Periprosthetic Fractures Treatment & Management

Casting, bracing, and protected weightbearing are indicated only for stable fractures in which the implant is not loose and alignment of the prosthesis and the limb both is acceptable for adequate function when the fracture heals.

Surgical options include replacement of the implant with a new implant, which also stabilizes the fracture, or fixation of the bone around the implant. Fixation options include intramedullary devices (rods, nails) or extramedullary devices (plates, screws).

The most important factor in treating peri-implant fractures is the status of the implant. Careful assessment of preoperative x-rays and comparison with previous x-rays (when available) is essential.

When the implant is loose,^{[4, 10, 15]} malaligned, or deformed, revision of the implant may be the best option. The potential difficulties of fixation and complications of nonunion or malunion are avoided by eliminating the fracture. Difficulties achieving fixation because the implant is in the way also are bypassed by removing the implant.

When the implant is not loose, its removal may be difficult, time consuming, and complicated by further fracturing of the bone or other complications of revision surgery. When the implant is stable and well aligned, the fracture usually can be treated with standard fixation methods while retaining the implant or prosthesis. An exception is when the bone stock for fracture stabilization is inadequate. If stable fracture fixation cannot be achieved, even if the implant is stable, the implant (or prosthesis) must be removed and joint replacement (or revision) is probably the best treatment.

Preoperative templating is required to ensure that adequate revision or fixation implants are available and the goals of surgery can be achieved. If screw fixation around a medullary stem or rod is planned, careful assessment of the implant's fit in the canal is necessary to ensure there will be room for the screws. Even unicortical screws require some space for their tip.

Treatment of peri-implant fractures by replacement of the implant

If the implant has failed, as in the case of a loose prosthetic replacement, the surgical treatment requires removal of the failed prosthesis and repeat replacement (revision) with a new prosthesis. The stem of the new prosthesis usually needs to be longer than the original so that it can bypass the fracture to stabilize it.

A case example of hip replacement after failed hip replacement is helpful. An 82-year-old woman with a preexisting loose hip replacement fell and sustained a periprosthetic femoral fracture (see image below).

Radiographic evaluation showed moderately severe osteolysis with probable subsidence of the cemented femoral component (with a gap in the stem-cement interface at the lateral aspect of the prosthesis). Because the stem was loose, an acute revision operation with removal of the prosthesis, strut medial allograft, and long-stem femoral revision was performed.^[16] The acetabular component also was revised with an uncemented component because it was found to be loose at surgery. Postoperatively, the patient did well, with partial weightbearing for 3 months and a stable prosthesis with allograft incorporation at 6 months.

If the fracture cannot be stabilized, despite a stable implant, because of inadequate bone to hold fixation devices, surgical treatment can include removal of the implant and replacement of the inadequate bone with a new prosthesis.

In this case, a case example of hip replacement after fracture at tip of hip lag screw is helpful. An elderly man sustained an intertrochanteric hip fracture and was treated with dynamic hip screw implant. The original fracture healed, but he had a new fracture at the tip of the lag screw after a fall (see image below). Fixation options were few because of inadequate bone stock, and he had a good result with removal of hardware and hip hemiarthroplasty.

Treatment of peri-implant fractures by open reduction internal fixation

If fixation of the fracture is chosen instead of replacement, the usual principles of fracture fixation must be followed. Stable anatomic fixation with preservation of soft tissue attachments through indirect reduction techniques should be achieved to obtain good results.^{[6, 12]} The surgeon must choose the device that fits the patient best with careful preoperative planning and intraoperative flexibility and creativity. A wide selection of implants must be available. Options include flexible intramedullary rods, rigid intramedullary rods, and special plates, possibly with cerclage wires.^{[17, 18, 19, 20]}

Flexible intramedullary rods (eg, Zickel supracondylar, Ender, and Rush rods) can be slipped alongside intramedullary stems. They can be placed through minimal incisions and act as an internal splint until fracture healing occurs.^{[12, 21]} They usually require some external protection (eg, cast, brace) and rarely allow unprotected motion or weightbearing. Preoperative radiographs must be studied carefully to be certain that there is enough room in the medullary canal for the implant. It may be difficult to maintain axial alignment and length with these devices. Their use mainly is indicated in patients in whom surgery is especially risky and the ability to place them with minimal surgical trauma outweighs the risk of imperfect reduction.

A case example of distal femur fracture with proximal hip replacement demonstrates this point. An elderly woman with a solid asymptomatic previous hip hemiarthroplasty fractured her distal femur in a fall. She was treated with Zickel supracondylar devices and healed without complication (see image below). At 3-year follow-up, the hip remains asymptomatic.

Rigid intramedullary rods (eg, antegrade, supracondylar, retrograde) are stronger than flexible rods and do not require external support. They cannot be used when a fracture has occurred around a stemmed implant (because the stem is in the way) but can provide rigid fixation for other peri-implant fractures. Advantages of intramedullary fixation include indirect reduction with less stripping of periosteal blood supply and preservation of soft tissues and the fracture hematoma with its bone forming cells and factors. Soft tissue protection increases the chance of union and decreases the chance of infection.

Biomechanically, the intramedullary position of the nail is stronger compared to plates because of increased resistance to torque forces and increased load transfer to the bone.^{[12, 21]} A case example of a fracture at the end of a blade plate treated with a retrograde nail is as follows: A young man who fractured his hip in a high-speed motor vehicle accident less than 2 years ago refractured his femur at the distal end of his plate after another motor vehicle accident. Rigid fixation was obtained with retrograde rod (see image below).

The following is a case example of a fracture above a total knee replacement treated with an antegrade nail: An elderly woman with bilateral knee replacements sustained bilateral distal femur fractures proximal to her knee replacements. Rigid fixation and healing of both fractures was achieved with antegrade nailing (see image below).

A case example of pathologic fracture above a plate treated with an antegrade nail follows: An elderly woman with pathologic humerus lesion from metastatic breast cancer was treated initially with plate fixation that failed. Intramedullary fixation that was stable enough to restore function and decrease pain was required to improve quality of life (see image below).

Plates and screws are also commonly used to repair periprosthetic fractures.^{[22, 23]} Although plates can be placed with indirect reduction techniques to minimize soft tissue damage and newer plate designs provide more "biologic" fixation,^[21] they usually destroy at least some of the periosteal blood supply and always disrupt the fracture hematoma. Plating techniques allow direct fracture reduction. This achieves more exact anatomic alignment, which may be crucial for long-term joint function.^[12]

Plating techniques allow for interfragmentary compression more readily. This creates a more rigid construct allowing early motion. Although intramedullary rods act as internal splints, plates can be placed as a tension band and/or neutralize the forces acting on interfragmentary screws.^[21] Special plates are usually required, allowing a combination of cerclage wires and screws to hold the plate to the bone while avoiding the intramedullary implant. Fractures of the calcar during hip replacement can be treated with cerclage wires or Parham bands.^{[9, 24]}

A case example of a fracture at the distal end of a hip replacement treated with a plate is as follows: An elderly woman sustained a low-energy injury to her leg, with fracture occurring at the tip of a preexisting hip replacement. She had a solid hip arthroplasty; thus, open reduction internal fixation with plate, cerclage wires, and screws was performed. The fracture healed without evidence of prosthetic failure (see image below).

A case example of fracture at the proximal end of a supracondylar nail treated with a plate follows: An elderly woman with previous supracondylar femur fracture presented with a new fracture at the proximal tip of her supracondylar rod after a motor vehicle accident. Open reduction internal fixation with a plate was performed with a good result (see image below).

Newer fixed-angle locking unicortical screw plates now allow improved less invasive fixation than was allowed with older techniques, which used allografts and cerclage wires. Unicortical screws can be placed with far less periosteal stripping than cerclage wires. Mihalko and associates^[25] showed that cables can resist bending loads, but Schmotzer and associates^[26] demonstrated that cables resist torsional loads poorly compared to screws. The authors' cadaver research has shown that it takes 6 cerclage wires to equal the rotational and anteroposterior stability of a single unicortical screw with a lateral plate.

In a relevant case example, a 73-year-old man with periprosthetic femur fracture distal to a well-fixed total hip replacement stem presented with a nonunion after 3 attempts at plate fixation using cerclage wires for proximal fixation. Open reduction internal fixation was accomplished with 2 "combi" fixed-angle locking screw plates (anterior and lateral placement to help control both anterolateral and mediolateral forces) with healing within 3 months (see image below).

In another relevant case example, a 49-year-old woman with periprosthetic femur fracture 2 cm distal to a well-fixed total hip replacement stem presented with nonunion after 3 attempts at plate fixation using cerclage wires for proximal fixation and one attempt at retrograde rod fixation. Open reduction internal fixation was accomplished with a less invasive surgical stabilization (LISS) fixator and an anterior LC-DC plate. The anterior plate included a lag screw and the LISS was inserted using minimally invasive technique (including percutaneous proximal unicortical screw placement). She was clinically healed by 3 months and radiographically healed by 5 months (see image below).

Postoperative care varies depending on the fracture, implant, method of fixation or replacement, quality of the bone, and ability of the patient to comply with instructions. In general, cemented prostheses and rigid intramedullary rods allow immediate weightbearing without casting or bracing. Uncemented prostheses often require protected weightbearing initially. Plate fixation and flexible intramedullary rods may require protected weightbearing and bracing or even casting. Physical or occupational therapy is often useful to maximize function.

The fracture should be monitored with radiographs and clinical examination until it heals. The patient should be monitored until rehabilitated to full potential. Prostheses should be checked yearly to detect early loosening or osteolysis.

Complications are more common when treating periprosthetic fractures than when treating fractures without an implant. Surgery is technically more difficult, and bone quality is poorer. Increased operating time and increased blood loss are expected. Failure of fixation occurs when inadequate stability is achieved. Infection rates are increased because of increased soft tissue damage from more difficult surgical dissection.^[27] Deep venous thrombosis, pulmonary emboli, and systemic complications should be expected and treated early.

A good outcome and prognosis is expected if the surgeon restores the biomechanical function of the limb. Failure to do so results in a poor outcome.^[28]

When treating periprosthetic fractures, the surgeon must evaluate the stability of the implant carefully. Loose implants used for fixation allow motion at the fracture site that interferes with healing and physically interferes with the placement of more stable fracture fixation. Loose prostheses used for joint replacement are painful and interfere with adequate fracture fixation. If the implant is loose or malaligned, the implant should be revised while the fracture is fixed at the same setting. If the implant is stable and sufficient bone stock is available for fracture stabilization, the implant should be retained while the fracture is fixed using standard treatment principles. When treating peri-implant fractures of the femur, the surgeon should have a flexible approach, using the best-fitting device, following basic fracture principles of rigid internal fixation and restoration of the anatomy and preservation of soft tissue attachments.

For optimal results when treating periprosthetic fractures, assess the stability of the fracture, restore mechanical stability, respect the biological environment, and have flexibility and choose the device that fits.^[29]

Current efforts to treat periprosthetic fractures focus on ways to avoid the fracture and new implants for improved fixation. New designs of replacement prostheses include changes in the shape of stems to better share load with the bone and avoid the osteoporosis of stress shielding, which weakens the bone and predisposes for fracture. New plate designs, such as the low contact dynamic compression plate, decrease the contact area of plates and decrease the osteoporosis of stress shielding. Changes in materials decrease bone destruction from osteolysis. Less rigid metals (eg, such as titanium vs stainless steel) share the load better. Fixed-angle plate systems (eg, LISS), allow more stable fixation with minimally invasive techniques (see image below).