Leon D. Rybak, M.D.

Quantitative magnetic resonance imaging evidence of synovial proliferation is associated with radiographic severity of knee osteoarthritis
Krasnokutsky, Svetlana; Belitskaya-Levy, Ilana; Bencardino, Jenny; Samuels, Jonathan; Attur, Mukundan; Regatte, Ravinder; Rosenthal, Pamela; Greenberg, Jeffrey; Schweitzer, Mark; Abramson, Steven B; Rybak, Leon
2011 Oct;63(10):2983-2991, Arthritis & rheumatism
OBJECTIVE: To evaluate the relationships between both quantitative and semiquantitative assessments of the degree of knee synovitis on 3T magnetic resonance imaging (MRI) and the severity of knee osteoarthritis (OA) on radiography. METHODS: Fifty-eight patients with knee OA underwent nonfluoroscopic fixed-flexion knee radiography. In addition, dynamic contrast-enhanced 3T MRI of the knees was performed, before and after gadolinium administration, to quantify synovial membrane volume (SV) as a measure of synovial proliferation (expressed as the quantitative SV), and semiquantitative measures of synovitis were also applied using both contrast-enhanced and unenhanced images. Two radiologists scored the knee radiographs using the Osteoarthritis Research Society International atlas; interreader agreement was assessed using kappa statistics and concordance correlation coefficients. Multiple linear and logistic regression analyses were used to assess associations among variables, while controlling for the effects of age, body mass index, sex, and meniscal extrusion. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated for measures of disease activity. RESULTS: The Kellgren/Lawrence (K/L) grade of radiographic knee OA severity (beta = 0.78), the diseased compartment joint space width (dcJSW) (beta = -0.22), and the diseased compartment joint space narrowing (dcJSN) score (beta = 0.53) were each significantly associated with the quantitative SV (P = 0.0001, P = 0.0003, and P = 0.0001, respectively). Furthermore, the quantitative SV strongly correlated with the total volume of subchondral bone marrow lesions (BMLs) (beta = 0.22, P = 0.0003). The K/L grade, dcJSW, and dcJSN score were each significantly associated with the semiquantitative Boston Leeds Osteoarthritis Knee Score (BLOKS) for the extent of infrapatellar synovitis (OR 9.05 [95% CI 1.94, 42.3] for K/L grade; OR 0.75 [95% CI 0.54, 1.03] for dcJSW; and OR 2.22 [95% CI 1.15, 4.31] for dcJSN score) and extent of joint effusion (OR 5.75 [95% CI 1.23, 26.8] for K/L grade; OR 0.70 [95% CI 0.50, 0.98] for dcJSW; and OR 1.96 [95% CI 1.02, 3.74] for dcJSN score). In addition, the semiquantitative synovitis grade on contrast-enhanced MRI was significantly associated with the K/L grade (beta = 0.036, P = 0.0040) and dcJSN score (beta = 0.015, P = 0.0266), and also significantly associated with the BLOKS synovitis score. CONCLUSION: Synovitis is a characteristic feature of advancing knee OA and is significantly associated with the K/L grade, JSW, JSN score, and total volume of BMLs on radiographs. Furthermore, BLOKS scoring of synovitis on unenhanced MRI is associated with measurements of synovitis on contrast-enhanced MRI
— id: 137878, year: 2011, vol: 63, page: 2983, stat: Journal Article,

Bisphosphonate-related complete atypical subtrochanteric femoral fractures: diagnostic utility of radiography
Rosenberg, Zehava Sadka; La Rocca Vieira, Renata; Chan, Sarah S; Babb, James; Akyol, Yakup; Rybak, Leon D; Moore, Sandra; Bencardino, Jenny T; Peck, Valerie; Tejwani, Nirmal C; Egol, Kenneth A
2011 Oct;197(4):954-960, American journal of roentgenology
OBJECTIVE: The objective of our study was to evaluate the diagnostic utility of conventional radiography for diagnosing bisphosphonate-related atypical subtrochanteric femoral fractures. MATERIALS AND METHODS: Retrospective interpretation of 38 radiographs of complete subtrochanteric and diaphyseal femoral fractures in two patient groups-one group being treated with bisphosphonates (19 fractures in 17 patients) and a second group not being treated with bisphosphonates (19 fractures in 19 patients)-was performed by three radiologists. The readers assessed four imaging criteria: focal lateral cortical thickening, transverse fracture, medial femoral spike, and fracture comminution. The odds ratios and the sensitivity, specificity, and accuracy of each imaging criterion as a predictor of bisphosphonate-related fractures were calculated. Similarly, the interobserver agreement and the sensitivity, specificity, and accuracy of diagnosing bisphosphonate-related fractures (i.e., atypical femoral fractures) were determined for the three readers. RESULTS: Among the candidate predictors of bisphosphonate-related fractures, focal lateral cortical thickening and transverse fracture had the highest odds ratios (76.4 and 10.1, respectively). Medial spike and comminution had odd ratios of 3.8 and 0.63, respectively. Focal lateral cortical thickening and transverse fracture were also the most accurate factors for detecting bisphosphonate-related fractures for all readers. The sensitivity, specificity, and overall accuracy for diagnosing bisphosphonate-related fractures were 94.7%, 100%, and 97.4% for reader 1; 94.7%, 68.4%, and 81.6% for reader 2; and 89.5%, 89.5%, and 89.5% for reader 3, respectively. The interobserver agreement was substantial (kappa > 0.61). CONCLUSION: Radiographs are reliable for distinguishing between complete femoral fractures related to bisphosphonate use and those not related to bisphosphonate use. Focal lateral cortical thickening and transverse fracture are the most dependable signs, showing high odds ratios and the highest accuracy for diagnosing these fractures
— id: 137889, year: 2011, vol: 197, page: 954, stat: Journal Article,

Primary synovial chondrosarcoma of the hip joint in a 45-year-old male: case report and literature review
Rybak, Leon David; Khaldi, Lubna; Wittig, James; Steiner, German C
2011 Oct;40(10):1375-1381, Skeletal radiology
Synovial chondrosarcoma is a rare tumor, seen most commonly arising from antecedent synovial chondromatosis, the more common benign entity. The distinction between the two can be difficult on the basis of clinical, imaging, and histologic criteria. The authors report a case of pathologically proven synovial chondrosarcoma of the hip in a 45-year-old male initially treated for presumed synovial chondromatosis. The case is made more unusual by the fact that no evidence of co-existent synovial chondromatosis was noted at histology. The literature as regards synovial chondrosarcoma, both de novo and secondary cases, is reviewed
— id: 136993, year: 2011, vol: 40, page: 1375, stat: Journal Article,

Clear cell sarcoma of soft tissue involving the elbow joint
Smilowitz N.R.; Villalobos C.E.; Rybak L.D.; Wittig J.C.
2011 ;22(1):104-108, Current Orthopaedic Practice
— id: 133419, year: 2011, vol: 22, page: 104, stat: Journal Article,

Articular cartilage skiving: the concept defined
Takemoto, R C; Gage, M J; Rybak, L; Walsh, M; Egol, K A
2011 Jun;36(5):364-369, Journal of hand surgery (British volume)
'Skiving' is commonly used to refer to the condition when the subchondral plate is disrupted and the overlying cartilage physically displaced without the screw tip entering the joint. In this study we sought to define radiographic parameters of skiving and compare radiographs with computed tomography (CT) for accuracy in determining joint skiving. Cadaveric specimens of the distal radius were implanted with a volar plate and screws. Arthrotomies were performed to definitively assess the positions of the screws. Standard and anatomic tilt radiographs as well as CT were performed. Orthopaedic surgeons and radiologists evaluated the images and reported whether screw penetration or skiving had occurred. For screws which penetrated or skived, measurements were made to record the distances from the screw tips to the subchondral plate. Sensitivity, specificity and percent correct interpretations were 53%, 83%, 60% respectively for radiographs; and 100%, 72%, 69% for CT. Screws penetrating the articular surface protruded an average 2.3 mm (range 2-2.6 mm) from the subchondral plate and those skiving protruded 1.4 mm (range 1-1.8 mm). This study shows that articular skiving can occur with penetration of the subchondral plate of up to 1.8 mm. CT has a greater sensitivity and lower specificity in determining skiving compared to radiographs
— id: 134436, year: 2011, vol: 36, page: 364, stat: Journal Article,

The lumbar facet joint: a review of current knowledge: part 1: anatomy, biomechanics, and grading
Varlotta, Gerard P; Lefkowitz, Todd R; Schweitzer, Mark; Errico, Thomas J; Spivak, Jeffrey; Bendo, John A; Rybak, Leon
2011 Jan;40(1):13-23, Skeletal radiology
We present a two-part review article on the current state of knowledge of lumbar facet joint pathology. This first article discusses the functional anatomy, biomechanics, and radiological grading systems currently in use in clinical practice and academic medicine. Facet joint degeneration is presented within the larger context of degenerative disc disease to enable the reader to better understand the anatomical changes underlying facet-mediated lower back pain. Other less-common, but equally important etiologies of lumbar facet joint degeneration are reviewed. The existing grading systems are discussed with specific reference to the reliability of CT and MR imaging in the diagnosis of lumbar facet osteoarthritis. It is hoped that this discussion will stimulate debate on how best to improve the diagnostic reliability of these tests so as to improve both operative and non-operative treatment outcomes
— id: 114816, year: 2011, vol: 40, page: 13, stat: Journal Article,

The lumbar facet joint: a review of current knowledge: Part II: diagnosis and management
Varlotta, Gerard P; Lefkowitz, Todd R; Schweitzer, Mark; Errico, Thomas J; Spivak, Jeffrey; Bendo, John A; Rybak, Leon
2011 Feb;40(2):149-157, Skeletal radiology
This article is the second article in a two-part review on lumbar facet joint pathology. In this review, we discuss the current concepts and controversies regarding the proper diagnosis and management of patients presenting with presumed facet-mediated lower back pain. All efforts were made to include the most relevant literature from the fields of radiology, orthopaedics, physiatry, and pain management. Our focus in this article is on presenting the evidence supporting or refuting the most commonly employed injection-based therapies for facet-mediated lower back pain
— id: 116219, year: 2011, vol: 40, page: 149, stat: Journal Article,

Interleukin-1 receptor antagonist (IL-1RN) gene variations predict the severity and progression of knee osteoarthritis
Attur M.; Oh C.; Krasnokutsky S.; Samuels J.; Rybak L.; Bencardino J.; Greenberg J.D.
2010 ;62:707-707, Arthritis & rheumatism
Purpose: We have previously shown that carriage of an IL1RN haplotype (CTA) was associated with substantially lower odds of radiographic severity (KL score, joint space width [JSW]) (Ann Rheum Dis. 2010). In this 24 month prospective study we assessed whether IL1-RN haplotypes predicted disease progression in patients with symptomatic knee OA. Methods: Ninety-seven (N=97) patients from NYUHJD who met ACR criteria for symptomatic knee OA were genotyped for single nucleotide polymorphisms (SNPs) in the IL-1b and IL-1RN genes. Standardized fixed-flexion radiographs were taken on all patients at baseline and 24 months. Radiographic progression of signal (more painful) knee OA was determined by change in JSW over 24 months. To account for variations in baseline JSW, we defined progression as greater than 30% joint space narrowing (JSN) of the diseased compartment over 24 months, rather than in change in absolute JSW in millimeters. Results: Decreases in JSW ranged from zero to 3.7 mm over the 24 months; 19 of 97 patients exhibited < 30% JSN. (Figure presented) Patients with the IL-1RN (rs419598/rs315952/9005) TTG haplotype exhibited increased radiographic knee OA severity at baseline compared to those without TTG (p>0.08). These TTG patients exhibited increased risk for radiographic progression at 24 months that approached significance based on <=30% JSN [OR = 2.85; 95%CI=0.68-11.67; p>0.15]. In contrast, OA patients with IL-1RN CTA haplotype showed decreased risk for JSN over 24 months in the signal knee [OR= 0.33; 95%CI=0.170-1.014; p>0.05]. Differences in reported VAS pain between the CTA and TTG group were significant at 24 months (p> 0.01), indicating that while these patients were not distinguishable by radiograph or symptoms at onset, IL1RN haplotype predicted symptomatic differences at two years. Finally, the TTG haplotype group of patients expressed relatively increased IL-1b gene expression [15.683 +/- 9.407 (p>0.0001)] as assessed by TaqMan QPCR in peripheral blood leukocytes. The TTG patients also exhibited decreased sIL-1Ra [283.64 +/- 36.4 pg/ml (p>0.001) in plasma samples compared to IL-1RN CTA haplotype protective groups [IL-1b (fold change), 5.444 +/- 10.083; sIL-1Ra, 370.35 +/- 43.3pg/ml] of patients respectively. Conclusion: IL-1RN gene family polymorphisms, which appear to affect host production of IL-1Ra, merit evaluation as biomarkers that predict the risk of progression in patients with symptomatic knee OA
— id: 130940, year: 2010, vol: 62, page: 707, stat: Journal Article,

INTERLEUKIN-1 RECEPTOR ANTAGONIST GENE VARIATIONS PREDICT THE SEVERITY AND PROGRESSION OF KNEE OSTEOARTHRITIS
Attur, M.; Oh, C.; Krasnokutsky, S.; Samuels, J.; Rybak, L.; Bencardino, J.; Kraus, V.; Kornman, K.; Abramson, S. B.
2010 OCT ;18(12):S172-S172, Osteoarthritis & cartilage
— id: 120557, year: 2010, vol: 18, page: S172, stat: Journal Article,

Chest wall mass in a 50-year-old woman
Chatha, Deep S; Rybak, Leon D; Wittig, James C; Desai, Panna
2010 May;468(5):1462-1466, Clinical orthopaedics & related research
— id: 109035, year: 2010, vol: 468, page: 1462, stat: Journal Article,

Primary Rosai-Dorfman disease of bone: a clinicopathologic study of 15 cases
Demicco, Elizabeth G; Rosenberg, Andrew E; Bjornsson, Johannes; Rybak, Leon D; Unni, K Krishnan; Nielsen, G Petur
2010 Sep;34(9):1324-1333, American journal of surgical pathology
Sinus histiocytosis with massive lymphadenopathy or Rosai-Dorfman disease (RDD) is a rare histiocytic proliferative disorder of unknown etiology. Most patients present with lymph node involvement manifesting as adenopathy; however, RDD may arise primarily in a variety of extranodal sites, including bone. We report herein our experience with 15 cases of primary intraosseous RDD. The patients include 8 females and 7 males, who ranged in age from 3 to 56 (mean 27) years. The lesions arose in a variety of anatomical locations, including the tibia, femur, clavicle, skull, maxilla, calcaneus, phalanx, metacarpal, and sacrum. Radiographically, the lesions were lytic with well defined and usually sclerotic margins. Histologically, the lesions demonstrated the classic features of RDD and consisted of a mixed inflammatory infiltrate with numerous large histiocytes with abundant eosinophilic cytoplasm which exhibited emperipolesis. Some cases also contained numerous neutrophils. Immunohistochemical stains showed that the large histiocytes were S-100 positive. Follow-up information was available for 12 patients. Five patients eventually developed additional extraosseous manifestations, including testicular, lymph node, and subcutaneous lesions. One of these 5 also developed a new bony lesion within the sternum. One patient developed additional lesions within multiple bones of the hand and wrist, without extraosseous disease. One patient had stable bony lesions, whereas 5 remained disease free after treatment
— id: 134369, year: 2010, vol: 34, page: 1324, stat: Journal Article,

Orthopaedic Case of the Month: A 30-year-old Woman with a Painful Forearm Mass
Hochfelder, J; Rybak, L D; Garcia, R; Wittig, J C
2010 Nov;468(11):3139-3144, Clinical orthopaedics & related research
— id: 113657, year: 2010, vol: 468, page: 3139, stat: Journal Article,

Radiographic severity of knee osteoarthritis predicts quantitative Bone Marrow Lesions on MRI
Krasnokutsky S.; Regatte R.; Bencardino J.; Rybak L.; Belitskaya-Levy I.; Samuels J.; Attur M.
2010 ;62:137-137, Arthritis & rheumatism
Objective: To evaluate the relationship of quantitative assessment of Bone Marrow Lesions (BML) with knee OA severity by radiographic findings. Methods: 58 OA patients (mean age 62+/-10, mean BMI 27+/-3, 59% female) underwent standardized nonfluoroscopic fixed-flexion knee radiographs. Two radiologists read the X-rays for KL grade, joint space width (JSW), and, using the OARSI atlas, joint space narrowing (JSN) and osteophytes; interreader agreement was assessed using Kappas and concordance correlation coefficients. Linear and logistic regression analysis was performed to assess associations while controlling the effects of age, sex and BMI. 3T-MRI included sagittal T2-weighted fat saturated spin-echo images (TR/TE=4000ms/75ms, FOV=15cm, matrix=256x128, slice thickness=3.0mm, receiver bandwidth 130Hz/pixel) and in/out of phase of FLASH images. Compartment-wise (medial tibial, lateral tibial, medial femur, lateral femur) BML volumes were quantified with T2-weighted fat saturated images and in/out of phase images respectively. BML volumes were dichotomized for statistical analysis. Results: KL score was a significant predictor of total BML volume (OR = 8.41, p = 0.0235). Medial tibial JSW, OARSI medial JSN, and medial tibial plateau osteophytes approached significance as predictors of BML volume at the medial tibia (OR = 0.71, p = 0.0551; OR = 2.16, p = 0.0597; and OR = 2.68, p = 0.0875, respectively). OARSI lateral JSN was a significant predictor of BML volume at the lateral tibia (OR = 3.62, p = 0.0169). Lateral tibial plateau osteophytes were predictors of total BML volume (OR = 4.58, p = 0.0299) and of BML volume at the lateral tibia (OR = 2.31, p = 0.0685). Lateral femoral condyle osteophytes approached significance as a predictor for BML at the lateral femur (OR = 2.25, p = 0.0651). Furthermore, quantitative BML volume strongly correlated with total quantitative synovial volume measured on MRI (beta= 0.22, p = 0.0003). Conclusions: Our data indicate that BML volume on MRI is a characteristic feature of progressive stages of OA, which not only correlates with JSN and osteophytes, but does so in a compartment-specific way. The data suggest that the altered mechanical forces that promote compartmental disease in OA lead to BML, JSN and osteophyte formation. Whether BML further contribute to cartilage loss, and are therefore targets of therapeutic intervention, remains to be determined
— id: 130946, year: 2010, vol: 62, page: 137, stat: Journal Article,

Myositis ossificans within the intercondylar notch treated arthroscopically
Leung, Allen H; Rybak, Leon D; Rose, Donald J; Desai, Panna
2010 Sep;39(9):927-930, Skeletal radiology
We present a case of intraarticular myositis ossificans in the right knee of a child. Myositis ossificans (MO), though relatively rare in childhood and even more uncommon within a joint, should be included in the differential diagnosis of an intra-articular mass when indicated by the typical clinical, radiographic, and histologic findings. An 11-year-old male presented with a history of trauma to his right knee. Four weeks after the initial injury, an MRI demonstrated evidence of an ACL rupture with a 'cystic mass' within the intercondylar notch along the anterior surface of the torn ligament. At subsequent arthroscopy, the mass noted on MRI was removed. The histology was consistent with MO. The authors believe this to be the first case of MO in the intercondylar notch detected by MRI, treated by arthroscopy, and confirmed by histology
— id: 111372, year: 2010, vol: 39, page: 927, stat: Journal Article,

Thermal ablation of spinal osteoid osteomas close to neural elements: technical considerations
Rybak, Leon D; Gangi, Afshin; Buy, Xavier; La Rocca Vieira, Renata; Wittig, James
2010 Oct;195(4):W293-W298, American journal of roentgenology
OBJECTIVE: The purpose of this study was to evaluate experience with and determine the efficacy and safety of thermal ablation in the management of spinal osteoid osteomas close to neural elements. MATERIALS AND METHODS: The records of all patients with osteoid osteomas of the spine managed with thermal ablation at two academic centers from 1993 to 2008 were reviewed. RESULTS: Seventeen patients (13 male patients, four female patients; mean age, 25.9 years) had lesions in the lumbar (seven patients), thoracic (six patients), cervical (three patients), and sacral (one patient) regions of the spine. Two lesions were in the vertebral body, one was within the dens, and the others were in the posterior elements. The mean lesion diameter was 8.8 mm, and the mean distance between the lesion and the closest neural element was 4.3 mm. The lesions were managed with laser (13 lesions) or radiofrequency (four lesions) ablation. Special thermal protection techniques involving the epidural injection of gas or cooled fluid were used. Pain levels were assessed immediately before the procedure and on the day after the procedure. Long-term follow-up findings were available for 11 patients. No complications were encountered, and all patients reported relief of pain. The 11 patients who participated in long-term follow-up reported continued relief of pain. CONCLUSION: Percutaneous thermal ablation can be used to manage spinal osteoid osteomas close to the neural elements. Special thermal protection techniques may add a margin of safety
— id: 112562, year: 2010, vol: 195, page: W293, stat: Journal Article,

Hand osteoarthritis (OA) a predictor of accelerated progression in knee OA?
Samuels J.; Petchprapa C.; Carpenter E.L.; Krasnokutsky S.; Attur M.; Rybak L.; Bencardino J.
2010 ;62:708-708, Arthritis & rheumatism
Purpose: There is insufficient understanding regarding how generalized OA involving the hand and knee differs from isolated knee OA, which may result from other factors such as obesity or trauma. The purpose of these studies is to determine whether the presence of hand OA involving interphalangeal (IP) and first carpometacarpal (CMC) joints, alone or in combination, predicts progression of patients with symptomatic knee OA. Methods: Hand radiographs were obtained on 94 patients at NYUHJD who met ACR criteria for symptomatic knee OA, and who were enrolled in a two-year NIH-sponsored prospective study. The patients completed standardized fixed-flexion knee radiographs at baseline and 24 months, with progression the signal (more painful) knee OA determined by change in joint space width (JSW) and KL score. For these analyses, the patients were separated into two groups by results on their signal knee: 17 progressors, defined by at least 30% decreased JSW over 24 months, and 77 non-progressors. For each set of hand x-rays, 2 radiologists evaluated 18 IP joints and 2 CMC joints for joint space narrowing and/or osteophytes, and whether or not there was erosive change at the IP joints; we averaged the scores from the two readers. Results: Kappa scores between the two scoring radiologists for the IP and CMC joints, and for the presence of erosive IP disease, were 0.79, 0.87 and 0.96, respectively. The overall mean IP score was 5.6 and 1st CMC score was 0.9, while medians were 5 and 1.0, respectively. The 17 progressors had a higher average IP (but not CMC) score than the non-progressors, 7.2+/- 5.4 vs. 5.0+/-4.6, p=0.13. Since the IP scores were not normally distributed, we further analyzed data by dichotomizing the study populations into two groups using the median IP total (5) as the cutoff point. When so analyzed, the presence of hand OA increased the odds ratio of knee OA progression to 2.8 (p=0.096). Of interest, the severity of knee OA correlated with hand OA scores: the average total hand OA scores (out of 20 joints) increased with baseline KL score, with mean scores of 3.8+/-5.5, 6.1+/-6.1 and 7.2+/-5.6 for KL 1 to 3 (p=0.06). There is also an increasing trend of total hand OA joint scores by KL score (p=0.042) when dichotomized around the median (5 joints), and with IP scores alone (p=0.026). The 8 patients with radiographic evidence of erosive IP disease, as compared with the 31 non-erosive IP OA patients (>5 IP joints) and the 54 without IP OA, demonstrated faster knee OA progression over 2 years by average KL increases (1.00, 0.35, 0.30) and decreases in joint space width (0.65, 0.56, 0.36), although perhaps given small numbers, this was not statistically significant (p=0.839). Conclusions: In cross-sectional analysis, the quantitative burden of hand OA correlates with the radiographic severity of knee OA (KL). Moreover, radiographic hand OA at the IP joints, but not at the 1st CMC joint, predicts more rapid progression of knee OA. Erosive IP disease may be an even stronger predictor than non-erosive IP disease of accelerated progression of knee OA
— id: 130937, year: 2010, vol: 62, page: 708, stat: Journal Article,

Osteoblastoma of the sternum--case report and review of the literature
Villalobos, Camilo E; Rybak, Leon D; Steiner, German C; Wittig, James C
2010 ;68(1):55-59, Bulletin of the NYU Hospital for Joint Diseases
Osteoblastoma is an extremely rare entity that represents less than 1% of all bone tumors, and affects twice as many males as females with peak incidence between 15 and 20 years. Osteoblastomas commonly affect axial bones, long bones, bones of the foot and hand, and less commonly the pelvis, scapula, ribs, and clavicle. Osteoblastoma does not have a classic presentation, but can vary with the location and size of the tumor. The main complaint is often progressive pain localized at the tumor site. Osteoblastoma is a benign tumor with an aggressive behavior. The treatment is wide surgical resection, otherwise it continues to enlarge and destroy the bone and surrounding structures. We report a 32-year-old male with an osteoblastoma of this sternum who was treated with an en-bloc resection and reconstruction with Marlex((R)) and a methylmethacrylate plate
— id: 133491, year: 2010, vol: 68, page: 55, stat: Journal Article,

Orthopaedic . Radiology . Pathology Conference: Painful Distal Femur Lesion in a 13-year-old Girl
Harsha, Asheesh; Villalobos, Camilo E; Rybak, Leon D; Borys, Dariusz; Wittig, James C
2009 Aug;467(8):2200-2205, Clinical orthopaedics & related research
— id: 94599, year: 2009, vol: 467, page: 2200, stat: Journal Article,

Fire and ice: thermal ablation of musculoskeletal tumors
Rybak, Leon D
2009 May;47(3):455-469, Radiologic clinics of North America
Thermal ablation of tumors is a rapidly growing field that has found various applications in the musculoskeletal system. Radiofrequency ablation (RFA) has become the reference standard for treatment of most osteoid osteomas. More recently, RFA has been applied to several other forms of primary tumors and in the treatment and palliation of osseous metastases. Cryoablation using new closed systems has also become available for the percutaneous treatment of both primary and metastatic lesions, and the initial results have been promising
— id: 99232, year: 2009, vol: 47, page: 455, stat: Journal Article,

Chondroblastoma: radiofrequency ablation--alternative to surgical resection in selected cases
Rybak, Leon D; Rosenthal, Daniel I; Wittig, James C
2009 May;251(2):599-604, Radiology
PURPOSE: To demonstrate that radiofrequency (RF) ablation can be used safely and effectively to treat selected cases of chondroblastoma. MATERIALS AND METHODS: Approval was obtained from institutional review boards, research was in compliance with HIPAA protocol. The need to obtain informed consent was waived for retrospective review of patient records. The records of patients with biopsy-proved chondroblastoma who were treated with RF ablation at two academic centers from July 1995 to July 2007 were reviewed. RF ablation was performed with a single-tip electrode by using computed tomography for guidance. Lesion characteristics were determined from imaging studies obtained at the time of the procedure. Symptoms were assessed before and 1 day after the procedure. Longer-term follow-up was obtained from medical records. RESULTS: Thirteen male and four female patients were treated (mean age, 17.3 years). The lesions were located in the proximal humerus (n = 7), proximal tibia (n = 4), proximal femur (n = 3), and distal femur (n = 3). The mean volume of the lesions was 2.46 mL. All patients reported relief of symptoms on postprocedure day 1. Three patients were lost to follow-up. Of the 14 patients for whom longer-term (mean, 41.3 months; range, 4-134 months) follow-up was available, 12 had complete relief of symptoms with no need for medications and full return to all activities. The patient who had the largest lesion of the study required surgical intervention because of collapse of the articular surface in the treatment area. Residual viable tumor was found at surgery. Another patient experienced mechanical problems that were thought to be unrelated to the RF ablation and was rendered pain-free after subsequent surgical treatment. CONCLUSION: Percutaneous RF ablation is an alternative to surgery for treatment of selected chondroblastomas. Larger lesions beneath weight-bearing surfaces should be approached with caution due to an increased risk of articular collapse and recurrence
— id: 99225, year: 2009, vol: 251, page: 599, stat: Journal Article,

Primary leiomyosarcoma of the proximal tibia: case report and review of the literature
Kitay, Alison; Rybak, Leon; Desai, Panna; Villalobos, Camilo E; Wittig, James C
2008 ;66(1):49-53, Bulletin of the NYU Hospital for Joint Diseases
— id: 81348, year: 2008, vol: 66, page: 49, stat: Journal Article,

Femoroacetabular impingement: can the alpha angle be estimated?
Nouh, Mohamed R; Schweitzer, Mark E; Rybak, Leon; Cohen, Jodi
2008 May;190(5):1260-1262, American journal of roentgenology
OBJECTIVE: Femoroacetabular impingement is an important entity with well-described radiographic findings. One of the criteria of the cam type of femoroacetabular impingement is femoral head-neck dysplasia, denoted mathematically as the 'alpha angle.' Several observers have reported that direct measurement of the angle may not be necessary because subjective appraisal may yield similar results. We sought to scientifically determine the accuracy of a subjective assessment, using the calculated angle as the gold standard. MATERIALS AND METHODS: At 1.5 T, 50 consecutive patients' hips were evaluated on sets of oblique axial images. Two musculoskeletal radiologists recorded their subjective opinion as to the alpha angle using a confidence scale of 1-5. Direct mathematic measurement of the alpha angle was done by a third independent observer and correlated with the subjective results. Correlations between the subjective and measured angles and interobserver variation were calculated. RESULTS: Statistically, significant variability was seen in the subjective assessment of the alpha angle. When the alpha angle was > 55 degrees, the area under the receiver operating characteristic curve (AUC) was 0.606, indicating that visual assessment is a poor predictor of a wide alpha angle. Even in patients with a measured normal alpha angle (< 55 degrees), slightly fewer than half were subjectively thought to possibly, likely, or definitely have abnormal angles. Similarly, more than half of the abnormal cases (alpha angles > 55 degrees) were subjectively thought to possibly or probably be normal. CONCLUSION: Subjective assessment of alpha angles is suboptimal unless one is quite confident of a bone abnormality
— id: 79145, year: 2008, vol: 190, page: 1260, stat: Journal Article,

Treatment of acute salmonella epiphyseal osteomyelitis using computed tomography-guided drainage in a child without sickle cell disease
Abdelgawad, Amr Atef; Rybak, Leon D; Sheth, Manoj; Rabinowitz, Simon S; Jayaram, Nadubeethi; Sala, Debra A; van Bosse, Harold J P
2007 Nov;16(6):415-418, Journal of pediatric orthopaedics. Pt. B
Salmonella osteomyelitis occurs infrequently in children without sickle cell disease. Similarly, acute osteomyelitis of the epiphysis has been rarely reported. We present a case of primary epiphyseal osteomyelitis caused by Salmonella in the distal femur of an otherwise healthy 17-month-old child. Before isolating an organism, parenteral nafcillin provided ineffective clinical, radiographic, and laboratory responses. Repeated fluoroscopic-guided percutaneous surgical drainages allowed for identification of the Salmonella, but did not resolve the epiphyseal infection, as the infection focus was missed. In the effort to eradicate the infection yet minimize further trauma to the epiphysis, computed tomography-guided drainage was performed and the infection subsequently resolved. Owing to its greater localization accuracy and minimal invasiveness, the computed tomography-guided intervention allowed for precise drainage without compromising the contiguous growth plate. At latest follow-up, the patient was ambulating well, had a normal knee examination, and had no evidence of leg length discrepancy or growth disturbance
— id: 86539, year: 2007, vol: 16, page: 415, stat: Journal Article,

Elbow Mass in a 9-year-old Girl
Chatha, Deep S; Rybak, Leon D; Wittig, James C; Desai, Panna
2007 Oct;463:237-243, Clinical orthopaedics & related research
— id: 73168, year: 2007, vol: 463, page: 237, stat: Journal Article,

Painful Tibial Lesion in a 16-year-old Girl
Chatha, Deep S; Rybak, Leon D; Wittig, James C; Desai, Panna
2007 Nov;464:247-252, Clinical orthopaedics & related research
— id: 73167, year: 2007, vol: 464, page: 247, stat: Journal Article,

Ankle Pain in a 31-year-old Man
Chatha, Deep S; Rybak, Leon; Wittig, James; Desai, Panna
2007 Dec;465:271-276, Clinical orthopaedics & related research
— id: 73401, year: 2007, vol: 465, page: 271, stat: Journal Article,

Cortico-medullary continuity in bizarre parosteal osteochondromatous proliferation mimicking osteochondroma on imaging
Rybak, Leon D; Abramovici, Luigia; Kenan, Samuel; Posner, Martin A; Bonar, Fiona; Steiner, German C
2007 Sep;36(9):829-834, Skeletal radiology
Bizarre parosteal osteochondromatous proliferation (BPOP), or Nora's lesion, is an unusual surface-based lesion of bone found most commonly in the hands and feet. In the original description of the lesion and in all publications that followed, one of the key imaging characteristics used to define this entity was the lack of cortico-medullary continuity with the underlying bone. The authors present 4 unique cases of pathologically proven BPOP in which cortico-medullary continuity with the underlying bone was demonstrated on imaging. It is believed that florid reactive periostitis, BPOP and turret osteochondroma may reflect points along the same continuum with trauma the likely inciting event. The authors suggest that, given this continuum, it may be possible to have BPOP lesions demonstrating overlapping imaging features with osteochondroma. If this is the case, strict adherence to the standard imaging criterion of lack of continuity between the lesion and the underlying bone may lead to misdiagnosis of these unusual cases of BPOP as osteochondromas
— id: 78630, year: 2007, vol: 36, page: 829, stat: Journal Article,

Age-related degenerative changes of the posterior cruciate ligament or PCL "ligamentopathy"
Rybak, LD; Schweitzer, M; Kim, D
2005 JUN 21 ;184(4):69-69, American journal of roentgenology
— id: 56259, year: 2005, vol: 184, page: 69, stat: Journal Article,

Magnetic resonance imaging of sports-related muscle injuries
Rybak, Leon D; Torriani, Martin
2003 Apr;14(2):209-219, Topics in magnetic resonance imaging
Magnetic resonance imaging (MRI) is increasingly being used to evaluate muscle injuries because of its unparalleled anatomic resolution and high sensitivity in detecting acute and chronic soft-tissue abnormalities. These features allow detection of characteristic injury patterns that lead to accurate diagnoses and grading of severity. The precise assessment of muscle injuries with MRI plays an important role in determining the treatment plan and prognosis of injured athletes. The article begins with a review of the anatomy and MRI characteristics of normal muscle. The general mechanisms of muscle injury and associated MRI findings are discussed, with emphasis on the most common injuries in both the upper and lower extremities. Several mimics of muscle injury are briefly outlined
— id: 56307, year: 2003, vol: 14, page: 209, stat: Journal Article,

Teres minor atrophy: A sign of axillary denervation injury following shoulder trauma
Bencardino, JT; Petchprapa, CN; Rybak, LD; Hassankhani, A; Palmer, WE
2002 ;225:371-371, Radiology
— id: 114525, year: 2002, vol: 225, page: 371, stat: Journal Article,

Soft tissue aneurysmal bone cyst: a clinicopathologic study of five cases
Nielsen, G Petur; Fletcher, Christopher D M; Smith, Michael A; Rybak, Leon; Rosenberg, Andrew E
2002 Jan;26(1):64-69, American journal of surgical pathology
We describe five primary soft tissue tumors that had histologic features identical to intraosseous aneurysmal bone cyst. The tumors occurred in three females and two males, who ranged in age from 8 to 37 years (median 28 years). They arose in the deep soft tissue of the upper extremities, thigh, and groin region and typically presented as a rapidly growing mass; no involvement of the adjacent bones was identified. The tumors ranged in size from 2.5 to 9 cm (median 4 cm). Grossly, they were surrounded by a thin rim of bone and on sectioning had hemorrhagic cystic spaces delineated by fibrous septa. Histologically, the cystic spaces were filled with blood and the fibrous septa were composed of fibroblasts, osteoclast-type giant cells, and woven bone. Cytogenetic analysis of one tumor showed 46,XY,t(17;17)(p13;q12), a result similar to that which has been reported for intraosseous aneurysmal bone cyst. The differential diagnosis includes a variety of bone-forming and giant cell-containing tumors, the most important being extraskeletal osteosarcoma. Follow-up showed that four patients are free of disease 16 months to 10 years after surgery; one tumor regrew after incomplete initial excision, but the patient has been free of disease 16 months after a second operation. Soft tissue aneurysmal bone cyst is an uncommon benign tumor that can be treated by simple excision, and it should be distinguished from a variety of other reactive and neoplastic processes
— id: 56308, year: 2002, vol: 26, page: 64, stat: Journal Article,