E-Poster Presentation ESA-SRB-ANZBMS 2021

A 68-year-old Vietnamese woman sustained a right sided atypical femoral fracture (AFF), along with left metacarpal and distal radius fractures, following a fall from standing height. She was taking risedronate weekly for 6 years with prior vertebral insufficiency fractures. She had well-controlled hypertension, on perindopril.

Lumbar spine and femoral neck T-scores 11 years ago were -3.47 and -3.15, respectively. Six years ago, lumbar spine and femoral neck T-scores were -3.15 and -3.17, respectively.  

Biochemical investigations (table 1) were consistent with primary hyperparathyroidism (PHPT). Despite prolonged antiresorptive therapy, bone turnover markers were in the upper range of normal in the setting of recent fracture and PHPT. No prior calcium testing was available.

Risedronate was ceased, and vitamin D supplementation commenced. An intramedullary nail was inserted in the AFF site, with an uneventful post-operative course. No concerning features of the contralateral femur were found on plain films and bone scintigraphy. The left metacarpal and left distal radius fractures were managed non-operatively.

Neck ultrasonography and parathyroid technetium-99m sestamibi demonstrated left inferior parathyroid adenoma. She underwent a minimally invasive parathyroidectomy soon after her femoral intramedullary nail insertion, with normalisation of serum calcium. Histology demonstrated a parathyroid adenoma.

This patient has concurrent issues of fragility fractures, bisphosphonate-associated AFF, and PHPT, posing a dilemma with future management. Bone turnover is high in PHPT and low in AFF, and to our knowledge there is only one case report of coexistence of both these conditions. The unexpected finding of PHPT in this patient on long term bisphosphonates highlights the importance of conducting a secondary screen for potentially reversible causes of osteoporosis at diagnosis and where treatment failure occurs. The increased cortical porosity found in PHPT may have increased the risk for developing an AFF. The incidence of AFFs in patients receiving antiresorptive therapies for PHPT is unknown.