The concept of notice before unilateral termination of the contract of employment, either by the employer or by the employee, is based on the principle of enabling the other party to get prepared for making suitable alternative arrangements. However, this condition is normally relaxable in respect of the employee by providing a buy-out option available to him, subject to the employer's acceptance, and for the employer to pay the notice salary in lieu of notice if so provided for in the contract. Otherwise, non-compliance by anyone would certainly constitute a breach of the contract resulting in damages if contested by the aggrieved party.
If the employer finds an immediate substitute to fill the vacancy consequent on the resignation of an employee serving the notice period, to accommodate the substitute forthwith in the interest of the organization, he can make a counteroffer of paying the salary for the unserved notice period to the resignee and relieve him forthwith. Similarly, under the same pretext of the interest of the work of the organization, the employer has the discretion to turn down the buy-out option of the employee. The normal practice followed by most organizations is not allowing long leave during the notice period. That's the reason behind the proportionate extension of the notice period which cannot be legally found fault with.
Probably the poster might have an alternative job on the expiry of the notice period of 90 days during which he met with an unfortunate accident. Therefore, in such a situation, he can ask the prospective employer to extend the joining time or request the present employer either to waive the notice period of 60 days he was on leave due to the accident or permit him to buy it out.