Background

Discogenic back pain is a major dilemma facing both patients and practitioners alike. Patients experiencing discogenic low back pain, with or without radiculopathy, often find themselves with few effective therapeutic options. Pharmacotherapy is frequently insufficient to resolve symptoms adequately and fails to address the pathophysiology of the disease. Surgical intervention is often indicated, but patients fear the long term sequelae associated with operative procedures. Selective Endoscopic Discectomy (SED) allows practitioners to offer a minimally invasive, definitive treatment for lumbar disc herniations and annular tears.

Purpose

SED is a minimally invasive spinal surgical technique, performed with FDA approved endoscopic surgical instruments, allowing surgeons to address both lumbar disc herniations and annular tears. It has been well documented as a safe treatment with a high degree of efficacy in the short term₁,₂. This study extends the length of the postoperative follow-up in order to further demonstrate the procedure's benefit. Patients representing up to a six-year post operative timeframe are included in these data.

Study inclusion procedure/participant demographics

This is a retrospective study of patients operated upon by Michael A. Steingart, DO over a six year period from 05/1999 through 11/2005 with a mean post-operative timeframe of 2 years. Patients were mailed a questionnaire requesting subjective information concerning pre and post operative pain levels as well as their pre and post operative functional status. Respondent patients' subjective data was augmented with objective data collected from patient charts. Patents that did not respond to the questionnaire were included if subjective pain level data could be attained from their charts as reported during encounters. Their objective information was also retrieved from the charts. A total of 155 patients' data are represented in this study.

Objective Data

The patients varied in age from 18-71 at the time if surgery with a mean age of 43. There were 90 male and 65 female patients in the study. Patients had BMIs ranging from 15-50 with a mean of 29. 29 (19%) patients had histories of prior surgery. 10 (6%) had the SED procedure repeated. Of those 10, 7 (70%) had post operative trauma leading to the repeated procedure. 5 (3%) patients had diagnoses of spinal stenosis, 35 (23%) were smokers, 7 (5%) had spondylolysis, 14 (9%) had degenerative disc disease, 8 (5%) had fibromyalgia, 9 (6%) had epidural fibrosis, and 2 (1%) had scoliosis. 3 (2%) had chronic depression, 6 (4%) experienced a post operative fall, and 2 (1%) had histories of narcotic pain medicine abuse.

No patients were operated with L1-L2 pathology. 5 (3%) were operated at L2-L3. 34 (22%) were operated at L3-L4. 99 (64%) had L4-L5 pathology. 86 (55%) were operated

at L5-S1. 82 (53%) patients were operated with 1 or more herniations. 83 (54%) were treated for annular tears. There were 11 (7%) patients with both a tear and a herniation.

The smallest disc extraction amounts were 1 gram for L2-L3, 0.3 grams for L3-L4, 0.2 grams for L4-L5, and 0.1 grams for L5-S1. The largest extraction amounts were 8.7 grams for L2-L3, 8.7 grams for L3-L4, 9.7 grams for L4-L5, and 11.6 grams for L5-S1. The mean disc extraction for L2-L3 was 4.9 grams, L3-L4 was 3.4 grams, L4-L5 was 4.4 grams, and L5-S1 was 4.2 grams.

99 procedures were conducted for right sided pathology, 118 for left sided and 7 for central pathology.

Subjective Data

Patient reported pre operative back pain levels had a range of 0-10 with a mean of 8.98. Pre operative leg pain was reported to have a range from 0-10 with a mean of 8.67. Post operatively, back pain was reported to range from 0-10 with a mean of 3.36. Post operative leg pain was reported to also range from 0-10 with a mean of 2.47.

31 (20%) patients reported that they were not able to work pre operatively and had no work status change post operatively. 4 (3%) improved from no work pre operatively to partial duty post operatively. 26 (17%) improved from no work to full duty work following surgery.

2 (1 %) patients were on partial duty pre operatively but were not able to return to work following surgery. 1 (<1 %) had no change from partial work status after surgery. 15 (10%) patients were able to return to full work status following surgery from partial duty pre operatively.

4 (3%) reported that they were able to work pre operatively but were unable to return to work post operatively. 67 (43%) were able to work full duty both pre and post operatively.

5 (3%) reported that they were retired and therefore were not included in any work status data.

10 (6%) of the patients reported no improvement of either back or leg pain post operatively.

Only one (<1 %) patient reported an increase of leg pain post operatively while no patents reported increased back post operatively.

Interpretation

Figure 1

Figure 1

Patient data extending up to six years post operatively demonstrates that pain resolution appears to be lasting, at least through that timeframe.

Figure 2

Figure 2

Figure 3

Figure 3

125 (80.6%) of the patients were between the ages of 30 and 60. However, there were no noticeable trends relating to age and efficacy. The surgery achieved a mean improvement in back pain from 8.98 to 3.36 on a scale of 1-10 (62.2%). Back pain improved from a

mean of 8.76 to 2.47 (71.5%). It appears that patients experienced more significant pain resolution in the legs than in the back.

Figure 4

Figure4

The most common co-morbidity encountered in the population was excessive weight (n=115). 61 (39.3%) of the participants were in the overweight class, 34 (21.9%) were considered obese, and 20 (12.9%) were morbidly obese. One (<1%) patient had a BMI of 50. There was no appreciable difference in post operative pain reduction between those in the weight co-morbid group and the general population.

The second most common co-morbidity was smoking (n=35). Smokers averaged 8%-10% less pain reduction post operatively than the general population.

Epidural fibrosis (n=9) appeared to have the largest impact on outcome. Those with epidural fibrosis achieved 64.9% less pain reduction in the back and 74.7% less in the legs that the general population. However, those patients still did receive some symptomatic benefit from the procedure.

Of the 11 patients that reported no improvement or worsening of symptoms, 5 (45%) had epidural fibrosis, 3 (27%) had DDD, 3 (27%) had BMI values of >35, and 5 (45%) were reported smokers.

Figure 5

Figure 5

Men and women both showed improvement in pain post operatively, however men reported a greater improvement that women did. Because the pain data was self reported, its subjective nature makes it hard to assess whether this difference is actual or perceived. This pattern was consistent throughout the population sample though.

Figure 6

Figure 6

Patients in general appeared to improve regardless of the number of pathologic levels addressed. There was however, a noticeable downward trend in outcomes as the number of levels operated increased.

Figure 7

Figure7

The mean amount of disc removed during the SED procedure was 4.18 grams (SD 2.46). There were 40 (18%) levels operated upon with the amount removed being more than 1 SD below the mean, 78 (35%) levels less than 1 SD below, 77 (34%) levels less than 1 SD above the mean, and 30 (13%) levels more than 1 Sd above the mean. The largest amount removed was 11.6 grams while the smallest removal was 0.1 grams. The data shows that patients with larger amounts of disc removed had more significant improvement.

Figure 8

Figure 8

Patients with lumbar herniations experienced greater reductions in both back and leg pain when compared with patients with annular tears. There was some crossover in patients presenting with dual pathology. Those results are included in both data sets.

Conclusion

Selective Endoscopic Discectomy is a safe and effective procedure when performed by a trained surgeon. While herniations were more successfully treated, it is clearly beneficial in the treatment and management of both herniations and annular tears. Patients overall experienced a significant improvement from the procedure. There were a few groups however, that did not receive as great a reduction in symptoms as did others. Primarily, those with epidural fibrosis, spinal stenosis, and chronic pain disorders tended to have more modest results. These conditions are not a contraindication to the procedure though as all groups did benefit from the surgery. Of particular note is the fact that weight did not seem to impact the procedure's success.

It is also evident that surgeries involving larger amounts of disc removal had a greater success. The reason for the improved results is not known. Patients with single level pathology experienced more improvement than those with multiple level defects. Patients of all ages have similar success rates as did both male and female candidates. The effects of the surgery appear to be long lasting and can be considered definitive. As long as realistic expectations and careful candidate selection and evaluation are performed, surgeons and patients alike can have confidence in the SED procedure.