Pathogenesis, Diagnosis, and Treatment of Lumbar Zygapophysial (Facet) Joint Pain

1. Pathogenesis, Diagnosis, and Treatment of Lumbar Zygapophysial (Facet) Joint Pain Anesthesiology :Vol 106(3)March 2007

2. Facet intervention – 2nd m/c procedure in pain management certers in US • But every aspect (from Dx to Tx) of l-z jt pain remains in controversy • l-z jt pain • lumbar facet jt 를 구조적 & 기능적으로 이루는 모든 구조물로부터 발생하는 pain (fibrous capsule, synovial membrane, hyaline cartilage surfaces, and bony articulations.)

3. l-z jt : potential pain generator in chr LBP pts • Facet jt capsule & surrounding structure에 stretching 이나 local compressive force에 의해 자극되는 nociceptor가 많다 • Facet jt & its n supply 자극시 back or leg pain 유발 • Local anesthetic(LA)하 spine op 시 facet capsule 자극으로 pain 유발됨 • 상당수 chronic LBP환자에서 facet jt or medial br block시 pain 감소

4. Anatomy and Innervation • True synovial jt • Joint space, synovial memb, hyaline cartilage surface, fibrous capsule • Dual innervation from medial branch • Same level and one level above • Medial br also innervate multifidus m, interspinous m & lig, periosteum of neural arch • 일부에서는 facet jt 에 additional innervation 있기도 함 • False negative result in diagnostic MBB

6. Histologic study • Richly innervated encapsulated, unencapsulated, free nerve endings • Low threshold, rapidly adapting mechanosensitive neuron • Suggest proprioceptive function • Sympathetic efferent fibers • Degenerative lumbar disorder시에 facet jt cartilage & synivial tissue에 PG, IL-1β, IL-6, TNF α같은 inflammatory mediator 발견

7. Function and Biomechanics • Support and stabilize spine, prevent inj by limiting motion • Facet jt oriented parallel to the sagittal plain • substantial resistance to axial rotation • minimal resistance to shearing force • upper lumbar sipne • jt oriented more in a coronal plain • tend to protect against flexion and shearing force • minimal protection against rotation • lower lumbar spine

9. Tropism • same level 의 paired facet jt 에서 sagittal plain에 대한 orientation이 각각 틀림 • general population에서 20~40%의 incidence • 대부분에서 facet joint tropism과 intervertebral disc degeneration & herniation사이에 positive relation • Weight bearing • normal facet jt carry 3~25% of axial burden • inc in pts with degenerative disc dis, facet arthritis • compressive load가 증가해도 facet load 는 slightly inc • 따라서 전체 stress중 l-z jt가 받는 proportion은 감소

10. Mechanisms of Injury Cadaveric and Animal studies • 대부분 l-z jt pain은 일생동안 쌓이는 repetitive strain and/or low-grade trauma에 인함 • L4-5, L5-S1에서의 jt displacement가 두드러짐 • Upper 3 facet jt • lat. Bending 시에 maximum jt displacement and greatest strain • Lower 2 facet jt • forward flexion시 greatest strain • L4-5 를 ant.thoracolumbar plate로 fixation • inc in intervertebral angulation at L3-4, L5-S1 • inc strain bilaterally at L3-4, L5-S1

12. repetitive strain and inflammation → synovial l-z jt 에 fluid filling & distension → jt capsule stretching 으로 pain 유발 • articular recess 의 distension → spinal canal or neural foramen의 nerve root compression → sciatica 유발 가능 • capsular irritation 은 또한 paraspinal m. 의 reflex spasm유발 가능

13. persistent facet joint pain • inflammatory chemicals or algesic mediators (substance P, phospholipase A2) • both nociceptive and proprioceptive nerve ending 에 neuronal sensitization → mechanical threshold 감소 • persistent nociceptive input에 의해 peripheral sensitization 유발 → 자극 지속시 central sensitization and neuroplasticity 발생

14. Human studies 1. osteoarthritis • chronic facet jt strain • radiologic study : sagittaly oriented facet jt and degenerative spondylolisthesis • loss of disc height, osteophyte formation, degenerative hypertrophy of facets • degeneration and loss of structural integrity of intervertebral disc ↔ degeneratrive change of l-z jt

15. 2. Inflammatory arthritis (RA, AS, reactive arthritis), synovial impingement, chondromalacia facetae, pseudegout, synovial inflammation, villinodular synovitis, acute & chronic infection 3. intrafacetal synovial cyst : 9.5% in pts with LBP 4. Trauma • most involve L5-S1 • mech of inj : hyperflexion, distraction, rotation

16. Prevalence • Exact prevalence is unclear • 10~15% in LBP

18. Pain Referral Patterns • Pain generating : jt capsule > synovium or articular cartilage • All lumbar facet jt : produce pain referred to groin (more common in lower facet jt pathology) • Upper facet jt pain : flank, hip, upper lat.thigh로 퍼짐 • Lower facet jt pain : deep thigh(usually lat and/or post) • 드물게 L4-5, L5-S1 facet jt pain이 lower lat leg, foot으로 extend • Osteophyte, synovial cyst, facet hypertrophy있는 환자에서 radicular sx

20. Diagnosis History and physical examination • No historic and physical examination findings can reliably predict response to diagnostic facet jt blocks

22. Radiologic findings • LBP환자에서 CT상 degenerative facet disease incidence는 40~85% • CT 가 MRI 보다 more sensitive • Asymptomatic pts에서는 facet jt의 severe OA관찰되지 않음 • Radiologic imaging으로 diagnostic l-z jt block의 결과 예측하기는 힘들다 • 많은 연구결과에서 radiologic imaging 만으로 l-z jt pain 진단 어렵다

23. Diagnostic Blocks • most reliable for diagnosing l-z jt as pain generators • Intraarticular block & MBB • equally effective in Dx l-z jt pain • Median branch n. 근처에 lat & intermediate br. 주행하므로 low volume anesthetics로도 같이 block 될 수 있다 • 이 신경들이 paraspinal m & fascia, ligaments, S-I jt, skin에 innervation 하므로 l-z jt 정상인 LBP 환자에서도 증상개선가능 • US guided medial branch & intraarticular block • fluroscopically guided inj. 과 accuracy 유사 • MBB가 기술적으로 쉽기 때문에 radiofrequency denervation 전 prognostic tool로 사용

24. False positive blocks • High false positive rate : 25~40% • unaffected by the type of block (intraarticular or MBB) • 원인 • placebo response, use of sedation, use of superficial LA, spread of injectate to other pain generating structure False negative blocks • 원인 • LA did not ingulf target nerve, aberrant or additional innervation, inadvertent venous uptake

26. Treatment Conservative treatment and pharmacotherapy • Tailored exercise program, yoga • Acupuncture • NSAID and AAP : widely considered as 1st line drug • Antidepressant (chronic LBP), m relaxant (acute LBP) • Psychotherapy

27. Intraarticular steroid injections • L-z joint pain이 active inflammatory process에 의한경우 intermediate term relief 가능 • SPECT 결과상 + 환자에서 dramatically better pain relief • Radionuclide bone scintigraphy • Inflammation, degenerative change, inc metabolic function 에 의한 synovial change 구분 가능

29. Radiofrequency Denervation • Sacroiliac jt pain, discogenic pain, intractable saictica에서도 사용 • Placing electrode parallel to target n • Sup articular proc 의 lat neck 지나서 electrode 위치 • Sensory stimulation(usually at ≤ 0.5V) • Electrode 가 target medial br 에 가까이 있음을 확인 • Multifidus m contraction 으로도 확인 가능

30. Paraspinal tenderness • Succesful Tx 의 predictor • Failed Tx • Axial rotation and hyperextension 시 pain • Duration of pain • Previous back surgery • RF denervation 후 pain relapse • Typically occurs between 6mo~1yr • Efficacy 감소 없이 Repeated neurotomy 가능 • High-temp RF MB abrasion, pulsed RF, cryodenervation, phenol neurolysis 도 사용

31. Complications after Intraarticular Injections and Radiofrequency Denervation • Steroid : impaired insuline sensitivity • Infection : septic arthritis, epidural abscess, meningitis • Spinal anesthesia, PDH • Numbness, dysesthesia after RF denervation : transient and self limiting • Burn • Neuritis : m/c Cx after RF (<5%) • Thermal inj to ventral rami

32. Surgery • Facet arthropathy pts에서 surgical Tx의 결과는 만족스럽지 못함 • Arthrodesis 후 pain 호전되는 이유중 하나는 pedicle screw fixation시 medial branch 를 rhizotomy