Article

Stiff-knee gait (SKG) is a common abnormal gait pattern in patients after stroke
characterized by insufficient knee flexion (KF) during swing. Overactivity of the
rectus femoris (RF) is considered the primary cause of SKG. Inadequate push-off
has been indicated as an additional cause in the recent literature, as KF depends
on knee flexion velocity in preswing (KFV). We used the peak of vertical
acceleration of the malleolus (PMVA) as a kinematic-based indirect measure of
push-off and studied its relationship with KF and KFV in a sample of 20 healthy
subjects walking fast (v = 95 +/- 5%heights(-1)), at self-selected speed (v = 74
+/- 5%heights(-1)), slow (v = 54 +/- 6%heights(-1)) and very slow (v = 38 +/-
5%heights(-1)) and in a sample of 52 stroke patients with SKG (age 60 +/- 11, v =
20 +/- 11%heights(-1)). In healthy subjects PMVA occurred before knee flexion
acceleration (p<0.001) and hip flexion acceleration (p<0.001). KF appeared as a
bottom-up mechanism driven by the ankle push-off. From a regression analysis, the
PMVA-KFV cause-effect relationship resulted strictly linear, with R(2) = 0.967,
KFV = 0+7.1xPMVA, P<0.0001. Data from SKG patients were compared to this normal
cause-effect model. For 44/52 patients the reduced KFV was combined with lack of
push-off. Data from 8/52 patients only were statistically outside the 95%CI of
the model, thus requiring for a braking mechanism to explain KFV reduction. In
stroke adults of our sample the push-off impairment (85% of cases) and not the
inappropriate knee extension moment produced by the thigh muscles was the primary
cause of SKG. This result could explain the low average efficacy (<10 degrees )
of focal and surgical treatments at the quadriceps. The presented model could be
used to differentiate the primary cause of SKG between inadequate push-off and
braking activity of the thigh muscles, thus increasing the effectiveness of the
selected treatment.
CI - Copyright (c) 2013 Elsevier B.V. All rights reserved.

Langue : ANGLAIS