Orthopedic Board Review: Spondylolisthesis Diagnosis & Classification MCQs
Key Takeaway
For orthopedic board exams, mastering spondylolisthesis involves understanding its classification, particularly the Wiltse-Newman system. Focus on differentiating types like isthmic (e.g., in gymnasts with pars defects) from degenerative. Recognizing clinical presentations, imaging findings, and appropriate treatment pathways is crucial for successful diagnosis and question resolution.
A 14-year-old competitive gymnast presents with insidious low back pain exacerbated by extension. On examination, there is hamstring tightness and a palpable step-off at L5. You are presented with the following radiograph. Describe the findings and name the specific condition and classification.
Candidate: This is a lateral radiograph of the lumbar spine showing an anterior slip of L5 on S1, indicative of spondylolisthesis. Given the age and clinical history of a gymnast, this is likely an isthmic spondylolisthesis, secondary to a stress fracture of the pars interarticularis. I would classify this as a Wiltse-Newman Type II (isthmic) spondylolisthesis.
Candidates often fail to describe the radiographic grade of the slip using the Meyerding classification. Furthermore, failing to mention the 'Scotty dog' sign on oblique views or not acknowledging the clinical triad of extension pain, tight hamstrings, and step-off sign indicates a lack of holistic clinical reasoning.
A high-scoring answer describes the findings systematically: "The radiograph demonstrates a Meyerding Grade [I/II] isthmic spondylolisthesis at L5-S1. The key pathological feature is a bilateral pars interarticularis defect. The diagnosis is consistent with the Wiltse-Newman Type II classification, driven by repetitive micro-trauma in the context of the patient's sporting activity. I would follow up with oblique radiographs to confirm the defect ('Scotty dog' sign) or an MRI if I suspected an active stress reaction (pre-spondylolysis) versus a chronic non-union."
The patient has failed 6 months of conservative management and the slip has progressed from Grade I to Grade II. Discuss your management strategy, focusing on surgical decision-making.
Candidate: Given the progression of the slip and failure of conservative management, surgical intervention is now indicated. I would offer an instrumented posterolateral fusion of L5-S1. In some cases, a decompression might be required if there is radiculopathy, but fusion is the essential element to stabilize the segment and prevent further slip progression.
Candidates often focus solely on 'fusion' and neglect to address the *why* (progressive instability). They may also suggest 'reduction' of the slip as a routine step, failing to realize the high risk of iatrogenic L5 nerve root injury associated with aggressive reduction maneuvers.
The ideal response structures the plan by priority: 1. Indications: Documented progression and clinical failure. 2. Procedure: Instrumented posterolateral fusion. 3. Reduction: Discuss the debate—"I would perform an in-situ fusion; while reduction corrects alignment, it increases the risk of traction neuropraxia to the L5 nerve root, which is particularly vulnerable during the relocation of a high-grade slip." 4. Ancillary procedures: Mention interbody fusion (TLIF/ALIF) to restore sagittal balance and disc height if indicated by the patient's lordosis profile.
