Epidemiology and imaging of the subchondral bone in articular cartilage repair

Articular cartilage and the subchondral bone act as a functional unit. Following trauma, osteochondritis dissecans, osteonecrosis or osteoarthritis, this intimate connection may become disrupted. Osteochondral defects—the type of defects that extend into the subchondral bone—account for about 5% of all articular cartilage lesions. They are very often caused by trauma, in about one-third of the cases by osteoarthritis and rarely by osteochondritis dissecans. Osteochondral defects are predominantly located on the medial femoral condyle and also on the patella. Frequently, they are associated with lesions of the menisci or the anterior cruciate ligament. Because of the close relationship between the articular cartilage and the subchondral bone, imaging of cartilage defects or cartilage repair should also focus on the subchondral bone. Magnetic resonance imaging is currently considered to be the key modality for the evaluation of cartilage and underlying subchondral bone. However, the choice of imaging technique also depends on the nature of the disease that caused the subchondral bone lesion. For example, radiography is still the golden standard for imaging features of osteoarthritis. Bone scintigraphy is one of the most valuable techniques for early diagnosis of spontaneous osteonecrosis about the knee. A CT scan is a useful technique to rule out a possible depression of the subchondral bone plate, whereas a CT arthrography is highly accurate to evaluate the stability of the osteochondral fragment in osteochondritis dissecans. Particularly for the problem of subchondral bone lesions, image evaluation methods need to be refined for adequate and reproducible analysis. This article highlights recent studies on the epidemiology and imaging of the subchondral bone, with an emphasis on magnetic resonance imaging.     

99mTc-MDP bone SPECT in evaluation of the knee in asymptomatic soccer players

OBJECTIVE: To evaluate stress fractures in leg (particularly around the knee, tibia, and femur) and knee pathology in active asymptomatic (no symptoms in the preceding month) soccer players. METHOD: The study included 42 asymptomatic soccer players (21 women, 21 men; age range 19-31 years). Players from seven teams in the major female professional and amateur male soccer leagues were examined by technetium-99m-methylene diphosphonate ((99m)Tc-MDP) bone scintigraphy during the soccer season. Four hours after intravenous injection of 20 mCi (99m)Tc-MDP, standard imaging included anterior planar spot images of the legs, lateral images of the knee, and single photon emission computed tomography (SPECT). RESULTS: Although the players were asymptomatic, increased tracer uptake, indicating stress fracture, was found in 28 (66%). Most of the stress fractures were in the tibia (62%) and femur (5%). In the 42 subjects (84 legs), 35 sites (42%) showed rupture of the posterior horn of the lateral meniscus and bone bruising of the tibial plateau, 16 sites (19%) showed rupture of the anterior horn of the medial meniscus, 11 sites (13%) showed bone bruising of the lateral femoral condyle, eight sites (10%) showed bone bruising of the medial femoral condyle, and there was avulsion injury to the infrapatellar tendon insertion in the anterior tibia in 34 sites (40%). There were 11 anterior cruciate ligament injuries. CONCLUSION: Bone SPECT is very accurate, easy to perform, cost effective, may give valuable information before magnetic resonance imaging studies in the detection of meniscal tears, and may be used successfully when magnetic resonance imaging is unavailable.     

Treatable chondral injuries in the knee: frequency of associated focal subchondral edema

OBJECTIVE: In the knee, chondral flaps and fractures are radiographically occult articular cartilage injuries that can mimic meniscal tears clinically; once correctly diagnosed, these injuries can be treated surgically. We investigated an associated MR imaging finding--focal subchondral bone edema--in a series of surgically proven lesions. MATERIALS AND METHODS: Two musculoskeletal radiologists retrospectively reviewed the MR studies of 18 knees with arthroscopically proven treatable cartilage infractions, noting articular surface defects and associated subchondral bone edema; subchondral edema was defined as focal regions of high signal intensity in the bone immediately underlying an articular surface defect on a T2-weighted or short inversion time inversion recovery (STIR) image. RESULTS: The first observer saw focal subchondral edema deep relative to a cartilage surface defect in 15 (83%) of the 18 cases; in two additional cases a surface defect was seen without underlying edema. The second observer identified 13 knees (72%) with surface defects and associated subchondral edema and three with chondral surface defects and no associated edema. Subchondral edema was seen more frequently on fat-suppressed images and on STIR images than non-fat-suppressed images. CONCLUSION: Focal subchondral edema is commonly visible on MR images of treatable, traumatic cartilage defects in the knee; this MR finding may prove to be an important clue to assist in the detection of these traumatic chondral lesions.     

胫骨平台骨折及膝关节附属结构损伤的MRI诊断

目的评价胫骨平台骨折合并膝关节附属结构损伤的MRI表现.资料与方法 27例胫骨平台骨折病例经X线平片检查后作MRI扫描,分析不同类型胫骨平台骨折所合并的膝关节附属结构损伤的MRI形态学表现.结果 MRI能准确显示骨折所合并的膝关节附属结构的损伤性病变,包括关节软骨断裂、半月板撕裂和移位、侧副韧带和肌腱的撕裂、关节腔脂肪血性积液等,其中双髁骨折引起的损伤最为严重,撕脱骨折引起的损伤较轻.结论 MRI能准确诊断胫骨平台骨折合并的膝关节附属结构损伤,应作为膝关节外伤的常规检查手段.     

Chronic medial knee pain without history of prior trauma: correlation of pain at rest and during exercise using bone scintigraphy and MR imaging

Objective  The objective of this study was to correlate chronic medial knee pain at rest and during exercise with bone scintigraphic uptake, bone marrow edema pattern (BMEP), cartilage lesions, meniscal tears, and collateral ligament pathologies on magnetic resonance MR imaging (MRI). Materials and methods  Fifty consecutive patients with chronic medial knee pain seen at our institute were included in our study. Pain level at rest and during exercise was assessed using a visual analog scale (VAS). On MR images, BMEP volume was measured, and the integrity of femoro-tibial cartilage, medial meniscus, and medial collateral ligament (MCL) were assessed. Semiquantitative scintigraphic tracer uptake was measured. Multivariate linear regression analysis was performed. Results  At the day of examination, 40 patients reported medial knee pain at rest, 49 when climbing stairs (at rest mean VAS 33 mm, range 0–80 mm; climbing stairs mean VAS, 60 mm, range 20–100 mm). Bone scintigraphy showed increased tracer uptake in 36 patients (uptake factor, average 3.7, range 2.4–18.0). MRI showed BMEP in 31 studies (mean volume, 4,070 mm³; range, 1,200–39,200 mm³). All patients with BMEP had abnormal bone scintigraphy. Ten percent of patients with pain at rest and 8% of patients with pain during exercise showed no BMEP but tracer uptake in scintigraphy. Tracer uptake and signal change around MCL predicted pain at rest significantly (tracer uptake p = 0.004; MCL signal changes p = 0.002). Only MCL signal changes predicted pain during exercise significantly (p = 0.001). Conclusion  In chronic medial knee pain, increased tracer uptake in bone scintigraphy is more sensitive for medial knee pain than BMEP on MRI. Pain levels at rest and during exercise correlate with signal changes in and around the MCL.     

Initial evaluation of the acutemultiple-ligament-injured knee

The multiple-ligament-injured knee is an orthopaedic emergency. The initial assessment of this injury mustinclude a thorough and expedient physical examination, with particular attention directed to the vascularity of the extremity. Vascular injuries should be ruled out immediately because a pulseless extremity may result in a below-knee amputation if the leg is not reperfused within 6 to 8 hours. All patients with a normal vascular examination must have serial pulse examinations or undergo an arteriogram, because intimal tears may present on a delayed basis. The neurological examination, particularly of the peroneal nerve, should be documented. A detailed examination of the knee ligaments is performed on the anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament, and posterolateral anatomic structures. Initial and postreduction radiographs require thorough evaluation to assess for peri-articular fractures, direction of dislocation, and adequacy of reduction. Magnetic resonance imaging will provide detailed information about the ligaments, bone or subchondral bone, menisci, and articular cartilage. The physical examination must be correlated with the magnetic resonance imaging findings for preoperative planning. This article provides a treatment algorithm that can be helpful in the initial assessment and decision-making process of the multiple-ligament-injured knee.     

MRI对急性膝关节骨挫伤的临床应用价值

目的：探讨MRI对急性膝关节骨挫伤的临床应用价值。方法：对117例X线平片显示阴性并行MRI检查的外伤性膝关节病例进行回顾性分析,MRI检查时间为外伤后2h．5天,重点观察股骨下端、胫腓骨上端及髌骨的骨质信号,前后交叉韧带、内外侧副韧带、内外侧半月板的完整性和信号情况。结果：急性外伤后骨挫伤的发生率为87．2％（102／117）,合并韧带损伤62例,半月板损伤49例,关节软骨损伤17例,隐性骨折21例。结论：急性膝关节外伤后骨挫伤的发生率较高,MRI能准确显示骨挫伤的部位、范围以及临近结构的损伤,对临床诊断、治疗具有重要意义。     

Occult intraosseous fracture: detection with MR imaging

Magnetic resonance (MR) images were retrospectively evaluated in eight patients who had recent, symptomatic knee injuries and in whom plain radiographs showed no fractures. T2-weighted images revealed irregular, intraosseous areas of high signal intensity; T1-weighted and proton density images revealed speckled or linear regions of low signal intensity in corresponding areas. In the seven patients whose injuries did not result from direct contusion, abnormalities occurred in subchondral locations. Two patients underwent bone scintigraphy, which showed increased activity in locations corresponding to areas of abnormality noted on MR images. Two patients underwent follow-up MR imaging at 6 weeks and 3 months, which showed complete resolution of the abnormalities. The authors speculate that the MR imaging findings represent microscopic compression fracture of trabecular bone and discuss the related entity, stress fracture.     

Lumbosacral transitional vertebral articulation: evaluation by planar and SPECT bone scintigraphy

It has been suggested that low back pain (LBP) may arise from lumbosacral transitional vertebral articulation (LSTVA) itself. It is known that bone scintigraphy is a valuable tool for the recognition of pain arising from bone and articular diseases. Therefore we aimed to show planar and SPECT bone scintigraphic findings of LSTVA and compare them with the LBP and X-ray findings. Twenty-eight patients (aged 20-63 years) in whom LSTVA had been identified radiographically were evaluated with planar bone scintigraphy, utilizing 99mTc methylene diphosphonate; and single photon emission computed tomography (SPECT) bone scintigraphy. Eighteen patients had LBP whereas 10 had not. There were 25 type IIA, one type IIB and two type IIIA LSTV articulation. On planar images, normal or non-focal minimally increased uptake superimposed on the upper sacroiliac joint was seen in patients without degenerative changes regardless of LBP whereas SPECT showed non-focal mild increased uptake on the area medial to the upper sacroiliac joint. Planar scans showed normal to non-focal mild, and mild-to-moderately increased uptake whereas SPECT demonstrated focal mild-to-moderately and markedly increased uptake in patients with degenerative changes without LBP and with LBP, respectively. The X-ray results showed an association of LBP degenerative changes, and the SPECT results showed a focal, markedly increased, uptake. We conclude that this focal, markedly increased, uptake may show the metabolically active degenerative changes of LSTV articulation and may help to reveal the pain arising from LSTVA. Therefore we propose that bone scintigraphy may be considered for the evaluation of patients with LBP thought to arise from LSTV articulation.     

Avulsion fracture of the ulnar sublime tubercle in overhead throwing athletes

BACKGROUND: Injuries to the ulnar collateral ligament are relatively common in throwing athletes and result from either acute traumatic or repeated valgus stress to the elbow. Avulsion fracture of the sublime tubercle of the ulna is a rarely reported site of ulnar collateral ligament injury. PURPOSE: We retrospectively reviewed our cases of ulnar collateral ligament injuries to study avulsion fractures of the sublime tubercle of the ulna. STUDY DESIGN: Case series. METHODS: Data, including radiographs and magnetic resonance imaging scans, were obtained by review of hospital and office records and by follow-up examination. Of 33 consecutive patients treated for ulnar collateral ligament injuries, 8 had avulsion fractures of the sublime tubercle of the ulna. All eight were male baseball players with dominant arm involvement, an average age of 16.9 years, and an average follow-up of 23.6 months. RESULTS: Six of eight patients had failure of nonoperative treatment and required surgical repair. Two of the six underwent ulnar collateral ligament reconstruction and four had direct repair of the sublime tubercle avulsion with bioabsorbable suture anchors. At last follow-up, all eight had returned to their preinjury level of activity. No patient had residual medial elbow pain or laxity. CONCLUSIONS: Diagnosis of sublime tubercle avulsion fracture is made with history, physical examination, and radiographic studies. Magnetic resonance imaging can help identify an avulsion fracture not visible radiographically and can help determine whether direct repair or reconstruction is needed.     

膝关节骨与韧带急性损伤的MRI研究

目的:探讨MRI检查中急性膝关节骨损伤与韧带损伤之间的合并关系以及临床应用价值。方法:38例急性膝部骨损伤病人,行MRI重点观察STIR序列的损伤情况。骨损伤分为显性骨折(X线检查可见)与隐性骨损伤(X线检查未见异常),韧带损伤包括撕裂与完全断裂。结果:38例共45处骨损伤,包括显性骨折28处(73%)、隐性骨损伤(骨挫伤)17处(44%)。84%病例的骨损伤累及胫骨。86%的病例合并多韧带损伤,最常累及内侧副韧带、前交叉韧带与后交又韧带,74%的损伤韧带非邻近骨损伤部位。结论:急性膝部骨损伤最常累及腔骨,常合并多韧带损伤,但韧带损伤多不靠近骨损伤部位。MRI脂肪抑制序列能直观地显示韧带的撕裂与完全断裂,且能发现相当多的隐性骨损伤病例。     

Transient lateral patellar dislocation: review of imaging findings, patellofemoral anatomy, and treatment options

Transient patellar dislocation is a common sports-related injury in young adults. Although patients often present to the emergency department with acute knee pain and hemarthrosis, spontaneous reduction frequently occurs, and half of cases are unsuspected clinically. Characteristic magnetic resonance imaging (MRI) findings often lead to the diagnosis. The purpose of this review is to illustrate the MRI findings of lateral patellar dislocation and concomitant injuries, such as kissing contusions of the medial patella and lateral femoral condyle; osteochondral and avulsion fractures; and injuries of the medial patellofemoral ligament/retinacular complex. This article will also briefly review patellofemoral anatomy and passive, active, and static stabilizers. Predisposing factors for patellar instability, including trochlear dysplasia, patella alta, and lateralization of the patella or tibial tuberosity and their relevant measurements will also be highlighted. Treatment options, including surgery, such as medial patellofemoral ligament reconstruction, tibial tuberosity transfer, and trochleoplasty, and their postoperative imaging appearances will also be discussed.     

Bone injury associated with anterior cruciate ligament and meniscal tears: assessment with bone single photon emission computed tomography

RATIONALE AND OBJECTIVES: Acute injury of the menisci and ligaments about the knee joint is often associated with accompanying bone injury. The role of bone single photon emission computed tomography (SPECT) was assessed in this clinical setting. MATERIALS AND METHODS: Knee SPECT was performed in 94 patients with suspected ACL, meniscal tear, or both and was correlated with arthroscopy (n = 74), magnetic resonance imaging (MRI) (n = 37), or both. Scintigraphic findings were categorized based on their anatomic location and on uptake intensity (0-3 grade scale). RESULTS: Correlation with arthroscopy: Eleven patients had a normal arthroscopy of which in 10, SPECT images detected no abnormality. Sixty-three patients had abnormal arthroscopic findings, whereas all had abnormal SPECT studies. Thirty-eight patients had an anterior cruciate ligament (ACL) tear on arthroscopy. In this type of injury SPECT images detected increased uptake in the posterior aspect of the lateral tibial plateau (LTPp) with a positive predictive value (PPV) of 93% and a negative predictive value (NPV) of 97%. In 55% of the patients, increased uptake was also detected in the region of the middle sulcus of the lateral femoral condyle (LFCm): a "kissing" pattern. Tear of the medial meniscus was diagnosed by arthroscopy in 43 patients. SPECT images detected increased uptake in the medial tibial plateau (MTP) with a PPV of 78% and a NPV of 83%. Correlation with MRI: all seven cortical fractures seen on MRI were detected on SPECT. Twenty-eight patients had MRI findings suggestive of an ACL injury. Accompanying bone bruises were seen in 18 of them (64%). On SPECT images, all 28 patients with an ACL tear had increased uptake in the LTPp. Intensity of uptake in patients with associated bone bruise, however, was significantly higher; mean intensity grade 2.4 +/- 0.7 in case of accompanying bone bruise compared with 1.4 +/- 0.8 in case of an ACL tear without associated bone injury, P< 0.01. CONCLUSION: Results of the study suggest that bone SPECT is valuable in acute knee trauma for assessment of ACL, meniscal tears, or both and for detection of associated bone injury.     

Magnetic resonance imaging of bone bruising in the acutely injured knee--short-term outcome

AIM: To investigate the short-term outcome and associated injuries of bone bruising in the acutely injured knee. METHOD AND MATERIALS: Thirty patients (age range 17-39 years, mean 28 years) with bone bruising identified on magnetic resonance imaging (MRI) after an acute knee injury were rescanned 12-14 weeks post-injury. The volume of bone bruising was measured on coronal STIR (short TI inversion recovery) images and correlation made with the presence and type of ligamentous and osteochondral injuries. RESULTS: All bone bruises were present on repeat MRI. Twenty of the 30 patients (67%) had associated anterior cruciate ligament (ACL) injuries, seven of the 30 (23%) had collateral ligament injuries and three of the 30 (10%) had no associated ligamentous injuries. Greater than 50% reduction in bone bruise volume was demonstrated at repeat scanning in 24 of the 30 patients (80%) and less than 50% in five of the 30 patients (17%). One patient showed an increase in volume of bone bruising at follow-up. There was no correlation between initial size or size reduction of bone bruising and the presence/absence or type of associated injuries. In 21 patients the bone bruises resolved from the periphery, whilst eight patients showed bone bruises that resolved towards the joint margin, all of whom had associated osteochondral injuries. Of the 30 patients, 17 showed bone bruising that extended to the joint margin, 10 of whom had associated osteochondral injuries on MRI. On clinical review some degree of knee pain was still present in all but one of the patients reviewed. The single patient who reported complete resolution of symptoms was one of the three patients with isolated bone bruising. CONCLUSION: Bone bruises persist for at least 12-14 weeks, which is longer than previously quoted. Two discrete patterns of bone bruise resolution have been demonstrated. The size and persistence of bone bruising is not related to the presence or absence or type of associated ligamentous injuries.     

The effect of a geographic lateral bone bruise on knee inflammation after acute anterior cruciate ligament rupture

We prospectively evaluated 40 patients who had knee inflammation after isolated anterior cruciate ligament rupture with or without an associated "geographic" bone bruise/subchondral fracture of the lateral femoral condyle. All patients with acute ruptures documented by magnetic resonance imaging within 1 week of injury were evaluated for a geographic bone bruise/subchondral fracture of the lateral femoral condyle. Two groups of 20 patients each (bone bruise versus no bone bruise) were then enrolled. Variables measured at 1, 2, 3, and 4 weeks after injury included pain, range of motion, effusion, and number of days with an antalgic gait. Patients with a bone bruise had increased size and duration of effusion, increased number of days required to nonantalgic gait without external aids, increased days to achieve normal range of motion, and increased pain scores at measured time intervals. This study confirms results of previous clinical and histologic studies showing an associated articular cartilage lesion, otherwise known as bone bruise/subchondral fracture, is clinically significant. There appears to be an association between a geographic bone bruise and increased disability in patients with acute anterior cruciate ligament ruptures. Patients with a geographic bone bruise may require longer to reach normal homeostasis (range of motion, pain, neuromuscular control) before undergoing anterior cruciate ligament reconstruction.     

膝关节类风湿关节炎MRI与X线平片对比

目的　评价MRI与X线平片在膝关节类风湿关节炎中的诊断价值。方法　 34个膝关节行MRI与X线检查 ,13例进行了MRI增强扫描。结果　MRI显示 34个膝均存在骨破坏 ,2 1个膝骨硬化 ,2 2个半月板有信号改变 ,15个膝关节软骨信号改变 ,10个膝胫骨移位 ,8个膝后交叉韧带拉直 ,13例MRI增强扫描显示血管翳附着、滑膜增殖和关节积液。X线显示 1个膝有骨破坏 ,11个膝伴骨硬化 ,16个膝关节间隙狭窄 ,8个膝胫骨移位。结论　MRI诊断膝关节类风湿关节炎优于X线平片     

Magnetic Resonance Imaging of Cruciate Ligament Injuries of the Knee

The anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) are important stabilizers of the knee. These ligaments are commonly injured in sports and motor vehicle accidents. An accurate diagnosis of cruciate ligament injuries is vital in patient care. Magnetic resonance imaging (MRI) can diagnose cruciate ligament injuries with high accuracy. The imaging diagnosis should be based on primary signs, although the secondary signs are sometimes useful, particularly in chronic cases. The detection of associated injuries of other structures of the knee, including menisci, collateral ligaments, cartilage, and bone, are also important. Accurate interpretation of the MRI examination requires a meticulous MRI technique, knowledge of the imaging anatomy, and understanding of the lesion appearance. This pictorial essay reviews the MRI appearance of normal and injured cruciate ligaments. Mechanisms of injury, primary and secondary MRI signs, and associated abnormalities are discussed.     

Subchondral insufficiency fractures of the femoral head

The aim of this study was to increase awareness of, and to show the variable clinical and radiological features of, subchondral insufficiency fractures of the femoral head. The clinical and radiological findings in 7 patients with subchondral insufficiency fractures of the femoral head were reviewed retrospectively. The diagnosis was confirmed histologically in 4 patients. Radiographs were performed in all patients, MRI in 5 and scintigraphy in 4 patients. Radiographs showed varying degrees of femoral head collapse in 4 patients. In the remaining 3 patients radiographs showed a normal femoral head, regional osteoporosis and focal sclerosis, respectively. Magnetic resonance imaging showed a low-signal band on T1- and T2-weighted images in the subchondral bone adjacent or parallel to the articular surface associated with bone marrow oedema. Scintigraphy showed increased uptake in the femoral head. Insufficiency fractures of the femoral head are easily overlooked or confused with avascular necrosis and, when there is significant joint destruction, osteoarthritis. Unsuspected insufficiency fracture of the femoral head can lead to significant and rapid loss of bone stock in osteoporotic patients waiting for arthroplasty for osteoarthritis. Increased awareness of this condition will hopefully lead to earlier diagnosis and a successful outcome of conservative treatment.     

MRI demonstration of hypertrophic articular cartilage repair in osteoarthritis

Transection of the anterior cruciate ligament in the dog produces changes in the unstable joint typical of osteoarthritis, although full-thickness cartilage ulceration is rare. Information concerning the late fate of the cartilage after transection is meager. In the present study magnetic resonance imaging (MRI) was used to evaluate cartilage abnormalities 3 years after transection. Plain radiographs of the osteoarthritic and contralateral knees were obtained serially. MRI was performed 3 years after anterior cruciate ligament transection, at which time all three animals exhibited knee instability. Radiographs of the osteoarthritic knees showed osteophytes and subchondral sclerosis with progression between 2 and 3 years. On MRI, articular cartilage margins in the knee were indistinct, and the cartilage was thicker than that in the contralateral knee (maximum difference= 2.7 mm). This increase in thickness is consistent with biochemical data from dogs killed up to 64 weeks after creation of knee instability, which showed marked increases in cartilage bulk and in proteoglycan synthesis and concentration. The findings emphasize that increased matrix synthesis after anterior cruciate ligament transection leads to functional cartilage repair sustained even in the presence of persistent alteration of joint mechanics.