Background A key issue in the treatment of periprosthetic joint infection (PJI) is the correct diagnosis. The main problem is lack of diagnostic tools able to diagnose a PJI with high accuracy. Alpha-defensin has been proposed as a possible solution, but in the current literature, there is a lack of independent validation. Questions/purposes We performed a prospective study to determine (1) what is the sensitivity, specificity, and positive and the negative predictive values of the alpha-defensin immunoassay test in diagnosing PJI; and (2) which clinical features may be responsible for false-positive and false-negative results? Methods Preoperative aspiration was performed in all patients presenting with a painful hip/knee arthroplasty, including both primary and revision implants. Metallosis, other inflammatory comorbidities, and previous/concomitant antibiotic therapy were not considered as exclusion criteria. An inadequate amount of synovial fluid for culture was an exclusion criterion. A total of 156 patients (65 knees, 91 hips) were included in this prospective study. At the time of revision, synovial fluid samples were taken to perform the alpha-defensin assay. During surgical débridement of tissue, samples for cultures and histologic evaluation were taken, and samples were cultured until positive or until negative at 14 days. A diagnosis of PJI was confirmed in 29 patients according to the International Consensus Group on PJI. Results The sensitivity of the alpha-defensin immunoassay was 97% (95% confidence interval [CI], 92%–99%), the specificity was 97% (95% CI, 92%–99%), the positive predictive value was 88% (95% CI, 81%–92%), and the negative predictive value was 99% (95% CI, 96%–99%). Among four false-positive patients, two had metallosis and one had polyethylene wear. The false-negative case presented with a draining sinus, and intraoperative cultures were also negative. Conclusions Alpha-defensin assay appears to be a reliable test, but followup evaluation is needed to estimate longer term performance of the test. The authors believe that alpha-defensin has demonstrated itself to be sufficiently robust that PJI diagnostic criteria now should include this test. Future studies are needed to compare the differences among the diagnostic capability of the available tests, in particular when metallosis is present, because metallosis may predispose the test to a false-positive result. Level of Evidence Level I, diagnostic study.

Background: Meniscus allograft transplantation (MAT) is an option for symptomatic patients who have undergone subtotal meniscectomy and can potentially result in pain relief and increased function. Hypothesis: Professional soccer players would benefit from arthroscopic MAT in terms of pain, knee function, and return to play at 36-month follow-up. Study Design: Case series; Level of evidence, 4. Methods: Twelve male patients who had undergone MAT (6 medial, 6 lateral) were prospectively evaluated at 12- and 36-month follow-up. The mean age at the time of surgery was 24.5 ± 3.6 years (range, 19-29 years), and the mean time from meniscectomy to surgery was 37 ± 31 months (range, 2-82 months). The transplantation was performed in patients who had undergone subtotal meniscectomy using an arthroscopic bone plug–free technique with a single tibial tunnel plus “all-inside” meniscus sutures. The anterior horn of the transplanted meniscus was sutured to the capsule and to the remnant of the anterior horn of the native meniscus. Seven patients (58%) underwent concurrent procedures. All patients were evaluated at follow-up by the Tegner, Lysholm, International Knee Documentation Committee (IKDC) subjective, IKDC objective, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and visual analog scale (VAS) for pain scores. Information regarding rehabilitation, return to play, and return to official competition was recorded. Results: Eleven of the 12 patients (92%) returned to play soccer. At 36-month follow-up, 9 patients (75%) were still playing as professionals (Tegner score of 10), whereas 2 patients (17%) were playing as semiprofessionals (Tegner score of 9). The mean time from surgery to the end of rehabilitation was 7.5 ± 2 months, whereas the mean time to official competition was 10.5 ± 2.6 months. Patients demonstrated significant improvements on the median Tegner score from 8 (interquartile range, 3-10) to 10 (interquartile range, 9-10) (P = .0391); the mean Lysholm score from 67 ± 14 to 92 ± 10 (P = .0021); the mean IKDC subjective score from 61.8 ± 16.3 to 85.3 ± 9.8 (P = .0026); the mean IKDC objective score from 1 A, 8 B, 1 C, and 2 D to 7 A and 5 B (P = .0077); the mean WOMAC score from 77.1 ± 15.9 to 92.2 ± 9.1 (P = .0242); and the mean VAS score from 61 ± 16 to 29 ± 32 (P = .0029) at 12-month follow-up. There were no significant improvements in these outcomes at 36-month follow-up. One patient developed a knee infection after MAT plus anterior cruciate ligament allograft reconstruction. This complication was successfully treated, but the patient stopped playing soccer (Tegner score of 3 at 36-month follow-up), and this was considered a failure (8%). Conclusion: Arthroscopic MAT in professional soccer players allowed a return to play at the same level (Tegner score of 10) in 75% of the cases at 36-month follow-up.