Thicker polyethylene inserts (≥ 13 mm) increase the risk for early failure after primary cruciate-retaining total knee arthroplasty (TKA): a single-centre study of 7643 TKAs.

PURPOSE: This study investigates whether thicker (PE) inserts lead to a greater risk for revision after TKA. The differences between the TKA designs of three manufacturers (NexGen, PFC Sigma, Triathlon) are also compared. METHODS: A total of 7643 primary TKA surgeries were included. PE inserts were divided into two groups-"thick PE inserts" with a thickness of 13 mm (mm) or more and "standard PE inserts" with a thickness of less than 13 mm. Three cruciate-retaining (CR) TKA designs (NexGen, PFC Sigma, Triathlon) were included in the study. The differences in failure rates between groups were investigated using Kaplan-Meier survival curves and Cox regression model with hazard ratios (HR). Failure rates were investigated short-term (< 2 years) and long-term (the whole follow-up period). The TKA designs were analysed both together and separately. RESULTS: During the whole follow-up period, there were 184 (2.4%) aseptic revisions. The thick PE insert group showed an increased risk for revision compared to the standard PE insert group in both short-term (< 2 years; HR 2.0, CI 1.3 to 3.2) and long term (> 2 years; HR 1.6, CI 1.1 to 2.3) follow-up. The highest revision rate was observed in patients who received the Triathlon TKA with a thicker PE insert (HR 2.6, CI 1.2 to 5.7). CONCLUSION: The results indicate that thicker PE inserts are associated with increased risk for revision in primary TKA. Further research is required to ascertain whether more conformed PE inserts or constrained knee designs instead of thick CR inserts will ultimately lead to better clinical outcomes. LEVEL OF EVIDENCE: III.

Implant survival of the most common cemented total hip devices from the Nordic Arthroplasty Register Association database.

Background and purpose - According to previous Nordic Arthroplasty Register Association (NARA) data, the 10-year implant survival of cemented total hip arthroplasties (THAs) is 94% in patients aged 65-74 and 96% in patients aged 75 or more. Here we report a brand-level comparison of cemented THA based on the NARA database, which has not been done previously. Patients and methods - We determined the rate of implant survival of the 9 most common cemented THAs in the NARA database. We used Kaplan-Meier analysis with 95% CI to study implant survival at 10 and 15 years, and Cox multiple regression to assess survival and hazard ratios (HRs), with revision for any reason as endpoint and with adjustment for age, sex, diagnosis, and femoral head material. Results - Spectron EF THA (89.9% (CI: 89.3-90.5)) and Elite THA (89.8% (CI: 89.0-90.6)) had the lowest 10-year survivorship. Lubinus (95.7% survival, CI: 95.5-95.9), MS 30 (96.6%, CI: 95.8-97.4), and C-stem THA (95.8%, CI: 94.8-96.8) had a 10-year survivorship of at least 95%. Lubinus (revision risk (RR) = 0.77, CI: 0.73-0.81), Müller (RR =0.83, CI: 0.70-0.99), MS-30 (RR =0.73, CI: 0.63-0.86), C-stem (RR =0.70, CI: 0.55-0.90), and Exeter Duration THA (RR =0.84, CI: 0.77-0.90) had a lower risk of revision than Charnley THA, the reference implant. Interpretation - The Spectron EF THA and the Elite THA had a lower implant survival than the Charnley, Exeter, and Lubinus THAs. Implant survival of the Müller, MS 30, CPT, and C-stem THAs was above the acceptable limit for 10-year survival.

Adverse reaction to metal debris after Birmingham hip resurfacing arthroplasty.

BACKGROUND AND PURPOSE: Concern has emerged about local soft-tissue reactions after hip resurfacing arthroplasty (HRA). The Birmingham Hip Resurfacing (BHR) was the most commonly used HRA device at our institution. We assessed the prevalence and risk factors for adverse reaction to metal debris (ARMD) with this device. PATIENTS AND METHODS: From 2003 to 2011, BHR was the most commonly used HRA device at our institution, with 249 implantations. We included 32 patients (24 of them men) who were operated with a BHR HRA during the period April 2004 to March 2007 (42 hips; 31 in men). The mean age of the patients was 59 (26-77) years. These patients underwent magnetic resonance imaging (MRI), serum metal ion measurements, the Oxford hip score questionnaire, and physical examination. The prevalence of ARMD was recorded, and risk factors for ARMD were assessed using logistic regression models. The mean follow-up time was 6.7 (2.4-8.8) years. RESULTS: 6 patients had a definite ARMD (involving 9 of the 42 hips). 8 other patients (8 hips) had a probable ARMD. Thus, there was definite or probable ARMD in 17 of the 42 hips. 4 of 42 hips were revised for ARMD. Gender, bilateral metal-on-metal hip replacement and head size were not factors associated with ARMD. INTERPRETATION: We found that HRA with the Birmingham Hip Resurfacing may be more dangerous than previously believed. We advise systematic follow-up of these patients using metal ion levels, MRI/ultrasound, and patient-reported outcome measures.

Three metal-on-metal hip replacement devices from the same manufacturer--a short- to mid-term survival.

The aim of this retrospective study was to evaluate short- to mid-term results of three different metal-on-metal hip devices from the same manufacturer. A total of 329 hip operations were performed in a single academic unit between 2004 and 2010 using either Birmingham hip resurfacing or Synergy--Birmingham and Synergy--R3 total hip arthroplasty. The overall survival rate at the end of the follow-up time for Birmingham hip resurfacing was 88%, for Synergy--Birmingham total hip arthroplasty 95%, and for Synergy--R3 total hip arthroplasty 81% (p = 0.036). Five revision operations were performed due to adverse reaction to metal debris. Head sizes > 50 mm had lower revision rates compared to smaller ones. Synergy--R3 had a poor survival already at short-term. The mid-term survival of Birmingham hip resurfacing arthroplasty was inferior compared to previous studies.

Cancer incidence and cause-specific mortality in patients with metal-on-metal hip replacements in Finland.

BACKGROUND AND PURPOSE: Metal-on-metal hip implants have been widely used, especially in the USA, Australia, England and Wales, and Finland. We assessed risk of death and updated data on the risk of cancer related to metal-on-metal hip replacements. PATIENTS AND METHODS: A cohort of 10,728 metal-on-metal hip replacement patients and a reference cohort of 18,235 conventional total hip replacement patients were extracted from the Finnish Arthroplasty Register for the years 2001-2010. Data on incident cancer cases and causes of death until 2011 were obtained from the Finnish Cancer Registry and Statistics Finland. The relative risk of cancer and death were expressed as standardized incidence ratio (SIR) and standardized mortality ratio (SMR). SIR/SIR ratios and SMR/SMR ratios, and Poisson regression were used to compare the cancer risk and the risk of death between cohorts. RESULTS: The overall risk of cancer in the metal-on-metal cohort was not higher than that in the non-metal-on-metal cohort (RR = 0.91, 95% CI: 0.82-1.02). The risk of soft-tissue sarcoma and basalioma in the metal-on-metal cohort was higher than in the non-metal-on-metal cohort (SIR/SIR ratio = 2.6, CI: 1.02-6.4 for soft-tissue sarcoma; SIR/SIR ratio = 1.3, CI: 1.1-1.5 for basalioma). The overall risk of death in the metal-on-metal cohort was less than that in the non-metal-on-metal cohort (RR = 0.78, CI: 0.69-0.88). INTERPRETATION: The overall risk of cancer or risk of death because of cancer is not increased after metal-on-metal hip replacement. The well-patient effect and selection bias contribute substantially to the findings concerning mortality. Arthrocobaltism does not increase mortality in patients with metal-on-metal hip implants in the short term. However, metal-on-metal hip implants should not be considered safe until data with longer follow-up time are available.

Adverse reaction to metal debris after ReCap-M2A-Magnum large-diameter-head metal-on-metal total hip arthroplasty.

BACKGROUND AND PURPOSE: The clinical findings of adverse reaction to metal debris (ARMD) following large-diameter-head metal-on-metal total hip arthroplasty (LDH MoM THA) may include periarticular fluid collections, soft tissue masses, and gluteal muscle necrosis. The ReCap-M2a-Magnum LDH MoM THA was the most commonly used hip device at our institution from 2005 to 2012. We assessed the prevalence of and risk factors for ARMD with this device. METHODS: 74 patients (80 hips) had a ReCap-M2a-Magnum LDH MoM THA during the period August 2005 to December 2006. These patients were studied with hip MRI, serum chromium and cobalt ion measurements, the Oxford hip score questionnaire, and by clinical examination. The prevalence of ARMD was recorded and risk factors for ARMD were assessed using logistic regression models. The mean follow-up time was 6.0 (5.5-6.7) years. RESULTS: A revision operation due to ARMD was needed by 3 of 74 patients (3 of 80 hips). 8 additional patients (8 hips) had definite ARMD, but revision was not performed. 29 patients (32 hips) were considered to have a probable or possible ARMD. Altogether, 43 of 80 hips had a definite, probable, or possible ARMD and 34 patients (37 hips) were considered not to have ARMD. In 46 of 78 hips, MRI revealed a soft tissue mass or a collection of fluid (of any size). The symptoms clicking in the hip, local hip swelling, and a feeling of subluxation were associated with ARMD. INTERPRETATION: ARMD is common after ReCap-M2a-Magnum total hip arthroplasty, and we discourage the use of this device. Asymptomatic patients with a small fluid collection on MRI may not need instant revision surgery but must be followed up closely.

Effect of femoral head size on risk of revision for dislocation after total hip arthroplasty: a population-based analysis of 42,379 primary procedures from the Finnish Arthroplasty Register.

BACKGROUND AND PURPOSE: Previous population-based registry studies have shown that larger femoral head size is associated with reduced risk of revision for dislocation. However, the previous data have not included large numbers of hip resurfacing arthroplasties or large metal-on-metal (> 36-mm) femoral head arthroplasties. We evaluated the association between femoral component head size and the risk of revision for dislocation after THA by using Finnish Arthroplasty Register data. PATIENTS AND METHODS: 42,379 patients who were operated during 1996-2010 fulfilled our criteria. 18 different cup/stem combinations were included. The head-size groups studied (numbers of cases) were 28 mm (23,800), 32 mm (4,815), 36 mm (3,320), and > 36 mm (10,444). Other risk factors studied were sex, age group (18-49 years, 50-59 years, 60-69 years, 70-79 years, and > 80 years), and time period of operation (1996-2000, 2001-2005, 2006-2010). RESULTS: The adjusted risk ratio in the Cox model for a revision operation due to dislocation was 0.40 (95% CI: 0.26-0.62) for 32-mm head size, 0.41 (0.24-0.70) for 36-mm head size, and 0.09 (0.05-0.17) for > 36-mm head size compared to implants with a head size of 28 mm. INTERPRETATION: Larger femoral heads clearly reduce the risk of dislocation. The difference in using heads of > 36 mm as opposed to 28-mm heads for the overall revision rate at 10 years follow-up is about 2%. Thus, although attractive from a mechanical point of view, based on recent less favorable clinical outcome data on these large heads, consisting mainly of metal-on-metal prostheses, one should be cautious using these implants.

Risk of cancer with metal-on-metal hip replacements: population based study.

OBJECTIVE: To assess the risk of cancer associated with modern primary metal-on-metal hip replacements. DESIGN: Population based study. SETTING: Nationwide retrospective comparative register. PARTICIPANTS: 10,728 patients who underwent metal-on-metal total hip arthroplasty and 18,235 patients who underwent conventional metal-on-polyethylene, ceramic-on-polyethylene, and ceramic-on-ceramic total hip arthroplasty (the non-metal-on-metal cohort) in the Finnish Arthroplasty Register 2001-10. Data on cancer cases up to 2010 for these cohorts were extracted from the Finnish Cancer Registry. MAIN OUTCOME MEASURES: The relative risk of cancer was expressed as the ratio of observed to expected number of cases from the Finnish population--that is, the standardised incidence ratio. The relative risk of cancer in the metal-on-metal cohort compared with the non-metal-on-metal cohort was estimated with analyses of these ratios and Poisson regression. RESULTS: The overall risk of cancer in patients with metal-on-metal hip implants was similar to that in the Finnish population (378 observed v 400 expected, standardised incidence ratio 0.95, 95% confidence interval 0.85 to 1.04). The overall risk of cancer in patients with metal-on-metal hip implants was also no higher than in patients who had received non-metal-on-metal hip implants (relative risk 0.92, 0.81 to 1.05). CONCLUSIONS: Metal-on-metal hip replacements are not associated with an increased overall risk of cancer during a mean follow-up of four years.

Incidence of osteotomies around the knee for the treatment of knee osteoarthritis: a 22-year population-based study.

PURPOSE: Both tibial and femoral osteotomies have been used for the treatment of knee osteoarthritis (OA). Due to the clinical success of total knee arthroplasty (TKA) the current role and incidence of osteotomies remains unknown. The aim of this population-based study was to assess the incidence of osteotomies and compare it with that of knee arthroplasties. METHODS: From the Finnish National Hospital Discharge Register, we identified all patients, aged 18 years or more, who had undergone osteotomy for the treatment of knee OA between 1987 and 2008. The number of arthroplasties was extracted from the Arthroplasty Register. RESULTS: A total of 6,004 osteotomies were performed for 5,734 patients. The average osteotomy incidence has steadily decreased by 6.2%, and TKA incidence has increased by 9.8% annually. However, in patients aged less than 50 years the osteotomy incidence has increased by 1.4% annually. The decline of osteotomy incidence has been steeper in females than in males (9.0% vs. 3.6%), and during the last decade osteotomies were more commonly performed in male patients. CONCLUSION: Incidence of osteotomies for the treatment of knee OA has decreased during last two decades. However, in patients aged less than 50 years the osteotomy incidence has slightly increased. In a comparison by gender, females are more likely to undergo arthoplasty than osteotomy, and it would therefore appear that the current use of osteotomies is predominantly reserved for the treatment of knee OA in relatively young males.

The LifeShirt system for wireless patient monitoring in the operating room.

We examined the functionality and reliability of a wearable physiological monitoring system (LifeShirt) during normal daily activities and in a hospital operating room (OR) environment. The garment collects physiological data such as oxygen saturation, and stores them in a recorder from which it can be read afterwards. Ten normal subjects wore the shirt continuously for 8 h per day. Feedback from the testers was quite positive, although the collected data varied in quality. Ten hospital patients also wore the shirt during endoscopy. The data collected during the hospital stay were qualitatively adequate. Measuring respiratory function caused the biggest problems. The study showed that intelligent garment technology could be used in an OR environment for patient monitoring, albeit not in realtime. It may also be useful in home follow-up.