A Comprehensive Description of the Lateral Patellofemoral Complex: Anatomy and Anisometry

Abstract

Background: The lateral patellofemoral complex (LPFC) is an important stabilizer of the patella composed of the lateral retinacular structures including the lateral patellofemoral ligament (LPFL), the lateral patellomeniscal ligament (LPML), and the lateral patellotibial ligament (LPTL). While the isolated anatomy of the LPFL has been previously described, no previous study has investigated the entirety of the LPFC structure, length changes, and radiographic landmarks. An understanding of LPFC anatomy is important in the setting of LPFL injury or previous lateral release resulting in iatrogenic medial instability requiring LPFC reconstruction. Purpose: To both qualitatively and quantitatively describe the anatomy and length changes of the LPFC on gross anatomic dissections and standard radiographic views. Study Design: Descriptive laboratory study. Methods: Ten nonpaired cadaveric specimens were utilized in this study. Specimens were dissected to identify distinct attachments of the LPFL, LPML, and LPTL. Ligament lengths, footprints, and centers of each attachment were described with respect to osseous landmarks using a 3-dimensional coordinate measuring device. Ligament length changes were also assessed from 0° to 90° of flexion. Radiopaque markers were subsequently utilized to describe attachments on standard anteroposterior and lateral radiographic views. Results: The individual elements of the LPFC were identified in all specimens. The LPFL patellar attachment had an average total length of 22.5 mm (range, 18.3-27.5 mm), involving a mean of 59% (range, 50%-75%) of the sagittal patella. Based on the average patellar size, a mean of 63% of the LPFL attached to the patella, and the remainder (11.1 ± 1.4 mm) inserted into the patellar tendon. The femoral attachment of the LPFL had a mean maximum length of 24.4 ± 4.3 mm. The center of the LPFL femoral attachment was a mean distance of 13.5 ± 3.2 mm anterior and distal to the lateral epicondyle. The LPFL demonstrated significant shortening, especially in the first 45° of flexion (7.5 ± 5.1 mm). In contrast, the LPTL (5.5 ± 3.0 mm) and LPML (10.0 ± 3.3 mm) demonstrated significant shortening from 45° to 90°. On lateral radiographs, the center of the femoral attachment of the LPFL was a mean total distance of 19.2 ± 7.2 mm from the lateral epicondyle. Conclusion: The most important findings of this study were the correlative anatomy of 3 distinct lateral patellar ligaments (LPFL, LPML, and LPTL) and their anisometry through flexion. All 3 components demonstrated significant shortening during flexion. The quantitative and radiographic measurements detailed the LPFL osseous attachment on the patella; soft tissue attachment on the patellar tendon; and finally, the osseous insertion on the femur distal and anterior to the lateral epicondyle. Similarly, the authors documented the meniscal insertion of the LPML and defined a patellar insertion of the LPTL and LPML as a single attachment. These data allow for reproducible landmarks to aid in the understanding and reconstruction of the lateral patellar restraints. Clinical Relevance: The data produced from this investigation provide a comprehensive description of these 3 lateral patellar stabilizers (LPFL, LPML, LPTL). These data can be used intraoperatively to facilitate anatomic reconstructions of the lateral patellar stabilizers.

Lateral Patellofemoral Ligament Reconstruction: A Biomechanical Comparison of 2 Techniques

“…Specifically, a previous study from our institution demonstrated that the LPFL is significantly looser at 45° to 90° of flexion compared with full extension. 14 Interestingly, both reconstruction groups appeared to mimic this loosening of the native LPFL up to 60°. In contrast to that study, however, the LRR and reconstruction groups in the current investigation had a significant decrease in medial patellar translation from 60° to 90°, returning to a value similar to that observed in full extension.…”

“…2,5 In this study, 2 anchor locations along the lateral aspect of the patella were utilized (superolateral and proximal to the distal aspect of the lateral facet of the articular surface) that corresponded with previous anatomic descriptions of the patellar insertion of the LPFC. 14 In addition, in this study, fixation of the graft was performed with the knee in full extension without additional direct tension applied. This approach mirrors the senior author's approach to MPFL reconstruction to prevent overtensioning of the graft.…”

“…While the suture of the quadriceps was held taut by the assistant, a small hole was drilled at the superolateral aspect of the patella and just proximal to the distal aspect of the lateral facet of the patella. These locations were based on the anatomic insertion of the LPFC on the patella 14 in addition to the clinical experience of the senior author. These holes were tapped, and a 3.0-mm PEEK suture anchor (Arthrex) was placed in each bone tunnel.…”

“…The femoral insertion of the LPFL was identified anterior and distal to the lateral epicondyle, as determined from previous anatomic dissections evaluating the femoral origin of the LPFL that were performed at our institution. 14 This location was confirmed via manual palpation by tracing the thickening of the LPFL to its femoral attachment. A Beath pin was then inserted at this location, followed by an 8-mm reamer.…”