Evaluation and Treatment of Spinal Injuries in the Obese Patient




Given the increasing incidence and severity of obesity in the adult population, orthopaedic surgeons are evaluating and treating more acutely injured obese patients. Management of obese patients is complicated given their body habitus and associated medical comorbidities. Although evaluation and treatment are almost the same as for nonobese patients, some special considerations are necessary to prevent errors in diagnosis and treatment of obese trauma patients. This article focuses on spine injuries in obese patients. Predisposition to spinal injury, effective evaluation and early management, principles of treatment planning, operative technical pearls, and postoperative management are discussed.


Given the increasing incidence and severity of obesity in the adult population, orthopaedic surgeons are evaluating and treating more acutely injured obese patients. Management of obese patients with spinal injuries and disorders is complicated given their body habitus and associated medical comorbidities. Although evaluation and treatment are almost the same as for nonobese patients, some special considerations are necessary to prevent errors in diagnosis and treatment of obese trauma patients. Predisposition to spinal injury, effective evaluation and early management, principles of treatment planning, operative technical pearls, and postoperative management are discussed.


Predisposition to spinal injury


Studies on the relationship between obesity and spinal disease have focused primarily on degenerative changes and low back pain. Much less is understood about the relationship between obesity and spinal injury. A large body habitus can make gross inspection and palpation of an injury difficult, placing greater importance on clinical suspicion and imaging. Determining if obesity predisposes blunt trauma patients to spinal injury could help guide evaluation in the emergency setting.


Data on the relationship between obesity and spinal injury after blunt trauma are sparse. Obesity is highly correlated with sleep apnea. Sleep apnea leads to a 7-fold risk for motor vehicle accidents. Brown and colleagues performed a retrospective review of 1153 blunt trauma patients requiring admission to the intensive care unit comparing obese (body mass index [BMI], calculated as weight in kilograms divided by the square of height in meters >30 kg/m 2 ) and nonobese patients. Obese patients had significantly fewer head injuries but more chest and lower extremity injuries. There was no difference in the overall incidence of spinal fractures (14% vs 16% in obese vs nonobese) or the anatomic region involved. Bolaunger and colleagues prospectively evaluated 743 obese blunt trauma patients. Obese patients had a higher incidence of rib fractures, pulmonary contusions, pelvic fractures, and extremity fractures, and were less likely to have incurred head trauma and liver injuries. Again, no significant relationship between obesity and spinal injury or type of injury was found.




Initial evaluation and early management


The principles of acute trauma care are no different in obese patients versus nonobese patients. Following the ABCs and complete removal of clothing and exposure, care should be directed toward a meticulous clinical evaluation. Spinal immobilization may be more difficult in the obese patient given heavier extremities, a relatively short, thick neck region, poorly fitting cervical collars, or problems fitting and transporting patients on the gurney. Sandbags may help augment cervical stabilization, or 1 person may need to be dedicated to holding in-line cervical traction if there is suspicion for cervical injury. To maintain spinal precautions during a log roll, additional personnel are needed and palpation of the spine should be deeper and more focused.


Imaging


Thorough imaging is paramount in any obese blunt trauma patient. Plain radiographs in obese patients may be of poor quality for several reasons. The large soft tissue envelope makes obtaining accurate images of the correct anatomy difficult for inexperienced technician. Also, the amount of penetration necessary may deteriorate the quality of the image. Body habitus and difficulty depressing the shoulders makes inclusion of the cervicothoracic junction on lateral cervical radiographs nearly impossible. Magnification error may be an issue. Ravi and Rampersaud showed that linear clinical measurements obtained on digital radiographs are subject to significant magnification errors based on the patient’s BMI. Consequently, clinical decision making that is based on linear measurements obtained from radiographs that do not account for this error is invalid. They suggest that in a scenario where this measurement is crucial, such as during dynamic radiographs or measuring for signs of instability in the cervical spine, this error can be corrected by comparison with morphometric data from computed tomography (CT) or magnetic resonance imaging (MRI).


CT provides rapid, accurate bony images and has largely supplanted plain radiography for the evaluation of spinal injury. The Eastern Association for the Surgery of Trauma (EAST; www.east.org/tpg.asp ) recommended in its 2009 update, using CT as the only screening modality as plain radiographs do not contribute any additional information. However, a potential problem may arise with size limitations of the CT scanner. Ginde and colleagues performed a detailed survey of 262 nonacademic and 136 academic hospitals across the United States to determine the characteristics of available CT scanners. In the nonacademic hospitals, 25% of CT scanners had a maximum weight limit of 159 kg (350 pounds) and only 10% could accommodate patients more than 204 kg (450 pounds). At academic hospitals, 10% had limits of 159 kg and 21% could scan patients more than 204 kg. Only 21% of centers designated as Bariatric Centers of Excellence had large-weight CT capacity equipment. To determine if a large animal scanner is available to image heavier patients, the investigators also surveyed 145 zoos and veterinary hospitals. Only 2 zoos had large animal scanners but both refused to allow human imaging. Sixteen veterinary hospitals had large scanners (up to 907 kg [2000 pounds]) but 12 of these had strict policies prohibiting human use. If faced with this dilemma, the morbidly obese patient may need to be transported long distances to a facility with appropriate imaging capabilities.


The obese patient may also be difficult to image with MRI. In evaluating MRI capabilities, 64% of nonacademic and 59% of academic facilities had a weight limit of 159 kg for their MRI scanners. Weight limits of 159 kg or a body diameter of 60 cm are common and prohibitive for effective MRI imaging in obese patients. Open-system MRI scanners can accommodate significantly larger patients but the images are often poor quality. Other difficulties include increased transport time, positioning, and longer scan time, which leads to patient discomfort and motion with resulting poor quality images.


Early Medical Management


The medical comorbidities associated with obesity and the subsequent perioperative medical management were discussed in a previous article. Optimization of pulmonary function and toilet, oxygenation, blood counts, venous thromboembolism prophylaxis, and nutritional assessment are vital for successful outcomes.




Initial evaluation and early management


The principles of acute trauma care are no different in obese patients versus nonobese patients. Following the ABCs and complete removal of clothing and exposure, care should be directed toward a meticulous clinical evaluation. Spinal immobilization may be more difficult in the obese patient given heavier extremities, a relatively short, thick neck region, poorly fitting cervical collars, or problems fitting and transporting patients on the gurney. Sandbags may help augment cervical stabilization, or 1 person may need to be dedicated to holding in-line cervical traction if there is suspicion for cervical injury. To maintain spinal precautions during a log roll, additional personnel are needed and palpation of the spine should be deeper and more focused.


Imaging


Thorough imaging is paramount in any obese blunt trauma patient. Plain radiographs in obese patients may be of poor quality for several reasons. The large soft tissue envelope makes obtaining accurate images of the correct anatomy difficult for inexperienced technician. Also, the amount of penetration necessary may deteriorate the quality of the image. Body habitus and difficulty depressing the shoulders makes inclusion of the cervicothoracic junction on lateral cervical radiographs nearly impossible. Magnification error may be an issue. Ravi and Rampersaud showed that linear clinical measurements obtained on digital radiographs are subject to significant magnification errors based on the patient’s BMI. Consequently, clinical decision making that is based on linear measurements obtained from radiographs that do not account for this error is invalid. They suggest that in a scenario where this measurement is crucial, such as during dynamic radiographs or measuring for signs of instability in the cervical spine, this error can be corrected by comparison with morphometric data from computed tomography (CT) or magnetic resonance imaging (MRI).


CT provides rapid, accurate bony images and has largely supplanted plain radiography for the evaluation of spinal injury. The Eastern Association for the Surgery of Trauma (EAST; www.east.org/tpg.asp ) recommended in its 2009 update, using CT as the only screening modality as plain radiographs do not contribute any additional information. However, a potential problem may arise with size limitations of the CT scanner. Ginde and colleagues performed a detailed survey of 262 nonacademic and 136 academic hospitals across the United States to determine the characteristics of available CT scanners. In the nonacademic hospitals, 25% of CT scanners had a maximum weight limit of 159 kg (350 pounds) and only 10% could accommodate patients more than 204 kg (450 pounds). At academic hospitals, 10% had limits of 159 kg and 21% could scan patients more than 204 kg. Only 21% of centers designated as Bariatric Centers of Excellence had large-weight CT capacity equipment. To determine if a large animal scanner is available to image heavier patients, the investigators also surveyed 145 zoos and veterinary hospitals. Only 2 zoos had large animal scanners but both refused to allow human imaging. Sixteen veterinary hospitals had large scanners (up to 907 kg [2000 pounds]) but 12 of these had strict policies prohibiting human use. If faced with this dilemma, the morbidly obese patient may need to be transported long distances to a facility with appropriate imaging capabilities.


The obese patient may also be difficult to image with MRI. In evaluating MRI capabilities, 64% of nonacademic and 59% of academic facilities had a weight limit of 159 kg for their MRI scanners. Weight limits of 159 kg or a body diameter of 60 cm are common and prohibitive for effective MRI imaging in obese patients. Open-system MRI scanners can accommodate significantly larger patients but the images are often poor quality. Other difficulties include increased transport time, positioning, and longer scan time, which leads to patient discomfort and motion with resulting poor quality images.


Early Medical Management


The medical comorbidities associated with obesity and the subsequent perioperative medical management were discussed in a previous article. Optimization of pulmonary function and toilet, oxygenation, blood counts, venous thromboembolism prophylaxis, and nutritional assessment are vital for successful outcomes.




Treatment planning


Classification systems and treatment algorithms guiding spinal injury treatment are constantly evolving. The Spine Trauma Study Group has proposed more comprehensive classification systems for both cervical and thoracolumbar injury, helping to guide operative versus nonoperative treatment. These systems improve on previous systems by factoring in 3 important parameters: injury morphology, neurologic status, and integrity of soft tissue supports including posterior ligaments and intervertebral discs. Body habitus is another important patient characteristic that should be considered when determining operative versus nonoperative treatment as nonoperative stabilization of a spinal injury in an obese patient may not be feasible with the commonly used rigid orthoses.


Bracing


The absolute surgical indications for patients with spinal injuries are (1) progressive neurologic deficit in the presence of surgically correctable compression or (2) instability or unstable ligamentous injury. Nonoperative care and/or bracing are valid options in most other injuries. However, bracing should be approached as a complex treatment option requiring close monitoring for signs of failure or complications. A large body habitus impairs 3- or 4-point immobilization necessary for orthotic immobilization at all spinal levels. Thus, motion at the involved spinal levels still occurs despite proper fitting. Evidence of bracing failure in obese patients is most evident in scoliosis treatment. In the obese patient, the brace offers less mechanical support of the spine and is frequently not as well tolerated compared with thinner patients. Given the inefficiency and complications from bracing and the large lever arm placed on the spine by a large ventral panniculus, the authors believe that strong consideration should be given to surgical fixation of potentially unstable thoracolumbar injuries in obese patients.




Operative pearls and pitfalls


Surgical Exposure


The surgical exposure should be dictated by the involved pathologic anatomy as in nonobese patients. Dorsal approaches and the anterior cervical Smith-Robinson approach are more difficult in obese patients and may require technique and equipment modifications as discussed later. Ventral approaches to the thoracolumbar spine are significantly deeper given the large panniculus. Complications from this approach were prospectively studied by Peng and colleagues in 74 cases of obese versus nonobese patients for degenerative pathology. Although obese patients did require longer surgical duration and a larger incision, there were no significant differences in blood loss, analgesic use, time to ambulation or discharge, and complications. All of their cases were performed by a single experienced vascular access surgeon at a major academic center. Such an experienced access surgeon should be available for this approach.


Operating Table


The Amsco surgical table (Amsco 3085, Steris Corp, Montgomery, AL, USA) is our basic mobile surgical table and can accommodate 454 kg (1000 pounds) in its normal orientation. To facilitate intraoperative imaging, the head section can be inserted into the leg section. This orientation can only hold 227 kg (500 pounds). If the patient is too wide, 2 tables may be placed side-by-side in opposite orientations. Adapters for 3-point cranial fixation or traction tongs can be attached to the top of the bed.


Allowing the abdomen to hang free in the prone position facilitates vena cava decompression, decreased venous pressure in the operative field, and less operative blood loss. The spinal Jackson table (Mizuho OSI, Union City, CA, USA) allows this, is radiolucent, and can hold up to 227 kg. The table delivers automatic massage to its pads and pressure points and can be rotated for 360-degree fusion without repositioning the patient.


Positioning


Patient positioning should allow optimal exposure and visualization of the spinal segment involved while ensuring patient safety. Anesthesia concerns were discussed in a previous article and are of paramount concern. Patient positioning should safely place the anatomy in an optimal position for the desired procedure, that is, cervical extension or lumbar flexion for decompression or flexion/extension for reduction of traumatic deformities. There should be access for obtaining localizing radiographs. In a 2004 review, Goodkin and Laska found that “(a) large body habitus or operating table limitations preventing adequate radiographic visualization of the operative level” was one of the most common causes of wrong level surgery.


Specific Positions


Supine position


The supine position permits exposure of the anterior spine via an anterior cervical, transthoracic, or transabdominal approach. The anterior cervical approach may be complicated by excessive tissue around the neck and submandibular panniculus. Cervical extension as tolerated helps to smooth out skin folds. Chin straps or tape with a topical adhesive may be used. Tape is placed from the lateral shoulder to the base of the bed to depress the shoulder for lateral cervical radiographs. However, care should be taken not to place excess traction. Roh and colleagues evaluated the usefulness of somatosensory evoked potential monitoring during 809 consecutive cervical spine surgeries. In 2.1% of cases, positioning led to a critical change in somatosensory evoked potentials. The most common corrective maneuver was release of tape and traction. Arm boards may be attached to the side of the bed and a sheet can be wrapped around the body and secured with tape for arm support.


Prone positioning


Compared with other positions, the prone position has the greatest potential for respiratory compromise manifested by increased peak airway pressure and abdominal compression manifested by increased venous congestion. The spinal Jackson table best minimizes these problems. This table also has customized padding to minimize compression at pressure points. The head should be placed in stable foam padding in a neutral position. The arms should not be hyperabducted or extended over the head to protect from peripheral nerve or brachial plexus traction injury. The axillae should be free or padded without compression. The transverse chest support should be at the nipple line, the cephalad hip support is on the anterior superior iliac spine, and the caudal support at the mid to proximal thigh. The abdominal panniculus, genitalia, and Foley catheter should hang freely. Reston or an equivalent padding is placed under the knees and blankets are placed under the feet to affect at least 20 degrees of flexion at the knee. Make sure that no body part is resting directly on any lines, tubes, cords, drains, or compression devices ( Fig. 1 ).


Oct 6, 2017 | Posted by in ORTHOPEDIC | Comments Off on Evaluation and Treatment of Spinal Injuries in the Obese Patient
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