Elbow joint loads during simulated activities of daily living: implications for formulating recommendations after total elbow arthroplasty.

BACKGROUND: Overloading of the elbow joint prosthesis following total elbow arthroplasty can lead to implant failure. Joint moments during daily activities are not well contextualized for a prosthesis's failure limits, and the effect of the current postoperative instruction on elbow joint loading is unclear. This study investigates the difference in elbow joint moments between simulated daily tasks and between flexion-extension, pronation-supination, and varus-valgus movement directions. Additionally, the effect of the current postoperative instruction on elbow joint load is examined. METHODS: Nine healthy participants (age 45.8 ± 17 years, 3 males) performed 8 tasks; driving a car, opening a door, rising from a chair, lifting, sliding, combing hair, drinking, emptying cup, without and with the instruction "not lifting more than 1 kg." Upper limb kinematics and hand contact forces were measured. Elbow joint angles and net moments were analyzed using inverse dynamic analysis, where the net moments are estimated from movement data and external forces. RESULTS: Peak elbow joint moments differed significantly between tasks (P < .01) and movement directions (P < .01). The most and least demanding tasks were, rising from a chair (13.4 Nm extension, 5.0 Nm supination, and 15.2 Nm valgus) and sliding (4.3 Nm flexion, 1.7 Nm supination, and 2.6 Nm varus). Net moments were significantly reduced after instruction only in the chair task (P < .01). CONCLUSION: This study analyzed elbow joint moments in different directions during daily tasks. The outcomes question whether postoperative instruction can lead to decreasing elbow loads. Future research might focus on reducing elbow loads in the flexion-extension and varus-valgus directions.

[Complaints after total joint arthroplasty: caused by infection or metal hypersensitivity?] / Klachten na plaatsing van een gewrichtsprothese.

Besides periprosthetic joint infection, metal hypersensitivity should be considered when complaints persist after total joint arthroplasty. To date, there is no consensus on the diagnosis, and believers and non-believers of metal hypersensitivity exist. The pathogenesis of metal hypersensitivity is complex and involves a type-4 delayed hypersensitivity reaction with both a cutaneous and systemic response. It is unclear if complaints after total joint arthroplasty (after eliminating other causes) are caused by metal hypersensitivity. Furthermore, it is not known whether sensitization is a cause or a consequence of complaints after total joint arthroplasty. Currently, the patch test is the best screening test to diagnose metal hypersensitivity, but the accuracy has not been defined. We present a female patient with a painful left elbow three years after total elbow replacement. Because of the increasing volume of total joint prostheses, we aim to create awareness for metal hypersensitivity and the according diagnostic dilemmas.

[Complaints after total joint arthroplasty: caused by infection or metal hypersensitivity?] / Klachten na plaatsing van een gewrichtsprothese.

Besides periprosthetic joint infection, metal hypersensitivity should be considered when complaints persist after total joint arthroplasty. To date, there is no consensus on the diagnosis, and believers and non-believers of metal hypersensitivity exist. The pathogenesis of metal hypersensitivity is complex and involves a type-4 delayed hypersensitivity reaction with both a cutaneous and systemic response. It is unclear if complaints after total joint arthroplasty (after eliminating other causes) are caused by metal hypersensitivity. Furthermore, it is not known whether sensitization is a cause or a consequence of complaints after total joint arthroplasty. Currently, the patch test is the best screening test to diagnose metal hypersensitivity, but the accuracy has not been defined. We present a female patient with a painful left elbow three years after total elbow replacement. Because of the increasing volume of total joint prostheses, we aim to create awareness for metal hypersensitivity and the according diagnostic dilemmas.

LOFIT (Lifestyle front Office For Integrating lifestyle medicine in the Treatment of patients): a novel care model towards community-based options for lifestyle change-study protocol.

BACKGROUND: A healthy lifestyle is indispensable for the prevention of noncommunicable diseases. However, lifestyle medicine is hampered by time constraints and competing priorities of treating physicians. A dedicated lifestyle front office (LFO) in secondary/tertiary care may provide an important contribution to optimize patient-centred lifestyle care and connect to lifestyle initiatives from the community. The LOFIT study aims to gain insight into the (cost-)effectiveness of the LFO. METHODS: Two parallel pragmatic randomized controlled trials will be conducted for (cardio)vascular disorders (i.e. (at risk of) (cardio)vascular disease, diabetes) and musculoskeletal disorders (i.e. osteoarthritis, hip or knee prosthesis). Patients from three outpatient clinics in the Netherlands will be invited to participate in the study. Inclusion criteria are body mass index (BMI) ≥25 (kg/m2) and/or smoking. Participants will be randomly allocated to either the intervention group or a usual care control group. In total, we aim to include 552 patients, 276 in each trial divided over both treatment arms. Patients allocated to the intervention group will participate in a face-to-face motivational interviewing (MI) coaching session with a so-called lifestyle broker. The patient will be supported and guided towards suitable community-based lifestyle initiatives. A network communication platform will be used to communicate between the lifestyle broker, patient, referred community-based lifestyle initiative and/or other relevant stakeholders (e.g. general practitioner). The primary outcome measure is the adapted Fuster-BEWAT, a composite health risk and lifestyle score consisting of resting systolic and diastolic blood pressure, objectively measured physical activity and sitting time, BMI, fruit and vegetable consumption and smoking behaviour. Secondary outcomes include cardiometabolic markers, anthropometrics, health behaviours, psychological factors, patient-reported outcome measures (PROMs), cost-effectiveness measures and a mixed-method process evaluation. Data collection will be conducted at baseline, 3, 6, 9 and 12 months follow-up. DISCUSSION: This study will gain insight into the (cost-)effectiveness of a novel care model in which patients under treatment in secondary or tertiary care are referred to community-based lifestyle initiatives to change their lifestyle. TRIAL REGISTRATION: ISRCTN ISRCTN13046877 . Registered 21 April 2022.

Elbow joint biomechanics during ADL focusing on total elbow arthroplasty - a scoping review.

BACKGROUND: Overloading is hypothesized to be one of the failure mechanisms following total elbow arthroplasty (TEA). It is unclear whether the current post-operative loading instruction is compliant with reported failure mechanisms. Aim is therefore to evaluate the elbow joint load during activities of daily living (ADL) and compare these loads with reported failure limits from retrieval and finite element studies. METHODS: A scoping review of studies until 23 November 2021 investigating elbow joint load during ADL were identified by searching PubMed/Medline and Web of Science. Studies were eligible when: (1) reporting on the elbow joint load in native elbows or elbows with an elbow arthroplasty in adults; (2) full-text article was available. RESULTS: Twenty-eight studies with a total of 256 participants were included. Methodological quality was low in 3, moderate in 22 and high in 3 studies. Studies were categorized as 1) close to the body and 2) further away from the body. Tasks were then subdivided into: 1) cyclic flexion/extension, 2) push-up, 3) reaching, 4) self-care, 5) work. Mean flexion-extension joint load was 17 Nm, mean varus-valgus joint load 9 Nm, mean pronation-supination joint load 8 Nm and mean bone-on-bone contact force 337 N. CONCLUSION: The results of our scoping review give a first overview of the current knowledge on elbow joint loads during ADL. Surprisingly, the current literature is not sufficient to formulate a postoperative instruction for elbow joint loading, which is compliant with failure limits of the prosthesis. In addition, our current instruction does not appear to be evidence-based. Our recommendations offer a starting point to assist clinicians in providing informed decisions about post-operative instructions for their patients.

Postoperative management of total elbow arthroplasty: Results of a European survey among orthopedic surgeons.

BACKGROUND: The number of complications after total elbow arthroplasty (TEA) is high and survival rates are low compared to hip and knee arthroplasties. The most common reason for revision is aseptic loosening, which might be caused by overloading of the elbow. In an attempt to lower failure rates, current clinical practice is to restrict activities for patients with a TEA. However, postoperative management of TEA is a poorly investigated topic, as no evidence-based clinical guidelines exist and the aftercare is often surgeon-based. In this study we evaluated the current postoperative management of TEA among orthopedic surgeons. METHODS: An online survey of 30 questions was sent to 635 members of the European Society for Surgery of the Shoulder and the Elbow (SECEC/ESSSE), about 10% (n = ± 64) of whom are considered dedicated elbow specialists. The questions were on characteristics of the surgeon and on the surgeon's preferred postoperative management, including items to be assessed on length of immobilization, amount of weight bearing and axial loading, instructions on lifelong activities, physiotherapy, and postoperative evaluation of the elbow. RESULTS: The survey was completed by 54 dedicated elbow specialists from 17 different countries. Postoperative immobilization of the elbow was advised by half of respondents when using the triceps-sparing approach (52%), and even more with the triceps-detaching approach (65%). Postoperative passive movement of the elbow was allowed in the triceps-sparing approach (91%) and in the triceps-detaching approach (87%). Most respondents gave recommendations on weight bearing (91%) or axial loading (76%) by the affected elbow, but the specification shows significant variation. CONCLUSION: The results from this survey demonstrate a wide variation in postoperative care of TEA. The lack of consensus in combination with low survival rates stresses the need for clinical guidelines. Further research should focus on creating these guidelines to improve follow-up care for TEA.

Mid-term results of the Latitude primary total elbow arthroplasty.

BACKGROUND: The Latitude total elbow prosthesis is a third-generation implant, developed to restore the natural anatomy of the elbow. Literature on this prosthesis is scarce. The aim of this study was to analyze the mid-term results of the Latitude total elbow prosthesis. METHODS: We retrospectively evaluated 62 patients (21 men and 41 women). The mean age at the time of surgery was 65 years (range, 28-87 years). The main indication for surgery was inflammatory arthritis. The outcome measures were complications, reoperations, self-reported physical functioning, pain, satisfaction, objectively measured physical functioning, and radiologic signs of loosening. Kaplan-Meier survival analysis was used to determine survival with revision as the endpoint. RESULTS: Sixty-nine primary Latitude prostheses were placed in 62 patients between 2008 and 2019. Six patients (7 prostheses) died, 3 elbows underwent revision, and 9 patients were lost to follow-up. A total of 44 patients (50 prostheses) were available for follow-up. The mean length of follow-up was 51 months (range, 10-144 months). Kaplan-Meier survival analysis showed a survival rate of 82% at 10 years after surgery. The main reason for revision was aseptic loosening. Radial head dissociation was seen in 8 patients (24%), but none had complaints. Self-reported and objectively measured physical functioning yielded good results, although 23 patients (46%) did show radiolucent lines on radiographs. CONCLUSION: Latitude total elbow arthroplasty is considered a successful procedure with low pain scores, high patient satisfaction, and good physical functioning. Survival rates nonetheless remain low and complication rates remain high yet are comparable to those of other elbow arthroplasties. We recommend biomechanical studies to concentrate on specific postoperative loading instructions to minimize wear and consequent loosening.

Triceps Insufficiency After Total Elbow Arthroplasty: A Systematic Review.

BACKGROUND: The incidence of triceps insufficiency after total elbow arthroplasty (TEA) varies in the literature, and a consensus on treatment strategy is lacking. We review the incidence, the risk factors, the clinical presentation, and the diagnosis and treatment of triceps insufficiency after TEA. Based on this information, we have formulated recommendations for clinical practice. METHODS: We performed a systematic review of the literature from January 2003 to April 2020 to identify studies that investigated triceps function following TEA by searching the PubMed, Cochrane, and Embase databases. Eligible studies (1) reported on triceps function following primary or revision TEA for every indication, regardless of technique (e.g., bone grafts), (2) included ≥6 adult patients, (3) had the full-text article available, and (4) had a minimum follow-up of 1 year. RESULTS: Eighty studies with a total of 4,825 TEAs were included. The quality was low in 15 studies, moderate in 64 studies, and high in 1 study. The mean incidence of triceps insufficiency was 4.5%. The rates were highest in patients after revision TEA (22%), in those with posttraumatic arthritis as an indication for surgery (10.2%), and after a triceps-reflecting approach (4.9%). Most studies used the Medical Research Council scale to score triceps function, although cutoff points and the definition of triceps insufficiency differed among studies. Surgical treatment showed favorable results with anconeus tendon transfer and Achilles allograft repair when compared with direct repair. CONCLUSIONS: The incidence of triceps insufficiency varies greatly, probably due to a lack of consensus on the definition of the term. Therefore, we recommend the guidelines for clinical practice that are presented in this article. These guidelines assist clinicians in providing the best possible treatment strategy for their patients and help researchers optimize their future study designs in order to compare outcomes. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Prospective cohort study comparing a triceps-sparing and triceps-detaching approach in total elbow arthroplasty: a protocol.

BACKGROUND: New surgical approaches have been developed to optimise elbow function after total elbow arthroplasty (TEA). Currently, there is no consensus on the best surgical approach. This study aims to investigate the functional outcomes, prosthetic component position and complication rates after a triceps-sparing and a triceps-detaching approach in TEA. METHODS AND ANALYSIS: A multicentre prospective comparative cohort study will be conducted. All patients with an indication for primary TEA will enrol in either the triceps-sparing or the triceps-detaching cohort. Primary outcome measure is elbow function, specified as fixed flexion deformity. Secondary outcome parameters are self-reported and objectively measured physical functioning, including triceps force, prosthetic component position in standard radiographs and complications. DISCUSSION: The successful completion of this study will clarify which surgical approach yields better functional outcomes, better prosthetic component position and lower complication rates in patients with a TEA. ETHICS AND DISSEMINATION: The Medical Ethics Review Board of University Medical Center Groningen reviewed the study and concluded that it is not clinical research with human subjects as meant in the Medical Research Involving Human Subjects Act (WMO), therefore WMO approval is not needed (METc2019/544). TRIAL REGISTRATION NUMBER: NTR NL8488.

Should all hip and knee prosthetic joints be aspirated prior to revision surgery?

AIMS: It is essential to exclude a periprosthetic joint infection (PJI) prior to revision surgery. It is recommended to routinely aspirate the joint before surgery. However, this may not be necessary in a subgroup of patients. The aim of our study was to investigate if specific clinical and implant characteristics could be identified to rule out a PJI prior to revision surgery. METHODS: We retrospectively evaluated clinical and implant characteristics of patients who underwent a hip or knee revision surgery between October 2015 and October 2018. Patients were diagnosed with a PJI according to the MSIS diagnostic criteria. RESULTS: A total of 156 patients were analyzed, including 107 implants that were revised because of prosthetic loosening and 49 because of mechanical failure (i.e. instability, malalignment or malpositioning). No PJI was diagnosed in the group with mechanical failure. In the prosthetic loosening group, 20 of 107 were diagnosed with a PJI (19%). Although there was a significantly lower chance of having a PJI with an implant age of > 5 years combined with a CRP < 5 mg/L, an infection was still present in 3 out of 39 cases (8%). CONCLUSION: Implants with solely mechanical failure without signs of loosening and low inflammatory parameters probably do not require a synovial fluid aspiration. These results need to be confirmed in a larger cohort of patients. In case of prosthetic loosening, all joints need to be aspirated before surgery as no specific characteristic could be identified to rule out an infection.

Long-term results of the iBP elbow prosthesis: beware of destructive metallosis!

BACKGROUND: The aim of this study was to review the long-term results of the instrumented Bone Preserving (iBP) elbow prosthesis. METHODS: Thirty-one patients (10 M, 21F, 28-77 year) were retrospectively evaluated using the Oxford Elbow Score (OES), Disabilities of Arm, Shoulder and Hand Outcome Measure (DASH), Mayo Elbow Performance (MEPS), physical examination and standard radiographs. Kaplan-Meier survival analysis was used. RESULTS: Thirty-seven primary iBPs have been placed in 31 patients between 2000 and 2007. Six patients (8 prostheses) had died, 10 elbows had been revised and three patients (4 prostheses) were lost to follow-up. Fourteen patients (15 prostheses) were available for follow-up. The main indication for surgery was rheumatoid arthritis. Mean follow-up was 11 years (8-15). Kaplan-Meier survival analysis showed a survival of 81% at 10 years after surgery. Main reason for revision was particle disease and loosening due to instability and malalignment. Eleven of 14 patients were satisfied, although radiographs showed radiolucencies in 11 patients. CONCLUSION: The iBP elbow prosthesis gives a survival rate of 81% 10 years after surgery with a progressive decline beyond 10 years. However, many patients have radiolucencies. Discrepancy between clinical signs and radiological results warrants structural follow-up, to assure quality of bone stock in case revision surgery is indicated. The study was reviewed and approved by the Medical Ethical Committee of University Medical Center Groningen (METc2016/038). LEVEL OF EVIDENCE: Level IV, Case series.

Do CAS measurements correlate with EOS 3D alignment measurements in primary TKA?

PURPOSE: Objective of this study was to compare intraoperative computer-assisted surgery (CAS) alignment measurements during total knee arthroplasty (TKA) with pre- and postoperative coronal alignment measurements using EOS 3D reconstructions. METHODS: In a prospective study, 56 TKAs using imageless CAS were performed and coronal alignment measurements were recorded twice: before bone cuts were made and after implantation of the prosthesis. Pre- and postoperative coronal alignment measurements were performed using EOS 3D reconstructions. Thanks to the EOS radiostereography system, measurement errors due to malpositioning and deformity during acquisition are eliminated. CAS measurements were compared with EOS 3D reconstructions. Varus/valgus angle (VV), mechanical lateral distal femoral angle (mLDFA) and mechanical medial proximal tibial angle (mMPTA) were measured. RESULTS: Significantly different VV angles were measured pre- and postoperatively with CAS compared to EOS. For preoperative measurements, mLDFA did not differ significantly, but a significantly larger mMPTA in valgus was measured with CAS. CONCLUSION: Results of this study indicate that differences in alignment measurements between CAS measurements and pre- and postoperative EOS 3D are due mainly to the difference between weight-bearing and non-weight-bearing position and potential errors in validity and reliability of the CAS system. EOS 3D measurements overestimate VV angle in lower limbs with substantial mechanical axis deviation. For lower limbs with minor mechanical axis deviation as well as for mMPTA measurements, CAS measures more valgus than EOS. Eventually the results of this study are of clinical relevance, since it raises concerns regarding the validity and reliability of CAS systems in TKA. LEVEL OF EVIDENCE: IIb.

Tibial component with and without stem extension in a trabecular metal cone construct.

PURPOSE: The purpose of this study was to investigate stability and strain distribution of a tibial plateau reconstruction with a trabecular metal cone while the tibial component is implanted with and without a stem, and whether prosthetic stability was influenced by bone mineral density. Trabecular metal cones are designed to fill up major bone defects in total knee arthroplasty. Tibial components can be implanted in combination with a stem, but it is unclear whether this is necessary after reconstruction with a trabecular metal cone. Implanting a stem can give extra stability, but may have negative side effects. METHODS: Tibial revision arthroplasties with trabecular metal cones were performed after reconstruction of a 2B bone defect according to the Anderson Orthopedic Research Institute classification. Components were implanted in seven pairs of cadaveric tibiae; one tibia of each pair was implanted with stem and the other without. All specimens were loaded to one bodyweight alternating between the medial and lateral tibial component. Implant-bone micro-motions, bone strains, bone mineral density and correlations were measured and/or calculated. RESULTS: Tibial components without a stem showed only more varus tilt [difference in median 0.14° (P < 0.05)], but this was not considered clinically relevant. Strain distribution did not differ. Bone mineral density only had an effect on the anterior/posterior tilt [ρ: -0.72 (P < 0.01)]. CONCLUSION: Tibial components, with or without a stem, which are implanted after reconstruction of major bone defects using trabecular metal cones produce very similar biomechanical conditions in terms of stability and strain distribution. If in vivo studies confirm that a stem extension is not mandatory, orthopaedic surgeons can decide not to implant a stem. LEVEL OF EVIDENCE: II.

The Validity of a New Low-Dose Stereoradiography System to Perform 2D and 3D Knee Prosthetic Alignment Measurements.

INTRODUCTION: The EOS stereoradiography system has shown to provide reliable varus/valgus (VV) measurements of the lower limb in 2D (VV2D) and 3D (VV3D) after total knee arthroplasty (TKA). Validity of these measurements has not been investigated yet, therefore the purpose of this study was to determine validity of EOS VV2D and VV3D. METHODS: EOS images were made of a lower limb phantom containing a knee prosthesis, while varying VV angle from 15° varus to 15° valgus and flexion angle from 0° to 20°, and changing rotation from 20° internal to 20° external rotation. Differences between the actual VV position of the lower limb phantom and its position as measured on EOS 2D and 3D images were investigated. RESULTS: Rotation, flexion or VV angle alone had no major impact on VV2D or VV3D. Combination of VV angle and rotation with full extension did not show major differences in VV2D measurements either. Combination of flexion and rotation with a neutral VV angle showed variation of up to 7.4° for VV2D; maximum variation for VV3D was only 1.5°. A combination of the three variables showed an even greater distortion of VV2D, while VV3D stayed relatively constant. Maximum measurement difference between preset VV angle and VV2D was 9.8°, while the difference with VV3D was only 1.9°. The largest differences between the preset VV angle and VV2D were found when installing the leg in extreme angles, for example 15° valgus, 20° flexion and 20° internal rotation. CONCLUSIONS: After TKA, EOS VV3D were more valid than VV2D, indicating that 3D measurements compensate for malpositioning during acquisition. Caution is warranted when measuring VV angle on a conventional radiograph of a knee with a flexion contracture, varus or valgus angle and/or rotation of the knee joint during acquisition.

Assessment of prosthesis alignment after revision total knee arthroplasty using EOS 2D and 3D imaging: a reliability study.

INTRODUCTION: A new low-dose X-ray device, called EOS, has been introduced for determining lower-limb alignment in 2D and 3D. Reliability has not yet been assessed when using EOS on lower limbs containing a knee prosthesis. Therefore purpose of this study was to determine intraobserver and interobserver reliability of EOS 2D and 3D knee prosthesis alignment measurements after revision total knee arthroplasty (rTKA). METHODS: Forty anteroposterior and lateral images of 37 rTKA patients were included. Two observers independently performed measurements on these images twice. Varus/valgus angles were measured in 2D (VV2D) and 3D (VV3D). Intraclass correlation coefficients and the Bland and Altman method were used to determine reliability. T-tests were used to test potential differences. RESULTS: Intraobserver and interobserver reliability were excellent for VV2D and VV3D. No significant difference or bias between the first and second measurements or the two observers was found. A significant mean and absolute difference of respectively 1.00° and 1.61° existed between 2D and 3D measurements. CONCLUSIONS: EOS provides reliable varus/valgus measurements in 2D and 3D for the alignment of the knee joint with a knee prosthesis. However, significant differences exist between varus/valgus measurements in 2D and 3D.

Does imageless computer-assisted TKA lead to improved rotational alignment or fewer outliers? A systematic review.

BACKGROUND: Computer-assisted surgery (CAS) has been developed to enhance prosthetic alignment during primary TKAs. Imageless CAS improves coronal and sagittal alignment compared with conventional TKA. However, the effect of imageless CAS on rotational alignment remains unclear. QUESTIONS/PURPOSES: We conducted a systematic and qualitative review of the current literature regarding the effectiveness of imageless CAS during TKA on (1) rotational alignment of the femoral and tibial components and tibiofemoral mismatch in terms of deviation from neutral rotation, and (2) the number of femoral and tibial rotational outliers. METHODS: Data sources included PubMed, MEDLINE, and EMBASE. Study selection, data extraction, and methodologic quality assessment were conducted independently by two reviewers. Standardized mean difference with 95% CI was calculated for continuous variables (rotational alignment of the femoral or tibial component and tibiofemoral mismatch). To compare the number of outliers for femoral and tibial component rotation, the odds ratio and 95% CI were calculated. The literature search produced 657 potentially relevant studies, 17 of which met the inclusion criteria. One study was considered as having high methodologic quality, 15 studies had medium, and one study had low quality. RESULTS: Conflicting evidence was found for all outcome measures except for tibiofemoral mismatch. Moderate evidence was found that imageless CAS had no influence on postoperative tibiofemoral mismatch. The measurement protocol for measuring tibial rotation varied among the studies and in only one of the studies was the sample size calculation based on one of the outcome measures used in our systematic review. CONCLUSIONS: More studies of high methodologic quality and with a sample size calculation based on the outcome measures will be helpful to assess whether an imageless CAS TKA improves femoral and tibial rotational alignment and tibiofemoral mismatch or decreases the number of femoral and tibial rotational outliers. To statistically analyze the results of different studies, the same measurement protocol should be used among the studies.

The influence of computer-assisted surgery on rotational, coronal and sagittal alignment in revision total knee arthroplasty.

BACKGROUND: Despite good results of primary total knee arthroplasty (TKA), the number of revision total knee arthroplasties (rTKAs) is rising. Proper implant position is essential, since malposition leads to worse clinical outcome. In rTKA most anatomical landmarks have disappeared because of extensive bone loss, making it more difficult to adequately implant the knee prosthesis. In primary TKA, computer-assisted surgery (CAS) leads to better prosthetic alignment than mechanical navigation guides. Literature about the use of CAS in rTKA is scarce though, and the effect on rotational prosthetic alignment has not been investigated yet. Hence the primary objective of this study is to compare rotational prosthetic alignment when using CAS in rTKA compared to a mechanical navigation guide. Secondary objectives are to compare prosthetic alignment in the coronal and sagittal planes. It is hypothesized that CAS leads to better rotational, coronal and sagittal prosthetic alignment when used during rTKA. METHODS/DESIGN: A prospective clinical intervention study with use of a historical control group will be conducted. Forty-four patients with a minimum age of 18 to be admitted for CAS-rTKA between September 2012 and September 2015 will be included in the intervention group. Forty-four patients with a minimum age of 18 who underwent rTKA with the use of a mechanical navigation guide between January 2002 and April 2012 will form the historical control group. Both groups will be matched according to gender and type of revision prosthesis. Rotational prosthesis alignment will be evaluated using a CT-scan of the knee joint. DISCUSSION: Proper implant position is essential, since malposition leads to worse clinical outcome. Several studies show a significantly positive influence of CAS on prosthetic alignment in primary TKA, but literature about the use of CAS in rTKA is limited. The purpose of this study is thus to investigate the influence of CAS during rTKA on postoperative prosthetic alignment, compared to mechanical navigation guides. TRIAL REGISTRATION: Netherlands National Trial Register NTR3512.

Poorer survival after a primary implant during revision total knee arthroplasty.

PURPOSE: Revision total knee arthroplasty (rTKA) is a complex procedure. Depending on the degree of ligament and bone damage, either primary or revision implants are used. The purpose of this study was to compare survival rates of primary implants with revision implants when used during rTKA. METHODS: A retrospective comparative study was conducted between 1998 and 2009 during which 69 rTKAs were performed on 65 patients. Most common indications for revision were infection (30%), aseptic loosening (25%) and wear/osteolysis (25%). During rTKA, a primary implant was used in nine knees and a revision implant in 60. RESULTS: Survival of primary implants was 100% at one year, 73% [95% confidence interval (CI) 41-100] at two years and 44% (95% CI 7-81) at five years. Survival of revision implants was 95% (95% CI 89-100) at one year, 92% (95% CI 84-99) at two years and 92% (95% CI 84-99) at five years. Primary implants had a significantly worse survival rate than revision implants when implanted during rTKA [P = 0.039 (hazard ratio = 4.56, 95% CI 1.08-19.27)]. CONCLUSIONS: Based on these results, it has to be considered whether primary implants are even an option during rTKA.