In Vitro Application of a Wireless Sensor in Flexion-Extension Gap Balance of Unicompartmental Knee Arthroplasty

Summary

This protocol presents a cadaveric study of a wireless sensor used in medial unicompartmental knee arthroplasty. The protocol includes the installation of an angle measuring device, standardized Oxford unicompartmental knee arthroplasty osteotomy, preliminary assessment of flexion-extension balance, and application of the sensor to measure flexion-extension gap pressure.

Abstract

Unicompartmental knee arthroplasty (UKA) is an effective treatment for end-stage anteromedial osteoarthritis (AMOA). The key to UKA is the flexion-extension gap balance, which is closely related to postoperative complications such as bearing dislocation, bearing wear, and arthritis progression. The traditional gap balance assessment is performed by indirectly sensing the tension of the medial collateral ligament by a gap gauge. It relies on the surgeon's feel and experience, which is imprecise and difficult for beginners. To accurately assess the flexion-extension gap balance of UKA, we developed a wireless sensor combination consisting of a metal base, a pressure sensor, and a cushion block. After osteotomy, the insertion of a wireless sensor combination allows the real-time measurement of intra-articular pressure. It accurately quantifies the flexion-extension gap balance parameters to guide further femur grinding and tibia osteotomy, to improve the accuracy of gap balance. We conducted an in vitro experiment with the wireless sensor combination. the results showed that there was a difference of 11.3 N after applying the traditional method of flexion-extension gap balance performed by an experienced expert.

Introduction

Knee osteoarthritis (KOA) is a global burden¹, for which the stepwise treatment strategy is currently adopted. For end-stage unicompartmental KOA, unicompartmental knee arthroplasty (UKA) is an effective choice, with a 10-year survival rate of over 90%². Medial UKA only replaces the severely worn medial compartment and preserves the natural lateral compartment, medial collateral ligament (MCL), and cruciate ligament³. The principle is to make the flexion gap and extension gap approximately the same by tibial osteotomy and femoral grinding, and to restore MCL tension after imp....

Protocol

The protocol was approved by the Ethics Committee of Xuanwu Hospital (grant number: 2021-224) and was conducted in accordance with the Declaration of Helsinki. Informed consent was obtained from next of kin to use the cadavers.

1. Installation of angle measuring device

1. Turn on the switch of the femur and tibia angle measuring device. Open the angle measurement software on the tablet computer, scan the QR codes of the two measuring devices, and click Bluetooth connection.
2. Place the two angle measuring instruments on the horizontal table, click the Calibration button to ....

Results

This in vitro study was performed on a 60-year-old female cadaver. With the S-size femoral prosthesis and 3 mm bearing the target, after performing femoral grinding and tibial osteotomy, the surgeon used the gap gauge to assess flexion-extension gap tension preliminarily and believed that balance was achieved.

After the femoral trial was installed, the wireless sensor was inserted into the medial joint space, and the intra-articular pressure was measured three times at 110° (flexion g.......

Discussion

Mobile-bearing UKA is an effective treatment for anteromedial KOA. It has the advantages of less trauma, quick recovery, and maintaining normal knee proprioception^11,12,13. The key to UKA is flexion-extension balance; that is, making the flexion gap and extension gap as equal as possible on the premise of restoring MCL tension¹⁴. The imbalance may lead to bearing dislocation, prosthesis wear, or progressi.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
angle measuring device	AIQIAO(SHANGHAI) MEDICAL TECHNOLOGY CO., LTD.	20203010141	angle measuring device of femur,angle measuring device of tibia
Oxford Partial Knee System	Biomet UK LTD.	20173130347	Oxford UKA
Wireless sensor combination	AIQIAO(SHANGHAI) MEDICAL TECHNOLOGY CO., LTD.	20212010325	a metal base,  a wireless sensor with three pressure probes, and a cushion block