Unexpected iatrogenic fracture in a patient on bisphosphonat
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Second hip fractures are common, affecting approximately 10% of those with previous fractures . The risk factors for these subsequent fractures are limited to intrinsic qualities such as age, cognitive impairments and low bone mass. In contrast, there has been interest in the association between long-term bisphosphonate (BP) therapy and risk for subsequent fracture. BP therapy is often commenced in patients with osteoporosis, as they increase bone density and reduce risk of future fractures.

Case notes:

A 66-year old osteoporotic woman presented to the emergency room with right sided hip pain following a mechanical fall. The patient was exiting her car when she slipped on the ice and landed on her right side. 10 years prior to her presentation, she sustained a right intertrochanteric femur fracture which was treated with a DHS. Since then, she has been on alendronate for her osteoporosis. On examination, there was clear shortening and external rotation of the right leg, but she was neurovascularly intact.

The patient's x-ray showed a subtrochanteric fracture distal to the DHS plate . She was booked for removal of the DHS followed by antegrade femoral nailing. During the operation, removal of the DHS failed with the usual technique as the side plate was cold welded to the hip screw. During the maneuver, they applied excessive torque and subsequently felt a sudden give. The possibility of a fracture was confirmed by fluoroscopy and the x-ray showed an iatrogenic subcapital femoral neck fracture. Failure to remove the hardware and the unexpected femoral neck fracture in conjunction with the unavailability of an arthroplasty surgeon, the procedure was decided to be aborted. The incision was closed in layer and skin traction was applied. The next day and after thorough planning, the DHS was removed using a standard posterior approach with the morselization of the femoral head. The difficulty experienced with the removal of the DHS is evident by its aesthetics following removal. Subsequently a total hip replacement was performed using a long fully porous coated stem prosthesis and periprosthetic cerclage wires were added to bypass the fracture site, with good implant positioning on post op x-ray

Following definitive management of her hip fracture, Alendronic acid treatment was stopped. Instead, the patient was started on vitamin D, calcium, denosumab and teriparatide as for patients who have failed typical osteoporosis therapy with a follow up in 3 months with the patient's family doctor and rheumatologist. The patient was followed up in arthroplasty clinic and was mobilizing well with no difficulties or complications. Her 2-year follow-up x-ray is shown with satisfactory position of the hardware.

Conclusively, this case explains the difficulties associated with the management of periprosthetic fractures following long term BP therapy. BP induced osteopetrosis makes bone abnormally dense and increases the risk of atypical fractures. The thickening of the bone is also found to engross hardware making its removal extremely difficult as found with this case. The management of such cases require extensive pre-operative planning and anticipation of difficult removal to ensure safe and successful outcomes.

Source : https://www.sciencedirect.com/science/article/pii/S2352644020300145?dgcid=rss_sd_all
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