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DMD: Equinus Contractures

Discussion

  • progressive paralytic equinovarus is an important reason for gait deterioration in pts w/ DMD;
  • equinus contracture compensates for incr quadriceps weakness & allows knees to lock by enabling wt line to pass in front of knee joint;
  • feet become progressively fixed in equinus & then equinovarus position;
  • posterior tibial muscle retains good f(x) despite progression of muscle weakness in other areas;

Indications for Surgery

  • progressive, rigid equinovarus contractures prevent pt from attaining comfortable position of feet in wheelchair or from wearing shoes;
  • surgical correction of equinovarus is indicated in pts who retain ability to ambulate;
  • if there are equinus contractures of the ankle but the function of quadriceps is still good, isolated Vulpius heel-cord lengthening is often valuable;
  • some authors have performed Z-lengthening but have cautioned about possibility of overcorrection;
  • procedure can add an average of 3 yrs of f(x) ambulation;

Operative Treatment

  • multiple tenotomies of Achilles, posterior tibial, FDL & FHL tendons, followed by use of AFO, has led to┬áimprovement in circulation & in position and comfort of the feet of these patients;
  • posterior tibial muscle retains good f(x) despite progression of muscle weakness in other areas;
  • its transfer thru interosseous membrane to dorsum of foot (lateral cuneiform) prevents recurrence of equinovarus & actively contributes to dorsiflexion of the foot;
  • heel cord lengthening is also performed;
  • tendon transfer allows this musculotendinous unit to serve as dorsiflexor & evertor rather than as plantar flexor & invertor