Is it permissible to combine the Dhuhr and Asr prayers and the Maghrib and Isha prayers due to a disability and leg amputation that causes hardship in performing ablution and sitting?

It is permissible for a sick person who finds it difficult to perform each prayer at its appointed time to combine the Dhuhr and Asr prayers, and the Maghrib and Isha prayers, either by performing them early (Jumu' Taqdeem) or delaying them (Jumu' Ta'kheer). This is the view of the Hanbalis and was strengthened by An-Nawawi. However, it is preferable to avoid disagreement by performing a "de facto" combination (Jumu' Suri), whereby the first prayer is performed at the very end of its prescribed time, and the second prayer at the very beginning of its prescribed time.