Arch Orthop Trauma Surg DOI 10.1007/s00402-010-1049-8 123 ARTHROSCOPY AND SPORTS MEDICINE Presence of subchondral bone marrow edema at the time of treatment represents a negative prognostic factor for early outcome after autologous chondrocyte implantation Philipp Niemeyer · Gian Salzmann · Matthias Steinwachs · Norbert P. Südkamp · Hagen Schmal · Philipp Lenz · Wolfgang Köstler Received: 3 October 2009  Springer-Verlag 2010 Abstract Introduction Since introduction of autologous chondro- cyte implantation (ACI), various factors have been described that inXuence the clinical outcome. The present paper investigates the inXuence of bone marrow edema at time of treatment on clinical function before and in the early clinical course after ACI. Methods 67 patients treated with ACI for cartilage defects of the knee joint were included. Presence of subchondral bone marrow edema was graded as absent (1), mild (2), moderate (3) or severe (4) using magnetic resonance (MR) imaging before surgery. All patients were assessed in terms of clinical function before surgery and 6 as well as 12 months after ACI using IKDC and Lysholm scores. Presence of subchondral edema was correlated with func- tional outcome. Results In 18 patients edema on initial MRI was graded as “absent”, while 17 patients had grade 2 edema, 19 patients had grade 3 edema and 13 patients had grade 4 edema. IKDC score increased signiWcantly from 49.8 points (SD § 14.9) to 72.3 points (SD § 17.5) at 12 months (p < 0.01). At all time points investigated, patients of group “4” showed inferior results to all other groups (p < 0.05). In addition, in patients without any edema, better clinical function was detected compared to all other groups before surgery (p < 0.05) and compared to group 3 at 6 months following ACI (p < 0.05). Conclusions Presence of severe subchondral bone mar- row edema seems to correlate with knee function in patients with cartilage defects and may be a reliable prognostic factor for the early clinical course after ACI. Keywords Subchondral edema · Autologous chondrocyte implantation · Cartilage repair · Cartilage defect · Cell transplantation · Knee joint Introduction Autologous chondrocyte implantation (ACI) is a common and accepted surgical treatment for symptomatic full thick- ness cartilage defects of the knee [1, 2]. Since its introduc- tion in 1994, diVerent technical modiWcations have been developed, most of them intending to lead to easier surgical application or to a more reliable cell delivery and more homogenous cell distribution in the defect [3–8]. Defect location has been identiWed as an important prognostic fac- tor, since obviously defects being located on the femoral condyles are associated with a better clinical outcome com- pared to patella defects [4, 9, 10]. In addition, there seems a tendency for improved outcome in younger patients with traumatic defects compared to older patients, comparable to alternative regeneration techniques [11, 12]. Furthermore, degeneration grade of the joint was identiWed as a further prognostic factor [13]. Except for these important observa- tions, the identiWcation of further prognostic factors that inXuence the patient’s outcome following ACI are not available. Since MRI plays an important role in the diagnosis of a cartilage defect and in the further clinical course following P. Niemeyer (&) · G. Salzmann · N. P. Südkamp · H. Schmal · P. Lenz · W. Köstler Department of Orthopedic Surgery and Traumatology, Freiburg University Hospital, Hugstetter Str. 55, 79095 Freiburg, Germany e-mail: philipp.niemeyer@uniklinik-freiburg.de M. Steinwachs Department of Cartilage Regeneration and Orthobiologics, Schulthess Clinic, Zurich, Switzerland