Interbody cage support improves reconstruction of sagittal balance after anterior selective fusion in Lenke type 5 idiopathic scoliosis patients

Abstract

Objective: To investigate the effect of interbody cage support on reconstruction of the sagittal profile after anterior selective correction in Lenke type 5 adolescent idiopathic scoliosis (AIS) patients.

Methods: In this retrospective study, a total of 40 AIS patients with a Lenke type 5 curve who underwent anterior selective fusion (ASF) using a single rod were studied. They were divided into two groups: Group A, bone grafting with an interbody titanium mesh cage (TMC); and Group B, bone grafting without a TMC. There were 19 female and 1 male patient aged 12-18 years in Group A, and 17 female and 3 male patients aged 13-20 years in Group B. All patients were followed up for more than 18 months. The coronal correction of the scoliosis and reconstruction of the sagittal profile were evaluated retrospectively.

Results: By final follow-up, more than 70% correction had been achieved for the primary curve and a spontaneous correction for the secondary curve in both groups. Satisfactory reconstructions on the sagittal plane were also observed. Similar changes were found in Group A and Group B, including increases in thoracic kyphosis, slight changes in thoracolumbar junctional kyphosis, no significant losses of lumbar lordosis, mild increases in proximal junctional measurement, and remarkable lordosis losses in the instrumented segments. With lessening of the sagittal balance and L(1) offset, a significant anterior shift of the C(7) plumb line was noted during follow-up in Group A, indicating a more balanced spine in this group.

Conclusion: Anterior selective single rod instrumentation and fusion is a recommended method for Lenke type 5C AIS. A structural interbody cage does not appear to improve the regional profile, nor the profiles in the instrumented area and the adjacent proximal and distal segments; yet could result in a better total balance in the long-term.

Figure 1

Depiction of the means of measurement used in this study. The measurements of the sagittal regional angulation and the balance include TK (from T₅ to T₁₂), the TJK (from T₁₀ to L₂), LL (from T₁₂ lower end plate to S₁ superior plate), SS (the angle of sacral slope), the SVA (the horizontal distance between C₇PL and the posterior superior corner of S₁), and the L₁ offset (the horizontal distance between C₇PL and the center of L₁). ll, line of the lower endplate; ul, line of the upper endplate.

Figure 2

Depiction of the means of measurement used in this study. The measurements of the sagittal segmental and junctional angles include the ISA (from the upper plate of the UIV to the lower end plate of the LIV), the PJM (between the upper plate of the second vertebra cephalad to the UIV and the lower end plate of the UIV), the DJM (between the upper plate of the second vertebra caudal to the LIV and the lower end plate of the LIV) and the DJK (between the upper plate of the first vertebra caudal to the LIV and the lower end plate of the LIV).