Biomechanics of the Upper Extremity Shoulder and Hip

Transcription

1 Biomechanics of the Upper Extremity Shoulder and Hip

2 The Shoulder Common Injuries

3 Shoulder Joint - Bones

4 Anatomical Structures Bursa - Fibrous, fluid-filled sac that reduces friction - Located between bones, tendons, and other structures Subacromial Bursae - Bursa between acromion process and insertion of supraspinatus muscle Coracoid Process - Curved process arising from upper neck of scapula - Overhangs shoulder joint

5 Shoulder - Anatomical Structures Shoulder Girdle - An incomplete bony ring in the upper extremity formed on each side by the scapula and clavicle Scapula - Flat, triangular bone on the upper posterior thorax Clavicle - Long, narrow S -shaped bone articulating with scapula and sternum - Collar bone Glenoid Fossa - Depression in lateral superior scapula - Socket for shoulder joint Glenoid Labrum - Ring of fibrocartilage around rim of glenoid fossa - Deepens socket for shoulder joint

6 The Shoulder Complex Articulations Sternoclavicular Joint Articulation between sternum and clavicle Acromioclavicular Joint (AC joint) Articulation between acromion process of scapula and lateral end of clavicle Scapulothoracic Joint Physiological joint between the scapula and thorax Glenohumeral Joint Articulation between the head of the humerus and the glenoid fossa of the scapula

7 Movements of the Shoulder Complex - Scapula - Rotation - Upward & Downward - Elevation & Depression - Protraction & Retraction - Glenohumeral - Flexion & Extension - Abduction & Adduction - Horizontal Abduction and Adduction - Internal & External Rotation - Dislocation

8 Movement Characteristics - Large range of motion (ROM) at shoulder Extreme ROM required by many activities Ex. Swimming, throwing, gymnastics - Ligaments and muscles provide stability (and sometimes instability) - Scapular and clavicular movements accompany any arm movement - Scapulohumeral Rhythm Movement relationship between humerus & scapula during arm raising movements

9 So what creates stability?

10 Shoulder Joint - Ligaments

11 Shoulder Rotator Cuff Infraspinatus Subscapularis Supraspinatus Teres Minor

12 Muscular Actions Rotator Cuff (muscles) Holds humerus in socket Stabilizes shoulder joint Four (4) muscles surrounding the shoulder joint: 1. Infraspinatus 2. Supraspinatus 3. Teres Minor 4. Subscapularis

13 Shoulder Muscle Strength - Generate greatest strength in adduction (why?) - Abduction used frequently in daily living - Weakest movements are internal and external rotation (why?) - Muscles generate high forces within joint - Almost 90% of body weight at 90 abduction - Implications?

14 Conditioning - Shoulder muscles easy to stretch and strengthen - Stretching - Active and passive - Strength Training Weight training, limb/body weight exercises < 5 lbs resistance (slow and controlled) - Rotator cuff strength and flexibility important - Stabilization of joint - Widely used in daily living

15 Conditioning Exercises

16 Contributions of Shoulder Musculature - Activities of daily living - Freestyle swimming - Overhand throwing - Golf swing

17 Muscle Roles - Example

18 Injury to the Shoulder Complex - Wide variety of possible injuries - Two Main Causes: - Trauma - Repetitive joint actions - Certain groups are more susceptible to certain injuries - Adolescents - Subluxations - Contact sport players - Fractures

19 Injury - Sprain - Rupture of fibers of ligament - Subluxation - Partial dislocation - Fracture - Break in bone, often clavicle - Ectopic Calcification - Hardening of organic tissue through deposit of calcium salts in areas away from the normal sites - Degeneration - Deterioration of tissue

20 Injury - Bursitis - Inflammation of bursa - Impingement Syndrome - Irritation of structures above shoulder joint - Due to repeated compression between greater tuberosity and acromion process - Subacromial Bursitis - Common from impingement syndrome - Bicipital Tendinitis - Inflammation of the tendon of the biceps brachii

21 Summary of Structures

22 Shoulder - Summary Questions - What does the shoulder complex enable us to do? - What stabilizes the structures of the shoulder? - What are potential injuries to the shoulder? - What causes these injuries? - How can injuries be prevented? - What are some exercises for stretching and strengthening the shoulder complex?

23 Part 2 Hip

24 The Hip Common Injuries

25 Hip Structure How does it differ from the shoulder?

26 Hip Function How do we use it?

27 Overview Part 1: Structure Function Kinematics Range of motion (ROM) Surface joint motion Part 2: Kinetics Statics Single Leg Stance, Twoleg Stance, Influence of body COM JRF Calculation Dynamics JRF during gait and locomotion Ambulatory Aides

28 Hip Joint Largest and most stable joint in human body Intrinsic Stability Rigid ball and socket Mobility in three planes Sagittal Frontal Transverse Regularly endures very large forces

29 Hip Joint Structure Hip Joint Head of femur Acetabulum of pelvis Recall pelvis is three fused bones Loose joint capsule Large ROM

30 Hip Joint Structure 1. External Iliac artery 2. Psoas major 3. Iliacus muscle 4. Iliac crest 5. Gluteus medius 6. Gluteus minimus 7. Greater trochanter 8. Vastus lateralis 9. Femoral shaft 10. Vastus medialis 11. Profunda femoris vessels 12. Adductor longus 13. Pectineus 14. Medial circumflex femoral vessels 15. Capsule of the hip joint 16. Femoral neck 17. Zona orbicularis of capsule 18. Head of femur 19. Acetabular labrum 20. Rim of acetabulum

31 Structure and Function Muscles of hip joint (previous slide) Identify muscles Locations of origin and insertion Distinguish function Bones and capsular structure (next slide) Muscle-Tendon Ligaments Cartilage

32 Joint Capsule

33 Acetabulum Alignment of cavity Obliquely, forward, outward and downward Deep Provides static stability Deepened further by labrum and transverse acetabular ligament Flat rim of fibrocartilage Unloaded Smaller diameter than femoral head Loaded Deforms about the femoral head Elastic deformation

34 Femoral Head Ball of the ball and socket Convex component Shape forms 2/3 of a sphere Variation in articular cartilage thickness Due to variation in loading patterns Results in different strength and stiffness across different regions of the joint

35 Femoral Neck Angular relation with femoral shaft Neck to Shaft Angle Angle of inclination of neck to shaft in frontal plane Freedom of motion Adults ~125º (90º-135º) Angle of Anteversion Angle of inclination in transverse plane Projection of the long axis of femoral head and transverse axis of femoral condyles Adults ~12º

36 Neck to Shaft Angle Coxa Valga Angle > 125º Coxa Vara Angle < 125º Excess angle: Affects moment created by gravity Affects muscle moment arm Affects muscle effort

37 Angle of Anteversion Angle > 12º Anteversion Portion of head is uncovered Internal rotation during gait To keep femoral head in cavity Angle < 12º Retroversion Tendency toward external rotation during gait Anteversion and retroversion are common in children Typically outgrown during maturation

38 Hip Joint Loading Medial and Lateral Trabeculae Systems JRF of femoral head parallels the trabeculae in femoral neck Epiphyseal plates are perpendicular to trabeculae of medial system Thus, perpendicular JRF in femoral head Abductor group contraction resists compressive forces in lateral region Gluteus medius, Gluteus minimus, Tensor fascia latae Aging Femoral Neck Cortical bone thins Trabeculae is resorbed May predispose neck to fracture

39 Hip Joint Kinematics Range of Motion (ROM) in 3 planes Sagittal 0-140º Flexion 0-15º Extension Frontal 0-30º Abduction 0-25º Adduction Transverse 0-90º External rotation 0-70º Internal rotation (with hip flexed)

40 Hip Joint Motion During Gait Flexion-Extension (~35-40º) Max flexion in late swing Max Extension at heel off Abduction-Adduction (~12º) During swing Max abduction just after toe-off Max adduction at heel strike through late stance External-Internal Rotation (~ 13º) ER through swing IR into heel strike through late stance

41 Hip Joint Motion During Gait

42 Aging and Hip Joint Motion ROM decreases with age During gait Shorter stride Decreased hip flexion-extension Decreased plantarflexion Decreased heel-floor angle of tracking limb Decreased dorsiflexion Decreased elevation of toe on forward limb

43 ROM During Daily Activities Necessary Hip ROM Flexion ~120º ER ~20º

44 Surface Joint Motion Gliding of femoral head in acetabulum Incongruence in femoral head Abnormal gliding Abnormal compression and/or distraction Increased wear Pain and degeneration

45 Summary Part 1 Structure, Function & Kinematics Structure Function Kinematics Range of motion (ROM) Surface joint motion

46 Part 2 Kinetics and Ambulatory Aids

47 Hip Joint Kinetics Abductor group is main stabilizer during single leg stance Implications for lower extremity injury?

48 Statics 2-leg stance Gravity line passes through pelvic girdle Thus, hip joint is fairly stable No muscle force necessary to maintain stance Assume each leg is 1/6 body weight What is the magnitude of JRF on each hip? So, what function would muscle force serve? Increase JRF? Decrease JRF?

49 Single leg stance Statics COM shifts (line of gravity) in all 3 planes Thus, moments are created These moments are controlled by muscle force COM shift is position dependent Shift in gravity line Shift in moment arm of gravity (through COM) Change in muscle torque required to hold position Thus, change in JRF

50 Frontal Plane COM (gravity line) A Neutral stance B Max tilt toward support limb C Tilt away from support limb D Pelvic sagging away from support limb Trendelenburg s Test

51 Frontal Plane COM (gravity line)

52 JRF Calculation Two general methods: 1. Simplified FBD JRF in frontal plane acting on femoral head during single leg stance Equilibrium with neutral pelvis Box Use equilibrium equations JRF on femoral head using equilibrium equations for single leg stance with pelvis level Box 8-2

53 Necessary Information Location of external forces Gravitational force of body (GRF) Stance leg and remaining Two free bodies Divided across hip joint Coplanar forces acting on these two bodies are then determined Box 8-2-2

54 Simplified FBD Two moments are required for stability A Muscle W VGRF J - JRF ΣM = 0 M Abductors = M Bodyweight

55 Equilibrium Calculation Textbook s slight of hand Magnitude of A was found by ((5/6)W*b)/c * where b and c were determined by imaging Direction of A (30º) was determined by imaging

56 JRF Calculation ΣF x = 0 ΣF y = 0 Known: W and A Find J x and J y Find J Find θ

57 Influence of Moment Arms Abductor Moment Arm (c) Gravitational Moment Arm (b) Ratio c/b Low ratio Small c Large b Yields greater JRF Short Abductor Moment Arm Typical in Coxa Valga Small ratio Elevated JRF Hip Replacement Surgery Movement of greater trochanter laterally Increases muscle moment arm Decreases JRF (adding life to new joint)

58 Dynamics JRF during walking Lower JRF in women Wider pelvis Different inclination of femoral neck-to-shaft Different general gait pattern

59 Dynamics Muscle Action

60 Peak JRF During Gait Stair Gait 2.6 to 5.5 BW Running & Skiing ~8 BW JRF Peaks Hip flexion ~100º Stair decent Low chair rise

61 External Support Ambulatory Aides Walking with a cane On which side should the cane be used? Why?

62 Ambulatory Aides

63 Summary Part 2: Kinetics and Ambulatory Aides Kinetics Statics Single Leg Stance Two-leg Stance Influence of body COM JRF Calculation Dynamics JRF during gait and locomotion Ambulatory Aides

64 General Summary Questions What do the shoulder and hip joints enable us to do? What stabilizes these structures? What are potential or common injuries to the shoulder? What causes these injuries? What are potential or common injuries to the hip? What causes these injuries? How can injuries be prevented? What are some exercises for stretching and strengthening the hip and shoulder?