Arterial supply of the femoral condyles

INTRODUCTION: The most frequent site for aseptic bone necrosis and osteochondrosis dissecans in the human knee joint is the medial femoral condyle. The aim of this study is to analyze the three-dimensional vascularization of the human knee joint and to find out if there are any differences in the blood supply of the medial and lateral femoral condyles which may explain the preponderance of aseptic bone necrosis in the medial side. MATERIAL AND METHODS: The femoral arteries of 14 unfixed lower extremities have been injected with epoxy resin. After documentation of the extraosseous course of the blood vessels the bone was macerated with 10% formic acid. The insertions of tendons and ligaments were investigated by light microscopy and immunohistochemistry. RESULTS: The arterial supply of the lateral femoral condyle originates from the upper lateral geniculate artery, the terminal ends of which penetrate the bone from lateral. Branches of the middle geniculate artery reach the bone from the medial wall of the intertubercular notch. The subchondral bone of the medial femoral condyle draws its blood supply mainly from the descending geniculate artery. Branches of the middle geniculate artery penetrate the medial femoral condyle only in the posterior part of the intercondylar fossa. These posterior vessels do not contribute to the supply of the subchondral bone. In the anterior part of the medial wall of the intercondylar fossa there is the wide femoral insertion of the posterior cruciate ligament. Injection techniques and immunohistochemical investigations show that the fibrocartilage of the chondral apophyseal insertion of the posterior cruciate ligament is avascular and acts as banier which impedes blood vessels to penetrate the bony surface in this region. The subchondral bone adjacent to the femoral insertion of the posterior cruciate ligament receives its blood supply from vessels that penetrate the bone at the medial wall of the medial femoral condyle. The blood vessels which supply the lateral parts of the medial condyle have the longest intraosseous course. The density of vessels within this region is largely reduced. CONCLUSIONS: The region adjacent to the femoral insertion of the posterior cruciate ligament is the most frequent site for osteochondrosis dissecans in the knee joint. Our results show that the arterial supply of the subchondral bone may be considered as a cofactor for the etiology of osteochondrosis dissecans.     

Osteonecrosis of the lateral femoral condyle following anterior cruciate ligament reconstruction: is bone bruising a risk factor?

Osteonecrosis of the knee is extremely rare following anterior cruciate ligament (ACL) reconstruction surgery. We report a case of osteonecrosis of the lateral femoral condyle in a patient after ACL reconstruction. The osteonecrotic lesion occurred in the same area as a large bone bruise, which was sustained at the time of the initial injury. We hypothesize that the combination of bone bruising and femoral tunnel drilling for ACL reconstruction may have compromised the overall vascularity of the articular cartilage and the subchondral bone, thereby resulting in osteonecrosis.     

Subchondral giant-cell tumor of the proximal tibia: arthroscopic treatment for accelerated articular cartilage and meniscal degeneration in two patients

Giant-cell tumor most commonly occurs in the distal femur and proximal tibia and characteristically involves the subchondral bone. Incomplete resection leads to recurrence rates of up to 50%. Intralesional curettage, adjuvant treatments, and polymethyl methacralate (PMMA) reconstruction is the current mainstay of treatment and has produced recurrence rates of less than 10%. Achieving adequate curettage while preserving the articular cartilage of the tibial plateau poses a significant challenge, especially when the tumor involves the subchondral bone. We report on 2 cases, both with symptomatic full-thickness tibial articular cartilage loss and one with a meniscal tear, after curettage, phenol cautery, and PMMA reconstruction of giant-cell tumor of the proximal tibia. Arthroscopic chondroplasty and planing of the exposed cement was performed in both cases, theoretically reducing focal areas of stress concentration that could lead to further meniscal damage and injury to the femoral condyle articular surface in weight-bearing. Partial meniscectomy for a complex meniscal tear was performed in one case. Eighteen months postoperatively, both patients were asymptomatic, working full-time, and participating in light physical activity. Repetitive heavy loading of the knee, such as running, was prohibited, and long-term follow-up is warranted to assess for further joint degeneration and need for total knee arthroplasty.     

Mechanical behavior of the subchondral bone in the experimentally induced osteoarthritis]

In order to evaluate the role of the subchondral bone (cancellous bone) in the development and progression of the joint degeneration, osteoarthritis of the knee joint was produced experimentally in the rabbits and viscoelasticity and strength of the subchondral bone from the femoral medial condyle have been investigated along with the pathological, histological study of the joint. The viscoelastic spectrometer and the Instron type testing machine were used. As the first change after operation, osteophyte formation around the joint margin has been observed before the initiation of the degeneration of articular cartilage and there is a possibility that mechanical properties of subchondral bone such as high deformability and low elasticity to the mechanism of osteophyte formation. Subchondral bone softening with marked increase of ultimate strain and phase lag, marked decrease of compressive elastic modulus and ultimate stress precedes or occurs concurrently with the degeneration of the articular cartilage. These facts indicate the relationship between the mechanical properties of the subchondral bone and joint degeneration. Once the joint degeneration starts, degeneration continues progressively while the subchondral bone tends to become brittle. These changes may be considered as a kind of functional adaptation to the damage or denudation of articular cartilage. It is postulated that some architectural changes of the subchondral bone may provide alterations of the mechanical properties. Biomechanical roles of the subchondral bone is suggested as one of the factors in the joint degeneration.     

Arthroscopic treatment of a large lateral femoral notch in acute anterior cruciate ligament tear

A 24-year-old professional soccer player suffered an acute anterior cruciate ligament tear associated with a radiologically evident impression fracture of the lateral femoral condyle, the so-called “lateral femoral notch sign”. Following MRI validation of the injury with detection of an additional lateral meniscus tear, arthroscopy was carried out 3 days after the injury. Due to the extended impression of about 5 mm, arthroscopically assisted closed reduction of the depression fracture was performed. A 3.2 mm tunnel was drilled at the lateral femoral condyle in a supero-inferior direction using an ACL tibial guide and the depressed area could be restored using an elevator. The resulting subchondral bone defect in the femoral condyle was filled with freeze–dried human cancellous bone allograft. As a one-stage procedure ACL reconstruction was carried out using a hamstring tendon technique. At 1-year follow up the patient has returned to full sporting function, including playing soccer with a radiographically reduced lateral femoral notch sign. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.     

Long-term results of arthroscopic excision of unstable osteochondral lesions of the lateral femoral condyle

The purpose of this study was to evaluate the long-term functional and radiological outcomes of arthroscopic removal of unstable osteochondral lesions with subchondral drilling in the lateral femoral condyle. We reviewed the outcome of 23 patients (28 knees) with stage III or IV osteochondritis dissecans lesions of the lateral femoral condyle at a mean follow-up of 14 years (10 to 19). The functional clinical outcomes were assessed using the Lysholm score, which improved from a mean of 38.1 (SD 3.5) pre-operatively to a mean of 87.3 (SD 5.4) at the most recent review (p = 0.034), and the Tegner activity score, which improved from a pre-operative median of 2 (0 to 3) to a median of 5 (3 to 7) at final follow-up (p = 0.021). The radiological degenerative changes were evaluated according to Tapper and Hoover's classification and when compared with the pre-operative findings, one knee had grade 1, 22 knees had grade 2 and five knees had grade 3 degenerative changes. The overall outcomes were assessed using Hughston's rating scale, where 19 knees were rated as good, four as fair and five as poor. We found radiological evidence of degenerative changes in the third or fourth decade of life at a mean of 14 years after arthroscopic excision of the loose body and subchondral drilling for an unstable osteochondral lesion of the lateral femoral condyle. Clinical and functional results were more satisfactory.     

Intraarticular location predicts cartilage filling and subchondral bone changes in a chondral defect

Background and purpose The natural history of, and predictive factors for outcome of cartilage restoration in chondral defects are poorly understood. We investigated the natural history of cartilage filling subchondral bone changes, comparing defects at two locations in the rabbit knee.

Animals and methods In New Zealand rabbits aged 22 weeks, a 4-mm pure chondral defect (ICRS grade 3b) was created in the patella of one knee and in the medial femoral condyle of the other. A stereo microscope was used to optimize the preparation of the defects. The animals were killed 12, 24, and 36 weeks after surgery. Defect filling and the density of subchondral mineralized tissue was estimated using Analysis Pro software on micrographed histological sections.

Results The mean filling of the patellar defects was more than twice that of the medial femoral condylar defects at 24 and 36 weeks of follow-up. There was a statistically significant increase in filling from 24 to 36 weeks after surgery at both locations.

The density of subchondral mineralized tissue beneath the defects subsided with time in the patellas, in contrast to the density in the medial femoral condyles, which remained unchanged.

Interpretation The intraarticular location is a predictive factor for spontaneous filling and subchondral bone changes of chondral defects corresponding to ICRS grade 3b. Disregarding location, the spontaneous filling increased with long-term follow-up. This should be considered when evaluating aspects of cartilage restoration.     

Spontaneous osteonecrosis of the knee: tibial plateaus

Spontaneous osteonecrosis of the medial tibial plateau is less recognized than osteonecrosis of the medial femoral condyle, but it presents in a similar manner. These patients have a sudden onset of pain on the medial side of the knee associated with a spectrum of MRI changes in the tibial subchondral bone. The small lesions can resolve with only minimal residual scar remaining in the subchondral zone. If the lesion is large, it can collapse or show MRI changes of osteonecrosis. Recognition of this problem may help avoid unnecessary intra-articular surgical intervention.     

Localized osteoarticular change due to joint immobilization; biomechanical test and bone densitometry in rat's hind limb model

Bone change induced by knee immobilization was assessed on dissected femurs and tibias to clarify the influences upon the mechanical properties and their demands. Fifty-eight Wistar-Imamichi male rats (11–12 weeks old, body weight 350–450 g) were subjected to knee joint immobilization (150° flexed position) on one side while the opposite side served as a control. Animals were killed in seven groups at time intervals of 1, 2, 3, 4, 5, 7, and 10 weeks. The hind leg was extirpated and prepared for (1) biomechanical analysis by the indentation method at the articular surfaces of the femoral condyle and head and at the subchondral bone of the proximal tibia, and for (2) dual-energy X-ray absorptiometry of the distal metaphysis of the femur. The biomechanical parameters measured induced dynamic stiffness and phase lag derived from forced oscillation (preload 3 N, cyclic load 2 N and 11 Hz, 35 Hz), and bone mineral density was analyzed. These were compared between the immobilized side and control side, and among the seven time groups. The biomechanical results showed an early change of osteocartilaginous properties at the femoral condyle, a late response at the tibial subchondral bone, and no change at the femoral head. The measurement of bone mineral density revealed that a very sensitive reaction started within 1–2 weeks. This study provides objective data demonstrating that disuse or lack of mechanical stress greatly affects the remodeling activity for homeostasis of joints, and dramatically impairs normal bone mineral density next to the immobilized joint in young animals.     

Spontaneous osteonecrosis of the knee: the result of subchondral insufficiency fracture

BACKGROUND: Spontaneous osteonecrosis of the knee is a superficial subchondral lesion classically seen in the medial femoral condyle; in general, it is markedly different in its clinicopathological presentation from the classic wedge-shaped subchondral osteonecrotic lesions seen in the hip, knee, and other joints. Recent reports on subchondral insufficiency fracture of the femoral head, which has marked morphological similarities with spontaneous osteonecrosis of the knee, led us to reevaluate a series of patients who had had operative treatment because of a clinical and pathological diagnosis of spontaneous osteonecrosis of the knee. METHODS: We reviewed the cases of fourteen patients who had had operative treatment of spontaneous osteonecrosis of the knee in order to reevaluate the gross and histological morphology of this lesion. The patients included eight women and six men who ranged in age from fifty-nine to eighty-eight years. In all patients, the diagnosis of spontaneous osteonecrosis of the knee had been based on clinical presentation, imaging studies, and pathological findings. The appearance of the lesion on plain radiographs was categorized into four stages, which corresponded to the gross and histological findings. In stage 1, the radiographic appearance is normal; in stage 2, a radiolucent oval area is seen subchondrally or there is slight flattening of the convexity of the condyle, or both; in stage 3, the radiolucent area is expanded and is surrounded by a sclerotic halo; and in stage 4, secondary osteoarthritic changes are apparent. RESULTS: No patient had a stage-1 lesion. Three patients, all of whom had a stage-2 lesion, were considered to have a subchondral insufficiency fracture of the medial femoral condyle. Another six patients, all of whom had a stage-3 lesion, were considered to have a subchondral fracture and associated focal osteonecrosis that was confined to the area between the fracture line and the articular surface. The remaining five patients, three of whom had a stage-3 lesion and two of whom had a stage-4 lesion, had indeterminate findings because the lesion had become detached from the condyle. CONCLUSIONS: Our histopathological findings suggest that the primary event leading to spontaneous osteonecrosis of the knee is a subchondral insufficiency fracture and that the localized osteonecrosis seen in association with this disease is the result of a fracture.     

Potential risk of cartilage damage in double bundle ACL reconstruction: impact of knee flexion angle and portal location on the femoral PL bundle tunnel

The aim of this study was to compare the impact of knee flexion angle and the level of the medial drilling portal on a potential damage to the subchondral bone in double bundle ACL reconstruction, drilling the femoral PL tunnel through an accessory medial portal. We hypothesized that a knee flexion angle of 70° and 90° or a high accessory medial portal will result in a potential damage to the subchondral bone of the lateral femoral condyle. In a sawbone knee model, the medial portal location was standardized as 0 mm above the meniscus (low portal) and 10 mm above the meniscus (high portal). Femoral PL bundle tunnels were drilled at three different knee flexion angels: 70°, 90°, and 110° of knee flexion. For each portal, ten specimens were used for every flexion angle. Drilling the PL tunnel through the high medial portal at a knee flexion angle of 70° resulted in damage of the subchondral bone plate in all specimens. At 110° of flexion the distance of the tunnel exit to the subchondral bone plate was significantly higher than at 70° of flexion for both the groups, drilling through the high and low medial portal (P < 0.05). Drilling through the low portal did not result in bone plate damage at 90 and 110° of knee flexion angle. Drilling of the femoral PL bundle tunnel through a high medial portal at low knee flexion angles may damage the subchondral bone of the lateral compartment. In ACL reconstruction restoring the AM and PL bundle separately, high medial portal drilling should be avoided. We recommend drilling of the femoral PL bundle tunnel through a low medial portal in high knee flexion.     

Interspecies comparison of subchondral bone properties important for cartilage repair

Microfracture repair tissue in young adult humans and in rabbit trochlea is frequently of higher quality than in corresponding ovine or horse models or in the rabbit medial femoral condyle (MFC). This may be related to differences in subchondral properties since repair is initiated from the bone. We tested the hypothesis that subchondral bone from rabbit trochlea and the human MFC are structurally similar. Trochlea and MFC samples from rabbit, sheep, and horse were micro‐CT scanned and histoprocessed. Samples were also collected from normal and lesional areas of human MFC. The subchondral bone of the rabbit trochlea was the most similar to human MFC, where both had a relatively thin bone plate and a more porous and less dense character of subchondral bone. MFC from animals all displayed thicker bone plates, denser and less porous bone and thicker trabeculae, which may be more representative of older or osteoarthritic patients, while both sheep trochlear ridges and the horse lateral trochlea shared some structural features with human MFC. Since several cartilage repair procedures rely on subchondral bone for repair, subchondral properties should be accounted for when choosing animal models to study and test procedures that are intended for human cartilage repair. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:63–70, 2015.

     

Osteochondral autografts transfer for post-traumatic osteochondral defect of the knee-2 to 5 years follow-up

The treatment of post-traumatic osteochondral defects of the weight-bearing surface of the knee in young active patients remains a significant challenge. We report the results of an osteochondral autograft transfer (OAT) in 18 patients (mean age 29 years) with post-traumatic focal osteochondral defects of the knee. Sixteen lesions were over the femoral condyle and two were over the tibial plateau. The average size of the lesion was 4.1 cm² (from 2.25 to 6 cm²), and the subchondral bone involved no more than 1 cm in depth. Osteochondral grafts were harvested from the non-weight-bearing area of the femoral condyle. Ten patients also had concomitant surgical procedures. The average follow-up was 42 months (from 24 to 64 months). All patients were evaluated by Lysholm and Tegner activity scores and plain radiographs. Nine patients had MRI, eight patients had second-look arthroscopy and two had a biopsy. Sixteen patients (89%) had good to excellent results, while two patients with lesion over the tibial surface had fair results. The biopsy revealed survival of hyaline cartilage. For small to medium osteochondral lesion over the femoral condyle of the knee in selected patients, osteochondral autografting yielded promising short to mid-term results.     

Changes of cancellous bone mass in rat mandibular condyle following ovariectomy.

Changes in cancellous bone of the rat mandibular condyle following estrogen deficiency were histomorphometrically examined with 120-day-old female Fischer rats. Sixty-four animals were either ovariectomized bilaterally (ovx) or subjected to sham surgery (sham), and eight from each group were killed at 7, 14, 30, and 60 days after surgery. Seven intact animals were killed on day 0. Before killing, tetracycline and calcein were administered to all animals. Following histological observation, bone histomorphometry of the mandibular condyle was done using a confocal laser scanning microscope and an image analyzer. The sampling site was divided into two regions for analysis: (1) a "subchondral region," formed by the region connected to cartilage; and (2) a "central region," formed by the region beneath the former. The changes in these two regions were analyzed separately. In the sham group's condyle, the bone volume of the subchondral and central regions increased with the passage of time, although the bone turnover became low. This bone gain could be due to the effects of growth and the mechanical stimulus by occlusal load. In the subchondral region of the ovx group's condyle, the bone volume decreased significantly at 7 days, but recovered to reach approximately the same value as the sham group from 14 days onward. In the central region of the ovx group's condyle, the bone volume was unchanged, but revealed a significantly lower value than that of the sham group at 60 days (p < 0.01). Thus, ovariectomy inhibited bone gain, which was observed in the sham group's condyle even though there was no bone loss. On the other hand, the trabecular separation in the ovx's condyle of both the subchondral and central regions increased considerably and small marrow cavities interconnected to form a large bone marrow. Therefore, the ovx rat mandibular condyles dynamically altered their structures under the effects of estrogen deficiency and occlusal loads. Consequently, estrogen deficiency induced transient subchondral bone loss and recovery, whereas, in the central region, it inhibited bone gain. This suggests that mechanical loading modulates the normal ovx-induced bone loss found in other parts of the skeleton.     

An unusual case of osteochondritis dissecans of the medial tibial plateau

We report the case of a 17-year-old boy with osteochondrosis of the medial tibial plateau treated with reasorbable screw. This is an unusual location for osteochondritis dissecans, a pathologic process resulting from ischemic necrosis and characterized by the detachment of a fragment of the cartilage together with the subchondral bone of the articular surface. The lesion may be located in many joints, most frequently in the knee, close to lateral side of the articular surface of the medial femoral condyle. Received: 22 May 2002, Accepted: 3 June 2002     

Subchondral fatigue fracture of the femoral head in military recruits

BACKGROUND: Subchondral stress fracture of the femoral head is a rare condition that usually occurs as an insufficiency fracture in people with poor bone quality. We evaluated the clinical characteristics of subchondral fatigue fractures of the femoral head that occurred in young, healthy military recruits. METHODS: Between January 1998 and November 2001, seven subchondral fatigue fractures of the femoral head were treated in five patients. The characteristics of this condition were ascertained by assessing the clinical course as well as radiographs, bone scintigrams, and magnetic resonance images. RESULTS: All patients were male military recruits in their early twenties in whom pain had developed within five months after recruitment. Definite abnormal findings were observed on the initial radiographs of four hips in three patients, and the femoral head was markedly collapsed in two of these four hips. Bone scintigrams were made of five hips in four patients, and all of them showed increased radionuclide uptake in the femoral head. In all affected hips, magnetic resonance images demonstrated a localized or diffuse bone-marrow-edema pattern in the femoral head and/or neck. A subchondral fracture line (a magnetic resonance crescent sign) was identified in all hips. In the patients who did not have collapse of the femoral head, the pain decreased gradually and disappeared completely within six months, with correspondingly improved findings on sequential magnetic resonance images. The patients with femoral head collapse were treated with total hip arthroplasty or an iliac bone strut graft. CONCLUSIONS: When a military recruit or an athlete reports hip pain, a diagnosis of subchondral fatigue fracture of the femoral head should be considered.     

The cause of subchondral bone cysts in osteoarthrosisA finite element analysis

Background?The etiology of subchondral bone cysts in arthrotic joints is unclear.Materials and methods?We used two-dimensional finite element analysis to evaluate the hypothesis that subchondral bone cysts in the osteoarthrotic hip joint may be the result of microfractures caused by localized cartilage defects or a thinned layer of cartilage. We evaluated the equivalent bone stress (von Mises (VM) stress) in the cancellous bone as an indicator of potential microfractures and further development of cystic lesions.Results?Cartilage defects induced stress peaks in the subchondral bone. This peak stress distribution corresponded to the clinical observation of development of acetabular and femoral subchondral cysts in a “kissing” position. A femoral subchondral bone cyst induced a stress peak at the corresponding acetabular site, whereas subchondral acetabular cysts did not increase stress in the femoral head. Acetabular cysts showed an increased level of stress at the lateral and medial border of the lesion which was much higher than the stress levels in the femoral head, indicating a tendency to faster growth.Interpretation?Our study supports the theory that stress-induced bone resorption may cause development of subchondral bone cysts in osteoarthrosis.     

The cause of subchondral bone cysts in osteoarthrosis: a finite element analysis

BACKGROUND: The etiology of subchondral bone cysts in arthrotic joints is unclear. MATERIALS AND METHODS: We used two-dimensional finite element analysis to evaluate the hypothesis that subchondral bone cysts in the osteoarthrotic hip joint may be the result of microfractures caused by localized cartilage defects or a thinned layer of cartilage. We evaluated the equivalent bone stress (von Mises (VM) stress) in the cancellous bone as an indicator of potential microfractures and further development of cystic lesions. RESULTS: Cartilage defects induced stress peaks in the subchondral bone. This peak stress distribution corresponded to the clinical observation of development of acetabular and femoral subchondral cysts in a "kissing" position. A femoral subchondral bone cyst induced a stress peak at the corresponding acetabular site, whereas subchondral acetabular cysts did not increase stress in the femoral head. Acetabular cysts showed an increased level of stress at the lateral and medial border of the lesion which was much higher than the stress levels in the femoral head, indicating a tendency to faster growth. INTERPRETATION: Our study supports the theory that stress-induced bone resorption may cause development of subchondral bone cysts in osteoarthrosis.     

Coronal fractures of the medial femoral condyle: a series of 6 cases and review of literature

Isolated coronal fracture of medial femoral condyle with intact lateral femoral condyle is extremely rare. We present our experience with such 6 cases of coronal fractures of medial femoral condyle. We reviewed all case records of cases of coronal fractures of femoral condyle which presented to our centre from Jan 2000 to Jun 2009. Of 72 such cases, 56 were of lateral condyle, 9 were bicondylar, and 7 were only medial femoral condyle fractures. However, one of the 7 cases was a skeletally immature child with a physeal injury and hence excluded. All the 6 patients with medial femoral condyle fractures were retrospectively evaluated both clinically and radiologically. Of the 6 patients with medial condyle fractures, three patients had an isolated medial femoral condyle fracture, while three of them had associated fractures. Four of these patients were identified at the initial presentation. However, the fracture was missed during initial evaluation in one of the patients, while another patient presented with neglected medial Hoffa fracture after 6 months of injury. Mechanism of injury was direct impact to the medial side of knee in flexion in 4 out of 6 cases. All cases were operated through medial or antero-medial approach, and fixation was achieved in all with antero-posterior screws. All cases united at a mean period of 4.6 months. Coronal fractures of the medial femoral condyle are very rare, and there is a highly likelihood of these fractures being missed by an average orthopaedic surgeon. A high index of suspicion is necessary for early diagnosis especially in cases of undisplaced fractures. Being intra-articular, the ideal management includes open reduction and internal fixation. Medial or antero-medial approach with antero-posterior screws is the preferred method for fixation.