Amiel and colleagues studied how a patellar tendon autograft is incorporated, nourished and remodeled after ACL reconstruction in a rabbit model.
Rabbit model: 37 left‑knee ACL reconstructions with medial‑third patellar tendon autograft, examined grossly, histologically and biochemically from 2 to 30 weeks.
Methods
Model
37 male New Zealand white rabbits
Age 6 to 8 months
Left ACL excised and reconstructed
Intervention
Medial one‑third quadriceps–patellar tendon autograft with a patellar bone portion
Graft passed through tibial and femoral tunnels at the native ACL insertions
Tensioned to 2.5 lb at 40° of flexion, fixed with screw and washer
Cast at 40° of flexion for 7 days
Assays
Gross morphology
Histology (H&E)
Type III collagen concentration
Glycosaminoglycan content
Reducible collagen crosslinks (DHLNL and HHMD)
Drawer testing
Time points
2 to 30 weeks after surgery
Key Findings
Patellar tendon autografts gradually took on the histologic features of normal ACL, with ligament‑like cell morphology by 30 weeks.
Type III collagen, absent from normal patellar tendon, appeared in grafts by 2 weeks, peaked at 6 weeks and at 30 weeks was comparable to normal ACL.
Glycosaminoglycan content climbed from the low level typical of patellar tendon to that of native ACL.
By 30 weeks, the graft's reducible crosslinks had shifted from the tendon pattern (low DHLNL, high HHMD) to the ACL pattern (high DHLNL, low HHMD).
Six of 37 grafts failed, losing their intra‑articular portion with fixation intact, and all failures were evident by 6 weeks.
Grafts were looser than the normal ACL at sacrifice despite 2.5 lb of tension at surgery, but this laxity did not progress from 2 to 30 weeks.
Board pearl
The authors proposed that the early graft relies on synovial fluid for nutrition, since revascularization occurs only after 6 weeks.
Authors' conclusion
These data suggest that when PT is placed in the anatomic and environmental milieu of the ACL, a “ligamentization” of the grafted tissue results; also the autograft initially depends on synovial fluid nutrition, as revascularization occurs after 6 weeks.
Amiel and colleagues studied how a patellar tendon autograft is incorporated, nourished and remodeled after ACL reconstruction in a rabbit model.
Rabbit model: 37 left‑knee ACL reconstructions with medial‑third patellar tendon autograft, examined grossly, histologically and biochemically from 2 to 30 weeks.
Methods
Model
37 male New Zealand white rabbits
Age 6 to 8 months
Left ACL excised and reconstructed
Intervention
Medial one‑third quadriceps–patellar tendon autograft with a patellar bone portion
Graft passed through tibial and femoral tunnels at the native ACL insertions
Tensioned to 2.5 lb at 40° of flexion, fixed with screw and washer
Cast at 40° of flexion for 7 days
Assays
Gross morphology
Histology (H&E)
Type III collagen concentration
Glycosaminoglycan content
Reducible collagen crosslinks (DHLNL and HHMD)
Drawer testing
Time points
2 to 30 weeks after surgery
Key Findings
Patellar tendon autografts gradually took on the histologic features of normal ACL, with ligament‑like cell morphology by 30 weeks.
Type III collagen, absent from normal patellar tendon, appeared in grafts by 2 weeks, peaked at 6 weeks and at 30 weeks was comparable to normal ACL.
Glycosaminoglycan content climbed from the low level typical of patellar tendon to that of native ACL.
By 30 weeks, the graft's reducible crosslinks had shifted from the tendon pattern (low DHLNL, high HHMD) to the ACL pattern (high DHLNL, low HHMD).
Six of 37 grafts failed, losing their intra‑articular portion with fixation intact, and all failures were evident by 6 weeks.
Grafts were looser than the normal ACL at sacrifice despite 2.5 lb of tension at surgery, but this laxity did not progress from 2 to 30 weeks.
Board pearl
The authors proposed that the early graft relies on synovial fluid for nutrition, since revascularization occurs only after 6 weeks.
Authors' conclusion
These data suggest that when PT is placed in the anatomic and environmental milieu of the ACL, a “ligamentization” of the grafted tissue results; also the autograft initially depends on synovial fluid nutrition, as revascularization occurs after 6 weeks.