Age and Sex-Specific Joint Biomechanics in Response to Partial and Complete ACL Injury in the Porcine Model

Context: Pediatric anterior cruciate ligament (ACL) injury rates are increasing and are highest in adolescent females. Complete ACL tears are typically surgically reconstructed, but there are few guidelines and very limited data regarding the need for surgical reconstruction or rehabilitation for partial ACL tears in skeletally immature patients. Objective: To evaluate the impact of partial (anteromedial bundle) and complete ACL transection on joint laxity and tissue forces under anterior and rotational loads in male and female stifle joints throughout skeletal growth in the porcine model. Design: Descriptive Laboratory Study. Setting: Laboratory. Patients or Other Participants: Sixty male and female Yorkshire cross-breed pigs aged 1.5, 3, 4.5, 6, and 18 months (n=6/age/sex). Main Outcome Measure(s): Joint laxity was measured in intact, anteromedial bundle-transected, and ACL-transected joints under applied anterior-posterior drawer and varus-valgus torque using a robotic testing system. The loading of the soft tissues in the stifle joint was measured under each condition. Results: Anterior-posterior joint laxity increased by 13–50% (p<0.05) after anteromedial bundle transection and 75–178% (p<0.05) after ACL transection. Destabilizations after anteromedial bundle transection increased with age (p<0.05) and were greater in late adolescent females than late adolescent males (p<0.05). In anteromedial bundle-transected joints, the posterolateral bundle resisted the anterior load. In ACL-transected joints, the medial collateral ligament (MCL) contribution was largest, followed by the medial meniscus. MCL contribution was larger while medial meniscus contribution was smaller in males versus females. Conclusions: Partial ACL transection resulted in moderate increases in joint laxity, while the remaining bundle performed the primary ACL function. Destabilizations due to partial ACL transection were largest in late adolescent joints, indicating that operative treatment should be considered in active, late adolescent patients. Increased forces in the MCL and medial meniscus after ACL transection suggest that rehabilitation protocols may need to focus on protecting these tissues.

Conservative Rehabilitation of Partial Anterior Cruciate Ligament Tear - A Case Report

The anterior cruciate ligament is one of the most important ligaments in the knee joint (ACL). The ACL is necessary for appropriate knee joint mobility and mechanics. When the ACL is torn, patients may experience issues with their knee's function, as well as instability and the sensation of 'falling away' while walking. The anterior cruciate ligament acts as a main restraint on tibia-to-femur translation (anterior shear). Depending on the angle of knee flexion, this function is allocated to either anteromedial or posterolateral bundle. When the knee is fully extended, the posterolateral bundle is tense; however, when the knee flexes, the posterolateral bundle loosens and the anteromedial bundle tightens. We report the case of a 32-year-old man who twisted his leg while jogging, resulting in a partial thickness ACL rupture and mild joint effusion along the periarticular surface of the right knee, as revealed by radiological symptoms and MRI.Conservative rehabilitation in a patient aged 32 year shows good results and so the surgery was not performed. Initially 10 weeks protocol was managed in hospital under the guidance of a therapist including strengthening, stretching and conditioning of lower limb muscles, later on as pain reduced and patient achieved functional pain free range 12 week protocol was further set for home program.

Failure load of the femoral insertion site of the anterior cruciate ligament in a porcine model: comparison of different portions and knee flexion angles

Background This study compared the failure load of the femoral insertion site of the anterior cruciate ligament between different portions and knee flexion angles. Methods In total, 87 fresh-frozen, porcine knees were used in this study. Three knees were used for histological evaluation; the remaining 84 knees were randomly divided into 4 groups: anterior anteromedial bundle, posterior anteromedial bundle, anterior posterolateral bundle, and posterior posterolateral bundle groups (n=21 per group). The anterior cruciate ligament femoral insertion site was divided into these four areas and excised, leaving a 3-mm square attachment in the center of each bundle. Tibia-anterior cruciate ligament-femur complexes were placed in a material testing machine at 30°, 120°, and 150° of knee flexion (n=7), and the failure load for each portion was measured under anterior tibial loading (0.33 mm/s). Results Histological study showed that the anterior cruciate ligament femoral insertion site consisted of direct and indirect insertions. Comparison of the failure load between the knee flexion angles revealed that all the failure loads decreased with knee flexion; significant decreases were observed in the failure load between 30 and 150° knee flexion in the posterior anteromedial bundle and posterior posterolateral bundle groups. Comparison of the failure load according to different portions revealed a significant difference between the anteromedial and posterolateral bundle groups at 150° of knee flexion, but no significant difference among the groups at 30° of flexion. Conclusions Although the failure load of the posterior portion decreased significantly in the knee flexion position, it (mainly consisting of indirect insertion) plays a significant role against anterior tibial load in the knee extension position; this appears to be related to the characteristics of the insertion site. Reflecting the complex structure and function of the ACL, this study showed that the failure load of the femoral insertion site varies with differences in positions and knee flexion angles.

Sex-Specific Function and Morphology of the Anterior Cruciate Ligament During Skeletal Growth in a Porcine Model

Pediatric anterior cruciate ligament (ACL) injuries are on the rise, and females experience higher ACL injury risk than males during adolescence. Studies in skeletally immature patients indicate differences in ACL size and joint laxity between males and females after the onset of adolescence. However, functional data regarding the ACL and its anteromedial and posterolateral bundles in the pediatric population remain rare. Therefore, this study uses a porcine model to investigate the sex-specific morphology and function of the ACL and its bundles throughout skeletal growth. Hind limbs from male and female Yorkshire pigs aged early youth to late adolescence were imaged using magnetic resonance imaging to measure the size and orientation of the ACL and its bundles, then biomechanically tested under anterior-posterior drawer using a robotic testing system. Joint laxity decreased (p<0.001) while joint stiffness increased (p<0.001) throughout skeletal growth in both sexes. The ACL was the primary stabilizer against anterior tibial loading in all specimens, while the functional role of the anteromedial bundle increased with age (p<0.001), with an earlier shift in males. ACL and posterolateral bundle cross-sectional area and ACL and anteromedial bundle length were larger in males than females during adolescence (p<0.01 for all), while ACL and bundle sagittal angle remained similar between sexes. Additionally, in situ ACL stiffness correlated with cross-sectional area across skeletal growth (r2=0.75, p<0.001 in males and r2=0.64, p<0.001 in females), but not within age groups. This study has implications for age and sex-specific surgical intervention strategies and suggests the need for human studies.

Three-Dimensional CT Evaluation of Tunnel Positioning in ACL Reconstruction Using the Single Anteromedial Bundle Biological Augmentation (SAMBBA) Technique

Background: Remnant preservation may confer important advantages in the anterior cruciate ligament (ACL)–reconstructed knee. However, the presence of a large remnant may obscure visualization and impair the ability to correctly place tunnels during surgery. Purpose: To determine whether tunnel placement during anatomic ACL reconstruction using the single anteromedial bundle biological augmentation (SAMBBA) technique is consistent and precise when a large native remnant is preserved. Study Design: Case series; Level of evidence, 4. Methods: Included in this study were 99 patients undergoing an ACL reconstruction during which at least 50% of the native ACL was preserved. The femoral tunnel was created using an outside-in specific guide. The tibial tunnel was positioned in the anteromedial region of the ACL footprint, and the remnant was carefully preserved while drilling and passing the semitendinosus graft through it. Postoperatively, 3-dimensional computed tomography (3D CT) was used to evaluate tunnel placement. The mean tunnel locations were calculated and the standard deviation was used to evaluate precision of positioning. Inter- and intrareader agreement were determined to assess reliability of evaluation of tunnel position. Results: The center of the femoral tunnel was positioned at a mean 19.4% (SD, 2%) of the depth of the notch and a mean 23.1% (SD, 3.5%) of the lateral wall height. The center of the tibial tunnel was positioned at a mean 36.3% (SD, 3.8%) of the anteroposterior length of the tibial plateau and at a mean 47.0% (SD, 2.7%) of the mediolateral width. The small standard deviations demonstrate that this technique allows precise tunnel placement. The tunnel positions achieved were consistent with previous anatomic studies of femoral and tibial anteromedial bundle insertion. Intra- and interobserver reliability were high. Conclusion: Three-dimensional CT evaluation demonstrated that despite the presence of a large remnant, placement of femoral and tibial tunnels for anatomic ACL reconstruction using the SAMBBA technique is consistent and precise.

Ossicle in Anterior Cruciate Ligament: A Rare Occurrence

The occurrence of an intra-articular ossicle is not rare in the knee, with reports suggesting the existence of meniscal osscile. There are also reports describing the attachment of the posterolateral bundle of the anterior cruciate ligament (ACL) to an accessory ossicle. However, despite an extensive search of the English literature we did not find much written about an intrasubstance ossicle in the ACL. We present the case of a 13-year-old male with an intrasubstance ossicle in the anteromedial bundle of the ACL of his right knee.