Allograft Anterior Cruciate Ligament Research Articles

The Majority of Patients Aged 40 and Older Having Allograft Anterior Cruciate Ligament Reconstruction Achieve a Patient Acceptable Symptomatic State

To evaluate patient satisfaction, retear rates, and patient-reported outcomes (PROs) in patients aged 40 and older undergoing allograft anterior cruciate ligament reconstruction (ACLR). The secondary goal was to compare these parameters between groups of patients with intact versus failed grafts, and to evaluate these in relation to a historically reported International Knee Documentation Committee (IKDC) patient-acceptable symptoms state (PASS) score. Records of patients aged 40 and older who underwent ACLR between 2005 and 2016 at a single institution with a minimum 2-year follow-up were retrospectively reviewed. Patient-reported satisfaction, outcome scores, and failure rates were analyzed. The rate of achieving a previously defined IKDC PASS score based on younger cohorts was reported, and an updated PASS threshold for older patients was calculated. 201 patients were included with a mean age of 48.6 years (range: 40-68) and mean follow-up of 6.2 years (range: 2.8-11.2). 182 (90.5%) patients reported satisfaction following surgery. 16 (8.0%) patients experienced failure of their ACLR, 10 of which underwent revision ACLR. The median IKDC score in the intact ACLR group was 86.2, compared to 66.7 in the failure group (P < .001). In total, 134 (72.4%) patients in the intact group achieved the historical PASS score of 75.9 on IKDC compared to only 4 (25%) in the failure group (χ2= 15.396, P < .001). An updated IKDC PASS threshold for older cohorts was calculated to be 66.7. Patients aged 40 and older who underwent allograft ACLR had an 8.0% failure rate at a mean follow-up of 6 years. Graft failure in patients aged 40 and older was associated with worse PROs. The majority of patients achieved the historically reported IKDC PASS threshold. Additionally, an updated age-appropriate IKDC PASS score of 66.7 was calculated to aid in future ACLR studies assessing older patients. Level IV.

Effect of Freshly Isolated Bone Marrow Mononuclear Cells and Cultured Bone Marrow Stromal Cells in Graft Cell Repopulation and Tendon-Bone Healing after Allograft Anterior Cruciate Ligament Reconstruction.

Graft cell repopulation and tendon-bone tunnel healing are important after allograft anterior cruciate ligament reconstruction (ACLR). Freshly isolated bone marrow mononuclear cells (BMMNCs) have the advantage of short isolation time during surgery and may enhance tissue regeneration. Thus, we hypothesized that the effect of intra-articular BMMNCs in post-allograft ACLR treatment is comparable to that of cultured bone marrow stromal cells (BMSCs). A rabbit model of hamstring allograft ACLR was used in this study. Animals were randomly assigned to the BMMNC, BMSC, and control groups. Fresh BMMNCs isolated from the iliac crest during surgery and cultured BMSCs at passage four were used in this study. A total of 1 × 107 BMMNCs or BMSCs in 100 µL phosphate-buffered saline were injected into the knee joint immediately after ACLR. The control group was not injected with cells. At two and six weeks post operation, we assessed graft cell repopulation with histological and cell tracking staining (PKH26), and tendon-bone healing with histological micro-computed tomography and immunohistochemical analyses for collagen I and monocyte chemoattractant protein-1 (MCP1). At two weeks post operation, there was no significant difference in the total cell population within the allograft among the three groups. However, the control group showed significantly higher cell population within the allograft than that of BM cell groups at six weeks. Histological examination of proximal tibia revealed that the intra-articular delivered cells infiltrated into the tendon-bone interface. Compared to the control group, the BM cell groups showed broader gaps with interfacial fibrocartilage healing, similar collagen I level, and higher MCP1 expression in the early stage. Micro-CT did not reveal any significant difference among the three groups. BMMNCs and BMSCs had comparable effects on cell repopulation and interfacial allograft-bone healing. Intra-articular BM cells delivery had limited benefits on graft cell repopulation and caused higher inflammation than that in the control group in the early stage, with fibrocartilage formation in the tendon-bone interface after allograft ACLR.

Quantitative assessment of neural elements in a rat model using nerve growth factor after remnant-preserving anterior cruciate ligament reconstruction: a histological and immunofluorescence pilot study

BackgroundImmunofluorescence analyses of anterior cruciate ligament (ACL) allografts following remnant-preserving ACL reconstruction using Achilles tendon allografts have provided evidence for the presence of neural elements. In this study, we aimed to examine the expression of neural elements and quantify the presence of neural cells in ACL remnants and Achilles allografts using nerve growth factor (NGF) therapy after remnant-preserving ACL reconstruction.MethodsExperiments were conducted on 5 pairs of rats (approximately 8 weeks old and weighing 320 g at the time of surgery). Longitudinally, split Achilles tendons from the paired rats were freshly frozen and later defrosted with warm saline and allografted onto the right ACL of the other rat that was partially detached at the femoral attachment site. A sham operation was conducted on the left knee to be used as a control. NGF was injected into both knee joints every week for 6 weeks after surgery. The presence of neural cells in the ACL of the sham-operated knee, allografted Achilles tendon, and ACL remnant was examined 6 weeks post-surgery using H and E and immunofluorescent staining.ResultsH and E staining did not reveal neural cells in any of the three groups. However, immunofluorescence analysis showed the presence of nestin-positive neural elements in the normal ACL tissues as well as ACL remnants. Additionally, neural elements were examined in 7 of the 8 (87.5%) allograft tissues. Quantitative analysis showed no difference in the number or area of nuclei among the three groups. However, the number and area of neural cells in the Achilles allografts were significantly lower than those in the other two groups (p = 0.000 and p = 0.001, respectively).ConclusionOur observations indicate that ACL remnants promote the new ingrowth and persistence of neural cells. We suggest that the ingrowth of neural elements can support the persistence and new ingrowth of mechanoreceptors, thereby enhancing the functional stability of knee joints. Moreover, the expression of neural cells in the Achilles allografts was lower than that in normal ACL tissues and ACL remnants in the quantitative evaluation, thereby confirming the essential role of ACL remnants in knee joint functionalization.

Terminal Sterilization of Anterior Cruciate Ligament (ACL) Allografts: A Systematic Review of Outcomes

Anterior cruciate ligament (ACL) injuries are common and reconstruction can be completed with either autograft or allograft tissue. However, there is concern about an increased failure rate with allograft tissue. The purpose of this study was to systematically review the available evidence to determine the effect of irradiation and level of dose on the failure rates of allograft in ACL reconstruction. A literature search was performed using PubMed, Scopus, and Web of Science from January 2000 to September 2013. Inclusion criteria consisted of the following: (1) primary, unilateral, single-bundle allograft ACL procedure, (2) studies with data documenting graft type and terminal sterilization technique, (3) subjective assessments of outcome, and (4) objective assessments of outcome. Studies without reported subjective and objective outcomes and those pertaining to revision ACL reconstruction were excluded. Failures were defined and compared between irradiated and non-irradiated grafts, as well as between grafts irradiated with 1.2 - 1.8 Mrad and those with 2.0 - 2.5 Mrad. Of the 242 articles identified via initial search, 17 studies met the final inclusion criteria. A total of 1,090 patients were evaluated in this study, all having undergone unilateral primary ACL reconstruction with allograft tissue with 155 failures. The failure rate between non-irradiated (98/687, 14.7%) and irradiated (57/408, 14.0%) was not statistically significant (p = 0.86). Grafts in the high-dose irradiation group (27/135, 20.0%) had a statistically significant higher (p < 0.001) rate of failure than those in the low-dose irradiation group (30/273, 10.6%). The irradiation of an allograft increases the risk of failure after an ACL reconstruction but the use of lower doses of radiation decreases that risk.

TightRope Versus Biocomposite Interference Screw for Fixation in Allograft ACL Reconstruction: Prospective Evaluation of Osseous Integration and Patient Outcomes.

Background:Anterior cruciate ligament (ACL) reconstruction is a commonly performed procedure with many options regarding graft choice and graft fixation. The purpose of this study was to compare suspensory and aperture fixation in terms of femoral osseous integration of the bone block after ACL reconstruction with an Achilles tendon allograft.Methods:After institutional review board approval and patient consent were obtained, 37 patients underwent ACL reconstruction with an Achilles tendon allograft. The patients were randomized according to the graft femoral fixation technique, which was with either a suspensory device (Arthrex TightRope) or aperture fixation by a biocomposite interference screw (Arthrex BioComposite Interference Screw or DePuy Mitek MILAGRO Interference Screw). Tibial fixation, performed with a biocomposite screw and knotless anchor, was identical in all patients. All patients underwent a computed tomography (CT) scan at 6 months to evaluate bone block incorporation of the femoral graft within the femoral tunnel, which was the study’s primary outcome. Secondary outcome measures included a postoperative visual analogue scale (VAS) pain score, range-of-motion measures, and International Knee Documentation Committee scores. Demographic data were collected.Results:Thirty-three patients (89%) completed the study’s 6-month follow-up, at which time the femoral ossification score was significantly greater in the aperture fixation group (p = 0.025). There was no substantial difference between the 2 groups with regard to any other outcome measure.Conclusions:Performing Achilles tendon allograft ACL reconstruction with femoral aperture fixation results in greater femoral bone block incorporation at 6 months postoperatively compared with what is seen after suspensory fixation.Level of Evidence:Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Stem Cell–Infused Anterior Cruciate Ligament Reconstruction

Anterior cruciate ligament (ACL) tears are unfortunate but common injuries in the athletic population. The standard of care for ACL tears is a surgical intervention to reconstruct the ACL to restore knee functionality as well as quality of life. In recent years, bone marrow aspirate concentrate (BMAC) has seen increasing use in various orthopaedic settings. This increase can be attributed to the potential beneficial qualities that mesenchymal stem cells, progenitor cells, and growth factors, all of which are present in BMAC, can provide. In this technical note and accompanying video, we describe an anatomic allograft ACL reconstruction infused with BMAC to utilize BMAC's potential benefits.

Independent Suture Tape Internal Brace Reinforcement of Bone-Patellar Tendon-Bone Allografts: Biomechanical Assessment in a Full-ACL Reconstruction Laboratory Model.

Internal bracing for anterior cruciate ligament (ACL) surgery is a relatively new concept. The purpose of this study was to evaluate the effects of an "independent" button-fixed internal brace on the biomechanical properties of ACL reconstruction in a full-construct experimental model. Three groups (n = 10 each) were tested in a full-construct porcine-bone model with human bone-patellar tendon-bone allografts using different reconstruction techniques: interference screw fixation on femur and tibia (S-S group), adjustable-loop device (ALD) fixation on the femur with tibial interference screw without suture tape (ALD-S group), and with internal brace (ALD-S-IB group). Measured outcomes included cyclic displacement, stiffness, and ultimate load to failure. The ALD-S-IB group (2.9 ± 0.8 mm) displaced significantly less than the ALD-S (4.2 ± 0.9 mm; p = 0.015) and S-S group (4.3 ± 1.1 mm; p = 0.017). No significant difference was found between the ALD-S and the S-S group. Construct stiffness was significantly higher for the ALD-S-IB group (156 ± 23 N/mm) and the ALD-S group (122 ± 28 N/mm) than for the S-S group (104 ± 40 N/mm; p = 0.003 and p = 0.0042), but there was no significant difference between both ALD groups. Similarly, ultimate loads in the ALD-S-IB (758 ± 128 N) and the ALD-S groups (628 ± 223 N) were significantly greater than in the S-S group (416 ± 167 N; p < 0.001 and p = 0.025), but there was no significant difference between ALD groups. Adding an internal brace reinforcement to an ALD in a full-construct experimental model significantly decreased cyclic displacement by 31% without increasing construct stiffness or ultimate load significantly. These results indicate that suture tape internal bracing of bone-patellar tendon-bone allograft ACL reconstruction decreases cyclic displacement during experimental testing, which has clinical implications regarding initial construct stability.

REDUCTION IN HAMSTRING AUTOGRAFT DIAMETER AS A RESULT OF ACL RECONSTRUCTION PREPARATION USING LONGITUDINAL TENSION AND CIRCUMFERENTIAL COMPRESSION

Background: Previous studies have investigated the effect of tension and circumferential compression on the diameter of fresh-frozen anterior cruciate ligament (ACL) allografts, but no study has described the effect on soft tissue ACL autografts harvested for implantation in the operating room for ACL reconstruction. The purpose of this study was to elucidate how hamstring autograft diameter changes during preparation for ACL reconstruction with compression in addition to tensioning. We hypothesized that autograft diameter would decrease as the graft was prepared with both tension and circumferential compression. Operative complications related to graft compression were also investigated. Methods: 100 ACL reconstruction surgeries (Age M = 15.3 ± 2.2 years; 53% male) were identified among two orthopedic surgeons. Hamstring tendon grafts were prepared in a standardized procedure to produce a looped graft for all-inside ACL reconstruction. Autografts were tensioned to 15-20 lbs and then their tibial and femoral diameters were measured using cylindrical sizing blocks. The graft diameters were measured again after placement under a saline soaked gauze for 10 minutes with the sizing blocks in place. A Wilcoxon signed rank test with correction for continuity was performed to detect significant change in autograft diameters after compression. Results: Treatment of hamstring autografts with longitudinal tension and circumferential compression significantly decreased the median tibial and femoral graft diameters by 0.75 mm. The median tibial diameter decreased from 9.50 mm to 8.75 mm (p &lt; 0.0001) and the median femoral diameter decreased from 9.50 mm to 8.50 mm (p &lt; 0.0001). 72% of all autografts had the same tibial and femoral diameters at implant. No intraoperative complications were noted with implantation of compressed grafts in smaller diameter tunnels. Conclusions: Median diameters of ACL hamstring autografts harvested in the OR decreased by 0.75 mm after treatment with circumferential compression using cylindrical sizing blocks. This decreased the socket size by one to two 0.5 mm sizes with no adverse events noted intra-operatively due to the compression of the grafts or the smaller sockets. Clinical Relevance: Graft integration in a bone tunnel is dependent on optimal fit of the graft inside the tunnel. If the tunnel is too small, the graft will not fit and if it is too large, it may allow joint fluid into the tunnel leading to tunnel widening and incomplete integration. Pre-tensioning a graft has been noted for many years to be an important way to properly establish the length-tension relationship of a graft. Here, we show that circumferential compression of the graft prior to implantation significantly changes the size of the graft, and thus the size of the tunnels required for implantation. In addition to providing better graft tunnel match, using smaller tunnels requires less bone removal which is particularly advantageous for pediatric, revision, and double bundle ACL reconstruction techniques where space for tunnel drilling is limited.

Risk of Infection After Allograft Anterior Cruciate Ligament Reconstruction: Are Nonprocessed Allografts More Likely to Get Infected? A Cohort Study of Over 10,000 Allografts

Background: Allograft tissue is frequently used in anterior cruciate ligament reconstruction (ACLR). It is often irradiated and/or chemically processed to decrease the risk of disease transmission, but some tissue is aseptically harvested without further processing. Irradiated and chemically processed allograft tissue appears to have a higher risk of revision, but whether this processing decreases the risk of infection is not clear. Purpose: To determine the incidence of deep surgical site infection after ACLR with allograft in a large community-based sample and to evaluate the association of allograft processing and the risk of deep infection. Study Design: Cohort study; Level of evidence, 3. Methods: The authors conducted a cohort study using the Kaiser Permanente Anterior Cruciate Ligament Reconstruction Registry. Primary isolated unilateral ACLR with allograft were identified from February 1, 2005 to September 30, 2015. Ninety-day postoperative deep infections were identified via an electronic screening algorithm and then validated through chart review. Logistic regression was used to evaluate the likelihood of 90-day postoperative deep infection per allograft processing method: processed (graft treated chemically and/or irradiated) or nonprocessed (graft not irradiated or chemically processed). Results: Of 10,190 allograft cases, 8425 (82.7%) received a processed allograft, and 1765 (17.3%) received a nonprocessed allograft. There were 15 (0.15%) deep infections during the study period: 4 (26.7%) coagulase-negative Staphylococcus, 4 (26.7%) methicillin-sensitive Staphylococcus aureus, 1 (6.7%) Peptostreptococcus micros, and 6 (40.0%) with no growth. There was no difference in the likelihood for 90-day deep infection for processed versus nonprocessed allografts (odds ratio = 1.36, 95% CI = 0.31-6.04). Conclusion: The overall incidence of deep infection after ACLR with allograft tissue was very low (0.15%), suggesting that the methods currently employed by tissue banks to minimize the risk of infection are effective. In this cohort, no difference in the likelihood of infection between processed and nonprocessed allografts could be identified.

Short-Term Effects of the Kinesio Taping® on Early Postoperative Hip Muscle Weakness in Male Patients With Hamstring Autograft or Allograft Anterior Cruciate Ligament Reconstruction.

Objective: Kinesio taping® (KT) is a widely used treatment method in musculoskeletal rehabilitation. Little is known about the KT treatment and hip strength in patients with anterior cruciate ligament reconstruction (ACLR). The purpose of this study was to investigate the effectiveness of the KT treatment on hip muscle weakness in early rehabilitation of ACLR and the possible determinants of the ACLR-hip strength deficit (HSD). Design: Double-blind sham-controlled study. Setting: Rehabilitation department. Patients: A total of 26 male patients who underwent unilateral ACLR using hamstring autograft or allograft 4 days before. Interventions: The patients were randomized to receive the knee KT treatment (n = 13) with lymphatic correction plus muscle (biceps/rectus femoris) facilitation or sham KT (n = 13) for 10 days. In addition, the same ACLR rehabilitation program was applied to all the patients. Main Outcome Measures: The baseline data included demographic and clinical characteristics, postoperative swelling, knee motion loss and knee pain, and bilateral strength of the knee and hip muscle groups, except for rotator. Then, percentage values of hip HSD and knee strength limb symmetry index were calculated. The hip strength measurements in ACLR-operated leg were repeated on the 5th to 10th days of KT. Results: Changes in all hip strength values over time were significant in both groups (P < .01). In intergroup analysis of 5th and 10th days, improvements in the flexor (only 10th day), extensor, and adductor hip strength on operated leg were in favor of KT group (P < .05). In addition, the postoperative thigh swelling and knee strength limb symmetry index values were correlated with the HSD outcomes in baseline data (P < .05). Conclusions: ACLR-HSD can be caused by postoperative increased swelling and reduced knee strength. The KT treatment with lymphatic correction and muscle facilitation can be used in the treatment of postoperative hip muscle weakness after ACLR.

Opening Wedge High Tibial Osteotomy and Anterior Cruciate Ligament Reconstruction or Revision

High tibial osteotomy (HTO) is a valid treatment option for young active patients with medial tibiofemoral osteoarthrosis (OA) and varus deformity. Sometimes medial OA is combined with symptomatic anterior cruciate ligament (ACL) deficiency. Although isolated HTO (with possible delayed ACL reconstruction) might be indicated in the older population, young active patients may require combined HTO and ACL reconstruction. In addition, an abnormally increased tibial slope may predispose to ACL reconstruction failure and should be addressed for a successful ACL revision. The combination of HTO and ACL reconstruction produces good results, with resumption of normal daily activities, as well as recreational sports, and does not seem to increase the risk of complications compared with isolated HTO. The purpose of this Technical Note is to describe our indications, planning, and technique for opening wedge HTO fixed with a spacer plate and anatomic soft-tissue (autograft or allograft) ACL reconstruction, with proximal extracortical suspension and distal interference screw fixation.

Enhanced ACL Graft Incorporation by Novel Minimally Invasive Activation of Endogenous Stem Cells

Objectives:The ultimate healing of a ligament graft to bone is a lengthy process that results in reparative tissue that is distinctly different from a native ligament insertion. This known structural aberration results in inferior biomechanical properties and can contribute significantly to recurrent injury as well as compromised function. Thus, technology allowing for accelerated biologic incorporation as well as the recapitulation of a native insertion would be of great benefit to patients. We hypothesized that the treatment of anterior cruciate ligament (ACL) reconstruction bone tunnels with bone morphogenetic protein (BMP) DNA combined with a pulse of ultrasound (US) energy would lead to activation of endogenous stem cells and result in enhanced graft incorporation.Methods:Soft tissue allograft ACL reconstruction was performed in nine mini-pigs using cortical screw post fixation. A collagen scaffold was added to the terminus of each tendon graft limb contained within the corresponding bone tunnel. On post-operative day 14, a lipid microsphere solution containing DNA encoding either green fluorescence protein (GFP, n=3 pigs) or BMP-6 (n=6 pigs) was delivered into the bone tunnels percutaneously under fluoroscopic guidance. The bone tunnels in the US treated group were then immediately treated with a transcutaneous US energy pulse at the site of the bone tunnels, whereas the control group did not receive US delivery. At five days post-treatment the cells occupying the bone tunnels of the GFP treated pigs (n=3) were harvested and subjected to fluorescence-activated cell sorting (FACS) analysis to assess for expression of GFP as well as known mesenchymal stem cell (MSC) markers (CD29, CD44, CD90). Six weeks post-treatment the BMP/US treated pigs (n=3) and control pigs (n=3) were sacrificed and their knee joints were scanned using microCT. Biomechanical testing of anterior-posterior (AP) knee laxity was performed via application of sinusoidal AP-directed shear loads for 12 cycles. Load to failure was assessed by removal of the joint capsule, menisci, collateral ligaments, and the PCL leaving only the ACL graft intact. The tibia and femur were then mounted on a universal material testing machine with a 5kN load cell and distracted until failure of the ACL graft or graft-bone interface.Results:FACS analysis done 5 days after GFP gene delivery showed that 40-50% of the cells occupying the US treated bone tunnels expressed GFP and this was significantly more than the cells in untreated bone tunnels (p< 0.05). In addition, 12-22% of the cells in the bone tunnels expressed MSC markers. Quantification of bone volume in ACL reconstruction tunnels showed significantly higher values in BMP-6/US treated animals (fig 1A,B,C; *p<0.05, t-test). AP laxities at ±20N of BMP-6/US treated pigs were lower than untreated pigs (fig 1D). The linear stiffness (fig 1E) and maximum load to failure (fig 1F) were both significantly higher than untreated pigs, demonstrating stronger graft-bone integration among the treated animals. (*p<0.05, t-test).Conclusion:Endogenous stem cell gene expression can be altered in a large animal model via novel minimally invasive techniques and this can result in enhanced ligament biomechanical properties. Minimally invasive biologic technology such as this would likely be of significant benefit to the treatment of patients undergoing ligament reconstruction procedures and more research regarding these technologies is certainly warranted.

Clinical evaluations of anterior cruciate ligament reconstruction with platelet rich plasma

To investigate the clinical outcomes of autologous platelet rich plasma (PRP) for anterior cruciate ligament (ACL) reconstruction. Between August 2014 and August 2016, 42 patients with ACL ruptures who underwent arthroscopic ACL reconstruction were randomly divided into 2 groups: 21 patients received graft soaked with PRP (trial group) and 21 patients received routine graft in ACL reconstruction (control group). Because 6 patients failed to be followed up, 17 patients of trial group and 19 of control group were enrolled in the study. There was no significant difference in gender, age, body mass index, side, injury reason, disease duration, Kellgren-Lawrence grade, and preoperative visual analogue scale (VAS), Lysholm score, and International Knee Documentation Committee (IKDC) activity scores between 2 groups ( P>0.05). VAS score, Lysholm score, and IKDC activity scores were used to evaluate pain and function at 3 and 12 months postoperatively. Further, second arthroscopy and MRI examination were performed at 12 months postoperatively. The patients in both groups were followed up 3 to 12 months with an average of 9.83 months. The VAS score, Lysholm score, and IKDC activity scores were significantly improved at 3 and 12 months after operation in 2 groups ( P<0.05), and the scores of trial group were significantly better than those of control group at 3 months ( P<0.05), but no significant difference was found between 2 groups at 12 months ( P>0.05). No complications of effusion, infection, and allergy were observed in 2 groups during follow-up. MRI showed good position of ACL grafts and good signal quality of the graft in the majority of the cases. However, mixed hyperintense and presence of synovial fluid at the femoral bone-tendon graft interface were found in 3 patients of trial group and 4 patients of control group, indicating poor remodeling ligamentation. MRI score was 3.53±1.13 in trial group and was 3.21±0.92 in control group, showing no significant difference ( t=0.936, P=0.356). The second arthroscopy examination showed ligament remodeling score was higher in trial group than control group ( t=3.248, P=0.014), but no significant difference was found in synovial coverage score and the incidence of cartilage repair ( t=2.190, P=0.064; χ2=0.090, P=0.764). PRP application in allograft ACL reconstruction can improve knee function and relieve pain after operation, which may also accelerate graft remodeling.

What Factors Influence the Biomechanical Properties of Allograft Tissue for ACL Reconstruction? A Systematic Review.

Allograft tissue is used in 22% to 42% of anterior cruciate ligament (ACL) reconstructions. Clinical outcomes have been inconsistent with allograft tissue, with some series reporting no differences in outcomes and others reporting increased risk of failure. There are numerous variations in processing and preparation that may influence the eventual performance of allograft tissue in ACL reconstruction. We sought to perform a systematic review to summarize the factors that affect the biomechanical properties of allograft tissue for use in ACL reconstruction. Many factors might impact the biomechanical properties of allograft tissue, and these should be understood when considering using allograft tissue or when reporting outcomes from allograft reconstruction. What factors affect the biomechanical properties of allograft tissue used for ACL reconstruction? We performed a systematic review to identify studies on factors that influence the biomechanical properties of allograft tissue through PubMed and SCOPUS databases. We included cadaveric and animal studies that reported on results of biomechanical testing, whereas studies on fixation, histologic evaluation, and clinical outcomes were excluded. There were 319 unique publications identified through the search with 48 identified as relevant to answering the study question. For each study, we recorded the type of tissue tested, parameters investigated, and the effects on biomechanical behavior, including load to failure and stiffness. Primary factors identified to influence allograft tissue properties were graft tissue type, sterilization methods (irradiation and chemical processing), graft preparation, donor parameters, and biologic adjuncts. Load to failure and graft stiffness varied across different tissue types, with nonlooped tibialis grafts exhibiting the lowest values. Studies on low-dose irradiation showed variable effects, whereas high-dose irradiation consistently produced decreased load to failure and stiffness values. Various chemical sterilization measures were also associated with negative effects on biomechanical properties. Prolonged freezing decreased load to failure, ultimate stress, and ultimate strain. Up to eight freeze-thaw cycles did not lead to differences in biomechanical properties of cadaveric grafts. Regional differences were noted in patellar tendon grafts, with the central third showing the highest load to failure and stiffness. Graft diameter strongly contributed to load-to-failure measurements. Age older than 40 years, and especially older than 65 years, negatively impacted biomechanical properties, whereas gender had minimal effect on the properties of allograft tissue. Biologic adjuncts show potential for improving in vivo properties of allograft tissue. Future clinical studies on allograft ACL reconstruction should investigate in vivo graft performance with standardized allograft processing and preparation methods that limit the negative effects on the biomechanical properties of tissue. Additionally, biologic adjuncts may improve the biomechanical properties of allograft tissue, although future preclinical and clinical studies are necessary to clarify the role of these treatments. Based on the findings of this systematic review that emphasize biomechanical properties of ACL allografts, surgeons should favor the use of central third patellar tendon or looped soft tissue grafts, maximize graft cross-sectional area, and favor grafts from donors younger than 40 years of age while avoiding grafts subjected to radiation doses > 20 kGy, chemical processing, or greater than eight freeze-thaw cycles.

“Proprietary Processed” Allografts: Clinical Outcomes and Biomechanical Properties in Anterior Cruciate Ligament Reconstruction

Background: The processing of allograft tissues in anterior cruciate ligament (ACL) reconstruction continues to be controversial. While high-dose irradiation of grafts has received scrutiny for high failure rates, lower dose irradiation and “proprietary-based” nonirradiated sterilization techniques have become increasingly popular, with little in the literature to evaluate their outcomes. Recent studies have suggested that the specifics of allograft processing techniques may be a risk factor for higher failure rates. Purpose: To assess these proprietary processes and their clinical outcomes and biomechanical properties. Study Design: Systematic review. Methods: A systematic review was performed using searches of PubMed, EMBASE, Google Scholar, and Cochrane databases. English-language studies were identified with the following search terms: “allograft ACL reconstruction” (title/abstract), “novel allograft processing” (title/abstract), “allograft anterior cruciate ligament” (title/abstract), “anterior cruciate ligament allograft processing” (title/abstract), or “biomechanical properties anterior cruciate ligament allograft” (title/abstract). Duplicate studies, studies not providing the allograft processing technique, and those not containing the outcomes of interest were excluded. Outcomes of interest included outcome scores, complication and failure rates, and biomechanical properties of the processed allografts. Results: Twenty-four studies (13 clinical, 11 biomechanical) met inclusion criteria for review. No demonstrable difference in patient-reported outcomes was appreciated between the processing techniques, with the exception of the Tutoplast process. The clinical failure rate of the Tutoplast process was unacceptably high (45% at 6 years), but no other difference was found between other processing techniques (BioCleanse: 5.4%; AlloTrue: 5.7%; MTF: 6.7%). Several studies did show an increased failure rate, but these studies either combined processing techniques or failed to delineate enough detail to allow a specific comparison for this study. The biomechanical studies showed overall maintenance of satisfactory biomechanical properties throughout multiple testing modes with normalization to the percentage of control specimens. Conclusion: A comparison of proprietary allograft processing techniques is difficult because of the variability and lack of specificity of reporting in the current literature. Among the available literature, except for the Tutoplast process, no notable differences were found in the clinical outcomes or biomechanical properties. Future study with a longer follow-up is necessary to determine the role and limitations of these grafts in the clinical setting.

A prospective randomized comparison of two distinct allogenic tissue constructs for anterior cruciate ligament reconstruction

BackgroundConduct a prospective randomized study to compare clinical outcomes of anterior cruciate ligament (ACL) reconstruction using quadrupled hamstring tendon (HT) allograft or doubled tibialis anterior (TA) allograft. Limited level 1 data exist comparing outcomes of different soft tissue allograft constructs for ACL reconstruction. We hypothesized no difference would exist in the patient reported outcomes (PRO), arthrometric testing, or rate of re-rupture between the two constructs. MethodsNinety eight subjects undergoing primary ACL reconstruction were randomized to HT (n=47) or TA (n=51) allograft. Subjects completed validated (PRO) measures pre-operatively, and six months and two years post-operatively. Arthrometric testing was performed at six months to assess integrity of the reconstruction. ResultsFifty-eight percent of subjects (57/98) completed a two-year follow up. Allograft re-tear rates were similar between groups (6.2% HT vs. 4.0% TA, respectively, p=1.0). The relative risk of re-tear in the HT group was 1.5 compared to the TA group (p=0.7). The TA group improved significantly more on the physical portion of the VR-12 (p=0.046) and Lysholm score (p=0.014) compared to the HT group. There was no difference in the change from baseline for the other PRO scores at two years. ConclusionsOur data indicate no difference in graft failure rate and similar improvement from baseline in most PRO scores between treatment groups after two years. Based on these findings, TA allograft appears to provide a reliable and satisfactory option for patients who elect to undergo allograft ACL reconstruction.

Temporal Changes in Cellular Repopulation and Collagen Fibril Remodeling and Regeneration After Allograft Anterior Cruciate Ligament Reconstruction

Background: Distinguishing recipient cells from donor ligament cells is difficult in the early graft-healing phase after anterior cruciate ligament (ACL) reconstruction. The ability to track the distribution and differentiation of recipient cells using genetically engineered transgenic (Tg) animals would have significant clinical and research effects on graft healing after ACL reconstruction. Hypothesis: Kusabira-Orange Tg pigs may allow the tracking of recipient cells infiltrating the graft after ACL reconstruction. The repopulation of recipient cells within the graft would be apparent even in the early graft-healing phase when necrotic donor cells are still present. Study Design: Descriptive laboratory study. Methods: In 17 genetically engineered Tg pigs, which carried the red fluorescent protein Kusabira-Orange, ACL reconstruction was performed on the right knee using a digital flexor tendon harvested from wild-type pigs. Tissue samples harvested at different time points were subjected to histological, immunohistochemical, and electron microscopic analyses. Results: At 3 weeks postoperatively, recipient cells expressing red fluorescence embraced the graft and were infiltrating the central part of the graft. These cells with oval nuclei gradually infiltrated the gap of collagen fibers, losing their regular orientation. At 6 weeks, cellularity within the graft had doubled to match that of the native ACL, while acellular necrotic regions still existed centrally. Ubiquitous cellular distributions resembling the native ACL were observed at 24 weeks. Electron microscopic analysis showed that the mean collagen fibril diameter and density gradually decreased over 24 weeks. Conclusion: Genetically engineered pigs carrying the Kusabira-Orange gene were useful animal models for analyzing intrinsic and extrinsic cellular dynamics during the course of graft healing after ACL reconstruction. Cellular repopulation by recipient cells occurred in the very early stage, and the cellular distribution within the graft resembled that in the native ACL by 24 weeks, but the reconstructed graft had not restored the ultrastructure of the native ACL by that stage. Clinical Relevance: In allograft ACL reconstruction in a pig model, cellular repopulation was completed by 24 weeks after surgery, but the collagen matrix had not resumed the ultrastructure of the native ACL. Surgeons should be aware that risks may remain with returning to sports activities at 24 weeks after surgery.

Hamstring Autograft Had Better Long-Term Survivorship Than Tibialis Posterior Tendon Allograft for Anterior Cruciate Ligament Reconstruction.

Bottoni CR, Smith EL, Shaha J, Shaha SS, Raybin SG, Tokish JM, Rowles DJ. Autograft versus allograft anterior cruciate ligament reconstruction: a prospective, randomized clinical study with a minimum 10-year follow-up. Am J Sports Med. 2015 Oct;43(10):2501-9. ### Question: In patients having anterior cruciate ligament (ACL) reconstruction, how does hamstring autograft compare with tibialis posterior tendon allograft for long-term outcomes? ### Design: Randomized (allocation concealed), blinded (physical therapist supervising rehabilitation), controlled trial with a minimum of 10 years of follow-up. ### Setting: Tripler Army Medical Center, Honolulu, Hawaii. ### Patients: 99 patients who were ≥18 years of age and had symptomatic ACL deficiency were enrolled. 95% of patients were on active military duty at the time of surgery. Exclusion criteria were multiligamentous injuries, previous knee ligament surgery, or time remaining in Hawaii of <6 months. Follow-up was available for 97 patients (mean age, 29 years; 87% men). ### Intervention: Patients were allocated to ACL reconstruction with hamstring autograft …

Two-Stage Revision Anterior Cruciate Ligament Reconstruction: Bone Grafting Technique Using an Allograft Bone Matrix

Outcomes of primary anterior cruciate ligament (ACL) reconstruction have been reported to be far superior to those of revision reconstruction. However, as the incidence of ACL reconstruction is rapidly increasing, so is the number of failures. The subsequent need for revision ACL reconstruction is estimated to occur in up to 13,000 patients each year in the United States. Revision ACL reconstruction can be performed in one or two stages. A two-stage approach is recommended in cases of improper placement of the original tunnels or in cases of unacceptable tunnel enlargement. The aim of this study was to describe the technique for allograft ACL tunnel bone grafting in patients requiring a two-stage revision ACL reconstruction.

An Arthroscopic Second-Look Study on the Effect of Remnant Preservation on Synovialization of Bone–Patellar Tendon–Bone Allograft in Anterior Cruciate Ligament Reconstruction

To assess the effects of preserved more anterior cruciate ligament (ACL) remnant on synovial coverage, knee stability, and function after bone patellar-tendon-bone (BPTB) allograft reconstruction through second-look arthroscopy and follow-up study. From June 2007 to February 2009, 51 patients received single bundle BPTB allograft ACL reconstruction and second arthroscopic examination. The patients were divided into 4 types according to the types of ACL remnant: type 1, 18 had bridging between the posterior cruciate ligament and the tibia; type 2, 21 had bridging between the intercondylar notch roof and the tibia; type 3, 4 had bridging between the lateral condyle and the tibia; and type 4, 8 subjects had no ACL remnants. Clinical results were evaluated with the KT-1000 maximum displacement test and Lysholm scale at mean 12.3- and 53.5-month follow-up. Second-look synovium coverage was recorded as follows: covering 25% or less, 25% to 50%, 50% to 75%, and more than 75%. Mean percentage of synovium coverage, Lysholm scale, and KT-1000 side-to-side difference were poorer in types 3 and 4 than the other 2 types at mean 12.3-month follow-up without statistical differences. The result of the final follow-up was comparable with the first one. Four patients had ruptured grafts and accepted revision surgery. Three of them belonged to types 3 and 4, and 1 patient with sport trauma belonged to type 2. There were other 11 patients with different types of impingement and partial absorption of grafts. Although lack of statistical power, follow-up study and second-look arthroscopy showed that preserved type 3 and 4 ACL remnant caused poorer synovium coverage and might lead to earlier failure when using BPTB allograft. Early minor laxity at 12.3-month follow-up seemed to be not progressive at the final follow-up. Level III, case-control study.