Abstracts

ORIGINAL ARTICLE

Lumbosacral column arthtodesis with a system's implant

Afrane Serdeira^I; Tarcísio Eloy Pessoa de Barros Filho^II; Eduardo Puertas^III; José Laredo Filho^IV; Rodrigo Di Mare Arbo^V; Alexandre M. Glass^V

^IDoctor in Medicine. Assistant Professor at the Orthopedics and Traumatology Department of the São Lucas Hospital of the PUCRS

^IIAssociate Professor at the Department of Orthopedics and Traumatology of the FMUSP, Head of the Vertebral Spine Discipline

^IIIDoctor in Medicine, Adjunct Professor and Head of the Column Group of the Orthopedics and Traumatology Department of the DOT-UNIFESP-EPM

^IVTitular Professor at the Orthopedics and Traumatology Department of the UNIFESP-EPM. Rector of the Administration of UNIFESP-EPM

^VResident Physicians of the Orthopedics and Traumatology Department of São Lucas Hospital of PUCRS

^{Correspondence} Correspondence to Service of Orthopedics and Traumatology São Lucas Hospital - PUCRS Av Ipiranga, 6690 CEP 90610-000 Porto Alegre –RS e-mail – afrane@terra.com.b

SUMMARY

Lumbosacral column arthrodesis with bone graft and metallic fixation (A-Systems implant) was carried out in 40 patients with spondylolisthesis and lumbosacral instability of the following types: isthmic-lytic in 13, degenerative in 19, traumatic in 2, pathological in 1, and surgical in 5.

Preoperative, immediate postoperative, and late postoperative clinical and radiological evaluation was carried out. Clinical follow-up ranged from 10 to 46 months (mean follow-up: 11 months).

Patient's and Physician's overall evaluation showed the following results: good results in 36 (39%) patients; improvement as compared to preoperative condition in 3 (7.5%); unchanged condition in 1 (2.5%); normalized labor capability in 29 (72.5%) patients; improvement of 75% in labor capability in 9 (22.5%) patients; and improvement of 50% in 2 (5%) patients. As for the Prolo rate, an increase to 9-10 (excellent) was seen in 21 (52.5%) patients; an increase to 7 and 8 (good) was seen in 14 (35%); an increase to 5 to 6 (moderate) was found in 5 (12.5%) patients. No patient had a Prolo rate of 2, 3, or 4 (poor).

Mean time until return to normal activities ranged from 3 to 12 months (mean: 7 months).

As compared to similar methods reported in literature, the implant has been shown to be equaally effective, with the following advantages: simplicity, use at different levels; rigidity following assembly.

Keywords: Spine; Arthrodesis; Spinal fusion; Prostheses and implants.

INTRODUCTION

In 1992 we started a research to make an implant for lumbosacral column fixation with the following acteristics: easy to use; no need for complicated tools; rigidity and safety. The implant was generically called AS1 (Implant A Series 1). It consisted of a U-shaped shaft or two bars connected to clips and pediculate screws for tridimensional assembly.

Some improvements were progressively implemented to increase resistance and make implant insertion easier, the original project being preserved. The improved version was called A-Systems.

Improved fit of pediculate screws and shafts has led to decreased surgical time. Following mechanical research we started the present study by using the device in a clinical study.

MATERIAL AND METHODS

Study population

Fourteen medical records of operated patients were included into the study. The following data according to modified Delfino ^[2] protocol were recorded: gender, age, diagnosis, lesion site, evaluation of lesion, orthopedic evaluation (pain, mobility, muscular force, and claudication), neurological evaluation (sensitiviy, reflexes, and sphincteral functions), and imaging tests (plain radiographs, computed tomography, clinical and laboratory evaluation).

Twenty-eight female (70%) and 12 male (30%) patients aged 16 to 76 years (mean age: 43.5 years) had spondylolisthesis and instability. According to of Wiltse et al.^[11], study patients were categorized as follows: type II-A (isthmic-lytic) in 13 patients; type III (degenerative: stenoses in 12; disk degeneration in 6; and stenosis of lateral recess in 1) in 19 patients; type IV (traumatic) in 2; type V (metastatic tumor) in 1; type VI (postlaminectomy syndrome) in 5. Lesions were predominantly found at the L5-S1 level.

Description of the implant:

A-Systems fixation system consists of the following (Figure 1):

1. U-shaped or straight stainless steel shafts ASTM EF 138 measuring 6.5 mm diameter and 50-to-150 mm long. Surface is treated to obtain an increased friction coefficient;

2. Pediculate screws consisting of 3 parts: beginning with saw-toothed thread with miller tool for spongy bone (30-mm, 35-mm, 40mm, and 45-mm long and 5.5-mm, 6.5-mm, and 7.5-mm diameter). The 8-mm intermediate portion is hexagon-shaped and followed by millimeter thread measuring 30 mm long and 4 mm diameter and ended by another hexagon-shaped end measuring 3 mm fitting the approriate tubular screwdriver. Each screw has a 8-mm nut and two semicylyndrical washers of plane face measuring 9 mm x 9 mm.

3.Fixation clips (Figure 2) consist of two units measuring 33 mm long and 10 mm wide; one end is provided with an oblong opening measuring 12 mm long and 5 mm wide to fix pediculate screw in order that lateral sliding be possible. The clip connects the shaft and the screw. When connected, they form a tridimensional unit.

4. Stabilizer: a device placed between the bars so as to avoid lateral bend following system assembly, as needed.

Surgical tools:

Tools used for implant fixation are (Figure 3): a) starter with a pyramidal end; b) pedicle guide; c) double hexagon tubular screwdriver, one of which measuring 8 mm that is used to fit the pediculate screw and hexagon nut; and the other one measuring 3 mm is internally used to block the screw thread during final turn of the nut; d) a conventional 8-mm hexagon screwdriver; e) 3.5-mm hexagon slotted screwdriver; f) impactor; g) stretching and compression clampls; h) bar cutter and shaft modeler.

Surgical Technique:

Patients under general anesthesia were placed in ventral decubitus over 4 polyurethane foam pads covered with soft foam on the radiotransparent operation table. Following skin antisepsis a 10-cm incision was longitudinally made along lumbosacral region.

Fat tissue is dissected so as to expose spinous processes. Paravertebral musculature is subperiosteally detached and supraspinous, interspinal, and ligament flavum. The point corresponding to pedicle is identified before pediculate screw insertion.

This point is identified by crossing two imaginary lines, one of which is transverse and crosses the transverse process; the other line is longitudinal and is approximately 2 mm distant from the upper articular facet where cortical perforation is made with the sharp pyramidal end.

The guide is used in the pedicle to guide screw insertion, allowing one to radiographically control direction and deepness.

Screws are then fixed (two for each level). Laminectomies and removal of foramina are then perfomed whenever needed.

Gluteal fascia is dissected through the same incision and spongy bone grafts are removed from the iliac crest. The latter are then inserted between spinous apophyses. This step must always precede shaft and clip insertion. Otherwise, space for grafting will be decreased and pseudarthroses can develop.

Assembly consists of placement of the first washer with the curved face against the clip. Previously assembled shafts and connector clips are applied on screws.

The second washer is put over the clips and nuts are then inserted. Continuous aspiration drainage tube is placed in iliac crest and arthrodesis area, gluteal and toracolumbar fascias are sutured (Vicril #0), subcutaneous tissue is sutured with vicril #00, and skin is sutured with nylon #000 (polyamide).

Separate stitches are used. Finally, a dry dressing is applied following skin cleaning with saline solution.

Immediate postoperative period:

Seven days following surgery lumbosacral radiographs (frontal and lateral views) are obtained and compared with previous radiographs.

Evaluation of Results:

- Postoperative Recovery:

The following criteria were used: time (number of days) when the patient sat and walked, hospitalization stay, hospitalization time period, incapacity duration until return to work and follow-up of the patient.

- Neurological Signs and Symptoms:

Preoperative and postoperative comparison of vesical and intestinal functions, mobility, pain, and reflexes was carried out.

- Radiological Criteria:

Pre- and postoperative radiographs were analyzed. The following variables were analyzed: graft integration, decrease in bone shifts, implant localization, and eventual implant displacements (Figure 4).

- Complications:

Complications were reported since their appearance: pain, delayed fracture healing (graft integration after 6 months), pseudarthrosis (lack of healing after 9 months), nervous lesion, bedsore, and infection.

- Implant status:

Implant status was evaluated by analyzing postoperative radiographs based upon the following points: no problem, loose screws, broken screws, loose nuts, loose clips, broken shafts, broken wire, and defects in screw-bone interface.

- Final Evaluation:

Objective evaluation: the quantitative classification was adopted using Prolo rate ^[5] that evaluates labor (economical) status and functional status (pain) (Chart 1).

Subjective Evaluation: patient's and physician's opinion was taken into account according to the following categories: good, improved, unaltered, worse; and 100%, 75%, 50%, 25% labor capability; and total disability.

- Statistical Analysis:

Descriptive statistical analyses of quantitative variables and absolute and relative frequency distribution (%) of qualitative variables was performed. A significance level of 0.05 was adopted and significant results were marked with an asterisk (*).,

RESULTS

Clinical Analysis:

- Neurological Signs and Symptoms:

a) Functions:

Vesical and intestinal functions remained altered in the patient who had an explosion fracture. No changes were observed in these functions in the remaining patients.

b) Pain and Sensitivity:

Following surgery pain totally subsided in 30 patients (75%) (Table 1).

c) Reflexes (Tables 2 and 3):

- Mobility (Table 4):

Functional Evaluation:

- Labor capability (Table 5):

- Labor incapacity duration:

Four patients (10%) returned to work within 3 to 4 months; 15 patients (37.5%) returned to work within 3 to 5 months; 18 patients (45%) returned to work within 5 to 7 months; and 3 patients (7.5%) returned to work within more than 12 months.

- Implant status:

Thirty-eight implants (95%) had no complications until study conclusion; in 2 patients (5%) loose clip developed due to faulty technique. Breakage of screws and shafts were not observed.

- Postoperative follow-up:

Postoperative follow-up ranged from 10 to 46 months (mean: 11 months).

- Complications:

Eleven complications (27.5%) developed: 5 associated with implant fixation; 2 associated with pseudarthrosis; 2 associated with delayed graft integration; and 1 associated with sacral bedsore and secondary infection due to faulty technique. The other six complications were not related with the implant: 4 were due to pain in the bone graft donor area secondary to rami cluneum lesion; one was due to transient pain in the anterior iliac crest; and 1 was due to lumbar pain persistence.

- Final results

Good results were observed in 36 (90%) patients. Improvement as compared to preoperative status was seen in 3 (7.5%) patients and 1 (2.5%) patient whose condition was considered unaltered did not return (lost to follow-up), . These results are based upon the objective study of medical records, patient's satisfaction, and physician's opinion (Figure 5).

DISCUSSION

Medical records of 40 patients were studied according to similar protocols described in literature.

All patients were submitted to surgical therapy for lumbosacral stabilization following failure of conservative therapy.

Data concerning distribution of signs and symptoms according to age (range: 16-76 years) are similar to those reported by Rissanen [6], Twoney and Taylor [9], Frymoyer ^[3], Barros F^o et al. and Basile ^[1].

In contrast, data concerning gender were not similar: in our studies female:male ratio was 28:12 (70%:30%) while Rosenberg ^[7] has reported that the incidence of degenerative spondylolisthesis is 6 times greater in female patients

All patients had instability, as shown by evidence found in preoperative evaluation ^[10] and by direct examination during surgery. This finding was confirmed after vertebral decompression of posterior elements (neural arches and articular processes) according to Kanwaldeep and Herkowitz ^[4].

All patients had severe pain and sensitivity changes with predominance of L5-root lesion. Improvement was evident following surgey.

Based upon data shown in tables, reflexes significantly improved following surgery.

Painful mobility returned to normal in 30 patients (75%) while mildly decreased painful mobility remained in 10 patients (25%). Motion range returned to normal in 30 patients (75%), remained decreased in 9, and slightly improved in 1 (25%).

Mobility improvement is a very positive factor for patient's quality of life. In 29 patients (72.5%) labor capability returned to normal, had a 75% improvement in 9 (22.5%) and 50% improvement in 2 (5%).

This evaluation is based upon patient's and physician's opinion and is subject to some subjective distortion. The classification described by Prolo et al.^[5] was used so as to reduce distortions.

The Prolo rate increased when preoperative and postoperative values were compared, thus confirming a significant improvement.

The sum of the economic and functional degrees provides a result defining patient's clinical condition as follows: an increase to 9-10 (excellent) was seen in 21 (52.5%) patients; an increase to 7 and 8 (good) was seen in 14 (35%); an increase to 5 to 6 (moderate) was found in 5 (12.5%) patients. No patient had a Prolo rate of 2, 3, or 4 (poor).

Implant analysis showed no complication in 38 (95%) patients until study conclusion. Loose clip was seen in 2 patients (5%) due to faulty technique. Screw or shaft breakages were not seen.

Considering the great diversity of implants and fixation methods available today and constant improvements of these resources, we concluded that an important point is the experience with an easy-to-use system validated by scientific research.

The surgeon must be aware of technical peculiarities of the implant, advantages, difficulties, and required care for its use.

Based upon mechanical study results ^[8], the A-Systems implant system is adequate. We adopted it and the present study confirmed its efficacy.

CONCLUSIONS:

1. The inner fixator A-Systems is indicated for surgical treatment of lumbosacral column diseases requiring arthrodesis.

2. It can be used in the posterior side of vertebral bodies of the lumbosacral column.

3. It allows one to perform short arthrodesis since the method is based upon pediculate support;

4. Final results were good even when lumbar pediculate fixation or sacral threads were used.

5. Early mobilization of patients is possible with a low rate of mechanical failure and pseudarthrosis.

6. The complication rate is not greater than those seen in similar series described in literature.

REFERÊNCIAS BIBLIOGRÁFICAS

Trabalho recebido em 22/05/2003.

Aprovado em 27/07/2003

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