Superior Patellar Dislocation Misdiagnosed as Patellar Tendon Rupture: The Value of Ultrasonography

Superior dislocation of the patella with intact patellar tendon is a rare condition. Most cases in literatures were diagnosed by clinical examination and plain radiography; however there are many cases that were misdiagnosed as patellar tendon rupture. In this case, we demonstrate the use of ultrasound for diagnosis of superior dislocation of the patella in the emergency department. We also include a literature review of similar cases and discuss the advantages of different types of imaging for diagnosis in this condition

Comparison of medial tibiofemoral joint mechanics between all-suture anchors and transtibial pullout technique for posterior medial meniscal root tears

Abstract Background The posterior medial meniscal root tear (PMMRT) seriously impacts the tibiofemoral joint biomechanics. Two available techniques for PMMRT repair include the transtibial pullout (TPO) repair and all-suture anchor (ASA) repair techniques. These techniques have not been compared biomechanically. Methods A total of 20 fresh porcine cadaveric knee specimens were used. All 20 knees were randomly and evenly distributed into four groups (five specimens per group): (1) intact posterior meniscal root, (2) PMMRT, (3) TPO repair technique for PMMRT, and (4) ASA repair technique for PMMRT. The tibiofemoral contact mechanics were investigated using a pressure sensor. All knee specimens were tested by being loaded with 600 N axial compressive force at three different flexion angles (0°, 45°, and 90°). The contact surface area, contact pressure, peak pressure, and time-zero displacement were recorded. Results The PMMRT caused a significant decrease in contact surface area, an increase in contact pressure, and peak pressure from the reference values observed in the intact meniscus group (P = 0.05, 0.016, and 0.008, respectively). After fixation, no significant difference was observed between the ASA and intact group. Meanwhile, significant differences were found between the TPO and intact group in terms of contact surface area, contact pressure, and peak pressure. In the comparison between the two techniques, the ASA group demonstrated higher contact surface area than the TPO group at the average knee flexion angle (p = 0.05). Conclusion For most testing conditions, the ASA technique demonstrated superior biomechanical property in terms of contact surface area compared with the TPO technique under compressive loading conditions. The ASA technique could also restore the tibiofemoral contact mechanics to be comparable with those of the native intact knee. Meanwhile, a significant difference in tibiofemoral mechanics, compared with the intact knee, could be observed in the TPO technique