Complications associated with pedicle screws

Protocol and results of a day-surgical program for the removal of lumbar pedicle screw implants

The removal of potentially painful lumbar pedicle screw implants is a recognized procedure not yet extensively reported in the literature. The extensive dissection required to accomplish it is such that this operation is generally done on an inpatient basis. A defined protocol of pre-, intra-, and postoperative care was instituted in the senior author's practice in 1995, with the goal of accomplishing these operations on a day-surgical basis. We report the results of 70 such procedures performed in the calendar years 1995-1999 with attention to the efficacy of the protocol in facilitating ambulatory care. The protocol is safe and effective.

Successful treatment for rhabdomyosarcoma by total spondylectomy in a child

A 7-year-old girl with a retroperitoneal rhabdomyosarcoma having invaded the L3 vertebra was treated by combination therapy consisting of chemotherapy, surgical resection and intraoperative radiation. Surgically, total spondylectomy was performed through a combined anterior and posterior procedures, and the spine was reconstructed with fibula bone grafts using a pedicle screw system made of titanium alloy. Transverse junction plates were not used at operation because of their bulkiness for the patient. Five days postoperatively, the rods dislodged from the screws and the grafted bones leaned. A Chance fracture-like transverse fracture of the L4 vertebra occurred during the revisional operation. Transverse plates and sublaminar wires were used to reduce the fracture and achieved stability. Six years postoperatively, the spine was completely fused and no local recurrence or metastasis is detected.

Indications and outcomes of reconstructive surgery in chronic pain of spinal origin

STUDY DESIGN

Peer-reviewed literature was reviewed and summarized.

OBJECTIVE

To synthesize the indications and published outcomes of reconstructive lumbar spine surgery for the treatment of chronic pain of spinal origin.

METHODS

A literature review was conducted.

RESULTS

The most common indication for reconstructive lumbar surgery is pain that is refractory to nonsurgical treatment. Lumbar fusion has been shown to improve symptoms in carefully selected patients with incapacitating pain.

CONCLUSIONS

A successful arthrodesis is the fundamental surgical goal for patients with chronic pain of spinal origin. However, a successful fusion does not always correlate with a successful clinical result.

Intradiscal electrothermal treatment for chronic discogenic low back pain: prospective outcome study with a minimum 2-year follow-up

STUDY DESIGN

Prospective longitudinal study with a minimum 2-year follow-up.

OBJECTIVE

To assess the long-term outcome of a group of patients with chronic discogenic low back pain who had failed to improve with comprehensive nonoperative care and who were subsequently treated with intradiscal electrothermal therapy (IDET).

SUMMARY OF BACKGROUND DATA

Previous reports of patient outcomes at 1 year after IDET have demonstrated statistically significant improvement.

METHODS

The study group comprised 58 patients with chronic symptoms of more than 6 months who failed to improve with nonoperative care and subsequently underwent IDET. VAS pain scores, SF-36 scores, and sitting tolerance times were collected pretreatment and at 6, 12, and 24 months.

RESULTS

Mean duration of pre-IDET symptoms was 60.7 months. The minimum follow-up at data collection was 24 months. The study group (n = 58) demonstrated a significant improvement in pain as demonstrated by statistically significant improvement in VAS scores and bodily pain SF-36 scores. The IDET-treated group demonstrated a significant improvement in physical function as noted by statistically significant improvement in sitting tolerance times and physical function SF-36 scores. Bodily pain and physical function scores demonstrated significant improvement between the 1- and 2-year observation points. Additionally, quality of life improvement was demonstrated by a statistically significant improvement in all the SF-36 subscales.

CONCLUSIONS

A cohort of patients with chronic discogenic low back pain who had failed to improve with comprehensive nonoperative care demonstrated a statistically significant improvement in pain, physical function, and quality of life at 2 years after IDET.

Evaluation of the fixation and strength of a "rescue" revision pedicle screw

One potential complication of pedicle screw instrumentation is long-term nerve root irritation, most commonly resulting from medial or inferior screw malpositioning. This study evaluated the pullout strength and fatigue strength properties of a novel "rescue" revision screw designed to reduce the sequelae of medial screw malpositioning by eliminating threads along the section of the screw corresponding to the pedicular region. The results of this study revealed that a rescue screw with threads eliminated from one half of its circumference provided comparable pullout strength to fully threaded pedicle screws in cadaveric specimens. In addition, mechanical testing of the rescue screw did not show a decrease in fatigue strength characteristics compared with controls. These results suggest that the rescue screw may offer a way to decrease nerve root irritation caused by canal impingement without jeopardizing the overall strength of the spinal construct.

Inadvertent sacral bar transfixation of the cauda equina

We present a case of inadvertent sacral bar transfixation of the cauda equina as a complication of posterior pelvic internal fixation. The "safe zone" for sacral bar placement is narrow, especially in the presence of fracture displacement. This complication can be avoided by achieving fracture reduction before internal fixation. Intraoperative fluoroscopy, including inlet and lateral sacral views, should be used in addition to tactile guidance to confirm the reduction. Even after prolonged compression, hardware removal under direct visualization can alleviate radicular symptoms with less effect on motor deficit.

Thoracic pedicle screw fixation in spinal deformities: are they really safe?

STUDY DESIGN

A retrospective study.

OBJECTIVE

To determine the safety of pedicle screw fixation in thoracic deformity correction.

SUMMARY OF BACKGROUND DATA

Pedicle screw fixation enables enhanced correction of spinal deformities. However, the technique is still not widely applied for thoracic deformities for fear of neurologic complications.

MATERIALS AND METHODS

A total of 462 patients subjected to thoracic pedicle screw fixation for spinal deformities were analyzed after a minimum follow-up of 2 years. Etiologic diagnoses were idiopathic scoliosis in 330, congenital kyphoscoliosis in 68, kyphosis in 50, and others in 14. They were reviewed using the medical records and preoperative, intraoperative, and postoperative roentgenograms. Computed tomography was performed when screw position was questionable.

RESULTS

A total of 4604 thoracic pedicle screws were inserted (10.1 screws/patient). There were 67 screw malpositions (1.5%) in 48 patients (10.4%). The malpositions were inferior in 33, lateral in 18, superior in 12, and medial in 4. Screw-related neurologic complications occurred in four patients (0.8%); these comprised a transient paraparesis and three dural tears. Other complications comprised 11 intraoperative pedicle fractures, 35 screw loosenings, 9 postoperative infections, and 1 pneumothorax. There were no significant screw-related neurologic or visceral complications that adversely affected the long-term result. The deformity correction was 69.9% for idiopathic scoliosis and 60.7% for congenital scoliosis. The sagittal plane deformity correction was 47 degrees for kyphosis.

CONCLUSIONS

Thoracic pedicle screw fixation is a reliable method of treating spinal deformities, with an excellent deformity correction and a high margin of safety.

The use of evoked EMG in detecting misplaced thoracolumbar pedicle screws

STUDY DESIGN

Experimental study performed using an animal model.

OBJECTIVES

To determine if EMG responses generated by the electrical stimulation of thoracolumbar pedicle screws could be used to predict the screw position.

SUMMARY OF BACKGROUND DATA

Evoked EMG has been used successfully to predict pedicle screw position in the lumbar spine. No data have been published on its effectiveness in the thoracic spine.

METHODS

A total of 91 screws were inserted into the pedicles from T8 to L2 in six sheep. Monitoring electrodes were placed into transversus abdominus at three levels, the lower two intercostal spaces, and into psoas. A constant voltage stimulus was applied to a probe inserted into each pedicle, and then to each pedicle screw after it had replaced the probe. The threshold voltage required to evoke EMG activity in the relevant myotome was noted. After monitoring the position of each screw was determined by gross dissection.

RESULTS

EMG responses in abdominal and intercostal muscles were successfully evoked by thoracic pedicle screw stimulation. Of the 91 screws, 50 were within the pedicle and required an average voltage of 15.12 V to stimulate an EMG response, compared with the 41 misplaced screws that had an average voltage of 7.63 V (P < 0.0001). Using a threshold of 10 V the technique has a sensitivity of 94% and a specificity of 90%.

CONCLUSION

Electrical stimulation of pedicle screws and EMG recording in abdominal and leg muscles in sheep provide a reliable indication of pedicle screw position. This technique can be directly applied to human thoracolumbar surgery, but differences in pedicle size would mean that new threshold voltage criteria would need to be established.