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Editorial Commentary: Anterolateral Hinge Position Decreases the Slope in Opening-Wedge High Tibial Osteotomy: A Key Point in Treating an Anterior Cruciate Ligament–Deficient, Varus Knee

      Abstract

      The orthopaedic surgeon who performs opening-wedge high tibial osteotomy (HTO) has to be aware of the behavior of the tibial slope depending on variations in the location of the hinge and in the inclination of the osteotomy. The most important point is that changing both the inclination and the rotation axis of the osteotomy cut affects the tibial slope. There is a natural trend to unintentionally increase the tibial slope when performing an opening-wedge HTO. However, an increased tibial slope has been established as a risk factor for both primary and recurrent anterior cruciate ligament (ACL) injuries, whereas slope-reducing osteotomies decrease anterior tibial translation and protect the ACL graft. To reduce tibial slope in opening-wedge HTO, it seems more practical to internally rotate the osteotomy, establishing an anterolateral hinge, than to change the inclination of the cut, given that it seems more predictable and technically easier to perform internal rotation during surgery. Trying to achieve both internal rotation and extension increases the complexity of the osteotomy. Not every osteotomy needs to have an anterolateral hinge; in fact, decreasing the tibial slope would be a disadvantage in the posterior cruciate ligament–deficient knee. However, for the ACL-deficient knee with varus malalignment, aiming to decrease the tibial slope using an anterolateral hinge could be considered during preoperative planning.
      In the study “The Ideal Hinge Axis Position to Reduce Tibial Slope in Opening Wedge High Tibial Osteotomy Includes Proximalization/Extension and Internal Rotation,” Eliasberg, Hancock, Swartwout, Robichaud, and Ranawat
      • Eliasberg C.
      • Hancock K.
      • Swartwout E.
      • Robichaud H.
      • Ranawat A.
      The ideal hinge axis position to reduce tibial slope in opening wedge high tibial osteotomy includes proximalization/extension and internal rotation.
      present a model used to find the effect on tibial slope when varying the axis angle of rotation and inclination of the osteotomy. This study included computed tomography scans from 10 patients with medial osteoarthritis, who are usual candidates for this type of surgery. A linear regression of their data from the modeling was also included. It was shown that rotating the hinge axis by 9.0° externally would result in increasing the tibial slope by 1° whereas rotating it 8.7° internally would decrease the tibial slope by 1°. For the same 1° change in tibial slope, much larger inclinations were needed in the sagittal plane: 21.8° of flexion or 21.6° of extension.
      There is a natural trend to unintentionally increase the tibial slope when performing an opening-wedge high tibial osteotomy (HTO). A meta-analysis evaluating slope changes after this type of osteotomy quantified the mean increase in tibial slope as 2°.
      • Nha K.-W.
      • Kim H.-J.
      • Ahn H.-S.
      • Lee D.-H.
      Change in posterior tibial slope after open-wedge and closed-wedge high tibial osteotomy: A meta-analysis.
      This finding could be related to the typical anteromedial approach that is used for this surgical procedure and the tendency to perform the cut from a slightly anterior direction toward the posterolateral proximal tibia, externally rotating the hinge axis. Cadaveric studies have shown that a posterolateral hinge increases the tibial slope in comparison to a neutral lateral hinge position.
      • Wang J.H.
      • Bae J.H.
      • Lim H.C.
      • Shon W.Y.
      • Kim C.W.
      • Cho J.W.
      Medial open wedge high tibial osteotomy: The effect of the cortical hinge on posterior tibial slope.
      A recent clinical study from Kaya et al.
      • Kaya H.
      • Dastan A.E.
      • Bicer E.K.
      • Taskiran E.
      Posteromedial open-wedge high tibial osteotomy to avoid posterior tibial slope increase.
      showed similar findings. Osteotomies from the posteromedial tibia directed to an anterolateral hinge position showed a statistically significant mean decrease in tibial slope of 3°.
      • Kaya H.
      • Dastan A.E.
      • Bicer E.K.
      • Taskiran E.
      Posteromedial open-wedge high tibial osteotomy to avoid posterior tibial slope increase.
      Moon et al.,
      • Moon S.W.
      • Park S.H.
      • Lee B.H.
      • et al.
      The effect of hinge position on posterior tibial slope in medial open-wedge high tibial osteotomy.
      in their retrospective clinical study, similarly found a mean increase of 3.19° in tibial slope in their patients, with a hinge axis that, on average, was externally rotated 4.92° toward a posterolateral position.
      Eliasberg et al.
      • Eliasberg C.
      • Hancock K.
      • Swartwout E.
      • Robichaud H.
      • Ranawat A.
      The ideal hinge axis position to reduce tibial slope in opening wedge high tibial osteotomy includes proximalization/extension and internal rotation.
      add important information for planning an opening-wedge HTO. According to the authors, one could rotate the hinge axis in the axial plane by multiples of 9° to increase or decrease the tibial slope by 1° until enough rotation occurs to obtain the desired amount of tibial slope change. Alternatively, one may change the inclination in the sagittal plane by 22° to obtain 1° of change, but this seems less practical. One may also combine rotation with some sagittal inclination to gain an extra degree. Probably, the most important point to have in mind when planning the operation is that changing both the inclination and the rotation axis affects the tibial slope. Nevertheless, the findings from this study should be further confirmed in the clinical setting to evaluate if the linear regression calculations of the model are replicated.
      It would have been of interest if Eliasberg et al.
      • Eliasberg C.
      • Hancock K.
      • Swartwout E.
      • Robichaud H.
      • Ranawat A.
      The ideal hinge axis position to reduce tibial slope in opening wedge high tibial osteotomy includes proximalization/extension and internal rotation.
      had evaluated the effect of larger opening-wedge gaps on the tibial slope. This would enrich the model and allow for extrapolations for opening wedges that are different from the 10-mm gap used in this study. However, in their study, Kaya et al.
      • Kaya H.
      • Dastan A.E.
      • Bicer E.K.
      • Taskiran E.
      Posteromedial open-wedge high tibial osteotomy to avoid posterior tibial slope increase.
      evaluated changes in the tibial slope in patients with an anterolateral hinge when the opening wedge was less than 10° compared with 10° or greater and found no statistically significant differences in the slope between these measures.
      The opportunity to control the final tibial slope change after an opening-wedge HTO with preoperative planning is a key factor. Eliasberg et al.
      • Eliasberg C.
      • Hancock K.
      • Swartwout E.
      • Robichaud H.
      • Ranawat A.
      The ideal hinge axis position to reduce tibial slope in opening wedge high tibial osteotomy includes proximalization/extension and internal rotation.
      showed that the surgeon could mathematically predict the resulting tibial slope depending on hinge-axis rotation and inclination. When one is aiming to decrease the tibial slope, I think it is more practical to internally rotate the osteotomy, establishing an anterolateral hinge, than to change the inclination of the cut to achieve proximalization or extension. It seems more predictable and technically easier to perform internal rotation during surgery. In the meantime, trying to perform both internal rotation and extension increases the complexity of the cut.
      There might be cases in which increasing the slope is not a problem for the patient, but that is not the case for a patient with an anterior cruciate ligament (ACL)–deficient knee in varus malalignment. Varus alignment has been shown to increase tension in the ACL.
      • van de Pol G.J.
      • Arnold M.P.
      • Verdonschot N.
      • van Kampen A.
      Varus alignment leads to increased forces in the anterior cruciate ligament.
      Meanwhile, an increased tibial slope has been established as a risk factor for both primary and recurrent ACL injuries, with slope-reducing osteotomies being able to decrease anterior tibial translation and protect the ACL graft.
      • Lee C.C.
      • Youm Y.S.
      • Do Cho S.
      • et al.
      Does posterior tibial slope affect graft rupture following anterior cruciate ligament reconstruction?.
      • Wang Y-l
      • Yang T.
      • Zeng C.
      • et al.
      Association between tibial plateau slopes and anterior cruciate ligament injury: A meta-analysis.
      • Wordeman S.C.
      • Quatman C.E.
      • Kaeding C.C.
      • Hewett T.E.
      In vivo evidence for tibial plateau slope as a risk factor for anterior cruciate ligament injury: A systematic review and meta-analysis.
      • Imhoff F.B.
      • Mehl J.
      • Comer B.J.
      • et al.
      Slope-reducing tibial osteotomy decreases ACL-graft forces and anterior tibial translation under axial load.
      A paradox will result if an opening-wedge HTO is performed in a way in which it is both beneficial (improves alignment) and harmful (increases slope) to an ACL-deficient knee. Therefore, there is a call to avoid increasing the slope when treating this type of patient with an opening-wedge HTO.
      • Winkler P.W.
      • Hughes J.D.
      • Musahl V.
      Editorial Commentary: Respect the posterior tibial slope and make slope-reducing osteotomies an integral part of the surgical repertoire.
      Varus is one of the problems the surgeon must address in an ACL-deficient knee when deciding treatment, especially in the revision ACL surgery scenario; furthermore, the surgeon should aim to correct the varus deformity and decrease the slope—or at least not increase it.
      Not every osteotomy needs to have an anterolateral hinge. In fact, decreasing the tibial slope would be a disadvantage in the posterior cruciate ligament (PCL)–deficient knee.
      • Novaretti J.V.
      • Sheean A.J.
      • Lian J.
      • De Groot J.
      • Musahl V.
      The role of osteotomy for the treatment of PCL injuries.
      As the tibial slope increases, the posterior translation of the tibia diminishes, stabilizing the PCL-deficient knee. During the preoperative planning in such patients, it is desirable to seek an increase in the tibial slope with a posterolateral hinge.
      Finally, when planning an opening-wedge HTO, I recommend individualizing every patient according to his or her condition. In the patient who needs only correction of varus alignment, one should aim for a neutral lateral hinge—or slightly anterolateral hinge—to maintain the original tibial slope. In contrast, in the patient with an ACL-deficient knee, one should plan to internally rotate the direction of the cut, aiming for an anterolateral hinge, whereas in the PCL-deficient knee, one should externally rotate the cut to obtain a posterolateral hinge that increases the tibial slope.
      Today, the orthopaedic surgeon working in sports medicine and knee surgery should understand and appropriately perform the different osteotomies around the knee. The opening-wedge HTO is indicated in different scenarios, typically when varus alignment is associated with medial osteoarthritis, medial-compartment cartilage injury, meniscal insufficiency, or ligament insufficiency. It is crucial to know how to perform this opening-wedge osteotomy with a predictable result both in the coronal plane and in the sagittal plane, with the resulting tibial slope required in each patient.

      Supplementary Data

      References

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