MON-509 Crack in My Bone of Certain Significance: Clinical Vignette and Literature Review

Abstract

Background: Overall incidence of periprosthetic fractures is <1% to 2.3% while that of postoperative periprosthetic fractures (<90 days) is 2.1%.1 Factors associated with postoperative periprosthetic fractures include uncemented femoral stem, osteoporosis, females sex, higher age, high BMI, anatomical deformities and previous surgery.1 We present an intriguing case of POST-OP periprosthetic fracture in a woman with normal bone mineral density (BMD) and discuss potentially unrecognized risk factors. Case: 77 year old woman, with a history of osteoarthritis, on daily Celecoxib 200 mg for three decades, was seen in Osteoporosis clinic. She underwent elective left total hip replacement. On postoperative day 1 she experienced acute left hip pain. CT showed acute spiral periprosthetic left hip fracture with intact femoral and acetabular components of the arthroplastic joint. Surgical revision with replacement of a longer stem was done. She returned to protected weight-bearing activity with a cane 3 months after surgery, with significant limitation of hip muscle strength and some pain in the involved hip. She continued taking Celecoxib. Bone density scan showed a BMD of 1.514 g/cm2 and a T-score of +2.8 at L1-L4, 0.950 g/cm2 and -0.6 at femoral neck, and 0.885 g/cm2 and -1.0 at hip. Serum calcium, albumin, phosphorous, vitamin D, creatinine and bone alkaline phosphatase were normal. Free kappa light chains were elevated, 4.53 mg/dL (0.33-1.94) and alpha-2 fraction was 14% (8.6-13.1). She had no proteinuria or skeletal lesions and was diagnosed with monoclonal gammopathy of undetermined significance (MGUS). It is unclear whether chronic use of selective COX-2 inhibitors and/or MGUS played a role in development of the periprosthetic fracture in our patient. Discussion: Previous studies show that selective COX-2 inhibitors can affect bone health by increasing BMD, simultaneously decreasing fracture healing.2 Individuals with MGUS have 1.7 fold risk of overall and 6.3 fold of vertebral fractures.3 Our patient was female, elderly and had uncemented stem, however, we speculate that MGUS and long-term COX-2 inhibitor use may have contributed to fracture risk in this patient. Since periprosthetic fractures are associated with significant morbidity, delayed healing and worse outcomes, it may be prudent for physicians to assess for such risk factors prior to surgery in order to identify at risk patients.