The limits of passive motion are variable between and unrelated within normal tibiofemoral joints

Abstract

Patient-to-patient differences should be accounted for in both clinical evaluations and computational models of knee laxity. Accordingly, the objectives were to determine how variable the laxities are between knees by determining the range of the internal-external (I-E), varus-valgus (V-V), anterior-posterior (A-P), and compression-distraction (C-D) limits of passive motion, and how related the laxities are within a knee by determining whether these limits are correlated with one another. The limits in I-E (AE 3 Nm), V-V (AE 5 Nm), A-P (AE 45 N), and C-D (AE 100 N) were measured in 10 normal human cadaveric knees at 0˚to 120˚flexion in 15i ncrements using a six degree-of-freedom load application system. The ranges from 15˚to 120˚flexion of the I-E limits were greater than 3.6˚, of the A-P limits were greater than 1.8 mm, and of the varus limits were greater than 1.4˚. The ranges from 30˚to 120f exion of the distraction limits were greater than 2.0 mm. Twenty-four of the 28 pair-wise comparisons between the limits had a correlation coefficient less than 0.65. These results demonstrate that a patient-specific approach, including all degrees of freedom of interest, is necessary during clinical evaluations of laxity and when creating and validating computational models of the tibiofemoral joint. Keywords: limits of passive motion; patient-specific modeling; laxity; knee It is important to characterize the patient-to-patient differences in the laxities of the tibiofemoral joint of the normal human knee in various degrees of freedom. The laxities of the normal human knee are often used both as a benchmark by orthopedic surgeons when evaluating laxities before, during, and after surgical interventions (e.g., total knee arthroplasty) 1 and as a gold standard by researchers when validating computational models of the tibiofemoral joint.2,3 Passive kinematics of the tibiofemoral joint are guided by the interaction between the soft tissue restraints and the articular geometry. However, the restraints from both the soft tissues and articular geometry are different between individuals. 4 Because the laxities are a measure of the function of the soft tissue restraints and the articular geometry, abnormal laxities indicate abnormal function. Therefore, it is critical to characterize the patientto-patient differences in the laxities so they may be accounted for during clinical evaluations of laxity and when creating computational models of the knee to study the behavior of the soft tissue restraints.There are two types of patient-to-patient differences that are of interest with regards to the laxities of the tibiofemoral joint. The first is the variability of the laxities between knees. If there is a wide variability as characterized by a wide range of the laxities, then a patient-specific approach would be necessary both during clinical evaluations of laxity and when creating computational models of the knee to study the behavior of the soft tissue restraints. The second is the relationship between the laxity in one ...

Analysis of differences in laxities and neutral positions from native after kinematically aligned TKA using cruciate retaining implants

“…Following dissection, each knee was aligned in a six degree‐of‐freedom load application system using alignment fixtures so that the flexion‐extension (F‐E) and I‐E rotation axes of the load application system were coincident with the F‐E and longitudinal rotation axes of the tibiofemoral joint as described previously (Fig. ).…”

“…These two surgically induced changes may cause differences in the passive biomechanics of the tibiofemoral joint after KA TKA from native because the passive biomechanics are determined by the interaction between the articular geometry and the soft tissue restraints . Two important metrics commonly used to characterize passive biomechanics are laxities and neutral positions. The laxities are a measure of the constraint provided by both the articular surfaces and the soft tissue restraints .…”

Changes in the rotational axes of the tibiofemoral joint caused by resection of the anterior cruciate ligament

“…A schematic of the load application system. 37,40 The system consists of two assemblies. The femoral assembly allows two degrees of freedom, flexion-extension (F-E) rotation and medial-lateral (M-L) translation.…”

A novel method for defining ligament characteristics in subject specific dynamic surgical planning

“…Subject specific information is needed in these models to better represent patient variability in the population (Roth et al, 2015;Harris et al, 2016). Few computational model studies (Ewing et al, 2016;Baldwin et al, 2012;Bloemeker et al, 2012) have been able to estimate ligament soft tissue properties of cadavers from the knee laxity data recorded experimentally.…”

“…Often, the details in published models varied considerably, including the number and complexity of included structures, material behaviour, or the use of generic versus subject-specific representations of bone and cartilage geometry (Harris et al, 2016). Regardless of the complexity, subject specific information has been identified as important inputs to knee models (Roth et al, 2015;Harris et al, 2016). Most TKR computational models use either CT or MRI as input.…”