A 63-year-old man underwent primary total hip arthroplasty (THA) of the right hip for degenerative arthritis with a proximal, porous-coated, tapered-wedge stem. The patient complained of significant pain and progressive restriction of function at the 1-year follow-up assessment.
Continuous radiolucencies were seen in Gruen zones 1, 2, 6, and 7 on anteroposterior radiographs and in zones 8 and 9 on the lateral radiographs ( Fig. 61.1 ). A pedestal was identified near the lateral distal cortex at the tip. The radiographs suggested incomplete bony ingrowth.
Due to persistent restriction of functional activities, the patient needed a revision THA. Explantation of the femoral implant resulted in a type I Paprosky bone loss, making it difficult for the larger primary tapered-wedge stem to obtain stable fixation in the metaphysis. An Emperion stem was used to achieve adequate fit and fill in the metaphyseal and diaphyseal regions. Intraoperatively, adequate lateral entry was obtained for reaming, and disruption of pedestal was required to allow sequential reamers to pass through ( Fig. 61.2 ). Restoration of offset, leg length, and stable fixation were achieved with the use of an Emperion stem.
A 70-year-old man presented with a cemented THA and internal fixation that had been done to treat a periprosthetic fracture. The cemented acetabular cup demonstrated an eccentric position of the femoral head that suggested polyethylene wear ( Fig. 61.3 ). Radiolucencies in zones 1, 5, and 7 suggested osteolysis, and a varus angulation deformity was identified at the site of the healed fracture.
Due to aseptic loosening of the femoral component, revision THA was performed with an S-ROM stem because proximal bone was adequate (i.e., Paprosky type I/II defect). Angular femoral deformity precluded insertion of a straight femoral component. A transverse osteotomy was made at the apex of the deformity, which also assisted in the removal of cement. The implant length was chosen to achieve two cortical diameters of intimate bony contact beyond the osteotomy. After removal of the hardware, cemented femoral component, and proximal cement mantle, an osteotomy was performed with minimal stripping of the muscular envelope. The distal osteotomy fragment was prepared with cylindrical reamers to allow a firm press-fit (prophylactic cables minimized hoop stresses during reaming and implantation), followed by milling of the proximal fragment after the removal of residual cement. The proximal section was then reduced independently to ensure adequate soft tissue tension. The revision implant impacted the proximal segment against the distal, which allowed axial but not rotational displacement until the osteotomized bones were well apposed.
Appropriate sizing of the stem is crucial because the distal splines maintain rotational stability at the fracture site. A long S-ROM stem was implanted using a transverse osteotomy ( Fig. 61.4 ).
A 57-year-old man with degenerative hip arthritis previously underwent an intertrochanteric osteotomy. Examination and radiographic assessment identified arthritis of the hip joint with a varus deformity at the metadiaphyseal level ( Fig. 61.5 ). The proximal metaphysis was widened, but the bone stock was adequate for proximal fixation.
Conversion to a THA was challenging because of the widened proximal metaphysis, rotational remodeling of the neck and metaphyseal region, and angular deformity of the proximal diaphysis. THA with an S-ROM implant was performed in conjunction with a transverse osteotomy at the apex of the deformity ( Fig. 61.6 , A ). Sequential reaming of the distal segment and adequate sizing of the distal stem ensured rotational stability of the construct. The proximal cone helped in achieving adequate fit and fill in the proximal metaphysis (see Fig. 61.6 , B ). Independent adjustment of version and offset enabled an optimal biomechanical reconstruction in light of the deformed proximal femur. Fixation of the S-ROM stem was achieved with a healed osteotomy ( Fig. 61.7 ).
Restoration of biomechanical function and stable fixation of components are universal goals of total hip arthroplasty (THA). Significant bone loss in the setting of revision THA creates a formidable reconstructive challenge.
The complexity of femoral revision arthroplasty is evident in the wide variety of implants used and techniques described. Initial techniques were developed by extension from primary cemented THAs, using long stems fixed with cement. Extensively porous-coated, monoblock, cementless revision stems designed to bypass the proximally deficient bone and obtain fixation in distal intact bone were also developed. Because metaphyseal and diaphyseal bone loss varies, it is difficult to achieve appropriate length, femoral offset, and anteversion with a monoblock stem of any type.
Modular, cementless femoral components with independent proximal and distal fixation options have become the main implants used in revision THA. One type is a tapered, fluted, modular, distally fixing stem. The other type is a modular femoral prosthesis incorporating an independent porous-coated sleeve that achieves proximal fixation coupled with a smooth stem with coronal splines in the distal portion that achieves rotational stability in the femoral diaphysis. These stems allow reconstruction to be tailored to the anatomy of the femur, producing independent fit and fill of the stem in the proximal metaphyseal and diaphyseal bone. Modularity also enables placement of version irrespective of fixation to maximize the range of motion and improve stability. High-offset options can help to achieve optimal biomechanics without negatively affecting leg length.
This chapter focuses on proximally fixing, cementless, modular stems. The prototype is the S-ROM stem (DePuy Orthopedics, Warsaw, Ind.). The Emperion (Smith & Nephew, Memphis, Tenn.) is a similar type of stem. We review the designs, indications for use, and reported outcomes for these stems.
Indications and Contraindications
Assessment of the degree of bone loss after removal of cemented or cementless components during revision surgery determines the type of revision stem needed. Adequate metaphyseal bone stock is essential for the use of proximal, porous-coated, modular stems. A reasonable judgment can be made from preoperative radiographs. Patients with type I or II femoral defects of the Paprosky classification ( Table 61.1 ) are ideal candidates for the use of these stems. These defects are usually encountered during revision of an undersized, non–porous-coated, cementless implant (type I) or early stages of aseptic loosening of porous-coated implants (type II). Some cases of type IIIA femoral defects may be accommodated by these revision systems. However, use of these stems for severe bone loss, such as type IIIB and type IV defects, has been associated with inferior results.