Results of Surgical Treatment of Low-Grade Adult Isthmic Spondylolisthesis

Fig. 23.1

Radiographs of a 16-year-old female with a 2-year history of chronic low back pain worse in extension. Right (a) and left (b) CT sagittal reconstruction and axial (c) of L4 demonstrate bilateral L4 pars defects (arrows). Postoperative lateral (e) and AP (f) following 4.5 mm titanium laminar screws placed across the pars defects after decompressing the defects and placement of structural grafts harvested from the iliac crest through the same incision

Extension-based lumbo-sacral back pain unresponsive to non-surgical care

Normal disc [1]

No slip [1]

Excellent relief of pain with a direct pars injection with lidocaine and steroid [2].

Though no specific age cutoff for performance of direct pars repair exists, less favorable clinical and radiologic results have consistently been reported in patients older than 20–30 years of age [3–6].

Kimura was the first to report on direct pars bone grafting without supplemental internal fixation in 1968 [7]. That same year Scott developed a cerclage-wiring fixation technique to provide compression across and augment stability of the pars defect, though these results were not reported until 1986 [8]. In 1970 Buck described the use of a single lag screw for pars osteosynthesis [9] with multiple descriptions of surgical outcomes using this technique being reported. Subsequently, Morscher [10] developed a modular hook-screw construct in which a custom screw inserted across the pars defect could attach to a hook inserted under the lamina which, when tightened via a lock nut, would provide additional compression across the defect. Finally, with the introduction of Cotrel-Dubosset instrumentation, intrasegmental spondylolysis fixation using a pedicle screw-hook or pedicle screw-rod construct was developed, with the first report appearing in 1991 [2]. This contemporary construct for direct pars repair has continued to evolve with each generation of spinal implants with favorable outcomes being reported.

In 2011 Drazin and colleagues [11] presented a comprehensive overview of direct surgical repair of spondylolysis in athletes, including a systematic review of 60 years of the English-language literature pertaining to the clinical and radiologic outcomes of pars defect repair in patients aged 24 years or younger. A total of 18 articles using a variety of surgical techniques were identified, with half of them reporting specifically on outcomes of pars repair in athletes. Clinical and radiologic outcome data were summarized and the modified Henderson criteria [12] were applied to subjectively assess patients’ postoperative pain and ability to return to preoperative activity level. None of the included studies were level I randomized controlled trials with the majority being retrospective case series. The predominant level of involvement was L5 in both athletes and non-athletes (96 % and 92 % respectively) with patient age ranging from 12 to 60 years between the 18 studies.

The most commonly used surgical technique identified by Drazin et al. [11] was Buck’s single lag screw fixation with six of the studies reporting on this method. Excellent results were consistently identified by study authors with >90 % of athletes returning to their preoperative level of physical activity [13–17]. Buck reported somewhat lower success rates in his original series of non-athletes with 81 % of patients reporting no or minimal symptoms postoperatively [9]. The less rigid Scott wiring technique has been shown to provide less satisfactory clinical results with 0–75 % of patients reporting good or excellent outcomes [5, 15, 18, 19]. Modifications of the Scott, or Songer [20] technique using pedicle screws and a cerclage wire have provided 73–100 % good or excellent results [3, 21]. The earliest report of pars repair by pedicle screw-hook fixation [22] identified 81 % good or excellent outcomes, though the mean age of this cohort was 32.4 years. More recent studies examining outcomes of contemporary screw-hook constructs have observed excellent results, with 100 % of patients <30 years of age achieving good or excellent postoperative function [6, 23].

Since the publication of this systematic review, ongoing investigations into the outcome of pars repair have been performed. At an average follow-up of 9 years Giudici et al. [24] observed good or excellent results according to Odom’s criteria in 43 %, 63 %, and 84 % in 52 patients age 25 years or less undergoing surgery using Buck’s, Scott’s, or modified Scott’s technique respectively. In general, patients experiencing a poor outcome had bone graft resorption and progression of slippage. Clegg et al. [25] who reported on 49 patients (mean age 17.4 years) undergoing pars also used a modified Scott. At an average of 21.7 months following surgery, 96 % of patients reported no or mild to moderate symptoms on the ODI or SF-36. Kim et al. [26] performed a Buck’s fusion in 25 patients aged 15–29 with spondylolysis and reported 88 % good or excellent results according to Kirkaldy–Willis criteria [27].

In a cohort of patients with symptomatic lumbar spondylolysis who responded to direct pars injection and negative discography treated by Shin et al. [28] pars repair using either a pedicle screw-hook construct (n = 23) or direct pars screw (n = 17) was performed. Clinical outcomes rated by the oswestry disability index (ODI) and VAS scores were better in the pars screw patients than in those treated with a screw-hook construct with patients demonstrating successful union having better postoperative results. Hioki et al. [29] reported a similar phenomenon in 44 athletes with a mean age of 24.2 years treated with cerclage wiring of their pars defect, with patients obtaining bilateral bony union (67.4 %) achieving higher postoperative JOA score improvements than those with unilateral union (13 %) or nonunion (19.6 %).

Minimally invasive approaches to pars repair have also recently been reported with satisfactory clinical results. Amoretti et al. [30] performed percutaneous CT-guided cannulated screw fixation of bilateral L5 spondylolysis defects in ten consecutive patients with an average age of 57 years. Patients tolerated the outpatient procedure well with minimal blood loss and no cases of screw malposition. Significant decreases in VAS measurements (7.8 ± 0.9 preop to 1.5 ± 1.1 at 2 years, p < 0.001) and ODI scores (62.3 ± 17.2 preop to 15.1 ± 6.0 at 2 years, p < 0.001) were observed with no cases of slip progression or instrumentation failure. More recently, Widi et al. [31] employed a similar approach of cannulated screw placement across the pars under fluoroscopic guidance through tubular retractors in three patients with a mean age of 21.7 years. All three patients demonstrated satisfactory bone healing at 6 months postoperatively and had returned or were planning to return to their preoperative sporting activities.

Decompression and Fusion for Low-Grade Isthmic Spondylolisthesis

While low-grade spondylolisthesis is present from early childhood, symptoms in adults generally present once the disc at L5-S1 degenerates, leading to foraminal compression of the L5 nerve roots (Fig. 23.2). Adult patients with isthmic spondylolysis who do not meet the criteria for pars repair and who fail traditional methods of conservative management are candidates for surgical decompression and stabilization. Though controversy exists regarding the optimal surgical technique for management of low-grade adult isthmic spondylolisthesis, three surgical interventions should rarely, if ever, be used in this patient population and are worth mentioning.

Fig. 23.2

Preoperative and postoperative images of a 51-year-old woman with bilateral L5 radiculopathy. Preoperative right (a), mid, and left (c) sagittal T2 (b) demonstrate a grade 1 isthmic spondylolisthesis with bilateral L5 foraminal compression secondary to disc. Preoperative (d) and postoperative PA (e) and lateral (f) radiographs following posterior decompression with Gill laminectomy and bilateral disc excision. Reconstruction is performed with bilateral pedicle screws and a posterior lumbar interbody cage

Dynamic stabilization techniques should not be used in patients with isthmic spondylolisthesis given that motion across the spondylolysis contributes to patient symptomatology and solid stabilization is required for symptom relief [32].

Indirect decompression via interspinous process spacer placement is also not indicated given that these devices require intact posterior elements to create distraction and therefore will not function as intended in the presence of a pars defect.

Decompression alone has extremely poor results in patients with lytic spondylolisthesis. While decompression alone can be an option in some cases of degenerative spondylolisthesis, decompression and instrumented fusion is the gold standard in treating symptomatic low-grade adult isthmic spondylolisthesis [33].

A variety of anterior, posterior, and combined (360°) surgical approaches exist for the surgical management of low-grade adult isthmic spondylolisthesis, each with their own proposed advantages and disadvantages. Posterior lumbar decompression and instrumented fusion is the most commonly employed technique for surgical management of adult low-grade isthmic spondylolisthesis. It can be performed through bilateral paramedian (i.e., Wiltse) approaches or the widely familiar midline posterior incision and has the advantage of allowing for direct decompression of the neural elements. If concerns regarding the ability to obtain a posterolateral fusion (PLF) exist, or one wishes to attempt to restore lumbar lordosis across the degenerated disc or release the annulus to facilitate slip reduction, interbody fusion through either a posterior (PLIF) or transforaminal (TLIF) approach can be added to obtain a 360° or circumferential fusion. While interbody fusion can be associated with higher rates of neural injury, adequate release of perineural adhesions and avoidance of overzealous nerve retraction can help minimize these complications. Distraction of the posterior elements during the decompression, either through the pedicle screws or the bone, helps provide more room around the nerve to gain safer access to the disc space.

Stand-alone anterior lumbar interbody fusion (ALIF) has been used for many years to treat spondylolisthesis and has the advantages of a large surface area for fusion with low postoperative pain and rapid surgical recovery. However, removal of the last remaining restraints to anterior translation, the anterior longitudinal ligament, and annulus fibrosus, in the setting of compromised posterior elements can exacerbate instability and may result in graft extrusion and/or slip progression, resulting in recommendations for the performance of supplemental posterior instrumented fusion [34]. Further, this technique relies solely on indirect decompression of the neural elements and may be associated with significant approach-related complications including retrograde ejaculation [35] and vascular injury [36]. In light of these disadvantages and the development of techniques to reconstruct and fuse the anterior column from a posterior approach, stand-alone ALIF is rarely performed in this patient population.

Two previous systematic reviews have examined the evidence pertaining to surgical management of adult low-grade isthmic spondylolisthesis in an attempt to identify the optimal method of treatment. In 2005 Kwon et al. summarized English-language studies examining surgical management of adult low-grade isthmic spondylolisthesis in at least five patients and reporting on fusion rate and/or clinical outcome. Their primary objective was to determine which surgical technique, posterior alone, anterior alone, or a 360° procedure, led to superior radiographic fusion and clinical outcome. A total of 34 studies reporting on more than 1,000 patients were included, four of which were prospective randomized controlled trials. The remaining 30 were retrospective studies with only six describing a comparison of two surgical techniques.

With respect to radiographic outcome, patients undergoing a combined anterior (ALIF, PLIF, or TLIF) and posterior procedure demonstrated a significantly higher fusion rate (98.2 %, 167/170) compared to patients undergoing isolated posterior (83.3 %, 741/890) or anterior (74.0 %, 57/77) surgery (p < 0.0001). Clinical success, as defined by the authors of each individual study, was significantly higher in both the stand-alone anterior (89.6 %, 60/67) and combined groups (86.4 %, 108/125) compared to the posterior-only group (74.8 %, 609/814, p = 0.005), though no difference between the anterior and combined groups was observed (p = 0.65). Subgroup analysis demonstrated significantly improved radiographic fusion rates (90.2 % vs. 77.4 %, p < 0.0001) and rates of clinical success (84.9 % vs. 64.4 %, p < 0.0001) in patients in whom internal fixation had been placed. Success rates were also substantially lower in smokers and patients involved in workers compensation or litigation. After identifying the limitations and weakness of the current literature, the authors conclude that the highest rates of radiographic and clinical success were observed in patients undergoing combined anterior and posterior approaches with the placement of posterior instrumentation.

Subsequently, Jacobs et al. [37] performed a similar review of studies in which a minimum of ten patients were treated with surgery for low-grade isthmic spondylolisthesis in which at least one radiographic, functional, or clinical outcome was reported. A total of 29 studies, including eight prospective RCTs, were identified for study inclusion. In attempting to determine the best method of surgical treatment, instrumented versus uninstrumented PLF was examined in four of the RCTs with no significant benefit of supplemental instrumentation being observed in any of these studies [38–41]. Results from the remaining RCTs also failed to demonstrate a clinical benefit of the addition of ALIF [42], supplemental direct decompression [43], or bone graft substitute [44] to PLF.

In the remaining 21 case series, 24 surgical treatment groups were reported. Good or excellent clinical outcomes were observed in 60–98 % of patients undergoing PLF (15 groups) with fusion rates ranging from 81 % to 100 %. ALIF was employed in five groups with fusion occurring in 47–90 % of patients and 85–94 % experiencing a good or excellent clinical outcome. Only two groups reported on the use of posterior interbody fusion, with 80 and 95 % of patients obtaining radiographic fusion, but only 45 % of patients having a good or excellent clinical outcome (one group). Based on these results, the authors conclude that, though PLF is the most common treatment method employed and therefore appears to be the accepted gold standard, scientific evidence to support this consensus does not exist. They also state that further RCTs examining the role of instrumentation in posterior lumbar fusion and comparing surgical approaches (anterior vs. posterior vs. circumferential) in the treatment of low-grade adult isthmic spondylolisthesis are required.

Since publication of these systematic reviews investigators continue to work towards identifying the optimal treatment strategy for adult low-grade isthmic spondylolisthesis, with three English-language RCTs comparing alternative surgical techniques having been published [45–47]. In 2011 Audat et al. examined surgical fixation with or without reduction and PLIF for the treatment of symptomatic low-grade isthmic spondylolisthesis in a prospective, randomized, double-blinded study. No significant difference was observed between the groups with regard to operative time or LOS. Complication rates were also similar between the two groups during the hospital stay. At final follow-up, only one patient in the in situ fusion group (n = 21) experienced a pseudarthrosis requiring reoperation, while all patients in the reduction and PLIF group (n = 20) obtained a solid fusion. While both groups demonstrated improvements in quality of life following surgery, improvements on the ODI were significantly better in the reduction and PLIF group compared to the in situ PLF group at 3 years (0.04 vs. 0.15, p < 0.005).

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