The Diagnostic Value Of Digital Radiographic Measurements For Injuries To The Distal Tibiofibular Syndesmosis

BackgroundThe distal tibiofibular syndesmosis consists of an anterior (the anterior inferior tibiofibular ligament; ATiFL), a posterior part (the posterior inferior tibiofibular ligament; PTiFL and a transverse ligament; TL) and in-between, the interosseous ligament (IL)-the most distal condensation of fibers of interosseous membrane. They play a fundamental role in stabilization of ankle. Previously, distal tibiofibular syndesmosis injuries were reported as accounting for 1%-11% of ankle injuries. Currently, however, from 17% to 74% of ankle injures among young athletes. The syndesmosis injuries can cause external and inversion instability of the ankle joint. Syndesmotic injuries may result in chronic instability. When instability can be objectively documented with clinical and radiographic criteria it is defined as mechanic instability. Based on clinical symptoms only, such as the subjective sensation of the ankle giving way or feelings of instability on an uneven surface, instability can be the result of widening of the ankle mortise.If this condition is not recognized or left untreated permanent disability or an abduction of the talus may result. Osteoarthritis of the ankle joint will then develop. Thus, early recognition and treatment of Syndesmotic injuries is of the utmost importance for a normal painless ankle with a functional gait.Several diagnostic studies are available for detecting acute injury to ankle ligaments such as arthroscopy, MRI and radiographs. Arthroscopy and MRI are more sensitive and accurate in detecting the ligament injury than radiographs. Clearly there are limitations in their practicality because of cost and convenience. During the past decade, digital radiology have undergone significant developments and to do so. The image quality have been improved significantly, and the wide latitude in exposure factors has also been greatly expanded, and the radiation exposure to the patient has been reduced, and more importantly, the digital image have the powerful post-processing capabilities, so that the digital image could became more information-rich, layering stronger, clearer, and making digital images of bone structure and articular cartilage and soft tissue of the show is better than conventional films. Digital radiography examination of their easy, convenient, fast and cheap has become the most conventional means of inspection in the assessment of tibiofibular syndesmosis injury. With the development of the computer technology, network technology and digital radiographic technology, variety of medical imaging-related protocols and standards formulated, as well as PACS / RIS systems and long-range of sophisticated diagnostic imaging system sophisticated, the traditional reading pattern of light-box displays are converting to "soft-reading" method on PACS workstation. However, the assessments of tibiofibular are previously obtained through the traditional film, and with little regard for gender, age, height and weight and other factors exist.ObjectivesThis study was designed to know (1)what characteristics of the tibiofibular overlap(TFO), the tibiofibular clear space(TFCS) and the medial clear space by observing the digital radiographic images on PACS workstation, (2)how the patient's gender, age, height and weight affects the parameters including the tibiofibular clear space, the tibiofibular overlap, the medial clear space, the width of fibula and the distance between the distal tip of the anterior aspect of the tibia and the anterior cortex of the fibula intersected the joint line(abbreviated the distance) by measuring the tibiofibular joint and ankle joint space in the digital X-ray of normal people in China, and illustrate the importance of the digital X-ray in diagnosis of early and accurate tibiofibular syndesmotic injuries.Methods1. Subjects and collection of images(1) From June, 2007 to October in, 2008, a total of 492 cases of normal volunteers ankle(without any diseases and injuries in ankles before ) were collected.(2) Devices: GE Revolution XR/D DDR, EIZO Radiforce G22 Medical displays, height and weight electronic scale.(3) Record basic information of the volunteers: name, gender, age, height, weight.(4) Take digital radiographs including anterior-posterior(AP) view, in which the X-ray beam is directed at the center of the ankle in line with the foot, and mortise(M) view that is taken in about 20°of internal rotation of the foot ,and lateral(LAT) view that is taken mediolateral with the beam perpendicular to the cassette and centered 1-2cm proximal to the medial malleolar tip. In order to decrease the influence of ankle positioning, when the AP view and M view were taking, self-made stent were applied.2. Analyzing and measuring images of the digital radiographs(1) Image data was saved in accordance with the DICOM standard ,and then ,the image data was sent to the PACS workstation. A soft-reading method on PACS workstation was employed to evaluate and measure the detection of the parameters.(2) Measurement parameters①The tibiofibular overlap(TFO),is measured as a horizontal distance between the medial border of the fibula and lateral border of the anterior tibial tubercle;②The tibiofibular clear space(TFCS), is the second parameter. It is described as the distance between either or the incisure of the tibia, and the medial border of the fibula;③The width of fibula; The distance are measured 1cm above, and parallel to the tibial plafond for each of the above parameters.④The medial clear space is measured 0.5cm beneath it on o line parallel to the superior talar joint surface.⑤The lateral radiographs are measured with a technique to assess the position of the fibula relative to anterior cortex of the tibia in the anteroposterior plane. Two lines were made: the first line is drawn from the distal tip of the anterior aspect of the tibia to the distal tip of the posterior aspect of the tibia, and the second line is drawn perpendicular to the first line at the point where the anterior cortex of the fibula intersects the joint line. The distance between the distal tip of the anterior aspect of tibia and the second line provided the lateral measurement.3. Data processing and statistical analysisImported all the experimental data into SPSS 13.0 software, and firstly normal probability graph of p-p method was used to test all data normality. Secondly stepwise regression analysis were used to evaluate the relationship between the distances and the patient's gender, height, age, body weight. Finally, formulate the normal people of tibiofibular syndesmosis of the evaluation indicators of the 95% reference range. A P value of 0.05 was chosen as the level of significance.ResultsIn this study, the vast majority of image quality is outstanding, which the edge of bone is sharp, and the ankle joint of the gap shows clear. Some poor quality images through adjusting the gray-scale and contrast also obtain good visual effects. More importantly, partial amplification allows the distal tibiofibular joint local to show more clearly, and since digital images have good spatial resolution that allows images to be non-distortion in the screeners, and the image also is not appear jagged edge deformation and twist. Joint space is not since amplification and measurement data happen to change, so measurement is very convenient and accurate. ~*The distance is measured with a technique to assess the position of the fibula relative to anterior cortex of the tibia in the anteroposterior plane. Two lines were made: the first line is drawn from the distal tip of the anterior aspect of the tibia to the distal tip of the posterior aspect of the tibia, and the second line is drawn perpendicular to the first line at the point where the anterior cortex of the fibula intersects the joint line. The distance between the distal tip of the anterior aspect of tibia and the second line provided the lateral measurement.ConclusionsResult of this study is that the linear regression relationship is existed betweenthe tibiofibular syndesmosis parameters with weight, age, height and gender, and the fitting regression equations are statistical significance. However, all of the adjusted coefficients of determination are very small, the biggest adjustment to the coefficient is only 0.248, it can consider the parameters are affected little by gender, age, height and weight, almost can not be considered. So they can be used to assess the early diagnosis of tibiofibular syndesmotic injuries.Although the survey results show that the variation of the TFCS explained by weight, height, age and gender is only 24.8%, but it is still recommended to use the ratio between the TFCS and the width of fibular to assess in order to minimize the impact of individual differences. And the influence of the rest parameters by weight, height, age and gender are not more than 6%, thus they are similar to ignore.According to analysis of these experimental data can found TFCS normal range of reference values is (2.48 mm -5.46mm), and the range of wide ratio between TFCS and the width of fibular is (0.14- 0.42). If TFCS is greater than 5.46mm or the ratio is greater than 42% of, it should doubt the existence of tibiofibular syndesmosis injury. In this case, something must be considered including TFO, medial clear space, injury mechanism and clinical symptoms and so on. It is necessary to bilateral contrast examination of digital radiograph or MRI to guide the early clinical treatment. At open reduction (?)d internal fixation (ORIF), TFCS should not be less than 2.48mm or TFCS of less than 14% of the width of fibular to avoid fixed tightly, otherwise, it could be emergence of postoperative activity ankle pain, and affected the restore of the ankle function. The TFO is considered to be abnormal when it measures less than 3.18mm (or 28% fibular width) on the AP and 1mm or less on M view. Medial clear space normal reference range is (3.04mm - 5.00mm). If the distance is more than 5.00mm or wider than the superior tibiotalar clear space, it should be considered the existence of the deltoid ligament injury, and at the same time ,it should also pay attention to whether the presence of tibiofibular joint diastasis. Since the deltoid ligament injury often combine with the tibiofibular syndesmosis injury, so the ankle stress films or MRI examination is needed for further diagnosis. At open reduction and internal fixation (ORIF), to ensure that the medial ankle joint space is not less than 3.04mm, otherwise the ankle mortise is so narrow that it could be cause ankle pain after activity, and even left long-term pain.A cyclic hinge structure is formed by the ATiFL, PTiFL, TL, IL and it can be maintained a certain tension. If in front of or behind the ligament are ruptured in injury it can be made the ring structure relaxed, and resulted in varying degrees of fibular displacement. So, in the lateral view, if the distance is greater than 12.87mm, it may be existed posterior dislocation of fibula, and the tibiofibular syndesmosis ligament injury.Postural ankle projection, image measurement methods and understand the image acquisition parameters are essential to application of digital radiograph to the diagnosis of tibiofibular syndesmosis injury. Application of elastic band tied both lower limbs together to prevent external rotation. By identifying two parallel lines which one is 10mm above the tibial plafond, and the other is 5mm beneath the superior tibiotalar plafond and the highest point of the medial talar dome, the measurement can be simply and intuitively completed and also can avoid different people, time and space to lead to different results. There is image information only on previous X-ray film, and no image acquisition parameters. So it is difficult for clinician to make the right judgment. Previously, the judgment rely on visual of the clinician to determine whether the tibiofibular syndesmosis has widened, which approach is entirely subjective judgments, except to rule out whether there is existence the fracture, it is difficult to exist as to whether the separation of tibiofibular syndesmosis to make accurate judgments. However, digital radiographic images not only have information-rich images, but also have image Acquisition information. Through PACS workstation clinician can be very convenient to get precise measurements, which make clinician to diagnose tibiofibular syndesmosis injury more objectively.Even though Several parameters to assess ankle and Syndesmotic integrity on digital radiographic images have been made a preliminary definition in this study, but application of these parameters to guide clinical should still be considered generally, such as the influence of patient height, age, weight and gender, as well as medical history, clinical symptoms and a detailed body search, to make the assessment and judgments to guide the early clinical diagnosis and treatment.Finally, all of the experimental data were collected under non-weight-bearing, which are a certain difference with physiological weight-bearing status.