Patellar Size Variation at the Quadriceps Tendon–Bone Block Harvest Site: A Magnetic Resonance Imaging Study to Evaluate the Safe Zone for Harvesting a Sufficient Bone Block

Abstract

Background: Quadriceps tendon (QT) autografts with and without a bone block are the least studied and least used options for anterior cruciate ligament reconstruction surgery. In particular, there is a lack of literature describing patellar anatomy. Until now, guidelines for patellar bone block harvesting have been based solely on personal experience. In this study, we intended to derive recommendations from physical regularities and objective criteria. Purpose: To determine the maximal, individual-related length and depth of the bone block that can be safely harvested and to provide guidelines to help surgeons make decisions on graft choice. Study Design: Descriptive laboratory study. Methods: The study group consisted of 50 male participants and 50 female participants (mean age, 29.4 ± 7.9 years) who underwent 3.0-T magnetic resonance imaging of their knee. Patellar height was determined at the center of the middle third of the QT insertion on the patella and the medial and lateral endpoints; the depth was measured at the midpoints of the respective heights. Results: The mean width of the QT and the mean thickness were 49.0 ± 7.6 and 7.3 ± 1.0 mm, respectively. The mean patellar thickness in reference to the medial endpoint, the center, and the lateral endpoint was 18.3 ± 2.4, 17.9 ± 2.3, and 15.1 ± 2.3 mm, respectively, whereas the mean patellar height was 35.1 ± 4.1, 36.7 ± 4.2, and 35.1 ± 3.9 mm. In general, the tendon and patellar dimensions were significantly larger in male participants than in female participants ( P = .016). Conclusion: Bone block harvesting, with its depth not exceeding 50% of the patellar thickness and its length accounting for <50% of the patellar height, poses the least risk for a patellar fracture when located medial to midline. If the bone block is excised from the medial half of the central area (the latter is defined by the middle third of the QT insertion), with the outer edge of the saw positioned at the medial border of the central area, a graft of 15 mm length, 10 mm width, and 8 mm depth can be safely harvested in all White male participants and almost all female participants taller than 165 cm, according to our findings. Clinical Relevance: This is the first study presenting recommendations for patellar bone block harvesting at the quadriceps tendon insertionbased on physical regularities and objective criteria and not on personal experience.

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

“…Although we did not find a correlation with the cut depth as a percentage of patellar thickness, the cuts were below the 50% threshold suggested by Negrin et al. 23 and were on average around 30% of the thickness. Although no significant difference was associated with patellar width in this study, patellar height was associated with an increased fracture risk for the BQT specimens, thus indicating the implications of patellar morphology on fracture potential.…”

“…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.…”

“… 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. 15 examined morphologic parameters associated with patellar fracture after QT autograft harvest.…”

Harvesting a second graft from the extensor mechanism for revision ACL reconstruction does not delay return of quadriceps function

“…Surgeons may prefer an extensor mechanism graft instead of HS autograft due to HS variable size, slower healing, diminished knee flexion strength and the theoretical risk of compromising a secondary stabilizer to the ACL [4, 8, 19]. Additionally, both QT and BTB grafts can be taken with a bone block which may also be used to address osseous defects from the primary surgery and can be adjusted in length based on patient anatomy [19, 23]. With increasing use of extensor mechanism grafts in primary and revision ACL reconstruction, a better understanding of outcomes when two grafts are taken from the extensor mechanism is needed.…”

Current trends in graft choice for primary anterior cruciate ligament reconstruction – part II: In‐vivo kinematics, patient reported outcomes, re‐rupture rates, strength recovery, return to sports and complications

“…Recently safe zones for bone block harvest have been described. A precise surgical technique is recommended, with harvest localization medial to midline and without exceeding 50% of the patellar thickness and patellar height [ 30 , 93 ]. Compared to patella fractures, ruptures of the quadriceps or patella tendon after ACL-R are even rarer 1% and mainly reported only as case reports [ 69 , 83 , 87 , 118 ].…”