Proximal femur replacement has been one of the standard procedures in orthopedic oncology to reconstruct large bone resections of the proximal femur after primary tumors and metastasis ^[1]. This technique has expanded to non-oncologic indications such as severe femoral bone loss secondary to a failure of primary total hip replacement or multiple revision procedures ^[2]. Although long-term survival of the implant and functionality is achieved ^[3], different complications have been described, being aseptic loosening of the femoral stem one of the main ones, which has been reported to reach 93.8% after 10 years of index surgery ^[4]. We report a case series of four patients, two women and two men, with different medical records, treated with proximal femoral endoprosthesis, who subsequently presented aseptic loosening (2 patients) and septic loosening (2 patients), so they were taken to surgical management with a novel augmentation technique to ensure primary stability of the construct.

This case series includes four patients with an average age of 49.5 years (35–70 years), two women and two men, referred to the Orthopedic Surgery Department of the San Ignacio University Hospital at the Pontificia Universidad Javeriana of Bogota. Two of them with a history of oncological disease (proximal femoral chondrosarcoma and inguino-vulvar myofibroblastic sarcoma), assessed in conjunction with the oncological orthopedic service, ruling out a tumor relapse through local images and extension exams; another patient with a history of firearm injury to the left thigh with multiple secondary complications, which required various reconstructive procedures; and the oldest patient with a history of total hip replacement. The main complaint of the four patients was pain not caused by trauma, and none presented fever or associated systemic inflammatory response symptoms. Initial assessment radiographs of all patients showed signs of loosening of the prosthetic material and with microbiological cultures were established, septic etiology of the loosening in two of the patients and aseptic etiology in the other two patients (Fig. 1). Septic loosening was treated by a two-stage joint revision, once the patient showed no clinical signs of infection, C-reactive protein and arthrocentesis where negative, que second stage was performed. As a preliminary study, an arthrocentesis was performed in the four patients and active periprosthetic joint infection was ruled out, so they were scheduled for revision surgery of prosthetic components. Outpatient clinical control was carried out in an average time of 2 years (8 months–4 years), beginning at 2, 4, and 8 weeks after surgery. The patients present complete resolution of pain; surgical wounds were completely healed without local signs of infection. Femur radiographs showed the implant in adequate position, without any sign of loosening or failure. However, one of the patients (history of firearm injury) required the removal of the osteosynthesis material due to the persistence of the bone infectious process 1 year after the surgical procedure.

Surgical technique

The patient is placed in lateral decubitus position with standard skin cleaning and preparation with chlorhexidine and iodide solution and iodide surgical drape. A hip posterolateral extended approach to the femoral diaphysis is performed to expose the entire endoprosthesis. The endoprosthesis is removed and resection of a segment of femoral diaphysis is done. This resection was performed to remove all devitalized bone tissue. Intraoperatively, the vitality and bleeding of the bone is verified, any segment that shows that it is in poor condition must be resected. Next distal femur preparation is performed with femoral reamers. Retrograded cementation and insertion of the new femoral cemented stem of greater diameter; coupling and fixing the rest of the endoprosthesis. Afterward dissection and exposure of the distal femur application of condylar support plate by a MIPO technique or using a provisional fixation with two Kirschner nails. The position is verified under image intensifier. Definitely, fixation was done with 5 distal locked screws and 2 periprosthetic screws on the distal diaphysis of the femur. Application of a cement mantle to achieve an adequate interface between the endoprosthesis and the plate and that the holes of the plate become full with cement is an essential step that allows better stability (Figs. 2 and 3). Finally, proximal fixation of the plate is performed with surgical cables which are tightened and closed. Inpatient management and rehabilitation follow during the first 3 days, allowing immediate mobilization of adjacent joints and weight-bearing. Follow-up was carried out until the 4^th post-operative year. No patient required revision or presented radiological signs of loosening.

Aseptic and septic loosening of the femoral stem is one of the major causes of implant failure in proximal femur endoprosthesis ^[5]. The main symptom is pain, which usually occurs in the middle third of the thigh, leading to progressive functional decline as in our patient. The initial approach must rule out periprosthetic joint infection because it would implicate variations in management options ^[6]. We present a group of patients in which a novel surgical technique is used to provide primary stability of a proximal femur endoprosthesis is achieved using multiple methods. In the first instance, thicker steam was used to decrease the possibility of movement ^[7]. Retrograde cementing technique was performed, which is widely known since Barrack et al. proved in 1992 that it decreases the loosening rate significantly ^[8]. Recently, in 2019, Phelon et al. reported that cemented femoral endoprosthesis is a versatile option that allows immediate full weight-bearing. Augmenting the construct with a condylar plate fixed with periprosthetic screws and surgical cables is an option that ensures more rigidity in primary stability. Literature shows its use, especially in distal femur periprosthetic fractures ^[9]. Song et al. reported that fixation of periprosthetic fractures with locking plates provided satisfactory results with a low risk of complications and additional surgeries ^[10]. In addition, a cement mantle was built between the endoprosthesis to achieve an adequate interface between the endoprosthesis and the plate and avoid metallosis or corrosion between the different metals. Using the following keywords, a literature search was performed on PUBMED and EMBASE: Proximal femur endoprosthesis, aseptic loosening, Augmentation, condylar plate, polymethylmethacrylate. We found no articles reporting this technique in aseptic loosening of proximal femur endoprosthesis. Different therapeutic options have been studied for endoprosthesis aseptic loosening including the use of bone allografts, especially for large femoral bony defects ^[11], use of wire mesh and cerclage wiring with impaction bone allograft into which the femoral stem is implanted ^[12], and total femur prosthesis, which provides good functional results but high rates of complications such as infection (13–18%), dislocation (6–10%), and material failure (3–6%) [13, 14]. In the case of periprosthetic infection, the approach must ensure infection control in the first instance to ensure better results. The revision could be performed in one or two stages with reinfection rates of up to 37% ^[15]. The clinical relevance of our technique is that it allows early mobilization and weight-bearing, allowing rapid rehabilitation and return to the previous functionality. Our series of patients shows good clinical results on the immediate post-operative period, 2 weeks and 2 months and 4 years follow-up, especially with complete resolution of thigh pain and no radiological signs of development of new loosening of the endoprosthesis (Fig. 4 and 5).

Septic and aseptic loosening is one of the most common complications of proximal femur endoprosthesis, resulting in significant pain and functional decline in patients. We present a novel surgical technique that allows primary stabilization of the construct that allows early rehabilitation, improvement of functionality, and no signs of new loosening in a period of 4-year follow-up.

One of the main objectives of orthopedic surgery is to restore the functionality and quality of life of patients. In this paper, we present a novel surgical technique to treat septic and aseptic loosening of proximal femur endoprosthesis that allows to recover functionality in the short, medium, and long term.