Core decompression may be used as adjunct for treatment in some cases of Legg-Calvé-Perthes disease (LCPD). The primary application is for patients with onset at 12 years of age or older. We recommend classifying these older patients as idiopathic juvenile osteonecrosis and treating them similarly to adults with avascular necrosis. Juvenile osteonecrosis may benefit from core decompression combined with shelf acetabuloplasty during the early stages of necrosis. Younger children with LCPD may benefit from decompression by fenestration of the femoral head. Experience in adult-onset osteonecrosis and our early experience suggest that some patients may benefit from these adjunctive treatments.
When Legg-Calvé-Perthes disease (LCPD) develops at age 12 years or older, the results are generally poor, with or without current methods of treatment. These juvenile patients are more likely to become Stulberg class V even when the necrotic segment is less than 50% of the femoral head. Joseph and colleagues reported 62 patients aged 12 years or older at onset. In their series, neither the Catterall group nor the Herring grade correlated with final outcome and none benefited from containment treatment.
We propose the term idiopathic juvenile osteonecrosis to distinguish this age group from younger children with Perthes disease and from adults with osteonecrosis of the femoral head. One difference is that the femoral head in the older pediatric age group does not reconstitute as rapidly as in younger children with LCPD. Another difference between juvenile osteonecrosis and younger children with Perthes disease it that the older age group has less remodeling capacity of the femoral head or acetabulum.
Compared with adults, juvenile osteonecrosis may have a slightly more favorable prognosis. In adults, the rate of bone resorption exceeds the rate of bone deposition. This difference causes a weakness in the structural integrity of the bone followed by subchondral fracture and collapse. Ficat identified that stage III osteonecrosis in adults is associated with a break in the articular surface. However, there is a transitional stage in which a subchondral fracture may be present without segmental collapse. Young children have thick articular cartilage that may be more resistant to deformation and disruption than that of older children. Adolescents may also tolerate some subsidence of the necrotic fragment without disruption of the articular surface. Restoring support to the joint surface before cartilage fracture may preserve joint function.
The treatment rationale of the femoral head should be tailored to address these differences between adult and childhood osteonecrosis of the femoral head. Joseph and colleagues suggested that an alternative method of treatment of juvenile osteonecrosis should be investigated. He concluded that the success of treatment depends on necrotic bone resorption (elimination), new bone formation in its place, and a remodeling process that is protected from further deformation by adequate containment. It is our opinion that early core decompression combined with containment in the form of a shelf acetabuloplasty can meet these objectives and may improve outcomes compared with the natural history and with previous treatment methods for this age group. Core decompression and shelf acetabuloplasty (labral support) for idiopathic juvenile osteonecrosis is the focus of this article.
Core decompression
Core decompression was reported as a possible solution for LCPD in the 1930s. Details and examples of cases were not described, but Ferguson and Howorth indicated that drilling in the active stage resulted in earlier and more complete healing.
The objectives of core decompression are to remove necrotic bone, reduce venous congestion, and encourage revascularization. Removal of necrotic bone has been identified as a key component for success of core decompression. Some investigators advocate arthroscopic inspection to ensure removal of necrotic bone.
The principle objective of decompression is to reduce intraosseous pressure to decrease venous congestion and improve capillary blood flow. The bone marrow pressure in the femoral head and neck is increased in patients who develop osteonecrosis. The pressure is reduced and venous flow improved in some patients following decompression by drilling or by proximal femoral osteotomy. Vascularity of the proximal femur is also enhanced by the angiogenesis caused by the trephine opening new vascular channels. In children, the growth plate of the proximal femur is a barrier to revascularization. Reossification of the femoral head is facilitated by removal or fenestration of the epiphyseal plate. Thus, core decompression has several beneficial effects for revascularization of the femoral head.
Numerous investigators have compared core decompression with nonoperative management for osteonecrosis of the femoral head. Improved outcomes have been noted following core decompression in the early stages of necrosis. Fairbank and colleagues reported satisfactory long-term results of core decompression performed in Ficat stages I and II ( Fig. 1 ). Ficat and Arlet classified patients with a crescent sign as stage II. Stage III indicates flattening and collapse of the femoral head. Other investigators have included the crescent sign as stage III with or without femoral head collapse.
Techniques for core decompression have ranged from multiple small drillings with 3.2-mm Steinmann pins to expanding reamers and trapdoor procedures that remove large amounts of necrotic bone. Small pin drillings have been less effective for larger lesions with higher intraosseous pressures. More complete removal of necrotic bone has been recommended for larger lesions in later stages of disease, including stage III, as long as the articular cartilage is intact.
Maintaining a sturdy structural support in the decompressed area during the revascularization process helps prevent disruption of the articular cartilage. Gradual substitution of necrotic bone or implant material by living bone keeps the decline of the bone’s mechanical properties to a minimum. Various graft materials and adjunctive techniques have been used following core decompression. Liebermann and colleagues and Chang and colleagues performed core decompressions with bone grafting and partially purified bone morphogenic proteins as adjuncts. Keizer and colleagues noted improved outcomes with autograft compared with allograft. For patients with Ficat stage III necrosis, free vascularized fibular grafting is beneficial. Free vascularized fibular grafting in children and adolescents for stage III osteonecrosis has better reported outcomes than those performed in adults.
In the adult population, the prognosis depends on several factors, including the size of the lesion, the location, and the bone quality of the uninvolved portion of the femoral head. The smaller the lesion, the better the result, regardless of whether it is Ficat stage I or II. Koo and Kim reported that patients with less than 30% of femoral head involvement did not develop progression of the osteonecrosis, whereas all the hips with more than 40% involvement collapsed. The location of involvement of hip osteonecrosis is also an important factor. Lateral lesions fare worse compared with those with medial or lateral involvement. These factors also apply to juvenile osteonecrosis but the adolescent age group with open growth plates may have a more favorable prognosis when treated later in the course of disease.
Several investigators identified that the femoral epiphyseal height is unlikely to improve after collapse. Femoral head flattening has also been found to be a prognostic factor in the adult population. These investigators recommended that surgery should be performed as early as possible to prevent collapse. However, even in the presence of femoral head collapse, core decompression may help relieve pain.
Surgical technique
The critical component for performing an adequate core decompression is to place the trephine in the center of the necrotic defect as close as possible to the articular surface ( Fig. 2 A, B), although this does not mean the center of the femoral head. We prefer to perform the procedure on a radiolucent table and drape the lower extremity free to be able to manipulate the limb and verify the guidewire position. Recently, a lateral decubitus position has been the preferred method.
The guidewire and trephine are inserted proximal to the level of the lesser trochanter to minimize the risk of subtrochanteric fracture from the stress riser created by the core tunnel. Once the guide is properly placed, the trephine is advanced. Trephines that are from 8 mm to 10 mm in diameter are recommended. We have also used an expandable reamer that allows further debridement in the subchondral region (see Fig. 2 C). The bone is then curetted and the tunnel is washed. Radiopaque contrast is injected in the tunnel before grafting to verify that there has been adequate debridement and no intra-articular penetration (see Fig. 2 C). Bone grafting is performed with either bone graft substitutes or autograft. Our current preference is to use synthetic material that solidifies and provides some early mechanical support before resorption (see Fig. 2 D).
Several investigators advocate multiple small-diameter drill holes. These investigators have identified that patients with earlier Ficat stage and smaller lesions (<200°) required less revision surgery than those with larger lesions. Others have performed core decompression followed by grafting with tibia or fibula. They found that patients younger than 30 years of age had better results. They concluded that the most critical portion of the procedure was the removal of the necrotic tissue and packing of bone graft, as the type of strut graft had minimal effect on the procedure. Urbaniak and colleagues used vascularized fibular grafting and reported 5-year survival rates of 89% for Ficat Stage II hips and 77% for Stage III hips. Regardless of method of bone grafting, authors have reported better outcomes in patients younger than 30 years of age.
Surgical technique
The critical component for performing an adequate core decompression is to place the trephine in the center of the necrotic defect as close as possible to the articular surface ( Fig. 2 A, B), although this does not mean the center of the femoral head. We prefer to perform the procedure on a radiolucent table and drape the lower extremity free to be able to manipulate the limb and verify the guidewire position. Recently, a lateral decubitus position has been the preferred method.
The guidewire and trephine are inserted proximal to the level of the lesser trochanter to minimize the risk of subtrochanteric fracture from the stress riser created by the core tunnel. Once the guide is properly placed, the trephine is advanced. Trephines that are from 8 mm to 10 mm in diameter are recommended. We have also used an expandable reamer that allows further debridement in the subchondral region (see Fig. 2 C). The bone is then curetted and the tunnel is washed. Radiopaque contrast is injected in the tunnel before grafting to verify that there has been adequate debridement and no intra-articular penetration (see Fig. 2 C). Bone grafting is performed with either bone graft substitutes or autograft. Our current preference is to use synthetic material that solidifies and provides some early mechanical support before resorption (see Fig. 2 D).
Several investigators advocate multiple small-diameter drill holes. These investigators have identified that patients with earlier Ficat stage and smaller lesions (<200°) required less revision surgery than those with larger lesions. Others have performed core decompression followed by grafting with tibia or fibula. They found that patients younger than 30 years of age had better results. They concluded that the most critical portion of the procedure was the removal of the necrotic tissue and packing of bone graft, as the type of strut graft had minimal effect on the procedure. Urbaniak and colleagues used vascularized fibular grafting and reported 5-year survival rates of 89% for Ficat Stage II hips and 77% for Stage III hips. Regardless of method of bone grafting, authors have reported better outcomes in patients younger than 30 years of age.
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