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.

Underestimation of malignancy in biopsy-proven cases of stromal fibrosis

OBJECTIVE

To determine the rate of underestimation of malignancy in patients with biopsy-proven stromal fibrosis.

METHODS

Following institutional review board approval, we retrospectively reviewed the charts of patients with biopsy-proven stromal fibrosis who underwent percutaneous breast biopsy in the 5-year period between 1 January 2005 and 31 December 2009. The medical records and the histopathology in patients who underwent repeat biopsy and/or surgical excision at the site of stromal fibrosis within 2 years were reviewed. Interval stability for up to 2 years was documented in patients who did not undergo additional biopsy or surgical excision. An upgrade was defined as any patient with biopsy-proven stromal fibrosis or fibroadenoma with evidence of malignancy at the site of biopsy within 2 years.

RESULTS

365 cases of stromal fibrosis were identified, of which 25 (7%) were upgraded to in situ or invasive malignancy on repeat biopsy or surgical excision. 7 were upgraded to ductal carcinoma in situ and 18 were upgraded to invasive cancer. Of the upgraded cases, 8 out of 24 (32%) were considered concordant with a benign diagnosis. The false-negative rate, that is, cases of stromal fibrosis concordant with benignity, but with subsequent upgrade, comprised 2% of all cases.

CONCLUSION

In biopsy-proven cases of stromal fibrosis, there is a 7% upgrade to malignancy. We recommend that all instances of stromal fibrosis with radiology-pathology discordance undergo repeat biopsy or surgical excision. Cases that demonstrate radiology-pathology concordance can be safely categorized as a Breast Imaging Reporting and Data System 3 (BI-RADS® 3) lesion with a 6-month follow-up, owing to a false-negative rate for missed cancer of 2%.

ADVANCES IN KNOWLEDGE

We now recommend that concordant cases of stromal fibrosis be categorized as BI-RADS 3 with a short-term follow-up, as this results in a missed cancer rate of 2%.

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.

Contrast visibility for indirect MR arthrography with different protein contents and agent relaxivities at different field strengths: an in vitro model

OBJECTIVES

Protein binding and relaxivity are major determinants of the relative effectiveness of an MR arthrographic contrast agent. We sought to evaluate the optimal concentrations of high and usual relaxivity agents in two different proteinous environments at variable field strength for two MR contrast agents of different relaxivities.

MATERIALS AND METHODS

At 1.5, 3.0 and 7.0 T, gadobenate dimeglumine (Multihance) with high-relaxivity in proteinous environment and gadoteridol (Prohance) with more typical behavior were studied at 1.25, 2.5, 5, and 10 mmol in 1.7 g/dL and 3g/dL albumin (mimicking protein content of normal and inflammatory synovial fluids, respectively) vs. pure normal saline, as a control. Analysis of image signal intensity (SI) and relaxivity values was done.

RESULTS

In our study a change in concentration had no significant effect on T1 SI. In contrast, nearly every change in concentration led to a significant change in T2 SI. In 1.25 mmol concentration, there was no effect on T1 SI of either protein concentrations while higher concentrations showed significant decreased SI in either protein carrier compared to saline. The SI of Gadoteridol was significantly higher (p<0.0001) than that of gadobenate at each of 3T and 7 T, but was significantly lower (p<0.001) at 1.5 T in saline solution while this was not significant for either protein carrier. Both protein carriers had significant effect on T1 (p=0.0124) and T2 (p=0.0118) relaxivities. Also solution concentration significantly (p<0.01) affected both T1 and T2 relaxivities. Field strength did not affect T1 relaxivity (p=0.02511) while it significantly affected T2 relaxivity (p<0.001). This was significant (p=0.035) in case of gadoteridol at 3T.

CONCLUSION

1.25 mmol concentration of both gadoteridol and gadobenate solutions yields the best diagnostic T1 SI specially in higher fields (3T and 7 T) and avoid the deleterious effect of increasing concentration on T2 SI. Gadoteridol is suggested on 3T field indirect MR arthrograms. Protein had no positive effect on either SI or relaxivities in any joint model.

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

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.

MRI of bone marrow edema-like signal in the pathogenesis of subchondral cysts

OBJECTIVE

To determine if a relationship exists between bone marrow edema-like signal and subchondral cysts on magnetic resonance imaging (MRI).

DESIGN

Retrospective cohort of 32 patients with two sequential knee MRI. Patients with acute trauma, infection, neoplasm, or osteonecrosis were excluded. The degree of osteoarthritis was assessed using an adaptation of the Baltimore Longitudinal Study of Aging (BLSA) scale. Initial and follow-up exams were reviewed for presence, location, size and changes of marrow edema-like signal, subarticular cysts and cartilage abnormality. All locations in the knee were aggregated for analysis with descriptive statistics.

RESULTS

The mean time interval between exams was 17.52 months (range 2.1-40.1 months). There were 23 cysts: 11 (47.8%) new, 6 (26.1%) increased size, 1 (4.4%) decreased size, and 5 (21.7%) no change in pre-existing lesions. Cysts always arose from regions of marrow edema-like signal. There were 68 subarticular areas of marrow edema-like signal: 16 (23.5%) new, 23 (33.8%) increased size, 17 (25%) decreased size, 11 (16.2%) resolved and 1 (1.5%) no change in pre-existing lesion. Marrow edema-like signal size always changed with cyst development: increased in 6/11 (54.5%), decreased in 2/11 (18.1%) and resolved in 3/11 (27.2%). Change in cyst size was always accompanied by a change in edema-like signal size. An MRI visible cartilage abnormality was adjacent to 87% (20/23) of cysts. The mean BLSA score changed from 2.6 to 3.6 indicating an overall progression of osteoarthritis.

CONCLUSION

Subchondral cysts develop in pre-existing regions of subchondral bone marrow edema-like signal.

Magnetic resonance imaging of para-acetabular insufficiency fractures in patients with malignancy

AIM

To describe the characteristic magnetic resonance imaging (MRI) findings of para-acetabular insufficiency fractures in patients with malignancy, and compare the MRI appearance of these fractures with that of metastatic bone disease.

MATERIALS AND METHODS

MRI examinations were reviewed in 16 patients with a known malignant tumour and severe hip pain that raised the possibility of local recurrence or metastatic disease. Six patients had received pelvic irradiation, and three patients were receiving steroid medication.

RESULTS

The total number of fractures detected was 21: a solitary fracture was present in 11 patients and five patients had bilateral para-acetabular fractures. Two patients had associated sacral insufficiency fractures, and one of them had stress fractures involving both acetabular columns. Conventional radiography allowed the diagnosis of 14 (67%) fractures; six (28%) radiographic examinations were negative; and one (5%) examination was equivocal for fracture. Available scintigraphic and computed tomography (CT) studies revealed typical findings of fracture. Using MRI, insufficiency fractures appeared as linear regions of low signal intensity on T1- and T2-weighted images. Marked marrow oedema was evident in all cases. Fractures characteristically were parallel to the superior acetabulum in a curvilinear fashion in 18 (86%) instances, and were oblique in three (14%) instances. The fractures demonstrated considerable enhancement after intravenous gadolinium administration. No associated soft tissue masses were documented.

CONCLUSION

Para-acetabular insufficiency fractures are a cause of hip pain, which may mimic skeletal metastasis in the patient with malignancy and pelvic irradiation. Recognition of the characteristic MRI findings of these fractures can preclude misdiagnosis and unnecessary bone biopsy.

Indirect magnetic resonance arthrography

Indirect MR arthrography is useful for evaluation of joints such as the elbow, wrist, ankle and shoulder where there is a large synovial surface area relative to joint volume. It allows simultaneous assessment of both intra-articular and extra-articular soft tissues with the added advantage of minimal invasiveness. The established and potential uses of this imaging technique are reviewed below and the pathology that is demonstrated by this technique is discussed.

Elbow synovial fold syndrome: MR imaging findings

OBJECTIVE

We describe the anatomy and MR imaging appearance of elbow plicae.

MATERIALS AND METHODS

First, five cadavers were evaluated by sectioning and using MR arthrography for evidence of normal or prominent synovial folds to determine the potential origin of elbow plicae. Next, 164 consecutive MR images were evaluated to determine the frequency of the plicae in a clinical population. Last, we retrospectively studied a selected group of eight patients who underwent preoperative MR imaging and in whom enlarged synovial folds were confirmed at surgery.

RESULTS

In the cadavers, the synovial fold appeared to originate from the synovium adjacent to a posterior fat pad. In the clinical population, half the patients showed a synovial fold at the same location; however, most folds were less than or equal to 2 mm in thickness. The eight patients presented clinically with symptoms mimicking an intraarticular body. The synovial fold in symptomatic patients was seen posteriorly just above the olecranon and averaged 3 mm in thickness.

CONCLUSION

A synovial fold extending from the posterior fat pad in the elbow is a frequent finding on MR imaging. In a subgroup of patients, plicae, when thickened, may present clinically as a locking elbow. However, overlap exists between the thicknesses of symptomatic and asymptomatic plicae.

MR imaging of the posterior cruciate ligament graft: initial experience in 15 patients with clinical correlation

PURPOSE

To describe the magnetic resonance (MR) appearance of the posterior cruciate ligament (PCL) graft in the 1st postoperative year and to correlate the MR findings with clinical examination findings.

MATERIALS AND METHODS

Nineteen MR examinations were performed in 15 patients (with 15 grafts) 1-33 months after PCL reconstruction. Results of clinical follow-up were available in 14 patients. Graft shape and thickness were recorded, and intrasubstance signal intensity at T2-weighted imaging was graded. The MR findings were correlated with the time between surgery and clinical examination.

RESULTS

At MR imaging, 13 grafts appeared intact, one could not be assessed owing to hardware artifact, and one initially appeared disrupted. Graft thickness was 7-19 mm. There was no significant difference between graft thickness versus time since surgery and signal intensity versus time since surgery (P =.14). In two of three patients who underwent sequential MR examinations, graft thickness and intrasubstance signal intensity decreased as the time between reconstruction and MR imaging increased. Two of 14 patients who underwent physical examination had a posterior drawer, and one also had an anterior cruciate ligament graft tear. Both patients with knee instability demonstrated intact PCL graft fibers at MR imaging. There was no correlation between knee stability and graft thickness, signal intensity, or shape.

CONCLUSION

After PCL reconstruction, MR imaging in the 1st year depicts a thickened graft with increased signal intensity. There does not appear to be a relationship between clinical stability and findings at MR imaging.

Partial tears of the distal biceps tendon: MR appearance and associated clinical findings

PURPOSE

To describe the magnetic resonance (MR) appearance and associated clinical findings of partial distal biceps tendon tears.

DESIGN

Twenty elbow MR images at 1.5 T, performed over a 7 year period, were reviewed for an appearance of partial tears in the distal biceps. These images were assessed by two musculoskeletal radiologists for the extent of: (a) abnormal signal intensity within the tendon, and the presence of (b) bicipitoradial bursitis, and (c) bony microavulsive injury of the radial tuberosity. Medical records for nine of the 20 cases were reviewed for the clinical findings of ecchymosis, trauma, sensation of a "pop", loss of function, and acuity of onset.

RESULTS

Twenty partial distal biceps tendon tears were seen. All displayed an abnormally increased signal in the distal biceps tendon. Three of 20 (15%) showed a 25% to 50% tear, ten of 20 (50%) showed a 50% tear, and seven of 20 (35%) showed a 75% to 90% tear. Bicipitoradial bursitis was seen in 11 of 20 (55%) cases. Bony microavulsive injury of the radial tuberosity was observed in 10 of 20 (50%). Of the nine cases reviewed for associated clinical findings, surprisingly, only three (33%) experienced an acute traumatic episode with an abrupt onset of pain. An insidious onset was reported in four of nine (44%). Sensation of a "pop" was recorded in only two of nine (22%) cases. Ecchymosis and loss of function were not seen in any of the cases. Finally, surgical conformation was obtained for three cases.

CONCLUSION

Partial distal biceps tendon tears have a characteristic MR appearance, demonstrate little functional deficit, and may be attritional in their etiology due to the observation of a low number of patients reporting trauma or an acute onset.

MRI of the foot and ankle: prevalence and distribution of occult and palpable ganglia

The purpose of this study was to evaluate the prevalence and anatomic distribution of occult and palpable ganglia of the foot and ankle as seen by MRI. Within a 7-year period MRI of the ankle was performed on 2813 patients, and MRI of the foot on 2277 patients using a 1.5T magnet. In all, 167 ganglia in 155 patients were detected. MR images of these patients were reviewed retrospectively by two observers with regard to prevalence, imaging characteristics, and exact anatomic location of ganglia. Clinical findings and (when available) surgical reports were also reviewed. One hundred fifty-seven ganglia in 145 patients were present on MR images of the ankle, and 10 ganglia in 10 patients on MR images of the foot, resulting in a prevalence of 5.6% (157/2813) in the ankle, and a prevalence of 0.4% (10/2277) in the foot. The most common location was the tarsal sinus or tarsal canal (57/167 ganglia [34.1%]). However, only four of these (7%) were palpable as a soft-tissue mass. The second most common location was around the Lisfranc joint (23/167 [13.8%]), of which 11/23 [47.8%] were clinically palpable. Palpable ganglia were statistically larger in size than occult ganglia measured in any of three diameters (P = 0.01-0.002). In addition, ganglia of the foot and ankle represented 42% of all clinically suspected soft-tissue masses. Ganglia in the foot and ankle are an infrequent finding on routine MRI of the foot and ankle. When they occur, these ganglia are most frequently located in the tarsal sinus and tarsal canal, where they are occult to clinical palpation. If ganglia are clinically palpable, they are most commonly located around the Lisfranc joint. In addition, palpable ganglia are larger than occult ganglia.

Partial interosseous ligament tears of the wrist: difficulty in utilizing either primary or secondary MRI signs

PURPOSE

Prior reports on scapholunate ligament (SLL) and lunotriquetral ligament (LTL) tears have evaluated complete tears. As these complete tears have markedly different biomechanical manifestations and surgical considerations than do partial tears, we evaluated the accuracy of MR and the usefulness of secondary MR signs to diagnose partial interosseous ligament tears.

METHOD

Fifty wrists in 50 patients underwent arthroscopy following 1.5 T MR. Images were evaluated by two independent blinded observers for normal or partially torn SLL and LTL and for three secondary signs potentially seen as mechanical sequelae of tears: osseous offset, arc disruption, or focal osteoarthritis.

RESULTS

Arthroscopically, there were 16 SLL and 14 LTL partial tears. Accuracy of primary MR signs of partial tears was lower than that described in the literature for complete tears [sensitivity/specificity (kappa) = 0.56/0.56 (0.12)-SLL, 0.31/0.76 (0.13)-LTL]. Secondary signs showed low sensitivity but high specificity, particularly for LTL tears: arc disruption [0.17/0.83 (0.43)-SLL, 0.0/1.00 (1.0)- LTL], focal osteoarthritis [0.32/0.78 (0.18)-SLL, 0.11/0.91 (0.12)-LTL], and focal osseous offset [0.39/0.75 (0.10)-SLL, 0.26/0.93 (0.39)-LTL]. Additionally, there was poor interobserver consistency for both primary and secondary signs.

CONCLUSION

The sensitivity of morphologic evaluation for diagnosing partial intercarpal ligament tears, particularly those of the LTL, is limited. Secondary signs increase specificity but have low sensitivity, and with the exception of arc disruption, all signs had poor interobserver agreement.

Temporal behavior of intraarticular gadolinium

PURPOSE

As imaging delays during MR arthrography can result in suboptimal studies and potential pitfalls in diagnosis, we sought to evaluate the temporal behavior of intraarticular Gd-DTPA.

METHOD

We prospectively studied four shoulders, four knees, and four hips. Two of each group received either an intraarticular injection of 3 mmol/L Gd-DTPA and iodinated contrast medium or 2 mmol/L Gd-DTPA and 0.9% saline. We measured contrast-to-noise ratio (CNR) and joint distention on serial T1-weighted sequences. Retrospectively, we measured CNR and imaging delays in 31 MR arthrography patients (20 shoulders, 7 knees, and 4 hips).

RESULTS

In the shoulder, maximal CNR and joint distention occurred at 15 min. CNR decreased 53% by 1 h. In the knee, maximal distention occurred at 1 h, whereas CNR peaked at 2.75 h and then declined 20 and 86% by 3.5 and 6.25 h, respectively. In the hip, peak CNR and distention occurred at 0.5 h. CNR declined 53% by 2 h. Both contrast mixtures yielded similar results.

CONCLUSION

MR arthrography may tolerate imaging delays of 1 h for the shoulder, 2 h for the hip, and 3.5 h for the knee.

Injuries to the distal gastrocnemius muscle: MR findings

PURPOSE

The purpose of this work was to demonstrate the MR findings of injuries to the distal gastrocnemius muscle.

METHOD

Twenty patients with clinically confirmed injuries to the distal gastrocnemius muscle underwent MRI. The injuries were evaluated with regard to abnormal morphology or signal abnormality, site, and degree of tearing.

RESULTS

Twenty-three injuries to the distal gastrocnemius occurred in 20 patients, with involvement of the myotendinous junction in 22 of 23 (96%) injuries. An interstitial tear of the proximal Achilles tendon was present in one instance. Myotendinous strains were the most common injuries (10/23; 43%); partial tears (7/23; 30%) and complete tears (5/23; 22%) of the myotendinous junction or proximal Achilles tendon were less frequent. When an injury to the gastrocnemius myotendinous junction was present, involvement of the medial head (19/22; 86%) was more frequent than involvement of the lateral head (3/22; 14%).

CONCLUSION

MRI allows accurate imaging of distal gastrocnemius muscle injuries. When occurring, distal gastrocnemius muscle injuries most frequently involve the myotendinous junction of the medial gastrocnemius head and occasionally the lateral gastrocnemius head or the proximal Achilles tendon.

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.

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 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.

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.

Utility of MR arthrography in the diagnosis of adhesive capsulitis

OBJECTIVE

Arthrographically, adhesive capsulitis is characterized by decreased joint volume; histologically, the capsule and synovium are thickened. We therefore compared using MR arthrography the joint volumes and capsule/synovial thickness of patients with and without adhesive capsulitis in order to assess the utility of MR arthrography in diagnosing adhesive capsulitis.

DESIGN AND PATIENTS

The 1.5 T MR arthrography images of 28 subjects with (n=9) and without (n=19) adhesive capsulitis were compared. Adhesive capsulitis was diagnosed when there was an injected glenohumeral joint volume of less than 10 ml. Two masked observers working in consensus assessed the images for the relative amount of fluid in the biceps tendon sheath and axillary recess, corrugation at the margin of the capsule, capsule/synovial thickness, abnormalities of the rotator interval capsule, and for the presence of a cuff tear.

RESULTS

There was a trend towards differences in capsular and synovial thickness (P>0.07) between the subjects with and without adhesive capsulitis; however, the controls had thicker synovium/capsules. Surprisingly, the amount of fluid in the axillary recess and biceps tendon sheath was not significantly different between the groups (P>0.25). There were more tears of the rotator cuff in controls than in patients with adhesive capsulitis (6, 3 vs 1, 1: complete, partial). Also, both corrugation (7 vs 0) and interval abnormalities (7 vs 0) were more common in the controls.

CONCLUSION

There appear to be no useful MR arthrographic signs of adhesive capsulitis. Capsular/synovial thickness, static fluid volume, and the presence of corrugation are inconclusive as MR arthrographic signs for distinguishing shoulders with adhesive capsulitis from those without.

MR imaging findings of entrapment of the flexor hallucis longus tendon

OBJECTIVE

In this retrospective study, we describe the MR imaging patterns of various causes of flexor hallucis longus tendon entrapment.

CONCLUSION

Entrapment of the flexor hallucis longus tendon may be due to an enlarged os trigonumtarsitarsi, calcaneal fracture, and soft-tissue scar. These disorders have characteristic imaging findings that may be revealed on MR imaging.

Subtendinous bone marrow edema patterns on MR images of the ankle: association with symptoms and tendinopathy

OBJECTIVE

We sought to describe a pattern of subtendinous bone marrow edema on MR images of the ankle and to determine if there is an association with location of symptoms and overlying tendinopathy.

MATERIALS AND METHODS

At 1.5 T, 141 MR examinations of the ankle (116 clinical examinations of patients with chronic pain, 25 of asymptomatic control patients) were performed using T1-weighted, proton density-weighted fast spin-echo, and T2-weighted fat-suppressed fast spin-echo sequences. Images were retrospectively reviewed by two musculoskeletal radiologists for presence of bone marrow edema occurring in a subcortical location associated with the course of the medial or lateral tendon groups, as well as focal thickening or increased T2 signal within the tendons. These findings were correlated with clinical information regarding symptom location. The association of subtendinous marrow edema with tendinopathy and symptom location was statistically analyzed.

RESULTS

Subtendinous bone marrow edema was present at 26 sites on 24 ankle MR examinations (17%) (at the medial malleolus [n = 17] associated with the posterior tibialis tendon, at the lateral malleolus [n = 6] and the calcaneus [n = 2] associated with the peroneus longus and brevis tendons, and at the cuboid [n = 1] associated with the peroneus longus tendon). These subtendinous bone marrow edema patterns were significantly associated with overlying tendon abnormality medially (p = 0.001) and laterally (p = 0.001), and with symptoms medially (p = 0.0016) but not laterally (p = 0.078).

CONCLUSION

On MR images of the ankle, bone marrow edema localized in a subtendinous location is associated with overlying tendinopathy medially and laterally and with ankle pain medially.

Relationships of cervical, thoracic, and lumbar bone mineral density by quantitative CT

PURPOSE

The purpose of this work was to compare, using quantitative CT (QCT), vertebral bone mineral density (BMD) in the cervical, thoracic, and lumbar spine in healthy volunteers.

METHOD

QCT of the vertebral bodies of C2, C5, T12, and L4 was performed on 50 healthy volunteers (25 women, 25 men; mean age 31.7 years). Trabecular BMD analysis was performed at each level.

RESULTS

Mean BMDs (mg/cm3 calcium hydroxyapatite) for women and men were highest at C5 (BMD women/men 341.6/300.6 mg/cm3) and C2 (297.2/269.6 mg/cm3) and lowest at T12 (193.1/184.9 mg/cm3) and L4 (186.2/180.1 mg/cm3). The BMD of C2 was statistically significantly different from that of C5, T12, and L4 (p < 0.0001) for both genders. Also, the BMD of C5 differed significantly from that of T12 and L4 (p < 0.0001). The BMD of C5 showed significant gender differences (p = 0.002). Correlation coefficient showed a strong correlation between the BMD of T12 and L4 for both genders (women, r = 0.67; men, r = 0.90).

CONCLUSION

Trabecular BMD of C2 and C5 measured by QCT is significantly higher than trabecular BMD of T12 and L4 in nonosteoporotic volunteers of both genders.

Utilization of "used" vials: cost-effective technique for MR arthrography

Because full vials of commercially available MR arthrographic contrast are expensive, we hypothesized that the small residual contrast in a "used" vial would be adequate for MR arthrography. After sterility testing and quantity analysis of the residual contrast in 28 vials, this method was successfully used in 10 patients. J. Magn. Reson. Imaging 2000;12:953-955.

MR imaging of the Achilles tendon: overlap of findings in symptomatic and asymptomatic individuals

OBJECTIVE

To differentiate MR imaging characteristics of symptomatic as compared with asymptomatic Achilles tendons.

DESIGN

1.5 T MR images of 94 feet (88 patients) with "abnormal" MR examinations were retrospectively evaluated and clinically correlated. Two masked, independent observers systematically evaluated for intratendon T2 signal, tendon thickness, presence of peritendonitis, retrocalcaneal bursal fluid volume, pre-Achilles edema, bone marrow edema at the Achilles insertion, and tears (interstitial, partial, complete). These findings were correlated with symptoms (onset and duration) and physical examination results (tenderness, palpable defects, increased angle of resting dorsiflexion).

RESULTS

Of the 94 ankles, 64 ankles (32 females, 29 males) were clinically symptomatic. No relationship between Achilles tendon disorders and age or gender was identified. Asymptomatic Achilles tendons frequently demonstrated mild increased intratendon signal (21/30), 0.747 cm average tendon thickness, peritendonitis (11/30), pre-Achilles edema (12/30), and 0.104 ml average retrocalcaneal bursal fluid volume. Symptomatic patients had thicker tendons (0.877 cm), greater retrocalcaneal fluid volume (0.278 ml), more frequent tears (23/64), a similar frequency of peritendonitis (22/64) but less frequent pre-Achilles edema (18/64). Sixty-four percent of the Achilles tendon tears were interstitial. Except for two interstitial tears in control patients, the majority of Achilles tears were in symptomatic patients (14/16). Only symptomatic tendons demonstrated partial or complete tendon tears. In addition, calcaneal edema was found almost exclusively in actively symptomatic patients. Thicker tendons were associated more often with chronic symptoms and with tears. When present in symptomatic patients, peritendonitis was usually associated with acute symptoms. The presence of pre-Achilles edema, however, did not distinguish acute from chronic disorders.

CONCLUSION

There is significant overlap of MR findings in symptomatic and asymptomatic Achilles tendons. Furthermore, there is apparently a spectrum of disease in symptomatic tendons ranging from subtle intratendinous and peritendinous signal to partial and complete tendon tear.

Are L5 fractures an indicator of metastasis?

OBJECTIVE

To determine whether L5 vertebral body fractures are an indicator of malignancy.

DESIGN AND PATIENTS

A retrospective study of L5 vertebral body fractures was carried out using plain radiographs, CT, and/or MRI. Over a 5-year period, 51 patients with L5 vertebral body fractures were seen at our institution. Since L1 vertebral body fractures are common, 51 age- and gender-matched (20 men, 31 women; mean age 60 years) patients with L fractures were utilized as the control group. The frequency of neoplastic infiltration of the vertebrae was compared between these two populations to determine whether pathologic fracture was more frequent at L5.

RESULTS

Twelve (24%) of the L5 fractures were pathologic compared with four (8%) of the L1 fractures (chi-square test, P<0.05). Neoplasm types included multiple myeloma (n=4), prostate (n=3), breast (n=2), lung (n=2), melanoma (n=2), bladder, colon, and leukemia (each n=1).

CONCLUSION

Although most L5 fractures are not pathologic, there is an increased incidence of pathologic fractures in this location compared with L1. Therefore, a fracture of L5 should raise the suspicion of metastasis.

Prevertebral soft tissue swelling following trauma: usefulness following tube placement

OBJECTIVE

Prevertebral soft tissue swelling (PVSTS) is an important marker of spinal trauma. In patients with missed or occult cervical fractures, it may be the only indication of serious injury. It has been anecdotally suggested that PVSTS is not useful following placement of a nasogastric (NGT) or endotracheal (ETT) tube because of possible iatrogenic trauma and/or soft tissue compression. Consequently, we investigated trauma patients for evidence of PVSTS, comparing radiographs performed before and after placement of NGTs and/or ETTs.

DESIGN AND PATIENTS

PVSTS at the C2 and C6 levels was measured on lateral cervical spine radiographs in 102 patients with cervical spine fractures. Measurements were obtained in 66 patients before and after placement of either an NGT (23), ETT (8), or both an NGT and ETT (35). They were also obtained in 36 control patients with fractures and neither an NGT nor ETT, at presentation and after an interval temporally matched to that in the patients with tubes in place.

RESULTS

The group with ETTs showed variable changes to PVSTS (31% increase, 63% decrease, and 6% no change). The group with NGTs also showed variable changes to PVSTS (33% increase, 53% decrease, and 13% no change). The group with ETTs and NGTs similarly showed variable changes to PVSTS (25% increase, 72% decrease, 3% no change). Surprisingly, the control group showed similar temporal changes without tube placement (49% increase, 36% decrease, 13% no change). Analyses using the one-tailed F-test of the ratio of the variance of the tube to non-tube groups and the Mann-Whitney test were performed. No significant difference was found in the prevertebral soft tissues at the C2 level between those with tubes in place and the control subjects. However, at the C6 level there was statistical significance between the groups with NGTs and both NGTs and ETTs versus the non-tube groups. Probability under the F-test for the groups with NGTs and both NGTs and ETTs was 0.001 and 0.005, respectively. Under the Mann-Whitney test, P values for groups with NGTs and both NGTs and ETTs were 0.0002 and 0.0001, respectively.

CONCLUSION

The appearance of PVSTS showed variable and unpredictable changes following ETT, NGT, or combined ETT/NGT placement at the C2 level. This appears to be an artifact of temporal changes. However, at the C6 level, the presence of PVSTS following NGT or ETT and NGT placement (but not ETT placement alone) may be an accurate indirect sign of cervical spine injury.

Complications of total hip arthroplasty: MR imaging-initial experience

PURPOSE

To investigate the use of standard magnetic resonance (MR) imaging sequences with simple parameter modifications for the detection and characterization of total hip arthroplasty (THA) complications.

MATERIALS AND METHODS

An initial phantom study was performed with cobalt-chrome and titanium prostheses to establish the imaging parameters for a subsequent clinical study. In the clinical study, coronal and transverse MR imaging of 14 THA prostheses was performed before and after intravenous contrast material administration in 12 patients who were being considered for revision arthroplasty. The images were reviewed for evidence of juxtaarticular or periprosthetic abnormalities, patterns of contrast enhancement, and quality of periprosthetic tissue depiction.

RESULTS

Phantom study results showed improved periprosthetic tissue depiction with use of thin sections, increased frequency-encoding gradient strength, and fast spin-echo sequences. The clinical study results demonstrated periprosthetic abnormalities in 11 cases: mechanical loosening in two cases (including one case with an associated periprosthetic fracture); granulomatosis, eight; and infection, one. In 100% of cases, tissue depiction around the femoral component was judged to be of "diagnostic quality." Tissue depiction around the acetabular component was of diagnostic quality in five (36%) cases. In all seven surgically confirmed cases, a correct diagnosis was made preoperatively with MR imaging.

CONCLUSION

By using simple modifications to standard MR imaging sequences, diagnostic-quality MR imaging of THA complications can be performed, particularly around the femoral prosthetic stem.

Can imaging findings help differentiate spinal neuropathic arthropathy from disk space infection? Initial experience

PURPOSE

To determine if radiographic, computed tomographic (CT), and magnetic resonance (MR) imaging findings can help differentiate spinal neuropathic arthropathy from disk space infection.

MATERIALS AND METHODS

Imaging studies in 33 patients were evaluated, including 14 patients with spinal neuropathic arthropathy (12 radiographic, seven CT, and six MR studies) and 19 with disk space infection (13 radiographic, nine CT, and 12 MR studies). Potential imaging discriminators, including endplate sclerosis or erosions, osteophytes, spondylolisthesis, facet involvement (narrowing or erosions), vacuum disk, paraspinal soft-tissue mass, joint disorganization, and osseous joint debris, were recorded, as were MR imaging signal intensity and gadolinium-enhancement characteristics.

RESULTS

The most helpful findings for diagnosis of spinal neuropathic arthropathy were vacuum disk on radiographs and CT images, debris on radiographs and CT and MR images, disorganization on radiographs and CT and MR images, facet involvement on radiographs and CT and MR images, spondylolisthesis on CT and MR images, diffuse signal intensity patterns in vertebral bodies on MR images, and rim enhancement of disks on gadolinium-enhanced MR images. Findings that were not helpful included endplate sclerosis and erosions, osteophytes, paraspinal soft-tissue mass, and decreased disk height.

CONCLUSION

Vacuum disk, facet involvement, vertebral body spondylolisthesis, joint disorganization and debris, and gadolinium-enhancement patterns of vertebral bodies and disks may help differentiate spinal neuropathic arthropathy from infection.

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.

Tear of the peroneus longus tendon: MR imaging features in nine patients

PURPOSE

To determine the magnetic resonance (MR) imaging features that characterize tear of the peroneus longus tendon at the midfoot.

MATERIALS AND METHODS

Medical records and MR images in nine patients with a tear of the middle segment of the peroneus longus tendon were retrospectively reviewed. All nine patients had undergone routine ankle MR imaging; three had undergone additional oblique coronal MR imaging. Surgical proof of a tear was available for three patients.

RESULTS

Partial tear was present in four patients, and complete tear was present in five. Partial tears were characterized by heterogeneous signal intensity and thickening of the tendon. Complete tears were characterized by discontinuity of the tendon. Additional findings included fluid in the tendon sheath (n = 6), marrow edema of the lateral calcaneal wall (n = 3), enlarged peroneal tubercle (n = 3), and tear of the peroneus brevis tendon (n = 2). The extent of the tear was better assessed with oblique coronal MR images.

CONCLUSION

The characteristic MR imaging appearance of complete or partial tear of the middle portion of the peroneus longus tendon includes foci of increased signal intensity in the distal tendon, morphologic alterations, and/or discontinuity of tendon. Bone marrow edema along the lateral calcaneal wall may be suggestive of the diagnosis. Additional oblique coronal midfoot MR images may help in assessment of the extent of the tear.

Indirect wrist MR arthrography: the effects of passive motion versus active exercise

PURPOSE

In the wrist, to determine whether passive motion or active exercise yields a better indirect MR arthrographic effect following intravenous gadolinium administration.

DESIGN AND PATIENTS

Twenty-six consecutive patients were studied by indirect wrist MR arthrography. In half active exercise and in half passive motion was performed. Four regions of interest were studied including the distal radioulnar joint, the radiocarpal joint, the midcarpal joint, and the triangular fibrocartilage. Ranges and means of signal intensity were calculated. Surgical follow-up was performed in 22 patients.

RESULTS

The joint fluid intensity was greatest in the distal radioulnar joint. Fluid signal intensity was greater and more consistent in the passive motion group although the results did not achieve statistical significance. Imaging accuracy appeared similar in the two groups and was excellent for the triangular fibrocartilage (100%) and scapholunate ligaments (96%).

CONCLUSION

Active exercise and passive motion yield similar degrees of wrist arthrographic effect, but the effect of passive motion is somewhat more consistent. Preliminary data show good accuracy for internal derangements.

Is computed tomography of nonvisualized C7-T1 cost-effective?

The authors determined the cost-effectiveness of computed tomography (CT) of the inadequately visualized C7-T1 level on conventional radiography in a retrospective cohort study. Routine cervical spine radiography was performed in 360 trauma patients in whom the C7-T1 level was not adequately visualized, but there was no evidence of lower cervical spine injury. In these patients, CT of C7-T1 was performed and reviewed for the presence, location, and pattern of fracture. An orthopaedic surgeon was consulted regarding his proposed treatment and the presumed natural history without treatment of each C7-T1 injury identified. Based on Medicare reimbursement data, cost-effectiveness was then calculated for 1) each fracture identified, 2) each fracture that required surgical fixation secondary to risk of further neurologic sequelae (definitely unstable), and 3) each fracture that required either surgical fixation or halo immobilization secondary to the risk of development of cervical instability and arthritis (potentially or definitely unstable). Eleven of 360 fractures of C7-T1 were identified. The cost-effectiveness of CT for averting potential sequelae was $9,192 for each fracture identified, $16,852 identified for each potentially or definitely unstable fracture identified, and $50,557 for each definitely unstable fracture identified. Computed tomography of the inadequately visualized C7-T1 level on plain radiography is cost-effective, especially given the relatively young age of the trauma population and therefore the high associated morbidity of the sequelae of these injuries over time.

MR imaging of inflammatory joint diseases of the foot and ankle

Pain affecting the foot and ankle is a common complaint frequently attributable to inflammatory joint diseases. Although conventional radiography is regarded as the initial step in the diagnostic investigation, MR imaging may contribute to further evaluation of these patients due to the direct visualization of the inflammatory soft tissue formed in the disease and its effects on bone, cartilage and para-articular structures. The high spatial resolution of MR imaging combined with tissue characterization often allows initial detection of inflammatory joint abnormalities at a stage that precedes radiographic evaluation. The typical MR appearance of certain inflammatory joint disorders may be helpful in narrowing the wide differential diagnosis. Furthermore, MR imaging can be used for an exact assessment of the extent of the disorder as well as its complications. Accurate diagnostic information can guide the clinician in further diagnostic tests and implementation of proper therapeutic treatment.

Internal derangements of the shoulder: decision tree and cost-effectiveness analysis of conventional arthrography, conventional MRI, and MR arthrography

PURPOSE

In a patient with internal derangement of the shoulder, the diagnostic method of choice is controversial. Conventional arthrography can diagnose most rotator cuff tears accurately; however, in many institutions MR arthrography is usually necessary to diagnose labral tears. We utilized decision tree methodology to compare the cost-effectiveness of conventional arthrography and conventional MRI with a hypothetical algorithm in which a patient underwent arthrography, performed with admixed gadolinium, which if negative, was followed by MRI.

DESIGN

The use of double-contrast arthrography alone, conventional MRI alone, and gadolinium-enhanced MRI used as an adjunct to conventional arthrography were modeled for the diagnosis of full-thickness rotator cuff tears (RCT), partial RCTs, labral tears, and the absence of cuff/labral tears using decision analysis methodology. English language medical publications were searched to determine the base probabilities for the accuracy of the diagnostic tests. The outcome utilities ranged from -1 to +1 to reflect the value of correct diagnostic evaluation. Charges for diagnostic tests and appropriate surgical treatments were based on 1997 Medicare reimbursement rates for professional fees and hospital charges in an outpatient setting. Sensitivity analyses were performed to evaluate the effects of uncertainty regarding the prevalence of each disease state and the accuracy of several diagnostic tests.

RESULTS

In the base-case analysis, the average effectiveness of double-contrast arthrography alone, MRI alone and arthrography selectively followed by MRI were 0.6610, 0.6715, and 0.7204, respectively. The average costs for each of these strategies were $1090, $2033, and $2339, respectively.

CONCLUSION

Arthrography performed with admixed diluted gadolinium, which if negative is immediately followed by MRI, was somewhat more expensive than conventional MRI. However, because of much greater effectiveness, cost-effectiveness was significantly higher for our proposed algorithm. Conventional arthrography without gadolinium, although less expensive, had severely limited effectiveness.