domingo, 3 de enero de 2010

Generalidades sobre alargamientos óseos por medio de Fijador Externo

 Se trata de la formación de hueso nuevo lentamente, por medio de el alargamiento del callo que se forma después de una fractura (programada) en el hueso, en donde este "callo" puede irse dirigiendo para corregir alguna deformidad congénita o adquirida que se encuentre antes del tratamiento.
Se efectúa con ayuda de un fijador externo que permite ir cambiando paulatinamente el largo y alineación de la extremidad.
Existen múltiples tipos de fijadores, de los que se seleccionará el mas adecuado para la deformidad o proceso de alargamiento que se requiera. 
El método es aplicable a todas las extremidades, pero es más común usarlo en las extremidades inferiores, donde la alineación es mas delicada que en las superiores, ya que estas son las encargadas de mantener el apoyo del peso corporal.
El alargamiento puede efectuarse casi a cualquier edad (cumpliendo siempre ciertas condiciones), sin embargo la edad ideal es en la adolesencia y juventud; debido a que en esta edad el esqueleto se encuentra casi en el término del crecimiento, pudiendo determinar su forma final, asimismo el potencial de reparación ósea del niño es mayor. 
    • In addition, the patient has the maturity to undergo an arduous treatment process.
    • Bone healing, however, is slower with advancing age.
  • For certain indications, this procedure can be performed in younger patients (with severe congenital abnormalities) or in adults (with nonunions and acquired deformities).
  • Classification for types of procedures performed using with Ilizarov method:
    • Extremity lengthening
    • Angular correction
    • Repair of nonunion
    • Restoration of lost bone
    • Correction of contracture
    • Fracture treatment
  • Synonyms: Limb lengthening; Callotasis
Signs and Symptoms
In deciding whether this treatment method is appropriate for a given individual, the physician should determine the degree of functional impairment, degree of patient adaptation, and degree of patient understanding and motivation to undergo a treatment that lasts for many months.
Physical Exam
The patient should be checked for pin-tract problems, nerve function, and joint ROM at each visit (1,2).
Special Therapy
Physical Therapy
  • Patients may benefit from:
    • Instruction on appropriate weightbearing and transfers
    • Maintaining joint ROM
    • Strengthening
    • Monitoring the correction process daily
First Line
NSAIDs should not be taken for a long period because they may suppress bone healing.
  • Surgery (to create the osteotomy and attach the fixator) is performed with the patient under general anesthesia (bone elongation usually is performed later).
  • The external fixator frame is assembled on the patient's limb according to its shape and the goal of treatment.
    • Several PINS or rings are needed above and below the site of bone correction.
    • Threaded distraction rods are positioned to provide the needed correction over time (Fig. 1).
  • The osteotomy is performed once the bone is stabilized.
    • Use a small incision.
    • Try to limit as much as possible the disruption of the blood supply.
    • Often, the fixator is extended to an adjacent bone for stability.
  • If the needed correction is minor, it can be performed while the patient is under anesthesia, but usually no distraction or lengthening is performed at the time of the surgery.
    View Figure
    Fig. 1. The Ilizarov method may be used to lengthen a limb. Bone regenerates to fill in the gap.
  • P.229

  • Distraction:
    • Started 7–10 days postsurgery (approximately the time the healing callus is 1st seen radiographically)
    • Continued at a rate of 1 mm per day:
      • Usually divided into at least 4 segments so the tissues are not stretched too suddenly
      • In this way, the callus is stretched slowly (distraction osteogenesis).
  • Once the desired length is achieved, the new bone is allowed to strengthen, which occurs with time and weightbearing.
  • The fixator is removed when the bone appears strong enough.
  • The total time spent in the fixator can be estimated by the lengthening index:
    • Time (per centimeter of length gained) needed for the process of lengthening and consolidation
    • Averages 1–1.6 months/cm
  • The results usually are good, although problems and complications may require additional procedures before completion.
  • An 80–90% success rate may be expected (14), although the healing time often is prolonged.
  • Nonunion
  • Joint stiffness or subluxation
  • Fracture
  • Nerve injury
Patient Monitoring
  • Patients must be seen periodically during the procedure to monitor the correction process and to check on the status of the pin sites.
  • Radiographs usually are necessary.
1. Paley D, Lamm BM, Katsenis D, et al. Treatment of malunion and nonunion at the site of an ankle fusion with the Ilizarov apparatus. Surgical technique. Bone Joint Surg 2006;88A:119–134.
2. Patil S, Montgomery R. Management of complex tibial and femoral nonunion using the Ilizarov technique, and its cost implications. JBone Joint Surg 2006;88B:928–932.
3. Cho TJ, Choi IH, Chung CY, et al. Isolated congenital pseudarthrosis of the fibula: Clinical course and optimal treatment. J Pediatr Orthop 2006;26:449–454.
4. McGarvey WC, Burris MW, Clanton TO, et al. Calcaneal fractures: Indirect reduction and external fixation. Foot Ankle Int 2006;27:494–499.
Patient Teaching
  • Patients should be told of the duration of treatment (usually many months).
  • They should be helped to make arrangements for school or work and for care after the procedure.
    • Admission to a rehabilitation hospital sometimes is indicated.
  • Patients should be assessed to determine whether they have the level of maturity needed for the treatment.
  • Patients may be allowed to bear weight and to swim with the device, if the surgeon allows.