What's the most appropriate measurement to assess the rotatory instability of ACL injuries? - by Stress X-ray
Author(s):
Kim S. (South Korea (ROK))
,
Kim S. (South Korea (ROK))
Affiliations:
Park Y.
,
Park Y.
Affiliations:
Lee H.
,
Lee H.
Affiliations:
Kim K.
,
Kim K.
Affiliations:
Jeong H.
,
Jeong H.
Affiliations:
Kim J.
,
Kim J.
Affiliations:
Yun B.
,
Yun B.
Affiliations:
Kim D.
Kim D.
Affiliations:
ESSKA Academy. Kim S. 05/09/18; 209365; P04-837 Topic: Basic Science
Dr. Seong Hwan Kim
Dr. Seong Hwan Kim
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Abstract
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Objectives: There are no articles on which specific knee flexion angle would give more accurate diagnosis for clinical rotatory instability(pivot shift) for ACL injury. The aim of this study is to evaluate diagnostic efficiency of rotatory instability in each flexion angle.

Methods: A total 79 cases with 42 cases of complete ACL tear and 37 normal subjects were enrolled. For each patient, radiographs of both knees using stress telos device were taken. The side-to-side differences between the injured and the contralateral uninjured knees were measured from dynamic radiographs. The values of conventional measurement methods (medial-medial[MM], lateral-lateral [LL]) were assessed, and the difference between the values of LL-MM was calculated[DLM]. All radiologic measurements were obtained from a PAC monitor using a mouse point cursor and an automated computer calculation.
The clinical rotatory instability was confirmed with pivot shift test, and the correlation between pivot shift and the measured value was analyzed using ROC curves. Receiver-Operating Characteristic (ROC) curves were plotted to evaluate diagnostic efficacy of each group.

Results: The mean side to side difference on dynamic radiographs using stress device were measured in MM methods as ; 30° position in MM : 5.86±1.85mm, 45° position in MM: 4.04±2.02mm, 60° position in MM: 3.9±2.31mm, 90° position in MM: 2.87±2.42mm. The mean side to side difference on dynamic radiographs using stress device were measured in LL methods as ; 30° position in LL : 8.02±2.91mm, 45° position in LL: 5.13±2.53mm, 60° position in LL: 3.53±2.46mm, 90° position in LL: 2.99±2.43mm. The mean difference on dynamic radiographs using stress device were measured in DLM methods as 30° position in DLM : 2.17±2.7mm, 45° position in DLM: 1.08±2.2mm, 60° position in DLM: -0.37±3.02mm, 90° position in DLM: 0.13±3.38mm.
The area under the ROC curve (AUC) was calculated for each position to acquire the diagnostic pivot shift (30° position in DLM: 0.792; p=0.000, 45° position in DLM: 0.654; p=0.028, 60° position in DLM: 0.476; p=0.736, 90° position in DLM: 0.429; p=0.311). The result revealed 30° position in DLM had the largest. Moreover, the 97.4% of sensitivity and 96.8% specificity was found to confirm rotatory instability when the cut off value was set as 2.0mm of DLM.

Conclusions: The difference of the value between MM and LL methods in position of 30° knee flexion was significantly superior to the other position to confirm rotatory instability(pivot shift) and the position on 60° and 90° knee flexion was not meaningful. Moreover, 2mm of cut off value of DLM was found in stress radiograph at 30° knee flexion to diagnose in pivot shift.

Keywords:
knee instability; anterior cruciate ligament; anterior cruciate ligament rupture; rotatory instability, stress radiograph
Objectives: There are no articles on which specific knee flexion angle would give more accurate diagnosis for clinical rotatory instability(pivot shift) for ACL injury. The aim of this study is to evaluate diagnostic efficiency of rotatory instability in each flexion angle.

Methods: A total 79 cases with 42 cases of complete ACL tear and 37 normal subjects were enrolled. For each patient, radiographs of both knees using stress telos device were taken. The side-to-side differences between the injured and the contralateral uninjured knees were measured from dynamic radiographs. The values of conventional measurement methods (medial-medial[MM], lateral-lateral [LL]) were assessed, and the difference between the values of LL-MM was calculated[DLM]. All radiologic measurements were obtained from a PAC monitor using a mouse point cursor and an automated computer calculation.
The clinical rotatory instability was confirmed with pivot shift test, and the correlation between pivot shift and the measured value was analyzed using ROC curves. Receiver-Operating Characteristic (ROC) curves were plotted to evaluate diagnostic efficacy of each group.

Results: The mean side to side difference on dynamic radiographs using stress device were measured in MM methods as ; 30° position in MM : 5.86±1.85mm, 45° position in MM: 4.04±2.02mm, 60° position in MM: 3.9±2.31mm, 90° position in MM: 2.87±2.42mm. The mean side to side difference on dynamic radiographs using stress device were measured in LL methods as ; 30° position in LL : 8.02±2.91mm, 45° position in LL: 5.13±2.53mm, 60° position in LL: 3.53±2.46mm, 90° position in LL: 2.99±2.43mm. The mean difference on dynamic radiographs using stress device were measured in DLM methods as 30° position in DLM : 2.17±2.7mm, 45° position in DLM: 1.08±2.2mm, 60° position in DLM: -0.37±3.02mm, 90° position in DLM: 0.13±3.38mm.
The area under the ROC curve (AUC) was calculated for each position to acquire the diagnostic pivot shift (30° position in DLM: 0.792; p=0.000, 45° position in DLM: 0.654; p=0.028, 60° position in DLM: 0.476; p=0.736, 90° position in DLM: 0.429; p=0.311). The result revealed 30° position in DLM had the largest. Moreover, the 97.4% of sensitivity and 96.8% specificity was found to confirm rotatory instability when the cut off value was set as 2.0mm of DLM.

Conclusions: The difference of the value between MM and LL methods in position of 30° knee flexion was significantly superior to the other position to confirm rotatory instability(pivot shift) and the position on 60° and 90° knee flexion was not meaningful. Moreover, 2mm of cut off value of DLM was found in stress radiograph at 30° knee flexion to diagnose in pivot shift.

Keywords:
knee instability; anterior cruciate ligament; anterior cruciate ligament rupture; rotatory instability, stress radiograph
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