Keywords PCL - treatment - PRP - growth factors - knee brace
The posterior cruciate ligament (PCL) is the largest and strongest ligament in the
knee. PCL injuries are secondary to high-energy trauma such as car accidents or sports
injuries.[1 ]
[2 ] This injury typically affects males, with a prevalence ranging from 73 to 97% whether
isolated or combined.[1 ]
[3 ]
PCL injuries typically present concurrently with other knee injuries, including anterior
cruciate ligament (ACL), medial collateral ligament (MCL), or posterolateral corner
(PLC) injury. However, isolated injuries of the PCL also play a role in complex posterior
injuries of the knee. PCL injuries can be partial (usually referred as grade I or
II) or complete (grade III). The majority of grade III PCL tears is associated with
multiligament knee injuries, with one study reporting that 79% of these injuries involved
the PCL in a trauma setting.[4 ] Complete PCL injuries were associated with ACL tears in 46% of patients, MCL tear
in 31%, and PLC injury in 62% of patients in a trauma setting.[1 ]
[2 ] In their series of PCL reconstructions, Spiridonov et al reported that only 18%
were isolated PCL tears.[5 ]
Isolated partial PCL injuries may be treated nonoperatively thanks to its inherent
healing potential.[6 ]
[7 ] It should be mentioned although that partial PCL injuries may heal in an elongated,
lax, or attenuated morphology.[6 ]
[8 ]
[9 ] On the other hand, acute multiligamentary knee injuries with a concomitant or chronic
PCL tear are believed to be best treated with surgery.[10 ] The purpose of this chapter is to describe our conservative treatment strategy to
partial isolated PCL injuries.
Treatment of Partial PCL Injuries
Treatment of Partial PCL Injuries
PCL conservative treatment is a good option in grade I and II isolated injuries (partial
tears) provided the following conditions are met:
Minimum posterior drawer on physical exam.
Less than 10 mm of posterior tibial translation on stress radiographs ([Fig. 1 ]).
Continuity of PCL fibers on the magnetic resonance imaging (MRI).
Fig. 1 Stress X-rays (gravitational) showing a partial tear of isolated posterior cruciate
ligament injury (Courtesy of Dr. Xavier Cuscó).
Our conservative treatment strategy is based on three main modalities: ultrasound-guided
platelet-rich plasma (PRP), use of a specific PCL brace, and early rehabilitation
based on quadriceps strengthening.
Administration of PRP
PRP can be a coadjuvant biological treatment in selected patients to enhance PCL lesion
healing.[11 ] The specific type of PRP that we use is the PRGF Endoret system (BTI Biotechnology
Institute, Álava, Spain). Patients come to our clinic fasting for at least 4 hours.
Blood samples are extracted using the appropriate tubes with 3.8% citrate solution
provided in the kit, which are then placed in a BTI System IV centrifuge machine (BTI
Biotechnology Institute, Álava, Spain). Typically, between four and six blood tubes
were extracted to obtain 9 or 10-mL tube of plasma. This blood is centrifuged at 1800 rpm
for 8 minutes at 580 g. This results in the sedimentation of red and white cells at
the bottom and platelets with plasma on the top part of the tubes.[12 ] The centrifugation process creates two fractions: fraction one is the upper part
of the supernatant and is the plasma poor in platelets (PPP); fraction two is the
plasma rich in platelets (PRP), which is obtained by extracting the layer just over
the white cells ([Fig. 2 ]). It is paramount to avoid aspiration of white cells when obtaining fraction two
so that no inflammatory reaction is elicited after the injection. The growth factors
are activated using CaCl2 at a ratio of 2 IU (international units) per one cc of PRP,
maintaining the tubes at room temperature. The activated PPP–PRP at a 50/50 ratio
is then injected within the PCL under ultrasound guidance.
Fig. 2 Aspect of blood samples after centrifugation. Note the two fractions of the preparation
along with the white and red blood cells layers. PPP, plasma poor in platelets; PRP,
plasma rich in platelets.
The ultrasound-guided PCL injection allows the permanent visualization of the needle
so that one can better control its pathway to the ligament and the exact location
where the PRGF is infiltrated ([Fig. 3 ]). The best access pathway is the one that will have the shortest and safest trajectory
to the ligament with adequate and permanent visualization of the needle and the popliteal
neurovascular bundle. For the PCL we use the two planes, the longitudinal or long
axis and the transverse or short axis. To better identify and infiltrate the PCL,
the patient is placed prone with a bump under the ankles to perform a slight knee
flexion. Then, the ultrasound is used to identify the popliteal neurovascular structures
and the PCL ([Fig. 3 ]). We first begin with the identification of the popliteal fossa in the sagittal
plane and the probe is placed in a longitudinal position with respect to the PCL.
The ligament runs from the intercondylar part of the medial femoral condyle to the
posterior and central part of the lateral tibial plateau. The PCL is seen as a hypoechoic,
well-defined structure. We then perform thorough and extensive skin asepsis around
the infiltration area. The needle is then advanced parallel to the probe in the long
axis in sterile conditions until it reaches the PCL. The exact location of the needle
is controlled at all times using both longitudinal axis and transverse axis, and the
PRGF is finally administered in the longitudinal axis inside (∼4–5 cc of PRGF) and
surrounding the ligament. The remaining part of the PRGF is then administered intraarticularly.
The process is repeated two more times typically 2 weeks apart.
Fig. 3 Specific posterior cruciate ligament knee brace from Medi, the M4.s posterior cruciate
ligament Dynamic Brace showing the mechanism to counteract posterior tibial sag (Courtesy
of Medi Bayreuth Spain SL).
The Specific PCL Brace
The patient is placed in the specific M4.s PCL Dynamic Brace (Medi, Bayreuth, Germany)
as soon as he/she comes to our clinic with the PCL injury ([Fig. 4 ]). The brace applies a constant or dynamic anterior force to counteract posterior
sag of the tibia, and therefore helps the healing of the PCL in the right tension.[6 ]
[13 ] The brace hinge should be placed at the level of the femoral condyles, and the straps
tightened sequentially following the manufacturer's order. Then, the posterior padded
support is tightened to correct the posterior tibial sag. Care should be especially
taken to avoid excessive tensioning of the posterior padded support so as to avoid
skin injuries. Plain lateral radiographs at 90 degrees of knee flexion are obtained
before and after the application of the specific PCL brace to assure that the tension
of the brace is adequate to reduce posterior tibial sag. The brace is worn at all
times during the first 3 months, and discontinued at rest only during the following
month. The patient is evaluated weekly during the first month to assure adequate tolerance
and positioning of the brace.
Fig. 4 Ultrasound-guided injection of PRGF Endoret (BTI) inside the posterior cruciate ligament
sheath (Courtesy of Dr. Marta Rius and Dr. Ramón Cugat). *Determines axial view of
posterior cruciate ligament body. FC, femoral condyle.
Rehabilitation Program
The patient undergoes an early rehabilitation program to avoid excessive stiffness
and muscular atrophy, while protecting the PCL to assure adequate healing. During
the first month, the patient typically performs daily isometric quadriceps strengthening
exercises. The patient undergoes weekly gentle mobilization to avoid excessive stiffness,
always with the brace on. Range of motion is typically limited to 60 degrees the first
month, 120 degrees by the second month, and full motion by the end of the third month.
Crutches are recommended during the first 6 to 8 weeks. Progression to dynamic quadriceps
strengthening exercises is typically performed at 4 to 6 weeks.
Results
The results of 13 soccer players with partial PCL injuries (eight grade I and five
grade II) treated with the current treatment strategy have been reported.[14 ] Patients had a mean (range) age of 24.4 (18–29) years, being the right knee in seven
and the left knee in six patients. The brace was kept for a mean (range) time of 4.3
(4–5) months. At the end of the treatment, 12 (92.3%) patients achieved a Tegner score
of nine and one (7.7%) patient achieved a Tegner score of seven. Evidence of PCL healing
on MRI was observed and return to play was achieved in all patients
Discussion
The principal objective of the present chapter is to evaluate that partial PCL injuries
may be treated conservatively through a combination of ultrasound-guided PRGF infiltration
to enhance the healing of the ligament, a specific PCL brace to correct the posterior
tibial sag and provide the ligament of a better chance to heal in the appropriate
tension, and an early rehabilitation program to avoid stiffness and muscle atrophy.
However, this treatment protocol requires further clinical research to confirm its
usefulness.
The optimization of the treatment and results after PCL injuries is warranted. Some
authors have described an increased radiographic progression of osteoarthritis and
lower functional outcomes after nonoperative treatment in isolated PCL tears in the
long-term.[10 ]
[15 ] Shelbourne et al evaluated isolated PCL tears that were conservatively treated with
rehabilitation programs without biological therapies or knee brace and observed radiographic
evidence of moderate or severe osteoarthritis in 11% at a mean of 17 years after the
injury.[10 ] Despite the majority of patients reported good subjective outcome scores, incidence
of osteoarthritis in middle-aged individuals may have a higher impact later in their
life's.
There are limited clinical studies evaluating the outcomes after conservative treatment
of PCL tears. Torg et al reported that isolated PCL tears responded favorably to nonoperative
treatment at a follow-up of 5.7 years.[16 ] However, upon further evaluation, the authors found good subjective functional scores
and a healed appearance of the PCL on MRI at short-term follow-up (1.7 and 2.6 years)
after isolated PCL injury, but less than satisfactory objective scores.[16 ] As a result, these authors concluded that the PCL treated nonoperatively likely
healed with laxity and led to poor objective outcomes.
The effectiveness of PRP is still controversial due to insufficient literature or
lack of consensus on the clinical outcomes, likely related to the high heterogeneity
of PRP preparation methods used leading to very different products to be applied.[17 ]
[18 ] Studies demonstrating a clear benefit on the application of PRP or PRGF to treat
PCL injuries are missing. However, some studies have concluded that PRP can enhance
healing in partial ACL injuries,[19 ]
[20 ]
[21 ] and may increase the maturation process of postoperative ACL grafts.[22 ]
[23 ]
[24 ] Because the PCL is histologically similar to the ACL, it might be argued that the
treatment with PRP/PRGF infiltrations can enhance the healing process of partial PCL
tears. Anatomically speaking, the PCL is fully covered by synovial tissue, so intra-articular
injections of PRP/PRGF may not reach the ligamentous tissue in cases where this membrane
is not severely damaged. Therefore, ultrasound-guided local infiltration of PRGF completely
inside the synovial sheath is a better choice to assure that the PRP reaches the damaged
tissue ([Fig. 3 ]).
There is limited evidence on the effectiveness of a specific PCL knee brace to allow
adequate ligament healing. Jacobi et al reported that the use of a dynamic PCL brace
for 4 months after an isolated acute PCL tear significantly reduced the initial posterior
sag of 7.1 mm to 2.3 and 3.2 mm at 12 and 24 months, respectively.[6 ] On MRI, the PCL was in continuity in 95% of the patients at 6 months. Moreover,
the Lysholm score did not show a statistically significant difference between the
preinjury period and the 12- and 24-month postinjury periods.[6 ] The absence of significant differences is a desired finding, as the patients were
able to return to the preinjury functionality.
Conclusions
A combination of ultrasound-guided PRGF infiltration to enhance the healing of the
ligament, a specific PCL brace to correct the posterior tibial sag and provide the
ligament of a better chance to heal in the appropriate tension, and an early rehabilitation
program to avoid stiffness and muscle atrophy may be considered as a treatment option
for conservative partial PCL injuries. This treatment modality was effective to achieve
adequate MRI-based healing in 100% and a return to play in 90% of soccer players.
