coflex device, interspinous spacer, lumbar microlaminectomy, neurogenic intermittent claudication., spinal stenosis
M Eldin. Coflex- Augmented Lumbar Microdecompression / Microlaminectomy(Comparative Pilot Study(. The Internet Journal of Minimally Invasive Spinal Technology. 2012 Volume 5 Number 1.
Degenerative lumbar canal stenosis (LCS) is a dynamic pathology where symptoms increase in extension (standing and walking) and relieved in flexion (standing flexion or sitting). Standing and walking narrows the foramina and spinal canal resulting in entrapment; whereas sitting increases the area relieving entrapment. The primary level affected is L4–L5, followed by L3–L4, L5–S1, L2–L3, and L1–L2.5,8,11,15,32,41 Patients with no motor deficits or sphincteric troubles are generally treated conservatively for an adequate time interval up to 3 months. Failure of conservative treatment is the indication of intervention. Depending on the pathological components in the affected motion segment, surgical decompressive options include laminectomy, laminotomy, foraminotomy, micro- or interlaminar decompression. In addition, fusion may be indicated in cases where the motion segment is seen to be unstable. Turner et al. (1992) analyzed the success rate of decompressive surgery for lumbar spinal stenosis of many studies and reported a mean rate of good to excellent outcomes of 64% in the first year.2-4,7,12,13,17,31,38
The concept of motion segment preservation and soft tissue preservation and the increasing number of patients with degenerative spinal disease warrant the need of new approaches and devices. As an alternative to conservative treatment and decompressive surgery, other treatments have been developed for patients suffering from LCS, including micro-techniques and many interspinous devices.1,3,5,6,10,14,16,20,21,23,25,29,30,35,39,42 During the surgical micro-decompression, the thickened bones and ligaments are removed, in a minimally invasive approach called microlaminectomy, re-establishing the normal diameter of the spinal canal. Advantages of the decompression / microlaminectomy procedure include that it can be done under local anaesthesia (in risk patients), standing up and walking is possible few hours after surgery, and patients can go home after 1 or 2 days.3,14,25,26,33,35,39,42 In case of mild to moderate stenosis, as the 'minimallest' surgery, a coflex spacer can be implanted between the spinous process in height of the spinal stenosis. Because spacers allow for minimal tissue resection, making the procedure less invasive, their application is likely to be beneficial. Coflex device between the spinous process in height of the spinal stenosis can provide biomechanical strengths and dynamic stabilization without motion segment fixation, presenting a good alternative procedure. The augmentation of decompression / microlaminectomy procedure with a Coflex spacer leads to dilatation of the neural foramen & the diameter of the spinal canal, restriction of extension, reducing the pressure in the posterior annulus and can, thus, eliminate the complaints.5,6,10,16,21-25,30,32,34,36,37,40,43
This study was conducted because over 35,000 people outside the U.S. have been implanted with the coflex device. Early clinical results for the coflex, in Germany reported 86 % relief in LBP that allowed patients to significantly increase their walking distance, together with reduced post-operative disability and pain scores as compared with pre-operative scores.10,30,43 This study is a multi-center, prospective, controlled study that compares the 1-year clinical and radiological results of lumbar minimally invasive microdecompression / microlaminectomy augmented with the implantation of the coflex device as compared to the microdecompression / microlaminectomy approach alone in treating patients with LCS. We selected patients older than 40 years of age with degenerative segmental stenosis & neurogenic claudication.
Materials And Methods
Our study is a multi centre prospective, case controlled study, done in Egypt to evaluate the 1-year results of lumbar minimally invasive microdecompression microlaminectomy alone as compared to those augmented with the implantation of the coflex device in treating patients with LCS. The Coflex implant is a functionally dynamic interspinous implant (U-shaped titanium). From June 2008 until December 2009 we included 50 patients within this study. Median follow-up was 10.5 months. At the time of follow-up all patients had questionnaires, clinical examination and x-ray taken.
Cases were classified into 2 groups, A and B. Group A (Microlaminectomy-Coflex) includes 25 cases treated with microdecompression / microlaminectomy augmented with the implantation of the Coflex® Dynamic Interspinous Device (Paradigm Spine GmbH, Germany). Group B (Microdecompression-alone) includes 25 cases treated with isolated decompressions. Whether the Coflex device would be inserted in addition to decompression or whether decompression alone would be performed was decided preoperatively according to patients' predilection and their economic state. We evaluated the clinical and radiological outcomes of Coflex inserted patients and compared the results with those of the patients in the decompression alone group. Cases in both groups exhibited comparable clinical parameters concerning age, sex and operative levels addressed mostly the L3-L4 and L4-L5 interspaces.
(Fig. 2, 3)
The procedures were done by, or under direct supervision of a single consultant neurosurgeon. The patients had the procedure done either under spinal anesthesia with or without sedation, or under a light general anesthetic. Patients were placed on a radiolucent table in the prone position, on surgical nonmetallic frame avoiding hyperlordosis of the spinal segment(s) to be operated upon. A neutral position or a slight kyphosis may be advantageous for surgical decompression as well as for appropriate interspinous distraction. The level to be treated is identified by fluoroscopy.
The incision is closed in anatomical layers. The drain is not routinely utilized. The procedure is typically performed in less than an hour. Postoperatively, patients are mobilized the night of surgery, after complete recovery from anesthesia and discharged within 2 days, with external brace for 4 weeks postoperatively.
Data were collected preoperatively and postoperatively at 1week, 1 month, 3 months, 6 months and 1 year following surgery. Patients were asked to grade their low-back and leg pain using the numeric verbal rating (NVR) scale for pain. Patients were asked about their satisfaction with the surgical procedure using the validated outcome measurement specific to lumbar spinal stenosis, namely, the Oswestry Disability Index Questionnaire (ODI).2,4,18,28 The differences in the patients' preoperative and postoperative condition were compared between groups.
The numeric verbal rating (NVR) scale for pain intensity is a self-report tool for evaluation of a patient’s subjective pain. NVR scale means a numeric representation of pain, with “no pain” anchored at one end of the scale, marked as zero and “worst possible pain” anchored at the other end, marked as 10. The patient is asked to mark where the pain intensity falls along the continuum, marking his pain into number. Then according to the results of NVR scale, patients were categorized into 4 categories: pain free (0), improved pain (1-4), fair (5-7), and bad (8-10) categories. Significant relief was defined as pain relief of 50% or greater; otherwise it is non-significant (less than 50%). Significant pain relief includes patients in the pain free & improved pain categories, while non-significant pain relief includes patients in the fair & bad categories. Duration of pain relief was judged to be short-term, if relief was less than 6 months. If relief lasted for at least 6 up to 12 months, it was considered long-term. Success was defined as all of the following: 1) no or minimal remaining pain; 2) work not adversely affected; 3) no use of analgesic medications; and 4) patient satisfaction with the procedure.18,28 Activities of daily living (ADL) were also assessed, on a 4 point scale: excellent (4) in patients with no symptoms; good (3) in patients with symptoms but no problem in ADL; fair (2) in patients with some problems in ADL; and poor (1) in patients with major problems in ADL.
The Oswestry Disability Index (Oswestry Low Back Pain Disability Questionnaire) is an extremely important tool that we use to measure a patient's permanent functional disability. The test has been around for more than 25 years and is considered the “gold standard” of low back functional outcome tools. It simply answers some questions by choosing the 'best answer' that describes the 'typical' pain and/or limitations within the last week or two; and score answers with points. After finishing the questionnaire, add up points, divide that number by 50, and multiply by 100 to get the percent disability. ODI scoring 0% to 20% means minimal disability (patient can cope with most living activities, no treatment is indicated apart from exercise), 21%-40% moderate disability (patient experiences more pain and difficulty with sitting lifting and standing, patient managed by conservative means), 41%-60% severe disability (pain remains the main problem, activities of daily living are affected, require a detailed investigation), 61%-80% crippled (back pain impinges on all aspects of the patient's life, intervention is required), and 81%-100 are either bed-bound or exaggerating their symptoms.28
At each follow-up visit, pain and function evaluations is performed to confirm the absence of complications. Clinical outcome scores and incidence rates of adverse effects, device failures, and revision surgeries, if any, are calculated.
Radiological Outcome & Image Interpretation
Postoperatively a follow-up MRI scan is done at 3 months. X-rays are done at 1 week, 3 month and one year visits. Follow-up X-ray films are analyzed to confirm maintenance of distraction and the absence of device-related radiological complications. To compare the results between the two groups pre- and post-operatively, the changes in the disc height, endplate angles, and dynamic lumbar movement were assessed. Distances were measured between the most anterior or posterior points on each vertebral body, excluding osteophytes. Endplate angles and foraminal height were measured. Endplate angles were measured on the images between adjacent vertebral bodies at the treated level. The differences in the patients' preoperative and postoperative images were compared between groups. There were no significant differences in preoperative state of the radiologic parameters between groups.
The clinical and radiologic results of the patients in the device inserted group were compared with those of the patients in the decompression alone group.
From June 2008 until December 2009, 50 patients with mild to moderate spinal stenosis were treated, 22 (44%) male, 28 (56%) female. The most prevalent diagnosis for intervention was segmental stenosis. Fourty six out of 50 patients in the study had a segmental form of stenosis, (discogenic, liganentous, bony, or mixtures), four cases had mild degree of degenerative retrololisthesis. All decompression alone group cases were segmental stenosis cases. The rest of the cases, including those with mild retrolithesis, were included in the Coflex group.
The average length of follow-up was 10.5 (range 6 to 16) months and the average age at the time of the operation was 45 years (range 40 to 72). The mean age of the patients in the Coflex group (A) was 46.9 years (range 40-72 years), and the mean age of the patients in the micro-decompression alone group (B) was 50 years (range 40-65 years). Twenty-two out of 25 patients had the Coflex implanted at 1 level (mainly L4-5, or L3-4). There were two implantations at the L5- S1 level in the study. Three out of 25 patients had the Coflex implanted at 2 levels.
The mean pre- and postoperative VAS scores were 7.2 and 2.2, respectively, in Group (A), and 8.8 and 3.4 in Group (B). Both groups of patients showed significant improvement in their VAS and ADL scores in comparison with their preoperative scores. A significant number of patients showed pain relief in both groups. Preoperatively, in Group (A) 18 out of 25 (72%), & in Group (B) 20 out of 25 (80%) patients had moderate or severe low back pain (LBP), respectively. Early postoperative assessment showed that the LBP disappeared in12 out of 20 (60%) in Group (A), and in 12 out of 18 (72.2%) in Group (B). The rest of patients did improve with time. The mean severity of LBP in Group (A) mostly disappear, and in Group (B) decreased by 75% (from moderate to mild) at the 1-year follow-up. Mean preoperative walking distance was < 1000m in 24 out of 25 (96%) in Group (A), and in 22 out of 25 (88%) in Group (B). Postoperatively all cases in both groups (100%) patients could walk >1000m. Significant pain relief (> 50%) in months was calculated. The short-term pain relief outcome, which was assessed 3 months after the operation, indicated a success rate (significant pain relief) 88% in Group (A) and 93% in Group (B). However, late follow-up which was assessed 12 months after the operation indicated a success rate of 97% in Group (A) and 82% in Group (B). Significant pain relief was manifest in both groups at early follow-up visits. The results of pain relief throughout the study were best at early follow-up visits in Group (B), and in late follow-up visits in Group (A). Regarding Coflex, follow-up visits did show an increase of patient’s satisfaction, and twenty two patients (92%) stated that they would undergo this surgery again. According to the questionnaires, 23 (92%) patients were satisfied or very satisfied; only 2 patients (8%) were not totally satisfied. The mean preoperative ODI score was 60 (range 30 to 80). The mean postoperative ODI score was 10 (range 0 to 30).
Coflex is a relatively new, but already documented motion-preserving implant. Its addition to the microlaminectomy procedure was shown to be superior to microdecompression surgery alone in this pilot study performed in Egypt, in mild-to moderate neurogenic intermittent claudication patients. A total of 28 devices were implanted in 25 patients. The Coflex group had a comparable early and significantly greater late, percentage of patients with an improvement in symptom severity as compared to the control group at each postoperative visit. The Coflex group also had a significantly greater percentage of patients with an improvement in physical function than did the control group at each postoperative visit. At all follow-up time points, the Coflex group scored significantly better than the control group, except for the mild postoperative back discomfort early in the study. Though this series has limitations of a smaller 1-year follow-up, it nevertheless confirms the satisfactory results of its implantation and its superiority augmenting decompression. We will continue to follow the patients enrolled in this study and will report on the longer follow-up.
In Group (B) postoperative complications occurred in 2 (8%) patients, (1 seroma, 1 superficial wound infection). At 1 year follow-up, 2(8%) patients presented with recurrence of symptoms due to epidural fibrosis. In Group (A) postoperative complications occurred in 3 (12%) patients, (1 seroma, 2 worsening of existing numbness). All were temporary. No broken, deformed or migrated Coflex was found. However, minimally deviated coflex in one patient, after back trauma, indicated the need for revision. That patient had the double level coflex devices removed due to traumatic fracture of the intervening spinous process. He needed no further management. No patients needed further fusion within 1 year postoperatively, 1 patient presented with recurrent disc herniation. There were no infectious complications.
(Fig. 5, 6, and 7)
Radiologically, there were significant differences in anterior and posterior disc height and foraminal height between the two groups. Coronal and lordotic angles were reduced postoperatively in the device group but not in the micro-decompression alone group.
The radiological results could be concluded in the following:
1. Endplate Angles: in Group (B) in neither flexion nor extension was there any difference in the change in endplate angles after the decompression. No difference was seen above, below or at single or double level procedure. Endplate Angles in Group (A) that were acute preoperatively, always become less acute postoperatively; and the foraminal height always increases.
2. Maintained Dynamic Movements: no difference was noted in the level(s) treated in both groups. In Group (A), postoperative flexion and extension views showed maintenance of the dynamic movements at the operated level.
3. Disc Height: in Group (B) no significant changes in both anterior and posterior disc heights was noted. Group (A), showed significant changes after the procedure in both anterior and posterior disc heights.
Important questions to be answered rose from our previous preliminary study, done to assess the safety and effectiveness of Coflex® Dynamic Interlaminar-Interspinous Distraction Stabilization (DIDS) device (Paradigm Spine GmbH, Germany) (28). Our previous study was treating patients with degenerative diseases of the lumbar spine (DDLS), especially lumbar canal stenosis (LCS), to confirm indications for Coflex implantation, and to evaluate the short-term clinical outcomes of patients. The first inquiry was about the reported benefits and improvements, is it secondary to the decompression done or to the spacer implanted? The second inquiry was about declaration of the real benefits of the Coflex device over decompression alone.
Lumbar posterior decompressive surgery has many ways and different techniques, including formal wide laminectomy, laminotomy, partial laminectomy, hemilaminectomy, and interlaminar approaches.2-4,12-14,17,19,25,31,38,42 Lumbar canal stenosis is frequently accompanied by multilevel affection and concomitant disc problems. Moreover, traditional decompressive surgery does not always eliminate the patient's pain. We all know the incidence and the big problem of failed back syndrome. Moreover, iatrogenic instability 2ry to the invasive decompression may warrant a more aggressive fixation procedure and, as many authors have indicated, rigid fusion may have a chance of adjacent joints & segment degeneration, ending in an endless circle of pathological dynamic events causing more pain and disability.7,13,27 That led us to the choice of micro-laminectomy as the decompressive procedure to be studied, sticking to the minimally invasive phenomenon we believe in.
It is a fact that the success rate for micro-laminectomy and traditional laminectomy are the same. Generally, the success rate for one level herniation is over 95% in obtaining relief of most leg pain and associated symptoms. Avoiding the major mechanical sequelae of formal laminectomy, still small percentage of individuals does not improve substantially following micro-laminectomy. Katz et al, have noted deterioration of the early results of decompressive surgery over time. In Katz’s series, 17% of patients ultimately underwent a second procedure for instability or recurrent stenosis.18,19 It was stated that this small percentage had nerve damage that was present prior to surgery due to pressure on the nerve, changing the pain into a neuropathic type of pain. Due to the fact that it is impossible to diagnose whether permanent nerve damage is present prior to surgery, and that curing a postoperative persistent pain syndrome after a failed laminectomy is a major unsolved problem. That explanation, to us, solved nothing of the real problem. These results pushed us to re-look, re-evaluate, and re-think of the cases again, looking for better solutions and good explanations. Microdecompressive surgery was used as the control in this study. Comparison with reported results of microlaminectomy, physical, functional and symptom severity improvements for patients treated with the Coflex are better. Despite a 1-year relatively short follow-up in the current study, it is clear that the performance of the Coflex patients compares favorably to that of patients undergoing surgical microdecompression alone.
Many spine surgeons don't recognize the fact that the facet joint is the corner stone of LCS pathological events. Despite removing the herniated disc fragment and surgically decompressing the nerve roots, the remainder of the pathology, the facet, remains loaded and arthropathic in place. That correlation explains the fact that some people do have periodic or continuous backache or leg pain, postoperatively. Augmenting the decompression with unloading of the facets should theoretically cure most of those people of their back and leg pains.
The Coflex is an axially compressible U-shaped device, made of titanium, which is interposed between the spinous processes. By implanting it in a somewhat compressed condition, the device can expand further with flexion thereby reducing the buckling of the ligamentum flavum and off-loading the facet joints. However, the results of its clinical application have rarely been reported.5,8,10,16,20,21,22,28,30,34,37,43 Tsai et al., assessed the motion segment after destabilization and insertion of the Coflex, and concluded that the Coflex offered nonrigid fixation and can return a partially destabilized specimen back to the intact condition in terms of motion in flexion/extension and axial rotation.37 Kong et al., reported a favorable result with Coflex in spinal stenosis in terms of adjacent level degeneration when compared with a posterior interbody fusion group.23 The author, in this study, assumed that interspinous implantation can be a good adjuvant augmenting microlaminectomy procedure for mild to moderate spinal stenosis. Moreover, it puts less stress on the adjacent levels than decompression surgery alone in which elements of disc space collapse or narrowing is present.
Radiologically, in our study, Coflex device insertion does induce a significant change in disc and foraminal heights, a finding that was not noticed with decompression alone. There was also an apparent difference in postoperative back pain and ADL score between the two groups. Of course, pain improvement has resulted from the effects of decompression by a way or another. However, the pain after surgical decompression alone would recur with time, as found in our results. So, long term follow-up is required. Changes of disc height or foraminal height require mechanical and structural transformation as distinct from motion changes. Changes in intervertebral angles with Coflex have also been reported using plain radiographs. An increase in the angles toward lordosis was noted in the erect posture from supine. The posterior disc height did show an increase irrespective of posture and number of operated levels. Postoperatively, the anterior disc height appeared to increase, albeit minimally, in single-level implantation. In double levels, the disc height expectedly reduced postoperatively. We also reported increases in the cross-sectional area of the dural sac and intervertebral foramina. Our study demonstrated that the Coflex, distracting the interspinous processes, increased the dimensions of the spinal canal and neural foramina at the implanted level in extension, but it did not alter the dimensions of the adjacent, intact levels in the extended, flexed, or neutral positions. These effects are expected to significantly reduce the pressure in the facet joints and posterior annulus and nucleus at the implanted disc level, without altering the mean pressures at adjacent levels. These effects produce a clinical benefit for LSS patients treated with the Coflex. The addition of these beneficial effects to the decompressive procedure should raise the good outcomes, clinical and radiological.
Clinically, the study confirmed the known positive effect of decompression of neural structures on claudication and leg pain. In addition, the moderate and/or severe LBP could be relieved in most of the patients. The decreased preoperative walking distance, partly due to LBP, partly due to claudication, improved significantly. Also, the patient satisfaction was extremely high and the majority would undergo surgery again. Therefore, we think that the decompression with additional coflex implantation can not only improve the claudication but also the accompanying LBP. The rate of complications in our study was very low.
Procedural aspects of Coflex implantation also compare favorably to those reported for decompressive surgery. The mean operative time for the Coflex procedure was more than that reported for microlaminectomy procedures by only 5-10 minutes, which is not a big issue. In addition, the mean blood loss of 60 ml during the microdecompression procedure did not increase in the coflex group.
Because group B served as a control in the current study, definitive comparisons between the Coflex and microdecompressive microlaminectomy could be made. The current study is one of the new comprehensive evaluations of LSS conducted to date. Care was taken in the current study to address the importance of protocol design, to clarify the new philosophy of LCS management, and to have solid comparative conclusions. Limitations only include a moderate sample size and a follow-up period of 1 year. A report will be published based on the late follow-up data for all patients. Despite these limitations, the current study provides evidence that immediate pain relief and increase in function can be provided by the Coflex with a low rate of morbidity. This clinical improvement is greater than that associated with microlaminectomy alone.
The Coflex device was helpful in alleviating pain and improving ADL performance in patients with lumbar spinal stenosis. It corrected segmental scoliosis and restricted extension. However, there should be careful selection to apply of this device in segmental canal stenosis patients, for better results to follow. The addition of coflex device to the micro-decompression procedure, improves the clinical and radiological outcomes much, in properly-selected cases. The addition of coflex as a method of dynamic stabilisation after neural decompression reduces low back pain without fusion. We could demonstrate that the implantation of coflex is safe and effective. Further prospective studies will be needed and are planned.