Endoscopic Repair of Ischial Tuberosity Avulsion Fracture

Abstract

Background:

The ischial tuberosity apophysis serves as an attachment site for the hamstring muscle complex in the pediatric pelvis. Once the apophysis begins to ossify around age 13 to 15 years, decreasing elasticity makes the physis the weakest part of the hamstring attachment to the pelvis. An avulsion injury of the hamstring muscle group in the adolescent therefore results in a fracture in the adolescent and is the functional equivalent to a 3-tendon proximal hamstring injury in an adult. Ischial tuberosity fractures have a higher rate of non-union than other pelvic apophyseal injuries. Endoscopic surgery offers the advantage of smaller incisions, reduced wound complications, and expedited recovery compared with an open procedure.

Indications:

Controversy exists over which fractures benefit from surgical fixation. Patients with an ischial tuberosity avulsion fracture that is displaced more than 20 mm or that remains symptomatic despite at least 3 months of conservative management are common indications for surgery.

Technique Description:

The patient is positioned in the prone position and under fluoroscopic guidance 2 endoscopic portals are created. The sciatic nerve is visualized, neurolysis performed, and then protected throughout the remainder of the case. The ischial tuberosity is located along with the avulsed apophysis and hamstring tendon. The bony surfaces are prepared. The fracture fragment is reduced and 3 partially threaded cannulated screws are percutaneously passed across the fracture. The interval between the semimembranosus and conjoined tendons was closed with a suture.

Results:

There are no results published specific to this technique. Outcome papers are lacking, but cohort studies show significant displacement increases risk for non-union. Displaced ischial tuberosity fractures are also thought to risk sciatic nerve irritation and decreased hamstring strength.

Discussion/Conclusion:

Recent advancements in periarticular endoscopic surgery of the hip have enabled this historically open procedure to be performed in a minimally invasive fashion. This technique achieves robust fixation of the avulsed fragment and the benefits of anatomic repair of the hamstring origin while avoiding the larger incision and soft tissue dissection required for an open procedure. In time, this technique may become standard of care much like other sports medicine procedures which have transitioned from open to arthroscopic with the development of suitable tools and techniques.

Patient Consent Disclosure Statement:

The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

Here, we present our technique for endoscopic open reduction and internal fixation of an ischial tuberosity avulsion fracture in an adolescent athlete.

The authors’ disclosures are seen here.

The pediatric pelvis contains several apophyses which do not contribute to longitudinal growth but serve as muscular attachment sites in a child. The ischial tuberosity apophysis serves as the attachment site for the hamstring muscle complex—specifically the biceps femoris, and semimembranosus and semitendinosus origins.^5,7

There is a narrow window of time, during which the adolescent is nearing skeletal maturity, that the majority of these pelvic apophyseal injuries occur. They are most common in males and typically occur between ages 13 and 16.^1,3,6 The anterior inferior iliac spine is the most common fracture site accounting for approximately 49% of apophyseal fractures about the pelvis.^6,8 This is followed by the anterior superior iliac spine with another 30% and then the ischial tuberosity with 19%.^6,8 Common mechanisms of injury for the ischial tuberosity avulsion injury are running, sprinting, kicking, and other explosive movement patterns.^3,6

Our patient is a 17-year-old high school lacrosse player who presented after an injury in which his right leg planted and twisted with immediate right hip pain. His injury was managed conservatively with physical therapy at an outside institution for 3 months. He continued to endorse posterior hip and buttock pain along with reduced strength of the hamstring muscle group and was unable to return to athletics. On examination, he had pain with the proximal hamstring stretch test.

Preoperative imaging showed avulsion of the ischial tuberosity with significant displacement on both the anteroposterior and lateral plain film images seen on this slide.

Here, we see the T2-weighted magnetic resonance images in both the coronal and axial planes that confirm the ischial tuberosity avulsion fracture with the proximal hamstring origin attached to the bony fragment. At 3 months post injury, there is still a significant amount of fluid and edema seen at the fracture site without evidence of bony bridging.

Here, we see sagittal images confirming involvement of all 3 tendons and displacement of the fracture with no contact between the bony surfaces.

Historically, these fractures have been managed conservatively with reasonable outcomes; however, fractures with displacement greater than 20 mm are associated with a higher risk of pain, sciatic nerve symptoms, and residual weakness. Twenty millimeters of displacement has become a threshold for considering open fixation; however, this remains a point of debate among pediatric and sports medicine surgeons. Achieving a good exposure and dangers of retraction on the neurovascular structures are among the challenges of open fixation. The advent of endoscopic techniques for proximal hamstring repair in the skeletally mature patient potentially makes operative fixation in these patients more appealing. ⁴

We recommend this technique for patients with an acute fracture that has moderate displacement (20-30 mm) of the fracture fragment. We would not use the endoscopic approach for a chronic injury or in a non-union and would prefer to perform an open procedure in order to identify and protect the sciatic nerve while preparing the fracture site.

Our surgical technique for endoscopically assisted reduction and fixation is presented here. The patient is placed in a prone position either on a normal operating room table with pillows to support the torso or on a Wilson frame. It is important to build a bump of pillows or towels at the edge of the bed to maintain knee flexion and consequently to reduce tension on the hamstring complex during the procedure.

We create 3 portals within the gluteal fold and one more proximally. Fluoroscopic guidance is used to ensure adequate and safe positioning of the portals. A 5-mm incision is made 2 cm distal to the ischial tuberosity overlying the hamstring tendon. A 30° endoscope is inserted through this portal with the pump set to 35 mm Hg. An accessory portal is created using an outside-in technique, under direct visualization 5 cm proximal to the first portal. A third portal is made in the gluteal crease 4 cm lateral to the viewing portal to assist with repair and neurolysis. When placing the lateral portal, we do this under direct visualization. We recommend that the surgeon errs superficial and corrects the trajectory to a steeper angle as needed while visualizing the nerve with the arthroscope.

The initial interval is within the bursal space between the gluteus maximus and the hamstring tendons/ischial tuberosity. The interval between the hamstring tendon complex and the sciatic nerve is then developed and dissection undertaken to visualize the sciatic nerve. Scar and adhesions are variably present depending on the individual patient's response to the initial injury. A careful sciatic neurolysis is performed with blunt dissection and a radiofrequency device. An operative assistant holds the foot and calf from the beginning of the case to the end of this step and immediately alerts the surgeon to any movement.

Next, the ischial tuberosity fracture fragment is identified with direct visualization and confirmed with fluoroscopy. The fracture site is also identified and fully visualized proximally and laterally. It is gently mobilized with a periosteal elevator. Both surfaces are prepared using an arthroscopic rasp. Fluoroscopic imaging is used to confirm mobilization and complete preparation of the proximal fracture bed. The interval between the semimembranosus and conjoined tendons is then identified and gently split longitudinally to visualize the bony surface underneath and create a pathway for the screws. This allows them to be placed directly against bone for better compression and then to be covered by the tendons to reduce the risk of the hardware being symptomatic.

The fracture fragment is reduced and temporarily fixed with 1 to 2 K wires. We prefer to use the accessory distal and posterolateral portals for K wire and screw placement as these have the most direct access for screw and wire passage. This is similar to the trajectory needed for anchor placement in endoscopic hamstring repair. Three partially threaded 4.0-mm cannulated screws are passed across the fracture with excellent compression of the fracture seen here. Position of each wire and cannulated screw was confirmed on radiograph imaging.

Here, we see another K wire, which will be replaced with a cannulated screw.

Final intraoperative fluoroscopic imaging is seen here.

Following this, the interval between the semimembranosus and conjoined tendons is closed with a simple absorbable suture.

This final image demonstrates the proximity of the sciatic nerve and the more superficial and smaller posterior cutaneous nerve of the thigh. One must be mindful of the anatomy in this region and protect the sciatic nerve throughout the case.

This slide highlights some tips and tricks to be able to perform the case safely and effectively. We recommend draping the surgical leg so that it is able to be moved during the case. Extending the hip and/or flexing the knee will detension the hamstring complex which is helpful during fracture reduction and fixation. It will also take tension off the sciatic nerve. We recommend locating and clearly visualizing the sciatic nerve early on in the case and then remaining cognizant of its location throughout the remainder of the case to minimize the risk of injury. Make the lateral portal and a direct visualization, initially erring more superficial and redirecting to a steeper angle as needed. If needed, based on the individual patient's anatomy, a switching stick can be placed in the posteromedial portal and used to gently retract the nerve laterally away from the ischial tuberosity. Splitting the hamstring tendons in the line of their fibers provides access for the K wire and cannulated screws. This also enables the split to be closed over the screw head, thus minimizing the chance of irritation from the metalware.

Postoperatively, the patient is made touchdown weight bearing for 2 weeks; they are kept in a hinged knee brace locked at 50° flexion to prevent tension on the repair. During phase 2, weight bearing is progressed to 50% of body weight. The knee brace remains in use to protect the repair, locked at 30° during the day and 50° at night while sleeping. This phase lasts until 6 weeks postoperative and a radiograph is obtained at this stage prior to progressing to phase 3.

Phase 3 of the protocol focuses on normalizing gait and functional movements with work on hip and core strengthening. In phase 4, we continue strengthening and begin working on sport-specific movements. We avoid explosive or sprinting activities until after the 12-week mark. Patients are allowed to return to sport when it is deemed they may do so safely by the treating surgeon in conjunction with their physical therapist. They need to have dynamic control of their lower extremity with excellent core and hip strength. We also use nerve glide techniques to minimize postoperative scarring around the sciatic nerve.

At the 6-week follow-up appointment, imaging shows anatomic reduction of the fracture fragment with excellent healing. Clinically, the patient was pain free, fully weight bearing, and looking to increase his physical activity level.

There are no reported outcomes in the literature specifically relating to endoscopic repair of an ischial tuberosity avulsion fracture. However, recent meta-analysis of pelvic apophyseal avulsion fractures shows a higher success rate and higher return to sport rate when these injuries are treated surgically. ² In particular, if the fragment was displaced more than 15 mm or the patient had high functional demands, operative treatment was shown to improve outcomes. The advent of a more minimally invasive technique offers multiple benefits to patient and surgeon and may be a more appealing choice of surgical fixation to achieve an anatomic repair for these young and active patients.

Here are our references. Thank you for your interest.