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Evaluation of Accuracy of Preoperative Planning of the Femurofibular Angle in Open-Wedge High Tibial Osteotomy for Mild Medial Knee Osteoarthritis.

ABSTRACT:

Objective

The purpose of this study was to evaluate the usefulness of preoperative planning of the femurofibular angle (FFA) in medial open-wedge high tibial osteotomy (OWHTO) for mild medial knee osteoarthritis.

Methods

Thirty-two patients (32 knees) with mild medial knee OA were retrospectively reviewed. The patients underwent preoperative planning of the FFA for OWHTO. For preoperative planning, a full-length weight-bearing X-ray photograph of the lower limb was opened within Adobe Photoshop Software, and a targeted corrective mechanical axis line of the lower limb and its intersecting point at the lateral tibial plateau surface was drawn using rectangle selection and filling tools. A frame, which encircled the tibia and fibula, was created around the predicted osteotomy plane and then rotated until the ankle center was on the targeted mechanical axis line. Subsequently, a distal femoral condyle line and a proximal fibula axis line were drawn, and the angle between the two lines was measured and defined as the femurofibular angle (FFA). During biplane OWHTO, the preoperatively determined FFA was used to complete the correction of the mechanical axis. During follow-up, the postoperative mechanical weight-bearing line (WBL) of the lower limb, the mechanical femorotibial angle (mFTA), and the FFA were measured and compared with the preoperatively determined values.

Results

The mechanical WBL shifted from a preoperative value of 25.36 ± 5.02% to a postoperative value of 56.19 ± 0.10% from the medial border along the mediolateral width of the tibial plateau, and it was 56.57 ± 0.08% at the final follow-up (P < 0.01). The preoperatively determined value was 56.25%, and no significant difference was found compared with postoperative week-one and final follow-up values (P > 0.05). The mFTA was corrected from a preoperative varus of 4.02 ± 0.63° to a postoperative week-one valgus of 2.37 ± 0.28°, and it had a valgus of 2.48 ± 0.39° at the final follow-up (P < 0.01). No significant difference in the valgus was found compared with the postoperative week-one, final follow-up and preoperatively determined valgus of 2.34 ± 0.26° (P > 0.05). The postoperative week-one and final follow-up FFAs were 90.34 ± 1.53° and 90.33 ± 1.52°, respectively, and no significant difference was found compared with the preoperatively determined value of 90.12 ± 1.72° and the intraoperative setting value of 90.25 ± 1.67° (P > 0.05). All corrected values were within the acceptable range of preoperative planning.

Conclusion

Preoperative planning of the FFA may be useful in OWHTO for patients with mild medial knee OA. Satisfactory correction of the postoperative targeted mechanical axis line of the lower limb can be obtained.

SUBMITTER: Wang P

PROVIDER: S-EPMC7985241 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Background:Medial opening-wedge high tibial osteotomy (HTO) is one of the most common and effective HTO techniques, in which the proximal tibia is cut medially, leaving an intact lateral hinge of bone that can be opened to a variable amount for the desired correction, but the technical complications of lateral cortex fracture and intra-articular fracture are well described. The lateral bone hinge for medial opening-wedge HTO is crucial. If the hinge is too small, the tibia can fracture and become unstable, requiring further fixation. If the hinge is too large, the osteotomy can propagate into the joint as an intra-articular fracture when opening the osteotomy. Purpose:We propose a new technique that utilizes digital preoperative templating to improve the accuracy of the cut. Preoperative digital templating may allow the surgeon to reproducibly obtain a lateral bone hinge of 10 mm, while also reducing radiation exposure relative to the traditional fluoroscopically assisted technique. Methods:Ten cadaver extremities from five cadavers were matched into pairs and randomized into two groups: those with and without preoperative templating. The templating protocol measures the distance between two points on the medial and lateral cortices, and 20 mm is subtracted to determine the depth of the saw cut (10 mm for the hinge and another 10 mm because the proximal tibia is oval in shape). The control method was done by making the cut using fluoroscopy with tactile feedback. Postoperative computed tomography scans were obtained of all legs to measure the width of the lateral bone hinge. Intraoperative fluoroscopy used during both techniques and the numbers of fluoroscopy shots were recorded. Results:We found neither the treatment group with preoperative planning nor the control group with the conventional technique had bone hinge widths that were different from the ideal 10 mm. The average hinge widths for the treatment and control groups were 11.2 and 11.5 mm, respectively. However, the treatment group was exposed to significantly less intraoperative fluoroscopy during the osteotomy cut. The average total number of fluoroscopy shots was 2.2 in the treatment group versus 6.3 for the control group. Conclusions:This new preoperative planning technique achieves similar accuracy of the lateral bone hinge when compared to current methods but exposes the patient, surgeon, and staff to significantly less intraoperative radiation.