Business segment information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011 unit segment	Dec. 31, 2010	Dec. 31, 2009
Business segment information
Number of GBUs									3
Number of reporting segments									3
Business Segments by GBU information
Net sales	$ 151,525	$ 144,747	$ 143,551	$ 139,165	$ 143,796	$ 138,906	$ 142,845	$ 138,823	$ 578,988	$ 564,370	$ 545,635
Percent of Total Net Sales									100.00%	100.00%	100.00%
Spine
Business Segments by GBU information
Net sales									304,217	306,404	279,425
Percent of Total Net Sales									52.00%	54.00%	51.00%
Orthopedics
Business Segments by GBU information
Net sales									165,904	154,198	151,054
Percent of Total Net Sales									29.00%	27.00%	28.00%
Sports Medicine
Business Segments by GBU information
Net sales									$ 108,867	$ 103,768	$ 115,156
Percent of Total Net Sales									19.00%	19.00%	21.00%