Incidence of atypical femoral fractures in the treatment of bone metastasis: An alert report

Frequency and pathogenesis of periprosthetic atypical femoral fractures associated with total knee arthroplasty: A multicenter prospective study with complementary histopathological and biomechanical analysis

INTRODUCTION

Although the diagnostic criteria for atypical femoral fracture (AFF) exclude periprosthetic fractures, reports of periprosthetic femoral fractures with characteristics of AFF are rapidly increasing. In this study, we investigated the frequency and pathogenesis of periprosthetic AFF associated with total knee arthroplasty (TKA) based on a theory of AFF subtypes that divides AFFs into two main types: fragility stress fractures of the bowed femoral shaft in the mid-shaft and "typical" subtrochanteric AFFs due to suppression of bone turnover (e.g., by bisphosphonates).

PATIENTS AND METHODS

This multicenter prospective study of AFFs was conducted from 2015 through 2022. Clinical, pathological, and morphological characteristics were investigated in patients with periprosthetic AFFs associated only with non-stem TKA. Then, biomechanical investigation of the periprosthetic AFF was performed by computer tomography-based finite element analysis (CT/FEA) using two models with different load axes to examine how the correction of lower limb alignment by TKA influences the tensile stress distribution of the femur and the location of the AFF.

RESULTS

Four of 61 AFFs (6.6%) were identified to be periprosthetic AFF (1 mid-shaft; 3 subtrochanteric). Periprosthetic AFFs had characteristics including mechanical stress due to bowing deformity and potentially suppressed bone turnover due to long-term exposure to specific drugs (e.g., bisphosphonates and glucocorticoids). Although 2 periprosthetic AFFs appeared to involve a bowed femur, one with both of the aforementioned characteristics occurred in the subtrochanteric region, which would be an unusual site for a bowed AFF, and it was demonstrated histologically to have biological activity at the fracture site, suggesting a stress fracture. Furthermore, CT/FEA revealed that tensile stress distribution changed proximally as load axis was shifted laterally according to correction of lower limb alignment by TKA.

CONCLUSION

Orthopedic surgeons should recognize the presence of TKA-associated periprosthetic AFF caused by various factors including specific drugs, bowing deformity, and lower limb alignment. X-rays of the full-length femurs should be checked regularly after TKA, especially in patients with bowed femurs or long-term exposure to specific drugs.

Surgical management and outcomes following atypical subtrochanteric femoral fractures - results from a matched-pair analysis of the registry for geriatric trauma of the German Trauma Society

BACKGROUND AND OBJECTIVES

The outcomes of patients with atypical subtrochanteric fractures (ASFs) remain unclear. Data from a large international geriatric trauma registry were analysed to examine the outcome of patients with ASFs compared to patients with typical osteoporotic subtrochanteric fractures (TSFs).

MATERIALS AND METHODS

Data from the Registry for Geriatric Trauma of the German Trauma Society (Deutsche Gesellschaft für Unfallchirurgie [DGU]) (ATR-DGU) were analysed. All patients treated surgically for ASFs or TSFs were included in this analysis. Across both fracture types, a paired matching approach was conducted, where statistical twins were formed based on background characteristics sex, age, American Society of Anesthesiologists (ASA) score and walking ability. In-house mortality and mortality rates at the 120-day follow-up, as well as mobility at 7 and 120 days, the reoperation rate, hospital discharge management, the hospital readmission rate at the 120-day follow-up, health-related quality of life, type of surgical treatment and anti-osteoporotic therapy at 7 and 120 days, were assessed as outcome measures using a multivariate logistic regression analysis.

RESULTS

Amongst the 1,800 included patients, 1,781 had TSFs and 19 had ASFs. Logistic regression analysis revealed that patients with ASFs were more often treated with closed intramedullary nailing (RR = 3.59, p < 0.001) and had a higher probability of vitamin D supplementation as osteoporosis therapy at 120 days (RR = 0.88, p < 0.002). Patients with ASFs were also more likely to live at home after surgery (RR = 1.43, p < 0.001), and they also tended to continue living at home more often than patients with TSFs (RR = 1.33, p < 0.001). Accordingly, patients with TSFs had a higher relative risk of losing their self-sufficient living status, as indicated by increased rates of patients living at home preoperatively and being discharged to nursing homes (RR = 0.19, p < 0.001) or other hospitals (RR = 0.00, p < 0.001) postoperatively.

CONCLUSIONS

Surgical treatment of ASFs was marked by more frequent use of closed intramedullary fracture reduction. Furthermore, patients with ASFs were more likely to be discharged home and died significantly less often in the given timeframe. The rate of perioperative complications, as indicated by nonsignificant reoperation rates, as well as patient walking abilities during the follow-up period, remained unaffected.

Macrophage heterogeneity in bone metastasis

Previous studies illustrated that macrophage, a type of innate immune cell, plays critical roles in tumour progression and metastasis. Bone is the most frequent site of metastasis for several cancer types including breast, prostate, and lung. In bone metastasis, osteoclast, a macrophage subset specialized in bone resorption, was heavily investigated in the past. Recent studies illustrated that other macrophage subsets, e.g. monocyte-derived macrophages, and bone resident macrophages, promoted bone metastasis independent of osteoclast function. These novel mechanisms further improved our understanding of macrophage heterogeneity in the context of bone metastasis and illustrated new opportunities for future studies.

Prevalence of Precursory Signs of Atypical Femoral Fractures in Patients Receiving Bone-Modifying Agents for Bone Metastases: A Cross-Sectional Study

Patients on bone-modifying agents (BMAs) for bone metastases are at risk of atypical femoral fractures (AFFs), which can lead to a sudden deterioration in performance status. In this study, we sought to determine the prevalence of radiographic precursory signs of AFF in patients on oncologic BMAs. Forty-two patients (23 men, 19 women; mean age 68.8 ± 10.0 years) on oncologic BMAs (zoledronate for >3 years and/or denosumab for >1 year) and without clinical symptoms were enrolled between 2019 and 2021. All patients were receiving denosumab at enrollment and 5 had previously used zoledronate. The mean duration of BMA use was 31.2 ± 18.5 months. Radiographs of both femurs were screened for precursory signs of AFF (e.g., thickening of the lateral cortex). The patients were divided into two groups according to thickening status and compared by duration of BMA use. They were also divided into three groups by duration of BMA use (12-23 months, n = 18; 24-59 months, n = 19; ≥60 months, n = 5), and the prevalence of apparent thickenings was examined. As a result, 18 patients (42.9%) showed minute local or diffuse thickening and 10 (23.8%) showed apparent local thickening. The duration of BMA use was significantly longer in patients with apparent thickening than in those without (47.3 ± 23.6 months [n = 10] versus 26.2 ± 13.5 months [n = 32]; p < 0.05). The prevalence of apparent thickening increased with increasing duration of BMA use (12-23 months, 5.6%; 24-59 months, 31.6%; ≥60 months, 60.0%). In conclusion, radiographic precursory signs of AFF are common in patients on oncologic BMAs. Radiographic screening for AFF could be relevant in patients who have been on long-term oncologic BMAs, even if asymptomatic. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Diffuse Pulmonary Metastases at Presentation of Giant Cell Tumor of Bone: A Case Report and Synthesis of Literature

CASE

We present a 23-year-old man with acute-on-chronic shoulder pain with an aggressive-appearing, destructive lesion of the left proximal humerus and diffuse lung metastases. Biopsy revealed conventional giant cell tumor of bone (GCTB) without sarcomatous differentiation, treated with resection and proximal humerus reconstruction. Without systemic treatment, his pulmonary metastases demonstrated modest spontaneous regression, with no impairment of pulmonary function.

CONCLUSIONS

Although GCTB is known to metastasize to lungs, these deposits most commonly follow local recurrence. We describe a young adult with diffuse pulmonary nodules at initial presentation, although still following an indolent clinical course without the need for additional systemic therapy.

Individualized Bone-Protective Management in Long-Term Cancer Survivors With Bone Metastases

Antiresorptive therapy is an important component of a multimodal approach to treating patients with advanced malignancies and metastatic bone disease. Over the past decade, overall survival of affected patients has improved in most cancer entities, and long-term disease control is a realistic goal in many cases. There are emerging clinical studies showing the benefits of an initial antiresorptive therapy using bisphosphonates or denosumab. However, some adverse events of these therapies, such as osteonecrosis of the jaw, correlate with the cumulative doses given, and there is an increasing clinical need for new antiresorptive concepts to treat long-term survivors. This review summarizes the clinical evidence of antiresorptive therapies across different cancers with bone involvement and presents concepts of dose-reduction protocols for long-term survivors with established metastatic bone disease. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Two cases of atypical femoral fracture in cancer patients administered with bone-modifying agents

Objective: We report two cases of atypical femoral fracture (AFF) in patients with cancer.

Patients: Two patients, a 53-year-old woman with breast cancer and a 77-year-old man with prostate cancer, could not walk after being injured in a fall. They used bone-modifying agents (BMA) for the prevention of bone metastasis for three and four years, respectively.

Results: Intramedullary nails were placed to fix the femoral fractures in each patient. Neither of them had pathological metastatic femoral fractures based on fracture site specimens; however, severe suppression of bone turnover at the fracture site was suspected. Both patients could ambulate with a T-cane and were free of hip pain after surgery. Radiographs showed no callus formation at the fracture site.

Conclusion: Based on the two cases of AFF in patients with cancer related to BMA use, we should consider that the incidence of AFF may be associated with long-term BMA use.

Current concept of stress fractures with an additional category of atypical fractures: a perspective review with representative images

Stress fractures have traditionally been classified into three categories: fatigue fractures due to overuse of bone with normal elastic resistance; insufficiency fractures due to everyday physiological stress on fragile bone with poor elastic resistance; and pathologic fractures due to bone weakness involving tumors. The concept of atypical fractures has emerged and is considered a type of stress fracture. However, there has been some inconsistency in interpretation when using the traditional classification of stress fractures, and atypical femoral fractures (AFFs) can potentially be classified into subtypes: "typical" AFFs involving bone turnover suppression due to specific drugs (e.g. bisphosphonates) and fragility fractures of the bowed femoral shaft. In this article, the classification of stress fractures is redefined with the addition of atypical fractures as a fourth category, in which biological activity for fracture healing is absent, to promote consistent understanding and interpretation of clinical conditions involving stress fractures.

Case Report: Prophylactic Plate Fixation for Incomplete Atypical Ulnar Fractures Resulting From the Use of Denosumab for Bone Metastases

Patients with bone metastases are treated with long-term bone resorption inhibitors such as bisphosphonates and denosumab. However, resorption inhibitors have been known to cause fractures, such as atypical femoral fractures (AFFs). In recent years, there have been an increasing number of reports of atypical ulna fractures (AUFs) caused by bone resorption inhibitor usage. Treatment of AUFs is complicated, especially when they occur in patients with bone metastases, because it is difficult to discontinue bone resorption inhibitor treatment without the risk of aggravating metastatic lesions. Prophylactic surgery is recommended in AFFs when fractures are predicted, but there are few reports of prophylactic surgery for AUFs. Here, we report a case of incomplete AUF in a 74-year-old woman which was surgically treated with prophylactic plate fixation. The patient had been using denosumab for 6 years to treat bone metastases due to thyroid cancer. After surgery, no fractures were observed for 2 years without discontinuing denosumab, and her forearm function was adequate. AUFs are rare and difficult to treat, so oncologists who treat bone metastases need to pay special attention to diagnose this incomplete AUF before the fracture worsens. We believe that detection of a possible fracture and prophylactic surgery can improve prognosis.