Posterior clearance increases the knee extension angle in cruciate retaining type total knee arthroplasty: Intraoperative evaluation using a navigation system

Postero-Central Slice Osteotomy of the Proximal Tibia: A Novel Technique for Correcting Resistant Tight Extension Gaps in Posterior-Stabilized Total Knee Arthroplasty for Varus Osteoarthritis

BACKGROUND

The aim of total knee arthroplasty (TKA) is to circumvent the pain due to advanced osteoarthritis of the knee joint and correct the limb alignment and biomechanics to improve patients' quality of life. Apart from medio-lateral balancing, balancing flexion and extension gaps is a prerogative to achieve good results. This study proposes a novel surgical technique of postero-central slice osteotomy of the proximal tibia (PCSO-PT) for correcting tight extension gaps in posterior-stabilized (PS) knees and assesses its clinical and functional outcomes.

METHODS

A prospective study was conducted on 84 consecutive knees with tricompartmental osteoarthritis and varus deformity, requiring PCSO of the proximal tibia during PS TKA between January 2016 and July 2018. Knee Society scores, flexion deformity, range of motion, antero-posterior instability, and complications were assessed at regular intervals for a minimum of two years postoperatively.

RESULTS

Residual flexion deformities less than 11° after posterior capsular release were successfully corrected by the osteotomy. The mean preoperative flexion deformity of 18.1 ± 2.5° improved to 8.6 ± 2.2° intraoperatively after posterior capsular release from the femoral end and to 0.65 ± 0.76° intraoperatively immediately after the osteotomy, with no residual flexion deformity noted in any patient six weeks postoperatively. It had no negative effect on the significant post-TKA improvement of the mean Knee Society score from 32 ± 12 preoperatively to 94 ± 3 at the terminal follow-up. A direct correlation between preoperative flexion deformity and a resistant, tight extension gap (P = 0.003) was noted. There was no increase in coronal plane or sagittal plane instabilities in midflexion or on mobilization throughout the follow-up period, nor were any major adverse effects noted in this period.

CONCLUSION

A postero-central slice osteotomy of the proximal tibia is an effective and safe alternative to overcoming tight extension during TKA after femoral-end capsular release, instead of capsular release from the tibial end or midcapsular region.

Additional Distal Femoral Resection Minimally Improves Terminal Knee Extension: A Systematic Review and Meta-Regression Challenging the Dogma

Background

Additional distal femoral resection is a common technique to address a flexion contracture during primary total knee arthroplasty (TKA) but can lead to midflexion instability and patella baja. Prior reports regarding the magnitude of knee extension obtained with additional femoral resection have varied. This study sought to systematically review research describing the effect of femoral resection on knee extension and to perform meta-regression to estimate this relationship.

Methods

A systematic review was conducted using MEDLINE, PubMed, and Cochrane databases by combining the terms ("flexion contracture" OR "flexion deformity") AND ("knee arthroplasty" OR "knee replacement") to identify 481 abstracts. In total, 7 articles reporting change in knee extension after additional femoral resection or augmentation across 184 knees were included. The mean value for knee extension, its standard deviation, and the number of knees tested were recorded for each level. Meta-regression was performed using weighted mixed-effects linear regression.

Results

Meta-regression estimated that each 1mm resected from the joint line produced a 2.5° gain of extension (95% confidence interval, 1.7 to 3.2). Sensitivity analyses excluding outlying observations estimated each 1mm resected from the joint line produced a 2.0° gain of extension (95% confidence interval, 1.9 to 2.2).

Conclusions

Each millimeter of additional femoral resection is likely to produce only a 2° improvement in knee extension. Thus, an additional resection of 2 mm is likely to improve knee extension by less than 5°. Alternative techniques, including posterior capsular release and posterior osteophyte resection, should be considered in correcting a flexion contracture during TKA.

Intraoperative changes in medial joint gap after posterior femoral condylar resection, posterior osteophyte removal, and femoral component placement during primary total knee arthroplasty

BACKGROUND

"Mid-flexion stability" is important for superior patient satisfaction following total knee arthroplasty (TKA). Thus, it is important to control medial joint gap intraoperatively as a countermeasure. However, reports on the precise intraoperative changes in medial joint gap during TKA are scarce. This study evaluated the intraoperative changes in medial joint gap during TKA.

METHODS

We studied 167 knees with varus osteoarthritis that underwent 80 cruciate-retaining (CR) and 87 posterior-stabilized (PS) TKAs between January 2018 and December 2020. We measured the intraoperative changes in medial joint gap with a tensor device at 137.5 N.

RESULTS

The medial joint gap after posterior femoral condylar resection was significantly increased not only at 90° of flexion but also at 0° of extension in CR and PS TKAs (p < 0.01). The medial joint gap after posterior osteophyte removal was significantly increased not only at 0° of extension but also at 90° of flexion in CR and PS TKAs (p < 0.01). The medial joint gap at 0° of extension was reduced by 0.60 mm after femoral component placement in PS TKA.

CONCLUSION

Surgeons need to pay close attention to these intraoperative changes in medial joint gap by measuring the medial joint gap before and after each procedure or assuming the changes in those values before bone cutting to achieve superior patient satisfaction following TKA.

Effect of Posterior Osteophytes on Total Knee Arthroplasty Coronal Soft Tissue Balance: Do They Matter?

BACKGROUND

Achieving coronal plane balance in total knee arthroplasty (TKA) is of paramount importance. There is concern that obtaining balancing before removal of posterior osteophytes may lead to asymmetrical extension balance once removed. We hypothesized that there is a particular posterior osteophyte size and location that does not result in significant change in coronal gap balancing.

METHODS

In this study of 245 robotic arm-assisted TKAs, the size and location of posterior osteophytes were obtained from preoperative computer tomography scans. Gap measurements at 10°-25° and 90° flexion after removal of medial and lateral osteophytes, before and after posterior osteophyte removal and bone resection were compared with respect to the size and location of posterior osteophytes.

RESULTS

The largest size posterior osteophytes measured >10 mm in 8.2% of cases, 5-10 mm in 34.7%, <5 mm in 23.7%, and 23.7% had no osteophytes. The mean osteophyte size was 5.7 mm. The cohorts with and without posterior osteophytes were both found to have significant but similar changes in all gaps after osteophyte removal and bone resection (mean 0.8-1.4 mm, P < .0001 and mean 0.7-1.7 mm, P < .0001, respectively). Osteophyte size and location had no significant effect on the change in postresection gaps. This included osteophytes greater than 10 mm, but their incidence was small.

CONCLUSION

There is a small significant change in gaps between initial assessment and subsequent TKA bone resections, with or without posterior osteophytes. Our study found that where the surgeon thoroughly removes the medial and lateral osteophytes on initial exposure, posterior osteophytes <10 mm can be ignored during initial knee coronal balancing.

Efficacy of posterior capsular release for flexion contracture in posterior-stabilized total knee arthroplasty

Purpose

Posterior capsular contracture causes stiffness during knee extension in knee osteoarthritis. Furthermore, in posterior-stabilized total knee arthroplasty (PS-TKA), a unique design such as the cam mechanism could conflict with the posterior capsule (PC) causing flexion contracture (FC). However, few studies have focused on the anatomical aspects of the PC. This study aimed to investigate the anatomical site and forms of posterior capsular attachment to the femoral cortex, and to evaluate the efficacy of posterior capsular release for FC by assessing changes in knee extension angles using a navigation system.

Methods

Attachment sites of the PC were investigated in 10 cadaveric knees using computed tomography. PS-TKA was performed in six cadaveric knees using a navigation system to evaluate the efficacy of posterior capsular release for FC. Posterior capsular release was performed stepwise at each part of the femoral condyle.

Results

The gastrocnemius tendon and PC were integrally attached to the femoral cortex at the medial and lateral condyles, whereas the PC at the intercondylar fossa was independently attached directly to the femoral cortex. Moreover, the PC at the intercondylar fossa was attached most distally among each femoral condyle. Posterior capsular release at the intercondylar fossa allowed 11.4° ± 2.8° improvement in knee extension. This angle was further improved by 5.5° ± 1.3°, after subsequent capsular release at the medial and lateral condyles.

Conclusion

The forms and sites of posterior capsular attachment differed based on the part of the femoral condyle. Stepwise posterior capsular release was effective for FC in PS-TKA.

Level of evidence

III.