The main finding of this study is that patients who underwent combined ACLR and biplanar anterior closing-wedge osteotomy showed significant improvements in the Lysholm score, IKDC subjective score, and Tegner activity level without residual instability, major complications and deterioration of knee arthritis for at least 2 years. These findings support our hypothesis that such combined procedures can effectively restore knee stability, reduce PTS, and yield satisfactory clinical outcomes in patient with varus malalignment with primary ACL injury associate increased PTS.
Although the understanding of the importance of the lower extremity deformity for ACLR has deepened, correcting lower extremity deformity in treating ACL injuries is not well understood. Slope-reducing osteotomy is an invasive and technically demanding procedure. Previous case series preferred to perform it in patients who experienced primary or multiple failed ACLR. However, patients with steep lower extremity deformity still remain at high risk for graft failure after primary isolated ACLR. Moreover, revision ACLR is associated with worse clinical outcomes as compared with primary ACL reconstruction24. Therefore, correction of lower extremity deformities that are risk factors for ACLR failure is acceptable during primary ACLR. In our current study, the indication for biplanar anterior closing-wedge osteotomy in primary ACLR is combination of varus, steep posterior tibial slope (＞12°) and MMPRT.
For Coronal plane deformity. It is well-known that valgus high tibial osteotomy (HTO) is a successful treatment option for early medial osteoarthritis with varus alignment. Some clinical studies and systematic reviews reported good results of combined HTO and ACLR in the treatment for patients with varus and ACL deficiency3,15,21. However, regrading slope correction, open-wedge HTO is not very effective. Indeed, open-wedge HTO has a natural tendency to unintentionally increase the tibial slope. A meta-analysis assessed the change in PTS after HTO as a mean increase of 2°18. Therefore, if the main goal is to decrease the PTS rather than to correct the varus, open-wedge HTO is not appropriate. By comparison, anterior closing wedge tibial osteotomy can directly and effectively decrease the PTS and is technically easier. Biomechanically, Imhoff et al11 reported that a 10° anterior closing-wedge osteotomy can significantly reduce the anterior tibial translation in the ACL-deficient knee and decrease the ACL-graft forces at axial load condition. Similarly, Yamaguchi et al28 also found anterior closing-wedge osteotomy led a significant reduction on the anterior tibial translation and graft force. The positive biomechanical results of slope-reducing osteotomy as also supported by good clinical outcomes 1,5,24,25. With these in mind, in the setting of ACL insufficiency increased PTS and varus alignment, we performed combined ACLR and biplanar anterior closing-wedge osteotomy for coronal and sagittal correction. Recently, Imhoff et al10 demonstrated that combined varus and slope correction anterior closing-wedge osteotomy can significantly decrease the anterior tibial translation and ACL graft forces. The author also found that an isolated varus correction in the ACL-deficient knee can lead to higher anterior translation and internal tibial rotation, resulting in a more unstable knee10.
The exact angle that needs to be corrected on both coronal and sagittal planes is controversial. In this study, the weight bearing line of lower extremity was set to 50% position of the tibial plateau on coronal plane. We did not overcorrect weight-bearing line into valgus condition, which may also increase the forces of ACL grafts17. In addition, since the patients were young and did not have severe knee degeneration, we believed that a 50% weight-bearing line was the most appropriate for these patients. Regarding slope correction, Sonnery-Cottet et al25 performed a combined ACL revision with slope-correction osteotomy in 5 patients, to correct the mean PTS from 13.6° preoperatively to 9.2° postoperatively. Dejour et al5 reported 9 patients who second revision ACL reconstruction combined with anterior closing-wedge osteotomy. The PTS decreased from 13.2° ± 2.6° preoperatively to 4.4° ± 2.3° postoperatively. Akoto et al1 reported outcomes of 22 patients undergoing revision ACLR and slope-correction osteotomy combined with lateral extra-articular tenodesis. The mean preoperative PTS was 15.3°, and the mean postoperative PTS was 8.9°. Most of these studies performed anterior closing-wedge osteotomy in the setting of primary or second revision ACLR. Of note, they were different from Song et al24, which reported 9 patients after anterior closing-wedge osteotomy in setting of primary ACLR, and the mean PTS was reduced to 8.1° postoperatively. In our study, we aim to correct the PTS to 7° to 10°. At the final follow-up time, the mean PTS was 7.8°,which was similar with Sonnery-Cottet20 et al, Akoto et al1 and Song et al24.
Another important reason for performing biplanar anterior closing-wedge osteotomy in our study was the concomitant MMPRT. MMPR is a critical stabilizer of the knee, acting as a mechanical block or wedge against anterior tibial translation and transmitting shear force with compressive force. Previous studies have shown that the PTS is affected by both the coronal and sagittal planes: on the coronal plane, Samuelsen et al demonstrated that MMPRT can magnify the effect of the increased PTS on ACLR graft forces.20; On the sagittal plane, the varus deformity is an important prognostic factor in meniscal healing and long-term outcomes following MMPRT repair14. Therefore, in this study, we choose MMPRT as one of surgical indications of performing slope-reducing osteotomy. We believe that, for patients with MMPRT repair, biplanar anterior closing-wedge osteotomy can provide a good mechanical environmental condition for MMPR repair; and for patients required partial MMPR meniscectomy, osteotomy slope-reducing osteotomy can reduce anterior tibial translation following ACL reconstruction 4 and protect ACLR graft.
There were several limitations to our study. Firstly, this study was a retrospective study with a relatively small number of patients. Secondly, the relatively short follow-up time was insufficient to evaluate the long-term efficacy of such combined procedure. Thirdly, the slope and varus correction ACWTO is mainly aimed at correcting the sagittal deformity. However, for patients with lower extremity bone deformity mainly from varus rather than PTS, for patients with lower extremity bone deformity mainly derived from varus rather than PTS, the increased correction of the sagittal face may lead to torsion and fracture of the posterior tibial cortex, which may affect fracture healing and knee function. Lastly, due to the lack of control group, the clinical efficacy of this study was not compared with that of isolated ACLR, combined ACLR and HTO, or combined ACLR and anterior closing-wedge osteotomy, which needs to be further studied.