Editorial Commentary: Goldilocks and the Three Grafts: Managing Tendon Harvest and Graft Length Problems in Autograft Anterior Cruciate Ligament Reconstruction

Autograft hamstring tendon harvest in anterior cruciate ligament (ACL) reconstruction can occasionally result in a graft length that is inadequate for creation of a robust ACL graft. Patients at risk for an abnormally short hamstring may also be high risk for ACL reinjury. Graft augmentation with allograft may be a suboptimal solution to this problem. Therefore, a reliable means for preoperative estimation of hamstring tendon length by magnetic resonance imaging measurement could avoid this pitfall. However, even with a reliable correlation between magnetic resonance imaging measurement and actual harvested tendon length, establishing a simple, clinically relevant threshold below which hamstring grafts should be avoided remains elusive. By contrast, all-soft-tissue quadriceps autograft avoids the potential length problems inherent to both bone tendon bone (graft–tunnel mismatch) and hamstring tendon grafts, but intermediate- and long-term outcome studies are still needed to validate all-soft-tissue quadriceps autograft in ACL reconstruction.     

Arthroscopic anterior cruciate ligament reconstruction with quadriceps tendon-patellar bone autograft

BACKGROUND: Surgical reconstruction of the anterior cruciate ligament (ACL) is indicated in the ACL-deficient knee with symptomatic instability and multiple ligaments injuries. Bone patellar tendon-bone and the hamstring tendon generally have been used. In the present study, we describe an alternative graft, the quadriceps tendon-patellar bone autograft, by using arthroscopic ACL reconstruction. METHODS: From March of 1996 through March of 1997, a quadriceps tendon-patellar bone autograft was used in 12 patients with ACL injuries. RESULTS: After 15 to 24 months of follow-up, the clinical outcome for those patients with this graft have been encouraging. Ten patients could return to the same or a higher level of preinjury sports activity. According to the International Knee Documentation Committee rating system, 10 of the 12 patients had normal or nearly normal ratings. Recovery of quadriceps muscle strength to 80% of the normal knee was achieved in 11 patients in 1 year. CONCLUSION: The advantages of the quadriceps tendon graft include the following: the graft is larger and stronger than the patellar tendon; morbidity of harvest technique and donor site is less than that of patellar tendon graft; there is little quadriceps inhibition after quadriceps harvest; there is quicker return to sports activities with aggressive rehabilitation. A quadriceps tendon-patellar autograft is a reasonable alternative to ACL reconstruction in patients who are not suitable for either a bone-patellar tendon-bone autograft or a hamstring tendon autograft.     

Editorial Commentary: Reduce the Failure Risk: A Challenge to Reduce the Risk of Using Hybrid Graft in Anterior Cruciate Ligament Reconstruction

Hybrid grafting (augmentation of small hamstring autografts with allograft tissue) is preferred by many surgeons for anterior cruciate ligament (ACL) reconstruction. Although a recent, well-conducted, systematic review reported no significant differences in failure risk between hybrid graft and autograft ACL reconstruction, a trend toward a greater failure risk using the hybrid graft existed in many of the included studies. Three potential causes of hybrid graft ACL reconstruction failure that are absent in autograft ACL reconstruction are different levels of graft revascularization and ligamentization, differences in the tendon-bone healing capacity between the allograft and autograft portions in the bone tunnel, and processing of the graft. Research advances in these areas will further reduce the failure risk of hybrid graft ACL reconstruction.     

Quadriceps tendon-patellar bone autograft for anterior cruciate ligament reconstruction: a technical note

The quadriceps tendon autograft can be used for primary and revision anterior cruciate ligament (ACL) reconstruction. Despite several successful clinical reports, graft fixation issues remain, and the ideal technique for fixation continues to be controversial. We present a technique of ACL reconstruction with quadriceps tendon autograft (QTA) using a patellar bone block. The tendon end is fixed in the femoral tunnel and the bone plug in the tibial tunnel using reabsorbable interference screws. The advantages of this technique are related to the increase in stiffness of the graft, the achievement of a more anatomic fixation, and a reduction in synovial fluid leakage.     

Editorial Commentary: With Appropriate Anterior Cruciate Ligament Graft Selection,All-Inside Reconstruction Results in Excellent Outcomes: Stay “Inside” and Be Cognizant of Hamstring Graft Diameter Expectations in Shorter Patients

All-inside anterior cruciate ligament (ACL) reconstruction is a minimally invasive and anatomic technique with predictably excellent results. The array of graft choices that exists for skilled arthroscopists include semitendinosis autograft with or without gracilis, quadriceps tendon autograft, and patellar tendon autograft and allograft. The advantages of all-inside ACL reconstruction include independent femoral socket creation and less pain compared with a full tibial tunnel in the early postoperative period. This is a technique that should not trump appropriate graft selection. It is expected that autografts will fare better in younger patients who participate in activities at greater risk for ACL injuries. Selection of a semitendinosis autograft results in predictably excellent results when graft diameters are 8 mm or greater. Quadrupling the semitendinosis and adding the gracilis when needed can provide sufficient graft diameter in many patients. However, caution should be taken when harvesting hamstring grafts from shorter patients. Semitendinosis tendons in such patients are sometimes not long enough to quadruple and can result in a diameters less than 8 mm even when the gracilis is added. With appropriate graft selection, staying “inside” for ACL reconstruction is expected to result in great objective and subjective outcomes for our patients.     

Femoral Tunnel Defect Filled With a Synthetic Dowel Graft for a Single-Staged Revision Anterior Cruciate Ligament Reconstruction

Bone defects are a common obstacle to successful revision anterior cruciate ligament (ACL) reconstruction. We describe the use of a synthetic bone graft plug to fill a cylindric defect after femoral interference screw removal. During revision ACL reconstruction performed through a 2-incision technique, we placed an outside-in guidewire for a new femoral tunnel that converged with the femoral screw from the primary ACL reconstruction. The screw was removed, and the resultant defect appeared very similar to the cylindric bone defect left after an osteochondral graft harvest. The confluence of the defect and the planned femoral tunnel would have allowed a “windshield wiper” effect of the graft at the lateral wall of the notch. We filled the screw defect with a synthetic bone graft plug to limit the aperture size of the femoral tunnel and to buttress the tendinous portion of the revision ACL graft, while maintaining proper anatomic graft position. In this article, we present a readily available all-arthroscopic option for repairing cylindric bone defects without the risk of an allograft or the morbidity of an autograft for a single-stage revision ACL reconstruction.     

Editorial Commentary: Revision Anterior Cruciate Ligament Using Soft Tissue Autograft Quadriceps Is Effective but Not Recommended for All Comers

The average revision rate is between 3.2% and 11.1%following primary anterior cruciate ligament (ACL) reconstructions,¹ and an objective failure rate of 13.7% has been reported for revision ACLR.² Prior implants, positioning of tunnels, and muscle weakness from the prior reconstruction present challenges. Additionally, graft choice for the revision reconstruction is restricted, depending on the primary reconstruction. Revision ACL reconstruction with the all-soft tissue quadriceps tendon autograft is a viable option with 83.3% of the patients surpassing the minimally clinically significant difference for International Knee Documentation Committee (IKDC) scores, which is similar to outcomes for revision ACL reconstruction (ACLR) using bone-patella-bone and hamstring tendon autografts. Furthermore, objective strength data suggest that it is possible to achieve equal limb symmetry index strength ratios even in the setting of prior bone-patella tendon-bone autograft. However, although I am cautiously optimistic regarding soft tissue quadriceps autograft in revision ACLR, I would be hesitant to recommend it for all comers. In my experience, young high school/collegiate female athletes with primary reconstruction using BPTB autograft may not be able to tolerate a secondary insult to the extensor mechanism via quadriceps tendon (QT) autograft harvest, where hematoma and arthrofibrosis could be concerns. Furthermore, increased posterior tibial slope may require evaluation and treatment, and the addition of a lateral extra-articular tenodesis may reduce residual rotatory laxity in ACL revision patients.     

Different aspects of the cyclops lesion following anterior cruciate ligament reconstruction: A multifactorial etiopathogenesis

After anterior cruciate ligament (ACL) reconstruction using a patellar-tendon autograft, 65 patients underwent second-look arthroscopy in conjunction with hardware removal. In 23 patients, hypertrophic tissue was found in the anterior part of the knee. This tissue presented different aspects, from a well-synovialized nodule to a more disorganized fibrous tissue according to patients' complaints. Endoscopic resection of this offending tissue was generally sufficient to obtain a satisfactory result. In patients presenting a loss of extension, the notch frequently had to be enlarged. We have found a multifactorial pathogenesis to be likely: the nodule is a natural fibroproliferative tissue process originating either from drilling debris from the tibial tunnel or from remnants of the ACL stump and, more rarely, from broken graft fibers. Sometimes, when the graft is malpositioned, the scar tissue can result from repeated graft impingement on the notch at terminal extension. Formation of this aberrant tissue should be prevented by proper positioning of the graft, by enlargement of the narrowed notch in chronic cases, by using drills of increasing diameters to avoid production of osteocartilaginous fragments, by meticulous resection of all drilling debris and ACL remnants around the tibial tunnel, and by enlarging the notch roof if any contact with the graft is present when the knee is fully extended intraoperatively. (Arthroscopy 1998 Nov-Dec;14(8):869-76.)     

Editorial Commentary: During Anterior Cruciate Ligament Reconstruction,Lateral Extra-Articular Procedures Have Risks and Should be Reserved for Proper Indications: Do Not LET ALL Revision Anterior Cruciate Ligament Reconstructions Be the Same

Recently, there has been renewed interest in performing a lateral extra-articular procedure (LEAP), either an anterolateral ligament (ALL) reconstruction or a LET (lateral extra-articular tenodesis) to address a deficiency of the anterolateral complex (ALC) of the knee during anterior cruciate ligament (ACL) reconstruction. The ALC consists of the superficial and deep aspects of the iliotibial band with its Kaplan fiber attachments on the distal femur, along with the ALL, a structure within the anterolateral capsule. The ALC functions to provide anterolateral rotatory stability as a secondary stabilizer of the ACL. The evidence to date is that the addition of a LEAP to a revision ACL reconstruction may reduce the risk of repeat graft failure and rotatory laxity. However, in some cases, performing a LEAP may not confer any additional benefit and add unwarranted risk including lateral pain, reduced quadriceps strength, longer time to recovery, and overconstraint of the lateral compartment with associated cartilage damage. Perhaps LEAP is best indicated for high-risk patients (young, active in pivoting sports, high-grade pivot-shift, generalized ligamentous laxity or knee hyperextension, Segond fracture, chronic ACL lesion, lateral femoral notch sign, lateral coronal plane laxity, concurrent meniscus repair, or ALC injury on magnetic resonance imaging). Other modifiable risk factors should not be ignored (graft choice, graft size, tunnel position, graft fixation, associated injuries such as a lateral meniscal root tear, or anatomic factors such as an increased posterior tibial slope). Do not LET ALL revision anterior cruciate ligament reconstructions be the same! A lateral extra-articular procedure may sometimes, but not always, reduce the risk of further failure.     

Quadriceps Tendon Graft for Anterior Cruciate Ligament Reconstruction: THE GRAFT OF THE FUTURE!

Anterior cruciate ligament (ACL) reconstruction is one of the most common orthopaedic surgeries performed on active people in the world. One of the most important surgical decisions is graft type for use in the reconstruction. Despite extensive research on optimal graft choice for ACL reconstruction, discrepancy exists among practicing surgeons' graft preference. Recently, the quadriceps tendon has gained popularity for use as a graft source for ACL reconstruction.The all soft tissue quadriceps graft offers many advantages over other autograft choices. Histologically it has 20% more collagen fibrils per cross-sectional area than the patellar tendon (PT). Biomechanically, its ultimate load is 70% > than that of a similar width PT graft, while its modulus is more similar to the native ACL than either the PT or hamstring graft. Anatomically the quadriceps tendon has significantly more volume than the PT. Thus, even after harvest of the quadriceps graft, the remaining quadriceps tendon is still 80% stronger than the intact PT!The length and cross-sectional area of the quadriceps tendon graft can be tailored to the needs of the patient. On any patient over 5 feet tall, a graft length of 7 cm can be obtained. Because the thickness of the tendon is almost twice the thickness of the same patient's PT, a graft diameter from 7 to 11 mm can easily be achieved. Thus, this graft can be customized for both primary and revision surgeries.Harvest site morbidity is minimal. An incision less than 2 cm in an area with no significant cutaneous nerves without harvest of any patella bone leads to no significant harvest site pain, numbness, or palpable defect.Clinical outcomes using this graft are excellent. Our prospective data on nearly 1,000 grafts, with a mean patient age of 20 years old, show a 4.2% failure rate. Thus, the all soft tissue quadriceps graft will be the surgical choice for ACL reconstruction for future athletes.     

Clinical outcomes after ACL reconstruction with free quadriceps tendon autograft versus hamstring tendons autograft. A retrospective study with a minimal follow-up two years

ObjectiveThe aim of this retrospective study was to compare the clinical outcomes of anatomic single bundle ACL reconstruction using either a free quadriceps tendon autograft or a quadrupled hamstring autograft with a minimum follow-up of 24 months.MethodsConsecutive patients undergoing ACL reconstruction using either a free quadriceps tendon autograft or hamstring tendon autograft from January 2013 to December 2014 were included. ACL reconstruction was done in all patients due to isolated ACL tears. Patients with associated cartilage lesions > Outerbridge III, meniscal lesions in need of meniscectomy or repair as well as patients with prior knee surgery on the affected or contralateral knee were excluded. The primary outcome evaluation was the side-to-side difference in instrumented Lachman testing. Secondary outcome evaluation consisted in the Lysholm, modified Cincinnati and SF-36 scores. Side-to-side difference in range of motion and thigh diameter was also documented.ResultsAfter applying the inclusion/exclusion criteria, a total of 82 patients were identified and 72 (87.8%) presented to the hospital for follow-up. There were 39 patients with quadriceps graft (30.64 ± 8.71, range: 18–53 years) and 33 patients with hamstrings (28.60 ± 6.74, range: 18–46 years). No statistically significant difference between groups was detected with regard to KT-1000 measurements (p = 0.326). No significant difference was found between the mean postoperative Lysholm (p = 0.299), the modified Cincinnati (p = 0.665) and the general SF-36 scores between groups (p = 0.588). Less side-to-side thigh diameter difference was noted in the quadriceps graft group (p = 0.026).ConclusionIn conclusion, similar clinical results, in terms of stability and subjective measures, can be obtained after ACL reconstruction both with a free quadriceps and a 4-strand hamstring tendons autograft.Level of evidenceLevel III, Therapeutic Study.     

Graft failure versus graft fixation in ACL reconstruction: histological and immunohistochemical studies in rabbits

The causes of graft failure after anterior cruciate ligament (ACL) reconstruction are multifactorial including the methods of graft fixation. The purpose of this study was to examine the ACL graft failure in three different methods of graft fixations including interference screw fixation, suture-post fixation and combined interference screw and suture-post fixation. We hypothesized that the fixation method after ACL reconstruction can affect the graft healing in tibial tunnel. Eighteen New Zealand white rabbits were categorized into three groups according to the method of fixation in unilateral ACL reconstruction with long digital extensor autograft. Histological examination demonstrated that the combined fixation and suture-post fixation groups showed significantly better integration between tendon and bone (P = 0.04). In immunohistochemical analysis, the combined fixation and suture-post fixation groups showed significantly higher BMP-2 and VEGF expressions than interference screw (P < 0.01). The tendon–bone healing after ACL reconstruction was affected by the method of graft fixation. Combined fixation with interference screw and suture-post reduced graft-tunnel micromotion and improved the graft healing in tibial tunnel.     

Early application of negative work via eccentric ergometry following anterior cruciate ligament reconstruction: a case report

STUDY DESIGN: Case report. OBJECTIVES: To present a progressively increasing negative-work exercise program via eccentric ergometry early after anterior cruciate ligament reconstruction (ACL-R) and to suggest the potential of negative work to amplify the return of quadriceps size and strength. CASE DESCRIPTION: The patient was a 26-year-old highly active recreational athlete who sustained an ACL tear while skiing in January 2004 and then again while skiing in February 2005. This individual underwent an arthroscopically assisted ACL-R with a double-loop semitendinosusgracilis autograft initially, then a patellar tendon autograft following his ACL graft rupture. Beginning within 3 weeks after surgery, a progressive negative-work exercise program was initiated using an eccentric ergometer. The patient completed 31 training sessions of 5 to 30 minutes in duration over a 12-week period following the ACL-R and 33 training sessions of the same frequency and duration following the ACL revision. OUTCOMES: Following ACL-R, quadriceps volume increased 28% (involved lower extremity) and 14% (uninvolved lower extremity) during the 12-week training program. Following revision, quadriceps volume returned to similar levels at the same postoperative period as those achieved after the initial surgery (2% less on the involved side and 2% greater on the uninvolved side). Quadriceps strength, 15 weeks after ACL-R, exceeded preoperative measures by an average of 20% (involved) and 14% (uninvolved). Quadriceps strength after ACL revision exceeded all previous measures. DISCUSSION: This case report suggests that if gradually and progressively applied, negative work via eccentric ergometry can be both safe and efficacious early after ACL-R. Eccentric exercise may mitigate the prevalent muscle size and strength deficits commonly observed after ACL-R. The results of this case suggest a need for continued research with early negative work interventions following ACL-R.     

Femoral tunnel placement in anterior cruciate ligament reconstruction: rationale of the two incision technique

Endoscopic anterior cruciate ligament (ACL) reconstruction can be performed through one-incision or two-incision technique. The current one-incision endoscopic ACL single bundle reconstruction techniques attempt to perform an isometric repair placing the graft along the roof of the intercondylar notch, anterior and superior to the native ACL insertion. However the ACL isometry is a theoretical condition, and has not stood up to detailed testing and investigation. Moreover this type of reconstruction results in a vertically oriented non-anatomic graft, which is able to control anterior tibial translation but not the rotational component of the instability. Femoral tunnel obliquity has a great effect on rotational stability. To improve the obliquity of graft, an anatomical ACL reconstruction should be attempt. Anatomical insertion of ACL on the femur lies very low in the notch, spreading between 11 and 9–8 o'clock position and the center lies lower than at 11 o'clock position. Femoral aiming devices through the tibial tunnel aim at an isometric placement, and they do not aim at an anatomic position of the graft. Also, a placement of tunnel in a position of 11 o'clock is unable to restore rotational stability. The two-incision technique, with the possibility to position femoral tunnel independently by tibial tunnel, allows us to place femoral tunnel entrance in a position of 10 'clock that can most accurately reproduce the anatomic behaviour of the ACL and can potentially improve the response of the graft to rotatory loads. This positioning results in a more oblique graft placement, avoiding problem related to PCL impingement during knee flexion. Further studies are required to understand if this kind of reconstruction can ameliorate proprioception as well as clinical outcome at a long-term follow-up.     

Editorial Commentary: Anterior Cruciate Ligament Hamstring Autografts Should Be Avoided in Patients Younger Than 25 Years Old: Autograft–Allograft Hybrids Remain Controversial

Some studies have reported no difference between autograft and hybrid anterior cruciate ligament reconstructions. However, other studies have shown a significantly greater revision rate. Consequently, surgeons are reluctant to perform hybrid reconstructions in younger patients with diminutive hamstring autografts and have turned to other autograft graft sources (e.g., quadriceps tendon, patellar tendon). Until we can perform high-quality prospective studies that can definitively answer this question, we should consider avoiding autograft hamstring reconstructions in patients younger than 25 years old so that we are not faced with the dilemma of implanting an undersized autograft or a hybrid graft, as both may be at increased risk for failure.     

Editorial Commentary: Osseous Anatomy of the Knee in Female Patients is a Significant Risk Factor for Anterior Cruciate Ligament Injury and Anterior Cruciate Ligament Graft Failure

Risk for anterior cruciate ligament (ACL) injury is greater in female than in male patients for a myriad of reasons, with osseous anatomy about the knee proving to be one significant risk factor for ACL injury and/or ACL graft failure. While femoral intercondylar notch size/shape and posterior tibial slope have been well-examined in this regard for their contribution to potential ACL injury, morphology of the lateral femoral condyle is a newer entity that may be linked to risk for ACL injury. Smaller/stenotic femoral intercondylar notches, increased posterior tibial slope of the lateral tibial plateau, and increased posterior condylar depth of the lateral femoral condyle have all been shown to increase risk for ACL injury and/or ACL graft failure. Such associations provide knee surgeons with food for thought when considering procedures such as notchplasty, staged anterior closing wedge high tibial osteotomy, and anterolateral ligament reconstruction/augmentation at the time of primary or revision ACL reconstruction. Further investigation into the links between pre-operative imaging parameters and outcomes following such concomitant procedures is required in order for any significant conclusions to be drawn.     

Editorial Commentary: Femoral Notch Volume: Too Much Information?

Femoral intercondylar notch size and volume are some of the many morphometric knee measures that have been associated with increased risk of anterior cruciate ligament (ACL) injury. The merits of relatively simple measures such as notch width versus more complex 3-dimensional notch volume have been debated, and there is some evidence suggesting that volumetric measures may have a stronger association with injury risk. The application for this information is, however, unclear. Notch volume appears to be just one of many nonmodifiable risk factors that contribute in a small way to the complex puzzle that is ACL injury risk. Although studying notch morphology may be an interesting academic exercise, it is difficult to see how notch measurements would be useful for injury prevention or to improve care after ACL injury.     

Comparing 2-year outcomes of anterior cruciate ligament reconstruction using either patella-tendon or semitendinosus-tendon autografts: a non-randomised prospective study

PURPOSE: To compare the results of anterior cruciate ligament (ACL) reconstructions using either a patella-tendon autograft or a semitendinosus-tendon autograft. METHODS: Based on surgeon experience and preference, 68 patients underwent ACL reconstruction using either a quadruple-strand semitendinosus autograft (n = 34) or a central one-third bone-patella tendon-bone autograft (n = 34). Each patient was assessed preoperatively and postoperatively at 3, 6, and 24 months using the International Knee Documentation Committee (IKDC) knee score, Biodex muscle strength and endurance testing, and the KT1000 instrumented arthrometer test of knee laxity to anterior translation. All assessments at the 2-year follow-up were performed by the same physician and physiotherapist. RESULTS: While ACL reconstruction improved knee stability and IKDC knee scores significantly, there was no statistically significant difference between semitendinosus- and patella-tendon autograft reconstructions in terms of long-term knee score or laxity to anterior translation. Semitendinosus graft reconstruction was associated with less donor-site morbidity and hamstring weakness. Meniscectomy was associated with poorer long-term knee scores. CONCLUSION: ACL reconstruction is associated with a significantly better IKDC knee score and laxity measurement at 2-year follow-up. However, we were unable to demonstrate a significantly better long-term outcome in knee score or laxity to anterior translation with either a patella-tendon autograft or a semitendinosus-tendon autograft.     

Ligament-muscle reflex arc after anterior cruciate ligament reconstruction: electromyographic evaluation

The purpose of this study was to determine if a ligament-muscle reflex arc exists between the bone-patellar tendon-bone autograft after anterior cruciate ligament (ACL) reconstruction and the hamstring muscle group. We studied four patients, average age 34.2 years (range 32–36 years). The mean time between the ACL reconstruction and the study examination was 56.2 months (range 5–108 months). All patients underwent a second-look arthroscopy for meniscal injuries, cyclops lesions, or adhesions. Five patients with a normal ACL served as a control group before we performed an arthroscopic meniscectomy. Electromyographic (EMG) activity was measured using fine wire electrodes under two different testing conditions. No unequivocal EMG activity could be detected in the ACL-reconstructed knees when we pulled on the graft or in the controls. Three of four patients and all controls felt pain when we touched the graft or normal ACL or applied strain on it with the hook. In conclusion, the ACL autograft presents a noxious sensory innervation, the Lachman test maneuver stimulates a reflex arc with hamstrings activation, and an unequivocal ligament-muscle reflex arc from the graft to the hamstring muscle group could not be demonstrated.     

Histological comparison of after reconstruction of fate of ligamentous insertion anterior cruciate ligament： autograft vs allograft

Objective ：To analyze the histological results and the biological remodeling of ligamentous insertion after the reconstruction of anterior cruciate ligament （ ACL ） with autograft or allograft tendon. Methods： Extensor digitorum tendon was harvested from hind limb as graft material and transplanted to reconstruct the resected ACL in 12 mongrel dogs. Each free tendon end was secured by holding sutures and then the sutures were tied to the post screw at the femoral and tibial bony tunnel outlet after transplantation respectively. Autograft was randomly performed on one side of knee while allograft on the other side of knee. After transplantation, the histological analysis was undertaken at the 6th, 12th weeks and the 6th month using hematoxylineosin （HE） stain under light microscope. Results： The insertion structure of normal ACL typically consisted of four layers, i. e. , dense connective tissue, fibrocartilage, mineralized fibrocartilage and bone. There was a distinct regular tidemark line between fibrocartilage and mineralized fibrocartilage. At the 6th week postoperatively, loose connective tissue presented in the interspace between graft and bony tunnel wall in both autograft and allograft groups. At the 12th week postoperatively, the collagenons fibers between autograft and tunnel wall became well organized and the four layers of insertion with discontinuous tidemark line were demonstrated indistinctly in autograft group but not in allograft group. At the 6th month postoperatively, both of a clear and continuous tidemark line and distinct four layers could be seen in autograft group. In allograft group, only a waved discontinuous tidemark line was shown and either the anatomic morphology or the maturity of insertion was inferior to that of autograft group. Conclusions： At the 6th month postoperatively, although the ligament-eartilage insertion is primarily formed after ACL reconstruction with autograft or allograft tendon, the histological morphology and the maturation of insertion of autograft tendon are better than those of allograft group, which suggests that postoperative rehabilitation should be paid more attention and could be safer if little delayed during ACL reconstruction with allograft tendon.