Types of Orthoses

for the Lower Extremity

In the field of orthotics, FIOR & GENTZ specialises the development of orthotic joints for the production of custom-made orthoses for the lower extremity. In this area, one primarily differentiates between orthoses for patients with paralyses and supportive orthoses. The designation of an orthosis is based on the International Classification for Standards (ICS), which is developed and maintained by the International Organization for Standardization (ISO). The names indicate which anatomical joints and body parts are covered by the orthosis. For example, an AFO (ankle-foot orthosis) covers the ankle and the foot. In the past, orthoses were called splints, braces, side bars or side bars/bands orthoses. These terms should no longer be used in order to standardise the communication in an interdisciplinary team consisting of patients, physicians, physiotherapists and orthotists.

A custom-made orthosis offers the advantage of being individually adaptable to the patient’s needs. With a unilateral (one-sided) construction, the orthotic joint is placed next to the ankle joint. With a bilateral (double-sided) construction, one orthotic joint is placed on the inside and the other one on the outside next to the ankle joint. Both a unilateral and a bilateral construction can be used at knee level as well. The configuration of the orthosis with the correct orthotic joints depends on the clinical picture and the functional deviations of the patient determined during the physical examination. The adjustability of the functional elements of the orthotic joints allows an optimal adaptation of the orthotic functions to the requirements.

The different types of orthoses that are relevant in the area of the lower extremity are summarised below.

AFO (Ankle-Foot Orthosis)

AFO is the abbreviation of ankle-foot orthosis. The name is derived from the body parts that are covered by the orthosis: ankle and foot.

An AFO used in cases of paralysis compensates for the functional deviations resulting from the patient’s clinical picture. These include, in particular, a paralysis of the plantar flexors or dorsal flexors. Orthotic joints by FIOR & GENTZ have adjustable and dynamic functional elements that allow the orthosis function to be adapted to the patient’s needs. If, for example, the plantar flexors are weak, the orthosis compensates for the missing safety when standing and walking. If the dorsal flexors are weak, the functional elements enable the patient, among other things, to walk without stumbling by lifting the forefoot during swing phase.

KAFO (Knee-Ankle-Foot Orthosis)

KAFO is the abbreviation of knee-ankle-foot orthosis. The name is derived from the body parts that are covered by the orthosis: knee, ankle and foot.

A KAFO used in cases of paralysis compensates for the functional deviations resulting from the patient’s clinical picture. These include, in particular, a paralysis of the knee or hip extensors. Orthotic joints by FIOR & GENTZ have adjustable and dynamic functional elements that allow the orthosis function to be adapted to the patient’s needs. If, for example, the knee extensors are weak, functional elements for the stance phase control are integrated into the orthosis.

The orthotic joints used at knee level can be divided into three groups:

  • free moving
  • locked
  • automatic

The following video describes the functional differences of the three groups:

KAFOs with Free Moving Knee Joints

Free moving knee joints move freely during stance phase and swing phase. They are used for patients whose knee-securing muscles have moderate to strong residual function. They are available with or without posterior offset. In the case of free moving knee joints without posterior offset, the knee control is achieved purely through muscle strength. The mechanical knee axis (P) is positioned in congruence to the anatomical compromise axis (P1). In the case of free moving knee joints with posterior offset, the muscular stance phase control is supported by the mechanical joint. The mechanical knee axis (P) is not positioned in congruence to the anatomical compromise axis (P1), but behind it.

A KAFO with a free moving knee joint helps the patient to develop a natural gait. During stance and in stance phase during gait, the knee is protected from giving way. In swing phase the knee flexion is about 60°, which corresponds to a physiological angle.

KAFOs with Locked Knee Joints

Locked knee joints are locked during stance and swing phase. They can be unlocked for sitting. They are used for patients whose knee-securing muscles have little to no residual function. If the course of therapy permits, the locked knee joint can be converted in to a free moving knee joint with posterior offset.

This traditional orthotic treatment gives the patient the highest level of safety, as the locking prevents the knee from giving way under any circumstances. However, the patient must compensate for the lack of knee flexion during swing phase. This results in an unnatural gait. Typical compensation mechanisms include hip hiking – a lifting of the hip on the orthotically fitted side – and circumduction – a circular swinging motion of the orthotically fitted leg. These compensatory mechanisms result in an increased use of energy when walking. They also bear the risk of secondary diseases such as wear of the joints in hips, spine and shoulders.

Therefore, the production of orthoses with locked knee joints is not advisable. Only in exceptional cases, e.g. if there is a severe extension deficit (a contracture) in the anatomical knee joint and this deficit cannot be treated through physiotherapy, is the production of an orthosis with a locked knee joint recommended.

KAFOs with Automatic Knee Joints

KAFOs with automatic system knee joints are locked during stance phase and move freely during swing phase. They are also suitable for patients whose knee-securing muscles have little to no residual function. A KAFO with an automatic knee joint helps the patient to develop a natural gait. During stance and in stance phase during gait, the locked joint protects the knee from giving way. Automatic joints are therefore also called "stance control orthoses" (SCO). In the swing phase, the locking is disabled and the knee can flex at a physiological angle of about 60°.

Automatic knee joints represent the current state of the art and in most cases are preferable to a treatment with a locked knee joint.

The Different Types of KAFOs in Comparison

Free Moving
A KAFO with free moving knee joints is suitable for patients whose knee-securing muscles have moderate to strong residual function. In stance phase (mid stance) the knee flexion angle is 5°, which corresponds to physiological value.

Locked
A KAFO with locked knee joints is suitable for patients whose knee-securing muscles have little to no residual function. In stance phase (mid stance) the knee flexion angle is 5°, which corresponds to a physiological value. Nevertheless, contractures can cause deviating non-physiological angles.

Automatic
A KAFO with automatic knee joints is suitable for patients whose knee-securing muscles have little to no residual function. In stance phase (mid stance) the knee flexion angle is 5°, which corresponds to a physiological value.

 

Free Moving
A KAFO with free moving knee joints moves freely during swing phase. In mid swing the knee flexion is 60°, which is a physiological value.

Locked
A KAFO with locked knee joints is locked during swing phase. In mid swing the knee flexion angle is 5° in accordance with the default setting, which is not a physiological value.

Automatic
A KAFO with automatic knee joints is automatically unlocked during swing phase, therefore it can move freely. In mid swing the knee flexion is 60°, which is a physiological value.

 

Free Moving
In a KAFO with free moving knee joints, the body's centre of gravity is balanced during swing phase. As a result, an energy-efficient gait is possible.

Locked
In a KAFO with locked knee joints, the hip must be lifted during the swing phase (hip hiking). This shifts the body's centre of gravity, which in turn leads to an unnatural tilt of the upper body and an increased use of energy.

Automatic
In a KAFO with automatic knee joints, the body's centre of gravity is balanced during swing phase. As a result, an energy-efficient gait is possible.

 

Free Moving
In a KAFO with free moving knee joints, the leg swings in a straight line during swing phase. This enables a physiological motion sequence.

Locked
In a KAFO with locked knee joints, the knee cannot flex. Instead of swinging in a straight line, the orthosis leg must thus be guided forward in a semi-circular movement (circumduction).

Automatic
In a KAFO with automatic knee joints, the leg swings in a straight line during swing phase. This enables a physiological motion sequence.

 

The Different Types of KAFOs in Comparison – Summary

Free Moving
A KAFO with free moving knee joints is used in cases of slight weakness of the knee-securing muscles. Orthoses with free moving knee joints result in a natural gait.

Locked
A KAFO with locked knee joints is used to treat severe to complete paralysis of the knee-securing muscles. This traditional form of orthotic treatment leads to an unnatural gait and can result in health problems.

Automatic
A KAFO with automatic knee joints is used to treat severe to complete paralysis of the knee-securing muscles. This modern form of orthotic treatment results in a natural gait.

KO (Knee Orthosis)

A knee orthosis only covers the knee. In contrast to a KAFO or an AFO, there is no joint at ankle level. Knee orthoses are used postoperatively to protect and support the knee joint. This can significantly alleviate knee pain. Common indications are injuries to the cruciate ligament, injuries to the capsular ligamentous apparatus and meniscus injuries. The majority of the orthotic joints used for this purpose have gear segments and are classified by FIOR & GENTZ in the category articulated side bars for knee orthoses. The pivot point of the gear segment joints simulates the movement of the anatomical pivot point. Thus, the complex ligamentous apparatus is not unnecessarily loaded.

Other Designations of Orthoses

The following terms used in connection with lower leg orthoses can be confusing. They usually describe the various features and functions of a specific AFO, which is misleading because other types of orthoses also feature them. In the following, you will find an overview of the most common designations:

DAFO (Dynamic AFO)
This term is often used for plastic orthoses that are flexible in the ankle area. They are used, among other things, for the treatment of patients with isolated peroneal deficiency. They are not suitable as  orthoses for patients with paralyses, however, because the ground reaction force is not transferred to the lower leg shell. Although the name suggests otherwise, DAFOs are not the only AFOs with dynamic properties.

FRAFO (floor-reaction AFO)
A FRAFO is a rigid lower leg orthosis with an anterior shell. As the name suggests, this orthosis works via the ground reaction force. However, other modern orthoses for patients with paralyses (such as an AFO with a NEURO SWING system ankle joint) also make use of this principle of force transmission.

HAFO (hinged AFO)
HAFOs are plastic orthoses with a posterior shell. The lower leg shell is a separate component that is connected to the foot piece via an articulated connection. Every orthosis with an ankle joint has such an articulated connection, which is why the specification is misleading. In HAFOs, an elastomer joint is usually used as a connecting element, which is not suitable for transmitting the ground reaction force.

PLSAFO (posterior-leaf-spring AFO)
The PLSAFO combines the dynamic properties of a DAFO with the ground reaction force effect of a FRAFO. It is equipped with an integrated carbon leaf spring that connects the foot piece and the lower leg shell. The dynamics of the orthosis are achieved by positioning the leaf spring behind the Achilles tendon. However, posterior-leaf-spring AFOs do not have a defined pivot point. Therefore, there is no congruence between the axis of the anatomical ankle joint and the area in which the dynamics of the orthosis act. This causes the orthosis shells to shift on the patient's leg.
In addition, the physiological ground reaction force of the heel lever is eliminated by positioning the leaf spring behind the heel. At the same time, the ground reaction force of the forefoot lever is unnaturally increased by the artificial extension. Both can lead to non-physiological neurological reactions.

SAFO (solid AFO)
The term SAFO is used worldwide for rigid AFOs made of polypropylene. Such an orthosis uses the ground reaction force. However, by definition it has no dynamics, resulting in non-physiological movement patterns. The rigid fixation of the anatomical ankle joint can also cause contractures.

SMO (supramalleolar orthosis)
A SMO is an orthosis covering the ankle, which can have dynamic properties. However, a SMO does not transfer ground reaction force to the lower leg and is therefore not suitable as an orthosis for patients with paralyses.

FIOR & GENTZ

Gesellschaft für Entwicklung und Vertrieb von orthopädietechnischen Systemen mbH

Dorette-von-Stern-Straße 5
D-21337 Lüneburg

Phone: +49 4131 24445-0
Fax: +49 4131 24445-57
Email: info(at)fior-gentz.de


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