Rod fracture and lengthening intervals in traditional growing rods: is there a relationship?

Purpose: Is there any relationship between lengthening intervals and rod fracture in traditional growing rod (TGR) surgery?

Methods: A multicenter EOS database was queried for patients who had: (1) dual growing rods for EOS; (2) minimum 2-year follow-up; (3) a minimum of 2 lengthenings; and (4) revision surgery due to rod fracture. Of 138 patients who met the criteria: 56 patients experienced at least one-rod fracture (RF group) and 82 patients had no rod fractures (NRF group). In addition to each patient's lengthening intervals, demographics, construct details, and radiographic parameters were compared.

Results: RF and NRF patients had a mean pre-op age of 5.7 years (range 1.3-10.7) and 7.3 years (range 1.6-12.8), respectively (p < 0.001). There was no significant association between etiologies and rod fracture or between BMI and rod fracture (p = 0.979). There was no significant difference between lengthening intervals between the RF and NRF groups (p > 0.05). RF and NRF patients had statistically similar mean pre-op major curve size and max kyphosis (p = 0.279; p = 0.619, respectively). Stainless steel rods fractured more frequently compared with Titanium rods (SS 49.2 % vs. Ti 38 %; p = 0.004). Rod fracture occurred more in rods smaller than 4 mm (p = 0.011).

Conclusions: Lengthening intervals were not statistically different in RF and NRF groups and there was no association between lengthening interval and rod fracture in TGR cases. It was shown that patients who had rod fracture were younger and were more likely to have SS rods with smaller than 4 mm diameter.