Risk of reoperation within 12 months following osteosynthesis of a displaced femoral neck fracture is linked mainly to initial fracture displacement while risk of death may be linked to bone quality: a cohort study from Danish Fracture Database

Figures & data

Figure 1. Case selection for inclusion in this study.

Figure 2. Degree of fracture displacement. The fractures were divided into 2 groups: “Mildly displaced” fractures: Garden type II fractures (A) with ≥ 20° posterior tilt measured on the axial view (B), Garden type III fractures (C), and “Severely displaced” fractures: Garden type IV fractures (D).

Figure 3. Cortical thickness index (CTI) is thickness of the cortices (white line minus black line) in relation to the diameter of the bone (white line) 10 cm below the tip of trochanter minor (grey vertical line). CTI = (white line – black line)/white line.

Table 3. Cox regression analysis of risk of reoperation

Factor	Univarible analyses HR (CI)	Multivariable analysis HR (CI)
Age
Per 1 year increase	1.0 (0.99–1.01)	1.0 (0.99–1.02)
Sex
Female	1	1
Male	0.64 (0.44–0.93)	0.57 (0.38–0.87)
ASA score
1–2	1	1
3–4	1.3 (0.88–1.9)	1.5 (0.96–2.2)
Hours to surgery
< 12	1	1
12–24	1.7 (1.1–2.6)	1.7 (1.1–2.6)
24–36	1.1 (0.53–2.1)	0.94 (0.44–2.0)
> 36	0.95 (0.42–2.2)	0.95 (0.40–2.3)
Test for overall effect	p = 0.05	p = 0.06
Cortical thickness index
Per 0.1 increase	0.95 (0.76–1.2)	1.0 (0.80–1.4)
Fracture type
Mildly displaced	1	1
Severely displaced	2.5 (1.8–3.7)	3.1 (2.0–4.7)
Reduction ^a
Fully reduced	1	1
Partly reduced	1.6 (0.92–2.9)	2.0 (1.1–3.8)
Not reduced	1.8 (1.2–2.7)	1.6 (1.1–2.5)
Test for overall effect	p < 0.01	p = 0.03
Angle of implants to the lateral cortex of the femoral shaft in AP
> 125°	1	1
≤ 125°	2.0 (1.0–3.8)	1.7 (0.90–3.4)
Protrusion of implant
No protrusion	1	1
Protrusion	2.1 (0.94–4.9)	2.4 (1.0–5.5)

^a See footnotes Table 2.

Table 2. Demographics and measurements of included cases. Values are frequency (%)

	Reoperated ^a	Dead ^a	Total ^b
Factor	n = 124 (19) ^b	n = 117 (18) ^b	n = 654
Sex
Male	40 (15)	53 (20)	269 (41)
Female	84 (22)	64 (17)	385 (59)
Age
≤ 50	5 (9)	1 (2)	54 (8)
51–60	17 (16)	10 (9)	109 (17)
61–70	65 (29)	25 (11)	227 (35)
71–80	13 (13)	15 (15)	97 (15)
81–90	18 (17)	30 (29)	104 (16)
> 90	6 (10)	36 (58)	63 (10)
Cortical thickness index
< 0.3	2 (13)	7 (46)	15 (2)
0.3–0.4	15 (19)	22 (28)	78 (12)
0.4–0.5	45 (19)	53 (22)	238 (36)
0.5–0.6	45 (17)	28 (11)	263 (40)
0.6–0.7	11 (25)	4 (9)	44 (7)
> 0.7	0 (	0 (	0 (0)
Hours to surgery
< 12	27 (15)	25 (14)	182 (28)
12–24	75 (23)	61 (19)	325 (50)
24–36	12 (16)	13 (17)	77 (12)
36–48	5 (16)	7 (23)	31 (5)
> 48	2 (10)	7 (35)	20 (3)
Fracture displacement
Mildly displaced ^c	43 (12)	67 (19)	356 (54)
Severely displaced ^d	81 (27)	50 (17)	298 (46)
Quality of reduction
Fully reduced ^e	33 (13)	38 (16)	245 (37)
Partly reduced ^f	18 (21)	16 (19)	85 (13)
Not reduced ^g	73 (23)	62 (19)	322 (49)
Angle of implants ^h
> 125°	112 (18)	111 (18)	621 (95)
≤ 125°	10 (33)	5 (17)	30 (5)
Protrusion of implant into the joint
No protrusion	118 (19)	113 (18)	636 (97)
Protusion	6 (33)	4 (22)	18 (3)

^a Percentage of the number of cases in each subgroup.

^b Percentage of the total number of patients.

^c Garden II with > 20° posterior tilt or Garden III type fracture.

^d Garden IV type fracture.

^e Non-displaced in AP view, < 10° posterior tilt (PT).

^f Non-displaced in AP view, ≥ 10° PT.

^g Displaced in AP view.

^h Angle of implants to the lateral cortex of the femoral shaft in AP.

Table 4. Cox regression analysis of risk of death

Factor	Univarible analysis HR (CI)	Multivariable analysis HR (CI)
Age
Per 1 year increase	1.07 (1.05–1.08)	1.05 (1.03–1.07)
Sex
Female	1	1
Male	1.1 (0.83–1.7)	1.6 (1.1–2.4)
ASA score
1–2	1	1
3–4	5.7 (3.8–8.4)	3.7 (2.4–5.7)
Hours to surgery
< 12	1	1
12–24	1.4 (0.88–2.4)	1.4 (0.85–2.2)
24–36	1.3 (0.64–2.5)	1.1 (0.58–2.3)
> 36	2.2 (1.1–4.1)	1.3 (0.65–2.6)
Test for overall effect	p = 0.2	p = 0.6
Cortical thickness index
Per 0.1 increase	0.58 (0.48–0.71)	0.72 (0.58–0.89)
Fracture type
Mildly displaced	1	1
Severely displaced	0.89 (0.62–1.3)	1.6 (1.1–2.5)
Reduction ^a
Fully reduced	1	1
Partly reduced	1.2 (0.68–2.2)	0.91 (0.48–1.7)
Not reduced	1.3 (0.84–1.9)	1.1 (0.69–1.7)
Test for overall effect	p = 0.5	p = 0.9
Angle of implants to the lateral cortex of the femoral shaft in AP
> 125°	1	1
≤ 125°	0.94 (0.38–2.3)	0.85 (0.34–2.1)
Protrusion of implant
No protrusion	1	1
Protrusion	1.3 (0.47–3.5)	2.0 (0.72–5.5)

^a See footnotes Table 2.

Table 5. Estimates of risk of reoperation and death for predefined cases 1 year postoperatively. Values are percentages

Sex, ASA score		CTI 0.5		CTI 0.4
Displacement		Estimated risk of		Estimated risk of
	Age	death	reoperation	death	reoperation
Male, 1–2
Mild	50	2	4	3	3
	60	4	4	5	4
	70	6	4	8	4
	80	10	4	14	4
Severe	50	3	10	5	10
	60	6	11	8	11
	70	10	12	13	12
	80	16	13	22	12
Male, 3–4
Mild	50	8	5	11	5
	60	13	5	17	5
	70	21	6	28	6
	80	33	6	42	6
Severe	50	12	15	17	15
	60	20	16	27	16
	70	32	17	41	16
	80	48	18	59	17
Female, 1–2
Mild	50	1	6	2	6
	60	2	6	3	6
	70	4	7	5	7
	80	7	7	9	7
Severe	50	2	17	3	17
	60	4	19	5	18
	70	6	20	9	19
	80	10	21	14	20
Female, 3–4
Mild	50	5	9	7	9
	60	8	9	11	9
	70	14	10	18	10
	80	22	11	29	10
Severe	50	8	25	11	24
	60	13	26	18	26
	70	21	27	28	27
	80	33	29	43	28

All estimates are made with the surgical parameters as for an optimal surgery: surgical delay < 12 hours, reduction to non-displaced with < 10° posterior tilt, with implant-angle > 125° and without implant protrusion into the joint.

CTI = Cortical thickness index