What is the Long-term Wear of a 5-Mrad Highly Crosslinked Polyethylene Liner? A 14-year RSA Study.

BACKGROUND: Lower doses of irradiation (≤ 5 Mrad) during the manufacture of highly crosslinked polyethylene acetabular liners may result in less crosslinking and an increased wear rate. Radiostereometric analysis (RSA) studies have found that wear of more highly irradiated highly crosslinked polyethylene liners (7 to 10 Mrad) decreases at longer-term follow-up compared with earlier reports of the same cohorts. Although wear of 5-Mrad irradiated liners appears to increase at midterm follow-up, it is unclear whether that remains true at longer follow-up. QUESTIONS/PURPOSES: We asked: (1) In patients who underwent THA with a 5-Mrad highly crosslinked polyethylene liner, what is the wear rate evaluated with RSA during the first 14 years? (2) Does the wear rate decrease after 6 years in situ? METHODS: This is a brief follow-up of prior RSA studies performed at 2 and 6 years. We prospectively reviewed the longer-term wear rate in 13 patients who underwent primary THAs with the same design of a 5-MRad irradiated crosslinked acetabular liner and a 28-mm cobalt-chromium articulation. Of the initial 30 patients who were enrolled, 13 (43%) were available at the 14-year timepoint; nine patients had died, 1 patient had withdrawn, 1 had an intraoperative fracture, 3 patients were too infirm to have radiographs, 2 had no baseline RSA radiographs, and 1 had poor-quality RSA images. Tantalum markers were inserted during surgery, and all patients had RSA radiographic examinations at 1 week, 6 months, and 1, 2, 6, and 14 years postoperatively. RESULTS: The mean ± standard deviation proximal, 2D, and 3D wear rates calculated between 1 year and 14 years were 0.019 ± 0.013 mm, 0.022 ± 0.015 mm, and 0.025 ± 0.019 mm per year, respectively. No patient had proximal 2D or 3D wear rates exceeding 0.06 mm per year. An increasing wear rate over time was measured for proximal and 2D wear rates between 6 and 14 years (0.024 and 0.030 mm per year) compared with that between 1 and 6 years (0.008 and 0.010 mm per year; p = 0.03). CONCLUSION: The proximal, 2D, and 3D wear of a highly crosslinked polyethylene liner produced using 5-Mrad radiation remains low in the longer-term. With the small numbers available in a long-term RSA study such as this, we confirmed that the wear rate did not decrease at longer-term follow-up, unlike previous RSA studies of more highly irradiated highly crosslinked polyethylene liners. Nevertheless, the wear rate remains very low and below the threshold typically associated with the development of osteolysis (0.1 mm/year of wear). This should provide assurance to orthopaedic surgeons monitoring patients with this 5-Mrad irradiated liner in situ, while providing useful information to manufacturers of future highly crosslinked polyethylene liners. LEVEL OF EVIDENCE: Level IV therapeutic study.

Long-term migration characteristics of the Corail hydroxyapatite-coated femoral stem: a 14-year radiostereometric analysis follow-up study.

BACKGROUND: The magnitude and pattern of acceptable long-term migration of cementless femoral stems are not well understood. The Corail hydroxyapatite-coated cementless stem is a clinically successful and commonly used femoral stem with a long-term migration pattern not previously described in the literature. The aim of this study was to assess the long-term migration of the Corail hydroxyapatite-coated cementless stem using radiostereometric analysis (RSA) at 14-year follow-up, thereby establishing a benchmark acceptable long-term migration pattern for hydroxyapatite-coated cementless prostheses. MATERIALS AND METHODS: A prospective cohort of 29 patients (30 hips) undergoing primary total hip arthroplasty for primary hip osteoarthritis were enrolled into a study to characterise the migration of the Corail cementless stem. A total of 13 patients (4 males, 9 females) with mean age 82 (range 68-92) underwent repeat RSA radiographs at minimum 10 years post-operation (mean 13.9 years, range 13.3-14.4). Subsidence of the stem was measured and compared to prior measurements taken at 6 months and 1, 2, and 6 years. RESULTS: None of the 13 patients have been revised. The migration at 6 months, 1 year, 2 years, and 6 years has been previously recorded. At mean 14-year follow-up, the cohort mean subsidence of the cementless stem was 0.70 mm (range - 0.06 to 3.61 mm). For each stem followed up at 6 months and 14 years, the mean subsidence over this period was 0.05 mm (range - 0.14 to 0.57 mm). There is no significant difference in mean subsidence at 6 months and 14 years (p = 0.43). CONCLUSIONS: The long-term pattern of the subsidence of the Corail femoral stem has not previously been described. Subsidence occurs within the first 6 months, after which there is persistent stabilisation of the implant to 14 years. This study provides a description of a long-term acceptable migration pattern to which new hydroxyapatite-coated cementless prostheses may be compared. LEVEL OF EVIDENCE: II.

Mid-term migration of a cementless, porous acetabular cup: A 5 year Radiostereometric analysis.

PURPOSE: The aim of the study was to determine the 5 year migratory and wear patterns, adverse events and clinical outcomes of a cementless, porous acetabular cup. METHODS: RSA imaging of a cohort of 11 patients was retrospective analysed at 5 years post Total Hip Arthroplasty (THA). Changes in pain, function and symptoms of the hip at 5 years post-THA were compared to preoperative and 2 year postoperative assessments on the Harris Hip Score (HHS) and Hip dysfunction and Osteoarthritis Outcome Score (HOOS). RESULTS: The majority of cup migration occurred up to 6 months and stabilised thereafter (6 months to 5 years, p = 0.091-0.866, Wilcoxon Signed Rank test). The direction of rotation around the 3 axes was evenly distributed among the cups between anterior-posterior rotation, internal-external rotation and increased-decreased inclination. The majority of the cups translated proximally, at an average migration of 0.36 mm (±95%CI 0.17) at 5-years post-THA. Following initial bedding in, up to 6 months, there was no detectable polyethylene wear between 6 months and 5 years. At 5 years postoperatively, a statistically significant difference was observed across all HOOS subscales in comparison to preoperative values, with higher means reported at 5 years (p < 0.001). The total mean HHS displayed a statistically significant improvement, increasing from 'poor' preoperatively to 'good' at 5 years post-THA. CONCLUSION: Following initial migration between discharge and 6 months, the cementless porous acetabular cup demonstrated a tendency for stabilisation from 6 months up to 5 years post-THA, suggesting good mid-term fixation. Additionally, improvements in clinical outcome measures of pain, function and quality-of-life remained high following THA at 5 years post-surgery.

Orthopaedic triaging by podiatrists: a prospective study of patient satisfaction and service efficiency.

BACKGROUND: The Southern Adelaide Local Health Network is serviced by one orthopaedic surgeon specialising in foot and ankle surgery. In 2011, the waiting list to see the surgeon was expanding and the need for assistance was growing. The Department of Podiatry agreed to provide a podiatrist to assist in the management of the outpatient waiting list. Although patient outcome is an important outcome measure, we were interested in evaluating the service with respect to how satisfied patients were with seeing a podiatrist. Therefore, the primary aim of the study was to evaluate patient satisfaction with podiatry-led clinics for the orthopaedic outpatient waiting list. Secondary outcomes included discharge rate and efficiency of care. METHODS: We prospectively recruited a consecutive sample discharged from the Department of Podiatry between 1 May and 1 November 2013 to complete the Client Satisfaction Survey (CSQ-8). This survey was used to evaluate the satisfaction of patients following discharge from the Department of Podiatry. RESULTS: There were 49 patients (16 men, 33 women) enrolled in the survey during the 6-month period. Of the 49 patients discharged, 21 (43%) were discharged from the outpatient waiting list. Twenty-eight patients (57%) were referred on to the Department of Orthopaedic Surgery for opinion and management. The mean (± s.d.) number of appointments for each patient was 1.3±0.6. Overall, patients were very satisfied with the assessment and/or treatment they received. CONCLUSION: A podiatrist, working at an extended scope of practice and in collaboration with an orthopaedic surgeon, can successfully and efficiently assess and treat patients on an orthopaedic outpatient waiting list. Patients generally reported a high level of satisfaction with the process and would return to the clinic again if necessary. Hospital networks wanting to efficiently reduce waiting lists may endorse task substitution for appropriately skilled podiatrists.

Wear of a 5 megarad cross-linked polyethylene liner: a 6-year RSA study.

BACKGROUND: One cross-linked polyethylene (XLPE) liner is manufactured using a lower dose of radiation, 5 Mrad, which may result in less cross-linking. The reported in vivo wear rate of this XLPE liner in patients undergoing THA has varied, and has included some patients in each reported cohort who had greater than 0.1 mm/year of wear, which is an historical threshold for osteolysis. Previous studies have measured wear on plain radiographs, an approach that has limited sensitivity. QUESTIONS/PURPOSES: We therefore measured the amount and direction of wear at 6 years using Radiostereometric analysis (RSA) in patients who had THAs that included a cross-linked polyethylene liner manufactured using 5 Mrad radiation. METHODS: We prospectively reviewed wear in 30 patients who underwent primary THAs with the same design of cross-linked acetabular liner and a 28-mm articulation. Tantalum markers were inserted during surgery and all patients had RSA radiographic examinations at 1 week, 6 months, 1, 2, and 6 years postoperatively. RESULTS: The mean proximal, two-dimensional (2-D) and three-dimensional (3-D) wear rates calculated between 1 year and 6 years were 0.014, 0.014, and 0.018 mm/per year, respectively. The direction of the head penetration recorded between 1 week and 6 years was in a proximal direction for all patients, proximolateral for 16 of 24 patients, and proximomedial for eight of 24 patients. CONCLUSIONS: The proximal, 2-D and 3-D wear of a XLPE liner produced using 5 Mrad of radiation was low but measurable by RSA after 6 years. No patients had proximal 2-D or 3-D wear rates exceeding 0.1 mm/year. Further followup is needed to evaluate the effect of XLPE wear particles on the development of long-term osteolysis.

Implementation of a quality care management system for patients with arthritis of the hip and knee.

The Orthopaedic Unit of the Repatriation General Hospital (RGH) in Adelaide, South Australia has implemented a quality care management system for patients with arthritis of the hip and knee. The system not only optimises conservative management but ensures that joint replacement surgery is undertaken in an appropriate and timely manner. This new service model addresses identified barriers to service access and provides a comprehensive, coordinated strategy for patient management. Over 4 years the model has reduced waiting times for initial outpatient assessment from 8 to 3 months and surgery from 18 to 8 months, while decreasing length of stay from 6.3 to 5.3 days for hips and 5.8 to 5.3 days for knees. The service reforms have been accompanied by positive feedback from patients and referring general practitioners in relation to the improved coordination of care and enhanced efficiency in service delivery.

Total knee replacement in the morbidly obese: a literature review.

BACKGROUND: The 'obesity epidemic' is expected to result in an increased incidence of knee osteoarthritis and hence total knee replacements (TKRs). Reviews have demonstrated the conflicting results of TKR for all obese (body mass index (BMI) >30). The aim of this literature review was to specifically evaluate outcomes of TKR in patients with morbid obesity (MO; BMI >40). METHODS: A systematic review of medical databases (PubMed, Medline, Cochrane Library, ScienceDirect) by use of keywords from January 1990 to September 2009 was undertaken. RESULTS: Clinical and functional Knee Society Scores (KSS) improve after TKR for patients with MO. The post-operative functional KSS was, in general, less than in controls. Radiographic analysis was inconclusive because of small study populations and short duration of follow-up. All studies reporting complications noted a greater prevalence in MO patients (10-30%). Of concern was the significantly higher prevalence of deep prosthetic infection (3-9-times that of controls). The morbidly obese also had a significantly higher incidence of wound complications. TKR did not result in weight loss for MO patients, and therefore has no benefit on weight-related medical conditions. Bariatric surgery in MO under 65 years of age has been shown to be a cost-effective and clinically effective method of weight reduction. This surgery also results in significant improvement in weight-related medical conditions, the KSS and knee pain. CONCLUSIONS: Given the increase in complications for MO patients after TKR, these patients should be advised to lose weight before surgery and, if suitable, would probably benefit from bariatric surgery.