Department of Orthopaedics, Rush University Medical Center, 1611 W. Harrison St., Ste 300, Chicago, IL, 60612, USA.
McGaw Medical Center at Northwestern University, Chicago, IL, 60611, USA.
Knee Surg Sports Traumatol Arthrosc. 2021 Mar;29(3):757-763. doi: 10.1007/s00167-020-05999-2. Epub 2020 May 2.
A comprehensive understanding of the biomechanical properties of the medial patellofemoral complex (MPFC) is necessary when performing an MPFC reconstruction. How components of the MPFC change over the course of flexion can influence the surgeon's choice of location for graft fixation along the extensor mechanism. The purpose of this study was to (1) determine native MPFC length changes throughout a 90° arc using an anatomically based attachment and using Schöttle's point, and (2) compare native MPFC length changes with different MPFC attachment sites along the extensor mechanism.
Eight fresh-frozen (n = 8), cadaveric knees were dissected of all soft tissue structures except the MPFC. The distance between the femoral footprint (identified through anatomical landmarks and Schottle's point) and the MPFC was calculated at four attachment sites along the extensor mechanism [midpoint of the patella [MP], the center of the osseous footprint of the MPFC (FC), the superomedial corner of the patella at the quadriceps insertion (SM), and the proximal extent of the MPFC along the quadriceps tendon (QT)] at 0°, 20°, 40°, 60°, and 90° of flexion.
Length changes were investigated between the MPFL femoral attachment site and the radiographic surrogate of the MPFL attachment site, Schottle's Point (SP). Paired t tests at each of the four components showed no differences in length change from 0° to 90° when comparing SP to the anatomic MPFC insertion. MPFL length changes from 0° to 90° were greatest at the QT point (13.9 ± 3.0 mm) and smallest at the MP point (2.7 ± 4.4 mm). The FC and SM points had a length change of 6.6 ± 4.2 and 9.0 ± 3.8, respectively. Finally, when examining how the length of the MPFC components changed through flexion, the greatest differences were seen at QT where all comparisons were significant (p < 0.01) except when comparing 0° vs 20° (n.s.).
The MPFC demonstrates the most significant length changes between 0° and 20° of flexion, while more isometric behavior was seen during 20°-90°. The attachment points along the extensor mechanism demonstrate different length behaviors, where the more proximal components of the MPFC display greater anisometry through the arc of motion. When performing a proximal MPFC reconstruction, surgeons should expect increased length changes compared to reconstructions utilizing distal attachment sites.
在进行髌股内侧支持带复合体（MPFC）重建时，需要全面了解 MPFC 的生物力学特性。MPFC 在弯曲过程中各组成部分的变化如何会影响外科医生选择在伸肌机制上进行移植物固定的位置。本研究的目的是：（1）使用解剖学基础附着点和 Schöttle 点，确定整个 90°弧中 MPFC 的固有长度变化；（2）比较不同 MPFC 附着点在伸肌机制上的固有 MPFC 长度变化。
解剖了 8 个新鲜冷冻（n=8）、尸体膝关节，除了 MPFC 之外，所有软组织结构都被解剖。在伸肌机制的四个附着点（髌骨中点 [MP]、MPFC 骨足印的中心 [FC]、髌骨上极在股四头肌止点处 [SM]和股四头肌肌腱近端的 MPFC 延伸处 [QT]）上，计算股骨足迹（通过解剖标志和 Schottle 点确定）与 MPFC 之间的距离，在 0°、20°、40°、60°和 90°的弯曲度下。
在 MPFL 股骨附着点和 MPFL 附着点的放射学替代物 Schottle 点（SP）之间研究了长度变化。在四个组件中的每一个组件中进行的配对 t 检验显示，从 0°到 90°，SP 与解剖学上的 MPFC 插入点之间的长度变化没有差异。MPFL 从 0°到 90°的长度变化在 QT 点最大（13.9±3.0 mm），在 MP 点最小（2.7±4.4 mm）。FC 和 SM 点的长度变化分别为 6.6±4.2 和 9.0±3.8。最后，当检查 MPFC 成分在弯曲过程中如何变化时，在 QT 处观察到最大的差异，所有比较均具有统计学意义（p<0.01），除了 0°与 20°之间的比较（无统计学意义）。
MPFC 在 0°至 20°的弯曲中显示出最大的长度变化，而在 20°至 90°之间表现出更多的等距行为。伸肌机制上的附着点表现出不同的长度行为，其中 MPFC 的更近端成分在运动弧中表现出更大的各向异性。当进行近端 MPFC 重建时，与利用远端附着点的重建相比，外科医生应预计会有更大的长度变化。
