Revising A Failed First MPJ Implant In A Patient With Chronic Pain

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Author(s): 
Stephen L. Barrett, DPM, MBA, and Julie Lee, DPM

   The patient understood that due to her CRPS, she would be required to have an epidural block in addition to the general anesthetic. She started on gabapentin (Neurontin, Pfizer) preoperatively. We also advised her that because of the severity of her pain syndrome, it was unrealistic to expect a complete reduction of pain. However, we noted that she should expect significant improvement and be able to wear a normal shoe without pain. She understood that additional denervation surgery could be required. There was an extensive discussion with her about her current mental status — specifically whether she was depressed — in order to gain some insight into whether she needed psychiatric treatment prior to surgery.

   Based on direct questioning of the patient as well as her ability to demonstrate in our discussion that she had realistic expectations, did not admit to any depression or anxiety, and understood the likelihood of not attaining a 100 percent result, we determined that there were no psychological issues and that the patient had a strong understanding of the benefits and risk of the surgery. (We routinely use the PHQ-9 depression questionnaire to rule out clinical depression.) We were also able to determine that her pain was not centrally mediated as she had no pain if there was no weight bearing or movement in her left foot.

   We encountered significant scar tissue around the left first MPJ but the bone quality was good. Using loupe magnification in this area, we isolated and performed neurolysis of several small nerve branches. The common peroneal nerve was severely entrapped as evidenced by an “hourglass” deformity.

Why Clinicians Should Be Wary About Assumptions About The Source Or Sources Of Pain

This case illustrates a very complex foot syndrome, which five specialists, including orthopedists and podiatrists, previously under-diagnosed. Interestingly, the patient related that all five previous physicians recommended fusion of the first MPJ. However, none of the physicians had even examined her proximally to determine that she also had serious peripheral nerve entrapment, which was an overall major contributor to her pain syndrome. The universal assumption was that her pain was coming from her joint pain, nothing more.

   This illustrates how we can become very biased and have “tunnel vision” when patients present to us with a “defined” problem.

   Fusing the first MPJ in a fit 45-year-old patient can lead to significant biomechanical impairment. The patient was adamant against first MPJ fusion. The subsequent pathomechanics resulting from a first MPJ fusion would ultimately lead to a breakdown of the lateral forefoot and have additional translation to the lower extremity of aberrant mechanics with subsequent pathology.

   The patient is now more than two years post-op and is completely free of pain with normal gait and full pain-free function. She takes no pain medications or anticonvulsants.

What We Can Learn From This Case

• When a patient presents with a previously failed surgery, especially in the forefoot, it is vitally important to evaluate the entire patient to see if there is coexistent proximal pathology, such as equinus or peripheral nerve entrapment.

• Determine the psychology of the patient in order to frame a goal of his or her expectations of a positive outcome.

• It is perfectly acceptable to operate on a patient with chronic pain as long as one takes the perioperative measures consisting of pre-op medication (NSAIDs and anticonvulsants), a spinal or epidural block, administration of ketamine during the case, pre-emptive local anesthetic analgesia and meticulous postoperative pain management.

• Do not place a short-stemmed Swanson implant without grommets.

   Dr. Barrett is an Adjunct Professor within the Arizona Podiatric Medicine Program at the Midwestern University College of Health Sciences. He is a Fellow of the American College of Foot and Ankle Surgeons.

   Dr. Lee is in private practice in Dallas, Texas.

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