Using computer navigation in 25 patients with an acute isolated ACL rupture, undergoing soft issue ACL reconstruction using autologous hamstring graft, the addition of femoral aperture fixation to cortical suspensory fixation significantly reduced both the anterior translation and internal rotation during the pivot shift, without altering the length-tension of the graft.
and aims: The influence of the method of graft fixation used on the
function of a soft tissue ACL graft remains unknown. Our aim was to compare the
effect of the method of femoral fixation used on the ability of soft tissue ACL graft to
control the pivot shift.
Patients presenting with an acute isolated ACL rupture and who satisfied the
study criteria, were invited to participate. Study participants underwent an “anatomical”
ACL reconstruction using an autologous hamstring graft. Computer navigation was
used to measure the anterior translation (AT) and internal rotation (IR) during the pivot
shift test. This was performed prior to reconstruction, and was repeated twice. First,
following ACL reconstruction using tibial interference screw and femoral cortical
fixation (or “button”), and again, following femoral interference screw fixation. The length
of the intra-articular graft was measured before and after the addition of the femoral screw.
Changes in AT and IR at each stage were compared using statistical analysis (p<0.05)
Between 1st March 2015 to 21st June 2015, twenty-five patients took part in
the study. There were 69 potential candidates for this study but 44 patients were found
to have additional injuries at arthroscopy that excluded them from the study. There
were 10 male and 15 females. The mean age of the patients was 25 years (SD = 6.2).
Sixteen of the knees were dominant, 9 were non-dominant.
We used paired samples tests to compare AT before reconstruction with that after
reconstruction using femoral cortical fixation, and with that after the addition of the
femoral interference screw. Similarly we compared IR before reconstruction with that
after reconstruction with cortical fixation, and then aperture fixation on the femoral
side. For each comparison a post-hoc power analysis using generalised linear models
confirmed adequate power of the study. Before ACL reconstruction, the mean AT was
14.2mm (SD 7.3), and IR was 17.2 (SD 5.5). Following reconstruction using
femoral cortical suspension these figures were significantly reduced to 6.2mm (SD
3.5), and 12.5 (SD 3.2), P<0.001, respectively. The addition of the aperture
fixation was associated with a further significant reduction to 4.6mm (SD 3.2), and
10.4 (SD 2.7), respectively, P<0.001. There was no measurable change in the length of
the intra-articular graft.
The addition of femoral aperture fixation to suspensory fixation,
significantly reduces the anterior translation and internal rotation that occurs during the
pivot shift test. When the same bone tunnels are used, the method of graft fixation used
significant effects the bio-mechanical function of a soft tissue ACL graft.