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.

Biography:

Joe is a Core Surgical Trainee (CT2) in Trauma and Orthopaedics at the University Hospitals of Derby and Burton NHS Foundation Trust. He has a particular interest in upper limb surgery, alongside clinical education and research. Joe has been involved in a range of research, audit and quality improvement projects including work in hand surgery, scaphoid morphology, theatre sustainability and surgical safety. He is currently undertaking a Postgraduate Certificate in Medical Education with the University of Warwick. Alongside his training, Joe works as an Immediate Care Doctor with Nottingham Rugby supporting the medical management of professional rugby players.