Prospective Single-Arm, Multi-Center Trial of a Patient-Specific Interpositional Knee Implant: Early Clinical Results

F.X Koeck*, 1, C Luring1, J Goetz1, M Handel1, M Tingart2, J Grifka1, J Beckmann1
1 Department of Orthopaedic Surgery, University of Regensburg, Germany
2 Department for Orthopaedics and Trauma Surgery, University of Aachen, Germany

Article Metrics

CrossRef Citations:
Total Statistics:

Full-Text HTML Views: 688
Abstract HTML Views: 429
PDF Downloads: 187
Total Views/Downloads: 1304
Unique Statistics:

Full-Text HTML Views: 453
Abstract HTML Views: 294
PDF Downloads: 141
Total Views/Downloads: 888

Creative Commons License
© Koeck et al.; Licensee Bentham Open.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted, non-commercial use, distribution, and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Department of Orthopedic Surgery, University of Regensburg, Kaiser-Karl-V-Allee 3, D-93077 Bad Abbach, Germany; Tel: ++49-9405-180; Fax: ++49-9405-18-2925; E-mail:



The treatment of unicompartmental arthritis in younger patients is challenging. The aim of this study is to report final safety and efficacy analysis results for the iForma patient–specific interpositional device, which is designed for the treatment of isolated medial or lateral compartment arthritis of the knee.


From June 2005 to June 2008 78 subjects (42 men, 36 women) received an iForma implant. The mean age was 53 years, the mean Body Mass Index 29.0. We surveyed the WOMAC scores, the visual analog pain scale and the Knee Society Scores.


The mean follow up was 16.4 months. The mean WOMAC knee scores increased from 48.3 before surgery to 71.3 after 24 months. A reduction in pain was achieved for all five pain measures using a standard visual analog scale (VAS). Knee Society Knee Score improved from 39.2 before to 61.9 24 month after surgery. The Knee Society Function Scores improved form preoperative 64.5 to 82.5 2 years postoperative. The preoperative range of motion could be restored. The overall revision rate was 24%. 15 implants were removed early, 4 knees were revised without implant removal.


Within narrow indication of patients with unicompartmental disease, the iForma device can provide improvement in knee function and reduction in pain, however, with a significant higher risk of early revision compared to traditional arthroplasty. Respecting this limitation it may be an alternative option for arthritic patients with unicompartmental disease who have contraindications to High Tibial Osteotomy or are too young for knee replacement; the iForma device further has the distinct advantage of time and cost saving compared to those procedures.

Keywords: Unicompartmental knee arthritis, Hemiarthroplasty, Interpositional implant, patient-specific.