147 / 244
C.H. BROWN
146
• These steps allow a tibial tunnel of a known
length to be drilled, allowing the issue of
graft-tunnel length mismatch to be addressed.
• The tibial tunnel is initially drilled with a
small diameter drill bit such as the 4.5 or
5mm fully fluted drill bit. The guide pin is
repositioned eccentrically in the desired
direction within the drilled tunnel using a
small clamp inserted through the AL portal,
and the tunnel is sequentially drilled by 1mm
increments up to the final diameter of the
tibial tunnel. These steps allow the tibial
tunnel to be positioned as far medially in the
tibial attachment site as possible.
GRAFT TENSIONING
At the present time, the optimal graft tension
and knee flexion angle for a single-bundle ACL
reconstruction are unknown. The usual graft
excursion pattern for a femoral tunnel
positioned near the center of the ACL
attachment site results in the ACL graft
tightening (pulling into the tibial tunnel) during
the last 30 degrees of extension. In this
situation, the graft is fixed at 20 degrees of
flexion with a posterior force applied to the
anterior tibia to hold the tibia in a reduced
position. A spring-loaded tensioning device is
used to tension the ACL graft. For 5-strand
hamstring tendon grafts, a 60N load is applied.
For 6-strand hamstring tendon grafts, a 70N
load is applied.
GRAFT FIXATION
The graft is fixed with a tapered 7-9mm or
8-10mm, 30mm long bioabsorbable inter
ference screw (fig. 15).
Fig. 15