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A 74-year-old man presents for total hip arthroplasty (THA). His past medical history is significant for hypertension, dyslipidemia, and osteoarthritis restricting ambulation.
Objectives
1. Review the common surgical approaches to THA and associated positioning.
2. Contrast general vs. neuraxial anesthesia and postoperative outcomes.
3. Discuss the common intraoperative complications associated with THA.
4. Describe postoperative analgesia options with risk and benefits.
1. Review the common surgical approaches to THA and associated positioning
There are several commonly utilized surgical approaches to THA – although little consensus on the optimal approach exists. Each has been extensively documented with purported differences in recovery speed, postoperative cosmetic appearance, and long-term functional outcome; despite this, there is little data to support the superiority of one approach over another [1]. The method chosen is largely secondary to the training and experience of the surgeon but most are performed using the anterolateral and posterolateral approaches [2].
The choice of surgical approach will determine the patient’s position, either supine (anterior, anterolateral, or lateral/transgluteal approach) or lateral decubitus (lateral transtrochanteric, or posterior approach). In the lateral decubitus position, anesthesiologists must remain vigilant of pressure points (e.g., axillary roll to prevent neurovascular compromise) and maintain a neutral cervical spine orientation. In cases where neuraxial anesthesia is utilized, emergent airway management can be required intraoperatively.
2. Contrast general vs. neuraxial anesthesia and postoperative outcomes
By 2030, it is estimated that there will be greater than 500,000 THAs performed annually in the United States [3]. The utilization rates of neuraxial (NA), combined NA–general, and general anesthesia (GA) based on a representative sample of lower extremity arthroplasty in the United States are detailed in Table 18.1 [4].
| Anesthetic modality | Utilization ratea |
|---|---|
| Neuraxial (spinal or epidural) | 11.1% |
| Neuraxial + general | 14.2% |
| General | 74.8% |
a 382,286 cases from 2006 to 2010.
Many large studies have attempted to determine the effects, if any, of the anesthetic modality on perioperative THA morbidity, mortality, and outcomes. Two systematic reviews have evaluated anesthetic modality and secondary benefits for THA procedures. In a Cochrane review of 2,567 patients undergoing hip fracture repair, Parker et al. found no difference between GA and NA effects on morbidity and mortality [5]. However, they did determine that NA reduces the incidence of postoperative delirium. Macfarlane et al. reviewed 1,239 patients and were also unable to find a difference in morbidity and mortality with respect to the anesthetic modality [6]. Given the low event rate, negative results could be interpreted two ways: (1) there may be no benefit or (2) the sample size is underpowered to observe an effect. Recently, a large, retrospective database review of several hundred thousand patients suggested there was a significant association between anesthetic modality for THA and postoperative morbidity and mortality [7]. This data concluded that NA confers significant advantages over GA with respect to morbidity and intensive care utilization,although there were no effects on 30-day mortality (Table 18.2) [4, 7]. Other reported benefits of NA over GA include improved postoperative analgesia, reduced blood loss, decreased discharge time from the PACU, and faster mobilization [8–9].
| Outcome | Odds ratio (GA:NA) | p-value |
|---|---|---|
| Intensive care unit admission | 1.82 | <0.001 |
| Mechanical ventilation | 1.57 | 0.0085 |
| Blood transfusion | 1.14 | <0.0001 |
| Pulmonary compromise | 3.34 | 0.0105 |
| Pneumonia | 1.51 | 0.0029 |
| Infection | 1.45 | <0.001 |
| Acute renal failure | 1.83 | 0.0014 |
| Cerebrovascular event | 3.15 | 0.0271 |
| Cardiac complications (excluding MI) | 1.13 | 0.0171 |
528,495 cases from 2006 to 2010.
Despite the described benefits, NA is not without risk; the most catastrophic outcome, although extremely rare, being spinal hematoma. A large case series of 37,171 patients undergoing lower extremity orthopedic surgery under spinal anesthesia produced no cases of spinal hematoma [10]. Among 62,856 patients undergoing combined spinal–epidural (CSE), there were four confirmed cases of spinal hematoma, each associated with postoperative epidural removal and DVT prophylaxis [10]. Although the risk of spinal hematoma may never be zero, it may be minimized by adhering to guidelines regarding neuraxial procedures in patients receiving antithrombotic or antiplatelet therapy [11], avoiding procedures in patients with coagulopathy, and avoiding multiple attempts.
The totality of published evidence suggests that NA is superior to GA for THA for postoperative morbidity, but there is no long-term outcome difference in mortality.
3. Discuss the common intraoperative complications associated with THA
While a common and safe surgical procedure, THA is associated with several significant perioperative complications. The most common or most severe complications include venous thromboembolism (VTE), bone cement implantation syndrome (BCIS), peri-prosthetic fracture, nerve injury, and vascular injury.
Venous thromboembolism
Venous thromboembolism formation begins intraoperatively but most commonly presents in the postoperative period. For patients not receiving prophylaxis, the contemporary estimate of symptomatic VTE after THA is 4.3% [12]. Pharmacologic prophylaxis reduces this risk by approximately 50% [12]. Compared with low-molecular weight heparin (LMWH) the new oral anticoagulants, dabigatran, apixaban, rivaroxaban, are no more effective at reducing the incidence of VTE but carry a higher incidence of bleeding [13]. Pneumatic sequential compression devices can also be utilized for preventing DVT [14]. While superior to low-dose warfarin, their efficacy in the presence of either LMWH or anti-Xa inhibitors has not been established and LMWH remains the gold standard for DVT prophylaxis [12]. The use of NA has also been found to decrease the incidence of postoperative fatal pulmonary embolism (PE) from 0.12 to 0.02% [15]. Practitioners must be aware of the plan for postoperative VTE prophylaxis in patients receiving NA, review anticoagulation guidelines with respect to NA, and develop a plan prior to prophylaxis initiation.
Bone cement implantation syndrome
Bone cement implantation syndrome is characterized by hypotension, hypoxia, increased pulmonary vascular resistance, arrhythmia, and, in its most severe form, complete cardiovascular collapse. Risk factors for BCIS include increasing age, poor cardiovascular reserve, pre-existing pulmonary hypertension, and use of a long-stem femoral prosthesis. Bone cement implantation syndrome, manifesting as cardiovascular collapse or death, is estimated to occur in 0.02 to 0.12% of cases; however, less severe symptoms, hypotension and transient desaturation, may be as high as 2% and 17% respectively [16]. The incidence of subclinical BCIS is likely higher.
The pathophysiology of BCIS is not completely defined. It occurs after pressurization of the femoral canal with the prosthesis or reduction of the prosthetic hip. Pressurization pushes air, bone marrow, and cement monomers into the circulatory system. Proposed theories include vasodilation secondary to cement monomers, histamine release, and complement activation. The prevailing theory, however, is the embolic model, which induces both mechanical and vasoactive mediator release, resulting in the hemodynamic and hypoxic changes.
Notably, cemented procedures account for approximately 70% of all THAs performed because of longer term durability of cemented prostheses. Using short-stem prostheses, creating a vent hole in the distal femur, meticulous irrigation and drying of the insertion site, and minimization of inhalational anesthetics can potentially reduce BCIS. Management includes increasing inspired oxygen concentration, optimizing fluid resuscitation, and the judicious use of vasopressors or inotropic agents.
Peri-prosthetic fracture
Intraoperative peri-prosthetic fracture is rare (<2%), occurring most often in the femoral portion of the arthroplasty [17–18]. Identified risk factors include advanced age (>80 years), female gender, revision surgery, osteoporosis, rheumatoid arthritis, and uncemented prostheses [17–18]. An intraoperative fracture predicts greater morbidity and mortality up to one year after surgery and likely reflects the underlying comorbidities contributing to the increased risk of fracture.
The primary concerns for the anesthesiologist when a peri-prosthetic fracture occurs include the possibility of increased blood loss or the increased chance for BCIS. The limited anesthetic duration of subarachnoid block may be an issue due to the additional surgical time required to repair the inadvertent fracture.
Nerve injury
Nerve injury in the operative limb can occur secondary to compression from retractors, direct laceration from instruments, traction, ischemia, or thermal injury from extruded cement. Multiple nerves can be injured including the femoral, lateral femoral cutaneous (LFCN), sciatic, obturator, or superior gluteal nerves.
The estimated incidence of nerve injury is widely variable. In primary THA, the reported estimates range from 0.09 to 3.7% with a recent retrospective review of nearly 13,000 patients reporting 0.72% [19]. However, in patients undergoing THA via the anterior approach, LFCN palsy has been reported to be 15% [20]. Additionally, the subclinical nerve palsy rate is unknown. Identified risk factors include female gender, revision surgery, and leg lengthening of greater than 4 cm [21]. Neuraxial anesthesia is not a risk factor for postoperative nerve injury after THA [19].
Vascular injury
Vascular injury resulting in hemorrhage is potentially severe though relatively uncommon (<0.2%) [17]. The mechanism is similar to that of nerve injury with inadvertent puncture/avulsion from surgical instruments. Vessels most at risk include the external iliac, femoral, obturator, and superior gluteal vessels. The specific vessel injured is related to the surgical approach and the proximity of the vessel.
4. Describe the postoperative analgesia options with risk and benefits
Effective postoperative analgesia facilitates rehabilitation and more rapid discharge. Improved analgesia may improve long-term functional outcome and reduce the incidence of chronic pain; although further study is needed. The majority of patients are well managed with multimodal analgesia. This may include intrathecal opiates, intravenous or oral opioids, and opioid-sparing adjuncts. Where not medically contraindicated, both acetaminophen and non-steroidal anti-inflammatories (NSAIDs) should be utilized. Challenges can be encountered with patients undergoing revision surgery or opioid-tolerant patients (Table 18.3).
Multimodal analgesic options.
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