Purpose

In order to improve the supply-demand mismatch of osteochondral allografts (OCA), this study’s purposes were: 1) determine if an oval contralateral lateral femoral condyle (LFC) OCA can attain an acceptable surface contour match compared to an oval ipsilateral medial femoral condyle (MFC) OCA for large oval defects of the MFC; 2) determine if a single oval OCA can attain a better surface contour match compared to a mastercard technique for large oval defects of the MFC.

Methods

120 fresh frozen human femoral condyles were matched by tibial width (±2mm) into 30 groups of four condyles (1 MFC recipient, 3 donor condyles). Three fellowship-trained orthopaedic surgeons each performed transplants on 10 recipients. The recipient MFC was initially imaged using nano-CT. A 17x36mm oval “defect” was created in the recipient MFC. Donor transplant groups: MFC oval dowel, LFC oval dowel, and mastercard. Oval donor transplant order was randomized (MFC vs LFC), followed by the mastercard transplant. Following the first transplant, the recipient condyle was nano-CT imaged, digitally reconstructed, and superimposed on the initial native condyle nano-CT scan. The donor plug was then carefully removed and the process was repeated for the other two donor constructs. Dragonfly 3D and Excel were used to determine the root mean square (RMS) of both the surface height deviation and circumferential step-off height deviation between the native and donor cartilage surfaces for each transplant (whole surface and by quadrant [anterior, posterior, medial, lateral]). ANOVA with Sidak’s multiple comparison tests were used to compare the RMS surface deviation and step-off heights between the three donor groups. A sample size of seven condyles was determined based on previously published work and increased to 10 groups to ensure adequate power.

Results

RMS surface deviation (±SD) from the native surface: MFC oval = 0.59±0.28mm; LFC oval = 0.58±0.15mm; mastercard = 0.78±0.19mm. Medial and lateral oval grafts had significantly less surface deviation than the mastercard grafts (p=0.004 & 0.002 respectively). The lateral oval grafts had significantly less surface deviation than the mastercard grafts in the anterior (p=0.02) and posterior (p=0.036) quadrants. The lateral and medial oval grafts had significantly less surface deviation than the mastercard grafts for the medial (p<0.0001) and lateral (p=0.007 & 0.014 respectively) quadrants.
RMS step-off height deviation (±SD) from the native surface: MFC oval = 0.67±0.18mm; LFC oval = 0.70±0.13mm; mastercard = 0.85±0.16mm. The medial and lateral oval grafts had significantly less step-off than the mastercard grafts (p<0.0001 & p=0.002 respectively). The lateral and medial oval grafts had significantly less step-off heights than the mastercard graft for the medial quadrant (p<0.001) and the medial oval graft had significantly less step-off than the mastercard graft for the lateral quadrant (p=0.012).

Conclusion

Oval MFC & LFC OCA grafts produce a significantly better surface contour and graft:native cartilage interface match to the native MFC than mastercard grafts for oval defects 17x36mm in size. Contralateral LFC grafts are therefore acceptable for MFC defects, which may allow for a quicker match, quicker patient care, and less wastage of valuable donor tissue.