- Email: [email protected]
The technique of microfracture for the treatment of articular cartilage defects in the knee
THE TECHNIQUE OF MICROFRACTURE FOR THE TREATMENT OF ARTICULAR CARTILAGE DEFECTS IN THE KNEE THOMAS J. GILL, MD, and JOHN D. MACGILLIVRAY, MD
The premise of the microfracture technique is to stimulate the underlying bone marrow and rely on the stereotyped vascular response to injury to heal a full-thickness defect in articular cartilage. Microfracture is indicated for both traumatic and degenerative lesions. The technique is useful for both unipolar and kissing (bipolar) lesions and in both the primary treatment and revision settings. There are no contraindications to the tectmique based on the size or location of the lesion. The technique has been shown to result in statistically significant improvement (P < .05) in pain, swelling, and functional testing. Patient satisfaction is high, and complications are low. The technique is cost effective and does not burn any bridges in regard to future surgery on the knee, if needed. A recent magnetic resonance imaging study of healing after the microfracture procedure showed variable rates of healing, although clinical results were good. Strict adherence to limited postoperative weight bearing and the use of continuous passive motion appear to be as important as the operative technique in obtaining optimal results after microfracture. KEY WORDS: microfracture, cartilage, technique, rehabilitation, results Copyright © 2001 by W.B. Saunders Company
The technique of microfracture was developed by Richard Steadman. ~4 The premise of the technique is to stimulate the underlying bone m a r r o w and rely on the stereotyped vascular response to injury to heal the full-thickness chondral defect, s Initially, full-thickness chondral defects caused by injury or drilling fill with blood and quickly organize into a fibrous clot. Blood cells and undifferentiated bone m a r r o w elements and platelets become trapped in the defect." Blood cells and undifferentiated cells modulate into fibroblasts, which produce a reparative granulation tissue. With progressive fibrosis, the defect forms a scar at 10 days, which becomes less vascular and more sclerotized. The fibrous tissue undergoes a progressive hyalinization and chondrification to produce a fibrocartilaginous mass that heals the defect. Microfracture is indicated for both traumatic and degenerative full-thickness chondral defects. ~-5 The technique is useful for both unipolar and kissing (bipolar) lesions and in both the primary treatment and revision settings. There are no contraindications to the technique based on the size or location of the lesion, although smaller (<400 mm2), acute (<12 weeks after injury) femoral and trochlear lesions have the most predictable results. Relative contraindications to microfracture include chondral defects greater
From the Department of Orthopedic Surgery, Massachusetts General
Hospital, Boston, MA, and Sports Medicine/Shoulder Service, The Hospital for Special Surgery, New York, NY. Address reprint requests to Thomas J. Gill, MD, Assistant Professor of Orthopedic Surgery, Harvard Medical School, Department of Orthopedic Surgery, Massachusetts General Hospital, WACC-508, 15 Parkman St, Boston, MA 02114. Copyright © 2001 by W.B. Saunders Company
1048-6666/01/1102-0011535.00/0 doi: 10.1053/otor.2001.21416
than 5 to 10 m m deep and the presence of a malalignment. 7
SURGICAL TECHNIQUE A routine, 10-point diagnostic arthroscopy is performed with careful attention to examination of the posterior aspects of the medial and lateral femoral condyles. If any surface changes are noted on the articular surfaces, a probe is used to assess the quality of the cartilage. Any unstable flaps are sharply debrided with an arthroscopic shaver or currette. Next, a currette is used to debride the calcified cartilage layer from the base of the full-thickness defect. A shaver is generally not used because it is difficult to control the a m o u n t of bone removed, and the subchondral bone is more likely to be violated. The importance of removing this calcified cartilage layer has been studied in horses by Frisbie et al. s Removal of tlle calcified cartilage layer greatly enhances the percentage of the defect that is filled. This is presumably because a better surface is provided for the superclot to adhere to and because improved chondral nutrition through subchondral diffusion is allowed. The calcified zone is separated from the tangential, transitional, and radial zones by the tidemark. In the immature animal, the basal layers of cartilage are partially nourished by diffusion from the vasculature of the subchondral bone. In the adult animal, little if any nutrient is able to diffuse across the tidemark because of heavy deposition of apatites in the calcified zone. 6'L~The calcified zone functions also act as an efficient barrier to cellular invasion. This explains w h y osteochondral allografts appear to be clinically immune privileged after transplantation, m Once the chondral defect has been adequately debrided, any associated intra-articular disease is addressed before
Operative Techniques in Orthopaedics, Vol 11, No 2 (April), 2001: pp 105-107
105
the microfracture is performed. A surgical awl (Linvatec, Largo, FL) is then used to make multiple small holes (microfractures) in the exposed bone of the chondral defect spaced 1 to 2 mm apart. Care is taken not to cormect the holes. The microfracture method is preferred because it creates less thermal injury than drilling, it is able to access difficult areas of the articular surface, and it provides a controlled depth penetration. On completion, a rough surface is generated for adherence of the ensuing blood clot containing the undifferentiated mesenchymal cells from the subchondral bone. The most peripheral aspects of the lesion must be penetrated by the awl to aid the healing of the repair tissue to the surrounding articular surface. Once the area has been microfractured, the arthroscopic pump is turned off. Marrow bleeding is observed flowing from the small holes and filling the defect.
POSTOPERATIVE REHABILITATION AFTER MICROFRACTURE The postoperative management after microfracture is perhaps as important as the surgical technique. 3.~ Unlike the typical rehabilitation after debridement and drilling procedures, patients are kept at protected weight-bearing for 6 to 8 weeks. Additionally, they are sent home with a continuous passive motion (CPM) machine for 8 weeks. ~1 If CPM is not available, they are instructed to perform a full-knee, passive range of motion (ROM) 1,500 times per day. Postoperative weight-bearing status depends on the location of the lesion. Patellar and trochlear groove lesions may be weight-bearing as tolerated in a hinged brace with a 30 ° flexion stop. This protects the lesions because the patella does not engage the trochlear groove until after 30 ° of flexion. Patients remove their brace when they are not weight-bearing. A CPM machine is used from 10° to 90 ° for at least 8 hours per day (generally at night). If a CPM machine is not available, patients are instructed to cycle their knee over the edge of a table 1,500 times per day. If the microfractured area is in the medial or lateral compartment, the patient is kept strictly touch-down weight-bearing (15% weight-bearing) with a CPM protocol similar to that used in patellofemoral lesions. The CPM machine is set at I cycle per minute, using the largest ROM that the patient finds comfortable. If the lesions are in non-weight-bearing regions of the compartments, weightbearing may begin as early as 6 weeks postoperatively, depending on the size of the affected area. After the 6- to 8-week period of protected weight-bearing, patients are instructed to begin active ROM exercises and progress to full weight-bearing. No cutting, twisting, or jumping sports are allowed until at least 4 months postoperatively.
RESULTS OF MICROFRACTURE FOR TRAUMATIC CHONDRAL DEFECTS The first study on the long-term results of microfracture for traumatic chondral defects was presented at the first
106
annual meeting of the International Cartilage Repair Society. 7 The study was performed at the Steadman Hawkins Sports Medicine Foundation, where the results of microfracture were reviewed in over 100 patients operated on by Steadman for a full-thickness chondral defect. The average follow-up was 6 years. Microfracture resulted in statistically significant reduction (P < .05) in pain, swelling, and all functional parameters studied. The ability to walk 2 miles and descend stairs showed significant improvement. There was also a significant improvement in the ability to perform activities of daily living, do strenuous work, and participate in strenuous sport. Of note, improvement in symptoms of pain and swelling continued to be observed until 2 years postoperatively. Maximum functional improvement was not achieved until 2 to 3 years postoperatively. 7 Eighty-six percent of patients rated their knee as feeling normal to nearly normal after their microfracture. Only 14% of patients had their level of sports participation reduced after microfracture. There was no statistically significant difference in the outcome of patellofemoral lesions, medial compartment lesions, and lateral compartment lesions. Larger lesions tended to have more pain at final follow-up than smaller lesions, though this was not statistically significant. Chondral defects treated within 3 months of injury had significantly less pain and better scores for their activities of daily living than defects treated more than 3 months from injury, regardless of lesion size. More recently, 1 of us (J.D.M.) reviewed the results of a microfracture for isolated chondral defects of the medial femoral condyle at The Hospital for Special Surgery, New York, NY. Nineteen patients were studied at a mean follow-up of 3 years. The mean size of the chondral defects was 3.2 cm 2. The calcified cartilage layer was not routinely debrided, and patients did not routinely use CPM or limited weight bearing for 6 weeks. Subjectively, 74% had minimal or no pain, and 63% rated their overall condition as good/excellent on the modified Cincinnati questionnaire. ~2 Objectively, 1 patient had swelling, and all patients had either mild or no crepitus on examination. Follow-up magnetic resonance imaging (MRI) was performed on all patients by using a special cartilage sequence to determine tile intensity and morphologic characteristics of the reparative fibrocartilage, bone edema, bony overgrowth, interface with the adjoining cartilage, percent fill of the defect, and appearance of the adjacent and opposing surfaces. Despite the good subjective results achieved, only 42% of the patients had 67% to 100% fill of the defect on MRI, 21% had 31% to 66% fill, and the remaining 37% only had 0% to 30% fill. There was no correlation between the size of the defect and the percent fill. Four patients had a smooth transition at the fibrocartilage/articular cartilage interface, whereas the other 15 had a fissure.
CONCLUSION The healing of articular cartilage requires a source of cells, provision of a matrix, removal of stress concentration, an intact subchondral plate, and some mechanical stimulaGILL AND MACGILLIVRAY
tion. ~3 The clinical results a n d s e c o n d - l o o k a r t h r o s c o p i e s in studies that h a v e recently been p r e s e n t e d confirm the d u r a b l e quality of the repair tissue g e n e r a t e d b y the microfracture technique. The variable a p p e a r a n c e of the repair tissue in the MR/ s t u d y at the Hospital for Special S u r g e r y m a y be c a u s e d b y i n c o m p l e t e r e m o v a l of the calcified cartilage d u r i n g the s u r g e r y , and m o r e i m p o r tantly, b y the lack of strict, restricted w e i g h t - b e a r i n g and CPM postoperatively. Five principal factors affect the quality of the cartilagin o u s repair tissue in a full-thickness c h o n d r a l defect treated b y microfracture: 1) d u r i n g the d e b r i d e m e n t , the calcified cartilage layer m u s t be r e m o v e d while care is taken n o t to a b r a d e the s u b c h o n d r a l bone; 2) the s u b c h o n dral b o n e m u s t be p e n e t r a t e d b y the awl with a 1 to 2 m m s p a c i n g of the holes to allow c o n n e c t i v e tissue to fill the defect a n d a d h e r e to the base of the defect; 3) p o s t o p e r a tive articular function m u s t be m a i n t a i n e d t h r o u g h early CPM; 4) strict, protected w e i g h t - b e a r i n g m u s t be enforced; a n d 5) a b n o r m a l m e c h a n i c a l axes s h o u l d be corrected, especially for d e g e n e r a t i v e lesions. These factors are essential for a high quality cartilaginous metaplasia to occur. The m i c r o f r a c t u r e tecl-mique is a cost effective, technically feasible, h i g h l y efficacious p r o c e d u r e available to all s u r g e o n s w h o p e r f o r m a r t h r o s c o p y of the knee. It is a reasonable first a p p r o a c h to the t r e a t m e n t of c h o n d r a l defects b e c a u s e it does not b u r n a n y bridges in r e g a r d to future p r o c e d u r e s , such as a m o s a i c p l a s t y or a u t o l o g o u s c h o n d r o c y t e transplantation, if the m i c r o f r a c t u r e fails. Recent studies s h o w the beneficial effect of g r o w t h factors, such as b o n e m o r p h o g e n e t i c protein (BMP), on the healing of c h o n d r a l defects. '4 O n e of us (T.J.G.) is s t u d y i n g the use of the b o n e m o r p h o g e n i c protein-2 in a p r i m a t e m o d e l a n d its effect on the quality of the repair tissue after the m i c r o f r a c t u r e technique. The use of such g r o w t h factors m a y p l a y a significant role in the future t r e a t m e n t of c h o n d r a l defects, particularly w h e n c o m b i n e d with a technique such as microfracture.
MICROFRACTURE FOR CHONDRAL DEFECTS
REFERENCES 1. Steadman JR, Rodkey WG, Briggs KK, et al: The microfracture technique in the management of complete cartilage defects in the knee joint. Orthopade 28:26-32, 1999 2. Steadman JR, Rodkey WG, Briggs KK, et al: The microfracture procedure: Rationale, technique, and clhlical observations for tile treatment of articular cartilage defects. J Sports Trauma 20:61-70, 1998 3. Steadman JR, Rodkey WG, Briggs KK, et al: The microfracture: Microfracture technique for full-thickness chondral defects: Technique and clinical results. Op Tech Orthop 7:300-304, 1997 4. Steadman JR, Rodkey WG, Briggs KK, et al: Microfracture procedure for treatment of full-thickness chondral defects: Technique, clinical resvlts and basic science status, in Harner CD, Vince KG, Fu FH, (eds): Techniques in Knee Surgery. Media, PA, Williams & Wilkins, 2000, pp 23-31 5. Gill TJ: The treatment of articular cartilage defects using microfracture and debridement. Am J Knee Surg 13:33-40, 2000 6. Mankin HI: The reaction of articular cartilage to iniury and osteoarthritis. N Engl J Med 291:1285-1292, 1974 7. Gill TJ, Steadman JR, Rodrigo JJ, et al: Indications and long-term clinical results of microfracture. Presented at the 2nd Symposium of the International Cartilage Repair Society, Boston, MA, November, 1998 8. Frisbie DD, Trotter GW, Powers BE, et al: Arthroscopic subchondral bone plate microfracture technique augments healing of large chondral defects in the radial carpal bone and medial femoral condyle of horses. Vet Surg 28:242-255, 1999 9. Mankin HJ: The articular cartilages: A review. AAOS Instr Course Lect, 19:204-224, 1970 10. Brown KLB, Cruess RL: Bone and cartilage transplantation in orthopaedic surgery. J Bone Joint Surg Am 64:270-279, 1982 11. Rodrigo J, Steadman JR: Improvement of hall-thickness chondral defect healing in the human knee after debridement and microfracture using continuous passive motion. Am J Knee Surg 7:109-116, 1994 12. Barber-Westin SD, Noyes FR, McCloskey JW: Rigorous statistical reliability, validity, and responsiveness testing of the Cincinnati Knee Rating System in 350 subjects with uninjured, injured, and anterior cruciate ligament-recontructed knees. Am J Sports Med 27:402-416, 1999 13. Rand JA: Arthroscopy and articular cartilage defects. Contemp Orthop 11:13-30, 1985 14. Sellers RS, Peluso D, Morris EA: The effect of recombinant human bone morphogenic protein-2 (rhBMP-2) on the healing of full-thickness defects of articular cartilage. J Bone Joint Surg Am 79:1452-1463, 1997
107
The premise of the microfracture technique is to stimulate the underlying bone marrow and rely on the stereotyped vascular response to injury to heal a full-thickness defect in articular cartilage. Microfracture is indicated for both traumatic and degenerative lesions. The technique is useful for both unipolar and kissing (bipolar) lesions and in both the primary treatment and revision settings. There are no contraindications to the tectmique based on the size or location of the lesion. The technique has been shown to result in statistically significant improvement (P < .05) in pain, swelling, and functional testing. Patient satisfaction is high, and complications are low. The technique is cost effective and does not burn any bridges in regard to future surgery on the knee, if needed. A recent magnetic resonance imaging study of healing after the microfracture procedure showed variable rates of healing, although clinical results were good. Strict adherence to limited postoperative weight bearing and the use of continuous passive motion appear to be as important as the operative technique in obtaining optimal results after microfracture. KEY WORDS: microfracture, cartilage, technique, rehabilitation, results Copyright © 2001 by W.B. Saunders Company
The technique of microfracture was developed by Richard Steadman. ~4 The premise of the technique is to stimulate the underlying bone m a r r o w and rely on the stereotyped vascular response to injury to heal the full-thickness chondral defect, s Initially, full-thickness chondral defects caused by injury or drilling fill with blood and quickly organize into a fibrous clot. Blood cells and undifferentiated bone m a r r o w elements and platelets become trapped in the defect." Blood cells and undifferentiated cells modulate into fibroblasts, which produce a reparative granulation tissue. With progressive fibrosis, the defect forms a scar at 10 days, which becomes less vascular and more sclerotized. The fibrous tissue undergoes a progressive hyalinization and chondrification to produce a fibrocartilaginous mass that heals the defect. Microfracture is indicated for both traumatic and degenerative full-thickness chondral defects. ~-5 The technique is useful for both unipolar and kissing (bipolar) lesions and in both the primary treatment and revision settings. There are no contraindications to the technique based on the size or location of the lesion, although smaller (<400 mm2), acute (<12 weeks after injury) femoral and trochlear lesions have the most predictable results. Relative contraindications to microfracture include chondral defects greater
From the Department of Orthopedic Surgery, Massachusetts General
Hospital, Boston, MA, and Sports Medicine/Shoulder Service, The Hospital for Special Surgery, New York, NY. Address reprint requests to Thomas J. Gill, MD, Assistant Professor of Orthopedic Surgery, Harvard Medical School, Department of Orthopedic Surgery, Massachusetts General Hospital, WACC-508, 15 Parkman St, Boston, MA 02114. Copyright © 2001 by W.B. Saunders Company
1048-6666/01/1102-0011535.00/0 doi: 10.1053/otor.2001.21416
than 5 to 10 m m deep and the presence of a malalignment. 7
SURGICAL TECHNIQUE A routine, 10-point diagnostic arthroscopy is performed with careful attention to examination of the posterior aspects of the medial and lateral femoral condyles. If any surface changes are noted on the articular surfaces, a probe is used to assess the quality of the cartilage. Any unstable flaps are sharply debrided with an arthroscopic shaver or currette. Next, a currette is used to debride the calcified cartilage layer from the base of the full-thickness defect. A shaver is generally not used because it is difficult to control the a m o u n t of bone removed, and the subchondral bone is more likely to be violated. The importance of removing this calcified cartilage layer has been studied in horses by Frisbie et al. s Removal of tlle calcified cartilage layer greatly enhances the percentage of the defect that is filled. This is presumably because a better surface is provided for the superclot to adhere to and because improved chondral nutrition through subchondral diffusion is allowed. The calcified zone is separated from the tangential, transitional, and radial zones by the tidemark. In the immature animal, the basal layers of cartilage are partially nourished by diffusion from the vasculature of the subchondral bone. In the adult animal, little if any nutrient is able to diffuse across the tidemark because of heavy deposition of apatites in the calcified zone. 6'L~The calcified zone functions also act as an efficient barrier to cellular invasion. This explains w h y osteochondral allografts appear to be clinically immune privileged after transplantation, m Once the chondral defect has been adequately debrided, any associated intra-articular disease is addressed before
Operative Techniques in Orthopaedics, Vol 11, No 2 (April), 2001: pp 105-107
105
the microfracture is performed. A surgical awl (Linvatec, Largo, FL) is then used to make multiple small holes (microfractures) in the exposed bone of the chondral defect spaced 1 to 2 mm apart. Care is taken not to cormect the holes. The microfracture method is preferred because it creates less thermal injury than drilling, it is able to access difficult areas of the articular surface, and it provides a controlled depth penetration. On completion, a rough surface is generated for adherence of the ensuing blood clot containing the undifferentiated mesenchymal cells from the subchondral bone. The most peripheral aspects of the lesion must be penetrated by the awl to aid the healing of the repair tissue to the surrounding articular surface. Once the area has been microfractured, the arthroscopic pump is turned off. Marrow bleeding is observed flowing from the small holes and filling the defect.
POSTOPERATIVE REHABILITATION AFTER MICROFRACTURE The postoperative management after microfracture is perhaps as important as the surgical technique. 3.~ Unlike the typical rehabilitation after debridement and drilling procedures, patients are kept at protected weight-bearing for 6 to 8 weeks. Additionally, they are sent home with a continuous passive motion (CPM) machine for 8 weeks. ~1 If CPM is not available, they are instructed to perform a full-knee, passive range of motion (ROM) 1,500 times per day. Postoperative weight-bearing status depends on the location of the lesion. Patellar and trochlear groove lesions may be weight-bearing as tolerated in a hinged brace with a 30 ° flexion stop. This protects the lesions because the patella does not engage the trochlear groove until after 30 ° of flexion. Patients remove their brace when they are not weight-bearing. A CPM machine is used from 10° to 90 ° for at least 8 hours per day (generally at night). If a CPM machine is not available, patients are instructed to cycle their knee over the edge of a table 1,500 times per day. If the microfractured area is in the medial or lateral compartment, the patient is kept strictly touch-down weight-bearing (15% weight-bearing) with a CPM protocol similar to that used in patellofemoral lesions. The CPM machine is set at I cycle per minute, using the largest ROM that the patient finds comfortable. If the lesions are in non-weight-bearing regions of the compartments, weightbearing may begin as early as 6 weeks postoperatively, depending on the size of the affected area. After the 6- to 8-week period of protected weight-bearing, patients are instructed to begin active ROM exercises and progress to full weight-bearing. No cutting, twisting, or jumping sports are allowed until at least 4 months postoperatively.
RESULTS OF MICROFRACTURE FOR TRAUMATIC CHONDRAL DEFECTS The first study on the long-term results of microfracture for traumatic chondral defects was presented at the first
106
annual meeting of the International Cartilage Repair Society. 7 The study was performed at the Steadman Hawkins Sports Medicine Foundation, where the results of microfracture were reviewed in over 100 patients operated on by Steadman for a full-thickness chondral defect. The average follow-up was 6 years. Microfracture resulted in statistically significant reduction (P < .05) in pain, swelling, and all functional parameters studied. The ability to walk 2 miles and descend stairs showed significant improvement. There was also a significant improvement in the ability to perform activities of daily living, do strenuous work, and participate in strenuous sport. Of note, improvement in symptoms of pain and swelling continued to be observed until 2 years postoperatively. Maximum functional improvement was not achieved until 2 to 3 years postoperatively. 7 Eighty-six percent of patients rated their knee as feeling normal to nearly normal after their microfracture. Only 14% of patients had their level of sports participation reduced after microfracture. There was no statistically significant difference in the outcome of patellofemoral lesions, medial compartment lesions, and lateral compartment lesions. Larger lesions tended to have more pain at final follow-up than smaller lesions, though this was not statistically significant. Chondral defects treated within 3 months of injury had significantly less pain and better scores for their activities of daily living than defects treated more than 3 months from injury, regardless of lesion size. More recently, 1 of us (J.D.M.) reviewed the results of a microfracture for isolated chondral defects of the medial femoral condyle at The Hospital for Special Surgery, New York, NY. Nineteen patients were studied at a mean follow-up of 3 years. The mean size of the chondral defects was 3.2 cm 2. The calcified cartilage layer was not routinely debrided, and patients did not routinely use CPM or limited weight bearing for 6 weeks. Subjectively, 74% had minimal or no pain, and 63% rated their overall condition as good/excellent on the modified Cincinnati questionnaire. ~2 Objectively, 1 patient had swelling, and all patients had either mild or no crepitus on examination. Follow-up magnetic resonance imaging (MRI) was performed on all patients by using a special cartilage sequence to determine tile intensity and morphologic characteristics of the reparative fibrocartilage, bone edema, bony overgrowth, interface with the adjoining cartilage, percent fill of the defect, and appearance of the adjacent and opposing surfaces. Despite the good subjective results achieved, only 42% of the patients had 67% to 100% fill of the defect on MRI, 21% had 31% to 66% fill, and the remaining 37% only had 0% to 30% fill. There was no correlation between the size of the defect and the percent fill. Four patients had a smooth transition at the fibrocartilage/articular cartilage interface, whereas the other 15 had a fissure.
CONCLUSION The healing of articular cartilage requires a source of cells, provision of a matrix, removal of stress concentration, an intact subchondral plate, and some mechanical stimulaGILL AND MACGILLIVRAY
tion. ~3 The clinical results a n d s e c o n d - l o o k a r t h r o s c o p i e s in studies that h a v e recently been p r e s e n t e d confirm the d u r a b l e quality of the repair tissue g e n e r a t e d b y the microfracture technique. The variable a p p e a r a n c e of the repair tissue in the MR/ s t u d y at the Hospital for Special S u r g e r y m a y be c a u s e d b y i n c o m p l e t e r e m o v a l of the calcified cartilage d u r i n g the s u r g e r y , and m o r e i m p o r tantly, b y the lack of strict, restricted w e i g h t - b e a r i n g and CPM postoperatively. Five principal factors affect the quality of the cartilagin o u s repair tissue in a full-thickness c h o n d r a l defect treated b y microfracture: 1) d u r i n g the d e b r i d e m e n t , the calcified cartilage layer m u s t be r e m o v e d while care is taken n o t to a b r a d e the s u b c h o n d r a l bone; 2) the s u b c h o n dral b o n e m u s t be p e n e t r a t e d b y the awl with a 1 to 2 m m s p a c i n g of the holes to allow c o n n e c t i v e tissue to fill the defect a n d a d h e r e to the base of the defect; 3) p o s t o p e r a tive articular function m u s t be m a i n t a i n e d t h r o u g h early CPM; 4) strict, protected w e i g h t - b e a r i n g m u s t be enforced; a n d 5) a b n o r m a l m e c h a n i c a l axes s h o u l d be corrected, especially for d e g e n e r a t i v e lesions. These factors are essential for a high quality cartilaginous metaplasia to occur. The m i c r o f r a c t u r e tecl-mique is a cost effective, technically feasible, h i g h l y efficacious p r o c e d u r e available to all s u r g e o n s w h o p e r f o r m a r t h r o s c o p y of the knee. It is a reasonable first a p p r o a c h to the t r e a t m e n t of c h o n d r a l defects b e c a u s e it does not b u r n a n y bridges in r e g a r d to future p r o c e d u r e s , such as a m o s a i c p l a s t y or a u t o l o g o u s c h o n d r o c y t e transplantation, if the m i c r o f r a c t u r e fails. Recent studies s h o w the beneficial effect of g r o w t h factors, such as b o n e m o r p h o g e n e t i c protein (BMP), on the healing of c h o n d r a l defects. '4 O n e of us (T.J.G.) is s t u d y i n g the use of the b o n e m o r p h o g e n i c protein-2 in a p r i m a t e m o d e l a n d its effect on the quality of the repair tissue after the m i c r o f r a c t u r e technique. The use of such g r o w t h factors m a y p l a y a significant role in the future t r e a t m e n t of c h o n d r a l defects, particularly w h e n c o m b i n e d with a technique such as microfracture.
MICROFRACTURE FOR CHONDRAL DEFECTS
REFERENCES 1. Steadman JR, Rodkey WG, Briggs KK, et al: The microfracture technique in the management of complete cartilage defects in the knee joint. Orthopade 28:26-32, 1999 2. Steadman JR, Rodkey WG, Briggs KK, et al: The microfracture procedure: Rationale, technique, and clhlical observations for tile treatment of articular cartilage defects. J Sports Trauma 20:61-70, 1998 3. Steadman JR, Rodkey WG, Briggs KK, et al: The microfracture: Microfracture technique for full-thickness chondral defects: Technique and clinical results. Op Tech Orthop 7:300-304, 1997 4. Steadman JR, Rodkey WG, Briggs KK, et al: Microfracture procedure for treatment of full-thickness chondral defects: Technique, clinical resvlts and basic science status, in Harner CD, Vince KG, Fu FH, (eds): Techniques in Knee Surgery. Media, PA, Williams & Wilkins, 2000, pp 23-31 5. Gill TJ: The treatment of articular cartilage defects using microfracture and debridement. Am J Knee Surg 13:33-40, 2000 6. Mankin HI: The reaction of articular cartilage to iniury and osteoarthritis. N Engl J Med 291:1285-1292, 1974 7. Gill TJ, Steadman JR, Rodrigo JJ, et al: Indications and long-term clinical results of microfracture. Presented at the 2nd Symposium of the International Cartilage Repair Society, Boston, MA, November, 1998 8. Frisbie DD, Trotter GW, Powers BE, et al: Arthroscopic subchondral bone plate microfracture technique augments healing of large chondral defects in the radial carpal bone and medial femoral condyle of horses. Vet Surg 28:242-255, 1999 9. Mankin HJ: The articular cartilages: A review. AAOS Instr Course Lect, 19:204-224, 1970 10. Brown KLB, Cruess RL: Bone and cartilage transplantation in orthopaedic surgery. J Bone Joint Surg Am 64:270-279, 1982 11. Rodrigo J, Steadman JR: Improvement of hall-thickness chondral defect healing in the human knee after debridement and microfracture using continuous passive motion. Am J Knee Surg 7:109-116, 1994 12. Barber-Westin SD, Noyes FR, McCloskey JW: Rigorous statistical reliability, validity, and responsiveness testing of the Cincinnati Knee Rating System in 350 subjects with uninjured, injured, and anterior cruciate ligament-recontructed knees. Am J Sports Med 27:402-416, 1999 13. Rand JA: Arthroscopy and articular cartilage defects. Contemp Orthop 11:13-30, 1985 14. Sellers RS, Peluso D, Morris EA: The effect of recombinant human bone morphogenic protein-2 (rhBMP-2) on the healing of full-thickness defects of articular cartilage. J Bone Joint Surg Am 79:1452-1463, 1997
107