Accuracy of cervical pedicle screw placement using the funnel technique

STUDY DESIGN

This was a cadaver study assessing the accuracy of cervical pedicle screw placement.

OBJECTIVE

To evaluate the accuracy of the funnel technique of screw placement.

SUMMARY OF BACKGROUND DATA

Although excellent results have been reported in clinical studies, with no major neurovascular injuries, several cadaveric studies have shown a high pedicle perforation rate during screw placement.

METHODS

Ten fresh frozen cervical spines (C2-C7) were used (120 pedicles, 20 pedicles per level). The average specimen age was 79.6 years (range 65-97); the average height was 159 cm (range 155-175). The male-to-female ratio was 3:7. Pedicle width and angulation were measured on preoperative axial computed tomography (1-mm slices). By use of four bony landmarks and the funnel technique, screws were placed under direct vision. Critical perforations (documented contact of a screw with, or an injury to, a spinal cord, nerve root, or vertebral artery) and noncritical perforations (a perforation with no critical contact) were recorded.

RESULTS

In seven pedicles (5.8%) the procedure was aborted because of a small or nonexistent pedicle medullary canal. Ninety-four pedicle screws (83.2%) were placed correctly, whereas 11 pedicles (9.7%) had noncritical perforations and 8 pedicles (7.1%) had critical perforations. The majority of the critical and noncritical perforations were at C3, C4, and C5.

CONCLUSIONS

Axial computed tomography is necessary for the preoperative planning. Because of the small diameter and steep angulation of cervical pedicles, every spine surgeon who intends to use pedicle screws should first master the technique on cadavers.

Postoperative pain control using epidural catheters after anterior spinal fusion for adolescent scoliosis

STUDY DESIGN

A prospective review of patients undergoing epidural catheter placement after anterior spinal fusion and instrumentation for adolescent scoliosis was performed. Data were collected using visual analog pain scores reflecting the patients' perception of their pain control.

OBJECTIVES

To present the authors' technique for epidural catheter placement and dosing protocol, and to demonstrate the results from postoperative pain control after anterior spinal instrumented fusion for 10 consecutive patients.

SUMMARY OF BACKGROUND DATA

The literature regarding the benefits of epidural catheters after spinal surgery is contradictory, even with controlled studies comparing epidural catheters with intravenous morphine patient-controlled anesthesia. The authors believe that this lack of consensus stems from varied epidural dosing protocols and techniques in catheter placement, which they have witnessed anecdotally at their own institution. This prompted the authors to develop and refine a standardized dosing and catheter placement protocol for pain control after spinal surgery.

METHODS

Epidural catheters were placed intraoperatively before wound closure, then removed on postoperative Day 5. Dosing consisted of fentanyl (1 microg/kg) and hydromorphone (5 microg/kg) diluted in preservative-free saline (0.2 mL/kg). After surgery, dosing consisted of 0.1% ropivacaine and hydromorphone (10 microg/ml) continuously infused at 0.2 mL/kg/hour. Postoperative pain control was assessed on each postoperative day using a visual analog pain scale with choices ranging from 0 to 10.

RESULTS

The arithmetic mean of the median pain scores after surgery was 2.1. The mean of the maximum pain scores for the 5 days was 4.1. Three patients required an epidural bolus and a 20% increase in the epidural infusion rate. One patient was judged to be excessively sleepy, so the epidural infusion rate was decreased by 20%. Pruritus requiring diphenhydramine developed in three patients. No other adverse effects related to epidural analgesia were noted. No catheters were accidentally pulled out or disconnected.

CONCLUSION

By following the dosing protocol described, epidural catheters can be used safely and effectively to control postoperative pain after anterior instrumentation and spinal fusion for adolescent scoliosis.

A dual epidural catheter technique to provide analgesia following posterior spinal fusion for scoliosis in children and adolescents

BACKGROUND

The authors report their experience with the use of a dual epidural catheter technique in controlling pain following long posterior spinal fusion and instrumentation for scoliosis in children and adolescents.

METHODS

Following completion of the surgical procedure and prior to wound closure, the upper catheter was inserted with the tip directed cephalad to T1-4 while the tip of the lower catheter was positioned at the L1-4 level. As the surgical wound was being closed, the catheters were dosed with fentanyl and hydromorphone followed by a continuous infusion of ropivacaine plus hydromorphone. Postoperative pain was assessed every 2-4 h using a visual analogue score or an observational behavioural score (0=no pain, 10=worst imaginable pain). There were 14 patients ranging in age from 5-17 years (12.7 +/- 3.5) and in weight from 19-68 kg (44.3 +/- 17.5). The epidural catheters were left in place until the fifth postoperative day.

RESULTS

The mean of the median pain score from each patient was 1.5 +/- 1.6, 1.6 +/- 1.5, 1.4 +/- 1.3, 1.1 +/- 1.1 and 0.9 +/- 0.9, respectively, on postoperative days 1 through 5. The mean of the maximum pain scores was 3.5 +/- 2.3 (range 0-7), 4 +/- 1.6 (range 2-6), 3.1 +/- 1.7 (range 1-6), 2.4 +/- 1.5 (range 0-4) and 2.2 +/- 1.4 (range 0-4), respectively, on postoperative days 1 through 5.

CONCLUSION

No adverse effects related to epidural analgesia were noted.

The use of pedicle-screw internal fixation for the operative treatment of spinal disorders

Pedicle screws have dramatically improved the outcomes of spinal reconstruction requiring spinal fusion. Short-segment surgical treatments based on the use of pedicle screws for the treatment of neoplastic, developmental, congenital, traumatic, and degenerative conditions have been proved to be practical, safe, and effective. The Funnel Technique provides a straightforward, direct, and inexpensive way to very safely apply pedicle screws in the cervical, thoracic, or lumbar spine. Carefully applied pedicle-screw fixation does not produce severe or frequent complications. Pedicle-screw fixation can be effectively and safely used wherever a vertebral pedicle can accommodate a pedicle screw--that is, in the cervical, thoracic, or lumbar spine. Training in pedicle-screw application should be standard in orthopaedic training programs since pedicle-screw fixation represents the so-called gold standard of spinal internal fixation.

Successful short-segment instrumentation and fusion for thoracolumbar spine fractures: a consecutive 41/2-year series

STUDY DESIGN

A retrospective review of all the surgically managed spinal fractures at the University of Missouri Medical Center during the 41/2-year period from January 1989 to July 1993 was performed. Of the 51 surgically managed patients, 46 were instrumented by short-segment technique (attachment of one level above the fracture to one level below the fracture). The other 5 patients in this consecutive series had multiple trauma. These patients were included in the review because this was a consecutive series. However, they were grouped separately because they were instrumented by long-segment technique because of their multiple organ system injuries.

OBJECTIVES

The choice of the anterior or posterior approach for short-segment instrumentation was based on the Load-Sharing Classification published in a 1994 issue of Spine. The purpose of this review was to demonstrate that grading comminution by use of the Load-Sharing Classification for approach selection and the choice of patients with isolated fractures who are cooperative with spinal bracing for 4 months provide the keys to successful short-segment treatment of isolated spinal fractures.

SUMMARY OF BACKGROUND DATA

The current literature implies that the use of pedicle screws for short-segment instrumentation of spinal fracture is dangerous and inappropriate because of the high screw fracture rate.

METHODS

Charts, operative notes, preoperative and postoperative radiographs, computed tomography scans, and follow-up records of all patients were reviewed carefully from the time of surgery until final follow-up assessment. The Load-Sharing Classification had been used prospectively for all patients before their surgery to determine the approach for short-segment instrumentation. Denis' Pain Scale and Work Scales were obtained during follow-up evaluation for all patients.

RESULTS

All patients were observed over 40 months except for 1 patient who died of unrelated causes after 35 months. The mean follow-up period was 66 months (51/2 years). No patient was lost to follow-up evaluation. Prospective application of the Load-Sharing Classification to the patients' injury and restriction of the short-segment approach to cooperative patients with isolated spinal fractures (excluding multisystem trauma patients) allowed 45 of 46 patients instrumented by the short-segment technique to proceed to successful healing in virtual anatomic alignment.

CONCLUSIONS

The Load-Sharing Classification is a straightforward way to describe the amount of bony comminution in a spinal fracture. When applied to patients with isolated spine fractures who are cooperative with 3 to 4 months of spinal bracing, it can help the surgeon select short-segment pedicle-screw-based fixation using the posterior approach for less comminuted injuries and the anterior approach for those more comminuted. The choice of which fracture-dislocations should be strut grafted anteriorly and which need only posterior short-segment pedicle-screw-based instrumentation also can be made using the Load-Sharing Classification.

Surgical anatomy of the cervical pedicles: landmarks for posterior cervical pedicle entrance localization

The posterior entrance to the cervical pedicle is described using quantitative and descriptive parameters. Fifty-three spines (C2-C7) were evaluated using a digital caliper and by visual inspection using four bony landmarks: the lateral vertebral notch and inferior articular process (C2-C7), the medial pedicle cortex at C2, and the transverse process at C7. Three distances were defined. (1) At C2, the average medial pedicle cortex-pedicle distance was 7.2 mm. (2) The lateral vertebral notch-pedicle distances showed that the entrances were located close to the notch at C2, almost at the notch at C3 and C4, and gradually moved medially away from the notch from C5 to C7. The pedicles were rarely located lateral to the lateral vertebral notch. (3) The inferior articular process-pedicle distance was large at C2, the shortest at C3, and gradually increased toward C7. Three relations were defined. (1) The pedicles were located mostly in the intermediate third of the inferior facet at C2; in the lateral third at C3, C4, and C7; or in the lateral or intermediate thirds at C5 and C6. Only C2 and C6 pedicles were located in its medial third. (2) The pedicles were located mostly below the lateral vertebral notch at C2, at C3-C6, or almost equally above and at the notch at C7. (3) Most of the C7 pedicles were located below the midline of the transverse process. The location of the pedicle entrance was unique at each cervical level. Their distribution followed the cervical spinal cord enlargement. These landmarks should assist with safe placement of pedicle screws.

Assessment of coping strategies of child abusing mothers

OBJECTIVE

Mothers who had physically abused their children were assessed to determine whether these mothers had a general coping skills deficit.

METHOD

Abusing mothers (n = 17) were compared to nonabusing mothers of conduct problem children (n = 16). Coping was measured by several methods, each designed to address the insufficiencies of the others.

RESULTS

In comparison to the nonabusing mothers, independent ratings indicated that abusing mothers exhibited a pattern of coping characterized by greater use of emotion-focused coping strategies and less use of effective problem-focused strategies. Finally, using self report ratings of coping, abusing mothers perceived their coping to be more ineffective than the nonabusing mothers.

CONCLUSIONS

The possibility that the observed coping skills deficit may be indicative of a deficit in emotional responding to stress was discussed and suggestions were given for therapeutic interventions with child abusing mothers.

Morphologic characteristics of human cervical pedicles

STUDY DESIGN

Cervical pedicle morphology was investigated using manual and computed tomography measurements.

OBJECTIVES

Normal anatomic variations of the cervical pedicles were measured to evaluate their safety as anchors for posterior cervical fixation systems.

SUMMARY OF BACKGROUND DATA

There have been no cervical pedicle measurements on a large number of specimens. No study has ever measured the inner pedicle diameter.

METHODS

Fifty-three spinal columns (C2-C7) of Euro-American origin identified by age, sex, and height (318 vertebrae or 636 pedicles) were measured using a digital caliper, a goniometer, and computed tomography scanning.

RESULTS

The pedicle axis lengths were similar from C3 to C7 (except for shorter C2 pedicles). In the horizontal plane, the medial inclination of the pedicles followed the cervical spinal cord enlargement. In the sagittal plane, the pedicles were directed superiorly in the upper spine and inferiorly in the lower cervical spine. Some pedicles had no medullary canal (i.e., were solid cortical bone: 0.9% C2, 2.8% C3 and C4, and 3.8% C5 pedicles). The outer pedicle width was smaller than the height in most of the pedicles. The inner pedicle width was equal to or smaller than 2 mm in 13.2% C2, 72.6% C3, 67.0% C4, 62.3% C5, 51.9% C6, and 16.0% C7. The outer pedicle width was equal to or smaller than 4 mm in 8.5% C2, 75.5% C3, 35.8% C4, 13.2% C5 and C6, and 6.6% C7 pedicles. The thinnest pedicle cortex was always the lateral cortex, which protects the vertebral artery. Measurements of the posterior pedicle projection also were taken.

CONCLUSIONS

These data provide anatomic limitations to pedicle screw use in the cervical spine.

Comparing Mersilene* tape and stainless steel wire as sublaminar spinal fixation in the Chagma baboon (Papio ursinus)

The development of segmental instrumentation has been a major advancement in the treatment of spinal problems, but the use of sublaminar stainless steel wire (SSW) has not been without untoward effects. This study reports a comparison of Mersilene* tape (MT) and stainless steel wire (SSW) used for sublaminar fixation in the Chagma baboon (Papio Ursinus). A similar comparative study has not been reported, although the local effects of sublaminar SSW in the spinal canal have previously been described. The adult Chagma baboon was selected as the experimental animal due to its partial upright posture and spinal anatomy, similar to that of the human. Six levels of the thoracolumbar spine were instrumented with custom designed Harrington hooks and regular one-quarter inch threaded rods used as a distraction system. The four intervening laminae were fixed to the rods using doubled-over, eighteen gauge sublaminar SSW in six cases and five millimeter MT in six cases. Computed axial tomography used to measure the AP diameter of the bony spinal canal revealed the AP space occupied by the SSW and MT to be 32 percent and 14.8 percent respectively. In the MT group, the overlying dura mater was found to be totally intact and revealed no signs of abnormal tissue response. A well-formed connective tissue membrane consisting of dense connective tissue surrounded the MT and was found to consist of more mature fibers than that found in the SSW group. The dura-implant interface was examined histologically and a distinct membrane was identified between the dura and the superficial aspect of the MT's, as well as intervening between the two MT's. Following removal of the MT, in contrast to the SSW, it was apparent that the underlying dura was not injured, most probably due to the soft consistency of the Mersilene* tape and the well-formed overlying membrane. On clinical grounds the fixation in both groups was adequate but the MT group formed a well-circumscribed membrane that made removal of the MT easier and potentially safer. The AP space occupied by the spinal implant was also found to be less with MT as opposed to SSW.

Long-term intravenous therapy with use of peripherally inserted silicone-elastomer catheters in orthopaedic patients

We studied the results of prolonged intravenous therapy with antibiotics through a central venous silicone-elastomer catheter that had been peripherally inserted in thirty-five orthopaedic patients. The catheters remained in place for an average of twenty-nine days (range, five to seventy-four days). The 20-gauge (one-millimeter-diameter) catheters used in our study were smaller in diameter than the triple-lumen catheters or the double-lumen Hickman catheters used in previous studies. The catheters in our study were left indwelling for as long as, or for longer than, those in other studies. Our patients had no serious complications related to the insertion or use of the catheter. However, three (8 per cent) of thirty-eight inserted catheters failed mechanically and had to be removed. Two additional catheters (5 per cent) were removed because the lumen became plugged. One catheter in each of these groups was not replaced, because a catheter was no longer necessary. We believe that the problems with the catheters were related to the small diameter of the tubing that was used in our series. Use of the small-diameter catheter reduces the risk of cardiac tamponade and other complications associated with catheters that have larger diameters, and small-diameter catheters can remain indwelling for a long time. The peripheral route of insertion eliminates the risk of pneumothorax associated with the subclavian route of placement and allows for greater ease of insertion. In addition, the use of catheters made of silicone elastomer reduces the risk of thrombosis and infection, which are associated with catheters made of polyethylene.(ABSTRACT TRUNCATED AT 250 WORDS)

Osteochondroma of the scapula

Osteochondromas are common primary bone tumors which are usually located in the distal femur. In a large retrospective study from the Mayo clinic, osteochondromas comprised 36% of benign bone tumors and nearly 10% of all bone tumors. While the scapula is rarely involved, this is the most common tumor of the scapula. Clinical signs of this lesion include shoulder pain and limited range of motion. Patients may present with winging of the scapula. Computed tomography is often necessary to fully define the location and character of the lesion. We present the case of a 14-year-old girl with pain and limited range of motion of the left shoulder. The diagnosis was that of osteochondroma of the scapula.

Treatment of L5-S1 spondyloptosis by staged L5 resection with reduction and fusion of L4 onto S1 (Gaines procedure)

STUDY DESIGN AND OBJECTIVES

A retrospective study was performed on the two-stage Gaines procedure for the treatment of spondyloptosis, evaluating indications, techniques, results, and patient satisfaction.

SUMMARY OF BACKGROUND DATA

Sixteen consecutive patients from two institutions were included. Their average age was 24 years. Average follow-up was 3.9 years, with 11 patients included in follow-up 2 or more years. Ten patients (63%) had a preoperative neurologic deficit--three with cauda equina syndrome, one with foot drop. All patients had severe back or radicular symptoms and significant disability or severe deformity.

METHODS

Patient examinations, interviews, chart review, and radiographic measurements all were performed independently. A subjective questionnaire was administered to each patient comparing preoperative with postoperative changes in pain, function, and appearance, as well as their overall outcome assessment.

RESULTS

Postoperatively, 12 patients (75%) had early neurologic deficits, with seven of these having had a preoperative deficit. Four of these seven had a persistent deficit at follow-up, one with a permanent foot drop and three with documented weakness that was still improving at follow-up. The patient with preoperative foot drop remained unchanged, and the remaining seven patients with early deficit all recovered within 1 year. All three patients with preoperative cauda equina syndrome recovered postoperatively. The subjective questionnaire results revealed extremely high patient satisfaction. They reported significant improvement in pain, function, and appearance.

CONCLUSIONS

Despite the relatively high complication rate, with appropriate patient selection, planning, and surgical technique, this procedure appears to be a sound method for treating severe cases of spondyloptosis, yielding very high patient satisfaction.

The load sharing classification of spine fractures

STUDY DESIGN

A 3 to 4 year follow-up was performed on a consecutive series of 28 patients who had three-column spinal fractures surgically stabilized by short-segment instrumentation with first generation VSP (Steffee) screws and plates and autograft fusion. The follow-up revealed 10 patients with broken screws.

BACKGROUND DATA

Retrospective examination of preoperative radiographs and computed tomographic axial and sagittal reconstruction images clearly demonstrated that the screw fractures all occurred in patients with a disproportionately greater amount of injury to the vertebral body.

RESULTS

A point system (the load sharing classification) was developed that grades: 1) the amount of damaged vertebral body, 2) the spread of the fragments in the fracture site, and 3) the amount of corrected traumatic kyphosis.

CONCLUSIONS

This point system can be used preoperatively to: 1) predict screw breakage when short segment, posteriorly placed pedicle screw implants are being used, 2) describe any spinal injury for retrospective studies, or 3) select spinal fractures for anterior reconstruction with strut graft, short-segment-type reconstruction.

Monitoring of motor tracts with spinal cord stimulation

STUDY DESIGN

Sensory- and motor-evoked potentials were recorded after high thoracic (T2) epidural electrical stimulation of the spinal cord. Under general anesthesia, 22 cats underwent single or repetitive spinal cord stimulation.

OBJECTIVES

Sensory-evoked potentials were recorded after antidromic activation of the posterior column sensory fibers at lower electrical intensities (< 5 V). Motor tract activation was accomplished by recording the ventral root and muscle action potential using single pulse stimulation (> 50 V).

METHODS

Sensory-evoked potentials were recorded from the lumbar spinal cord (n = 20), dorsal root (n = 80), and peroneal nerve (n = 40). Motor-evoked potentials were recorded from the ventral root (n = 40) and the hindlimb musculature (n = 10).

RESULTS

The lumbar spinal-evoked response resisted lesioning and showed a minimal change after a spinal cord hemisection. Dorsal rhizotomy abolished the ipsilateral peroneal nerve action potential, indicating antidromic activation of afferent fibers. Motor responses did not change after the dorsal rhizotomy, suggesting involvement of nonsensory pathways.

CONCLUSIONS

These findings indicate that spinal cord stimulation activates sensory and motor tracts that can be recorded at various sites along the central or the peripheral nervous system.

Free fibular transfer in a growing individual (long-term results)

We present a case report of a 4-year-old in whom the distal fibula and epiphyseal plate had been traumatically destroyed. A free vascularized epiphyseal transfer using the ipsilateral proximal fibula was performed which provided good bony stability at the ankle, as well as excellent long-term growth characteristics. We demonstrate immediate postoperative results, as well as long-term (5 years) follow-up.

Dissociation of somatosensory and motor evoked potentials in a patient with an intramedullary spinal tumor

We describe a patient with an intramedullary spinal tumor who demonstrated postoperative improvement of motor and sensory function despite the lack of somatosensory evoked potentials (SSEPs) before and after intraoperative monitoring. The motor system was evaluated by direct spinal cord stimulation across the tumor bed. The resultant evoked compound muscle action potentials and compound nerve activities were normal. Although there is sufficient clinical evidence that SSEPs are sensitive to posterior and posterolateral ischemic insults of the spinal cord, the technique should be employed with an awareness of its limitations in monitoring the descending tracts which have a different blood supply and occupy more anterior locations in the spinal cord.

Skin expansion as preparation for an opening wedge osteotomy of the mid-foot in arthrogryposis

A case report is presented in which tissue expansion is used to provide the additional skin needed during an opening wedge mid-foot osteotomy to correct a varus foot deformity in a patient with arthrogryposis multiplex congenita. Tissue expansion is a relatively new method of acquiring coverage for wounds which may have advantages over previous techniques. The risks and drawbacks of this technique will be described in detail.

"Backfiring" in spinal cord monitoring. High thoracic spinal cord stimulation evokes sciatic response by antidromic sensory pathway conduction, not motor tract conduction

Spinal cord stimulation has been advocated as an alternative to motor cortex stimulation for motor tract activation. To test this theory, evoked responses were recorded from lumbar spinal cord (L2; n = 14), spinal roots (L4-L7; n = 112), peripheral nerves (sciatics; n = 28), and hind limb muscles (n = 28) after epidural stimulation of the T1-T2 segment of the spinal cord in dogs (n = 12), cats (n = 2), and monkeys (n = 2). The spinal response evoked by spinal cord stimulation was resistant to a dorsal hemisectioning (depth, 7-8 mm) of the midthoracic spinal cord. A minimal attenuation of latency and amplitude occurred with dorsal hemisectioning, suggesting signal transmission through descending or ascending pathways in the ventrolateral and ventral quadrants of the spinal cord. The sciatic nerve response was abolished by a dorsal column transection (depth, 3-4 mm) or ipsilateral lumbar dorsal rhizotomy (four dorsal roots). This shows that the evoked response recorded from the sciatic nerve in our animals was not travelling, as we expected, through the ventral roots, but rather was conducted antidromically through sensory fibers in dorsal roots.

Magnetic resonance imaging evaluation of the spinal canal following arthrodesis and removal of sublaminar wires

Seven patients who underwent posterior spinal fusion with Harrington instrumentation and sublaminar wires, and subsequently had these implants removed, were evaluated for evidence of spinal canal compromise with magnetic resonance imaging (MRI) at the sites of the sublaminar wires. All fusions were solid. The sites of 33 wires (27 levels) were evaluated with MRI. The average time the wires were in the spinal canal was 24.6 months. The average time following wire removal at the time of MRI was 61.7 months. Twenty-eight of 33 (85%) wire sites had no evidence of spinal canal compromise. Five sites had minimal (less than 15%) spinal canal compromise. The permanent structural changes in the spinal canal attributable to sublaminar wires appears to be quite modest.

Experimental evaluation of seven different spinal fracture internal fixation devices using nonfailure stability testing. The load-sharing and unstable-mechanism concepts

Fracture site immobilization capabilities of seven internal spine fixation systems were experimentally evaluated: Harrington double distraction (plain, supplemented with Edwards sleeves, supplemented with sublaminar wires), Luque rectangle, Kaneda device, transfixed Kaneda device, and Steffee plates. Stability evaluation involved comparing the three-dimensional motion that occurred across an experimentally created L1 slice fracture, and the load resistance of the implants when subjected to axial, flexion, extension, lateral bending, and torsional loads. Each implant was tested on 15 different vertebral segments from 200-250-lb calves. All implants load-shared with the fractured vertebral column to varying degrees. All except the Steffee plate system showed an obvious biomechanical weakness in one or more load modes. The unstable 4R-4bar mechanism configuration of bilevel spinal implants was identified. Mechanism configurations allow free movement with little or no resistance to the applied load until load sharing by the spinal column stops the collapse and resists the applied load.

Internal forces and moments in transpedicular spine instrumentation. The effect of pedicle screw angle and transfixation--the 4R-4bar linkage concept

The three-dimensional components of force and moment within the plates and screws of a bilevel transpedicular spine implant construct subjected to different physiological loads were determined by experimental and finite element methods. The effect of pedicle screw angle and transfixation were studied. Untransfixed 0 degrees pedicle-to-pedicle (P-P) angle constructs with limited screw-bone torsional resistance are unstable 4R-4bar linkages. They will not resist lateral load or (when not in a rectangular position) axial load until the spinal column load shares. Untransfixed constructs with (0 degrees less than P-P angle less than 60 degrees) are structures. However, as P-P angle approaches 0 degrees, the structure becomes more flexible (unstable) and some internal force and moment components exponentially increase (starting at approximately a 30 degrees P-P angle). Transfixation eliminated the linkage instability and associated exponential increase in internal loads. These observations apply to all bilevel systems that allow no relative joint motion between pedicle screw and longitudinal member. If relative motion does exist, other types of linkage instability can occur.

Herpes zoster: a consideration in the differential diagnosis of radiculopathy

Herpes zoster probably occurs more often than generally thought. Since it produces a radicular distribution of pain, it should be included in the differential diagnosis of radiculopathy. A case is presented in which evaluating the radicular low back pain before the characteristic rash appears was misleading. Careful history-taking concerning the exact nature of the pain and sensory changes is needed to differentiate between zoster and radiculopathy, if no rash is evident.

Removal of sublaminar wires after spinal fusion

Eighteen patients who had had spinal fusion using Harrington rods with sublaminar wires underwent removal of the implants because of tenderness over the implants. There were no important complications. At final follow-up, no patient had a change in neurological function as compared with the preoperative assessment, and all reported relief of the preoperative tenderness. We concluded that the removal of rods and sublaminar wires from patients who have had a spinal fusion is clinically safe and effective.

Response variability of somatosensory evoked potentials during scoliosis surgery

Somatosensory evoked potentials (SSEP) were recorded from the scalp for intraoperative monitoring of patients undergoing surgical correction of spine deformities or spine fractures. Alterations in the SSEP with distraction, spine manipulation, anesthesia, hypotension, and other intraoperative variables are described. When loss of the SSEP occurred and a waiting period was undertaken until it returned, all patients with an SSEP present upon closing, which was within +/- 2 SD of their anesthetized control values, had no neurologic complications. Alterations in SSEP consisting of increases in latency of 15% and decreases in amplitude of 50% were not associated with any postoperative neurologic deficits.

Mersilene tapes as a substitute for wire in segmental spinal instrumentation for children

Sublaminar wires for segmental fixation have been a useful adjunct to internal fixation of the spine. Concern over broken wires in the spinal canal or fear of cut-through in soft bone led to the use of Mersilene tape to supplement Harrington or Luque rod fixation in six scoliotic children. No problems of infection or hardware loosening were noted. Mersilene tapes for segmental fixation may be useful where there is concern for wires in the spinal canal or with patients with soft bone and flexible curves.

Osteoid osteoma of the spine: surgically correctable cause of painful scoliosis

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Treatment of spondyloptosis by two stage L5 vertebrectomy and reduction of L4 onto S1

A new method of treatment of spondyloptosis is presented utilizing a staged approach. The first stage consists of a vertebral body resection of L5 along with the L4-5 and L5-S1 discs. The second stage procedure consists of removal of the loose posterior element, the articular processes, and pedicles of L5 and reduction of L4 onto the sacrum. The technique for the procedure is reviewed along with its results in two operated patients.

Stabilization of thoracic and thoracolumbar fracture-dislocations with Harrington rods and sublaminar wires

Seventeen unstable thoracic and thoracolumbar fracture-dislocations have been treated by Harrington double-distraction rod technique supplemented by doubled 18-gauge stainless-steel wires applied to two intact laminae above and below the injury. Fourteen of the 17 cases were grossly comminuted and translated beyond 50% of the width of the spinal column. No external bracing was used in the 13 patients with neurologic deficits. At the time of follow-up examinations (greater than 22 months in all patients) there was no loss of reduction or fixation in any patient. Solid fusion was achieved in all patients.

A plea for judgment in management of thoracolumbar fractures and fracture-dislocations. A reassessment of surgical indications

Until basic knowledge of fracture anatomy and stability includes experiments with comminuted anterior column injuries, posterior column injuries, and these injuries in combination with ligament and capsular injuries, and until the long-term implications of the long fusion in an otherwise healthy patient are fully known, clinicians making decisions about individual patients must assemble all the variables that bear on the patient's ability to heal and become fully functional again before making a decision about surgical stabilization of the thoracolumbar fracture. An assessment of plain roentgenograms, tomograms, and CAT scans and an understanding of the anatomy of the fracture site provide essential but insufficient data for clinical decisions about patients.

Experimental evaluation of Harrington rod fixation supplemented with sublaminar wires in stabilizing thoracolumbar fracture-dislocations

Segments of the spinal column of calves were instrumented with Harrington rods with and without sublaminar wires. Grossly unstable lesions were created by resecting a 2-cm segment from the central spinal segment. Testing on an Instron tester documented the improvement in stability provided by the sublaminar wires in this grossly unstable experimental fracture. Improved stability was seen in resisting axial loading, lateral bending, and forward flexion loading. Rotational stability was particularly improved.

A systematic approach to the amount of Achilles tendon lengthening in cerebral palsy

A simple technique of determining how much lengthening to provide to the Achilles tendon has been developed. This clinical technique is based on a detailed preoperative neuromuscular assessment of patients with cerebral palsy.

A new orthosis for immediate postoperative bracing in idiopathic scoliosis

The "crutch-type scoliosis brace" and the KSO are leather covered aluminum braces, which have been successfully used in treating scoliosis patients at the Kosair Spinal Deformity Center both nonoperatively and postoperatively. This report defines the measurements, materials, and construction details for effective use of these braces and reports the very encouraging results of the KSO in a group of instrumented idiopathic scoliotic patients.

Benefits of the Harrington compression system in lumbar and thoracolumbar idiopathic scoliosis in adolescents and adults

Adolescent and adult scoliosis exhibits deformity present in all three planes of orientation, but the principal correcting effect of the Harrington distraction system is in the frontal plan. Sagittal and horizontal deformity was addressed by adding the compression system. Twenty patients were treated with combined apparatus. The mean preoperative frontal curve was 52 degrees, and the mean postoperative curve was 16 degrees. The average preoperative tilt angel was 31 degrees, and the average postoperative angle was 8 degrees. Thoracolumbar kyphosis was reduced, and lumbar lordosis was maintained. The combined apparatus addresses the triplanar curvature more effectively than the single distraction system.

Effect of the Harrington compression system on the correction of the rib hump in spinal instrumentation for idiopathic scoliosis

To analyze the effect of the Harrington compression system on the rib hump in thoracic idiopathic scoliosis, intraoperative measurements were made on 21 cases during correction with the distraction system and after addition of the compression system. The data show that the compression system makes a major contribution to the correction of total rib deformity in over two-thirds of the patients, and the correction of the rib valley is much more significant than correction of the rib hump. Analysis of postoperative spine roentgenograms seems to indicate that the extent of the rib correction does not correlate with spine derotation as measured by the system of Nash and Moe. The improvement in rib correction achieved by addition of the compression system appears to result from changes centered about the costovertebral joints.