Allograft Donor Characteristics Significantly Influence Graft Rupture After Anterior Cruciate Ligament Reconstruction in a Young Active Population

Comparison of autograft and allograft outcomes in adolescent ACL reconstruction: a propensity score analysis

PURPOSE

To assess 3-year clinical and functional outcomes, complication rates and graft survival in adolescents with closed growth plates subjected to primary unilateral anterior cruciate ligament reconstruction (ACLR) with a hamstring autograft or an allograft. The failure rate reported in the literature reaches up to 20%.

METHODS

We reviewed the records of 170 patients subjected to ACLR with a single-bundle autograft or an allograft from 2017 to 2020 with 3-year follow-up. Application of 1:2 Propensity Score Matching (PSM) considering age, sex, body mass index, injury to surgery interval, graft diameter and pre-injury Tegner Activity Scale (TAS) scores and Lysholm Knee Score (LKS) yielded 38 allografts and 62 autografts. We compared functional outcomes using the TAS, LKS and International Knee Documentation Committee (IKDC) at 18 and 36 months and the failure rates, defined as need for revision surgery, before and after PSM.

RESULTS

Mean age ranged from 15.8 (standard deviation [SD], 1.2) to 15.9 (SD, 0.9) years and the pre-injury TAS ranged from 7.3 (SD, 1.0) to 7.3 (SD, 1.2) in allograft and autograft patients, respectively. Analysis of the LKS, TAS and IKDC values demonstrated comparable levels both before and after PSM, except for the pre-matching IKDC score and the post-matching TAS score at 36 months, which were significantly higher in autograft than allograft patients (p = 0.024 and p = 0.039, respectively). As regards graft failure, before PSM significantly more allografts (12/54) than autografts (5/116) required revision surgery (p < 0.001). After matching, the difference (6/38 vs 3/62, p = 0.079) was no longer significant.

CONCLUSION

Our cohort of active adolescent who underwent primary unilateral ACLR had a higher absolute number of failures in the allograft group compared to the autograft group, emphasizing the need for careful clinical consideration. However, after applying PSM, this difference, while numerically still present, lost statistical significance. This finding may suggest that when an allograft is deemed the most appropriate choice based on patient characteristics, its use may not necessarily expose the patient to a definitively higher risk of failure.

Myths and Facts About Allograft Use in Anterior Cruciate Ligament Reconstruction: A Detailed Review of the Literature

» Patient-Specific Graft Selection: Graft selection for anterior cruciate ligament reconstruction (ACLR) requires a nuanced approach that considers various patient-specific factors, such as age, activity level, comorbidities, and surgical goals. Generally, allografts are preferred for older patients with less active lifestyles, whereas autografts are more suitable for younger, active patients because of autografts' lower retear rates.» Impact of Sterilization Techniques: Sterilization and processing techniques significantly affect the biomechanical properties and outcomes of allografts. While high-dose irradiation reduces allograft strength and compromises healing, low-dose irradiation or nonirradiated grafts offer superior biomechanical and clinical outcomes. However, standardized sterilization protocols are yet to be established.» Comparative Outcomes of Allografts and Autografts: Evaluating the literature on allografts vs. autografts in ACLR remains challenging because of the significant variability in patient characteristics, outcome measures, graft strength testing, and sterilization techniques across studies.

Allograft to bone-tunnel integration in a canine anterior cruciate ligament reconstruction model: a comparison study of allograft preparation methods

The procedure of anterior cruciate ligament (ACL) allograft preparation can be divided into fresh-frozen method (FF-allograft) or freeze-dried method (FD-allograft). This study aims to biomechanically and histologically compare the graft to bone tunnel integration between the two allografts. In-vitro results indicated that FF-allograft and FD-allograft showed excellent biocompatibility and biomechanics, while FD-allograft showed a denser collagen fiber arrangement than FF-allograft and autograft. Then, in-vivo preformation of the FF-allograft, FD-allograft, and autograft on bone tunnel integration was evaluated via a canine ACL reconstruction model. In-vivo results indicated that no signs of infection or osteoarthritis were shown in the femur-graft-tibia complexes, but more vascularity and synovitis formed around the implanted FF-allograft. Micro-computed tomography showed that peri-graft bone in the FF-allograft group was significantly increased and remodeled compared with the FD-allograft group; Histologically, the FF-allograft group exhibited similar graft-bone tunnel healing to the FD-allograft group. Tartrate-resistant acid phosphatase (TRAP) staining showed significantly more osteoclasts presented in the FD-allograft group compared to the FF-allograft group. Meanwhile, a significantly higher failure load was shown in the FF-allograft group when compared with the FD-allograft group (P < 0.05). In conclusion, the FF-allograft integrated more firmly into the bone tunnel than the FD-allograft when used in ACL reconstruction.

New Graft Choices for ACL Reconstruction: Update Article

Reconstruction of the anterior cruciate ligament (ACL) is a common procedure for injuries to this ligament, especially in athletes. There are different types of grafts used, and the choice depends on several factors. Autologous grafts, from the patients themselves, are the most common option, with rapid incorporation and a lower failure rate. Allografts from donors have their role in specific cases. Synthetic grafts, used in the 1980s, have advantages such as the absence of morbidity at the donor site, but studies have shown long-term complications. Hybrid grafts, combining autologous grafts and allografts, have gained interest, allowing a larger diameter and reducing morbidity. Peroneus longus tendon autograft has received attention, with positive results, good knee function and less hypotrophy of the thigh at the donor site. Autologous quadriceps tendon graft has gained popularity, with results comparable to patellar and flexor tendon grafts, lower morbidity at the donor site and a lower rate of re-rupture. The choice of graft has evolved, with autologous flexor grafts being preferred for less active patients and patellar grafts with bone fragments for high-performance athletes. Allografts, synthetic and hybrid grafts have their role in specific circumstances. The choice must be based on scientific evidence, considering advantages and disadvantages. ACL reconstruction is a complex procedure that requires individual considerations to select the most appropriate graft.

Outcomes of ACL Reconstruction Utilizing Supercritical CO2-Sterilized Allografts

Background

Allograft tendons are perceived to have a high ACL graft failure rate in primary anterior cruciate ligament (ACL) reconstruction (ACLR). Historical series may be biased by graft processing methods that degrade the biomechanical properties of donor tendons such as irradiation. Supercritical carbon dioxide (SCCO2) is a validated method of terminally sterilizing biomaterials at physiological temperatures without irradiation, but in vivo use of SCCO2-processed tendon allografts for primary ACLR has not been reported to date.

Hypothesis

ACLR with SCCO2 allografts would result in acceptable failure rates, subjective knee scores, and clinical evaluation at 2 years postoperatively.

Study Design

Case series; Level of evidence, 4.

Methods

Patients underwent primary ACLR with terminally sterilized SCCO2-processed human gracilis, peroneus longus, semitendinosus, tibialis anterior, and tibialis posterior tendon allografts. Patient demographics were collected, along with tendon donor age and sex. At 1 year postoperatively, subjective International Knee Documentation Committee (IKDC) and ACL-Return to Sport After Injury (ACL-RSI) scores were collected, as well as clinical evaluation. At 2 years postoperatively, the IKDC and ACL-RSI scores were repeated, and return to sports and further knee injuries were recorded.

Results

A total of 144 patients with a medianage of 26 (IQR 14) years formed the study group. Patients were predominately male (58%). The loss to follow-up rate was 8% (n = 12). The mean age of allograft tendon donors was 37 (range 17-58) years, and the majority were male (83%). The mean allograft diameter was 8.9 ± 1.0 mm. At 2 years, ACL graft failureoccurred in 5% (n = 7). All graft failureswere in patients aged ≤25 years (P = .007). Neither donor age (≤40 or >40 years) nor donor sex was associated with graft failure (P > .05). The median IKDC subjective score was 95 and ACL-RSI score was 75. There were no revisions for sepsis within the first 2 years postoperatively.

Conclusion

SCCO2 processing of allograft tendons demonstrated satisfactory clinical and patient-reported outcomes at 24 months postoperatively in a consecutive series of patients with primary ACLR, with similar ACL graft failure rates and subjective knee scores compared with those reported in published series of hamstring tendon autograft and fresh frozen nonirradiated allograft.

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.

Revision Rates After Primary Allograft ACL Reconstruction by Allograft Tissue Type in Older Patients

Background

While there is extensive literature on the use of allograft versus autograft in anterior cruciate ligament (ACL) reconstruction, there is limited clinical evidence to guide the surgeon in choice of allograft tissue type.

Purpose

To assess the revision rate after primary ACL reconstruction with allograft and to compare revision rates based on allograft tissue type and characteristics.

Study Design

Cohort study; Level of evidence, 3.

Methods

Patients who underwent primary allograft ACL reconstructions at a single academic institution between 2015 and 2019 and who had minimum 2-year follow-up were included. Exclusion criteria were missing surgical or allograft tissue type data. Demographics, operative details, and subsequent surgical procedures were collected. Allograft details included graft tissue type (Achilles, bone-patellar tendon-bone [BTB], tibialis anterior or posterior, semitendinosus, unspecified soft tissue), allograft category (all-soft tissue vs bone block), donor age, irradiation duration and intensity, and chemical cleansing process. Revision rates were calculated and compared by allograft characteristics.

Results

Included were 418 patients (age, 39 ± 12 years; body mass index, 30 ± 9 kg/m2). The revision rate was 3% (11/418) at a mean follow-up of 4.9 ± 1.4 years. There were no differences in revision rate according to allograft tissue type across Achilles tendon (3%; 3/95), BTB (5%; 3/58), tibialis anterior or posterior (3%; 5/162), semitendinosus (0%; 0/46), or unspecified soft tissue (0%; 0/57) (P = .35). There was no difference in revision rate between all-soft tissue versus bone block allograft (6/283 [2%] vs 5/135 [4%], respectively; P = .34). Of the 51% of grafts with irradiation data, all grafts were irradiated, with levels varying from 1.5 to 2.7 Mrad and 82% of grafts having levels of <2.0 Mrad. There was no difference in revision rate between the low-dose and medium-to high-dose irradiation cohorts (4% vs 6%, respectively; P = .64).

Conclusion

Similarly low (0%-6%) revision rates after primary ACL reconstruction were seen regardless of allograft tissue type, bone block versus all-soft tissue allograft, and sterilization technique in 418 patients with mean age of 39 years. Surgeons may consider appropriately processed allograft tissue with or without bone block when indicating ACL reconstruction in older patients.

Anterior Screw Insertion Results in Greater Tibial Tunnel Enlargement Rates after Single-Bundle Anterior Cruciate Ligament Reconstruction than Posterior Insertion: A Retrospective Study

Background and Objectives: Tunnel enlargement (TE) is a widely reported phenomenon after anterior cruciate ligament reconstruction (ACLR). Given the paucity of knowledge in the literature, it remains unclear whether screw position in the tunnel affects TE. This retrospective cohort study evaluated differences in postoperative tunnel enlargement rates (TER) and clinical results between anterior and posterior tibial interference screw insertion during single-bundle ACLR using autologous hamstring grafts. Materials and Methods: A group of consecutive patients that underwent primary arthroscopic single-bundle ACLR in our hospital were screened and divided into two groups based on the position of the tibial interference screw (determined by Computer Tomography within 3 days after surgery): anterior screw position group (A) and posterior screw position group (B). The bone tunnel size was measured using magnetic resonance imaging (MRI) performed 1 year after surgery. International Knee Documentation Committee (IKDC) score and the Knee Injury and Osteoarthritis Outcome Score (KOOS) were used for clinical results 1 year postoperatively. Results: 87 patients were included. The TER of Group A is higher than that of Group B (43.17% vs. 33.80%, p = 0.024). Group A showed a significant increase (12.1%) in enlargement rates at the joint line level than group B (43.77% vs. 31.67%, p = 0.004). Moreover, KOOS and IKDC scores improved in both groups. There were no significant differences in clinical outcomes between the two groups. Conclusions: One year after ACLR, patients with posterior screw showed significantly lower TE than patients with anterior screw. However, the position of screw did not lead to differences in clinical results over our follow-up period. Posterior screw position in the tibial tunnel maybe a better choice in terms of reducing TE. Whether the different screw positions affect the long-term TE and long-term clinical outcomes needs to be confirmed by further studies.

A Prospective, Double-Blind Evaluation of Anterior Cruciate Ligament Reconstruction With Tibialis Tendon Allograft: Donor Age Does Not Alter Outcomes

Purpose

To evaluate the effect of graft donor age on outcomes of anterior cruciate ligament (ACL) reconstruction with nonirradiated, fresh-frozen tibialis tendon allografts.

Methods

This prospective, randomized, double-blind, single surgeon, 2-year follow-up study enrolled 40 patients (28 female, 12 male who underwent ACL reconstruction with tibialis tendon allografts. Results were compared with historical outcomes for allografts from donors aged 18 to 70 years. Analysis was determined by Group A (<50 years) and Group B (>50 years). Objective and subjective International Knee Documentation Committee (IKDC) forms, KT-1000 testing, and Lysholm scores were used for the evaluation.

Results

Follow-up on average of 24 months was completed in 37 patients (92.5%; Group A = 17, Group B = 20). Average patient age at surgery for Group A was 42.1 years (range 27-54) and Group B was 41.7 years (range 24-56). None of the patients required additional surgery during the initial 2-year follow-up. At 2-year follow-up, there were no significant differences in subjective outcomes. IKDC objective ratings for Group A were A-15 and B-2, and Group B were A-19 and B-1 (P = .45). Average IKDC subjective scores for Group A were 86.1 (± 16.2) and Group B were 84.1 (± 15.6) (P = .70). KT-1000 side to side differences for Group A were 0-4, 1-10, and 2-2, and Group B were 0-2, 1-10, 2-6 (P = .28). Average Lysholm scores for Group A were 91.4 (± 16.7) and Group B were 88.1 (± 12.3) (P = .49).

Conclusions

Donor age was not associated with clinical outcomes after ACL reconstruction using nonirradiated, fresh-frozen tibialis tendon allografts.

Level of Evidence

II, prospective prognostic trial.

Optimal Graft Choice in Athletic Patients with Anterior Cruciate Ligament Injuries: Review and Clinical Insights

Anterior cruciate ligament (ACL) rupture is a common sporting-related knee injury with a potentially detrimental impact on the athlete’s career, yet there is no formal consensus on the optimal graft choice for reconstructing the ruptured ACL in this specific population. Options for reconstruction include autograft, allograft, and artificial grafts. However, each has associated failure risk and donor site morbidity. Our operational definition of the athlete is a skeletally mature individual participating in high level activity with the expectation to return to pre-injury level of activity. The athlete has unique injury characteristics, post-operative expectations, and graft demands that differ to the general population. Long-term outcomes are of particular importance given on-going mechanical demands on the reconstructed knee. Therefore, the purpose of this review is to consolidate current literature on the various ACL reconstruction graft options, with a focus on the optimal graft for returning the athlete to activity with the lowest rate of re-injury.

Reporte de caso de postcirugía de ligamento cruzado anterior

El ligamento cruzado anterior (LCA) es la lesión de la rodilla con mayor prevalencia en los atletas. Los avances en la técnica quirúrgica y la fijación de injertos han permitido a los pacientes participar en una rehabilitación funcional postoperatoria temprana. Este tratamiento está dirigido a lograr un mayor rango de movimiento, progresando hacia la movilización, fortalecimiento y control neuromuscular propioceptivo de la articulación. Existen varios protocolos de rehabilitación con variaciones en ejercicios específicos, progresión a través de fases y componentes claves que permiten la recuperación funcional. El objetivo final de la fisioterapia es devolver al paciente al nivel de rendimiento anterior a la lesión, incluidos el movimiento y la fuerza, sin dañar ni alargar el injerto. Presentamos el reporte de un caso con una lesión de LCA compleja, que recupero la funcionalidad de la articulación por aplicación de plan de tratamiento fisioterapéutico de forma inmediata a su intervención quirúrgica.

Bone Mesenchymal Stem Cells Contribute to Ligament Regeneration and Graft-Bone Healing after Anterior Cruciate Ligament Reconstruction with Silk-Collagen Scaffold

Anterior cruciate ligament (ACL) reconstruction was realized using a combination of bone mesenchymal stem cells (BMSCs) and silk–collagen scaffold, and an in vivo evaluation of this combination was performed. By combining type I collagen and degummed silk fibroin mesh, silk–collagen scaffolds were prepared to simulate ligament components. BMSCs isolated from bone marrow of rabbits were cultured for a homogenous population and seeded on the silk–collagen scaffold. In the scaffold and BMSC (S/C) group, scaffolds were seeded with BMSCs for 72 h and then rolled and used to replace the ACL in 20 rabbits. In the scaffold (S) group, scaffolds immersed only in culture medium for 72 h were used for ACL reconstruction. Specimens were collected at 4 and 16 weeks postoperatively to assess ligament regeneration and bone integration. HE and immunohistochemical staining (IHC) were performed to assess ligament regeneration in the knee cavity. To assess bone integration at the graft–bone interface, HE, Russell–Movat staining, micro-CT, and biomechanical tests were performed. After 4 weeks, vigorous cell proliferation was observed in the core part of the scaffold in the S/C group, and a quantity of fibroblast-like cells and extracellular matrix (ECM) was observed in the center part of the graft at 16 weeks after surgery. At 4 and 16 weeks postoperatively, the tenascin-C expression in the S/C group was considerably higher than that in the S group (4 w, p < 0.01; 16 w, p < 0.01). Furthermore, bone integration was better in the S/C group than in the S group, with histological observation of trabecular bone growth into the graft and more mineralized tissue formation detected by micro-CT (4 w, bone volume fraction (BV/TV), p = 0.0169, bone mineral density (BMD), p = 0.0001; 16 w, BV/TV, p = 0.1233, BMD, p = 0.0494). These results indicate that BMSCs promote ligament regeneration in the knee cavity and bone integration at the graft–bone interface. Silk–collagen scaffolds and BMSCs will likely be combined for clinical practice in the future.