Avoiding Intraoperative Femur Fractures

Devin Walsh

Anand Patel

Matthew E. Deren

Eric M. Cohen

Introduction

The DAA is a popular approach for THA that offers an intramuscular and internervous interval for exposure. The DAA has been extensively evaluated, and systematic reviews highlight improved early functional outcomes for patients who undergo THA via this approach, further enhancing its popularity.¹ The DAA is minimally invasive and technically demanding. Although it offers excellent acetabular exposure and visualization, exposure of the proximal femur can be a challenge, particularly early in its adoption, and may require specialized instrumentation and soft tissue release for adequate femoral preparation. Consequently, intraoperative femur fracture (IFF) is a historically feared complication of the DAA.

IFFs require quick recognition and adept understanding of treatment algorithms to appropriately treat the fracture and preserve the integrity of the THA. In this chapter, we provide an overview of IFFs, including risk factors, classification, and treatment algorithms. In addition, we discuss steps to prevent IFFs, including patient evaluation and selection for the DAA, preoperative planning, and intraoperative techniques to further mitigate fracture risk.

Review of Intraoperative Femur Fractures

Influence of the Learning Curve

IFFs are a potential complication of the DAA for THA given its learning curve, technical challenge, and potentially difficult exposure for femoral preparation. There is a variable incidence of IFFs during the DAA for THA in the literature; they have been reported to range from 0.8% to 7% and are influenced in part by a surgeon’s experience and technique.²^,³^,⁴^,⁵

There have been several studies that reported an increase in IFFs during the “learning curve” of the DAA. Hartford and Bellino⁶ reviewed 500 consecutive DAA THAs and found the IFF rate for the first 100 cases was 7% and the IFF rate for cases 400 to 500 was 0%. Similarly, Masonis et al² reviewed complications of the first 300 consecutive DAA THA cases and found an IFF rate of 4.8% in the first 62 cases and no IFFs thereafter. Jewett and Collis³ reviewed the complications of the first 800 cases and found IFFs and femoral perforations occurred early in their series, with none of these complications occurring after the first 400 cases. The learning curve is due to the difficulty of femoral exposure, orientation, and anatomy unique to the DAA and highlights the need to have an expert understanding of surgical techniques and anatomy.

Risk Factors for Intraoperative Femur Fractures

Risk factors for IFFs during the DAA for THA are generally factors that increase the difficulty of femoral exposure, femoral preparation, and femoral implant insertion. Understanding these risks is paramount for surgical planning and to mitigate complications. Numerous studies have examined THA cases via the DAA in which IFF occurs to elicit identifiable risk factors for this occurrence.

Hartford and Knowles⁷ evaluated 500 consecutive THAs performed via the DAA and found the risk factors for IFFs to be female sex, a body mass index >40 kg/m², a lower Dorr ratio, and a smaller stem size. Additionally, Berend et al⁸ found an association between age and sex as risk factors for IFFs, with older females being at higher risk for fracture. Femoral stem design has also been identified as a risk factor for IFFs, with shorter stems having a higher periprosthetic fracture rate than standard stems and flat single-taper wedge-design stems having a higher periprosthetic fracture rate compared with a dual-taper implant (Figure 18.1).⁹^,¹⁰

FIGURE 18.1 Intraoperative fluoroscopy of (A) a shorter single- taper wedge stem (Trilock, DePuy Synthes) converted to (B) a longer dual wedge stem (Summit, DePuy Synthes) for IFF via the DAA.

There are additional general risk factors for IFFs during THA that are not limited to a single surgical approach. These include the use of uncemented stems, advanced age, female sex, osteoporosis, obesity, and indications for THA other than osteoarthritis.¹¹^,¹² A general surgical technique can also predispose to IFFs because the use of a minimally invasive exposure that makes femoral preparation more challenging increases the risk of IFFs as does the use of a calcar reamer.¹³^,¹⁴

The incidence of IFFs during DAA is not different for procedures performed on a standard operating room table versus a traction table. Cohen et al¹⁵ reviewed 487 THA cases via the DAA performed by surgeons who were specifically past the learning curve on either a traction table or a standard flat table. The overall incidence of IFFs was found to be 2.46%, and there was no statistical difference between cases preformed on a traction table compared with a standard table. In that series, only 0.4% of DAA THA cases required component revision due to an observed IFF, and most fractures were managed using cerclage wiring without any actual change in patient outcomes. A systematic review evaluated DAA THAs on a standard table versus a traction table and found an intraoperative fracture rate of 1.3% for a standard table and 1.7% for a traction table; however, these results are difficult to interpret because DAA THA “learning curve” studies were included.¹⁶

Classification of Intraoperative Femur Fractures

The Vancouver classification of periprosthetic femur fractures developed by Duncan and Masri is a reliable and validated system for classifying IFFs during THA.¹⁷ Fractures are classified by their location, the stability of the implant, and bone quality. A modification to the Vancouver classification for intraoperative periprosthetic femur fractures further subdivides each fracture as a cortical perforation, nondisplaced fracture, or displaced unstable fracture pattern. The Vancouver classification for intraoperative periprosthetic femur fractures includes type A, type B, and type C fractures. Type A fractures are confined to the proximal metaphysis and include fractures of the greater trochanter, lesser trochanter, and calcar. Type B fractures occur in the proximal diaphysis. Type C fractures extend beyond the femoral stem and may even include the distal femoral metaphysis. As mentioned, each fracture type can be further subclassified as cortical perforation (subtype 1), nondisplaced (subtype 2), or displaced (subtype 3).¹⁷^,¹⁸^,¹⁹

Treatment of Intraoperative Femur Fractures

The treatment of periprosthetic IFF depends on the location of the fracture, the fracture profile, and the stability of the implant (Table 18.1). In general, during DAA THA, the surgeon must maintain direct observation of the calcar region during femoral instrumentation. If an IFF is
suspected, intraoperative imaging should be obtained to assess the proximal femur, with biplanar visualization used to confirm the stem position and/or IFF pattern.

TABLE 18.1 Treatment Algorithm for Intraoperative Femur Fractures Based on the Vancouver Classification

Fracture type	Characteristics	Treatment
Type A (proximal metaphysis)	Greater trochanter	Fixation with screws, cerclage wires or cables, or specialized hook plates
	Lesser trochanter	Displaced fractures with amenable bone stock can be treated with cerclage wires or cables
	Calcar	Broach or implant removal, cerclage wiring or cabling, implant reinsertion
Type B (proximal diaphysis)	Nondisplaced, stable implant	Cerclage wires or cables
Type B (proximal diaphysis)	Displaced, unstable implant	Implant removal, fracture fixation with cable plate and screws, upsize implant to bypass fracture by 2-3 cortical widths
Type C (distal to stem)	Nondisplaced	ORIF or ORIF with cerclage wires or cables and bypass with longer stem
Type C (distal to stem)	Displaced	ORIF or ORIF with cerclage wires or cables and bypass with longer stem
Cortical perforations		Bone grafting from acetabular reaming or femoral head/neck, cerclage wiring, or cabling to prevent fracture propagation; upsizing femoral implant as needed to bypass fracture by 2-3 cortical widths
ORIF, open reduction and internal fixation.
Fracture treatment is based on location, displacement, and stability of the implant.

Although some authors have argued for nonoperative management of greater trochanteric fractures, it is our opinion that displaced type A greater trochanteric fractures should almost always be addressed surgically to prevent migration of the greater trochanter and the associated patient morbidity that comes from functional loss of the abductor mechanism. These fractures can be treated with screws, cerclage wires or cables, specialized hook plates, or a combination of the aforementioned. We recommend an additional direct lateral incision to access an isolated greater trochanter fracture for open reduction and internal fixation (ORIF), but this may also be accomplished with an extensile femoral approach and internal rotation of the femur.

Fractures of the calcar are treated based on the degree of displacement and their distal propagation. Nondisplaced calcar fractures that do not extend distally past the lesser trochanter can usually be treated nonoperatively. Calcar fractures that extend distally to the lesser trochanter should be treated with broach or implant removal, wire or cable fixation, and implant reinsertion (Figure 18.2).

FIGURE 18.2 A postoperative radiograph of an intraoperative right calcar fracture treated with a cerclage wire and primary stem reinsertion.

Type A fractures of the lesser trochanter are a rare intraoperative occurrence. If they are displaced and bone stock is appropriate, they can also be fixed with cables or wires placed through the distal tendon mass and then cerclaged around the femur. Type A cortical perforations can often be treated with bone grafting from acetabular reamings or the previously cut femoral head and neck. To prevent propagation of cortical perforations, cabling can be performed proximal and distal to the perforation site along with the use of a stem that bypasses the perforation site by two to three cortical diameters.¹⁷^,¹⁸^,¹⁹

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