Bivertebral autostable claws for the proximal fixation in thoracic adolescent idiopathic scoliosis surgery


Study design

Retrospective monocentric study.


To report radiologic outcomes of a consecutive series of AIS patients, operated with a bivertebral autostable claw for the upper instrumentation over a 5-year period.

Summary of background data

The upper fixation represents the weakest part of long constructs because of local anatomy and the high pull-out forces. Various implants have been proposed, but proximal junctional failures (PJF) and shoulder imbalance still occur with variable incidence. The autostable claw is a new implant, safe, and low profile, combining the mechanical strength of hooks with the initial stability of pedicle screws.


All AIS patients operated between January 2010 and July 2015 for a Lenke 1 or 2 curve with the bivertebral autostable claw were included. A minimum 2-year follow-up was required. Full-spine biplanar stereoradiographs were performed preoperatively, within 8 weeks postoperative and at latest examination. Local and global sagittal and coronal parameters were analyzed and complications were reported.


237 patients (191 Lenke 1 and 46 Lenke 2) were included, with a mean follow-up of 4.1 ± 0.6 years. PJF occurred in 2 patients (0.8%), and radiologic PJKs were observed in 8.4% of the series. Shoulder balance was efficiently restored or maintained in 88.2%.


The bivertebral autostable claw is a safe and robust alternative to pedicle screws for proximal fixation in AIS long constructs. Compression and/or distraction can be applied to level shoulders, and mechanical failures remain rare at 4-year follow-up.

Level of evidence


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Correspondence to A. L. Simon.

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Conflict of interest

ALS (none), EF (none), KM (other from Implanet, outside the submitted work), BI (other from Implanet, Zimmer Biomet, and Medtronic, outside the submitted work).

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Retrospective study approved by the Local Ethic Committee.

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Simon, A.L., Ferrero, E., Mazda, K. et al. Bivertebral autostable claws for the proximal fixation in thoracic adolescent idiopathic scoliosis surgery. Spine Deform (2020) doi:10.1007/s43390-020-00040-5

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  • Adolescent idiopathic scoliosis
  • Upper instrumented vertebra
  • Autostable claw
  • Shoulder balance
  • Sagittal balance