J Korean Soc Spine Surg.  2008 Mar;15(1):9-17. 10.4184/jkss.2008.15.1.9.

Polyaxial Screws with Thick Rod versus Monoaxial Screws with Thin Rod in Video-Assisted Thoracoscopic Scoliosis Surgery (VATS)

• Kim HS
• Kim JY
• Park JO
• Moon SH
• Lee HM
• Ha JW
• Kim HJ
• Wei H
• Lee SK
• Moon ES

• KMID: 1482838
• DOI: http://doi.org/10.4184/jkss.2008.15.1.9

Abstract

STUDY DESIGN: Prospective controlled cohort study
OBJECTIVE
To analyze the clinical outcome of video-assisted thoracoscopic surgery (VATS) between two different types of implants. SUMMARY OF LITERATURE REVIEW: The problem of correction loss has been reported with VATS, and different screws and rods have been developed to overcome this problem. Different implants will have varying effects in correctional outcome after VATS.
MATERIALS AND METHODS
A total of 39 cases of idiopathic adolescent scoliosis treated with VATS between June 2001 and January 2005 were included in the study (mono-axial screws and a 4.5 mm rod: thin rod group=19 cases; poly-axial reduction screws and a 5.5 mm diameter rod: thick rod group=20 cases). All patients were followed for over 2 years postoperatively. For the comparison of surgical outcomes between the two groups, radiographic measurements were performed in the coronal and sagittal planes.
RESULTS
Preoperative scoliosis angle (thin rod group 49.8degrees, thick rod group 47.1degrees), age, BMI, Risser stage, union time, operative time, and blood loss showed no statistical difference between the two groups. Postoperative average correction rate of scoliosis angle was 69% (15.8degrees) in the thin rod group and 70% (14.1degrees) in the thick rod group. However, correction rate after 2 years was 51% (24.5degrees) in the thin rod group and 60% (18.7degrees) in the thick rod group, showing statistically significant difference. There was a tendency toward correction loss in the thin rod group (8.7degrees vs. 4.6degrees p=0.0057).
CONCLUSION
Postoperative correction rate was satisfactory in both groups. However, the thin rod group showed substantial correction loss. Therefore, poly-axial screws and thick rods are more suitable in VATS correction of scoliosis.

Keyword

Scoliosis; VATS; Pedicle screw; Rod

MeSH Terms

Adolescent
Cohort Studies
Humans
Operative Time
Prospective Studies
Scoliosis
Thoracic Surgery, Video-Assisted

Figure

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  Fig. 1. (A) 14+7 year old female with type IBN curve pattern. Preoperative operative AP view shows 52 degree scoliosis angle. (B) Immediate postoperative x-ray shows 18 degree. (C) 2 weeks later, whole spine standing AP view shows reduction loss about 14 degree. (D) 2 years later whole spine standing AP view

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  Fig. 2. The Change of Correction Angle

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