Core Decompression With or Without Bone Marrow Aspirate Concentrate
This article outlines the evidence and history behind the use of core decompression to manage osteonecrosis of the femoral head and discusses its modern evolution to include bone marrow aspirate concentrate.
Paul Enns, MD; Simon Greenbaum, MD; Ran Schwarzkopf, MD, MSc; and James Slover, MD, MS
Osteonecrosis remains a leading cause of arthroplasty in younger patients. Despite decades of studying its etiology and pathophysiology, orthopaedic surgeons have only a modest ability to prevent or slow the progression of the sequelae of the disease.
The primary surgical treatment for early-stage osteonecrosis has been femoral head core decompression, and in this article, we outline the evidence and history behind core decompression and discuss its modern evolution to include bone marrow aspirate concentrate (BMAC).
Early Days of Core Decompression
French surgeons Paul Ficat and Jacques Arlet were among the first to identify femoral head core decompression as a possible treatment for osteonecrosis: They noticed symptomatic relief in patients who underwent the procedure to obtain core biopsy samples of affected femoral heads. They and others later described the technique as a joint-preserving procedure to treat early stages of femoral head osteonecrosis. [1-3]
Dr. David Hungerford was among the first surgeons in the US to use core decompression in the treatment of osteonecrosis of the femoral head with.  The Center for Osteonecrosis Education and Research at Johns Hopkins University was created by Dr. Hungerford and his colleagues, Dr. Michael Mont and Dr. Lynne Jones, to facilitate progress in understanding, diagnosing, and treating osteonecrosis.  Their work identified the success rate of the core decompression procedure (65%) compared with non-operative treatment, as well as its effectiveness in relation to pre- and post-collapse states of the femoral head. 
The original core decompression procedures were performed with a 6- or 8-mm hollow trephine. The technique evolved and was subsequently modified to include single or multiple tracts created by drills and trephines of various diameters. Core decompression gained popularity as a surgical option for managing osteonecrosis, as it is significantly less invasive than major operations such as rotational osteotomy, which does not address the etiology of osteonecrosis.
Although core decompression was a revolutionary procedure for osteonecrosis of the femoral head, the success rate remained relatively low. Frustrated with the limitations of the procedure, surgeons shifted their research focus toward potential improvements to the technique.
Small Studies with BMAC
In the early 2000s, Hernigou and Beaujean published a variation of the core decompression technique that included the use of bone marrow aspirated from the patient’s iliac crest.  The aspirate was processed, concentrated, and re-introduced into the decompressed femoral head. Their paper detailed the preparation of the bone marrow aspirate after harvest and the number of colony-forming units (CFUs) that were re-injected. 
Patients with pre-collapse disease who were treated with BMAC and core decompression had slower disease progression and a lower rate of conversion to total hip arthroplasty (THA) than patients who did not receive BMAC. Those with higher Harris Hip Scores (HHS) preoperatively also had better outcomes, as did those who received higher concentrations of CFUs.  The BMAC technique described in the paper by Hernigou and Beaujean would prove to be a vital step forward not only in the application, but also in the research of using BMAC augmentation with core decompression.
More evidence pointing toward the possible advantages of using BMAC in core decompression procedures came from a 5-year prospective, controlled, double-blind trial by Gangji et al,  who were able to accurately identify the amount and composition of the aspirate in terms of CD34+ mononuclear cells and fibroblast CFUs. Despite small numbers in the study – 24 hips in the pre-collapse stage among 19 patients, they showed statistically significant improvements in slowing of disease progression, Visual Analog Pain Scale (VAS) scores, Lequesne index, and Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index in the BMAC group. There was an early advantage with slower radiologic progression, but no difference in overall time to THA. 
Sen et al  compared core decompression with core decompression plus BMAC in a prospective, randomized controlled study of 51 pre-collapse hips in 40 patients. The follow-up period was 24 months. They found significant improvement in the HHS at 12, but not 24, months in the core decompression plus BMAC patients. The mean survival rate of the femoral head was roughly 5 weeks greater in the BMAC group. No significant differences were observed between groups in radiographic progression or improvement in magnetic resonance imaging (MRI) features. Interestingly, patients with osteonecrosis caused by trauma had better outcomes than those with non-traumatic osteonecrosis. 
A prospective, randomized clinical trial with 2-year follow-up by Tabatabee et al  included 28 hips (18 patients) with either pre-collapse or early post-collapse (ARCO stage I-III) femoral heads. The hips were randomized to either core decompression or core decompression plus BMAC. No correlation was seen between outcomes and specific number of mononuclear cells (MNCs) injected in the BMAC. All patients had significant reduction in VAS and WOMAC scores at 24 months, but only patients who received BMAC showed significant improvement in slowing of disease progression on MRI. 
Larger Studies, Longer Follow-Up
Kang et al  recently published a larger retrospective review with longer follow-up. They examined 106 hips in 100 patients with an average of 4.28 years of follow-up. The hips were evenly divided into 2 treatment group, core decompression or core decompression plus BMAC. The researchers found no difference in stage progression between groups, but they observed greater improvement in survivorship and slower conversion to THA at 3 years with core decompression plus BMAC compared with core decompression alone. 
Recently, Hernigou et al  expanded on their previous work using BMAC with core decompression in a study of 250 hips in 125 patients with an average of 25 years of follow-up (range, 20 to 30 years). All patients had bilateral femoral head osteonecrosis caused by corticosteroid use and were in the pre-collapse stage. In each patient, the more severely affected side was treated with core decompression plus BMAC, while the less severely affected side was treated with core decompression alone.
Hips treated with core decompression alone were 3 times more likely to undergo THA as those treated with core decompression plus BMAC.  Significant improvements were seen in progression to collapse, HHS and WOMAC (both early- and long-term follow-up), VAS scores (early follow-up), need for THA, and need for revision or re-revision THA in hips treated with core decompression plus BMAC compared with core decompression alone. 
Results of Meta-Analyses
Systematic reviews and meta-analyses comparing outcomes with core decompression alone and core decompression plus BMAC have recently been published by Wang et al  and Hua et al. 
The meta-analysis by Wang et al  included 540 patients who were followed for up to 60 months in 14 randomized controlled trials comparing core decompression alone with core decompression plus BMAC. Patients were almost evenly split between treatments. The investigators analyzed data on VAS score, WOMAC, HHS, conversion to THA, volume of postoperative necrotic zone, and adverse events.
The VAS and WOMAC outcomes significantly favored the core decompression plus BMAC group at up to 24 months . The conversion to THA rate was also significantly lower in this group. Greater improvement in the HHS and the volume of necrotic zone postoperatively was seen in hips treated with core decompression plus BMAC. There was no difference in adverse events between the 2 groups. 
Hua et al  included data from 32 studies published between 1988 and 2018, among them 3 randomized control trials, 26 case series, and 3 case control studies with a total of 2441 hips treated with core decompression alone, core decompression with autologous bone graft (AB), or core decompression with BMAC. The majority of hips (43%) were affected by osteonecrosis caused by corticosteroid use, followed by alcohol use and idiopathic causes. 
Aggregating data, Hua et al  showed favorable effect size trends for success with core decompression plus AB, followed by core decompression plus BMAC. Core depression alone was the least successful intervention. This was also true for THA conversion and disease progression: Using either core decompression plus AB or core decompression plus BMAC slowed disease progression and time to THA conversion compared with core decompression alone. 
However, the overall success rate of all treatments was shown to be 65%, which is the same success rate that Mont et al  reported in the early 1990s. Hips treated in the pre-collapse stage were more likely to have a higher success rate. 
Although meta-analyses generally indicate a benefit to BMAC, these studies are not without their limitations. The heterogeneity of both classic core decompression technique (number and diameter of tracts) and the grafting material (bone marrow aspirate concentrates of various preparations, with or without allograft bone) adds a layer of confounding to meta-analyses of trials utilizing different techniques for the classic and adjunctive core decompression groups.
Additional confounders include the multiple grading systems being used for hip osteonecrosis and the variety of etiologies of hip osteonecrosis. It is possible, for example, that patients with systemic disease such as vasculitis, sickle cell, or autoimmune conditions will continue to have similar unfavorable biology at the necrotic focus after core decompression, while patients with osteonecrosis caused by short-term, high-dose corticosteroid therapy may have a significantly better biologic milieu at the necrotic focus at the time of core decompression. These confounders must be taken into consideration when discussing the evidence for adding BMAC to core decompression.
The core decompression literature discussed in this article presents a range of retrospective, prospective, and meta-analysis data. This literature spans from the early 1990s to present day and includes classic core decompression alone and newer modifications such as core decompression plus BMAC.
The body of evidence suggests that core decompression plus BMAC is a safe and effective modification to the classically describe core decompression procedure. Although core decompression plus BMAC has been shown to benefit patients with osteonecrosis of the femoral head, questions remain as to whether this benefit is only seen in the short term and whether it can be applied broadly to patients with osteonecrosis of different etiologies.
As in many areas of orthopaedics, the literature on core decompression is a heterogenous body of work, with small patient volumes and short follow-up periods. Although systematic reviews and meta-analyses can better aggregate the data, high-quality studies are needed to achieve high-quality levels of evidence.
It is striking to consider that evidence summaries in the early 1990s and late 2010s both demonstrate an overall success rate of around 65%, even with the addition of augments such as BMAC. [6,14] Despite this, core decompression plus BMAC, in combination with careful selection and counseling of patients (those with pre-collapse disease and a specific etiology that can be eliminated), can provide significant benefit and prolong or lessen the need for THA in this younger patient population.
The evidence for adding BMAC to core decompression shows some promising results. However, further work is needed to definitively determine the value of adding BMAC to core decompression for different patient groups and to evaluate which patients will benefit from this treatment strategy.
Paul Enns, MD, and Simon Greenbaum, MD, are NYU/ISK Adult Reconstruction Fellows at NYU Langone Health, New York, New York. Ran Schwarzkopf, MD, MSc, and James Slover, MD, MS, are from the Division of Orthopedics, Adult Joint Reconstruction, at NYU Langone Health, New York, New York.
Disclosures: The authors have no disclosures relevant to this article.
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