Incidence and prevalence of back and leg pain is very high: All of us see patients with backache and sciatic pain in our day-to-day practice. It is only next to respiratory tract infection as a major cause for attending a clinic. In all urban settings with changed life style, lack of exercises, bad postures, excessive use of vehicles and disturbed nutrition; problem of discogenic backache and sciatica is on the rise.

Back surgery is in bad repute: It is reported in literature that incidence of surgery for the disc related problems is not over 5-8% of the patients affected. It is also observed that a patient is likely to be more willing for an intervention for a coronary artery blockage but there is a great reluctance about surgery for the back. This reluctance may be based on ignorance and fear about outcomes of disc surgery or interventions.

Lack of concepts in assessment and monitoring of leg pain: There are certain areas of confusion and controversy related to care of the back. Even though MRI scan has become a gold standard in imaging analysis of the back problems, it still has as high as 30%, of false positive for disc pathologies, as it has a strong undercurrent of age changes which may not be symptomatic. Clinical assessment of patients with pain in the lower limb is not very well established yet. It is still based on straight leg raising test that only establishes a presence of mechanical compromise in a nerve root canal and not inflammation or related cause of pain. Monitoring of patients with lower limb pain through their conservative care and natural resolution to asymptomatic stage is still based on very primitive ideas and concepts.

What’s new? These problems are now tackled by introduction of new concepts in back and sciatica care that have made a paradigm shift in management of sciatica and backache.

These are:

1. Ability to distinguish local nociception [pain felt at site of its origin] and or referred pain [pain felt at any site along nerve carrier] in patients with lower limb pain based on remote palpation of related nerve.
2. Ability to answer for sure, where is pain coming from? By clinical examination and added invasive imaging studies.
3. Ability to access and address the pain generator in case of back and leg pain in most minimally invasive way.
4. Monitor natural resolution of back and sciatic pain based on nerve palpation.
5. Address pain due to inflammation in case of back and leg pain by needle techniques.
6. Endoscopy is a new SPINE (Safe Precise Innovative Novel Enabling) solution for disc problems offered under local anaesthetic and as a day care.

This article dwells on the philosophy of minimally invasive spine surgery and spinal endoscopy solution for disc problems. This procedure is offered under local anaesthetic. It helps in establishing a better correlation between pain generator and symptoms, and improving image-symptom correlation and outcome for the patient.

Let us see how we approach this problem differently
History Taking : Patient with back and leg pain is assessed by noting pain intensity on a visual analogue scale [scale where 0 is no pain and 10 is pain severe enough to make patient cry] and location of pain on a pain diagram. These help in proper record keeping and monitoring. History taking is not complete before noting duration of present and past complaints and remissions and exacerbations. At end of history we can say we have acute, sub acute or chronic back or leg pain. Based on pain patterns, a primary diagnosis of pain generator can be guessed.

Examination is focused on a fundamental question. Is the pain, which patient is complaining about, “local pain, arising from site which is talked about or is it coming there from other site through a local nerve supply?” matching pain patterns and known pain generators can help in localizing the pain generator.

Where is pain coming from?
New thinking for pain diagnosis is based on our experience of operating all our patients under local anaesthetic. It has a strong basis in studies by Stephen Kuslich on tissue origin of pain in low back and sciatica. This study is palpation of tissues under serial local anaesthetic during open surgery. Patient undergoes a traditional open posterior midline approach surgery where local anaesthetic is given in a layer, after palpating tissues in that layer, right from skin to annulus of the disc, through subcutaneous tissue, fascia, muscle and annulus.

Results
It was found that backache arises from posterior annulus, anterior epidural tissues, anterior facet capsule or end plates. The pain in back and buttocks can arise from simultaneous affection of posterior annulus and nerve root, which is inflamed. Sciatica was noted only in stretched and inflamed nerve roots. It was thus concluded that pain in leg can only arise from nerve root affection, basically mechanical and chemical to start with. It was also found that palpation and probing of non-inflamed nerve only elicited paraesthesia and not pain.

New Imperative
It is thus imperative for us to find a clinical correlate of the nerve root inflammation in patients of sciatica and backache with buttock pain. Clinically, this is done through elicitation of “Gore sign”, described by the author in 1998 and since copyrighted. This is palpation of deep peroneal and sural nerves on lateral aspect of ankle and calcaneus and correlation of these painful nerves with inflammation related to L5 and S1 level respectively.

McKenzie’s Philosophy : Significant test available for backache assessment is McKenzie’s Test. A patient with back and buttock or leg pain is asked to move through normal possible range of movements. Change in intensity and location of pain is noted. McKenzie’s test is positive, indicating an annulus with good integrity and a possibility of pain relief by exercises. Here, the pain reduces considerably and becomes more central from a peripheral location as the patient does an end-stage movement, mainly extension. Repeated end-stage movement of extension then may relieve pain and disability over time.

Treatment based classification of backache: Backache could need traction when associated with back spasm, mild lower limb radiation of pain, which may or may not centralize.

Backache needing immobilization and manipulation, when patient has severe spasm, list on flexion or even at rest and lateralisation of spine with severe pain.
Backache needing exercises or special exercises when pain centralizes and McKenzie’s test is positive. This treatment-based classification has simplified our approach to backache.

Analysis of sciatica : Sciatica is analyzed based on palpation of nerve and straight leg raising test during neurological examination. Treatment based staging of sciatica is: stage of [tender nerve] nerve sensitization needing anti-inflammatory medication and rest. Next stage of nerve mechanical compromise is detected by positive straight leg raising. Last is stage of nerve dysfunction is indicated by neural deficit, sensory or motor.

Discogenic pain? The level of pathology starts with continuation of backache and sciatica is discogenic in many cases. Apart from serious pathologies like infections, tumours and cauda equina lesions, most chronic cases happen to be discogenic. Clinical assessment then can be summed up by asking following questions in a patient with back and leg pain.

1. Is the pain sciatic pain? [Depending on location and pain pattern]
2. If yes which root is affected? L5 or S1? If No is it local nociception?
3. Is it discogenic? Based on McKenzie’s test. If pain increases in extension or is paraspinal is it facetal?
4. If discogenic which disc?
5. Non-Invasive imaging like MRI scan can give better clue to affected disc. The painful disc may be showing changes of internal disc derangement or it may have an annular tear. This tear in combination with a nuclear fragment can present classically as disc herniation.
6. Invasive imaging may be needed for better morphological analysis and pain and disc correlation. This is done by invasive discography. Analysis in this way helps in identifying anatomical target for our surgery. As all pain generators are in inter vertebral foramen an approach that is transforaminal is most logical.

A disc annulus is torn in a degenerative disc from inside out and allows initially leakage of cytokines including TNF alpha from disc centre to peridiscal nerve root. This may induce periradicular inflammation. This is treatable by use of periradicular instillation of steroid. If annular tear is also associated with nuclear fragmentation it probably results in nuclear herniation. Natural course of resulting sciatica can be positive when we have a healed annular tear and absorption of nuclear fragments by macrophages and relief of inflammation. A negative outcome is persistent pain due to persistent annular tear and a nuclear fragment and inflammation around a stretched root. Failure of natural resolution of pain due to failure of healing of annulus, or mechanical presence of nuclear fragment is then treated by surgery. Minimally invasive surgery thus has a physiological target. It is the persistent pain generators!!! All of them are accessible through foramen under local anaesthetic.

Minimally invasive surgery is based on least surgical corridor sufficient enough to target foraminal pain generators. To increase the effectiveness added modalities of laser and radio frequency modulation is used. As the patient is awake throughout surgery and under local anaesthetic [awake-aware state surgery] it is safe and simple. It does not need IV fluids or blood transfusion. There is no need of dressings and patient can take bath next day and with pain as a guide for activities can return to work very rapidly.

Author has an experience of transforaminal Endoscopic surgery and laser Foraminoplasty of over 450 cases done in last 6 years beginning December 1999. It offers a better pain and pathology correlation and a safe and precise solution to sciatica.

Gore Sign Spinoffs
Use of gore sign for assessment has given spin offs in form of better diagnosis of difficult knee pain patients where 40% of pain could be sciatic pain. Author observes that pain complained around knee mainly on lateral aspect, associated with change in location and increase with walking to calf or thigh, more pain and tingling on sitting cross legged, inability or difficulty of knee flexion and difficulty in full knee extension on prolonged sitting are associated feature of this nerve mediated knee pain which is most likely to be discogenic sciatic pain.

Author also has significant observation of heel pain correlated with a tender sural nerve [affection of S1 root] in more than 30% patients of heel pain. As these knee and heel pains are not locally arising pains but referred neuralgias they need a different approach and use of usual anti-inflammatory medications may not be effective.

How is Spinal Endoscopy Done?
Endoscopic surgery is done in a prone patient on a radiolucent table under guidance of C arm IITV. A needle is initially put in intervertebral foramen. Depending on need a radiculogram and a discogram is done. Use of blue dye indigo carmine in addition to radio opaque dye is done during discography. Blue dye helps identification of degenerated acidic disc fragments under Endoscopy, as they are stained blue. After accessing affected disc it is excised by use of manual instruments or use of laser. Laser is also used for bone cutting as in facet under cutting for lateral Foraminoplasty. Use of bipolar radio frequency cautery is done for annular shrinkage and tightening. In almost 65% patients pain is relieved on table. Postoperative course is rest for upto 2 days and then rapid mobilization. Set of back hardening exercises are started by 3 weeks and a full functional rehab is possible by 4 to 6 weeks.

This new paradigm for the first time considers patient perspective of pain generation process and also what a patient wants.

Endoscopic Spine Surgeon, Pune (gore@vsnl.com).