COVID-19 and Spontaneous Resolution of Lumbar Disk Prolapse: A Retrospective Cohort Study of Patients Awaiting Microdiscectomy

Abstract

Background Between individual patients with lumbar disk prolapse (LDP), the natural course of disease is significantly variable. Spontaneous resolution is reported to occur in up to 70% of cases. However, we currently cannot predict for whom and when this will occur. Neurosurgical intervention is indicated for LDP patients with nontolerable pain after at least 8 to 12 weeks of conservative management, or significant neurologic deficit. Channeling essential resources in the National Health Service (NHS) to fight the COVID-19 pandemic led to the postponement of most elective operations, including microdiskectomy. This left many LDP patients previously considered to be surgical candidates with conservative-only options in the interim. To our knowledge, we are the first center to report the specific impact of the peri- and postpandemic period on waiting list times, delayed elective microdiskectomy, and the incidence of spontaneous LDP resolution.

Methods Retrospective case series of a prospectively collected electronic departmental database identified LDP patients who would have been impacted by the COVID-19 pandemic at some point in their care pathway (March 2020–February 2022). Further information was obtained from electronic patient records.

Results In total, 139 LDP patients were listed for elective microdiskectomy at the time of postponement of elective surgery. Over a third of LDP patients (n = 47, 33.8%), in shared decision with the responsible neurosurgeon, had their rescheduled microdiskectomy canceled due to clinical improvement (14.1%), radiologic regression (6.5%), or both (12.2%).

Conclusion Our single-center retrospective analysis revealed that for over a third of LDP patients, the prolonged postpandemic waiting list times for elective microdiskectomy resulted in their surgery not taking place either due to spontaneous clinical improvement or proven radiologic regression. Considering this, a prolonged conservative approach to LDP may be appropriate in some patients, allowing time for natural resolution, while avoiding perioperative risks.

Keywords

spontaneous resolution - disk prolapse - microdiskectomy - coronavirus-19 - pandemic

Introduction

The natural course of disease of lumbar disk prolapse (LDP) varies greatly between patients. Spontaneous resolution is reported to occur in up to 70% of cases without the need for surgical intervention.[1] However, we currently cannot predict for whom and exactly when this will occur. Conservative, nonsurgical approaches are used to manage the symptoms of all LDP patients in the first instance, including analgesia, physiotherapy, and involvement of a multidisciplinary pain team.[2] [3]

In our service pathway, a patient with LDP who continues to experience nontolerable radicular pain after 8 to 12 weeks of nonsurgical approaches[4] or experiences any major neurologic deficit[5] (e.g., foot drop) will be referred for magnetic resonance imaging (MRI) of the lumbar spine by their general practitioner (GP) or physical therapist. If there is radiologic evidence of nerve root compression by a herniated lumbar disk, the patient will be referred to the neurosurgical service.

At clinic review and assessment, the decision to undergo surgical intervention versus other management options is shared between patient and surgeon, and includes ascertaining patient preferences, concerns, expectations, as well as quoting relevant literature sources. Frequently chosen sources include the Spine Patient Outcome Report Trial (SPORT)[6] and the Maine Lumbar Spine Studies, which report 5-year[7] and 10-year[8] outcomes.

The coronavirus-19 (COVID-19) pandemic was declared by the World Health Organization (WHO) on March 11, 2020.[9] During this time, the National Health Service (NHS) had to mobilize resources to combat the huge strain on the health service and minimize the spread of COVID-19 infection. This resulted in limitations within the elective spinal service.[2] [3] First, there was a significant reduction in spinal clinical appointments. Patients referred to our center were required to go through a vetting process prior to being considered suitable for a clinic appointment, meaning a prolonged period between GP referral and consultation with a spinal surgeon. If a referral was accepted, their clinic appointment was usually via telephone or video consultation due to the drastic reduction in in-person clinical encounters during the “lockdown,” in line with the government safety guidance.[10] [11] [12]

Second, the pandemic fired a “double hit” at all elective surgical cases. In addition to all elective microdiskectomies being canceled from March 2020 (first hit), there was subsequently a large backlog of patients once elective operations were permitted to resume (second hit). Jain et al predicted this backlog of elective spinal cases to take between 7 and 16 months to recover.[13] Well into 2023, we are still combatting the knock-on effect on surgical waiting list times.

Together, this “double hit” meant multiple LDP patients who were already deemed surgical candidates had no option but to rely on conservative measures alone for a significantly prolonged period. During this time, there was potential for symptom progression and/or major neurologic deficit.

To our knowledge, we are the first to report the direct effect of the pandemic on the incidence of spontaneous clinical and/or radiologic LDP resolution. This article also adds to the existing literature addressing the impact of COVID-19 on spinal service provision. We hope that our findings will add to the limited evidence base utilized by spinal surgeons when discussing management plans with LDP patients in the clinic.

Methods

This was a retrospective case series at a single institution of a prospectively collected electronic departmental database. Further information obtained from electronic patient records included neurosurgical clinic letters, GP referral letters, and other relevant correspondence. The primary outcome measure was to analyze the frequency of patients who did not require surgical intervention after clinical and/or radiologic regression of their LDP. The secondary outcome measure was to analyze the mean time at which regression occurred.

We considered the period of March 2020 to February 2022 an ideal opportunity to analyze the impact of the COVID-19 pandemic on a specialized spinal service. Inclusion criteria were patients added to the waiting list for elective microdiskectomy up to 9 months prior to and 24 months following the date elective surgery in NHS Tayside was suspended (March 27, 2020).[14] Both primary and revisional microdiskectomies were included in the analysis.

Anonymous patient data were collected and analyzed using Microsoft Excel.

Results

When elective surgery was permitted to resume, the NHS Tayside neurosurgical department followed a surgical pathway to minimize patient risk of contracting COVID-19.

Patients at low risk of infection followed a planned surgical pathway (PSP; green pathway). Unscheduled admissions and some elective patients who were unable to strictly isolate were considered medium risk (yellow pathway). Patients with known or highly suspected COVID-19 infection were deemed high risk (red pathway).

In the 14 days prior to surgery, patients on the PSP were encouraged to minimize social contact (but not fully isolate) for 11 days, and test negative for COVID-19 within 72 hours prior to their surgery. If negative, the patient would have to fully self-isolate for the remaining 72 hours and be admitted on the morning of surgery. If positive, the operation was canceled and rescheduled after a period of at least 8 weeks from initial COVID-19 diagnosis.[14] This measure considers evidence in the literature proving recent COVID-19 infection to increase the risk of postoperative mortality.[15]

In response to the new guidance published by Antimicrobial Resistance and Healthcare Associated Infection (ARHAI) Scotland in November 2021,[16] NHS Tayside developed a new pathway system for elective surgical patients. The new system consisted of a respiratory pathway (those at risk of infection with COVID-19 or another respiratory pathogen) and a nonrespiratory pathway (illustrated in [Fig. 1]). In addition to the surgical pathways, the main hospital was split into two separate “zones” including a green “COVID-free” zone and a blue “potential COVID” zone to prevent further spread of infection.

Fig. 1 The respiratory and nonrespiratory pathway protocol (NHS Tayside). AGP, aerosol generating procedures; ETT, endotracheal tube; LMA, laryngeal mask airway; PAFT, post-AGP fallow time; PPE, personal protective equipment.

Our center received 2,567 neurosurgical referrals between March 2020 and February 2022. Of these, 718 referrals were patients with radiologic evidence of LDP (see [Fig. 2]). The remaining referrals (n = 2,565) were for other degenerative or oncologic lumbar pathology (n = 814) or pathology elsewhere in the central or peripheral nervous system (n = 1,033). Out of the LDP referrals (n = 718), 636 were classified as “routine” referrals by the referrer.

Fig. 2 Data collection from referral to progression or cancelation of surgery. LDP, lumbar disk prolapse; SR, spontaneous resolution.

In total, 497 LDP patients were discharged due to either spontaneous resolution or other underlying reasons before being listed for surgery. The remaining 139 patients were listed P2-P4 patients for elective lumbar microdiskectomy. Fifty-seven patients were allocated to the blue zone and 9 to the green zone. This information was not available for the remaining 73 patients.

After being listed for surgery, and surgery being delayed because of the COVID-19 pandemic, 59 LDP patients were removed from the waiting list in the period from 2020 to 2022. Twelve patients canceled their operation for other reasons. Such reasons included anesthetic concerns (n = 1), change of mind (n = 4), other medical complications (n = 1), and surgeon's recommendation (n = 3). For the remaining three patients, the reason for cancelation remains unknown, with no deaths reported. Forty-seven patients (33.8%) were removed from the waiting list due to spontaneous radiologic improvement (n = 9, 6.5%), clinical improvement (n = 21, 14.1%), or both (n = 17, 12.2%; see [Table 1]). In the cohort of patients whose most recent MRI revealed a reduction in disk size, three were unable to be contacted by the neurosurgical department, making it unclear if they did have any ongoing clinical symptoms despite radiologic evidence of improvement. The lack of further contact with the department or further correspondence from the GP suggests not, but this cannot be simply assumed. In the cohort of patients with clinical improvement only, there was radiologic evidence of an unchanged MRI in two patients. For the other 19 patients with resolution of lumbar and/or sciatic pain, a repeat MRI was not performed as the patient was happy to be removed from the waiting list and resume conservative measures or be discharged from the service.

Table 1 Groupings of LDP patients experiencing resolution—clinically, radiologically, or both

	Clinical and radiologic improvement	Radiologic improvement only		Clinical improvement only
		Persistent pain	Uncontactable	No MRI performed	Persistent disk on MRI
Number of patients	17 (36.2%)	6 (12.7%)	3 (6.4%)	19 (40.4%)	2 (4.3%)
Total number of patients	17 (36.2%)	9 (19.1%)		21 (44.7%)

Abbreviation: LDP, lumbar disk prolapse; MRI, magnetic resonance imaging.

In the “surgical candidates” who experienced clinical and/or radiologic improvement, the average time from symptom onset to removal from the surgical waiting list was 720 days (∼2 years from onset; see [Table 2]). The average time from addition to the surgical waiting list to clinical and/or radiologic improvement was 319 days (∼10 months).

Table 2 Time frames ranging from symptom onset to cancelation of microdiskectomy in lumbar disk prolapse patients experiencing radiologic and/or clinical resolution

Time (d)	Mean	Minimum	Maximum	Median	SD
Symptom onset to referral	200.0	6	1,096	117.5	216.9
Symptom onset to first clinic appointment	368.1	63	1,278	355.5	259.3
Symptom onset to addition to waiting list	437.1	58	1,392	365.0	323.8
Symptom onset to cancelation of surgery	720.4	100	1,826	693.0	370.8
Referral to first clinic appointment	368.0	63	1,278	355.5	259.3
Referral to addition to waiting list	268.7	5	1,995	200.5	339.8
Referral to cancelation of surgery	553.7	14	2,301	457.0	366.3
First clinic appointment to cancelation of surgery	406.4	14	2,267	323.5	341.9
Addition to waiting list to cancelation of surgery	318.7	9	839	301.0	165.8

Abbreviations: SD, standard deviation.

Discussion

Pathology of Lumbar Disk Prolapse

It remains difficult to accurately predict the course of disease of LDP on a patient-to-patient basis. Spontaneous resolution of patient symptoms may occur with time. This can either happen in isolation or along with an accompanying reduction in disk prolapse size on MRI.[17] However, 1 to 2% of all LDP cases are at risk of developing cauda equina syndrome (CES).[18] [19]

Spontaneous disk prolapse resolution was first documented almost 40 years ago by Guinto et al,[20] but the underlying mechanism is still not fully understood. There are currently three proposed explanations for spontaneous resolution, with the first being that the herniated fragment gradually becomes dehydrated and “shrinks” and the second claiming the posterior longitudinal ligament provides a tension that “pulls” the fragment back into the disk space.[17]

The third and most supported hypothesis is that resorption of the herniated disk occurs as a result of an inflammatory reaction.[17] Normally, the intravertebral disk is an immune-privileged site, guarded from the immune system by the annulus fibrous. But, in the instance of LDP, immune cells can interact with the herniated cells and initiate an inflammatory response that promotes disk resorption.[17] Evidence suggests that macrophages (which produce matrix-degrading enzymes) and neovascularization (by providing a passageway for immune components to enter the degenerate matrix) facilitate this inflammatory mechanism.[21]

Current Treatment of Lumbar Disk Prolapse

Initial conservative interventions involve adequate analgesia (including antineuropathic agents), physical therapy, and multidisciplinary team.[22] Based on the current evidence that over 70% of sciatica patients experience spontaneous resolution within 6 weeks of symptom onset,[1] spinal surgeons and neurosurgeons focus on exhausting different nonsurgical options and encouraging patients to persevere with conservative measures initially before considering microdiskectomy. Following the guidance of The UK National Low Back and Radicular Pain Pathway (2017), the NHS only recommends surgical intervention after a minimum of 8 to 12 weeks of radicular pain not responding to conservative measures, or if there is evidence of serious or progressive neurologic deficit.[4]

LDP affects approximately 9% of adults worldwide and has a high associated economic burden.[17] Because of the uncertain natural history of disease, it may be difficult to decide when to offer microdiskectomy. While surgery is associated with significant costs to the health care system, this cost may be acceptable after accounting for swifter symptom relief, earlier return to work, and gain in quality-adjusted life years (QALYs).[23] Patients who experience rapid pain relief will also likely feel reassured about their recovery, and more quickly return to normal activities. On the other hand, a stepwise approach to treating patients with LDP may be the more cost-effective option.[24] Awaiting spontaneous resolution without surgery avoids the potential possibility of complications and poor postoperative outcomes. Regardless of the treatment decision, patients must be adequately counseled about the risks and benefits of early surgery compared with prolonged conservative management to facilitate shared and informed decision-making.

Expanding our knowledge about the physiology of LDP resorption, in combination with the identification of prognostic indicators, will enable individualized treatment approaches and may result in subsequent reduction of costs for the health care system.[17]

Conservative versus Surgical Treatment

Several large cohort studies have been conducted to examine spontaneous disk resolution, its prognostic factors, and predictive outcomes. These include Weber,[25] the Maine Lumbar Spine Study,[7] and SPORT.[6] Overall, these studies indicate that early surgery achieves better outcomes for LDP patients in the short term.[6] [7] [17] [25] [26] [27] However, in the long term, outcomes of early surgery become almost identical to those observed with prolonged conservative management.[6] [7] [17] [25] [26] [27]

SPORT found no statistically significant difference in outcome between surgical and conservative management of LDP patients.[6] Two other similar randomized controlled trials also found comparable outcomes for both treatment arms at 2-year follow-up.[26] [28] However, Österman et al[28] reported surgery to be significantly superior to conservative management if the LDP affected the L4/L5 disk. The group postulated that the spinal level of LDP could potentially be used as a predictive tool for determining the efficacy of surgery.

Even very large disk prolapses can undergo spontaneous resolution,[29] with most reducing to only a third of their original volume by 6 months.[21] This increased capacity for resorption may be influenced by larger LDPs having an even greater associated inflammatory response.

Timing of Surgery

The optimal timing of microdiskectomy for LDP is yet to be defined.[26] Equally, potential prognostic factors for worse postoperative outcomes are difficult to identify.[6] [30]

Several studies, including Hurme and Alaranta,[32] Rothoerl et al,[31] Nygaard et al,[33] and Ng and Sell,[33] have shown that in comparison to patients undergoing surgery after greater than 8 months of prolonged sciatica, patients undergoing early surgery (<2–4 months from symptom onset) have favorable postoperative outcomes. Another possible contributing factor to postoperative outcome is the specific choice and intensity of conservative approach used prior to surgery. The presurgery physiotherapy for patients with degenerative lumbar spine disorder (PREPARE) trial found LDP patients who underwent more intensive presurgery physical therapy to have better pain control, physical activity levels, and improved psychological well-being compared with patients who were given simpler advice to “stay active” prior to their upcoming surgery.[34]

We do not yet have any well-established prognostic markers to predict surgical outcome and facilitate clinical decisions. However, one recent study identified high levels of plasminogen activator inhibitor-1 (a marker of fibrinolysis) to be consistently associated with poorer surgical outcome in LDP patient samples.[17]

COVID-19 Pandemic

The first case of COVID-19 was reported in Wuhan, China, on December 31, 2019.[35] [36] On the March 11, 2020, WHO declared a global pandemic,[37] leading to the cancelation of NHS services and resource reallocation described earlier.

Deer et al reported the pandemic causing significant disruption in the care of chronic pain conditions, with patients being at greater risk of decreased mobility, reduction in overall health status, and increased use of opioid analgesics.[38] This finding reiterates the importance of optimizing long-term conservative approaches for LDP patients subject to chronic pain.

Waiting times for LDP patients from referral to surgery can be as long as 18 weeks.[39] For most patients, this means prolonged pain and physical restriction. On top of this well-recognized issue in the NHS, the pandemic resulted in a reduction in the number of available clinic appointments.[40] Interestingly, despite the longer waiting times, there were fewer patients being added to the list, with the number of referrals to specialist spinal surgeons falling to half during the pandemic.[41] Many patients with LDP were reluctant to make a GP appointment, simply unable to access an appointment, or presented at a later stage of disease[42] due to fear of catching COVID-19 or due to other lockdown-associated issues. Late presentation, coupled with delayed surgery, puts LDP patients at greater risk of irreversible neurologic deficit, loss of function, pain, and impaired quality of life.[38]

When elective surgery was permitted to resume, the NHS created specific guidelines[43] to ensure the continuation of quality elective surgical services as well as prioritize the safety of patients and staff.[44] These included prioritizing appropriate patients, preoperative reverse transcription polymerase chain reaction (RT-PCR) test, self-isolation for 14 days, and dedicated operating theaters for elective operations.[44]

COVID-19 Response and Elective Spinal Surgery: Existing Literature

We know the majority of LDPs have the potential to resolve spontaneously and that surgical intervention comes with additional peri- and postoperative complications.[45] The COVID-19-related delay in elective surgery, and thus the increased volume of patients receiving prolonged conservative management, provided us with the unique opportunity to further study the occurrence of spontaneous LDP resolution.

The existing literature covering the impact of the COVID-19 pandemic on spinal surgery mainly focuses on the changing neurosurgical workload (i.e., numbers of referrals, emergency attendances, surgeries performed), infection rates, and the efficacy of COVID-related implementations within the service.[2] [3] [9] [11] [12] [13] [35] [41] [44] [46] [47] [48] [49] Spinal surgery case volume was reported to have decreased by 52 to 70% over the pandemic.[10] [35] The literature also supports an observed reluctance of patients to burden the health care systems further[2] [42] in comparison to the more “peaceful” and less-pressurized prepandemic era where patients may have been more likely to overestimate symptom severity and contribute to overuse of the spinal service.[50]

Although studies report on both acute and elective spinal cases, there are no studies specifically looking at patients with LDP and the incidence of spontaneous resolution. There are also few studies reporting on complications associated with prolonged surgical waiting times for LDP. However, Norris et al looked at factors affecting when, and if, patients rescheduled their elective spinal surgery during the pandemic. The group reported that 6.1% of patients did not reschedule, but permanently canceled their surgery secondary to spontaneous clinical improvement.[51] Unlike our study, they did not report LDP resolution in depth or consider timing to resolution.

We found only one case report specifically examining spontaneous resolution of LDP as a direct result of the COVID-19 pandemic.[29] Naidoo reported a 51-year-old woman with massive L5/S1 disk herniation to experience full clinical and radiologic resolution without surgery. In this specific case, the patient refused surgery due to fear of contracting COVID-19, despite being counseled in clinic about the significant risk of permanent neurologic deficit and CES. She continued with conservative approaches, and within 3 months her symptoms completely resolved, with repeat MRI showing near-complete resolution. This illustrates that even sizable disk prolapses have the potential to resolve without surgery.

Conclusion

To our knowledge, our single-center, retrospective analysis is the first to report multiple LDP patients who had their elective microdiskectomy delayed secondary to the COVID-19 pandemic to later have their surgery canceled because of spontaneous clinical and/or radiologic resolution. Spontaneous resolution occurred in over a third of cases, within 1 to 3 years of symptom onset. Considering this, a prolonged conservative approach to LDP may be appropriate in some patients, allowing time for natural resolution, while avoiding any perioperative risks.

Next steps include systematic review of studies comparing early surgery versus prolonged conservative management to establish a prediction model for the outcomes of conservatively managed patients. There is also a need for larger retrospective studies akin to ours with a longer observational period. This will enable a thorough analysis of the outcomes of conservatively managed LDP patients on a larger, longer-term scale. Further studies are also required to reveal any potential prognostic factors indicative of spontaneous resolution. Potential parameters to investigate might include mechanism of LDP (e.g., trauma), timing of onset, level of prolapse, and other imaging characteristics (e.g., disk size).

Conflict of Interest

None declared.

Author Contributions

D.H. and M.O. were responsible for conception and design of the study. Acquisition of data was done by M.O., D.H., B.M., K.M., J.M., and H.S. Analysis and interpretation of data and drafting of the article were done by D.H. and M.O. Critical revision of the article was done by M.O., H.P., D.B., and A.S. Review of the submitted version of the manuscript was done by M.O. and D.H. M.O. approved the final version of the manuscript on behalf of all the authors.

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Publication History

Received: 23 September 2023

Accepted: 06 November 2023

Accepted Manuscript online:
08 November 2023

Article published online:
24 January 2024