Endoscopic Osteochondroma Resection for Treatment of Ischiofemoral Impingement Through Posterior Approach: A Case Report

Supplemental Digital Content is Available in the Text.

Abstract:

Narrowing of the ischiofemoral space leading to the entrapment of neurovascular structures is the pathologic basis of ischiofemoral impingement (IFI). In our clinical practice, we encountered a patient with secondary IFI because of an osteochondroma in the lesser trochanter region, presenting with typical posterior hip pain. Traditional surgical methods typically involve lesion resection through a posterolateral approach to the hip, with only a few patients reported using hip arthroscopy. We present a modified posterior hip arthroscopic technique for resecting an osteochondroma near the lesser trochanter. This technique allows for rapid access to the lesion site and provides clear visualization of the sciatic nerve under arthroscopy, facilitating safe and thorough lesion resection.

Level of evidence V, Case Study.

INTRODUCTION

Ischiofemoral impingement (IFI), first described by Johnson et al¹ in 1977, is characterized by abnormal contact between the lateral aspect of the ischial tuberosity and the lesser trochanter of the femur. Although IFI is considered rare, there is a lack of comprehensive studies on its pathophysiology, diagnosis, and treatment. The narrowing of the ischiofemoral space underlies this impingement, with causes typically categorized as primary (congenital) or secondary (acquired).² Osteochondroma, also known as exostosis, is a common benign bone tumor. It can develop on any bone but predominantly appears at the metaphyses of long bones, with approximately 90% occurring at the metaphysis of the distal femur, tibia, and humerus.^3,4 In contrast, proximal femur involvement is relatively rare.^5,6 Osteochondromas are often asymptomatic and usually discovered incidentally. Symptomatic patients may present with pain because of mechanical pressure exerted by the tumor on surrounding blood vessels and nerves, fracture of the tumor's bony stalk, or the development of bursitis.⁷ Osteochondromas located at the lesser trochanter can cause impingement by narrowing the space between the ischium and femur, particularly in certain hip joint positions. Tumor-induced narrowing of the ischiofemoral space leading to IFI has been documented,⁸ but the literature primarily focuses on diagnosis and clinical presentation, with limited discussion on treatment options. In general, if conservative treatment fails, surgical intervention methods include open approaches and hip arthroscopy,^9–11 which are feasible surgical options but not yet standardized. Articles on the resection of lesions to treat IFI through hip arthroscopy have been reported, but most studies involve arthroscopic resection with the patient in the supine position.¹² In recent years, the direct posterior hip arthroscopic approach with the patient in the prone position has gained increasing attention.^13,14

In this article, we report a case of osteochondroma resection in the lesser trochanteric region using this posterior hip arthroscopic technique with the patient in the prone position, achieving satisfactory outcomes. This case represents a novel treatment option that has not been previously documented.

Case Report

On December 24, 2023, a 23-year-old man presented to our orthopedic clinic with a complaint of posterior left hip pain persisting for >2 months (Figure 1A). The pain was intermittently exacerbated by activities such as squatting or prolonged walking, which rendered him unable to walk during flare ups. However, the pain subsided with rest. The patient reported no underlying medical conditions or history of hip joint trauma. On physical examination, no swelling was observed in the left hip joint, and there was minimal tenderness around the hip area. The patient exhibited a normal gait but reported posterior left hip pain and lower limb numbness on attempting to squat. The range of motion for hip flexion and extension was largely within normal limits. However, passive flexion with external rotation elicited posterior hip pain. An MRI scan was ordered by the outpatient physician (Figure 1C, F), which revealed an osteochondroma at the proximal left femur, accompanied by significant surrounding soft tissue edema. Given the severity of the pain and its impact on the patient's daily activities, surgical intervention was recommended, and the patient consented to hospitalization for the procedure. After admission, a computed tomography (CT) scan of the hip was performed (Figure 1B, D, E), which demonstrated a spike-like bony protrusion at the medial border of the lesser trochanter of the proximal left femur, measuring approximately 3.3 cm in length. The patient's preoperative visual analog scale (VAS) score was 7. Based on these radiologic findings, a diagnosis of proximal femur osteochondroma with secondary posterior IFI was confirmed.

Figure 1.

Preoperative radiographic examination. A, X-ray imaging; (B, E) CT 3-dimensional reconstruction imaging; (C, F) MRI with red arrows indicating perilesional soft tissue edema; (D) CT slice images showing the narrowest interspace between the femur and ischium in red, measuring 15 mm.

Surgical Technique

After excluding surgical contraindications, hip arthroscopy was performed to excise the osteochondroma lesion (Figure 2). Under general anesthesia, the patient was positioned prone. Using C-arm fluoroscopy, the lesion on the posterior surface of the hip was identified and marked (Figure 3B). The path of the sciatic nerve was also roughly delineated. Three portal sites were marked (Figure 3A): the posterolateral portal (viewing portal), the posteroinferior portal (working portal), and the posteromedial portal (nerve protecting portal). After preparing and draping the surgical field, the procedure commenced. A camera was introduced through the viewing portal. Under visualization, straight forceps were inserted through the working portal to bluntly dissect the subcutaneous fascia and muscle fibers down to the bone surface at the posteromedial margin of the proximal femur, thereby identifying the osteochondroma lesion. The sciatic nerve was located medially. Dynamic internal and external rotation of the hip demonstrated the impingement between the bony protrusion and the sciatic nerve (Figure 4A, B. Video 1, Supplemental Digital Content 1, http://links.lww.com/JSM/A524). A rubber sleeve (Figure 4C) was inserted through the posteromedial portal to retract the sciatic nerve medially, away from the lesion area. The surrounding tissues of the lesion were released to fully expose its base. A basket forceps was used to obtain a sample of the lesion tissue for examination. An electric burr was then used to grind down the lesion from its top to the base until it was flush with the cortical bone surface (Figure 4D. Video 2, Supplemental Digital Content 2, http://links.lww.com/JSM/A525). Fluoroscopy confirmed the complete resection of the lesion. Internal and external rotation of the hip postresection confirmed that the sciatic nerve impingement had resolved, indicating thorough decompression (Figure 4E, F. Video 3, Supplemental Digital Content 3, http://links.lww.com/JSM/A526). The surgical field was irrigated, the portals were closed, and the surgery was completed.

Figure 2.

Schematic illustration of endoscopic osteochondroma resection for treatment of IFI through posterior approach.

Figure 3.

Location of the surgical portal sites; (A) surface projection of the surgical portals; (B) fluoroscopic determination of the position of the surgical portals.

Figure 4.

Intraoperative arthroscopic images of osteochondroma resection. A, B, Impingement between the bony protrusion and the sciatic nerve during internal and external rotation of the hip; (C) the sciatic nerve is retracted medially for protection using a rubber sleeve; (D) resection of the lesion is performed using a burr; (E, F) after lesion excision, the impingement of the sciatic nerve disappears on internal and external rotation of the hip.

Postoperative Rehabilitation

On returning to the ward, the patient underwent routine monitoring of vital signs and received nonsteroidal anti-inflammatory drugs (NSAIDs) for pain management, along with supportive care. The patient was able to ambulate 6 hours postsurgery.

RESULTS

In the early postoperative period, the patient's posterior left hip pain significantly improved (Figure 5A‒D), with no signs of sciatic nerve injury. On the first postoperative day, the VAS score was 2, and the patient could squat independently without pain. Postoperative CT scans confirmed the complete resection of the osteochondroma lesion. At the 3-month follow-up, the modified Harris Hip Score improved from 39 preoperatively to 92 postoperatively, with a VAS score of 0.

Figure 5.

Postoperative imaging and intraoperative pathologic findings.

DISCUSSION

Osteochondroma-Induced Ischiofemoral Impingement

Osteochondroma is a benign tumor characterized by excessive endochondral bone growth. These tumors are typically solitary but can occur at various anatomical sites. A study by researchers from Southern Medical University analyzed 431 patients of solitary osteochondromas in China and found that the majority occurred at the distal femur and proximal tibia, with <3% involving the proximal femur.⁴ Osteochondromas are usually asymptomatic. In the patient we report, the osteochondroma was situated below the lesser trochanter of the femur, with a screw-like protrusion extending inward and upward. This resulted in a narrowed ischiofemoral space, leading to impingement during hip movement, causing the patient to experience posterior hip pain and lower limb numbness, thereby affecting daily activities. The narrowing of the ischiofemoral space is the pathologic basis for IFI.^15–18 Imaging studies can elucidate the cause and precise location of IFI impingement. Vicentini et al¹⁹ demonstrated that MRI comparisons, with and without quadratus femoris muscle edema, and measurements of the ischiofemoral space, revealed significant narrowing in patients with IFI. Their statistical analysis established an ischiofemoral space of ≤17 mm as a diagnostic threshold for IFI. In our patient, MRI measurements indicated an ischiofemoral space of 15 mm. However, the ischiofemoral space is dynamic, narrowing most during hip extension, adduction, and external rotation. These movements can serve as diagnostic tests for IFI, because they provoke impingement.²⁰ It is crucial to note that the MRI of our patient also revealed an anterolateral labral tear of the hip joint, which could complicate the assessment of the pain source.²¹ Studies indicate that patients with acetabular labral tears may experience posterior hip pain.²² Differential diagnosis can be achieved through impingement tests, particularly when posterior hip pain and radiating numbness of the lower limb are elicited during hip extension, adduction, and external rotation.

Treatment of Ischiofemoral Impingement

Treatment for patients with IFI typically begins with conservative methods, including oral NSAIDs, traditional physical therapies, or local injections.²³ When conservative treatments fail, surgical interventions, such as open approaches and hip arthroscopy for lesion excision, become viable options. Previous case reports have described various surgical approaches for IFI treatment. For instance, 1 patient of IFI caused by an osteochondroma was successfully treated with an open excision using an anterior approach to the ischiofemoral space.⁵ Another report detailed the use of a transverse posterior approach,²⁴ highlighting its aesthetic advantages and better visualization of neurovascular structures. Although these reports did not mention complications, open incisions carry a higher risk of trauma. In addition, the intraoperative use of retractors to expose deep tissues may endanger surrounding neurovascular structures, potentially leading to delayed recovery. Despite these risks, open incision treatments for IFI were considered reliable until recent advancements in endoscopic techniques and equipment. With the development of minimally invasive techniques, hip arthroscopy has become an increasingly popular method for treating IFI. Hip arthroscopy for IFI can typically be performed through 2 approaches: the ischiofemoral space approach (posterior) and the peritrochanteric space approach (anterolateral).²⁵ The anterolateral approach is more familiar to surgeons and is commonly used for arthroscopic treatments of IFI. Patients generally require only a supine position for the surgery. During the procedure, a 70 degrees scope can provide a comprehensive 360-degree view of the lesser trochanter, making this approach particularly advantageous for IFI caused by lesser trochanter lesions. Safran et al²⁶ reported successful excision of the lesser trochanter using the anterolateral approach for hip arthroscopy, resulting in satisfactory outcomes. There is limited literature on hip arthroscopy using the posterior approach. Ge et al¹³ reported a case of endoscopic ischial tuberosity osteophyte resection for IFI treatment, choosing this approach to better expose the lesion area of the ischial tuberosity. In our case, we opted for the posterior approach because the osteochondroma extended posteromedially, with its apex extremely close to the sciatic nerve. The primary surgical challenge was the risk of sciatic nerve injury. Thus, visualizing the sciatic nerve and implementing protective measures facilitated a safer excision of the tumor.

We propose several recommendations to enhance surgical outcomes and minimize complications in the treatment of osteochondroma-induced IFI: (1) Modified posterior approach: position the incision closer to the lesion to avoid excessive soft tissue dissection. Initially, localize the osteochondroma using X-ray imaging. At the same level, insert the arthroscope and surgical instruments to quickly expose the lesion at the posterior aspect of the lesser trochanter and the sciatic nerve. (2) Cautious use of radiofrequency ablation: given the proximity of the lesion to the sciatic nerve, exercise caution when using radiofrequency ablation. Blunt dissection with straight forceps can create a potential space through the fascia and muscle fibers toward the lesion. Once the lesion and sciatic nerve are exposed, minimize the use of radiofrequency ablation to prevent thermal injury to the nerve. (3) Appropriate nerve protection measures: intraoperative observations indicated that the osteochondroma was closely adherent to the sciatic nerve, with dynamic impingement occurring during hip extension and external rotation. Implement nerve protection before lesion excision. Use an additional medial incision to place a rubber sleeve around the sciatic nerve, retracting it away from the lesion to provide a larger working space for lesion removal. (4). Intraoperative neurophysiologic monitoring: real-time monitoring of nerve functional activity helps in early identification of nerve injury, thereby minimizing the risk of permanent damage. This technique ensures the safe and effective removal of the osteochondroma while protecting the sciatic nerve.

The primary objective of the surgery is to excise the osteochondroma lesion completely. According to Khare et al²⁷, the surgical excision of the entire cartilaginous cap and the periosteum covering it is fundamental to preventing recurrence of osteochondromas. Surgeons may opt to extend the resection area by slowly removing some of the surrounding healthy bone tissue with a burr. It is crucial to avoid injuring the medial circumflex femoral artery, located above the lesser trochanter. In addition, use intraoperative fluoroscopy and dynamic observation of the lesion with hip internal and external rotation to assess the extent of lesion removal and achieve comprehensive decompression.

In the most recent 3-month postoperative follow-up evaluation, the patient expressed high satisfaction with the results. Postoperative CT images showed effective lesion clearance. The patient's modified Harris score improved from 39 preoperatively to 92 postoperatively, and the VAS score decreased from 7 to 0.

Conclusions

From this case, we draw the following conclusions: Osteochondromas in the lesser trochanter region are rare but can cause IFI, which can be clearly diagnosed through imaging and physical examination. Using a posterior approach in hip arthroscopy provides excellent exposure of structures surrounding the lesser trochanter, including the sciatic nerve. Implementing reasonable measures to protect the sciatic nerve intraoperatively allows for the complete removal of lesions near the trochanter, and dynamic observation of sciatic nerve decompression can be directly performed. Satisfactory outcomes can be achieved postoperatively for patients, as demonstrated by significant improvements in clinical scores and patient satisfaction.