Anatomical Assessment of the Hoffa Fat Pad During Insertion of a Tibial Intramedullary Nail—comparison of Three Surgical Approaches

Background: Interlocking nailing is a standard procedure in the surgical treatment of tibial fractures. Despite it has been described to be a safe technique with excellent functional results compared with conservative treatment, a common problem is the development of anterior knee pain. The anatomic relation of Hoffa’s fat pad with its nociceptors to the nail entry point has not been investigated, yet. Methods: Eighteen formalin-fixed lower cadaver extremities of 11 cadavers (five females, six males) were matched into three groups: three approaches (medial paratendinous, transligamentous, and lateral paratendinous) were performed and the anterosuperior tibial cortex was opened with a cheese cutter. To investigate the relationship of the nail entry point and Hoffa’s fat pad, the joint capsule was incised, and Hoffa’s fat pad was exposed and then dissected carefully. Damage to the fat pad was recorded as well as meniscal lesions, cartilage lesions, and ligamentous lesions. After full extension and flexion of the knee joint, the motion of Hoffa’s fat pad (millimeter) was recorded with a measuring gauge. The zone for safe nail insertion (millimeter square) without any lesion to intra-articular structures was recorded. Results: Violation of Hoffa’s fat pad was recorded if the lateral and transligamentous approach were used. With the medial approach, no damage of the fat pad was recorded. Total mean lateralization of the fat pad from extension to flexion over 90 degrees was 18.5 mm compared with its location in the fully extended knee. The safe zone for nail insertion without violation of menisci, cartilage, or ligaments was a triangle in the posteromedial aspect of the Hoffa with a mean dimension of 19.4 mm2. Conclusion: On the basis of our results, we can recommend the nail insertion via a medial paratendinous surgical approach to avoid injuries to the Hoffa fat pad and to menisci, cartilage, and ligaments.