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Fundamentals of Revision Knee Arthroplasty: Diagnosis, Evaluation, and Treatment is a unique and very timely book designed for surgeons who are beginning to more commonly encounter knee revisions in their practice. Unlike many traditional books on revision, Fundamentals of Revision Knee Arthroplasty does not focus on the most difficult and challenging of cases. Rather, Fundamentals of Revision Knee Arthroplasty is intended to guide the surgeon in the evaluation of the failed or painful total joint replacement, review basic tenants and surgical principles of revision arthroplasty, and guide the surgeon in determining whether a given case is one that should be managed or is best referred to a tertiary orthopedic center. Along with their 32 contributors, Dr. David J. Jacofsky and Dr. Anthony K. Hedley provide detailed information inside Fundamentals of Revision Knee Arthroplasty , including appropriate preoperative evaluation, equipment requirements, surgical planning, need for augments and allograft, and surgical techniques. Surgeons will be tackling knee revision surgery more frequently as the number of these cases is exponentially increasing. Fundamentals of Revision Knee Arthroplasty provides a \"go-to\" resource to turn to for guidance by community arthroplasty surgeons, arthroplasty fellows, and residents.

Purpose The purpose of this systematic review and meta-analysis is to evaluate the joint awareness after unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA). It was hypothesized that patients with UKA could better forget about their artificial joint in comparison to TKA. Methods A search of major literature databases and bibliographic details revealed 105 studies evaluating forgotten joint score in UKA and TKA. Seven studies found eligible for this review were assessed for risk of bias and quality of evidence using the Newcastle–Ottawa Scale. The forgotten joint score (FJS-12) was assessed at 6 months, 1 year, and 2 years. Results The mean FJS-12 at 2 years was 82.35 in the UKA group and 74.05 in the TKA group. Forest plot analysis of five studies ( n  = 930 patients) revealed a mean difference of 7.65 (95% CI: 3.72, 11.57, p  = 0.0001; I 2  = 89% with p  < 0.0001) in FJS-12 at 2 years. Further sensitivity analysis lowered I 2 heterogeneity to 31% after exclusion of the study by Blevin et al. (MD 5.88, 95%CI: 3.10, 8.66, p  < 0.0001). A similar trend of differences in FJS-12 between the groups was observed at 6 months (MD 32.49, 95% CI: 17.55, 47.43, p  < 0.0001) and at 1 year (MD 25.62, 95% CI: 4.26, 46.98, p  = 0.02). Conclusions UKA patients can better forget about their artificial joint compared to TKA patients. Level of evidence III.

BackgroundSince the optimal surgery for isolated medial knee osteoarthritis (OA) is unclear, this study aimed at comparing the effectiveness of unicondylar knee replacement (UKR) with total knee replacement (TKR) for simple medial knee OA.MethodsLiterature searches of PubMed, Embase, Web of Science, and the Cochrane Library were searched up to 1th April 2020. Only studies comparing UKR with TKR for isolated medial knee OA were included. Data collection and extraction, quality assessment, and data analyses were performed according to the Cochrane standards.ResultsA total of 13 articles with 1888 patients were included, among which, 944 and 944 underwent UKR and TKR, respectively. The analyzed postoperative outcomes were mostly within 5 years of follow-up. The meta-analysis showed that UKR improved knee general function (P < 0.00001) and health (P = 0.02), moreover, reduced post-operative pain (P = 0.01) and complications (P < 0.05) more than TKR. There were no significant differences in postoperative revision (P = 0.252), high-activity arthroplasty score (HAAS) (P = 0.307) and Oxford knee score (OKS) (P = 0.15) between the two techniques.ConclusionsThe patients of UKR could achieve better clinical results than that of TKR, moreover, there were negligible differences between the two techniques in postoperative revision in the early and mid-term follow-up and surgeons should be aware of the important reasons for revision of UKR. Thus, UKR instead of TKR should be performed in patients with late-stage isolated medial knee OA.

Purpose The influence of lateral patellofemoral osteoarthritis (PFOA) in medial unicompartmental knee arthroplasty (UKA) is controversial. Our aim was to identify radiographic factors that may lead to progressive PFOA after implantation of a fixed-bearing medial UKA and their impact on patient-reported outcomes (PROMs). Methods A retrospective consecutive cohort of patients undergoing medial UKA with a minimum follow-up of 60 months between September 2011 and January 2017 was identified. All UKAs had a fixed-bearing design with cemented femoral and tibial components. PROMs included documentation of the Oxford Knee Score (OKS). The following radiographic parameters were evaluated on conventional radiographs and computer tomography (CT) scans: patella tilt angle, patella congruence angle, Caton-Deschamps index, medial and lateral patellofemoral degeneration (Kellgren-Lawrence Classification (KL)), mechanical anteroposterior axis, femoral torsion, tibial tuberosity to trochlear groove distance (TTTG), anteroposterior translation of the femoral component. A hierarchical multiple regression analysis and partial Pearson correlation analysis (SPSS) were used to evaluate for predictors of progression of lateral PFOA. Results Forty-nine knees allowed PFOA assessment and had an average follow-up of 62 months (range 60–108). Twenty-three patients did not exhibit any progression of lateral PFOA. Twenty-two progressed with 1 stage, whereas four had progressed 2 stages according to the KL classification. TTTG negatively correlated with progressive lateral PFOA ( r  =  − 0.436, p  = 0.01). Progression of lateral PFOA did not correlate with OKS at last follow-up ( p  = 0.613). Conclusion A decreased TTGT correlated with radiographic progression of lateral PFOA after medial fixed-bearing cemented UKA. PFOA however did not influence PROMs at a minimum of five years postoperatively.

Purpose Unicompartmental Knee Arthroplasty (UKA) recorded an increased incidence of around 30% per year in the United States. Patient’s experience and satisfaction after surgery were traditionally assessed by pre, and post-surgical scores and Patient-Reported Outcome Measures (PROMs) scales. Traditional scales as Western Ontario and McMaster University Osteoarthritis Index (WOMAC) and Oxford Knee Score (OKS) reported high ceiling effect. Patients treated by UKA usually perform well; therefore, it is necessary to have a PROMs’ scale with a low ceiling effect as the Forgotten Joint Score-12 (FJS-12). PROMs have to be validated in the local language to be used. This study aims to perform a psychometric validation of the Italian version of FJS-12 for UKA for the first time. Methods Between January 2019 and October 2019, 44 patients were included. Each patient completed both the FJS-12 Italian version and the WOMAC Italian version in preoperative follow-up, after 2-week and 1-month, 3-month, and 6-month postoperative follow-up. Cronbach’s α, intraclass correlation coefficient (ICC), standard error of measurement (SEM), and minimal detectable change (MDC) were calculated to evaluate the reliability. The Pearson coefficient was used to assess validity. The Effect Size (ES) was used to test the responsiveness. Results A range of Cronbach’s α between 0.90 and 0.95 indicated good internal consistency for the FJS-12. The test–retest reliability was acceptable (i.e., the ICC was higher than 0.7) at each follow-up. The Pearson correlation coefficient between the FJS-12 and WOMAC was − 0.11 (n.s.) at preoperative follow-up, r  = 0.47 ( P  = 0.001) at 1 month, r  = 0.57 ( P  < 0.001) at 3 months, and r  = 0.57 ( P  < 0.001) at 6 months. Therefore, except for the preoperative period, the validity of the FJS-12 score was assessed. Conclusion The FJS-12 represents a valid and reliable tool with a low ceiling effect to assess the outcomes improvement in UKA patients. Therefore, validating and translating this score in different languages could help perform more accurate studies on outcomes after UKA. Level of evidence Level III, diagnostic study.

Purpose Tibial plateau fractures are serious complications of Oxford mobile-bearing unicompartmental knee arthroplasty (OUKA). This study examined where the fracture lines arises and evaluated the keel–cortex distances (KCDs) using three-dimensional computed tomography (3D-CT) and the effects of technical error (assessed by tibial component positions) and proximal tibial morphology on the KCDs. Methods This retrospective study included 217 OUKAs with cementless tibial components. Fifteen patients had tibial fractures after surgery. Anterior and posterior KCDs and fracture line origins were assessed using 3D-CT postoperatively. Proximal tibial morphology was assessed using the medial eminence line (MEL), which runs parallel to the tibial axis and passes through the tip of the medial intercondylar eminence of the tibia on long-leg anteroposterior radiograph. Knees had overhanging medial tibial condyle if the MEL passed medially to the medial tibial cortex. KCDs were compared between patients with/without fractures. Tibial component positions were evaluated, considering effects of tibial morphologies and component positions on fracture prevalence and KCDs. Results Fracture lines were found between the keel and posterior cortex in 12/15 patients. Posterior KCDs were significantly shorter in patients with fractures than in patients without (2.7 ± 1.6 mm vs 5.2 ± 1.7 mm, P  < 0.001). Patients with medial overhanging condyles were more likely to have fracture (10/51 vs 5/166, P  < 0.001) and had significantly shorter posterior KCD than those without (3.6 ± 1.5 mm vs 5.5 ± 1.8 mm, P  < 0.001). Patients with tibial component that was set too medial, low, and valgus had higher rates of fracture than those without (7/39 vs 8/178, P  = 0.008). Medial ( r  = 0.30, P  < 0.001), low ( r  = -0.33, P  < 0.001), and valgus implantations ( r  = 0.35, P  < 0.001) of tibial components were related to shorter posterior KCDs. Conclusion Short posterior KCD after OUKA is a risk factor for postoperative tibial fracture. Patients with either malposition of the tibial component (too medial, low, and valgus) and/or a medial overhanging condyle exhibit a shorter distance of posterior KCD and higher rate of fracture. Level of evidence: Level III.

Purpose The aim of this study was to assess the return to amateur sports of patients under 65 years, following medial unicompartmental knee arthroplasty (mUKA) versus lateral unicompartmental knee arthroplasty (lUKA). It was hypothesized that patients younger than 65 years who underwent lateral or medial unicondylar knee replacement will result in similar rates to amateur sports, at a minimum follow-up of 2 years. Method Patients who underwent medial or lateral UKA participated in a 2-year follow-up program, where they were clinically evaluated for their return to amateur sports, using the University of California, Los Angeles (UCLA) activity scale and the High-Activity Arthroplasty Score (HAAS). Furthermore, subgroup analyses by gender and age were performed. Power analysis was performed to ensure sample size considering that lUKA is implanted ten times less frequently than its medial counterpart. Results There were 85 patients who completed the entire minimum 2-year follow-up of which 73 belonged to the mUKA group and 12 to the lUKA group. No preoperative differences were found between the groups regarding the gender, the affected side, age, and mean follow-up. Both groups showed statistically significant improvement ( p  < 0.05) in their return to amateur sports in all parameters (UCLA and HAAS). No differences among the two groups were found at T 0 and T 1 (n.s.) . All subgroups showed a statistically significant improvement ( p  < 0.05) with respect to the preoperative value, except for UCLA for lUKA with less than 60 years and HAAS for males in the lUKA group (n.s.). No differences were found among subgroups both at T o and T 1 (n.s.). Conclusion Both mUKA and lUKA procedures enabled all young and active patients a certain return to amateur sports 2 years after surgery, regardless of age and gender. UKA, medial or lateral, should always be considered for the treatment of isolated osteoarthritis in young and active patients with high functional demands. Level of evidence Cohort Study, Level of Evidence III. Registration Researchregistry6221 – Research Registry www.researchregistry.com .

Purpose Given an increasingly overweight population, unicompartmental knee replacements (UKRs) are being performed in patients with higher body mass indices (BMIs). There are concerns that cemented fixation will not last. Cementless fixation may offer a solution, but the long term results in different BMI groups has not been assessed. We studied the effect of BMI on the outcomes of cementless UKRs. Methods A prospective cohort of 1000 medial cementless mobile-bearing UKR with a mean follow up of 6.6 years (SD 2.7) were analysed. UKRs were categorised into four BMI groups: (1) ≥ 18.5 to < 25 kg/m 2 (normal), (2) 25 to < 30 kg/m 2 (overweight), (3) 30 to < 35 kg/m 2 (obese class 1) and (4) ≥ 35 kg/m 2 (obese class 2). Implant survival was assessed using endpoints reoperation and revision. Functional outcomes were assessed. Results Ten-year cumulative revision rate for the normal ( n  = 186), overweight ( n  = 434), obese class 1 ( n  = 213) and obese class 2 ( n  = 127) groups were 1.8% (CI 0.4–7.4), 2.6% (CI 1.3–5.1), 3.8% (CI 1.5–9.2) and 1.7% (CI 0.4–6.8) with no significant differences between groups ( p  = 0.79). The 10-year cumulative reoperation rates were 2.7% (CI 0.8–8.2), 3.8% (CI 2.2–6.6), 5.2% (CI 2.5–10.7) and 1.7% (CI 0.4–6.8) with no significant differences between groups ( p  = 0.44). The 10-year median Oxford Knee Score were 43.0, 46.0, 44.0 and 38.0 respectively. Conclusion Cementless mobile-bearing UKR has low 10-year reoperation and revision rates across in all BMI groups, and there are no significant differences between the groups. Although higher BMI groups had slightly worse functional outcomes, the improvement in function compared to preoperatively  tended to be better. This study suggests that BMI should not be considered a contraindication for the cementless mobile-bearing UKR.

Purpose Posterior cruciate ligament (PCL) deficiency is considered to be a contraindication for unicompartmental knee replacement (UKR); however, there is no evidence to support or contradict this. There are occasional circumstances where UKR in PCL deficient patients have been performed where the patient otherwise satisfies the indications for UKR. The aim of this paper is to describe the outcome of UKR in PCL deficient patients. Methods A retrospective study of patients with painful medial compartment osteoarthritis and PCL deficiency treated with Oxford UKR between 2006 and 2015 was undertaken. Clinical records from a prospectively recorded database were reviewed and outcomes were assessed based on revision rate, Oxford Knee Score (OKS), American Knee Society score and Tegner Activity Score. Results Nine patients were identified. The median age at surgery was 51 years (range 42–80) and median follow-up was 6 years (range 1–10). There was one bearing dislocation requiring open exchange. The outcome of seven patients was excellent (OKS > 41). Two patients, who were both elderly, had good outcomes (OKS 41 and 39). One patient had a poor outcome, but it is not clear if this was related to the knee as she had a learning disability and examination and radiographs of the knee were satisfactory. Conclusion The results of this small series suggest that excellent results can be achieved with UKR for selected patients with medial osteoarthritis in a PCL deficient knee that was functioning well before the osteoarthritis developed. On the basis of this a larger study should be undertaken. Until more results are available PCL deficiency should be considered a relative contra-indication to UKR. Level of evidence IV.

Purpose The purpose of this study was to evaluate implant migration of the fixed-bearing Sigma ® medial unicompartmental knee arthroplasty (UKA). UKA is a regularly used treatment for patients with medial osteoarthritis (OA) of the knee. UKA has a higher revision rate than total knee arthroplasty. Implant migration can be used as a predictor of implant loosening. Methods A prospective radiostereometric cohort study was performed. Forty-five patients with medial OA of the knee were included and received a cemented Sigma ® UKA. The patients were followed for 24 months with radiostereometric analysis (RSA) and clinical outcome scores (Oxford knee score). Clinical precision was based on double determinations taken at 4 and 12 months. Tibial implants were classified as stable (difference in MTPM < 0.2 mm between 1 2 and 24 months) or as continuously migrating (difference in MTPM > 0.2 mm between 12 and 24 months). Results No significant differences in migration were found for the femoral component. For the tibial component, a difference of 0.05 mm was shown for translation on the x -axis between 4 months and 12 ( p  < 0.01) and between 4 months and 24 months ( p  < 0.01). A difference of − 0.23 to − 0.50° was shown for rotation around the x -axis ( p  < 0.01) and a difference of − 0.11° was shown for rotation around the z -axis between 4 and 12 months ( p  = 0.02). These differences in migration over time were small and fall within the clinical precision of the measurements. Tibial components were divided into a stable group ( N  = 26) and a continuously migrating group ( N  = 11), which showed a significant difference in maximal total point motion (MTPM) ( p  < 0.01). The Oxford knee score improved significantly from poor before surgery (23.2) to good at follow-up (37.5–40.9). Conclusions The Sigma ® UKA showed low implant migration and good clinical outcomes, suggesting that the Sigma UKA can be used in clinical practice. However, continuous migration was found in 30% of our patients which could indicate a risk of later revision surgery in this group. Level of evidence II.