Avulsion fracture of the head of the fibula (the "arcuate" sign): MR imaging findings predictive of injuries to the posterolateral ligaments and posterior cruciate ligament

OBJECTIVE: The purpose of this study was to describe the significance of an avulsion fracture of the head of the fibula ("arcuate" sign) and its association with injuries of the knee on MR imaging. MATERIALS AND METHODS: We conducted a retrospective search of 2318 patients who underwent conventional radiography and MR imaging after an episode of knee trauma. Patients were included in this study if they had an avulsion fracture of the head of the fibula revealed on conventional radiography and underwent arthroscopy. Thirteen patients, all of whom were men, satisfied the inclusion criteria. Ten patients underwent further explorative surgery. The clinical, radiographic, MR imaging, and surgical findings were then reviewed. RESULTS: The avulsion fracture of the styloid process of the fibular head was apparently related to injuries of the arcuate complex in all 13 patients. Radiographically, the bony fragment was horizontally oriented and similar in size in most patients, ranging from 8 to 10 mm in length and from 2 to 5 mm in width. On MR imaging, the fibular avulsion was identified in 11 of the 13 patients. The other two patients had marrow edema in the fibular styloid process, although the avulsion fracture was not evident. All patients had injuries of the posterior cruciate ligament (six tibial avulsions, seven midsubstance tears). No patient had a tear of the anterior cruciate ligament. Disruption of the lateral collateral ligament was evident in seven patients, and one patient had a tear of the popliteal tendon. During surgery, six patients had disruption of the arcuate complex, but this disruption could not be identified on the MR images. CONCLUSION: An avulsion fracture of the fibular head generally involves the styloid process and causes injury of some of the major stabilizers in the posterolateral corner. Avulsion fractures are strongly associated with disruption of the posterior cruciate ligament.     

MR evaluation of the "arcuate" sign of posterolateral knee instability

OBJECTIVE: The purpose of this study was to evaluate associated knee injuries using MR imaging in patients with the "arcuate" sign, a term referring to avulsion fracture of the proximal fibula on conventional radiographs. MATERIAL AND METHODS: MR imaging of 18 cases (17 patients, both knees in one patient) with the arcuate sign on conventional radiographs was retrospectively interpreted to evaluate the associated meniscal, ligamentous, and bony injuries. In 12 cases, MR findings were correlated with surgical results. RESULTS: In all cases, avulsed bony fragments from the proximal pole of the fibula were attached to the fibular collateral ligament, the biceps femoris tendon, or both. Tear of the posterolateral capsule was seen in 12 cases (67%). Injury of the cruciate ligaments was noted in 16 cases (89%): injury to both the anterior cruciate ligament and posterior cruciate ligament was seen in nine cases (50%), injury to only the anterior cruciate ligament was seen in four, and injury to the posterior cruciate ligament only was noted in three. Bone bruises or gross fractures were seen in all cases: bone bruises on the anteromedial femoral condyle were noted in nine cases (50%) and were seen on the anteromedial tibial condyle in five cases (28%). Tear of the medial meniscus was seen in five cases (28%) and tear of the lateral meniscus in four cases (22%). Injury to the popliteus was seen in six cases (33%). Joint effusion was associated in all cases. CONCLUSION: MR imaging is useful for evaluation of associated soft-tissue injuries in patients with the arcuate sign on conventional radiographs. Avulsion injury to the proximal fibula is an important indicator of the internal derangement of the knee and for predicting the mechanism of an injury with varus stress. Cruciate ligament tear and bone bruises on the anteromedial condyle of the femur and tibia are common associated findings.     

MR imaging,MR arthrography,and specimen correlation of the posterolateral corner of the knee: an anatomic study

OBJECTIVE: We sought to evaluate the anatomy of the posterolateral aspect of the knee with anatomic dissection, MR imaging, MR arthrography, and sectional anatomy. MATERIALS AND METHODS: We assessed the posterolateral corner of the knee during dissection of one gross anatomic specimen. MR imaging and MR arthrography were performed in seven additional knee specimens. T1-weighted spin-echo MR images were obtained in the standard imaging planes as well as in the coronal oblique plane. The specimens underwent T1-weighted spin-echo MR imaging after administration of intraarticular contrast material and were sectioned into planes corresponding to those of the MR images. RESULTS: At anatomic dissection, the following posterolateral structures were identified: the arcuate ligament (medial and lateral limbs), fabellofibular ligament, popliteofibular ligament, popliteus tendon and its two posterior attachments to the lateral meniscus, fibular collateral ligament, direct and anterior arms of the tendon of the long head of the biceps femoris muscle, and direct and anterior arms of the tendon of the short head of the biceps femoris muscle. Correlation of MR imaging and anatomic findings showed that the popliteofibular ligament and oblique popliteal ligament were found in 57% and 100% of specimens, respectively. At least one of the two limbs of the arcuate ligament was identified in 71% of specimens. The fabellofibular ligament was not identified on MR images in any of the specimens. The anteroinferior and posterosuperior popliteomeniscal fascicles were identified in all specimens. CONCLUSION: The posterolateral corner of the knee comprises complex and variable anatomic structures. Recognition of these variations is important in the assessment of MR images of the knee.     

Anterior rim tibial plateau fractures and posterolateral corner knee injury

The aim of this study was to review MRI findings of clinically suspected posterolateral corner knee injuries and their associated internal derangements. Sixteen knees in 15 patients who had evidence of a posterolateral corner knee injury on the physical exam underwent MRI to evaluate the posterolateral corner of the knee and to look for associated injuries. Two musculoskeletal radiologists reviewed the scans. Surgery was performed on 10 of the knees. Tibial plateau fractures were present in 6 knees; 5 of the fractures were anteromedial rim tibial plateau fractures. The popliteus muscle was injured in 13 knees and the biceps femoris in 6 knees. The lateral collateral ligament was ruptured in 12 knees. The posterior cruciate ligament was completely ruptured in 7 knees and avulsed from its tibial attachment in 1 knee. Eleven knees had a complete anterior cruciate ligament rupture. The anterior cruciate ligament was edematous without complete disruption of all fibers in 3 knees. There was excellent correlation between the MRI results and operative results in regard to the presence of a posterolateral corner injury of the knee (9 of the 10 knees had a posterolateral corner injury). In our study MRI readily detected posterolateral corner injuries. Posterolateral corner injuries of the knee are frequently associated with a variety of significant injuries, including cruciate ligament tears, meniscus tears, and fractures. Fractures of the peripheral anteromedial tibial plateau are not common; however, given their relatively common occurrence in this study, they may be an indicator of a posterolateral corner injury to the knee.     

Successful LCL reconstruction and PCL repair for LCL tear and PCL avulsion following total knee arthroplasty

Total knee arthroplasty represents a well-established and successful procedure; however, ligament incompetence is known to negatively affect surgical outcomes. Here we present an unusual case of early total knee arthroplasty failure secondary to femoral posterior cruciate ligament (PCL) avulsion and associated lateral collateral ligament (LCL) tear, treated successfully with primary PCL repair and LCL reconstruction. For LCL reconstruction, a peroneus longus allograft was passed through an anterior to posterior bony tunnel in the fibular head and docked into a horizontal femoral tunnel. Level of evidence Case report, Level IV.     

Iliotibial band avulsion fracture: a case report with differential diagnosis

Avulsion injuries of the knee are common sequelae of significant trauma given the number of ligamentous and tendinous insertions around the joint. Commonly discussed avulsion fractures of the lateral knee include the Segond fracture of the lateral tibial plateau and the arcuate complex avulsion fracture of the fibular styloid process. A less common avulsion fracture is the iliotibial (IT) band avulsion fracture involving the anterolateral corner of the tibia (Gerdy’s tubercle). It is crucial to identify IT band avulsion fractures because of the frequent associated internal derangements of the knee. This case report describes the imaging of an acute IT band avulsion fracture and compares these findings with other lateral knee avulsion fractures.     

MRI of the popliteofibular ligament: isotropic 3D WE-DESS versus coronal oblique fat-suppressed T2W MRI

Objective The objective was to compare isotropic 3D water excitation double-echo steady state (WE-DESS) MRI with coronal oblique fat-suppressed T2-weighted (FS T2W) images in the identification of the popliteofibular ligament (PFL). Materials and methods A prospective analysis of 122 consecutive knee MRIs was performed in patients referred for knee pain from the orthopaedic clinic. In addition to the standard knee sequences, isotropic WE-DESS volume acquisition through the whole knee and coronal oblique FS T2W fast spin echo sequences through the posterolateral corner were obtained. The presence of the popliteus and biceps femoris tendons, lateral collateral and PFL was documented. Anterior cruciate ligament injury was present in 33 cases and these were excluded from the study because of the risk of associated PFL injury, leaving a total of 89 cases. Of the 42 patients in whom arthroscopic evaluation was subsequently obtained, none were found to have an injury to the PFL. Results The lateral collateral ligament, biceps femoris and popliteus tendon were identified in all cases on all sequences. The PFL was seen in 81 (91.0%; 95% CI 85.1–97.0%) patients using the WE-DESS sequence and 63 (70.8%; 95% CI 61.3–80.2%) patients using the coronal oblique FS T2W sequence, a statistically significant difference (p < 0.00005). Conclusion Isotropic 3D WE-DESS MRI significantly enhances our ability to identify the popliteofibular ligament compared with coronal oblique fat-suppressed T2-weighted images.     

A physeal-sparing fibular collateral ligament and proximal tibiofibular joint reconstruction in a skeletally immature athlete

The purpose of this report was to describe the surgical technique for and outcomes after a modified physeal-sparing posterolateral corner reconstruction in a 12-year-old skeletally immature male with a mid-substance fibular collateral ligament tear, a proximal posterior tibiofibular ligament tear, and an anterior cruciate ligament avulsion fracture of the medial tibial eminence. A modified physeal-sparing posterolateral corner reconstruction was used to provide a near-anatomic reconstruction of the fibular collateral ligament and proximal posterior tibiofibular ligament. An anterior cruciate ligament repair was also performed. Varus stress radiographs obtained at 6 months postoperatively demonstrated resolution of lateral knee stability. Physical examination results demonstrated stability to anterior tibial translation and a stable proximal tibiofibular joint. Computed tomography showed that the surgical technique successfully avoided breeching the patient’s physes.     

Anatomical variations in the anatomy of the posterolateral corner of the knee

This cadaveric study of 22 knees described the anatomy of the deeper structures of the posterolateral corner, the popliteus–tendon complex, arcuate ligament complex, the popliteofibular ligament, and the coronary ligament. Most variations occurred in the popliteofibular ligament; the variations and the different nomenclatures used in the literature for these structures make it difficult to diagnose and repair injuries to them. Untreated injuries may result in chronic functional instability to the posterolateral corner of the knee.     

The arcuate ligament revisited: role of the posterolateral structures in providing static stability in the knee joint

Purpose

To determine the involvement of the posterolateral structures including the lateral collateral ligament, the popliteus muscle–tendon unit, the arcuate ligament (popliteofibular ligament, fabellofibular ligament, popliteomeniscal fascicles, capsular arm of short head of the biceps femoris and anterolateral ligament) and the posterior cruciate ligament in providing restraint to excessive recurvatum, tibial posterior translation and external tibial rotation at 90° of flexion.

Methods

Ten fresh-frozen cadaveric knees were tested with dial test, posterior drawer test and recurvatum test. The values were collected, using a surgical navigation system, on intact knees, following a serial section of the posterolateral corner (lateral collateral ligament, arcuate ligament and popliteus muscle–tendon unit), followed by the additional section of the posterior cruciate ligament.

Results

The mean tibial external rotation, recurvatum and posterior drawer were, respectively, measured at 9° ± 4°, 2° ± 3° and 9 ± 1 mm on intact knees. These values increase to 12° ± 5°, 3° ± 2° and 9 ± 1 mm after cutting the lateral collateral ligament; 17° ± 6° (p < 0.05), 3° ± 2° and 10 ± 1 mm after sectioning the arcuate ligament; 18° ± 7°, 3° ± 2° and 10 ± 1 mm after sectioning the popliteus muscle–tendon unit and 27° ± 6° (p < 0.05), 5° ± 3° (p < 0.05) and 28 ± 2 mm (p < 0.05) after the additional section of the posterior cruciate ligament.

Conclusion

Among the different structures of the posterolateral corner, only the arcuate ligament has a significant role in restricting excessive primary and coupled external rotation. The popliteus muscle–tendon unit is not a primary static stabilizer to tibial external rotation at 90° of knee flexion. The posterior cruciate ligament is the primary restraint to excessive recurvatum and posterior tibial translation. The posterior cruciate ligament and the arcuate ligament have predominant role for the posterolateral stability of the knee. The functional restoration of these ligaments is an important part of the surgical treatment of posterolateral ligamentous injuries.     

Ultrasound of the knee with emphasis on the detailed anatomy of anterior,medial, and lateral structures

Objective

To describe the detailed ultrasound anatomy of the anterior, medial, and lateral aspects of the knee and present the ultrasound examination technique used.

Materials and Methods

We present ultrasound using images of patients, volunteer subjects, and cadaveric specimens. We correlate ultrasound images with images of anatomical sections and dissections.

Results

The distal quadriceps tendon is made up of different laminas that can be seen with ultrasound. One to five laminas may be observed. The medial retinaculum is made up of three anatomical layers: the fascia, an intermediate layer, and the capsular layer. At the level of the medial patellofemoral ligament (MPFL) one to three layers may be observed with ultrasound. The medial supporting structures are made up of the medial collateral ligament and posterior oblique ligament. At the level of the medial collateral ligament (MCL), the superficial band, as well as the deeper meniscofemoral and meniscotibial bands can be discerned with ultrasound. The posterior part, corresponding to the posterior oblique ligament (POL), also can be visualized. Along the posteromedial aspect of the knee the semimembranosus tendon has several insertions including an anterior arm, direct arm, and oblique popliteal arm. These arms can be differentiated with ultrasound. Along the lateral aspect of the knee the iliotibial band and adjacent joint recesses can be assessed. The fibular collateral ligament is encircled by the anterior arms of the distal biceps tendon. Along the posterolateral corner, the fabellofibular, popliteofibular, and arcuate ligaments can be visualized.

Conclusion

The anatomy of the anterior, medial, and lateral supporting structures of the knee is more complex than is usually thought. Ultrasound, with its exquisite resolution, allows an accurate assessment of anatomical detail. Knowledge of detailed anatomy and a systematic technique are prerequisites for a successful ultrasound examination of the knee.     

Acute injury of the ligaments of the knee: magnetic resonance evaluation

Eleven acutely injured knees and 13 normal knees were examined by magnetic resonance imaging (MRI) to assess the value of this modality in detecting acute ligamentous injury of the knee. The presence of torn ligaments in the injured knees was determined by arthroscopy and/or arthrotomy in ten cases and clinical follow-up in one case. The anterior and posterior cruciate ligaments (ACL and PCL) were demonstrated by sagittal spin echo (SE) images through the intercondylar notch (TE = 30 ms; TR = 2,000 ms). The tibial and fibular collateral ligaments (TCL and FCL) were evaluated on coronal SE images (TE = 30 ms, TR = 200 or 530 ms; TE = 120 ms, TR = 2,000 or 2,120 ms). The ACL and PCL were considered torn on MR if they appeared disrupted or were not seen in their normal anatomical positions. The collateral ligaments were considered torn if abnormal high-intensity signal was noted in adjacent soft tissues on TE = 120 ms images or if disruption of a ligament was apparent. Eleven of 15 torn ligaments and 80 of 81 normal ligaments were correctly identified by these criteria. It is concluded that MR imaging may be useful in detecting acute injury of ligaments of the knee.     

Ultrasonographic visualization and assessment of the anterolateral ligament

Purpose

Injury to the anterolateral ligament (ALL) of the knee has recently received attention as a potential risk factor for failure of anterior cruciate ligament reconstruction. However, evaluation of the anterolateral ligament is currently difficult, and radiologic data are sparse with regard to the normal appearance of this ligament. The purpose of the present study was to determine whether the ALL could be identified and visualized using ultrasonography.

Methods

Ten non-paired, fresh-frozen cadaveric knees underwent ultrasound by an experienced musculoskeletal radiologist using a Siemens S2000 Acuson Ultrasound machine with a 14-MHz linear transducer. After first identifying anatomical landmarks by palpation, a thin band of tissue originating in the vicinity of the fibular collateral ligament (FCL) origin was identified and followed up distally. The tibia was held at 30° of flexion and internally rotated to verify tightening of the structure. Under ultrasound guidance, 25-gauge hypodermic needles were placed at what were sonographically determined to be the origin and insertion points of the ligament. One-tenth of a CC of aniline blue dye was injected. The specimens were then dissected to confirm the presence and location of the ALL. If an ALL was found, distances between the epicentre of the injected dye and the actual origin and insertion points were calculated. Additionally, ligament length based on dissection images and ultrasound images was calculated.

Results

Eight of ten specimens had an anterolateral structure that originated from the lateral femoral epicondyle just posterior and superior to the origin of the FCL and inserted on the lateral plateau approximately halfway between Gerdy’s tubercle and the fibular head. The average length based on ultrasound was 3.8 cm (±.7; range 3.1–4.7) and 4.1 cm (±1.1; range 2.6–6.1) based on dissection. Length based on dissection and ultrasound had minimal agreement (ICC = .308; 95 % confidence interval .257–.382, p = .265). The average width of the structure on dissection was .8 cm (±.24; range .5–1.2). The mean distance from ultrasound-determined origin and insertion points to anatomical origin and insertion based on dissection was 10.9 mm (±2.9, range 7.0–15.8) and 12.5 mm (±5.7 range 3.2–19.3), respectively. Inter-observer reliability was excellent for all measurements based on dissection and ultrasound.

Conclusion

Ultrasound was unable to reliably identify the anterolateral structure from its femoral to tibial attachment sites. Distinguishing it from the posterior IT band and anterolateral capsule was challenging, and it is possible that the structure is a thickened band of fascia rather than a true ligament. As a clinical diagnostic tool, ultrasound likely offers little utility in the evaluation of the ALL for injury.

Level of evidence

IV.

     

Anatomical reconstruction of popliteofibular ligament using looped biceps femoris tendon: a case report

We describe a case of popliteofibular ligament (PFL) injury, successfully treated with a new anatomic reconstruction technique looping the biceps femoris tendon (BT). The anterior half of the BT was split longitudinally from the fibular insertion, cut at the proximal end and left attached at the insertion. The proximal end of the BT was looped back in a slit made in the popliteal tendon (PT) at the original anatomical insertion site of the PFL, and passed through the tunnel from the posterior and the baseball suture was tightened on the anterior cortex of fibular head.     

Popliteofibular ligament reconstruction for posterolateral external rotation instability of the knee

The aim of this study was to assess the clinical outcome of popliteofibular ligament (PFL) reconstruction for posterolateral external rotation instability of the knee. PFL reconstruction was performed consecutively in 22 patients with chronic external rotation instability of the knee. The inclusion criterion for surgery was tibial external rotation of 10° more than the contralateral uninjured knee without varus laxity. A double bone tunnel was created at the PFL insertion of the fibular head through the lateral incision of the knee joint and a single bone tunnel at the popliteus tendon insertion on the femoral side. A semitendinosus autograft tendon or tibialis anterior allograft tendon was introduced through the fibular tunnel as a loop, then both free ends of the graft were introduced through the femoral tunnel and a bioabsorbable interference screw was used to fix the graft. The minimum follow-up was 2 years. Clinical review included the International Knee Documentation Committee (IKDC) scale and tibial external rotation assessment. All patients’ preoperational tibial external rotation averaged 15° more than the contralateral uninjured knee. operatively the tibial external rotation was decreased, average −3° compared with the contralateral side. This difference was statistically significant. The final IKDC grades were: 22 cases with grade D preoperatively, and 6 were grade A, 8 were grade B, 7 were grade C and 1 was grade D postoperatively. In this small clinical series, PFL reconstruction technique was shown to correct pathological excessive tibial external rotation.     

An analysis of an anatomical posterolateral knee reconstruction: an in vitro biomechanical study and development of a surgical technique

BACKGROUND: To date, no surgical technique to treat posterolateral knee instability anatomically reconstructs the 3 major static stabilizing structures of the posterolateral knee: the fibular collateral ligament, the popliteus tendon, and the popliteofibular ligament. HYPOTHESIS: Static varus and external rotatory stability would be restored to the reconstructed knee with a posterolateral knee injury. METHODS: The anatomical locations of the original fibular collateral ligament, popliteus tendon, and popliteofibular ligament were reconstructed using a 2-graft technique. Ten cadaveric specimens were tested in 3 states: intact knee, knee with the 3 structures cut to simulate a grade III injury, and the reconstructed knee. RESULTS: For the varus loading tests, joint stability was significantly improved by the posterolateral reconstruction compared to the cut state at 0 degrees, 30 degrees, 60 degrees, and 90 degrees of flexion. There were no significant differences between the intact and reconstructed knees at 0 degrees, 60 degrees, and 90 degrees for varus translation. For the external rotation torque tests, external rotation was significantly higher for the cut state than for the intact or reconstructed posterolateral knee. There was no significant difference in external rotation between the intact and reconstructed posterolateral knees at any flexion angle. CONCLUSIONS: This 2-graft technique to reconstruct the primary static stabilizers of the posterolateral knee restored static stability, as measured by joint translation in response to varus loading and external rotation torque, to knees with grade III posterolateral injuries.     

Anatomic and biomechanical study of the lateral collateral and popliteofibular ligaments

The position of the fibula around the proximal tibia varies in different people; it was therefore hypothesized that this variation would affect the orientation of the lateral collateral ligament and the popliteofibular ligament complex. This hypothesis was studied in 10 cadaveric knees by measuring the orientation and length changes in these structures as the knee was flexed. The data were correlated with tibiofibular joint position. The strength of the ligaments was also tested. There were significant correlations between fibular head position and ligament orientation with the knee extended. The lateral collateral ligament slackened significantly with knee flexion, whereas the popliteofibular ligament complex did not. The structures became significantly steeper in the sagittal plane as the knee was flexed. The lateral collateral ligament passed through vertical at 70 degrees of knee flexion and was thus poorly oriented to withstand tibial external rotation. The lateral collateral and popliteofibular ligaments had tensile strengths of 309 and 186 N, respectively. The popliteofibular ligament is dominant when the knee is flexed, because of the slackening of the lateral collateral ligament, and so it should always be reconstructed. The anatomic variation causes some knees to have better ligament orientations to withstand posterolateral tibial displacements and, conversely, other knees may be inherently more difficult to stabilize by reconstruction.     

The meniscofibular ligament: an MRI study

Aim

To describe the appearances and determine the prevalence of the meniscofibular ligament (ligamentum fibulare-MFibL) on MRI of the knee.

Subjects and methods

Retrospective observational review of 160 knee MRI studies (152 patients) which was performed for a variety of clinical presentations over a period of 31 months. The images were assessed independently by two musculoskeletal radiology Fellows.

Results

The MFibL was optimally visualised on far lateral sagittal oblique fat suppressed PDW FSE images. The MFibL appeared as a curvilinear or straight, hypointense band of variable thickness extending between the inferior margin of the posterior third of the lateral meniscus and the fibular head. The ligament was demonstrated in 42.5% (n = 68) of the total knee MRI studies, but this prevalence increased to 63% (56/88) in the presence of fluid in the posterolateral corner of the joint.

Conclusion

The MFibL is commonly seen on far lateral fat suppressed oblique sagittal PD weighted MR images, particularly in the presence of fluid in the posterolateral corner, and should be recognised as a normal structure in the posterolateral corner of the knee.