Journal of Hand Surgery - June 2022 - S131

Abstract
S131
A-0884 Observations on the isometry of the volar
STT ligament reconstruction using the 3LT scaphoid
tunnel - a CAD simulation using scaphoid CT data
Alex Magnussen1, Julien Ballerini2 and Nicholas Smith3
1Imperial College NHS Trust, London, UK
2Newclip Technics, Nantes, France
3Macquarie University, Sydney, Australia
Objective: The volar scaphotrapeziotrapezoidal ligament
(vSTTL) is thought to be a critical stabiliser of
the scaphoid, and relevant in scapho-lunate instability.
In Brunelli's reconstruction, the scaphoid tunnel
exited dorsally in the distal scaphoid, which allowed
an isometric vSTTL reconstruction. The Three
Ligament Tenodesis (3LT) aims to reconstruct both
vSTT and dorsal scapho-lunate ligament (dSLL) with
the same slip of flexor carpi radials passed though a
more longitudinal tunnel. A 3mm drill is passed from
the dorsal, proximal scaphoid and should exit volar in
the region of the scaphoid tubercle at the isometric
point of the vSTTL. Anecdotally this is technically
challenging and a truly isometric volar exit point
can be difficult to achieve. A more radial than ideal
exit point can be observed radiographically in a
number of publications dealing with techniques
which employ the 3LT type tunnel, such as the 3LT,
Henry, Corella and ANAFAB reconstructions. This
raises the question of whether the osseous anatomy
of the scaphoid allows connecting the isometric
scaphoid attachments of the vSTTL and dSLL with a
single intra-osseous tunnel in a reproducible fashion.
We sought to investigate this question using
three dimensional computer models derived from
CT data from patients with normal scaphoids.
Methods: We collected 6 consecutive wrist CT scans
of patients with normal scaphoids and no arthrosis.
Using DICOM-to-print (3d Systems Inc) we created
3D reconstructions of the scaphoid using semi-automatic
segmentation based on greyscale with the
other carpals subtracted. This data was then
exported as a 3D pdf. Based on existing knowledge
of the isometric points of the scaphoid, the senior
author marked entry and exit points for the bone
tunnel on these models. A 3mm virtual tunnel was
then created between these points using proprietary
CAD software.
Results: In the 6 scaphoid models created, only one
tunnel remained intraosseous. 4 showed the tunnel
breaking out through the ulna cortex into the scaphocapitate
joint and in the final model the tunnel
broke out through the volar cortex.
Conclusions: Techniques using a longitudinal " 3LT "
tunnel may be more technically challenging than
previously appreciated. Our results have shown
that, due to the true bony anatomy of the scaphoid,
the operating surgeon may often need to compromise
on isometry of the vSTT reconstruction in
order to keep the bone tunnel intraosseous.
A-0885 Sonographically controlled percutaneous
pulley release - a progress report
Damian Sutter, Aline Treier and Esther V€ogelin
University Hospital Bern, Switzerland
Introduction: Over the past decade percutaneous
surgery in trigger finger has become increasingly
popular. Higher quality ultrasound (US) probes
made it easy to visualize structures adjacent to the
flexor tendon. We report on our progress developing
a novel sonographically assisted percutaneous technique
to release the A1 pulley in trigger finger after
primary trials it in cadaver hands. A guide instrument
is inserted in the intra-sheath position from distal to
proximal underneath the A1 pulley through a small
incision at the base of the finger. This guide protects
the flexor tendons and allows for safe insertion of a
hook knife which is used to release the A1 pulley in a
safe manner. This technique has been implemented
in November 2018. Due to difficulty with proper
placement of the knife, a refined guide instrument
was introduced in November 2019. The evolution of
the technique including our complications are
reported.
Method: Procedures are perfomed in local anaesthesia.
The pulley, flexor tendon, nerves and arteries are
located sonographically. The guide instrument is
inserted through a transverse incision at the base
of the finger. Two different designs were used
since November 2018. The guide is inserted from
distal to proximal under the A1 pulley and palmar
to the flexor tendon. The tip of the hook knife can
then be positioned just to the proximal edge of the
A1 pulley. By retraction of the hook knife, the pulley
is divided. Successful release can be assessed clinically
and under US control.
Results: Between November 2018 and October 2019
27 patients (32 fingers) have been operated using the
first guide iteration (group 1). 53 patients (74 fingers)
were treated §between November 2019 and
September 2021 using a refined guide instrument
design (group 2). 9 patients required conversion to
open release in group 1 due to unfavorable knife
position. With open inspection possible in these
patients, 5 partial lesions to the FDS tendons were
observed. Postoperative infections occurred in two
patients of group 1. Both presented late (12 and 21
Journal of Hand Surgery - June 2022

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