A New Method of Immobilization in the Treatment of Knee Ligament Injuries

WILLIAM B. HANSON, M.D.


Knee ligament injuries present a difficult problem to every orthopedist. The author has long been of the opinion that immobilization procedures typically used, either for conservative or operative treatment, have been poor. After experimenting with many methods, it has been found that the Fig. 1 combination is superior to other methods. It incorporates most of the current surgical and anatomical principles.

No matter how loose the thigh portion of the cast becomes the trochanteric pad incorporated in this splint prevents valgus stress on the knee by pressing on the bony prominence of the greater trochanter.

Internal rotation is maintained by the pelvic band and by rotating the foot internally within the cast. Maintenance of internal rotation is paramount for two reasons: 1) Any external rotational forces affecting the tibia during and after repair of the medial collateral ligaments and posterior capsule will cause laxity in this repair. The result will be not only valgus instability but anterior instability as well; 2 ) Internal rotation must be maintained to relieve the anterior cruciate ligament repair of stress. If the knee is held in internal rotation as described by Slocum and Larson in their magnificent article on "Rotary Instability of the Knee," 1 the lateral collateral ligament, popliteal muscle, posterior cruciate ligament, fascia lata, and posterior lateral capsule prevent anterior subluxation. The author has tested this hypothesis many times and has found it to be valid.

In cases of injury to the lateral ligament, pelvic band pressure against the opposite iliac crest controls varus stress on the knee.

In summary, this splint-cast combination controls valgus, varus, rotation, and anterior subluxation.

Technique

After anterior cruciate and medial collateral ligament repair has been carried out, a long-leg cast is applied, maintaining the knee in 30 degrees of flexion and the tibia in maximum internal rotation. A large piece of felt is applied to the entire lateral and posterior surfaces of the foot to prevent pressure sores. After the cast sets, the leg is held with the hip in 10 degrees of internal rotation and the splint is attached with a roll of five-inch plaster. The trochanteric pad is adjusted firmly against the greater trochanter and the waist band buckled.

If the principles incorporated in this splint are understood, it can be used for any combination of ligamentous injuries. This is done by making the proper adjustments in the flexion-extension attitude of the knee, rotation of the tibia, and adjustment of the trochanter pad and pelvic band.

Postoperatively the knee should be x-rayed periodically. In fact, the method should not be used unless this is done. This is necessary to assure that the remaining intact ligaments are not being overstretched and that the knee is not subluxing medially or laterally in cases of marked ligamentous instability. It is essential to be alert to the development of pressure areas on the outer border of the foot. If the area is adequately padded with felt, pressure sores can be prevented.

The patient is encouraged to carry out straight-leg lifts and quadriceps and gastrocnemius setting-up exercises. The cast is usually removed at six weeks; occasionally, a cylinder is used for an additional 10 to 14 days. This removal, of course, is followed by a vigorous exercise program.

In the author's hands this method has produced results that are dramatically better than those obtained with other methods. Quadriceps atrophy is lessened because of better immobilization and an increased sense of security on the part of the patient.

Work is proceeding on an adjustable splint which will fit all patients, thus avoiding the problems involved in getting the splint ready for use at the time of surgery.

This brace has been used in treating femoral fractures in combination with long-leg casts, but as yet not enough experience has been gained to justify a report.

Descriptors: Cast; immobilization; knee ligament injuries; pelvic-band; treatment; trochanteric pad.

References:
1. J. Bone and Joint Surg. 5O-A:2:211-225, March 1968.