Thirteen patients (fourteen knees) who had an avulsion fracture
of the posterior cruciate ligament from the tibia between 1993 and
1997 were analyzed retrospectively (Table I). All patients were treated by
the senior author (S.-J.K.) with use of an arthroscopic
procedure. The six male and seven female patients in the study were
between the ages of seventeen and fifty-seven years (average, thirty-five
years) at the time of the operation. Eight left and six right knees
were injured. The injury was caused by a motor-vehicle accident
in the six male patients and by a fall in the seven female patients
(some of whom fell while skiing). Three of the motor-vehicle accidents involved
the patient striking the dashboard of an automobile, and three were
motorcycle accidents resulting in direct trauma to the proximal
part of the tibia while the knee was flexed. The falls resulted
in a twisting injury to the knee in two patients and a hyperflexion
injury in three; the injury mechanism was unknown in two patients.
Eleven patients had an acute fracture, and two (Cases 3 and 4)
had a nonunion of a tibial avulsion fracture. Eleven patients underwent
surgery four to ten days (average, 6.3 days) after the injury. In
the two patients with a nonunion, the surgery was done at nineteen
and twenty months after the injury. One of these patients (Case
3) had ipsilateral open comminuted fractures of the tibia and fibula
and a contralateral femoral fracture, and the avulsion fracture of
the posterior cruciate ligament was overlooked at the initial examination.
The patient still demonstrated grade-II posterior instability (grading
system described below) and knee discomfort twenty months after
the injury. The other patient (Case 4) had grade-II posterior instability
and posterolateral rotatory instability nineteen months after the
injury. Reconstruction of the posterior cruciate ligament was planned
for these patients, but when the ligament was viewed arthroscopically
the fibers were found to be intact and fibrotic scar tissue was
seen to cover the tibial attachment of the posterior cruciate ligament.
The diagnosis of avulsion fracture of the posterior cruciate
ligament was made when the patient demonstrated posterior instability
on physical examination and a bone fragment was seen on radiographs. Magnetic
resonance imaging was performed in six patients in whom fracture
fragments could not be identified accurately on radiographs or in
whom intra-articular injury was suspected. Six patients had an isolated
avulsion fracture of the posterior cruciate ligament, and seven
had additional ligament injuries or fractures. Four associated ligament injuries
included avulsion of the anterior cruciate ligament (in two patients),
rupture of the medial collateral ligament (in one patient),
and posterolateral rotatory instability (in one patient). Five patients
(six knees) who had concomitant fractures (distal femoral, proximal
tibial, tibial condylar, and phalangeal) underwent open reduction
and internal fixation before the arthroscopic surgery. No patient had
a neurovascular injury.
Surgery was performed in patients who had an avulsion fracture
of the posterior cruciate ligament and posterior knee instability
of at least grade II. Posterior instability was determined by performing the
posterior drawer test, making posterior stress radiographs, and
measuring knee laxity with use of the knee ligament arthrometer
(KT-2000; MEDmetric, San Diego, California). The posterior drawer test
was performed at 90° of knee flexion and was graded according to
the amount of posterior translation (grade I indicates <5
mm; grade II, 5 to 10 mm; and grade III, >10 mm). The posterior
translation was estimated by palpating the amount of step-off of
the medial tibial plateau under the medial femoral condyle. The
side-to-side difference in the posterior translation was measured
on the posterior stress radiographs and with use of the knee arthrometer.
Lateral radiographs were made with the knee flexed 90° while maximal
manual load was applied to the proximal part of the tibia12. Posterior translation of the tibia
on stress radiographs was determined by measuring the distance between
the posterior aspect of the medial tibial plateau and the posterior
part of the medial femoral condyle (as determined by drawing the
most posterior tangent line to each plateau and condyle). Measurement
of the corrected posterior translation with the KT-2000 arthrometer
(with the testing done at a 30-lb [133-N] force)
was performed as described by Daniel et al.13.
Examination under anesthesia before the surgery revealed grade-II
posterior instability in eleven knees and grade-III in three knees.
Two patients (Cases 3 and 11) who had an associated avulsion fracture
of the anterior cruciate ligament also demonstrated grade-II anterior
instability, as determined by the Lachman test (grade I indicates <5 mm
of tibial excursion; grade II, 5 to 10 mm; and grade III, >10
mm). One patient (Case 12) had a grade-II rupture of the medial
collateral ligament as revealed by the valgus stress test at 30°
of knee flexion (grade I indicates <5 mm of opening of
the joint surface; grade II, 5 to 10 mm; and grade III, >10
mm).
The size of the bone fragment determined the fixation method.
Bone fragment size was measured with a ruler on preoperative radiographs.
The sizes of small or comminuted fragments were estimated at the
time of arthroscopy with use of the 5-mm vertical tip of
a probe. If a fragment involved one or both tibial condyles and
was >20 mm (classified as large), fixation was performed
with one or two cannulated screws. A 10 to 20-mm (medium) fragment was
fixed with more than one Kirschner wire, regardless of tibial condylar
involvement. A <10-mm (small) fragment that was not comminuted
was fixed with 23-gauge wire suture. Small comminuted
fragments were fixed with multiple sutures (PDS [polydioxanone] or
Ethibond [polyester], Ethicon, Somerville, New
Jersey) through a single tibial tunnel with use of Endobutton (Acufex, Mansfield,
Massachusetts) or through two tibial tunnels (Table II).
Patients were seen for final follow-up twenty-four to seventy-two
months (average, thirty-nine months) following surgery. All patients
were examined by one of us (S.-J.K.) and had radiographs made
of the knees. The postoperative function of the knee was evaluated
according to the International Knee Documentation Committee (IKDC) form14.
Surgical Procedures
Three arthroscopic portals are used (Fig. 1). The posteromedial
portal is located adjacent to the posterior aspect of the medial
femoral condyle and 3 cm proximal to the joint line. The posterolateral
portal is located along the posterior edge of the lateral femoral
condyle and 1 to 2 cm proximal to the joint line. The anteromedial
portal is located just medial to the medial border of the patellar
tendon and adjacent to the patella. While the knee is viewed through
the posteromedial portal, the posterior septum behind the posterior
cruciate ligament is perforated with use of a switching stick that
is introduced through the posterolateral portal (Figs. 2-A and 2-B). If mobilization
and manipulation of the fracture fragment is necessary, the posterior
septum behind the posterior cruciate ligament should be removed with
use of a motorized shaver.
While the knee is viewed through the posteromedial portal (Fig. 3), hematoma and
soft tissue interposed in the fracture bed are debrided with use
of a curet and a motorized shaver that are passed through the posterolateral
portal. The size of the fracture fragment is measured by comparing
it with the 5-mm vertical tip of a probe. The fracture
fragment is manipulated and temporarily reduced into the
anatomical position with use of a probe that is passed through the posterolateral
portal.
If the fracture fragment is large enough (10 mm), it is fixed
with cannulated screws or multiple pins. A tibial posterior cruciate
ligament guide (Acufex) placed through the anteromedial portal is
used to secure the fracture fragment and to insert one or two guide-pins
to temporarily fix it. A curet or dural elevator passed through
the posterolateral portal may be used to prevent migration of the
fragment during drilling (Fig. 4). An image intensifier can be used
to confirm the reduction of the fragment and to identify the position
of the pin inside the fragment. After confirmation of the reduction
and the placement of the guide-pins into the fragment, one or two
cannulated screws are inserted along the guide-pins if there is
a single bone fragment of >20 mm. If the fracture fragment
is too small to be fixed with a cannulated screw, the guide-pins
or Kirschner wires can be used for permanent fixation.
If the fracture fragment is <10 mm, or if the large fragment
becomes comminuted during the insertion of screws, a 23-gauge
wire or multiple sutures can be used. A long 18-gauge spinal
needle is inserted through the posterolateral sheath and passed through
the posterior cruciate ligament just proximal to the fracture fragment.
A 23-gauge wire is passed through the lumen of the needle
(Fig. 5).
The end of the wire is grasped with use of a grasper and is pulled
out through the sheath placed in the anteromedial portal (Fig. 6).
For the fixation of small comminuted fragments with use of multiple
sutures, a looped 26-gauge wire is passed through the lumen of a
spinal needle. The end of the looped wire is extracted through a sheath
placed in the anteromedial portal and a strand of suture is passed
through the looped wire, which is then pulled back through the posterolateral portal.
Thus, the strand of suture passes through the posterolateral portal,
through the posterior cruciate ligament, and out of the anteromedial
portal. To achieve firm suture fixation, this procedure should be
repeated at least five or six times.
With use of the tibial posterior cruciate ligament guide, a bone
tunnel is then made from the anterior tibial cortex to the lateral
edge of the site of the avulsion of the posterior cruciate ligament.
Before the guide-pin is inserted, an appropriate-length stop is attached
to the guide-pin to prevent overdrilling. As soon as the guide-pin
is removed, a looped wire is passed through the tunnel until the
looped tip appears out of the posterior aperture. After confirmation
that the looped wire is through the tunnel lateral to the avulsion
site, the tibial posterior cruciate ligament guide is removed. Another
bone tunnel is made on the medial edge of the avulsion site. A second
looped wire is passed through the medial bone tunnel with use of
the same method. The tip of the medial looped wire is grasped with
a grasper introduced through a sheath in the anteromedial portal,
and the looped wire is pulled out through the sheath. The looped
wire that was placed laterally can be extracted through a sheath
in the posterolateral portal (Fig. 7). Each end of the 23-gauge
wire or the multiple sutures previously sewn through the posterior
cruciate ligament is passed through the looped wire outside of the
anteromedial and posterolateral sheaths. Each looped wire is pulled
distally, leading each end of the 23-gauge wire or the
multiple sutures through the medial and lateral bone tunnels (Fig. 8). Each end of
the 23-gauge wire or the multiple sutures is pulled tightly
and tied over the tibial cortex while an anteriorly directed force
is applied to the tibia with the knee flexed at an angle of 70°
to 90° (Fig. 9).
While the wire or sutures are tied, the fracture fragment is held
reduced in anatomical position. The reduction can be confirmed by
viewing with the arthroscope. During the arthroscopic procedures,
the potential for extravasation of fluid into the leg with resultant
compartment syndrome should be monitored, especially in patients
who have severe soft-tissue or osseous injuries.
Postoperative Rehabilitation
The limb is placed in a long leg hinged brace that is locked
in full extension for three weeks after the surgery. While
wearing the brace, patients are encouraged to start quadriceps
muscle-strengthening exercises and to walk using crutches.
Weight-bearing is not permitted during the first three weeks. After
three weeks, passive range-of-motion exercises are started and walking
with partial weight-bearing and the use of crutches is permitted. The
brace is locked in full extension during walking. At six weeks,
the brace is unlocked to allow motion and full weight-bearing is
permitted. At eight weeks, the brace is removed and patients are encouraged
to increase activity gradually. If multiple pins have been used,
they are removed eight weeks after the operation.
Four injuries of the posterior cruciate ligament with a small
comminuted bone fragment were fixed with multiple absorbable sutures
(PDS #1 or #0) with Endobutton, and two were fixed
with multiple nonabsorbable sutures (Ethibond #2). Two
injuries with a small bone fragment that was not comminuted were
fixed with a 23-gauge wire (Figs. 10-A and 10-B). Two knees that had a medium-sized
fragment were fixed with two Kirschner wires (Figs. 11-A and 11-B). A medium-sized
fragment in one knee (Case 2) was fixed with multiple absorbable
sutures because the fragment became comminuted during the insertion
of the Kirschner wire. In four patients, a large single bone fragment
that involved the condyles was fixed with one or two cannulated
screws (Figs. Figs. 12-A and 12-B). A concomitant avulsion injury
of the anterior cruciate ligament was fixed with multiple absorbable sutures
at the same time in two patients. One patient who had a nonunion
and posterolateral instability was treated with Clancy’s
biceps rerouting technique15.
All avulsion fractures had osseous union, at an average of three
months after the procedure. A fracture was considered to be united
when the fracture line was no longer visible radiographically. The eleven
patients who underwent the operation in the acute phase, including
two patients (three knees) in whom postoperative arthrofibrosis
developed, showed no or trace posterior instability as determined
with the posterior drawer test following the procedure. However,
the two patients who had a delayed operation had grade-I posterior
instability after the surgery. The average side-to-side
difference in the posterior translation measured on posterior stress
radiographs was 1.9 mm (range, 1.2 to 2.9 mm) in the patients who
underwent the operation in the acute phase (and in whom postoperative arthrofibrosis
did not develop), 3.0 mm (2.7, 2.7, and 3.5 mm) in the patients
in whom postoperative arthrofibrosis developed,
and 5.1 mm (5.0 and 5.2 mm) in the patients who had a delayed
operation. The postoperative side-to-side difference
in the corrected posterior translation as measured with
the KT-2000 arthrometer averaged 1.1 mm (range, 0.5 to 2.2 mm) in
the patients who underwent the operation in the acute phase, 1.8
mm (1.5, 1.8, and 2.1 mm) in the patients in whom postoperative
arthrofibrosis developed, and 3.7 mm (3.3 and 4.1 mm) in the patients
in whom the surgery was delayed. According to the assessment with
the IKDC form at the final evaluation, of the nine patients who
underwent the operation in the acute phase, five were classified
as having grade-A function and four were classified as having grade-B
function. The two patients in whom postoperative arthrofibrosis developed
were classified as having grade-B function, and the two who had
a delayed operation had grade-C.
Complications
Of the eleven knees that were treated in the acute phase, three
(Cases 2, 6, and 7) had residual limitation of motion after the
surgery. These patients were immobilized for two or three
months after the procedure because of concomitant injury. One patient
(Case 2) had a comminuted fracture of the distal part of the femur,
which was treated by open reduction and internal fixation with use
of a dynamic compression plate. However, the patient could not start
early rehabilitation because of insecure fixation,
and the range of motion of the knee was 5° to 50° four months after
the surgery. The other two stiff knees were in one patient who had
bilateral avulsion fracture of the posterior cruciate
ligament as well as a traumatic hemothorax with multiple
fractures, including comminuted fractures of both femoral
shafts, a fracture of the left tibial shaft, and a fracture of the
right lateral tibial condyle. The range of flexion of the right knee
was 25° to 70° and that of the left knee was 10° to 95° six months
after the surgery. Arthroscopic lysis of adhesions was performed
in all three stiff knees. After subsequent physiotherapy,
all three knees recovered a nearly normal range of motion (average,
5° of flexion contracture to 135° of flexion).
The posterior cruciate ligament is an important stabilizer of
the knee joint; therefore, when the tibial insertion of the posterior
cruciate ligament is avulsed the knee subluxates posteriorly16. There is general consensus that
avulsion fractures of the posterior cruciate ligament from the tibia should
be treated surgically. Meyers4 reported
that five avulsion fractures of the posterior cruciate ligament
that were treated nonoperatively did not unite; he recommended early
repair of even minimally displaced avulsion fractures. Torisu6 reported that open reduction led
to a satisfactory result in all of twelve patients with an avulsion
fracture of the posterior cruciate ligament (eight had an excellent
result and four had a good result). However, open reduction requires
the patient to be in a prone position, and the dissection is difficult.
Recently, a variety of arthroscopically assisted techniques for
the treatment of intra-articular fractures of the knee joint have
been reported. Arthroscopic techniques with use of sutures, Kirschner wires,
screws, and staples to repair avulsion fractures of the anterior
cruciate ligament from the tibia have been described17-19.
Martinez-Moreno and Blanco-Blanco9 first reported an experimental percutaneous
fixation technique with use of arthroscopic visualization to fix
avulsion fractures of the posterior cruciate ligament in cadaveric
knees. They showed that an arthroscopic technique was possible,
and they considered it to be an effective alternative to arthrotomy
and percutaneous pinning. Littlejohn and Geissler11 reported
on one patient who had an avulsion fracture of the posterior cruciate
ligament that was reduced with the aid of an arthroscope and was
stabilized with use of three cannulated screws with the help of
a tibial anterior cruciate ligament guide. In 1997, we reported
that we had treated an avulsion fracture of the posterior cruciate
ligament with use of arthroscopic reduction and internal fixation
with two cannulated screws10.
In that operation, a tibial posterior cruciate ligament guide was
used to manipulate and anatomically reduce the avulsion fragment
and to hold it in place while the Kirschner wires were guided.
If the avulsed fragment is small or comminuted, a screw cannot
be placed into it. We do not know of any report describing an arthroscopic
or open technique for fixation of small or comminuted fracture fragments.
In the new technique described here, we use two tibial tunnels to
fix avulsed fragments. Sutures passed through the small comminuted
fragments are then passed through the two tibial tunnels and tied
to one another. This creates a wide contact area between the fragments
and the fracture bed. We recommend wire fixation for small fragments that
are not comminuted; however, wire fixation is not effective for
comminuted fracture fragments because the wire has a tendency to
split the stump of the posterior cruciate ligament as well as the fracture
fragments.
All patients in our study had union of the fracture site. Eleven
patients who had undergone the operation within ten days after the
injury had good stability on posterior drawer testing. Posterior
instability was found in two patients, both of whom had had a delayed
operation. Torisu7 reported that
excellent results were obtained when operations were done within
seven weeks after injuries and that results were less satisfactory
when operations were delayed more than eleven weeks after injuries.
Meyers4 also reported that knees
treated with a delayed operation had a slightly positive posterior
drawer sign at the time of follow-up. We concur that early surgical
fixation of the avulsed fragment is important to achieve stability.
However, a delayed operation can be effective if the patient has
discomfort in the posteriorly subluxated knee despite conservative
treatment.
Arthrofibrosis developed in two patients (three knees) after
arthroscopic reduction and fixation. These patients had sustained
multiple fractures around the knee or damage to other structures
and had been immobilized for a prolonged period. Early range of
motion after surgery may prevent the development of arthrofibrosis.
Although the arthroscopic reduction and fixation technique is
difficult, we found the method effective in the treatment of avulsion
fractures of the posterior cruciate ligament. We were able to anatomically
reduce the fractures under direct vision and also to identify and
treat associated intra-articular pathology without arthrotomy. Except
for arthrofibrosis, there was no serious morbidity or complication.
Arthroscopically assisted suture repair was especially useful for
the treatment of small or comminuted avulsion fractures of the posterior
cruciate ligament.
In conclusion, we have demonstrated that avulsion fractures of
the posterior cruciate ligament can be fixed with use of arthroscopic
methods. If the fracture fragment is large or medium-sized, screws
or multiple pins can be used. Small or comminuted fragments can
be fixed with use of wire or multiple sutures.