S. Hellinger

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. 脊柱微創(chuàng)外科 Minimally invasive spine surgery .

Endoscopic resection of intraspinal facet cysts

S. Hellinger

Authors working place: 999035 Munich， Department of Orthopedic Surgery， Isar Hospital， GER

【Abstract】 Objective To investigate the clinical outcomes and surgical techniques of percutaneous endoscopic resection of intraspinal facet cysts. Methods Seven patients diagnosed with intraspinal facet cysts treated endoscopically were included in this prospective trial. All patients underwent a minimum of 6 weeks of nonoperative management prior to the endoscopic resection. Transforaminal endoscopic cyst resection or interlaminar approach cyst resection were performed depending on the morphology of the cysts. A retrospective analysis of hospital charts， MRI images was performed for each patient included in this study. The follow up was up to one year. In selected cases a comparison of imaging was performed after surgery. Results The patient’s postoperative outcomes were graded using visual analog scale （VAS） and Macnab criteria. Furthermore， the morphological comparison of the removed cysts was included following endoscopic resection of their facet cysts. The average duration of the surgery was 53 minutes. There was no significant blood loss. Two patients achieved an excellent outcome； four reported a good result and one had a fair result. The patients with good and fair outcome noticed that their radicular pain and claudication were relieved after surgery very well， but in some cases low back pain was still bothersome. Conclusions Endoscopic surgery in the hand of skilled surgeons seemed to be a good option for the treatment of facet cysts. It helps to avoid collateral damage and an increased instability. The endoscopic visualization allows a proper preparation and resection of the pathological structures and a good decompression of the spinal channel. Before an open laminectomy with or without fusion the endoscopic technique should be considered.

【Key words】 Spine； Surgical procedures， minimally invasive； Spinal canal； Bone cysts

Introduction

Intraspinal extradural cystic lesions， although increasingly reported， are an uncommon cause of lumbar radicular pain due to compression of spinal nerve roots［1-2］. The clinical features are indistinguishable from those of lumbar disc herniations or spinal canal stenosis，with low back pain preceding radicular leg pain or even claudication spinalis as most common symptoms［3-8］. The diagnosis of intraspinal cyst induced radicular pain is based on appropriate history， clinical examinationand imaging studies. The primary imaging technique for patients suffering from sciatica is MRI in supine position to identify intraspinal cystic lesions with a sensitivity of 90% compared to CT scanning with a sensitivity of 70%［9-12］.

Several types of intraspinal cysts have been reported， such as extradural arachnoid cysts［13-14］，perineural （Tarlov） cysts［15-16］， dermoid cysts［17-18］，neurofibroma with cystic degeneration［19］， and synovial or ganglion cysts， which are the most often detected cystoid structures in the spinal channel. Cysts in close vicinity of the zygapophysial joints （Z-joints） of the lumbar spine are generally considered synovial cysts or ganglion cysts， most commonly found at the single-most mobile segment of L4-5［12，20-21］.

Nonoperative treatment strategies include the use of nonsteroidal antiinflammatory drugs， physical therapy， epidural steroids， and CT guided needle aspiration and intra-articular injection as first line therapy in the treatment of patients with symptomatic synovial cysts［22-23］. Surgical excision is recommended to patients with cysts that cause neurological deficits or intractable pain or for patients in whom adequate conservative management has failed［3，8，24-25］.

The surgical technique depends on the size and localization of the cyst. When complete laminectomies were performed up to the 1980s［6］， minimally invasive surgical techniques evolved over the last decades and microsurgical resection after partial hemilaminectomy today is found sufficient［26］.

Because facet cysts are directly related to degenerated facet joints， the distinct risk of spinal instability following removal of these lesions exists. In part to address these concerns， minimally invasive technique that was initially developed for endoscopic lumbar discectomy is utilized in the surgical treatment. Minimally aggressive techniques reduce the risk of approach-related iatrogenic soft-tissue injury and have been shown to decrease intraoperative blood loss，postoperative pain， length of hospital stay and the development of postoperative segmental instability.

Although the relevant reports in the international literature are increasing， the controversy about conservative versus surgical treatment and the need for concomitant fusion still exists. Endoscopic techniques by less surgical damage on the joint as well as the stabilizing paraspinal muscles are helping to avoid this necessity. Juxtafacet cysts are quite uncommon causes of radiculopathy， low back pain and neurogenic claudication are often associated with significant spinal degenerative disease. To define the etiologic， clinical，histological， and surgical features of lumbar facet cysts an exact consideration is necessary.

Material and Methods

The endoscopic surgery demands a high level of endoscopic skills. Depending on the morphology of the cysts it can be done via interlaminar or transforaminal approach （Fig.1a， Fig.2a）. Special endoscopic instruments like burrs and kerrisons allow a proper preparation by slightly removing bone （Fig.1b， Fig.1c，F(xiàn)ig.2b， Fig.2c）. Meanwhile L5- S1allows a simple interlaminar approach； L4-5requires a special bony preparation. The total careful dissection from the neural structures is obligatory to avoid a cerebrospinal fluid leakage by dural tears. The resection of the cyst required a piecemeal removal under direct visualization. To precede with these special instruments as an endoscopic spine system （Spinendos）， high-speed burrs and Kerrisons are necessary. The different endoscopic techniques will be described.

Seven patients diagnosed with facet cysts， treated endoscopically were included in this prospective trial. All patients underwent a minimum of 6 weeks of nonoperative management prior the endoscopic resection. A retro perspective analysis of hospital charts，MRI images was performed for each patient included in this study. The follow up was up to one year. In selected cases a comparison of imaging after surgery was performed （Fig.2d， Fig.3d）.

GENERAL INTRODUCTION TO ENDOSCOPIC SURGICAL TECHNIQUES

Truly minimally invasive techniques are favourable to reduce the approach- related soft tissue injury （scar tissue）， intraoperative blood loss， hospital and rehabilitation time and postoperative pain.

· smaller incision- less trauma

· reduce blood loss

· reduce hospitalization time

· earlier return to work and daily activities

· less postoperative pain and medication

· direct approach to the pathology

· safe the dorsal approach for possible later interventions

· favourable access for revision surgeries -less scar tissue / in the case of revision surgery after endo-dorsal approach is still virgin

· does not preclude any further interventions

· local anesthesia

· lower complications rate

· can be performed on an outpatient basis

· cost effective （disposable costs / but shorter operating and inpatient time）

Endoscopic surgical techniques

Meanwhile the approach to the lower lumbar spine allows an effective interlaminar endoscopic surgery is the transforaminal way preferred for the higher levels of the lumbar spine due to the anatomical relation of interlaminar window， foramen， disc and facet joint. The quality and range of the instruments used have been consequently improved. Today an adequate constant visual control is applicable and due to associated appropriately fine-tuned instrumentations like blunt drills， endoscopic Kerrisons， high speed burrs and shavers， even anatomically difficult access which requires bone resection can be performed. Especially for the removal of facet cysts the most effective way should be chosen， sometimes demanding special extensive bony decompression with a high-speed burr.

Special requirements to facilitate proper endoscopic cyst decompression

Surgical skills of the surgeon for endoscopic spine surgery achieved in workshops and by visiting experienced endoscopic spine surgeons （e.g.， Spinendos training program） （Fig.3a）.

Proper endoscopic equipment with working channel scope， instruments for bony decompression （blunt burrs， endo-kerrison）， appropriate video equipment， irrigation pump， High Radiofrequency device with steerable probe （Elliquence）.

The specially designed endoscopic high speed burr （Fig.3b， 3c， 3d） with diamond and Rosen tip or sometimes bendable handpiece （Nouvag / Spinendos）enables now an adequate removal of bone with safety for decompression.

Transforaminal posterolateral: Inside -Inside technique

The transforaminal access to the posterior epidural space and the recessus， especially in the L5-S1segment is very often limited by a high iliac crest，narrowing of the intervertebral foramen by anatomical degenerative changes of the facet joint and flavum or capsula hypertrophy. But lateral or intraforaminal cystic formations are demanding this technique. Entering the posterolateral epidural space through the Kambin triangle：below the exiting nerve root， Superior Articulare Process （SAP） and boarder of the pedicle， it does enable a good direct visualization on the pathology. Very often parts of the SAP need to be removed using previously mentioned new instruments like highspeed drills （Nouvac）， endokerrison （Spinendos） and handburrs. This can improve the access and positioning of the endoscope to perform decompression cysts in the posterolateral spinal channel. The disc if not extruded remains intact during this procedure.

Transforaminal surgical procedure

Patient is positioned prone on a radiolucent table. A pelvic role and cushions may be used for adeqate positioning. Disinfections of the skin and sterile draping is applied.

Anatomic landmarks like Midline， Iliac Crest，Disc Space and the Mid Pediculare Line are marked as guidance points using a flouroscope. This subsequent procedure is performed under AP and lateral fluroscopic guidance. All C-Arm images shall always show parallel endplates. A good positioning of the C-Arm is mandatory to avoid unnecessary radiation as well as for safe OR time. TIPP：raise the radiolucent table in order to have one fixed position for AP and lateral view.

The entry point is determined individualy usinganterior and lateral fluroscopic guidance， taking into consideration：

A） The pathology

B） The anatomic structures.

Fig.1　Transforaminal endoscopic resection a：Posterolateral cyst before decompression； b：Fluoroscopic compression； c：Endoscopic cyst decompression； d：After posterolateral decompression

Fig.2　Interlaminar approach cyst resection a：Medial cyst before decompression； b：Interlaminar cyst resection by kerrison； c：Interlaminar identification of cyst； d：After interlaminar decompression

Fig.3　Specially designed tools a：Endoscopic system； b：Endoscopic high-speed burr； c：Use of endoscopic high-speed burr； d：Fluoroscopic control of high-speed burr

Local anesthesia at the determined entry point as well subsequent cannula / drill insertion path is applied before a small skin incision， using a scalpel.

CAUTION：advancing access or widening instruments towards the foramen， the potenial risk of nerve root irritation as well as injury has to be taken into account. Local anesthesia not at the nerve root and good communication with a responsive patient are important.

Under fluroscopic guidance and observation of the neural structures a （16” - 18”） spinal needle is introduced and positioned towards the individual target point.

A guide wire is inserted （toward the pathologic lesion） and after the spinal needle has been removed carefully， dilators are carefully introduced towards the foramen performing clockwise rotations. Now a special working sleeve is introduced over the dilator，lateralizing the outcoming nerve root and the dilator isremoved. Now under full endoscpic views as well as fluroscopic control a variety of burrs， kerrison， punches，hooks and bipolar probes in alternate turns are used to remove the bone of the facet and decompress the nerve root and dura in the spinal canal.

Interlaminar endoscopic decompression

In the recent years the endoscopic interlaminar access gained more and more interests， since the traumatization of conventional approaches is under discussion and transforaminal lateral approaches especially towards pathologies located at the spinal canal L5- S1， are very often limited or even impossible because of the iliac crest or narrow disc space. Also the learning curve for the new anatomy of the foraminal region is very often a limitation.

The interlaminar endoscopic approach is simplifying the learning curve by using experiences achieved in microsurgery. But due to the muscle splitting technique by a working canula collateral damages are significantly reduced. The working area is truly limited on the region of the interlaminar window，yellow ligament and epidural channel. Important for the resection of juxtafacet cysts is the proper bony decompression with partial removal of the inferior articular process for exact visualization of the cyst and precise separation from the neural structures. Sometimes， especially in the upper levels an extensive removal of the lamina and the lateral facet joint by the high-speed burr is unavoidable.

Interlaminar surgical procedure

Patient is placed in prone position on a radiolucent table. A pelvic role and cushions may be used for adequate positioning. Disinfections of the skin and sterile draping is applied.

Anatomic landmarks like Midline， Interlaminar Window， Disc Space and the Zygapophyseal Joints are marked as guidance points on the patients using X-ray. This subsequent procedure is performed under lateral fluroscopic guidance. All C-Arm images shall always show parallel endplates.

The entry point is determined individually using anterior and lateral fluroscopic guidance， taking into consideration：

A） The pathology

B） The anatomic structures

C） Far medial of the interlaminar window to allow insertion of the working canula in a lateral direction below the obliquely zygapophyseal joints.

Under lateral fluroscopic guidance a dilator is inserted without a guiding wire carefully towards the ligamentum flavum and the inferior lateral edge of the lamina. Over the Dilator a beveled working sleeve is inserted to the same target and the dilator is removed. The canula will be fixed by the bony margin of the upper lamina. With a high speed Rosen- or diamondburr a bony removal of Lamina and part of the facet joint is possible. The yellow ligament has to be opend with a blunt dissector and removed by endokerrisons. After identification of the cyst adhesion with dura and nerve root will be separated with the dissector. The beveled canula should be turned over the cyst protecting the neural structures by the bevel. Now the cyst can be removed with different graspers and punches. At the end the canula will be turned to visualize the neural structures and to control the decompression by a palpation hook.

Results

The patient’s postoperative outcomes were graded using VAS and Macnab citeria. Furthermore the morphological control of the removed cysts is included following endoscopic resection of their facet cysts. The average duration of the surgery was 53 minutes. There was no significant blood loss. Two patients achieved an excellent outcome； four reported a good result and one kept fair. The patients with good and fair outcome had relief of radicular pain and claudication after surgery very well， but in some cases low back pain was still bothersome.

Discussion

Kao proposed the term “juxta-facet cyst” （from latin， Juxta means closely adjacent to”） in 1974 to describe both synovial and ganglion cysts［27］. Sincethen variable terminologies have been introduced in the literature， such as synovial cysts［9，25，28-29］， ganglion cysts［30］， pseudocysts［31］， lumbar intraspinal facet cysts or fibrous cysts［4］， and cystic formations of the mobile spine［32］. To add confusion to both entity and nomenclature atypical cysts have been observed and reported as “ectopic” synovial tissue［33-34］.

In a symptomatic population of 852 patients undergoing positional MRI， Niggemann et al［35］. diagnosed 50 patients with intraspinal juxtafacet cysts （= 5.87%）. For their study they excluded patients with extraspinal and dorsal juxtafacet cysts， so the overall prevalence of juxtafacet cysts must be estimated higher.

The cysts develop within a very short period of time. Mostly found in the hand， elbow， hip and knee， they are rarely found in the lumbar spinal channel 0.01 ［ 102， S. 323 ］ and 3.6 % ［ 20， S. 410 ］. And even more rarely in the thoracic and cervical regions. The pathogenesis of discal cyste is still not clearly understood. Synovial and ganglion cysts， often described as pseudotumors， and often a degenerative spondylolisthesis and / or instability is observed alongside ［ 79， S. 484 ］. The cause of this pathology is discussed controversially：Hypermobility / Instabilty / Facet degenerertation.

1. The etiology of both intra spinal cysts is not clearly understood yet and several histopathological explainations or mechanical explanations are discussed diversely.

a） Osteoarthritic changes

b） Degenerative spondylolisthesis in the affected segment

c） Mechanical irritation of the facet joint due to hypermobility ［ 1， S. 518 ］

d） Chronic or direct trauma

2. Leaking synovial liquid followed by slime degernation of the particular connective tissue.

3. Myxoid degeneration and softening of collagen connective tissue of the joint capsule ［ 1， S. 518 ］

4. Metaplasia of pluripotent mesenchymal cells ［ 1，S. 518 ］

5. Embryonic synovial tissue in the periarticular fibrous connective tissue growing through constant stimulus

6. Proliferation of fibroblasts with increasing hyaluronic acid forming due to irritation

7. Benign neoplastic origin

In the cases of persitant low back pain and radiculopathy a synovial cysts can easily be misdiagnosed.

Very often a histological separation between synovial and ganglion cyst via MRI is not possible，also the clinical symptoms are the same. Sometimes ganglioncysts can be found even inside synovial cysts and a bleeding into the cysts makes a qualified histology of the content sometimes impossible ［ 84， S. 178 ］.

Since the clinical symptoms， localization and therapeutic options are similar； the exact definition does not seem so relevant. In 2002 Shima ［ 80， S. 18 ］，proposed to categorize both cysts as degenerative intraspinal cysts. Other authors named them periarticular cysst， joint cysts， synovial cysts or as mentioned juxta facet cysts. There is no uniform nomenclature.

Synovial cyst can be related to degenerated facet joints and histologically be separated from the ganglion cyst. The outer synovial cell layer is a soft synovial epithelium and in direct contact with the adjacent capsule. The origin is the synovia ［ 32， S. 1056 ］. The cyst is filled with a clear， serous or xanthochrome liquid， containing substantial mucopolysacchrids. Sehti et al［27，36］. described that the vast majority of patients presenting synovial cysts are likely to be asymptomatic［37］.

Typically ganglion cysts show a loose connective tissue coating and are filled with a more protein enriched viscous liquid as well. Ganglion cysts are from mucoid degeneration of periarticular connective tissue.

TREATMENT OPTIONS

Newly developed synovial cysts that do not compress nerve and / or adjacent structures usually react positively to conservative treatment. Epidural corticosteroid injections provided short-term relief［29］. If a cyst does not respond to alternative treatment like，temporary immobilization， rest， epidural injections，physiotherapy， steroid injections and / or selective blocks， medication， bracing a surgical removal either by micro fenestration， hemilaminectomy， CT guided punctures with steroids or endoscopic excision canachieve very satisfactory clinical results［4］. There is no common therapeutic treatment guidlines， even though these would be highly appreciated.

After micro-decompression surgery for lumbar spinal stenosis the incidence of intraspinal facet cysts peaks up to 8.6% after 3 to 12 months with a 70% chance of spontaneous regression after 6 - 36 months. Half of the reported cases were asymptomatic. The development of postoperative intraspinal facet cysts was found to be statistically significantly related to the presence of postoperative segmental and rotational instability including a progression of spondylolisthesis and disc degeneration［38］.

A full excision of the cyst needs to be performed either endoscopically or microscopically. The author chooses the transforaminal or interlaminar endoscopic treatment of the cysts because he wanted to avoid trauma and scar tissue to the dorsal structures. A reduced trauma of the paraspinal muscles by this technique allows us to expect a decreased risk of segmental instability avoiding a fusion. The endoscopic technique for cyst removal is a relativlely new option［39］. The long lasting experience of the author in endoscopic spine surgery helped to adapt this technique as a new standard for the decompression of these cysts.

A simple puncture or squeezing of the cysts should be avoided， since it does not treat the cause of the symptoms and results show a higher recurrence rate. The traversing nerve root should be clearly identified before the cyst is carefully separated from the dura mater and dissected either en bloc or by piecemeal using endoscopic graspers and other dissection devices. After the liquid or mucoid filling is fully discharged and no other material （neither neovascularization nor cellular infiltration， like in herniated discs） is found in the cyst［40］， the sight needs to be cleared under direct visualization. Then the original source should be sealed using bipolar RF.

Conclusion

Endoscopic surgery in the hand of skilled surgeons seems to be a good option for the treatment of facet cysts. It helps to avoid collateral damage and an increasing instability. The endoscopic visualization allows a proper preparation and resection of the pathological structures and a good decompression of the spinal channel. Before an open laminectomy with or without fusion the endoscopic technique should be considered.

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（本文編輯：王萌）

內(nèi)鏡下椎管內(nèi)小關(guān)節(jié)囊腫切除 S. Hellinger. Department of Orthopedic Surgery， Isar Hospital， Munich， 999035，GER

【摘要】目的 探討經(jīng)皮內(nèi)鏡囊腫切除術(shù)治療椎管內(nèi)小關(guān)節(jié)囊腫的臨床療效及手術(shù)技巧。方法 7 例采用經(jīng)皮內(nèi)鏡治療的椎管內(nèi)小關(guān)節(jié)囊腫患者納入本前瞻性研究。所有患者在術(shù)前均進(jìn)行了 6 周以上的非手術(shù)治療。根據(jù)囊腫形態(tài)不同，分別采用經(jīng)皮內(nèi)鏡椎間孔入路囊腫切除術(shù)和椎板間入路囊腫切除術(shù)治療。分析入組患者的住院表，每例均行 MRI 檢查，部分患者行術(shù)后影像學(xué)檢查。隨訪 1 年以上。結(jié)果 采用疼痛視覺(jué)模擬評(píng)分 （visual analogue scale，VAS） 和 MacNab 改良的療效評(píng)定標(biāo)準(zhǔn)對(duì)患者術(shù)后療效進(jìn)行評(píng)估。經(jīng)皮內(nèi)鏡切除小關(guān)節(jié)囊腫后進(jìn)行囊腫形態(tài)觀察。平均手術(shù)時(shí)間為 53 min。無(wú)明顯手術(shù)出血。依據(jù) MacNab 標(biāo)準(zhǔn)，2 例優(yōu)，4 例良，1 例可。在良和可的病例中，術(shù)后放射性疼痛和跛行癥狀緩解較好，而部分患者仍殘留腰痛。結(jié)論 對(duì)于熟練的外科醫(yī)生，經(jīng)皮內(nèi)鏡手術(shù)是治療椎管內(nèi)小關(guān)節(jié)囊腫的一種較好選擇。可以避免副損傷和術(shù)后不穩(wěn)定的增加。經(jīng)皮內(nèi)鏡可視系統(tǒng)為病理結(jié)構(gòu)的切除和良好的椎管減壓提供了條件。在行伴或不伴融合的椎板切除術(shù)之前應(yīng)該首先考慮經(jīng)皮內(nèi)鏡技術(shù)。

【關(guān)鍵詞】脊柱；外科手術(shù)，微創(chuàng)性；椎管；骨囊腫

DOI：10.3969/j.issn.2095-252X.2016.05.002中圖分類號(hào)：R687.4， R616.5

收稿日期：（2016-02-06）