Hip Fractures
Although the hip joint comprises the acetabulum, the femoral head, the femoral neck, the greater and lesser trochanters, and the proximal femoral shaft, the term "hip fracture" typically connotes an injury to the femoral neck or the region between the greater and lesser trochanters, so-called inter-trochanteric fractures.
Hip fractures may be seen in younger patients with high energy mechanisms of injury (a motor vehicle collision, for instance), but most cases are seen in older patients after a low energy mechanism of injury such as a fall from a standing height. Many of these fractures are associated with osteoporosis, other medical conditions that cause falls, and generalized frailty. These fractures impose great burdens on patients, their families and society.
Consistent with the old saying, “we come into the world under the brim of the pelvis and go out through the neck of the femur,” hip fractures are indeed associated with a high mortality risk. About one third of elderly patients with a low energy hip fracture are apt to die within a year of the injury. Hip fractures from falls are a marker for senescence and decline, though the added biological stress of the fracture and its treatment no doubt contributes to this mortality risk. On the other hand, many hip fracture patients have excellent rehabilitation potential and must be astutely assessed and adeptly managed to optimize post-injury function.
Structure and Function
The proximal femur comprises the femoral head, the femoral neck, the greater and lesser trochanters, and the proximal femoral shaft (Figure 1).
The hip capsule attaches at the base of the femoral neck. The femoral head and neck are thus designated “intracapsular” and the remainder of the proximal femur defined as “extracapsular.”
Intracapsular femoral neck fractures (Figure 2) can be further classified by their specific location in the neck: subcapital (under the head), transcervical (across the neck), and basi-cervical (base of neck).
Extracapsular fractures (Figure 3) occur in the area between and within the greater and lesser trochanters and are called “intertrochanteric” fractures. Fractures that occur in the proximal femur just distal to the lesser trochanter are called “subtrochanteric” fractures.
The blood supply to the hip varies by region, and thus the region in which a fracture occurs strongly influences the fracture’s healing potential and appropriate treatment.
The blood supply to the proximal femur is primarily from the medial and lateral femoral circumflex arteries. Together, they form an extracapsular vascular ring at the base of the femoral neck. Ascending cervical arteries branch off this ring and run parallel to the femoral neck to feed the femoral head, see Figure 4.
Healing of femoral neck fractures can be compromised by the lack of blood supply. Moreover, disruption of the blood supply running along the neck can deprive the femoral head of necessary perfusion. Thus, avascular necrosis (osteonecrosis) of the femoral head can result even if the neck fracture itself heals.
By contrast to the femoral neck, the intertrochanteric region of the femur is well-lined with periosteum and has relatively dense cancellous bone and robust blood supply. All of these features enhance fracture healing potential. When an intertrochanteric fracture is restored to normal alignment (“reduced anatomically”) and held in place with a suitable fixation device, the fracture usually unites uneventfully.
Hip fractures can be displaced by gravity and the pull of various muscles attached to the fracture fragments. For instance, the gluteus medius and minimus can abduct the greater trochanter. The piriformis, superior and inferior gemelli, obturator internus, and quadratus femoris (the so-called short external rotators) can externally rotate the proximal fragment. Lastly, the iliopsoas, which inserts on the lesser trochanter, can flex the proximal fragment of a subtrochanteric fracture.
Patient Presentation
Both young and old people with a hip fracture usually present with groin pain and, in the case of displacement, a shortened and externally-rotated leg.
The most commonly encountered scenario is an older patient presenting after a low-energy trauma, such as a simple fall from standing height. In some cases, the “trauma” may be nothing more than simply twisting while lying in bed or standing erect. Here, the fracture is heralded by severe, persistent groin pain.
Less commonly, younger patients will present with an acute hip fracture after a high-energy trauma such as a motor vehicle collision. They typically will be unable to bear weight and report severe hip or groin pain.
Needless to say, care of the patient must be directed to the whole patient, and not just the bony injury. In the case of high energy trauma in young people, a full trauma evaluation and resuscitation is indicated. In the case of an elderly person, the cause of the fall must be discovered. Was there a stroke or heart attack? Recall that if there were a brief moment of unconsciousness, patients might not remember how or why they collapsed. (In the absence of a good description of the actual fall from the patient directly, assume until proven otherwise that a medical event precipitated the injury.) Next, the patient must be examined closely for other, perhaps less painful or obvious injuries. Last, especially in the case of a patient who fell and could not get up for a prolonged period, hypothermia and dehydration may be present and must be treated.
Objective Evidence
Obtaining a complete history and performing a thorough examination looking for bruising, deformity (e.g., shortened and externally rotated), tenderness, and motion at the fracture site is key. Initial imaging for suspected hip fractures should include x-rays of an AP pelvis and AP and lateral views of the affected hip.
Minimally-displaced or non-displaced hip fractures may present with subtle disruption of the trabecular lines. In some cases, there will be no discernible x-ray findings. A fracture in that case is termed “occult” – present, but not seen on radiographs. The only clue to the presence of an occult hip fracture is pain and an unwillingness/inability to bear weight. The presence of an occult hip fracture can be suggested by a positive response on the log-roll test, where the affected leg is internally and externally rotation to isolate the source of pain as originating from the hip joint (Figure 5). This maneuver is done gently, to avoid displacement of a non-displaced fracture.
If an occult hip fracture is suspected, an MRI of the hip should be obtained. In settings where MRI is contraindicated or not readily available, a CT scan or bone scan could be utilized. CT is very sensitive for demonstrating breaches in bone continuity but is associated with high radiation exposure. Bone scans typically use technetium labeled diphosphonate, a molecule that attaches to the hydroxyapatite matrix deposited at the site of bone formation. Because the bone scan assesses a metabolic response (and not static anatomy), positive findings may not be apparent for up to 72 hours after the administration of the labelling compound.
The hip radiographs should be closely examined for absence of the normal bone trabeculae. These trabeculae are lines that form in response to either compressive and tensile forces (Figure 6). The Singh index is a radiographic metric based on the progressive loss of trabeculae. The Singh index can be used to determine cancellous bone density, specifically for assessing whether the bone will be sufficiently dense to support screws or other fixation devices within the femoral neck without coming loose. The Singh Index is particularly useful in pre-injury assessment of femoral bone quality as well.
While there is no laboratory test that can detect a hip fracture, once a hip fracture is diagnosed, pre-operative blood tests and all other pre-operative tests (e.g. EKG and CXR) should be performed expeditiously. A delay to surgery and unnecessary immobilization must be avoided because a delay of more than 48 hours likely imposes additional mortality risk. Patients should not undergo extensive “pre-operative clearance” testing, especially if the test results will not affect the immediate treatment plan.
Blood tests to assess for malnutrition and treatable causes of metabolic bone disease should be obtained in all elderly patients and in young patients with stress fractures. These tests include serum calcium and 25(OH)D, magnesium, phosphate, creatinine and electrolytes, albumin, alkaline phosphate (ALP), in addition to vitamin B12, thiamine, calcitonin, testosterone and parathyroid hormone (PTH) as indicated.
Further investigations to prevent complications and additional future fractures should be conducted as indicated (see “APGAR SCORE” below), but not at the expense of treatment delay.
Epidemiology
In the United States, there are approximately 250,000 hip fractures seen each year. The global incidence of hip fractures varies widely by country, ranging from nearly 600 per 100,000 person-years in Scandinavian countries to fewer than 75 in countries such as Tunisia and Ecuador. This variation likely reflects genetics, but also proximity to the equator, as sunlight exposure and vitamin D levels are protective.
Although age-standardised rates may have stabilised and possibly started to fall in some regions since the year 2000, the overall numbers continue to rise, owing to population growth among the aged. This effect is expected to be greatest in Asia, where the aged population effect will peak latest.
Differential Diagnosis
In the setting of high-energy trauma, a patient presenting with groin pain could have a pelvic fracture or a hip dislocation. These diagnoses can be excluded by either an AP pelvis radiograph or a CT scan of the pelvis.
The differential diagnosis of gradual, atraumatic hip pain includes labral tears, osteoarthritis, inflammatory arthritis, avascular necrosis, septic arthritis, trochanteric bursitis, tendinopathy, primary or metastatic bone tumors, hernia, genitourinary causes, vascular claudication, or lumbar radiculopathy. While even this partial differential diagnosis is extensive, a thorough history and physical exam coupled with screening radiographs of the hip and pelvis will often quickly narrow it to a more manageable list.
Red Flags
Unstable Vital Signs
It is unusual for an isolated hip fracture, even in the setting of a high-energy trauma, to produce hemodynamic instability. If a patient presents with marked hypotension, an immediate evaluation for other sources of blood loss with chest, pelvis, and/or femur radiographs is called for. An elderly patient with a hip fracture who was alone on the floor for a prolonged period may be dehydrated or hypothermic. In addition, a myocardial infarction or stroke may have precipitated the fall. These conditions, too, may present with unstable vital signs or altered mental status.
Cancer
If a patient with a history of cancer reports antecedent pelvic, groin, or thigh pain, or presents with an isolated lesser trochanteric fracture, an oncologic work-up should be considered. This oncological assessment is one of the very few situations for which a delay to surgery might be warranted. (The management of metastatic disease is discussed in, Metastatic Bone Disease and Pathological Fractures)
Abuse
The possible diagnosis of elder abuse is suggested by a delayed presentation for treatment, a mechanism of injury reported by a caregiver that is implausible or inconsistent, or objective signs of neglect or abuse outside the hip injury itself.
Treatment Options and Outcomes
Perioperative Management
Hip fractures are nearly always managed operatively. Ideally, a patient is taken to surgery within 24-48 hours after injury, as bed rest and immobilization can be lethal. Common clinical care pathways for the management of fragility hip fractures will include monitoring vital signs; obtaining an EKG and chest radiograph; establishing IV access and giving fluid resuscitation; collecting pre-operative testing samples; assessing nutrition, pain, bowel and bladder issues; and examining and protecting the skin.
While awaiting surgery, patients should be in bed with appropriate cushioning and padding to ensure comfort and protection from pressure injuries. The heels, sacrum and (both) hips are particularly vulnerable areas. Pre-operative traction is generally not recommended.
At some centers, femoral nerve blocks are given on presentation. These blocks can markedly reduce the need for opiate pain medications and reduces the risk of delirium and respiratory complications in the elderly.
Surgical Options
Femoral Neck Fractures
For femoral neck fractures that are not displaced (or only minimally displaced and stable), treatment with fixation offers a high chance of success. Displaced fractures, however, are at a high risk of non-union, malunion and osteonecrosis. Because of the potentially poor functional outcomes with attempted fixation, displaced femoral neck fractures, especially in older patients, are treated with joint replacement (arthroplasty).
One of the most commonly used devices for fixing non-displaced femoral neck fractures is a series of parallel screws or pins (Figure 7). These screws are designed to be firmly fixed in the head but are able to slide. This sliding allows the fracture fragments to compress with weight bearing. Surgical fixation does not always lead to appropriate fracture healing. This poor outcome may be caused the severity of the patient’s injury. Alternatively, non-union or mal-union may also be caused by a failure to adequately address fracture displacement, instability or poor bone quality at the time of surgery. In recent years, there has been a trend away from fixing femoral neck fractures when any of these parameters are questionable. (Notably, in younger patients, it may be reasonable to err on the side of attempted fixation even if healing is not assured. These patients stand to gain more if surgery is successful and can better tolerate a second operation if it is not.)
Options for arthroplasty include either a partial hip replacement, known as a “hemiarthroplasty” or total hip replacement (see Figure 8). In both operations, the femoral head is removed, the edges of the neck fracture are smoothed, and a metallic stem is inserted into the femur which holds a prosthetic femoral head. For hemiarthroplasty, the head inserted is the same size as the one removed, and is left to articulate with the pelvis directly. With a total hip replacement, cartilage is removed from the acetabulum, and a prosthetic cup is inserted. This cup then articulates with the (smaller) head on the femoral stem.
Because hemiarthroplasty is only a partial joint replacement, the operation is less expensive than a total hip arthroplasty, and is faster and easier to perform. Because a large head is used, the joint is also more stable. On the other hand, because a total hip replacement replaces both sides of the hip joint, it tends to last longer and is associated with less activity-related hip pain. With those considerations in mind, the choice between the two should be based on life expectancy and functional demands. That is, a total hip arthroplasty should be reserved for a patient apt to live long enough and be active enough to reap the specific benefits of the procedure.
The presence of an artificial metal head articulating with native hyaline cartilage is well-tolerated if the cartilage is in good condition. If there is cartilage damage, motion of the head will further damage the cartilage and produce accelerated arthritis and pain. It is therefore critical to assess for any evidence of pre-existing arthritis on the preoperative imaging or in the patient’s medical history. The more arthritis that is present, the lower the threshold for employing total hip arthroplasty should be. Note also that because many patients present with dehydration and hypothermia (among other metabolic derangements), it is easy to over estimate patients’ frailty and in turn ascribe a shorter life expectancy and functionality to them. Prognosis and likely functional demands should be assessed critically.
Extracapsular Fractures
Patients with extracapsular (intertrochanteric) fractures can be treated with either dynamic hip screws (Figure 9), proximal femur plates and screws, or intramedullary nails. The choice will depend on the fracture morphology, the cost and availability of implants, and the surgeon’s expertise and preference. In almost all instances, extracapsular hip fractures will unite, with the final outcome dictated not by the status of the bone, but the patient’s overall response to the injury, treatment and rehabilitation.
Non Operative Care
In circumstances where a patient has multiple life-threatening co-morbidities or very low functional demands (e.g., was not able to walk before fracture either), operative intervention may only hasten the patient’s demise and fail to offer benefits that offset the necessary biological and financial costs. Palliative care and pain management should be considered for patients with limited life expectancy and low functional expectations, after appropriate discussions with the patient or designated decision maker.
Complications
Geriatric hip fractures can be devastating injuries. The 1-year mortality rate among patients 65 and older is approximately 20%-30%, with higher rates seen among the especially old or the especially frail. Even a previously well and independent women with an otherwise normal life expectancy faces a 10-15% 1-year mortality risk attributable to the fracture.
Of those who survive the first 12 months, fewer than half recover to their preinjury level of independence.
Beyond the usual medical and anaesthetic related conditions, early surgical complications specific to the fracture care include nerve or vascular injury, implant fracture, and loss of reduction or fixation.
In the fixation group, longer term complications include non-union of the fracture, infection, hardware failure, and avascular necrosis (AVN) of the femoral head. (AVN is usually manifested within 2 years, but may appear as late as 4 years, after surgery.)
Possible late complications of arthroplasty include dislocation of the prosthesis, loosening of the prosthetic components (from infection or simple wear and tear) and periprosthetic fractures. These usually lead to revision arthroplasty if the patient is fit enough.
Risk Factors and Prevention
Common risk factors for hip fractures in the geriatric population include osteoporosis, frailty and sarcopenia, prior fragility fractures, and medical conditions associated with an elevated risk for falling, such as neurologic disease, use of sedating medications and visual impairment.
There are several useful fracture risk assessment tools such as the “FRAX” risk calculator (available at https://www.sheffield.ac.uk/FRAX/tool.aspx), that utilize patient-specific factors such as age, weight, sex, smoking history, alcohol use and fracture history to help predict fracture risk.
While bisphosphonates decrease the risk of hip fracture among patients with osteoporosis, these drugs do not appear to prevent fracture in those with normal bone mineral density.
Environmental risks should also be considered: frayed carpet rugs, slippery floors, and poor lighting can increase the risk of falls. Reducing the risk of falls and the fragility fractures they cause requires medical, physical, and environmental optimization with coordination across all care providers. Educational programs for the public addressing fall prevention might also reduce hip fracture risk.
One of the most predictive factors for a future fragility fracture is a prior fragility fracture. Many older hip fracture patients will have previously suffered a prior fragility fracture of the wrist, thoracic spine or proximal humerus. As such, a low energy wrist fracture or spinal compression fracture should be a red flag, prompting vigorous intervention to prevent a future (and more lethal) hip fracture. Indeed, intervention is indicated even after a hip fracture – to prevent a second one.
Miscellany
Other Hip Fractures
The discussion above centered on the typical, low-energy geriatric hip fractures. There are other hip fractures of note, beyond the scope of this chapter:
- Patients who are taking bisphosphonates for osteoporosis can suffer an “atypical femoral fracture” in the subtrochanteric region or more distally in the femoral shaft. This fracture starts as an incomplete break on the lateral cortex and propagates medially. The majority of patients report a history of pain in the thigh or groin region in the weeks of months prior to the fracture which may occur simply while they are walking and in the absence of any overt trauma, though the pain from this event may cause patients to lose their balance and fall.
- A stress fracture of the superior femoral neck can, if not treated, propagate across the neck. This propagation can produce an overtly displaced fracture (see https://orthopaedia.com/page/Stress-Fractures-Female-Athletic-Triad).
- Isolated fracture of the greater or lesser trochanter are rare injuries, likely caused by muscular avulsion. Fracture of the lesser trochanter may be caused by avulsion force of the iliopsoas muscle; fracture of the greater trochanter may be caused by the pull of the gluteus medius and gluteus minimus muscles. Isolated trochanter fractures are usually treated non-operatively.
Medical Care Beyond Urgent Fracture Treatment
For geriatric patients with hip fractures, the bony injury is only part of the burden of diagnosis. Indeed, it may be more helpful to consider the patient suffering from “geriatric hip fracture syndrome” or a “hip attack,” as there are many associated medical, social, psychological and other problems to which attention must be paid. Echoing the aphorism cited above, that “we come into the world under the brim of the pelvis and go out through the neck of the femur” an “APGAR SCORE” checklist has been proposed to remind providers of other steps besides direct fracture care that should be undertaken for all patients with geriatric hip fracture.
- Alimentation & Nutrition — Assess albumin, vitamin D, and calcium, and consult a nutritionist. Patients with dysphagia should also have a speech and swallow assessment.
- Polypharmacy — Make sure that only necessary medications are being taken.
- Gait — Screen patients with the Get Up and Go test postoperatively and prescribe physical therapy to enhance and maintain function.
- Advance Care Planning — Clarify and document the patient's preferences and goals. Geriatric hip fracture may herald the beginning of the end of life.
- Reversible Cognitive Impairment — Prevent delirium by providing hearing and visual aids if needed, promote sleep hygiene, provide good pain control, and reduce polypharmacy and risk factors for infection.
- Social Support — Screen for depression and optimize social support systems.
- Cataracts and Other Visual Impairments — Refer patients for a thorough ophthalmological consultation: the rate of hip fracture in those who are visually impaired can be 3x higher compared to people who can see well.
- Osteoporosis — "Own the bone" by providing bone mineral density testing and treatment of osteoporosis if found.
- Referrals — Communicate with a hip fracture patient's primary care physician to provide post- operative care; send the patient to an expert for osteoporosis treatment if need.
- Environmental Safety — Recommend a social worker's evaluation for home-hazard interventions. A house can be "elder-proofed" by removing frayed floor rugs that invite a fall, among others.
References
Part or all of this article or section is derived from Hip Fractures by Orthopaedia.com, used under CC-BY-NC-SA
