Hip-Rotation Control Straps
ERIC HOFFMAN, B.A., C.P.O.*New York, New York
Some children with spina bifida, cerebral palsy and other neuromuscular disorders display deviant walking patterns which include markedly abnormal rotation at the hip. Fitting these patients with bilateral knee-ankle-foot orthoses (KAFOs), with or without knee locks, reduces many of their gait deviations, but does not resolve hip malalignment.
Traditional means of controlling rotation include pelvic bands and hip joints, spreader bars and Silesian bandages. Pelvic bands and single-axis hip joints are the most common solution employed for hip-rotation control. The metal band, if fitted to the torso between both iliac crests and greater trochanters and lying across the sacrum, grasps the pelvis securely so that, in conjunction with KAFOs, limb rotary control is achieved. A pelvic band and hip joints, however, add pounds to the juvenile orthoses. Single-axis hip joints limit frontal as well as transverse plane motion and are bulky. In addition, the lower-limb orthoses joined by the pelvic band must now be donned as a unit, a time-consuming, difficult task even for older children, especially if the child refuses assistance.
Alternatively, a metal spreader bar can be used to lock both legs in a fixed relationship, so that each leg in effect works against the other when the patient attempts to rotate his hip. While fairly effective in controlling rotation, the spreader bar also restricts frontal plane motion, prohibits reciprocal gait, and often requires the patient to wear the orthoses over trousers or to purchase specially modified clothing equipped with snaps or zippers on the medial trouser seams. The traditional controls of hip malrotation are often so restrictive that whatever gains are achieved are overshadowed by the functional disadvantages.
Silesian bandages appear to solve some of the problems encountered with metal components. The bandage is lightweight, streamlined and not very restrictive. In order to function optimally, however, a prosthetic-type socket must be employed to achieve proper attachment of the strap. On the lateral aspect, the attachment should be posterior and superior to the greater trochanter while the anterior attachment should be equidistant above and below a point corresponding to ischial tuberosity level. These attachment points are not ordinarily on conventional KAFOs. In order to control external rotation, some clinicians have attached a Silesian bandage only to the lateral upright, but such a single attachment does not offer maximum control.
As no lightweight control for severe internal rotation existed, New York University developed an internal-rotation control strap which combines features of the prosthetic Silesian bandage and the University of California auxillary suspension strap. The new strap controls internal rotation yet allows reciprocal gait and does not restrict sitting. It was developed for a study population of children having either spina bifida with L2-L5 lesions or spastic cerebral palsy who originally wore metal and leather KAFOs connected to a full pelvic band by means of single-axis hip joints. The hip joints and pelvic bands were removed from the child's orthoses and replaced by a fabric waist belt having two posterior tapes connected obliquely between the belt and the lateral upright of each KAFO. The tapes are relatively taut when the patient stands, thus externally rotating the limbs effectively. The attachment of each tape is anterior and distal to the anatomic hip joint, so that when the patient flexes the hips to 90 deg., as in sitting, the tapes slacken automatically. The control strap is lightweight, easy to don, cosmetic and does not irritate sensitive skin. All seven children originally fitted with the internal rotation control strap are still wearing them with good effect. The longest wear period to date is 20 months.
R.W. is a 5-year-old boy who has spina bifida at the L3-4 level and has had bilateral gluteus medius tendon transfers. The patient presented a crouched gait and ankle weakness and was currently wearing bilateral metal and leather hip-knee-ankle-foot orthoses (HKAFOs). He ambulated with a Rollator with the hip joints unlocked. Upon removal of the pelvic band and joints from his orthoses, he moved with marked internal rotation. An internal-rotation control strap was fabricated and attached to his orthoses (Figs. 1 -2 ). The strap improved his leg position considerably, and he was able to walk with as much rotational correction as with the pelvic band.
Utilizing similar principles, an external-rotation control strap has also been developed. Even simpler than the internal-rotation control, it does not require a waist belt. It consists of a single anterior strap connecting the proximal lateral uprights or thigh shells of bilateral KAFOs. As the strap is shortened, the orthoses internally rotate the limbs. The strap is located at the approximate level of the greater trochanter and inguinal crease, very close to the axis of the hip joint in the frontal plane, so that little or no restriction is experienced in flexion or extension when the child walks and sits. Nylon chafes are mounted on the orthoses and a single Velcro strap used, doubling back on itself at each chafe. The strap is comfortable, lightweight and washable and is donned and doffed easily for dressing or toileting.
L.M. is a 5-year-old girl with spina bifida at the L4-LS level who had bilateral derotational osteotomies at age 4. She was originally seen wearing bilateral HKAFOs with hip joints unlocked. When the pelvic band and hip joints were removed, she presented marked external rotation. Because of severe pes valgus, plastic/metal KAFOs were fabricated for more precise ankle control; an external-rotation control strap was added (Fig. 3 ) to permit the patient to ambulate satisfactorily without external rotation.
In conclusion, two effective, simple rotation control straps have been developed that can, in many cases, replace metal pelvic bands and hip joints on bilateral knee-ankle-foot orthoses. The straps are lightweight, cosmetic and comfortable. They are easily fabricated and can be used as an inexpensive diagnostic tool as well as a definitive orthotic component.
Fabrication Procedures for the Internal-Rotation Control Strap
Fabrication of the internal-rotation control strap is simple, and all required materials are available in the usual prosthetic-orthotic laboratory: approximately one meter each of 3.75 and 2.5 cm wide Dacron webbing, 50 cm each of 3.75 and 2.5 cm Velcro hook and pile, one 3.75 cm steel loop; two pieces of .125 cm thick polyethylene sheeting, 2.5 x 7.5 cm; and a square of .25 cm thick PE-LITE 3.75 x 3.75 cm. Leather may be used for the belt; however, Dacron is washable, a necessary consideration for incontinent patients, and is less expensive.
First, the patient's waist circumference is measured and a waist belt fabricated using 3.75 cm Dacron with a closure of Velcro and a steel loop (Fig. 4). On the back a 2.5 cm square of polyethylene is sewn to the outer surface, at the middle of the belt. A hole is punched through the square and belt, and the internally threaded half of a Chicago screw is inserted. The PE-LITE square is sewn to the belt over the base of the screw. The belt is then fitted to the patient, who is wearing KAFOs. The distance from the Chicago screw to the upper end of each lateral upright is measured, making sure to pass the tape measure above the apex of each buttock. Fifteen centimeters are added to the measurement on each side, and two 2.5 cm Dacron tapes are made. One end of each tape is reinforced with a 1.53 cm square of polyethylene and approximately 12.5 cm of Velcro hook sewn on the other end, followed by 15 cm of pile.
A hole is punched in the reinforced end of each tape for attachment to the Chicago screw on the waist belt. The completed belt is then fitted to the patient. Each tape is passed over the apex of the buttock to the upper end of the lateral upright. An attachment point is located on the upright, distal to the anatomic hip joint. This allows the tapes to remain taut when the hip is flexed partially and to slacken in full 90 deg. flexion. The attachment must be distal and posterior to the anatomical hip joint. A hole is drilled and tapped and an 8-32 screw and a nylon chafe attached. The oblique tapes are tightened until the desired amount of external rotation is reached. The patient is checked sitting and walking to confirm that hip flexion is not hindered. If flexion is affected, the tape attachment must be relocated.
Fabrication Procedures for the External-Rotation Control Strap
Nylon chafes are attached to the proximal lateral uprights or shells of the knee-ankle-foot orthoses as close as possible to the level of the anatomic hip joint. A Velcro pile strap 2.5 cm in width is then made, the length being 30 cm longer than the dimension between the lateral midlines of each leg. The strap should have approximately 15 cm of Velcro hook on each end. The ends of the strap are inserted through the nylon chafes and the strap tightened until the hips are in the desired degree of relative internal rotation.
*Child Prosthetics and Orthotic Studies, New York University Post-Graduate Medical School, 317 East 34th Street, New York, NY 10016.