Acetabulum



Acetabulum


Kerellos Nasr, MD

Stephanie Dickason, PT

Rahul Banerjee, MD


Dr. Banerjee or an immediate family member is a member of a speakers’ bureau or has made paid presentations on behalf of AO North America and Smith & Nephew; serves as a paid consultant to Smith & Nephew; and serves as a board member, owner, officer, or committee member of the American Academy of Orthopaedic Surgeons. Neither of the following authors nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this article: Mr. Dickson and Dr. Nasr.



Introduction

Fractures of the acetabulum, or hip socket, account for 10% of injuries to the pelvis. These fractures have a bimodal distribution. Young patients sustain these fractures through high-energy mechanisms, such as motor vehicle collisions or falls from a height. Elderly patients sustain lower-energy injuries, such ground-level falls.

The treatment of acetabular fractures is determined by the characteristics of the patient and the specific nature of the fracture. Most nondisplaced acetabular fractures may be treated without surgery. Displaced acetabular fractures in younger patients require surgical treatment to restore a stable, congruent articular surface. Anatomic restoration of the articular surface helps to prevent the development of future hip arthritis in this patient population. Elderly patients with displaced acetabular fractures often still require surgery in order to have a stable functional hip. However, in many cases, surgical treatment will include total hip arthroplasty in this patient population.

Due to the varied nature of acetabular fractures, the surgical approach and subsequent rehabilitation is unique depending on the specific characteristics of the fracture, the type of treatment, and, in cases of operative treatment, the surgical approach.


Classification

Letournel and Judet classified acetabular fractures into two groups: elementary fracture patterns and associated fracture patterns (Figure 69.1). Elementary fracture patterns (with the exception of the transverse fracture) involve a fracture of a single column of the acetabulum and include:



  • Anterior wall fractures


  • Anterior column fractures


  • Posterior wall fractures


  • Posterior column fractures


  • Transverse fractures (a single fracture line that spans both columns)

The associated fracture patterns include fractures that have at least two elementary forms and are more complex in nature. These include:



  • Posterior wall posterior column fractures


  • Anterior column (or wall) posterior hemitransverse fractures


  • Transverse posterior wall fractures


  • T-type fractures


  • Both column fractures

The classification is useful in describing the fracture pattern and helps to determine the surgical approach, as discussed later.


Management of Acetabular Fractures

Many acetabular fractures will require surgical treatment in order to restore a stable congruent joint. In select cases, nonoperative treatment may be preferred. Indications for nonoperative treatment include:



  • Nondisplaced fractures (<2 mm)


  • Displaced fractures not involving weight-bearing dome


  • Hip joint stability is maintained


  • Both column fractures that retain secondary congruency of the hip joint


  • Medical conditions that make the risks of surgery outweigh its benefits

Most acetabular fractures will require surgical treatment to achieve anatomic reduction of the articular surface, create a stable congruent joint, and provide stable fixation to allow
early range of motion (ROM). Indications for surgical treatment include:



  • Fractures involving the weight-bearing dome with 2-mm displacement


  • Hip joint instability or incongruity


  • Intra-articular incarcerated fragments


  • Irreducible fracture dislocations






Figure 69.1 Illustration of the Letournel Acetabular Fracture Classification. (Reproduced with permission from Bucholz RW, Heckman JD: Rockwood & Green’s Fractures in Adults, ed 5. Philadelphia, PA, Lippincott Williams & Wilkins, 2001.)

In elderly patients, surgical treatment will often include total hip arthroplasty in conjunction with or instead of internal fixation. The indications for total hip arthroplasty include:



  • Osteoporotic bone that prevents stable fixation


  • Extensive comminution that would not allow adequate joint reduction


  • Extensive injury to the articular cartilage of the acetabulum or femoral head


  • Previous history of degenerative joint disease


Surgical Approach

Surgical treatment of acetabular fractures is performed through one of several commonly used approaches. The surgical approach is chosen based on the fracture pattern. Three of the main surgical approaches include the Kocher-Langenbeck approach, the ilioinguinal approach, and the extensile iliofemoral approach. The choice of surgical approach is determined by fracture pattern and surgeon preference, and impacts the postoperative rehabilitation.


Kocher-Langenbeck Approach

The Kocher-Langenbeck approach allows access to the posterior and superior surface of the acetabulum, thus is well suited for treatment of fractures of the posterior column or posterior wall and certain types of transverse fractures (Figure 69.2). It is similar to the posterior approach for hip replacement but exposes more of the ischium and outer table of the ilium.

The skin is incised a few centimeters lateral and distal to the posterior superior iliac spine and carried to the greater trochanter, then curved distally following the lateral aspect of the femoral shaft, ending distal to the gluteus maximus insertion. Sharp dissection is taken down to the fascia over the gluteus maximus proximally and the iliotibial (IT) band distally in line with skin incision. The IT band is sharply incised inline with the skin incision and the gluteus maximus is bluntly split, making sure to not injure the superior gluteal neurovascular bundle.

The trochanteric bursa is dissected posteriorly to allow exposure of the short external rotators: the piriformis, gemelli, and obturator internus. Care should be taken to achieve hemostasis during this exposure. The gluteus maximus insertion may
be partially or totally incised in order to increase exposure, if needed. The sciatic nerve can now be carefully visualized; it typically runs anterior (or deep) to the piriformis and posterior (or superficial) to the rest of the external rotators. It is at risk from the injury and during surgery, particularly the peroneal division. The short external rotators are then incised 1 cm lateral to their femoral insertions to avoid damaging the medial circumflex artery, which carries the majority of the femoral head blood supply. Injury to the quadratus femoris should be avoided for the same reason. Injury to the blood supply from the trauma or surgery may lead to avascular necrosis in the postoperative period. The short external rotators are reflected posteriorly, protecting the sciatic nerve. With the placement of retractors, the greater and lesser sciatic notches and ischial spine are exposed, thus the posterior column is now visible. The hip joint can be inspected with the use of a capsulotomy and distraction of the joint, utilizing traction through the femur.






Figure 69.2 Illustration of the Kocher-Langenbeck approach. (Copyright AO Foundation, Switzerland. Available at: www.aosurgery.org.)

Performing a trochanteric osteotomy may extend the Kocher-Langenbeck approach. The osteotomy allows for greater exposure superior and anterior to the acetabulum, and is useful with certain posterior fracture patterns and some transverse fractures. The osteotomy is carried from the tip of the trochanter to the vastus tubercle. The osteotomized fragment, which has the insertions of the gluteus medius and minimus (depending on the technique, it may also have the insertion of the vastus lateralis) is reflected anteriorly. By reflecting the fragment, cephalad exposure is increased, which also allows for surgical hip dislocation for direct visualization of the articular surface. After surgical fixation, the osteotomized fragment is reduced and stabilized with lag screws.

After completion of fixation, thorough débridement of any necrotic muscle, especially the gluteus medius and minimus, and loose bony fragments should be removed to decrease the incidence of heterotopic ossification. The short external rotators are reattached to the femur and the gluteus maximus and IT band are repaired.

The Kocher-Langenbeck approach requires release of the short external rotators of the hip and retraction of the abductor muscles. As a result of this and in combination with the injury, these muscle groups are often weak after surgery and should be addressed during rehabilitation.


Ilioinguinal Approach

The ilioinguinal approach, as developed by Letournel, is an anterior approach to the acetabulum that allows for access of the anterior column (Figure 69.3). This approach is predominantly used for anterior wall or anterior column fractures, anterior column posterior hemitransverse fractures, T-type fractures, transverse fractures, and associated both-column fractures. This approach does not allow direct exposure of the articular surface of the acetabulum; therefore, the joint is reduced indirectly by careful reduction of extra-articular anatomy.

The skin is incised 1 to 2 cm proximal to the pubic symphysis and curved to the iliac crest; the external oblique is released, leaving tissue to repair, allowing the surgeon to subperiosteally elevate the iliacus, exposing the internal iliac fossa. The external oblique aponeurosis is cut from the anterior superior iliac spine (ASIS) moving superior to the external inguinal ring, ending at the lateral border of the rectus sheath. In the medial aspect of the wound, the spermatic cord (in males) or the round ligament (in females) is mobilized; the transversus abdominis is released starting from the ASIS to the conjoint tendon and the pubic tubercle from the inguinal ligament. The ilioinguinal and lateral femoral cutaneous nerves must be protected as they are encountered. The external iliac artery and vein cross the surgical field, and are scrupulously protected as the surgeon works around them.






Figure 69.3 Illustration of the ilioinguinal approach. (Copyright AO Foundation, Switzerland. Available at: www.aosurgery.org.)

With deep dissection through the ilioinguinal approach, three windows are created through which reduction of fracture fragments is performed and fixation can be implanted. The lateral window is lateral to the iliopsoas and provides access from the sacroiliac (SI) joint to iliopectineal eminence, thus the internal iliac fossa. The middle window lies between the iliopsoas and the external iliac vessels. Through this window, the surgeon can work on the pelvic brim, quadrilateral plate,
and the lateral third of the superior pubic ramus. The medial window is medial to the external iliac vessels. During the deep dissection, the surgeon must investigate any retropubic anastomoses between the obturator and external iliac (or inferior epigastric) vessels, known as the corona mortis. If present, the anastomoses should be ligated.

Direct exposure of the quadrilateral lamina and the interior aspect of the pelvic brim is possible through the anterior intrapelvic approach, which is often used in conjunction with the ilioinguinal approach. In these cases, the medial and middle window of the ilioinguinal approach may be replaced by the anterior intrapelvic approach.

To perform the anterior intrapelvic approach, a transverse incision Pfannenstiel-type incision is made approximately 1 to 2 cm proximal to the pubic symphysis. Dissection is taken down to the musculature. The rectus abdominus fascia is incised through the linea alba, giving entrance to the space of Retzius between the bladder and the bony pubis. The distal insertion of the rectus should be maintained as the more proximal posterior insertion is elevated from the posterior surface of the pubic rami. The surgeon stands on the contralateral side from the fracture and must release the iliopectineal fascia to enter the true pelvis. The corona mortis must be identified and ligated. With subperiosteal elevation of the iliopsoas and retraction of the external iliac vessels, the pelvic brim is now seen. Direct exposure of the medial aspect of the quadrilateral lamina is possible through this approach. The obturator neurovascular bundle is encountered and should be protected.

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Oct 14, 2018 | Posted by in ORTHOPEDIC | Comments Off on Acetabulum
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