Biomechanics Flashcards
Varum and valgum throughout development
Birth = genu varum (15-20 degrees) 2-4 years = straight (0 degrees) 4-6 years = genu valgum (5-15 degrees) 6-12 years = straight (0 degrees) 12-14 years = genu valgum (5-10 degrees) 14+ years = straight (0 degrees)
Ankle equinus
Less than 10 degrees dorsiflexion
Ankle joint stable position
Ankle joint is most stable in maximally dorsiflexed position
STJ axis
- 42 degrees from sagittal plane, 16 degrees from transverse plane
- Neutral position is 2/3 the distance from the most supinated position
STJ ROM
- Average ROM is 25-30 degrees (highly variable)
- Minimum of 12 degrees is required for normal ambulation
Femur ankle of inclination
Long axis of the neck vs long axis of the shaft
- Birth = 140 degrees
- Adults = 120-130 degrees
Femur ankle of declination (antetorsion)
AKA angle of femoral torsion - long axis of neck vs coronal plane of distal condyles
- 1 year = 39 degrees
- Adult = 6 degrees
Angle of anteversion
Long axis of neck of femur relative to pelvis
- Birth = 60 degrees
- Adult = 10-12 degrees
Metatarsal length
Longest - 2 - 3 - 5 - 4 - 1 Shortest
Metatarsal distal protrusion
Longest - 2 - 3 - 1 - 4 - 5 Shortest
Bohlers angle
Angle between posterior to middle facet and anterior to middle facet of calcaneus
- Normal = 20-40 degrees
- Average = 30-35 degrees
- Decreases in calcaneal fracture
Bohler’s angle bottoms out
Gissane’s angle
AKA critical angle or crucial angle - angle between middle facet to sinus tarsi and sinus tarsi to anterior facet
- Normal: 120-145
- Increases in calcaneal fracture
Gissane’s angle gets greater
Fowler-Philip angle
Angle from posterior calcaneus to plantar calcaneus
- Normal = 44-69 degrees
- Pathology = >75 degrees
Total angle
- Calcaneal inclination able + Fowler-philip angle
- Greater than 90 degrees may be observed in a Haglund’s deformity
Parallel pitch lines
- Line across plantar calcaneus
- Line perpendicular to first line
- At dorsal calcaneus, draw line perpendicular to second line (parallel to first line)
- If the posterior tubercle of the calcaneus extends above the third line there is a Haglund’s deformtiy
Meary’s angle
Lateral x-ray
- Straight line through mid axis of the talus and mid axis of the 1st metatarsal
- Normal = 0 degrees
- Mild flatfoot = 1-15 degrees
- Severe flatfoot = >15 degrees
Calcaneal inclination angle
- Average 20-25 degrees
- Value does not change with pronation/supination
- Decreased in pes planus, increased in pes cavus
Angle of Hibbs
Lateral x-ray
- Long axis of 1st metatarsal and long plantar axis of calcaneus (calcaneal inclination)
- Normal = 135=140
- Pes cavus = <150
Kites angle
AP x-ray
- Long axis of talus and long axis of calcaneus
- Normal = 20-40 degrees
- Increased in pronation, decreased in supination
Limb length discrepancy
A true LLD requires a 5 mm discrepancy to cause a significant functional and structural problem
- Shorter leg supinates
- Longer leg pronates
- Compensatory scoliosis by 13-14 years old
Windlass mechanism
As the hallux is dorsiflexed, the plantar fascia is pulled under the head of the metatarsal. This brings the calcaneus toward the head of the 1st metatarsal, thereby creating an elevated medial longitudinal arch.
SACH heel
- A rounded heel (rockerbottom)
- Allows more cushioned fluid motion through the heel contact phase of gait
Cobra pad
- Prefabricated orthotic providing arch support and off-loading the heel
- Usually felt and easily fit into dress shoes
Metatarsal bar
- Pad placed just behind metatarsal heads to reduce pressure on 2nd, 3rd and 4th met heads
Denver bar
- Placed under metatarsal bones to support transverse arch of foot
- Extends from metatarsal heads to TMTJ
Dancer’s pad
- Off-loads 1st metatarsal head
- Indications: sesamoiditis or fractured sesamoid
Low-dye strap
- A strapping technique achieved with tape that alleviates the strain associated with pronation, particularly plantar fasciitis
Spastic gait
- Internal rotation and adduction of entire limb
- Flexion of hip, knee and ankle
- Seen in cerebral palsy, familial spastic diplegia, paraplegia and hemiplegia
Dyskinetic gait
- A constant movement abnormality with a high degree of variability
- Motion involving considerable effort, often with deliberate almost concentrated steps
- Seen in cerebral palsy, Huntington’s chorea and dystonia muscular deformities
Ataxic gait
- Marked instability during single limb stance with alternating wide/narrow base during double support
- During swing, limb swings widely and crosses midline
- Seen in MS, tabes dorsalis, diabetic polyneuropathy and Fredrich’s ataxia
Waddling gait
- Labored gait exhibiting difficulty with balance and pelvic stability
- Lumbar lordosis
- Seen in muscular dystrophies, spinal muscular atrophy and congenital dislocated hip
Steppage gait
- Swing phase drop foot
- Seen in CMT, Guillain-Barre syndrom, CVA, paralytic drop foot and fascioscapulohumeral dystrphy
Vaulting gait
- Gait changes include a high step rate, increased lateral trunk movement, scissoring and instability from step to step
- Seen in myotonic dystrophy
Equinus gait
- Ankle plantarflexion during swing phase with no heel contact
- Seen in cerebral palsy, CMT, muscular dystrophy, spinal muscular atrophy, Schizophrenia, osseous block of ankle and habitual toe walkign
Fenistrating gait
- Shuffling gait with loss of reciprocal arm swing, decreased velocity, decreased stride length and increase step rate
- Seen in Parkinson’s disease
Trendelenberg gait
- Stance phase of each step leads to a contralateral tilt of the pelvis with a deviation of the spine to the affected side
- Seen with dislocated hip or weakness of the gluteus medius muscle
Calculate STJ neutral
- Add the amount of maximum eversion of the calcaneus from the bisection of the lower 1/3 of the leg and the maximum amount of inversion of the calcaneus from the bisection of the lower 1/3 of the leg
- Next, take 1/3 of the total range of motion
- Lastly, subtract this amount from the maximum amount of eversion
