The Role of Surveillance in Predicting Fracture in Pediatric Patients With Incidentally Discovered Nonossifying Fibromas and Fibrous Cortical Defects: Is It Worth It?

BACKGROUND

Nonossifying fibroma (NOF) and fibrous cortical defect (FCDs), the most common benign pediatric bone lesions, are usually incidental x-ray findings. Surveillance of characteristic lesions has been recommended to monitor for enlargement and assess fracture risk. However, no accepted fracture risk prediction guidelines exist, so indications for prophylactic surgery are unclear. The study's purposes were to (1) characterize the timing of NOF/FCD-associated fractures, (2) quantify the resources devoted to surveillance, and (3) evaluate the potential for surveillance to prevent pathologic fracture.

METHODS

A single institution retrospective review was conducted to identify pediatric patients (below 18 y old) with clinical-radiographic documentation of an NOF or FCD diagnosis from 2012 to 2020. Patients who presented with fracture were tallied but excluded from the surveillance analysis. Patients without at least one follow-up visit were also excluded. Lesional radiographic features were characterized on initial imaging. The number of visits and imaging studies devoted to surveillance were tabulated. The number of fractures and prophylactic surgeries were recorded to quantify the potential of surveillance to prevent pathologic fractures.

RESULTS

The study population presenting without fracture consisted of 301 patients with 364 lesions with a mean follow-up of 20 months. By contrast, over the same period, 38 patients presented with NOF/FCD associated pathologic fractures. Surveillance included 1037 additional imaging tests over 1311 follow-up visits, or on average, 3.4 imaging studies and 4.4 visits per patient. During surveillance, only 2 (0.55%) lesions fractured. Another 10/364 (2.8%) patients underwent curettage and grafting, suggesting that-at best-the potential for preventing pathologic fracture by surveillance, assuming all 10 patients who underwent surgery would have subsequently fractured along with the 2 documented fractures, is 3.3% of lesions (12/364).

CONCLUSIONS

The small number of fractures and surgeries during the follow-up period probably does not justify additional resources for surveillance beyond the initial visit, except in symptomatic patients with large lesions. However, subsequent visits may play a role in educating patients and their families regarding the natural history of these lesions.

LEVEL OF EVIDENCE

Prognostic Level II-retrospective study.

Right Biceps Pseudo-Tumor from COVID-19 Vaccination

Delayed hypersensitivity reactions (DHRs) have been reported in association with COVID-19 vaccines, particularly those that are mRNA-based. Classic DHRs result in induration, erythema, tenderness, and urticaria. However, soft tissue mass is an uncommon complication of a COVID-19 vaccination-associated DHR and is rarely reported in the literature. We present a case of a 49-year-old male who recognized a mildly painful, firm soft tissue mass within the biceps mimicking neoplasm six months after receiving the booster dose of the Moderna vaccine. Non-operative conservative treatment modalities, including heating pads, ice packs, acetaminophen, and ibuprofen, failed to improve the patient's mass. The mass, which proved histologically to be an inflammatory pseudo-tumor, did not recur after complete excision. While there have been many reported cases of DHRs following COVID-19 vaccinations, we present this case to raise awareness of the development of pseudo-tumors as a possible, yet rare, clinical manifestation of DHRs following vaccination.

Ancient Schwannoma of the Thigh: Metaplastic Ossification, Cartilage Formation, and Extensive Calcification

Benign soft tissue masses that present with atypical features on imaging may erroneously be diagnosed as malignant processes. An ancient schwannoma, a schwannoma variant with pronounced degenerative features, is one possible etiology of an incidental soft tissue tumor. This case report describes a 69-year-old male with a history of lung carcinosarcoma who presented to the orthopedic oncology office following an incidental positron emission tomography-computed tomography (PET-CT) finding of a posterior, lateral thigh mass with extensive calcifications. Subsequent excision and pathological analysis revealed an ancient schwannoma with advanced degenerative features, including metaplastic bone and cartilage formation. Various degenerative changes may typically be identified with pathological analysis. In addition to the degenerative findings on pathological analysis, our case highlights an atypical instance where extensive calcification and ossification are evident radiographically. This case emphasizes the importance of considering ancient schwannoma when a calcified soft tissue mass is encountered, in addition to the list of more common calcified soft tissue masses.

Nonossifying Fibroma Involving Epiphysis of Long Bone-Case Report and Review of the Literature

Nonossifying fibroma (NOF) is a common benign bone neoplasm and is usually observed in the first 2 decades of life. Most NOFs occur in the metaphysis of long bones of the lower extremities and migrate toward the diaphysis during skeletal maturation. Epiphyseal involvement by NOF has been rarely reported, with only one case found in the English literature. The authors report the second case of NOF involving the epiphysis of a long bone, the proximal tibia of a 21-year-old woman. Clinicians and pathologists should be aware of the rare possibility of epiphyseal involvement of long bones by this condition. Pathologists should select appropriate immunohistochemistry markers to rule out alternative diagnoses.

A Case Report of Progressive Paget Disease Mimicking a Malignancy: A Second Episode 21 Years Later

Paget osteosarcoma is a rare but serious complication of Paget disease requiring immediate management before further malignant transformation. This case report examines the progression of a previously reported case of Paget disease with atypical pseudotumor manifestation, mimicking osteosarcoma over a 21-year time lapse. After presenting with substantial pain and elevated alkaline phosphatase levels, imaging proved extensive bony expansion of the lesion with high-grade trabecular and cortical thickening and extraosseous soft-tissue extension, prompting the need for biopsy to rule out Paget sarcoma. The atypical features of the pseudotumor's development helps distinguish key radiographic and clinical criteria for malignant development.

Cell cycle arrest and apoptosis are early events in radiosensitization of EWS::FLI1+ Ewing sarcoma cells by Mithramycin A

PURPOSE

The oncogenic fusion protein EWS::FLI1 is an attractive therapeutic target in Ewing sarcoma (ES). Mithramycin A (MithA) is a potent and specific inhibitor of EWS::FLI1 that can selectively radiosensitize ES cells through transcriptional inhibition of DNA double-strand break (DSB) repair. Here, we evaluate temporal changes in cell cycle progression and apoptosis in ES cells treated with MithA and/or ionizing radiation (RTx), testing the hypothesis that combining MithA with ionizing radiation would synergistically impair cell cycle progression and enhance apoptotic elimination to a greater extent than either agent alone.

MATERIALS AND METHODS

Four EWS::FLI1+ ES cell lines TC-71, RD-ES, SK-ES-1, and A673, and one EWS::ERG cell line (CHLA-25) were exposed to 10nM MithA or vehicle and followed 24 h later by exposure to 2 Gy x-radiation or sham irradiation. Reactive oxygen species (ROS) activity was evaluated by cytometric assay, and assay of antioxidant gene expression by RT-qPCR. Cell cycle changes were evaluated by flow cytometry of nuclei stained with propidium iodide. Apoptosis was assessed by cytometric assessment of Caspase-3/7 activity and by immunoblotting of PARP-1 cleavage. Radiosensitization was evaluated by clonogenic survival assay. Proliferation (EdU) and apoptosis (TUNEL) were evaluated in SK-ES-1 xenograft tumors following pretreatment with 1 mg/kg MithA, followed 24 h later by a single 4 Gy fraction of x-radiation.

RESULTS

MithA-treated cells showed reduced levels of ROS, and were associated with increased expression of antioxidant genes SOD1, SOD2, and CAT. It nonetheless induced persistent G0/G1 arrest and a progressive increase of the sub-G1 fraction, suggesting apoptotic degeneration. In vitro assays of Caspase-3/7 activity and immunoblotting of Caspase-3/7 dependent cleavage of PARP-1 indicated that apoptosis began as early as 24 h after MithA exposure, reducing clonogenic survival. Tumors from xenograft mice treated with either radiation alone, or in combination with MithA showed a significant reduction of tumor cell proliferation, while apoptosis was significantly increased in the group receiving the combination of MithA and RTx.

CONCLUSIONS

Taken together, our data show that the anti-proliferative and cytotoxic effects of MithA are the prominent components of radiosensitization of EWS::FLI1+ ES, rather than the result of acutely enhanced ROS levels.

Shoulder Pseudo-Tumor from COVID-19 Vaccine

Hypersensitivity reactions to the COVID-19 mRNA vaccines were identified in the initial 2020 trials. Appearance of a soft tissue mass is a rare manifestation of this hypersensitivity reaction. In this patient, bilateral injections resulted in the appearance of shoulder masses. Magnetic resonance imaging showed localized pseudo-tumorous edema in both shoulders, one subcutaneous and the other intramuscular. This is only the second case of a mass-like reaction to the COVID-19 vaccine mimicking a possible soft tissue neoplasm. Improper vaccination administration technique may have contributed to this complication. The case is presented to increase awareness of this potential pseudotumor.

Extramedullary Hematopoiesis Adjacent to Vertebral Fracture in a Patient with Pernicious Anemia: Support for a Mechanical Extrusion Mechanism

CASE

A 68-year-old woman presented with a paraspinal mass of indeterminate imaging characteristics. Workup and computed tomography-guided Fine Needle Aspiration (FNA) aspiration revealed extramedullary hematopoiesis (EMH) adjacent to a prior compression fracture in the setting of pernicious anemia.

CONCLUSION

The combination of findings suggests a possible relationship of the compression fracture and the EMH because of traumatic extravasation of marrow contents, with the patient's underlying anemia possibly providing an underlying predisposition to EMH.

Modification to Mirels scoring system location component improves fracture prediction for metastatic disease of the proximal femur

BACKGROUND

Correctly identifying patients at risk of femoral fracture due to metastatic bone disease remains a clinical challenge. Mirels criteria remains the most widely referenced method with the advantage of being easily calculated but it suffers from poor specificity. The purpose of this study was to develop and evaluate a modified Mirels scoring system through scoring modification of the original Mirels location component within the proximal femur.

METHODS

Computational (finite element) experiments were performed to quantify strength reduction in the proximal femur caused by simulated lytic lesions at defined locations. Virtual spherical defects representing lytic lesions were placed at 32 defined locations based on axial (4 axial positions: neck, intertrochanteric, subtrochanteric or diaphyseal) and circumferential (8 circumferential: 45-degree intervals) positions. Finite element meshes were created, material property assignment was based on CT mineral density, and femoral head/greater trochanter loading consistent with stair ascent was applied. The strength of each femur with a simulated lesion divided by the strength of the intact femur was used to calculate the Location-Based Strength Fraction (LBSF). A modified Mirels location score was next defined for each of the 32 lesion locations with an assignment of 1 (LBSF > 75%), 2 (LBSF: 51-75%), and 3 (LBSF: 0-50%). To test the new scoring system, data from 48 patients with metastatic disease to the femur, previously enrolled in a Musculoskeletal Tumor Society (MSTS) cross-sectional study was used. The lesion location was identified for each case based on axial and circumferential location from the CT images and assigned an original (2 or 3) and modified (1,2, or 3) Mirels location score. The total score for each was then calculated. Eight patients had a fracture of the femur and 40 did not over a 4-month follow-up period. Logistic regression and decision curve analysis were used to explore relationships between clinical outcome (Fracture/No Fracture) and the two Mirels scoring methods.

RESULTS

The location-based strength fraction (LBSF) was lowest for lesions in the subtrochanteric and diaphyseal regions on the lateral side of the femur; lesions in these regions would be at greatest risk of fracture. Neck lesions located at the anterior and antero-medial positions were at the lowest risk of fracture. When grouped, neck lesions had the highest LBSF (83%), followed by intertrochanteric (72%), with subtrochanteric (50%) and diaphyseal lesions (49%) having the lowest LBSF. There was a significant difference (p < 0.0001) in LBSF between each axial location, except subtrochanteric and diaphyseal which were not different from each other (p = 0.96). The area under the receiver operator characteristic (ROC) curve using logistic regression was greatest for modified Mirels Score using site specific location of the lesion (Modified Mirels-ss, AUC = 0.950), followed by a modified Mirels Score using axial location of lesion (Modified Mirels-ax, AUC = 0.941). Both were an improvement over the original Mirels score (AUC = 0.853). Decision curve analysis was used to quantify the relative risks of identifying patients that would fracture (TP, true positives) and those erroneously predicted to fracture (FP, false positives) for the original and modified Mirels scoring systems. The net benefit of the scoring system weighed the benefits (TP) and harms (FP) on the same scale. At a threshold probability of fracture of 10%, use of the modified Mirels scoring reduced the number of false positives by 17-20% compared to Mirels scoring.

CONCLUSIONS

A modified Mirels scoring system, informed by detailed analysis of the influence of lesion location, improved the ability to predict impending pathological fractures of the proximal femur for patients with metastatic bone disease. Decision curve analysis is a useful tool to weigh costs and benefits concerning fracture risk and could be combined with other patient/clinical factors that contribute to clinical decision making.

Orchestrated delivery of PTH [1-34] followed by zoledronic acid prevents radiotherapy-induced bone loss but does not abrogate marrow damage

Postradiotherapy bone fragility fractures are a frequent late-onset complication in cancer survivors. There is a critical need to develop preventative interventions, and the use of Food and Drug Administration-approved drugs remains an attractive option. Prior data from our lab and others have shown that parathyroid hormone [1-34] mitigates radiotherapy-induced bone loss, but only for the duration of drug delivery. Utilizing a murine hindlimb radiotherapy model, we investigated whether orchestrated delivery of single-dose zoledronic acid could extend these anabolic benefits after cessation of parathyroid hormone delivery. We then explored the potential use of parathyroid hormone as a bone marrow radioprotectant. While the addition of zoledronic acid to parathyroid hormone increased irradiated bone mass, there was no increase in femur bending strength. In this model, the parathyroid hormone was not effective as a marrow radioprotectant, although this could be due to the short course of parathyroid hormone treatment. Marrow repopulation kinetics differed from those in total body irradiation, with hematopoietic stem cell repopulation occurring relatively early at four weeks postirradiation. Furthermore, we found radiation induced a loss of marrow stromal cells and an increase in inflammatory monocytes. Statement of Clinical Significance: Staged delivery of parathyroid hormone and zoledronic acid shows promise as an off-the-shelf intervention to mitigate post-radiotherapy bone damage in cancer patients, but parathyroid hormone is unlikely to function as a broad-spectrum marrow radioprotectant.

Prophylactic surgical treatment using CT-based rigidity analysis vs. after the fact fracture treatment of pathologic femoral lesions

Background

Accurate comparison of prophylactic surgical treatment (PST) to after fracture treatment (AF) of patients with femoral metastatic disease requires more accurately identifying patients for impending fracture, such as with CT-based structural rigidity analysis (CTRA). This study compares a more accurately defined PST group (of impending fractures defined by CTRA) to AF for metastatic femoral disease.

Methods

PST patients were enrolled and treated by the PI in a longitudinal multicenter study of impending pathologic fractures evaluated for accuracy by CTRA. The AF patients were also treated by the senior author and were identified by retrospective chart review. Fifty-five patients were treated surgically for metastatic femoral lesions and were divided into three groups for the purpose of this study: Group I (AF), Group II (PST-high), and Group III (PST-low). Demographic information, comorbidities, and clinical variables of interest were collected by retrospective chart review; cost data was collected by collaboration with our hospital financial personnel (office of the Chief Financial Officer).

Results

Survival showed statistically significant differences favoring Group II. Transfusions in Group I were nearly twice those of Groups II and III, but there was no statistically significant (NS) difference between groups. Estimated blood loss (EBL) was generally with NS difference. Similarly, there were NS differences in LOS between groups. Discharge disposition showed statistically significant differences between groups (P=0.012, global). Discharge to home was highest in Group II (76%) and lowest in Group I (27%). Discharge to rehab was lowest in Group II (24%) and highest in Group I (47%). There were no discharges to hospice or morgue in Group II, while both occurred in Group I. Mean direct and total costs were highest in Group I ($18,837 and $31,997, respectively) and lowest in Group II ($16,094 and $27,357) but the differences were NS.

Conclusions

This study shows benefits of PST over AF in a group of PST patients more accurately defined to have impending pathologic fractures by CTRA definition.

Solitary Radiolucent Erdheim-chester Disease: A Case Report and Literature Review

Background:

Erdheim-chester disease (ECD) is a rare non-Langerhans histiocytosis of unknown etiology, which typically presents with bilateral symmetric osteosclerosis and multi-organ involvement. Lesions may be intraosseous or extraosseous and involve the heart, pulmonary system, CNS, and skin in order of decreasing likelihood.

Objective:

The objective of this study is to discuss a case of erdheim-chester disease and conduct a review of the literature.

Case:

We describe a rare case of erdheim-chester in an asymptomatic 37-year-old male who was diagnosed after suffering a right ulnar injury. Subsequent evaluation revealed a solitary radiolucent ulnar lesion without multi-system involvement.

Results & Conclusion:

The case is unique in its solitary distribution, lytic radiographic appearance, and asymptomatic presentation preceding pathologic fracture. This presentation may simulate multiple other bone lesions.

Total Femoral Replacement for Complicated Echinococcus Infection: Sixteen-Year Follow-up

CASE

Osseous hydatidosis caused by Echinococcus is rare, especially in long bones. To the best of our knowledge, this is the third femoral hydatidosis case with successful osseous eradication through total femoral resection and total femoral megaprosthesis. Unlike the previous 2 cases, we uniquely illustrate recurrent soft-tissue hydatidosis episodes requiring additional hydatid resections for local control with no evidence of disease at final 16-year follow-up, the longest follow-up period of the 3 reported cases.

CONCLUSION

Despite radical bone resection for osseous hydatidosis eradication, additional complex surgical interventions may be needed to locally control soft-tissue disease.

Progressive loss of implant fixation in a preclinical rat model of cemented knee arthroplasty

Aseptic loosening of total knee arthroplasty continues to be a challenging clinical problem. The progression of the loosening process, from the initial well-fixed component, is not fully understood. In this study, loss of fixation of cemented hemiarthroplasty was explored using 9-month-old Sprague-Dawley rats with 0, 2, 6, 12, 26 week end points. Morphological and cellular changes of cement-bone fixation were determined for regions directly below the tibial tray (epiphysis) and distal to the tray (metaphysis). Loss of fixation, with a progressive increase in cement-bone gap volume was found in the epiphysis (0.162  mm³ /week), but did not progress appreciably in the metaphysis (0.007 mm³ /week). In the epiphysis, there was an early and sustained elevation of osteoclasts adjacent to the cement border and development of a fibrous tissue layer between the cement and bone. There was early formation of bone around the cement in the metaphysis, resulting in a condensed bone layer without osteoclastic bone resorption or development of a fibrous tissue layer. Implant positioning was also an important factor in the cement-bone gap formation, with greater gap formation for implants that were placed medially on the tibial articular surface. Loss of fixation in the rat model mimicked patterns found in human arthroplasty where cement-bone gaps initiate under the tibial tray, at the periphery of the implant. This preclinical model could be used to study early biological response to cemented fixation and associated contributions of mechanical instability, component alignment, and periprosthetic inflammation.

Evaluation of triage tool for low-grade cartilage tumors: Four-quadrant approach

BACKGROUND AND OBJECTIVES

The "four-quadrant approach" (FQA) for triage of benign enchondromas (E) and low-grade malignant chondrosarcomas (LGC) divides patients into treatment categories based on the presence or absence of pain and observation of aggressive or benign radiographic features. This article evaluates the usefulness of the FQA in predicting E versus LGC and operative versus nonoperative outcome.

METHODS

Patients had working diagnosis of E or LGC, 1-year minimum follow-up, imaging, clinical data, outcomes, and no radiographic evidence of high-grade chondrosarcoma. Statistical analysis determined whether quadrant distribution correlated to E versus LGC and operative versus nonoperative intervention.

RESULTS

Of 56 lesions (49 patients), 9 were LGC and 47 E. Twenty-five lesions (all 9 LGC, 16 E) were treated operatively and 31 (all E) nonoperatively. There were statistically significant correlations between quadrant distribution and both tumor type (p = 1.9 × 10^-6 ) and operative intervention (p = 6.28 × 10^-6 ).

CONCLUSIONS

The FQA is a promising diagnostic tool to distinguish between E and LGC hyaline cartilage tumors, along with determining operative versus nonoperative intervention. Prospective evaluation is warranted.

Altered mechanical behavior of demineralized bone following therapeutic radiation

Post-radiotherapy (RTx) bone fragility fractures are a late-onset complication occurring in bone within or underlying the radiation field. These fractures are difficult to predict, as patients do not present with local osteopenia. Using a murine hindlimb RTx model, we previously documented decreased mineralized bone strength and fracture toughness, but alterations in material properties of the organic bone matrix are largely unknown. In this study, 4 days of fractionated hindlimb irradiation (4 × 5 Gy) or Sham irradiation was administered in a mouse model (BALB/cJ, end points: 0, 4, 8, and 12 weeks, n = 15/group/end point). Following demineralization, the viscoelastic stress relaxation, and monotonic tensile mechanical properties of tibiae were determined. Irradiated tibiae demonstrated an immediate (day after last radiation fraction) and sustained (4, 8, 12 weeks) increase in stress relaxation compared to the Sham group, with a 4.4% decrease in equilibrium stress (p < .017). While tensile strength was not different between groups, irradiated tibiae had a lower elastic modulus (-5%, p = .027) and energy to failure (-12.2%, p = .012) with monotonic loading. Gel electrophoresis showed that therapeutic irradiation (4 × 5 Gy) does not result in collagen fragmentation, while irradiation at a common sterilization dose (25 kGy) extensively fragmented collagen. These results suggest that altered collagen mechanical behavior has a role in postirradiation bone fragility, but this can occur without detectable collagen fragmentation. Statement of Clinical Significance: Therapeutic irradiation alters bone organic matrix mechanics and which contribute to diminished fatigue strength, but this does not occur via collagen fragmentation.

Intra-articular Extraskeletal EWSR1-Negative NR4A3-Positive Myxoid Chondrosarcoma: A Case Report

CASE

Extraskeletal myxoid chondrosarcomas (EMCs) are rare soft-tissue malignancies. Intra-articular occurrence is even more rare. To our knowledge, this case is one of only 2 reported intra-articular EMC cases of the knee free of local recurrence and/or amputation at follow-up. This case is also distinctive for being fluorescence in-situ hybridization-negative for the typical EMC-balanced translocation t(9;22) which fuses EWSR1 with NR4A3, harboring instead a variant translocation resulting in fusion of NR4A3 with a less common gene fusion partner.

CONCLUSION

This is a unique case of intra-articular EMC of the knee with a rare molecular fingerprint and an unusually positive outcome.

Proximal humerus reconstruction in orthopedic oncology

Proximal humeral reconstructive options following radical resection of proximal humeral primary and metastatic bone malignancies have evolved over time. With the relatively recent advent of the reverse total shoulder (RTSA), this technique has been increasingly employed in this setting over hemiarthroplasty techniques. An array of options, including proximal humeral allograft-prosthetic composites (including both RTSA and hemiarthroplasty), megaprostheses, and osteoarticular allografts, is reviewed from the perspective of their indications, techniques, complications, and published results. An extensive case-based pictorial presentation illustrates these options.

LCH of the Scapula in a 2-Year-Old Masquerading as an ABC: A Case Report and Literature Review

We describe a unique case of Langerhans Cell Histiocytosis (LCH) arising in the scapula of a 2-year old male child masquerading as an aneurysmal bone cyst (ABC) at clinical presentation and on imaging. Scapular involvement is only occasionally noted in LCH cases. Solitary bone involvement in our patient’s age group is uncommon in LCH without multi-organ involvement. Careful pathologic examination and immunohistochemistry was crucial in establishing this diagnosis due to the presence of a solitary lesion with fluid-fluid levels.

Fracture risk assessment and clinical decision making for patients with metastatic bone disease

Metastatic breast, prostate, lung, and other cancers often affect bone, causing pain, increasing fracture risk, and decreasing function. Management of metastatic bone disease (MBD) is clinically challenging when there is potential but uncertain risk of pathological fracture. Management of MBD has become a major focus within orthopedic oncology with respect to fracture and impending fracture care. If impending skeletal-related events (SREs), particularly pathologic fracture, could be predicted, increasing evidence suggests that prophylactic surgical treatment improves patient outcomes. However, current fracture risk assessment and radiographic metrics do not have high accuracy and have not been combined with relevant patient survival tools. This review first explores the prevalence, incidence, and morbidity of MBD and associated SREs for different cancer types. Strengths and limitations of current fracture risk scoring systems for spinal stability and long bone fracture are highlighted. More recent computed tomography (CT)-based structural rigidity analysis (CTRA) and finite element (FE) analysis methods offer advantages of increased specificity (true negative rate), but are limited in availability. Other fracture prediction approaches including parametric response mapping and positron emission tomography/computed tomography measures show early promise. Substantial new information to inform clinical decision-making includes measures of survival, clinical benefits, and economic analysis of prophylactic treatment compared to after-fracture stabilization. Areas of future research include use of big data and machine learning to predict SREs, greater access and refinement of CTRA/FE approaches, combination of clinical survival prediction tools with radiographically based fracture risk assessment, and net benefit analysis for fracture risk assessment and prophylactic treatment.

Radiation-induced changes to bone composition extend beyond periosteal bone

BACKGROUND

Cancer patients receiving radiotherapy for soft tissue sarcomas are often at risk of post-irradiation (post-RTx) bone fragility fractures, but our understanding of factors controlling radiation-induced bone injury is limited. Previous studies have evaluated post-RTx changes to cortical bone composition in the periosteum of irradiated tibiae, but have not evaluated effects of irradiation in deeper tissues, such as endosteal or mid-cortical bone, and whether there are differential spatial effects of irradiation. In this study, we hypothesize that post-RTx changes to cortical bone composition are greater in endosteal compared to mid-cortical or periosteal bone.

METHODS

A pre-clinical mouse model of limited field hindlimb irradiation was used to evaluate spatial and temporal post-RTx changes to the metaphyseal cortex of irradiated tibiae. Irradiation was delivered unilaterally to the hindlimbs of 12-wk old female BALB/cJ mice as 4 consecutive daily doses of 5 Gy each. RTx and non-RTx tibiae were obtained at 0, 2, 4, 8, and 12 wks post-RTx (n = 9 mice/group/time). Raman spectroscopy was used to evaluate spatial and temporal post-RTx changes to cortical bone composition in age-matched RTx and non-RTx groups.

RESULTS

Significant early spatial differences in mineral/matrix and collagen crosslink ratios were found between endosteal and periosteal or mid-cortical bone at 2-wks post-RTx. Although spatial differences were transient, mineral/matrix ratios significantly decreased and collagen crosslink ratios significantly increased with post-RTx time throughout the entire tibial metaphyseal cortex.

CONCLUSIONS

Irradiation negatively impacts the composition of cortical bone in a spatially-dependent manner starting as early as 2-wks post-RTx. Long-term progressive post-RTx changes across all cortical bone sites may eventually contribute to the increased risk of post-RTx bone fragility fractures.

Early Changes in Cement-Bone Fixation Using a Novel Rat Knee Replacement Model

Trabecular resorption from interdigitated regions between cement and bone has been found in postmortem-retrieved knee replacements, but the viability of interdigitated bone, and the mechanism responsible for this bone loss is not known. In this work, a Sprague-Dawley (age 12 weeks) rat knee replacement model with an interdigitated cement-bone interface was developed. Morphological and cellular changes in the interdigitated region of the knee replacement over time (0, 2, 6, or 12 weeks) were determined for ovariectomy (OVX) and Sham OVX treatment groups. Interdigitated bone volume fraction (BV/TV) increased with time for Sham OVX (0.022 BV/TV/wk) and OVX (0.015 BV/TV/wk) group, but the rate of increase was greater for the Sham OVX group (p = 0.0064). Tissue mineral density followed a similar increase with time in the interdigitated regions. Trabecular resorption, when it did occur, started at the cement border with medullary-adjacent bone in the presence of osteoclasts. There was substantial loss of viable bone (~80% empty osteocyte lacunae) in the interdigitated regions. Pre-surgical fluorochrome labels remained in the interdigitated regions, and did not diminish with time, indicating that the bone was not remodeling. There was also some evidence of continued surface mineralization in the interdigitated region after cementing of the knee, but this diminished over time. Statement of clinical significance: Interdigitated bone with cement provides mechanical stability for success of knee replacements. Improved understanding of the fate of the interdigitated bone over time could lead to a better understanding of the loosening process and interventions to prevent loss of fixation. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2163-2171, 2019.

Limited field radiation therapy results in decreased bone fracture toughness in a murine model

Fragility fractures are a well-known complication following oncologic radiotherapy, and it is suspected that radiation-induced embrittlement of bone within the treatment field may contribute to fracture risk. To explore this phenomenon, a mouse model (BALB/cJ) of fractionated, limited field, bilateral hindlimb irradiation (4x5 Gy) was used. The effects of radiation on femoral (cortical) bone fracture toughness, morphology, and biochemistry-including advanced glycation end products (AGEs)-were quantified and compared to Sham group samples prior to irradiation and at 0, 4, 8, and 12 weeks post-irradiation. Additionally, alterations to bone fracture toughness mediated directly by radiation (independent of cellular mechanisms) were determined using devitalized mouse cadaver femurs. Finally, the contribution of AGEs to reduced fracture toughness was examined by artificially ribosylating mouse femurs ex vivo. These data demonstrate that in vivo irradiation results in an immediate (-42% at 0 weeks, p < 0.001) and sustained (-28% at 12 weeks, p < 0.001) decrease in fracture toughness with small changes in morphology (-5% in cortical area at 12 weeks), and minimal changes in bone composition (tissue mineral density, mineral:matrix ratio, and AGE content). Irradiation of devitalized femurs also reduced fracture toughness (-29%, p < 0.001), but to a lesser extent than was seen in vivo. While artificial ribosylation decreased fracture toughness with time, the extent of glycation needed to induce this effect exceeded the AGE accumulation that occurred in vivo. Overall, hindlimb irradiation induced a substantial and sustained decrease in bone fracture toughness. Approximately half of this decrease in fracture toughness is due to direct radiation damage, independent of cellular remodeling. Collagen glycation in vivo was not substantially altered, suggesting other matrix changes may contribute to post-radiotherapy bone embrittlement.

Longitudinal Effects of Single Hindlimb Radiation Therapy on Bone Strength and Morphology at Local and Contralateral Sites

Radiation therapy (RTx) is associated with increased risk for late-onset fragility fractures in bone tissue underlying the radiation field. Bone tissue outside the RTx field is often selected as a "normal" comparator tissue in clinical assessment of fragility fracture risk, but the robustness of this comparison is limited by an incomplete understanding of the systemic effects of local radiotherapy. In this study, a mouse model of limited field irradiation was used to quantify longitudinal changes in local (irradiated) and systemic (non-irradiated) femurs with respect to bone density, morphology, and strength. BALB/cJ mice aged 12 weeks underwent unilateral hindlimb irradiation (4 × 5 Gy) or a sham procedure. Femurs were collected at endpoints of 4 days before treatment and at 0, 1, 2, 4, 8, 12, and 26 weeks post-treatment. Irradiated (RTx), Contralateral (non-RTx), and Sham (non-RTx) femurs were imaged by micro-computed tomography and mechanically tested in three-point bending. In both the RTx and Contralateral non-RTx groups, the longer-term (12- to 26-week) outcomes included trabecular resorption, loss of diaphyseal cortical bone, and decreased bending strength. Contralateral femurs generally followed an intermediate response compared with RTx femurs. Change also varied by anatomic compartment; post-RTx loss of trabecular bone was more profound in the metaphyseal than the epiphyseal compartment, and cortical bone thickness decreased at the mid-diaphysis but increased at the metaphysis. These data demonstrate that changes in bone quantity, density, and architecture occur both locally and systemically after limited field irradiation and vary by anatomic compartment. Furthermore, the severity and persistence of systemic bone damage after limited field irradiation suggest selection of control tissues for assessment of fracture risk or changes in bone density after radiotherapy may be challenging. © 2017 American Society for Bone and Mineral Research.

Osseous Myopericytoma Simulating a Giant Cell Tumor of Bone: A Case Report

CASE

Myopericytoma is a benign perivascular myoid neoplasm that typically presents in the dermal and subcutaneous soft tissues of the distal aspect of the extremities. These types of tumor form a clinicopathological spectrum with myofibromas, angiopericytomas, angioleiomyomas, and glomus tumors. Intraosseous myopericytomas are exceptionally rare, and to our knowledge, no cases of myopericytoma involving long bones previously have been described. We present a case of myopericytoma occurring in the distal aspect of the femur of a 36-year-old man.

CONCLUSION

This case report describes a unique location of this tumor, which demonstrates that myopericytomas have a more diverse tropism than previously indicated.

Chordoma arising from benign multifocal notochordal tumors

This case reports a 25-year-old woman initially diagnosed with adjacent benign notochordal cell tumors (BNCTs) of L3 and L4 based on needle biopsy of L3 and stable imaging over a 3-year period who was ultimately found to have a chordoma arising from a BNCT at L3. It illustrates the potential relationship between benign and malignant notochordal tumors and the difficulty in distinguishing them by clinical, radiological, and even histopathological means.

PTH(1-34) and zoledronic acid have differing longitudinal effects on juvenile mouse femur strength and morphology

Treatment of secondary pediatric osteoporosis-particularly that due to chronic diseases, immobilization, and necessary medical treatments-is currently limited by a poor understanding of the long-term efficacy and safety of skeletal metabolism modifying drugs. This study aimed to characterize longitudinal effects of representative anabolic (parathyroid hormone, PTH) and anti-catabolic (zoledronic acid, ZA) drugs on skeletal morphology, mechanical strength, and growth in juvenile mice. BALB/cJ mice aged 4 weeks were given PTH(1-34) or vehicle (control) daily for 8 weeks, or 4 weekly doses of ZA, and evaluated at time points 0-26 weeks after treatment initiation. There were no enduring differences in body length or mass between treatment groups. ZA increased femur size as early as week 0, including increased distal femur bone volume and diaphyseal cross-sectional area, persisting through week 26. PTH treatment only transiently increased bone size, including distal femur volume at weeks 4-12. ZA decreased diaphyseal cortical tissue mineral density (TMD) at 12-26 weeks versus controls; PTH decreased TMD only at 2 weeks (vs. controls). ZA increased bending strength at 0-12 weeks and flexural strength at week 4 (vs. controls), but decreased flexural strength and modulus at week 26. PTH treatment increased bending strength only at 4 weeks, and did not affect flexural strength. Overall, ZA rapidly and persistently increased femur strength and size, but compromised bone material quality long-term. In healthy juvenile mice, limited-duration PTH treatment did not exert a strong anabolic effect, and had no adverse effects on femur strength, morphology, or growth. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1707-1715, 2017.

Peri-Implant Distribution of Polyethylene Debris in Postmortem-Retrieved Knee Arthroplasties: Can Polyethylene Debris Explain Loss of Cement-Bone Interlock in Successful Total Knee Arthroplasties?

BACKGROUND

Loss of mechanical interlock between cement and bone with in vivo service has been recently quantified for functioning, nonrevised, cemented total knee arthroplasties (TKAs). The cause of interlocking trabecular resorption is not known. The goal of this study is to quantify the distribution of PE debris at the cement-bone interface and determine if polyethylene (PE) debris is locally associated with loss of interlock.

METHODS

Fresh, nonrevised, postmortem-retrieved TKAs (n = 8) were obtained en bloc. Laboratory-prepared constructs (n = 2) served as negative controls. The intact cement-bone interface of each proximal tibia was embedded in Spurr's resin, sectioned, and imaged under polarized light to identify birefringent PE particles. PE wear particle number density was quantified at the cement-bone interface and distal to the interface, and then compared with local loss of cement-bone interlock.

RESULTS

The average PE particle number density for postmortem-retrieved TKAs ranged from 8.6 (1.3) to 24.9 (3.1) particles/mm2 (standard error) but was weakly correlated with years in service. The average particle number density was twice as high as distal (>5mm) to the interface compared to at the interface. The local loss of interlock at the interface was not related to the presence, absence, or particle density of PE.

CONCLUSION

PE debris can migrate extensively along the cement-bone interface of well-fixed tibial components. However, the amount of local bone loss at the cement-bone interface was not correlated with the amount of PE debris at the interface, suggesting that the observed loss of trabecular interlock in these well-fixed TKAs may be due to alternative factors.

Soft-Tissue Tumors: A Pictorial- and Case-Based Guide to Diagnosis and Management

General orthopaedic surgeons must learn how to appropriately evaluate patients with soft-tissue masses who present at their office. Although the incidence of benign soft-tissue sarcomas substantially outnumbers that of malignant soft-tissue sarcomas, the mismanagement of soft-tissue tumors markedly increases a patient's morbidity. The appropriate use of imaging modalities helps general orthopaedic surgeons accurately diagnose a soft-tissue mass, initiate appropriate management of a soft-tissue mass, and gain a better understanding of which patients with soft-tissue lesions should be referred to an orthopaedic oncologist.

Parathyroid Hormone (1-34) Transiently Protects Against Radiation-Induced Bone Fragility

Radiation therapy for soft tissue sarcoma or tumor metastases is frequently associated with damage to the underlying bone. Using a mouse model of limited field hindlimb irradiation, we assessed the ability of parathyroid hormone (1-34) fragment (PTH) delivery to prevent radiation-associated bone damage, including loss of mechanical strength, trabecular architecture, cortical bone volume, and mineral density. Female BALB/cJ mice received four consecutive doses of 5 Gy to a single hindlimb, accompanied by daily injections of either PTH or saline (vehicle) for 8 weeks, and were followed for 26 weeks. Treatment with PTH maintained the mechanical strength of irradiated femurs in axial compression for the first eight weeks of the study, and the apparent strength of irradiated femurs in PTH-treated mice was greater than that of naïve bones during this time. PTH similarly protected against radiation-accelerated resorption of trabecular bone and transient decrease in mid-diaphyseal cortical bone volume, although this benefit was maintained only for the duration of PTH delivery. Overall, PTH conferred protection against radiation-induced fragility and morphologic changes by increasing the quantity of bone, but only during the period of administration. Following cessation of PTH delivery, bone strength and trabecular volume fraction rapidly decreased. These data suggest that PTH does not negate the longer-term potential for osteoclastic bone resorption, and therefore, finite-duration treatment with PTH alone may not be sufficient to prevent late onset radiotherapy-induced bone fragility.

Parathyroid hormone attenuates radiation-induced increases in collagen crosslink ratio at periosteal surfaces of mouse tibia

As part of our ongoing efforts to understand underlying mechanisms contributing to radiation-associated bone fragility and to identify possible treatments, we evaluated the longitudinal effects of parathyroid hormone (PTH) treatment on bone quality in a murine model of limited field irradiation. We hypothesized PTH would mitigate radiation-induced changes in the chemical composition and structure of bone, as measured by microscope-based Raman spectroscopy. We further hypothesized that collagen crosslinking would be especially responsive to PTH treatment. Raman spectroscopy was performed on retrieved tibiae (6-7/group/time point) to quantify metrics associated with bone quality, including: mineral-to-matrix ratio, carbonate-to-phosphate ratio, mineral crystallinity, collagen crosslink (trivalent:divalent) ratio, and the mineral and matrix depolarization ratios. Irradiation disrupted the molecular structure and orientation of bone collagen, as evidenced by a higher collagen crosslink ratio and lower matrix depolarization ratio (vs. non-irradiated control bones), persisting until 12weeks post-irradiation. Radiation transiently affected the mineral phase, as evidenced by increased mineral crystallinity and mineral-to-matrix ratio at 4weeks compared to controls. Radiation decreased bone mineral depolarization ratios through 12weeks, indicating increased mineral alignment. PTH treatment partially attenuated radiation-induced increases in collagen crosslink ratio, but did not restore collagen or mineral alignment. These post-radiation matrix changes are consistent with our previous studies of radiation damage to bone, and suggest that the initial radiation damage to bone matrix has extensive effects on the quality of tissue deposited thereafter. In addition to maintaining bone quality, preventing initial radiation damage to the bone matrix (i.e. crosslink ratio, matrix orientation) may be critical to preventing late-onset fragility fractures.

Image intensive soft tissue sarcoma surveillance uncovers pathology earlier than patient complaints but with frequent initially indeterminate lesions

INTRODUCTION

Post-treatment surveillance follow-up soft-tissue sarcomas is controversial. Protocols are highly variable. This study retrospectively evaluates an image intense protocol to assess benefits of identifying true pathology compared to incidental findings.

METHODS

A retrospective chart review was conducted on a single orthopedic oncologist's soft tissue sarcoma patients under a consistent protocol (TAD). Study population included patients who underwent resection of non-metastatic soft tissue sarcoma (AJCC stages I-III) and either died within surveillance period or completed 5 years of follow-up.

RESULTS

Thirty-nine patients met the strict study criteria. 24/39 (61.5%) patients were identified to have a local recurrence (6), chest metastasis (6), isolated distant recurrence (9), or new primary tumor (3). Of those 24 patients with true pathology, 13 (54%) or 33% (13/39) of all patients potentially benefited from discovery via imaging before patient complaint. Chest CT was the first to reveal all lung metastases. For balance, 32/39 (82%) patients had at least 1 initially "indeterminate" lesion on imaging. Of those, 91% (29/32)-74% of all patients (29/39)-proved to be inconsequential by final follow up.

CONCLUSION

Of the true pathology identified, over half were not evident on clinical presentation, emphasizing the importance of a routine surveillance. However, an image intense surveillance program has a high rate of initially indeterminate findings. J. Surg. Oncol. 2016;113:818-822. © 2016 Wiley Periodicals, Inc.

Does CT-based Rigidity Analysis Influence Clinical Decision-making in Simulations of Metastatic Bone Disease?

BACKGROUND

There is a need to improve the prediction of fracture risk for patients with metastatic bone disease. CT-based rigidity analysis (CTRA) is a sensitive and specific method, yet its influence on clinical decision-making has never been quantified.

QUESTIONS/PURPOSES

What is the influence of CTRA on providers' perceived risk of fracture? (2) What is the influence of CTRA on providers' treatment recommendations in simulated clinical scenarios of metastatic bone disease of the femur? (3) Does CTRA improve interobserver agreement regarding treatment recommendations?

METHODS

We conducted a survey among 80 academic physicians (orthopaedic oncologists, musculoskeletal radiologists, and radiation oncologists) using simulated vignettes of femoral lesions presented as three separate scenarios: (1) no CTRA input (baseline); (2) CTRA input suggesting increased risk of fracture (CTRA+); and (3) CTRA input suggesting decreased risk of fracture (CTRA-). Participants were asked to rate the patient's risk of fracture on a scale of 0% to 100% and to provide a treatment recommendation. Overall response rate was 62.5% (50 of 80).

RESULTS

When CTRA suggested an increased risk of fracture, physicians perceived the fracture risk to be slightly greater (37% ± 3% versus 42% ± 3%, p < 0.001; mean difference [95% confidence interval {CI}] = 5% [4.7%-5.2%]) and were more prone to recommend surgical stabilization (46% ± 9% versus 54% ± 9%, p < 0.001; mean difference [95% CI] = 9% [7.9-10.1]). When CTRA suggested a decreased risk of fracture, physicians perceived the risk to be slightly decreased (37% ± 25% versus 35% ± 25%, p = 0.04; mean difference [95% CI] = 2% [2.74%-2.26%]) and were less prone to recommend surgical stabilization (46% ± 9% versus 42% ± 9%, p < 0.03; mean difference [95% CI] = 4% [3.9-5.1]). The effect size of the influence of CTRA on physicians' perception of fracture risk and treatment planning varied with lesion severity and specialty of the responders. CTRA did not increase interobserver agreement regarding treatment recommendations when compared with the baseline scenario (κ = 0.41 versus κ = 0.43, respectively).

CONCLUSIONS

Based on this survey study, CTRA had a small influence on perceived fracture risk and treatment recommendations and did not increase interobserver agreement. Further work is required to properly introduce this technique to physicians involved in the care of patients with metastatic lesions. Given the number of preclinical and clinical studies outlining the efficacy of this technique, better education through presentations at seminars/webinars and symposia will be the first step. This should be followed by clinical trials to establish CTRA-based clinical guidelines based on evidence-based medicine. Increased exposure of clinicians to CTRA, including its underlying methodology to study bone structural characteristics, may establish CTRA as a uniform guideline to assess fracture risk.

LEVEL OF EVIDENCE

Level III, economic and decision analyses.

CT-based Structural Rigidity Analysis Is More Accurate Than Mirels Scoring for Fracture Prediction in Metastatic Femoral Lesions

BACKGROUND

Controversy continues regarding the appropriate assessment of fracture risk in long bone lesions affected by disseminated malignancy.

QUESTIONS/PURPOSES

The purpose of this ongoing Musculoskeletal Tumor Society-sponsored, multi-institutional prospective cross-sectional clinical study is to compare CT-based structural rigidity analysis (CTRA) with physician-derived Mirels scoring for predicting pathologic fracture in femoral bone lesions. We hypothesized CTRA would be superior to Mirels in predicting fracture risk within the first year based on (1) sensitivity, specificity, positive predictive value, and negative predictive value; (2) receiver operator characteristic (ROC) analysis; and (3) fracture prediction after controlling for potential confounding variables such as age and lesion size.

METHODS

Consented patients with femoral metastatic lesions were assigned Mirels scores by the individual enrolling orthopaedic oncologist based on plain radiographs and then underwent CT scans of both femurs with a phantom of known density. The CTRA was then performed. Between 2004 and 2008, six study centers performed CTRA on 125 patients. The general indications for this test were femoral metastatic lesions potentially at risk of fracture. The enrolling physician was allowed the choice of prophylactic stabilization or nonsurgical treatment, and the local treating oncology team along with the patient made this decision. Of those 125 patients, 78 (62%) did not undergo prophylactic stabilization and had followup sufficient for inclusion, which was fracture through the lesion within 12 months of CTRA, death within 12 months of CTRA, or 12-month survival after CTRA without fracture, whereas 15 (12%) were lost to followup and could not be studied here. The mean patient age was 61 years (SD, 14 years). There were 46 women. Sixty-four of the lesions were located in the proximal femur, 13 were in the diaphysis, and four were distal. Osteolytic lesions prevailed (48 lesions) over mixed (31 lesions) and osteoblastic (15 lesions). The most common primary cancers were breast (25 lesions), lung (14 lesions), and myeloma (11 lesions). CTRA was compared with Mirels based on sensitivity/specificity analysis, ROC, and fracture prediction by multivariate analysis. For the CTRA, reduction greater than 35% in axial, bending, or torsional rigidities at the lesion was considered at risk for fracture, whereas a Mirels score of 9 or above, as suggested in the original manuscript, was used as the definition of impending fracture.

RESULTS

CTRA provided higher sensitivity (100% versus 66.7%), specificity (60.6% versus 47.9%), positive predictive value (17.6% versus 9.8%), and negative predictive value (100% versus 94.4%) compared with the classic Mirels definition of impending fracture (≥ 9), although there was considerable overlap in the confidence intervals. ROC curve analysis found CTRA to be better than the Mirels score regardless of what Mirels score cutoff was used. After controlling for potential confounding variables including age, lesion size, and Mirels scores, multivariable logistic regression indicated that CTRA was a better predictor of fracture (likelihood ratio test = 10.49, p < 0.001).

CONCLUSIONS

CT-based structural rigidity analysis is better than Mirels score in predicting femoral impending pathologic fracture. CTRA appears to provide a substantial advance in the accuracy of predicting pathological femur fracture over currently used clinical and radiographic criteria.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Unexpected radiographic lucency following grafting of bone defects with calcium sulfate/tricalcium phosphate bone substitute

OBJECTIVE

To report the development of unexpected radiographic lucency (URL) corresponding to the use of a commercially available calcium sulfate/tricalcium phosphate composite used to treat benign osseous lesions.

MATERIALS AND METHODS

This is a retrospective comparative study of patients with and without URL after treatment with curettage and grafting with calcium sulfate/tricalcium phosphate. The charts of 87 patients meeting the inclusion criteria were reviewed for demographic, clinical, and radiographic data. The group with URL was compared to those with more typical patterns of graft incorporation.

RESULTS

Thirteen of 87 cases (15%) showed URL. There was no difference with respect to the pathologic subtype, anatomic location, or specific bone for the presence of URL. Of patients with URL, one (7.7%) required reoperation and regrafting, whereas among patients without URL, five (6.7%) had clinical complications, with one requiring reoperation and regrafting, and one requiring radiofrequency ablation.

CONCLUSIONS

The majority of patients treated with calcium sulfate/tricalcium phosphate cementing after curettage of low-grade bone lesions go on to uneventful healing in our series. In a minority of patients, URL occurs in lieu of the more typical pattern of centripetal incorporation. However, there is no increase in complications associated with URL. Based on these findings, patients should be informed of the possibility of this risk, although there appears to be little risk of clinically relevant adverse consequences. Physicians should be aware of this complication in order to avoid mistaking it for recurrence of the primary lesion.

Ewing's sarcoma of bone tumor cells produces MCSF that stimulates monocyte proliferation in a novel mouse model of Ewing's sarcoma of bone

Ewing's sarcoma of bone is a primary childhood malignancy of bone that is treated with X-radiation therapy in combination with surgical excision and chemotherapy. To better study Ewing's sarcoma of bone we developed a novel model of primary Ewing's sarcoma of bone and then treated animals with X-radiation therapy. We identified that uncontrolled tumor resulted in lytic bone destruction while X-radiation therapy decreased lytic bone destruction and increased limb-length asymmetry, a common, crippling complication of X-radiation therapy. Osteoclasts were indentified adjacent to the tumor, however, we were unable to detect RANK-ligand in the Ewing's tumor cells in vitro, which lead us to investigate alternate mechanisms for osteoclast formation. Ewing's sarcoma tumor cells and archival Ewing's sarcoma of bone tumor biopsy samples were shown to express MCSF, which could promote osteoclast formation. Increased monocyte numbers were detected in peripheral blood and spleen in animals with untreated Ewing's sarcoma tumor while monocyte number in animals treated with x-radiation had normal numbers of monocytes. Our data suggest that our Ewing's sarcoma of bone model will be useful in the study Ewing's sarcoma tumor progression in parallel with the effects of chemotherapy and X-radiation therapy.

Simulating activities of daily living with finite element analysis improves fracture prediction for patients with metastatic femoral lesions

Predicting fracture risk for patients with metastatic femoral lesions remains an important clinical problem. Mirels' criterion remains the most formalized radiographic scoring system with good sensitivity (correctly identifying clinical fractures) but relatively poor specificity (correctly identify cases that do not fracture). A series of patients with metastatic femoral lesions had Computed Tomography (CT) scans, were followed prospectively for 4 months, and categorized into fracture (n = 5), non-fracture (n = 28), or stabilized (n = 11) groups. CT based-Finite Element (FE) modeling was used to predict fracture for these cases using axial compression (AC), level walking (LW), and aggressive stair ascent (ASA) loading conditions. The FE predicted fracture force was greater for the non-fracture compared to the fracture group for all loading cases. The ability of the FE models to predict fracture cases (sensitivity) was similar for the groups (Mirels, AC, LW: 80%, ASA: 100%). The ability of the models to correctly predict the non-fracture cases (specificity) was improved for AC (71%) and LW (86%) loading conditions, when compared to Mirels specificity (43%), but poorer for the ASA (21%) conditions. The results suggest that FE models that assess fracture risk using LW conditions can improve fracture prediction over Mirels scoring in a clinical population.

Long-term loss of osteoclasts and unopposed cortical mineral apposition following limited field irradiation

Late-onset fragility fractures are a common complication following radiotherapy for metastatic disease and soft tissue sarcomas. Using a murine hindlimb focal irradiation model (RTx), we quantified time-dependent changes in osteoclasts and mineral apposition rate (MAR). Mice received either a single, unilateral 5 Gy exposure or four fractionated doses (4 × 5 Gy). Osteoclast numbers and MAR were evaluated histologically at 1, 2, 4, 8, 12, and 26 weeks post-RTx. Radiation induced an early, transient increase in osteoclasts followed by long-term depletion. Increased osteoclast numbers correlated temporally with trabecular resorption; the resorbed trabeculae were not later restored. Radiotherapy did not attenuate MAR at any time point. A transient, early increase in MAR was noted in both RTx groups, however, the 4 × 5 Gy group exhibited an unexpected spike in MAR eight weeks. Persistent depletion of osteoclasts permitted anabolic activity to continue unopposed, resulting in cortical thickening. These biological responses likely contribute to post-radiotherapy bone fragility via microdamage accumulation and matrix embrittlement in the absence of osteoclastic remodeling, and trabecular resorption-induced decrease in bone strength. The temporal distribution of osteoclast numbers suggests that anti-resorptive therapies may be of clinical benefit only if started prior to radiotherapy and continued through the following period of increased osteoclastic remodeling.

Treatment Planning and Fracture Prediction in Patients with Skeletal Metastasis with CT-Based Rigidity Analysis

PURPOSE

Pathologic fractures could be prevented if reliable methods of fracture risk assessment were available. A multicenter prospective study was conducted to identify significant predictors of physicians' treatment plan for skeletal metastasis based on clinical fracture risk assessments and the proposed CT-based Rigidity Analysis (CTRA).

EXPERIMENTAL DESIGN

Orthopedic oncologists selected a treatment plan for 124 patients with 149 metastatic lesions based on the Mirels method. Then, CTRA was performed, and the results were provided to the physicians, who were asked to reassess their treatment plan. The pre- and post-CTRA treatment plans were compared to identify cases in which the treatment plan was changed based on the CTRA report. Patients were followed for a 4-month period to establish the incidence of pathologic fractures.

RESULTS

Pain, lesion type, and lesion size were significant predictors of the pre-CTRA plan. After providing the CTRA results, physicians changed their plan for 36 patients. CTRA results, pain, and primary source of metastasis were significant predictors of the post-CTRA plan. Follow-up of patients who did not undergo fixation resulted in 7 fractures; CTRA predicted these fractures with 100% sensitivity and 90% specificity, whereas the Mirels method was 71% sensitive and 50% specific.

CONCLUSIONS

Lesion type and size and pain level influenced the physicians' plans for the management of metastatic lesions. Physicians' treatment plans and fracture risk predictions were significantly influenced by the availability of CTRA results. Due to its high sensitivity and specificity, CTRA could potentially be used as a screening method for pathologic fractures.

The distribution of implant fixation for femoral components of TKA: a postmortem retrieval study

Aseptic loosening of total knee arthroplasty (TKA) components is the foremost cause of implant failure in the long term. While tibial component loosening is of primary concern, femoral loosening may become a clinical problem due to younger, more active patients seeking TKA, and also high-flexion designs. In this study, we analyzed the fixation for 19 non-revised, postmortem retrieved, femoral components of TKA with time in service ranging from 1 to 22 years. We found that the average total contact fraction for cemented components was 9.5% and had a power law response (decrease) with years in service. The average initial interdigitation depth was 0.7mm, and the average current interdigitation depth was 0.13mm. Loss of interdigitation was 81%. Over all, minimal fixation seems necessary for long-term success of TKA femoral components.

Focal therapeutic irradiation induces an early transient increase in bone glycation

Advanced glycation end products (AGEs) are an abnormal modification of the collagenous matrix in bone, and their accumulation contributes to alteration of mechanical properties. Using a mouse model of focal external radiotherapy, we quantified the time-dependent changes in the glycation of bone collagen after 4 daily fractions of 5 Gy exposure to unilateral hindlimb. Fluorometric analysis of decalcified femurs demonstrated a significant and transient increase in the quantity of pentosidine, pyridinolines and nonspecific AGEs per unit of collagen at one week postirradiation. These differences did not persist at 4, 8, 12 or 26 weeks postirradiation. Radiation had no effect on bone collagen content. We hypothesize that following the transient increase in glycation products, these crosslinks are then removed as a result of increased postirradiation osteoclast activity and continued mineralization of the bone.