Subchondral Area Research Articles

Spontaneous collapse of the tibial plateau: radiological staging

This paper proposes a radiological staging system for necrosis of the tibial plateau, similar to those already developed for the hip and the medial femoral condyle. We retrospectively studied the clinical case histories and radiographic findings of 14 patients (15 affected knees) with histologically proven osteonecrosis of the tibial plateau. Stage I was marked by normal radiograph, but increased uptake in bone scan and subchondral areas of abnormal marrow signal intensity in magnetic resonance imaging (MRI), as reported in other osteonecrosis sites. Stage II was characterised by cystic and sclerotic changes, and stage III fracture of the medial rim of the medial tibial plateau and tibial plateau collapse were present. Stage IV was marked by joint narrowing. These changes appeared earlier and were more pronounced when there was genu varum/valgum or involvement of the lateral tibial plateau. The radiological evolution of the disease appears to follow a four-stage course over a period of roughly one year from the onset of symptoms.

Fundamental subchondral bone changes in spontaneous knee osteoarthritis

Osteoarthritis has an unknown aetiology, and tissue samples from early stage human osteoarthritis tissue cannot be reliably obtained. Therefore understanding the development of OA relies on using animal models: such as the spontaneous changes seen in the Dunkin-Hartley guinea pig strain, which are biochemically, histologically and radiologically similar to human OA. We investigated the role of bone change in early OA development using the non-OA developing Bristol strain-2 as control from 3 to 36 weeks by standard microfocal X-ray imaging and histological techniques. The patella, tibia and femur epiphyseal region and immediate subchondral area were analysed for bone density at all ages. We found that both radiological and histological osteoarthritis scores increased progressively for the Dunkin-Hartley, but not for the BS2 demonstrating its value as a control. The Dunkin-Hartley had a higher bone density and greater subchondral bone thickness from 24 weeks of age. We conclude that prior to any gross osteoarthritis pathology the Dunkin-Hartley are undergoing subchondral bone remodelling, thus demonstrating the fundamental role of early bone remodelling in the development of osteoarthritis.

MR imaging findings in transient osteoporosis of the hip

Purpose: The authors sought to describe the magnetic resonance (MR) imaging findings including perfusion imaging, in association with the course of acute bone marrow oedema syndrome (aBMEs), in a group of patients with acute hip pain and a final diagnosis of transient osteoporosis of the hip (TOH). Materials and methods: From 217 patients referred with a probable diagnosis of avascular necrosis (AVN) of the femoral head, we identified 42 patients who had clinical and radiographic findings not relevant to AVN. MR imaging examinations were performed on a 1.0T scanner. Perfusion imaging was performed in 20 patients. The bone marrow oedema (BME) was classified in four stages. In addition, the presence or absence of oedema in the subchondral area and the presence of other subchondral lesions were recorded. Acetabular bone marrow was also assessed for the presence of oedema. The quantitative measurements included: maximum size of the effusion, percentage of enhancement (PE) and time of peak enhancement of abnormal marrow compared to the first pass, on the perfusion images. Results: Osteopenia was present on plain radiographs in 87% of cases. The most common pattern of BME was extending to the femoral head and neck. Acetabulum was involved in 16.6%. In 22.6% the BME spared the subchondral region of the femoral head. There were two cases (4.7%) with subchondral changes. A joint effusion was noted in 33 of the 42 patients. On perfusion imaging, a delayed peak enhancement was noted in 20 patients between 40 and 65 s after the first pass of contrast. No patient had any evidence of femoral head collapse or change in sphericity on follow-up MRI. None of the patients developed avascular necrosis in a time frame of 18 months from the onset of the acute hip pain. Conclusion: The aBMEs MR imaging pattern varies and is most commonly appearing on X-rays as osteopenia. Absence of subcondral lesions, delayed peak enhancement of the abnormal marrow on perfusion images, and sparing of subchondral zone from marrow oedema are MR imaging findings highly correlated to TOH.

Paper #128 An optimal donor site for the weight bearing area of the femoral condyle in an autologous osteochondral transplantation

Localized articular cartilaginous lesions present a challenging clinical problem. To relieve pain and resume joint function, the articular cartilage should be repaired with hyaline cartilage of good congruity. Autologous osteochondral transplantation, which is one of the useful techniques to repair cartilaginous lesion, has several advantages including the initial stabilization of the osteochondral graft followed by a bony union at the subchondral area and the elimination of the risk of disease transmission. However, there are few reports regarding the selection of the donor site in autologous osteochondral transplantation. Therefore, we have measured the cartilage thickness and the surface curvature of the femoral condyle taken from cadavers and attempted to determine the optimal location of the donor site for the chondral lesion in the weight bearing area of both medial and lateral femoral condyles. Eight cadarveric femoral condyles were sectioned sagittally. To analyze the thickness and surface curvature of the cartilage, photographs of the sliced condyles were taken. The film was digitized and a morphological analysis was performed using an NIH image program. As a unit of analysis, the cartilage layer of the sliced condyle was divided into 1-cm-long compartment on both sides of the sulcus terminalis. The thickness was measured at the center of each compartment and the curvature of the surface of each compartment was calculated as the reciprocal of the curvature radius. The curvature radius of the cartilage surface was measured as the radius of a circle passing three points that divided each compartment equally. Thereafter, because chondral lesion is predominantly observed in the weight bearing area of the medial and lateral femoral condyles located 2 to 3cm posterior to the sulcus terminalis, the cartilage in this area was assumed as a recipient site. To determine the optimal donor site of this presumptive chondral lesion, we compared the thickness and curvature of the recipient sites with those of each compartment. The differences in thickness and curvature between each compartment and the recipient sites were calculated and mapped schematically on the femoral condyle. The average thickness of the cartilage was 1.69 mm (range, 0.22 to 3.65 mm), with the maximum curvature 27.2 m-1 and the minimum −20.0 m-1. When the recipient site was assumed to be the weight bearing area of the medial and lateral condyles, the most compatible donor site in terms of the cartilage thickness and curvature was located anterior to the sulcus terminalis in the middle portion of the lateral condyle with a thickness difference of less than 0.07 mm and a curvature difference less than 2.22 m-1. The anterior portion of the lateral femoral condyle can be an optimal donor site for the chondral lesion in the weight bearing area of both medial and lateral femoral condyles.

The BEHAC nail--a new intramedullary implant for managing 2-stage fractures of the humerus

The BEHAC-nail is a new implant for the treatment of complex humeral fractures, particularly for segmental fractures. It is an elastic intramedullary implant that is inserted retrograde into the distal humerus. The special feature of this nail is its proximal "loop design" which reduces the implant penetration at the proximal fixation site in the subchondral area of the humeral head in comparison to implants with tips such as Rush pins or Hackethal's nails. Thus, the risk of nail migration and perforation of the humeral head is less with the BEHAC-nail than with other nails. Another advantage of the "loop design" is that the humeral head fragment can be fixed adequately. Even short proximal fragments can be stabilized with this design. In contrast a short humeral head fragment cannot be held with implants like the UHN, HVN or Seidel's nail. The BEHAC-nail is a useful implant for segmental fractures of the humerus.

Distinct focal lesions of the femoral head: imaging features suggesting an atypical and minimal form of bone necrosis.

To document the imaging findings observed in patients with an unusual pattern of abnormality of the femoral head, most likely representing osteonecrosis. The imaging findings in 11 patients (10 men, 1 woman; age range 32-55 years) with a distinct lesion of the femoral head were reviewed with particular attention to the morphologic appearance, location, and extent of the lesion(s) in the proximal femur. The 16 lesions identified in these patients extended to the subchondral area. Articular collapse was not evident in any hip. Radiography and CT showed areas of mixed bone sclerosis and osteolysis surrounded by sclerotic margins. On MR imaging, the signal intensity characteristics of the osseous lesion(s) were most commonly similar to those of fluid. Histopathologic findings, available in two hips, were typical of osteonecrosis. There was evidence of correlation of the site of the lesion with the known general distribution and anastomoses of arteries supplying the femoral head. A distinct, focal lesion of the femoral head is believed to represent an atypical form of bone necrosis. Its restriction to a small portion of the femoral head may relate to localized vascular anatomy. Recognition of the quite characteristic imaging findings can prevent misdiagnosis and may have implications for the prediction of the natural course of the disease.

Articular area responses to mechanical loading: effects of exercise, age, and skeletal location.

How reliable are reconstructions of body mass and joint function based on articular surface areas? While the dynamic relationship between mechanical loading and cross-sectional geometry in long bones is well-established, the effect of loading on the subchondral articular surface area of epiphyses (hereafter, articular surface area, or ASA) has not been experimentally tested. The degree to which ASA can change in size and shape is important, because articular dimensions are frequently used to estimate body mass and positional behavior in fossil species. This study tests the hypothesis that mechanical loading influences ASA by comparing epiphyses of exercised and sedentary sheep from three age categories: juvenile, subadult, and adult (n = 44). ASA was measured on latex molds of subchondral articular surfaces of 10 epiphyses from each sheep. Areas were standardized by body mass, and compared to diaphyseal cross-sectional geometrical data. Nonparametric statistical comparisons of exercised and control individuals found no increases in ASA in response to mechanical loading in any age group. In contrast, significant differences in diaphyseal cross-sectional geometry were detected between exercised and control groups, but mostly in juveniles. The conservatism of ASA supports the hypothesis that ASA is ontogenetically constrained, and related to locomotor behavior at the species level and to body mass at the individual level, while variations in diaphyseal cross-sectional geometry are more appropriate proxies for individual variations in activity level.

Strut-Autografting with and without Osteogenic Protein-1

Osteonecrosis of the femoral head frequently leads to collapse of the articular cartilage and to disabling osteoarthritis, which ultimately may necessitate joint arthroplasty. One treatment method that has had moderate success is the so-called trapdoor approach, which involves excavation of diseased (necrotic) bone followed by bone-grafting. Augmentation of this procedure with various growth and differentiation factors may improve the outcome. We developed a canine model that mimics the clinical situation with trapdoor bone-grafting. The objective of this study was to evaluate the effect of the addition of osteogenic protein-1 on healing following the trapdoor procedure with strut-autografting. Thirty-four skeletally mature dogs were used in the experiment. After capsulotomy, a trapdoor was created in the anterolateral surface of the femoral head and a 2-cm-diameter subchondral area of bone was removed. In the phase-I experiments, seven dogs had no treatment of the defect (Group I) and nine dogs were treated with strut-grafting (Group II). In phase II, the procedure was modified by collapsing the trapdoor into the created defect intraoperatively in eighteen dogs, which were divided into three equal groups: six untreated defects were left collapsed (Group III), six were treated with bone graft (Group IV), and six were treated with bone graft augmented with osteogenic protein-1 (Group V). Three of the seven femoral heads in Group I (untreated defect) and one of the nine heads in Group II (grafting without collapsing of the trapdoor) had evidence of cartilage collapse. Inspection of sagittal slices and radiographs revealed an unfilled residual defect in all Group-I heads, whereas all Group-II heads were well healed. The mean normalized stiffness value was significantly larger in Group II than it was in Group I. On visual inspection, depression was noted in all of the femoral heads in Group III (untreated defect; trapdoor left collapsed). In both Group IV and Group V (grafting without and with osteogenic protein-1), the trapdoor cartilage appeared to be essentially normal. Groups IV and V had more radiographic healing than did Group III. The defects in Group V (grafting with osteogenic protein-1) healed faster radiographically than did those in Group IV (grafting without osteogenic protein-1). Moderate-to-excellent healing was seen both radiographically and biomechanically by four months in the groups treated with grafting, with and without osteogenic protein-1, whereas untreated defects did not heal. Symptomatic osteonecrosis of the femoral head is a clinical challenge. The animal model in the current study is a useful tool for the evaluation of methods to treat osteonecrosis of the femoral head. Studies investigating additional time-periods between implantation of osteogenic protein-1 and assessment of results as well as different doses of osteogenic protein-1 are warranted.

Subchondral changes in transient osteoporosis of the hip.

To review the subchondral changes on MR imaging in transient osteoporosis of the hip (TOH) and to consider the pathophysiology. MR images of 12 hips of 11 consecutive patients with TOH were retrospectively studied. The diagnoses of TOH were confirmed on the basis of previously published criteria, including decreased bone density of the femoral head and/or neck on radiographs, bone marrow edema (BME) pattern on MR images, spontaneous resolution of the symptoms and a return to normal radiodensity. All 12 hips showed a BME pattern in the femoral head and/or neck. Linear patterns of very low signal intensity were identified on T1-weighted images in the subchondral area within the diffuse low signal intensity area in all 12 hips. On T2-weighted images, a low signal intensity line was observed in the corresponding area in eight hips only. These linear patterns were thought to represent subchondral fracture lines. The presence of a subchondral fracture may be important when considering the pathophysiology of TOH.

Osteonecrosis of the patella: Imaging features

Osteonecrosis of the patella, although uncommon, has become important to recognize because it can be a cause of pain in the knee. We describe the imaging manifestations of nontraumatic osteonecrosis of the patella in seven clinical cases. The lesions uniformly involved the superior aspect of the patella. Conventional radiography displayed increased radiodensity, subchondral radiolucent areas, and typical demarcation line surrounding the ischemic region. MR imaging and bone scintigraphy demonstrated the characteristic features of osteonecrosis. Recognition of the imaging findings of osteonecrosis involving the patella can preclude misdiagnosis and may obviate unproductive invasive diagnostic procedures.

Early MRI findings of rapidly destructive coxopathy

To diagnose rapidly destructive coxopathy (RDC) in its early stages and understand the pathomechanism of associated joint destruction, ten cases of RDC were followed by periodic MRI from onset of the disease. In the initial stage (stage 1) of RDC, when radiographs revealed slight narrowing of the joint space, a small subchondral area of low signal intensity was observed on T 1-weighted images (T1WI) and inhomogeneous high intensity was observed on T 2-weighted images (T2WI) in the antero-lateral portion of the femoral head. When radiographs showed obliteration of the joint space (stage 2), MRI revealed a diffuse area of low intensity on TIWI and high intensity on T2WI in the proximal femur, including the femoral neck and head, suggesting extensive bone marrow edema. The femoral head and acetabulum were aggressively destroyed (stage 3) in all cases 3 to 6 months after the diffuse abnormal pattern was observed on MRI. MRI in stage 3 cases showed low intensity areas on both T1WI and T2WI. RDC did not show the band-like pattern of low intensity on T1WI and high intensity on T2WI that typify MRI findings in cases of osteonecrosis. When joint space narrowing is observed radiographically, the diffuse abnormal pattern of low intensity on T1WI and high intensity on T2WI induced by a subchondral small lesion might be an early sign of RDC.

Pathology of femoral head collapse following transtrochanteric rotational osteotomy for osteonecrosis.

We investigated the pathology of femoral head collapse following transtrochanteric anterior rotational osteotomy. Six femoral heads were obtained during total hip arthroplasty some 2-12 years after osteotomy. In all cases, the preoperatively necrotic lesions exhibited mostly osteonecrosis with accumulation of bone marrow cell debris and trabecular bone with empty lacunae, although repair tissue such as granulation tissue and appositional bone formation were observed in limited areas in some cases. In the transposed intact articular surface of the femoral head, osteoarthritic changes such as fissure penetration to the subchondral bone and osteophyte formation were commonly observed. In newly created subchondral areas at weight-bearing sites, trabecular thickness and the number of trabecular bones had decreased, with few osteoblasts, osteoclasts, and osteocytes being present, resulting in a coarse lamellar structure of the trabecular bone. These findings suggest that transposed areas in cases of failure consist mostly of low-turnover osteoporotic lesions which could cause collapse of the femoral head.

Subchondral magnetic resonance imaging changes in early osteoarthrosis associated with tibial osteonecrosis

The authors report on 41 patients with acute or subacute knee pain and early or midstage degenerative arthrosis with osteonecrotic lesions in the subchondral and metaphyseal region of the medial proximal tibia. Each lesion was identified only on magnetic resonance images (MRI). These MRI changes are classified and the clinical course is defined during a follow-up period averaging 4.5 years. Radiographically, 22 patients had minimal degenerative changes; 12 had moderate arthritis; and 7 were normal. With MRI, 3 distinct types of lesions were identified. Type A lesions had localized areas of decreased signal in the subchondral area. Type B lesions had diffuse signal changes with extension into the metaphysis. Type C lesions had metaphyseal involvement as well as a marginated serpentine subchondral rim usually associated with advanced osteonecrosis. There were 9 type A lesions, 23 type B, and 9 type C. At the end of 1 year, 33 patients (80%) had no or mild symptoms, and 8 (20%) had persistent moderate pain. At 4.5-year follow-up, most patients had symptoms consistent with progressive osteoarthrosis, 12 patients had severe symptoms (29%), 17 (41%) had mild or moderate symptoms, and only 12 (29%) were asymptomatic or had minimal symptoms. The type of MRI change seen initially was predictive of prognosis. Only 6 (19%) of the 32 patients with type A or B findings had severe symptoms at last follow-up. Six (66%) of the 9 patients with a type C MRI lesion had severe symptoms or had an operation by last follow-up. Twelve patients had follow-up MRI at a mean 15 months (range, 12 to 18 months) after the initial evaluation. The type A and B changes were either absent or significantly reduced. The type C subchondral marginated rim changes remained but metaphyseal involvement was reduced. There appears to be a spectrum of tibial subchondral MRI changes associated with sudden onset of medial knee pain in patients with early osteoarthritis of the knee. These changes may be indicative of osteonecrosis. The initial MRI classification is useful in predicting prognosis. Recognition of this problem may avoid unnecessary intra-articular surgery.

Idiopathic bone marrow edema lesions of the femoral head: predictive value of MR imaging findings.

To determine the frequency of several subchondral magnetic resonance (MR) imaging features observed in bone marrow edema lesions of the femoral head and to determine their value for differentiation of irreversible from transient lesions. The authors reviewed MR images of 72 femoral head lesions in 42 men and 25 women (median age, 48 years) with equivocal radiographic findings and bone marrow edema seen at MR imaging (T1- and T2-weighted images in all patients and contrast material-enhanced T1-weighted images in 39 patients). Follow-up MR images showed 57 lesions to be transient and 15 to be irreversible. The presence and size of subtle subchondral features observed on initial MR images were compared for both types of lesion. Lack of any additional subchondral change on T2-weighted or contrast-enhanced T1-weighted images had 100% positive predictive value for transient lesions. For irreversible lesions, presence of a subchondral area of low signal intensity at least 4 mm thick or 12.5 mm long had positive predictive values of 85% and 73%, respectively, on T2-weighted images and 87% and 86%, respectively, on contrast-enhanced T1-weighted images. Careful assessment of subchondral changes enables confident differentiation between early irreversible lesions and transient bone marrow edema lesions.

The Hawkins sign.

HomeRadiologyVol. 210, No. 1 PreviousNext Signs in ImagingThe Hawkins SignEdwin F. Donnelly1Edwin F. Donnelly1Author AffiliationsDepartment of Radiology, Vanderbilt University Medical Center, 21st Ave S and Garland, R-1318B MCN, Nashville, TN 37232-2675.Edwin F. Donnelly1Published Online:Jan 1 1999https://doi.org/10.1148/radiology.210.1.r99ja08195MoreSectionsFull textPDF ToolsImage ViewerAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinked In References 1 Hawkins LG. Fractures of the neck of the talus. J Bone Joint Surg 1970; 52: 991-1002. Crossref, Medline, Google Scholar2 Mulfinger GL, Trueta J. The blood supply of the talus. J Bone Joint Surg 1970; 52: 160-167. Google Scholar3 Peterson L, Goldie IF. The arterial supply of the talus: a study on the relationship to experimental talar fractures. Acta Orthop Scand 1975; 40: 1026-1034. Google Scholar4 Penny JN, Davis LA. Fractures and fracture: dislocations of the neck of the talus. J Trauma 1980; 20: 1029-1037. Crossref, Medline, Google Scholar5 Lorentzen JE, Christensen SB, Krogsoe O, Sneppen O. Fractures of the neck of the talus. Acta Orthop Scand 1977; 48: 115-120. Crossref, Medline, Google ScholarArticle HistoryAccepted: Aug 17 1998Received: Feb 09 1998Revision received: Mar 13 1998Revision received: Apr 14 1998Published in print: Jan 1999 FiguresReferencesRelatedDetailsCited ByWorld Journal of Clinical Cases, Vol. 7, No. 14Médecine et Chirurgie du Pied, Vol. 31, No. 4Journal of Korean Foot and Ankle Society, Vol. 19, No. 4Case Reports in Orthopedics, Vol. 2013Journal of Digital Imaging, Vol. 25, No. 1Clinics in Podiatric Medicine and Surgery, Vol. 29, No. 2The Journal of Foot and Ankle Surgery, Vol. 50, No. 3Journal of Trauma: Injury, Infection & Critical Care, Vol. 68, No. 1Foot & Ankle International, Vol. 31, No. 9Recommended Articles RSNA Education Exhibits RSNA Case Collection Vol. 210, No. 1 Metrics Altmetric Score PDF download

Gross, histological and histomorphometric features of the navicular bone and related structures in the horse

Forelimb navicular bones and associated soft tissues were collected from 3 groups of horses and subjected to pathological examinations. The groups consisted of 38 horses with clinical navicular disease (ND) and 2 control groups, with no history of forelimb lameness, consisting of 25 age-matched mature horses (A-MC) and 9 immature horses (IC). Histological and histomorphometric studies were performed on tissue samples from 10 ND, 10 A-MC and 5 IC horses. Gross changes seen only in ND horses included: full thickness defects in the palmar surface fibrocartilage, palmar cortex erosion, medullary lysis, flexor digitorum profundus tendon (FDPT) surface fibrillation, FDPT core lesions and adhesions between the FDPT and navicular bone. Palmar surface partial thickness fibrocartilage loss and distal border fragmentation were seen with a significantly greater incidence in ND than in A-MC and not observed in IC. Remodelling of the proximal border, FDPT surface colouration, palmar surface fibrocartilage colouration and proximal border entheseous bone were identified in ND and A-MC but not in IC. Mid-ridge synovial fossae and horizontal depressions in the palmar surface were identified in all groups. Histologically palmar fibrocartilage thinning and loss were associated with reduced palmar fibrocartilage cell density and chondrocyte cluster formation. Palmar fibrocartilage fibrillation, palmar cortical bone defects, fibromyxoid stromal change in the medulla, medullary pseudocyst formation and entheseous new bone formation were all seen in ND. The adjacent FDPT showed fibrillation, tag formation and degeneration of the dorsal surface. Necrotic foci were also present within the body of the tendon. Although not always present, medullary bone pseudocysts, separate mineralised foci and most changes on the dorsal surface of the FDPT were specific to ND. Bone histomorphometric parameters were compared among groups. Cross-sectional area reduced from the sagittal ridge to the medial and lateral margins of each navicular bone. IC navicular bones had a smaller subchondral area, subchondral bone volume and a greater osteoid volume than in the AC, indicating that these differences were age-related. In ND the medullary area was decreased but the trabecular bone volume increased. The palmar subchondral area was increased but contained bone with an increased porosity and osteoid volume. Changes occurred from the medial to the lateral margins of the bone in horses with ND indicating remodelling of the bony elements throughout the bone in ND. The histological and histomorphometric changes in the navicular bone and palmar fibrocartilage were considered similar of those found in articular hyaline cartilage and subchondral bone in osteoarthritis.

Early irreversible osteonecrosis versus transient lesions of the femoral condyles: prognostic value of subchondral bone and marrow changes on MR imaging.

The purpose of this study was to determine the MR imaging features that enable differentiation between early irreversible osteonecrosis and transient lesions in nontraumatic lesions of the femoral condyle having the "bone marrow edema" pattern on MR imaging. We reviewed 23 nontraumatic painful lesions of the femoral condyle in 23 patients (12 men and 11 women; mean age, 62 years). All patients had undergone radiography of the knee with findings that were normal or inconclusive. Also, all patients underwent MR imaging that revealed the bone marrow edema pattern in a condyle. Lesions observed after trauma, surgery, or glucocorticoid medication, or with epiphyseal collapse or degenerative joint disease on initial plain radiographs, were excluded from this study. Of the 23 lesions, 14 showed complete resolution (and were designated as transient epiphyseal lesions). The remaining nine lesions were irreversible and, on follow-up radiographic and MR imaging studies, evolved to collapsed osteonecrosis (and were designated as early osteonecrosis). The presence and size of the subchondral features observed by two radiologists on initial MR studies were compared for both irreversible and transient epiphyseal lesions. Initial MR imaging characteristics indicative of an early irreversible osteonecrosis included a subchondral area of low signal intensity on T2-weighted images with a thickness of more than 4 mm (sensitivity, 100% and 100%; specificity, 82% and 74% for the two observers) or a length of more than 14 mm (sensitivity, 89% and 88%; specificity, 93% and 87% for the two observers), focal epiphyseal contour depressions, and lines of low signal intensity located deep in the affected condyle. The extent of edema was similar for both transient epiphyseal lesions and early osteonecrosis. Careful assessment of MR imaging changes occurring in the subchondral area can enable confident differentiation between transient epiphyseal lesions and early irreversible osteonecrosis of the femoral condyle.

Chondroblastoma of the Foot

A total of 322 cases of chondroblastoma were referred to the Armed Forces Institute of Pathology between 1960 and 1990. Ten additional cases of chondroblastoma were treated at Walter Reed Army Medical Center between 1985 and 1993. Forty-two of these involved the foot, two of which were treated at Walter Reed Army Medical Center. Patients with chondroblastoma of the foot were male in 35 (81%) cases, with a mean age of 25.5 years, which was significantly different from the mean age of 17.3 years in patients with chondroblastoma of the long bones (P < 0.0001). Chondroblastoma of the foot is most commonly found in the posterior subchondral areas of the talus and calcaneus as well as in the calcaneal apophysis. Radiographically, the lesion was associated with an articular surface or apophyseal area in all cases and appeared radiolucent, with little to no matrix production. The margins were generally well defined. Cystic features were noted grossly and histologically in 24 (57%) specimens, a feature seen in only 21% of all chondroblastomas overall. Treatment consists of thorough curetting and bone grafting with good oncologic and functional results.

Bone strength and material properties of the glenoid

The quality of the glenoid bone is important to a successful total shoulder replacement. Finite element models have been used to model the response of the glenoid bone to an implanted prosthesis. Because very little is known about the bone strength and the material properties at the glenoid, these models were all based on assumptions that the material properties of the glenoid were similar to those of the tibial plateau. The osteopenetrometer was used to assess the topographic strength distribution at the glenoid. Strength at the proximal subchondral level of the glenoid averaged 66.9 MPa. Higher peak values were measured posteriorly, superiorly, and anteriorly to the area of maximum concavity of the glenoid joint surface known as the bare area. One millimeter underneath the subchondral plate, average strength decreased by 25%, and at the 2 mm level strength decreased by 70%. The contribution of the cortical bone to the total glenoid strength was assessed by compression tests of pristine and cancellous-free glenoid specimens. Strength decreased by an average of 31% after the cancellous bone was removed. The material properties of the glenoid cancellous bone were determined by axial compression tests of bone specimens harvested from the central part of the glenoid subchondral area. The elastic modulus varied from approximately 100 MPa at the glenoid bare area to 400 MPa at the superior part of the glenoid. With the elastic constants used as a predictor of the mechanical anisotropy, the average anisotropy ratio was 5.2, indicating strong anisotropy. The apparent density was on average 0.35 gr. cm−3, and the Poisson ratio averaged 0.263. According to our findings the anisotropy of the glenoid cancellous bone, details concerning the strength distribution, and the load-bearing function of the cortical shell should be considered in future finite element models of the glenoid.

Cartilage and bone morphology in osteochondritis dissecans.

Osteochondritis dissecans (OD) is a syndrome that can be characterized as a non-infectious disturbance of enchondral ossification or as a post-traumatic event. OD occurs in the joint cartilage and physis of long bones, as well as in the talus or metacarpal head especially of young athletes. The medial femoral condyle is the most commonly affected site. The causes of osteochondritis dissecans are poorly understood. Thirty human osteochondral cylinders from patients (aged 16-44 years) with osteochondritis dissecans of the medial femoral condyle (grades IV and V according to Rodegerdts and Gleissner) were harvested intraoperatively from osteochondritic areas as part of a cartilage-bone transplantation. Light microscopy, electron microscopy, and immunohistochemistry using poly- and monoclonal antibodies against collagens and glycosaminoglycans revealed differences between osteochondrotic and normal cartilage. Staining with toluidine blue at pH 1 shows a decrease in acidic glycosaminoglycans in OD. Modified pentachrome staining showed a thinned subchondral growth plate compared to normal osteochondral samples. Borders to the healthy tissue are clearly visible micro- and macroscopically. Scanning electron microscopy revealed structural differences in the subchondral area. Immunohistochemistry found a general decrease in glycosaminoglycan content and a change in composition. Only faint staining for chondroitin and keratan sulfates was observed in osteochondritic cartilage, whereas increased staining was shown for keratan sulfate in bone.