Distal Phalanx Depth Variation and Implications for Zone I Flexor Tendon Anchor Repairs: A CT and X-Ray Comparative...

Area of Science:

• Orthopedic surgery
• Hand surgery
• Biomedical imaging

Background:

• Suture anchors in Zone I flexor tendon repairs pose risks of dorsal cortex penetration and nail bed injury.
• Preoperative measurements are crucial for selecting safe anchor-drill systems, but radiograph accuracy and safety thresholds need clarification.

Purpose of the Study:

• Quantify distal phalanx depths using radiographs and CT scans.
• Verify the accuracy of radiograph measurements against CT scans.
• Assess compatibility of measurements with current anchor systems and determine safe depth thresholds.

Main Methods:

• Retrospective review of 30 adult subjects (120 digits) with paired lateral radiographs and CT scans.
• Independent measurement of distal phalanx base depths by two reviewers using both imaging modalities.
• Statistical analysis to compare measurements, calculate safe depth thresholds, and compare with anchor system specifications.

Main Results:

• Radiographs showed a predictable, linear relationship with CT scans, with slight overestimation (mean bias ≤ 0.6 mm).
• Maximum safe depths varied by digit (3.8-4.9 mm, increasing with oblique drilling), with some anchor systems exceeding these limits, especially in smaller fingers.
• Distal phalanx size differed between male and female digits.

Conclusions:

• Digital radiographs offer sufficient accuracy for preoperative planning with a safety margin.
• Distal phalanx dimensions vary by digit and gender, necessitating caution in female patients and for ring/little fingers.
• Retrograde oblique drilling is recommended to enhance bone purchase and reduce penetration risks.