A cadaveric analysis of contact stress restoration after osteochondral transplantation of a cylindrical cartilage defect

Abstract

Osteochondral transplantation is a successful treatment for full-thickness cartilage defects, which without treatment would lead to early osteoarthritis. Restoration of surface congruency and stability of the reconstruction may be jeopardized by early mobilization. To investigate the biomechanical effectiveness of osteochondral transplantation, we performed a standardized osteochondral transplantation in eight intact human cadaver knees, using three cylindrical plugs on a full-thickness cartilage defect, bottomed on one condyle, unbottomed on the contralateral condyle. Surface pressure measurements with Tekscan pressure transducers were performed after five conditions. In the presence of a defect the border contact pressure of the articular cartilage defect significantly increased to 192% as compared to the initially intact joint surface. This was partially restored with osteochondral transplantation (mosaicplasty), as the rim stress subsequently decreased to 135% of the preoperative value. Following weight bearing motion two out of eight unbottomed mosaicplasties showed subsidence of the plugs according to Tekscan measurements. This study demonstrates that a three-plug mosaicplasty is effective in restoring the increased border contact pressure of a cartilage defect, which may postpone the development of early osteoarthritis. Unbottomed mosaicplasties may be more susceptible for subsidence below flush level after (unintended) weight bearing motion.

Fig. 1

Tekscan K-4000 measuring device with two thin (0.089 mm) and flexible pressure sensors, which were able to conform to the anatomy of the medial and lateral knee compartments. The sensors consist of printed circuits divided into grids of load-sensing regions. Each sensor measured 28 × 33 mm, with a total of 572 pixels with a surface per pixels of 1.27 mm²

Fig. 2

a Knee-testing device. b Circular plastic cap for positioning of Tekscan sensor. c Tekscan sensor in situ. d Special mould for OATS. e Three-plug mosaicplasty placed flush in full-thickness osteochondral defect

Fig. 3

a Typical example of Tekscan report on load distribution for a cartilage defect without any reconstruction. b The mosaicplasty area (region 1) is a circle consisted of square pixels with a diameter of 12 pixels. The border area (region 2) is a ring with a diameter of 3 pixels around the defect circle. A transition zone of 1 pixel around the mosaicplasty area is found between regions 1 and 2

Fig. 4

Graph showing the border contact pressure for three groups; bottomed (blue line), unbottomed (green line) and the whole group (grey line). In presence of a defect (b) the border contact surface pressure was significantly higher compared to the intact (preoperative) situation (a), performing a mosaicplasty made the border pressure decline to approach preoperative values (c), and after motion with and without weight the border contact pressure remained stable (c–e). Standardized deviation values are presented in Table 1

Fig. 5

Graph showing the mosaicplasty contact pressure for three groups; bottomed (blue line), unbottomed (green line) and the whole group (grey line). The mosaicplasty area had almost complete lack of contact pressure after creating a defect (b), in presence of the mosaicplasty the contact surface pressure was regained (c vs. a) and the contact pressure remained stable after non-weight bearing and weight bearing motion (c–e). Standardized deviation values are presented in Table 1