Poliomyelitis is a viral infection of the motor neurons in the spinal cord, causing acute flaccid paresis.1 Survivors of poliomyelitis often exhibit gait abnormalities due to lower-limb pareses.2 A typical polio gait pattern is difficult to describe. Polio patients often are creative with compensations to maintain their walking function,3 which was the case in the patient described in this study.
Lower-limb orthoses are often prescribed to reduce gait abnormalities.2 A Dutch population-based study by Ivanyi et al.4 reported that the need for lower-limb orthoses exists in approximately 16% of polio survivors. Brehm et al.2 report the usage of knee-ankle-foot orthoses (KAFOs) by a substantial number of persons with a history of poliomyelitis. A KAFO is often prescribed to provide knee stability in the sagittal plane during stance in case of quadriceps weakness, which is a common finding in polio survivors. However, in some cases, it might be possible to compensate proximal muscle weakness with other methods, for instance with an ankle-foot orthosis.5 This case study illustrates the possibility to optimize gait in a patient with severe quadriceps weakness, using a lightweight custom-made orthopedic shoe. This idea was triggered by the observation of the patient's own walking compensation strategy. The Medical Research Ethics Committee (MREC) of the University Medical Center Utrecht approved our research proposal.
This case study concerns a 37-year-old woman of Iraqi origin who had lived in the Netherlands for 4 years. She suffered from weakness of the quadriceps muscles of the right leg due to poliomyelitis anterior acuta which was diagnosed at the age of 9 months. There was no medical intervention until the age of 31 years, at that time she underwent surgery in Baghdad, Iraq. A tendon transposition was performed, by which the m. biceps femoris of the right leg was attached to the patella so it was supposed to work as an extensor of the knee. She reported that, after surgery, her walking deteriorated. She noted that her toes clawed while she was walking, which induced muscle fatigue and cramp and also prevented her from wearing normal shoes. She developed a particular way of walking, wearing a slipper to prevent her toes from clawing (see physical examination), but this meant she was not able to walk outside, especially in cold or rainy weather. She attended our outpatient clinic, asking for a solution that would enable her to walk outside again.
The patient was a healthy looking woman. Her right leg was approximately 2 cm shorter than the left and her right foot was smaller than the left (Figure 1A). On the right heel there was hyperkeratosis, caused by contact with the floor during walking with the slipper (Figure 1B). No biceps femoris tendon was palpable on the right side. Strength assessments using the Medical Research Council's clinical method6 showed that the strength of the knee extensors on the right side was MRC 1 (visualized contraction of the m. quadriceps and the transposed m. biceps femoris). Knee flexors were MRC 4, probably because the m. biceps femoris was missing as a flexor. Knee external rotation was MRC 1 (due to the transposition of the m. biceps femoris, which is normally the strongest external rotator of the knee). Hip flexors on the right side were MRC 3. The rest of the muscles of the hip, knee, ankle, and foot had normal strength (MRC 5). Range of motion (ROM) of the ankle was as follows: dorsiflexion/plantarflexion, 20/0/40 degrees; inversion/eversion (defined as a triplanar motion around the axis of motion of the subtalar joint, but measured in the frontal plane), 10/20 degrees. ROM of hip and knee was normal, and there was no hyperextension in both knees. The ligamentous integrity of the hips, knees, and ankles was normal on both sides.
Examination of barefoot walking showed that there was no first or third rocker on the right side; she landed on her whole foot sole and her heel stayed in contact with the floor during stance phase while her toes were clawing. She walked very slowly, with small steps. She was able to walk this way for no more than about 20 m, because of muscle fatigue and cramp of the toe flexors. She demonstrated her unusual method of walking, in which she wore a slipper on the front part of her foot, so that her heel hung down over the back edge of the slipper (Figures 1C,D). This allowed her to walk faster and for about 200 m, after which she developed pain in the back of her right knee. During the entire part of the stance phase of the right leg, the knee was fully extended.
Although gait deviations that minimize the penalty of quadriceps weakness have been described in patients with poliomyelitis,7 this deviation, or rather compensation strategy, might be considered quite unique.
The probable mechanism behind the barefoot walking pattern was that contraction of the long flexors of the toes, which are weak plantarflexors, was needed to enforce the eccentric contraction of the plantarflexors (calf muscles), causing a backward tilt of the lower leg to keep the knee extended during the stance phase. The flexion of the toes may also have moved the center of pressure anteriorly and, therefore, increased the extension moment of the knee.
The probable mechanism behind her compensation strategy with the slipper was that the knee extension moment was increased in two ways. In the first place, the plantarflexion knee extension couple was increased because the plantar flexion torque of the triceps surae is maximal when the ankle is in dorsiflexion.8,9 The calf muscles and long flexors were probably lengthened so as to produce sufficient force, so that active contraction of the long flexors was not necessary to keep the knee extended. In the second place, the forefoot wedge created by the slipper probably moved the center of pressure anteriorly and therefore moved the line of action of the ground reaction force further anterior of the knee, increasing the extension moment at the knee. This compensation strategy was less tiring for the patient.
MANAGEMENT STRATEGIES EMPLOYED
In view of the extreme muscle weakness of the extensors of the knee, a KAFO was attempted. It was a UTX swing, designed and developed by Dr. Nils Van Leerdam of Ambroise Holland bv (750 g, knee joined locked during support phase and open in swing phase, pelottes on the anterior side of the leg and fastened with Velcro bandages, and side bar on the lateral side of the limb).
The patient was not very comfortable with this solution because of its inconvenience and weight, and it did not solve the problem. The clawing of the toes remained and still caused muscle fatigue and cramping in the toe flexors. Similarly, when she walked barefoot without the slipper, her walking distance was a maximum of 20 m with the KAFO. It seemed that the clawing of the toes could not be prevented by locking her knee with a KAFO. In that stage, we assumed that a ground reaction ankle-foot orthosis (GRAFO) would not have solved the problem either and that the clawing of the toes could only be prevented by her own solution: a forefoot wedge in combination with a ridge to let her heel hang down. This triggered the idea of copying her compensation strategy in a shoe prescription (see Figures 2A, B).
FINDINGS AND OUTCOMES
The shoe was built in a slight dorsal flexion position of the ankle, and a ridge was made to allow the heel to hang down in the shoe, in order to passively lengthen the calf muscles and long toe flexors. The ridge was softened with Professional Protective Technology (PPT) padding to prevent damage to the soft tissue of the foot. A rocker bar placed distally from the metatarsophalangeal joints was provided to increase the extension moment of the knee.10 A trial period with fine tuning was necessary to achieve the optimal result which is shown in Figures 2C,D. These shoes enabled her to walk about 500 m. The walking distance while wearing the shoes was limited because of fatigue, rather than pain in the back of the knee. The shoe limited pain because it probably decreased the extension moment around the knee (compared with her gait while wearing the slipper) while maintaining sufficient extension moment for knee stability. Most importantly, the shoes prevented the toes from clawing, so no muscle fatigue occurred. Because of the distally placed rocker bar, a third ankle rocker appeared. She was very satisfied with the final result. Meanwhile, a second and third pair of custom-made orthopedic shoes have been made in the same way.
DISCUSSION AND CONCLUSION
The proposed biomechanical explanation is based upon orthotic theory and is not supported by an analysis in a gait laboratory. EMG data would have been informative in comparing the patient's solution and walking with the custom-made shoe. For future studies, it is recommended to perform a gait laboratory analysis. In this case, the clinical outcome and patient satisfaction are obvious.
It seemed that clawing of the toes could only be prevented by her own solution. It is disputable whether this is really the case. Maybe with physical therapy, her coordination could have been corrected so that she would have been able to walk with a KAFO or preferably, with a GRAFO, without the clawing of her toes. As this patient only spoke Iraqi, communication and thus rehabilitation would have been difficult, and success was not guaranteed. Moreover, when trying the KAFO, the patient indicated that she was not comfortable with that solution for its inconvenience and weight and that she would prefer her own compensation strategy with the slipper rather than the KAFO. Copying her compensation strategy in a shoe prescription was a pragmatic but successful solution, which enabled this patient to walk for longer stretches and also outside, to her full satisfaction. Clinicians who might consider a similar solution for a patient should monitor the knee closely in follow-up visits because of the risks of a recurvatum deformity.
Patients can be very creative in compensating for certain problems. As a neuromuscular expertise center (appointed by the Dutch Society for Muscle Diseases), the rehabilitation department of the University Medical Center, Utrecht, gives high priority to patient empowerment. Ensuring good compliance is a reason for clinicians and technicians to stay as close as possible to the patient's wishes and ideas when developing a successful solution. Therefore, it is recommended to seriously examine a patient's own compensation strategy. It can be a guide in clinical practice, providing that potentially damaging aspects are taken into account.
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