Risk of Periprosthetic Joint Infection in Patients With Multiple Arthroplasties.

BACKGROUND: Risk of subsequent periprosthetic joint infection (PJI) in a second prosthetic joint following initial PJI has been shown to be 19%-20%. We sought to identify (1) the risk of developing a second PJI for our patients with multiple prosthetic joints and (2) the effect of bacteremia on development of a subsequent PJI. METHODS: We retrospectively reviewed all patients treated surgically for PJI by a single surgeon from 2003 to 2014. Time between initial and subsequent infection, bacteremia, and risk factors for PJI were identified. RESULTS: Of 167 patients treated for PJI, 76 had multiple prosthetic joints. Thirteen percent (10/76) developed a PJI in a second location. Excluding simultaneous infections, the rate was 8.3% (6/72), despite having a 57% incidence of immunosuppression, diabetes, renal failure, smoking, or steroid use. Average follow-up for patients with 1 PJI was 4.6 years (range 0.03-13.6). Seventy percent (7/10) of patients with multiple infections were bacteremic at the time of initial infection compared to 18.1% (12/66) of patients with a single infection (P = .0004). Excluding the 4 simultaneous infections (all bacteremic), the risk of developing an infection in a second joint was 20% if bacteremic and 5.2% if not bacteremic. CONCLUSION: Our study identified the risk of developing a subsequent PJI to be one half of previous studies. Bacteremia at the time of PJI is an important factor for developing subsequent PJI. Multiple prosthetic joints may be less hazardous than previously thought for patients with PJI suggesting that suppressive antibiotics may only be necessary in cases with bacteremia.

Association of atypical femoral fractures with bisphosphonate use by patients with varus hip geometry.

BACKGROUND: There is increasing evidence associating "atypical" femoral fractures with prolonged exposure to bisphosphonate therapy. The cause of these fractures is unknown and likely multifactorial. This study evaluated the hypothesis that patients with primary osteoporosis who sustain atypical femoral fracture(s) while on chronic bisphosphonate therapy have a more varus proximal femoral geometry than patients who use bisphosphonates for primary osteoporosis but do not sustain a femoral fracture. METHODS: The femoral neck-shaft angle was measured on the radiographs of 111 patients with atypical femoral shaft fracture(s) and thirty-three asymptomatic patients; both groups were on chronic bisphosphonate therapy. Patients with characteristic lateral cortical thickening, stress lines, and thigh pain were included in the fracture group. RESULTS: The mean neck-shaft angle of the patients who sustained atypical femoral fracture(s) while taking bisphosphonates (case group) differed significantly from that of the patients on bisphosphonate therapy without a fracture (129.5° versus 133.8°; p < 0.001). Fifty-three (48%) of the patients in the case group had a neck-shaft angle that was lower than the lowest angle in the control group (128°). Side-to-side comparison in patients with a unilateral pathologic involvement and an asymptomatic contralateral lower limb did not demonstrate any significant difference between the neck-shaft angles in the two limbs. CONCLUSIONS: Patients on chronic bisphosphonate therapy who presented with atypical femoral fracture(s) had more varus proximal femoral geometry than those who took bisphosphonates without sustaining a fracture. Although no causative effect can be determined, a finding of varus geometry may help to better identify patients at risk for fracture after long-term bisphosphonate use.