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DEVELOPMENT OF AN OBJECTIVE MEASUREMENT TOOL FOR THE PIVOT SHIFT PHENOMENON OF THE KNEE
Presentation O-204
Knee Biomechanics
S207
DEVELOPMENT OF AN OBJECTIVE MEASUREMENT TOOL FOR THE PIVOT SHIFT PHENOMENON OF THE KNEE David R. Labbe (1, 2), Jacques A. de Guise (1, 2), Véronique Godbout (3), Julio Fernandes (3), Nicola Hagemeister (1, 2)
1. École de technologie supérieure, Canada; 2. Centre hospitalier de l’Université de Montréal (CHUM), Canada; 3. Hôpital du Sacré-Cœur de Montréal, Canada
Introduction Rupture of the anterior cruciate ligament (ACL) of the knee results in an increased laxity in the sagittal plane as well as in a posterolateral rotatory instability. The pivot shift test, which reproduces this instability, is the only manual test which correlates to subjective indicators of knee function [Kocher, 2005]. This test is graded in a subjective manner during which the clinician evaluates the amplitude and suddenness of a relative movement between the femur and the tibia. This grading relies heavily and the clinician’s experience and is known to have poor repeatability, especially in less experienced clinicians [Noyes, 1991].
recordings were taken. Kinematic parameters were extracted from these recordings and compared to the clinical grades given by the surgeons.
Results Despite obvious differences in technique, all surgeons where in agreement concerning the grade for all subjects who were evaluated by two to four different surgeons. Antero-posterior (AP) translation and acceleration are the two kinematic parameters which best correlated with the pivot shift grade.
The objective of this study is to develop a system which allows a quantitative measurement of the displacement between the femur and the tibia during the pivot shift test.
Methods Skin displacement artefacts are a major obstacle when measuring relative bone movements of small amplitude. To remedy this problem, we have developed an attachment system upon which electromagnetic sensors, an accelerometer and a gyroscope were mounted (Figure 1).
Figure 2: Logarithm of AP acceleration divided by flexion speed according to pivot shift grade
Discussion
Figure 1: The femoral and tibial components of a motion sensor attachment system. Sixteen subjects and 7 orthopaedic surgeons participated in this study. Each subject had the attachment system placed on one of his/her limbs and a calibration procedure was performed to identify joint centers and anatomical axes. A surgeon then performed the pivot shift manoeuvre as he does in his practice and attributed a clinical grade to the shift he produced; this was done for both the subject’s limbs. For some of the subjects, the entire protocol was then repeated by one or several other surgeons. A total of 38 knee 16th ESB Congress, Oral Presentations, Wednesday 9 July 2008
The logarithm of the sum of linear accelerations divided by angular frequency of flexion is the parameter which gives the most significant differences between all grades except between 0 and 1 (Figure 2). This is not surprising as acceleration is very low for these grades. The division by angular frequency allows for a certain normalization of the different techniques used. These results show that objective measurement of the pivot shift is possible and that kinematic differences between individual grades exist despite the fact that clinicians use very different approaches to the pivot shift test.
References Kocher et al. Am J Sports Med, 32(3):629-34,2004. Noyes et al. Am J Sports Med, 19(2):148-55,1991. Journal of Biomechanics 41(S1)
Knee Biomechanics
S207
DEVELOPMENT OF AN OBJECTIVE MEASUREMENT TOOL FOR THE PIVOT SHIFT PHENOMENON OF THE KNEE David R. Labbe (1, 2), Jacques A. de Guise (1, 2), Véronique Godbout (3), Julio Fernandes (3), Nicola Hagemeister (1, 2)
1. École de technologie supérieure, Canada; 2. Centre hospitalier de l’Université de Montréal (CHUM), Canada; 3. Hôpital du Sacré-Cœur de Montréal, Canada
Introduction Rupture of the anterior cruciate ligament (ACL) of the knee results in an increased laxity in the sagittal plane as well as in a posterolateral rotatory instability. The pivot shift test, which reproduces this instability, is the only manual test which correlates to subjective indicators of knee function [Kocher, 2005]. This test is graded in a subjective manner during which the clinician evaluates the amplitude and suddenness of a relative movement between the femur and the tibia. This grading relies heavily and the clinician’s experience and is known to have poor repeatability, especially in less experienced clinicians [Noyes, 1991].
recordings were taken. Kinematic parameters were extracted from these recordings and compared to the clinical grades given by the surgeons.
Results Despite obvious differences in technique, all surgeons where in agreement concerning the grade for all subjects who were evaluated by two to four different surgeons. Antero-posterior (AP) translation and acceleration are the two kinematic parameters which best correlated with the pivot shift grade.
The objective of this study is to develop a system which allows a quantitative measurement of the displacement between the femur and the tibia during the pivot shift test.
Methods Skin displacement artefacts are a major obstacle when measuring relative bone movements of small amplitude. To remedy this problem, we have developed an attachment system upon which electromagnetic sensors, an accelerometer and a gyroscope were mounted (Figure 1).
Figure 2: Logarithm of AP acceleration divided by flexion speed according to pivot shift grade
Discussion
Figure 1: The femoral and tibial components of a motion sensor attachment system. Sixteen subjects and 7 orthopaedic surgeons participated in this study. Each subject had the attachment system placed on one of his/her limbs and a calibration procedure was performed to identify joint centers and anatomical axes. A surgeon then performed the pivot shift manoeuvre as he does in his practice and attributed a clinical grade to the shift he produced; this was done for both the subject’s limbs. For some of the subjects, the entire protocol was then repeated by one or several other surgeons. A total of 38 knee 16th ESB Congress, Oral Presentations, Wednesday 9 July 2008
The logarithm of the sum of linear accelerations divided by angular frequency of flexion is the parameter which gives the most significant differences between all grades except between 0 and 1 (Figure 2). This is not surprising as acceleration is very low for these grades. The division by angular frequency allows for a certain normalization of the different techniques used. These results show that objective measurement of the pivot shift is possible and that kinematic differences between individual grades exist despite the fact that clinicians use very different approaches to the pivot shift test.
References Kocher et al. Am J Sports Med, 32(3):629-34,2004. Noyes et al. Am J Sports Med, 19(2):148-55,1991. Journal of Biomechanics 41(S1)