Midterm operative results of midline lumbar

interbody fusion using cortical bone trajectory

screws for lumbar degenerative spondylolisthesis

T. Tsutsumimoto, M. Yui, H. Misawa

Spine Center, Yodakubo Hospital, Nagawa, Japan

Background

Midline lumbar interbody fusion (MIDLIF) using cortical bone trajectory (CBT)

screws is an alternative method to the traditional posterior lumbar fusion using

pedicle screws. Because CBT screw entry points are much closer to the midline

than traditional pedicle screw entry points, and the trajectory is directed from

inferomedial to superolateral, MIDLIF using CBT screws offers the ability to perform

the decompression and fusion through the same surgical window, with the

advantages of decreased approach-related morbidity. However, there is a paucity of

evidence demonstrating the midterm clinical effectiveness of this technique in

patients with lumbar degenerative spondylolisthesis (LDS).

Purpose

To evaluate the midterm operative results of the MIDLIF using CBT

screws in patients with LDS.

Patients

Mean age at surgery (range), y 57.9 (42–76)

Sex (female/male) 13/8

Level (L3-4/L4-5) 3/18

Follow-up period (range), y 3.2 (2–5)

Inclusion criteria

Patients with single-level LDS and same-level

stenosis, who underwent a single-level MIDLIF

using CBT screws

No previous lumbar surgery

22 cases

21 cases

2 years follow-up or more

Retrospective analysis: 2012-2015

Surgical technique

N Flex

1. In the prone position, a midline 5-cm incision was made on

the skin over the spinous processes at the listhetic segment.

2. The dorsolumbar fascia was incised, and bilateral muscle

dissection was performed along the spinous processes over

the lamina gently up to the lateral edge of the pars

interarticularis and facet joints.

3. The holes for CBT screws were created from the inferomedial

to superolateral direction under fluoroscopic control. Care

was taken to avoid injury to the upper joint capsule during

the procedure.

4. Bilateral laminotomy and facetectomy were performed. We

routinely perform bilateral facetectomy to obtain the local

bone as much as possible, perform slip reduction easily, and

increase segmental lordosis as much as possible.

5. After the intervertebral disc removal, the interbody cages and

the local bone harvested during the decompression were

placed.

6. The CBT screws were finally placed. Subsequently, slip

reduction was accomplished under the fluoroscopic control by

pulling the CBT screws within the listhetic vertebrae

posteriorly by using a rod persuader placed over the cranial

screw head. Finally, the screws were compressed into each

other to create lordosis.

Methods

Clinical evaluation

Visual analogue scale (VAS) for both back pain (LBP) and leg pain (LP)

Oswestry Disability Index (ODI)

Radiographic evaluation: standing full-length radiographs

%slip: B/A x 100

Slip angle (SA)

Sagittal vertical axis (SVA)

Pelvic incidence (PI)

Pelvic tilt (PT)

Lumbar lordosis (LL)

PI minus LL (PI-LL)

LL

SVA

C7

PT

PI

A

B SA

Outcomes of MIDLIF using CBT screws (2–5 years)

The average intraoperative blood loss was 193.2 ml, with an average operative time of 176.8 minutes.

No intraoperative complications, including dural tear, pedicle fractures, and nerve root injury, occurred.

There was a case of surgical site infection, which was cured by debridement and antibiotics with implant retention.

Union was achieved in 85.7% (18/21) of patients.

During the follow-up period, one case underwent reoperation because of lumbar disc herniation at the cranial adjacent level three years after surgery.

Preop (N = 20) Postop (N= 20) P

ODI 36.2% (14.0–84.0%) 7.3% (0–10%) <0.01

VAS-LBP 5.4 (0–10) 0.5 (0–2.7) <0.01

VAS-LP 7.3 (1.5–10) 0.8 (0–4.4) <0.01

Outcomes of MIDLIF using CBT screws (2–5 years)

Outcomes of MIDLIF using CBT screws (2–5 years)

Preop Postop P

SA° 8.3 10.7 <0.01

%slip 16.7 4.0 <0.01

SVA (mm) 48.4 27.6 0.01

PT° 19.5 15.4 <0.01

LL° 38.5 43.9 0.01

PI° 51.1 50.1 0.09

PI-LL° 12.7 6.2 <0.01

Radiographic parameters

Conclusion

MIDLIF using CBT screws is safe, and the midterm operative

results are acceptable. This technique seems to be an

encouraging alternative to traditional lumbar fusion surgery in

LDS patients.

None of the authors has any potential conflict of interest.