Fusion and Repeat Discectomy following Single Level Open Lumbar Discectomies. Survival Analysis 

Mortimer JR, Hoffman C
Mana Orthopaedics, Wellington, NZ

Background: single level discectomy for lumbar disk herniation is the most common spinal surgery performed in the US. Reoccurrence, and back pain secondary to spinal instability are among reasons for dissatisfaction post-surgery. Many patients will require revision discectomy and/or fusion procedures.

Aim: the Aim of this study is to describe the rates, indications, complications and demographics of patients undergoing lumbar fusions and repeat discectomies, following single level lumbar discectomies by one surgeon between 2000-2016.

Methods: retrospective descriptive study of 522 patients treated with primary single level open lumbar discectomy. Demographics data, original MRI reports, evidence of repeat discectomy or fusion gathered from a private database, ACC reports, regional Public hospital databases and imaging databases.

Measures: demographic data; age, gender, duration of symptoms, morphology of disk prolapse, and single level vs multilevel disk disease. Outcome measures; all complications, all spinal operations, all fusions, all repeat discectomies, isolated repeat discectomy and isolated fusion for ‘back pain’.

Results: 522 patients met criteria with a mean follow up of 7.7 years. 20% of all patients required at least one re-operation of any type. 5.9%, 10.5% and 10.4% at 1, 2 and 5 years respectively. 54 (10.3%) patients required primary fusion. Indications for fusion were any back pain (69%),back pain alone (38%),reoccurrence of HNP alone(32%),  back pain + reoccurrence(28%), discitis(1.0%). Mean time to fusion was 93 weeks post-op. mean rate was 14.3 per 1000person-years. 87% 10 year survival. 42 (8.0%) had a revision same level discectomy. Mean time to revision was 102 weeks post-op. Mean rate 12 per 1000 person years. 83.0% 10 year survival. 3.1% of patients required adjacent level discectomy. There were no statistically significant differences on rates of re-operation with the measured risk factors. Total complication rate was 8.0%.

Conclusion: Reoccurrence and back pain secondary to instability following single level discectomy is common problem after discectomy for lumbar disk prolapse. 20% of patients who undertake will eventually require a surgery on their spine. Pain, whether back or leg dominant, is the most common indication for repeat operation. Repeat discectomy, fusion or a combination being the most common repeat operation.