Surface electromyography signal characteristics of lower limb muscles in children with unilateral developmental dysplasia of the hip

Table 1 General information of the two groups of children, mean ± SD

	Gender		Affected side		Treatment age (months)	Average follow-up (months)	Last follow-up age (months)	Last follow-up height (cm)	Last follow-up weight (kg)
	Male	Female	Left	Right
CR group (n = 28)	4	24	20	8	14.96 ± 6.94	51.64 ± 34.85	66.86 ± 34.56	112.89 ± 18.09	21.71 ± 11.15
Salter group (n = 31)	7	24	19	12	35.52 ± 16.20a	51.0 ± 34.76	85.35 ± 38.78a	121.71 ± 20.32	25.06 ± 11.83

^aP < 0.05 vs closed recovery group.

CR group: Closed reduction treatment.

Table 2 Comparison of surface electromyography signals of the affected and healthy lower limbs of the 2 groups of children when standing, median (25^th percentile-75^th percentile)

	Closed reduction group					Salter osteotomy group
	Affected side	Healthy side	The ratio of the affected side to the healthy side	Affected side CCR	Healthy side CCR	Affected side	Healthy side	The ratio of the affected side to the healthy side	Affected side CCR	Healthy side CCR
Tensor fasciae latae	3.62 (1.93-6.02)	3.92 (2.11-5.78)	0.91 (0.64-1.23)	0.61 (0.49-0.76)	0.64 (0.52-0.76)	4.66 (2.91-7.51)	3.85 (2.42-6.98)	1.18 (0.80-1.81)	0.68 (0.57-0.81)	0.62 (0.48-0.76)
Gluteus maximus	1.49 (1.21-2.61)	1.75 (1.22-2.52)	0.97 (0.84-1.24)			2.00 (1.47-2.24)	1.96 (1.32-3.81)	1.04 (0.59-1.47)
Rectus femoris	1.92 (1.09-4.74)	2.64 (1.18-3.97)	0.91 (0.80-1.26)	0.25 (0.11-0.44)	0.22 (0.18-0.42)	2.18 (1.60-6.55)	2.31 (1.43-6.85)	0.95 (0.68-1.32)	0.33 (0.15-0.60)	0.36 (0.16-0.54)
Hamstring muscles	6.55 (3.17-13.82)	8.94 (3.37-12.51)	0.94 (0.73-1.37)			5.39 (3.69-12.29)	7.08 (2.25-13.54)	0.99 (0.60-1.31)
Tibialis anterior muscle	4.97 (2.03-10.40)	4.71 (2.01-10.78)	0.99 (0.81-1.23)	0.40 (0.30-0.56)	0.44 (0.32-0.55)	4.98 (3.53-7.32)	4.58 (2.15-8.93)	0.99 (0.81-1.12)	0.47 (0.37-0.60)	0.49 (0.28-0.58)
Musculus gastrocnemius	5.75 (3.20-9.28)	5.60 (3.99-8.47)	0.99 (0.86-1.23)			4.44 (3.53-7.32)	6.14 (3.86-8.75)	0.93 (0.85-1.05)

CCR: Co-contraction ratio.

Table 3 Comparison of surface electromyography signals of the affected and healthy lower limb muscles during walking in the 2 groups of children, median (25^th percentile-75^th percentile)

	Closed reduction group					Salter osteotomy group
	Affected side RMS	Healthy side RMS	RMS the ratio of the affected side to the healthy side	Affected side CCR	Healthy side CCR	Affected side RMS	Healthy side RMS	RMS the ratio of the affected side to the healthy side	Affected side CCR	Healthy side CCR
Tensor fasciae latae	35.71 (28.15-54.12)	31.60 (24.05-49.63)	1.06 (0.91-1.32)	0.78 (0.67-0.85)	0.78 (0.69-0.83)	49.31 (32.33-73.58)a	44.17 (28.94-66.38)a	1.21 (0.83-1.43)	0.82 (0.75-0.87)	0.78 (0.75-0.83)
Gluteus maximus	12.57 (6.61-17.96)	11.01 (6.73-16.73)	0.97 (0.86-1.11)			11.04 (6.52-15.75)	14.64 (7.44-18.98)	0.88 (0.75-1.14)
Rectus femoris	18.33 (14.44-27.31)	21.75 (15.57-28.71)	1.01 (0.77-1.14)	0.46 (0.37-0.52)	0.46 (0.37-0.56)	27.36 (19.24-37.04)a	25.20 (17.81-28.91)	1.06 (0.82-1.59)	0.54 (0.46-0.65)a	0.51 (0.38-0.56)
Hamstring muscles	23.77 (15.42-33.71)	23.57 (17.73-36.53)	0.95 (0.79-1.12)			22.81 (16.25-30.26)	22.64 (19.13-34.34)	0.87 (0.73-1.12)
Tibialis anterior muscle	38.44 (31.50-50.36)	37.43 (28.64-45.24)	1.02 (0.89-1.18)	0.48 (0.43-0.55)	0.47 (0.41-0.56)	39.05 (17.71-55.28)	39.07 (19.24-50.23)	0.99 (0.86-1.16)	0.53 (0.43-0.58)	0.54 (0.43-0.59)
Musculus gastrocnemius	37.43 (30.52-52.19)	39.00 (29.82-58.29)	0.99 (0.88-1.12)			34.57 (23.70-47.55)	36.65 (25.49-47.08)	1.05 (0.92-1.15)

^aP < 0.05 vs closed recovery group.

RMS: Root mean square; CCR: Co-contraction ratio.