Proximal tibiofibular joint pain after insertion of a tibial intramedullary nail: two case reports with accompanying computed tomography and cadaveric studies.

Intramedullary nail (IMN) fixation is a proven, efficient, and effective surgical intervention for diaphyseal tibia fractures. We present a case report of two patients who sustained diaphyseal tibial fractures, were treated with IMN fixation, and subsequently developed lateral and posterolateral knee pain secondary to interlocking screw penetration into the proximal tibiofibular joint (PTFJ). We performed a retrospective radiographic review of 50 consecutive knee computed tomographic scans to define the fibula's respective anatomic relationship to the tibia on axial computed tomographic images in addition to a cadaveric study of four IMN implants to evaluate the orientation of the medial inserted proximal oblique interlock screw with three-dimensional reconstructive fluoroscopy. The "danger zone" was found to be from 44.7 degrees to 72.1 degrees on the right and from 40.6 degrees to 73.0 degrees on the left. The cadaveric computed tomographic study showed the projected screw placement angles to be 45 degrees for the Synthes IMN, 45 degrees for the Stryker IMN, 48 degrees for the DePuy IMN, and 63 degrees for the Smith & Nephew IMN. These findings were correlated to an anatomically based "clock face" guide. To our knowledge, this report is the first to illuminate a PTFJ injury with the initial presenting complaint of lateral and posterolateral knee pain from a medially inserted proximal oblique interlocking screw after IMN for a diaphyseal tibia fracture. Using the proposed reproducible "clock face" diagram and understanding the computed tomography-derived PTFJ "danger zone" for placement of proximal oblique interlock screws for IMN fixation of tibia fractures, surgeons can avoid violation of the PTFJ.