Lateral Unicompartmental Knee Arthroplasty Research Articles

Long-Term Outcomes in Unicompartmental Knee Arthroplasty: Survivorship of Medial versus Lateral Unicompartmental Knee Arthroplasty

Unicompartmental knee arthroplasties (UKAs) currently represent an important portion of knee arthroplasty procedures and their usage is on an upward trend. Despite offering better functional outcomes and a quicker recovery compared to total knee arthroplasties (TKAs), UKAs are often scrutinized for their longevity. This article provides an in-depth examination of the technical nuances and survival rates of medial versus lateral UKAs, drawing on recent advances and findings in the field.This manuscript thoroughly evaluates the comparability of patient populations undergoing medial and lateral UKAs, considering their anatomical, biomechanical, and demographic differences. It delves into the specific technical challenges associated with each type and systematically assesses the factors that influence failure, including the intricacies of implant design and patient-specific variables.Despite relevant anatomical and biomechanical contrasts between medial and lateral UKAs, recent literature points to comparable survival rates. The prevalence of early failures within the initial five years post-operation underscores the criticality of precise patient selection and refined surgical techniques. The paper succinctly summarizes pivotal literature and provides essential guidance for optimizing UKA survivorship. It underscores the importance of meticulous patient selection and precise surgical techniques, alongside the identification and mitigation of potential pitfalls that impact outcomes. Finally, robotic technology in UKA has considerably enhanced the precision and reproducibility, representing a viable solution to effectively meet and achieve the recommended technical objectives.

Perfect Indications and How to Avoid Complications in Lateral Unicompartmental Knee Arthroplasty

Lateral unicompartmental knee arthroplasty (LUKA) is a favorable alternative to distal femoral osteotomy and total knee arthroplasty in patients with isolated lateral compartment knee osteoarthritis; however, it only accounts for less than 1% of the total number of knee replacements documented in national joint registries. The anatomy and biomechanics of the lateral knee compartment differ from the medial side, with a greater intrinsic laxity of the lateral collateral ligament complex compared to medial structures. Indications and surgical techniques must be tailored to each unicompartmental replacement to optimize outcomes and mitigate complications. This article will discuss the clinical indications, preoperative evaluation and workup, surgical technique, and outcomes for LUKA.

UNICOMPARTMENTAL KNEE ARTHROPLASTY: WHAT IS THE OPTIMAL ALIGNMENT CORRECTION TO ACHIEVE SUCCESS? THE ROLE OF KINEMATIC ALIGNMENT. STATE OFF THE ART REVIEW

Unicompartmental knee arthroplasty (UKA) is in many ways the ultimate kinematic operation as the express aim is to resurface the diseased side of the joint and restore pre-arthritic alignment and balance while maintaining integrity of both cruciate ligaments. An increasing body of knowledge relates the outcomes of UKA to pre-arthritic anatomy rather than an arbitrarily defined neutral. The Coronal Plane Alignment of the Knee (CPAK) classification provides a validated technique for calculating pre-arthritic limb alignment (the Arithmetic Hip-Knee-Ankle Ankle (aHKA)) and Joint Line Obliquity (JLO) and will enable a greater understanding of the interactions between pre-arthritic anatomy, choice of prosthetic position and outcomes. When pre-arthritic alignment is not taken into consideration a post-operative limb alignment of mild to moderate varus for medial UKA and moderate valgus for lateral UKA appears produces the best outcomes. When pre-arthritic anatomy is taken into account superior results have been reported with restoration of pre-arthritic limb alignment and joint line obliquity. Restriction boundaries have yet to be clearly defined for tibial component coronal and Hip-Knee-Ankle (HKA) angles when applying this new paradigm, but existing evidence would suggest a 60 varus limit for the tibial coronal angle may be a reasonable starting point. Lateral UKA has inherent differences in terms of tibial component positioning and ligament balance targets. Mobile bearing UKA demands a three-dimensional understanding of the effect of implant position on bearing stability. Modification of technique is necessary to produce anatomic tibia component angles with equipment designed for mechanical alignment. Robotic technology allows accurate understanding of pre-arthritic anatomy, precise reproduction of patient specific virtual planning, equally precise manipulation of soft tissue balance and future research using these platforms likely to further clarify in terms of ideal patient specific component and limb alignment targets.

Lateral unicompartmental knee arthroplasty: is really a good option?

Lateral unicompartmental knee arthroplasties (LUKA) account for only < 1% of all knee arthroplasties and for only 5-10% of all unicompartmental knee replacements. This means that there is less published literature on these procedures and that the surgeon's experience with them is smaller than with medial UKA. The aim of this study was to analyze the survival and the clinical-functional outcomes of LUKA according to the type of bearing surface (all-polyethylene versus metal-backed) used. This was a retrospective study including 42 LUKAs operated between 2009 and 2021. Two fixed polyethylene-bearing models were used: the all-polyethylene ACCURIS knee (38%) and the metal-backed Triathlon PKR system (62%). Demographic parameters, knee range of motion (ROM), tibiofemoral alignment, implant survival (as estimated with the Kaplan-Meier curve), and clinical-functional outcomes (as measured with the Knee Society Score) were analyzed. Average patient age was 65.5 (range, 36-87) years and mean follow-up was 8.2 (range, 2.1-12.8) years. Thirty LUKAs (71.4%) were implanted in women. The main reason for performing a LUKA was osteoarthritis (88.1%). No patient developed post-surgical complications or had to be re-operated. Overall LUKA survival was 100% at 1-year and 5-year's follow-up. Knee Society Score, knee ROM and tibiofemoral alignment all improved significantly post-surgery (p < 0.001). The clinical Knee Society Score increased from 46.5 ± 14.5 pre-surgery to 93.5 ± 10.3 post-surgery, the functional Knee Society Score increased from 48.1 ± 13.5 pre-surgery to 94.6 ± 9.3 post-surgery, maximum flexion increased from 108.5 ± 8.7 degrees pre-surgery to 121 ± 8.9 degrees post-surgery and tibiofemoral alignment was corrected from 13.1 ± 1.74 degrees pre-surgery to 5.7 ± 0.8 degrees post-surgery. There were no statistically significant clinical-functional improvement or knee ROM differences between groups (p < 0.05, respectively). LUKA is a valid and definitive option for patients with lateral tibiofemoral osteoarthritis, with a survival rate of > 95% at 5-years follow-up. Clinical-functional outcomes are the same, irrespective of the tibial component used.

All-Polyethylene Tibial Component in Unicompartmental Knee Arthroplasty Offers Excellent Survivorship and Clinical Outcomes at Short-Term Follow-Up: A Multicenter Retrospective Clinical Study.

Background and Objectives: The ten-year survivorship of unicompartmental knee arthroplasty (UKA) is up to 96%, varying from implants and hospitals; however, most of registry studies do not distinguish between metal-back (MB) tibial implants and all-polyethylene (AP) tibial implants. The aim of the present retrospective clinical study was to analyze the clinical outcomes and survivorship of medial and lateral UKA with a newly designed all-polyethylene tibial plateau at short-term follow-up. Materials and Methods: A retrospective analysis of prospectively collected consecutive patients who underwent medial or lateral UKA with AP tibial plateau was conducted, with a minimum follow-up of 1 year. Primary outcomes were clinical score (VAS, OKS, and KOOS) variations from baseline up to the latest follow-up. Secondary outcomes were Likert scale variations from baseline to the follow-up, evaluation of the influence of demographic factors (age and BMI) at the time of surgery on the clinical outcomes, and evaluation of revision rate up to the last follow-up. Results: The final study population included 99 knees. The mean VAS score for the medial group significantly decreased from 7.61 ± 1.65 (pre-intervention) to 2.74 ± 2.26 (post-intervention). Similar improvements were registered for the OKS as well, for both the medial group (from 22.5 ± 12.6 to 36.6 ± 10.6, with a delta of 14.11 (10.05 to 18.17)) and the lateral group (from 22.6 ± 12.6 to 36.9 ± 11.8, with a delta of 14.24 (8.65 to 19.83)). Moreover, all the KOOS subscales reported an amelioration, both in medial UKA and lateral UKA. Furthermore, a logistic regression of delta VAS was performed in relation to the other clinical questionnaires and the demographic factors. For both medial and lateral UKAs, no statistically significant correlation was found between the VAS scale regression and the demographic factors. The survival rate free from any revision of the cohort at the latest follow-up was 96.32%. Conclusions: All-polyethylene tibial component in unicompartmental knee arthroplasty demonstrates significant improvements in clinical scores and a low failure rate at short-term follow-up.

Unicompartmental knee arthroplasty for lateral compartment knee osteoarthritis: a credible surgical approach and short-term clinical outcomes.

We aimed to investigate the technical advantages and clinical outcomes of lateral unicompartmental knee arthroplasty (LUKA) through the medial parapatellar approach. From August 2022 to June 2024, 104 patients who underwent LUKA via the medial parapatellar approach were enrolled. The operation time, hospital stays, surgical complications and follow-up period were collected. Pre- and postoperative Range of movement (ROM), Oxford knee score (OKS) and Hospital for special surgery knee score (HSS) were recorded and further investigated by paired-samples t-test analysis. Primary demographic data of the retrospective case series collected include gender (30 males and 74 females), age (63.1 ± 8.37years, range 49-84years), operation time (86 ± 17min, range 52-135min), hospital stays (4.0 ± 1.1days, range 3-8days) and follow-up period (9.9 ± 5.7months, range 1-23months). There was a significant improvement in ROM (P < 0.001), OKS (P < 0.001) and HSS (P < 0.001) compared to preoperative values. Patient satisfaction at 1-month postoperative follow-up was up to 95%. The incidence of deep venous thrombosis was 16.3%. There was no incidence of postoperative infection. The medial parapatellar approach is a understandable, easy to master and credible surgical approach for LUKA, showing a striking improvement in clinical outcomes without adverse events in the short-term follow-up.

Severe Lateral Facet Patella Osteoarthritis Is Not Associated With Increased Failure at Mean 10 Years After Lateral Unicompartmental Knee Arthroplasty

BackgroundThe purpose of this study was to determine if severe lateral patella facet osteoarthritis was related to lower survivorship and poor patient-reported outcomes following fixed-bearing lateral unicompartmental knee arthroplasty (UKA). MethodsThere were 61 patients who underwent a fixed-bearing, nonrobotically assisted, lateral UKA between May 7, 2003 and December 18, 2019 and met the inclusion criteria. The patello-femoral joint was examined intraoperatively for chondral damage prior to UKA implantation. Severe lateral facet patella osteoarthritis (LFPOA) was defined as Outerbridge grades 3 or 4 changes on the lateral facet. All patients completed subjective functional outcomes questionnaires and a clinical examination at a minimum of 4 years following UKA. ResultsSevere LFPOA was identified in 28 (46%) patients. At a mean follow-up of 10.9 years, there were no statistically significant differences in any Knee Osteoarthritis Outcomes Score (KOOS) subscale or Kujala scores between patients who had and did not have severe LFPOA. There was no statistically significant difference in the percentage of patients who achieved Patient Acceptable Symptom State for the KOOS subscale scores between groups. Mean survival in patients who did not have severe LFPOA was 16.6 years (95% confidence interval, 15.4 to 17.7) compared to 18.9 years (95% confidence interval, 17.6 to 20.2) in patients who had severe LFPOA (P = 0.62). ConclusionsSevere LFPOA did not result in lower survival or inferior functional outcomes compared to patients who did not have severe osteoarthritis at an average 10-year follow-up after fixed-bearing lateral UKA.

Previous arthroscopy does not decrease survivorship or functional outcomes for unicompartmental knee arthroplasty patients.

Arthroscopic procedures for osteoarthritis (OA), in particular arthroscopic meniscectomy, have poorer long-term clinical outcomes compared to those managed non-operatively. In addition, previous arthroscopy is associated with worse outcomes following subsequent total knee arthroplasty (TKA), however there is limited data on the impact on subsequent unicompartmental knee arthroplasty (UKA) outcomes. The aim of the study is to investigate whether patients who had arthroscopy prior to UKA have differences in survivorship or functional outcomes compared to those with no prior arthroscopy. All patients who received either a primary medial or lateral UKA at four large tertiary hospitals were included (n = 2,272). Patient data (age, sex, ethnicity, body mass index (BMI), American Society of Anesthesiologists (ASA) status and surgical data) was recorded following systematic review of all clinical notes and radiographs. Differences between survival curves were analysed using log-rank curves. Differences between categorical data was compared using Fisher's exact or Chi-squared tests, and differences between continuous variables were compared using t-tests. There was no difference between the survival curves for UKA patients with previous arthroscopy compared to those with no previous arthroscopy (10 years: 91% UKA with previous arthroscopy vs. 92% no previous arthroscopy; 15 years: 78% previous arthroscopy vs. 86% no previous arthroscopy; p = 0.50). Oxford Knee Score (OKS) was comparable between patients who had previous arthroscopy and those who had no previous arthroscopy at 6 months (38.8 vs. 39.3, p = 0.45), 5 years (42.0 vs. 40.4, p = 0.11) and 10 years (40.8 vs. 40.2, p = 0.71). In this large patient cohort with comprehensive review of clinical data and outcomes, we found that prior arthroscopy did not affect survivorship or functional outcomes of UKA patients.

Long-term functional success and robust implant survival in lateral unicompartmental knee arthroplasty: A case series with a mean follow-up of twenty two and a halfyears.

Lateral unicompartmental knee arthroplasty (UKA) is an accepted treatment option in cases of end-stage lateral osteoarthritis. While lateral UKA has many proposed advantages compared to total knee arthroplasty, its technical challenges and relatively small number of cases make this an uncommon procedure. The aim of this study was to report the survivorship and functional outcomes beyond 20years of follow-up of isolated UKA. Between January 1988 and October 2003, 54 lateral UKAs were performed in a single center. The fitted prosthesis was a fixed plate and cemented polyethylene (PE). All patients had isolated lateral tibiofemoral osteoarthritis, including five open meniscectomies, three arthroscopies, and three open reductions of lateral tibial plateau fractures. Patients with a minimum of 20years of follow-up were included in the final analysis. Of the 54 UKA, 22 died before reaching the minimum follow-up period and four were lost to follow-up. Twenty-eight were included in the final analysis. Among them, 21 patients remained alive and an additional seven were deceased after 20years. The mean age at the last follow-up was 84.8 ± 11.9years with a mean follow-up duration of 22.5 ± 2.1years. Of the 28 knees, eight underwent revision surgery (5 for the progression of osteoarthritis; 2 for aseptic loosening; 1 for PE wear). Kaplan-Meier survival analysis revealed a survival rate at 20 and 25years of 72.3% (CI 59.1; 88.6). The average time to revision was 14.9 ± 4.9years. At the last follow-up, the mean function Knee Society Score (KSS) was 41.5 ± 32.9 and the mean objective KSS score was 79.4 ± 9.7. In the unrevised population, 94.7% of patients (n = 18) reported being satisfied or very satisfied with the surgery. Lateral UKA remains a viable treatment option for patients with isolated lateral tibiofemoral osteoarthritis, providing satisfactory 20-year implant survivorship and high patient satisfaction.

Starting up a Lateral Unicompartmental Knee Arthroplasty Practice – Is Outcome Affected?

BackgroundIn the past, the utilization of lateral unicompartmental knee arthroplasty (UKA) has been limited at national levels, despite the fact that an estimated 10% of patients who have an indication for arthroplasty, present with isolated lateral compartment osteoarthritis (OA). Units dedicated to UKA have reported good outcomes. Identifying patients for the procedure has been less clear, and the procedure has been perceived to be technically more demanding than medial UKA. This may result in a reluctance to start a lateral UKA practice and challenge the early phase. Therefore, this paper aimed to present the outcomes and learning curve when starting up a lateral UKA practice, as this theme remains unelucidated. MethodsThere were 85 primary fixed-bearing lateral UKAs, with a minimum of 1-year follow-up, performed between 2016 and 2022 by 2 arthroplasty surgeons with existing UKA practices. The indications were primary (n = 79) or post-traumatic (n = 6) OA. Patient-reported outcome measures (PROMs) were assessed at 3, 12, and 24 months. A cumulative sum (CUSUM) analysis was used to evaluate surgical duration and the 12-month Oxford Knee Score (OKS). ResultsMedian (interquartile range) 12-month OKS, activity and participation questionnaire, and Forgotten Joint Score (FJS) were 43 (37.5 to 46), 78 (42.5 to 98.5), and 72 (55 to 90), respectively. The OKS outcomes did not reveal adverse effects from the learning curve. A performance shift in surgical duration was observed around case 33. Kaplan-Meier implant survival reached 95.4% at 7 years for the endpoint “implant revision” and 93.5% for “implant revision or implant addition.” ConclusionsStarting up a lateral UKA practice is safe and efficient for surgeons who have prior medial UKA experience, provided strict adherence to indications. While surgical duration indicated a learning curve over approximately 33 cases, PROMs remained stable, suggesting proficient outcomes irrespective of the learning curve.

Clinical Outcomes and Survivorship of Lateral Unicompartmental Knee Arthroplasty: A Large Single Surgeon Cohort

BackgroundLateral unicompartmental knee arthroplasty (UKA) is an effective treatment for isolated lateral compartment osteoarthritis. However, due to the rarity of the procedure, long-term outcomes and survivorship are poorly understood. We report the clinical and radiographic outcomes after lateral UKA. MethodsWe retrospectively reviewed a consecutive series of patients who underwent lateral UKA by a single fellowship-trained arthroplasty surgeon from 2001 to 2021 with a minimum 2 year follow up. There were 161 knees in 153 patients (average age 69 years) that met inclusion criteria, with a mean follow up of 10.0 years (range 0.05 to 22.2). All patients underwent the procedure via a minimally invasive lateral parapatellar approach with a fixed-bearing implant. Patient demographics, complications, radiographic findings, patient-reported outcomes, and the need for revision surgery were evaluated. Survivorship was defined with the end point as revision of components. ResultsThere were 8 patients (5.0%) who underwent conversion to total knee arthroplasty for lateral UKA implant failure or progression of arthritis. There were 3 patients (1.9%) who underwent ipsilateral medial UKA due to medial compartment arthritis progression with preserved mechanical alignment and patellofemoral joint. There were 8 additional procedures that did not require implant changes, including 5 irrigation and debridements for acute periprosthetic joint infection (3.1%), 2 wound closures for dehiscence (1.3%), and one loose body removal (0.6%). ConclusionsLateral UKA showed a survivorship rate of 98.0% at 5 years, 96.0% at 10 years, and 94.5% at 15 years. When including patients who underwent additional surgery for the progression of arthritis, survivorship was 97.4% at 5 years, 95.4% at 10 years, and 91.3% at 15 years. Lateral UKA should be seen as a durable treatment option for isolated lateral compartment osteoarthritis.

Robotic-arm-assisted lateral unicompartmental knee arthroplasty leads to high implant survival and patient satisfaction at mean 10-year follow-up.

There is a lack of literature reporting on long-term outcomes following robotic-arm-assisted lateral unicompartmental knee arthroplasty (UKA). This study assessed the long-term survivorship, patient-reported satisfaction and pain scores following robotic-arm-assisted lateral UKA for lateral compartment osteoarthritis (OA). A single surgeon's database was reviewed to identify all patients who underwent robotic-arm-assisted lateral UKA with a cemented, fixed-bearing prosthesis prior to May 2015. Patients were contacted to determine implant survivorship, satisfaction and pain. Kaplan-Meier models were applied to analyse survival. A total of 77 knees (70 patients) with a mean follow-up of 10.2 ± 1.5 years (range: 8.1-13.3) were included. Five knees were revised, corresponding to a 10-year survivorship of 96.1% and estimated survival time of 12.7 ± 0.3 years (95% confidence interval: 12.2-13.2) with all-cause revision as the endpoint. Unexplained pain (40.0%) and progression of OA (40.0%) in contralateral compartments were the most reported reasons for revision. Among patients without revision, 94.4% were either satisfied or very satisfied with their lateral UKA and the average pain score was 1.1. Robotic-arm-assisted lateral UKA led to high implant survivorship and patient satisfaction, and low pain scores at long-term follow-up. Progression of OA in contralateral compartments and unexplained pain were the most frequent reasons for revision. These findings support the continued use of robotic-arm-assisted lateral UKA for lateral compartment OA; however, its clinical value over conventional techniques remains to be established in prospective comparative studies. Therapeutic Level IV.

ACCURACY OF REGISTRY-REPORTED REASONS FOR UNICOMPARTMENTAL KNEE ARTHROPLASTY REVISION

IntroductionA key outcome measured by national joint registries are revision events. This informs best practice and identifies poor-performing surgical devices. Although registry data often record reasons for revision arthroplasty, interpretation is limited by lack of standardised definitions of revision reasons and objective assessment of radiologic and laboratory parameters. Our study aim was to compare reasons for unicompartmental knee arthroplasty (UKA) revision reported to the New Zealand Joint Registry (NZJR) with reasons identified by independent clinical review.MethodsA total of 2,272 patients undergoing primary medial and lateral UKA at four large tertiary hospitals between 2000 and 2017 were included. A total of 158 patients underwent subsequent revision with mean follow-up of 8 years. A systematic review of clinical findings, radiographs and operative data was performed to identify revision cases and to determine the reasons for revision using a standardised protocol. These were compared to reasons reported to the NZJR using Chi-squared and Fisher exact tests.ResultsOsteoarthritis progression was the most common reason for revision on systematic clinical review (30%), however this was underreported to the registry (4%, p&lt;0.001). A larger proportion of revisions reported to the registry were for ‘unexplained pain’ (30% of cases vs. 4% on clinical review, p&lt;0.001). A reason for revision was not reported to the registry for 24 (15%) of cases.Discussion and ConclusionWe found significant inaccuracies in registry-reported reasons for revision following UKA. These included over-reporting of ‘unexplained pain’, under-reporting of osteoarthritis progression, and failure to identify a reason for revision. Efforts to improve registry capture of revision reasons for UKA should focus on increasing accuracy in these three areas. This could be addressed through standardised recording methods and tailored revision reason options for UKA for surgeons to select when recording the reasons.

Association of Preoperative Subchondral Bone Marrow Oedema with Outcomes after Lateral Unicompartmental Knee Arthroplasty.

To determine whether the presence of preoperative subchondral bone marrow oedema (SBME) is associated with inferior outcomes after lateral unicompartmental knee arthroplasty (LUKA). Descriptive study. Place and Duration of the Study: Department of Orthopaedic Surgery, Chongqing Orthopaedic Hospital of Traditional Chinese Medicine, Chongqing, China, from January 2019 to June 2022. Data on patients treated with LUKA were obtained from the Medical Registry Database. Two groups were made based on the presence and absence of SBME on preoperative magnetic resonance imaging (MRI). The visual analogue scale (VAS), American Knee Society Scores (AKSS), and rate of patient satisfaction were compared between the two groups. A total of 20 patients treated with LUKA were reviewed. The SBME was present in 9 cases and absent in 11 cases. Patients with SBME had inferior scores at preoperative evaluation and at 1, 3, and 6 months postoperatively. However, there was no significant difference between the groups at the 12-month follow-up. Eight (88.9%) patients with SBME were satisfied with the LUKA surgery versus 9 (81.8%) patients without SBME, showing no significant differences between groups. Presence of preoperative SBME is associated with inferior functional outcomes after LUKA within six months of follow-up. Bone marrow, Oedema, Knee, Arthroplasty, Outcome, Patient satisfaction.

Associated patellofemoral osteoarthritis is not a contraindication for unicompartmental knee replacement. Report of one hundred ten prostheses with an average 6-year follow-up

IntroductionAssociated patellofemoral joint osteoarthritis (APFJ-OA) has typically been considered a contraindication for unicompartmental knee arthroplasty (UKA) in the treatment of femorotibial joint osteoarthritis. However, this contraindication is being challenged. The aim of this study was to assess clinical and functional outcomes, complications, and implant survival in medial or lateral UKA, regardless of clinical symptoms or radiographic signs of APFJ-OA. MethodsThis retrospective, comparative study included patients treated with medial or lateral UKA regardless of preoperative symptoms or signs of APFJ-OA, with a minimum 2-year follow-up. Intraoperatively, knees were subdivided based on APFJ-OA grade, according to the Outerbridge classification. Clinical and functional outcomes were analyzed using the 2011 Knee Society Score (KSS) at the last follow-up control. APFJ-OA was treated systematically, in a tailored, stepwise fashion according to its severity. Complications and implant survival rates were evaluated. Two-sided paired T-test, ANOVA, and Kruskal–Wallis tests were used with a significance level of 5%. ResultsFinally, 110 UKAs were assessed 81 (73.6%) medial and 29 (26.4%) laterals. The average follow-up was 6 years (2–19.5). According to Outerbridge, 22 knees (20%) were in grade 2, 59 (53.6%) were in grade 3, and 29 (26.4%) were in grade 4. All three groups showed a statistically significant increase in KSS scores and range of motion. There were no significant differences in clinical KSS improvement and flexion contracture between Outerbridge groups (average 35.7 and −4.9, respectively). Group 3 showed statistically significant improvement in functional KSS when compared to group 2 (68.8 vs 61.2). In maximum flexion, groups 3 and 4 did significantly better than group 2 (20° vs 15°). Three prostheses (2.7%) needed revision after 7, 8.6, and 12 years due to aseptic tibial loosening. Implant survival was 100% at 5 (64 of 64), 97% at 7 (30 of 31), 93% at 9 (14 of 15), and 89% at 12 years, respectively (8 of 9). ConclusionClinical and functional results, complications, and survival of medial or lateral UKA were not negatively affected by APFJ-OA assessed intraoperatively using the Outerbridge classification after an average follow-up of 6 years. We consider that APFJ-OA is not a contraindication for UKA when treated systematically according to its severity. Level of evidenceIV.

Lateral Unicompartmental Knee Arthroplasty for Osteoarthritis Secondary to Lateral Meniscectomy: High Functional Results and Survivorship and Low Osteoarthritis Progression at a Mean 10 Years of Follow-up.

Meniscectomy, whether partial or total, is a common knee surgery, but it considerably increases the risk of knee osteoarthritis (OA). Lateral meniscectomy has more severe consequences than medial meniscectomy, leading to faster OA progression and worse clinical outcomes. Unicompartmental knee arthroplasty (UKA) is a suitable treatment option for lateral OA and has demonstrated better outcomes than total knee arthroplasty (TKA). The aims of this study were to evaluate the clinical and functional results, OA progression in the medial compartment, and implant survivorship following lateral UKA in patients with OA secondary to lateral meniscectomy and to compare these outcomes with those of patients who underwent lateral UKA for primary lateral OA. Between 2001 and 2017, 214 lateral UKAs were performed. Of these, 42 were performed for OA secondary to lateral meniscectomy. The control group was composed of patients who underwent lateral UKA for primary lateral OA and was formed through a 1:1 case-control matching process based on sex, age, body mass index, and operation date. The outcomes that were studied included range of motion, Knee Society Score, University of California Los Angeles (UCLA) Activity Score, Tegner Activity Scale, Forgotten Joint Score, visual analog scale for pain, OA progression in the medial compartment, and implant survivorship. At a mean follow-up of 10.2 years, both groups demonstrated significant improvements (p < 0.01) after lateral UKA in all clinical and functional scores except the UCLA Activity Score and Tegner Activity Scale. No significant differences in clinical and functional scores were found between the groups. However, patients with OA secondary to meniscectomy exhibited significantly less OA progression in the medial compartment (p = 0.035) and higher 10-year implant survival (97.6% versus 83.3%). Lateral UKA is an effective treatment option for OA secondary to lateral meniscectomy, providing excellent functional outcomes and survivorship. Patients with post-meniscectomy OA exhibited less OA progression in the medial compartment than patients with primary OA and, consequently, had better 10-year implant survivorship. Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Effect of lower limb alignment on outcome after lateral unicompartmental knee arthroplasty: a retrospective study

PurposeThe objective of this study was to investigate the correlation between lower limb alignment and patient outcomes after lateral unicompartmental knee arthroplasty (LUKA).MethodsIn this retrospective study, the information of 51 patients who underwent lateral UKA was collected after an average of 27months of follow-up (13 to 60 months). Evaluation indicators include the AKS and WOMAC score. The Kellgren-Lawrence grade is used to evaluate the severity of osteoarthritis, while the hip-knee-ankle (HKA) angle is utilized to measure the valgus angle of lower limb alignment.ResultPatients with postoperative valgus (≥ 3°) alignment had the best outcomes, while those with varus (≤-3°) alignment had the worst outcomes (p < 0.001). Furthermore, it was noted that patients with preoperative mild valgus (≤ 4°) alignment had worse postoperative outcomes than those with severe valgus (≥ 7°) alignment (p < 0.05). The study also revealed a positive correlation between postoperative valgus and WOMAC scores (p < 0.001), whereas a negative correlation was observed between the change in valgus angle and WOMAC scores (p = 0.005).ConclusionDuring follow-ups, we found that lower limb alignment seems to be an independent predictor of postoperative outcomes. It is recommended that more than 3° of valgus alignment should be maintained after LUKA. Surgeons performing lateral UKA should be cautious of overcorrecting alignment, particularly in patients with preoperative mild valgus alignment.

Lateral UKA can be a safe solution in a young patients' population: a 10-year follow-up report.

This study aimed to assess the long-term survivorship and functional outcomes of fixed-bearing lateral unicompartmental knee arthroplasty (UKA) in a young patients' population with osteoarthritis limited to the lateral compartment. The study included a cohort of consecutive patients who underwent lateral UKA between January 2008 and December 2014 at a single high-volume surgical center. The surgical procedures were performed by experienced surgeons using a lateral parapatellar approach and fixed-bearing implants. Patient follow-up included a retrospective re-evaluation, clinical assessments, patient-reported outcome measures (PROMs), and X-ray analysis. A total of 40 lateral UKAs were analyzed, with 19 performed on the left and 21 on the right knee. The mean age of the patients at the time of surgery was 57.6 years, and the mean BMI was 24.8. At the final follow-up, 80% of patients achieved excellent outcomes (OKS > 41), and 20% had good outcomes (OKS: 34-41). No patients exhibited fair or poor outcomes. The mean FJS at the final follow-up was 82.8. The mean WOMAC was 10.5. Kaplan-Meier survival analysis revealed a survivorship rate of 93.1% at 10 years, considering revision for any reason as endpoint. Lateral UKA proved to be an effective treatment option for osteoarthritis affecting the lateral compartment of the knee. The study demonstrated a high survivorship rate and favorable functional outcomes at a mean follow-up of 132.7 months. These findings highlight the potential benefits of fixed-bearing lateral UKA in selected patients with lateral compartment knee pathology.

Short term outcomes following robotic arm-assisted lateral unicompartmental knee arthroplasty.

Robotic-arm assisted medial unicompartmental knee arthroplasty (RA-UKA) is associated with improved accuracy of implant positioning and excellent early functional outcomes. However, there is paucity of evidence regarding outcomes following RA-UKA for isolated lateral compartment osteoarthritis. The purpose of this study was to assess the short-term clinical and patient reported outcomes of lateral compartment UKA, utilising robotic-arm assistance. This was a retrospective study of prospectively collected data of 21 consecutive patients who underwent lateral RA-UKA. The study included 9 (42.9%) males and 12 (57.1%) females with a mean age of 63.4 ± 9.2 years. The Oxford Knee Score (OKS) was measured pre-operatively and at 1-year post-operatively, while range of motion (ROM) and complications were also recorded. There was significant improvement of OKS at 1 year's follow up compared with the baseline score (21.8 ± 5.6 vs. 45.2 ± 2.8 respectively; p < 0.001). There was also an improvement in pre-operative ROM when compared to ROM at 1 year's follow up (123.5° ± 8° vs. 131.5° ± 6.3° respectively; p < 0.001). None of the study patients underwent revision surgery within 1 year's follow-up. In our study, lateral RA-UKA resulted in significant improvements in clinical and patient reported outcomes with low complications rates. Further long-term comparative studies are needed to assess the utility of lateral RA-UKA vs. conventional UKA.

Surgical technique of lateral unicompartmental knee arthroplasty and discussion of the maximum correction value in the treatment of knee valgus deformity

To investigate the surgical technique and the short-term effectivenss of lateral unicompartmental knee arthroplasty (LUKA) through lateral approach in the treatment of valgus knee and to calculate the maximum value of the theoretical correction of knee valgus deformity. A retrospective analysis was performed on 16 patients (20 knees) who underwent LUKA and met the selection criteria between April 2021 and July 2022. There were 2 males and 14 females, aged 57-85 years (mean, 71.5 years). The disease duration ranged from 1 to 18 years, with an average of 11.9 years. Knee valgus was staged according to Ranawat classification, there were 6 knees of type Ⅰ, 13 knees of type Ⅱ, and 1 knee of type Ⅲ. All patients were assigned the expected correction value of genu valgus deformity by preoperative planning, including the correction value of lateral approach, intra-articular correction value, and residual knee valgus deformity value. The actual postoperative corrected values of the above indicators were recorded and the theoretical maximum correctable knee valgus deformity values were extrapolated. The operation time, intraoperative blood loss, incision length, hospital stay, hip-knee-ankle angle (HKA), mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibia angle (mMPTA), joint line convergence angle (JLCA), posterior tibial slope (PTS), range of motion (ROM), Hospital for Special Surgery (HSS) score, and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score were also recorded for effectiveness evaluation. The patients' incision length averaged 13.83 cm, operation time averaged 85.8 minutes, intraoperative blood loss averaged 74.9 mL, and hospital stay averaged 6.7 days. None of the patients suffered any significant intraoperative neurological or vascular injuries. All patients were followed up 10-27 months, with a mean of 17.9 months. One patient with bilateral knee valgus deformities had intra-articular infection in the left knee at 1 month after operation and the remaining patients had no complication such as prosthesis loosening, dislocation, and infection. The ROM, HSS score, and WOMAC score of knee joint significantly improved at each time point after operation when compared to those before operation, and the indicators further improved with time after operation, the differences were all significant ( P<0.05). Imaging measurement showed that HKA, mLDFA, JLCA, and PTS significantly improved at 3 days after operation ( P<0.05) except for mMPTA ( P>0.05). Postoperative evaluation of the knee valgus deformity correction values showed that the actual intra-articular correction values ranged from 0.54° to 10.97°, with a mean of 3.84°. The postoperative residual knee valgus deformity values ranged from 0.42° to 5.30°, with a mean of 3.59°. The actual correction values of lateral approach ranged from 0.21° to 12.73°, with a mean of 4.26°. LUKA through lateral approach for knee valgus deformity can achieve good early effectiveness. Preoperative planning can help surgeons rationally allocate the correction value of knee valgus deformity, provide corresponding treatment strategies, and the maximum theoretical correction value of knee valgus deformity can reach 25°.