Background: Tibial deflexion osteotomy (TDO) is sometimes indicated for revision anterior cruciate ligament (ACL) reconstruction in knees with posterior tibial slope (PTS) ≥12° and aims to decrease PTS to around 5°. When planning TDO, measuring the anterior tibial metaphyseal height (aHt) could help ascertain whether the available metaphyseal bone would be sufficient to create the wedge and leave adequate residual bone.
Purpose: To (1) determine whether, compared with knees with normal native PTS (<12°), aHt is greater in knees with excessive native PTS (≥12°), and (2) verify if, aiming to decrease PTS to 5°, supratuberosity TDO in knees with excessive native PTS could be performed without tibial tuberosity osteotomy, leaving a minimum of 15 mm of residual bone for fixation staples or plates.
Study design: Cross-sectional study; Level of evidence, 3.
Methods: True lateral radiographs of 350 consecutive patients scheduled for ACL reconstruction were digitized to measure PTS, tibial medial plateau length, tibial anterior and posterior metaphyseal heights and inclinations, and patellar height. Measurements were compared between knees with PTS <12° and those with ≥12°. The wedge height required for supratuberosity TDO was estimated for knees with excessive PTS, aiming for a target PTS of 5°, to determine the proportion of knees that would have residual aHt <15 mm.
Results: A total of 326 knees had adequate true lateral radiographs. The mean PTS was 9.8°± 3.1° (range, 1°-20°) and exceeded 12° in 83 (25%) knees. There were no significant differences between knees with normal versus excessive PTS when comparing aHt (30.7 ± 4.5 mm vs 31.6 ± 4.9 mm; P = .270) and medial tibial plateau length (43.1 ± 5.4 mm vs 43.3 ± 5.6 mm; P = .910). Setting the target mPTS at 5° for supratuberosity TDO, the mean residual aHt was 25.0 ± 4.4 mm, and 7 (8%) knees had a residual aHt <20 mm, of which only 1 (1%) had residual aHt <15 mm. Setting the target mPTS at 0°, the mean residual aHt was 21.3 ± 4.2 mm, and 36 (43%) knees had a residual aHt <20 mm, of which only 4 (5%) had residual aHt <15 mm.
Conclusion: aHt was not significantly different between knees with normal versus excessive PTS. Estimation of the wedge height required for supratuberosity TDO to reduce excessive PTS to 5° revealed sufficient metaphyseal bone for wedge removal in all knees. Furthermore, 99% of knees would have sufficient residual bone (aHt, ≥15 mm) to accommodate fixation staples or plates, without the need for tibial tuberosity osteotomy.
Keywords: ACL; ACLR; anterior cruciate ligament; posterior tibial slope; reconstruction; tibial deflexion osteotomy.