RESUMEN
BACKGROUND: Tumor prostheses are established as a standard procedure in tumors of the lower extremities. Septic and aseptic loosening remains the main reason for the failure of tumor prostheses. Due to bone defects, the possibilities of anchoring revision prostheses are limited. Trabecular metal cones are established in prosthetic revision surgery. However, the use of segmental trabecular metal cones in a custom-made tumor revision prosthesis has not yet been described. OBJECTIVE: A 58-year-old patient, who initially received a resection of the distal femur and reconstruction with a tumor prosthesis due to chondrosarcoma, attended our clinic. Because of aseptic loosening of this tumor prosthesis, revision surgery was indicated. METHODS: On account of huge bone defects, a reconstruction using a modular standard prosthesis was not possible. In order to prevent further resection of the bone and not replace the total femur, a custom-made revision tumor prosthesis was implanted. RESULTS: After preoperative planning and explantation of the loosened prosthesis, a partially cemented custom-made revision tumor prosthesis was successfully implanted using a Revitan® Curved revision stem with a custom-made Revitan® -Taperadapter and a custom-made segmental trabecular metal cone connected to a custom-made titanium segmental distal femur and a Zimmer® NexGen® RH Knee Tibia with a straight stem (Zimmer, Inc., USA). CONCLUSIONS: The application of segmental trabecular metal in a custom-made revision tumor prosthesis offers a new option to the previously existing treatment strategies.
Asunto(s)
Neoplasias Óseas/cirugía , Condrosarcoma/cirugía , Fémur/cirugía , Procedimientos de Cirugía Plástica/métodos , Prótesis e Implantes , Humanos , Masculino , Persona de Mediana Edad , Diseño de Prótesis , Falla de PrótesisRESUMEN
The purpose of our study was to calculate the optimal tibial resection depth in total knee arthroplasty. The data from 464 navigated total knee arthroplasties were analysed. An implant with a minimum insert thickness of 8 mm was used. Data regarding leg axis, joint line, insert thickness and tibial resection depth were recorded by the navigation device. An algorithm was developed to calculate the optimal tibial resection depth. The required tibial resection significantly correlates with the preoperative leg axis (p < 0.001). In valgus deformities the required resection depth averaged 5.1 mm and was significantly reduced compared to knees with a neutral leg axis (6.8 mm, p < 0.001) and varus deformities (8.0 mm, p < 0.001). Manufacturers recommend undercutting the high side of the tibial plateau to the depth of the thinnest insert available. However, our study demonstrates that in valgus deformities a reduced tibial resection depth is preferable. Hence, unnecessary bone loss can be avoided.
Asunto(s)
Artroplastia de Reemplazo de Rodilla/métodos , Tibia/patología , Tibia/cirugía , Adulto , Anciano , Anciano de 80 o más Años , Algoritmos , Femenino , Humanos , Masculino , Persona de Mediana EdadRESUMEN
OBJECTIVE: Precise implantation of hip resurfacing arthroplasty by imageless computer navigation. Hence a malalignment of the femoral component, leading to early loss of the implant, can safely be avoided. INDICATIONS: Coxarthrosis in patients with normal bone mineral density; only minor deformity of the femoral head that enables milling around the femoral neck without notching. CONTRAINDICATIONS: Osteoporosis; large necrosis of the femoral head; metal allergy; small acetabular seat and corresponding wide femoral neck, leading to needless acetabular bone loss; pregnancy, lactation. SURGICAL TECHNIQUE: Hip joint exposure by a standard surgical approach, bicortical placement of a Schanz screw for the navigation array in the lesser trochanter. Referencing of the epicondyles, the four planes around the femoral neck and head by use of the navigation pointer. Planning of the desired implant position on the touchscreen of the navigation device; a guide wire is inserted into the femoral head and neck using the navigated drill guide; navigated depth drilling is performed. The femoral head is milled using the standard instruments. The acetabular bone stock is prepared with the conventional instrumentation; high-viscosity cement is finger-packed on the reamed head and the femoral component is inserted. Hammer blows should be avoided to prevent microfractures. Verification of the implant position by the navigation device; displacement of the Schanz screw; joint reposition and closure of the wound. POSTOPERATIVE MANAGEMENT: Standard postoperative management after hip arthroplasty. RESULTS: The comparison of 40 navigated and 32 conventionally implanted ASR prostheses resulted in a significant reduction of outliers by use of computer navigation (navigated procedures: one outlier, conventional procedure: nine outliers; p<0.001). Accuracy of the navigation device was tested by analysis of planned and verified implant position: CCD angle accuracy was 1 degrees , antetorsion accuracy was 1 degrees , and offset accuracy was 1.5 mm. An ongoing computed tomography-based anatomic study proved a varus-valgus accuracy of the navigation device of 1 degrees .
Asunto(s)
Artroplastia de Reemplazo de Cadera/instrumentación , Inestabilidad de la Articulación/cirugía , Robótica/instrumentación , Cirugía Asistida por Computador/instrumentación , Adulto , Anciano , Diseño de Equipo , Análisis de Falla de Equipo , Femenino , Humanos , Masculino , Persona de Mediana Edad , Resultado del TratamientoRESUMEN
Femoral malrotation in total knee arthroplasty causes flexion gap instability. Conventional instruments mostly reference the posterior condylar angle (PCA). The aim of this study was to verify whether the computer-navigated flexion gap (GAP) method produces a rectangular flexion gap and if a balanced flexion gap could also be achieved by referencing the PCA. A total of 100 knee prostheses were analysed using the navigated GAP method, and flexion gap symmetry along with femoral rotation were recorded. The GAP technique resulted in a rectangular flexion gap with adequate femoral rotational alignment. If the PCA technique had been used, only 51% of the femoral components would have been implanted in correct femoral rotation; the remaining 49% would have implanted with flexion gap instability. The GAP technique produces a rectangular flexion gap. The referencing of the PCA was shown to be less reliable. Thus, modern knee prosthesis instrumentation should not base femoral rotation solely on the PCA.