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Distraction osteogenesis

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orthoprince
orthoprince

This document discusses distraction osteogenesis, a technique where new bone is formed between vascular bone surfaces that are gradually pulled apart. It involves three phases: a latency period, distraction period where the bone surfaces are distracted 1mm per day, and consolidation period. Histologically, a fibrous interzone forms between the bone surfaces that takes on the role of a growth plate, with intramembranous ossification forming new bone columns across the gap. Key factors for successful new bone formation include stability of fixation, atraumatic corticotomy, and appropriate distraction rate and rhythm.

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DISTRACTION OSTEOGENESIS
Mechanical induction of new bone that occurs between vascular bony surfaces that are gradually pulled apart by gradual distraction. New bone formed bridges the gap & remodels to normal bone macrostructure. Tension stress effect on growth & genesis of tissues.
Developed by Ilizarov in 1956 Highly modular fixators allow formation of new bone in almost any plane as D.O follows the vector of applied force. Age: as long as Pt had # healing potential. INDICATION: bone grafting, LLD, nonunion, deformity, bone defects 2* to trauma, infection, tumor.
Advantages over bone grafting Reduces donor site morbidity Autograft is limited No fear of transmission of antigens, bacteria, viruses, dead foreign bodies. In infected wounds. Risk of # in B.G over extended period of time B.G will never incorporate in to living B.
Components of D.O  Application of ext.fix – stability, applies forces  Corticotomy  Postop period 1. Latency period 2. Distraction P. 3. Consolidation P.
DEFINITION CORTICOTOMY: low energy osteotomy, performed using an osteotome to cut only the cortical surface thus preserving the medullary canal, nutrient vessel, endosteum, periosteum LATENCY PERIOD: Initial healing response is allowed to bridge the cut surfaces before distraction is initiated.
Rate: no of millimeter that the bone surfaces are pulled apart each day. Rhythm: no of distractions per day Healing index: no of centimeters of N.B divided by no of months from the surgery to date of full wt bearing.
Transformation osteogenesis: conversion of non osseous tissues such as fibrocartilage in nonunion in to normal bone. Done through comb compression & distraction forces, augmented by corticotomy. Bone transportation: regeneration of intercalary B.D through corticotomy & distraction & tranf. Osteogenesis.
Critical factors for B. formation Stability of fixation [circular F] Atraumatic corticotomy. Rate Rhythm of distraction.
HISTOLOGY LATENCY P: similar to # healing DISTRACTION P: mesenchymal cells begin to organize in to bridge of collagen & immature vascular sinusoids, bridge formed always parallel to direction of distraction. I Week Distraction: central zone of relatively avascular fibrous tissue bridges the 7 mm of C.gap. FIZ: fibrous interzone [no osteoid/ O.B]
Distraction osteogenesis
II WEEK - Distraction Clusters of osteoblasts appear on each side of FIZ adj to vascular sinuses. Collagen bundles fuse with osteoid like M. 1* bone spicules –enlarge gradually by circumferential apposition. Later osteoid began to mineralize the 1*B.S  PMF[primary mineralisation front] PMF – extend from both corticotomy site, towards the central FIZ.
III Week Mineralization process continues. As the gap increases, bridge is formed by elongation of bone spicules. Large thin sinusoids surround each micro column of new bone  MCF [micro column formation]. At the end of D., FIZ ossifies & MCF unifies completely bridging the gap.
Microcolumn new bone formation
Physiology Fibrous interzone assumes the role of growth plate. [pseudo G.P] Intramembranous ossification in its purest form. [if stability] Local & regional blood supply is most important determining factor.
Pathophysiology Excessive rate Sporadic rhythm Frame stability Poor local & regional stability Traumatic corticotomy Inadequate consolidation phase. Initial diastasis.
Rate & Rhythm: biosynthetic pathways at cellular levels , protein synthesis & mitosis. Macromotion: [shear force] disrupt the delicate bone & vascular channels Peripheral vascular disease Traumatic corticotomy- disturb the local blood flow Initial diastasis- inhibit the formation of 1* fibrovascular bridge.
Indications for increase in R & R Young Pt [up to 12-14 yrs] X ray  premature consolidation. X ray  uncompleted bone cut at the site of corticotomy. In any event, increase in distraction speed & rhythm cannot exceed 2 mm/ day.
Indication for reduction  Severe pain at the site of distraction, esp after creating 3-4 cm gap.  Clinical signs of peripheral vascular & neurological deficiency.  X ray slow development of regeneration Reduction in D cann’t be less than .25- .50 mm/ day .
Ilizarov recommended that the number of actual distractions (rhythm of distraction) should be at least four, achieving a total of 1 mm of total distraction (rate of distraction) in four divided doses. constant distraction over a 24-hour period produces a significant increase in the regenerate quality
ASSESSMENT Corticotomy: check for completeness in C-arm. Distracting <2 mm, angulation < 10-15*, rotating < 20-30*. Adequate reduction of corticotomy gap. Length & alignment of D.G checked weekly or biweekly by X ray. N.B mineralization appears by 3rd wk of D. –fuzzy, radiodense columns extending from both cut surfaces
N.B formation should span entire cross sectional area of host bone cut surfaces. N.B appears bulging, FIZ is narrowing distraction should be accelerated. N.B shows as hour glass appearance, FIZ widens D. rate reduced.
USG: not regularly used. Cyst formation stop distraction, gap is gradually closed. QCT: [Quantitative C.T] measuring the mineralization of osteogenic area. Compared with similar region on normal contralateral limb described as % of normal. Normally FIZ- 25-35%, PMF- 40-55%, MCF- 60-70%.
Triphasic bone scan: both sides of distraction gap should be hot in all three phases. If it is cold, stop distraction.
consolidation Plain x rays – monthly basis, condition of the cortex & medullary canal are noted in the osteogenic area – orthogonal views Bone density may appear reduced. QCT- demonstrates stability.
ACCORDION TECH Monofocal compression- distraction tech for nonunion treatment. Alternate compression & distraction maneuver is used 2-3 times to stimulate bone neogenesis. Local scar tissues are initially crushed to be transformed in to tissues capable of neogenesis.

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Distraction osteogenesis

  • 2. Mechanical induction of new bone that occurs between vascular bony surfaces that are gradually pulled apart by gradual distraction. New bone formed bridges the gap & remodels to normal bone macrostructure. Tension stress effect on growth & genesis of tissues.
  • 3. Developed by Ilizarov in 1956 Highly modular fixators allow formation of new bone in almost any plane as D.O follows the vector of applied force. Age: as long as Pt had # healing potential. INDICATION: bone grafting, LLD, nonunion, deformity, bone defects 2* to trauma, infection, tumor.
  • 4. Advantages over bone grafting Reduces donor site morbidity Autograft is limited No fear of transmission of antigens, bacteria, viruses, dead foreign bodies. In infected wounds. Risk of # in B.G over extended period of time B.G will never incorporate in to living B.
  • 5. Components of D.O  Application of ext.fix – stability, applies forces  Corticotomy  Postop period 1. Latency period 2. Distraction P. 3. Consolidation P.
  • 6. DEFINITION CORTICOTOMY: low energy osteotomy, performed using an osteotome to cut only the cortical surface thus preserving the medullary canal, nutrient vessel, endosteum, periosteum LATENCY PERIOD: Initial healing response is allowed to bridge the cut surfaces before distraction is initiated.
  • 7. Rate: no of millimeter that the bone surfaces are pulled apart each day. Rhythm: no of distractions per day Healing index: no of centimeters of N.B divided by no of months from the surgery to date of full wt bearing.
  • 8. Transformation osteogenesis: conversion of non osseous tissues such as fibrocartilage in nonunion in to normal bone. Done through comb compression & distraction forces, augmented by corticotomy. Bone transportation: regeneration of intercalary B.D through corticotomy & distraction & tranf. Osteogenesis.
  • 9. Critical factors for B. formation Stability of fixation [circular F] Atraumatic corticotomy. Rate Rhythm of distraction.
  • 10. HISTOLOGY LATENCY P: similar to # healing DISTRACTION P: mesenchymal cells begin to organize in to bridge of collagen & immature vascular sinusoids, bridge formed always parallel to direction of distraction. I Week Distraction: central zone of relatively avascular fibrous tissue bridges the 7 mm of C.gap. FIZ: fibrous interzone [no osteoid/ O.B]
  • 12. II WEEK - Distraction Clusters of osteoblasts appear on each side of FIZ adj to vascular sinuses. Collagen bundles fuse with osteoid like M. 1* bone spicules –enlarge gradually by circumferential apposition. Later osteoid began to mineralize the 1*B.S  PMF[primary mineralisation front] PMF – extend from both corticotomy site, towards the central FIZ.
  • 13. III Week Mineralization process continues. As the gap increases, bridge is formed by elongation of bone spicules. Large thin sinusoids surround each micro column of new bone  MCF [micro column formation]. At the end of D., FIZ ossifies & MCF unifies completely bridging the gap.
  • 14. Microcolumn new bone formation
  • 15. Physiology Fibrous interzone assumes the role of growth plate. [pseudo G.P] Intramembranous ossification in its purest form. [if stability] Local & regional blood supply is most important determining factor.
  • 16. Pathophysiology Excessive rate Sporadic rhythm Frame stability Poor local & regional stability Traumatic corticotomy Inadequate consolidation phase. Initial diastasis.
  • 17. Rate & Rhythm: biosynthetic pathways at cellular levels , protein synthesis & mitosis. Macromotion: [shear force] disrupt the delicate bone & vascular channels Peripheral vascular disease Traumatic corticotomy- disturb the local blood flow Initial diastasis- inhibit the formation of 1* fibrovascular bridge.
  • 18. Indications for increase in R & R Young Pt [up to 12-14 yrs] X ray  premature consolidation. X ray  uncompleted bone cut at the site of corticotomy. In any event, increase in distraction speed & rhythm cannot exceed 2 mm/ day.
  • 19. Indication for reduction  Severe pain at the site of distraction, esp after creating 3-4 cm gap.  Clinical signs of peripheral vascular & neurological deficiency.  X ray slow development of regeneration Reduction in D cann’t be less than .25- .50 mm/ day .
  • 20. Ilizarov recommended that the number of actual distractions (rhythm of distraction) should be at least four, achieving a total of 1 mm of total distraction (rate of distraction) in four divided doses. constant distraction over a 24-hour period produces a significant increase in the regenerate quality
  • 21. ASSESSMENT Corticotomy: check for completeness in C-arm. Distracting <2 mm, angulation < 10-15*, rotating < 20-30*. Adequate reduction of corticotomy gap. Length & alignment of D.G checked weekly or biweekly by X ray. N.B mineralization appears by 3rd wk of D. –fuzzy, radiodense columns extending from both cut surfaces
  • 22. N.B formation should span entire cross sectional area of host bone cut surfaces. N.B appears bulging, FIZ is narrowing distraction should be accelerated. N.B shows as hour glass appearance, FIZ widens D. rate reduced.
  • 23. USG: not regularly used. Cyst formation stop distraction, gap is gradually closed. QCT: [Quantitative C.T] measuring the mineralization of osteogenic area. Compared with similar region on normal contralateral limb described as % of normal. Normally FIZ- 25-35%, PMF- 40-55%, MCF- 60-70%.
  • 24. Triphasic bone scan: both sides of distraction gap should be hot in all three phases. If it is cold, stop distraction.
  • 25. consolidation Plain x rays – monthly basis, condition of the cortex & medullary canal are noted in the osteogenic area – orthogonal views Bone density may appear reduced. QCT- demonstrates stability.
  • 26. ACCORDION TECH Monofocal compression- distraction tech for nonunion treatment. Alternate compression & distraction maneuver is used 2-3 times to stimulate bone neogenesis. Local scar tissues are initially crushed to be transformed in to tissues capable of neogenesis.