Benefits of the paraspinal muscle-sparing approach versus the conventional midline approach for posterior nonfusion stabilization: comparative analysis of clinical and functional outcomes

Abstract

Background: The influence of approach on outcomes of posterior nonfusion stabilization has not been described. This paper analyzes the influence of surgical approach on functional outcome with nonfusion stabilization.

Methods: We performed a prospective consecutive cohort outcome analysis of 88 patients who had undergone posterior nonfusion stabilization of the lumbar spine at 178 levels using the Dynesys system (Zimmer Spine, Inc, Warsaw, Indiana). Patients needing decompression (n = 42) were operated through a midline approach using microscopic laminotomy/foraminotomy with or without discectomy, followed by posterior nonfusion stabilization with Dynesys. None of the patients had a complete laminectomy. Patients not needing decompression (n = 46) underwent the procedure via the bilateral paraspinal muscle-sparing approach and were subsequently stabilized. Clinical and functional outcomes data were collected using the visual analog scale (VAS), Treatment Intensity Score (TIS), Oswestry Disability Index (ODI), and SF-36. Average follow-up was 18 months (range, 12-36 mo).

Results: All outcome measures in both groups showed significant improvement at last follow-up. Between the groups a significant difference was apparent in the reduction of the TIS when measured at 1 week and 6 weeks. The preoperative, 1-week, and 6-week values were 66, 48, and 40, respectively (P < 0.05), for the midline group and 80, 32, and 28 (P < 0.05) for the paraspinal group. This trend continued through 3 to 6 months after the procedure but did not reach statistical significance. In the paraspinal group, pain scores showed a nonsignificant trend toward lower values in the first month, compared with values in the midline group. Patients reported excellent to fair results, with the exception of three patients in the midline group and two in the paraspinal group, who rated the procedure as fair.

Conclusions: Significantly fewer patients required postoperative narcotics in the paraspinal group than in the midline group. This improvement in early outcomes suggests a significant early benefit to the less tissue-destructive muscle-sparing approach in posterior nonfusion stabilization procedures.

Keywords: Posterior nonfusion spinal stabilization; muscle-sparing approach; paraspinal approach.

Figure 1

Photograph showing lumbar spine with pedicles marked on the skin per anteroposterior fluoroscopy. A linear mark is then made connecting the lateral edge of the pedicles.

Figure 2

(a) Photograph of Dynesys implanted via the midline approach in cases where a decompression was performed. (b) Photograph of Dynesys implanted via musclesparing approach.

Figure 3

Graph showing TIS significantly improved at 6 weeks for patients who underwent posterior nonfusion stabilization via paraspinal muscle-sparing approach versus the midline muscle-stripping approach.

Figure 4

Illustration showing the modified Wiltse muscle-sparing approach. Note the approach between the multifidus and longissimus muscles.

Figure 5

(a), (b), (c). T2 weighted MRI of patients showing changes in the paraspinal muscles of a patient undergoing posterior nonfusion stabilization via the anatomy-preserving muscle-sparing approach vs (d), typical changes seen in a midline muscle stripping approach. Note the extensive high signal seen in the paraspinal muscles of the patient undergoing the midline approach.