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Surgical options for the treatment of lumbar disk herniation include traditional open lumbar diskectomy involving subperiosteal dissection of the paraspinous muscles and retraction with a Taylor or Markham/Meyerding retractor, open lumbar microdiskectomy employing an operating microscope and Williams retractor, and minimally invasive microdiskectomy using a muscle-splitting approach and tubular retractors. The traditional approach for lumbar microdiskectomy and nerve root decompression has proven successful for short-term symptomatic relief of radicular leg pain in the majority of patients. When compared with a traditional approach to diskectomy, use of the operating microscope provides better anatomical visualization via a smaller skin incision to minimize potential complications, which include bleeding, infection, instability of the lumbar spine, persistent back pain and/or radicular pain, nerve root injury, dural tear, air embolism, injury to abdominal viscera, and/or major vascular injury.1,2

Refinement of the microsurgical approach has led to the development of minimally invasive techniques that utilize muscle-splitting tubular dilators aimed to minimize approach-related complications. Compared with an open microdiskectomy, a muscle-splitting, percutaneous approach to the lumbar disk space decreases the length of incision, minimizes soft tissue dissection by preserving natural tissue planes, and provides excellent visualization of the surgical anatomy. The demonstrated benefits include decreased postoperative pain, reduced length of hospital stay, and earlier mobilization and return to work, especially in patients with significant comorbidities.3–5 The use of a minimally invasive approach for lumbar diskectomy is ideal for patients in whom the requisite larger incision and muscle dissection of an open approach could bring significant additional morbidity and make visualization of the surgical anatomy more challenging. In our opinion, this makes minimally invasive microdiskectomy the preferred approach over open microdiskectomy in elderly patients and in patients with far lateral disk herniation, recurrent disk disease, excessive soft tissue or paraspinal muscle atrophy, obesity, and multiple medical comorbidities. In contrast, for thin, young, healthy patients, the advantage of minimally invasive microdiskectomy compared with open microdiskectomy is debatable. Although the decision of surgical approach is usually dictated by surgeon experience and comfort level, certain pathologies and situations may be best treated using one technique as opposed to another. Increasing a surgeon’s technique repertoire will greatly aid that surgeon in performing the best surgery for a given problem, rather than treating all problems with a single surgical technique.

Preoperative Evaluation

All patients presenting with a history of leg pain suggestive of nerve root compression from disk herniation should undergo a detailed history and physical examination to ensure the pain is radicular in nature, to detect any motor or sensory deficit, and to rule out nonneurogenic etiologies for their pain. Imaging studies must be performed and should correlate the level of radiographic findings to the distribution of physical findings. Preoperative radiographic evaluation should include magnetic resonance imaging (MRI) or computed tomography (CT) myelogram to identify nerve root impingement secondary to disk herniation and detect the presence or absence of stenosis. In addition, anteroposterior (AP), lateral, and flexion-extension lumbar radiographs should be obtained to evaluate for the presence of instability. Patients most likely to benefit from surgical treatment are those presenting with unilateral radiculopathy who are without spinal instability or significant back pain, and who have failed 6 to 8 weeks of conservative management.

Operative Technique

The patient is brought to the operating room where general endotracheal anesthesia is induced. The patient is placed prone on a Jackson table using a Wilson frame. The fluoroscopic monitor is placed at the foot of the patient opposite the operating surgeon for comfortable viewing. It is preferable to position the operating microscope base on the same side as the surgeon and the C-arm base on the opposite side. Should an endoscope be used, the viewing tower for endoscopic imaging is placed opposite to the surgeon with the C-arm base on the same side.

After the patient is positioned, a preoperative localizing radiograph is obtained with a Steinmann pin using lateral fluoroscopy to determine the operative level and plan the surgical approach. Once the appropriate disk level (s) is (are) identified, the site of entry is marked 1.5 cm lateral to midline, ipsilateral to the pathology. An 18 to 20 mm skin incision centered over the disk level of root compression is drawn to facilitate the surgical approach for a single-level procedure. For two-level procedures the incision should be planned midway between the affected levels. A stab skin incision is made with a #15 blade. A Steinmann pin or K-wire is then carefully passed through the paraspinous musculature and docked onto the lumbar lamina rostral to the level of interest. Fluoroscopic guidance is used to ensure the proper level and contact with the bony lamina to prevent introduction of the pin into the interlaminar space, where dural puncture or nerve root injury may ensue.

The lamina of interest is exposed using monopolar electrocautery to dissect away overlying soft tissue, then removed using pituitary rongeours to expose the inferolateral aspect of the rostral lamina and medial aspect of the facet joint. Once the bony anatomy is identified, a small up-angled curette is used to delineate the caudal extent of the rostral lamina and detach the affixed ligamentum flavum from its undersur-face. The remainder of the operation takes place in the typical manner. A laminotomy and medial facetectomy are performed, followed by careful removal of the underlying ligamentum flavum to reveal the thecal sac and nerve root. Once the nerve root is identified, it is gently retracted medially and a diskectomy is performed in the traditional fashion. Once the disk space and neural foramen have been explored for residual fragments and adequate decompression of the nerve root is confirmed, the surgical wound is copiously irrigated with antibiotic solution. Hemostasis is achieved with a combination of bipolar electrocautery, bone wax, and application of operative hemostatic agent such as thrombin/powdered Gelfoam (Pfizer, New York, NY). The working channel is carefully removed, with inspection of muscle for bleeding, which is stopped with bipolar cautery. The wound is then closed in layers; closure of the fascia overlying the paraspinal musculature is not necessary.6

Discussion

Traditional open lumbar laminectomy and foraminotomy for the treatment of lumbar disk herniation was first described by Mixter and Barr in 1934, then revised by Love in 1939, who proposed a method that subsequently became the gold standard for open surgical treatment of lumbar disk herniation.^7,8 This approach for single-level lumbar diskectomy involves making a 5 to 10 cm skin incision and subperiosteal dissection of the paraspinous musculature, which results in significant postoperative lumbar back pain and muscle spasm. Further, subsequent laminotomy and medial facetectomy has the potential for creating bony instability if excess pars or facet removal occurs. Chronic postoperative pain or gross instability often necessitate a subsequent lumbar fusion procedure.^1,2,9–11

The introduction of a microsurgical technique by Yasargil and Caspar in 1977 utilizing the operating microscope offered better visualization of the operative field and reduced skin incision size and lamina resection, thereby minimizing trauma to adjacent motion segments and decreasing postoperative pain. However, the techniques of microlaminotomy and conventional laminectomy both involve subperiosteal dissection of paraspinous musculature and utilize similar style retractors, with the potential for significant postoperative back pain and muscle spasm.12,13 The literature demonstrates that the microsurgical technique offers shorter operative time, less intraoperative blood loss, and decreased length of hospital stay with comparable patient satisfaction and long-term clinical results compared with open lumbar diskectomy.^13–16 This suggests that further reduction of incision size and muscle dissection should follow the same trends.

The minimally invasive approach for microdiskectomy utilizes a muscle-splitting tubular retractor system through which modified traditional tools and techniques of micro-diskectomy for nerve root decompression may be applied. This method, first introduced by Foley and Smith in 1997, minimizes the morbidity associated with the traditional open and microscopic approaches while providing similar, if not superior, operative field visualization.^17,18 Studies comparing microscopic lumbar laminectomy have demonstrated the minimally invasive technique can result in a shorter hospital stay, less intraoperative blood loss, decreased postoperative narcotic use, and a faster return to work without a significant difference in complication rate and with similar short- and long-term clinical outcomes.^16–20

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Promising Advances in Minimally Invasive Spine Surgery Alternative Approaches for Lumbar Fusion: eXtreme Lateral Interbody Fusion (XLIF) Minimally Invasive Lumbar Interbody Fusion: Choosing Between Approaches Minimally Invasive Lumbar Laminectomy for Stenosis Alternative Approaches for Lumbar Fusion: Axial Lumbar Interbody Fusion (AxiaLIF) Minimally Invasive Instrumentation Systems

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