Etiologies
While there are numerous etiologies of lower back pain, the vast majority will have a nonspecific etiology. Many patients presenting with nonspecific pain may have musculoskeletal pain and symptoms may improve within weeks [1].
Mechanical lower back pain is most common and is due to an anatomical or functional abnormality without underlying malignant, neoplastic, or inflammatory disease. Some of the most common causes include [7, 15]:
• Lumbar strain or sprain | • Spinal stenosis |
• Degenerative disk disease or facet joint arthropathy | • Osteoporotic compression fracture |
• Herniated disk | • Spondylolisthesis |
Neurological findings commonly result due to compression of a spinal nerve root, or the spinal cord itself, and include impaired reflexes, sensory loss, and motor weakness in corresponding extremities [1, 16]. Physical findings may help to narrow the differential diagnosis, such as pain that worsens with lower back flexion, which likely indicates compression fracture or herniated disc, and pain that worsens with extension and is relieved with flexion, which likely indicates spondylolysis or spondylolisthesis [10].
Nonmechanical etiologies are various and can include [15]:
• Neoplastic process | • Referred visceral cause: |
• Infectious process | – Pelvic organ disease |
• Paget’s disease | – Gastrointestinal disease |
• Inflammatory arthritis | – Renal disease |
– Aortic Aneurysm |
Conservative Treatment
Most acute pain, which is less than 4 weeks in duration, and most nonspecific lower back pain resolves over time without any treatment. Controlling pain and maintaining daily function, while symptoms gradually diminish is the goal for most patients [7, 17]. Spontaneous recovery is more than 50–75% at 4 weeks and more than 90% at 6 weeks [7].
There are numerous recommendations to treat acute lower back pain, some of which include the following:
Patients should remain active and ambulatory:
Providers should target symptom relief:
NSAIDs or acetaminophen should be used as needed for up to 2–4 weeks [8, 20]. Additionally, some patients may also benefit from nonbenzodiazepine antispasmodics, but treatment should be limited to short term, 1–3 weeks [21]. Furthermore, evidence shows no benefit to physical therapy in the initial 2–3 weeks of acute low back pain [22–25].
Subacute lower back pain is defined as pain that occurs between 4 and 12 weeks of symptoms, with chronic pain persisting beyond 12 weeks. For those with chronic pain, the goal of treatment involves controlling pain, maintaining overall function, and preventing disability [26]. Some recommendations for subacute and chronic lower back pain include the following:
Patients should be advised to remain active:
Providers should target symptom relief:
Short courses of NSAIDs and acetaminophen should be used for acute exacerbations of subacute and chronic pain [8]. Additionally, short-term use of opioid analgesics has been recommended for severe acute exacerbations but should not be used for long-term therapy. Opioids may be used in rare circumstances in severely disabled patients with chronic low back pain who have not responded to alternative measures [28]. Muscle relaxants and benzodiazepines have not shown sufficient efficacy for subacute and chronic low back pain [29, 30]. Additionally, depression is common in patients with chronic low back pain, and antidepressant medications may be used as conservative therapy in these patients [31–34].
Some nonsurgical interventional therapies may be considered for patients who have not responded to noninvasive therapies, who are not interested in surgery, or in those who are poor surgical candidates. For further reference, please see the chapter on pain in the spine rehabilitation patient. These may include the following:
Epidural Steroid Injections:
Epidural steroid injections in those with radiculopathy due to a herniated disc may provide moderate improvement in pain and disability at 3 months, but no benefit at 1 year [35, 36]. This is completed through placement of a needle into the epidural space to administer corticosteroids. Intervals for injections should be at least 1 month, and additional injections are generally not indicated if the initial injection does not improve symptoms [36]. Generally, injections may be recommended in patients with radiculopathy who have not improved with conservative treatment over 6 weeks and desire nonsurgical treatment [35, 36].
Surgical Intervention
Only a small minority of patients with low back pain may require surgery. Generally, spinal procedure rates have been rising in the United States, particularly for spinal fusion [37]. The most likely indications for surgery are severe or progressive motor weakness, or signs and symptoms of cauda equina syndrome. In the absence of such indications, there is no evidence that early referral for surgery improves outcomes for disc prolapse with radiculopathy or for symptomatic spinal stenosis [38, 39]. In these patients, surgery may be an elective option for those with persistent disabling symptoms of low back pain and significantly impaired quality of life, who have not responded to conservative management.
In the following section, several types of surgical interventions for lumbar back pain will be discussed, including:
Lumbar laminectomy
Lumbar laminectomy and discectomy
Lumbar instrumented fusion
The section will examine the indications for the procedure, a description of the procedure if appropriate, as well as a discussion of outcomes.
Types of Surgeries
Lumbar Laminectomy
Indications
Lumbar laminotomy and laminectomy is one of the most commonly performed spine procedures . Complications from this procedure have been reducing over the last several years with the advent of microtechniques, magnification, perioperative antibiotics, and better neurodiagnostic testing [40]. One of the most common indications for a lumbar laminectomy is spinal stenosis, or narrowing of the intraspinal canal, the lateral recesses, and/or the neural foramina [41]. Most commonly, this is caused by degenerative arthritis affecting the spine or by spondylosis [41]. Symptoms range from axial low back pain, radiating radicular leg pain, paresthesia, weakness, gait instability, and loss of normal bladder or bowel function. These symptoms typically occur as the result of a chronic, debilitating condition, but may occur acutely, such as with trauma, or disk herniation. The levels most commonly affected are L4–L5, followed by L3–L4, L2–L3, and then L5–S1 [42].
Description of Procedure
Lumbar laminectomy consists of removal of the inferior lamina (hemilaminotomy) or removal of the entire lamina on one or both sides (laminectomy). Frequently, the spinous process is removed as well, and overlying connective tissues, the ligamentum flavum underlying and spanning the interlaminar space, and muscle may be transected in order to gain access to the vertebrae. Further lumbar decompression involves removal of the medial aspects of the inferior articular process of the superior lamina, as well as the superior articular process of the inferior lamina (medial facetectomy and foraminotomy).
Outcomes
Postoperative complications :
Thecal sac or nerve root injury
This can result in complications such as cerebrospinal fluid leak and/or sensory and motor deficits, which occurs from injury to the traversing and exiting nerve roots. Complications frequently occur during dissection of the lateral recess, as visualization is often poor [42].
Durotomy
This is one of the most common complications and may result in postoperative problems such as durocutaneous fistulas, pseudomeningoceles, and arachnoiditis [43, 44]. Incidence has been shown to be around 16%, and in revision spine surgeries rates are high, with a range between 2.1 and 15.9% [45–48].
Hematoma
This can occur from inadequate hemostasis or starting NSAIDs or prothrombotic agents too early in the postoperative period, and should be considered in a patient with progressively worsening back and/or leg pain following the operation [42].
Generally, elderly patients with comorbidities are at a higher risk for complications and adverse outcomes [49].
Pain Control
Several studies have investigated the short- and long-term implications of lumbar laminectomy on pain control. In the short term, some studies have demonstrated variable rates of bodily pain control following lumbar laminectomy, with several finding an overall benefit in the first few months [50–52]. There are conflicting studies regarding long-term benefit on pain control. While some show maintained benefit of surgery for several years, others show a general decline over time, with no statistical significance after a few years [50, 51, 53, 54]. More studies are needed to assess long -term outcomes beyond 2–3 years [52].
Rate of Reoperation
In some patients, the overall benefit from the initial lumbar laminectomy may diminish over time. Prior to reoperation, patients may begin to complain of symptoms such as back pain, radiculopathy, weakness, sensory deficits, and neurogenic claudication. Several studies have analyzed the rates of reoperation, with ranges between 14 and 23% [55–57]. One study showed that approximately 55% of the cohort underwent an additional decompression alone, while 44% underwent decompression and fusion. The lifetime risk of fusion following a first-time laminectomy was 8% [56]. Generally, outcomes vary significantly among studies and centers, showing that local expertise and other procedural factors may influence the outcome [58].
Lumbar Laminectomy with Discectomy
Indications
Degenerative disc disease is extremely common, with an estimated prevalence of 12 million Americans alone. Approximately one million of these patients undergo surgeries each year, with about 200,000–300,000 being lumbar discectomies [59, 60]. The indications for a laminectomy are the same as those discussed in the prior section. A discectomy is typically performed to excise a lumbar disc herniation. The purpose of surgery in this situation is to remove the portion of the disc impinging upon a nerve root, causing radiculopathy, and in extreme cases, cauda equina syndrome. The most important determinant supporting surgical intervention for discectomy is the correlation between the distribution of the radicular leg pain and the nerve root compression seen on preoperative imaging studies [61].
Outcomes
Postoperative complications:
Dural injury
Nerve root or vessel damage
Recurrence of disc herniation
This results in reoperation, ranging from 3 to 18% in those undergoing first-time surgery [65]. Some postoperative patients may initially maintain a pain-free interval prior to presenting with recurrence of pain in the original distribution. One study showed that at 2 years, roughly 23% of patients demonstrated radiographic evidence of recurrent disc herniation at the level of prior discectomy on serial imaging, with 10.2% of these patients with symptoms [66].
Infection
Thromboembolic complications
Complication rates are reported from 0.1 to 1%, with rates of lower extremity thrombosis likely higher [69].
Other
Nerve palsies may occur, which are often related to positioning during surgery, or symptoms may persist, which is typically due to inadequate removal of the herniated disc, wrong-level surgery, or nerve injury due to retraction.
Pain Control
Robust evidence exists for early improvement in pain or function at 2–3 months following lumbar laminectomy and discectomy [70]. Most patients have pain reduced to a point of clinical irrelevance, though roughly 14% of patients report persistent pain between 6 months and 2 years [65]. Benefits of surgical intervention may diminish over time. One study indicated that after 2 years, between 11.6 and 27.8% of patients reported persistence of pain, depending on the extent of disc resection [65]. Generally, a majority of patients who undergo the procedure maintain resolution of presurgical pain in the long term [65, 71].
Rates of Reoperation
At roughly 2 years, approximately 23% of patients demonstrated radiographic evidence of a recurrent disc herniation on serial imaging, at the level of prior discectomy. However, risk can vary, frequently depending upon the size of the defect in the annulus [51, 65, 71, 72]. Generally, the reoperation rate following an initial discectomy is around 14% [55, 73, 74]. One study indicated roughly 63% of the reoperations are discectomies, 14% are fusions, and approximately 23% are decompressions. Additionally, patients with one reoperation after a lumbar discectomy had approximately a 25.1% cumulative risk of further spine surgery in the 10-year follow-up [73].
Lumbar Instrumented Fusion
Indications
One of the most common procedures for chronic, nonspecific lower back pain with apparent degenerative disc changes is lumbar vertebral fusion. Though controversial, some of the most common indications for fusion include the following: mechanical pain; grade II or higher spondylolisthesis; ischemic spondylolisthesis; history of repeated (>2) discectomies; history of bilateral facetectomy; spinal stenosis without spondylolisthesis if unstable; radiographically documented instability, with associated pain or progressive neurological deficits [75–78]. Other indications may be even more controversial, including decompression with grade I spondylolisthesis, chronic axial low back pain of unknown etiology, and following a unilateral facetectomy. However, more recent data suggests improved outcomes with fusion as opposed to laminectomy alone in patients with grade I spondylolisthesis and stenosis [78–81]. Additionally, fusions are indicated for treatment of patients with deformity, spinal trauma, and oncological conditions [80].
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