Rotation osteotomy of the distal femur influences coronal femoral alignment and the ischiofemoral space

Archives of Orthopaedic and Trauma Surgery https://doi.org/10.1007/s00402-020-03704-z ORTHOPAEDIC SURGERY Rotation osteotomy of the distal femur influences coronal femoral alignment and the ischiofemoral space Christian Konrads1 · Marc‑Daniel Ahrend1 · Myriam Ruth Beyer1 · Ulrich Stöckle2 · Sufian S. Ahmad1,2 Received: 28 August 2020 / Accepted: 3 December 2020 © The Author(s) 2020 Abstract Introduction Despite the fact that osteotomies around the knee represent well-established treatment options for the redistribution of loads and forces within and around the knee joint, unforeseen effects of these osteotomies on the remaining planes and adjacent joints are still to be defined. It was, therefore, the aim of this study to determine the influence of a distal femoral rotation osteotomy on the coronal limb alignment and on the ischiofemoral space of the hip joint. Materials and methods Long-leg standing radiographs and CT-based torsional measurements of 27 patients undergoing supracondylar rotational osteotomies of the femur between 2012 and 2019 were obtained and utilized for the purpose of this study. Postoperative radiographs were obtained after union at the osteotomy site. The hip–knee–ankle angle (HKA), the mechanical lateral distal femur angle (mLDFA), and the ischiofemoral space were measured. Comparison between means was performed using the Wilcoxon–Mann–Whitney test. Results Twenty-seven patients underwent isolated supracondylar external rotation osteotomy to reduce the overall antetorsion of the femur. The osteotomy resulted in a 2.4° ± 1.4° mean increase in HKA and 2.4 mm ± 1.7 mm increase in the ischiofemoral space (p < 0.001). Conclusion Supracondylar external rotation osteotomy of the femur leads to valgisation of the coronal limb alignment and increases the ischiofemoral space. This is resultant to the reorientation of the femoral antecurvature and the femoral neck. When planning a rotational osteotomy of the lower limb, this should be appreciated and may also aid in the decision regarding osteotomy site. Keywords Hip impingement · Derotation · Torsional alignment · Long-leg axis · Anterior knee pain Abbreviations AMA Anatomic mechanical angle of the femur HKA Hip–knee–ankle angle mLDFA Mechanical lateral distal femoral angle mLPFA Mechanical lateral proximal femoral angle mMPTA Mechanical medial proximal tibial angle * Christian Konrads 1 Department for Trauma and Reconstructive Surgery, BG Klinik, University of Tübingen, Tübingen, Germany 2 Center for Musculoskeletal Surgery, Charité–University Medical Center Berlin, Berlin, Germany Introduction Osteotomies around the knee represent powerful modalities for the treatment of bony deformities and degenerative joint disease. The intended effects of these osteotomies act on joints by redistributing loads and force vectors. Rotational osteotomies of the femur influence the overall femoral antetorsion and demonstrate a direct influence on both the knee and hip joints. The vectors of the quadriceps muscle are ultimately altered by a rotational osteotomy of the femur, subsequently influencing lateral force vectors acting on the patella. Furthermore, the orientation of the femoral neck in space is also influenced by femoral anteversion. Clear evidence linking torsional abnormalities of the femur to hip disease is present [3, 4, 10, 15]. It is, therefore, important to consider all possible effects of an osteotomy during surgical planning and expand planning beyond the plane of interest. This would reduce the 13 Vol.:(0123456789) Archives of Orthopaedic and Trauma Surgery likelihood of creating an unwanted conflict on a different level. This study will be dealing with the influence of a distal supracondylar rotation osteotomy around the knee on both the coronal limb alignment and the ischiofemoral space of the hip. Given that the orientation of the curvature of the femur is likely to change during a rotation osteotomy, the question of whether the curvature may influence the coronal alignment is valid. Furthermore, the ischiofemoral space has been described as a conflict between the femur and the ischium and is gaining recognition as a cause of hip pain. High femoral antetorsion was shown to be associated with a reduced ischiofemoral space, due to which proximal torsional correction osteotomies have been proposed as efficient treatment options [4, 5, 9]. The aim of this study was to retrospectively determine the influence of supracondylar rotation osteotomies of the femur on the long-leg axis in the frontal plane and on the ischiofemoral space of the hip. We hypothesized that supracondylar external rotation osteotomy of the femur leads to valgisation of the long-leg axis and increase in the ischiofemoral space of the hip. Fig. 1  Flowchart demonstrating inclusion 13 Materials and methods Patients Patients undergoing rotational osteotomy of the femur were considered eligible for inclusion in the study, provided that sufficient pre- and postoperative radiographs were available. Indication for surgery was patella maltracking with retropatellar pain in patients with femoral antetorsion (= femoral internal rotation) of more than 30°. Patients were excluded if a correction in a plane other than the axial plane was performed. No magnification device was present on the postoperative radiograph. Exclusion was necessary, if X-ray quality was defined as inferior, or in the case of missing consent regarding the utility of clinical data. Considering the above criteria, 27 legs of 26 patients undergoing osteotomy were considered eligible for inclusion in the study (Fig. 1). Surgical procedure All osteotomies were planned using a landmark based deformity analysis [12, 14]. A medial subvastus approach was established [6, 21]. Supracondylar osteotomy was Archives of Orthopaedic and Trauma Surgery performed and a TomoFix MDF plate (DePuy Synthes, Solothurn, Switzerland) was used for fixation [2]. Radiographs Long-leg weight-bearing radiographs were obtained in accordance to Paley with a 1.3 m cassette (Global Imaging Baltimore, MD) [12]. Long-leg antero-posterior standing radiographs were obtained with the patient standing in a bipedal stance in front of the long film cassette. The radiography tube was positioned in a distance of 305 cm. The selected film cassette was of sufficient length to include the hips, knees, and ankles. The magnification with this setup was approximately 5%. A calibration device (250-mm steel ball) was used to calibrate the radiographs. The X-ray beam was centered on the level of the knee joints. Radiologic technical assistants were instructed to position both legs with the patella centered between the femoral condyles. It was of ultimate importance to ensure a standardized radiography. Femoral torsion was measured using axial CT slides. As multiple methods for measuring femoral torsion exist [8, 13], instead of using the simpler method by Jarrett [7], we measured the femoral torsion (...truncated)