Mid-term survivorship and patient-reported outcomes of robotic-arm assisted partial knee arthroplasty.

Introduction Unicompartmental knee arthroplasty (UKA) is a bone-preserving alternative to total knee arthroplasty (TKA) for isolated compartmental osteoarthritis (OA). The medial compartment is most frequently affected due to varus malalignment, while lateral disease, associated with valgus alignment, is less common. Although UKA offers faster recovery and improved function compared to total knee replacement, direct comparisons between medial and lateral UKA outcomes are limited. This study aims to compare patient-reported outcomes between medial and lateral UKA using a retrospective case-matched design. Methods A retrospective case-matched study was conducted on patients who underwent fixed-bearing UKA performed by a single fellowship-trained surgeon between 2008 and 2023. All procedures followed a standardized surgical and rehabilitation protocol. Lateral UKA cases were matched 1:1 with medial UKA cases for age (±1 year), sex, and follow-up duration (±6 months). The primary outcome was the Forgotten Joint Score-12 (FJS-12) at the latest follow-up. Statistical comparisons used independent t-tests for continuous variables and chi-squared or Fisher's exact tests for categorical data, with significance set at p < 0.05. Effect sizes were quantified using Cohen's d. Results The cohort included equal numbers of medial (n = 25) and lateral (n = 25) UKA cases with no significant differences in demographics. The mean age was 59.3 years, and the mean follow-up was 7.6 years. The mean normalized FJS-12 scores were 56.8 (standard deviation {SD}: 37.7) for medial UKA and 57.4 (SD: 36.0) for lateral UKA (p = 0.86), with a negligible effect size (Cohen's d = 0.05). The item-by-item analysis of the 12 components of the FJS-12 revealed no statistically significant differences between groups across activity-specific domains, including walking, standing, climbing stairs, and sports participation. The graphical distribution of FJS-12 scores showed substantial overlap between the two cohorts. No implant revisions or major complications were recorded in either group. Conclusion In this case-matched analysis of medial and lateral UKA performed by a single surgeon, patient-reported outcomes were equivalent at mid-term follow-up. Both medial and lateral UKA demonstrated comparable joint "forgettability" and functional integration, with no revisions observed. These findings indicate that, when performed with appropriate patient selection and consistent surgical technique, lateral UKA can achieve outcomes equivalent to medial UKA. The results support the safe and effective use of lateral UKA as a viable option for isolated lateral compartment disease.

The number of unicompartmental knee arthroplasties (UKAs) is growing worldwide. Because lateral UKAs are performed much less frequently than medial UKAs, the limited information leaves unclear whether UKAs have comparable survival and health-related quality of life (HRQoL) of the lateral UKA to medial UKAs. We therefore compared the (1) survivorship and (2) HRQoL after lateral versus medial cemented mobile-bearing UKAs and (3) determined whether there is an association of survival to modifications of surgical technique in one of three phases. We retrospectively reviewed 558 patients who underwent mobile-bearing UKAs from 2002 to 2009. From the records we determined revision of the joint for any reason and revision for aseptic loosening. Patients reported their physical function, pain, and stiffness as measured by the WOMAC, SF-36 physical-component summary (PCS), and Lequesne knee score. Information regarding implant survival was collected for 93% of the patients. We analyzed the patients separately by three phases based on surgical changes associated with each phase (1: initial technique; 2: improved cementing; 3: additional bone resection to ensure backward sliding of the inlay without impingement). The minimum followup was 2.1 years (mean, 6 years; range, 2.1-9.8 years). Implant survival was 88% at 9 years. We found similar implant survival rates for medial (90%) and lateral UKAs (83%). In all HRQoL measures, patients receiving a medial UKA had better mean scores compared with patients who had a lateral UKA: WOMAC physical function (23 versus 34, respectively) and pain (21 versus 34) and SF-36 PCS (41 versus 38). There were no survival differences by surgical phase. Our observations suggest a medial UKA is associated with superior HRQoL when compared with a lateral UKA, although implant survival is similar.

Many studies have found associations between unicompartmental knee arthroplasty (UKA) and implant survival, but controversy still exists regarding the relative survival of medial versus lateral UKA over mid-to long-term follow-up. The purpose of this study was to compare survival and clinical outcomes of medial and lateral UKAs. In this meta-analysis, we reviewed studies that assessed implant survival in patients who underwent medial or lateral UKA with short- to mid-term (<10years) or long-term (>10years) follow-up, and that used assessments, such as pain and function scores, to compare postoperative scores on knee outcome scales. A total of eight studies (33,999 knees with medial UKA and 2,853 with lateral UKA) met the inclusion criteria and was analyzed in detail. There were no significant differences between medial and lateral UKA in pain score (95% CI: -0.37 to 0.88; P = 0.42), function score (95% CI: -0.19 to 0.60; P = 0.31), short- to mid-term survival (medial, 32,083/33,483; lateral, 2,636/2,726; OR 0.98, 95% CI: 0.64 to 1.48;P = 0.91), or long-term survival (medial, 479/516; lateral, 110/127; OR 2.51, 95% CI:0.67 to 9.43; P = 0.17). In addition, both groups had substantial proportions of knees with short- to mid-term survival (95.6% by medial UKA and 94.6% by lateral UKA) and long-term survival (92.8% by medial UKA and 86.6% by lateral UKA). This meta-analysis found no significant differences in short- to mid-term and long-term survival of medial and lateral UKAs. Similarly, patients treated with medial UKA showed no difference in pain relief or functional improvement compared to patients treated with lateral UKA. These results suggest that both UKA techniques are viable treatment options for patients with unicompartmental knee osteoarthritis over long-term follow-up, although further high-quality studies are needed to address some remaining uncertainties regarding the clinical benefits of these procedures.

Background. Results of numerous contemporary studies indicate that medial and lateral unicompartmental knee arthroplasty (UKA) are almost equally effective both in clinical and functional aspects with no statistically significant difference in most cases. Furthermore, both operations tend to reach the effectiveness of total knee arthroplasty (TKA), despite the common opinion that any UKA is a more complex and skill challenging surgery with a less predictable outcome. The purpose — to asses if UKA in the patients with end-stage lateral unicompartmental osteoarthritis is an effective surgical intervention that may allow obtaining good and excellent medium-term functional results, that are comparable to the results of the medial unicompartmental arthroplasty, and to see if there are any benefits in comparison to the total knee arthroplasty (TKA). Materials and Methods. 140 middle-aged and elderly adults with end-stage osteoarthritis underwent knee arthroplasty at Vreden National Medical Research Center of Traumatology and Cheboksary Federal Center of Traumatology, Orthopedics and Arthroplasty. Group I (lateral UKA) (the main ) consisted of 15 patients with knee arthritis and type I Krakow valgus knee deformity, who underwent the lateral UKA with a fixed all-polyethylene tibial component. Group II (medial UKA) included 58 patients with end-stage medial unicompartmental osteoarthritis, who underwent the medial UKA using an endoprosthesis of a similar design. Group III (TKA) was represented by 67 patients with gonarthrosis accompanied by type II Krackow valgus knee deformity, who underwent the total knee arthroplasty with cruciate retaining (CR) prosthesis. The comparison between the groups was carried out regarding the achieved range of motion, functional result (using Oxford Knee Score and Forgotten Joint Score), as well as the rate of different types of complications. Results. During the study, two main objectives were set. The first was to compare the outcomes of the lateral and medial UKA. It was revealed that the lateral UKA allowed the patients to obtain good function of the operated knee, with the best results among the compared groups on the Forgotten Joint Score. The second objective was to compare the results of the lateral UKA and TKA in the patients with type II Krackow knee valgus deformity. Here, our study revealed that the group of UKA (group I) compared to the TKA had better results according to Forgotten Joint Score (71.5±5.3 vs 65.2±7; p = 0.9) and had a slightly lower range of motion according to Oxford Knee Score (34.6±2.3 versus 35.9±2.2; p = 0.7). It is worth noting that in both cases the difference was not statistically significant. Conclusion. Despite the fact that the lateral UKA made it possible to achieve a good functional outcome, the integral score was the same as in the groups with the medial UKA and the total knee arthroplasty. The older patients were more satisfied with the results of the partial arthroplasty than with the results of the total.

Lateral unicompartmental knee arthroplasty (UKA) is relatively less common than medial UKA. There has been no comparative analysis of the constitutional phenotypes of knees that underwent medial and lateral UKA. Therefore, this study aimed to compare the Coronal Plane Alignment of the Knee (CPAK) classification of knees that underwent medial and lateral UKA. Furthermore, the study analyzed whether CPAK phenotypes were maintained or altered after medial or lateral UKA. We retrospectively analyzed consecutive patients who underwent UKA. A radiological analysis was conducted using an EOS imaging system, and demographic data of patients undergoing UKA were collected. Performed measurements included the mechanical hip-knee-ankle angle (mHKA), lateral distal femur angle (LDFA), and medial proximal tibia angle (MPTA), which were analyzed both before and after UKA. The CPAK classification was used to classify knee alignment phenotypes. A total of 310 knees of 244 patients were included in the study that underwent non-robotically assisted, fixed-bearing UKA (279 medial; 31 lateral). Preoperatively, the most common categories for knees were Type I (varus mechanical axis, 53.8%) in medial UKA and Type III (valgus alignment, 77.4%) in lateral UKA. Postoperatively, Type II (neutral mechanical axis) became the most common type for both groups, accounting for 34.1% in the medial UKA group and 25.8% in the lateral UKA group. Only 31.3% preserved their preoperative CPAK classification after the surgery (32.3% and 22.6%, respectively). The CPAK classification differs significantly between knees that underwent medial and lateral UKA. While 31.3% of knees maintained their native knee phenotype, there is a tendency towards a neutrally aligned classification after surgery for both medial and lateral UKA. The CPAK classification optimizes preoperative categorization and may assist surgeons in tailoring personalized therapies to improve clinical outcomes. Level III.

In the last decade, interest in partial knee arthroplasties and bicruciate retaining total knee arthroplasties has increased. In addition, patient-related outcomes and functional results such as range of movement and ambulation may be more promising with less invasive procedures such as bicompartmental arthroplasty (BCA). The purpose of this study is to evaluate clinical and radiological outcomes after a third-generation patellofemoral arthroplasty (PFA) combined with a medial or lateral unicompartmental knee arthroplasty (UKA) at mid- to long-term follow-up. A total of 57 procedures were performed. In 45 cases, a PFA was associated with a medial UKA and, in 12, with a lateral UKA. Patients were followed with validated patient-reported outcome measures (Oxford Knee Score (OKS), EuroQol five-dimension questionnaire (EQ-5D), EuroQoL Visual Analogue Scale (EQ-VAS)), the Knee Society Score (KSS), the Forgotten Joint Score (FJS), and radiological analysis. The mean follow-up was nine years (6 to 13). All scores significantly improved from preoperatively to final follow-up (mean and SD): OKS from 23.2 (8.1) to 42.5 (3.5), EQ-5D from 0.44 (0.25) to 0.815 (0.1), EQ-VAS from 46.7 (24.9) to 89.1 (9.8), KSS (Knee) from 51.4 (8.5) to 94.4 (4.2), and KSS (Function) from 48.7 (5.5) to 88.8 (5.2). The mean FJS at final follow-up was 79.2 (4.2). All failures involved the medial UKA + PFA group. Overall, survival rate was 91.5% for all the combined implants at ten years with 95% confidence intervals and 22 knees at risk. Excellent clinical and radiological outcomes were achieved after a third-generation PFA combined with a medial or lateral UKA. BCA with unlinked partial knee prostheses showed a good survival rate at mid- to long-term follow-up. Cite this article: Bone Joint J2021;103-B(5):840-845.

PurposeIn patients with monocompartmental knee osteoarthritis, unicompartmental knee arthroplasty (UKA) can be performed. This study compared the medial versus lateral UKA in patients with monocompartimental knee arthroplasty. It was hypothesised that both implants achieve a similar outcome in OKS.MethodsThe UKAs were fixed-bearing medial PPK (Zimmer-Biomet, Warsaw, Indiana, USA) and fixed-bearing lateral Zuk (Lima Corporate, Udine, Italy). An intraarticular drain was placed and removed on the first postoperative day. Enoxaparin sodium 4000 units subcutaneously daily for 45 days was used as thromboembolic prophylaxis. The Italian version of the OKS was used for the clinical assessment. The following complications were also recorded: anterior knee pain, infection and revision surgeries.ResultsData from 203 patients were collected. The mean age of the patients was 68.9 ± 6.7 years and the mean BMI was 28.1 ± 4.1 kg/m2. The mean OKS on admission was 22.1 ± 4.5 points. On admission, women, patients older than 70 years, and those with a BMI lower than 28 kg/m2 who underwent lateral UKA evidenced lower OKS. At the last follow-up, 26.7 and 26.9 months for the lateral and medial UKA, respectively, no between groups difference in OKS was evidenced. No patients experienced complications.ConclusionMedial and lateral UKA achieve similar outcomes in OKS at a minimum of two years of follow-up.

Rotational alignment errors can occur in unicompartmental knee arthroplasty if anatomical landmarks are misused: A preoperative CT scan analysis

The aim of this study was to compare the intraoperative kinematics of medial and lateral unicompartmental knee arthroplasty (UKA) with those of the native knee using a navigation system. Six fresh-frozen cadaveric knees were included in the study. Medial UKA was performed in all right knees and lateral UKA was performed in all left knees. All UKA procedures were performed with a computerised navigation system. The tibial internal rotation angle and coronal alignment of the mechanical axis during passive knee flexion were assessed as rotational and varus/valgus kinematics before and after surgery using the navigation system. The rotation angles of the tibia in the early flexion phase of medial UKA were significantly larger than those of native knees (p = 0.008at minimum knee flexion, p = 0.008at 0° knee flexion). The rotational kinematics of lateral UKA was similar to those of the native knees throughout knee flexion. There were no significant differences in varus/valgus kinematics between native and UKA knees. The rotational kinematics of the native knee was not restored after medial UKA but was preserved after lateral UKA. There were no significant differences in the varus/valgus kinematics after either medial or lateral UKA when compared with those of the native knees. Thus, the geometry of the medial tibial articular surface is a determinant of the ability to restore the rotational kinematics of the native knee. Surgeons and implant designers should be aware that the anatomical medial articular geometry is an important factor in restoration of the native knee kinematics after knee arthroplasty.

Different optimal alignment but equivalent functional outcomes in medial and lateral unicompartmental knee arthroplasty

Update This article was updated on February 6, 2019, because of a previous error. On page 105, in the subsection titled “Outcomes and Design” the sentence that had read “Furthermore, in a retrospective review, Houdek et al. 48 , at a mean follow-up of 8 years, demonstrated improved survivorship of 9,999 metal-backed compared with 1,645 all-polyethylene tibial components, over all age groups and most BMI categories” now reads “Furthermore, in a retrospective review, Houdek et al. 48 , at a mean follow-up of 8 years, demonstrated inferior survivorship of 9,999 metal-backed compared with 1,645 all-polyethylene tibial components, over all age groups and most BMI categories.” An erratum has been published: J Bone Joint Surg Am. 2019 Mar 20;101(6):e26.

Annual revision rates of partial versus total knee arthroplasty: A comparative meta-analysis

Image-based robotic tools improve the accuracy of unicompartmental knee arthroplasty (UKA) positioning, but few studies have examined its effect on axial alignment. The aim of this study was to compare the characteristics of tibial and femoral implant positioning, mainly the tibial rotation, during medial or lateral UKA, performed with an image-based robotic assisted system. A total of 71 UKA performed between September 2021 and June 2022 (53 medial and 18 lateral) were analyzed. All data regarding implant positioning (rotation, coronal and sagittal alignment) for tibial and femoral components were obtained using MAKO® software (Stryker®, Mahwah, USA) intra-operatively. The lateral UKA had a mean internal tibial rotation of 15.4 ± 3°, a mean external femoral rotation of 0.96 ± 2.4°, and a mean tibial slope of 4.7 ± 1.3°. The medial UKA had a mean internal tibial rotation of 0.18 ± 2.7°, a mean internal femoral rotation of 0.35 ± 2.2°, and a mean tibial slope of 5.4 ± 1.3°. The tibial rotations, femoral valgus, tibial varus and tibial size significantly differed between medial and lateral UKA (p < 0.05). There was no significant difference in femoral rotation, flexion, femoral size, slope, and polyethylene thickness between medial and lateral UKA. Medial and lateral UKA had significantly different implantation characteristics related to the biomechanics of the knee compartments. Image-based robotic UKA allowed precise femorotibial positioning per-operatively to match native kinematic alignment.

Lateral and Medial Unicompartmental Knee Arthroplasty Have Similar Reoperation Rates, Patient-Reported Outcomes, and Functional Performance in a Two-Year Follow-Up Period.

A Comprehensive Evaluation of Lateral Unicompartmental Knee Arthroplasty Short to Mid-Term Survivorship, and the Effect of Patient and Implant Characteristics: An Analysis of Data From the Dutch Arthroplasty Register