Chapter 9: Mechanisms and Characteristics of Sports Trauma

1. Chapter 9: Mechanisms and Characteristics of Sports Trauma

3. Mechanical Injury • Trauma is defined as physical injury or wound sustained in sport, produced by internal or external force • Mechanical injury results from force or mechanical energy that changes state of rest or uniform motion of matter • Injury in sports can be the result of external forces directed on the body or can occur within the body internally

4. Tissue Properties • Relative abilities to resist a particular load • Strength pressure or power is used to imply force (defined as a push or pull) • Load can be a singular or group of outside or internal forces acting on the body. • Stress is resistance to a load • Body tissues are viscoelastic and contain both viscous and elastic properties • Point at which elasticity is almost exceeded is the yield point • When exceeded mechanical failure occurs resulting in damage

5. Tissue Stresses • Tension (force that pulls and stretches tissue) • Stretching (pull beyond yield point resulting in damage) • Compression (force that results in tissue crush) • Shearing (force that moves across the parallel organization of tissue) • Bending (force on a horizontal beam that places stress within the structure)

6. Soft Tissue Trauma • Soft tissue or non -bony tissue is categorized as inert (noncontractile) and contractile tissue • Inert tissues include, ligaments, skin, cartilage, capsules, fascia, dura mater and nerve roots • Contractile tissue involves muscles and its parts including tendons and bony insertions

7. Skin Injuries • Break in the continuity of skin as a result of trauma • Anatomical Considerations • Skin (external covering) or integument represents the largest organ of the bogy and consists of 2 layers • Epidermis • Dermis (corium) • Soft pliable nature of skin makes it easy to traumatize

8. Injurious Mechanical Forces • Include friction, scraping, compression, tearing, cutting and penetrating • Wound Classifications • Friction blister • continuous rubbing over skin surface that causes a collection of fluid below or within epidermal layer • Abrasion • Skin is scraped against rough surface resulting in capillary exposure due to skin removal • Skin Bruise (contusion) • Compression or crush injury of skin surface that produces bleeding under the skin

9. Laceration • Wound in which skin has been irregularly torn • Skin Avulsion • Skin that is torn by same mechanism as laceration to the extent that tissue is completely ripped from source • Incision • Wound in which skin has been sharply cut • Puncture • Penetration of the skin by a sharp object

10. Skeletal Muscle Injuries • High incidence in athletics • Anatomical Characteristics • Composed of contractile cells that produce movement • Possess following characteristics • Irritability • Contractility • Conductivity • Elasticity

11. Three types of muscle • Cardiac • Smooth • Striated (skeletal) • Skeletal Muscle

12. Acute Muscle Injuries • 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

13. Can penetrate to skeletal structures causing a bone bruise • Usually rated by the extent to which muscle is able to produce range of motion • Blow can be so severe that fascia surrounding muscle ruptures allowing muscle to protrude • Signs & Symptoms of Severe Contusions • Athlete reports being struck by hard object • Impact causes pain and transitory paralysis • Due to pressure on and shock to motor and sensory nerves • Palpation reveals hardened area • Possible ecchymosis or tissue discoloration

14. 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

15. 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 • Pathologically, strain is very similar to contusion or sprain with capillary or blood vessel hemorrhage

17. Tendon Injuries • Wavy parallel collagenous fibers organized in bundles - upon loading • Can produce and maintain 8,700- 18,000 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 reabsorption of collagen fibers • Results in weakening tendons • Collagen reabsorption occurs in early period of sports conditioning and immobilization making tissue susceptibility to injury – requires gradual loading and conditioning

20. 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

21. Overexertional Muscle Problems • Reflective in muscle soreness, decreased joint flexibility, general fatigue (24 hours post activity) • 4 indicators of possible overexertion • Muscle Soreness • Overexertion in strenuous exercise resulting in muscular pain • Generally occurs following participation in activity that individual is unaccustomed

22. 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 24-48 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 • Treat with static or PNF stretching and ice application within 48-72 hours of insult

23. Muscle Stiffness • Does not produce pain • Result of extended period of work • Fluid accumulation in muscles, with slow reabsorbtion back into bloodstream, resulting in swollen, shorter, thicker muscles --resistant to stretching. • Light activity, motion, massage and passive mobilization assists in reducing stiffness • Muscle Cramps • Painful involuntary skeletal muscle contraction • Occurs in well-developed individuals when muscle is in shortened position • Experienced at night or at rest

24. 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

25. Myofascial Trigger Points • Discrete, hypersensitive nodule within tight band of muscle or fascia • Classified as latent or active • Latent trigger point • Does not cause spontaneous pain • May restrict movement or cause muscle weakness • Become aware of presence when pressure is applied

26. 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 • 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

27. Chronic Musculoskeletal Injuries • Progress slowly over long period of time • Repetitive acute injuries can lead to chronic condition • Constant irritation due to poor mechanics and stress will cause injury to become chronic • Chronic muscle injuries • Representative of low grade inflammatory process with fibroblast proliferation and scarring • Acute injury is improperly managed

28. Myositis/fascitis • Inflammation of muscle tissue • Fibrositis or inflammation of connective tissue • Plantar fascitis • Tendinitis • Gradual onset, with diffuse tenderness due to repeated microtrauma and degenerative changes • Obvious signs of swelling and pain • 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

29. Ectopic Calcification (myositis ossificans) • Striated muscle becomes chronically inflamed resulting in myositis • Can result in muscle that lies directly above bone • Osteoid material accumulates rapidly and will either resolve in 9-12 months or mature with repeated trauma • With maturation, surgery is required for removal • Common sites, quadriceps and brachial muscle

30. 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

31. Synovial Joints • Anatomical Characteristics • Consist of cartilage and fibrous connective tissue • Joints are classified as • Synarthrotic - immovable • Amphiarthrotic - slightly moveable • Diarthrotic - freely moveable (synovial articulations) • Synovial Joint characteristics • Capsule or ligaments • Capsule is lined with synovial membrane • Hyaline cartilage • Joint cavity with synovial fluid • Blood and nerve supply with muscles crossing joint

33. Joint Capsule • Bones are held together by a fibrous cuff • Consists of bundles of collagen and function to maintain relative joint position • Extremely strong and can withstand cross- sectional forces • Will be slack or taut depending on joint movement

34. Ligaments • Sheets or bundles of collagen that form connection between two bones • Both intrinsic (inside the capsule) and extrinsic (outside the capsule) • Similar composition to tendons • Strong in the middle, weak at the ends • When placed under undo stress may result in avulsion injury • Viscoelastic properties are primary factor in ligamentous injuries

35. Constant compression or tension causes ligament deterioration while intermittent stress strengthens • Repeated microtrauma overtime makes capsule and ligaments more susceptible to major acute injuries • Act as protective backup for joint • Primary protection is dynamic action of muscle • Under fast loading conditions, ligament will fail, however, they provide maximal protection during rapid movements • Will adapt based on Roux’s law of functional adaptation (organ will adapt structurally to an alteration, qualitative or quantitative of function)

36. Synovial Membrane • Lines articular capsule • Single layer of flattened cells and villi • Secretes and absorbs fluid - serves as lubricant • Fluid contains hyaluronic acid (changes viscosity) • Fast movement - thins fluid • Slow movement - fluid thickens • Articular Cartilage • Provides firm flexible support - semifirm connective tissue with primarily ground substance • No direct blood or nerve supply

37. Fibrocartilage: makes up vertebral disks, symphysis pubis and menisci • Elastic: external ear and eustachian tubes • Hyaline: composes nasal septum, larynx, trachea, bronchi, and articular ends of bone • Covers ends of bones in diarthrodial joints which serves as cushion and sponge • Can undergo compression and return to normal shape • Degeneration producing microtrauma can occur following abnormal compressive forces • Receives nourishment from synovium • Provides motion control, stability and load transmission

38. Additional Synovial Joint Structures • Fat • Pads located in elbow, knee, to fill spaces between bones that form joints (lie between synovial membrane and the capsule) • Articular Disks • Additional fibrocartilanginous disks • Vary in shape and size and connected to capsule • Exist in joints that operate in 2 planes of motions • Aid in dispersion of synovial fluid • Meniscus

39. Nerve Supply • Capsule, ligaments, outer aspects of synovial membrane and fat pads are well supplied • Inner structures (synovial membrane, cartilage and articular cartilage) also supplied • Myelinated mechanoreceptors provide joint position sense in fibrous capsule • Non-myelinated fibers supply blood vessels and pain receptors

40. Types of Synovial Joints • 6 types • Ball and socket - allows movement in all plane (hip) • Hinge - allows for flexion and extension (elbow) • Pivot - rotation about and axis (cervical atlas and axis) • Ellipsoidal - elliptical convex and concave articulation (wrist) • Saddle - reciprocally convex-concave (carpometacarpal joint of thumb) • Gliding - all sliding back and forth (carpal joints)

41. Functional Synovial Joints • Differ in their ability to withstand trauma depending on skeletal, ligamentous, and muscular organization • Synovial Joint Stabilization • Muscle tension helps to limit synovial joint movement • With stretching of the capsule, muscle reflex contractions prevent overstretching • Nerve supply is governed by Hilton’s Law (capsule, skin and muscle have same nerve supply) • Ligaments can extend due to right angle structural design but are not elastic

42. Joint structure vs. ligament contribution to joint stability • Muscles absorb forces involved in load transmission and may provide dynamic stabilizing through integration into joint capsule and by crossing joints • Articular Capsule and Ligaments • Help maintain anatomical integrity and structural alignment of joints • Ligaments have spiral arrangement of collagenous tissue • Ligaments tend to be stronger in the middle and weak at the ends • Respond quicker than muscle to over-stretching

43. Synovial Joint Trauma • Major factor in injury is viscoelastic properties of ligaments and capsule • While constant compression is damaging, periodic tension increases overall strength of tissue • Subject to same mechanical forces that cause injury • Synovial Joint Injury Classifications • Acute Joint Injuries • Sprains • Result of traumatic joint twist that causes stretching or tearing of connective tissue • Graded based on the severity of injury

44. 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 • Grade III - extremely painful, inevitable loss of function, severe instability and swelling, and may also represent subluxation

45. Can result in joint effusion and swelling, local temperature increase, pain and point tenderness, ecchymosis (change in skin color) and possibly an avulsion fracture • Most vulnerable joints include ankles, knees, and shoulders • Sometimes difficult to distinguish between sprain and tendon strain • Repeated joint twisting could result in arthritis or chronic inflammation

46. Acute Synovitis • Synovial membrane can be acutely injured via contusion or strain • Irritation of membrane results in increased fluid production and swelling occurs • Results in joint pain along with skin sensitivity • With proper treatment, effusion and pain will diminish • Subluxations, Dislocations and Diastasis • High level of incidence in fingers and shoulder • Subluxations are partial dislocations causing incomplete separation of two bones • Luxation presents with total disunion of bone apposition between articular surfaces • Diastisis is the disjointing of 2 parallel bones or rupture of a solid joint (symphysis pubis)

47. Factors associated with dislocations - 1) loss of limb function, 2) gross deformity, 3)swelling and point tenderness • 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”

48. Chronic Joint Injuries • Stem from microtrauma and overuse • Include, osteochondrosis, osteoarthritis, and in adolescence epiphyseal injuries • Major cause involves failure of muscle to control or limit deceleration • To prevent, a combination of chronic fatigue and training should be avoided, and protective gear should be used to enhance active absorption of impact forces

49. Osteochondrosis • Also known as osteochrondritis 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

50. Osteoarthritis • Wearing away of hyaline cartilage as a result of normal use • Changes in joint mechanics lead to joint degeneration (the result of repeated trauma to tissue involved) • May be the result of direct blow, pressure of carrying and lifting heavy loads, or repeated trauma from an activity such as running or cycling • Commonly affects weight bearing joints but can also impact shoulders and cervical spine • Symptoms include 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