Possible magic item effects?

In 2nd ed ADAD I found an effect called sharpness.
It is similar in effect to Vorpal in that an attack roll of a natural 20 results in partial dismemberment.
However, this effect did not automatically result in death the way Vorpal does and targets a randomly determined appendage rather than just causing a decapitation.

When I game-master in future I was thinking that I'd add this effect to specific artifacts in a campaign. This ability is extremely powerful and possibly game breking

Rules:
Strong necromancy and transmutation; CL 16th; Craft Magic Arms and Armor, keen edge; Price +4 bonus.
On a roll of a natural 20 (confirmed as a critical) the weapon causes dismemberment of the target. This results in bonus bleed damage dependent on the dismembered limb. Dismemberment does not cause death although damage caused can. Damage continues at a rate of 1d6 per round until a DC 16 heal check is made or 1 point of magical healing occurs.
Roll a d4 to determine limb removed:
1 or 2 - Arm: 2d6 bleed damage, target loses use of left arm until it is regenerated. -2 STR, -2 DEX
Spells with somatic components can still be used if one arm remains
3 or 4 - Leg: 4d6 bleed damage, target loses use of left leg until it is regenerated. -2 CON, -3 DEX, -15 move speed

Opinions?

ouch^^

Brutal and effective.
It would suit an evil NPC or PC pretty well.

+4 enhancement bonus is brutally expensive, so I'd leave it as is. Only one lower that Vorpal anyway. If you saved all your money up to level 8, you could just afford a weapon with it, maybe.

Naturally, it'd have some restrictions. Only makes sense on slashing weapons for instance. Creatures with a lot of arms (eg Hekatonkheires) would be effectively immune to losing an arm, or creatures with a lot of legs (eg Giant Centipede) would be immune to losing legs. And of course things with no arms or legs would be immune. Things with no blood wouldn't take the Con damage or the bleed damage.


See also: Called Shots.