Understanding the Implications of Pressure at the Patient Cushion Interface During Posterior Spine Surgery

Eligibility

Inclusion Criteria:
  • Patients scheduled for spine surgery in the prone position
  • Surgery estimated to take over 4 hours

Exclusion Criteria:

  • Patients who do not have the ability to provide verbal sensory feedback
  • Patients with pre-existing impairment of sensation at the anterolateral aspect of the thighs
  • Patients under 10 years old
  • Patients scheduled for a minor revision surgery, less than 4 hours

Contact

PI
Dr Ron El-Hawary

Description

For spine surgery the patient is most commonly positioned prone in order to improve exposure of the spine. Surgery tables can vary, but the patient is generally supported on the hips and upper chest in order to allow the abdomen to remain pendulous, reducing blood loss. Unfortunately, in this position, injuries to the lateral femoral cutaneous nerve (LFCN) have been reported as well as pressure sores near the iliac crests. The LFCN is a sensory nerve that generally originates at the roots of L2 and L3. It follows the anterosuperior iliac spine and runs behind the inguinal ligament and then superficial to the sartorius muscle. Adding to the complexity of the anatomy, Doklamyai et al. have found the anatomy to be variable and that asymmetry and multiple branches can occur.

Mirovsky et al. reported that injury to the LFCN was found in 20% of 105 patients undergoing elective spine surgery. Fortunately, all but 3% of the patients completely recovered after six months. It is believed that the incidence could be even higher but that complications are often under reported. Even though patients are informed that LFCN injury can be a complication after spine surgery they are still shocked to feel the numbness in their legs and fear that this is a direct complication of the surgery itself. Pressure mats have been widely used to study the interface pressures during wheelchair seating as well as bed sores in long term care facilities. However, these mats have not yet been used to study pressure as it relates to the incidence of LFCN damage and pressure sores occurring during spine surgery.

The objectives of this study are to quantify the pressure at the patient cushion interface and to determine 1) if there is any correlation with pressure and increased risk of developing pressure sores or damage to the LFCN; 2) if there is any correlation with dermatomal somatosensory evoked potential (dSSEP) signal decay and increased risk of LFCN damage.

Sample size= 40