Hoffa Fractures

Partial articular, coronal plane fractures of the posterior part of femoral condyles are called Hoffa fractures. It was first described by Albert Hoffa; a German surgeon in 1904.

They are rare and account for less than 1% of distal femoral fractures. In one study on supracondylar intercondylar fractures of distal femur, 38% had a coronal fracture. Of these 76% were unicondylar and rest were bicondylar. 85% of unicondylar fractures involved the lateral condyle.

They are three times more common in the lateral femoral condyle probably because of following reasons;

1) Physiologic genu valgum which puts greater compressive stresses on the lateral side

2) Frontal impact on a flexed knee is more likely to involve the outer aspect resulting in shearing force on the posterior part of lateral femoral condyle.

Mechanism of injury

High velocity injuries such as road traffic accidents are the most common mechanism of injury. Usually the patient reports a history suggestive of direct hit over the front of the knee which was flexed varying degrees, resulting in a vertical shearing force on the posterior femoral condyles.

Clinical features

Clinically patients present with inability to weight bear and haemarthrosis of knee. Usually there is no deformity. The knee is usually stable in extension, but varus-valgus instability may be present in a partially flexed position when examined under anaesthesia.

Imaging

About 1/3 of these injuries are missed on the x-rays especially if undisplaced as the anterior part of the condyle is intact. In the AP view irregularity or step in the subchondral line of involved condyle may be seen. Lateral view may show loss of normal overlap of condyles or break in the subchondral line. If fracture is displaced, step or discontinuity may be seen on careful examination. Oblique view may be necessary to show the fracture line clearly. CT scan is a must to clearly delineate the fracture line, detect comminution and to identify the associated injuries.

Classification

As per AO classification, it is classified as type 33B3 fracture. Letenneur in 1978, classified these fracture into 3 types depending on the distance of the fracture line from the posterior femoral cortex and it’s direction, but subsequent studies failed to validate the classification.

Type I- Fracture line parallel to the posterior femoral cortex involving the entire posterior condyle.

Type II- Fracture occurs in the area behind the line parallel to the posterior femoral cortex. The posterior condyle is divided into one thirds and depending on the relationship of fracture line to the thirds the type II is subclassified into A,B and C.

Type III- Oblique fracture of posterior femoral condyle.

A cadaveric study found that type I and III fractures have preservation of soft tissue attachments and the type II fragments lack soft tissue attachments and are prone for osteonecrosis and nonunion.

Management

As they are intra-articular fractures, they should be treated by anatomical reduction, rigid internal fixation and early mobilisation to restore function. Nonoperative treatment results in poor outcomes as there is high chance of displacement. In addition, being an intra-articular fracture prolonged immobilisation will result in joint stiffness.

The surgical approach will depend on the condyle involved, location and orientation of fracture line and the presence of comminution. Standard medial or lateral parapatellar approach is sufficient if there is no posterior comminution. Once the arthrotomy is done, the patella is dislocated if necessary and the knee is deeply flexed exposing the posterior condyle.

Swashbuckler approach, a variation of lateral parapatellar approach that spares the quadriceps muscle belly may be used in Hoffa fractures of lateral femoral condyle. In lateral Hoffa fractures with posterior comminution, Gerdy’s tubercle osteotomy and proximal retraction of iliotibial band may be necessary.

In medial Hoffa fractures with posterior comminution, subvastus approach with arthrotomy of knee anterior and posterior to the medial collateral ligament may be necessary.

  •     Supine position on a radiolucent table.
  •     Tourniquet optional.
  •     Knee flexed to 300 degrees with a cushion or rolled towels behind the knee.
  •     Anterior midline incision.
  •     Develop medial skin flap protecting the infrapatellar branch of saphenous nerve
  •     Elevate the vastus medialis from the intermuscular septum.
  •     Anterior capsulotomy done at the anterior margin of medial collateral ligament to expose the medial condyle.
  •     Retract the patella laterally.
  •     Flex the knee maximally to expose the posterior condyle.
  •     If needed another capsulotomy may be done posterior to the medial collateral ligament to expose the posterior condyle better.

In patients with Hoffa fractures of both condyles combined lateral parapatellar and medial subvastus approach may be used. Minimally invasive approaches with arthroscopic assistance have been described but their role is not yet established.

Reduction may be difficult especially if there is delay in treatment. The attachment of cruciate ligament on the inner aspect may make manipulation of fragment difficult especially if the fragment has only part of the cruciate insertion and the ligament is torn longitudinally into two bundles. Use of Schanz screw on the outer surface as a joystick for manipulation and use of pelvic reduction forceps for compression may be necessary.

Fixation can be done with 3.5 mm or 4.5mm screws. At least 2 parallel screws must be used to prevent rotation of fragment. Screws are usually inserted from anterior to posterior. Ideally the screws should be perpendicular to the fracture line. If there is comminution avoid excessive compression. Articular surface should be avoided if possible; otherwise use the smallest diameter screws and countersunk the screw heads.  Headless screw may as well be used for fixation but their role is not yet established. In presence of comminution, small plates may be used as a buttress for fixation.

If fragment is small, a posterior approach and posterior to anterior screws may be necessary. Postoperatively early mobilisation is advised if fixation is stable but weight bearing is delayed till the fracture is consolidated.

 

Further Reading

  1. Hoffa A. Lehrbuch der Frakturen und Luxationen. 4th ed.Stuttgart: Ferdinand Enke-Verlag, 1904, 453.
  2. Letenneur J, Labour PE, Rogez JM, et al. Fractures de Hoffa : a propos de 20 observations. Ann Chir 1978;32:213-219.
  3. Sean E York, Daniel N Segina, Kamran Aflatoon, David P Barei, Bradford Henley, Sarah Holt, Stephen K Benirschke. The Association between Supracondylar-Intercondylar Distal Femoral Fractures and Coronal Plane Fractures. JBJS Vol 87-A Number 3. 2005; 564- 569.
  4. Starr AJ, Jones AL, Reinert CM. The “swashbuckler”: a modified anterior approach for fractures of the distal femur. J Orthop Trauma 1999;13:138–140.
  5. Liebergall M, Wilber JH, Mosheiff R, Segal D. Gerdy’s tubercle osteotomy for the treatment of coronal fractures of the lateral femoral condyle. J Orthop Trauma 2000;14:214–215.
  6. Hofmann AA, Plaster RL, Murdock LE. Subvastus (southern) approach for primary total knee arthroplasty. Clin Orthop Relat Res 1991;269:70–77.
  7. Viskontas DG, Nork SE, Barei DP, Dunbar R. Technique of reduction and fixation of unicondylar medial Hoffa fracture. Am J Orthop (Belle Mead NJ) 2010;39:424–428.
  8. https://www2.aofoundation.org/wps/portal/surgery?bone=Femur&segment=Distal&classification=33-B3.2/3&showPage=indication
  9. http://en.wikipedia.org/wiki/Albert_Hoffa

 

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