Lumbar canal stenosis is a common degenerative spinal condition in elderly patients, often managed surgically through decompressive procedures such as laminectomy. While laminectomy effectively relieves neural compression and improves function, it can compromise the structural stability of the spine – particularly when wide decompression involves the resection of posterior elements, including the posterior tension band ^[1]. Post-operative spinal instability is a recognised complication, especially in patients with underlying risk factors such as severe osteoporosis ^[2,3]. Instability may present months or even years after surgery, often with progressive pain, reduced mobility, and functional decline, despite initial post-operative improvement. Accurate diagnosis through clinical evaluation and radiological imaging is essential, as symptoms can mimic infection or recurrent stenosis. Timely surgical stabilisation, tailored to bone quality and biomechanical considerations, is critical to restore spinal stability and improve patient outcomes ^{[4,5,6,7,8,9,10,11,12]}.

• A 58-year-old male operated 2 years back for lumbar canal stenosis. The patient underwent an L4 wide laminectomy. After index surgery, the patient improved initially and was doing well. He started to do his daily activities and gradually lift heavy weight as well.
• Two months after index surgery, the patient developed severe low back pain. Progressively, his standing and walking distance reduced.
• Gradually, due to pain, the patient started to move due to pain and was bedridden. He could not stand due to pain
● Patient presented to our outpatient department 2 years after index surgery with significant low back ache and difficulty in turning in bed, unable to stand and walk. On further asking, he had no history of fever after surgery.
● On examination
o Severe tenderness in the lumbosacral region. Visual Analogue Scale (VAS) score 7 out of 10
The passive straight leg raising test was free, and the distal pulses okay.
o Neurology was intact.
● Patient was admitted for further management

Diagnostic assessment and interpretation
• Routine blood investigations to rule out infection were done. Complete blood count (CBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) were normal.
• X-rays, anteroposterior and lateral views, were done. The anteroposterior view showed a previous laminectomy and severe osteoporosis. Flexion-extension view in the lateral view showed severe angular instability at L4-L5 and end-plate sclerosis (Fig. 1).

Figure 1: X-rays done at initial visit.

• Magnetic resonance imaging (MRI) done showed significant intradiscal degeneration and fluid accumulation in the disk (Fig. 2)

Figure 2: Magnetic resonance images at the time of presentation.

• Surrounding facet degeneration was also seen
• We considered that this could be the following:
o Post-operative infection
 To rule that out, we did routine blood investigations such as CBC, ESR and CRP. It came out to be normal ^[13].
o Post-operative Instability
• Studies have shown that the chances of postoperative instability range from 43 to 55%. However, if the facets are spared, the incidence reduces to 10–43% ^[1,14,15,16].
• In a single-level lumbar spine surgery where the posterior tension band has been removed, the chances of postoperative instability, which leads to spondylolisthesis, are higher. As the number of decompressed levels increases, the chances of instability further increase.

Intervention
● On pre-operative planning
o On pre-operative X-rays (Fig. 1), we could anticipate severe osteoporosis. Due to this
▪ Our plan was on fixing 2 levels above and 2 levels below it.
▪ There was significant angular instability and osteoporosis, so if we were to put in a cage, there would be chances of cage back-out.
● Hence, to achieve fusion, we decided to locally harvest the bone graft and mix it with a bone graft substitute and insert it into the disc space.
● Intraoperative findings (Fig. 3 and 4)

Figure 3: Intraoperative images showing locally harvested bone graft mixed with bone graft substitute.

Figure 4: Inserting graft material into disk space with funnel.

o Violated L4 facet bilaterally,
o Broken L4 pars interarticularis
o Osteoporotic bones
o Intra-discal fluid aspirated out – clear fluid obtained and sent for culture and sensitivity, and Tubercular testing
o Pedicle screws put in, and disc space curetted and packed in with bone graft harvested locally, mixed with bone graft substitute using a funnel.
● Post-operative period
o Patient was kept lying in bed with the allowance of log rolling.
o The cultures sent for testing came out to be negative. Hence, we could conclude that this was an aseptic pathology and the causative etiology was iatrogenic instability that was caused during the index surgery and was not addressed then, which lead to progressive angular instability and disk degeneration
o Patient was discharged on post-operative day 3 after dressing and removal of the drain.
An immediate post-operative X-ray was done (Fig. 5).

Figure 5: Immediate post-operative X-rays showing pedicle screw fixation done from L3 to S1 and L4-L5 disk space packed with bone graft and bone graft substitute.

● Postoperatively, after 1 month – the patient came for follow-up. Pain was reduced drastically.
o VAS score – 4 out of 10.
o Patient could comfortably turn in bed
o Suture line was healthy without any pus discharge
● A post-operative 1-month X-ray was done (Fig. 6)

Figure 6: One-month follow-up X-ray.

o Showed good implant position; the patient was mobilized
o Satisfactory bone formation in the intradiscal area was noted
o Patient was mobilized. On mobilisation, the patient was walking with a walker, and his walking distance was improving.

Posterior lumbar decompression remains a cornerstone in the management of lumbar canal stenosis, particularly in elderly patients. While decompressive laminectomy effectively alleviates neural compression, it may inadvertently compromise spinal stability, especially when wide decompression involves resection of posterior stabilising elements such as the lamina, spinous processes, interspinous ligaments, and facet joints ^[1]. Iatrogenic post-operative instability is a well-recognised but often underestimated complication, with reported incidence varying widely depending on the extent of decompression, number of levels involved, and preservation of the posterior tension band ^[3] (Fig. 7).

Figure 7: Diagrammatic representation of post-operative instability and how is measured.

Several studies have demonstrated that a wide laminectomy significantly alters the biomechanics of the lumbar spine, increasing segmental motion and shear forces, thereby predisposing it to progressive instability and spondylolisthesis ^[1,2,16]. Yang et al. ^[17] and Bisschop et al. ^[18] highlighted that factors such as facet joint violation, pre-existing degenerative changes, disc degeneration, and poor bone quality markedly increase the risk of post-operative instability. In single-level decompression, the incidence of instability may be relatively low; however, when the posterior tension band is disrupted, the likelihood of delayed instability rises substantially ^[14,15], as also reported by Ramhmdani et al. ^[19] in their case series on iatrogenic spondylolisthesis following lumbar laminectomy.
The present case illustrates a classic but delayed presentation of post-operative iatrogenic instability, where the patient initially experienced symptomatic relief after surgery but subsequently developed progressive mechanical low back pain and functional deterioration. The absence of neurological deficits, normal inflammatory markers, and lack of systemic symptoms posed a diagnostic challenge, as post-operative infection and recurrent stenosis are often considered first ^[13]. However, dynamic radiographs demonstrating significant angular instability at the operated level, along with MRI findings of intradiscal degeneration and fluid accumulation, were key in establishing the diagnosis. Intradiscal fluid accumulation following decompression may mimic infectious spondylodiscitis ^[13]; however, negative laboratory parameters and sterile intraoperative aspirate confirmed an aseptic degenerative pathology. Such aseptic disc degeneration has been described in the setting of chronic instability, where abnormal micromotion leads to disc hydration changes, endplate sclerosis, and progressive collapse ^[20,21]. This emphasises the importance of correlating clinical, radiological, and laboratory findings to avoid misdiagnosis and inappropriate management. Bone quality plays a pivotal role in both the development of post-operative instability and the success of revision surgery. Severe osteoporosis, as seen in our patient, not only predisposes to instability but also limits surgical options. Interbody cages, though biomechanically advantageous, carry a significant risk of subsidence, migration, and retropulsion in osteoporotic spines. Studies by Park and Chung ^[22] and Zhang et al. ^[23] have demonstrated increased implant-related complications in patients with poor bone mineral density ^[24]. Therefore, in the present case, a long-segment posterior fixation spanning two levels above and below the unstable segment was chosen to distribute stresses over a larger construct and minimise the risk of implant failure ^{[25,26,27,28,29]}. The decision to avoid cage insertion and instead use locally harvested autograft mixed with bone graft substitute for interbody fusion was guided by both biomechanical and biological considerations. Bone grafting provides a favourable osteoconductive and osteoinductive environment while reducing the risk of cage-related complications. Previous studies have shown satisfactory fusion rates using bone grafts and graft substitutes, particularly when combined with rigid posterior instrumentation, even in osteoporotic patients ^{[20,21,30,31,32,33]}. This case underscores the critical importance of intraoperative assessment of spinal stability during index decompression surgery. Preservation of facet joints and posterior elements, whenever feasible, and a low threshold for adding instrumented fusion in the presence of suspected instability are essential to prevent delayed complications. Newer decompression techniques, such as unilateral laminotomy for bilateral decompression ^[14] and “over-the-top” approaches ^[34] (Fig. 8), have been shown to reduce the risk of iatrogenic instability by preserving posterior stabilising structures ^[1,15].

Figure 8: Diagramatic representation of over-the-top decompression.

• A good pre-operative assessment of various anatomical factors must be done using radiological images, such as X-rays and MRI, to rule out instability or factors that may contribute to instability
• When possible – Protection of posterior tension band should be done using newer techniques
• Intraoperatively – Protecting facet joint, assessment of stability must be done – if instability suspected, it must be addressed using instrumented fusion
• Multiple factors (ex: destruction of pedicle or facet, bone quality, location of instability) help in deciding levels of fixation.

• Lumbar canal stenosis is one of the common pathologies causing low back pain and dysfunction in elderly populations. During surgical planning, radiological images such as X-rays and MRI should be used to rule out instability or factors that can contribute to instability.
• Posterior decompression with or without fusion is one of the most commonly performed surgeries for lumbar canal stenosis. However, many factors can lead to instability.
• Intraoperative assessment of instability must be done, and if suspected or proven, it must be addressed with instrumented fusion. Because if left unaddressed, it can lead to progressive degeneration over time, causing progressive instability.
• This progressive instability can be addressed with long segment instrumentation, and interbody fusion using bone graft can be done. To accelerate fusion, this bone graft can be mixed with a bone graft substitute.