(Fig 2-C.13) MRI Characteristics of Different Graft Type

https://youtu.be/AfF9nLUkKco

https://youtu.be/uDgqFi3itg0

1. Bone-Patellar-Tendon-Bone (BPTB) Autograft

✅ Early Postoperative Period (First Month)

• Signal Intensity: In the first month, BPTB autograft tendons typically show a low-intensity signal on both T1 and T2 sequences. 
• This appearance is similar to the original patellar tendon, reflecting the relatively avascular nature of the donor structure.

✅ Remodeling Phase (Up to 16-18 Months)

• Changes: During the remodeling phase, the graft undergoes significant changes.
  It is enveloped by synovial tissue and becomes vascularized, leading to an increased MRI signal.
• Signal Intensity: The MRI signal intensity may increase for up to 16-18 months postoperatively.

✅ Long-Term Postoperative Period

• Final Appearance: After this period, the graft's signal stabilizes and closely resembles the original ACL's.
• Patellar Tendon Changes: A central defect in the patellar tendon, resulting from BPTB harvest, typically fills with scar tissue by 2 years postoperatively.
  Persistent thinning at the harvest site and a thickened appearance of the surrounding patellar tendon are common thereafter.

2. Doubled Semitendinosus and Gracilis Tendon Graft

✅ Graft Composition

• Strands: This graft type is composed of four separate strands.
• MRI Appearance: Intermediate and even fluid signals between the strands can be a normal finding on T2-weighted sequences.
• Comparison: Such findings are considered abnormal for a BPTB graft, which consists of a single strand.

3. Allografts

✅ Maturation Process

• Comparison with Autografts: Allografts demonstrate a similar pattern of signal intensity changes as autografts but have a significantly longer maturation process.
• MRI Signal: It has been observed that allografts maintain a higher signal intensity compared to autografts for up to 2 years following ACL reconstruction.

 

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