Deformity of the femoral head following vascular infarct in piglets

Figures & data

Table 1.  Categorization of 26 piglets according to postoperative periods

Postoperative period (weeks)	Stage of human LCPD simulated	Number of piglets	Femoral length (cm); mean (SD)	Body weight (kg); mean (SD)
Early period
2 weeks	Avascular or early fragmentation	6	10.2 (0.7)	15 (2.9)
4 weeks		6	11.5 (0.3)	22 (3.3)
Intermediate period
12 weeks	Fragmentation or healing	7	15.8 (3.1)	62 (17)
Late period
20 weeks	Skeletal maturity	7	18.8 (4.3)	107 (21)

Figure 1. Histological specimen of right (Rt) and left (Lt) femurs extracted from a piglet killed at postoperative week 4.The left femoral head (Lt) showed avascular necrosis of the capital femoral epiphysis.Marked reduction in size of ossific nucleus (*) and considerable hyperplasia of articular cartilage (arrow) were seen in the operated femur. (Hematoxylin and eosin, ×1).

Figure 2. Gross (A) and radiographic (B) findings from extracted femurs from a piglet killed at postoperative week 20 showing (to the right) decreased epiphyseal height (44%), generalized flattening of the articular surface, coxa magna (16%), and severe GT overgrowth.

Table 2.  Responses of the femoral head in 26 piglets with vascular infarct

Postoperative weeks	2	4	12	20	rs ^a	P–value
Experimented animal number	6	6	7	7
Coxa plana
Decrease in epiphyseal height (≥10%)
Appearance rate, number	1	4	4	7	0.55	0.004
Mean height, mm (95% CI)
Operated side	9.5	6.9 (3.1–11)	10 (8.3–12)	9.7 (8.7–11)
Normal side	11	11 (10–12)	15 (14–17)	17 (16–18)
Mean decrease (95% CI), mm	1.5	4.1 (0.4–7.8)	5.0 (3.4–6.6)	7.5 (5.6–9.4)	0.76	0.002
%	14	37 (4–71)	33 (23–44)	43 (34–53)	0.42	0.1
Flattening of articular surface
Appearance rate, number	1	2	4	7	0.62	0.001
Extent, number
Localized	1	1	1	2
Generalized	0	1	3	5
Coxa magna (≥10%)
Appearance rate, number	0	1	5	6	0.70	<0.001
Mean diameter, mm (95% CI)
Operated side	–	29	40 (36 –44)	43 (40–47)
Normal side	–	25	33 (31–35)	37 (35–39)
Mean increase, mm (95% CI)	–	4.1	6.9 (3.2–11)	6.8 (3.9–9.6)	0.22	0.5
%	–	16	21 (10–32)	18 (11–26)	0.02	0.9
Greater trochanter overgrowth (≥ 20%)
Appearance rate, number	4	4	6	7	0.34	0.09
Grade, number
Mild	4	2	2	0
Severe	0	2	4	7
Lateral subluxation
Appearance rate, number	0	0	5	7	0.84	<0.001

^a rs: Spearman's correlation coefficient.

Figure 3. Gross (A) and radiographic (B) findings from extracted femurs from a piglet sacrificed at postoperative week 20 showing (to the right) subluxation of the femoral head with severe collapse of head and dysplasia of the acetabulum.