Uncemented Modular Stems
Brian P. Chalmers
Kevin I. Perry
Patients may have proximal femoral anatomic abnormalities that make it difficult to fit a conventional off-the-shelf uncemented femoral component, for a number of reasons. These include developmental dysplasia of the hip (DDH) (Figure 9.1), Perthes disease (Figure 9.2), other developmental anomalies, and trauma.
Patients with DDH often have complex proximal femoral anatomy, including excessive femoral neck anteversion, a valgus neck shaft angle, metaphyseal-diaphyseal mismatch with a stenotic diaphyseal canal, and proximal femoral hypoplasia, rendering femoral component placement during primary total hip arthroplasty (THA) challenging; furthermore, these patients often have prior proximal femoral hardware from prior surgery compromising metaphyseal fixation.
Although cemented femoral fixation allows for appropriate compensation of these complex deformities, uncemented femoral fixation allows for biologic ingrowth and potentially superior long-term component durability in this relatively young patient population.
Uncemented combined metaphyseal and diaphyseal fixation allows improved component fixation in patients with metaphyseal-diaphyseal mismatch and prior proximal femoral hardware.
The modularity of an uncemented, modular femoral stem is technically easier and allows surgeons to appropriately restore femoral version and offset to optimize hip stability in patients with complex proximal femoral deformities.
Because these implants use ream-only techniques for femoral preparation they are well suited to situations in which proximal sclerotic bone makes bone preparation with a broach difficult (Figure 9.3).
Sterile Instruments and Implants
Routine hip retractors
Uncemented primary acetabular component of surgeon’s choice (with instrumentation)
Uncemented primary uncemented modular stem (with instrumentation)
Lateral decubitus position
The surgical approach should allow good femoral exposure and be extensile if needed. Milling of the proximal femur for the modular sleeve requires more exposure than routine roach-only or ream and broach femoral preparation.
It may be wise to avoid the direct anterior approach in this patient population because of complex and altered anatomy on both the femoral and acetabular sides that need to be addressed and because making the approach very extensile is challenging.
Figure 9.2 ▪ A, Radiograph of patient with history of Perthes disease and abnormally shaped proximal femoral metaphysis. B, Radiograph after THA using modular femoral stem to management bone deformity. (Courtesy of Daniel J. Berry, MD.)