Distraction Osteogenesis: Ilizarov Bone Lengthening

Distraction Protocol

Distraction rate 1.0 mm/day

Increments per day 4×

Latency period 5 days

Playback

Live Readouts

Elapsed time

0.0 d

Lengthening

0.0 mm

Phase

Latency

Increment size

0.25 mm

Regenerate quality (rate × rhythm vs. Ilizarov optimum)

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Regenerate maturity

Radiographic union

How it works

Distraction osteogenesis exploits Ilizarov's law of tension-stress: when living bone is cut (a corticotomy) and the two fragments are then pulled apart gradually and steadily, the tissue bridging the gap does not scar over — it responds to the mechanical tension by forming new bone through intramembranous ossification, without a cartilage intermediate.

Clinical gold standard (rate & rhythm):
  daily rate  ≈ 1 mm / day
  rhythm      ≈ 4 increments × 0.25 mm
Interfragmentary strain (Perren):
  ε = Δl / l   (strain per increment, gap width l)
Too fast (ε too high) → fibrous, non-mineralizing tissue
Too slow (ε too low)  → premature bony bridging, distraction stalls

This simulator tracks every millimetre of regenerate as a thin slice, born at the moment of its own distraction increment and carrying the "quality" of the protocol at that instant. Each slice then mineralizes over time following

dM/dt = Q · k · (1 − M)

where M is that slice's mineral maturity (0→1), k a fixed consolidation-rate constant, and Q the protocol quality factor — peaked at 1 mm/day delivered as 4×0.25 mm increments, exactly the regimen Ilizarov's own clinical series established as optimal. Push the rate too high and the regenerate stays translucent and fibrous (risk of non-union); drop it too low and the same tissue mineralizes and bridges before you reach your target length (premature consolidation) — both are real failure modes in limb-lengthening surgery, alongside pin-tract infection and joint contracture, which is why rate and rhythm are titrated weekly against X-rays in practice.

Distraction rate — total daily lengthening in mm; sets how fast the fixator is turned.
Increments per day — how that daily amount is split; more, smaller turns (the classic 4×/day) reduce the strain spike per increment and improve regenerate quality for the same total rate.
Latency period — days after the corticotomy before distraction begins, giving early callus time to form so it can be pulled apart rather than re-fractured.

Native cortical bone Mineralizing regenerate External fixator (rings & rods)

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