Connor G Ziegler1, John P Fulkerson2, Cory Edgar2. 1. Department of Orthopaedic Surgery, University of Connecticut Health Center, Farmington, Connecticut, USA connor.ziegler@gmail.com. 2. Orthopedic Associates of Hartford, Hartford, Connecticut, USA.
Abstract
BACKGROUND: Studies have reported methods for radiographically delineating medial patellofemoral ligament (MPFL) femoral tunnel position on a true lateral knee radiograph. However, obtaining a true lateral fluoroscopic radiograph intraoperatively can be challenging, rendering radiographic methods for tunnel positioning potentially inaccurate. PURPOSE: To quantify the magnitude of MPFL femoral tunnel malposition that occurs on true lateral and aberrant lateral knee radiographs when using a previously reported radiographic technique for MPFL femoral tunnel localization. STUDY DESIGN: Descriptive laboratory study. METHODS: Ten fresh-frozen cadaveric knees were dissected to expose the MPFL femoral insertion and surrounding medial knee anatomy. True lateral and aberrant lateral knee radiographs at 2.5°, 5°, and 10° off-axis were obtained with a standard mini C-arm in 4 orientations: anterior to posterior, posterior to anterior, caudal, and cephalad. A previously reported radiographic method for MPFL femoral localization was performed on all radiographs and compared in reference to the anatomic MPFL attachment center. RESULTS: The radiographic point, as previously described, was a mean distance of 4.1 mm from the anatomic MPFL attachment on a true lateral knee radiograph. The distance between the anatomic MPFL attachment center and the radiographic point significantly increased on aberrant lateral knee radiographs with as little as 5° of rotational error in 3 of 4 orientations of rotation when a standard mini C-arm was used. This corresponded to a malposition of 7.5, 9.2, and 8.1 mm on 5°-aberrant radiographs in the anterior-posterior, posterior-anterior, and cephalad orientations, respectively (P < .005). In the same 3 orientations of rotation, MPFL tunnel malposition on the femur exceeded 5 mm on 2.5° aberrant radiographs. CONCLUSION: The commonly utilized radiographic point, as previously described for MPFL femoral tunnel placement, results in inaccurate tunnel localization on a true lateral radiograph, and this inaccuracy is perpetuated with aberrant radiography. Aberrant lateral knee imaging of as little as 5° off-axis from true lateral has a significant effect on placement of a commonly used radiographic point relative to the anatomic MPFL femoral attachment center and results in nonanatomic MPFL tunnel placement. CLINICAL RELEVANCE: This study demonstrates that radiographic localization of the MPFL femoral tunnel results in inaccurate tunnel placement on a true lateral radiograph, particularly when there is deviation from a true lateral fluoroscopic image, which can be difficult to obtain intraoperatively. Assessing anatomy directly intraoperatively, rather than relying solely on radiographs, may help avoid MPFL tunnel malposition.
BACKGROUND: Studies have reported methods for radiographically delineating medial patellofemoral ligament (MPFL) femoral tunnel position on a true lateral knee radiograph. However, obtaining a true lateral fluoroscopic radiograph intraoperatively can be challenging, rendering radiographic methods for tunnel positioning potentially inaccurate. PURPOSE: To quantify the magnitude of MPFL femoral tunnel malposition that occurs on true lateral and aberrant lateral knee radiographs when using a previously reported radiographic technique for MPFL femoral tunnel localization. STUDY DESIGN: Descriptive laboratory study. METHODS: Ten fresh-frozen cadaveric knees were dissected to expose the MPFL femoral insertion and surrounding medial knee anatomy. True lateral and aberrant lateral knee radiographs at 2.5°, 5°, and 10° off-axis were obtained with a standard mini C-arm in 4 orientations: anterior to posterior, posterior to anterior, caudal, and cephalad. A previously reported radiographic method for MPFL femoral localization was performed on all radiographs and compared in reference to the anatomic MPFL attachment center. RESULTS: The radiographic point, as previously described, was a mean distance of 4.1 mm from the anatomic MPFL attachment on a true lateral knee radiograph. The distance between the anatomic MPFL attachment center and the radiographic point significantly increased on aberrant lateral knee radiographs with as little as 5° of rotational error in 3 of 4 orientations of rotation when a standard mini C-arm was used. This corresponded to a malposition of 7.5, 9.2, and 8.1 mm on 5°-aberrant radiographs in the anterior-posterior, posterior-anterior, and cephalad orientations, respectively (P < .005). In the same 3 orientations of rotation, MPFL tunnel malposition on the femur exceeded 5 mm on 2.5° aberrant radiographs. CONCLUSION: The commonly utilized radiographic point, as previously described for MPFL femoral tunnel placement, results in inaccurate tunnel localization on a true lateral radiograph, and this inaccuracy is perpetuated with aberrant radiography. Aberrant lateral knee imaging of as little as 5° off-axis from true lateral has a significant effect on placement of a commonly used radiographic point relative to the anatomic MPFL femoral attachment center and results in nonanatomic MPFL tunnel placement. CLINICAL RELEVANCE: This study demonstrates that radiographic localization of the MPFL femoral tunnel results in inaccurate tunnel placement on a true lateral radiograph, particularly when there is deviation from a true lateral fluoroscopic image, which can be difficult to obtain intraoperatively. Assessing anatomy directly intraoperatively, rather than relying solely on radiographs, may help avoid MPFL tunnel malposition.
Authors: Julian Mehl; Alexander Otto; Brendan Comer; Cameron Kia; Franz Liska; Elifho Obopilwe; Knut Beitzel; Andreas B Imhoff; John P Fulkerson; Florian B Imhoff Journal: Knee Surg Sports Traumatol Arthrosc Date: 2019-08-13 Impact factor: 4.342
Authors: P Koenen; S Shafizadeh; T R Pfeiffer; A Wafaisade; B Bouillon; A C Kanakamedala; V Jaecker Journal: Knee Surg Sports Traumatol Arthrosc Date: 2018-05-11 Impact factor: 4.342
Authors: Miho J Tanaka; Jorge Chahla; Jack Farr; Robert F LaPrade; Elizabeth A Arendt; Vicente Sanchis-Alfonso; William R Post; John P Fulkerson Journal: Knee Surg Sports Traumatol Arthrosc Date: 2018-10-28 Impact factor: 4.342