Intraoperative load-sensing drives the level of constraint in primary total knee arthroplasty: Surgical technique and review of the literature

Abstract

Total knee arthroplasty is a traditional surgical procedure aimed to restore function and relief pain in patients with severe knee osteoarthritis. Recently, many medial pivot knee systems were deigned to replicate the normal knee kinematic: a highly congruent medial compartment and a less conforming lateral tibial plateau characterize these devices. A slightly asymmetric soft tissue balancing is mandatory using medial pivot designs to obtain a correct and physiological knee biomechanics leading good outcomes and long survival rates. This article describes a new surgical technique using a modern third generation TKA design combined with wireless load-sensor tibial trials to improve the correct knee load balancing with a minimal conformity of the polyethylene insert. The use of wireless load-sensing tibial trials has several benefits: it is an intraoperative, objective and dynamic tool allowing surgeons to optimize in real time soft tissue balancing. The meaning of a "truly balanced knee" is still a controversial issue in the current literature.

Medial Pivot in Total Knee Arthroplasty: Literature Review and Our First Experience

“…A “ball-in-socket articulation” with a stable and point is obtained on the medial compartment, whereas a rolling from anterior to posterior occurs in the lateral condyle during the knee motion reproducing a physiological knee biomechanic. 20 …”

Achieving a Balanced Knee in Robotic TKA

“…Modes of failure, such as aseptic loosening, polyethylene wear, and instability, can often be attributed to the technical performance of the operation [ 14 , 15 , 16 , 17 ]. Traditional methods of component alignment and ligament balance are either performed without objective measurement or are subject to measurement errors [ 18 ], which contribute to some early and late failures of TKA. Additionally, even with seemingly well-aligned and balanced knees, many patients are dissatisfied with the outcome of their operation.…”

Sensor guided unicompartmental to total knee arthroplasty revision: Surgical technique

“…At this point ( Figure 3 ), the femoral and tibial component trials are inserted and the Postero-Stabilized (PS) Verasense tibial sensor is inserted, the knee is brought to extension (not hyperextension) and the extensor mechanism is temporarily closed with a clamp. 2 Please note that the trial is routinely inserted and then removed so that it can be re-zeroed due to the small plastic deformation of the trial that occurs with initial implantation which may alter the load measurements. With the patella relocated in the trochlear groove, load measurements are then documented at 10°, 45°, and 90° of flexion following a uniform data collection protocol.…”

“…At this point, the distribution of compartment forces during intraoperative Range Of Motion (ROM) drives the selection of the liner and, accordingly, the level of constraint. As previously described, 2 the authors consider stable knees those showing a pressure of <50 lbs on the medial compartment, <35 lbs on the lateral compartment, and a mediolateral intercompartmental difference within 15 lbs. The mean intercompartmental force differences during trial ultimately drives our surgical technique and 15 lbs is usually considered as the parameter to differentiate “balanced” from “unbalanced” knees.…”

“…Because of these challenges, the authors developed a surgical technique that could combine balancing the knee during revision surgery with the use of the less constrained polyethylene option. To achieve this, we started evaluating 2 a novel device (VERASENSE, Orthosensor, FL) designed to support soft tissue balancing during primary TKA. This intraoperative sensing technology dynamically quantifies intraarticular loads during TKA trial with the goal of correcting any residual imbalance in real time.…”