Medial pivot prosthesis has a better functional score and lower complication rate than posterior-stabilized prosthesis: a systematic review and meta-analysis

Medial Pivot prostheses generate less noise than mobile bearing and cruciate retaining total knee arthroplasties

PURPOSE

After total knee arthroplasty (TKA), patients may experience noise generated by their replaced knee. This study aimed to assess the impact of prosthesis design on noise generation.

METHOD

This single centre comparative retrospective study was conducted including 200 patients who underwent a TKA between 2020 and 2022 with a minimum of 2 years of follow-up. The SKV, IKS, satisfaction score and Kuriyama questionnaires were completed. Three prosthesis designs were assessed: Medial Pivot (MP) - Microport®, Mobile Bearing (MB) - Amplitude® and Cruciate Retaining (CR) - Stryker®.

RESULTS

The MP design generated less noise than the MB or CR design. In the MP group, 74.5% of patients did not describe any noise compared to 61.4% for the MB group and 62.1% for the CR group. The rate of patients experiencing noise from their prosthesis was 32%. The majority of patients were very satisfied (68%) or satisfied (24%) with their surgery. Patients who had a silent prosthesis were more satisfied than those who had a prosthesis that generated noise, with a greater proportion of patients in the satisfied/very satisfied group (93% versus 84%); p = 0.02. The average SKV score was 81.8 (± 4.7) in the silent group versus 75 (± 4.6) in the noise group (NS). The functional difference (IKS function score) between the two groups was not statistically significant (36 (± 2.5); 34.6 (± 3.4) vs. p = 0.12).

CONCLUSION

The MP design generates less noise than MB and CR at two years of follow-up after a TKA.

LEVEL OF EVIDENCE III

Retrospective comparative study.

Posterior Cruciate Ligament Preservation versus Posterior Cruciate Ligament Sacrifice: Comparing Patient Outcomes in Medial Congruent Total Knee Arthroplasty

This study aimed to compare outcomes and complication rates between posterior cruciate ligament (PCL) retention and excision utilizing a medial congruent (MC) polyethylene insert in total knee arthroplasty (TKA) in a specialized ambulatory surgery center (ASC) dedicated to hip and knee arthroplasty. A retrospective review was performed between May 2023 and October 2023 analyzing 398 patients who underwent primary MC TKA by high-volume joint arthroplasty surgeons (n = 9) with either PCL preservation (n = 264) or sacrifice (n = 134) in a single free-standing ASC. Patients were matched chronologically on a 2:1 basis. Demographics, baseline function, 90-day complications, and patient-reported outcomes were recorded for each patient. There were no differences in preoperative baseline function or patient-reported outcome measures, Charlson Comorbidity Index, or American Society of Anesthesiologists class among patient groups. The PCL-preserve and PCL-sacrifice cohorts showed significant variation in 12-week postoperative Knee Injury and Osteoarthritis Outcome, Junior (KOOS, JR.) scores. Specifically, the number of patients who achieved the minimal clinically important difference (MCID) in KOOS, JR. scores was higher in the PCL-sacrifice group (p < 0.05). Yet, no complications within the 90-day period were associated with PCL status and other patient-reported outcomes. This study comparing outcomes between MC TKAs with PCL retention and sacrifice suggests that both techniques are viable options with similar functional outcomes, pain scores, and complication rates, which may have benefits in an ASC setting. The PCL-sacrifice group exhibited a statistically significant increase in patients who achieved the MCID in KOOS, JR. score compared with the PCL-preserving at early follow-up. Future research should employ prospective, randomized designs to further validate these findings and explore long-term implications.

Medial and lateral knee contact forces and muscle forces during sit-to-stand in patients one year after unilateral total knee arthroplasty

Understanding how forces are transmitted through the knee after TKA is essential, as it may explain why many patients experience pain or functional limitations during various activities. This study compared knee muscle forces and knee contact forces (KCF) during sit-to-stand in patients one year after unilateral total knee arthroplasty (TKA) with either a medial ball-and-socket (MBS) or posterior stabilized (PS) implant and compared them to a group of similarly healthy aged controls (CTRL). A musculoskeletal model and static optimization estimated lower limb kinematics, knee kinetics, muscle forces, and KCFs. The normalized sit-to-stand cycle was compared among the groups using statistical nonparametric mapping, and peak between-limb differences were compared using discrete statistics. The PS group required greater forward lean during the sit-to-stand task, causing greater spine flexion, posterior pelvic tilt, and decreased hip flexion on the operated limb. PS and MBS groups favoured their non-operated limb, resulting in less range of motion throughout the lower limb, lower knee kinetics, muscle forces, and KCFs on the operated limb. Compared to the controls, the MBS and PS groups had reduced medial compartment KCF. The control group did favour their dominant limb over their non-dominant limb. Post-operative rehabilitation should continue to promote greater use of the operated knee to have more symmetrical loading between operated and non-operated limbs and improve strength and mobility at the hip and ankle joints. One year after surgery, TKA patients remain with reduced muscle forces and KCF on their operated limb during a sit-to-stand task, regardless whether they received an MBS or PS implant.

Performance of medial pivot, posterior stabilized and rotating platform total knee arthroplasty based on anteroposterior stability and patient-reported outcome measures; a multicentre double-blinded randomized controlled trial of 210 knees

BACKGROUND

Despite advancements in total knee arthroplasty (TKA), 10-20% of patients remain dissatisfied after surgery. Improved anteroposterior (AP) stability provided by medial pivot (MP) implants may theoretically lead to higher patient satisfaction.

METHODS

AP stability and patient-reported outcome measures (PROMs) at one-year postsurgery were compared between patients who underwent TKA with MP- (n = 121), posterior stabilized (PS; n = 53) and rotating platform (RP; n = 57) implants in a double-blind multicentre randomized controlled trial (Dutch Trial Register: NL6856, 21-02-2018). AP stability was assessed at 30°, 60° and 90° of knee flexion using a KT-2000 arthrometer. PROMs were measured preoperative and one-year postsurgery.

RESULTS

MP-TKA provided significant better AP stability at early flexion (30°) compared to PS- and RP-TKA (median [IQR]; 1.79 [1.14-2.77] mm vs. 3.31 [2.51-4.08] mm vs. 2.82 [1.80-4.03] mm, p < 0.001). Additionally, MP-TKA provided significant better AP stability at mid-flexion (60°) compared to PS-TKA (1.75 [1.23-2.36] mm vs. 2.14 [1.49-2.83] mm, p = 0.014). PROM improvements were comparable between implant designs. AP laxity of ≥ 4 mm at early flexion was independently of implant design associated with significantly worse Kujala scores. The incidence of ≥ 4 mm AP laxity at any knee angle was however not significantly different between implant designs.

CONCLUSION

MP-, PS- and RP-TKA all provide excellent and comparable results. Although MP-TKA provided better AP stability at early flexion compared to PS- and RP-TKA, this was found to be unrelated to improved PROMs in favour of MP-TKA. More studies focusing on early and mid-flexion performance based differences between MP and other TKA designs are required to confirm our findings. Other non-implant related factors may play a more important role in the performance of TKA and are potentially worthwhile examining.

A commentary on 'Clinical evaluation of the first semi-active total knee arthroplasty assisting robot made in China: a retrospective propensity score-matched cohort study'

We were highly interested in the article entitled 'Clinical evaluation of the first semi-active total knee arthroplasty assisting robot made in China: a retrospective propensity score-matched cohort study' by Yang et al. The authors aim to conduct the postoperative prosthesis position and clinical functions of the semi-active total knee arthroplasty assisting robot (RATKA) using a 1:2 propensity score matching. However, we came across what we believed were flaws in the study methodology and results about the prothesis and tourniquet, and we would like to discuss them with the authors in conjunction with our own research.

PCL retention demonstrates better functional scores and gait patterns in total knee arthroplasty using a medial congruent insert-a prospective study

PURPOSE

Despite Total Knee Arthroplasty (TKA) being one of the most successful procedures for end stage arthritis, nearly 20% of patients undergoing this procedure remain dissatisfied. Various design options have been introduced to reduce this cohort of patients. One such option has been the introduction of the medial congruent (MC) polyethylene design. This study was undertaken to evaluate outcome measures and gait analysis in patients undergoing bilateral single stage TKA where the posterior cruciate ligament (PCL) was retained or excised in contralateral knees.

METHODS

60 bilateral TKA's were performed by a single surgeon using a MC design option from July to Sep 2021. The study lots included patients between the ages of 55 and 70 years with fixed varus deformity of degenerative aetiology, and Kellgren Lawrence Grade 3 and 4 radiological changes. Exclusion criteria were previous surgery to the lower extremities, sero positive arthropathies, post traumatic arthritis, valgus deformity, flexion contractures > 20°, and any pre-existing pathology impacting gait, e.g., poliomyelitis, or neuromuscular disorders. The PCL was retained or sacrificed on contralateral sides for the purpose of this study. Functional scores, outcomes and gait analysis on level and gradient walking were evaluated at a follow-up of 18 months.

RESULTS

At 18, months the Range of Motion (ROM) improved from a preoperative value of 97.3 ± 11.5 to 110.3 ± 6.1 on the PCL retained side (MC-PCL) and from 96.5 ± 10.8 to 113 ± 5.8 on the PCL excised side (MC-PCLX). Knee Society Score (KSS-2011) improved from a preoperative value of 21.2 ± 4.5 to 89.8 ± 3.4 at 18 months postoperatively on the MC-PCL side and from 21.5 ± 4 to 88.2 ± 3.7 on the MC-PCLX side. Forgotten Joint Score (FJS-12) was 8.8 ± 0.7 on the MC-PCL side and 8.1 ± 0.9 on the MC-PCLX side 18 months after surgery. Our gait analysis evaluation demonstrated a lower forefoot pressure in the MC-PCL group in comparison to the MC-PCLX group when subjects were made to walk on a 30° upward incline. This difference was found to be statistically significant.

CONCLUSION

In this study, while ROM was greater in the MC-PCLX study lot, patient satisfaction was higher in the MC-PCL study lot. Gait assessment demonstrated lower forefoot pressure while ascending an incline of 30° in the MC-PCL study lot as compared to the MC-PCLX study lot approximating normal gait patterns.

LEVEL OF EVIDENCE

II.

Larger Medial Contact Area and More Anterior Contact Position in Medial-Pivot than Posterior-Stabilized Total Knee Arthroplasty during In-Vivo Lunge Activity

This study aimed to compare the in-vivo kinematics and articular contact status between medial-pivot total knee arthroplasty (MP-TKA) and posterior stabilized (PS) TKA during weight-bearing single-leg lunge. 16 MP-TKA and 12 PS-TKA patients performed bilateral single-leg lunges under dual fluoroscopy surveillance to determine the in-vivo six degrees-of-freedom knee kinematics. The closest point between the surface models of the femoral condyle and the polyethylene insert was used to determine the contact position and area. The nonparametric statistics analysis was performed to test the symmetry of the kinematics between MP-TKA and PS-TKA. PS-TKA demonstrated a significantly greater range of AP translation than MP-TKA during high flexion (p = 0.0002). Both groups showed a significantly greater range of lateral compartment posterior translation with medial pivot rotation. The contact points of PS-TKA were located significantly more posterior than MP-TKA in both medial (10°–100°) and lateral (5°–40°, 55°–100°) compartments (p < 0.0500). MP-TKA had a significantly larger contact area in the medial compartment than in the lateral compartment. In contrast, no significant differences were observed in PS-TKA. The present study revealed no significant differences in clinical outcomes between the MP and PS groups. The PS-TKA demonstrated significantly more posterior translations than MP-TKA at high flexion. The contact points are located more posteriorly in PS-TKA compared with MP-TKA. A larger contact area and medial pivot pattern during high flexion in MP-TKA indicated that MP-TKA provides enhanced medial pivot rotation.