The subchondral bone, formed by the subchondral bone plate and the subarticular spongiosa, plays a key role in supporting the articular cartilage. Marrow stimulation techniques such as subchondral drilling are clinically important treatment options for symptomatic small cartilage defects. However, The heat generated from the metal-bone interface during drilling due to the friction can cause thermal osteonecrosis. , recent clinical evidence suggests that they may induce alterations in the subchondral bone plate such as intralesional osteophytes, which persist and may play a role in the degeneration of the repair tissue.

Little is known about whether they induce deleterious changes in the Human Chondral & Subchondral bone.

The aim of this study was to compare the condral & Sub-chondral Histoligical damage induced by different drilling techniques.

To the best of our knowledge this is the first time to inspect it, In- Situ, on Human tissue.

Chronic articular cartilage defects do not heal spontaneously. However, acute traumatic osteochondral lesions or surgically inflicted lesions extending into subchondral bone, spongialization, abrasion or microfracture by drilling causing the release of pluripotent mesenchymal stem cells from the bone marrow, may heal with repair tissue consisting of fibrous tissue, fibrocartilage or hyaline-like cartilage. There for Marrow stimulation techniques as subchondral drilling or microfractures represent ones of the most frequently used methods for chondral and osteochodral defects repair and considered as standard techniques. [10-12]

It's well know and logical to understand that the high temperature around the drilling hole can lead to thermal injury. [1] Temperatures over 47 C degrees for one minutes are associated thermal osteonecrosis [2,3]. The presence of this necrotic bone may delay healing and predispose to infection.[1] Many studies evaluate the thermal necrosis of the drill into the bone [3-6]. In case of osteochondral lesion, drilling of the injury area is the most common practice in orthopedics surgeries for knee, hip, talus and others. In one study that evaluate the difference between drilling and microfractures and the impact in the cartilage healing revealed distinct differences between microfracture and drilling for acute subchondral bone structure and osteocyte necrosis {4] other study evaluate the healing difference between drilling and burring in rabbits knee, showing degenerative changes in both technique and histology longer lived repair the cartilage with 2 mm drilling[5] The main objective of this study is to evaluate for first time in humans, best to our knowledge, the difference between drilling with KWires compared to drill in terms of thermal osteonecrosis and histo-pathological damage.

Methodes:

The specimens will be achieved from 2 groups of patients. The first group correspond to traumatic subcapital fractures with previous non hip pain complains No osteoarthritis changes in the x-ray. The second group the specimens achieve from hip arthroplasty surgery due to osteoarthritic changes.

The femoral head will be obtain during surgery. Drill will be performed in 3 contiguous areas. First Area by Nailing, Second by KW drilling and 3rd area drilled by regular drill obtaining a triangle with the three drilled epicenters. All will be tested with 2 different diameters - 3.5 mm & 1.75mm. All 3 methods will be checked with and without cooling - by laviation with saline during the drilling/nailing. Temperature measurements using Thermocouples having 1 mm wire diameter will be used for temperature measurement.

Parameters as Drilling speed, Drilling depth and Orientation to line of sress- trabeculae- would be uniform.

Histological aspect:

The specimen will be fixed with adequate amount of buffered 4% formalin for 24 to 48 hours with subsequent gentle decalcification in ethylenediaminetetraacetic acid. Then, the specimen will be cut with a strong knife/ or scalpel into parallel slices 3 to 5 mm thick and washed in running water for 12 hours. And after this, the sections from abnormal areas, including articular surface will be submitted for paraffin embedding.

The histological slides will be stained by hematoxilin-eosin (H&E), PAS, Masson trichrome, and Alcian blue. The lesions (degeneration, hemorrhage, necrosis and others) will be measured by micrometer in the microscope.

Inclusion Criteria:

• adults over 18 who agreed to participate in the study and signed an informed consent form.
• Patients who went through partial or complete arthroplasty of the hip due to traumatic or degenerative changes - respectively.

Exclusion Criteria:

• The refusal of the patient to use sampling for any reason, including the desire for burying the organ / tissue
• rheumatic - autoimmune diseases that may affect the hip joint (eg: psoriasis, rheumatoid arthritis, stc')
• Any chonic medications usage that might affect bone and cartilage (eg: Bifosfantim, Alendronate, Risedronate, Ibandronate)
• Any suspected pathology of bone: malignancies, infections, Avascular Necrosis etc'

all Adults who went through partial or complete replacement of the hip in our institute