An unambiguous technique for locating the adductor tubercle and using it to identify the joint line.

BACKGROUND: If the adductor tubercle could be accurately located, it would be a useful landmark for identifying the joint line during knee arthroplasty. This study aimed to develop an intraoperative technique to improve its locating accuracy.

METHODS: Evaluation of bone specimens and cadaveric knees revealed that the proximal slope of the adductor tubercle (PSAT) turns from the medial surface vertically into the superior surface of the medial condyle, which forms a distinctive edge. This provided an ideal landmark that could be unambiguously engaged using a tipped instrument. Using the PSAT as a reference point, we measured the distance to the joint line (the proximal-distal condylar length; PDCL) in eight pairs of cadaveric knees, and evaluated the inter-observer variability. Next, we measured 120 knees undergoing total knee arthroplasty to test this technique in a normal population. Finally, we divided each PDCL by the respective anterior-posterior condylar length (APCL) to create a ratio that could predict the PDCL regardless of knee size.

RESULTS: The intra-class correlation coefficient (ICC) was 0.86 for the cadaveric measurements. The mean PDCL from the operated knees was 46mm (coefficient of variance (CV): eight percent). The mean PDCL/APCL ratio was 0.77 (CV: six percent). The high ICC and low CV indicated that using the PSAT was a reliable technique.

CONCLUSION: The PSAT is an ideal surgical landmark. The tipped instrument engagement technique with it may help to unambiguously locate the adductor tubercle in order to identify the joint line during knee arthroplasty.