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Lumbar pseudoarthrosis


Introduction

Pseudoarthrosis is a common complication following fusion operations. It can be found in both instrumented and noninstrumented fusions but more commonly occurs following noninstrumented fusion. Pseudoarthrosis is defined as symptomatic nonunion after 1 year of a fusion surgery. The symptoms can vary from mechanical back pain, radicular pain, or focal deformity due to construct failure. Pseudoarthrosis can also be identified radiographically in asymptomatic patients. Additionally, the rate of pseudoarthrosis also varies depending on the number of fused levels. There are known risk factors that increase the risk of pseudoarthrosis and include osteoporosis, smoking, malnutrition, rheumatoid arthritis, age, radiation therapy, and the use of immunosuppressants. Pseudoarthrosis can also lead to failure at the bone-metal interface causing haloing of the pedicle as well as hardware failure. For cases of lumbar spinal pseudoarthrosis requiring reoperation, fusion adjuncts such as bone morphogenetic protein have been found to increase rate of fusion. Additionally, reduction of the modifiable risk factors predisposing to pseudoarthrosis should be attempted to improve the likelihood of fusion following revision.

Example Case

  • Chief complaint: back pain and leg pain

  • History of present illness: A 29-year-old male presents with a history of back pain and left leg numbness. He underwent a L5-S1 decompression and fusion at that time. He had improvement of the leg pain but no change in his back pain. He underwent revision a year later with a spinous process device to help his back pain. Immediately postoperatively, he had pain in L5 distribution down his left leg. He presented with back pain and burning leg pain and imaging was done ( Fig. 11.1 ).

    Fig. 11.1, Preoperative magnetic resonance images. (A) T2 sagittal and (B) T2 axial images demonstrating hyperintensity of the L5-S1 disc space, L5-S1 vertebral edema, and left L5-S1 foraminal stenosis.

  • Medications: hydrocodone, tizanidine

  • Allergies: no known drug allergies

  • Past medical and surgical history: L5-S1 fusion x 2

  • Family history: noncontributory

  • Social history: engineer, no smoking history, occasional alcohol

  • Physical examination: awake, alert, and oriented to person, place, and time; cranial nerves II–XII intact; bilateral deltoids/biceps/triceps 5/5; interossei 5/5; iliopsoas/knee flexion/knee extension/dorsi, and plantar flexion 5/5

  • Reflexes: 2+ in bilateral biceps/triceps/brachioradialis; 2+ in bilateral patella/ankle; no clonus or Babinski; negative Hoffman; sensation intact to light touch

  • Belal Elnady, MD

  • Orthopaedic Surgery

  • Assiut University

  • Assiut, Egypt

  • Mohamed El-Fiki, MBBCh, MS, MD

  • Neurosurgery

  • Alexandria University

  • Alexandria, Egypt

  • John G. Heller, MD

  • Orthopaedic Surgery

  • Emory University

  • Atlanta, Georgia, United States

  • Langston Holly, MD

  • Neurosurgery

  • University of California at Los Angeles

  • Los Angeles, California, United States

Preoperative
Additional tests requested

  • L-spine flexion-extension x-rays

  • Laboratory studies (ESR, CRP, CBC)

  • L-spine flexion-extension x-rays

  • CT L-spine high resolution

  • Complete electrodiagnostic study

  • Lower extremity dopplers

None Flexion-extension lumbar x-rays
Surgical approach selected L5-S1 TLIF

  • If instability demonstrated,

  • Stage 1: L5-S1 OLIF

  • Stage 2: L5-S1 percutaneous posterior fusion

  • Stage 1: L5-S1 ALIF and removal of TLIF

  • Stage 2: Left L5-S1 foraminotomy, L5-S1 instrumented posterolateral fusion

If convinced symptoms are due to the pseudoarthrosis, L5-S1 MIS posterolateral fusion
Goal of surgery Stabilize spine Stabilize spine, decompress foramina Stabilize spine, decompress left L5-S1 nerve roots Stabilize spine, treat pseudoarthrosis
Perioperative
Positioning Prone, no pins

  • Stage 1: lateral

  • Stage 2: prone

  • Stage 1: supine

  • Stage 2: prone, no pins

Prone, no pins
Surgical equipment Fluoroscopy

  • IOM

  • Fluoroscopy

  • Endoscope

  • Tubular retractor

  • Surgical navigation

Fluoroscopy

  • Fluoroscopy

  • Surgical navigation

  • Surgical microscope

Medications None None None None
Anatomical considerations Dura, nerve root Abdominal viscera, great vessels, segmental radicular artery Common iliac vessels namely left common iliac vein, posterior annular defect, left L5-S1 nerve roots Thecal sac, spinal nerves, pedicles
Complications feared with approach chosen Dural tear, CSF leak Lumbar plexus injury, durotomy, end plate fracture, psoas weakness, retroperitoneal hematoma Persistent left leg pain, nerve injury, infection Retrograde ejaculation with ALIF, CSF leak, nerve root injury
Intraoperative
Anesthesia General General General General
Exposure L5-S1

  • Stage 1: L5-S1

  • Stage 2: L5-S1

  • Stage 1: L5-S1

  • Stage 2: L5-S1

L5-S1
Levels decompressed L5-S1

  • Stage 1: L5-S1

  • Stage 2: L5-S1

  • Stage 1: L5-S1

  • Stage 2: L5-S1

L5-S1
Levels fused L5-S1

  • Stage 1: L5-S1

  • Stage 2: L5-S1

  • Stage 1: L5-S1

  • Stage 2: L5-S1

L5-S1
Surgical narrative Position prone, posterior midline incision, subperiosteal dissection, removal of interspinous implant, decortication of the posterolateral elements, pedicle screw insertion at L5-S1, fascetectomy and transforaminal discectomy, removal of loose interbody cage, good debridement of the disc space and remove all fibrous tissue until bleeding cancellous bone seen, insertion of new interbody cage filled with bone graft, gentle compression over pedicle screws to stabilize cage, insertion of bone graft in the posterolateral gutter to achieve 360-degree fusion, closure of wound in layers

  • Stage 1: position right lateral with left side up, mild flexion of left hip nad mild flexion of table, x-ray to mark (anterior, posterior, midpoint) L5-S1 disc, traverse skin incision, dissect bluntly external and internal obliques and transversus muscles, dissect transversalis fascia as laterally as possible to avoid peritoneum, place tubular retractor toward midline after identifying retroperitoneal fat until anterior psoas border and intervertebral space is felt, release adhesions between peritoneum and anterior border of psoas muscle, medial limit is lateral border of ALL, direct tubular retractor obliquely centered on L5-S1 disc posterior to lumbar plexus, repeated fluoroscopy during annulus release and end plate preparation, remove old prosthesis, place interbody.

  • Stage 2 (same day): position prone, placement of percutaneous L5-S1 pedicle screws using x-rays, placement of rods, layered closure

  • Stage 1: position supine, transverse left anterior incision to access retroperitoneal space, identify left ureter and mobilize across midline with peritoneal contents, medial border of left iliac vein exposed, ligate medial branches off of vein to allow tension-free retraction to the left, ligate median sacral vessels, bluntly dissect across to the right side of L5-S1 disc, mobilize right iliac vessels, place right Brau blade, place left iliac vein retractor making sure to not tear vein at bifurcation, L5-S1 complete discectomy with removal of lower portion of L5 and upper portion of S1 to remove TLIF cage, prepare surfaces for fusion, place cage that is assembled in situ and actively distracts segments to normal height and lordotic angle, place BMP.

  • Stage 2 (same day): position prone, midline incision, subperiosteal dissection, fully expose and decorticate left L5 transverse process and sacral ala, place pedicle screws bilaterally at L5-S1, use combination of local bone and iliac crest bone graft, layered closure with subfascial drain

Position prone, place percutaneous dynamic reference frame, use navigated probe to create two separate 1-inch incisions over L5 and S1 pedicle screw entry sites, dissect through muscle and fascia and using the bovie, expose L5 transverse process and sacral ala using microscope bilaterally, harvest iliac crest autograft, decorticate L5 transverse process/facet complex/sacral ala, place autograft bone over it, place navigated percutaneous pedicle screws, confirm accuracy with O-arm, lock rods, standard closure
Complication avoidance Good debridement of disc space, gentle compression over pedicles to compress screws, attempt to achieve 360-degree fusion Mild flexion of left hip to relax left psoas, be aware of nerves under internal oblique muscle, avoid extended muscular dissections, use anatomical corridors around disc with anterior border of psoas and left lateral border of aorta or left iliac artery with minimal retraction of psoas not beyond coronal plane to avoid injury to genitofemoral nerve Two-staged approach, ligate medial branches off of left iliac vein, ligate median sacral vessels, remove lower portion of L5 and upper portion of S1 to allow removal of TLIF cage, place cage that distracts to provide indirect decompression, standard closure, BMP Surgical navigation, minimally invasive approach, iliac crest autograft
Postoperative
Admission Intermediate care Floor Floor Floor
Postoperative complications feared CSF leak, wound infection End plate fracture, psoas weakness, injury to segmental radicular artery, nerve root injury, major vessel injury Persistent left leg pain, nerve injury, infection Screw misplacement, pseudoarthrosis
Anticipated length of stay 2 days 1–3 days 3–4 days 3 days
Follow-up testing L-spine x-rays 2 months, 6 months, 1 year after surgery

  • L-spine x-rays immediately after surgery, 1 day, 1 month, every 3 months until adequate fusion assured after surgery

  • CT L-spine every 3 months until fusion assured

  • ESR/CRP until normalization

  • L-spine AP and lateral 6 weeks, 3 months, 6 months, 12 months after surgery

  • CT L-spine 6 or 12 months after surgery

  • L-spine AP/lateral x-rays after surgery, 6 weeks, 3 months, 6 months, 1 year, 2 years after surgery

  • Bone stimulator

Bracing None None None LSO brace for 3 months
Follow-up visits 2 weeks, 2 months, 6 months, 1 year after surgery 10 days, 1 month, every 3 months until fusion after surgery 6 weeks, 3 months, 6 months, 12 months after surgery 2 weeks, 6 weeks, 3 months, 6 months, 1 year, 2 years after surgery
AP , Anteroposterior; ALIF , anterior lumbar interbody fusion; ALL , anterior longitudinal ligament; BMP , bone morphogenic protein; CBC , complete blood count; CRP , C-reactive protein; CSF , cerebrospinal fluid; CT , computed tomography; ESR , erythrocyte sedimentation rate; IOM , intraoperative monitoring; LSO, lumbar-sacral orthosis; MIS , minimally invasive surgery; OLIF, oblique lateral interbody fusion; TLIF , transforaminal lumbar interbody fusion.

Differential diagnosis

  • ▪

    Pseudoarthrosis

  • ▪

    Discitis

  • ▪

    Osteomyelitis

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