Non-anatomical capsular closure of a standard parapatellar knee arthrotomy leads to patellar maltracking and decreased range of motion: a cadaver study

Purpose A parapatellar approach disrupts the medial soft tissue stabilizers of the patella. We hypothesized that soft tissue realignment during arthrotomy closure of native cadaveric knees influences patellar kinematics leading to decreased range of motion. Methods Parapatellar arthrotomy was performed in seven native human cadaveric knees that did not contain arthroplasty components. Capsular closure was performed with figure-of-eight sutures in five different positions for each specimen. The capsule was closed anatomically, and then shifted 1.5 or 3 cm distal, or 1.5 or 3 cm proximal relative to surgical markings of the patellar poles. In each closure position, real-time patellar kinematics and range of motion were recorded using a navigation system with patellar tracking function. Results Maximum knee flexion was significantly reduced with closure shifted 3 cm proximal (133 degrees +/- 8.2 degrees, p < 0.001) or distal (139 degrees +/- 6.4 degrees, p < 0.05) compared to anatomical closure (147 degrees +/- 4.1 degrees). All closure positions significantly influenced patellar rotation at 45 degrees, 90 degrees, and 120 degrees of flexion (p < 0.001). Closure 1.5 or 3 cm distal increased lateral patellar shift relative to the mechanical axis (p < 0.01). Patellar tilt was significantly decreased at 90 degrees and 120 degrees by closure 3 cm distal (p < 0.01) and at 120 degrees when closed 1.5 cm distal (p < 0.05). Conclusions Imprecise arthrotomy closure significantly impacted patellar kinematics and passive range of motion. Therefore, every effort should be made to provide anatomical closure of the extensor mechanism to preserve native patellar movement kinematics. Level of evidence V.