The use of alendronate to prevent early collapse of the femoral head in patients with nontraumatic osteonecrosis. A randomized clinical study

BACKGROUND

Osteonecrosis of the femoral head is the most common diagnosis leading to total hip arthroplasty in young adults. Joint-preserving treatment options have been mainly surgical, with inconsistent results. Alendronate (a bisphosphonate agent) has been shown to lower the prevalence of vertebral compression fractures and could potentially retard the collapse of an osteonecrotic femoral head. The purpose of this study was to test the effect of alendronate in preventing early collapse of the femoral head in patients with nontraumatic osteonecrosis.

METHODS

Forty patients with Steinberg stage-II or III nontraumatic osteonecrosis of the femoral head and a necrotic area of >30% (class C) were randomly divided into alendronate and control groups of twenty patients each. Patients in the alendronate group took 70 mg of alendronate orally per week for twenty-five weeks, while the patients in the control group did not receive this medication or a placebo. The patients were observed for a minimum of twenty-four months. Harris hip scores, plain radiographs, and magnetic resonance imaging scans were obtained.

RESULTS

During the study period, only two of twenty-nine femoral heads in the alendronate group collapsed, whereas nineteen of twenty-five femoral heads in the control group collapsed (p < 0.001). One hip in the alendronate group underwent total hip arthroplasty, whereas sixteen hips in the control group underwent total hip arthroplasty (p < 0.001).

CONCLUSIONS

Alendronate appeared to prevent early collapse of the femoral head in the hips with Steinberg stage-II or IIIC nontraumatic osteonecrosis. A longer duration of follow-up is needed to confirm whether alendronate prevents or only retards collapse.

LEVEL OF EVIDENCE

Therapeutic Level I.

The effects of contact pressure elevations and aseptic necrosis on the long-term outcome of congenital hip dislocation

The relationship between excessive articular contact pressure, aseptic necrosis, and the long-term outcome with unilateral congenital dislocation of the hip (CDH) was studied in a series of 84 patients treated by closed reduction and followed for an average of 29.2 years. Contact stress was estimated from archived radiographs taken at the time of maturity and at several follow-up visits. At a recent review, each patient was rated both clinically for pain and function and radiographically for deformity, degeneration, and aseptic necrosis. For each of 431 archived films, articular contact stress (force/area) was estimated mathematically, based upon a frontal plane equilibrium (force) analysis and a landmark-based inference of three-dimensional head surface (area). Good correlation with final deformity (Spearman rho = 0.78) was obtained when the hips were ranked in terms of a new cumulative overpressure index Pc, defined as a time-pressure product involving years of pressure exposure beyond a 2 MPa pressure damage level. An unsatisfactory outcome occurred in 90.4% of the hips experiencing Pc greater than 10 MPa-years (most of which had aseptic necrosis involvement), whereas the outcome was satisfactory in 80.9% of hips with Pc less than 10 MPa-years.

Hypofibrinolysis, thrombophilia, osteonecrosis

In the context of additional characterization of the pathoetiologic associations of heritable hypofibrinolysis and thrombophilia with osteonecrosis of the hip, the authors assessed 15 women and 21 men at entry to a 12-week treatment study of the amelioration of Ficat Stages I or II osteonecrosis by low molecular weight heparin (Enoxaparin). All 36 patients had osteonecrosis of the hip; four patients had unifocal osteonecrosis, 25 patients had two joints affected, five had three affected joints, and two had four affected joints. In 11 of 15 women (73%), hyperestrogenemia of pregnancy (20%) or exogenous estrogen supplementation (53%) were associated with the development of osteonecrosis. Five gene mutations affecting coagulation and nine serologic coagulation tests were studied. Compared with control subjects, patients were more likely to have heterozygosity and homozygosity for the hypofibrinolytic 4G polymorphism of the plasminogen activator inhibitor-1 gene. Moreover, the plasminogen activator inhibitor-1 gene product, plasminogen activator inhibitor activity, the major determinant of hypofibrinolysis, was 10 times more likely to be high (> 21.1 U/mL) in patients than in control subjects (31% versus 3%), with a median of 15.7 versus 6.3 U/mL. Compared with controls, patients were more likely to have the thrombophilic methylenetetrahydrofolate reductase gene mutation. In addition, the thrombophilic methylenetetrahydrofolate reductase gene product, homocysteine, was four times more likely to be high (> 13.5 umol/L) in patients than in control subjects (20% versus 5%), with a median of 9.1 versus 7 umol/L. Twenty-three percent of patients had low levels (< 65%) of the thrombophilic free protein S versus 3% of control subjects. Patients were more likely than control subjects to have hypofibrinolytic high lipoprotein (a) (> or = 35 mg/dL), 33% versus 13%. Median lipoprotein (a) was higher in patients than in control subjects, 15 versus 5 mg/dL. Heritable hypofibrinolysis and thrombophilia, often augmented in women by hyperestrogenemia, seem to be major pathoetiologies of osteonecrosis. If the association between coagulation disorders and osteonecrosis reflects cause and effect, as postulated, then anticoagulation with Enoxaparin should be a promising therapy for patients with osteonecrosis.

Decrease in the mesenchymal stem-cell pool in the proximal femur in corticosteroid-induced osteonecrosis

We have evaluated bone-marrow activity in the proximal femur of patients with corticosteroid-induced osteonecrosis and compared it with that of patients with osteonecrosis related to sickle-cell disease and with a control group without osteonecrosis. Bone marrow was obtained by puncture of the femoral head outside the area of necrosis and in the intertrochanteric region. The activity of stromal cells was assessed by culturing fibroblast colony-forming units (FCFUs). We found a decrease in the number of FCFUs outside the area of osteonecrosis in the upper end of the femur of patients with corticosteroid-induced osteonecrosis compared with the other groups. We suggest that glucocorticosteroids may also have an adverse effect on bone by decreasing the number of progenitors. The possible relevance of this finding to osteonecrosis is discussed.

Dislocation after total hip arthroplasty using Hueter anterior approach

A prospective study including 1764 hips has been carried out to evaluate the frequency of dislocation while using the Hueter anterior approach and the correlated factors. The dislocation group was compared with the patients without dislocation. We observed 27 dislocations (1.5%). The dislocation rate when using 28 mm head diameter was 0.5%. Two patients underwent a revision for recurrent dislocations. Correlated factors for dislocation were male sex, high body mass index, etiology of osteonecrosis, low head diameter, high bleeding, and low postoperative ROM. Dislocation risk while using Hueter approach is one of the lowest in the literature. The main disadvantages are the necessity for a specific orthopedic table and a more difficult exposure of the femur.

The prevalence of acetabular retroversion among various disorders of the hip

BACKGROUND

Acetabular retroversion can result from posterior wall deficiency in an otherwise normally oriented acetabulum or from excessive anterior coverage secondary to a malpositioned acetabulum, or both. Theoretically, a retroverted acetabulum, which adversely affects load transmission across the hip, may occur more frequently in hips with degenerative arthritis. The aim of this study was to assess the prevalence of acetabular retroversion in normal hips and in hips with osteoarthritis, developmental dysplasia, osteonecrosis, and Legg-Calvé-Perthes disease.

METHODS

We retrospectively examined anteroposterior radiographs of the pelvis of 250 patients (342 hips). Fifty-six patients (112 hips) had normal findings; sixty-six patients (seventy hips) had osteoarthritis; sixty-four (seventy-four hips), developmental dysplasia; thirty (thirty-six hips), osteonecrosis of the femoral head; and thirty-four (fifty hips), Legg-Calvé-Perthes disease. The sole criterion for a diagnosis of acetabular retroversion was the presence of a so-called cross-over sign on the anteroposterior radiograph of the pelvis.

RESULTS

The prevalence of acetabular retroversion was 6% (seven of 112 hips) in the normal group, 20% (fourteen of seventy hips) in the osteoarthritis group, 18% (thirteen of seventy-four hips) in the developmental dysplasia group, 6% (two of thirty-six hips) in the group with osteonecrosis of the femoral head, and 42% (twenty-one of fifty hips) in the group with Legg-Calvé-Perthes disease. In patients with Legg-Calvé-Perthes disease, the prevalence of acetabular retroversion was 68% in twenty-five hips with Stulberg class-III, IV, or V involvement. In contrast, only four (16%) of twenty-five hips with Stulberg class-I or II involvement had acetabular retroversion. The difference was significant (p = 0.0002). Patients with osteoarthritis, developmental dysplasia, or Legg-Calvé-Perthes disease are significantly more likely to have acetabular retroversion than are normal subjects (p < 0.05).

CONCLUSIONS

Acetabular retroversion occurs more commonly in association with a variety of hip diseases, in which the prevalence of subsequent degenerative arthritis is increased, than has been previously noted.

Prediction of collapse with magnetic resonance imaging of avascular necrosis of the femoral head

In order to predict the probability of collapse of a femoral head in which there is avascular necrosis, we used magnetic resonance imaging to evaluate sixty-six hips (fifty patients) in which avascular necrosis was in the early stages and in which collapse of the head was not yet visible. The hips were followed radiographically for an average of forty-nine months (range, sixteen to eighty-four months), and with magnetic resonance imaging for an average of forty-four months (range, twelve to seventy-three months). Twenty-one (32 per cent) of the femoral heads had collapsed by thirty-two months. Of the twenty-three femoral heads in which necrosis involved at least one-fourth of the diameter of the head and encompassed at least two-thirds of the major weight-bearing area, seventeen (74 per cent) had collapsed by thirty-two months.

Does alendronate prevent collapse in osteonecrosis of the femoral head?

Progression of collapse in osteonecrosis of the femoral head is related to the repair response, especially bone resorption around the necrotic region. A preliminary clinical study was done to determine whether systemic alendronate would prevent collapse and lead to pain relief in patients with osteonecrosis of the femoral head. Fourteen patients (20 hips) with osteonecrosis of the femoral head received daily administration of 5 mg alendronate (alendronate group) for 1 year. Eight patients (13 hips) with osteonecrosis of the femoral head did not receive alendronate (control group). All patients had measurements of biochemical markers of bone turnover at entry into the study, and the patients in the alendronate group repeated the measurements at 3 months, 6 months, and 12 months. All patients had clinical and plain radiographic examinations at entry into the study and at 3 months, 6 months, and 12 months. The alendronate group showed a greater decrease of biochemical marker of bone resorption than biochemical marker of bone formation. The alendronate group showed a lower frequency of collapse of the femoral head and reported less hip pain than the control group. Our results suggest alendronate has the potential to prevent collapse of the femoral head, even with extensive necrosis, presumably by inhibiting bone resorption in the necrotic region.

LEVEL OF EVIDENCE

Therapeutic study, level II (prospective comparative study). See the Guidelines for Authors for a complete description of levels of evidence.

Free vascularized fibular grafting for the treatment of postcollapse osteonecrosis of the femoral head

BACKGROUND

Osteonecrosis of the femoral head, a disease primarily affecting young adults, is often associated with collapse of the articular surface and subsequent arthrosis. Free vascularized fibular grafting has been reported to be successful for patients with early stages of osteonecrosis, but little is known about its efficacy after the femoral head has collapsed.

METHODS

We retrospectively reviewed the results in a consecutive series of 188 patients (224 hips) who had undergone free vascularized fibular grafting, between 1989 and 1999, for the treatment of osteonecrosis of the hip that had led to collapse of the femoral head but not to arthrosis. The average duration of follow-up was 4.3 years (range, two to twelve years). We defined conversion to total hip arthroplasty as the failure end point, and we analyzed the contribution, to failure, of the size of the lesion, amount of preoperative collapse of the femoral head, etiology of the osteonecrosis, age of the patient, and bilaterality of the lesion. We used the Harris hip score to evaluate clinical status preoperatively and at the time of the most recent follow-up.

RESULTS

The overall rate of survival was 67.4% for the hips followed for a minimum of two years and 64.5% for those followed for a minimum of five years. The mean preoperative Harris hip score was 54.5 points, and it increased to 81 points for the patients in whom the surgery succeeded; 63% of the patients in that group had a good or excellent result. There was a significant relationship between the outcome of the grafting procedure and the etiology of the osteonecrosis (p = 0.017). Patients in whom the osteonecrosis was idiopathic, associated with alcohol abuse, or posttraumatic fared worse than did those with other causes, including steroid use. Survival of the joint was not significantly related to the size of the femoral head lesion, but there was an increased relative risk of conversion to total hip arthroplasty with increasing lesion size and amount of collapse. Neither patient age nor bilaterality significantly affected outcome.

CONCLUSIONS

Patients with postcollapse, predegenerative osteonecrosis of the femoral head appear to benefit from free vascularized fibular grafting, with good overall survival of the joint and significant improvement in the Harris hip score. The results of this femoral head-preserving procedure in patients with postcollapse osteonecrosis are superior to those of core decompression and nonoperative treatment, as reported in the literature. Patients with larger lesions and certain diagnoses, such as idiopathic and alcohol-related osteonecrosis, have worse outcomes.

Acetabular fractures: long-term follow-up of open reduction and internal fixation

Eight-seven acetabular fractures in eighty-seven patients underwent open reduction and internal fixation at Vanderbilt University Hospital from 1984 to 1989. Fifty-six were treated by orthopaedic traumatologists. Fifty-six patients returned for long-term follow-up (range 24-80 months, average 43). Harris hip ratings were used to clinically grade the results. Poor results were found in 43%. Eighty-three percent of the patients with poor results had satisfactory surgical reductions with < 3 mm of residual displacement. Factors other than surgical reduction contributed significantly to the poor results. These included hip dislocation associated with the fracture, class III or IV heterotopic ossification, development of avascular necrosis, and age > 40 years. These factors in addition to adequacy of surgical reduction allow us to better counsel patients as to long-term prognosis.

Subcapital correction osteotomy in slipped capital femoral epiphysis by means of surgical hip dislocation

OBJECTIVE

The aim of treatment of slipped capital femoral epiphysis is an anatomically aligned epiphysis with normal blood supply. This result can be achieved by open subcapital reorientation of the epiphysis or by a wedge osteotomy of the femoral neck. Other procedures have, so far, not gained optimal control over the risk of avascular necrosis.

INDICATIONS

Acute epiphyseolysis. Chronic epiphyseolysis for which trimming of the metaphyseal overhang to permit free flexion and internal rotation without impingement would leave less than two thirds of the femoral neck diameter intact.

CONTRAINDICATIONS

Ankylosis of the hip joint at an advanced stage. Destruction of the femoral head.

SURGICAL TECHNIQUE

The blood supply to the epiphysis from the medial femoral circumflex artery can be preserved by surgical hip dislocation and a soft-tissue flap derived subperiosteally from the retinaculum and external rotators. This soft-tissue flap permits not only the detachment of the epiphysis, but also complete callus resection from the femoral neck without causing tension in the retinaculum. Dislocation of the femoral head ensures its manual protection during curettage of the epiphyseal plate and, ultimately, allows anatomic reduction under visual control of the retinaculum. With the head dislocated there is less risk to the integrity of the retinaculum due to unintentional manipulation of the leg than there would be, if the head remained in the socket.

RESULTS

From 1996 to 2005, 30 hips with a diagnosis of slipped capital femoral epiphysis were treated according to the technique described. The average follow-up time was 55 months (24-96 months). Femoral head necrosis did not occur. Distribution across sexes was well balanced. Girls were 12 years old at the time of the operation and boys were 14 years old on average. Posterior displacement was measured at 30-70 degrees. In six hips there was a so-called acute on chronic slip. Two hips required revision due to screw failure, a difficulty that was addressed by the introduction of fully threaded wires. One hip had to be revised because the fully threaded wire bent. After reoperation, shortening of maximum 1 cm was seen in these three cases. In one patient with ectopic bone formation at the anteroinferior femoral neck, internal rotation in flexion is reduced by half.

Subchondral fractures in osteonecrosis of the femoral head: comparison of radiography, CT, and MR imaging

OBJECTIVE

Our objective was to compare the sensitivity of unenhanced radiography, CT, and MR imaging in revealing subchondral fractures.

SUBJECTS AND METHODS

Forty-five subjects with stage I and stage II osteonecrosis of the femoral head were included in the study as part of a multicenter clinical trial to evaluate the effectiveness of recombinant human bone morphogenetic protein as an adjuvant treatment to core decompression. Patients were evaluated with radiography, CT, and MR imaging 6 and 12 months after surgery.

RESULTS

At 6 months, 18 fractures were shown on CT scans, but only 12 were detected on radiographs and six, on MR images. At 12 months, 20 subchondral fractures were detected on CT scans, but only 17 were seen on radiographs and 11, on MR images. Compared with CT, MR imaging has a sensitivity and specificity of 38% and 100%, and unenhanced radiography has a sensitivity and specificity of 71% and 97%, respectively. On T2-weighted MR images, the subchondral fractures were visualized as crescentic high-signal-intensity lines, and in all patients, on the corresponding CT scans, the fracture clearly breached the femoral cortex.

CONCLUSION

CT reveals more subchondral fractures in osteonecrosis of the femoral head than unenhanced radiography or MR imaging. The high-signal-intensity line seen on T2-weighted MR images appears to represent fluid accumulating in the subchondral fracture, which may indicate a breach in the overlying articular cartilage.

Hip arthroplasty in patients with chronic renal failure

Patients with chronic renal failure who underwent total hip arthroplasty were retrospectively evaluated. Thirty hips in patients with renal transplants and 16 hips in patients on chronic renal dialysis were reviewed. The average follow-up period was 54 months. The renal transplant patients exhibited generally satisfactory results. Their postoperative course was comparable to that of patients with avascular necrosis undergoing hip reconstruction without underlying renal disease. However, patients undergoing hip arthroplasty while on chronic renal dialysis had poor results (81%), including a deep infection rate of 19%. It was concluded that total hip arthroplasty be reserved for patients who are expecting a renal transplant or preferably those who have already received a successful transplant.

Total hip arthroplasty in patients on long-term renal dialysis

End-stage renal failure patients on long-term renal dialysis who underwent total hip arthroplasty (THA) were followed. Fifteen hips were implanted in 12 patients. There was a high mortality (58%) and high overall early complication rate (58%) with a deep infection rate of 13%. Of patients, 76% (n = 11) had good clinicoradiologic outcome of the THA before their death or at their latest follow-up. THA in patients on dialysis, however, should be reserved for those among this group who are expected to have a better life expectancy.

Hinge abduction of the hip. Diagnosis and treatment

Hinge abduction is an abnormal movement of the hip which occurs when a femoral head, deformed as a result of avascular necrosis or Perthes' disease, fails to slide within the acetabulum. Patients with this condition present with pain and shortening and in some cases arthrodesis has been recommended. We report 27 cases in which the diagnosis had been established by arthrography. The satisfactory results of abduction-extension osteotomy of the femur in 26 hips with this condition are reported.

The management of necrosis-associated and idiopathic bone-marrow oedema of the proximal femur by intravenous iloprost

Bone-marrow oedema can occur both in isolation and in association with necrosis of bone, but it has not been shown whether each respond to the same methods of treatment.

We treated 16 patients with isolated oedema and 17, in which it was associated with necrosis of the proximal femur, with the prostacyclin derivative iloprost, which has been shown to be effective in the idiopathic form. The Harris hip score, the range of movement, the extent of the oedema as measured by MRI, pain on a visual analogue scale and patient satisfaction were recorded before and subsequent to treatment.

In both groups, we were able to show a significant improvement (p < 0.001) in these observations during the period of follow-up indicating that iloprost will produce clinical improvement in both circumstances.

The natural history of symptomatic osteonecrosis in adults with sickle-cell disease

BACKGROUND

Adult patients with sickle-cell disease are at risk for the development of osteonecrosis of the hip. However, there is little information in the literature about the rate of progression of osteonecrosis once symptoms begin. The purpose of this study was to evaluate the natural history of the symptomatic hip in adult patients with osteonecrosis and sickle-cell disease.

METHODS

Ninety-two symptomatic hips in sixty-four consecutive adult patients with sickle-cell disease were initially evaluated between 1980 and 1987. Sixty symptomatic hips had radiographic evidence of osteonecrosis at the initial evaluation: forty-three were classified as stage II; two, as stage III; and fifteen, as stage IV, according to the system of Steinberg et al. The other thirty-two hips had lesions (stage I) that were evident only on magnetic resonance imaging. All patients were evaluated after a mean duration of follow-up of seventeen years.

RESULTS

Of the seventy-five hips without collapse of the femoral head at the initial evaluation, sixty-five demonstrated collapse within five years after the diagnosis. The average time between the diagnosis and collapse was forty-two months for stage-I hips and thirty months for stage-II hips. At the most recent follow-up examination, ninety hips had had collapse of the femoral head and eighty-eight of the ninety-two hips had had surgery because of intractable pain.

CONCLUSIONS

Symptomatic osteonecrosis of the hip in sickle-cell disease has a high likelihood of leading to femoral head collapse, necessitating surgical intervention. When osteonecrosis develops, the deterioration is rapid and, in most patients, operative intervention is necessary because of intractable pain.

LEVEL OF EVIDENCE

Prognostic study, Level II-1 (retrospective study). See Instructions to Authors for a complete description of levels of evidence.

Avascular necrosis of bone in severe acute respiratory syndrome

AIM: To report the incidence of avascular osteonecrosis (AVN) in severe acute respiratory syndrome (SARS) patients.

MATERIALS AND METHODS: Sixty-seven SARS patients who had large joint pain between March 2003 and May 2003 underwent both plain radiographs and magnetic resonance imaging (MRI) examination on the same day. All patients received steroids and ribavirin treatment. All plain radiographs and MR images were analysed by two experienced musculoskeletal radiologists. Any abnormalities, location, extent, morphology, the number, size and signal intensity of lesions were evaluated.

RESULTS: Twenty-eight patients were identified with AVN, The mean time to diagnosis of AVN was 119 days after the onset of SARS, or 116 days after steroid use. Three patients had early bilateral AVN of the femoral head, four patients of one femoral head, five patients of the bilateral hips and knees, four patients of the ipsilateral hip and knees, 10 patients of the knee(s), one patient of the right proximal fibula, and one patient of the knees and talus. Results of hip, knee and ankle plain radiographs were negative.

CONCLUSION: AVN can occur in the patients with SARS. AVN had a strong association with steroid use. More studies are required to confirm whether the virus itself can also lead to AVN.

Quantifying the extent of femoral head involvement in osteonecrosis

BACKGROUND

There are numerous methods for quantifying the extent of osteonecrosis of the femoral head. However, there is no consensus regarding which method is the most reliable. The purpose of this study was to determine the reliability and prognostic accuracy of three commonly used methods for quantifying the extent of osteonecrosis of the femoral head.

METHODS

Thirty-nine hips in twenty-five patients who had stage-I or II osteonecrosis of the femoral head, according to the grading system of the Association Research Circulation Osseous, were independently examined on two separate occasions by three observers of different specialty backgrounds and experience. Each observer used three methods to quantify the extent of osteonecrosis of the femoral head: (1) the index of necrotic extent, (2) the modified index of necrotic extent, and (3) the percentage of femoral head involvement. The interobserver and intraobserver agreement was determined for each method, and the ability of each method to predict the time to subchondral collapse was analyzed statistically.

RESULTS

There was significantly valid agreement among the observers for all three methods (p < 0.001 for all three). The correlation coefficients demonstrated substantial agreement among raters when they measured the index of necrotic extent and the percent involvement and nearly perfect agreement when they measured the modified index of necrotic extent. Survivorship analysis revealed that the percent involvement (p < 0.05), index of necrotic extent (p < 0.007), and modified index of necrotic extent (p < 0.04) were prognostically significant predictors of subchondral fracture.

CONCLUSIONS

Our results indicate that the index of necrotic extent, modified index of necrotic extent, and estimation of the percentage of involvement of the femoral head are reproducible and reliable methods for quantitatively evaluating the extent of osteonecrosis of the femoral head. We believe that the three methods can be utilized with confidence. Furthermore, they are clinically useful for identifying hips at greatest risk for subchondral collapse.

Relationship Between Bone Marrow Edema and Development of Symptoms in Patients With Osteonecrosis of the Femoral Head

OBJECTIVE

The purpose of this study was to determine the significance of risk factors on MR images for predicting the outcome of patients with osteonecrosis of the femoral head.

SUBJECTS AND METHODS

Eighty-three asymptomatic or minimally symptomatic hips in 61 consecutive patients were followed up prospectively. Inclusion criteria included osteonecrosis of the femoral head identified by typical MRI findings, with no radiographic evidence of progression of collapse, and Harris hip score of 85 points or more. Every 3 months, the patients underwent clinical and radiographic examination, and MR images were obtained at 6- to 12-month intervals. Follow-up continued until worsening of hip pain with Harris hip score of less than 70 points or surgery. Asymptomatic hips were followed up for at least 24 months. The mean clinical and radiographic follow-up period after the initial diagnosis was 60 months (range, 3-168 months).

RESULTS

Thirty-six (43%) of the 83 hips were symptomatic at the last follow-up. Bone marrow edema was present in 28 hips (34%) during the follow-up period. Twenty-seven (96%) of the 28 hips were symptomatic, and bone marrow edema significantly correlated with worsening of hip pain (p < 0.0001). The necrotic volume of hips with bone marrow edema was significantly larger than those without bone marrow edema (p < 0.0001). Bone marrow edema was found to be the most significant risk factor for worsening of pain (p < 0.0001).

CONCLUSION

Bone marrow edema strongly correlated with necrotic volume and was the most significant risk factor for worsening of hip pain. A large necrotic volume of 30% or more may be the second useful indicator for predicting future worsening of hip pain.

MR imaging of bone marrow edema and joint effusion in patients with osteonecrosis of the femoral head: relationship to pain

OBJECTIVE

Our aim was to determine the occurrence of bone marrow edema and joint effusion and their relationship to pain in patients with osteonecrosis of the femoral head on the basis of MR imaging.

MATERIALS AND METHODS

There were 71 patients with osteonecrosis of the femoral head based on characteristic radiographic and MR imaging findings. All patients had surgical confirmation of the disease. Both hips were affected with osteonecrosis in 39 patients, whereas only one hip was involved in 31 patients. The last patient underwent an arthroplasty of one hip during the study and had only one hip imaged. We evaluated a total of 110 hips in this study, of which 98 were painful. We staged osteonecrosis of the femoral head, using the classification of Steinberg et al. The 31 unaffected hips served as controls. Bone marrow edema and joint fluid were evaluated on MR images. Bone marrow edema was defined as an ill-defined area of low signal intensity on T1-weighted images with corresponding high signal intensity on T2-weighted or inversion recovery images localizing to the femoral head, neck, and intertrochanteric region. The amount of joint fluid was graded from 0 to 3.

RESULTS

The peak of bone marrow edema occurred in stage III disease (72%); its odds ratio was seven times greater than that for stage I osteonecrotic hips. Effusions of a grade greater than or equal to 2 were seen most often in stage III disease (92%), compared with 10% in the control hips. With an effusion, bone marrow edema was 12.6 times greater when the hip was painful than when it was not.

CONCLUSION

Both bone marrow edema and joint effusions existed with a peak occurrence in stage III disease. Bone marrow edema seems to have a stronger association with pain than does joint effusion in osteonecrosis of the femoral head.

Congenital dislocation of the hip: an evaluation of closed reduction

A retrospective study of 59 congenitally dislocated hips was undertaken to assess the relationship between the quality of a closed reduction and the eventual outcome. Good closed reductions were associated with rapid improvement of the acetabular angle and the center edge (CE) angle and a low incidence of avascular necrosis (AVN). Adequate reductions with up to 7 mm of widening of the joint on arthrogram had a good final outcome in 11 of 13 hips with a slower rate of improvement of the acetabular and CE angles and a low rate of AVN. Hips with poor or indeterminate reductions had an acceptable outcome in only five of 23 hips, did not benefit from prolonged closed treatment, and had a 57% incidence of AVN. Patients with marked ligamentous laxity often fared poorly, required prolonged treatment, and had a high incidence of AVN.

The pattern of bone marrow oedema on MRI in osteonecrosis of the femoral head

It has been suggested that transient osteoporosis or the bone marrow oedema syndrome (BMOS) may be the initial phase of osteonecrosis of the femoral head (ONFH) and that there may be a common pathophysiology. In this study, we have assessed the MR images of 200 consecutive patients with ONFH in respect of the BMO pattern in order to test this hypothesis. This pattern was not observed in the early stage of ONFH. The initial abnormal finding detected on the MR images was an abnormal band of intensity at the junction between the necrotic area and the normal bone. Structural damage of the head seems to result in the appearance of the BMO pattern and the development of pain in ONFH. There was no finding to support the existence of a continuum between BMOS and ONFH.

Hypoxia-inducible factor-1 is a positive regulator of Sox9 activity in femoral head osteonecrosis

Legg-Calve-Perthes disease (LCPD) is a juvenile form of ischemic osteonecrosis of the femoral head leading to femoral head deformity and premature osteoarthritis. Femoral head osteonecrosis occurs due to blood supply disruption which results in hypoxic injury to the femoral head. Hypoxia-inducible factor-1 α (HIF-1α) is a master regulator of cellular response to hypoxia. A pig model of ischemic osteonecrosis of femoral head has been shown to have radiographic and histopathologic changes resembling LCPD. Our preliminary studies showed that the cartilage layer was thicker in the hypoxia group compared to the control group. The mechanism underlying this cartilage response is not known. To explore the hypoxia-induced downstream gene activity following the femoral head ischemia, porcine microarray analysis of gene profiles of chondrocytes from normal and ischemic femoral heads was performed. In the ischemic side, the expression of Sox9, a transcription factor required for chondrocyte differentiation, was upregulated along with HIF-1α. Expressions of Sox9 target genes, such as type II collagen and aggrecan, were also increased. Microarray results were confirmed by quantitative real-time RT-PCR. In addition, immunohistochemistry assay demonstrated that both HIF-1α and Sox9 were upregulated in chondrocytes in ischemic femoral heads compared with normal controls. To investigate the possible molecular mechanisms of hypoxia on Sox9 activity, we tested the effect of HIF-1α on Sox9 expression in vitro. We made a luciferase reporter construct driven by 2kb Sox9 promoter. Transient transfection assay showed that HIF-1α activated Sox9 promoter activity in a dose-dependent manner. Sox9 is known to activate type II collagen target gene expression. To test the effect of HIF-1α on Sox9-mediated transcription, HIF-1α was cotransfected with Sox9 in type II collagen reporter assay. Our results demonstrated that HIF-1α enhanced Sox9-mediated transcriptional activity. Moreover, coimmunoprecipitation assay showed that HIF-1α associated with Sox9 directly. Taken together, these findings indicate that HIF-1α activates Sox9 expression and enhances Sox9-mediated transcriptional activity and that HIF-1α physically interacts with Sox9. We speculate that HIF-1α upregulation of Sox9 activity may have a chondroprotective role following femoral head ischemia.

Biophysical stimulation with pulsed electromagnetic fields in osteonecrosis of the femoral head

BACKGROUND

Osteonecrosis of the femoral head is the end point of a disease process that results in bone necrosis, joint edema, and cartilage damage. It leads to joint arthritis that necessitates total hip arthroplasty in many patients. Because of its positive effects on osteogenesis and its chondroprotective effect of articular cartilage, pulsed electromagnetic field stimulation has been proposed as a method to prevent or delay the progression of osteonecrosis.

METHODS

A retrospective analysis of the results of treatment with pulsed electromagnetic field stimulation of seventy-six hips in sixty-six patients with osteonecrosis of the femoral head was performed. Patients with Ficat stage I, II, or III osteonecrosis of the femoral head were treated with pulsed electromagnetic field stimulation for eight hours per day for an average of five months. Clinical and diagnostic imaging information was collected at the start of the treatment and at the time of follow-up. The primary end point analyzed was the avoidance of hip surgery, and the secondary end point was limiting the radiographic progression (according to Ficat stage) of osteonecrosis of the femoral head.

RESULTS

Fifteen hips required a total hip arthroplasty; twelve of these hips were in patients with Ficat stage-III disease. The need for total hip arthroplasty was significantly higher in patients with Ficat stage-III disease than in patients with Ficat stage-I (p < 0.0001) or II (p < 0.01) disease at the beginning of treatment. Pulsed electromagnetic fields preserved 94% of Ficat stage-I or II hips. Furthermore, radiographic progression (according to Ficat stage) occurred in twenty hips (26%). Pain, present in all patients at the start of the treatment, disappeared after sixty days of stimulation in thirty-five patients (53%) and was of moderate intensity in seventeen patients (26%).

CONCLUSIONS

The results of this study confirm that pulsed electromagnetic field treatment may be indicated in the early stages of osteonecrosis of the femoral head (Ficat stages I and II). Pulsed electromagnetic field stimulation may be able to either preserve the hip or delay the time until surgery. The authors hypothesize that the short-term effect of pulsed electromagnetic field stimulation may be to protect the articular cartilage from the catabolic effect of inflammation and subchondral bone-marrow edema. The long-term effect of pulsed electromagnetic field stimulation may be to promote osteogenic activity at the necrotic area and prevent trabecular fracture and subchondral bone collapse.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions to Authors on jbjs.org for a complete description of levels of evidence.