Evaluation parameters of graft maturation on second-look arthroscopy following anterior cruciate ligament reconstruction: a systematic review

Meniscal resection increases the risk of residual knee laxity even in patients undergoing anatomic double-bundle anterior cruciate ligament reconstruction with eight strands of hamstring autografts

PURPOSE

To compare the midterm clinical outcomes of different meniscal surgeries in patients undergoing anatomic double-bundle anterior cruciate ligament reconstruction (DB-ACLR) with eight strands of hamstring (HT8) autografts and explore the potential predictive risk factors for residual knee laxity.

METHODS

From 2010 to 2017, a total of 410 patients who underwent anatomic trans-tibial DB-ACLR with HT8 autografts (169 patients without meniscal surgery, 105 patients with meniscal repair, and 136 patients with meniscal resection) were included in this study. The equivalent graft diameter was introduced to make the total graft size of DB-ACLR comparable with that of single-bundle ACLR and calculated as the square root of the quadratic sum of the diameter for each bundle. Residual laxity was defined as excessive anterior tibial translation or residual pivot shift at any follow-up visit, while graft rupture was confirmed by second-look arthroscopy or magnetic resonance imaging.

RESULTS

The mean follow-up period was 8.3 ± 2.2 years. The mean equivalent graft diameter was 9.9 ± 0.7 mm. Graft rupture was confirmed in 16 (3.9%) patients, while residual laxity was detected in 72 (17.6%) patients (34 [25.0%] in the meniscal resection group vs. 22 [13.0%] in the no meniscal surgery group, p = 0.021). In the multivariate logistic regression analysis, high-grade preoperative knee laxity (odds ratio OR 2.04, p = 0.020), equivalent graft diameter < 9 mm (OR 3.31 compared with 9-10 mm, p = 0.012; OR 3.28 compared with ≥ 10 mm, p = 0.019), and meniscal resection (OR 1.94 compared with no meniscal surgery, p = 0.045) were associated with residual laxity.

CONCLUSION

During a midterm follow-up, meniscal resection increased the risk of residual knee laxity even in patients undergoing anatomic DB-ACLR with HT8 autografts. Increasing the hamstring graft diameter and preserving the menisci are important strategies for ACLR to restore knee stability.

LEVEL OF EVIDENCE

Level III.

Comparison of ligamentization potential between anterior cruciate ligament-derived cells and adipose-derived mesenchymal stem cells reseeded to acellularized tendon allograft

Aims

To test the hypothesis that reseeded anterior cruciate ligament (ACL)-derived cells have a better ability to survive and integrate into tendon extracellular matrix (ECM) and accelerate the ligamentization process, compared to adipose-derived mesenchymal stem cells (ADMSCs).

Methods

Acellularized tibialis allograft tendons were used. Tendons were randomly reseeded with ACL-derived cells or ADMSCs. ACL-derived cells were harvested and isolated from remnants of ruptured ACLs during reconstruction surgery and cultured at passage three. Cell suspensions (200 µl) containing 2 × 106 ACL-derived cells or ADMSCs were prepared for the purpose of reseeding. At days 1, 3, and 7 post-reseeding, graft composites were assessed for repopulation with histological and immunohistochemical analysis. Matrix protein contents and gene expression levels were analyzed.

Results

In the graft reseeded with ACL-derived cells, a large number of elongated cells that integrated into the matrix were evident at day 3 and day 7. However, in the graft reseeded with ADMSCs, only a small number of elongated cells were found integrated into the matrix. Immunofluorescence for Ki-67 and type I collagen confirmed the pronounced production of type I collagen by Ki-67-positive ACL-derived cells integrated into the ECM. A messenger RNA (mRNA) expression assay demonstrated significantly higher gene expression levels of types I (p = 0.013) and III (p = 0.050) collagen in the composites reseeded with ACL-derived cells than ADMSCs.

Conclusion

ACL-derived cells, when reseeded to acellularized tendon graft, demonstrated earlier better survival and integration in the tendon ECM and resulted in higher gene expression levels of collagen, which may be essential to the normal ligamentization process compared to ADMSCs. Cite this article: Bone Joint Res 2022;11(11):777–786.

Adjustable-Loop Cortical Suspensory Fixation Results in Greater Tibial Tunnel Widening Compared to Interference Screw Fixation in Primary Anterior Cruciate Ligament Reconstruction

Background: Although the use of adjustable-loop suspensory fixation has increased in recent years, the influence of the shortcomings of suspensory fixation, such as the bungee-cord or windshield-wiper effects, on tunnel widening remains to be clarified. Hypothesis/Purpose: The purpose of this study was to compare adjustable-loop femoral cortical suspensory fixation and interference screw fixation in terms of tunnel widening and clinical outcomes after anterior cruciate ligament reconstruction (ACLR). We hypothesized that tunnel widening in the adjustable-loop femoral cortical suspensory fixation (AL) group would be comparable to that in the interference screw fixation (IF) group. Methods: This study evaluated patients who underwent primary ACLR at our institution between March 2015 and June 2019. The femoral and tibial tunnel diameters were measured using plain radiographs in the immediate postoperative period and 2 years after ACLR. Tunnel widening and clinical outcomes (Lysholm score, 2000 International Knee Documentation Committee subjective score, and Tegner activity level) were compared between the two groups. Results: There were 48 patients (mean age, 29.8 ± 12.0 years) in the AL group and 44 patients (mean age, 26.0 ± 9.5 years) in the IF group. Tunnel widening was significantly greater in the AL group than that in the IF group at the tibia anteroposterior (AP) middle (2.03 mm vs. 1.32 mm, p = 0.017), tibia AP distal (1.52 mm vs. 0.84 mm, p = 0.012), tibia lateral proximal (1.85 mm vs. 1.00 mm, p = 0.001), tibia lateral middle (2.36 mm vs. 1.03 mm, p < 0.001), and tibia lateral distal (2.34 mm vs. 0.85 mm, p < 0.001) levels. There were no significant differences between the two groups with respect to femoral tunnel widening and clinical outcomes. Conclusions: Tibial tunnel widening was significantly greater in the AL group than in the IF group at 2 years after primary ACLR. However, the clinical outcomes in the two groups were comparable at 2 years.

Bone-patellar tendon-bone autograft maturation is superior to double-bundle hamstring tendon autograft maturation following anatomical anterior cruciate ligament reconstruction

PURPOSE

The primary purpose of this study was to evaluate the second-look arthroscopic findings 1 year postoperatively and magnetic resonance imaging (MRI) findings 2 years after anterior cruciate ligament reconstruction (ACLR) using bone-patellar tendon-bone autograft (BTB) or hamstring tendon autograft (HT). Secondary purpose included clinical results from physical examination, including range of motion, Lachman test, pivot shift test, and knee anterior laxity evaluation, and the clinical score for subjective evaluations at 2 years after surgery.

METHODS

Between 2015 and 2018, 75 patients with primary ACL injuries were divided into either the BTB group (n = 30) or HT group (n = 45). When using HT, an anatomical double-bundle ACLR was performed. BTB was indicated for athletes with sufficient motivation to return to sporting activity. Graft maturation on second-look arthroscopy was scored in terms of synovial coverage and revascularization. All participants underwent postoperative MRI evaluation 2 years postoperatively. The signal intensity (SI) characteristics of the reconstructed graft were evaluated using oblique axial proton density-weighted MR imaging (PDWI) perpendicular to the grafts. The signal/noise quotient (SNQ) was calculated to quantitatively determine the normalized SI. For clinical evaluation, the Lachman test, pivot shift test, KT-2000 evaluation, Lysholm score, and Knee injury and Osteoarthritis Outcome Score (KOOS) were used.

RESULTS

Arthroscopic findings showed that the graft maturation score in the BTB group (3.6 ± 0.7) was significantly greater than that in the anteromedial bundle (AMB; 2.9 ± 0.2, p = 0.02) and posterolateral bundle (PLB; 2.0 ± 0.9, p = 0.001) in the HT group. The mean MRI-SNQs were as follows: BTB, 2.3 ± 0.5; AMB, 2.9 ± 0.9; and PLB, 4.1 ± 1.1. There were significant differences between BTB, AMB, and PLB (BTB and AMB: p = 0.04, BTB and PLB: p = 0.003, AMB and PLB: p = 0.03). Second-look arthroscopic maturation score and MRI-SNQ value significantly correlated for BTB, AMB, and PLB. No significant differences were detected in clinical scores. There was a significant difference (p = 0.02) in the knee laxity evaluation (BTB: 0.9 ± 1.1 mm; HT: 2.0 ± 1.9 mm).

CONCLUSION

BTB maturation is superior to that of double-bundle HT based on morphological and MRI evaluations following anatomical ACLR, although no significant differences were found in clinical scores. Regarding clinical relevance, the advantages of BTB may help clinicians decide on using the autograft option for athletes with higher motivation to return to sporting activity because significant differences were observed in morphological evaluation, MRI assessment, and knee anterior laxity evaluation between BTB and double-bundle HT.

LEVEL OF EVIDENCE

Level IV.

Effect of Muscle Cell Preservation on Viability and Differentiation of Hamstring Tendon Graft In Vitro

Muscle tissue is often removed during hamstring tendon graft preparation for anterior cruciate ligament (ACL) reconstruction. The purpose of the study was to test whether preservation of muscle remnants on a tendon graft is beneficial to the graft healing process following ACL reconstruction. Co-culturing of tendon-derived cells (TDCs) and muscle-derived cells (MDCs) was performed at various ratios, and their potential for cell viability and multilineage differentiation was compared to a single TDC cell group. Ligamentous and chondrogenic differentiation was most enhanced when a small population of MDCs was co-cultured with TDCs (6:2 co-culture group). Cell viability and osteogenic differentiation were proportionally enhanced with increasing MDC population size. MDCs co-cultured with TDCs possess both the ability to enhance cell viability and differentiate into other cell lineages.

Mesenchymal stromal cells and platelet-rich plasma promote tendon allograft healing in ovine anterior cruciate ligament reconstruction

PURPOSE

The effect of bone marrow mesenchymal stromal cells (BMSCs) and platelet-rich plasma (PRP) on tendon allograft maturation in a large animal anterior cruciate ligament (ACL) reconstruction model was reported for the first time. It was hypothesised that compared with non-augmented ACL reconstruction, BMSCs and PRP would enhance graft maturation after 12 weeks and this would be detected using magnetic resonance imaging (MRI).

METHODS

Fifteen sheep underwent unilateral tendon allograft ACL reconstruction using aperture fixation and were randomised into three groups (n = 5). Group 1 received 10 million allogeneic BMSCs in 2 ml fibrin sealant; Group 2 received 12 ml PRP in a plasma clot injected into the graft and bone tunnels; and Group 3 (control) received no adjunctive treatment. At autopsy at 12 weeks, a graft maturation score was determined by the sum for graft integrity, synovial coverage and vascularisation, graft thickness and apparent tension, and synovial sealing at tunnel apertures. MRI analysis (n = 2 animals per group) of the signal-noise quotient (SNQ) and fibrous interzone (FIZ) was used to evaluate intra-articular graft maturation and tendon-bone healing, respectively. Spearman's rank correlation coefficient (r) of SNQ, autopsy graft maturation score and bone tunnel diameter were analysed.

RESULTS

The BMSC group (p = 0.01) and PRP group (p = 0.03) had a significantly higher graft maturation score compared with the control group. The BMSC group scored significantly higher for synovial sealing at tunnel apertures (p = 0.03) compared with the control group. The graft maturation score at autopsy significantly correlated with the SNQ (r = - 0.83, p < 0.01). The tunnel diameter of the femoral tunnel at the aperture (r = 0.883, p = 0.03) and mid-portion (r = 0.941, p = 0.02) positively correlated with the SNQ.

CONCLUSIONS

BMSCs and PRP significantly enhanced graft maturation, which indicates that orthobiologics can accelerate the biologic events in tendon allograft incorporation. Femoral tunnel expansion significantly correlated with inferior maturation of the intra-articular graft. The clinical relevance of this study is that BMSCs and PRP enhance allograft healing in a translational model, and biological modulation of graft healing can be evaluated non-invasively using MRI.