maximizing the potential of minimally invasive spine

of 10/10
ONVENTIONAL open surgeries have been widely used for decades in the treatment of various spinal dis- orders. Although conventional open spinal surgery has been considered the standard for most spinal disorders, the clinical outcomes following open surgery can vary. Suboptimal clinical results often occur even after techni- cally successful open spine surgeries. Although contribut- ing factors to the suboptimal outcomes in those cases may be related to poor patient selection, postsurgical scarring, or adjacent level disease, the significant soft tissue and mus- cle injuries that occur during exposure for open spine surg- eries may also be important contributing factors. Minimally invasive spine surgery was developed to decrease the rate of approach-related morbidity associated with conventional open spine surgery in an effort to im- prove clinical outcomes. 10,20,35,39 Based on that philosophy, various approaches and techniques have evolved to mini- mize the disruption of normal surrounding tissues. Al- though the approach and techniques can differ between open spine surgery and MIS, the surgical goals are equiva- lent and should not be compromised in MISs. Over the past several decades, MISs have been gaining momentum and popularity in many surgical specialties, including spine surgery. In 1991 Obenchain 27 first reported a case of laproscopic lumbar discectomy. Since that initial report, MIS has become routinely used in the treatment of degenerative spine diseases, as in herniated disc removal, decompression of spinal stenosis, and fusions for degener- ative spinal disorders. Compared with those in convention- al open spine surgeries, the clinical outcomes of MISs have indicated that the procedure is at least equally effective. Moreover, recovery time, pain, and the time required to return to work after surgery are reduced for MIS of the spine in several clinical series involving degenerative pathology. 9,11,19 Although we have witnessed favorable pre- liminary clinical results in applying minimally invasive strategies, long-term outcome studies supported by validat- ed outcome measuring instruments are pending. Moreover, it would be interesting to determine the impact of MIS on fusion rates, adjacent segment disease, and sustained pain relief. As spine surgeons become more experienced with the techniques and technology associated with MIS, the indications for MIS continue to expand. 12 Interestingly, the benefit of decreasing approach-related morbidity might be far greater for more complex surgeries in spinal trauma, spinal deformity, and spinal oncology. In this report, we discuss the techniques in, and the rationale for, using MIS in these complex spinal disorders and provide illustrative cases for each. Neurosurg. Focus / Volume 25 / August 2008 Neurosurg Focus 25 (2):E19, 2008 Maximizing the potential of minimally invasive spine surgery in complex spinal disorders P ATRICK C. HSIEH, M.D., 1 TYLER R. KOSKI, M.D., 2 DANIEL M. SCIUBBA, M.D., 1 DAVE J. MOLLER, M.D., 2 BRIAN A. O’SHAUGHNESSY , M.D., 2 KHAN W. LI, M.D., 1 ZIYA L. GOKASLAN, M.D., 1 STEPHEN L. ONDRA, M.D., 2 RICHARD G. FESSLER, M.D., 2 AND JOHN C. LIU, M.D. 2 1 Department of Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, Maryland; and 2 Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, Illinois Minimally invasive surgery (MIS) in the spine was primarily developed to reduce approach-related morbidity and to improve clinical outcomes compared with those following conventional open spine surgery. Over the past several years, minimally invasive spinal procedures have gained recognition and their utilization has increased. In particular, MIS is now routinely used in the treatment of degenerative spine disorders and has been shown to be as effective as conventional open spine surgeries. Although the procedures are not yet widely recognized in the context of complex spine surgery, the true potential in minimizing approach-related morbidity is far greater in the treatment of complex spinal diseases such as spinal trauma, spinal deformities, and spinal oncology. Conventional open spine surgeries for complex spinal disorders are often associated with significant soft tissue disruption, blood loss, prolonged recovery time, and postsurgical pain. In this article the authors review numerous cases of complex spine disorders managed with MIS techniques and discuss the current and future implications of these approaches for complex spinal pathologies. (DOI: 10.3171/FOC/2008/25/8/E19) KEY WORDS complex spine disorder deformity minimally invasive spine surgery oncology trauma C 1 Abbreviations used in this paper: MIS = minimally invasive surgery; SPO = Smith–Petersen osteotomy. Unauthenticated | Downloaded 12/12/21 01:51 AM UTC

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NSJ-Spine january 2004ONVENTIONAL open surgeries have been widely used for decades in the treatment of various spinal dis- orders. Although conventional open spinal surgery
has been considered the standard for most spinal disorders, the clinical outcomes following open surgery can vary. Suboptimal clinical results often occur even after techni- cally successful open spine surgeries. Although contribut- ing factors to the suboptimal outcomes in those cases may be related to poor patient selection, postsurgical scarring, or adjacent level disease, the significant soft tissue and mus- cle injuries that occur during exposure for open spine surg- eries may also be important contributing factors.
Minimally invasive spine surgery was developed to decrease the rate of approach-related morbidity associated with conventional open spine surgery in an effort to im- prove clinical outcomes.10,20,35,39 Based on that philosophy, various approaches and techniques have evolved to mini- mize the disruption of normal surrounding tissues. Al- though the approach and techniques can differ between open spine surgery and MIS, the surgical goals are equiva- lent and should not be compromised in MISs.
Over the past several decades, MISs have been gaining momentum and popularity in many surgical specialties,
including spine surgery. In 1991 Obenchain27 first reported a case of laproscopic lumbar discectomy. Since that initial report, MIS has become routinely used in the treatment of degenerative spine diseases, as in herniated disc removal, decompression of spinal stenosis, and fusions for degener- ative spinal disorders. Compared with those in convention- al open spine surgeries, the clinical outcomes of MISs have indicated that the procedure is at least equally effective. Moreover, recovery time, pain, and the time required to return to work after surgery are reduced for MIS of the spine in several clinical series involving degenerative pathology.9,11,19 Although we have witnessed favorable pre- liminary clinical results in applying minimally invasive strategies, long-term outcome studies supported by validat- ed outcome measuring instruments are pending. Moreover, it would be interesting to determine the impact of MIS on fusion rates, adjacent segment disease, and sustained pain relief. As spine surgeons become more experienced with the techniques and technology associated with MIS, the indications for MIS continue to expand.12 Interestingly, the benefit of decreasing approach-related morbidity might be far greater for more complex surgeries in spinal trauma, spinal deformity, and spinal oncology. In this report, we discuss the techniques in, and the rationale for, using MIS in these complex spinal disorders and provide illustrative cases for each.
Neurosurg. Focus / Volume 25 / August 2008
Neurosurg Focus 25 (2):E19, 2008
Maximizing the potential of minimally invasive spine surgery in complex spinal disorders
PATRICK C. HSIEH, M.D.,1 TYLER R. KOSKI, M.D.,2 DANIEL M. SCIUBBA, M.D.,1
DAVE J. MOLLER, M.D.,2 BRIAN A. O’SHAUGHNESSY, M.D.,2 KHAN W. LI, M.D.,1
ZIYA L. GOKASLAN, M.D.,1 STEPHEN L. ONDRA, M.D.,2 RICHARD G. FESSLER, M.D.,2
AND JOHN C. LIU, M.D.2
1Department of Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, Maryland; and 2Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, Illinois
Minimally invasive surgery (MIS) in the spine was primarily developed to reduce approach-related morbidity and to improve clinical outcomes compared with those following conventional open spine surgery. Over the past several years, minimally invasive spinal procedures have gained recognition and their utilization has increased. In particular, MIS is now routinely used in the treatment of degenerative spine disorders and has been shown to be as effective as conventional open spine surgeries. Although the procedures are not yet widely recognized in the context of complex spine surgery, the true potential in minimizing approach-related morbidity is far greater in the treatment of complex spinal diseases such as spinal trauma, spinal deformities, and spinal oncology. Conventional open spine surgeries for complex spinal disorders are often associated with significant soft tissue disruption, blood loss, prolonged recovery time, and postsurgical pain. In this article the authors review numerous cases of complex spine disorders managed with MIS techniques and discuss the current and future implications of these approaches for complex spinal pathologies. (DOI: 10.3171/FOC/2008/25/8/E19)
KEY WORDS • complex spine disorder • deformity • minimally invasive spine surgery • oncology • trauma
C
1
Abbreviations used in this paper: MIS = minimally invasive surgery; SPO = Smith–Petersen osteotomy.
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Spinal Trauma
More than 150,000 Americans annually suffer from trau- matic injuries to the spine.33 These injuries are often relat- ed to high-velocity and high-impact incidents such as motor vehicle collisions or traumatic falls. Spinal cord in- juries, pain, and deformity can result from trauma to the spinal column. In addition, spinal injuries are often associ- ated with other musculoskeletal or visceral injuries based on the mechanism of injury. Early surgical interventions can prevent neurological deterioration or perhaps even re- verse neurological injury. Surgery can also improve pain when bracing and other nonsurgical therapies fail, and it can provide immediate spinal stability for unstable injuries in a critically ill patient and prevent delayed spinal defor- mities.
Injuries to the cervical spine account for one-third of all spinal fractures and one-half to two-thirds of all spinal cord injuries.18 In cervical spine injuries, the traditional Smith– Robinson anterolateral approach to the anterior spine is a prime example of an minimally invasive strategy. Although this approach has been used to address pathology in the anterior cervical spine for . 50 years, it has not been wide- ly recognized as a minimally invasive tactic. Interestingly, however, the Smith–Robinson approach exemplifies the underlying principle of MIS to minimize approach-related morbidity. The procedure involves a direct route of dissec- tion through natural tissue planes to reach the spine without significant soft tissue or muscle injury. The Smith–Robin- son approach for anterior cervical spine surgery is widely accepted as one of the most successful and gratifying pro- cedures in spine surgery. One reason for its success is the limited approach-related soft tissue and muscle injuries from surgical exposure. For posterior cervical spine in- juries, both decompression and instrumented fusions can be performed via a muscle-splitting approach with mini-
mal-access retractors.9,13,36,43,44,47 As is the case for degener- ative cervical disease, central and foraminal decompression and instrumented fusion can be performed via minimally invasive approaches for cervical spine injuries.
Of all spine injuries, 30% involve the thoracic spine and 42.5% the lumbosacral spine.18 Thoracolumbar injuries are often associated with high-impact and high-velocity trau- mas. Injury to the thoracolumbar spine can range from compression fractures and burst fractures to flexion dis- traction injuries with fracture dislocation. Various classifi- cation systems have been formulated to stratify thora- columbar spine injuries in an attempt both to offer a mechanically sound description of the insult and to provide a framework for treatment.5,6,24,41,42 In general, stable frac- tures are treated with medical observation and bracing, whereas unstable fractures are treated with operative inter- ventions.
Open surgical treatments with anterior, posterior, or combined approaches have been widely used for thora- columbar spine injuries over the years. Although these the- rapeutic approaches are successful in providing neural de- compression and stabilization, they are associated with prolonged surgical time, significant blood loss, increased infection rate, and significant approach-related soft tissue and muscle destruction. In addition, patients are often af- flicted with significant pain despite successful surgical recovery.
In an effort to improve clinical outcomes, several mini- mally invasive approaches and techniques have been de- veloped to minimize approach-related morbidity. The most common application of MIS for thoracolumbar injuries is in percutaneous cement augmentation by vertebroplasty or kyphoplasty of compression fractures and burst frac- tures.30–32 These percutaneous interventions have been shown to be highly effective in improving spinal stability from vertebral insufficiency and pain relief. Moreover,
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FIG. 1. Case 1. Left: Sagittal CT scan demonstrating a flexion distraction injury at the T-11 level. Right: Axial CT scan obtained through the fracture site, revealing that there is no central canal compromise.
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kyphoplasty has been shown to improve spinal deformity by the restoration of vertebral body height.32 In addition to percutaneous cement augmentation, percutaneous instru- mentation with or without fusion is now being performed for spinal stabilization following thoracolumbar in- juries.33,34,37 Compared with conventional open spine surg- eries, percutaneous instrumentation procedures are associ- ated with minimal soft tissue disruption, decreased blood loss, reduced infection rate, and less operative time in most cases. Particularly in patients with polytrauma or those with significant medical comorbidities, complex open spine surgery may not be possible. Unlike open surgery, percutaneous instrumentation is an alternative that can pro- vide spinal stabilization of thoracolumbar injuries with a decreased perioperative morbidity rate.
Illustrative Cases
Case 1. This 87-year-old man with ankylosing spondyli- tis and multiple medical comorbidities fell while at home and presented to our institution with severe back pain and lower-extremity weakness. A CT scan demonstrated a high- ly unstable flexion distraction injury (AO Type C injury) at T-11 without spinal canal compromise (Fig. 1). An open multilevel instrumented thoracolumbar fusion was initially recommended to the patient; however, during the preopera- tive medical clearance, the perioperative morbidity and mortality risks associated with a prolonged and extensive surgical intervention was considered by the medical service to be too great. Given the highly unstable T-11 fracture sur- gical intervention was required, and percutaneous instru- mented fusion of T-9 to L-1 was recommended and per- formed without arthrodesis, without complication. Because the patient had preexisting ankylosis of the spine from ankylosing spondylitis, arthrodesis was felt to be unneces- sary and thus not performed. The surgery was completed in 2 hours and 53 minutes, and the total blood loss for this pro-
cedure was 150 ml. Spinal fracture reduction and stabiliza- tion was achieved following the percutaneous instrumenta- tion (Fig. 2). Postoperatively, the patient did not require any blood transfusions or fluid resuscitation. He was able to par- ticipate in physical therapy, and he was transferred to a rehabilitation facility after the hospitalization.
Case 2. This 18-year-old man suffered an L-5 burst frac- ture after skydiving (Fig. 3). He was initially treated with orthotic bracing; however, increasing back pain subse- quently developed together with a foot drop. Surgical de- compression and stabilization of the fracture was offered to the patient. An L-5 anterior vertebrectomy was also dis- cussed, and minimally invasive decompression and pedicle screw fixation of L4–S1 were also offered to allow healing of the L-5 body fracture. The patient underwent a mini- mally invasive L-5 laminectomy and L4–S1 percutaneous instrumentation placement without any complications (Fig. 4). Given the goal of instrumentation removal after healing of the L-5 vertebral body fracture, arthrodesis was not per- formed in this case. The patient had an uncomplicated post- surgical recovery, and he was discharged home 3 days after surgery with significant pain and neurological improve- ment. Three months after surgery, a CT scan demonstrated healing of the L-5 vertebral fracture, and thus the percuta- neous instrumentation was subsequently removed. Flexion and extension radiographs obtained following instrumenta- tion removal revealed a normal range of motion in the lum- bosacral spine (Fig. 5). Six years after the initial surgery, the patient was still extremely satisfied with the operation. He is without any significant lower-back pain and requires no routine analgesics.
Cases Review. These illustrative cases demonstrate that MIS can be applied to traumatic spine injuries and lead to operative goals identical to those sought in conventional open surgeries. In both patients, spinal fixation was ach- ieved with percutaneous instrumentation. In our experi-
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FIG. 2. Case 1. Left: Lateral radiograph demonstrating percutanous placement of pedicle screws and rod. Right: Anteroposterior radiograph showing the percutaneous pedicle screw instrumentation construct.
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ence, percutaneous instrumentation and minimally invasive decompression, compared with open surgeries, lead to a substantial reduction in the infection rate, blood loss, the transfusion rate, and cardiopulmonary complications from fluid resuscitation. These advantages are particularly valu- able in patients with medical comorbidities or those with multiorgan traumas who are at risk for significant medical complications perioperatively.
In contrast, a potential disadvantage of MIS feared by spine surgeons is the inability to perform adequate arthro- desis and achieve long-term osseous fusion. In actuality, excellent arthrodesis can be successfully achieved through MIS by facet joint arthrodesis or interbody arthrodesis. Moreover, our illustrative cases revealed that the biological milieu of the patient has a significant impact. In patients with ankylosing spondylitis, as in the patient in Case 1, ankylosis is likely to ensue with spinal stabilization and apposition of the fracture sites. With ankylosis of the spine from ankylosing spondylitis and subsequent healing of the T-11 fracture, instrumentation removal was unnecessary in our patient. In addition, the removal of percutaneous instru- mentation is challenging with current minimally invasive techniques. In the patient in Case 2, the L-5 fractured body was allowed to heal with internal fixation. With the healed vertebral body a posterior fusion was unnecessary, and in- strumentation could be removed subsequently to salvage spinal mobility across the previously fractured level. This scenario is far more desirable in a young individual com- pared with a fusion across the lumbosacral junction.
Spinal Deformity
Spinal deformity with imbalance of coronal and sagittal alignment of the spine from various causes can result in neurological compromise, poor cosmesis, and pain. These factors can impart significant debilitation of psychosocial and functional well-being.2 In cases of severe spinal defor- mity, patients can suffer considerable physiological com- promise, including a decline in cardiopulmonary capacity. Surgical treatment for spinal deformity is indicated in patients with severe kyphoscoliosis, rapid curve progres- sion, severe pain, or poor cosmesis.
Dating back to the early 20th century, traditional surgical treatment for spinal deformity involves long-segment
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FIG. 3. Case 2. Axial CT scan demonstrating the L-5 burst frac- ture with bone fragment retropulsion into the canal and encroach- ment of the spinal canal and lateral recess.
FIG. 4. Case 2. Left: Axial CT scan revealing spinal canal and lateral recess decompression following minimally invasive laminectomy. Right: Sagittal CT scan demonstrating no significant residual retropulsion of the L-5 burst frac- ture and acceptable sagittal alignment following percutaneous instrumentation,.
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spinal fusions. Surgeries for the correction of a spinal de- formity are time-consuming and technically demanding. In addition, these surgeries are often associated with a high perioperative morbidity rate. The overall complication rate in adult patients undergoing spinal deformity surgery ranges from 40 to 86%, and major morbidities occur in ~
20% of cases.1,4,22 Other than neurological injury, major complications include infection, myocardial infarction, car- diac failure, pulmonary embolism, acute respiratory dis- tress syndrome, transfusion-related lung injury, renal fail- ure, and even death. Patients older than 60 years with medical comorbidities have a particularly increased risk.4
It has been projected that adults 55–64-years-old are the fastest growing segment of our population. As the elderly population expands over the next decade, there will be an increasing number of patients presenting with degenerative spine diseases and adult degenerative scoliosis. More patients will seek surgical treatment to improve pain symp- toms and quality of life. Most of the elderly patients will have medical comorbidities and an increased risk of peri- operative complications; therefore, any intervention that can reduce the perioperative morbidity associated with spinal deformity surgery in the elderly may have a signifi- cant impact on clinical outcomes and reduce healthcare costs.
The first attempt to utilize minimally invasive proce- dures in spinal deformity surgery occurred in 1993 with the use of endoscopic techniques in thoracic spine surgery.23
Thoracoscope-assisted procedures for spinal deformity are performed for anterior releases to increase both the flexi- bility of the spine and the fusion surface area with anterior intervertebral fusions.25,26,40 Advantages of thoracoscopic surgery for spinal deformity include decreased surgical trauma, scarring, postoperative pain, and perioperative morbidity. In addition, compared with posterior approach- es, anterior procedures in spinal deformity surgeries can re- duce the number of fusion segments required to achieve curve correction.26
Over the past several years, minimal-access lateral ap- proaches to the lumbar spine have been developed for lum- bar interbody fusion.8,28,38 Through small flank incisions and by using the retroperitoneal approach, anterior lumbar disectomy and interbody fusion can be performed from
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FIG. 5. Case 2. Lateral flexion (left) and extension (right) radiographs demonstrating normal excursion of the lum- bosacral spine without spinal instability.
FIG. 6. Case 3. Long-cassette posteroanterior (left) and lateral (right) radiographs showing the preoperative coronal and sagittal alignment, respectively.
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L1–2 down to L4–5 through minimal-access retractors. With variation in the approaches, direct access to the thora- columbar segments and even the thoracic spine can be per- formed safely and with ease. These lateral approaches are particularly useful in the treatment of lumbar or thoraco- lumbar curves that are associated with adult degenerative scoliosis. They allow anterior releases to increase the flex- ibility of the spine in patients with rigid curves, and they allow placement of large intervertebral grafts to increase the fusion surface area. Strategically placed interbody grafts can result in substantial sagittal and coronal corrections. Furthermore, similar to the experience with thoracoscope- assisted surgeries, anterior releases and correction of curves via minimally invasive lateral approaches in the lumbar spine can result in a decreased number of fusion levels.
Minimally invasive techniques can be applied in spinal deformity surgery via posterior approaches as well as the anterior approaches. Percutaneous instrumentation can be applied for additional segmental stabilization following anterior releases and intervertebral fusions. Moreover, SPOs can be performed through minimal-access retractors with decreased disruption of normal soft tissues. With the latest percutaneous instrumentation technologies, safe clo- sure of osteotomies can be performed to increase segmen- tal lordosis and to allow apposition of osseous surfaces for subsequent fusion.
Illustrative Case
Case 3. This 61-year-old woman with a history of ado- lescent idiopathic scoliosis had been monitored for her spinal deformity for many years (Fig. 6). Over the last few years, she experienced late progression of the adolescent idiopathic scoliosis (Lenke Curve Type 5) with increasing pain and deformity. After nonsurgical management of her symptoms failed, surgical correction of the deformity and instrumented fusion of the spine were recommended. A 2- stage minimally invasive approach was then applied. In the first stage, she underwent the placement of percutaneous instrumentation from T10–L3 in conjunction with SPOs at T11–12, T12–L1, and L1–2 through a minimal access tubular retractor. Posterior deformity correction was per- formed using segmental instrumentation after the SPO releases. To provide anterior support and fusion, the second stage of the procedure was performed 8 days after the first stage. Direct lateral discectomies and interbody arthrodesis with cage placement were performed through minimal- access retractors at T12–L1, L1–2, and L2–3. The total operative time was 8 hours for the first-stage procedure and 5 hours for the second. Estimated blood loss in the patient was 1 L over both procedures, and the patient received only 2 units of transfused blood during both perioperative peri- ods. Postoperative standing long-cassette radiographs demonstrated balanced coronal and sagittal alignment (Fig. 7). The patient had an uncomplicated recovery, and she was discharged from the hospital 11 days following the first- stage procedure.
Case Review. Over recent years, minimally invasive surgical approaches, techniques, and technologies have evolved to allow spinal deformity surgeons to accomplish traditional goals through smaller incisions, with limited normal tissue disruption and minimal-access retractors. Our illustrative case reveals that deformity correction and stabilization of the spine while preserving coronal and sagittal balance are possible with MISs. In degenerative disease, MIS has been shown to decrease blood loss, the hospitalization stay, and the postoperative recovery period. Minimally invasive surgery in spinal deformity is still in its infancy and experience with the procedure is too limited to draw generalized conclusions; however, our early experi- ence with minimally invasive procedures in spinal defor- mity has been associated with decreased perioperative blood loss and need for transfusions. The reduced blood loss will decrease the cardiopulmonary morbidity that typ- ically follows aggressive fluid resuscitation. Moreover, the decreased transfusion rate will reduce the likelihood of transfusion-related lung injuries, which has become the most common cause of death after blood transfusion.1,45,46
Additional clinical experience with minimally invasive procedures in spinal deformity will determine if these fac- tors can truly decrease major perioperative complication rates in the elderly and improve their clinical outcomes.
Spinal Oncology
Currently, . 1.4 million new cases of cancer are diag- nosed annually in the U.S., with ~ 500,000 patients in these cases dying annually from metastatic disease. Although primary tumors of the spine are not common, improve-
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6 Neurosurg. Focus / Volume 25 / August 2008
FIG. 7. Case 3. Long-cas- sette posteroanterior (left) and lateral (right) radiographs revealing postoperative improvement of the thora- columbar curve with mainte- nance of coronal and sagittal balance.
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ments in the treatment of systemic cancer combined with advancements in imaging technology will likely result in an increasing incidence of spine metastases. Symptomatic lesions may contribute to substantial pain and neurological dysfunction in a large proportion of patients, and thus sound treatment of spinal metastases is especially relevant.
In general, the treatment of metastatic lesions in the spine is considered palliative at best, with survival chiefly affect- ed by the extent and control of systemic disease. Nonethe- less, the management of metastatic spinal lesions can dras- tically improve quality of life, especially as it pertains to debilitating pain and loss of ambulatory ability. Although the treatment of these tumors has involved radiation thera- py as the primary modality, surgical intervention has be- come an essential component of care. In a recent prospec- tive randomized trial Patchel et al.29 showed that surgical decompression plus radiation therapy was superior to radi- ation therapy alone in the treatment of metastatic epidural spinal cord compression with regard to neurological func- tion. Surgeries performed in that study involved direct de- compressive procedures with spinal reconstruction. Al- though these procedures were not minimally invasive, the application of techniques less destructive to the paraspinal soft tissues would likely provide similar results if the goals of decompression and stabilization were equally met.
Patients with systemic cancer face a greater likelihood of surgical complications and postoperative morbidity.3,7,21 For instance, it has been shown repeatedly in the literature that
the resection of a spine tumor is associated with more post- operative surgical site infections than spine operations for other indications.3 Factors likely contributing to such peri- operative morbidity include lower preoperative functional status, poorer nutrition, immunosuppression, chronic ste- roid use, and in some cases previous radiation to the site of surgery. Thus, for cases in which surgery is being consid- ered, large tissue dissection can lead to increased wound complications. Minimally invasive spine surgeries through smaller incisions can mitigate such wound complications by limiting collateral damage to surrounding soft tissues during exposure and instrumentation.
One of the first minimally invasive techniques used to treat spine tumors was percutaneous placement of poly- methylmethacrylate cement. With fluoroscopic guidance, this cement can be placed percutaneously to fill the verte- bral body directly (vertebroplasty) or after kyphosis has been reduced via internal expansion of a balloon device (kyphoplasty).14,15 The application of cement often provides immediate pain relief, likely as a result of the stabilization of fractures and reduction in micromobility, but also possi- bly due to thermal damage to small pain fibers resulting from the exothermic reaction involved during cement cur- ing. Regardless, although such treatment can provide ex- cellent and immediate pain relief via a noninvasive percu- taneous approach, it does nothing to treat the local oncological disease.
Hence, cement augmentation techniques are often com-
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FIG. 8. Case 4. Left: Preoperative sagittal T2-weighted MR image demonstrating metastatic spine tumor involve- ment of the T-4 and T-5 vertebral bodies. There are pathological fractures of the vertebral bodies with retropulsion of bone into the spinal canal. Right: Preoperative axial T2-weighted MR image at the T-5 level revealing severe spinal cord compression and loss of cerebrospinal fluid space around the cord.
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bined with radiation therapy.16 Classically, such treatment involves the standard delivery of ionizing radiation to the diseased spinal segment and to 2 segments above and below the index level. In cases of local tumor recurrence, however, such radiation therapy cannot be repeated be- cause of the potentially supratherapeutic dosage of radia- tion directed at the spinal cord and neighboring tissues. Therefore, radiation that can be delivered in a focal manner has been used more recently to overcome this problem. Such techniques, commonly referred to as “radiosurgery” or “image-modulated radiation therapy,” are used to deliv- er multiple doses of radiation to the lesion, with each dose representing only a small proportion of the total dose. By changing the trajectory through normal tissue during each exposure (radiosurgery) or by carefully collimating the ra- diation so that there is a steep decline in radiation intensity around the lesion (image-modulated radiation therapy), larger doses of ionizing energy can be delivered to the path- ological segment while minimizing damage to surrounding nonneoplastic tissues. Such techniques thus allow treat- ment of recurrent spine lesions and tumors usually consid- ered radiation insensitive.17
Although both percutaneous vertebroplasty/kyphoplasty and radiosurgery are effective in addressing pain or local disease control, they do not address the spinal instability and deformity resulting from metastatic tumor involve- ment. The evolution of MIS for spinal tumors in recent years has involved direct removal of the lesion with instru- mented fixation of the spine. Through minimal-access tu- bular retractors placed at the diseased levels, direct tumor resection and spinal cord decompression can be performed with limited soft tissue and muscle dissection. Moreover, stabilization can be achieved in a similar minimally inva-
sive manner by using simultaneous percutaneous instru- mentation with cement reconstruction and/or placement of an intervertebral structural graft.
Illustrative Case
Case 4. This 39-year-old man with a 6-month history of back pain presented to an outside hospital with increasing back pain associated with lower-extremity paresthesia. During a medical workup, the patient was found to have T- 4 and -5 vertebral fractures and a right lung mass on radi- ography. A biopsy specimen of the lung mass indicated pri- mary lung adenocarcinoma. Computed tomography and MR imaging of his spine demonstrated pathological frac- tures of T4 and -5 vertebral bodies from metastasis with significant epidural disease (Fig. 8). The patient also had intermittent paresthesia and mild lower-extremity weak- ness of 4+/5 in strength. He was offered a minimally inva- sive laminectomy and vertebrectomy of T4–5 for decom- pression with an instrumented fusion of the thoracic spine involving T1–8. After obtaining informed consent, the patient underwent percutaneous instrumented fusion of T1–8 with laminectomy and costotransversectomy for ver- tebrectomy of the T-4 and -5 metastatic tumor through bilateral expandable minimal-access retractors (Fig. 9). An intervertebral distractible cage was placed through the min- imal-access retractor for reconstruction of the T4–5 anteri- or and middle columns following vertebrectomy. The patient tolerated the procedure well without complications. The total operative time was ~ 7 hours, and the total esti- mated blood loss was 1.2 L. The patient had preoperative anemia, and he subsequently required 2 units of transfused blood during the perioperative period. A postoperative CT
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FIG. 9. Case 4. Intraoperative photograph showing the 2-level vertebrectomy performed through minimal-access retractors along with simultaneous percutaneous instrumented fusion.
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demonstrated circumferential decompression of the disease at T-4 and -5 with circumferential instrumented reconstruc- tion of the spine (Fig. 10). The patient had an uncomplicat- ed postoperative course, and he was discharged from the hospital 5 days after his surgery.
Case Review. In the surgical treatment of patients with metastatic spine tumors, the theoretical limitation of os- seous fusion with MIS is insignificant. Patients with symp- tomatic metastatic spine tumors generally have an average lifespan of ~ 6–12 months. Treatment goals in these pa- tients are the preservation of neurological function, stabi- lization of the spine, and improvement in pain. Generally, decompression and instrumentation without arthrodesis are sufficient to achieve these goals in most of these patients. Furthermore, almost all of these patients will receive ste- roids and chemotherapy and undergo radiation treatment. Therefore, even the most meticulous arthrodesis techniques may not result in osseous fusion in long-term survivors.
In our illustrative case, a 2-level thoracic laminectomy and vertebrectomy for a symptomatic metastatic spinal tumor was performed with successful decompression of the spinal cord through bilateral minimal-access retractors. Final instrumented reconstruction and stabilization of the spinal column was performed with the placement of a dis- tractable cage through the minimal-access retractor and the placement of percutaneous pedicle screw instrumentation. In the patient in this case, circumferential decompression and reconstruction of the spinal column was completed successfully without complications. In our early experi- ence, compared with the open procedures, MIS of the spine for these cases resulted in decreased blood loss and faster recovery in the subacute recovery phase at ~ 2–4 weeks fol- lowing surgery. Furthermore, the smaller incisions and lim- ited soft tissue disruption led to a reduction in the infection rate and wound complications. Overall, a wide variety of MIS options are now available for the treatment of patients
with metastatic spine tumors. Combinations of the various MIS options with medical therapies, such as chemotherapy and radiation therapy, will likely continue to improve our ability to treat patients with cancer.
Conclusions
As spine surgeons become more experienced and facile with MIS techniques and procedures, the application of these strategies for complex spinal disorders will continue to increase. Currently, advancements in surgical technolo- gy and techniques as well as early clinical results have dri- ven surgeons to expand the use of MIS in the spine. Never- theless, prospective and long-term clinical studies are needed to demonstrate the true clinical benefits. Although the case illustrations herein were presented to outline the great potential of using MIS in severe spinal pathologies, future prospective studies on outcomes following open spine surgery vs. MISs for such disorders will likely dem- onstrate the tangible benefits of the different approaches.
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FIG. 10. Case 4. Postoperative CT scan (A) demonstrating central canal decompression with cage placement for ante- rior reconstruction. Postoperative anteroposterior (B) and lateral (C) radiographs showing the final construct following circumferential T4–5 decompression and T1–8 percutaneous instrumented fusion.
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