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Debridement of Chondral Defects of the Knee

- Discussion: (see osteochondral injury)
- these injuries are distinct from degenerative arthritic lesions and management of these lesions should remain distinct as well;
- theory is that penetration of subchondral bone causes bleeding from underlying vessels which allows clot formation in the cartilaginous defect and subsequent formation of fibrocartilage;
- some argue that subchondral drilling may be preferable to abrasion arthroplasty;
- for smaller chondral/osteochondral lesions, most authors recommend debridement and either abrasion arthroplasty or microfracture technique;
- thermal chondroplasty:
- involves simple debridement of chondral surface inorder to achieve a smooth stable surface;
- in the report by Edwards RB, et al, the authors compared the effects of treatment with bipolar and monopolar radiofrequency energy on 30 OCD sections harvested from 22 patients with spontaneously occurring chondromalacia who were undergoing knee arthroplasty;
- significant chondrocyte death, as determined by cell viability staining with confocal laser microscopy, was observed with each group;
- bipolar devices produced significantly greater depths of chondrocyte death than did the monopolar device;
- bipolar caused cell death to subchondral bone more often (13 of 20 specimens) than did  monopolar (0 of 10 specimens);
- authors recomend caution when treating fibrillated cartilage with radiofrequency energy, particularly with the bipolar devices tested;
- references:
- Thermal chondroplasty of chondromalacic human cartilage. An ex vivo comparison of bipolar and monopolar radiofrequency devices.
- Is there a role for radiofrequency-based ablation in the treatment of chondral lesions?
                   - Arthroscopic Evaluation of Radiofrequency Chondroplasty of the Knee
Four-year results from a randomized controlled study of knee chondroplasty with concomitant medial meniscectomy: mechanical debridement versus radiofrequency chondroplasty.

- abrasion arthroplasty:
- alternatively, Johnson LL (1991) has demonstrated that during and following arthroscopic surgery, blood clot generated during the case attaches to the surgically incised surfaces (including debrided chondral defects) and further, he demonstrated that this clot does not dislodge w/ passive flexion and extension of the knee;
- w/ this evidence, it may not be necessary to drill the chondral defect, since the majority of blood clot is formed from synovial bleeding;
- further, these observations imply that patients should be kept non wt bearing during the initial postoperative phase, in order to avoid clot dislodgement;
- references:
- Arthroscopic Abrasion Arthroplasty Historical and Pathological Perspective: Present Status.
- The potential for regeneration of articular cartilage in defects created by chondral shaving and subchondral abrasion. An experimental investigation in rabbits.
- microfracture:
- spongialization:
            - refers to the full thickness debridement of the chondral defect, down to cancellous bone;
- the theory behind this concept is that the debridement needs to reach below the tidemark layer inorder to reach a well vasculized surface which contains pleuropotential stem cells (that can subsequently grow into fibrocartilage).
- empirically, it has been observed that this deep debridement is associated w/ prolonged postoperative pain, slow recovery, and joint fibrosis;
   - arthroscopy of the degenerative knee

Isolated chondral fractures of the knee.

Characteristics of the Immediate Postoperative Blood Clot Formation in the Knee Joint.

The biological effect of continuous passive motion on the healing of full-thickness defects in articular cartilage. An experimental investigation in the rabbit.

Mesenchymal Cell Based Repair of Large Full Thickness Defects in Articluar Cartilage.

Restoration of injured or degenerated articular cartilage.

Osseous injury associated with acute tears of the anterior cruciate ligaments.

Occult posttraumatic osteochondral lesions of the knee: Prevalence, classification, and short term sequelae evaluated with MR imaging.

Spontaneous repair of superficial defects in articular cartilage in a fetal lamb model.