Reliable patient-reported outcome measure and survivorship of UKA for primary spontaneous osteonecrosis.

PURPOSE: Primary Spontaneous osteonecrosis of the knee (SPONK) was a result of a subchondral insufficiency fracture based on histopathological examinations. There were few studies examining patients who underwent unicompartmental knee arthroplasty (UKA) for the treatment of primary SPONK. The aim of this study was to investigate (1) patient-reported outcome measure (PROM), (2) survivorship of revision as end point and (3) survivorship of complication as end point in patients with primary SPONK. METHODS: The clinical examinations of a consecutive series of 61 medial UKAs for primary SPONK of the medial femoral condyle from 2008 to 2012 were evaluated retrospectively at our institution. There were 18 males and 43 females with a mean age of 73.7 years (60-91). In all patients, preoperative radiographs were analyzed according to the stage of primary SPONK. We conducted Kaplan-Meier survival analyses using revision and complications for any reasons as the end point. RESULTS: Mean follow-up was 6.6 years (range 6-10). UKA using Physica ZUK (LIMA Corporate. UD, Italy) for SPONK improved patients' 2011 Knee Society symptom score, patient satisfaction, patient activities, EQ-5D and postoperative ranges of motion compared with their preoperative status (P < 0.01). Revision surgery was required in one knee (1.6%) due to postoperative fracture of the medial tibial plateau after a fall that occurred 6 months postoperatively. The projected rate of survivorship of UKA was 90.4% at 10 years (95% confidence interval 0.80-1). The projected rate of survivorship with complication at end point was 87.7% at 10 years (95% confidence interval 0.76-0.99). CONCLUSION: The present study demonstrated that primary spontaneous osteonecrosis of the knee (SPONK) can be successfully be treated with UKA at a mean follow-up of 6.6 years. LEVEL OF EVIDENCE: II.

Elevation of fibrin degradation product (FDP) values prevents the negative conversion of serum CRP values after total knee arthroplasty.

BACKGROUND: It is essential as an orthopedic surgeon to diagnose prosthetic joint infection (PJI) at an early stage and to carry out precise treatment as well as preventing the deterioration of functional prognosis as much as possible. We suspected that PJI might have been caused because the negative conversion of creatinine reactive protein (CRP) has been prolonged after total knee arthroplasty (TKA) and patients with no serum CRP negative conversion have been treated with antibiotics to avoid the morbidity of PJI. The purpose of the present study is to investigate the factors associated with prolongation of the negative conversion of CRP, with the exclusion of PJI patients. METHODS: We performed a retrospective case control study at our institution from August 2014 to August 2016. We classified the patients into two groups based on whether it required ≥20 days (Group A, n = 23) or <20 days (Group B, n = 23) for CRP levels to normalize. Serum D-Dimer and fibrin degradation product (FDP) values were measured at 1, 2, 5, 9, 12, 16, 19, 23, 26, and 30 days after TKA. Exclusion criteria include anticoagulant oral administration cases before TKA, venous thromboembolism (VTE) by postoperative lower limb venous echocardiography before and after TKA, CRP re-elevation cases, and patients with PJI. The cutoff points for D-dimer and FDP levels for screening tests were calculated from the receiver operating characteristic (ROC) curve. RESULTS: The ROC analysis of D- Dimer values at 30 days after TKA yielded an AUC of 0.891 (95% confidence interval (CI) 0.858-1.000), which indicates nearly an excellent test. The cutoff point of 22.1 µg/dl for FDP value (Younden Index: 22.1 µg/dl) showed a sensitivity of 81.8% (95% CI 70.1-92.8) and a specificity of 80.0% (95% CI 67.9-89.1). CONCLUSION: We revealed that CRP values of patient with an FDP level ≥22.1 µg/dl at 30 days after TKA necessarily showed negative conversion without antibiotic administration, when examining a patient with elevated serum CRP of minor criteria in the definition of PJI proposed by MSIS (other criteria do not apply). LEVEL OF EVIDENCE: Ⅲ.