[Postoperative malrotation after closed reduction and intramedullary nailing of the femur: a retrospective 5-year analysis]

Generic Implant Positioning Technology Based on Hole Projections in X-Ray Images

Implant placement plays a key role in trauma and orthopedics. In this paper, a generic technological concept for implant positioning assistance is outlined. The system utilizes conventional radiographic devices for imaging and tracking and embeds into surgical workflows without the need for complex navigation equipment. It is based on feature extraction from cylindrical hole-projections in X-ray images for determining spatial alignment of implant and anatomy. Basic performance of a prototype system was experimentally verified in terms of tracking accuracy and robustness under varying conditions. In a second step, the system was developed into a set of application modules, each serving a pressing clinical need: Plating of the proximal humerus, cephalic nail and dynamic hip-screw placement, general anatomic plating, distal nail interlocking with adjustment of femoral anteversion and corrective osteotomies. Module prototypes were tested according to their degree of maturity from feasibility assessment in wet-labs to clinical handling tests. Orientation tracking of reference objects yielded an accuracy and precision of 0.1±0.71 deg (mean±standard deviation) with a maximum error of 4.68 deg at unfavorable conditions. This base-performance translated, e.g., into a precision of ±1.2 mm (standard deviation) screw-tip to joint distance at proximal humerus plating, or into a precision of lag screw positioning in the femoral head of ±0.6 mm in craniocaudal and ±1.6 mm in anterioposterior direction. The concept revealed strong potential to improve surgical outcomes in a broad range of orthopedic applications due to its generic and simplistic nature. Comprehensive validation activities must follow for clinical introduction.

Correction of Torsional Deformity Following Nail Osteosynthesis of a Subtrochanteric Fracture

Torsional deformity is a frequent complication following nail osteosynthesis of a subtrochanteric fracture. This complication is difficult to assess intraoperatively, but can cause major functional restrictions. The authors consider that a clinical assessment should be complemented by a postoperative radiological control standardised with torsion CT. Thus, torsion deformity can be recognised immediately and easily corrected if necessary. This can help to avoid long-term damage that requires considerable surgery. The video shows details of torsion correction after a ca. 5-week old subtrochanteric femoral fracture, which had been initially treated with a femur nail. Before torsion correction, the internal torsion on the right femur was 22° and the external torsion on the left femur was 2°. Thus, the total deformation of the external torsion on the left side was 24°. We note the indication for removal of the nail, torsion correction and reosteosynthesis with long PFNA. The postoperative CT control confirmed that the torsion correction was adequate with internal torsion of 25° on the operated left side.

[The relevant axial deviation: Diagnostics and therapy for correction osteotomies of the femur]

Intraoperative assessment of the femoral axis, length and torsion can be difficult. A postoperative torsional discrepancy is a common but rarely diagnosed condition. A clinical evaluation of femoral torsion is limited, especially in the early postoperative period. Conventional radiographs are a reliable diagnostic tool for evaluation of discrepancies of leg length and axis. Computed tomography remains the gold standard for assessment of torsional discrepancies. Because of the wide variability of the physiological femoral torsion, the clinical impact of a torsional discrepancy in individual cases remains unclear. There is a general recommendation for revision in cases of intraindividual deviations of more than 15°; however, most patients with deviations even greater than 15° are asymptomatic. Therefore, the indications for correction should be carefully considered in each individual case. The patient level of activity is a crucial point in decision-making for correction osteotomy. Before correction osteotomy, the surgeon has to make a detailed biomechanical analysis of the leg. Early correction is recommended in most cases. Detailed knowledge of the patient medical history is needed for preoperative planning. Prior surgeries can have a significant impact on the choice of the surgical approach and stabilization technique.