DIFFICULTIES WITH THE N+7 RULE IN ENDOSCOPIC ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION

In an effort to facilitate the use of interference screw fixation in t he tibia, a method to orient the tibial tunnel termed the ''N + 7 Rule '' was prospectively applied to 60 consecutive endoscopic anterior cru ciate ligament reconstructions performed by a single surgeon. Four cas es were excluded because a breach in the described protocol for applic ation of the N + 7 rule was identified at the time of the operation. O f the remaining 56 cases, 28 (50%) were fixed with an interference scr ew on the tibia, whereas 28 (50%) required fixation with sutures tied over a post. The 28 cases not amenable to interference screw fixation included 17 cases in which the tibial tunel was too long and 11 cases in which the tunnnel was too short, It appears that the applicability of the N + 7 rule to an individual surgeon's practice may be altered b y small variations in operative technique.