Bone density is higher in cam-type femoroacetabular impingement deformities compared to normal subchondral bone.

OBJECTIVE: Cam-type femoroacetabular impingement (FAI) deformities have been associated with early osteoarthritic degeneration of the hip. Degeneration depends on many factors such as joint morphology and dynamics of motion. Bone mineral density (BMD) appears to be a manifestation of the above, and may be a potentiator. Thus the goal of this study was to assess subchondral BMD of cam deformities in symptomatic and asymptomatic FAI subjects, and to compare to normal controls. METHODS: Subjects undergoing surgical correction of a symptomatic cam-type deformity were recruited ("Surgical"). Asymptomatic volunteers were also recruited and classified as normal ("Control") or having a deformity ("Bump") based on their alpha angle measurement. All subjects (n = 12 per group) underwent computed tomography (CT) with a calibration phantom. BMD was determined in volumes of interest around the femoral head and neck to a depth of 5 mm. BMD was compared between groups in each section using spine BMD as a covariate. RESULTS: No differences were seen between groups in the peripheral bearing surface. The Bump group exhibited higher BMD than Controls within the head/neck junction (P < 0.05). When compared to normal subchondral bone in the peripheral level of Controls, BMD in the deformity was up to 78% higher in Bump subjects and up to 47% higher in Surgical subjects (P < 0.05). CONCLUSION: Subchondral BMD of cam deformities is higher than that of normal subchondral bone in the peripheral region of the femoral head, regardless of symptom status. The expected increased subchondral stiffness may increase contact stresses in the joint tissues leading to accelerated degeneration.

Increased acetabular subchondral bone density is associated with cam-type femoroacetabular impingement.

OBJECTIVE: Femoroacetabular impingement (FAI) has been associated with significant acetabular cartilage damage and subsequent degenerative arthritis. Subchondral bone, often neglected in osteoarthritis studies, may play an important role in the degenerative cascade. Hence the goal of this study was to assess acetabular subchondral bone mineral density (BMD) in subjects with asymptomatic or symptomatic cam deformities compared to normal control subjects. The relationship between BMD and the alpha angle, a quantitative measure of the deformity, was also analyzed. METHODS: Patients diagnosed with symptomatic cam FAI were recruited ('Surgical') as well as subjects from the general asymptomatic population, classified from CT imaging as normal ('Control') or having a cam deformity ('Bump') based on their alpha angle measurement. There were 12 subjects in each group. All subjects underwent a CT scan with a calibration phantom. BMD was calculated in regions of interest around the acetabulum from CT image intensity and the phantom calibration. BMD was compared between groups using spine BMD as a covariate. The relationship between BMD and alpha angle was assessed by linear regression. RESULTS: In the antero-superior regions bone density was 15-34% higher in the Bump group (P < 0.05) and 14-38% higher in the Surgical group (P < 0.05) compared to Controls. BMD correlated positively with the alpha angle measurements (R(2) = 0.44, P < 0.001). CONCLUSION: BMD was elevated in subjects with cam-type deformities, with the severity of the deformity more correlative than symptom status. Similarities to the symptomatic group suggest that hips with an asymptomatic deformity may already be in early stages of joint degeneration.

Olympic fencers: adaptations in cortical and trabecular bone determined by quantitative computed tomography.

UNLABELLED: We investigated how cortical bone, trabecular bone, and muscle adapt in US Olympic Fencing Team members. These athletes demonstrate femoral cortical bone expansion, greater distal femoral trabecular bone density, and greater muscle mass compared to controls. This is the first study to investigate musculoskeletal adaptations in Olympic fencers. PURPOSE: Wolff's law states that bone remodels according to mechanical forces placed upon it. Our goal was to determine how cortical and trabecular bone adapt in Olympic athletes who perform intermittent high-impact activity. MATERIALS AND METHODS: Nine males from the 2004 US Olympic Fencing Team and nine matched controls were evaluated by quantitative computed tomography. Femurs were scanned at 50% and 75% along the shaft. We evaluated cortical thickness (C.Th), cortical (C.Ar), trabecular (Tb.Ar), and total bone areas (Tot.Ar), proportions of C.Ar and Tb.Ar to Tot.Ar, cortical (C.BMD.), trabecular (Tb.MBD), and total bone densities (Tot.BMD), muscle (M.Ar), and thigh areas (Th.Ar). RESULTS: Fencers had greater C.Th (+24.5 to 38.8%), C.Ar (+16.9 to 19.6%), C.Ar/Tot.Ar (+6.3 to 16.3%), and lower Tb.Ar/Tot.Ar (-23.5% to -23.8%; p<0.05). Fencers demonstrated a positive difference in C.Th in the dominant vs. nondominant thigh at 50% (+5.4%, p = 0.040) and at 75% (+13.8%, p = 0.048 by analysis of covariance). Fencers had 54% greater Tb.BMD at 75% (p = 0.025), but not at 50% (p = 0.63). There was no difference between groups for C.BMD (p = .66 at 50%, p = 0.88 at 75%). Fencers had greater M.Ar (+30%) and asymmetrically greater M.Ar (+12.2%) in the dominant thigh (p < 0.004). CONCLUSION: In world-class athletes who perform intermittent, high-impact activity, cortical bone expands, trabecular bone density is greater, and muscle mass is greater. This is the first study to examine musculoskeletal adaptations in Olympic fencers.

Is the hip capsule thicker in diseased hips?

OBJECTIVES: The purpose of this study was to compare the thickness of the hip capsule in patients with surgical hip disease, either with cam-femoroacetabular impingement (FAI) or non-FAI hip pathology, with that of asymptomatic control hips. METHODS: A total of 56 hips in 55 patients underwent a 3Tesla MRI of the hip. These included 40 patients with 41 hips with arthroscopically proven hip disease (16 with cam-FAI; nine men, seven women; mean age 39 years, 22 to 58) and 25 with non-FAI chondrolabral pathology (four men, 21 women; mean age 40 years, 18 to 63) as well as 15 asymptomatic volunteers, whose hips served as controls (ten men, five women; mean age 62 years, 33 to 77). The maximal capsule thickness was measured anteriorly and superiorly, and compared within and between the three groups with a gender subanalysis using student's t-test. The correlation between alpha angle and capsule thickness was determined using Pearson's correlation coefficient. RESULTS: Superiorly, the hip capsule was significantly greater in cam- (p = 0.028) and non-FAI (p = 0.048) surgical groups compared with the asymptomatic group. Within groups, the superior capsule thickness was significantly greater than the anterior in cam- (p < 0.001) and non-FAI (p < 0.001) surgical groups, but not in the control group. There was no significant correlation between the alpha angle and capsule thickness. There were no gender differences identified in the thickness of the hip capsule. CONCLUSION: The thickness of the capsule does not differ between cam- and non-FAI diseased hips, and thus may not be specific for a particular aetiology of hip disease. The capsule is, however, thicker in diseased surgical hips compared with asymptomatic control hips.Cite this article: K. S. Rakhra, A. A. Bonura, R. Nairn, M. E. Schweitzer, N. M. Kolanko, P. E. Beaule. Is the hip capsule thicker in diseased hips? Bone Joint Res 2016;5:586-593. DOI: 10.1302/2046-3758.511.2000495.

Correlation between the distal anterior femoral cortical axis and femoral rotational alignment: an anatomic study.

PURPOSE: To determine the correlation between the distal anterior femoral cortical axis (DAFCA) and the femoral rotational alignment/axis. METHODS: Magnetic resonance images (MRI) of 82 knees in 34 men and 23 women aged 16 to 47 (mean, 33.4) years were reviewed by a musculoskeletal radiologist. Their diagnoses included meniscal tear (n=4), chondromalacia (n=25), anterior cruciate ligament tears (n=11), and normal (n=42). In all patients the collateral ligaments were intact. The transepicondylar axis (TEA), posterior condylar axis (PCA), Whiteside line (WL), and joint line were drawn on the images, and the condylar twist angle (CTA), TEA-WL angle, DAFCA, epicondylar cortical angle (ECA), and condylar cortical angle (CCA) were measured. The correlations among ECA, CCA, and CTA (control) were assessed. RESULTS: The mean distances between the joint line and the TEA, PCA, and DAFCA were 30.8, 22.1, and 62.2 mm, respectively. The angles subtended by the intersection between the standard axes (TEA, PCA, and WL) and the DAFCA were determined. There was correlation between the CTA and ECA (r=0.34, p<0.05), between the ECA and the CCA (r=0.80, p<0.0001), and between the CTA and the CCA (r=- 0.19, p=0.08). CONCLUSION: There was correlation between the DAFCA and TEA and PCA; DAFCA can be used to determine the femoral rotational alignment when the standard landmarks are distorted by severe soft tissue and bone loss.

Indirect MR arthrography of the knee: effects of low-intensity ultrasound on the diffusion rate of intravenously administered Gd-DTPA in healthy volunteers.

RATIONALE AND OBJECTIVES: To evaluate whether application of low-intensity ultrasound may increase the diffusion rate of intravenously administered gadopentetate dimeglumine (Gd-DTPA) and increase the amount of joint fluid on indirect magnetic resonance (MR) arthrography. METHODS: Conventional MR imaging, indirect MR arthrography, and power Doppler ultrasonography were performed before and after application of therapeutic, pulsed low-intensity ultrasound in 12 asymptomatic knees of 12 volunteers. Intra-articular diffusion of intravenously administered Gd-DTPA as measured by signal intensity differences of the intra-articular joint fluid before and after ultrasound treatment was assessed. In addition, the amount of joint fluid was rated, and differences in synovial blood flow as evidenced by power Doppler ultrasonography were noted. RESULTS: All volunteers tolerated well the application of therapeutic low-intensity ultrasound. A significant increase in intra-articular diffusion of intravenously administered Gd-DTPA was noted in all knees, and an increase in joint fluid was noted in 8 of 12 knees (66.6%). Detection of power Doppler flow signal in the synovium of the suprapatellar recess was possible in one instance at posttreatment exam. CONCLUSIONS: Use of pulsed, therapeutic low-intensity ultrasound may increase the diffusion rate of intravenously administered Gd-DTPA and may induce joint effusion.

MR imaging of bone marrow disorders.

This article discusses the MR imaging findings in osteomyelitis and septic arthritis. Criteria for differentiation of osteomyelitis from diabetic neuroarthropathy are presented. The article also presents an overview of MR imaging of avascular necrosis and criteria to differentiate transient osteoporosis from the edema pattern of avascular necrosis.

Magnetic resonance imaging of diffuse bone marrow disease.

MR is a highly sensitive alternative to plain films, CT, and radionuclide studies for the imaging of normal and abnormal marrow and can characterize differences between fatty, fibrotic, cellular, hypercellular, and hemosiderotic marrow. MR is helpful in depicting the extent of disease and has been a useful method to follow the clinical course of many disorders. It has been found to be particularly useful in explaining the unrepresentative biopsy, as the distribution of many diseases is frequently heterogeneous as exemplified by the mixed fatty and cellular patterns of aplastic anemia, myeloma, lymphoma, and skeletal metastases. Patterns of cellular and fatty marrow in the epiphysis and apophysis after marrow reconversion were not completely understood prior to the introduction of MR scanning. Because it has the advantage of imaging the entire bone marrow compartment (unlike the situation with biopsy on aspiration), MR allows a better understanding of the distribution of skeletal disease.

Magnetic resonance imaging analysis of soft tissue disruption after flexion-distraction injuries of the subaxial cervical spine.

STUDY DESIGN: A retrospective study was performed with the use of magnetic resonance imaging to evaluate the type and degree of soft tissue disruption associated with flexion-distraction injuries of the subaxial spine. OBJECTIVE: To determine what soft tissue structures are injured in flexion-distraction injuries of the subaxial spine. SUMMARY OF BACKGROUND DATA: Prior published reports of unilateral and bilateral cervical facet dislocations have described the analyzed mechanisms and biomechanics of this injury subtype. No retrospective magnetic resonance imaging analysis of associated soft tissue disruption has been documented. METHODS: Magnetic resonance imaging evaluations of the cervical spine were obtained for all patients with a flexion-distraction injury, Stages 2 (unilateral facet dislocation) and 3 (bilateral facet dislocation), between September 1994 and May 1998. Two neuroradiologists, blinded to both clinical and radiographic findings, graded all the soft tissue structures for evidence of attenuation or disruption. The soft tissue structures were graded on a scale of 1 (intact), 2 (indeterminate), or 3 (disrupted). RESULTS: For this study, 48 patients satisfied the inclusion criteria: 25 with unilateral facet dislocation and 23 with bilateral facet dislocation. Disruption to the posterior musculature, interspinous ligament, supraspinous ligament, facet capsule, ligamentum flavum, and posterior and anterior longitudinal ligaments was found in a statistically significant number of patients with bilateral facet dislocation. For most of these structures, disruption was found to be statistically significant in patients with a unilateral facet dislocation, except for the posterior longitudinal ligament, in which significance was not consistently demonstrated using 95% confidence intervals in the binomial testing. In a comparison between unilateral and bilateral facet dislocations using a two-sided Fisher's exact test, it was found that disruption to the anterior and posterior longitudinal ligaments and the left facet capsule were statistically significant, with all three more prominent in bilateral facet dislocation. A multivariate analysis between unilateral and bilateral facet dislocations showed that disruption to the anterior longitudinal ligament was associated significantly with a bilateral facet dislocation. Disc disruption was found to be associated significantly with both injury types, but was more common in bilateral facet dislocation, although this difference in intergroup comparisons was not statistically significant. CONCLUSIONS: Unilateral and bilateral facet dislocations of the subaxial spine are associated with damage to numerous soft tissue structures that provide stability to the lower cervical spine. Damage to the posterior longitudinal ligament did not occur consistently in unilateral facet dislocations. Bilateral facet dislocations were associated significantly with disruption to the posterior and anterior longitudinal ligaments and left facet capsule, as compared with unilateral facet dislocations. Magnetic resonance imaging allows visualization of these disruptions.

Magnetic resonance imaging of the biceps complex.

A variety of disorders primarily involving the long head of the biceps tendon is discussed. By virtue of its particular intra-articular position, this tendon may be affected by primary articular and degenerative processes because of impingement by the coracoacromial arch. Disorders of the biceps, including traumatic tears and displacement out of the bicipital groove, are best evaluated by MR imaging.

MR imaging of the diabetic foot.

Diabetes is a common disease with potentially devastating complications affecting the foot and ankle. A combination of vascular disease, peripheral neuropathy, and immunopathy result in a cascade of conditions including ischemia/infarction, tendinopathy, atrophy, edema, deformity, neuropathic osteoarthopathy, callus, ulceration, and infection. The MR imaging appearance of these complications will be discussed. Recognition of these MR imaging patterns facilitates formulation of medical or surgical treatment plans.

MR imaging of inflammatory conditions of the ankle and foot.

Infection and noninfection inflammatory diseases commonly affect the foot and ankle; they have a significant impact on the cost of medical care and are a major source of referral for MR imaging evaluation. Recognition of the MR imaging appearance of the various manifestations of these disorders is important so that prompt and appropriate medical or surgical management can be instituted. This article emphasizes MR imaging of the most important diseases in this category, diabetic foot infection and the rheumatoid foot, but will also discuss manifestations in the foot and ankle of various other inflammatory diseases, such as gout and seronegative spondyloarthropathies.

MRI of the ankle and hindfoot.

MRI of the ankle and hindfoot has become a widely used diagnostic test. The major indications for MRI of this region are disorders of tendons and bones. Avascular necrosis is common in the foot, usually seen after talus fractures or spontaneously in the metatarsal heads. Other causes of a marrow edema pattern include occult fractures, arthritic disorders, reactions to altered biomechanics, osteomyelitis, and regional migratory osteoporosis. The most frequently diseased tendons in the ankle are the Achilles, posterior tibial, and peroneal. MRI can be used to diagnose most disorders of these tendons, as well as stage these disorders to allow appropriate therapy. Most of these tendon disorders follow a recognized sequence of progression using the Achilles tendon as a model.

Hallux valgus and hallux rigidus: MRI findings.

The purpose of this article is to describe the MR findings of Hallux Valgus (HV) and Hallux Rigidus (HR). Twenty-four patients (11 with HV, 4 with HR, and 9 with both HV and HR) were studied at 1.5 Tesla MRI. Two separate observers evaluated the first ray blindly for the following signs: sesamoid position, sesamoid proliferation, hypertrophy of the median eminence, presence of a lateral facet, presence of an adventitial bursa, shape of the first metatarsal head, relative length of the first metatarsal, joint space loss, osteophytes (dorsalor lateral), marrow edema, geodes, subchondral sclerosis, intra-articular ossicle, and pes planus. The most common findings observed in HV were a hypertrophic medial eminence (95%), sesamoid proliferation (90%) and adventitial bursitis (70%). The most common findings observed in HR were osteophytes (77% and 69%), geodes, and marrow edema. We conclude that traditional routine radiograph signs of HV and HR may be applied to MR images.

The PCL line: an indirect sign of anterior cruciate ligament injury.

A new sign of anterior cruciate ligament (ACL) tear based on secondary changes of the posterior cruciate ligament (PCL) is described. Thirty-one patients with magnetic resonance (MR) examinations of the knee suspicious for ACL injury and 50 normal controls were examined. In each patient a line was drawn adjacent and parallel to the posterior margin of the distal portion of the PCL and was extended proximally. A positive PCL line did not intersect the medullary cavity of the femur. A positive line correctly predicted ACL injury in 19 of 22 patients.

Occult osseous injuries after ankle sprains: incidence, location, pattern, and age.

We retrospectively evaluated 109 magnetic resonance studies in patients with prior ankle sprains to investigate the frequency and pattern of bone bruises. Patterns of bone bruises were then correlated with the ligaments injured. In addition, the age of the injury was determined from medical records to correlate the presence of bone bruises with the temporal period from injury. Bone bruises occurred in 39% of ankle sprains. Multiple bone bruises were seen in 40% of those with bone bruises; they occurred more frequently in patients with multiple ligaments injured. The marrow changes may be secondary to impaction, rotary instability of the ankle, and microavulsion vectors. Bone bruise-like lesions were seen at an average of 8.4 weeks in age but were seen more than a year after the injury. We conclude that bone bruises frequently occur in patients with ankle sprains, and the marrow changes may be caused by one of the three proposed mechanisms.

Traumatic focal posterior tibialis muscle denervation.

The purpose of this case presentation is to demonstrate posterior tibialis muscle (PTM) denervation as a cause of traumatic plantarflexion inversion weakness. In a 42-year-old woman, severe pain, swelling, and ecchymosis over the medial aspect of her left ankle developed after she twisted it while playing tennis. Plantarflexion inversion weakness developed (grade 3/5). The strength of all other muscle groups of the lower extremity was normal. Her pin and light touch sensation were normal in the left lower extremity. Deep tendon reflexes were equal and active at both knees and ankles. A magnetic resonance image of the left leg, ankle, and foot performed 1 month after injury demonstrated an intact posterior tibialis tendon behind the medial malleolus and edema-like increased signal intensity in the PTM on the T1-weighted image consistent with denervation. On electromyographic testing, there were continuous fibrillation and positive sharp wave potentials in every site tested in the PTM without any voluntary motor unit activity. The left extensor hallucis, left gastrocnemius, and lumbar paraspinal muscles were normal. In conclusion, combined magnetic resonance imaging and electromyographic studies supported denervation of the PTM as the cause of plantarflexion inversion weakness, rather than posterior tibialis tendon rupture in this patient.

Posterior tibial tendon dysfunction: secondary MR signs.

We evaluated four potential secondary magnetic resonance imaging signs to aid in clinical diagnosis of posterior tibial tendon (PTT) tears. Seventy-one ankles (25 PTT tears and 46 controls) were evaluated for the following secondary signs: (1) PTT sheath fluid, (2) a distal tibial spur located just anterior to the PTT, (3) unroofing of the talus, and (4) "bone bruise"--like medullary lesions. Two musculoskeletal radiologists rated their confidence using a scale and were compared for level of agreement. The presence of PTT sheath fluid had modest specificity and fair to moderate sensitivity. Tibial spurring and unroofing of the talus had excellent specificity and fair sensitivity. Bone bruise-like lesions were commonly seen in cases and controls. Examination of divergence of opinion between the two radiologists revealed pitfalls in interpretation of PTT sheath fluid and bone bruise-like lesions, which were commonly the result of adjacent vessels and inhomogeneous fat saturation, respectively. We conclude that secondary signs of PTT tears with high specificities include unroofing of the talus, tibial spurring, and PTT sheath fluid.

MR imaging of ankle marrow.

In this article the authors have attempted to distinguish the varying types of marrow disorders by the imaging characteristics. This is a challenging area but quite rewarding because the images can often be very specific.

Magnetic resonance imaging of ankle ligament injuries correlated with time.

Ankle sprain is one of the most commonly treated injuries of the lower extremity. The treatment depends on the severity of the injury and the time at which it occurred. The physician must rely on the history as related by the patient to determine the age of the injury. Magnetic resonance imaging has been proven to help determine the severity of the injury but has not been used to determine the age of the injury. The present study was conducted to identify the typical findings of acute and chronic ankle sprains as a means of dating an ankle sprain based on its appearance on magnetic resonance imaging.