Intractable Fractures of the Bilateral Proximal Ulnae After 8 Years of Zoledronate Treatment for Breast Cancer Bone Metastasis

Atypical fractures at non-classical sites associated with anti-resorptive therapy: a systematic review

Osteoporosis is common, affecting more than 20% of women and 6% of men globally over the age of 50. Anti-resorptive drugs, bisphosphonates and denosumab, have been effective treatments for osteoporosis for more than 30 years. Rare complications of anti-resorptive therapy include medication-related osteonecrosis of the jaw and atypical femur fractures (AFF). The American Society for Bone and Mineral Research (ASBMR) proposed a case definition for these atypical femoral fractures in 2010, which was updated in 2013. However, atypical fractures at non-classical sites have been increasingly described. We aimed to systematically identify atypical fracture cases excluded from the ASBMR AFF case definition in patients receiving anti-resorptive medication for longer than 3 yr. A structured search of electronic databases, including PubMed, Medline (Ovid), Embase (Ovid), Cochrane, and Web of Sciences, and hand-searching of conference abstracts were undertaken. All full-text articles written in English describing an atypical fracture in patients (aged >18 yr) and receiving anti-resorptive medication for >3 yr were included, with data extracted and analyzed by two independent reviewers. Sixty-six articles were identified, describing 151 cases of atypical fractures in 114 individuals. The most frequent fracture site was the ulna, followed by the tibia. All patients were taking anti-resorptive treatment prior to or at the time of fracture, most frequently alendronate monotherapy (44%). Most commonly, fractures were transverse in nature (95%), following minimal or no trauma (96%), and non-comminuted (98%) with cortical thickening of the surrounding bone (69%). Anti-resorptive treatment was ceased following an atypical fracture in the majority (89%). Atypical fractures are rare and should not deter physicians from appropriate anti-resorptive therapy for osteoporosis. However, clinicians should be alert to their presence at additional sites to the femur. An update of the current ASBMR AFF case definition to include other skeletal sites could be timely.

Multiple Stress Fractures in a Young Cancer Patient on Long-Term Zoledronic Acid: A Case Report and Review of Literature

Bisphosphonates are commonly used in the treatment of osteoporosis and metastatic cancer patients with bone complications. Stress fractures are a well-known complication of long-term bisphosphonate treatment. Cancer patients receive much higher cumulative doses of bisphosphonates than osteoporotic patients and are subject to a higher risk of bisphosphonate-associated stress fractures. While there is an increasing number of reports of bisphosphonate-associated atypical femoral fractures (AFFs) and non-femoral stress fractures in osteoporotic patients, reports of such fractures in cancer patients are much rarer, especially non-femoral stress fractures. We present the first case report of an atypical subtrochanteric femur fracture following a sequential bilateral Jones fracture in a young non-osteoporotic patient with metastatic breast cancer after 12 years of zoledronic therapy. She sustained a left Jones fracture after seven years of zoledronic acid therapy and a right Jones fracture after 11 years of zoledronic acid therapy. She continued receiving regular zoledronic acid after these stress fractures and sustained a right subtrochanteric fracture after 12 years of zoledronic acid therapy. Both Jones fractures were treated conservatively, while the right subtrochanteric fracture was surgically fixed. Zoledronic acid was stopped after she sustained the AFF. This study highlights the need to look out for stress fractures beyond the commonly reported AFFs and atypical ulnar fractures when administering zoledronic acid to cancer patients.

Zoledronate reduces loading-induced microdamage in cortical ulna of ovariectomized rats

As a daily physiological mechanism in bone, microdamage accumulation dissipates energy and helps to prevent fractures. However, excessive damage accumulation might bring adverse effects to bone mechanical properties, which is especially problematic among the osteoporotic and osteopenic patients treated by bisphosphonates. Some pre-clinical studies in the literature applied forelimb loading models to produce well-controlled microdamage in cortical bone. Ovariectomized animals were also extensively studied to assimilate human conditions of estrogen-related bone loss. In the present study, we combined both experimental models to investigate microdamage accumulation in the context of osteopenia and zoledronate treatment. Three-month-old normal and ovariectomized rats treated by saline or zoledronate underwent controlled compressive loading on their right forelimb to create in vivo microdamage, which was then quantified by barium sulfate contrast-enhanced micro-CT imaging. Weekly in vivo micro-CT scans were taken to evaluate bone (re)modeling and to capture microstructural changes over time. After sacrifice, three-point-bending tests were performed to assess bone mechanical properties. Results show that the zoledronate treatment can reduce cortical microdamage accumulation in ovariectomized rats, which might be explained by the enhancement of several bone structural properties such as ultimate force, yield force, cortical bone area and volume. The rats showed increased bone formation volume and surface after the generation of microdamage, especially for the normal and the ovariectomized groups. Woven bone formation was also observed in loaded ulnae, which was most significant in ovariectomized rats. Although all the rats showed strong correlations between periosteal bone formation and microdamage accumulation, the correlation levels were lower for the zoledronate-treated groups, potentially because of their lower levels of microdamage. The present study provides insights to further investigations of pharmaceutical treatments for osteoporosis and osteopenia. The same experimental concept can be applied in future studies on microdamage and drug testing.

Atypical Ulnar Fracture in an Older Woman with Osteoporosis with a Five-Year History of Denosumab Treatment: A Case Report

Atypical ulnar fracture (AUF) is a rare condition that may occur in patients treated with bisphosphonates. We describe the clinical course of a patient who had an AUF during treatment with denosumab. An 86-year-old woman treated with denosumab for 5 years experienced a complete transverse fracture of the proximal left ulna after falling from a standing height. Intraoperative photographs showed cortical thickening around the fracture site. Therefore, we diagnosed the patient with AUF and performed internal fixation with a locking plate. However, a re-fracture occurred 2.5 months after surgery, which was treated with locking plate replacement with a longer one with a bone graft. One year after the second surgery, the fracture healed. To our knowledge, this is the second case report of an AUF occurring during denosumab treatment. Our case highlights the importance of careful follow-up of patients receiving not only bisphosphonate, but also denosumab.

Levels of Evidence: Level V (Therapeutic)

Diagnostic Criteria and Treatment of Atypical Ulnar Fractures Associated With Prolonged Bisphosphonate Therapy: Multicenter Case Analysis

PURPOSE

Atypical ulnar fracture (AUF) related to prolonged bisphosphonate therapy is a rare complication. We propose diagnostic criteria of AUFs and present a treatment algorithm.

METHODS

Twelve AUFs in 10 patients were studied. The diagnosis of AUF was based on the case definition of atypical femoral fracture (AFF). We investigated clinical and radiographic characteristics of AUFs according to major and minor features of AFFs, and modified the case definition of an AFF to fit the characteristics of AUFs. All AUFs were treated surgically. The radiographic union of fractures was investigated, and delayed fracture healing was defined as a delay of 6 months or more.

RESULTS

The average point at which AUFs occurred was at a point 35.1% along the proximal diaphysis of the total ulnar length. All major features of AFFs were identified in the 12 AUFs. Among the minor features, generalized cortical thickening was observed in 6 AUFs, prodromal symptoms in 2 AUFs, bilateral involvement in 2 patients, and delayed fracture healing in 10 AUFs (5 delayed union, 5 nonunion). Initially, 11 of 12 AUFs were treated with plating, and 1 was treated with intramedullary nailing. Two nonunions were revised with sclerotic bone resections, bone grafts, and plate fixation. Finally, union was achieved in 9 AUFs.

CONCLUSIONS

The case definition of AFFs can be used for the diagnosis of AUFs, although some modifications must be included in the case definition. Plating is useful in managing AUFs, although sclerotic bone resections and bone grafts may be required. Atypical ulnar fractures occurred in patients who took bisphosphonates longer than AFFs or those whose bisphosphonates were discontinued a few years earlier. Therefore, physicians should be aware of AUFs in those patients and, if necessary, perform a screening test to look for atypical fractures in other bones.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic V.

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.