Amputee Rehabilitation and Exercise News

Introduction

In late 2002, Stephen Kemp, Managing Director of Hydraujoint Ltd, himself a trans-tibial amputee, approached John Henley-King of Massey University Research Services about the possibility of obtaining some assistance with the design and prototyping of an exercise device to improve muscle strength and functional capacity of amputees. The device is intended to be used by amputees in their own home in an unsupervised exercise setting, and so must be inherently safe and easy to use. As a first step in this process, this literature review has been compiled to provide a basis for design and development. The review will address the issues of the relationship between muscle strength and functional capacity in trans-tibial amputees, the effectiveness of strength training in amputees, the requirements of any exercise devices or regimes for amputees, and will touch briefly on the incidence and control of phantom pain.

Literature Review

Reduction in thigh muscle strength in trans-tibial amputees has been shown to be highly correlated with muscle atrophy and reduction in clinical function (Renstrom, Grimby, & Larsson, 1983). In this study, thirty-two trans-tibial amputees participated in examinations of their isometric and isokinetic knee extension and flexion strength using an isokinetic dynamometer, and the degree of atrophy of the thigh muscles. The muscle strength in the amputated leg with and without prosthesis was significantly lower than the strength in the non-amputated leg. Knee extension strength was significantly correlated to the mean muscle fibre area of the vastus lateralis, but there was no correlation between strength and the cross-sectional area of the quadriceps muscles. The reduction in knee extension and flexion strength in the amputated leg both with and without prosthesis compared with the non-amputated leg was larger than the reduction in cross-sectional areas of the quadriceps and hamstring muscles, which could indicate that other factors such as changes in motor unit recruitment patterns are important in the reduction of muscle strength. Isometric and isokinetic knee extension and flexion strength values in the amputated leg with prosthesis were significantly correlated to step length, maximal walking speed and circumference of the thigh. Because step length is a major determinant of walking speed and efficiency, this result indicates that trans-tibial amputees with improved thigh muscle strength will have better walking capacity.

Muscle strength has been shown to be an important factor in fall prevention in the elderly. Hurley and Roth (Hurley & Roth, 2000) indicate that indicate that strength training in the elderly, among other things:

             (i) produces substantial increases in the strength, mass, power and quality of skeletal muscle;

             (ii) can increase endurance performance;

             (iii) normalises blood pressure in those with high normal values;

             (iv) reduces insulin resistance;

             (v) decreases both total and intra-abdominal fat;

             (vi) reduces risk factors for falls; and

             (vii) may reduce pain and improve function in those with osteoarthritis in the knee region.

In recent studies in New Zealand (Campbell, Borrie, & Spears, 1989; Campbell, Robertson, Gardner, Norton, & Buchner, 1999) it has been shown that a low intensity, community based exercise programme including strength training reduces the risk of falling in older adults. The incidence and fear of falling is pervasive among amputees, and Miller and co-workers (Miller, Deathe, Speechley, & Koval, 2001; Miller, Speechley, & Deathe, 2001) showed that balance confidence was a major protective factor. Thigh muscle strength is a major determinant of balance confidence, and so improvement of thigh muscle strength in amputees would be expected to improve balance, and so reduce the incidence of falls.

The gait of trans-tibial amputees is significantly different from that of non-amputees, in particular, stride length is lower, and preferred walking speed is slower. These differences have been shown to resemble the effect of additional load on the ankle of a normal walker (Eke-Okoro, 1999). That is, the knee flexor and extensor muscles must exert larger forces in the amputee to compensate for the lack of ankle torques. There is some rather inconsistent evidence that a slightly increased moment of inertia of the prosthesis is preferred by amputees. This could be because the increased inertia reduces the work required of the knee extensors during late swing phase of gait (Hillery & Wallace, 2000).

In normal walking, the gait on left and right sides is highly symmetrical. This symmetry is not observed in amputees. In general, step length, step time and swing time are significantly longer on the amputated side, while stance time and single support time are significantly shorter on the amputated side (Isakov, Keren, & Benjuya, 2000). Isakov et al also found large differences in muscle timing and relative activation between the sound and amputated limbs which they attributed to the prosthetic foot impeding forward motion in early swing phase and the need to support the knee on the amputated side in early stance (Isakov, Burger, Krajnik, Gregoric, & Marincek, 2001).

The absence of ankle plantar-flexion muscles has been considered a major disability in amputee gait because these are the major producers of forward propulsion. The amputee overcomes this problem by using other muscles or changing the characteristics of gait (Michel & Do, 2002). One of the strategies most often observed to achieve this is “hip-hiking” (increasing the angle of the pelvis in the frontal plane during swing phase). This strategy has quite serious consequences for walking duration because it rapidly fatigues the hip abductor muscles. It has been shown that those amputees with strong hip abductor muscles display increased weight-bearing on the amputated limb, improved gait parameters, and reduced medio-lateral excursion of the centre of pressure under the amputated limb (Nadollek, Brauer, & Isles, 2002). Nadollek at al conclude that:

             This research confirms the asymmetrical nature of amputee stance and demonstrates symmetry of strength and gait measures between limbs. The correlations between hip abductor muscle strength, weight distribution and gait measures illustrates the importance of pre- and post-operative training of these muscles.

It is generally accepted that the energy cost of walking with a lower-limb prosthesis is higher than that of normal walking, and that the extra energy required may be reduced by appropriate physical conditioning (Ward & Meyers, 1995). Endurance training has been shown to be effective in increasing VO2max, anaerobic threshold, and maximum workload for amputees, to a point where there is no significant difference from normal control subjects. An appropriate programme based on individual anaerobic threshold has been shown to be effective in this respect (Chin et al., 2001). Because the metabolic cost of walking is high for amputees, and they are generally less fit than normal control subjects, amputee walking endurance is much lower than that of the non-amputee. Walking endurance is a useful measure of functional capacity in lower-limb amputees, and is often measured using the two-minute walk test. This is a simple test that measures the total distance walked in two minutes at a self-selected pace, and it has been proven reliable and sensitive to the effects of rehabilitation and physical training (Brooks et al., 2002; Brooks, Parsons, Hunter, Devlin, & Walker, 2001).

Strength training of the knee muscles in trans-tibial amputees at several fixed angular speeds has demonstrated increases in both size of the knee extensor and flexor muscles and their ability to produce force (Klingenstierna, Renstrom, Grimby, & Morelli, 1990). In this study, the intact leg was also trained, but did not demonstrate the magnitude of changes found in the amputated limb. The subjects reported that they considered they could walk more than twice the distance achieved before training and could manage better without mobility aids. The study also indicated a larger increase in the size and strength of type II (fast twitch, anaerobic) fibres compared with type I fibres, which indicates that the training forces were sufficient to activate almost all the motor units in the muscle.

In a similar study, Moirenfeld et al (Moirenfeld, Ayalon, Ben-Sira, & Isakov, 2000) measured concentric strength and endurance of the thigh muscles using an isokinetic dynamometer. They found that peak torque for extension and flexion was significantly higher in the sound limb, and that the fatigue index for flexion torque was significantly higher in the sound limb (p<0.01) which they attributed to the degree of muscle atrophy on the amputated side. They concluded that:

             It is of great importance to reduce the bilateral deficit and the degree of atrophy as soon as possible in order to improve the level of performance. By choosing a correct strength and endurance training programme, one may expect to get a significant and good reaction from the muscles of the amputated limb as is expected from training the muscles of a sound limb.

Many exercise regimes and training programmes have been found helpful in the process of rehabilitation of amputees and reintegration into the workforce. These may be divided into four main components: flexibility, muscle strength, cardiovascular training, and balance and gait (Esquenazi & DiGiacomo, 2001). Kegel at al (Kegel, Burgess, Starr, & Daly, 1981) showed that the use of biofeedback in a controlled isometric exercise program produced increases in muscle bulk below the knee. Isokinetic (constant speed) exercise has been shown to be effective in increasing the strength of debilitated muscles. However, this is usually achieved using a specific, and usually very expensive, isokinetic dynamometer that was designed for use by non-amputees. Consequently, amputees find the device difficult to use, even if they are able to gain access to one. Modifications to an isokinetic dynamometer to allow use by trans-tibial amputees with short stumps were described by Marin and co-workers (Marin, Spellman, Kenyon, & Belandres, 1992), and it appears that most practitioners would consider modification of existing exercise equipment as a first step in achieving an appropriate exercise regime for trans-tibial amputees.

There is a large body of literature on the incidence of phantom pain and stump pain in amputees, but there appears to be very little published research dealing with the effect of exercise on either phantom or stump pain. A recent study (Nikolajsen & Staehelin Jensen, 2000) concludes:

             Phantom pain is experienced by 60% to 80% of patients following limb amputation but is only severe in about 5% to 10% of cases. The mechanisms underlying pain in amputees are not fully understood, but factors in both the peripheral and central nervous system play a role.

A recent paper (Vichitrananda & Pausawasdi, 2001) has reported relief from severe phantom limb pain using Midazolam (a benzodiazepine) which acts to enhance the action of the inhibitory neurotransmitter gamma aminobutyric acid (GABA) in the brain and the action of glycine (also an inhibitory neurotransmitter) on receptors in spinal neurons. This result may indicate that the pain results from the imbalance of self-sustaining neural activity exceeding inhibitory control. Consequently, it is feasible that an appropriate exercise regime could ameliorate the incidence and severity of both phantom and stump pain by affecting cortical reorganisation and peripheral neural circuits involved in physical activity.

Conclusions

1. Trans-tibial amputees would benefit from both general physical fitness training and strength and endurance training of knee flexor and extensor muscles and hip abductor muscles.

2. Reduction in gait asymmetry may be achieved by increasing muscular strength and endurance in the amputated limb.

3. Improvements in muscular strength and endurance will result in enhanced functional capacity in trans-tibial amputees as measured by the two-minute walk test.

4. The design of any exercise device to improve muscular strength and endurance must allow for use by amputees with short stumps and must accommodate training of the hip abductor muscles in addition to the knee flexors and extensors.

5. The effect of any strength or exercise programme on the incidence and severity of phantom pain is, at present, unknown.

Alan Walmsley PhD IFNHH

Massey University

Wellington

2 December 2003

References

Brooks, D., Hunter, J. P., Parsons, J., Livsey, E., Quirt, J., & Devlin, M. (2002). Reliability of the two-minute walk test in individuals with transtibial amputation. Archives of Physical Medicine and Rehabilitation, 83(11), 1562-1565. Brooks, D., Parsons, J., Hunter, J. P., Devlin, M., & Walker, J. (2001). The 2-minute walk test as a measure of functional improvement in persons with lower limb amputation. Archives of Physical Medicine and Rehabilitation, 82(10), 1478-1483. Campbell, A. J., Borrie, M. J., & Spears, G. F. (1989). Risk factors for falls in a community-based prospective study of people 70 years and older. Journal of Gerontology, 44(4), M112-117. Campbell, A. J., Robertson, M. C., Gardner, M. M., Norton, R. N., & Buchner, D. M. (1999). Falls prevention over 2 years: a randomized controlled trial in women 80 years and older.[comment]. Age & Ageing, 28(6), 513-518. Chin, T., Sawamura, S., Fujita, H., Nakajima, S., Ojima, I., Oyabu, H., et al. (2001). Effect of endurance training program based on anaerobic threshold (AT) for lower limb amputees. Journal of Rehabilitation Research & Development., 38(1), 7-11. Eke-Okoro, S. T. (1999). Exploration of paretic gait by differential loading in normals. Clinical Biomechanics, 14(2), 136-140. Esquenazi, A., & DiGiacomo, R. (2001). Rehabilitation after amputation. Journal of the American Podiatric Medical Association, 91(1), 13-22. Hillery, S. C., & Wallace, E. S. (2000). Trans-tibial amputee gait adaptations as a result of prosthetic inertial manipulation. Disability & Rehabilitation, 22(8), 383-386. Hurley, B. F., & Roth, S. M. (2000). Strength training in the elderly: effects on risk factors for age-related diseases. Sports Medicine, 30(4), 249-268. Isakov, E., Burger, H., Krajnik, J., Gregoric, M., & Marincek, C. (2001). Knee muscle activity during ambulation of trans-tibial amputees. Journal of Rehabilitation Medicine, 33(5), 196-199. Isakov, E., Keren, O., & Benjuya, N. (2000). Trans-tibial amputee gait: time-distance parameters and EMG activity. Prosthetics & Orthotics International, 24(3), 216-220. Kegel, B., Burgess, E. M., Starr, T. W., & Daly, W. K. (1981). Effects of isometric muscle training on residual limb volume, strength, and gait of below-knee amputees. Physical Therapy, 61(10), 1419-1426. Klingenstierna, U., Renstrom, P., Grimby, G., & Morelli, B. (1990). Isokinetic strength training in below-knee amputees. Scandinavian Journal of Rehabilitation Medicine, 22(1), 39-43. Marin, R., Spellman, N., Kenyon, M., & Belandres, P. V. (1992). Isokinetic exercise system modification for short below-the-knee residual limbs. Archives of Physical Medicine & Rehabilitation., 73(9), 883-885. Michel, V., & Do, M. C. (2002). Are stance ankle plantar flexor muscles necessary to generate propulsive force during human gait initiation? Neuroscience Letters, 325(2), 139-143. Miller, W. C., Deathe, A. B., Speechley, M., & Koval, J. (2001). The influence of falling, fear of falling, and balance confidence on prosthetic mobility and social activity among individuals with a lower extremity amputation. Archives of Physical Medicine and Rehabilitation, 82(9), 1238-1244. Miller, W. C., Speechley, M., & Deathe, B. (2001). The prevalence and risk factors of falling and fear of falling among lower extremity amputees. Archives of Physical Medicine and Rehabilitation, 82(8), 1031-1037.

Moirenfeld, I., Ayalon, M., Ben-Sira, D., & Isakov, E. (2000). Isokinetic strength and endurance of the knee extensors and flexors in trans-tibial amputees. Prosthetics & Orthotics International, 24(3), 221-225. Nadollek, H., Brauer, S., & Isles, R. (2002). Outcomes after trans-tibial amputation: the relationship between quiet stance ability, strength of hip abductor muscles and gait. Physiotherapy Research International, 7(4), 203-214. Nikolajsen, L., & Staehelin Jensen, T. (2000). Phantom limb pain. Current Review of Pain, 4(2), 166-170. Renstrom, P., Grimby, G., & Larsson, E. (1983). Thigh muscle strength in below-knee amputees. Scandinavian Journal of Rehabilitation Medicine – Supplementum, 9, 163-173. Vichitrananda, C., & Pausawasdi, S. (2001). Midazolam for the treatment of phantom limb pain exacerbation: preliminary reports. Journal of the Medical Association of Thailand, 84(2), 299-302. Ward, K. H., & Meyers, M. C. (1995). Exercise performance of lower-extremity amputees. Sports Medicine., 20(4), 207-214.