Patellar fracture type and prognosis in condylar total knee arthroplasty.

Fractures of the patella occurred following implantation of 36 condylar total knee arthroplasties in 35 patients. The end results were evaluated in relation to fracture type after an average 4.5-year follow-up period. The follow-up observations included a physical examination, quantitative knee score, and roentgenographic evaluations of extremity alignment and implant position. Twenty-two of the 36 knees had a good or excellent knee score and 14 had a fair or worse score at the time of the latest follow-up evaluation. The satisfactory knees had an average arc of motion of 100 degrees, while the unsatisfactory knees had an average arc of motion of 80 degrees. Fourteen fractures through the mid-body or superior pole of the patella not involving the implant, cement, or quadriceps mechanism (Type I) and two nondisplaced fractures through the inferior pole of the patella (Type IIIB) were managed nonoperatively, with all knees rating either a good or excellent score. Fractures of the patella disrupting the quadriceps mechanism or implant/bone/cement composite (Type II) were managed operatively in the six knees. Fractures of the inferior pole of the patella with disruption of the patellar ligament (Type IIIA) were managed operatively in seven of eight knees (one patient refused surgery). Lateral fracture-dislocations were managed operatively in all six knees. Six of the knees operated upon had a good or better score, and nine knees were rated as poor or failed. Those fractures alignment and implant position were seen had the more severe patellar fractures and poorest outcomes.(ABSTRACT TRUNCATED AT 250 WORDS)