Anterior Cruciate Ligament and Synovial Tophi Deposition Causes Knee Locking

Transcription

1 DOI / Case Report Anterior Cruciate Ligament and Synovial Tophi Deposition Causes Knee Locking Che-Wei Liu Hsin-Pu Hsieh Chin-Yu Chen Hsi-Ting Lin,* Knee locking is a condition in which the knee cannot be extended completely, primarily because of intraarticular mechanical blockage. The most common cause of blockage is meniscal lesions, particularly, the bucket-handle lesion. [] Gouty arthritis is a metabolic disorder characterized by elevated urate and urate monohydrate crystal deposition in the serum. The crystals are responsible for causing a hot and swollen knee during an acute gouty attack. We report a case of gouty arthritis of the knee in which tophi deposition over ACL caused mechanical knee blockage. In the case of progressive knee locking with a history of gouty arthritis, MRI may be helpful to rule out other knee-locking factors, such as meniscal and ACL. However, direct visualization of the intraarticular anatomy of the organ may be more direct in ruling out and treating the underlying causes of mechanical blockage. Key words: Gout, Knee locking, Tophi deposition INTRODUCTION Knee locking is a condition in which the knee cannot be extended completely, primarily because of intraarticular mechanical blockage. The most common cause of blockage is meniscal lesions, particularly, the bucket-handle lesion. [] Other less common causes, such as ruptured anterior cruciate ligament (ACL) stump [2] and isolated posterior cruciate ligament tears, [3] may lead to mechanical blockage and hinder knee extension. Gouty arthritis is a metabolic disorder characterized by elevated urate and urate monohydrate crystal deposition in the serum. The crystals are responsible for causing a hot and swollen knee during an acute gouty attack. Tophaceous deposition may cause erosion of bony structures, which is a widely recognized indicator of chronic gout, but typically lacks obvious symptoms. [4] Tophaceous deposition rarely causes mechanical knee blockage. We report a case of gouty arthritis of the knee in which tophi deposition over ACL caused mechanical knee blockage. CASE REPORT A 4-year-old basketball player was admitted to the outpatient department, reporting sporadic Department of Surgery, Cathy General Hospital, Taipei, Taiwan Submitted November, 05, 204; final version accepted December, 29, 204. *Correspondence author: Hsi-Ting Lin (ctlin099@yahoo.com.tw) 輔仁醫學期刊第 3 卷第 4 期 205 2

2 Che-Wei Liu Hsin-Pu Hsieh Chin-Yu Chen Hsi-Ting Lin pain with swelling in the right knee for the past 9 months. In addition, the patient experienced progressive knee locking for the last 3 months. A thorough history review revealed no specific trauma of the knee. Laboratory findings revealed an elevated uric acid level of 7.6 mg/dl. The patient was prescribed colchicine and allopurinol for gouty arthritis. The pain and swelling over the right knee were alleviated by the medical treatment; however, it was unsuccessful in improving the loss of range of motion. A moderate joint effusion and medial joint line tenderness were observed on physical examination. No subcutaneous tophi deposition was observed over the knee and the rest of the body. The range of motion was and was limited by pain and impingement during a forceful full-knee extension. Varus and valgus stress tests revealed no sign of collateral instability. Lachman and posterior drawer tests were not significant for anteroposterior instability. The McMurray test result was positive. The 45 posteroanterior flexion weight-bearing and lateral radiographs of the right knee revealed no significant fracture, presence of loose body, or degenerative joint disease. Magnetic resonance imaging (MRI) was conducted to rule out meniscal pathology. However, MR images revealed increased signal intensity on the proton density-weighted image over the ACL (Figure ). No meniscal tear was observed. The radiological impressions indicated an ACL tear with impingement or a reduced bucket-handled tear of the meniscus; hence, arthroscopy was performed. Arthroscopy of the right knee revealed superficial whitish tophi deposition over the surface of meniscus and partial tear of the medial meniscus (Figure 2c). Inspection over the intercondylar notch revealed tophi deposition over the ACL sheath and ligament substance. Tophi impingement was observed during knee extension (Figures 2a and 2b). The patient was treated using shaving arthroplasty to remove the impinging tophi (Figure 2d) and manipulation. Following arthroscopic treatment, full-knee extension was restored in the patient. The patient was postoperatively treated with colchicine and allopurinol to prevent acute gout attack. The pathological examination of the tophi revealed urate monohydrate crystals. Figure. Hyperintensity signal and irregular appearance in an anterior cruciate ligament in a proton-density image resembling an anterior cruciate ligament tear. 22 Fu-Jen Journal of Medicine Vol.3 No.4 205

3 Anterior cruciate ligament and synovial tophi deposition causes knee locking Figure 2. (a) Massive synovial tophi and tophi over anterior cruciate ligament sheath blocking knee extension (b) Partial resection of synovial tophi (c) Partial tear of medial meniscus (d) The knee after thorough debridement of intraarticular tophi. DISCUSSION Knee locking may be caused by mechanical or functional factors such as pain and muscular spasm (false locking). Meniscal lesions and torn ACL are well-documented causes of mechanical knee locking, 2. Mechanical knee locking is frequently induced by degenerative joint disease, torn cruciate ligaments, and loose articular bodies, and less commonly by a metabolic or tumoral disorder. Among these causes, impingement of the intercondylar tophi with intraligamentous tophi deposition in the ACL is peculiarly rare. [] Gouty arthritis causes pain and false locking of the knee. However, direct mechanical locking caused by gouty arthritis, as observed in the case presented in this study, is a rare occurrence. Tophaceous gout in the knee typically develops in the chronic phase of gouty arthritis and may appear at intra- or extraarticular locations or within the subcutaneous tissue. Subcutaneous or extraarticular tophi typically manifest at a later stage and often occur together with intraarticular tophaceous depo- 輔仁醫學期刊第 3 卷第 4 期

4 Che-Wei Liu Hsin-Pu Hsieh Chin-Yu Chen Hsi-Ting Lin sition. However, when intraarticular tophi manifest without the subcutaneous tophi and unknown hyperuricemia or previous episodes of gouty arthritis, this condition may be undetected by plain radiography. [5] MR images of the tophaceous gout in the knee are typically nonspecific because the tophi have a wide spectrum of signal intensity characteristics, which reflect their variable compositions and relative proportions of protein, fibrous tissue, crystals, and hemosiderin. Most lesions are isointense relative to muscle on T-weighted images. On T2- weighted images, most lesions show low-to-intermediate heterogeneous signal intensities although the lesions may exhibit high signal intensities in the presence of high protein or in cases of inflammation with local edema. The differential diagnosis of the tophaceous gout of the knee should include chronic rheumatoid arthritis, pigmented villonodular synovitis (PVNS), localized nodular synovitis, and amyloidosis. Chronic rheumatoid arthritis typically presents with marked synovial proliferation and synovitis, together with tissue debris or rice bodies, which are less common in tophaceous gout. PVNS is almost invariably monoarticular and typically presents as a profoundly dark T2 signal, reflecting the proliferating synovium, together with the paramagnetic effect of hemosiderin. Although the appearance of amyloidosis on an MR image may indicate gout, factors such as clinical information, laboratory data, and characteristic MRI patterns should allow us to perform accurate diagnoses. However, percutaneous needle aspiration or arthroscopy may be necessary in some equivocal cases6. Bucket-handle tear commonly causes knee blockage that hinders extension; however, partial tear of the meniscus without its displacement rarely limits knee extension. MRI is expensive and rarely employed for gout, but its use is valuable in detecting abnormalities in patients with limited excursion or walking disability of the knee joint. In addition, the observations in this study highlight that large intraarticular tophi and bony erosions may occur in patients without visible subcutaneous tophi. [5] Arthroscopy is not routinely indicated for gouty arthritis. However, in the case of mechanical blockage, arthroscopy may be prescribed early to prevent flexion contracture of the knee joint. To summarize, intraarticular tophi deposition is an early manifestation of gouty arthritis. It may occur before any subcutaneous tophi are observed. In the case of progressive knee locking with a history of gouty arthritis, MRI may be helpful to rule out other knee-locking factors, such as meniscal and ACL. However, direct visualization of the intraarticular anatomy of the organ may be more direct in ruling out and treating the underlying causes of mechanical blockage. REFERENCES. Allum RL, Jones JR. The locked knee. Injury 986; 7: Monaco BR, Noble HB, Bachman DC. Incomplete tears of the anterior cruciate ligament and knee locking. JAMA 982; 247: Swenning TA, Prohaska DJ. Isolated posterior cruciate ligament tear presenting as a locking 24 Fu-Jen Journal of Medicine Vol.3 No.4 205

5 Anterior cruciate ligament and synovial tophi deposition causes knee locking knee. Arthroscopy 2004; Block C, Hermann G, Yu TF. A radiological reevaluation of gout: a study of 2,000 patients. Am J Roentgenol 980; Yu KH. Intraarticular tophi in a joint without previous gouty attack. J Rheumatology 2003; 30: Gentili. A, Sorenson. S, S M. MR imaging of soft-tissue masses of the foot. Semin Musculoskelet Radiol 2002:4-52. 輔仁醫學期刊第 3 卷第 4 期

6 Che-Wei Liu Hsin-Pu Hsieh Chin-Yu Chen Hsi-Ting Lin 前十字韌帶痛風石沉積造成膝關節僵鎖 劉哲瑋 謝心圃 陳勁宇 林希鼎,* 膝關節鎖定合併伸直不能之現象常起因於半月板提把形破裂造成的夾擊現象 在較少見的狀況, 前十字韌帶斷裂造成的斷片夾擊及後十字韌帶斷裂的夾擊也會造成膝關節機械性僵直伸直不能的現象 痛風為常見的新陳代謝疾病, 常造成尿酸結晶堆積於膝關節 踝關節及大腳趾關節引起紅腫熱痛現象尤其在急性痛風發作期間 慢性痛風石沉積可能造成硬骨及軟骨侵蝕及破壞關節 膝關節鎖定及伸直不能之現象為痛風石沉積少見的症狀, 本個案報告在此提出以供鑑別診斷 關鍵字 : 痛風, 膝部伸直不能, 痛風石沉積 臺北市國泰醫院外科部骨科 投稿日期 :204 年 月 05 日接受日期 :204 年 2 月 29 日 * 通訊作者 : 林希鼎電子信箱 :ctlin099@yahoo.com.tw 26 Fu-Jen Journal of Medicine Vol.3 No.4 205