Examples

Predictors for Failure/Success of the Vascularized Fibular Graft in Avascular Necrosis of the Femoral Head

Student

Robert A. Gallo,
HMC Box #31,
717-531-8148,
august_gallo@yahoo.com

Faculty Sponsor

Vincent Pellegrini

Research Period

2001

Objectives

  1. Determine the effect of pre-operative Steinberg stage on the outcome of the vascularized fibular graft in the treatment of avascular necrosis (AVN) of the femoral head.
  2. Determine the effect of pre-operative size of the necrotic lesion (using radiographs and MRIs) on the outcome of the vascularized fibular graft in the treatment of AVN of the femoral head.
  3. Determine the effect of pre-operative prednisone use, cigarette smoking, and alcohol abuse, and post-operative prednisone use on the outcome of the vascularized fibular graft in the treatment of AVN of the femoral head. 

Background

Three-quarters of a century have passed since Haenisch provided the initial report of ischemic necrosis of the femoral head.1,2 Since that time, the incidence of avascular necrosis (AVN) has dramatically increased due to a number of factors, including improved diagnosis due to the advent of MRI, increased use of corticosteroids, and a longer lifespan of those afflicted with diseases associated with AVN.

Avascular necrosis of the femoral head remains a devastating illness. Untreated, AVN relentlessly progresses to joint destruction within five years.3 Worse yet, conventional methods of treating hip dysfunction do not yield satisfactory results in AVN patients. Avascular necrosis patients tend to be much younger than typical candidates for total hip arthroplasty (THA); indeed, the average age at THA for those with AVN is 38 years old,4 far younger than the recommended minimal age for THA. 5 In addition, THA tends to yield poorer results in AVN patients than age-matched controls.4

Through the years, many surgical procedures have been proposed to combat the progression of AVN. The most promising treatment proposed in recent years is the vascularized fibular bone graft procedure pioneered by Urbaniak, et al. In a prospective study of AVN patients treated with this operation less than 30% of hips required a THA within five years of the procedure.6 Few confirmatory reports have appeared in the literature to date.7,8

The vascularized fibular graft has become an especially popular method for the treatment of AVN among patients younger than 45 years old. Despite the enormous potential of the procedure, there is much to be learned about its precise indications. Urbaniak reported excellent results among all patients with only a slight drop-off in efficacy based on increasing stage.6 Others noted much poorer results when collapse of the femoral head occurred prior to surgery.7 Some suggested that the size of the necrotic lesion may also play a role in the success of the graft.7

Despite its encouraging results, the procedure represents a considerable operative undertaking and requires an extensive six-month rehabilitation period. While the efficacy of the vascularized fibular graft procedure has been well-documented, little data exist to ascertain the subgroup most likely to derive long-term benefit from the operation. Therefore, the purpose of our investigation is to refine the indications for the procedure and identify predictors of success as well as failure following this operation.

Methods

From 1990-1998, we performed 36 vascularized fibular graft procedures on 30 AVN patients at Strong Memorial Hospital, Rochester, New York, and Milton S. Hershey Medical Center, Hershey, Pennsylvania. The vascularized fibular graft procedure was performed using the method outlined by Urbaniak.6 In addition, eight non-vascularized fibular grafts were done on patients whose lower extremity vasculature was not suitable for the vascularized graft procedure. In this report, we will retrospectively analyze the results of the vascularized fibular graft. The initial inclusion criteria for the procedure were: (1) patient age less than 45 years; (2) Steinberg stage II, III, or IV AVN; (3) pain in the affected hip; (4) suitable vasculature for anastomosis. We will exclude all those who we were unable to follow for at least approximately two years post-operatively.

Stage

We classified each hip pre-operatively using the Steinberg staging system.9

We will assess the post-operative status of each patient using two methods. The length of time from surgery to THA will be the definitive outcome parameter. In those that did not yet receive THA, we will grade the hip progression objectively via follow-up radiographs. Follow-up radiographs will be assessed using three criteria: collapse/non-collapse of the head, joint-space narrowing, and healing of the end of the graft to the native bone. For Stage IV hips, progression will be defined by decreased joint space and deepened collapsed, while earlier stage hips will be noted to progress if the hip collapsed post-operatively. We will use a Chi-square test to determine relationship of each stage compared to the individual outcome parameters outlined above.

Size

We will use the pre-operative radiograph imaged closest to the date of the procedure for evaluation. We will determine each hip's radiographic area and volume of necrosis using a modified system proposed by Steinberg.9 Two independent observers will each trace the femoral head (using the narrow portion of the femoral neck as the base) and the lesion, marked by a sclerotic rim, on both AP and frog-lateral views. The tracings will be scanned into a computer using ScanJet and the percent area of necrosis will be analyzed using NIH image. The radiographic percent volume of necrosis will be determined by multiplying the areas obtained in each view. We will average the percentages determined by each observer to yield the final percentage of necrosis for each femoral head.

The preoperative MRIs will be evaluated similarly. Each set of MRI scans for each patient will be digitized. The area of necrosis and total area of the femoral head on each image will be analyzed by two independent observers using NIH image. We will obtain the area of necrosis and area of the femoral head for each image and then add these values together to yield total volume of necrosis and total volume of femoral head. We will calculate the percent necrosis of the femoral head from this composite data. If a patient had both coronal and transverse images, we will average the percent necrosis.

We will determine the amount of correlation between the two observers by the Pearson correlation test, while we analyzed the statistics similarly with a Chi-square test using 40% on radiographs and 35% on MRI as the cut-off for two comparison groups. A paired t-test will be used to determine the relationship of size to stage.

Etiology

Pre- and post-operative systemic prednisone use (regardless of amount), smoking one or more packs of cigarettes per day pre-operatively, and consumption of at least six alcoholic beverages per day prior to the operation will be compared to the survival of the graft. Chi-square tests will be used to evaluate these statistics.

Institutional Review Board approval is pending.

Student's Responsibilities

  1. Perform chart review to determine pre-operative stage and etiologic considerations (prednisone use, cigarette smoking, and alcohol consumption).
  2. Obtain and evaluate lesion size on pre-operative radiographs and MRIs.
  3. Perform chart review to determine outcome status [total hip arthroplasty (THA) vs. no THA] and evaluate necessary post-operative radiographs.
  4. Perform necessary statistical analyses.
  5. Prepare manuscript. 

Sponsor's Responsibilities

  1. Alert student of newly obtained follow-up radiographs.
  2. Provide guidance to research and manuscript preparation. 

References

1.  Haenisch. Arthritis dissecans der Hufte. Zentralbl Chir. 1925;52:999.

2.  Hungerford DS, Lennox DW. Diagnosis and treatment of ischemic necrosis of the femoral head. In Evarts (ed): Surgery of the Musculoskeletal System

3.  Meyers MH. Osteonecrosis of the femoral head: pathogenesis and long-term results of treatment. Clinical Orthopaedics and Related Research. 1998;231:51.

4.   Mont MA, Hungerford DS. Non-traumatic avascular necrosis of the femoral head. Journal of Bone and Joint Surgery. 1995;77A:459.

5.  Dorr LD, Takei GK, Conaty JP. Total hip arthroplasty in patients less than forty-five years old. Journal of Bone and Joint Surgery. 1983;65A:474-479.

6.  Urbaniak JR, Coogan PG, Gunneson EB, Nunley JA. Treatment of osteonecrosis of the femoral head with free vascularized fibular grafting. Journal of Bone and Joint Surgery. 1995;77A:681-694.

7.  Sotereanos DG, Plakseychuk AY, Rubash HE. Free vascularized fibula grafting for the treatment of osteonecrosis of the femoral head. Clinical Orthopaedics and Related Research. 1997;344:243-256.

8.  Malizos KN, Soucacos PN, Beris AE. Osteonecrosis of the femoral head: hip salvaging with implantation of a vascularized fibular graft. Clinical Orthopaedics and Related Research. 1995;314;67-75.

9.  Steinberg ME, Hayken GD, Steinberg DR. Classification and staging of osteonecrosis. 277-284.

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