With experience, it is now clear that in a number of clinical situations percutaneous discectomy is particularly useful. Perhaps APLD could have the greatest impact in a patient who has had a reherniation at the site and level of previous disc surgery. Patients who reherniate after open back surgery constitute approximately 5% of that patient population. Of great importance is that success rates are lower for patients who are reoperated on with an additional open discectomy at the same level as previous surgery; moreover, these patients are exposed to a much higher morbidity as a result of the lack of tissue planes due to epidural fibrosis.
We have found that APLD can be an excellent procedure for this patient population. Since the route of the instrumentation in APLD takes a posterolateral course that avoids the epidural space, the presence of epidural fibrosis does not complicate the procedure or add morbidity, as it does in an open discectomy. Interestingly, excellent success rates have been reported (as high as 90%) in this patient population.4 These results have been confirmed by other investigators. Mirovsky et al.12 described the results with 10 patients with lumbar disc reherniation at the same level as an earlier open operation. With average follow-up of 2.5 years, 70% of their patients showed complete or significant pain relief while avoiding reoperation. Sixty percent showed diminution in motor deficit as well. Failures were in patients with spinal stenosis or segmental instability. In our own experience with 21 patients, 20 of whom had follow-up of 3 years or greater, 18 out of 20 were treated successfully.
The reason for the excellent success rate in this group of difficult-to-treat patients may be secondary to the fact that epidural fibrosis decreases the chances for a free fragment occurring. In addition, because of the epidural fibrosis, relatively small changes in the disc pressure may provide greater symptomatic relief. Last, it must not be overlooked that this patient population has already experienced an open discec-tomy and may be more satisfied with only partial pain relief in exchange for avoiding a repeat open operation. It is in this patient population that we believe that APLD is still markedly underutilized. Certainly, when one weighs the risk versus benefit of APLD, with its lack of morbid-ity and excellent success rates in this difficult to treat group of pa-tients, APLD appears to be the procedure of first choice in this clinical situation.
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