Weightbearing ovine osteochondral defects heal wit

Authors: Tomasz L Nosewicz Mikel L Reilingh C Niek van Dijk Georg N Duda Hanna Schell

Publish Date: 2011/12/21

Volume: 20, Issue: 10, Pages: 1923-1930

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Abstract

It is unknown what causes donor site morbidity following the osteochondral autograft transfer procedure or how donor sites heal Contact pressure and edge loading at donor sites may play a role in the healing process It was hypothesized that an artificially created osteochondral defect in a weightbearing area of an ovine femoral condyle will cause osseous bridging of the defect from the upper edges resulting in incomplete and irregular repair of the subchondral bone plateTo simulate edge loading large osteochondral defects were created in the most unfavourable weightbearing area of 24 ovine femoral condyles After killing at 3 and 6 months osteochondral defects were histologically and histomorphometrically evaluated with specific attention to subchondral bone healing and subchondral bone plate restorationOsteochondral defect healing showed progressive osseous defect bridging by sclerotic circumferential bone apposition Unfilled area decreased significantly from 3 to 6 months P = 0004 whereas bone content increased ns Complete but irregular subchondral bone plate restoration occurred in ten animals In fourteen animals an incomplete subchondral bone plate was found Further common findings included cavitary lesion formation degenerative cartilage changes and cartilage and subchondral bone collapseOsteochondral defect healing starts with subchondral bone plate restoration However after 6 months incomplete or irregular subchondral bone plate restoration and subsequent failure of osteochondral defect closure is common Graft harvesting in the osteochondral autograft transfer procedure must be viewed critically as similar changes are also present in humansThe osteochondral autograft transfer OATS procedure is commonly used for resurfacing articular cartilage defects 22 25 38 39 In OATS the lateral and medial trochlea 15 16 femoral condyles 12 13 as well as the intercondylar notch 16 are common harvesting sites Graft size varies between 27 and 10 mm in diameter and up to 30 mm in depth 12 13 15 16 Through graft harvesting a full thickness osteochondral defect OCD is artificially created in a healthy joint surface Although small traumatic OCDs do not cause many problems 25 34 the defects created through harvesting are considerably larger 12 15Donor site morbidity 12 13 22 26 29 37 is a frequent complication following the OATS procedure Patients may present with pain decreased knee function and knee instability 12 22 26 29 37 To minimize donor site morbidity investigators state to harvest osteochondral grafts from less or even nonweightbearing areas of the femoral condyle 13 17 22 However biomechanical studies have shown significant contact pressures in all recommended donor sites of the human knee 1 8 10 35 Surprisingly little research has been performed in the clinical outcome of these donor sites Following graft harvesting Valderrabano et al 37 found that donor site morbidity was associated with a discontinued subchondral bone plate on MRI

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