Postoperative Imaging of the Knee

Cruciate and Collateral Ligaments: 2-Dimensional and 3-Dimensional MR Imaging-Aid to Knee Preservation Surgery

Being a major load-bearing and dynamic functional joint of the body, the knee joint is prone to injuries to the menisci and ligaments. Injury to one or more of these structures leads to accelerated or premature osteoarthritis and chronic debilitation. The estimated cost of these injuries in terms of diagnosis, treatment, rehabilitation, and person-hours lost amounts to over a billion dollars annually. Understanding the relevant anatomy of knee cruciate and collateral ligaments, their biomechanical functional role, and imaging considerations are essential to assist multi-disciplinary communications and timely patient treatments for improved management. MRI is considered the gold standard over other imaging modalities like X-ray, ultrasound (US), and Computed Tomography (CT) for diagnosing and assessing such injuries. High-resolution 2D and 3D MRI are considerably helpful in planning for knee preservation surgery, and this article reviews the role of such imaging as a valuable aid to knee preservation surgery in pre-and post-operative states. Relevant arthroscopy correlations have been illustrated.

Postoperative Knee and Shoulder

Arthroscopic surgery in the knee most commonly addresses ligament, meniscal, or articular cartilage abnormalities. Similarly, arthroscopic surgery of the shoulder most commonly addresses tendon and labral abnormalities. The expected postoperative MRI findings depend on both the procedure performed and the time since surgery. Identifying complications and failed procedures relies on both clinical and imaging evaluations.

Magnetic resonance imaging can increase the diagnostic accuracy in symptomatic meniscal repair patients

PURPOSE

The purpose of this study was to evaluate meniscal repair healing in symptomatic patients through combined clinical assessment, magnetic resonance imaging (MRI) and re-arthroscopy. This study investigated the diagnostic accuracy of MRI and clinical assessment in determining failed meniscal repair in symptomatic meniscal repair patients, as verified by re-arthroscopy.

METHODS

Eighty patients were included. All had undergone a primary meniscal repair followed by an MRI and re-arthroscopy due to clinical symptoms of a meniscal lesion. A validated semi-quantitative scoring system was employed for identifying MRI-diagnosed healing failure. The clinical assessment was divided into joint swelling, joint-line tenderness, locking and a positive McMurray's test. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of MRI and positive clinical findings were calculated using second-look arthroscopy as a standard.

RESULTS

The MRI results showed healing of 22 (27.5%) of the menisci and 58 (72.5%) unhealed menisci, whereas second-look arthroscopy identified 15 (19%) healed menisci and 65 (81%) unhealed menisci. The isolated MRI findings were 0.85, 0.8, 0.95 and 0.55 for sensitivity, specificity, PPV and NPV, respectively. The PPVs of the clinical assessments were 0.78, 0.85 and 0.94, with one, two and three clinical findings, respectively. A grade 3 MRI combined with joint-line tenderness presented a PPV of 0.98.

CONCLUSION

A supplementary MRI will increase diagnostic accuracy when fewer than three clinical findings are present in a symptomatic meniscal repair patient. The clinical relevance of this finding is that MRI contributes to enhancing the diagnostic accuracy of an unhealed meniscal repair when there are limited clinical signs of meniscal pathology.

LEVEL OF EVIDENCE

III.

Computed Tomography Assessment of Anatomic Graft Placement After ACL Reconstruction: A Comparative Study of Grid and Angle Measurements

Background:

The anatomic placement of anterior cruciate ligament (ACL) grafts is often assessed with postoperative imaging. In clinical practice, graft angles are measured to indicate anatomic placement on magnetic resonance imaging, whereas grid measurements are performed on computed tomography (CT). Recently, a study indicated that graft angle measurements could also be assessed on CT. No consensus has yet been reached on which measurement method is best suited to assess anatomic graft placement.

Purpose:

To compare the ability of grid measurements and angle measurements to identify anatomic versus nonanatomic tunnel placement on CT performed in patients undergoing ACL reconstruction.

Study Design:

Case series; Level of evidence, 4.

Methods:

A total of 100 knees undergoing primary reconstruction with a hamstring graft (HAM group), 91 undergoing reconstruction with a bone–patellar tendon–bone graft (BPTB group), and 117 undergoing revision ACL reconstruction (REV group) were assessed with CT. Grid measurements of the femoral and tibial tunnels and angle measurements of grafts were performed. Graft placement, rated as anatomic or nonanatomic, was assessed with both methods. Pearson chi-square, analysis of variance, Kruskal-Wallis, and weighted kappa tests were performed as appropriate.

Results:

The grid assessment classified 10% of the HAM group, 4% of the BPTB group, and 17% of the REV group as nonanatomic (P < .001). The angle assessment classified 37% of the HAM group, 54% of the BPTB group, and 47% of the REV group as nonanatomic. The weighted kappa between angle measurements and grid measurements was low in all groups (HAM: 0.009; BPTB: 0.065; REV: 0.041).

Conclusion:

The agreement between grid measurements and angle measurements was very low. The angle measurements seemed to overestimate nonanatomic tunnel placement. Grid measurements were better in identifying malpositioned grafts.