Intraoperative alignment correlates well with long standing radiographs - The X-ray grid method in complex knee surgery

Varus or valgus deformities have a decisive influence on the development and progression of knee pain, patellofemoral pathologies and osteoarthritis of the knee joint [1], [2], [3], [4]. A full-length anteroposterior standing radiograph of both legs (long standing radiograph; LSR) with centered patellae is a crucial step in the standardized diagnostics of knee joint pathologies and lower limb deformities [5]. It allows for a comprehensive analysis of the extent and origin of a mechanical axis deviation (MAD) using the so called malalignment test [6,7]. For surgical interventions influencing the mechanical axis (osteotomies, limg lengthening, joint replacement), the LSR is still the gold standard for preoperative planning [8].

However, in fracture cases or non-unions, preoperative alignment control is impossible, making intraoperative control even more important since malalignment negatively affects the outcome [9]. As intraoperative navigation and other techniques are technically demanding and time consuming, fluoroscopic methods for intraoperative alignment control (IAC) are still common practice in knee arthroplasty, deformity correction, and fracture treatment [10], [11], [12].

The cautery cable technique or the use of an alignment rod are most frequently described [12,13]. In both methods, the surgeon must precisely overlay the centers of the femoral head and ankle joint so that a radiopaque line passes through both joint centers in the fluoroscopic imaging. A third image of the knee joint with centered patellae then allows an evaluation of the MAD, since it is the vertical distance to the center of the knee joint line [5]. However, with these methods, the reference line must be strictly maintained by the surgeons and might easily be changed by accident. For this reason, a custom-made X-ray grid was developed in our department and is routinely placed under the patient in deformity corrections for decades. A similar technique with an “alignment grid” was first published by Saleh et al. in 1991, but without detailed evaluation [14]. The two imaging procedures (LSR and IAC) differ in the acquisition technique, the position of the patient (upright and supine) and weight bearing. However, the surgeon needs to know in which cases the IAC has similar values compared to the LSR and why deviations occur in other cases. In the fracture case, the grid technique has already been validated for the assessment of the femoral axis compared to conventional radiographic imaging [15].

The aim of this study is to compare preoperative LSR and intraoperative IAC alignment in two different imaging modalities in order to quantify differences and identify risk factors for deviations. The MAD was set as the primary outcome parameter and it was hypothesized that the presented fluoroscopic IAC using the X-ray grid allows for comparable MAD values as the preoperative LSR.

留言 (0)

沒有登入
gif