COMPARATIVE STUDY ON THE TREATMENT OF DISC HERNIATIONS

Objective: To compare the results of treatment of patients with low back pain and radiculalgia resulting from disc herniation associated with disc degeneration through instrumentation with pedicle screws and dynamic rod, with root release and without diskectomy compared with other non-instrumented techniques (microdiskectomy with or without foraminotomy). Methods: This is a retrospective descriptive study of interventions for patients with herniated discs in the Traumatology and Neurosurgery that used the following variables: age, sex, type of technique, surgical time, time of evolution, degree of satisfaction, and complications. Two groups were formed: instrumentation with dynamic rods and non-instrumented techniques, comparing the results of each group. The software used was the SPSS v20.0. Results: We presented 142 interventions carried out between 2009 and 2012, 86 with dynamic instrumentation and 56 by other decompression techniques without instrumentation. No statistically significant differences were observed between age and sex groups and time elapsed until intervention. We found statistically significant differences (p=0.001) in surgical time, which was lower in the instrumented technique. No significant differences were found in complications between the techniques in both re-operations and in infections. Conclusions: In this study, we found no significant differences between the use of instrumentation with dynamic rods with respect to other non-instrumented surgical techniques in the treatment of herniated discs over 6 months of evolution or the complications and the degree of the patients’ satisfaction. Keyword: Intervertebral disc displacement/therapy; Diskectomy; Pedicle screws.


INTRODUCTION
Chronic back pain is one of the greatest problems related to decreased quality of life of the patient.Nonetheless, the surgical approach to disc hernias of more than six months of evolution, associated with degenerative discopathies that do not respond to conservative treatment, continues to be a challenge. 1e often encounter studies in scientific journals that present poor disc hernia surgery outcomes within the context of degenerative pathology, and even with no degenerative pathology, in cases where they have evolved over time. 2 Thus, the concept of postdiscectomy syndrome has emerged to define a clinical profile of the recurrence of lumbar and radicular pain related to periradicular fibrosis, instability of the operated segment, degeneration of the segment, etc. 3 Distinct surgical techniques have been developed to treat this problem, among which is included dynamic stabilization of the operated segment. 4The goal of this technique is to stabilize the segment, without fusion in order to reduce mobility and also to reduce and/or prevent postsurgical degeneration. 5,6Other indications, not addressed in this study, are used to prevent the adjacent segment syndrome, only applicable in cases of fusion with or without instrumentation. 7ur objective is to compare the results of treatment in patients with low back pain and radiculalgia secondary to a herniated disc associated with disc degeneration, using instrumentation with pedicle screws and dynamic rods, releasing the root without discectomy, with those of the other technique still considered the gold standard for disc surgery, microdiscectomy with or without foraminotomy.Given that we compared two different techniques, we analyzed whether the impingement of the intervertebral disc, a recognized cause of the onset of fibrosis, 8 and whether laminectomy and/or foraminotomy, possible causes for segmental instability, 9 would have better clinical outcomes in reducing possible postlaminectomy segmental instability than to not carry out discectomy and than the use of dynamic stabilization.

METHOD
This was a retrospective review of the surgeries performed in patients with disc herniations by the Traumatolgy and Neurosurgery Services from 2009 to 2012.
The variables collected were: age, sex, BMI, type of technique used, surgical time, time of disease progression until surgery, patient satisfaction level (1=poor, 2=average, 3=good, 4=excellent), and the presence of complications (infections, failure of the osteosynthesis materials, reinterventions, follow-up in pain treatment centers).
The study was approved by Institutional Rewiew Board of the Hospital de León (the number of the research protocol was 1622), the patients signed the informed consent form for participation in the study, and all the data was anonymized.
The inclusion criteria were: Patients between 18 and 65 years of age, who suffered from low back pain and radiculalgia secondary to disc herniation associated with disc degeneration at a single level (confirmed by magnetic resonance imaging), and who underwent medical treatment and rehabilitation for at least six months.All the patients were informed about the surgical procedures and signed the informed consent form.We excluded patients with non-lumbar disc hernias or without medical histories, patients with less than six months of disease progression, who had undergone previous surgeries, and who had stenosis, listhesis, segmental instability, infections, tumors, scoliosis, vertebral fractures, or severe systemic illnesses.
We organized the patients into two groups by technique: one group with dynamic rod instrumentation and release of the compressed root without discectomy and the other with simple discectomy.We compared the results obtained in each group.For the statistical analysis, we used SPSS v20.0 software.The level of significance was established at 95%.

Surgical intervention and indication
The patients were operated in the prone position under general anesthesia.They received prophylactic antibiotics with the anesthetic induction and two hours prior to the surgery.The patients who underwent surgery in the Neurosurgery Service received antibiotic prophylaxis 90 minutes before the surgery began.The level to be operated on was determined intraoperatively using a fluoroscope.

Release and dynamic stabilization technique
Pedicular instrumentation system with dynamic rods: The conventional technique without a microscope was used.An incision was made in the skin and then a dissection by planes with an electric scalpel.A foraminotomy or a flavectomy was performed to decompress the nerve root.The procedure continued with the placement of transpedicle screws assisted by a fluoroscope and the dynamic rod was installed.Discectomies or bone grafts (arthrodesis) were not performed in any of the cases.

Simple discectomy technique
Microdiscectomy: An incision is made in the skin, then dissection by planes using an electric scalpel or a cold scalpel and scissors is performed.Once the space is located, it is confirmed using the fluoroscope.From this point on, the procedure continues under the microscope.Once the space where the disc hernia is found, the root is located and the protruding disc and the foraminal disc fragments are removed, and then we move on to the discectomy.The patient receives a vial of extended release corticosteroid and a compound to prevent fibrosis.A foraminotomy is performed in cases where the space is compromised and a laminectomy when there is a disk fragment sequestered inside the channel or in cases of large volume disc hernias.

RESULTS
One hundred and forty-two patients, who underwent surgery between 2009 and 2012, with an average follow-up time of 44 months (ranging from 16-65 months), were included in the study.Instrumentation with dynamic rods was used in 86 patients and other techniques without instrumentation were used in the other 56 patients (18 patients underwent microdiscectomies with foraminotomy and 38, microdiscectomies without foraminotomy).The distribution by sex was 70 males (49%) and 72 females (51%).The average age was 43.67 years (ranging from 21 to 65 years of age) and the average BMI was 25.25 (from 15.4 to 36.9).The average surgical time was 109 minutes (ranging from 45 to 275 minutes).The average clinical follow-up time prior to surgery was 17.9 months (ranging from 6 to 192 months).The most common locations were L4-L5 right (39 patients, 25.7%), L5-S1 left (39 patients, 25.7%), L4-L5 left (35 patients, 23%), and L5-S1 right (25 patients, 16.4%).
We did not observe any statistically significant differences in the composition of the groups in terms of age, sex, time of disease progression until the intervention, BMI, location of the hernia, or duration of postoperative follow-up.Statistically significant differences were observed (p=0.001) between surgical times, with an average of 84 minutes ±22.58) for the dynamic technique and 150 minutes (±38.76) for the discectomies.(Table 1) There were 25 reinterventions (16.4%), 5 infections (3.3%), and 13 referrals to the pain treatment center for follow-up (8.6%).There were no significant differences between the comparison groups either for reinterventions (p=0.344),infections (p=0.447), or for follow-up in the pain treatment center (p=0.706).(Table 2) There was no significant difference either in the levels of patient satisfaction between the groups (p=0.825),averaging higher than 3 in both groups, or in terms of responses to the question about whether they would undergo the surgery again (chi square p=0.103).
The only point where differences were encountered was in the use of corticosteroids prior to surgery, higher in the group of patients without instrumentation (p=0.001).
The population sample with the lowest satisfaction with the surgery (those who left a poor or average rating, who would not recommend the technique, and who would not undergo the surgery again) was a group of 23 patients (65% of whom were women) with an average age of 44 years ±8, slightly overweight (BMI=25.6), with L4-L5 involvement (52%), and being treated with psychoactive drugs (56%).
The main complications reported in the dynamic approach group were residual pain and instrumentation failure, while in the other technique group hernia recurrence and dural injuries were predominant.

DISCUSSION
Degenerative disc disease and disc hernias are the most common problems in patients with low back pain 10 and one of the most common causes of work leave.Nevertheless, the treatment of disc hernias is very controversial and there are a multitude of studies that present contradictory conclusions. 11or example, the results published by Weber 10 reported that prolonged conservative treatment has outcomes after four years of follow-up similar to those achieved through early surgery.After this, several observational cohort studies were conducted that presented worse results from conservative treatment as compared to early surgery.They came to the conclusion that, after two months of sciatica, outcomes from conservative treatment are worse than those from surgical intervention. 12,13All of these results must be viewed with caution because the studies were not based on randomized populations and included patients who did not receive the same analgesic regimens or follow the same recommendations, making the outcomes not totally comparable.
In their observational studies, Nygaard et al. 14 , Ng and Sell 15 concluded that surgery following from eight to twelve months of sciatica produced worse results than surgery performed earlier.However, we must keep in mind that it is difficult to make patients with persistent sciatica wait for 8-12 months of conservative treatment.Furthermore, this study should have been conducted with a randomized population, recording the symptoms as a function of time, as was not the case.
][18] From all these results, we can conclude that early surgery (a clinical history of sciatica for 6-12 weeks) does not lead to better long-term results.The only benefits are a faster decline of the radiculopathy and an earlier recovery.This, however, can be considered a valuable advantage for the part of the population that is unable to, unwilling to, or cannot wait for the natural course of the disease or for the possibility of a delayed surgery if necessary.
The general recommendation is to wait for a period of 6 to 12 weeks after the onset of symptoms, except in cases of cauda equina or rapid loss of motor function. 13,19However, taking all the studies into account, perhaps we should rethink this indication because in our study we excluded patients who had undergone surgery after less than 6 months of progression.
Currently, there are numerous techniques for treating degenerative disc disease with debatable results. 15In the last century, surgical treatment for pain in degenerative disc diseases began with discectomies and decompressions.The first lumbar discectomy was performed by Mixter and Barr 20 in 1934, and became the most used technique.Today, the microdiscectomy, a less traumatic procedure that permits smaller incisions of the skin and muscle tissue, is being performed.The simple discectomy and the microdiscectomy are considered to be the gold standards for the surgical treatment of lumbar disc hernias. 2 However, these techniques have not yielded good results in the treatment of chronic back pain following disc suppression, since low back pain and sciatica persisted in up to 40% of cases, although in only 20% in our sample.
Back pain and sciatica following discectomy may be due to segmental instability and to the concept of chronic degenerative instability. 22,24ormerly, fixation systems were static, but today dynamic stabilization systems are beginning to be used.These devices preserve movement and can be classified as prosthetic or dynamic.With prosthetic devices, the disc, the nucleus, and the facet joints are completely substituted by the prosthesis, replacing the anatomic structure and functions of the lumbar movement segment.These systems are technically more complex, require longer surgical time, and have more complications. 2nstead, dynamic stabilization devices function together with the movement segment, without replacing any anatomical structure.Semirigid fixation is the most commonly used term to describe these devices, a questionable concept and one we do not share since dynamic systems do not produce fusion.In fact, there is no graft involved, it is only intended to offer stabilization without the tension that conventional rigid fixation produces.
The devices restrict movement to a certain extent and allow the load to be shared between the device and the movement segment.For the long-term survival of the device, the loads and the movement must be shared with the device, which complements the kinematics of the segment in motion.If this does not happen, the device can end up failing from overuse (breakage or loosening).This must be avoided since the device must endure for an indefinite period of time.They bring the advantages of easy conversion to conventional stabilization or replacement of parts, compatibility with minimally invasive procedures, and restoration of anatomical lordosis. 25ynamic stabilization is used to eliminate lumbar pain and stabilize degenerated discs.These systems enable a more physiological transmission of forces between the anterior and posterior components of the lumbar spine, while maintaining mobility and controlling abnormal movements in the lumbar segment. 26,27These semirigid stabilization systems restore normal spine functions and protect the adjacent segments. 27,28In our review, there was only one case of degeneration of the adjacent disk.
In our review of the articles that analyze the outcomes of treatments for disc herniations, we observed that there are discrepancies among the scientific works in terms of methodology, surgical outcomes, and follow-up.Perhaps the main issues are data collection bias and the great variability among the individual characteristics of the patients presented by the different studies. 29n our study, the fact that the patients were separated into two cohorts, each of which was operated, treated, and analyzed by a different service was a limitation because the results are not entirely comparable.

CONCLUSIONS
There are no significant differences between the use of dynamic rods and other non-instrumented surgical techniques in the treatment of disc herniations with more than 6 months of evolution in terms of complications or of the level of patient satisfaction.
We did find a statistically significant difference between the

Table 1 .
Comparison of variables between the instrumented technique and discectomy.