Pathogenesis Diagnosis and Treatment of Lumbar Zygapophysial

Pathogenesis, Diagnosis, and Treatment of Lumbar Zygapophysial (Facet) Joint Pain Anesthesiology :Vol 106(3)March 2007    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 구조 물로부터 발생하는 pain (fibrous capsule, synovial membrane, hyaline cartilage surfaces, and bony articulations.)  l-z jt : potential pain generator in chr LBP pts     Facet jt capsule & surrounding structure에 stretching 이 나 local compressive force에 의해 자극되는 nociceptor 가 많다 Facet jt & its n supply 자극시 back or leg pain 유발 Local anesthetic(LA)하 spine op 시 facet capsule 자극 으로 pain 유발됨 상당수 chronic LBP환자에서 facet jt or medial br block 시 pain 감소 Anatomy and Innervation  True synovial jt  Joint space, synovial memb, hyaline cartilage surface, fibrous capsule Same level and one level above    Dual innervation from medial branch  Medial br also innervate multifidus m, interspinous m & lig, periosteum of neural arch 일부에서는 facet jt 에 additional innervation 있기 도함  False negative result in diagnostic MBB  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 α 같은 inflammatory mediator 발견 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 tend to protect against flexion and shearing force minimal protection against rotation lower lumbar spine  jt oriented more in a coronal plain     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 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  Weight bearing     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 forward flexion시 greatest strain inc in intervertebral angulation at L3-4, L5-S1 inc strain bilaterally at L3-4, L5-S1  Lower 2 facet jt   L4-5 를 ant.thoracolumbar plate로 fixation    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  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 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 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 Prevalence  Exact prevalence is unclear  10~15% in LBP 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 Diagnosis History and physical examination  No historic and physical examination findings can reliably predict response to diagnostic facet jt blocks Radiologic findings      LBP환자에서 CT상 degenerative facet disease incidence는 40~85% CT 가 MRI 보다 more sensitive Asymptomatic pts에서는 facet jt의 severe OA관찰 되지 않음 Radiologic imaging으로 diagnostic l-z jt block의 결과 예측하기는 힘들다 많은 연구결과에서 radiologic imaging 만으로 l-z jt pain 진단 어렵다 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. 주행하 므로 low volume anesthetics로도 같이 block 될 수 있 다 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 False positive blocks   High false positive rate : 25~40%  unaffected by the type of block (intraarticular or MBB) placebo response, use of sedation, use of superficial LA, spread of injectate to other pain generating structure 원인  False negative blocks  원인  LA did not ingulf target nerve, aberrant or additional innervation, inadvertent venous uptake 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 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 구 분 가능 Radiofrequency Denervation     Sacroiliac jt pain, discogenic pain, intractable saictica에서도 사용 Placing electrode parallel to target n Sup articular proc 의 lat neck 지나서 electrode 위 치 Sensory stimulation(usually at ≤ 0.5V)   Electrode 가 target medial br 에 가까이 있음을 확인 Multifidus m contraction 으로도 확인 가능  Paraspinal tenderness  Succesful Tx 의 predictor Axial rotation and hyperextension 시 pain Duration of pain Previous back surgery Typically occurs between 6mo~1yr Efficacy 감소 없이 Repeated neurotomy 가능  Failed Tx     RF denervation 후 pain relapse    High-temp RF MB abrasion, pulsed RF, cryodenervation, phenol neurolysis 도 사용         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 Surgery   Facet arthropathy pts에서 surgical Tx의 결과는 만 족스럽지 못함 Arthrodesis 후 pain 호전되는 이유중 하나는 pedicle screw fixation시 medial branch 를 rhizotomy