I. Quantitative Description of Motion
Identifying Abnormal Motion in the Transverse Plane
Rotational abnormalities are a common problem in many neuromuscular disorders, such as cerebral palsy and myelomeningocele. Torsional bony deformities, identified during the clinical examination, may be present in the femur and/or tibia. Abnormal segment position may be seen in gait such as asymmetrical pelvic rotation with one side of the pelvis retracted or externally rotated and the contralateral pelvis protracted or internally rotated. Finally, there may be abnormal rotations at the hip, knee and ankle joints during gait as well.
During observational gait analysis, the focus for identifying rotational abnormalities is usually on foot progression (the orientation of the foot to the direction of progression) and the position of the knees. That is, if the knees are pointing inwards, it is assumed that there is internal hip rotation and/or femoral anteversion. Gait analysis can document segment and joint motion in the transverse plane to allow accurate identification of the location of rotational abnormalities -- including pelvic motion -- that can be difficult to determine visually.
Test Your Knowledge
In Video 4, a child with cerebral palsy is seen with bilateral rotational abnormalities. When observing this video recording, make note of the foot progression angles (internal, normal or external) and the position of the knees (pointing inwards, straight forward or pointing outwards). Using this visual representation and the following clinical data pertaining to the hip, femur and tibia,
hip internal rotation, right side: 80°; left side: 85°
hip external rotation, right side: 25°; left side: 20°
hip anteversion, right side: 45°; left side: 50°
tibial torsion, right side: 10° external; left side: 5° external (normal: 20 to 25 degrees external),
identify the possible source of the transverse plane gait abnormalities in this child.
Click here to download Video 4
Video 4. Side and front views of an 8-year-old girl with cerebral palsy spastic diplegia. The visual impression of rotational abnormalities includes internal foot progression and inpointing knees, bilaterally.
This patient's pelvic, bilateral hip and foot motions in the transverse plane are shown in Figure 8. Data show an asymmetric pelvis with the right side held posterior to the left throughout the gait cycle. Hip motion is also asymmetrical with normal rotation of the right hip and internal rotation of the left hip throughout the gait cycle. Foot progression is internal, bilaterally.
Transverse plane rotation of right (red) and left (green) pelvis and hip and foot progression for a patient with cerebral palsy (Video 4). The left side pelvis is rotated externally and the right internally. There is internal rotation of left hip and normal rotation of right hip. Foot progression is internal of normal bilaterally. Note asymmetry in pelvic and hip motion in gait analysis data that is not appreciated on visual observation or clinical examination. Blue band on each plot indicates first standard deviation of the mean normal reference in degrees.
Why is the visual impression of the ambulating patient inconsistent with this quantitative motion data? Some of this inconsistency can be explained by the differences in identifying hip position as either: 1) the angle between the pelvic and thigh segments, or 2) the absolute position of the thigh segment alone (as identified by the direction that the knee is pointing). Gait analysis data (Figure 8) specify hip motion as the relative angle between the pelvic and thigh segments. Therefore, if the right pelvis is pointing inward and the hip rotation is neutral (no internal or external rotation), the thigh segment and knee position will appear as pointing inward (internally). In the case presented, however, the visual impression of an internal thigh rotation does not indicate internal hip rotation because the pelvis is rotated internally.
A closer look at left side data shows internal rotation of the left hip in the 25 to 30 degree range. Visually, one would expect greater internal rotation of the left thigh segment if not for the pelvis on the left side, which is rotated externally from 10 to 30 degrees. The internal tibial torsion (normal bi-malleolar axis: 20 to 25 degrees external) contributes to the internal foot progression, bilaterally. In studying Video 4, one can appreciate that it is not possible to accurately identify the actual rotation of the pelvis and hip joint in the transverse plane from the video recording.
A treatment approach based on a reasonably symmetrical clinical assessment of the rotational abnormalities and visual impression of symmetry in gait may result in an unexpected treatment outcome. This may help explain some of the unpredictability in surgical outcomes in the patient with cerebral palsy in which surgical decisions were made without gait analysis.
Identifying the Role of Segment Versus Joint Position in the Sagittal Plane
One of the most common problems observed in the patient with cerebral palsy is a "drop foot" in late swing. In some cases, the foot or toe may contact the ground in swing, resulting in reduced stability and possible falling. Drop foot creates a less stable position of the foot on landing, referred to as a "toe initial contact." The primary cause of drop foot is generally thought to be excessive equinus in swing due to tibialis anterior muscle weakness, and/or ankle plantar flexor tightness or spasticity. In those patients, where normal or at least a neutral passive range of motion is possible, an ankle-foot orthosis is often prescribed.
During observational gait analysis, when a drop foot is suspected, all too often, the observer concentrates on the orientation of the foot in late swing and at initial contact, (the foot is pointed downward in swing resulting in a toe contact). A common error in these circumstances is to presume that this orientation is due to ankle position alone, that a plantar-flexed ankle only causes the foot to point downward. It is important in cases such as these to appreciate not only the role of the ankle, but also that of the knee in positioning the foot segment, as is illustrated in the next example.
Test Your Knowledge
In this child with cerebral palsy, note the position of the right foot in swing and at initial contact (Video 5). Using this image and the following clinical data pertaining to ankle dorsiflexion,
dorsiflexion (with knee fully extended), right side: -15°; left side: -15°
dorsiflexion (with knee flexed to 90°), right side: -5°; left side: -5°
propose a possible treatment for the drop foot and toe contact in this patient.
Click here to download Video 5
Video 5. Side and front views of a 7-year-old-girl with cerebral palsy spastic diplegia. The visual impression of side view includes a drop foot in terminal swing with a toe initial contact, bilaterally. Also note greater than normal knee flexion at initial contact, bilaterally.
The sagittal plane knee and ankle motion for this child's right side is shown in Figure 9. (Figure 9) Ankle data show that the ankle dorsiflexes normally in mid swing and is in a neutral position at initial contact. The use of an ankle-foot orthosis (AFO) set in a neutral position would lead to the same gait deviation of a toe initial contact because the ankle is not the primary problem. An examination of the knee angle in swing shows reduced and delayed peak knee flexion in swing and greater than normal flexion at initial contact. This results in a foot segment orientation in space with the toe lower than the heel in late swing and at initial contact. (Figure 10) Therefore, correcting this problem of foot orientation needs to be addressed at the knee and not at the ankle joint. Thus, the expense incurred from the improper use of an AFO (which, because the ankle is not the primary problem, would result in the same gait deviation, and therefore no functional improvement) would be further compounded by the expense of then applying the appropriate treatment to manage the primary problem of reduced knee extension at initial contact.
Sagittal plane kinematics for the right knee and ankle in a patient with cerebral palsy (Video 5). There is less than normal knee extension in terminal swing and the knee angle at initial contact is about 35 degrees (Point A). The ankle angle at initial contact is slightly dorsiflexed (Point B). Application of an ankle-foot orthosis set in neutral would not change the kinematics and the patient would continue to have a toe initial contact. Blue band on each plot indicates first standard deviation of the mean normal reference in degrees.
Illustration of the changes in absolute foot segment position at initial contact for: a) knee in full extension and neutral ankle, and b) knee in 30 degrees flexion and neutral ankle. These illustrations demonstrate that foot attitude is influenced not only by ankle position, but also knee position.
Observe the position of the foot (Video 5), ankle, and knee in the sagittal plane. Note that out-of-plane rotations (for example, abnormal transverse plane rotations) render identification of the sagittal plane angles from biplanar video records inaccurate (illustrating the point made earlier in the paper regarding the fallacy of drawing quantitative values from video records).
In both of these examples, gait analysis data provided additional information that altered the treatment decision based on the visual and clinical information alone. Even clinicians experienced in visual assessments can benefit by these additional data.
Cite this: Clinical Gait Analysis and Its Role in Treatment Decision-Making - Medscape - Sep 01, 1999.