Studies also report major neurological effects. Burning leg pain, loss of strength and motor function, and nerve root injuries can leave patients with long-term, disabling results. In a small number of men having spinal surgery, retrograde ejaculation is always possible. In this condition, sperm is no longer released from the penis but moves back up the urethra toward the bladder instead.
There may be problems with the implant itself. Sometimes the device sinks down into the bone. This condition is called subsidence. The implant may also move or migrate. Either of these problems can change the disc height and load-bearing surface of the implant. Reoperation may be needed to correct the problem.
There is always a concern about adjacent-level disease. The hope is that disc replacement will reduce this common effect after spinal fusion. But there are a small number of cases of adjacent-level disease reported even with disc replacement.
Overall, disc replacement is reported to be a safe and effective way to correct pain and disability in patients with mild to moderate degenerative disc disease. The risk of adverse events is between 0.5 and 12 per cent depending on type of complication. Surgeon experience and technique contribute to some of these problems. Implant design may also be a factor. Research is ongoing to improve results and reduce problems with the various types of devices available.