Magnetic resonance imaging of the knee

Posterior tibial bone bruising associated with posterior-medial meniscal tear in patients with acute anterior cruciate ligament injury

PURPOSE

To evaluate whether medial-sided bone bruising was associated with postero-medial meniscal tears in patients with an acute rupture of their anterior cruciate ligament (ACL).

METHODS

A retrospective analysis of 150 consecutive patients who had an MRI scan within 8 weeks of their ACL rupture that underwent an ACL reconstruction was performed. Based on the intra-operative findings, two groups were identified: Group A (N = 75) had no postero-medial meniscal tear associated with the acute ACL rupture and Group B (N = 75) had a postero-medial meniscal tear found at time of reconstruction. All patients' pre-operative MRI scans were reviewed for bone bruising in the following anatomic sites: lateral femoral condyle (LFC), lateral tibial plateau (LTP), medial femoral condyle (MFC), and medial tibial plateau (MTP).

RESULTS

MTP bone bruising was found to be more prevalent in cases that had a postero-medial meniscal tear in the setting of an acute ACL injury (p = 0.046). MTP Grade 2 or 3 bone bruising was more common in patients that had a postero-medial meniscal tear (p = 0.046). There was a slightly higher incidence of grade 2 or 3 MTP bone bruising in cases with a postero-medial meniscal tear, although this did not reach statistical significance (n.s.) There was no difference in LFC, LTP or MFC bone bruising in patients with or without a postero-medial meniscal tear (n.s) for all.

CONCLUSIONS

Medial-sided bone bruising; especially present on the posterior tibial plateau may result from a higher injury force during the injury to the ACL. The identification of medial bone bruising on pre-operative MRI imaging following an acute ACL rupture should raise the suspicion of an associated postero-medial meniscal tear.

LEVEL OF EVIDENCE

III.

The prevalence of soft tissue injuries in nonoperative tibial plateau fractures as determined by magnetic resonance imaging

OBJECTIVE

To determine the incidence of meniscus tears and complete ligament disruption in nondisplaced and minimally displaced tibial plateau fractures, which are otherwise amenable to nonoperative management.

DESIGN

Prospective clinical study.

SETTING

Level I urban trauma center.

INTERVENTION

Magnetic resonance imaging of 20 consecutive nonoperative tibial plateau fractures.

RESULTS

Magnetic resonance imaging was performed on 20 consecutive nonoperative (nondisplaced or minimally displaced) tibial plateau fractures to determine the frequency of significant soft tissue injuries. Ninety percent (18 of 20) had magnetic resonance imaging-diagnosed significant injuries to the soft tissues, including 80% (16 of 20) with meniscal tears, and 40% (8 of 20) with complete ligament disruptions.

CONCLUSIONS

This study found a high prevalence of soft tissue injuries with nondisplaced fractures of the tibial plateau and cautions the physician and patient with respect to future knee function and possible arthrosis.

Magnetic resonance imaging follow-up study of bone bruises associated with anterior cruciate ligament ruptures

PURPOSE

The purpose of this study was to perform a magnetic resonance imaging (MRI) follow-up study of bone bruises in a group of patients with acute anterior cruciate ligament (ACL) ruptures that were reconstructed and followed-up for a minimum of 2 years.

TYPE OF STUDY

Cohort study.

METHODS

The study group included 21 patients with a mean age of 31 years whose initial MRI scans showed associated bone bruises. Patients were included if they had an acute isolated ACL tear, no documentation of an episode of repeated injury to the affected knee during the follow-up period, and no evidence of cartilaginous injury at the time of arthroscopy. All patients had preoperative MRI scans and underwent arthroscopic ACL reconstruction using a bone-patellar tendon autograft an average of 2 months after injury. The preoperative MRI scans were analyzed using a 3-level grading system based on the appearance and location of bone bruises. A second MRI of the knee was obtained from 24 to 64 months postoperatively (average 34 months). The presence of resolution of bone bruises was determined and correlation with clinical scoring established.

RESULTS

This study showed resolution of all type I lesions and 91% of type II lesions (10 of 11). In all type III lesions, an articular cartilage thinning and depression was observed after 2 years of follow-up. In 15 patients (71%), MRI showed that the bone bruises had resolved without apparent sequelae. In the remaining 6 patients (29%), sequelae of the osteochondral lesion were evident on MRI.

CONCLUSIONS

According to our clinical data, there was no correlation between scores obtained from patients with resolved lesions against those with osteochondral sequelae. Although long-term clinical implications of these findings are uncertain, a severe occult osteochondral lesion sustained at the time of ACL rupture seems to be persistent on MRI even after a successful reconstruction.

Usefulness of 99Tcm-MDP knee SPET for pre-arthroscopic evaluation of patients with internal derangements of the knee

The aim of this study was to ascertain whether knee SPET can localize lesion sites in patients with internal derangements of the knee. We performed knee SPET as a pre-arthroscopic examination in 63 consecutive patients. SPET imaging was performed with a triple-headed SPET camera 4 h after the injection of 99Tcm-methylene diphosphonate. Arthroscopic diagnoses were as follows: 28 medial meniscus injuries, 24 lateral meniscus injuries, 31 anterior cruciate ligament (ACL) injuries, three posterior cruciate ligament injuries and one medial collateral ligament injury. Of 30 patients with crescent-shaped increased activity at the medial tibial plateau, 22 had medial meniscus injuries (positive predictive value: PPV 73%); of 17 patients with crescent-shaped activity at the lateral tibial plateau, 13 had lateral meniscus injuries (PPV 76%). Of 18 patients with increased activity at ACL attachment sites (primary sign), 17 had ACL injuries (PPV 94%). Of 27 patients with increased activity at bone impaction sites of ACL injury (secondary sign), 22 had ACL injuries (PPV 81%). Of 32 patients who had either a primary or secondary sign, 26 had ACL injuries (PPV 81%). We conclude that knee SPET is very useful in the management of internal derangements of the knee, particularly in determining the need for arthroscopy by localizing lesion sites.

The Painful Knee: Arthroscopy or MR Imaging?

While neither arthroscopy nor magnetic resonance (MR) imaging is perfect, both can delineate pathologic changes in the knee with reasonable accuracy. The greatest advantage of MR imaging is that it is noninvasive and can be used to detect pathologic changes both inside and outside the synovial cavity. Arthroscopy has the distinct advantage of allowing definitive treatment at the time of diagnosis in most cases, but carries with it the potential risks associated with any invasive diagnostic technique. Both modalities are expensive, and their judicious use is therefore dictated, especially in this era of cost containment. The decision to use one or both studies is best made by the orthopaedic surgeon.