Selecting the Upper Instrumented Vertebra One Level Caudal to the Upper End Vertebra is Associated With Better Five-Year Directional Shoulder Balance in Lenke Type 1A Adolescent Idiopathic Scoliosis
Kota Watanabe, Satoshi Suzuki, Kazuki Takeda, Takahito Iga, Toshiki Okubo, Masahiro Ozaki, Soya Kawabata, Narihito Nagoshi, Morio Matsumoto, Masaya NakamuraStudy Design:
Retrospective single-center radiographic cohort study.
Objective:
To evaluate whether selecting the upper instrumented vertebra (UIV) one level caudal to the upper end vertebra (UEV) is associated with better five-year directional shoulder balance in Lenke type 1A adolescent idiopathic scoliosis.
Summary of Background Data:
Excessive main thoracic (MT) correction may worsen postoperative shoulder balance when proximal thoracic compensation is insufficient. Whether UIV=UEV-1 provides a durable shoulder-balance benefit in homogeneous Lenke type 1A curves remains unclear.
Methods:
Eighty-one patients with complete preoperative, one-month, two-year, and five-year radiographs were analyzed: 30 underwent UIV=UEV and 51 underwent UIV=UEV-1 posterior spinal fusion. Radiographic shoulder height (RSH), clavicle angle, and T1 tilt were analyzed as signed values. The primary outcome was five-year signed RSH; the key secondary outcome was five-year signed clavicle angle. Multivariable and sequential models evaluated early MT correction and late proximal alignment.
Results:
Preoperative shoulder-balance parameters were comparable between groups. At five years, signed RSH was closer to zero in the UIV=UEV-1 group than in the UIV=UEV group (6.5±8.8
Conclusions:
In selected Lenke type 1A curves, UIV=UEV-1 was associated with better five-year radiographic directional shoulder balance. This association was consistent with controlled MT correction and favorable proximal coronal alignment, although causality cannot be inferred.
Level of Evidence:
Level III.