General Classification of Musculoskeletal Sports Injuries
Musculoskeletal sports injuries can be classified as traumatic or overuse injuries.
Traumatic Injuries
Description: Result from specific episode(s) of trauma, whether recent (acute) or in the more distant past (subacute or chronic)
Bone
Description: Traumatic injury to a bone most commonly results in fracture, although rarely, another result occurs, such as subperiosteal hematoma.
Descriptive terms:
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Closed fracture is a fracture that does not produce an open wound in the skin.
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Open fracture is when an open wound in the skin communicates with the fracture site.
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Descriptive terms for direction of fracture line:
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Fracture at right angles to the long axis of a bone is called transverse.
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Fracture line at other angles to the long axis of a bone is called oblique.
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Bone twisted apart creates spiral configuration of fracture.
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Comminuted fracture is when a bone is broken into three or more pieces.
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Avulsion fracture is a “pull-off” fracture; a piece of bone is pulled off by the ligament or by tendon attachment.
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Greenstick fracture is an incomplete fracture in children: one side of a bone is broken, whereas the other side appears bent.
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Torus fracture is localized buckling in the cortex of the bone, common in children.
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Epiphyseal fracture is a fracture that involves the growth center at the end of a long bone in children.
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Joint
Description: Traumatic injury to joint and supporting structures (capsule or ligaments) often results in an instability episode referred to as dislocation or subluxation. Rarely, another result occurs from a direct blow, such as joint contusion or hemarthrosis.
Classification:
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Dislocation is complete displacement of joint surfaces so that they no longer make normal contact at all; important to distinguish first-time or recurrent dislocation
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Subluxation is partial displacement of joint surfaces, usually transient in nature; important to distinguish first-time or recurrent subluxation
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Dislocation or subluxation implies damage to ligaments or other supporting structures of a joint; important to ascertain injury to those tissues; discussed in the following section
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Ligament
Description: Traumatic injury to a ligament is referred to as sprain.
Classification:
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First-degree sprain: Tear of only a few ligament fibers; mild swelling, pain, disability; no instability of joint created
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Second-degree sprain: Tear of a moderate number of ligament fibers, but ligament function is still intact; however, ligaments may be somewhat stretched. Moderate amount of swelling, pain, disability; slight to no instability of joint
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Third-degree sprain: Complete rupture of a ligament; severe swelling and disability; definite joint instability; instability may be classified as:
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1+ joint surfaces normally stabilized by ligament(s) displaced 3–5 mm from their normal position
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2+ joint surfaces separated by 6–10 mm
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3+ joint surfaces separated by >10 mm
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Muscle–Tendon Unit
Strain
Description: Traumatic injury to muscle or tendon caused by indirect force (i.e., contraction of muscle itself) is referred to as strain
Classification:
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First-degree strain: Tear of only a few muscle or tendon fibers; mild swelling, pain, disability; can also be characterized by patient’s ability to produce strong, but painful, muscle contraction
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Second-degree strain: Disruption of moderate number of muscle or tendon fibers, but muscle–tendon unit still intact; moderate amount of pain, swelling, disability; characterized by patient’s weak and painful attempts at muscle contraction
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Third-degree strain: Complete rupture of muscle–tendon unit; may be at origin, muscular portion, musculotendinous junction, within tendon itself, or at tendon insertion; characterized by extremely weak attempts at muscle contraction
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Deep Muscle Contusion
Description: Traumatic injury to muscle caused by direct force may produce deep muscle contusion; typically affects quadriceps or brachialis muscles involved in contact or collision sports; may lead to myositis ossificans and therefore permanent loss of function
Myositis Ossificans
Description: Heterotopic bone formation caused by deep muscle contusion or strain, particularly after marked hematoma formation
Common sites: Quadriceps; biceps, triceps, brachialis; hip girdle; groin; and lower leg
Risk factors: Severe contusion; continuing to play after injury; massaging injured area; early application of heat; passive, forceful stretching; overly rapid rehabilitation; premature return to sport; re-injury of same site; individual propensity to heterotopic bone formation
Calcification: Follows injury by 3–6 weeks
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May continue to develop for ≥6 weeks
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May remodel or reabsorb over 3–12 months, particularly if close to musculotendinous junction
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Treatment:
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Treat strain or contusion with basic athletic first aid (see Chapter 43, Comprehensive Rehabilitation of the Athlete ) represented by the mnemonic PRICES: p rotection, r est, i ce, c ompression, e levation, and s upport; followed by progressive symptom-guided rehabilitation
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Excision rarely necessary
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Warranted only in cases of persistent weakness or limited range of motion
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Only after calcification matures (6–12 months)
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High rate of recurrence if excised too early
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Exertional Rhabdomyolysis
Description: Breakdown of skeletal muscle cells with leakage of cellular contents, including myoglobin, creatine kinase (CK), and aldolase through damaged sarcolemma into serum as result of prolonged, heavy, or repetitious exercise
Presentation: Muscle pain and tenderness, muscle swelling, muscle cramps, and reddish brown urine
Laboratory tests: Urinalysis (urine dipstick positive for hemoglobin; microscopic exam reveals few to no red blood cells); elevated CK (normal: 200 U/L; subclinical to mild rhabdomyolysis: 600 U/L; most clinical cases: 10,000 U/L; and severe cases: reports 200,000 U/L); and elevated serum myoglobin (normal, 5–70 g/L; elevated only up to 6 hours after injury if renal function is normal)
Etiology: Intense exercise causes local tissue hypoxia, resulting in elevation of adenosine triphosphate (ATP) and consequent failure of sodium–potassium pump with potassium efflux and calcium influx; anaerobic glycolysis with lactic acid overproduction and, in severe cases, metabolic acidosis; sarcolemma permeability; and, in severe cases, cell death
Common predisposing features: Heat, humidity, dehydration, poor physical conditioning (may also occur in well-conditioned athlete with very intense or repetitive exercise), high altitude, recent viral infection, sickle cell trait, and hereditary defects in ATP synthesis
Clinical course:
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Most cases are subclinical and never diagnosed or minimal (visible myoglobinuria without muscle pain and spontaneous healing)
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Mild-to-moderate cases respond well to aggressive hydration; without nephrotoxic cofactors, dehydration, and acidosis, damage is usually not persistent; lasting systemic complications are rare; muscle has remarkable capacity for repair
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Severe cases are common in patients with dehydration or acidosis; they are characterized by systemic complications:
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Acute tubular necrosis and renal failure caused by combination of renal hypoperfusion, acidosis, and myoglobin sludging in renal tubules
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Acute compartment syndrome (rhabdomyolysis causes muscle swelling, which increases intramuscular pressure, causing vicious cycle of damage; in athletes with chronic compartment syndrome, increased compartment pressure may reduce tissue perfusion and cause rhabdomyolysis)
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Hyperkalemia
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Hypocalcemia
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Hyperphosphatemia
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Diffuse intravascular coagulopathy (DIC)
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Cardiac dysrhythmia
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Treatment:
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Aggressive early hydration to maintain renal perfusion and clear myoglobin, thereby preventing acute tubular necrosis and renal failure
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May require 4–12 L of normal saline during first 24 hours
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Diuretic (furosemide) may be necessary to maintain kidney function
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Alkalinization of urine with bicarbonate
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Myoglobin is less nephrotoxic and more soluble in alkaline urine
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Uric acid is more soluble and less likely to crystallize in alkaline urine
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Caveat: Alkalinization with bicarbonate may increase precipitation of calcium in injured muscles, causing heterotopic bone formation. Safer approach may be oral acetazolamide, 250 mg, three times daily, if plasma bicarbonate level is >13–15 mEq/L.
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Correct hyperkalemia, hyperphosphatemia, and hypocalcemia. Avoid IV calcium, except to treat tetany, because of the risk of heterotopic bone formation.
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Fasciotomy, if necessary for compartment syndrome
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Treat DIC if it does not resolve spontaneously
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Dialysis if necessary
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Other Soft Tissues
Description: Traumatic injury to bursa with bursal swelling is referred to as traumatic bursitis, it is usually caused by bleeding into bursa. Traumatic injuries to other soft tissues include various contusions and hematomas. Lacerations may involve musculoskeletal tissues.
Shearing injuries: Avulsions, abrasions, or blisters
Morel–LavallÉe Lesion
Description: A posttraumatic, closed, degloving soft tissue injury in which the skin and subcutaneous tissues are separated from fascia superficial to the underlying muscle plane creating a space that fills with fluid and is susceptible to necrosis and infection.
Presentation: Diagnosis of Morel–Lavallée lesions is often missed or delayed. There may be a large swollen area where a hematoma develops often in the pelvis area. There is soft tissue swelling with or without ecchymosis. Typically, there is asymmetry of the skin contour and hypermobility. Underlying soft fluctuance is also present with minimal or absent tenderness. Often, chronic lesions will have decreased sensation and cracked areas on the skin.
Imaging: MRI is the preferred imaging modality of choice. In acute lesions, fluid collection will be a homogeneous collection that is hypointense on T1-weighted images and hyperintense on T2-weighted images. In chronic situations, the fluid will be hyperintense on both T1- and T2-weighted images ( Fig. 42.1 ).
