Acetabular labrum tears are the most common type of intra-articular hip disorders1. Injury, dysplastic hip, femoral acetabular impingement, capsular slackness, and degenerative joint disease (DJD) are associated with labral tears1. Disruption of the labrum can destabilize the joint and worsen the degenerative changes2. A paralabral cyst (PC) is a benign cyst frequently associated with tears of the labrum of the shoulder or hip3. Most PCs are asymptomatic and are incidental findings on different imaging modalities. PCs and associated labral tears can be evaluated with various radiologic modalities. Among them, magnetic resonance imaging (MRI) can effectively reveal a PC; however, its ability to diagnose labral tears is limited. Symptomatic cysts are rare but require critical evaluation. A paralabral ganglion cyst has rarely been identified as a potential source of nerve compression4,5. There is a paucity of literature showing PC of degenerative hip joint producing a clinically detectable mass effect that can incite significant femoral mononeuropathy. The present report intends to represent an unusual case of a ganglion cyst secondary to labral tear associated with hip joint pathology, causing femoral mononeuropathy.
The patient was informed that data concerning the case would be submitted for publication, and he provided consent.
A 61-year-old man presented with a 5-year history of pain in the left hip and a 6-month history of swelling in the left groin. During the ensuing 3 months, he had progressively worsening pain with radiation to the knee and below. He complained of hypoesthesia over the anteromedial side of the left thigh and proximal muscle weakness in the left lower limb. Pain and swelling were gradual in onset and were not associated with any history of trauma. His sleep was disturbed due to pain, and he needed analgesics on a daily basis for the last 3 months before presenting to our clinic. On clinical examination, a diffuse swelling in the groin lateral to femoral vessels was found, which was tender on deep palpation. The left hip joint movements were painful and terminally restricted. The examination of the spine was normal. Neurologic assessment demonstrated quadriceps weakness, sensory deficit (anteromedial thigh), and diminished patellar tendon reflex. Routine blood test results were within normal limits. An anteroposterior radiograph of the left hip joint showed severe DJD (Fig. 1). Radiograph and MRI of the lumbosacral spine were normal. Neurophysiologic studies revealed left femoral neuropathy. The MRI of both hips with a screening of the spine demonstrated a 5.3 × 2.9-cm cystic lesion arising from the anterior rim of the left hip joint, extending into the anterior compartment of the groin and into the pelvis (Fig. 2). The cyst displayed low signal intensity on T1-weighted magnetic resonance image and high signal intensity on T2-weighted magnetic resonance image. Adjacent to the anterior acetabular tear, a PC of the left hip joint was seen. Computed tomography-guided aspiration confirmed gelatinous material which was negative on culture. After aspiration, the patient did have some temporary relief, but the symptoms were not adequately resolved. Given the severe pain and functional disability, the patient was counseled and advised total hip replacement (THR) with excision of the cyst. After appropriate preoperative planning, he underwent left THR through an anterolateral surgical approach. Intraoperatively after hip dislocation and neck cut, on excising the anterior labrum, the acetabular cyst was encountered and 5 mL of gelatinous material was drained from the anterior superior margin of the acetabulum cyst. Intraoperatively, it was noted that the cyst had no connection with the joint space. The joint capsule was found to be intact. The cystic lesion was dissected up to its base and was completely excised. Resected cyst tissue was sent for histopathologic examination, which reported a ganglion cyst, affirming the diagnosis of labral tear-associated paralabral ganglion cyst. The postoperative course was uneventful, and the patient underwent a protocol of physical rehabilitation. He was pain free and showed a considerable reduction in neurologic symptoms, with the disappearance of swelling at regular follow-up. On follow-up at 6 months, the symptoms of compressive neuropathy had almost completely resolved, and he returned to normal life activity. His Harris hip score increased from 33.9 preoperatively to 91.6 at 2-year follow-up. Repeat MRI scan at 2-year follow-up showed complete resolution with no recurrence of the cyst (Fig. 3), and he remained pain free at 4-year follow-up.
Although rare, cysts around the hip joint often pose difficult and challenging problems in the differential diagnosis and treatment. The use of advanced diagnostic imaging has increased dramatically, leading to a corresponding increase in the detection of these cysts as incidental findings. The exact etiology is unknown, but bursae around the hip joint, synovium herniation into the adjacent soft tissue, dislodgment of the synovium during the embryonic period, and degenerative or inflammatory processes in an adjacent joint or a tendon sheath have been proposed as conceivable etiologic variables6. Histologically, PCs belong to 2 major categories: the ganglion cyst and the synovial cyst7. The lack of distinct clinical and imaging features presents a diagnostic difficulty. PCs are often associated with labral tears8. The authors speculate that the reason for an acetabular labral tear in our case may attribute to DJD2. Furthermore, poor blood perfusion to the anterior acetabular labrum renders it more susceptible to “wear and tear” process. Tear of the acetabulum labrum is an acquired biomechanical lesion that is common in hip osteoarthritis and may be attrition in nature9. Acetabular labral tears occur long before the arthritis sets in and may eventually cause degenerative hip disease. Although asymptomatic, cystic lesions around the joint can exert painful compression on the adjacent neurovascular structures when they become enlarged10. Patients with a cyst of the hip joint may present with groin or thigh pain, sciatica or radicular pain, inguinal swelling, inguinal lymphadenopathy, large pulsatile groin mass, soft mass, or a growing mass misdiagnosed as hernia or tumor10-12. Cysts around the hip joint are known to cause femoral neuropathy. These are mostly synovial cysts10. Femoral compressive neuropathy secondary to a ganglion cyst is extremely rare, and only a few reports are present in the literature4,5,10. The authors suggest that in the present case, the gelatinous fluid in the large cyst was under hydrostatic pressure to a level sufficient to cause femoral compressive neuropathy both directly and indirectly. Kalacı et al. reported femoral neuropathy caused by compression from a ganglion cyst of the hip joint4. There was no associated acetabular labral tear with the PC, and the hip joint was normal. Herein, the authors present a unique case of femoral compressive mononeuropathy secondary to a paralabral ganglion cyst associated with DJD. Therapeutic strategies for cystic lesion of the hip vary depending on size, location, presence or absence of any mass effect, symptom severity, and the underlying or associated conditions. Small and asymptomatic cystic swellings can be addressed by conservative management10. Image-guided cyst aspiration10 has a place in the management of the mass effect of the enlarging cyst, but given the risk of incomplete evacuation owing to thick gelatinous fluid and recurrence, the authors have suggested that it should be limited to groups of patients who demand minimal invasive procedure and refuse for any surgical intervention13. In view of the high recurrence rate after conservative surgical treatment, we recommend complete cyst excision to limit the chance of recurrence14. Kanauchi et al. showed excellent outcome with arthroscopic labral repair and cyst aspiration in patients desiring minimal invasive treatment15. The authors speculate that complete resolution is less certain until the underlying disease has been treated. Furthermore, when a cystic lesion is associated with hip joint pathology, as in the present case, conservative treatments, simple aspirations, and arthroscopic repair are not successful and there is a need for surgical treatment10,16. As a part of holistic approach, the patient in the present case was advised THR to provide superior pain relief, stability of the hip joint, and improved range of motion. In addition to THR, excision of the cyst from the base of the sac was also advised to resolve the compressive symptoms and reduce the recurrence rate.
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