Eric Po-Yan Ho

Knee rotational stability during pivoting movement is restored after anatomic double-bundle anterior cruciate ligament reconstruction.

Background: The restoration of knee rotational stability after anatomic double-bundle anterior cruciate ligament (ACL) reconstruction has been demonstrated in the cadaveric model and with passive stress tests on humans but not yet with dynamic functional biomechanical tests performed by human participants. Purpose: To prospectively investigate the range of tibial rotation of ACL-deficient and ACL-reconstructed knees during a pivoting task. The authors hypothesized that there would be a significant increase in tibial internal rotation in the ACL-deficient knee compared with the contralateral knee and that the increased rotation would return to normal after anatomic double-bundle ACL reconstruction. Study Design: Case series; Level of evidence, 4. Methods: Ten men with unilateral ACL injury performed a high-demand jump-landing and pivoting task before and after ACL reconstruction with mean follow-up of 11 months. The range of tibial rotation of the injured, reconstructed, and intact knees during the pivoting movement was measured by an optical motion analysis system. Paired t tests were performed to investigate any significant difference between the 2 limbs preoperatively and postoperatively and within the injured limb before and after the surgical treatment. Statistical significance was set at P < .05. Results: The range of tibial rotation was higher in the ACL-deficient knee (12.6° ± 4.5°) than in the intact knee (7.9° ± 3.1°) preoperatively (P < .05). The increased rotation was reduced in the reconstructed knee (8.9° ± 3.0°) after ACL reconstruction versus the intact knee postoperatively (8.2° ± 2.6°) (P < .05). There was no significant difference in the tibial rotation between the intact knee and the reconstructed knee postoperatively (P > .05). Conclusion: As assessed with a dynamic functional pivoting movement, the anatomic double-bundle ACL reconstruction successfully restores knee rotational stability from an impaired level.

Knee stability assessment on anterior cruciate ligament injury: Clinical and biomechanical approaches

Anterior cruciate ligament (ACL) injury is common in knee joint accounting for 40% of sports injury. ACL injury leads to knee instability, therefore, understanding knee stability assessments would be useful for diagnosis of ACL injury, comparison between operation treatments and establishing return-to-sport standard. This article firstly introduces a management model for ACL injury and the contribution of knee stability assessment to the corresponding stages of the model. Secondly, standard clinical examination, intra-operative stability measurement and motion analysis for functional assessment are reviewed. Orthopaedic surgeons and scientists with related background are encouraged to understand knee biomechanics and stability assessment for ACL injury patients.

Comparison of 2 Surgical Techniques for Reconstructing Posterolateral Corner of the Knee: A Cadaveric Study Evaluated by Navigation System

PURPOSE This study aimed to evaluate the immediate effect on knee kinematics by 2 different techniques of posterolateral corner (PLC) reconstruction. METHODS Five intact formalin-preserved cadaveric knees were used in this study. A navigation system was used to measure knee kinematics (posterior translation, varus angulation, and external rotation) after application of a constant force and torque to the tibia. Four different conditions of the knee were evaluated during the biomechanical test: intact knee and PLC-sectioned knee and PLC-reconstructed knee by the double-femoral tunnel technique and single-femoral tunnel technique. RESULTS Sectioning of the PLC structures resulted in significant increases in external rotation at 30° of flexion from 11.2° (SD, 2.6) to 24.6° (SD, 6.2), posterior translation at 30° of flexion from 3.4 mm (SD, 1.5) to 7.4 mm (SD, 3.8), and varus angulation at 0° of flexion from 2.3° (SD, 2.1) to 7.9° (SD, 5.1). Both reconstruction techniques significantly restored the varus stability. The external rotation and posterior translation at 30° of flexion after reconstruction with the double-femoral tunnel technique were 10.2° (SD, 1.3) and 3.4° (SD, 2.7), respectively, which were significantly better than those of the single-femoral tunnel technique. CONCLUSIONS Both techniques of reconstruction showed improved stability compared with PLC-sectioned knees. The double-femoral tunnel technique in PLC reconstruction showed better rotational stability and resistance to posterior translation than the single-femoral tunnel technique without compromising varus stability. CLINICAL RELEVANCE PLC reconstruction by a double-femoral tunnel technique achieves better rotational control and resistance to posterior translation.

Review of knee arthroscopy performed under local anesthesia

Local anesthesia for knee arthroscopy is a well documented procedure with diagnostic and therapeutic role. Numerous therapeutic procedures including partial menisectomy, meniscus repair, abrasion chondroplasy, synovectomy, loose body removal can be performed safely and comfortably. Appropriate case selection, anesthetic strategy and technical expertise are the key to smooth and successful surgery.

Anterior cruciate ligament bundle measurement by MRI.

ObjectiveAn accurate in vivo method of measuring dimensions of the anteromedial (AM) and posterolateral (PL) anterior cruciate ligament (ACL) bundles has not been established. The purpose of this study was to measure each individual bundle using double oblique axial MR imaging of the ACL, to compare this with cadaveric measurements, and to investigate the range of measurements seen in normal subjects.Materials and methodsIn five cadaveric knees, measurements obtained of the proximal, middle, and distal segments of each ACL bundle from double oblique axial MR images were compared with direct measurements following anatomical dissection. Thereafter, the size of both bundles from 24 normal knees was measured using an identical MR technique. Inter-observer variation was calculated using intraclass correlation.ResultsACL bundle measurement in the cadaveric knees had a strong correlation (r = 0.93) with measurements obtained following anatomical dissection. No significant difference existed between measurements obtained from cadaveric knees and living normal subjects (p > 0.05). Interobserver correlation for MR measurements was excellent (R = 0.92–0.93). Overall, the long and short axis of the AM bundle were significantly larger than those of the PL bundle (p < 0.05). Also, men showed significantly larger AM and PL bundles than women (p < 0.05). Bundle size was not related to age or knee dominance.ConclusionThe individual ACL bundles can be accurately measured on double oblique axial MR imaging. The AM bundle is larger in caliber than the PL bundle. Both bundles are larger in men than in women and there is no significant side-to side difference.

Can MRI predict the clinical instability and loss of the screw home phenomenon following ACL tear

Our purpose was to determine the relationship between tibiofemoral translation on magnetic resonance imaging and clinical instability of the knee following anterior cruciate ligament (ACL) injury. Within 66 patients (43 males, 23 females, mean age 30.25 years), 15 of 19 patients (80%) with an intact ACL had a demonstrable normal screw home movement, while 24 of 47 patients (51%) with an ACL tear had absence of the screw home movement. Patients with clinical instability had greater tibial translation and excursion at the lateral compartment (P=.0001). Following ACL injury, there is demonstrable absence of the normal screw-home movement with anterior tibial translation and excursion related to presence of clinical instability.