KEY NOTES CHAPTER 7: THE TRUNK AND UROGENITAL SYSTEM - Perineal Reconstruction. Flashcards
What forms the pelvic diaphragm?
• Formed by the two levator ani muscles and two coccygeus muscles.
• Levator ani is composed of: ∘ Puborectalis ∘ Pubococcygeus ∘ Iliococcygeus ∘ Levator prostatae or levator vaginae.
- These muscles form a hammock between pubis, coccyx and lateral pelvic walls.
- Puborectalis muscles unite posterior to the anorectal junction to form a muscular sling, creating the angle between rectum and anal canal.
Outline the perineal anatomy
Perineum = region of the trunk inferior to the pelvic diaphragm.
Boundaries
∘ Pubic symphysis and inferior pubic rami
∘ Ischial rami and ischial tuberosities
∘ Sacrotuberous ligaments and coccyx.
How is the perineum subdivided?
Anterior and posterior triangles divided by Transverse line between ischial tuberosities, with perineal body at midpoint.
1 Urogenital triangle: contains female external genitalia, or male root of scrotum and penis.
- pierced by urethra (and vagina).
From deep to superficial:
- deep transverse perineal muscles,
- perineal membrane,
- superificial perineal pouch (contains bulbospongiosus, ischiocavernosus, superficial transverse perineal muscles).
2 Anal triangle:
- anus
- external anal sphincter
- levator ani
- ischioanal fossae: contains internal pudendal vessels and pudendal nerve (perineal sensation).
What is the main blood supply of the perineum?
1 Femoral artery -> superficial and deep external pudendal arteries.
2 Internal iliac artery -> internal pudendal and inferior gluteal arteries.
What common pathologies result in perineal defects?
∘ Resection of gynaecological, colorectal and urological malignancy.
∘ Debridement of sepsis, particularly Fournier’s gangrene.
∘ Inflammatory bowel disease, e.g. Crohn’s disease and ulcerative colitis.
∘ Trauma, e.g. open pelvic fractures.
How are gynaecological invasive malignancy managed?
Within a gynaecological MDT
• Most cases are SCCs; vulval melanomas and vaginal adenocarcinomas are rarer.
Vulva
• SCC usually treated by excision with 1cm margins + adjacent areas of VIN.
+/- Defunctioning colostomy (larger areas).
+/- Elective inguinal lymph node dissection.
Vagina
• Primary SCC often treated with chemoradiotherapy.
• Pelvic exenteration surgery indicated for:
- high posterior tumours.
- advanced stage and recurrent tumours
pelvic exenteration, leaving significant dead space.
How is anorectal invasive malignancy managed?
Planning within colorectal MDT.
• 2011 Anal Cancer Position Statement by the Association of Coloproctology of Great
Britain and Ireland “plastic surgical input should form part of the anal cancer
MDT when reconstruction is considered”.
Delayed healing rate of perineal wounds is:
- 40-70% with direct closure.
- 15-25% with flap reconstruction.
Anal
• Primary anal SCC = chemoradiotherapy.
• Abdomino-perineal resection (APR) of distal rectum and anal skin for salvage if tumour is unresponsive or recurrent.
Rectum • Low rectal tumours (mostly adenocarcinomas) usually require - APR + permanent end-colostomy +/- ∘ Posterior vaginal wall ∘ Bladder ∘ Prostate and seminal vesicles.
- Multivisceral involvement = posterior / total pelvic exenteration +/- coccyx or sacrum excision.
- Advanced tumours = neo-adjuvant chemoradiotherapy.
How is a perineal defect assessed?
Volume deficit
Radiotherapy
Diversion
Function
How does the volume of the defect affect the type of reconstruction?
- thin defect -> skin graft or thin local flaps.
- large dead space (risk of perineal hernia) -> bulky flap required
What problems does irradiation pose?
∘ Preclude the use of local tissues for reconstruction.
∘ Increase incidence of wound-healing problems.
∘ Increase risk of fistulation.
How does external beam radiation affect wound healing?
Causes:
- small vessel thrombosis,
- fibroblast dysfunction,
- altered cytokine milieu contributing to neutrophil dysfunction.
What should be discussed in the MDT regarding diversion and function?
- Stoma positioning on abdominal wall should be discussed before RA recon.
- Can sexual function, faecal and urinary continence be restored?
When is perineal reconstruction indicated?
1 Extensive skin loss 2 Vaginal resection 3 Pelvic or perineal dead space 4 Excision of the pelvic floor 5 Excision after radiotherapy.
What are the principles of reconstruction?
Import suitable, vascularised, non-irradiated tissue to:
∘ Manage dead space.
∘ Provide a substitute for the pelvic floor.
∘ Reconstruct the vagina.
What are the commonly used pedicled flaps in perineal reconstruction?
Fasciocutaneous
- Lotus petal
- Superior gluteal artery perforator (SGAP)
- Inferior gluteal artery perforator (IGAP)
- Posterior thigh
- ALT
- Pudendal-thigh (‘Singapore’ flap)
Myocutaneous
- Vertical rectus abdominis myocutaneous (VRAM)
- Inferior gluteal artery myocutaneous (IGAM)
- Gracilis
Omentum
Colon
Describe the lotus petal flap.
- The possible skin paddle options fan out like lotus flower. Flap that lies in buttock crease is most commonly used.
- Based on internal pudendal artery perforators as it traverses the ischioanal fossa near the midline of the perineum (identification of pedicle during dissection unnecessary).
- Flap can be transposed or advanced (V-Y).
Describe the SGAP flap.
- Superior gluteal artery (branch of internal iliac) emerges from pelvis superior to piriformis, deep to gluteus maximus.
- Surface marking = 1∕3 along line from posterior superior iliac spine (PSIS) to apex of greater trochanter.
- Sometimes difficult to reach all perineal defects.
Describe the IGAP flap.
- Inferior gluteal artery (branch of internal iliac) emerges inferior to piriformis, deep to gluteus maximus.
- Surface marking = 1∕2 along line joining PSIS and ischial tuberosity.
- Travels inferolaterally between greater trochanter and ischial tuberosity.
- While deep to gluteus it gives many myocutaneous perforators to inferior buttock skin.
- Also gives a descending branch - the basis of the posterior thigh flap.
Describe the posterior thigh flap.
• Descending branch of IGA.
• Can be large transposition flap or
• Large V-Y advancement flap
based on IGA and profunda femoris perforators.
- Profunda perforators are on a line joining ischial tuberosity to lateral femoral condyle.
• Flap is sensate (posterior cutaneous nerve of thigh).
Describe the ALT flap.
• Based on descending branch of lateral circumflex femoral artery.
• Tunnelled medially, deep to sartorius and rectus femoris into perineum.
∘ Femoral nerve branches to rectus femoris should be preserved.
• Vastus lateralis can be included for additional bulk.
Describe the pudendal-thigh (Singapore or Wee flap).
- FC flap based on posterior labial branch of internal pudendal artery.
- Sensation: posterior labial branch of pudendal nerve.
- Designed on non-hair-bearing skin in the groin crease, lateral to labia majora.
- The flap’s base is posterior (posterior fourchette level).
• For vaginal reconstruction, bilateral flaps are raised and tunnelled to the midline.
∘ Sutured together outside body to form an ‘inside-out’ tube which is pushed in to invert it and form neo-vagina.
Describe the VRAM flap.
- Based on DIEA.
- Flap size and reach can be augmented by extending skin flap obliquely to costal margin.
- Trans-pelvic inset: rotate 180 on its long axis and fold posteriorly over the pelvic brim.
- Fascial-sparing harvest allows primary closure of abdominal wall.
- Recent extraperitoneal tunneling of flap (Nigriny) described (in cases where peritoneal cavity not breached for cancer ablation).
Describe the IGAM flap.
• Similar to IGAP, but includes a strip of gluteus maximus (
Describe the gracilis flap.
• Raised with or without skin
• Based on medial circumflex femoral artery.
• Skin paddle is unreliable over the distal muscle.
• Vagina can be reconstructed using bilateral gracilis myocutaneous flaps:
∘ Skin paddles are sutured together to fabricate a tube.
∘ Pedicle location limits flap rotation and depth of the neo-vaginal vault.
Describe the use of omentum to obliterate dead space.
- Omentum (not the omentum flap) can be pulled inferiorly to fill pelvic dead space.
- Not usually robust enough to prevent hernia.
- May have been excised previously.
How is colon used to reconstruct the vagina?
- 12-14 cm segment of rectosigmoid can be transposed to the perineum, based on superior haemorrhoidal artery.
- Bowel lumen is sutured closed at one end to form a blind-ending tube.
- Prone to over-secretion of mucus.
What is your reconstructive strategy for the perineum?
Small defects:
- no radiotherapy: direct closure.
- radiotherapy: skin graft / local flap e.g. rhomboid.
Superficial defects (e.g. vulvectomy) - FC flaps e.g. lotus flap.
Complex small defects (e.g. sinuses, fistulas)
- gracilis.
Complex large defects (e.g. APR, pelvic exenteration)
- no radiotherapy: local FC / MC flaps.
- radiotherapy: VRAM / ALT.
Vaginal reconstuction
- Partial: VRAM / gluteal flap.
- Total: tubed VRAM / Singapore / (colon).
CME Perineal Reconstruction
CME
How are flaps for perineal reconstruction categorised?
- Abdominally based reconstruction
- Groin flaps
- Thigh flaps
What types of abdominally based flaps are commonly used?
- VRAM
- muscle-sparing VRAM
- DIEP
How is a rectus abdominis myocutaneous flap raised for vaginal reconstruction?
- Lithotomy position, catheterised.
- Plastics to mark paramedian incision and right VRAM flap (with or without oblique extension at costal margin). Type III muscle flap.
- Rectus is divided superiorly and dissection continued inferiorly to DIE pedicle.
- Flap is mobilised and rotated into pelvis (note direction of rotation in case de-rotation is necessary).
- Skin paddle is inset into perineal or pelvic component of defect, or folded for vaginal reconstruction.
What types of groin flaps are commonly used?
- Wee flap: internal pudendal perforators.
- Lotus flap (Sawada): superficial perineal artery perforators (branch of internal pudendal).
- gluteal fold flap (Hashimoto): internal pudendal artery perforators.
- propeller flaps (Sinna): internal pudendal artery perforator-based.
How are bilateral groin flaps marked?
Bilateral groin fasciocutaneous flap reconstruction of vulvectomy composite soft-tissue defect.
How are bilateral propeller flaps based on the interanl pudendal artery perforators marked?
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What types of thigh flaps are commonly used?
- Thigh flaps generally favoured when abdominal access by ablative team not required.
- Gracilis flap: (type II muscle / myocutaneous) primary
blood supply from ascending branch of medial circumflex femoral artery, arising from profunda femoris. Secondary segmental branches of superficial femoral artery distally. Distal skin paddle may be unreliable. - Posterior thigh flap: descending branch of inferior gluteal artery (later propeller designs (Sinna) based on perforators of IGA).
- Medial thigh perforator flap
- Pedicled anterolateral
thigh flap (Wang): descending
branch of the lateral circumflex femoral artery perforators.
How are bilateral gracilis flaps marked and raised for reconstruction of the perineum?
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Show another example of bilateral gracilis myocutaneous flaps following vulvectomy.
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