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Kevin T Foley

Publications and source records attributed to Kevin T Foley.

At least 19 recordsLinked to original sources
PubMed2006

Motion compensation associated with single-level cervical fusion: where does the lost motion go?

STUDY DESIGN: Seven adult human cadaveric cervical spines (C2-T1) were biomechanically tested in a programmable testing device. OBJECTIVE: Compare the effects of incremental single-level fusion at different levels of the cervical spine. SUMMARY OF BACKGROUND DATA: Clinical studies have reported degenerative symptomatic disc disease at disc levels adjacent to fusion. No known study has attempted to delineate the effects of single-level fusion at different levels of the cervical spine. METHODS: The spines were tested in flexion, extension, right and left lateral bending, and right and left axial rotation for 7 different conditions: harvested and 6 independent single-level fused conditions (i.e., C2-C3, C3-C4, C4-C5, C5-C6, C6-C7, and C7-T1). Segmental motion and global stiffness data were normalized to the harvested condition and compared using a 1-way analysis of variance followed by a SNK test (P < 0.01). RESULTS: Motion compensation was distributed among the unfused segments with significant compensation at the segments adjacent to fusion. Significant increases occurred at the level above C3-C4 and C4-C5 fusions, and below for C5-C6 and C6-C7 fusions in both flexion and extension. CONCLUSIONS: Increase motion compensation occurred at segments immediately adjacent to a single-level fusion. Significant differences occurred at the level above the fusion site for the C3-C4 and C4-C5 fusion in both flexion and extension. When the lower levels (C5-C6, C6-C7) were fused, a significant amount of increased motion was observed at the levels immediately above and below the fusion. However, greater compensation occurred at the inferior segments than the superior segments for the lower level fusions (C5-C6, C6-C7).

Aged↗
PubMed2006

Minimally invasive transforaminal lumbar interbody fusion: indications, technique, and complications.

The authors provide an overview of the minimally invasive transforaminal lumbar interbody fusion (TLIF) procedure including indications, technique, and complications. This novel technique is a method of achieving circumferential lumbar fusion using a unilateral dorsal approach. Minimally invasive TLIF uses a tubular retractor that is inserted via a muscle-dilating exposure, thereby minimizing the approach-related morbidity. This procedure is ideal for refractory mechanical low-back and radicular pain associated with spondylolisthesis, degenerative disc disease, and recurrent disc herniation. The authors' clinical experience and review of the medical literature indicate that TLIF can be effectively and safely performed in a minimally invasive fashion.

Humans↗
PubMed2006

Percutaneous placement of posterior cervical screws using three-dimensional fluoroscopy.

STUDY DESIGN: The placement of percutaneous posterior cervical screws using three-dimensional fluoroscopic guidance was performed in intact human cadaver specimens. OBJECTIVES: To determine the accuracy and feasibility of placing entirely percutaneous posterior cervical screws using a novel form of spinal image guidance. SUMMARY OF BACKGROUND DATA: Conventional image guidance has been shown to increase the accuracy of many open cervical instrumentation procedures. There are presently no published studies reporting this novel method for guiding the percutaneous placement of posterior cervical screws. METHODS: An isocentric C-arm was used to obtain CT images of three intact cadaver specimens. A percutaneous dynamic reference array was attached to the C2 spinous process of each specimen. Light-emitting diodes attached to the C-arm were tracked with an electro-optical camera. The image data set was then transferred to the image-guided workstation, which performed an automated registration. Using the workstation, trajectories were planned for bilateral C1-C2 transarticular, C3-C6 lateral mass, and C7 pedicle screw placement. Through 1.5-cm incisions, a drill guide fitted with light-emitting diodes was used for sequential, image-guided drilling, tapping, and placement of cannulated 4.0 mm screws at each level. Postprocedure, thin-cut CT scanning was used to determine the accuracy of screw placement. RESULTS: A total of 41 of 42 percutaneous screws (97.6%) were accurately placed. All of the transarticular atlantoaxial and subaxial lateral mass screws showed no evidence of foramen transversarium, neural foramen, or facet joint violation. One of the C7 pedicle screws had a minor cortical wall violation. CONCLUSION: This study demonstrates the feasibility of placing percutaneous posterior cervical screws. Three-dimensional fluoroscopy appears to enable highly accurate, percutaneous three-dimensional cervical spine navigation.

Bone Screws↗
PubMed2005

Minimal access surgical techniques in the management of the painful lumbar motion segment.

STUDY DESIGN: Review article. OBJECTIVES: To provide an overview of current minimally invasive lumbar fusion techniques. SUMMARY OF BACKGROUND DATA: Minimally invasive lumbar fusion techniques have only recently been developed. The goals of these procedures are to reduce approach-related soft tissue injury while allowing the surgery to be conducted in an effective manner. METHODS.: Pertinent literature and the authors' clinical experience are reviewed. RESULTS: Minimally invasive techniques have been developed for intertransverse process, posterior lumbar interbody, and transforaminal lumbar interbody fusions. The indications, advantages, and disadvantages of each technique are described. It is emphasized that while they appear promising, the clinical results of these techniques remain preliminary with few long-term studies available for critical review. CONCLUSIONS: Preliminary clinical evidence suggests that minimally invasive lumbar fusion techniques will benefit patients with spinal disorders.

Humans↗
PubMed2005

Disc arthroplasty in the management of the painful lumbar motion segment.

STUDY DESIGN: A review of the published literature regarding lumbar arthroplasty. OBJECTIVE: To describe the current state of lumbar total disc replacement and, in particular, the recent clinical results of the Charité and ProDisc trials. SUMMARY OF BACKGROUND DATA: Lumbar fusion remains the surgical procedure of choice for patients with chronic low back pain unresponsive to nonsurgical management. Lumbar fusion is a strictly palliative procedure with suboptimal clinical results obtained by a significant proportion of patients. Adjacent segment disease is thought to limit the long-term clinical results with up to 20% of patients requiring secondary surgical interventions within the decade following a "successful" lumbar fusion. Total disc replacement has been developed as a potential means to improve the long-term outcome of these patients. METHODS: Literature review of total lumbar disc replacement. RESULTS: The surgical decision-making process, a description of current lumbar disc arthroplasty devices, and early clinical results are described. CONCLUSION: In appropriately chosen patients, lumbar disc arthroplasty provided clinical results similar to those obtained with interbody fusion at 2 years. The long-term results with respect to the effect of these devices on adjacent segment degeneration are not known, as the incidence of adjacent segment degeneration is not an endpoint of the current trials.

Arthroplasty↗
PubMed2005

Minimally invasive transforaminal lumbar interbody fusion (TLIF): technical feasibility and initial results.

Forty-nine patients underwent minimally invasive transforaminal lumbar interbody fusion (TLIF) from October 2001 to August 2002 (minimum 18-month follow-up). The diagnosis was degenerative disc disease with herniated nucleus pulposus (HNP) in 26, spondylolisthesis in 22, and a Chance-type seatbelt fracture in 1. The majority of cases (n = 45) were at L4-L5 or L5-S1. A paramedian, muscle-sparing approach was performed through a tubular retractor docked unilaterally on the facet joint. A total facetectomy was then conducted, exposing the disc space. Discectomy and endplate preparation were completed through the tube using customized surgical instruments. Structural support was achieved with allograft bone or interbody cages. Bone grafting was done with local autologous or allograft bone, augmented with recombinant human bone morphogenetic protein-2 in some cases. Bilateral percutaneous pedicle screw-rod placement was accomplished with the Sextant system. There were no conversions to open surgery. Operative time averaged 240 minutes. Estimated blood loss averaged 140 mL. Mean length of hospital stay was 1.9 days. All patients presenting with preoperative radiculopathy (n = 45) had resolution of symptoms postoperatively. Complications included two instances of screw malposition requiring screw repositioning and two cases of new radiculopathy postoperatively (one from graft dislodgement, the other from contralateral neuroforaminal stenosis). Narcotic use was discontinued 2-4 weeks postoperatively. Improvements in average Visual Analogue Pain Scale and Oswestry Disability Index (preoperative to last follow-up) scores were 7.2-2.1 and 46-14, respectively. At last follow-up, all patients had solid fusions by radiographic criteria. Results of this study indicate that minimally invasive TLIF is feasible and offers several potential advantages over traditional open techniques.

Adult↗
PubMed2004

An improved biomechanical testing protocol for evaluating spinal arthroplasty and motion preservation devices in a multilevel human cadaveric cervical model.

OBJECT: An experimental study was performed to determine the biomechanical end-mounting configurations that replicate in vivo physiological motion of the cervical spine in a multiple-level human cadaveric model. The vertebral motion response for the modified testing protocol was compared to in vivo motion data and traditional pure-moment testing methods. METHODS: Biomechanical tests were performed on fresh human cadaveric cervical spines (C2-T1) mounted in a programmable testing apparatus. Three different end-mounting conditions were studied: pinned-pinned, pinned-fixed, and translational/pinned-fixed. The motion response of the individual segmental vertebral rotations was statistically compared using one-way analysis of variance and Student-Newman-Keuls tests (p < 0.05 unless otherwise stated) to determine differences in the motion responses for different testing methods. CONCLUSIONS: A translational/pinned-fixed mounting configuration induced a bending-moment distribution across the cervical spine, resulting in a motion response that closely matched the in vivo case. In contrast, application of pure-moment loading did not reproduce the physiological response and is less suitable for studying disc arthroplasty and nonfusion devices.

Aged↗
PubMed2004

In vitro biomechanics of cervical disc arthroplasty with the ProDisc-C total disc implant.

An in vitro biomechanical study was conducted to compare the effects of disc arthroplasty and anterior cervical fusion on cervical spine biomechanics in a multilevel human cadaveric model. Three spine conditions were studied: harvested, single-level cervical disc arthroplasty, and single-level fusion. A programmable testing apparatus was used that replicated physiological flexion/extension, lateral bending, and axial rotation. Measurements included vertebral motion, applied load, and bending moments. Relative rotations at the superior, treated, and inferior motion segment units (MSUs) were normalized with respect to the overall rotation of those three MSUs and compared using a one-way analysis of variance with Student-Newman-Keuls test (p < 0.05). Simulated fusion decreased motion across the treated site relative to the harvested and disc arthroplasty conditions. The reduced motion at the treated site was compensated at the adjacent segments by an increase in motion. For all modes of testing, use of an artificial disc prosthesis did not alter the motion patterns at either the instrumented level or adjacent segments compared with the harvested condition, except in extension.

Aged↗
PubMed2004

Segmental lumbar lordosis: manual versus computer-assisted measurement using seven different techniques.

OBJECTIVES: Obliteration of end-plate landmarks by interbody fusion has made the traditional measurement of segmental lumbar lordosis nearly impossible. Because the L4-L5 and L5-S1 levels are most likely to be subjected to fusion procedures or arthroplasty and contribute to more than half of normal lumbar lordosis, it is crucial to identify a reproducible and accurate means of measuring segmental lordosis at these levels. METHODS: Twelve spinal surgeons measured lordosis at L4-L5 and L5-S1 on 10 separate radiographs using three techniques for L4-L5 and four techniques for L5-S1. With use of identical radiographs, measurements first were made using a manual method and then were repeated with a computer-assisted method. Measurements were analyzed for both intraobserver and interobserver error. RESULTS: The individual data demonstrated an intraobserver variance of 9.56 and a standard deviation of 3.092 for computerized measurements compared with 7.742 and 2.782 for manual measurements. The interobserver variance was 4.107 with a standard deviation of 2.027 for the computerized group compared with 4.221 and 2.055 for manual measurements. When analyzed as a group to evaluate interobserver error, the pooled data yielded variance of 19.235 for the computerized group and 19.117 for the manual measurements. CONCLUSIONS: Variance calculations identified the Cobb technique and the posterior vertebral body technique as the least variable measurement techniques for the L4-L5 and L5-S1 levels, respectively; however, there was no statistical significance. In direct comparison, the manual and computer-assisted techniques were found to be statistically equivalent with similar degrees of variance. We believe that the anterior vertebral technique, which did not demonstrate a significant difference from other techniques, will prove to be the most reliable method of assessing segmental lumbar lordosis in patients before surgery, after interbody fusion, and after motion-sparing disc arthroplasty.

Artifacts↗
PubMed2003

Minimally invasive lumbar fusion.

STUDY DESIGN: Review article. OBJECTIVES: To provide an overview of current techniques for minimally invasive lumbar fusion. SUMMARY OF BACKGROUND DATA: Minimally invasive techniques have revolutionized the management of pathologic conditions in various surgical disciplines. Although these same principles have been used in the treatment of lumbar disc disease for many years, minimally invasive lumbar fusion procedures have only recently been developed. The goals of these procedures are to reduce the approach-related morbidity associated with traditional lumbar fusion, yet allow the surgery to be performed in an effective and safe manner. METHODS: The authors' clinical experience with minimally invasive lumbar fusion was reviewed, and the pertinent literature was surveyed. RESULTS: Minimally invasive approaches have been developed for common lumbar procedures such as anterior and posterior interbody fusion, posterolateral onlay fusion, and internal fixation. As with all new surgical techniques, minimally invasive lumbar fusion has a learning curve. As well, there are benefits and disadvantages associated with each technique. However, because these techniques are new and evolving, evidence to support their potential benefits is largely anecdotal. Additionally, there are few long-term studies to document clinical outcomes. CONCLUSIONS: Preliminary clinical results suggest that minimally invasive lumbar fusion will have a beneficial impact on the care of patients with spinal disorders. Outcome studies with long-term follow-up will be necessary to validate its success and allow minimally invasive lumbar fusion to become more widely accepted.

Animals↗
PubMed2003

Minimally invasive fusion: summary statement.

Ideally, minimally invasive surgery (MIS) allows less extensive manipulation of surrounding tissues than a conventional open procedure while accomplishing the same goals and objectives at the target structure. Long-term follow-up combined with appropriate outcome measures are necessary to prove the safety and effectiveness of MIS. For MIS procedures to be widely adopted, they must have an acceptable learning curve. Special skills are needed and are beyond those of traditional open surgery, By definition, as compared with conventional open surgeries, minimally invasive procedures typically involve smaller incisions and less extensive surgical manipulation of the tissues that surround the target structure. Ideally, once the target structure has been reached, the minimally invasive procedure should accomplish the same goals and objectives as its open surgical counterpart. Thus, although minimally invasive surgeries are aimed at reducing the morbidity associated with open surgical approaches, they should not hinder the surgeon's ability to perform a successful operation. In other words, minimal invasion should not equate to minimally effective.

Clinical Competence↗
PubMed2003

Intraoperative spinal navigation.

STUDY DESIGN: Review article. OBJECTIVES: To provide a detailed overview of current methods for intraoperative spinal navigation using image-guided surgical technology. SUMMARY OF BACKGROUND DATA: The development of novel intraoperative navigational techniques has been an important advancement in the field of spine surgery. These techniques, commonly referred to as image-guided surgery (IGS), provide simultaneous, multiplanar views of spinal anatomy. They can be used for detailed preoperative planning and allow the spinal surgeon to track the position of surgical instruments in real time. IGS technology can increase the accuracy of spinal instrumentation procedures and improve patient safety. METHODS: The relevant medical literature was reviewed, as was the authors' clinical and laboratory experience with intraoperative spinal navigation. RESULTS: Image-guided spinal instrumentation procedures in the cervical, thoracic, and lumbar spine have lower rates of screw misplacement than do those performed without image guidance. In a typical IGS spinal procedure, surgical instruments are tracked in the operating room, and their positions are superimposed onto preoperatively acquired computed tomography scans (CT-based image guidance) or intraoperatively acquired fluoroscopic images (virtual fluoroscopy). A new development, the combination of isocentric C-arm fluoroscopy with computer-assisted image guidance, allows the C-arm to create intraoperative CT images that can be used for image-guided navigation without the need for a surgeon-dependent registration step. Each of these technologies has distinct advantages and limitations. CONCLUSIONS: Intraoperative spinal navigation has advanced rapidly in recent years, beneficially affecting a variety of surgical procedures. Future technological developments will widen its clinical application and minimize its shortcomings.

Adult↗
PubMed2003

Three-dimensional fluoroscopy-guided percutaneous thoracolumbar pedicle screw placement. Technical note.

The authors sought to evaluate the feasibility and accuracy of three-dimensional (3D) fluoroscopic guidance for percutaneous placement of thoracic and lumbar pedicle screws in three cadaveric specimens. After attaching a percutaneous dynamic reference array to the surgical anatomy, an isocentric C-arm fluoroscope was used to obtain images of the region of interest. Light-emitting diodes attached to the C-arm unit were tracked using an electrooptical camera. The image data set was transferred to the image-guided workstation, which performed an automated registration. Using the workstation display, pedicle screw trajectories were planned. An image-guided drill guide was passed through a stab incision, and this was followed by sequential image-guided pedicle drilling, tapping, and screw placement. Pedicle screws of various diameters (range 4-6.5 mm) were placed in all pedicles greater than 4 mm in diameter. Postoperatively, thin-cut computerized tomography scans were obtained to determine the accuracy of screw placement. Eighty-nine (94.7%) of 94 percutaneous screws were placed completely within the cortical pedicle margins, including all 30 lumbar screws (100%) and 59 (92%) of 64 thoracic screws. The mean diameter of all thoracic pedicles was 6 mm (range 2.9-11 mm); the mean diameter of the five pedicles in which wall violations occurred was 4.6 mm (range 4.1-6.3 mm). Two of the violations were less than 2 mm beyond the cortex; the others were between 2 and 3 mm. Coupled with an image guidance system, 3D fluoroscopy allows highly accurate spinal navigation. Results of this study suggest that this technology will facilitate the application of minimally invasive techniques to the field of spine surgery.

Bone Screws↗
PubMed2002

The Cervical Spine Study Group anterior cervical plate nomenclature.

The authors review historical and biomechanical aspects of anterior cervical plate (ACP) systems. They propose a novel classification system for ACPs based on the biomechanical and graft-loading properties of these systems. A retrospective review of the literature comprising both clinical and laboratory investigations regarding the ACP system was undertaken. Comparison of each system is considered in the context of the biomechanical attributes and graft-loading properties of each type of plate. Salient characteristics reviewed include restriction of screw backout, screw-angle variability, and mobility at the screw-plate interface. A new classification system for ACPs is proposed that primarily considers the ability of the construct to restrict screw backout, as well as the properties of the plate-screw interface--that is, the capacity for rotational or translational movement. A new classification system is presented that provides unified, biomechanically descriptive nomenclature. Using this nomenclature, the ACP devices currently available and those developed in the future can be uniformly categorized.

Biomechanical Phenomena↗
PubMed2002

Influence of lower extremity strength of healthy older adults on the outcome of an induced trip.

OBJECTIVES: To determine whether decreased lower extremity strength contributes to trip-related falls in older adults. DESIGN: A cross-sectional sample of older adults were safety-harnessed and tripped while walking using a concealed, mechanical obstacle. Lower extremity strength was compared between trip outcome groups. SETTING: A biomechanics research laboratory. PARTICIPANTS: Seventy-nine healthy, community-dwelling adults aged 65 and older (50 women). MEASUREMENTS: Ankle, knee, and hip flexion and extension strength were measured isometrically and isokinetically. Measured strengths were subjected to a factor analysis. Strength factor scores were compared between those who recovered from the trip and those who fell by three previously identified mechanisms: during-step, after-step, and elevating-response falls. RESULTS: Seven common factors, one associated with each direction of exertion at each joint and one with the time rate of moment increase, explained 88% of the variance in measured strength. The during-step (n=5) fallers were significantly stronger in the ankle extension (plantarflexion), knee flexion, overall extension, and total strength factors than those who successfully recovered using a similar, lowering strategy (n=26). The elevating-response faller (n=1) was stronger in the plantarflexion and overall extension factors than most of those who recovered using a similar, elevating strategy (n=11). Two of three after-step fallers were among the weakest subjects tested. CONCLUSION: Weak older adults and the strongest older adults may be at greater risk of falling from a trip, although by different mechanisms. High strength may increase the likelihood of a during-step or elevating-response fall; decreased strength may increase the likelihood of an after-step fall.

Accidental Falls↗
PubMed2002

Percutaneous pedicle screw fixation of the lumbar spine: preliminary clinical results.

OBJECT: Standard techniques for pedicle screw fixation of the lumbar spine involve open exposures and extensive muscle dissection. The purpose of this study was to report the initial clinical experience with a novel device for percutaneous posterior fixation of the lumbar spine. METHODS: An existing multiaxial lumbar pedicle screw system was modified to allow screws to be placed percutaneously by using an extension sleeve that permits remote manipulation of the polyaxial screw heads and remote engagement of the screw-locking mechanism. A unique rod-insertion device was developed that linked to the screw extension sleeves, allowing for a precut and -contoured rod to be placed through a small stab wound. Because the insertion device relies on the geometrical constraint of the rod pathway through the screw heads, minimal manipulation is required to place the rods in a standard submuscular position, there is essentially no muscle dissection, and the need for direct visual feedback is avoided. Twelve patients (six men and six women) who ranged in age from 23 to 68 years underwent pedicle screw fixation in which the rod-insertion device was used. Spondylolisthesis was present in 10 patients and osseous nonunion of a prior interbody fusion was present in two. All patients underwent successful percutaneous fixation. Ten patients underwent single-level fusions (six at L5-S1, three at L4-5, and one at L2-3), and two underwent two-level fusions (one from L3-5 and the other from L4-S1). The follow-up period ranged from 10 to 19 months (mean 13.8 months). CONCLUSIONS: Although percutaneous lumbar pedicle screw placement has been described previously, longitudinal connector (rod or plate) insertion has been more problematic. The device used in this study allows for straightforward placement of lumbar pedicle screws and rods through percutaneous stab wounds. Paraspinous tissue trauma is minimized without compromising the quality of spinal fixation. Preliminary experience involving the use of this device has been promising.

Adult↗
PubMed2002

Microendoscopic lumbar discectomy: technical note.

OBJECTIVE: The microendoscopic discectomy (MED) technique was initially developed in 1997 to treat herniated lumbar disc disease. Since then, thousands of cases have been successfully performed at more than 500 institutions. This article discusses the technical aspects of this procedure and presents a consecutive case series. METHODS: A total of 150 consecutive patients underwent MED. MED is performed by a muscle-splitting approach using a series of tubular dilators with consecutively increasing diameters. A tubular retractor is then inserted over the final dilator, and a specially designed endoscope is placed inside the tubular retractor. The microdiscectomy is performed endoscopically while the surgeon views the procedure on a video monitor. RESULTS: Clinical outcomes were determined using a modified MacNab criteria, which revealed that 77% of patients had excellent, 17% had good, 3% had fair, and 3% had poor outcomes. The average hospital stay was 7.7 hours. The average return to work period was 17 days. Complications primarily included dural tears, which occurred in 8 patients (5%) and were seen early on in the patient series. Complication rates diminished as the surgeon's experience with this technique increased. CONCLUSION: MED for lumbar herniated disc disease can be performed safely and effectively, resulting in a shortened hospital stay and faster return to work; however, there is a learning curve to this procedure.

Adult↗