Achondroplasia natural history study (CLARITY): 60-year experience in orthopedic surgery from four skeletal dysplasia centers

Table 4 Incidence of laminectomy procedures by birth cohort

Birth Cohort	Total patients	Patients with laminectomies surgery N (%)	Age at first laminectomy surgery Mean ± SD	Total number of laminectomy surgeries	Years contributed	Surgeries per 1000 person years	Incidence rate ratio (95% CI)
2010–date	239	2 (0.8)	2.99 ± 1.90	2	811.62	2.46	Reference
2000–2009	356	7 (2.0)	10.18 ± 3.80	10	3481.37	2.87	1.17 (0.65 – 2.11)
1990–1999	314	38 (12.1)	20.97 ± 4.19	57	4639.11	12.29	5.00 (3.01–8.30)
1980–1989	231	32 (13.9)	27.60 ± 6.08	50	4085.37	12.24	4.98 (2.99–8.29)
< 1980	234	73 (31.2)	50.61 ± 14.56	152	8158.95	18.63	7.57 (4.61–12.44)
TOTAL	1374	152 (11.1)		271	21,176.42

Incidence was represented by person-year (surgeries per 1000 years) and the incidence rate ratio, which standardized the number of patients and years contributed in each cohort. A total of 271 laminectomy procedures were performed in 152 patients. Patients born before 1980 had the highest incidence rate ratio for laminectomy surgeries

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