Fractures of the acetabulum are becoming more common due to high speed vehicles on bad roads. They assume great clinical significance since it involves a major weight bearing joint in the lower extremity. Anatomical reduction is a prerequisite for good long term function of the hip joint, which may be obtained either by closed or open methods. But more often than not it requires open reduction and stable internal fixation to facilitate early active or passive motion. There is unanimity of opinion that joint congruity is essential for good long term function . Hence displaced acetabular fractures merit a stable internal fixation.

The Major Factors Affecting the Results are

The degree of initial displacement
The damage to the weight bearing dome of the acetabulum
The degree of hip joint instability
The adequacy of reduction either open or closed
Associated pelvic ring injury
Associated damage to neuro-vascular structures and viscera
The late complications of Avascular necrosis of the Femoral head, Heterotrophic ossification, chondrolysis, sciatic or femoral nerve injury.

Acetabulum is contained within two columns of innominate bone, the anterior column and the posterior column,It forms the socket in which the head of femur articulates forming the hip joint.

Surgical Anatomy

It is useful to regard the acetabulum as contained within the open arms of an inverted Y formed by two columns of bone;

The anterior or ilio-pubic column, which runs obliquely downwards inwards and anteriorly from the anterior part of the superior iliac crest to the pubic symphysis.
The posterior or ilio-ischial column , voluminous & thick , descends caudad from the level of angle of the great sciatic notch to the ischial tuberosity. The weight bearing dome area , though anatomically not a distinct entity is of the greatest clinical significance since an unreduced / malreduced fracture of the weight bearing dome will inevitably result in a post traumatic arthritis of the hip joint.

Acetabulum between two columns

Mechanism of Injury

There are two basic mechanism of injury,

Direct impact on the greater trocanter,

Dash board injury wherein the force is transmitted from the lower end of the femur through the shaft to the femoral head breaking the acetabulum

Fractures of the acetabulum are classified as,

Classification

Judet & Letournel classification is based on the concept of columns. This classification is the most scientific and is largely followed.

Elementary Fractures

Posterior wall fractures
Posterior column fractures
Anterior wall fractures
Anterior column fractures
Transverse fractures

Associated Fractures

T shaped fractures
Posterior column + Posterior wall fractures
Transverse + Posterior fractures
Anterior wall / anterior column + Posterior hemitransverse fractures
Both column fractures

Simple Fractures

Consisting of fractures of posterior or anterior lip, isolated fractures of posterior or anterior column or plain transverse fracture.

Complex Fractures

Consisting of fractures which are T shaped, fractures of both columns or fractures of lip associated with fracture of the column. Some centres classify these injuries depending on the direction of the dislocation of the head of the femur i.e. central dislocation, posterior dislocation or anterior dislocation.

Imaging

Imaging consists of plain x-rays and C.T. scan of the pelvis.

Plain X-rays

X-ray of pelvis with both hips.

Columns of Acetabulum in A.P View

There are six important radiological landmarks of the acetabulum visible in this view namely;
Pelvic brim
Ilio-ishchial line.
The tear drop or radiological U
Weight bearing dome or the roof of the acetabulum
Anterior lip
Posterior lip

Lines on A.P View

By studying these landmarks one can get a fairly good idea about the nature of the injury.

Special X-rays

Iliac Oblique View : delineating the posterior column and the anterior lip.

Columns of Acetabulum in Iliac Oblique View

Obturator Oblique View : delineating anterior column and posterior lip.

Columns of Acetabulum in Obturator Oblique View

Inlet View of the Pelvis : Taken with patient supine and the X-ray beam directed 45 degrees caudad.

Outlet View of the Pelvis : Taken with patient supine and the X-ray beam directed 45 degrees cephelad. These two views are essential to visualise pelvic ring injuries.

C.T. Scan

C.T. Scan of the pelvis; is an useful aid in identifying impacted fractures of the acetabular wall,incarcerated bone fragments in the joint, the degree of comminution, unrecognised dislocations of the sacroiliac joints and other sacroiliac pathology. A three-dimensional reconstruction of a fracture using C.T. Scan images greatly aids decision making and planning the steps of surgical reconstruction.

Columns of Acetabulum as seen in C.T Scan

Management

A patient suspected to have acetabular injury is usually hemodynamically compromised. The first aid includes a rapid clinical evaluation, resuscitation, starting intravenous line, passing a urinary catheter and immobilisation with traction. Once the patient is stable, X-rays and C.T. Scan are performed. Radiographs and C.T. Scan are studied to assess the type and site of the fracture, the degree of comminution, the amount of displacement, type of dislocation and the bone quality.

Non Operative Treatment

Indications

Displacement less than 2 mm
Severe comminution : Poor bone quality
Medical contraindications
Late presentation
Local infection
Non availability of adequate surgical facilities
Adequate intact weight bearing dome with congruent head ( Matta) Methodology of non operative treatment Longitudinal traction through supracondylar femur or upper tibia Lateral traction through a schanz screw in the sub trochanteric region It is not advisable to pass trans trochanteric screw for lateral traction because it increases the chances of inflammation / infection of the trochanteric burgs, which will make the patient unfit for surgery at a later date if decided. Assess reduction by X-rays. Maintain traction for six to eight weeks. While in traction it is important to continue isometric exercises.

Operative Treatment

Consists of open reduction & internal fixation using either Kochar-Langanback or ilio-inguinal approach or combined approaches. The surgery is best carried out between 5 to 7 days after the injury.

Surgical Considerations

Aims of Surgery

Socket Restoration
Socket Stabilisation
Congruent Reduction
Early Mobilisation
Delayed Weight Bearing

According to Letournel the prerequisite for a good result is adequate relocation of the femoral head under a sector of the roof. The prognosis after the acetabular reconstruction depends on variety of factors namely;
Associated injuries
Damage to the articular cartilage
Avascularity of the femoral head and of the fractured acetabular fragments
Interval between injury and surgery
Quality of surgery

Preoperative Planning

Preoperative planning includes detailed analysis of various injuries. Common associated injuries are to the sacro iliac joint, knee ligaments, rib cage, head of femur. Also look for pelvic visceral injuries. Complex bicolumn fractures may require about 3 to 4 units of blood. In absence of 3D C.T. Scan analysis it is essential to make line drawings from the X-rays and mark a scheme of fracture pattern on the innominate bone and carry the same to the operation theatre for better three dimensional visualisation. The surgery should ideally be an elective surgery preferably between 3 and 10 days after the injury to allow for the pre operative planning. Immediate surgery may be considered for neuro vascular injury or irreducible dislocation. Prophylactic iv. antibiotics are given 2 hours before surgery and repeated 8 hourly following the first dose for a period of 3 to 5 days.

Approaches

The choice of surgical approach is decided by the major column or lip injury There are four basic surgical approaches :
Kochar-Langenbeck approach
Ilio-inguinal approach
Straight lateral approach
Extended ilio-femoral approach

Out of these, the first two, the Kochar-Langenbeck approach is mainly used for posterior injuries, and Ilio-inguinal approach is mainly used for anterior injuries and some times even for combined injuries, are the commonly used approaches.

Tricks & Hints

The following tricks and hints may be useful during the stressful part of the surgery ;
The articular surface of the hip joint must be adequately exposed

A schanz screw in the iliac crest and one in the femoral neck connected with a multi directional distractor will allow adequate distraction of the joint and may also help in achieving reduction by the the principle of ligamentotaxis

A 5 mm schanz screw with a T handle inserted in the ischeal tuberosity will allow manipulation of the lower part of the posterior column helping to get rotational control over it.

Holes may be drilled into the outer cortex of pelvic bone to get purchase for the pointed reduction forceps.

Work within the fracture.

Sites of Application of Implants

The accompanying diagrams show the areas of innominate bone which have good quality bone for stable implant purchase. Know the anatomy well to prevent joint penetration by the screw.

The prognosis after the acetabular reconstruction depends on variety of factors, many of which are not under the control of the surgeon, namely; associated injuries to head, chest or pelvic viscera or nerves, damage to the articular cartilage and avascularity of the femoral head and of the fractured acetabular fragments.

Areas of Implant Fixation

Post-operative Management

The patient is put on skeletal traction applying 3 kg weight for a period of ten days to reduce post operative muscle spasm and associated pain. Traction has no value in distracting the joint or supplementing inadequate fixation. Use of epidural analgesia and C.P.M. helps in early post operative period . Use of low molecular weight heparin to prevent deep vein thrombosis and indomethacin to prevent hetertrophic ossification are left to surgeons discretion.

Complications

The common complications of surgery for the acetabular fractures are :
Traction injury to the sciatic nerve
Wound hematoma
Wound infection
Intra articular implants
Heterotrophic ossification
Avascular necrosis of head of femur and of fracture fragments
Protrusio acetabuli
Early degenerative arthrosis
Implant loosening

Conclusion

Fractures of acetabulum are like jigsaw puzzle, challenging and stimulating. If solved well they are most satisfying, if not , they are most frustrating. To achieve a good result it is essential to understand the post traumatic anatomy by analysis of x-rays and C.T. Scan, to use correct surgical approach, to reduce all the fragments anatomically and stabilise them well using suitable implants, to start early non weight bearing mobilisation and delayed weight bearing. Managing these complex injuries is a team approach.

References

Judet R., Judet J., Letourne E. (1964) , Fractures of acetabulum : Classification & surgical approaches for open reduction. J.Bone and joint surgery 46 A (8) : 1615 - 1647

Letournel E. (1980) , Acetabular fractures , classification and Management. C.O.R.R. 151 : 81 - 106

Matta J.M, Anderson L.M., Epstein H.C., Hendricks P (1986), Fractures of Acetabulum : a retrospective analysis. C.O.R.R. 205:230

Pennal G.F. , Davidson J. , Garside H. , Lewis J. (1980 ) Results of treatment of acetabular fractures . C.O.R.R. 151 : 115 - 123

Rowe C.R. , Lowell J.D. (1961), Prognosis of fractures of acetabulum. J. Bone and joint surgery 43 A (1) : 30 - 59

Tile M. (1964) Fractures of Pelvis and acetabulum. Williams & Wilkins, Baltimore.

Tile M. , Joyce M. , Kellar J. (1984) Fractures of acetabulum : Classification , management protocol and early results of treatment. Orthopaedic transection of J.Bone and joint surgery 8 (3)

Tile M. , Schatzker J. Rationale of operative fracture care. Springer Verlag, Berlin , Heidelberg, New York