Anterolateral rotatory instability of the knee.

Recent publications have generated renewed interest in the anatomy of the anterolateral capsule. Knowledge of the biomechanical function of the anterolateral components is lacking. Further research is required to evaluate the influence of the anterolateral capsule on rotatory laxity of the knee. The role of surgical procedures, such as an extra-articular tenodesis or lateral plasty, has to be defined based on quantification of the injury. This article seeks to summarize the current literature and discusses the role of the anterolateral capsule and reconstructive techniques in combined ligamentous knee trauma. Level of evidence V.

Outcomes of untreated posterolateral knee injuries: an in vivo canine model.

PURPOSE: The purpose of our study was to determine if sectioning the canine fibular collateral ligament, popliteus tendon, and popliteofibular ligament would result in residual posterolateral instability and produce measureable evidence of early-onset arthritis on ultra-high field MRI. METHODS: The fibular collateral ligament, popliteus tendon, and popliteofibular ligament were surgically sectioned in six canines. Six months postoperatively, both limbs were biomechanically tested involving 3.25 Nm varus and 1.25 Nm internal and external rotation torques at 28.5° (mean full extension), 60°, and 90° of flexion. A 7.0-tesla MRI scanner acquired T (1ρ)-weighted images, and relaxation time constants were calculated. RESULTS: Compared to the non-operative knees, varus angulation significantly increased by 2.0°, 8.0°, and 12.4° in the operative knees at full extension, 60° flexion, and 90° flexion, respectively. External rotation was significantly increased by 8.1° at full extension, 12.2° at 60°, and 8.2° at 90°. Internal rotation was significantly increased by 9.1° at full extension and 12.4° at 60°. T (1ρ) MRI mapping revealed a significant increase in relaxation times in the medial compartment of the surgical knees compared to controls. CONCLUSION: This study validated that grade III surgically created posterolateral knee injuries do not heal and that the canine knee developed early-onset changes of the medial compartment, indicative of early-onset osteoarthritis, developed in the operative knees.

Anatomy and biomechanics of the posterolateral aspect of the canine knee.

The purpose of this study was to describe the anatomy and characterize the biomechanics of the posterolateral aspect of the canine knee. Ten adult canine knees were each used for anatomy and biomechanical testing. Distances and motion limits were measured using a 6 degree-of-freedom electromagnetic tracking system. Canine knee dissection reproducibly identified structures present in the human posterolateral knee. The course and attachment sites of the fibular collateral ligament, popliteofibular ligament, and popliteus tendon were similar to human anatomy. Sequential sectioning of the fibular collateral ligament, popliteofibular ligament, and popliteus tendon all significantly increased varus translation at full extension, 60 degrees , and 90 degrees of knee flexion. Sectioning of the fibular collateral ligament significantly increased external rotation at flexion angles near full extension, while popliteus tendon sectioning also significantly increased external rotation at 90 degrees of knee flexion. Based on the fact that the anatomy of the fibular collateral ligament, popliteus tendon, popliteofibular ligament, and the biomechanical properties of the canine posterolateral knee are similar to the human knee, we believe the canine knee is a suitable model to study the natural history of posterolateral knee injuries. The canine model will also prove valuable in the validation of reconstruction techniques and studying the potential development of medial compartment osteoarthritis following posterolateral knee injuries.

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/s(2); side-to-side difference: 4.2 ± 5.4 m/s(2)) compared with patients in the low-grade group (involved knee: 4.2 ± 1.6 m/s(2); side-to-side difference: 1.2 ± 1.2 m/s(2)) (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.

Treadmill vs. overground running gait during childhood: a qualitative and quantitative analysis.

Conventional gait labs are limited in their ability to study running gait due to their size. There is no consensus in the literature regarding the ability to extrapolate results for adult treadmill running to overground. This comparison has not been studied in children. Twenty-four healthy children (mean age 11.7) ran overground at a slow running speed while motion capture, ground reaction force, and surface electromyography (EMG) data were obtained. The same data were then collected while participants ran for 6min on an instrumented treadmill at a speed similar to their overground speed. The kinematic, kinetic, and EMG data for overground and treadmill running were compared. Sagittal plane kinematics demonstrated similar hip and knee waveforms with the exception of more knee extension just before toe off. Ankle kinematic waveforms were similar during stance phase but treadmill running demonstrated decreased dorsiflexion during swing. Kinetic data was significantly different between the two conditions with treadmill running having a more anterior ground reaction force compared to overground. Due to the numerous differences between overground and treadmill gait demonstrated in this study, it is felt that the use of an instrumented treadmill is not a surrogate to the study of overground running in a pediatric population. This data set will function as a normative data set against which future treadmill studies can be compared.

Improving outcomes for posterolateral knee injuries.

Until recently, the posterolateral corner of the knee was noted both for its complex anatomy and diagnostic challenges. To improve the understanding of the posterolateral knee, we completed a comprehensive and stepwise research program with a focus on five primary areas: (1) surgical approach and relevant anatomy; (2) diagnosis; (3) clinically relevant biomechanics; (4) natural history; and (5) surgical treatment. Based on this comprehensive research program, the diagnosis and outcomes following treatment of posterolateral knee injuries have been significantly improved comparing the preoperative state to the state of the knee at a minimum 2 year follow-up in the cases series presented here. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:485-491, 2014.

Injuries to the medial collateral ligament and associated medial structures of the knee.

*The superficial medial collateral ligament and other medial knee stabilizers-i.e., the deep medial collateral ligament and the posterior oblique ligament-are the most commonly injured ligamentous structures of the knee. *The main structures of the medial aspect of the knee are the proximal and distal divisions of the superficial medial collateral ligament, the meniscofemoral and meniscotibial divisions of the deep medial collateral ligament, and the posterior oblique ligament. *Physical examination is the initial method of choice for the diagnosis of medial knee injuries through the application of a valgus load both at full knee extension and between 20 degrees and 30 degrees of knee flexion. *Because nonoperative treatment has a favorable outcome, there is a consensus that it should be the first step in the management of acute isolated grade-III injuries of the medial collateral ligament or such injuries combined with an anterior cruciate ligament tear. *If operative treatment is required, an anatomic repair or reconstruction is recommended.

Correlation of valgus stress radiographs with medial knee ligament injuries: an in vitro biomechanical study.

BACKGROUND: The amount of medial compartment opening for medial knee injuries determined by valgus stress radiography has not been well documented. The purpose of this study was to develop clinical guidelines for diagnosing medial knee injuries using valgus stress radiography. HYPOTHESIS: Measurements of medial compartment gapping can accurately differentiate between normal and injured medial structure knees on valgus stress radiographs. STUDY DESIGN: Controlled laboratory study. METHODS: Valgus stress radiographs were obtained on 18 adult lower extremities using 10-N.m and clinician-applied valgus loads at 0 degrees and 20 degrees of flexion to intact knees and after sequential sectioning of the superficial medial collateral ligament proximally and distally, the meniscofemoral and meniscotibial portions of the deep medial collateral ligament, the posterior oblique ligament, and the cruciate ligaments. Three independent observers of different experience levels measured all of the radiographs during 2 separate occasions to determine intraobserver repeatability and interobserver reproducibility. RESULTS: Compared with the intact knee, significant medial joint gapping increases of 1.7 mm and 3.2 mm were produced at 0 degrees and 20 degrees of flexion, respectively, by a clinician-applied load on an isolated grade III superficial medial collateral ligament simulated injury. A complete medial knee injury yielded gapping increases of 6.5 mm and 9.8 mm at 0 degrees and 20 degrees , respectively, for a clinician-applied load. Intraobserver repeatability and interobserver reproducibility intraclass correlation coefficients were .99 and .98, respectively. CONCLUSION: Valgus stress radiographs accurately and reliably measure medial compartment gapping but cannot definitively differentiate between meniscofemoral- and meniscotibial-based injuries. A grade III medial collateral ligament injury should be suspected with greater than 3.2 mm of medial compartment gapping compared to the contralateral knee at 20 degrees of flexion, and this injury will also result in gapping in full extension. Clinical Significance Valgus stress radiographs provide objective and reproducible measurements of medial compartment gapping, which should prove useful for definitive diagnosis, management, and postoperative follow-up of patients with medial knee injuries.

Fibular collateral ligament anatomical reconstructions: a prospective outcomes study.

BACKGROUND: After the development and biomechanical validation of an anatomical fibular collateral ligament reconstruction using a semitendinosus graft, this technique has subsequently been applied clinically. HYPOTHESIS: An anatomical reconstruction of a grade III fibular collateral ligament tear using a semitendinosus graft restores the knee to near-normal lateral compartment stability and results in improved patient outcomes. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: A prospective study of 20 patients with an average age of 24 years (range, 16-45 years) who had an anatomical reconstruction of the fibular collateral ligament using a semitendinosus graft was performed. All patients were preoperatively and postoperatively evaluated with the modified Cincinnati and International Knee Documentation Committee (IKDC) subjective scoring systems, with the IKDC objective subscores for lateral and posterolateral knee stability and with varus stress radiographs. The patients were followed for an average of 2 years. RESULTS: Sixteen patients were available for follow-up. Six of the patients had an isolated fibular collateral ligament reconstruction. The average preoperative modified Cincinnati score was 28.2, and the average IKDC subjective score was 34.7. Postoperatively, there was a significant improvement of both the modified Cincinnati score (to 88.5) and the IKDC subjective outcome score (to 88.1). The Cincinnati component symptom and functional subscores were also evaluated. The average preoperative symptom subscore was 9.1 and the functional subscore was 19.1. Postoperatively, there was a significant improvement in both scores; symptom subscores improved to 43.0 and functional subscores improved to 45.5. Preoperative varus stress radiographs demonstrated an average differential of 3.9 mm (range, 2.5-6.2 mm) of lateral compartment gapping between the injured and noninjured knee. At an average of 2 years postoperatively, varus stress radiographs demonstrated an average side-to-side lateral compartment gap differential of -0.4 mm. CONCLUSION: An anatomical fibular collateral ligament reconstruction using a semitendinosus graft results in improved patient outcomes and near-normal lateral compartment stability in patients with grade III injuries of the fibular collateral ligament.

Medial knee injury: Part 2, load sharing between the posterior oblique ligament and superficial medial collateral ligament.

BACKGROUND: There is limited information regarding directly measured load responses of the posterior oblique and superficial medial collateral ligaments in isolated and multiple medial knee ligament injury states. HYPOTHESES: Tensile load responses from both the superficial medial collateral ligament and the posterior oblique ligament would be measurable and reproducible, and the native load-sharing relationships between these ligaments would be altered after sectioning of medial knee structures. STUDY DESIGN: Descriptive laboratory study. METHODS: Twenty-four nonpaired, fresh-frozen adult cadaveric knees were distributed into 3 sequential sectioning sequences. Buckle transducers were applied to the posterior oblique ligament and the proximal and distal divisions of the superficial medial collateral ligament; 10 N.m valgus moments and 5 N.m internal and external rotation torques were applied at 0 degrees , 20 degrees , 30 degrees , 60 degrees , and 90 degrees of knee flexion. RESULTS: With an applied valgus and external rotation moment, there was a significant load increase on the posterior oblique ligament compared with the intact state after sectioning all other medial knee structures. With an applied external rotation torque, there was a significant load decrease on the proximal division of the superficial medial collateral ligament from the intact state after sectioning all other medial knee structures. With an applied external rotation torque, the distal division of the superficial medial collateral ligament experienced a significant load increase from the intact state after sectioning the posterior oblique ligament and the meniscofemoral division of the deep medial collateral ligament. CONCLUSION: This study found alterations in the native load-sharing relationships of the medial knee structures after injury. Sectioning both the primary and secondary restraints to valgus and internal/external rotation of the knee alters the intricate load-sharing relationships that exist between the medial knee structures. CLINICAL SIGNIFICANCE: In cases in which surgical repair or reconstruction is indicated, consideration should be placed on repairing or reconstructing all injured medial knee structures to restore the native load-sharing relationships among these medial knee structures.

Medial knee injury: Part 1, static function of the individual components of the main medial knee structures.

BACKGROUND: There is a lack of knowledge on the primary and secondary static stabilizing functions of the posterior oblique ligament (POL), the proximal and distal divisions of the superficial medial collateral ligament (sMCL), and the meniscofemoral and meniscotibial portions of the deep medial collateral ligament (MCL). HYPOTHESIS: Identification of the primary and secondary stabilizing functions of the individual components of the main medial knee structures will provide increased knowledge of the medial knee ligamentous stability. STUDY DESIGN: Descriptive laboratory study. METHODS: Twenty-four cadaveric knees were equally divided into 3 groups with unique sequential sectioning sequences of the POL, sMCL (proximal and distal divisions), and deep MCL (meniscofemoral and meniscotibial portions). A 6 degree of freedom electromagnetic tracking system monitored motion after application of valgus loads (10 N.m) and internal and external rotation torques (5 N.m) at 0 degrees , 20 degrees , 30 degrees , 60 degrees , and 90 degrees of knee flexion. RESULTS: The primary valgus stabilizer was the proximal division of the sMCL. The primary external rotation stabilizer was the distal division of the sMCL at 30 degrees of knee flexion. The primary internal rotation stabilizers were the POL and the distal division of the sMCL at all tested knee flexion angles, the meniscofemoral portion of the deep MCL at 20 degrees , 60 degrees , and 90 degrees of knee flexion, and the meniscotibial portion of the deep MCL at 0 degrees and 30 degrees of knee flexion. CONCLUSION: An intricate relationship exists among the main medial knee structures and their individual components for static function to applied loads. CLINICAL SIGNIFICANCE: Interpretation of clinical knee motion testing following medial knee injuries will improve with the information in this study. Significant increases in external rotation at 30 degrees of knee flexion were found with all medial knee structures sectioned, which indicates that a positive dial test may be found not only for posterolateral knee injuries but also for medial knee injuries.

Force measurements on the posterior oblique ligament and superficial medial collateral ligament proximal and distal divisions to applied loads.

BACKGROUND: There is limited information regarding load responses of the posterior oblique and superficial medial collateral ligaments to applied loads. HYPOTHESES: The degree of knee flexion affects loads experienced by the posterior oblique ligament and both divisions of the superficial medial collateral ligament. The posterior oblique ligament provides significant resistance to valgus and internal rotation forces near knee extension. Different load responses are experienced by proximal and distal divisions of the superficial medial collateral ligament. STUDY DESIGN: Descriptive laboratory study. METHODS: Twenty-four nonpaired, fresh-frozen cadaveric knees were tested. Buckle transducers were applied to the proximal and distal divisions of the superficial medial collateral and posterior oblique ligaments. Applied loads at 0 degrees, 20 degrees, 30 degrees, 60 degrees, and 90 degrees of knee flexion consisted of 10 N m valgus loads, 5 N.m internal and external rotation torques, and 88 N anterior and posterior drawer loads. RESULTS: External rotation torques produced a significantly higher load response on the distal superficial medial collateral ligament than did internal rotation torques at all flexion angles with the largest difference at 90 degrees (96.6 vs 22.5 N). For an applied valgus load at 60 degrees of knee flexion, loads on the superficial medial collateral ligament were significantly higher in the distal division (103.5 N) than the proximal division (71.9 N). The valgus load response of the posterior oblique ligament at 0 degrees of flexion (19.1 N) was significantly higher than at 30 degrees (10.6 N), 60 degrees (7.8 N), and 90 degrees (6.8 N) of flexion. At 0 degrees of knee flexion, the load response to internal rotation on the posterior oblique ligament (45.8 N) was significantly larger than was the response on both divisions of the superficial medial collateral ligament (20 N for both divisions). At 90 degrees of flexion, the load response to internal rotation torques reciprocated between these structures with a significantly higher response in the distal superficial medial collateral ligament division (22.5 N) than the posterior oblique ligament (9.1 N). CONCLUSION: The superficial medial collateral ligament experienced the largest load response to applied valgus and external rotation torques; the posterior oblique ligament observed the highest load response to internal rotation near extension. CLINICAL RELEVANCE: This study provides new knowledge of the individual biomechanical function of the main medial knee structures in an intact knee and will assist in the interpretation of clinical knee motion testing and provide evidence for techniques involving repair or reconstruction of the posterior oblique ligament and both divisions of the superficial medial collateral ligament.

Radiographic identification of the primary medial knee structures.

BACKGROUND: Radiographic landmarks for medial knee attachment sites during anatomic repairs or reconstructions are unknown. If identified, they could assist in the preoperative evaluation of structure location and allow for postoperative assessment of reconstruction tunnel placement. METHODS: Radiopaque markers were implanted into the femoral and tibial attachments of the superficial medial collateral ligament and the femoral attachments of the posterior oblique and medial patellofemoral ligaments of eleven fresh-frozen, nonpaired cadaveric knee specimens. Both anteroposterior and lateral radiographs were made. Structures were assessed within quadrants formed by the intersection of reference lines projected on the lateral radiographs. Quantitative measurements were performed by three independent examiners. Intraobserver reproducibility and interobserver reliability were determined with use of intraclass correlation coefficients. RESULTS: The overall intraclass correlation coefficients for intraobserver reproducibility and interobserver reliability were 0.996 and 0.994, respectively. On the anteroposterior radiographs, the attachment sites of the superficial medial collateral ligament, posterior oblique ligament, and medial patellofemoral ligament were 30.5 +/- 2.4 mm, 34.8 +/- 2.7 mm, and 42.3 +/- 2.1 mm from the femoral joint line, respectively. On the lateral femoral radiographs, the attachment of the superficial medial collateral ligament was 6.0 +/- 0.8 mm from the medial epicondyle and was located in the anterodistal quadrant. The attachment of the posterior oblique ligament was 7.7 +/- 1.9 mm from the gastrocnemius tubercle and was located in the posterodistal quadrant. The attachment of the medial patellofemoral ligament was 8.9 +/- 2.0 mm from the adductor tubercle and was located in the anteroproximal quadrant. On the lateral tibial radiographs, the proximal and distal tibial attachments of the superficial medial collateral ligament were 15.9 +/- 5.2 and 66.1 +/- 3.6 mm distal to the tibial inclination, respectively. CONCLUSIONS: The attachment locations of the main medial knee structures can be qualitatively and quantitatively correlated to osseous landmarks and projected radiographic lines, with close agreement among examiners.

Radiographic identification of the primary posterolateral knee structures.

BACKGROUND: It is often difficult to identify the attachment sites of the fibular collateral ligament, popliteus tendon, and popliteofibular ligament for chronic posterolateral knee injuries or during revision surgeries. Descriptions of radiographic landmarks for these attachment sites would assist in the intraoperative identification of their locations and also allow for postoperative assessment of the placement of reconstruction tunnels. HYPOTHESIS: Identification of qualitative and quantitative radiographic landmarks for the attachments of the main posterolateral knee structures are reproducible among observers of various experience levels and allow for improved intraoperative and postoperative identification of these attachment sites. STUDY DESIGN: Descriptive laboratory study. METHODS: Dissections were performed on 11 cadaveric knee specimens. The attachments and locations of the investigated structures were labeled with radiopaque markers. The positions of the attachments relative to other attachment sites, labeled bony landmarks, and superimposed reference lines were quantified on anteroposterior and lateral radiographs. Measurements were performed by 3 independent examiners. Intraobserver and interobserver reliability was determined using intraclass correlation coefficients. RESULTS: Overall intraclass correlation coefficients for intraobserver reproducibility and interobserver reliability were calculated to be 0.981 and 0.983, respectively. On the anteroposterior view, the perpendicular distances from a line intersecting the femoral condyles to the popliteus tendon, proximal fibular collateral ligament, and lateral gastrocnemius tendon were 14.5, 27.1, and 34.5 mm, respectively. On the lateral view, the femoral attachments of the fibular collateral ligament, popliteus tendon, and lateral gastrocnemius tendon were 4.3, 12.2, and 13.1 mm, respectively, from the lateral epicondyle. In addition, the fibular collateral ligament and popliteus tendon were located within 1 mm of a reference line projected along the posterior femoral cortex distally, and also were located within the posteroinferior quadrant bound by the posterior femoral cortex extension reference line and another reference line perpendicular to it at the posterior margin of Blumensaat's line. CONCLUSION: Comprehensive qualitative and quantitative guidelines for assessing posterolateral knee structures on both anteroposterior and lateral knee radiographs were described. CLINICAL SIGNIFICANCE: This radiographic information regarding the attachment sites of posterolateral structures can serve as a valuable reference for preoperative, intraoperative, and postoperative assessments of surgical reconstructions.

A comparative analysis of 7.0-Tesla magnetic resonance imaging and histology measurements of knee articular cartilage in a canine posterolateral knee injury model: a preliminary analysis.

BACKGROUND: There has recently been increased interest in the use of 7.0-T magnetic resonance imaging for evaluating articular cartilage degeneration and quantifying the progression of osteoarthritis. PURPOSE: The purpose of this study was to evaluate articular cartilage cross-sectional area and maximum thickness in the medial compartment of intact and destabilized canine knees using 7.0-T magnetic resonance images and compare these results with those obtained from the corresponding histologic sections. STUDY DESIGN: Controlled laboratory study. METHODS: Five canines had a surgically created unilateral grade III posterolateral knee injury that was followed for 6 months before euthanasia. The opposite, noninjured knee was used as a control. At necropsy, 3-dimensional gradient echo images of the medial tibial plateau of both knees were obtained using a 7.0-T magnetic resonance imaging scanner. Articular cartilage area and maximum thickness in this site were digitally measured on the magnetic resonance images. The proximal tibias were processed for routine histologic analysis with hematoxylin and eosin staining. Articular cartilage area and maximum thickness were measured in histologic sections corresponding to the sites of the magnetic resonance slices. RESULTS: The magnetic resonance imaging results revealed an increase in articular cartilage area and maximum thickness in surgical knees compared with control knees in all specimens; these changes were significant for both parameters (P <.05 for area; P <.01 for thickness). The average increase in area was 14.8% and the average increase in maximum thickness was 15.1%. The histologic results revealed an average increase in area of 27.4% (P = .05) and an average increase in maximum thickness of 33.0% (P = .06). Correlation analysis between the magnetic resonance imaging and histology data revealed that the area values were significantly correlated (P < .01), but the values for thickness obtained from magnetic resonance imaging were not significantly different from the histology sections (P > .1). CONCLUSION: These results demonstrate that 7.0-T magnetic resonance imaging provides an alternative method to histology to evaluate early osteoarthritic changes in articular cartilage in a canine model by detecting increases in articular cartilage area. CLINICAL RELEVANCE: The noninvasive nature of 7.0-T magnetic resonance imaging will allow for in vivo monitoring of osteoarthritis progression and intervention in animal models and humans for osteoarthritis.

Medial plica irritation: diagnosis and treatment.

Medial plica irritation of the knee is a very common source of anterior knee pain. Patients can complain of pain over the anteromedial aspect of their knees and describe episodes of crepitation, catching, and pseudo-locking events with activities. Patients commonly have pain on physical examination upon rolling the plica fold of tissue over the anteromedial aspect of their knees and often have tight hamstrings. The majority of the patients will respond well to a non-operative treatment program consisting of quadriceps strengthening along with concurrent hamstring stretching. In cases which do not respond initially to an exercise program, an intraarticular steroid injection may be indicated. In those few patients who do not respond to a non-operative treatment program, an arthroscopic resection of their medial plica may be indicated, especially in those cases where a shelf-like plica has been found to be causing damage to the articular cartilage of the medial femoral condyle.

The external rotation recurvatum test revisited: reevaluation of the sagittal plane tibiofemoral relationship.

BACKGROUND: Posterolateral corner injuries can be difficult to diagnose. The external rotation recurvatum test was one of the first clinical tests described to diagnose these injuries. Since its earliest description, it has been reported that a positive test result occurred with posterior translation of the proximal tibia with respect to the distal femur as the knee went into recurvatum, external rotation, and varus angulation. PURPOSE: To document the sagittal plane relationship of the tibiofemoral joint in patients with posterolateral knee instability and a positive external rotation recurvatum test finding, and to determine possible injury patterns associated with this test. STUDY DESIGN: Case series; Level of evidence, 4. MATERIALS AND METHODS: In a series of 134 consecutive patients with posterolateral knee injuries, all patients demonstrating a positive external rotation recurvatum test result were identified, and bilateral hyperextension lateral radiographs were subsequently obtained to assist with preoperative planning for surgical reconstruction of their knee injuries. RESULTS: Of the 134 patients with posterolateral knee injuries, 10 demonstrated a positive external rotation recurvatum test finding. All 10 patients were noted to have a combined anterior cruciate ligament and posterolateral knee injury, with the proximal tibia noted to be subluxated anterior with respect to the distal femur on all hyperextension lateral knee radiographs. The percentage of patients with combined anterior cruciate ligament and posterolateral knee injuries with a positive external rotation recurvatum test result was 30%. CONCLUSION: Posterolateral corner knee injuries are often difficult to diagnose, and as a result, correct interpretation of pertinent clinical knee examination findings is essential. Regarding posterolateral knee injuries, the interpretation of a positive external rotation recurvatum test result needs to be redefined to demonstrate that the tibia actually subluxates anterior to the femur, which produces an increase in genu recurvatum clinically. Moreover, the presence of a positive external rotation recurvatum test finding should alert the clinician to the presence of a probable combined posterolateral knee and anterior cruciate ligament injury.

Kinematic evaluation of the modified Weaver-Dunn acromioclavicular joint reconstruction.

BACKGROUND: Few reconstructive methods to treat displaced acromioclavicular separations have been evaluated using kinematic data. HYPOTHESIS: The modified Weaver-Dunn reconstruction restores intact acromioclavicular joint motion during passive scapular plane abduction. STUDY DESIGN: Controlled laboratory study. METHODS: Acromioclavicular joint motion was recorded during passive humeral elevation in 3 states: an intact shoulder, an "injured" state in which the acromioclavicular and coracoclavicular ligaments were transected, and finally in a reconstructed state using a modified Weaver-Dunn reconstruction. Measurements were taken with an electromagnetic motion analysis system attached to rigid pins placed in the clavicle, scapula, humerus, and sternum during passive scapular plane humeral elevation. RESULTS: Total translatory motion of the acromioclavicular joint in the cut state was significantly greater than both the intact and reconstructed states in the medial/lateral (intact, 4.3 mm; cut, 7.9 mm; reconstructed, 2.6 mm), anterior/posterior (intact, 4.8 mm; cut, 6.1 mm; reconstructed, 4.9 mm), and superior/inferior (intact, 4.1 mm; cut, 8.0 mm; reconstructed, 4.8 mm) directions. The maximum and minimum positions of the reconstructed state were significantly more anterior and inferior than in the intact state. A significant increase in acromioclavicular axial rotation was also found between the intact and cut state. CONCLUSION: The modified Weaver-Dunn reconstruction was found to restore motion of the acromioclavicular joint to near-intact values, but created a more anterior and inferior position of the clavicle with respect to the acromion. CLINICAL RELEVANCE: These kinematic data support the modified Weaver-Dunn reconstruction as a kinematically sound procedure to treat displaced acromioclavicular joint injuries.

Biomechanical analysis of an isolated fibular (lateral) collateral ligament reconstruction using an autogenous semitendinosus graft.

BACKGROUND: The fibular collateral ligament is the primary stabilizer to varus instability of the knee. Untreated fibular collateral ligament injuries can lead to residual knee instability and can increase the risk of concurrent cruciate ligament reconstruction graft failures. Anatomic reconstructions of the fibular collateral ligament have not been biomechanically validated. PURPOSE: To describe an anatomic fibular collateral ligament reconstruction using an autogenous semitendinosus graft and to test the hypothesis that using this reconstruction technique to treat an isolated fibular collateral ligament injury will restore the knee to near normal stability. STUDY DESIGN: Controlled laboratory study. METHODS: Ten nonpaired, fresh-frozen cadaveric knees were biomechanically subjected to a 10 N.m varus moment and 5 N.m external and internal rotation torques at 0 degrees, 15 degrees, 30 degrees, 60 degrees, and 90 degrees of knee flexion. Testing was performed with an intact and sectioned fibular collateral ligament, and also after an anatomic reconstruction of the fibular collateral ligament with an autogenous semitendinosus graft. Motion changes were assessed with a 6 degree of freedom electromagnetic motion analysis system. RESULTS: After sectioning, we found significant increases in varus rotation at 0 degrees, 15 degrees, 30 degrees, 60 degrees, and 90 degrees, external rotation at 60 degrees and 90 degrees, and internal rotation at 0 degrees, 15 degrees, 30 degrees, 60 degrees, and 90 degrees of knee flexion. After reconstruction, there were significant decreases in motion in varus rotation at 0 degrees, 15 degrees, 30 degrees, 60 degrees, and 90 degrees, external rotation at 60 degrees and 90 degrees, and internal rotation at 0 degrees, 15 degrees, and 30 degrees of knee flexion. In addition, we observed a full recovery of knee stability in varus rotation at 0 degrees, 60 degrees, and 90 degrees, external rotation at 60 degrees and 90 degrees, and internal rotation at 0 degrees and 30 degrees of knee flexion. CONCLUSION: An anatomic fibular collateral ligament reconstruction restores varus, external, and internal rotation to near normal stability in a knee with an isolated fibular collateral ligament injury. CLINICAL SIGNIFICANCE: An anatomic reconstruction of the fibular collateral ligament with an autogenous semitendinosus graft is a viable option to treat nonrepairable acute or chronic fibular collateral ligament tears in patients with varus instability.

Non-nearest-neighbor dependence of the stability for RNA bulge loops based on the complete set of group I single-nucleotide bulge loops.

Fifty-nine RNA duplexes containing single-nucleotide bulge loops were optically melted in 1 M NaCl, and the thermodynamic parameters DeltaH degrees, DeltaS degrees, DeltaG 37 degrees, and TM for each sequence were determined. Sequences from this study were combined with sequences from previous studies [Longfellow, C. E., et al. (1990) Biochemistry 29, 278-285; Znosko, B. M., et al. (2002) Biochemistry 41, 10406-10417], thus examining all possible group I single-nucleotide bulge loop and nearest-neighbor sequence combinations. The free energy increments at 37 degrees C for the introduction of a group I single-nucleotide bulge loop range between 1.3 and 5.2 kcal/mol. The combined data were used to develop a model for predicting the free energy of a RNA duplex containing a single-nucleotide bulge. For bulge loops with adjacent Watson-Crick base pairs, neither the identity of the bulge nor the nearest-neighbor base pairs had an effect on the influence of the bulge loop on duplex stability. The proposed model for prediction of the stability of a duplex containing a bulged nucleotide was primarily affected by non-nearest-neighbor interactions. The destabilization of the duplex by the bulge was related to the stability of the stems adjacent to the bulge. Specifically, there was a direct correlation between the destabilization of the duplex and the stability of the less stable duplex stem. The stability of a duplex containing a bulged nucleotide adjacent to a wobble base pair also was primarily affected by non-nearest-neighbor interactions. Again, there was a direct correlation between the destabilization of the duplex and the stability of the less stable duplex stem. However, when one or both of the bulge nearest neighbors was a wobble base pair, the free energy increment for insertion of a bulge loop is dependent upon the position and orientation of the wobble base pair relative the bulged nucleotide. Bulge sequences of the type ((5'UBX)(3'GY)), ((5'GBG)(3'UU)) and ((5'UBU)(3'GG)) are less destabilizing by 0.6 kcal/mol, and bulge sequences of the type ((5'GBX)(3'UY)) and ((5'XBU)(3'YG)) are more destabilizing by 0.4 kcal/mol than bulge loops adjacent to Watson-Crick base pairs.