Complications after hip arthroplasty and the association with hospital procedure volume

Figures & data

Schematic representation of exclusion of patients from the study population.

Table 1. Baseline characteristics of the study cohort (n = 50,080)

	All admissions	Males	Females
	n = 50,080	n = 14,966,	n = 35,114,
Characteristics: Primary total hip replacement		30%	70%
Mean age, years (SD)	68.7 (10.6)	65.9 (11.0)	70.0 (10.1)
Median age, years (range)	70 (15–99)	67 (15–99)	71 (15–99)
Median duration of admission, days (range)	9 (1–137)	8 (1–137)	9 (1–133)
Median duration of preoperative admission,
days (range)	1 (0–80)	1 (0–80)	1 (0–76)
Acute, unplanned admission, n (%)	504 (1.0)	132 (0.9)	372 (1.1)
Any co-morbidity, n (%)	3,423 (6.8)	1,164 (7.8)	2,259 (6.4)
Specialist:
Orthopedic surgeon, n (%)	50,038 (99.9)	14,956 (99.9)	35,082 (99.9)
General surgeon, n (%)	34 (0.1)	9 (0.1)	25 (0.1)
Other surgeon, n (%)	8 (< 0.1)	1 (< 0.1)	7 (< 0.1)
Died during admission (all causes), n (%)	114 (0.2)	42 (0.3)	72 (0.2)
Complication during admission, n (%)	1,115 (2.2)	350 (2.3)	765 (2.2)
Re-admitted with a complication at least
once within 3 months	1,765 (3.5)	595 (4.0)	1,170 (3.3)
Any unfavorable outcome ^a	2,880 (5.8)	947 (6.3)	1,933 (5.5)
Diagnosis
Osteoarthritis, n (%)	48,313 (96.5)	14,260 (95.3)	34,053 (97.0)
Aseptic bone necrosis, n (%)	937 (1.9)	419 (2.8)	518 (1.5)
Congenital deformity of hip, n (%)	141 (0.3)	37 (0.2)	104 (0.3)
Rheumatoid arthritis, n (%)	121 (0.2)	31 (0.2)	90 (0.3)
Other, n (%)	568 (1.1)	219 (1.5)	349 (1.0)

^a Complication during index admission and/or re-admission due to complication up to 3 times within 3 months of surgery.

Table 2. Characteristics of first 3 re-admissions within 3 months of surgery

	First		Second		Third
	n = 4,364		n = 759		n = 167
	n	% (95% CI)	n	% (95% CI)	n	% (95% CI)
Second total hip replacement	423	9.7 (8.8–10.6)	25	3.3 (2.0–4.6)	3	1.8 (–0.2 to 3.8)
Complication during index admission	156	3.6 (3.0–4.1)	34	4.5 (3.0–6.0)	6	3.6 (0.8–6.4)
Re-admission was acute/unplanned	2,534	58.1 (56.6–59.5)	397	52.3 (48.8–55.9)	72	43.1 (35.6–50.6)
Mortality during re-admission	83	1.9 (1.5–2.3)	9	1.2 (0.4–2.0)	5	3.0 (0.4–5.6)
Readmission was due to complication	1,765	40.4 (39.0–41.9)	322	42.4 (38.9–46.0)	70	41.9 (34.4–49.4)
Complications specified:	1,765	100	322	100	70	100
Mechanical complication of device	892	50.5 (48.2–52.9)	212	65.8 (60.7–71.0)	43	61.4 (50.0–72.8)
Infection	526	29.8 (27.7–31.9)	73	22.7 (18.1–27.2)	20	28.6 (18.0–39.2)
Dislocation	47	2.7 (1.9–3.4)	10	3.1 (1.2–5.0)	0	0.0 (0.0–0.0)
Pulmonary embolism	58	3.3 (2.5–4.1)	5	1.6 (0.2–2.9)	1	1.4 (–1.4 to 4.2)
Deep vein thrombosis	61	3.5 (2.6–4.3)	4	1.2 (0.03–2.5)	1	1.4 (–1.4 to 4.2)
Other	180	10.2 (8.8–11.6)	18	5.6 (3.1–8.1)	5	7.1 (1.1–13.2)

Table 3. Adjusted associations of all risk factors with mortality per hospital group

	Early mortality during index admission
	Crude OR (95% CI)	Adjusted OR (95% CI)
Hospital volume as no. of total hip procedures ^a per year
> 400 (nh = 7 / np = 8,813) ^b	ref	ref
300–400 (nh = 12 / np = 10,260)	0.94 (0.52–1.7)	0.8 (0.44–1.5)
200–300 (nh = 20 / np = 12,413)	1.2 (0.67–2.0)	1.1 (0.6–2)
100–200 (nh = 42 / np = 16,196)	0.91 (0.53–1.6)	0.76 (0.44–1.3)
< 100 (nh = 13 / np = 2,398)	0.18 (0.02–1.3)	0.17 (0.02–1.2)
Female sex	0.73 (0.5–1.1)	0.58 (0.39–0.86)
Age (quartiles of no. of patients)
≤ 65	ref	ref
66–72	1.8 (0.81–4.0)	2 (0.88–4.4)
73–79	5.6 (2.8–11)	5.8 (2.9–12)
≥ 80	11 (5.5–22)	11 (5.4–22)
Co–morbidity ^c
Score 0	ref	ref
Score 1	3.9 (2.3–6.4)	2.7 (1.6–4.6)
Score 2	6.8 (3.1–15)	4.2 (1.9–9.3)
Score 3	12 (4.7–29)	6 (2.3–16)
Diagnosis
Osteoarthritis	ref	ref
Aseptic bone necrosis	3.3 (1.5–7.6)	3.2 (1.4–7.6)
Congenital deformity of hip	–	–
Rheumatoid arthritis	4.3 (0.59–31)	2.3 (0.29–18)
Other	12 (6.7–22)	7.9 (4.1–15)
Acute, unplanned admission	6.5 (3–14)	3 (1.2–7.2)
Duration of index admission	1 (1–1.1) ^d	1 (0.95–1) ^e
Duration of preoperative admisison	1.1 (1–1.1) ^f	– ^g
Complication during index admission	18 (12–27)	13 (8.4–21)

^a Fractures and hemiarthroplasties excluded.

^b n_h = no. of hospitals / n_p = no. of patients in group.

^c Charlson co-morbidity index, adapted by Deyo et al. for ICD–9 databases

^d Results with 2 decimals: 1.04 (1.02–1.05).

^e Results with 3 decimals: 0.972 (0.947–0.999).

^f Results with 2 decimals: 1.06 (1.03–1.10).

^g Not in final multivariable model.

Table 4. Crude and adjusted associations of all risk factors with complications during index admission and re–admission

	Complication during index admission		Re-admission due to complication
	Crude OR (95% CI)	Adjusted OR (95% CI)	Crude OR (95% CI)	Adjusted OR (95% CI)
Hospital volume as no. of total hip procedures ^a per year
> 400 (nh = 7 / np = 8,813) ^b	ref	ref	ref	ref
300–400 (nh = 12 / np = 10,260)	2.2 (1.7–2.8)	2.2 (1.7–2.7)	1.3 (1.1–1.5)	1.3 (1.1–1.5)
200–300 (nh = 20 / np = 12,413)	2 (1.6–2.5)	1.9 (1.5–2.4)	1 (0.89–1.2) ^c	1 (0.88–1.2) ^d
100–200 (nh = 42 / np = 16,196)	2 (1.6–2.5)	1.8 (1.5–2.3)	0.96 (0.84–1.1)	0.94 (0.82–1.1)
< 100 (nh = 13 / np = 2,398)	2.3 (1.7–3.2)	1.9 (1.4–2.6)	1.1 (0.9–1.4)	1.1 (0.87–1.4)
Female sex	0.93 (0.82–1.1)	0.78 (0.68–0.9)	0.83 (0.75–0.92)	0.79 (0.71–0.87)
Age (quartiles of no. of patients)
≤ 65	ref	ref	ref	ref
66–72	1.3 (1.1–1.6)	1.2 (1–1.5) ^e	1.1 (0.93–1.2)	1.1 (0.98–1.3)
73–79	2 (1.7–2.4)	1.5 (1.3–1.8)	1.5 (1.3–1.7)	1.6 (1.4–1.8)
≥ 80	2.6 (2.2–3.2)	1.5 (1.3–1.9)	1.7 (1.5–2)	1.9 (1.6–2.2)
Co–morbidity ^f
Score 0	ref	ref	ref	ref
Score 1	2.1 (1.7–2.5)	1.7 (1.3–2.1)	1.5 (1.3–1.8)	1.4 (1.2–1.7)
Score 2	2.5 (1.7–3.7)	1.8 (1.2–2.7)	1.7 (1.2–2.4)	1.5 (1.1–2.2)
Score 3	3.1 (1.9–5.3)	1.9 (1–3.4) ^g	2 (1.2–3.3)	1.8 (1.1–2)
Diagnosis
Osteoarthritis	ref	ref	ref	ref
Aseptic bone necrosis	2.1 (1.5–2.9)	1.8 (1.3–2.6)	1.8 (1.4–2.3)	1.8 (1.4–2.4)
Congenital deformity of hip	–	–	0.19 (0.03–1.4)	0.22 (0.03–1.6)
Rheumatoid arthritis	1.2 (0.37–3.7)	0.6 (0.16–2.2)	3 (1.6–5.4)	2.6 (1.4–4.8)
Other	3.9 (2.8–5.3)	2.5 (1.7–3.5)	1.8 (1.2–2.5)	1.8 (1.2–2.5)
Acute, unplanned admission at index admission	1.8 (1.2–2.9)	– ^h	0.81 (0.49–1.4)	– ^h
Duration of index admission	1.1 (1.1–1.1) ^i	1.1 (1.1–1.1) ^j	1 (1–1) ^k	1 (0.98–1) ^l
Duration of preoperative admission	1 (1–1.1) ^m	0.87 (0.84–0.91)	0.99 (0.96–1)	– ^h
Complication during index admission	NA	NA	2 (1.6–2.5)	1.9 (1.5–2.5)

^a Fractures and hemiarthroplasties excluded.

^b n_h = no. of hospitals / n = no. of patients in that group.

^c Results with 2 decimals: 1.04 (0.89–1.20).

^d Results with 2 decimals: 1.02 (0.88–1.19).

^e Results with 2 decimals: 1.22 (1.01–1.46).

^f Charlson co-morbidity index, adapted by Deyo et al. for ICD–9 databases.

^g Results with 2 decimals: 1.89 (1.04–3.41).

^h Not in final multivariable model.

ⁱ Results with 2 decimals: 1.10 (1.09–1.10).

^j Results with 3 decimals: 1.103 (1.095–1.110).

^k Results with 3 decimals: 1.004 (0.996–1.012).

^l Results with 3 decimals: 0.986 (0.977–0.995).

^m Results with 2 decimals: 1.04 (1.02–1.06).