Anterior cruciate ligament (ACL) graft tears can occur as complications of anterior cruciate ligament reconstruction or as a consequence of a traumatic reinjury.
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Epidemiology
An anterior cruciate ligament graft injury occurs in ~7% of patients with an anterior cruciate ligament reconstruction 1.
Risk factors
Factors that increase the likelihood of developing ACL graft tear or reinjury are 1-5:
younger age (<25 years)
high level of activity
high-risk cutting/pivoting sports and activities (e.g. football/soccer)
hamstring autograft
improper tunnel placement
reinjury during the ligamentization period (in particular 4-8 months after reconstruction)
Clinical presentation
Common complaints include recurrent or persistent pain, instability, laxity or limited range of motion after ACL reconstruction. History might reveal a reinjury.
Complications
ACL graft tears can lead to the following conditions 4:
chronic instability
ligamentous injury
stiffness
Pathology
An ACL graft tear is a partial or complete discontinuity of the graft and accounts for graft failure.
Etiology
Causes of ACL graft tears include the following 4-7:
surgical errors (e.g. tunnel malposition and subsequent graft shearing)
poor graft incorporation
untreated concomitant injuries (e.g. posterolateral corner injury)
repeat traumatic injury
Location
ACL graft tears may be located in the intra-articular portion of the graft or within the femoral or tibial tunnels 4. The posterolateral bundle is more frequently affected than the anteromedial bundle 9.
Radiographic features
Plain radiograph
Plain radiographs are of limited value in the detection of an anterior cruciate ligament graft tear. They might depict secondary signs such as an anterior tibial translation or potential causes like tunnel malposition or signs of screw divergence 8.
CT
CT might be done for the evaluation of tibial and femoral tunnels in the setting of preoperative planning.
MRI
MRI allows the detection and evaluation of suspected anterior cruciate ligament graft tears, which can be best depicted in coronal and sagittal views. In addition, MRI can be used for the workup of concomitant chondral, meniscal and ligamentous injuries 4-9.
Primary imaging signs
graft fiber discontinuity or fluid-signal intensity defect
abnormal (horizontal) fiber orientation
lax graft fibers or fiber disarray
graft thinning
focal area of increased graft signal
Secondary imaging signs
bone bruises in the lateral compartment at the condylopatellar sulcus and the posterolateral tibia
uncovering of the posterior horn of the lateral meniscus
buckling of the posterior cruciate ligament
Radiology report
The radiological report should include a description of the following 3-8:
location and grade of the graft tear (partial tear, disruption)
possible etiology if evident
concomitant chondral injuries and meniscal tears
possible concomitant ligamentous injuries
evidence of malalignment
Treatment and prognosis
The management of anterior cruciate ligament graft injury depends on clinical signs and symptoms on patient age and activity as well as on concomitant injuries.
Partial anterior cruciate ligament graft tears can be managed conservatively 4.
Full-thickness tears in the setting of recurrent instability and/or malalignment are likely treated with graft revision surgery. Depending on the exact etiology of the graft rupture and associated findings such as chondral and/or meniscal injuries revision surgery might be done as a one-stage or two-stage procedure 10.
Differential diagnosis
Conditions that can mimic the presentation and/of the appearance of an ACL graft tear include 4-6:
mucoid degeneration of the graft
graft impingement
-
graft ligamentization
focal areas of signal alteration
occurs in immature grafts (up to 4 years after ACL reconstruction)
-
multistranded hamstring grafts
focal areas of signal alteration
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