Periprosthetic infections following total knee arthroplasty (TKA) are diagnostically challenging. We evaluated the sensitivity and specificity of ESR and CRP, false negative rates, whether false negative rates differed between early post-operative and late infections, and the predictive ability of ESR and CRP to differentiate infected patients. Between 2000 and 2007, a prospectively collected database was reviewed to identify patients with suspected periprosthetic infections, and who had ESR and CRP laboratory values. One hundred and thirteen patients were identified. False negative rates were calculated. Finally, receiver operating characteristic curves were used to determine the predictive ability of ESR and CRP to differentiate infected from non-infected patients. CRP had a sensitivity of 95% and specificity of 20%. ESR had a sensitivity of 91% and a specificity of 33%. The false negative rate was 9.2% for ESR, 5.3% for CRP, and 11.1% for combined ESR and CRP. False negative rates were higher for early post-operative infections. Although ESR and CRP can be excellent adjunctive diagnostic tools, we emphasise that because some patients may not mount a sufficient immune response, the entire clinical picture must be evaluated, and periprosthetic infection should not be ruled out on the basis of ESR and CRP results alone.

ABSTRACT:We determined the effect of pre-operative bone structure upon the temporal effects of remodeling after total hip arthroplasty (THA) in a series of uncemented implants. We evaluated 345 patients (375 hips), who had either Dorr Type-A (238 hips) or Type-B (137 hips) bone, and who received a proximally-coated cementless THA and were followed for a mean of 6 years. Outcomes evaluated included aseptic survivorship, Harris hip scores, and radiographic evaluation for patterns of remodeling. The aseptic survivorship (97.5% vs. 98%) and the mean final Harris hip scores (92 vs. 94 points) were similar between Types-A and -B bone, respectively. Bone remodeling was seen significantly earlier and over a longer duration for patients who had Type-B bone. At 5-years, periprosthetic condensation (78% vs. 54%) and cortical hypertrophy (53% vs. 37%) were significantly higher and radiolucencies at any zone were lower (53% vs. 37%) in Type-B compared to Type-A bone. There was increased condensation in men and higher cortical hypertrophy in women. Various radiographic remodeling differences may not negatively impact clinical outcome at mid-term follow-up.Morphologic bone type appears to be predictive of physiologic response to loading. ß

The current study was conducted to examine the clinical and radiographic outcomes of cementless bipolar arthroplasty in patients who had type C bone at the time of the procedure. A total of 87 patients (105 hips) who had type C femora and had undergone cementless bipolar hemiarthroplasty with a proximally coated cementless prosthesis for the treatment of displaced femoral neck fractures at a single institution were reviewed. Patients included 83 women and 4 men who had a mean age of 84 years (range, 72-100 years) and were followed for a mean of 6 years (range, 2-11 years). Outcomes evaluated included aseptic implant survivorship, surgical complications, Harris Hip scores, and radiographic findings. At final follow-up, there were no revisions for aseptic implant loosening. The overall aseptic implant survivorship was 95%, with 5 patients undergoing revision surgery for aseptic reasons. Three revisions were because of periprosthetic fractures after falls, 1 revision was because of intractable groin pain, and 1 revision was because of recurrent dislocations. The surgical complication rate was 8.5%, which included 3 septic revisions, 2 avulsion fractures of the greater trochanter after falls, 2 superficial wound infections, 1 recurrent dislocation, and 1 wound hematoma. The mean Harris Hip score had improved to 80 points (range, 30-97 points) at final follow-up. Despite generally poor bone quality and medical comorbidities, elderly patients with displaced femoral neck fractures achieved excellent clinical outcomes, with few perioperative complications, through the use of proximally coated cementless bipolar hemiarthroplasty.