Wednesday, October 30, 2001 9:08–9:51 amGeneral Session 3: Outcomes—Nonoperative Versus Operative 9:08 Assessment of lumbar interbody fusion status by discogram technique: rate of concordant pain response, determination of pseudarthrosis and results of revision surgery

Abstract

Purpose of study: The determination of the etiology of persistent pain after lumbar interbody fusion is often difficult, especially with metallic interbody constructs. Our study evaluates a unique discogram technique for determination of interbody fusion status. We evaluate the rate of concordant pain response on injection of interbody fusion constructs. We also determine the results of revision surgery after discogram evidence of failed fusion.Methods used: Twenty-four patients were referred for evaluation of lumbar interbody fusion and adjacent levels by discogram technique. Referrals noted appearance of solid fusion on standard radiographic studies but persistent low back pain. Adjacent levels were evaluated in addition to the level of interbody fusion. Presenting symptom was predominantly low back pain (n=24) with variable lower extremity symptoms. Pseudarthrosis was dramatically documented when dye flowed around and through interbody cages or surrounded allograft arthrodesis. Solid arthrodesis was documented with inability to inject dye or with dye flowing around solid construct. A retrospective review of prereferral studies noted the appearance of fusion with lack of halo formation, appearance of bone incorporating into the vertebral bodies and less than 5 degrees of motion on flexion–extension lateral radiographs. When pseudarthrosis with concordant response was documented, patients were given the option of revision surgery. Clinical response to revision surgery was evaluated independently by a questionnaire completed by the patient. A minimum of 2-year follow-up postoperatively was required for study inclusion.of findings: Twenty-four patients (16 women, 8 men) with persistent postoperative low back pain and appearance of solid fusion on standard radiographs underwent discogram evaluation of interbody fusion and adjacent levels. All patients were sent a back pain questionnaire by an independent reviewer with a 79% (17 of 24) response. Average time from fusion to the discogram study was 17 months. Pseudarthrosis was demonstrated in 58% (14 of 24) of the patients evaluated. Concordant pain response was seen in only one level that was documented solid on interbody discogram. Any level with pseudarthrosis was always accompanied by a concordant pain response (p<.0001). Adjacent level concordant pain response was seen in 8% (2 of 24) of patients with a solid fusion. All but one (13 of 14) of the pseudarthrosis group elected to have revision surgery. One of the adjacent levels response group also elected further surgery. Symptomatic improvement in pain was found in 79% (11 of 14) of the surgical revisions of patients with concordant pain response.Relationship between findings and existing knowledge: Studies have noted pseudarthrosis intraoperatively in levels noted solid on standard radiographic studies. McAfee demonstrated a wide variation in techniques used to document solid fusion. We provide an additional technique to evaluate lumbar interbody fusion.Overall significance of findings: The interbody fusion discogram provides a dramatic demonstration of pseudarthrosis in patients with persistent low back pain, despite appearance of solid fusion on standard radiographs. There is a strong statistical correlation of concordant pain response and discogram documentation of pseudarthrosis. Interbody fusion discogram technique allows demonstration of pseudarthrosis, documents response at adjacent levels and predicts successful outcome with revision surgery.Disclosures: No disclosures.Conflict of interest: No conflicts.