Doctors don't make you sign an indemnity form; they cannot do that. At most they make you sign a form where you acknowledge that you understand the risks of the procedure you are having. This will partially protect the doctor in that the patient cannot afterwards claim they weren't aware of the possibility that they could develop a given complication. Doctors cannot indemnify themselves against malpractice. When you check in at a hospital for a medical procedure, the hospital makes you sign an indemnity form that protects the hospital. This indemnity would cover injuries that are not the result of gross negligence by the hospital - things like patients being injured when slipping in the shower or nurses dropping patients when moving them to a different bed.
Suppose a patient dies under anaesthesia and it turns out the death occurred because the anaesthesia machine had not been working properly as a result of the hospital failing to have the machine correctly serviced. In such a case the hospital can definitely be sued with a high probability of success.
Suppose a patient dies under anaesthesia and it turns out the death occurred because the anaesthetist administered penicillin to the patient after the patient had already declared to the hospital upon checking in that they are allergic to penicillin. Suppose the anaesthetist then argues that they weren't aware of the allergy in part because they didn't conduct a pre-surgical consultation with the patient to assess their medical condition (gross negligence by the anaesthetist) and because the hospital didn't furnish the anaesthetist with the patient's medical information (gross negligence by the hospital). In such a case both the anaesthetist and hospital can definitely be sued with a high probability of success.
The prescription period for a malpractice claim is three years after the malpractice has become known (not necessarily after the malpractice was actually committed). The Medical Protection Society (the malpractice insurance provider used by most doctors in private practice) settles hundreds of malpractice suits every year. These cases usually don't get much publicity because the patient is required to sign a confidentiality agreement that prohibits them from discussing their case.
Doctor's make you sign an 'Informed Consent' form stating that you as patient acknowlegde that there are risks involved in said procedure/therapy and that you have been made aware of them and that you give permission for the doctor to continue with said procedure/therapy. The patient can decline to sign the form and in effect decline the said procedure/therapy.
If the form was signed, and any of the mentioned complications do occur, the doctor is safe because the patient was aware of the risks yet agreed to continue. Now obviously an orthopaedic surgeon can't have a female patient sign an Informed Consent stating that she might lose her uterus, the form has to make sense and be relevant to the said procedure/therapy. (On a side note: During a thyroidectomy, severing the Recurrent laryngeal nerves causing the patient unable to speak for the rest of his life is most likely not negligence)
Assuming that the form is relevant and makes sense, and the doctor was negligent, then he the form doesn't help him much.
The problem comes in proving a doctor negligent. He has MPS that he pays a few thousand rand per month and MPS has some of the best trained lawyers around. Negligence isn't a set-in-stone standard that can easily be measured. Negligence will be determined by looking at what the average doctor would be able to do in a similar situation.
His best bet would be to go and talk to Attorneys specializing in Medical Negligence (CP van Zyl). They'll listen to his story and decide whether it's a worthy case. If not they will kindly turn him away.
My guess is, that even if he wins, he won't make millions out of it.