6. Spine MCQs

Normally, moving from standing to sitting causes the pelvis to tilt posteriorly, increasing functional acetabular anteversion and accommodating hip flexion. Patients with fused spines (ankylosing spondylitis) cannot posteriorly tilt their pelvis, increasing the risk of anterior impingement and posterior dislocation when sitting. Therefore, the acetabular component should be placed in increased anteversion to compensate.

A stiff lumbosacral spine (e.g., ankylosing spondylitis or prior fusion) impairs the pelvis's ability to tilt backward during sitting. This increases relative acetabular retroversion, significantly increasing the risk of posterior dislocation.

Although the patient has sustained a complete spinal cord injury, an anterior decompression, even performed late, can gain an additional level of root function. In the quadriplegic patient, this can mean the difference between dependent and independent function. Posterior procedures do not afford adequate access to the retropulsed bony fragments compromising the canal.

Through-the-knee amputations had significantly worse scores for the objective performance measures of self-selected walking speed, independence in transfers, walking, and stair-climbing. Through-the-knee amputees also had worse SIP scores than AKA and BKA patients. Physicians were also less satisfied with both the clinical and the cosmetic recovery. Patients actually reported less pain than those with an AKA or BKA, making 'more severe pain' the exception.

DISCUSSION: The on-field evaluation and management of a seriously injured athlete requires that health care teams have a game plan in place and proper equipment that is readily available. The initial step, which consists of stabilizing the head and neck by manually holding them in a neutral position, is then followed by assessment of breathing, pulses, and level of consciousness. If the athlete is breathing, management should consist of mouth guard removal and airway maintenance. If the athlete is not breathing, the face mask should be removed, with the chin strap left in place. The airway must be established, followed by initiation of assisted breathing. CPR is instituted only when breathing and circulation are compromised. In the unconscious athlete or if a cervical spine injury is suspected, the helmet must not be removed until the athlete has been transported to an appropriate facility and the cervical spine has been completely evaluated.

The patient has a grade I isthmic spondylolisthesis at L5-S1. He has an L5 radiculopathy with foraminal stenosis. Any further treatment needs to include an arthrodesis and foraminal decompression. Isolated interbody fusion is contraindicated in patients with spondylolisthesis, as is total disk arthroplasty. Therefore, the best procedure is a posterior fusion with instrumentation and bone graft along with a foraminal decompression.

Popliteal artery entrapment syndrome is most commonly caused by an anomalous path of the popliteal artery, typically passing medial to (or behind) the medial head of the gastrocnemius, leading to compression during active plantar flexion.

DISCUSSION: The MRI scan shows a far lateral disk herniation. With the L4-5 disk, a far lateral herniation abuts the left L4 nerve root. The findings would be consistent with those of a left L4 radiculopathy and would include pain or a sensory deficit on the anteromedial aspect of the knee, diminished patellar tendon reflex, and quadriceps weakness, perhaps making it difficult to walk up and down stairs.

The patient’s curve is beyond the limit for bracing to be effective (40 degrees). Therefore, surgical treatment should be utilized. King type II curves (predominant thoracic curve with secondary lumbar curve) historically has used selective posterior thoracic fusion with segmental hook systems and rotation maneuvers to correct the thoracic curve and compensatory lumbar curve. The patient’s primary curve is thoracic and lumbar fusion would be contraindicated.

DISCUSSION: The superior cluneal nerves (L1, L2, and L3) are at greatest risk when harvesting iliac crest bone graft during a posterior decompression and fusion. The nerves pierce the lumbodorsal fascia and cross the posterior iliac crest beginning at 8 cm lateral to the posterior superior iliac spine. The ilioinguinal and iliohypogastric nerves innervate anterior structures, and the lateral femoral cutaneous nerve lies in proximity to the anterior superior iliac spine and is at risk with anterior iliac crest bone graft harvesting. The superior gluteal nerve courses through the sciatic notch and supplies motor branches to the gluteus medius, minimus, and tensor fascia lata muscles. REFERENCES: An HS: Principles and Techniques of Spine Surgery. Baltimore, MD, Williams and Wilkins, 1998, pp 770-773. Kurz LT, Garfin SR, Booth RE: Harvesting autogenous iliac bone grafts: A review of complications and techniques. Spine 1989;14:1324-1331.

Infantile idiopathic scoliosis occurs more commonly in boys, with a 3 to 1 male to female ratio. Neural axis abnormalities, hip dysplasia, and congenital heart disease are all associated with the condition; spontaneous correction frequently occurs. Curve progression can be predicted by the rib vertebral angle difference or the phase of the rib head. Rib overlap of the apical vertebral body or a rib vertebral angle difference of greater than 20 degrees indicates that the curve is likely to progress. Gender, family history, and age at presentation have not been found to be risk factors for progression.

Adequate decompression of the cervical cord can be achieved in a variety of ways depending on the pathoanatomy of the compression, but kyphosis is a relative contraindication to laminectomy alone. For laminectomy to be effective, the lordosis must be maintained so the cord can displace posteriorly away from the anterior structures. In addition, removing the posterior tension band increases the probability that the kyphosis will progress, therefore increasing the force against the front of the cord as it tents across the kyphosis.

Posterior spinal fusion is the treatment of choice for scoliosis in patients with Duchenne muscular dystrophy once they are no longer able to walk. This treatment improves quality of life and upright wheelchair positioning. Its effect on pulmonary function is less clear, as pulmonary function will continue to decline because of the underlying muscle disease. While bracing and wheelchair modifications may slow the progression of the curve, progression will continue. Surgical intervention at this stage does not have to include the pelvis, which, in general, is indicated in curves of greater than 40 degrees, and when pelvic obliquity is greater than 10 degrees. Fixation to the pelvis should also be considered in lumbar curves where the apex is lower than L1. Surgical treatment usually can be safely performed if the vital capacity is greater than 35%.

DISCUSSION: The patient has an L5 radiculopathy secondary to an L4-5 disk herniation that is compressing the traversing L5 nerve root.

The instantaneous axis of rotation is the axis about which each vertebral segment rotates, but is theoretical depending on how it is defined, and varies depending on multiple factors. It is not a fixed point but can move depending on the position of the spine, and it is affected by degenerative conditions, fractures, injuries, and other anatomic changes of the spine. There are three axes of movement with 6 degrees of freedom (rotation and translation movements about each axis).

This patient has ankylosing spondylitis (AS) and has suffered a shear fracture through C5-6. Due to the presence of neurological deficits, posterior decompression and fusion with a long construct (such as from C3-T2) is indicated.The C-spine is the most common site of fracture in AS and is most susceptible to hyperextension injuries. When surgical intervention is required, multiple points of fixation both above and below the fracture are necessary. This is due to co-existing osteoporosis and abnormally increased forces from long lever arms of the ankylosed spine, both of which make the construct susceptible to failure and screw pullout.Kubiak et al. reviewed the orthopaedic management of AS. They report bone scan, MRI or fine-cut CT is necessary because fractures are often missed on plain x-rays because of distortion of anatomy or difficulty with positioning.Whang et al. reviewed spinal injuries in 12 patients with AS and 18 patients with DISH. Most injuries involved C5-C7. Patients with AS were more likley to have severe neurologic injury (41% ASIA A) than DISH (44% ASIA E). There was 81% good-excellent outcome and 4 deaths related to halo vest use.Figure A is a sagittal CT reconstructed image showing a nondisplaced shear fracture through the C6 vertebral body and C5 posterior elements. Illustrations A and B are postop AP and lateral radiographs showing posterior decompression and C3-T2 fusion with lateral mass fixation in the cervical spine and pedicle screw fixation in the upper thoracic spine.Incorrect Answers:performed through a posterior approach. If there is significant osteoporosis and the risk of construct failure is high, a 360-approach may be necessary.

Spinal shock results in temporary loss or depression of all or most spinal reflex activity below the level of the injury. Hypotension and bradycardia caused by loss of sympathetic tone is a possible complication, and the bulbocavernosus reflex is typically absent.

Conus medullaris syndrome describes isolated loss of bowel and bladder function, usually at T12-L1 but can include T11-L2.

Although symptomatic thoracic disk herniations can affect more caudal structures, even to the point of paralysis, the pattern of radiating pain has been described as either following the dermatomal band around the chest or feeling to the patient as if the pain passes straight anteriorly to the chest wall.

Postoperative vertebral subluxation with pain, restricted movement, and further neural compression does occur following extensive decompressive laminectomy. Resection of posterior elements has been regarded as benign, and some degree of forward slipping is not always associated with an increase in pain. Postoperative instability appears to be predominantly related to extenuating circumstances, such as a primary neural disorder, rheumatoid arthritis, degenerative spondylolisthesis, or recurrent severe trauma after decompression. An analysis of 182 patients with extensive decompression involving at least one part of one facet joint showed that in thirteen of them progressive spondylolisthesis developed postoperatively. Three of the patients had been treated for a herniated disc and ten, for degenerative spondylolisthesis. When subluxation did occur, it was within the first few weeks after operation and progressed for as long as two years. All patients with progression were older than fifty-two-years and were in more pain than those whom subluxation did not occur. An extensive review of 6000 patients in whom a wide resection was performed, including hemifacetectomy and either a total facetectomy or removal of the pars interarticularis, or both, found that only 2 percent of those patients required fusion or instability. An admonition was given by that author not to remove facet joints or pars interarticularis areas in patients who are less than thirty-years old, since these patients are most susceptible to postoperative instability. Older individuals with advanced degenerative changes at the level of the disc, as well as posteriorily, tolerate extensive laminectomy better. When the disc is maximally narrowed, no further settling of the space is possible and marginal osteophytes enhance stability.Extensive laminectomy in patients with degenerative spondylolisthesis does result in postoperative instability. In the study by White and Wiltse, further subluxation did occur in 66 percent of patients who were operated on for degenerative spondylolisthesis , whereas it was observed in only 2 percent of the spondylolisthesis or disc patients who did not havespondylolisthesis postoperatively. The extent of decompression and facet removal must be limited in the patient with degenerative spondylolisthesis or a fusion of the transverse processes included as part of the treatment. Internal fixation devices have been used in these circumstances to prevent further subluxation while the fusion is consolidating. Wiltse outlined some guidelines for spinal fusion in spinal stenosis: (1) the patient who is less than sixty years old and had degenerative spondylolisthesis with a total loss of posterior stability due to removal of the articular processes (a one-level fusion of the transverse processes); (2) the patient who is less than fifty-five and had a midline decompression for degenerative spondylolisthesis with facet preservation; and(3) the patient who is less than fifty years old with isthmic spondylolisthesis, if the posterior elements have been removed. Simple degenerative spinal stenosis seldom requires a fusion, even if all posterior stability has been lost. The problem with obtaining a successful spinal fusion is real and conditions are less than optimum in these instances.