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).
