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Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_12 | Pages 6 - 6
23 Jun 2023
Callary S Barends J Solomon LB Nelissen R Broekhuis D Kaptein B
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The best treatment method of large acetabular bone defects at revision THR remains controversial. Some of the factors that need consideration are the amount of residual pelvic bone removed during revision; the contact area between the residual pelvic bone and the new implant; and the influence of the new acetabular construct on the centre of rotation of the hip. The purpose of this study was to compare these variables in two of the most used surgical techniques used to reconstruct severe acetabular defects: the trabecular metal acetabular revision system (TMARS) and a custom triflanged acetabular component (CTAC).

Pre- and post-operative CT-scans were acquired from 11 patients who underwent revision THR with a TMARS construct for a Paprosky IIIB defect, 10 with pelvic discontinuity, at Royal Adelaide Hospital. The CT scans were used to generate computer models to virtually compare the TMARS and CTAC constructs using a semi-automated method. The TMARS construct model was calculated using postoperative CT scans while the CTAC constructs using the preoperative CT scans. The bone contact, centre of rotation, inclination, anteversion and reamed bone differences were calculated for both models.

There was a significant difference in the mean amount of bone reamed for the TMARS reconstructions (15,997 mm3) compared to the CTAC reconstructions (2292 mm3, p>0.01). There was no significant difference between overall implant bone contact (TMARS 5760mm2 vs CTAC 5447mm2, p=0.63). However, there was a significant difference for both cancellous (TMARS 4966mm2 vs CTAC 2887mm2, p=0.008) and cortical bone contact (TMARS 795mm2 vs CTAC 2560mm2, p=0.001). There was no difference in inclination and anteversion achieved. TMARS constructs resulted on average in a centre of rotations 7.4mm more lateral and 4.0mm more posterior.

Modelling of two different reconstructions of Paprosky IIIB defects demonstrated potential important differences between all variables investigated.


Bone & Joint Open
Vol. 3, Issue 12 | Pages 977 - 990
23 Dec 2022
Latijnhouwers D Pedersen A Kristiansen E Cannegieter S Schreurs BW van den Hout W Nelissen R Gademan M

Aims

This study aimed to investigate the estimated change in primary and revision arthroplasty rate in the Netherlands and Denmark for hips, knees, and shoulders during the COVID-19 pandemic in 2020 (COVID-period). Additional points of focus included the comparison of patient characteristics and hospital type (2019 vs COVID-period), and the estimated loss of quality-adjusted life years (QALYs) and impact on waiting lists.

Methods

All hip, knee, and shoulder arthroplasties (2014 to 2020) from the Dutch Arthroplasty Register, and hip and knee arthroplasties from the Danish Hip and Knee Arthroplasty Registries, were included. The expected number of arthroplasties per month in 2020 was estimated using Poisson regression, taking into account changes in age and sex distribution of the general Dutch/Danish population over time, calculating observed/expected (O/E) ratios. Country-specific proportions of patient characteristics and hospital type were calculated per indication category (osteoarthritis/other elective/acute). Waiting list outcomes including QALYs were estimated by modelling virtual waiting lists including 0%, 5% and 10% extra capacity.


Orthopaedic Proceedings
Vol. 104-B, Issue SUPP_12 | Pages 96 - 96
1 Dec 2022
Bohm E Rolfson O Sayers A Wilkinson JM Overgaard S Lyman S Finney K Franklin P Dunn J Denissen G Halstrom B W-Dahl A Van Steenbergen L Ayers D Ingelsrud L Navarro R Nelissen R
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Increased collection of patient-reported outcome measures (PROM) in registries enables international comparison of patient-centered outcomes after knee and hip replacement. We aimed to investigate 1) variations in PROM improvement, 2) the possible confounding factor of BMI, and 3) differences in comorbidity distributions between registries.

Registries affiliated with the International Society of Arthroplasty Registries (ISAR) or OECD membership countries were invited to report aggregate EQ-5D, OKS, OHS, HOOS-PS and KOOS-PS values. Eligible patients underwent primary total, unilateral knee or hip replacement for osteoarthritis within three years and had completed PROMs preoperatively and either 6 or 12 months postoperatively, excluding patients with subsequent revisions. For each PROM cohort, Chi-square tests were performed for BMI distributions across registries and 12 predefined PROM strata (male/female, age 20-64/65-74/>75, high or low preoperative PROM scores). Comorbidity distributions were reported for available comorbidity indexes.

Thirteen registries from 9 countries contributed data, n~130000 knee (range 140 to 79848) and n~113000 hip (range 137 to 85281). Mean EQ-5D index values (10 registries) ranged from 0.53 to 0.71 (knee) and 0.50 to 0.70 (hips) preoperatively and 0.78 to 0.85 (knee) and 0.83 to 0.87 (hip) postoperatively. Mean OKS (6 registries) ranged from 19.3 to 23.6 preoperatively and 36.2 to 41.2 postoperatively. Mean OHS (7 registries) ranged from 18.0 to 23.2 preoperatively and 39.8 to 44.2 postoperatively. Four registries reported KOOS-PS and three reported HOOS-PS. Proportions of patients with BMI >30 ranged from 35 to 62% (10 knee registries) and 16 to 43% (11 hip registries). For both knee and hip registries, distributions of patients across six BMI categories differed significantly among registries (p30 were for patients in the youngest age groups (20 to 64 and 65 to 74 years) with the lowest baseline scores. Additionally, females with lowest preoperative PROM scores had highest BMI. These findings were echoed for the OHS and OKS cohorts. Proportions of patients with ASA scores ≥3 ranged from 7 to 42% (9 knee registries) and 6 to 35% (8 hip registries).

PROM-score improvement varies between international registries, which may be partially explained by differences in age, sex and preoperative scores. BMI and comorbidity may be relevant to adjust for.


Orthopaedic Proceedings
Vol. 104-B, Issue SUPP_10 | Pages 82 - 82
1 Oct 2022
Scheper H Mahdad R Elzer B Löwik C Zijlstra W Gosens T van der Lugt J van der Wal R Poolman R Somford M Jutte P Bos K Kooijman C Maree H Nelissen R Visser LG De Boer MG
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Background

The duration and extent of postoperative wound leakage after joint arthroplasty in patients with or without a complicated course, like a prosthetic joint infection (PJI), is currently unknown. Adequate differentiation between normal postoperative wound leakage and wound leakage due to a postoperative PJI is important and prevents unnecessary surgical procedures. We investigated the association between postoperative wound leakage and development of PJI in patients who used a previously developed mobile wound care app.

Methods

A multicenter, prospective cohort study with patients aged 18 years or older after primary implantation or revision of a total joint arthroplasty. During 30 post-operative days after arthroplasty, patients recorded their wound status in the woundcare app. An algorithm calculated a daily score from imputed data. If the daily score exceeded a predefined threshold, the patients received an alert that advised them to contact their physician.


Orthopaedic Proceedings
Vol. 104-B, Issue SUPP_10 | Pages 20 - 20
1 Oct 2022
Scheper H Van der Wal R Mahdad R Keizer S Delfos N Van der Lugt J Veldkamp KE Nolte P Schippers E Wattel H Visser LG Nelissen R De Boer MG
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Background

Treatment of staphylococcal prosthetic joint infection (PJI) usually consists of surgical debridement and prolonged rifampicin combination therapy. Tailored antimicrobial treatment alternatives are needed due to frequent side effects and drug-drug interactions with rifampicin combination therapy. We aimed to assess the effectiveness of several alternative antibiotic strategies in patients with staphylococcal PJI.

Methods

In this prospective, multicenter registry-based study, all consecutive patients with a staphylococcal PJI, treated with DAIR or one-stage revision surgery between January 1st, 2015 and November 3rd, 2020, were included. Patients were treated according to a predefined protocol for PJI. Antimicrobial treatment strategies differed between centers, which was accepted and used as pseudorandomization. Depending on the hospital patients were admitted to, they were treated with either a long-term rifampicin strategy (consisting of 12 weeks rifampicin combination therapy) ore one of several short-term rifampicin strategies, consisting of only five days of rifampicin combination treatment, started immediately postoperative, followed by clindamycin, flucloxacillin or vancomycin monotherapy. Patients were stratified in different groups, depending on the used antimicrobial strategy. Cox proportional hazards models were used to compare outcome between the groups.


Bone & Joint Open
Vol. 2, Issue 10 | Pages 806 - 812
1 Oct 2021
Gerritsen M Khawar A Scheper H van der Wal R Schoones J de Boer M Nelissen R Pijls B

Aims

The aim of this meta-analysis is to assess the association between exchange of modular parts in debridement, antibiotics, and implant retention (DAIR) procedure and outcomes for hip and knee periprosthetic joint infection (PJI).

Methods

We conducted a systematic search on PubMed, Embase, Web of Science, and Cochrane library from inception until May 2021. Random effects meta-analyses and meta-regression was used to estimate, on a study level, the success rate of DAIR related to component exchange. Risk of bias was appraised using the (AQUILA) checklist.


Orthopaedic Proceedings
Vol. 101-B, Issue SUPP_14 | Pages 67 - 67
1 Dec 2019
Scheper H van der Wal R Mahdad R Keizer S Delfos N van der Lugt J Veldkamp KE Hall ML van Elzakker E Boer MGJD Visser LG Nelissen R
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Aims

Current antibiotic treatment strategies for prosthetic joint infection (PJI) are based mostly on observational retrospective studies. High-quality data from prospective cohorts using identical treatment strategies may improve current clinical practice. We developed a regional network of collaborating hospitals and established a uniform treatment protocol. Data from all patients diagnosed with a PJI are prospectively registered in a an online database. With this quality registry we aim to study the outcome of antibiotic and surgical strategies while adhering to a pre-established treatment protocol.

Methods

A working group of orthopaedic surgeons, infectious disease specialists and microbiologists was established. The working group reached consensus on definition of PJI and a uniform treatment protocol, based on current guidelines and expert-based clinical experience. A website was built to communicate information to colleagues and patients (www.protheseinfectie.nl). In each participating hospital weekly multidisciplinary meetings were started to discuss all PJI cases. All patients are included in an online quality registry and followed for at least two years. We aim to enroll >600 patients with a knee or hip PJI. Research will focus on the duration of antibiotic treatment, antibiotic suppressive therapy and comparison of different oral antibiotic treatment strategies in relation to successful treatment outcomes.


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_17 | Pages 43 - 43
1 Dec 2018
Scheper H Derogee R van der W. R Mahdad R de Boer M Nelissen R Visser L
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Aim

Early discharge of patients after joint arthroplasty leaves patients responsible for monitoring their postoperative wound by themselves. This might result in a delayed presentation of postoperative complications. The use of a mobile woundcare app by patients after arthroplasty might result in (1) earlier report of complications, (2) an increase in patient satisfaction and (3) insight in the incidence and duration of postoperative wound leakage. Therefore, the ease of use and perceived usefulness of using a postoperative mobile woundcare app in patients after joint arthroplasty was investigated.

Method

A cohort study was conducted in 2017 in 2 Dutch Hospitals. Eligible cases were all consecutive patients that received an arthroplasty and who owned a smartphone. During the first 30 postoperative days, patients filled in daily reviews of their wound and took a photo of the wound. Based on the review, an underlying algorithm calculated daily a score that prompted a mobile alert if needed, which advised patients to contact the hospital. Patients filled in a form on day 30 and day 90 in order to document occurrence of any postoperative wound complication. On day 15 and 30, patients were requested to fill in a questionnaire evaluating the perceived usefulness and the ease of use of the App.


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_15 | Pages 99 - 99
1 Nov 2018
Pijls B Sanders I Kuijper E Nelissen R
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The main problem of infected orthopaedic implants is that the presence of microorganisms in an organized biofilm making them difficult accessible for antibiotics. This biofilm consists of a complex community of microorganisms embedded in an extracellular matrix that forms on surfaces such as an implant. Non-contact induction heating uses pulsed electromagnetic fields to induce so-called ‘eddy currents’ within metal objects which causes them to heat up. This heat causes thermal damage to the bacterial biofilm hence killing the bacteria on the metal implant. The purpose of this study is to determine the effectiveness of induction heating on killing Staphylococcus epidermidis in a biofilm. S. epidermidis biofilms were grown on Titanium alloy (Ti6Al4V) coupons and subsequently were heated with a custom-built induction heater to temperatures of 60°C, 70°C, 80°C and 90°C for 3.5 minutes. Temperature was controlled with an infra-red thermal sensor and micro-controller. We also included two control conditions without induction heating: C1 without induction heating and C2 with chlorhexidine 0.5% in 70% alcohol without induction heating. Experiments were repeated 5 times. In the C1 group (no induction heating), 1.3 * 10(7) colony forming units (CFU)/cm(−2) of S. epidermidis were observed. For 60°C, 70C, 80 C and 90C, a 3.9-log reduction, 5.3-log reduction, 5.5-log reduction and 6.1-log reduction in CFU/cm(−2) were observed, respectively. For the C2 (chlorhexidine) there was a 6.7-log reduction CFU/cm(-2). We concluded that induction heating of Titanium coupons is effective in reducing bacterial load in vitro for S. epidermidis biofilms.


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_15 | Pages 101 - 101
1 Nov 2018
Veltman E Lenguerrand E Moojen D Whitehouse M Nelissen R Blom A Poolman R
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Administration of perioperative antibiotic prophylaxis (AP) reduces the risk of prosthetic joint infection (PJI) following primary total hip (THA) and knee (TKA) arthroplasty. The optimal type of antibiotic used, and duration of prophylaxis are subject to debate. We compared the risk of revision surgery for PJI in the first year following THA and TKA by AP regimen. A national survey collecting information on hospital-level AP regimen policy was conducted across the Netherlands and linked to data from the LROI arthroplasty registry for 2011–2015. PJI status was defined using the surgical indication reported at revision by surgeons in the registry form. Restricted cubic splines Poisson model adjusted for hospital clustering were used to conduct the comparisons on 130,712 THAs and 111,467 TKAs performed across 99 institutions. These included 399 THAs and 303 TKAs revised for an indication of PJI. Multiple shot of Cefazolin (MCZ), of cefuroxime (MCX) and single shot of Cefazolin (SCZ) were respectively administrated to 87%, 4% and 9% of patients. For THA, the rates of revision for PJI were respectively 31/10,000 person-years 95%CI[28, 35], 39[25, 59] and 23[15, 34] in the groups which received MCZ, MCX and SCZ; respectively, the rates for TKA were 27[24, 31], 40[24, 62] and 24[16, 36]. No evidence of difference between AP regimens was found in the unadjusted and adjusted model (age, gender, BMI and ASA grade). Further work is advocated to confirm whether there is an association between AP regimen collected at patient-level and the risk of subsequent revision for PJI.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_9 | Pages 86 - 86
1 May 2017
Meessen J Peter W Gorissen I Cannegieter S Tilbury C Wolterbeek R Verdegaal S Vermeulen H van der Linden H Dekker J Tordoir R Onstenk R Benard M Meijer V Slagboom P Nelissen R Vlieland TV
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Objective

Total Hip Arthroplasty (THA) and Total Knee Arthroplasty (TKA) bring relief of pain and functional disability to patients with end stage osteoarthritis, however the literature on their impact on patients’ level of physical activity (PA) is scarce.

Methods

Cross-sectional study, performed in 2012, in 515 patients who underwent THA/TKA surgery in 2010–2011 and a random sample of persons aged >40 years from the Dutch general population participating in a national survey in the same period. PA in minutes per week (min/week) and adherence to the Dutch recommendation for health enhancing PA was measured by means of the Short QUestionnaire to ASsess Health enhancing PA (SQUASH) Additional assessments included socio-demographic characteristics, the presence of comorbidities, BMI and Short Form-12. Multivariable linear (total min/week) and logistic regression analyses (meeting PA recommendation), adjusting for confounders, were performed for THA and TKA separately.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_8 | Pages 54 - 54
1 Apr 2017
Voorn V Marang- van de Mheen P van der Hout A Vlieland TV Nelissen R van Bodegom L
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Backgroud: Allogeneic transfusion rates after primary hip and knee arthroplasty are used as quality indicators for hospitals, but hospital comparisons may be hampered by low event rates. Extended hospital stay is often used and may be more suitable as an alternative. This study aims to assess whether transfusion rates and extended hospital stay can be used to reliably rank hospitals.

Methods

We used the baseline data from the LISBOA implementation trial, where data on patient characteristics and outcomes were collected in a sample of approximately 100 patients undergoing elective primary total hip or knee arthroplasty for each of the 23 participating hospitals. We calculated the reliability of ranking (Rankability) of transfusion rates and extended hospital stay (> 4 postoperative days), using fixed and random effects logistic regression analysis, by dividing the between-hospital variation to the sum of within and between-hospital variation. Rankability thus shows which part of the hospital differences are true differences and not due to random variation.

Results

1163 total hip and 986 total knee procedures were assessed. After adjustment for patient characteristics the odds ratio (OR) of receiving a transfusion in a hospital after total hip ranged from 0.72 to 1.38 and from 0.30 to 3.30 in total knee. Rankability was 17% for hip and 36% for knee arthroplasty, meaning that only 17% and 36% are true hospital differences. Larger hospital variation was found for extended hospital stay (OR range [0.28–3.51] for hip and [0.10–9.95] for knee arthroplasty), and better rankability.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_8 | Pages 88 - 88
1 Apr 2017
Oostlander A Moerman A Zadpoor A Schoeman M Nelissen R Valstar E
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Background

Periprosthetic osteolysis is the most common long-term complication of a total joint arthroplasty, often resulting in aseptic loosening of the implant. As we aim at developing a safe and minimally invasive implant refixation procedure, thorough characterisation of the properties of the periprosthetic tissue is needed.

Methods

In this pilot study, the periprosthetic tissue of eleven patients undergoing hip revision surgery due to aseptic loosening was obtained. Histology, confocal microscopy, atomic force microscopy (AFM) and nanoindentation were performed to structurally and mechanically characterise the tissue. The study was approved by the Medical Ethical Committee of the Leiden University Medical Center.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_8 | Pages 25 - 25
1 Apr 2017
Schoeman M Oostlander A de Rooij K Löwik C Valstar E Nelissen R
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Background

Aseptic loosening of prostheses is the most common cause for failure in total joint arthroplasty. Particulate wear debris induces a non-stop inflammatory-like response resulting in the formation of a layer of fibrous periprosthetic tissue at the bone/implant interface. The current treatment is an invasive revision joint replacement surgery. However, this procedure has a high morbidity rate, therefore, a less invasive alternative is necessary. One approach could be to re-establish osseointegration of the joint prosthesis by inducing osteoblast differentiation in the periprosthetic tissue. Therefore, the aim of this study was to investigate the capacity of periprosthetic tissue cells to differentiate into the osteoblast lineage.

Methods

Periprosthetic tissue samples were collected during revision surgery of aseptic loosened hip prostheses, after which cells were isolated by collagenase digestion. Of 14 different donors, cells from passage 1 till 3 were used for differentiation experiments. During 21 days, cells were cultured under normal and several osteogenic culture conditions. Cultures were stained for alkaline phosphatase (ALP) activity and mineral deposits in the extracellular matrix.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_1 | Pages 13 - 13
1 Jan 2017
Meessen J Saberi Hosnijeh F Wesseling J Slagboom E Uitterlinden A Nelissen R van Meurs J Meulenbelt I
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Osteoarthritis (OA) is a prevalent, age-related joint disease, characterized by diverse progressive changes in articular cartilage and subchondral bone. Disease management is severely hampered by the absence of tools to classify patients based on underlying disease mechanisms. For that matter, increased BMI is a known risk factor for OA in the weight bearing knee joint, but also for hand OA.1The increased risk for OA is therefore thought to be influenced by systemic factors accompanying BMI. It was hypothesized that differences in metabolic state could be underlying OA phenotypes. In the current study we set out to explore the potential role of a large range of metabolites in blood as sensitive biomarker of OA.

Plasma samples were taken from the Rotterdam Study, CHECK-, GARP/NORREF- and the LUMC-arthroplasty cohorts. OA was defined as having had arthroplasty for primary OA, stratified per location (any, hip or knee). In total 647 persons with Total Joint Arthroplasty (TJA) were included and 2125 persons were considered as controls (i.e. they had a Kellgrenn-Lawrence Score of <2 indicating no radiographic OA was present) in any of the studied joints. A total of 231 different metabolites were assessed by using the BrainShake NMR platform. Since parts of the metabolites were highly correlated, we used Principal Component Analyses (PCA) to reduce the data. 23 factors were identified, accounting for 91,4% of the variance in the data. Logistic regression models were applied to investigate the identified factors for their association to arthroplasty for primary OA, independent of age, sex, BMI and cholesterol-lowering medication (statins).

The models showed two different factors robustly associated to arthroplasty as result of primary OA. A table represents the associations of these factors to arthroplasty adjusted for age, sex and BMI, as the information on statin-use was not known for all subjects. Analyses showed that additional correction for statins did not change the results. When stratifying the arthroplasty phenotypes for joint location, factor 11, characterized by e.g. linoleic acid, was found to be associated to arthroplasty in the hip (THA). Similarly, Factor 22, representing saturated fatty acids and degree of unsaturation, was consistently associated with arthroplasty, independent of the site. When analyzing the metabolites involved in the factors individually these associations were confirmed for most contributors of the factors, except the ratio of saturated fatty acids to total fatty acids.

Our preliminary analyses showed that persons with arthroplasty for primary OA compared to controls have different values for factors composed for fatty acids. The identification of groups of fatty acid metabolites as being connected to OA phenotypes indicates an inflammation driven pathway which might give a better understanding of the mechanisms behind OA.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_1 | Pages 61 - 61
1 Jan 2016
Budhiparama NC Mow CS Nelissen R
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Computer navigation has been introduced as an adjunct to Total Knee Arthroplasty (TKA) to assure precision positioning, accurate bone resection and optimal component alignment. Using Computer Assisted Navigation in TKA was a hotly debated issue in United States and elsewhere. Although Computer Navigation has progressed from the 1st generation to the current 3rd generation system, there are still no clearly tangible, apparent long term clinical benefits.

There is some evidence that using Computer Assisted Surgery may lower the incidence of malalignment of mechanical limb axis compared to conventional component placement methods, but it is unclear whether this marginal benefit will translate to concrete positive long term outcomes. AAHKS survey results indicated that the majority of Orthopedic Surgeons were not using computer navigated surgical techniques. The implementation of CAS met with so many hurdles and obstacles because its approach consumes more time and a long learning curve, which translates to added cost and complexity. It is also labor and equipment intensive but only increases accuracy in the “right” hands. Lack of popularity for CAS has induced the innovation of Patient Specific Jigs which has been proven to be extremely accurate, efficient with respect to time and allows surgeons to navigate the operation prior to the procedure.

Since CAS remains unpopular in the US, it would be even less popular in Asia for the obvious reasons of high cost, lack of experts to handle technical difficulties, lack of publicity, and the paucity of beneficial expert testimonies. The “Better, Cheaper, Faster” culture is fully ingrained in the minds of most Asian Arthroplasty surgeons and CAS would seem to only fulfill the “Better”, but not the “Cheaper and Faster” expectations in most hands.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXXVII | Pages 52 - 52
1 Sep 2012
Van Der Linden H Van Der Zwaag H Konijn L Van Der Steenhoven T Van Der Heide H Nelissen R
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Introduction

Malrotation following total knee replacement is directly related to poor outcome. The knowledge of proximal and distal rotational axes and angles of the femur is therefore of high importance. The aim of the study was to determine whether the most used proximal and distal femoral angles; femoral anteversion angle (FAA) and posterior condylar angle (PCA) were different within individuals, between right, left and gender. As well, we studied whether the “inferior condylar angle” is correlated to the PCA and therefore useful in determining the rotation of the distal femur.

Material and Methods

From 36 cadavers the femora were obtained and after removing the soft tissue a Computed Tomography (CT) scan was made. Three angles were measured: (i) the FAA between femoral columnar line (FHNL) and posterior condylar line (PCL), (ii) the PCA between anatomical transepicondylar line (TEL) and PCL, (iii) the inferior condylar angle (ICA) between the TEL and inferior condylar line (ICL). Statistical analysis of comparative relationships between the different angles was examined by calculating correlation coefficients and a paired t-test.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XL | Pages 198 - 198
1 Sep 2012
Valstar E Wolterbeek N Garling E Mertens B Nelissen R
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The mobile-bearing variant of a single-radius design is assumed to provide more freedom of motion compared to the fixed-bearing variant because the insert does not restrict the natural movements of the femoral component. This would reduce the contact stresses and wear which in turn may have a positive effect on the fixation of the prosthesis to the bone and thereby decreases the risk for loosening. The aim of this prospective randomized study was to evaluate early migration of the tibial component and kinematics of a mobile-bearing and fixed-bearing total knee prosthesis of the same single-radius design.

According to a prospective randomized protocol 20 Triathlon single-radius posterior- stabilized knee prostheses were implanted (9 mobile-bearing and 11 fixed-bearing). Fluoroscopy and roentgen stereophotogrammetric analysis were performed 6 and 12 months post-operatively.

The 1 year post-operative roentgen stereophotogrammetric analysis results showed considerable early migrations in 3 mobile-bearing patients and 1 fixed-bearing patient. The range of knee flexion was the same for the mobile-bearing and fixed- bearing group. The mobile insert was following the femoral component during motion.

This study showed no apparent distinction in early migration and kinematics between mobile-bearing and fixed-bearing single-radius total knee prostheses. Des- pite the mobile insert was following the femoral component during motion, and therefore performed as intended, no kinematic advantages of the mobile-bearing total knee prosthesis were seen. It is concluded that a mobile insert in single-radius total knee prostheses is redundant and will not lead to additional benefits.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXXVII | Pages 176 - 176
1 Sep 2012
Keurentjes J Fiocco M Schreurs B Pijls B Nouta K Nelissen R
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Introduction

The Kaplan Meier estimator is widely used in orthopedics. In situations where another event prevents the occurrence of the event of interest, the Kaplan Meier estimator is not appropriate and a competing risks model has to be applied. We questioned how much bias is introduced by erroneous use of the Kaplan Meier estimator instead of a competing risks model in a hip revision surgery cohort.

Methods

In our previously published cohort study, 62 acetabular revisions (58 patients) were performed between January 1979 and March 1986. Twenty to twenty-five years after surgery, no patients were lost to follow-up. Thirteen patients underwent revision surgery. During the 20 to 25 years follow-up, 30 patients (33 acetabular revisions) died of causes unrelated to their hip surgery.


Orthopaedic Proceedings
Vol. 93-B, Issue SUPP_IV | Pages 537 - 537
1 Nov 2011
Van der Linden E Wolterbeek N Valstar E Nelissen R
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Purpose of the study: Congruence between the femoral component and the insert has been proposed to decrease wear in total knee arthroplasty (TKA). This congruence should favour unidirectional movement between the components because multidirectional movements carry a risk factor for wear up to 30-fold higher than unidirectional movements. This study explored in vivo displacements between the insert and the femoral component of a prosthesis in order to determine whether they meet the required kinematic criteria.

Material and methods: Twelve patients (7 women, 5 men) aged 45 to 79 years with BMI from 23 to 35 underwent knee surgery for osteoarthritis and were included in this study. The prosthesis was a mobile plateau pros-thesis implanted by the same surgeon using a navigation system. During the procedure, four tantalum beads were implanted in the polyethylene under stereotaxic guidance. The postoperative evaluation was performed at six months with the clinical evaluation (KSS, WOMAC) a 3D fluoroscopic protocol (walking, stairs, get up and go) and a radiostereometric analysis (RSA).

Results: Active flexion under weight bearing was 118 (range 102–125) and the mean KSS 165. The videofluoroscopy combined with RSA showed congruent axial rotation between the femoral component and the insert in the flexion arc 0/60 with a mean difference of 0.38 per degree of flexion (SD 1.85). Beyond 60° flexion, the posterior displacement of the condyle was greater than the insert rotation.

Discussion: Compared with other 3D videofluoroscopic studies, this analysis adds greater accuracy due to the implantation of tantalum beads in the insert, enabling a study of insert displacement in relation to the metal components. This method demonstrates that for the implant studied here, rotation of the insert follows the displacement of the femoral component exactly from 0 to 60° flexion, this is a gliding displacement. Then beyond 60°, a gliding plus rolling movement occurs displacing the femoral component posteriorly.

Conclusion: This in vivo study in patients with a mobile plateau knee prosthesis demonstrates that the insert has a rotation exactly like the femoral component and that complete congruency is maintained between the femoral component and the insert with a pure gliding contact from 0 to 60° flexion. The prerequisite criteria for this type of prosthesis designed to reduce the wear factor are thus confirmed.