Biomechanical study of ACL reconstruction grafts

Single bundle hamstrings autograft preparation techniques for anterior cruciate ligament reconstruction: current concepts

Anterior cruciate ligament reconstruction (ACLR) is one of the most common orthopedic procedures, and huge variation exists in the surgical technique. Single bundle hamstrings autograft reconstruction is a common method and has good clinical outcomes. A criticism of the hamstrings autograft is a small graft diameter, often less than 8-mm, which has been associated with increased re-rupture rates. Several graft preparation techniques for single bundle hamstrings autograft exist. Perioperative decisions include the number of tendons utilized, number of graft strands, graft configuration, and femoral and tibial fixation methods. Awareness of the minimum tendon and graft length required to produce each graft variation is necessary to avoid common pitfalls. However, intraoperative graft modification is possible to maximize graft diameter, and obtain proper fixation. The objective of this current concepts review is to describe the indications, surgical anatomy, technique, intraoperative tips, clinical outcomes, and complications for single bundle hamstrings autograft preparation techniques in ACLR.

Biomechanical characteristics of the meniscocapsular junction of the posterior segment of the medial meniscus

PURPOSE

Despite extensive literature available on the mechanical properties of knee ligaments and menisci, research on the mechanical properties of the meniscus-capsular junction (MCJ) is lacking. This study aims to investigate the biomechanical behavior of the MCJ of the medial meniscus using a tensile failure test.

MATERIALS AND METHODS

Seven dissected cadaveric knees were used for biomechanical analysis. Tensile failure tests were performed using an INSTRON ElectroPuls E1000 stress system to measure stress/strain curves, maximum load at failure, elastic limit load, elongation at break, elongation at the elastic limit, and linear stiffness, were collected and analyzed.

RESULTS

All ruptures occurred at the MCJ. The MCJ displayed similar mechanical properties to knee ligaments. Average values were: maximum load at failure (63.9 ± 3.2 N), yield load (52.9 N ± 2.6 N), elongation at break (2.5 mm ± 0.3 mm), elongation at the elastic limit (1.25 mm ± 0.15 mm), strain at break (47.0% ± 3.5%), strain at yield (23.2% ± 2.3%), and stiffness (56.6 ± 9. N/mm-1).

CONCLUSION

The meniscus-capsular junction's mechanical properties are similar to other knee ligaments and may play a role in knee stability. The findings provide insights into the the behavior of the meniscus-capsular junction could have clinical implications for diagnosing and surgical treatment of meniscocapsular lesions.

Plastic and elastic biomechanical properties of anterior cruciate ligament autografts

BACKGROUND

Anterior cruciate ligament (ACL) rupture is a common orthopedic injury, occurring in roughly 68.6 per 100,000 persons annually, with the primary treatment option being ACL reconstruction. However, debate remains about the appropriate graft type for restoring the native biomechanical properties of the knee. Furthermore, plastic graft elongation may promote increased knee laxity and instability without rupture. This study aims to investigate the plastic properties of common ACL-R graft options.

METHODS

Patellar tendon (PT), hamstring tendon (HT), and quadriceps tendon (QT) grafts were harvested from 11 cadaveric knees (6 male and 5 female) with a mean age of 71(range 55-81). All grafts were mechanically tested under uniaxial tension until failure to determine each graft's elastic and plastic biomechanical properties.

RESULTS

Mechanically, the QT graft was the weakest, exhibiting the lowest failure force and the lowest failure stress (QT < HT, p = 0.032). The PT was the stiffest of the grafts, having a significantly higher stiffness (PT > QT, p = 0.0002) and Young's modulus (PT > QT, p = 0.001; PT > HT, p = 0.041). The HT graft had the highest plastic elongation at 4.01 ± 1.32 mm (HT > PT, p = 0.002). The post-yield behavior of the HT tendon shows increased energy storage capabilities with the highest plastic energy storage (HT > QT, p = 0.012) and the highest toughness (HT > QT, p = 0.032).

CONCLUSION

Our study agrees with prior studies indicating that the failure load of all grafts is above the requirements for everyday activities. However, grafts may be susceptible to yielding before failure during daily activities. This may result in the eventual loss of functionality for the neo-ACL, resulting in increased knee laxity and instability.

Preserving the Semitendinosus Distal Attachment Is Associated With Improved Graft Remodeling After ACL Reconstruction

BACKGROUND

The semitendinosus (ST) tendon can be used by itself as a graft for anterior cruciate ligament (ACL) reconstruction. An increasing number of these procedures are being done while preserving the ST's tibial attachment, but there are no data on the remodeling of an attached ST (aST) graft.

PURPOSE

To compare graft remodeling on magnetic resonance imaging (MRI) scans at 1 year after ACL reconstruction between standard free ST graft and aST graft.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

This prospective study enrolled 180 patients who were undergoing ACL reconstruction: 90 with the ST graft and 90 with the aST graft. The analysis was performed 1 year after the surgery. The main endpoint was the signal-to-noise quotient (SNQ) on MRI scans (T1-weighted sequence). The secondary endpoints were tibial tunnel widening (TTW), graft maturation (Howell classification), retear rate, new surgery rate, Simple Knee Value, Lysholm score, International Knee Documentation Committee (IKDC) score, postoperative Tegner score, difference between pre- and postoperative Tegner scores, ACL-Return to Sport after Injury (ACL-RSI), return-to-sports rate, and time to return to sports.

RESULTS

The mean adjusted SNQ was 1.18 (95% CI, 0.72-1.65) in the aST group and 3.88 (95% CI, 3.42-4.34) in the ST group (P < .001). The new surgery rate was 2.2% in the aST group and 10% in the ST group (P = .029). The median Lysholm score was significantly higher in the aST group (99; interquartile range [IQR], 95-100) than in the ST group (95; IQR, 91-99) (P = .004). The mean time to return to sports was significantly shorter in the aST group (248.73 ± 141.62 days) than the ST group (317.23 ± 144.69 days) (P = .002). No statistically significant difference was found between groups in the TTW (P = .503), Howell graft maturity grade (P = .149), retear rate (P > .999), Simple Knee Value (P = .061), postoperative Tegner score (P = .320), pre- to postoperative difference in Tegner score (P = .317), ACL-RSI (P = .097), IKDC score (P = .621), and return-to-sports rate (P > .999).

CONCLUSION

At 1 year postoperatively, remodeling of an ST graft assessed using MRI is better when its distal attachment is left intact.

Characterizing the viscoelastic properties of the anterolateral ligament and grafts commonly used in its reconstruction

BACKGROUND

Current anatomic anterolateral ligament reconstruction is typically performed using either a gracilis tendon or an iliotibial band graft based on their quasi-static behavior. However, there is limited knowledge about their viscoelastic behaviors. This study aimed to characterize the viscoelastic properties of the anterolateral ligament, distal iliotibial band, distal gracilis tendon and proximal gracilis tendon for graft material choice in anterolateral ligament reconstruction.

METHODS

All the tissues were harvested from thirteen fresh-frozen cadaveric knees and subjected to preconditioning (3-6 MPa), sinusoidal cycle (1.2-12 MPa), dwell at constant load (12 MPa), and load to failure (3%/s). The quasi-static and viscoelastic properties of the soft tissues were computed and compared using a linear mixed model (p < 0.05).

FINDINGS

The hysteresis of anterolateral ligament (mean:0.4 Nm) was comparable with gracilis halves (p > 0.85) but iliotibial band (6 Nm) was significantly higher (p < 0.001,ES = 6.5). In contrast, the dynamic creep of anterolateral ligament (0.5 mm) was similar to iliotibial band (0.7 mm, p > 0.82) whereas both gracilis halves were significantly lower (p < 0.007,ES > 1.4). The elastic modulus of anterolateral ligament (181.4 MPa, p < 0.001,ES > 2.1) was the lowest compared to the grafts materials (distal gracilis tendon:835 MPa, distal gracilis tendon:726 MPa, iliotibial band:910 MPa). Additionally, the failure load of the anterolateral ligament (124.5 N, p < 0.001,ES > 2.9) was also the lowest.

INTERPRETATION

The mechanical properties of the gracilis halves and iliotibial band were significantly different from anterolateral ligament, except for hysteresis and dynamic creep, respectively. Our findings showed that the gracilis halves may be a more appropriate graft choice for anterolateral ligament reconstruction due to its low energy dissipation and permanent deformation under dynamic loads.

Less than 1% risk of donor-site quadriceps tendon rupture post-ACL reconstruction with quadriceps tendon autograft: a systematic review

PURPOSE

The purpose of this study is to develop a comprehensive complications profile for quadriceps tendon-autograft anterior cruciate ligament reconstruction (QT ACL-R).

METHODS

A traditional and grey literature search was conducted in accordance with PRISMA and R-AMSTAR guidelines. PubMed, EMBASE, MEDLINE, CINAHL, Cochrane, Web of Science, and many grey literature sources were searched from inception to May 29, 2022. All studies were searched and screened in duplicate with included studies being of all levels of evidence, reporting complications, and with patients of all ages undergoing primary ACL reconstruction with quadriceps tendon autograft in the last 15 years. Studies were excluded if they had cadaveric or animal subjects or were reviews. Risk of bias assessment was conducted using MINORS criteria for non-randomised studies and Cochrane's RoB 2.0 for randomised studies. Data were summarised with weighted event rates generated under a random-effects model.

RESULTS

A total of 55 studies (5315 reconstructions) were included: 32 used quadriceps tendon with bone block (B-QT), 19 used all-soft tissue quadriceps tendon (S-QT), and four did not report the QT graft subtype used. Included patients had an age range of 6.2-58 years and an average reported follow-up time of 28.1 months (range, 6-90 months) for non-randomised studies and 34.3 months (range, 0.233-120 months) for randomised studies. Pooled incidence rates for clinically relevant major complications included contralateral ACL injury at 6.0%, postoperative meniscal issues at 5.4%, cyclops lesions at 4.8%, graft failure at 4.1%, patellar fracture at 2.2%, hardware removal at 1.7%, infection at 1.5%, and donor-site quadriceps tendon rupture at 0.7%. Pooled incidence rates for clinically relevant minor complications included anterior knee pain at 9.7%, kneeling pain at 9.5%, sensation deficits at 4.4%, loss of extension at 4.2%, donor-site tendinopathy at 3.9%, cosmetic issues at 1.8%, and hematoma at 1.5%.

CONCLUSIONS

QT ACL-R resembles other graft types in its rates and types of postoperative complications. In this exploratory systematic review, no complications of QT ACL-R were found to be disproportionately represented in the literature. This graft type should remain an option with comparable complication rates to other graft choices.

LEVEL OF EVIDENCE

Level IV.

REGISTRATION

This study was preregistered under PROSPERO with preregistration code CRD42022302078.

Hamstring Graft Preparation for ACL Reconstruction

Anterior cruciate ligament (ACL) reconstruction represents one of the most common procedures in orthopedic surgery. It usually involves the harvest of both gracilis and semitendinosus tendons from the ipsilateral knee. Different methods of hamstring graft preparation have been proposed in recent years, to create an adequate graft diameter reducing morbidity linked to gracilis tendon harvesting procedure. More recently, the use of only 1 of the tendons (semitendinosus) in a tripled or quadrupled arrangement has been described, especially in an all-inside type of reconstruction. Having a thicker tendon with a quadrupled semitendinosus (ST), instead of double gracilis and ST enables to have a graft with enough diameter to resemble more closely the native ACL and decreases the risk of graft re-rupture. The present study aims to describe different options of hamstring graft preparing, listing and analyzing each configuration to help surgeons to choose the most suitable graft type for their patients.

Categorize the existing clamps used for tensile test of human graft- a systematic review

BACKGROUND

The use of tendon allografts for orthopedic repair has gained wide acceptance in recent years, most notably in anterior cruciate tendon reconstruction. Multiple studies support the use of tendon allografts and the benefits of its use are well accepted and understood. One of the important criteria of the use of tendon allografts is statistically similar histological and biomechanical properties to autographs. The aim of this systematic literature review is to investigate and categorize existing clamps used in the determination of the biomechanical properties of tendons such as maximum load, maximum strength, modulus of elasticity, ultimate strain, and stiffness. A variety of clamps for use during the endurance test of tendons were categorized according to the temperature used during the measurement. The clamps are divided into three groups: room temperature, cooled and heated clamps. The second goal of our review is to overview of clamps on the following aspects: name of clamp, author and date, type of clamps, type of endurance test (static or dynamic), type preloading (dynamic or static), type of tendon and measured and calculated parameters, and summarize in Table 3, as a comprehensive catalogue.

METHODS

This systematic review was carried out in keeping with the PRISMA 2020 E&E and the PRISMA-S guidelines and checklists. A search was conducted for publications dating between 1991 and February 28th 2022 through three electronic databases (Web of Science, Scopus, and PubMed). We used Critical Appraisal Skills Program checklist to check the quality of included articles.

RESULTS

The database search and additional sources resulted in 1725 records. 1635 records eliminated during the screening for various reasons (case report, other languages, book chapter, unavailable text/conference abstract, unrelated topic). The number of articles used in the final synthesis was 90. A variety of clamps for use during the endurance test of tendons were identified and categorized according to the temperature used during the measurement. Based on this, the clamps are divided into three groups: room temperature, cooled or heated clamps.

CONCLUSIONS

On the basis of the systematic literature review, mechanical parameters determined by usage with cooled clamps proved to be more reliable than with those at room temperature and with heated clamps. The collected information from the articles included name of clamp, author and date, type of clamps, type of endurance test (static or dynamic), type preloading (dynamic or static), type of tendon and measured and calculated parameters given in Table 3. summarized. The main advantage of the cooled clamps is that there is no limit to the type and length of the tendon. This study provides an overview of clamps and does not represent the modernity of any method.

Biomechanical properties of common graft choices for anterior cruciate ligament reconstruction: A systematic review

BACKGROUND

This systematic review explores the differences in the intrinsic biomechanical properties of different graft sources used in anterior cruciate ligament (ACL) reconstruction as tested in a laboratory setting.

METHODS

Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, two authors conducted a systematic review exploring the biomechanical properties of ACL graft sources (querying PubMed, Cochrane, and Embase databases). Using the keywords "anterior cruciate ligament graft," "biomechanics," and "biomechanical testing," relevant articles of any level of evidence were identified as eligible and included if they reported on the biomechanical properties of skeletally immature or mature ACL grafts solely and if the grafts were studied in vitro, in isolation, and under similar testing conditions. Studies were excluded if performed on both skeletally immature and mature or non-human grafts, or if the grafts were tested after fixation in a cadaveric knee. For each graft, failure load, stiffness, Young's modulus, maximum stress, and maximum strain were recorded.

FINDINGS

Twenty-six articles were included. Most studies reported equal or increased biomechanical failure load and stiffness of their tested bone-patellar tendon-bone, hamstring, quadriceps, peroneus longus, tibialis anterior and posterior, Achilles, tensor fascia lata, and iliotibial band grafts compared to the native ACL. All recorded biomechanical properties had similar values between graft types.

INTERPRETATION

Most grafts used for ACL reconstruction are biomechanically superior to the native ACL. Utilizing a proper graft, combined with a standard surgical technique and a rigorous rehabilitation before and after surgery, will improve outcomes of ACL reconstruction.

Predicting the Effect of Localized ACL Damage on Neighbor Ligament Mechanics via Finite Element Modeling

The anterior cruciate ligament (ACL) plays a pivotal role in support of the knee under loading. When damaged, it is known that substantial changes in the mechanics of the neighboring ligaments can be observed. However, a localized damage approach to investigating how ACL deficiency influences the neighboring ligaments has not been carried out. To do this, a finite element model, incorporating a continuum damage material model of the ACL, was implemented. Localized ACL damage was induced using high quadriceps force loading. Once damaged, anterior shear forces or tibial torque loadings were applied to the knee joint. The relative changes in stress contour and average mid-substance stress were examined for each of the neighboring ligaments following localized ACL damage. It was observed that localized ACL damage could produce notable changes in the mechanics of the neighboring knee ligaments, with non-homogenous stress contour shape changes and average stress magnitude being observed to increase in most cases, with a notable exception occurring in the MCL for both loading modes. In addition, the ligament bearing the most loading also changed with ACL deficiency. These changes carry implications as to morphological effects that may be induced following localized ACL damage, indicating that early diagnosis of ACL injury may be helpful in mitigating other complications post injury.

Local variations in mechanical properties of human hamstring tendon autografts for anterior cruciate ligament reconstruction do not translate to a mechanically inferior strand

A ruptured anterior cruciate ligament (ACL) is often reconstructed with a multiple-strand autograft of a semitendinosus tendon alone or combined with a gracilis tendon. Up to 10% of patients experience graft rupture. This potentially results from excessive local tissue strains under physiological loading which could either result in direct mechanical failure of the graft or induce mechanobiological weakening. Since the original location in the hamstring tendon cannot be traced back from an autograft rupture site, this study explored whether clinical outcome could be further improved by avoiding specific locations or regions of human semitendinosus and/or gracilis tendons in ACL grafts due to potential mechanical or biochemical inferiority. Additionally, it examined numerically which clinically relevant graft configurations experience the lowest strains - and therefore the lowest rupture risk - when loaded with equal force. Remnant full-length gracilis tendons from human ACL reconstructions and full-length semitendinosus- and ipsilateral gracilis tendons of human cadaveric specimens were subjected to a stress-relaxation test. Locations at high risk of mechanical failure were identified using particle tracking to calculate local axial strains. As biochemical properties, the water-, collagen-, glycosaminoglycan- and DNA content per tissue region (representing graft strands) were determined. A viscoelastic lumped parameter model per tendon region was calculated. These models were applied in clinically relevant virtual graft configurations, which were exposed to physiological loading. Configurations that provided lower stiffness - i.e., experiencing higher strains under equal force - were assumed to be at higher risk of failure. Suitability of the gracilis tendon proper to replace semitendinosus muscle-tendon junction strands was examined. Deviations in local axial strains from the globally applied strain were of similar magnitude as the applied strain. Locations of maximum strains were uniformly distributed over tendon lengths. Biochemical compositions varied between tissue regions, but no trends were detected. Viscoelastic parameters were not significantly different between regions within a tendon, although semitendinosus tendons were stiffer than gracilis tendons. Virtual grafts with a full-length semitendinosus tendon alone or combined with a gracilis tendon displayed the lowest strains, whereas strains increased when gracilis tendon strands were tested for their suitability to replace semitendinosus muscle-tendon junction strands. Locations experiencing high local axial strains - which could increase risk of rupture - were present, but no specific region within any of the investigated graft configurations was found to be mechanically or biochemically deviant. Consequently, no specific tendon region could be indicated to provide a higher risk of rupture for mechanical or biochemical reasons. The semitendinosus tendon provided superior stiffness to a graft compared to the gracilis tendon. Therefore, based on our results it would be recommended to use the semitendinosus tendon, and use the gracilis tendon in cases where further reinforcement of the graft is needed to attain the desired length and cross-sectional area. All these data support current clinical standards.

Continuous-Loop Tape Technique Has Greater Stiffness and Less Elongation Compared With Tied-Suture Fixation of Full-Thickness All-Soft Tissue Quadriceps Tendon Autografts

Background

Many graft fixation techniques are utilized for full-thickness soft tissue quadriceps tendon autografts during anterior cruciate ligament reconstruction (ACLR).

Purpose

To determine the tensile properties of all-soft tissue quadriceps tendon graft fixation using a tied-suture versus continuous-loop tape technique. It was hypothesized that the continuous-loop tape technique would have less cyclic elongation and greater ultimate load to failure and stiffness compared with a commonly used tied-suture technique.

Study Design

Controlled laboratory study.

Methods

Sixteen fresh-frozen human knee specimens were used to harvest a full-thickness all-soft tissue quadriceps tendon graft; half were secured using a Krackow suture technique with 2 braided sutures, and half were secured using a continuous-loop tape suspensory fixation button with a rip-stop stitch. Cyclic and permanent elongation, toe- and linear-region stiffness, and ultimate load were determined. Statistical analysis was performed at P <.05.

Results

The tied-suture fixation group demonstrated significantly higher permanent elongation (11.7 ± 3.6 vs 4.2 ± 1.0 mm, P < .001) and cyclic elongation (5.9 ± 1.3 vs 2.0 ± 0.4 mm, P < .001) compared with the continuous-loop tape fixation group. There was a significantly higher linear-region stiffness with continuous-loop tape fixation compared with tied-suture fixation (98.8 ± 12.7 vs 85.5 ± 7.5 N/mm, P = .022). No significant difference in ultimate load between groups (517.1 ± 149.2 vs 465.6 ± 64.6 N) was found. The mode of failure was tendon pull-through for the continuous-loop tape group and suture breakage in the tied-suture group (P < .001).

Conclusion

Continuous-loop tape fixation is superior to tied-suture fixation in regard to elongation and stiffness for all-soft tissue quadriceps tendon grafts, but there was no significant difference in ultimate load.

Clinical Relevance

Continuous-loop tape fixation of all-soft tissue quadriceps tendon grafts for ACLR is a valid technique with superior tensile properties.

Biomechanical Strength of All-Inside ACL Reconstruction Grafts Using Side-to-Side and Backup Fixation

Background:

The all-inside anterior cruciate ligament reconstruction (ACLR) procedure uses a single hamstring tendon folded twice and secured to itself to form a 4-stranded graft. There are several possible configurations for preparing the graft.

Purpose:

To investigate the biomechanical properties of a new graft preparation technique in comparison with 2 commonly used configurations.

Study Design:

Controlled laboratory study.

Methods:

Five porcine flexor tendons were prepared into the test graft configuration: side-to-side fixation with a backup fixation at the button loop (graft M). The test configuration was compared with the results of a previous study that included grafts with simple interrupted sutures (graft A; n = 5) and end-to-end fixation (graft C; n = 5). All grafts were subjected to the same mechanical testing protocol to determine the mean failure load, stiffness, rate of elongation, and total elongation during both cyclic loading and pull to failure. Differences between groups were evaluated.

Results:

Graft A had a significantly lower failure load (637 ± 99 N) compared with graft M (883 ± 66 N; P = .002) and graft C (846 ± 26 N; P = .002). Graft A also had significantly lower stiffness (166 ± 12 N/mm) compared with graft M (215 ± 8 N/mm; P < .001) and graft C (212 ± 11 N/mm; P < .001). Graft C had a significantly lower elongation during cyclic loading (3.42 ± 0.24 mm) compared with graft M (4.37 ± 0.74 mm; P = .026) and graft A (4.90 ± 0.88 mm; P = .006). The unsecured fixation was the weakest graft, with the lowest failure load and stiffness. The new side-to-side configuration and end-to-end configuration were equally strong.

Conclusion:

The new side-to-side configuration was not biomechanically superior to the end-to-end configuration; however, they were both stronger than unsecured fixation.

Clinical Relevance:

As the all-inside ACLR is gaining popularity, this study provides surgeons with a new method of preparing grafts and evaluates the method with respect to currently used configurations.

Effect of Vancomycin Soaking on Anterior Cruciate Ligament Graft Biomechanics

PURPOSE

To evaluate the effect of soaking of anterior cruciate ligament (ACL) grafts in vancomycin solution on graft biomechanical properties at the time of implantation.

METHODS

The central third of patellar tendons was harvested from mature bovine knees and prepared as a tendon-only graft or a bone-tendon-bone (BTB) graft. Tendons were wrapped in gauze soaked in vancomycin solution (VS) (5 mg/mL) or normal saline (NS) and left to stand for 30 minutes at room temperature, simulating graft exposure times in the operating room during ACL reconstruction. Tensile testing was carried out on a materials testing system with (1) low-magnitude loading (60 N at 3 mm/s) with repeated testing of tendon-only grafts; and (2) high-magnitude loading (600 N at 10 mm/min) of BTB grafts. For tendon-only grafts, specimens were first wrapped in NS-soaked gauze and underwent testing, with repeated testing performed after wrapping in gauze soaked in VS or buffered VS (pH 7.0). For BTB grafts, specimens were randomly assigned to treatment with VS or NS.

RESULTS

For tendon-only grafts, there was no difference in Young's modulus (YM) after soaking with VS soaking (baseline, 12.69 MPa; treatment, 16.07 ± 4.44 MPa; P = .99) or buffered VS (baseline, 12.45 ± 4.55 MPa; treatment, 15.56 ± 2.83 MPa; P = .99). For BTB grafts, there were no differences in elongation strain (VS, 46.8% ± 7.0%; NS, 31.5% ± 13.5%, P = .19) or YM (VS, 158.4 ± 15.8 MPa; NS, 158.5 ± 23.3 MPa, P = .99).

CONCLUSIONS

According to controlled biomechanical tests, vancomycin soaking of patellar tendon grafts does not adversely affect time-zero material properties.

CLINICAL RELEVANCE

This study suggests that vancomycin wrapping has no immediate adverse effects on the biomechanical properties of ACL grafts. Randomized controlled trials are warranted to validate the widespread use of vancomycin soaking of tendon grafts for infection prophylaxis during ACL reconstruction.

A study of knee anterior cruciate ligament biomechanics with respect to energy and relaxation

BACKGROUND

This research aimed to study the biomechanical properties of sheep tendon under torsion and the tendon energy absorption performance with an externally imposed initial force.

METHODS

Tendons of nine healthy knees of sheep were investigated. In both tests, we investigated energy and relaxation at rotations of 0°, 90°, 180°, and 360°. For both tensile force and tensile displacement at a sampling period of 100 milliseconds, the maximum value of 89 N was selected as the maximum tension state for 600 s of relaxation duration for testing relaxation, and analysed of the average force of the last 30 s.

FINDINGS

The difference of energy levels of the tendons are significant between twisted groups (180° and 360°) and untwisted group (0°) (P < 0.05); The relaxation force decreases significantly with twisted groups (90°,180°, and 360°) and untwists group (0°) (P < 0.05). The nine-group tendons show no significant difference at torsion 90° and 180° (P = 0.466). Peak force test shows significant differences between the twisted groups (90°,180°, and 360°) and untwisted group (0°) (P < 0.05).

INTERPRETATION

The torsion tendon has lower energy absorption and relaxation than the untwisted counterparts; thus, it may be more prone to damage. These results are useful for providing guidance on anterior cruciate ligament reconstruction.

Use of hamstring autograft to reconstruct the patellar tendon after endoprosthetic replacement of the proximal tibia for bone sarcomas

The surgical treatment of bone sarcoma involves wide surgical resection and endoprosthetic replacement. Surgical resection for proximal tibia bone sarcoma includes the patellar tendon. The secondary extension lag is a common complication and, although many have been described, the options for reconstruction of the patellar tendon are suboptimal. We propose adding a biological reinforcement, the hamstring tendons, to our extensor mechanism reconstruction technique (polyprolene mesh and gastrocnemius flap). We describe the surgical technique and, using an illustrative case, compare the outcome of this technique with the outcome following reconstruction without reinforcement. Level of evidence: Level III.

Presoaking of Semitendinosus Graft With Vancomycin Does Not Alter Its Biomechanical Properties: A Biomechanical In Vitro-Controlled Study Using Graft From Living Donors

PURPOSE

To compare the biomechanical properties of human semitendinosus graft presoaked with or without vancomycin under a load to failure tensile test.

METHODS

Thirty semitendinosus grafts harvested during anterior cruciate ligament reconstruction were included. These were dissected equally into 2 halves and subsequently randomly allocated to a vancomycin group and to a control group. A digital caliper was used to precisely measure each samples thickness, length, and width. For the vancomycin group, samples were presoaked in a solution of 5 mg/mL vancomycin for a duration of 10 minutes and the control group samples were presoaked in a physiological serum equally for 10 minutes. Mechanical testing was performed on a universal testing machine (Instron 5566-A) after a preconditioning of 10 cycles of 1 mm extension and a progression of 10 mm/min to failure for each sample. The stress-strain curve was obtained to determine the elastic modulus (Young's modulus), the ultimate tensile stress, the ultimate tensile elongation (UTE) before failure and the elasticity limit.

RESULTS

For the control group, the average Young's modulus value was 4.8 ± 0.8, the average UTS was 25.2 ± 5.2 MPa, the average percentage of UTE was 78 ± 17%, and the average elasticity limit value was 17.3 ± 5.3 MPa. For the vancomycin group, the average Young's modulus value was 4.7 ± 0.9, the average ultimate tensile stress was 24.1 ± 6.1 MPa, the average percentage of UTE was 82 ± 14%, and the average elasticity limit value was 18.5 ± 5.9 MPa. No significant difference was observed between the 2 groups for all investigated parameters.

CONCLUSIONS

Presoaking of human semitendinosus graft with vancomycin does not alter its biomechanical properties.

CLINICAL RELEVANCE

This study demonstrates that vancomycin presoaking used to prevent post-anterior cruciate ligament reconstruction septic arthritis does not affect immediate biomechanical properties of semitendinosus tendons.

Biomechanical effects of stitches on the intra-articular mid-substance of quadruple hamstring-tendon grafts for anterior cruciate ligament reconstruction - a pilot comparative cadaveric study

Background

There is little data in the literature regarding the preparation methods of the intra-articular portion of quadruple hamstring-tendon grafts for anterior cruciate ligament (ACL) reconstruction. The aim of this study was to compare the biomechanical properties of a sutured transplant to that of a non-sutured transplant. The hypothesis was that adding stitches to the intra-articular portion of the graft increased its resistance.

Method

A comparative cadaveric study was carried out on five pairs of knees. The average age of the cadavers was 68 years. The exclusion criterion was past knee surgery. In the Sutured Group (SG) two stitches were made on the grafts. No stitches were made on the grafts of the Non-sutured Group (NSG). A tensile failure test was carried out using an Instron® loading machine. The maximal load to failure and stiffness were recorded and we observed the mode of failure for each graft. Statistical analysis was performed using the Wilcoxon rank sum test. Level of significance was set at p < 0.05.

Results

The hypothesis proposed was not confirmed; adding stitches to the intra-articular portion of the four-strand hamstring-tendon graft does not increase its biomechanical properties. The maximal load to failure was 233.5 N ± 40.6 (186.7–274.5 N) for the NSG, 19.6% higher than for the SG which was 195.2 N ± 42.9 (139.0–238.2 N). Nevertheless, the difference observed was not statistically significant (p = 0.188). The stiffness of the grafts for the NSG was 23.5 N/mm ± 5.3 (17.8–29 N/mm) and 19.7 N/mm ± 5.5 (13.2–24.7 N/mm) for the SG grafts. Overall stiffness values for the NSG were 19% higher than those of the SG; however, the results were not statistically significant (p = 0.438). The failure mode was a rupture at the fixation point except for one sample from the SG which failed at an intra-articular stitch.

Conclusion

Whilst the initial hypothesis was not verified, nevertheless, the maximal loads to failure and stiffness were approximately 20% higher when there were no intra-articular stitches compared to the situation where stitches were added to the intra-articular portion of the graft. This was a cadaveric pilot study and, therefore, whilst we are not able to extend our results to clinical practice, the outcomes would indicate the need for further development of this and related protocols deriving from the question of whether there is weakening the graft when adding stitches to its mid-substance. These results remain to be confirmed by further research.

Biomechanical Comparison of Graft Preparation Techniques for All-Inside Anterior Cruciate Ligament Reconstruction

Background:

All-inside anterior cruciate ligament reconstruction (ACLR) is an emerging technique used to treat ACL injuries. The all-inside technique uses a 4-stranded graft made from a single tendon that is looped on itself. The 4 strands of the graft must be secured to each other to become a closed-loop structure. Various suture configurations exist to secure the graft to adjustable loop devices, and there is a lack of data to support one technique over another. In addition to the primary sutures used to fasten the graft together, accessory sutures can be tied over the button as secondary fixation.

Purpose:

To evaluate biomechanical properties of 4-stranded grafts prepared in 5 different configurations.

Study Design:

Controlled laboratory study.

Methods:

Porcine flexor tendons (N = 25) were prepared in 5 different configurations (n = 5 tendons per group): simple-interrupted sutures (unsecured fixation), side-to-side fixation with and without secondary fixation, and end-to-end fixation with and without secondary fixation. The grafts were put through the same mechanical testing protocol (cyclic loading, pull to failure) to measure average load at graft failure, average displacement at failure, average stiffness, and average elongation rate. Differences between graft preparation techniques were investigated using 1-way analyses of variance (ANOVAs) with post hoc t tests (P < .05).

Results:

Significant 1-way ANOVAs for each biomechanical property were found. Unsecured fixation was the weakest graft preparation with the lowest stiffness (167 ± 12 N/mm), lowest ultimate failure load (637 ± 99 N), and highest elongation rate (0.0033 ± 0.0007 mm/s). End-to-end fixation without secondary fixation showed the highest ultimate failure load (846 ± 26 N), highest stiffness (212 ± 10 N/mm), and lowest rate of elongation (0.0025 ± 0.0001 mm/s). End-to-end fixation, both with and without secondary fixation, as well as side-to-side fixation with secondary fixation showed significantly higher ultimate failure loads than grafts with unsecured fixation. End-to-end fixation performed better than side-to-side fixation; however, for most variables, the difference was not statistically significant. Secondary fixation did not provide significant improvement.

Conclusion:

The all-inside ACL graft with simple-interrupted sutures is biomechanically inferior to a graft that has its free ends secured to the adjustable tibial loop. Adding secondary fixation to the tibial button does not significantly change the biomechanical properties. Further clinical studies are required to determine whether these findings translate into differences in clinical outcome.

Clinical Relevance:

All-inside ACLR is gaining popularity in hamstring ACL reconstructive techniques. These results provide surgeons with guidance on the best graft preparation method when using a single quadrupled hamstring tendon graft.

Every layer of quadriceps tendon's central and medial portion offers similar tensile properties than Hamstrings or Ilio-Tibial Band Grafts

PURPOSE

The aim of our cadaveric study was to compare the mechanical properties of different parts of the quadriceps' tendon in a load to failure analysis as compared to three other, and most common types of grafts that are used to perform ligament's reconstruction.

METHODS

Ten fresh-frozen cadavers (5 women, 5 men) were selected from our anatomical department. Mean age at death was 64 years (48-87 years). Tendons were harvested to prepare (1) different quadriceps tendon's specimens: lateral portion (QTlat), medial portion superficial layer (QTMsup) and deep layer (QTMdeep) and central portion superficial (QTCsup) and deep layers (QTCdeep) (2) Patellar Tendon (PT), (3) Gracilis+Semi-Tendinosus specimens (GST). Specimens were stored at - 40 °C in a freezing solution. Specimens were securely attached to a dedicated loading platform, measurements were done using a validated software. Load to failure testing was then carried out. Young's Elastic moduli, ultimate Stress (MPa) and Deformation (%) were analysed.

RESULTS

The elastic moduli of the PT was significantly higher than all other grafts, all medial and central QT layers (superficial and deep) were significantly higher than its lateral part (QTlat). In terms of Ultimate Stress, all grafts were significantly greater than QTlat, PT and GST were significantly superior to QT central portions and to ITB but there did not differ with the medial portion of QT. ITB ultimate stress values were significantly higher than QTlat. The ultimate deformations of all grafts were similar.

CONCLUSIONS

This study provides reference values in in order to characterize different parts of the QT that presents anatomically and Mechanically with complex characteristics. Every Layer of Quadriceps Tendon's Central and Medial Portion Offered Similar Mechanical Properties than Two Strand Hamstrings or Ilio-Tibial Band.

Quadrupled Semitendinosus ACL Reconstruction Combining Cortical Button in Femur and Interference Screw in Tibia

Anterior cruciate ligament (ACL) reconstruction with hamstring tendons has gained popularity in the past and is the most used type of graft in several national registries. It usually involves the harvest of both gracilis and semitendinosus tendons from the ipsilateral knee. More recently, the use of only 1 of the tendons (semitendinosus) in a tripled or quadrupled arrangement has been described, especially in an all-inside type of reconstruction. Having a thicker tendon with a quadrupled semitendinosus (ST), instead of double gracilis and ST enables to a have a graft with enough diameter to resemble more closely the native ACL and decreases the risk of graft rerupture. This Technical Note aims to present a way of reconstructing the ACL using a quadrupled ST graft, with suspensory cortical button in femur and interference screw in tibia, as an alternative to the all-inside technique.

A Biomechanical Comparison of Alternative Graft Preparations for All-Inside Anterior Cruciate Ligament Reconstruction

PURPOSE

To biomechanically compare alternative graft constructs for all-inside anterior cruciate ligament (ACL) reconstruction in the event that the semitendinosus harvested is too narrow or too short to make a graft larger than 8 mm.

METHODS

Bovine extensor tendons were used to make 6 different 9-mm-diameter grafts: traditional 4-strand, anastomosis 4-strand, 6-strand, 3-strand, button-fixation 4-strand, and loop-and-tack 4-strand grafts. The grafts were then subjected to cyclic biomechanical testing followed by failure loading. Force at 3 and 5 mm of displacement and ultimate force were recorded for all grafts.

RESULTS

Compared with the traditional 4-strand graft, the only graft that showed significant biomechanical differences during the cyclic phase of testing was the button-fixation 4-strand graft, which was characterized by lower force at 3 mm of displacement (74 ± 34 N vs 122 ± 13 N, P = .004) and 5 mm of displacement (122 ± 35 N vs 172 ± 3 N, P = .006). During failure loading, ultimate force was significantly lower for both the 6-strand graft (491 ± 186 N, P = .041) and button-fixation 4-strand graft (326 ± 27 N, P < .001) than for the traditional 4-strand graft (778 ± 176 N). All other grafts were equivalent for the parameters tested.

CONCLUSIONS

The anastomosis 4-strand, 3-strand, and loop-and-tack 4-strand grafts do not biomechanically differ in cyclic loading and ultimate force from traditional 4-strand grafts. This study supports the use of anastomosis 4-strand, 3-strand, or loop-and-tack 4-strand grafts in the event that a traditional all-inside 4-strand graft cannot be prepared from a harvested semitendinosus tendon in ACL reconstruction.

CLINICAL RELEVANCE

This study tests and describes alternatives to the traditional 4-strand semitendinosus autograft for all-inside ACL reconstruction in the event that the harvested tendon is not adequate.

Quadriceps augmentation of undersized hamstrings during ACL reconstruction

BACKGROUND

Double hamstring autograft for anterior cruciate ligament (ACL) reconstruction is a well-established graft option; however, a major concern with this method arises when the prepared graft is too small. Resorting to allograft can be a solution to this problem, but some surgeons prefer to use autograft in particular situations and some patients may refuse allograft. We investigate the merits of using autogenous quadriceps tendons to augment the insufficient hamstrings and compare the autograft composite graft to a standard hamstrings graft of equal size.

METHODS

Semitendinosus, gracilis, and quadriceps tendons were harvested from 10 matched pairs of human cadaver lower extremities. Within each pair, a routine hamstring ACL graft (control) consisting of the semitendinosus and gracilis tendons, and an quadriceps augmented hamstrings graft of equal size comprised of the semitendinosus and quadriceps tendons, were prepared. A freeze-clamp mount was used to biomechanically test each graft construct. Tensile failure load, displacement, energy absorbed, and stiffness were determined and statistically compared within each pair and mode of graft failure was established.

RESULTS

No statistically significant differences were found between the quadriceps augmented hamstrings graft versus standard control grafts. Average values for peak failure load and graft displacement at the point of first failure were nearly identical. All ACL graft constructs failed at the mid-substance.

CONCLUSIONS

This study demonstrates no statistical difference in the biomechanical properties of an isolated hamstring ACL autograft versus a quadriceps augmented ACL autograft of equal size at time zero.

CLINICAL RELEVANCE

This is a potentially new and reliable method for quadriceps tendon autograft augmentation of hamstring autograft for ACL reconstruction.

A bigger suture diameter for anterior cruciate ligament all-inside graft link preparation leads to better graft stability: An anatomical specimen study

BACKGROUND

In anterior cruciate ligament reconstruction, different suture types are used for graft link preparation. Thus the aim of this study was to determine whether differences in the diameter of the suture used influence biomechanical stability of the prepared graft. We hypothesized that the use of a greater suture diameter leads to a higher load to failure rate in tested graft links.

METHODS

In an anatomic specimen study, ligament preparation was enrolled in 15 cadaveric knees. The material used was the semitendinosus/gracilis tendon, which was fresh frozen (-80°) after harvesting for four weeks. The grafts were then defrosted, randomized into two groups and prepared with the same technique: 12 with a suture; FiberWire No. 2 and 12 with a FiberWire No. 0.

RESULTS

Overall, the group using FiberWire No. 2 presented with a mean load to failure rate of 730.67N, mean overall final elongation of the graft was 5.98mm. In the FiberWire No. 0 group mean load to failure was with a mean overall elongation of the graft of 6.96mm. Significant differences (P=0.006) between the two groups with regard to the load to failure rate were found, with FiberWire No. 2 withstanding forces better. There was no difference in elongation of the grafts or mode to failure between the two groups.

CONCLUSIONS

Graft preparation with a bigger suture type is recommended to gain better load to failure rates, also in smaller-diameter grafts. Regarding the elongation rate, different suture types did not influence the outcome.

LEVEL OF EVIDENCE

Anatomical specimen study, Level III.

Hamstring Graft Incorporation According to the Length of the Graft Inside Tunnels

BACKGROUND

Anterior cruciate ligament (ACL) reconstruction with a quadrupled semitendinosus (ST4) graft is an evolution of the standard technique with 2 hamstring tendons (semitendinosus + gracilis [STG]). However, there is no published comparison of how well these 2 types of hamstring grafts are incorporated into the bone tunnels. Because the ST4 graft is shorter, there is less graft material inside the tunnels.

PURPOSE

To use magnetic resonance imaging (MRI) to compare graft incorporation in the tibial bone tunnels 1 year after ACL reconstruction with either an STG graft or ST4 graft.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Sixty-two patients who underwent ACL reconstruction were enrolled prospectively: 31 with an ST4 graft and 31 with an STG graft. The same surgical technique, fixation method, and postoperative protocol were used in both groups. Graft incorporation and ligamentization were evaluated with MRI after 1 year of follow-up. The following parameters were evaluated: signal-to-noise quotient (SNQ), tibial tunnel enlargement, signal intensity at the bone-graft interface, and graft signal according to the Howell scale. The number of participants needed to show that the mean SNQ did not differ between the 2 techniques was 31 in each group (with a 1-sided alpha of 2.5% and a 1-sided beta of 10.0%). The Student t test was used to compare the distribution of continuous secondary endpoints.

RESULTS

The mean SNQ was 5.2 ± 4.5 for the STG group and 5.9 ± 3.7 for the ST4 group ( P = .5100). The mean tibial tunnel widening was 93.7% ± 51.7% for the STG group versus 80.0% ± 42.9% for the ST4 group ( P = .2605). The groups did not differ in signal intensity at the bone-graft interface ( P = .7502) or in graft signal according to the Howell scale ( P = .4544).

CONCLUSION

At the 1-year postoperative follow-up, incorporation and ligamentization of the STG and ST4 grafts were the same based on MRI analysis. The results were at least as good with the ST4 technique as with the standard STG technique in terms of incorporation and ligamentization.

Static tensioning promotes hamstring tendons force relaxation more reliably than cycling tensioning

BACKGROUND

Graft elongation might be a major reason for increased anterior laxity after anterior cruciate ligament (ACL) reconstruction. This study analyzed the force relaxation values and their stabilization when single strands of the gracilis and semitendinosus tendons underwent cyclic and static tensioning at 2.5% strain level, and compared the efficiency of static and cyclic tensioning in promoting force relaxation.

METHODS

Eighteen gracilis tendons and 18 semitendinosus tendons from nine male cadavers (mean age: 22.44years) were subjected to 10 in vitro cyclic loads at 2.5% strain level, or to a static load at 2.5% strain level.

RESULTS

During cyclic loading, the reduction in force values tended to stabilize after the sixth cyclic load, while, in the case of static loading, this stabilization occurred by the second minute. Comparing static and cyclic loading, the gracilis tendon had similar mechanical responses in both conditions, while the semitendinosus tendon showed greater force relaxation in static compared with cyclic loading.

CONCLUSIONS

Considering that the semitendinosus tendon is the main component of the hamstring graft, its biomechanical response to loading should guide the tensioning protocol. Therefore, static tensioning seems more effective for promoting force relaxation of the semitendinosus tendon than cyclic tensioning. The gracilis tendon showed a similar mechanical response to either tensioning protocols.

Cadaveric Study Comparing the Biomechanical Properties of Grafts Used for Knee Anterolateral Ligament Reconstruction

PURPOSE

To measure the biomechanical properties (maximum load, stiffness, and elongation) of the anterolateral ligament (ALL), gracilis, and iliotibial band (ITB) within the same subject.

METHODS

Thirteen unpaired knees were used (7 women, 6 men). The donors had a mean age at death of 54 years (range: 37 to 70 years). The mechanical properties of two types of ALL grafts were evaluated: ITB and two-strand gracilis. The mechanical properties of ALL were also measured. Validated methods were used to perform the tensile tests to failure and to record the results. Student's t-test was used to compare the various samples.

RESULTS

The maximum load to failure was 141 N (±40.6) for the ALL, 200.7 N (±48.7) for the gracilis, and 161.1 N (±27.1) for the ITB. Only the gracilis had a significantly higher failure load than ITB and ALL (P = .001 and P = .03). The stiffness was 21 N mm^-1 (±8.2) for the ALL, 131.7 N mm^-1 (±43.7) for the gracilis, and 39.9 N mm^-1 (±6) for the ITB. The elongation at failure was 6.2 mm (±3.2) for the ALL, 19.9 mm (±6.5) for the gracilis, and 20.8 mm (±14.7) for the ITB.

CONCLUSIONS

The gracilis had the highest maximum load to failure. The ITB's mechanical properties most closely resemble those of the ALL.

CLINICAL RELEVANCE

The biomechanical properties of each potential ALL graft can be factored in when deciding which type of graft to use.

Kinematic outcomes following ACL reconstruction

Anterior cruciate ligament (ACL) reconstruction aims to restore the translational and rotational motion to the knee joint that is lost after injury. However, despite technical advancements, clinical outcomes are less than ideal, particularly in return to previous activity level. A major issue is the inability to standardize treatment protocols due to variations in materials and approaches used to accomplish ACL reconstruction. These include surgical techniques such as the transtibial and anteromedial portal methods that are currently under use and the wide availability of graft types that will be used to reconstruct the ACL. In addition, concomitant soft tissue injuries to the menisci and capsule are frequently present after ACL injury and, if left unaddressed, can lead to persistent instability even after the ACL has been reconstructed. Advances in the field of biomechanics that help to objectively measure motion of the knee joint may provide more precise data than current subjective clinical measurements. These technologies include extra-articular motion capture systems that measure the movement of the tibia in relation to the femur. With data gathered from these devices, a threshold for satisfactory knee stability may be established in order to correctly identify a successful reconstruction following ACL injury.

Change in Size of Hamstring Grafts During Preparation for ACL Reconstruction: Effect of Tension and Circumferential Compression on Graft Diameter

BACKGROUND

There is good consensus that anterior cruciate ligament (ACL) grafts should be pretensioned to remove creep prior to implantation, but the literature contains little information on the influence of graft preparation or circumferential compression on graft size. The purpose of this study was to investigate how the size of hamstring allografts changes as they are prepared for ACL reconstruction. We hypothesized that grafts decrease in diameter as they are prepared with both tension and circumferential compression. We also investigated the interrater reliability of graft diameter measurements during each step of graft preparation.

METHODS

Twenty pairs of fresh-frozen human hamstring tendons obtained from an allograft supplier were prepared in a standardized fashion for ACL reconstruction (suturing followed by longitudinal tensioning followed by circumferential compression followed by relaxation). Four blinded raters measured each graft in a sequential manner after each graft preparation step. Interrater reliability was assessed using the intraclass correlation coefficient ICC(2,1). The mean allograft diameter at each time point was calculated and compared across all time points using repeated-measures analysis of variance (ANOVA).

RESULTS

Subjecting the grafts to both tension and circumferential compression significantly decreased their mean diameter (to 7.38 mm compared with 8.28 mm at baseline; p = 0.044). Interrater reliability revealed almost perfect agreement at each measurement interval, with the ICC ranging from 0.933 to 0.961.

CONCLUSIONS

The average diameter of hamstring ACL grafts decreases by almost 1 mm after they are subjected to both tension and circumferential compression within a standard cylindrical sizing block.

CLINICAL RELEVANCE

Because ACL bone tunnels are drilled in 0.5-mm increments, preparing soft-tissue grafts with circumferential compression in addition to tension may allow creation of tunnels that are one to two incremental sizes smaller. This could permit less bone removal, which may be particularly applicable for certain reconstruction techniques such as pediatric, double-bundle, or revision ACL reconstruction, in which limited space is available for tunnel drilling.