Introduction

Back pain affects millions of people and is one of the most common reasons why patients consult with a medical professional. Many of these patients have back and or leg pain because of lumbar spinal stenosis with or without instability. Conservative treatment in the form of physical therapy, chiropractic care, medications, and injections should be the first line of care if a patient does not present with new neurologic insult. If these conservative modalities fail, then surgery must be considered.

Most lumbar spine surgery involves decompressing the soft tissue, which often includes a herniated disc (Fig. 8-1) or hypertrophied ligamentum flavum. Lumbar spine surgery also involves decompressing the bony elements, which can include hypertrophied facet joints, spinous processes, and lamina that make up the spinal canal. By decompressing both soft and bony tissue, spine surgery can often make patent both central and neuroforaminal narrowing that may be impinging on the spinal cord or nerve roots. Thoroughly decompressing the stenosis and nerve roots can reliably relieve leg pain and its associated symptoms of numbness and weakness. However, there are instances wherein there is obvious instability, spinal spondylolisthesis (Fig. 8-2), or the potential for instability. In this situation, a surgeon must consider both decompressing the stenosis along with stabilizing the affected spinal segments.

Fig. 8-1 Large herniated L4–L5 lumbar disc requiring decompressive surgery.

Fig. 8-2 Significant L5–S1 spondylolisthesis requiring surgery.

Particular ways to achieve fusion of the lumbar spine are discussed throughout the literature. Spinal fusion is a very successful procedure when chosen for patients with the correct indications for surgery. Newer surgical technologies and minimally invasive surgery have been touted to result in quicker recovery and less morbidity for the patient. However, lumbar spinal surgery and fusion with any approach has its associated relevant complications.

Some very serious complications of lumbar spine fusion have been reported, including nerve root injury, paralysis, massive blood loss, blindness, heart attack, stroke, and death. A comprehensive preoperative workup can help to stratify those patients at the most risk for medical complications. In some instances, optimization of a patient’s preexisting medical conditions (e.g., untreated diabetes, hypertension, reactive airway disease) should be taken to minimize their risks before surgery. Expert intraoperative anesthetic monitoring and care, as well as postoperative monitoring, can significantly decrease many of these complications. The surgeon must work effectively and efficiently to address the patient’s disease but also keep operative time as low as possible. Increased operative time often leads to increased complications, including increased blood loss, infection, and possibly blindness from being prone for too long (>8 hours).

The most commonly discussed complications directly related to lumbar spinal fusion include infections, dural tears, pseudoarthrosis, and adjacent segment degeneration (ASD). These specific complications are all important to understand, and if they occur, they must be recognized and treated rapidly, and as such will be elaborated on in more depth.

Selected Complications

Infection

Patients undergoing lumbar spinal fusion typically receive prophylactic intravenous (IV) antibiotics within 1 hour of surgery and postoperatively in several doses. This perioperative regimen, along with proper intraoperative sterility, has decreased infection rates dramatically. However, postoperative spinal wound infection is not an uncommon complication (Fig. 8-3). If not properly recognized and treated, a wound infection can be devastating and affect the ultimate desired surgical outcome.

Fig. 8-3 Normal postsurgical fusion (A) compared with postsurgical infection (B).

A review of the literature shows that postoperative wound infections are common and range from 1% to 6% after lumbar spine fusions.¹ Staphylococcus aureus was the most common pathogen cultured, but some patients have multiple organisms causing an infection. Multiple studies have assessed risk factors for postoperative wound infections (Table 8-1).

Table 8-1 Patient and Surgical Risk Factors for Postoperative Wound Infections

Patient Risk Factors for Postoperative Wound Infections	Surgical Risk Factors for Postoperative Wound Infections
>60 years of age	Complex spine procedures
Smoking	Fusing multiple levels
Diabetes	Spinal revisions
History of previous surgical infections	Anterior or posterior reconstruction
Obesity and increased body mass index	Increased operative times
Alcohol abuse

Age greater than 60 years, smoking, diabetes, previous surgical infection, increased body mass index, and alcohol abuse were statistically significant risk factors. In addition to these factors, more complex spine procedures that involved multiple levels being fused, tumors, surgical revisions, and anterior or posterior reconstructions, also increased the rates of postoperative infections and complications.²

Early detection is of paramount importance for appropriate care of any postoperative infection. Patients with postoperative infection may complain of classic symptoms, including fever, chills, nausea or vomiting, erythema, and drainage from the incision. Patients also may have more insidious complaints such as an increase in pain after an initial improvement postsurgically. If an infection is suspected, it is important to have the patient urgently come to the clinic or a nearby hospital for immediate evaluation. Thankfully, suspected infection is often the result of much less serious superficial wound dehiscence. This can usually be treated with dressing changes and oral antibiotics as needed. When treating wound dehiscence, it is imperative to have the patient follow up closely for several evaluations to ensure the wound is healing appropriately. If the patient remains symptomatic and the incision is not healing, then further workup, including imaging in the form of magnetic resonance imaging (MRI) or computed tomography (CT), is warranted. This may show a postoperative abscess, seroma (fluid collection), hematoma, or even an undetected cerebrospinal fluid (CSF) leak.

If a wound infection is diagnosed after a spinal fusion, aggressive treatment is essential. Many physicians also obtain an infections blood workup, including complete blood count, erythrocyte sedimentation rate, C-reactive protein test, and blood cultures with sensitivities. MRI or CT scans with and without contrast are sometimes obtained to evaluate the underlying pathology. Suspected deep tissue infections require deep wound irrigation and debridement. At the same time, targeted wound cultures and sensitivities must be taken and sent to pathology for further analysis. Wound irrigation and debridement may be required multiple times before closure of the wound is possible.

When one has a deep infection, there is much debate on whether instrumentation needs to be removed at the time of irrigation and debridement. Instrumentation is a foreign body and thus can be a nidus for infection because bacteria can form a glycocalyx, or an extracellular adhesive slime. This bacteria-generated layer can make it difficult or impossible for antibiotics to penetrate the bacteria and rid the area of infection. If the infection is of late onset, there may be evidence of full bony fusion. In that instance, hardware may be removed. However, with earlier infection, the hardware may need to remain in place to maintain structural stability of the lumbar spine. Aggressive debridement of soft tissue, bone, and surgical hardware is obviously needed in that circumstance. In all instances of wound infection, it is important to consult a patient’s primary care physician as well as infectious disease specialists. Typically, an infection requires 4 to 8 weeks of IV antibiotics through a peripherally inserted central catheter line with the choice of antibiotics chosen by an infectious disease specialist and dependent on the results of the cultures and sensitivities of the organism.

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