Machine learning applications for the prediction of extended length of stay in geriatric hip fracture patients

Table 1 Baseline data comparison. Counts (%) unless otherwise specified

Features	Non-eLOS (n = 383)	eLOS (n = 380)	Statistic (t/χ2 )	P value
Sex			5.418	0.020
Male	107 (27.9)	136 (35.8)
Female	276 (72.1)	244 (64.2)
Age (yr)			0.096	0.757
60-85	255 (66.6)	257 (67.6)
> 85	128 (33.4)	123 (32.4)
BMI (kg/m2)			2.578	0.461
< 18.5	48 (12.5)	44 (11.6)
18.5-24.9	220 (57.4)	239 (62.9)
25.0-29.9	99 (25.8)	82 (21.6)
> 30.0	16 (4.2)	15 (3.9)
Fracture type			20.516	P < 0.001
Femoral neck fracture	165 (43.1)	226 (59.5)
Intertrochanteric fracture	218 (56.9)	154 (40.5)
ASA classification			20.313	P < 0.001
I-II	197 (51.4)	134 (35.3)
III-IV	186 (48.6)	246 (64.7)
Admission time			5.340	0.021
Monday to Thursday	248 (64.8)	215 (56.6)
Friday to Sunday	135 (35.2)	165 (43.2)
Time from injury to admission			5.513	0.019
≤ 24 h	322 (84.1)	294 (77.4)
> 24 h	61 (15.9)	86 (22.6)
Comorbidities	3.99 2.22	4.19 2.25	1.221	0.223
Hypertension	207 (54.0)	245 (64.5)	8.588	0.003
Diabetes	85 (22.2)	112 (29.5)	5.279	0.022
ACS	59 (15.4)	66 (17.4)	0.537	0.464
Cerebral infarction	120 (31.3)	150 (39.5)	5.531	0.019
AKI	8 (2.1)	17 (4.5)	3.423	0.064
DVT	66 (17.2)	91 (23.9)	5.263	0.022
History of smoking	14 (3.4)	17 (4.5)	0.328	0.567
Oral anticoagulant use	71 (18.5)	71 (18.7)	0.003	0.959
History of fracture	77 (20.1)	83 (21.8)	0.348	0.556
Hip fracture	21 (5.5)	29 (7.6)	1.438	0.230
Lumbar fracture	25 (6.5)	24 (6.3)	0.014	0.905
Delayed surgery	153 (39.9)	267 (70.3)	70.842	P < 0.001
Type of surgery
THA	52 (13.6)	95 (25.0)	16.002	P < 0.001
HHA	106 (27.7)	127 (33.4)	2.968	0.085
Reduction and fixation	225 (58.7)	158 (41.6)	22.488	P < 0.001
Duration of surgery	96.62 ± 27.83	118.43 ± 24.32	1.743	0.082
Intraoperative blood loss	164.54 ± 85.26	162.33 ± 104.20	-0.321	0.748
Blood transfusion	127 (33.2)	132 (34.7)	0.212	0.645
ICU transfer	103 (26.9)	111 (29.2)	0.508	0.476
Type of anaesthesia			0.769	0.380
General	336 (87.7)	341 (89.7)
Regional	47 (12.3)	39 (10.3)
Heart rate at admission (60-100)	339 (88.5)	331 (87.1)	0.353	0.553
Laboratory examination at admission
RBC (≥ 4.3)	86 (22.5)	87 (22.9)	0.021	0.884
WBC (3.5-9.5)	208 (54.3)	217 (57.1)	0.605	0.437
Hb (≥ 110)	251 (65.5)	268 (70.5)	2.184	0.139
PLT (125-350)	321 (83.8)	306 (80.5)	1.406	0.236
N (40-75)	65 (17.0)	81 (21.3)	2.327	0.127
HCT (≥ 40)	82 (21.4)	65 (17.1)	2.272	0.132
K (3.5-5.1)	260 (67.9)	265 (69.7)	0.305	0.581
Ca (≥ 2.1)	257 (67.1)	260 (68.4)	0.152	0.697
Na (137-145)	248 (64.8)	229 (60.3)	1.640	0.200
ALB (30-40)	233 (60.8)	243 (63.9)	0.787	0.375
ALT (9-50)	347 (90.5)	342 (90.0)	0.079	0.779
AST (15-40)	338 (88.3)	316 (83.2)	4.040	0.044
LDH (120-246)	188 (49.1)	179 (47.1)	3.000	0.584
BUN (3.6-9.5)	304 (79.4)	302 (79.5)	0.001	0.973
Cr (58-110)	205 (53.5)	221 (58.2)	1.660	0.198
PT (9.4-12.5)	77 (20.1)	93 (24.5)	2.103	0.147
APTT (25.1-36.5)	326 (85.1)	331 (87.1)	0.630	0.427
INR (0.8-1.2)	311 (81.2)	304 (80.0)	0.176	0.675
FIB (2.38-4.98)	344 (89.8)	344 (90.5)	0.108	0.742
D-dimer (≤ 6500)	218 (56.9)	165 (43.4)	13.902	P < 0.001
Cardiac colour ultrasound at admission
AV (≥ 1.0)	367 (95.8)	347 (91.3)	6.446	0.011
EF (≥ 70)	208 (54.3)	217 (57.1)	0.605	0.437
Laboratory examination after surgery
Hb (≥ 110)	87 (22.7)	92 (24.2)	0.237	0.626
ALB (30-40)	310 (80.9)	303 (79.7)	0.175	0.676
Cr (58-110)	222 (58.0)	232 (61.1)	0.755	0.385

BMI: Body mass index; ASA: American society of anaesthesiologists; ACS: Acute coronary syndromes; AKI: Acute kidneyinjury; DVT: Deep venous thrombosis; THA: Total hip arthroplasty; HHA: Hip hemiarthroplasty; ICU: Intensive care unit; RBC: Red blood cell; WBC: White blood cell; Hb: Hemoglobin; PLT: Platelets; N: Neutrophile granulocyte; HCT: Hematocrit; K: Kalium; Ca: Calcium; Na: Natrium; ALB: Albumin; ALT: Alanine aminotransferase; AST: Aspartate aminotransferase; LDH: Lactate dehydrogenase; BUN: Blood urea nitrogen; Cr: Creatinine; PT: Prothrombin time; APTT: Activated partial thromboplastin time; INR: International normalized ratio; FIB: Fibrinogen; AV: Aortic velocity; EF: Ejection fraction.