Core Decompression for Osteonecrosis of the Femoral Head

Abstract

Background:

Osteonecrosis, also known as avascular necrosis (AVN), of the femoral head occurs due to a reduced blood supply, leading to bone death, increased intraosseous pressure, and collapse. Primary risk factors include prolonged corticosteroid use, excessive alcohol consumption, and trauma—among various other causes. Core decompression is an effective treatment for relieving pressure and stimulating healing in the early stages of osteoarthritis.

Indications:

Core decompression for AVN is indicated for precollapse stages, such as Association Research Circulation Osseous (ARCO) 1 and 2. However, it is typically contraindicated in later, postcollapse stages, such as ARCO 3 and 4.

Technique Description:

In the supine position on a hip arthroscopy table with a post, traction can be applied to the operative limb, and any concomitant intracapsular pathology can be addressed before core decompression. A lateral incision is made over the proximal femur at the level of the greater trochanter. A guidewire is introduced into the necrotic region of the femoral head under fluoroscopic guidance. A lateral reamer is used to drill from the lateral cortex to beneath the subchondral surface. An expandable reamer and curettes are used to remove necrotic bone. Calcium phosphate bone graft substitute was injected into the femoral head and allowed to cure.

Results:

Overall, after core decompression for AVN, most patients demonstrate significant improvements in patient-reported outcomes (PROs) at a 2-year follow-up. The radiographic survival rate has been reported to be >76.9% at a 2-year follow-up. Total hip arthroplasty survival rates have been reported to be >72.1% at a 2-year follow-up.

Discussion/Conclusion:

Core decompression is an effective early-stage intervention for AVN of the femoral head, resulting in significant improvements in PROs and high radiographic survival rates at a 2-year follow-up. Future research may investigate optimal patient selection and high-quality studies exploring adjunctive therapies to maximize long-term outcomes.

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

In this video, we present the technique of core decompression for treating osteonecrosis, also known as avascular necrosis (AVN), of the femoral head. The procedure was performed by Dr Shane Nho and his team at Midwest Orthopaedics at Rush.

Background

AVN of the femoral head is characterized by impaired microvascular circulation in portions of the femoral head, leading to death of local bone tissue.^2,3,4,12 As a result, the homeostatic mechanisms that maintain the compressive strength of healthy bone are blunted, causing the diseased subchondral bone to become weak. If left untreated, the femoral head articular surface will eventually collapse, leading to severe degeneration of the hip joint.^2,3,4,12

Between 10,000 and 20,000 new cases of AVN occur annually in the United States alone. ¹³ Unfortunately, AVN of the femoral head most commonly affects younger patients between the ages of 20 and 40 years.^3,12 There are several potential risk factors contributing to the pathophysiology of AVN—including corticosteroid use, excessive alcohol consumption, and trauma—particularly injuries that can disrupt blood supply to the femoral head, such as femoral neck fractures or hip dislocations.^3,4,12 Other risk factors include systemic inflammatory conditions (eg, lupus), metabolic derangements (eg, hyperlipidemia and hyperuricemia), and many more archaic risk factors (eg, deep-sea diving).

The diagnosis for AVN is primarily based on imaging, including both plain radiographs and advanced imaging, with magnetic resonance imaging (MRI) being the gold standard because of its high sensitivity for detecting bone marrow change at any AVN stage.^7,9

There are various classification systems, such as the Association Research Circulation Osseous (ARCO), Ficat, and Steinberg classifications. The revised ARCO classification system, which is based on both plain radiographs and MRI, categorizes osteonecrosis of the femoral head into 4 distinct stages, as illustrated here.^2,5,7,9 Stages 1 and 2 encompass osteonecrosis without collapse of the articular surface, while stages 3 and 4 occur after collapse has taken place.

The current conservative management strategies have had questionable efficacy in the precollapse phases of osteonecrosis. These may provide some short symptomatic relief but do not address the underlying cause and rarely prevent progression of the disease.^2,4,12 In the early precollapse stages of the disease process, core decompression has been shown to be an effective surgical intervention in the treatment of AVN, delaying or obviating the need for total hip arthroplasty (THA), which remains the mainstay for symptomatic postcollapse osteonecrosis.^2,3

Indications

Core decompression is believed to decrease intraosseous pressure, restore blood flow to the affected area, and alleviate pain. It is indicated in the precollapse stages of AVN, such as ARCO 1 and 2, but contraindicated later in the disease after collapse has occurred in the cases ² of ARCO 3 and 4. Core decompression often combines a structural and/or biological augment, such as synthetic bone substitutes, vascularized bone grafts, bone marrow aspirate concentrate (BMAC), or platelet-rich plasma (PRP).

Here we present the case of a 23-year-old man with a past medical history of remote childhood leukemia in complete remission who presented with a chief complaint of left groin pain. His symptoms began atraumatically 2 months prior and had consistently been rated as a 6 from 10 in severity, and sharp in character. Aggravating factors included any form of weightbearing activity, despite exercise routine modifications and the use of oral anti-inflammatory medications. The physical examination demonstrated a limited range of motion, positive flexion, adduction, internal rotation, and log roll tests, and a positive Stinchfield test. Preoperative radiographs demonstrated a nonarthritic hip with a mild cam deformity. Although subtle, some lucencies can be appreciated in the superolateral aspect of the femoral head and neck. Preoperative MRI demonstrated a small acetabular labral tear and AVN of the femoral head.

On the T1 coronal image shown on the left, the red asterisk denotes the serpentine hypointense line extending to the subchondral plate, which is pathognomonic for osteonecrosis. Notably, the femoral head articular surface remains round and without evidence of collapse. On the T2 image shown on the right, the small labral tear is indicated by the white arrow. Also noted is edema in the superolateral aspect of the femoral head, which corresponds to the periphery of the segment of the head affected by osteonecrosis. Particularly when AVN is suspected, we prefer a noncontrast MRI. Typically, a 1.5-T magnet with a quality hip coil can produce satisfactory images.

Given the patient's persistent symptoms despite an adequate course of nonsurgical treatment, the patient was indicated for a left hip core decompression with an injection of a synthetic bone graft substitute. In cases such as this, where hip pain could also be attributed to borderline CAM-type femoroacetabular impingement (FAI), one may consider adding hip arthroscopy and concomitant treatment of FAI, including labral repair and femoroplasty. Unfortunately for this patient, his insurance carrier refused to authorize the arthroscopic portion of the procedure; thus, the patient elected to move forward with core decompression alone, understanding that his symptoms may not be resolved entirely postoperatively. Utilizing hip arthroscopy at the time of core decompression can also help to prevent iatrogenic damage to the femoroacetabular joint surface.

Technique Description

General anesthesia was administered, and the patient was transferred to a lower extremity suspension table. Using fluoroscopy, the radiopaque scalpel blade handle was used to mark the orientation of the femoral neck. A small 1-cm incision was then made in the skin, and the lateral cortex of the proximal femur was palpated with a spinal needle. A threaded guidewire was then advanced into the femoral head, aiming toward the affected region of the head seen on the prior MRI, using a combination of anteroposterior (AP) and lateral fluoroscopy.

Throughout the procedure, the C-arm is rotated to obtain a lateral view of the femoral neck. On the hip arthroscopy table, we recommend leaving the operative limb in neutral rotation such that the x-ray beam can be oriented 10° to 15° above the floor to match the patient's femoral neck version. This prevents the nonoperative hip from being captured in the x-ray field and obscuring the operative hip.

With the trajectory of the guidewire confirmed, a soft tissue protective sleeve was placed over the guide wire and advanced to the level of the lateral femoral cortex. A cannulated drill was then advanced over the guidewire to the level of the femoral head subchondral bone, and the drill was exchanged for an expandable reamer (Arthrex), which was then manually advanced into the femoral head and slowly expanded, thereby removing as much of the diseased subchondral bone as possible while minimizing removal of bone from the femoral neck. Expansion of the reamer should be performed under fluoroscopy, utilizing both AP and lateral views, to ensure the subchondral plate is not inadvertently violated. After the reamer has been maximally expanded, it is closed and withdrawn while leaving the soft tissue protective sleeve in place. A distally perforated and cannulated trocar was then advanced to the level of the decompression cavity and used to irrigate the socket. Then, a calcium phosphate bone graft substitute (Arthrex) was prepared on the back table, injected into the femoral head under fluoroscopic guidance, and allowed to cure. The trocar and soft tissue protective sleeve were then removed, and the wound was closed in standard fashion, and a sterile dressing was applied.

Here we highlight some technical points of the procedure. ¹⁰ Utilization of fluoroscopy throughout the entirety of the decompression is crucial when aligning instruments to the necrotic regions of the femoral head. The lowest diameter reamer should be used while gradually progressing to larger sizes until low resistance is achieved. The use of bone graft substitutes is readily available and can be obtained in larger quantities than autografts. Finally, the combination of arthroscopic and fluoroscopic visualization of the hip joint during the core decompression can be utilized to ensure no iatrogenic damage is done to the joint. When additional pathology exists, such as FAI and acetabular labral tears, we recommend completing the arthroscopic portion of the procedure in its entirety, aside from capsular closure, before the core decompression. Once the decompression is complete, the hip capsule can be closed, and the case can be completed.

Results

Our rehabilitation protocols for patients having undergone core decompression mirror those of other protocols following traditional hip arthroscopy and are split into 4 distinct phases. ⁸ Phase 1 spans from the immediate postoperative period to week 6. Patients are immediately placed in an abduction brace and instructed to use their crutches with flat-foot weightbearing on the operative leg. Patients can then wean from crutches between weeks 4 and 6. Phase 2 spans from weeks 6 to 12. Here, patients can initiate strength and gait training. This phase involves concentric strengthening followed by progression to eccentric strengthening. Phase 3 spans from months 3 to 4 and includes functional training in all planes, with the primary goal of returning to a preinjury level of activity by 16 weeks. This also includes beginning sport-specific movements. Phase 4 encompasses 4 months and beyond. During this phase, patients are allowed to gradually return to high-impact cardiovascular exercises, such as running and plyometrics. The goal of the final phase is to return to unrestricted sporting activity.

Discussion/Conclusion

Regarding the surgical treatment of AVN of the hip, Hoogervorst et al ⁶ conducted a retrospective cohort study involving 61 femoral heads in 40 patients. They evaluated survivorship from radiographic progression of disease as well as conversion to THA after core decompression augmented with BMAC. Survivorship from radiographic progression at 2 and 5 years was found to be 78.3% and 53.3%, respectively. ⁶ Survivorship from conversion to THA at 2 and 5 years was found to be 72.1% and 54.6%, respectively. ⁶

Mei et al ¹¹ also conducted a retrospective study on 64 hips in 59 patients comparing patients who underwent core decompression alone with those who underwent core decompression with an allogenic nonvascularized bone graft. Radiographic survival rates at a 2-year follow-up were found to be 76.9% and 77.3% in the 2 groups, respectively. ¹¹ In total, there was no difference in the rate of conversion to THA in either group. ¹¹

While there are numerous options for augmenting core decompression with biologic or structural augmentations, our preference is to utilize an off-the-shelf bone graft substitute, as it works well, is readily accessible, and is relatively inexpensive compared to biologic augmentation. A 2021 systematic review of 11 studies involving 560 hips found no conclusive evidence that biologic augmentation of core decompression with BMAC, PRP, or bone morphogenetic protein improves patient-reported outcomes or decreases rates of conversion to THA. ¹

Future research is needed to quantify the impact of synthetic bone graft substitutes on outcomes after core decompression.