Vertebral body growth during growing rod instrumentation:  growth preservation or stimulation?
METHODS
Retrospective review, case series.


OBJECTIVE
Determination of whether growing rod treatment with routine lengthening every 6 months causes growth stimulation of individual vertebrae within instrumentation levels (WIL).


BACKGROUND
The Hueter-Volkmann law states that distractive forces exerted upon growing physes stimulate growth and vice versa, a principle that has been in clinical use for decades. In previous studies, it has been shown that vertebral endplates might respond in a similar manner to distraction. It has been proven that fusionless instrumentation, which is the mainstay of treatment after failure of conservative measures for early-onset scoliosis, allows near-normal vertebral growth but the issue of how individual vertebrae respond to distraction has not yet been analyzed.


METHODS
This institution's database, including the radiographic data for growing rod patients, was analyzed retrospectively. Vertebral level heights within and outside instrumentation levels were measured in postindex and postfinal follow-up x-rays, and the amount of growth that has taken place in a minimum follow-up period of 2 years was calculated and then compared for statistical significance.


RESULTS
Twenty patients (6 M, 14 F, average age, 71.0 mo) met the inclusion criteria. The average follow-up was 49 months (range, 26 to 72 mo). Lengthenings were performed every 6 months regularly. The average height of vertebrae WIL was 15.9 mm (range, 10.0 to 21.1 mm) in postindex and 22.9 mm (range, 15.0 to 32.9 mm) in the final follow-up; vertebrae outside instrumentation levels was 18.1 mm (range, 13.5 to 22.1 mm) postindex and 23.3 mm (range, 14.8 to 28.8 mm) in the final follow-up. The average growth was 5.2±3.4 mm in outside instrumentation levels and 7.0±2.9 mm in WIL. These values were significantly different statistically (P<0.01).


CONCLUSIONS
Growing rod treatment performed with regular lengthenings every 6 months appears to stimulate growth in individual vertebral bodies WIL.


METHODS
Level IV.
Department of Orthopaedics and Traumatology, Hacettepe University, Ankara Turkey.
Z Deniz
ZD
Olgun
Houman
H
Ahmadiadli
Ahmet
A
Alanay
Muharrem
M
Yazici
D001852:Bone Lengthening / Q000295:instrumentation*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D011183:Postoperative Complications; D011859:Radiography; D012189:Retrospective Studies; D012600:Scoliosis / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy*; D013131:Spine / Q000000981:diagnostic imaging / Q000254:growth & development* / Q000601:surgery; D016896:Treatment Outcome