Spondylolysis/Spondylolistheses

M. Timothy Hresko

Pars Repair

Operative Indications

Failed nonoperative treatment of documented pars intra-articularis defect
MRI—absence of intervertebral disk degeneration
Less than 5 mm of translation of superior vertebral body
Pain relief on pars injection

Positioning

Prone on radiolucent table (Figure 7.1A)
Flex hips to reduce anterior pelvis tilt and lumbar lordosis (Figure 7.1B)

Procedure-Specific Checklist

Implant for your specific procedure
Intraoperative fluoroscopy to confirm surgical site at correct location
Compare to preop imaging—be cognizant of transitional LS vertebrae

Surgical Approach

Surface landmark of dimple of Venus (posterior iliac spine) at level of S1 spinous process
Midline approach 8 cm cephalad from S1
Raise skin flap to iliac crest
Elevate muscle from L5 lamina to L4-L5 facet, lateral to base of transverse process (if using Scott wire technique elevate to tip of TP and ventral on the specific vertebrae)
Maintain ligament of posterior process to L4, L5, S1

Figure 7-1 ▪ A, Position on radiolucent table with hip flexed 30° to 45°. B, Incision based on surface anatomy of posterior iliac spine and iliac crest. (Courtesy of Children’s Orthopaedic Surgery Foundation.)

Techniques in Steps

Common to All Technique

Obtain bone graft from iliac crest—cancellous
Use Rongeur, curette, or burrs to clean out pars defect
Buck screw technique (Figure 7.2A-C)
- Preoperative CT to confirm lamina intact—absence of bifid lamina
- Use fluoroscopy and K-wire to plan path for cannulated drill AP and lateral fluoroscopy
- Burr starting point at inferior aspect of ipsilateral lamina
- Percutaneous insertion of threaded guide pin for cannulated drill inserted midline and distal to incision, angled lateral and ventral under fluoroscopy
- Advance guide pin to pars defect
- Place bone graft
- Advance guide pin to anterior superior cortex
- Drill over wire and far cortex
- Remove wire and place solid 4.5 mm screw—bicortical
- Repeat on contralateral side
- Decorticate base of TP and lamina
- Place additional bone graft on lamina
- Close wound

Scott wire technique (Figures 7.3 and 7.4)

Pass loop wire over lateral aspect of TP to base of TP
- Alternative is place pedicle screw or bone screw and washer in pedicle and loop wire under the washer
Decorticate base of TP and lamina

Pass free end of wire through posterior ligament in “figure of 8” fashion and secure on contralateral side of spinous process

Figure 7-2 ▪ A, Image of lateral lumbar spine showing insertion angle of drill and screw. B, AP and lateral of lumbar spine Buck screw. C, Oblique image showing bicortical fixation. (Courtesy of Children’s Orthopaedic Surgery Foundation.)

Figure 7-3 ▪ Scott wiring AP and lateral. (Courtesy of Children’s Orthopaedic Surgery Foundation.)

Figure 7-4 ▪ Pedicle screw plus wiring MR4201677. (Courtesy of Children’s Orthopaedic Surgery Foundation.)

Insert bone graft in pars defect and lamina ventral to wire
Place contralateral wire in a similar fashion
Tighten both wires
Close wound

Pedicle screw
- Place bilateral polyaxial pedicle screws avoiding facet joint
- Decorticate base of TP and lamina
- Insert bone graft into pars defect, base of TP, and lamina
- Implant secured to posterior process. Implant options:
  - Contour 4.5 mm rod in “U” shape passed rod inferior to L5 spinous process
  - Polyethylene cord instead of rod (physician directed use, not FDA approved)
  - Wire
- Insert rod into pedicle screw head and compress