ALBA-studien

Ove Furnes (Ortopedisk klinikk ved Helse Bergen HF - Haukeland universitetssykehus/Klinisk institutt 1 ved Universitetet i Bergen) og Tesfaye Hordofa Leta (Ortopedisk klinikk ved Helse Bergen HF - Haukeland universitetssykehus/VID vitenskapelige høgskole) svarer på spørsmål om ALBA-studien.Siden 1990-tallet har man i Norge brukt antibiotika i sementen (ALBC – antibiotics loaded bone cement) ved protesekirurgi. Allerede i 1997 kom en rapport fra Nasjonalt register for leddproteser i Norge (NRL) som viste færre infeksjoner ved hofteprotesekirurgi ved bruk av antibiotika i sementen. Registerstudier er vanligvis å regne som observasjonsstudier, og resultatene er ikke ratet like høyt som randomiserte kliniske forsøk. Dermed kunne man velge bort denne kunnskapen, slik man gjorde i USA. Der er det ikke en gang lov (ikke FDA-godkjent) å bruke sement med antibiotika til primærproteser hos lavrisikopasienter, kun til revisjonsoperasjoner

Computerized navigation: A useful tool in total knee replacement.

Background: The purpose of computer assistance in a total knee replacement is to achieve optimal alignment, size, and positioning of the implant. The method is safe and accurate and may be particularly useful in cases with abnormal anatomy. Description: The classical computer-assisted system for total knee replacement was developed with real-time surgical navigation using infrared optical tracking arrays. The tracking arrays are attached to the tibial and femoral shafts, as well as to surgical tools, allowing the surgeon to move the tools relative to the knee. The computer-assisted systems allow the surgeon to combine the “measured resection” and “gap balancing” techniques.publishedVersio

Short-term outcome of 1,465 computer-navigated primary total knee replacements 2005–2008: A report from the Norwegian Arthroplasty Register

Background and purpose: Improvement of positioning and alignment by the use of computer-assisted surgery (CAS) might improve longevity and function in total knee replacements, but there is little evidence. In this study, we evaluated the short-term results of computer-navigated knee replacements based on data from the Norwegian Arthroplasty Register. Patients and methods: Primary total knee replacements without patella resurfacing, reported to the Norwegian Arthroplasty Register during the years 2005–2008, were evaluated. The 5 most common implants and the 3 most common navigation systems were selected. Cemented, uncemented, and hybrid knees were included. With the risk of revision for any cause as the primary endpoint and intraoperative complications and operating time as secondary outcomes, 1,465 computer-navigated knee replacements (CAS) and 8,214 conventionally operated knee replacements (CON) were compared. Kaplan-Meier survival analysis and Cox regression analysis with adjustment for age, sex, prosthesis brand, fixation method, previous knee surgery, preoperative diagnosis, and ASA category were used. Results: Kaplan-Meier estimated survival at 2 years was 98% (95% CI: 97.5–98.3) in the CON group and 96% (95% CI: 95.0– 97.8) in the CAS group. The adjusted Cox regression analysis showed a higher risk of revision in the CAS group (RR = 1.7, 95% CI: 1.1–2.5; p = 0.02). The LCS Complete knee had a higher risk of revision with CAS than with CON (RR = 2.1, 95% CI: 1.3–3.4; p = 0.004)). The differences were not statistically significant for the other prosthesis brands. Mean operating time was 15 min longer in the CAS group. Interpretation: With the introduction of computer-navigated knee replacement surgery in Norway, the short-term risk of revision has increased for computer-navigated replacement with the LCS Complete. The mechanisms of failure of these implantations should be explored in greater depth, and in this study we have not been able to draw conclusions regarding causation

Antibiotic-loaded bone cement in prevention of periprosthetic joint infections in primary total knee arthroplasty: A register-based multicentre randomised controlled non-inferiority trial (ALBA trial)

Introduction The current evidence on the efficacy of antibiotic-loaded bone cement (ALBC) in reducing the risk of periprosthetic joint infections (PJI) after primary joint reconstruction is insufficient. In several European countries, the use of ALBC is routine practice unlike in the USA where ALBC use is not approved in low-risk patients. Therefore, we designed a double-blinded pragmatic multicentre register-based randomised controlled non-inferiority trial to investigate the effects of ALBC compared with plain bone cement in primary total knee arthroplasty (TKA). Methods and analysis A minimum of 9,172 patients undergoing full-cemented primary TKA will be recruited and equally randomised into the ALBC group and the plain bone cement group. This trial will be conducted in Norwegian hospitals that routinely perform cemented primary TKA. The primary outcome will be risk of revision surgery due to PJI at 1-year of follow-up. Secondary outcomes will be: risk of revision due to any reason including aseptic loosening at 1, 6, 10 and 20 years of follow-up; patient-related outcome measures like function, pain, satisfaction and health-related quality of life at 1, 6 and 10 years of follow-up; risk of changes in the microbial pattern and resistance profiles of organisms cultured in subsequent revisions at 1, 6, 10 and 20 years of follow-up; cost-effectiveness of routine ALBC versus plain bone cement use in primary TKA. We will use 1:1 randomisation with random permuted blocks and stratify by participating hospitals to randomise patients to receive ALBC or plain bone cement. Inclusion, randomisation and follow-up will be through the Norwegian Arthroplasty Register. Ethics and dissemination The trial was approved by the Western Norway Regional Committees on Medical and Health Research Ethics (reference number: 2019/751/REK vest) on 21 June 2019. The findings of this trial will be disseminated through peer-reviewed publications and conference presentations. Trial registration number NCT04135170.publishedVersio

Computer Navigation in Total Knee Replacement Surgery. Effect on Outcome

Background: In total knee replacement surgery (TKR), the surgeon aims to align the implant according to the mechanical axis of the limb. Among knee surgeons the dominating belief is that good alignment reduces wear and loosening of the implant, and optimizes patellar tracking, range of motion and function of the knee, although the evidence is limited. Computer navigation has been used in total knee replacement surgery for more than a decade to improve the alignment (abbr. CAS – computer assisted surgery). The term “navigation” in this setting refers to positioning of the implant relative to the anatomy of the knee. Conventional (traditional) navigation, or positioning, is performed by the use of intramedullary or extramedullary rods to align the implant according to the mechanical axis of the limb (abbr. CONV – conventional TKR). In contrast, with the classical image-less computer navigation there is no need of intramedullary rods, and image-less computer navigation utilizing infrared cameras and advanced software, is shown to be more accurate than conventional navigation. However, it is costly and time consuming. The purpose of this thesis was to investigate the relationship between use of computer navigation and outcome. Methods: To what extent this new technology must improve the outcome to become cost-effective, was evaluated in an economic model. One register study analyzes the outcome of computer navigated TKR, another register study investigates the survivorship and revision causes of the most common implant brands, and a randomized clinical trial (RCT) evaluates the functional and radiological outcome of CAS. Results/discussion: Paper I shows that CAS might be cost-effective in TKR if the hospital volume is high and the cost of the equipment does not increase relative to the prices of today. Age of the patient is not likely to have any influence on costeffectiveness. However, the cost-effectiveness depends on a marginal improvement of implant survivorship. Based on the findings in paper IV with improved alignment and marginally improved functional scores, there is some reason to be optimistic in regard to impact on survivorship. On the contrary, the findings in paper II, with increased risk of revision in the short term, suggest that there might not be an improved survivorship with CAS in the long term, at least not the way it has been used in Norway. Results in Norway may differ from the results in other countries and is probably dependent on education of the surgeons in the use of this new technology, and also of the patient volume and thereby the surgeon’s experience with CAS. Additionally, the design of the implant and its compatibility with the computer navigation software and hardware, might affect the results as suggested in paper II. To further elucidate this aspect, a register study was performed analyzing revision causes and survivorship of the most used TKR implants in Norway. The mobilebearing LCS Complete seemed to perform inferiorly when computer navigated, and we suspected that the mobile-bearing design was difficult to navigate properly. To separate the negative effect of computer navigation from other causes of inferior survivorship, we decided to conduct a register study excluding the computer navigated knees, investigating revision causes and survivorship (paper III). Paper III showed that the LCS Complete and the LCS Classic both had a 7-fold increased risk of revision due to aseptic loosening of the tibial components, compared to the most used knee implant in Norway - the Profix knee. Even the femoral component had an increased risk of revision due to aseptic loosening. However, the 5 years Kaplan- Meier survival rates were 94.9 and 95.6 for the LCS Complete and LCS Classic, respectively, compared to 96.3 for the Profix. This difference is by many, not considered clinically significant, but the risk of aseptic loosening is more alarming and proven to be independent of CAS. The project will continue to evaluate the reasons for aseptic loosening in the LCS knees by collaboration with other national registers and by studying revised and unused implants in the laboratory. The positive results of CAS, in paper IV, urge us to continue the evaluation of this technology as it develops, through repeated register analyses and clinical trials investigating improved types of navigation. The thesis is part of a larger project investigating long term survivorship with radiostereometric analysis and long term follow-ups. Conclusion: Computer navigation in total knee replacement surgery has increased the operation time and resulted in inferior short term survivorship in Norway. However, the technology is more accurate than conventional technique, and the functional results are marginally improved by CAS. If these positive effects result in a better long term survivorship of the implant, the technology is getting more userfriendly and the operation time is reduced, the technology is likely to be costeffective and beneficial for the patients

Survivorship and relative risk of revision in computer-navigated versus conventional total knee replacement at 8-year follow-up: A study of 23,684 cases reported to the Norwegian Arthroplasty Register, 2005–2014

Background and purpose — The long-term effects of computer-assisted surgery in total knee replacement (CAS) compared to conventionally operated knee replacement (CON) are still not clear. We compared survivorship and relative risk of revision in CAS and CON based on data from the Norwegian Arthroplasty Register. Patients and methods — We assessed primary total knee replacements without patellar resurfacing reported to the Norwegian Arthroplasty Register from 2005 through 2014. The 5 most used implants and the 3 most common navigation systems were included. The groups (CAS, n = 3,665; CON, n = 20,019) were compared using a Cox regression analysis adjusted for age, sex, ASA category, prosthesis brand, fixation method, previous surgery, and diagnosis with the risk of revision for any reason as endpoint. Secondary outcomes were reasons for revision and effects of prosthesis brand, fixation method, age (± 65 years), and hospital volume. Results — Prosthesis survival and risk of revision were similar for CAS and CON. CAS had significantly fewer revisions due to malalignment. Otherwise, no statistically significant difference was found between the groups in analyses of secondary outcomes. Mean operating time was 13 minutes longer in CAS. Interpretation — At 8 years of follow-up, CAS and CON had similar rates of overall revision, but CAS had fewer revisions due to malalignment. According to our findings, the benefits of CAS at medium-term follow-up are limited. Further research may identify subgroups that benefit from CAS, and it should also emphasize patient-reported outcomes

Did a New Design of the Oxford Unicompartmental Knee Prosthesis Result in Improved Survival? A Study From the Norwegian Arthroplasty Register 2012-2021

Background Unicompartmental knee arthroplasty (UKA) has generally shown higher revision rates than TKA, and this is particularly true for the femoral component. A twin-peg femoral component (Oxford Partial) has replaced the single-peg version (Oxford Phase III) of the widely used Oxford medial UKA, with the aim of improving femoral component fixation. The introduction of the Oxford Partial Knee also included a fully uncemented option. However, there has been relatively little evidence regarding the effect of these changes on implant survival and revision diagnoses from groups not associated with the implant design. Questions/purposes Using data from the Norwegian Arthroplasty Register, we asked: (1) Has the 5-year implant survival (free from revision for any cause) improved with the medial Oxford unicompartmental knee after the introduction of new designs? (2) Did the causes of revision change between the old and new designs? (3) Is there a difference in risk for specific revision causes between the uncemented and cemented versions of the new design? Methods We performed a registry-based observational study using data from the Norwegian Arthroplasty Register, a nationwide, mandatory and governmental registry with a high reporting rate. Between 2012 and 2021, 7549 Oxford UKAs were performed, and 105 were excluded due to combinations of the three designs, lateral compartment replacement, or hybrid fixation, leaving 908 cemented Oxford Phase III single-peg (used from 2012 to 2017), 4715 cemented Oxford Partial twin-peg (used from 2012 to 2021), and 1821 uncemented Oxford Partial twin-peg (used from 2014 to 2021), UKAs available for the analysis. The Kaplan-Meier method and Cox regression multivariate analysis were used to find the 5-year implant survival and the risk of revision (hazard ratio), when adjusting for age, gender, diagnosis, American Society of Anesthesiologists grade, and time period. The risk of revision for any cause and the risk of revision for specific causes were compared, first for the older with the two new designs, and second for the cemented with the uncemented version of the new design. Revision was defined as any operation exchanging or removing implant parts. Results The 5-year Kaplan-Meier overall implant survival (free from revision for any cause) for the medial Oxford Partial unicompartmental knee did not improve over the study period. The 5-year Kaplan-Meier survival was different (p = 0.03) between the groups: it was 92% (95% confidence interval [CI] 90% to 94%) for the cemented Oxford III, 94% (95% CI 93% to 95%) for the cemented Oxford Partial, and 94% (95% CI 92% to 95%) for the uncemented Oxford Partial. However, the overall risk of revision during the first 5 years was not different between the groups (Cox regression HR 0.8 [95% CI 0.6 to 1.0]; p = 0.09 and 1.0 [95% CI 0.7 to 1.4]; p = 0.89 for the cemented Oxford Partial and the uncemented Oxford Partial, respectively, compared with cemented Oxford III [HR 1]). The uncemented Oxford Partial had a higher risk of revision for infection (HR 3.6 [95% CI 1.2 to 10.5]; p = 0.02) compared with the cemented Oxford III. The uncemented Oxford Partial had a lower risk of revision for pain (HR 0.5 [95% CI 0.2 to 1.0]; p = 0.045) and instability (HR 0.3 [95% CI 0.1 to 0.9]; p = 0.03) compared with the cemented Oxford III. The cemented Oxford Partial had a lower risk of revision for aseptic femoral loosening (HR 0.3 [95% CI 0.1 to 1.0]; p = 0.04) compared with the cemented Oxford III. When comparing the uncemented and cemented versions of the new design, the uncemented Oxford Partial had a higher risk of revision for periprosthetic fracture (HR 15 [95% CI 4 to 54]; p = 0.001) and infection within the first year (HR 3.0 [95% CI 1.5 to 5.7]; p = 0.001) than the cemented Oxford Partial. Conclusion Considering that we found no difference in overall risk of revision during the first 5 years but we found a higher risk of revision for infection, periprosthetic fracture, and higher per implant cost, we currently would recommend against the use of uncemented Oxford Partial over the cemented Oxford Partial or the cemented Oxford III.publishedVersio

An economic model to evaluate cost-effectiveness of computer assisted knee replacement surgery in Norway

Background: The use of Computer Assisted Surgery (CAS) for knee replacements is intended to improve the alignment of knee prostheses in order to reduce the number of revision operations. Is the cost effectiveness of computer assisted surgery influenced by patient volume and age? Methods: By employing a Markov model, we analysed the cost effectiveness of computer assisted surgery versus conventional arthroplasty with respect to implant survival and operation volume in two theoretical Norwegian age cohorts. We obtained mortality and hospital cost data over a 20-year period from Norwegian registers. We presumed that the cost of an intervention would need to be below NOK 500,000 per QALY (Quality Adjusted Life Year) gained, to be considered cost effective. Results: The added cost of computer assisted surgery, provided this has no impact on implant survival, is NOK 1037 and NOK 1414 respectively for 60 and 75-year-olds per quality-adjusted life year at a volume of 25 prostheses per year, and NOK 128 and NOK 175 respectively at a volume of 250 prostheses per year. Sensitivity analyses showed that the 10-year implant survival in cohort 1 needs to rise from 89.8% to 90.6% at 25 prostheses per year, and from 89.8 to 89.9% at 250 prostheses per year for computer assisted surgery to be considered cost effective. In cohort 2, the required improvement is a rise from 95.1% to 95.4% at 25 prostheses per year, and from 95.10% to 95.14% at 250 prostheses per year. Conclusions: The cost of using computer navigation for total knee replacements may be acceptable for 60-year-old as well as 75-year-old patients if the technique increases the implant survival rate just marginally, and the department has a high operation volume. A low volume department might not achieve cost-effectiveness unless computer navigation has a more significant impact on implant survival, thus may defer the investments until such data are available

Survival rates and causes of revision in cemented primary total knee replacement. A report from the Norwegian Arthroplasty Register 1994–2009

We evaluated the rates of survival and cause of revision of seven different brands of cemented primary total knee replacement (TKR) in the Norwegian Arthroplasty Register during the years 1994 to 2009. Revision for any cause, including resurfacing of the patella, was the primary endpoint. Specific causes of revision were secondary outcomes. Three posterior cruciate-retaining (PCR) fixed modular-bearing TKRs, two fixed non-modular bearing PCR TKRs and two mobilebearing posterior cruciate-sacrificing TKRs were investigated in a total of 17 782 primary TKRs. The median follow-up for the implants ranged from 1.8 to 6.9 years. Kaplan-Meier 10-year survival ranged from 89.5% to 95.3%. Cox’s relative risk (RR) was calculated relative to the fixed modularbearing Profix knee (the most frequently used TKR in Norway), and ranged from 1.1 to 2.6. The risk of revision for aseptic tibial loosening was higher in the mobile-bearing LCS Classic (RR 6.8 (95% confidence interval (CI) 3.8 to 12.1)), the LCS Complete (RR 7.7 (95% CI 4.1 to 14.4)), the fixed modular-bearing Duracon (RR 4.5 (95% CI 1.8 to 11.1)) and the fixed non-modular bearing AGC Universal TKR (RR 2.5 (95% CI 1.3 to 5.1)), compared with the Profix. These implants (except AGC Universal) also had an increased risk of revision for femoral loosening (RR 2.3 (95% CI 1.1 to 4.8), RR 3.7 (95% CI1.6 to 8.9), and RR 3.4 (95% CI 1.1 to 11.0), respectively). These results suggest that aseptic loosening is related to design in TKR

Early aseptic loosening of a mobile-bearing total knee replacement

Background and purpose - Registry-based studies have reported an increased risk of aseptic tibial loosening for the cemented Low Contact Stress (LCS) total knee replacement compared with other cemented designs; however, the reasons for this have not been established. We made a retrieval analysis with the aim of identifying the failure mechanism. Patients and methods - We collected implants, cement, tissue, blood, and radiographs from 32 failed LCS Complete cases. Damage to the tibial baseplate and insert was assessed. Exposure to wear products was quantified in 11 cases through analysis of periprosthetic tissue and blood. Implant alignment and bone cement thickness was compared with a control group of 43 non-revised cases. Results - Loosening of the tibial baseplate was the reason for revision in 25 retrievals, occurring at the implant-cement interface in 16 cases. Polishing was observed on the lower surface of the baseplate and correlated to the level of cobalt, chromium, and zirconium in the blood. No evidence of abnormally high polyethylene wear was present. For each 1 mm increase in cement thickness the odds of failure due to aseptic loosening decreased by 61%. Greater varus alignment was associated with a shorter time to failure. The roughness, Ra, of a new LCS baseplate's lower surface was 3.7 (SD 0.7) microm. Interpretation - Debonding of the tibial component at the implant-cement interface was the predominant cause of tibial aseptic loosening. A thin cement layer may partly explain the poor performance. Furthermore, the comparatively low tibial surface roughness and the lack of a keeled stem may have played a role in the failures observed