Uncemented femoral revision arthroplasty using the modular revision prosthesis MRP-TITAN revision stem.

OBJECTIVE: Restoration of a painless hip joint capable of bearing weight by uncemented implantation of a rotationally stable, modular revision stem anchored in the diaphysis. INDICATIONS: Prosthetic stem loosening with osteolytic bone defects (defect classification types I-III according to Paprosky). Material failure with broken prosthesis. Sub- and/or periprosthetic femoral fractures. Tumors. CONTRAINDICATIONS: Extensive osteolysis preventing diaphyseal anchorage of the prosthesis. SURGICAL TECHNIQUE: Transgluteal approach to the hip joint. Removal of the loose prosthetic stem and, if cemented, the bone cement as well. Excision of intramedullary granulation tissue. Reaming of the medullary cavity with flexible reaming shafts and form-fit, uncemented implantation of the star-shaped modular revision stem with diaphyseal press fit. If there is extensive loss of metaphyseal bone stock, augmentation with autogenous/allogenic bone should be performed. POSTOPERATIVE MANAGEMENT: Mobilization on two underarm crutches from the 1st postoperative day. Removal of the Redon drains after 48 h. Partial loading with 20 kg for 6 weeks postoperatively. If plain radiographs show unchanged seating of the prosthesis after 6 weeks, loading can be increased by 10 kg per week until full weight bearing is achieved; thrombosis prophylaxis is continued throughout. Radiologic checkups after 3, 6, and 12 months. After that, the patient should be checked annually.
RESULTS: 45 patients (n = 48 prostheses) with an average age of 67.2 years (min.-max. 42.4-87.4 years) were investigated. The average implantation time of the Modular Revision Prosthesis MRP-TITAN revision stem was 4.7 years (min.-max. 1.0-9.0 years). The Harris Hip Score for Paprosky bone defect types I-III had increased from 25.6 preoperatively to 71.4 postoperatively at the time of the final follow-up (< or = 0.05). Extensively defective bone was diagnosed preoperatively in 32 patients (> or = Paprosky IIB). Plain radiographs showed stable anchorage without migration in 44 patients. In one case, the stem (implantation time 2.36 years) was replaced due to increasing axial subsidence (> or = 5 mm). Good integration of bone graft with subsequent defect regeneration was seen in all patients with bone transplant (n = 30). Postoperative dislocation occurred in six patients and required closed reduction in four cases. Open reduction was performed in two patients, whereby the external rotation angle of the prosthetic neck was corrected without dismantling the distally anchored prosthetic stem components. The mechanical failure rate over the follow-up period of 9 years was one out of the 48 prospectively investigated prostheses. Rate of survival according to Kaplan-Meier was 97%.