The posterior cruciate ligament (PCL) is comprised of a bundle
of ligament fibers attaching the posterior aspect of the tibia to the femur
in the knee joint. The PCL acts as the primary restraint to posterior translation
of the tibia (shin) on the femur. It also acts secondarily as a stabilizer
of the normal motion of the knee.
INJURY
Injury to the PCL most commonly results from direct impact to the proximal
aspect of the tibia such as a fall directly onto a bent knee or hitting
the glove box in automobile accidents. This can occur as an isolated
ligament injury, such as in direct blows, or with combined instability
as would occur in a twisting injury.
DIAGNOSIS
An accurate diagnosis and early intervention is essential in order to optimize
outcome. After obtaining a careful history, the following special tests
aid in determining which structures are involved:
Posterior drawer test--with the knee in 90 degrees of flexion, look for
a 'sag' of the tibia on the femur
Posterior Lachman--with the knee in 30 degrees of flexion, the examiner
pushes posteriorly on the tibia while holding the femur
Posterior-lateral rotary laxity--valgus stress testing and internally
and externally rotating the ankles with the knee in flexion while looking
for increases in rotation
Reverse pivot shift--the examiner puts a valgus (medial) force on the
knee while externally rotating and extending the knee, looking for the
tibia to 'shift'
It is important to take a careful history for mechanism of injury and
perform tests carefully, as PCL ruptures can mimic that of an ACL. An MRI
aids in confirming the diagnosis and identifying associated pathology.
It has been well documented that injury to the PCL left untreated will
lead to eventual medial and subsequent patellofemoral osteoarthritic changes.
Therefore, we usually choose to reconstruct complete tears of the PCL,
as well as any other structures associated with the instability. Proximal
tears of the PCL that detach from the bone can be repaired by reattaching
the ligament back to its origin. Mid-substance tears require reconstruction
in active people.
SURGICAL
TECHNIQUE
Following a thorough examination of all other compartments of the knee
for any other damaged tissue, the PCL is well probed to determine the integrity
of the remaining fibers. If there is adequate tissue of good quality with
some of the remaining fibers still attached, then a PCL repair is performed.
If the tissue is irreparably damaged a reconstruction using a donor graft
is performed.
For a repair, a suture punch is used to pass sutures into the posterior
cruciate ligament. The sutures are then guided through a tunnel that is
bored from the insertion site of the PCL through the femoral condyle, exiting
on the medial border of the femur. The sutures are then tied in a fisherman's
slip knot down to the bone, and then to each other. After this, any associated
capsular tearing is then repaired.
If there is inadequate tissue to affect a repair, then a PCL reconstruction
is carried out. First, the intercondylar notch is cleaned out, removing
the remaining torn posterior cruciate ligament fibers. Then, under direct
fluoroscopic control, a hole is drilled from the anterolateral aspect of
the tibia to the posterior slope of the tibia. A second tunnel is then
drilled in the femur from inside the medial femoral condyle at the insertion
of the ligament to the medial border of the medial femoral condyle. A #1-nylon
suture is then captured and pulled through both tunnels. A bone-patella
tendon-bone graft is then excised from the central third of the patella
tendon or preferably a donor tissue graft is passed up through the tibia
and then through the femur. Interference fit screws are then fixed first
to the femoral side and then to the tibial side with the tibia being held
in an anterior reduced position. Elimination of posterior sag confirms
the positioning. Marcaine is instilled and the patient is brought to the
postoperative recovery room.
POST-OP CARE
The postoperative program for a PCL repair differs from that of a PCL reconstruction.
For both procedures patients are seen the day after surgery for a dressing change
and review of home exercise program. They are instructed on icing, elevation,
pain control, and crutch-assisted weight bearing. Passive extension range of
motion exercises, quad and adduction sets, and ankle pumps are to be performed
hourly starting day 1 post-op. Straight leg raises in all planes but prone are
to be performed for 4 sets of 25 repetitions daily, as well as non-operative
single-leg cycling. A hinged neoprene brace is used for 1 month, with possible
range of motion restrictions if a primary PCL repair or subsequent capsule repair
was performed. With reconstruction, a well placed patella tendon graft mimics
the normal kinematics of the knee joint and therefore does not require range
of motion restrictions post-operatively. Careful adherence to a guided rehabilitation
program is essential for a successful return to activities. The full rehabilitation
program for each type of PCL treatment is explained at PCL
reconstruction rehabilitation and PCL
repair rehabilitation.
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