I believe I have answered the similar question few minutes back.

Its not usual things which happen after surgery. we have to do some intervention . I cant  comments in detaila withiout seeing x rays.

There is no blame culture in surgical interventions . Since fracture femur though a routine procedure for orthopaedic surgeon it is a major operation generally and also from the patients perspective. Every major surgical intervention has its own complications which is beyond surgeon s control factors or circumstantial factors. Your mother's compliance plays also a major factor in these situations and which is always the factor either taken from bone weakness or physiotherapy wise. Get to discuss with your index surgeon what further can be done in the betterment of your mother rather than blaming . If it is a Dynamic hip  Screw or Cannulated screw fixations the screws are meant to back out from the neck of femur once there is controlled collapse at the fracture site in the process of union. Probably this is what you are talking about which is in good favour of fracture union. Please do not be on the offensive side towards the surgeon since every doctor on this earth wants a good result from his patients since every doctor will put his heart and mind while doing any procedure to make patient better which also gives good credit to doctor. Discuss with your surgeon and sort things out so that your mother gets better

This problem occurs with weak bones, if there is no union, probably a replacement by hemi or total will be required. Its no one to be blamed for, weak bone may sometimes not hold the implant. You can consult in person with details.

May be due to osteoporosis or early weight bearing, although fracture neck femur is notorious for non Union, need a new surgey

1)implant removal and revision may be required 2) nobody or nothing to be blamed.it usually happens due to weak bones. Please don't look to put blame on anybody or thing as it doesn't serve the purpose of getting  the patient better. This approach is wrong.no doctor will ever want to do wrong for his patient 3)can't push same pin again 4)only new pin/screw will not do 5) discuss further revision surgeon options with your primary surgeon as only the surgeon knows the quality of bone and soft tissues already faced inside.

The case that you explained is possible and relatively common The same Pin cannot be pushed back as can come out again More details can be said after you share Age of the patient Any co morbid conditions Pre and post operative X-rays

Please share all the X-ray films only then the question can be answered

Kindly provide X-rays and other investigations you have