Older age and multi-joint external fixator are two risk factors of complications in ulnar lengthening in children with hereditary multiple exostosis

Table 3 Clinical results of group B

Subject	Preoperative	FFU	Wilcoxon test		P value of Spearman correlation analysis
Subject	Preoperative	FFU	Z	P	Age	Gender	Follow-up	Type	IL^a
US (mm)	23.40 ± 4.84	0.70 ± 3.09	− 2.805	< 0.05	0.724	0.554	0.475	0.619	Na
RAA (°)	31.30 ± 5.36	21.70 ± 3.40	− 2.805	< 0.05	0.337	0.921	0.772	0.525	0.242
CS (%)	72.30 ± 4.35	28.30 ± 3.43	− 2.807	< 0.05	0.148	0.171	0.148	0.333	0.358
MEPS	74.50 ± 3.69	96.00 ± 3.944	− 2.919	< 0.05	0.080	0.486	0.365	1.000	0.554
Elbow flexion (°)	106.50 ± 4.74	127.00 ± 2.58	− 2.850	< 0.05	0.581	0.076	0.462	0.949	0.361
Forearm pronation (°)	69.00 ± 3.94	84.00 ± 3.16	− 2.836	< 0.05	0.064	0.606	0.868	0.251	0.598
Forearm supination (°)	83.00 ± 4.22	83.50 ± 4.12	− 1.000	0.317	0.122	0.447	0.174	0.214	0.122
Complications (n)
Deviation of ulna axis		4 case
Poor regenerate bone formation		4 case
Neurovascular complications		0 case
Fracture after fixator removal		0 case
Pin site infection		1 cases
Redislocation of radial head		0 case
Recurrence of exostosis		0 case

Abbreviations: US ulnar shortening, RAA radial articular angle, CS carpal slip, MEPS Mayo Elbow Performance Score, FFU final follow-up, IL improved length, Na not available. ^aIL = |US(preoperative)-US(FFU)|. P value < 0.05 statistically significant

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