Background <p>Accurate measurement of tibial rotation in anterior cruciate ligament (ACL) injury remains challenging because most devices rely on skin-referenced measurements and do not account for concurrent femoral rotation. Moreover, conventional assessments focus on central axial internal rotation (CAIR) rather than the more physiological medial pivotal rotation (MPR), which reflects the pivot-shift phenomenon. This study aimed to (1) develop a portable automated knee arthrometer to measure anterior translation (AT), CAIR, and MPR; (2) assess its reliability and validity in skin- and bone-referenced measurements; (3) investigate the skin-bone relationship considering concurrent femoral rotation; and (4) compare MPR with conventional CAIR for clinical utility.</p> Methods <p>Six cadaveric lower limbs were evaluated under intact, ACL-sectioned, and combined ACL- and anterolateral ligament-sectioned conditions. AT was measured using a laser displacement sensor. Tibial and femoral rotations were measured using skin- and bone-referenced sensors. Intrarater and interrater reliability were assessed, and validity was evaluated by comparison with Lachmeter for AT and Mako for CAIR. The relationship between skin- and bone-referenced rotation was analyzed using regression, and the increase in rotation after ACL sectioning was compared between MPR and CAIR.</p> Results <p>The arthrometer demonstrated excellent intrarater and interrater reliability for AT, CAIR, and MPR (ICCs &gt; 0.90). It showed higher interrater reliability than the Lachmeter in injured knees (<i>P</i> = .004). Validity against reference devices was acceptable. Although skin- and bone-referenced rotational measurements differed significantly (<i>P</i> &lt; .001), cadaver-wise regression showed strong correlation for net tibial rotation (R²: 0.833 for CAIR; 0.715 for MPR). The increase in MPR after ACL sectioning was significantly greater than that of CAIR (4.31° vs. 1.49° at 4&#xa0;N·m, <i>P</i> &lt; .001).</p> Conclusions <p>The arthrometer showed excellent reliability and acceptable validity for assessing AT, CAIR, and MPR. Although skin-referenced measurements differ from true osseous rotation, they may provide clinically meaningful assessments for within-subject comparisons. MPR increased more than CAIR after ACL sectioning, suggesting it may serve as a superior marker for ACL deficiency.</p>

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Validation and reliability of a novel portable automated knee arthrometer: a cadaveric study bridging the skin-to-bone gap and suggesting medial pivotal rotation as a superior marker for ACL deficiency

  • Geunwu Gimm,
  • Sungwoo Park,
  • Man Soo Kim,
  • Hyuk-Soo Han,
  • Sungwan Kim

摘要

Background

Accurate measurement of tibial rotation in anterior cruciate ligament (ACL) injury remains challenging because most devices rely on skin-referenced measurements and do not account for concurrent femoral rotation. Moreover, conventional assessments focus on central axial internal rotation (CAIR) rather than the more physiological medial pivotal rotation (MPR), which reflects the pivot-shift phenomenon. This study aimed to (1) develop a portable automated knee arthrometer to measure anterior translation (AT), CAIR, and MPR; (2) assess its reliability and validity in skin- and bone-referenced measurements; (3) investigate the skin-bone relationship considering concurrent femoral rotation; and (4) compare MPR with conventional CAIR for clinical utility.

Methods

Six cadaveric lower limbs were evaluated under intact, ACL-sectioned, and combined ACL- and anterolateral ligament-sectioned conditions. AT was measured using a laser displacement sensor. Tibial and femoral rotations were measured using skin- and bone-referenced sensors. Intrarater and interrater reliability were assessed, and validity was evaluated by comparison with Lachmeter for AT and Mako for CAIR. The relationship between skin- and bone-referenced rotation was analyzed using regression, and the increase in rotation after ACL sectioning was compared between MPR and CAIR.

Results

The arthrometer demonstrated excellent intrarater and interrater reliability for AT, CAIR, and MPR (ICCs > 0.90). It showed higher interrater reliability than the Lachmeter in injured knees (P = .004). Validity against reference devices was acceptable. Although skin- and bone-referenced rotational measurements differed significantly (P < .001), cadaver-wise regression showed strong correlation for net tibial rotation (R²: 0.833 for CAIR; 0.715 for MPR). The increase in MPR after ACL sectioning was significantly greater than that of CAIR (4.31° vs. 1.49° at 4 N·m, P < .001).

Conclusions

The arthrometer showed excellent reliability and acceptable validity for assessing AT, CAIR, and MPR. Although skin-referenced measurements differ from true osseous rotation, they may provide clinically meaningful assessments for within-subject comparisons. MPR increased more than CAIR after ACL sectioning, suggesting it may serve as a superior marker for ACL deficiency.