High grade spondylolisthesis correction by a posterior only approach using the new multiplanar adjusting screw

2005

BACKGROUND CONTEXT

The Edwards technique has been very effective in reducing high grade spondylolisthesis. A new Multi-Planar Adjusting (MPA) spinal screw with a 160° pivoting reduction post was developed to make spinal deformity and spondylolisthesis correction easier, finely controlled, with reliable rigid fixation.

PURPOSE

This study was undertaken to compare the Edwards technique for reduction of high grade spondylolisthesis to a modified technique using the MPA screw construct.

STUDY DESIGN/ SETTING

Fifteen consecutive patients with high grade spondylolisthesis had posterior correction by the same surgeon. Four with MPA construct were prospectively followed 3 yrs (2–4 yrs) compared to 11 retrospectively reviewed patients with Edwards construct followed 6 yrs (4–10 yrs).

PATIENT SAMPLE

There were 7-grade 5 (spondyloptosis), 2-grade 4, and 6-grade 3 patients. Two patients had acute cauda equina syndrome, one had chronic bladder urgency, and 1 had complete footdrop. The Edwards group avg 17 yrs (13–34 yrs), with 9 females and 2 males. The MPA group avg 16 yrs (13–22 yrs), all female.

OUTCOME MEASURES

For the MPA group, Oswestry, Visual Analog pain Scores (VAS), pain medication use, and work status were followed. For the Edwards group, patient satisfaction rating, VAS scores, medication use, and work status were followed. Radiographs were obtained at 6 wks, and 3, 6, 9, 12, 24 mo, and yearly thereafter.

METHODS

Patients were treated with decompression and posterior instrumented spondylolisthesis reduction and fusion from L4/L5-S1 without anterior surgery. Four had MPA and 11 had Edwards constructs. Sacral dome osteotomies were performed in grades 4 and 5. MPA and Edwards constructs applied corrective forces of distraction, sacral flexion, posterior translation by gradually pulling the L5 vertebra into sagittal alignment. Edwards utilized lateral S1/S2 alar screws stabilizing the construct base. MPA used S1 pedicle screws and iliac or S2 screws. MPA construct was rigid using smooth 5.5mm titanium rods, whereas Edwards was semi-rigid using ratcheted stainless steel rods with washers. Edwards patients were braced due to the semi-rigid fixation. MPA patients with spondyloptosis were braced.

RESULTS

Full correction was achieved in all cases by the application of reduction forces through the instrumentation. All 3 patients with cauda equina syndrome recovered. New neurologic deficits occurred in two patients with spondyloptosis, 1 unilateral footdrop and one bilateral 4/5 quad strength. One with pre-op footdrop failed to improve. In the MPA group, there were no cases of implant failure or screw pullout and the average operative time was 8 hours. In the Edwards group, 2 infections, 2 nonunions with construct loosening, and 2 had S2 screw pullout requiring revision, and average operative time was 11 hours. Excluding the hardware failure patients, the functional outcomes, VAS pain scores, and pain medication use are similar in the two groups, showing improved pain and function.

CONCLUSION

Though these numbers are small, it does appear that the Multi-Planar Adjusting screw allowed for the full reduction capability of the Edwards technique with improved fixation (rigid vs. semi-rigid, S1 pedicle vs. alar screws, optional iliac screws) and easier assembly (decreased OR time). The MPA spondylolisthesis construct appears to be an easier alternative to the Edwards technique for reducing high grade spondylolisthesis.