Cath Lab Digest

      Upon the initial exam, the patient is alert and oriented. She is in no acute distress. The lower extremity exam shows her neurologic component to have decreased epicritic sensation to the plantar and dorsal feet, and a significant decrease in vibratory sensation to both feet. She has a negative Tinel’s sign in the tarsal tunnel bilaterally. Semmes Weinstein monofilament testing shows a complete absence of
sensation to all areas tested on the plantar skin. Achilles and patella reflex are normal bilaterally and symmetrically. The patient has a negative Babinski response. The manual muscle power is normal for all muscle groups tested.

      The vascular exam shows palpable pedal pulses, immediate capillary refill, superficial venous fill time (SVFT) within normal limits, no varicosities and normal distal cooling. Her dermatologic exam shows texture, turgor and temperature all within normal limits. She has no pedal lesions and no ulcerations. The orthopedic exam shows a pes planus foot type with gastrocsoleal equinus.

      We performed our typical workup for this type of patient prior to considering cryosurgery of the posterior tibial nerve. This involves injection of 1 cc of 1% lidocaine directly into the posterior tibial nerve at the level of the ankle. If the patient has a significant decrease in symptoms, this suggests he or she would be a good candidate for cryosurgery of the posterior tibial nerve. This patient had 100 percent pain relief after a diagnostic nerve block of the posterior tibial nerve, which lasted for approximately five hours. We subsequently scheduled the patient for cryosurgery of the posterior tibial nerve, using diagnostic ultrasound to assist in exact placement of the cryosurgery probe.

      We then followed up with the patient in one week, in one month and four months following surgery. She relates a 90 percent reduction in her painful diabetic neuropathy. She now does not need to take any of her previous medications for the diabetic neuropathic pain.

Combining Cryosurgery With Ultrasound: A Guide To Surgical Technique

      The procedure involves palpating the posterior tibial artery just proximal to the level of the medial malleolus. We begin by providing anesthesia using a 1 cc syringe of 1% lidocaine with 100,000 dilution of epinephrine. One would inject this solution subcutaneously with a tuberculin syringe 2.5 cm superior to the medial malleolus directly over the posterior tibial artery. We proceed to prep the area in the usual sterile manner with Betadine^® and protect the area with a Sound-Seal^® thin film dressing (BioVisual Technologies), an FDA-approved protective film dressing for diagnostic ultrasound exams.

      Cover the area with the sterile dressing and mark the incision site using a sterile pen. A #11 sterile blade provides for a transverse 3 mm full-thickness skin incision. Take care not to violate any deeper structures. (In the aforementioned case
study, we performed the procedure in the office under local anesthesia and without tourniquet assistance.) Using a blunt probe, gently penetrate the fascial tissue in the direction of the neurovascular bundle.

      Use the diagnostic ultrasound machine carefully to help create a tunnel for the cryosurgery probe. Insert the probe into the incision site while under the guidance of the diagnostic ultrasound scanner. We use the HydroStep^® Standoff pad to help facilitate compliance over bony prominences such as the medial malleolus. The standoff pad also moves vital structures into specific ultrasound focus zones. The combination of compliance and the shifting of structures deeper into focus zones provides better image quality and resolution.