Revenue recognition (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 02, 2022	Apr. 03, 2021
Disaggregation of Revenue [Line Items]
Total net sales	$ 117,290	$ 81,778
Pain Treatments
Disaggregation of Revenue [Line Items]
Total net sales	52,053	41,530
Restorative Therapies
Disaggregation of Revenue [Line Items]
Total net sales	34,360	21,821
Surgical Solutions
Disaggregation of Revenue [Line Items]
Total net sales	30,877	18,427
U.S.
Disaggregation of Revenue [Line Items]
Total net sales	104,081	74,538
International
Disaggregation of Revenue [Line Items]
Total net sales	$ 13,209	$ 7,240