Chapter 9 Mechanisms and Characteristics of Musculoskeletal and

Chapter 9: Mechanisms and Characteristics of Musculoskeletal and Nerve Trauma © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

Mechanical Injury • ______ is defined as physical injury or wound, produced by internal or external force • ________ results from force or mechanical energy that changes state of rest or uniform motion of matter © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• Tissue Properties – ____ • An external force acting on the body causing internal reactions within the tissues – _______ • Ability of a tissue to resist a load • Greater stiffness = greater magnitude load can resist – ____ • Internal resistance to a load – ______ • Internal change in tissue (i. e. length) resulting in deformation © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

Figure 9 -1 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

– Body tissues are viscoelastic and contain both viscous and elastic properties – _________ • 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• Tissue Loading – ______ • Force that pulls and stretches tissue – Compression • Force that results in tissue crush – two forces applied towards one another – _______ Figure 9 -2 • Force that moves across the parallel organization of tissue © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

– Bending • ____ force pairs act at opposite ends of a structure (4 points) • Three forces cause bending (3 points) • Already bowed structures encounter axial loading – ______ • Loads caused by twisting in opposite directions from opposite ends • Shear stress encountered will be perpendicular and parallel to the loads Figure 9 -2 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

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 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) © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

Musculotendinous Unit Injuries • High incidence in _____ • Anatomical Characteristics – Composed of contractile cells that produce movement – Possess following characteristics • • Irritability Contractility Conductivity Elasticity © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

Skeletal Muscle – Three types of muscle • _________ • Striated (skeletal) Figure 9 -3 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• Muscle ______ – 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 _____ or muscle rupture © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

– 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 ______ 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

– Time required for healing may be ______ – 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 reinjury © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• Muscle _______ – – – • 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 _____, 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• Muscle Spasms – A reflex reaction caused by trauma – Two types • ____ - alternating involuntary muscular contractions and relaxations in quick succession • ____ - rigid contraction that lasts a period of time – May lead to muscle or tendon injuries © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• Muscle Soreness – – – Overexertion in strenuous exercise resulting in muscular ______ Generally occurs following participation in activity that individual is unaccustomed Two types of soreness 1) Acute-onset muscle soreness - accompanies fatigue, and is transient muscle pain experienced immediately after exercise 2) Delayed-onset muscle soreness (_____) - 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• Tendon Injuries – Wavy parallel collagenous fibers organized in bundles - upon loading • Can produce and maintain 8, 700 - 18, 000 lbs/in 2 • 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

– Repetitive stress on tendon will result in microtrauma and _______, 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• Tendinitis – _________, with diffuse tenderness due to repeated microtrauma and degenerative changes – Obvious signs of swelling and pain – Key to treatment is _______ – May require substitution of activity in order to maintain fitness without stressing injured structure – Without proper healing condition may begin to degenerate and be referred to as tendinosis • Less inflammation, more visibly swollen with stiffness and restricted motion • Treatment involves stretching and strengthening Figure 9 -5 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• Tenosynovitis – Inflammation of ________ – 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• Myofascial Trigger Points – Discrete, hypersensitive nodule within tight band of ____________ – 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

– 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• _________ – Result of sudden ____ to body – Can be both deep and superficial – ______ 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

© 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• Atrophy and Contracture – _____ is wasting away of muscle due to immobilization, inactivity, or loss of nerve functioning – _______ 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

Synovial Joints Injuries • Each joint has both _____ or articular cartilage and a fibrous connective tissue capsule • Additional synovial joint characteristics – Capsule and ligaments for support – Capsule is lined with synovial membrane – Hyaline cartilage – Joint cavity with synovial fluid – Blood and nerve supply with muscles crossing joint – Menisci (fibrocartilage)© 2011 Mc. Graw-Hill Higher Education. All rights reserved.

Figure 9 -8 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• Ligament _____ – 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• 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 _____ is critical © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• Dislocations and Subluxations – Result in separation of bony articulating surfaces – _________ • Partial dislocations causing incomplete separation of two bones • Bones come back together in alignment – _________ • 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

– Dislocation (cont. ) • ______________ of the joint are disrupted • Joint often becomes susceptible to subsequent dislocations • _____ 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• Osteoarthritis – Wearing away of ______ cartilage as a result of normal use – Changes in joint mechanics lead to joint degeneration – 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 Figure 9 -10 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

– ________ • Bursa are __________that develop in areas of friction • Sudden irritation cause acute bursitis, while overuse and constant external compression 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

– Capsulitis and Synovitis • ________ 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

Bone Injuries • Anatomical Characteristics – Dense connective tissue matrix – Outer compact tissue – Inner porous cancellous bone including Haversian canals Figure 9 -12 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

– Bone Functions • • • Body support Organ protection Movement (through joints and levers) Calcium storage Formation of blood cells (hematopoiesis) – Types of Bone • • • Classified according to shape _______- skull, ribs, scapulae Irregular bones - vertebrae and skull _______- wrist and ankle Long bones (humerus, ulna, tibia, radius, fibula, femur) - bones most commonly injured © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

– Gross Structures • ______ -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 • ______ - dense, white fibrous covering which penetrates bone via Sharpey’ fibers - contains blood vessels and osteoblasts © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• Bone Fractures – Classified as either _________ • 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

– Mechanism of Injury • Fracture may be direct (at point of force application) or indirect • Sudden violent and forceful muscle contraction – Types of fractures • • _____ Comminuted Linear Transverse Oblique _____ Impacted Depressed Figure 9 -13 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

– __________ • 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, ______ is useful, x-ray is effective after several weeks © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• Typical causes include – – – Coming back to competition too soon after injury Changing events without proper conditioning Starting initial training too quickly Changing training habits (______, 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• Nerve Injuries – Compression and tension are primary mechanisms – May be acute or chronic – 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 – _________ • • 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

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 - ________________________ • Body build, structural make-up, habitual incorrect application of skill may also predispose individual to injury © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• 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 ________________________________ – 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 © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

• ___________ – 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 Co. G • May be primary cause of injury © 2011 Mc. Graw-Hill Higher Education. All rights reserved.

– Injury generally becomes ______ and athletic participation must stop – Athletic trainer should attempt to correct _______ conditions – Postural conditions can make individual exceedingly more prone to injury © 2011 Mc. Graw-Hill Higher Education. All rights reserved.