Accuracy of haptic assessment of patellar symmetry in total knee arthroplasty

Resection resulting in asymmetrically thick patellar arthroplasty in knee arthroplasty may lead to increased compression forces, wear, fracture, or loss of quadriceps power. Assessing the cut patella between the thumb and forefinger (haptic assessment) represents a convenient way to recognize asymmetry. In 2 test series, 8 orthopedic surgeons evaluated 24 precut solid foam patellae of varying asymmetric thickness by feeling the patella between thumb and forefinger, without visualization. Of 384 responses, in 73.2% asymmetry was underestimated, 10.4% assessments were exact, and in 16.4% asymmetry was overestimated. Specifically, 35.9% were correct within 1 mm, 60.7% within 2 mm, 81% within 3 mm, and 91.4% within 4 mm. The thickest half of the patella was correctly identified in 90.6% of responses. Haptic assessment of patellar symmetry is a useful technique in knee arthroplasty.