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The cranial cruciate ligament (CrCL) counteracts cranial

tibial translation, excessive internal rotation, and

hyperextension of the stifle joint. In the CrCL-deficient

stifle, alteration of joint biomechanics negatively impacts

surrounding structures such as the menisci and cartilage,

and likely cause accelerated progression of osteoarthritis. In

order to suppress rapid progression of stifle osteoarthritis,

normal loading and contact biomechanics of the stifle must

be restored. Multiple surgical treatments exist, all of which

attempt to eliminate cranial translation and hyperextension,

as well as restore normal range of internal rotation2.

Extracapsular stabilization (ES) is a suture technique that

has been used to correct stifle instability since the 1960s.

It involves the use of synthetic materials to stabilize the

stifle through femoral and tibial fixation points such that

sufficient periarticular fibrosis can be produced for long-

term stability and function. Once fibrous connective tissue

has formed, the suture material is no longer needed as a

single form of stability2.

For ES, femoral and tibial fixation points should be placed

in anatomic locations that are as isometric as possible; i.e.

should remain the same distance apart throughout range of

motion-- too lax and cranial tibial translation prevails, too

taught and range of motion will be restricted or the suture

may rupture. In theory, the use of isometric points will

allow for greater stifle stability for a longer duration, until

sufficient connective tissue has formed2.

To date, the recommended femoral fixation point is located

at the caudal border of the lateral condyle adjacent to

the level of the fabella’s distal pole. It is also acceptable

to circumscribe the lateral fabella as an anchor point. The

recommended tibial fixation point is located at the bony

protuberance 2mm caudal to the sulcus of the long digital

extensor tendon, as proximal as possible while avoiding the

joint. Care should also be taken surrounding the long digital

extensor tendon while creating this bone tunnel2.

Once the bone tunnel has been created, pass the suture

lateral-medial through the bone tunnel, then back lateral

under the patellar ligament or through a second bone

tunnel depending on which technique you use. With the

other side of the suture, circumscribe the lateral fabella,

ending with both strands on the lateral aspect of the

stifle. Pass both strands of suture through a crimp clamp

(primary crimp clamp) in the center. Place a secondary crimp

clamp on each strand of suture and crimp both. Apply

the tensioning device to the construct on the inside of the

secondary crimp clamps. Tension the construct to eliminate

thrust and drawer, and upon achieving adequate tension

crimp the primary crimp clamp. The secondary crimp clamps

may now be removed as their sole purpose was to tension

the construct. The completed procedure can be seen

below2.

Two other stifle stabilization techniques herein discussed

are osteotomy techniques, which rely on a tibial osteotomy

to alter biomechanics of the stifle joint. By producing a 90

degree angle between the attachment of the quadriceps

and the tibial plateau, the need for a CrCL to constrain

tibial thrust is essentially eliminated. These osteotomy

techniques focus on adjusting the biomechanics to produce

a stabile stifle joint without a CrCL. The Tibial Tuberosity

Advancement (TTA) procedure advances the tibial tuberosity

to create the 90 degree angle, while the Tibial Plateau

Leveling Osteotomy (TPLO) rotates the contact surface

of the tibial plateau. The two procedures differ, as the

TTA alters the location of quadriceps insertion relative to

the tibial plateau, while the TPLO alters the tibial plateau

relative to hock2.

The TTA procedure advances the tibial tuberosity through a

linear cut along the cranial portion of the tibial tuberosity.

This cut portion is advanced forward until the quadriceps

insertion is oriented 90 degrees to the tibial plateau.

Specially designed implants are used to maintain the new

position of the tibial tuberosity. These implants include

a cage that is the width of the amount of advancement

required to achieve the 90 degree angle, and a plate to act

as a tension band to hold the construct in place2.

Cranial Cruciate Ligament RuptureArticle by Olivia Doane, BS Biomedical & Mechanical Engineering. Edited by Steven M. Fox, MS, DVM, MBA, PhD

CONTINUED ON NEXT PAGE Messenger | November 2015 25

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As shown below, begin by making the transcortical

osteotomy ¾ of the way up (distal to proximal). For the

remaining ¼ of the cut, only cut the near cortex and

leave the far cortex intact. This is to assist in placement

of the proximal portion of the plate while the bone is

still intact, yet allows the remaining proximal ¼ to be cut

after the plate is applied. Place the proximal screws in the

tibial tuberosity, and then complete the osteotomy. The

predetermined size cage is then placed in the gap, and

the remaining distal screws in the plate are applied. The

completed procedure is shown below2.

The TPLO procedure rotates the tibial plateau to meet the

hock at approximately a 90 degree angle. A circular cut is

made in the tibial plateau, and the cut bone is rotated a

patient-dependent predetermined distance. The calculated

distance to be rotated is measured intra-operatively

along the osteotomy line using calipers, and a mark is

made on either side of the osteotomy line to note correct

post-rotational positioning. Complete the transcortical

osteotomy. Rotate the free-cut bone the measured distance

so that the two marks align, and hold alignment in place

using temporary fixation such as a k-wire. Apply the

specialized TPLO bone plate to the construct and remove

the temporary fixation2. [Many surgeons use alignment jigs

for this procedure.]

The below images show different end results of the three

techniques discussed to correct stifle instability due to

cruciate ligament rupture. In the first image, a completed

ES procedure does not alter the tibial plateau angle, but

instead temporarily relies on the strength of the suture

material to counteract cranial tibial translation, excessive

internal rotation, and hyperextension of the stifle joint.

Once fibrous connective tissue has formed in the location

of the suture, this organic fibrous tissue assumes the forces

there before managed by the artificial suture. For the TTA

and TPLO procedures, it is shown below that the resulting

forces are perpendicular to each other. This essentially

compensates for the missing CrCL2.

In conclusion, there are several methods of cruciate

stabilization that are effective, however it is important to

consider several factors prior to deciding what method to

use. A recent study found that TPLO and ES are the most

commonly performed and recommended procedures.

The same study found that ES was the most common

recommendation for small dogs, while TPLO was the

most common recommendation for large dogs. It is also

important to note that extracapsular stabilization requires

relative technical ease and low surgical cost, while TTA and

TPLO both have a larger learning curve and higher surgical

cost. Individual patient factors such as activity level and age

will also influence the technique of choice1.

1 Duerr, F., Martin, K., Rishniw, M., Palmer, R., & Selmic, L. (2014). Treatment of canine cranial cruciate ligament disease. Vet Comp Orthop Traumatol, 6/2014.

2 Muir, P. (2010). Advances in the canine cranial cruciate ligament. Ames, Iowa: Wiley-Blackwell.

Securos Surgical Insight