Femoral Neck Fractures
Femoral neck fractures represent one of the most common fracture types treated by orthopaedic surgeons. They primarily occur in elderly patients with poor bone quality after minor trauma, but they also occur in younger patients after high-energy events. Treatment of the elderly patient with an isolated femoral neck fracture requires different management techniques from those required for the younger patient. An elderly patient′s hip fracture requires management often dictated by the patient′s medical condition. A younger patient with a high-energy hip fracture often has other associated injuries, some of which could be life threatening, which require treatment prior to or subsequent to treatment of the hip fracture.
Femoral neck fractures in elderly patients (generally considered to be patients older than 65 years of age) represent a large and growing proportion of appendicular fractures treated by orthopaedic surgeons. The cost of hip fracture care to the health care system as well as to patients and families is substantial and increasing. Appropriate treatment strategies can minimize the long-term burden of hip fracture in elderly patients by improving survival, improving the likelihood of return to pre-fracture living and ambulation status, and decreasing health care resource utilization. In the young patient, a femoral neck fracture can be a life-changing event. Hip preservation is the favored method for treatment of young patients. Inadequate treatment (lack of anatomic reduction, use of implants that fail to maintain the reduction) and difficulties with healing can lead to substantial disability and continued pain, requiring patient time away from family and work and perhaps requiring subsequent reconstructive procedures. Arthroplasty in a young and active patient after failed fixation attempt(s) is sometimes required, but is suboptimal (due to higher activity demands in younger patients, longer life expectancies, and durability of implants).
Orthopaedic surgeons encounter multiple challenges when managing femoral neck fractures. In elderly patients, once medical optimization has occurred, the surgeon must decide whether nonoperative or operative management is indicated. If operative management is indicated, multiple questions must be answered. Is the fracture nondisplaced or displaced? Does the fracture require an open reduction? Should the fracture be treated with arthroplasty instead of reduction and internal fixation? What kind of arthroplasty may be necessary, and why? What surgical approach will yield the most favorable results? In younger patients, native hip preservation is the favored method of fracture treatment, so how will the reduction be obtained? What fixation devices are required? What if there is an ipsilateral femoral shaft or acetabular fracture associated with the femoral neck fracture? What is the urgency of fracture treatment?
An appropriate history, physical examination, and radiography are all vital in the treatment of the femoral neck fracture patient, as in the treatment of all injured patients. The orthopaedic consultant should determine if the mechanism of injury is high energy (such as in a motor vehicle crash), low energy (such as a fall from the standing position), or nontraumatic (such as a spontaneous fracture). This information helps guide the surgeon′s course of action. Low-energy or nontraumatic femoral neck fractures likely indicate inferior bone quality, which could be due to osteoporosis (in the older patient) or metabolic abnormalities or neoplasms (in any patient). High-energy injuries should prompt the surgeon to look for associated injuries to the ipsilateral lower extremity (especially femoral shaft, knee, and acetabular fractures) as well as to the other extremities and the pelvis (in addition to considering head, neck, and thoracoabdominal trauma). The physical examination should pay close attention to the neurovascular status of the injured lower extremity, especially after high-energy injury mechanisms. Adequate radiographs of the pelvis and of the entire ipsilateral femur are required to rule out other associated injuries, such as acetabular, pelvic, or femoral shaft fractures, all of which may prompt a change in management strategy for the femoral neck fracture.
Classification
Hip fracture classification schemes are routinely utilized to describe femoral neck fracture patterns. Multiple schemes have been proposed, each of which accounts for different characteristics of the fracture itself. Although these classification schemes are widely used, it is questionable whether their use is routinely accurate or whether they sufficiently enable accurate communication with other clinicians. A classification scheme should accurately describe the injury, guide the treatment, predict the prognosis, be useful for research, have good intraobserver and interobserver reliability, and be easy to use. Because of the problems inherent in many classification systems, many surgeons prefer to know simply whether a femoral neck fracture is either nondisplaced or displaced.
The most commonly used and understood system is the Garden classification for femoral neck fractures (Fig. 25.1). It has limited reliability as originally described.1 Garden type I fractures are considered nondisplaced but are actually valgus-impacted; they are thought to be stable-pattern injuries that do well with in-situ percutaneous treatment without reduction. They may also be incomplete fractures, with an intact inferior hinge. Garden type II fractures are truly nondisplaced fractures, with alignment of the fractured femoral neck being identical to the pre-fracture condition. Garden types III and type IV fractures are displaced with varus alignment. The Garden type III fracture still maintains bony contact between the fracture surfaces, resulting in angulation of the fracture (and distorted orientation of radiographically apparent trabecular patterns). On the other hand, the Garden type IV fracture represents a completely displaced fracture, and trabeculae in the femoral head and inferior femoral neck often maintain normal orientation, despite their displacement from one another. A simplified version of the Garden classification, with “non-displaced” fractures representing Garden I and II fractures and “displaced” fractures representing Garden III and IV fractures, has higher reliability of use.2
Another classification scheme utilized for femoral neck fractures is that compiled by the Arbeitsgemeinschaft fur Osteosynthesefragen (AO) in collaboration with the Orthopaedic Trauma Association (OTA) (Fig. 25.2).3 This classification scheme takes into account displacement, location of fracture along the femoral neck (subcapital, transcervical, or basicervical), and verticality of the fracture line, all of which are thought to impact treatment method and eventual outcome.
Yet another classification scheme that is routinely utilized by orthopaedic practitioners is the Pauwels classification (Fig. 25.3). Like the Garden classification, it is also of limited reliability.4 The Pauwels classification describes the vertical angle of the fracture relative to the horizontal. The lower this angle (i.e., a more horizontal fracture line), the more likely it is that weight-bearing forces (oriented perpendicular to the horizontal) will result in compression across the fracture line. Conversely, the higher the angle (i.e., a more vertical fracture line), the more likely it is that weight-bearing forces will result in shearing of the fracture line. Fracture “verticality” affects fracture behavior during healing, and may have implications on surgical treatment methods, including implants utilized for fracture fixation. Younger patients, who often require high-energy mechanisms to sustain femoral neck fractures, tend to sustain more vertically oriented (i.e., Pauwels type III) fractures than do older patients who sustain lower-energy mechanism fractures.
Nonoperative Management
Nonoperative management of femoral neck fractures has traditionally been reserved for the elderly patient who is nonambulatory and noncommunicative, or who is considered likely to expire during surgery or in the immediate postoperative period. Indications for nonoperative treatment of a femoral neck fracture treatment are uncertain, however. Nonambulatory and noncommunicative patients experience pain. Unstable femoral neck fracture patterns (i.e., Garden 3 or 4 fractures) are likely to be more painful than stable fracture patterns. The ability to mobilize out of bed is important for the frail elderly patient, and severe fracture pain caused by movement may prevent out-of-bed mobilization. Bed rest in frail elderly patients is associated with increased risk of thromboembolic disease, pneumonia, and pressure ulcer formation. Frail elderly patients often are substantially deconditioned and sick at the time of fracture, and further deconditioning is rapid and may not be tolerated. A retrospective review of a population database of operative versus nonoperative management of elderly hip fracture patients found that the 30-day mortality rate for nonoperatively managed patients was 18.8%, as opposed to 11% for operatively managed patients.5 However, in the same study, when examining a cohort of 62 patients managed nonoperatively and comparing with a cohort of 108 patients managed operatively, mortality in the nonoperative group approached 73%. Upon further examination, when nonoperatively managed patients were stratified according to mobilization versus bed rest, no significant difference was noted in 30-day mortality rates for operatively managed patients (29%) and those nonoperatively managed patients treated with immediate mobilization (19%). The authors found that bed rest after nonoperative hip fracture management was associated with a 2.5-fold increase in 30-day mortality.
Treatment of the nondisplaced or valgus-impacted fracture without surgery should be considered with caution. Although these fractures are often considered to be stable, rates of nonunion can be high (up to 39% without surgery).6–9 Furthermore, surgical repair after late displacement of femoral neck fractures may be more difficult than fixation of a stable and nondisplaced fracture. Arthroplasty may be required in a patient with late displacement, despite the fact that straightforward fracture repair with screws or a fixed-angle fixation device may have been reasonable at the time of injury. Rates of fracture nonunion and osteonecrosis may be increased with late fracture displacement. For all of these reasons, early operative management in the stable patient, even for stable and nondisplaced or impacted fractures, may be desirable.
Young patients with femoral neck fractures are treated with surgical repair as a matter of course. Nonoperative management for the young femoral neck fracture patient is not generally considered. Occasionally, severe injuries that may accompany the femoral neck fracture in a young patient may preclude immediate or early fixation. However, fixation that is delayed until the patient′s physiology stabilizes is still routinely performed.
Surgical Indications
In a young patient with a femoral neck fracture, surgery is typically performed when the patient′s condition will allow. Most often, early fixation is desired. Elderly patients are generally treated with internal fixation for nondisplaced or valgus-impacted fracture, and with hip arthroplasty (total or hemiarthroplasty) for displaced fractures. The definition of “young” is variable and often based on the surgeon′s experience and the patient′s baseline preinjury and intended postinjury activity levels. Some patients younger than 65 may have multiple medical comorbidities and a sedentary activity level, whereas many elderly patients may be reasonably healthy and active, and even athletic, and may warrant consideration as “young” patients. Careful consideration of the patient′s health status and treatment preferences, as well as baseline activity level (for work, recreation, and activities of daily living), are necessary prior to embarking on a course of treatment for the older femoral neck fracture patient.
Implant Selection
Elderly patients with femoral neck fractures require treatment that is based on their bone quality, which is often substantially compromised (with little trabecular bone in the femoral neck). In contrast, young patients most often have normal trabecular bone throughout the femoral head and neck region. The mechanism of injury for younger patients generally involves higher energy than that in the simple fall from a standing position. This high-energy mechanism often results in fracture comminution, which must be dealt with accordingly to avoid shortening of the femoral neck during healing. Also, the orientation of the femoral neck fracture in young patients may be more vertical than that seen with most elderly patients, requiring implants that are better able to resist shear forces during ambulation.
A commonly accepted fixation construct for femoral neck fractures in elderly patients is a three-screw technique. These screws are often partially threaded, to generate compression across the fracture site during implantation. In elderly patients, poor bone quality means that screw-mediated fracture compression may be compromised. Instead, these screws rely on three-point fixation, with a key point of contact being at the inferior aspect of the fracture on a stable medial femoral neck cortex (described below). In younger patients, good bone quality may improve the ability of the screws to generate compression across the femoral neck fracture during implantation. However, inferomedial femoral neck comminution may result in a situation where vertically oriented weight-bearing forces are not supported by an intact medial cortex, leading to further fracture displacement. The vertical nature of many femoral neck fractures in young patients may compound this problem. To address this factor and obtain contact between the fixation screws and the intact inferomedial cortex in a Pauwels type III femoral neck fracture, a highly oblique screw may be needed with a starting point below the level of the lesser trochanter. This is not advised, as screws in that position may pose an increased risk for peri-prosthetic subtrochanteric femur fracture.
Three-screw fixation, however, may be used successfully for young patients with femoral neck fractures with certain configurations. If the orientation of the fracture line is perpendicular to the axis of the femoral neck (i.e., Pauwels type II), then lag screws aligned parallel to this axis will also be perpendicular to the femoral neck fracture line, and they can create good compression across the fracture (Fig. 25.4). Also, unless circumferential fracture comminution has occurred, interdigitation of the fracture line can allow for length-stable compression (preventing coxa breva) and for rotational control of the fracture. If the surgeon is concerned about fracture shortening during the healing process, then compression can be achieved intraoperatively utilizing partially threaded lag screws, and then those screws can either be supplemented or replaced with fully threaded, length-stable screws that can then prevent further collapse and avoid coxa breva.10
Multiple other fixation options exist for femoral neck fractures in young patients. A three-screw technique, with screws parallel to the axis of the femoral neck, may be insufficient to resist shearing of a vertically oriented (Pauwels type III) femoral neck fracture. The screws are generally not perpendicular to the fracture line, and therefore screw-mediated fracture compression is not ideal. In order for the inferiormost screw to contact a stable, intact medial calcar to prevent inferior displacement of the head segment, the screw must start below the level of the lesser trochanter, with concomitant risk of subtrochanteric fracture. Therefore, different fracture fixation constructs are often chosen.
A nonparallel screw technique, with one horizontal screw oriented perpendicular to a vertical (Pauwels type III) fracture line and one or more oriented along the femoral neck axis, has been described (with variable outcomes).11–13 In this case, reduction is first obtained, and then compression across the fracture site is achieved through use of the first (horizontal) screw. A true lag screw can be useful here. Once this screw has been placed, then three further screws are placed for further supplementation of fixation (Fig. 25.5).
Screw-only constructs have been examined and compared with fixed-angle implants. A biomechanical study demonstrated that three screws oriented parallel to the femoral neck axis constitute a construct that is inferior to that of a compression hip screw, a dynamic condylar screw, and a locking proximal femur plate for stabilization of a vertically oriented femoral neck fracture.14 Currently, a large international prospective trial is underway to identify whether a traditional three-screw construct is superior or inferior to a compression hip screw for the treatment of femoral neck fractures,15 as there is controversy over which implant may be better for stabilizing femoral neck fractures.16 Compression hip screws are often used for basicervical femoral neck fractures, as they do not require medial calcar support to resist displacement with weight bearing. They may provide a reasonable option for the treatment of vertically oriented femoral neck fractures. Locking proximal femoral plates were not designed for use in the treatment of femoral neck fractures, even though they appeared biomechanically superior to the other constructs utilized to stabilize a vertically oriented femoral neck fracture.14 A recent report demonstrated catastrophic failure in 36.8% of femoral neck fracture patients treated with a locking proximal femur plate.17
Surviving the Night
For the orthopaedic surgeon on call, the presentation of a young patient with a femoral neck fracture may be a source of consternation. Femoral neck fractures in young patients result from high-energy mechanisms of injury, and therefore other injuries are often present. Dogma also dictates that a femoral neck fracture in a young patient is a surgical emergency,18 and that outcomes are likely to be improved with rapid (i.e., emergent) surgical fracture repair.
A measured approach is appropriate in the young trauma patient with a femoral neck fracture. What is the patient′s overall condition? Are there injuries to the head, spine, chest, abdomen, pelvis, or other extremities? The patient who succumbs to massive thoracic trauma will not be able to express gratitude about the hip that was salvaged by emergency surgery. Sometimes the hip fracture needs to take a back seat to the treatment of other injuries that directly affect the patient′s physiology.
What should be done for the young patient presenting at night with a femoral neck fracture as an isolated injury? The patient will best be served by a perfect reduction with good fixation. A good reduction is associated with improved long-term outcomes after repair of femoral neck fractures.19 Late-night surgery for a femoral neck fracture might not be in a stable patient′s best interest. It is possible that daytime surgery, with rested surgeons, routine orthopaedic surgical teams (including operating room personnel familiar with orthopaedic surgery and fracture care), and normal-hours hospital resources (including fluoroscopy services) may be of benefit in improving outcomes. Slightly lower rates of mild complications (nail removal due to pain) were noted in femoral and tibial shaft fracture patients treated during the day than were noted in those treated at night in one prospective study20; daytime femoral neck fracture repair surgery (more uncommon and, possibly, more complex than tibial or femoral nailing) may have improved outcomes as compared with nighttime surgery. There is some evidence that mortality rates for hip fracture patients are improved when operated on during the day, in a dedicated trauma room, as opposed to at night.21
Principles of Treating Elderly Patients
The bulk of femoral neck fracture patients are elderly. Although the femoral neck fracture is often the proximate cause of the elderly patient′s admission, it is often not the only problem facing the patient. Many elderly hip fracture patients have multiple comorbidities, such as hypertension, diabetes mellitus, dementia, and renal insufficiency. Many of these patients routinely take eight or more medications daily. Some of these medications can cause cognitive impairment or disequilibrium, resulting in an increased risk of falls. Dehydration, with associated orthostatic hypotension, also places the elderly patient at an increased fall risk. Infections (e.g., urinary tract infection, pneumonia) may not present with classic signs of pain, malaise, and fever, but instead as confusion and disorientation, and may also lead to falls. Failure to recognize and address these multiple causes of falls places elderly patients at higher risk of hip fracture.
Historically, the tendency among orthopaedic practitioners treating elderly hip fracture patients was to concentrate on the fracture alone. However, with the multiple comorbidities that are found in most elderly hip fracture patients, the fracture may not represent the patient′s most pressing problem. Stabilization of the fracture, when appropriate, is known to be important for patient mobilization. Prolonged bed confinement is detrimental to outcome. This has been known for many years; substantial evidence exists that mortality rates are increased for elderly hip fracture patients who wait longer than 72 hours,22 48 hours,23 or even 24 hours24 between hospital admission and operative fracture treatment. A recent meta-analysis corroborated these findings.25 This has resulted in a headlong rush to the operating room for fracture treatment in such patients. However, does the surgical delay directly lead to increases in mortality for elderly hip fracture patients? Or is the delay the consequence of the health status of the patient, who must be optimized prior to surgery, with longer optimization required for more unhealthy patients—the ones who, ostensibly, are at higher mortality risk due to their multiple comorbidities?
The importance of teamwork between multiple medical and surgical services in the management of elderly hip fracture patients has become obvious. Four basic models have been described26,27: (1) patients are admitted to the orthopaedic service, and a geriatric medical consultation is only obtained if it is desired by the admitting orthopaedic surgeon28; (2) patients are admitted to the orthopaedic service, and daily geriatric medical consultation is obtained as a standard29,30; (3) patients are admitted to a geriatric medical service, and the orthopaedic service serves as the consulting service31–33; (4) thorough integration of medical and orthopaedic services—a true comanagement model.34–37
Recent attention has focused on the so-called Rochester model of geriatric hip fracture patient care,36 an example of the fourth model described above. Highland Hospital, in Rochester, New York, established a geriatric fracture center in 2004, modeled after the Cleveland Clinic′s Acute Care for the Elderly (ACE) unit.38 The geriatric fracture center functions with the following stipulations: most (if not all) hip fracture patients require surgical fracture treatment; risk of iatrogenic illness (e.g., pneumonia, pressure ulcers, venous thromboembolism) is diminished by rapid surgical treatment and by a true comanagement method (geriatric and orthopaedic service “co-ownership”); protocol standardization reduces the likelihood of missed management steps that could lead to poorer outcomes; and patient discharge planning begins at the time of hospital admission.34 This type of management program has resulted in encouraging patient outcomes, and, despite increased utilization of resources during the inpatient stay, seems to demonstrate lower overall costs associated with the care of elderly hip fracture patients.37
Hemiarthroplasty
Displaced femoral neck fractures in elderly patients are routinely treated with arthroplasty-type procedures instead of fracture fixation. Rates of failure requiring repeat intervention for displaced femoral neck fracture in elderly patients who undergo reduction and fixation have led to the routine use of arthroplasty for such patients as a first-line treatment.39 The putative advantages of arthroplasty include the immediate ability to weight bear without difficulty and the reduced risk of secondary interventions.39 The putative disadvantages of arthroplasty include the lack of durability of implants (i.e., revision may be necessary in the future), the risk of dislocation, the increased risk of infection, and residual hip pain (in the patient treated with hemiarthroplasty). Sometimes it can be difficult to select the best treatment option for the reasonably active, physiologically young but chronologically elderly patient with a displaced femoral neck fracture. If arthroplasty is chosen, then should the arthroplasty be cemented or non-cemented? Should it be a total hip arthroplasty or a hemiarthroplasty? If a hemiarthroplasty is selected, should it be bipolar or unipolar?
Cemented Versus Noncemented Hemiarthroplasty
Hemiarthroplasty of the hip is often considered for the elderly patient with a displaced femoral neck fracture (Fig. 25.6). Early hemiarthroplasty implant designs appeared to be intended for use as simple spacers, with little concern for function. The Austin-Moore prosthesis was an example of a noncemented prosthesis with a non-ingrowth surface. Occasionally, stability would be achieved via bone growth through two large fenestrations in the proximal portion of the prosthesis. However, early stability was minimal, and the prosthesis would often be mobile in the proximal femur, with resultant residual pain with ambulation.40 This seems to obviate the rationale behind its use—an implant that will be durable and enable early patient mobilization.
Cementation of current generation hemiarthroplasty prostheses leads to immediate stability of the prosthesis in the proximal femur. Micromotion between the femur and the prosthesis is essentially nonexistent, and therefore pain with weight bearing is minimized. In a patient who is frail, early postoperative mobilization is essential, and successful prompt weight bearing is more likely if residual pain does not prevent it. Cement techniques for elective hip arthroplasty procedures often entail pressurization of the injected cement. This has been demonstrated to cause embolization of marrow contents, which in this case includes cement polymer and monomer.41 Cement monomer has been implicated in cardiovascular collapse for under-resuscitated patients.42 Although this is not normally a problem for the elective hip arthroplasty patient, who likely has been optimized for surgery in a gradual fashion, it could pose a substantial problem for the ill and frail hip fracture patient. Pressurization beyond thumb packing perhaps should be discouraged for the elderly hip fracture patient undergoing cemented hip hemiarthroplasty. Cementation of femoral hemiarthroplasty components has been associated with transient but significant drops in cardiac output and stroke volume.43 However, recent data have indicated that cardiovascular and respiratory complications are similar following cemented and noncemented hemiarthroplasty,44 and that early mortality is apparently not increased by use of cemented arthroplasty.45
Current designs for noncemented hip hemiarthroplasty prostheses are substantially improved relative to the original Austin-Moore prosthesis. Most of these components are proximally porous coated or fully porous coated, which enables bony ingrowth during the healing phase. The geometries of these components are also more angular than round, enabling some rotational stability during ambulation. Tapered prosthesis designs enable firm seating of the component, which may reduce settling of the component when rising to ambulate from bed or chair (thereby minimizing start-up thigh pain). However, noncemented hemiarthroplasty designs still require bony ingrowth for full stabilization of the prosthesis, which takes weeks to months. Finally, the surgical time for noncemented hemiarthroplasty is shorter than that for cemented hemiarthroplasty. It is up to the surgeon to weigh the risks and benefits of cemented versus noncemented hip hemiarthroplasty designs, and to tailor this to the patient′s needs.
Bipolar Versus Unipolar Hemiarthroplasty
Prosthesis designs for hip hemiarthroplasty include different types of heads—bipolar and unipolar. The unipolar prosthesis design consists of a metallic (usually cobalt chrome) head seated directly onto the prosthesis neck, secured through press-fit of a Morse taper. Bipolar prosthesis designs generally include a small metal head seated onto the prosthetic neck and articulating with a polyethylene-lined metallic head that in turn articulates with the native acetabulum. The bipolar design, therefore, has two mobile surfaces, as compared with the unique surface that articulates with the acetabulum in the unipolar design. Thus, the bipolar prosthesis is theorized to improve hip motion and decrease wear of the native acetabulum. The theory of improved motion has been challenged,46 as has the theory of decreased cartilage wear.47 It is possible that the polyethylene bearing surface decreases load transmission to the native acetabular cartilage, thereby decreasing wear. Bipolar hemiarthroplasty designs may represent increased cost with little demonstrated clinical benefit as compared with unipolar hemiarthroplasty designs.48
Total Hip Arthroplasty
Historically, total hip arthroplasty (THA) as a treatment for femoral neck fractures has been reserved for those elderly patients with displaced fractures who have preexisting arthrosis in the ipsilateral hip. Treating femoral neck fracture patients with THA has a poor reputation, due to a high historical incidence of hip dislocation (as compared with elective THA patients). As femoral neck fracture patients with preexisting hip arthrosis are relatively uncommon, and as historical THA dislocation rates after femoral neck fracture have been relatively high, it has not been a commonly utilized treatment for the elderly femoral neck fracture patient.
More recently, however, THA has experienced resurgence as a treatment of choice for subsets of patients with femoral neck fractures (Fig. 25.7). Wear of acetabular cartilage after hip hemiarthroplasty is a real phenomenon,49–51 and may be associated with low but perceptible levels of groin pain at best and substantially disabling pain at worst. Also, patient longevity is increasing, and elderly patients are now remaining highly active later in life as compared with elderly patients of a few decades ago. What should a surgeon do with the 55-year-old active patient, otherwise healthy, with a displaced and unreconstructable femoral neck fracture? Life expectancy in the United States is 78.7 years.52 Our 55-year-old patient can be expected, therefore, to live 20+ more years after the femoral neck fracture. For such a patient who is interested in maintaining a high activity level, is hip hemiarthroplasty the best treatment option?
Total hip arthroplasty has many potential advantages over hip hemiarthroplasty. It eliminates the risk of pain associated with articulation of the metal prosthesis with the native acetabulum. Also, acetabular chondral wear is eliminated if THA is performed. However, dislocation rates remain higher than seen with elective THA performed for primary hip arthrosis, even when performed by experienced surgeons (up to 3% for primary THA53–56 versus 9% for THA after femoral neck fracture57). There are many theories about why this may be the case. Earlier THA designs utilized small prosthetic heads (e.g., 22 mm), which increased the risk of dislocation while decreasing the rate of volumetric polyethylene wear. Also, the hip arthrosis patient generally has a stiff capsule and a tight peri-hip musculature. All these factors may serve to minimize motion of the hip both before and after arthroplasty. This may not be the case for the femoral neck fracture patient without preexisting arthrosis; the peri-hip tissues may be looser, and the expectation of the patient may be for immediately normal hip motion, all of which may lead to an increased risk of dislocation.
With the knowledge that hip dislocation rates after THA for femoral neck fracture treatment are higher than those for treatment of primary hip arthrosis, it is incumbent upon the surgeon to take steps to minimize that risk. Current-generation polyethylene liners and other, nonpolyethylene, bearing surfaces (ceramic and metal) have reduced concerns over volumetric wear of THA components. Larger prosthetic femoral head sizes are now available (I routinely use 36-mm heads), which may reduce the dislocation risk, although this has not been proven for femoral neck fracture treatment with THA. Careful attention to acetabular component position and to tensioning of peri-hip musculature is vital. Surgical approaches historically associated with lower rates of dislocation, such as the anterolateral (Watson-Jones) approach, may be helpful for minimizing risk of dislocation. The direct anterior (Heuter) approach, which involves preservation of all muscle attachments to the proximal femur during hip arthroplasty, may be of substantial benefit in reducing postoperative dislocation risk.
Surgical Anatomy
Osseous Anatomy
The femoral neck subtends a 131-degree angle with the shaft of the femur, and is anteverted ~ 10 degrees. The greater and lesser trochanters are relatively posterior structures. Reproducing normal osseous anatomy when treating femoral neck fractures is important for fracture stability (with fixation), for hip stability (with arthroplasty), and for normal muscle balancing around the hip, and important for reestablishing normal gait. When it is unclear if the patient has the appropriate femoral neck anatomy, contralateral hip radiographs or an anteroposterior radiograph of the pelvis may be beneficial for comparison. The profiles of both (bilateral) lesser trochanters can be compared. If the profile of the sidebeing replaced matches the opposite side profile, then the correct femoral rotation has been achieved. Careful attention to rotation of the leg and flexion of the hip is important when attempting to compare profiles of the lesser trochanters.
Vascular Anatomy
The main blood supply to the femoral head is the ascending branch of the medial femoral circumflex artery.58 This vessel passes posterior to the obturator externus muscle, and anterior to the obturator internus and piriformis muscles, and then closely apposes itself to the posterior femoral neck as it sends an arborization of perforating vessels into the hip capsule. Lesser contributions of blood supply to the femoral head include the inferior metaphyseal branch of the lateral femoral circumflex artery and the artery of the ligamentum teres. Alone, these minor contributors to femoral head blood supply (artery of ligamentum teres to perifoveal head, inferior metaphyseal artery to inferior femoral head) are insufficient to maintain femoral head viability in the setting of a disrupted medial femoral circumflex artery. Small anastomoses, which may be important for reestablishing a blood supply to the femoral head in the setting of a femoral neck fracture,59 exist between the medial femoral circumflex artery and the artery of the ligamentum teres.
Tips and Tricks
During open reduction of femoral neck fractures, avoid retractor placement over the posterosuperior femoral neck, as this could further compromise femoral head blood supply.
The main contributor to blood supply of the femoral head, the medial femoral circumflex artery, is at risk during posterior approaches to the hip joint, such as the Kocher-Langenbeck approach to a posterior wall acetabular fracture. It is recommended that tenotomies of the piriformis and conjoint tendons, when required, be performed ~ 15 mm from their insertions on the proximal femur to protect the femoral head blood supply.58 Also, during exposure of the anterior aspect of the hip joint, the surgeon should be cognizant of the location of the terminal branches (retinacular vessels) of the medial femoral circumflex artery, which are on the posterosuperior femoral neck. Retractor placement over the superior aspect of the femoral neck should therefore be avoided.
The blood supply to the femoral head may be interrupted without frank disruption of the blood vessels, either by kinking due to fracture deformity or by increased intracapsular pressure. Theoretically, rapid reduction of hip dislocations and femoral neck fractures can reduce the period of time that kinked vessels remain occluded, and therefore may reduce the risk of osteonecrosis after isolated hip dislocation60 or femoral neck fracture.19 After fracture treatment, the role of capsular decompression is uncertain. Risk of osteonecrosis after femoral neck fracture has been demonstrated to be higher when intracapsular pressure at the injured hip is ≥ 30 mmHg higher than the contralateral side.61 The clinical efficacy of capsular decompression in preventing osteonecrosis of the femoral head after treatment of femoral neck fractures is uncertain, but it may be beneficial.62 Most orthopaedic surgeons do not routinely perform capsulotomy when treating femoral neck fractures.63 When utilized, capsulotomy is generally performed anteriorly (to avoid the posterior vessels), either with a knife or a soft tissue elevator and under fluoroscopic guidance (Fig. 25.8). Anecdotal reports of a rush of blood being seen during capsulotomy are not universal, and it is difficult to judge if a percutaneous capsulotomy is successful. However, a recent cadaveric study demonstrated successful capsular decompression with percutaneous knife techniques in 20 of 20 attempts.64
Tips and Tricks
Capsulotomy performed after percutaneous fixation of minimally displaced proximal humerus fractures may be of benefit. Capsulotomy is performed anteriorly, by passing a knife or elevator along the anterior femoral neck under fluoroscopy. To prevent dissociation of the scalpel blade from the handle, an adherent circumferential wrap around the blade–handle junction may be helpful.
Surgical Approaches
Watson-Jones
Video 25.1 Watson–Jones Approach for ORIF of a Femoral Neck Fracture
The Watson-Jones approach provides exposure of the hip joint from an anterolateral perspective. One incision is generally used. The patient is placed in the supine position with a bump beneath the ipsilateral flank. If the patient is placed on a radiolucent table, then the entire ipsilateral lower extremity is prepped and draped to the level of the costal margin. If the patient is placed onto a fracture table, then the foot is not prepped if it remains within the boot attachment. Skeletal traction may be desirable, and a traction pin may be placed through the ipsilateral distal femur, proximal tibia, or calcaneus. A disadvantage of free-leg preparation on a radiolucent table is an inability to perform static traction without an invasive maneuver (i.e., a traction pin), whereas the potential disadvantages of fracture table use are the inability to remove the leg from the boot intraoperatively (the foot and ankle are not sterile) for manipulation of the leg, and difficulty countering posterior sag that may occur at the fracture site without open reduction.
An incision is made in line from the iliac crest, halfway between the anterior superior iliac spine and the gluteus medius pillar, toward the tip of the greater trochanter, and then curving gently such that it proceeds distally along the midaxial proximal lateral thigh in line with the proximal femoral shaft (Fig. 25.9). The incision is performed through skin and soft tissues down to the fascia overlying the interval between the tensor fascia lata anteriorly and the gluteus medius posteriorly. The fascia is incised and the interval is developed. The proximal aspect of the vastus lateralis is elevated off the anterior aspect of the hip capsule. The hip capsule is identified and a capsulotomy is performed, generally in an inverted T-shaped fashion, with the horizontal portion of the T perpendicular to the femoral neck and located at the base of the neck. The T proximally extends to the location of the labrum; care is exercised to avoid labral injury. Retraction of soft tissues is often aided by placement of a Hohmann retractor on the anterior wall of the acetabulum. This surgical approach seems to offer better visualization of the base of the femoral neck than it does of the subcapital region.
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