Referred to by various names, the anterior intrapelvic approach (also known as AIP, Stoppa, modified Stoppa, extended Pfannenstiel, ilioanterior, third window) aims to expose the medial intrapelvic surface of the innominate bone for repair of acetabular and pelvic ring injuries. Recognizing it as either an extension of the Pfannenstiel approach or later of the Stoppa and Rives' approach to treat abdominal wall hernias, Cole and Bolhofner1 proposed a novel use of this preperitoneal/retroperitoneal interval as an additional way to access the intrapelvic portion of the pelvis to complement the classical surgical tactics for the reduction and fixation of acetabular fractures.
The use of the preperitoneal space to access and treat these complex injuries has evolved from the initial clinical series of fracture cases to its common use by acetabular fracture surgeons. Along the way, contributors addressed anatomy and safety concerns, specific technical issues, clinical outcomes, and prognosis mainly through retrospective cohort studies. The raised interest for this tactic has now culminated, in knowledge translation terms, with the development of instruments and implants for specific use with this approach.
This article aims to follow the progress of the AIP approach over time, highlighting key developments for the specialist orthopedic trauma surgeon interested in pelvis and acetabular fracture care to consider.
In the Beginning
Hirvensalo et al2 then Cole and Bolhofner,1 respectively, sequentially described the use of the preperitoneal space for the care of injuries to the pelvis. Hirvensalo et al2 described “the ilioanterior approach” as an anterior access to the infrapectineal intrapelvic portion of the innominate bone for 18 pelvic ring injuries. They described typically using a low Pfannenstiel (and in 2 cases of simultaneous laparotomy, a low midline) approach, detaching the rectus abdominis and pectineus muscles from the rami, dissecting subperiosteally along the inner surface of the pelvic brim back to the sacroiliac joint, leaving undisturbed the iliopectineal fascia, external iliac vessels, psoas, and femoral nerve. The obturator vessels and nerve were protected, and the collaterals (the corona mortis anastomoses) were protected. They additionally mentioned exposing the iliac fossa (through the first window of the ilioinguinal approach) when a fracture line extended to this region.
The following year, Cole and Bolhofner1 reported their initial experience with an “Extended Pfannenstiel”/“Modified Stoppa” exposure to facilitate the reduction and fixation of the medially displaced portion of the acetabulum in 55 cases of fracture. Cole and Bolhofner presented theirs as an additional “intrapelvic” approach, the only 1 available at that time being Letournel's3 ilioinguinal. Meanwhile, contemporaries4 described the use of the third window of the ilioinguinal approach described by Letournel3 as a means to visualize the important neurovascular structures (external iliac vessels and obturator vessels and nerve) by working from the contralateral side of the injury, a change from the original technique described by Letournel in written correspondence with K.A. Mayo (1995).
Technique: The Early Years
The early report of the approach for acetabular fracture care1 describes using the classical Pfannenstiel interval splitting the linea alba between heads of the rectus abdominis muscle to gain access to the preperitoneal space as surgeons typically do for symphyseal disruptions. Care is taken to stay extraperitoneal (typically approximately 10 cm above the symphysis pubis but below the linea semicircularis). The distal rectus is sharply elevated from the superior symphysis body and ramus. The catheterized bladder is then visualized and protected while the dissection is carried posteriorly along the brim identifying a “plethora” of vessels (the corona mortis), communicating between the inferior epigastric/external iliac and obturator systems, which are ligated and divided to secure access. The obturator nerve and vessels are carefully protected throughout the case, and their retraction must be performed carefully and only if necessary. The iliopectineal and obturator fasciae are sharply elevated from the pelvic brim to expose the iliac fossa, the medial wall and obturator fossa, the pectineal eminence, and the quadrilateral surface of the acetabulum. Further posterior dissection (along with hip flexion) allows mobilization and elevation (anterior retraction) of the external iliac vessels and provides exposure to the sacroiliac joint and adjacent portion of the sacral ala, where a Hohmann retractor can be placed while protecting the lumbosacral plexus and iliolumbar vessels. These retractors along with malleable retractors and/or abdominal retractors (eg, Deavers) held from the ipsilateral side to the injury allow safe retraction of adjacent structures. Free draping of the leg allows free motion of the hip and relaxation of the retracted structures. The resultant exposure provides visualization of the pelvic brim from sacroiliac joint to the pubic symphysis bilaterally (as needed) and from the iliac fossa and sciatic buttress down the posterior column to the lesser sciatic notch, exposing the quadrilateral surface.
Cole and Bolhofner first labeled this approach the “extended Pfannenstiel” because of its similar rectus abdominis dissection. On further study, authors discovered that this surgical plane had been described for abdominal wall hernia repair through the use of a mesh and appropriately credited Stoppa,4 qualifying their own approach as a deeper dissection of Stoppa's description along the pelvic brim.
All authors describe the need to access the iliac fossa and sacroiliac joint through the first window of the ilioinguinal3 or an Avila approach5 and the use of combined anterior and posterior approach by adding the Kocher-Langenbeck in cases where visualization of posterior portions of the acetabulum is needed. Sagi et al6 additionally described the use of Smith-Petersen approach (and/or an anterior superior iliac spine osteotomy) to better visualize the anterior portion of the joint and anterior wall.
This original detailed description by Cole and Bolhofner would set what has remained usual practice for many acetabular surgeons (supine, slight Trendelenburg position, radiolucent table, free draping of the entire limb and hindquarter including the lower abdomen) using this access with and without the ilioinguinal approach.
They additionally described indirect reduction maneuvers and fixation techniques, which remain key resources. They specifically described the use of direct medial to lateral reduction with a spiked pusher or disc, lateral traction from a Schanz pin placed in the proximal femur, and use of a bone hook in the sciatic notch to bring forward the posterior column. Cole and Bolhofner also achieved provisional fixation with K-wires and illustrated definitive indirect reduction and fixation techniques by means of buttressing implants or by spanning bridging strategies (Fig. 1) first anchored at the sciatic buttress posteriorly and extending anteriorly along the ramus or across the symphysis. These formed the basis of the fixation strategies still used for lesions in this area. Qureshi et al7 (with Bolhofner as a senior author) later further described steps to “infrapectineal plating” as a technical trick.
After the original 1994 description, surgeons borrowed hand-held retractors from other surgical specialties (Deavers, Taylors, Harringtons, Pryor-Peans, and so on) and variable sizes malleable retractors7 or fixed retractor systems to secure a deep surgical field to emulate Cole's described approach and fixation strategies. The extent of exposure has correspondingly expanded with time (Fig. 2).
Evolution of the approach then followed the typical innovation curve of initial enthusiasm followed by healthy doubt,8 as surgeons sought to clarify limitations and to establish landmarks to assure safe surgery.9 Kacra et al10 identified pertinent local vital structures and then described their anatomical positions and variations based on the surgical dissection of 5 cadaveric specimens (10 hemipelves). Specifically, they reported a variable origin and number of obturator artery and vein with 1/10 arteries originating from the inferior epigastric and 2/10 specimens showing 2 obturator veins branching into the external iliac vein. They reported the presence of a “corona mortis” in 40% of cases, a number smaller than some clinical reports but in line with the original cadaveric studies by Teague et al.11
Kacra et al also reported the location of structures to the linea terminalis (LT) (attachment site of the iliopectineal fascia) either as a distance from the LT (Fig. 3) or as a measurement in millimeters from the sacroiliac joint where the structures crossed the LT. The distance of the obturator vessels to the LT therefore ranged from 15 to 30 mm from the posterior root to the midpoint of the LT, while averaging approximately 22 mm just above the obturator canal. They measured the obturator nerve to lie between 18 and 22 mm from the LT along its course (Fig. 3) and the nerve crossing the LT on average between 18 and 22 mm from the right and left SI joints, respectively.
Finally, they reported a variable amount of branching for the iliolumbar artery and vein and that their branches will typically cross the iliopectineal line 1–20 mm from the SI joint, prompting the necessity for careful visualization and dissection of the above structures during surgical exposure and plate application. In that respect, cadaver dissection-based training is strongly recommended before use of the AIP.
Another contribution addressed the unknown location of the joint from the intrapelvic side raised as a concern by many authors2,7 by mapping a “safe zone” for extraarticular placement of simulated 4-mm diameter screws inserted perpendicular to the medial surface of the innominate bone. Based on analysis of 100 pelvis computed tomography scans of supine uninjured patients, Guy et al12 (Fig. 4) offered intraoperatively reproducible measurements based on bony landmarks with the patient in the same supine position at the time of surgery. Zhang et al13 recently cleverly identified a “safe” and a “dangerous” zone, which considers screw orientation using computed tomography data and a 3-dimensional model.
Growing case experience and familiarity with anatomy saw surgeons extend the limits of dissection through careful soft tissue mobilization and handling, rendering the use of the second window of the ilioinguinal approach rarely necessary—the utilitarian first window always remaining part of the strategy when indicated (see Video, Supplemental Digital Content,http://links.lww.com/BOT/A287).
Through a novel and ingenious method, Bible et al14 dissected 10 cadaver specimens to the extent of the current approach, then mapped and quantified the extent of bone surface exposed. Among other findings, they demonstrated access to a 1.5- to 2-cm strip of bone superior to the pelvic brim and access to 5 cm2 of the quadrilateral surface (see Figure, Supplemental Digital Content 1, http://links.lww.com/BOT/A247).
Capping off the AIP's technique section, Sagi et al7 illustrated specific retractor and reduction clamp placements and plate fixation configurations successfully used in a cohort of 57 patients (see Figure, Supplemental Digital Content 2, http://links.lww.com/BOT/A248). In addition to sharing with experienced surgeons their insights into these successful tactics in print, this study remains a reference for teaching intrapelvic acetabulum fracture surgery—its figures being used and cited regularly.
In noting this field's technical evolution, one must mention the contributions of Keel et al15 and Ruchholtz et al16 who described alternate but similar access routes to the intrapelvic innominate bone. More specifically, Keel et al15 reported a cadaver dissection and clinical series of 19 patients, using a paramedian incision (pararectus approach) at the lateral edge of the rectus abdominis muscle sheath, through the conjoint tendon. Similar to Ponsen et al,17 who mobilized vessels through a midline approach, the Bernese group use the pararectal route to create 5 surgical windows around vital structures, reportedly facilitating their mobilization and providing access to the pelvic brim and quadrilateral surface. They reported similar results as AIP studies with few intraoperative complications and good radiographic outcome based on a strict protocol. Using a different strategy, Ruchholtz et al described a novel 2-incision minimally invasive method for the treatment of anterior acetabular fractures: 1 incision as a pararectal but through and in line with the abdominal wall muscles and a second adjacent to the symphysis and pubic body. They reported on 19 of 26 cases with more than 12-month follow-up where access to the pelvic brim, iliac fossa, and quadrilateral plate was easily achieved with the use of a fixed retractor system.
Furthermore, concerning the AIP, 2 recent technical articles addressed the management of superomedial roof impaction (also known as “gull wing sign”)18—a radiographic finding associated with increased patient age19 and harbinger of poor prognosis.18 The 2 groups described reduction and fixation techniques of the impacted medial joint segment to restore joint congruity, following which the segment is supported by buttress fixation. Casstevens et al20 reported a reduction of the fracture primarily through the fracture line at the pelvic brim, only accessible through the AIP approach with an alternate plan to osteotomize the inner table of the ilium adjacent to the fracture if the first technique proved unsuccessful. Fixation was achieved through “rafting” screws. They reported excellent–good radiographic and clinical results in the 6 patients included for review. Similarly, Laflamme et al described in their series of 9 patients a direct visualization technique where the anterior column is reduced and the quadrilateral plate is hinged posteriorly allowing direct visualization of the femoral head and adjacent cartilage. The fragment is reduced and held with an elevator, then fixated with rafting screws. Cancellous bone graft or calcium phosphate bone cement (few cases) was used to fill the underlying bone void. They report reduction within 3 mm in 6 of 9 cases and conversion to total hip replacement in 3 of 9 cases.
As a resultant of the “evolution” of this approach, authors claim a number of advantages listed in the following table (Table 1).
Early in the description of this approach, it became apparent that access to many fracture patterns was possible through the AIP. Cole and Bolhofner1 specifically listed the following as indications: displaced anterior column or wall fractures, associated both column fractures, anterior column or wall fractures associated with a posterior hemitransverse component, and some transverse and T-shaped fractures.
Sciatic buttress comminution and fractures greater than 3 weeks old make use of this approach difficult (and not recommended),1,21 and this approach is contraindicated for use alone for fractures with pure posterior pathology.
The list has not significantly grown over time, perhaps only in defining the use or not of the Ilioinguinal's first window (40%–60% depending on the fracture type) and the ability to reduce the “gull wing” deformity as mentioned above. Archdeacon et al22 warned of difficult dissection and risk for cystotomy and contamination in patients with a history of gynecological or urological surgery, increased bleeding when an AIP approach follows prostatectomy or radiation, and consideration for an alternate approach in such cases is advised. Additional contraindications include abdominal distension and or ileus.1
Commercialization as Dissemination
Increased use, publications,24–33 and clinical interest for the AIP identified specific clinical gaps and needs driving the field to further evolve. Knowledge translation (or dissemination) takes many forms with “bench-to-bedside” serving as a common expression: commercialization is a specific form of dissemination. In the case of the AIP, many vendors focused their R&D efforts and responded to patients' and surgeons' needs by designing novel implants and instruments (Fig. 5) to support the surgical exposure and fixation strategies for specific use with this approach. The early, mid- and long-term outcomes of these strategies still remain undefined.
The intent of this review is not to describe an approach to allow all surgeons to start operating acetabular fractures. It is rather aimed at students of this injury to facilitate their “apprenticeship” and at experienced trauma surgeon so that he or she considers it part of the armamentarium by understanding the progress made to date, having available a set of resources to guide safe care and maximize the probability of improving reduction and ultimately patient outcome.
The AIP is not meant to replace classic approaches but to serve as an adjunct for a specific set of pathologies.
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