Pelvic obliquity and measurement of hip displacement in children with cerebral palsy

Figures & data

Figure 1a. Pelvic obliquity in a 12-year-old girl with cerebral palsy in GMFCS level IV. Measurement of migration percentage (MP). MP = a/b × 100. MP =46% in the left hip and 32% in the right hip.

Figure 1b. Measurement of pelvic obliquity (PO). PO =15°, left side elevated.

Figure 1c. Measurement of pelvic adjusted migration percentage (PAMP). PAMP =59% in the left hip and 15% in the right hip.

Table 1. Distribution of age and Gross Motor Function Classification System (GMFCS) levels

Age (years)	GMFCS level
	II	III	IV	V	Total
< 3	18	8	10	17	53
3–5	18	14	17	14	63
6–8	17	9	15	12	53
9–11	5	12	15	10	42
12–14	3	7	15	8	33
15–18	1	10	8	5	24
Total	62	60	80	66	268

Table 2. Interrater reliability estimated by intraclass correlation coefficient (ICC)

Factor	ICC	95% CI
Pelvic obliquity	0.97	0.96–0.98
MP right	0.88	0.78–0.94
MP left	0.89	0.78–0.94
PAMP right	0.91	0.83–0.95
PAMP left	0.93	0.86–0.96

MP: migration percentage;

PAMP: pelvic adjusted migration percentage;

p < 0.001 for all measurements.

Figure 2. Number of pelvic radiographs related to the degree of PO. Negative value = left side of pelvis elevated, positive value = right side of pelvis elevated.

Figure 3. Difference between MP in the right and left hip related to PO. Negative PO value = left side of pelvis elevated, positive PO value = right side of pelvis elevated.

Figure 4. Difference between PAMP on the right and left hip related to PO. Negative PO value = left side of pelvis elevated, positive PO value = right side of pelvis elevated.

Table 3. Difference between PAMP and MP on the high side of pelvic obliquity

Pelvic obliquity (degrees)	1–4	5–9	≥10
Number of radiographs	148	57	7
PAMP–MP
mean difference (90% percentiles)	1.9 (0 to 7)	6.5 (0 to 14)	11
median difference (range)	0 (–4 to 10)	6 (–5 to 16)	9 (0 to 24)

For abbreviations, see Table 2