Is it obligatory for someone whose right index finger has been amputated to raise a substitute finger during the Tashahhud?

The Hadith of Ibn Umar (may Allah be pleased with them both) indicates that the gesturing in the Tashahhud is done with the index finger of the right hand. Scholars have stated that if the index finger of the right hand is amputated, one should not gesture with other fingers or with the left hand, because each hand has its own posture and Sunnah in sitting. So, if the right index finger is amputated or ailing, the gesturing is waived for that person.