1 Faculty of Medicine, Department of Rehabilitation, and School of Mathematics, the Statistical Laboratory, Tel Aviv University, Tel Aviv, Israel; Department of Spinal Rehabilitation, Loewenstein Rehabilitation Hospital, Raanana, Israel.
2 Department of Spinal Rehabilitation, Loewenstein Rehabilitation Hospital , Raanana, Israel.
3 Faculty of Medicine, Department of Rehabilitation, and School of Mathematics, the Statistical Laboratory, Tel Aviv University , Tel Aviv, Israel.