Aims. The practice of overlapping surgery has been increasing in the delivery of orthopaedic surgery, aiming to provide efficient, high-quality care. However, there are concerns about the safety of this practice. The purpose of this study was to examine the safety and efficacy of a model of partially overlapping surgery that we termed ‘swing room’ in the practice of primary total
This conversation represents an attempt by several
arthroplasty surgeons to critique several abstracts presented over
the last year as well as to use them as a jumping off point for trying
to figure out where they fit in into our current understanding of
multiple issues in modern
We assessed the long-term outcomes of a large cohort of patients who have undergone a periacetabular osteotomy (PAO), and sought to validate a patient satisfaction questionnaire for use in a PAO cohort. All patients who had undergone a PAO from July 1998 to February 2013 were surveyed, with several patient-reported outcome measures (PROMs) and radiological measurements of preoperative acetabular dysplasia and postoperative correction also recorded. Patients were asked to rate their level of satisfaction with their operation in achieving pain relief, restoration of activities of daily living, ability to perform recreational activity, and their overall level of satisfaction with the procedure.Aims
Methods
Total hip arthroplasty (THA) is one of the most successful surgical procedures. The objectives of this study were to define whether there is a correlation between socioeconomic status (SES) and surgical complications after elective primary unilateral THA, and investigate whether access to elective THA differs within SES groups. We conducted a retrospective, population-based cohort study involving 202 hospitals in Ontario, Canada, over a 17-year period. Patients were divided into income quintiles based on postal codes as a proxy for personal economic status. Multivariable logistic regression models were then used to primarily assess the relationship between SES and surgical complications within one year of index THA.Aims
Methods
The aim of this study was to identify the minimal clinically important difference (MCID), minimal important change (MIC), minimal detectable change (MDC), and patient-acceptable symptom state (PASS) in the Forgotten Joint Score (FJS) according to patient satisfaction six months following total hip arthroplasty (THA) in a UK population. During a one-year period, 461 patients underwent a primary THA and completed preoperative and six-month FJS, with a mean age of 67.2 years (22 to 93). At six months, patient satisfaction was recorded as very satisfied, satisfied, neutral, dissatisfied, or very dissatisfied. The difference between patients recording neutral (n = 31) and satisfied (n = 101) was used to define the MCID. MIC for a cohort was defined as the change in the FJS for those patients declaring their outcome as satisfied, whereas receiver operating characteristic curve analysis was used to determine the MIC for an individual and the PASS. Distribution-based methodology was used to calculate the MDC.Aims
Methods
Aims. Routine surveillance of primary
Objectives. The primary aim of this study was to assess the reproducibility of the recalled preoperative Oxford Hip Score (OHS) and Oxford Knee Score (OKS) one year following arthroplasty for a cohort of patients. The secondary aim was to assess the reliability of a patient’s recollection of their own preoperative OHS and OKS one year following surgery. Methods. A total of 335 patients (mean age 72.5; 22 to 92; 53.7% female) undergoing total hip arthroplasty (n = 178) and total knee arthroplasty (n = 157) were prospectively assessed. Patients undergoing
Aims. The primary aim of this paper was to outline the processes involved in building the Partners Arthroplasty Registry (PAR), established in April 2016 to capture baseline and outcome data for patients undergoing arthroplasty in a regional healthcare system. A secondary aim was to determine the quality of PAR’s data. A tertiary aim was to report preliminary findings from the registry and contributions to quality improvement initiatives and research up to March 2019. Methods. Structured Query Language was used to obtain data relating to patients who underwent total
Objectives. The diagnosis of periprosthetic joint infection (PJI) is difficult and requires a battery of tests and clinical findings. The purpose of this review is to summarize all current evidence for common and new serum biomarkers utilized in the diagnosis of PJI. Methods. We searched two literature databases, using terms that encompass all
The burden of revision total hip arthroplasty (rTHA) continues to grow. The surgery is complex and associated with significant costs. Regional rTHA networks have been proposed to improve outcomes and to reduce re-revisions, and therefore costs. The aim of this study was to accurately quantify the cost and reimbursement for a rTHA service, and to assess the financial impact of case complexity at a tertiary referral centre within the NHS. A retrospective analysis of all revision hip procedures was performed at this centre over two consecutive financial years (2018 to 2020). Cases were classified according to the Revision Hip Complexity Classification (RHCC) and whether they were infected or non-infected. Patients with an American Society of Anesthesiologists (ASA) grade ≥ III or BMI ≥ 40 kg/m2 are considered “high risk” by the RHCC. Costs were calculated using the Patient Level Information and Costing System (PLICS), and remuneration based on Healthcare Resource Groups (HRG) data. The primary outcome was the financial difference between tariff and cost per patient episode.Aims
Methods
This study compares the re-revision rate and mortality following septic and aseptic revision hip arthroplasty (rTHA) in registry data, and compares the outcomes to previously reported data. This is an observational cohort study using data from the German Arthroplasty Registry (EPRD). A total of 17,842 rTHAs were included, and the rates and cumulative incidence of hip re-revision and mortality following septic and aseptic rTHA were analyzed with seven-year follow-up. The Kaplan-Meier estimates were used to determine the re-revision rate and cumulative probability of mortality following rTHA.Aims
Methods
This study describes the variation in the annual volumes of revision hip arthroplasty (RHA) undertaken by consultant surgeons nationally, and the rate of accrual of RHA and corresponding primary hip arthroplasty (PHA) volume for new consultants entering practice. National Joint Registry (NJR) data for England, Wales, Northern Ireland, and the Isle of Man were received for 84,816 RHAs and 818,979 PHAs recorded between April 2011 and December 2019. RHA data comprised all revision procedures, including first-time revisions of PHA and any subsequent re-revisions recorded in public and private healthcare organizations. Annual procedure volumes undertaken by the responsible consultant surgeon in the 12 months prior to every index procedure were determined. We identified a cohort of ‘new’ HA consultants who commenced practice from 2012 and describe their rate of accrual of PHA and RHA experience.Aims
Methods
Aims. Post-operative migration of cemented acetabular components as
measured by radiostereometric analysis (RSA) has a strong predictive
power for late, aseptic loosening. Also, radiolucent lines predict
late loosening. Migration has been reduced by systemic bisphosphonate
treatment in randomised trials of
Aims. Failure of irrigation and debridement (I&D) for prosthetic joint infection (PJI) is influenced by numerous host, surgical, and pathogen-related factors. We aimed to develop and validate a practical, easy-to-use tool based on machine learning that may accurately predict outcome following I&D surgery taking into account the influence of numerous factors. Methods. This was an international, multicentre retrospective study of 1,174 revision total
The aim of this study was to estimate time to arthroplasty among patients with hip and knee osteoarthritis (OA), and to identify factors at enrolment to first-line intervention that are prognostic for progression to surgery. In this longitudinal register-based observational study, we identified 72,069 patients with hip and knee OA in the Better Management of Patients with Osteoarthritis Register (BOA), who were referred for first-line OA intervention, between May 2008 and December 2016. Patients were followed until the first primary arthroplasty surgery before 31 December 2016, stratified into a hip and a knee OA cohort. Data were analyzed with Kaplan-Meier and multivariable-adjusted Cox regression.Aims
Methods
The volume of ambulatory total hip arthroplasty (THA) procedures is increasing due to the emphasis on value-based care. The purpose of the study is to identify the causes for failed same-day discharge (SDD) and perioperative factors leading to failed SDD. This retrospective cohort study followed pre-selected patients for SDD THA from 1 August 2018 to 31 December 2020. Inclusion criteria were patients undergoing unilateral THA with appropriate social support, age 18 to 75 years, and BMI < 37 kg/m2. Patients with opioid dependence, coronary artery disease, and valvular heart disease were excluded. Demographics, comorbidities, and perioperative data were collected from the electronic medical records. Possible risk factors for failed SDD were identified using multivariate logistic regression.Aims
Methods
After total
Registry studies on modified acetabular polyethylene (PE) liner designs are limited. We investigated the influence of standard and modified PE acetabular liner designs on the revision rate for mechanical complications in primary cementless total hip arthroplasty (THA). We analyzed 151,096 primary cementless THAs from the German Arthroplasty Registry (EPRD) between November 2012 and November 2020. Cumulative incidence of revision for mechanical complications for standard and four modified PE liners (lipped, offset, angulated/offset, and angulated) was determined using competing risk analysis at one and seven years. Confounders were investigated with a Cox proportional-hazards model.Aims
Methods
Golf is a popular pursuit among those requiring total hip arthroplasty (THA). The aim of this study was to determine if participating in golf is associated with greater functional outcomes, satisfaction, or improvement in quality of life (QoL) compared to non-golfers. All patients undergoing primary THA over a one-year period at a single institution were included with one-year postoperative outcomes. Patients were retrospectively followed up to assess if they had been golfers at the time of their surgery. Multivariate linear regression analysis was performed to assess the independent association of preoperative golfing status on outcomes.Aims
Methods
The aim of this study was to assess medium-term improvements following total hip arthroplasty (THA), and to evaluate what effect different preoperative Oxford Hip Score (OHS) thresholds for treatment may have on patients’ access to THA and outcomes. Patients undergoing primary THA at our institution with an OHS both preoperatively and at least four years postoperatively were included. Rationing thresholds were explored to identify possible deprivation of OHS improvement.Aims
Methods
A recent report from France suggested an association between the use of cobalt-chrome (CoCr) femoral heads in total hip arthroplasties (THAs) and an increased risk of dilated cardiomyopathy and heart failure. CoCr is a commonly used material in orthopaedic implants. If the reported association is causal, the consequences would be significant given the millions of joint arthroplasties and other orthopaedic procedures in which CoCr is used annually. We examined whether CoCr-containing THAs were associated with an increased risk of all-cause mortality, heart outcomes, cancer, and neurodegenerative disorders in a large national database. Data from the National Joint Registry was linked to NHS English hospital inpatient episodes for 374,359 primary THAs with up to 14.5 years' follow-up. We excluded any patients with bilateral THAs, knee arthroplasties, indications other than osteoarthritis, aged under 55 years, and diagnosis of one or more outcome of interest before THA. Implants were grouped as either containing CoCr or not containing CoCr. The association between implant construct and the risk of all-cause mortality and incident heart failure, cancer, and neurodegenerative disorders was examined.Aims
Methods
Femoral cement-in-cement revision is a well described technique to reduce morbidity and complications in hip revision surgery. Traditional techniques for septic revision of hip arthroplasty necessitate removal of all bone cement from the femur. In our two centres, we have been using a cement-in-cement technique, leaving the distal femoral bone cement in selected patients for septic hip revision surgery, both for single and the first of two-stage revision procedures. A prerequisite for adoption of this technique is that the surgeon considers the cement mantle to be intimately fixed to bone without an intervening membrane between cement and host bone. We aim to report our experience for this technique. We have analyzed patients undergoing this cement-in-cement technique for femoral revision in infection, and present a consecutive series of 89 patients. Follow-up was undertaken at a mean of 56.5 months (24.0 to 134.7) for the surviving cases.Aims
Methods
Due to the opioid epidemic in the USA, our service progressively decreased the number of opioid tablets prescribed at discharge after primary hip (THA) and knee (TKA) arthroplasty. The goal of this study was to analyze the effect on total morphine milligram equivalents (MMEs) prescribed and post-discharge opioid repeat prescriptions. We retrospectively reviewed 19,428 patients undergoing a primary THA or TKA between 1 February 2016 and 31 December 2019. Two reductions in the number of opioid tablets prescribed at discharge were implemented over this time; as such, we analyzed three periods (P1, P2, and P3) with different routine discharge MME (750, 520, and 320 MMEs, respectively). We investigated 90-day refill rates, refill MMEs, and whether discharge MMEs were associated with represcribing in a multivariate model.Aims
Methods
The proportion of arthroplasties performed in the ambulatory setting has increased considerably. However, there are concerns whether same-day discharge may increase the risk of complications. The aim of this study was to compare 90-day outcomes between inpatient arthroplasties and outpatient arthroplasties performed at an ambulatory surgery centre (ASC), and determine whether there is a learning curve associated with performing athroplasties in an ASC. Among a single-surgeon cohort of 970 patients who underwent arthroplasty at an ASC, 854 (88.0%) were matched one-to-one with inpatients based on age, sex, American Society of Anesthesiologists (ASA) grade, BMI, and procedure (105 could not be adequately matched and 11 lacked 90-day follow-up). The cohort included 281 total hip arthroplasties (THAs) (32.9%), 267 unicompartmental knee arthroplasties (31.3%), 242 primary total knee arthroplasties (TKAs) (28.3%), 60 hip resurfacings (7.0%), two revision THAs (0.3%), and two revision TKAs (0.3%). Outcomes included readmissions, reoperations, visits to the emergency department, unplanned clinic visits, and complications.Aims
Methods
The current study aimed to compare robotic arm-assisted (RA-THA), computer-assisted (CA-THA), and manual (M-THA) total hip arthroplasty regarding in-hospital metrics including length of stay (LOS), discharge disposition, in-hospital complications, and cost of RA-THA versus M-THA and CA-THA versus M-THA, as well as trends in use and uptake over a ten-year period, and future projections of uptake and use of RA-THA and CA-THA. The National Inpatient Sample was queried for primary THAs (2008 to 2017) which were categorized into RA-THA, CA-THA, and M-THA. Past and projected use, demographic characteristics distribution, income, type of insurance, location, and healthcare setting were compared among the three cohorts. In-hospital complications, LOS, discharge disposition, and in-hospital costs were compared between propensity score-matched cohorts of M-THA versus RA-THA and M-THA versus CA-THA to adjust for baseline characteristics and comorbidities.Aims
Methods
The purpose of this study is to evaluate early outcomes with the use of a smartphone-based exercise and educational care management system after total hip arthroplasty (THA) and demonstrate decreased use of in-person physiotherapy (PT). A multicentre, prospective randomized controlled trial was conducted to evaluate a smartphone-based care platform for primary THA. Patients randomized to the control group (198) received the institution’s standard of care. Those randomized to the treatment group (167) were provided with a smartwatch and smartphone application. PT use, THA complications, readmissions, emergency department/urgent care visits, and physician office visits were evaluated. Outcome scores include the Hip disability and Osteoarthritis Outcome Score (HOOS, JR), health-related quality-of-life EuroQol five-dimension five-level score (EQ-5D-5L), single leg stance (SLS) test, and the Timed Up and Go (TUG) test.Aims
Methods
The prevalence of ipsilateral total hip arthroplasty (THA) and total knee arthroplasty (TKA) is rising in concert with life expectancy, putting more patients at risk for interprosthetic femur fractures (IPFFs). Our study aimed to assess treatment methodologies, implant survivorship, and IPFF clinical outcomes. A total of 76 patients treated for an IPFF from February 1985 to April 2018 were reviewed. Prior to fracture, at the hip/knee sites respectively, 46 femora had primary/primary, 21 had revision/primary, three had primary/revision, and six had revision/revision components. Mean age and BMI were 74 years (33 to 99) and 30 kg/m2 (21 to 46), respectively. Mean follow-up after fracture treatment was seven years (2 to 24).Aims
Methods
Aseptic loosening is a leading cause of uncemented arthroplasty failure, often accompanied by fibrotic tissue at the bone-implant interface. A biological target, neutrophil extracellular traps (NETs), was investigated as a crucial connection between the innate immune system’s response to injury, fibrotic tissue development, and proper bone healing. Prevalence of NETs in peri-implant fibrotic tissue from aseptic loosening patients was assessed. A murine model of osseointegration failure was used to test the hypothesis that inhibition (through Patient peri-implant fibrotic tissue was analyzed for NETs biomarkers. To enhance osseointegration in loose implant conditions, an innate immune system pathway (NETs) was either inhibited (Aims
Methods
We studied the safety and efficacy of multimodal thromboprophylaxis in patients with a history of venous thromboembolism (VTE) who undergo total hip arthroplasty (THA) within the first 120 postoperative days, and the mortality during the first year. Multimodal prophylaxis includes discontinuation of procoagulant medications, VTE risk stratification, regional anaesthesia, an intravenous bolus of unfractionated heparin prior to femoral preparation, rapid mobilization, the use of pneumatic compression devices, and chemoprophylaxis tailored to the patient’s risk of VTE. Between 2004 to 2018, 257 patients with a proven history of VTE underwent 277 primary elective THA procedures by two surgeons at a single institution. The patients had a history of deep vein thrombosis (DVT) (186, 67%), pulmonary embolism (PE) (43, 15.5%), or both (48, 17.5%). Chemoprophylaxis included aspirin (38 patients), anticoagulation (215 patients), or a combination of aspirin and anticoagulation (24 patients). A total of 50 patients (18%) had a vena cava filter in situ at the time of surgery. Patients were followed for 120 days to record complications, and for one year to record mortality.Aims
Methods
Periprosthetic femoral fractures (PPF) are a serious complication of total hip arthroplasty (THA) and are becoming an increasingly common indication for revision arthroplasty with the ageing population. This study aimed to identify potential risk factors for PPF based on an analysis of registry data. Cases recorded with PPF as the primary indication for revision arthroplasty in the German Arthroplasty Registry (Endoprothesenregister Deutschland (EPRD)), as well as those classified as having a PPF according to the International Classification of Diseases (ICD) codes in patients’ insurance records were identified from the complete datasets of 249,639 registered primary hip arthroplasties in the EPRD and included in the analysis.Aims
Methods
Joint registries typically use revision of an implant as an endpoint and report survival rates after a defined number of years. However, reporting lifetime risk of revision may be more meaningful, especially in younger patients. We aimed to assess lifetime risk of revision for patients in defined age groups at the time of primary surgery. The New Zealand Joint Registry (NZJR) was used to obtain rates and causes of revision for all primary total hip arthroplasties (THAs) performed between January 1999 and December 2016. The NZJR is linked to the New Zealand Registry of Births, Deaths and Marriages to obtain complete and accurate data. Patients were stratified by age at primary surgery, and lifetime risk of revision calculated according to age, sex, and American Society of Anesthesiologists (ASA) classification. The most common causes for revision were also analyzed for each age group.Aims
Methods
We present the development of a day-case total hip arthroplasty (THA) pathway in a UK National Health Service institution in conjunction with an extensive evidence-based summary of the interventions used to achieve successful day-case THA to which the protocol is founded upon. We performed a prospective audit of day-case THA in our institution as we reinitiate our full capacity elective services. In parallel, we performed a review of the literature reporting complication or readmission rates at ≥ 30-day postoperative following day-case THA. Electronic searches were performed using four databases from the date of inception to November 2020. Relevant studies were identified, data extracted, and qualitative synthesis performed.Aims
Methods
Previous research has demonstrated increased early complication rates following total hip arthroplasty (THA) in obese patients, as defined by body mass index (BMI). Subcutaneous fat depth (FD) has been shown to be an independent risk factor for wound infection in cervical and lumbar spine surgery, as well as after abdominal laparotomy. The aim of this study was to investigate whether increased peritrochanteric FD was associated with an increased risk of complications in the first year following THA. We analyzed prospectively collected data on a consecutive series of 1,220 primary THAs from June 2013 until May 2018. The vertical soft tissue depth from the most prominent part of the greater trochanter to the skin was measured intraoperatively using a sterile ruler and recorded to the nearest millimetre. BMI was calculated at the patient’s preoperative assessment. All surgical complications occuring within the initial 12 months of follow-up were identified.Aims
Methods
We performed a prospective, randomised study comparing the rates of glove perforation using double latex gloving with or without a disposable protective glove liner (Paraderm) on 118 patients undergoing primary or revision arthroplasty of the hip or knee by one surgeon (FRH). The patients were randomly allocated into two groups: in group 1 an inner and outer pair of latex gloves were worn as double gloves and in group 2 the glove liner was worn between the two latex gloves. There was glove perforation in at least one outer glove in 99 operations (84%). The operating surgeon was aware of the perforation in 21 of these. There were 22 perforations of the inner glove. Group 1 had a significantly higher perforation rate per operation (p <
0.05) than group 2. Our findings show that protective glove liners significantly reduce the rate of perforation of the inner glove during
The prevalence of combined abnormalities of femoral torsion (FT) and tibial torsion (TT) is unknown in patients with femoroacetabular impingement (FAI) and hip dysplasia. This study aimed to determine the prevalence of combined abnormalities of FT and TT, and which subgroups are associated with combined abnormalities of FT and TT. We retrospectively evaluated symptomatic patients with FAI or hip dysplasia with CT scans performed between September 2011 and September 2016. A total of 261 hips (174 patients) had a measurement of FT and TT. Their mean age was 31 years (SD 9), and 63% were female (165 hips). Patients were compared to an asymptomatic control group (48 hips, 27 patients) who had CT scans including femur and tibia available for analysis, which had been acquired for nonorthopaedic reasons. Comparisons were conducted using analysis of variance with Bonferroni correction.Aims
Methods
Intravenous dexamethasone has been shown to reduce immediate postoperative pain after total hip arthroplasty (THA), though the effects are short-lived. We aimed to assess whether two equivalent perioperative split doses were more effective than a single preoperative dose. A total of 165 patients were randomly assigned into three groups: two perioperative saline injections (Group A, placebo), a single preoperative dose of 20 mg dexamethasone and a postoperative saline injection (Group B), and two perioperative doses of 10 mg dexamethasone (Group C). Patients, surgeons, and staff collecting outcome data were blinded to allocation. The primary outcome was postoperative pain level reported on a ten-point Numerical Rating Scale (NRS) at rest and during activity. The use of analgesic and antiemetic rescue, incidence of postoperative nausea and vomiting (PONV), CRP and interleukin-6 (IL-6) levels, range of motion (ROM), length of stay (LOS), patient satisfaction, and the incidence of surgical site infection (SSI) and gastrointestinal bleeding (GIB) in the three months postoperatively, were also compared.Aims
Methods
There is evidence that prior lumbar fusion increases the risk of dislocation and revision after total hip arthroplasty (THA). The relationship between prior lumbar fusion and the effect of femoral head diameter on THA dislocation has not been investigated. We examined the relationship between prior lumbar fusion or discectomy and the risk of dislocation or revision after THA. We also examined the effect of femoral head component diameter on the risk of dislocation or revision. Data used in this study were compiled from several Finnish national health registers, including the Finnish Arthroplasty Register (FAR) which was the primary source for prosthesis-related data. Other registers used in this study included the Finnish Health Care Register (HILMO), the Social Insurance Institutions (SII) registers, and Statistics Finland. The study was conducted as a prospective retrospective cohort study. Cox proportional hazards regression and Kaplan-Meier survival analysis were used for analysis.Aims
Methods
Natural Language Processing (NLP) offers an automated method to extract data from unstructured free text fields for arthroplasty registry participation. Our objective was to investigate how accurately NLP can be used to extract structured clinical data from unstructured clinical notes when compared with manual data extraction. A group of 1,000 randomly selected clinical and hospital notes from eight different surgeons were collected for patients undergoing primary arthroplasty between 2012 and 2018. In all, 19 preoperative, 17 operative, and two postoperative variables of interest were manually extracted from these notes. A NLP algorithm was created to automatically extract these variables from a training sample of these notes, and the algorithm was tested on a random test sample of notes. Performance of the NLP algorithm was measured in Statistical Analysis System (SAS) by calculating the accuracy of the variables collected, the ability of the algorithm to collect the correct information when it was indeed in the note (sensitivity), and the ability of the algorithm to not collect a certain data element when it was not in the note (specificity).Aims
Methods
Psychological factors play a critical role in patient presentation, satisfaction, and outcomes. Pain catastrophizing, anxiety, and depression are important to consider, as they are associated with poorer outcomes and are potentially modifiable. The aim of this study was to assess the level of pain catastrophizing, anxiety, and depression in patients with a range of hip pathology and to evaluate their relationship with patient-reported psychosocial and functional outcome measures. Patients presenting to a tertiary-centre specialist hip clinic were prospectively evaluated for outcomes of pain catastrophizing, anxiety, and depression. Validated assessments were undertaken such as: the Pain Catastrophizing Scale (PCS), the Hospital Anxiety Depression Scale (HADS), and the 12-Item Short-Form Health Survey (SF-12). Patient characteristics and demographics were also recorded. Multiple linear regression modelling, with adaptive least absolute shrinkage and selection operator (LASSO) variable selection, was used for analysis.Aims
Patients and Methods
The purpose of this exploratory study was to investigate if the 24-hour activity profile (i.e. waking activities and sleep) objectively measured using wrist-worn accelerometry of patients scheduled for total hip arthroplasty (THA) improves postoperatively. A total of 51 THA patients with a mean age of 64 years (24 to 87) were recruited from a single public hospital. All patients underwent THA using the same surgical approach with the same prosthesis type. The 24-hour activity profiles were captured using wrist-worn accelerometers preoperatively and at 2, 6, 12, and 26 weeks postoperatively. Patient-reported outcomes (Hip Disability and Osteoarthritis Outcome Score (HOOS)) were collected at all timepoints except two weeks postoperatively. Accelerometry data were used to quantify the intensity (sedentary, light, moderate, and vigorous activities) and frequency (bouts) of activity during the day and sleep efficiency. The analysis investigated changes with time and differences between Charnley class.Aims
Patients and Methods
Total hip arthroplasty (THA) has well known subjective benefits,
but little is known objectively about the recovery of mobility in
the early post-operative period. A total of 33 patients aged >
60 years who underwent elective
primary THA had their activity monitored for 30 days post-operatively
using an at-home (Fitbit) ankle accelerometer. Their mean age was
70.7 years (61 to 86); 15 (45.5%) were female. The rate of compliance
and the mean level of activity were determined. Comparisons between subgroups
based on age, body mass index (BMI), surgical approach, and the
destination of the patients when discharged were also performed.Aims
Patients and Methods
The long term biological effects of wear products
following total hip arthroplasty (THA) are unclear. However, the indications
for THA are expanding, with increasingly younger patients undergoing
the procedure. This prospective, randomised study compared two groups of patients
undergoing THA after being randomised to receive one of two different
bearing surfaces: metal-on-polyethylene (MoP) n = 22 and metal-on-metal
(MoM) n = 23. We investigated the relationship between three variables:
bearing surface (MoP Our results demonstrated significantly higher mean cobalt and
chromium (Co and Cr) blood levels in the MoM group at all follow-up
points following surgery (p <
0.01), but there were no significant
differences in the chromosomal aberration indices between MoM and
MoP at two or five years (two years: p = 0.56, p = 0.08, p = 0.91, p
= 0.51 and five years: p = 0.086, p = 0.73, p = 0.06, p = 0.34)
for translocations, breaks, loss and gain of chromosomes respectively.
Regression analysis showed a strong linear relationship between
Cr levels and the total chromosomal aberration indices in the MoM
group (R2 = 0.90016), but this was not as strong for
Co (R2 = 0.68991). In the MoP group, the analysis revealed
a poor relationship between Cr levels and the total chromosomal
aberration indices (R2 = 0.23908) but a slightly stronger
relationship for Co (R2 = 0.64292). Across both groups,
Spearman’s correlation detected no overall association between Co and Cr
levels and each of the studied chromosomal aberrations. There remains
no clear indication which THA bearing couple is the most biocompatible,
especially in young active patients. While THA continues to be very
successful at alleviating pain and restoring function, the long-term
biological implications of the procedure still require further scrutiny. Cite this article:
Tranexamic acid (TXA), an inhibitor of fibrinolysis,
reduces blood loss after total knee arthroplasty. However, its effect
on minimally invasive total hip arthroplasty (THA) is not clear.
We performed a prospective, randomised double-blind study to evaluate
the effect of two intravenous injections of TXA on blood loss in
patients undergoing minimally invasive THA. In total, 60 patients (35 women and 25 men with a mean age of
58.1 years; 17 to 84) who underwent unilateral minimally invasive
uncemented THA were randomly divided into the study group (30 patients,
20 women and ten men with a mean age of 56.5 years; 17 to 79) that
received two intravenous injections 1 g of TXA pre- and post-operatively
(TXA group), and a placebo group (30 patients, 15 women and 15 men
with a mean age of 59.5 years; 23 to 84). We compared the peri-operative
blood loss of the two groups. Actual blood loss was calculated from
the maximum reduction in the level of haemoglobin. All patients
were followed clinically for the presence of venous thromboembolism. The TXA group had a lower mean intra-operative blood loss of
441 ml (150 to 800) This prospective, randomised controlled study showed that a regimen
of two intravenous injections of 1 g TXA is effective for blood
conservation after minimally invasive THA. Cite this article:
Periprosthetic fractures are an increasingly
common complication following joint replacement. The principles
which underpin their evaluation and treatment are common across
the musculoskeletal system. The Unified Classification System proposes
a rational approach to treatment, regardless of the bone that is
broken or the joint involved. Cite this article:
This study reports the results of 38 total hip
arthroplasties (THAs) in 33 patients aged <
50 years, using the
JRI Furlong hydroxyapatite ceramic (HAC)-coated femoral component.
This represents an update of previous reports of the same cohort
at ten and 16 years, which were reported in 2004 and 2009, respectively.
We describe the survival, radiological and functional outcomes at
a mean follow-up of 21 years (17 to 25). Of the surviving 34 THAs,
one underwent femoral revision for peri-prosthetic fracture after
21 years, and one patient (one hip) was lost to follow-up. Using
aseptic loosening as the end-point, 12 hips (31.5%) needed acetabular
revision but none needed femoral revision, demonstrating 100% survival
(95% confidence interval 89 to 100). In young patients with high demands, the Furlong HAC–coated femoral
component gives excellent long-term results. Cite this article:
In this study we evaluated whether pre-operative
Western Ontario and McMaster Universities (WOMAC) osteoarthritis
scores can predict satisfaction following total hip arthroplasty
(THA). Prospective data for a cohort of patients undergoing THA
from two large academic centres were collected, and pre-operative
and one-year post-operative WOMAC scores and a 25-point satisfaction
questionnaire were obtained for 446 patients. Satisfaction scores
were dichotomised into either improvement or deterioration. Scatter
plots and Spearman’s rank correlation coefficient were used to describe
the association between pre-operative WOMAC and one-year post-operative WOMAC
scores and patient satisfaction. Satisfaction was compared using
receiver operating characteristic (ROC) analysis against pre-operative,
post-operative and δ WOMAC scores. We found no relationship between pre-operative WOMAC scores and
one-year post-operative WOMAC or satisfaction scores, with Spearman’s
rank correlation coefficients of 0.16 and –0.05, respectively. The
ROC analysis showed areas under the curve (AUC) of 0.54 (pre-operative
WOMAC), 0.67 (post-operative WOMAC) and 0.43 (δ WOMAC), respectively,
for an improvement in satisfaction. We conclude that the pre-operative WOMAC score does not predict
the post-operative WOMAC score or patient satisfaction after THA,
and that WOMAC scores can therefore not be used to prioritise patient
care. Cite this article:
Valid and reliable techniques for assessing performance
are essential to surgical education, especially with the emergence
of competency-based frameworks. Despite this, there is a paucity
of adequate tools for the evaluation of skills required during joint
replacement surgery. In this scoping review, we examine current
methods for assessing surgeons’ competency in joint replacement
procedures in both simulated and clinical environments. The ability
of many of the tools currently in use to make valid, reliable and
comprehensive assessments of performance is unclear. Furthermore,
many simulation-based assessments have been criticised for a lack
of transferability to the clinical setting. It is imperative that
more effective methods of assessment are developed and implemented
in order to improve our ability to evaluate the performance of skills
relating to total joint replacement. This will enable educators
to provide formative feedback to learners throughout the training
process to ensure that they have attained core competencies upon
completion of their training. This should help ensure positive patient
outcomes as the surgical trainees enter independent practice. Cite this article:
Total hip replacement causes a short-term increase
in the risk of mortality. It is important to quantify this and to identify
modifiable risk factors so that the risk of post-operative mortality
can be minimised. We performed a systematic review and critical
evaluation of the current literature on the topic. We identified
32 studies published over the last 10 years which provide either
30-day or 90-day mortality data. We estimate the pooled incidence
of mortality during the first 30 and 90 days following hip replacement
to be 0.30% (95% CI 0.22 to 0.38) and 0.65% (95% CI 0.50 to 0.81),
respectively. We found strong evidence of a temporal trend towards
reducing mortality rates despite increasingly co-morbid patients.
The risk factors for early mortality most commonly identified are
increasing age, male gender and co-morbid conditions, particularly
cardiovascular disease. Cardiovascular complications appear to have
overtaken fatal pulmonary emboli as the leading cause of death after
hip replacement. Cite this article:
We have evaluated the extent to which diabetes affects the revision rate following total hip replacement (THR). Through the Danish Hip Arthroplasty Registry we identified all patients undergoing a primary THR (n = 57 575) between 1 January 1996 and 31 December 2005, of whom 3278 had diabetes. The presence of diabetes among these patients was identified through the Danish National Registry of Patients and the Danish National Drug Prescription Database. We estimated the relative risk for revision and the 95% confidence intervals for patients with diabetes compared to those without, adjusting for the confounding factors. Diabetes is associated with an increased risk of revision due to deep infection (relative risk = 1.45 (95% confidence interval 1.00 to 2.09), particularly in those with type 2 diabetes (relative risk = 1.49 (95% confidence interval 1.02 to 2.18)), those with diabetes for less than five years prior to THR (relative risk = 1.69 (95% confidence interval 1.24 to 2.32)), those with complications due to diabetes (relative risk = 2.11 (95% confidence interval 1.41 to 3.17)), and those with cardiovascular comorbidities prior to surgery (relative risk = 2.35 (95% confidence interval 1.39 to 3.98)). Patients and surgeons should be aware of the relatively elevated risk of revision due to deep infection following THR in diabetes particularly in those with insufficient control of their glucose level.
We prospectively assessed the efficacy of a ceramic-on-metal
(CoM) hip bearing with uncemented acetabular and femoral components
in which cobalt–chrome acetabular liners and alumina ceramic heads
were used. The cohort comprised 94 total hip replacements (THRs) in 83 patients
(38 women and 45 men) with a mean age of 58 years (42 to 70). Minimum
follow-up was two years. All patients had pre- and post-operative
assessment using the Western Ontario and McMaster Universities osteoarthritis
index (WOMAC), Oxford hip score and Short-Form 12 scores. All showed
a statistically significant improvement from three months post-operatively
onwards (all p <
0.001). After two years whole blood metal ion levels were measured and
chromosomal analysis was performed. The levels of all metal ions
were elevated except vanadium. Levels of chromium, cobalt, molybdenum
and titanium were significantly higher in patients who underwent
bilateral THR compared with those undergoing unilateral THR (p <
0.001).
Chromosomal analysis demonstrated both structural and aneuploidy
mutations. There were significantly more breaks and losses than
in the normal population (p <
0.001). There was no significant
difference in chromosomal aberration between those undergoing unilateral
and bilateral procedures (all analyses p ≥ 0.62). The use of a CoM THR is effective clinically in the short-term,
with no concerns, but the significance of high metal ion levels
and chromosomal aberrations in the long-term remains unclear. Cite this article:
We present the development and results of a nationwide, prospective, observational follow-up programme including patient-reported outcome measures (PROMs) for the Swedish Hip Arthroplasty Register. The programme started in 2002 and has gradually expanded to include all units performing total hip replacement in Sweden. The self-administered PROMs protocol comprises the EQ-5D instrument, the Charnley class categorisation and visual analogue scales for pain and satisfaction. These current analyses include 34 960 total hip replacements with complete pre- and one-year post-operative questionnaires. Patients eligible for total hip replacement generally report low health-related quality of life and suffer from pain. One year post-operatively the mean EQ-5D index increased to above the level of an age- and gender-matched population, with a considerable reduction of pain (p <
0.001). Females, younger patients and those with Charnley category C reported a lower EQ-5D index pre-operatively than males, older patients and Charnley category A or B, respectively (all p <
0.001). In a multivariable regression analysis Charnley category C, male gender and higher age were associated with less improvement in health-related quality of life (p <
0.001). Nationwide implementation of a PROMs programme requires a structured organisation and effective data capture. Patients’ response rates to the Registry are good. The continuous collection of PROMs permits local and national improvement work and allows for further health-economic evaluation.
Autologous retransfusion and no-drainage are
both blood-saving measures in total hip replacement (THR). A new combined
intra- and post-operative autotransfusion filter system has been
developed especially for primary THR, and we conducted a randomised
controlled blinded study comparing this with no-drainage. A total of 204 THR patients were randomised to autologous blood
transfusion (ABT)
(n = 102) or no-drainage (n = 102). In the ABT group, a mean of
488 ml ( The use of a new intra- and post-operative autologous blood transfusion
filter system results in less total blood loss and a smaller maximum
decrease in haemoglobin levels than no-drainage following primary
THR. Cite this article:
We report a systematic review and meta-analysis of published randomised controlled trials evaluating the efficacy of tranexamic acid (TXA) in reducing blood loss and transfusion in total hip replacement (THR). The data were evaluated using the generic evaluation tool designed by the Cochrane Bone, Joint and Muscle Trauma Group. We identified 11 clinical trials which were suitable for detailed extraction of data. There were no trials that used TXA in revision THR. A total of seven studies (comprising 350 patients) were eligible for the blood loss outcome data. The use of TXA reduced intra-operative blood loss by a mean of 104 ml (95% confidence interval (CI) −164 to −44, p = 0.0006, heterogeneity I2 0%), postoperative blood loss by a mean of 172 ml (95% CI −263 to −81, p = 0.0002, heterogeneity I2 63%) and total blood loss by a mean of 289 ml (95% CI −440 to −138, p <
0.0002, heterogeneity I2 54%). TXA led to a significant reduction in the proportion of patients requiring allogeneic blood transfusion (risk difference −0.20, 95% CI −0.29 to −0.11, p <
0.00001, I2 15%). There were no significant differences in deep-vein thrombosis, pulmonary embolism, infection rates or other complications among the study groups.
An 81-year-old woman presented with a fracture
in the left femur. She had well-fixed bilateral hip replacements
and had received long-term bisphosphonate treatment. Prolonged bisphosphonate
use has been recently linked with atypical subtrochanteric and diaphyseal
femoral fractures. While the current definition of an atypical fracture
of the femur excludes peri-prosthetic fractures, this case suggests
that they do occur and should be considered in patients with severe
osteopenia. Union of the fracture followed cessation of bisphosphonates
and treatment with teriparatide. Thus, this case calls into question
whether prophylactic intramedullary nailing is sufficient alone
to treat early or completed atypical femoral fractures.
In 2004 we described the ten-year prospective results of 38 total hip replacements using the Furlong hydroxyapatite-ceramic-coated femoral component in 35 patients <
50 years old. We have now reviewed the surviving 35 arthroplasties in 33 patients at a mean of 16 years (10.3 to 19.9). The mean age of the surviving patients at the time of operation was 41.3 years (26.0 to 49.0). Of these, eight have undergone revision of their acetabular component for aseptic loosening. None of the femoral components has had revision for aseptic loosening giving a survival rate of 100% at 16 years (95% confidence interval 89% to 100%). The Furlong hydroxyapatite-ceramic-coated femoral component gives excellent long-term survival in young and active patients.
We undertook a randomised controlled trial to
compare the piriformis-sparing approach with the standard posterior approach
used for total hip replacement (THR). We recruited 100 patients
awaiting THR and randomly allocated them to either the piriformis-sparing
approach or the standard posterior approach. Pre- and post-operative
care programmes and rehabilitation regimes were identical for both
groups. Observers were blinded to the allocation throughout; patients
were blinded until the two-week assessment. Follow-up was at six
weeks, three months, one year and two years. In all 11 patients
died or were lost to follow-up. There was no significant difference between groups for any of
the functional outcomes. However, for patients in the piriformis-sparing
group there was a trend towards a better six-minute walk test at
two weeks and greater patient satisfaction at six weeks. The acetabular
components were less anteverted (p = 0.005) and had a lower mean
inclination angle (p = 0.02) in the piriformis-sparing group. However,
in both groups the mean component positions were within Lewinnek’s
safe zone. Surgeons perceived the piriformis-sparing approach to
be significantly more difficult than the standard approach (p =
0.03), particularly in obese patients. In conclusion, performing THR through a shorter incision involving
sparing piriformis is more difficult and only provides short-term
benefits compared with the standard posterior approach.
Between December 2004 and June 2006, 136 patients (156 total hip replacements), were sent from the waiting list of the Cardiff Vale NHS Trust to the NHS Treatment Centre, Weston-super-Mare, in an attempt to reduce the waiting time for total hip replacement. Because of concerns about their outcome, each patient was contacted and invited to attend a review appointment with a consultant specialising in hip and revision hip replacement. A total of 98 patients (113 hips) were reviewed after a mean of 23 months (11 to 30). There were 104 cemented hips, seven hybrid and two cementless. An acetabular inclination of >
55° was seen in 18 (16%). Radiolucent lines around the acetabular component were seen in 76 (67%). The femoral component was in more than 4° of varus in 47 (42%). The medial floor had been breached in 13 (12%) and there was a leg-length discrepancy of more than 1 cm in ten (9%). There were three dislocations, one femoral fracture, one pulmonary embolus, one deep infection and two superficial wound infections. To date, 13% (15 hips) have been revised and a further 4% (five hips) await revision, mostly for a painful loose acetabular component. The revision rate far exceeds the 0.5% five-year failure rate reported in the Swedish Registry for the components used. This initiative and the consequent need for correction of the problems created, has significantly increased the workload of our unit.
The Norwegian Arthroplasty Register has shown that several designs of uncemented femoral stems give good or excellent survivorship. The overall findings for uncemented total hip replacement however, have been disappointing because of poor results with the use of metal-backed acetabular components. In this study, we exclusively investigated the medium-to long-term performance of primary uncemented metal-backed acetabular components. A total of 9113 primary uncemented acetabular components were implanted in 7937 patients between 1987 and 2007. These were included in a prospective, population-based observational study. All the implants were modular and metal-backed with ultra-high-molecular-weight polyethylene liners. The femoral heads were made of stainless steel, cobalt-chrome (CoCr) alloy or alumina ceramic. In all, seven different designs of acetabular component were evaluated by the Kaplan-Meier survivorship method and Cox regression analysis. Most acetabular components performed well up to seven years. When the endpoint was revision of the acetabular component because of aseptic loosening, the survival ranged between 87% and 100% at ten years. However, when the endpoint was revision for any reason, the survival estimates were 81% to 92% for the same implants at ten years. Aseptic loosening, wear, osteolysis and dislocation were the main reasons for the relatively poor overall performance of the acetabular components. Prostheses with alumina heads performed slightly better than those with stainless steel or CoCr alloy in subgroups. Whereas most acetabular components performed well at seven years, the survivorship declined with longer follow-up. Fixation was generally good. None of the metal-backed uncemented acetabular components with ultra-high-molecular-weight polyethylene liners in our study had satisfactory long-term results because of high rates of wear, osteolysis, aseptic loosening and dislocation.
We analysed which pre-operative factors could be used to predict the length of in-patient stay following unilateral primary total hip replacement undertaken for osteoarthritis. Data were collected prospectively from 2302 patients undergoing primary total hip replacement over a nine-year period. The relationships between the various pre-operative factors and length of stay were studied separately using either Student’s t-test or Pearson’s correlation, and then subjected to multiple linear regression analysis. The mean length of stay was 8.1 days (median 7; 3 to 58). After adjusting for the effects of other pre-operative factors, younger age, male gender, higher combined Harris hip function and activity score, higher general health perception dimension of the Short-Form 36 score, and non-steroidal anti-inflammatory drug use were all found to be significantly associated with a reduced length of stay.
The National Institute for Clinical Excellence (NICE) published the guidelines on the selection of prostheses for primary hip replacement in 2000. They supported the use of cemented hip prostheses to the exclusion of uncemented and hybrid implants. The information from the Trent (and Wales) Regional Arthroplasty Study has been examined to identify retrospectively the types of hip prostheses used between 1990 and 2005, and to assess the impact that the guidelines have had on orthopaedic practice. The results show that the publication of the NICE guidelines has had little impact on clinical practice, with the use of uncemented prostheses increasing from 6.7% (137) in 2001 to 19.2% (632) in 2005. The use of hybrid prostheses has more than doubled from 8.8% (181) to 22% (722) of all hips implanted in the same period. The recommendations made by NICE are not being followed, which calls into question their value.
Peri- and sub-prosthetic fractures, or pathological fractures below an existing well-fixed femoral component, with or without an ipsilateral knee replacement, present a difficult surgical challenge. We describe a simple solution, in which a custom-made prosthesis with a cylindrical design is cemented proximally to the stem of an existing, well-fixed femoral component. This effectively treats the fracture without sacrificing the good hip. We describe five patients with a mean age of 73 years (60 to 81) and a mean follow-up of 47 months (6 to 108). The mean overlap of the prosthesis over the femoral component was 7.5 cm (5.5 to 10). There have been no mechanical failures, no new infections and no re-operations. We suggest that in highly selected cases, in which conventional fixation is not feasible, this technique offers a durable option and avoids the morbidity of a total femoral replacement.
We have evaluated the quality of life and functional outcome after unilateral primary total hip replacement (THR). Between 5 January 1998 and 31 July 2000, we recruited a consecutive series of 627 patients undergoing this procedure and investigated them prospectively. Each was assessed before operation and reviewed after six months, 18 months, three years and five years. The Short Form-36 Health Survey (SF-36) and Harris Hip scores were evaluated at each appointment. All dimensions of the SF-36 except for mental health and general health perception, improved significantly after operation and this was maintained throughout the follow-up. The greatest improvement was seen at the six-month assessment. On average, women reported lower SF-36 scores pre-operatively, but the gender difference did not continue post-operatively. The Harris Hip scores improved significantly after operation, reaching a plateau after 18 months. The improved quality of life was sustained five years after THR.
Little is known about the efficacy of graduated compression stockings in preventing venous thromboembolism after hip surgery. We conducted a prospective, randomised single-blind study to determine whether the addition of compression stockings to fondaparinux conferred any additional benefit. The study included 874 patients, of whom 795 could be evaluated (400 in the fondaparinux group and 395 in the fondaparinux plus compression stocking group). Fondaparinux was given post-operatively for five to nine days, either alone or combined with wearing stockings, which were worn for a mean 42 days (35 to 49). The study outcomes were venous thromboembolism, or sudden death before day 42. Duplex ultrasonography was scheduled within a week of day 42. Safety outcomes were bleeding and death from venous thromboembolism. The prevalence of deep-vein thrombosis was similar in the two groups 5.5% (22 of 400) in the fondaparinux group and 4.8 (19 of 395) in the fondaparinux plus stocking group (odds ratio 0.88, 95% confidence interval 0.46 to 1.65, p = 0.69). Major bleeding occurred in only one patient. The addition of graduated compression stockings to fondaparinux appears to offer no additional benefit over the use of fondaparinux alone.
We report a retrospective review of the incidence of venous thromboembolism in 463 consecutive patients who underwent primary total hip arthroplasty (487 procedures). Treatment included both total hip replacement and hip resurfacing, and the patients were managed without anticoagulants. The thromboprophylaxis regimen included an antiplatelet agent, generally aspirin, hypotensive epidural anaesthesia, elastic compression stockings and early mobilisation. In 258 of these procedures (244 patients) performed in 2005 (cohort A) mechanical compression devices were not used, whereas in 229 (219 patients) performed during 2006 (cohort B) bilateral intermittent pneumatic calf compression was used. All operations were performed through a posterior mini-incision approach. Patients who required anticoagulation for pre-existing medical problems and those undergoing revision arthroplasty were excluded. Doppler ultrasonographic screening for deep-vein thrombosis was performed in all patients between the fourth and sixth post-operative days. All patients were reviewed at a follow-up clinic six to ten weeks after the operation. In addition, reponse to a questionnaire was obtained at the end of 12 weeks post-operatively. No symptomatic calf or above-knee deep-vein thrombosis or pulmonary embolism occurred. In 25 patients in cohort A (10.2%) and in ten patients in cohort B (4.6%) asymptomatic calf deep-vein thromboses were detected ultrasonographically. This difference was statistically significant (p = 0.03). The regimen followed by cohort B offers the prospect of a low incidence of venous thromboembolism without subjecting patients to the higher risk of bleeding associated with anticoagulant use.
We carried out a retrospective cohort study of 3309 patients undergoing primary total hip replacement to examine the impact of tobacco use and body mass index on the length of stay in hospital and the risk of short term post-operative complications. Heavy tobacco use was associated with an increased risk of systemic post-operative complications (p = 0.004). Previous and current smokers had a 43% and 56% increased risk of systemic complications, respectively, when compared with non-smokers. In heavy smokers, the risk increased by 121%. A high body mass index was significantly associated with an increased mean length of stay in hospital of between 4.7% and 7%. The risk of systemic complications was increased by 58% in the obese. Smoking and body mass index were not significantly related to the development of local complications. Greater efforts should be taken to reduce the impact of preventable life style factors, such as smoking and high body mass index, on the post-operative course of total hip replacement.
Using the Trent regional arthroplasty register, we analysed the survival at ten years of 1198 consecutive Charnley total hip replacements carried out across a single health region of the United Kingdom in 1990. At ten years, information regarding outcome was available for 1001 hips (83.6%). The crude revision rate was 6.2% (62 of 1001) and the cumulative survival rate with revision of the components as an end-point was 93.1%. At five years, a review of this series of patients identified gross radiological failure in 25 total hip replacements which had previously been unrecognised. At ten years the outcome was known for 18 of these 25 patients (72%), of whom 13 had not undergone revision. This is the first study to assess the survival at ten years for the primary Charnley total hip replacement performed in a broad cross-section of hospitals in the United Kingdom, as opposed to specialist centres. Our results highlight the importance of the arthroplasty register in identifying the long-term outcome of hip prostheses.