Keywords
posterior cruciate ligament - avulsion fracture - pediatric
Posterior cruciate ligament (PCL) avulsion fracture of the tibial insertion is a very
rare injury in children. In addition to performing an attentive clinical examination,
radiologic studies are fundamental for its correct diagnosis and treatment. Its management
may be either conservative or operative. So far, only a few cases treated conservatively
have been reported in the pediatric population, with controversial results.[1]
[2]
[3]
[4] The present case is singular for the early diagnosis and the conservative management
with accurate clinical and radiological follow-up controls until complete recovery.
Case Report
An 11-year-old boy was transferred to our institution with right knee pain and swelling
after a fall while skiing occurred on the same day. He described the hitting of the
frontal aspect of his leg. A physical examination revealed swelling and tenderness
on the patella, the lateral aspect of the distal femur, and the medial aspect of the
proximal tibia. Because of the pain, the knee could not be examined properly. The
range of motion was severely limited by the pain, but a neurovascular examination
was normal. Standard radiographs showed prepatellar intra-articular effusion and an
isolated avulsion fracture with the elevation of the tibial attachment of the PCL
([Fig. 1A, B]). The diagnosis was subsequently confirmed by computed tomographic scanning, and
other bone lesions were excluded ([Fig. 1E–H]). The tibial fragment measured 11 × 4 mm and presented a maximal displacement of
7 mm. No other ligamentous, meniscal, or chondral injuries were observed in a magnetic
resonance imaging examination ([Fig. 1C, D]). Because of minimal displacement, we decided to treat the avulsion fracture in
a conservative way. The knee was immobilized for 6 weeks, with a long leg cast with
30 degrees of knee flexion. The patient was asked to walk with crutches, avoiding
weight bearing. After removing the cast, the patient was allowed to begin gentle range-of-motion
activities and weight bearing. The patient was asked to report for regular clinical
and radiological controls every 4 to 6 weeks until 3 months after the trauma. No pain
or instability was detected during a physical examination, and magnetic resonance
imaging showed progressive consolidation of the fracture over time. Subsequently,
the patient was allowed to progressively return to sport activities, reporting only
rare episodes of knee joint swelling and slight pain during severe exertion. In addition,
the patient was asked to fill in the functional knee score of Tegner and Lysholm (1985).[5] With a result of 90/100, the outcome was evaluated as good.
Fig. 1 (A) Anteroposterior and (B) lateral radiograph of the right knee, showing prepatellar intra-articular effusion
and isolated avulsion fracture with elevation of the tibial attachment of the posterior
cruciate ligament (arrow). (C) Sagittal T2- and (D) T1-weighted magnetic resonance imaging sequences showing gross knee effusion, the
avulsion fracture and no posterior cruciate ligament injuries. (E) Coronal, (F) axial, (G) sagittal, and (H) 3D reconstruction computed tomographic images showing fracture of the tibial attachment
of the posterior ligament with dislocated tibial fragment measuring 11 × 4 mm and
presenting a maximal displacement of 7 mm. 3D, three-dimensional.
A computed tomographic scanning and a magnetic resonance imaging performed 10 months
after the trauma showed complete consolidation of the tibial attachment of the PCL
([Fig. 2A–D]). At this time, the patient has returned to his previous level of physical activity,
reporting no complaints. A physical examination revealed no pain or instability of
the knee, and muscular strength was comparable to the strength of the contralateral
leg.
Fig. 2 (A) Sagittal T2- and (B) T1-weighted magnetic resonance imaging sequences of the right knee showing no posterior
cruciate ligament injuries. (C) 3D reconstruction, (D) coronal, (E) axial, and (F) sagittal computed tomographic images showing complete consolidation of the previously
fractured tibial attachment of the posterior cruciate ligament. 3D, three-dimensional.
Fourteen months after the trauma, we re-evaluated the patient for the last time. He
was completely asymptomatic, the clinical examination was normal, and the functional
knee score of Tegner and Lysholm gave an excellent result with 100/100 points. We
decided to discontinue this tight surveillance, and the patient was asked to report
for annual controls until complete skeletal growth is achieved.
Written informed consent was obtained from the patient's parents regarding publication
of this case report and its accompanying images.
Discussion
The most important finding of our study was that tibial avulsion fractures of the
PCL can be managed conservatively with satisfactory outcomes in pediatric patients.
Injuries to the PCL are infrequent at all ages, especially compared with those against
the anterior cruciate ligament (ACL).[6] In children, PCL injuries typically involve the avulsion fracture of either the
tibial[1]
[2]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17] or femoral[3]
[18]
[19]
[20]
[21]
[22]
[23]
[24] insertion sites, while midsubstance tears are uncommon.[4]
[25]
[26] In skeletally immature knees, the ligaments appear to be much stronger than the
physis, predisposing to osteochondral avulsions rather than ligamentous tears.[23]
[27]
Sport traumas and traffic accidents are the main reported sources of PCL injuries.
PCL injuries can result from a direct anterior blow to the proximal tibia, hyperflexion,
or more rarely from sudden hyperextension.[6]
[28] Forced posteriorly twisting injury has also been observed.[13]
PCL injuries generally present with immediate pain, swelling, and limitation of the
range of motion. Due to protective reflex muscle spasms and painful mobilization,
appropriate knee examination is often difficult. Clinical findings, such as a posterior
sag sign, positive posterior drawer, or quadriceps-active test, are classically related
to PCL insufficiency.[6] However, they may not be obvious in the acute phase, and only re-examination under
anesthesia or several days after the trauma may reveal them.[7]
[8]
[12] No clinical sign can differentiate between ligamentous tears and avulsion fractures.
PCL avulsion fractures are often associated with other injuries in the same knee.
Therefore, an attentive examination of all structures is recommended.[6] Because of potential neurovascular damages, attention must be paid to evaluating
the perfusion, sensibility, and motricity of the limb.[19]
For these reasons, radiologic studies are fundamental for correct diagnosis and management.
Standard radiographs may be useful in the case of a bony avulsed fragment, but one
certainly cannot rule out avulsion fractures, especially in the case of incomplete
knee ossification.[1]
[2]
[11]
[24]
[29] Every pediatric patient with suspected PCL insufficiency should benefit from a magnetic
resonance imaging screening. Associated intra-articular injuries have often been reported,[4]
[8]
[12]
[15]
[18]
[19]
[20]
[22]
[23] and magnetic resonance imaging appears to be the best noninvasive modality in diagnosing
them.[30] Specific classifications have been proposed for the more frequently observed avulsion
fractures of the ACL, while none has been defined for those of the PCL.[29] In these cases, descriptions of the displacement of the avulsed fragment and of
the potential associated injuries are still needed.
In the absence of pertinent guidelines, the management of this injury in children
is inspired by indications deriving from ACL avulsion fractures and adult traumatology.
If the avulsed fragment is not displaced or is minimally displaced, nonoperative treatment
may be suggested.[31]
[32] Surgical reduction and fixation should be considered in the case of a displaced
fragment or conservative treatment failure.[11]
[32] PCL injuries combined with other ligamentous or meniscal damages should also be
treated operatively.[33]
The results in the few reported cases of PCL injuries managed conservatively are controversial,
with apparent good outcomes in some patients[1]
[2] and poor ones in others.[3]
[4] Operative management with open reduction and several types of internal fixations
have often been reported with similar good results,[7]
[8]
[9]
[10]
[11]
[12]
[13]
[18] even in the case of delayed treatment.[17] Arthroscopic fixation has also been reported.[34]
While choosing the most suitable management, one should consider the potential risks
of both operative and nonoperative treatments. Potential persistent ligamentous insufficiency
following conservative treatment may be associated with secondary displacement, pseudoarthritis,
and articular degeneration with early osteoarthritis and/or meniscal injuries.[24]
[35]
[36]
[37] On the contrary, iatrogenic physeal injury can be associated with length and angular
growth disorders depending on the skeletal maturity and its remaining growth potential.[19]
[38]
[39] This surgical risk should be estimated by considering the chronologic, skeletal,
and physiologic age of the patient.[25] The desire to return to elite competitions should be questioned in skeletally immature
athletes, and operative management should be proposed if it is present.[11] Long-term prognosis after careful treatment of PCL avulsion fractures seems to be
good, with typically no or minimal strength, mobility, and stability deficits.[7]
[10]
[11]
[12]
[18] Young treated athletes report complete returns to sport activities with no restrictions
or complaints.[10]
[11]
Conclusion
PCL avulsion fracture is a very rare finding in children, and no definitive indications
for its appropriate management exist. Several authors have recommended the surgical
approach, and only a few patients treated conservatively have been reported. With
this report, we demonstrate that PCL avulsion fracture can be treated conservatively
in selected cases with good results, avoiding potential surgical-related complications.
Tight clinical and radiological follow-up is mandatory to achieve the best treatment
outcome. Nevertheless, a rapid switch to a surgical approach must be proposed in a
case of failure.
