Unicondylar Knee Replacement Research Articles

Risk factors associated with revision for prosthetic joint infection following knee replacement: an observational cohort study from England and Wales

SummaryBackgroundProsthetic joint infection is a devastating complication of knee replacement. The risk of developing a prosthetic joint infection is affected by patient, surgical, and health-care system factors. Existing evidence is limited by heterogeneity in populations studied, short follow-up, inadequate power, and does not differentiate early prosthetic joint infection, most likely related to the intervention, from late infection, more likely to occur due to haematogenous bacterial spread. We aimed to assess the overall and time-specific associations of these factors with the risk of revision due to prosthetic joint infection following primary knee replacement.MethodsIn this cohort study, we analysed primary knee replacements done between 2003 and 2013 in England and Wales and the procedures subsequently revised for prosthetic joint infection between 2003 and 2014. Data were obtained from the National Joint Registry linked to the Hospital Episode Statistics data in England and the Patient Episode Database for Wales. Each primary replacement was followed for a minimum of 12 months until the end of the observation period (Dec 31, 2014) or until the date of revision for prosthetic joint infection, revision for another indication, or death (whichever occurred first). We analysed the data using Poisson and piecewise exponential multilevel models to assess the associations between patient, surgical, and health-care system factors and risk of revision for prosthetic joint infection.FindingsOf 679 010 primary knee replacements done between 2003 and 2013 in England and Wales, 3659 were subsequently revised for an indication of prosthetic joint infection between 2003 and 2014, after a median follow-up of 4·6 years (IQR 2·6–6·9). Male sex (rate ratio [RR] for male vs female patients 1·8 [95% CI 1·7–2·0]), younger age (RR for age ≥80 years vs <60 years 0·5 [0·4–0·6]), higher American Society of Anaesthesiologists [ASA] grade (RR for ASA grade 3–5 vs 1, 1·8 [1·6–2·1]), elevated body-mass index (BMI; RR for BMI ≥30 kg/m2vs <25 kg/m2 1·5 [1·3–1·6]), chronic pulmonary disease (RR 1·2 [1·1–1·3]), diabetes (RR 1·4 [1·2–1·5]), liver disease (RR 2·2 [1·6–2·9]), connective tissue and rheumatic diseases (RR 1·5 [1·3–1·7]), peripheral vascular disease (RR 1·4 [1·1–1·7]), surgery for trauma (RR 1·9 [1·4–2·6]), previous septic arthritis (RR 4·9 [2·7–7·6]) or inflammatory arthropathy (RR 1·4 [1·2–1·7]), operation under general anaesthesia (RR 1·1 [1·0–1·2]), requirement for tibial bone graft (RR 2·0 [1·3–2·7]), use of posterior stabilised fixed bearing prostheses (RR for posterior stabilised fixed bearing prostheses vs unconstrained fixed bearing prostheses 1·4 [1·3–1·5]) or constrained condylar prostheses (3·5 [2·5–4·7]) were associated with a higher risk of revision for prosthetic joint infection. However, uncemented total, patellofemoral, or unicondylar knee replacement (RR for uncemented vs cemented total knee replacement 0·7 [95% CI 0·6–0·8], RR for patellofemoral vs cemented total knee replacement 0·3 [0·2–0·5], and RR for unicondylar vs cemented total knee replacement 0·5 [0·5–0·6]) were associated with lower risk of revision for prosthetic joint infection. Most of these factors had time-specific effects, depending on the time period post-surgery.InterpretationWe have identified several risk factors for revision for prosthetic joint infection following knee replacement. Some of these factors are modifiable, and the use of targeted interventions or strategies could lead to a reduced risk of revision for prosthetic joint infection. Non-modifiable factors and the time-specific nature of the effects we have observed will allow clinicians to appropriately counsel patients preoperatively and tailor follow-up regimens.FundingNational Institute for Health Research.

Assessing the non-inferiority of prosthesis constructs used in total and unicondylar knee replacements using data from the National Joint Registry of England, Wales, Northern Ireland and the Isle of Man: a benchmarking study

ObjectivesTo investigate the relative performance of knee replacement constructs compared with the best performing construct and illustrate the substantial variability in performance.DesignA non-inferiority study.SettingEngland and Wales.ParticipantsAll primary total and unicondylar...

How long does a knee replacement last? A systematic review and meta-analysis of case series and national registry reports with more than 15 years of follow-up

SummaryBackgroundKnee replacements are the mainstay of treatment for end-stage osteoarthritis and are effective. Given time, all knee replacements will fail and knowing when this failure might happen is important. We aimed to establish how long a knee replacement lasts.MethodsIn this systematic review and meta-analysis, we searched MEDLINE and Embase for case series and cohort studies published from database inception until July 21, 2018. Articles reporting 15 year or greater survival of primary total knee replacement (TKR), unicondylar knee replacement (UKR), and patellofemoral replacements in patients with osteoarthritis were included. Articles that reviewed specifically complex primary surgeries or revisions were excluded. Survival and implant data were extracted, with all-cause survival of the knee replacement construct being the primary outcome. We also reviewed national joint replacement registry reports and extracted the data to be analysed separately. In the meta-analysis, we weighted each series and calculated a pooled survival estimate for each data source at 15 years, 20 years, and 25 years, using a fixed-effects model. This study is registered with PROSPERO, number CRD42018105188.FindingsFrom 4363 references found by our initial search, we identified 33 case series in 30 eligible articles, which reported all-cause survival for 6490 TKRs (26 case series) and 742 UKRs (seven case series). No case series reporting on patellofemoral replacements met our inclusion criteria, and no case series reported 25 year survival for TKR. The estimated 25 year survival for UKR (based on one case series) was 72·0% (95% CI 58·0–95·0). Registries contributed 299 291 TKRs (47 series) and 7714 UKRs (five series). The pooled registry 25 year survival of TKRs (14 registries) was 82·3% (95% CI 81·3–83·2) and of UKRs (four registries) was 69·8% (67·6–72·1).InterpretationOur pooled registry data, which we believe to be more accurate than the case series data, shows that approximately 82% of TKRs last 25 years and 70% of UKRs last 25 years. These findings will be of use to patients and health-care providers; further information is required to predict exactly how long specific knee replacements will last.FundingThe National Joint Registry for England, Wales, Northern Ireland, and Isle of Man and the Royal College of Surgeons of England.

Blood loss following medial unicondylar knee replacements without a tourniquet: is there a need to group and save?

&lt;p class="abstract"&gt;&lt;strong&gt;Background:&lt;/strong&gt; There are current trends towards not using a tourniquet in total knee replacement (TKR), but there is nothing published on what the effects of not using a tourniquet on unicondylar knee replacements (UKR) may be in terms of blood loss.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods:&lt;/strong&gt; A retrospective case series of 36 consecutive UKR from our institution were analysed. All procedures were carried out without a tourniquet and also utilised a standardised interventions protocol including withholding of anticoagulants and antiplatelet medications, administration of periarticular local anaesthetic and adrenaline injection, and both IV and topical tranexamic acid. Outcomes measured were estimated intra-operative blood loss, overall blood loss through comparison of pre and post-operative haemoglobin laboratory values, and the need for post-operative blood transfusion.&lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Results:&lt;/strong&gt; Most patients (61.1%) experienced an estimated intra-operative blood loss of less than100 mls. There was a mean haemoglobin drop of 16.1 g/l (range 1–26, SD ±5.9), with a mean post operatively haemoglobin level of 125.1 g/l (range 107-142, SD ±8.7). No patients required a blood transfusion.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Conclusions:&lt;/strong&gt; A low level of blood loss is encountered when UKR is undertaken without a tourniquet and with our standard interventions to reduce bleeding. The level of post-operative haemoglobin and absence of requirement for blood transfusion suggests that this operation can be undertaken without the need for a group and save. It is our hope that surgeons will be encouraged to perform this procedure without a tourniquet and benefit from the cost-saving opportunity of not performing a group and save.&lt;/p&gt;

A nature friendly knee arthroplasty for prayer and meditation in Asiatic lifestyle

Introduction: India is a country where many religions coexist together. Prayer & meditation form an integral part of Indian lifestyle. Also 90% of India’s population lives in the rural areas. Medial compartment osteoarthritis is the most common type of arthritis in India. Total knee replacement has longer rehabilitation time, morbidity and cost. In addition, it doesn’t allow squatting and sitting cross legged. With rise in unicondylar knee replacements for medial compartment osteoarthritis, patient’s satisfaction is much higher.Hypothesis of this paper was to investigate whether sitting cross-legged easily on floor for prayer and meditation, contributed to higher levels of patients satisfaction in unicondylar knee replacement significantly.Material & Methods: this retrospective study was done with study population of 36 patients of which, 33 knees of unicondylar knee replacement (mean age 61.7) and 25 knees of total knee replacement (mean age 63.5). We used modified Oxford knee score to compare the functional outcome and Likert scale for grading the patient’s satisfaction level. Results: study outcome after unicondylar knee replacement was extremely satisfactory for all patients measured with modified Oxford knee score and is better than total knee replacement. The mean Oxford score for 33 knees with unicondylar knee replacement is 47.18 and for 25 knees with total knee replacements is 46.35. But viewing by satisfaction index point of view, patients are highly satisfied with unicondylar knee replacement because of ability to squat and sit cross-legged used for praying and meditation and other social habits.

Dervan rim sign new, simple radiological sign for unique Indian medial femoral condylar osteoarthritis

Introduction: OA knee is most common form of arthritis in Asian population. The medial compartment of knee is most commonly involved. Most X-ray studies have been from the Western Caucasian patients with different genetic pool, habitus and lifestyle. The accepted norm for surgical intervention like unicondylar knee replacement or High Tibial Osteotomy is bone on bone Arthritis which has simultaneous affection of both medial Tibial & Femoral compartments. We however noted a different radiological pattern also causing severe pain on medial side of knee, without bone on bone arthritis. This was labeled DERVAN RIM SIGN.Materials and Method: This pilot Study describes a new radiological sign based on standard Anteroposterior Xray of knee joint, taken in standing weight bearing position with toes and patella pointing forwards in 15 degrees of flexion.The findings of this sign and correlation to selective medial condylar femoral cartilage loss in 25 patients are confirmed with1 MRI of knee joint 17 patients2 Arthroscopy of knee joint 3 patients3 Open Arthrotomy during Unicondylar knee Arthroplasty 5 patientsResults: 100 percent correlation is seen in all 25 cases between the Dervan RIM sign & Eburnation and loss of Medial femoral cartilage in the three modalities of visual confirmation viz MRI, Arthroscopy or Visual examination in open surgery. Mild involvement of the Tibial condyle was noted in all cases and this was the cause of absence of bone on bone Arthritis.

Increase in the Tibial Slope in Unicondylar Knee Replacement: Analysis of the Effect on the Kinematics and Ligaments in a Weight-Bearing Finite Element Model.

Introduction Unicompartmental arthroplasty (UKA) of the knee in patients with isolated medial osteoarthritis yields adequate results; however, the survival rate is inferior to that of total knee arthroplasty (TKA). A key factor in the longevity of the implant is the positioning; however, the optimal tibial slope in UKA has not been determined. The aim of this study was to establish a finite element (FE) model and investigate the effect of the tibial slope on the strain of the ligaments, kinematics, inlay movement, and load in the nonreplaced patellofemoral compartment in a medial mobile bearing UKA. Materials and Methods An FE model of a leg was established with a virtual UKA implantation with three different tibial slopes (0°, 5°, and 10°). Subsequently, the knee was flexed from 14–73°. In addition, the ground reaction force and the muscles were simulated. ResultsWith a higher tibial slope, there was more external rotation of the tibia. An increased tibial slope provided a lateral shift of the patella in the trochlear groove and a more anterior position of the inlay. The ligament strains were also changed, specifically, the anterior portion of the medial collateral ligament and the posterior cruciate ligament (PCL). Discussion This study established the first model of a quasidynamic mobile bearing UKA in a leg under weight-bearing conditions. With an increasing tibial slope, there was a higher external rotation of the tibia that created different femorotibial and retropatellar kinematics and different strains in the ligaments. This knowledge adds important information for the optimal tibial slope that has to be determined individually depending on the patient's preoperative kinematics, desired postoperative kinematics, ligament status, and location of the retropatellar chondral damage.

Estimating an Individual’s Probability of Revision Surgery After Knee Replacement: A Comparison of Modeling Approaches Using a National Data Set

Tools that provide personalized risk prediction of outcomes after surgical procedures help patients make preference-based decisions among the available treatment options. However, it is unclear which modeling approach provides the most accurate risk estimation. We constructed and compared several parametric and nonparametric models for predicting prosthesis survivorship after knee replacement surgery for osteoarthritis. We used 430,455 patient-procedure episodes between April 2003 and September 2015 from the National Joint Registry for England, Wales, Northern Ireland, and the Isle of Man. The flexible parametric survival and random survival forest models most accurately captured the observed probability of remaining event-free. The concordance index for the flexible parametric model was the highest (0.705, 95% confidence interval (CI): 0.702, 0.707) for total knee replacement and was 0.639 (95% CI: 0.634, 0.643) for unicondylar knee replacement and 0.589 (95% CI: 0.586, 0.592) for patellofemoral replacement. The observed-to-predicted ratios for both the flexible parametric and the random survival forest approaches indicated that models tended to underestimate the risks for most risk groups. Our results show that the flexible parametric model has a better overall performance compared with other tested parametric methods and has better discrimination compared with the random survival forest approach.

Comparison of Continuous Adductor Canal Catheters and Single-shot Peripheral Nerve Blocks Providing Analgesia After Unicondylar Knee Replacement, as Part of an Enhanced Recovery After Surgery Program

With the current trend toward ambulatory joint replacements, it is important to identify the approach to postoperative analgesia which best balances comfort and mobility. Adductor canal blocks provide analgesia after unicondylar knee replacement and can be performed with either an infusion catheter [adductor canal block catheter (ACB-C)] or as a single-shot injection [adductor canal block single-shot injection (ACB-SS)]. We conducted a retrospective analysis comparing the perceived quality of analgesia achieved by the 2 techniques, hypothesizing that patients receiving ACB-Cs would have less opioid consumption and lower pain scores than those who received ACB-SSs. After Institutional Review Board approval, we identified patients who underwent unicondylar knee arthroplasty between August and December 2015. Patients designated American Society of Anesthesiologists physical status 1 to 3 were included. Those discharged home on postoperative day (POD) 0 or provided an alternative nerve block were excluded. The primary outcome was opioid consumption over POD 1. Morning and afternoon pain scores were also evaluated. Of the 125 patients identified, there were 17 exclusions. Of those remaining, 69 received an ACB-C and 38 received an ACB-SS. The median amount of opioid use was lower in the ACB-C group than in the ACB-SS group [12 mg (8, 16) vs. 26 mg (20, 31.5), P&lt;0.0001]. Patients treated with ACB-Cs had lower pain scores in the morning [0 (0, 1) vs. 3.5 (0, 5), P&lt;0.0001] and afternoon [0 (0, 0) vs. 4 (0, 5), P&lt;0.0001] on POD 1. Our data suggest an association between adductor canal catheters and both lower opioid consumption and pain scores. A prospective randomized trial is required to confirm this finding and help determine the optimal intervention.

Patient-specific instrumentation improves alignment of lateral unicompartmental knee replacements by novice surgeons

PurposePatient-specific instrumentation (PSI) has the potential to offer numerous benefits—not least of all, improved resection accuracy; but its potential has not been realised in clinical studies. An explanation may be the focus of such studies on the total knee replacement (TKR—a common procedure, with which surgeons are generally very familiar. Consequently, we sought to investigate the potential role of PSI in guiding novice surgeons to perform the more technically demanding and less familiar lateral unicondylar knee replacement (LUKR).MethodsTwelve orthopaedic trainees naive to LUKR were instructed to perform the procedure according to a pre-operative plan. These were carried out on synthetic sawbones and were completed once with conventional instrumentation alone and once with the adjunct of PSI, allowing a comparison of the plan adherence achieved by the two sets of instrumentation.ResultsThere was a tendency for PSI to demonstrate improved plan adherence, though a statistically significant improvement was only seen in compound rotational error of the femoral implant (p = 0.004). PSI was, however, able to produce narrower standard deviations in the mean translational displacement of the femoral implant and also the mean rotational displacement of both implants, suggesting a higher degree of precision.ConclusionsOur study provides some evidence that PSI can improve the ability of novice surgeons to replicate a pre-operative plan, but our results suggest the need for larger-scale clinical studies to establish the role of PSI in this procedure.

Patients Unicondylar Knee Replacement vs. Total Knee Replacement

The aim of this review article is to analyse the clinical effectiveness of total knee replacement (TKR) compared to unicondylar knee replacement (UKR) on patients. In terms of survival rates, revision rates and postoperative complications. The keywords used were: knee arthroplasty. Nearly three thousand articles were found on 25 August 2016. Of those, only twenty-five were selected and reviewed because they were strictly focused on the topic of this article. Compared with those who have TKR, patients who undergo UKR have higher revision rates at 5, 10 and 15 years. The reported overall risk of postoperative complications for patients undergoing TKR is 11%, compared with 4.3% for patients undergoing UKR. In conclusion, UKR have higher revision rates than TKR. However, an increased risk of postoperative complications after TKR.

Rates of hip and knee joint replacement amongst different ethnic groups in England: an analysis of National Joint Registry data.

Despite a health care system that is free at the point of delivery, ethnic minorities may not always get care equitable to that of White patients in England. We examined whether ethnic differences exist in joint replacement rates and surgical practice in England. 373,613 hip and 428,936 knee National Joint Registry (NJR) primary replacement patients had coded ethnicity in Hospital Episode Statistics (HES). Age and gender adjusted observed/expected ratios of hip and knee replacements amongst ethnic groups were compared using indirect standardisation. Associations between ethnic group and type of procedure were explored and effects of demographic, clinical and hospital-related factors examined using multivariable logistic regression. Adjusted standardised observed/expected ratios were substantially lower in Blacks and Asians than Whites for hip replacement (Blacks 0.33 [95% CI, 0.31-0.35], Asians 0.20 [CI, 0.19-0.21]) and knee replacement (Blacks 0.64 [CI, 0.61-0.67], Asians 0.86 % [CI, 0.84-0.88]). Blacks were more likely to receive uncemented hip replacements (Blacks 52%, Whites 37%, Asians 44%; P<0.001). Black men and women aged <70 years were less likely to receive unicondylar or patellofemoral knee replacements than Whites (men 10% vs 15%, P=0.001; women 6% vs 14%, P<0.001). After adjustment for demographic, clinical and hospital-related factors, Blacks were more likely to receive uncemented hip replacement (OR 1.43 [CI, 1.11-1.84]). In England, hip and knee replacement rates and prosthesis type given differ amongst ethnic groups. Whether these reflect differences in clinical need or differential access to treatment requires urgent investigation.

Five-Year Survival of 20,946 Unicondylar Knee Replacements and Patient Risk Factors for Failure: An Analysis of German Insurance Data.

Improvements in implant design and surgical technique of unicondylar knee arthroplasty have led to reduced revision rates, but patient selection seems to be crucial for success of such arthroplasties. The purpose of the present study was to analyze the 5-year implant survival rate of unicondylar knee replacements in Germany and to identify patient factors associated with an increased risk of revision, including >30 comorbid conditions. Using nationwide billing data of the largest German health-care insurance for inpatient hospital treatment, we identified patients who underwent unicondylar knee arthroplasty between 2006 and 2012. Kaplan-Meier survival curves with revision as the end point and log-rank tests were used to evaluate 5-year implant survival. A multivariable Cox regression model was used to determine factors associated with revision. The risk factors of age, sex, diagnosis, comorbidities, type of implant fixation, and hospital volume were analyzed. Hazard ratios (HRs) and 95% confidence intervals (95% CIs) were calculated. During the study period, a total of 20,946 unicondylar knee arthroplasties were included. The number of unicondylar knee arthroplasties per year increased during the study period from 2,527 in 2006 to 4,036 in 2012. The median patient age was 64 years (interquartile range, 56 to 72 years), and 60.4% of patients were female. During the time evaluated, the 1-year revision rate decreased from 14.3% in 2006 to 8.7% in 2011. The 5-year survival rate was 87.8% (95% CI, 87.3% to 88.3%). Significant risk factors (p < 0.05) for unicondylar knee arthroplasty revision were younger age (the HR was 2.93 [95% CI, 2.48 to 3.46] for patient age of <55 years, 1.86 [95% CI, 1.58 to 2.19] for 55 to 64 years, and 1.52 [95% CI, 1.29 to 1.79] for 65 to 74 years; patient age of >74 years was used as the reference); female sex (HR, 1.18 [95% CI, 1.07 to 1.29]); complicated diabetes (HR, 1.47 [95% CI, 1.03 to 2.12]); depression (HR, 1.29 [95% CI, 1.06 to 1.57]); obesity, defined as a body mass index of ≥30 kg/m2 (HR, 1.13 [95% CI, 1.02 to 1.26]); and low-volume hospitals, denoted as an annual hospital volume of ≤10 cases (HR, 1.60 [95% CI, 1.39 to 1.84]), 11 to 20 cases (HR, 1.47 [95% CI, 1.27 to 1.70]), and 21 to 40 cases (HR, 1.31 [95% CI, 1.14 to 1.51]) (>40 cases was used as the reference). Apart from known risk factors, this study showed a significant negative influence of obesity, depression, and complicated diabetes on the 5-year unicondylar knee replacement survival rate. Surgical indications and preoperative patient counseling should consider these findings. Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Comparative Fixation and Subsidence Profiles of Cementless Unicompartmental Knee Arthroplasty Implants

BackgroundAseptic loosening is the primary cause of failure for both cemented and cementless unicondylar knee replacements (UKRs). Micromotion and subsidence of tibial baseplate are two causes of failure, due to poor fixation and misalignment, respectively. MethodsStair ascent activity profiles from Bergmann et al and Li et al were used. Biphasic Sawbones models were prepared according to the surgical techniques of traditional and novel cementless UKRs. Implants were tested for 10,000 cycles representing post-operative bone interdigitation period, and micromotion was observed using speckle pattern measurements, which demonstrated sufficient resolution. Additionally, the test method proposed by Liddle et al was used to measure subsidence with pressure sensors under increasingly lateralized loading. ResultsMean displacement due to micromotion for mediolateral and anteroposterior plane was consistently greater for traditional cementless UKR. Mean displacement for axial micromotion was significantly higher for traditional UKR at the anterior aspect of the implant; however, values were lower for the medial periphery of the implant. Subsidence was significantly lower for the novel design with increasingly lateralized loading, and indentation was not observed on the test substrate, when compared to the traditional design. ConclusionOur findings demonstrate that the novel cementless design is capable of fixation and elimination of subsidence in laboratory test settings. Both designs limit micromotion to below the established loosening micromotion value of 150 μm. The L-shaped keel design resists both micromotion and subsidence and may prevent failure modes that can lead to aseptic loosening for UKRs. These findings are highly relevant for clinical application.

Accuracy of estimating Unicondylar Knee Replacement implant varus/valgus angles from antero-posterior radiographs

Unicondylar Knee Replacement (UKR) is an orthopedic surgical procedure to reduce pain and improve function in the knee. Load-bearing long-standing antero-posterior (AP) radiographs are typically used postoperatively to measure the leg alignment and assess the varus/valgus implant orientation. However, implant out-of-plane rotations, user variability, and X-ray acquisition parameters introduce errors in the estimation of the implant varus/valgus estimation. Previous work has explored the accuracy of various imaging modalities in this estimation. In this work, we explored the impact of out-of-plane rotations and X-ray acquisition parameters on the estimation of implant component varus/valgus angles. For our study, we used a single CT scan and positioned femoral and tibial implants under varying orientations within the CT volume. Then, a custom software application was used to obtain digitally reconstructed radiographs from the CT scan with implants under varying orientations. Two users were then asked to manually estimate the varus/valgus angles for the implants. We found that there was significant inter-user variability (p < 0.05) in the varus/valgus estimates for the two users. However, the ‘ideal’ measurements, obtained using actual implant orientations, showed small errors due to variations in implant orientation. We also found that variation in the projection center does not have a statistically significant impact (p < 0.01) on the estimation of implant varus/valgus angles. We conclude that manual estimates of UKR implant varus/valgus orientations are unreliable.

Can Both Cruciate Ligaments Be Preserved in Knee Arthroplasty? Eight- to Nine-Year Follow-Up of a Bicompartmental Knee Replacement.

Preservation of native knee anatomy may confer improved patient satisfaction, as suggested by patient satisfaction scores in unicondylar versus total knee replacement. Bicompartmental knee replacement (BKR) implants similarly promote native tissue preservation. We retrospectively reviewed 42 consecutive patients who underwent BKR from 2006 to 2007. Outcome measures were evaluated. At an average follow-up of 103 months (range 87-110), 34/42 (81%) of implants survived. Among the retained implants, the Knee Society Score (KSS) grade was excellent in 26/34 (76.5%), good in 5/34 (14.7%), fair in 3/34 (8.8%), and poor in 0/34 (0%) of cases. Midterm results of BKR demonstrated 81% survival and 76% with excellent KSS grading. Despite a 20% revision rate at the short-term follow-up, the retained implants functioned well at the midterm follow-up.

Indications and Borderline Indications for Medial Mobile Bearing Unicondylar Knee Replacement

Beside the possibility of bicondylar knee replacement, patients with isolated anteromedial osteoarthritis also have the possibility of unicondylar knee replacement. Therefore some requirements are essential such as functionally intact cruciate and collateral ligaments, intact cartilage in the lateral compartment and an intraoperative flexion of more than 100°. An instability or contracture of the cruciate or collateral ligaments, a varus deformity more than 15°, a flexion deformity of more than 15°, an intraoperative flexion less than 100° as well as failed upper tibial osteotomy are seen as contraindications. In addition, a rheumatoid arthritis and a full thickness cartilage defect in the central part of the lateral compartment are seen as a contraindication because of the risk of a progression of the disease. With respect to these contraindications, excellent functional outcome and survival rates could be demonstrated in the long term. An expansion of these criteria, especially in patients with an insufficiency of the cruciate ligaments or after failed upper tibial osteotomy should only be done in certain cases after careful assessment of the benefits and risks. These patients should be informed about the lack of long-term results and the higher risk of complications. Quite commonly, the criteria of Kozinn and Scott are used for patient selection. These criteria were originally established for fixed-bearing prosthesis and have no relevance on mobile-bearing prosthesis. Criteria such as age, level of activity, weight, chondrocalcinosis and anterior knee pain have no effect on the clinical outcome or the long-term survival of a mobile-bearing prosthesis.

The cost of adverse events from knee surgery in the United Kingdom: An in-depth review of the National Health Service Litigation Authority database

BackgroundThere has been a significant rise in the number and value of claims against the National Health Service (NHS), with limited studies on litigation in orthopaedic surgery and none in knee surgery alone. We aimed to examine claims against the NHS involving all aspects of knee surgery with respect to costs and trends. Clinical relevanceTo raise awareness of the reasons for litigation in knee surgery, thus potentially improve patient care and reduce future claims. MethodsWe analysed the NHS litigation authority (NHSLA) database for all orthopaedic surgery claims reported to the NHSLA between 2005 and 2010, with calculation of litigation success rates and odds ratios for those relating to knee surgery. ResultsThere were 515 cases identified from the 4609 orthopaedic cases in the NHSLA database (11.2%): 298 (58%) involving total knee replacements (TKRs), 11 (2%) involving unicondylar knee replacements, and 90 cases (30%) remaining open. The total pay out for closed cases was £10.45 million and amputation following TKR resulted in the highest single pay out. Litigation success rates for claimants were highest for retained drains (100%), incorrect prosthesis/prosthesis size (78%), renal failure (75%), poor outcome requiring further surgery (74%) and malalignment (71%). There were also 60 cases of delayed diagnosis which resulted in pay outs totalling £2.90 million. Based on these data, projected future pay out costs for the open TKR cases were estimated to be £2.71 million. ConclusionLitigation success rates for TKR were highest following technical errors such as malalignment compared to events less under the surgeon's control, such as infection. The number of claims involving incorrect prosthesis/size continues to be of concern. Despite the increased availability of imaging modalities, missed diagnosis also resulted in substantial pay outs.

Sense or nonsense of unloader braces

Unloader knee braces are a viable and cost-effective alternative in for treatment of medial osteoarthritis of the knee in selected patients. They provide the potential to predict which patients could benefit from a high tibial osteotomy (HTO) and which patients should better be treated which a unicondylar or bicondylar knee replacement. A direct clinical benefit in pain reduction as well as improved knee function has been shown in several clinical studies; however, the underlying mechanism remains uncertain. A potential reduction of the load in the medial compartment of the knee joint by reducing the varus or valgus deformity as well as a reduction of enhanced muscle contraction is discussed. Despite the promising short-term results, possible long-term benefits of unloader braces are controversial. As possible reasons, natural progression of the underlying osteoarthritis as well as compliance of the patients to wear the braces diminishes significantly with time.

(iv) Technology assisted unicompartmental knee replacement: results and functional outcomes

Abstract This review article focuses on the use of technology to assist implantation of Unicondylar Knee Replacements (UKR) for medial osteoarthritis of the knee. We provide the reader with an overview of the current published articles in peer reviewed journals investigating computer navigation, robotic-assisted surgery, patient-specific implants and instrumentation. The literature on technology assisted UKR does show a trend towards less outliers and greater accuracy, in terms of implant positioning and restoration of mechanical axis. There is also a key role for technology to play in the training of future surgeons in technically demanding procedures such as UKR. However, long-term differences in patient outcome and implant survivorship have yet to be shown and further high quality studies are required with longer follow-up to demonstrate that any improvement in accuracy and consistency translates to improvements in actual patient outcomes.