Made it so prosthetics can't replace legs. Compiled and tested.

code/__DEFINES/traits.dm

@@ -78,6 +78,7 @@
 #define	TRAIT_CROCRIN_IMMUNE    "crocin_immune"
 #define TRAIT_NYMPHO			"nymphomania"
 #define TRAIT_MASO              "masochism"
+#define TRAIT_PARA              "paraplegic"
 
 // common trait sources
 #define TRAIT_GENERIC "generic"

code/datums/traits/negative.dm

@@ -191,6 +191,7 @@
 	name = "Paraplegic"
 	desc = "Your legs do not function. Nothing will ever fix this. But hey, free wheelchair!"
 	value = -3
+	mob_trait = TRAIT_PARA
 	human_only = TRUE
 	gain_text = null // Handled by trauma.
 	lose_text = null
@@ -242,8 +243,12 @@
 	var/slot_string = "limb"
 
 /datum/quirk/prosthetic_limb/on_spawn()
-	var/limb_slot = pick(BODY_ZONE_L_ARM, BODY_ZONE_R_ARM, BODY_ZONE_L_LEG, BODY_ZONE_R_LEG)
 	var/mob/living/carbon/human/H = quirk_holder
+	var/limb_slot
+	if(H.has_trait("TRAIT_PARA"))//Prevent paraplegic legs being replaced
+		limb_slot = pick(BODY_ZONE_L_ARM, BODY_ZONE_R_ARM)
+	else
+		limb_slot = pick(BODY_ZONE_L_ARM, BODY_ZONE_R_ARM, BODY_ZONE_L_LEG, BODY_ZONE_R_LEG)
 	var/obj/item/bodypart/old_part = H.get_bodypart(limb_slot)
 	var/obj/item/bodypart/prosthetic
 	switch(limb_slot)

code/modules/vehicles/ridden.dm

@@ -60,7 +60,7 @@
 	if(key_type && !is_key(inserted_key))
 		to_chat(user, "<span class='warning'>[src] has no key inserted!</span>")
 		return FALSE
-	if(canmove && (user.get_num_lehs() < legs_required))
+	if(canmove && (user.get_num_legs() < legs_required))
 		to_chat(user, "<span class='warning'>You don't have enough legs to operate the pedals!</span>")
 		canmove = FALSE
 		addtimer(VARSET_CALLBACK(src, canmove, TRUE), 20)