1. Chapter 9: Mechanisms and Characteristics of Musculoskeletal and Nerve Trauma

2. Mechanical Injury
Trauma is defined as physical injury or wound, produced by internal or external force
Mechanical injury results from force or mechanical energy that changes state of rest or uniform motion of matter

3. Tissue Properties Load Stiffness Stress Strain
An external force acting on the body causing internal reactions within the tissues
Stiffness
Ability of a tissue to resist a load
Greater stiffness = greater magnitude load can resist
Stress
Internal resistance to a load
Strain
Internal change in tissue (i.e. length) resulting in deformation

4. Figure 9-1

5. Body tissues are viscoelastic and contain both viscous and elastic properties
Yield point
Point at which elasticity is almost exceeded is the yield point
If deformation persists, following release of load permanent or plastic changes result
When yield point is far exceeded mechanical failure occurs resulting in damage

6. Tissue Loading Tension Compression Shearing
Force that pulls and stretches tissue
Compression
Force that results in tissue crush – two forces applied towards one another
Shearing
Force that moves across the parallel organization of tissue
Figure 9-2

7. Bending
Two force pairs act at opposite ends of a structure (4 points)
Three forces cause bending (3 points)
Already bowed structures encounter axial loading
Torsion
Loads caused by twisting in opposite directions from opposite ends
Shear stress encountered will be perpendicular and parallel to the loads
Figure 9-2

8. Traumatic vs. Overuse Injuries
Nature of physical activity dictates that over time injury will occur
Debate over acute vs. chronic injuries
When injury is acute – something has initiated the injury process
Injury becomes chronic when it doesn’t properly heal
Could define relative to mechanism
Traumatic (i.e. a direct blow) vs. Overuse (i.e. repetitive dynamic use over time)

9. Musculotendinous Unit Injuries
High incidence in athletics
Anatomical Characteristics
Composed of contractile cells that produce movement
Possess following characteristics
Irritability
Contractility
Conductivity
Elasticity

10. Three types of muscle Cardiac Smooth Striated (skeletal)
Skeletal Muscle
Three types of muscle
Cardiac
Smooth
Striated (skeletal)
Figure 9-3

11. Muscle Strains Stretch, tear or rip to muscle or adjacent tissue
Cause is often obscure
Abnormal muscle contraction is the result of 1)failure in reciprocal coordination of agonist and antagonist, 2) electrolyte imbalance due to profuse sweating or 3) strength imbalance
May range from minute separation of connective tissue to complete tendinous avulsion or muscle rupture

12. Muscle Strain Grades
Grade I - some fibers have been stretched or actually torn resulting in tenderness and pain on active ROM, movement painful but full range present
Grade II - number of fibers have been torn and active contraction is painful, usually a depression or divot is palpable, some swelling and discoloration result
Grade III- Complete rupture of muscle or musculotendinous junction, significant impairment, with initially a great deal of pain that diminishes due to nerve damage

13. Pathologically, strain is very similar to contusion or sprain with capillary or blood vessel hemorrhage
Time required for healing may be lengthy
Often involves large, force-producing muscles
Treatment and recovery may take 6-8 weeks depending on severity
Return to play too soon could result in re-injury

14. Muscle Cramps Muscle Guarding
Painful involuntary skeletal muscle contraction
Occurs in well-developed individuals when muscle is in shortened position
Experienced at night or at rest
Muscle Guarding
Following injury, muscles within an effected area contract to splint the area in an effort to minimize pain through limitation of motion
Involuntary muscle contraction in response to pain following injury
Not spasm which would indicate increased tone due to upper motor neuron lesion in the brain

15. Muscle Spasms A reflex reaction caused by trauma Two types
Clonic - alternating involuntary muscular contractions and relaxations in quick succession
Tonic - rigid contraction that lasts a period of time
May lead to muscle or tendon injuries

16. Muscle Soreness
Overexertion in strenuous exercise resulting in muscular pain
Generally occurs following participation in activity that individual is unaccustomed
Two types of soreness
Acute-onset muscle soreness - accompanies fatigue, and is transient muscle pain experienced immediately after exercise
Delayed-onset muscle soreness (DOMS) - pain that occurs hours following activity that gradually subsides (pain free 3-4 days later)
Potentially caused by slight microtrauma to muscle or connective tissue structures
Prevent soreness through gradual build-up of intensity

17. Tendon Injuries
Wavy parallel collagenous fibers organized in bundles - upon loading
Can produce and maintain 8, ,000 lbs/in2
Collagen straightens during loading but will return to shape after loading
Breaking point occurs at 6-8% of increased length
Tears generally occur in muscle and not tendon

18. Repetitive stress on tendon will result in microtrauma and elongation, causing fibroblasts influx and increased collagen production
Repeated microtrauma may evolve into chronic muscle strain due to re-absorption of collagen fibers
Results in weakening tendons
Collagen re-absorption occurs in early period of sports conditioning and immobilization making tissue susceptibility to injury – requires gradual loading and conditioning

19. Tendinitis
Gradual onset, with diffuse tenderness due to repeated microtrauma and degenerative changes
Inflammation of the tendon
Obvious signs of swelling and pain
Crepitus
Sticking of tendon due to accumulation of inflammatory by-products on irritated tissue
Key to treatment is rest
May require substitution of activity in order to maintain fitness without stressing injured structure
Figure 9-5

20. Tendinosis Tendinopathy
Without proper healing tendinitis may begin to degenerate and result in tendinosis
Less inflammation, more visibly swollen with stiffness and restricted motion
Sometimes a tender lump will appear
More common in middle or old age
Treatment involves stretching and strengthening
Tendinopathy
Does not imply a particular pathology
Often used to refer to either tendinitis or tendinosis

21. Tenosynovitis Inflammation of synovial sheath
In acute case - rapid onset, crepitus, and diffuse swelling
Chronic cases result in thickening of tendon with pain and crepitus
Often occurs in long flexor tendon of the digits and the biceps tendon
Due to nature of injury anti-inflammatory agents may be helpful

22. Myofascial Trigger Points
Discrete, hypersensitive nodule within tight band of muscle or fascia
Classified as latent or active
Develop as the result of mechanical stress
Either acute trauma or microtrauma
May lead to development of stress on muscle fiber = formation of trigger points
Latent trigger point
Does not cause spontaneous pain
May restrict movement or cause muscle weakness
Become aware of presence when pressure is applied

23. Active trigger point Causes pain at rest
Applying pressure = pain = jump sign
Tender to palpation with referred pain
Tender point vs. trigger point
Found most commonly in muscles involved in postural support

24. Contusions Result of sudden blow to body
Can be both deep and superficial
Hematoma results from blood and lymph flow into surrounding tissue
Localization of extravasated blood into clot, encapsulated by connective tissue
Speed of healing dependent on the extent of damage
Chronically inflamed and contused tissue may result in generation of calcium deposits (myositis ossificans)
Prevention through protection of contused area with padding

26. Atrophy and Contracture
Atrophy is wasting away of muscle due to immobilization, inactivity, or loss of nerve functioning
Contracture is an abnormal shortening of muscle where there is a great deal of resistance to passive stretch
Generally the result of a muscle injury which impacts the joint, resulting in accumulation of scar tissue

27. Synovial Joints Injuries
Hyaline and/or articular cartilage
Fibrous connective tissue capsule
Ligaments
Capsule with synovial membrane
Joint cavity with synovial fluid
Blood and nerve supply
Muscles
Menisci (fibrocartilage)

28. Figure 9-8

29. Ligament Sprains
Result of traumatic joint twist that causes stretching or tearing of connective tissue
Graded based on the severity of injury
Grade I - some pain, minimal loss of function, no abnormal motion, and mild point tenderness
Grade II - pain, moderate loss of function, swelling, and instability with tearing and separation of ligament fibers
Grade III - extremely painful, inevitable loss of function, severe instability and swelling, and may also represent subluxation

30. Can result in joint effusion and swelling, local temperature increase, pain and point tenderness, ecchymosis (change in skin color) and possibly an avulsion fracture
Greatest difficulty with grade 1 & 2 sprains is restoring stability due to stretched tissue and inelastic scar tissue which forms
To regain joint stability strengthening of muscles around the joint is critical

31. Dislocations and Subluxations
Result in separation of bony articulating surfaces
Subluxation
Partial dislocations causing incomplete separation of two bones
Bones come back together in alignment
Dislocations
High level of incidence in fingers and shoulder
Occurs when at least one bone in a joint is forced out of alignment and must be manually or surgically reduced
Gross deformity is typically apparent with bilateral comparison revealing asymmetry

32. Dislocation (cont.) Stabilizing structures of the joint are disrupted
Joint often becomes susceptible to subsequent dislocations
X-ray is the only absolute diagnostic technique
Able to see bone fragments from possible avulsion fractures, disruption of growth plates or connective tissue
Dislocations (particularly first time) should always be considered and treated as a fracture until ruled out
“Once a dislocation, always a dislocation”
Figure 9-9

33. Osteoarthritis Wearing away of hyaline cartilage
Changes in joint mechanics lead to joint degeneration
Commonly affects weight bearing joints but can also impact shoulders and cervical spine
Symptoms
Pain (as the result of friction)
Stiffness
Prominent morning pain; localized tenderness
Creaking, grating
Either generalized joint pain or localized to one side of the joint
Figure 9-10

34. Bursitis Bursa are fluid filled sacs that develop in areas of friction
Sudden irritation can cause acute bursitis, while overuse and constant external compression can cause chronic bursitis
Signs and symptoms include swelling, pain, and some loss of function
Repeated trauma can lead to calcification and degeneration of internal bursa linings
Figure 9-11

35. Capsulitis and Synovitis
Capsulitis is the result of repeated joint trauma
Synovitis can occur acutely but will also develop following mistreatment of joint injury
Chronic synovitis can result in edema, thickening of the synovial lining, exudation can occur and a fibrous underlying develops
Motion may become restricted and joint noises may develop

36. Bone Injuries Anatomical Characteristics
Dense connective tissue matrix
Outer compact tissue
Inner porous cancellous bone including Haversian canals
Figure 9-12

37. Bone Functions Types of Bone Body support Organ protection
Movement (through joints and levers)
Calcium storage
Formation of blood cells (hematopoiesis)
Types of Bone
Classified according to shape
Flat bones - skull, ribs, scapulae
Irregular bones - vertebrae and skull
Short bones- wrist and ankle
Long bones (humerus, ulna, tibia, radius, fibula, femur) - bones most commonly injured

38. Gross Structures Diaphysis -shaft - hollow and cylindrical
- covered by compact bone
- medullary cavity contains yellow
marrow and lined by endosteum
Epiphysis - composed of cancellous bone and
has hyaline cartilage covering
- provides areas for muscle attachment
Periosteum - dense, white fibrous covering which penetrates bone via Sharpey’ fibers
- contains blood vessels and osteoblasts

39. Bone Growth
Ossification occurs from synthesis of bones organic matrix (work of osteoblasts and osteoclasts)
Involves growth of diaphysis and the epiphyseal growth plates (towards one another)
As cartilage matures, immature osteoblasts replace to ultimately form solid bone
Deforming forces, premature injury and growth plate dislocation can alter growth patterns and/or result in deformity of bone
Bone diameter increases via the activity of osteoblasts adding to the exterior while osteoclasts break down bone in medullary cavity
At full size, bone maintains state of balance between osteoblastic and -clastic activity

40. Changes in activity and hormonal levels can alter balance
Bone loss begins to exceed external bone growth overtime
As thickness decreases, bones are less resistant to forces --osteoporosis
Bone’s functional adaptation to stresses follows Wolff’s Law --every change in form and function or in its function alone is followed by changes in architectural design

41. Bone Fractures Classified as either closed or open
Closed fractures are those where there is little movement or displacement
Open fractures involve displacement of the fractured ends and breaking through the surrounding tissue
Serious condition if not managed properly
Signs & symptoms
Deformity, pain, point tenderness, swelling, pain on active and passive movements
Possible crepitus
X-ray will be necessary for definitive diagnosis

42. Mechanism of Injury Types of fractures
Fracture may be direct (at point of force application) or indirect
Sudden violent and forceful muscle contraction
Types of fractures
Greenstick
Comminuted
Linear
Transverse
Oblique
Spiral
Impacted
Depressed

43. Less common types of fractures
Avulsion
Separation of bone fragment from cortex via pull of ligament or tendon
Blowout fracture
Serrated fracture
Depressed fracture
Contrecoup fracture

44. Bone Loading Characteristics
Bone Strength & Shape
Strength of bone can be impacted by changes in shape and direction
Long bones with gradual changes are less prone to injury
Cylindrical and hollow nature of bones make them very strong - resistant to bending and twisting
Bone Loading Characteristics
Bones can be stressed or loaded to failure by tension, compression, bending, twisting and shearing

45. Long Bone Load Characteristics (cont.)
Either occur singularly or in combination
Amount of load also impacts the nature of the fracture
More force results in a more complex fracture
While force goes into fracturing the bone, some energy and force is also absorbed by adjacent soft tissues
Bone has elastic properties allowing it to bend
Typically brittle and a poor shock absorber
Brittleness increases under tension forces, more so than under compression

46. Stress fractures
No specific cause but with a number of possible causes
Overload due to muscle contraction, altered stress distribution due to muscle fatigue, changes in surface, rhythmic repetitive stress vibrations
Bone becomes susceptible early in training due to increased muscular forces and initial remodeling and resorption of bone
Progression involves, focal microfractures, periosteal or endosteal response (stress fx) linear fractures and displaced fractures
Early detection is difficult, bone scan is useful, x-ray is effective after several weeks

47. Typical causes include
Coming back to competition too soon after injury
Changing events without proper conditioning
Starting initial training too quickly
Changing training habits (surfaces, shoes….etc)
Variety of postural and foot conditions
Signs and symptoms
Focal tenderness and pain, (early stages)
Pain with activity, (later stages) with pain becoming constant and more intense, particularly at night, (exhibit a positive percussion tap test)
Common sites involve tibia, fibula, metatarsal shaft, calcaneus, femur, pars interarticularis, ribs, and humerus
Management varies between individuals, injury site and extent of injury

48. Epiphyseal Conditions
Three types can be sustained by adolescents (injury to growth plate, articular epiphysis, and apophyseal injuries)
Occur most often in children ages years old
Classified by Salter-Harris into five types (see photo on next slide)
Apophyseal Injuries
Young physically active individuals are susceptible
Apophyses are traction epiphyses in contrast to pressure epiphyses.
Serve as sites of origin and insertion for muscles
Common avulsion conditions include Sever’s disease and Osgood-Schlatter’s disease

49. Figure 9-16

50. Osteochondrosis
Also known as osteochondritis dissecans and apophysitis (if located at a tubercle/tuberosity)
Causes not well understood
Degenerative changes to epiphyses of bone during rapid child growth
Possible cause includes 1)aseptic necrosis (disrupted circulation to epiphysis, 2) fractures in cartilage causing fissures to subchondral bone, 3) trauma to a joint that results in cartilage fragmentation resulting in swelling, pain and locking
With the apophysis, an avulsion fracture may be involved, including pain, swelling and disability

51. Nerve Trauma
Abnormal nerve responses can be attributed to injury or athletic participation
The most frequent injury is neuropraxia produced by direct trauma
Lacerations of nerves as well as compression of nerves as a result of fractures and dislocations can impact nerve function

52. Anatomical Characteristics
Provides sensitivity and communication from the CNS to muscles, sense organs and various systems in the periphery
Neuron cell body has a large nucleus with branched dendrites which respond to neurotransmitter substances

53. Anatomical Characteristics
Each nerve cell has an axon that conducts nerve impulse
Axons are encased in neurilemmal sheaths (Schwann and satellite cells)
Various neurological cells in CNS help to form framework for nervous tissue
Nerve Injuries
Compression and tension are primary mechanisms
May be acute or chronic

54. Nerve Injuries
Physical trauma causes pain and can result in a host of sensory responses (pinch, burn, tingle, muscle weakness, radiating pain)
Long term problems can go from minor nerve problems to paralysis
Neuropraxia
Interruption in conduction through nerve fiber
Brought about via compression or blunt trauma
Impact motor more than sensory function
Temporary loss of function
Pain can be referred as well

55. Body Mechanics and Injury Susceptibility
Body moves very effectively in upright position - able to overcome great forces even with inefficient lever system
Body must overcome inertia, muscle viscosity and unfavorable angles of pull
Mechanical reasons for injury - hereditary, congenital, or acquired defects may predispose athlete to injury
Body build, structural make-up, habitual incorrect application of skill may also predispose individual to injury

56. Microtrauma and Overuse Syndrome
Injuries as a result of abnormal and repetitive stress and microtraumas fall into a class with certain identifiable syndromes
Frequently result in limitation or curtailment of sports involvement
Often seen in running, jumping, and throwing activities
Some of these injuries while small can be debilitating
Repetitive overuse and stress injuries include
Achilles tendinitis, shin splints, stress fx, Osgood-Schlatter's disease, runner’s and jumper’s knee, patellar chondromalacia and apophyseal avulsion

57. Postural Deviations Often an underlying cause of injury
May be the result of unilateral muscle or bony and soft tissue asymmetries
Sports activities may cause asymmetries to develop
Results in poor pathomechanics
Imbalance is manifested by postural deviations as body tries to regain balance relative to CoG
May be primary cause of injury

58. Injury generally becomes chronic and athletic participation must stop
Athletic trainer should attempt to correct postural conditions
Postural conditions can make individual exceedingly more prone to injury