Pain improvement and reoperation rate after full-endoscopic decompression for lateral recess stenosis: a 10-year follow-up

Lateral recess stenosis is a common form of spinal stenosis. Its main characteristics are degeneration of the surrounding structures, from the intervertebral disc to the facet joint and the ligamentum flavum. Sciatica is the most common presentation, which can be initially managed with medications and physical therapy [1, 2]. When conservative treatments fail in some patients with severe stenosis and/or motor weakness, surgical management to free the nerve from compression by surrounding structures is essential [1, 2].

To date, there is no consensus on surgical technique for lateral recess stenosis [3‐8]. The most widely used approach is a microscope-assisted partial facetectomy. Other techniques include lumbar fusion, as well as laser-assisted [9] and full-endoscopic [10, 11] decompression, which showed less tissue traumatization, shorter surgery duration, and better patient acceptance [12].

Full-endoscopic interlaminar decompression (FEI) for lateral recess stenosis (LRS) uses a 7.9-mm-diameter probe that contains a working channel of 4.2 mm inside with a 25-degree angled lens at the tip of the probe [12]. All surgical instruments are used through this working channel. The decompression can be done using an interlaminar approach. High-speed burr and cutting instruments cut the bone and ligament that compress the nerve. Continuous irrigation with water and a 25-degree angle lens allows the surgeon to have a clear vision of the nerve and surrounding tissue.

The early evidence was based on a prospective, randomized, controlled study conducted in Germany [11]. Of 161 patients, 95% reported a significant improvement in improvement in pain [11], comparable to the conventional technique, but with less operative time, surgical complications, postoperative pain level, and analgesic requirement [11]. However, the steep learning curve of this technique must be noted [12‐15].

Long-term studies that use the same technique have not yet been conducted. Using our database, this study aimed to share long-term clinical outcomes and reoperation rates.

Our local institutional review board approved the study. One hundred and twenty-nine patients were treated with FEI for LRS during 2009–2013. Study variables such as the Oswestry Disability Index (ODI), Visual Analog Scale (VAS), neurological findings, and complications of all patients with complete records were analyzed.

The clinical and imaging criteria for offering FEI for LRS at our institution are radicular symptoms for more than three months without improvement with a conservative approach or weakness of the muscle supplied by the entrapped nerve root without apparent spinal instability in the flexion and extension films. MRI of the lumbar spine showed lateral recess stenosis with nerve root compression. This procedure was not offered to patients with gross spinal instability or predominant mechanical back pain. All patients have unilateral radicular symptoms. Those with bilateral leg symptoms of central canal stenosis will be studied in another study (Figs. 1 and 2).

Both patients and clinicians measured clinical outcomes. The patient's leg and back pain self-assessment was performed using VAS and ODI in the clinic before the patient met with their doctors. Neurological functions were assessed by clinicians who may or may not participate in the study. Our institute is an international hospital serving both local patients and international patients who fly in for treatment and fly out after treatment is over. The follow-up examination was performed one week, one month, three months, and one year after the operation. International patients received an online questionnaire by email during the same follow-up period. At approximately ten years after surgery (mean follow-up duration 10.05 years (95%CI 9.79–10.32)), 66 local patients received a telephone interview, while 63 international patients received an email with a questionnaire containing the same set of questions as the telephone interview. For simplicity, we asked whether they currently have leg or back pain, whether the pain disturbs their quality of life, and whether they have undergone further fusion or decompression surgery in the lumbar spine or not, if not already indicated in medical records.

Few studies reported long-term outcomes of minimally invasive decompression for spinal stenosis with a follow-up of more than ten years [16]. Most long-term studies followed the patient for 2—5 years [17‐21]. To our knowledge, this study is the first study to report long-term outcomes of full-endoscopic uniportal decompression for lateral recess stenosis with a mean follow-up period of 10 years.

The initial results showed favorable results with a low complication rate (Tables 5 and 6). Most patients reported having no leg pain, and ODI and VAS scores dropped significantly at the initial follow-up. The advantages of FEI-LRS include fewer tissue traumatizations, a short hospital stay, and results comparable to the standard microsurgical technique [11]. Our institute is an international hospital that serves both domestic and international patients. The international patients flew in for treatment and returned home after treatment. Clinical follow-up is challenging for this group as they rarely respond to follow-up emails or phone calls. We saw this as an opportunity to develop a new platform to collect data from these patients for future research and to improve the quality of care. Although our sample size is relatively small, approximately two-thirds of the patients reported having little or no back or leg pain for a very long time and were still satisfied with the results.

The reoperation rate in our group is similar to the previous rate reported in other long-term studies [22‐27]. Two out of 4 cases who underwent fusion surgery underwent it because there was the progression of the spondylolisthesis. Radicular and back pain recurred after two years in one case and after five years in another. On the other hand, out of the 8 cases that were documented for stable grade 1 spondylolisthesis and responded to the follow-up call at ten years, six patients reported having little or no back or leg pain and still had a good quality of life. We selectively perform postoperative scans on individuals who experience back pain or leg pain. We diagnose postoperative spinal instability if the patient develops new mechanical back pain after the FEI-LRS procedure. Similar to most spinal conditions, the patient will undergo a period of conservative treatment and will opt for surgical stabilization only if conservative measures prove unsuccessful. Although many long-term studies showed promising results from decompression without fusion in a group of lumbar stenosis with stable spondylolisthesis [22‐27], more studies with a minimum follow-up period of 10 years could be needed to confirm this finding. One case had a new herniated disc after a traumatic event. Since it happened at the decompressed segment, we offered him a fusion even without spondylolisthesis. Two patients received another decompression surgery a few months and four years after the first surgery at another institute. These two patients did not return to our institute for investigations when pain recurred. This, again, is another challenge in developing a systematic and proactive follow-up measure for quality improvement.

FEI for LRS is an effective procedure for patients with predominant unilateral radicular symptoms. Its benefit can be seen through the 10-year follow-up. A systematic and proactive follow-up strategy should be developed for international patients to increase the follow-up rate.