Estimating Scaphoid Lengths Using Anatomical Measurements in the Wrist

Area of Science:

• Orthopedic surgery
• Anatomy
• Biomechanical engineering

Background:

• Scaphoid nonunions with humpback deformity present challenges in reconstructive surgery.
• Surgeons debate restoring normal scaphoid length versus overexpansion for optimal carpal alignment.
• Precise estimation of original scaphoid length is crucial for defining overexpansion and achieving successful outcomes.

Purpose of the Study:

• To compare the precision of estimating normal scaphoid length using intact adjacent bone dimensions versus the contralateral scaphoid.
• To provide a reliable method for determining scaphoid length in reconstructive surgery.

Main Methods:

• Creation of 3D virtual bone models from bilateral CT scans of 28 healthy wrist pairs.
• Measurement of scaphoid length at the central axis.
• Derivation of ipsilateral scaphoid length estimates using capitate length and distal radius width.
• Calculation of estimation precision based on the 95% range of observed differences.

Main Results:

• The average difference between actual and ipsilateral estimated scaphoid length was 0.1 mm, with a precision of ±2.2 mm.
• The average difference between actual and contralateral estimated scaphoid length was also 0.1 mm, but with a higher precision of ±1.4 mm.
• Contralateral scaphoid length estimation demonstrated superior precision.

Conclusions:

• Estimation of scaphoid length using the contralateral scaphoid is more precise than using ipsilateral radius and capitate dimensions.
• Restoring scaphoid length at least 1.4 mm longer than the contralateral length may ensure adequate overexpansion for reconstruction.
• This information is valuable for setting target lengths in scaphoid reconstruction and investigating the effects of overexpansion on clinical function.