1997 Volvo Award winner in clinical studies. The effect of pedicle screw instrumentation on functional outcome and fusion rates in posterolateral lumbar spinal fusion: a prospective, randomized clinical study.

STUDY DESIGN: A prospective randomized clinical study. OBJECTIVES: To evaluate supplementary pedicle screw fixation (Cotrel-Dubousset) in posterolateral lumbar spinal fusion. SUMMARY OF BACKGROUND DATA: The rationale behind lumbar fusion is to eliminate pathologic motion to relieve pain. To improve fusion rates and to allow reduction, a rigid transpedicular screw fixation may be beneficial, but the positive effect of this may be counter-balanced by an increase in complications. METHODS: The inclusion criteria were severe, chronic low back pain from spondylolisthesis Grades 1 and 2 or from primary or secondary degenerative segmental instability. One hundred thirty patients were randomly allocated to receive no instrumentation (n = 66) or Cotrel-Dubousset instrumentation (n = 64) in posterolateral lumbar fusion. Variables were registered at the time of surgery and at 1 and 2 years after surgery. RESULTS: Follow-up was achieved in 97.7% of the patients. Fusion rates deduced from plain radiographs were not significantly different between instrumented and noninstrumented groups. The functional outcome assessed by the Dallas Pain Questionnaire improved significantly in both groups, and there were no significant differences in results between the two groups, except for significantly better (P < 0.06) functional outcome in relation to daily activities in the instrumented group when neural decompression had been performed. The global patients' satisfaction was 82% in the instrumented group versus 74% in the noninstrumented group (not significant). Fixation of instrumentation increased operation time, blood loss, and early reoperation rate significantly. Patients experienced only a few minor postoperative complications; none were major. Two infections appeared in the Cotrel-Dubousset group. Significant symptoms from misplacement of pedicle screws were seen in 4.8% of the instrumented patients. CONCLUSIONS: Lumbar posterolateral fusion with pedicle screw fixation increases the operation time, blood loss, and reoperation rate, and leads to a significant risk of nerve injury. The functional outcome improves significantly with high patient satisfaction, with or without instrumentation. No significant differences were observed between the two groups in functional outcome and fusion rate. The only gain in functional outcome from instrumentation was found in the daily activity category in patients with supplementary neural decompression. The results of this study do not justify the general use of pedicle screw fixation alone as an adjunct to posterolateral lumbar fusion.

Interobserver and intraobserver agreement of radiograph interpretation with and without pedicle screw implants: the need for a detailed classification system in posterolateral spinal fusion.

STUDY DESIGN: A prospective randomized clinical study in which four observers evaluated radiographs of posterolateral fusion masses. OBJECTIVES: To evaluate the accuracy of radiograph interpretation of the posterolateral spinal fusion mass when using a detailed classification system and to analyze the influence of metallic internal fixation devices on radiologic inaccuracy. SUMMARY OF BACKGROUND DATA: In general, the literature describing the classification criteria used for radiograph interpretation of spinal posterolateral fusion has serious deficiencies. There is a need for a detailed classification system. METHODS: Seventy patients were randomly allocated to receive no instrumentation (n = 36) or Cotrel-Dubousset instrumentation (n = 34) in posterolateral lumbar fusion. All four observers participated in a prestudy discussion and evaluated the radiographs (anteroposterior, lateral) taken at the 1-year follow-up evaluation. The observers scored the radiographs twice (30 days apart). Each level on each side was judged separately. A continuous intertransverse bony bridge involving at minimum one of the two sides indicated a fusion at that level. "Fusion" indicated this quality of fusion at all intended levels. If the fusion was doubtful on both sides of the interspace, the individual case could not be classified as "fused." RESULTS: The mean interobserver agreement was 86% (Kappa 0.53), and the mean intraobserver agreement was 93% (Kappa 0.78). No difference in interobserver and intraobserver agreement was found between patients with and without supplementary pedicle screw fixation. All mean Kappa values were classified as fair or good. The four observers identified a mean fusion rate of 81%. CONCLUSION: It is extremely difficult to interpret radiographic lumbar posterolateral fusion success. Such an assessment needs to be performed by use of a detailed radiographic classification system. The classification system presented here revealed good interobserver and intraobserver agreement, both with and without instrumentation. The classification showed acceptable reliability and may be one way to improve interstudy and intrastudy correlation of radiologic outcomes after posterolateral spinal fusion. Instrumentation did not influence reproducibility but may result in slightly underestimated fusion rates.

Smoking as a predictor of negative outcome in lumbar spinal fusion.

STUDY DESIGN: A review of the smoking habits in 426 patients who had been followed prospectively for 2 years after a lumbar spinal fusion procedure was conducted. OBJECTIVE: To analyze the effect of pre- and postoperative smoking on clinical and functional outcome after lumbar spinal fusion. SUMMARY OF BACKGROUND DATA: Several animal models have shown a negative effect of nicotine on spinal fusion. At this writing, the clinical effect of nicotine on spinal fusion has not been fully clarified. METHODS: The study comprised 426 patients who underwent lumbar spinal fusion between 1993 and 1997. These patients received a mailed questionnaire regarding their tobacco consumption before and after their surgery. All other data, including preoperative clinical and functional status, were collected prospectively during a 2-year follow-up period. To assess functional outcome, the Dallas Pain Questionnaire was used. RESULTS: The questionnaire was answered by 396 patients (93%). Of these patients, 54.5% (20% more than the background population) were smokers before the operation. Smoking of more than 10 cigarettes daily before the operation and attempted fusion at two or more levels increased the risk of nonunion: odds ratio, 2.01 (P < 0.016) and odds ratio, 3.03 (P < 0.001), respectively. Smoking cessation increased fusion rates to near those of nonsmokers. Smoking had no influence on functional outcome, as assessed by the Dallas Pain Questionnaire, but preoperative smoking predicted a negative answer to the question "Would you undergo the same treatment again, now that you know the result?" (odds ratio, 1.65; P < 0.054). CONCLUSIONS: Smoking was shown to have a negative effect on fusion and overall patient satisfaction, but no measurable influence on the functional outcome as assessed by the Dallas Pain Questionnaire.

Mechanical and histological analysis of bone-pedicle screw interface in vivo: titanium versus stainless steel.

OBJECTIVE: To investigate the differences in bone interface between titanium and stainless steel pedicle screws in the lumbar spine. METHODS: Eighteen adult mini-pigs that underwent total laminectomy, posterolateral spinal fusion (L4-L5) were randomly selected to receive stainless steel (9) or titanium pedicle screw devices (9). In both groups, the devices were CCD (Sofamore Danek) type with the same size and shape. The postoperative observation time was 3 months. Screws from L4 were harvested along their long axis of pedicle for histomorphometric study. Bone-screw interface and bone volume from thread were examined using linear intercept techniques. Mechanical testing (torsional test and pull-out test) was performed on the screws from L5. RESULTS: The titanium screw group had a significantly higher maximum torque (P < 0.05) and angle related stiffness (P < 0.05) measured by torsional test. In the pull-out tests, no differences were found between the two groups in relation to the maximum load, stiffness and energy to failure. Direct bone contact with the screw in percentage was 29.4% for stainless steel and 43.8% for titanium (P < 0.05). No differences in the bone purchase between the vertebral body part and pedicle part were found. CONCLUSION: Pedicle screws made of titanium have a better bone-screw interface binding than screws made of stainless steel. Torsional tests are more informative for bone-screw interface study. Pull-out tests seem less valuable when comparing bone purchase of screws made from different materials.

Postmodernism in marriage and family therapy training: doctoral students' understanding and experiences.

The purpose of this study is to advance our understanding of how doctoral students perceive postmodernism's influence in the field of Marriage and Family Therapy (MFT). According to the literature, postmodernism has had a profound impact on many fields, including MFT. However, tracking of how postmodernism is actually being rendered in theory, research, practice, and training warrants investigation. This study utilized focus group interviews to investigate the perceptions of MFT doctoral students. Findings suggest that while participants are attracted to postmodern tenets, they also report feeling a mixture of liberation and excitement with confusion and fear regarding how postmodernism is influencing MFT models of therapy.

[Results after surgical treatment of unstable thoracolumbar fractures]. / Resultat efter operativ behandling af ustabile torakolumbale columnafrakturer.

Seventy-eight patients with unstable, one-level fracture of the thoracolumbar spine and no neurological impairment were treated with short segment fixation, transpedicular autologous bone transplantation and posterolateral fusion. Kyphotic deformity and anterior column height improved significantly. Complications consisted of one case of late deep infection, three cases of seroma, four cases with 5 mm schantz screw breakage and two cases with screw loosening. Mild to moderate pain was present in 79% of the patients at follow-up, median 32 (13-72) months. Sixty-seven percent of the patients had returned to previous activity levels of employment. Short posterior internal fixation, transpedicular transplantation and posterolateral fusion allowed neurologically intact patients to be mobilized early, to spend median 12 days in hospital, and carried no risk of deterioration in neurological function.

[Anterior lumbar intercorporal spondylodesis. Radiological and functional therapeutic results]. / Forreste lumbal interkorporal spondylodese. Radiologisk og funktionelt behandlingsresultat.

The purpose of this investigation was to identify risk factors in relation to non-union following lumbar intercorporal spondylodesis and to correlate this result with the functional outcome as assessed by the Dallas Pain Questionnaire (DPQ). This comprises questions concerning daily activities, work-leisure activities, anxiety-depression and social interest, measured on visual analog scales. During the period 1979-87 a total of 132 patients were operated with spondylodesis, diagnosed as suffering from spondylolisthesis or disc degeneration. Minimal follow-up was one year. Radiological graft incorporation was complete in 52% of the cases, partial in 24% and lacking in 24%. The rate of functional outcome follow-up was 72%. Seventy percent claimed an improvement in three out of four categories. Thirty percent claimed no improvement or worsened condition. The DPQ showed signs of poor prognosis for age groups above 45 (p < 0.04) and those with former spine surgery (p < 0.02). The questionnaire showed significantly better results for the group with perfect or doubtful union compared to the group with non-union (p < 0.006). In conclusion this investigation demonstrates a success rate of 70% for anterior lumbar interbody fusion. There is a tendency to poorer prognosis for patients with previous spine surgery and age above 45 years. The Dallas Pain Questionnaire correlates significantly to X-ray analysis and seems to be a useful tool for the description of individual biopsychosocial changes following spine surgery.

[The effect of pedicle screw instrumentation on posterolateral spinal fusion. A prospective, randomized study with a two-year follow-up]. / Effekten af pedikelskrueinstrumentering ved posterolateral lumbal spondylodese. Et prospektivt randomiseret studium med to års opfølgning.

The aim was to evaluate the effect of supplementary pedicle screw fixation (Cotrel-Dubousset [CD]) in posterolateral lumbar spinal fusion. The study comprises 130 patients undergoing lumbar or lumbosacral fusion for spondyloisthesis grades I-II or degenerative segmental instability conditions. The patients were randomly allocated for no instrumentation (n = 66) or CD instrumentation (n = 64) in posterolateral lumbar fusion. A 97.7% follow-up was achieved. There were no significant differences between the two groups concerning fusion rates assessed by X-ray or functional outcomes assessed by Dallas Pain Questionnaire. The global patient satisfaction was 82% in the instrumented group versus 74% in the noninstrumented group. Instrumentation increased both operation time, blood loss, and early re-operation rates significantly. A high patient satisfaction was found in both groups. However, the results from this study do not justify the general use of pedicle screw fixation alone as an adjunct to posterolateral lumbar fusion.

Video based analysis of dynamic midfoot function and its relationship with Foot Posture Index scores.

INTRODUCTION: Various studies have demonstrated significant as well as non-significant relationships between static evaluation of foot posture and injury likelihood. Therefore, the relationship of static and dynamic measures needs to be established as in clinical settings time consuming dynamic methods are often not feasible. PURPOSE: Assess reliability of a new method to quantify midfoot movement and validate the use of Foot Posture Index (FPI) classification as predictor of dynamic foot function during walking. METHOD: Foot type was classified using FPI in 280 randomly selected adult participants (mean age 43.4 years). A Video Sequence Analysis (VSA) system was used to quantify midfoot kinematics during walking. Navicula drop (DeltaNH) and minimal navicula height (NHL) were compared with FPI. RESULTS: The Intraclass Correlation Coefficients (ICC) for DeltaNH and NHL ranged from 0.65 to 0.95 with a coefficient of repeatability of 1.4 mm for DeltaNH and 4.5 mm for NHL. System precision was estimated at 0.99 mm for DeltaNH and 3.18 mm for NHL. DeltaNH was significantly positively correlated with FPI scores while NHL decreased with increasing FPI. However, the FPI model predicted only 13.2% of the variation in DeltaNH and 45% of the variation in NHL during walking (p<0.001). CONCLUSION: The VSA was proven as a reliable and precise method to quantify midfoot kinematics. FPI scores and individual components of the FPI show strong statistical relationships to dynamic measures but individual predictions remain questionable. Dynamic midfoot measures are recommended for clinical foot assessments.

Stabilisation surgery for chronic low back pain: indications, surgical procedures, and outcome.

Spinal fusion was introduced as a treatment option for chronic low back pain >70 years ago. However, few areas of spinal surgery have caused as much controversy. The debate about whether to use an anterior-, posterior- or anterior + posterior approach has persisted since the 1930s. Within the last 10 years, the effects of different spinal fusion procedures have been tested in 10 randomized controlled trails (RCT). A highly significant improvement over preoperative status was found in all 10 studies. Two recent RCTs have dealt with the question of conservative versus operative treatment of patients with low back pain, and both studies have shown a significant better functional outcome for spinal fusion in situ, compared with a more or less organized exercise programme at 2-year follow-up. The choice of postoperative rehabilitation strategy has also been shown to be of importance for overall functional outcome. One study has demonstrated the importance of the inclusion of coping schemes, and questioned the role of intensive exercises in a rehabilitation programme for spinal fusion patients.

Retrograde ejaculation after retroperitoneal lower lumbar interbody fusion.

We have studied the incidence and functional outcome of retrograde ejaculation as a postoperative complication of anterior lumbar interbody fusion. A questionnaire, specifically designed to analyse this problem, has been used over a 6 to 13 year follow-up. Out of 50 men, 41 completed the questionnaire; 2 complained they had permanent retrograde ejaculation after the operation; one stopped ejaculating for 6 months, and thereafter had a 50% reduction. The Dallas pain questionnaire showed that retrograde ejaculation did not have a negative effect on the functional outcome, but male genital dysfunction was a complication of anterior spinal fusion in 8% of cases.

A comparison of ampicillin plus sulbactam versus clindamycin and gentamicin for treatment of postpartum infection.

Thirty-six hospitalized patients, 18 in each of two groups, with postpartum upper genital tract infection were enrolled in a randomized, prospective study comparing treatment with sulbactam/ampicillin, to treatment with clindamycin/gentamicin. One (5.5%) clinical failure was reported in each group. Side effects were minimal in both groups and did not warrant discontinuation of treatment. The in vitro activity of ampicillin versus sulbactam/ampicillin (1:2) was evaluated and these data were compared with data from other drugs commonly used for aerobic and anaerobic infections. Sulbactam eliminated resistance to ampicillin in all anaerobic and most aerobic isolates.

Intramuscular imipenem/cilastatin treatment of upper reproductive tract infection in women: efficacy and use characteristics.

We evaluated the efficacy, patient and medical staff acceptance, and costs of intramuscular therapy with imipenem/cilastatin for mild to moderate upper reproductive tract infection in hospitalized women in an open study. Thirty-five patients were enrolled, and 29 successfully completed the protocol. Of these, 90% were satisfactorily treated with imipenem/cilastatin given intramuscularly. Twenty-eight of 29 subjects tolerated the intramuscular injections well, although 7 women noted mild to moderate discomfort during injection. All patients who had previously received intravenous therapy (24/29) stated that they preferred the intramuscular injections to continuation or reinitiation of intravenous treatment. Therapy with intramuscular imipenem/cilastatin (assuming a marketed price per gram of approximately $30) was associated with cost savings in comparison with other regimens offering similar antibacterial coverage. Initial care provider resistance to treatment with intramuscular imipenem/cilastatin was overcome due to patient satisfaction. Intramuscularly administered imipenem/cilastatin was effective, generally well tolerated, and resulted in cost saving. Intramuscular administration of imipenem/cilastatin may be a preferred antibiotic treatment in patients with mild to moderate infection due to susceptible microorganisms.

Radiological and functional outcome after anterior lumbar interbody spinal fusion.

Outcome after anterior spinal fusion has mainly been studied radiologically and reported fusion rates vary greatly. The aim of this study was to investigate radiological and long-term clinical outcome. The study comprised 120 consecutive patients, operated on during the period 1979-1987, with single-or two-level anterior interbody spinal fusion due to disc degeneration or isthmic spondylolisthesis with lumbar instability. In 64 patients a supplemental facet joint fusion was performed. Clinical outcome was evaluated 5-13 years after surgery using the patient-administered Dallas Pain Questionnaire (DPQ). Radiological outcome was determined on the basis of radiographs taken at a 2-year follow-up assessed by independent observers. The radiological follow-up rate was 98%. Complete fusion was found in 52%, questionable fusion in 24%, and definitive pseudoarthrosis in 24% of patients. Radiological results were poor in patients who had undergone previous spinal surgery (P < 0.05) and in those with two-level fusion (P < 0.05). The DPQ reply rate was 80%. Sixty-six patients claimed improvement in all functional groups. Patients with complete or questionable union had significantly better results than did those with non-union (P < 0.01). Poorer functional outcome was found in patients who had undergone previous spinal surgery (P < 0.01) or fusion at the L4/L5 level (P < 0.05), in those who had responded poorly to the preoperative test brace (P < 0.05), and in those above 45 years old at the time of surgery (P < 0.05). Radiological and functional outcome did not vary according to whether patients were treated postoperatively with a plaster jacket or with facet screw fixation. The study demonstrated a functional success rate of approximately 66% following anterior lumbar spinal fusion after a mean follow-up of 8 years. There was a clear tendency for poorer prognosis for patients who had undergone previous spinal surgery, those aged above 45 years, those operated at the L4/L5 level and those who had responded poorly to the preoperative test brace. DPQ scores correlated well with radiological outcome.

Functional outcome after posterolateral spinal fusion using pedicle screws: comparison between primary and salvage procedure.

Lumbar spinal fusion is a commonly performed surgical procedure, yet both the indications for its performance and its results remain controversial. It is generally believed that apart from situations where obvious measurable instability exists, a repeat surgical procedure such as spinal fusion does not improve the functional outcome in more than an average of 50% of cases. The aim of this study was to analyse functional outcome after posterolateral lumbar or lumbosacral spinal fusion, comparing primary and salvage procedures. It was designed as a prospective case/referent study with a 2-year follow-up. A total of 39 patients underwent a short posterior fusion with Cotrel-Dubousset (CD) pedicle screw fixation after earlier surgery of the lumbar spine. Two patients were erroneously omitted from the study at the index, so 37 patients were included in the salvage group. In the same period, 69 patients underwent lumbar fusion with pedicle screw fixation (CD) as primary surgery (referent group). Functional outcome was assessed by means of the Dallas Pain Questionnaire preoperatively and 1 and 2 years postoperatively. Fusion rates were determined by ordinary X-ray evaluation by two independent observers. Patients who had undergone previous spinal surgery had a significant improvement in functional outcome in terms of daily activity, work and leisure-time activities and anxiety/depression. With regard to social functioning, a significantly inferior outcome was found after the salvage procedure. The return-to-work rates at 2 years after surgery were 50% in the salvage group and 53% in the referent group. There was a significant correlation between radiological evaluation of the fusion mass and the functional outcome. The fusion rate was 76% in the salvage group and 72% in the referent group. This study demonstrates that a posterolateral spinal fusion can be effectively used as a salvage procedure. The functional and radiological outcome of the patients with revision surgery did not differ from those of the group of patients who underwent primary surgery. There was, however a clear indication of inferior social functioning after revision surgery.

Posterolateral spinal fusion at unintended levels due to bone-graft migration: no effect on clinical outcome in 19/130 patients.

In a prospective randomized study, we evaluated the risk of lumbar posterolateral spinal fusion at an unintended level due to bone graft migration. 130 patients underwent fusion supplemented by pedicle screw fixation (Cotrell-Dubousset, 64 patients) or uninstrumented fusion (66 patients). This was assessed by two independent observers on antero-posterior, and lateral radiographs taken 1 year after surgery. All patients had ben operated on at the preoperatively planned levels. Both observers agreed that fusion had taken place at an unintended level in 19 cases (14%). We found a tendency towards a higher risk of this "complication" when using supplementary pedicle screw fixation. The functional outcome, assessed by the Dallas Pain Questionnaire and the Low Back Pain Rating scale, was similar in patients having fusion at an unintended level and in patients fused only at the intended levels. There was no difference between the two groups concerning reoperation rates, postoperative smoking or social status. We conclude that unintended fusion occurs and tends to be commoner with the use of pedicle screw instrumentation. However, this complication seems not to affect the functional outcome if fusion has taken place at the intended level.

Titanium-alloy enhances bone-pedicle screw fixation: mechanical and histomorphometrical results of titanium-alloy versus stainless steel.

Several types of pedicle screw systems have been utilized to augment lumbar spine fusion. The majority of these systems are made of stainless steel (Ss), but titanium-alloy (Ti-alloy) devices have recently been available on the market. Ti-alloy implants have several potential advantages over Ss ones. High bioactivity and more flexibility may improve bone ingrowth and mechanical fixation, and the material also offers superior magnetic resonance imaging (MRI) and computed tomography (CT) resolution and significantly less signal interference. However, no data are available from loaded spinal constructs regarding bony ingrowth and mechanical fixation. The aim of this study was to analyse the effect of Ti-alloy versus Ss pedicle screws on mechanical fixation and bone ingrowth in a loaded mini-pig model. Eighteen adult mini-pigs underwent total laminectomy and posterolateral spinal fusion at L3-L4, and were randomly selected to receive either Ss (n = 9) or Ti (n = 9) pedicle screw devices. In both groups, the device used was compact Cotrel-Dubousset instrumentation (Sofamore Danek) of an identical size and shape. The postoperative observation time was 3 months. Screws from L3 were used for histomorphometric studies. Mechanical testing (torsional tests and pull-out tests) was performed on the screws from L4. The Ti screws had a higher maximum torque (P < 0.05) and angular stiffness (P < 0.07), measured by torsional testing. In the pull-out tests, no differences were found between the two groups with respect to the maximum load, stiffness and energy to failure. No correlation between removal torque and the pull-out strength was found (r = 0.1). Bone ongrowth on Ti was increased by 33% compared with Ss (P < 0.04), whereas no differences in bone volume around the screws were shown. Mechanical binding at the bone-screw interface was significantly greater for Ti pedicle screws than for Ss, which was explained by the fact that Ti screws had a superior bone ongrowth. There was no correlation between the screw removal torque and the pull-out strength, which indicates that the peripheral bone structure around the screw was unaffected by the choice of metal.

Recombinant bone morphogenetic protein-7 as an intracorporal bone growth stimulator in unstable thoracolumbar burst fractures in humans: preliminary results.

The study presented here is a pilot study in five patients with unstable thoracolumbar spine fractures treated with transpedicular OP-1 transplantation, short segment instrumentation and posterolateral fusion. Recombinant bone morphogenetic protein-7 in combination with a collagen carrier, also referred to as OP-1, has demonstrated ability to induce healing in long-bone segmental defects in dogs, rabbits and monkeys and to induce successful posterolateral spinal fusion in dogs without need for autogenous bone graft. Furthermore OP-1 has been demonstrated to be effective as a bone graft substitute when performing the PLIF maneuver in a sheep model. Five patients with single-level unstable burst fracture and no neurological impairment were treated with intracorporal OP-1 transplantation, posterior fixation (USS) and posterolateral fusion. One patient with osteomalacia and an L2 burst fracture had an additional intracorporal transplantation performed proximal to the instrumented segment, i.e. OP-1 into T 12 and autogenous bone into T 11. Follow-up time was 12-18 months. On serial radiographs, Cobb and kyphotic angles, as well as anterior, middle and posterior column heights, were measured. Serial CT scans were performed to determine the bone mineral density at fracture level. In one case, radiographic and CT evaluation after 3 and 6 months showed severe resorption at the site of transplantation, but after 12 months, new bone had started to fill in at the area of resorption. In all cases there was loss of correction with regard to anterior and middle column height and sagittal balance at the latest follow-up. These preliminary results regarding OP-1 as a bone graft substitute and stimulator of new bone formation have been disappointing, as the OP-1 device in this study was not capable of inducing an early sufficient structural bone support. There are indications to suggest that OP-1 application to a fracture site in humans might result in detrimental enhanced bone resorption as a primary event.

Can autologous bone culture predict spinal fusion capacity?

The capacity of the individual patient to initiate osteoblast proliferation as a predictor for successful lumbar spinal fusion has not yet been reported. The objectives of this study were, first, to analyze the relationship between in vitro osteoblast proliferation and clinical bony fusion in the individual patient in order to predict the fusion outcome and, second, to measure the effect of preoperative tobacco smoking on osteoblast proliferation. Sixty-one patients (mean age 46 years) underwent posterolateral lumbar fusion in the period 1994-1995. Thirty-eight patients received CD pedicle screw implants and 23 received posterolateral fusions alone. During surgery, autogenous iliac bone was harvested and 1 g of trabecular bone without blood or bone marrow was then isolated for cell culturing. The cultures were classified as excellent (confluence within 4 weeks), good (confluence between 4 and 6 weeks) and poor (no or poor growth). Spine fusion was evaluated by two independent observers from plain anterior-posterior, lateral, and flexion/extension radiographs taken 1 year postoperatively, and the functional outcome was measured by the Dallas Pain Questionnaire (DPQ). Twenty-three patients had excellent, 19 good, and 19 poor in vitro osteoblast proliferation. Bony fusion was obtained in 77% of patients: 83% in the CD instrumentation group and 70% in the non-instrumentation group (NS). There was no significant correlation between osteoblast proliferation and spinal fusion or functional outcomes when analyzing the CD instrumentation and non-instrumentation groups together or separately. Elderly patients had a significantly poorer osteoblast proliferation than younger patients (P < 0.008). Preoperative tobacco consumption had no discernible effect on osteoblast proliferation, and no correlation between smoking and fusion was found. Further refinement of autologous osteoblast culturing may provide a biological tool for selection of patients who require biological enhancement of their bone fusion capacity. The poorer osteoblast proliferation related to advanced age supports the important negative biological influence of age on bony fusion. However, with more sensitive testing and better discrimination, other results are possible - or can in any event not be excluded.