lecture 8 Pathological gait.pdf

Biomechanics I Dr. Noha Elserty Pathological gait Impaired gait in common Orthopedic conditions Gluteus Medius Weakness Gluteus medius weakness may occur as either a frank injury to the gluteus...

Biomechanics I Dr. Noha Elserty Pathological gait Impaired gait in common Orthopedic conditions Gluteus Medius Weakness Gluteus medius weakness may occur as either a frank injury to the gluteus medius or secondarily following an injury to another aspect of the limb. GRFV passes medially to hip joint and creates a strong adduction moment around hip joint so, there is tendency of pelvis and trunk to drop laterally to the opposite side toward non-stance limb and this action should be compensated by abductors muscles activity. so, the opposite hip and pelvis drops during this phase (LR, MST) if the gluteus medius has insufficient strength to hold the pelvis level. For example, if the right gluteus medius is weak, when the individual is in midstance on the right, the left hip and pelvis drops. This is a Trendelenburg gait. Compensation: an individual may compensate for a gluteus medius deficiency by lean the trunk laterally towards the ipsilateral side of weakness during midstance. 1 Biomechanics I Dr. Noha Elserty Moving the HAT directly over the limb reduces the moment arm of the gravitational force as it shifts the GRFV toward the affected side. So, the weak gluteus medius. is not required to exert as much force. If the GRFV passes via hip joint, no moment will be created. If it passes lateral to the joint, it will create abduction moment which will be compensated by activity in adductor moment. Unilateral weakness cause Trendelenburg gait, while bilateral weakness cause waddling gait. This type of gait on the long run cause scoliosis, back pain, and fatigue. 2 Biomechanics I Dr. Noha Elserty Gluteus maximus weakness During initial contact and loading response the GRFV passes anterior to hip joint and creates flexion moment that should be compensated by extensor muscle action (extensor maximus). When gluteus maximus muscle is weak, it fails to compensate the flexion moment so there is tendency for excessive hip flexion (jack knifing). Compensation: The patient will try to prevent trunk from falling forward by leaning the trunk backward to shift the GRFV behind the axis of hip joint. This pattern of gait called gluteus maximus gait. If the weakness is bilateral there is a backward lean of the trunk during the entire stride. On the long run this cause sever lumbar lordosis. Hip joint abnormalities: Three conditions around the hip joint will lead to difficulties in stabilizing the pelvis using the abductors: congenital dislocation of the hip (CDH, also known as developmental dysplasia of the hip), coxa vara and slipped femoral epiphysis. In all three, the effective length of the gluteus medius is reduced because the greater trochanter of the femur moves proximally, towards the pelvic brim. Since the muscle is shortened, it is unable to function efficiently and thus contracts with a reduced tension. In CDH and severe cases of slipped femoral epiphysis, a further problem exists in that the normal hip joint is effectively lost, to be replaced by a false hip 3 Biomechanics I Dr. Noha Elserty joint, or pseudarthrosis. This abnormal joint is more laterally placed, giving a reduced lever arm for the abductor muscles. The combination of reduced lever arm and reduced muscle force gives these subjects a powerful incentive to walk with lateral trunk bending. In many cases, particularly in older people with CDH, the false hip joint becomes arthritic and they add a painful hip to their other problems. Pain is frequently also a factor in slipped femoral epiphysis. Unequal leg length: When walking with an unequal leg length, the pelvis tips downwards on the side of the shortened limb, as the body weight is transferred to it. This is sometimes described as ‘stepping into a hole’. The pelvic tilt is accompanied by a compensatory lateral bend of the trunk. Functional leg length discrepancy Four gait abnormalities (circumduction, hip hiking, steppage and vaulting) are closely related, in that they are designed to overcome the same problem – a functional discrepancy in leg length. An ‘anatomical’ leg length discrepancy occurs when the legs are actually different lengths, as measured with a tape measure or, 4 Biomechanics I Dr. Noha Elserty more accurately, by long-leg x-rays. A ‘functional’ leg length discrepancy means that the legs are not necessarily different lengths (although they may be) but that one or both are unable to adjust to the appropriate length for a particular phase of the gait cycle. For natural walking to occur, the stance phase leg needs to be longer than the swing phase leg. If it is not, the swinging leg collides with the ground and is unable to pass the stance leg. The way that a leg is functionally lengthened (for the stance phase) is to extend at the hip and knee and to plantarflex at the ankle. Conversely, the way in which a leg is functionally shortened (for the swing phase) is to flex at the hip and knee and to dorsiflex at the ankle. Failure to achieve all the necessary flexions and extensions is likely to lead to a functional leg discrepancy and hence to one of these gait abnormalities. This usually occurs as the result of a neurological problem. Spasticity of any of the extensors or weakness of any of the flexors tends to make a leg too long in the swing phase, as does the mechanical locking of a joint in extension. Conversely, spasticity of the flexors, weakness of the extensors or a flexion contracture in a joint makes the limb too short for the stance phase. Circumduction An increase in functional leg length is particularly common following a ‘stroke’, where a foot drop (due to anterior tibial weakness or paralysis) may be accompanied by an increase in tone in the hip and knee extensor muscles. Ground contact by the swinging leg can be avoided if it is swung outward, in a movement known as circumduction. The swing phase of the other leg will usually be normal. The movement of circumduction is best seen from in front or behind. 5 Biomechanics I Dr. Noha Elserty Hip hiking Hip hiking is a gait modification in which the pelvis is lifted on the side of the swinging leg, by contraction of the spinal muscles and the lateral abdominal wall. The movement is best seen from behind or in front. hip hiking is commonly used in slow walking with weak hamstrings, since the knee tends to extend prematurely and thus to make the leg too long towards the end of the swing phase. 6 Biomechanics I Dr. Noha Elserty Steppage Steppage is a very simple swing phase modification, consisting of exaggerated knee and hip flexion, to lift the foot higher than usual for increased ground clearance. It is best observed from the side. It is particularly used to compensate for a plantarflexed ankle, commonly known as foot drop, due to inadequate dorsiflexion control. Vaulting The ground clearance for the swinging leg will be increased if the subject goes up on the toes of the stance phase leg, a movement known as vaulting. This causes an exaggerated vertical movement of the trunk, which is both ungainly in appearance and wasteful of energy. It may be observed from either the side or the front. Vaulting is a stance phase modification, whereas the related gait abnormalities (circumduction, hip hiking and steppage) are swing phase modifications. For this reason, vaulting may be a more appropriate solution for problems involving the swing phase leg. Like hip hiking, it is commonly used in slow walking with hamstring weakness, when the knee tends to extend too early in the swing phase. It 7 Biomechanics I Dr. Noha Elserty may also be used on the ‘normal’ side of an above-knee amputee whose prosthetic knee fails to flex adequately in the swing phase. Abnormal hip rotation Because the hip is able to make large rotations in the transverse plane, for which the knee and ankle cannot compensate, an abnormal rotation at the hip involves the whole leg, with the foot showing an abnormal ‘toe in’ or ‘toe out’ alignment. The gait pattern may involve both stance and swing phases and is best observed from behind or in front. Abnormal hip rotation may result from one of three causes: 1. A problem with the muscles producing hip rotation 2. A fault in the way the foot makes contact with the ground 3. As a compensatory movement to overcome some other problem. Problems with the muscles producing hip rotation usually involve spasticity or weakness of the muscles which rotate the femur about the hip joint. For example, Imbalance between the medial and lateral hamstrings is a common cause of rotation; weakness of biceps femoris or spasticity of the medial hamstrings will cause internal 8 Biomechanics I Dr. Noha Elserty rotation of the leg. Conversely, spasticity of biceps femoris or weakness of the medial hamstrings will result in an external rotation. Several foot disorders will produce an abnormal rotation at the hip. Inversion of the foot, whether due to a fixed inversion (pes varus) or to weakness of the peroneal muscles, will internally rotate the whole limb when weight is taken on it. 9