Sports Medicine: Just the Facts

LAXITY

Looseness, usually referring to a ligament compared
with the normal contralateral side

• Grade I:(1+): up to 5 mm


• Grade II:(2+): from 6 to 10 mm


• Grade III:(3+): >10 mm

NERVE INJURIES (SEDDON CLASSIFICATION)

• Neurapraxia:No structural damage to nerve with
  complete recovery expected


• Axonotomesis:Disruption of the axon and myelin
  sheath with resulting degeneration of the axon distal
  to the site of injury; recovery expected


• Neurotmesis:Partial or complete tear of nerve with
  disruption of axon, myelin sheath, and connective
  tissue elements; recovery not expected

NERVE INJURIES (SUNDERLAND CLASSIFICATION)

• Type 1:Neurapraxia


• Type 2:Axonotomesis


• Type 3:Neurotmesis—loss of nerve fiber continuity
  with perineurium and epineurium intact


• Type 4:Neurotmesis—loss of nerve fiber continuity
  with only epineurium intact


• Type 5:Neurotmesis—complete transection of nerve

STRAIN (CLASSIFICATION):

• 1st Degree:Minimal damage to the muscle, tendon,
  or musculotendinous unit


• 2nd Degree:Partial tear to the muscle, tendon, or
  musculotendinous unit


• 3rd Degree: Complete disruption to the muscle,
  tendon, or musculotendinous unit

BIBLIOGRAPHY

Beaty, Kasser (eds.): Rockwood & Green’s Fractures in Children,
5th ed. Baltimore, MD, Lippincott, Williams & Wilkins, 2001.
Bigliani LU, Morrison D, April EW: The morphology of the
acromion and its relationship to rotator cuff tears. Orthop
Trans(10):228, 1986.
Bucholz, Heckman (ed.): Rockwood & Green’s Fractures in Adults,
5th ed. Baltimore, MD, Lippincott, Williams & Wilkins, 2001.
DeLee, Drez (eds.): Orthopaedic Sports Medicine: Principles
and Practices, 2nd ed. Philadelphia, Elsevier Science, 2003.
Fairbank TJ: Knee joint changes after meniscectomy. JBJS(B)
30(4):664–670, 1948.

Helms CL: Fundamentals of Skeletal Radiology, 2nd ed. Mosby,

Churchill, W. B. Saunders, 1995.

Newman Dorland WA, (Ed.): Dorland’s Illustrated Medical

Dictionary, 29th edn., Mosby, Churchill, W. B. Saunders, 2000.

Outerbridge RE: The etiology of chondromalacia of the patellae.

JBJS(B)(43):752–755, 1961.

Seddon JH: Three types of nerve injury. Brain66(4):237–288,

1943.

Sunderland S: A classification of peripheral nerve injuries pro-

ducing loss of function. Brain74:491–516, 1951.

Tria AJ, Klein KS: An Illustrated Guide to the Knee. New York:

Churchill Livingstone, 1992.

8 BASICS IN EXERCISE

PHYSIOLOGY

Patricia A Deuster, PhD, MPH

David O Keyser, PhD

SKELETAL MUSCLE PHYSIOLOGY

THE SKELETAL MUSCLE FIBER

BASICUNITS

• The primary components of skeletal muscle include
  the sarcomere, the myofilaments, the myofibril
  (basic unit of contraction), the muscle fiber (cell),
  fascicles (bundles of about 150 muscle fibers each),
  and a muscle (Fig. 8-1). The sarcomere, an area from
  Z-disk to Z-disk and the functional contraction unit
  of a myofibril, contains two types of myofilaments:
  thick (myosin) and thin (actin) myofilaments, which
  are repeated throughout the muscle myofibril.


• Other important structures within a sarcomere are
  I-bands, A-bands, H-zones (absence of actin), and
  M-bands (sarcomere’s center). Transverse tubules
  (T-tubules: see Excitation-Contraction Coupling),
  found at the A–I junction of the sarcomere, and the
  sarcoplasmic reticulum(SR) are the primary regula-
  tors of calcium influx into muscle units. The muscle
  cell membrane is the sarcolemma.

MUSCLEPROTEINS

•Key skeletal muscle proteins include actin, myosin,

troponin, and tropomyosin. Actin and myosin make

up the myofilaments within the myofibril, with

myosin being the site of ATP binding. A troponin

complex on the actin molecule acts as a calcium bind-

ing site to initiate contraction, and tropomyosin is

found in the thin filaments of muscle fibers, where it

inhibits contraction until modified by troponin.

34 SECTION 1 • GENERAL CONSIDERATIONS IN SPORTS MEDICINE