Decompression, also known as marsupialization, was first reported by Dr. Wine, WM in the United States and has a history of more than 30 years since then.
The cyst decompression is performed by opening a window on the surface of the cystic lesion, locally opening the bone and cyst wall, draining the cystic fluid, and making a plug to keep the drainage port open, so that the pressure inside and outside the cystic cavity can be balanced, and the cystic cavity can be gradually reduced and its shape can be restored under the functional activity of the jaws. Usually, the decompression time after open window surgery is 6 to 18 months, and those whose cysts disappear after decompression do not need stage II surgery, while those whose cysts do not disappear completely can have stage II surgery to scrape out the reduced cysts. The purpose of open window decompression surgery is not to eradicate the cyst directly, but to reduce the cystic cavity, restore the shape of the jaw bone, and protect the morphology and function of the jaw bone to the greatest extent.
1.Surgical indications
Decompression surgery is clinically applicable to all kinds of mandibular odontogenic cystic lesions, especially for huge cystic lesions with remarkable efficacy.
(1) Mandibular odontogenic keratotic cysts, including multiple keratotic cysts of the jaws (basal cell nevus syndrome).
(2) Monocystic (wall-type) enameloblastoma of the mandible.
(3) Juvenile mandibular cysts.
(4) Some large maxillary odontogenic cysts.
2. Preoperative preparation
(1) Imaging examination: mandibular panoramic film, frontal and lateral cranial X-ray, cranial CT examination.
(2) Clinical examination: cystic lesions with or without cystic fluid can be punctured to clarify the diagnosis when the diagnosis is unclear.
(3) Routine local or general anesthesia laboratory tests to exclude contraindications to surgery.
(4) 6h fasting before general anesthesia surgery, half an hour intramuscular injection of phenobarbital and atropine before surgery.
3.Anesthesia and body position
(1) Anesthesia: general anesthesia is recommended, especially for adolescent and elderly patients with good safety; local anesthesia can be performed for some patients as appropriate.
(2) Position: supine position for general anesthesia and supine or sitting position for local anesthesia.
4.Surgical steps
(1) Opening window design: an intraoral incision is used, usually chosen in the bony weak zone of the oral mucosal cyst wall or the central zone of the cyst, which facilitates the centripetal reduction of the cystic cavity. For teeth with no retention value within the scope of the lesion, such as obstructed teeth and severe caries, the bone around the extraction sockets can be trimmed as the opening window; while other patients who need to retain dental function are selected in the location of the free gingiva near the vestibular groove; for cysts occurring in the mandibular ascending branch, the opening window can be designed in the area of the posterior pad of the molar; if the cysts involve bilateral mandibles to a large extent, two opening windows can be prepared.
(2) Scope of excision: cut through the mucoperiosteum, reveal the lesion area, excise 1.0cm×2.0cm of the cyst surface bone cortex and attached cyst wall, drain the cyst fluid, rinse the cyst cavity, and send the cyst wall tissue for pathological examination during the operation.
(3) Open window treatment: open window residual cyst wall and mucosa suture packing, first single-strand packing thread as the backing, covered with iodine-imitated petroleum jelly gauze package to fill the open window, and finally finish packing with the remaining single-strand thread.
5.Intraoperative and postoperative precautions
(1) When removing the bone wall and capsule wall of the open window, pay attention to protect the integrity of the rest of the capsule wall to avoid excessive exposure of the bone wall to affect bone regeneration.
(2) The size and morphology of the cystic cavity should be explored after opening the window intraoperatively to check whether there is any separation, and if there is an obvious interatrial septum it should be removed to form a complete cystic cavity.
(3) One week after surgery, the bag should be unpacked, and a plugging device should be made and worn at the same time to avoid the closure of the opening window and to keep the drainage port open. The design of the plugging device should take into account the issues of fixation, occlusion and comfort.
(4) Postoperatively, the cystic cavity should be flushed several times a day to keep the cystic cavity clean and avoid infection.
(5) Regular postoperative follow-up every 1 to 3 months, clinical examination of cyst wall shrinkage and healing, gradual adjustment of the plug shape, as well as panoramic film and CT examination to measure the change of lesion length and diameter. If the cyst recedes to the open window, the plugging device is removed and clinical observation is performed; if the cyst cavity does not disappear completely, second-stage cyst scraping is performed.
(6) For patients who cannot review on time or have poor medical compliance, the choice of open window decompression should be cautious.
6.Return of tissue defect repair
(1) The change of jaw bone morphology after open window decompression is a slow process, and the cyst cavity shrinks while the shape line gradually changes from irregular to regular and oval, and the location which is difficult to reach or difficult to scrape the cyst wall completely during surgery such as mandibular ascending branch and tooth root retreats to the area of open window drainage opening, thus the phase II surgery can scrape the cyst wall completely. This explains in one way the relatively low recurrence rate of decompression surgery.
(2) We found that the originally pushed inferior alveolar nerve canal gradually returned to its normal position after the opening, and it seems that these structures have a memory, an interesting phenomenon that may need to be explained by studying the electrophysiology of the bone. Likewise, another unexplained phenomenon is the ability of the pushed teeth to automatically rotate and return to their normal position, forming a good occlusal relationship with the opposing teeth, a treatment effect that is difficult to achieve with any manual intervention. It was also found that for rapidly growing cases, new bone formation began 3 months after the opening and the lesion shrank rapidly; the lesion shrank relatively quickly in adolescent patients with a short opening period, while the opening period was relatively long in the elderly.
7. Diagnosis and management of intraoperative and postoperative complications
(1) The choice of intraoperative opening window is very important and is the key to determine the success of decompression surgery. The preservation of healthy functional teeth is significant.
(2) The production of the postoperative plugging device and the repeated removal and rinsing within 1 week after fitting are particularly important to avoid the normal use of the plugging device due to the retraction and growth of the tissue around the opening window.
(3) Daily irrigation and regular plugging during postoperative follow-up are beneficial to the normal growth of cysts toward the open window, and failure to cooperate well often affects the healing of cysts; abandonment of the plugging device often causes closure of the open window leading to recurrence of cysts.
(4) Patients who have their stoppers removed and undergo second-stage scraping should not be operated for more than 3 months to avoid cyst regrowth.
8.Experience and commentary
(1) Although giant keratotic cysts and unicystic enameloblastoma of the jaws are benign tumors, the recurrence rate of conventional conservative treatment is high and the loss of functional shape of radical surgery is large, so it is quite tricky to choose the treatment plan. Decompression surgery has shown its unique superiority in treating these diseases by controlling postoperative recurrence while preserving the jawbone, and it is easy to operate, less invasive, less risky, and economical, and thus has a broad application prospect. Reviewing the literature, most scholars believe that decompression can reduce the postoperative recurrence rate on the basis of preserving the functional morphology of the jaws, and therefore can be the preferred method for the conservative treatment of giant cystic lesions of the jaws.
(2) As early as the 1960s and 1970s, decompression surgery was applied to treat jaw cysts, and although good results were obtained clinically, this treatment method did not become mainstream. Nowadays, the concept of functional surgery is widely accepted, and it is necessary to introduce the value of decompression in jaw surgery and to evaluate it objectively through clinical and experimental studies.