Ata A. Rahnemai-Azar

Structural Properties of the Anterolateral Capsule and Iliotibial Band of the Knee

Background: The role of the anterolateral capsule in knee stability has recently been advocated by studies reporting that a distinct ligament exists in this area. Defining the structural properties of the anterolateral capsule can provide insight into its contribution to joint stability. The structural properties of the iliotibial band also need to be determined, as it is a common graft used for extra-articular tenodesis. Purpose/Hypothesis: The purpose of this study was to determine the structural properties of the anterolateral capsule and iliotibial band. The hypothesis was that the iliotibial band will have comparable structural properties to the anterolateral capsule because it is generally an accepted graft for extra-articular reconstruction surgeries. Study design: Controlled laboratory study. Methods: Nine human cadaveric knees (average age, 57 ± 10 years) were dissected to assess the presence of a discrete capsular thickness originating from the lateral femoral epicondyle to the lateral tibial plateau between the Gerdy tubercle and the fibular head. For each knee, 2 constructs were prepared: (1) a bone–anterolateral capsule–bone specimen and (2) a strip of iliotibial band attached to the Gerdy tubercle. Structural properties, including ultimate load, ultimate elongation, and stiffness, were determined for the anterolateral capsule and the iliotibial band. After tensile testing, plain radiographs were obtained for evaluation of the Segond fracture. A paired t test was used to compare the structural properties of the anterolateral capsule with the iliotibial band. Significance was set at P < .05. Results: Two of the 9 specimens were found to have a discrete thickening of the anterolateral capsule. The iliotibial band had almost 50% higher ultimate load and nearly 3 times higher stiffness (487.9 ± 156.9 N and 73.2 ± 24.1 N/mm, respectively) compared with the anterolateral capsule (319.7 ± 212.6 N and 26.0 ± 11.5 N/mm, respectively) (P < .05 for both). The anterolateral capsule had about double the ultimate elongation compared with the iliotibial band (15.5 ± 7.3 and 8.6 ± 1.4 mm, respectively; P < .05). Conclusion: The anterolateral capsule demonstrated significantly reduced structural properties compared with the iliotibial band. The anterolateral capsule did not have a higher ultimate load compared with the posteromedial capsule as reported in the literature. Clinical Relevance: The decision to perform an extra-articular reconstruction using an iliotibial band graft should be considered carefully. Unnecessary reconstructions using soft tissue grafts with structural properties that far exceed that of the anterolateral capsule may result in overconstraint of the ACL-reconstructed knee.

The Influence of Meniscal and Anterolateral Capsular Injury on Knee Laxity in Patients with Anterior Cruciate Ligament Injuries

Background: The role of the anterolateral capsule (ALC) as a secondary restraint to quantitative rotatory laxity of patients with an anterior cruciate ligament (ACL) injury is currently debated. Purpose/Hypothesis: The purpose was to determine the influence of concomitant ALC injuries as well as injuries to other soft tissue structures on rotatory knee laxity in patients with an ACL injury. It was hypothesized that a concomitant ALC injury would be associated with increased rotatory knee laxity as measured during a quantitative pivot-shift test. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Forty-one patients with an ACL injury (average age, 23 ± 6.9 years) were enrolled. Two blinded musculoskeletal radiologists reviewed magnetic resonance imaging (MRI) scans for the presence of ACL injuries and concomitant soft tissue injuries including the ALC, medial collateral ligament, lateral collateral ligament, posterolateral corner, medial meniscus, and lateral meniscus. A standardized pivot-shift test was performed under anesthesia, and rotatory laxity was quantified according to anterior translation of the lateral tibial compartment during the pivot-shift maneuver. The Student t test was used to analyze the data. Statistical significance was set at P < .05. Results: A complete ACL rupture was confirmed in all of the patients. MRI evidence of an ALC injury was observed in 21 (51%) of the patients. Patients with MRI evidence of an ALC injury had significantly higher rotatory knee laxity (3.6 ± 1.5 mm) compared with those without an ALC injury (2.7 ± 1.5 mm; P = .04). Lateral and medial meniscus injuries were detected in 17 (41%) and 19 (46%) patients, respectively. Patients with MRI evidence of either a medial meniscus injury or lateral meniscus injury had significantly higher rotatory knee laxity compared with patients without these injuries (medial meniscus: 3.7 ± 1.4 mm vs 2.7 ± 1.6 mm, respectively; lateral meniscus: 3.7 ± 1.7 mm vs 2.7 ± 1.3 mm, respectively) (P = .03 for both). Conclusion: MRI evidence of a concomitant injury to the ALC, medial meniscus, or lateral meniscus is associated with increased knee rotatory laxity in patients with an ACL injury. These structures may function as important secondary stabilizers in an ACL-injured knee. Careful assessment and proper treatment of injuries to these secondary stabilizers should be considered, especially in knees with a high level of the pivot shift.

Anterolateral ligament of the knee, fact or fiction?

however, an anterolateral ligament (ALL) was never seen in any of the examined species. This suggests a negative selection against this feature in our own evolution. We have also dissected several fetuses aged 18–22 weeks, and again no distinguishable anterolateral ligament was identified within the capsule. When evaluating the macroscopic anatomy, histology and radiology of the anterolateral capsule in adult human cadaveric specimens, only 30 % of the specimens showed a discrete capsular thickening of 2–4 mm on magnetic resonance imaging (MRI), much thinner than, for example, the LCL. During arthroscopic trans-illumination of these same specimens, no thickening of the anterolateral capsule was seen. Interestingly, on further analysis, internal rotation and flexion of the knee caused a fold in the anterolateral capsule, mimicking a thickening. Histology of this capsular thickening was performed and compared with that of the LCL. The LCL showed a clear linear alignment of collagen fibres, while the anterolateral capsule showed some alignment but not pronounced enough to constitute a true ligament [3]. In our experience of evaluating the anatomy of the anterolateral capsule in more than 150 patients with an A heated debate is ongoing regarding the anatomy of the anterolateral capsule of the knee. Current literature provides a multitude of descriptions. Researchers have argued that the capsule contains a true ligament, while others suggest it merely displays a thickening; yet others fail to show any distinguishable capsular structures. Given the recent surge in the literature on the anterolateral capsule of the knee, it is of great importance to be meticulous in evaluating every aspect of it, including the anatomy, histology, biomechanics, kinematics and clinical implication prior to recommending on its repair or reconstruction. While performing anatomic dissections on 24 different animal species, we have consistently found a double lateral collateral ligament (LCL) in three types of primates;

Validation of Quantitative Measures of Rotatory Knee Laxity.

Background: Prior attempts to quantify the pivot-shift examination have been too invasive or impractical for clinical use. A noninvasive method for quantifying rotatory knee laxity is needed. Hypothesis: Greater quantitative measurements of rotatory knee laxity (both of the involved knee as well as compared with the contralateral healthy knee) are associated with an increasing clinical pivot-shift grade. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 103 patients undergoing anatomic single-bundle anterior cruciate ligament (ACL) reconstruction at 4 international centers underwent a standardized pivot-shift test preoperatively on both knees while anesthetized. Clinical grading of the pivot shift was performed according to the International Knee Documentation Committee (IKDC) knee ligament rating system. Two different quantitative technologies were used to measure rotatory knee laxity: an inertial sensor and an image analysis were independently used to measure tibial acceleration and lateral compartment translation, respectively, during the pivot-shift test. Patients were dichotomized to “high-grade” (abnormal and severely abnormal) or “low-grade” (normal and nearly normal) rotatory knee laxity groups based on the clinical pivot-shift test result of the involved side. Tibial acceleration and lateral compartment translation of the involved knee and the side-to-side difference between the involved and contralateral knees were separately compared between the high- and low-grade rotatory knee laxity groups utilizing t tests; significance was set at P < .05. Results: Forty-three patients were in the low-grade rotatory knee laxity group, and 60 patients were in the high-grade rotatory knee laxity group. Patients in the high-grade knee laxity group had significantly higher lateral compartment translation as measured with the image analysis (involved knee: 3.8 ± 2.3 mm; side-to-side difference: 2.5 ± 2.4 mm) compared with patients in the low-grade group (involved knee: 2.0 ± 1.4 mm; side-to-side difference: 1.4 ± 1.5 mm) (both P < .01). As measured with the inertial sensor, tibial acceleration for patients in the high-grade group was significantly higher (involved knee: 7.2 ± 5.3 m/s2; side-to-side difference: 4.2 ± 5.4 m/s2) compared with patients in the low-grade group (involved knee: 4.2 ± 1.6 m/s2; side-to-side difference: 1.2 ± 1.2 m/s2) (both P < .01). Conclusion: The inertial sensor and image analysis techniques were able to detect differences between low- and high-grade pivot-shift test results. A quantitative assessment of the pivot-shift test could augment the diagnosis of an ACL injury and improve the ability to detect changes in rotatory knee laxity over time.

Increased Lateral Tibial Plateau Slope Predisposes Male College Football Players to Anterior Cruciate Ligament Injury.

BACKGROUND There are conflicting reports regarding the role of osseous morphologic characteristics such as an increased tibial slope as associated with an anterior cruciate ligament (ACL) injury. Few studies have analyzed the role of a combination of osseous morphologic characteristics in matched case control studies. The aim of this study was to determine if there is an association between osseous morphologic characteristics and ACL injury in male college American-football players. METHODS Ninety male U.S. National Collegiate Athletic Association (NCAA) Division-I college football players who underwent magnetic resonance imaging (MRI) for a knee injury between 2005 and 2014 were included. Subjects with an ACL injury (ACL-injured group) were matched for age, height, weight, and body mass index to subjects without an ACL injury (control group). Several osseous morphologic characteristics including medial and lateral condylar width, medial and lateral plateau width, notch width, bicondylar width, notch width index, and medial and lateral tibial slopes were measured and were compared between groups. Conditional logistic regression was used to analyze the data. Significance was set at p < 0.05. RESULTS According to univariable analysis, a narrower lateral femoral condyle (odds ratio, 0.82 [95% confidence interval (95% CI), 0.68 to 0.97]), increased medial tibial plateau slope (odds ratio, 1.42 [95% CI, 1.09 to 1.85]), and increased lateral tibial plateau slope (odds ratio, 1.43 [95% CI, 1.15 to 1.78]) were significantly associated with ACL injury. Multivariable analysis revealed that increased lateral tibial slope (odds ratio, 1.32 [95% CI, 1.03 to 1.70]) was the sole independent predictor of ACL injury. CONCLUSIONS Based on this study, osseous morphology, specifically increased lateral tibial slope, is associated with ACL injury in male college football players. These data might help to improve prevention strategies to lower ACL injury. LEVEL OF EVIDENCE Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

The Segond Fracture Is an Avulsion of the Anterolateral Complex.

Background: The Segond fracture was classically described as an avulsion fracture of the anterolateral capsule of the knee. Recently, some authors have attributed its pathogenesis to the “anterolateral ligament” (ALL). Biomechanical studies that have attempted to reproduce this fracture in vitro have reported conflicting findings. Purpose: To determine the anatomic characteristics of the Segond fracture on plain radiographs and magnetic resonance imaging (MRI), to compare this location with the location of the ALL described in prior radiographic and anatomic publications, and to determine the fracture’s attachments to the soft tissue anterolateral structures of the knee. Study Design: Case series; Level of evidence, 4. Methods: A total of 36 anterior cruciate ligament–injured patients with Segond fractures (33 male, 3 female; mean age, 23.2 ± 8.4 years) were enrolled. MRI scans were reviewed to determine the anatomic characteristics of the Segond fracture, including the following: proximal-distal (PD) length, anterior-posterior (AP) width, medial-lateral (ML) width, PD distance to the lateral tibial plateau, AP distance to the Gerdy tubercle (GT), and AP distance from the GT to the posterior aspect of the fibular head. The attachment of the anterolateral structures to the Segond fragment was then categorized as the iliotibial band (ITB) or anterolateral capsule. Interrater reliability of the measurements was determined by calculating the Spearman rank correlation coefficient. MEDLINE, Web of Science, and the Cochrane Library were searched from inception to May 2016 for the following keywords: (1) “Segond fracture,” (2) “anterolateral ligament,” (3) “knee avulsion,” (4) “lateral tibia avulsion,” and (5) “tibial plateau avulsion.” All studies describing the anatomic location of the Segond fracture and the ALL were included in the systematic review. Results: On plain radiographs, the mean distance of the midpoint of the fracture to the lateral tibial plateau was 4.6 ± 2.2 mm. The avulsed fracture had a mean PD length of 9.2 ± 2.5 mm and a mean ML width of 2.4 ± 1.4 mm. On MRI, the mean distance of the proximal fracture to the tibial plateau was 3.4 ± 1.6 mm. The mean PD length was 8.7 ± 2.2 mm, while the mean AP width was 11.1 ± 2.2 mm. The mean distance between the GT and the center of the fracture was 26.9 ± 3.3 mm, while the mean distance between the GT and the posterior fibular head was 53.9 ± 4.4 mm. The mean distance of the midpoint of the fracture to the tibial plateau was 7.8 ± 2.7 mm, while the center of the fracture was 49.9% of the distance between the GT and the posterior aspect of the fibular head. Analysis of soft tissue structures attached to the fragment revealed that the ITB attached in 34 of 36 patients and the capsule attached in 34 of 36 patients. One patient had only the capsule attached, another had only the ITB attached, and the last showed neither clearly attached. A literature review of 20 included studies revealed no difference between the previously described Segond fracture location and the tibial insertion of the ALL. Conclusion: The results of this study confirmed that while the Segond fracture occurs at the location of the tibial insertion of the ALL, as reported in the literature, MRI was unable to identify any distinct ligamentous attachment. MRI analysis revealed that soft tissue attachments to the Segond fracture were the posterior fibers of the ITB and the lateral capsule in 94% of patients.

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.

Knee instability scores for ACL reconstruction

Despite abundant biological, biomechanical, and clinical research, return to sport after anterior cruciate ligament (ACL) injury remains a significant challenge. Residual rotatory knee laxity has been identified as one of the factors responsible for poor functional outcome. To improve and standardize the assessment of knee instability, a variety of instability scoring systems is available. Recently, devices to objectively quantify static and dynamic clinical exams have been developed to complement traditional subjective grading systems. These devices enable an improved evaluation of knee instability and possible associated injuries. This additional information may promote the development of new treatment algorithms and allow for individualized treatment. In this review, the different subjective laxity scores as well as complementary objective measuring systems are discussed, along with an introduction of injury to an individualized treatment algorithm.

In situ force in the anterior cruciate ligament, the lateral collateral ligament, and the anterolateral capsule complex during a simulated pivot shift test

The role of the anterolateral capsule complex in knee rotatory stability remains controversial. Therefore, the objective of this study was to determine the in situ forces in the anterior cruciate ligament (ACL), the anterolateral capsule, the lateral collateral ligament (LCL), and the forces transmitted between each region of the anterolateral capsule in response to a simulated pivot shift test. A robotic testing system applied a simulated pivot shift test continuously from full extension to 90° of flexion to intact cadaveric knees (n = 7). To determine the magnitude of the in situ forces, kinematics of the intact knee were replayed in position control mode after the following procedures were performed: (i) ACL transection; (ii) capsule separation; (iii) anterolateral capsule transection; and (iii) LCL transection. A repeated measures ANOVA was performed to compare in situ forces between each knee state (*p < 0.05). The in situ force in the ACL was significantly greater than the forces transmitted between each region of the anterolateral capsule at 5° and 15° of flexion but significantly lower at 60°, 75°, and 90° of flexion. This study demonstrated that the ACL is the primary rotatory stabilizer at low flexion angles during a simulated pivot shift test in the intact knee, but the anterolateral capsule plays an important secondary role at flexion angles greater than 60°. Furthermore, the contribution of the “anterolateral ligament” to rotatory knee stability in this study was negligible during a simulated pivot shift test.