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Background: Patellar bone deficiency in revision total knee arthroplasty (TKA) determines the surgical procedure. Different reconstructive and ablative techniques, dependent on the remaining bone stock, are described., Indication: The primary patella implant can be retained in up to 50 % of revision situations. Reasons for replacement are aseptic and septic loosening, implant failure, expanding osteolysis, maltracking of the patella and "metal-backed" prosthesis. The aim of the reconstruction is the stable fixation and proper tracking of the implant by restoring the extensor mechanism., Surgical Procedure: Dependent on the extent of bone loss and the availability of a patellar rim, the following surgical procedures are recommended. When the remaining bone thickness is 10 mm or more: implantation of a polyethylene "onlay-type" patella; when it is between 6-9 mm and there is an intact patellar rim: reconstruction with a biconvex "inlay-type" patella implant, where the biconvex shape replaces the bone defect partially. When there is deficient bone stock (less than 6 mm) or no cortical patellar rim then augmenting procedures with autologous spongiosa and procedures such as "impaction bone grafting", "trabecular metal" prosthesis, where the trabecular part of the implant serves as the base for the cemented polyethylene button, "gull-wing" osteotomy, which is an adapting and configuring technique of osteotomy; and in exceptional cases patelloplasty or patellectomy are used., Conclusion: Regarding the importance of the patellar component in biomechanics of the joint and function of the extensor mechanism, the reconstruction of the patella should be the primary aim. Patelloplasty or patellectomy should be avoided.

Purpose: Few complications have been reported for lumbar total disc replacement (TDR) and hybrid TDR fixations. This study evaluated retrieved implants and periprosthetic tissue reactions for two cases of osteolysis following disc arthroplasty with ProDisc-L prostheses., Methods: Implants were examined for wear and surface damage, and tissues for inflammation, polyethylene wear debris (polarized light microscopy) and metal debris (energy-dispersive X-ray spectroscopy)., Results: Despite initial good surgical outcomes, osteolytic cysts were noted in both patients at vertebrae adjacent to the implants. For the hybrid TDR case, heterotopic ossification and tissue necrosis due to wear-induced inflammation were observed. In contrast, the non-hybrid implant showed signs of abrasion and impingement, and inflammation was observed in tissue regions with metal and polyethylene wear debris., Conclusions: In both cases, wear debris and inflammation may have contributed to osteolysis. Surgeons using ProDisc prostheses should be aware of these rare complications.

Background: The presence of erosions is used for diagnosis and monitoring of disease activity in juvenile idiopathic arthritis (JIA). Assessment of carpal bone erosions in children is challenging due to lack of normal references., Objective: To define normal appearances of bony depressions in the wrist on radiographs and MRI., Materials and Methods: MRI and radiography of the wrist were performed in 88 healthy children, 5-15 years of age. We assessed the number of bony depressions within the carpals/proximal metacarpals on both modalities, separately and combined., Results: A total of 75 carpal depressions were identified on radiography compared to 715 on MRI. The number of bony depressions identified radiographically showed no statistically significant difference across age-groups. Within the metacarpals, there was no significant difference between bony depressions identified by MRI or radiography, except at the bases of the second metacarpal., Conclusion: Bony depressions that resemble erosions are normal findings in the wrist in children. MRI identifies more depressions than radiographs in the carpus. Some bony depressions occur at typical locations and should be accounted for when assessing the wrist in JIA to avoid overstaging.

It was the aim of the present study to find out which radiological imaging techniques allow assessing the extent of bisphosphonate-associated osteonecrosis of the jaw (BONJ) in an adequate way. Twenty-four patients suffering from BONJ were included in the study. Before surgery, each patient was examined with panoramic radiograph, contrast-enhanced magnetic resonance imaging (MRI) and non-enhanced computed tomography. The detectability of BONJ was assessed for the three imaging techniques. The extent of the jaw region affected by BONJ was determined in MRI and CT scans and compared to the intra-operative situation. The detectability of BONJ lesions was 54% for panoramic radiographs, 92% for MRI scans and 96% for computed tomography (CT) scans. The intra-operatively assessed extent of BONJ correlated significantly with the measurements on CT scans (p = 0.0004) but did not correlate significantly with the measurements in MRI scans (p = 0.241). The intra-operatively measured extent of BONJ differed significantly from the CT measurements (p = 0.00003) but not from the MRI data (p = 0.137). Although MRI as well as CT have a high detectability for BONJ lesions that exceeds that of panoramic radiographs by far, both techniques show problems with the exact assessment of the extent of BONJ lesions in the individual patients. Therefore, the relevance of MRI and CT for the preoperative assessment of the extent of BONJ lesions is limited. Future research should focus on the identification of imaging techniques that allow assessing the extent of BONJ lesions with a higher accuracy.

We present the clinical case of an 18-year-old woman who complained of acute hip pain. MRI showed an intra-articular tumor 4 cm in size with osteolysis (18 mm) on the distal region of the femoral head-neck junction. Focal pigmented villonodular synovitis infiltrating the bone was diagnosed. A complete resection of the tumor including the osteolytic area was done by an arthroscopic procedure. There was no sign of relapse after 8 months of follow-up, with no pain and complete function of the hip. Arthroscopic treatment has the advantage of minimal surgical trauma and good mid-term results for treating a focal lesion in selected cases.

Joint pain is one of the major symptoms in early leukemia. We report on a 16-year-old girl who presented with groin pain and an osteolytic bone lesion. Acute lymphoblastic leukemia was diagnosed, but the laboratory workup and radiologic imaging revealed atypical results. Particularly in early precursor B-cell acute lymphoblastic leukemia, comparable initial symptoms and signs have been reported in adolescents; therefore, we recommend performing a bone marrow aspiration early on in cases of suspected osteolytic bone lesions.

We present a case of a pathologic humerus fracture in a patient with the initial diagnosis of Gaucher's disease, which is the most frequent form of lipidosis transmitted as an autosomal recessive trait. It often results in orthopaedic complications with pain, osteonecrosis, fractures and joint infractions. If there is cause for suspicion, beta-glucocerebrosidase in white blood cells should be measured because of the important consequences for treatment. Therapy with a modified enzyme is effective in managing the disease.

Background: Giant cell lesions of the bone present similar histological features. The differential diagnosis comprises central giant cell granuloma, giant cell tumor of bone, and osteitis fibrosa cystica (brown tumor) in combination with hyperparathyroidism. Since these lesions may mimic metastatic bone disease in patients with a history of cancer, a malignant process has to be considered. Since the treatment and prognosis of these entities-benign versus malignant osteolytic bone processes-differ greatly, definitive differential diagnosis is of utmost importance., Case Report: Two patients presenting with osteolytic lesions of the maxilla are reported here. In both cases a history of cancer (breast and prostate) suggested bone spreading of these malignant tumors. The clinical and histological findings were similar in both patients. One lesion was diagnosed as central giant cell granuloma, the other was found to be brown tumour in osteitis fibrosa cystica as an initial manifestation of hyperparathyroidism., Discussion: The presented cases demonstrate the difficulties in establishing the correct diagnosis of patients found to have osteolytic lesions of the jawbones which is critical for the appropriate management of these patients. The article discusses the different entities of osteolytic lesions of the jawbones and the necessary diagnostic and therapeutic approach.

The incidence of focal progressive osteolysis after THR is about 8% and 56%. Most often osteolysis is correlated with macrophage-induced osteoclastic bone resorption as a sequel of inflammatory reaction to wear particles. Recently these findings were published in respect to allergic reactions to implants, their alloying constituents, or bone cement. We report about a patient who developed bilateral localized osteolysis just below the cement mantle 5 years after cemented THR with a Müller straight stem. In the middle of the osteolysis small fragments of bone cement could be detected. Epicutaneous testing showed no reaction against cobalt, chromium, or nickel. Further epicutaneous testing in respect to ingredients of the bone cement were refused by the patient. Histological examination revealed a histiocytic reaction to wear particles and surrounding giant cells. To our knowledge, this is the first case of bilateral localized osteolysis after cemented total hip replacement. Taking all results of the current case into account, it is still unclear if a lymphocytic allergic contact reaction did contribute to the sequel of this case. Reports of immunologically induced incompatibility to components of bone cement, the development of extended testing procedures, and further scientific research should contribute to optimizing the care of patients.

We studied 37 intradiploic epidermoid cysts, reviewing typical and atypical radiological features and the differential diagnosis. The most common clinical feature was a long standing lump in the scalp, occurring in 25 patients (67.7%). Plain films were the most cost-effective radiological technique in diagnosis. The typical finding was a well-defined lytic lesion with sclerotic border, seen in 29 cases (78%). Atypical lesions were those larger than 5 cm and/or with an ill-defined edge, being observed in 8 cases (22%). CT and MRI were the best methods for assessing atypical ones. In all cases with typical radiological findings a preoperative diagnosis of intradiploic epidermoid cyst was suggested.

Diagnosis of bone tumours is still based on plain films and, if necessary, computed tomography because crucial morphologic criteria such as ossification of tumour matrix, patterns of bone destruction and formation of new bone are not clearly visualized by MRI. Only in a few cases is MRI helpful for characterization of bone lesions. Although MRI is of limited value for differential diagnosis of bone tumours, it may be very helpful for planning of biopsy or surgery by virtue of its ability to demonstrate tumour extent and soft tissue changes. For local staging and follow-up of primary bone tumours MRI is clearly the method of choice. MRI strategy should be coordinated with clinical requirements in order to ensure optimum evaluation of tumour extent, effectiveness of chemotherapy and detection of local recurrence.