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Pain Scale and
Radiological Comparison of Lumbar Discectomy Patients with and without Lumbar
Disc Prosthesis

 

INTRODUCTION:

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Intervertebral discs(IVDs) have composite structures
surrounded by a collagen rich annulus fibrosus composed of rich core pulps of
gelatinous proteoglycan. (Orthop Clin North Am. 2011 Oct; 42(4): 487–499.Biomechanics of Intervertebral Disc Degeneration, Nozomu Inoue, Alejandro A. Espinoza Orías). The proteoglycan in the nucleus pulposus provides high
water content, and in turn, contributes to sustain large loads applied to the
vertebral body(Orthop Clin North Am. 2011 Oct; 42(4): 487–499.Biomechanics of Intervertebral Disc Degeneration, Nozomu Inoue, Alejandro A. Espinoza Orías). And IVDs are mainly avascular so it
is not surprising that degenerative disk disease(DDD) is a common phenomenon in
middle age(Spine J. 2005
May-Jun;5(3):297-309.Influence of spine morphology on intervertebral disc loads
and stresses in asymptomatic adults: implications for the ideal spine. Keller TS1, Colloca CJ, Harrison DE, Harrison DD, Janik TJ.). The
treatment of DDD is highly variable; it ranges from intensive rehabilitation to
surgical stabilisation of the spine(Lee WT
S?NGAPORE med j). The use of an artificial disc for symptomatic
DDD has been practiced for many years and is currently in various phases of
development and clinical trials(Journal of Neurosurgery: Spine
September
2004 / Vol. 1 / No. 2 / Pages 143-154, Neurological complications of lumbar
artificial disc replacement….). There are a wide variety
of new products, procedures and techniques currently in development to enhance
spine surgery and many spine surgeons believe that artificial disc technology
holds real promise for significiantly improving the standart of care for many
patients(Journal of Neurosurgery: Spine September 2004 /
Vol. 1 / No. 2 / Pages 143-154, Neurological).

Janz
et al. performed the first total discectomy and insertion of disc prosthesis(Buttner-Janz, K. Schellnack and H. Zippel, An
alternative treatment). Since the day the prosthesis was first used,
more than 15 patent applications were filed for disc prosthesis device. And
almost all of them general opinion was the artificial intervertebral disc is
preferably  designed to restore disc
height and natural disc curvature, allow  for a natural range of motion, absorb shock
and provide resistance to motion and axial compression(Siemionow
KB, Hu X, Lieberman H, The Fernstrom ball revisited, Eur Spine J, 443-448,2012).
So insertion of disc prosthesis
intends to avoid fusion related negative side effects by means of motion
preservation(Zigler J, MD Lumbar Artificial Disc Surgery for Chronic
Back Pain, Spine-Health, 2005)).

It
remains unclear whether the early fair to good results obtained with an
artificial disc will be consistently maintened with a longer follow-up period.
Therefore we investigated whether it will be a meaningful and benefical result,
protecting the disc height and foramen diameter that disc prosthesis can get
it. And we want to present the results of our clinic comparetively with only
discectomy patients.

 

 

MATERIALS
AND METHODS:

               The ethics committee approval of this study was taken from Erzurum Regional Training and Research Hospital. This study presents the retrospective examinations of  114 patients who were diagnosed with lumbar disc hernia and underwent surgery between 2010 and 2014 in the Neurosurgical Clinic of Erzurum Regional Training and Research Hospital. Patients were divided into two groups. There were 57 patients in group 1 who were performed single level discectomy and there were 57 patients in group 2 who were placed lumbar disc prosthesis after single level discectomy. A total of 57 lumbar total disc prosthesis (TDP) were inserted. We used NUBACTM disc prosthesis constructed in a unique two-piece design of a polyaryletherketone(PEEK) biomaterial with an inner ball/socket articulation launched by Victrex® in 1998. There were 32 males and 25 females in group 1 and the mean age was 38.4 (31-45). And in group 2 there were 33 males, 24 were females and the mean age was 39.1 (33-45) as seen in table 1. 30 of the patients in group 1 were operated from L4-L5 segment and 27 of the patients were operated from L5-S1 segment. And in group 2, 31 patients were operated from L4-L5 segment and 26 patients were operated from L5-S1 segment. For all the patients in our study  the exclusion criterias were previous disc surgery, spondylolisthesis, spinal stenosis, Pfirrmann grade 4-5 and overheight patient (BMI >30).               Preoperatively and postoperatively in the 3rd year, the disc height from the middle of the superior border of the disc to the middle of the inferior border of the disc with the inclusion of both endplates and the diameter of the foramen from the largest region were measured with x-ray graphies for all patients. In our radiology department, all patients are x-rayed at the same position and at the same distance.                And patients rated their pain on the Visual Analogue Scale (VAS) preoperatively and postoperatively in the 3rd year. For group 2 patients we used NUBACTM disc prosthesis constructed in a unique two-piece design of a polyaryletherketone(PEEK) biomaterial with an inner ball/socket articulation launched by Victrex® in 1998.                 Statistical analyzes were performed using paired t test and linear regression. P < 0.05 was considered statistically significiant.   SURGICAL TECHNIQUE: This surgical technique provides the following main steps: 1) patient positioning in a prone position; 2) 3-5 cm long median skin incision 3)subperiosteal exposure of the index interlaminar space; 4) limited laminectomy (involving both the inferior edge of the hemilamina above and the superior edge of the hemilamina below), resection up to the medial one third of the facet joint, and partial flavectomy; 5) minimum nerve root retraction; 6) removal of eventual free disc fragments and annular cutting to obtain a small window (4 mm x 6 mm) through the annulus; 7) total nucleus pulposus evacuation and curettaging of both two end plates to make the intervertebral space both space-efficient and firm  8) annular window dilatation; 9) trial spacer implant sizing; 10) implant insertion into the disc cavity   RESULTS:             The mean disc height of the patients in group 1 preoperatively was 9.6 mm (range from 6.01 to 10.27) and postoperatively 3rd year the mean disc height was 6.63 mm (range from 5.07 to 8.4) as seen in table 2. For the group 2 preoperatively the mean disc height was 9.01 (range from 6.52 to 11.2) and postoperatively 3rd year the mean height was 9.03 (range from 7.1 to 10.81) as seen in table 3. When group 1 and group 2 was compared statistically; there was a significant difference between the two groups (p <0.05).                For the group 1 patients, the foramen diameter avarage value decreased from 17.11 mm to 10.4 mm, whereas in the prosthesis group, the foramen diameter decreased to 16.21 mm from 16.45 mm, postoperatively. When group 1 and group 2 was compared statistically; there was a significant difference between the two groups (p <0.05). When VAS of all patients were evaluated it was seem that in the discectomy group VAS decreased from 8.6 (range from 10 to 8) to 3.91 (range from 5 to 1) and at the prosthesis group it decreased from 9 (range from 10 to 7) to 3.02 (range from 4 to 1). The decrease in VAS values in both groups was statistically significant. In our study, in the only discectomy group a recurrence rate of 15 % was observed. And no recurrence was seen in the patient group with a lumbar disc prosthesis. In tree patients, the disc prostheses were displaced, and they had to be surgically removed. The complication rate in our study was observed to be 5% as seen in table 4.     DISCUSSION: After lumbar discectomy alteration on the disc over time modifies the mechanical performance of the disc and naturally leads to a reduction in the height of the intersomatic space (J Biomech Eng. 2011 Jul; 133(7)). As a result this damage leads specifically to an arthrosic reaction, the source of pain and osteophytic processes ( Nat Rev Rheumatol. 2013 Apr; 9(4): 216–224). In this context, it becomes meaningful to consider lumbar disc prosthesis as a procedure that provides normalization of the disc height. By restoring the disc height, the spinal canal and foramina are returned to their physiological limits and tension is reduced in the posterior facet joints (Lemaire JP, Carrier H, Sarialiel H). And also to avoid degenerative cascade in adjacent vertebral segments and to treat patients with more physiologic method, replacing the intervertebral disc is an effective option. (Degeneration of the intervertebral disc, Jill PG Urban and Sally Roberts). McGirt et al. showed in their work that an 18% loss of disc height was observed 3 months after lomber discectomy and 26% loss after 2 years (McGirt MJ1, Eustacchio S, Varga P, Vilendecic M.). About this subject studies by evaluating the radiological findings have been made several times. As sample Yorimitsu et al. observed a significant reduction in disc heights in a series of 72 patients who had undergone standard lumbar discectomy(Yorimitsu E, et al., Long-term outcomes). We saw in our this study the disc distance decreased in patients group 1 after surgery 3rd years. And when we did a regression analysis about this to evalute the effect of disc space loss on patients' pain after discectomy; we saw that every 1 mm decrease in the disc height led to increasing the pain of the patients by 0.277 points. No doubt that the lomber disc prosthesis can protect the disc space after discectomy(Tropiano P, Huang RC, 2003, Issue 4). In 2007, Karatoprak et al. conducted a study of 34 patients with lumbar disc prosthesis and found that disc heights increased from 4.6 mm to 12.1 mm after an average period of two years(Karatoprak O, et al., Turc, 2007. 41(4)). It looks like an excellent result on a 2-year follow-up.  We believe that longer follow-up clinical and radiological results will be useful. And at the same article they argue that flexion – extansion range  of the affected discs increases. This increase seems to be continuing in 2 year follow-ups(Karatoprak O, Turc, 2007. 41(4): p. 281-5). Tropiano et al. reported patient satisfaction after disc prosthesis as 87% and rate of return to daily activities and previous job was 72% in his study with minimum one year follow-up(Tropiano P, Huang RC, Girardi FP, Marnay T. 2003;16:362-8). Bertagnoli et al. published short term outcomes of 104 patients treated with Prodisc II in their prospective study. Authors reported 41% mean reduction of pain according to VAS scores, 24% mean reduction in ODI and 96% patient satisfaction; rate of return to work was found to be 50% in two years follow-up. In radiographic evaluation mean preoperative disc height of 4 mm. was increased to 13 mm postoperatively, preoperative range of motion was increased from 3 to 7 degrees postoperatively(Bertagnoli R, Yue JJ, Shah RV, Nanieva R, Pfeiffer F, Fenk-Mayer A, et al. The treatment of disabling multilevel lumbar discogenic low back pain with total disc arthroplasty utilizing the ProDisc prosthesis: a prospective study with 2-year minimum follow-up. Spine 2005;30:2192-9) And we claim that maintaining the disc height also preserves the foramen diameter. In order to understand the effect of lumbar disc prosthesis placement on the diameters of the foramina at the discectomy site, the foramen diameters of the patients in both groups were measured preoperatively and 3rd year after surgery in our study. The results showed statistically significantly better results regarding the foramen diameters of the group with a total disc prosthesis and we saw that every 1 mm increase in the diameter of the foramen led to a reduction in the VAS of the patient by 0.086. Besides all these, usage of disc prosthesis can reduce the need for second surgery. In our study, in simple discectomy group a recurrence rate of 15% was observed, and this finding was consistent with the literature(Yorimitsu E, et al., Long-term outcomes of standard discectomy for lumbar disc herniation: a follow-up study of more than 10 years, Spine (Phila Pa 1976), 2001.26(6): p. 652-7). In our study, no recurrence was seen in the patient group with a lumbar prosthesis. In tree patients, the disc prostheses were displaced in the first  year after surgery. Only one of these tree patients was admitted to the hospital with complains of radiculopathic pain. The others seemed with back pain. All of these tree patients  had no neurological problems but hey had to be surgically removed. The complication rate in our study was observed to be 5% . This value was interpreted as a value close to the results in the literature. In their study, Tropiano et al. found no recurrence after a follow-up of one year in their patients with lumbar disc prosthesis, with a complication rate of 9% and a reoperation rate of 6%. They reported no mechanical failure of the implants or loosening. Tropiano in this article defended that total disc replacement has the potential to replace fusion as the gold standard surgical treatment of degenerative disc disease(Tropiano P, Huang RC, Girardi FP, Lumbar disc replacement: preliminary results with Prodisc2 after a minimum follow-up period of 1 year, Clinical Spine, 2003, Issue 4). CONCLUSIONS: In the light of the obtained results, it can be interpreted that the use of lumbar disc prosthesis is more effective in reducing pain compared to performing discectomy only. Many biomechanical studies have shown that normal mechanical functions of a disc can be restored by a disc prosthesis. Upcoming data on long-term outcome, implant durability and possible very late complications will determine the future of lumbar disc replacement surgery. Performing a total discectomy eliminates the chance of a disc herniation and will hopefully retard spondylosis, stenosis, and instability at the dynamically stabilized segment. By restoring the anatomic disc height, the artificial disc would increase the exiting foraminal height and prevent compression on the exiting nerve roots at the level stabilized.  We think that it is important to offer an alternative to surgical treatment of this disease which is quite common in society.  Based on the results obtained in this study, it can be concluded that using total disc prosthesis in appropriate patients is more favorable regarding pain and spinal physiology when compared to simple discectomy or using the fusion technique if there is no posterior colon destruciton. At the moment, we are of the opinion that although it might take more effort to optimize the design and reduce costs and risks, prosthetic disc replacement will be the future of spine care.              

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