Ankle arthroscopy has generally been performed with use of anterior
portals with the patient in the supine position. Little has been
published on ankle arthroscopy performed with use of posterior portals,
particularly with the patient in the prone position. The purpose
of the present study was to evaluate the relative safety and efficacy
of ankle arthroscopy with use of posterior portals with the limb
in the prone position.
Thirteen fresh-frozen cadaver specimens were used. Posterolateral
and posteromedial portals were established. Arthroscopy was performed,
and the extent of the talar dome that could be visualized was marked.
Four-millimeter plastic cannulae were filled with oil and were placed
in the portals for use as reference landmarks on magnetic resonance
imaging studies. The proximity of the portal cannulae to the adjacent structures
was measured on standard magnetic resonance images and then during
careful dissection. The distances measured by dissection were compared
with the measurements made on magnetic resonance images.
An average of 54% (range, 42% to 73%) of the talar dome could be
visualized. The average distance between a cannula and adjacent
anatomic structures after dissection was 3.2 mm (range, 0 to 8.9
mm) to the sural nerve, 4.8 mm (range, 0 to 11.0 mm) to the small
saphenous vein, 6.4 mm (range, 0 to 16.2 mm) to the tibial nerve,
9.6 mm (range, 2.4 to 20.1 mm) to the posterior tibial artery,
17 mm (range, 19 to 31 mm) to the medial calcaneal nerve, and 2.7
mm (range, 0 to 11.2 mm) to the flexor hallucis longus tendon. The
magnetic resonance images demonstrated very similar distances except
in the case of the distance between the posteromedial cannula and
the tibial nerve, which often was difficult to specifically identify
on magnetic resonance imaging studies.
The findings of the present cadaveric study suggest that, with the
patient in the prone position, arthroscopic equipment may be introduced
into the posterior aspect of the ankle without gross injury to the
posterior neurovascular structures. Limited clinical trials should
be carried out to confirm this finding.