ABSTRACT
STUDY DESIGN: 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). SUMMARY OF BACKGROUND DATA: 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. LEVEL OF EVIDENCE: Level IV.
