Chapter 28 Lumbar Microdiscectomy
Lumbar Disc Herniation
• Lumbar disc herniation (LDH) is one of the most common injuries to the lumbar spine. LDH most commonly occurs between ages 30 and 50. Approximately 95% of LDH occur at the L4/L5 and L5/S1 levels.
• Disc herniations are broken into two classifications: contained and sequestered.
1 Contained herniations include protruded/bulging discs, in which the nucleus has not perforated the annulus fibrosis, and prolapsed discs, in which the nucleus has perforated the annulus but is contained by the posterior longitudinal ligament (PLL).
• Flexion/rotation of the lumbar segments has been shown to lead to an increase in intradiscal pressure and LDH.
1 The greatest amount of lumbar flexion/extension range of motion (ROM) occurs at the L4/L5 and L5/S1 segments, which creates an increased risk for herniation at these levels.
• Many herniations will spontaneously disappear or decrease in size over the course of several months.
• Less than 2% of disc herniations require surgery and less than 15% of patients with disc herniations will have underlying nerve root compression.
• Indications for microdiscectomy include evidence of cauda equina syndrome, significant motor weakness, or intractable pain. In addition, the patient will have failed conservative treatment, which includes nonsteroidal anti-inflammatory drugs (NSAIDs), physical therapy for 8 to 12 weeks, and epidural steroid injections.
Surgical Overview
• A small incision (ranging from 3 to 6 cm) is made along the midline, over the interspace of the affected level.
• The paraspinal musculature is stripped subperiosteally, and a retractor with a 5-pound weight is placed over the facet to open the interspace. The interspinous ligament is kept intact.
• The microscope is then introduced, part of the lateral aspect of the ligamentum flavum is resected, and a foraminotomy is performed. The nerve root is then retracted medially.
Rehabilitation Overview
• The rehabilitation program following an LMD begins on the day of surgery. Patients who undergo an LMD are hospitalized for approximately 1 to 2 days.
• The treatment in the acute stage is primarily one of education. Patients must have a basic understanding of the mechanism of injury for disc herniations, to avoid the risk of reherniation following microdiscectomy.
• The recurrence rate following LMD is reported as being between 3% and 19%. Morgan-Hough et al. performed a retrospective analysis of 531 patients who underwent primary microdiscectomy over a 16-year period. They calculated a revision rate of 7.9% and reported that contained protrusions were almost three times more likely to require revision surgery compared to extruded or sequestered discs. Seventy-six percent of the recurrent herniations occurred between 3 and 48 months following primary LMD.
• The physical therapist must consider the work done by Nachemson on intradiscal pressure and loads when educating the patient on body mechanics, posture, and exercise.
• At the Hospital for Special Surgery (HSS), all patients are instructed in log-roll transfers, when performing supine to sit, and a basic home exercise program consisting of abdominal setting, gluteal sets, and ankle pumps, before leaving the hospital.
• Patients are discharged from the hospital on the first or second postoperative day. Criteria for discharge include patient demonstration of proper supine-sit transfers, a basic understanding of body mechanics during ADL to avoid lumbar flexion, independent ambulation, with or without an assistive device, and demonstration of independence with donning/doffing a lumbar orthosis.
• Patients are provided with an activity guide upon discharge from the hospital, to provide a basic framework for the progression of activity following LMD before initiating formal physical therapy.
• During the first 4 weeks postoperatively, patients are encouraged to walk and continue with the basic exercise program described previously. Patients must continue to avoid lifting, bending, twisting, and prolonged sitting during this period in an attempt to allow healing and diminish postoperative pain.
• Patients begin formal outpatient physical therapy between 4 and 6 weeks postoperatively and are seen two to three times per week for 8 to 14 weeks.
• The phases of tissue healing, along with symptom behavior, recovery of motor deficits, and the restoration of muscle imbalances, will dictate the progression in the rehabilitation program following LMD.
• Ahlgren et al. looked at the effect of annular repair on the healing strength of the intervertebral disc in sheep spines following a partial discectomy. They determined that at 6 weeks following partial discectomy, disc strength ranged between 60% and 75% of the control values. As a result, patients must make every attempt to minimize intradiscal pressures during the first 6 weeks post-LMD.
• A systematic review of randomized controlled trials was conducted by Ostelo et al. to determine the effectiveness of active treatments following primary lumbar disc surgery. After looking at 13 studies that fulfilled the inclusion criteria, they determined that there is strong evidence that intensive exercise programs initiated 4 to 6 weeks postoperatively are more effective on functional status and faster return to work.
