Highly Cross-Linked Polyethylene Reduces Wear and Revision Rates in Total Hip Arthroplasty: A 10-Year Double-Blinded Randomized Controlled Trial.

BACKGROUND: Highly cross-linked polyethylene (XLPE) was developed to address the problem of wear and osteolysis associated with metal-on-conventional ultra-high molecular weight polyethylene (UHMWPE) bearing surfaces. The purpose of this study was to compare in vivo wear rates and clinical and radiographic outcomes between XLPE and UHMWPE in a prospective double-blinded randomized controlled trial with a minimum of 10 years of follow-up. METHODS: We randomized 122 patients to receive either a conventional UHMWPE liner (Enduron; DePuy) or an XLPE liner (Marathon; DePuy). Ninety-one patients were assessed clinically and radiographically at a minimum of 10 years (range, 10.08 to 12.17 years). Oxford Hip Scores and Short Form-12 Health Survey scores were collected. The radiographs were analyzed for osteolysis and for 2-dimensional (2-D), 3-dimensional (3-D), and volumetric wear using validated software. RESULTS: All 122 patients were accounted for at the 10-year follow-up evaluation. Twelve patients had undergone revision surgery, 21 patients had died (1 of whom had previously undergone revision surgery), and 2 patients were unable to return for follow-up, leaving 91 patients available for clinical and radiographic evaluation. At a minimum of 10 years, 3-D wear rates were significantly lower (p < 0.001) in the XLPE group (mean, 0.03 mm/yr) than in the conventional UHMWPE group (mean, 0.27 mm/yr). The prevalence of osteolysis was also significantly lower in the XLPE group (38% versus 8%, p < 0.005), as was the revision rate (14.6% versus 1.9%, p = 0.012), with 10 of the 12 revisions being in the Enduron group. There was no significant difference between the clinical scores of the 2 groups. CONCLUSIONS: XLPE liners have significantly reduced wear and are associated with a greater implant survival rate at 10 years compared with conventional UHMWPE liners. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Oxford hip scores at 6 months and 5 years are associated with total hip revision within the subsequent 2 years.

BACKGROUND: The Oxford hip score (OHS) is commonly reported in research studies as a reflection of pain and function but it is unclear whether it predicts subsequent prosthesis failure. QUESTIONS/PURPOSES: We determined whether OHS obtained at 6 months and 5 years after surgery predicts risk of revision within the subsequent 2 years. METHODS: We reviewed data from the New Zealand Joint Registry between January 1999 and December 2010. OHS at 6 months was available for 17,831 total hip patients. Patients were separated into four categories based on their OHS: 10,458 (59%) scored 42-48, 4726 (26%) scored 34-41, 1592 (9%) scored 27-33, and 1028 (6%) scored 0-26. Five-year OHSs were available for 3665 patients. Of these patients, 2619 (72%) scored 42-48, 657 (18%) scored 34-41, 225 (6%) scored 27-33, and 164 (4%) scored 0-26. RESULTS: For patients with a 6-month OHS, revision risk within 2 years was 0.4% in the 42-48 group, 1.0% in the 34-41 group, 1.7% in the 27-33 group, and 6.2% in the 0-27 group. For patients with 5-year OHS, revision risk within 2 years was 0.3%, 1.1%, 3.6%, and 6.1%, respectively. Increase in revision risk for the 0-27 versus the 42-48 OHS group was 15-fold at 6 months and 18-fold at 5 years. CONCLUSIONS: Our data suggest patients with an OHS of 42-48 at 6 months need a 5-year postoperative appointment. Those patients with a 5-year OHS of 42-48 need not be followed up for a further 5 years.

Redefining the cast index: the optimum technique to reduce redisplacement in pediatric distal forearm fractures.

BACKGROUND: The aim of this study was to identify the optimal cast index (CI) level that reduces the risk of fracture redisplacement. The CI is the ratio of sagittal to coronal width from the inside edges of the cast at the fracture site. Previous studies have used 0.7 as the standard. METHODS: Case records and radiographs of 1001 children who underwent a manipulation under anesthesia for a displaced fracture of the distal forearm were studied. Redisplacement was defined as > 15 degrees of angulation and/or > 80% of translational displacement on check radiographs at 2 weeks. Angulation (degrees) and translational displacement (%) were measured on the initial and check radiographs. The CI was measured on the check radiographs. The CI has previously been validated in an experimental study. RESULTS: The adequacy of reduction after manipulation was determined by translation and angulation of the radius and ulna in anteroposterior and lateral plain film radiographs. From the 1001 patients who qualified for the study, fracture redisplacement was seen in 107 (10.6%) cases at the 2-week follow-up. A total of 752 (75%) patients had CIs of ≤ 0.8, whereas 249 (25%) had casting indices of ≥ 0.81. In patients with CIs of ≤ 0.8, the displacement rate was only 5.58%. However, in patients with CIs of ≥ 0.81, the displacement rate was 26%. A high CI was the sole factor that was significantly higher in the redisplacement group. No statistically significant difference was seen for age, sex, or surgeon seniority. Statistical differences were not noted in initial angular deformity or initial displacement. DISCUSSION: The CI is a simple reliable radiographic measurement to predict the redisplacement of forearm fractures in children. A plaster with a CI of > 0.81 is prone to redisplacement. High CIs are associated with redisplacement of fractures and should be avoided when molding casts in distal forearm fractures. LEVELS OF EVIDENCE: Level III--retrospective comparative study.

Do joint registries report true rates of hip dislocation?

BACKGROUND: Despite advances in primary THA, dislocation remains a common complication. In New Zealand (NZ), dislocations are reported to the National Joint Registry (NJR) only when prosthetic components are revised in the treatment of a dislocation. Closed reductions of dislocated hips are not recorded by the NJR. QUESTIONS/PURPOSES: We compared the true dislocation rate for patients receiving primary THA in the Wellington region with the rate reported by the NZ NJR for the same group of patients. METHODS: The NZ NJR identified 570 patients undergoing primary THA from January 1, 2008, to December 31, 2009, with addresses in the Wellington region. The mean age was 67.5 years (range, 27-96 years). The minimum followup was 2 years (mean, 3 years; range, 2-4 years). RESULTS: Six patients required revision of at least one component for dislocation. There was 100% agreement between the hospital database and the NJR. Using the NJR criteria of revision of any component as an end point, the dislocation rate in the Wellington region after primary THA was 1.05%. The hospital database identified a further eight patients who presented with a dislocation of their primary THA and underwent a closed reduction. These patients were not recorded by the NJR. The true rate of all dislocations, which includes closed reductions, was 2.46%. CONCLUSIONS: This article documents the discrepancy between the NZ NJR reported rate of revision for dislocation and the true rate of dislocation in primary THA. We recommend documentation of all dislocations by NJR in their database to allow more accurate comparisons between centers and research outcomes. LEVEL OF EVIDENCE: Level IV, clinical research study. See Guidelines for Authors for a complete description of levels of evidence.

Highly crosslinked polyethylene reduces wear in total hip arthroplasty at 5 years.

BACKGROUND: Although hip arthroplasty reliably relieves pain and improves function, problems have arisen with wear and osteolysis. Highly crosslinked polyethylene has been developed to address this problem although at present there is limited clinical evidence it does so longer term. QUESTIONS/PURPOSES: We compared the in vivo wear of standard versus highly crosslinked polyethylene (HXLP) in primary total hip arthroplasty at a minimum of 5-year followup. METHODS: We enrolled 122 patients in a prospective, double-blinded, randomized trial and followed them annually to assess their progress. Annual radiographs were analyzed using previously validated edge detection software to assess for two-dimensional, three-dimensional, and volumetric wear. The mean follow up was 5.5 years (range, 4.1 to 7 years). RESULTS: The two-dimensional wear measurements for HXLP showed lower wear compared to the conventional group (0.05 mm/year versus 0.26 mm/year, respectively). Three-dimensional and volumetric wear were similarly lower in the HXLP group. CONCLUSIONS: Highly crosslinked polyethylene undergoes substantially less wear than conventional polyethylene at medium term. The effect of hip arthroplasty longevity will need to be assessed with longer-term studies, but this may lead to a decreased need for revision as a result of less wear and osteolysis.

A double-blind, prospective, randomized controlled trial comparing highly cross-linked and conventional polyethylene in primary total hip arthroplasty.

Highly cross-linked polyethylene was developed to reduce articular bearing wear in total hip arthroplasty. In vitro studies have shown reduced wear in comparison with conventional polyethylene. A double-blind, prospective, randomized trial was performed comparing highly cross-linked and conventional polyethylene in 119 patients. The primary outcome variables were linear, 3-dimensional, and volumetric wear as determined by analysis of digitized radiographs using validated wear measurement software. Linear, 3-dimensional, and volumetric wear rates were significantly less in the highly cross-linked polyethylene group between 6 months and 4 years postoperatively (P < .05). The data presented here show that highly cross-linked polyethylene reduces short-term polyethylene wear. The intermediate and long-term clinical results of highly cross-linked polyethylene remain unknown pending further follow-up.

The influence of steroid injections on the incidence of infection following total knee arthroplasty.

AIM: To investigate whether a relationship exists between preoperative intra-articular steroid injections and postoperative wound healing in total knee arthroplasty (TKA). Similar research studies on total hip arthroplasty (THA) have found higher rates of post surgical problems in hips that have been injected with steroids. METHODS: Thirty-eight patients with TKA postoperative wound infection, and 352 TKA patients without postoperative wound infection were compared against corticosteroid injected and non-injected patients. Variables measured were diabetes, cigarette smoking, knee scores, number of injections, injection administrator, and preoperative injection intervals. RESULTS: No significant difference emerged in rates of infection or between smoking rates and diabetes. Number of injections, preoperative injection interval and injection administrator did not significantly influence outcome. A significant difference exists between each group's knee scores. CONCLUSIONS: Injecting knees with corticosteroids prior to TKA did not increase the incidence of postoperative wound infection.

Hybrid total hip replacement: outcome after a mean follow up of 10 years.

BACKGROUND: Total hip replacement is one of the most successful surgical procedures of the modern surgical era. The method of fixation of implants continues to evolve, and as cemented acetabular fixation appears to be less durable than anticipated, the use of a cemented stem and an uncemented acetabulum - a so-called 'hybrid hip'- has become more popular. This paper reports the results of hybrid total hip replacement at an average of 10 years postoperatively. METHODS: Primary hybrid total hip replacements carried out by a single surgeon in 1994 and 1995 were identified; patients were sent Oxford Hip Score and EuroQuol-5 Dimension quality-of-life questionnaires and, where necessary, a radiograph appointment. Questions about diabetes, cigarette smoking and hip dislocation were included. First postoperative and final radiographs were compared for stem subsidence, cup migration, stem position, osteolysis of the femur and pelvis, and evidence of loosening of both components. RESULTS: At 10-year follow up the revision rate for femoral component loosening was 2.9%. Fifteen per cent showed some abnormality at the femoral interface, not related to stem size and more common in titanium stems. Average hip score was 20.9, and quality-of-life measures indicated a high level of satisfaction. CONCLUSIONS: Hybrid total hip replacement gives excellent clinical outcomes with low revision rates for both components. The one-piece uncemented cup offers important advantages over modular devices, the use of which should be re-evaluated.

Osteosarcoma in New Zealand: an outcome study comparing survival rates between 1981-1987 and 1994-1999.

AIMS: To review the data and outcome of patients with osteosarcoma in New Zealand from 1994 to 1999 and to compare this to data retrieved from a similar study from 1981 to 1987. METHODS: Data from 1994-1999 was obtained from the New Zealand Cancer Registry; raw data was also retrieved from the 1981-1987 study. RESULTS: There were 96 cases in the 1981-1987 cohort and 84 cases in the 1994-1999 cohort. Overall, 5-year survival from osteosarcoma improved from 32.3% to 44.0% between the cohorts. When the cohorts were compared, there was a trend toward improved outcome in most subgroups CONCLUSIONS: The outcome in patients with osteosarcoma in New Zealand has improved over the study period and is similar to that seen in the overseas literature.

Femoral revision with a fluted, tapered, modular stem seventy patients followed for a mean of 3.9 years.

Fluted tapered revision femoral stems have been used successfully in Europe. Modularity makes these implants more versatile, but outcomes of modular designs have not been reported. We report a retrospective review of 70 such stems with a mean follow-up of 47 months. Combined metaphyseal/diaphyseal bone loss was present preoperatively in 36 (51%) of 70 hips. Three hips (4.3%) were re-revised or in need of re-revision, and worst-case survival was 87%. The mean postoperative patient-assessed Oxford Hip Score was 21.1. Restoration of proximal bone was noted in 56%. Complications included mean subsidence of 9.9 mm, dislocation in 7 (10%) of 70 hips, and fracture or cortical perforation in 17 (24.2%) of 70. These results are equivalent to, or better than, reported results of other types of cementless revision femoral stems.

Does pelvic osteolysis occur with a nonmodular uncemented acetabular component?

We present a radiographic follow-up of an uncemented, nonmodular, pure titanium-backed acetabular component at 6 to 12 years postimplantation. Between 1990 and 1992, 130 primary total hip arthroplasties were carried out by 1 surgeon using this implant, in association with both cemented and uncemented femoral components. There were 19 deaths, 5 revisions, and 19 hips lost to follow-up, leaving 87 hips available for review at a mean of 9.6 years. Two revisions were for infection, whereas 3 well-fixed cups were changed at the time of revision of a loose femoral component to allow downsizing to a 28-mm head. No cup has been revised for aseptic loosening. There was no radiographic evidence of periacetabular osteolysis or loosening of any of the cups, even in a subgroup of 31 patients who were 60 years or younger at the time of implantation.

Complications and outcomes of single-stage bilateral total knee arthroplasty.

BACKGROUND: A recent literature review by the senior authors of this study revealed that simultaneous bilateral knee arthroplasty is uncommon and controversial. Reported complications include myocardial infarction, deep venous thrombosis, pulmonary embolus, thromboembolic complications, pseudo-obstruction, postoperative ileus and death. This present study was designed to identify complications of single-stage bilateral total knee arthroplasty to compare with reports in the international literature. METHODS: A retrospective study of 40 cases of simultaneous total knee arthroplasty carried out by the senior authors at Wellington over the last 10 years, examined details of surgery, anaesthesia, preoperative and postoperative management to identify the occurrence of complications. Thirty-one patients completed an Oxford Knee Score, a EuroQuol-5 Dimension (EQ-5D) questionnaire and reported their experience of the bilateral procedure. RESULTS: Complications reported in the international literature did not occur in the patients studied. Complications that did occur included urinary retention, wound infections and oedema of the limbs or knees. The mean Oxford Knee Score was 20.79. In 2003 the New Zealand national mean for primary total knee arthroplasty was 23.35. The EQ-5D revealed high patient satisfaction and good functional status. CONCLUSIONS: While the outcomes and cost benefits of single stage bilateral replacement are established, the risk of complications remains. This study establishes the low complication rate associated with this procedure in the senior authors' hands, and documents the high patient satisfaction. The study demonstrates that, in selected patients, simultaneous bilateral knee replacement surgery can be performed with good outcomes without a definite increase in perioperative risk.

Influence of preoperative medical status and delay to surgery on death following a hip fracture.

BACKGROUND: A retrospective study of 138 patients with fractured hips was undertaken to determine if a delay to surgery beyond 24 h influenced 1-year mortality. In particular, the results of the subgroup of patients who were in the American Society of Anesthesiologists (ASA) Class 3 or 4 were considered. METHODS: Patients were found using ICD-9 database information. One-year mortality data was collected from Births, Deaths and Marriages -- the New Zealand government agency that collects and stores statistics on these events. RESULTS: The 1-year mortality rate was 17.4%. Age, operation type and time to surgery did not significantly affect 1-year mortality. American Society of Anesthesiologists' Class 1 and 2 patients had a significantly lower 1-year mortality (5.3%) than ASA Class 3 and 4 patients (22.4%) (P = 0.02). CONCLUSION: Time to surgery did not significantly affect 1-year mortality within each ASA Class.

Proximal femoral osteotomy for the treatment of hip arthritis in young adults.

BACKGROUND: The outcome of proximal femoral osteotomy for hip arthritis in young adults performed at the Wellington Hospital (Wellington, New Zealand) was reviewed. METHODS: Seventeen patients underwent 21 proximal femoral osteotomies for the treatment of hip arthritis at Wellington Hospital between 1992 and 1999. Thirteen patients (17 hips) were contacted and were able to complete a questionnaire form specific for hip pain and function. RESULTS: There was a response rate of 76.5% (13 out of a possible 17 patients undergoing proximal femoral osteotomy) at a mean 3 years 4 months postoperatively. Of these, one patient has had a total hip joint replacement and one patient is currently on the waiting list for a total hip joint replacement. Three other patients (three hips) report moderate or severe hip pain. The remaining eight patients (12 hips) report having mild or no hip pain. Questionnaire results show a postoperative decrease in hip pain in most patients. Hip function as assessed by the questionnaire was essentially unchanged. CONCLUSIONS: Proximal femoral osteotomy is a satisfactory option for young patients with degenerative hip arthritis. The operation is only likely to be useful in the treatment of pain.

Ankle fractures: functional and lifestyle outcomes at 2 years.

BACKGROUND: Ankle fractures form a high proportion of the total number of fractures treated in New Zealand. International studies show that there are mixed functional outcomes with differing fracture types and subsequently differing lifestyle outcomes. METHODS: Fracture clinic records and orthopaedic admissions books for Wellington Public Hospital, Capital Coast Health, -Wellington, were retrospectively reviewed to gain a population of patients who sustained ankle fractures for the period January--December 1998. These patients were asked to fill in postal questionnaires detailing their current ankle function and lifestyle, two years after fracturing their ankle. The patients' radiographs were reviewed to classify the types of ankle fractures sustained. RESULTS: Of 141 patients that sustained ankle fractures, 74 were followed up 2 years after their ankle fracture. All fracture types averaged Olerud-Molander ankle scores of 71.1. Weber A fractures averaged ankle function scores of 90, Weber B fractures 80, and Weber C fractures 78. Four patients (5%) achieved 'poor' results, 12 (16%) patients achieved a 'fair' result, 30 (41%) patients gained a 'good' result, 27 (36%) patients attained 'excellent' results. Lifestyle outcomes were reflected in the patient's ankle function outcomes (P < 0.05). CONCLUSION: Patients who sustain ankle fractures can be expected to be still experiencing functional difficulties two years post-treatment.

Chemical eluates from ultra-high molecular weight polyethylene and fibroblast proliferation.

Although polyethylene wear particles have been implicated in osteolysis and implant loosening, this study is the first to test whether chemical eluates extracted from ultra-high molecular weight polyethylene (UHMWPE) could also be involved in this process. Eluates were prepared from UHMWPE bar stock and examined for their effects on (3)H-thymidine incorporation by human foreskin fibroblasts grown in 96-well culture plates. Low concentrations of eluates stimulated (3)H-thymidine uptake; whereas, high concentrations inhibited uptake in a dose-dependent manner. Maximum inhibition of proliferation for eluates (87+/-0.03% inhibition, n = 45 paired wells) was greater than that observed for particles (54+/-0.07% inhibition, n = 45 paired wells). Ethylene oxide sterilization of UHMWPE reduced (3)H-thymidine uptake at low eluate concentrations relative to sterilization by gamma-irradiation. It was concluded that leachable eluates from UHMWPE implantse contribute to the osteolytic process at the bone-implant interface.

Polyethylene particles from a hip simulator cause (45)Ca release from cultured bone.

Periprosthetic osteolysis is a dominant factor in the success or failure of total hip prostheses. Polyethylene wear debris has been implicated in the process of bone resorption and subsequent implant loosening. The present study is the first to examine the effect of ultra high molecular weight polyethylene (UHMWPE) wear debris produced by a hip simulator on calvarial bone resorption in vitro. (45)Ca release was measured in cultured mouse calvarial bone samples. Although short-term exposure to UHMWPE particles (2 h) decreased (45)Ca release, longer-term exposure for 1-2 days increased release in a dose-dependent manner. After one-day exposure to 7.5 x 10(6) particles per mL, 18% more (45)Ca was released from cultured calvarial bone than from control samples. It was concluded that UHMWPE wear particles either directly or indirectly stimulated osteoclasts to activate bone resorption. Polyethylene wear debris contributes to the osteolytic process at the bone-implant interface.