Principles Of Lower-Extremity Bracing

Jacquelin Perry, M.D. Helen J. Hislop, Ph.D.


96-page monograph published in 1967 by the American Physical Therapy Association, 1740 Broadway, New York, N.Y. 10019. May be obtained from the Association for $2.00.

This illustrated monograph is based on Instructional Courses on the Principles of Lower Extremity Bracing presented by the staff of Rancho Los Amigos Hospital at the annual conferences of the American Physical Therapy Association in 1966 and 1967. It is reprinted from the September 1967 issue of Physical Therapy, with minor alterations.

Mechanics of Walking

Clinical Interpretation; Relationship between Lesion Specificity and Bracing (Perry).

Braces should offer stability for standing, with flexibility for the functional tasks of walking: forward progression, single limb balance, and limb length adjustment. Stance involves heel strike, with weight acceptance as the essential requirement; mid-stance requires trunk glide; push-off needs balance assist; swing phase is divided into early swing with pick-up and late swing with reach. Requirements for stability depend on the site of lesion, rather than its peripheral manifestation, thus different devices are indicated for pes equinus from poliomyelitis and from stroke.

Paralytic Dysfunction

Pathomechanics (Perry); Bracing the Unstable Knee in Flaccid Paralysis (Marilyn Lister, P.T.); Brace Design for Flaccid Paralysis (David Heizer, CO.); Bracing for Patients with Traumatic Paraplegia (Edwin Edberg, P.T.); Long-Leg Brace Design for Traumatic Paraplegia (Heizer).

Flaccidity may originate in the anterior horn (poliomyelitis); axons (infectious neuronitis); myoneural junction (myasthenia gravis); or muscle fibers (muscular dystrophy). Injuries in the lumbar and sacral segments of the spinal cord also cause flaccidity. Unlike poliomyelitis, however, cord injury obliterates precise awareness of position, necessitating reliance on remote sensory clues.

The individual with unilateral paralysis; near vertical hip-trunk alignment; absence of knee flexion contracture; and a foot that rests flat on the floor may wear a free-knee brace. It has a posteriorly offset knee joint and a 90-degree dorsiflexion stop with a weak spring or a hydraulic ankle. This brace restricts knee motion only during stance. Use of the brace consumes less energy during swing and simplifies sitting and climbing. However, the knee may collapse on ramp descent. The locked-knee brace, indicated for greater weakness or malalignment, has three points of fixation -high posterior thigh cuff, anterior knee control (drop or bail locks) and a shoe with stirrup. Bracing varies according to the patient's extent of strength, sensation, mobility, spasticity, and motivation. Four movable segments (lumbar spine, hips, knees and ankles) must be controlled, either by muscular activity, postural alignment, or braces. Spinal orthoses impede dressing, walking, climbing, and sitting. Hip stability is achieved by active hip and trunk hyperextension and crutches, rather than by a pelvic band. Ankles are best stabilized by an adjustable joint locked in seven to ten degrees dorsiflexion, with a heavy shoe shank and stirrup. A heel cushion absorbs the force of heel strike. Patients with Brown-Sequard syndrome utilize one long-leg and one short-leg brace. Those with cauda equina lesions can walk with two short-leg braces.

Control Dysfunction

Pathomechanics (Perry); Control of Lower Extremity Movement in Cerebral Palsy (Virginia Scaramuzza Guess, P.T.); Bracing the Unstable Knee and Ankle in Hemiplegia (Margaret Inaba, P.T.); Short-Leg Brace Design for Hemiplegia (Heizer).

Evaluating cerebral damage is a complex problem because of (1) the patient's impaired intellect; (2) intermingling of mass patterns and selective function; (3) sensory disorders; and (4) spasticity. The patient with primitive patterns only can walk by alternating the mass flexor response at early swing with the extensor pattern in the weight-accepting phase of stance. Because other phases of gait combine flexion and extension patterns, the required coordination is beyond the patient's capability.

Cerebral palsy often presents mixed flexion and extension patterns and perceptual dysfunction. Physical therapy, bracing, and surgery aim to block interference and to develop useful responses. One must ascertain the level at which the child can perform easily and the factors which cause difficulty. Overactive abnormal patterns and resulting deformity may simulate weakness. Facilitation techniques encourage useful movement, but are time-consuming and often effective only during treatment, whereas bracing prolongs desired activity. The Ilfeld hip splint (Fig. 1 ) blocks unwanted hip adduction. The hip action brace, consisting of thigh cuffs attached to a pelvic band, controls spastic adductors, yet allows hip flexion, extension, and abduction. Twisters (Fig. 2 )-steel helical cable encased in rubber tubing secured to a pelvic band and shoe caliper-alter rotation. The extension pattern is augmented by a knee cage, by standing which causes joint compression, and by surgical release of hip flexors. The aim of knee restriction is not local stability, but erect positioning of the whole child so he can develop his extensor pattern. A short-leg brace with the ankle set in slight plantar flexion prevents dorsiflexion. A brace ankle locked at 90 degrees reduces hyperextension of the knee.

Hemiplegics who cannot stabilize the knee during stance because of severe hyperextension caused by weak quadriceps, impaired proprioception, or marked plantar flexor spasticity, may be aided by a short-leg brace locked in slight dorsiflexion or by surgical diminution of posterior muscles. Others have unwanted knee flexion resulting from weak hip and ankle extensors, sensory deficit, or knee flexion contracture. Their treatment aims to strengthen the extension synergy, develop plantar flexor tightness, and correct knee contracture. The last may be reduced by prone positioning with calf and ankle weights, a knee cage or plaster splints, progressive casting, prolonged weight-bearing to stimulate mass extension, or surgery. A long-leg brace is insufficient to stabilize the trunk over the weight-bearing extremity; thus, if any bracing is indicated, a short-leg brace will be adequate, and is lighter, permits the knee to flex during swing, and is easily donned.

Drop foot results from such conditions as spastic or tight plantar flexors, or dorsiflexors that are weak or that function late in forward swing phase. Resisting the total flexion pattern reinforces dorsiflexors. Flaccid drop foot responds to a coil spring brace, which is light, adjustable, and inconspicuous. A dorsiflexion spring assist improves function in the presence of slight plantar spasticity, but will aggravate severe spasticity. A brace allowing ten degrees plantar flexion offers sensory clues by acting as a weight during swing and impacting the leg at weight-acceptance. Motion may be limited by set screws at the ankle of the double adjustable ankle brace (Fig. 3 ). A pretibial shell and an ankle locked in slight plantar flexion ameliorate extreme knee extension difficulty. A high longitudinal arch support for valgus and a lateral heel wedge for varus are more effective than T-straps. Equinovarus is treated with a sturdy brace or surgical transfer of the tibialis anterior.

Structural Insufficiency

Pathomechanics (Perry); Structural Insufficiencies of the Knee in Rheumatoid Arthritis (Guess); Bracing Design for Knee Joint Instability (Heizer).

Bones and ligaments subjected to excessive strain deform initially, then develop extra connective tissue which may restrict movement painfully. Muscular contraction ordinarily protects joints by compressing them. The arthritic, however, avoids contracting muscles in order to escape painful compression. Thus, when he bears weight, he unwittingly accepts unprotected stress, increasing erosion of bones already softened by inflammatory hyperemia, inactivity, and cortisone.

Marked ligamentous adaptation to strain occurs in the posterior knee capsule of the child who substitutes hip and ankle extension for absent quadriceps activity, or walks over an equinus deformity with resulting genu recurvatum. Maximal bracing during childhood insures structural stability in later years. Inactivity is devastating to the arthritic, even one with swollen aching joints. Three problems encountered are flexion contracture, postoperative extension contracture, and ligamentous instability. Braces complement the intensive quadriceps and hamstrings strengthening program. Corrective splinting to reduce flexion is effective, if the tibia can move forward on the femur to avoid posterior knee subluxation. Extension and flexion splints must be used alternately. If the ligaments are lax, external stability may be provided by a knee cage with anterior control and uprights extending from the upper thigh to the ankle; by a conventional long-leg brace; or by a long-leg brace with pretibial shell (Fig. 4 ). Brace design should provide great corrective and supportive forces without exceeding tissue pressure tolerance. Thus, the tiny condylar pads are less effective than the large pretibial shell. The shell is trimmed according to the need for valgus, flexion, or recurvatum correction. Residual knee flexion can be incorporated in a knee brace with a fan lock to permit alignment in flexion; or a dial lock for restriction either of flexion or extension. Bending the uprights to accommodate flexion is undesirable because the brace is thereby weakened.

-Reviewed by Joan E. Edelstein, R.P.T.

Jacquelin Perry, M.D. and Helen J. Hislop, Ph.D. are Editors