What leads to unfavourable Cybex test results for quadriceps power after modified tension band osteosynthesis of patellar fractures?

This study recruited 20 patients who had undergone modified tension band wiring for patellar fracture, with a mean follow up of 30 months. Subjects were grouped according to results of Cybex isokinetic testing at 60 degrees /s angular velocity. Subjects with <30% deficit as compared with the contralateral knee constituted group I, and those with >30% similar deficit formed group II. Plain radiography and HSS scoring were also performed. According to patient satisfaction, HSS scoring and Cybex testing, results were good in 80%, 90% and 55% of cases, respectively. Statistical analysis revealed that there were no significant differences between the two groups in terms of age, gender, duration of follow up, fracture type (two-part or comminuted), dominancy, time interval between trauma and surgery, or duration of immobilisation. The number of patients with >1 mm articular incongruity postoperatively was significantly higher in group II, which also had significantly higher incidences of >1 cm thigh atrophy and pain and thus increased deficits. We suggest that articular incongruity should be limited strictly to 1mm in surgery for patellar fractures.