Cortical Bone Erosion Research Articles

Prevalence of cone beam computed tomography imaging findings according to the clinical stage of bisphosphonate-related osteonecrosis of the jaw

Investigations of cone beam computed tomography (CBCT) for bisphosphonate-related osteonecrosis of the jaw (BRONJ) imaging are rare. The purpose of this study was to investigate the prevalence of typical radiological findings of BRONJ in CBCT. Twenty-seven CBCTs of BRONJ sites were assessed on the basis of the radiological findings (cancellous bone destruction, cortical bone erosion, sequestration, osteosclerosis, and periostal bone formation) and put in relation to the severity of the BRONJ sites. Cancellous bone destruction and cortical bone erosion were the most common findings. Occurrence seems to decrease with decreasing BRONJ severity. Sequestration and osteosclerosis were less frequent and could be seen across all stages. Periosteal bone formation occurred in high-stage BRONJ only. Cancellous bone destruction, cortical bone erosion, sequestration, and osteosclerosis can be seen across all stages and prevalence seems to decrease with decreasing severity of BRONJ. The occurrence of periosteal new bone formation seems to start in high-stage BRONJ.

Bone erosion in rheumatoid arthritis: mechanisms, diagnosis and treatment

Bone erosion is a central feature of rheumatoid arthritis and is associated with disease severity and poor functional outcome. Erosion of periarticular cortical bone, the typical feature observed on plain radiographs in patients with rheumatoid arthritis, results from excessive local bone resorption and inadequate bone formation. The main triggers of articular bone erosion are synovitis, including the production of proinflammatory cytokines and receptor activator of nuclear factor κB ligand (RANKL), as well as antibodies directed against citrullinated proteins. Indeed, both cytokines and autoantibodies stimulate the differentiation of bone-resorbing osteoclasts, thereby stimulating local bone resorption. Although current antirheumatic therapy inhibits both bone erosion and inflammation, repair of existing bone lesions, albeit physiologically feasible, occurs rarely. Lack of repair is due, at least in part, to active suppression of bone formation by proinflammatory cytokines. This Review summarizes the substantial progress that has been made in understanding the pathophysiology of bone erosions and discusses the improvements in the diagnosis, monitoring and treatment of such lesions.

Magnetic Resonance Imaging of Pressure Sores in Spinal Cord Injured Patients: Accuracy in Predicting Osteomyelitis

Identify key magnetic resonance imaging (MRI) features that have a significant correlation with osteomyelitis of pressure ulcers in spinal injury patients. Retrospective review study. Adult patients admitted to the National Spinal Injuries Centre with spinal cord injury (SCI) and signs of pressure ulceration investigated with MRI. Analysis of MRI examinations and clinical records collected over a 4-year period. Images were independently assessed by 2 experienced radiologists for osteomyelitis based on assigned predictive indicators including cortical bone erosion, soft tissue edema, deep collections, heterotopic new bone, hip effusion, and abnormal signal change of the marrow. Thirty-seven patients underwent 41 MRI scans. The prevalence of osteomyelitis was highly correlated with cortical bone erosion (r = 0.84) and abnormal bone marrow changes on T1-weighted images (r = 0.82).

MRI of the temporo-mandibular joint: which sequence is best suited to assess the cortical bone of the mandibular condyle? A cadaveric study using micro-CT as the standard of reference

To determine the best suited sagittal MRI sequence out of a standard temporo-mandibular joint (TMJ) imaging protocol for the assessment of the cortical bone of the mandibular condyles of cadaveric specimens using micro-CT as the standard of reference. Sixteen TMJs in 8 human cadaveric heads (mean age, 81 years) were examined by MRI. Upon all sagittal sequences, two observers measured the cortical bone thickness (CBT) of the anterior, superior and posterior portions of the mandibular condyles (i.e. objective analysis), and assessed for the presence of cortical bone thinning, erosions or surface irregularities as well as subcortical bone cysts and anterior osteophytes (i.e. subjective analysis). Micro-CT of the condyles was performed to serve as the standard of reference for statistical analysis. Inter-observer agreements for objective (r = 0.83-0.99, P < 0.01) and subjective (κ = 0.67-0.88) analyses were very good. Mean CBT measurements were most accurate, and cortical bone thinning, erosions, surface irregularities and subcortical bone cysts were best depicted on the 3D fast spoiled gradient echo recalled sequence (3D FSPGR). The most reliable MRI sequence to assess the cortical bone of the mandibular condyles on sagittal imaging planes is the 3D FSPGR sequence. MRI may be used to assess the cortical bone of the TMJ. • Depiction of cortical bone is best on 3D FSPGR sequences. • MRI can assess treatment response in patients with TMJ abnormalities.

Superimposed Infection in Mandibular Osteoradionecrosis

Radiation therapy can result in osteoradionecrosis (ORN) and mucosal ulceration predisposing to infection. Fourteen patients presenting with infectious sequelae related to mandibular ORN were retrospectively reviewed. In most patients, infection followed diagnosis of ORN; but in 4 patients, ORN was not diagnosed until after the time of infection and imaging. An early imaging finding of ORN was lingual cortical defects near the last molar. Pain followed by erythema, purulent drainage, and subperiosteal abscess by imaging were the most common signs of infection. In most patients, conservative management eventually failed and segmental mandibulectomies were required. Soft tissue infection with characteristic bone findings such as subperiosteal abscess and cortical bone erosions helps to distinguish infected ORN from recurrent tumor or sterile ORN. In patients previously treated with radiation who present with infection, pain or an avid PET scan with bone involvement, the mandible should be scrutinized.

Expansile dentigerous cyst invading the entire maxillary sinus: a case report

J Korean Assoc Oral Maxillofac Surg 2012;38:245-8) Reported cases of a large dentigerous cyst involving the whole maxillary sinus are uncommon. A 22-year-old female patient suffering from swelling of the right infraorbital area and cheek with dull pain was referred to our department. Findings on computed tomography (CT) and magnetic resonance imaging (MRI) revealed a huge mass containing a displaced maxillary third molar involving the right maxillary sinus as a whole, with partial erosion of the posterior sinus cortical bone. Under general anesthesia, the mass was enucleated using the Caldwell-Luc approach, and, following histopathological analysis, was diagnosed as a dentigerous cyst. The case was followed for a period of seven years, and no evidence of sinus infection or recurring cyst formation was observed during that time. 1 .�Cysticdevelopentis� usuallyrelatedtouneruptedthirdmolarormaxillarycanine,� andithasthetendencyofdisplacingtherelatedtooth.�A� cystformedaroundthemaxillarythirdmolarmayinvade� themaxillarysinus,�growingunnoticedtosuchextensive� sizeastooccupyaconsiderableportionofthemaxillary� sinus.�Asthecystgrows,�thebonywallsoverlyingthecyst� thinout,�givingrisetoaneggshellsensationuponpalpation� andpossiblytransmittingpressuretothewallsofthesinus;� thuscausingophthalmologicandnasalsymptomstodevelop 2 .� Someuntreateddentigerouscystsmay-inrarecases-grow�

Multimodality imaging of chronic tophaceous gout

The diagnosis of gout is usually based on clinical presentation and laboratory findings. Imaging plays a role in the assessment and grading of articular damage related to chronic, long-standing disease, which is characterized by granulomatous synovitis, tophi, and erosions. Multimodality imaging of chronic tophaceous gout may be useful in clinical practice for a variety of purposes, including assessment of disease-related anatomical changes and monitoring of articular and soft-tissue lesions over time, especially in response to urate-lowering therapy. Radiography remains the primary imaging technique. Ultrasonography may detect monosodium urate crystals on cartilage, is helpful to assess small joint effusion, to guide to joint aspiration, and to evaluate the volume of tophi. Computed tomography is considered to be more sensitive than plain radiography in the detection and evaluation of cortical bone erosions associated with tophi. MRI represents the only imaging modality which provides visualization of bone marrow oedema associated with erosions and may be useful to characterize and distinguish tophi from other soft tissue nodules.

A Case of an Extensive Dentigerous Cyst in the Maxillary Sinus Leading to Epiphora and Nasal Obstruction

BackgroundThe dentigerous cyst is defined as a cyst that originates by the separation of the follicle from around the crown of an unerupted tooth. The clinical examination reveals a missing tooth or teeth and possibly a hard swelling, sometimes resulting in facial asymmetry and possible pathologic fracture. A large maxillary cyst involves the whole sinus and can transmit pressure to the walls of the sinus and, consequently, cause ophthalmologic and nasal symptoms to develop. ObjectivesTo report the case of an extensive dentigerous cyst with swelling of the right cheek, accompanied by unilateral nasal obstruction and epiphora. Case ReportA 21-year-old man presented with swelling of the right cheek, right-sided nasal obstruction, and watering of the right eye. Panoramic radiography revealed a relatively large and well-defined radiolucency enveloping an unerupted maxillary canine tooth. Computed tomography scan showed a cystic lesion measuring 5.2 cm horizontally, 4.3 cm vertically, and 4 cm sagittally, with expansion and erosion of the anterosinus cortical bone. The mass was seen to extend into the right half of the nasal cavity up to the right ethmoid air cells, and was in contact with the base of the skull. The bony margins of the right maxillary antrum were thinned out, the osteomeatal complex was pushed medially-superiorly, and the pterygoid plates were intact. Excision of the dentigerous cyst of the right maxilla was performed using the Caldwell-Luc approach under general anesthesia. ConclusionA dentigerous cyst arising from an unerupted tooth should be considered in the differential diagnosis of nasal obstruction, watering or epiphora of the eye, and fistula of the gingivobuccal sulcus.

Ability of ultrasound imaging to detect erosions in a bone phantom model

ObjectivesThe authors examined the validity, interobserver reliability and interscanner variation in detecting bone erosions with ultrasonography using a custom-made phantom.Methods21 bovine bones were used. Artificial erosions were made into 15...

Assessment of Achilles enthesitis in the spondyloarthropathies by colour Doppler energy ultrasound in the context of the ‘enthesis organ’

Objectives: To identify the characteristic features of Achilles enthesitis of the spondyloarthropathies (SpA) detectable by colour Doppler energy ultrasound (CDEU) in the context of the ‘enthesis organ’.Methods: Seventy patients with SpA and 15 healthy subjects were clinically evaluated and underwent CDEU examination of the Achilles entheses. The CDEU images were evaluated according to five distinctive CDEU features of enthesitis in the context of the enthesis organ.Results: Fifty-six of the 70 SpA patients (80%) showed at least one abnormal finding of the enthesitis on CDEU examination, affecting 91 of 140 Achilles entheses examined (65%). Only 22 of 140 Achilles entheses (15.7%) showed abnormal vascularization in the peri-sesamoidal and periosteal areas or in the area of enthesis fibrocartilage. In addition, 67 (47.9%) and 18 (12.9%) of 140 Achilles entheses examined showed cortical bone irregularities and erosions, respectively, at areas of the periosteal and the enthesis fibrocartilage. Sixteen (88.9%) of 18 clinically detected Achilles enthesitis and six (75%) of eight Achilles entheses with swelling on clinical examination presented corresponding abnormalities on CDEU examination. The Doppler twinkling artefact (TA) was observed consistently in all normal entheses and completely disappeared upon stabilization of the probe application. The C-reactive protein (CRP) level was higher in the patients with cortical bone erosion than in those without erosion.Conclusions: This study demonstrates the characteristic features of enthesitis detectable by CDEU in the context of the enthesis organ and shows a good correlation with clinical as well as with laboratory findings.

Computerized tomographic findings in bisphosphonate-associated osteonecrosis of the jaw in patients with cancer

To study bisphosphonate-associated osteonecrosis of the jaw with respect to radiographic, demographic, and clinical features. Thirty-two patients with painful exposed bone in the jaws subsequent to treatment with bisphosphonates for various neoplastic diseases were examined with both dental panoramic radiograph and multislice spiral computerized tomography (CT). Each case was assessed for the following radiologic signs: structural alteration of trabecular bone, cortical bone erosion, osteosclerosis, small sequestrum, extensive sequestrum, and presence of periosteal new bone. The McNemar, chi2, and Kruskall-Wallis tests were performed to analyze the association between radiologic signs, demographic data, clinical aspects of the lesion, and type and duration of bisphosphonate therapy. Hierarchical cluster analysis was used to group patients into categories on the basis of CT signs and dental panoramic radiograph signs. The agreement between CT and dental panoramic radiograph clusters was analyzed by kappa index. Dental panoramic radiograph proved positive for features of osteonecrosis in 18 cases and CT in 30. Computerized tomography was far superior to dental panoramic radiograph in detecting all the radiologic signs. The cluster analysis applied to CT signs showed a classification of the 32 patients in 4 categories characterized by an increasing number of signs coherent with the clinical extension of the lesions. Structural alteration of trabecular bone and cortical bone erosion, a constant finding in the 30 positive CTs, could be sometimes differentiated only with difficulty from those due to recent extraction. Dental panoramic radiograph missed the correct diagnosis of sequestration in 15 cases. Intense periosteal reaction was often found. The most extensive maxillary lesions were associated with new bone formation in Schneider mucous membrane, never described previously, and oroantral communications. Dental panoramic radiograph were found to be of limited use in assessing bisphosphonate-associated osteonecrosis of the jaw in patients for whom CT imaging was subsequently ordered.

The Role of the Otorhinolaryngologist in the Management of Central Skull Base Osteomyelitis

Skull base osteomyelitis (SBO) typically evolves as a complication of external otitis in diabetic patients and involves the temporal bone. Central SBO (CSBO) mainly involves the sphenoid or occipital bones without coexisting external otitis. We characterized a group of patients with CSBO. The endoscopic nasopharyngeal and clival biopsy technique is described. Medical records of patients diagnosed as having SBO were retrospectively analyzed (from 2001 to 2006). Patients' symptoms and signs, laboratory findings, imaging characteristics, endoscopic clival and periclival histopathology results, treatment, and outcome were retrieved. Of 20 patients with SBO, 6 patients without external otitis were studied (age range, 54-76 years; 5 men; mean follow-up, 21 months). All patients suffered from unilateral headache, three of six patients had serous otitis media (SOM), three of six patients had cranial nerve (CN) palsies, and five of six patients had elevated acute-phase reactants. Computed tomography (CT) findings were clival cortical bone erosion and adjacent soft tissue swelling. Magnetic resonance (MR) findings were texture changes and enhancement of the involved bones and soft tissues. Biopsy specimens revealed chronic inflammation. All six patients were treated with antibiotics for 3-6 months. Headache disappeared in five of six patients, SOM resolved in two of three patients, and CN palsies partially recovered in two of three patients. Imaging findings improved in five of six patients. CSBO may mimic malignancy and represents a diagnostic challenge. Typical clinical picture and imaging findings together with a positive response to ciprofloxacin may suffice to establish the diagnosis and obviate the need for biopsies. When in doubt, nasopharyngeal and clival biopsies are performed to rule out malignancy.

SAPHO Syndrome: MR Appearance of Vertebral Involvement

To retrospectively evaluate the magnetic resonance (MR) imaging findings of vertebral involvement in patients with synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome. Ethics committee approval and informed patient consent were not required for this retrospective study. MR images obtained in 12 patients (seven female, five male; mean age, 42 years; range, 16-65 years) with SAPHO syndrome involving the spine were reviewed. One vertebral lesion separated by one or more normal vertebrae was analyzed as a distinct lesion. For each lesion, the number of associated vertebrae with abnormal signal intensity (SI) (ie, single vertebra, two adjacent vertebrae, or more than two adjacent vertebrae) was noted. The following MR imaging findings were evaluated: cortical bone erosion, abnormal vertebral body SI compared with normal vertebral body SI, increased anteroposterior diameter of the vertebral body, soft-tissue involvement, vertebral body height loss of more than 30%, and abnormal SI of the adjacent intervertebral disk compared with the SI of the other disks. Of 24 vertebral lesions found, 17 involved a single vertebra, four involved two adjacent vertebrae, and three involved three or four adjacent vertebrae. Vertebral corner cortical erosion was present in all lesions, and 23 (96%) lesions had anterior vertebral corner involvement. The erosion was confined to a vertebral corner in five (21%) lesions and included the adjacent endplate and/or the anterior cortex of the vertebral body in the remaining 19 (79%) lesions. In four (17%) lesions, involvement of two adjacent vertebral corners on either side of an intervertebral disk mimicked to some extent early disk space infection. An adjacent disk space was narrowed in six (25%) lesions and exhibited abnormal SI in two (8%). Prevertebral tissue thickening was observed in eight (33%) lesions. Erosion of a vertebral body corner is consistently seen on MR images of SAPHO vertebral lesions and may support the diagnosis of SAPHO syndrome in the appropriate clinical context.

Increased Myeloid Cell Responses to M-CSF and RANKL Cause Bone Loss and Inflammation in SH3BP2 “Cherubism” Mice

While studies of the adaptor SH3BP2 have implicated a role in receptor-mediated signaling in mast cells and lymphocytes, they have failed to identify its function or explain why SH3BP2 missense mutations cause bone loss and inflammation in patients with cherubism. We demonstrate that Sh3bp2 "cherubism" mice exhibit trabecular bone loss, TNF-alpha-dependent systemic inflammation, and cortical bone erosion. The mutant phenotype is lymphocyte independent and can be transferred to mice carrying wild-type Sh3bp2 alleles through mutant fetal liver cells. Mutant myeloid cells show increased responses to M-CSF and RANKL stimulation, and, through mechanisms of increased ERK 1/2 and SYK phosphorylation/activation, they form macrophages that express high levels of TNF-alpha and osteoclasts that are unusually large. M-CSF and RANKL stimulation of myeloid cells that overexpress wild-type SH3BP2 results in similar large osteoclasts. This indicates that the mutant phenotype reflects gain of SH3BP2 function and suggests that SH3BP2 is a critical regulator of myeloid cell responses to M-CSF and RANKL stimulation.

Periarticular Bone Findings in Rheumatoid Arthritis: T2-Weighted Versus Contrast-Enhanced T1-Weighted MRI

The purpose of this study was to establish the relative predictive value of T2-weighted and contrast-enhanced T1-weighted MRI techniques for bone erosions that are evident on CT. Because it is known that MRI depicts abnormalities in the periarticular bone of patients with rheumatoid arthritis, we wanted to compare the outcomes of T2-weighted versus contrast-enhanced T1-weighted MRI techniques. Eleven patients with rheumatoid arthritis underwent CT imaging of their most affected wrist. Fast spin-echo T2-weighted MR images were then acquired with spectral fat saturation. Enhanced T1-weighted spin-echo images acquired before and after IV administration of gadopentetate dimeglumine were used to determine the percent enhancement. Imaging examinations were scored for 15 anatomic zones. The CT score was based on cortical bone erosion. The MR score was based on periarticular bone marrow signal alteration. Both T2-weighted MR images with spectral fat saturation and enhanced T1-weighted images were concordant for the presence or absence of bone abnormalities in 122 of 165 zones (74%). Of the 43 zones that were discordant for an abnormality by the two MR techniques, the T2-weighted images were positive in five zones, and enhanced T1-weighted images were positive in 38 zones (p < 0.001). Of the 43 zones that were discordant by the two MR techniques, enhanced T1-weighted images were concordant with CT in 20 zones, whereas the T2-weighted images were concordant with CT in 23 zones (p = 0.76). A greater proportion of lesions detected by the T2-weighted images were "edema-like" signal patterns. In rheumatoid arthritis, contrast-enhanced T1-weighted MRI depicts more periarticular bone abnormalities than fat-suppressed T2-weighted MRI. These MR techniques are equally predictive of frank, erosive disease that is evident on CT.

Image-Guided Corticosteroid Injection of Calcific Tendonitis of Gluteus Maximus

Gluteus maximus tendonitis with its clinical and imaging patterns has been described in radiologic, orthopedic, and rheumatology texts and journals. Image-guided treatment, however, is not a familiar approach and has only been described in one case report in the English literature to the best of our knowledge. We present 4 patients with calcific tendonitis of the gluteus maximus who presented with excruciating pain in the posterior upper thigh with limitation of daily activities. The diagnosis was based on the characteristic radiologic appearances of calcifications in the tendon with cortical bone erosion and muscle edema. Treatment was with image-guided (fluoroscopy or computed tomography) injection of a local anesthetic and corticosteroid. All patients were pain-free on follow up.

Diagnostic value of magnetic resonance imaging and computed tomography for oral masses in dogs

The purpose of this study was to determine the diagnostic value of magnetic resonance imaging (MRI) and computed tomography (CT) in oral masses of dogs. Nineteen dogs underwent clinical, MR and CT examinations. Eleven malignant and ten non-malignant masses were evaluated. Osteosarcoma was the most commonly found malignant oral mass and gingival hyperplasia was the most commonly found benign mass. The results showed that MRI provided more accurate information regarding the size of the masses and invasion of adjacent structures although MRI and CT show similar accuracy in assessment of bone invasion. Calcification and cortical bone erosion was better seen on CT images. Whereas contrast-MRI provided useful additional information, contrast-CT had no added benefit. In general, oral masses located in the caudal mandible, oropharynx and maxilla are better evaluated using MRI, once the histological type has been verified.

Increase in expression of receptor activator of nuclear factor kappaB at sites of bone erosion correlates with progression of inflammation in evolving collagen-induced arthritis.

The receptor activator of nuclear factor kappaB (RANK)/RANK ligand (RANKL) pathway is critical in osteoclastogenesis and bone resorption and has been implicated in the process of focal bone erosion in arthritis. This study was undertaken to identify in vivo the hitherto-unknown origin and localization of RANK-expressing osteoclast precursor cells at sites of bone erosion in arthritis. DBA-1 mice were immunized with bovine type II collagen/Freund's complete adjuvant and were given an intraperitoneal booster injection of type II collagen on day 21. Arthritis was monitored visually, and joint pathology was examined histologically. RANK and RANKL expression were analyzed using specific immunohistochemistry, and tartrate-resistant acid phosphatase (TRAP) staining was performed. In addition, TRAP and cathepsin K messenger RNA expression were analyzed by in situ hybridization. A marked increase in the number of cells expressing RANK correlated with the progression of synovial inflammation and clinical disease severity in evolving collagen-induced arthritis (CIA). Interestingly, RANK expression demonstrated a gradient pattern with increased numbers of RANK-positive cells within the synovial infiltrate in areas closer to periosteum and cortical bone. Cells expressing RANK included cells in synovial tissue, bone lining cells on the surface of trabecular bone at sites of erosion, and cells in periosteal areas adjacent to synovial inflammation. In areas where RANK-positive cells were abundant, TRAP-positive, multinucleated osteoclast-like cells were also present at sites of focal bone erosion, suggesting differentiation of synovially derived RANK-positive osteoclast precursor cells into osteoclasts. In addition, TRAP- and cathepsin K-double-positive osteoclast-like cells were detected on the synovial side of cortical bone at sites of early and advanced cortical bone erosion. Sites of RANK expression also correlated well with sites of RANKL expression, and there was a close correlation of the temporal expression of the receptor-ligand pair. Cells expressing RANK increased in abundance with the progression of arthritis in evolving CIA, and sites of RANK-expressing cells correlated with sites of TRAP-positive, multinucleated osteoclast-like cells as well as with sites of RANKL expression. These data support the hypothesis that the RANK/RANKL pathway plays an important role in the process of bone erosion in CIA.

Periosteal chondroma: MR characteristics.

The purpose of this study was to describe the MR characteristics of periosteal chondroma. MR images of 12 proven cases of periosteal chondroma were analyzed with reference to tumor morphology and size. MR features were correlated with radiographic and pathologic findings. Tumor size ranged from 1 to 7 cm in maximum diameter with a mean value of 2.6 cm. On MR images, a soft tissue mass at the bone surface with pressure erosion of adjacent cortical bone could be identified in all cases. All lesions were bordered by a hypointense rim (100%) and frequently showed a lobulated configuration (75%). Edema of medullary bone or soft tissues was not observed in any of the cases. Signal intensity of cartilaginous tumor tissue was typically hypo-or isointense relative to muscle on T1-weighted (100%) and hyperintense relative to fat on T2-weighted (92%) and T2*-weighted (100%) MR images. Radiographically significant calcifications of the tumor matrix, present in half of the cases, caused focal signal loss on MR images of all pulse sequences. Contrast enhancement was observed predominantly at the periphery of the lesions (100%), which on pathologic examinations typically contained fibrovascular bundles, surrounding the cartilage lobules. Periosteal chondroma appears to have a relatively typical MR appearance, which reflects the histologic composition of the lesion. In addition to radiography, MRI therefore can substantially aid in the preoperative diagnosis of this rare bone lesion.

Calcific tendinitis of the gluteus maximus tendon with abonormalities of cortical bone

Calcific tendinitis of the gluteus maximus tendon is unusual and only eight cases associated with erosions of cortical bone have been reported. We present three further cases which demonstrate variation in appearances of the amorphous calcification in the tendon and cortical erosions on plain radiographs. Isotope bone scans show focal increased activity and computed tomography (CT) clearly demonstrates erosion of cortical bone and calcification within the tendon insertion of gluteus maximus. Follow-up examinations in two cases demonstrated resolution of the changes. We believe this series demonstrates the radiological features and natural history of a common condition occurring at an unusual site. Its recognition is important in order to avoid unnecessary surgical intervention. Resolution of the calcification and cortical erosions has not been previously described.