Risk factors predicting less favorable outcomes in endoscopic lumbar discectomies

Abstract

Background: Endoscopic lumbar discectomy was among the first minimally invasive spine procedures commonly performed. As such, all the benefits of minimal invasion were seen, including less pain, less soft tissue destruction, and faster recovery. While outcomes compare favorably to micro and open discectomy, not all patients fare equally well. This paper examines independent risk factors to assess their correlation to suboptimal outcomes after endoscopic lumbar discectomy.

Methods: Retrospective analysis of clinical outcomes of 55 consecutive patients treated with endoscopic discectomy between June 2018 and March 2019 by the author. Primary outcome measures were postoperative reductions of visual analog score (VAS) for back and leg pain modified MacNab criteria as well as time to narcotic independence. Risk factors examined included smoking, facet disease, adjacent segments disc degeneration, obesity, alcohol abuse, and psychiatric illness.

Results: There were 31 males and 24 females with a mean age of 41.76±12.53. Most patients suffered from contained herniations (49.1%) followed by extruded herniations (18.2%). Follow-up ranged from 6-18 months. The most common surgical levels were L5-S1 level (30.9%), L4-S1 (29.1%), and L4-5 (25.5%). The mean return to work (RTW) was 23.83±26.01 weeks. The average body mass index (BMI) was 29.11±4.75. The average time for narcotic independence was 9.64±7.29 days. MacNab outcomes showed that 47.3% (26/55) had excellent, 36.4% good (20/55), 12.7% fair (7/55), and 3.6% had poor (2/55), respectively. The VAS scores for the back (7.69 to 2.65) and leg (6.78 to 2.65) pain reduced significantly (P<0.0001). Smoking (P=0.048), psychiatric disease (P=0.029), disc herniations larger than 10 mm, facet disease, obesity (BMI >30), diabetes, and alcohol abuse was associated with fair and poor MacNab outcomes.

Conclusions: Endoscopic lumbar discectomy safely and reliably reduces axial pain and radiculopathy from lumbar disc herniations. Risk factors associated with incomplete pain relief are large herniations, obesity, instability, smoking, advanced facet degeneration, and decreased ability to cope with the surgery.

Keywords: Endoscopic discectomy; outcome; risk factors.

Figure 1

Age distribution of endoscopy patients examined for risk factors of less favorable outcomes after the outpatient decompression procedure. The black line indicates the expected normal distribution of the patients’ age. Std., standard; Dev., deviation.

Figure 2

The quantile-quantile plot of the age of endoscopy patients examined for risk factors of less favorable clinical outcomes following the outpatient transforaminal decompression procedure. The average age was 41.8±12.5 years ranging from 18 to 71 years.

Figure 3

Exemplary case of a 61-year-old male complaining of low back pain and right lower extremity radiculopathy to the foot both level 8 in severity 3 months after a motor vehicle accident. The patient suffered from facet joint degeneration and had a history of alcohol abuse and had a BMI of 28. Physical examination revealed loss of lumbar lordosis, paraspinal muscle spasms, tenderness over the lumbar facet joints, and decreased range of motion to flexion and extension. The patient had a positive straight leg raise on the right side. (A,B,C) The MRI scan showed L3–4 disc bulge with facet fluid and hypertrophy, L4–5 left paracentral herniation with annular tear and bilateral facet hypertrophy, and L5–S1 left paracentral disc herniation with facet degeneration and fluid suggestive of instability; (A,B) the axial cuts also suggested foraminal stenosis noted at L4–5, L5–S1 due to facet degeneration. Initially, the patient was treated with a left-sided endoscopic discectomy at L4–5 and L5–S1; (D,E) intra-operative findings showed large annular tears with annular insufficiency. The postoperative course showed no relief of axial pain and dysesthesia radicular pain due to irritation of the dorsal root ganglion; (F,G) this patient had three risk factors: large annular defects, facet degeneration, stenosis. Ultimately, an ALIF was performed to lessen both axial and radicular pain. BMI, body mass index; MRI, magnetic resonance imaging; ALIF, anterior lumbar interbody fusion.