Abstract
PurposeTo use serial PET/MRI imaging to radiographically evaluate the metabolic activity of the ACL graft over the first post-operative year.MethodsSix patients undergoing primary ACL reconstruction were recruited in this prospective study in an inpatient university hospital. All patients underwent femoral and tibial suspensory cortical fixation with quadrupled semitendinosus autograft hamstring ACL reconstruction by an orthopaedic surgeon. Simultaneous 18F-FDG PET and MRI of both the operative and non-operative knee was performed at three, six, and 12 months post-operatively. Quantification of the mean standardized uptake value (SUV) within the whole-knee, as well as tibial tunnel, femoral tunnel, and intra-articular graft regions of interest (ROIs).ResultsPET whole-knee activity was increased at all time-points post-operatively compared to the control, non-operative knee. Activity decreased over time, yet considerable generalized activity remained 1 year post-operatively, with relative intensity 34% percent higher than control. When the operative knee was divided into three whole-regions, there was greater activity in the tibia at three than 12 months, the femur at six than 12 months, and in the tibia compared to the intra-articular region at 3 months. When they were separated into sub-regions, results demonstrated greater activity closer to the joint surface.ConclusionsPET/MRI evaluation of ACL graft reconstructions demonstrates evolving biologic activity within the graft and both tunnels. Focal areas of increased activity within the tunnels may indicate of ligamento-osseous morphologic changes. These data suggest that graft incorporation continues well beyond 1 year post-operatively.Level of evidenceLevel IV.
Highlights
The current standard of care for anterior cruciate ligament (ACL) injuries involves the use of quadriceps, bone-patellar tendon-bone, hamstring autograft, or allograft tissues
Total knee positron emission tomography (PET) activity based on averaged standardized uptake value (SUV) (Fig. 1, Table 2) was increased at all time points in the operative knee when compared to the non-operative knee (3month, p = 0.000; 6-month, p = 0.001; 12-month, p = 0.006)
When the knees were separated into three distinct whole regions [Fig. 3], there was a statistically significant difference at the three-month time-point, with increased PET activity in the tibia when compared with the activity within the tibial and intra-articular regions (p = 0.006)
Summary
The current standard of care for anterior cruciate ligament (ACL) injuries involves the use of quadriceps, bone-patellar tendon-bone, hamstring autograft, or allograft tissues. Korbin et al Journal of Experimental Orthopaedics Another imaging modality, SPECT/CT (Single-photon emission computed tomography/computed tomography), has previously been used with diphosphonate bone tracers to evaluate changes in biomechanical loading and the subchondral bone plate [12]. SPECT/CT (Single-photon emission computed tomography/computed tomography), has previously been used with diphosphonate bone tracers to evaluate changes in biomechanical loading and the subchondral bone plate [12] Higher amounts of this bone tracer uptake has been shown to be significantly related to a higher degree of osteoarthritis in knees postACL reconstruction [14]. We chose to combine positron emission tomography (PET), an effective tool for evaluating metabolic activity, with MRI, to demonstrate a more accurate picture of the biological activity within the knee
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