Flip Autograft Technique for Anterolateral Femoral Deficiency in Total Knee Arthroplasty

Bone deficiency is commonly encountered in revision total knee arthroplasty (TKA); however, it can also pose a challenge in the primary setting. Given the variety and complexity of possible bone defects, multiple classification systems have been described. The most widely utilized classification system is the Anderson Orthopaedic Research Institute, which is summarized in Table 1 []. This classification system was designed for use in revision arthroplasty as the surgeon is often left with bony defects of various magnitudes after removal of cemented components. However, the Anderson Orthopaedic Research Institute classification system has utility for preoperative planning in primary arthroplasty as well. Current options for addressing bony defects in knee arthroplasty include cement with or without screws for smaller defects [], autologous bone graft, morselized or structural allograft, modular systems (stems, wedges, cones), and limb salvage systems []. Specific techniques are useful for the proximal tibia and distal and posterior femur defects, but there are limited options to address unilateral anterior femoral deficiency.

Previous literature has described excellent results with autograft in the proximal tibia utilizing both femoral and tibial donor bones []. The tibial flip autograft technique utilizes a wedge of bone from the proximal tibia that is flipped to augment the deficient compartment, thereby creating an adequate foundation for the tibial prosthesis [,]. This technique may be used to address both valgus and varus deformities of the tibia in TKA patients. Other tibial augmentation techniques have been described in which bone from the distal femoral resection is used to augment peripheral tibial plateau deformities [,].

While multiple reliable techniques of tibial augmentation have been published, studies discussing the application of this technique to counteract anterior femoral deficiency or in the setting of a valgus knee are missing from the literature. With limited hardware choices, it is important for the arthroplasty surgeon to have the option of autograft when anterior femoral defects are encountered. We present a technique to address significant anterolateral femoral deficiency in the setting of primary TKA.

Loss of anterior femoral bone is occasionally present in patients undergoing both primary and revision TKA, making a surgical technique to augment for bone loss a useful tool for hardware placement. When a primary TKA is recommended for patients suffering loss of anterior femoral bone, a flip autograft technique can be applied by which an autograft from the distal femur is utilized to provide a base to cement the final femoral implants. In addition to utilization for anterior femoral bone loss, this technique can be used to address a valgus deformity as well.

We performed a standard medial parapatellar approach in a patient with a valgus deformity, tri-compartmental degenerative arthritis with complete joint space narrowing, subchondral sclerosis, osteophytes, and an atrophic patella with chronic changes to the anterior femoral trochlea (Fig. 1a–c ). After insertion of the femoral intramedullary cutting guide, the decision can be made to take an additional cut from the distal femur to account for flexion contracture, if warranted. Proximal tibial resection can then be completed. Due to anterolateral femoral deficiency, the subsequent femoral sizing and resection are planned using the anteromedial femoral surface, and the femoral cuts are completed using an anterior referencing cutting block. One has to be cognizant of a hypoplastic lateral femoral condyle, which can lead to a femoral component that is internally rotated. The tibial and femoral components are then trialed; the femoral component may be found to be unstable due to the deficient anterolateral cortex (Fig. 2). A graft can be fashioned from the resected distal femoral bone. The graft was denuded of any residual cartilage, and a rongeur and curette were used to prepare the anterior surface of the femur; an additional option would be to consider drill holes to encourage bone healing. Once sized and prepared, the graft was secured with 2 4.0-mm fully threaded cancellous screws that are countersunk below the surface (Fig. 3). The lateral aspect can then be leveled to the previously cut surfaces of the distal femur (anterior and anterior chamfer) (Fig. 4). The femoral component should be trialed again, and once it is stable, the final components can subsequently be cemented in place. The decision to utilize a stem is only necessary if the surgeon is concerned about the overall bone quality of the distal femur. If resurfacing of the patella is possible, this should be completed. This is sometimes impossible, however, in patients with significant atrophy along with a pre-existing longitudinal insufficiency fracture from wear, as was present in this case (Fig. 5). Standard wound closure should be performed following the procedure. Postoperatively, the patient was allowed to be weight-bearing as tolerated, and no restrictions were placed on range of motion.

There are multiple options to address femoral defects in revision TKA including cement with or without screws, autologous bone graft, morselized or structural allograft, modular systems (stems, wedges, and other augments), and limb salvage systems []. However, the options to address unilateral anterior femoral defects in the primary TKA setting are limited. Modular systems with wedges have been used; however, these are expensive and often require additional bone resection to fit the wedge []. Cement with screws is another option. Lotke et al. and Ritter and Harty reported favorable results using methylmethacrylate for large tibial defects in primary TKA [,].

The bone-implant interface in a knee with metal augmentation forms a complex shape, which creates a continuing concern regarding implant loosening and failure. While allograft is widely used and readily available, it is less structurally sound than autogenous bone and comes with the risks of disease transmission and early graft resorption []. Autogenous bone grafts provide more predictable and successful results than allografts, along with the added benefit of conserving existing bone stock if a revision becomes necessary in the future [, , ]. They also offer the potential to restore bone stock.

Dorr described a few prerequisites for complete graft incorporation []. Surface preparation of host bone to expose viable bony bed is critical along with definition of the defect and preparation of the graft so that excellent fit and fixation can be obtained []. The graft should ideally be covered by the component to prevent resorption of the unstressed graft. Correct alignment is of utmost importance to prevent failure by collapse or from overload.

The tibial flip autograft technique was first described by Franceschina and Swienckowski in 1999 and has been modified over the years to address multiple tibial deformities []. In a case series of 7 tibial flip autografts in the setting of TKA, all patients had their varus deformity corrected, all grafts achieved union, and all were vascularized without hardware loosening at an average of 35 months of follow-up []. An article by Nagumo et al. reported on a modification of this technique to address valgus deformity in TKA after failed high tibial osteotomy with excellent results as well []. The graft had healed at the 3-month follow-up, and the patient had full range of motion without evidence of hardware failure or loosening at 2 years after surgery []. These techniques, in which tibial deformities are successfully corrected, are directly applicable to cases of femoral deficiency and support the success of our technique. Another technique described to address lateral tibial deformity in TKA utilizes resected femoral condylar bone to supplement the tibial plateau in a similar fashion that the femoral condyle was supplemented in our case. Two articles describing this technique report excellent outcomes with an average follow-up of 4 years [,]. All the grafts achieved union, without graft resorption, necrosis, or collapse at the most recent follow-up [,]. Additionally, when the anterolateral aspect of the femur with a high lateral ridge is utilized for sizing to prevent notching of the femur, it leads to a large cement mantle. The technique described here may be of use on the medial side.

There is literature highlighting the success of tibial autograft, but it is scarce regarding femoral autograft. It stands to reason that a well-established technique that allows healing, immediately provides graft material without donor site morbidity, and preserves bone stock would be a favorable treatment option. We believe that this novel application of flip autograft with excellent short-term results is a viable technique for treatment of femoral deficiency in TKA.

Anterolateral bone loss during TKA is a rare occurrence in the primary setting. There are some clues seen on preoperative radiographs that give the surgeon an idea of the amount of bone loss; however, current implant systems do not normally have a vast array of augmentation strategies to overcome this issue intraoperatively. This bone loss can result in component instability and may lead to early failure if not addressed. In this article, we discussed an augmentation strategy that uses available host autograft while using the standard cuts for primary TKA. We presented a technique using a standard posterior stabilized implant with a 3-year follow-up and good incorporation of bone graft. We think that this technique is a simple yet elegant solution to this rare condition with good results in this case.

Research reported in this publication was supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Number 5U54GM104942-05. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: M. J. Dietz is a paid consultant for Heraeus Medical, is a scientific advisory board member in Peptilogics, and is a research committee member in AAHKS.

For full disclosure statements refer to https://doi.org/10.1016/j.artd.2022.02.001.

The author(s) confirm that informed consent has been obtained from the involved patient(s) or if appropriate from the parent, guardian, power of attorney of the involved patient(s); and, they have given approval for this information to be published in this article.

Supplementary data related to this article can be found at https://doi.org/10.1016/j.artd.2022.02.001.