Selective Thoracic Fusion for Adolescent Idiopathic Scoliosis: Long-Term Radiographic and Functional Outcomes*

Abstract

Introduction

Selective thoracic fusions (STFs) were introduced by Moe to treat the structural thoracic curve when a more flexible lumbar component existed. It is unknown how the curves behave and how the patients function beyond 20 years after surgery.

Methods

Of the 152 eligible patients with STF, 67 were traced and contacted and 40 completed outcome questionnaires (Oswestry Disability index [ODI], Scoliosis Research Society–30 [SRS-30]) and had follow-up standing radiographs. The preoperative, postoperative, 1-year, and follow-up films were compared, and the lumbar spine on follow-up assessed for signs of degeneration—disc space narrowing, osteophyte formation, rotatory subluxation, and lateral spondylolisthesis.

Results

The average follow-up was 32.7 years. There were 27 Lenke 1C, 10 Lenke 2C, and 3 Lenke 1B curves. A posterior fusion was performed in 37, with a Harrington rod used in 28 and all-hook constructs in 12 with fusion to T10 (1), T11 (10), T12 (22), or L1 (7). The average preoperative right thoracic curves were 56.1°, 36.2° 1 year postoperation, and 38.6° at follow-up. The average preoperative lumbar curve was 44.6°, being 35.2° at 1 year postoperation, and 36.9° at follow-up. Five patients had additional surgery, 3 pseudarthrosis repairs (one with extension of the fusion to L4), 1 implant removal, and 1 microdiscectomy 35 years postoperatively. At follow-up, the average ODI was 8.7 (0–62) and the average SRS-30 3.8 (1.4–4.9). Nine patients took nonnarcotic medication, usually weekly or less, with only one taking daily narcotics. The most common lumbar radiographic finding was disc space narrowing at the apex of the lumbar curve, and osteophytes at L2–L3. There was no correlation of the lumbar changes to ODI, with a tendency to more medication use with longer follow-up (older subjects).

Conclusion

At an average 33-year follow-up, the lumbar curve in STF is unchanged, with patients functioning well and mild radiographic changes in the lumbar spine.

Introduction

The surgical treatment of adolescent idiopathic scoliosis (AIS) is aimed at curve correction, prevention of progression, and achieving a solid arthrodesis while maintaining coronal and sagittal balance. The curve classification system of King et al. brought recognition of the false double major curve (King 2), whereby the role of fusion of only the thoracic curve with a selective thoracic fusion (STF) was introduced [1]. This principle was further discussed by Lenke in the new classification system of Lenke 1B and 1C curve patterns [2].

Spontaneous lumbar curve correction has been observed with an STF, and short-term results have shown curve correction maintenance [3], [4], [5], [6], [7], with long-term studies including STF cases in the review of the outcome of fusion for AIS [8], [9]. There are three long-term studies of STF cases with a span of 7–20 years that report good outcomes [3], [10], [11].

This study was undertaken to investigate the long-term results of STF to answer the following three questions.

• Is the curve correction in the thoracic and balancing lumbar curves maintained?

• How do the patients function at follow-up in regard to health-related quality of life (HRQOL) measures?

• What are the radiographic changes in the lumbar curve below the fusion?