Geometric Determinism in Pediatric Femoral Head Osteonecrosis: High-Degree Valgus Redirection Osteotomy as a Boundary-Condition Reset for Self-Organized Remodeling with Instrumented Gait Restoration
Chi-Ming Chiang
Chi-Ming Chiang
1) Center for General Education, Chung Yuan Christian University, Taiwan, China.
2) Department of Orthopedics, Chon-Inn Hospital, Chon-Inn Medical Corporation, Taiwan, China.
Background Pediatric femoral neck fractures complicated by nonunion and femoral head osteonecrosis
may enter a mechanically self-reinforcing collapse phenotype, in which varus malalignment and a high
Pauwels angle bias interfragmentary motion toward destructive shear, perpetuating resorption and
growth disturbance. Conventional fixation can stabilize implants yet leave the adverse load-transfer
geometry—the underlying mechanical “algorithm”—unchanged.
Methods: We treated a 10-year-old girl with femoral neck nonunion and osteonecrosis after failed
pinning using a high-degree valgus redirection osteotomy fixed with a compression hip screw/angled
plate. Conceptually, the osteotomy served as a boundary-condition reset: it reduced the effective Pauwels
angle, converted shear-dominant input into axial compression, and redirected the weight-bearing arc
away from necrotic sectors toward viable cartilage and apophyseal reserve. Serial radiographs and
intraoperative fluoroscopy documented correction, fixation, and healing. Instrumented gait analysis
(pre- vs post-operative) provided an objective functional endpoint.
Results: Union was achieved with restoration of alignment and without hardware migration. During
longitudinal follow-up, the femoral head remodeled toward a more spherical, congruent articulation
consistent with load-directed remodeling (Wolff’s Law). Gait kinematics normalized, including resolution
of Trendelenburg pelvic drop and recovery of stance-phase hip extension and ankle dorsiflexion toward
normative traces.
Conclusion: In pediatric femoral neck nonunion with osteonecrosis, high-degree valgus redirection
osteotomy can be interpreted as an engineering intervention that reprograms mechanical inputs. By
resetting boundary conditions from destructive shear to constructive compression and reassigning the
weight-bearing arc to viable tissue, the procedure can enable self-organized remodeling corroborated
by objective gait restoration.
