Vapc Prescription Procedures For Knee Orthoses And Knee-Ankle-Foot Orthoses
Gustav Rubin, M.D., FACS, *
Malcolm Dixon, B.S., M.A., RPT *
Michael Danisi, C.O. *
It is the purpose of this paper to present the VAPC Clinic Team's approach to the prescription of knee orthoses (KO's) and knee-ankle-foot orthoses (KAFO's).
To conform to recently accepted procedure the use of eponyms has been avoided wherever possible. Because the total elimination of eponyms from orthotic literature is still in transition, the parenthetical inclusion, such as the term, "Swedish Knee Cage" (Fig. 1 ), will be noted in the KO-KAFO chart (Fig. 2 ). This is, as indicated, a metal "rigid three-point pressure KO" and should be distinguished from a plastic contoured "rigid three-point pressure KO" such as the IRM SKKO shown in Fig. 3.
In the accompanying KO-KAFO chart the authors have placed emphasis upon the knee. As Viel has indicated the "key problem remains knee stability" . AFO and shoe component charts (Fig. 4 & Fig. 5 ) have been included, which, with the KAFO chart, aid in the representation of a total KAFO orthotic system.
The development of an orthotic prescription proceeds through several stages:
- Patient's History
- Physical Demands of Patient's Vocational and Recreational Pursuits
- Physical Status
- Gait Characteristics
- Determination of Functional Requirements of Components
- Selection of Components
- Discussion with the Patient to Obtain His Acceptance of the Prescription
- Prescription of the Orthosis
Information should be elicited about the character of the terrain where the patient will walk and, when indicated, frequency and duration of clonic episodes, conditions within the home environment (stairs, etc.), age, general health and past experience with orthoses.
Physical Demands of the Patient's Vocational and Recreational Pursuits
These factors will directly influence selection of components. An example of this consideration is given later. Most patients present unique problems which can be evaluated only on an individual basis.
When clinically indicated, a referral to an internist for an examination including cardiopulmonary evaluation should be made, especially when a great amount of effort will be required, as with bilateral KAFO's. Neuro-musculo-skeletal evaluation including the conditions of joints and their supporting structures should be given particular attention by the Clinic Team. Other consultants should be called upon for opinions where necessary, as, for example, dermatologists.
The patient who can ambulate or stand should be required to do so, even if assistance or parallel bars are needed. The problems that are manifested, in association with the findings of the first three stages, will lead the Clinic Team directly to the next stage, determination of the functional requirements of the orthoses.
Determination of the Functional Requirements of the Components Needed
The format developed by McCollough is very useful. He suggests the use of the following symbols "to indicate desired control of designated function":
- F =
- FREE — Free motion.
- A =
- ASSIST — Application of an external force for the purpose of increasing the range, velocity, or force of a motion.
- R =
- RESIST — Application of an external force for the purpose of decreasing the velocity or force of a motion.
- S =
- STOP — Inclusion of a static unit to deter an undesired motion in one direction.
- v =
- Variable — A unit that can be adjusted without making a structural change.
- H =
- HOLD — Elimination of all motion in prescribed plane (verify position).
- L =
- LOCK — Device includes an optional lock.
The authors use in a clinical trial a stock shoe clasp or a stock polypropylene AFO to aid in evaluation of the anticipated response to AFO's. This is particularly helpful to determine if spring loading will precipitate clonus when mild to moderate spasm exists.
Selection of the Most Desirable Components For the Individual Patients
This decision will take into account not only the function of the components but also the weight, cosmesis, and sturdiness of the materials. A 118-lb. city-dwelling female will usually require a different prescription for the same condition than would a 250-lb. male farm worker. For the farm worker, in contrast to the city dweller, it would usually be advisable to sacrifice cosmesis for strength and durability of components. As indicated above, the AFO components (Fig. 4 ) and the shoe components (Fig. 5 ) have been charted separately and those charts should be used in conjunction with the KAFO chart to arrive at a prescription.
Discussion With the Patient
The prescription developed by the Clinic Team should be discussed with the patient to obtain his cooperation. When possible, a device similar to that planned for him should be shown to the patient. He may refuse to accept change and prefer to continue with an orthosis of a type to which he is accustomed rather than a more modern orthosis. Prescription over the patient's objection will almost invariably lead to rejection.
When all of the factors discussed above have been considered thoroughly the prescription will usually "fall into place."
KO's and KAFO's
The following orthoses are discussed briefly in the order in which they are referred to in Fig. 2 .
Rigid Three-Point Pressure KO
(Fig. 1 )
There are several variants of this KO. The simplest is of metal and fabric, the metal rigid three-point pressure KO (Fig. 1 ). Examples of plastic "rigid three-point pressure KO's" have been demonstrated by Lehneis (the IRM SK KO), (Fig. 3 ) and by Nitschke (the PTS KO) . The metal device is available commercially and the latter two require custom fabrication. The area of clinical application of these orthoses is described in the chart. Their principal function is to limit knee hyperextension by virtue of the three-point pressure design. The mediolateral support that is provided by rigid orthoses of this type is only present in the hyperextended position. As soon as knee flexion occurs the effectiveness of the M-L support is lost.
KO With Offset Knee Joints or Knee Locks
(Fig. 6 and Fig. 7 )
These may be used to stop or lock the knee to control hyperextension. If the knee hyperextension is between 5 deg. and 15 deg. the offset knee joints may be satisfactory and a trial with offset joints should be made since knee motion will be retained. If these joints are not adequate, i.e., if the knee is in slight flexion, or in excessive hyperextension, it will be necessary to use knee locks. For the offset knee joints to function properly and prevent knee collapse in flexion several prerequisites must exist, 1) the knee must hyper-extend at least 5 deg., 2) there should be no hip flexion contracture, 3) there should be no ankle dorsiflexion deformity, and 4) there should be adequate power from the gluteus maximus and the soleus.
Knee Stabilizing AFO
(Fig. 8 )
This design is designated an AFO because no component of the orthosis crosses the knee joint; nevertheless, its principal action is on the knee joint , and it, therefore, is included here. It may be used if, in addition to the need for knee stabilization, there is a concommitant requirement for an ankle orthosis. The ankle orthosis should incorporate a dorsiflexion stop adjusted in plantarflexion to produce a knee extension force. There must also be an absence of hip flexion contracture as well as retention of fair hip extensor power . The authors prefer to use this orthosis when quadriceps power is rated not less than "poor" and with an intact opposite lower limb. When the indications for its use are present, this orthosis allows the patient to retain an important freedom, knee motion. It is useful when mild or moderate knee flexion instability is present.
The Spiral KO
(Fig. 9 )
The Spiral KO is an elastic fabric KO reinforced with flexible stays. It is useful only for mild instability and functions primarily as a "reminder" type of orthosis, i.e., as the patient ambulates the restraints introduced "remind" him to bring his knee to full extension on weight-bearing, and thereby stabilize the knee. Its presence also "reminds" the patient to favor the knee when it is used for mild medio-lateral instability. The stays add only minimal resistance to knee instability.
(Fig. 10 )
This orthosis includes the unique feature of suprapatellar-cuff suspension in the manner of the cuff suspension of the PTB prosthesis. It can be fabricated with drop locks at the knee for moderate or severe flexion instability. When used to resist mediolateral ligament laxity, a knee lock is unnecessary except in extreme cases.
Double-Bar or Single-Bar KAFO
(Fig. 11 )
Traditionally this is the term used to describe a KAFO fabricated with either aluminum or steel medial and/or lateral bars, with or without (as specifically indicated) an ankle joint, and with either a solid stirrup or a split stirrup. Offset knee joints or knee locks may be used. Variants may employ all polypropylene (Fig. 12 ), polypropylene and polyethylene (Fig. 13 ), pneumatic knee joint locks (Fig. 14 ), or a KAFO of polypropylene plus a shoe clasp (Fig. 15 ).
Hinged Elastic KO
(Fig. 16 )
The hinged elastic KO is slightly more effective for resistance to medio-lateral knee ligament laxity than is the spiral KO, and is used if the complaints are mild. The improved resistance to M-L displacement and the addition of limited A-P displacement resistance are achieved with hinged medial and lateral metal struts and knee locks. These provide resistance restraints rather than true locking because of the elasticity of the cuffs.
Double Anterior Loop KO (Lenox Hill Derotation Orthosis)
(Fig. 17 )
The double anterior loop KO is essentially a metal KO fabricated to provide resistance to medio-lateral displacement and limited resistance to anteroposterior placement due to ligament laxity. A stop to A-P displacement is added when knee locks are employed. Suspension is achieved by the use of circular latex-rubber straps, a disadvantage when circulatory or edema problems are present.
Plastic "Shell" KO
(Fig. 18 )
The plastic "shell" KO is a custom made, contoured solid knee orthosis providing knee immobilization. The figure shows the minimum length of this device that was adequate in the illustrated instance. To achieve maximum efficiency the orthosis should reach as far as possible proximally and distally and yet allow hip and ankle motion. Suspension is achieved by contouring the orthosis over the suprapatellar area and above the flare of the femoral condyles.
Ischial Ring KAFO
(Fig. 19 )
This double bar KAFO utilizes a knee lock and limited-motion or locked ankle joints to achieve direct weight transmission from the ischial tuberosity to the floor. If weight-bearing is accomplished efficiently on the ischial seat, the hip joint can be at least partially protected against vertical impact trauma. The difficulty with this orthosis is that many patients will not tolerate the required extent of localized pressure on the ischial tuberosity and will release the anterior strap of the orthosis to allow the ischial tuberosity to slip forward and down .
Double-Bar KAFO With Dial Knee
(Fig. 20 )
The Dial Knee is employed to achieve gradual correction of a knee flexion contracture which is still amenable to correction and not rigidly fixed. The dial permits the knee to be locked into increasingly greater degrees of extension.
Double-Bar KAFO With Knee Flexion Stop And Extension Aid
(Fig. 6 )
This orthosis is useful for unilateral knee flexion instability, in the presence of poor or absent quadriceps function and an intact opposite extremity. A flexion stop at no more than 60 deg. will give the patient an opportunity to recover from sudden knee flexion collapse, and the extension aid, plus gravity, will then help him restore stability by bringing the leg to extension against the stop of offset knee joints (Fig. 6 ) .
The Quadrilateral Socket KAFO
(Fig. 21 )
This design provides ischial, gluteal, and proximal thigh-bearing; i.e., the socket, as it encompasses the thigh, provides supportive features. The upward forces on the hip joint are therefore greater than in the case of a properly worn ischial ring orthosis, and toleration by the patient is also greater. This orthosis is useful for partially unweighting the femur just below the hip, and useful to a more limited degree for unweighting the hip joint itself .
As indicated in Section G of Fig. 2 , under the column labeled "Elaboration," when a lesser degree of unweighting is required than would be provided with the quadrilateral socket KAFO, a gluteal corset KAFO may be employed. When the patient has good control of extensor power at the knee, offset knee joints can be used. Otherwise the orthosis should be fabricated with knee locks. The orthosis illustrated in Fig. 22 was fabricated for a patient who could not wear the PTB orthosis because of peripheral neuritis and absence of sensation in the PTB cuff support area. This device is quite similar to the immediate precursor of the VAPC PTB orthosis .
Bilateral Double-Bar KAFO's For the Paraplegic
(Fig. 23 )
In KAFO's for the paraplegic patient, the knees must locked in the neutral position, ankles must be dorsiflexed about 10 deg., and the patient must lean his pelvis forward and his trunk backward to allow the patient to balance with the center of gravity over the
mid-foot, as illustrated by the Scott-Craig orthosis . Because of the retention of proprioception the poliomyelitis patient knows where his lower limbs are but the spinal cord patient must learn to sense position, and, as a result "polio patients accomplish greater levels of ambulation than spinal cord injured patients with the same motor deficit" .
Single Lateral-Bar Quadrilateral Socket KAFO
The single-lateral bar quadrilateral socket KAFO is not only useful for the patient with hemophiliac knee arthritis as recorded on the chart, but, when not used with a quadrilateral socket, lightweight patients who need bilateral orthoses will frequently find single lateral-bar KAFO's more comfortable. The impact of medial bars against each other is obviated. In the specific instance of the patient with hemophilia, the elimination of the medial bar removes a potential source of contusion of the opposite limb.
In the case of the hemophiliac knee with a quadrilateral socket KAFO, it may be found worthwhile to hinge the socket laterally rather than medially, to avoid the possibility of inadvertent contusion against the scrotum as the patient swings the socket open, a problem which we have encountered.
An attempt has been made to outline in a concise form our Clinic Team's basic approach to lower-limb orthosis prescription. The word "basic" should be emphasized since the Clinic Team does not limit itself to the devices described here, but have used, at various times, other devices as they are reported. These have not been discussed since an encyclopedic approach has not been attempted. It has been our purpose to present our point of view, and, therefore, the charts included illustrate the foundation upon which we build. They are intended to have one function only—that of teaching tools. The authors do not presume to instruct certified orthotists or physicians with long experience in prescription procedures.
- Supervisor, Orthotics Laboratory, Veterans Administration Prosthetics Center, 252 Seventh Avenue, New York, N.Y. 10001
- Committee on Prosthetics Research and Development, Seventh Workshop panel on lower-extremity orthotics, Orth. and Pros., March, 1971, pp. 1-31.
- Dixon, M., and R. Palumbo, Polypropylene knee orthosis with suprapatellar latex strap, Orth and Pros. 29:3, pp. 29-31, September, 1975.
- Hussey, Robert W. and E. Shannon Stauffer, Spinal cord injury: requirements for ambulation. Arch. of Phys. Med., 54: pp. 544-547, Dec. 1973.
- Lehmann, J. F. and G. G. Warren, Ischial and patellar-tendon weight-bearing braces: function, design, adjustment, and training. Bull. of Pros. Res., 10-19, pp. 6-19, Spring, 1973.
- Lehmann, J.F., C.G. Warren, D. Hertling, M. McGee, B.C. Simons, and A. Dralle, "Craig-Scott orthosis: biomechanical and functional evaluation," Arch. Phys. Med. Rehab., 57: pp. 438-442, September 1976.
- McCollough, Newton C. III: Comprehensive management of musculoskeletal disorders in hemophilia, CPRD, National Academy of Sciences, Washington, DC, 1973, pp. 90-91.
- Perry, Jacqueline and Helen Hislop, Principles of lower extremity bracing, American Physical Therapy Association, 1740 Broadway, New York, New York.
- Rubin, Gustav and Malcolm Dixon, The modern ankle-foot orthoses, Bull. of Pros. Res., 10-19, pp. 20-41, Spring, 1973.
- Rubin, Gustav, and Michael Danisi: A knee-stabilizing ankle-foot orthosis, Orth. and Pros., 29-3: pp. 11-14. September, 1975.
- Rubin, G., D. Bonarrigo, M. Danisi, and M. Dixon, The shoe as a component of the orthosis, Orth. and Pros. 30:2, pp. 13-25, June, 1976.
- Scott, Bruce A., Engineering principles and fabrication techniques for the Scott-Craig long log brace for paraplegics, Orth. and Pros. pp. 14-17, December, 1971.
- Staros, A and Maurice LeBlanc, Orthotic components and systems. Atlas of Orthotics, American Academy of Orthopedic Surgeons, C.V. Mosby Company, 1975.
- VA Prosthetics Center Staff Improvement and innovation: some case studies in orthotics, Orth. and Pros. Appl. J., pp. 283-297, Sept., 1963.
- Viel, Eric. Critique of lower extremity bracing, Orth. and Pros., pp. 28-33, September 1968.