Primary Total Hip Arthroplasty Procedures Research Articles

Bone loss: Accommodating a growing void

The rising number of primary total hip arthroplasty procedures being performed annually is assoaced with a concomitant increasing burden of revision total hip surgery. Acetabular and/or femoral bone loss encountered at the time of revison surgery can present a challenging problem. This brief review defines methods by which to classfiy bone loss patterns, presents options for treatment, and reports on clinical outcomes of different treatment.

Is the Anterior Approach Safe? Early Complication Rate Associated With 5090 Consecutive Primary Total Hip Arthroplasty Procedures Performed Using the Anterior Approach

BackgroundFew publications have raised concern with the safety of the anterior approach (AA) to total hip arthroplasty (THA). The purpose of this study is to report the early complications with AA THA in a combined, multicenter patient population from three different institutions. MethodsThe study cohort consisted of 5090 consecutive primary procedures in 4473 patients who had undergone THA utilizing the anterior approach between August 2006 and July 2013. Surgeries were performed by five surgeons at three sites that maintain prospective databases. Preoperative, intraoperative, and postoperative data were recorded on all patients. Demographic data including age, gender, and BMI were queried, as well as all intraoperative and postoperative complications in the first 90 days. ResultsThe 5090 patients had a mean body mass index of 27.5, and mean age of 63.6 years. The overall 90-day complication rate was 1.9%. There were 41 intraoperative femur fractures including 29 calcar fractures, 9 greater trochanter fractures and 3 femoral shaft fractures. There were 7 postoperative femur fractures including 3 greater trochanter fractures, 2 calcar fractures, and 2 femur fractures. Other complications included 15 superficial infections, 5 deep infections, 12 dislocations, 8 hematomas, 3 cases of cellulitis, 2 sciatic nerve palsies, 1 peroneal nerve palsy, and intrapelvic bleed. The nonsurgical complication rate was 1.4%. Deep vein thrombosis occurred in 0.3% of cases. ConclusionThis large multicenter study of consecutive AA THAs demonstrates an acceptable risk profile within the first 90 days after surgery.

Caracterização de artroplastias de quadril e joelho e fatores associados à infecção

ObjectiveTo characterize arthroplasty procedures, calculate the surgical infection rate and identify related risk factors. MethodsThis was a retrospective cohort study. Data on operations performed between 2010 and 2012 were gathered from documental sources and were analyzed with the aid of statistical software, using Fisher's exact test, Student's t test and the nonparametric Mann‐Whitney and Wilcoxon tests. Results421 total arthroplasty procedures performed on 346 patients were analyzed, of which 208 were on the knee and 213 on the hip. It was found that 18 patients (4.3%) were infected. Among these, 15 (83.33%) were reoperated and 2 (15.74%) died. The prevalence of infection in primary total hip arthroplasty procedures was 3%; in primary total knee arthroplasty, 6.14%; and in revision of total knee arthroplasty, 3.45%. Staphylococcus aureus was prevalent. The length of the surgical procedure showed a tendency towards being a risk factor (p=0.067). ConclusionThe prevalence of infection in cases of primary total knee arthroplasty was greater than in other cases. No statistically significant risk factors for infection were identified.

Do lifestyle restrictions and precautions prevent dislocation after total hip arthroplasty? A systematic review and meta-analysis of the literature

Objective: A systematic literature review and meta-analysis on the effectiveness of lifestyle restrictions and precautions to prevent dislocation after total hip arthroplasty. Data sources: MEDLINE and the Cochrane Library were searched in February 2015, with additional hand searching of systematic reviews and reference lists. Review methods: This review was conducted in accordance with the PRISMA statement for reporting systematic reviews and meta-analysis. PubMed and the Cochrane Library were searched from their start date through to February 2015. Randomized controlled trials and comparative case series in English, Dutch or German language were included. Only primary total hip arthroplasty procedures managed with different postoperative restrictions and precautions protocols were included. Primary outcome was the total hip arthroplasty dislocation rate, secondary outcomes were patient functioning, return to activities of daily living and patient satisfaction. Results: A total of 119 eligible articles were identified, six were included: three randomized controlled trials, one retrospective matched cohort study, one retrospective and one prospective cohort study, describing 1122 procedures (restrictions group: n = 528; no restrictions group: n = 594). Both the standard posterior and anterolateral surgical approaches were included. There were eight dislocations (1.5%) in the restricted group, vs. six dislocations (1.0%) in the unrestricted group. Patients in the unrestricted group resumed activities significantly faster and were more satisfied with their pace of recovery. Conclusion: A more liberal lifestyle restrictions and precautions protocol will not lead to worse dislocation rates after total hip arthroplasty, but will lead to earlier and better resumption of activities and higher patient satisfaction. These results appear to hold up for various surgical approaches.

Does intraoperative fluoroscopy improve component positioning in total hip arthroplasty?

Accurate placement of components is imperative for successful outcomes after total hip arthroplasty (THA). Although technology-assisted techniques offer the potential for greater accuracy in prosthesis positioning, the need for additional resources prevents their widespread use. The goal of this study was to compare primary THA procedures performed with and without intraoperative fluoroscopic guidance with regard to accuracy of prosthesis placement, operative time, and postoperative complications. The authors reviewed 341 consecutive cases (330 patients) undergoing primary THA at the authors' institution from September 2007 to January 2010. Postoperative anteroposterior radiographs were used to measure acetabular inclination angle, leg length discrepancy, and femoral offset discrepancy. Operative time and postoperative complications related to implant positioning were recorded. Mean acetabular inclination angle, leg length discrepancy, and offset discrepancy for control vs study groups were 43.0° (range, 32.2°-61.4°) vs 43.8° (range, 29.0°-55.1°), 4.75 mm (range, 0-25) vs 4.24 mm (range, 0-27), and 8.47 mm (range, 0-9.7) vs 7.70 mm (range, 0-31), respectively. Complication rates were not significantly different between the control (8.1%) and study (5.3%) groups. Mean operative time was significantly higher in the study group compared with the control group (59.8 vs 52.8 minutes) (P<.0001). The findings showed that intraoperative fluoroscopy may not improve prosthesis accuracy or decrease postoperative complication rates compared with a freehand technique. Because of significantly increased operative time and cost associated with fluoroscopic guidance, the authors discourage the use of this technique in uncomplicated primary THA performed at high-volume arthroplasty institutions.

Variation in hospital-level risk-standardized complication rates following elective primary total hip and knee arthroplasty.

Little is known about the variation in complication rates among U.S. hospitals that perform elective total hip arthroplasty (THA) and total knee arthroplasty (TKA) procedures. The purpose of this study was to use National Quality Forum (NQF)-endorsed hospital-level risk-standardized complication rates to describe variations in, and disparities related to, hospital quality for elective primary THA and TKA procedures performed in U.S. hospitals. We conducted a cross-sectional analysis of national Medicare Fee-for-Service data. The study cohort included 878,098 Medicare fee-for-service beneficiaries, sixty-five years or older, who underwent elective THA or TKA from 2008 to 2010 at 3479 hospitals. Both medical and surgical complications were included in the composite measure. Hospital-specific complication rates were calculated from Medicare claims with use of hierarchical logistic regression to account for patient clustering and were risk-adjusted for age, sex, and patient comorbidities. We determined whether hospitals with higher proportions of Medicaid patients and black patients had higher risk-standardized complication rates. The crude rate of measured complications was 3.6%. The most common complications were pneumonia (0.86%), pulmonary embolism (0.75%), and periprosthetic joint infection or wound infection (0.67%). The median risk-standardized complication rate was 3.6% (range, 1.8% to 9.0%). Among hospitals with at least twenty-five THA and TKA patients in the study cohort, 103 (3.6%) were better and seventy-five (2.6%) were worse than expected. Hospitals with the highest proportion of Medicaid patients had slightly higher but similar risk-standardized complication rates (median, 3.6%; range, 2.0% to 7.1%) compared with hospitals in the lowest decile (3.4%; 1.7% to 6.2%). Findings were similar for the analysis involving the proportion of black patients. There was more than a fourfold difference in risk-standardized complication rates across U.S. hospitals in which elective THA and TKA are performed. Although hospitals with higher proportions of Medicaid and black patients had rates similar to those of hospitals with lower proportions, there is a continued need to monitor for disparities in outcomes. These findings suggest there are opportunities for quality improvement among hospitals in which elective THA and TKA procedures are performed.

Preoperative planning of primary total hip arthroplasty using conventional radiographs

Objectivethe objective of this study was to present an analog method for preoperative planning of primary total hip arthroplasty procedures based on measuring the components by overlaying the transparencies of the prosthesis on the preoperative radiographs and checking the accuracy, both for predicting the size of the acetabular and femoral components used and for restoring the offset and correcting the dysmetria. Methodsbetween March 2005 and July 2009, 56 primary total hip arthroplasty procedures performed on 56 patients at the Mario Covas State Hospital in Santo André were analyzed. The measurements on the femoral and acetabular components obtained through planning were compared with those that were used in the surgery. The offsets measured through the preoperative planning were compared with those measured on the postoperative radiographs. Dysmetria was evaluated before and after the operation. Resultsaccuracy of 78.6% (p<0.001) in predicting the size of the acetabular component and 82.2% (p<0.001) in predicting the femoral nail was observed. The offsets measured through preoperative planning were statistically similar to the offsets measured on the postoperative radiographs. After the operation, we observed absolute equalization in 48.2% of the cases. In 87.5%, the dysmetria was less than or equal to 1cm and in 69.6%, it was less than or equal to 0.5cm. Conclusionsthe accuracy was 78.6% and 82.2%, respectively, for the acetabular and femoral components. The offsets that were planned preoperatively were statistically similar to those measured on postoperative radiographs. We found absolute equalization in 48.2% of the cases.

Planejamento pré‐operatório de artroplastias totais primárias de quadril com o uso de radiografias convencionais

Objectivethe objective of this study was to present an analogue method for preoperative planning of primary total hip arthroplasty procedures based on measuring the components by overlaying the transparencies of the prosthesis on the preoperative radiographs and checking the accuracy, both for predicting the size of the acetabular and femoral components used and for restoring the offset and correcting the dysmetria. Methodsbetween March 2005 and July 2009, 56 primary total hip arthroplasty procedures performed on 56 patients at the Mario Covas State Hospital in Santo André were analyzed. The measurements on the femoral and acetabular components obtained through planning were compared with those that were used in the surgery. The offsets measured through the preoperative planning were compared with those measured on the postoperative radiographs. Dysmetria was evaluated before and after the operation. Resultsaccuracy of 78.6% (p<0.001) in predicting the size of the acetabular component and 82.2% (p<0.001) in predicting the femoral nail was observed. The offsets measured through preoperative planning were statistically similar to the offsets measured on the postoperative radiographs. After the operation, we observed absolute equalization in 48.2% of the cases. In 87.5%, the dysmetria was less than or equal to 1cm and in 69.6%, it was less than or equal to 0.5cm. Conclusionsthe accuracy was 78.6% and 82.2%, respectively, for the acetabular and femoral components. The offsets that were planned preoperatively were statistically similar to those measured on postoperative radiographs. We found absolute equalization in 48.2% of the cases.

Reduced length of hospital stay after the introduction of a rapid recovery protocol for primary THA procedures

Background and purpose Rapid recovery protocols after total hip arthroplasty (THA) have been introduced worldwide in the last few years and they have reduced the length of hospital stay. We show the results of the introduction of a rapid recovery protocol for primary THA for unselected patients in our large teaching hospital.Patients and methods In a retrospective cohort study, we included all 1,180 patients who underwent a primary THA between July 1, 2008 and June 30, 2012. These patients were divided into 3 groups: patients operated before, during, and after the introduction of the rapid recovery protocol. There were no exclusion criteria. All complications, re-admissions, and reoperations were registered and analyzed.Results The mean length of hospital stay decreased from 4.6 to 2.9 nights after the introduction of the rapid recovery protocol. There were no statistically significant differences in the rate of complications, re-admissions, or reoperations between the 3 groups.Interpretation In a large teaching hospital, the length of hospital stay decreased after introduction of our protocol for rapid recovery after THA in unselected patients, without any increase in complications, re-admissions, or reoperation rate.

AB0361 Changes in number of total hip arthroplasty procedures and patient backgrounds in cases of rheumatoid arthritis

BackgroundHip joints are important for daily like activities, which become limited when destruction occurs. Joint destruction caused by rheumatoid arthritis (RA) can be limited by administration of a biological drug,...

The outcomes of hip resurfacing compared to standard primary total hip arthroplasty in Men

BackgroundThe purpose of this study was to evaluate the clinical and radiographic outcomes of hip resurfacing patients and compare them to standard primary total hip arthroplasty procedures performed during the same period of time.MethodsOne hundred and fourteen consecutive men who had a mean age of 50 years (range, 20 to 85 years) and who had undergone 120 hip resurfacing arthroplasties between 2007 and 2009 were compared to 117 consecutive men (120 hips) who had undergone a standard total hip arthroplasty during the same time period. The mean follow-up was 42 months (range, 24 to 55 months) for both groups. Outcomes evaluated included implant survivorship, hip scores, activity levels, and complication rates.ResultsIn the resurfacing hip arthroplasty cohort, implant survivorship was 98% with two patients requiring a revision surgery one for femoral neck fracture and another for femoral head loosening. In comparison, implant survivorship was 99% in the standard total hip arthroplasty cohort, with 1 revision due to peri-prosthetic fracture which was successfully treated with a femoral component revision. In the resurfacing and standard hip arthroplasty cohorts, the mean post-operative Harris hip scores had improved to 96 and 94 points, respectively and were statistically similar. The resurfacing cohort had achieved a significantly higher mean post-operative University of California Activity Score (6.7 versus 5 points). There were no differences in the complication rates between the two cohorts.ConclusionWhen patients meet the appropriate selection criteria in the hands of experienced and high-volume arthroplasty surgeons, hip resurfacing provides excellent results at short- to mid-term follow-up.

Long-term results of cementless hip arthroplasty with ceramic-on-ceramic articulation

PurposeThe goal of the study was to evaluate long-term results of hip arthroplasty in patients with ceramic-on-ceramic articulation.MethodsThe follow-up involved 220 primary total hip arthroplasty procedures (188 patients, 101 women and 87 men) after implantation of the Mittelmeier cementless hip endoprosthesis. The mean age of patients at surgery was 44.5 years and the mean follow-up was 19.6 years, with a minimum of 12.3 years. Dysplastic, idiopathic and post-traumatic coxarthrosis were the most frequent forms of degenerative hip changes. The Merle d’Aubigné and Postel classification, as modified by Charnley, was used for clinical evaluation.ResultsVery good results were obtained in 39.5 % of the patients, good results in 43.6 %, satisfactory results in 9.1 % and poor results in 7.8 %. Twelve-year survival for the whole prosthesis was 86.36 %, for the acetabulum 89.99 % and for the stem 91.36 %.ConclusionsLong-term results of hip arthroplasty using the Mittelmeier prosthesis are fairly encouraging with their low incidence of loosened prosthesis components after surgery.

Glove perforation time and frequency in total hip arthroplasty procedures

The aim of the present study was to investigate glove perforation rate and time and evaluate the factors affecting glove perforation in total hip arthroplasty (THA). Nine hundred seventy-nine gloves used in 57 THA procedures were assessed according to the perforation. Forty-four (77.2%) procedures were primary THA and 13 (22.8%) were revision THA. Gloves were changed when perforated, become dirty with blood or blood products, and before bone cementing. All gloves were filled with water at the end of the operation and controlled for perforation. Two hundred and one surgical gloves used during scrubbing and removed after draping the patient were examined as the control group. The location (which finger), number and time of the perforation, surgery type and duration, and distribution of the perforation location according to the surgical team were assessed. Patients' mean age was 62.9 ± 14.6 (range: 33 to 97) years and the mean surgery duration was 162.9 ± 32.0 minutes. Thirty-two glove perforations were noted in 19 of the operations. Of these perforations, 28 belonged to the surgeons and first assistants. There was no significant difference between the dominant or non-dominant hand according to the location of perforations. Perforations in the first and second fingers of the gloves accounted for 81.3% of all perforations. There was no significant difference in terms of number of gloves used, perforation numbers and operation duration between the primary and revision THA procedures. Two perforated gloves (0.99%) were found in the control group and the difference between the number of perforations in the control and study groups was significant (p=0.048). We recommend the use of two pairs of gloves to avoid the risk of contamination and protect the surgical team from infectious disease in major surgeries like THA. Surgical gloves should be changed when they are excessively contaminated with surgical fluids and the surgeon and first assistant should also change their outer gloves at an average of every 90 minutes.

Long-Term Trends in Hip Arthroplasty Use and Volume

We used Medicare administrative data to examine trends in primary and revision total hip arthroplasty (THA) use and hospital volume. Between 1991 and 2005, primary and revision THA use increased by 40.9% and 16.8%, respectively. The percentage of primary THA procedures performed in high-volume hospitals (those in the highest quintile of volume) increased slightly from 58.0% of all procedures in 1991 to 58.7% in 2005 ( P < .01). The percentage of revisions performed in high-volume hospitals increased from 60.9% to 62.4% ( P < .01). The percentage of primary THA procedures performed by low-volume hospitals remained relatively stable ( P = .36), whereas the percentage of revision THA performed by low-volume hospitals declined ( P < .001). In aggregate, these results suggest minimal evidence that regionalization of THA is occurring.

Auditorías clínicas del procedimiento de la artroplastia total de cadera y su impacto en la mejora de la calidad asistencial

Background Clinical audits are critical and systematic quality analysis of medical care. Total hip arthroplasty (THA) is a routine practice and cost-effective, although there is little information on the quality of care of it. Objective To evaluate the impact of a clinical audit cycle in the quality of care in the primary THA procedures for non-traumatic cause. Patients and methods A series of two audits (first audit in 2005 and second one in 2007) were performed. Patients of both sexes with non-traumatic primary THA and with a follow-up of 6 months were included. Time (days) in hospital stay and the rate (percentage) of readmissions were used as indicators of management; and as indicators of clinical practice: the index (percentage) of dislocation and the rate (percentage) of infection. Both audits were compared with respect to these indicators. Results A total of 160 patients (79 and 81, first and second audit respectively) were analysed. Management indicators: median (range) of hospital stay was 8 (7-78) and 7 (6-16), p < 0.001, and the percentage of readmissions 5% (4/79) and 0 (0/81), p = 0.057. Indicators of clinical practice: the rate of dislocation was 8% (6/79) and 0 (0/81), p = 0.013, and the rate of infection 1% (1/79) and 1% (1/81), p = 1. A multivariate analysis did not find other factors related to these indicators. Conclusions The implementation of a clinical audit cycle has improved the quality of care of primary THA procedures for non-traumatic cause.

Postoperative use of bisphosphonates and risk of revision after primary total hip arthroplasty: A nationwide population-based study

Background Recently, bisphosphonates have been linked with mechanisms that may influence longevity of orthopedic implants. We therefore evaluated the association between the use of bisphosphonates and the risk of revision after primary total hip arthroplasty (THA). Methods We conducted a nationwide population-based nested case–control study using medical databases in Denmark. From the Danish Hip Arthroplasty Register (DHR) we included primary THA patients diagnosed with either osteoporosis or a previous osteoporotic fracture ( n = 16,145). Among these patients we identified 632 cases that were revised after primary THA in the period 1995–2006. The cases were matched on gender, age and year of primary THA surgery with 1262 non-revised osteoporotic THA controls. Using conditional logistic regression we estimated the risk of revision due to all causes and due to specific causes according to postoperative bisphosphonate use. Results The 10-year cumulated implant revision rate in the underlying cohort of 16,145 primary THA procedures among osteoporotic patients was 8.3% (95% confidence interval (CI): 7.3–9.3). The use of bisphosphonates was associated with an adjusted relative risk of revision due to deep infections of 2.59 (95% CI; 1.30–6.53). Further, the duration of bisphosphonates use up to 120 days, 120 and 240 days, and more than 240 days was associated with adjusted relative risks of revision due to all causes of 2.77 (95% CI; 1.65–4.64), 1.33 (95% CI; 0.63–2.72), and 0.58 (95% CI; 0.32–1.05) respectively. Conclusions The use of bisphosphonates following primary THA was associated with an increased risk of revision due to deep infection. However, long-term use was associated with a reduced risk of revision of any type. Further research is warranted in order to clarify whether these associations are truly causal.

Effect of Procedure Duration on Total Hip Arthroplasty and Total Knee Arthroplasty Survivorship in the United States Medicare Population

There is limited information regarding the effects of procedure duration on total hip arthroplasty (THA) and total knee arthroplasty (TKA) implant survivorship in the United States. We examined the association between procedure duration with primary THA and TKA survivorship at 8 years in the Medicare population. Medicare claims data from 1997 to 2004 were used to identify primary THA and TKA procedures. Procedure duration was determined from the claims data by using anesthesia time as a proxy (Silber et al). Implant survivorship at 8 years (revision end point) was evaluated. Kaplan-Meier analysis and Cox regression were used to determine implant survivorship and hazard ratios associated with procedure duration.

Transtrochanteric approach to the hip

Once routinely used, trochanteric osteotomy in total hip arthroplasty now is usually limited to difficult primary and revision cases. Many variations of the osteotomy and many various techniques for the trochanter reattachment have been described. Our specific surgical technique is presented as well as its advantages and drawbacks. Primary total hip arthroplasty procedures requiring the enhanced exposure provided by trochanteric osteotomy is needed in patients with hip ankylosis or fusion, protrusio acetabuli, proximal femoral deformities, developmental dysplasia, or abductor muscle laxity. Trochanteric osteotomy, in revision arthroplasties, facilitates the removal of well-fixed femoral components and enhance acetabular exposure. In all cases trochanteric osteotomy remains useful to preserve the periarticular muscles and restore the geometry of the artificial hip which are the best ways to prevent dislocation.

Trochanteric osteotomy and fixation during total hip arthroplasty.

Once used routinely, trochanteric osteotomy in total hip arthroplasty now is usually limited to difficult primary and revision cases. There are three types: the standard trochanteric osteotomy and its variations, the trochanteric slide, and the extended trochanteric osteotomy. Each has unique indications, fixation techniques, and complications. Primary total hip arthroplasty procedures requiring the enhanced exposure provided by trochanteric osteotomy may be needed in patients with hip ankylosis or fusion, protrusio acetabuli, proximal femoral deformities, developmental dysplasia, or abductor muscle laxity. Trochanteric osteotomies in revision arthroplasties, primarily the extended trochanteric osteotomy, facilitate the removal of well-fixed femoral components, provide direct access to the diaphysis for distal fixation, and enhance acetabular exposure.

Primary Total Hip Arthroplasty Using a Grit-Blasted, Press-Fit Femoral Prosthesis. Long-Term Results with Survivorship Analysis

This report presents the initial experience with the use of a grit-blasted, press-fit femoral prosthesis. The first 300 consecutive primary total hip arthroplasty procedures using a collarless, three-dimensional tapered, straight, titanium alloy stem with a grit-blasted surface (performed in 299 patients) were evaluated with independent clinical and radiographic follow-up examinations up to sixteen years. Eight different types of acetabular components, including a cementless all-polyethylene socket in 80 percent of the cases, were used. Radiographic evaluation, performed by an independent observer using a zonal analysis method, included assessment of component migration, Enghs implant-bone femoral fixation score, implant-bone demarcations, and periprosthetic osteolysis. The average duration of long-term radiographic follow-up was 12.6 years (range; 10 to 16 years). At last examination only five hips were lost to follow-up and 69 patients were deceased. The overall mechanical failure rate (i.e. unstable with or without revision) of the femoral component was 2 percent. The femoral revision rate was 7 percent (two hips for aseptic loosening, five hips for septic loosening, and twelve hips with osseointegrated stems for severe progressive femoral osteolysis) and the acetabular revision rate was 27 percent (revised for either socket migration or progressive peri-acetabular osteolysis or both). Survivorship, based on any revision (femoral or acetabular) was 89 percent at ten years and 62 percent at fourteen years; survivorship of the femoral component was 95 percent at ten years and 90 percent at fourteen years. The incidence of femoral periprosthetic osteolysis, by radiographic examination at ten years or more was 47 percent, including 12 hips (5 percent) with distal endosteal osteolysis. Femoral implant-bone fixation was stable, bone-ongrowth in 97 percent; stable, fibrous-fixation in 1 percent, and unstable, fibrous-fixation in 2 percent of the cases. The grit-blasted, press-fit, collarless, tapered femoral component continued to per-form well clinically and radiographically up to sixteen years of follow-up despite the challenging environment of periprosthetic osteolysis associated with the acetabular component design. The high incidence of failure among the cementless all-polyethylene sockets was not unexpected and the use of this acetabular implant was discontinued in 1985. While considered a "first-generation" cementless stem, this implant is still in use virtually without design modifications. This study demonstrates the durability of the results of the grit-blasted femoral component and indicates that such an implant offers a viable alternative for fixation without bone cement. (Hip International 2002; 2: 55-72).