Abstract
Introduction
Standard surgical exposure reduces blood flow to the patella during total knee arthroplasty (TKA). Reduction of patellar blood flow has resulted in patellofemoral complications including osteonecrosis and patellar fracture, necessitating revision surgery. Eversion of the patella is typically used to gain access to the knee joint in most TKA surgical approaches. More recently, the development of minimally invasive surgery (MIS) techniques has avoided patellar eversion by subluxing the patella. The present study is the first to measure patellar blood flow during MIS TKA with the knee in both extension and 90 degrees of flexion followed by lateral retraction and then eversion of the patella.
Methods
Patellar blood flow was measured using laser Doppler flowmetry in 40 patients during MIS TKA. Patients included 32 women and 8 men who had a mean age of 73 years (range, 52 to 88 years) and a mean weight of 59 kg (39 to 85 kg). The pre-operative diagnoses were osteoarthritis in 36 patients and rheumatoid arthritis in four patients. All patients underwent MIS TKA using the mini-midvastus approach. After initial blood flow was assessed with the leg in full extension, further measurements were performed after lateral retraction and after eversion of the patella. Then, blood flow was assessed with the knee in 90 degrees of flexion followed by lateral retraction and then eversion of the patella.
Results
For measurements made during knee extension, a significant reduction in flow was observed during eversion of the patella compared with the neutral patellar position (P < 0.001). However, no significant difference was found between lateral retraction of the patella and the neutral patellar position. A significant reduction in flow was noted when the leg was flexed from full extension to 90 degrees (P < 0.001). For measurements made with the knee in 90 degrees of flexion, a significant reduction in flow was observed during eversion of the patella (P = 0.002) and a significant increase was noted during lateral retraction of the patella compared with the neutral position (P < 0.001).
Conclusion
Patella eversion may result in traction both on medial vessels and those within the quadriceps mechanism, whereas, lateral retraction reduces the force exerted on the arteries within the quadriceps after the medial blood supply was interrupted by medial arthrotomy. In addition, the position of the leg had a great impact on patellar blood flow. MIS TKA without patellar eversion may be useful for preventing a reduction in patellar blood flow.
