Limb lengthening: slower distraction rates may expedite patient joint recovery

Limb-lengthening procedures are predicated on bone health, with little consideration for soft tissues. For instance, a distraction rate of 1 mm/day is conventionally prescribed to patients based on bone remodeling, with little regard for muscles. Nonhuman animal studies suggest that the use of slower than conventional distraction rates mitigate muscle damage and the decline in joint function, but such human data are elusive. Because muscle mechanics largely govern overall joint mechanics, we compared the knee function (range of motion and strength) of patients who underwent femoral lengthening at conventional versus slower distraction rates (Avg ± SD; 0.91 ± 0.13 or 0.54 ± 0.15 mm/day, respectively) to implicate underlying muscle function. Both groups were of similar age (<i>d</i> = 0.10, <i>P</i> = 0.425) and underwent similar lengthening magnitudes (<i>d</i> = 0.12, <i>P</i> = 0.671). At terminal distraction phase, the slower distraction rate group exhibited a 56% greater recovery in knee range of motion (<i>d</i> = 1.25, <i>P</i> = 0.008) and a 44% greater knee extensor strength versus convention (<i>d</i> = 1.02, <i>P</i> = 0.046). At the same mutual day after surgery, despite not achieving statistical significance, the slower versus conventional distraction rate group exhibited a 39% greater recovery in knee range of motion (<i>d</i> = 0.48, <i>P</i> = 0.180) and similar knee extensor strength (<i>d</i> = 0.11, <i>P</i> = 0.430). Despite our meager sample size, using a slower than conventional distraction rate in limb-lengthening patients elicited superior joint function at terminal distraction and numerically better joint function at ∼3 mo after surgery. Therefore, considering muscle health, in addition to bone health, when devising limb-lengthening procedures may expedite patient recovery.<b>NEW & NOTEWORTHY</b> Limb-lengthening procedures are predicated on bone health, with little consideration for muscle health. Here, we show that using slower than conventional limb-lengthening rates, which better accommodate muscle remodeling, expedites the recovery of patient joint function.