Introduction
Foraminal stenosis and herniated discs are common pathologies seen in primary care and chronic pain clinics. The radicular pain caused by these anatomic abnormalities may be difficult to manage medically, and invasive surgical interventions can result in significant complications. Typically, discectomy and spinal fusion are considered gold standard techniques to treat radiculopathic pain. These operations require general anesthesia, postoperative recovery, and can result in limited postoperative spinal range of motion. By contrast, foraminotomy serves as a safe, minimally invasive alternative that is performed under local anesthesia and can preserve intervertebral range of motion. , Foraminotomy is a particularly appealing option for patients who fail conservative medical management and are poor surgical candidates. In appropriate patients, foraminotomy is an interventional option to decompress nerve roots and provide significant radiculopathic symptom relief and pain control.
In cases of cervical radiculopathy, two approaches with comparable results are often employed; full-endoscopic posterior cervical foraminotomy (FE-PCF), and microscopic posterior cervical foraminotomy (MI-PCF). The appropriately trained pain management specialist can utilize a minimally invasive keyhole transforaminal approach and facilitate nonfusion, nondiscectomy foraminotomy; minimizing blood loss, surgical trauma, and loss of intervertebral range of motion. , ,
Indications
Indications for cervical foraminotomy
Unilateral cervical radiculopathy and resistant cervical neuropathic pain secondary to cervical foraminal stenosis are the primary indications for cervical foraminotomy; however, consideration for foraminotomy is generally reserved for patients who fail to respond to conservative management for a minimum of 6 weeks. Conservative management generally includes immobilization, massage, physical therapy, cervical steroid injections, and oral medications. In the event of conservative management failure, posterior cervical foraminotomy (PCF) may be considered if the patient has radicular symptoms in the absence of central spinal cord compression. , In addition, cervical radiculopathy should generally be secondary to lateral or foraminal disc herniation narrowing foraminal space, osteophytic nerve compression, or primary foraminal stenosis, and compressive disease should be limited to two or less unilateral cervical levels. Lateral disc herniation leading to narrowing cervical foramina is critical, as cervical myelin must not be mobilized toward the midline. , For consideration of foraminotomy for cervical radiculopathy, nerve pain symptoms should be consistent with anatomic pathology seen on imaging studies. , Patients may require repeat foraminotomy following previous endoscopic foraminotomy if symptoms recur; however, consideration for repeat foraminotomy requires evaluation of each patient’s specific circumstances, and consideration of the factors that led to treatment failure.
Indications for lumbar foraminotomy
Like cervical foraminotomy, operative intervention for lumbar radiculopathy and neuropathic pain is typically reserved for patients who fail to respond to conservative management. In general, we consider indications for cervical and lumber foraminotomy to be similar; however, neurogenic claudication, leg pain, and symptoms of sciatica may be more common in lumbar foraminal stenosis and may serve as indications for lumber foraminotomy.
Contraindications
Contraindications to foraminotomy serve to protect patients from poor outcomes and assist the interventionalist in risk-mitigation strategies. As is the case with most operative interventions, active infection, previous spinal surgery with hardware, and operative field tumor serve as direct contraindications to foraminotomy. Spinal segmental instability and significant anatomic abnormalities including significant chronic kyphosis, severe degenerative changes, and evidence of spinal cord compression are all contraindications to foraminotomy. , Significant vertebral body pathology including fracture, and concomitant myelopathy are also contraindications to foraminotomy.
Preoperative considerations
An individualized approach to perioperative evaluation should be employed to optimize patient outcomes with careful individual considerations of operative indications and contraindications present in each case. Preoperative evaluation with radiologic studies, particularly MRI is essential. MRI evaluation serves to characterize foraminal size, degree of disease progression, and presence of concomitant contraindications to foraminotomy.
In general, a posterior approach is most often preferred over an anterior approach for cervical foraminotomy, as an anterior approach carries an increased risk of visceral injury and recurrent laryngeal nerve palsy as well as worse cosmetic outcomes. PCF postoperative outcomes can be further optimized by taking special care to characterize biomechanical measurements preoperatively to determine the intervertebral range of motion, facet joint space, and intervertebral disc pressure.
For lumbar foraminotomy, a posterolateral approach may be used for foraminal and extra foraminal stenosis, a lateral approach is preferred for recess stenosis with or without herniation, and a transforaminal approach is used for central spinal stenosis.
Irrespective of location however, the key to successful operative management of disc herniation and foraminal stenosis is exposure of the target nerve root. Therefore, careful analysis of MRI studies should be undertaken to identify the position of the working cannula by first identifying anatomic landmarks; caudal pedicle, disc space, and the posterior wall of the cranial and caudal vertebrae. The procedural needle trajectory will be planned using preoperative image studies. With appropriate preoperative planning and patient selection, the likelihood of positive foraminotomy outcomes can be optimized.
Physical examination
Patients should be thoroughly evaluated prior to consideration for operative intervention. Typically, appropriate patients demonstrate unilateral radiculopathy, pain, and dermatomal paresthesias. In more severe cases patients may have depressed deep tendon reflexes (in cases of lumbar radiculopathy), and unilateral weakness.
Specific physical examination maneuvers may be utilized to differentiate the cause of pain in a patient experiencing radicular symptoms before imaging studies are obtained. The Spurling maneuver, a foraminal compression test, is particularly specific for a diagnosis of cervical radiculopathy. Traction or neck distraction has been shown to be highly specific for radiculopathy as well if these maneuvers result in an improvement in symptoms. The combination of suspicious patient history and symptomatology with positive provocative and relieving examination maneuvers should prompt imaging evaluation.
Radiologic examination
MRI is the imaging study of choice, and it should be utilized preoperatively to confirm spinal stenosis, herniated disc, or foraminal narrowing or defect. Preoperative imaging will also guide procedural planning. ,
Procedure
Lumbar foraminotomy: Transforaminal approach
To perform lumbar foraminotomy, the patient is placed in a comfortable prone position under C-arm fluoroscopy. Local anesthetic is used to anesthetize the surgical field. Needle entry point is determined using the intersection of the skin and the horizontal plane of the spinous process 8–13 cm lateral to the midline, depending on the level of intervention. After initial needle insertion to establish the operative approach, the needle is replaced with a guide wire. Drilling is initiated through the superior articular process (SAP) in the direction of the intervertebral disc of interest. The foramen is widened, and the ventral portion of the SAP, as well as part of the inferior articular process (IAP) are removed. After the operative window is established, sequential dilation is used to dilate the operative tunnel so that the working cannula can be placed. Proper position of the working cannula can be confirmed with C-arm fluoroscopy ( Fig. 7.1 ).
