- Mechanism: ACL Tear:
- Physical Exam of ACL Tears:
(see
knee exam)
-
Anterior Drawer Test
-
Anteromedial Rotatory Stability:
-
Anterolateral Rotatory Instability
-
Clunk Test
-
Lachman
-
Losee Test
-
Pivot shift
-
Reverse Pivot Shift Test
-
Hemarthrosis:
- greater than70% of pts w/ acute hemarthrosis
will have ACL tear;
- severe swelling of the knee typically develops within two hours of injury because of
hemarthrosis;
-
hemarthrosis will develop over 6-24 hours;
- if effusion develops immediately after injury, one should suspect an osteochondral fracture;
- presence or absence of fat in aspirated fluid is key distinction;
- Discussion:
- ensure that patient has a FROM and no indication of
arthrofibrosis:
-
pivot shift with a positive
Lachman's;
-
combined injuries:
-
posterior laxity;
-
MCL instability:
- in most cases, the torn MCL will go on to heal if treated conservatively;
- ACL reconstruction should be delayed until medial laxity is not present, otherwise the combined instability
may comprimise the final result;
-
posterolateral instability:
- should be managed operatively along with the ACL reconstruction;
- neglected posterolateral instability may lead to ACL reconstruction failures;
-
meniscal tear:
- strongly consider
repair at the time of ACL reconstruction;
- pass sutures prior to the ACL reconstruction but delay tying sutures down until the reconstruction is completed;
- references:
- Treatment of acute isolated and combined ruptures of the anterior cruciate ligament. A long term follow up study.
C Anderson and J Gillquist.
Am. J. Sports Med.
Vol 20. 1992. p 7-12.
-
Decreased range of motion following acute versus chronic anterior cruciate ligament reconstruction.
- Diff Dx:
- consider
quadriceps or
patella tendon rupture;
-
PCL ruptures may give a "false positive" Lachman test;
- Radiographs:
- hyper-extension lateral view allows assessment of slope of intercondylar roof in relation to the tibial plateau;
- this may help with placement of the tibial tunnel (helps avoid graft impingement);
-
Segond fracture
- small avulsion frx of lateral tibial condyle just below joint line is now recognized as a sign of injury of ACL;
- small avulsion frx of proximal part of the tibia that is seen just proximal to fibular head on the anteroposterior roentgenogram, is nearly always associated w/ torn ACL;
-
references:
-
Patella baja in anterior cruciate ligament reconstruction of the knee.
- Lateral capsular sign: x-ray clue to a significant knee instability.
Woods GW.
Stanley RF.
Tullos HS. American Journal of Sports Medicine.
7(1):27-33, 1979 Jan-Feb.
-
Relation of the fibular head sign to other signs of anterior cruciate ligament insufficiency. A follow-up letter to the editor.
-
Patellar tendon graft reconstruction for midsubstance anterior cruciate ligament rupture in junior high school athletes. An algorithm for management.
-
Assessment of patellar height after autogenous patellar tendon anterior cruciate ligament reconstruction.
-
Fracture of the posterior aspect of the lateral tibial plateau: radiographic sign of anterior cruciate ligament tear.
- MRI of Knee:
- normal anatomy:
- distal ligament may show a striated signal caused by interspersed fat and synovium between the 2 bundles;
- proximal ligament appears dark
- any discontinuity or signal change in the ligament is indicative of ACL tear;
-
indirect signs of ACL tear:
- always look for signs of additional injury (meniscal tear, PCL tear, LCL tear);
- femoral osteochondral lesions and/or tibial plateau bone bruises may diminish the eventual postoperative result;
- often there will be focal areas of increased signal in the lateral tibial plateau and femoral condyle.
-
pivot shift injury: combination of signal changes in lateral femoral condyle and posteror lateral tibial plateau:
- abnormal slope of ACL;
- avulsion of the anterior tibial spine;
- segond fracture: capsular avulsion fracture of the lateral tibial plateau;
- kissing contusions involving the anterior tibia and femur resulting from hyperextension injury;
- references:
-
The accuracy of selective magnetic resonance imaging compared with the findings of arthroscopy of the knee.
- "Bone Bruises" on magnetic resonance imaging evaluation of anterior cruciate ligament injuries. BK Graf et al.
Am J. Sports Med. Vol 21. 1993. p 220-223.
- Associated Findings:
-
varus knee:
- whereas a varus knee probably does not contribute to ACL tear, it is well known that a varus
knee will have a negative influence on both operative and non-operative treatment;
- w/ signficant varus deformity consider
high tibial osteotomy prior to ACL reconstruction;
- references:
- High tibial osteotomy and ligament reconstruction in varus angulated, ACL deficient knees: a two to seven year follow up study. FR Noyes et al.
Am J. Sports Med. Vol 21: 2. 1993.
-
osteochondral defects
-
meniscal tear:
- menisci may become trapped between femoral and tibial condyles.
- vertical longitudinal & "
bucket-handle tear;"
- as tibia subluxates anteriorly, the posterior horns of menisci become trapped between articular surfaces of femur and tibia;
- if torn meniscus fragment remains forward of the femoral condyle when the tibia reduces, knee is "locked;"
- note that the combination of ACL tear and meniscal tear is especially likely to contribute to instability, and early osteo-arthritis;
- ACL tears combined w/ medial meniscal tears result in more anterior translation than lateral meniscal tears;
- management:
- Shelbourne KD. and Johnson GE. 1993, advocate staged treatment of concomitant bucket hand and ACL injuries;
- theoretical advantages of staged repair and reconstruction:
- more aggressive use of repair rather than removal of a displaced torn meniscus;
- prevention of problems in regaining range of motion;
- allows a second look to judge the success of meniscal repair;
- allows time for the patient to prepare for ACL reconstruction;
- references:
- Locked bucket-handle meniscal tears in knees with chronic anterior cruciate ligament deficiency.
Shelbourne KD. Am. J. of Sports Medicine.
21(6):779-82; discussion 782, 1993
Nov-Dec.
-
MCL tear:
- treated non operatively, most MCL tears will heal with non operative treatment;
- some surgeons will delay ACL reconstruction until there is near complete resolution of medial instability;
- references:
-
The treatment of acute combined ruptures of the anterior cruciate and medial ligaments of the knee.
-
Reconstruction of the anterior cruciate ligament alone in the treatment of a combined instability with complete rupture of the medial collateral ligament. A prospective study.
-
posterolateral instability:
- these patients may demonstrate an asymmetric recurvatum deformity, which is most pronounced during gait;
- exam: external rotation recurvatum test and
reverse pivot shift test
-
LCL instability should be managed concurrently w/ ACL reconstruction;
- it is important to distinguish this type of instability from one plane posterior instability;
- isolated PCL/ACL reconstruction will correct the one plane instability but will not correct the rotatory instability;
- in fact, ACL reconstruction may actually increase the patient's sensation of rotatory instability;
- references:
- Treatment of acute and chronic combined ACL and Posterolateral Knee Injuries.
RF LaPrade et al.
Sports Medicine Arthroscopic Review.
Vol 5. 1997. p 91-99.
-
incomplete knee extension:
- most often is a result of a "cyclops lesion," which is due to a stum
