- Case report
- Open Access
Traumatic deep vein thrombosis in a soccer player: A case study
© Echlin et al; licensee BioMed Central Ltd. 2004
- Received: 27 April 2004
- Accepted: 14 October 2004
- Published: 14 October 2004
A 42 year-old male former semi-professional soccer player sustained a right lower extremity popliteal contusion during a soccer game. He was clinically diagnosed with a possible traumatic deep vein thrombosis (DVT), and sent for confirmatory tests. A duplex doppler ultrasound was positive for DVT, and the patient was admitted to hospital for anticoagulation (unfractionated heparin, warfarin). Upon discharge from hospital the patient continued oral warfarin anticoagulation (six months), and the use of compression stockings (nine months). He followed up with his family doctor at regular intervals for serial coagulation measurements, and ultrasound examinations. The patient's only identified major thrombotic risk factor was the traumatic injury. One year after the initial deep vein thrombosis (DVT) the patient returned to contact sport, however he continued to have intermittent symptoms of right lower leg pain and right knee effusion.
Athletes can develop vascular injuries in a variety of contact and non-contact sports. Trauma is one of the most common causes of lower extremity deep vein thrombosis (DVT), however athletic injuries involving lower extremity traumatic DVT are seldom reported. This diagnosis and the associated risk factors must be considered during the initial physical examination. The primary method of radiological diagnosis of lower extremity DVT is a complete bilateral duplex sonography, which can be augmented by other methods such as evidence-based risk factor analysis. Antithrombotic medication is the current standard of treatment for DVT. Acute thrombolytic treatment has demonstrated an improved therapeutic efficacy, and a decrease in post-DVT symptoms.
There is a lack of scientific literature concerning the return to sport protocol following a DVT event. Athletic individuals who desire to return to sport after a DVT need to be fully informed about their treatment and risk of reoccurrence, so that appropriate decisions can be made.
- Deep Vein Thrombosis
- Postthrombotic Syndrome
- Deep Vein Thrombosis Recurrence
- Lower Extremity Deep Vein Thrombosis
- Deep Vein Thrombosis Risk
Athletes are susceptible to a variety of vascular injuries, secondary to either repetitive motion, or high-speed collisions . The differential diagnosis for lower extremity trauma in sport seldom invites a diagnosis of vascular injury, such as a deep vein thrombosis (DVT). Failure of the physician to recognize a vascular injury can have catastrophic limb or life threatening (pulmonary embolism) implications. The epidemiology, diagnosis, treatment, and recurrence of DVT, as well as the prevention of post-thrombotic symptoms are the most current areas of clinical research. Research-based guidelines concerning an athlete's return to sport after a DVT is an important area for future investigation.
A 42 year old Polish born male former semi-professional soccer player was seen on May 16th, 2003 in the emergency department, with the chief complaint of right leg pain. The patient had been playing soccer 10 days prior to this visit, and recalled a traumatic "tackle" injury to the posterior area of his right lower extremity. He denied experiencing any sensation of tearing or popping in the right knee during the index trauma, and was able to complete the game with only minor discomfort. On day 3 post-injury the patient noted severe pain in his knee and calf with ambulation. The patient visited his primary doctor on post-injury day 8 and was diagnosed with a right lower extremity soft tissue injury. A right lower extremity echo-doppler ultrasound (US), and a semi-quantitative D-dimer automated latex procedure were ordered to rule out a vascular disorder. The US investigation demonstrated a DVT in the distal femoral, popliteal, and distal calf veins, with a heterogenous mass (5 cm × 3 cm × 4 cm, resembling a hematoma) without a doppler signal in the right popliteal fossa. The D-dimer result was also positive for a suspected thrombosis (1.0–2.0 ug/ml; range = <0.25 ug/ml). The patient was instructed by his physician to proceed immediately to the emergency department for further evaluation and treatment.
The past medical and family history of the patient was non-contributory for a history of thrombophilia or other thrombotic major risk factors. The patient had a remote (11 years old) surgical history of a right-sided inguinal hernia that could have created scar tissue contributing to vascular obstruction and stasis. The initial emergency department examination demonstrated an exquisitely tender right calf with a 3 cm difference in mid-calf girth (10 cm. distal from each inferior patellar pole); a 1+ right knee supra patellar effusion; and a palpable popliteal mass with visible ecchymosis. Laboratory tests (CBC, Lytes, PT, PTT, ESR, CPK, Anti-throbomin, Factor V Leiden, Lupus Screen, ANA, Anti-Cardiolipin, Protein C, and Protein S) were negative for metabolic, hematological or familial abnormalities. A repeat US investigation confirmed the results of the previous outpatient results. The patient was anticoagulated simultaneously with unfractionated heparin and Warfarin sulfate. A multiview plain film x-ray examination of the right lower extremity demonstrated no fracture, dislocation, or bony mass.
A magnetic resonance image (MRI) of the right knee was done several days after admission, to verify a torn right knee meniscal cartilage that had been previously diagnosed. The official MRI radiological report included a small free-edge tear of the posterior horn root junction of the lateral meniscus, chondromalasia (lateral patella and lateral femoral articular cartilage), and a moderate joint effusion with a bursal cyst or dilated semimembranous-gastronemius bursa.
Anticoagulation was achieved on day 6 of the patient's hospitalization. He was discharged on 5 mg of warfarin per day, with instructions to continue the use of compression stockings. The patient was also advised to follow up with his primary physician for regular monitoring, and to avoid contact or collision activities during anticoagulation.
The patient was maintained on warfarin for six months, with weekly physician monitoring (symptoms, PT, INR) for the first three months post-injury. The monitoring interval was changed to once per month for the remainder of the treatment period. Hematologic investigations (APTT, PT, INR, Cardiolipin antibody, C-reactive protein, Lupant anticoagulant, Factor V Leiden, Antithrombin, ANA, Protein C, Protein S, and RPR) were obtained three months post injury. There were no contributory thrombophilic factors found in these investigations. Laboratory levels of Protein C activity 22% (range = 70–140%), Protein S activity 48% (range = 75–140%), INR 2.57 (range = 0.88–1.12), and PT 27.5 sec (range = 9.6–12.0 sec); APTT 38.5 sec (range = 23.4–35.4 sec) were found to be appropriately reactive to the anticoagulant therapy.
The patient underwent two arthrocentesis procedures to remove small amounts of serous fluid from the joint, and each time was injected with a lidocaine/corticosteroid combination. US examinations after the hospitalization period failed to demonstrate a recurrence or new onset of DVT, however residual echogenic material characteristic of a chronic thrombus was demonstrated in the popliteal vein. Compression stocking use was maintained after hospital discharge, and was discontinued after nine months. The patient returned to soccer after anticoagulation, with a full understanding of his increased risk of DVT recurrence.
One-year post injury the patient continued to suffer from intermittent right lower extremity discomfort and swelling often unrelated to activity. An elective arthroscopy was recently performed on the patient's right knee to investigate his long-standing meniscal disruption and effusion. The arthroscopy demonstrated several areas of arthrosis (patellar lateral and medial facets, lateral and medial femoral condyles), and a torn lateral meniscus. Appropriate partial lateral menisectomy and debridement, and chondroplasty of the areas of arthrosis were preformed. An arthroscopic examination of the posterior compartment demonstrated a small cleft-like area just medial to the semimembranosis where the Baker's cyst likely originated. The patient returned to the orthopedist one week post-op with a large (150 cc's) hemarthrosis that was aspirated from the knee. He was requested to follow-up in one month for re-evaluation.
This case study illustrates the importance of considering deep vein thrombosis in the diagnosis of sport-related extremity trauma. DVT is classically related to venous stasis, intimal injury, and coagulation diathesis (Virchow's triad). The estimated incidence of DVT from all causes is 0.5 to 1.6 per 1000 persons per year, and may be an underestimation due to the number of DVT that are asymptomatic .
Standard risk factors for DVT are immobilization, pregnancy, recent surgery (particularly orthopedic), malignancy, older age, smoking, coagulation deficits or hypercoagulable states, connective tissue disorders, sex steroid administration, severe dehydration, and major trauma. Bates et al.  presented a table of the estimated relative risk (RR) for individual DVT risk factors. These factors include inherited conditions (e.g. Factor V Leiden, RR = 50, Antithrombin deficiency, RR = 25, Protein C and S deficiency, RR = 10); acquired conditions (e.g. major surgery or trauma, RR = 5–200; history of venous thromboembolism, RR = 50); and hereditary, environmental, or idiopathic conditions (e.g. hyperhomocysteinemia, and elevated levels of Factor VIII, RR = 3: elevated levels of Factor IX, RR = 2.3).
Coagulation diathesis through congenital or acquired thrombophilia may promote coagulation . Coagulation deficits in previously healthy athletes are becoming increasingly identified through laboratory tests, and must be considered as contributing factors for DVTs [4–7]. Hilberg et al.  found that the risk of hereditary exists in elite athletes, corresponds to the general population. These authors proposed that countermeasures (e.g. early anticoagulation during periods of immobilization/injury; single dose of low molecular weight heparin and/or leg exercises on long-distance flights; and avoiding hemoconcentration with adequate hydration) for athletes who are carriers of a congenital coagulation deficit .
The testing for hypercoagulable states in an individual after a single episode of thrombosis is a costly, yet routine procedure in many centers. The common assumption that an identified presence of a thrombophilic abnormality increases the risk of recurrence, and justifies prolonged therapy is without clear supportive evidence. A review of the current literature concerning the treatment of individuals with coagulation deficits concludes that there is no clear evidence that modifying treatment because of an identified hypercoaguable state alters the outcome, or that more intensive therapy is required in patients with laboratory evidence of thrombophillia .
Exercise is thought to act as a protective mechanism against thrombosis, due to the controlled balance between the exercise activated coagulation and fibrinolytic pathways . Upper extremity thrombosis that is not related to primary diseases or well known risk factors are rare (2–4% of DVTs).This type of thrombosis has been documented in a variety of sports as effort thrombosis or "Paget-Schroetter's syndrome" [9–14]. This syndrome is been described as a primary thrombosis of the subclavicular and axillary veins, usually proceeded by a strenuous effort or repetitive action involving retroversion and hyperabuction of the extremity . Vascular compression by adjoining bone, ligament and muscle or resulting intimal traumas have been documented as contributing factors toward the development of upper and lower extremity thrombosis [15–27].
Lower extremity DVT with a traumatic sporting injury in otherwise healthy active adults is seldom mentioned in the medical literature [16–29]. This lack of reported cases of this type of thrombosis may be due to either underreporting or incorrect diagnosis. Very few cases of sport-related lower extremity DVT involved direct externally trauma [29, 30]. There is one case report (Finnish language) that specifically related DVT development to soccer-related trauma , and one case report of lower extremity DVT in a soccer player with coagulation deficiencies . There is also one case report in the literature of a traumatic popliteal thrombosis in a hockey player, which resulted in a fatal pulmonary embolism (PE) .
The popliteal, posterior tibial and peroneal veins are susceptible to intimal trauma by the sudden hyperextension and torsion that the lower extremity experiences in a soccer "kick" or "tackle" motion. The popliteal arteries and veins are susceptible to direct, sheering, and muscular compressive forces due to their anatomical position, especially with rapid knee hyperextension or anterior dislocation [13, 22].
The literature demonstrates the importance and efficacy of a complete bilateral duplex sonography as the primary method of DVT diagnostic investigation . US findings can be augmented by other methods (e.g. evidence-based risk factor analysis) [33, 34]. A review of the current literature also suggests the need for comprehensive evidence-based guidelines concerning the use of radiological diagnostic investigations of suspected DVT .
Anticoagulation is effective in preventing DVT propagation and PE, but has no chemical fibrinolytic activity. This type of therapy allows for intrinsic fibrinolysis to occur. Radiographically demonstrable clot lysis occurs in only 50% of anticoagulated patients, and the incidence of complete resolution is less than 5%. Intrinsic fibrinolysis that occurs slowly does not preserve the function of the venous valves, which become fibrotic and fixed after a few weeks of being trapped in clot .
The symptoms experienced by individuals without complete clot resolution include heavy or achy legs, edema, throbbing paresthesia, purities, numbness, stiffness, and difficulty standing or ambulating. Postthrombotic syndrome (PTS) is characterized by brawny edema of the leg, stasis dermatitis, hyperpigmentation, induration, ulceration and chronic leg pain. This syndrome is associated with an extraordinary level of chronic pain and disability, and approximately 40% of the total cost of treating DVT is spent on PTS .
Zeigler et al.  investigated the long-term clinical outcome of individuals with a first DVT. These authors found that 82% of the patients suffered from recurrent symptoms, with a mean follow-up period of 6.6 years. Four level DVT, calf vein thrombosis, recurrence of ipsilateral DVT, and a non-sufficient oral anticoagulation are of prognostic significance for developing clinically relevant symptoms within 10 to 20 years after the first DVT .
There is growing evidence that the early lysis provided by thrombolytic therapy is more likely to preserve valve function, decreasing the likelihood of DVT recurrence, and the occurrence of PTS [38, 39]. Recent trials of new antithrombotic agent used an endpoint of 'symptomatic recurrent DVT', which was defined as the combination of persistent or recurrent symptoms along with the radiographic evidence of primary clot progression or new thrombus formation. The rate of symptomatic recurrent DVT was reported to be between 4–7%, and does not reflect those individuals who simply continue to be symptomatic after the primary event .
The general knowledge concerning quality of life and burden of illness in patients with persistent post-DVT symptoms is limited. This issue is especially important to the athletic patient, as participation in sport is usually an extremely important component of quality of life. For routine monitoring of outcomes in chronic venous disorders there are questionnaires that are available [40, 41]. Hedner et al.  have recently developed an instrument that measures health and treatment-related quality of life factors in DVD patients.
The athlete's primary concern upon the initial DVT diagnosis is return to play. The issue of return to sport after a lower extremity DVTs has only been addressed only once in the literature concerning return to non-contact sport . General guidelines for sedentary individuals allow for a gradual return to return to daily activities over a six week period , with no contact activities allowed during the period of anticoagulation. Roberts and Christie  provided a theoretical framework, based on the natural history of animal models for the safe and expeditious return of the athlete. These authors suggested a protocol that combines a graduated return to activity and anticoagulation therapy with regular physician based reevaluation .
An athlete who wants to return to a contact or collision sport should be informed of the possible increased risk of recurrent DVT that he or she may face, above the current estimates derived from the general population. There is no current evidence in the literature that investigates the specific risk factor of a traumatic collision, and the recurrence of a DVT. This lack of evidence suggests that the patient and physician should work together to make an informed return to play decision involving the patient's current individual risk profile, the likelihood of DVT recurrence, athletic goals, and the perceived importance of the particular sport to quality of life.
The potential limitations of this case study include the lack of testing for prothrobin mutation, and fibrynolitic parameters (level of tPA, PAI-1 or PAI-1 polymorphism 4G/5G).
The authors would like to acknowledge the contribution Jefferey E. Michaelson MD, Ms. Elaine Skopelja MALS, Tsveti P. Markova MD, James Rosebolt MD, Madeleine L. Echlin, Alexia D. Estabrook MSLS, AHIP, Carole M. Gilbert MSLS, AHIP, and Don DeCenzo LTA in the preparation of this paper.
Dr. Upshur is supported by a New Investigator Award from the Canadian Institute of Health Research and a Research Scholar Award from the Department of Family Medicine and Community Medicine, University of Toronto.
- Arko FR, Harris J, Zarins CK, Olcott C: Vascular complications in high-performance athletes. J Vasc Surg 2001, 33: 935-942. 10.1067/mva.2001.115162View ArticlePubMedGoogle Scholar
- Hansson P, Sorbo J, Eriksson H: Recurrent venous thromboembolism after deep vein thrombosis: incidence and risk factors. Arch Intern Med 2000, 160: 769-774. 10.1001/archinte.160.6.769View ArticlePubMedGoogle Scholar
- Bates SM, Ginsberg JS: Treatment of deep-vein thrombosis. N Engl J Med 2004, 351: 268-277. 10.1056/NEJMcp031676View ArticlePubMedGoogle Scholar
- Fiala KA, Hoffman SJ, Ritenour DM: Traumatic hemarthrosis of the knee secondary to hemophilia A in a collegiate scoccer player: a case report. J Athl Train 2002, 37: 315-319.PubMed CentralPubMedGoogle Scholar
- Hilberg T, Moessmer G, Hartard M, Jeschke D: Clinical sciences and orthopedics: Case report homozygous APC resistance in an elite athlete. Int J Sports Med 1999, 20: 198-200.View ArticlePubMedGoogle Scholar
- Hilberg T, Jeschke D, Gabriel HHW: Hereditary thrombophilia in elite athletes. Med Sci Sports Med 2002, 34: 218-221.Google Scholar
- Wong C, Bracker M: Coagulopathy presenting as calf pain in a racquetball player. J Fam Pract 1993, 37: 390-393.PubMedGoogle Scholar
- Smith JE: Effects of strenuous exercise on hemostasis. Br J Sports Med 2003, 37: 433-435. 10.1136/bjsm.37.5.433PubMed CentralView ArticlePubMedGoogle Scholar
- Adams JT, DeWeese JA: "Effort thrombosis" of the axillary and subclavian veins. J Trauma 1971, 11: 923-930.View ArticlePubMedGoogle Scholar
- Zell L, Kindermann W, Marscall F, Scheffler P, Gross J, Buchter A: Paget-Schrotter syndrome in sport activities. Angidogy 2001, 52: 337-342.Google Scholar
- Chaudhry MA, Hajarnavis J: Paget-von Schrotter syndrome: Primary subclavian-axillary vein thrombosis in sport activities (Case Reports). Clin J Sports Med 2003, 13: 269-271. 10.1097/00042752-200307000-00012View ArticleGoogle Scholar
- DiFelice GS, Paletta GA, Phillips BB, Wright RW: Effort thrombosis in elite throwing athlete. Am J Sports Med 2002, 30: 708-712.PubMedGoogle Scholar
- Zigun JR, Schneider SM: "Effort" thrombosis (Paget-Schroetter's syndrome) secondary to martial arts training. Am J Sports Med 1988, 16: 189-190.View ArticlePubMedGoogle Scholar
- Medler RG, McQueen DA: Effort thrombosis in a young wrestler. J of Bone Joint Surg 1993, 75-A: 1071-1073.Google Scholar
- Scheffler P, Uder M, Gross J, Pindur G: Dissection of the proximal subclavian artery with consecutive thrombosis and embolic occlusion of the hand arteries after playing golf. Am J Sports Med 2003, 31: 137-140.PubMedGoogle Scholar
- Huges DG, Dixon PM: Pool players' thrombosis. Br Med J 1987, 295: 1652.View ArticleGoogle Scholar
- Porubsky GL, Brown SI, Urbaniak JR: Ulnar artery thrombosis: A sports-related injury. Am J Sports Med 1986, 14: 170-175.View ArticlePubMedGoogle Scholar
- Walsh M, Moriarty J, Peterson J, Friend G, Chodock R, Rogan M: Portal venous thrombosis in a backpacker: the role of exercise. A case report. Phys Sports Med 1996, 24: 75-78. 80–81View ArticleGoogle Scholar
- Topper SM, Berger RA: Radial artery thrombosis in a young athlete: a case report. Am J Sports Med 1998, 26: 297-299.PubMedGoogle Scholar
- Delecau CM: Deep venous thrombosis in umpires. South Med J 1992, 85: 670.View ArticleGoogle Scholar
- Gorard DA: Effort thrombosis in an American football player. Br J Sports Med 1990, 24: 15.PubMed CentralView ArticlePubMedGoogle Scholar
- Kwolek CJ, Sundram S, Schwarcz TH, Hyde GL, Endean ED: Popliteal artery thrombosis associated with trampoline injuries and anterior knee dislocations in children. Am Surg 1998, 64: 1183-1186.PubMedGoogle Scholar
- Slawski DP: Deep vein thrombosis complicating rupture of the medial head of gastrocnemius muscle. J Ortho Trauma 1994, 8: 263-264.View ArticleGoogle Scholar
- Ali MS, Kutty MS, Corea JR: Deep vein thrombosis in a jogger. Am J Sports Med 1984, 12: 16.View ArticleGoogle Scholar
- Gasser SI, Rao S, Fillion DT: Case report: pulmonary embolism after an isolated ACL tear. Medscape Ortho Sports Med J 1997., 1:Google Scholar
- Balaji MR, DeWeese JA: Adductor canal outlet syndrome. J Am Med Assoc 1981, 245: 167-170. 10.1001/jama.245.2.167View ArticleGoogle Scholar
- Williams JS Jr, Williams JS Sr: Deep vein thrombosis in a skier's leg. Phys Sportsmed 1994, 22: 79-84.Google Scholar
- Robbe R, Mair S, Johnson D, Madaleno J: Thrombosis of the greater saphenous vein in a college football place kicker. Ortho 2002, 25: 531-532.Google Scholar
- Risse M, Reuhl J, Ogbuihi S, Weiler G: Traumatic venous aneurysm of the popliteal vein with outcome: a case report and review of the literature. J Foren Sci 2001, 46: 1492-1497.View ArticleGoogle Scholar
- Lehtinen M, Soppi E, Koivumen E, Jarventie G: Deep vein thrombosis in a young athlete. Doudecim 1988, 104: 1073-1076.Google Scholar
- Watson AS, Gray D, Godfrey J, Muller A: Deep venous thrombosis following sports injury to the calf – A potentially dangerous complication. Sports Training, Med and Rehab 1991, 2: 273-278.View ArticleGoogle Scholar
- Heyers TM: Management of venous thrombembolism. Past, present, and future. Arch Intern Med 2003, 163: 759-768. 10.1001/archinte.163.7.759View ArticleGoogle Scholar
- Motykie GD, Caprini JA, Arcelus JI, Zebala LP, Lee CE, Finke NM, Tamhane A, Reyna JJ: Risk factor assessment in the management of patients with suspected deep vein thrombosis. Int Ang 1999, 19: 47-51.Google Scholar
- Constans J, Boutinet C, Salmi RS, Saby JC, Nelzy ML, Baudouin P, Sampoux F, Marchand JM, Boutami C, Dehant V, Pulci S, Gauthier JP, Cacareigt-Bourdenx V, Barcat D, Conri C: Comparison of four clinical prediction scores for the diagnosis of lower limb deep venous thrombosis in outpatients. Am J Med 2003, 115: 236-440. 10.1016/S0002-9343(03)00432-7View ArticleGoogle Scholar
- Zierler BK: Screening for acute dvt: optimal utilization of vascular diagnostic laboratory. Sem Vasc Surg 2001, 14: 206-214. 10.1053/svas.2001.25492View ArticleGoogle Scholar
- Baldwin ZK, Comerota AJ, Schwartz LB: Catheter-directed thrombolysis for deep-vein thrombosis. Vasc Endovasc Surg 2004, 38(Research Library):1-9.View ArticleGoogle Scholar
- Ziegler S, Schillinger M, Maca TH, Minar E: Post-thrombotic syndrome after the primary event of deep venous thrombosios 10 to 20 years ago. Thromb Res 2001, 101: 23-33. 10.1016/S0049-3848(00)00370-4View ArticlePubMedGoogle Scholar
- Kahn SR, Ginsberg JS: The post-thrombotic syndrome: current knowledge, controversies, and directions for future research. Blood Reviews 2002, 16: 155-165. 10.1016/S0268-960X(02)00008-5View ArticlePubMedGoogle Scholar
- Burroughs KE: New considerations in the diagnosis and therapy of deep vein thrombosis. South Med J 1999, 92: 517-520.View ArticlePubMedGoogle Scholar
- Mathias SD, Prebil LA, Putterman CG, Chmiel JJ, Throm RC, Comerota AJ: A health-related quality of life measure in patients with deep vein thrombosis: A validation study. Drug Info J 1999, 33: 1173-1187.Google Scholar
- Lampling DL, Scrotter S, Kurz X, Kahn SR, Abenhaim L: Evaluation of outcomes in chronic venous disorders of the leg: development of a scientifically rigorous, patient-reported measure of symptoms and quality of life. J Vasc Surg 2003, 37: 410-419. 10.1067/mva.2003.152View ArticleGoogle Scholar
- Hedner E, Carlsson J, Kulich KR, Stigendal L, Ingelgard A, Wiklund I: An instrument for measuring health-related quality of life in patients with deep vein thrombosis (DVT): development and validation of deep venous thrombosis quality of life (DVTQOL) questionnaire. Health and Quality of Life Outcomes 2004, 2: 30. 10.1186/1477-7525-2-30PubMed CentralView ArticlePubMedGoogle Scholar
- Roberts WO, Christie DM: Return to training and competition after deep vein thrombosis. Med Sci Sports Exer 1992, 24: 2-5.View ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an open-access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.