An analysis of preoperative shoulder and neck balance and surgical outcome in 111 adolescent idiopathic scoliosis patients with two subtypes of Lenke 1 curves

Chris Yin Wei Chan MD, MSOrth, Chee Kidd Chiu MBBS, MSOrth, Yun Hui Ng MBBS, Saw Huan Goh MBBS, Xin Yi Ler MBBS, Sherwin Johan Ng MBBS, Xue Han Chian MBBS, Pheng Hian Tan MBBS and Mun Keong Kwan MBBS, MSOrth
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  • Department of Orthopaedic Surgery (NOCERAL), Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
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OBJECTIVE

The incidence of postoperative shoulder imbalance following posterior spinal fusion (PSF) is still high in Lenke 1 curves despite following current treatment recommendations for upper instrumented vertebra (UIV) selection. The objective of this retrospective study was to identify differences in preoperative shoulder balance and to report the surgical outcome of two subtypes of Lenke 1 curves (flexible vs stiff) in patients with adolescent idiopathic scoliosis (AIS).

METHODS

The authors grouped patients’ curves as Lenke 1–ve (flexible) when their preoperative proximal thoracic side bending (PTSB) Cobb angle was < 15° and as Lenke 1+ve (stiff) when the PTSB Cobb angle was 15°–24.9°. The authors hypothesized that these two subtypes had distinct preoperative and postoperative shoulder and neck balance following PSF using pedicle screw constructs.

RESULTS

Fifty patients had Lenke 1 (flexible) curves and 61 had Lenke 1 (stiff) curves. The mean preoperative T1 tilt for patients with Lenke 1 (flexible) was −4.9° ± 5.3°, and for those with Lenke 1 (stiff) curves it was −1.0° ± 5.3° (p < 0.001). Mean cervical axis (CA) was −0.1° ± 3.2° for Lenke 1 (flexible) curves and 2.3° ± 3.5° for Lenke 1 (stiff) curves (p < 0.001). Preoperative radiographic shoulder height (RSH) and clavicle angle (Cla-A) were similar between the two curve subtypes. Following surgery, there were significant differences between the subtypes in terms of T1 tilt (p < 0.001), RSH (p = 0.014), and Cla-A (p = 0.031). Interestingly, 41.0% of patients with a Lenke 1 (stiff) curve had +ve T1 tilt compared to 2.0% in Lenke 1 (flexible) group. Moreover, 26.2% of patients with the Lenke 1 (stiff) curve had +ve RSH compared to 12.0% of those with Lenke 1 (flexible) curves. And, 24.6% of patients with Lenke 1 (stiff) had +ve Cla-A compared to 10.0% of those with Lenke 1 (flexible) curves.

CONCLUSIONS

Lenke 1 (flexible) and Lenke 1 (stiff) curves had distinct preoperative T1 tilt and CA measurements. Following PSF, the authors noted +ve T1 tilt in 41% of patients with Lenke 1 (stiff) curves versus 2.0% in those with Lenke 1 (flexible) curves. The authors also noted a significant difference in postoperative RSH and Cla-A measurements.

ABBREVIATIONS AIS = adolescent idiopathic scoliosis; CA = cervical axis; CB = coronal balance; Cla-A = clavicle angle; CSSB = cervical supine side bending; L Cobb = lumbar Cobb angle; LIV = lowest instrumented vertebra; LSB Cobb = lumbar side bending Cobb angle; MT = main thoracic; MT Cobb = MT Cobb angle; MTSB Cobb = MT side bending Cobb angle; PSF = posterior spinal fusion; PSI = postoperative shoulder imbalance; PT = proximal thoracic; PT Cobb = PT Cobb angle; PTSB = PT side bending; PTSB Cobb = PTSB Cobb angle; RSH = radiographic shoulder height; SBCI = side bending correction index; UIV = upper instrumented vertebra.

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Contributor Notes

Correspondence Mun Keong Kwan: National Orthopaedic Centre of Excellence for Research and Learning (NOCERAL), University of Malaya, Kuala Lumpur, Malaysia. munkeong42@hotmail.com.

INCLUDE WHEN CITING Published online August 28, 2020; DOI: 10.3171/2020.5.SPINE20397.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

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