| Summary: | Purpose. To evaluate the associations between isolated anteromedial (AM) or posterolateral (PL) bundle tear of the anterior cruciate ligament (ACL), the time from injury to surgery, and various clinical tests. Methods. 36 women and 189 men aged 16 to 52 (mean, 26.4) years underwent ACL reconstruction of the right (n=107) and left (n=118) knees. Patients were evaluated for the International Knee Documentation Committee Subjective Knee Score, Cincinnati Knee Rating System Score, anterior drawer test, Lachman test, pivot shift test, KT1000 arthrometer measurement, isokinetic muscle tests of the extensors, and functional tests (single leg hop and timed hop test). Examination under anaesthesia (EUA) was also performed, followed by diagnostic arthroscopy. The integrity of the ACL bundles was tested using a probe. The AM and PL bundles were morphologically intact if structurally present, and functionally intact if not lax on probing. Results. Of the 225 patients, 8 had isolated AM bundle tears, 2 had isolated PL bundle tears, and 215 had complete ACL tears in terms of function. The corresponding numbers were 30, 13, and 182 in terms of morphology. Compared with patients with complete ACL tear, the mean time from injury to surgery was significantly shorter in patients with isolated AM or PL bundle tear in terms of function (17.5 vs. 5.6 months, p±0.001) and morphology (17.5 vs. 8.8 months, p±;0.001). Compared with patients with complete ACL tear, those with a functionally intact PL bundle had a higher rate of negative pivot shift test in preoperative evaluation (1% vs. 17%, p=0.002) and EUA (1% vs. 63%, p±0.001), and had a higher rate of negative Lachman test in EUA (1% vs. 25%, p=0.02). Conclusion. The time from injury to surgery was shorter in patients with isolated bundle ACL tear. In patients with ACL deficiency, the pivot shift test was useful in detecting an intact PL bundle.
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