Cranial Cruciate Ligament Rupture
Cranial Cruciate Ligament Rupture

Cranial Cruciate Ligament Rupture

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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 fabellas 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

    Securos Surgical Insight

  • 072015

    As shown below, begin by making the transcortical

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

    remaining 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 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