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Joseph C. Hsieh and Richard D. Penn

✓ Medical management of adult spasticity, a condition of increased muscle tone and deep tendon reflexes, is often challenging and complex. Oral medications such as baclofen often have unacceptable supraspinal side effects at effective doses. Intrathecal baclofen delivered by an implanted catheter and pump system provides good relief of spasticity while overcoming these limitations. In this paper the authors survey the use of oral and intrathecal baclofen therapy, detail the surgical process, and explain the risks and benefits of the procedure.

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Joseph C. Hsieh, Doniel Drazin, Alexander O. Firempong, Robert Pashman, J. Patrick Johnson and Terrence T. Kim

Object

Revision spine surgery, which is challenging due to disrupted anatomy, poor fluoroscopic imaging, and altered tactile feedback, may benefit from CT image-guided surgery (CT-IGS). This study evaluates accuracy of CT-IGS–navigated screws in primary versus revision spine surgery.

Methods

Pedicle and pelvic screws placed with the O-arm in 28 primary (313 screws) and 33 revision (429 screws) cases in which institutional postoperative CT scans were available were retrospectively reviewed for placement accuracy. Screw accuracy was categorized as 1) good (< 1-mm pedicle breach in any direction or “in-out-in” thoracic screws through the lateral thoracic pedicle wall and in the costovertebral joint); 2) fair (1- to 3-mm breach); or 3) poor (> 3-mm breach).

Results

Use of CT-IGS resulted in high rates of good or fair screws for both primary (98.7%) and revision (98.6%) cases. Rates of good or fair screws were comparable for the following regions: C7–T3 at 100% (good or fair) in primary versus 100% (good or fair) in revision; T4–9 at 96.8% versus 100%; T10–L2 at 98.2% versus 99.3%; L3–5 at 100% versus 99.2%; and pelvis at 98.7% versus 98.6%, respectively. On the other hand, revision sacral screws had statistically significantly lower rates of good placement compared with primary (100% primary vs 80.6% revision, p = 0.027). Of these revision sacral screws, 11.1% had poor placement, with bicortical screws extending > 3 mm beyond the anterior cortex. Revision pelvic screws demonstrated the highest rate of fair placement (28%), with the mode of medial breach in all cases directed into the sacral-iliac joint.

Conclusions

In the cervical, thoracic, and lumbar spine, CT-IGS demonstrated comparable accuracy rates for both primary and revision spine surgery. Use of 3D imaging of the bony pedicle anatomy appears to be sufficient for the spine surgeon to overcome the difficulties associated with instrumentation in revision cases. Although the bony structures of sacral pedicles and pelvis are relatively larger, the complexity of local anatomy was not overcome with CT-IGS, and an increased trend toward inaccurate screw placement was demonstrated.

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Sunil Jeswani, Doniel Drazin, Joseph C. Hsieh, Faris Shweikeh, Eric Friedman, Robert Pashman, J. Patrick Johnson and Terrence T. Kim

Object

Traditionally, instrumentation of thoracic pedicles has been more difficult because of their relatively smaller size. Thoracic pedicles are at risk for violation during surgical instrumentation, as is commonly seen in patients with scoliosis and in women. The laterally based “in-out-in” approach, which technically results in a lateral breach, is sometimes used in small pedicles to decrease the comparative risk of a medial breach with neurological involvement. In this study the authors evaluated the role of CT image–guided surgery in navigating screws in small thoracic pedicles.

Methods

Thoracic (T1–12) pedicle screw placements using the O-arm imaging system (Medtronic Inc.) were evaluated for accuracy with preoperative and postoperative CT. “Small” pedicles were defined as those ≤ 3 mm in the narrowest diameter orthogonal to the long axis of the pedicle on a trajectory entering the vertebral body on preinstrumentation CT. A subset of “very small” pedicles (≤ 2 mm in the narrowest diameter, 13 pedicles) was also analyzed. Screw accuracy was categorized as good (< 1 mm of pedicle breach in any direction or in-out-in screws), fair (1–3 mm of breach), or poor (> 3 mm of breach).

Results

Twenty-one consecutive patients (age range 32–71 years) had large (45 screws) and small (52 screws) thoracic pedicles. The median pedicle diameter was 2.5 mm (range 0.9–3 mm) for small and 3.9 mm (3.1–6.7 mm) for large pedicles. Computed tomography–guided surgical navigation led to accurate screw placement in both small (good 100%, fair 0%, poor 0%) and large (good 96.6%, fair 0%, poor 3.4%) pedicles. Good screw placement in very small or small pedicles occurred with an in-out-in trajectory more often than in large pedicles (large 6.8% vs small 36.5%, p < 0.0005; vs very small 69.2%, p < 0.0001). There were no medial breaches even though 75 of the 97 screws were placed in postmenopausal women, traditionally at higher risk for osteoporosis.

Conclusions

Computed tomography–guided surgical navigation allows for safe, effective, and accurate instrumentation of small (≤ 3 mm) to very small (≤ 2 mm) thoracic pedicles.