Extracapsular Stabilization 195either by passing it through a full-thickness
bone tunnel and then through a button medially
that lags up against the bone, or using a bone
anchor. The femoral portion of the suture can
also be anchored by passing it around the proxi-
mal fabella (fabellofemoral ligament). The tibial
portion of the suture can also be anchored by
passing the suture from lateral to medial under
the patellar tendon and then back through a
bone tunnel or medially then laterally through
two bone tunnels. Few studies have been con-
ducted to compare the various forms of anchor-
ing, but oneex vivostudy showed that the TR
procedure, which uses full thickness bone tun-
nels anchored medially with buttons, provided
more resistance to cranial tibial displacement
than did LFTS (Choateet al. 2013).
Methods of securing suture ends
The method of securing the suture can affect the
strength of the construct. In general, monofila-
ment sutures can be joined using one or multi-
ple knots and/or crimp clamps. When tying a
monofilament suture with square knots, more
throws will increase knot security (Caporn &
Roe 1996) but also increases the profile of the
knot, which can cause tissue irritation and
necrosis of the overlying skin. Four to five total
throws are typically used, starting with a square
knot (rather than a surgeon’s knot). In order
to avoid losing suture tension during the first
knot, a hemostat is often used to grasp the first
throw while throwing the second.
Metal crimp clamps negate the need for a
bulky knot and allow the use of a tensioning
device which holds the suture taut while crimp-
ing the clamp, facilitating placement of a tight
suture without assistance. The success of crimp
clamp fixation is equal to or better than knots in
most studies (Andersonet al. 1998; Peyckeet al.
2002; Banwellet al. 2005; Vianna & Roe 2006),
but using crimp clamps weakens the suture at
the crimp site (Sicardet al. 2002) and slippage
of the suture through the clamp is also a con-
cern (Burgesset al. 2010). If crimp clamps are
used, it has been suggested that more than one
crimp clamp should be placed to lessen the risk
of slippage (McCartneyet al. 2007), and that a
crimping system which creates multiple crimps
is used (Maritatoet al. 2012).
The strongest combination of monofilament
loop configuration and securing method is not
known. In a biomechanical study comparing
various double-loop suture configurations that
were secured using crimp clamps, the single-
strand, double-loop configuration using an
interlocking knot along with a crimp clamp was
mechanically superior to five other configura-
tions (Wallaceetal. 2008), while a different study
found this construct to be inferior to all tested
constructs, with the strongest construct being a
single-strand, double-loop secured purely with
crimp clamps, but no double-loop, double-
strand constructs were tested (Aisaet al. 2015).
Anotherex vivostudy comparing various knots
to crimp clamps found that single-strand con-
structs secured with crimp clamps were as good
or better than single-strand constructs secured
with knots, but a double-loop construct secured
with a self-locking knot was superior to all
single-strand constructs (Peyckeet al. 2002).
Multifilament sutures can also be joined
using one or multiple knots or crimp clamps.
Knot security between types of multifilament
sutures is variable (Burgesset al. 2010) due to
differences in base material and suture coating.
Multifilament sutures may have an increased
incidence of slippage through a crimp clamp
(Burgesset al. 2010; Maritatoet al. 2012) and,
therefore, knots are commonly used. The knot
profile is lower when knotting a multifilament
compared to a monofilament.Stifle position while securing suture
As the suture is secured, cranial tibial sub-
luxation and internal tibial rotation should be
reduced. The recommended degree of applied
suture tension is controversial. The surgeon
should be cognizant of over-tightening as this
can limit normal range of motion and increase
the contact pressure on the joint surfaces (Tonks
et al. 2010). Under-tightening can predispose
to inadequate stabilization and premature loos-
ening. In order to mitigate under- and over-
tightening, one author recommends that the sti-
fle should be placed in approximately 100◦of
flexion when securing the suture (Fischeret al.
2010), while the TR protocol has the stifle placed
at 140◦when tying the suture. It has been sug-
gested that the ideal angle for tightening the