Instrumentation failure following pediatric spine deformity growth-sparing surgery using traditional growing rods or vertical expandable prosthetic titanium ribs

Table 3 Timing of instrumentation failure in vertical expandable prosthetic titanium rib technique

	Index surgery	Lengthening surgery				P for trend
	Index surgery	1st–3rd	4th–6th	7th–9th	≥ 10th	P for trend
No. of surgeries	31	167	133	85	39	-
No. of IFs (%)	2 (6.5)	12 (7.2)	2 (1.5)	2 (2.4)	0 (0)	0.01*
No. of anchor loosenings/dislocations (%)	2 (6.5)	8 (4.8)	1 (0.8)	0 (0)	0 (0)	< 0.01*
No. of rod breakages (%)	0 (0)	1 (0.6)	0 (0)	2 (2.4)	0 (0)	0.55
No. of implant protrusions (%)	0 (0)	2 (1.2)	1 (0.8)	0 (0)	0 (0)	0.24
No. of proximal junctional kyphoses (%)	0 (0)	1 (0.6)	0 (0)	0 (0)	0 (0)	0.31

IF: instrumentation failure
*Statistically significant association between the number of lengthening surgeries performed and the surgery-based incidence of IF in the Cochran–Armitage test

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