Summary
The ACTOCA score is a reliable tool to evaluate integration of osteochondral allograft transplantations.
Abstract
Introduction
Fresh osteochondral allograft (FOCA) transplantation is indicated for osteochondral lesions larger than 2 cm.
Several imaging modalities have been advocated to assess graft healing and survival. Imaging assessment of bone aspects such as osseous integration and cystic changes has shown to be key to graft survival after FOCA transplantation. To accurately evaluate these aspects, computed tomography (CT) has been found to have a considerably higher spatial resolution than standard MRI.
Aim
To describe a new semiquantitative computed tomography (CT) scoring system for multi-feature analysis of cartilage defect repair by osteochondral allografts for the knee and to assess its intra-observer and inter-observer variability.
Method
A semiquantitative assessment CT osteochondral allograft (ACTOCA) scoring system was designed based on fresh osteochondral allograft transplantations for the knee. The system includes five CT features.
1. Graft signal density relative to host bone The graft signal density appears equivalent (0), superior (1), or inferior (2) to host bone.
2. Osseous integration at the host-graft junction Osseous integration is evaluated at the host-graft junction, looking for crossing trabeculae without a discernible cleft (0), or presence of a discernible cleft < 3 mm (1) or > 3 mm (2).
3. Surface percentage with a discernible cleft at the host-graft junction The presence of less than 30% (0) or more than 30% (1) of surface with a discernible cleft at the host-graft junction is evaluated.
4. Cystic changes of graft and/or host-graft junction The presence of cystic changes is evaluated at the graft and/or host- graft junction looking for absence of cysts (0), cysts smaller than 3 mm (1), and cysts larger than 3 mm (2).
5. Presence of intra-articular fragments The absence (0) or pres- ence (1) of intra-articular fragments is evaluated.
Inter-observer variability was calculated by three observers blinded to the patient’s medical history and treatment. Intra-observer variability was also determined. The kappa coefficient (?) was calculated to analyze reliability of the system according to three observers (inter-observer reliability) and by one observer on two separate occasions (intra-observer reliability)
Results
A total of 50 FOCA were performed between 2017 and 2019 in our institution. There were 27 males and 23 females with a mean age of 35.9 ± 7.11 (range 17-48) years at the time of index surgery with a mean BMI 24.6 ± 2.98 (range 18-29).
Inter-observer agreement was moderate to substantial for all CT score components and intra-observer agreement was moderate to almost perfect for all CT score components (? > 0.5, p < 0.05).
Conclusions
The ACTOCA score is a reliable tool to evaluate integration of osteochondral allograft transplantations. It provides an accurate evaluation of bone changes and may help to standardize CT scan reports following osteochondral allograft transplantation for the knee.