International Orthopaedics https://doi.org/10.1007/s00264-022-05373-6 ORIGINAL PAPER Computerized tomography scan evaluation after fresh osteochondral allograft transplantation of the knee correlates with clinical outcomes Pablo Eduardo Gelber1,2 · Eduard Ramírez‑Bermejo1 · Alex Grau‑Blanes1 · Aránzazu Gonzalez‑Osuna1 · Oscar Fariñas3 Received: 16 December 2021 / Accepted: 6 March 2022 © The Author(s) 2022 Abstract Purpose To determine the correlation between the assessment computed tomography osteochondral allograft (ACTOCA) scoring system and clinical outcomes scores. The hypothesis was that the ACTOCA score would show sufficient correlation to support its use in clinical practice. Methods We prospectively collected data from all consecutive patients who underwent cartilage restitution with fresh osteo- chondral allograft (FOCA) transplantation for osteochondral lesions of the knee and had a minimum follow-up of two years. CT scans were performed at three, six and 24 months post-operatively. A musculoskeletal radiologist blinded to the patients’ medical history evaluated the scans using the ACTOCA scoring system. Clinical outcomes collected preoperatively and at three, six and 24 months postoperatively were evaluated using the International Knee Documentation Committee (IKDC), Kujala, the Western Ontario Meniscal Evaluation Tool (WOMET), and the Tegner Activity Scale. Results The mean total ACTOCA score showed a statistically significant correlation with the clinical outcome. The correla- tion was optimal at 24 months. We found a high negative correlation with the IKDC, Kujala and Tegner (− 0.737; − 0.757, and − 0.781 respectively), and a moderate negative correlation with WOMET (− 0.566) (p < 0.001). IKDC, Kujala, WOMET, and Tegner scores showed a significant continuous improvement in all scores (p < 0.001). Conclusion The mean total ACTOCA score showed a linear correlation with clinical results in IKDC, Kujala, WOMET, and Tegner scores, being the highest at 24 months post-surgery. This finding supports the use of ACTOCA to standardize CT scan reports following fresh osteochondral allograft transplantation in the knee. Keywords Osteochondral allograft · Cartilage repair · CT · Fresh OCA · Transplantation · Correlation Introduction [3]. In patellofemoral osteochondral lesions, an evolution to osteoarthritis has not been described [4], but surgery of Osteochondral knee lesions in active young patients have a symptomatic osteochondral lesions in the patellofemoral joint devastating effect on daily life [1]. Large symptomatic osteo- have to be considered when non-operative treatment fails [5]. chondral lesions are a complex treatment challenge [2]. If Osteochondral lesions larger than 2 ­cm2 are the main untreated, progressive worsening of tibiofemoral osteochon- indication for FOCA transplantation where osteochondral dral lesions and evolution to osteoarthritis can be expected cores from a size-matched, fresh cadaver are matched to the patient’s knee injury [6]. Good clinical and functional outcomes can be expected after FOCA transplantation, even * Pablo Eduardo Gelber personal@drgelber.com at longer follow-up [7–10]. The imaging assessment of bone aspects such as cystic 1 Department of Orthopaedic Surgery, Hospital de La Santa changes and osseous integration is key to graft survival after Creu I Sant Pau, Universitat Autonoma de Barcelona, C/Sant FOCA transplantation [2]. As strong evidence is lacking as Quintí 89, 08041 Barcelona, Catalunya, Spain to whether magnetic resonance imaging (MRI) is reliable to 2 ICATME-Hospital Universitari Dexeus, Universitat correlate with clinical outcome scores [11, 12], a semiquan- Autonoma de Barcelona, Barcelona, Spain titative ACTOCA scoring system was recently developed 3 Barcelona Tissue Bank, Banc de Sang I Teixits, Barcelona, and validated [13]. The ACTOCA includes five CT features Spain 13 Vol.:(0123456789) International Orthopaedics relative to the aspect of the transplanted graft and the host Any anatomic deformity or biomechanical alteration of bone (graft signal density, osseous integration, surface per- the tibiofemoral joint and/or patellofemoral joint was cor- centage with a discernible cleft, cystic changes, and pres- rected to avoid further cartilage degradation of the graft. ence of intra-articular fragments). However, the correlation The articular cartilage defect was sized and reamed to a between ACTOCA scores and clinical outcome scores has depth of approximately 8 to 10 mm. Fresh osteochondral not yet been explored. allografts were obtained following screening and process- The objective of this study was to determine the correla- ing requirements of the local authorized tissue bank. The tion between ACTOCA scores and clinical outcome scores. osteochondral allograft was irrigated using pulsatile lavage. The hypothesis was that the ACTOCA score would show A bone-dowel technique was performed for isolated defects sufficient correlation to support its use in clinical practice. with a well-defined affected area in an easily accessible sur- face of the knee such as the femoral condyles, mid-patella, or trochlea. The shell technique was used for asymmetric lesions, such as those involving the whole patella or those Material and methods affecting a high-degree dysplastic trochlea. In cases of post- traumatic complex lesions of the tibial plateau with a con- In this prospective study, we included all consecutive comitant meniscal deficiency, we transplanted a 10-mm-high patients undergoing cartilage repair with FOCA transplan- medial or lateral tibial plateau including the corresponding tation for osteochondral knee lesions between August 2017 meniscus. The bone-dowel technique obtained a press-fit and August 2019. Surgery was carried out by a single sur- fixation. Other techniques required fixation with bioabsorb- geon at an academic medical centre, and all patients had a able pins or interfragmentary screws [14–16]. minimum follow-up of two years. In the first phase of rehabilitation, from zero to six weeks, Inclusion criteria were patients younger than 50 years the goal was graft protection by avoidance of weight-bear- undergoing cartilage repair with FOCA transplantation for ing. The day after surgery, progressive range of motion symptomatic osteochondral knee lesions with chronic onset (ROM) exercises using a continuous passive motion device after a minimum of six months of non-operative treatment were started. Weight-bearing and ROM varied based on sev- in accordance with standard clinical practise at our institu- eral variables but the goal was to avoid stressing the trans- tion. The surgical procedure was indicated in patients with planted graft. A gradual transition to partial and full weight- large focal full-thickness chondral and osteochondral defects bearing was allowed after six to ten weeks. [9] (> 2 ­cm2) on the tibial plateau, femoral condyles, trochlea, and/or patella. Concomitant realignment osteotomy was performed in CT assessment cases of tibiofemoral FOCA with tibiofemoral malalignment greater than 3° from the neutral mechanical axis into the CT scans were performed postoperatively on day one to rule involved compartment. Patellofemoral joints with a TTTG out any technical errors and then at three, six and 24 months. distance greater than 15 mm had an associated tibial tuber- Post-operative CT studies were obtained on a 16-multidetec- cle anteromedialization osteotomy. Concomitant meniscal tor system (Brillance, Philips Healthcare) using a reduced insufficiency was corrected with lateral or medial meniscal dose protocol with the lowest scan length required to include allograft transplantation, as needed. Exclusion criteria were the allograft. Multiplanar reformatted 2-mm contiguous sag- inflammatory arthritis, large degenerative lesions compris- ittal and coronal images were later obtained. Collimation ing all three compartments, BMI > 30 kg/m2, diabetes, sys- was performed for all CTs to increase image quality and temic inflammatory diseases, infection or history of osteo- reduce the patient’s overall radiation exposure. myelitis in the graft recipient area, and active neoplasia. For this imaging study, we used the previously published The study was approved by the ethics committee of our and validated comprehensive ACTOCA score [13]. The institution (IIBSP-ALO-2018–21). Informed consent was ACTOCA includes five CT features relative to the aspect of obtained from each patient following the guidelines laid the transplanted graft and the host bone; graft signal density, down by our local ethics committee. osseous integration, surface percentage with a discernible cleft, cystic changes, and presence of intra-articular frag- ments. Axial views were used to evaluate the patella-femoral Surgical technique joint, and sagittal views were used to evaluate the femoral condyles and tibia. Each parameter was scored, and the total An arthroscopic evaluation of all compartments of the knee summation was calculated. A lower total score indicates bet- was performed to confirm the size and depth of the lesion ter incorporation of the graft, with possible scores ranging and to address any concurrent intra-articular pathology. from zero to eight (Table 1, Figs. 1 and 2). 13 International Orthopaedics Table 1  ACTOCA scoring CT features CT score system 1. Graft signal density relative to host bone 0: Equivalent 1: Superior 2: Inferior 2. Osseous integration at host-graft junction 0: Crossing trabeculae 1: Discernible cleft < 3 mm 2: Discernible cleft > 3 mm 3. Surface percentage with a discernible cleft at host-graft junction 0: < 30% 1: > 30% 4. Cystic changes of graft and/or host-graft junction 0: Absent 1: Present < 3 mm 2: Present > 3 mm 5. Presence of intraarticular fragments 0: Absent 1: Present All CT scans were evaluated by a musculoskeletal radi- ologist blinded to the patient’s medical history. Functional evaluation Clinical results were collected preoperatively and at three, six and 24 months post-operatively. At each time point, participants completed several patient-reported outcome instruments to measure clinical results. The scores used were the IKDC, Kujala, WOMET, and the Tegner activity scale [17–20]. Secondary outcomes Sociodemographic data were collected at baseline to char- acterize the study sample and explore age, sex at birth, Fig. 1  CT scan taken at 6 months and surgical image of a medial femoral condyle FOCA obtaining a low ACTOCA score (1 point) involved side, and BMI as potential confounding variables. Concomitant procedures (osteotomy, ligamentous repair/ reconstruction, meniscal allograft transplantation) were recorded at the time of surgery. Osteochondral allograft type (patellofemoral, femoral condyle, or tibial) was also noted. Statistical analysis Statistical analysis was performed using the statistical pack- age IBM SPSS V26.0 (IBM Corp. Armonk, NY). Descrip- tive statistics were used to determine patient and lesion char- acteristics. The results are given as a number of cases and/or percentage for categorical data, and as mean, standard devia- tion and range for quantitative data. Variables repeated dur- ing the trial (functional scales and CT) were analysed using ANOVA tests for repeated measures with Greenhouse–Geis- ser correction to avoid sphericity. The correlation between clinical results and imaging results was analysed by Pear- Fig. 2  CT scan taken at 24 months and surgical image of a trochlear son’s correlation coefficient. The overall level of significance and patellar FOCA obtaining a high ACTOCA score (6 points) was set at 0.05 for two-sided tests. 13 International Orthopaedics The power calculation was done according to IKDC Results from preoperative to 24 months postoperatively. A 5-point threshold for clinical relevance was set a priori. This num- A total of 38 patients (24 males; 63%) met the inclu- ber is in fact lower than multiple reported studies to detect sion criteria. The mean post-operative follow-up was minimal changes and similar to what was reported in a 38 months (range, 30–48 months). Patients’ mean age was recent study by Magnuson et al. [21]. According to the 36.63 ± 6.63 years (range, 18–46 years). Thirty-one of the power calculation, to generate a power of 80%, an alpha 38 patients (81.6%) received unipolar OCA transplants, of 0.05, and a standard deviation of 10 points, this study defined as involving ≥ one non-apposing articulating sur- required 30 patients. faces, and 71 (18.4%) received bipolar transplants, defined as involving two opposing articulating surfaces. Baseline demographic data and clinical characteristics are presented in Table 2. No statistically significant differences were noted for ACTOCA or functional scales (IKDC, Kujala, WOMET, or Tegner) according to sex at birth, age, BMI, concomi- tant procedures, or osteochondral allograft type. Regarding Table 2  Patient demographics and specific knee data (N = 38) osteotomies, no statistically significant differences were Factor found between patients with or without osteotomies on CT evolution (p = 0.819), IKDC evolution (p = 0.139), Kujala Age (years) 36.63 ± 6.63 evolution (p = 0.158), WOMET evolution (p = 0.299), and BMI 23.92 ± 2.57 24/14 Tegner evolution (p = 0.138). Male/female Lesion location Femoropatellar joint (%) 55.3 Evolution of clinical scores -Isolated patella (%) 76 -Femoral groove + patella (%) 24 Femoral condyle (%) 34.2 Pre-operative and post-operative comparisons of clinical -Medial (%) 70 scores at three, six and 24 months showed a significant -Lateral (%) 30 continuous improvement in IKDC, Kujala, WOMET, and Tibia (%) 10.5 Tegner scores (p < 0.001) (Table 3). -Medial (%) 75 -Lateral (%) 25 FOCA type Unipolar (%) 81.6 Bipolar (%) 18.4 Table 4  ACTOCA scores FOCA technique 3 months 6 months 24 months Greenhouse– Plug (%) 55.3 Geisser (p) Shell (%) 34.2 ACTOCA 2.16 ± 0.92 1.34 ± 1.21 1.05 ± 1.33 < 0.001 Small fragment (%) 10.5 (0–4) (0–4) (0–4) Tibial tubercle osteotomy (%) 18.4 High tibial osteotomy (%) 18.4 The values are given as the mean ± standard deviation with the range in parentheses Table 3  Clinical scores Preop 3 months 6 months 24 months Green- house– Geisser IKDC 31.26 ± 9.4 41 ± 10.95 47.58 ± 13.5 60.47 ± 18.81 < 0.001 (15–53) (21–65) (20–76) (20–88) Kujala 38.84 ± 12.46 49.63 ± 12.87 58.13 ± 14.4 69.5 ± 17.1 < 0.001 (17–63) (27–76) (30–94) (30–97) WOMET 38.74 ± 14.87 46.68 ± 15.07 53.13 ± 16.48 65.5 ± 18.2 < 0.001 (13–79) (18–75) (14 – 87) (25–98) Tegner 1.97 ± 0.91 1.89 ± 0.89 2.08 ± 0.78 2.76 ± 1.03 < 0.001 (1–4) (1–4) (1–4) (1–4) 13 International Orthopaedics ACTOCA evolution showed a high negative correlation with the ACTOCA score and a moderate negative correlation with WOMET. The ACTOCA scores improved significantly at three, six and To our knowledge, this is the first study to analyse the cor- 24 months post-surgery (p < 0.001) (Table 4). relation between CT and clinical outcomes using ACTOCA scores. To date, the gold standard imaging modality to assess Correlation between clinical outcomes and mean graft incorporation after fresh osteochondral allograft has ACTOCA score been MRI. However, recent studies have shown that the MRI total score does not correlate meaningfully with clinical out- The total ACTOCA score correlated with the clinical results come scores. In a systematic review and meta-analysis of 32 (Table 5). studies carried out to evaluate the correlation between clini- We observed a moderate negative correlation with cal outcome and MRI after cartilage repair, Windt et al. [22] the IKDC score at six months (Pearson correlation coef- found conclusive evidence that such correlation was lacking. ficient, − 0.535; p = 0.001) and a high negative correla- In another study, Wang et al. [12] investigated 43 patients tion with IKDC at 24 months (Pearson correlation coef- treated with FOCA after a previous cartilage repair surgi- ficient, − 0.737; p < 0.001). There was a low negative cal procedure. They found that the total OCAMRISS score, correlation with the Kujala score at six months (Pearson one of the most widely used MRI scores, did not correlate correlation coefficient, − 0.343; p = 0.035) and a high nega- meaningfully with clinical outcome scores. Other authors tive correlation with Kujala at 24 months (Pearson corre- have also failed to find a correlation between MRI scores lation coefficient, − 0.757; p < 0.001). The correlation with and clinical results [23, 24]. In contrast with these results WOMET at 24 months showed a low negative correlation using MRI, using the ACTOCA scoring system, we found a (Pearson correlation coefficient, − 0.566; p < 0.001), and the high correlation between CT scan and clinical results. This correlation with Tegner at 24 months showed a high nega- difference may be due to CT scans offering a better evalu- tive correlation (Pearson correlation coefficient, − 0.781; ation of bone integration and cystic changes that have been p < 0.001). shown to have a great impact on clinical results after FOCA. The recently developed and validated ACTOCA scoring system [13] includes five CT features: density relative to host Discussion bone, integration at the host-graft junction, surface percent- age with a discernible cleft at the host-graft junction, cystic The main finding of this study was that the ACTOCA score changes, and intra-articular fragments. Interobserver agree- showed a statistically significant correlation with the clinical ment was found to be was moderate to substantial for all CT outcome. This correlation between the mean total ACTOCA score components, and intra-observer agreement was moder- score and the clinical outcome was the highest at 24 months ate to almost perfect for all CT score components (κ > 0.5, after surgery. At this time, IKDC, Kujala, and Tegner p < 0.05), showing that ACTOCA score is a reliable scoring system to evaluate osteochondral allograft transplants. Although imaging assessment of bone aspects such as Table 5  Correlation between total ACTOCA score and clinical out- osseous integration and cystic changes is of great impor- comes scores tance to graft survival after FOCA transplantation, few stud- Pearson correlation p value ies have evaluated this transplantation using CT. Anderson coefficient et al. [25] recently developed a CT scoring system and eval- uated the relationship of OCA bone parameters measured IKDC 3 months − 0.116 0.488 on CT with clinical outcomes. However, unlike our study, 6 months − 0.535 0.001* only one postoperative CT scan was collected (at a mean of 24 months − 0.737 < 0.001* 5.8 months after surgery), and the clinical score the closest KUJALA 3 months − 0.027 0.872 to CT findings was used. This score, therefore, reflected a 6 months − 0.343 0.035* different post-surgery period for each patient, and this could 24 months − 0.757 < 0.001* have made their results less conclusive. WOMET 3 months − 0.069 0.682 Brown et al. [26] investigated osseous integration and 6 months − 0.274 0.096 early clinical results following FOCA with cylindrical grafts 24 months − 0.566 < 0.001* to the femoral condyle. They reported an overall CT assess- TEGNER 3 months − 0.177 0.287 ment of graft incorporation as a percentage of incorporation 6 months − 0.313 0.056 based on CT images and found the mean level of incorpo- 24 months − 0.781 < 0.001* ration of all grafts was grade 2 (50–75%). They did not, * Significant however, evaluate the correlation between clinical outcomes 13 International Orthopaedics and the percentage of incorporation on CT. Cook et al. [27] Author Contributions All authors contributed to the study conception reported their results of a series of 18 patients who under- and design. Material preparation, data collection and analysis were per- formed by Pablo Eduardo Gelber and Eduard Ramírez-Bermejo. The went OATS to the femoral condyle, evaluating CT arthro- first draft of the manuscript was written by Eduard Ramírez-Bermejo grams post-operatively. Similarly to other imaging studies and all authors commented on previous versions of the manuscript. All of FOCA procedures, again CT arthrograms did not corre- authors read and approved the final manuscript. late with functional outcomes. It may be because they only evaluated bony integration and articular congruity. Funding Open Access Funding provided by Universitat Autonoma de Barcelona. In our study, using the ACTOCA scoring system to evalu- ate FOCA from CT images, we found a statistically signifi- Declarations cant correlation with clinical outcomes. Furthermore, the pre-operative and post-operative clinical scores at three, six Ethical approval The study was approved by the clinical research eth- and 24 months reflected a significant, continuous improve- ics committee at our institution (IIBSP-ALO-2018-21) and conducted ment on IKDC, Kujala, WOMET, and Tegner scores. in accordance with the ethical standards laid down in the 1964 Dec- The present study has several limitations. First, there laration of Helsinki and its later amendments. Informed consent was obtained from all individual participants included in the study. was no comparison group, and the sample size was small. In addition, the cohort was relatively heterogeneous with Consent to participate Informed consent was obtained from all indi- respect to osteochondral allograft type and concomitant vidual participants included in the study. procedures. However, no statistically significant differ- Consent to publish The authors affirm that human research par- ences were noted for ACTOCA or functional scales (IKDC, ticipants provided informed consent for publication of the images in Kujala, WOMET, or Tegner) according to sex at birth, age, Figs. 1 and 2; and Tables 1, 2, 3, 4 and 5. BMI, concomitant procedures, or osteochondral allograft type. Competing interests The authors declare no competing interests. The absence of differences between patients with or with- out osteotomy may be related to the fact that osteotomies Open Access This article is licensed under a Creative Commons Attri- were performed only in cases of tibiofemoral FOCA with bution 4.0 International License, which permits use, sharing, adapta- tion, distribution and reproduction in any medium or format, as long tibiofemoral malalignment greater than 3° from the neutral as you give appropriate credit to the original author(s) and the source, mechanical axis into the involved compartment or in case provide a link to the Creative Commons licence, and indicate if changes of patellofemoral FOCA with TTTG distance greater than were made. The images or other third party material in this article are 15 mm. The remaining cases had normal preoperative val- included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in ues. Therefore, patients with osteotomy and without oste- the article's Creative Commons licence and your intended use is not otomy presented a comparable alignment once operated. permitted by statutory regulation or exceeds the permitted use, you will Second, all CT scans were evaluated by a single musculo- need to obtain permission directly from the copyright holder. To view a skeletal radiologist blinded to the patient’s medical history. copy of this licence, visit http://​creat​iveco​mmons.​org/​licen​ses/​by/4.​0/. Nevertheless, a recent study showed that ACTOCA provides a moderate to a substantial interobserver agreement and a moderate-to-almost-perfect intra-observer agreement [13]. And third, CT scans expose patients to high doses of radia- References tion. This limitation, however, was significantly reduced 1. 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