Paper 292: Comparison of Patellofemoral Cartilage between Primary Bone Patellar Tendon Bone Autografts versus Other Primary Grafts at the Time of ACL Revision Surgery- A Prospective MOON Cohort Study

Abstract

The optimal graft choice for primary ACL reconstruction continues to remain controversial. Excellent outcomes have been documented for both HS and BPTB autograft ACLRs; however, an association between postoperative patellofemoral osteoarthritis and primary graft source has been reported in the literature. The aim of this study was to determine if there is an association between primary BPTB autograft selection for ACL reconstruction and arthroscopic evidence of patellofemoral cartilage degeneration at the time of ACL revision surgery. Using the MOON database, patients that had ACL revision surgery during 2002 and 2003 were identified and stratified according to the graft type used for their primary ACL reconstruction (BPTB vs non-BPTB). Exclusion criteria were: previous ACL revision surgery, history of extensor mechanism injury, or prior extensor mechanism surgery. Patients with a BPTB autograft failure were compared to patients with a non-BPTB graft failure. The primary outcome measure was the Outerbridge grade of the patellofemoral joint at the time of ACL revision surgery. The Outerbridge grade was reported for 3 regions in the patellofemoral compartment: entire (any surface of the cartilaginous compartment), central (the area directly underneath the patella autograft harvest site), and peripheral (cartilaginous area surrounding the patella autograft harvest site). A Chi square analysis was used to determine if there was a difference in the Outerbridge grade of the patellofemoral compartment anatomic region in the BPTB and non-BPTB groups. Logistic regression was used to determine if there were patient variables associated with the cartilage status of the patellofemoral joint. Variables evaluated were: time elapsed from primary ACL reconstruction to ACL revision surgery, age, gender, height, weight, and patellar alignment. A total of 86 patients had undergone ACL revision surgery during 2002-2003. There were no differences in gender, age, height, or weight between the BPTB and non-BPTB groups. Average time from primary reconstruction to revision was 23.06 months (SD: 55.17). There was no difference in the percentages of patients with documented Outerbridge grade = 2 changes on the patella in the two groups: entire patella (39.2% BPTB vs 37.14% non-BPTB p=0.846); central (33.3% BPTB vs 34.3% non-BPTB, p=0.539); peripheral (29.4% BPTB vs 31.4% non-BPTB, p=0.179). The two groups also had no difference in the percentage of patients with Outerbridge grade = 2 changes in the trochlea: entire trochlea (29.4% BPTB vs 31.4% non-BPTB, p=0.841); central trochlea (29.4% BPTB vs 31.4% non-BPTB, p=0.992); peripheral (12% BPTB vs 17.2% non-BPTB, p=0.66). Logistic regression showed that < 1% of the chondral damage in the patellofemoral compartment can be attributed to having a BPTB graft at primary ACL reconstruction (p=0.8459), and 7% of chondral damage can be attributed to patient age at the time of revision surgery (p=0.0055). The time elapsed from primary ACL reconstruction to ACL revision surgery, gender, height, weight, and patellar alignment did not show a significant contribution to the presence of chondral damage in the patellofemoral compartment for either group. At the time of ACL revision surgery, there was no association between the arthroscopic appearance of the patellofemoral compartment and the graft used for primary ACL reconstruction. In the absence of early evidence patellofemoral arthrosis, this study would support either HS or BPTB autografts for primary ACL reconstruction.