• 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.
  

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.
  

• 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.

Columns of Acetabulum in A.P View

• X-ray of pelvis with both hips.
• 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 Methodology of non operative treatment Longitudinal traction through supracondylar femur or upper tibia. It is not advisable to pass trans-trochanteric screw for lateral traction because it increases the chances of inflammation / infection of the trochanteric bursa, 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 Kocher-Langenbeck or ilio-inguinal approach or combined approaches. The surgery is best carried out between 5 & 7 days after the injury.

Surgical Considerations

Aims of Surgery :

• Socket Restoration.
• Socket Stabilisation.
• Congruent Reduction.
• Early Mobilisation.
• Delayed Weight Bearing.

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 at the start of anaesthesion and repeated 12 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 :

• Kocher-Langenbeck approach.
• Ilio-inguinal approach.
• Straight lateral approach.
• Extended ilio-femoral approach.

Out of these, the first two are the commonly used approaches. The Kocher-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.

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 has good quality bone for stable implant purchase. Know the anatomy well to prevent joint penetration by the screw.

Areas of Implant Fixation

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.

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.