Study design: Retrospective review of patients with cervical spondylosis treated with three-level anterior cervical discectomy and fusion with plate fixation.

Objective: To assess the radiographic and clinical outcome of three-level instrumented anterior cervical discectomy.

Summary of Background data: Three-level cervical discectomy without plate fixation has shown high rates of pseudarthrosis and poor outcomes. The addition of internal fixation may improve these parameters.

Methods: 46 patients were observed for an average of 17.6 months (range, 6–51). All had three level anterior cervical discectomy and fusion with tricortical iliac crest autograft (4 cases), fibular ring allograft (38 cases), or titanium cage (four cases). Allografts and cages were filled with iliac crest autograft. All patients had semi-rigid plating. Clinical and radiographic follow-up data were obtained. Clinical outcomes were measured as described by Robinson and with the Nurick scale.

Results: Forty-four patients achieved solid fusion. Two patients had additional surgery for junctional disease, and in one of them pseudarthrosis repair was also performed. One asymptomatic pseudarthrosis was noted. With a successful result defined as an excellent or good outcome accompanied by significant pain relief, 38 patients had a successful result (83%). Radiographic adjacent level disease was diagnosed in 11 patients postoperatively and was symptomatic in 5.

Conclusion: Three-level anterior cervical discectomy with plate fixation has a high rate of fusion, a low complication rate, and acceptable outcome in the treatment of multilevel cervical spondylosis.

In this retrospective study 27 patients who had undergone revision discectomies for recurrent lumbar disc herniations were surveyed to assess their clinical outcomes. The patients chosen for the study were compared to a control group of 30 matched patients who had undergone only a primary discectomy. The spine module of the MODEMS® outcome instrument was used to evaluate the patients’ satisfaction, their pain and functional ability following discectomy, as well as their quality of life. All patients were also asked whether they were improved or worsened with surgery. Those undergoing revision surgery were asked whether the improvement following the second surgery was more or less than the improvement following the first surgery. Differences in residual numbness/tingling in the leg and/or the foot as well as in frequency of back and/or buttock pain were identified. Nevertheless improvement due to the repeat discectomy was not statistically different from those who underwent just the primary operation. Based upon patient derived outcome data with a validated instrument, revision discectomy is as efficacious as primary discectomy in selected patients.

Nitric oxide (NO) is a free radical labile gas which has important physiological functions and is synthesised by the action of a group of enzymes called nitric oxide synthases (NOS) on L- arginine. We have shown that nitric oxide modulates fracture healing¹. Bone morphogenic proteins (BMP) are potent differentiating factors that augment the process of new bone formation. Recombinant human BMP-2 (rhBMP-2) enhances spinal fusion². With progression of fusion there is a remodelling of the fusion mass bone accompanied with a decrease in the fusion mass size. It is not known whether nitric oxide has a role in spinal fusion or rhBMP-2 enhanced spinal fusion.

We studied this in a novel rat intertransverse fusion model using a defined volume of bone graft (7 caudal vertebrae) along with 157 mm3 of absorbable Type-1 collagen sponge (Helistat®) carrier, which was compacted and delivered using a custom jig for achieving a similar graft density from sample to sample. The control groups consisted of a sham operated group (S, n=20), an autograft + carrier group (AC, n=28) and a group consisting of 43 μg of rhBMP-2 (Genetics Institute, Andover, MA) mixed with autograft + carrier (ACB, n=28). Two experimental groups received a nitric oxide synthase (NOS) inhibitor, N^G-nitro L-arginine methyl ester (L-NAME, Sigma Chemicals, St Louis, MO) in a dose of 1 mg/ml ad lib in the drinking water (ACL, n=28) and one of these experimental groups had rhBMP-2 added to the graft mixture at the time of surgery (ACLB, n=28). Rats were sacrificed at 22 days and 44 days, spinal columns dissected and subjected to high density radiology (faxitron) and decalcified histology. The faxitrons were subjected to image analysis (MetaMorph).

On a radiographic score (0–4) indicating progressive maturation of bone fusion mass, no difference was found between the AC and ACL groups, however, there was a significant enhancement of fusion when rhBMP-2 was added (ACB group, 3.3±0.2) when compared to the AC group (1±0) (p< .001). However, on day 44, the ACLB group (3.3±0.2) showed significantly less fusion progression when compared to the ACB group (4±0) (p< 0.01). There was a 25% (p< 0.05) more fusion-mass-area in day 44 of ACLB group (297±26 mm³) when compared to day 44 of the ACB group (225±16 mm³) indicating that NOS inhibition delayed the remodelling of the fusion mass. Undecalcified histology demonstrated that there was a delay in graft incorporation whenever NOS was inhibited (ACL and ACLB groups).

Our results show that the biology of autograft spinal fusion and rhBMP-2 enhanced spinal fusion can be potentially manipulated by nitric oxide pathways.