Distraction forces on the spine in early-onset scoliosis: A systematic review and meta-analysis of clinical and biomechanical literature

• Published in: Journal of biomechanics Vol. 124; p. 110571
• Main Authors: Lemans, Justin V.C., Wijdicks, Sebastiaan P.J., Koutsoliakos, Ioannis, Hekman, Edsko E.G., Agarwal, Aakash, Castelein, René M., Kruyt, Moyo C.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 19.07.2021; Elsevier Limited
• Subjects: Age; Biomechanical engineering; Biomechanics; Distraction; Early-onset scoliosis; Failure; Fractures; Growing rods; Intervertebral discs; Literature reviews; Meta-analysis; Optimization; Patients; Pediatrics; Pedicle screws; Quality assessment; Regression analysis; Safety; Scoliosis; Segments; Spine; Structural failure; Systematic review; Transplants & implants; Early-onset scoliosis; Biomechanics; Distraction; Safety; Growing rods; Spine
• ISSN: 0021-9290; 1873-2380
• DOI: 10.1016/j.jbiomech.2021.110571

Distraction-based growing rods are frequently used to treat Early-Onset Scoliosis. These use intermittent spinal distractions to maintain correction and allow for growth. It is unknown how much spinal distraction can be applied safely. We performed a systematic review and meta-analysis of clinical and biomechanical literature to identify such safety limits for the pediatric spine. This systematic review and meta-analysis was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Three systematic searches were performed including in-vivo, ex-vivo and in-silico literature. Study quality was assessed in all studies and data including patient- or specimen characteristics, distraction magnitude and spinal failure location and ultimate force at failure were collected. Twelve studies were included, 6 in-vivo, 4 ex-vivo and 2 in-silico studies. Mean in-vivo distraction forces ranged between 242 and 621 N with maxima of 422–981 N, without structural failures when using pedicle screw constructs. In the ex-vivo studies (only cervical spines), segment C0-C2 was strongest, with decreasing strength in more distal segments. Meta-regression analysis demonstrated that ultimate force at birth is 300–350 N, which increases approximately 100 N each year until adulthood. Ex-vivo and in-silico studies showed that yielding occurs at 70–90% of ultimate force, failure starts at the junction between endplate and intervertebral disc, after which the posterior- and anterior long ligament rupture. While data on safety of distraction forces is limited, this systematic review and meta-analysis may aid in the development of guidelines on spinal distraction and may benefit the development and optimization of contemporary and future distraction-based technologies.