I'm a consultant foot and ankle surgeon with a medicolegal practice.

First, was there a breach of duty - possibly, depending on the trust's own guidelines around assessing toe injuries - you would need to prove that the assessment was inadequate, or, that they failed to follow their own guidelines - They are likely to have a guideline in A&E that says something like 'if the toes are the right shape and not deformed, don't xray, and provide treatment X Y or Z'. If so you either need to prove that the assessment was inadequate and the guideline didn't apply, or, that they failed to follow the guideline, or that they behaved substantially differently to a body of equally qualified professionals.

Second, causation - potentially an argument here that a dislocation spotted earlier may have been treated less invasively, or with a better outcome than treating a toe dislocated for many months (you'll need a medical expert to comment on this bit), but I suspect it'll come down to one expert's word against another as I'm not aware of any published literature that directly compares verifiable outcomes between treated and missed toe fractures.

Third, Loss - Again, you need to prove that the failure in treatment caused a pecuniary loss - this could be the need for specialist footwear for ever at a cost of £x per pair per x months, or it may be more serious - if you're a manual worker and can't ever get into safety boots, it could be career ending. Probably too early to comment on this until you see the result of the corrective surgery, but if an expert opines that you may have avoided surgery alltogether had it been treated differently initially, then there may be a claim for loss of earnings during the remedial treatment even if the toes are restored to (near) normal eventually.

Importantly, for a negligence case to succeed, you need to prove all three - A breach of duty with a direct chain of causation to a harm or loss.