Journal of Pediatric Orthopaedics - 2026-09-01 - Journal Article
T1-T12 and T1-S1 Lengths at Maturity in Patients With Skeletal Dysplasia.
Avendano JP, Elsabbagh Z, ElNemer W, Durand WM, Sponseller PD
Topics
Key Takeaway
Skeletally mature patients with achondroplasia achieve a mean T1-T12 length of 27.8 cm and T1-S1 of 46.1 cm, both within expected adult ranges, with cardiopulmonary comorbidities present in only 9% of the cohort and not correlated with spinal length.
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Summary
This study characterized T1-T12 and T1-S1 spinal lengths at skeletal maturity in patients with skeletal dysplasia to establish reference data and evaluate association with cardiopulmonary comorbidities. Using PSSG methodology in 68 skeletally mature patients, achondroplasia patients demonstrated significantly greater T1-T12 (27.8 vs. 21.1 cm, P<0.001) and T1-S1 (46.1 vs. 35.6 cm, P<0.001) lengths than short-trunk dysplasia patients. Cardiopulmonary comorbidities occurred in 9% of patients and showed no clear association with measured spinal lengths.
Key Limitation
The absence of longitudinal growth data means this cross-sectional snapshot cannot establish whether achieved spinal lengths resulted from natural growth, surgical intervention, or both, limiting direct application to surgical decision-making.
Original Abstract
BACKGROUND
Growing-spine surgery aims to promote thoracic growth in skeletally immature patients by achieving adequate T1-T12 length. Surgical decision-making often relies on assumptions regarding spinal length thresholds and their relationships to cardiopulmonary function. This study aimed to characterize thoracic (T1-T12) and total spine (T1-S1) lengths in skeletally mature patients with skeletal dysplasias, with a primary focus on achondroplasia, and to evaluate whether these measurements were associated with cardiopulmonary comorbidities.
METHODS
A retrospective review was conducted of skeletally mature patients with confirmed skeletal dysplasia evaluated at a single institution between 2018 and 2023. Patients with scoliosis >30 degrees or prior spinal deformity surgery were excluded. T1-T12 and T1-S1 lengths were measured using the Pediatric Spine Study Group (PSSG) methodology. Patients with achondroplasia were analyzed as the primary cohort, with patients with short-trunk skeletal dysplasia, including spondyloepiphyseal dysplasia (SED) and mucopolysaccharidosis type IV (MPS IV), serving as a contextual comparison group.
RESULTS
Of 68 patients aged (mean and SD) 37±16.7 y, 58 had achondroplasia and 10 had other skeletal dysplasias. In the cohort, mean T1-T12 and T1-S1 lengths were 26.2 and 43.3 cm, respectively. Patients with achondroplasia demonstrated greater T1-T12 (27.8±2.8 cm vs. 21.1±5.0 cm; P <0.001) and T1-S1 (46.1±4.4 cm vs. 35.6±7.1 cm; P <0.001) spinal lengths than short-trunk skeletal dysplasia patients. Cardiopulmonary comorbidities were present in 6 patients (9%) and were not clearly associated with spinal length.
CONCLUSIONS
Skeletally mature patients with skeletal dysplasias, particularly achondroplasia, can achieve T1-T12 and T1-S1 lengths within expected adult ranges. These findings provide reference data for spinal length at maturity in patients with achondroplasia, with contextual comparison to related short-trunk skeletal dysplasias, and may help inform expectations regarding thoracic growth and cardiopulmonary risk in the context of growth-friendly surgical treatment.
LEVEL OF EVIDENCE
Level IV.