Guideline for RSA and CT-RSA implant migration measurements: an update of standardizations and recommendations.

Opening remarks: These guidelines are the result of discussions within a diverse group of RSA researchers. They were approved in December 2023 by the board and selected members of the International Radiostereometry Society to update the guidelines by Valstar et al. [1]. By adhering to these guidelines, RSA studies will become more transparent and consistent in execution, presentation, reporting, and interpretation. Both authors and reviewers of scientific papers using RSA may use these guidelines, summarized in the Checklist, as a reference. Deviations from these guidelines should have the underlying rationale stated.

A prospective randomized study of Refobacin Bone Cement R versus Palacos R + G.

Aims: Refobacin Bone Cement R and Palacos R + G bone cement were introduced to replace the original cement Refobacin Palacos R in 2005. Both cements were assumed to behave in a biomechanically similar fashion to the original cement. The primary aim of this study was to compare the migration of a polished triple-tapered femoral stem fixed with either Refobacin Bone Cement R or Palacos R + G bone cement. Repeated radiostereometric analysis was used to measure migration of the femoral head centre. The secondary aims were evaluation of cement mantle, stem positioning, and patient-reported outcome measures. Methods: Overall, 75 patients were included in the study and 71 were available at two years postoperatively. Prior to surgery, they were randomized to one of the three combinations studied: Palacos cement with use of the Optivac mixing system, Refobacin with use of the Optivac system, and Refobacin with use of the Optipac system. Cemented MS30 stems and cemented Exceed acetabular components were used in all hips. Postoperative radiographs were used to assess the quality of the cement mantle according to Barrack et al, and the position and migration of the femoral stem. Harris Hip Score, Oxford Hip Score, Forgotten Joint Score, and University of California, Los Angeles Activity Scale were collected. Results: Median distal migration (y-axis) at two years for the Refobacin-Optivac system was -0.79 mm (-2.01 to -0.09), for the Refobacin-Optipac system was -0.75 mm (-2.16 to 0.20), and for the Palacos-Optivac system was -1.01 mm (-4.31 to -0.29). No statistically significant differences were found between the groups. Secondary outcomes did not differ statistically between the groups at the two-year follow-up. Conclusion: At two years, we found no significant differences in distal migration or clinical outcomes between the three groups. Our data indicate that Refobacin Bone Cement R and Palacos R + G are comparable in terms of stable fixation and early clinical outcomes.

Influence of immigrant background on the outcome of total hip arthroplasty: better outcome in 280 native patients in Bosnia and Herzegovina than in 449 immigrants living in Sweden.

BACKGROUND: Despite the overall success of THA, between 5 and 20% report unsatisfactory results. Several factors may cause this variable outcome. 1 of them might be ethnicity which, because of its potential social impact on living conditions, may influence quality of life too. It should be studied whether patients born and being operated in their home country Bosnia and Herzegovina (BH) had similar results as immigrants being operated in Sweden (IS). METHODS: Data of 280 patients were collected prospectively from questionnaires in the BH group. Patients of the IS group were eligible if both of their parents were born outside the Nordic countries, not having Swedish as their native language. Data were gained from the Swedish Arthroplasty Registry (SAR), 449 patients were included. Outcomes were pain VAS, satisfaction VAS, EQ-VAS, and the EQ-5D. Logistic and linear regression models including age, sex, diagnosis, type of fixation, surgical incision, marital status and educational level were analysed to compare those 2 groups. RESULTS: There were considerable differences in patient demographics between the 2 groups. Before the operation, patients in the BH group reported more problems with self-care and usual activities, even after adjustment for confounding factors (p < 0.0005). Patients in the IS group reported a higher EQ-VAS and more pain VAS (p < 0.0005), the difference in the EQ-VAS was not significant after adjustment for confounding factors (p = 0.41). After 1 year patients in the BH group reported better scores in all dimensions of the EQ-5D (p ⩽ 0.005) apart from self-care. After adjustment for confounding factors, patients in the BH group were more satisfied too (p < 0.0005). CONCLUSIONS: Immigrated patients (IS group) seemed to experience less benefit from THA 1 year after the operation despite more symptoms preoperatively. There were considerable limitations affecting the results. Nevertheless, the data are a point of concern, and it is suggested to take more multidimensional care of immigrant patients.

The importance of BMPs and TGF-ßs for endochondral bone repair - A longitudinal study in hip arthroplasty patients.

Introduction: Osseointegration of hip implants, although a decade-long process, shows striking similarities with the four major phases of endochondral bone repair. In the current study we investigated the spatiotemporal involvement of bone morphogenic proteins (BMPs) and transforming growth factor betas (TGF-ßs) throughout the process of bone repair leading to successfully osseointegrated hip implants. Materials and methods: Twenty-four patients that had undergone primary total hip arthroplasty (THA) due to one-sided osteoarthritis (OA) were investigated during a period of 18 years (Y) with repeated measurements of plasma biomarkers as well as clinical and radiological variables. All implants were clinically and radiographically well anchored throughout the follow-up. Eighty-one healthy donors divided in three gender- and age-matched groups and twenty OA patients awaiting THA, served as controls. Plasma was analyzed for BMP-1, -2, -3, -4, -6, -7 -9 and TGF-ß1, -ß2, -ß3 by use of a high-sensitivity and wide dynamic range electrochemiluminescence technique allowing for detection of minor changes. Results: Spatiotemporal changes during the follow-up are presented in the context of the four phases of endochondral bone repair shown in earlier studies and transposed to the current study based on similarities in biomarker responses. Phase 1: Primary proinflammatory phase lasting from surgery until day 7, Phase 2: Chondrogenic phase from day 7 until 18 months postsurgery, Phase 3: Secondary proinflammatory and cartilage remodeling phase lasting from 18 months until 7Y, Phase 4: coupled bone remodeling from 7Y until 18Y postsurgery. BMP-1 increased sharply shortly after surgery and remained significantly above healthy during the chondrocyte recruitment, proliferation, and hypertrophy phases with a subsequent return to control level at 5Y postsurgery. BMP-2 was above healthy controls before surgery and 1 day after surgery before decreasing to control level and remaining there throughout the follow-up. BMP-3 was at control level from presurgery until 6M after surgery when it increased to a peak at 2Y during the cartilage hypertrophy phase followed by a gradual decrease to control level at 10Y during the phase of bone formation. In the following, BMP-3 decreased below controls to a nadir 15Y postsurgery during coupled bone remodeling. BMP-4 was at control level from presurgery until 10Y postsurgery when it increased to a sharp peak at 15Y after surgery followed by a return to the level of healthy at 18Y. BMP-6 did not differ from healthy during the follow-up. BMP-7 was at control level from presurgery until 1Y postsurgery before gradually increasing to a peak at 10Y during the early phase of osteogenesis with a gradual return to control level at 18Y during the phase of coupled bone remodeling. BMP-9 was above OA before surgery followed by a decrease to basal level on day 1 after surgery and a renewed increase to a plateau above controls lasting from 6 W until returning to the level of healthy at 18Y postsurgery, i.e., throughout the phases of cartilage formation, cartilage hypertrophy and remodeling, bone formation and coupled bone remodeling. TGF-ß1 was above controls presurgery before decreasing to baseline shortly after surgery followed by a renewed increase at 6 M to a peak at 2Y during cartilage hypertrophy/remodeling followed by a gradual return to baseline at 10Y during early osteoblastogenesis. TGF-ß2 was at control level from presurgery until the phase of cartilage remodeling at 5Y when it increased sharply to a peak at 7Y with a gradual return to baseline at 18Y postsurgery. TGF-ß3 remained at control level throughout the study. Conclusion: This study shows that the involvement of BMPs and TGF-ßs in endochondral bone repair is a process of stepwise recruitment of individual biomarkers characterized by distinct, yet overlaping, spatiotemporal patterns that extend from the early phase of pre-chondrocyte recruitment until the late phase of coupled bone remodeling.

Corrigendum: Similar outcome with a new anteverted or a straight standard stem: a randomized study of 72 total hip arthroplasties evaluated with clinical variables, radio-stereometry, and DXA up to 2 years.

When we checked our data in our article "Similar outcome with a new anteverted or a straight standard stem: a randomized study of 72 total hip arthroplasties evaluated with clinical variables, radiostereometry, and DXA up to 2 years" by Karin Rilby, Maziar Mohaddes, Emma Nauclér, and Johan Kärrholm, Acta Orthop 2021; 92, Published online October 21, 2021 we noticed that the numbers in Table 7 (Supplementary data) were incorrect. We have not been able to fully reconstruct the reason for this error. We are sorry for this mistake. Even if the corrected numbers are different the overall conclusions will be same and also the statistical significances.

Gait pattern in patients treated with a total hip arthroplasty due to an acute displaced cervical neck fracture: a randomised comparison between 29 cases with a cemented femoral stem and 16 cases with an uncemented femoral stem.

BACKGROUND: The choice between cemented or uncemented stem fixation in the treatment of a femoral neck fracture may influence patient rehabilitation and the resulting gait pattern, due to potential differences in implant positioning and fixation. We used gait analysis to study temporal gait parameters, hip kinematics and kinetics in patients who, 2 years previously, had been randomised to treatment with a cemented or uncemented stem and due to an acute femoral neck fracture. METHODS: 45 Patients implanted with a cemented Lubinus SP II (n = 29) and an uncemented (n = 16) Corail stem were studied. Gait analysis was performed using a 16-camera motion capture system and force plates. 28 subjects served as controls. Temporal gait parameters, hip kinematics and kinetics were analysed. The patients had no or minimum pain (median Harris pain score 44, range 40-44) and the majority had no limp (median Harris limp score 11, range 5-11). RESULTS: Temporospatial gait parameters and abduction-adduction motions and moments did not differ between patients with cemented or uncemented stems (p > 0.05). Patients with cemented stems did, however, show more hip flexion and less extension during walking than those with an uncemented stem (p < 0.05). Moreover, the flexion-extension range was less in the cemented group (p < 0.04). Compared with controls, the hip fracture patients walked more slowly, with a shorter stride length and a longer stance phase. CONCLUSIONS: Increased hip flexion and reduced extension in patients using the Lubinus SP II cemented stem could be an effect of its anteverted neck, but this question requires further study. Despite acute treatment with THA, hip fracture patients demonstrated a change in gait pattern compared with controls 2 years after the operation. This suggests that these changes are caused by the presence of an implant, or the soft-tissue trauma partly caused by the surgery than by any degenerative disease present in patients undergoing elective surgery.ClinicalTrials.gov Identifier: NCT04791605.

No difference in clinical outcome but in RSA in total knee arthroplasty with the ATTUNE vs. the PFC Sigma: a randomized trial with 2-year follow-up.

BACKGROUND AND PURPOSE: Despite usage of the ATTUNE total knee arthroplasty (TKA) for about 10 years, few randomized trials exist. We evaluated whether the ATTUNE CR design showed improved clinical results compared with the PFC Sigma CR after 2 years and if there was a difference in tibial component migration. PATIENTS AND METHODS: 96 patients with knee osteoarthritis were randomly treated with cemented ATTUNE or PFC Sigma TKA. 42 patients with the ATTUNE and 48 with the PFC Sigma attended the 2-year follow-up. Patient-reported outcome measurements (PROMs), migration measured with RSA, implant position, and the development of radiolucent zones were studied. Non-parametric tests and repeated measures analysis were used at the statistical evaluation. RESULTS: The Oxford Knee Score (OKS) at 2 years (primary outcome) and neither of the secondary PROM outcomes differed between the groups (mean difference OKS ATTUNE - PFC: -0.08, 95% confidence interval [CI] -2.9 to 2.7). RSA showed posterior tilt of the tibial component in the ATTUNE group with proximal lift-off anteriorly and subsidence of the tibial tray posteriorly. In contrast, the PFC Sigma tibial component tilted forward (mean difference ATTUNE - PFC: -0.7°, CI -1.1° to -0.4°) with maximum subsidence in the front and maximum lift-off of the posterior edge. The postoperative implant positions and the extension of radiolucent lines around the tibial component at 2 years did not differ. CONCLUSION: We found no significant differences in clinical outcome between the 2 groups but minor differences in migration pattern of the tibial component. The clinical long-term significance of this finding if any is not known.

Outcome of patients with osteoarthritis aged 90 to 101 years after cemented total hip arthroplasty: 1,385 patients from the Swedish Arthroplasty Register.

BACKGROUND AND PURPOSE: Few studies have focused on nonagenarians treated with total hip arthroplasty (THA). We investigated 30- and 90-day postoperative mortality, patient-reported outcome measures (PROMs), reoperation rate, risk factors for reoperation, and relative patient survival in nonagenarians or older. PATIENTS AND METHODS: 167,091 patients with primary cemented THA performed for osteoarthritis between 1992 and 2019 were identified in the Swedish Arthroplasty Register. Patients were divided into age groups based on age at time of surgery: 60-74 (n = 90,285), 75-89 (n = 75,421), and > 90 years (n = 1,385). Mortality rate, PROMs (pain-Likert scale, satisfaction-Likert scale, EQ-VAS, n = 67,553), reoperation rate, risk factors for reoperation, and relative patient survival were studied. RESULTS: The nonagenarians had the highest postoperative mortality rate, 1.7% and 2.6% at 30 and 90 days, respectively. Nonagenarian females reported significantly lower pre- and postoperative EQ-VAS compared with patients aged 60-89 years but reported least pain and highest patient satisfaction 1 year after surgery. At 2 years the nonagenarians had highest reoperation frequency-2.7%-due to infection (1.5%), dislocation (0.8%), and periprosthetic fracture (0.4%). Increasing age, male sex, and polished stem were associated with higher risk of reoperation within 2 years. 8-year age- and sex-matched relative survival was highest among nonagenarians (study group/matched population: ≥ 90 years 3.4, 95% confidence interval [CI] 3.0-3.8; 75-89 years: 1.4, CI 1.4-1.4, and 60-74 years: 1.1, CI 1.1-1.1). CONCLUSION: 30- and 90-day postoperative mortality and reoperation rates were higher in nonagenarians but PROM data showed least pain and highest patient satisfaction 1 year after surgery with THA among female nonagenarians with primary osteoarthritis.

Fracture pattern and risk factors for reoperation after treatment of 156 periprosthetic fractures around an anatomic cemented hip stem.

BACKGROUND AND PURPOSE: The Lubinus SP2 stem has been associated with a very low risk of periprosthetic femoral fractures (PPFFs). We aimed, primarily, to study the radiographic morphology of PPFFs close to a Lubinus SP2 stem. Secondarily, we analyzed whether higher reoperation rate was correlated to the revision method chosen or to the characteristics of the fracture and of the bone. PATIENTS AND METHODS: The study included 156 femoral fractures close to a Lubinus cemented stem. These fractures were treated in 40 hospitals in Sweden between 2006 and 2011 and were followed up until 2019. Data from the Swedish Arthroplasty Register was used. Medical records and radiographs were studied. The fractures were classified according to the Vancouver classification. The fracture location and anatomy were delineated. We also measured the remaining attachment index (RAI) and the canal thickness ratio. RESULTS: Vancouver type C (n = 101) and spiral fractures (n = 67, 41 in Vancouver C and 26 in Vancouver B) were the most common fracture types. 4 fractures were avulsion of the greater trochanter. The remaining 51 fractures occurred around the stem (B1: 25, B2: 16, and B3: 10). B fractures were more commonly reoperated on (18 of 51, 35%) than type C fractures (11 of 101, 11%, P = 0.001). In most femurs with type B3 fracture, the fracture line covered an area only around the stem, but in all B1 and in 11 of 16 B2 fractures, it was extended even distal to the stem. ORIF instead of stem revision in B2 fractures, use of short stems or plates, and inadequate reduction of the fractures were risk factors for subsequent reoperations. CONCLUSION: The higher reoperation rate in type B fractures, compared with fractures distal to the stem, could be caused by their higher degree of complexity and reduced capacity for healing in the region around the stem.

Computed tomography-based radiostereometric analysis in orthopedic research: practical guidelines.

Early implant migration is an indicator of the long-term survival/failure of implants. CT-based radio-stereometric analysis (CT-RSA) is a precise method for measuring and visualizing implant migration in vivo using image processing of CT scans. This makes the method widely applicable to orthopedic researcher. Since its development in the early 2000s, CT-RSA has benefited from breakthroughs in CT and computing technology. These advancements have allowed for the acquisition of images with higher resolution at a much lower radiation dose. As a result, the measurement precision of CT-RSA is now comparable to that of the current gold standard technology while still compatible with most ethical considerations regarding radiation exposure. In this review we present bests practices for the successful execution of CT-RSA research projects. These practices are based on experience from projects on the hip, knee, shoulder, lower back, cervical spine, foot, pelvis, and wrist.

Increasing risk of revision due to infection after primary total hip arthroplasty: results from the Nordic Arthroplasty Register Association.

BACKGROUND AND PURPOSE: The incidence of periprosthetic joint infection after total hip arthroplasty (THA) may be increasing. We performed time-trend analyses of risk, rates, and timing of revision due to infection after primary THAs in the Nordic countries from the period 2004-2018. PATIENTS AND METHODS: 569,463 primary THAs reported to the Nordic Arthroplasty Register Association from 2004 to 2018 were studied. Absolute risk estimates were calculated by Kaplan-Meier and cumulative incidence function methods, whereas adjusted hazard ratios (aHR) were assessed by Cox regression with the first revision due to infection after primary THA as primary endpoint. In addition, we explored changes in the time span from primary THA to revision due to infection. RESULTS: 5,653 (1.0%) primary THAs were revised due to infection during a median follow-up time of 5.4 (IQR 2.5-8.9) years after surgery. Compared with the period 2004-2008, the aHRs for revision were 1.4 (95% confidence interval [CI] 1.3-1.5) for 2009-2013, and 1.9 (CI 1.7-2.0) for 2014-2018. The absolute 5-year rates of revision due to infection were 0.7% (CI 0.7-0.7), 1.0% (CI 0.9-1.0), and 1.2% (CI 1.2-1.3) for the 3 time periods respectively. We found changes in the time span from primary THA to revision due to infection. Compared with 2004-2008, the aHR for revision within 30 days after THA was 2.5 (CI 2.1-2.9) for 2009-2013, and 3.4 (CI 3.0-3.9) for 2013-2018. The aHR for revision within 31-90 days after THA was 1.5 (CI 1.3-1.9) for 2009-2013, and 2.5 (CI 2.1-3.0) for 2013-2018, compared with 2004-2008. CONCLUSION: The risk of revision due to infection after primary THA almost doubled, both in absolute cumulative incidence and in relative risk, throughout the period 2004-2018. This increase was mainly due to an increased risk of revision within 90 days of THA. This may reflect a "true" increase (i.e., frailer patients or more use of uncemented implants) and/or an "apparent" increase (i.e., improved diagnostics, changed revision strategy, or completeness of reporting) in incidence of periprosthetic joint infection. It is not possible to disclose such changes in the present study, and this warrants further research.

Does choice of bearings influence the survival of cementless total hip arthroplasty in patients aged 20-55 years? Comparison of 21,594 patients reported to the Nordic Arthroplasty Register Association dataset 2005-2017.

BACKGROUND AND PURPOSE: The bearings with the best survivorship for young patients with total hip arthroplasty (THA) should be identified. We compared hazard ratios (HR) of revision of primary stemmed cementless THAs with metal-on-metal (MoM), ceramic-on-ceramic (CoC), and ceramic-on-highly-crosslinked-polyethylene (CoXLP) with that of metal-on-highly-crosslinked-polyethylene (MoXLP) bearings in patients aged 20-55 years with primary osteoarthritis or childhood hip disorders. PATIENTS AND METHODS: From the Nordic Arthroplasty Register Association dataset we included 1,813 MoM, 3,615 CoC, 5,947 CoXLP, and 10,219 MoXLP THA in patients operated on between 2005 and 2017 in a prospective cohort study. We used the Kaplan-Meier estimator for THA survivorship and Cox regression to estimate HR of revision adjusted for confounders (including 95% confidence intervals [CI]). MoXLP was used as reference. HRs were calculated during 3 intervals (0-2, 2-7, and 7-13 years) to meet the assumption of proportional hazards. RESULTS: Median follow-up was 5 years for MoXLP, 10 years for MoM, 6 years for CoC, and 4 years for CoXLP. 13-year Kaplan-Meier survival estimates were 95% (CI 94-95) for MoXLP, 82% (CI 80-84) for MoM, 93% (CI 92-95) for CoC, and 93% (CI 92-94) for CoXLP bearings. MoM had higher 2-7 and 7-13 years' adjusted HRs of revision (3.6, CI 2.3-5.7 and 4.1, CI 1.7-10). MoXLP, CoC, and CoXLP had similar HRs in all 3 periods. The 7-13-year adjusted HRs of revision of CoC and CoXLP were statistically non-significantly higher. CONCLUSION: In young patients, MoXLP for primary cementless THA had higher revision-free survival and lower HR for revision than MoM bearings. Longer follow-up is needed to compare MoXLP, CoC, and CoXLP.

Similar results after five years with the use of the Fitmore or the CLS femoral components.

Although the Fitmore Hip Stem has been on the market for almost 15 years, it is still not well documented in randomized controlled trials. This study compares the Fitmore stem with the CementLeSs (CLS) in several different clinical and radiological aspects. The hypothesis is that there will be no difference in outcome between stems. In total, 44 patients with bilateral hip osteoarthritis were recruited from the outpatient clinic at a single tertiary orthopaedic centre. The patients were operated with bilateral one-stage total hip arthroplasty. The most painful hip was randomized to either Fitmore or CLS femoral component; the second hip was operated with the femoral component not used on the first side. Patients were evaluated at three and six months and at one, two, and five years postoperatively with patient-reported outcome measures, radiostereometric analysis, dual-energy X-ray absorptiometry, and conventional radiography. A total of 39 patients attended the follow-up visit at two years (primary outcome) and 35 patients at five years. The primary outcome was which hip the patient considered to have the best function at two years. At two and five years, more patients considered the hip with the CLS femoral component as superior but without a statistically significant difference. There were no differences in clinical outcome, magnitude of femoral component migration, or change of bone mineral density at five years. At three months, the Fitmore femoral component had subsided a median -0.71 mm (interquartile range (IQR) -1.67 to -0.20) and the CLS femoral component -0.70 mm (IQR -1.53 to -0.17; p = 0.742). In both groups the femoral head centre had migrated posteriorly (Fitmore -0.17 mm (IQR -0.98 to -0.04) and CLS -0.23 mm (IQR -0.87 to 0.07; p = 0.936)). After three months neither of the femoral components showed much further migration. During the first postoperative year, one Fitmore femoral component was revised due to aseptic loosening. Up to five years, we found no statistically significant difference in outcomes between the Fitmore and the CLS femoral components. The slightly worse outcomes, including one revised hip because of loosening, speaks against the hypothesis that the Fitmore femoral component should be advantageous compared to the CLS if more patients had been recruited to this study.

What is the Role of Stem Size and Offset in the Risk of Nonseptic Revision of the Exeter® 150-mm Stem? A Study From the Swedish Arthroplasty Register.

BACKGROUND: The Exeter® stem is used worldwide, often in older patients, and it is the second most commonly used cemented stem design in Sweden. Previous studies have shown that for cemented stems with a composite beam, the smallest sizes result in an increased risk of revision for mechanical failure. However, little is known about whether the survivorship of the polished Exeter stem, which generally has been shown to be good, might be associated with design parameters such as stem dimensions or offset at extreme implant sizes. QUESTION/PURPOSE: Are differences in (1) stem size or (2) offset of the standard Exeter V40 150-mm stem associated with differences in the risk of stem revision for aseptic loosening? METHODS: Between 2001 and 2020, 47,161 Exeter stems were reported to the Swedish Arthroplasty Register, with very high coverage and completeness documented during the period studied. In this cohort, we included patients with primary osteoarthritis who underwent surgery with a standard Exeter stem length of 150 mm and V40 cone with any type of cemented cups that had had at least 1000 reported insertions. This selection resulted in a study cohort representing 79% (37,619 of 47,161) of the total number of Exeter stems in the registry during that time. The primary study outcome was stem revision for aseptic indications such as loosening, periprosthetic fracture, dislocation, and implant fracture. A Cox regression was performed, with adjustment for age, gender, surgical approach, year of surgery, use of highly crosslinked polyethylene cups, and femoral head size and length dictated by the shape of the head trunnion. Adjusted hazard ratios are presented with 95% confidence intervals. Two separate analyses were performed. The first analysis excluded stems with the highest offsets (50 mm and 56 mm, which were not available for stem size 0). The second analysis excluded stem size 0 to include all offsets. Because stem survival was not proportional over time, we divided the analyses into two insertion periods, 0 to 8 years and beyond 8 years. RESULTS: Stem size 0 (compared to size 1) was associated with an increased risk of revision up to 8 years when all stem sizes were included (first analysis 0 to 8 years, HR 1.7 [95% CI 1.2 to 2.3]; p = 0.002). Forty-four percent (63 of 144) of revisions of size 0 stems were for periprosthetic fracture. There was no consistent association between stem size and risk of aseptic stem revision when size 0 was excluded in the second analysis beyond 8 years. The most common offset (44 mm) was associated with an increased risk of revision (compared with 37.5 mm) up to 8 years when all sizes were included (first analysis, HR 1.6 [95% CI 1.1 to 2.1]; p = 0.01). In the second analysis (beyond 8 years, all offsets included), offset of 44 mm was compared with offset of 37.5 mm; compared with the first period, this offset was associated with a reduced risk (HR 0.6 [95% CI 0.4 to 0.9]; p = 0.005). CONCLUSION: We found overall high survival of the Exeter stem, with generally little or no influence of stem variations on the risk of aseptic revision. However, stem size 0 was associated with an increased risk of revision mainly for periprosthetic fractures. If the femoral anatomy offers a choice between sizes 0 and 1 in patients with poor bone quality who are at risk of periprosthetic fracture, our data speak in favor of choosing the larger stem if the surgeon believes it is safe to insert the larger size, or, if available, another stem design that has a documented lower risk of this complication. For patients with good cortical bone quality but very narrow canals, a cementless stem may also be a good alternative. LEVEL OF EVIDENCE: Level III, therapeutic study.

No difference in outcome or migration but greater loss of bone mineral density with the Collum Femoris Preserving stem compared with the Corail stem: a randomized controlled trial with five-year follow-up.

AIMS: The aim of this study was to compare the mid-term patient-reported outcome, bone remodelling, and migration of a short stem (Collum Femoris Preserving; CFP) with a conventional uncemented stem (Corail). METHODS: Of 81 patients who were initially enrolled, 71 were available at five years' follow-up. The outcomes at two years have previously been reported. The primary outcome measure was the clinical result assessed using the Oxford Hip Score (OHS). Secondary outcomes were the migration of the stem, measured using radiostereometric analysis (RSA), change of bone mineral density (BMD) around the stem, the development of radiolucent lines, and additional patient-reported outcome measures (PROMs). RESULTS: There were no statistically significant differences between the groups regarding PROMs (median OHS (CFP 45 (interquartile range (IQR) 35 to 48); Corail 45 (IQR 40 to 48); p = 0.568). RSA showed stable stems in both groups, with little or no further subsidence between two and five years. Resorption of the femoral neck was evident in nine patients in the CFP group and in none of the 15 Corail stems with a collar that could be studied. Dual X-ray absorbiometry showed a significantly higher loss of BMD in the proximal Gruen zones in the CFP group (mean changes in BMD: Gruen zone 1, CFP -9.5 (95% confidence interval (CI) -14.8 to -4.2), Corail 1.0 (95% CI 3.4 to 5.4); Gruen zone 7, CFP -23.0 (95% CI -29.4 to -16.6), Corail -7.2 (95% CI -15.9 to 1.4). Two CFP stems were revised before two years' follow-up due to loosening, and one Corail stem was revised after two years due to chronic infection. CONCLUSION: The CFP stem has a similar clinical outcome and subsidence pattern when compared with the Corail stem. More pronounced proximal stress-shielding was seen with the CFP stem, suggesting diaphyseal fixation, and questioning its femoral neck-sparing properties in the long term. Cite this article: Bone Joint J 2022;104-B(5):581-588.

Similar risk of cancer in patients younger than 55 years with or without a total hip arthroplasty (THA): a population- based cohort study on 18,771 exposed to THA and 87,683 controls.

BACKGROUND AND PURPOSE: Concerns related to a potentially increased risk of cancer after total hip arthroplasty (THA) have frequently surfaced, especially since the novel EU medical device regulation classified cobalt as carcinogenic. We assessed the risk of cancer after THA in a nationwide cohort of patients younger than 55 years at surgery. PATIENTS AND METHODS: In this population-based longitudinal cohort study, 18,771 individuals exposed to THA were identified in the Swedish Hip Arthroplasty Registry (SHAR) and compared with 87,683 unexposed individuals who were matched by age, sex, and residence. Diagnoses, socioeconomic background, and dates of death were obtained from the Swedish Cancer Register, the National Patient Register, and Statistics Sweden. Primary outcome was the adjusted risk of any cancer after the first THA; secondary outcomes were specific cancer forms. RESULTS: We found no enhanced adjusted risk of developing any cancer, either in exposed females compared with unexposed females (hazard ratio [HR] 1.1, 95% confidence interval [CI] 0.95-1.2), or in exposed males (HR 1.1, CI 0.99-1.2). When analysing specific cancers, increased adjusted risks were found for thyroid and pancreas cancer in exposed females, and for cancer of the stomach, skin melanoma, and prostate cancer in exposed males. INTERPRETATION: This study indicates that there is no statistically significant increased overall risk of cancer in young THA-exposed patients. The potentially slightly enhanced risk for specific cancers may be due to residual confounding resulting from risk factors not accounted for and merits further investigation.

Influence of implant variations on survival of the Lubinus SP II stem: evaluation of 76,530 hips in the Swedish Arthroplasty Register, 2000-2018.

Background and purpose - Almost all prosthetic implant brands include several variations. Most studies on implant performance investigate an implant system without sub-analysis of implant attributes. We studied the influence of design variations during the last 2 decades on implant survival of the most frequently used cemented femoral stem, the Lubinus SPII, reported to the Swedish Arthroplasty Register (SHAR). Patients and methods - Between 2000 and 2018, 100,032 cemented Lubinus SP II stems had been reported to SHAR. Patients with primary osteoarthritis operated on with stem length 150 mm together with a cemented cup from the same manufacturer (n = 76,530) were included in this analysis. Primary study outcome was non-infectious stem revision. Cox regression with adjustment for age, sex, surgical approach, and year of surgery was used. Hazard rates (HR) are presented with 95% confidence intervals (CI). Results - Average follow-up was 7.6 years (SD 4.2). At 18 years the overall stem survival was 99.1 (CI 98.9-99.3). Increased revision rate was observed for stems with extra offset, when a long or an extra-long head length had been used. Smaller stem sizes, in particular the smallest stem size (01), substantially increased the rate of mechanical failure as reflected by an almost 10 times increased rate of revision compared with the standard size (2). Interpretation - In this study with larger sample size and longer follow-up than previously presented from the same register, we observed more pronounced effects of previously documented design variations. Based on our results, surgeons using the Lubinus SPII stems are advised to consider an alternative solution if a Lubinus stem size 01, Lubinus extra offset, or an extra-long head seems to be the most suitable choice at the preoperative planning.

No difference in gait pattern between a short collum femoris-preserving and a conventional stem: 44 randomised total hip arthroplasty patients stem evaluated after 2 years.

BACKGROUND: The uncemented collum femoris-preserving (CFP) stem offers preservation of the femoral neck and a more conservative soft tissue resection, which may facilitate a more normal walking pattern. We used gait analysis to evaluate if patients operated with a CFP stem showed more favourable hip kinematics and kinetics when compared with a group of patients operated with a conventional uncemented stem. METHODS: 44 patients randomised to receive either a CFP or a Corail stem were studied and were operated using a direct lateral incision. Gait analysis was performed 2 years after the operation with a 12-camera motion capture system and 2 force plates. Hip kinematics and kinetics were analysed and 66 subjects served as controls. RESULTS: None of the variables: speed, stride, cadence and stance showed any statistical significant difference between the 2 study groups. Neither did the hip kinematics and kinetics. Compared to controls, patients operated with the CFP stem showed an increased stance (62.5% vs. 61.1%, p < 0.006) and decreased hip abduction (-2.1° vs. -6.5°). Patients operated with the Corail stem showed decreased speed (1.18 vs. 1.23 m/second), and stride length (1.26 vs. 1.33 m), decreased hip extension (-7.5° vs. -12.8°) and range of hip flexion/extension (38° vs. 40.9°), as well as their hip adduction that was increased (6.3° vs. 4°), whereas their hip abduction was reduced (-2.8° vs. -6.5°), (p < 0.004) compared to the controls. CONCLUSIONS: Use of a CFP stem did not significantly influence any of the gait parameters studied when compared to a standard stem, but still both stems studied were associated with gait deviations when compared to controls. Whether these differences could be attributed to the stem used, the underlying hip disease, or both is still unknown.

Similar outcome with a new anteverted or a straight standard stem: a randomized study of 72 total hip arthroplasties evaluated with clinical variables, radiostereometry, and DXA up to 2 years.

Background and purpose - The anatomical uncemented stem, SP-CL (Static Physiologicus - CementLess), designed to facilitate insertion and to avoid stress concentration at solitary contact points, has been on the market since 2014 but is not well documented. We studied its clinical performance, migration, and associated bone remodeling in a randomized controlled trial, with the Corail stem as control. Patients and methods - 79 patients (80 hips) were primarily recruited and 71 patients (72 hips, 36 SP-CL, 36 Corail) attended the last follow-up at 2 years. The Oxford Hip Score (OHS) was the primary outcome. In addition, we assessed stem migration, changes in bone mineral density, and development of radiolucencies by RSA, DXA, and conventional radiography. Results - At 2 years Oxford Hip Score was similar between the SP-CL and Corail stem. At 2 years the SP-CL stems showed a median distal migration of 0.23 mm (-0.1 to 5.2) and the Corail stems of 0.11 mm (-0.4 to 4.4). The SP-CL stems showed slightly more loss of bone mineral density in Gruen region 7 (p = 0.003). Interpretation - We found no difference in clinical results between the SP-CL and the well-documented Corail stem. The same stem stability was reached between 1 and 2 years postoperatively for both stems. As a next step we think that the SP-CL stem should be studied in a multi-center setting, before being accepted for general use.

The risk of revision following total hip arthroplasty in patients with inflammatory bowel disease, a registry based study.

Inflammatory bowel disease (IBD) is characterized by chronic inflammation of the intestinal tract and is associated with decreased bone mineral density. IBD patients are at higher risk of osteopenia, osteoporosis and fracture compared to non-IBD patients. The impact of IBD on the performance of orthopedic implants has not been well studied. We hypothesized that a history of IBD at the time of primary total hip arthroplasty (THA) would increase the risk of subsequent failure as assessed by revision surgery. A retrospective implant survival analysis was completed using the Swedish Hip Arthroplasty Registry and the Sweden National Patient Register. A total of 150,073 patients undergoing THA for osteoarthritis within an 18-year period were included in the study. THA patients with (n = 2,604) and without (n = 147,469) a history of IBD at the time of THA were compared with primary revision as the main endpoint and adjusted using sex, age category and comorbidity (Elixhauser scores) as covariates. We found that patients with a history of IBD had a relatively higher risk of revision surgery for septic causes while the non-IBD patients had a relatively higher risk of revision for aseptic causes (p = 0.004). Our findings suggest there may be an association between gut health and THA performance.