Outline of arthrodesis Man
What is elastrohydrodynamic lubrication?
Primary lubrication mechanism for articular cartilage during dynamic function
What is the normal hip range of motion?
Hip Biomechanic Pearls
Joint reaction force (R) in the hip can reach three to six times body weight (W)--Primarily as a result of contraction of the muscles crossing the hip
Decreases with cane in contralateral hand
Stability-Deep-seated ball-and-socket joint is intrinsically stable.
Sourcil-Condensation of subchondral bone under superomedial acetabulum
R is maximal at this point
Gothic arch-Remodeled bone supporting the acetabular roof; Sourcil at its base
Decreases R; Increases shear across the neck
Leads to shortening of the lower extremity
Alters muscle tension resting length of the abductors
May cause a persistent limp
Valgus angulation: Increases R/Decreases shear
Neutral or valgus angulation better for THA
PMMA resists shear poorly
Hip Joint Arthrodesis:
24-30 degrees of flexion
increases o2 consumption
decrease gait efficiency by 50%
Knee joint Biomechanics
Functional ROM 0-90
110 degrees-rising from a chair
Knee rotation varies with flexion
no rotation at full extension, but with 90 flexion can rotate 45 degrees ER, 30 degrees IR.
Arthrodesis of the knee joint
10-15 degrees flexion
0-7 degrees valgus
5-10 degrees external rotation
5 degrees hindfoot valgus
70% loss of saggital motion in the foot.
1st metatarsal bears most of the load during standing
2nd metatarsal carries the most load with gait.
What is the motion segment of the spine?
two vertebrae and the intervening soft tissue
Internal Rotation- 45 degrees
Hand to mouth
90 degrees of flexion if unilateral
65 and 110 if bilateral
hand to mouth/hand to ass
10-20 degrees of dorsiflexion
max grip strength
if bilateral, then the opposite should be in 10 degrees of palmar flexion