21/22: Orthosis Overview - Mahoney Flashcards
define orthosis
- A prescription orthopedic device to be worn in shoes to assist in the realignment of lower extremity joint malfunctions or to aid in the maintenance of structural alignment following surgery
- A prescription in-shoe medical device designed to alter the magnitude and temporal patterns of the reaction forces acting on the plantar surface of the foot to allow more normal foot and lower extremity function and to decrease pathologic loading forces on the structural components of the foot and lower extremity during weightbearing (this is mostly referring to an accomadative device)
most accurate way to define orthoses
mechanism of action
mechanism of action classifications
- Functional/Root/Neutral [maintain normal foot function at STJ and MTJ]
- Accommodative [does not attempt to control motion at STJ and MTJ]
Allows improved functioning of joints proximal and distal to the STJ and MTJ
functional
- theoretically also controls ankle, knee, and hip problems
Provides comfort from plantar lesions and bony prominences
accommodative
alters function of the foot vs. alters magnitude and temporal loading patterns of injured plantar foot structures
functional v. accommodative
which is softer? which maintains shape better? open or closed cell foams
open
closed
As the number of open cells decreases, the ability of the material to withstand compression increases
most important step of orthosis fabrication
casting of the foot
negative vs. positive cast
neg = the mold of the foot made from plaster or taken in foam material
pos = Made from plaster material poured into the negative cast OR from laser scan.
negative casting technique
aka neutral casting technique
NWB with patient supine or prone and foot held with STJ in neutral and MTJ locked by maximally pronating MTJ (exerting dorsiflexion force on 4th and 5th metatarsals)
CPMS method
- Place thumb beneath the 4th and 5th metatarsal heads or grasp (lift) the 4th and 5th toes in the toe sulcus
- Gently dorsiflex 4th and 5th metatarsals until you meet slight resistance (foot still should be in 10-20° of a plantarflexed position at ankle) or gently dorsiflex the foot to 90° when lifting the 4th and 5th toes
negative casting technique is for what type of orthosis
functional
why would you want to additonally plantarflex the medial column/first metatarsal when casting the foot?
to increase the amount of forefoot valgus which enhances the windlass mechanism function and decreases tension on the plantar fascia
when 2nd metatarsal lines up with middle of tibia
STJ is in neutral
plastering the foot
- Place splint around heel, 1/2 of length on each side of foot at a height justbelow malleoli. 2. Mold lateral side first into arch and then medial side overlapping lateral
half - Mold the excess into the plantar/posterior aspect of heel
- Fold excess plaster on plantar of heel towards posterior aspect
- The sides of the plaster are folded onto the plantar aspect of the foot, starting with lateral side first. Any excess is folded under the sulcus of the toes
- The patient’s skin is pulled away from skin on the dorsum of the foot after the plaster is set by squeezing the skin together. The cast is ready to be removed
when it feels rough and grainy
removing the cast
The cast is then grasped along the medial and lateral
aspects of the heel with the fingertips of one hand, still holding the foot in neutral. After the heel is freed, pull the cast straight towards the big toe. Rotate the heel gently to allow removal of the toes from the cast
*** what is the correct placement of the foot/ankle for neutral position casting?
STJ neutral, MTJ pronated, ankle dorsiflexed (not beyond 90)
intrinsic modification
adding or taking away from the positive cast
Adjustments are made to the positive mold based on biomechanical evaluation
what is the technique for making an accommodative orthotic?
Semi-weight bearing (sitting in chair) impression with the patient seated in upright position with hip, knee, and ankle flexed at 90
foam box technique
- Maintain STJ in neutral with one hand and grasp lower leg with other hand
- Lift foot and place on foam
- Apply downward pressure to dorsal aspect of knee to drive heel into foam
- Apply downward pressure to midfoot and then forefoot
- Foot is withdrawn from foam by doctor
making additions to the finished product
extrinsic modification
most common: A rearfoot post (wedge) is attached to the underside to improve stability in the rearfoot (makes it fit better and more stable within the shoe itself)
CAD/CAM scans negative cast or the foot directly, how is the positive cast then made?
A physical positive cast can be milled out of a block of wood, OR the orthosis can be milled directly out of a block of polypropylene from a “virtual” positive
which is inherently more stiff? milled or pressed orthotic
milled
which of the following statements are true?
- Modifications made to the positive mold are called intrinsic modifications
- Modifications made to the orthosis are called intrinsic modifications
- CAD/CAM technology can use laser scans of the foot
- CAD/CAM technology can use laser scans of the negative mold
- true
- false, extrinsic
- true
- true
where does a functional orthotic end? accommodative?
functional: Ends behind metatarsal heads and just lateral to 1st metatarsal and just medial to 5th metatarsal
accommodative: Full length (to sulcus or tip of toes) and full width (so they need to be a softer material)
As long as the orthotic attempts to control abnormal STJ and MTJ motion by having a firm longitudinal arch and the cast is taken in neutral position …
the length and/or width of the orthotic is really not a defining characteristic as to whether it is functional or accomodative
true or false: you are generally going to make a functional device narrower than anatomy
true
top covers are _____ modifications
extrinsic
- A top cover can be added to help keep the foot from sliding around on the orthosis, to make the anterior edge of the orthosis more comfortable, and to help accommodate osseous structures that may rub against the orthosis and cause irritation
- The top cover can extend to the metatarsal parabola, to the sulcus of the toes, or to the ends of the toes
what is spenco?
closed cell expanded rubber foam top cover
poron of ppt is open cell with more cushioning but doesn’t last as long
mechanical objective of a functional orthosis
- Resists ground reaction forces that cause abnormal motion to occur during stance phase of gait
- attempts to prevent excessive compensatory pronation or supination
- does nothing during swing phase
- makes foot stable at push off
- controls hypermobility of joints
if made correctly, functional orthosis will produce (5)
- proper STJ and MTJ pronation and supination
- normal ankle dorsi and plantarflexion
- normal knee flexion at heel contact
- proper hip flexion and extension
- efficient internal and external rotation
goals of an accommodative orthotic
- relieves high pressure areas, reduces shock, limits shear forces
- primarily accommodates plantar lesions
- use in neuropathic, vascularly impaired, arthritis feet, feet with inoperable bony or soft tissue prominence
a functional device is one which …
- Most commonly is made from a weightbearing position of the foot
- Resists abnormal compensatory supination or pronation of the foot
- Offloads pressure on bony prominences
- Makes the foot stable at heel strike
- Makes the foot stable at swing phase
2 is the correct answer
4- push off not heel strike
