[The mid- or long-term clinical results of prosthetic disc nucleus replacement in the treatment of lumbar disc disease].

OBJECTIVE: To evaluate the mid- or long-term clinical results and the factors that influence the outcomes of prosthetic disc nucleus (PDN) replacement in the treatment of lumbar disc disease.

METHODS: Thirty-four patients who underwent the PDN replacement from March 2002 to October 2003 were followed for an average of 52.6 months (range from 48 to 66 months). Twenty patients were discogenic low back pain, 14 patients were lumbar disc herniation. The follow-up results were evaluated by using the Oswestry disability index (ODI) and the visual analogue scales (VAS) through direct examinations and questionnaires. ODI was 58.4% preoperatively, and VAS was 7.4. Radiography was also used to measure the range of motion (ROM) and disc height of the operative segment, and findings were compared with those on preoperative radiographs.

RESULTS: Twelve months after operation, a significant proportion of patients recovered from low back pain or leg pain, ODI decreased to averaged 18.2%. VAS decreased to 1.8, the average increase of the postoperative disc height was 17.6%, ROM was 9.2 degrees. At the final followup, all patients with deteriorated leg radicular symptoms improved, ODI increased from 18.2% 12 months after operation to averaged 31.2%. Low back pain became more serious in 18 patients. VAS increased from 1.8 to 3.1, the average decrease of the postoperative to preoperative disc height was 13.5%, ROM decreased to 6.8 degrees. The rate of degeneration or breakages of the end plates was 64.7% (22/34), implant device migrations were observed in 25 patients.

CONCLUSIONS: The mid- or long-term outcome of PDN replacement in the treatment of degenerative lumbar disc disease is not as encouraging as that of the short-term follow-up. It is neither effective in term of restoration of the intervertebral disc height nor increase of the ROM of the operative segment, complication rates are significantly higher, and inferior results are to be expected. The selection of suitable surgical candidates and determination of valid indications for operative treatment are very important.