I broke my sacrum when I fell from the second story of a building that was under construction. It's not a simple break -- this one is called a U-shape sacral fracture. I had surgery and they plated the break. I still don't have bowel or bladder control. How long does that take to come back?
It sounds like you not only broke your sacrum, you did it in a way that may have caused injury to the spinal nerves. The nerves that come down the spinal canal end at the sacrum in a group called the cauda equina (literally "horse's tail" because that's what they look like). These are the nerves that help control bowel and bladder function as well as sensation and motor function of the groin and legs.
In a fracture of this type, the force of the impact shifts the fractured bone into the spinal nerves that exit through tiny holes in the sacral bone. In cases like this, there is often tearing of the nerve roots and rupture of the dural sac (thin protective membrane around the nerves).
Further damage to the sacral nerves can occur as the bone fracture fragments push into the dural sac cutting into the nerves. The damage sets up an inflammatory response with bleeding, swelling, and eventual scar tissue formation from S2 to S4. Early surgery is advised in order to get the pressure off the nerves and help them recover.
Now that you have finished the first step in treatment, you are understandably eager to get back to normal. Nerve healing is a very, very slow process. You can expect this to take months up to a year or more. You will notice gradual improvement over time. A physiotherapist can help you recover strength in the muscles that control urination and defecation.
Keep in mind there is a chance that full recovery won't happen if the damage to the nerves is just too much. Keeping a journal of your symptoms can be helpful in recognizing subtle changes because recovery is going to be slow. Seeing small but steady changes can help prevent discouragement. Your surgeon will be able to offer you a more accurate timeline for recovery based on your symptoms the first few months.
Reference: Hong-wei Chen, et al. Isolated U-Shaped Sacral Fracture with Cauda Equina Injury. In Orthopedics. April 2011. Vol. 14. No. 4. Pp. E81562 (1-5).
