Journal List > J Korean Soc Spine Surg > v.15(1) > 1035837

Kim, Kim, Park, Moon, Lee, Ha, Kim, Wei, Lee, and Moon: Polyaxial Screws with Thick Rod versus Monoaxial Screws with Thin Rod in Video-Assisted Thoracoscopic Scoliosis Surgery (VATS)

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 (monoaxial screws and a 4.5 mm rod: thin rod group=19 cases; polyaxial 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 49.8。, thick rod group 47.1。), 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% (15.8。) in the thin rod group and 70% (14.1。) in the thick rod group. However, correction rate after 2 years was 51% (24.5。) in the thin rod group and 60% (18.7。) in the thick rod group, showing statistically significant difference. There was a tendency toward correction loss in the thin rod group (8.7。 vs. 4.6。 p=0.0057).

Conclusion

Postoperative correction rate was satisfactory in both groups. However, the thin rod group showed substantial correction loss. Therefore, polyaxial screws and thick rods are more suitable in VATS correction of scoliosis.

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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
jkss-15-9f1.tif
Fig. 2.
The Change of Correction Angle
jkss-15-9f2.tif
Table 1.
Demographic & Operative Data
  Thin rod group Thick rod group p value
Case 19 20  
Age (yr) 18.2 5.3 16.6 2.6 0.7747
Sex (M:F) 2:17 1:19 0.5139
BMI (Kg/cm2) 18.8 2.3 19.5 2.3 0.2177
Risser grade 14.1 1.5 13.9 1.2 0.4119
Fusion No. 17.3 0.8 16.9 0.9 0.1632
Op time (min) 453 73 491 83 0.1723
Blood loss (mL) 1824 443 1844 448 0.6750
Table 2.
Coronal Radiographic Measurement
  Perop Postop 1st Standing Pod 6 m Pod > 2yrs CLA
Thin rod group 49.8±9.6 15.8±7.5 21.2±7.0 24.2±8.3 24.5±7.8 8.7±3.2
Thick rod group 47.1±6.7 14.1±5.8 18.4±5.7 19.5±6.2 18.7±6.2 4.6±2.5
p value 0.4884 0.4315 0.184 0.051 0.0111 0.0057

correction loss angle between immediate postop and pod>2yrs

Table 3.
Sagittal Radiographic Measurement
  Thoracic Kyphosis Lumbar Lordosis
  Preop Last F/U Preop Last F/U
Thin rod group 18.8±7.5 17.8±6.5 40.8±13.6 42.7± 9.3
Thick rod group 17.7±7.2 20.1±6.6 40.1±12.7 42.3±12.4
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