New Zealand Joint Registry data underestimates the rate of prosthetic joint infection

Figures & data

Table 1. Patient demographics (n = 4,009)

Mean age (SD)	69 (11)
Sex
Male	1,684 (42%)
Female	2,325 (58%)
Hospital
Auckland Hospital	770 (19%)
Middlemore Hospital	1,744 (37%)
North Shore Hospital	1,495 (43%)
Joint
Hips	1,852 (46%)
Knees	2,157 (54%)
Indication
Osteoarthritis	3,593 (90%)
Fracture	172 (4%)
Rheumatoid arthritis	86 (2%)
Other inflammatory arthritides	27 (0.5%)
Neoplasm	57 (1%)
Others	74 (2%)

Table 2. New Zealand Joint Registry data

	Number of primary procedures
PJIs within 2 years	Hips n = 1,852	Knees n = 2,157	Total n = 4,009
NZJR data, n Percent (95% CI)	11 0.59 (0.24–0.94)	16 0.74 (0.38–1.10)	27 0.67 (0.42–0.92)
Audit data, n Percent (95% CI)	19 1.03 (0.57–1.49)	24 1.11 (0.66–1.56)	43 1.07 (0.75–1.39)

Table 3. NZJR data versus audit data

	Patients missed by NZJR	Patients captured by NZJR
Hips/knees	8/8	11/16
Debridement in situ only	7	4
Modular exchange procedure	5	7
Staged revision	4^a	15
Excisional procedure	0	1
Total	16	27

a 2 reported as acetabular loosening