A more detailed description of indications for MISS follows in the “Patient History” section of this chapter.

As with any medical intervention, risks must be weighed against benefits. MISS can offer select patients with alternatives to undergoing open surgical procedures. There are, however, contraindications for MISS including, but not limited to¹⁰:

The patient’s history should include questions to assess the quality of the pain and its impact on the patient’s daily activities, including nighttime pain that interferes with sleep. Identifying the mechanism of injury is essential if there is an inciting event. However, symptoms may also develop insidiously. The clinician must ask the patient about any current or past treatments, bladder or bowel incontinence, saddle anesthesia, history of malignancy, inflammatory conditions, infections, history of immunosuppression, and drug use. A comprehensive review of systems may reveal red flag signs that suggest underlying infection, inflammatory disease, or malignancy, such as fever, night sweats, or unintentional weight loss.¹¹

Patients with disc herniations are generally younger, typically 30 to 50 years old, and have a history of an acute inciting event such as lifting a heavy object, bending, or twisting motions.¹² They may experience localized back pain with associated radicular pain in the arms or legs depending on the location of the herniation (cervical vs. lumbar). There may be weakness, numbness, or paresthesia in specific nerve root distributions due to mechanical and/or chemical irritation of an adjacent nerve root. Patients may also have limited trunk flexion and pain exacerbated by straining, sneezing, and coughing. Seated positioning also worsens pain because of increased pressure applied to the disc.¹¹ It is also important to inspect the circulatory system, as vascular claudication may mimic neurogenic pathology.

Lumbar spinal stenosis is the most common indication for lumbar spine surgery in patients over 65 years old.¹³ Lumbar spinal stenosis classically presents as pain exacerbated by prolonged ambulation, standing upright, and low back extension, owing to the degenerated intervertebral discs, hypertrophy of the facet joints, and thickening of the ligamentum flavum protruding into the spinal canal.¹⁴ The pain is relieved by forward flexion and rest. Neurogenic claudication is an important characteristic of lumbar spinal stenosis. Symptoms are typically bilateral, but usually asymmetric involving the back, buttock, and legs. Pain in addition to numbness and tingling is present in most patients. Symptoms of numbness and tingling typically involve the entire leg and rarely affect an isolated nerve root distribution.¹⁵ Patients may report that walking upstairs is easier than downstairs, as the back is forward flexed with ascending stairs. If patients present with new-onset bowel or bladder dysfunction, bilateral lower extremity weakness, and saddle anesthesia, they may have developed cauda equina syndrome requiring emergent surgical decompression.

Patients with symptomatic spondylolisthesis may present similarly to those affected by spinal stenosis, given that symptoms arise when translation of the vertebral body compresses neural elements from canal narrowing. The clinician should pay special attention to any history of trauma when evaluating for spondylolisthesis, as pars interarticularis defects result from chronic repetitive loading in hyperextension or acute trauma. Low-grade slips and canal stenosis may decompress with forward flexion or sitting, leading to pain relief. As in spinal stenosis, pushing a grocery cart or walking upstairs results in flexion of the spinal column and thereby pain relief.¹⁶ Classically, patients complain of pain that radiates to the buttocks and both lower extremities. If the spondylolisthesis becomes unstable, as evidenced by progression on lateral flexion and extension x-rays, surgery is indicated.

The most common etiology of vertebral compression fractures is osteoporosis, and therefore it is the most common fragility fracture. Vertebral compression fractures demonstrate a bimodal age distribution, as younger patients sustain these injuries from high-energy trauma such as motor vehicle accidents or fall from height. Once the patient has been stabilized, the initial evaluation of spine fractures includes assessment of the neurologic function of the upper and lower extremities, bladder, and bowel. Many high-energy compression fractures have associated abdominal, cerebral, and extremity injuries.

There are many adults who suffer from spinal deformities, such as scoliosis, and live with significant pain and many comorbidities. Open surgical procedures to correct these deformities can be risky, sometimes requiring extensive surgical reconstruction to correct the deformity. Less invasive surgical options can help reduce the risk of complications. Mummaneni et al. previously developed a minimally invasive surgery deformity algorithm (MISDEF) for selection of patients to undergo MISS.¹⁷ These patients were selected based on sagittal parameters, and those with higher degrees of imbalance were not selected. This algorithm was revised to incorporate newer technique options, known as minimally invasive spinal deformity algorithm 2 (MISDEF2).¹⁷ In this updated algorithm, patients are grouped in classes I through IV, compared with previously being grouped in classes I to III. Patients are first grouped according to whether their deformity is fixed or flexible and subsequently on presence or absence of sagittal and coronal deformities.

The range of motion (ROM) examination of the neck and back is important to assess because loss of ROM and pain elicited in specific planes can help localize the lesion. Normal cervical spine ROM is 0 to 45 degrees of flexion and extension, 0 to 70 degrees of rotation, and 0 to 40 degrees of lateral bending.¹⁸

Lumbar spine ROM is assessed with the patient in a standing position and should be observed with the practitioner at the back or side of the patient. The practitioner may stabilize the patient by placing their hands on the pelvis to ensure that motion only occurs at the spine. Motion occurs in three planes and includes four directions, as follows: forward flexion—52 degrees ±9; extension—19 degrees ±9; lateral flexion/side bending—31 degrees ±6; rotation—32 degrees ±9.¹⁹

Palpation of the spine helps to identify focal tenderness from muscles, tendons, ligaments, and joints. The examiner should begin at the cervical region including the shoulders then work down to the lumbosacral region including the sacroiliac joints. Severe point tenderness may suggest the presence of a fracture or underlying infection such as an epidural abscess.²⁰ It is important to note a palpable step-off deformity, which may be present in the setting of an acute trauma or severe spondylolisthesis.

Muscle strength testing is performed to evaluate for muscle weakness from a neurologic deficit, poor endurance, or muscle imbalance. Strength can be evaluated in multiple ways including manual muscle testing or functional strength testing. The most accepted method of evaluating muscle strength is the Medical Research Council Manual Muscle Testing scale that tests key muscles of the upper and lower extremities against the examiner’s resistance.²¹ Strength is graded on a scale of 0 to 5, and commonly tested key muscles and the corresponding spinal nerve roots include: