Case Summary

• Two females, 74 (Patient 1) and 58 (Patient 2) years old, came to the pain management center over a year after their respective TKR.

• Patient 1, reported 6-10/10 left lateral leg pain, aching in quality with shooting pain, in the distribution of the peroneal nerve. 

• Patient 2, described 10/10 burning pain down her right lateral calf to her foot.

• Both were taking duloxetine and gabapentin with inadequate pain control. Both received a diagnostic peroneal nerve blocks, Patient 1 reported 90% improvement and Patient 2 reported 100% improvement. They both received a temporary sciatic PNS implantation (SPRINT system, SPR Therapeutics, Cleveland OH). 

• Patient 1 noted no pain at her 1 month follow up and stated she no longer used a cane to walk. She returned 2 months after her PNS placement, reported no pain w/ 5hrs of device usage per day, and had the leads removed. She was called one year after removal of the stimulator and continues to have no pain.

• Patient 2 reported continuous usage of her PNS at her 2 week follow up and 0/10 pain. One week afterwards the leads were accidentally dislodged while she was in the shower, she did not notice a return of her pain. She reported a few months of relief after her stimulator was dislodged, then reported a slow return to her baseline pain.

Discussion and Conclusion

• PNS can be considered in the treatment algorithm for patients with chronic knee pain and post TKR pain (2-7). 

• Given success with more conservative management (physical therapy, pharmacotherapy, TENS, nerve block/RF denervation), PNS is not a first line choice (2-4, 10). Li et al surveyed pain providers and found PNS to most frequently be a 4th line intervention, and the most common indication was persistent post-surgical pain after 3 months (10). 

• Pilot studies have shown that peripheral nerve stimulation for 60 days can provide pain relief that is sustained for periods of time longer than the stimulator is active (2-7, 11). Reviews discuss improvement in pain well after the 60 days the PNS is in place (2–7), which is in line with the experience of our patients. 

• PNS might be considered an alternate intervention for the 10-34% of patient who have unfavorable pain outcomes after TKR (1).

• While most case reports of knee pain management using peripheral nerve stimulator describe placement of leads over saphenous nerve.

• Li et al survey data showed the distal common peroneal, tibial, and sural nerves were the most commonly targeted (10)

• In these two cases, we placed them over the peroneal nerve since the pain distribution was more lateral. This approach is in line with more recent survey data (10)

References

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