A COMPARISON OF IN VIVO KNEE KINEMATICS DURING A LEG PRESS ACTIVITY BETWEEN ACL
DEFICIENT AN D MEDIAL OSTEOARTHRITIC KNEES
+1Yoneta, K; 1Gamada, K; 2Miyaji, T; 2Yonekura, A; 2Miyamoto, T; 2Kidera, K; 2Shindoh, H; 3Banks, S A
+1Hiroshima International University, Hiroshima, Japan, 2Nagasaki University, Nagasaki, Japan, 3University of Florida, Gainesville, FL
[email protected]
INTRODUCTION:
A long-term effect of chronic anterior cruciate ligament (ACL)
deficiency is development of degenerative changes in the knee [1].
Andriacchi et al. [2] noted cartilage homeostasis would not be
maintained by abnormal kinematics after ACL rupture and cartilage
degeneration would initiate. However, no study to date has compared
kinematics between ACL deficient knees and primary osteoarthritic
(OA) knees. Therefore, the aim of this in vivo study was to determine if
a difference in knee kinematics exists between normal, ACL deficient
and primary medial OA knees. Using a leg press activity, we can
examine semi weight-bearing lower limbs kinematics without
complicating compensatory motions such as trunk lean, which occurs in
squatting and gait.
METHODS:
Enrolled in this IRB approved study were nine ACL deficient knees
and their contralateral healthy knees of 9 male patients with a mean age
of 27.0 (SD: 7.6) years, as well as 15 knees with primary medial OA of
9 patients (2 males and 7 females) with a mean age of 68.1 (SD: 8.2)
years. All of the OA patients were over 40 years of age and indicated for
surgical treatment. The radiographic grade of OA using the Kellgren–
Lawrence System averaged 1.9 ± 0.3 (grade 1: 5 knees, grade 2: 6 knees,
grade 3: 4 knees). The ACL deficient patients were between 20 and 40
years and preferred ACL reconstruction. The other inclusion criteria for
all groups was the ability to perform a leg press activity. Exclusion
criteria included knee ligament injuries other than ACL, history of
contralateral knee injuries, and age less than 20 years. An interval from
injury to testing were between 1 and 38 months for the ACL injured
knees. Normal knees were the contralateral asymptomatic knees of the
ACL deficient knee and had no signs of radiographic knee OA.
Informed written consent was obtained from all subjects.
Knee kinematics were analyzed using a 3D-to-2D registration
technique utilizing CT scan and lateral fluoroscopic images [3]. During
fluoroscopic imaging, subjects were seated in a leg press device with a
fixed footplate and sliding seat. The leg press activity was repeated 3
times with target knee flexion of 90o. The resisting load for ACL
deficient and OA knees were 10kg and 5kg, respectively, plus 8.7% of
the subject’s body weight. Patients practiced the activity until they felt
comfortable before a radiographic exposure.
All knees underwent CT scanning with a 0.5 mm slice pitch spanning
approximately 150 mm above and below the knee joint line. Geometric
bone models of the femur and the tibia were created from the images.
The exterior cortical bone edges in the CT images were segmented using
3D-Doctor software (Able Software Corp., Lexington, MA) and were
converted into polygonal surface models using Geomagic Studio
(Geomagic, Research Triangle Park, NC, USA). The cylindrical axis of
the posterior femoral condyles [4] and the tibial plateau plane with the
posterior co-tangent at the level of the top of the fibular head were used
as references for femoral and tibial coordinate systems, respectively.
Kinematics were analyzed in 5° flexion increments for the leg press
activity. The average maximum extension/flexion angle was 7 ± 5° / 81
± 8°. Statistical comparisons were performed using values between 10°
and 65° of flexion, where observations from all knees were available.
Repeated measures analysis of variance and post-hoc pair-wise
comparison (Tukey-Kramer test) were used to compare the 3 knee
groups. The level of significance was set at p<.05.
RESULTS:
The OA knees demonstrated greater tibial external rotation during leg
press than normal knees between 40° and 65° flexion (Fig 1a), and ACL
deficient knees at 60° and 65° flexion. In addition, the OA knees
demonstrated more anterior lateral femoral condylar contact between
10° and 65° flexion than normal and ACL deficient knees (Fig 1b).
DISCUSSION:
The OA knees showed greater external tibial rotation during the leg
press activity for flexion over 20°, which was consistent with a study on
a squatting activity by Saari et al.[5]. The kinematics between ACL
deficient and contralateral knees showed no significant differences.
Brandsson et al. [6] examined knee kinematics while ascending a
platform (height 8 cm) from about 55°–65° of knee flexion to full
extension, and reported that the tibial center in the ACL deficient knees
was more dorsally displaced and the tibia more externally rotated than
the contralateral side. Reasons for this inconsistency may include the
activity, load, and/or hip position between the leg press and platform
ascending activities.
A 3D-to-2D registration technique using lateral fluoroscopy or
radiography is a well-established to measure dynamic weight-bearing
knee kinematics in vivo with standard errors within 2.2 mm for
translations and 1.8 degrees for rotations [3]. Moreover, the leg press
activity can reduce the variability of loads, body positions, and hip
kinematics, and more consistent kinematics are expected, providing
greater sensitivity to detect changes in knee kinematics as a function of
load and activity.
In conclusion, OA knees showed reduced tibial internal rotation than
ACL deficient and normal knees during a leg press activity. The
mechanism of knee OA secondary to ACL injury may not be same as in
primary knee OA.
Figure 1: Tibial external rotation (a) and lateral contact translation (b) as
a function of knee flexion angle during a leg-press activity.
＊Significant differences: Different between OA and Normal
†Significant differences: Different between OA and ACL
Error bars represent ± 1 SD
Figure 2: The medial and lateral femoral condylar contact points are
shown between 10° and 50° flexion. The tibial plateau represents an
average for all knees.
REFERENCES:
[1] H. Louboutin et al., Knee (2008). [2] T. P. Andriacchi, S. Koo, and
S. F. Scanlan, J Bone Joint Surg Am 91 Suppl 1, 95 (2009). [3] S. A.
Banks, and W. A. Hodge, IEEE transactions on bio-medical engineering
43, 638 (1996). [4] M. Logan et al., Am J Sports Med 32, 720 (2004).
[5] T. Saari et al., J Biomech 38, 285 (2005). [6] S. Brandsson et al.,
Acta Orthop Scand 72, 372 (2001).
Poster No. 879 • ORS 2011 Annual Meeting