An unusual complication of anterior spinal instrumentation: hemothorax contralateral to the side of the incision. A case report

Hemoptysis Due to Anterior Scoliosis Implants: A Case Report

CASE

A twenty-five-year-old man presented with recurrent episodes of hemoptysis requiring hospitalization and interventional embolization. Instrumentation that had been implanted ten years previously for anterior spinal correction and fusion to treat adolescent idiopathic scoliosis adjoined the medial border of the right lung. The instrumentation eroded the lung during respiration, which prompted the formation of adhesions and fibrosis. Because of the risk of additional hemoptysis events, we performed revision thoracotomy, removal of the spinal instrumentation, and partial lobectomy.

CONCLUSION

This rare and serious complication underscores the importance of meticulous surgical technique to ensure proper implant placement and of vigilant monitoring for late iatrogenic injury.

Hemothorax caused by the trocar tip of the rod inserter after minimally invasive transforaminal lumbar interbody fusion: case report

Minimally invasive surgery (MIS) for transforaminal lumbar interbody fusion (MIS-TLIF) is widely used for lumbar degenerative diseases. In the paper the authors report a unique case of a hemothorax caused by the trocar tip of the rod inserter after MIS-TLIF. A 61-year-old woman presented with thigh pain and gait disturbance due to weakness in her lower right extremity. She was diagnosed with a lumbar disc herniation at L1-2 and the MIS-TLIF procedure was performed. Immediately after surgery, the patient's thigh pain resolved and she remained stable with normal vital signs. The next day after surgery, she developed severe anemia and her hemoglobin level decreased to 7.6 g/dl, which required blood transfusions. A chest radiograph revealed a hemothorax. A CT scan confirmed a hematoma of the left paravertebral muscle. A chest tube was placed to treat the hemothorax. After 3 days of drainage, there was no active bleeding. The patient was discharged 14 days after surgery without leg pain or any respiratory problems. This complication may have occurred due to injury of the intercostal artery by the trocar tip of the rod inserter. A hemothorax after spine surgery is a rare complication, especially in the posterior approach. The rod should be caudally inserted in the setting of the thoracolumbar spine.

Single screw-rod anterior instrumentation for thoracolumbar burst fractures with incomplete neurological deficit

PURPOSE

To evaluate the outcome of single screwrod anterior instrumentation for thoracolumbar burst fractures with incomplete neurological deficit.

METHODS

16 men and 5 women aged 22 to 55 (mean, 34) years underwent single screw-rod anterior instrumentation for thoracolumbar burst fractures with incomplete neurological deficit. The vertebrae involved were T10 (n=2), T11 (n=2), T12 (n=7), L1 (n=8), and L2 (n=2). No patient had disruption of the posterior ligament complex. Postoperatively, a thoracolumbar sacral orthosis was used until solid fusion. Outcome measures included neurological recovery, degree of kyphosis, complications, and pain and functional status of the patients.

RESULTS

The mean follow-up duration was 36 (range, 13-50) months. All patients recovered neurologically by at least one grade. Of the 21 patients, 6 improved from grade B to grade C (n=4) or grade D (n=2), 13 from grade C to grade D, and 2 from grade D to grade E. The mean degree of kyphosis improved from 23º ± 5º to 7º ± 3º. Seven patients had complications including ipsilateral basal atelectasis (n=3), urinary tract infection (n=1), haematuria (n=1), postoperative ileus (n=1), and superficial wound infection (n=1). None had iatrogenic visceral or vascular injury, pseudoarthrosis or hardware-related complications. Only one patient had severe back pain persistently.

CONCLUSION

Single screw-rod anterior instrumentation supplemented with an orthosis can be an alternative for double screw-rod anterior instrumentation for thoracolumbar burst fractures in patients with smaller vertebral bodies.

Delayed-iatrogenic injury of the thoracic aorta by an anterior spinal instrumentation

We present a case of a 15-year-old girl who presented to us with an unusual low back pain. About 7 years ago, this patient had corrective surgery for her idiopathic left thoracolumbar scoliosis. Recent surgery revealed a laceration of the posterior wall of the thoracic aorta by an impending screw thread. This injury was repaired by the vascular surgeons and, subsequently, the patient had full recovery without any complications.

Late spontaneous hemothorax complicating anterior spinal instrumentation in adolescent idiopathic scoliosis

STUDY DESIGN

Case report.

OBJECTIVE

Describes a case report of a 16-year-old woman treated for adolescent idiopathic scoliosis (AIS) by anterior spinal fusion and instrumentation, who developed a spontaneous massive intrathoracic bleeding 10 months after surgery.

SUMMARY OF BACKGROUND DATA

Hemothorax (HT) is a known rare postoperative complication of anterior spinal scoliosis surgery. However, spontaneous HT has never been described as a late complication, in relationship to diaphragm movement over the anterior instrumentation material.

METHODS

Retrospective case report.

RESULTS

A 16-year-old woman with Lenke type I AIS underwent a successful anterior spinal fusion with instrumentation. After surgery, there were no complications, however, she experienced a distressing grating sensation while breathing. Ten months after surgery, the patient developed a spontaneous HT that needed emergency surgery. Erosion of a small artery in the scar tissue around the most caudal screw of the instrumentation proved to be the cause of the late HT. Subsequent dynamic magnetic resonance imaging showed the relationship between the moving diaphragmatic muscles and the most caudal screws of instrumentation material during breathing. Sixteen months after the initial surgery, the anterior instrumentation was removed.

CONCLUSION

Late spontaneous HT in patients with anterior fusion and instrumentation for AIS is a rare but life-threatening complication.

Influence of screw positioning in a new anterior spine fixator on implant loosening in osteoporotic vertebrae

STUDY DESIGN

A biomechanical study was designed to assess implant cut-out of three different angular stable anterior spinal implants. Subsidence of the implant relative to the vertebral body was measured during an in vitro cyclic loading test.

OBJECTIVES

The objective of the study was to evaluate two prototypes (Synthes) of a new anterior spine fixator with different screw angulations in comparison to the established MACSTL(R) Twin Screw Concept (Aesculap). The influence of factors like load-bearing cross-sectional area, screw angulation and bone mineral density upon implant stability should be investigated.

SUMMARY OF BACKGROUND DATA

Epidemiologic data predict a growing demand for appropriate anterior spinal fixation devices especially in patients with inferior structural and mechanical bone properties. Although different concepts for anterior spinal instrumentation systems have been tried out, implant stability is still a problem.

METHODS

Three angular stable, anterior spinal implants were tested using 24 human lumbar osteoporotic vertebrae (L1-L5; age 84 (73-92)): MASC TL system (Aesculap); prototype 1 (MP1) with 18 degrees and prototype 2 (MP2) with 40 degrees screw angulation (both Synthes). All implants consisted of two screws with different outer screw diameters: 7-mm polyaxial screw with 6.5-mm stabilization screw (MASC TL), two 5-mm locking-head screws each (MP1 and MP2). Bone mineral density (BMD) and vertebral body width of the three specimen groups were evenly distributed. The specimens were loaded in craniocaudal direction (1Hz) for 1000 cycles each at three consecutive load steps; 10-100 N, 10-200 N and 10-400 N. During cyclic loading subsidence of the implant relative to the vertebral body was measured in the unloaded condition. Cycle number at failure (defined as a subsidence of 2 mm) was determined for each specimen. A survival analysis (Cox Regression) was performed to detect differences between implant groups at a probability level of 95%.

RESULTS

High correlations were found between BMD and number of cycles until failure (MP1; r = 0.905, P = 0.013; MP2: r = 0.640, P = 0.121; MACS TL: r = 0.904, P = 0.013) and between load bearing cross sectional area and number of cycles until failure (MP1: r = 0.849, P = 0.032;MP2: r = 0.692, P = 0.085; MACS TL: r = 0.902, P = 0.014). Both Prototypes survived significantly longer than the MACS TL implant (MP1: P = 0.012, MP2: P = 0.014). The survival behaviour of MP1 and MP2 was not significantly different (P = 0.354).

CONCLUSIONS

Implant stability within each implant group was influenced by BMD and load bearing cross-sectional area. The angulation of the two screws did not have a significant influence on cut-out. As conclusion from this study, promising approaches for further implant development are: 1) increase of load-bearing cross-sectional area (e.g., larger outer diameter of the anchorage device), 2) screw positioning in areas of higher BMD (e.g., opposite cortex, proximity to pedicles or the endplates).

Thoracic vertebral screw impingement on the aorta in an in vivo bovine model

STUDY DESIGN

A bovine model was used to evaluate the effects of thoracic vertebral screw impingement of the aorta.

OBJECTIVES

To evaluate the histologic and biomechanical changes in aortic wall tissue that was severely impinged by abutting instrumentation.

SUMMARY OF BACKGROUND DATA

Case reports of vascular injury associated with spinal instrumentation generally describe intraoperative injury; some report delayed presentation of large vessel damage. Risks associated with placing instrumentation adjacent to large vessels are largely unknown.

METHODS

Six 1-month-old calves underwent left-sided thoracotomies, exposing the anterior thoracic spine and aorta. With the heads removed, screws were inserted in reverse fashion into T6 through T11, leaving the screw tips 1 cm proud and abutting the aorta. After 3, 6, or 12 months (2 calves each), the spines were resected with the adjacent aorta and underwent radiographic, histologic, and biomechanical testing.

RESULTS

Computed tomography revealed varying degrees of vessel impingement. Although there were no frank ruptures, 96% of aortic specimens showed histopathologic changes, including 52% with wall thinning; 43% were no longer impinged, yet 60% of these had increased collagen (scar). Biomechanical testing of screw-impinged aortas demonstrated a lower failure stress (1.2 +/- 0.5 N/mm vs. 1.8 +/- 0.4 N/mm, P = 0.016) but no difference in failure strain (42 +/- 9% vs. 32 +/- 10%, P = 0.06) than controls.

CONCLUSIONS

Major impingement of vertebral screws on the aorta caused acute and chronic histopathologic and biomechanical changes in the vessel wall. This model represents a severe form of vessel penetration by a screw that confirms such a "worst case" scenario results in marked compromise of the vessel wall integrity. The sequelae of less severe impingement are unknown.

Structures at risk following anterior instrumented spinal fusion for thoracic adolescent idiopathic scoliosis

OBJECTIVES

With the increasing popularity of anterior instrumented spinal fusion for adolescent idiopathic scoliosis, there has also been a rising concern over the proximity of the descending aorta to the screw tips and the possibility of vessel wall erosion over time. This computed tomography (CT) study attempts to define the relative position of the thoracic aorta and other vital structures to the spine (preoperatively) and to the projected instrumentation (postoperatively) by level and curve magnitude in deformity patients.

METHODS

Twenty consecutive patients (17 female, 3 male) with an average age of 14.5 years (range 12.4-18.5 years) and a right main thoracic/Lenke 1 curve (average 55.2 degrees , range 50-66 degrees ) underwent preoperative and postoperative CT scanning as part of their planned open anterior spinal fusion with instrumentation. All images were analyzed for proximity (distance from the midvertebral body) and position to (as defined relative to the center of the vertebral body in the axial plane) the spine preoperatively and the projecting screw tip postoperatively. As a control, 10 age-matched nondeformity thoracic CT scans were analyzed to assess the relative position of the thoracic aorta to the vertebral bodies by level. Preoperative and postoperative plain radiographs were also analyzed for curve magnitude, correction, and fusion levels to assess the possible effect of these variables on the various thoracic structures.

RESULTS

The postoperative curve magnitude averaged 26.9 degrees (range 17-40 degrees ; 51% correction) using 151 screws (7.5 screws/patient) and an average follow-up of 4.1 years (range 3.2-7.0 years). Screw-to-spinal-canal distance averaged 5.3 mm (range 3.5-8.2 mm) at an average of +4.5 degrees (range -11 degrees to +15 degrees ) from the coronal axis. Screw tip extrusion (distance beyond the far cortex) averaged 2.8 mm (0-5 mm). The trachea, azygous vein, esophagus, and lungs/pleura were not found to be at risk from screw penetration. The postoperative screw-tip-to-descending-aorta distance varied by vertebra level, with the periapical and distal screws being positioned closer to the aorta (1.6-2.4 mm) (P < 0.05). Additionally, 23 of 151(15%) screws were thought to be adjacent (</=2 mm) to the aorta. This includes 4 of 60 (7%) of the proximal screws but 6 of 40 (15%) of the periapical screws and 13 of 51 (26%) of the distal screws (P < 0.05). There were no screws compressing the aorta and no perioperative or postoperative complications.

CONCLUSIONS

The course of the thoracic aorta may vary in individuals; however, in deformity patients, it generally moves from a relatively anterolateral position proximally to a posteromedial position at the apex. Distally, it moves more anteriorly. Consequently, the aorta moves closer to the screw tips both at the apex and distally, whereas the distal screws are more frequently juxtaposed to the descending aorta (P < 0.05).

A biomechanical analysis of triangulation of anterior vertebral double-screw fixation

OBJECTIVE

This study tested the hypothesis that triangulation of two anterior vertebral screws without penetration of the cortex offers more resistance to pullout than two screws placed in parallel and penetrated.

DESIGN

The pullout strength for two parallel or two triangulated anterior vertebral screws fixation, with a uni-cortical or bi-cortical purchase, were tested and compared to the strength of a single-screw fixation with a bi-cortical purchase. Four porcine spines (six months old) were used for biomechanical test and bone mineral density was measured for each specimen before testing.

BACKGROUND

The potential hazards from penetration by anterior vertebral cortex screws including neurovascular and organs injuries are well documented. However, bi-cortical screw penetration is widely recognized as necessary for good anterior spinal stabilization. The authors are not aware of any biomechanical study on the anterior placement of triangulated vertebral screws without penetration and its effect on the fixation strength of anterior vertebral device remains unclear.

METHODS

In this study five modes of screw fixations in lateral vertebral bodies were performed: Group A, triangulated screws with one screw penetration; Group B, triangulated screws without penetration; Group C, parallel penetrating screws; Group D, parallel nonpenetrating screws; and Group E, a single-screw with bi-cortical purchase. Biomechanical analysis with a material testing system machine was performed to determine the pull out strength of each configuration.

RESULTS

The results showed that the pullout strength in the various double-screw fixation modes were statistically increased as compared to that of the single-screw with bi-cortical purchase mode. There existed statistical differences (P<0.05) between Groups A and B, Groups C and D and Groups D and E, respectively. However, no significant difference was found between Groups B and C (P=0.144).

CONCLUSIONS

Based on the current data, triangulation of two anterior vertebral screws without penetration of the cortex (Group B) achieved pullout strengths similar to that of two-parallel double-cortical screws (Group C). The authors believe that this is an attractive alternative in anterior spinal instrumentation avoiding the potential risks of cortical penetration. However, in the event of pullout failure, the triangulation configuration will produce a more disastrous consequence.

RELEVANCE

Triangulation of two anterior vertebral screws without penetration of the cortex achieve pullout strengths similar to that of two-parallel double-cortical screws. This is an attractive alternative in anterior spinal instrumentation that avoids the potential risks of cortical penetration.