BioMechanics Exam 3

Question 1

Glenohumeral motion arthrokinematic goal

Answer 1

Combine rotation (roll) and translation (slide) to keep humeral head centered on glenoid
Eliminate unwanted slide with active and passive restraints

Question 2

Passive restraints of glenohumeral joint

Answer 2

Bony geometry
Labrum
Capsuloligamentous structures
Long head of bicep
Negative intra-articular pressure

Question 3

Arm abduction

Answer 3

Rotator cuff muscles down and deltoid up

Question 4

Major abductors of humerus

Answer 4

Supraspinatus
-Initiates abduction
Lateral deltoid
-Most active after 30 degrees of abduction
-Superior dislocating component neutralized by infraspinatus, subscapularis, and teres minor

Question 5

Phase one of GH abduction

Answer 5

Setting phase initiated by supraspinatus

Question 6

Phase two of GH abduction

Answer 6

The scapula has greater motion, approaching a 1:1 ratio with the humerus

Question 7

Phase three GH joint abduction

Answer 7

Later in range, the glenohumeral joint again dominates the motion

Question 8

What muscle is susceptible to damage from impingement?

Answer 8

Supraspinatus

Question 9

Know how the roll slide mechanism can prevent impingement

Answer 9

When the supraspinatus pulls, a roll is created by abduction and is countered with slide action

Requires external rotation of humerus to clear greater tuberosity

Requires upward rotation of scapula to elevate lateral end of acromion

Question 10

Know how the roll slide mechanism can lead to impingement?

Answer 10

When the supraspinatus pulls, a roll is created by abduction and is not countered with slide action

Question 11

Primary impingement

Answer 11

Structural stenosis of subacromial space

Question 12

Secondary impigment

Answer 12

Functional stenosis of subacromial space due to abnormal arthrokinematics

Question 13

Hip

Answer 13

Attaches hip to trunk
Deeper labrum at hip
Hips are weight bearing joints

Question 14

Shoulder

Answer 14

Attaches arms to trunk

Question 15

Parts of hip

Answer 15

Ilium, sacrum, ischium, pubis

Question 16

acetabulum

Answer 16

Makes pelvic bowl
Has parts of the ilium, ischium and the pubis
Is socket
Horse shoe shape
Only posterior head of femur attaches to the socket

Question 17

Fovea capitis

Answer 17

head of femur dimple to make the joint more stable
Is an attachment point for ligamentum teres
Affects ligamentum teres attachment and size

Question 18

Ligamentum teres

Answer 18

Provides stability for hip
Ligament between the femoral head and the acetabulum.
Does not exist in the shoulder

Question 19

The hip joint

Answer 19

Is a ball and socket joint, made up of the top of the thigh bone called the femoral head (the ball) and the part of the pelvis called the acetabulum (the socket).

Question 20

Fovea brevis

Answer 20

Small fovea capitis diameter
Smaller, narrower ligamentum teres
Less stable hip

Question 21

Fovea magnus

Answer 21

Large fovea capitis diameter

Question 22

Fovea plane

Answer 22

Shallow fovea capitis
Ligament has less surface area

Question 23

Fovea profunda

Answer 23

Deep fovea capitis

Question 24

Fovea capitis Index Equation

Answer 24

Ratio between diameter of femoral head to diameter of fovea capitis
Has small clinical role to predict hip issues
Good to take several pictures under different magnification

Question 25

Angles of the acetabulum

Answer 25

Angle of acetabular torsion Center Edge Angle of the acetabulum

Question 26

Angle of acetabular torsion

Answer 26

Orientation of medial and front and down

Question 27

Center edge angle (CEA)

Answer 27

Average range: 25-40 degrees Function: Provide lateral stability of the pelvis (pushing in opposition to pelvis that is being pushed outward from wedged sacrum) and to prevent superior dislocation Angle created with vertical line through vertical head of femur to the superior edge of the acetabulum Measure of how deep the acetabulum is a way to evaluate risk of dislocation

Question 28

CEA of less than 15 degrees

Answer 28

Certain dislocation

Question 29

CEA of 15-25 degrees

Answer 29

Possible dislocation

Question 30

Hip abductors

Answer 30

Gluteus minimus Gluteus medius Center of gravity is in-front of the hip which causes a lever Hip abductors causes pelvis to go back up to keep it stable

Question 31

Single leg raise (SLR)

Answer 31

2 BW Way to evaluate lower back issues Do you have pain/numbness at the knee?

Question 32

Single leg stance (SLS)

Answer 32

3x BW Just picking your leg up Walking = 5x BW Running = 10x BW

Question 33

Trendelenburg sign

Answer 33

Pelvis tips when one leg is lifted up Shows issue with hip abductors

Question 34

Angulation of Femur

Answer 34

Two angulations made by the neck of the femur and the femoral shaft Angle of inclination and angle of torsion

Question 35

Angle of inclination of femur

Answer 35

In frontal plane Between femoral head and neck and the femoral shaft Angle created from the intersection of a line down the shaft of the femur and the neck of the femur AOI of the femur approximates 125 degrees With a normal angle of inclination, the greater trochanter lies at the level of the center of the femoral head

Question 36

Angle of torsion

Answer 36

In the transverse plane Between the femoral head and neck and an axis through the distal femoral condyles

Question 37

Coxa valga

Answer 37

Excessive angle over 125 degrees clinical, 140 degrees technical angle of inclination Lengthens the limb Reduces the moment arm of the hip abductors which makes force greater Reduces the load on the femoral neck Increases the load on the femoral head Hip would dislocate since this angle is higher than normal

Question 38

Coxa vara

Answer 38

110 degrees and below technical Below 125 degrees clinical Shortens the limb Increases the moment arm of hip abductors Increases the load on the femoral neck Reduces the load on the femoral head

Question 39

Angle of torsion

Answer 39

An axis through the femoral head and neck in the transverse plane

Question 40

SCFE Slipped capital femoral ephysis

Answer 40

Caused by someone moving through coxa valga and normal Issue with childhood obesity Get change in angle from added weight or from trauma Happens on bilateral and unilateral sides Symptom is groin pain while walking Are treated with a hip brace, growth plates

Question 41

Deviations from normal angle of torsion

Answer 41

10-15 degrees males 18-20 degrees female Born with extreme anteversion of 40 degrees Angle moves back towards these values

Question 42

Retroversion

Answer 42

0-9 degrees

Question 43

Excessive anteversion

Answer 43

21-more degrees