Vol.:(0123456789) 1 3 Archives of Orthopaedic and Trauma Surgery https://doi.org/10.1007/s00402-018-3032-8 KNEE REVISION SURGERY Signifcant increase of pathogen detection rate by dry arthroscopic biopsies at suspected low-grade infection following total knee arthroplasty: a prospective observational study Sebastian F. Baumbach 1  · Wolf C. Prall 1,2  · Andreas M. Scharpf 2  · Viktoria Hererich 1  · Maximilian Schmidt 3  · Norbert P. Suedkamp 3  · Amelie Stoehr 4  · Hermann O. Mayr 2,3 Received: 28 May 2018 © Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Introduction The diferentiation between stif-knee and low-grade periprosthetic joint infection (PJI) is the current diagnos- tic challenge in total knee (TKA) revision arthroplasty. The aim of this study was to investigate the additional value of dry biopsies, compared to wet biopsies, in patients presenting with knee stifness following primary TKA. Materials and methods Single center, prospective observational study. Consecutive patients with joint stifness of unknown origin following primary TKA were enrolled. Patient assessment followed the diagnostic standard algorithm. During diag- nostic arthroscopy, synovial fuid (synovial WBC, PMN%) and fve dry biopsies (dry) were collected. Then fuid was infused and another fve microbiology (wet) and fve histological biopsies gathered, all from identical locations. The primary outcome parameter was the diference between the pathogens in wet and dry biopsies. Results 71 patients (61% females, 67 ± 10 years) were eligible. Preoperative blood serology mean CRP (0.7 ± 1.5 mg/ dl; p = 0.852), WBC (6.6 ± 1.7 G/l; p = 0.056), and synovial fuid mean WBC (1639 ± 2111; p = 0.602), PMN% (38 ± 28; p = 0.738) did not difer between patients with negative, positive wet or dry biopsies. The histology was in 11% positive (p = 0.058). In 32% at least one pathogen was detected, 48% from wet, 44% from dry biopsies. An inhomogeneous distribution was found. Cutibacterium acnes (100%) was solely found in wet, Micrococcus luteus (75%), Staphylococcus capitis (67%), and Micrococcus lylae (100%) were predominantly found in dry biopsies. Additional dry biopsies increased the pathogen detection rate by 49%. Conclusion The addition of dry biopsies to the current standard diagnostic algorithm for PJI increased the pathogen detec- tion rate by 49%. Keywords Total knee arthroplasty · Periprosthetic joint infection · Diagnostic · Arthroscopy · Biopsies Introduction Total knee arthroplasty (TKA) is frequently conducted and in general considered safe. Still, despite advances in the operative setting, technique, and implant design, up to 20% of patients remain dissatisfed [1, 2]. Symptoms, next to acute infection and malalignment, are unreasonable high expectations, functional limitations, and residual pain. The latter two are usually sub-summarized as knee stifness [3]. The most common cause of revision surgery is periprosthetic joint infections (PJI) [4, 5]. These can be divided into acute and delated onset. The actual numbers are a matter of debate. Whereas acute infection usually can be diagnosed easily, low-grade PJI diagnostics remain a considerable hurdle [6, 7]. * Hermann O. Mayr hermann.mayr@uniklinik-freiburg.de 1 Department of General, Trauma, and Reconstructive Surgery, Munich University Hospital LMU, Nussbaumstrasse 20, 80336 Munich, Germany 2 Department of Knee, Hip and Shoulder Surgery, Schön Klinik München Harlaching, Harlachinger Strasse 51, 81547 Munich, Germany 3 Department of Orthopaedics and Traumatology, Freiburg University Hospital, Hugstetterstrasse 55, 79106 Freiburg, Germany 4 OCM Clinic Munich, Steinerstr. 6, 81369 Munich, Germany