Low back pain is among the commonest causes of absenteeism from work and loss of pay. Back pain can be caused by a plethora of causes ranging from degeneration to spinal instability. Although most of back pain causing conditions are not remediable to surgery or interventions, the number of patients undergoing procedures for back pain keeps increasing by the year. A significant proportion of these patients may not get any relief or their symptoms may recur after some time. Therefore it is important to look into and understand the causes of failures of such surgeries, in order to improve their success. Lets look at them in a simplistic view.
Wrong diagnosis or poor clinical correlation with radiology.
This is perhaps the most cause of surgical failure. For good outcomes, there has to good correlation between the symptomatology, clinical findings and the radiological findings on MRI and X-rays. The greater the correlation, better the chances of success. If the patient continues to have pain, similar to that before the surgery, chances are that the pain source was wrongly attributed to and treated. This is not unusual because it may not be possible to isolate the pain generators in the spine accurately. This is where the symptoms, clinical findings and the radiological findings need to looked at and interpreted.
If all things match, then the chances of surgical intervention are very good. In certain conditions, all these aspects fit well whereas in others the correlation may not be exact. A patient with pain along back of thigh and calf, weakness in foot and a prolapsed intervertebral disc on MRI is good clinico-radiologic correlation, with higher chances of success than a patient with back pain and prolapsed intervertebral disc on MRI.
Similarly a patient with back pain worsening on bending forward with spondylolisthesis (abnormal motion between two adjacent spinal segments) on X-rays has good correlation and chances of surgery success than back pain with normal x-rays.
Recurrent disease or adjacent level disease
In this scenario patient has good relief after a procedure or surgery, and then symptoms reappear after some time which can vary from a few weeks to years. It depends on the nature of the disease treated. Discs can prolapse again at the same level in 5% of the patients, stenosis can recur after surgery for canal or foraminal stenosis causing compression or pinching of nerve roots. As we all know that spine is made from multiple vertebra and after one spinal level is operated, the stress on the adjacent levels increase and they become more prone to accelerated degeneration. So it is not unusual to have pain and other symptoms arising from the same level or the adjacent level.
Recurrence of disease at the same level may produce symptoms similar to those experienced by the patient before the surgery. Disease at adjacent levels may produce slightly different symptoms as a different nerve root level is getting compressed.
Failure of primary surgery due to technical reasons
We must also consider technical reasons for failure of a spine surgery. If the goals of the surgical intervention are not achieved satisfactorily, then symptoms may persist. For example, if a fragment from an extruded lumbar disc is missed during surgery and continues to put pressure on the nerve causing persistent pain. This is quite common as some areas of the operative field are not in vision and can only be probed blindly. Similarly inadequate decompression of nerves in surgery for lumbar canal stenosis causes persistent pain.
Persistent pain from scarring or failed fusion
Some patients may start having pain after 6-12 weeks after surgery. Scarring is a part of the normal healing process after any injury, and same also happens after spine surgery. Scar tissue does not have any nerve fibres, so in itself scar is not painful. However, scar tissue can be a cause of back pain or leg pain by entrapping the nerve roots in the scar tissue. As scar tissue does not have the normal elastic properties of healthy tissues, the nerve roots entrapped in scar tissue cause pain with movements. Scar tissue or Epidural fibrosis is considered by some to be amongst the most common causes of back pain after surgery.
Another cause of pain in patients who underwent spine fixation with instrumentation(screws and rods) is implant failure and failure of fusion. The aim of fusion surgeries is to achieve bony union between the adjacent spinal vertebrae. This is helped by the titanium screws and rods by reducing movements between the adjacent vertebrae. If the bone fail to fuse over time, the implants may fail as even titanium implants also undergo wear and tear and loose strength eventually. Screws and rods break under normal stress when the bony union does not occur. This causes reappearance of back pain which gradually worsens over time after a painless period. Causes of fusion failure vary from patient factors like severe osteoporosis to technical issues relating to surgery.
These are the basic causes of persistent or recurrent back pain after surgery for lumbar spine diseases. There are many more. Treatment for residual symptoms or recurrent back pain is not simple and should be treated by a highly experienced team involving spine surgeon, pain management specialist and physiotherapist.
Disclaimer: This article is for general public awareness only and can not replace expert medical advice. Please visit a doctor for advice.
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