Changes of distal joint after the femoral medullary cavity is blocked with bone cement

Hongyu LI; Hong AN; Bin LIANG; Rongzhu LI; Wen TIAN; Minke WEI

ABSTRACT

BACKGROUND:

There are so many researches on the complication of artificial joint of bone cement on clinics, but the effect of implanting artificial joint of bone cement on the structure of distal joint is unclear.

OBJECTIVE:

To explore the structural changes of distal joint after blocking the proximal and middle femoral medullary cavity with bone cement.

DESIGN:

Controlled observation.

SETTING:

The People's Hospital of Guangxi Zhuang Autonomous Region.MATERIALSA total of 26 healthy adult New Zealand rabbits, of clean grade and both genders,weighing 2.6-3.5 kg,were offered by the Experimental Animal Center of Chongqing Medical University.Polymethyl methacrylate (PMMA) TJ bone cement,16# antrum needle for puncture (outer diameter 1.6 mm,inner diameter 1.05 mm,length 80 mm), light microscope of Japan Olympus Company (BH-2), and transmission electron microscope of Japan Hitachi Company (H-600).

METHODS:

The experiment was completed in the Experimental Animal Center of Chongqing Medical University from July 2005 to April 2006.Eighteen rabbits were randomly selected as model group,while other 8 ones ware served as control group.The rabbit model was established by infusing femoral medullary cavity of left side with PMMA.Due to the specific anatomic structure of appearing the third trochanter, the anesthetized rabbits were adopted to incise the lateral greater trochanter below the third trochanter through spatium intermusculare of posterior lateral femur, remaining the neck of femur, so as to expose intertrochanteric fossa and entry of medullary cavity,which was expanded to 1/2 length of femur by using cavity file of different thickness repeatedly. Then wound surface was washed fob many times to remove the destroyed myeloid tissues, and was dried with strips. Bone cement was prepared by manually stirring powder with solution at a ratio of 21, until it demonstrated dough shape. In order to control the depth of bone cement into femoral medullary cavity, a small piece of dough-shaped bone cement was filled in middle femoral stenosis as cavity blocker.Ten minutes later,the solidified bone cement was re-blended as dough shape and implanted into medullary cavity fully.Afterwards, the bone cement was completely solidified and the incision was sutured. At the 4th, 8th and 16th weeks postoperatively,6 rabbits of each model group and all controlled rabbits were killed respectively to obtain the samples of distal femoral articular synovium, cartilage and subchondral bone. The histological examinations included hematoxyiin-eosin (HE) staining, toluidine blue (TB) staining and immunohistochemistry. Transmission electron microscope was used to detect the changes of cartilage and subchondral bone in distal joint of left femur.MAIN OUTCOME

MEASURES:

①The structural changes of distal femoral articular synovium, cartilage and subchondral bone by HE staining,TB staining,immunohistochemistry.②The histological changes of distal articular cartilage and subchondral bone in left femur by transmission electron microscope.

RESULTS:

①HE stainingThe damages to articular cartilage,synovial tissues and subchondral bone aggravated with time.At the 16th week of modeling,the articular cartilage was destructed,the bone structure was severely damaged,with the synovial tissue proliferation and swelling;TB staining (the 16th week)All the layers of articular cartilage appeared loss of stain; Immunohistochemistry (the 16th week) Collagen Ⅱ of the chondrocytes was positively stained. And transforming growth factor (TGF)-β1 staining of articular synoviocytes and chondrocytes appeared positive.②Transmission electron microscope The lesions to articular chondrocytes and bone cells aggravated progressively with time, part of which presented necrosis and collapse at the 16th week.

CONCLUSION:

The intramedullary blood circulation is severely damaged after blocking the proximal and middle femoral medullary cavity with bone cement. Conversely, the bone metabolism disorders in dista0 femur. which results in the degeneration or necrosis of distal femur, cartilage and synovial tissue.