How Variable Are Achilles Allografts Used for Anterior Cruciate Ligament Reconstruction? A Biomechanical Study

Donor age has no relevant role in biomechanical properties of allografts used in anterior cruciate ligament (ACL) reconstruction: A systematic review

PURPOSE

Surgeons generally consider the donor age as a factor that negatively influences the quality of allograft used in anterior cruciate ligament (ACL) reconstruction, however, the available evidence does not clearly support this statement. The purpose of the study was to investigate if donor age influences the biomechanical properties of allografts used in ACL reconstruction.

METHODS

A comprehensive literature search was conducted for all relevant articles using MEDLINE (PubMed), Scopus, and Cochrane Collaboration Library, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis. Studies including the analysis of the correlation between biomechanical properties of the allografts and donor age were selected. The role of donor age was labelled as 'none' if absent, 'higher' or 'lower' if the properties were higher or lower in older specimens with respect to younger. The correlation was defined as 'weak' or 'strong' according to each study definition.

RESULTS

No conflicting role of donor age was reported for modulus of elasticity, load to failure, strain, stiffness and displacement. The only parameters where the significant results were consistent were the tensile strength and the stress (low or moderate correlations). When considering the tested samples with a donor's age <65 years, a significant role of age was reported in only four out of 13 groups of graft tested (patellar tendon, fascia lata, anterior tibialis tendon and posterior tibialis tendon).

CONCLUSION

The current literature did not allow to state that the donor age negatively influences the biomechanical properties of allografts, making it impossible to identify a clear age cut-off value to exclude them from ACL reconstruction procedures.

LEVEL OF EVIDENCE

Level IV, systematic review.

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.

Peracetic Acid-Ethanol Processed Human Tendon Allograft: A Morphological, Biochemical, and Biomechanical Study In Vitro

OBJECTIVE

To clarify the morphological, biochemical, and biomechanical effects of peracetic acid-ethanol sterilization processing to human hamstring tendon allografts for different time periods.

METHODS

Thirty-two fresh-frozen human hamstring tendon allografts obtained from an allograft supplier were prepared and incubated in peracetic acid-ethanol solution (PES) containing 1% v/v peracetic acid and 24% v/v ethanol. Specimens were randomly classified into four groups according to the PES processing time (untreated as the control group, 30 min as the PES30 group, 120 min as the PES120 group, and 240 min as the PES240group). Light microscopy with hematoxylin-eosin and toluidine blue were performed, along with transmission electron microscopy (TEM) to measure the collagen fibril diameters and their distributions, from which the collagen fibril index (CFI) and mass average diameter (MAD) were calculated. The thermal stability and collagen denaturation were analyzed by differential scanning calorimetry (DSC) and collagen denaturation test by α-chymotrypsin. Cyclic loading and failure testing were applied on five tendons from each group, from which the cyclic creep strain, elastic modulus, maximum stress, maximum strain, and strain energy density were calculated.

RESULTS

Tendons in the control, PES30, PES120 groups showed similar regularly aligned collagen fibers in light microscopy images, while the images from the PES240 group revealed relatively disordered and heterogeneous collagen bundles with larger interfiber spaces. TEM analysis showed that the mean diameter (F = 3.09, P = 0.04) was lower in the PES120 group (87.15 ± 4.76 nm) than it was in the control group (99.39 ± 9.19 nm) but not statistically (P = 0.05). Moreover, the CFI value in the PES30 group (65.37 ± 4.14%) was the lowest among groups (all P ≤ 0.01), while no variance existed in density and MAD among groups (F = 2.09, P = 0.13, and F = 0.27, P = 0.85, respectively). The onset temperature (H = 8.74, P = 0.03) and peak temperature (H = 9.97, P = 0.02) were decreased in the PES30 group compared to the control group (P = 0.02 and P = 0.01, respectively), but there were no differences in enthalpy of denaturation among groups (F = 2.20, P = 0.17). The collagen denaturation test revealed lower hydroxyproline concentrations in PES-treated specimens with no statistical differences among groups (H = 8.86, P = 0.07). The maximum stress showed variance (F = 10.52, P < 0.01) that it was higher in PES30 group (68.29 ± 10.86 MPa) compared to the PES120 and the PES240 group, while it was lower in the PES120 group (19.40 ± 4.94 MPa) compared to the control and the PES30 group (all P < 0.05). The strain energy density (F = 7.34, P < 0.01) was over 4 times higher in the PES30 group (7.39 ± 2.51 MPa) than it was in the PES120 group (1.56 ± 0.64 MPa, P < 0.01).

CONCLUSION

PES treatment for 30 min has no adverse effect on the properties of human hamstring tendon allografts, longer processing time could not promise better properties preservation.

Indirect markers for length adjustment in distal biceps tendon allograft reconstruction

Chronic musculotendinous retraction, shortening and fibrosis after distal biceps tendon tears makes a primary reconstruction often difficult or even impossible. Interposition reconstruction with allograft provides a solution, however there is no consensus about appropriate intraoperative graft length adjustment. Therefore, the purpose of this study was to find a practical reference value for distal biceps tendon length adjustment. Three-dimensional surface models of healthy distal biceps tendons were created based on 85 MRI scans. The tendon length was measured from the myotendinous junction to the insertion on the bicipital tuberosity. Inter-epicondylar distance (IED) and radial head diameter (RHD) were measured on antero-posterior radiographs as a surrogate for patient size. Correlations between the tendon length and IED, RHD and patient’s height (PH) were calculated. Mean length of the external part of the distal biceps tendon was 69mm (female 64mm, male 71mm). The tendon length in mm was on average 1.1 times of the IED (mm), 3 times of the RHD (mm) and 0.4 times of PH (cm). Herewith, the tendon length could be predicted within a narrow range of +/-1cm in 84% by using IED, 82% by using RHD and 80% by using PH. Intra- and inter-reader reliabililty of IED and RHD was excellent (R² = 0.938–0.981). The distal biceps tendon length can be best predicted within 1cm with an accuracy of 82–84% using the IED and RHD with an excellent intra- and inter-reader reliability.

Anterior Cruciate Ligament Reconstruction Graft Preference Most Dependent on Patient Age: A Survey of United States Surgeons

PURPOSE

The purpose of this study was to define the anterior cruciate ligament (ACL) reconstruction (ACLR) graft preference of surgeons and to explore factors associated with their predilection.

METHODS

A 15-question survey regarding ACLR graft preference in various situations was completed by 514 American Orthopaedic Society for Sports Medicine and Arthroscopy Association of North America surgeons. Surgeon and practice demographics, along with various patient factors, were evaluated with bivariate and multivariable models for association with surgeon preference. Surgeons were also queried about their preference for their own ACLR. For surgeons who personally sustained an ACL, an additional 6 questions inquired about their experience.

RESULTS

Surgeons reported the 5 most important factors in patient graft choice, in order: patient age, graft failure in literature and practice, pivot sport, and patient preference. Autograft patellar and quadriceps tendon were strongly preferred for younger, pivoting athletes (P < .001), among those with fellowship training (47% vs 33%, P = .006), in academic practices (52% vs 44%, P = .003), and in more sports medicine-specific practices, with a higher number of ACLRs performed per year (P < .001). Northeast, Southeast, Midwest, and Southwest surgeons had lower hamstring autograft preference (P < .001). Non-fellowship-trained surgeons preferred hamstring autograft (P = .010). Allograft was preferred for older patients (P < .001). Nonsignificant predictors included highest level of athlete for whom an ACLR had been performed, level of athlete serving as team physician, and years in practice. No factors were associated with surgeon preference for their own ACLR despite deeming these factors important for patients. ACL tears were reported by 13% of respondents, with 86% stating it influenced their decision to enter orthopaedics.

CONCLUSIONS

Patient age was the most important factor in graft choice, with patellar and quadriceps tendon autograft the preferred graft for ACLR for younger, pivoting athletes. Fellowship training and practice demographics were also correlated with graft choice for patients.

CLINICAL RELEVANCE

Graft preference for ACLR varies among surgeons and is associated with surgeon experience and patient characteristics, including patient age, type of sport, and patient preference.

Different sterilization and disinfection methods used for human tendons - a systematic review using mechanical properties to evaluate tendon allografts

Background

It is important to know the biomechanical properties of an allograft. This is because when looking to do a transplant of a tendon, the tendon must have very similar biomechanical properties to the original tendon. To use tendon allografts, it is critical to properly sterilize the tendon before implantation. In past decades, several sterilization procedures have been used. This study aimed to systematically evaluate the existing literature to compare the values of failure load/ultimate strength and Young’s modulus of elasticity of different sterilization methods on commonly used tendon allografts. Five major scientific literature databases (Web of Science, Science Direct, Scopus, PLOS ONE, Hindawi) and additional sources were used.

Results

Studies used had to show a particular sterilization method. Studies were identified to meet the following inclusion criteria: is a controlled laboratory study, gamma irradiation (dose reported), and other sterilization methods. Search for publications dated between 1991 and March 31st, 2020. The database search and additional sources resulted in 284 records. Two hundred thirty records eliminated during the screening for various reasons. The number of articles used in the final synthesis was 54.

Conclusions

Identified sterilization methods (gamma irradiation, ethylene oxid, supercritical carbon dioxide (SCCO2), BioCleanse, Electron Beam) are offered as a catalog of potential methods.

As a result of the broadness of the present research, it provides an overview of sterilization methods and their effect on the mechanical properties (failure load and Young’s modulus of elasticity) of tendons. It does not stand for the state-of-the-art of any single process. Based on a systematic literature review, we recommend freezing and gamma irradiation or electron beam at 14.8–28.5 kGy. These methods are effective at keeping or improving the mechanical properties, while fully sterilizing the inside and the outside of the tendon. Other sterilization method (ethylene oxide, supercritical carbon dioxide (SCCO2), BioCleanse) deteriorated the mechanical properties. These methods are not recommended.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04296-4.

Superior Capsular Reconstruction with Achilles Tendon Allograft

Superior capsular reconstruction (SCR) has become an increasingly popular choice in the treatment of massive, irreparable rotator cuff tears, pseudoparalysis, and in cases in which revision of previous rotator cuff repair is indicated. The SCR procedure is intended to restore the superior stabilizing forces of a deficient rotator cuff. This technique is accomplished by substituting an autograft or allograft between the superior glenoid and the greater tuberosity of the humerus, thus keeping the humeral head centered in the glenoid during shoulder forward flexion and abduction. Since its advent, numerous techniques have been described for this procedure. A fascia lata autograft was initially described; however, many surgeons in the United States have advocated for the use of a humeral dermal allograft. Yet, biomechanical studies have demonstrated elongation and thinning of this material. Thus, the Achilles tendon allograft may be an attractive choice for SCR, given its previous success with ligamentous and tendinous reconstructions. In this article, we present our technique of SCR using an Achilles tendon allograft.

The influence of donor and recipient characteristics on allograft tendons: a systematic review

Tendon allograft has been an important alternative graft option aside from autograft. The outcome of reconstruction surgery is determined by donor and recipient related factors. The purpose of this article was to identified all studies reporting donor and recipient characteristics, including the age and gender of donors, along with the age, gender, activity level and smoking status of recipients, that affect the biomechanical properties and post-transplantation outcomes of allograft tendons. The systematic study search was based on MEDLINE via PubMed, Embase and the Cochrane Library databases. The reference lists of the included studies were used for hand searching (snowballing). The searching process was performed by two independent investigators, using search MESH term: "tendon", "allograft", and "person". Studies evaluating the influence of donor and recipient biological characteristics on the mechanical property and transplantation outcome of allograft were included. A total of 12 studies were selected for qualitative synthesis, including 6 studies evaluated the influence of donor characteristics, including age and gender, on the mechanical strength of tendon allograft. 6 studies assessed the influence of recipient characteristics, including age, gender, smoking status, and activity level, on the clinical outcome. As a conclusion, tendon allografts from donor younger than 40 years old were expected to have a higher mechanical property. Young patients or patients with a high level of activity were not recommended to receive allograft tendon when autograft is optional. There is no strong evidence supporting that neither donor or recipient gender affects the tendon allograft transplantation outcomes. Smoking history could increase the risk of complications.