Lateral Harvest of an Osseous-Based Quadriceps Tendon Autograft Results in Thinner Remaining Patellar Bone

Abstract

Background: Patellar fracture after quadriceps tendon (QT) autograft harvest for anterior cruciate ligament reconstruction (ACLR) has been reported in up to 8.8% of patients. Purpose: To determine the thickness of the remaining patellar bone across the QT graft harvest location while providing clinical guidance for safely harvesting a patellar bone block when using a QT graft in ACLR. Study Design: Descriptive laboratory study. Methods: Medial and lateral QT graft boundaries were marked using a bone saw on 13 cadaveric patellae, and 3-dimensional computed tomography models were created. After the harvest of a virtual bone block with a maximum depth of 10 mm, the thickness of the remaining bone was measured across the graft harvest location in 9 zones. The thickness of the remaining bone was analyzed according to zone, graft harvest location, and patellar facet length. Risk zones were defined as <50% total patellar depth remaining. Results: We observed substantial variability in QT bone block harvest location, in which the distance between the lateral boundary of the harvest location and the lateral patellar cortex was from 21.2% to 49.2% of the axial patellar width. There was significantly less bone remaining in the lateral columns (mean ± SD, 7.56 ± 2.19 mm) compared with the medial columns (9.83 ± 2.10 mm) of the graft harvest location ( P = .028). The number of risk zones was significantly associated with distance to the lateral cortical edge, with an increase in 0.59 zones with every 1-mm decrease in distance to the lateral cortex edge ( b = -0.585; R 2 = 0.620; P = .001). With every 1-mm increase in the distance of the lateral cortex to the lateral graft boundary, the thickness of bone remaining in the lateral column increased by 0.412 mm ( P < .001). No risk zones were encountered when the lateral boundary of the harvest location was created 18.9 mm from the lateral edge of the patella or 43% of the total patellar width from the lateral edge. Conclusion: Harvest of a more laterally based QT autograft bone block resulted in thinner remaining patellar thickness, increasing the potential of encountering a risk zone for fracture. Clinical Relevance: Care should be taken to avoid harvesting the patellar bone block too laterally during ACLR.

Patellar Fracture Forces Are Not Affected by Proximal Versus Distal Bone Block Anterior Cruciate Ligament Reconstruction Harvest Sites in a Cadaveric Model

“…The potential effects of the location and depth of the harvest site have been explored. 22 , 23 Harvesting the bone plug from the lateral portion of the patella 22 and a depth of harvest greater than 50% were associated with fracture. 23 Moreover, Ferrer et al.…”

Adverse Events and Complications After Primary ACL Reconstruction With Quadriceps Tendon Autograft: A Systematic Review

“… 10 , 41 , 43 A study by Fu et al 10 describes eccentric harvest, harvesting of more than 50% of the anteroposterior thickness or of the mediolateral width, and stress risers at the corner of the graft harvest site as potential risk factors for iatrogenic patellar fracture after QTPB ACLR. 33 In a biomechanical analysis, Perry et al 33 demonstrated significantly less remaining patellar bone in a lateral column QT graft harvest compared with a medial column harvest, potentially demonstrating a risk for patellar fracture.…”

“…9 Conversely, harvesting of a patellar bone plug can increase donor-site morbidity and poses a risk for patellar fracture, which has been reported to occur in up to 8.8% of cases, especially when an eccentric harvest is performed. 9,33,36,44 Despite these findings, there have been no significant differences reported regarding complications between the all-soft tissue QT and QTPB techniques.…”