History

The patient is a 41-year-old female with a history of rheumatoid arthritis who had undergone numerous joint replacements in the past, including bilateral total knee and hip arthroplasties. Her left THR was complicated by a late-onset coagulase-negative Staphylococcus infection which was treated by 2-stage exchange arthroplasty. She then did well until approximately 6 months prior to the current visit, when she developed new onset of left groin and proximal thigh pain, present with every step. She denied any fevers, chills, or weight loss and had not noticed any erythema or drainage at the surgical wound site.

Physical Examination

On examination, the patient was in no acute distress. She ambulated with a slightly antalgic gait on the left. Her left hip incision was well healed and nontender. The left hip had full range of motion, with reproduction of her groin pain at the limits of motion. Neurovascular examination of the left lower extremity was unremarkable.

Radiology Studies

The patient’s left THR was originally done using an S-ROM prosthesis (Figure1).

This was revised to an extensively porous-coated stem following her infection; an extended trochanteric osteotomy was used to gain access to the femoral canal and was fixed using cerclage wires (Figure 2)

An AP radiograph at the time of presentation (Figure 3) revealed a fracture of the femoral stem at the level of the proximal cerclage wire, with slight varus angulation.

The lateral view (Figure 4) reveals no apparent abnormality.

Diagnosis

Fractured femoral stem

Discussion

Fracture of the femoral stem is a rare mode of failure for total hip arthroplasty. A 1995 survey study [7] reported 172 stem fractures out of 64,483 cases (including both cemented and cementless prostheses), for an incidence of 0.27%. This low rate has been attributed in part to metallurgical advancements as well as improved stem design. However, even Charnley had previously reported a fracture rate of only 0.23% among his first 6500 cemented hip replacements [2].

With cemented stems, metal fatigue has been implicated as the usual cause of fracture [3]. The location of the break is typically in the middle third of the stem. The time interval between surgery and stem fracture is highly variable, and patients usually present with recent-onset pain in a previously asymptomatic and well-functioning hip. Both varus malposition of the stem and patient obesity have implicated as risk factors [1,3], although valgus malposition may also predispose stems to failure [11]. Gruen [5] postulated that cantilever bending of a cemented stem that is well-fixed distally but loose proximally could lead to fatigue fracture, and radiographs of fractured stems have typically demonstrated a deficient cement mantlein the calcar region [1,3]. In addition, several case reports in the literature describe fatigue fracture occurring through a stress riser due to laser etching of the stem [8] or accidental scoring with a drill bit [6] at a region of high stress. At present, no studies have specifically analyzed fracture rates or mechanisms of exclusively cementless prostheses.

Removal of an extensively porous-coated femoral stem can be problematic because bone ingrowth occurs along the entire length of the coating. If the stem is fractured, gaining access to the distal piece presents an additional challenge. Removal of a well-fixed component requires disruption of the bone-prosthesis interface circumferentially, and concerns have been raised about weakening of the bone due to the “gutters” which are cut into the surrounding cortex [4]. To overcome this problem, several companies have developed hollow trephines which are sized to allow overdrilling of the distal femoral stem while minimizing cortical bone loss. However, successful use of these devices depends upon the fracture being through the cylindrical portion of the stem. If the fracture is more proximal (as in the present case), a larger trephine would be required, with an increased risk of eccentric reaming and perforation of the cortex.

Alternatively, direct access to the femoral stem can be gained via a cortical window (which provides only limited access) or a femoral osteotomy. Paprosky [10] has described an “extended trochanteric osteotomy” which allows wide access to the femoral canal for removal of an intact or broken stem. With this technique, a tongue of bone comprising one-third of the femoral circumference is elevated, with the soft-tissue attachments of the gluteus medisu and minimus and vastus lateralis left intact [10]. At the end of the case, the osteotomy is reattached using multiple cables or cerclage wires. Excellent outcomes have been reported using this technique, with a nonunion rate of only 1% at nearly 4-year follow-up [9].

Clinical Course

The patient opted to undergo revision of the left femoral component. A direct lateral approach was used for exposure via the previous skin incision. Once the hip was dislocated, the proximal portion of the broken stem was found to be grossly loose and was removed without difficulty. However, the distal piece remained solidly fixed in the femoral diaphysis. An attempt was made to overdrill the distal portion of the stem using a hollow trephine designed for that purpose. This was not successful, however, as the break had occurred several millimeters proximal to the cylindrical portion of the stem. Finally, an extended trochanteric osteotomy was performed in order to gain access to the distal piece. The remainder of the stem was then removed, the canal was reamed, and a new fully porous-coated femoral prosthesis implanted. The osteotomy was repaired using cerclage wires (Figure 5). The acetabular component was found to be well fixed and was not revised. Postoperatively, the patient had good relief of her symptoms and was doing well as of her most recent follow-up visit.

Figure 5

Case Discussion

This patient presented with a fractured porous-coated stem requiring revision arthroplasty. Removal of the well-fixed distal piece was challenging because the fracture had occurred proximal to the cylindrical portion of the stem and thus trephines could not be effectively used. Ultimately, an extended trochanteric osteotomy enabled the distal piece to be removed. Postoperatively, the patient has done well. This case underscores the importance of having multiple plans of attack ready, along with the appropriate equipment, before proceeding with a challenging revision hip arthroplasty.

References

1. Carlsson, AS, Gentz C-F, Stenport J. Fracture of the femoral prosthesis in total hip replacement according to Charnley. Acta Orthop Scand 48:650-655 (1977).
2. Charnley J. Fracture of femoral prostheses in total hip replacement: A clinical study. Clin Orthop Rel Res 111:105-120 (1975).
3. Galante JO. Causes of fractures of the femoral component in total hip replacement. J Bone Joint Surg [Am] 62-A:670-673 (1980).
4. Glassman AH, Engh CA. The removal of porous-coated femoral hip stems. Clin Orthop Rel Res 285:164-180 (1992).
5. Gruen TA, McNeice GM, Amstutz HA. “Modes of failure” of cemented stem-type femoral components: a radiographic analysis of loosening. Clin Orthop Rel Res 141:17-27 (1979).
6. Harper MC, Ralston M. Accidental drill bit scoring of a total hip arthroplasty femoral component with subsequent fatigue fracture. Clin Orthop Rel Res 173:173-177 (1983).
7. Heck DA, Partridge CM, Reuben JD, Lanzer WL, Courtland GL, Keating M. Prosthetic component failures in hip arthroplasty surgery. J Arthroplasty 10:575-580 (1995).
8. Lee EW, Kim HT. Early fatigue failures of cemented, forged cobalt-chromium femoral stems at the neck-shoulder junction. J Arthroplasty 16:236-238 (2001).
9. Miner TM, Momberger NG, Chong D, Paprosky WG. The extended trochanteric osteotomy in revision hip arthroplasty: A critical review of 166 cases at mean 3-year, 9-month follow-up. J Arthroplasty 10 (Suppl 1):188-194 (2001).
10. Paprosky WG, Weeden SH, Bowling JW. Component removal in revision total hip arthroplasty. Clin Orthop Rel Res 393:181-193 (2001).
11. Wroblewski BM. Fractured stem in total hip replacement: A clinical review of 120 cases. Acta Orthop Scand 53:279-284 (1982).