Minimally Invasive Resection of Lumbar Synovial Cysts and Foraminal Disks

Lumbar synovial cysts have been described in the literature as an uncommon cause of low back and radicular pain. These synovial cysts arise from facet joints in the lumbar spine, much less commonly in the cervical spine, and even less in the thoracic spine. These cysts are highly associated with instability, which is brought about by degeneration and excessive motion in mobile segments of the spine. ¹ Spondylolisthesis with synovial cyst has been reported to be as high as 50%. ² These cysts present with low back and more commonly radicular pain. They occur equally in males and females, more so at the L4–5 level ( ▶ Fig. 43.1, ▶ Fig. 43.2). They have not been known to resolve spontaneously except in sporadic reports. Treatment with image-guided cyst aspiration or injection has not provided good long-term outcomes. ³ The more definitive treatment is thus surgical, with excision of the cyst either in an open technique, which includes facetectomy, or minimally invasive through an ipsilateral or a contralateral approach. ⁴ Here, we discuss the contralateral approach to synovial cyst resection, which spares the facet joint and helps reduce the risk of iatrogenic postoperative instability that might require later fusion. ⁵^, ⁶

Fig. 43.1 Sagittal T2 magnetic resonance image of a left-sided synovial cyst at L4–5.

Fig. 43.2 Axial T2-weighted magnetic resonance image showing the left L4–5 fluid-filled synovial cyst.

43.1.2 Patient Selection

Patients who would benefit from minimally invasive resection of lumbar synovial cysts are those with incapacitating symptoms of low back or radicular pain or both for whom all methods of conservative treatment, including physical therapy, pain medication, and image-guided cyst aspiration or rupture, or steroid injection, have been unsuccessful.

43.1.3 Preoperative Preparation

All patients should have their medical and surgical histories reviewed. Patients with high-risk comorbidities, like cardiac or pulmonary disease, should be evaluated by a specialist. Patients with other medical issues should be cleared and optimized medically by their internist, primary doctor, or a 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.

43.1.4 Operative Procedure

After general anesthesia and administration of prophylactic antibiotics, the patient is gently rolled into prone position on an operating room table. The choice of the table depends on the surgeon’s preference; however, a Jackson frame or an OSI table (Union City, California) is most commonly used. The abdomen is made to hang freely, thus reducing intra-abdominal pressure and thus venous bleeding. The lumbar lordosis is reduced by hip flexion, thus increasing the interlaminar spaces. All bony prominences are padded. The midline is marked. This is very important, as many can lose orientation as to where the midline is and attempt to mark it after draping. The lumbar area is then prepared and draped in a sterile condition. Fluoroscopy is used to identify the correct level. The skin incision is planned to be either horizontal ⁷ or vertical 15 to 30 mm lateral to the midline at the corresponding spinal level on the opposite side of the cyst. Longitudinal incisions are preferable as they can be easily extended for current or future spinal surgery. The skin and underlying muscles under the projected incision are injected with lidocaine and epinephrine. The incision is made. The subcutaneous fat is bluntly dissected with scissors, and the fascia is incised. Using the narrowest of dilators, the spinous process of the affected level is palpated and confirmed under fluoroscopy. Sequential serial concentric dilators are introduced over the first dilator, and the paraspinal muscles are dissected away from the base of the spinous process and laminae. Eventually, an 18- or 22-mm working channel is selected. The 22-mm channel is generally chosen for heavier patients, in whom a longer tube (80 to 100 mm) is necessary. The working channel is then fixed in position by using a table-mounted arm, and the microscope is brought in. The surgical microscope provides better magnification and illumination, and it also avoids the surgeon colliding with the assistant’s loupes and headlight.

A bayonetted monopolar is used to remove the muscle plug that invariably overlies the laminae. Using a 3-mm power drill and bone punches, the interlaminar space is enlarged by removing the caudal margin of the rostral lamina. The ligamentum flavum is then excised, exposing the dural sac ( ▶ Fig. 43.3). Most of the bone resection with the drill is performed with the ligamentum flavum still intact. With the dura protected ventrally by a blunt or malleable dissector, the ventral base of the spinous process and the contralateral ligamentum flavum are resected, exposing the contralateral side of the spinal canal ( ▶ Fig. 43.4). The synovial cyst can then be seen attached to the contralateral facet joint. With chronic cysts, it can be quite difficult at times to develop a plane of dissection between the cyst and the dura, as they may be adherent ( ▶ Fig. 43.5). It is important to be very careful dissecting the cyst from the dura without creating a tear in the latter. The cyst is freed circumferentially with dissectors and eventually removed completely ( ▶ Fig. 43.6, ▶ Fig. 43.7). It may not always be delivered whole, and it may be necessary to enter the cyst and partially collapse it. Irrigation is then performed with antibiotic-impregnated saline. Valsalva maneuver may be performed to check for spinal fluid leaks. The tube is then removed. The fascia is closed with simple interrupted absorbable suture, and the skin is closed with 4–0 absorbable suture and Dermabond.