Scott R Nodzo1, Maximilian Kasparek2, Kilian Rueckl3, Friedrich Boettner3. 1. Adult Reconstruction and Joint Replacement Division, Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA. spodzo@gmail.com. 2. Department of Orthopedic Surgery, Vienna General Hospital, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria. 3. Adult Reconstruction and Joint Replacement Division, Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA.
Abstract
PURPOSE: The medial parapatellar arthrotomy (MPPA) is a commonly utilized surgical approach; however, the placement of the arthrotomy and its influence on intraoperative patellar tracking has not been evaluated. METHODS: Six knees from three fresh frozen cadavers with transthoracic amputations were operated on. All underwent standard posterior stabilized total knee arthroplasty using a medial parapatellar approach placed at the border of the vastus medialis oblique (VMO)-quadriceps junction. Patellae were resurfaced in the standard fashion. All patellae tracked normally with the first arthrotomy placed at the junction of the VMO-quadriceps tendon using the "no touch" technique. Measurement of patellar lift-off from the implant surface of the medial aspect of the trochlea on the femoral component was made at 50°, 75°, and 90° of flexion and a merchant view radiograph taken to evaluate radiographic patellar tilt. To simulate a more lateral placement of the MPPA, a 5-6 mm slice of quadriceps tendon was then removed from the lateral aspect of the tendon from the patellar insertion to the most proximal portion of the arthrotomy. This simulated a 5-6 mm more lateral placement of the parapatellar arthrotomy. The same measurements and radiographs were taken as described previously. Two more times the same size slices was removed from the quadriceps tendon with subsequent measurements and radiographs obtained. RESULTS: The mean patellar lift-off with the first arthrotomy was 0 ± 0 mm for 50°, 75°, and 90° of flexion. The mean lift with the second arthrotomy was 2 ± 2, 3 ± 3, and 4 ± 3 mm respectively. The third arthrotomy had a mean patellar lift-off of 3 ± 2, 4 ± 3, and 8 ± 2 mm respectively, while the fourth arthrotomy had a mean lift-off of 6 ± 2, 8 ± 2, and 9 ± 4 mm. There was a significant correlation between percentage of quadriceps cut at 1 cm above the superior pole of the patella and patellar lift-off at 50° (R 2 = 0.70; p < 0.0001), 75° (R 2 = 0.68; p < 0.0001), and 90° (R 2 = 0.68; p < 0.0001) of flexion. CONCLUSION: The location of the MPPA has a significant influence on intraoperative assessment of patellar tracking. An MPPA more lateral in the quadriceps tendon may independently influence the patellar tilt observed intraoperatively and should be taken into consideration when evaluating intraoperative patella tracking. An understanding of the independent influence the MPPA has on patellar tracking may decrease the need for lateral release if the surgeon notes the MPPA was made more than 5-10 mm from the junction of the VMO-quadriceps tendon junction.
PURPOSE: The medial parapatellar arthrotomy (MPPA) is a commonly utilized surgical approach; however, the placement of the arthrotomy and its influence on intraoperative patellar tracking has not been evaluated. METHODS: Six knees from three fresh frozen cadavers with transthoracic amputations were operated on. All underwent standard posterior stabilized total knee arthroplasty using a medial parapatellar approach placed at the border of the vastus medialis oblique (VMO)-quadriceps junction. Patellae were resurfaced in the standard fashion. All patellae tracked normally with the first arthrotomy placed at the junction of the VMO-quadriceps tendon using the "no touch" technique. Measurement of patellar lift-off from the implant surface of the medial aspect of the trochlea on the femoral component was made at 50°, 75°, and 90° of flexion and a merchant view radiograph taken to evaluate radiographic patellar tilt. To simulate a more lateral placement of the MPPA, a 5-6 mm slice of quadriceps tendon was then removed from the lateral aspect of the tendon from the patellar insertion to the most proximal portion of the arthrotomy. This simulated a 5-6 mm more lateral placement of the parapatellar arthrotomy. The same measurements and radiographs were taken as described previously. Two more times the same size slices was removed from the quadriceps tendon with subsequent measurements and radiographs obtained. RESULTS: The mean patellar lift-off with the first arthrotomy was 0 ± 0 mm for 50°, 75°, and 90° of flexion. The mean lift with the second arthrotomy was 2 ± 2, 3 ± 3, and 4 ± 3 mm respectively. The third arthrotomy had a mean patellar lift-off of 3 ± 2, 4 ± 3, and 8 ± 2 mm respectively, while the fourth arthrotomy had a mean lift-off of 6 ± 2, 8 ± 2, and 9 ± 4 mm. There was a significant correlation between percentage of quadriceps cut at 1 cm above the superior pole of the patella and patellar lift-off at 50° (R 2 = 0.70; p < 0.0001), 75° (R 2 = 0.68; p < 0.0001), and 90° (R 2 = 0.68; p < 0.0001) of flexion. CONCLUSION: The location of the MPPA has a significant influence on intraoperative assessment of patellar tracking. An MPPA more lateral in the quadriceps tendon may independently influence the patellar tilt observed intraoperatively and should be taken into consideration when evaluating intraoperative patella tracking. An understanding of the independent influence the MPPA has on patellar tracking may decrease the need for lateral release if the surgeon notes the MPPA was made more than 5-10 mm from the junction of the VMO-quadriceps tendon junction.
Authors: Michael J Archibeck; David Camarata; James Trauger; James Allman; Richard E White Journal: Clin Orthop Relat Res Date: 2003-09 Impact factor: 4.176
Authors: Wolf Petersen; Ingo Volker Rembitzki; Gerd-Peter Brüggemann; Andree Ellermann; Raymond Best; Andreas Gösele- Koppenburg; Christian Liebau Journal: Int Orthop Date: 2013-09-22 Impact factor: 3.075