Abstract

Objective: Recurrent disc herniation after lumbar discectomy is a significant problem that may necessitate repeated surgical intervention. Traditionally, it has been advocated to perform a complete or radical lumbar discectomy in an attempt to reduce the chance of reherniation. However, radical discectomy has shown to be associated with collapse of disc space, instability, and chronic back pain. Although, limited discectomy is expected to have some role in maintaining stability and preventing collapse, it has shown higher rate of reherniation. The higher rate of reherniation is thought to be associated with remnant loose disc pieces in the disc space, and relatively large annular defect for removing the disc. We report our short term experience with the use of Micro IITM nucleotome kit (Clarus Medical, LLC, MN, USA) for discectomy. The procedure was expected to have some benefit in removing loose pieces inside the annulus with small annular incision, thus reducing the chance of reherniation. Material and Methods: Thirty-seven patients (16 male and 21 female) who underwent discectomy with automated open lumbar discectomy (AOLD) technique, in one side of single level, between November 2006 and February 2007 were enrolled in this study. The patients were evaluated by the preoperative and postoperative Visual Analogue Scale (VAS), Oswestry Disability Index (ODI), and presence or absence of recurrent disc herniation during the follow-up. Results: The average follow-up period was 10.9 months (range, 9.2-13 months). The average ODI dropped from 61.95 to 20.7%, the VAS for leg pain from 8 to 1.67, and the VAS for back pain from 5.32 to 2.5. There was no recurrence of disc herniation during the follow up. Conclusions: AOLD has shown to be an efficient procedure in preventing early recurrent lumbar disc herniation. The procedure is expected to be an alternative to make up for the weakness of conventional limited discectomy in terms of reherniation. A further long term follow-up with larger population is needed.

Sources of support

This study was supported by a grant from the Wooridul Spine Foundation.

Introduction

Reherniation rates following discectomy has been shown in previous studies from 7 to 26%. 3,9,16,22,25,33,35,36 It is usually associated with relapsing back and leg pain and may necessitate repeated surgical intervention, such as further disc excision with or without interbody fusion. 20,21 Historically, it has been advocated to perform a radical discectomy, including curettage of endplates in an attempt to leave no source for reherniation. 6 As this ‘conventional' procedure showed many postoperative problems such as disc space collapse, destabilization, and resulting chronic back pain, a subtotal discectomy has been introduced. Subtotal discectomy removed as much disc material as possible without curettage of endplates. Spengler 32 later showed a still less invasive method which removed only extruded fragments and loose pieces in the disc space. However, this limited discectomy has shown to be associated with higher recurrence rate, despite its superior outcome than subtotal discectomy in terms of postoperative Visual Analogue Scale (VAS), Oswestry Disability Index (ODI), and required pain medication. 5 Carragee et al. 5 compared 30 patients who underwent subtotal discectomy, with 46 patients who underwent limited discectomy alone. Although, the overall outcome showed more satisfactory results in limited discectomy group, its higher recurrence rate cannot be ignored nor it can be settled simply by preoperative warning. In our opinion, the higher recurrence rate was probably due to the remnant loose pieces in the disc space, and relatively large annular defect for the discectomy. We report our experience of discectomy using Micro II ™ nucleotome kit. The procedure is called automated open lumbar discectomy (AOLD). It was expected to have some benefit in reducing the recurrence rate, by its small annular incision and automated removal of loose pieces inside the disc space. The purpose of this study is to evaluate short term result of AOLD in terms of recurrence of the disc. The techniques of AOLD are also introduced.

Materials and Methods

Thirty-seven patients who underwent discectomy with AOLD technique between November 2006 and February 2007 were evaluated retrospectively. There were 16 men and 21 women, and their mean age was 50.8 years (range, 25-79 years). All patients were treated conservatively for average 3.5 months (range, 1 week-20 month) before the surgery. All patients had preoperative magnetic resonance imaging and computed tomography scan. The inclusion criteria for the study was soft disc herniation in one side of single level, without severe stenosis, spondylolysis, or spondylolisthesis. Disc herniation in multiple level, or bilateral disc herniation were excluded in this study. All surgeries were performed by 2 surgeons.

Results

The levels of disc herniation were L2-3 (3 cases), L3-4 (4 cases), L4-5 (18 cases), and L5-S1 (12 cases). Seventeen of thirty-seven patients presented with preoperative leg weakness including one foot drop. Five patients had previous spinal surgery in other level or other side. Two patients had history of discectomies at the same side of same level, and had recurrence of the disc. There were 26 noncontained disc and 11 contained disc. Fourteen demonstrated upward or down ward migration of the disc.

A dramatic drop in the intensity of pain was noted in all operated patients. The average VAS for leg pain and back pain dropped from 8 to 1.67, and from 5.32 to 2.5 respectively. The average ODI dropped from 61.95 to 20.7%. The mean follow-up period was 10.9 months (range, 9.2-13 months). There was no decrease in disc height in the X-rays followed during the period of this study. There were no major postoperative complications and no recurrence of the disc.

Discussion

The recurrence of back or sciatic pain after primary discectomy can be caused by a true recurrence of disc herniation, new disc herniation at a different disc, epidural fibrosis, local arachnoiditis, facet syndrome, secondary spinal stenosis, instability, and spondylodiscitis. 10,11 The definition of recurrent disc herniation has varied among the different authors. It was sometimes defined as the disc herniation developing in the same level as the prior discectomy, either on the same or the opposite side, whereas other authors included the herniation at a new level. 2,7,8,12,13,15,17,19,20,30,34 Whether we classify the disc herniation of the opposite side, or new level, into the recurrence of disc or not, the most troublesome recurrence is the recurrence of disc at the same level and side of prior discectomy. The source of recurrent disc is the remnant disc of previously operated level. In an attempt to leave no remnant disc, historically a radical discectomy which includes curettage of endplates has been performed. Since it has shown to be associated with disc space collapse, instability, and resulting chronic back pain, less destructive discectomies are being performed in most of the institutes these days. Some prefer subtotal discectomy which removes as much disc as possible without endplate curettage, while others prefer limited discectomy which removes extruded fragment with or without removal of loose disc pieces inside the annulus. The limited discectomy is expected to have some role in mechanical stability and reducing postoperative back pain. However it is also true that many surgeons have avoided this procedure in fear of recurrence of the disc. Barrios et al. 3 reported that in the 75 patients who underwent a subtotal microdiscectomy, 5 (7%) went on to have reherniation and recurrent symptoms over 3 years of follow-up. Carragee et al. 5 prospectively observed their 30 patients undergoing subtotal discectomy, and compared them with a historical cohort of 46 patients treated with limited discectomy alone. The reherniation rate in the limited discectomy group was 18 versus 9% in the subtotal discectomy group at follow-up. 5 However, despite a higher reherniation rate, patients in the limited discectomy group had significantly better VAS (back) and ODI scores at 6 and 12 months (no difference in 2 years), and required less pain medication after surgery. The limited discectomy group also showed significantly shorter convalescent period and continuation of work in heavier occupation categories with less restriction. However, considering all these results, a limited discectomy is still a challenging choice for a surgeon because of its high risk of recurrence. The reherniation of disc, especially in early postoperative period, is one of the most upsetting complications for both the surgeon and patient. In many times, it is not a problem that can be settled simply by preoperative explanation of overall results, or by warning about the potential for reherniation.

Besides the insufficient removal of disc, there is another factor that seems to influence the rate of recurrence. Carragee et al. 5 reported reherniation rates seen with specific annular defect types in their series of 187 limited discectomy patients. The overall reherniation for all subjects was 6.1%. The highest rate of reherniation occurred in large or massive annular defect. These defects, measuring > 6 mm, showed a recurrent rate of 27.3%. 4 Cinotti et al. 8 found that 42% of patients with recurrent disc herniation related the onset of radicular pain to an isolated injury or to a precipitating event. It was different from primary disc herniation, where a constitutional weakness of annular tissue, exposure to repetitive lifting, exposure to vibrations, and smoking were the risk factors for herniation. 1,23,28 Suk et al. 34 reported in their series of 28 patients with recurrent lumbar disc herniation, that 32.1% of the patients related the onset of radicular pain to a traumatic event. The authors of these studies explained that the annular incision performed at surgery made the operated disc more susceptible to sudden prolapsed, particularly under conditions of mechanical overload experienced during sports activity or lifting. 8,34

Therefore, according to literatures, reherniation of the disc after discectomy may be influenced by both insufficient discectomy and large annular defect. For years, we have sought a way that could make up for the demerits of both subtotal discectomy and limited discectomy. Theoretically, if the loose pieces inside the annulus could be removed sufficiently without making a large annular defect, the rate of reherniation would be lowered. In the discectomy using AOLD technique, the annular incision is as small as 3 mm. It is smaller than incisions usually needed for limited lumbar discectomy. In conventional limited discectomy, it is necessary to retract the traversing nerve root, since the loose pieces inside the disc space are usually connected with annulus near the midline. To remove these loose pieces, it is also inevitable to incise the medial portion of the annulus. In AOLD, the Micro II ™ nucleotome kit is inserted through the small hole which is less than 3 mm. Without further incision of the annulus, it can remove the loose pieces in the midline, or even in the contralateral side. Early studies by Key and Ford in 1948 and Smith and Walmsley in 1951 demonstrated that the outer annulus, having a small surrounding capillary network, had a healing process whereas the avascular inner annulus showed little or no healing. 24,31 Therefore, less invasive disruption of the posterior annulus would cause less disruption of blood supply and would improve subsequent disc healing. 26 Another merit of AOLD technique is its circular shape of annular incision as well as its size. In a finite element model comparing the influence of four annulotomy type (square, circular, cross, and slit) on motion segment stiffness and its subsequent increased external load transfer to facet joint, the large increase in facet load was produced in square and cross type while the smallest increase occurred by the circular incision. 29 Use of CO2 laser in AOLD technique, also has some benefit over use of pituitary forcep. After the automated aspiration using the nucleotome kit, the rest of loose pieces can be identified through the annular hole, by compressing the disc space from above. The use of pituitary forcep to remove these pieces, inevitably causes further damage to the annulus. By removing these pieces with CO2 laser, further enlarging of the annular hole can be avoided. In our series, though the follow-up periods were short, the height of disc space was maintained in all patients during the follow-up. Lee et al. 27 reported, in their retrospective review of 45 patients who underwent CO2 laser dissection followed by automated lumbar discectomy, that the procedure induced minimal disc height collapse with benefit of early discharge, early return to work. The mean disc height index decreased from preoperative 0.301 to postoperative 0.268 during the mean follow-up period of 31.2 months. 27 Our concept of discectomy is to remove the extruded disc as well as all the degenerated loose pieces inside the annulus, with least damage to the annulus and without further damage to the healthy nucleus. Our senior author (Lee SH) proposed to call this concept ““herniectomy””. Use of AOLD technique is expected to enable this herniectomy. There was no recurrence of disc during average 10.9 months of follow-up. Of course, the follow-up period is not long enough to judge the true efficacy of our procedure. A further follow-up with larger population should be performed. However, according to Conolly 9 who reported a 10.4% of recurrent disc herniation rate at 5 year follow-up in a retrospective study of 182 patients, the recurrences occurred as early as within 6 months of surgery in 74%. In addition to its frequentness, early reherniation of the disc is usually one of the most embarrassing situations that surgeons are concerned about. From this point of view, our short term result of AOLD in terms of recurrence rate, is meaningful enough.

Conclusion

After the removal of extruded fragments, the use of AOLD technique is supposed to remove loose pieces inside the disc space, with least damage to the annulus. The procedure has shown to be efficient in prevention of early recurrence of lumbar disc herniation. It is expected to be an alternative to make up for the weakness of conventional limited discectomy in terms of reherniation. A further long term follow-up with larger population is needed.

Correspondence to

Sang-Ho Lee, M.D., Ph.D. Department of Neurosurgery Wooridul Spine Hospital 47-4 Chungdam-dong, Gangnam-gu Seoul, 135-100, Korea Tel: +82-2-513-8151 Fax: +82-2-513-8146 E-mail: shlee@wooridul.co.kr

References