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

Table 2 Comparison of clinical and imaging characteristics across subchondral stress fracture of the femoral head stages at the patient level (one index hip per patient; n = 127), mean ± SD/n (%)

Parameter	Stage I (n = 13 patients)	Stage II (n = 52 patients)	Stage III (n = 62 patients)	P value
Age (year)	21.15 ± 2.76	19.96 ± 1.96	20.56 ± 1.92	0.105
Gender (male/female)	8/5	51/1	61/1	0.058
BMI (kg/m2)	21.13 ± 1.55	21.34 ± 1.94	21.78 ± 2.72	0.455
Time interval (month)	5.74 ± 3.19	7.71 ± 4.78	10.13 ± 6.41	0.005a
Bilateral involvement	5/13 (38.5)	5/52 (9.6)	2/62 (3.2)	0.001a
VAS score	5.84 ± 1.42	7.63 ± 1.42	6.57 ± 1.49	0.001a
Harris score	73.37 ± 7.21	64.15 ± 8.03	70.34 ± 8.26	0.001a
Hip flexion-extension ROM (º)	137.84 ± 9.76	117.78 ± 18.78	130.13 ± 15.98	0.001a
Hip inner-external rotation ROM (º)	68.47 ± 16.69	38.34 ± 21.65	56.43 ± 22.82	0.001a
BME
Grade 0	0	0	0
Grade 1	9	6	26
Grade2	2	17	14
Grade 3	2	29	22	0.001a
Effusion
Grade 0	9	0	0
Grade 1	3	2	30
Grade 2	1	14	26
Grade 3	0	36	6	0.001a
Tönnis Classification
Grade 0	11	0	0
Grade 1	2	42	20
Grade 2	0	10	41
Grade 3	0	0	1	0.001a
Laboratory findings
ALP (U/L)	82.38	77.31	71.84	0.225
CK (U/L)	122.23	107.77	115.39	0.608
TC (mmol/L)	3.9877	3.9071	3.7860	0.528
UA (μmol/L)	424.92	411.81	390.23	0.244

^aP < 0.05.

One index hip per patient (the more severely affected side in bilateral cases) was used for cross-stage comparisons, yielding n = 13, 52, and 62 patients in Stages I, II, and III, respectively. Bilateral involvement is reported at the patient level. ALP: Alkaline phosphatase; BMI: Body mass index; CK: Creatine kinase; ROM: Range of motion; TC: Total cholesterol; UA: Uric acid; VAS: Visual Analog Scale.