MRI evaluation of the postoperative knee: special considerations and pitfalls

MRI Assessment of Tendon Graft After Lateral Ankle Ligament Reconstruction: Does Ligamentization Exist?

BACKGROUND

No description exists in the literature about the normal evolution of tendon graft after a lateral ankle ligament (LAL) reconstruction.

PURPOSE

To assess the magnetic resonance imaging (MRI) characteristics and the evolution of the tendon graft during different moments in the follow-up after an endoscopic reconstruction of the LAL.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

This prospective study included 37 consecutive patients who underwent an endoscopic reconstruction of the LAL with an autograft using the gracilis tendon to treat chronic ankle instability (CAI) resistant to nonoperative treatment (CAI group) and 16 patients without ankle instability (control group). All patients in the CAI group underwent a postoperative assessment at 6, 12, and 24 months using the Karlsson score and MRI examination. Only patients with good and excellent results were included in the study. Graft assessment consisted of qualitative measurements and quantitative evaluations of the reconstructed anterior talofibular ligament (RATFL) and reconstructed calcaneofibular ligament (RCFL), including signal-to-noise quotient (SNQ) and contrast-to-noise quotient (CNQ) measurements in proton density-fat suppressed (PD-FS) and T1-weighted sequences. The analysis of variance test was used to compare the SNQ and the CNQ at different time points for each sequence.

RESULTS

The MRI signal at 6 months was increased compared with that of the control group. Next, a significant signal decrease from 6 to 24 months was noted on PD-FS and T1-weighted images. SNQ measurements on PD-FS weighted images for both the RATFL and the RCFL demonstrated a significantly higher signal (P < .01 and P = .01, respectively) at 6 months compared with that of the control group. Subsequently, the signal decreased from 6 to 24 months. Similarly, CNQ measurements on PD-FS weighted images for both the RATFL and the RCFL demonstrated a significantly higher signal (P < .01 and P < .01, respectively) at 6 months compared with that of the control group. Subsequently, the signal decreased from 6 to 24 months.

CONCLUSION

The present study demonstrated an evolution of the MRI characteristics, suggesting a process of graft maturation toward ligamentization. This is important for clinical practice, as it suggests an evolution in graft properties and supports the possibility of creating a viable ligament.

MR Imaging of the Lower Limb: Pitfalls, Tricks, and Tips

The purpose of this article is to discuss most common diagnostic pitfalls of the lower limb with specific attention to the knee, ankle, and foot joints. The knowledge of normal anatomic variants, correlation with age, symptoms, and medical history together with these potential MR imaging pitfalls is fundamental for an accurate interpretation of the imaging findings of the lower limb.

Anterior cruciate ligament reconstruction related complications: 2D and 3D high-resolution magnetic resonance imaging evaluation

Anterior cruciate ligament (ACL) injury is a common indication for sports-related major surgery and accounts for a large proportion of ligamentous injuries in athletes. The advancements in 2D and 3D MR imaging have provided considerable potential for a one-stop shop radiation-free assessment with an all-in-one modality examination of the knee, for both soft-tissue and bone evaluations. This article reviews ACL injuries and types of surgical managements with illustrative examples using high resolution 2D and 3D MR imaging. Various complications of ACL reconstruction procedures are highlighted with a focus on the use of advanced MR imaging and relevant arthroscopic correlations.

Two-year postoperative MRI appearances of anterior cruciate ligament hamstrings autografts are not correlated with functional outcomes, anterior laxity, or patient age

Aims

MRI has been suggested as an objective method of assessing anterior crucate ligament (ACL) graft “ligamentization” after reconstruction. It has been proposed that the MRI appearances could be used as an indicator of graft maturity and used as part of a return-to-sport assessment. The aim of this study was to evaluate the correlation between MRI graft signal and postoperative functional scores, anterior knee laxity, and patient age at operation.

Methods

A consecutive cohort of 149 patients who had undergone semitendinosus autograft ACL reconstruction, using femoral and tibial adjustable loop fixations, were evaluated retrospectively postoperatively at two years. All underwent MRI analysis of the ACL graft, performed using signal-to-noise quotient (SNQ) and the Howell score. Functional outcome scores (Lysholm, Tegner, International Knee Documentation Committee (IKDC) subjective, and IKDC objective) were obtained and all patients underwent instrumented side-to-side anterior laxity differential laxity testing.

Results

Two-year postoperative mean outcome scores were: Tegner 6.5 (2 to 10); Lysholm 89.8 (SD 10.4; 52 to 100); and IKDC subjective 86.8 (SD 11.8; 51 to 100). The objective IKDC score was 86% A (128 patients), 13% B (19 patients), and 1% C (two patients). Mean side-to-side anterior laxity difference (134 N force) was 0.6 mm (SD 1.8; -4.1 to 5.6). Mean graft SNQ was 2.0 (SD 3.5; -14 to 17). Graft Howell scores were I (61%, 91 patients), II (25%, 37 patients), III (13%, 19 patients), and IV (1%, two patients). There was no correlation between either Howell score or SNQ with instrumented anterior or Lysholm, Tegner, and IKDC scores, nor was any correlation found between patient age and ACL graft SNQ or Howell score.

Conclusion

The two-year postoperative MRI appearances of four-strand, semitendinosus ACL autografts (as measured by SNQ and Howell score) do not appear to have a relationship with postoperative functional scores, instrumented anterior laxity, or patient age at surgery. Other tools for analysis of graft maturity should be developed.

Cite this article: Bone Jt Open 2021;2(8):569–575.

Magnetic resonance imaging after anterior cruciate ligament reconstruction: A practical guide

Anterior cruciate ligament (ACL) reconstruction is one of the most common orthopedic procedures performed worldwide. In this regard, magnetic resonance imaging (MRI) represents a useful pre-operative tool to confirm a disruption of the ACL and to assess for potential associated injuries. However, MRI is also valuable post-operatively, as it is able to identify, in a non-invasive way, a number of aspects and situations that could suggest potential problems to clinicians. Graft signal and integrity, correct tunnel placement, tunnel widening, and problems with fixation devices or the donor site could all compromise the surgical outcomes and potentially predict the failure of the ACL reconstruction. Furthermore, several anatomical features of the knee could be associated to worst outcomes or higher risk of failure. This review provides a practical guide for the clinician to evaluate the post-surgical ACL through MRI, and to analyze all the parameters and features directly or indirectly related to ACL reconstruction, in order to assess for normal or pathologic conditions.

MR imaging of the postoperative knee

Advances in orthopedic and arthroscopic surgical procedures of the knee such as, knee replacement, ligamentous reconstruction as well as articular cartilage and meniscus repair techniques have resulted in a significant increase in the number of patients undergoing knee arthroscopy or open surgery. As a consequence postoperative MR imaging examinations increase. Comprehensive knowledge of the normal postoperative MR imaging appearances and abnormal findings in the knee associated with failure or complications of common orthopedic and arthroscopic surgical procedures currently undertaken is crucial. This article reviews the various normal and pathological postoperative MR imaging findings following anterior and posterior cruciate ligament, medial collateral ligament and posterolateral corner reconstruction, meniscus and articular cartilage surgery as well as total knee arthroplasty with emphasis on those surgical procedures which general radiologists will likely be faced in their daily clinical routine.

MR imaging in osteoarthritis: hardware, coils, and sequences

Whole-organ assessment of a joint with osteoarthritis (OA) requires tailored MR imaging hardware and imaging protocols to diagnose and monitor degenerative disease of the cartilage, menisci, bone marrow, ligaments, and tendons. Image quality benefits from increased field strength, and 3.0-T MR imaging is used increasingly for assessing joints with OA. Dedicated surface coils are required for best visualization of joints affected by OA, and the use of multichannel phased-array coils with parallel imaging improves image quality and/or shortens acquisition times. Sequences that best show morphologic abnormalities of the whole joint include intermediate-weighted fast-spin echo sequences. Also quantitative sequences have been developed to assess cartilage volume and thickness and to analyze cartilage biochemical composition.

Anterior cruciate ligament reconstruction grafts: MR imaging features at long-term follow-up--correlation with functional and clinical evaluation

PURPOSE

To assess the presence of increased intrasubstance signal intensity within anterior cruciate ligament (ACL) grafts and to assess whether such signal intensity changes are correlated to clinical assessments of graft instability and patient function 4-12 years after ACL reconstruction.

MATERIALS AND METHODS

Ethical permission and written informed patient consent were obtained. The study was HIPAA compliant. Forty-seven patients were included and underwent 1.5-T magnetic resonance (MR) imaging of the knee that was treated surgically. Signal intensity characteristics of the ACL graft were evaluated on sagittal intermediate-weighted and sagittal and axial T2-weighted fast spin-echo MR images. The amount of signal intensity change, femoral and tibial graft tunnel position, and orientation of ACL graft in the coronal plane were assessed. Objective index of graft stability or laxity was performed with arthrometric testing, and subjective function was assessed by using International Knee Documentation Committee (IKDC) scoring.

RESULTS

Increased intrasubstance graft signal intensity was found in 70 % (33 of 47) and in 64% (30 of 47) of patients on intermediate-weighted MR images and T2-weighted MR images, respectively. When present, intrasubstance graft signal intensity changes involved less than 25% of the maximal cross-sectional area of the graft in 70% (23 of 33) of cases on intermediate-weighted acquisitions and in 70% (21 of 30) of cases on T2-weighted acquisitions. No significant association was seen between graft signal intensity changes on intermediate-weighted and T2-weighted images and IKDC score (P = .667 and .698, respectively), arthrometric testing (P = .045-.99), and time since surgery (P = .592 and .610, respectively).

CONCLUSION

Small amounts of increased intrasubstance graft signal intensity on intermediate- and T2-weighted images can be seen after ACL reconstruction at long-term follow-up of 4 years or longer and do not necessarily correlate with findings of joint instability or functional limitations in patients after ACL repair.