Method for approximation and stabilization of pubic bones in bladder exstrophy

Abstract

FIELD: pediatric reconstructive urology.SUBSTANCE: intended for surgical approximation and stabilization of the pubic bones of the anterior pelvic semiring in patients with exstrophy-epispadias complex during primary closure of the bladder and anterior abdominal wall. A lower midline skin incision is made, continuing around the vesical plate, distal to the seminal tubercle. Then the subcutaneous tissue, the aponeuroses of the rectus abdominis muscle sheaths and the muscles themselves are dissected. They are pulled apart, revealing a retro-pubic space. The cystic plate is mobilized by separating it from the anterior abdominal wall and the sheaths of the rectus abdominis muscles. Between the cystic plate and the pubic bones, the fibromuscular trapezoid interpubic ligament (IPL) is identified and its targeted microdissection is performed under magnification of x3.5–6.5. In this case, the IPL is first separated from the sheaths of the rectus abdominis muscles and aponeurotic fibers, then from the detrusor in the supratriangular region, maintaining attachment to the pubic bones. During the dissection, the pubovesical and pubourethral ligaments adjacent to the IPL are cut off; after releasing the vesical plate, it is inverted into the pelvis and a urinary reservoir with a funnel-shaped neck oriented toward the urethra is formed. An N 8Ch catheter is inserted. Approximation of the bones is performed using IPL, for which, after mobilization of the medial parts of the pubic bones and installation of a bone holder, two opposite U-shaped N2 Vicryl sutures are applied through the lateral parts of the IPL, which are fixed to the periosteum of the pubic bones. The sutures are tightened, bringing the pubic bones closer together and stabilizing them. Then the paravesical tissue from the space of Retzius is mobilized and fixed to the neck of the bladder, the anterior abdominal wall is sutured layer by layer.EFFECT: method ensures controlled convergence and stabilization of the pubic bones, creating conditions for hermetic closure of the bladder and physiological growth of pelvic structures.1 cl, 5 dwg, 1 ex

Description

[0001] The invention relates to the field of medicine, namely to pediatric reconstructive urology, and is intended for surgical approximation and stabilization of the pubic bones of the anterior pelvic semiring in patients with an exstrophy-epispadias complex when performing primary closure of the bladder and anterior abdominal wall.

[0002] Bladder exstrophy is a rare congenital anomaly characterized by bladder eventration, interpubic diastasis, and malformation of the lower abdominal wall and pelvic organs [1, 6]. For primary closure, pubic bone approximation is used in most centers, as it is believed to reduce the risk of complications and facilitate hermetic closure; in current practice, it is achieved primarily by osteotomies combined with external and / or internal fixation. These methods are associated with high morbidity, the need for prolonged immobilization, and the likelihood of repeated increase in the interpubic distance as the pelvis grows [2-4].

[0003] For a long time, the prevailing idea was the absence of pronounced interpubic ligamentous structures in exstrophy [7, 8], as a result of which existing approaches did not include the use of native ligaments for approximation and were limited to osteotomies, external / internal fixation and implants. At the same time, modern anatomical and histological data indicate that the trapezoid interpubic ligament (TIL) corresponds in structure and topography to the complex of the anterior and posterior pubic ligaments and is likely a rudimentary element of the normal pelvic ligamentous apparatus [5, 9, 10], which justifies its use as a natural fibromuscular "anchor" for controlled approximation and stabilization of the pubic bones.

[0004] A known surgical treatment method involves approximation of the pubic bones in bladder exstrophy using bioabsorbable plates and screws. This method is based on the principle of internal symphysis stabilization without the use of traditional pelvic osteotomy. After simultaneous bladder closure and urethral reconstruction, the anterior pelvis is accessed through an infraumbilical incision, dissecting the retropubic space. The pubic bones are exposed and mobilized until the anteromedial sections are visualized. For initial approximation of the pubic bones, three strong, deep polyglactin sutures are placed through the bony tissue of the pubic rami. Mechanical approximation of the bones is then performed using a special instrument with a rib adapter. When the interpubic distance is reduced to less than 20 mm, the sutures are tightened.A bioabsorbable plate made of L- and D-lactide copolymers with trimethylene carbonate is then formed and installed. The plate is secured with 2.5 mm diameter, 7-12 mm long screws through drilled holes in the bone. This provides additional stabilization of the pubic symphysis without the need for metal components or subsequent surgical removal of the implant

[11] . Following fixation, the abdominal wall is closed in stages, excess skin is resected, and the umbilicus is formed. All patients are immobilized with soft bandages on their lower extremities for two weeks after surgery; external immobilization or traction are not used.

[0005] The disadvantages of this method include the fact that plate placement is not a standalone method for pubic bone reduction, as it requires preliminary mechanical approximation of the bones using bone sutures and instrumental traction. Therefore, the plate serves only as an auxiliary measure to maintain the already achieved position, rather than as the primary element of diastasis correction. Furthermore, in the studied series of patients, the method was used in children over one year of age, often after unsuccessful attempts at bladder closure and previous osteotomies. This precludes evaluating the effectiveness of this approach in primary cases and, especially, in newborns with soft, pre-ossified pelvic bones.

[0006] The long-term effectiveness of fixation after complete implant degradation also remains questionable, as diastasis recurrence is possible as the pelvis grows. Specifically, in one case series, a recurrence of the distance between the pubic bones was observed 6 months after surgery. This calls into question the system's ability to provide stable fixation in the context of ongoing skeletal growth. Furthermore, although the incidence of infectious complications was low, the risk of infection at the site of foreign material placement cannot be ruled out, especially in the context of repeated surgeries and scarring. Another limitation is that the bioabsorbable plate lacks osseointegrative properties and does not promote bone remodeling, unlike native ligamentous or cartilaginous structures. It is also unclear to what extent this type of fixation influences physiological growth and pelvic formation, especially over the long term.As the plate gradually deteriorates, the question arises of maintaining the achieved anatomical result without re-fixation.

[0007] A known surgical treatment method involves approximation of the pubic bones in children with exstrophy using external fixation without osteotomy. This procedure involves performing primary plastic surgery in newborns within the first day of life using a two-pin external fixator attached to the iliac bones. After induction of anesthesia and a standard infraumbilical approach, the bladder and abdominal wall are mobilized. Before bladder closure, metal pins are inserted percutaneously into the anterior iliac bones on both sides under radiographic control. The pins are oriented through the iliac wing toward the superior sciatic notch, taking into account the external rotation of the pelvis characteristic of exstrophy. An external stabilizing arch is secured through the inserted pins, ensuring approximation of the pubic bones without osteotomy.The system makes it possible to perform pelvic compression during closure of the abdominal wall and bladder without excessive tissue tension

[12] .

[0008] After bladder and abdominal wall closure, the fixator remains in place for six weeks and is removed on an outpatient basis. The advantage of this method is the lack of need for lower extremity immobilization, which reduces discomfort and facilitates child care. This approach demonstrates technical feasibility with interpubic diastasis of up to 4-5 cm, ensures stable pubic bone positioning in the postoperative period, reduces the risk of suture rupture and bladder prolapse, and promotes long-term increases in functional bladder capacity.

[0009] The disadvantages of this method include its limitations in cases of severe interpubic diastasis: when the distance between the pubic bones is more than 4-5 cm, pelvic approximation using external fixation alone may be difficult or insufficient to fully close the abdominal wall without tension, increasing the risk of suture failure and repeated interventions. The method technically depends on the correct placement of pins and precise compression control, which requires the participation of an experienced pediatric orthopedist. Incorrect placement can lead to device instability, as was observed in the case of a premature patient who experienced pin displacement, early deformity, and subsequent suture divergence, leading to a repeat osteotomy. This underscores the method's high sensitivity to technical errors, especially in newborns with low bone mineral density.

[0010] Furthermore, the external fixator remains in place for six weeks. While this avoids cast immobilization, it still requires additional care, carries potential risks of infection at the pin exit site, and can cause patient discomfort. Lack of complete pelvic immobilization can also lead to micromovements in the fixation area, especially with inadequate compression, increasing the risk of reconstruction failure.

[0011] The long-term effectiveness of this method in preventing recurrence of diastasis as the patient grows has not been confirmed, and there are no data on adult patients who underwent this type of procedure in infancy. Furthermore, this method does not correct the fundamental anatomical rotational abnormalities and pelvic underdevelopment characteristic of exstrophy, unlike osteotomy, which allows for correction of not only the width but also the orientation of the pelvic bones.

[0012] Thus, although the osteotomy-free external fixation method is a low-trauma alternative in neonates with moderate diastasis, its effectiveness is limited in severe forms of exstrophy, requires technical precision and multidisciplinary involvement, and does not exclude the possibility of diastasis recurrence or the need for subsequent intervention.

[0013] The closest approach to the claimed method is the STARS method, which involves reconstructing the symphysis in exstrophy using a tendon allograft inserted subperiosteally through the obturator foramina and wrapped around the pubic bones after their approximation using modified iliac osteotomies. The graft is fixed with sutures and reinforced with chondroperiosteal flaps. This method ensures stable approximation of the pubic bones and promotes bone formation in the symphysis area

[13] .

[0014] The disadvantages of the STARS method include technical complexity and the need for combined orthopedic and urological teams, the risk of pubic bone fracture during subperiosteal dissection, the potential for increased diastasis in the long-term follow-up in some patients, and limited data on the long-term fixation strength and biointegration of the allograft. Furthermore, the method requires the use of an external fixator and a hospital stay until its removal.

[0015] The problem that the claimed invention is aimed at solving is the development of a low-traumatic and physiological method for stabilizing the pelvic ring in patients with bladder exstrophy.

[0016] The technical result of achieving the set goal is the convergence of the pubic bones without performing osteotomies, which reduces surgical trauma, improves the anatomical conditions for bladder reconstruction and minimizes the risk of postoperative complications.

[0017] The essence of the pubic bone approximation method is to use TMS as a natural fibromuscular anchor to bring together and stabilize the pubic bones during their approximation.

[0018] The method involves identification and targeted mobilization of the trapezoid interpubic ligament with its separation from the detrusor muscle while fully preserving the attachment points to the pubic bones. Sutures are placed through the lateral sections of the trapezoid interpubic ligament with fixation to the periosteum of the pubic bones, which ensures their approximation and subsequent stabilization. In cases of severe interpubic diastasis, the intervention, if necessary, is supplemented by iliac osteotomies; in cases of moderate diastasis, osteotomies are not required [5].

[0019] The novelty of the proposed method is that the surgery begins with a lower midline skin incision extending around the cystic plate distal to the seminal tubercle. Subsequently, the subcutaneous tissue, aponeuroses of the rectus sheaths, and the muscles themselves are sequentially dissected, which are then separated to expose the retropubic space. The cystic plate is then mobilized and separated from the anterior abdominal wall and rectus sheaths. A dense, trapezoidal fibromuscular structure (TMS) is identified in the retropubic space between the cystic plate and the pubic bones, and targeted microdissection is performed under magnification (×3.5-6.5). First, the TMS is separated from the rectus sheaths and aponeurotic fibers, then from the detrusor in the supratriangular region, while its attachment to the pubic bones is preserved (Fig. 1).During dissection, the pubovesical and puborethral ligaments adjacent to the TMS are also dissected, which ensures a deeper descent of the vesical and urethral plates into the lesser pelvis (Fig. 2). After complete release of the vesical plate, it is inverted into the pelvis and a urinary reservoir with a funnel-shaped neck oriented towards the urethra is formed, followed by the insertion of an #8Ch catheter. The formed urinary reservoir with a funnel-shaped neck is shown in (Fig. 3). In cases of severe diastasis of the pubic bones (more than 4 cm) or persistent pelvic instability, bone approximation is performed using TMS: after mobilization of the medial parts of the pubic bones and installation of a bone holder, U-shaped #2 Vicryl sutures are applied through the lateral sections of the TMS, which fix it to the periosteum, bringing together and stabilizing the pubic bones. (Fig. 4) After this, the paravesical tissue from the space of Retzius is fixed to the neck of the urinary bladder, and the anterior abdominal wall is sutured layer by layer.Postoperatively, all patients are prescribed antibiotic therapy and anticholinergic drugs (oxybutynin); fixation is not used. Patients are discharged after their condition has stabilized. Thus, the TMS is used as an anatomically strong fibromuscular bridge for approximation and stabilization of the pubic bones during reconstructive surgery for bladder exstrophy. A schematic anatomy of the TMS location, where RAM is the rectus abdominis muscle, PVL is the pubovesical ligament, and PUL is the pubourethral ligament, is shown in (Fig. 5). Pelvic ring stabilization is critical for preventing suture failure, as excessive interpubic diastasis disrupts pelvic biomechanics and increases the risk of complications.

[0020] Clinical example of the method implementation

[0021] Example 1. The patient, a 6-month-old boy, was diagnosed with classic bladder exstrophy. He was under observation since birth due to the small size of the bladder plate (2.2 cm wide), polypoid changes, dense consistency, and the inability to invert it during examination under anesthesia. For a year, no growth of the bladder plate was observed. He was admitted to the center for primary closure. After standard preoperative preparation, the surgery was performed. Surgical access was achieved through a lower midline incision along the edge of the bladder plate. The skin, subcutaneous tissue, and aponeurosis were dissected layer by layer. The rectus abdominis muscles were spread apart, which allowed visualization of the bladder plate and retropubic space. During initial mobilization of the bladder plate, its inelasticity and the inability to invert were noted. In the retropubic space under magnification (magnifying glasses ×4.5) A dense, trapezoidal fibromuscular structure was visualized, extending from the supratriangular region of the detrusor upward and laterally to the rectus sheaths (RMS). Using microinstruments and a monopolar microelectrode, the RMS was dissected stepwise: first from the aponeurosis and sheaths of the rectus abdominis muscles, then from the detrusor. Hemostasis was achieved by bipolar coagulation of small vessels. With its attachment to the pubic bone periosteum preserved, the RMS remained anatomically intact. After complete mobilization of the RMS, the pubovesical and pubourethral ligaments were transected at their insertion into the RMS, allowing the vesical plate and urethral segment to penetrate deeper into the pelvis. This was accompanied by an immediate improvement in the elasticity of the vesical plate and its inversion without excessive tension. The bladder was reconfigured to form a funnel-shaped neck, and a No. 8Ch urethral catheter was installed.Given the 4.5 cm interpubic diastasis and persistent pelvic instability, a decision was made to approximate the pubic bones using transluminal ligament (TML). After exposing the pubic bone periosteum, the TML was used as an anatomical anchor: two opposing #2 Vicryl U-shaped sutures were placed through its lateral portions and fixed to the periosteum. After tightening the sutures, the diastasis decreased to 1.5 cm, establishing a stable position. Paravesical tissue from the space of Retzius was mobilized and fixed to the bladder neck with sutures, and layered closure of the anterior abdominal wall was performed. The postoperative period was uneventful. Antibacterial therapy and oxybutynin at a dosage of 0.4 mg / kg / day were prescribed. The boy was actively moving from the first day; no fixation was used. He was discharged on the 10th day. After 6 months, a stable increase in bladder capacity (from 12 ml to 32 ml) was noted, along with the absence of prolapse and the formation of a normal cervical position. The interpubic diastasis did not increase.A staged urethroplasty is planned. Therefore, in this case, the use of TMS allowed for successful one-stage closure of a small, non-growing vesical plate with effective pubic bone approximation without osteotomies, minimal trauma, and a good functional outcome.

[0022] The use of the claimed method, in which the trapezoid interpubic ligament is used as a natural fibromuscular anchor, ensures controlled convergence and stabilization of the pubic bones, creates conditions for the hermetic closure of the bladder and the physiological growth of pelvic structures.

[0023] The use of the proposed method makes it possible to avoid iliac osteotomies in cases of moderate interpubic diastasis and to reduce their volume in cases of severe interpubic diastasis, reduces the risk of surgical trauma, and eliminates the need for external immobilization.

[0024] Bibliography

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[0032] 8. Shattock, S.G. (1894). Specimens of epispadias and extroversio vesicae showing an attachment of the muscular wall of the bladder to the back of the pubic bones, etc. Tr. Path. Soc. London, 45(April), 117-124.

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[0034] 10. Xu, Z., Chapuis, P.H., Bokey, L., & Zhang, M. (2017). Nature and architecture of the puboprostatic ligament: a macro-and microscopic cadaveric study using epoxy sheet plastination. Urology, 110, 263-e1.

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Claims

A method for approximating and stabilizing the pubic bones in cases of bladder exstrophy and pubic bone diastasis greater than 4 cm, characterized in that a lower midline skin incision is made, continuing around the bladder plate, distal to the seminal tubercle, then the subcutaneous tissue, aponeuroses of the sheaths of the rectus abdominis muscles and the muscles themselves are dissected, they are moved apart, exposing the retropubic space, the bladder plate is mobilized with its separation from the anterior abdominal wall and the sheaths of the rectus abdominis muscles, the fibromuscular trapezoid interpubic ligament (IPL) is identified between the bladder plate and the pubic bones and its targeted microdissection is performed under a magnification of ×3.5-6.5, whereby the TMS is first separated from the sheaths of the rectus abdominis muscles and aponeurotic fibers, then from the detrusor in the supratriangular region, maintaining attachment to the pubic bones; During the dissection, the pubovesical and pubourethral ligaments adjacent to the TMS are cut off, after releasing the bladder plate, it is inverted into the pelvis and a urinary reservoir with a funnel-shaped neck oriented toward the urethra is formed, an N8Ch catheter is inserted, bone approximation is performed using the TMS, for which, after mobilizing the medial parts of the pubic bones and installing a bone holder, two opposite U-shaped N2 Vicryl sutures are applied through the lateral parts of the TMS, which are fixed to the periosteum of the pubic bones, the sutures are tightened, bringing together and stabilizing the pubic bones, then the paravesical tissue from the space of Retzius is mobilized and fixed to the neck of the bladder, the anterior abdominal wall is sutured layer by layer.

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