Postoperative start compared to preoperative start of low-molecular-weight heparin increases mortality in patients with femoral neck fractures

Figures & data

Figure 1. Flow chart for patients included in the study.

Figure 2. The timeline demonstrates the development in start of thromboprophylaxis from 2005–2014 for the patients observed in the study. Femoral neck fractures treated with bipolar hemiarthroplasty with known start of thromboprophylaxis (dalteparin or enoxaparin).

Figure 3. Postoperative mortality and risk of reoperation for patients with femoral neck fractures treated with hemiprostheses.

Table 1. Baseline characteristics of the patients/operations

	Preoperative start of prophylaxis	Postoperative start of prophylaxis
Hemiarthroplasties, n (%)	10,567 (52)	9,674 (48)
Mean age at fracture (SD)	82.3 (7.9)	82.6 (8.1)
Women, n (%)	7,648 (72)	6,941 (72)
ASA-groups, n (%)
ASA 1	311 (2.9)	249 (2.6)
ASA 2	3,490 (33)	3,238 (33)
ASA 3	5,862 (55)	5,550 (57)
ASA 4	748 (7.1)	531 (5.5)
ASA 5	9 (0.1)	4 (0.0)
Missing	147 (1.4)	102 (1.1)
Type of surgery, n (%)
Cemented with AB	8,513 (81)	5,959 (62)
Uncemented	1,787 (17)	3,439 (36)
Cemented without AB	51 (0.5)	36 (0.4)
Missing	216 (2.0)	240 (2.3)

Table 2. Mortality and risk of reoperation 7 days, 30 days and 180 days postoperatively after bipolar hemiarthroplasty due to femoral neck fractures. Cox relative risk ratio (RR) (with preoperative start of prophylaxis as reference) is given with adjustments for possible infl uences of sex, ASA-class, age of the patient at surgery, type of surgery, duration of surgery and year of surgery

	Total n (%)	Preoperative start n (%)	Postoperative start n (%)	RR (95% CI	p-value
7 days postoperative
Mortality	610 (3.0%)	290 (2.8%)	320 (3.4%)	1.36 (1.15–1.61)	< 0.001
Reoperations	39 (0.2%)	15 (0.1%)	24 (0.3%)	1.50 (0.75–2.99)	0.3
Reoperation due to infection	5 (0.0%)	2 (0.0%)	3 (0.0%)
Reoperation due to hematoma	5 (0.0%)	4 (0.0%)	1 (0.0%)
30 days postoperative
Mortality	1,580 (7.8%)	780 (7.7%)	800 (8.5%)	1.20 (1.08–1.33)	0.001
Reoperations	457 (2.3%)	215 (2.1%)	242 (2.6%)	1.07 (0.88–1.30)	0.5
Reoperation due to infection	261 (1.3%)	124 (1.2%)	137 (1.4%)	1.10 (0.85–1.42)	0.5
Reoperation due to hematoma	49 (0.2%)	31 (0.3%)	18 (0.2%)	0.55 (0.30–1.01)	0.05
180 days postoperative
Mortality	3,661 (18%)	1,869 (18%)	1,792 (19%)	1.13 (1.06–1.21)	< 0.001
Reoperations	642 (3.2%)	292 (2.9%)	350 (3.7%)	1.19 (1.01–1.40)	0.04
Reoperation due to infection	331 (1.6%)	151 (1.5%)	180 (1.9%)	1.25 (0.99–1.57)	0.06
Reoperation due to hematoma	52 (0.3%)	31 (0.3%)	21 (0.2%)	0.65 (0.36–1.18)	0.2

Table 3. Mortality and risk of reoperation 180 days postoperatively in patients receiving an uncemented and cemented hemiarthroplasty (HA). Cox relative risk ratio (RR) (with preoperative start of prophylaxis as reference) is given with adjustments for possible influences of sex, ASA-class, age of the patient at surgery, duration of surgery and year of surgery

	Total n (%)	Preoperative start n (%)	Postoperative start n (%)	RR (95% CI	p-value
Uncemented HA	5,226
Mortality	907 (17%)	294 (17%)	613 (18%)	1.22 (1.05–1.42)	0.008
Reoperations	240 (4.6%)	72 (4.0%)	168 (4.9%)	1.21 (0.91–1.61)	0.2
Reoperation due to infection	104 (2.2%)	28 (1.6%)	76 (2.2%)	1.36 (0.87–2.14)	0.2
Reoperation due to hematoma	21 (0.4%)	12 (0.7%)	9 (0.3%)	0.50 (0.20–1.25)	0.1
Cemented HA	14,472
Mortality	2,674 (18%)	1,540 (19%)	1,134 (20%)	1.11 (1.03–1.20)	0.01
Reoperations	381 (2.6%)	211 (2.6%)	170 (2.9%)	1.16 (0.94–1.43)	0.2
Reoperation due to infection	215 (2.0%)	118 (1.4%)	97 (1.6%)	1.19 (0.91–1.57)	0.2
Reoperation due to hematoma	31 (0.2%)	19 (0.2%)	12 (0.2%)	0.84 (0.40–1.76)	0.6

Table 4. Effect of postoperative start of thromboprophylaxis versus preoperative start 180 days postoperatively in healthy patients (ASA 1-2) and in morbid patients (ASA 3-5) with femoral neck fracture operated with bipolar hemiprosthesis. Cox relative risk ratio (RR) (with preoperative start of prophylaxis as reference) is given with adjustments for possible influences of sex, age of the patient at surgery, type of surgery, duration of surgery and year of surgery

	Total n (%)	Preoperative start n (%)	Postoperative start n (%)	RR (95% CI	p-value
ASA 1–2	7,288
Mortality	636 (8.7%)	329 (8.9%)	307 (9.1%)	1.12 (0.95–1.31)	0.1
Reoperations	217 (3.0%)	98 (2.7%)	119 (3.5%)	1.20 (0.91–1.60)	0.2
Reoperation due to infection	109 (1.5%)	54 (1.5%)	55 (1.6%)	1.16 (0.78–1.72)	0.5
Reoperation due to hematoma	18 (0.2%)	10 (0.3%)	8 (0.2%)	0.70 (0.26-1.90)	0.5
ASA 3–5	12,704
Mortality	2,990 (24%)	1,520 (24%)	1,470 (25%)	1.13 (1.05–1.22)	0.002
Reoperations	420 (3.3%)	190 (3.0%)	230 (3.9%)	1.18 (0.96–1.45)	0.1
Reoperation due to infection	219 (1.7%)	95 (1.5%)	124 (2.1%)	1.29 (0.97–1.71)	0.07
Reoperation due to hematoma	33 (0.3%)	20 (0.3%)	13 (0.2%)	0.65 (0.31–1.36)	0.3

Table 5. Mortality and risk of reoperation 180 days postoperatively in patients operated with hemiprosthesis with a preoperative start of thromboprophylaxis (n= 9,370) where the primary dose was of full standard (5 000 IU dalteparin or 40 mg enoxaparin) or half standard (2 500 IU dalteparin or 20 mg enoxaparin) dosage. Cox relative risk ratio (RR) (with full dose at start of prophylaxis as reference) is given with adjustments for possible influences of sex, ASA-class, age of the patient at surgery, type of surgery, duration of surgery and year of surgery

Preoperative start dose	Total n	Events	RR (95% CI)	p-value
Mortality	9,370	1,653 (18%)
Full	5,253	738 (14%)	1
Half	4,117	915 (22%)	0.98 (0.88–1.08)	0.6
Reoperations	9,370	264 (2.8%)
Full	5,253	108 (2.6%)	1
Half	4,117	156 (3.0%)	1.02 (0.79–1.32)	0.8
Reoperation due to infection	9,370	139 (1.5%)
Full	5,253	62 (1.5%)	1
Half	4,117	77 (1.5%)	1.10 (0.75–1.56)	0.6
Reoperation due to hematoma	9,370	27 (0.3%)
Full	5,253	18 (0.3%)	1
Half	4,117	9 (0.2%)	0.83 (0.36–1.92)	0.7