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30 patients who were enrolled, 13 (43%) were available at the 14-year timepoint; nine patients had died, 1 patient had withdrawn, 1 had an intraoperative fracture, 3 patients were too infirm to have radiographs, 2 had no baseline RSA radiographs, and 1 had poor-quality RSA images.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.

Risk factors for intra-articular involvement in proximal humeral fractures.

INTRODUCTION: Identification of intra-articular involvement in proximal humeral fractures is important for operative decision making. The aim of this study was to identify the risk factors associated with intra-articular involvement in proximal humeral fractures. MATERIALS AND METHODS: One hundred consecutive three-dimensional computed tomography reconstructions of proximal humeral fractures were identified. The fracture lines were then accurately transcribed onto a two-dimensional superior view of the humeral head and each fracture was assessed for intra-articular involvement. Statistical analyses were undertaken to identify risk factors for intra-articular involvement and extent of involvement. Furthermore, for each risk factor, common fracture patterns were identified and compared to anatomical landmarks. RESULTS: Overall, 58% of the fractures involved the articular surface. High-energy mechanism, female gender, age ≥ 65, and posterior dislocation were risk factors for intra-articular involvement. Low-energy mechanism, female gender, age ≥ 65, varus angulation, and posterior dislocation were risk factors for increased extension of the fracture onto the articular surface. CONCLUSION: Intra-articular involvement in proximal humeral fractures is influenced by demographics and fracture characteristics (mechanism of injury, angulation, and dislocation). Patients with identified risk factors should be appropriately evaluated for intra-articular fractures during preoperative planning to assist in operative decision making. LEVEL OF EVIDENCE: Basic science; anatomy study.

Reverse total shoulder arthroplasty compared to stemmed hemiarthroplasty for proximal humeral fractures: a registry analysis of 5946 patients.

BACKGROUND: There is an increasing trend toward the use of reverse total shoulder arthroplasty (RTSA) over stemmed hemiarthroplasty (HA) for the management of proximal humeral fractures. There are limited data available comparing the revision rates for RTSA and HA in the setting of a fracture. The aim of this study was to compare the revision rates for RTSA and HA when used for the treatment of a fracture and to analyze the effect of demographics and prosthesis fixation on these revision rates. METHODS: Data obtained from the Australian Orthopaedic Association National Joint Replacement Registry from April 16, 2004, to December 31, 2017, included all procedures for primary diagnosis proximal humeral fracture. The analyses were performed using Kaplan-Meier estimates of survivorship and hazard ratios from Cox proportional hazards models. RESULTS: Over the study period, there were 3049 (51%) RTSA and 2897 (49%) HA procedures. The cumulative percent revision rate at 9 years was lower for the RTSA than for the HA: 7.0% (95% confidence interval [CI], 4.8-10.1) compared with 11.7% (95% CI, 10.3-13.2). Between 0 and 6 months, the HA had a significantly lower revision rate than the RTSA (hazard ratio, 0.50; 95% CI, 0.34-0.72; P < .001). Between 6 month and 3 years, the HA had a significantly higher revision rate. For the RTSA, males have a significantly higher rate of revision compared with females. There is a higher rate of early revision due to instability in younger persons (55-64) and males. For both RTSA and HA, cemented prostheses have lower revision rates compared with cementless prostheses. CONCLUSIONS: RTSA has a significantly lower revision rate compared with HA for the treatment of proximal humeral fractures in females. Younger patients (<65) and males are at risk of early revision secondary to instability. In these patient groups, either alternatives to RTSA or further attention to fixation of tuberosities and shoulder rehabilitation may be indicated.

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.