Biomechanical experiment and clinical report of modified patellectomy for polar fracture of the patella.

OBJECTIVE: To study the influence of polar patel-lectomy and the site of reanchored the patellar tendon on femoral quadriceps extensing force. METHODS: The experiment was designed by using 5 lower limbs of cadavers for extracorporal biodynamic test. The maximal fixing force of the double stainless steel wire (0.4 mm in diameter) reanchoring the patellar ligament to the patellar cortical edge was measured. Clinically 21 patients with polar fractures were treated by removing the small fragments and reanchoring the patellar ligament to the cortical edge of the patella using the wires. RESULTS: Resection of the lower 1/4 part of the patella and the patellar ligament reanchored to cortical edge of the patella would not increase femoral quadriceps contracting force arm. But if the patellar tendon reanchored near the joint surface, much more extending force would be needed than the former (P<0.001). The maximal fixing force of the wires is 67.4 kg (60.9-72.5 kg). All the patients using this modified procedure gained satisfactory functional recovery. CONCLUSIONS: The modified partial patellecomy is a simple and effective procedure for choice.