A systematic literature review of time to return to work and narcotic use after lumbar spinal fusion using minimal invasive and open surgery techniques

Chronic low back pain is a leading common health problem for adult workers worldwide [1, 2]; it is the leading cause of activity limitation, job-related disability and absence from work, and it causes an enormous economic burden [3].

The Global Burden of Disease study [3] estimated that low back pain causes more global disability than any other condition. According to its estimates in 2010, the total costs of the condition in the United States exceed $100 billion annually, with two-thirds of these costs come from lost wages and decreased work productivity [4, 5].

Surgical treatment of the lumbar spine has been shown to be effective in reducing patient’s pain and improving function and disability relative to non-surgical treatment [6]. In addition, surgical treatment has been proven to be cost-effective over a 4-year period compared with none-surgical care [7].

A recent study examined the effects of lumbar spinal surgery on work productivity with regard to earnings and absence from work and concluded that reduced productivity losses, after disc herniation surgery, may offset the increased direct medical costs associated with surgery [8]. Lumbar spinal fusion surgery is a viable treatment option for reducing pain and improving function in patients with chronic pain refractory to non-surgical care [9].

Minimally invasive surgery (MIS) techniques for lumbar spinal fusion are equivalent to traditional open surgery (OS) procedures in terms of post-operation fusion rates [10], while MIS has the advantage of reducing tissue damage to the spinal muscles compared to OS [11].

The use of MIS techniques in lumbar spinal surgery has increased as improved patient outcomes and lower hospital costs have been recognized [12‐14].

Several studies have demonstrated short term benefits of MIS such as rapid mobilization, shorter length of hospital stay, reduced blood loss, less post-operation pain, reduced risk of infection, and reduced need for post-operation analgesics [15]. Better clinical outcomes compared to OS have been described for a number of different incision approaches such as transforaminal lumbar interbody fusion (TLIF), posterior lumbar interbody fusion (PLIF) and anterior lumbar interbody fusion (ALIF) [16, 17].

Parker et al. showed that MIS-TLIF was associated with reduced costs over 2 years with similar health utilities as OS-TLIF [18] and, MIS-TLIF lumbar spinal fusion resulted in a statistically significant reduction in total hospital costs [14]. However, the economic evaluations of MIS and OS paid little attention to the societal perspective related to initial return to work and productivity after MIS surgery. In addition, earlier narcotic independence following lumbar spinal fusion is another factor that may influence the ability to return to normal work activities.

This systematic literature review (SLR) focused on identifying evidence from published literature on time to return to work and post-operation narcotic use after lumbar spinal fusion operations using MIS or OS techniques. The main objective with the study was to determine whether there is evidence supporting the hypothesis that early post-operation benefits of MIS, compared to OS, have an effect on work productivity.

A literature review protocol was developed to design the systematic review detailed search strategies, criteria for study selection, and outcomes to be reported. The PRISMA 2009 checklist (Preferred Items for Systematic Reviews and Meta-Analyses) was used for reporting this review.

A total of 1212 unique records were obtained from all the searches; of which, 199 were retrieved from HTA agencies and conference proceedings. Out of these, 236 were selected for full text evaluation and, eventually, 36 studies were included for full text review and data-extraction. The selection process and the number of articles included at each consecutive step of the SLR are described in Fig. 1. The complete list of the included articles is available as supplementary material (Additional file 2: List of included studies).

With the improvement of MIS surgical techniques in spinal fusion and the development of fusion devices, more operations are today being performed using MIS techniques. A number of previous studies [16, 17] have demonstrated that MIS techniques for lumbar spinal fusion have improved the clinical outcomes including operation time, blood loss, complication rates and length of hospital stay, resulting in less hospital resource utilization; however the benefits of MIS techniques such as faster return to work and productivity which means reducing indirect costs to patients and society are less explored. This SLR was conducted to identify and summarize evidence on the time to return to work and the duration of post-operation narcotic use for patients who had lumbar spinal fusion operations using the MIS and OS techniques. Compared with a previous literature review, published by Parker et al. in 2012 [53], this SLR has a broader scope of time to return to work (e.g., time, rate, employment status, and sick leave) and less restrictions on the type of surgical technique that were used (e.g., TLIF or PLIF).

Out of a total of 36 included studies (including five abstracts [32, 41‐43, 46]), two thirds of the studies (n = 25) were observational studies and only five studies [28, 36, 38, 40, 48] were RCTs. This might to some extent reflect the actual situation in surgical research, i.e., retrospective case series are more commonly used, usually with small cohorts, while RCTs are more widely used for pharmacological therapies [54, 55]. TLIF was found to be the most frequently studied technique for lumbar spinal fusion operations regardless if MIS or OS was used. Twenty-seven studies described the position of the fusion or the number of levels that were fused for the study patients; out of which, nine studies [25‐27, 31, 32, 37, 47, 56, 57] included patients who had two or more levels fused (range from 14% - 57% of total studied patients), but the results were not presented separately by fusion levels. Therefore, the current SLR mainly provides evidence of the time to return to work and the post-operation narcotic use for patients after a single-level lumbar spinal fusion.

The current SLR identified four studies [18, 21‐23] that directly compared the time to return to work for patients who had lumbar spinal fusion with the MIS and OS procedures. The three US studies [18, 21, 22] showed almost half the time to return to work for patients who had MIS-TLIF (range of absolute mean: 7.0 to 8.5 weeks) compared to patients who had OS-TLIF (11.0 to 17.1 weeks). Additionally, more than 80% of the patients who received MIS-TLIF or OS-TLIF returned to work within 12 months after surgery [21, 22]. When patients who had MIS-ALIF were compared with OS-instrumented circumferential fusion, Kim et al. [23] reported similar times to return to work for both procedures (3.7 vs. 3.6 months), but no statistically significant difference. It should be noted that two different surgical fusion techniques have been performed at separate hospitals which may explain the lack of difference. Furthermore, the mean follow-up period was 8 months shorter for patients in the OS group compared to the MIS group (32.9 vs. 41.1 months). In this Korean study [23] the surgical techniques were different from the three US studies [18, 21, 22] and a stringent definition of return to work was applied: “return to full and unrestricted activity”, as a result, the time to return to work for both the MIS and the OS groups were different from the results presented in the US studies [18, 21, 22], potentially reflecting cultural practices in Korea. In Kim et al. [24], the time to return to full and unrestricted activity were also used and, therefore, longer times to return to work have been presented compared to the US studies for the MIS groups [18, 21, 22]. Another US study, conducted by Rouben et al. [25], reported a similar time to return to work (11 weeks) as the US studies [18, 21, 22] for patients who had MIS-TLIF. An US study by Gornet et al. [28] focused on only OS-ALIF reported time to return to work with 96 days (13.7 weeks). Based on the findings from these US studies [18, 21, 22, 28], it can be concluded that MIS patients return to work faster compared to OS patients.

The NICE checklist was followed for quality assessment in this review; in general the quality of the included studies was poor. Only four studies [28, 29, 38, 40] fulfilled most criteria and many of the included studies (n = 21) only fulfilled few or very few criteria, e.g., the patient samples were small ranging from eight to 72 patients per treatment arm, and were often from a single institution treated by only one or two surgeons. Clearly, there is a gap of evidence around how the time to return to work after lumbar spinal fusion operations differs between the MIS and OS techniques. The interpretation of the current evidence suggests that the time to work after MIS is shorter than after OS operations.

In addition to the time to return to work, several studies were found that reported on the rate of return to work and the employment rate before and after surgery. For patient who had MIS, 83%–97% return to work after surgery within 3 months to 6 years. For patients who had OS a greater variation in the share of patient who returned to work was observed ranging from 18% to 100% within 3 months to 4 years depending on the techniques being used, i.e., PLF, PLIF, TLIF and circumferential fusion. Information regarding the type of jobs the patients was working with before and after the surgery was limited. Kim et al. [35] and Takahashi et al. [27] reported that a substantial amount of patients had to change work or reduce working hours after surgery (47.1 and 59%, respectively).

With regard to the employment rate pre- and post-operation, the combined employment rate of full-time and part-time work was frequently reported. Studies focused on OS only in general showed a clear trend of increased employment rate after surgery. Three studies [28, 38, 39] that focused on OS-ALIF reported fairly consistent time to return to work of 6 months. The employment rate pre-operation ranged from 56% to 58%, while the employment rate 6 months post-operation ranged from 63% to 73%. In addition, only two Swedish cost-effectiveness studies [29, 30] were found that reported on sick-leave for patients who had lumbar spinal fusion with OS; no information on sick-leave was found for MIS in this SLR.

Six studies [23, 24, 34, 41‐43] were found describing the return to normal daily activities or full function post-operation. However, the definition of return to daily activities and full function was, generally, not clearly described.

Various factors may affect the return to work, which have not been widely and consistently assessed across the identified studies. Several studies reported the work status (e.g., full-time or part-time), type of work (e.g., heavy or light labour work) and workers’ compensation status prior to surgery led to different return rate or time duration after MIS or OS [26, 27, 29, 37, 38]. In addition, most studies reported patients’ clinical characteristics (e.g., blood loss, surgery time, interbody fusion technique and number of fusion levels), which may affect the return to work. Furthermore, surgery-related and neurological complications may be associated with the return to work. However, due to the small sample size and few observed complications, these factors have not been sufficiently studied [22, 43, 49, 51]. Recent reviews, in other conditions [58, 59], have reported that age, sex, education and other social-economic factors are important factors affecting the return to work, which could be investigated in future studies on MIS or OS in spinal infusion.

Altogether the results of time to and rate of return to work, and comparisons of pre- and post-operative employment rates show benefit for MIS compared to OS. A review of cost of illness studies on chronic low back pain [60] has showed that the direct cost associated with low back pain accounted for only 22% of the total costs, which indicated that the indirect cost caused by the loss of productivity contributed with a much larger share of the overall cost for chronic low back pain. The possibility to return to work faster after surgery and be productive may be one of the largest societal advantages of MIS compared to OS. Reduced absenteeism from work is not only important for the societal costs but also for patients’ quality of life; patients who are able to faster return to normal daily activities are more likely to recover faster due to effective relief of symptoms and disability [61, 62].

Post-operation narcotic use was at focus in 17 studies; out of which 11 studies directly compared MIS versus OS, but again only the three US studies [18, 21, 22] reported the duration of post-operation narcotic use. Similar results as for the time to return to work, MIS-TLIF was associated with half the period of narcotic use after surgery (range of absolute mean time of post-narcotic use: 2–3 weeks) compared to OS-TLIF (mean range: 3–9 weeks). The difference was statistically significant in Adogwa et al. [21] and Parker et al. [18] but not in Parker et al. [22] where patients in the OS-TLIF group had threefold longer narcotic use post-operation than MIS-TLIF (median: 3 vs. 9 weeks). It is likely that the advantages of the MIS procedure (e.g., less muscle damage) contributed to the shorter time of narcotic use during the recovery period after surgery. Duration of narcotic use after surgery may be affected by pre-operation narcotic uses, because patients who used narcotics pre-operation are more likely to continue their pain medications after surgery or require time to quit the narcotics due to, for example, rebound effect; however, the duration of pre-operation narcotic use was not available in these studies. No significant difference in the use of narcotics post-operation between MIS and OS was found in most studies that directly compared MIS to OS, but a majority of studies indicated less use of narcotics for patients after MIS.

Chronic back pain in the lumber region is one of leading cause of disability and there is a high incidence of psychiatric comorbidities (e.g., depression) [63] and substance abuse (narcotics or other drugs) [64] among patients with degenerative disc disease. None of the studies discussed the psychiatric situation of the patient and the abuse of narcotics among patients with disc degenerative disorders. Furthermore, most studies were observational studies and the decision to carry out OS or MIS spinal fusion operations often depended on surgeon’s proficiency and preference.

The post-operation narcotic use was not clearly, and consistently, defined across studies which limit the possibility to compare the results. Just as the time to return work, the narcotic use following spinal surgery operation is a likely differentiator between the MIS and OS procedures. Therefore, future clinical trials would benefit from more focus on the narcotic use post-operation.

This study shows that there is a gap of good quality data regarding the time to return to work and narcotic use after lumbar spinal fusion operations using MIS or OS techniques. This study also indicates that patients who have lumbar spinal fusion operations with the MIS procedure generally return to work after surgery more quickly and require less post-operation narcotics for pain control compared to patients who had OS. As the societal costs for these patients are likely to be significant, and the availability of studies with high quality is low, it is of great importance for future studies to include data collection regarding time to return to work and narcotic use during the post-operation follow-up period.