Computed tomography analysis of third webspace injections for interdigital neuroma

Area of Science:

• Anatomy
• Radiology
• Orthopedic Surgery

Background:

• Interdigital neuroma (IDN) injections may lack selective targeting of the common digital nerve.
• Investigating anatomical localization and extravasation extent of IDN injections is crucial.

Purpose of the Study:

• To evaluate the anatomical accuracy and spread of contrast material following injections for interdigital neuroma.
• To compare extravasation extent between different injection volumes (1 mL vs. 2 mL).

Main Methods:

• Radiopaque contrast was injected into the third webspace of 49 cadaveric specimens (29 with 2 mL, 20 with 1 mL).
• Computed tomography scans were obtained for each specimen.
• An independent, blinded foot and ankle surgeon analyzed the CT scans.

Main Results:

• All injections accurately reached the intended site.
• Contrast spread to the second webspace (>70%) and fourth webspace (>30%) in both volume groups.
• Extravasation was significantly greater with 2 mL compared to 1 mL in both medial-lateral and distal-proximal planes.

Conclusions:

• IDN injections are anatomically accurate but frequently involve adjacent webspaces.
• While 1 mL showed less extravasation, it did not prove superior in injection selectivity.
• Steroid injections for IDN are therapeutically accurate but limited for diagnostic purposes.