Sequential Damage Assessment of the Posterolateral Complex of the Knee Joint: A Finite Element Study

Background. The posterolateral complex (PLC), which consists of the popliteus tendon (PT), lateral collateral ligament (LCL), and popliteofibular ligament (PFL), is an indispensable structure of the knee joint. The aim of this study was to explore the functionality of the PLC by determining the specific role of each component in maintaining posterolateral knee stability. Methods. A finite element (FE) model was generated based on previous material property data and magnetic resonance imaging of a volunteer’s knee joint. The injury order of the PLC was set as LCL, PFL, and PT. A 134 N anterior load was applied to the tibia to investigate tibial displacement (TD). Tibial external rotation (TER) and tibial varus angulation (TVA) were measured under bending motions of 5 and 10 Nm. The instantaneous axis of rotation (IAR) of the knee joint under different rotation motions was also recorded. Results. The TD of the intact knee under a 134 N anterior load matched the values determined in previous studies. Our model showed consistent increases in TD, TVA, and TER after sequential damage of the PLC. In addition, sequential disruption caused the IAR to shift superiorly and laterally during varus rotation, and medially and anteriorly during external rotation. In the dynamic damage of the PLC, LCL injury had the largest effect on TD, TVA, TER, and IAR. Conclusions. Sequential injury of the PLC caused considerable loss of stability of the knee joint according to an FE model. The most significant structure of the PLC was the LCL.

A proposal for a new morphological classification of the popliteus muscle tendon with potential clinical and biomechanical significance

The purpose of this study was to characterize the morphological variations in the proximal attachments and create an accurate classification of the PPM for use in planning surgical procedures in this area, for evaluating radiological imaging and rehabilitation. One hundred and thirty-four lower limbs of body donors (52 woman and 82 man) fixed in 10% formalin solution were examined. The popliteus muscle was present in all 134 limbs. Four main types were identified with subtypes. The most common type was Type I (34.3%), characterized by a single tendon in the popliteus sulcus. Type II (30.6%) characterized by a main tendon in the popliteus sulcus and accessory bands. This type was divided into five subtypes (A–E) based on presence of specific accessory bands. Type III (15.3%) was characterized by two tendons in the popliteal sulcus. Type IV (19.4%) was characterized by two tendons in the popliteus sulcus and additional bands. This type was also divided into five subtypes (A–E) based on presence of specific accessory bands. The popliteofibular ligament was present in 90.3% of cases. A new classification based on a proximal attachment is proposed. The popliteus tendon is characterized by a very high morphological variability, which can affect posterolateral knee stability and the natural rotation of the tibia. Such a classification system may be useful for clinicians performing medical procedures within the knee joint, including orthopedic surgeons.

The popliteofibular ligament: a cadaveric ultrasound study

Objective The popliteofibular ligament (PFL) is an important stabilizer of the knee found within the posterolateral corner (PLC) of the joint. Injuries to the PLC can cause substantial patient morbidity. Accurate PFL visualization has been historically challenging, impeding injury diagnosis and treatment. The gold standard for in vivo PFL visualization is magnetic resonance imaging (MRI), but this procedure has slice thickness limitations, is costly, and is subject to longer wait times. Ultrasonographic (US) PFL assessment is a potentially viable alternative to MRI. This study aimed to determine the viability of US PFL assessment. Materials and methods Ten fresh-frozen lower limb specimens were evaluated for the presence and morphometric characteristics of the PFL via US using an 18.0-MHz linear transducer. The cadavers were then dissected and reassessed for the presence and morphometric characteristics of the PFLs for comparison with US findings. Moreover, the fracture of the fibular styloid process near the site of the insertion of the PFL (the arcuate sign) was simulated and assessed via US. Results The PFL was visualized and measured in all ten knees via both US and cadaveric assessments. There were no statistically significant differences in PFL morphometric characteristics determined via US examination and dissection. The fibular styloid fracture was easily identified in US examination. Conclusion US imaging is a viable alternative for accurate and effective assessment of the normal PFL. Moreover, the arcuate sign can be evaluated via US.

Arthroscopic anatomy of the posterolateral corner of the knee: anatomic relations and arthroscopic approaches

Introduction Although open-surgical techniques for the reconstruction of the posterolateral corner (PLC) are well established, the use of arthroscopic procedures has recently increased. When compared with open surgical preparation, arthroscopic orientation in the PLC is challenging and anatomic relations may not be familiar. Nevertheless, a profound knowledge of anatomic key structures and possible structures at risk as well as technical variations of arthroscopic approaches are mandatory to allow a precise and safe surgical intervention. Materials and methods In a cadaveric video demonstration, an anterolateral (AL), anteromedial (AM), posteromedial (PM) and posterolateral (PL) portal, as well as a transseptal approach (TSA) were developed. Key structures of the PLC were defined and sequentially exposed during posterolateral arthroscopy. Finally, anatomic relations of all key structures were demonstrated. Results All key structures of the PLC can be visualized during arthroscopy. Thereby, careful portal placement is crucial in order to allow an effective exposure. Two alternatives of the TSA were described, depending on the region of interest. The peroneal nerve can be visualized dorsal to the biceps femoris tendon (BT), lateral to the soleus muscle (SM) and about 3 cm distal to the fibular styloid (FS). The distal attachment of the fibular collateral ligament (FCL) can be exposed on the lateral side of the fibular head (FH). The fibular attachment of the popliteofibular ligament (PFL) is exposed at the tip of the FS. Conclusion Arthroscopy of the posterolateral recessus allows full visualization of all key structures of the posterolateral corner, which provides the basis for anatomic and safe drill channel placement in PLC reconstruction. A sufficient exposure of relevant anatomic landmarks and precise portal preparation reduce the risk of iatrogenic vascular and peroneal nerve injury.

Anatomy, magnetic resonance and arthroscopy of the popliteal hiatus of the knee: normal aspect and pathological conditions

The popliteal hiatus is a complex region, formed by the confluence of various structures connecting the meniscus, popliteal tendon, tibia and fibula. The main structures that can be found are the three popliteomeniscal fascicles (anterior, postero-inferior and postero-superior), the lateral and posterior meniscotibial ligaments, the popliteofibular ligament and the meniscofibular fascicle. These structures can be identified in most cases using magnetic resonance imaging, and their ‘static’ assessment can be performed. Arthroscopic assessment is useful in identifying and testing ‘dynamically’ the integrity of the structures around the popliteal hiatus. Injuries or abnormalities of the popliteal hiatus and its structures could result in meniscal hypermobility and subluxation; however, these injuries are often unrecognized. Possible abnormalities in this region, apart from the well-known bucket-handle meniscal tear, are the Wrisberg Type III discoid meniscus, and meniscal fascicles tears. Cite this article: EFORT Open Rev 2021;6:941-954. DOI: 10.1302/2058-5241.6.200089

Evidence-Based Clinical Anatomy of the Popliteofibular Ligament and Its Importance in Orthopaedic Surgery: Cadaveric Versus Magnetic Resonance Imaging Meta-analysis and Radiological Study

Background: The popliteofibular ligament (PFL) is a static stabilizer of the posterolateral corner of the knee, preventing varus angulation, tibial rotation, and posterior translation. The PFL is anatomically variable, and there is no current review that outlines its prevalence rate and morphological variations. Purpose: To investigate the anatomic prevalence and morphological qualities of the PFL in various global patient populations via a meta-analysis of relevant literature involving both cadaveric dissections and patient-based research using magnetic resonance imaging (MRI) scans. Study Design: Meta-analysis. Methods: We pooled literature data detailing PFL prevalence rates and performed a retrospective MRI study of 100 knees to determine the overall PFL prevalence. Data searches and analyses were performed according to Anatomical Quality Assurance and PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Results: There were 30 cadaveric studies and 11 MRI studies (including our radiological investigation), representing a total of 1595 lower limbs. The meta-analysis of cadaveric studies showed a higher prevalence of the PFL than the meta-analysis of MRI studies, with 98.4% (95% CI, 97.5%-99.2%) and 89.0% (95% CI, 73.9%-98.6%), respectively. Our MRI investigation reported a PFL prevalence of 92.0%. Conclusion: The PFL was found to be a constant or rarely absent anatomic structure of the human knee according to the analysis of cadaveric dissection studies, and it was identified notably less on MRI, albeit not significantly. Increasing PFL anatomic knowledge, including awareness of its prevalence and morphological diversity, will improve injury diagnoses, treatment methods, and prognoses.

Posterolateral corner of the knee: a systematic literature review of current concepts of arthroscopic reconstruction

Introduction Injuries of the posterolateral corner (PLC) of the knee lead to chronic lateral and external rotational instability and are often associated with PCL injuries. Numerous surgical techniques for repair and reconstruction of the PLC are established. Recently, several arthroscopic techniques have been published in order to address different degrees of PLC injuries through reconstruction of one or more functional structures. The purpose of this systematic review is to give an overview about arthroscopic techniques of posterolateral corner reconstructions and to evaluate their safeness. Materials and methods A systematic review of the literature on arthroscopic reconstructions of the posterolateral corner of the knee according to the PRISMA guidelines was performed using PubMed MEDLINE and Web of Science Databases on June 15th, 2020. Inclusion criteria were descriptions of surgical techniques to reconstruct different aspects of the posterolateral corner either strictly arthroscopically or minimally-invasive with an arthroscopic assistance. Results Arthroscopic techniques differ with regard to the extent of reconstructed units (popliteus tendon, popliteofibular ligament, lateral collateral ligament), surgical approach (transseptal, lateral) and biomechanical results (anatomic vs. non-anatomic reconstruction, restoration of rotational instability and/or lateral instability). Conclusion Different approaches to arthroscopic PLC reconstruction are presented, yet clinical results are scarce. Up to now good and excellent clinical results are reported. No major complications are reported in the literature so far.

Biomechanics and physical examination of the posteromedial and posterolateral knee: state of the art

The posteromedial and posterolateral corner structures contribute significantly to knee stability. The posterior oblique ligament is a primary restraint to internal rotation and a secondary restraint to valgus. The superficial fibres of the medial collateral ligament are the primary valgus restraint and also provide secondary internal and external rotation stability. The deep fibres of the medial collateral provide additional restraint to internal and external rotation as well as valgus. The posteromedial capsule provides a secondary restraint to valgus and posterior translation. The lateral (fibular) collateral ligament is the primary varus stabiliser. The popliteus tendon complex is a primary restraint to external rotation. The popliteofibular ligament is a secondary restraint to external rotation and varus. Many physical examination manoeuvres have been described to assess these structures. Manoeuvres assessing the posterolateral structures include the varus stress test, dial test, the posterolateral drawer, the external rotation recurvatum test, heel height test and the reverse pivot shift. Examination manoeuvres that assess the posteromedial structures include the valgus stress test, dial test, anterolateral drawer test and anteromedial drawer test. Proper application of physical examination manoeuvres in conjunction with other diagnostic modalities will allow providers to develop appropriate treatment plans.

Comparative Biomechanical Study Between Minimally Invasive Popliteus and LCL Reconstruction Versus LaPrade Technique

Background: Many aspects of the posterolateral corner (PLC) of the knee have been extensively studied within the past 20 years. Quantitative anatomic and biomechanical studies have demonstrated the importance of the 3 static stabilizers of the lateral side of the knee: the fibular collateral ligament, the popliteus tendon, and the popliteofibular ligament. There are various methods of reconstruction. However, currently, there is no consensus on the preferred reconstruction technique for treating patients with chronic PLC injuries. We have developed a new reconstructive technique for PLC based on tibiofibular-based technique, similar to LaPrade, and this technique is less invasive than the previous techniques. Hypothesis: There is no difference between minimally invasive popliteus and LCL reconstruction and LaPrade’s method in restoring the posterolateral stability of knees Methods: Six paired fresh-frozen cadaveric knees were assessed in the intact state and then dissected to simulate a grade III posterolateral knee injury. By using a “Blocked randomization”, each paired knee was randomized into 2 groups (1) reconstruction via LaPrade’s method, (2) minimally invasive popliteus and LCL reconstruction. Biomechanical testing using varus stress radiographs was performed to compare knee stability between 2 groups. Results: This study included six paired knees, three males and three females. The mean age of the cadaver was 70.8 years (range 57-85 years). No difference was found in the demographic data (sex distribution, lateral opening gap of intact knee and side-to-side difference of lateral opening gap of sectioned knee) between the 2 groups. The side-to-side difference in lateral joint opening on the varus stress radiographs significantly improved after PLC reconstruction in both groups (p <0.001, p <0.001), However, there were no differences between the 2 groups in side-to-side difference of lateral opening gap after reconstruction (Mean difference=-0.05 (95%CI, -0.46 to 0.36); p- value=0.039). Conclusion: Biomechanically, minimally invasive popliteus and LCL reconstruction is equivalent to LaPrade’s technique in restoring the stability of knees in case of grade III PLC injury. Additionally, this technique is less invasive than all traditional open technique of PLC reconstruction. The minimally invasive popliteus and LCL reconstruction technique may be a treatment option for grade III PLC injury. Keywords: posterolateral corner; ligament reconstruction; popliteus tendon; lateral collateral ligament; popliteofibular ligament; knee biomechanics; minimally invasive surgery