What is the proper technique for extracting a Bone-Patellar Tendon-Bone (BPTB) graft for Anterior Cruciate Ligament (ACL) reconstruction?

BPTB Graft Extraction Technique

The proper technique for extracting a BPTB graft involves harvesting the central third of the patellar tendon (10-11 mm width) with bone blocks from both the patella and tibial tubercle, using a mini-open mobile window approach to minimize anterior knee pain complications.

Graft Harvest Technique

Initial Measurements and Planning

• Measure the patellar tendon length before harvest; proceed only if the tendon is >45 mm and the total construct will be at least 70 mm 1
• Plan to harvest the central third of the patellar tendon with a standard width of 10-11 mm 1, 2

Tibial Bone Block Harvest

• Harvest a standard tibial tubercle bone plug first using oscillating saw or osteotome 2, 3
• The tibial bone block should be rectangular, typically 25 mm in length and 10 mm in width 3

Patellar Tendon Harvest

• Use a mini-open mobile window technique rather than a large longitudinal incision to reduce donor site morbidity 4
• Harvest the central third of the patellar tendon, maintaining consistent width throughout 2, 3
• Mark the tendon borders with a marking pen before making longitudinal incisions 2

Patellar Bone Block Harvest

• At the inferior pole of the patella, use oscillating saw to create a trapezoidal bone plug 2, 3
• The patellar bone block should be slightly wider proximally (approximately 10-11 mm) to match the tendon width 3
• Maintain bone block length of approximately 20-25 mm 3
• Alternative technique: Use electrocautery to harvest the tendon directly from the patella without a bone plug (BTA technique) if the construct length allows, which eliminates risk of perioperative patellar fracture 1

Graft Preparation

Bone Block Shaping

• Shape both bone blocks to fit tunnel diameter, typically creating a trapezoidal shape 2, 3
• Remove any sharp edges that could damage tunnel walls 2
• Drill holes in each bone block for suture passage and fixation 2, 3

Tendon Preparation

• Remove any remaining synovial tissue from the tendon surface 2
• Measure final graft length and diameter to confirm adequate dimensions 2
• Place heavy non-absorbable sutures through drill holes in bone blocks for graft passage 2, 3

Critical Technical Considerations

Avoiding Patellar Fracture

• Maintain adequate bone stock on the patella after harvest (at least 50% of patellar thickness remaining) 2
• Avoid creating stress risers by ensuring smooth transitions between harvested and remaining bone 2
• Consider the BTA technique (no patellar bone plug) in patients with smaller patellas or osteopenia 1

Minimizing Anterior Knee Pain

• Use the mini-open mobile window technique rather than traditional large incisions 4
• This approach has demonstrated no statistically significant difference in anterior knee pain compared to hamstring grafts when proper technique is used 4
• Ensure meticulous closure of the patellar tendon defect with strong sutures 2

Graft Quality Assessment

• Visually inspect the graft for adequate tissue quality and absence of degenerative changes 2
• Confirm bone block integrity without fractures 2
• Verify that tendon tissue is robust without evidence of tendinosis 2

Postoperative Rehabilitation Specific to BPTB

Early Phase (Weeks 1-4)

• Initiate isometric quadriceps exercises in the first postoperative week when pain-free 5
• Allow immediate weight-bearing with correct gait pattern, no pain, and no effusion 5
• Apply cryotherapy in the first week to reduce pain 5

Strengthening Phase (Weeks 4-12)

• For BPTB grafts specifically: Begin open kinetic chain exercises at 4 weeks postoperative in restricted ROM of 90-45° with extra resistance allowed (unlike hamstring grafts) 5
• Progress ROM to 90-30° at week 5,90-20° at week 6,90-10° at week 7, and full ROM at week 8 5
• Closed kinetic chain exercises can begin at week 2 postoperative 5

Common Pitfalls to Avoid

• Inadequate bone block size: Harvesting bone blocks that are too small compromises fixation strength and increases risk of pullout 2
• Excessive patellar bone removal: Taking more than 50% of patellar thickness significantly increases fracture risk 2
• Poor tendon width consistency: Harvesting a graft that tapers or widens creates stress concentrations 2
• Ignoring patellar tendon length: Proceeding with harvest when tendon is <45 mm results in inadequate graft length 1