Osteoarthritis of the temporomandibular joint in the Eastern Atlantic harbour seal (Phoca vitulina vitulina) from the German North Sea: a study of the lesions seen in dry bone

Table 2 Comparison of TMJ-OA lesion severity of affected individuals (at least one articular surface with a score > 0) between sexes in the different age classes as well as in the whole sample (Mann-Whitney U-Tests)

			N _affected	% _affected	M	Mdn	mean rank	U	z	p	d
Pooled	max TMJ-OA	male	507	58.8	1.43	1	459.43
		female	456	49.3	1.56	1	507.10
		total	963	53.9				104,152.0	−3.059	0.0022	0.172
	sum TMJ-OA	male	507	58.8	1.32	1	457.03
		female	456	49.3	1.45	1	509.77
		total	963	53.9				102,935.0	−3.567	0.0004	0.190
Juvenile/Subadult	max TMJ-OA	male	125	28.6	1.18	1	105.13
		female	98	20.7	1.38	1	120.76
		total	223	24.5				5266.5	−2.590	0.0096	0.242
	sum TMJ-OA	male	125	28.6	1.07	1	107.66
		female	98	20.7	1.16	1	117.53
		total	223	24.5				5583.0	−2.151	0.0315	0.152
Adult	max TMJ-OA	male	382	89.9	1.51	1	356.97
		female	358	79.2	1.61	1	384.94
		total	740	84.4				63,208.0	−1.997	0.0458	0.131
	sum TMJ-OA	male	382	89.9	1.40	1	351.51
		female	358	79.2	1.53	1	390.77
		total	740	84.4				61,122.5	−2.893	0.0038	0.184

TMJ-OA is more frequent in males. Conversely, higher mean score (M) and mean rank indicate that females are more severely affected. In all age groups (juveniles/subadults only, adults only, both groups pooled) the difference between sexes is significant (p < 0.05). However, the effect size (Cohen’s d) is always rather small. Mdn – median score

ISSN: 1746-6148