OBJECTIVE This was a prospective controlled study with lumbar degenerative disc disease
patients submitted to instrumented anterior lumbar interbody fusion (ALIF)
combined with posterior stabilization.
METHODS A sample with 64 consecutive patients was operated by the same surgeons over 4 years. Half of the ALIFs occurred at 2 levels, 43.8% at 3 levels, and 6.25% at 1 level. Interbody cages with integrated screws, filled with bone matrix and bone morphogenetic protein 2, were used.
RESULTS Half of the patients had undergone previous lumbar spine surgeries, 75% presented with associated degenerative listhesis, and 62.5% had posterior lumbar compression disease. Approximately 56% of the sample had at least 1 risk factor for nonunion. The Oswestry index changed from 71.81 ± 7.22 at the preoperative assessment to 24.75 ± 7.82 at the final follow-up evaluation, while the visual analogue pain scale changed from 7.88 ± 0.70 to 2.44 ± 0.87 (p < 0.001). Clinical and functional improvements increased with the number of operated levels, proving the efficacy of multilevel ALIF, performed in 93.75% of the sample. The global complication rate was of 7.82%, with no major complications. No cases of nonunion were observed. Conclusion Instrumented ALIF combined with posterior stabilization is a successful option for uni- and multilevel degenerative disc disease of the L3 to S1 segments, even in the significant presence of risk factors for nonunion and of previous lumbar surgeries, assuring very satisfactory clinical-functional and radiographic outcomes with a low medium-term complication rate.
Keywords: lumbar vertebrae/surgery; spinal fusion; prospective studies; scoliosis/surgery; risk factors.
OBJETIVO Estudo prospectivo controlado em pacientes com discopatia degenerativa
submetidos a artrodese intersomática lombar anterior instrumentada combinada
com estabilização posterior.
MÉTODOS Amostra com 64 pacientes consecutivos operados pelos mesmos cirurgiões ao longo de quatro anos. Metade das artrodeses intersomática lombar anterior foi efetuada em dois níveis, 43,8% em três níveis e 6,25% em um nível. Foram usadas caixas intersomáticas com parafusos integrados preenchidas com matriz óssea e proteína morfogenética óssea 2.
RESULTADOS Metade da amostra apresentava cirurgias prévias à coluna lombar, 75% listeses degenerativas associadas e 62,5% patologia compressiva posterior da coluna lombar. Aproximadamente 56% da amostra apresentavam pelo menos um fator de risco de não união da artrodese. O índice Oswestry passou de 71,81 ± 7,22 no pré-operatório para 24,75 ± 7,82 na avaliação no fim do tempo de seguimento, enquanto a escala visual analógica da dor passou de 7,88 ± 0,70 para 2,44 ± 0,87 (p < 0,001). A melhoria clínico-funcional foi crescente de acordo com a intervenção num número superior de níveis, o que comprova a eficácia da artrodese intersomática lombar anterior multinível, aplicada em 93,75% da amostra. A taxa global de complicações foi de 7,82% e de complicações major de 0%. Não se identificou qualquer caso de não união.
CONCLUSÃO A artrodese intersomática lombar anterior instrumentada combinada com estabilização posterior é uma opção de sucesso na discopatia degenerativa uni ou multinível dos segmentos de L3 a S1, mesmo em presença significativa de fatores de risco de não união e cirurgias prévias da coluna lombar, garante resultados clínico-funcionais e radiográficos muito satisfatórios e reduzida taxa de complicações em médio prazo.
Palavras-chave: vértebras lombares/cirurgia; fusão vertebral; estudos prospectivos; escoliose/cirurgia; fatores de risco.
|Citation: Moura DL, Lawrence D, Gabriel JP. Multilevel Anterior Lumbar Interbody Fusion Combined with Posterior Stabilization in Lumbar Disc Disease-Prospective Analysis of Clinical and Functional Outcomes*. 54(2):140. doi:10.1016/j.rbo.2017.11.006|
|Note: * Work developed at the Serviço de Ortopedia of the Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal.|
|Received: October 21 2017; Accepted: November 28 2017|
Anterior lumbar interbody fusion (ALIF) is a therapeutic option for lumbar spine degenerative disc disease and spondylolisthesis at the L3-L4, L4-L5 and L5-S1 levels, which are increasingly common conditions in modern society.1 In theory, the anterior interbody fusion has biomechanical and morbidity advantages over the posterior, oblique or lateral approaches.2,3 The anterior lumbar spine approach allows a better exposure of the disc space and the application of a larger interbody cage, thus effectively restoring the intervertebral space height, lumbar lordosis, the sagittal balance, and the physiological distribution of forces on the anterior and middle columns of Denis (80% of axial compressive forces occur in the anterior and middle columns); this, theoretically, reduces the risk of adjacent disc disease and the need for future surgical interventions. These factors, also theoretically, increase the potential for interbody fusion since the cage is more subjected to compression forces in the anterior column of Denis and the stimulus to bone fusion is more effective.1-6 In addition, the anterior cage position corresponds to the most vascularized region of the vertebral body, stimulating the fusion.4,5 The most effective discec-tomy under direct visualization through a wider space leaves less disc residues that can interpose themselves and impair the interbody fusion compared with other approaches, assuring a greater fusional area. The bigger interbody spacing provided by the larger cage also allows a significant increase in the intervertebral foramina height, which effectively decreases the conflict with spinal roots, as well as the symptomatology.3,7,8 Regarding morbidity, unlike the posterior approaches, which involve extensive paravertebral muscle dissection, and the lateral approach, which involves crossing the psoas muscle, the anterior lumbar spine approach does not interfere with any spinal muscle and does not include muscular detachments. Thus, theoretically, there is less bleeding, which may allow a faster postoperative pain relief (reducing the need for painkillers) and functional improvement (with shorter hospital stay), as well as earlier spine stability, because it does not interfere with the supporting musculature.3,5,6,8-10 Moreover, the anterior approach neither implies in the removal of posterior spinal elements, nor in the entry into the spinal canal or in the manipulation of the spinal roots to access the disc space; as such, it decreases the risk of iatrogenic injury and of complications in these important structures compared with the
Despite these theoretical advantages and the fact that ALIF has been described since the 1930s for the treatment of various lumbar spine conditions, its exact indications and clear advantages remain to be proven.1,2,8,11
Concerns regarding iatrogenic and potentially fatal large vessel damage, as well as the limited experience of orthopedic surgery in the anterior approach to the lumbar spine, often lead many surgeons away from this interbody fusion technique. Currently, large prospective studies on ALIF remain limited, and this technique is deferred to posterior, oblique, or lateral interbody fusions in many centers.
MATERIAL AND METHODS
This was a prospective controlled study in 64 consecutive patients with lumbar degenerative disc disease treated with ALIF combined with posterior stabilization over 4 years; all of the procedures were performed by the same surgeons and complied with the same therapeutic protocol.
The mean follow-up time was of 27.64 ± 11 months (minimum time of 12 moths; range: 12-48 months). All of the patients completed a conservative treatment period, including symptomatic control and physical therapy, before the surgical intervention. The patients were studied for diagnosis, symptomatology, nonunion risk factors (obesity, smoking, diabetes mellitus), multilevel surgery,2,12,13 surgical intervention characteristics, hospitalization, and ALIF-related complications. For the clinical-functional analysis, the Oswestry14 index of inactivity and the visual analogue pain scale were used;15 the preoperative values were compared with those obtained in the final evaluation of each patient. The radiological analysis included implant migration signs, fixation failure, and the presence of peri-implant osteolysis (indirect signs of nonunion). The variables were statistically treated using the IBM SPSS Statistics for Windows, Version 23.0 (IBM Corp., Armonk, NY) software. The Shapiro-Wilk normality test identified asymmetric variable distributions, and nonparametric statistical tests were applied. P-values < 0.05 were considered statistically significant. The present study was approved by the relevant institution.
The ALIF procedure is detailed in ►Table 1. The anterior approach to the lumbar spine is performed and completed by an experienced vascular surgeon. The ALIF procedure is complemented in a second operative time and in a second hospitalization with a posterior percutaneous transpedicular fixation (270º interbody fusion) or, if a decompressive laminoforaminectomy is required, with a posterolateral procedure (360º or circumferential interbody fusion). All of the surgical procedures are performed with intraoperative neuromonitoring. All of the patients are clinically and radio-graphically evaluated in the 1st week, at 6 weeks, at 3 months, at 6 months and 1 year postoperatively, followed by annual visits (►Figs. 1 and 2). Computed tomography (CT) scans were not performed to confirm union.
Most of the patients (75%, n = 48) were male, with a mean age of 53.63 ± 9.47 years old (range: 29-69 years old). Three-quarters of the sample (n = 48) had degenerative listhesis associated with disc disease, and 62.5% (n = 40) presented with a concomitant lumbar spine posterior compressive condition. Twenty patients had already been operated and presented with some degree of neurological deficit, ranging from decreased muscle strength to foot drop. The main symptoms were lumbosacral radiculopathy (96.88%; n = 62) and axial lumbar pain (65.63%; n = 42). Half of the patients had undergone previous lumbar spine interventions, which were divided between posterior lumbar interbody fusions (PLIFs) (n = 8) and transforaminal lumbar interbody fusions (TLIFs) (n = 4) in 1 level, laminectomies (n = 12), and microdiscectomies (n = 8) (►Fig. 3). All of the PLIF cases were nonunion situations, whereas the TLIF patients presented adjacent disc disease. Posterior fixation was maintained in cases of previous PLIFs and TLIFs. More than half of the patients (56.25%, n = 36) had at least 1 risk factor for nonunion of the interbody fusion, whose distribution is shown in ►Fig. 4. The distribution of surgical segments is shown in ►Fig. 5; ALIF was multilevel in 93.75% of the cases. The dimensions of the most frequently used interbody cages according to segment were: 14 mm/8º (n = 12) in L3-L4; 14 mm/8º (n = 12); 16 mm/8º (n = 12) in L4-L5; and 14 mm/12º (n = 12) and 15 mm/12º (n = 12) in L5-S1. Intra- and postoperative ALIF parameters are indicated in ►Table 2.
There was a statistically significant improvement between the preoperative evaluation and the final evaluation at the end of the follow-up period in both analyzed scores (►Figs. 6 e 7). The Oswestry index decreased from 71.81 ± 7.22 at the preoperative period to 24.75 ± 7.82 at the end of the follow-up period (p < 0.001), corresponding to a mean decrease of 47.06 ± 5.29 (37-54). The visual analogue scale of pain decreased from 7.88 ± 0.70 to 2.44 ± 0.87 (p < 0.001), corresponding to a mean reduction of 5.44 ± 0.61 (5-7). There was a significant direct correlation between both scores in the preoperative evaluation (rho = 0.79; p < 0.001) and the final evaluation (rho = 0.87; p < 0.001). Patients with prior neurological deficits had significantly less favorable preoperative scores (Oswestry: 74.40 ± 6.44; and visual analogue scale: 8.20 ± 0.77) compared with neurologically intact individuals (Oswestry: 70.64 ± 7.31; and visual analogue scale: 7.73 ± 0.62; p = 0.05 and p = 0.016, respectively). Patients with risk factors presented significantly lower preoperative and final Oswestry and analogue visual scale scores than individuals without any identified risk factor (►Table 3). When we analyzed each risk factor separately, we found significantly less favorable scores in obese, smokers, and diabetic patients, as well as in those with previous lumbar spine surgeries. Patients with concomitant posterior lumbar conditions who had undergone a laminoforaminectomy and a postlateral interbody fusion also had significantly less favorable scores (►Table 3). Patients with prior neurological deficits tended to present a more pronounced improvement in clinical-functional scores, with no statistical significance. A significant direct correlation was identified between the number of risk factors in each patient and the preoperative (rho = 0.67; p < 0.001) and final Oswestry indexes (rho = 0.79; p < 0.001), and the preoperative (rho = 0.39; p = 0.001) and final visual analogue scales (rho = 0.58; p < 0.001). Significant direct correlations were also confirmed between the number of operated levels and the mean surgical time (rho = 0.86; p < 0.001; 1 level = 50.00 ± 12.00; 2 levels = 94.38 ± 11.76; 3 levels = 126.43 ± 24.49 minutes), as well as the mean blood loss (rho = 0.52; p < 0.001; 1 level = 25.00 ± 5.00; 2 levels = 103.13 ± 81.75; 3 levels = 100.00 ± 13.61 mL). In addition, the mean improvement in both scores showed a significant direct correlation with the number of operated levels (rho = 0.40; p = 0.001), with the most marked improvement in the 3-level ALIF (►Table 4).
The ALIF complications were limited to 3 superficial infections of the surgical wound (4.69%), and to 3 small dehiscences of the surgical wound (3.13%). There were no major or fatal complications, such as laceration or large vessel thrombosis, or any intraoperative complications. There was no retroperitoneal hematoma, abdominal incisional hernia, retrograde ejaculation, or erectile dysfunction. There were no complications in the subsequent stabilization interventions made in a second surgical time. Thus, the overall complication rate was of 7.82%, and the major complication rate was of 0%. No case of nonunion, of implant migration or of adjacent disc disease development was identified during the follow-up period. Patients with complications presented a significantly higher mean age (64.50 ± 4.81 years old) compared to those with no complications (52.07 ± 8.95 years old) (p < 0.001).
We believe that ALIF combined with posterolateral fixation or interbody fusion is a surgical intervention that ensures a more solid, stable, and durable lumbar spine. It is a particularly important procedure in young patients, in whom the restoration of the sagittal balance and of the physiological loads on the Denis columns may decrease evolution to adjacent disc disease, posterior column overload, and early arthroscopy.2,4-6,8 Recent instrumented ALIF techniques have proven results in the literature, with a significant improvement in the clinical-functional scores after surgical intervention and interbody union rates > 90% and with
Despite the good stabilization of the current instrumented ALIF, we believe that, especially in the presence of nonunion risk factors, it is important to complement the construction with a posterior transpedicular stabilization to increase stability and maximize the desired interbody fusion, as well as to reduce the increased risk of nonunion in these cases. However, this topic is controversial, and the current literature is inconsistent. Some studies demonstrate that standalone instrumented ALIF without posterior stabilization does not yield significant differences in terms of clinical-functional and radiographic outcomes compared with circumferential lumbar interbody fusion, so a second surgery can be avoided in cases with no need of posterior decompression.3,6,7,9-11,18,19 However, other studies showed superior union rates for instrumented ALIFs combined with posterior fixation, demonstrating that, although ALIF fixation with an anterior plaque or cage-integrated screws significantly increases stability, it is still inferior compared with the posterior instrumentation.20-25 Moreover, the additional stability offered by posterior fixation or interbody fusion may probably contribute to decrease the intensity or even avoid symptoms in case of a nonunion ALIF, allowing these lack of fusions to be tolerated or asymptomatic. Further large randomized prospective studies are required to prove the effectiveness and safety of instrumented ALIF cages without additional stabilization.
The robustness of the anterior and of the posterior assembly and the noninductive potential of bone morphogenetic protein 2 (BMP-2) in the interbody cage may be responsible for the lack of any nonunion in this sample, even in the presence of a substantial number of patients with nonunion risk factors, and with half of them with previous lumbar spine surgeries. The use of Infuse® (Medtronic, Fridley, MN, USA) also avoids morbidity and possible complications during the obtainment of an iliac crest autograft.3,10 Although patients with previous PLIF nonunions had less favorable clinical-functional scores, the review using another approach (anterior approach) and ALIF resulted in very satisfactory outcomes.2,26
The increasing clinical-functional improvement according to the number of instrumented intervertebral segments should be analyzed with caution, since 1-level ALIF was performed in only 4 patients; as such, outcomes may be biased by the small size of this group in comparison with 2-level and 3-level ALIFs, with a consequent loss of statistical power. Nevertheless, we believe that these results can be justified because of 2- and 3-level ALIFs (corresponding to 93.75%) allow not only the individual treatment of such segments, but also avoid an eventual clinical deterioration due to adjacent disc disease, assuring a more reliable lumbar lordosis and sagittal physiological balance restoration compared to 1-level ALIF. The clinical-functional improvement observed in multilevel ALIFs also shows the reduced morbidity of the retroperitoneal anterior lumbar spine approach during the extension of the intervention to several segments; it also ensures that the multilevel intervention does not affect negatively the clinical-functional recovery, even if the surgical time and hemorrhagic losses are higher than in 1-level ALIF.
Despite the risk of potentially fatal complications associated with the anterior retroperitoneal abdominal approach, we consider that its execution and accountability (during the opening, the possible vascular complications treatment, the closing, and the follow-up of any approach-related complications in the postoperative period) by an expert surgeon may be an important factor for the reduced complication rate found in the present sample.2,3,6,8,16,27-30 In addition to the reduced morbidity characteristics of the retroperitoneal anterior approach, the experience of the surgeon allows us to save surgical time and reduce hemorrhagic losses, which may also contribute to the decreased complications rates, to the shorter hospitalization times, and to the clinical-functional improvement in our study.28,30
In summary, we consider that the very satisfactory clinical-functional and radiographic outcomes obtained in the present study are due to the biomechanical advantages of instrumented ALIF combined with posterior stabilization, to the frequent use of multilevel ALIF and its advantages in the more effective restoration of lumbar lordosis, to the surgical technique, both in its approach and procedure, and to the interbody cages with integrated screws and filled with bone matrix and BMP-2.
The main advantage of this prospective study is the uniform application of the same therapeutic protocol to all patients, and the fact that all of the procedures were performed by same surgeons, allowing a considerable bias reduction due to treatment variation. The main limitations of the present study were the lack of randomization or blinding and the fact that this is a convenience sample with heterogeneous group sizes.
The favorable biomechanics of instrumented ALIF combined with posterior stabilization is a satisfactory therapeutic option in uni- or multilevel degenerative disc disease in the L3-L4, L4-L5 and L5-S1 levels, associated or not with posterior compressive lumbar disease, even in the presence of significant nonunion risk factors and of previous lumbar spine surgeries. It assures very satisfactory clinical-functional and radiographic outcomes and a reduced complication rate in the medium-term.