J Korean Soc Spine Surg.  2010 Sep;17(3):139-146. 10.4184/jkss.2010.17.3.139.

A Comparison of Clinical Stability of Distal Instrument Fused Down to S1 with and without Sub-S1 Alar Screw in the Long Fusion using Segmental Pedicle Screw for Lumbar Degenerative Deformity

• Kim JH
• Kim SS
• Lim DJ
• Han JI
• Kim TY
• Park CK
• Suk SI

• KMID: 1459279
• DOI: http://doi.org/10.4184/jkss.2010.17.3.139

Abstract

STUDY DESIGN: This is a retrospective study.
OBJECTIVES
We wanted to assess the stability of distal instrumentation using the bilateral S1 and sacral alar screws for the treatment of degenerative lumbar deformity. SUMMARY OF LITERATURE REVIEW: Various instrumentation methods have been introduced for increasing the strength of lumbosacral fusion. However, there are not many clinical studies that have evaluated the effectiveness of a sub-S1 alar screw for treating degenerative lumbar deformity surgery.
MATERIALS AND METHODS
A total of 39 patients with degenerative lumbar deformity were treated by long fusion and we retrospectively analyzed these patients after a minimum follow-up of 1 year. All the patients underwent an operation with distal instrumentation using either bilateral S1 screws alone (the S1 group) or additional bilateral sub-S1 sacral alar screws (the SA group). There were 19 patients in the S1 group and 20 patients in the SA group. The stability of the distal instrumentation was assessed by breakage or backout of a rod and/or screws based on simple radiography.
RESULTS
Instability of the distal instrumentation was detected in 6 cases (32%) in the S1 group and in 1 case (5%) in the SA group. The SA group had a more stability of the distal instrumentation than that of the S1 group with a significant difference (P<0.05). Distal instrumentation was unstable in 6 (19%) of the 32 cases with an anterior metal cage through posterior interbody fusion at L5-S1 and in 1(14%) of 7 cases without it at L5-S1. There was no significant difference in the stability of distal instrumentation in each group according to whether or not their L5-S1 was treated with an interbody cage (P>0.05).
CONCLUSIONS
Bilateral sacral alar screws coupled with bilateral S1 screws can provide good distal fixation for stability of the distal instrumentation when performing long fusion for treating degenerative lumbar deformity.

Keyword

Long fusion; Sub-S1 screw; Alar screw; Degenerative lumbar deformity

MeSH Terms

Congenital Abnormalities
Follow-Up Studies
Humans
Retrospective Studies
Succinates
Succinates

Figure

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  Fig. 1. A 67 year-old female with degenerative lumbar scoliosis had a lumbar coronal deformity of 30°. (A, B) She was treated by pedicle screw fixation from T10 to S1 and sub-S1 alar screw. Posterior interbody fusion using metal cage was performed on L3-4 and L5-S1. Her deformity was corrected to 5° with distal instrumentation stable in the radiographs taken one and a half year after surgery. (C, D)

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