Aim. To systematically review the literature and anatomical atlases on LM morphology. Methods. Relevant studies were searched in PubMed (Medline) and Science Direct. Anatomical atlases were retrieved from multiple university libraries and online. Included atlases and studies were assessed at five items: visuals present(y/n), quality of visuals(in-/sufficient), labelling of multifidus (y/n), clear description of region of interest(y/n), description of plane has been described(y/n). This risk of bias assessment tool was developed to assess the quality of description of anatomy, since existing risk of bias tables have only been developed to assess the methodology of studies. Results. In total 69 studies and 19 anatomical atlases were included. Studies. - 52 of 69 studies, LM was described as a superficial muscle at the levels L4 – S1. Others presented the LM as deep intrinsic muscle. - Most used methods: MRI, ultrasound imaging or drawings. - 32 of 69 studies scored a total of five points at the risk of bias assessment, which means low risk of bias. Anatomical atlases. - LM is shown as a deep intrinsic back muscle covered by the erector spinae and fascia thoracolumbalis. - Most anatomical atlases (8/19) had a score of four points at the risk of bias assessment. Conclusion. Anatomy atlases reported different LM morphology compared to anatomical studies. Even between studies, there appears to be inconsistent reporting in LM anatomy. Variation in research methods that are used for measuring LM morphology could influence variation in describing and presenting LM morphology. Standardization of
