Chronic L5 pars fractures with back pain and spondylolisthesis

Introduction

The pars interarticularis represents a small piece of bone that connects the facet to the pedicle. Given its small size and location, the pars is prone to fracture from multiple sources. Pars fractures can lead to back pain and leg pain with foraminal stenosis, and it can also lead to lumbar spondylolisthesis, which is described as ventral subluxation of one vertebrae body on the other. It is classified as congenital/dysplastic, isthmic, degenerative, traumatic, or pathological based on the classification of Wiltse-Newman-MacNab, which has become the most widely accepted classification system (see Chapter 1 , Table 2). The degree of slippage is graded based on the Meyerding classification, scored from I to V (see Chapter 1 , Table 1). Grade I spondylolisthesis is defined as slippage less than 25%, grade II is displacement up to 50%, grade III is displacement up to 75%, grade IV is displacement of greater than 75%, and grade V is a complete subluxation of one body on another and is referred to as spondyloptosis.

Example case

Chief complaint: left leg pain and weakness
History of present illness: A 58-year-old female who is very active presents with a several-year history of pain and numbness in her left leg. It has worsened over the past 6 months. She now notices a foot drop after walking for a prolonged period of time. This does improve with rest. She also has back pain that is improved with rest. She has tried physical therapy with minimal improvement. She underwent imaging and this revealed chronic pars fractures of L5 with spondylolisthesis ( Figs. 32.1–32.3 ).

$Fig. 32.2, Preoperative computed tomography (CT) scans. (A) right parasagittal, (B) Sagittal CT, and (C) left parasagittal images demonstrating bilateral chronic pars fracture with grade II spondylolisthesis and foraminal stenosis.$

$Fig. 32.3, Preoperative lumbar x-rays. (A) Anteroposterior (AP) and (B) lateral lumbar x-rays demonstrating bilateral pars fracture with grade II spondylolisthesis without dynamic instability.$
Medications: estradiol, hydroxychloroquine
Allergies: adhesive, aspirin
Past medical and surgical history: malignant melanoma, Sjogren syndrome
Family history: noncontributory
Social history: office work, no smoking history, occasional alcohol
Physical examination: awake, alert, and oriented to person, place, and time; cranial nerves II–XII intact; bilateral deltoids/triceps/biceps 5/5; interossei 5/5; iliopsoas/knee flexion/knee extension/dorsi, and plantar flexion 5/5
Reflexes: 2+ in bilateral biceps/triceps/brachioradialis with negative Hoffman; 2+ in bilateral patella/ankle; no clonus or Babinski; sensation intact to light touch

	Lorin M. Benneker, MD Orthopaedic Surgery Spine Unit, Sonnenhofspital Bern, Switzerland	Carlo Bellabarba, MD Orthopaedic Surgery University of Washington Harborview Medical Center Seattle, Washington, United States	Jeff D. Golan, MD Neurosurgery McGill University Montreal, Quebec, Canada	James S. Harrop, MD Neurosurgery Jefferson University Philadelphia, Pennsylvania, United States
Preoperative
Additional tests requested	EOS® complete spine with spino-pelvic parameters DEXA Facet injections	None	None	None
Surgical approach selected	Stage 1: L5-S1 ALIF Stage 2: percutaneous posterior L5-S1 fusion	L5-S1 laminectomy, TLIF, posterior instrumented fusion	Left L5-S1 TLIF	Anterior L5-S1 graft with posterior L5-S1 instrumented fusion
Surgical approach if 21 Surgical approach if 80	ALIF Posterior decompression	Same approach Same approach	Same approach Same approach with caution	Same approach TLIF
Goal of surgery	Decompress left L5-S1 nerve roots, restoration of sagittal profile, fusion to improve back pain	Decompress left L5-S1 nerve roots, realignment, stabilization of spondylolisthesis	Decompress left L5-S1 nerve roots	Decompress spinal cord, stabilize lumbar spine
Perioperative
Positioning	Stage 1: supine with maximum lordosis Stage 2: prone	Prone on Wilson table	Prone	Stage 1: supine Stage 2: prone with no pins on Jackson table
Surgical equipment	IOM Fluoroscopy	IOM (MEP/SSEP) Fluoroscopy BMP	Fluoroscopy	Fluoroscopy
Medications	None	None	None	None
Anatomical considerations	Iliac vessels, parasympathetic plexus, L5 nerve roots	L5 nerve roots, L5-S1 pedicles, L5 pars interarticularis	Exiting L5 nerve roots, bony end plates of L5 and S1	Aorta, iliac vessels, inferior vena cava, L5 pars
Complications feared with approach chosen	L5 neuropraxia, persistent back pain	L5 nerve root palsy, failure of fixation, infection	Obtain adequate lordosis, instability	Pseudoarthrosis, kyphosis, intracanal fibrosis
Intraoperative
Anesthesia	General	General	General	General
Exposure	Stage 1: L5-S1 Stage 2: L5-S1	L5-S1	L5-S1	L5-S1
Levels decompressed	Stage 1: L5-S1 Stage 2: None	L5-S1	L5-S1	L5-S1 foramina indirectly
Levels fused	Stage 1: L5-S1 Stage 2: L5-S1	L5-S1	L5-S1	L5-S1
Surgical narrative	Stage 1: position supine with maximum lordosis, horizontal skin incision, split rectus, retroperitoneal exposure of L5-S1, confirm disc space with x-ray, discectomy and decompression through disc space after sequential distraction and reposition of segment, insertion of trial cages under fluoroscopic control, lordotic angle should be around 20 degrees based on preoperative calculations, insertion of final cage filled with allo/autograft and angular-stable screw fixation, soft drain, closure Stage 2 (same day): position prone, stab incisions and transpedicular placement of k-wires under fluoroscopic control, thread and insert poly axial screws, insert rods, angular-stable fixation in S1, sequential reduction to L5, closure	Position prone, midline longitudinal incision, subperiosteal exposure of L5-S1 interlaminar space out to L5 transverse process and S1 ala, place L5-S1 bilateral pedicle screws under fluoroscopy, place L5 screw heads more anterior than S1 to facilitate reduction, wait of L5 screw placement if challenging, place S1 screws bicortically with fix angled screws, AP x-ray to confirm acceptable screw position, L5-S1 laminectomy, identify L5 nerve root and decompress along its course through the foramen, L5-S1 discectomy, place bilateral rods with securing to S1 first, use reduction forceps to engage L5 to the rod, distract slightly across screws but avoid tension on L5 nerve root, end plate preparation by resection of cartilaginous part of end plate, apply interbody spacer packed with bone graft and BMP from most symptomatic side while protecting L5 and S1 nerve roots, verify appropriate position, compress across L5 and S1 nerve roots to enhance lordosis and compress across interbody, x-rays to confirm alignment and hardware position, decorticate remaining L5 and S1 posterior elements and apply BMP and morcellized bone graft, vancomycin powder, layered closure over a drain	Position prone with encouraged lordosis, midline incision for L5-S1 laminectomy, procurement of local bone, bilateral exposure of Kambin triangle, restore disc height by alternating distractions on left/right side using graduate disc distractors, place banana cage at anterior aspect of interbody space, place percutaneous L5-S1 pedicle screws using fluoroscopy, compress for lordosis, fill extra autologous bone in interbody space	Stage 1: general surgery exposure, fluoroscopy to identify L5-S1 disc space, anterior discectomy, L5-S1 interbody, close Stage 2: prone on Jackson table, minimally invasive L5-S1 pedicle screws
Complication avoidance	2 staged approach, sequential distraction of disc space, calculate preop lordotic angle, percutaneous pedicle screws	Place L5 screw heads more anterior than S1 to facilitate reduction, wait of L5 screw placement if challenging, place S1 screws bicortically with fix angled screws, BMP, place interbody from most symptomatic side	Hybrid approach, alternating distraction, percutaneous screws	Two-stage, minimally invasive posterior fusion
Postoperative
Admission	Floor	Floor	Floor	Spine Unit
Postoperative complications feared	L5 neuropraxia, persistent back pain	L5 nerve root palsy, failure of fixation, infection	Radiculopathy, pseudoarthrosis, graft subsidence, pain	Continued pain, nerve root injury
Anticipated length of stay	4 days	2 days	2–3 days	3–5 days
Follow-up testing	L-spine standing x-rays within 2 days, 2 months, 12 months after surgery	CT L-spine prior to discharge L-spine upright AP/lateral x-rays prior to discharge L-spine upright AP/lateral/flexion/extension x-rays 3 months, 6 months, 12 months after surgery	Standing x-rays and CT prior to discharge, physiotherapy	Lumbar x-rays 2 weeks after surgery
Bracing	None	None	None	6 weeks
Follow-up visits	2 months, 6 months, 12 months after surgery	3 weeks, 3 months, 6 months, 12 months after surgery	4–6 weeks and 6 months after surgery	2 weeks with APP, 3 months, 6 months, 1 year, 2 years after surgery

ALIF , Anterior lumbar interbody fusion; AP , anteroposterior, APP , advanced practice provider; BMP , bone morphogenic protein; CT , computed tomography; DEXA , dual-energy x-ray absorptiometry; IOM , intraoperative monitoring; MEP , motor evoked potential; SSEP , somatosensory evoked potential; TLIF, transforaminal lumbar interbody fusion.

Differential diagnosis

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Par fracture
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Isthmus spondylolisthesis
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Pedicle fracture

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