The patellar inferior pole: a new landmark of the anteromedial working portal for arthroscopic surgery of the posterior horn of the medial meniscus.

We assessed the patellar inferior pole (PIP) as a new landmark of the anteromedial (AM) instrumental portal for arthroscopic surgery of the posterior horn of the medial meniscus (PHMM). Fifty normal right knees in young adults (group 1) and 50 knees from adults of various ages undergoing arthroscopic surgery for relatively simple intra-articular pathologies or diagnosis (group 2) were included. In both groups, on 30 degrees flexion true lateral plain radiographs, the line passing through the PIP and the distalmost femoral condyle; (Kim's AM portal line) was drawn, then the length from the anterior end of the medial tibial plateau (MTP) to the meeting point of Kim's AM portal line with the MTP (length C) and the anteroposterior length of the MTP (length D) was measured. The length C was then taken as a percentage of length D (C-D percentage), and the distance between the PIP and the anterior joint line (length E) was measured. The average C-D percentages and lengths E were 110+/-33.6% and 14.8+/-3.8 mm in group 1, and 114+/-38.4% and 16.3+/-4.7 mm in group 2. There were no significant differences in the C-D percentages or the lengths E between the two groups. Also, in group 2, the AM portal was made at the PIP level, and we assessed the relative ease of instrument insertion to reach the PHMM and the body of the lateral meniscus (LM) using a scoring system of our own design. Fort-nine and 48 knees were classified as good for the PHMM and for the body of the LM, respectively. We concluded that the PIP can be used as a skin landmark for arthroscopic surgery of the PHMM.