Patellofemoral knee pain following total knee arthroplasty. Comparison between adjusted mechanical and inverse restricted kinematic alignment

Mechanical versus kinematic alignment for total knee arthroplasty: a meta-analysis

INTRODUCTION

The present meta-analysis compared mechanical versus kinematic alignment in total knee arthroplasty (TKA). The outcomes of interest were patient-reported outcome measures (PROMs), range of motion (ROM), and revision rate.

METHODS

This study was conducted according to the 2020 PRISMA statement. In July 2024, PubMed, Web of Science, Google Scholar, and Embase were accessed without time constraints. All the clinical studies that compared mechanical versus kinematic alignment in total knee arthroplasty were accessed.

RESULTS

30 studies (3133 TKAs) were collected. The mean duration of the follow-up was 30.8 ± 38 months. No difference was found in Knee KSS-F, Knee Society Score (KSS, P = 0.2) and its function subscale (P = 0.3), visual analogue scale (VAS, P = 0.3), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC, P = 0.2), Oxford Knee Score (OKS, P = 0.5). No difference was found in the rate of revision (P = 0.4). The ROM was slightly greater in the kinematic group (P < 0.0001).

CONCLUSION

PROMs and revision did not show a difference between mechanical and kinematic alignment in TKA. However, a minimal difference in the ROM was evidenced, which probably does not have clinical relevance.

LEVEL OF EVIDENCE

Level IV, systematic review and meta-analysis.

Conventionally instrumented inverse kinematic alignment for total knee arthroplasty: How is it done?

Purpose

For primary total knee arthroplasty (TKA), there is an increasing trend towards patient-specific alignment strategies such as kinematic alignment (KA) and inverse kinematic alignment (iKA), which by restoring native joint mechanics may yield higher patient satisfaction rates. Second, the most recent Australian joint registry report describes favourable revision rates for conventionally instrumented TKA compared to technology-assisted techniques such as those using navigation, robotics or custom-cutting blocks. The aim of this technique article is to describe in detail a surgical technique for TKA that: (1) utilises the principles of iKA and (2) uses conventionally instrumented guided resections thereby avoiding the use of navigation, robotics or custom blocks.

Methods

A TKA technique is described, whereby inverse kinematic principles are utilised and patient-specific alignment is achieved. Additionally, the patellofemoral compartment of the knee is restored to the native patellofemoral joint line. The sequenced technical note provided may be utilised for cemented or cementless components; cruciate retaining or sacrificing designs and for fixed or rotating platforms.

Results

An uncomplicated, robust and reproducible technique for TKA is described.

Discussion

Knee arthroplasty surgeons may wish to harness the emerging benefits of both a conventionally instrumented technique and a patient-specific alignment strategy.

Level of Evidence

Level V.

Current concept: personalized alignment total knee arthroplasty as a contrast to classical mechanical alignment total knee arthroplasty

Mechanical alignment (MA) total knee arthroplasty (TKA), with neutral leg alignment, mechanical component alignment, and parallel gaps, has achieved good long-term survival. Patient satisfaction, however, is not always perfect. In contrast to the MA, which aims for an ideal goal for all patients, an alternative has been proposed: kinematic alignment (KA)-TKA. In KA, the articular surface is replicated using components aligning with the three kinematic axes. KA-TKA has been gaining popularity, and in addition to the true or calipered KA, various derivatives, such as restricted KA, soft-tissue respecting KA, and functional alignments, have been introduced. Moreover, the functional approach encompasses several sub-approaches. This somewhat complicated scenario has led to some confusion. Therefore, the terminology needs to be re-organized. The term "personalized alignment (PA)" has been used in contrast to the MA approach, including all approaches other than MA. The term "PA-TKA" should be used comprehensively instead of KA and it represents the recent trends in distinct and unique consideration of each individual case. In addition to a comparison between MA and KA, we suggest that evaluation should be conducted to decide which approach is the best for an individual patient within the "personalized alignment" concept.

Functional alignment in robotic-assisted total knee arthroplasty: a systematic review

PURPOSE

The present study systematically reviewed current evidence on functional alignment (FA) in robotic total knee arthroplasty (TKA), discussing advantages and limitations, possible pitfalls, and prospects.

METHODS

This study was conducted according to the 2020 PRISMA statement. In August 2023, the following databases were accessed: PubMed, Web of Science, Google Scholar, and Embase with no additional filters or time constraints. All the clinical studies investigating functional alignment in robotic TKA were accessed. Only studies published in peer-reviewed journals were considered. The risk of bias was evaluated following the guidelines in the Cochrane Handbook for Systematic Reviews of Interventions. Non-randomized controlled trials (non-RCTs) were evaluated using the Risk of Bias in Nonrandomised Studies of Interventions (NRSI) (ROBINS-I) tool.

RESULTS

Data from 1198 patients (seven studies) were retrieved. The mean length of the follow-up was 17.1 ± 6.4 months. The mean age was 67.2 ± 5.4 years, and the mean BMI was 30.9 ± 2.7 kg/m2.

CONCLUSION

FA might improve resection accuracy, implant alignment, and gap balancing in TKA, and additional high-quality clinical trials are necessary to properly establish the superiority of FA to other alignment techniques in TKA. Long-term clinical trials are needed to investigate the impact of FA on implant survivorship.

LEVEL OF EVIDENCE

Level IV, systematic review and meta-analysis.

Widening of tibial resection boundaries increases the rate of femoral component valgus and internal rotation in functionally aligned TKA

PURPOSE

The purpose of this study was to investigate the influence of increasing the tibial boundaries in functional alignment on femoral component orientation in total knee arthroplasty (TKA).

METHODS

A retrospective review of a database of robotic-assisted TKAs using a digital joint tensioning device was performed (BalanceBot®; Corin). A total of 692 TKAs with correctable deformity were included. Functional alignment with a tibia-first balancing technique was simulated by performing an anatomic tibial resection to recreate the native medial proximal tibial angle within certain boundaries (A, 87-90°; B, 86-90°; C, 84-92°), while accounting for wear. After balancing the knee, the resulting amount of femoral component outliers in the coronal and axial plane was calculated for each group and correlated to the coronal plane alignment of the knee (CPAK) classification.

RESULTS

The proportion of knees with high femoral component varus (>96°) or valgus (<87°) alignment increased from 24.5% (n = 170) in group A to 26.5% (n = 183) in group B and 34.2% (n = 237) in group C (p < 0.05). Similarly, more knees with high femoral component external rotation (>6°) or internal rotation (>3°) were identified in group C (33.4%, n = 231) than in group B (23.7%, n = 164) and A (18.4%, n = 127) (p < 0.05). There was a statistically significant (p < 0.01) overall increase in knees with both femoral component valgus <87° and internal rotation >3° from group A (4.0%, n = 28) to B (7.7%, n = 53) and C (15.8%, n = 109), with CPAK type I and II showing a 12.9- and 2.9-fold increase, respectively.

CONCLUSION

Extending the tibial boundaries when using functional alignment with a tibia-first balancing technique in TKA leads to a statistically significant higher percentage of knees with a valgus lateral distal femoral angle < 87° and >3° internal rotation of the femoral component, especially in CPAK type I and II.

LEVEL OF EVIDENCE

Level IV.