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Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_20 | Pages 21 - 21
1 Apr 2013
Deep K Duffy S Freer I Goudie S Nalwad H Deakin A Payne A
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Introduction

Soft tissue balancing is an important aspect of total knee replacement surgery. Traditionally sequential medial soft tissue release is performed for balancing in varus deformity. Its effects on kinematics and dynamic Femoro-Tibial-Mechanical-Angle (FTMA) have been described in extension and 90° flexion in coronal plane. However most studies have missed what happens when the knee flexes from 0 to 90 degrees This study is one of the first to describe its effects on knee kinematics throughout flexion. The aim was to look at deviation of FTMA in coronal plane with traditional sequential medial release with and without measured stress applied in varus and valgus at each point of measurement through the range of flexion.

Methods

12 cadaveric knees were studied using a computer navigation system. Rigid bodies were fixed to femur and tibia. The knee was exposed as per doing TKR surgery with medial parapatellar approach with no disturbance to the collateral ligaments. The anatomy was registered using a infra red waves based passive tracker navigation system. FTMA was studied in extension, 0°, 5°, 30°,45°,60°,90° and maximum flexion. Sequential medial release was performed in 7 steps as described by Luring et al. The sequential steps were Step 1: 2 cm release (antero medial tibial sleeve), Step 2: Postero-medial release, Step 3: 4 cm medial sleeve release, Step 4: 6 cm medial sleeve release, Step 5: Deep medial collateral ligament, Step 6: posterior cruciate ligament (PCL) medial half only, Step 7: entire PCL.

At each step FTMA was measured with and without stressing at each point of flexion. A 10 Newton Meter moment arm was applied for varus and valgus stress force.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_1 | Pages 177 - 177
1 Jan 2013
Deep K Duffy S Freer I Goudie S Nalwad H Deakin A Payne A
Full Access

Traditionally sequential medial soft tissue release is performed for balancing in total knee arthroplasty for varus knees. Its effects on kinematics have been described in extension and 90° flexion in coronal plane. This is the first study to describe its effects on kinematics throughout flexion. 12 cadaveric knees were studied using a computer navigation system to assess kinematics. Femoro-Tibial-Mechanical-Angle(FTMA) was studied in extension, 0°, 5°, 30°,45°,60°,90° and maximum flexion. Sequential medial release was performed in 7 steps, described by Luring et al(Ref). At each step FTMA was measured without and with stressing. A 10 Newton Meter moment arm was applied for varus and valgus stress. Most of the initial release steps had little effect on FTMA without force applied, especially in the initial 60° of flexion. Application of varus force demonstrated very small changes. Application of valgus force demonstrated little change in initial arc of flexion until step 5 was reached (Table 1). Our study concludes the present sequence of medial release may not be correct and should be further investigated to modify the sequence for soft tissue balancing in TKR surgery.