Spinal Canal Remodeling and Indirect Decompression of Contralateral Foraminal Stenosis After Endoscopic Posterolateral Transforaminal Lumbar Interbody Fusion

OBJECTIVE: There is a lack of literature on indirect decompression in uniportal endoscopic posterolateral transforaminal lumbar interbody fusion (EPTLIF). Our aim is to evaluate the dimensions of the spinal canal and contralateral foramen before and after EPTLIF. METHODS: This is a retrospective study of patients who underwent EPTLIF in a tertiary spine centre over a 2-year period. The cross-sectional area of the spinal canal and the contralateral foramen at the level of fusion were measured on magnetic resonance imaging scan at 1-day postoperation and at the final follow-up. Patients were grouped according to the decompression performed as per the clinician’s judgement. RESULTS: One hundred fifty-two levels of fusion were performed in 120 patients. There was a statistically significant clinical improvement in visual analogue scale and Oswestry Disability Index scores postoperation. The measurements of the spinal canal area were 106.0 mm(2), 138.8 mm(2), and 195.5 mm(2); while contralateral foraminal area were 73.2 mm(2), 104.4 mm(2), and 120.7 mm(2) at preoperation, 1-day postoperation, and at the final follow-up, respectively (p < 0.001). For the subgroup analyses, spinal canal area measurements for the bilateral decompression cohort (n = 35) were 57.0 mm(2), 123.9 mm(2), and 191.8 mm(2); for the ipsilateral decompression cohort (n = 42) were 89.3 mm(2), 128.9 mm(2), 183.3 mm(2); and for the cohort without any decompression and only cage inserted (n = 75) were 138.3 mm(2), 151.2 mm(2), and 204.1 mm(2) (p < 0.001). Contralateral foraminal area measurements were 73.3 mm(2), 106.4 mm(2) and 120.4 mm(2) in the bilateral decompression cohort; 69.5 mm(2), 99.0 mm(2), 116.9 mm(2) in the ipsilateral decompression cohort; and 75.1 mm(2), 106.5 mm(2), 122.9 mm(2) in the cohort without any decompression (p < 0.001). CONCLUSION: Indirect decompression of both the spinal canal and the contralateral foramen can be achieved via EPTLIF. Decompression on an asymptomatic contralateral side is not necessary.