Repetitive Stress Injury

Evan D. Collins, M.D.
Methodist Dept of Orthopedics
Office: 713-441-3535
www.drevancollins.com

What is Repetitive Stress Injury?

Categorizing Pathology

  • Structural Problem
  • Disease-Biology
  • Capacity exceed a limit

Many Confusing Terms

  • Repetitive stress injury (RSI)
  • Cumulative trauma disorder (CTD)
  • "Overuse syndrome"
  • Work-related musculoskeletal disorders (WRMSDs)

Background

  • "Epidemic" in Australia in the 1980s
  • Similar "epidemic" in the U.S. in the 1990s - Spawned the development of ergonomics
  • Disagreement in the hand surgery literature over the veracity of repetitive stress injury
  • Sports literature

Pathophysiology

  • Pitner defined repetitive stress as a level of repetitive microtrauma that exceeds the ability of normal tissue to adapt
  • Repetitive microtrauma refers to discrete microscopic or molecular disruption of tissue after many cycles of stress, each of which is in the "physiologic" range

Tendon

  • Curwin showed the molecular collagen structure of tendons can elongate by ˜4% without tissue damage
  • Between 4 and 8%, cross-links rupture and the fibers slide past each other
  • Concept of creep implicated as possible mechanism in repetitive loading injuries of tendons
  • Shear stress or tension overload

Natural History of Tendinitis

  • Four Stages
    - Inflammation
    - Proliferation
    - Maturation
    - Fibrosis

Muscle

  • Muscle soreness develops 12-24 hours after unaccustomed activity and peaks at 1-3 days later
  • Three theories of etiology of muscle pain
    - Increased levels of creatinine kinase
    - Derangements in calcium metabolism
    - Ischemia secondary to inability to maintain ATP stores

Bone

  • Classic example of repetitive injury to bone is a stress fracture of the lower extremity
  • Pain is gradual, well-localized, follows a period of unaccustomed activity
  • Stress fracture pathophysiology well discussed in orthopaedic literature

Nerve

  • Role of repetitive stress injury as a possible etiology for many compression neuropathies of the hand and wrist is heavily debated
  • Not much pathophysiologic data to support

Musculotendinous Overuse Syndromes

DeQuervain's Syndrome

  • Stenosing tenosynovitis of 1st dorsal compartment
  • Most common tendonitis of the wrist in athletes
  • APL and EPB course in this sheath, often contain subsheath between APL and EPB
  • Shear stress from repetitive motion (especially radial and ulnar deviation combined with flexion and extension of the wrist) results in inflammation of the tenosynovium.
  • Associated with golf, racquet sports, and fishing

Finkelstein’s Test

1st Dorsal Compartment Release

Intersection Syndrome

  • Inflammation at the point of crossing of the "outriggers" (APL and EPB) with the radial wrist extensors (ECRL and ECRB)
  • Oarsmen and racquet sports are prone to this
  • Diagnostic injections
  • Splints

ECU Tendinitis

  • Second most common sports-related overuse syndrome according to Wood
  • Seen with motions requiring excessive ulnar deviation
  • Common in tennis players’ nondominant hand who use two-handed backhand
  • Provocative maneuvers
  • Diagnostic injections
  • Check for subluxation

FCR Tendinitis

  • Pain with resisted flexion of wrist
  • Abatement of symptoms with diagnostic injection confirms diagnosis
  • Concept of "radial tunnel" as described by Gabel
  • FCR release

FCR Release

FCU Tendinitis

  • Pain with resisted flexion and ulnar deviation of the wrist
  • May or may not involve pisotriquetral arthritis
  • Check for "misinform boost"
  • Diagnostic injections
  • Related to racquet sports in particular

Stenosing Tenosynovitis (Trigger finger)

  • Usually considered secondary to degenerative changes; however, it can be see as a result of contact pressure on the distal palm by a bat, racquet, or golf club
  • Repetitive contact can lead to acute inflammation which can produce trigger finger in athletes
  • Injection, splints
  • A1 pulley release

Focal Dystonias

  • Graphospasm or Writer's cramp
  • Fairly common among piano players and writers
  • Crampy pain with specific activity
  • Botox injections have been recently found to be successful for treatment

Exertional Compartment Syndrome

  • Rare syndrome, but known to occur in the anterior compartment of the lower leg
  • Also described cases in the upper extremity
  • Individuals such as oarsmen that sustain grip on a tool are susceptible
  • Diagnosis and treatment are the same as any compartment syndrome

Case of chronic exertional compartment syndrome of anterior calf

Neurovascular Syndromes

Carpal Tunnel Syndrome

  • Gelberman demonstrated elevated carpal tunnel pressure within the carpal canal with CTS.
  • Szabo's study suggests changes in carpal pressure with position and exercise in normal patients and CTS patients
  • Repetitive flexion and extension of wrist may "pump up" the carpal canal pressure

Szabo's study on dynamic carpal pressures

Ulnar Tunnel Syndrome

  • Also known as Cyclist's Palsy
  • Compression of ulnar nerve in Guyon's canal
  • Jackhammer operators,long-distance cyclists, and individuals active in Martial Arts

Handcuff neuropathy

  • Synonymous with Wartenberg's syndrome
  • Compression of the superficial radial nerve where it exits under the brachioradialis muscle
  • Can occur secondary to tight handcuffs
  • If patient has positive Tinel's, may need to do operative nerve decompression

Hypothenar Hammer Syndrome

  • Related to Judo, Karate, Cycling, Jackhammer usage similar activities to ulnar tunnel syndrome.
  • Trauma to ulnar artery distal to Guyon's canal
  • Pts present with digital ischemia, cold intolerance, pain in the palm
  • Remember Allen's test

Bowler's Thumb

  • Described by Dobyns in 1972
  • Compression neuropathy of ulnar digital nerve of thumb over sesamoid bone secondary to continuous pressure from the edge of the thumb hole in the bowling ball
  • Orthotic or other splint can be worn
  • Device to keep thumb straight can be placed in thumb hole of ball

Digital Ischemia in Baseball Players

  • Few case reports
  • Lowery did study and found significant incidence of digital ischemia in baseball catchers
  • Recommendation was to increase padding in gloves
  • Itoh found digital ischemia in pitchers
  • Thought to be secondary to lumbrical canal compression or vasospasm secondary to overstimulation of digital sympathetics