{"title":"Torsional Malalignment Syndrome: The Hidden Role of Medial Tibial Slope in Knee Varus and the Potential of PETS Treatment for Correction.","authors":"Hui Taek Kim, Hak Sang Kim","doi":"10.1097/BPO.0000000000003087","DOIUrl":null,"url":null,"abstract":"<p><strong>Background: </strong>In torsional malalignment syndrome (TMS), knee varus is observed when feet are neutral but disappears with external foot rotation. The underlying cause of this phenomenon-whether it results from visual alterations from limb rotation or reflects an additional structural abnormality in the lower extremity-along with the potential for simpler treatment options beyond rotational osteotomy, has not been previously investigated.</p><p><strong>Methods: </strong>Eighteen subjects with TMS and ten control subjects had weight-bearing orthoroentgenograms and non-weight-bearing 3D CT scans of the lower limb. Mechanical lateral distal femoral angle (mLDFA) and medial proximal tibial angle (MPTA) were measured. Changes in the mechanical axis during femoral rotation were analyzed with 2D and 3D CT images processed with Adobe Photoshop and PowerPoint. Morphologies of the distal femur and proximal tibia were evaluated. Six subjects received guided growth with percutaneous epiphysiodesis transphyseal screws (PETS).</p><p><strong>Results: </strong>TMS subjects showed significantly greater mLDFA and knee varus on weight-bearing radiographs, but not on 3D CT, indicating that weight-bearing contributes to the varus appearance. Although external rotation on 3D CT caused medial axis shift and mLDFA reduction in both groups, the degree of change in TMS subjects was similar to controls and insufficient to explain the pronounced varus, implying an additional structural abnormality. While femoral contours appeared normal, TMS subjects exhibited a significantly steeper posterior slope of the medial tibial plateau-averaging 7.0 degrees more than the lateral slope and also significantly steeper than in controls. In patients treated with PETS, the mean mLDFA improved from 90.2 to 88.1 degrees, and all reported cosmetic satisfaction, with no deterioration in LEFS or TLKSS scores.</p><p><strong>Conclusions: </strong>A steeper posterior slope of the medial tibial plateau likely contributes to knee varus in TMS subjects when feet are neutral. Although PETS doesn't address the underlying rotational deformity, it improved coronal alignment and appearance in selected patients without functional compromise, offering a simple and cosmetically effective treatment alternative.</p><p><strong>Level of evidence: </strong>Level III-diagnostic studies.</p>","PeriodicalId":16945,"journal":{"name":"Journal of Pediatric Orthopaedics","volume":" ","pages":""},"PeriodicalIF":1.5000,"publicationDate":"2025-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Pediatric Orthopaedics","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.1097/BPO.0000000000003087","RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"ORTHOPEDICS","Score":null,"Total":0}
引用次数: 0
Abstract
Background: In torsional malalignment syndrome (TMS), knee varus is observed when feet are neutral but disappears with external foot rotation. The underlying cause of this phenomenon-whether it results from visual alterations from limb rotation or reflects an additional structural abnormality in the lower extremity-along with the potential for simpler treatment options beyond rotational osteotomy, has not been previously investigated.
Methods: Eighteen subjects with TMS and ten control subjects had weight-bearing orthoroentgenograms and non-weight-bearing 3D CT scans of the lower limb. Mechanical lateral distal femoral angle (mLDFA) and medial proximal tibial angle (MPTA) were measured. Changes in the mechanical axis during femoral rotation were analyzed with 2D and 3D CT images processed with Adobe Photoshop and PowerPoint. Morphologies of the distal femur and proximal tibia were evaluated. Six subjects received guided growth with percutaneous epiphysiodesis transphyseal screws (PETS).
Results: TMS subjects showed significantly greater mLDFA and knee varus on weight-bearing radiographs, but not on 3D CT, indicating that weight-bearing contributes to the varus appearance. Although external rotation on 3D CT caused medial axis shift and mLDFA reduction in both groups, the degree of change in TMS subjects was similar to controls and insufficient to explain the pronounced varus, implying an additional structural abnormality. While femoral contours appeared normal, TMS subjects exhibited a significantly steeper posterior slope of the medial tibial plateau-averaging 7.0 degrees more than the lateral slope and also significantly steeper than in controls. In patients treated with PETS, the mean mLDFA improved from 90.2 to 88.1 degrees, and all reported cosmetic satisfaction, with no deterioration in LEFS or TLKSS scores.
Conclusions: A steeper posterior slope of the medial tibial plateau likely contributes to knee varus in TMS subjects when feet are neutral. Although PETS doesn't address the underlying rotational deformity, it improved coronal alignment and appearance in selected patients without functional compromise, offering a simple and cosmetically effective treatment alternative.
期刊介绍：
Journal of Pediatric Orthopaedics is a leading journal that focuses specifically on traumatic injuries to give you hands-on on coverage of a fast-growing field. You''ll get articles that cover everything from the nature of injury to the effects of new drug therapies; everything from recommendations for more effective surgical approaches to the latest laboratory findings.
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