Background context: Cauda equina following a prosthetic Disc nucleus replacement has never been reported.

Purpose: To describe a case of Cauda equina following migration of the Prosthetic disc nucleus and possible cause.

Study design: Case report and review of literature.

Patient Sample: Case report.

Outcome measures: 2 patients. Report of presenting symptoms and review of radiographs.

Method/description: A 24-year-old man presented with progressively worsening pain radiating down his right leg and low back pain. His MRI scan showed a disc bulge at L4/5 for which we underwent decompression and discetomy. 4 months later he presented again with same symptoms. MRI imaging showed a disc prolapse at L4/5. He underwent a revision decompression discectomy and a prosthetic disc nucleus replacement. On the 4th postoperative day he complained of urinary retention and was unable to move his right ankle with loss of sphincter tone. The plain radiographs showed that the prosthetic disc nucleus had migrated posteriorly. He was immediately taken to theatre, which showed posterior migration of the prosthetic disc nucleus compressing the theca and displacing the nerve root. The prosthetic disc nucleus was removed from the space relieving the tension of the nerve root and the theca.

Conclusions: Migration of Prosthetic disc nucleus can lead to cauda equina and this needs to be explained to the patient as possible risk factor. The angle of the vertebrae has to be measured before selecting a patient. If angle below 5 degree it is a high risk patient.