Surgical Dislocation of the Hip for the Treatment of a Femoral Head Chondroblastoma
A 17-year-old, high-level female athlete has persistent groin pain that’s limiting her performance. What is the best way to manage the lesion found in her femoral head?
Daniel Baquet, BA; Keenan Sobol, BA; and John A. Abraham, MD
Chondroblastoma is a rare tumor that represents 1% to 2% of all primary bone tumors. [1-7] Prior to being defined as a distinct neoplastic entity in 1942 by Jaffe and Lichtenstein,  this form of lesion was referred to as a “calcifying giant cell tumor” by Ewing  and later as an “epiphyseal chondromatous giant cell tumor” by Codman.  Further research has demonstrated that the epidemiology, histology, and clinical course of chondroblastomas differ greatly from those of giant cell tumors. [11,12]
Chondroblastomas most frequently arise from secondary ossification centers such as the epiphyses or apophyses of long bones, [1,6,7,13] particularly in the proximal femur, proximal humerus, and proximal tibia. [2,5,6,14-19] Early chondroblast cells are believed to originate in some capacity from the epiphyseal plate [1,6,8,20-23] and undergo active growth during the second decade of life, which is when most of these tumors develop. [1-3,6,7,17] Tumors involving the epiphysis have a 4.4 times higher rate of recurrence than tumors in other locations.  Despite being regarded as a benign tumor, chondroblastomas have demonstrated the ability to metastasize, called benign pulmonary metastases because the clinical course is more indolent than a malignant metastasis. [17,19,25-27]
The clinical presentation of a chondroblastoma often includes insidious onset of pain, local tenderness, decreased range of motion, and swelling. The tumor incites a significant inflammatory reaction, resulting in a joint effusion and edema on imaging. [1,2,4,7] Radiographic studies often reveal a well-defined circular lesion of the epiphysis or apophysis that usually appears hyperintense on T2-weighted magnetic resonance imaging (MRI). [1,28]
The location of the lesion is the most characteristic radiographic feature of chondroblastomas, with 85.5% of neoplasms having an epiphyseal component.  There may be evidence of concomitant aneurysmal bone cysts on imaging. However, recent studies have demonstrated no purported increased risk of recurrence or malignant transformation. [1,3,18,24,29]
Histologic analysis demonstrates a proliferation of mononuclear cells, with areas of well-defined polygonal chondroblasts invested in a chondroid matrix. [1,2,7,8,15] These cells can be multilobulated as well as multinucleated giant cells. [2,15] Areas of dystrophic calcification are often present, giving rise to the classic “chicken wire” appearance. Nonetheless, this finding is not specific or necessary for diagnosis. [2,19,20]
Treatment strategies are highly variable and depend on the size and location of the lesion; however, the primary modality consists of curettage and bone graft packing. Other treatment modalities include use of PMMA following curettage, radiofrequency ablation, cryosurgery, arthroscopy, and en bloc resection. The recurrence rate following most forms of treatment is between 10% and 35%. [17,19,30]
The treatment of chondroblastomas frequently present a unique challenge because the lesion is often situated between articular cartilage and the epiphyseal plate. [7,8,15,24,30] Recurrences have been attributed in part to limited surgical access to the tumor coupled with the perceived fear of damaging the growth plate or compromising blood supply.  Tumors in locations that are difficult to access, such as the proximal femur and pelvis, are associated with: [17,24,27,31] worse functional outcomes, increased recurrence rates, and greater propensity to metastasize.
These findings likely result from a combination of inadequate surgical resection due to difficulties in access and an innate predisposition for chondroblastomas to be more aggressive biologically than tumors in other locations [17,24,31,32] Although nothing can be done to influence the genetic composition of the tumor, measures can be taken to ensure the most adequate tumor resection possible.
Surgical dislocation of the hip is rarely attempted outside its use in arthroplasty. Ganz et al  have described an operative technique for surgical dislocation based on anatomic studies of the blood supply to the femoral head. This technique allows for a gap of up to 11 cm between the femoral head and the acetabulum and provides a 360 view of the femoral head and the acetabulum. Their technique was used successfully on 213 patients, none of whom developed avascular necrosis.  Avascular necrosis most commonly results from traumatic dislocations lasting greater than 6 hours; however, this technique allows for a safe and controlled dislocation in a much shorter time frame. 
Surgical dislocation of the hip provides excellent visualization, and in the case of a tumor excision, potentially allows complete tumor removal without compromising the integrity of the articular cartilage. In this article, we report the first time this method was used in treating a chondroblastoma of the proximal femoral epiphysis.
A 17-year-old, previously healthy, high-level female volleyball player presented for evaluation of atraumatic right hip pain that worsened with physical activity. The pain had gradually increased in intensity over 6 months until her performance started to falter.
On examination, she localized the pain to her right groin and denied any radicular symptoms. Additional signs of systemic illness could not be found. She had no recent weight loss, fevers, or other illnesses. She had no other prior injury to her right hip.
- Height 5 feet, 11 inches; weight 150 pounds
- Antalgic gait; walks without assistive devices
- Hip range of motion to 115 of flexion, 50 external rotation, and 30 internal rotation
- Pain with active and passive range of motion of the right hip
- Normal distal motor and sensory exam
- Palpable pedal pulses
Plain radiographs of the hip and pelvis were obtained but did not demonstrate any overt pathology (Figure 1). A direct MR arthrogram showed extensive bone marrow edema with a small 7×6-mm subchondral lesion in the cephalad aspect of the femoral head. The well-defined lesion did not produce any defect in the overlying cartilage.
Figure 1. Initial anteroposterior pelvis (left) and frog leg lateral (right) views of the patient’s right hip.
Over the next 6 weeks, the patient’s pain worsened despite her being non-weight-bearing. Repeat MRI demonstrated significant marrow edema in the right proximal femur, as well as a slight increase in the size of the previously noted subchondral lesion, which now measured 9×7 mm (Figure 2).
Figure 2. Coronal (top left) and axial (top right) T2 fat-saturated images show marrow edema and a right hip effusion along with a well-defined hyperintense lesion within the right femoral epiphysis. Coronal (bottom) T1-weighted image demonstrates a well-defined, hypointense lesion in the right femoral epiphysis.
Given the clinical presentation and the radiographic evidence of a well-defined circular lesion of the epiphysis, the differential diagnosis was narrowed down to either osteoid osteoma or chondroblastoma.
Attempting radiofrequency ablation would have greatly increased the risk of articular damage and femoral head collapse due to the proximity of the lesion to the weight-bearing articular surface of the proximal femur. Instead, surgical treatment consisted of curettage and bone grafting utilizing surgical dislocation of the hip to ensure complete intralesional excision.
- A posterior approach with a trochanteric flip osteotomy was performed to provide sufficient access to the joint capsule. In doing so, the external rotators were preserved and the medial femoral circumflex artery was protected by the obturator externus.
- An anterolateral capsulotomy was performed and the hip was dislocated anteriorly with flexion and external rotation of the leg. Both the femoral head and the acetabulum were viewed completely without any interference.
- The lesion was easily located and thorough curettage was performed while maintaining the integrity of the articular surface.
- Bone graft was packed into the resulting defect and successful reduction was accomplished by manual traction and internal rotation.
- The greater trochanter was reattached using 2 cortical screws (Figure 3).
Figure 3. Radiographs at 1 year postoperatively.
The patient had an uneventful postoperative course. After the initial postoperative rehabilitation period, the patient was able to return to a competitive level of sports.
At the 2-year follow-up visit, the patient had no evidence of recurrence. She had excellent hip function with only some mild but persistent trochanteric bursitis, which was effectively treated with screw removal.
Surgical removal of femoral head tumors presents many challenges, not only in preserving the integrity of the physis in younger patients, but also in achieving complete resection in a relatively inaccessible area. Although studies have argued that an open growth plate is not correlated with increased tumor recurrence, [1,2,4,14,19] Salihan et al  demonstrated poor functional outcomes in 32% of patients with an open physis following curettage.
The traditional approach for removal of chondroblastomas has been to access the tumor through the base of the femoral neck or through the greater trochanter. This approach provides limited exposure to the lesion, potentially accounting for a large number of tumor recurrences.  It has also resulted in several undesirable effects, such as seeding of the tumor, epiphyseal damage, angular deformities, and leg length discrepancies. [2,17,24,30]
Arthroscopy has produced good results in select cases when used as an adjunct in resecting femoral head tumors. [35,36] This method, however, has been shown to be technically challenging and associated with higher rates of damage to the articular cartilage. [17,19,30] Iwai described a trap door procedure to access the femoral head; however, this procedure can result in osteonecrosis and permanent damage to the articular surface. [5,37]
Several authors have described the use of radiofrequency ablation, which has had very positive results in small tumors that are not located in major weight-bearing areas, [38-40] and it remains a good potential treatment option, although data are still limited. The concern with radiofrequency ablation is potential damage to the overlying normal articular cartilage from the procedure.
The relative inaccessibility of chondroblastomas located in the periacetabular region, coupled with their inherent biologic propensity to behave more aggressively, highlights the need for thorough and complete removal. Studies by Ramappa et al  and Lin et al  emphasize the correlation between periacetabular tumors and a marked increase in recurrence, malignant transformation, and metastasis. However, for this tumor, local recurrence may not necessarily be indicative of a more aggressive biology, as this behavior may also result from inadequate initial removal.
Surgical dislocation of the femur allows complete visualization of the femoral head and the acetabulum, which provides the best method to perform a complete intralesional curettage while minimizing iatrogenic complications. This method of access offers promise for improved outcomes of benign femoral head tumors including chondroblastomas.
Daniel Baquet and Keenan Sobol are medical students at Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, Pennsylvania. John A. Abraham, MD, is an Associate Professor of Orthopaedic Surgery and Director of the Musculoskeletal Oncology Center at Thomas Jefferson University Hospital and the Kimmel Cancer Center, Philadelphia, Pennsylvania.
Adult Reconstruction Section Editor, Rothman Institute Grand Rounds
The authors have no disclosures relevant to this article.
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