CHAPTER 59 • KNEE INSTABILITY 353•Hamstring tendon grafts have received attention
because of the potential for lower donor site morbid-
ity (Miller and Gladstone, 1002; Fu et al, 1999).
Quadrupling of the grafts allows for increased tensile
strength and cross-sectional area. Potential disadvan-
tages of this technique include a longer healing time
required for soft tissue to bone fixation.
- The quadriceps tendon graft has been shown to have
an adequate tensile load and cross-sectional area for
ACL reconstruction (Fu et al, 1999). It serves as an
important replacement graft in revision ACL surgeries
and in multiple ligament injuries. - Additionally allograft tissues have been successfully
employed in ACL reconstruction. Advantages include
decreased operative time, the lack of graft harvest
morbidity, and unlimited graft supply. Disadvantages
include the potential for disease transmission, delayed
graft incorporation, increased cost, and the biome-
chanical effects of graft sterilization (Miller and
Gladstone, 1002; Fu et al, 1999).
PCL INJURIES
BASICS
- Reports of the incidence of PCL injuries vary widely
from 3% of all knee ligament injuries in the general
population to greater than 38% of such injuries in the
emergency room setting (Allen et al, 2002; Clancy et
al,1983; Fanelli and Edson, 1995; Miyasaka and
Daniel, 1991). One evaluation of college football
players reported chronic PCL injuries in approxi-
mately 2% of asymptomatic athletes (Parolie and
Bergfeld, 1986). - Fifty to ninety percent of PCL injuries are associated
with injury to other knee structures (Fanelli and
Edson, 1995; Clancy, Jr and Sutherland, 1994). Most
commonly, the posterolateral structures are involved.
In trauma settings up to 95% of PCL injuries have
other associated ligamentous injuries to the same knee
(Allen et al, 2002). - The mechanism of injury is most commonly a poste-
riorly directed force to the anterior of a flexed knee,
the so-called dashboard injury. In athletics, such
injuries can be caused by a fall on a flexed knee with
a plantarflexed foot. More rarely, PCL injuries can
result from hyperextension or hyperflexion and are
often associated with multiple ligament injuries
(Allen et al, 2002; St Pierre and Miller, 1999). - Unlike ACL injuries, the patient with a PCL injury
does not usually feel a pop and the athlete may not be
able to describe exactly how or when the injury
occurred (Shelbourne and Rubinstein, 1994). Patients
will often report nonspecific symptoms such as an
insecure feeling, a vague aching pain, or difficulty
climbing stairs.EVALUATION- The posterior drawer test is considered the gold stan-
dard of physical examination. The knee is flexed to
90 °and the hip to 45°, and the foot is firmly planted
on the examination table. Crucial to interpreting this
test is recognizing the starting point. There is nor-
mally a 10-mm step-off between the medial tibial
plateau to the medial femoral condyle with the knee
in 90°of flexion. Absence of a normal step-off sug-
gests PCL injury. This test is reported to be 90% sen-
sitive and 99% specific (Pournaras and Symeonides,
1991). - In the posterior drawer, the degree of laxity can be
assessed as follows. Displacement up to 5 mm is
grade I, and the tibial condyle remains anterior to the
femoral condyle. Five to ten millimeters of displace-
ment is grade II, and the tibia and femur are approxi-
mately flush. Greater than 10 mm of displacement is
grade III, and the tibia is displaced posterior to the
femoral condyle. - Other techniques include the posterior sag test, prone
drawer test, quadriceps active test, dynamic posterior
shift test, and the posterior Lachman. Due to the fre-
quent association with posterolateral corner injuries,
these structures should also be examined. Such exam-
inations include the reverse pivot shift and External
Rotation Thigh Foot Angle tests (Margheritini et al,
2002). - Stress radiographs should be obtained to evaluate for
avulsion fractures involving the PCL, fibular head, or
Gerdy’s tubercle. In chronic PCL injuries, there may
be evidence of medial compartment arthritic changes. - MRI can also contribute valuable information in the
diagnosis of PCL injuries with reported 100% sensi-
tivity in identifying complete PCL disruption (Gross
et al, 1992). MRI is also valuable in evaluating for
associated injury to other knee structures.
NATURALHISTORY- The natural history of the PCL injured knee remains
controversial. Some studies show high rates of patient
satisfaction, the ability of the patient to return to
preinjury athletic participation, and no increased inci-
dence in osteoarthritis following conservative treat-
ment of PCL injuries. - Other studies indicate that PCL injuries may not be so
benign. Multiple studies have demonstrated arthritic
changes in the medial compartment and patellofemoral
joint with chronic PCL injuries. Other potential delete-
rious effects include significant limitation in postinjury
activities and pain with activity.