Quadriceps tendon and patellar ligament: cryosectional anatomy and structural properties in young adults

Structural tensile properties analyses of 10-mm-wide central sections of quadriceps tendon-bone (QT-B) and bone-patellar ligament (B-PL) complexes from young male donors (mean age 24.9 years, range 19-32 years) were complemented by a cryosectional analysis: each QT-B complex was composed of the segment of the quadriceps tendon with the proximal half of the patella attached, each B-PL complex was composed of the distal half of the patella with the patellar ligament attached. A servohydraulic materials testing machine was used to assess ultimate failure load of 16 unconditioned and 16 preconditioned QT-B and B-PL complexes at an extension rate of 1 mm/s. Ligaments/tendons were preconditioned during 200 cycles from 50 to 800 N at 0.5 Hz. On cryosections the quadriceps tendons were significantly longer and thicker and exhibited a significantly larger bony attachment area than the patellar ligaments. Cross-sectional areas of 10-mm-wide, full-thickness, central parts of unconditioned quadriceps tendons were significantly greater and measured 64.6 +/- 8.4 mm2 with respect to the cross-sectional area of patellar ligaments, measuring 36.8 +/- 5.7 mm2 (P < 0.0025). Ultimate failure loads for unconditioned complexes resulted at 2173 +/- 618 N for QT-B complexes and at 1953 +/- 325 N for B-PL complexes (P = 0.43). Ultimate failure load values measured 2353 +/- 495 N for preconditioned QT-B complexes and 2376 +/- 152 N for preconditioned B-PL complexes, respectively (P = 0.77). Despite the fact that initial testing length, thickness, cross-sectional shape and area of unconditioned QT-B and B-PL complexes were significantly different, displacement at ultimate load, energy to failure and total energy were not. In terms of ultimate tensile strength, the 10-mm-wide central part of the QT-B complex compared favourably to the tensile properties of the human femur-anterior cruciate ligament-tibia complex from a comparable young age group. The evidence from anatomic, cryosectional and structural properties analyses suggests that the QT-B complex may be a valuable and versatile adjunct to the surgeon's armamentarium in reconstructive cruciate ligament surgery.