Postoperative Magnetic Resonance Imaging following Arthroscopic Primary Anterior Cruciate Ligament Repair

Mesenchymal Stem Cell Exosome and Fibrin Sealant Composite Enhances Rabbit Anterior Cruciate Ligament Repair

BACKGROUND

The anterior cruciate ligament (ACL) fails to heal after rupture, leading to joint instability and an increased risk of osteoarthritis. Mesenchymal stem/stromal cell (MSC) exosomes have reported wide-ranging therapeutic efficacy; however, their potential for augmenting ACL repair remains to be investigated.

PURPOSE

To evaluate the use of MSC exosomes with fibrin sealant on biological augmentation of ACL healing after suture repair and their effects on ACL fibroblast functions.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twelve rabbit knees underwent ACL transection and suture repair. MSC exosome and fibrin composite (Exosome+Fibrin) or fibrin (Fibrin) alone was used to supplement the suture repair in 6 knees. ACL repair was assessed by magnetic resonance imaging at 6 and 12 weeks postoperatively and by histologic and immunohistochemical analyses at 12 weeks. To investigate the mechanisms through which MSC exosomes augment ACL repair, metabolic activity, proliferation, migration, and matrix synthesis assays were performed using the primary ACL fibroblasts. RNA sequencing was also performed to assess global gene expression changes in exosome-treated ACL fibroblasts.

RESULTS

Based on magnetic resonance imaging findings, 5 of 6 Exosome+Fibrin-treated ACLs were completely or partially healed, as opposed to 5 of 6 Fibrin-treated ACLs appearing torn at 6 and 12 weeks postoperatively. Additionally, 4 of 6 Exosome+Fibrin-treated ACLs were isointense, as compared with 5 of 6 Fibrin-treated ACLs that were hyperintense, indicating improved remodeling and maturation of the repaired ACLs with Exosome+Fibrin treatment. Histologically, Exosome+Fibrin-treated ACLs showed more organized collagen fibers and abundant collagen deposition, with a high amount of collagen I and relatively lower amount of collagen III, which are consistent with the matrix structure and composition of the normal ACL. Cell culture studies using ACL fibroblasts showed that MSC exosomes enhanced proliferation, migration, and collagen synthesis and deposition, which are cellular processes relevant to ACL repair. Further gene set enrichment analysis revealed key pathways mediated by MSC exosomes in enhancing proliferation and migration while reducing matrix degradation of ACL fibroblasts.

CONCLUSION

The combination of MSC exosomes and fibrin sealant (Exosome+Fibrin) applied to a suture repair enhanced the morphologic and histologic properties of the ACL in a rabbit model, and these improvements could be attributed to the augmented functions of ACL fibroblasts with exosome treatment.

CLINICAL RELEVANCE

This work supports the use of MSC exosomes in biological augmentation of ACL healing after suture repair.

Anterior cruciate ligament autograft maturation on sequential postoperative MRI is not correlated with clinical outcome and anterior knee stability

PURPOSE

Magnetic resonance imaging (MRI) signal intensity is correlated to structural postoperative changes of the anterior cruciate ligament (ACL) autograft. The purpose of this study was to investigate the ACL autograft maturation process via MRI over 2 years postoperatively, compare it to a native ACL signal and correlate the results with clinical outcome, return to preinjury sports levels, and knee laxity measurements.

METHODS

ACL autograft signal intensity was measured in 17 male patients (age, 28.3 ± 7.0 years) who underwent ACL reconstruction with hamstring autograft at 6 weeks, 3-, 6-, 12-, and 24 months postoperatively by 3 Tesla MRI. Controls with an intact ACL served as control group (22 males, 8 females; age, 26.7 ± 6.8 years). An ACL/PCL ratio (APR) and ACL/muscle ratio (AMR) was calculated to normalize signals to soft tissue signal. APR and AMR were compared across time and to native ACL signal. Clinical outcome scores (IKDC, Lysholm), return to preinjury sports levels (Tegner activity scale), and knee laxity measurement (KT-1000) were obtained and correlated to APR and AMR at the respective time points.

RESULTS

The APR and AMR of the ACL graft changed significantly from the lowest values at 6 weeks to reach the highest intensity after 6 months (p < 0.001). Then, the APR and AMR were significantly different from a native ACL 6 months after surgery (p < 0.01) but approached the APR and AMR of the native ACL at 1- and 2 years after surgery (p < 0.05). The APR changed significantly during the first 2 years postoperatively in the proximal (p < 0.001), mid-substance (p < 0.001), and distal (p < 0.01) intraarticular portion of the ACL autograft. A hypo-intense ACL MRI signal was associated with return to the preinjury sports level (p < 0.05). No correlation was found between ACL MRI graft signal and clinical outcome scores or KT-1000 measurements.

CONCLUSION

ACL grafts undergo a continuous maturation process in the first 2 years after surgery. The ACL graft signals became hyper-intense 6 months postoperatively and approximated the signal of a native intact ACL at 12- and 24 months. Patients with a hypo-intense ACL graft signal at 2 years follow-up were more likely to return to preinjury sports levels. The results of the present study provide a template for monitoring the normal ACL maturation process via MRI in case of prolonged clinical symptoms. However, subjective outcome and clinical examination of knee laxity remain important to assess the treatment success and to allow to return to sports.

LEVEL OF EVIDENCE

III.

Suture tape augmentation ACL repair, stable knee, and favorable PROMs, but a re-rupture rate of 11% within 2 years

PURPOSE

The aim of this study is to investigate clinical and magnetic resonance imaging (MRI) outcomes after anterior cruciate ligament (ACL) repair using the suture tape augmentation (STA) technique.

METHODS

This prospective interventional case series included 35 patients who underwent STA ACL repair and were all followed up for 2 years. The ACL rupture was between 4 and 12 weeks old and per-operatively confirmed repairable. The International Knee Documentation Committee (IKDC), and Lysholm and Tegner scores were collected together with return to work (RTW), return to sport (RTS), re-rupture, and re-intervention rate. Lachman testing was performed and ACL healing was evaluated on MRI using a grading scale based on the ACL's morphology and signal intensity with grade 1 representing good ACL healing and grade 3 representing poor ACL healing.

RESULTS

The number of patients who returned to their pre-rupture level for IKDC, Lysholm, and Tegner scores at 2 years of follow-up are 17/26 (65.4%), 13/25 (52.0%), and 18/27 (66.7%) patients, respectively. Median RTW and RTS periods were 5.5 weeks (range 0-32 weeks) and 6 months (range 2-22 months), respectively. The Lachman side-to-side difference decreased significantly (P < 0.001) to less than 3 mm after surgery and remained stable. Four patients [11.4%, 95% CI (3.2, 26.7)] suffered from a re-rupture and three other patients [8.6%, 95% CI (1.8, 23.1)] needed a re-intervention for another reason than re-rupture. MRI follow-up of 31 patients showed overall grade 1 ACL healing in 14 (45.2%) patients, grade 2 ACL healing in 11 (35.5%) patients, and grade 3 ACL healing in 6 (19.4%) patients. A higher risk of re-rupture was associated with grade 3 ACL healing at 6 months post-operatively and a pre-operative Tegner score of  ≥  7.

CONCLUSION

This study shows that treatment of the acute, repairable ACL with the STA technique leads to a stable knee and favorable patient-reported outcome measures (PROMs). However, the re-rupture rate of 11.4% within the 2-year follow-up is a concern.

LEVEL OF EVIDENCE

IV.

Primary ACL Repair of a Chronic ACL Femoral Avulsion with 2-Year Clinical and Radiographic Outcomes: A Case Report

CASE

There has been a reemergence of anterior cruciate ligament (ACL) repair. We present the unique case of an ACL repair in a service member with a chronic tear. The patient went on to have a successful outcome with return to full activities without symptoms and functional outcomes scores equal to preinjury levels.

CONCLUSION

This case demonstrates a preserved ACL remnant after an ACL femoral avulsion secondary to scarring to the posterior cruciate ligament. ACL repair can produce excellent outcomes in the right population, and injury chronicity may not necessarily preclude successful repair in the setting of good-quality ACL remnant.

ACL Repair: A Game Changer or Will History Repeat Itself? A Critical Appraisal

Until the past decade the common thought was that the anterior cruciate ligament (ACL) was not able to heal and restore knee stability. In this manuscript a brief review of studies of the developers and the early adaptors of four different modern ACL repair techniques are presented. The present status and considerations for the future of ACL repair and its research are shared. After promising short- to midterm ACL healing results by the developers, the results of the early adaptors show more variety in terms of rerupture and reintervention for other reasons. Risk factors for failure are a young age, high preinjury sports activity level, midsubstance ruptures and impaired integrity of the ACL bundles and the synovial sheath. There is a call for more clinical data and randomized clinical trials. Conclusion: an important finding of the past decade is that the ACL is able to heal and subsequently restabilize the knee. Patient selection is emphasized: the ideal patient is a non-high athlete older than 25 and has an acute proximal one bundle ACL rupture. Further research will have to show if ACL repair could be a game changer or if history will repeat itself.

Anterior Cruciate Ligament Repair: Historical Perspective, Indications, Techniques, and Outcomes

Anterior cruciate ligament (ACL) repair was first reported in 1895 by Sir Arthur Mayo-Robson. Open primary ACL repair was performed throughout the 1970s and 1980s; however, rerupture rates were as high as 50% at mid-term follow-up. Throughout the 1980s and 1990s, synthetic graft materials received consideration; however, the outcomes were abysmal. Recently, with a better understanding of ACL healing and improvement in technique, there has been renewed interest in ACL repair. The potential advantages of ACL repair include improvements in knee kinematics and proprioception, avoiding graft harvest, and preserving bone stock. Although recent data on short-term outcomes suggest potential in properly indicated patients, medium- and long-term outcomes are largely unknown. ACL repair has the greatest potential in cases of proximal ACL rupture (modified Sherman type I and II proximal tears). Repair of midsubstance tears (modified Sherman type III tears) should be avoided. Caution is advised in athletes and younger patients because of higher failure rates. Today, ACL repair remains controversial and should be performed with caution because of limited medium- and long-term outcomes.

The healing potential of an acutely repaired ACL: a sequential MRI study

Background

Recently, there has been renewed interest in primary anterior cruciate ligament (ACL) repair. The aim of this study is to report early clinical and radiological results of a consecutive series of acute ACL tears treated with arthroscopic primary ACL repair within 14 days from injury.

Patients and methods

A consecutive series of patients with acute ACL tears were prospectively included in the study. Based on MRI appearance, ACL tears were classified into five types, and tissue quality was graded as good, fair, and poor. Patients with type I, II, and III tears and at least 50% of ACL tibial remnant intact with good tissue quality were ultimately included. Clinical outcomes were measured using the Tegner Lysholm Knee Scoring Scale (TLKSS), the Knee Injury and Osteoarthritis Outcome Score (KOOS), subjective and objective International Knee Documentation Committee (IKDC) scores, and KT-1000. Patients were also followed up with MRI evaluations at 1, 3, and 6 months postoperatively. ACL appearance was graded based on morphology (normal or abnormal) and signal intensity (isointense, intermediate, and hyperintense).

Results

The mean TLKSS was 98.1, the mean subjective IKDC was 97.6, and the mean KOOS was 98.2. The objective IKDC score was A in eight of ten patients and B in two patients. KT-1000 measurements showed a maximum manual side-to-side difference of less than 2 mm in eight of ten patients, whereas two patients showed a difference of 3 mm. The morphology of the repaired ACL was normal (grade 1) at 1 month follow-up in ten of ten cases, and this appearance persisted at 3 and 6 months postoperatively. The signal intensity at 1 month postoperatively was graded as isointense (grade 1) in four of ten patients, intermediate (grade 2) in five of ten patients, and hyperintense (grade 3) in one of ten patients. At both 3 and 6 months postoperatively, the signal intensity was graded as isointense (grade 1) in nine of ten patients and intermediate (grade 2) in one of ten patients.

Conclusions

Arthroscopic primary ACL repair performed acutely in a carefully selected group of patients with proximal ACL tears and good tissue quality showed good early clinical and radiological results.

Level of evidence

Level 4.