Abstract

Background: Degeneration of the intervertebral disc is the most common cause of low back pain. Continuous researches for an alternative option to surgical fusion have been successfully run over the last two decades. That, resulted in total intervertebral disc prosthesis for treatment of disc degeneration with motion segment preservation. The aim of this study is evaluation of the short term results of lumbar intervertebral disc prosthesis in treatment of degenerative lumbar disc disease in selected cases. Patients and Methods: This prospective study was carried out at Ain Shams University hospital in the period between August 2000 and March 2005.on 16 patients with disabling low back pain due to degenerative disc disease. Seven of them have also sciatica. The patients were selected according to 1- the age between 22 -48 years 2-chronic disc disease presented by sever low back pain with or without sciatica 3- good bone quality 4-all had moderate to sever degrees of disability according to the modified Stauffer and Coventry Scoring system which have not improved by medical treatment and physiotherapy, all patients have been treated by total disc replacement (SB Charite) after complete clinical , radiological investigation that included stress X-ray films and MRI study . One level replacement was done in 12 patients and double levels replacement were done in four patients' .The total number of the disc prostheses used in this study were twenty prostheses. The operation was done through an anterior retro- peritoneal approach in 15 cases and through transperitoneal approach in 1 case. The patients were followed up for an average period of 30 months (range7-60 months). Results The results were evaluated according to modified Stauffer and Coventerey. The patients were satisfied with the results. All have resumed the pre-disease activities and duties although two patients had low back pain that needs mild anti-inflammatory medications in low doses. Two patients have a displaced prosthesis (off-position from the mid-line in antero-posterior view only while the saggital view position was perfect in these patients like others). No major complications were recorded in relation to the surgical approach or to the prosthesis during surgery or immediately after; also no complications were reported in relation to the position of the prosthesis or its integrity and stability, and no ossification in the surgical bed, were detected in the follow up period up to 6 months in the early inserted prosthesis. Conclusion Although the number of cases in this study is limited and the follow up period is short, the maximum follow up period is five years, the results are satisfactory to the surgeons and to the patients. Comparing this results in relation to the activities and duties before surgery and in relation to the results and complications after spinal fusion surgery with its passive effect on the discs above and blow the fused segment. So the articulating disc prosthesis can be a successful solution for treatment of degenerative and prolapsed disc in well selected patients

Introduction

Degeneration of the intervertebral disc is theoretically the main cause of law back pain. Disc degeneration with ongoing decrease in disc volume due to loss of water content and reduced elasticity, induces subluxation of the facetal joints of the involved spinal segment. Under continuous loading, subluxated joints become arthritic and painful. These arthritic joints fail to maintain the range of segmental motion within the physiological limits. When degenerative disc disease affect multiple discs with posterior joint instability and spasm of paraspinal muscle degenerative scoliosis will develop.

Interbody fusion is a well established procedure for treatment of disc degeneration which can be performed utilizing different techniques. In majority of cases, segmental fusion allows immediate and significant relief of the preoperative complaints related to the degenerative instability. The long term results of lumbar fusion are not satisfactory to the patient, regardless the used technique.

Fusion of single spinal motion segment or more creates an unavoidable compensatory increase of motion at the levels adjacent to the fused segment due to an increase in stresses at these segments. This results in acceleration of the spondylosis in the adjacent segments either cranial or caudal to the fusion. A significant number of these patients eventually need an additional fusion (1).

Also Lumbar Fusion has many potential complications as, Loss of lumbar lordosis which results in flat back syndrome, sacroiliac pain, pelvic stress fracture, significant co-morbidity related to both instrumentation and graft donor site and pseudoarthrosis rate which reached up to 44% in some series. The need for additional external support and prolonged costly rehabilitation programs are also limiting factors for fusion (2).

The continuous researches for a new surgical option as an alternative to spinal fusion have successfully run over the last two decades. It reached the new concept in management of degenerative disc disease by controlled mobilization offered by intervertebral disc prosthesis in well selected cases

Spine surgeons using total disc replacement believe that preservation of function and segmental mobility has advantages over rigid elimination of movement by fusion (3).

Restoration of intervretebral disc height indirectly decompress the nerve root, can also relieve pressure on pain receptors in the annulus and even produce a healing effect on facet joints before irreversible changes occurs (4).

The first described attempt for disc arthroplasty was performed with a steal – ball endoprosthesis by Fernstrom in the late 1950s (5). Since that time a nonlinear progression of technology in lumbar disc arthroplasty has resulted in an extensive and diverse list of implant designs. The most famous types and commercially available artificial disc prosthesis are SB charite III and Prodisc. The SB charite is unconstrained device with 6° free motion between both the endplates and the core. The Prodisc is a semi constrained device with the polyethylene core fixed to the lower endplate. Instant axis of rotation of the SB charite III mimics the normal spinal segment but the instant axis of rotation of the Prodisc is fixed and located just below the inferior vertebral endplate at the center of the ployethelene core on the coronal and sgittal plane. During flexion and extension, the core of the SB charite III moves backward and forward similar to the nucleus pulposus and prevents excessive wear while protecting the facet joints from the sharp rise of stresses.

Primary indications for artificial disc replacement are

• Severe discopathies and directly related morbidities.

• Unremitting back pain from degenerative disc disease.

• Sciatic pan associated with degenerative changes in the disc.

• Post nucleotomy syndromes (6).

Since artificial disc is a stabilizing device, with the ability to restore the lost disc height, the indication for insertion may extend to secondary instabilities that are related to disc degeneration. i.e. degenerative spodylolithesis grade one and two in well selected cases with good bone quality. Juxtafusional degeneration syndromes could also be treated by disc prosthesis in order to preserve a motion segment instead of extension of the fused segment with expected future complications of the long segment fusion (7). Although American FDA study was just on the single level replacement for degenerative disc disease, multilevel replacement has been performed in Europe with similar results to single level disc replacement (8, 9).

Contraindications to disc replacement are:

1. Spinal instability as in: vertebral body fractures, spondylolithesis, prior removal of facet joints (iatrogenic spondylolisthesis)

2. Osteoporosis or osteomalacia

3. Spinal tumours

4. Spinal infections (active or latent)

5. Technical contraindications as: spinal deformities, marked obesity, previous retroperitoneal surgery, history of radiotherapy due to fibrosis and severe aortosclerosis due to high possibility of vascular injury. (10)

Material And Methods

• Prospective study was done on 16 patients at Ain Shams University between August 2000 and March 2005.Total disc replacement was done using SB charite III disc prosthesis.

• Preoperative physical examination included assessment of spinal range of motion, nerve root tension signs, and motor strength. The working ability, the physical activity and its restriction, proper praying and the use of analgesics. Patients were attributed a good, fair and poor results based on modification on the original classification by Stauffer and Coventry (11). (Table 1).

• The modification of Stauffer and Coventry scoring system included :

• • ---Pain score instead of pain relief percent.

  • Working ability instead of Return to work.

  • Physical and praying session restriction instead of physical restriction.

We use this scoring system for both pre and post operative evaluation.

All cases in this study preoperatively attributed as patients with poor criteria because they had no pain relief with the regular use of analgesics, they had great physical restriction and they became unable to work or to pray properly.

Proper selection of the patients depends on preoperative evaluation to establish the diagnosis and identify any contraindications. In addition to proper clinical examination, imaging studies for all patients included standing full length antero-posterior and lateral X.rays to determine the gross spinal balance as well as flexion – extension Lateral radiographs to document any translational instability.

MRI to determine disc degeneration, prolapse, herniation or sequestration and it also determine the status of the adjacent discs. (fig.1)

In two patients with previous surgeries gadolinium enhancement determine the significance of adhesions.

In this study 7 males and 9 females were operated upon, age ranged from (22 - 48 years) with average 35 years. (Table II)

Preoperative diagnosis was disabling low back pain without sciatica in 7 patients, low back pain and sciatica in 4 patients, low back pain and sciatica with list in 3 patients while 2 patients was complaining from L.B.P and had a history of previous discectomy. All patients had history of failed conservative treatment for period not less than 6 months.

Total 20 prostheses were implanted and the operated levels are:

• L 4-5 level 7 patients (44%).

• L 5-S1 level 5 patients (31%).

• L 4-5 / L 5-S1 levels 4 patients (25%).

Regarding surgical techniques the left sided retroperitoneal approach was adopted in 15 cases while the transperitoneal approach was used in 1 case as the peritoneal cavity was opened accidentally, it was so thin with adhesions, the operation was completed through a trans-peritoneal approach. Following the exposure of the disc space, mid vertebral line is marked and checked with fluoroscopy. The marking of the midline is extremely important since good positioning of the prosthesis depend on this step.

The anterior longitudinal ligament and the anterior annulus are opened through annular flap (to be sutured back after implantation of the prosthesis) (Fig.2). This was routinely done in 10 cases while the annulus was removed totally in 6 cases. Then the disc material was totally removed, during this step gradual distraction of the disc space was done by the use of lamina spreader in order to stretch the posterior annulus and to remove the posterior osteophytes if present.

Following the removal of the disc material and the cartilaginous end plate the posterior annulus is removed leaving only the lateral annulus. In the 3 cases with sciatic list there was a need for removal of the migrated disc fragment in order to decompress the spinal canal, so the posterior longitudinal ligament was opened to explore the spinal canal in those 3 cases.

Following disc space preparation, the size and height of the implant are determined, and the largest device that fits is selected. The lordosis of the metal endplate is chosen according to the preoperative standing lordosis of the patient. It is essential to check that the upper and lower endplates are relatively flat without any bumps for best contact of the metal endplate with the vertebral body. Fluoroscopic guidance insures midline insertion and posterior placement of the prosthesis to reduce the loads on the facetal joints later on. Before placing the polyethylene core between the metal endplates; the spinal canal is checked for any missed cartilaginous fragments missed during end plate preparation or bony fragments that many have fractured from the posterior lips of the vertebral bodies during insertion of the metal endplates and so continuous wash is recommended.

The retroperitoneal suction drain that was inserted before closure is removed 48 hours after surgery. The average intraoperative blood loss was 294CC and the average time for surgery was 3.5 hours.

Postoperatively the patients were advised to start walking, with an abdominal corset in the second day after surgery, the patient leave the hospital on the third postoperative day and continue on abdominal corset for two weeks .The stitches were removed on the 12th postoperative day. Limited flexion and extension was allowed after one week and gradually increased till the 8th week then the patient is encouraged to do full flexion and extension and rotation after 12 weeks after which the patient can resume heavy work and start Segood (Fig.3) (maximum flexion position during praying) 3 months after surgery. Generally patients should be so careful with the recently inserted prosthesis and should avoid incidental trauma or sudden twisting in the first 2 months to avoid any prosthetic displacement

Postoperatively plain X-Rays were done and patients reviewed at regular intervals (every week for the first month then every two weeks till the first three months. After that every month till the first six months then every three months till the first year) to be clinically assessed regarding pain sensation ,the use of analgesia, working ability and physical and praying restrictions. Patients were attributed a good, fair and poor results based on the modified Stauffer and Coventry scoring system that used preoperatively.

Results

In this study all patients had good results as compared with the pre-operative situation according to the modified Stauffer and Coventry scoring system.

Regarding pain:

• All patients improved regarding the preoperative disabling low back pain.

• Those patients with sciatica recovered.

• Two patients had infrequent back pain that was relieved by analgesics and with one year follow up the pain disappear.

Regarding working ability:

• All patients in this study return to their preoperative jobs and resume their daily activities.

• After 6 months no physical restrictions, they can work regularly and carry out average weights.

Regarding use of analgesics:

Most of our patients use analgesics few weeks after surgery. Only two patients continued to use analgesics for 3 months after surgery.

Discussion

Lumber disc replacement can lead to good functional outcome and reintegration into an active professional life in a well selected patient with lumbar degenerative disc disease after relatively short period of rehabilitation. Disc prosthesis is not a routine operation, the operative technique must be very precise and non traumatic, retroperitoneal approach is safer and easier than the transperitoneal one. The surgical outcome is influenced by proper patient selection and proper insertion of the prosthesis.

Conclusion

Lumber disc prosthesis is a genuen solution for degenerative disc disease whether associated with sciatica or not. It restores painless disc movement and prevents adjacent segment disease and facet joint arthropathy by preserving motion. It protects the neural elements by restoring disc height and hastens recovery time in comparison to arthrodesis. Short term results as measured by pain relief and disability are good in many studies, implants proved to be safe. Complications are usually related to the surgical approach rather than the prosthesis till now. Recovery times are shorter than arthrodesis. Long term follow up is recommended to confirm the solidity of our results.

Table 1 :Modified Stauffer and Coventry scoring system.

Figure 1: MRI showing disc prolapse with major displacement and heathy discs above and below in Sagittal and Axial cuts

Figure 2: showing the annular flap and the disc prosthesis in place.

Table 2: Study master table

Figure 3: Male patient 40 years old with L5-S1 disc prosthesis doing the proper Praying positions. (Full Extension, in the start then full flexion, in rekoaa and maximum flexion for Segood).

Figure 4: A-P view in patients with double level replacement with ideal position.

Figure 5a: A-P view in female patients 26 years old with side to side deviation

Figure 5b: Lateral x-ray with dynamic views of the same patient showing range of motion (extension/flexion) 8 months post-operative.

Figure 6a :Case presentation (case NO. 8) A-Male pt 24 years old with RT list and LT.sciatica the preoperative MRI show degenerated L4-5\L5-S1.

Figure 6b: Intraoperative leveling using image intensifier, complete discectomy was done and the largest prosthesis size was chosen.

Figure 6c: The prostheses in place, postoperative X-ray and the patient LT.sciatica improved.

References