Lateral Extra-articular Tenodesis Has No Effect in Knees With Isolated Anterior Cruciate Ligament Injury.

PURPOSE: To investigate knee kinematics in response to physical examinations to determine the effect of anterolateral capsular injury and lateral extra-articular tenodesis (LET) in anterior cruciate ligament (ACL)-deficient and -reconstructed knees. METHODS: Seven human lower limb cadavers were used in this study (mean age, 60 years; age range, 56-63 years). Physical examinations were performed, including the pivot-shift test, Lachman test, anterior drawer at 90°, and internal and external tibial rotation at 30°, 60°, and 90° of knee flexion. ACL injury and reconstruction and LET, all with and without an injured anterolateral capsule, were investigated. Tibial translation and rotation relative to the femur were measured by an electromagnetic tracking system during the physical examination. RESULTS: Anterior translation of the lateral knee compartment and internal tibial rotation during the pivot-shift test were highest in combined ACL-deficient and anterolateral capsule-deficient knees (12.3 ± 7.4 mm and 16.3° ± 8.5°, respectively). With the presence of an anterolateral capsular injury, a combined ACL reconstruction and LET reduced the anterior translation of the lateral knee compartment during the pivot-shift test significantly (P = .042), whereas anatomic ACL reconstruction did not. Internal tibial rotation displayed overconstraint when a LET was performed, especially when the anterolateral capsule was intact. CONCLUSIONS: ACL reconstruction in combination with a LET was able to reduce anterior tibial translation and internal tibial rotation in response to different physical examinations. However, combined ACL reconstruction and LET led to overconstraint of internal tibial rotation when the anterolateral capsule was intact. CLINICAL RELEVANCE: On the basis of our results, LET with ACL reconstruction restores stability in a combined ACL-injured and anterolateral capsule-injured knee. However, LET with ACL reconstruction overconstrains the knee in an isolated ACL injury.

Biomechanical evaluation of knee endpoint during anterior tibial loading: Implication for physical exams.

BACKGROUND: Physical exams that apply anterior tibial loads are typically used to evaluate knees with anterior cruciate ligament (ACL) injuries. The amount of anterior tibial translation that occurs during these exams can be difficult to assess due to a "soft" endpoint. Therefore, the objective of this study is to determine the biomechanical characteristics of the endpoint for the intact and ACL deficient knee using quantitative criteria. METHODS: Eight porcine knees were tested using a robotic testing system. An 89N anterior tibial load was applied to the intact and ACL deficient knee at 30°, 45°, 60° and 75° of flexion. The stiffness of the toe and linear regions was determined from the load-translation curve. The width of the transition region was defined by the distance between the points where the best-fit lines used to define the stiffness of the toe and linear regions diverged from the load-translation curve. RESULTS: Stiffness of the toe and linear regions significantly decreased after transecting the ACL at all flexion angles (71-85% and 38-62%, respectively). Width of the transition region was significantly increased in the ACL deficient knee at all flexion angles (approximately four to five times and four to nine times, respectively). CONCLUSIONS: The novel quantitative criteria developed in this study have the potential to be deployed in clinical practice by coupling them with data from knee arthrometers that are commonly used in clinical practice. Thus, additional information from the load-translation curve can be provided to improve the diagnosis of ACL injury.

Tensile properties of a split quadriceps graft for ACL reconstruction.

PURPOSE: Anatomic double-bundle ACL reconstruction can be performed using different grafts, such as quadriceps tendon. Grafts can be split in either coronal or sagittal planes to approximate the two bundles of the native ACL, but it is unknown whether a difference exists in the graft tensile properties depending on splitting plane. The purpose of this study was to evaluate the tensile properties of split human quadriceps tendon-bone grafts. METHODS: Twenty full-thickness quadriceps tendon-bone grafts were prepared to mimic grafts for double-bundle ACL reconstruction. Ten grafts were split in the sagittal plane, and ten were split in the coronal plane. Each graft underwent cyclic creep testing and load-to-failure testing to compare creep, ultimate load, ultimate elongation, stiffness, and tangent modulus between splitting planes. All parameters were compared between splitting groups (significance p < 0.05). RESULTS: Lateral halves of grafts split in the sagittal plane exhibited a percent creep of 42.5 ± 12.4 %, ultimate load of 445 ± 210 N, ultimate elongation of 7.3 ± 1.9 mm, stiffness of 75.7 ± 19.9 N/mm, and tangent modulus of 174.0 ± 99.8 MPa. No differences were found between halves within split tendons or between splitting planes (n.s.). CONCLUSIONS: Overall, splitting quadriceps tendon grafts for anatomic double-bundle ACL reconstruction results in similar tensile properties regardless of splitting plane. Surgeons can split quadriceps tendon in either splitting plane, but should take care to preserve fibres as much as possible. This study provides data that support the use of both coronal and sagittal splits of quadriceps tendons for anatomic double-bundle ACL reconstruction.

Correlation between a 2D simple image analysis method and 3D bony motion during the pivot shift test.

BACKGROUND: The pivot shift test is the most specific clinical test to detect anterior cruciate ligament injury. The purpose of this study was to determine the correlation between the 2D simple image analysis method and the 3D bony motion of the knee during the pivot shift test and assess the intra- and inter-examiner agreements. METHODS: Three orthopedic surgeons performed three trials of the standardized pivot shift test in seven knees. Two devices were used to measure motion of the lateral knee compartment simultaneously: 1) 2D simple image analysis method: translation was determined using a tablet computer with custom motion tracking software that quantified movement of three markers attached to skin over bony landmarks; 2) 3D bony motion: electromagnetic tracking system was used to measure movement of the same bony landmarks. RESULTS: The 2D simple image analysis method demonstrated a good correlation with the 3D bony motion (Pearson correlation: 0.75, 0.76 and 0.79). The 3D bony translation increased by 2.7 to 3.5 times for every unit increase measured by the 2D simple image analysis method. The mean intra-class correlation coefficients for the three examiners were 0.6 and 0.75, respectively for 3D bony motion and 2D image analyses, while the inter-examiner agreement was 0.65 and 0.73, respectively. CONCLUSIONS: The 2D simple image analysis method results are related to 3D bony motion of the lateral knee compartment, even with skin artifact present. This technique is a non-invasive and repeatable tool to quantify the motion of the lateral knee compartment during the pivot shift test.

Macroscopic anatomical, histological and magnetic resonance imaging correlation of the lateral capsule of the knee.

PURPOSE: The objective of the present study was to correlate macroscopic and microscopic anatomy of the lateral capsule of the knee joint with high-quality magnetic resonance imaging (MRI), with a hypothesis that a distinct lateral capsular ligament would be inconsistently observed via surgical dissection and that high-quality MRI imaging would correlate to findings from dissection. METHODS: Ten fresh-frozen human cadaveric knee specimens were utilized for this study. MRI of each knee was obtained pre- and post-dissection. The lateral knee was dissected and analysed for the presence or absence of a discrete capsular thickening or an independent ligamentous structure. A musculoskeletal radiologist analysed the pre- and post-dissection MRI. Subsequently, two specimens with positive lateral capsular thickening were prepared for histology. RESULTS: On macroscopic dissection, none of the ten specimens were found to have a discrete lateral capsular ligament. A palpable macroscopic thickening of the lateral capsule was identified in 4/10 specimens. MRI analysis revealed a 2-4 mm thickening of the central third of the lateral capsule in 3/10 specimens. On histological analysis, the lateral capsular thickening demonstrated properties similar to both capsule and ligament. CONCLUSIONS: In fresh-frozen cadaveric specimens, macroscopic and MRI evaluation of the lateral capsule of the knee revealed variations in morphology without consistent capsuloligamentous anatomy and specifically no discrete lateral capsular ligament. Further investigation in the form of clinical and mechanical relevance of the lateral capsular structures is of paramount importance before limited anatomical data can be utilized to drive clinical decision-making and patient care.

Experimental Execution of the Simulated Pivot-Shift Test: A Systematic Review of Techniques.

PURPOSE: To conduct a systematic review to identify and summarize the various techniques that have been used to simulate the pivot-shift test in vitro. METHODS: Medline, Embase, and the Cochrane Library were screened for studies involving the simulated pivot-shift test in human cadaveric knees published between 1946 and May 2014. Study parameters including sample size, study location, simulated pivot-shift technique, loads applied, knee flexion angles at which simulated pivot shift was tested, and kinematic evaluation tools were extracted and analyzed. RESULTS: Forty-eight studies reporting simulated pivot-shift testing on 627 cadaveric knees fulfilled the criteria. Reviewer inter-rater agreement for study selection showed a κ score of 0.960 (full-text review). Twenty-seven studies described the use of internal rotation torque, with a mean of 5.3 Nm (range, 1 to 18 Nm). Forty-seven studies described the use of valgus torque, with a mean of 8.8 Nm (range, 1 to 25 Nm). Four studies described the use of iliotibial tract tension, ranging from 10 to 88 N. Regarding static simulated pivot-shift test techniques, 100% of the studies performed testing at 30° of knee flexion, and the most tested range of motion in the continuous tests was 0° to 90°. Anterior tibial translation was the most analyzed parameter during the simulated pivot-shift test, being used in 45 studies. In 22% of the studies, a robotic system was used to simulate the pivot-shift test. Robotic systems were shown to have better control of the loading system and higher tracking system accuracy. CONCLUSIONS: This study provides a reference for investigators who desire to apply simulated pivot shift in their in vitro studies. It is recommended to simulate the pivot-shift test using a 10-Nm valgus torque and 5-Nm internal rotation torque. Knee flexion of 30° is mandatory for testing. LEVEL OF EVIDENCE: Level IV, systematic review of basic science studies.

Novel technique for evaluation of knee function continuously through the range of flexion.

Previous research has utilized robots to examine joint kinematics and in situ forces in response to loads applied at discrete flexion angles (static method). Recently, studies have applied loads continuously throughout flexion (continuous flexion method). However, the joint kinematics resulting from each of these methods have not been directly compared. Therefore, the objective of this study was to utilize a robotic testing system to compare kinematics and in situ forces of porcine knees in response to 89 N of anterior tibial load and 4 Nm of internal tibial torque between the static method (loads applied at 30°, 45°, 60°, and 75° of flexion) and the continuous flexion method (measured continuously from 30-75° of flexion) for both the anterior cruciate ligament (ACL) intact and ACL deficient (ACLD) knees. When anterior tibial load was applied the average differences in anterior tibial translation between the two methods for the intact state was 0.5±0.0 mm and for the ACLD state was 0.3±0.2 mm. The difference in the in situ forces in the ACL was 1.6±0.9 N. When internal tibial torque was applied the average differences in the resultant internal tibial rotation for the intact state was 0.9±0.4° and for the ACLD state was 1.0±0.5°. The difference in the in situ forces in the ACL was 3.3±2.0 N. Both methods are equally efficient in detecting significant differences (p<0.05) between intact and ACL deficient knee states. The continuous flexion method was also shown to be more efficient than the static method and provides continuous data on knee function throughout the range of motion.