Posterior tibial slope (PTS) ≥ 10 degrees is a risk factor for further anterior cruciate ligament (ACL) injury; BMI is not

Abstract

Purpose This case–control study aimed to assess the influence of BMI and PTS on subsequent ACL injury affecting either ACL graft or the native ACL of the contralateral knee after primary ACL reconstruction. Methods A retrospective case–control study was performed using a cohort of patients who underwent arthroscopic ACL reconstruction between 2010 and 2020 using the same surgical procedure: Hamstring tendon autograft. The study group (group I) included all the patients (n = 94) during this period who sustained a subsequent ACL injury. The control group (group II) consisted of 94 patients randomly selected (matched Group I in terms of sex, age, and ACL graft) who did not sustain any further ACL injury. PTS was measured by two blinded surgeons on lateral knee view radiographs of the operated knee after primary ACL. BMI in kg/m2 was measured during the preoperative anesthesia consultation. Exclusion criteria were: non-true or rotated lateral knee radiographs of the operated knee post-ACLR, associated knee ligament injury requiring surgical management, iterative knee surgeries, open growth plate, and related fracture. Results The mean posterior tibial slope in group I was 7.5° ± 2.9, and 7.2° ± 2.0 in group II. A PTS angle cutoff was set at 10 degrees. The rate of patients showing a PTS ≥ 10° was significantly higher in group I compared to group II (p < 0.01). Patients with PTS ≥ 10° were 5.7 times more likely to sustain a subsequent ACL injury, (OR: 5.7 95% CI[1.858–17.486]). The Average BMI in group I was 24.5 ± 3.7 kg.m−2 compared to group II which was 23.3 ± 3.0 kg.m−2. There were no significant differences in any of the four BMI categories between both groups (p value 0.289). A series of BMI cut-offs were also analyzed at 23 to30 kg/m2, and there was no significant difference between both groups. Conclusions A posterior tibial slope equal to or above 10 degrees measured on lateral knee radiographs was associated with 5.7 times higher risk of ACL graft rupture or contralateral native ACL injury; however, BMI was not.

Posterior Tibial Slope in Patients Undergoing Bilateral Versus Unilateral ACL Reconstruction: MRI and Radiographic Analyses

“…Last, none of these studies utilized both radiography and MRI to measure the PTS. 13,17,30,38 Thus, our study contributes an adequately powered casecontrol study to the existing literature incorporating both radiography and MRI, finding that patients who had undergone primary bilateral ACLR had a higher PTS on radiography and a higher LPTS on MRI compared with a matched unilateral ACLR control group.…”

“…Importantly, they found anteromedial bundle strain to increase by 0.6% for every 1°increase in the PTS. 27 Previous studies that have investigated the PTS among contralateral ACL injuries examined these patients as a subset of any subsequent ACLR procedure (graft failure or contralateral rupture) 13,30,38 or solely focused on adolescents. 17 This is an important distinction from the current study, as failure of a graft introduces a variety of other factors (eg, allograft vs autograft, graft type, tunnel position, and surgeon expertise) that would not affect the integrity of the native ACL.…”

“…Among the cited studies, several found nonsignificant differences when directly comparing the PTS of contralateral ruptured knees with controls. 13,30,38 Additionally, these previous subgroup comparisons were potentially underpowered, as comparisons often trended toward the contralateral injury group having a higher PTS than controls. Last, none of these studies utilized both radiography and MRI to measure the PTS.…”

“…34 Although numerous studies have focused on the relationship between the PTS and graft failure after ACLR, fewer have examined the association between the PTS and the risk for subsequent contralateral ACL injuries. 13,17,30,38 Importantly, previous studies have investigated the PTS in contralateral ACL injuries as a subset of any subsequent ACLR procedure (graft failure or contralateral rupture) or have focused on adolescents. 17 Among these, several found nonsignificant differences when directly comparing the PTS in contralateral ruptured knees to controls.…”

“…17 Among these, several found nonsignificant differences when directly comparing the PTS in contralateral ruptured knees to controls. 13,30,38 Furthermore, these comparisons have been limited to either lateral radiography or magnetic resonance imaging (MRI), 13,17,30,38 although it has been shown that PTS values derived from radiography versus MRI may differ by up to 5°. 23 To our knowledge, there have been no previous studies that have compared patients with a history of bilateral versus unilateral ACLR utilizing both radiography and MRI.…”