SECTION III: REGULAR AND SPECIAL FEATURES
Fracture of the patella is relatively common, comprising approximately 1% of all fractures.9 Often the etiology of the fracture is one of a few common entities. The differential diagnosis for pathologic fracture of the patella includes infections, tumor, degenerative conditions, and metabolic disorders. Pathologic fracture of the patella secondary to gout is much less common, with only sporadic published reports during the last several decades. To our knowledge, the current case is one of the few regarding pathologic patellar fracture secondary to gout.
A 48-year-old man with a history of gout slipped on a patch of ice and had a low-energy fall onto his knee. He instantly noted extreme pain and swelling in the region of his patella and was unable to bear weight on that leg. On presentation in the emergency room, he had a moderate knee effusion with intact skin and no erythema. A physical examination showed a gross deformity of his patella and tenderness to palpation over the patella. The patient's range of motion (ROM) was limited to 30° passive flexion. His distal neurovascular examination was normal. Plain radiographs showed a transverse fracture of the patella with approximately 5-mm superior displacement of the proximal fragment (Fig 1). His serum uric acid levels at presentation were 11.6 mg/dL with the upper limit of normal being 7.8 mg/dL. He originally was diagnosed with gout 5 years before this incident and it was thought be secondary to chronic renal insufficiency (baseline BUN/Cre = 51/3.1) of unknown etiology. The patient said he had not taken medication for his gout for some time as he had experienced no symptoms recently. Definitive fracture surgery was scheduled, and a knee immobilizer was placed on the extremity.
At the time of surgery, a standard midline longitudinal incision was made to expose the patella and retinaculum. The fracture was identified easily, and the soft tissues were sharply reflected from the fracture edges to allow observation of the fracture reduction. However, when the surface of the fracture was exposed, a caseous substance comprised much of the patella. This substance had the appearance and texture of gouty tophus, and a specimen was sent for pathologic confirmation. The tophus-like material was present only inside the patella. There was no extravasation into the surrounding tissues of the joint. The intraarticular examination of the knee was remarkable for the absence of any stigmata of gout. The patella then was reduced, and fixation was achieved with longitudinal K wires and an 18-gauge stainless steel tension-band wire. After fixation, the intraoperative ROM was approximately 100° flexion without any displacement or gapping of the fracture.
The tissue obtained from the patella was fixed in alcohol to allow for preservation of the diagnostic sodium urate crystals. Histologic evaluation revealed numerous large tophi composed of long, refractile, needle-shaped crystals (Fig 2A). These crystals were focally surrounded by a granulomatous reaction of histiocytes and foreign body giant cells in a background of fibrin, fibrous tissue, and reactive bone, confirming the diagnosis of gout. The crystals were strongly birefringent when viewed with polarized light (Fig 2B).
The patient did well postoperatively. He wore a hinged knee brace locked in extension for weightbearing and was allowed unrestricted active and active-assisted ROM when not bearing weight. Based on intraoperative findings, the patient was prescribed allopurinol and colchicine for presumptive treatment of gout. He was discharged without incident. The patient had a well aligned and healed patella with intact hardware at 5 months followup (Fig 3). There were no wound complications. At the 1-year followup the patient complained of some pain in his knee and had 0° to 90° ROM. He was seen by his medical doctor and given a prescription for allopurinol, but he does not take it regularly. He reports that he has not had any gout flares.
The first report of patellar tophi was by Peloquin and Graham who in 1955 described a patient with erosion of the cortex of the patella discovered at the time of surgery.7 In 1977, Burnham et al described a patient with pathologic fractures of the iliac crest and superior and inferior pubic rami secondary to gout.2 Greenberg reported what was thought to be the first case of a fracture in an extremity that was caused by erosion of the patella by gout.6 The patient had sudden knee pain associated with a popping sensation and subsequently was found to have a pathologic fracture of the distal pole of his patella. Espinosa-Morales and Escalante reported the case of a patient in whom gout was diagnosed to explain the cause of a patella fracture non-union.5 Chun and Thordarson reported the same in a patients with a fifth metatarsal nonunion.3 In 1999, Aboulafia et al described a patient who sustained an atraumatic patellar fracture.1 Subsequent radiographs and biopsy revealed a large central osteolytic lesion secondary to gout.1 There is one additional case report in the German literature that points to the rarity of this entity.4
Our patient had a history of gout for which he was only intermittently compliant with medical treatment. Gout is known to cause destruction of joints via deposition of crystals in the synovial tissue causing an inflammatory cascade that eventually leads to tophi deposition on the articular surface.8 Intraosseous tophi are much less common, but are becoming recognized as a possible cause of fracture in patients with gout. The differential diagnosis of osteolytic lesions of the patella includes infection, metabolic diseases, degenerative conditions, and tumors. Pathologic fracture secondary to gout is still rare, but it should be considered in the differential diagnosis for pathologic fracture.
The previously reported patients with patellar fracture secondary to gout were managed by the same treatment principles used for patients with nonpathologic patella fractures. Our patient and the patients in the other reports all did well postoperatively. It is important to consider gout a possible cause of a patient's pathologic fracture to provide the appropriate medical treatment.
1. Aboulafia AJ, Prickett B, Giltman L. Displaced pathological patella fracture due to gout. Orthopedics
2. Burnham J, Fraker K, Steinbach H. Pathologic fractures in an unusual case of gout. AJR Am J Roentgenol
3. Chun J, Thordarson DB. Nonunion of 5th metatarsal tuberosity fracture (dancer's fracture) associated with gout. Am J Orthop
4. Englehardt P, Buschor F. Pathological patella fracture in a gout tophus. [in German] Z Rhematol
5. Espinosa-Morales R, Escalante A. Gout presenting as non-union of a patellar fracture. J Rheumatol
6. Greenberg DC. Pathological fracture of the patella secondary to gout. a case report. J Bone Joint Surg
7. Peloquin L, Graham J. Gout of the patella. N Engl J Med
8. Rosenberg A. Bones,Joints, and Soft Tissue Tumors. In: Klatt EC, Kumar V, eds. Robbins Pathologic Basis of Disease
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9. Whittle AP, Wood GW. Fractures of the Lower Extremity. In: Canale ST, Campbell WC, eds. Campbell's Operative Orthopedics
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