A novel non-invasive method for measuring knee joint laxity in four dof: In vitro proof-of-concept and validation

Abstract

Knee joint laxity or instability is a common problem that may have detrimental consequences for patients. Unfortunately, assessment of knee joint laxity is limited by current methodologies resulting in suboptimal diagnostics and treatment. This paper presents a novel method for accurately measuring non-invasive knee joint laxity in four degrees-of-freedom (DOF). An arthrometer, combining a parallel manipulator and a six-axis force/moment sensor, average mean difference for translations of 0.08 mm and an average limit of agreement between-1.64 mm and 1.80 mm. The average mean difference for rotations was 0.10°and the limit of agreement were between-0.85° and 1.05°. The presented method eliminates several limitations present in current methods and may prove a valuable tool for assessing knee joint laxity. Current stress radiography is also only assessing single plane laxity, but is not limited by low reliability (Schulz et al., 2005) or STA (Garavaglia et al., 2007). The radiation exposure from such measurements may, however, induce serious health risks for both the patient and operator making the method unsuitable for many applications (Balonov and Shrimpton, 2012). Joint instability must be assessed in multiple DOF in order to fully understand the complexity of the joint structures and the interplay between ligaments (Hirschmann and Müller, 2015). Neither clinical tests, arthrometry nor 1D stress radiography possesses the potential to obtain this information. Furthermore, these methods potentially over-constrain the joint during measurements, by restricting out-of-plane motion, making it appear more stable and potentially shift the load distribution unnaturally in the joint (Woo et al., 1999). Methods capable of measuring unconstrained knee joint laxity in multiple DOF not restricted by the above limitations are a prerequisite to progress the field of research in knee instability and advance current clinical assessment of joint instability. Novel methods utilizing robotics for assessing knee joint laxity has, therefore, recently emerged (Branch et al., 2015; Lorenz et al., 2015). These methods exercise high repeatability and accuracy in the application of forces, however, they are still limited by their inability to measure true bone motion due to STA. By combining robotic technology with new medical image modalities, the aforementioned limitation can be overcome which may make it possible to conceive a laxity measurement method with high accuracy, multiplanar assessment and unaffected by STA. Therefore, this paper proposes such a novel method for measuring knee joint laxity in multiple DOF, combining parallel manipulator technology and low dose biplanar x-ray acquisition. Methods Development An in vivo arthrometer was custom developed, combining a parallel manipulator (H-820, Physik Instrumente, Germany) and a six axis force/moment (F/M) sensor (Omega85 SI-1900-80, ATI Industrial Automation, USA) (see Fig. 1). The parallel manipulator has a manufacturer reported repeatability of ±1 µm and the F/M sensor has a re...

Development and Evaluation of a Subject-Specific Lower Limb Model With an Eleven-Degrees-of-Freedom Natural Knee Model Using Magnetic Resonance and Biplanar X-Ray Imaging During a Quasi-Static Lunge

“…It should be noted that the biplane image reconstructions required manual operations, which could have increased the predicted error. The accuracy of TF kinematics using these kind of ICP reconstructions has recently been evaluated by Pedersen et al [52]. They found a mean difference and limits of agreement In conclusion, we have applied a subject-specific multibody musculoskeletal modeling workflow to the natural knee, capable of simultaneously simulating internal TF and PF secondary joint kinematics and contact forces.…”

“…This was necessary for the FDK residual forces of the model to approach zero and for the model itself to replicate realistic secondary TF joint kinematics and forces when compared to other studies [2,5,6,15]. In the future, we recommend that subject-specific ligament parameter estimates from laxity tests be included in hopes of increasing model accuracy [52]. In addition, ligament wrapping surfaces were not included, which are normally used to prevent the ligaments from penetrating the bone or cartilage surfaces.…”

“…LoA) of (0.08 mm and [-1.64 mm, 1.80 mm]) for translations measures and (0.10° and [-0.85°, 1.05°] for rotational measures when comparing reconstructions based on (1) bone marker frames versus (2) the ICP optimization mention above. Furthermore, Pedersen et al found root mean square errors of 0.88 mm and 0.49° for translational and rotational measures respectively[52].Extensive studies, requiring hundreds of repeated simulations, would be needed to assess the influence of parameters such as subject-specific geometries or soft tissue mechanical properties. Considering the model simulation time was on average 6 hours per trial, this left a sensitivity analysis out of the scope for this project.…”

Can Intraoperative Intra-Articular Loads Predict Postoperative Knee Joint Laxity Following Total Knee Arthroplasty? A Cadaver Study with Smart Tibial Trays

“…Ligament balancing is vital in the successful outcome of TKA [ 2 ]; however, parameters to assess joint balance intraoperatively are starkly different from those used during postoperative assessment. Moreover, postoperative joint stability is largely assessed manually at static flexion angles which contrasts the goal of achieving desired joint stability during loaded functional activities [ 8 ]. This cadaveric study not only measured and correlated intraoperative intra-articular load—a reliable metric to assess joint balance during TKA [ 6 ]—to postoperative joint laxity but also compared intraoperative loads measured at static flexion angles to postoperative loads during dynamic functional tasks using a physiological simulator.…”

“…While intra-articular loads are used to achieve joint stability intraoperatively, clinical assessment of postoperative joint stability typically relies on passive tests, such as the stress tests quantifying the varus–valgus laxity of the knee at multiple flexion angles [ 8 ], performed manually and subjectively by the surgeon. Thus, although two distinct parameters—intraoperative intra-articular loads and postoperative joint laxity—are used to achieve a common goal of improving joint stability, they have not been correlated in the literature.…”