What preoperative factors predict postoperative sitting pelvic position one year following total hip arthroplasty?

AIMS: The aims of this study were to measure sagittal standing and sitting lumbar-pelvic-femoral alignment in patients before and following total hip arthroplasty (THA), and to consider what preoperative factors may influence a change in postoperative pelvic position. PATIENTS AND METHODS: A total of 161 patients were considered for inclusion. Patients had a mean age of the remaining 61 years (sd 11) with a mean body mass index (BMI) of 28 kg/m2 (sd 6). Of the 161 patients, 82 were male (51%). We excluded 17 patients (11%) with spinal conditions known to affect lumbar mobility as well as the rotational axis of the spine. Standing and sitting spine-to-lower-limb radiographs were taken of the remaining 144 patients before and one year following THA. Spinopelvic alignment measurements, including sacral slope, lumbar lordosis, and pelvic incidence, were measured. These angles were used to calculate lumbar spine flexion and femoroacetabular hip flexion from a standing to sitting position. A radiographic scoring system was used to identify those patients in the series who had lumbar degenerative disc disease (DDD) and compare spinopelvic parameters between those patients with DDD (n = 38) and those who did not (n = 106). RESULTS: Following THA, patients sat with more anterior pelvic tilt (mean increased sacral slope 18° preoperatively versus 23° postoperatively; p = 0.001) and more lumbar lordosis (mean 28° preoperatively versus 35° postoperatively; p = 0.001). Preoperative change in sacral slope from standing to sitting (p = 0.03) and the absence of DDD (p = 0.001) correlated to an increased change in postoperative sitting pelvic alignment. CONCLUSION: Sitting lumbar-pelvic-femoral alignment following THA may be driven by hip arthritis and/or spinal deformity. Patients with DDD and fixed spinopelvic alignment have a predictable pelvic position one year following THA. Patients with normal spines have less predictable postoperative pelvic position, which is likely to be driven by hip stiffness. Cite this article: Bone Joint J 2018;100-B:1289-96.

Magnetic resonance imaging of injury to the medial collateral ligament of the elbow: a cadaver model.

The purposes of this study were to evaluate the usefulness of thin-section 3-dimensional Fourier Transform (3DFT) gradient echo imaging of the medial collateral ligament and to evaluate the usefulness of intraarticular gadolinium for the detection of tears of the ligament. Magnetic resonance imaging was performed on 5 fresh-frozen cadaveric elbows through use of T1-weighted and 3DFT gradient echo T2-weighted sequences. The elbows were then arthroscoped, and lesions were created in the medial collateral ligaments. Magnetic resonance imaging was then repeated with the T1 and 3DFT sequences. In addition, dilute gadolinium was then injected intra-articularly, and fat-suppressed T1-weighted images and 3DFT images were obtained. Magnetic resonance imaging findings were correlated with the appearance of the dissected ligament. We found that in the prearthroscopy specimens, the ligament was best seen on the 3DFT images reformatted into a slightly posteriorly obliqued coronal plane. In the post-arthroscopy elbows, 4 full-thickness perforations were detected with the 3DFT sequence; fat-suppressed T1-weighted images with intraarticular gadolinium detected these 4 as well as 1 partial inner surface tear. In conclusion, fat-suppressed T1-weighted magnetic resonance arthrography with gadolinium can provide information regarding inner surface partial tears and small full-thickness perforations.

Sonography of tears of the distal biceps tendon.

OBJECTIVE. The objective of this study was to describe the sonographic appearance of tears of the distal biceps brachii tendon. CONCLUSION. Sonography can reveal complete and partial tears of the distal biceps tendon, thus providing an alternative technique to MR imaging.

MR arthrography of the shoulder and hip after fluoroscopic landmarking.

PURPOSE: To describe a technique for intra-articular injection in the MR suite after conventional fluoroscopic landmarking in order to streamline MR arthrography. DESIGN AND PATIENTS: This technique was performed on 33 consecutive patients referred for MR arthrography of the shoulder to evaluate the glenoid labrum and on 15 consecutive patients referred for MR arthrography of the hip to evaluate the acetabular labrum. The patients were landmarked in the fluoroscopy suite, followed by a conventional MR examination. The intra-articular injection was then performed on the MR table and the MR arthrographic sequences obtained. RESULTS: One of the 48 injections was extra-articular, requiring a second injection. The other injections were performed without incident, and the average total procedure time for all injections was 10 min. CONCLUSIONS: This technique is a reliable method of streamlining intra-articular injections when performing conventional MR imaging prior to the MR arthrographic portion of the examination. It shortens the total MR examination time by eliminating a visit to the fluoroscopy suite in the middle of the MR study, and its use of a straight anterior approach for both the shoulder and hip joints should be familiar to most people who perform conventional arthrography.

Computerized bone densitometric analysis: operator-dependent errors.

PURPOSE: To determine the nature and relative frequency of operator-dependent data analysis errors in dual x-ray absorptiometry. MATERIALS AND METHODS: Over 40 months, 2,528 dual x-ray absorptiometric examinations of the forearm, femoral neck, and lumbar spine were performed by 11 technologists by using standard techniques and software. Each analysis was reviewed by a radiologist; errors were recorded and corrected. RESULTS: There were no forearm analysis errors. There were 24 (0.9%) femoral neck analysis errors, of which 23 resulted from misplacement of the analysis region. There were 33 (1.3%) spinal analysis errors, of which 24 resulted from misplacement of intervertebral disk space markers. Analysis errors of the femur and spine resulted in six misdiagnoses (0.2%). CONCLUSION: Misdiagnosis due to analysis errors is rare. Femoral neck analysis errors were easily detectable, but accurate spinal analyses depended on accurate identification of vertebral end plates and posterior elements. Nonetheless, these potentially serious errors can be detected and corrected if the analyses are reviewed and interpreted by a supervising physician who is familiar with the relevant anatomy, proper analysis techniques, and factors--such as artifacts--that adversely affect the accuracy of the analysis.

Incomplete intertrochanteric fractures: imaging features and clinical management.

PURPOSE: To present the imaging findings and treatment options for incomplete intertrochanteric fractures. MATERIALS AND METHODS: Among 31 patients with the magnetic resonance (MR) imaging diagnosis of incomplete intertrochanteric fracture, 30 also underwent radiography. MR and radiographic findings were compared. Note was made of fracture length and extent as depicted on the coronal and axial MR images, treatment (surgical vs conservative), and follow-up. RESULTS: Correlation between radiographic and MR findings was poor. Incomplete intertrochanteric fracture was the prospective radiographic diagnosis in only one case. Fracture in 18 patients was treated surgically and in 13 was managed conservatively. In both groups, the average age of the patients and length of the fractures and the percentage of separate fractures involving the greater trochanter and crossing the midline of the femur in the axial plane were the same. Fractures crossed the midline in the coronal plane in 50% of the surgical group but in only 23% of the nonsurgical group. Average time from injury to ambulation was 2 days less in the surgical group, but no difference in functional status was found subjectively between the two groups at clinical follow-up. CONCLUSION: Incomplete intertrochanteric fractures are a previously unrecognized subset of intertrochanteric fractures that are diagnosed unequivocally only with MR imaging.

Imaging of elbow disorders.

Numerous modalities are available for imaging the elbow. Radiographs should be the first imaging procedure performed for evaluation of an elbow abnormality. The use of advanced imaging modalities such as MR imaging, CT, and sonography also is discussed in this article.

Relationship of the meniscofemoral ligaments of the knee to lateral meniscus tears: magnetic resonance imaging evaluation.

This study sought to determine if the presence or absence of meniscofemoral ligaments exerts an influence on the prevalence of tears of the lateral meniscus. We reviewed the sagittal and coronal magnetic resonance images of 173 knees for lateral meniscus tears and the presence of the meniscofemoral ligaments. One or both meniscofemoral ligaments were present in 142 of 173 knees (82%). Fifty-four knees had lateral meniscus tears, 27 of which involved the posterior horn. Thirty-three percent of knees with meniscofemoral ligaments had a lateral meniscus tear, and 23% of knees without meniscofemoral ligaments had a lateral meniscus tear (no significant difference). We found no association between the presence of the meniscofemoral ligaments and tears of the lateral meniscus. Our study questions the importance of preserving or reconstructing these ligaments in instances of meniscal transplantation.

Scapulothoracic dissociation.

Scapulothoracic dissociation is an uncommon and devastating traumatic injury. A review of 72 cases in the English literature shows that a broad range of musculoskeletal and neurovascular injuries resulting from blunt trauma have been classified as scapulothoracic dissociation since the term was first used in 1984. A review of the current clinical signs and radiographic findings that define scapulothoracic dissociation, as well as a brief description of treatment options and outcomes, is presented.

Sonography of patellar abnormalities in children.

OBJECTIVE: We describe our experience using sonography to evaluate the patella and patellofemoral joint in three children with congenital abnormalities of the extensor mechanism of the lower extremity. CONCLUSION: Sonography can be used to evaluate the extensor mechanism and unossified patella in young children. Advantages of sonography over MR imaging are no need for sedation, speed of examination and ability to compare with the contralateral knee, low cost, and the sonographer's ability to dynamically evaluate the extensor mechanism.

Gradient-echo versus fat-suppressed fast spin-echo MR imaging of rotator cuff tears.

OBJECTIVE: The purpose of this study is to compare fat-suppressed T2-weighted fast spin-echo sequences with T2-weighted multiplanar gradient-echo sequences in revealing rotator cuff disorders. MATERIALS AND METHODS: Oblique coronal fat-suppressed fast spin-echo images and gradient-echo images of 39 patients who underwent surgery of the shoulder were retrospectively reviewed. Images from the two techniques were reviewed separately. Each set of images was interpreted twice by four musculoskeletal radiologists independently and without knowledge of the surgical findings. Sensitivity and specificity for both sequences were determined. The kappa statistic was used to calculate intraobserver and interobserver agreement of interpretations. RESULTS: For detecting any tear, the sensitivity of the four readers was 71-96% using fast spin-echo and 58-100% using gradient-echo imaging. Confidence intervals showed no difference between the two sequences. Sensitivity of detecting full-thickness tears was 83-100% for both sequences. Interobserver agreement was good. CONCLUSION: T2-weighted gradient-echo and fat-suppressed T2-weighted fast spin-echo sequences depict rotator cuff tears equally well and take less time to acquire than conventional dual-echo spin-echo sequences.

Meniscal position on routine MR imaging of the knee.

OBJECTIVE: To determine the prevalence of meniscal protrusion (i.e. location of the outer edge of a meniscus beyond the tibial articular surface), and to determine its relationship with internal derangement, joint effusion, and degenerative arthropathy. DESIGN AND PATIENTS: Sagittal and coronal MR images of 111 abnormal and 46 normal knees were evaluated for the presence of meniscal protrusion. We set 25% as the minimum amount of displacement considered abnormal because this was the smallest amount of displacement we could confidently discern. Presence of meniscal tear, anterior cruciate ligament (ACL) injury, joint effusion, or osteophytosis was also recorded. RESULTS AND CONCLUSION: Normal examinations demonstrated protrusion of the medial meniscus in 6.5% of sagittal images and 15% of coronal images, and of the lateral meniscus in 2% and 13%, respectively. Fisher's exact test demonstrated a statistically significant difference between the normal and abnormal groups for the medial meniscus on both sagittal (P < 0.0001) and coronal (P = 0.01) images, but not for the lateral meniscus in either plane (P > 0.2). A protruding medial meniscus was associated with effusion and osteophytosis (P < 0.05) but not with meniscal or ACL tear (P > 0.1). Posterior protrusion of the lateral meniscus was only associated with ACL injury (P < 0.0001); protruding anterior horns and bodies of lateral menisci were not associated with any of the four abnormalities. It is concluded that the medial meniscus may occasionally protrude more than 25% of its width, but protrusion is more often due to effusion and osteophytes. Protrusion of the posterior horn of the lateral meniscus is associated with ACL insufficiency, while protrusion of the body and anterior horn of the lateral meniscus is a normal variant.

Pseudodefect of the talar dome: an anatomic pitfall of ankle MR imaging.

PURPOSE: To identify a normal groove in the posterior aspect of the talus as a potential pitfall in interpretation of ankle magnetic resonance (MR) images. MATERIALS AND METHODS: In 40 patients, T1-weighted spin-echo and T2-weighted fast spin-echo sagittal MR images were retrospectively reviewed from 47 consecutive routine ankle examinations. The patients were referred for evaluation of ligament and tendon abnormalities, such as tendinitis and tear, and suspected osseous and osteochondral injuries. Images were assessed for the presence of an erosion-like defect in the posterior aspect of the talar dome. Radiographs were available in 13 cases. Sagittal T1-weighted spin-echo sequences were also performed in 14 embalmed cadaveric ankles, followed by sectioning and dissection of three specimens. RESULTS: A defect was seen in 45 of 47 ankle MR imaging examinations. Radiographs did not show the defect. All 14 cadaveric ankles demonstrated the defect at MR imaging. At anatomic dissection, the defect was a normal groove for the passage of the posterior talofibular ligament. CONCLUSION: The pseudodefect of the talar dome is a normal groove for the posterior talofibular ligament and should not be misinterpreted as an articular erosion or osteochondral defect.

Fat-suppressed MRI of musculoskeletal infection: fast T2-weighted techniques versus gadolinium-enhanced T1-weighted images.

PURPOSE: To investigate gadolinium's role in imaging musculoskeletal infection by comparing the conspicuity and extent of inflammatory changes demonstrated on gadolinium-enhanced fat-suppressed T1-weighted images versus fat-suppressed fast T2-weighted sequences. DESIGN: Eighteen patients with infection were imaged in a 1.5-T unit, using frequency-selective and/or inversion recovery fat-suppressed fast T2-weighted images (T2WI) and gadolinium-enhanced frequency-selective fat-suppressed T1-weighted images (T1WI). Thirty-four imaging planes with both a fat-suppressed gadolinium-enhanced T1-weighted sequence and a fat-suppressed T2-weighted sequence were obtained. Comparison of the extent and conspicuity of signal intensity changes was made for both bone and soft tissue in each plane. RESULTS: In bone, inflammatory change was equal in extent and conspicuity on fat-suppressed T2WI and fat-suppressed T1WI with gadolinium in 19 planes, more extensive or conspicuous on T2WI in three planes, and less so on T2WI in two planes. Marrow was normal on all three sequences in 10 cases. In soft tissue, inflammatory change was seen equally well in 20 instances, more extensively or conspicuously on the T2WI in 11 instances, and less so on T2WI in 2 instances. One case had no soft tissue involvement on any of the sequences. Five abscesses and three joint effusions were present, all more conspicuously delineated from surrounding inflammatory change on the fat-saturated T1WI with gadolinium. The average imaging time for the fat-saturated T1WI with gadolinium was 6.75 min, while that of the T2-weighted sequences was 5.75 min. CONCLUSION: Routine use of gadolinium is not warranted. Instead, gadolinium should be reserved for clinically suspected infection in or around a joint, and in cases refractory to medical or surgical treatment due to possible abscess formation.

MR imaging of Baker cysts: association with internal derangement, effusion, and degenerative arthropathy.

PURPOSE: To determine the prevalence of Baker cyst in a general orthopedic population and its association with effusion, internal derangement, and degenerative arthropathy. MATERIALS AND METHODS: Reports of 400 knee magnetic resonance imaging examinations were reviewed. Presence of Baker cyst, effusion, internal derangement (meniscal and/or anterior cruciate ligament tears), medial collateral ligament injury, and degenerative arthropathy was recorded. Uni- and multivariate logistic regressions were used to evaluate associations between Baker cyst and these conditions. Probabilities of having a Baker cyst given these conditions were also calculated. RESULTS: No association was found between Baker cyst and anterior cruciate ligament tear or medial collateral ligament injury. There were significant associations (P < .001) with effusion, meniscal tear, and degenerative arthropathy. There were also significant associations (P < .01) for effusion, meniscal tear, and degenerative arthropathy, independent of one another. Probability of having Baker cyst given the presence of any one variable was .08-.10; any two variables, .19-.21; and all three variables, .38. CONCLUSION: The association between Baker cyst and joint effusion was confirmed. A relationship with meniscal tear and degenerative joint disease independent of effusion was also demonstrated. The probability of having a Baker cyst increases as the number of these associated conditions increases.

Patellar height on sagittal MR imaging of the knee.

OBJECTIVE: The aim of this study was to determine if the radiographic assessment of patella alta using the patellar tendon:patella ratio can be applied to sagittal MR images of the knee. MATERIALS AND METHODS: Sagittal T1-weighted MR images of 46 knees were reviewed with corresponding radiographs. After lengths of the patella and patellar tendon were measured on the lateral radiographs and on the sagittal mid patellar images, the tendon:patella ratios were calculated. RESULTS: We found the mean tendon:patella ratio on radiographs to be 1.0 +/- 0.2 (SD) and on MR imaging, 1.1 +/- 0.1. These two values were not significantly different (p = .01) and had good-to-excellent correlation (r = .7). We found no statistical difference between the sexes on either radiographs or MR imaging, nor did we find statistical differences on MR imaging between the tendon:patella ratios of straight and wavy patellar tendons. CONCLUSION: As on radiographs, patellar height can be reliably assessed on sagittal MR imaging using the patellar tendon:patella ratio. On sagittal MR imaging, patella alta is suggested at values greater than 1.3 (1.1 + 2 SD).

The symptomatic accessory tarsal navicular bone: assessment with MR imaging.

PURPOSE: To determine if a symptomatic accessory navicular bone, a normal variant, displays a pattern of altered signal intensity on magnetic resonance (MR) images indicative of an abnormality that could account for the patient's foot pain. MATERIALS AND METHODS: Both feet were imaged in seven patients with an accessory navicular bone on radiographs and unilateral foot pain. Five patients had focal medial foot pain, and two had vague, diffuse pain. T1-weighted spin-echo and T2-weighted fat-suppressed sequences were used. RESULTS: A bone marrow edema pattern (BMEP) was noted in the accessory navicular bones of the five patients with focal pain and in the adjacent navicular tuberosities of three of them. The two patients with vague pain showed no osseous or soft-tissue abnormalities. Two patients with positive MR images underwent surgical excision of the accessory navicular bone, and histologic examination revealed osteonecrosis in one patient. CONCLUSION: The BMEP in a symptomatic accessory navicular bone is indicative of chronic stress and/or osteonecrosis. This information can furnish an objective basis for surgical or conservative management.

Benign soft tissue masses of the wrist and hand: MRI appearances.

We reviewed 20 cases of soft tissue masses of the hand and wrist, and compared the impressions from the original magnetic resonance (MR) imaging reports with the preoperative clinical impression and postoperative pathological diagnoses. The most commonly occurring masses were ganglia, lipomas, and giant cell tumors of tendon sheaths. MR imaging suggested the correct diagnosis in 16 of the 20 cases, whereas the clinical impression was correct in 10 instances. Confident was correct in 10 instances. Confident preoperative diagnosis may be made with MR imaging due to the characteristic appearances of many benign soft tissue tumors.

MRI of malignant fibrous histiocytoma of soft tissue: analysis of 13 cases with pathologic correlation.

We reviewed the magnetic resonance (MR) appearances of 13 malignant fibrous histiocytomas (MFH) of soft tissue and correlated each with the respective lesion's histopathology. The MR images were evaluated for signal intensity on T1- and T2-weighted spin echo sequences, homogeneity of the lesion, presence of internal low signal septations, and margin definition. Histologic subtypes of MFH included storiform-pleomorphic, giant cell, myxoid, and inflammatory. We could not establish a correlation between MR appearance and histopathology. Instead, our series exhibited general features suggestive of malignant soft tissue neoplasms, namely poor margin definition, internal low signal septation, and heterogeneous high signal intensity on T2-weighted images.