Total knee arthroplasty in femoral bowing: does patient specific instrumentation have something to add? A randomized controlled trial

Impact of the diaphyseal femoral deformity on the lower limb alignment in osteoarthritic varus knees

The impact of a diaphyseal femoral deformity on knee alignment varies according to its severity and localization. The aims of this study were to determine a method of assessing the impact of diaphyseal femoral deformities on knee alignment for the varus knee, and to evaluate the reliability and the reproducibility of this method in a large cohort of osteoarthritic patients. All patients who underwent a knee arthroplasty from 2019 to 2021 were included. Exclusion criteria were genu valgus, flexion contracture (> 5°), previous femoral osteotomy or fracture, total hip arthroplasty, and femoral rotational disorder. A total of 205 patients met the inclusion criteria. The mean age was 62.2 years (SD 8.4). The mean BMI was 33.1 kg/m² (SD 5.5). The radiological measurements were performed twice by two independent reviewers, and included hip knee ankle (HKA) angle, mechanical medial distal femoral angle (mMDFA), anatomical medial distal femoral angle (aMDFA), femoral neck shaft angle (NSA), femoral bowing angle (FBow), the distance between the knee centre and the top of the FBow (DK), and the angle representing the FBow impact on the knee (C'KS angle). The FBow impact on the mMDFA can be measured by the C'KS angle. The C'KS angle took the localization (length DK) and the importance (FBow angle) of the FBow into consideration. The mean FBow angle was 4.4° (SD 2.4; 0 to 12.5). The mean C'KS angle was 1.8° (SD 1.1; 0 to 5.8). Overall, 84 knees (41%) had a severe FBow (> 5°). The radiological measurements showed very good to excellent intraobserver and interobserver agreements. The C'KS increased significantly when the length DK decreased and the FBow angle increased (p < 0.001). The impact of the diaphyseal femoral deformity on the mechanical femoral axis is measured by the C'KS angle, a reliable and reproducible measurement.

The efficacy and safety of patient-specific instrumentation in primary total knee replacement: a systematic review and meta-analysis

INTRODUCTION

Patient-specific instrumentation (PSI) for primary total knee arthroplasty (TKA) surgery has been shown to increase accuracy of component positioning. However, it is unclear whether this also translates to actual benefits for patients in terms of better outcomes (efficacy) or less complications such as revisions (safety). We therefore systematically reviewed the literature to determine the efficacy and safety of PSI in primary TKA.

METHODS

Randomized controlled trials comparing PSI to non-PSI in primary TKA were included. A random effects model was used with meta-regression in case of heterogeneity.

RESULTS

Forty-three studies were included with a total of 1816 TKA in the PSI group and 1887 TKA in the control group. There were no clinically relevant differences between the PSI-group and non-PSI group regarding all outcomes. There was considerable heterogeneity: meta-regression analyses showed that the year the study was published was an important effect modifier. Early publications tended to show a positive effect for PSI compared to non-PSI TKA, whereas later studies found the opposite.

CONCLUSION

Based on evidence of moderate certainty, our study suggested that there were no clinically relevant differences in efficacy and safety between patients treated with PSI TKA and patients treated with non-PSI TKA.

Sagittal femoral bowing contributes to distal femoral valgus angle deviation in malrotated preoperative radiographs

Background

The coronal whole-leg radiograph is generally used for preoperative planning in total knee arthroplasty. The distal femoral valgus angle (DFVA) is measured for distal femoral bone resection using an intramedullary guide rod. The effect of coronal and sagittal femoral shaft bowing on DFVA measurement in the presence of malrotation or knee flexion contracture has not been well reported. The objectives of this study were: (1) to investigate the effects of whole-leg malrotation and knee flexion contracture on the DFVA in detail, (2) to determine the additional effect of coronal or sagittal femoral shaft bowing.

Methods

We studied 100 consecutive varus and 100 valgus knees that underwent total or unicompartmental knee arthroplasty. Preoperative CT scans were used to create digitally reconstructed radiography (DRR) images in neutral rotation (NR, parallel to the surgical epicondylar axis), and at 5° and 10° external rotation (ER) and internal rotation (IR). The images were also reconstructed at 10° femoral flexion. The DFVA was evaluated in each DRR image, and the angular variation due to lower limb malposition was investigated.

Results

The DFVA increased as the DRR image shifted from IR to ER, and all angles increased further from extension to 10° flexion. The DFVA variation in each position was 1.3° on average. A larger variation than 2° was seen in 12% of all. Multivariate regression analysis showed that sagittal femoral shaft bowing was independently associated with a large variation of DFVA. Receiver operating characteristic analysis showed that more than 12° of sagittal bowing caused the variation.

Conclusion

If femoral sagittal bowing is more than 12°, close attention should be paid to the lower limb position when taking whole-leg radiographs. Preoperative planning with whole-leg CT data should be considered.

Patient-specific instrumentation (PSI) in total ankle arthroplasty: a systematic review

BACKGROUND

Patient-specific instrument (PSI) may theoretically make total ankle arthroplasty (TAA) more accurate. Several studies have reported the outcomes of PSI TAA. The aim of this study is to systematically review the literature of PSI TAA.

METHODS

PubMed, Embase, Web of Science, and Cochrane Library databases were systematically reviewed according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines for PSI TAA. The quality of the included studies was evaluated according to Methodological Index for Non-Randomized Studies (MINORS).

RESULT

Nine articles were ultimately included in the systematic review. The implant position and function outcome of TAA was similar between PSI and SI. Prediction accuracy of implant size remained great difference. PSI can shorten the operative time and fluoroscopy time. The quality of current studies on PSI TAA is insufficient to produce high-level evidence.

CONCLUSION

PSI can get similar implant position and clinical outcome in TAA compared to SI, but current evidence is not strong enough to evaluate PSI TAA.