New trends in ACL research

Effect of suspension training on neuromuscular function, postural control, and knee kinematics in anterior cruciate ligament reconstruction patients

BACKGROUND

Suspension training (SET) is a method of neuromuscular training that enables the body to carry out active training under unstable support through a suspension therapy system. However, there have been few reports in the literature on the application of SET to anterior cruciate ligament reconstruction (ACLR) patients. It is not clear what aspects of the patient's function are improved after SET.

AIM

To investigate the effect of SET on the neuromuscular function, postural control, and knee kinematics of patients after ACLR surgery.

METHODS

Forty participants were randomized to an SET group or a control group. The SET group subjects participated in a SET protocol over 6 wk. The control group subjects participated in a traditional training protocol over 6 wk. Isokinetic muscle strength of the quadriceps and hamstrings, static and dynamic posture stability test, and relative translation of the injured knee were assessed before and after training.

RESULTS

The relative peak torque of the quadriceps and hamstrings in both groups increased significantly (P < 0.001), and the SET group increased by a higher percentage than those in the control group (quadriceps: P = 0.004; hamstrings: P = 0.011). After training, both groups showed significant improvements in static and dynamic posture stability (P < 0.01), and the SET group had a greater change than the control group (P < 0.05). No significant improvement on the relative translation of the injured knee was observed after training in either group (P > 0.05).

CONCLUSION

Our findings show that SET promotes great responses in quadriceps and hamstring muscle strength and balance function in ACLR patients.

Diffusion Tensor Imaging for Quantitative Assessment of Anterior Cruciate Ligament Injury Grades and Graft

BACKGROUND

As the need for quantitative assessment of anterior cruciate ligament (ACL) injuries and ACL graft increases, diffusion tensor imaging (DTI) becomes a more valuable measuring tool. However, DTI changes in differing injury grades of ACL and longitudinal graft remain unclear.

PURPOSE

To investigate the diagnostic performance of DTI in quantitatively assessing ACL injury severity and the development of ACL grafts within 6 months of surgery.

STUDY TYPE

A cohort study.

SUBJECTS

Thirty-five patients diagnosed with grades I-IV ACL injuries and 20 volunteers as controls were recruited.

FIELD STRENGTH/SEQUENCE

T₁ -weighted, T₂ -weighted, proton density (PD)-weighted, and DTI at 3.0T MRI.

ASSESSMENT

ACL injury grades in arthroscopic images and DTI quantitative data were evaluated from July 2016 to July 2018.

STATISTICAL TESTS

Chi-square test, analysis of variance, Spearman correlation analysis, and receiver operator characteristic (ROC) curves.

RESULTS

Both fractional anisotropy (FA) (r = -0.898, P < 0.05) and apparent diffusion coefficient (ADC) (r = 0.851, P < 0.05) were significantly correlated with the severity of ACL injuries. The area under the curve (AUC) values for differentiation between low- and high-grade ACL injuries with FA and ADC were 0.973 and 0.963, respectively. Although there were no significant differences in FA (P > 0.05) and ADC (P > 0.05) between grades I and II ACL injuries or in ADC (P > 0.05) between grades III and IV, there were significant differences in FA and ADC between two grades (P < 0.05). There were significant differences in FA (P < 0.05) and ADC (P < 0.05) between normal ACL and 3-month graft postoperation, as well as in ADC values between 3-month and 6-month graft postoperation (P < 0.05).

DATA CONCLUSION

DTI could be used to quantitatively evaluate the ACL injury grades and the development of ACL grafts. The diagnostic efficiency of FA values was higher than that of ADC values.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 3.

The influence of connective tissue growth factor on rabbit ligament injury repair

Objectives

The injured anterior cruciate ligament (ACL) is thought to exhibit an impaired healing response, and attempts at surgical repair have not been successful. Connective tissue growth factor (CTGF) is reported to be associated with wound healing, probably through transforming growth factor beta 1 (TGF-β1).

Methods

A rabbit ACL injury model was used to study the effect of CTGF on ligament recovery. Quantitative real-time PCR (qRT-PCR) was performed for detection of changes in RNA levels of TGF-β1, type 1 collagen (COL1), type 2 collagen (COL2), SRY-related high mobility group-box gene9 (SOX9), tissue inhibitor of metalloproteinase-1 (TIMP-1) and matrix metallopeptidase 13 (MMP-13). Expression of related proteins was detected by Western blotting.

Results

The current study showed that CTGF could promote the recovery of an injured anterior cruciate ligament. It can upregulate mRNA and expression of TGF-β1, COL1, COL2, SOX9, and tissue inhibitor of TIMP-1, and downregulate mRNA and expression of MMP-13, suggesting that the curative effect of CTGF on injured rabbit ligaments is through regulation of these cellular factors.

Conclusions

This finding revealed the healing role of CTGF in injured tissues and provides new possibilities of treating injured tissues and wound healing by using CTGF.

Cite this article: X. Sun, W. Liu, G. Cheng, X. Qu, H. Bi, Z. Cao, Q. Yu. The influence of connective tissue growth factor on rabbit ligament injury repair. Bone Joint Res 2017;6:399–404. DOI: 10.1302/2046-3758.67.BJR.2016-0255.R1.

The influence of connective tissue growth factor on rabbit ligament injury repair

Objectives

The injured anterior cruciate ligament (ACL) is deemed to exhibit an impaired healing response and attempts at surgical repair have not been successful. Connective tissue growth factor (CTGF) is reported to be associated with wound healing, probably through transforming growth factor beta1 (TGF-β1).

Methods

A rabbit ACL injury model was used to study the effect of CTGF on ligament recovery. Quantitative real-time PCR was performed for detection of changes in RNA levels of TGF-β1, type 1 collagen (COL-I), type 2 collagen (COL-II), SRY-related high mobility group-box gene9 (Sox9), metalloproteinase-1 (TIMP-1) as well as matrix metallopeptidase 13 (MMP-13). And expression of related proteins was detected by western blotting.

Results

The current study showed that CTGF could promote the recovery of inured anterior cruciate ligament. It can up-regulate the mRNA and expression of TGF-β1, COL-I, COL-II, Sox9, as well as the tissue inhibitor of TIMP-1, and down-regulated the mRNA and expression of MMP-13, suggesting the curative effect of CTGF on injured rabbit ligament is through regulating these cellular factors.

Conclusion

This finding revealed the mechanism of CTFG’s healing role in injured tissues and provided new possibilities of treating injured tissues and wound healing by using CTFG.

Stem cell therapy: a promising biological strategy for tendon-bone healing after anterior cruciate ligament reconstruction

Tendon-bone healing after anterior cruciate ligament (ACL) reconstruction is a complex process, impacting significantly on patients' prognosis. Natural tendon-bone healing usually results in fibrous scar tissue, which is of inferior quality compared to native attachment. In addition, the early formed fibrous attachment after surgery is often not reliable to support functional rehabilitation, which may lead to graft failure or unsatisfied function of the knee joint. Thus, strategies to promote tendon-bone healing are crucial for prompt and satisfactory functional recovery. Recently, a variety of biological approaches, including active substances, gene transfer, tissue engineering and stem cells, have been proposed and applied to enhance tendon-bone healing. Among these, stem cell therapy has been shown to have promising prospects and draws increasing attention. From commonly investigated bone marrow-derived mesenchymal stem cells (bMSCs) to emerging ACL-derived CD34+ stem cells, multiple stem cell types have been proven to be effective in accelerating tendon-bone healing. This review describes the current understanding of tendon-bone healing and summarizes the current status of related stem cell therapy. Future limitations and perspectives are also discussed.

Basic science of anterior cruciate ligament injury and repair

Injury to the anterior cruciate ligament (ACL) is one of the most devastating and frequent injuries of the knee. Surgical reconstruction is the current standard of care for treatment of ACL injuries in active patients. The widespread adoption of ACL reconstruction over primary repair was based on early perception of the limited healing capacity of the ACL. Although the majority of ACL reconstruction surgeries successfully restore gross joint stability, post-traumatic osteoarthritis is commonplace following these injuries, even with ACL reconstruction. The development of new techniques to limit the long-term clinical sequelae associated with ACL reconstruction has been the main focus of research over the past decades. The improved knowledge of healing, along with recent advances in tissue engineering and regenerative medicine, has resulted in the discovery of novel biologically augmented ACL-repair techniques that have satisfactory outcomes in preclinical studies. This instructional review provides a summary of the latest advances made in ACL repair. Cite this article: Bone Joint Res 2014;3:20-31.

Effect of meniscal and focal cartilage lesions on patient-reported outcome after anterior cruciate ligament reconstruction: a nationwide cohort study from Norway and Sweden of 8476 patients with 2-year follow-up

BACKGROUND

The effect of concomitant intra-articular injury on patient-reported outcome after anterior cruciate ligament (ACL) reconstruction is debated.

PURPOSE

To evaluate the effect of meniscal and articular cartilage lesions on patient-reported outcome 2 years after ACL reconstruction.

STUDY DESIGN

Cohort study (prognosis); Level of evidence, 2.

METHODS

The study included all patients with primary, unilateral ACL reconstruction registered in the Norwegian and the Swedish National Knee Ligament Registry from 2005 through 2008 who had completed the Knee Injury and Osteoarthritis Outcome Score (KOOS) Knee-Related Quality of Life subscale at a 2-year follow-up (mean ± SD, 2.1 ± 0.2 years) after surgery (n = 8476). Multiple linear regression analyses were used to evaluate the associations between each KOOS subscale (Pain, Other Symptoms, Activities of Daily Living, Sport and Recreation Function, Knee-Related Quality of Life) as the measure for patient-reported outcome and meniscal and cartilage lesions.

RESULTS

A total of 3674 (43%) patients had meniscal lesion(s), 1671 (20%) had partial-thickness (International Cartilage Repair Society [ICRS] grades 1-2) cartilage lesion(s), and 551 (7%) had full-thickness (ICRS grades 3-4) cartilage lesion(s). Multiple linear regression analyses detected no significant associations between meniscal lesions or partial-thickness cartilage lesions and the scores in any of the KOOS subscales at the 2-year follow-up. Full-thickness cartilage lesions were significantly associated with decreased scores in all of the KOOS subscales.

CONCLUSION

Patients with concomitant full-thickness cartilage lesions reported worse outcome in all of the KOOS subscales compared with patients without cartilage lesions 2 years after ACL reconstruction. Meniscal lesions and partial-thickness cartilage lesions did not impair patient-reported outcome 2 years after ACL reconstruction.