Subchondral stress fractures of the femoral head associated with military training: Clinical features and analysis

Table 3 Clinical and laboratory characteristics of subchondral stress fracture of the femoral head and osteonecrosis of the femoral head

Parameter	SSFFH (n = 127)	ONFH (n = 47)	P value
Age (years)	20.0 (19.0-21.0)	23.0 (20.5-29.0)	< 0.001a
BMI (kg/m2)	21.28 (20.07-22.53)	23.17 (21.20-25.79)	< 0.001a
Sex			0.116
Male	120 (94.5)	41 (87.2)
Female	7 (5.5)	6 (12.8)
Time from symptom onset to hospitalization (months)	6.0 (3.0-10.5)	6.0 (4.0-8.0)	0.736
Single-trauma history			0.703
None	29 (22.8)	10 (21.3)
Low-energy	50 (39.4)	22 (46.8)
Moderate-energy	44 (34.6)	15 (31.9)
High-energy	4 (3.1)	0 (0.0)
Alcohol exposure			< 0.001a
None	74 (58.3)	7 (14.9)
Light	34 (26.8)	12 (25.5)
Moderate	18 (14.2)	16 (34.0)
Heavy	1 (0.8)	12 (25.5)
Corticosteroid exposure			< 0.001a
None	125 (98.4)	6 (12.8)
Low	2 (1.6)	3 (6.4)
Moderate	0 (0.0)	12 (25.5)
High	0 (0.0)	26 (55.3)
Training intensity			< 0.001a
Low	2 (1.6)	18 (38.3)
Moderate	10 (7.9)	19 (40.4)
High	115 (90.6)	10 (21.3)
Laterality			< 0.001a
Unilateral	115 (90.6)	13 (27.7)
Bilateral	12 (9.4)	34 (72.3)
Tönnis grade			< 0.001a
Grade 0	2 (1.6)	3 (6.4)
Grade 1	19 (15.0)	17 (36.2)
Grade 2	44 (34.6)	20 (42.6)
Grade 3	62 (48.8)	7 (14.9)
VAS score	7.0 (6.0-8.0)	7.0 (6.0-8.0)	0.863
Harris Hip Score	68.90 ± 8.82	68.38 ± 7.68	0.724
Hip flexion-extension ROM (°)	133.0 (120.0-140.0)	130.0 (121.0-136.0)	0.457
Hip internal-external rotation ROM (°)	50.0 (30.5-70.5)	50.0 (40.0-70.0)	0.560
ALP (U/L)	71.0 (63.0-85.0)	69.0 (56.5-79.0)	0.225
CK (U/L)	95.0 (79.0-136.5)	87.0 (54.0-109.5)	0.002a
TC (mmol/L)	3.86 ± 0.72	4.33 ± 1.01	0.004a
UA (μmol/L)	402.61 ± 84.83	385.13 ± 81.77	0.225

^aP < 0.05. Data are presented as n (%), mean ± SD, or median (IQR). Median (IQR) and Mann-Whitney U tests were used for age, BMI, time interval, Visual Analog Scale, range of motion, alkaline phosphatase, and creatine kinase. Harris Hip Score and uric acid were compared with Student’s t tests; total cholesterol was compared with Welch’s t test. Categorical variables were compared with Fisher’s exact or Fisher-Freeman-Halton exact tests. Training intensity: Low ≤ 30 hour/week, moderate 31-45 hour/week, high > 45 hour/week. All analyses were patient-level. ALP: Alkaline phosphatase; BMI: Body mass index; CK: Creatine kinase; IQR: Interquartile range; ONFH: Osteonecrosis of the femoral head; ROM: Range of motion; SSFFH: Subchondral stress fracture of the femoral head; TC: Total cholesterol; UA: Uric acid; VAS: Visual Analog Scale.