Download Osteoid osteoma of the patella

Osteoid osteoma of the patella
Report of two cases
Ke Ma MD1, Lin Hao MD1, Xiaohui Niu MD1, Qing Zhang MD1
1
Department of Orthopedic Oncology, Beijing Jishuitan Hospital, Beijing, China
Each author certifies that he has no commercial associations (e.g., consultancies, stock
ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of
interest in connection with the submitted article.
Each author certifies that his institution has approved the reporting of this case report that all
investigations were conducted in conformity with ethical principles of research, and that
informed consent for participation in the study was obtained.
Work performed at Department of Orthopedic Oncology, Beijing Jishuitan Hospital, 31
Xinjiekoudongjie, Xicheng District, Beijing 100035, China.
Word Count: 1694 words.
Corresponding author: Qing Zhang MD, Department of Orthopedic Oncology, Beijing
Jishuitan Hospital, 31 Xinjiekoudongjie, Xicheng District, Beijing 100035, China. Tel:
861058516830. Fax: 861058516736 E-mail: [email protected].
Abstract
Osteoid osteoma is very rarely located in the patella, and can represent a significant
diagnostic challenge, resulting in a delay of treatment. Patients with osteoid osteoma of the
patella often present with knee pain that is also a typical symptom of trauma or of other
diseases such as arthritis, which are much more common than osteoid osteoma. We present
two young male patients diagnosed with osteoid osteoma of the patella. Each of these patients
had a history of intense knee pain; however, accurate diagnosis of osteoid osteoma in the
patella had been delayed for more than one year. CT scans or MRI showed a circumscribed
lesion of the patella in both patients, whereas X-ray examination (posteroanterior projection)
was not able to detect the tumor. Different surgical procedures were performed in these
patients for resection of the tumors, and the pathology findings confirmed the diagnosis of
osteoid osteoma. Both patients recovered completely from surgery.
Introduction
Osteoid osteoma is a benign bone neoplasm, most commonly distributed in the long bones,
especially in the proximal femur [1]. Osteoid osteoma is found more frequently in patients
between 10 and 30 years of age, and is seen more often in male patients. Intense pain is a
typical symptom, and is characterized by worsening at night. Radiographically, the typical
finding is a small radiolucent central nidus, usually less than 1.5 cm, surrounded by a
peripheral sclerotic reaction that may extend several centimeters. Radiographic findings and
the clinical presentation of pain may lead to a mistaken diagnosis of osteomyelitis or bone
abscess. The primary treatment of osteoid osteoma is surgical removal of the nidus and some of
the surrounding bone after precise localization of the nidus. Some of these patients can be
managed with nonsteroidal anti-inflammatory drugs.
The patella is a very rare location of osteoid osteoma and to the best of our knowledge, there
have been only 14 cases reported in the English-language literature [3, 4, 8, 9, 10]. Accurate
diagnosis of osteoid osteoma of the patella is critical for clinical decision making and patient
management; however, the diagnosis of osteoid osteoma of the patella presents a tremendous
challenge because patients often present with knee pain that is also a typical symptom of
trauma or of other diseases such as arthritis, which are much more common than osteoid
osteoma. Some young patients may be examined at the sports medicine clinic and receive no
diagnosis, even after arthroscopy [6]. Other patients may be misdiagnosed with
osteochondritis dissecans [12].
We report two cases of osteoid osteoma of the patella. Due to misdiagnoses, the treatment
was delayed before the patients were examined at our hospital. We used different surgical
procedures, including direct curettage and a navigation system, as warranted by the
characteristics of each case. The pathology findings confirmed the diagnosis.
Case 1
A 14-year-old boy presented to the outpatient office of our hospital in August 2007 with a one
year history of left knee pain and swelling. The pain was worse at night. Previously, the
patient had sought diagnosis and treatment at another hospital and was diagnosed with
previous trauma. He was not treated with any medications, and was told to rest; however,
after two weeks, his pain did not subside, so he sought care at our clinic.
Physical examination revealed slight atrophy of the left thigh. The range of motion of the left
knee joint was not limited. There was tenderness in the left patella. Laboratory tests were
normal. The lateral X-ray film showed a small round lesion (0.75 cm in diameter) in the
center of the left patella (Fig. 1). A CT scan showed the lesion to be located in the medullary
cavity of the patella. Reactive bone was noted on the anterior surface of the patella (Fig. 2).
In consideration of the patient’s symptoms and radiographs, a preoperative diagnosis of
osteoid osteoma was established.
A curettage operation was performed. An 8 cm anterior incision was made to reveal the
anterior surface of the patella, which was coarse at the site of the nidus. After grinding off the
cortical bone, the center of the lesion was found. After the removal of the nidus and 2 mm of
reactive bone, we filled the bone defect with spongy bone from his ilium to prevent a fracture.
The pathologic examination confirmed the diagnosis of osteoid osteoma (Fig. 3). The pain
was completely relieved, and the patient commenced normal exercise 48 hours after the
operation. After six months, the follow-up X-ray showed that the bone had healed (Fig. 4).
We have followed this patient for three years. He has remained pain free, and no recurrence
has been identified.
Case 2
A 29-year-old male presented to our outpatient department in September 2010 with a
two-year history of aching pain in his left knee. The pain was worse at night. Two months
after the onset of pain, the patient went to another hospital, but an X-ray examination did not
reveal the source of pain. MRI scans from another hospital in January 2009 showed effusion
in the left knee joint, yet no diagnosis was established. The pain worsened in 2010, and the
patient was subsequently diagnosed with mental illness due to his continuing complaint of
pain in his left knee in the absence of evidence of disease. He started taking anti-anxiety
medication paroxetine and oxazepam in March 2010. The CT performed at our outpatient
department in September 2010 revealed the lesion in the lower pole of the left patella (Fig. 5).
Physical examination revealed severe atrophy of the left thigh (Fig. 6). The range of motion
of the left knee joint was also limited (from 0° of extension to 90° of flexion). Tenderness
was elicited by squeezing the left patella. CT scans showed a well-defined nidus 5 mm in
diameter. Our preoperative diagnosis was osteoid osteoma based on the clinical presentation
and the CT findings.
A curettage procedure was performed. The lower pole of the patella was exposed, but the
nidus was deep to the cartilage and could not be seen (Fig. 7). To localize the lesion and limit
the damage to the cartilage, we used ISO-C navigation. The lesion was found just deep to the
cartilage, indicated by the pointer (Fig. 8), and was curetted. The pathologic findings
confirmed the diagnosis of osteoid osteoma (Fig. 9). Only one day after the operation, the
original pain had disappeared. Postoperative X-ray showed that the lesion was completely
removed (Fig. 10). Currently, there is no evidence of recurrence.
Discussion
Osteoid osteoma is very rare in the patella, and can cause a significant diagnostic challenge,
resulting in a delay of treatment. We report two cases of osteoid osteoma located in the
patella.
Because many other diseases of the patella are found more frequently than osteoid osteoma of
the patella, it is very important to be aware of this entity. The clinical symptoms can mimic
those of other more common diseases, such as osteomyelitis, focal abscess, osteoarthritis,
cortical stress fracture, osteoblastoma, chondromalacia patellae, and osteochondritis
dissecans. Therefore, a thorough patient history and careful examination of the radiographs
are important to making a correct diagnosis.
Both of our cases have demonstrated that a delayed diagnosis can result in significant
morbidity. In our cases, the time interval between the onset of symptoms and the proper
diagnoses was one year for the patient described as Case 1, and three years for the patient
described as Case 2. In our experiences, if the X-ray findings are not diagnostic in young
patients with typical knee pain. When other diseases such as osteoarthritis, osteomyelitis, and
abscess have been ruled out, a CT or MRI scan is necessary to confirm a diagnosis of osteoid
osteoma; however, it should be noted that the scans still require careful examination because
the nidus may be too small to be noticed initially.
The main feature useful in distinguishing osteoid osteoma from osteoblastoma is the size of
the lesion. Generally, osteoblastomas are larger, with a diameter in excess of 2 cm. In a stress
fracture, the radiolucency of osteoblastoma is usually more linear than that of osteoid
osteoma, running perpendicular to or at an angle to the cortex rather than parallel to it. A
cortical bone abscess can usually be differentiated by a linear, serpentine tract that extends
away from the abscess cavity [7]. Chondromalacia patellae, osteochondritis dissecans, and
osteoarthritis have clinical and radiographic characteristics different from those of osteoid
osteoma.
After the diagnosis of osteoid osteoma, surgical treatment is often needed. Any of several
surgical procedures may be appropriate, including patellectomy [10], excisional biopsy [12],
percutaneous resection with a cannulated skin-punch biopsy needle [2], or resection under CT
and arthroscopic guidance [5]. Patellectomy may affect the strength of the patellar tendon,
and result in limited range of motion when the knee is extended. An excisional biopsy may
result in patella baja as described by Vallianatos et al. [12]. Other minimally invasive
procedures require precise location of the nidus; otherwise a small lesion may be missed.
In the two cases we report here, different surgical procedures were chosen. The lesion in case
#1 was larger and easier to be reach through a dorsal approach, but the bone defect was also
larger after removal of the nidus. Consequently, we used an autograft from the ilium, and
learned by viewing subsequent X-ray films that the patella had healed. In case #2, the nidus
was smaller and beneath the cartilage. In order to locate the lesion precisely and limit the
damage to the cartilage, a navigation system was used during the operation. Each patient
achieved a good clinical outcome after surgery. The pain disappeared soon after the operation,
and the function of the knee joint recovered gradually. At present, there is no evidence of
recurrence.
In summary, osteoid osteoma in the patella is a very rare lesion. This entity can cause severe
symptoms, and become a diagnostic dilemma. It is important to include osteoid osteoma in
the differential diagnosis of persistent unexplained knee pain, particularly in young patients.
CT and MRI scans provide better images of the lesion, and may be necessary for a definitive
diagnosis. Proper treatment as warranted by the location and size of the lesion can lead to a
better clinical outcome.
References
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cannulated skin punch biopsy needle. Arch Orthop Trauma Surg, 2007. 127(4): p.
299-302.
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List of Figures
Fig. 1. The lateral view showed a small round lesion in the center of the left patella.
Fig. 2. CT showed the lesion in the medullar cavity of the patella.
Fig. 3. The pathological findings confirmed the diagnosis of osteoid osteoma
(Haematoxylin-eosin x100).
Fig. 4. The six-month follow-up X-ray showed that the bone had healed.
Fig. 5. The CT revealed the lesion in the lower pole of the left patella.
Fig. 6. Atrophy was obvious in the left thigh.
Fig. 7. The lesion could not be seen when the joint was opened.
Fig. 8. The lesion was found, indicated by the pointer, in the navigation system as shown in
the three-dimensional figures.
Fig. 9. The nidus, which consists of interconnected bone trabeculae, is adjacent to the
cartilage [Haematoxylin-eosin x40 in (A) and x100 in (B)].
Fig. 10. The ten-month follow-up X-ray showed that the bone had also healed in case 2.