To determine a relationship between the direction of the guide pin for the keyhole in the lateral meniscus (LM) transplantation and the line connecting the centers of both horns of the LM.
Forty-four resected tibial plateaus during total knee arthroplasty were used for anatomical and radiological evaluations. The inclusion criterion was medial compartment osteoarthritis. Exclusion criteria were osteoarthritic changes, meniscal tear, and previous fracture in the lateral compartment. Resected tibial plateaus were positioned so that the anterior and posterior parts of the lateral tibial spine (LTS) were overlapped accurately on fluoroscopic anteroposterior view. A wire (Pin-F) was drilled along the peak of the LTS. The insertion area of anterior and posterior horns of the LM was dissected carefully. The periphery and the center of the insertion area of both horns were marked. Another wire (Pin-A) was drilled along a line connecting the centers of both horns. An axial radiograph was taken for each prepared tibial plateau. A longitudinal line was drawn along each wire, and the angle between the 2 wires was measured using the imaging software. If the Pin-F was externally rotated relative to the Pin-A, the angle was designated as positive, and if the Pin-F was internally rotated, the angle was designated as negative.
The mean angle between Pin-F and Pin-A was -7.4° ± 9.6°. Thirty-three (75%) Pin-Fs were fixed in an internally rotated position, and 11 (25%) were fixed in an externally rotated position.
The axis of the LTS is not a reliable marker for the trough in the LM allograft transplantation.
The direction of most guide pins drilled along the LTS was not coincident with the line connecting the centers of both horns of the LM.