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Percutaneous Intradiscal Procedures
For Back Pain And Sciatica
Author: Dr Nathan Hore

Improved Outcomes With Advanced
Computer-Assisted Surgery
Author: Nicola O’Connell



Percutaneous Intradiscal Procedures
For Back Pain And Sciatica
Author: Dr Nathan Hore

Introduction
 At any given time, a significant proportion of the adult population is disabled by low back pain. With healthcare costs rising and the significant prevalence of spinal pain needing treatment, healthcare providers are challenged with the task of finding the most effective and economic treatment for these conditions. A number of accepted surgical procedures, ranging from minimally invasive to very invasive have emerged to treat this. Among other examples, these treatment modalities include annuloplasty, fusion, and discectomy, both open and percutaneous.

Degenerative Disc Disease
 Disc degeneration occurs during the natural aging process of a person. While everyone experiences disc degeneration as they age, not all are symptomatic. The pain generators for degenerative disc disease are most likely multi-factorial. The outer fibril portion of the disc, or annulus fibrosus, acts as a support structure and a “tire” to contain and protect the inner, gel-like portion of the disc, the nucleus pulposus. The outer third of the annulus is innervated and if damaged, may result in pain. The nucleus pulposus contains a number of inflammatory molecules. If the inflammogens come in contact with the pain fibers in the sensitized nerve endings of the outer annulus (or if nerves grow into the nucleus), back pain may result. If they come in contact with the posterior nerve root, leg or radicular pain may result. Patients classified as having degenerative disc disease typically present with axial (back) pain greater than radicular pain.

Spinal discs have very little blood supply and therefore cannot heal themselves as effectively as those tissues with adequate blood supply. However, over time the pain from chronic degenerative disc disease decreases as the inflammatory molecules dissipate. Patients needing treatment typically undergo a fusion procedure, which is major back surgery. In the past 5 years, however, less invasive treatment options have been introduced, such as annuloplasty.

Disc Herniation
 Another injury of the spinal disc that can cause pain is a disc herniation. A disc herniation happens when a portion of the disc protrudes into the spinal canal, compressing the nerve root and/or causing an inflammatory response. A large portion of disc herniations occur in the lower spine (L4/L5, L5/S1) because those vertebral levels bear the greatest load.

There are different types of disc herniations; one is a contained herniation with no nuclear penetration of the annulus. Another is an extruded herniation that protrudes beyond the annulus. The last is a sequestered herniation with a free fragment of nucleus pulposus. Disc herniations are typically seen in the posterolateral (near and far) or directly posterior in the disc. The symptoms typically present with a disc herniation are both back and leg pain.

Treatment Options
 Whether the disc will heal by itself will typically be determined in the first 6 weeks. During this period a patient may undergo conservative therapy to treat symptoms; which may include physical therapy, medications, and/or injections. If the patient does not improve with conservative therapy, more aggressive procedures may be considered.

For degenerative disc disease, annuloplasty or fusion may be considered. For disc herniation, the treatment depends on the nature of the herniation: if the herniation is contained, a percutaneous discectomy may be performed; if the herniation is not contained, open discectomy is typically recommended.

See Figure 1 for the typical treatment progression of a patient with leg/back pain.

Treatment options for degenerative disc disease refractory to conservative care include annuloplasty and fusion. Fusions have been performed for over 30 years for structural and degenerative conditions. In 1998, a new procedure was introduced to treat degenerative disc disease, called IDET (Intradiscal ElectroThermal™ Therapy) or annuloplasty. Fusion remains the gold standard for treating degenerative disc disease, but IDET may be a good treatment option for a very select group of patients.

IDET is a minimally invasive treatment for degenerative disc disease, especially with young patients who may experience accelerated degeneration from the added stress on adjacent segments from fusion1. It is an outpatient procedure that requires only local anesthesia and mild sedation. Using a posterolateral approach similar to discography, a needle is placed in the nucleus of the spinal disc. A catheter is then inserted through the needle into the disc and positioned along the posterior wall of the annulus. The thermal catheter is then heated using a specific algorithm, theoretically denaturing the chemically-sensitized nociceptors penetrating the nucleus of the disc, thereby eliminating the pain they cause and/or contracting the collagen within the annulus that has been weakened through the degenerative process, thus strengthening the annular wall. The patient typically goes home that day with a small bandage on the entry site.

A double-blind, prospective, randomised, placebo controlled study was published on IDET in 2004. Outcomes from this study showed that 40% of patients fitting very strict inclusion criteria achieved greater than 50% pain relief, while approximately 50% of patients realized no significant benefit2. So while IDET may provide an additional option for very carefully selected patients with discogenic pain, it is not a procedure for broad use.

The posterolateral lumbar fusion was first used to treat patients with degenerative disc disease in 1971. There are many ways to fuse two vertebrae together to reduce painful motion between segments, but they all have one thing in common: bone grafts. Hardware such as plates, screws, or cages may be used as an adjunct to the procedure to facilitate bone graft healing. Regardless of the method used, the ultimate goal is to eliminate motion between the two vertebral bodies that cause the pain. One literature review indicated that the studies available for fusion (47, no randomised studies) show 68% of patients had a satisfactory outcome (range 16-95%)3.

Disc Herniation
 Treatment options for disc herniations that do not respond to conservative care include percutaneous discectomy, open discectomy, and fusion. Fusion options are discussed above, so this section describes discectomy procedures.

Figure 1: Typical treatment progression of a patient with leg/back pain.

Similar to the progression of treatments for degenerative disc disease, open discectomy was introduced over 60 years ago, with a percutaneous approach following 20 years later to provide less invasive treatment options. Each technique has evolved over time to the most common procedures today, microdiscectomy (an open procedure) and DISC Nucleoplasty® (a percutaneous procedure).

Open Discectomy
 Microdiscectomy is performed under general anesthesia and the patient typically stays overnight following the procedure. While the patient lies on their stomach, a one-inch incision is made in the back. Material is removed from the symptomatic disc and retractors are used to keep the skin and muscle out of the surgeons working field. Usually bone and ligaments must be removed to give the surgeon access to the herniated disc. Tools and a microscope (or in some cases, an endoscope) are then used to remove disc nucleus tissue and any disc fragments to decompress the nerve root. Once the nerve is decompressed, sutures are used to close the surgical site and the patient is taken to recovery.

Percutaneous Discectomy
 Percutaneous discectomy is an outpatient procedure performed under fluoroscopic guidance. With the most common method, the patient lies on their stomach and a needle is inserted into the back and navigated into the disc under fluoroscopic guidance using a typical posterolateral discography approach. The patient is awake during the procedure for careful monitoring, using local anesthesia and a mild sedative to keep the patient comfortable. Once the needle is positioned within the disc a device is inserted through the needle to remove nucleus tissue. Once the disc is sufficiently decompressed, the needle and device is removed and the patient goes home that day with a small bandage over the entry site.

Since the introduction of a percutaneous approach to disc decompression approximately 40 years ago, many technologies have been introduced to more effectively decompress the disc. Chemonucleolysis was first used in the 1960s, involving the chemical dissolution of the nucleus by injection of an enzyme through the needle into the disc nucleus. By removing some of the disc tissue, chemonucleolysis decompressed the disc and relieved symptoms. Success rates approached almost 80% at 6-month follow up in a double-blind study4, but some serious complications reduced its use and it is no longer used in many parts of the world.

APLD and laser discectomy were the next techniques introduced. The APLD procedure uses a blunt-tipped, reciprocating, suction-cutting probe to remove nuclear tissue. One study of APLD showed a success rate of 77.5%5. Laser discectomy used a YAG laser to remove tissue and saw success rates above 75%6. Research of laser techniques showed that removing tissue at the centre of the disc decompresses a herniation at the periphery proving the mechanism of action of percutaneous discectomy7. Extensive set-up and the requirement of a large annular incision decreased the use of these techniques.

DISC Nucleoplasty™ is the most widely used method of percutaneous disc decompression today. Based on the knowledge learned from previous methods, DISC Nucleoplasty was launched in 2000. DISC Nucleoplasty requires entry to the disc through a 17-gauge needle, limiting annular damage with the smallest access available. DISC Nucleoplasty removes tissue in the disc nucleus using patented Coblation® technology, low temperature plasma excision. Studies have shown that DISC Nucleoplasty effectively removes nuclear tissue without damage to collateral tissue. An additional study showed that DISC Nucleoplasty significantly reduces intradiscal pressure when disc material is removed, which is the same premise for disc decompression as APLD and laser discectomy. Over 40,000 DISC Nucleoplasty procedures have been performed to-date with significant numeric pain scores reduction in 75-80%8,9 of patients, and sustained VAS (Visual Analog Score) pain score reduction10. A recent study also shows a promising biochemical healing response in the spinal disc when treated with Coblation technology. This data provides the first glimmer of hope in slowing down the degenerative process of the spine.

The Dekompressor™ is the newest instrument on the market for percutaneous discectomy, introduced in 2002. The Dekompressor uses an Archimedes pump principle: it utilises an auger to withdraw nucleus up the access cannula into a collection chamber. There is currently no reliable data available for this technique. Studies are needed to demonstrate safety and efficacy of the device.

References
  1. Pauza et al, A Randomized, Placebo controlled Trial of Intradiscal Electrothermal Therapy for the Treatment of Discogenic Low Back Pain. The Spine Journal 2004; 4:27-35
  2. Turner et al, Patient Outcomes after Lumbar Spinal Fusion. JAMA 1992; 268(7):907-11
  3. Fraser RD, Chymopapain for the Treatment of Intervertebral Disc Herniation-A Preliminary Report of a Double Blind Study. SPINE 1982; 7:608-612
  4. Davis GW et al, Automated Percutaneous Lumbar Diskectomy: A Prospective Study of 518 Cases with 1 Year Follow-up. SPINE 21
  5. Choy DS, Percutaneous Laser Disc Decompression (PLDD): Twelve Years Experience with 752 procedures in 518 patients. J Clin Laser Med Surgery 1988, 16(6):325-331
  6. Choy DS, Percutaneous Laser Disc Decompression (PLDD): Twelve Years Experience with 752 procedures in 518 patients. J Clin Laser Med Surgery 1988, 16(6):325-331
  7. Singh V. Piryani C. Liao K. Nieschulz S. Percutaneous Disc Decompression using Coblation (Nucleoplasty) in the Treatment of Chronic Discogenic Pain. Pain Physician. 2002; 5: 250-259
  8. Singh V. Piryani C. Liao K. Evaluation of Percutaneous Disc Decompression using Coblation in Chronic Back Pain with or without Leg Pain. Pain Physician. 2003; 6: 273-280
  9. Sharps L. Percutaneous Disc Decompression using Nucleoplasty. Presented at 6th International Congress of Spinal Surgery; Ankara, Turkey, September 2002
  10. O’Neill C. et al. Percutaneous Plasma Decompression Alters Cytokine Expression in Porcine Intervertebral Discs. The Spine Journal 2004; 4:88-98


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Improved Outcomes With Advanced
Computer-Assisted Surgery
Author: Nicola O’Connell

The degree of surgical accuracy achieved with hip and knee replacements can have a significant impact on post-operative recovery and the life of the implant, yet executing a consistently high level of precise accuracy is a challenge that every orthopaedic surgeon faces.

One of the key advantages of computer-guided orthopaedic surgery has been associated with improved alignment, but some surgeons have previously argued that the technology was not always 100 per cent reliable and added too much additional time to the operation.

Figure 1: DePuy’s Articular Surface Replacement
However, the technology has continued to advance and the new DePuy CI Computer Assisted Surgery System, the first, fully integrated customisable computer-assisted surgical package for hip resurfacing to be introduced to the UK, represents a highly sophisticated system. Surgeons at the local BUPA hospital in Cardiff are the first in the world – leading a global trial – to use the CI system alongside the DePuy Articular Surface Replacement (ASR) System (Ci ASR) for hip resurfacing.

“The breakthrough with this system is that it doesn’t use any preoperative scans or x-rays in theatre, and all of the bony landmarks are taken during the operation,” comments Cardiff-based orthopaedic consultant Dr Marci Maheson. “We are the first in the world to do a proper computer-guided resurfacing hip replacement on real-time patients in the same period of time that a standard resurfacing would be performed.”

The accuracy of the system is unparalleled, Dr Maheson finds. “Most surgeons can be within five to 10 degrees of accuracy, while the computer can achieve accuracy within degree. We have seen a 10-fold increase in accuracy when using the system. The majority of hips that fail within five to 15 years do so because they have not been put in sufficiently accurately. As this system allows you to put in the hip very accurately and very safely, we expect people’s hips will last longer and the number of revisions will be significantly reduced. This could certainly result in reduced NHS expenditure on repeat surgery.”

Approximately 35,000 total hip replacements are carried out in the NHS and 2,800 in Wales annually. In 10 to 15 per cent of these cases, the operation has to be repeated, either because the hip replacement has worn out or because there was a problem following the operation 1. Misalignment of the hip implant has been shown to be one of the leading reasons for such failures. Studies demonstrate that there is a six-fold increase in femoral neck fracture after resurfacing hip procedures if the implant is mal-positioned 2.

How The System Works
 Since ASR was pioneered more than 70 years ago, it has become increasingly widespread surgical practice and now represents a reliable alternative to total hip replacement 3, 4. As more hip bone is preserved, ASR patients can usually get back on their feet very quickly. The procedure tends to be particularly appealing for younger patients with active lifestyles.

The DePuy ASR system features tapered femoral implants, which allow a smaller diameter head to be used without increasing the risk of notching the femoral neck. A smaller head means use of a smaller cup, thereby reducing the amount of healthy bone removed from the acetabulum. It is designed around low profile instruments, allowing surgeons to operate through a smaller incision.

Figure 2: Pelvic Registration on the Ci ASR
The Ci ASR system is devised to provide precision and control at every step. The CI System comprises proprietary computer hardware, dedicated operating software and sophisticated surgical instruments. The software creates a simple, direct interface that provides the surgeon with intuitive control over the process from start to finish. The system allows the opportunity to plan, discuss and test surgery in advance, thus enabling the optimal procedure for each patient at the outset.

Consequently, surgeons continue to learn more as they conduct operations. Comments Dr Maheson: “We’re actually finding that the system is teaching the surgeon new ways to do the operation more efficiently and the post-operative x-rays are that much better.”

Knee surgery with the CI System
 The Cardiff team has also been involved in the development of knee surgery technology that includes computer-assisted, minimally invasive knee replacement surgery using the specialised Ci System. Computer assisted surgery with Ci allows the surgical team to see the interior of the knee on a computer screen and visualise incisions before making them, enhancing the accuracy and efficiency of minimally invasive surgery.

Again, this enhanced level of accuracy can have a major impact on outcome success. With total knee arthroplasty (TKA), recent literature demonstrates that there are still problems of postoperative malalignment and malalignment in the coronal plane is a major technical complication5. Yet proper axial alignment is key to the longevity of the implant: even minor malpositioning can lead to early loosening, increased polyethylene wear and poor function 6.

The use of computer-assisted surgery has been shown to significantly improve alignment accuracy. One prospective, randomised trial compared the outcome of 120 TKA patients who received an implant using a navigation system with 120 patients who were implanted using conventional procedure. In the CAS group, 97.5 per cent of patients had a mechanical alignment of between 0 and 2 degrees versus 77.5 per cent in the conventional group 6. In another prospective randomised controlled study, all 50 patients in the CAS group scored between 0 and two degrees of mechanical alignment 5. The procedure was also shown to be safe, with no specific complications related to the use of the CAS system.

Dr Rhys Williams, Cardiff-based consultant orthopaedic surgeon who specialises in knee and shoulder surgery, was initially sceptical about using the DePuy CI System. “We weren’t so convinced that it would improve accuracy, but once we started using it we found there were fewer cases where the knee had been put in slightly out of kilter,” he says. “It is not robotic surgery – it’s an aid that enhances what we do. It’s a very straightforward software flow pattern, and it gives me a lot of information as I go along.”

Figures 3, 4 & 5: The Ci-ASR in action
Dr Maheson believes the CI System will ultimately lead to an increase in minimal access surgery. He says: “I think that once the computer-guided system is adopted, we’ll see a much higher uptake of minimal access surgery, which has previously been largely abandoned due the high rate of complications. This system is safe, patients are benefiting from it in the medium and long term, and it should enable the average surgeon to put in an implant with the expertise of an expert.”

As Dr Williams is not the only surgeon to be initially sceptical of computer-guided surgery, it may take more time and education before the system is fully adopted. It is also necessary to go on a course in order to learn how to use the system, and operations are likely to take longer for surgeons who are new to it. But ultimately, this is a system that has the potential to revolutionise the way that hip and knee operations are carried out, enhancing outcomes and proving cost-effective in the long term.

As Dr Williams says: “Surgeons can easily learn how to use the system and the more they use it the easier it becomes. Meanwhile, patients gain the knowledge and confidence that the knee has been put in more accurately, the incision is slightly smaller so there is less damage to the tissues, the blood loss has been shown to be lower and surgeons gain the confidence that they are using a tool that helps them to do their job more accurately.”

References
  1. Beaulé P, Lee J, Le Duff M, Amstutz H and Ebramzadeh E. Orientation of the Femoral Component in Surface Arthroplasty of the Hip. J Bone and Joint Surgery, 86: 2015-2021, 2004
  2. McMinn D, Treacy R, Lin K, Pynsent PB. Metal on metal surface replacement of the hip: experience of the McMinn prosthesis. Clin Orthop, 329 (Suppl): 89-98, 1996
  3. Daniel J, Pynsent PB, McMinn DJW. Metal on metal resurfacing of the hip in patients under the age of 55 years with osteoarthritis. J Bone Joint Surg, Vol. 86-B, 2004
  4. Victor J, Hoste D. Image-based computer-assisted total knee arthroplasty leads to lower variability in coronal alignment Clin Orthop. 428: 131-9 2004.
  5. Sparmann M, Wolke B, Czupalla H, Banzer D, Zink A. Positioning of total knee Arthroplasty with and without navigation support. A prospective randomised study. J Bone Joint Surg, 85B, 830-5, 2003.

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