cross-linked polyethylene in total hip arthroplasty. A randomized controlled trial.

BACKGROUND Highly cross-linked polyethylene was introduced for clinical use in total hip arthroplasty with the expectation that it would exhibit less wear when compared with conventional polyethylene. The purpose of this study was to report the clinical and radiographic results, after a minimum of five years of follow-up, of a randomized, blinded, controlled trial comparing a conventional polyethylene with a first-generation highly cross-linked polyethylene. METHODS One hundred patients were enrolled in a prospective, randomized controlled study comparing highly cross-linked and conventional polyethylene acetabular liners in total hip arthroplasty. Fifty patients were in each group. At the time of follow-up, clinical outcomes were assessed and steady-state femoral head penetration rates (after bedding-in) for each patient were calculated with use of a validated radiographic technique. In addition, a statistical comparison of polyethylene wear between groups was performed with use of generalized estimating equations. RESULTS At a mean of 6.8 years postoperatively, there were no differences between the two polyethylene groups with regard to the Harris hip score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), or Short Form-12 (SF-12) score. The mean femoral head penetration rate in the first through fifth years was found to be significantly lower in the group treated with the highly cross-linked polyethylene (0.003 mm/yr [95% confidence interval, +/-0.027]) than it was in the group treated with conventional polyethylene (0.051 mm/yr [95% confidence interval, +/-0.022]) (p=0.006). Men treated with a conventional polyethylene liner had a significantly higher (p<or=0.012) femoral head penetration rate (0.081 mm/yr [95% confidence interval, +/-0.065]) than both men and women with a highly cross-linked liner (-0.013 mm/yr [95% confidence interval, +/-0.074] and 0.009 mm/yr [95% confidence interval, +/-0.028], respectively). The general estimating equations demonstrated that the group with a highly cross-linked polyethylene liner had a significantly lower femoral head penetration rate than the group with a conventional polyethylene liner (p=0.025), and a significantly higher femoral head penetration rate was demonstrated in men with a conventional polyethylene liner when compared with both men and women with a highly cross-linked liner (p=0.003). CONCLUSIONS At a minimum of five years postoperatively, the steady-state femoral head penetration rate associated with this first-generation highly cross-linked polyethylene liner was significantly lower than that associated with a conventional polyethylene liner. Long-term follow-up is required to demonstrate the clinical benefit of this new material.

Comparing Patient Outcomes After THA and TKA: Is There a Difference?

Both primary total hip (THA) and knee (TKA) arthroplasty relieve pain, restore function, and increase mobility. Despite these successes, there is controversy as to whether THA or TKA provides greater or similar improvement. We therefore compared primary THA and TKA patient results in terms of (1) willingness to have surgery again; (2) WOMAC change score; (3) whether expectations were met; and (4) satisfaction. Patients undergoing primary THA were more willing to undergo their surgery again (THA 96%, TKA 89%), demonstrated greater WOMAC change scores, more frequently reported their expectations were met (THA 78%, TKA 70%), and expressed greater overall satisfaction (THA 89%, TKA 81%). In addition, patients undergoing THA expressed higher satisfaction with pain reduction while performing activities (ie, walking, stairs, and sitting/lying) and their ability to perform daily activities (ie, stairs, transportation, getting up, lying in bed, and light domestic duties) when compared with patients undergoing TKA. Our data suggest primary THA offers superior short-term outcomes when compared with primary TKA.Level of Evidence: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

The John Insall Award: Gender-specific Total Knee Replacement: Prospectively Collected Clinical Outcomes

AbstractGender-specific total knee replacement design is a recent and debated topic. We determined the survivorship and clinical outcomes of a large primary total knee arthroplasty cohort, specifically assessing any differences between gender groups. A consecutive cohort of 3817 patients with 5279 primary total knee replacements (3100 female, 2179 male) with a minimum of 2 years followup were evaluated. Preoperative, latest, and change in clinical outcome scores (WOMAC, SF-12, KSCRS) were compared. While men had higher raw scores preoperatively, women had greater improvement in all WOMAC domains including pain (29.87 versus 27.3), joint stiffness (26.78 versus 24.26), function (27.21 versus 23.09), and total scores (28.35 versus 25.09). There were no gender differences in improvements of the SF-12 physical scores. Men had greater improvement in Knee Society function (22.1 versus 18.63) and total scores (70.01 versus 65.42), but not the Knee Society knee score (47.83 versus 46.64). Revision rates were 10.2% for men and 8% for women. Women demonstrated greater implant survivorship, greater improvement in WOMAC scores, equal improvements in SF-12 scores, and less improvement in only the Knee Society function and total scores. The data refute the hypothesis of inferior clinical outcome for women following total knee arthroplasty when using standard components. Level of Evidence: Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Comparison of Total Hip Arthroplasty Performed with and without Cement: A Randomized Trial

Total hip arthroplasty has been associated with excellent implant survival rates, but debate remains concerning the best fixation method for the components. A randomized controlled trial, which included 250 patients (mean age, sixty-four years) with osteoarthritis who were managed with total hip arthroplasty between October 1987 and January 1992, was conducted to compare the results of fixation with and without cement. Patients were followed for a mean of twenty years (range, seventeen to twenty-one years). Kaplan-Meier survivorship analysis at twenty years revealed significantly lower survival rates for cemented implants as compared with cementless implants. The cementless tapered stem had an extremely good survival rate of 99%. Radiographs showed evidence of mild stress-shielding around 95% of the cemented stems and 88% of the cementless stems; stress-shielding of grade 3 or greater was seen around the remaining 12% of the cementless stems.

Does morbid obesity affect the outcome of total hip replacement?: AN ANALYSIS OF 3290 THRS

We evaluated the outcome of primary total hip replacement (THR) in 3290 patients with the primary diagnosis of osteoarthritis at a minimum follow-up of two years. They were stratified into categories of body mass index (BMI) based on the World Health Organisation classification of obesity. Statistical analysis was carried out to determine if there was a difference in the post-operative Western Ontario and McMaster Universities osteoarthritis index, the Harris hip score and the Short-Form-12 outcome based on the BMI. While the pre- and post-operative scores were lower for the group classified as morbidly obese, the overall change in outcome scores suggested an equal if not greater improvement compared with the non-morbidly obese patients. The overall survivorship and rate of complications were similar in the BMI groups although there was a slightly higher rate of revision for sepsis in the morbidly obese group. Morbid obesity does not affect the post-operative outcome after THR, with the possible exception of a marginally increased rate of infection. Therefore withholding surgery based on the BMI is not justified.

The Fate of the Remaining Knee(s) or Hip(s) in Osteoarthritic Patients Undergoing a Primary TKA or THA

The purpose of this study was to determine the fate of the remaining hip(s) and knee(s) following an initial total hip or knee arthroplasty in 5352 patients with idiopathic osteoarthritis who were followed for a minimum ten years (mean 17.8 ± 5.7 years). Following an initial primary TKA, 46.0% of patients had a contralateral TKA, 2.3% had an ipsilateral THA and 1.3% had a contralateral THA. Following an initial primary THA, 30.5% of patients had a contralateral THA, 6.8% had an ipsilateral TKA and 2.9% had a contralateral TKA. Cox regression analysis demonstrated that BMI was the sole risk factor for a second THA, but both age less than sixty years and a higher BMI were significant factors for patients requiring an additional primary TKA.

Damage of an Oxinium femoral head and polyethylene liner following ‘routine’ total hip replacement

We present a case of early retrieval of an Oxinium femoral head and corresponding polyethylene liner where there was significant surface damage to the head and polyethylene. The implants were retrieved at the time of revision surgery to correct leg-length discrepancy just 48 hours after the primary hip replacement. Appropriate analysis of the retrieved femoral head demonstrated loss of the Oxinium layer with exposure of the underlying substrate and transfer of titanium from the acetabular shell at the time of a reduction of the index total hip replacement. In addition, the level of damage to the polyethylene was extensive despite only 48 hours in situ. The purpose of this report is to highlight the care that is required at the time of reduction, especially with these hard femoral counter-faces such as Oxinium. To our knowledge, the damage occurring at the time of reduction has not been previously reported following the retrieval of an otherwise well-functioning hip replacement.

Calf serum constituent fractions influence polyethylene wear and microbial growth in knee simulator testing

Calf serum lubricants consisting of various polypeptide constituent fractions are routinely used in knee wear simulators as part of the standardized test protocol. Three calf sera (bovine, new-born and alpha) were diluted as per the recommendation of ISO 14243-3 and used in displacement-controlled knee wear simulators to investigate their effects on polyethylene wear. Biochemical analyses included measuring total polypeptide degradation, electrophoretic profiles and low-molecular weight polypeptide concentrations to elucidate their involvement in the wear process. The effects of the various calf sera constituent fractions on microbial growth were also explored. The polyethylene wear rates and the results from the biochemical analyses for the three calf serum lubricants were all found to be statistically significantly different from each other. The lubricant derived from the alpha-calf serum was closest in constituent fractions to human synovial fluid. It also showed the lowest polyethylene wear rate (14.38 ± 0.85 mm3/million cycles) and the lowest amount of polypeptide degradation (7.77 ± 3.87%). Furthermore, the alpha-calf serum lubricant was associated with the least amount of change in the electrophoretic profile, the least change in low-molecular weight polypeptide concentration, and the lowest microbial growth in the presence of sodium azide (a microbial inhibitor conventionally used in implant wear testing). Replacing sodium azide with a broad spectrum antibiotic-antimycotic eradicated the microbial growth. Some speculation was entertained regarding the effect of alpha-calf serum on colloid-mediated boundary lubrication. Based on the results, it was recommended that ISO 14243-3 be modified to include guidelines on calf serum constituent fractions that would favour using alpha-calf serum in order to improve the fidelity of the simulation in knee implant wear testing.

Twenty-three-year outcome of the porous coated anatomic total hip replacement: a concise follow-up of a previous report.

We previously reported the ten to fourteen-year results for 311 Porous Coated Anatomic total hip replacements that had been inserted by two surgeons in 279 patients. The purpose of the present report is to update that study and to report the outcome beyond twenty years. The patients were followed prospectively with clinical assessment with use of the Harris hip score and radiographic analysis, and the results were collected in a database. Two hundred and sixty-eight hips were functioning at the time of death or at the time of the latest follow-up. A total of forty-three hips (14%) underwent major revision for all causes, and an additional four hips underwent minor revision. At a mean of twenty-three years of follow-up, Kaplan-Meier analysis revealed a survival rate of 83% with revision for any reason as the end point. The survival rate was 95% for the femoral component and 88% for the acetabular component with revision for any reason as the end point. The rate of survival of the acetabular component was significantly higher in hips with a 26-mm femoral head than in those with a 32-mm femoral head (91% compared with 80%; p = 0.026).

Randomised controlled trial comparing early migration of two collarless polished cemented stems using radiostereometric analysis

This was a safety study where the hypothesis was that the newer-design CPCS femoral stem would demonstrate similar early clinical results and micromovement to the well-established Exeter stem. Both are collarless, tapered, polished cemented stems, the only difference being a slight lateral to medial taper with the CPCS stem. A total of 34 patients were enrolled in a single-blinded randomised controlled trial in which 17 patients received a dedicated radiostereometric CPCS stem and 17 a radiostereometric Exeter stem. No difference was found in any of the outcome measures pre-operatively or post-operatively between groups. At two years, the mean subsidence for the CPCS stem was nearly half that seen for the Exeter stem (0.77 mm (-0.943 to 1.77) and 1.25 mm (0.719 to 1.625), respectively; p = 0.032). In contrast, the mean internal rotation of the CPCS stem was approximately twice that of the Exeter (1.61 degrees (-1.07 degrees to 4.33 degrees ) and 0.59 degrees (0.97 degrees to 1.64 degrees ), respectively; p = 0.048). Other migration patterns were not significantly different between the stems. The subtle differences in designs may explain the different patterns of migration. Comparable migration with the Exeter stem suggests that the CPCS design will perform well in the long term.