Revenue recognition - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2023	Jul. 02, 2022	Jul. 01, 2023	Jul. 02, 2022
Disaggregation of Revenue [Line Items]
Total net sales	$ 137,069	$ 140,331	$ 256,128	$ 257,621
U.S.
Disaggregation of Revenue [Line Items]
Total net sales	120,847	126,310	224,825	230,391
U.S. | Pain Treatments
Disaggregation of Revenue [Line Items]
Total net sales	55,617	58,055	96,612	105,929
U.S. | Restorative Therapies
Disaggregation of Revenue [Line Items]
Total net sales	31,844	35,433	64,332	64,379
U.S. | Surgical Solutions
Disaggregation of Revenue [Line Items]
Total net sales	33,386	32,822	63,881	60,083
International
Disaggregation of Revenue [Line Items]
Total net sales	16,222	14,021	31,303	27,230
International | Pain Treatments
Disaggregation of Revenue [Line Items]
Total net sales	6,024	5,859	11,355	10,038
International | Restorative Therapies
Disaggregation of Revenue [Line Items]
Total net sales	4,774	4,469	10,388	9,883
International | Surgical Solutions
Disaggregation of Revenue [Line Items]
Total net sales	$ 5,424	$ 3,693	$ 9,560	$ 7,309