A new contralateral atypical femoral fracture despite sequential therapy with teriparatide and strontium ranelate.Bone Rep. 2017;6:34-37. [PMID: 28377979 DOI: 10.1016/j.bonr.2017.01.002]

The effect of teriparatide on fracture healing after atypical femoral fracture: A systematic review and meta-analysis

This meta-analysis demonstrated that a greater prevalence of delayed union and nonunion and a longer time to fracture healing in the group that did not receive TPTD treatment after AFFs than in the group that received TPTD treatment.

PURPOSE

To date, there is no hard evidence for medical management after atypical femoral fracture (AFF), even though weak data indicate faster healing with teriparatide (TPTD). Herein, we aimed to investigate the effect of postfracture TPTD treatment on AFF healing using a pairwise meta-analysis focusing on delayed union, nonunion, and fracture healing time.

METHODS

A systematic search of the MEDLINE (PUBMED), Embase, and Cochrane Library databases was performed for studies investigating the effect of TPTD after AFF up to October 11, 2022. We compared the incidence of delayed union and nonunion and the time of fracture healing between the TPTD ( +) and TPTD (-) groups.

RESULTS

The 6 studies analyzed a total of 214 AFF patients, including 93 who received TPTD therapy after AFF and 121 who did not. The pooled analysis showed a significantly higher rate of delayed union in the TPTD (-) group than in the TPTD ( +) group (OR, 0.24; 95% CI, 0.11-0.52; P < 0.01; I² = 0%), and a higher nonunion rate was observed in the TPTD (-) group than in the TPTD ( +) group with low heterogeneity (OR, 0.21; 95% CI, 0.06-0.78; P = 0.02; I² = 0%). The TPTD (-) group required 1.69 months longer to achieve fracture union than the TPTD ( +) group, with statistical significance (MD =  - 1.69, 95% CI: - 2.44 to - 0.95, P < 0.01; I² = 13%). Subgroup analysis for patients with complete AFF showed that the TPTD (-) group had a higher rate of delayed union with low heterogeneity (OR, 0.22; 95% CI, 0.10-0.51; P < 0.01; I² = 0%), but there was no significant difference in the nonunion rate between TPTD ( +) and TPTD (-) groups (OR, 0.35; 95% CI, 0.06-2.21; P = 0.25; I² = 0%). Fracture healing took significantly longer in the TPTD (-) group (MD =  - 1.81, 95% CI: - 2.55 to - 1.08; P < 0.01; I² = 48%). The reoperation rate showed no significant difference between the two groups (OR, 0.29; 95% CI, 0.07-1.20; P = 0.09; I² = 0%).

CONCLUSIONS

The current meta-analysis supported the hypothesis that TPTD treatment following AFF might benefit fracture healing, lowering the rate of delayed union and nonunion and shortening the fracture healing time.

Are secondary effects of bisphosphonates on the vascular system of bone contributing to increased risk for atypical femoral fractures in osteoporosis?

Osteoporosis (OP) is a bone disease which affects a number of post-menopausal females and puts many at risk for fractures. A large number of patients are taking bisphosphonates (BPs) to treat their OP and a rare complication is the development of atypical femoral fractures (AFF). No real explanations for the mechanisms underlying the basis for development of where AFF develop while on BPs has emerged. The present hypothesis will discuss the possibility that part of the risk for an AFF is a secondary effect of BPs on a subset of vascular cells in a genetically at-risk population, leading to localized deregulation of the endothelial cell (EC)-bone cell-matrix units in nutrient channels/canals of the femur and increased risk for AFF. This concept of targeting ECs is consistent with location of AFF in the femur, the bilateral risk for occurrence of AFF, and the requirement for long term exposure to the drugs.

A brief review and clinical evidences of teriparatide therapy for atypical femoral fractures associated with long-term bisphosphonate treatment

The risk of bisphosphonate (BP)-associated atypical femur fracture (AFF) has markedly increased over recent decades due to suppression of bone turnover, accumulation of structural micro-damage and reduction of bone remodeling consequent to long-term BP treatment. These medications further delay bone union and result in challenging clinical management. Teriparatide (TPTD), a synthetic human parathyroid hormone, exhibits unique anabolic effects and can increase bone remodeling and improve bone microarchitecture, further promoting fracture healing and reducing the rate of bone non-union. In this study, we briefly define AFF as well as the effects of BPs on AFFs, detailed the role of TPTD in AFF management and the latest clinical therapeutic findings. We have confirmed that TPTD positively promotes the healing of AFFs by reducing the time to bone union and likelihood of non-union. Thus, teriparatide therapy could be considered as an alternative treatment for AFFs, however, further research is required for the establishment of effective clinical guidelines of TPTD use in the management of AFF.

Current concepts in the management of bisphosphonate associated atypical femoral fractures

Bisphosphonates are a class of drugs used as the mainstay of treatment for osteoporosis. Bisphosphonates function by binding to hydroxyapatite, and subsequently targeting osteoclasts by altering their ability to resorb and remodel bone. Whilst aiming to reduce the risk of fragility fractures, bisphosphonates have been associated with atypical insufficiency fractures, specifically in the femur. Atypical femoral fractures occur distal to the lesser trochanter, until the supracondylar flare. There are a number of the differing clinical and radiological features between atypical femoral fractures and osteoporotic femoral fractures, indicating that there is a distinct difference in the respective underlying pathophysiology. At the point of presentation of an atypical femoral fracture, bisphosphonate should be discontinued. This is due to the proposed inhibition of osteoclasts and apoptosis, resulting in impaired callus healing. Conservative management consists primarily of cessation of bisphosphonate therapy and partial weightbearing activity. Nutritional deficiencies should be investigated and appropriately corrected, most notably dietary calcium and vitamin D. Currently there is no established treatment guidelines for either complete or incomplete fractures. There is agreement in the literature that nonoperative management of bisphosphonate-associated femoral fractures conveys poor outcomes. Currently, the favoured methods of surgical fixation are cephalomedullary nailing and plate fixation. Newer techniques advocate the use of both modalities as it gives the plate advantage of best reducing the fracture and compressing the lateral cortex, with the support of the intramedullary nail to stabilise an atypical fracture with increased ability to load-share, and a reduced bending moment across the fracture site. The evidence suggests that cephalomedullary nailing of the fracture has lower revision rates. However, it is important to appreciate that the anatomical location and patient factors may not always allow for this. Although causation between bisphosphonates and atypical fractures is yet to be demonstrated, there is a growing evidence base to suggest a higher incidence to atypical femoral fractures in patients who take bisphosphonates. As we encounter a growing co-morbid elderly population, the prevalence of this fracture-type will likely increase. Therefore, it is imperative clinicians continue to be attentive of atypical femoral fractures and treat them effectively.

Medical Management of Patients After Atypical Femur Fractures: a Systematic Review and Recommendations From the European Calcified Tissue Society

CONTEXT

Atypical femur fractures (AFFs) are serious adverse events associated with bisphosphonates and often show poor healing.

EVIDENCE ACQUISITION

We performed a systematic review to evaluate effects of teriparatide, raloxifene, and denosumab on healing and occurrence of AFF.

EVIDENCE SYNTHESIS

We retrieved 910 references and reviewed 67 papers, including 31 case reports, 9 retrospective and 3 prospective studies on teriparatide. There were no RCTs. We pooled data on fracture union (n = 98 AFFs on teriparatide) and found that radiological healing occurred within 6 months of teriparatide in 13 of 30 (43%) conservatively managed incomplete AFFs, 9 of 10 (90%) incomplete AFFs with surgical intervention, and 44 of 58 (75%) complete AFFs. In 9 of 30 (30%) nonoperated incomplete AFFs, no union was achieved after 12 months and 4 (13%) fractures became complete on teriparatide. Eight patients had new AFFs during or after teriparatide. AFF on denosumab was reported in 22 patients, including 11 patients treated for bone metastases and 8 without bisphosphonate exposure. Denosumab after AFF was associated with recurrent incomplete AFFs in 1 patient and 2 patients of contralateral complete AFF. Eight patients had used raloxifene before AFF occurred, including 1 bisphosphonate-naïve patient.

CONCLUSIONS

There is no evidence-based indication in patients with AFF for teriparatide apart from reducing the risk of typical fragility fractures, although observational data suggest that teriparatide might result in faster healing of surgically treated AFFs. Awaiting further evidence, we formulate recommendations for treatment after an AFF based on expert opinion.

Antiresorptive-associated spontaneous fractures of both tibiae, followed by an atypical femur fracture during the sequential treatment with alendronate, denosumab then teriparatide

A 35-year-old man with juvenile idiopathic arthritis since childhood presented with bilateral atypical tibial fractures, followed by a later, single atypical fracture of the femur. The fractures were associated with 6 years of oral alendronate treatment immediately followed by subcutaneous denosumab therapy and later teriparatide therapy for osteoporosis. Atypical fractures are known to occur in the femur following bisphosphonate therapy; however, there are only a few documented cases of atypical fractures in the tibia. Our case highlights a rare but serious complication of a commonly prescribed antiresorptive agent. It also shows that teriparatide, while helpful in increasing bone mass, does not fully prevent the development of atypical fractures. Careful investigation should be considered in patients on long-term antiresorptive therapy presenting with bony tenderness to exclude an atypical fracture.

Proof of Concept on Functionality Improvement of Mesenchymal Stem-Cells, in Postmenopausal Osteoporotic Women Treated with Teriparatide (PTH1-34), After Suffering Atypical Fractures

Osteoporosis long-term treatment with nitrogen-containing bisphosphonates, has been associated with uncommon adverse effects, as atypical femoral fractures (AFF). Thus, treatment with teriparatide (TPTD; fragment of human parathyroid hormone; PTH_1-34) has been proposed for such patients. Besides its anabolizing effect on bone, TPTD may affect stem-cell mobilization and expansion. Bone marrow mononuclear cells (BMMNC) were isolated from five women that had suffered AFF associated to bisphosphonate treatment, before and after 6 months of TPTD therapy. The presence of mesenchymal stromal cells (CD73, CD90 and CD105 positive cells), gene expression of NANOG, SOX2 and OCT4, proliferation, senescence and capacity to differentiate into osteoblasts and adipocytes were analyzed. After TPTD treatment, BMMNC positive cells for CD73, CD90 and CD105 increased from 6.5 to 37.5% (p < 0.05); NANOG, SOX2 and OCT4 were upregulated, being statistically significant for NANOG (p < 0.05), and cells increased proliferative capacity more than 50% at day 7 (p < 0.05). Senescence was reduced 2.5-fold (p < 0.05), increasing differentiation capacity into osteoblasts and adipocytes, with more than twice mineralization capacity of extracellular matrix or fat-droplet formation (p < 0.05), respectively. Results show that TPTD treatment caused BMMNC "rejuvenation", increasing the number of cells in a more undifferentiated stage, with higher differentiation potency. This effect may favor TPTD anabolic action on bone in such patients with AFF, increasing osteoblast precursor cells. Such response could also arise in other osteoporotic patients treated with TPTD, without previous AFF. Furthermore, our data suggest that TPTD effect on stromal cells may have clinical implications for bone-regenerative medicine. Further studies may deepen on this potential.

The enigma of atypical femoral fractures: A summary of current knowledge

Atypical femoral fractures (AFF) are stress or ‘insufficiency’ fractures, often complicated by the use of bisphosphonates or other bone turnover inhibitors. While these drugs are beneficial for the intact osteoporotic bone, they probably prevent a stress fracture from healing which thus progresses to a complete fracture.

Key features of atypical femoral fractures, essential for the diagnosis, are: location in the subtrochanteric region and diaphysis; lack of trauma history and comminution; and a transverse or short oblique configuration.

The relative risk of patients developing an atypical femoral fracture when taking bisphosphonates is high; however, the absolute risk of these fractures in patients on bisphosphonates is low, ranging from 3.2 to 50 cases per 100,000 person-years.

Treatment strategy in patients with AFF involves: radiograph of the contralateral side (computed tomography and magnetic resonance imaging should also be considered); dietary calcium and vitamin D supplementation should be prescribed following assessment; bisphosphonates or other potent antiresorptive agents should be discontinued; prophylactic surgical treatment of incomplete AFF with cephalomedullary nail, unless pain free; cephalomedullary nailing for surgical fixation of complete fractures; avoidance of gaps in the lateral and anterior cortex; avoidance of varus malreduction.

Cite this article: EFORT Open Rev 2018;3:494-500. DOI: 10.1302/2058-5241.3.170070.

[Atypical distal tibial shaft fractures in a patient with bilateral TKA and antiresorptive treatment]

There are many cases in the literature that describe atypical femur fractures under antiresorptive therapy. Other localizations of fractures of this genesis, especially if occurring bilaterally, are rare. This case reports about the diagnosis, treatment and process of a 76-year old patient, who within a 4‑month period suffered from bilateral distal tibial shaft fractures, after years of treatment with bisphosphonates, strontium ranelate and denosumab.