Comprehensive guide to the modified Stoppa approach for quadrilateral surface and medial acetabular wall fractures - surgical anatomy, technique, and exam preparation
Reviewed by OrthoVellum Editorial Team
Orthopaedic clinicians and medical editors • Published by OrthoVellum Medical Education Team
Midline Approach | Quadrilateral Surface | Suprapubic Window
Retropubic space between bladder anteriorly and pubic symphysis posteriorly. This avascular plane is the key to the approach - develop it bluntly to access the medial pelvic wall without entering peritoneum or damaging bladder.
The modified Stoppa provides superior access to quadrilateral surface compared to ilioinguinal medial window. Direct visualization allows placement of buttress plates to prevent medial subluxation of femoral head.
Mobilize bladder posterolaterally off the quadrilateral surface. This is the key maneuver - gentle blunt dissection in correct plane. Foley catheter essential to decompress bladder and reduce injury risk.
Just as in ilioinguinal approach, corona mortis is encountered crossing superior pubic ramus. Must identify and ligate before proceeding laterally. Same 10-30% incidence and hemorrhage risk.
| Fracture Location | Best Approach | Rationale | Alternative |
|---|---|---|---|
| Quadrilateral surface alone | Modified Stoppa | Direct visualization, better plate placement | Ilioinguinal medial window (inferior access) |
| Anterior column (high) | Ilioinguinal | Need lateral and middle windows | Cannot access with Stoppa alone |
| Anterior column (low) + quadrilateral | Combined: Stoppa + lateral ilioinguinal | Stoppa for quadrilateral, lateral window for column | Full ilioinguinal but less quadrilateral access |
| Both-column with medial displacement | Stoppa + Kocher-Langenbeck | Stoppa for anterior, K-L for posterior | Ilioinguinal + K-L (traditional) |
Memory Hook:STOPPA reminds you of the systematic steps to safely access the quadrilateral surface intrapelvically
Memory Hook:RETZIUS describes the space of Retzius anatomy - the key surgical corridor for modified Stoppa
Memory Hook:CORONA mortis is the 'crown of death' - must ligate it in both Stoppa and ilioinguinal approaches
The modified Stoppa approach was adapted from the Stoppa hernia repair technique and popularized for acetabular fractures by Cole and Bolhofner in the 1990s. It provides intrapelvic access to the quadrilateral surface and medial acetabular structures.
Historical evolution:
Why it gained popularity:
Stoppa vs Ilioinguinal for Quadrilateral
The modified Stoppa approach provides superior access to the quadrilateral surface compared to the medial window of the ilioinguinal approach. Working intrapelvically allows direct visualization and plate application to prevent medial subluxation. However, Stoppa cannot access the iliac wing or high anterior column - these still require ilioinguinal lateral/middle windows.
Current indications:
The space of Retzius is the key anatomical space - a potential extraperitoneal space between the bladder and the posterior surface of the pubic symphysis.
Boundaries of space of Retzius:
| Structure | Location | Relationship to Approach | Clinical Significance |
|---|---|---|---|
| Bladder | Posterior to pubis | Must mobilize posterolaterally | Injury risk if not in correct plane - use Foley |
| Peritoneum | Covers bladder dome | Stay below peritoneal reflection | Entry causes bowel complications - repair if entered |
| External iliac vessels | Lateral pelvic sidewall | Lateral boundary of first window | Retract laterally for extended exposure |
| Obturator neurovascular bundle | Obturator foramen | On obturator internus | Identify and protect during dissection |
| Corona mortis | Superior pubic ramus | Encountered during lateral dissection | 10-30% incidence - ligate before proceeding |
Quadrilateral surface anatomy:
The bladder must be mobilized in the correct plane to prevent injury. Always place a Foley catheter to decompress the bladder before dissection. The correct plane is between bladder wall and pelvic bone - this is relatively avascular. If you see muscle fibers (detrusor), you're in the bladder wall. If you see peritoneum, you're too superficial. Use gentle blunt dissection with a sponge stick.
Window anatomy:
| Window | Boundaries | Exposes | Fixation |
|---|---|---|---|
| First Window (Medial) | Bladder (medial) and external iliac vessels (lateral) | Quadrilateral surface, superior ramus | Quadrilateral buttress plate |
| Second Window (Lateral) | External iliac vessels (medial) and psoas (lateral) | Low anterior column, pelvic brim | Infrapectineal plate if needed |
No true internervous plane exists for this approach.
The modified Stoppa approach works through the Space of Retzius (retropubic space), which is an extraperitoneal potential space. The dissection essentially separates the rectus abdominis muscles (inter-muscular) but then proceeds in a plane that is defined by fascial boundaries rather than nerve supplies.
Nervous Anatomy Distinction
Unlike the ilioinguinal approach which works between nerve territories (femoral/gluteal/lateral femoral cutaneous), the Stoppa approach is an intrapelvic, extraperitoneal approach. It avoids major traversing nerves of the anterior thigh. The obturator nerve is the only major nerve at risk, located on the pelvic sidewall on the obturator internus muscle.
Isolated quadrilateral surface fractures:
Associated both-column fractures:
T-type fractures:
Low anterior column with quadrilateral involvement:
The Stoppa approach is specifically designed for medial structures and excels where ilioinguinal medial window is limited.
Imaging assessment:
Fracture characteristics to document:
Implant planning:
Patient preparation:
Quadrilateral Plate Biomechanics
The quadrilateral buttress plate acts as an internal buttress preventing medial subluxation of the femoral head. It spans from the superior pubic ramus anteriorly to the ischium posteriorly, creating a shelf that resists medial displacement. Screw fixation into intact bone (ramus and ischium) provides stability. This is biomechanically superior to trying to reduce and fix the quadrilateral fragment itself.
Standard Position:
Setup Checklist:
| Variant | Incision | Exposure | Best For |
|---|---|---|---|
| Classical Stoppa | Pfannenstiel (transverse) | Medial only (first window) | Isolated quadrilateral surface |
| Modified Stoppa | Pfannenstiel or low midline | Medial with optional second window | Quadrilateral + low anterior column |
| Extended Stoppa | Extended midline or lateral extension | Medial + lateral ilioinguinal windows | Complex anterior fractures |
| Anterior Intrapelvic (Keel) | Single ilioinguinal-type | Combined medial and lateral access | Associated both-column fractures |
| Window | Boundaries | Access | Fixation Options |
|---|---|---|---|
| First Window | Bladder (medial), external iliac vessels (lateral) | Quadrilateral surface, superior ramus | Quadrilateral buttress plate |
| Second Window | External iliac vessels (medial), psoas (lateral) | Pelvic brim, low anterior column | Infrapectineal plating |
General Assessment:
Acetabular-Specific Assessment:
| Finding | Significance | Approach Implication |
|---|---|---|
| Anterior abdominal scars | Previous surgery | May preclude Stoppa if extensive adhesions |
| Midline laparotomy scar | Prior peritoneal entry | Increased difficulty in Stoppa |
| Pfannenstiel scar | Previous C-section/hernia | Usually still allows Stoppa |
| Groin mass/hernia | May need concurrent repair | Stoppa allows hernia inspection |
Standard Radiographs:
CT Scan (Essential):
| CT Finding | Measurement | Stoppa Indication |
|---|---|---|
| Quadrilateral displacement | Greater than 10mm medial | Strong indication |
| Femoral head subluxation | Medial migration visible | Requires buttress plate |
| Low anterior column | Fracture below iliopectineal eminence | Accessible via Stoppa |
| High anterior column | Fracture extends to iliac crest | Stoppa insufficient - need ilioinguinal |
| Fracture Pattern | Primary Approach | Additional Approach | Key Consideration |
|---|---|---|---|
| Isolated quadrilateral surface | Modified Stoppa | None usually needed | Direct buttress plate application |
| Low anterior column | Modified Stoppa | Lateral window if extensive | Assess column height on CT |
| High anterior column | Ilioinguinal | Not Stoppa | Stoppa cannot reach iliac wing |
| Associated both-column | Stoppa + K-L | Two approaches required | Stoppa for anterior, K-L for posterior |
| T-type fracture | Stoppa + K-L | Two approaches required | Stoppa for stem, K-L for transverse |
Pfannenstiel incision (preferred):
Low midline incision (alternative):
Pfannenstiel vs Midline
Most surgeons prefer the Pfannenstiel incision for modified Stoppa - it provides adequate exposure with better cosmetic results and lower wound complication rates. The low midline incision is reserved for cases requiring extensile exposure or when Pfannenstiel is contraindicated (previous incision, extensive scarring).
The incision choice depends on fracture pattern, patient factors, and surgeon preference.
| Complication | Incidence | Prevention/Management |
|---|---|---|
| Bladder injury | 1-3% | Foley catheter, correct plane dissection; repair primarily if injured, consult urology |
| Peritoneal entry | 5-10% | Stay below peritoneal reflection; repair if entered, no long-term consequence |
| External iliac vessel injury | Less than 1% | Gentle dissection if mobilizing for second window; have vascular backup |
| Corona mortis hemorrhage | 10-30% encounter it | Identify and ligate early; control with clips or ties if bleeding |
| Heterotopic ossification | 10-20% | Indomethacin 75mg daily x 6 weeks or single-dose radiation |
| Wound infection | 2-5% | Prophylactic antibiotics, minimize dead space, drain placement |
| Obturator nerve injury | Rare (less than 1%) | Identify and protect nerve during dissection |
Bladder injury management:
Vascular injury management:
The modified Stoppa approach has significantly lower nerve injury risk compared to ilioinguinal approach. No lateral femoral cutaneous nerve at risk (this is sacrificed in 10-15% of ilioinguinal cases). Femoral nerve is not dissected. Only obturator nerve at potential risk, and this is rarely injured with proper technique. This is a significant advantage of Stoppa for isolated quadrilateral fractures.
Foley catheter remains for 24-48 hours Monitor drain output (remove when less than 30mL/24h) DVT prophylaxis (LMWH or rivaroxaban) Early mobilization to chair with assistance
Toe-touch weight bearing (10-20kg) Hip and knee ROM exercises Avoid hip flexion greater than 90 degrees initially Continue DVT prophylaxis for 4-6 weeks
Partial weight bearing (50%) Increase ROM and strengthening X-rays at 6 weeks to assess healing Progress weight bearing based on healing
Full weight bearing when callus visible Progressive strengthening Return to activities as tolerated Monitor for post-traumatic arthritis
Bladder-specific care:
Long-term outcomes:
Functional Results:
| Outcome Measure | Modified Stoppa | Ilioinguinal | Significance |
|---|---|---|---|
| Quadrilateral reduction quality | Excellent | Good | Stoppa provides superior access |
| LFCN injury rate | 0% | 10-15% | No LFCN in Stoppa field |
| Overall nerve injury | Less than 2% | 5-10% | Less nerve dissection required |
| Wound complication | 2-5% | 5-8% | Smaller incision in Stoppa |
| Operating time (isolated QS) | Shorter | Longer | Less dissection needed |
Practice these scenarios to excel in your viva examination
"A 50-year-old female has an associated both-column acetabular fracture with 15mm medial displacement of the quadrilateral surface on CT. The femoral head is subluxing medially into the pelvis. What approach would you use for the anterior component and why?"
"During development of the space of Retzius in a modified Stoppa approach, you notice pink fluid in the wound and the anesthesiologist reports the Foley catheter is no longer draining. What is your immediate assessment and management?"
"A 40-year-old male has a T-type acetabular fracture. The transverse component is minimally displaced posteriorly, but the anterior component (stem of the T) shows a low anterior column fracture with quadrilateral surface involvement and 10mm displacement. The iliac wing and high anterior column are intact. Which approach(es) would you use and why?"
Space of Retzius Definition
Q: What is the space of Retzius and what are its boundaries? A: The space of Retzius is the retropubic extraperitoneal space between the bladder anteriorly and the posterior surface of the pubic symphysis. Boundaries: anterior = pubis, posterior = bladder and peritoneum, lateral = pelvic sidewall and external iliac vessels, inferior = pelvic floor.
Stoppa vs Ilioinguinal Access
Q: What is the primary advantage of modified Stoppa over ilioinguinal medial window for quadrilateral surface fractures? A: Superior direct visualization and access to the quadrilateral surface working intrapelvically. The Stoppa approach allows buttress plate application under direct vision, whereas ilioinguinal medial window has limited inferior and posterior access to the quadrilateral surface.
Quadrilateral Buttress Plate Function
Q: What is the biomechanical function of a quadrilateral buttress plate? A: The plate acts as an internal shelf preventing medial subluxation of the femoral head into the pelvis. It spans from superior pubic ramus anteriorly to ischium posteriorly, creating a mechanical buttress that resists medial displacement forces.
Nerve Injury Comparison
Q: Why does the modified Stoppa approach have lower nerve injury risk than ilioinguinal approach? A: The Stoppa approach does not dissect the lateral femoral cutaneous nerve (injured or sacrificed in 10-15% of ilioinguinal cases) and does not mobilize the femoral nerve. The only nerve at potential risk is the obturator nerve, which is rarely injured with proper technique.
When Stoppa Cannot Be Used
Q: What are the anatomical limitations of the modified Stoppa approach? A: Stoppa cannot access the iliac wing, sacroiliac joint, or high anterior column - it is limited to medial structures (quadrilateral surface, superior pubic ramus, low anterior column). These superior structures require ilioinguinal lateral window or separate lateral approach if fixation needed.
Major Trauma Services:
Training Pathway:
DVT Prophylaxis Guidelines:
Exam Relevance
For the Australian orthopaedic exam, you must understand indications for Stoppa vs ilioinguinal, know the key anatomical structures (space of Retzius, corona mortis), and be able to describe the surgical technique step-by-step. Acetabular fracture management is a common viva topic testing decision-making and surgical planning skills.
High-Yield Exam Summary