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Patient-specific Rods for Surgical Correction of Sagittal Imbalance in Adults

Technical Aspects and Preliminary Results

Solla, Federico, MD*; Barrey, Cédric Y., MD, PhD†,‡; Burger, Evalina, MD§; Kleck, Christopher J., MD§; Fière, Vincent, MD

doi: 10.1097/BSD.0000000000000721

Study Design: This was an innovative concept and a preliminary prospective series.

Objective: The aim of this study was to present the concept and the technical aspects of patient-specific rods (PSR), and compare preoperative and postoperative sagittal parameters (after PSR implantation), with a special focus on the difference pelvic incidence (PI)—lumbar lordosis (LL).

Background: Despite established techniques for planning and proven correlations between quality of life and sagittal alignment, some patients do not achieve optimal radiologic outcomes after surgery and are still hypolordotic and imbalanced. We hypothesize that the use of PSR could improve the correspondence between planning and surgical realization.

Methods: The planning was based on spinopelvic parameters evaluated on a full-spine x‐ray. The surgical procedure including osteotomies was simulated using a dedicated program to reach the following objectives: PI-LL<10 degrees, a pelvic tilt <20 degrees, and sagittal vertical axis <50 mm. From the virtually corrected spine, the rod curvature and length were defined. Two PSRs were thus precisely manufactured and bent to this specification. Adults with degenerative spinal disorders requiring a construct ≥5 levels were implanted with PSR and prospectively included. We compared ratios through the χ2 test.

Results: A total of 60 patients (mean age of 64.4 years old; range, 34–83) were included. Follow-up was carried out over a period of 1 year. Average pedicle screws construct was of 6.4 levels (range, 5–9). Eight patients underwent a pedicle subtraction osteotomy. PI-LL was <10 degrees at baseline in 29/60 patients, and at follow-up in 50/60 (odds ratio=5, P=E-5).

Conclusions: The ratio of patients with optimal PI-LL improved significantly from PSR implantation. In comparison with published data for conventional surgery, patients implanted with PSR were 2.6 times more likely to be optimally corrected. The expected benefits of PSR include the optimal execution of the plan, decreased mechanical complications, and reduced operating time, no longer requiring the bending of rods during surgery. A randomized trial on sagittal correction using PSR is ongoing.

*Orthopaedic and Scoliosis Surgery Unit, Lenval Hospital, Nice

Spine Unit, P. Wertheimer Hospital, University Hospitals of Lyon, Bron

University “Claude Bernard” Lyon 1, France

§Department of Orthopedics, University of Colorado SOM, Aurora, CO

Spinal Unit, Santy Orhopaedic Center and Mermoz Hospital Ramsay GDS, Lyon, France

F.S. received funding for congresses from Medicrea Int. C.Y.B. received funding for congresses from Medicrea Int., Medtronic, Implanet, Ethicon, and Noraker. C.J.K. is a paid consultant for MEDICREA Group and has received grants from DePuy Synthes, Medtronic Sofamor-Danek, Aesculap, SI-Bone, Vertiflex, MEDICREA Group, Orthofix, Integra Life Sciences Corporation, Pfizer, Spinal Kinetics, MTF, and Globus. E.B. is a paid consultant for DSM, Paradigm Spine, and Signus and has received grants from OMeGA, Globus, Aesculap, SI-Bone, Vertiflex, MEDICREA Group, Medtronic, Orthofix, Integra Life Sciences Corporation, Pfizer, Spinal Kinetics, Medtronic Sofamor-Danek, and Synthes. V.F. is a paid consultant for Medicrea Int. and Clariance and receives royalties from Medicrea Int. and Clariance.

Reprints: Federico Solla, MD, Orthopaedic and Scoliosis Surgery, Lenval Hospital, 57 Ave., De la Californie, Nice 06200, France (e-mail:

Received February 16, 2018

Accepted August 15, 2018

© 2019 by Lippincott Williams & Wilkins, Inc.