Influence of axial limb rotation on radiographic lower limb alignment: a systematic review

Archives of Orthopaedic and Trauma Surgery https://doi.org/10.1007/s00402-021-04163-w TRAUMA SURGERY Influence of axial limb rotation on radiographic lower limb alignment: a systematic review Marc‑Daniel Ahrend1,2 · Heiko Baumgartner1 · Christoph Ihle1 · Tina Histing1 · Steffen Schröter3 · Felix Finger1 Received: 9 May 2021 / Accepted: 1 September 2021 © The Author(s) 2021 Abstract Introduction The influence of limb malrotation on long-leg radiographs (LLR) is frequently discussed in literature. This systematic review aimed to describe the influence of limb rotation on alignment measurements alone and in combination with knee flexion, and determine its clinical impact. Materials and methods A literature search was conducted in June 2021 using the databases MEDLINE, Cochrane, Web of Science (Clarivate Analytics), and Embase. The search term ((radiograph OR X-ray) AND (position OR rotation) AND limb alignment) was used. Database query, record screening, and study inclusion and exclusion were performed by two reviewers independently. Experimental studies (using either specimens or synthetic bones) or clinical studies (prospective or retrospective using radiographs of patients) analyzing the influence of limb rotation on anatomic and mechanical limb alignment measurements were included. Characteristics and results of the included studies were summarized, simplified, and grouped for comparison to answer the research question. Studies were compared descriptively, and no meta-analysis was performed. Results A total of 22 studies were included showing large heterogeneity, comprising studies with cadavers, patients, and synthetic bones. Most studies (7 out of 8) reported that external rotation (ER) causes less apparent valgus and leads to more varus and internal rotation (IR) causes more valgus and leads to less varus. However, there is no consensus on the extent of rotation influencing alignment measures. Studies reported about an average change of > 2° (n = 4) and < 2° (n = 4) hip-kneeankle angle (HKA) between 15°IR and 15°ER. There is a consensus that the impact of rotation on mechanical alignment is higher if additional sagittal knee angulation, such as knee flexion, is present. All five studies analyzing the influence of rotation combined with knee flexion (5°–15°) showed an HKA change of > 2° between 15°IR and 15°ER. Conclusion Malrotation is frequently present on LLR, possibly influencing the measured alignment especially in knees with extension deficit. Surgeons must consider this when measuring and treating deformities (high tibial osteotomy or total knee arthroplasties), and analyzing surgical outcomes. Especially in patients with osteoarthritis with knee extension deficits or postoperative swelling, the effect of malrotation is significantly greater. Keywords Rotation · Limb alignment · Long-leg radiographs · Lower limb * Heiko Baumgartner Marc‑Daniel Ahrend Felix Finger 1 Department of Traumatology and Reconstructive Surgery, BG Trauma Center Tübingen, Eberhard-Karls University of Tübingen, Schnarrenberg‑Str. 95, 72076 Tübingen, Germany 2 AO Research Institute Davos, Davos, Switzerland 3 Department of Traumatology and Reconstructive Surgery, Diakonie Klinikum GmbH Jung-Stilling-Krankenhaus, Siegen, Germany Christoph Ihle Tina Histing Steffen Schröter 13 Vol.:(0123456789) Archives of Orthopaedic and Trauma Surgery Introduction Long-leg radiographs (LLR) show the lower limb from the femoral head to the ankle. They are obtained to determine the mechanical axis to analyze deformities and plan deformity corrections in the frontal plane [52]. Moreover, LLR are used in complex total knee arthroplasty to plan appropriate bone resections [15, 38] and are essential for postoperative evaluation. In the last 20 years, several studies analyzed factors that influence the measured parameters on LLR. Some claimed concerns regarding the reliability and accuracy of LLR. In daily clinical practice, limb rotation on LLR is a major topic: Is the limb properly positioned? How much limb rotation is present on the radiograph? How does it influence the measured limb alignment? Furthermore, there is no consensus on how much limb rotation can be accepted and how it influences treatment selection and surgical planning. Moreover, in clinical practice, surgeons must decide whether LLR should be repeated due to the presence of limb malrotation determined between additional radiation exposure for the patient and measurement inaccuracy. Therefore, this systematic literature review aimed to provide an overview of studies that discussed lower limb rotation on LLR to describe how limb rotation can influence anatomic and mechanic limb alignment measurements alone and in combination with knee flexion or varus/valgus alignment; and the impact on diagnosis, treatment selection, surgical planning, or surgical outcomes. We hypothesized that axial limb rotation influences the measured limb alignment and that there is a clinical impact in treatment planning or decision making. Materials and methods A literature search was conducted in June 2021 using the MEDLINE (PubMed), Web of Science (Clarivate Analytics), Cochrane Library, and EMBASE databases. The following search term was used: ((radiograph OR X-ray) AND (position OR rotation) AND limb alignment). References were managed using EndNote X9.3. Inclusion criteria for studies were as follows: – Studies published between 1989 and June 2021. – Experimental studies (using either specimens or synthetic bones), clinical studies (prospective or retrospective using radiographs of patients), and systematic reviews. – Studies that analyzed the influence of limb rotation on anatomic and mechanical alignment measurements. 13 Exclusion criteria for studies were as follows: – Conference abstracts, editorial letters, and book chapters. – Theoretical approaches. – Studies published in languages other than English. – Studies that analyzed the influence of rotation on only one bone (the tibia or femur). – Studies that measured tibiofemoral alignment, but not its measurement variability. – Studies that did not refer limb rotation measurements to the measured limb alignment. – Studies that measured the change of alignment influenced by a surgery (e.g., component position after total knee arthroplasties (TKA)], but not by limb rotation. All steps for the identification of studies (record identification, record screening, report eligibility assessment, and report exclusion and inclusion) were independently carried out by two reviewers. Any differences regarding the included studies between the two reviewers were discussed and a consensus was reached. References and citations of the finally included articles were scanned for additional relevant articles matching the abovementioned inclusion criteria (Fig. 1). Interpretation and analysis of the included articles Relevant data from the included articles were extracted and recorded in a separate table de (...truncated)