Table 2.

Comparison of peak muscle moment arms calculated in the model and those obtained from the in vitro experiments reported by Brown et al. (2003b)

		Function	Model peak (mm)	Experiment peak (mm)	Mean absolute difference (mm)
Superficial digital flexor	SDF	Flex MCP	32.2	32.9	1.3
Deep digital flexor	DDF	Flex MCP	31.6	33.2	1.7
Common digital extensor	CDE	Ext MCP	24.0	13.7	9.1*
Lateral digital extensor	LDE	Ext MCP	22.2	10.5	8.9*
Superficial digital flexor	SDF	Flex carpus	37.2	41.3	5.1
Deep digital flexor	DDF	Flex carpus	31.3	35.2	3.6
Ulnaris lateralis	UL	Flex carpus	29.4	30.2	0.7
Flexor carpi ulnaris	FCU	Flex carpus	35.3	35.6	0.5
Flexor carpi radialis	FCR	Flex carpus	29.6	30.0	1.0
Common digital extensor	CDE	Ext carpus	33.6	25.6	8.5*
Lateral digital extensor	LDE	Ext carpus	25.7	22.0	8.1*
Extensor carpi radialis	ECR	Ext carpus	27.3	24.3	1.6
Abductor pollicis longus	APL	Ext carpus	8.1	5.7	5.3

Data are for nine muscles crossing the carpal and MCP joints; SDF, DDF, CDE and LDE are biarticular muscles and therefore have moment arms at both joints. Mean absolute difference is the mean of the absolute difference between moment arms determined at 10° intervals across the simulated range of motion for a specific joint. Forelimb muscles were classified by their ability to flex the MCP joint (Flex MCP), extend the MCP joint (Ext MCP), flex the carpal joints (Flex carpus), or extend the carpal joints (Ext carpus).

^*Mean differences between model and experimental moment arms were much larger for CDE and LDE than for the other forelimb muscles because the experimental data for these muscles were unreliable when the carpus and MCP joints were extended beyond 180° (see Brown et al. 2003b).