Detecting Avascular Necrosis of the Lunate from Radiographs Using a Deep-Learning Model.

Deep-learning (DL) algorithms have the potential to change medical image classification and diagnostics in the coming decade. Delayed diagnosis and treatment of avascular necrosis (AVN) of the lunate may have a detrimental effect on patient hand function. The aim of this study was to use a segmentation-based DL model to diagnose AVN of the lunate from wrist postero-anterior radiographs. A total of 319 radiographs of the diseased lunate and 1228 control radiographs were gathered from Helsinki University Central Hospital database. Of these, 10% were separated to form a test set for model validation. MRI confirmed the absence of disease. In cases of AVN of the lunate, a hand surgeon at Helsinki University Hospital validated the accurate diagnosis using either MRI or radiography. For detection of AVN, the model had a sensitivity of 93.33% (95% confidence interval (CI) 77.93-99.18%), specificity of 93.28% (95% CI 87.18-97.05%), and accuracy of 93.28% (95% CI 87.99-96.73%). The area under the receiver operating characteristic curve was 0.94 (95% CI 0.88-0.99). Compared to three clinical experts, the DL model had better AUC than one clinical expert and only one expert had higher accuracy than the DL model. The results were otherwise similar between the model and clinical experts. Our DL model performed well and may be a future beneficial tool for screening of AVN of the lunate.

Enchondroma Detection from Hand Radiographs with an Interactive Deep Learning Segmentation Tool-A Feasibility Study.

Enchondromas are common benign bone tumors, usually presenting in the hand. They can cause symptoms such as swelling and pain but often go un-noticed. If the tumor expands, it can diminish the bone cortices and predispose the bone to fracture. Diagnosis is based on clinical investigation and radiographic imaging. Despite their typical appearance on radiographs, they can primarily be misdiagnosed or go totally unrecognized in the acute trauma setting. Earlier applications of deep learning models to image classification and pattern recognition suggest that this technique may also be utilized in detecting enchondroma in hand radiographs. We trained a deep learning model with 414 enchondroma radiographs to detect enchondroma from hand radiographs. A separate test set of 131 radiographs (47% with an enchondroma) was used to assess the performance of the trained deep learning model. Enchondroma annotation by three clinical experts served as our ground truth in assessing the deep learning model's performance. Our deep learning model detected 56 enchondromas from the 62 enchondroma radiographs. The area under receiver operator curve was 0.95. The F1 score for area statistical overlapping was 69.5%. Our deep learning model may be a useful tool for radiograph screening and raising suspicion of enchondroma.

Post-traumatic spinal hematoma in diffuse idiopathic skeletal hyperostosis (DISH).

OBJECTIVES: To determine the incidence of spinal hematoma and its relation to neurological deficit after trauma in patients with spinal ankylosis from diffuse idiopathic skeletal hyperostosis (DISH). MATERIALS AND METHODS: A retrospective review of 2256 urgent or emergency MRI referrals over a period of 8 years and nine months revealed 70 DISH patients who underwent CT and MRI scans of the spine. Spinal hematoma was the primary outcome. Additional variables were spinal cord impingement, spinal cord injury (SCI), trauma mechanism, fracture type, spinal canal narrowing, treatment type, and Frankel grades during injury, before and after treatment. Two trauma radiologists reviewed MRI scans blinded to initial reports. RESULTS: Of 70 post-traumatic patients (54 men, median age 73, IQR 66-81) with ankylosis of the spine from DISH, 34 (49%) had spinal epidural hematoma (SEH) and 3 (4%) had spinal subdural hematoma, 47 (67%) had spinal cord impingement, and 43 (61%) had SCI. Ground-level fall (69%) was the most common trauma mechanism. A transverse, AO classification type B spine fracture (39%) through the vertebral body was the most common injury type. Spinal canal narrowing (p < .001) correlated and spinal cord impingement (p = .004) associated with Frankel grade before treatment. Of 34 patients with SEH, one, treated conservatively, developed SCI. CONCLUSIONS: SEH is a common complication after low-energy trauma in patients with spinal ankylosis from DISH. SEH causing spinal cord impingement may progress to SCI if not treated by decompression. CLINICAL RELEVANCE STATEMENT: Low-energy trauma may cause unstable spinal fractures in patients with spinal ankylosis caused by DISH. The diagnosis of spinal cord impingement or injury requires MRI, especially for the exclusion of spinal hematoma requiring surgical evacuation. KEY POINTS: • Spinal epidural hematoma is a common complication in post-traumatic patients with spinal ankylosis from DISH. • Most fractures and associated spinal hematomas in patients with spinal ankylosis from DISH result from low-energy trauma. • Spinal hematoma can cause spinal cord impingement, which may lead to SCI if not treated by decompression.

Chondrosarcoma of the Chest Wall: A Single Institution Review of 50 Cases.

INTRODUCTION: Chondrosarcoma (CS) is most common primary osseous tumor of the chest wall. The aim of this study was to report results from surgical procedures and evaluate clinical factors predicting survival of patients with chest wall CSs treated in a single tertiary sarcoma center. MATERIALS AND METHODS: Fifty patients with primary CS located in the ribs and sternum were included. Details of the clinical data and oncological outcomes, including local recurrence (LR) and disease-specific survival (DSS), were collected. RESULTS: The tumor was primarily originated in the sternum in 6 patients (12.5%) and in ribs 2 to 11 in the remaining patients. Specimens were histologically graded 1 in 13 patients (26%), 2 in 28 (56%), 3 in 8 (16%), and 1 (2%) as mesenchymal grade 3 CS. R0 margins were obtained in all cases. Reconstruction was warranted in 47 (94%) cases. Local recurrence developed in 3 (6%) patients, and the median time to LR was 17 (range, 16-68) months. Eight (16%) patients developed metastasis. Increasing tumor volume was a statistically significant factor for reduction of DSS. CONCLUSIONS: Chondrosarcoma of the chest wall can be treated effectively with clear margins, resulting in lower LR rate and higher DSS than CS of the extremities and pelvis. Metastasis of the chest wall mostly occurs in high-grade tumors, and the locations of the metastases differ greatly from those observed in CS of the extremities and pelvis. Metastases are commonly extrapulmonary, indicating the need for postoperative follow-up with multiple imaging modalities to monitor recurrence and metastases.

Ankylosis of the cervical spine increases the incidence of blunt cerebrovascular injury (BCVI) in CTA screening after blunt trauma.

PURPOSE: To examine the incidence, location, and grade of blunt cerebrovascular injury (BCVI), as well as associated strokes in patients with ankylosis of the cervical spine, imaged with CT angiography (CTA) after blunt trauma. The related etiologies of ankylosis had an additional focus. MATERIALS AND METHODS: Altogether of 5867 CTAs of the craniocervical arteries imaged after blunt trauma between October 2011 and March 2020 were manually reviewed for a threshold value of ankylosis of at least three consecutive cervical vertebrae. BCVI was the primary outcome and associated stroke as the secondary outcome. Variables were craniofacial and cervical spine fractures, etiology and levels of ankylosis, traumatic brain injury, spinal hematoma, spinal cord injury, and spinal cord impingement, for which correlations with BCVI were examined. RESULTS: Of the 153 patients with ankylosis and blunt trauma of the cervical spine, 29 had a total of 36 BCVIs, of whom two had anterior and 4 posterior circulation strokes. Most of the BCVIs (n = 32) were in the vertebral arteries. Injuries were graded according to the Biffl scale: 17 grade II, 4 grade III, 14 grade IV, and 1 grade V. A ground-level fall was the most common trauma mechanism. Cervical spine fracture was the only statistically significant predictor for BCVI (OR 7.44). Degenerative spondylosis was the most prevalent etiology for ankylosis. CONCLUSION: Ankylosis of the cervical spine increases the incidence of BCVI up to sevenfold compared to general blunt trauma populations, affecting especially the vertebral arteries.

Unfavourable early outcomes of total trapeziectomy with RegJoint™ interposition: a report of 38 osteoarthritic hands in 34 patients.

This retrospective study analysed the results of total trapeziectomy with RegJoint™ interposition in 38 osteoarthritic hands in 34 patients. Patients were evaluated preoperatively, at follow-up visits, and at a mean final follow-up of 33 months (range 20-53) with plain radiographs, computed tomography, as well as with subjective and objective evaluations. Pain decreased and subjective outcomes and function improved significantly. Computed tomography 18 months after operation showed osteolysis in 24 cases. Three patients developed wrist pain 12-18 months after operation with MRI findings of a foreign-body reaction in each case. One of these patients was scheduled for revision surgery. Although the clinical results were satisfactory, the risk of foreign-body reaction and osteolysis is noteworthy. We conclude that the use of RegJoint™ should be reconsidered since the implant probably offers no benefit in the treatment of trapeziometacarpal osteoarthritis. Level of evidence: IV.

Cross-sectional area of the paraspinal muscles and its association with muscle strength among fighter pilots: a 5-year follow-up.

BACKGROUND: A small cross sectional area (CSA) of the paraspinal muscles may be related to low back pain among military aviators but previous studies have mainly concentrated on spinal disc degeneration. Therefore, the primary aim of the study was to investigate the changes in muscle CSA and composition of the psoas and paraspinal muscles during a 5-year follow up among Finnish Air Force (FINAF) fighter pilots. METHODS: Study population consisted of 26 volunteered FINAF male fighter pilots (age: 20.6 (±0.6) at the baseline). The magnetic resonance imaging (MRI) examinations were collected at baseline and after 5 years of follow-up. CSA and composition of the paraspinal and psoas muscles were obtained at the levels of 3-4 and 4-5 lumbar spine. Maximal isometric strength tests were only performed on one occasion at baseline. RESULTS: The follow-up comparisons indicated that the mean CSA of the paraspinal muscles increased (p < 0.01) by 8% at L3-4 level and 7% at L4-5 level during the 5-year period. There was no change in muscle composition during the follow-up period. The paraspinal and psoas muscles' CSA was positively related to overall maximal isometric strength at the baseline. However, there was no association between LBP and muscle composition or CSA. CONCLUSIONS: The paraspinal muscles' CSA increased among FINAF fighter pilots during the first 5 years of service. This might be explained by physically demanding work and regular physical activity. However, no associations between muscle composition or CSA and low back pain (LBP) experienced were observed after the five-year follow-up.

CT of facial fracture fixation: an experimental study of artefact reducing methods.

OBJECTIVES: This study aimed to determine the optimal post-operative CT imaging method that enables best visualization of facial bony structures in the vicinity of osteosynthesis material. METHODS: Conducted at Töölö Hospital (Helsinki, Finland), this study relied on scanning a phantom with CBCT, 64-slice CT and high-definition multislice CT with dual-energy scan (providing monochromatic images of 70-, 100-, 120- and 140-keV energy levels) and iterative reconstruction (IR) methods. Two radiologists assessed the image quality, and the assessments were analyzed. In addition, a physicist performed a semi-quantitative analysis of the metal-induced artefacts. RESULTS: The three subjects most easily assessed were the loose screw and both the bone structure and the fracture further away from the screw and the plate. Soft tissues adjacent to the screw and the plate remained more difficult for assessment. Both image interpreters agreed that the artefacts disturbed their assessments under dual energy. Metal artefacts disturbed the least under multislice CT with IR [adaptive statistical iterative reconstruction (ASiR) and VEO]. Neither interpreter found metal suppression helpful in CBCT. CONCLUSIONS: CBCT with or without a metal artefact reduction algorithm was not optimal for post-operative facial imaging compared with multislice CT with IR. Multislice CT with ASiR filtering offered good image quality performance with fast image volume reconstruction, representing the current sweet spot in post-operative maxillofacial imaging.

Surgical treatment of chronic acromioclavicular joint dislocation with autogenous tendon grafts.

BACKGROUND: Conservative treatment of acromioclavicular (AC) joint dislocation is not always successful. A consequence of persistent AC joint dislocation may be chronic pain and discomfort in the shoulder region as well a sensation of constant AC joint instability and impaired shoulder function. Stabilization of the AC joint may reduce these sequels. MATERIALS AND METHODS: Due to chronic AC joint dislocation, 39 patients in our hospital underwent coracoclavicular (CC) ligament reconstruction with autogenous semitendinosus and gracilis tendons between May 2005 and April 2011. We examined 25 patients after a mean of 4.2 years. The outcomes were Constant shoulder Score (CS), Disabilities of the Arm, Shoulder and Hand (DASH), pain (Visual Analog Scale, VAS), cross-arm test, stability of the AC joint, and complications. The follow-up visits included anteroposterior and axillary radiographs. RESULTS: Mean CS was 83 in the injured shoulder and 91 in the uninjured shoulder (p = 0.002). Mean DASH was 14. In 14 patients, the AC joint was clinically stable; pain was minor. In radiographs, osteolysis of the lateral clavicle and tunnel widening were markedly common. Fracture of the coracoid process occurred in 5 patients, and 3 suffered a fracture of the clavicle; 2 had a postoperative infection. CONCLUSIONS: Anatomic reconstruction of CC ligaments showed a moderate subjective outcome at the 4-year follow-up. After surgery, almost half the AC joints failed to stabilize. Lateral clavicle osteolysis and tunnel widening were notably common complications.

CT arthrography of the wrist using a novel, mobile, dedicated extremity cone-beam CT (CBCT).

PURPOSE: To evaluate the feasibility and intra- and interobserver agreement of CBCT arthrography of wrist ligaments, triangular fibrocartilaginous complex (TFCC), and to assess the sensitivity (SE), specificity (SP), accuracy (ACC), and positive and negative predictive value (PPV, NPV) of CBCT arthrography in the diagnosis of scapholunate (SLL) and lunotriquetral (LTL) ligament tears, TFCC, and cartilage abnormalities of the scaphoid and lunate with their corresponding radial surfaces (scaphoid and lunate fossa) using a novel, mobile, dedicated extremity CBCT scanner. MATERIALS AND METHODS: Fifty-two consecutively enrolled subjects (26 M, 26 F, mean age 38 years, range 18-66 years) with suspected wrist ligament tears underwent CBCT-arthrography before normally scheduled MR arthrography.An extremity CBCT was used for imaging with isotropic voxel size of 0.4 × 0.4 × 0.4 mm(3). Subsequent routine 1.5 T MRI was performed using a dedicated wrist coil.Two observers reviewed the anonymized CBCT images twice for contrast enhancement (CE) and technical details (TD), for tears of the SLL, LTL, and TFCC. Also, cartilage abnormalities of the scaphoid and lunate with their corresponding radial surfaces (scaphoid and lunate fossa) were evaluated. Inter- and intraobserver agreement was determined using weighted kappa statistics. Since no surgery was performed, MRI served as a reference standard, and SE and SP, ACC, PPV, and NPV were calculated. RESULTS: Intra- and interobserver kappa values for both readers (reader 1/reader 2; first reading/second reading) with 95 % confidence limits were: CE 0.54 (0.08-1.00)/ 0.75 (0.46-1.00); 0.73 (0.29-1.00)/ 0.45 (0.07-0.83), TD 0.53 (0.30-0.88)/ 0.86 (0.60-1.00); 0.56 (0.22-0.91)/ 0.67 (0.37-0.98), SLL 0.59 (0.25-0.93)/ 0.66 (0.42-0.91); 0.31 (0.06-0.56)/ 0.49 (0.26-0.73), LTL 0.83 (0.66-1.00)/ 0.68 (0.46-0.91); 0.90 (0.79-1.00)/ 0.48 (0.22-0.74); TFCC (0.72-1.00)/ (0.79-1.00); 0.65 (0.43-0.87)/ 0.59 (0.35-0.83), radius (scaphoid fossa) 0.45 (0.12-0.77)/ 0.64 (0.31-0.96); 0.58 (0.19-0.96)/ 0.38 (0.09-0.66), scaphoid 0.43 (0.12-0.74)/ 0.76 (0.55-0.96); 0.37 (0.00-0.75)/ 0.32 (0.04-0.59), radius (lunate fossa) 0.68 (0.36-1.00)/ 0.42 (0.00-0.86); 0.62 (0.29-0.96)/ 0.51 (0.12-0.91), and lunate 0.53 (0.16-0.90)/ 0.68 (0.44-0.91); 0.59 (0.29-0.88)/ 0.42 (0.00-0.84), respectively. The overall mean accuracy was 82-92 % and specificity was 81-94 %. Sensitivity for LTL and TFCC tears was 76-83, but for SLL tears it was 58 %. For cartilage abnormalities, the accuracy and negative predictive value were high, 90-98 %. CONCLUSIONS: A dedicated CBCT extremity scanner is a new method for evaluating the wrist ligaments and radiocarpal cartilage. The method has an overall accuracy of 82-86 % and specificity 81-91 %. For cartilage abnormalities, the accuracy and negative predictive value were high.

Arthrosis of glenohumeral joint after arthroscopic Bankart repair: a long-term follow-up of 13 years.

HYPOTHESIS: The purpose of the study was to establish radiologic and clinical occurrence of glenohumeral arthrosis after arthroscopic Bankart repair. MATERIALS AND METHODS: Between January 1994 and December 1998, an arthroscopic Bankart repair was performed in 187 patients at our institution. We were able to assess clinical and radiologic glenohumeral arthrosis in 72 of the 101 patients who met the inclusion criteria (74 shoulders) (71%) after a 13-year follow-up. An additional 9 patients were interviewed by telephone. Radiologic arthrosis was evaluated with the Samilson-Prieto classification and clinical arthrosis with an arthrosis-specific quality-of-life questionnaire (Western Ontario Osteoarthritis of the Shoulder test). In addition, functional impairment was assessed with the Constant score and subjective satisfaction with a questionnaire. RESULTS: Radiologic arthrosis was diagnosed in 50 of 74 shoulders (68%), with 40 (80%) of them classified as mild. The mean score on the Western Ontario Osteoarthritis of the Shoulder questionnaire was 280 points (85% of the best possible score), which is considered relatively good. The mean Constant score was 78 points, and 75% of the patients were extremely satisfied or satisfied with the final results of operative treatment. DISCUSSION: The radiologic evaluation and self-assessment of the patients imply that the incidence of glenohumeral arthrosis after arthroscopic Bankart repair is quite common but the symptoms are generally mild and comparable to nonoperative treatment. CONCLUSION: Arthrosis rarely causes more than minor subjective symptoms or a minor objectively perceived disadvantage during 13 years' follow-up.

Reliability of the hip-to-ankle radiograph in determining the knee and implant alignment after total knee arthroplasty.

Hip-to-ankle radiographs have been used to evaluate lower limb alignment before and after total knee arthroplasty. However, earlier studies have inappropriately used correlation to assess the reproducibility of the radiographs. We determined the reliability of the hip-to-ankle radiograph using the Bland-Altman analysis. Two consecutive hip-to-ankle radiographs were obtained in 52 patients (52 knees) after total knee arthroplasty. There was an excellent agreement between mechanical axis angles, tibiofemoral angles, and femoral and tibial component alignment in the two radiographs. There was also an excellent agreement between all intra and interobserver analyses. The hip-to-ankle radiograph appears to be a reliable and reproducible means for determining the alignment of the knee in the coronal plane after total knee arthroplasty. In routine follow-up, the short anteroposterior knee radiograph may provide sufficient information. However, only the hip-to-ankle radiograph provides accurate information on the weightbearing mechanical axis in patients with suspected lower limb malalignment.

Multidetector CT in shoulder fractures.

The aim of this study was to assess the multi-detector computed tomography (MDCT) findings in acute shoulder traumas compared to radiographic findings in patients referred to a level one trauma center. Two hundred and ten patients (128 male, 82 female, age 16-95 years, mean age 51.7 years) underwent shoulder MDCT due to acute trauma. Three main mechanisms of injury were established: falling (113 patients, 54%), traffic accidents (36 patients, 17%) and falling from a height (12 patients, 6%). Based on MDCT, a total of 311 fractures--152 in the scapula and 159 in the proximal humerus--occurred in 191 (91%) of the 210 patients. The two most common occult fractures were lesser tubercle and coracoid process fractures. In 20 (63%) of the patients with a comminuted fracture of proximal humerus the exact number of fracture fragments was underestimated in radiographs. MDCT with multiplanar reconstructions (MPR) is a recommended complementary examination in patients with complex proximal humerus fractures where the extent of the fractures and the position or origin of dislocated fragments is not clear on radiography. This may increase the accuracy of the fracture classification and reveal occult fractures in other parts of the shoulder.

Lisfranc fracture-dislocation in patients with multiple trauma: diagnosis with multidetector computed tomography.

BACKGROUND: We assessed acute phase multidetector computed tomography (MDCT) findings of Lisfranc fracture-dislocations in patients with multiple trauma referred to a Level I trauma center over a 29-month period. METHODS: Two hundred and eighty two patients (208 male and 74 female) between the ages of 13 and 89 (mean 42) years had, at the request of emergency room physicians, MDCT of the foot and ankle after acute injury. RESULTS: A total of 21 Lisfranc fracture-dislocations were found in 19 (7%) patients. Two main injury mechanisms were established: falling from high places in 10 injuries (48%) and traffic accidents in five (24%). Primary radiographs were available in 17 (81%) feet, and four (24%) had false negative radiographic results when compared to MDCT. In all Lisfranc fracture-dislocations MDCT showed the joint anatomy and the extent of dislocation better than primary radiographs, and in six (46%) of 13 true positive primary radiographs, MDCT revealed additional occult fractures in the Lisfranc joint. Multidetector CT revealed additional occult fractures in other parts of the foot and ankle in six (35%) of 17 feet. CONCLUSIONS: Standard radiography remains a primary diagnostic modality in acute foot and ankle trauma. Multidetector CT with high-quality multiplanar reconstruction (MPR) is recommended as a complementary examination in high-energy injury in patients with multiple trauma or in patients in whom radiographic images are equivocal. This may reveal Lisfranc fracture-dislocations, show the extent of the fracture-dislocation, and reveal occult fractures in other parts of the foot and ankle.

Wrist injuries; diagnosis with multidetector CT.

The aim of the study was to assess acute-phase multidetector CT (MDCT) findings in wrist injuries. We retrieved all emergency room MDCT requests processed in the period from August 2000 to May 2003. All patients with a wrist injury who underwent MDCT initially were included. Imaging studies were evaluated in relation to injury mechanism, fracture location, and fracture type. A total of 6422 MDCT examinations were performed during this 34-month period, and 38 patients (24 male, 14 female, age range 21-73 years, mean age 40 years) met the inclusion criteria. MDCT revealed 56 fractures and 7 dislocations in 29 patients. In 9 patients (24%) MDCT findings were normal. Eleven patients (29%) underwent surgical procedures. The main injury mechanism was a fall (58%). In 33 cases the primary radiograph was available. Compared to primary radiographs, MDCT revealed 9 occult fractures, mainly in small carpal bones. In 14 cases a suspected fracture (of the scaphoid in 7 cases) was ruled out by MDCT. Due to high-quality two-dimensional reformatting, MDCT examinations were not dependent on the wrist's position in the CT gantry. In the comparison with radiography, MDCT detected occult fractures and ruled out suspected fractures, both mainly in the small carpal bones. High-quality two-dimensional reformats gave significant information about the fracture anatomy. MDCT provides fast and valuable information in assessing complex wrist fractures or when the primary radiograph is equivocal.

Ankle and foot injuries: analysis of MDCT findings.

OBJECTIVE: The purpose of our study was to assess MDCT findings and the advantages of MDCT compared with radiography in patients referred to a level 1 trauma center for diagnostic evaluation of acute ankle and foot trauma. MATERIALS AND METHODS: During a period of 37 months, 388 patients underwent MDCT of the ankle and foot due to an acute trauma. Imaging studies (MDCT and radiography) were retrospectively reevaluated with respect to fracture location, fracture type, and mechanism of injury, and findings from the primary radiographs of the ankle and foot were compared with MDCT findings. RESULTS: Of the 388 patients, 344 (89%) had one or more fractures in the ankle or foot. A total of 517 fractures were found in all anatomic regions: ankle, calcaneus, talus, midfoot, and forefoot. The three most common occult fractures in the ankle not detected on primary radiography were isolated fractures of the posterior and medial malleolus and Tillaux fractures. The calcaneus was the most commonly fractured bone, and the sensitivity of radiography in the detection of calcaneal fractures was 87%. The sensitivity of radiography in the detection of talar fractures was 78%, whereas it was only 25-33% in the detection of midfoot fractures. A Lisfranc fracture-dislocation was not detected on primary radiography in five (24%) of 21 cases. The three main injury mechanisms were falling from a height (164 patients [48%]), a simple fall (68 patients [20%]), and a traffic accident (47 patients [14%]). CONCLUSION: In patients with injuries from high-energy polytrauma and in those with complex ankle and foot fractures, the sensitivity of radiography is only moderate to poor; in these cases, MDCT is recommended as the primary imaging technique.

MR imaging of fatigue stress injuries to bones: intra- and interobserver agreement.

The aim of this study was to determine the validity of MR imaging (MRI) in the assessment of stress-related injuries to bone.MR images of 50 military recruits (8 females and 42 males; 18-27 (mean 20) years of age) were retrospectively evaluated twice for stress injuries to bone by 4 radiologists (2 musculoskeletal radiologists, 2 radiology residents). Coronal T1-weighed (T1W) and STIR images, as well as axial and coronal T2-weighted (T2W) fat-suppressed images were taken using a 1.0T scanner. Rates for sensitivity, specificity, and accuracy of MRI of the stress-related injuries were calculated. Intraobserver and interobserver agreement was determined with kappa statistics. Rates for MRI sensitivity were 27-96%, for specificity 65-100%, and for diagnostic accuracy 58-97%. Lowest rates were seen when reading T1W images and highest when reading STIR images. Readers showed moderate to excellent intraobserver agreement (kappa 0.75-0.95). Interobserver agreement was fair to excellent (kappa 0.41-0.91), and the lowest values were seen in the interpretation of T1W images. Normal findings could be differentiated from various grades of stress injury to bone.MRI is a valid means of revealing the presence of stress injuries to bone and their staging. Observer agreement is good to excellent when using T2W images and STIR images, while T1W images are of lesser value.