Robotic Arthroplasty Clinical and cost Effectiveness Randomised controlled trial (RACER-knee): a study protocol.

INTRODUCTION: Robotic-assisted knee replacement systems have been introduced to healthcare services worldwide in an effort to improve clinical outcomes for people, although high-quality evidence that they are clinically, or cost-effective remains sparse. Robotic-arm systems may improve surgical accuracy and could contribute to reduced pain, improved function and lower overall cost of total knee replacement (TKR) surgery. However, TKR with conventional instruments may be just as effective and may be quicker and cheaper. There is a need for a robust evaluation of this technology, including cost-effectiveness analyses using both within-trial and modelling approaches. This trial will compare robotic-assisted against conventional TKR to provide high-quality evidence on whether robotic-assisted knee replacement is beneficial to patients and cost-effective for healthcare systems. METHODS AND ANALYSIS: The Robotic Arthroplasty Clinical and cost Effectiveness Randomised controlled trial-Knee is a multicentre, participant-assessor blinded, randomised controlled trial to evaluate the clinical and cost-effectiveness of robotic-assisted TKR compared with TKR using conventional instruments. A total of 332 participants will be randomised (1:1) to provide 90% power for a 12-point difference in the primary outcome measure; the Forgotten Joint Score at 12 months postrandomisation. Allocation concealment will be achieved using computer-based randomisation performed on the day of surgery and methods for blinding will include sham incisions for marker clusters and blinded operation notes. The primary analysis will adhere to the intention-to-treat principle. Results will be reported in line with the Consolidated Standards of Reporting Trials statement. A parallel study will collect data on the learning effects associated with robotic-arm systems. ETHICS AND DISSEMINATION: The trial has been approved by an ethics committee for patient participation (East Midlands-Nottingham 2 Research Ethics Committee, 29 July 2020. NRES number: 20/EM/0159). All results from the study will be disseminated using peer-reviewed publications, presentations at international conferences, lay summaries and social media as appropriate. TRIAL REGISTRATION NUMBER: ISRCTN27624068.

Robotic Assisted Patellofemoral Joint Replacement: Surgical Technique, Tips and Tricks.

In this article we wish to provide MAKO robotic knee users a surgical guide including tips and tricks on performing MAKO robotic-assisted patellofemoral joint replacements. The senior authors in this paper from the Exeter Knee Reconstruction Unit, United Kingdom are highly experienced MAKO users who have been performing MAKO assisted Patellofemoral joint replacements since 2017.

Use of computerised adaptive testing to reduce the number of items in patient-reported hip and knee outcome scores: an analysis of the NHS England National Patient-Reported Outcome Measures programme.

OBJECTIVE: Over 160 000 participants per year complete the 12-item Oxford Hip and Knee Scores (OHS/OKS) as part of the NHS England Patient-Reported Outcome Measures (PROMs) programme. We used a modern computational approach, known as computerised adaptive testing (CAT), to simulate individually tailored OHS and OKS assessment, with the goal of reducing the number of questions a patient must complete without compromising measurement accuracy. METHODS: We fit the 2018/2019 PROMs data to an item response theory (IRT) model. We assessed IRT model assumptions alongside reliability. We used parameters from the IRT model with data from 2017/2018 to simulate CAT assessments. Two simulations were run until a prespecified SE of measurement was met (SE=0.32 and SE=0.45). We compared the number of questions required to meet each cut-off and assessed the correlation between the full-length and CAT administration. RESULTS: We conducted IRT analysis using 40 432 OHS and 44 714 OKS observations. The OHS and OKS were both unidimensional (root mean square error of approximation 0.08 and 0.07, respectively) and marginal reliability 0.91 and 0.90. The CAT, with a precision limit of SE=0.32 and SE=0.45, required a median of four items (IQR 1) and two items (IQR 1), respectively, for the OHS, and median of four items (IQR 2) and two items (IQR 0) for the OKS. This represents a potential 82% reduction in PROM length. In the context of 160 000 yearly assessments, these methodologies could result in the omission of some 1 280 000 redundant questions per year, which equates to 40 000 hours of patient time. CONCLUSION: The application of IRT to the OHS and OKS produces an efficient and substantially reduced CAT. We have demonstrated a path to reduce the burden and potentially increase the compliance for these ubiquitous outcome measures without compromising measurement accuracy.

The biomechanics of metaphyseal cone augmentation in revision knee replacement.

The demand for revision knee replacement (RKR) has increased dramatically with rising patient life expectancy and younger recipients for primary TKR. However, significant challenges to RKR arise from osseous defects, reduced bone quality, potential bone volume loss from implant removal and the need to achieve implant stability. This study utilizes the outcomes of an ongoing RKR clinical trial using porous metaphyseal cones 3D-printed of titanium, to investigate 1) bone mineral density (BMD) changes in three fixation zones (epiphysis, metaphysis, and diaphysis) over a year and 2) the biomechanical effects of the cones at 6 months post-surgery. It combines dual-energy x-ray absorptiometry (DXA), computed tomography (CT) with patient-specific based finite element (FE) modelling. Bone loss (-0.086 ± 0.05 g/cm2) was found in most patients over the first year. The biomechanical assessment considered four different loading scenarios from standing, walking on a flat surface, and walking downstairs, to a simulated impact of the knee. The patient-specific FE models showed that the cones marginally improved the strain distribution in the bone and shared the induced load but played a limited role in reducing the risks of bone fracture or cement debonding. This technique of obtaining real live data from a randomized clinical trial and inserting it into an in-silico FE model is unique and innovative in RKR research. The tibia RKR biomechanics examined open up further possibilities, allowing the in-silico testing of prototypes and implant combinations without putting patients at risk as per the recommended IDEAL framework standards. This process with further improvements could allow rapid innovation, optimization of implant design, and improve surgical planning.

What is the patient experience following revision knee replacement: A systematic review and meta-analysis of the medium term patient reported outcomes.

AIMS: Revision knee replacement is an increasingly common procedure, however, information on patient-focused outcomes is limited. This systematic review and meta-analysis aimed to investigate the medium-term patient reported outcomes following a revision knee replacement. METHODS: We performed a systematic review of MEDLINE and EMBASE (from inception to 1st March 2021) for articles reporting five year or greater patient reported outcome measures (PROMs) following revision knee replacement. A meta-analysis of PROMs data was undertaken using the Standardised Mean Difference (SMD). Quality of methodology was assessed using Wylde's non-summative four-point system. The study was registered with PROPSERO (CRD42021199289). RESULTS: A total of 23 studies met the inclusion criteria containing 2414 patients at a mean minimum follow-up of 74 months (60-122). The reporting of PROMs were poorly standardised with several PROMs being used. The most commonly reported patient reported outcome was the Knee Society Score reported in 65% of studies (15/23). A meta-analysis of 629 eligible patients undergoing revision knee replacement revealed a significant improvement in pre-operative state with a SMD 2·05 95% CI 0.87, 3.23. CONCLUSION: This systematic review has found a significant and sustained improvement in patient-reported outcomes following a revision knee arthroplasty beyond five years. We found a variation in the usage and administration of PROMs which hinders a clear synthesis of results. Furthermore, the PROMs have not been robustly tested for validity in the context of a revision knee replacement.

Robotic-Assisted Patellofemoral Replacement-Correlation of Preoperative Planning with Intraoperative Implant Position and Early Clinical Experience: A Minimum 2-Year Follow-up.

Patello-femoral arthroplasty (PFA) is successful in a selected group of patients and yields a good functional outcome. Robotic-assisted knee arthroplasty has been shown to provide better implant positioning and alignment. We aim to report our early outcomes and to compare Mako's (Robotic Arm Interactive Orthopaedic System [RIO]) preoperative implant planning position to our intraoperative PFA implant position. Data for this study was prospectively collected for 23 (two bilateral) patients who underwent robotic-assisted PFA between April 2017 and May 2018. All preoperative implant position planning and postoperative actual implant position were recorded. Presence of trochlear dysplasia and functional outcome scores were also collected. There were 17 (two bilateral) female and 6 male patients with a mean age of 66.5 (range: 41-89) years. The mean follow-up period was 30 (range: 24-37) months. Eighteen knees (72%) had evidence of trochlear dysplasia. The anterior trochlear line was on average, 7.71 (range: 3.3-11.3) degrees, internally rotated to the surgical transepicondylar axis and on average 2.9 (range: 0.2-6.5) degrees internally rotated to the posterior condylar line. The preoperative planning range was 4-degree internal to 4-degree external rotation, 4-degree varus to 6-degree valgus, and 7-degree flexion to 3-degree extension. The average difference between preoperative planning and intraoperative implant position was 0.43 degrees for rotation (r = 0.93), 0.99 degrees for varus/valgus (r = 0.29), 1.26 degrees for flexion/extension (r = 0.83), and 0.34 mm for proudness (r = 0.80). Six patients (24%) had a different size component from their preoperative plan (r = 0.98). The mean preoperative Oxford Knee Score (OKS) was 16 and the mean postoperative OKS was 42. No patient had implant-related revision surgery or any radiological evidence of implant loosening at final follow-up. Our early results of robotic PFA are promising. Preoperative Mako planning correlates closely with intraoperative implant positioning. Longer follow-up is needed to assess long-term patient outcomes and implant survivorship.

Prosthetic joint infection of the knee - arthroscopic biopsy identifies more and different organisms than aspiration alone.

BACKGROUND: Prosthetic joint infection (PJI) causes significant morbidity and mortality following knee replacement surgery. Identifying causative organisms and antibiotic sensitivities is critical in increasing the chance of infection eradication. This study investigated whether biopsy alone was superior to aspiration alone for serological diagnosis in PJI following knee replacement. Secondly, we investigated whether biopsy identifies the same or new/different microbiological flora as aspiration. METHODS: Since December 2014, the Exeter Knee Reconstruction Unit (EKRU) has prospectively collated data regarding all PJIs referred from our local/regional network which have been reviewed via our Multi-Disciplinary Team (MDT). We identified and included consecutive patients from this MDT from Dec.2014-Mar.2020 and analysed their electronic records. Statistical analysis was performed using Stata. RESULTS: 65/100 patients studied had both pre-operative aspiration and biopsy. 31/65 (48%) had positive aspiration and biopsies. No aspirate samples were positive with corresponding biopsies negative. In 19/65 (29%) of infection positive patients, biopsy identified new (7) or additional (12) organisms not identified by aspiration. Aspiration had a sensitivity of 70%, specificity of 88%, positive predictive value of 90.3% and negative predictive value of 64.7%. Biopsy had a sensitivity of 97.5%, specificity of 88%, positive predictive value of 92.9% and negative predictive value of 95.7%. CONCLUSION: In 29% of confirmed PJI cases, arthroscopic biopsy identified either additional organisms in a polymicrobial PJI when compared to aspiration, or new positive results when aspiration alone was negative. This study demonstrates the benefits of arthroscopic biopsy for serological diagnosis in cases of knee PJI and aids treatment planning.

Personalised high tibial osteotomy has mechanical safety equivalent to generic device in a case-control in silico clinical trial.

Background: Despite favourable outcomes relatively few surgeons offer high tibial osteotomy (HTO) as a treatment option for early knee osteoarthritis, mainly due to the difficulty of achieving planned correction and reported soft tissue irritation around the plate used to stablise the osteotomy. To compare the mechanical safety of a new personalised 3D printed high tibial osteotomy (HTO) device, created to overcome these issues, with an existing generic device, a case-control in silico virtual clinical trial was conducted. Methods: Twenty-eight knee osteoarthritis patients underwent computed tomography (CT) scanning to create a virtual cohort; the cohort was duplicated to form two arms, Generic and Personalised, on which virtual HTO was performed. Finite element analysis was performed to calculate the stresses in the plates arising from simulated physiological activities at three healing stages. The odds ratio indicative of the relative risk of fatigue failure of the HTO plates between the personalised and generic arms was obtained from a multi-level logistic model. Results: Here we show, at 12 weeks post-surgery, the odds ratio indicative of the relative risk of fatigue failure was 0.14 (95%CI 0.01 to 2.73, p = 0.20). Conclusions: This novel (to the best of our knowledge) in silico trial, comparing the mechanical safety of a new personalised 3D printed high tibial osteotomy device with an existing generic device, shows that there is no increased risk of failure for the new personalised design compared to the existing generic commonly used device. Personalised high tibial osteotomy can overcome the main technical barriers for this type of surgery, our findings support the case for using this technology for treating early knee osteoarthritis.

Personalised high tibial osteotomy has mechanical safety equivalent to generic device in a case-control in silico clinical trial.

BACKGROUND: Despite favourable outcomes relatively few surgeons offer high tibial osteotomy (HTO) as a treatment option for early knee osteoarthritis, mainly due to the difficulty of achieving planned correction and reported soft tissue irritation around the plate used to stablise the osteotomy. To compare the mechanical safety of a new personalised 3D printed high tibial osteotomy (HTO) device, created to overcome these issues, with an existing generic device, a case-control in silico virtual clinical trial was conducted. METHODS: Twenty-eight knee osteoarthritis patients underwent computed tomography (CT) scanning to create a virtual cohort; the cohort was duplicated to form two arms, Generic and Personalised, on which virtual HTO was performed. Finite element analysis was performed to calculate the stresses in the plates arising from simulated physiological activities at three healing stages. The odds ratio indicative of the relative risk of fatigue failure of the HTO plates between the personalised and generic arms was obtained from a multi-level logistic model. RESULTS: Here we show, at 12 weeks post-surgery, the odds ratio indicative of the relative risk of fatigue failure was 0.14 (95%CI 0.01 to 2.73, p = 0.20). CONCLUSIONS: This novel (to the best of our knowledge) in silico trial, comparing the mechanical safety of a new personalised 3D printed high tibial osteotomy device with an existing generic device, shows that there is no increased risk of failure for the new personalised design compared to the existing generic commonly used device. Personalised high tibial osteotomy can overcome the main technical barriers for this type of surgery, our findings support the case for using this technology for treating early knee osteoarthritis.

Surgical treatment to realign the knee, called a high tibial osteotomy, is effective at relieving symptoms of knee osteoarthritis but the operation is difficult. A new personalised treatment with simpler surgery has been designed. The aim of this study was to investigate the safety of the new personalised treatment compared to the standard treatment. For the first time, a detailed computer simulation clinical trial was performed, using imaging data from 28 real patients. The computer simulation compared the risk of the implant failure between the personalised and standard treatments. The personalised treatment did not have a higher risk of implant failure than standard treatment. This supports further clinical studies looking at the benefits of personalised over standard realignment surgery. The personalised treatment has the potential to allow much more widespread use of realignment surgery to treat early knee osteoarthritis.

A Randomised Controlled Trial of Local Infiltration Analgesia Versus Femoral Nerve Block for Postoperative Analgesia Following Total Knee Arthroplasty.

Background Total knee replacement is often associated with significant postoperative pain. Although the use of a femoral nerve block is well-established, local infiltration analgesia has gained popularity in recent years. We compared single-shot local infiltration analgesia with a single-shot femoral nerve block for patients undergoing primary total knee arthroplasty. Methods A total of 194 patients were randomised to receive either local infiltration analgesia (150 ml bupivacaine 0.067% with adrenaline) or a femoral nerve block (20 ml 0.375% levobupivacaine). Both groups received spinal anaesthesia. The primary outcome measure was the total morphine consumption. Secondary outcome measures included: post-operative pain scores, rehabilitation goals, readiness for discharge, and physical, mental, and functional outcomes, including the Oxford Knee Score (OKS). Results A total of 69 patients in the local infiltration analgesia group and 79 patients in the femoral nerve block group were analysed. Median total morphine consumption was significantly greater in the local infiltration analgesia group as compared to the femoral nerve block group (54.67 mg vs 45 mg, respectively, p=0.0388). The post-operative OKS at six weeks was slightly more improved for the femoral nerve block group than for local infiltration analgesia (12.5 vs 9 point median improvements for the femoral nerve block and local infiltration analgesia groups, respectively, p=0.0261). There were no statistically significant differences in other secondary outcome measures. Conclusion A single-shot femoral nerve block significantly reduces the opioid requirement for primary total knee arthroplasty but is otherwise comparable to single-shot local infiltration analgesia.

Top ten research priorities for problematic knee arthroplasty.

AIMS: The James Lind Alliance aims to bring patients, carers, and clinicians together to identify uncertainties regarding care. A Priority Setting Partnership was established by the British Association for Surgery of the Knee in conjunction with the James Lind Alliance to identify research priorities related to the assessment, management, and rehabilitation of patients with persistent symptoms after knee arthroplasty. METHODS: The project was conducted using the James Lind Alliance protocol. A steering group was convened including patients, surgeons, anaesthetists, nurses, physiotherapists, and researchers. Partner organizations were recruited. A survey was conducted on a national scale through which patients, carers, and healthcare professionals submitted key unanswered questions relating to problematic knee arthroplasties. These were analyzed, aggregated, and synthesized into summary questions and the relevant evidence was checked. After confirming that these were not answered in the current literature, 32 questions were taken forward to an interim prioritization survey. Data from this survey informed a shortlist taken to a final consensus meeting. RESULTS: A total of 769 questions were received during the initial survey with national reach across the UK. These were refined into 32 unique questions by an independent information specialist. The interim prioritization survey was completed by 201 respondents and 25 questions were taken to a final consensus group meeting between patients, carers, and healthcare professionals. Consensus was reached for ranking the top ten questions for publication and dissemination. CONCLUSIONS: The top ten research priorities focused on pain, infection, stiffness, health service configuration, surgical and non-surgical management strategies, and outcome measures. This list will guide funders and help focus research efforts within the knee arthroplasty community. Cite this article: Bone Joint J 2020;102-B(9):1176-1182.

The Exeter Knee Infection Multi Disciplinary Team approach to managing prosthetic knee infections: A qualitative analysis.

BACKGROUND: A Knee Infection Multi-Disciplinary Team meeting was established in Exeter. This study was designed to qualitatively evaluate the impact of the MDT on those involved. MATERIALS AND METHODS: Semi-structured interviews of all members of the MDT at Exeter were undertaken and analysed using Nvivo software. Data was coded to identify common patterns and trends. RESULTS: The common themes identified were improved communication and standardisation of care. The main challenges identified were the timing of the meetings and funding. CONCLUSION: This study has used established qualitative techniques to evaluate the impact of the Exeter Knee Infection MDT.

Urgent Arthroplasty Interventions During the COVID-19 Pandemic: Operating Risks in Low-Prevalence Areas.

Background and objective Orthopaedic services have reorganised their delivery of care in response to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. In this study, we aimed to share our operating experience during the coronavirus disease 2019 (COVID-19) pandemic and analyse its effect on urgent hip and knee arthroplasty. Our study involved a comparative analysis between a cohort of patients from 2019 (pre-COVID) and another from 2020. Methods Tha data relating to patients undergoing urgent operations requiring arthroplasty interventions such as for infection, periprosthetic fracture (PPF) and neck of femur fracture (NOF) between April and July of 2020 and 2019 were reviewed prospectively and retrospectively. Patients were categorised according to the Royal College of Surgeons (RCS) case prioritisation and the COVID-19 risk assessment. Data were collected on 30-day mortality, readmissions, reoperations, complications, length of hospital stay and theatre efficiency. This was analysed, matched and compared. Statistical analysis was performed on categorical variables including the time to the theatre as well as dual consultant operating. Results A total of 46 consecutive patients were included in the 2020 cohort with a mean age of 78 years (range: 58-108 years). The median length of stay was 6.5 days (range: 3-35 days) and the median time to theatre for NOF patients was 23.8 hours (range: 16.2-87.7 hours). There were six complications and two deaths; one of the deaths was COVID-19-related. A total of 56 patients were included from 2019 with a mean age of 74.6 years (range: 45-88 years). The median length of stay was five days (range: 1-18 days) and the median time to theatre for NOF patients was 40.8 hours (range: 18.9-167 hours). There were four complications and one death. Conclusion Based on our findings, it is safe to perform complex surgery in a region of low community prevalence of COVID-19, and the outcomes were comparable to those from a pre-COVID-19 cohort.

Plasma Viscosity Has a Role in the Diagnosis of Prosthetic Joint Infection After Total Knee Arthroplasty.

BACKGROUND: The diagnosis of prosthetic joint infection (PJI) is challenging because no single test has consistently demonstrated an adequate discriminative potential. The combination of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) with adequate thresholds is well established. This study sought to investigate the role of plasma viscosity (PV) in the diagnosis of PJI following painful total knee arthroplasty. METHODS: The medical notes, and hematological and microbiology results of 310 patients who underwent revision for a painful total knee arthroplasty were evaluated. Infection was confirmed using Musculoskeletal Infection Society criteria in 102 patients (32.9%), whereas 208 patients (67.1%) were classified as noninfected. Serum investigations including ESR, CRP, and PV were analyzed using receiver observer curves and optimal cutoff points identified. RESULTS: There was a strong correlation between PV and both ESR and CRP. The area under curve was 0.814 for PV and 0.812 for ESR. Statistical analysis showed noninferiority of PV as compared to ESR in diagnosing PJI. A PV value of ≥ 1.81 mPa.s. had the best efficiency of 82.1%. Combining a CRP ≥ 13.5 mg/L with a PV ≥ 1.81 mPa.s. in a serial test approach yielded the highest specificity of 97.9% and positive likelihood ratio of 22.8. Sensitivity was 47.9% and a negative likelihood ratio of 0.53. CONCLUSION: PV is noninferior to ESR in diagnosing PJI. Its use is justified in clinical practice. It is cheaper, quicker, more efficient, and not influenced by hematocrit levels or medication. In this cohort, a PV value ≥ 1.81 mPa.s. would be an adequate cutoff to diagnose PJI in combination with CRP ≥ 13.5 mg/L.

Ten-year results for a single-surgeon series of Scorpio non-restrictive geometry (NRG) posterior stabilised (PS) total knee replacement.

BACKGROUND: To report the long-term results for a single-surgeon consecutive series of Scorpio non-restrictive geometry (NRG) posterior stabilised (PS) total knee replacement (TKR). MATERIALS AND METHODS: Forty-six consecutive patients who underwent 53 Scorpio NRG PS were identified. Change in range of motion (ROM) and Oxford Knee Score (OKS) over time were recorded. Radiographs were evaluated for alignment and radiolucent lines. Survival analysis for the prosthesis was calculated. RESULTS: At a mean of 10.1 years (range 9.1-10.9) following exclusions thirty-seven (69.8%) knees in thirty-one (67.4%) patients (6 bilateral) were available for review. None of the patients required revision surgery. Mean OKS score at 10 years was 37.8. The mean ROM significantly improved from 95° pre-operative to 117.5° at 5 years and 115° at 10 years (p = < 0.001). This equates to a value-added range of motion (VAROM) of 19° at 5 years and 15.6° at 10 years. There was a correlation between OKS and VAROM at 5 and 10 years. Radiological assessment did not reveal any evidence of progressive cement radiolucent lines nor component migration. CONCLUSION: In this series the Scorpio NRG PS showed 100% 10-year survivorship. We found a significant improvement in ROM and VAROM over time. This was not associated with increased signs of loosening.

Three-phase Technetium-99m bone scanning in patients with pain in the knee region after cemented total knee arthroplasty.

INTRODUCTION: Our aim was to question the usefulness of a three-phase bone scan in the evaluation of pain in the knee region after TKR. Our hypothesis was that an abnormal investigation had a poor association with the presence of infection or loosening, and did not provide any additional diagnostic information above that already available through other standard investigations. METHODS: A retrospective study over a 24-month period was performed comprising 118 patients investigated with a TPBS. Investigations were summarised and analysed, and were classified as entirely normal, possibly abnormal, and definitely abnormal. RESULTS: Thirty-three per cent (39/118) of TPBSs were reported as being entirely normal, 59% (69/118) as possibly abnormal, and 8% (10/118) as definitely abnormal. During the 24-month study period, 131 revision TKR procedures were performed at our institution; 9% (12/131) were investigated with TPBS and 91% (119/131) were not. No patient with an entirely normal pre-operative TPBS underwent revision TKR surgery. Eighty-five per cent (67/79) with an abnormal TPBS were managed conservatively. In our series, a TPBS had a positive predictive value of 2.53%, a negative predictive value of 100%, with an overall accuracy of 34.75% with 100% sensitivity (97.5% one-sided confidence interval 0-24.71%), and 33.62% specificity (95% confidence interval 53.29-72.37%), in the diagnosis of infection, or loosening with concurrent infection in determining the indication for revision surgery. CONCLUSION: A TPBS should only be considered following clinical evaluation, serological investigation, diagnostic imaging, and microbiological analysis of fluid obtained from arthrocentesis by a specialist revision arthroplasty surgeon. A TPBS may be useful in the situation where abnormal serology is present, but where repeated joint aspirations samples are inconclusive.

Three Cases of Femoral Stem Failure in Rotating Hinge Revision Total Knee Arthroplasty: Causes and Surgical Considerations.

Catastrophic failure of stemmed components in arthroplasty is an uncommon but a serious complication. Stem fractures and techniques for addressing these have been described following hip arthroplasty but much less so following total knee arthroplasty (TKA). We review three cases of catastrophic failure of the stem in rotating hinge revision TKA prostheses. We discuss the possible mechanism of failure and review the current literature addressing this topic. Metaphyseal support needs to be optimized in order to minimize load transfer to the stem and to the junction (and the risk of fracture) if a modular component is used. When constrained components are used, radiographs need to be carefully assessed for signs of proximal loosening. Nonmodular stems are also an option in this situation.