title: In vivo bone tunnel remodeling in symptomatic patients after ACL reconstruction: a retrospective comparison of articular and extra-articular fixation.
abstract: BACKGROUND
  there is only a paucity of studies dealing with bone remodeling within the tunnels after anterior cruciate ligament (ACL) reconstruction. The objective of this study was to evaluate the influence of tendon graft type and surgical fixation technique on bone tunnel remodeling in patients with symptomatic knees after ACL reconstruction.
  
  
  METHODS
  in a retrospective study 99mTc-HDP bone tracer uptake (BTU) in SPECT/CT of 57 knees with symptoms of pain and/or instability after ACL reconstruction was investigated. All 57 knees were subdivided according their anatomy (femur and tibia), fixation (articular versus extra-articular fixation) and graft types into eight groups: femoral-articular versus extra-articular fixation using bone-patellar tendon-bone (BPTB) and hamstring autografts; tibial-articular versus extra-articular fixation using patellar tendon and hamstring autografts; BTU grading for each area of the localisation scheme were recorded. Tunnel diameter and length was measured in the CT scans.
  
  
  RESULTS
  BTU was higher for the articular fixation in the femur and for the extra-articular fixation in the tibial tunnel. Patellar tendon graft fixation showed a significantly higher BTU in the superior-lateral and posterior-central area of the tibia, meaning the areas of the tibial tunnel near the entrance into the joint. Tunnel enlargement correlated significantly with increased BTU (p<0.05).
  
  
  CONCLUSIONS
  assessment of in vivo bone tunnel remodelling in symptomatic patients after ACL reconstruction revealed different patterns of BTU with regards to graft and fixation method.
authors.affiliation: Department of Orthopaedic Surgery and Trauma-tology, Kantonsspital Baselland, Bruderholz, Switzerland.
authors.forename: Dominic T
authors.initials: DT
authors.lastname: Mathis
authors.affiliation: Institute of Radiology and Nuclear Medicine, Kan-tonsspital Baselland, Bruderholz, Switzerland.
authors.forename: Helmut
authors.initials: H
authors.lastname: Rasch
authors.affiliation: Department of Orthopaedic Surgery and Trauma-tology, Kantonsspital Baselland, Bruderholz, Switzerland.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Hirschmann
keywords: ACL reconstruction; SPECT/CT; bone tunnel remodeling; fixation technique; hamstring graft; patellar tendon graft