Favorable early outcomes of medial unicompartimental knee arthroplasty in active patients presenting a degenerative medial meniscus root tear with meniscal extrusion and mild radiographic osteoarthritis

Medial fixed-bearing unicompartmental knee arthroplasty in patients with or without patellofemoral osteoarthritis: is there any difference in clinical outcomes?

PURPOSE

Patients with indication for medial UKA may present with some degree of patellofemoral joint degeneration. The main purpose of this study was to identify the impact of patellofemoral osteoarthritis (PFOA) on the clinical outcomes of medial fixed-bearing UKA.

METHODS

A retrospective cohort study evaluating the clinical outcomes of medial UKA in patients with isolated medial OA, with or without patellofemoral involvement. Data collected included demographic information, pain analog scale scores, range of motion (ROM), KOOS and Oxford Knee Score, and knee radiographs.

RESULTS

The statistical analysis included 112 patients. The average follow-up was 34.1 months. One patient in the non-PFOA group presented with deep vein thrombosis. No difference was found between groups regarding PROMs, OKS, Pain or KOOS. Postoperative range of motion values in Groups A and B were, respectively, 114.5 ± 2.4 and 112.5 ± 3.6 (p = 0.39). Postoperative Oxford Knee Scale in Groups A and B were, respectively, 40.2 ± 2.0 and 40.5 ± 2.5 (p = 0.86). Pain scale reduction in Groups A and B were, respectively, 5 ± 2.1 and 5.0 ± 2.6 (p = 0.17). Postoperative KOSS values in Groups A and B were, respectively, 80.6 ± 2.5 and 82.5 ± 3.0 (p = 0.45).

CONCLUSION

UKA is a good option for medial isolated tibiofemoral osteoarthritis in patients without PFOA (Iwano's Grade 1) or with asymptomatic PFOA (Iwano's Grade 2 and 3). Improvements in pain, Oxford Knee Score and KOOS were observed without differences between groups.

Medial meniscus posterior root tears with advanced osteoarthritis or subchondral insufficiency fracture are good indications for unicompartmental knee arthroplasty at a minimum 2-year follow-up

INTRODUCTION

The outcomes of unicompartmental knee arthroplasty (UKA) in the presence and absence of medial meniscus posterior root tears (MMPRTs) have not been compared. This study compared the characteristics and clinical outcomes of patients undergoing UKA with and without MMPRTs.

MATERIALS AND METHODS

This study analyzed 68 patients. The presence or absence of MMPRTs was evaluated using preoperative magnetic resonance imaging. Patient characteristics, clinical scores before surgery and at the final evaluation, and imaging findings were compared between patients with and without MMPRTs. Multiple regression analysis was conducted on postoperative visual analog scale (VAS)-pain scores.

RESULTS

MMPRTs were present in 64.7% (44/68) of patients. Patients with MMPRTs were significantly younger (67.8 ± 8.2 vs. 75.0 ± 7.1 years, p < 0.001) and had a shorter duration from the development of symptoms to the time of surgery than those without (6.8 ± 8.4 vs. 36.1 ± 38.9 months, p < 0.001). Component placement or lower-limb alignment did not significantly differ between the groups. Preoperative clinical scores were not significantly different between the groups; however, patients with MMPRTs showed significantly better postoperative VAS-pain scores than those without (10.0 ± 9.0 vs. 28.2 ± 26.0 points, p = 0.026). Multiple regression analysis of postoperative VAS-pain scores revealed the significant effect of duration from the development of symptoms to the time of surgery (p = 0.038).

CONCLUSIONS

Patients undergoing UKA with MMPRTs were younger with less radiographic osteoarthritic changes compared to those without MMPRTs, and their postoperative VAS-pain scores were significantly superior. The duration from the development of symptoms to the time of surgery significantly influenced postoperative pain in patients undergoing UKA.

Biomechanical impact of progressive meniscal extrusion on the knee joint: a finite element analysis

BACKGROUND

While measuring meniscal extrusion quantitatively is an early risk factor for knee osteoarthritis (KOA), the biomechanics involved in this process are not well understood. This study aimed to investigate the effects of varying degrees of medial and lateral meniscal extrusion and their material softening on knee osteoarthritis progression.

METHODS

Finite element analysis (FEA) was utilized to simulate varying degrees of meniscal extrusion (1-5 mm) in 72 knee joint models, representing progressive meniscal degeneration and material softening due to injury. Changes in von Mises stress of the cartilage and menisci and the load distribution on the tibial plateau's meniscus and cartilage were studied under balanced standing posture in both healthy and injured knees, and statistical analysis was performed using Spearman correlation.

RESULTS

Compared to healthy knees, peak stress in medial compartment tissues increased by over 40% with 4 mm of medial meniscus extrusion, and in lateral compartment tissues with 2 mm of lateral meniscus extrusion. Meniscus extrusion reduced the contact load between the meniscus and femoral cartilage but increased it between the tibial and femoral cartilages, with a maximum increase up to fivefold. Spearman correlation analysis indicated that meniscal extrusion significantly affected peak stress and contact loads in the respective knee compartment (p < 0.001), with a lesser impact on the opposite compartment. Notably, medial meniscal extrusion also significantly increased peak stress in the lateral tibial cartilage (p < 0.05).

CONCLUSIONS

The quantitative analysis revealed that meniscal extrusion significantly affected the biomechanics of soft tissues within the same compartment, with limited impact on the opposite side. Specifically, Medial extrusion beyond 4 mm significantly affected the biomechanics of the medial compartment, while lateral extrusion over 2 mm had a similar impact on the lateral compartment. Meniscal softening, without altering joint contact characteristics, primarily affected the biomechanics of the meniscus itself, with minimal impact on other soft tissues.

[Evolving indications for partial knee replacement : New aspects]

BACKGROUND

Partial knee replacement has proven to be an effective therapy for advanced unicompartmental arthrosis of the knee. Despite continuous advancements in implants and surgical techniques over the past decades, the global preference for total knee arthroplasty still persists for historical reasons.

OBJECTIVES

This report aims to illuminate advantages and disadvantages of partial knee replacement considering long-term results, the evolution of indication criteria over recent decades and new aspects in patient selection with potential improvements through emerging technologies.

MATERIAL AND METHODS

The analysis involves the examination of long-term results from clinical studies and registry data, highlighting the risk factors for potential failures and their influence on the development of indication criteria.

RESULTS

Present-day long-term results demonstrate excellent prosthetic survival, aligning with outcomes from total knee arthroplasty. New perspectives for expanding indication criteria are discussed, including the possible application of partial knee replacement in cases of severe varus deformity > 15°, anterior cruciate ligament insufficiency, young active patients, anterior knee pain, and/or patellofemoral arthritis, as well as mild radiographic arthritis with degenerative medial meniscus root tear and meniscal extrusion.

DISCUSSION

Indication criteria have consistently expanded in recent years, taking into account modern insights, and the application of advanced technologies can enhance precision and minimize surgical errors. Furthermore, this report emphasizes that revision rates are not the sole criterion for success and underscores the necessity for a comprehensive examination of clinical results.