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The posterior cruciate ligament (PCL) represents an intra-articular structure composed of two distinct bundles. Considering the anterior and posterior meniscofemoral ligaments, a total of four ligamentous fibre bundles of the posterior knee complex act synergistically to restrain posterior and rotatory tibial loads. Injury mechanisms associated with high-energy trauma and accompanying injury patterns may complicate the diagnostic evaluation and accuracy. Therefore, a thorough and systematic diagnostic workup is necessary to assess the severity of the PCL injury and to initiate an appropriate treatment approach. Since structural damage to the PCL occurs in more than one third of trauma patients experiencing acute knee injury with hemarthrosis, background knowledge for management of PCL injuries is important. In Part 1 of the evidence-based update on management of primary and recurrent PCL injuries, the anatomical, biomechanical, and diagnostic principles are presented. This paper aims to convey the anatomical and biomechanical knowledge needed for accurate diagnosis to facilitate subsequent decision-making in the treatment of PCL injuries. Level of evidence V.

Purpose To investigate the effect of modified Laprade technique on the reconstruction of posterolateral structure of knee and anterolateral ligament of knee in the treatment of posterolateral injury of knee. Methods From December 2013 to June 2020, multiple ligament injury patients who received surgery in our hospital were collected in this research. These patients underwent a modified Laprade technique for posterolateral structural reconstruction of the knee. Lysholm scores of patients pre- and post-operation were recorded. Result The operations of the observation group or the control group patients were completed. There were no significant differences in gender, age, preoperative knee range of motion and preoperative Lysholm score. At the time of follow-up 1 month after operation, there was no significant difference in knee range of motion, dial-up test angle and Lysholm score between the observation and the control group. When followed up 1 year after operation, the Lysholm score of the observation group was higher than that of the control group. The difference was statistically significant. The same situation occurred in the range of motion of the knee in both groups. However, there was still no significant difference between the two groups in the dial-up test 1 year after operation, whether the knee flexion was 30° or 90°. Conclusion For patients with posterolateral structure injury of knee, the modified Laprade technique is a feasible surgical technique.

This study evaluated the correlation between the number of transected posterolateral structures (PLS) and the grade of posterolateral rotational instability, determined the effect of the popliteus muscle‐tendon unit on the tibial rotation, and examined the effect of an isolated posterior cruciate ligament (PCL) and combined PCL‐PLS reconstruction on knee stability. Sectioning the popliteofibular and lateral collateral ligaments both caused an increase in tibial external rotation. Cutting the PT resulted in a statistically highly significant excessive external rotation and externally shifted neutral position of the tibia over the full range of motion. Tensioning the popliteus muscle‐tendon unit led to a statistically highly significant internally shifted neutral tibial rotation and a decreased internal and an increased external rotation without affecting the total rotational arcs. The isolated PCL reconstruction did not affect the external rotation, whereas the combined PCL‐PLS reconstruction reset the knee to nearly physiological laxity patterns.

BackgroundAlthough the validity of the “lateral gutter drive-through” (LGDT) test has been proved to offer high sensitivity and specificity in diagnosing the posterolateral rotational instability of knee joints, the real mechanism on how the injury pattern of individual posterolateral knee structure triggers the positive LGDT sign still remains unknown.HypothesisA certain amount of popliteus tendon (POP-T) laxity resulted from specific injury patterns of individual posterolateral knee structure or some degree of medial structural injury will lead to positive LGDT sign.Study designControlled laboratory study.MethodsSeven non-paired intact cadaveric knees were divided into four groups and tested under unique sequential sectioning sequences including: (1) distal POP-T and popliteofibular ligament (PFL) (n = 2); (2) PFL and distal POP-T (n = 3); (3) lateral collateral ligament (LCL), distal POP-T and PFL (n = 1); (4) superficial medial collateral ligament (sMCL), deep MCL, posterior oblique ligament (POL), anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) (n = 1). The LGDT tests and the measurements of external tibial rotational angle (ETRA) were first performed on all the intact knees and then at each time point when an additional structure was sectioned. Results of each LGDT test and the absolute value of increased ETRA compared with the intact knee were recorded. Each knee was tested at 30° of flexion. A navigation system was used to measure motion changes of the tibia with respect to the femur.ResultsInitially, the LGDT tests all showed negative on each of the intact knee. Isolated sectioning of the distal POP-T, PFL or the LCL produced increased but insignificant ETRA with the LGDT tests still negative. However, simultaneous sectioning of the distal POP-T and PFL produced significantly increased ETRA with the LGDT tests changed to positive. In addition, for the knee with medial structural injuries, the LGDT test could also be positive only when the posteromedial structures (sMCL, deep MCL, POL) and the cruciate ligaments (ACL and PCL) were all sectioned.ConclusionIn this cadaveric sequential sectioning study, the LGDT test showed positive merely at the following two situations: (1) the distal POP-T and PFL were both sectioned; (2) the posteromedial structures (sMCL, deep MCL and POL) and the cruciate ligaments (ACL and PCL) were all sectioned.Clinical relevanceAccuracy of the LGDT test in diagnosing acute or chronic posterolateral corner (PLC) injuries will improve with the information in this study. It was the combined POP-T and PFL injuries that finally led to a positive LGDT sign. However, one should be cautious to use the LGDT test in diagnosing the PLC injuries when posteromedial structures and cruciate ligaments were all involved.

This paper reports a novel method for reconstructing the posterolateral structures [lateral collateral ligament (LCL), popliteus tendon, popliteofibular ligament] based on an anatomical study of a cadaveric dissection. The popliteus tendon was found to always be attached to the anterior–inferior portion of the femoral attachment site of the LCL, and the average distance from the origin of the popliteal tendon in the femoral side to that of the LCL was 18.5 mm (17–20). The insertion site of the LCL in the fibular side was located anterior–inferior-superficially and the popliteofibular ligament was inserted into the posterior–superior-deep portion around the styloid process. Two femoral tunnels and one fibular head tunnel were made at the proximal and distal portion of the anatomical insertion sites.

The anterior cruciate ligament (ACL) is the major contributor to limit excessive anterior tibial translation (ATT) when the knee is subjected to an anterior tibial load. However, the importance of the medial and lateral structures of the knee can also play a significant role in resisting anterior tibial loads, especially in the event of an ACL injury. Therefore, the objective of this study was to determine quantitatively the increase in the in-situ forces in the medial collateral ligament (MCL) and posterolateral structures (PLS) of the knee associated with ACL deficiency. Eight fresh-frozen cadaveric human knees were subjected to a 134-N anterior tibial load at full extension and at 15°, 30°, 60°, and 90° of knee flexion. The resulting 5 degrees of freedom kinematics were measured for the intact and the ACL-deficient knees. A robotic/universal force-moment sensor testing system was used for this purpose, as well as to determine the in-situ force in the MCL and PLS in the intact and ACL-deficient knees. For the intact knee, the in-situ forces in both the MCL and PLS were less than 20N for all five flexion angles tested. But in the ACL-deficient knee, the in-situ forces in the MCL and PLS, respectively, were approximately two and five times as large as those in the intact knee (P, 0.05). The results of this study demonstrate that, although both the MCL and PLS play only a minor role in resisting anterior tibial loads in the intact knee, they become significant after ACL injury.

The objective of this study was to determine the effects of sectioning the posterolateral structures (PLS) on knee kinematics and in situ forces in the posterior cruciate ligament (PCL) in response to external and simulated muscle loads. Ten human cadaveric knees were tested using a robotic/universal force‐moment sensor testing system. The knees were subjected to three loading conditions: (a) 134‐N posterior tibial load, (b) 5‐Nm external tibial torque, and (c) isolated hamstring load (40 N biceps/40 N semimembranosus). The knee kinematics and in situ forces in the PCL for the intact and PLS‐deficient knee conditions were determined at full extension, 30°, 60°, 90°, and 120° of knee flexion. Under posterior tibial loading posterior tibial translation with PLS deficiency increased significantly at all flexion angles by 5.5 ± 1.5 mm to 0.8 ± 1.2 mm at full extension and 90°, respectively. The corresponding in situ forces in the PCL increased by 17–¶19 N at full extension and 30° of knee flexion. Under the external tibial torque, external tibial rotation increased significantly with PLS deficiency by 15.1 ± 1.6° at 30° of flexion to 7.7 ± 3.5° at 90°, with the in situ forces in the PCL increasing by 15–90 N. The largest increase occurred at 60° to 120° of knee flexion, representing forces two to six times of those in the intact knee. Under the simulated hamstring load, posterior tibial translation and external tibial and varus rotations also increased significantly at all knee flexion angles with PLS deficiency, but this was not so for the in situ forces in the PCL. Our data suggest that injuries to the PLS put the PCL and other soft tissue structures at increased risk of injury due to increased knee motion and the elevated in situ forces in the PCL.

Although the popliteofibular ligament (PFL) is an important posterolateral structure of the knee joint, the anatomical characteristics of this ligament remain unclear. We morphologically classified and measured the PFLs from 78 cadaver knees. The PFL was observed in all knees, and it was classified into type I (with one layer) or type II (with two layers). The mean lengths of the anterior and posterior margins were 12.7 and 6.8 mm, respectively; and the mean width and thickness were 10.4mm and 2.1mm, respectively. The PFL inclined forward at a mean sagittal angle of 20.7°, which is similar to the 21.2° of the posterior cruciate ligament, indicating that the PFL contributed to posterolateral rotatory stability.

Traumatische Verletzungen des posterolateralen Kapsel-Band-Komplexes am Kniegelenk sind normalerweise Folge eines erheblichen Rotationstraumas und gehen in der Regel mit intraartikulären Läsionen einher. Beschrieben werden 2 Fälle, bei denen es ohne Verletzung des Kniegelenks zu einer isolierten Ruptur im distalen Bereich der Sehne des M. biceps femoris kam. Intraoperativ wie auch histologisch fanden sich in beiden Fällen keine Hinweise auf degenerative Veränderungen. Die operative Versorgung führte in beiden Fällen zu einem guten funktionellen Ergebnis. Das bessere Ergebnis wurde allerdings mit einer rigideren operativen Fixation und limitierenden, protektiveren Nachbehandlung, wie sie auch bei der Rekonstruktion posterolateraler Kniegelenkverletzungen üblich ist, erreicht.

Purpose Posterolateral rotatory instability (PLRI) of the elbow occurs from an insufficient lateral collateral ligament complex (LCLC). For subacute LCLC injuries, lateral ulnar collateral ligament (LUCL) internal bracing rather than reconstruction may be a viable option. The purpose of the study was to compare the stabilizing effects of LUCL internal bracing to triceps tendon graft reconstruction in simulated PLRI. Methods Sixteen cadaveric elbows were assigned for either LUCL internal bracing ( n  = 8) or reconstruction with triceps tendon graft ( n  = 8). Specimen were mounted and a valgus rotational torque was applied to the ulna to test posterolateral rotatory stability. Posterolateral rotation was measured at 0°, 30°, 60°, 90° and 120° of elbow flexion. Cyclic loading was performed for 1000 cycles at 90° of elbow flexion. Three conditions were compared in each specimen: intact elbow, LUCL and radial collateral ligament (RCL) transected, and then either LUCL internal bracing or reconstruction with triceps tendon graft. Results Transection of the LUCL and RCL significantly increased posterolateral rotation in all degrees of elbow flexion compared to the intact condition ( P  < 0.05). Both LUCL internal bracing and reconstruction restored posterolateral rotatory stability to the native state between 0° and 120° of elbow flexion, with no significant difference in improvement between groups. Similarly, LUCL internal bracing and reconstruction groups showed no significant difference in posterolateral rotation compared to the intact condition during cyclic loading. Conclusions At time zero, both LUCL internal bracing and reconstruction with triceps tendon graft restored posterolateral rotatory stability. As such, this study supports the use of internal bracing as an adjunct to primary ligament repair in subacute PLRI.