Anterior cruciate ligament reconstruction: A literature review of the anatomy, biomechanics, surgical considerations, and clinical outcomes

Predictive Refined Computational Modeling of ACL Tear Injury Patterns

Anterior cruciate ligament (ACL) ruptures are prevalent knee injuries, with approximately 200,000 ruptures annually, and treatment costs exceed USD two billion in the United States alone. Typically, the initial detection of ACL tears and anterior tibial laxity (ATL) involves manual assessments like the Lachman test, which examines anterior knee laxity. Partial ACL tears can go unnoticed if they minimally affect knee laxity; however, they will progress to a complete ACL tear requiring surgical treatment. In this study, a computational finite element model (FEM) of the knee joint was generated to investigate the effect of partial ACL tears under the Lachman test (GNRB® testing system) boundary conditions. The ACL was modeled as a hyperelastic composite structure with a refined representation of collagen bundles. Five different tear types (I-V), classified by location and size, were modeled to predict the relationship between tear size, location, and anterior tibial translation (ATT). The results demonstrated different levels of ATT that could not be manually detected. Type I tears demonstrated an almost linear increase in ATT, with the growth in tear size ranging from 3.7 mm to 4.2 mm, from 25% to 85%, respectively. Type II partial tears showed a less linear incline in ATT (3.85, 4.1, and 4.75 mm for 25%, 55%, and 85% partial tears, respectively). Types III, IV, and V maintained a nonlinear trend, with ATTs of 3.85 mm, 4.2 mm, and 4.95 mm for Type III, 3.85 mm, 4.25 mm, and 5.1 mm for Type IV, and 3.6 mm, 4.25 mm, and 5.3 mm for Type V, for 25%, 55%, and 85% partial tears, respectively. Therefore, for small tears (25%), knee stability was most affected when the tears were located around the center of the ligament. For moderate tears (55%), the effect on knee stability was the greatest for tears at the proximal half of the ACL. However, severe tears (85%) demonstrated considerable growth in knee instability from the distal to the proximal ends of the tissue, with a substantial increase in knee instability around the insertion sites. The proposed model can enhance the characterization of partial ACL tears, leading to more accurate preliminary diagnoses. It can aid in developing new techniques for repairing partially torn ACLs, potentially preventing more severe injuries.

Number of intra-operative cyclic knee motion required to achieve stable graft tension in anterior cruciate ligament reconstruction; a prospective clinical study

BACKGROUND

Applying pretension by cyclic knee motion immediately before graft fixation in anterior cruciate ligament (ACL) reconstruction surgery decreases graft elongation during the postoperative course. However, the expected change in graft tension caused by cyclic knee motion remains unclear. We measured graft tension changes caused by cyclic knee motion during double-bundle ACL reconstruction.

METHODS

We included 39 patients undergoing primary anatomical double-bundle ACL reconstruction with autologous hamstrings as graft sources, at multiple centers between February 2021 and August 2022. After securing the anteromedial (AM) and posterolateral (PL) bundle grafts to the femoral cortex, they were initially tensioned to 40 N per bundle. After 10 cycles of knee extension and flexion motion, ranging from 0 to 90-110°, tension was re-measured and re-tensioned to 40 N if the graft tension had decreased. This was repeated thrice for 10 cycles on each graft. Every 10 cycles, we recorded graft tension changes (ΔGT) and compared the mean ΔGT in the AM and PL bundles. Furthermore, we assessed relationships between total ΔGT in each bundle, age, sex, and graft diameter.

RESULTS

Twenty-five women and 14 men with a mean age of 27.4 ± 12.4 years were included. The mean ΔGT in AM and PL bundles after every 10 cycles were 6.6 ± 3.7 N, 3.0 ± 2.3 N, 1.4 ± 1.5 N, and 9.9 ± 3.8 N, 4.9 ± 2.6 N, and 2.5 ± 1.9 N, respectively. There were significant differences in ΔGT in both bundles after every 10 cycles (p < 0.01). ΔGT in the AM bundle was significantly lower than in the PM bundle at the same number of cycles (p < 0.01). No correlation was observed between ΔGT in either bundle and age, sex, or graft diameter.

CONCLUSIONS

The initially applied graft tension decreased by intra-operative cyclic knee movement, and the changes in graft tension decreased after retention and repeated cycles. Three sets of 10 cycles knee motion may avoid initial tension loss of the hamstring autograft in the early phase after double-bundle ACL reconstruction.

Evolution of functional tissue engineering for tendon and ligament repair

This review paper is motivated by a Back-to-Basics presentation given by the author at the 2022 Orthopaedic Research Society meeting in Tampa, Florida. I was tasked with providing a brief history of research leading up to the introduction of functional tissue engineering (FTE) for tendon and ligament repair. Beginning in the 1970s, this timeline focused on two common orthopedic soft tissue problems, anterior cruciate ligament ruptures in the knee and supraspinatus tendon injuries in the shoulder. Historic changes in the field over the next 5 decades revealed a transformation from a focus more on mechanics (called "bioMECHANICS") on a larger (tissue) scale to a more recent focus on biology (called "mechanoBIOLOGY") on a smaller (cellular and molecular) scale. Early studies by surgeons and engineers revealed the importance of testing conditions for ligaments and tendons (e.g., high strain rates while avoiding subject disuse and immobility) and the need to measure in vivo forces in these tissues. But any true tissue engineering and regeneration in these early decades was limited more to the use of auto-, allo- and xenografts than actual generation of stimulated cell-scaffold constructs in culture. It was only after the discovery of tissue engineering in 1988 and the recognition of frequent rotator cuff injuries in the early 1990s, that biologists joined surgeons and engineers to discover mechanical and biological testing criteria for FTE. This review emphasizes the need for broader and more inclusive collaborations by surgeons, biologists and engineers in the short term with involvement of those in biomaterials, manufacturing, and regulation of new products in the longer term.

Effects of Platelet-Rich Osteoconductive-Osteoinductive Allograft Compound on Tunnel Widening of ACL Reconstruction: A Randomized Blind Analysis Study

The anterior cruciate ligament (ACL) is a commonly injured ligament in the knee. Bone tunnel widening is a known phenomenon after soft-tissue ACL reconstruction and etiology and the clinical relevance has not been fully elucidated. Osteoconductive compounds are biomaterials providing an appropriate scaffold for bone formation such as a demineralized bone matrix. Osteoinductive materials contain growth factors stimulating bone lineage cells and bone growth. A possible application of osteoinductive/osteoconductive (OIC) material is in ACL surgery. We hypothesized that OIC placed in ACL bone tunnels: (1) reduces tunnel widening, (2) improves graft maturation, and (3) reduces tunnel ganglion cyst formation. To test this hypothesis, this study evaluated the osteogenic effects of demineralized bone matrix (DBM) and platelet-rich plasma (PRP) on tunnel widening, graft maturation, and ganglion cyst formation. This was a randomized controlled clinical trial pilot study. A total of 26 patients that elected to have ACL reconstruction surgery were randomized between the OIC and control group. Measurements of tunnel expansion and graft-tunnel incorporation were conducted via the quantitative image analysis of MRI scans performed at six months after surgery for both groups. No patients had adverse post-operative reactions or infections. The use of OIC significantly reduced tunnel widening (p < 0.05) and improved graft maturation (p < 0.05). Patients treated with OIC had a significantly lower prevalence of ganglion cyst compared to the control group (p < 0.05). The use of OIC has measurable effects on the reduction of tunnel widening, improved graft maturation, and decreased size of ganglion cyst after ACL reconstruction. This study explored the utilization of biologics to minimize bone tunnel widening in ACL reconstruction surgery.

Incidence and risk factors for symptomatic venous thromboembolism following anterior cruciate ligament reconstruction

PURPOSE

To determine the incidence of symptomatic venous thromboembolism (VTE) following anterior cruciate ligament (ACL) reconstruction using a large national database and to identify corresponding independent risk factors.

METHODS

The Humana administrative claims database was reviewed for patients undergoing ACL reconstruction from 2007 to 2017. Patient demographics, medical comorbidities, as well as concurrent procedures were recorded. Postoperative incidence of VTE was measured by identifying symptomatic deep vein thrombosis (DVT) and pulmonary embolism (PE) at 30 days, 90 days, and 1 year postoperatively. Univariate analysis and binary logistic regression were performed to determine independent risk factors for VTE following surgery.

RESULTS

A total of 11,977 patients were included in the study. The incidence of VTE was 1.01% (n = 120) and 1.22% (n = 146) at 30 and 90 days, respectively. Analysis of VTE events within the first postoperative year revealed that 69.6% and 84.3% of VTEs occurred within 30 and 90 days of surgery, respectively. Logistic regression identified age ≥ 45 (odds ratio [OR] = 1.88; 95% confidence interval [CI] 1.32-2.68; p < 0.001), inpatient surgery (OR = 2.07; 95% CI 1.01-4.24; p = 0.045), COPD (OR = 1.51; 95% CI 1.02-2.24; p = 0.041), and tobacco use (OR = 1.75; 95% CI 1.17-2.62; p = 0.007), as well as concurrent PCL reconstruction (OR = 3.85; 95% CI 1.71-8.67; p = 0.001), meniscal transplant (OR = 17.68; 95% CI 3.63-85.97; p < 0.001) or osteochondral allograft (OR = 15.73; 95% CI 1.79-138.43; p = 0.013) as independent risk factors for VTE after ACL reconstruction.

CONCLUSIONS

The incidence of symptomatic postoperative VTE is low following ACL reconstruction, with the majority of cases occurring within 90 days of surgery. Risk factors include age ≥ 45, inpatient surgery, COPD, tobacco use and concurrent PCL reconstruction, meniscal transplant or osteochondral allograft.

LEVEL OF EVIDENCE

III.

Biomechanics of hamstring tendon, quadriceps tendon, and bone-patellar tendon-bone grafts for anterior cruciate ligament reconstruction: a cadaveric study

PURPOSE

The three most commonly used autografts for anterior cruciate ligament reconstruction (ACL) are: bone-patellar tendon-bone (BTB), hamstring tendons (HT), and quadriceps tendon (QT). A cadaveric study was performed to determine if there were any differences in mechanical and structural properties under biomechanical testing.

METHODS

Twenty-seven graft specimens were harvested from 9 human cadaveric legs. Mean donor age was 75.2 years (range 53-85 years). Twenty-two specimens (8 HT, 7 QT, and 7 BTB) completed cyclic preconditioning from 50 to 800 N for 200 cycles and a load to failure test at an extension rate of 1 mm/s. Structural and mechanical properties of BTB, HT, and QT grafts were compared using a one-way ANOVA and Tukey's honest significant difference.

RESULTS

There was no difference in the ultimate load to failure (N) across all 3 graft types (p = 0.951). Quadriceps tendon demonstrated greater cross-sectional area (mm²) when compared to both HT and BTB (p = 0.001) and was significantly stiffer (N/mm) than HT but not BTB (p = 0.004). Stress (N/mm²) of the HT at ultimate load was greater than QT but not BTB (p = 0.036). Elastic modulus (MPa) of HT was greater than both QT and BTB (p = 0.016).

CONCLUSION

There was no difference in the ultimate load to failure of BTB, HT, and QT grafts harvested from the same specimens. All 3 grafts had similar loads to failure with a significant increase in stiffness when compared to the native ACL. Furthermore, QT demonstrated more favourable structural properties compared to HT and BTB with greater cross-sectional area to both HT and BTB and greater stiffness compared to HT.

Ultrasound Imaging of the Anterior Cruciate Ligament: A Pictorial Essay and Narrative Review

Ultrasound has been extensively applied to the diagnosis of and guided interventions for knee disorders. However, although it is commonly affected during sports injuries, the anterior cruciate ligament (ACL) is not usually incorporated in the majority of ultrasound scanning protocols. In the past, because of its oblique trajectory and deeper location, the ACL was considered to be a challenging structure for ultrasound imaging. Owing to advances in ultrasound technology and knowledge of knee sono-anatomy, an increasing number of studies are investigating the clinical value of ultrasound in the diagnosis and management of ACL injuries. In this regard, the present review aims to elaborate on the sono-anatomy of the ACL, to summarize the evidence for ultrasound imaging for ACL lesions and to investigate whether it is useful in the pre-operative preparation and post-operative follow-up of ACL reconstruction.

Effects of Innovative Land-based Proprioceptive Training on Knee Joint Position Sense and Function in Athletes with Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial

Background: Proprioceptive deficits are one of the most important challenges after anterior cruciate ligament reconstruction (ACLR). Objectives: The current study aimed to investigate the effects of incorporating innovative land-based proprioceptive training into the conventional accelerated land-based rehabilitation protocol, as compared to the conventional accelerated land-based rehabilitation protocol alone, on knee function and joint position sense in male athletes after ACLR. Methods: Thirty male athletes with ACLR were randomly assigned to two rehabilitation groups. The conventional therapy (CT) group (n = 15) received conventional rehabilitation for six weeks, and the proprioception training (PT) group (n = 15) received the same conventional rehabilitation in addition to 12 sessions of innovative land-based proprioceptive training. Outcomes included joint position sense (JPS) errors, International Knee Documentation Committee (IKDC) form, and Visual Analog Scale (VAS). Results: There were significant differences in absolute errors (AE) (FAE = 56.81, P < 0.001) and variable errors (VE) (FVE = 60.95, P < 0.001) between the two groups. No significant differences were found in constant error (CE), VAS, and IKDC score between the two groups (P > 0.05). Both groups showed significant changes in terms of AE, VE, VAS, and IKDC after the intervention (P < 0.05). Percent changes after the intervention for AE, VE, CE, VAS, and IKDC were greater in the PT group than in the CT group, which were 70.19%, 69.22%, 66.20%, 38.50%, and 39.61%, respectively. Conclusions: Innovative land-based proprioceptive training incorporated into the conventional accelerated rehabilitation protocol offers the improvement of proprioception efficiency for individuals with ACL reconstruction, and therefore, it could be useful for clinicians when designing rehabilitation protocols to ensure the optimal engagement of proprioception.

A Review on Finite Element Modeling and Simulation of the Anterior Cruciate Ligament Reconstruction

The anterior cruciate ligament (ACL) constitutes one of the most important stabilizing tissues of the knee joint whose rapture is very prevalent. ACL reconstruction (ACLR) from a graft is a surgery which yields the best outcome. Taking into account the complicated nature of this operation and the high cost of experiments, finite element (FE) simulations can become a valuable tool for evaluating the surgery in a pre-clinical setting. The present study summarizes, for the first time, the current advancement in ACLR in both clinical and computational level. It also emphasizes on the material modeling and properties of the most popular grafts as well as modeling of different surgery techniques. It can be concluded that more effort is needed to be put toward more realistic simulation of the surgery, including also the use of two bundles for graft representation, graft pretension and artificial grafts. Furthermore, muscles and synovial fluid need to be included, while patellofemoral joint is an important bone that is rarely used. More realistic models are also required for soft tissues, as most articles used isotropic linear elastic models and springs. In summary, accurate and realistic FE analysis in conjunction with multidisciplinary collaboration could contribute to ACLR improvement provided that several important aspects are carefully considered.

Return to Play and Career Length After Anterior Cruciate Ligament Reconstruction Among Canadian Professional Football Players

BACKGROUND

For many athletes, a tear of the anterior cruciate ligament (ACL) represents a significant injury that requires a prolonged period away from the sport with substantial rehabilitation.

HYPOTHESIS

There will be no difference in return to play (RTP) and career length after hamstring tendon (HT) ACL reconstruction in a group of Canadian Football League professional players as compared with what has been already been reported in the literature among professional football players.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Data on athletes who sustained an ACL injury were collected by team physicians and head athletic trainers from 2002 to 2017 from 2 Canadian Football League teams. Patient details included age at the time of injury, initial injury date, position, practice versus game injury, and primary versus rerupture with injury-specific data, such as affected limb, concomitant injuries, graft choice, and procedure performed. RTP rates and career length data were collected through publically available internet sources. Comparisons between the non-RTP and RTP groups were made with independent-sample t tests. Binomial logistic regression was performed to determine variables (ie, games preinjury, graft type, meniscal injury, collateral ligament injury) that contributed to players not being able to RTP.

RESULTS

A total of 44 ACL reconstructions were performed over the study period (HT, n = 32 [72.7%]; bone-patellar tendon-bone [BPTB], n = 8 [18.2%]; allograft, n = 4 [9.1%]). Overall, 69.8% (n = 30) were able to RTP in at least 1 game, while 30.2% (n = 13) did not return. Mean time to return was 316.1 days (range, 220-427 days), or 10.4 months. For those players who did RTP, mean career length after ACL reconstruction was 2.8 seasons, or 34.4 games. The majority (56.8%) of injuries occurred early in the season. Breakdown by graft type demonstrated RTP rates among HT, BPTB, and allograft of 64.5% (n = 20), 87.5% (n = 7), and 75% (n = 3), respectively. Career length among HT, BPTB, and allograft was 2.9, 2.4, and 3 seasons. Logistic regression analysis found only concomitant medial collateral ligament (MCL) injuries to be a negative predictor for RTP. Meniscal injuries were associated with a decreased RTP rate and career length, but this was not statistically significant.

CONCLUSION

The RTP rates after ACL reconstruction in this study are similar to those reported in National Football League players. A concomitant injury to the MCL injury was a negative predictor of RTP. Meniscal injuries demonstrated a trend for decreased RTP rate and career length, but this was not a significant predictor. A large portion of injuries occur early in the season, and further study should be done to examine potential preventative strategies to reduce ACL injuries.

Engagement of the Secondary Ligamentous and Meniscal Restraints Relative to the Anterior Cruciate Ligament Predicts Anterior Knee Laxity

BACKGROUND

Patients with high-grade preoperative side-to-side differences in anterior laxity as assessed via the Lachman test after unilateral anterior cruciate ligament (ACL) rupture are at heightened risk of early ACL graft failure. Biomechanical factors that predict preoperative side-to-side differences in anterior laxity are poorly understood.

PURPOSE

To assess, in a cadaveric model, whether the increase in anterior laxity caused by sectioning the ACL (a surrogate for preoperative side-to-side differences in anterior laxity) during a simulated Lachman test is associated with two biomechanical factors: (1) the tibial translation at which the secondary anterior stabilizers, including the remaining ligaments and the menisci, begin to carry force, or engage, relative to that of the ACL or (2) the forces carried by the ACL and secondary stabilizers at the peak applied anterior load.

STUDY DESIGN

Controlled laboratory study.

METHODS

Seventeen fresh-frozen human cadaveric knees underwent Lachman tests simulated through a robotic manipulator with the ACL intact and sectioned. The net forces carried by the ACL and secondary soft tissue stabilizers (the medial meniscus and all remaining ligaments, measured as a whole) were characterized as a function of anterior tibial translation. The engagement points of the ACL (with the ACL intact) and each secondary stabilizer (with the ACL sectioned) were defined as the anterior translation at which they began to carry force, or engaged, during a simulated Lachman test. Then, the relative engagement point of each secondary stabilizer was defined as the difference between the engagement point of each secondary stabilizer and that of the ACL. Linear regressions were performed to test each association (P < .05).

RESULTS

The increase in anterior laxity caused by ACL sectioning was associated with increased relative engagement points of both the secondary ligaments (β = 0.87; P < .001; R² = 0.75) and the medial meniscus (β = 0.66; P < .001; R² = 0.58). Smaller changes in anterior laxity were also associated with increased in situ medial meniscal force at the peak applied load when the ACL was intact (β = -0.06; P < .001; R² = 0.53).

CONCLUSION

The secondary ligaments and the medial meniscus require greater anterior tibial translation to engage (ie, begin to carry force) relative to the ACL in knees with greater changes in anterior laxity after ACL sectioning. Moreover, with the ACL intact, the medial meniscus carries more force in knees with smaller changes in anterior laxity after ACL sectioning.

CLINICAL RELEVANCE

Relative tissue engagement is a new biomechanical measure to characterize in situ function of the ligaments and menisci. This measure may aid in developing more personalized surgical approaches to reduce high rates of ACL graft revision in patients with high-grade laxity.

No Difference between Extraction Drilling and Serial Dilation for Tibial Tunnel Preparation in Anterior Cruciate Ligament Reconstruction: A Systematic Review

Importance

This review highlights a lack of consensus and need for further study regarding optimal tibial tunnel preparation method in anterior cruciate ligament reconstruction (ACLR).

Objective

This review examines existing clinical and biomechanical outcomes of both extraction drilling (ED) and serial dilation (SD) as a technique for tibial tunnel preparation in ACLR.

Evidence Review

In accordance with PRISMA guidelines, three electronic databases (MEDLINE, EMBASE, and PubMed) were searched and systematically screened in duplicate from database inception to September 6, 2017 for English-language, human studies, of all levels of evidence that examined ED and/or SD for tibial tunnel preparation in ACLR. Data including patient demographics, tibial tunnel preparation techniques, biomechanical and clinical outcomes and complications were retrieved from eligible studies.

Findings

ED was used in 71 patients, who were mean age 29.9 years (range: 17-50), 68% male, and followed for mean 16.5 months (range: 3.8-46). SD was used in 70 patients (70 knees), who were mean age 29.3 years (range: 18-50), 69% male, and followed for mean 14.1 months (range: 3.8-46). There were no statistically significant differences (mean preoperative; mean postoperative) for either tibial preparation technique for Lysholm (50.1; 92.5), Tegner (3.5; 6.1), International Knee Documentation Committee (IKDC) (48.8; 92.7), and Lachman or laxity scores. However, ED demonstrated statistically significant increased postoperative tibial tunnel expansion (1.8 mm versus 1.4 mm) and (at 12 weeks) graft migration at the tibial fixation site (1.3 mm versus 0.8 mm). Across biomechanical studies, there were no statistically significant differences (ED; SD) with forces required to initiate graft slippage (156 N; 174 N), graft stiffness (187 N; 186.5 N), and screw torque (1.6 N/m; 1.8 N/m). ED demonstrated a lower mean load to failure for the graft construct (433 N versus 631 N; p<0.05).

Conclusions and Relevance

Though biomechanical data demonstrated lower mean load to failure for the graft using ED, clinical data suggest increased tibial tunnel expansion and post-operative graft migration at the tibial fixation site. Future studies with long-term follow-up data are required to ascertain the optimal technique for graft incorporation and postoperative success.

Level of Evidence

IV:Systematic Review of Level I-IV studies.

A new femoral fixation device for anterior cruciate ligament reconstruction using the outside-in technique and hamstring tendon graft: A comparison between two devices in cadaveric human knee models

BACKGROUND

A new device (T-anchor) was developed for ACL reconstruction and is implanted via the outside-in technique using hamstring grafts. The purpose of this study was to compare the T-anchor with the EndoButton Direct.

METHODS

This study was conducted on 30 cadaveric knees (15 matched pairs). There were two groups of 15 each in the T-anchor and EndoButton Direct groups. After the harvest of grafts, fixation site profile and graft length were measured by loading the grafts onto both devices. They were then tested on a universal testing machine to assess elongation after cyclic loading, load to failure, ultimate load, and mode of failure.

RESULTS

The fixation site profile was lower in the T-anchor group than in the EndoButton Direct group (2.3±0.4mm vs. 4.7±1.0mm, P<0.001). The length of the graft-device complex of the T-anchor specimens was longer than that of the EndoButton Direct specimens (125.0±8.9mm vs. 115.0±8.7mm, P<0.001). The mean cyclic elongation was lower for the T-anchor group when compared with the EndoButton Direct group (2.4±0.6mm vs. 3.9±2.6mm, P=0.015). There was no statistically significant difference in ultimate load and load to failure between the T-anchor and EndoButton Direct groups. For mode of failure, the T-anchor fared better (P=0.013) with all failures attributed to specimens.

CONCLUSIONS

In this cadaveric study, the new device, T-anchor, performed better than the EndoButton Direct with respect to the above-mentioned study parameters except for ultimate load and load to failure.

Osteogenic and tenogenic induction of hBMSCs by an integrated nanofibrous scaffold with chemical and structural mimicry of the bone–ligament connection

A novel electrospinning nanofiber collecting device was designed and utilized to fabricate an integrated PCL nanofibrous scaffold with a “random–aligned–random” structure.

Anterior Cruciate Ligament: Structure, Injuries and Regenerative Treatments

Anterior cruciate ligament (ACL) is one of the most vulnerable ligaments of the knee. ACL impairment results in episodic instability, chondral and meniscal injury and early osteoarthritis. The poor self-healing capacity of ACL makes surgical treatment inevitable. Current ACL reconstructions include a substitution of torn ACL via biological grafts such as autograft, allograft. This review provides an insight of ACL structure, orientation and properties followed by comparing the performance of various constructs that have been used for ACL replacement. New approaches, undertaken to induce ACL regeneration and fabricate biomimetic scaffolds, are also discussed.

Effect of perturbing a simulated motion on knee and anterior cruciate ligament kinetics

Current surgical treatments for common knee injuries do not restore the normal biomechanics. Among other factors, the abnormal biomechanics increases the susceptibility to the early onset of osteoarthritis. In pursuit of improving long term outcome, investigators must understand normal knee kinematics and corresponding joint and anterior cruciate ligament (ACL) kinetics during the activities of daily living. Our long term research goal is to measure in vivo joint motions for the ovine stifle model and later simulate these motions with a 6 degree of freedom (DOF) robot to measure the corresponding 3D kinetics of the knee and ACL-only joint. Unfortunately, the motion measurement and motion simulation technologies used for our project have associated errors. The objective of this study was to determine how motion measurement and motion recreation error affect knee and ACL-only joint kinetics by perturbing a simulated in vivo motion in each DOF and measuring the corresponding intact knee and ACL-only joint forces and moments. The normal starting position for the motion was perturbed in each degree of freedom by four levels (-0.50, -0.25, 0.25, and 0.50 mm or degrees). Only translational perturbations significantly affected the intact knee and ACL-only joint kinetics. The compression-distraction perturbation had the largest effect on intact knee forces and the anterior-posterior perturbation had the largest effect on the ACL forces. Small translational perturbations can significantly alter intact knee and ACL-only joint forces. Thus, translational motion measurement errors must be reduced to provide a more accurate representation of the intact knee and ACL kinetics. To account for the remaining motion measurement and recreation errors, an envelope of forces and moments should be reported. These force and moment ranges will provide valuable functional tissue engineering parameters (FTEPs) that can be used to design more effective ACL treatments.

The Effect of the Variation in ACL Constitutive Model on Joint Kinematics and Biomechanics Under Different Loads: A Finite Element Study

The biomechanics and function of the anterior cruciate ligament (ACL) have been widely studied using both experimental and simulation methods. It is known that a constitutive model of joint tissue is a critical factor in the numerical simulation. Some different ligament constitutive models have been presented to describe the ACL material behavior. However, the effect of the variation in the ligament constitutive model on joint kinematics and biomechanics has still not been studied. In this paper, a three-dimensional finite element model of an intact tibiofemoral joint was reconstructed. Three ACL constitutive models were compared under different joint loads (such as anterior tibial force, varus tibial torque, and valgus tibial torque) to investigate the effect of the change of the ACL constitutive model. The three constitutive models corresponded to an isotropic hyperelasticity model, a transversely isotropic hyperelasticity model with neo-Hookean ground substance description, and a transversely isotropic hyperelastic model with nonlinear ground substance description. Although the material properties of these constitutive equations were fitted on the same uniaxial tension stress-strain curve, the change of the ACL material constitutive model was found to induce altered joint kinematics and biomechanics. The effect of different ACL constitutive equations on joint kinematics depended on both deformation direction and load type. The variation in the ACL constitutive models would influence the joint kinematic results greatly in both the anterior and internal directions under anterior tibial force as well as some other deformations such as the anterior and medial tibial translations under valgus tibial torque, and the medial tibial translation and internal rotation under varus torque. It was revealed that the transversely isotropic hyperelastic model with nonlinear ground substance description (FE model III) was the best representation of the realistic ACL property by a linear regression between the simulated and the experiment deformation results. But the comparison of the predicted and experiment force of ligaments showed that all the three ACL constitutive models represented similar force results. The stress value and distribution of ACL were also altered by the change in the constitutive equation. In brief, although different ACL constitutive models have been fitted using the same uniaxial tension curve and have the similar longitudinal material property, the ACL constitutive equation should still be carefully chosen to investigate joint kinematics and biomechanics due to the different transverse material behavior.

The effect of early whole-body vibration therapy on neuromuscular control after anterior cruciate ligament reconstruction: a randomized controlled trial

BACKGROUND

Despite rehabilitation training, deficiency in knee joint position sense, muscular performance, postural control, and functional ability is common after anterior cruciate ligament reconstruction (ACLR). Whole-body vibration therapy (WBVT), which is initiated from 3 months postoperatively, has proven benefits. However, the effect of earlier WBVT is unknown.

PURPOSE

To investigate the effect of early WBVT on neuromuscular control after ACLR.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

A total of 48 patients with unilateral complete isolated ACL tears were recruited. Single-bundle hamstring ACLR was performed in all patients. After surgery, they were randomly assigned to either the reference or treatment group. Reference group patients received conventional ACL rehabilitation, while treatment group patients received 8 weeks of WBVT in addition to conventional rehabilitation, starting from 1 month postoperatively. Joint position sense, postural control, and knee isokinetic performance were assessed before surgery and at 1, 3, and 6 months postoperatively using the Biodex dynamometer, Biodex Stability System, and Cybex NORM, respectively. Knee range of motion (ROM), stability (manual testing and KT-1000 arthrometer), and functional ability (single-legged hop test, triple hop test, shuttle run test, and carioca test) were also examined. Two-way repeated-measures analysis of variance and the Mann-Whitney U test were used for statistical analysis.

RESULTS

There was no complication throughout the rehabilitation. All patients achieved full knee ROM and stable knee joints at 6 months after surgery. The WBVT group demonstrated significantly better postural control, muscle performance, single-legged hop, and shuttle run (P < .05) than the reference group, but there was no significant difference in knee joint position sense, triple hop, carioca, ROM, and stability (P > .05).

CONCLUSION

Early WBVT started from 1 month postoperatively was an effective training method without compromising knee ROM and stability. It improved postural control, isokinetic performance, single-legged hop, and shuttle run but not knee joint position sense, triple hop, and carioca.

Design Considerations for a Prosthetic Anterior Cruciate Ligament

Anterior cruciate ligament (ACL) tearing is a common knee injury often requiring reconstruction with an autograft or an allograft. A prosthetic ligament replacement with off-the-shelf availability could potentially provide significant advantages over the current options for both patients and surgeons. Limitations of previous prosthetics include lack of biocompatibility and susceptibility to fatigue, creep, and failure of bony incorporation. This paper describes design considerations and possible improvements for the next generation prosthetic ACL. Design controls, as mandated by the FDA, are a systematic set of practices within the design and development process used to ensure that a new medical device meets the needs of the intended users. The specified requirements, called the design inputs, for a prosthetic ACL are discussed pertaining to material and structural properties, resistance to creep and fatigue, ability to support secure initial fixation, biocompatibility, and long-term osseointegration. Design innovations to satisfy the design inputs are discussed with regards to material selection, textile pattern, bone tunnel features, and short term fixation. A risk analysis is presented along with descriptions of proposed testing. Design control methodology and tissue engineering may be used to develop a next generation prosthetic ligament, solving multiple problems, simultaneously, on a holistic level, providing major improvements over earlier devices and current treatment options.

Most british surgeons would consider using a tissue-engineered anterior cruciate ligament: a questionnaire study

Donor site morbidity, poor graft site integration, and incorrect mechanical performance are all common problems associated with autografts for anterior cruciate ligament (ACL) reconstructions. A tissue-engineered (TE) ligament has the potential to overcome these problems. We produced an online questionnaire relating to tissue engineering of the ACL to obtain input from practising clinicians who currently manage these injuries. 300 British orthopaedic surgeons specialising in knee surgery and soft tissue injury were invited to participate. 86% of surgeons would consider using a TE ACL if it were an option, provided that it showed biological and mechanical success, if it significantly improved the patient satisfaction (63%) or shortened surgical time (62%). 76% felt that using a TE ACL would be more appropriate than a patellar tendon, hamstring, or quadriceps autograft. Overall, most surgeons would be prepared to use a TE ACL if it were an improvement over the current techniques.

Differential cross-linking and radio-protective effects of genipin on mature bovine and human patella tendons

Gamma irradiation is a proven sterilization method, but is not widely used on allografts for anterior cruciate ligament reconstruction (e.g., patella tendon) due to radiation-induced decreases in mechanical strength. Addressing this drawback would improve the safety and supply of allografts to meet current and future demand. It was hypothesized that genipin-induced collagen cross-linking would increase the tensile modulus of patella tendon tissue such that 5 MRad gamma irradiation would not reduce the tissue mechanical strength below the original untreated values. Optimized genipin treatment increased the tensile modulus of bovine tendons by ~2.4-fold. After irradiation, genipin treated tissue did not significantly differ from native tissue, proving the hypothesis. Optimized genipin treatment of human tendons increased the tensile modulus by ~1.3-fold. After irradiation, both control and genipin-treated tissues possessed ~50-60% of their native tendon modulus, disproving the hypothesis. These results highlight possible age- and species- dependent effects of genipin cross-linking on tendon tissue. Cross-linking of human allografts may be beneficial only in younger donor tissues. Future research is warranted to better understand the mechanisms and applications of collagen cross-linking for clinical use.

Biocompatibility of polyhydroxyalkanoate as a potential material for ligament and tendon scaffold material

There is a strong need for new biodegradable materials that are suitable for scaffolds in tissue engineering of tendons and ligaments. In many cases, quick degradation rates are favorable, however, with respect to ligament and tendon replacement, slowly degrading polymers are clearly favored. Prime candidates are members of the large class of polyhydroxyalkanoates (PHAs), which are thermoplastic/elastomeric biopolyesters that are slowly degraded by surface erosion. Moreover, their physico-mechanical properties can be tailored during biosynthesis in bacteria or by chemical modifications. They may be spun into fibers, coated on surfaces or be part of composites. This study has investigated the biocompatability of seven different thermoplastic or elastomeric PHAs using L929 murine fibroblast cells. Cell viability and proliferation over 7 days was analyzed with live/dead staining and a picogreen assay. In addition, extracellular matrix production was measured with the hydroxyproline assay after 14 days. It was found that cell attachment to the PHA film ranged from 85-99% after 7 days. Three PHA films (PHBV (92/8), PHOUE-POSS and PHUE-O3) supported similar cell viability in comparison to the controls performed on tissue culture plastic (polystyrene), whereas the biomaterials (PHUA, PHUE, PHB and PHOUE) showed fewer viable cells than in controls. PHB, PHUE-O3, and PHBV with a water contact angle below 85 degrees supported a similar amount of collagen production in comparison to the tissue culture plastic controls. PHUA, PHUE, PHOUE, and PHOUE-POSS showed a decrease in collagen production in comparison to the controls after 14 days. Overall, PHB, PHBV, and PHUE-O3 demonstrated good performance with regards to potential use as a tissue-engineering scaffold.

Functional tests should be accentuated more in the decision for ACL reconstruction

A high pre-injury activity level, the desire of the patient to continue pivoting sports and fear of future give-way episodes are considered the most significant factors affecting the decision to perform anterior cruciate ligament reconstruction. However, since the functional status of the knee at the time of surgery affects the final outcome, assessments of knee function should be considered in the decision making for surgery. Individuals with anterior cruciate ligament injury can be classified as potential copers or non-copers from an existing screening examination. The purpose of this study was to investigate whether the functional tests incorporated in the original screening examination could contribute to explain those who later go through anterior cruciate ligament reconstruction and to examine whether changes to the content or the time of conducting the screening examination (before or after ten sessions of exercise therapy) could improve its explanatory value. One-hundred and forty-five individuals were included and prospectively followed for 15 months, after where 51% had gone through anterior cruciate ligament reconstruction and 49% were managed non-operatively. The only significant baseline differences between those who later went through anterior cruciate ligament reconstruction and those who were non-operatively treated were that those who had surgery were younger and had a higher activity level (P < 0.05). Regression analyses revealed that the explanatory value for those who later went through anterior cruciate ligament reconstruction significantly improved when the original screening examination was considered compared to only age, activity level and give-way episodes. Changes to the content further improved the explanatory value, with quadriceps muscle strength as the single variable with the highest impact. Finally, conducting the screening examination after ten sessions of progressive exercise therapy gave the overall highest explanatory values, suggesting that the screening examination should be conducted subsequent to a short period of rehabilitation to inform decision making for anterior cruciate ligament reconstruction.

Mechanical properties of radiation-sterilised human Bone-Tendon-Bone grafts preserved by different methods

Patellar tendon auto- and allo-grafts are commonly used in orthopedic surgery for reconstruction of the anterior cruciate ligaments (ACL). Autografts are mainly used for primary reconstruction, while allografts are useful for revision surgery. To avoid the risk of infectious disease transmission allografts should be radiation-sterilised. As radiation-sterilisation supposedly decreases the mechanical strength of tendon it is important to establish methods of allograft preservation and sterilisation assuring the best quality of grafts and their safety at the same time. Therefore, the purpose of this study was to compare the tensile strength of human patellar tendon (cut out as for ACL reconstruction), preserved by various methods (deep fresh freezing, glycerolisation, lyophilisation) and subsequently radiation-sterilised with doses of 0, 25, 50 or 100 kGy. Bone-Tendon-Bone grafts (BTB) were prepared from cadaveric human patella tendons with both patellar and tibial attachments. BTB grafts were preserved by deep freezing, glycerolisation or lyophilisation and were subsequently radiation-sterilised with doses of 0 (control), 25, 50 or 100 kGy. All samples were subjected to mechanical failure tensile tests with the use of Instron system in order to estimate their mechanical properties. All lyophilised grafts were rehydrated before performing of those tests. Obtained mechanical tests results of examined grafts suggest that deep-frozen irradiated grafts retain their initial mechanical properties to an extent which does not exclude their clinical application.