Acute Knee Trauma Research Articles

Dual-Energy CT Virtual Noncalcium Technique: Detecting Posttraumatic Bone Marrow Lesions—Feasibility Study

To evaluate traumatized bone marrow with a dual-energy (DE) computed tomographic (CT) virtual noncalcium technique. In this prospective institutional review board-approved study, 21 patients with an acute knee trauma underwent DE CT and magnetic resonance (MR) imaging. A software application was used to virtually subtract calcium from the images. Presence of fractures was noted, and presence of bone bruise was rated on a four-point scale for six femoral and tibial regions by two radiologists. CT numbers were obtained in the same regions. Consensus reading of independently read MR images served as the reference standard. Image ratings and CT numbers were subjected to receiver operating characteristic curve analysis. After exclusion of 16 regions owing to artifacts, MR imaging revealed 59 bone bruises in the remaining 236 regions (19 of 114 femoral, 40 of 122 tibial). Fractures were present in eight patients. Visual rating revealed areas under the curve of 0.886 and 0.897 in the femur and 0.974 and 0.953 in the tibia for observers 1 and 2, respectively. For CT numbers, the respective areas under the curve were 0.922 and 0.974. If scores of 1 and 2 (strong or mild bone bruise) were counted as positive, sensitivities were 86.4% and 86.4% and specificities were 94.4% and 95.5% for observers 1 and 2, respectively. The kappa statistic demonstrated good to excellent agreement (femur, kappa = 0.78; tibia, kappa = 0.87). This DE CT virtual noncalcium technique can subtract calcium from cancellous bone, allowing bone marrow assessment and potentially making posttraumatic bone bruises of the knee detectable with CT.

Novel use of gamma correction for precise 99mTc-HDP pinhole bone scan diagnosis and classification of knee occult fractures

The aim of this study was to introduce gamma correction pinhole bone scan (GCPBS) to depict specific signs of knee occult fractures (OF) on (99m)Tc-hydroxydiphosphonate (HDP) scan. Thirty-six cases of six different types of knee OF in 27 consecutive patients (male = 20, female = 7, and age = 18-86 years) were enrolled. The diagnosis was made on the basis of a history of acute or subacute knee trauma, local pain, tenderness, cutaneous injury, negative conventional radiography, and positive magnetic resonance imaging (MRI). Because of the impracticability of histological verification of individual OF, MRI was utilized as a gold standard of diagnosis and classification. All patients had (99m)Tc-HDP bone scanning and supplementary GCPBS. GCPBS signs were correlated and compared with those of MRI. The efficacy of gamma correction of ordinary parallel collimator and pinhole collimator scans were collated. Gamma correction pinhole bone scan depicted the signs characteristic of six different types of OF. They were well defined stuffed globular tracer uptake in geographic I fractures (n = 9), block-like uptake in geographic II fractures (n = 7), simple or branching linear uptake in linear cancellous fractures (n = 4), compression in impacted fractures (n = 2), stippled-serpentine uptake in reticular fractures (n = 11), and irregular subcortical uptake in osteochondral fractures (n = 3). All fractures were equally well or more distinctly depicted on GCPBS than on MRI except geographic II fracture, the details of which were not appreciated on GCPBS. Parallel collimator scan also yielded to gamma correction, but the results were inferior to those of the pinhole scan. Gamma correction pinhole bone scan can depict the specific diagnostic signs in six different types of knee occult fractures. The specific diagnostic capability along with the lower cost and wider global availability of bone scanning would make GCPBS an effective alternative.

Value of Information Analysis Used to Determine the Necessity of Additional Research: MR Imaging in Acute Knee Trauma as an Example

Value of Information Analysis Used to Determine the Necessity of Additional Research: MR Imaging in Acute Knee Trauma as an Example

Functional ultrasonography in the diagnosis of acute anterior cruciate ligament injuries: A field study

Functional ultrasonography is a rapid and inexpensive method of diagnosing anterior cruciate ligament (ACL) injuries. In previous studies, we assessed the diagnostic accuracy of this innovative method by experienced sonographers. The objective of the present study was to investigate whether an examiner without specialist expertise in arthrosonography can achieve similar positive results and whether this technique is effective as a screening tool that can help reduce the number of undetected ACL injuries. After a short period of training, a single examiner prospectively measured anterior tibial translation by ultrasonography in the injured and healthy knees of 41 patients with acute knee trauma. An ACL rupture was presumed to be present if the side-to-side difference in tibial translation exceeded 1 mm (Δ D > 1 mm). All patients who were enrolled in the study underwent arthroscopy or at least magnetic resonance imaging (MRI). Ultrasonography revealed the presence of an ACL lesion in 32 of 33 patients with arthroscopically confirmed ACL rupture (sensitivity: 97%, specificity: 87.5%). The mean side-to-side differences (Δ D) between injured (3.8 mm ± 1.5 mm) and uninjured ACLs (0.1 mm ± 0.7 mm) were statistically significant ( p < 0.05). Our study shows that an examiner without specialist knowledge in ultrasonography can accurately diagnose acute ACL injuries using functional ultrasonography. No additional mechanical tests (KT-1000/KT-2000) or MRI examinations are required. Functional ultrasonography is easy to learn and ensures a high level of diagnostic accuracy. It is well suited for applications in private practices and smaller hospitals with basic medical/surgical care.

Magnetic Resonance Imaging in Acute Traumatic and Chronic Meniscal Tears of the Knee

Background No previous research has investigated the diagnostic validity of magnetic resonance imaging for acute versus chronic meniscal tears using comparable materials and methods. Hypothesis There is no difference in the diagnostic validity of magnetic resonance imaging for acute versus chronic meniscal tears in young adults. Study Design Cohort study (diagnosis); Level of evidence, 2. Methods A total of 628 young adult military personnel underwent magnetic resonance imaging and arthroscopy of the knee over a 6-year period. Inclusion criteria were met by 82 patients with acute knee trauma (magnetic resonance imaging within 30 days from trauma) and 40 patients with chronic knee symptoms (symptoms lasting over 6 months before magnetic resonance imaging). The original magnetic resonance imaging and arthroscopy records were reviewed twice by a musculoskeletally trained radiologist, blinded to previous magnetic resonance imaging and arthroscopy findings. Interobserver correlations and intraobserver reliability were calculated and reported. Arthroscopy served as the gold standard when calculating the diagnostic values of magnetic resonance imaging for acute and chronic meniscal tears. Results The median age of the patients was 20 years (range, 18-25). Magnetic resonance imaging detected acute meniscal tears with sensitivity of 67%, specificity of 93%, and diagnostic accuracy of 88% and chronic meniscal tears with 64%, 91%, and 86%, respectively. There was no statistically significant difference in magnetic resonance imaging results between the 2 groups. Conclusion The diagnostic validity of magnetic resonance imaging is similar for meniscal tears in acute knee trauma and in knee symptoms lasting over 6 months in young adults. The results also suggest that effusion or hemarthrosis do not weaken the diagnostic validity of magnetic resonance imaging. The magnetic resonance imaging sensitivity achieved in the present study was relatively poor, but the specificity was good for both acute and chronic meniscal tears. Despite negative magnetic resonance imaging findings at the acute stage of knee trauma, patient monitoring and readiness for arthroscopy should be considered if justified by the patient's symptoms.

The efficacy of magnetic resonance imaging in acute multi-ligament injuries

This study compares MRI with examination under anaesthesia to surgical findings in evaluating soft tissue injuries in acute multi-ligament knee trauma. Pre-operative MRI was done for 44 patients who underwent surgery for grade III ACL and grade III medial collateral ligament (MCL) injury. In 21 cases both ACL and MCL were treated surgically, but in 23 only ACL. Intra-operative and MRI findings were compared. Accuracy of MRI for medial meniscal tears was 88.6%, sensitivity 80%, and specificity 91.2%; accuracy for lateral meniscal tears was 72.7%, sensitivity 55% and specificity 87.5%. Accuracy and sensitivity for severity of ACL tear was 93.2% and of MCL tear 86.4%. In 88.6% of the knees, bone bruises were visible, with anterolateral femoral and posterolateral tibial bone bruise being the most common. MRI revealed no chondral lesion, but arthroscopy revealed 11. In combined ACL-MCL ruptures, the incidence of concomitant injuries is high and the injuries are best detected with MRI.

MRI of Acute Meniscal Injury Associated with Tibial Plateau Fractures: Prevalence, Type, and Location

The purpose of this study was to evaluate the prevalence, type, and location of meniscal injuries, particularly to assess the prevalence of unstable meniscal tears in acute knee trauma with tibial plateau fractures. A total of 78 menisci were evaluated in 39 patients who had undergone knee MDCT and MRI. Meniscal tears were classified as horizontal, vertical (subdivided into longitudinal and radial), flap, bucket-handle, or complex. The presence of meniscal contusion was documented. The anterior horn, body, and posterior horn were assessed separately for both menisci. Knee arthroscopy was performed on 28 patients. Of the 39 patients in the study, 24 had detectable abnormal menisci, for a total of 33 abnormal menisci (42%). Among the 33 meniscal abnormalities were 11 longitudinal tears (33%), 17 contusions (52%), four flap tears (12%), six horizontal tears (18%), and six radial tears (18%). Among the 16 patients with meniscal tears (41% of the 39), 14 patients had an unstable tear. No significant correlation was found between degree of articular depression and site or morphologic features of the meniscal injury. Correspondingly, no statistical correlation was evident between normal menisci and degree of articular depression, nor was a significant correlation found between differing fracture groups and meniscal findings. A high percentage of patients (36%) with a tibial plateau fracture had an unstable meniscal tear. If a meniscal tear is detected preoperatively, meniscal surgery can be combined with fracture fixation, and reoperation can be avoided. A large number of meniscal contusions were found. Awareness of this abnormality can help radiologists increase specificity by avoiding false-positive findings of meniscal tear.

Value of Information Analysis Used to Determine the Necessity of Additional Research: MR Imaging in Acute Knee Trauma as an Example

To help guide future outcomes research regarding the use of magnetic resonance (MR) imaging in patients with acute knee trauma in an emergency department setting, with use of prospective data from a randomized clinical trial and value of information analysis. A total of 189 patients (123 male, 66 female; mean age, 33.4 years) were randomly assigned to undergo radiography alone (n = 93) or radiography and MR imaging (n = 96). Institutional review board approval and informed consent (parental consent for minors) were obtained. During 6 months of follow-up, data on quality of life and 39 cost parameters were collected. Value-of-information analysis was used to estimate the expected benefit of future research to eliminate the decision uncertainty that remained after trial completion. In addition, the parameters that were responsible for most of the decision uncertainty were identified, the expected benefits of various study designs were evaluated, and the optimal sample size was estimated. Only three parameters were responsible for most of the decision uncertainty: number of quality-adjusted life-years, cost of an overnight hospital stay, and friction costs. A study in which data on these three parameters are gathered would have an optimal sample size of 3500 patients per arm and would be expected to result in a societal benefit of euro 5.6 million or 70 quality-adjusted life-years. The optimal study design for use of MR imaging to evaluate acute knee trauma involves a trial in which there are 3500 patients per trial arm, and data on the number of quality-adjusted life-years, cost of an overnight hospital stay, and friction costs are collected.

Acute knee trauma: role of ultrasound

The purpose of this study was to determine the diagnostic accuracy of high spatial resolution ultrasonography (US) in the detection of lipohemarthrosis of the knee and to evaluate this sign as criteria of intra-articular fracture. Forty-eight patients with clinical suspicion of knee fracture were prospectively examined by conventional radiography, sonography examination and computed tomography (CT) within 48 h after trauma in order to depict direct (fracture line) and indirect (lipohemarthrosis) signs of intra-articular fracture. Lipohemarthrosis was defined as a multi-layered collection in the subquadricipital recess. CT was considered as the gold standard for both direct and indirect fracture criteria. CT imaging showed direct signs of intra-articular fracture in 31 patients (65%). Among these patients, 30 (97%) had a lipohemarthrosis. Conventional radiographs showed intra-articular fracture in 26 patients (54%). Among these, 18 (69%) had a lipohemarthrosis. Sonographic examinations could not depict any direct sign of intra-articular fracture but showed a lipohemarthrosis in 29 (93%) of patients with proven fracture via CT. This allowed the depiction of four out of five occult knee fractures. The sensitivity, specificity, positive predictive value, negative predictive value of sonography for the diagnosis of lipohemarthrosis was 97, 100, 100 and 94%, respectively, compared with 55, 100, 100 and 55% with conventional radiographs. Using lipohemarthrosis as criterion of fracture, the sensitivity, specificity, positive predictive value and negative predictive value of sonography for early detection of intra-articular knee fractures was 94, 94, 97 and 89%, respectively, compared with 84, 88, 93 and 75% with conventional radiographs. We concluded that, by showing lipohemarthrosis in the subquadricipital recess, high-resolution sonography is a reliable and accurate technique for the evaluation of intra-articular knee fractures.

Acute knee trauma: role of ultrasound

The purpose of this study was to determine the diagnostic accuracy of high spatial resolution ultrasonography (US) in the detection of lipohemarthrosis of the knee and to evaluate this sign as criteria of intra-articular fracture. Forty-eight patients with clinical suspicion of knee fracture were prospectively examined by conventional radiography, sonography examination and computed tomography (CT) within 48 h after trauma in order to depict direct (fracture line) and indirect (lipohemarthrosis) signs of intra-articular fracture. Lipohemarthrosis was defined as a multi-layered collection in the subquadricipital recess. CT was considered as the gold standard for both direct and indirect fracture criteria. CT imaging showed direct signs of intra-articular fracture in 31 patients (65%). Among these patients, 30 (97%) had a lipohemarthrosis. Conventional radiographs showed intra-articular fracture in 26 patients (54%). Among these, 18 (69%) had a lipohemarthrosis. Sonographic examinations could not depict any direct sign of intra-articular fracture but showed a lipohemarthrosis in 29 (93%) of patients with proven fracture via CT. This allowed the depiction of four out of five occult knee fractures. The sensitivity, specificity, positive predictive value, negative predictive value of sonography for the diagnosis of lipohemarthrosis was 97, 100, 100 and 94%, respectively, compared with 55, 100, 100 and 55% with conventional radiographs. Using lipohemarthrosis as criterion of fracture, the sensitivity, specificity, positive predictive value and negative predictive value of sonography for early detection of intra-articular knee fractures was 94, 94, 97 and 89%, respectively, compared with 84, 88, 93 and 75% with conventional radiographs. We concluded that, by showing lipohemarthrosis in the subquadricipital recess, high-resolution sonography is a reliable and accurate technique for the evaluation of intra-articular knee fractures.

Acute rotational trauma to the knee: poor agreement between clinical assessment and magnetic resonance imaging findings

To determine the incidence of anterior cruciate ligament (ACL) injuries in the general population; the pathology associated with a knee sprain verified by magnetic resonance imaging (MRI); and the agreement between clinical findings and MRI. Inclusion criterion was an acute rotational trauma to the knee associated with effusion. One hundred and fifty-nine consecutive patients, mean age 27 years and 36% women, were included after clinical assessment at the orthopedic emergency unit. Patients were referred to an MRI examination (1.0 or 1.5 T) performed within a median of 8 days of the initial visit. The annual incidence of MRI verified ACL injuries was 0.81/1000 inhabitants aged 10-64 years. Fifty-six percent (n=89) of those included had sustained an ACL injury of whom 38% had an associated medial meniscus tear. There was a poor agreement between initial clinical antero-posterior laxity and MRI verified presence of an ACL tear (kappa 0.281). Every second patellar dislocation was diagnosed as a ligament injury. Our findings indicate that the incidence of ACL injuries is higher than previously described. We also show that the first clinical examination after an acute knee trauma has a low diagnostic value. Further assessment with MRI improves the chances of a correct diagnosis of intraarticular pathology and is recommended in the early phase after a rotational knee trauma.

Development and efficiency of an acute knee trauma list

Following acute knee trauma some patients will require urgent arthroscopy. Traditionally surgery is undertaken as in-patient on the general trauma list. This system leads to blockage of beds, repeated starving of the patient and out-of-hour's surgery in many cases. We introduced a dedicated Day Surgery knee trauma list (KTL) to reduce in-patient admissions, waiting time and cost. The typical indications for urgent knee arthroscopy are locked knees secondary to meniscal tears, loose bodies or cruciate ligament ruptures; acute osteochondral fractures; and children with acute meniscal tears. This retrospective review compares the study group: patients on the knee trauma list during the first 8 months following introduction, and the control group: patients on the general in-patient trauma list over a similar period immediately prior to implementation of the new list. There were 49 patients in the control group with an average stay in hospital of 2.5 days. Out-of-hour's operations were performed in 13 patients and 3 patients required a repeat arthroscopy. Fifty-three patients were treated in the knee study group. The significant operations were meniscal repair in 7, fixation of osteochondral fragments in 3. None of the patients required overnight stay. Control group patients were more likely to have surgery performed by inexperienced non-specialist knee surgeons, whereas specialist knee surgeons staffed the knee trauma list. Specialist surgeons were available to staff the knee trauma list. As the majority of the control group had spent an average of 2.2 nights in hospital, there has been considerable savings to the hospital. Introduction of the Day Surgical Knee trauma list has reduced unnecessary admissions per week; episodes of prolonged starving, cost and have improved patient satisfaction and management.

Acute knee trauma: analysis of multidetector computed tomography findings and comparison with conventional radiography

To evaluate the multidetector computed tomography (MDCT) findings of acute knee trauma and to compare radiography with MDCT in patients referred to a level 1 trauma center. During a 5-year period, a total of 415 MDCT examinations were performed on 409 patients with acute knee trauma to reveal complex fracture anatomy or rule out a fracture. MDCT and primary radiographs were re-evaluated with respect to fracture location and trauma mechanism. Tibial plateau fractures were further analyzed depending on anatomical location: anterior-medial, anterior-lateral, posterior-lateral, and posterior-medial regions. Maximal depression of the tibial articular surface was measured. Findings on the primary knee radiographs were compared with MDCT findings. Of the 409 patients, 356 (87%) had a knee fracture. A total of 451 fractures were found in all anatomic regions: distal femur (n=49), proximal tibia (n=307), patella (n=23), and proximal fibula (n=72). Primary radiographs were available in 316 (76%) cases. Of these, 225 (71%) had MDCT in order to reveal the fracture anatomy better, and 91 (29%) had a subsequent MDCT after negative plain radiographs. Overall sensitivity of radiography was 83%, while negative predictive value was 49%. On radiography, tibial plateau articular depression was underestimated in all regions except when the fracture consisted of the whole half of the anterior or posterior plateau. The three main injury mechanisms were traffic accident, a simple fall, and sport. In 49 cases (15%), primary radiographs were suboptimal due to positioning. In severely injured patients, diagnostically sufficient radiographs are difficult to obtain, and therefore a negative radiograph is not reliable in ruling out a fracture. In these patients, MDCT is a fast and accurate examination and is also recommended in patients with tibial plateau fractures or complex knee injuries in order to evaluate the fracture adequately.

Acute Knee Trauma: Value of a Short Dedicated Extremity MR Imaging Examination for Prediction of Subsequent Treatment

To assess the predictive value of a short magnetic resonance (MR) imaging examination, in addition to or instead of radiography, performed in patients with acute knee trauma to identify those who require additional treatment versus those who do not and can be discharged without further follow-up. The randomized controlled trial and use of collected data for prediction modeling were approved by the institutional review board; informed consent was obtained. Patients with recent knee injury were included in the trial if radiography was ordered. They were randomized into a group undergoing only radiography and a group undergoing radiography plus immediate MR imaging. A 0.2-T dedicated extremity MR imager and four short pulse sequences were used. Univariable and multivariable logistic regression analysis was used to evaluate patient characteristics, trauma mechanism, and findings at radiography and MR imaging for their value in prediction of need for subsequent treatment within the 6-month follow-up. Data in 189 patients (123 male patients, 66 female patients; mean age, 33.4 years), 109 of whom underwent treatment after their initial visit, were analyzed. Age of 30 years or older, indirect trauma mechanism, radiographic results, and MR imaging results were significant predictors of need for treatment in univariable and multivariable analyses (P < .05). In the multivariable analysis, only abnormal MR imaging results were significantly predictive of need for treatment, and only when MR imaging replaced radiography (odds ratio, 2.61; 95% confidence interval: 1.12, 6.06). Implementation of a dedicated extremity MR imaging examination, in addition to or instead of radiography, performed in patients with traumatic knee injury improves prediction of the need for additional treatment but does not significantly aid in identification of patients who can be discharged without further follow-up. Value of a short MR imaging examination in the initial stage after knee trauma is limited.

Arthroscopic diagnosis and treatment of cartilage injuries of the knee joint in children

Experience in knee arthroscopy in children with acute knee trauma and sequelae of knee injuries is presented. There were 417 patients, aged 418, who were under treatment at the clinic in the period from 1994 to 2002. One hundred forty four patients (34.5%) had injury of articular cartilage. In 12 cases diagnostic and in 132 cases diagnostic and curative arthroscopy was performed. Evident advantages of arthroscopy in diagnosis of intraarticular knee structures injuries, especially cartilagenous tissue were emphasized. Protocol of diagnostic examination including clinical, roentgenologic, ultrasonographic methods as well as CT and MRT (as indicated) is suggested. Indications to knee arthroscopy in children and adolescents are determined. Clinical-arthroscopic classification of knee articular cartilage injuries is given. Due to exact diagnosis and adequate curative tactics total restoration of knee function was achieved in 75% of patients with articular cartilage injuries.

Long-term osseous sequelae after acute trauma of the knee joint evaluated by MRI

To evaluate the frequency and location and to determine the long-term MR changes in patients with edema-like bone marrow abnormalities after acute knee trauma. A cohort of 176 consecutive patients in a 29 month period with acute injury of the knee joint was examined with MRI. Forty-nine patients with bone marrow edema-like signal alteration on the initial MR examination were re-evaluated with MRI after a minimum of 2 years (mean 44 months). Signal alterations and contour abnormalities on the initial and follow-up MR examinations were classified. The volume of the edema was also measured. There was a prevalence of post-traumatic edema-like signal changes of 72% in 176 patients. In the follow-up group (n=49) the initial MR examination showed 80 areas of signal change with a mean volume of 15.5 cm3 (range 0.25-175 cm3). Thirty-five (44%) were signal changes without other bony or cartilaginous injuries, 19 (24%) were subchondral impaction fractures and 26 (33%) were osteochondral or chondral fractures. Sixty-nine percent of the lesions were located in the lateral, and 29% in the medial joint compartment. Three percent were patellar lesions. In seven of the 49 patients (14%) eight signal changes were seen on the follow-up MR examination. Six lesions were located in the same anatomic area as on the initial MR examination, and two new lesions had developed. The volume of the bone marrow edema was smaller in all persisting lesions (mean volume 2.26 cm3, range 0.3-4.8 cm3). Deterioration of the subchondral impaction, chondral/osteochondral fracture or lesions resembling osteonecrosis were not found in any patient. The majority of acute post-traumatic marrow signal changes are found in the lateral compartment and do not show additional osseous or chondral alterations. After a minimum of 2 years acute post-traumatic bone marrow edema-like signal alterations vanish in the majority of patients. Even more severe articular surface injuries such as subchondral bone impaction or chondral/osteochondral fractures will heal without obvious osseous long-term sequelae. Post-traumatic osteonecrosis, as reported in the literature, must be a rare event after acute knee trauma.

Applicability of Ottawa knee rule for knee injury in children.

Previous studies have shown that the application of the Ottawa knee rule (OKR) reduces the need for radiographs in adults with acute knee injuries. Our objectives were to describe the epidemiology and incidence of knee injuries in children with acute knee trauma and to validate the OKR in a pediatric population. A prospective, consecutive study. Two urban pediatric emergency departments. All children 18 years of age and under who presented with acute traumatic knee injury of less than 1 week's duration, excluding patients with a normal knee examination, superficial skin injuries, prior history of knee injury, underlying bone disease, serious injuries involving two or more organ systems, or altered mental status were enrolled. Physicians assessed each patient for 22 standardized clinical findings prior to radiography. The OKR was applied to each patient by the investigating physician. All 234 patients eligible for the study had radiographs of the affected knee. The median age was 13 years with a range of 2 to 18 years. Using the OKR criteria for obtaining knee radiographs, 12 of 13 patients with fractures were identified (sensitivity 92%; 95% CI= 64-99). The missed case was an 8-year-old male who had sustained a nondisplaced fracture of the proximal tibia after a fall. If the OKR were applied to the pediatric population, it would have reduced the need for radiography in 46% of children. In the pediatric population studied, the OKR did not identify all patients with knee fractures. Future studies may consider modifying the OKR to accommodate the differences between pediatric and adult patients to improve the sensitivity of the rule while maintaining its specificity, before it can be applied routinely in clinical practice.

Validation of the Ottawa knee rules in an emergency teaching centre.

Our objective was to determine the value of the Ottawa knee rules when applied by users with different levels of clinical training. We used a prospective patient survey by the medical students and surgery residents of a European university trauma centre. The study group consisted of 261 eligible patients who presented with acute knee trauma during a 6-month period. Radiography or follow-up was obtained for each patient. Data were separately analysed according to the degree of qualification of the initial examiner. The Ottawa knee rules had a sensitivity and a negative predictive value of 1.00. Variable degree of medical competence of the users did not alter the accuracy of the rules. Application of the rules would have reduced knee radiography requests by 25%. The Ottawa knee rules remain highly sensitive when applied by medical users with different levels of qualification, such as encountered in a teaching setting.

Use of the Ottawa knee rule: a cost minimization study

Purpose: To determine whether adoption of the Ottawa knee rule will decrease the cost of evaluating adult patients with acute blunt knee trauma compared with not using the rule. Materials and methods: A decision tree was constructed with two arms, one that included explicit use of the Ottawa knee rule and another that did not include adoption of the Ottawa knee rule. Probability estimates for the model were obtained from an internally generated data set, while cost estimates were obtained from hospital charges, Medicare reimbursement rates, and Department of Labor statistics. A societal perspective was adopted. Results: The baseline analysis indicated that adoption of the Ottawa knee rule results in an average savings per patient of US$3. Cost savings increase as the cost of radiography increases. However, under certain conditions, adoption of the Ottawa knee rule may result in increased costs, especially if the sensitivity of the rule drops below .94. Conclusions: Under most conditions, adoption of the Ottawa knee rule results in modest cost savings compared with not using the rule. Individual institutions may wish to determine whether their practice environment (fracture prevalence, cost of radiography, patient waiting time, etc.) is conducive to significant cost savings before formally adopting the knee rule.

The Lateral View: A Screening Method for Knee Trauma

Rationale and Objectives The authors performed this study to evaluate whether any one conventional radiographic view is sufficient as a screening method in the detection of acute knee trauma. Materials and Methods The authors prospectively assessed the efficacy of a single conventional radiograph of the knee in the detection of signs of knee fractures in 214 consecutive adults with acute knee trauma. The evaluated efficacy parameters included specificity, sensitivity, negative predictive value (NPV), and positive predictive value. The percentage reduction in the need for additional conventional radiographs was also calculated. Results Fifty-three of the 214 patients (24.8%) had a knee fracture. The sensitivity of the single lateral view in the detection of knee fractures was 100% (95% confidence interval [CI] = 94.3, 100). The lateral view of the traumatized knee was normal in 143 patients (66.8%). The probability of not having a fracture if the lateral view was normal (NPV) was also 100% (95% CI = 97.9, 100). The need for additional radiographs was reduced 67%. Conclusion A single lateral view as a screening tool for knee fractures has a very high sensitivity and NPV. Because more than 65% of the patients had a normal lateral view in this study, there can be a considerable amount of savings in terms of radiology services for these patients.