Chapter 33 Lower limb orthoses for persons who have had a stroke

• All orthotic intervention must be based on clearly identified objectives.

• The most useful type of lower limb orthosis in stroke rehabilitation is the ankle–foot orthosis (AFO)

• Control of stance phase is an important function of an AFO.

• The maximum angle of dorsiflexion of the AFO is limited by the length of the gastrocnemius.

• Articulated AFOs are only appropriate when gastrocnemius length is adequate.

• The angle of tibial inclination in the AFO is critical for control of knee hyperextension and second rocker.

• Early use of AFOs as a therapeutic aid to stroke rehabilitation should be considered.

Stroke: “A clinical syndrome (a collection of symptoms and signs) of focal (or global) disturbance of cerebral function, lasting no more than 24 hours or leading to death, with no apparent cause other than of vascular origin.”

This definition, published by Aho et al.² on behalf of the World Health Organization (WHO), is the broadly accepted standard definition of stroke. The definition is generally considered to include all cases of cerebral infarction, primary intracerebral hemorrhage, and subarachnoid hemorrhage.³⁹ A stroke may also involve the cerebellum and/or brain stem.

Pathophysiology

Pathological type

Intracerebral hemorrhage and cerebral infarction are the two major pathological types of stroke, with cerebral infarction leading to 81% of strokes.⁵ The third acute cerebrovascular disease, subarachnoid hemorrhage, may or may not result in a clinical stroke.

Although the pathological type of stroke is of clinical significance and influences immediate medical management, it is only a crude predictor of disability and social integration, which are important determinants of medium- and long-term health care needs.²⁴

The system of classification of stroke used in the Oxfordshire Community Stroke Project is widely used (Table 33-1).⁵

Table 33-1 Oxfordshire community stroke project classification of subtypes of cerebral infarction ⁵

Lacunar infarct (LACI)	Pure motor stroke, pure sensory stroke, sensorimotor stroke, or ataxic hemiparesis
Total anterior circulation infarct (TACI)	Combination of new higher cerebral dysfunction (e.g., dysphasia), homonymous visual field defect, and ipsilateral motor and/or sensory deficit of at least two areas (out of face, arm, and leg)
Partial anterior circulation infarct (PACI)	Only two of the three components of a TACI, or with higher cerebral dysfunction alone, or with a motor/sensory deficit more restricted than those classified as LACI (e.g., confined to one limb)
Posterior circulation infarct (POCI)	Any of ipsilateral cranial nerve palsy with contralateral motor and/or sensory deficit, bilateral motor and/or sensory deficit, disorder of conjugate eye movement, cerebellar dysfunction, or isolated homonymous visual field defect

Epidemiology

Many authors have commented on the difficulty of obtaining accurate data on the mortality rate, incidence, and prevalence of stroke.^7,^39,⁴⁰ However, according to WHO estimates, 15 million people suffer strokes each year, and five million are left permanently disabled.³ An estimated 5.5 million deaths from stroke occurred worldwide in 2002, of which approximately 20% to 25% occurred within the first month of stroke and 30% to 40% within the first year.³⁰

Wide geographic and age-related variations are noted, with stroke predominantly a disease of the elderly. Overall prevalence rate is 6 to 8 per 1,000 persons; however, the rate rises to 40 to 70 per 1,000 persons 65 years and older.¹⁶

A consequence of age-related prevalence coupled with the fact that most populations are aging is that the number of stroke survivors will increase even if the incidence does not.⁴³

The cost of stroke is enormous. The American Heart Association estimated that for 2003 in the United States alone, the total cost, including nursing home bills, was $59 billion US.⁴

Historical perspective

Historically, the rehabilitation community has been resistant to the use of orthoses in the treatment of persons who have suffered a stroke. This has been particularly true among therapy professionals who have been trained in certain neurological and neurodevelopmental approaches and believe that use of orthoses will in some way interfere with normal physiological recovery of patients. There now is growing acceptance of the use of orthoses, both for the lower and the upper limb, as an adjunct to therapy.

In situations where orthoses have been used, all too commonly they were considered at a late stage in the rehabilitation process, almost as a last resort. However, this also is changing with recognition of the benefits of early intervention. Orthoses used in the past were constructed from metal and leather and often poorly designed from a biomechanical point of view. Current good orthotic practice dictates that custom-fabricated plastic orthoses best meet the needs of patients and that traditional metal and leather designs should be consigned to history.

Current research

In 2003 the International Society for Prosthetics and Orthotics (ISPO) commissioned a systematic review of current research activity in orthotics in preparation for an international consensus conference on the orthotic management of stroke patients. A report of the conference, including recommendations, was published in 2004.¹³ In this review, Morris²⁷ concluded that “despite technological development, on the whole there remains a dearth of unbiased clinical research regarding the effectiveness of orthotic intervention for stroke with most studies reporting small numbers of subjects, short follow-up periods and often lacking an adequate control for comparison. The poor methodological basis for much of the clinical evidence leaves us prone to errors in interpretation. …”

Findings of the conference agreed that, according to the grading system proposed by Shekelle et al.,³⁷ weak evidence at level C (cross-sectional surveys or case reports) supported the beneficial effects of ankle–foot orthoses (AFOs) on the energy cost of gait, walking speed and cadence, step length, gait symmetry, weight bearing through the affected leg, control of equinus and varus, and hyperextension of the knee. No evidence supporting the view that AFOs could improve spasticity was found.⁸

In a 2004 systematic review of physiotherapy (physical therapy) and functional outcomes after stroke, Van Peppen et al.⁴² found that there was “no or insufficient evidence in terms of functional outcomes for (the use of) orthotics and assistive devices.”

The consensus conference sought to address these clear deficiencies in research evidence by including recommendations for research in its published report (Table 33-2). This conference also expressed concern at the inconsistent terminology used both within and between professional groups. It held the view that unless and until an agreed “lexicon” of terms was developed and implemented internationally, then establishing large-scale, multicenter trials would be difficult.

Table 33-2 Recommendations for research in orthotics

Agree on standard terminology and definitions

Clearly define biomechanical design, materials, and components

Perform well-controlled, multidisciplinary, multicenter research

Use “good practice points” in consensus conference report as basis for priority research

Adapted from Condie E, Campbell J, Martina J: Report of a consensus conference on the orthotic management of stroke patients, Copenhagen, 2004, ISPO.

Treatment recommendations

Functional deficit/biomechanical deficit

Regardless of the causes and precise pathology of stroke, detailed analysis of the biomechanical and functional effects on the patient is essential to the planning of appropriate treatment strategies.

Specifically, for the lower limb and trunk, knowledge of the kinetics and kinematics of normal gait will allow the clinician to identify abnormal patterns (or components) of stroke gait and motion (see Chapter 22).

Commonly, the justification for prescribing an AFO is to address the problem of a “dropped foot.” However, this group of patients faces many more significant challenges to mobility than simple swing phase equinus. Although it is true that in the early stages of recovery after stroke the foot and ankle are often flaccid, leading to difficulty clearing the toes during swing phase, the picture commonly changes over time to one in which the foot and ankle adopt a more typical position of persistent plantarflexion and supination. Many of the most significant gait problems facing stroke survivors occur in the stance phase of gait and are related to the abnormal biomechanical situation.

Although the population of stroke survivors is not homogeneous, a number of commonly encountered gait problems can be identified. Hemiparetic gait can be characterized as slow and stiff, with a reduction in both cadence and step length.³⁴ Poor coordination of movement leads to primary and compensatory gait deviations and a considerable increase in energy cost.²³

Hemiparetic gait is markedly asymmetrical, with the step length of the affected limb greater than that of the unaffected side, while the duration of stance is shorter and that of swing longer on the affected side. This situation is associated with difficulty in bearing weight through the affected limb.^29,³⁵ Initial contact of the foot on the ground typically occurs with the lateral forefoot because of tone-induced equinovarus deformity. Persistence of supination throughout stance affects both ankle stability and balance. Knee hyperextension in mid to late stance is common, and tibial progression in second rocker is impeded by the abnormally plantarflexed position of the foot. In swing, hip and knee flexion and ankle dorsiflexion are reduced or absent, with hip circumduction used to aid ground clearance.³³

Further complications of hemiparetic gait arise due to abnormal alignment of the ground reaction force (GRF) relative to the joints of the lower limb, leading to altered moments and increasing the demand on a damaged neuromuscular system. Any treatment that can achieve realignment of the GRF and reduce this demand is likely to improve mobility and function. In addition to realigning the joints to correct deformity, realignment of the GRF is fundamental to orthotic management.

Principles of assessment

Effective treatment of stroke depends on accurate assessment of deficits, knowledge of the range of treatments available, and setting realistic objectives or goals with involvement of the patient, family, and caregivers. The assessment process, at its optimum, is interdisciplinary in nature should include consideration of balance and posture and passive range of motion of the joints. However, muscle length and the effects of tone and spasticity are of equal, and arguably more, importance.

For example, gastrocnemius shortening is commonly encountered following stroke.^28,^38,⁴¹ As a result of the shortening, passive range of dorsiflexion in the affected leg is greater when the knee joint is flexed than when the knee is extended. Failure to consider this condition when providing an orthosis may lead to a situation in which the foot is dorsiflexed to a position that is inconsistent with the length of the gastrocnemius. The result of this inappropriate dorsiflexion may be prevention of full knee extension in terminal stance and, consequently, persistence of an external hip flexion moment at this important stage of gait (see Chapter 22). The maximum desirable angle of dorsiflexion in the orthosis is dictated by the length of the gastrocnemius.

The team with responsibility for assessment must be experienced and skilled in observational gait analysis. More sophisticated instrumented gait analysis systems can be used according to local availability and are a prerequisite for surgical procedures.²⁰