Objective: To determine the functional strength and gait adaptations utilized by patients with patellar fractures repaired by both partial patellectomy and open reduction, internal fixation (ORIF). We hypothesize that there will be no difference in thigh strength or gait biomechanics for ORIF subjects in side to side comparisons or to normal controls while partial patellectomy subjects will show side to side strength deficits and altered gait biomechanics.
Main Outcome Measures: Standard clinical evaluation including extensor lag, ROM and manual muscle testing, isometric knee dynamometer torque in extension and flexion, knee and hip kinematics (flexion angles) and knee and hip kinetics (external flexion moments) were assessed for subjects with patellar repairs by partial patellectomy and open reduction, internal fixation and for a normal, uninjured control group.
Results: Subjects: mean age: 42.8 ± 15.7 years, mean height: 172.5 ± 7.6 cm, mean mass: 83.4 ± 21.1 kg, mean time from surgery: 35.8 ± 20.0 months. Subjects were considered normal from standard clinical evaluations. For isometric extensor torque, there existed a mean side to side deficit for all fractures of 22% (p=0.005) on the involved leg. This was driven by the partial patellectomies alone due to their 20% deficit (p=0.050) while there was no significant deficit for ORIF subjects. Compared to controls, partial patellectomies alone were 38% weaker in extension (p=0.014) while ORIF subjects were not different. During gait, partial patellectomies saw decreased knee flexion angles (9.5°, p=0.03) compared to controls (15.6°) while ORIF subjects had increased knee flexion angles (26.8°, p=0.006).
Conclusions: By removing a sizeable fragment of the patella when performing a partial patellectomy, the effectiveness of the extensor mechanism is drastically reduced, showing long term functional impairments in both quadriceps strength and gait while fractures repaired by open reduction, internal fixation regain symmetric strength and gait patterns that are not different from uninjured controls.