Bilateral diaphyseal bone cysts of the tibia mimicking shin splints in a young professional athlete—a case report and depiction of a less-invasive surgical technique
Medial tibial stress syndrome is one of the most common causes of exertional leg pain in runners whereas musculoskeletal tumors and tumor-like lesions are rare encounters in orthopedic sports medicine practice.
Unicameral (simple) bone cyst is a well-known tumor-like lesions of the bone typically affecting children and adolescents. Bilateral occurrence is very rare though and has never been reported before in both tibiae. Failing to accurately diagnose a tumorous lesion can entail far-reaching consequences for both patients and physicians.
We report the case of large bilateral unicameral bone cysts of the diaphyseal tibiae mimicking medial tibial stress syndrome in a 17-year old professional athlete. This is the first report of symmetric tibial unicameral bone cysts in the literature. The patient complained about persisting shin splint-like symptoms over 5 months despite comprehensive conservative treatment before MRI revealed extensive osteolytic bone lesions in both diaphyseal tibiae. The patient-tailored, less-invasive surgical procedure, allowing the patient to return to his competitive sports level symptom-free 3 months after surgery and to eventually qualify for this years Biathlon Junior World Championships, is outlined briefly. Pathogenesis and various treatment options for this entity will be discussed.
This report will help to raise awareness for musculoskeletal tumors as differential diagnosis for therapy-refractory symptoms in young athletes and encourage medical staff involved in sports medicine and athlete support to perform early high quality imaging and initiate sufficient surgical treatment in similar cases. Moreover, our less-invasive surgical procedure aiming for a fast return to sports might be an optimal compromise between traditional open curettage with low risk of recurrence and a soft tissue-saving and bone-sparing minimal-invasive technique.
KeywordsMedial tibial stress syndrome Unicameral bone cyst Athlete Musculoskeltal tumor Shin splints
Extracorporeal shockwave therapy
Magnetic resonance imaging
Medial tibial stress syndrome
Non-steroidal anti-inflammatory Drug
Unicameral bone cyst
Medial tibial stress syndrome (MTSS), commonly known as ‘shin splints’, is one of the most common causes of exertional leg pain in runners. It is believed to be caused by a multifactorial spectrum of stress injuries including periostitis, tendinopathy, periosteal remodeling and stress reaction of the tibia . Diagnosis is mostly established by patients history and physical examination. Therapy is generally conservative including rest, stretching and strengthening exercises, ultrasound therapy, iontophoresis, extracorporeal shockwave therapy (ESWT), sports compression stockings, lower leg braces and application of NSAIDs . Frustrating long-term treatment intervals and delayed return to recreational and professional sports activity are feared . Therapy can turn out to be protracted and thus delay individual training plans and competition. To rule out tibial stress fracture additional imaging can be obtained.
Unicameral (simple) bone cyst (UBC) is a common tumor-like lesions of the bone. There is a strong predilection for the long bones of the proximal humerus and proximal femur, accounting for up to 85 % of all cases. Symptomatic cysts are typically observed between 5 and 15 years of age with a male predominance in a ratio of 3:1 . With skeletal maturation, the cyst may migrate from its initial epi-metaphyseal localization toward the diaphysis . UBCs are often painless and asymptomatic and present mostly as accidental radiographic findings or pathologic fracture. Its characteristic radiological appearance with a centrally located, well-cirumscribed osteolysis and sclerotic margins allows for definite surgical therapy without the need for preceding biopsy in most cases. Relevant differential diagnoses include aneurysmal bone cyst, fibrous dysplasia and giant cell tumor and can be ruled out by MRI in most cases. Although first recognized by Virchow in 1876, etiology is still unknown. Over the decades, many theories have been proposed, but none universally accepted. Consequently, treatment still remains non-uniform. The main indication for treatment is prevention of pathologic fracture . Localized at the lower extremities, UBC can cause persevering pain anf thus justify surgical therapy.
Etiology of UBC remains unknown. Among the accepted theories is the concept described by Cohen  in 1960 that UBCs have an elevated hydrostatic pressure due to developmental anomaly and therefore a decompression of the cavity is essential to obtain healing . Other therories supporting a disorder of physiologic intra-osseus pressure and blood circulation include that of Chigira  and Watanabe  suggesting that increased regional blood flow, in association with bone formation, produces a hydrodynamic disorder followed by venous obstruction leading to the formation of a bone cyst. Jaffe and Lichtenstein support Mikuliez’s theory that mechanical trauma leading to a defect in ossification is the most likely cause . The basic pathological process of UBC is one of bone resorption. A possible failure of prompt organization after intramedullary haemorrhage which interferes with the normal process of bony regeneration might be the initiating factor responsible for the production of that osseus cavity .
Regarding potential etiologic factors in the case described excessive workout during a period of rapid bone growth repetetively creating bony micro-lesions of the bone and causing a disturbance of hydrostatic pressure might have contributed to the development of UBC. Nevertheless UBC of bones of the lower extremity is not a common disorder encountered regularly in young athletes and such bilateral occurence of both tibiae is still unreported. Also other etiologic considerations have to be taken into account: Low-grade osteomyelitis as well as tumors and tumor-like lesions of the bone are suspected to act as precursor-lesion for the origination of UBC by some authors [16, 17, 18]. Bilateral appearance makes these etiologic theories very unlikely, though.
Therapeutically, radical excision of the cyst reduces the rate of recurrence but increases morbidity and complication rate . Some authors even postulate open surgery to be rarely justified for the initial treatment of a unicameral bone cyst  proposing alternative procedures. These inlcude simple drainage of the cyst by a percutaneously inserted cannulated screw, injection of steroids into the cyst and instillation of demineralized bone matrix or bone marrow aspirate. All procedures can be combinated at the surgeons preference. Data regarding recurrence rates of the above-mentioned techniques are inconsistent. In our own experience from more than 40 years of orthopaedic oncology, a resection of the internal lining and disruption of the cystic boundary is mandatory to reduce recurrence, especially in younger patients. Our experience is shared by various other authors [6, 7, 8]. Open curretage and autologous grafting of UBCs are more and more replaced by modern techniques with a less invasive approach and thus reduced morbidity.
This is, to our best knowledge, the first report of bilateral diaphyseal simple bone cysts of the tibiae. There have been reports of two or more unicameral bone cysts in the same patient at different locations [20, 21] and one prior report of symmetric unicameral bone cysts of the hamate bones  as well as one report of bilateral symmetrical cysts in the proximal epiphyseal tibiae . An extensive literature review from Abdel-Wanis  revealed 13 reported cases of multiple simple bone cysts before 2001. Nine of these 13 patients had bilateral cysts: three in the calcanei, two in femora, two in humeri, one in radius and ulna and one in carpal bones but none in the diaphyseal tibiae. Besides a case of a 13-year-old boy with bilateral distal femoral unicameral bone cysts associated with acquired generalized lipodystrophy as predisposing factor in 2010 , no bilateral cases of simple bone cysts outsides the field of oral and maxillofacial surgery have been published since. Notably none of the previously reported patients was a professional athlete.
Medial tibial stress syndrome (MTSS) or ‘shin splints’ is a common reason for excercise-related pain of the lower leg in young athletes, especially in running disciplines. Unless futher investigated by radiologic imaging, relevant differential diagnoses of shin splints can remain undetected. Musculoskeletal tumors and tumor-like lesions are rare encounters in sports medicine practice but have to be taken into consideration in any patient with therapy-refractory symptoms, especially in young patients. High vigilance to recognize tumor-related findings is necessary for any physician not routinely dealing with tumor orthopaedics. Additional diagnostics and definite therapy of suspicious musculoskeletal lesions should be performed in a highly experienced musculoskeletal tumor centre to prevent misdiagnosis and initiate individual treatment if required. Diagnostic errors may entail serious consequence not only for a future career in professional sports but also for life and limb of the affected patient.
Written informed consent was obtained from the patient for publication of this Case report and any accompanying images. A copy of the written consent is available for review by the Editor of this journal.
We thank Karen Becker and Prof. H. Höfler for performing the pathological analysis.
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