Anterior cruciate ligament (ACL) rupture is one of the most common knee injuries, particularly in young and physically active individuals. Despite advances in reconstruction techniques, graft failure and rerupture remain clinically relevant. Revision ACL surgery is more complex than primary reconstruction and is associated with inferior outcomes, with rerupture rates of approximately 13%, reaching up to 25% when both subjective and objective failure criteria are considered. The main goal of ACL reconstruction is to restore anteroposterior and rotational knee stability, prevent secondary meniscal and cartilage damage, and enable return to sport. Surgical outcomes depend on several intraoperative factors, including graft choice and tunnel geometry, which are particularly relevant in revision settings. Diagnosis of ACL rerupture is primarily clinical, based on instability tests (Lachman, anterior drawer, pivot shift), and supported by instrumental assessment such as the KT-1000 arthrometer, which provides an objective measure of joint laxity. Revision ACL reconstruction can be performed using different surgical techniques (single-bundle, double-bundle, or combined extra-articular procedures) and graft types (autograft or allograft). Surgical strategy depends on multiple factors such as meniscal and cartilage status, previous surgery characteristics, tunnel positioning/enlargement, and fixation devices. However, no consensus exists regarding the optimal approach in terms of mid- to long-term outcomes. A major long-term complication is the development of osteoarthritis, particularly in this typically young and active patient population. Identification of modifiable factors, such as surgical technique and graft type, may help reduce failure risk and joint degeneration. This study aims to evaluate clinical and radiographic outcomes over a follow-up period exceeding two years in patients undergoing revision ACL reconstruction with different surgical techniques and graft types. The study also integrates objective knee laxity assessment using KT-1000 and markerless motion analysis based on artificial intelligence. Functional movements are recorded via video and analyzed using Sports2D software, enabling 2D kinematic analysis without markers or sensors, providing quantitative functional data to complement clinical and radiographic evaluation.
Study Type
OBSERVATIONAL
Enrollment
150
IRCCS Rizzoli Orthopedic Institute
Bologna, Bologna, Italy
RECRUITINGSurvival rate
Failures will be recorded and documented in the case report form (CRF), during telephone questionnaires, and through the patient's clinical records (Electronic Health Record, SIR 2020, and hospital databases). The survival rate at follow-up will then be estimated using a Kaplan-Meier survival curve
Time frame: At least 24 months after surgery
Lysholm Knee Score
It is a validated measurement scale that assesses knee function through 8 items, allowing evaluation of knee condition in relation to the functional demands of activities of daily living. This assessment form is used to evaluate surgical outcomes in patients undergoing surgery for ligamentous or meniscal knee injuries. The final score is obtained by summing the scores of the individual items and ranges from 0 to 100. Scores are categorized into subgroups as follows: Excellent (95-100); Good (84-94); Fair (65-83); Poor (\<64)
Time frame: At least 24 months after surgery
International Knee Documentation Committee - Objective Knee Evaluation Form
The objective IKDC is a clinical assessment form completed by the investigator, which allows standardized classification of knee status through objective parameters. The evaluation is based on four main domains: joint effusion, range of motion, ligament stability (in particular Lachman test, pivot-shift test, and anterior/posterior drawer tests), and joint compartments (meniscal and ligament examination). The final outcome is not expressed as a continuous numerical score, but rather as a classification into four categories: A (Normal) B (Nearly normal) C (Abnormal) D (Severely abnormal) The final classification corresponds to the worst score obtained among the evaluated domains.
Time frame: At least 24 months after surgery
Anterior drawer test
It allows assessment of anterior tibial translation relative to the femur with the knee flexed at 90 degrees. An increased translation suggests a lesion of the reconstructed ACL (neo-ACL). It is graded on a scale from 0 to 3
Time frame: At least 24 months after surgery
Lachman test
It allows assessment of anterior tibial translation relative to the femur with the knee flexed at 30 degrees. Increased translation suggests a lesion of the reconstructed ACL (neo-ACL). It is graded on a scale from 0 to 3
Time frame: At least 24 months after surgery
Pivot shift test
This is a clinical examination maneuver used to assess rotational instability of the knee. The test is performed by applying a valgus and internal rotation stress during knee flexion; the occurrence of a tibial "shift" or "clunk" suggests a lesion of the reconstructed ACL (neo-ACL) associated with rotational instability. It is graded on a scale from 0 to 3.
Time frame: At least 24 months after surgery
Tegner Activity Scale
The Tegner Score is a physical activity rating scale that measures the level of participation in occupational and sports activities. The score ranges from 0 to 10, where: 0 indicates inability to work or severe disability due to knee problems; 10 indicates participation in competitive sports at national or international level (e.g., professional football). Intermediate levels describe progressively more demanding physical activities, distinguishing between activities of daily living, light or heavy work, and recreational or competitive sports. The Tegner Score is frequently used in combination with other instruments (such as the IKDC or Lysholm scores) to define the patient's functional level before injury and after treatment. In the context of this study, the score is collected through a direct patient interview conducted by the investigator.
Time frame: At least 24 months after surgery
WOMAC
The WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) is a self-administered questionnaire specifically developed to assess patients with hip and knee osteoarthritis. The instrument evaluates the impact of the disease on pain, stiffness, and physical function. The questionnaire consists of 24 items divided into three main domains: * Pain (5 items) * Joint stiffness (2 items) * Physical function (17 items) The total score is normalized on a 0-100 scale.
Time frame: At least 24 months after surgery
KT-1000
The KT-1000 is an objective assessment device that measures anterior tibial translation relative to the femur by applying a predefined force to translate the tibia anteriorly. Its use is part of routine clinical practice in the outpatient setting of the Second Orthopaedic and Trauma Clinic of the IOR and aims to quantitatively assess static anteroposterior knee laxity following anterior cruciate ligament reconstruction. The unit of measurement is millimetres
Time frame: At least 24 months after surgery
Post-operative movement analysis
Knee function will be assessed during functional tasks (walking, lunges, squat) using a markerless AI-based video analysis system (Sports2D). The software estimates 2D joint kinematics (hip, knee, ankle, trunk) from videos recorded in frontal and sagittal planes without the use of sensors or markers. The system is non-invasive, already used in clinical practice, and installed locally to ensure data protection. Videos are processed through an internal MATLAB script that extracts kinematic outputs (.mot and .trc files) using automated AI-based analysis. Data are anonymized via alphanumeric IDs, and videos are deleted after processing to minimize data retention.
Time frame: At least 24 months after surgery
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