Comparing Ways to Freeze the Nerve That Provides Thigh Sensation
Condition: Meralgia Paresthetica
MeSH terms: Femoral Neuropathy
Intervention: Nerve Injection- Nerve Stimulator; Nerve Injection - Ultrasound
Intervention description: For the neurostimulation nerve injection technique, the initial puncture site will be located medial to the anterosuperior iliac spine, just caudal to the inguinal ligament [7]. The 22-gauge insulated needle will be connected to a stimulator set at a current of 1.5 mA, a pulse width of 300 ms and a frequency of 2 Hz. A paresthesia referred to the lateral aspect of the thigh at a minimal stimulatory threshold of 0.6 mA (0.3ms) will be sought prior to the injection of local anesthetic [7]. A total of 5cc of 2%Xylocaine will be injected for the nerve injection/anesthesia.; For the ultrasound nerve injection group, after skin disinfection, the inguinal region of patients will be scanned using a high-frequency (6 to 13 MHz) linear array transducer covered with a sterile plastic cover. An ultrasound image showing the inguinal ligament and anterior superior iliac spine (ASIS) will be obtained. Using an out-of-plane technique, a 22-gauge nerve block needle will be inserted 1-2 cm medial to ASIS. The needle will be advanced until its tip rests under the inguinal ligament, immediately ventral to the iliopsoas muscle [6]. A total of 5cc of 2%Xylocaine will be injected for the nerve injection/anesthesia.
Phase: Phase 3
Study type: Interventional
Primary purpose: Diagnostic
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Enrollment: 21.0
Sex: All
Minimum age: 18 Years
Maximum age: 60 Years
Healthy volunteers: Accepts Healthy Volunteers
Keywords: Lateral Femoral Cutaneous Nerve Block; Meralgia Parasthetica; nerve stimulator; ultrasound

Summary:

      Background

      The sensation on the outside of portion of our thighs is provided by a nerve called the
      lateral femoral cutaneous nerve (LFCN). The investigators can inject freezing around the
      nerve to reduce the feeling around the thigh (i.e. anesthesia). Anesthesia, or freezing, of
      the lateral femoral cutaneous nerve can reduce pain for patients having A) hip and knee
      surgery [1,2], B) removal of a skin graft [3], and C) wound care. In addition, damage to the
      LFCN (i.e. Meralgia Paresthetica) has been associated with body armour and gun belt use in
      military and police personnel [4]. Although generally a benign condition, compression or
      injury to this nerve can be painful and require treatment. In addition, the actual
      variability in sensory distribution for this nerve has not been elucidated in a topographical
      fashion and will be measured in this study.

      Finding the most efficient and effective method for anesthesia of the LFCN can improve and
      positively impact the quality of pain control for patients. Ultrasound has improved the
      accuracy and efficiency of various other regional anesthesia techniques, and could also
      impact the safety. Therefore the investigators hypothesize that ultrasound guided lateral
      femoral cutaneous nerve block using the subinguinal technique will be statistically more
      efficacious and efficient when compare to neurostimulation based blockade.
    

Eligibility criteria:

        Inclusion Criteria:

          -  male and female between 18 and 60 years old

          -  American Society of Anesthesiologists classification 1-3

        Exclusion Criteria:

          -  adults who are unable to give their own consent

          -  pre-existing neuropathy (assessed by history and physical examination) -

          -  coagulopathy (assessed by history and physical examination and, if deemed clinically
             necessary, by blood work up i.e. platelets ≤ 100, International Normalized Ratio ≥ 1.4
             or prothrombin time ≥ 50)

          -  renal failure (assessed by history and physical examination and, if deemed clinically
             necessary, by blood work up i.e. creatinine ≥ 100)

          -  hepatic failure (assessed by history and physical examination and, if deemed
             clinically necessary, by blood work up i.e. transaminases ≥ 100)

          -  allergy to local anesthetic agents local anesthetic

          -  pregnancy based on patient self report of last menstrual cycle. If a patient
             wish/insist on participating in the study, and pregnancy status is unclear, a urine
             pregnancy test will be offered. Also risk of Lidocaine in pregnancy will be discussed
             with the patient as currently classified. We will convey that this risk is currently
             classified as a Risk Class B, which means that animal-reproduction studies have not
             demonstrated a fetal risk but there are no controlled studies in pregnant women. We
             will also discuss that animal-reproduction studies have shown an decrease in maternal
             fertility), but that was not confirmed in controlled studies in women in the first
             trimester and there is no evidence of a risk in later trimesters,

          -  prior surgery in the hip and lateral leg region

          -  prior lumbar surgery

          -  previous pelvic fracture

          -  previous L1, L2 or L3 lumbar radiculopathy, plexopathy or meralgia paresthetica

          -  chronic pain syndromes requiring opioid intake