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New Technique for Anatomic Reconstruction of the Scapholunate Ligament with Tendon Graft and SwiveLock Anchor Fixation: A Biomechanical Cadaveric Study
Timothy McGrath, MD; Excelsior Orthopaedics; Nikola Zivaljevic, MD, MBA, MHMS; SUNY at Buffalo
SUNY at Buffalo, Buffalo, NY, USA

A dorsal scapholunate ligament reconstruction, using either palmaris longus or extensor indicis proprius tendon graft and secured with two Arthrex 3.5mm PEEK SwiveLocks in bone tunnels, has similar elongation, stiffness and load to failure properties as the native dorsal scapholunate ligament.

8 matched wrist pairs were first evaluated radiographically and then dissected and randomly assigned to the control or reconstruction group. The control group had all but dorsal band of SL ligament resected. In the reconstruction group, all three portions of the SL-ligament were divided. Tendon graft was harvested and whipstitched on each end. Bone tunnels were drilled over K-wires in the lunate and scaphoid under fluoroscopic guidance The tendon was secured in the lunate tunnel, first with a SwivelLock as an interference screw then passed through the scaphoid andin antegrade fashion with a second SwivelLock anchor.

In both groups, the scaphoid and lunate were dissected out, pinned with 2 orthogonal K-wires in each of the bones, and potted in polymethylmethacrylate. A 5N pre-load was applied on the load frame, followed by 200 cycles from 5-20N. Load to failure was applied at 5mm/s. In initial testing, one control specimen failed during cycling and that pair was excluded from analysis. The data were analyzed using the nonparametric Wilcoxin Test. A significance level of 0.05 was accepted.

The reconstructed ligament elongated significantly more during cycling than the control group. The stiffness of the reconstructed ligament was significantly less than the control group. Load to failure was not significantly different (Table 1). Mode of failure in the reconstruction group was by breaking off the radial wall of the lunate (3), pulling out of the lunate (1) or pulling out of the scaphoid (3). The control group all failed by midsubstance tears.

This new technique for anatomic reconstruction of the vital dorsal band of the SL-ligament may provide secure enough bone tunnel fixation and obviate the need for prolonged pin fixation and immobilization that has traditionally been required in non-anatomic reconstruction techniques commonly used for chronic static and dynamic scapholunate instability. Our data supports consistent and reproducible load to failure in reconstructed group which might translate to future clinical application.

Table1:

Control

Mean ± St Deviation

Reconstruction

Mean ± St Deviation

p value

Elongation

0.081 ± 0.042 mm

0.589 ± 0.258 mm

0.028*

Stiffness

82.07 ± 44.1 N/mm

37.94 ± 10.4 N/mm

0.028*

Load to Failure

115.4 ± 63.15 N

70.8 ± 8.1 N

0.14

*statisticallysignificant


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