Normative scaphoid height-to-length ratio on computed tomography imaging: A new definition for scaphoid malunion?

Title : Normative scaphoid height-to-length ratio on computed tomography imaging: A new definition for scaphoid malunion?

Abstract:

Introduction: Scaphoid height-to-length (H/L) ratio is an established quantitative measurement of scaphoid deformity. There is no consensus for normal computed tomography (CT)-based H/L ratio for healthy scaphoids, including for age and gender. Our study aimed to establish normative CT-based reference values for scaphoid H/L ratio and define upper thresholds of normal morphology to propose a new definition of scaphoid malunion.

Methods: We performed a retrospective single-centre study of healthy scaphoids imaged by CT from May 2024 to May 2025. Non-healthy scaphoids were excluded based on pre-defined criteria. Sagittal CT reconstructions were used to measure scaphoid height (H) and length (L), from which H/L ratio was determined. Descriptive statistics were calculated. Subgroup analyses based on age (<50 vs. ≥50 years) and gender (male vs. female) and combined age and gender (male <50 years, male, ≥50 years, female <50 years old, female ≥50 years) were performed.

Results: A total of 195 scaphoid CT images were reviewed; 96 were excluded due to pathology (n=62), previous scaphoid surgery (n=19), carpal bone instability (n=7), and inadequate imaging (n=8). Final analysis included 99 scaphoids from 97 patients. Majority of patients were female (n=53; 54%) and <50 years old (n=59; 60%). Mean patient age was 43 years (range, 12–79 years). Mean H/L ratio was 0.60 (95% normal range, 0.53–0.68) with a 99^th percentile of 0.67. Scaphoid H/L ratio was consistent across all subgroups. Mean H/L ratio by gender (male, 0.61 [95% normal range, 0.53–0.69]; female, 0.60 [95% normal range, 0.52–0.68]) and age (<50 years, 0.60 [95% normal  range, 0.52–0.67]; ≥50 years, 0.61 [95% normal range, 0.53–0.69]) were calculated. 99^th percentile values by gender (male, 0.68; female, 0.67) and age (<50 years, 0.67; ≥50 years, 0.67) were calculated. Combined gender and age analyses demonstrated consistent mean H/L ratio and 99^th percentile valves.

Conclusion: Our study established normative CT-based scaphoid H/L ratios derived from healthy scaphoids across age and gender subgroups. We propose a H/L ratio >0.7 as the definition for scaphoid malunion. Its use may support in objective diagnosis of suspected scaphoid malunion and inform surgical management.