Purpose: To measure and compare the amount of anterior tibial subluxation (ATS) after anatomic ACL reconstruction for both acute and chronic ACL-deficient patients.
Methods: Fifty-two patients were clinically and radiographically evaluated after primary, unilateral, anatomic ACL reconstruction. Post-operative true lateral radiographs were obtained of both knees with the patient in supine position and knees in full passive extension with heels on a standardized bolster. ATS was measured on the radiographs by two independent and blinded observers. ATS was calculated as the side-to-side difference in tibial position relative to the femur. An independent t test was used to compare ATS between those undergoing anatomic reconstruction for an acute versus chronic ACL injury. Chronic ACL deficiency was defined as more than 12 weeks from injury to surgery.
Results: Patients averaged 26.4 ± 11.5 years (mean ± SD) of age, 43.6 % were female, and 48.1 % suffered an injury of the left knee. There were 30 and 22 patients in the acute and chronic groups, respectively. The median duration from injury to reconstruction for the acute group was 5 versus 31 weeks for the chronic group. After anatomic ACL reconstruction, the mean ATS was 1.0 ± 2.1 mm. There was no statistical difference in ATS between the acute and chronic groups (1.2 ± 2.0 vs. 0.6 ± 2.3 mm, n.s.). Assessment of inter-tester reliability for radiographic evaluation of ATS revealed an excellent intraclass correlation coefficient of 0.894.
Conclusions: Anatomic ACL reconstruction reduces ATS with a mean difference of 1.0 mm from the healthy contralateral limb. This study did not find a statistical difference in ATS between patients after anatomic ACL reconstruction in the acute or chronic phase. These observations suggest that anatomic ACL reconstruction, performed in either the acute or the chronic phase, approaches the normal AP relationship of the tibiofemoral joint.
Level of evidence: IV.
Keywords: ACL; Anatomic ACL reconstruction; Anterior tibial subluxation.