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 correlation with radiology
This is perhaps the most common cause of surgical failure. For good outcomes, there has to be a 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.
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 fibrosisis 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.
Lack of post operative Rehabilitation
The period after surgery is perhaps more important than the surgery. The surgery may address the problem at hand, but does not correct the cause of the problem. The post operative physiotherapy is important to correct the posture of the patient, and in keeping the muscles adjacent to the spinal column healthy and strong. Adjusting the workspace and working conditions as per the patient is also very important. The chances of getting the same spine problem or a new spinal problem again is quite high if rehabilitation protocols are not followed strictly.
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 is for the general awareness of the patients and cannot replace expert medical advice. Patient treatments need to be individualised and that can be decided based on clinical examination and evaluation by a trained physician.
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