Hypertrophy of the tensor fascia lata: A pseudotumor due to lumbar radiculopathy.

BACKGROUND: Pseudotumor of the tensor fascia lata (TFL) consists of a rare, benign soft tissue mass/hypertrophy of the TFL that appears on the anterolateral aspect of the proximal thigh. Notably, this condition often mimics a malignant tumor and may be misdiagnosed as a sarcoma. CASE DESCRIPTION: A 45-year-old male presented with left hip/groin pain, swelling, and a painful mass on the anterolateral aspect of the left hip/thigh. The symptoms had started 3 months ago following an L1-S1 lumbar laminectomy/fusion. The initial diagnosis was hip disease, and the patient underwent a left MR arthrogram. When this study demonstrated a tear of the left anterosuperior acetabular labrum plus an increased alpha angle causing femoroacetabular impingement, the patient then underwent a left hip arthroscopy. However, as he continued to complain of the hip mass, he was referred to an orthopedic oncologist whose presumptive diagnosis favored a sarcoma. Nevertheless, the pelvic MRI scan and ultrasound (US) confirmed the diagnosis of hypertrophy of the left TFL (US left 33.4 mm vs. right 14.4 mm). The patient was first treated with 50 units of locally injected botulinum. As there was no symptomatic relief, the plan was to repeat the injection within the next few months.
CONCLUSION: Hypertrophy of TFL may mimic a neoplasm such as a sarcoma and contributes to what appears to be a lumbar radiculopathy. However, MR and US imaging should readily identify TFL and rule out malignant lesions such as sarcomas. Copyright:

INTRODUCTION

Hypertrophy of the tensor fascia lata (TFL) muscle is a benign condition that is often mistaken for a tumor. Patients may present with palpable masses, pain, or both in the anterolateral thigh region and/or hip, and symptoms that mimic lumbar radiculopathy.[7] MR, ultrasound (US), and EMG/NCV studies are the preferred modalities to confirm the diagnosis of TFL hypertrophy.

Here, we present a 45-year-old male with a TFL pseudotumor/hypertrophy that contributed to an L5 radiculopathy.

CASE PRESENTATION

Clinical presentation and physical exam

A 45-year-old male presented with left hip/groin pain, swelling, and a painful mass of the anterolateral left hip (i.e. tendency for the left hip to “lock”)/thigh. These symptoms began 3 months following a lumbar laminectomy with an L1-S1 fusion. On examination, prominence of the left TFL was noted along with weakness of left hip abduction and decreased sensation of the left leg/thigh.

MR findings

An MR arthrogram demonstrated a tear of the left anterosuperior acetabular labrum with an increased alpha angle supporting femoroacetabular impingement. Nine months later the patient underwent a left hip arthroscopy with labral repair/base fixation, femoroplasty, and capsular closure. Although the left hip/groin pain improved, he continued to complain of the painful hip mass and was referred to an orthopedic oncologist with the presumed diagnosis of a sarcoma. The pelvic MRI scans demonstrated asymmetry due to hypertrophy of the left TFL [Figure 1a and b]. There was no soft tissue fluid collection or mass.

Figure 1:

(a) Axial and (b) coronal pelvic MRI scans demonstrating the hypertrophic tensor fascia lata (yellow) on the left as compared to the right side.

Ultrasound results for TFL

A substantially greater width of the TFL muscle was observed by high-resolution US on the left (33.4 mm) compared to the right (14.4 mm) side [Figure 2].

Figure 2:

High-resolution ultrasound images revealed a greater width of the tensor fascia lata muscle on the left (33.4 mm) compared to the right (14.4 mm) side.

EMG/NCV studies

The needle EMG showed chronic denervation/reinnervation changes of the left TFL with large amplitude polyphasic units and complex repetitive discharges. Increased polyphasic units were also observed in the gluteus medius, vastus medialis, and tibialis anterior. The EMG/NCV study suggested chronic lumbosacral radiculopathy involving L4 and L5 on the left.

Treatment with botulinum toxin

The patient underwent an injection of 50 units of botulinum toxin (diluted to 5 units per 0.1 ml) under electromyographic guidance. He attained no improvement of his left leg spasms. Nevertheless, the patient will undergo an injection of 100 units of botulinum toxin within the next 3 months.

DISCUSSION

There are only a few case reports and series in the literature concerning hypertrophy of the TFL [Table 1].[1-5,7,9] They typically describe a mass in the anterolateral thigh that must be differentiated from sarcomas. MRI is the gold standard for confirming TFL hypertrophy.[3,6] US also plays a valuable role in corroborating the diagnosis, along with electromyography [Table 1].[2[

Table 1:

Hypertrophy of the tensor fascia lata.

Treatment of TFL

The treatment of TFL usually involves regular strength training of the hip abductors. Botulinum toxin injections may also be beneficial by mitigating symptoms and decreasing the size of the TFL.[5]

Etiology of TFL

Two theories exist as to the etiology of pseudotumor of the TFL. These include mechanical vs denervation hypertrophy. For patients who have undergone hip surgery, altered biomechanics may lead to TFL. Compensatory hypertrophy may also occur following abductor tendon (gluteus minimus/ medius) tears.[2,4,10]

In this case, TFL was due to neurogenic hypertrophy related to L5 radiculopathy. While the pelvic MR and US studies revealed true hypertrophy of the TFL on the left side, the EMG showed somewhat non-specific complex repetitive discharges.[8]

Spine surgeons should be aware that postoperative patients may rarely develop TFL that is best confirmed on MR and US studies. Conservative treatment, including repeated injections of botulinum toxin, may be helpful in remediating persistent TFL symptoms/radiculopathy.