- Email: [email protected]
Cystic degeneration of the patella after arthroscopic chondroplasty and subchondral bone perforation
Arthroscopy:
The Journal of Arthroscopic
and Related Surgery
8(3):36tL369
Published by Raven Press, Ltd. 0 1992Arthroscopy Association of North America
Case Report
Cystic Degeneration of the Patella After Arthroscopic Chondroplasty and Subchondral Bone Perforation Marc T. Galloway,
M.D. and Frank R. Noyes, M.D.
Summary: Chondromalacia of the patella is frequently encountered in patients with anterior knee pain. Arthroscopic chondroplasty with perforation of subchondral bone remains a popular treatment alternative in spite of the inferior mechanical properties of the fibrocartilaginous tissue that this procedure is designed to promote. We report a case of cystic degeneration of the patella as a previously unrecognized complication following the procedure. Key Words: Chondromalacia-Chondroplasty-Cystic degeneration.
3,9), multiple operative procedures have been described for these disorders (14,7,1&15). Presently, chondroplasty with drilling of the subchondral bone is a popular treatment for moderate-to-severe chondromalacia. Although commonly practiced, few complications have been reported following this procedure. We present findings that we believe were direct results of subchondral bone perforation and that represent a previously unrecognized complication of this treatment.
The term “patellar chondromalacia” is commonly used to describe a variety of pathologies that cause the breakdown of patella articular cartilage and result in anterior knee pain. The etiology is highly variable and can range from mechanical malalignment to direct trauma involving the joint surface and underlying bone (l-4). Factors important in the progression of articular cartilage lesions have been well described and reflect both the mechanism and the extent of the initial injury (5). Superficial articular cartilage lacerations have been shown to remain stable, whereas those penetrating the subchondral bone undergo a limited repair response (5). Lesions that arise following severe blunt trauma or are presumably the result of sustained pressure overload have been observed to proceed through a series of well-defined structural alterations (1,2,5,6). The earliest changes are apparent cartilage softening followed by progressive fibrillation and eventual eburnation and destruction of subchondral bone (1,5,7,8). Although the majority of patients with chondromalacia respond to conservative management (l-
CASE REPORT A 30-year-old part-time policeman and crane operator presented with a 9 year history of anterior right knee aching that occurred after prolonged standing and kneeling. The patient recalled no injuries and denied effusion as well as “giving way” or locking episodes. He tolerated his symptoms for 2 years. Then, attempting to pivot, he experienced the immediate onset of severe anterior knee pain. He was treated with antiinflammatory agents without success and 2 months later underwent an arthroscopic plica excision and limited synovectomy. The patient presented to us 2 months later with continuation of his anterior knee pain. In addition, he had developed an activity-related effusion. During this physical examination we noted retropatella and medial and lateral retinacular tenderness with
From the Yale Sports Medicine Center (M.T.G.), New Haven, Connecticut, and Cincinnati Sportsmedicine (F.R.N.), Deaconess Hospital, Cincinnati, Ohio, U.S.A. Address correspondence and reprint requests to Dr. Frank R. Noyes, Deaconess Hospital, 311 Straight Street, Cincinnati, OH 45219, U.S.A.
366
CYSTIC DEGENERATION
367
OF THE PATELLA
mild retropatella crepitus. The Q angle was 20” and the patella could be subluxated laterally 25%. The apprehension sign was absent. Radiographs were normal. Figure 1 shows a lateral view of the knee. The patient was treated with physical therapy and antiinflammatory agents without success and required a second arthroscopy 2 years later for persistent symptoms. At this surgery, a focal area of softening of the lateral facet of the patella was identified and drilled. In addition, a small tear of the posterior horn of the medial meniscus was identified and resected. The patient’s symptoms of anterior knee pain improved and he returned to work, although he continued to have persistent aching after prolonged standing. The patient was next seen 5 years later, when he presented with new complaints of medial right knee pain and locking. The physical examination revealed moderate patellofemoral crepitus and mild retropatella tenderness. Exquisite medial joint line pain was present and McMurray test results were positive. Radiographs revealed a large cyst that involved the lateral facet of the patella (Fig. 1). Arthroscopy was performed for a presumed medial meniscal tear and for biopsy of the cyst. Operative findings At surgery, a 5 x 5 mm area of articular cartilage fissuring was present over the lateral facet. One cleft extended to the underlying bone. In general, it was not believed that the articular cartilage lesions had progressed from those changes noted at the patient’s previous arthroscopy. No eburnated bone was visualized and no communication of the cyst with the joint was observed. A tear of the posterior horn of the medial meniscus was also confirmed and a partial medial meniscectomy was performed.
FIG. 1. Lateral radiograph of the knee. Initial presentation (left). Five years after subchondral drilling (right).
FIG. 2. Intraoperative photograph demonstrating tion of interosseous cyst with the joint.
communica-
The cyst was exposed through a lateral incision. After opening the defect, we saw a clear, yellow mutinous material. The thin, fibrous lining of the cavity was curretted away revealing the three previously placed drill holes that communicated with the joint cavity through the clefts in the cartilage (Fig. 2). The lesion was packed with iliac crest bone graft following which the pre-patellar retinaculum was closed. The patient experienced no postoperative complications and returned to work 6 weeks after the surgery. One year following the procedure he continues to have occasional aching but notes overall improvement in his symptoms. Pathology Histology demonstrated that the cyst lining was made up of fibrous tissue amid areas of necrotic trabecular bone, and chronic inflammatory cells (Fig. 3). In addition, areas of mutinous degeneration and cartilaginous metaplasia were present in
Arthroscopy,
Vol. 8. No. 3, 1992
368
M. T. GALLOWAY
AND F. R. NOYES
FIG. 3. Photomicrograph. The cyst lining was composed of fibrous tissue amid areas of necrotic bone, hemorrhage, and cartilage.
the biopsy. These findings were believed to be consistent with a degenerative bone cyst. No evidence of hemosiderin deposits, nodular proliferations, or giant cells was present.
DISCUSSION Although the majority of this patient’s symptoms were caused by the meniscal tear, the incidental finding of a degenerative cyst 5 years after subchondral drilling represents a rare complication of the procedure. The differential diagnosis of these lesions includes aneurysmal bone cyst, inflammatory arthritis, unicameral bone cyst, pigmented villonodular synovitis, intraosseous ganglion, chondroblastoma, giant cell tumor, and degenerative cyst secondary to osteoarthritis (16). Resnick has emphasized the importance of excluding calcium pyrophosphate dihydrate deposition disease and hyperparathyroidism in patients who present isolated cystic changes of the patella (17,18). The histologic diagnosis in this patient is most consistent with a degenerative bone cyst, although the gross and histologic appearance of an intraosseous ganglion is quite similar. Feldman has suggested that degenerative bone cysts are distinct from intraosseous ganglia (19); communication with the joint and concurrent arthritis, although commonly observed in patients with degenerative cysts, Arthroscopy,
Vol. 8, No. 3. 1992
are rare in patients with interosseous ganglia (19). Moreover, intraosseous ganglia more often arise in the metaphyses of long bones and are seldom present in weight-bearing areas. Others agree that macroscopic communication of the cyst with the joint as well as the presence of necrotic bone or cartilage within the cyst suggest the diagnosis of degenerative bone cyst (20-22). Clinically, the distinction is probably unimportant. Treatment is related to the overall condition of the joint (presence or absence of arthritis) and in appropriate circumstances both intraosseous ganglia and degenerative bone cysts respond to curettage and bone grafting (21,23-25). Disagreement exists in the literature regarding the etiology of degenerative bone cysts. Rhaney and Lamb proposed that the insult is traumatic, resulting in osteonecrosis and eventual replacement by fibrous tissue (26). Ondrouch supported this proposal, and used a photoelastic model to demonstrate stress patterns in femoral heads similar in shape and distribution to observed subchondral cysts (27). Milgram, after studying >500 femoral heads, also supported this view. He believed that cysts formed from myxomatous cell proliferation within cancellous bone, and that joint communication was a late manifestation (28). Landells reported 2 patients who developed intraosseous cysts after trauma, and suggested that synovial fluid intrusion into the marrow space was
CYSTIC DEGENERATION responsible. To support this etiology, he cited the intraarticular communication of the cysts through clefts in articular cartilage, the absence of osteoelastic activity, and the flask-like contour of cysts (29). Resnick has demonstrated evidence supporting synovial fluid infusion and osteonecrosis as etiologies for degenerative bone cysts (30). In his study of 40 femoral heads, he found cysts arising deep in bone without joint communication as well those having direct intraarticular communication and containing articular cartilage (30). Solitary cysts of the patella are rare in unicompartmental patellofemoral disease. Stougard, in an autopsy study of 59 patients (118 knees), found evidence of chondromalacia in 90%. Of these, < 10% demonstrated bony changes, and cysts were only observed in aged patients (31). We believe that the development of a subchondral cyst in our patient represents a complication of subchondral bone perforation. The direct communication of the cyst to the joint space through the previously placed drill holes supports this view and suggests infusion of the synovial fluid as the pathoetiologic factor. Although we could argue that the cyst was a natural sequel of the patient’s arthritis, the lack of progression of articular cartilage changes, size of the cyst, and lack of associated cysts make this view less tenable. Arthroscopic chondroplasty with perforation of the subchondral bone remains a popular operative approach to patellar chondromalacia despite the inferior mechanical properties of the fibrocartilage this technique seeks to promote. This case represents a previously unrecognized complication of this procedure. REFERENCES 1. Bentley G. The surgical treatment of chondromalacia patella. J Bone Join? Surg 1978;60:74-81. 2. Bentley G, Dowd G. Current concepts in etiology and treatment of chondromalacia patella. Chin Orthop 1983;189:20928. 3. Install J. Chondromalacia patella: patella malalignment syndrome. Orthop Clin North Am 1979;10:117-27. 4. Vuorinen OP, Paakkala T, Tunturi T, et al. Chondromalacia patella results of operative treatment. Arch Orthop Trauma Surg 1985;104:175-81. 5. Mankin HG. The response of articular cartilage to mechanical injury. J Bone Joint Surg 1982;64:460-6. 6. Outerbridge RE, Dunlap JAY. The problem of chondromalacia patellae. C/in Orthop 1975;llO: 177-96.
OF THE PATELLA
369
7. Goodfellow J, Hungerford DS, Woods C. Patellofemoral joint mechanics and pathology. J Bone Joint Surg 1976;58: 291-9. 8. McBeath AA. The patellofemoral joint. In: Evarts CM, ed. Surgery of the musculoskeletal system; vol 4. 2nd ed. New York: Churchill Livingstone, 1990:3454. 9. DeHaven KE, Dorlin WA, Mayer PJ. Chondromalacia patella in athletes. Am J Sports Med 1979;7:5-11. 10. Childers JC. Elwood SC. Partial chrondrectomv and subchondral bone drilling for chondromalacia. C’iin Orrhop 1979;144:114-20. 11. Christenson F, Soballe K, Snerum L. Treatment of chrondromalacia patella by lateral retinacular release of the patella. Clin OrthoD 1988:234: 145-7. 12. Edwards DH, Bkntley G. Osteochondritis dessecans patellae. J Bone Joint Surg 1977;59:58-63. 13. Ferguson AB. Elevation of the insertion of the patella ligament for patellofemoral pain. J Bone Joint Surg 1982;64: 766-7 1. 14. Jenson TB, Hansen LB. Patellectomy for chondromalacia. Acta Orthop Stand 1989;16:17-19. 15. Steurer PA, Gradisar IA. Hoyt WA, Chu M. Patellectomy. A clinical study and biomechanical evaluation. C/in Orthop 1979;144:84-90. 16. Wientroub S. Salama R, Baratz M, Papo I. Unicameral bone cyst of the patella. C/in Orihop 1979;140: 159-61. 17. Resnick D. [Letter]. J Bone Joint Surg 1982;633. 18. Resnick D, Niwayama G, Goergen TG, Utsinger PD, Shapiro RF. Hasselwood DM, Wiesner KB. Clinical, radiographic and pathologic abnormalities in calcium pyrophosphate dihydrate deposition disease: pseudogout. Radiology 1977;122:1. 19. Feldman F, Johnson A. Intraosseous ganglian. AJR Am J Roenrgenol 1973;118:328-43. 20. Kambolis C. Bulloguh PG, Jaffe HL. Ganglianic cystic defects of bone. J Bone Joint Sum 1973:55:49&505. 21. Schajowicz F, Finz MC, Slulliiel JA. Juxta-articular bone cyst (intra-osseous ganglia). A clinicopathological study of 88 cases. J Bone Joint Surg 1979;61:107-16. 22. Willems D. Mulier JC, Martens M, Verhelst M. Ganglian cyst of bone. Report of two cases and review of the literature. Acta Orthop Stand 1973;44:655-62. 23. Carter TE. Detenbeck LC. Intraosseous ganglian cysts of the patella: report of a case. Tex Med 1974;70:95-6. 24. Crane AR, Scarano JJ. Synovial cysts (ganglia) of bone. Report of two cases. J Bone Joint Surg 1967;49:355-61. 25. Hicks JD. Synovial cysts in bone. Ausf N 2 J Surg 1956;26: 138-43. 26. Rhaney K, Lamb DW. The cyst of osteoarthritis of the hip. A radiological and pathological study. J Bone Joint Surg 1955;37:663. 27. Ondrouch AS. Cyst formation and osteoarthritis. J Bone Joint Surg 1963;45:755. 28. Milgram JW. Morphologic alterations of the subchondral bone in advanced degenerative arthritis. Clin Orthop 1983; 173:293-312. 29. Landells JW. The bone cysts of osteoarthritis. J Bone Joint Surg 1953;35:643. 30. Resnick D. Niwayama G. Degenerative disease of extraspinal locations. In: Diagnosis-of bone and joint disorders; vol 3; 2nd ed. Philadelphia: WB Saunders, 1988: 1365-1479. 31. Stougard J. Chondramalacia of the patella-incidence, macroscopical and radiological findings at autopsy. Acra Orthop Stand 1975;46:809.
Arthroscopy. Vol. 8, No. 3, 1992
The Journal of Arthroscopic
and Related Surgery
8(3):36tL369
Published by Raven Press, Ltd. 0 1992Arthroscopy Association of North America
Case Report
Cystic Degeneration of the Patella After Arthroscopic Chondroplasty and Subchondral Bone Perforation Marc T. Galloway,
M.D. and Frank R. Noyes, M.D.
Summary: Chondromalacia of the patella is frequently encountered in patients with anterior knee pain. Arthroscopic chondroplasty with perforation of subchondral bone remains a popular treatment alternative in spite of the inferior mechanical properties of the fibrocartilaginous tissue that this procedure is designed to promote. We report a case of cystic degeneration of the patella as a previously unrecognized complication following the procedure. Key Words: Chondromalacia-Chondroplasty-Cystic degeneration.
3,9), multiple operative procedures have been described for these disorders (14,7,1&15). Presently, chondroplasty with drilling of the subchondral bone is a popular treatment for moderate-to-severe chondromalacia. Although commonly practiced, few complications have been reported following this procedure. We present findings that we believe were direct results of subchondral bone perforation and that represent a previously unrecognized complication of this treatment.
The term “patellar chondromalacia” is commonly used to describe a variety of pathologies that cause the breakdown of patella articular cartilage and result in anterior knee pain. The etiology is highly variable and can range from mechanical malalignment to direct trauma involving the joint surface and underlying bone (l-4). Factors important in the progression of articular cartilage lesions have been well described and reflect both the mechanism and the extent of the initial injury (5). Superficial articular cartilage lacerations have been shown to remain stable, whereas those penetrating the subchondral bone undergo a limited repair response (5). Lesions that arise following severe blunt trauma or are presumably the result of sustained pressure overload have been observed to proceed through a series of well-defined structural alterations (1,2,5,6). The earliest changes are apparent cartilage softening followed by progressive fibrillation and eventual eburnation and destruction of subchondral bone (1,5,7,8). Although the majority of patients with chondromalacia respond to conservative management (l-
CASE REPORT A 30-year-old part-time policeman and crane operator presented with a 9 year history of anterior right knee aching that occurred after prolonged standing and kneeling. The patient recalled no injuries and denied effusion as well as “giving way” or locking episodes. He tolerated his symptoms for 2 years. Then, attempting to pivot, he experienced the immediate onset of severe anterior knee pain. He was treated with antiinflammatory agents without success and 2 months later underwent an arthroscopic plica excision and limited synovectomy. The patient presented to us 2 months later with continuation of his anterior knee pain. In addition, he had developed an activity-related effusion. During this physical examination we noted retropatella and medial and lateral retinacular tenderness with
From the Yale Sports Medicine Center (M.T.G.), New Haven, Connecticut, and Cincinnati Sportsmedicine (F.R.N.), Deaconess Hospital, Cincinnati, Ohio, U.S.A. Address correspondence and reprint requests to Dr. Frank R. Noyes, Deaconess Hospital, 311 Straight Street, Cincinnati, OH 45219, U.S.A.
366
CYSTIC DEGENERATION
367
OF THE PATELLA
mild retropatella crepitus. The Q angle was 20” and the patella could be subluxated laterally 25%. The apprehension sign was absent. Radiographs were normal. Figure 1 shows a lateral view of the knee. The patient was treated with physical therapy and antiinflammatory agents without success and required a second arthroscopy 2 years later for persistent symptoms. At this surgery, a focal area of softening of the lateral facet of the patella was identified and drilled. In addition, a small tear of the posterior horn of the medial meniscus was identified and resected. The patient’s symptoms of anterior knee pain improved and he returned to work, although he continued to have persistent aching after prolonged standing. The patient was next seen 5 years later, when he presented with new complaints of medial right knee pain and locking. The physical examination revealed moderate patellofemoral crepitus and mild retropatella tenderness. Exquisite medial joint line pain was present and McMurray test results were positive. Radiographs revealed a large cyst that involved the lateral facet of the patella (Fig. 1). Arthroscopy was performed for a presumed medial meniscal tear and for biopsy of the cyst. Operative findings At surgery, a 5 x 5 mm area of articular cartilage fissuring was present over the lateral facet. One cleft extended to the underlying bone. In general, it was not believed that the articular cartilage lesions had progressed from those changes noted at the patient’s previous arthroscopy. No eburnated bone was visualized and no communication of the cyst with the joint was observed. A tear of the posterior horn of the medial meniscus was also confirmed and a partial medial meniscectomy was performed.
FIG. 1. Lateral radiograph of the knee. Initial presentation (left). Five years after subchondral drilling (right).
FIG. 2. Intraoperative photograph demonstrating tion of interosseous cyst with the joint.
communica-
The cyst was exposed through a lateral incision. After opening the defect, we saw a clear, yellow mutinous material. The thin, fibrous lining of the cavity was curretted away revealing the three previously placed drill holes that communicated with the joint cavity through the clefts in the cartilage (Fig. 2). The lesion was packed with iliac crest bone graft following which the pre-patellar retinaculum was closed. The patient experienced no postoperative complications and returned to work 6 weeks after the surgery. One year following the procedure he continues to have occasional aching but notes overall improvement in his symptoms. Pathology Histology demonstrated that the cyst lining was made up of fibrous tissue amid areas of necrotic trabecular bone, and chronic inflammatory cells (Fig. 3). In addition, areas of mutinous degeneration and cartilaginous metaplasia were present in
Arthroscopy,
Vol. 8. No. 3, 1992
368
M. T. GALLOWAY
AND F. R. NOYES
FIG. 3. Photomicrograph. The cyst lining was composed of fibrous tissue amid areas of necrotic bone, hemorrhage, and cartilage.
the biopsy. These findings were believed to be consistent with a degenerative bone cyst. No evidence of hemosiderin deposits, nodular proliferations, or giant cells was present.
DISCUSSION Although the majority of this patient’s symptoms were caused by the meniscal tear, the incidental finding of a degenerative cyst 5 years after subchondral drilling represents a rare complication of the procedure. The differential diagnosis of these lesions includes aneurysmal bone cyst, inflammatory arthritis, unicameral bone cyst, pigmented villonodular synovitis, intraosseous ganglion, chondroblastoma, giant cell tumor, and degenerative cyst secondary to osteoarthritis (16). Resnick has emphasized the importance of excluding calcium pyrophosphate dihydrate deposition disease and hyperparathyroidism in patients who present isolated cystic changes of the patella (17,18). The histologic diagnosis in this patient is most consistent with a degenerative bone cyst, although the gross and histologic appearance of an intraosseous ganglion is quite similar. Feldman has suggested that degenerative bone cysts are distinct from intraosseous ganglia (19); communication with the joint and concurrent arthritis, although commonly observed in patients with degenerative cysts, Arthroscopy,
Vol. 8, No. 3. 1992
are rare in patients with interosseous ganglia (19). Moreover, intraosseous ganglia more often arise in the metaphyses of long bones and are seldom present in weight-bearing areas. Others agree that macroscopic communication of the cyst with the joint as well as the presence of necrotic bone or cartilage within the cyst suggest the diagnosis of degenerative bone cyst (20-22). Clinically, the distinction is probably unimportant. Treatment is related to the overall condition of the joint (presence or absence of arthritis) and in appropriate circumstances both intraosseous ganglia and degenerative bone cysts respond to curettage and bone grafting (21,23-25). Disagreement exists in the literature regarding the etiology of degenerative bone cysts. Rhaney and Lamb proposed that the insult is traumatic, resulting in osteonecrosis and eventual replacement by fibrous tissue (26). Ondrouch supported this proposal, and used a photoelastic model to demonstrate stress patterns in femoral heads similar in shape and distribution to observed subchondral cysts (27). Milgram, after studying >500 femoral heads, also supported this view. He believed that cysts formed from myxomatous cell proliferation within cancellous bone, and that joint communication was a late manifestation (28). Landells reported 2 patients who developed intraosseous cysts after trauma, and suggested that synovial fluid intrusion into the marrow space was
CYSTIC DEGENERATION responsible. To support this etiology, he cited the intraarticular communication of the cysts through clefts in articular cartilage, the absence of osteoelastic activity, and the flask-like contour of cysts (29). Resnick has demonstrated evidence supporting synovial fluid infusion and osteonecrosis as etiologies for degenerative bone cysts (30). In his study of 40 femoral heads, he found cysts arising deep in bone without joint communication as well those having direct intraarticular communication and containing articular cartilage (30). Solitary cysts of the patella are rare in unicompartmental patellofemoral disease. Stougard, in an autopsy study of 59 patients (118 knees), found evidence of chondromalacia in 90%. Of these, < 10% demonstrated bony changes, and cysts were only observed in aged patients (31). We believe that the development of a subchondral cyst in our patient represents a complication of subchondral bone perforation. The direct communication of the cyst to the joint space through the previously placed drill holes supports this view and suggests infusion of the synovial fluid as the pathoetiologic factor. Although we could argue that the cyst was a natural sequel of the patient’s arthritis, the lack of progression of articular cartilage changes, size of the cyst, and lack of associated cysts make this view less tenable. Arthroscopic chondroplasty with perforation of the subchondral bone remains a popular operative approach to patellar chondromalacia despite the inferior mechanical properties of the fibrocartilage this technique seeks to promote. This case represents a previously unrecognized complication of this procedure. REFERENCES 1. Bentley G. The surgical treatment of chondromalacia patella. J Bone Join? Surg 1978;60:74-81. 2. Bentley G, Dowd G. Current concepts in etiology and treatment of chondromalacia patella. Chin Orthop 1983;189:20928. 3. Install J. Chondromalacia patella: patella malalignment syndrome. Orthop Clin North Am 1979;10:117-27. 4. Vuorinen OP, Paakkala T, Tunturi T, et al. Chondromalacia patella results of operative treatment. Arch Orthop Trauma Surg 1985;104:175-81. 5. Mankin HG. The response of articular cartilage to mechanical injury. J Bone Joint Surg 1982;64:460-6. 6. Outerbridge RE, Dunlap JAY. The problem of chondromalacia patellae. C/in Orthop 1975;llO: 177-96.
OF THE PATELLA
369
7. Goodfellow J, Hungerford DS, Woods C. Patellofemoral joint mechanics and pathology. J Bone Joint Surg 1976;58: 291-9. 8. McBeath AA. The patellofemoral joint. In: Evarts CM, ed. Surgery of the musculoskeletal system; vol 4. 2nd ed. New York: Churchill Livingstone, 1990:3454. 9. DeHaven KE, Dorlin WA, Mayer PJ. Chondromalacia patella in athletes. Am J Sports Med 1979;7:5-11. 10. Childers JC. Elwood SC. Partial chrondrectomv and subchondral bone drilling for chondromalacia. C’iin Orrhop 1979;144:114-20. 11. Christenson F, Soballe K, Snerum L. Treatment of chrondromalacia patella by lateral retinacular release of the patella. Clin OrthoD 1988:234: 145-7. 12. Edwards DH, Bkntley G. Osteochondritis dessecans patellae. J Bone Joint Surg 1977;59:58-63. 13. Ferguson AB. Elevation of the insertion of the patella ligament for patellofemoral pain. J Bone Joint Surg 1982;64: 766-7 1. 14. Jenson TB, Hansen LB. Patellectomy for chondromalacia. Acta Orthop Stand 1989;16:17-19. 15. Steurer PA, Gradisar IA. Hoyt WA, Chu M. Patellectomy. A clinical study and biomechanical evaluation. C/in Orthop 1979;144:84-90. 16. Wientroub S. Salama R, Baratz M, Papo I. Unicameral bone cyst of the patella. C/in Orihop 1979;140: 159-61. 17. Resnick D. [Letter]. J Bone Joint Surg 1982;633. 18. Resnick D, Niwayama G, Goergen TG, Utsinger PD, Shapiro RF. Hasselwood DM, Wiesner KB. Clinical, radiographic and pathologic abnormalities in calcium pyrophosphate dihydrate deposition disease: pseudogout. Radiology 1977;122:1. 19. Feldman F, Johnson A. Intraosseous ganglian. AJR Am J Roenrgenol 1973;118:328-43. 20. Kambolis C. Bulloguh PG, Jaffe HL. Ganglianic cystic defects of bone. J Bone Joint Sum 1973:55:49&505. 21. Schajowicz F, Finz MC, Slulliiel JA. Juxta-articular bone cyst (intra-osseous ganglia). A clinicopathological study of 88 cases. J Bone Joint Surg 1979;61:107-16. 22. Willems D. Mulier JC, Martens M, Verhelst M. Ganglian cyst of bone. Report of two cases and review of the literature. Acta Orthop Stand 1973;44:655-62. 23. Carter TE. Detenbeck LC. Intraosseous ganglian cysts of the patella: report of a case. Tex Med 1974;70:95-6. 24. Crane AR, Scarano JJ. Synovial cysts (ganglia) of bone. Report of two cases. J Bone Joint Surg 1967;49:355-61. 25. Hicks JD. Synovial cysts in bone. Ausf N 2 J Surg 1956;26: 138-43. 26. Rhaney K, Lamb DW. The cyst of osteoarthritis of the hip. A radiological and pathological study. J Bone Joint Surg 1955;37:663. 27. Ondrouch AS. Cyst formation and osteoarthritis. J Bone Joint Surg 1963;45:755. 28. Milgram JW. Morphologic alterations of the subchondral bone in advanced degenerative arthritis. Clin Orthop 1983; 173:293-312. 29. Landells JW. The bone cysts of osteoarthritis. J Bone Joint Surg 1953;35:643. 30. Resnick D. Niwayama G. Degenerative disease of extraspinal locations. In: Diagnosis-of bone and joint disorders; vol 3; 2nd ed. Philadelphia: WB Saunders, 1988: 1365-1479. 31. Stougard J. Chondramalacia of the patella-incidence, macroscopical and radiological findings at autopsy. Acra Orthop Stand 1975;46:809.
Arthroscopy. Vol. 8, No. 3, 1992