Comparison of two extensile approaches to the knee: a cadaveric study evaluating quadriceps snip and extensile medial parapatellar approach

Abstract

PurposeThis study aimed to evaluate the mobility and excursion of the patella achieved by two different techniques for increasing exposure to the knee joint: the quadriceps snip and the extensile medial parapatellar approach. MethodSix matched intact fresh frozen cadaveric knees were used in this study. A standard medial parapatellar approach was undertaken and the patella excursion with a constant force of 5 kg was measured based on two fixed points at 0, 45 and 90 °s of knee flexion. The left knee in the matched pair was made extensile with a quadriceps snip and the right with an extensile medial parapatellar approach. The distance and change in distance as a percentage were then recorded at 0, 45 and 90 °s of knee flexion. ResultsBoth techniques increased the mobility of the patella and its excursion. Quadriceps snip was found to give an average increase in excursion of 7 mm (12% increase in excursion), while the extensile medial parapatellar approach increased the patella distance from a fixed point by 10 mm (15% increase in excursion). Maximum displacement of the patella was consistently found to occur at 5 kg. The angle of knee flexion at which the maximum excursion was achieved was variable. ConclusionThe quadriceps snip and extensile medial parapatellar approach both provide increased mobility of the patella in the cadaveric knee. When exploring the options to increase exposure to the knee, the operating surgeon may wish to employ either the extensile medial parapatellar approach or the quadriceps snip. There may be clinical advantage in developing the plane between vastus medialis and rectus femoris, as opposed to cutting across the quadriceps tendon.