Robotic assisted spinal surgery--from concept to clinical practice.

After several years of product development, animal trials and human cadaver testing, the SpineAssist--a miniature bone-mounted robotic system--has recently entered clinical use. To the best of the authors' knowledge, this is the only available image-based mechanical guidance system that enables pedicle screw insertion with an overall accuracy in the range of 1 mm in both open and minimally invasive procedures. In this paper, we describe the development and clinical trial process that has brought the SpineAssist to its current state, with an emphasis on the various difficulties encountered along the way and the corresponding solutions. All aspects of product development are discussed, including mechanical design, CT-to-fluoroscopy image registration, and surgical techniques. Finally, we describe a series of preclinical trials with human cadavers, as well as clinical use, which verify the system's accuracy and efficacy.

Functional outcomes of kyphoplasty for the treatment of osteoporotic and osteolytic vertebral compression fractures.

INTRODUCTION: Vertebral body compression fractures secondary to osteoporosis or malignant osteolysis are an increasingly common problem. The primary purpose of our study was to assess functional outcomes of kyphoplasty for the treatment of osteoporotic and osteolytic vertebral compression fractures. Our secondary purpose was to compare such functional outcomes in patients with osteoporosis versus multiple myeloma. METHODS: The 314 consecutive patients prospectively included in our study had progressive and painful compression fractures as a result of osteoporosis or multiple myeloma that were refractory to nonoperative modalities. Of those 314 patients, the 211 (67.2%) patients (155 with osteoporosis and 56 with multiple myeloma) who had complete preoperative and postoperative data formed our final study group. All patients tolerated the kyphoplasty procedure well (that is, there were no adverse events in terms of perioperative patient condition). Follow-up ranged from 1 to 235 weeks (mean 55.0 weeks). Functional outcomes were assessed by the SF-36 and Oswestry Disability Index at baseline and at follow-up examinations. Data were analyzed by Student's t-test and the level of significance was set at P

Kyphoplasty in the treatment of osteolytic vertebral compression fractures as a result of multiple myeloma.

PURPOSE: We prospectively evaluated the safety and efficacy of kyphoplasty in the treatment of osteolytic vertebral compression fractures resulting from multiple myeloma. The principle symptoms in multiple myeloma result from bone destruction, especially the spine. Kyphoplasty is a new technique that involves the introduction of inflatable bone tamps (IBT) into the vertebral body. The purpose of the IBT is to restore the vertebral body back toward its original height, while creating a cavity that can be filled with highly viscous bone cement. PATIENTS AND METHODS: Fifty-five consecutive kyphoplasty procedures were performed in 18 patients with osteolytic vertebral compression fractures resulting from multiple myeloma. Cement leakage and any complications were recorded. Early objective analysis was made by comparing preoperative and latest Short Form 36 Health Survey scores. Height restoration was estimated by measuring vertebral height on lateral radiographs. RESULTS: The mean age of patients was 63.5 years, mean duration of symptoms was 11 months, and mean follow-up was 7.4 months. There were no major complications related directly to use of this technique. On average, 34% of height lost at the time of fracture was restored. Asymptomatic cement leakage occurred at two (4%) of 55 levels. Significant improvement in SF36 scores occurred for Bodily Pain (23.2 to 55.4, P =.0008), Physical Function (21.3 to 50.6, P =.0010), Vitality (31.3 to 47.5, P =.010), and Social Functioning (40.6 to 64.8, P =.014). CONCLUSION: Kyphoplasty was efficacious in the treatment of osteolytic vertebral compression fractures resulting from multiple myeloma. Kyphoplasty is associated with early clinical improvement of pain and function as well as some restoration of vertebral body height.

Initial outcome and efficacy of "kyphoplasty" in the treatment of painful osteoporotic vertebral compression fractures.

STUDY DESIGN: An Institutional Review Board-approved Phase I efficacy study of inflatable bone tamp usage in the treatment of symptomatic osteoporotic compression fractures. OBJECTIVES: To evaluate the safety and efficacy of inflatable bone tamp reduction and cement augmentation, "kyphoplasty," in the treatment of painful osteoporotic vertebral compression fractures. SUMMARY OF BACKGROUND DATA: Osteoporotic compression fractures can result in progressive kyphosis and chronic pain. Traditional treatment for these patients includes bed rest, analgesics, and bracing. Augmentation of vertebral compression fractures with polymethylmethacrylate, "vertebroplasty," has been used to treat pain. This technique, however, makes no attempt to restore the height of the collapsed vertebral body. Kyphoplasty is a new technique that involves the introduction of inflatable bone tamps into the vertebral body. Once inflated, the bone tamps restore the vertebral body back toward its original height while creating a cavity that can be filled with bone cement. PATIENTS AND METHODS: Seventy consecutive kyphoplasty procedures were performed in 30 patients. The indications included painful primary or secondary osteoporotic vertebral compression fractures. Mean duration of symptoms was 5.9 months. Symptomatic levels were identified by correlating the clinical data with MRI findings. Perioperative variables and bone tamp complications or issues were recorded and analyzed. Preoperative and postoperative radiographs were compared to calculate the percentage height restored. Outcome data were obtained by comparing preoperative and latest postoperative SF-36 data. RESULTS: At the completion of the Phase I study there were no major complications related directly to use of this technique or use of the inflatable bone tamp. In 70% of the vertebral bodies kyphoplasty restored 47% of the lost height. Cement leakage occurred at six levels (8.6%).SF-36 scores for Bodily Pain 11.6-58.7, (P = 0.0001) and Physical Function 11.7-47.4, (P = 0.002) were among those that showed significant improvement. CONCLUSIONS: The inflatable bone tamp was efficacious in the treatment of osteoporotic vertebral compression fractures. Kyphoplasty is associated with early clinical improvement of pain and function as well as restoration of vertebral body height in the treatment of painful osteoporotic compression fractures.

Three-dimensional computed tomographic volume rendering techniques in endoscopic thoracoplasty.

BACKGROUND CONTEXT: Thoracoplasty is occasionally necessary to achieve an acceptable cosmetic result in the presence of a rib hump, especially in previously fused young adults with scoliosis. This usually requires the resection of four to five rib segments, and the morbidity associated with open posterior resection or of open anterior resection by means of thoracotomy is often considerable, apart from leaving an unsightly scar. We thought the use of an endoscopic internal rib resection technique would achieve the desired result with less morbidity. Our experience with using the technique of three-dimensional (3-D) computed tomographic (CT) volume rendering to plan our portals and releases for endoscopic scoliosis correction led us to believe the same techniques could be adapted to plan and endoscopically carry out the thoracoplasty. PURPOSE: To define the utility of 3-D CT volume rendering of the spine and thorax in the preoperative planning of endoscopic rib resection. STUDY DESIGN: A prospective evaluation of the utility of 3-D CT volume rendering for preoperative planning in patients with scoliosis undergoing endoscopic thoracoplasty for correction of rib humps. PATIENT SAMPLE: Four consecutive patients with previously fused scoliotic spines and pronounced right-sided rib humps requiring operative correction were selected. OUTCOME MEASURES: Outcome was assessed at a minimum follow-up of 6 months by clinical examination, patient satisfaction with the clinical result, and repeat helical CT scanning with 3-D reconstruction. METHODS: Four patients with previously fused scoliotic spines and pronounced rib humps underwent helical CT scanning with 3-D volume rendering, prior to endoscopic corrective surgery. All four patients had right-sided rib humps requiring corrective rib resection for cosmetic reasons. Using the technique of 3-D volume rendering, a vector plane was created to mirror the left scapula, and its intersections on the right chest wall were noted. The ribs to be resected were marked, and the length of rib resection was measured from the vector plane's intersection points with the ribs. In this way an estimate of the resection required to achieve the desired final position of the right elevated scapula could be determined. Entry portals were also estimated with vector lines to achieve optimal access to each rib. During surgery, the portal sites were assessed for access to the selected ribs. Also, the extent of rib resections was compared with the estimates. The final clinical outcome was assessed by clinical examination, patient satisfaction with the cosmetic result, and repeat helical CT scanning with 3-D reconstruction. RESULTS: The male to female ratio was 1:3, and the average age was 21 years. Our average estimated blood loss was 307 ml and average hospital stay was 4.75 days. The estimated portal sites were accurate and did provide for direct access to each selected rib involved in the deformity. We were able to resect the ribs at the points suggested by 3-D CT volume rendering, with the lengths of our resected segments matching our preoperative estimates. In all cases the elevated right scapula did descend into the rib resection bed, thus balancing the shoulder heights. An excellent cosmetic result was achieved in all cases as evaluated by clinical examination, patient's perception, and repeat helical CT scanning. CONCLUSION: The technique of 3-D CT volume rendering with vector plane estimates provides a reliable estimate of the rib resection required to achieve a cosmetically acceptable correction of the rib hump through minimally invasive techniques.

Laparoscopic lumbar interbody spinal fusion.

Laparoscopic ALIF is an evolving technique requiring the participation of a laparoscopic surgeon experienced in advanced laparoscopic techniques and knowledgeable in anterior lumbar spinal exposures. Initial enthusiasm for this technique was fostered by the development of interbody fusion devices and a method of exposing the anterior lumbar spine, which takes advantage of the ability of minimally invasive surgeries to improve exposure and visualization while minimizing collateral tissue damage and injury to healthy tissue. Preliminary studies have demonstrated laparoscopic ALIF feasibility. These same studies have been able to prove only minor advantages with the laparoscopic versus open technique using the current implants and bone grafting techniques for single-level disc disease. General acceptance of laparoscopic ALIF awaits further investigation. Reasons for a lack of general acceptance include the expense of the interbody fusion devices and laparoscopic equipment, the unfamiliarity of this advanced laparoscopic technique to spine and general surgeons, and the steep learning curve of the procedure. Intraoperative complications that arise are often severe, such as vascular injuries. Many skeptics appropriately believe that initial enthusiasm and zealousness must be tempered with scientific effort that provides data from long-term follow-up. For laparoscopic ALIF to gain general acceptance, randomized comparisons of laparoscopic ALIF to open ALIF and posterior lumbar spinal fusion and controlled studies with long-term follow-up documenting symptomatic outcome variables and spinal fusion rates must be completed. As new modalities are developed, minimally invasive techniques may facilitate their utility. The indications, procedures, and surgical principles of ALIF are unchanged, and physicians must not invent indications to justify the technique; however, eventually we may be able to redefine the indications to take full advantage of the endoscopic techniques and biological advances.

Prone position endoscopic transthoracic release with simultaneous posterior instrumentation for spinal deformity: a description of the technique.

STUDY DESIGN: A prospective series of 15 consecutive adult patients with spinal deformity who underwent endoscopic transthoracic release with simultaneous posterior instrumentation while positioned prone. OBJECTIVES: To describe the technique and clinical results of endoscopic transthoracic release performed with the patient prone (as opposed to lateral) on the concave side for scoliosis or on either side for kyphosis, with simultaneous posterior exposure, instrumentation, and correction of the deformity. SUMMARY OF BACKGROUND DATA: Use of endoscopic surgical techniques is rapidly advancing across all subspecialties. These techniques can be used to expose and operate on the spine in a less invasive fashion, thus avoiding damage to other tissues and facilitating earlier mobilization and rehabilitation. Current endoscopic techniques with the patient in the lateral decubitus position mimic open thoracotomy. A new technique is described with the patient positioned prone, which allows simultaneous posterior exposure. METHODS: Preoperative Cobb angle or thoracic kyphosis angle, maximal correction bending films, and postoperative Cobb angle or kyphosis angle were measured and compared. All perioperative morbidity, intraoperative complications, and surgical variables were prospectively documented and analyzed. RESULTS: There were no intraoperative technical problems with the endoscopic equipment or instruments and no immediate, 6-month, or 2-year postoperative complications related to the endoscopic component of the procedure. In the scoliosis patients, the average correction was 60%. In the kyphosis patients, the average correction was 39%. CONCLUSIONS: Transthoracic endoscopic techniques, compared with thoracotomy, offer a less invasive method of accessing the anterior spinal column, with the benefits of an excellent view of the area of the spine being instrumented, minimal soft tissue disruption, and an improved cosmetic result. With the simultaneous technique, staged or subsequent procedures can be eliminated, and a circumferential structural release as well as control of the mobilized spine can be achieved. This simultaneous technique can be extended for use in correction of a variety of thoracic spinal pathologies.

Endoscopic approaches to metastatic thoracic disease.

Traditional approaches to thoracic metastases and spinal cord compression have been well worked out and validated in the literature. Anterior decompression is clearly superior to laminectomy; vertebrectomy and reconstruction are indicated for sagittal collapse, instability, and pain; and surgical decompression is necessary in cases of bony impingement. The role of endoscopic and minimally invasive techniques in treatment of metastatic disease is evolving. Dr. Lieberman advocates the use of thoracoscopic anterior approaches as the principal application in these patients, whereas Dr. McLain has found that endoscopic assistance has vastly improved his results with posterolateral decompression. The two authors weigh the relative advantages and disadvantages of these approaches for the selected patient with metastatic thoracic disease.

Transperitoneal laparoscopic exposure for lumbar interbody fusion.

STUDY DESIGN: A prospective clinical trial of the transperitoneal laparoscopic approach to the lumbar spine in a consecutive series of patients undergoing anterior lumbar interbody fusion. OBJECTIVES: To determine safety and effectiveness, and to document technique and perioperative complications of a laparoscopic exposure for lumbar interbody fusion. SUMMARY OF BACKGROUND DATA: With the widespread adoption of laparoscopic techniques, the benefits of minimal access surgery are now well recognized--in general, gynecologic and urologic surgery. Only recently have minimal access techniques been applied to spinal procedures. METHODS: Forty-seven patients with symptomatic degenerative disc disease underwent transperitoneal laparoscopic exposure of the lumbar spine to facilitate implantation of cylindrical threaded interbody fusion cages. These patients were prospectively followed and all perioperative considerations and complications were documented and analyzed. The surgical technique of laparoscopic exposure will be described. RESULTS: The laparoscopic approach was attempted in 47 consecutive patients. Forty-four were completed laparoscopically--36 single level fusions, seven two level fusions, and one three level fusion. Early in the series, conversion to open surgery was required in one patient (case #3) because of bleeding from the presacral veins which hindered the view. In one case, mobilization of the great vessels proved to be difficult, and in one other case the patient could not tolerate abdominal insufflation. The mean blood loss for the entire group was 105 mls. Complications related to the endoscopic exposure were few. There were no injuries to major vascular structures or to bowel, and no mortalities. In two patients, the cages were malpositioned necessitating repeat endoscopic exposure for cage realignment. One patient required a laparotomy for a postoperative small bowel obstruction. The median postoperative stay was 4 days. CONCLUSIONS: Transperitoneal laparoscopic exposure for single or multiple level, anterior lumbar interbody fusion can be performed with low risk. Experience in open anterior spinal surgery and laparoscopic general surgery is vital in minimizing the risks.

Occipito-cervical fusion using posterior titanium plates.

Occipito-cervical fusion may be indicated for instability of the occipito-cervical junction or atlanto-axial spine secondary to a wide spectrum of pathology. Many techniques exist to stabilize the spine until fusion is achieved. Recent reports of plate fixation have been favorable. In this study we set out to determine the effectiveness and advantages of titanium plate fixation when used to stabilize the occipito-cervical junction. Thirteen patients with occipito-cervical instability or atlanto-axial instability underwent occipito-cervical fusion using posterior titanium plates. The plates were contoured to the occipito-cervical junction and fastened to the skull with screws, and to the spine with lateral mass screws. The patients were followed prospectively clinically and radiographically to a minimum of 24 months. Outcome parameters included peri-operative morbidity and complications, hardware integrity, spinal alignment, fusion, and neurological status. Twelve of thirteen patients went on to solid fusion radiologically and clinically, and recovered or improved from their myelopathy. One patient did not. Three patients had radiographic evidence that two screws were loose and one screw was broken. There were no instances of plate breakage. We conclude that titanium plate fixation of the occipito-cervical junction is versatile and stable. The plates maintain axial correction and allow for future MR imaging.

Anterior vertebral body screw pullout testing. A comparison of Zeilke, Kaneda, Universal Spine System, and Universal Spine System with pullout-resistant nut.

STUDY DESIGN: A biomechanical study of pullout of anteriorly implanted screws in cadaveric vertebral bodies. OBJECTIVES: To investigate and compare the pullout strength of the Zielke, Kaneda, Universal Spine System (USS) pedicle screw, and USS pedicle screw with a new pullout-resistant nut. SUMMARY OF BACKGROUND DATA: A common problem with anterior purchase regardless of the implant system is screw pullout at the proximal and distal ends of multilevel constructs. There is limited information on a solution to this problem. METHODS: The L1 to L4 vertebral bodies from four cadavers had one each of Zielke and Kaneda pedicle screws (Acromed Corp., Cleveland, OH), USS pedicle screw (Synthes Spine, Paoli, PA), and USS pedicle screw with pullout-resistant nut implanted transversely across the center of the vertebral body with bicortical purchase in a similar fashion as would be used clinically. The screws were extracted using a servohydraulic material testing system. The maximum axial forces were recorded. RESULTS: The Zielke and Kaneda screws had no significant difference in mean pullout strength (P = 0.542). The USS screw alone was less strong (P = 0.009). The USS screw and pullout-resistant nut increased the pullout strength by twofold (P = 0.00006). In the screw pullout tests, the mode of failure was at the screw thread's interface. The USS screw and pullout-resistant nut failed by imploding the body around the nut. With the USS screw and pullout-resistant nut, the pullout strength was determined by the compressive strength of the bone. CONCLUSIONS: The addition of a pullout-resistant nut to an anterior vertebral body screw improves the pullout strength by twofold and changes the mode of failure to rely ultimately on the inherent vertebral body strength rather than the screw's characteristics. The addition of a pullout-resistant nut may be applicable to multilevel implant constructs to prevent screw pullout at the top and bottom.

Cervical spine injuries in the elderly.

We reviewed 41 patients over the age of 65 years (mean 76.5) who had suffered cervical spine injuries, 12 of them with neurological deficit. Eleven patients died during treatment, mostly from respiratory disease. Seven patients were treated by surgical stabilisation, five by halo traction, and the rest by rigid collars or halo-vests. The cervical injury was missed at the first examination in four patients. We conclude that most injuries can be treated by a rigid collar, and that the use of a halo-vest or surgical stabilisation are effective alternatives. Bed rest and traction are poorly tolerated by old people. There should be a high index of suspicion that any elderly patient who presents with a history of a fall or minor trauma may have a cervical spine injury.

Heterotopic ossification after primary cemented and noncemented total hip arthroplasty in patients with osteoarthritis and rheumatoid arthritis.

OBJECTIVE: To compare the frequency and severity of heterotopic ossification (HO) in patients with osteoarthritis or rheumatoid arthritis who undergo cemented or noncemented total hip arthroplasty. DESIGN: A prospective case study. SETTING: A university referral centre. PATIENTS: One hundred and sixty one patients underwent 184 total hip arthroplasties. The 184 hips were categorized as follows: cemented total hip arthroplasty--60 osteoarthritis hips, 26 hips affected by rheumatoid arthritis; noncemented total hip arthroplasty--67 osteoarthritic hips, 31 hips affected by rheumatoid arthritis. INTERVENTIONS: Total hip arthroplasty. A standard approach was used to implant either a cemented or noncemented prosthesis. Radiographs were obtained of each hip preoperatively, immediately postoperatively and 6 weeks, 3 months, 6 months and 1 year postoperatively. MAIN OUTCOME MEASURES: Radiographs were graded in blind fashion for HO, according to the criteria of Brooker. Modified Harris hip scores were calculated at 1 and 2 years postoperatively. RESULTS: HO (incidence of Brooker grades 2, 3 and 4) was greater after cemented (22%) than noncemented (9%) total hip arthroplasty in osteoarthritic hips (p < 0.05), but there was no significant difference between the two types of prosthesis in hips affected by rheumatoid arthritis. When both types of prosthesis were considered together there was no significant difference in the incidence of HO between osteoarthritic hips (15%) and hips affected by rheumatoid arthritis (12%). With respect to Harris hip score, the presence of grade 4 HO was associated with a significantly (p < 0.05) lower score (50.6) than grade 3 (89.4) and grade 2 (91) HO. CONCLUSIONS: Cemented total hip arthroplasty increases the frequency of HO only in osteoarthritic hips. Compared with Brooker's grades 2 and 3 HO, grade 4 HO significantly lowers the Harris hip score after total hip arthroplasty.