Introduction: Osteonecrosis (ON) is a disabling disease, which often affects young adults after corticosteroid immunosuppression for organ transplantation. Reducing risk factors remains the only preventive measure for this condition. Our goal was to determine if diabetes has any influence in developing ON after kidney transplantation.

Materials and Methods: We identified 2881 renal transplantation patients with the following inclusion criteria: age > 16 years, no history of corticosteroid exposure. There were 1762 (61%) diabetics and 1119 (39%) non-diabetics. Mean age was 43 years (range, 16 to 77) and mean follow-up was 128 months (range, 36 to 242). Osteonecrosis free survivorship was defined as time from transplant to diagnosis of ON.

Results: Kaplan-Meier life table analysis at 5 years revealed that the incidence of ON was 4% for diabetics vs. 9% for non-diabetics (ON- free survivorship 96%, [95% confidence interval 0.952 to 0.970] vs. 91% [95% C.I. 0.896 to 0.929], respectively [p < 0.0001]). At 10 years, the ON incidence was 5% for diabetics vs. 10% for non-diabetics representing a 50% reduction.

Diabetes was the strongest independently predictive factor for ON-free survival (relative risk 0.47, p< 0.0001), while other factors were also independently significant but had a weaker relationship; (rejection episodes [RR 1.17, p=0.009], year of transplantation [RR 0.96, p=0.01]).

Discussion: Although the most common reason for renal transplantation, in adults, is diabetic nephropathy (61%), only a small fraction actually developed ON as compared to the non-diabetic population. The reason for this is unknown but might be related to lipid metabolism, high glucose levels, or neovascularization analogous to diabetic retinopathy.

Presence of diabetes is associated with a dramatic risk reduction in developing ON. The magnitude of the risk reduction was greatest for diabetes as compared to all other risk factors analyzed.

Introduction: The relationship between corticosteroids and osteonecrosis (ON) is well known. Limited data have suggested that statins modulate cholesterol metabolism and may protect against ON. We analyzed our, NIH supported, prospective renal transplant database to determine if statin usage reduces the incidence of corticosteroid-related osteonecrosis.

Materials and Methods: We identified 2881 renal transplantation patients who met our inclusion/exclusion criteria. There were 1752 male and 1129 female patients with mean age 43 years (range, 16 to 77). Mean follow-up was 128 months (range, 36 to 242 months). We identified 338 of 2881 patients as being on statins for over 1 year, commencing within 31 days of their transplant.

Results: Among the 338 patients on statins, 15 (4.4%) developed osteonecrosis vs. 180 of 2543 (7%) not on statins. Kaplan-Meier life table analysis of ON-free survival did not show a statistically significant relationship between statin exposure and development of ON (p=0.14, Log-Rank).

Discussion: We conclude that among our renal transplant patients, an association between statin usage and lower risk of osteonecrosis was not found, and if a reduction in incidence of ON actually exists, it is likely to be quite small. In addition, male gender and higher number of rejection episodes were independent predictive factors for ON.

Introduction: The treatment of asymptomatic osteonecrosis of the femoral head (ONFH) is controversial. The primary aim of this study was to define the optimal management of osteonecrotic lesions in patients with asymptomatic ONFH by determining the incidence of disease progression and the factors that might predict its occurrence. In order to assess the indications and timing for surgical intervention in these patients, the secondary aim was to determine whether or not pain precedes subchondral fracture in patients with asymptomatic disease.

Methods: The subjects in this study were patients with asymptomatic ONFH who were derived from two separate prospective, institutional review board-approved investigations in our institution. We determined the incidence of pain development and radiographic evidence of fracture and the temporal relationship of these events. Statistical analyses were performed to determine what factors affected either radiographic progression or the appearance of symptoms.

Results: Of the 37 hips, 12 (32%) were symptomatic at 2 years. Of these painful hips, six (50%) were associated with the simultaneous presence of a subchondral fracture. When analyzing the relationship of pain with fracture, 5 of 6 hips developed symptoms at an average of 8.1 months (1 to 28 months) prior to fracture. Three symptomatic patients had spontaneous resolution of the ONFH. Cox regression analysis revealed that an index of necrosis of > 50 and a greater extent of radiographic involvement correlate with a higher risk for developing symptoms and a subchondral fracture. If an index of necrosis of 50 is set as the lower limit for intervention, 78% of hips that fractured and 93% of hips that did not were identified.

Discussion: Asymptomatic ONFH with small lesions are amenable to observation, and intervention may be withheld until the appearance of symptoms. Asymptomatic ONFH with extensive femoral head involvement has a high probability of early progression to symptomatic ONFH and subchondral fracture. In these cases, early intervention may be beneficial in preventing fractures which may occur without any preceding symptoms. An index of necrosis of 50 is proposed as a threshold for intervention, as it is a good discriminator between those that did and did not fracture, and had a positive predictive value of 77.8%. The only independent predictor of both pain and collapse was the extent of femoral head involvement.

Introduction: The authors systematically reviewed the available literature in order to define the outcomes for avascular necrosis (AVN) and spontaneous osteonecrosis of the knee (SPONK) after unicompartmental knee arthroplasty (UKA) or total knee arthroplasty (TKA).

Materials and Methods: A literature review yielded seven reports with Hospital for Special Surgery (HSS) or Knee Society Score (KSS) outcomes for arthroplasty secondary to either AVN or SPONK. The mean pre-operative, post-operative, and difference in KSS or HSS scores plus the mean revision rates for the arthroplasties for each underlying disease (AVN and. SPONK) were tabulated and reported in this order. The reported means were weighted by the number of knees in each study.

Results: A total of 63 TKAs were performed for AVN and 85 TKAs were performed for SPONK. Additionally, 74 UKAs were performed for SPONK. TKAs performed secondary to AVN had mean KSS scores of 50.6, 90.2, and 39.4 points. The revision rate was 12.5% (SD=10.45). TKAs performed for SPONK had mean HSS scores of 55.6, 82.5, and 27 points. The revision rate was 5.9% (SD=2.79). UKAs performed for SPONK had mean HSS scores of 54, 83.1, and 29.1 points with a revision rate was 9.7% (SD=5.9).

Discussion: Although the KSS for TKAs performed for AVN match the KSS performed in osteoarthritic patient populations receiving TKAs, the revision rate is higher in the AVN group. The HSS scores for patients with SPONK receiving TKAs or UKAs are similar although the revision rate is higher for UKAs.