Mobile vs. fixed bearing unicondylar knee arthroplasty: A randomized study on short term clinical outcomes and knee kinematics

doi:10.1016/j.knee.2006.05.003

The Knee

Volume 13, Issue 5, October 2006, Pages 365-370

https://doi.org/10.1016/j.knee.2006.05.003 Get rights and content

Abstract

The literature contains limited yet controversial information regarding whether a fixed or a mobile bearing implant should be used in unicompartmental knee arthroplasty (UKA). This randomized study was to further document the performance and comparison of the two designs.

Fifty-six knees in 48 patients (mean age of 72 years) undergoing medial UKA were randomized into a fixed bearing (Miller/Galante) or a mobile bearing (Oxford) UKA. The 2 year clinical outcomes (clinical scores), radiographic findings, and weight bearing knee kinematics (assessed using RSA) were compared between the two groups.

The mobile bearing knees displayed a larger and an incrementally increased tibial internal rotation (4.3°, 7.6°, 9.5° vs. 3.0°, 3.0°, 4.2° respectively at 30°, 60°, 90° of knee flexion) compared to the fixed ones. The medial femoral condyle in the mobile bearing knees remained 2 mm from the initial position vs. a 4.2 mm anterior translation in the fixed bearing knees during knee flexion. The contact point in the mobile bearing implant moved 2 mm posteriorly vs. a 6 mm anterior movement in the other group. The mobile bearing knees had a lower incidence of radiolucency at the bone implant interface (8% vs. 37%, p < 0.05). The incidence of lateral compartment OA and progression of OA at patello–femoral joint were equal. No differences were found regarding Knee Society Scores, WOMAC, and SF-36 scores (p > 0.05). This study indicates that mobile bearing knees had a better kinematics, a lower incidence of radiolucency but not yet a better knee function at 2 years.

Introduction

The clinical results of unicondylar knee arthroplasty (UKA) have improved significantly over the past 30 years thanks to improved implant designs, new materials, advances in surgical techniques and proper patient selection. Recent studies have shown that 10-year survivorship of above 90% has been achieved [1], [2], [3], [4]. UKA has been regarded as a reliable procedure in the treatment of unicompartmental osteoarthritis.

However, whether a fixed or a mobile miniscal bearing UKA should be used is still controversial. Direct comparison has been made in several studies [5], [6], [7], however, the reported results have been variable. While Emerson [5] found a better component survivorship in the mobile bearing UKAs, Gleeson [6] revealed that patients receiving a fixed bearing UKA had better knee function and pain relief. Yet in another study by Confalonieri [7], no significant difference in clinical outcomes was found.

This randomized prospective study was conducted to further document the comparison between fixed and mobile bearing UKAs. We focused on knee kinematics, development of radiolucencies at the tibial component and clinical outcomes two years after the surgery. Our hypothesis was that the mobile bearing prosthesis generates closer to normal knee kinematics and therefore has a better functional outcome as well as improved tibial component fixation.

Section snippets

Patient recruitment

Between May 2001 to June 2003, 56 knees in 48 patients (34 male, 14 female, mean age of 72 years) undergoing unicompartmental knee arthroplasty for medial compartmental osteoarthritis (OA) were randomized into a fixed (Miller/Galante, Zimmer, Warsaw, USA) or a mobile meniscal bearing (Oxford, Biomet, UK) knee prosthesis. The inclusion criteria followed those outlined by Kozinn and Scott [8]: Noninflammatory osteoarthritis of the medical compartment, a mechanical axis deformity < 10° varus or 5°

Kinematic analysis

Knee kinematics was evaluated for the first 22 knees (11 fixed and 11 mobile bearing knees) at 2 years postoperative. The reason to have 22 knees examined for kinematics was due to a power calculation of detecting a 0.3 mm difference in translation and 3° difference in rotation with a power of 80% at 0.05 significant level. Kinematics assessment was conducted with the patients standing on the examined leg performing knee flexion of 0°, 30°, 60°, 90°. Radiographs were taken respectively at each

Missing data

Two mobile bearing knees were revised before 2 years: one for early infection and another for aseptic loosening of the tibial component. Two patients with three UKA (one mobile and two fixed bearings) died of unrelated courses before 2 year follow-up. While the basic information including age, gender, BMI was presented for these four patients (Table 1), they were excluded from the comparisons of 2 year results.

Statistics

Statistics was performed using SPSS. Mann–Whitney U-tests or Chi-square test were used to compare the two groups regarding patient demographics, radiographic assessment and clinical outcomes. ANOVA were used to compare the overall differences in kinematics between the two groups. Differences at each knee flexion position were also compared using Mann–Whitney U-tests. A p < 0.05 was regarded as statistically significant.

Kinematics

The mobile bearing knees showed a larger and an incremental increase in tibial internal rotation than the fixed bearing knees (4.3°, 7.6°, 9.5° vs. 3.0°, 3.0°, 4.2°, respectively, at 30°, 60°, 90° of knee flexion) (Fig. 3), with significant difference at 90° (Mann–Whitney U-test, p = 0.043). The medial femoral condyle in the mobile bearing knees remained 2 mm from the initial position in relation to the tibia during knee flexion, whereas it moved 4.2 mm anteriorly from the initial position in the

Discussion

Knee joint kinematics has been used as an indicator to evaluate the performance of the replaced joint after knee joint arthroplasty [11], [12], [13]. While it is still not clear if the restoration of normal knee kinematics is possible or necessary in knee joint arthroplasties, mimicking a normal knee function after joint arthroplasties may be expected to ensure a lasting and good functioning joint [12]. Normal knee kinematics during knee flexion is characterized as 5–10° tibial internal

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Cited by (104)

Unicompartmental Knee Arthroplasty vs Total Knee Arthroplasty: A Risk-adjusted Comparison of 30-day Outcomes Using National Data From 2014 to 2018
2022, Arthroplasty Today
When clinically indicated, the choice of performing a total knee arthroplasty (TKA) vs a unicompartmental knee arthroplasty (UKA) is dictated by patient and surgeon preferences. Increased understanding of surgical morbidity may enhance this shared decision-making process. This study compared 30-day risk-adjusted outcomes in TKA vs UKA using a national database.
We analyzed data from the National Safety and Quality Improvement Program database, for patients who received TKA or UKA between 2014-2018. The main outcomes were blood transfusion, operation time, length of stay, major complication, minor complication, unplanned reoperation, and readmission. Comparisons of odds of the outcomes of interest between TKA and UKA patients were analyzed using multivariate regression models accounting for confounders.
We identified 274,411 eligible patients, of whom 265,519 (96.7%) underwent TKA, while 8892 (3.3%) underwent UKA. Risk-adjusted models that compared perioperative and postoperative outcomes of TKA and UKA showed that the odds of complications such as blood transfusion (adjusted odds ratio [aOR], 19.74; 95% confidence interval [CI]: 8.19-47.60), major (aOR, 1.87; 95% CI: 1.27-2.77) and minor complications (aOR, 1.43; 95% CI: 1.14-1.79), and readmission (aOR, 1.41; 95% CI: 1.16-1.72) were significantly higher among patients who received TKA than among those who received UKA. In addition, operation time (aOR, 7.72; 95% CI: 6.72-8.72) and hospital length of stay (aOR, 1.11; 95% CI: 1.05-1.17) were also higher among the TKA recipients compared to those who received UKA.
UKA is associated with lower rates of adverse perioperative outcomes compared to TKA. Clinical indications and surgical morbidity should be considered in the shared-decision process
A Morphometric Fixed-Bearing Unicompartmental Knee Arthroplasty Can Reproduce Normal Knee Kinematics. An In Vitro Robotic Evaluation
2022, Arthroplasty Today
A new morphometric fixed-bearing unicompartmental knee arthroplasty (UKA) system has been introduced to address the anatomical patient-specific challenges. It was our hypothesis that accurate restoration of the patient-specific anatomy would restore normal knee kinematics after UKA. Therefore, we aimed in this cadaveric study to analyze the impact of a medial morphometric UKA on (1) the varus-valgus and anterior-posterior stability of the knee, (2) the knee kinematics during standardized activities of the daily living, and (3) the patellar tracking, measured using a dedicated robotic testing protocol.
Eight human knee specimens underwent full-leg computed tomography CT scanning and comprehensive robotic assessments of tibiofemoral and patellofemoral kinematics. Specimens were tested in the intact state and after implantation of a fixed-bearing medial UKA. Assessments included passive flexion, laxity testing and simulations of level walking, lunge, and stair descent.
Medial and lateral joint laxity after UKA closely resembled intact laxity across the full arc of flexion. Anterior-posterior envelope of motion showed a close match between the intact and UKA groups. Net rollback and average laxity were both not statistically different. Simulation of activities of daily living showed a close match in the anterior-posterior motion profile between the medial condyle and lateral condyle. Patellar tilt and medial-lateral shift during knee flexion matched closely between groups.
Functional assessment of this UKA system shows nearly identical behavior to the intact knee. Fixed-bearing UKA with morphometric, compartment-specific geometry and precise mechanical instrumentation replicates complex knee balance and kinematics.
Rapidly progressive osteoarthritis in the medial patellar facet due to lateral femoral placement after medial unicompartmental knee arthroplasty. A case report
2021, International Journal of Surgery Case Reports
Factors that affect patellofemoral (PF) osteoarthritis (OA) after unicompartmental knee arthroplasty (UKA) remain unclear. We report a case in which the lateral placement of the femoral component resulted in rapidly progressive OA in the medial patellar facet.
The patient was an 84-year-old woman who had increased pain in the left knee due to varus knee OA for 1 year and underwent medial UKA. One month after the surgery, the patient complained of limited knee flexion of 90° with anterior knee pain, and around 7-mm lateral placement of the femoral component was observed on a postoperative radiograph and computed tomography scan. Six months after the surgery, rapidly progressive OA with subchondral bone depression in the medial facet was observed and this has been ongoing till the last follow-up of 3 years. The knee flexion is limited 105° now, and the patient complains of quadriceps weakness with anterior knee pain when stair-climbing and standing up from a chair.
Lateral placement of the femoral component in medial UKA may cause progressive PF OA with limited knee flexion and anterior knee pain, which could be attributed to impingement between the femoral component and the medial patellar facet.
Surgeons should be careful regarding the lateral placement to prevent symptomatic PF OA from occurring after medial UKA.
Component positioning of the first 300 mobile bearing unicompartmental knee arthroplasties
2021, Journal of Orthopaedics
The Oxford® Partial Knee has excellent long-term survivorship but high surgical times indicate a learn curve. This retrospective review included a radiographic evaluation of component placement of the initial 300 procedures following conversion from fixed bearing implant use. The anteroposterior and sagittal femoral angles were considered inaccurate in 1.7% and 3.9% of cases, respectively. The anteroposterior and sagittal tibial angles were considered inaccurate in 18.7% and 6.0% of cases, respectively. Overall, a learning curve appears to be present regarding the anteroposterior tibial component angle, with the greatest percentage of inaccuracies occurring within the initial 20 cases.
Ten-Year Results of Unicompartmental Knee Arthroplasty in Patients With Psychological Distress
2020, Journal of Arthroplasty
Although the influence of psychological distress on the outcomes of total knee arthroplasty has been described extensively, its effect on unicompartmental knee arthroplasty (UKA) is poorly defined. Furthermore, most studies in arthroplasty literature had short follow-ups of ≤1 year. We investigated the influence of psychological distress on long-term patient-reported outcomes and analyzed the change in mental health after UKA in a cohort with minimum 10 years of follow-up.
Prospectively collected data of 269 patients undergoing UKA in 2004-2007 were reviewed. Patients were stratified into those with psychological distress (36-item Short-Form health survey [SF-36] Mental Component Summary [MCS] <50, n = 111) and those without (SF-36 MCS ≥50, n = 158). Clinical outcomes were obtained preoperatively, at 2 years, and 10 years. Multiple regression was used to control for age, gender, body mass index, Charlson Comorbidity Index, American Society of Anesthesiologists class, and baseline scores. The rate of expectation fulfillment and satisfaction was compared.
Psychologically distressed patients had poorer Knee Society Knee Score, Function Score, Oxford Knee Score, and SF-36 Physical Component Summary preoperatively, at 2 years, and 10 years. However, an equal proportion in each group attained the minimal clinically important difference for each score. Distressed patients had a comparable rate of satisfaction (91% vs 95%, P = .136) but lower fulfillment of expectations (89% vs 95%, P = .048). The percentage of distressed patients declined from 41% to 35% at follow-up. The mean SF-36 MCS improved by 6.9 points.
Although psychologically distressed patients had relatively greater pain and poorer function preoperatively and up to 10 years after UKA, a similar proportion of them experienced a clinically meaningful improvement in patient-reported outcomes.
In vivo kinematic comparison before and after mobile-bearing unicompartmental knee arthroplasty during high-flexion activities
2020, Knee
Many patients who undergo unicompartmental knee arthroplasty (UKA) have an expectation that their knee flexion would increase following its replacement. Additionally, the survival rate of mobile-bearing UKA (MB-UKA) is high. However, the effect on the patient's kinematics remains unknown. This study aimed to clarify the kinematic effect of MB-UKA knees during high-flexion activities by comparing the in vivo kinematics before and after surgery.
A squatting motion was performed under fluoroscopic surveillance in the sagittal plane before and after MB-UKA. To estimate the spatial position and orientation of the knee, a two-dimensional/three-dimensional registration technique was used. The femoral rotation and varus–valgus angle relative to the tibia and anteroposterior (AP) translation of the medial and lateral side of the femur on the plane perpendicular to the tibial mechanical axis in each flexion angle were evaluated.
Regarding the varus–valgus angle, the preoperative knees indicated a significant varus alignment compared with the postoperative knees from 10° to 60° of flexion. There were no significant differences in the femoral rotation angle, AP translation, and kinematic pathway before and after MB-UKA in the mid-flexion of the range of motion.
There were differences between the varus–valgus knee kinematics before and after MB-UKA, from 10 to 60° of flexion, but no difference from midrange of flexion to deep flexion. In addition, the rotational knee kinematics before and after MB-UKA was not significantly different.

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Mobile vs. fixed bearing unicondylar knee arthroplasty: A randomized study on short term clinical outcomes and knee kinematics

Abstract

Introduction

Section snippets

Patient recruitment

Kinematic analysis

Missing data

Statistics

Kinematics

Discussion

Knee

Knee

J Orthop Sci

J Arthroplasty

J Arthroplasty

The Oxford medial unicompartmental arthroplasty: a ten-year survival study

J Bone Joint Surg Br

Oxford medial unicompartmental knee arthroplasty. A survival analysis of an independent series

J Bone Joint Surg Br

Results of unicompartmental knee arthroplasty at a minimum of ten years of follow-up

J Bone Joint Surg Am

Long-term clinical results of the medial Oxford unicompartmental knee arthroplasty

Clin Orthop

Comparison of a mobile with a fixed bearing unicompartmental knee implant

Clin Orthop

Unycondilar knee arthroplasty

J Bone Joint Surg Br