Bone-patellar tendon-bone ACL grafts show more tunnel motion than hamstring grafts
SEATTLE ─ Patients with bone-patellar tendon-bone grafts have more tunnel motion rather than mid-substance stretch 6 weeks after ACL reconstruction when compared to patients with hamstring grafts, according to data presented at the American Orthopaedic Society for Sports Medicine Annual Meeting.
James N. Irvine, MD, and colleagues at the University of Pittsburgh prospectively studied 16 patients who had anatomic single-bundle ACL reconstruction done either with bone-patellar tendon-bone (BTB) grafts or hamstring grafts. Average patient age was 20 years, and both groups had identical tunnel locations, drilling and fixation. Data were available for 6 BTB patients and 6 hamstring patients.
The researchers embedded six 0.8-mm tantalum beads into the ACL grafts before implantation. Pairs of beads were placed within each bone tunnel and in the graft mid-substance. They obtained CT scans 6 weeks after surgery and used them to create 3-D femur and tibia bone models. Irvine and colleagues then fit cylindrical coordinate systems to the bone tunnels to assess tunnel motion and collected dynamic stereo X-ray images while patients walked and descended stairs. They defined graft-tunnel motion as the maximum displacement of the implanted beads along the bone tunnel axis after foot strike.
According to study results, both groups exhibited graft motion within the femoral and tibial tunnels, with more femoral tunnel graft motion seen in the BTB group during walking and stair descent. There was more BTB graft motion in the femoral tunnel than in the tibial tunnel.
For the hamstring grafts, researchers observed more graft motion in the tibial tunnel than in the femoral tunnel.
The researchers found no difference in knee kinematics between the grafts and no evidence of faster integration of BTB grafts over hamstring grafts. Furthermore, there was no detectable mid-substance strain in either group and no difference in knee kinematics, Irvine said.
“Quantitive MRI will be useful to further assess graft healing. Additional time points would be useful to better define rehabilitation protocols and return to sport,” he said.
A 1-year follow-up test is underway to see if the pattern reverses as graft-tunnel healing progresses. – by Kristine Houck, MA, ELS
Irvine JN. Paper #22. Presented at: American Orthopaedic Society for Sports Medicine Annual Meeting; July 10-13, 2014; Seattle.
Disclosure: Irvine has no relevant financial disclosures.