Unilateral Diskectomy through a Midline Incision

Back pain is one of the most common complaints in the patient population as a whole. ¹ Over a period of 7 years, from 2000 to 2007, the total number of adults with back pain increased by 29%, from 30.2 million to 38.9 million, whereas the total number of adults with chronic back pain increased by 64%, from 7.8 to 12.8 million. ¹ These increases led to an increase in annual medical expenditures from $15.6 billion in 2000 to 2001 to $35.7 billion in 2007. Only a few of those patients will have with radiculopathy. Therefore, identification of these patients with a thorough history and physical examination is the first step in the management of lumbar disk disease.

Back pain in and of itself is not pathognomonic of a herniated intervertebral disk (HIVD) ² but can be due to myriad pathologies in the lumbar spine. A patient with a herniated lumbar disk will complain of back and leg pain that is exacerbated by coughing, sneezing, or any Valsalva maneuver. The pain can sometimes originate in the buttock area rather than the lower back and radiate down the affected side. Patients may recall lifting a heavy object or doing an activity they are not used to before the onset of symptoms. Just as often, patients will have the insidious onset of leg pain after a variable history of back pain. ² Back pain may not be a presenting symptom in younger patients.

The location of pain and paresthesias is helpful in localizing the level of herniation. Central or paracentral herniations, or those occurring within the canal, will compress the nerve root that exits at the level below ( ▶ Fig. 41.1, ▶ Fig. 41.2). As such, a central or paracentral disk herniation at L3–4 will compress the L4 root. Foraminal or far lateral herniations, on the other hand, will affect the root exiting at that level; for example, an L3–4 foraminal disk herniation will compress the L3 nerve.

Several physical examination findings in concert are found in lumbar disk disease. The straight leg-raising test is positive on the herniated side and occasionally with large herniations, on the opposite side as well. Conditions that mimic a herniated disk, such as hip disease, greater trochanteric bursitis, spine tumors or infections, fractures, synovial cysts, shingles, and peripheral vascular disease should be excluded by history and physical examination. ³

Fig. 41.1 Sagittal T1-weighted magnetic resonance imaging in a patient with a 1-month history of severe left leg pain involving the thigh and top of the foot. Examination shows limitation of straight leg raising and knee extension. A large herniated disk is seen behind the body of L4 (arrow).

Fig. 41.2 Axial T2-weighted magnetic resonance imaging shows the extradural herniated fragment (arrow) within the canal.

41.2 Patient Selection

Great knowledge has been gained from the Spine Patient Outcomes Research Trial (SPORT). ⁴ Comparison of surgical and nonsurgical treatments for lumbar herniated disks showed that both groups had significant improvement. The surgical group, based on as-treated analysis, had greater improvement than the nonsurgical group. Faster pain relief and return to premorbid functional status were seen in the surgical group. ⁵ A 4- to 6-week trial of conservative therapy is encouraged before surgical intervention is considered. Decompression can be entertained at an earlier time if the patient suffers from progressive weakness or intractable pain. Bowel or bladder symptoms require urgent surgery, as these may represent cauda equina syndrome. The reoperation rate of HIVD was found to be 11% at 5 years, which increased to 15% after 8 years. ⁵ Almost half of reoperations for reherniated disks were at the same level. ⁵

The imaging modality of choice is magnetic resonance imaging (MRI). MRI provides excellent soft tissue anatomical detail, and, in reoperations, MRI with gadolinium may distinguish enhancing scar tissue from nonenhancing disk. ⁶ Not every disk herniation or reherniation is symptomatic. It remains extremely important for the surgeon to correlate the history and physical examination findings with any radiologic findings and, as such, predict whether a patient may benefit from surgical intervention. Computed tomographic myelography may be used in cases where MRI interpretation is complicated by artifact from hardware or when a patient has an implant that is not MRI compatible, such as spinal cord stimulators or cardiac pacemakers.

41.3 Preoperative Preparation

All patients should have their medical and surgical histories reviewed and, if needed, be evaluated and cleared by a specialist, internist, primary doctor, or surgical comanagement service. All blood thinners, like aspirin, Coumadin (Bristol-Myers Squibb, New York, New York), anti-inflammatory medications, and Plavix (Sanofi-Aventis, Bridgewater, New Jersey), should be discontinued for at least a week before surgery. Basic blood tests, like a complete blood count, basic metabolic profile, and coagulation profile, should be checked within a 30-day period before the date of the procedure.

On the day of surgery, patients should be reevaluated for any major changes in their symptoms, and any necessary changes to the treatment plan made. The intended surgical site should be inspected for lesions that may prevent surgery, and the level and side should be clearly marked. Radiographs should be rechecked to confirm pathology. Prophylactic antibiotics are given intravenously within 30 minutes from incision. The procedure is typically performed with the patient under general endotracheal anesthesia; however, recent reports describe disk surgery under local analgesia with encouraging results.

41.4 Operative Procedure

After anesthesia is induced, the patient is rolled prone onto the operating room table. In case of obese patients, the lateral decubitus position is an option. In the decubitus position, however, the surgeon and assistant have to stand on the same rather than on opposite sides of the table, which is somewhat awkward. Also, confirming the level with intraoperative radiographs is more cumbersome compared with the prone position.

The choice of operating room table is determined by the surgeon’s preference. The ideal table will allow adequate exposure of the surgical site; will allow the abdomen to hang freely, reducing venous pressure and bleeding during the procedure; and will not induce undue pressure on any particular portion of the body. Our preference is the OSI Jackson table (Mizuho OSI, Union City, California). The Wilson frame or gel laminectomy rolls are less attractive alternatives. Also, with the former, the patient is inconveniently elevated, necessitating step stools for the surgeon and assistant.

Before an incision is made, a time-out is called, and the identity of the patient, the level, and the laterality are confirmed. Antibiotics are intravenously administered. Ideally, the proposed incision should be directly over the disk space. It should be 2 to 3 inches long, but experienced surgeons may use a smaller incision ( ▶ Fig. 41.3). The skin is infiltrated with 1% lidocaine with 1/200,000 parts epinephrine for hemostasis. The skin is incised sharply through the superficial fat to the thoracolumbar fascia. Bleeding is controlled with bipolar electrocautery. A self-retaining retractor is placed, and the spinous processes are palpated. The fascia is traversed on the symptomatic side with electrocautery. The spinous process is marked with an Allis clamp (Integra Life Sciences Corporation, Plainsboro, New Jersey), and a localizing radiograph is taken to confirm the level ( ▶ Fig. 41.4). The use of preoperative markers taped to the skin or marking the skin preoperatively with indelible markers is inadequate. If there is ever any question of the level during the procedure, a localizing radiograph should be repeated.