Comparing Ways to Freeze the Nerve That Provides Thigh Sensation
Condition: Meralgia Paresthetica
MeSH terms: Femoral Neuropathy
Study type: Interventional
Phase: Phase 3

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.
    

Detailed description: 
      Purpose of the Study:

      The goal of this study is to compare the ultrasound-guided subinguinal injection technique to
      the neurostimulation-guided injection technique for lateral femoral cutaneous nerve block.
      The neurostimulation technique uses an electrical field to stimulate the nerve when a needle
      is close proximity. One older study showed it is better than using landmarks in achieving
      anesthesia of the lateral femoral cutaneous nerve, but no studies have compared it to using
      ultrasound to freeze the nerve [7]. The primary outcome will be relative efficiency, i.e. the
      total anesthesia-related time (defined as the sum of performance and onset times). This is
      looking at how long it takes for the procedure (needle insertion, medication injection), plus
      the time it takes for the thigh to go numb. Secondary outcomes will include relative success
      rate, procedural discomfort, number of needle passes and topographical sensory distribution
      of this nerve in this cohort of patients .

      Methodology:

      Selection of Human Subjects:

      With the approval of the Defence Research & Development Canada Human Research Ethics
      Committee (HREC), a total of 27 volunteers will be recruited. Subjects will be recruited by
      advertising within the CF Health Services Centre Facility and by email notification to CF
      members in the National Capital region through the DWAN. If there is insufficient volunteers,
      those people that have volunteered, will be contacted by email to inquire if they are aware
      of any other people that maybe be interested in volunteering so that the study can be
      finalized. If they know if anyone, they will be asked to forward the initial email to those
      people, asking them to contact the investigator if they wish to have more information.
      Interested civilian volunteers and Class "A" reservists will be approached from the cohort of
      patients that responded to the original communication email.

      Once patients have submitted their names for consideration, they will be contacted to review
      whether they meet inclusion/exclusion criteria.

      Data Analyses:

      the investigators expect the success rates to be similar for both groups. However our
      hypothesis is that the performance time and the onset time could be different. Therefore the
      main outcome is the total anesthesia-related time (sum of performance and onset times).
      According to Shannon et al [7], the total anesthesia-related time for the neurostimulation
      technique is 10.1 +/- 4.7 min (performance time: 9.5 +/- 4.7 min and onset time: 0.8 +/- 0.9
      min). Using a paired T-test to compare both techniques, a difference of 30% in total
      anesthesia time would represent an effect size of 0.74 and require a total of 17 subjects
      undergoing bilateral blocks to obtain a 2-tailed α error of 0.05 and a ß error of 0.2. Since
      onset and total anesthesia-related times can only be measured for successful blocks and since
      the investigators expect a success rate of 85% for neurostimulation, the investigators will
      recruit 25 patients to account for those who do not reach the postulated end point.

      Normality of the continuous data will first be assessed with the Kolmogorov-Smirnov test.
      Continuous data will then analyzed using a paired T-test. For categorical data, the
      Mann-Whitney U test and Chi-square test will be used as appropriate. Hypotheses tested will
      be 2-tailed. P < 0.05 will be considered statistically significant.

      Risks:

      Participation in this study will be voluntary and volunteers can withdraw consent at any time
      without having any effect on access to future medical care. There will likely minor
      discomfort during the procedure similar to having freezing before a dental procedure or blood
      drawn. Patients can ask us to stop the procedure at any time. The chance of minor discomfort
      for up to a day or two after the injection can occur and can be managed with over the counter
      acetaminophen or ibuprofen. The investigators do not expect any limitations to daily
      activities.

      Furthermore, side effects associated with lateral femoral cutaneous nerve blocks have not
      been reported and are likely rare. [8].

      Confidentiality/Anonymity

      Patients' confidentiality/anonymity will be protected through two mechanisms:

        -  research subjects are identified by serial numbers

        -  access to patient's research data will be restricted to primary investigators only

      Approximate Time Involvement

      The approximate time commitment is 1.5 hour.

      Roles and Responsibilities of Research Team

      Recruitment, study planning and organization will be done by Gaurav Gupta. Technical
      procedures, data collection and manuscript preparation will be shared tasks by the entire
      research team.
    

Intervention name(s): Nerve Injection- Nerve Stimulator; Nerve Injection - Ultrasound
Intervention type(s): Drug; Drug
Intervention description(s): 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.
Other intervention name(s): Lateral Femoral Cutaneous Nerve Block- Neurostimulation; Lateral Femoral Cutaneous Nerve Block- Ultrasound
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Diagnostic
Keywords: Lateral Femoral Cutaneous Nerve Block; Meralgia Parasthetica; nerve stimulator; ultrasound