Derek F Amanatullah

California State University, Sacramento, Sacramento, California, United States

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Publications (27)25.05 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The optimal management of pathologic long bone lesions remains a challenge in orthopedic surgery. The goal of the current study was to investigate the effect of defect depth on the torsional properties of the distal femur. A laterally placed distal metaphyseal cylindrical defect was milled in the cortex of the distal femur in 20 composite models. The proximal extent of the defects was constant. By decreasing the radius of the cylinder that intersected this predefined cord, 4 different radii defining 4 different depths of resection of the distal femur were created for testing: 17%, 33%, 50%, and 67% cortical defects, when normalized to the width of the femur at the level of resection. Each femur was mounted into a hydraulic axial/torsion materials testing machine and each specimen underwent torsional stiffness testing and torsional failure in external rotation. The specimens with less than a 33% cortical loss consistently demonstrated a superiorly oriented spiral fracture pattern, while the specimens with greater than a 50% cortical loss consistently demonstrated an inferiorly oriented transverse fracture pattern. The cortical defects were all statistically (P<.05) less stiff in torsion as the defect grew larger. There was a strong linear correlation between the mean torsional stiffness and cortical defect size (r(2)=0.977). This observation is supported by finite element analysis. The amount of femur remaining is crucial to stability. This biomechanical analysis predicts a critical loss of torsional integrity when a cortical defect approaches 50% of the width of the femur. [Orthopedics. 2014; 37(3):158-162].
    Orthopedics 03/2014; 37(3):158-62. · 1.05 Impact Factor
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    ABSTRACT: EDUCATIONAL OBJECTIVES As a result of reading this article, physicians should be able to: 1. Identify at-risk populations for giant cell tumor of bone. 2. Recognize the biology that drives giant cell tumor of bone. 3. Describe modern surgical and adjuvant techniques to effectively treat giant cell tumor of bone. 4. Recognize the complications associated with radiation therapy, poor resection, and adjuvant treatments. Giant cell tumor of bone (GCT) is a benign, locally aggressive bone tumor. Giant cell tumor of bone primarily affects the young adult patient population. The natural history of GCT is progressive bone destruction leading to joint deformity and disability. Surgery is the primary mode of treatment, but GCT has a tendency to recur locally despite a range of adjuvant surgical options. Pulmonary metastasis has been described. However, systemic spread of GCT rarely becomes progressive, leading to death. This review presents the clinicopathologic features of GCT and a historical perspective that highlights the current rationale and contro-versies regarding the treatment of GCT. [Orthopedics. 2014;37(2):112-120.].
    Orthopedics 02/2014; 37(2):112-20. · 1.05 Impact Factor
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    ABSTRACT: Several risk factors for dislocation after total hip arthroplasty (THA) have been identified including operative-, patient-, and implant-related factors. The following case report describes the dislocation of a revision THA without disruption of the constrained liner or containment ring. The possible mechanisms leading to this type of failure include lever-out impingement and poor abductor function, or tension secondary to prior surgery. Dislocation without disruption of containment ring has not been described for the Pinnacle Acetabular Cup with the Enhanced Stability Constrained Liner (DePuy Orthopaedics, Warsaw, Indiana).
    American journal of orthopedics (Belle Mead, N.J.) 12/2013; 42(12):566-8.
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    ABSTRACT: Congenital pseudarthrosis of the radius or ulna is a rare entity. It is associated with neurofibromatosis, but occurs much less commonly than congenital pseudarthrosis of the tibia. Pseudarthrosis of the forearm can lead to pain, deformity, and limited forearm rotation. Nonsurgical management leads to poor results, as do surgical treatments such as open reduction internal fixation and conventional bone grafting. The transfer of a free vascularized fibula to the forearm pseudarthrosis has been more successful, and it is our preferred method of treatment for children with this condition. Because the transfer is often performed in young children, there is the potential for valgus deformity at the ankle after the fibula is removed. We describe here our technique for the transfer, including the technique for distal tibiofibular fusion (Langenskiöld procedure) after removal of the fibular graft. In addition, we present the results of 5 patients who have undergone this combination of procedures for pseudarthrosis of the forearm at our institution.
    Techniques in hand & upper extremity surgery 09/2013; 17(3):144-50.
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    ABSTRACT: Incorrect registration during computer assisted total knee arthroplasty (CA-TKA) leads to malposition of implants. Our aim was to evaluate the tolerable error in anatomic landmark registration. We incorrectly registered the femoral epicondyles, femoral and tibial centers, as well as the malleoli and documented the change in angulation or rotation. We found that the distal femoral epicondyles were the most difficult anatomic landmarks to register. The other bony landmarks were more forgiving. Identification of the distal femoral epicondyles has a high inter-observer and intra-observer variability. Our observation that there is less than 2mm of safe zone in the anterior or posterior direction during registration of the medial and lateral epicondyles may explain the inability of CA-TKA to improve upon the outcomes of conventional TKA.
    The Journal of arthroplasty 04/2013; · 1.79 Impact Factor
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    ABSTRACT: Osteonecrosis of the hip accounts for about 10% of all total hip arthroplasty cases and presents a significant challenge for those patients with and without femoral head collapse. Subtrochanteric femur fractures have been reported with numerous types of proximal femoral implants. Care must be taken to avoid penetrating the lateral cortex of the proximal femur inferior to the distal border of the lesser trochanter. Core decompression requires a 3 mm to 20 mm defect in the lateral femoral cortex. Subtrochanteric femur fractures are a well-known complication of core decompression as well. We present a case of a subtrochanteric fracture following the removal of a porous tantalum implant.
    Case reports in orthopedics. 01/2013; 2013:946745.
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    ABSTRACT: Objective: ADAMTS (a disintegrin and metalloproteinase with thrombospondin type-1 motif) zinc metalloproteinases are important during the synthesis and breakdown of cartilage extracellular matrix. ADAMTS-12 is upregulated during in-vitro chondrogenesis and embryonic limb development, however the regulation of ADAMTS-12 expression in cartilage remains unknown. The transcription factor c-Maf is a member of Maf family of basic ZIP (bZIP) transcription factors. Expression of c-Maf is highest in hypertrophic chondrocytes during embryonic develop- ment and postnatal growth. We hypothesized that c-Maf and ADAMTS-12 are co-expressed during chondrocyte differentiation and that c-Maf regulates ADAMTS-12 expression during chondrogenesis. Design: Promoter analysis and species alignments identified potential c-Maf binding sites in the ADAMTS-12 promoter. c-Maf and ADAMTS-12 co-expression was moni- tored during chondrogenesis of stem cell pellet cultures. Luciferase expression driven by ADAMTS-12 promoter segments was measured in the presence and absence of c-Maf, and syn- thetic oligonucleotides were used to confirm specific binding of c-Maf to ADAMTS-12 promoter sequences. Results: In-vitro chondrogenesis from human mesenchymal stem cells revealed co- expression of ADAMTS-12 and c-Maf during differentiation. Truncation and point mutations of the ADAMTS-12 promoter evaluated in reporter assays localized the response to the proximal 315 bp of the ADAMTS-12 promoter, which contained a predicted c-Maf recognition element (MARE) at position -61. Electorphoretic-mobility-shift-assay confirmed that c-Maf directly in- teracted with the MARE at position -61. Conclusions: These data suggest that c-Maf is involved in chondrocyte differentiation and hypertrophy, at least in part, through the regulation of ADAMTS-12 expression at a newly identified MARE in its proximal promoter.
    Cartilage 12/2012;
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    ABSTRACT: BACKGROUND: Methicillin-resistant Staphylococcus aureus infections are a well-documented risk of surgery and are becoming increasingly difficult to treat owing to continued acquired resistance. A new antibiotic for treatment of Staphylococcus aureus is telavancin. CASE DESCRIPTION: A patient at our institution was prescribed telavancin for multiple spinal abscesses before spinal surgery. Routine preoperative testing revealed an international normalized ratio (INR) of 2.05 with no clear cause. Careful review of the patient's medication history and prescriber information revealed that telavancin may interfere with prothrombin time (PT/INR) testing. In vitro testing by our laboratory confirmed an association between telavancin dose and an increase in PT/INR. An alternative reagent for PT/INR testing unaffected by telavancin dose revealed a PT/INR of 0.97. LITERATURE REVIEW: Telavancin interacts with artificial phospholipid surfaces used to monitor coagulation while having no actual effect on coagulation. PURPOSES AND CLINICAL RELEVANCE: All physicians, especially orthopaedic surgeons, should be aware of the effects of telavancin and ensure proper measures are taken to acquire the true INR by switching the reagent used to test PT/INR or ensuring the PT/INR is drawn before telavancin dosing.
    Clinical Orthopaedics and Related Research 11/2012; · 2.79 Impact Factor
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    ABSTRACT: Traditional surgical approaches often involve making large skin incisions and extensively dissecting healthy tissue to access diseased anatomy. Obviously more desirable is to make smaller incisions and more focused dissections and achieve the same postsurgical outcomes. Minimally invasive surgery (MIS) is gaining popularity in many orthopedic fields, but MIS techniques are not without risk. Continued use of these techniques is a topic of debate. If alignment is satisfactory with MIS, and if the complication rates of MIS are similar to those of traditional approaches, it seems sensible to consider the less invasive approaches to enable earlier patient recovery and improve cosmesis. Skeptics claim that there is no advantage in using MIS over time-tested approaches and are concerned that MIS approaches are being implemented before being properly subjected to peer review.
    American journal of orthopedics (Belle Mead, N.J.) 10/2012; 41(10):E140-4.
  • Derek F Amanatullah, Shintaro Yamane, A Hari Reddi
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    ABSTRACT: Hyaline articular cartilage will not heal spontaneously, and lesions in hyaline articular cartilage often result in degenerative joint disease. Considerable progress has been made with respect to the responsive stem cells, inductive signals and extracellular scaffolding required for the optimal regeneration of cartilage. However, many challenges remain, such as topographic differences in the functional zones of articular cartilage. We hypothesized that a distinct set of differentially expressed genes define the surface, middle and deep zones of hyaline articular cartilage. Microarray analysis of bovine articular cartilage from the superficial and middle zones revealed 52 genes differentially expressed ≥ 10-fold and 114 additional genes differentially expressed ≥ five-fold. However, no genes were identified with a ≥ five-fold difference in expression when comparing articular cartilage from the middle and deep zones. There are distinct, differential gene expression patterns in the superficial and middle zones of hyaline articular cartilage that highlight the functional differences between these zones. This investigation has implications for the tissue engineering and regeneration of hyaline articular cartilage. Copyright © 2012 John Wiley & Sons, Ltd.
    Journal of Tissue Engineering and Regenerative Medicine 07/2012; · 4.43 Impact Factor
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    ABSTRACT: Expression of chondrocyte-specific genes is regulated by mechanical force. However, despite the progress in identifying the signal transduction cascades that activate expression of mechanoresponsive genes, little is known about the transcription factors that activate transcription of mechanoresponsive genes. The DNA elements that confer mechanoresponsiveness within a cartilage gene promoter have yet to be identified. We have established an experimental system to identify the DNA elements and transcription factors that mediate the mechanoresponse of a promoter to nominal compressive stress in primary human chondrocytes and stem cells in a three-dimensional culture system. Our results demonstrate that the proximal 3 Kb of the human cartilage oligomeric matrix protein promoter is sufficient to mediate a mechanoresponse in human articular chondrocytes and stem cells, and that the magnitude of mechanoresponse correlates to the regulation of the endogenous gene at the RNA and protein level. This information is critical to understanding how mechanical force regulates the transcriptional activation of cartilage genes in three-dimensional culture.
    Tissue Engineering Part A 07/2012; 18(17-18):1882-9. · 4.64 Impact Factor
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    ABSTRACT: Oblique fractures of the medial malleolus can arise from the application of axial force at various anatomic positions of the ankle, including supination-external rotation, pronation-external rotation, or pronation abduction. Although a variety of techniques exist to provide fixation of horizontal medial malleolus fractures, the optimal technique and pattern for internal fixation remains unclear. The aim of this study was to evaluate the mechanical properties of four different fixation methods for fractures of the medial malleolus. Identical oblique osteotomies were created in synthetic distal tibiae using a jig. The specimens were divided into four fixation groups: contoured 2.0 mm mini-fragment T-plate, figure-of-eight tension band wire, construct two parallel 4.0 mm cancellous screws, and two divergent 4.0 mm cancellous screws. The specimens were tested using offset axial tension at 10 mm/min until 2 mm of joint line displacement. The average stiffness in tension and force at 2 mm of joint line displacement of the plate construct was significantly greater than any of the other constructs (p < 0.05), whereas the average stiffness in tension of the other three groups were not significantly different from each other (p > 0.05). Using a contoured 2.0 mm mini-fragment T-plate as the method of fixation resulted in an at least 25% stiffer construct during tension and required at least 24% more force for 2 mm of joint line displacement when compared with more traditional methods of fixation in an osteotomy model of an oblique medial malleolus fracture.
    The journal of trauma and acute care surgery. 04/2012; 72(4):948-53.
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    ABSTRACT: This study qualified and evaluated the mechanical properties of three different screw orientations used for fixation of vertical shear fractures of the medial malleolus. Identical vertical osteotomies were created in synthetic distal tibiae using a jig. The specimens were assigned to one of the three fixation groups (n = 8 per group): (1) parallel: two 40 mm length, 4.0 mm diameter screws placed parallel to each other in the transverse plane; (2) convergent: two 40 mm length, 4.0 mm diameter screws placed 25 degree convergent to each other in the transverse plane; and (3) divergent: two 40 mm length, 4.0 mm diameter screws placed 15 degree divergent to each other in the transverse plane. The specimens were tested using offset axial loading at 1 mm/s until 2 mm of displacement. The average stiffness was 102 N/mm ± 51 N/mm for the parallel group, 109 N/mm ± 37 N/mm for the convergent group, and 185 N/mm ± 73 N/mm for the divergent group. The average stiffness of the divergent group was significantly greater than either the parallel (p < 0.05) or convergent (p < 0.05) groups. The divergent group was 81.4% more stiff than the parallel group and 69.7% more stiff than the convergent group. The average load at 2 mm of displacement was 324 N ± 87 N for the parallel group, 373 N ± 95 N for the convergent group, and 512 N ± 170 N for the divergent group. The average load at failure of the divergent group was significantly (p < 0.05) greater than the parallel groups. The divergent group was required 58.0% more force at 2 mm of displacement than the parallel group and 37.3% more force at 2 mm of displacement than the convergent group. The use of a divergent screw pattern resulted in a stiffer fixation construct that requires more force for 2 mm of displacement when used to stabilize an osteotomy model of vertical shear medial malleolus fractures.
    The journal of trauma and acute care surgery. 03/2012; 72(3):751-4.
  • Derek F Amanatullah, Amir A Jamali
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    ABSTRACT: A low-contact stress, high-congruity, mobile-bearing patellofemoral joint arthroplasty decreases the contact force in the patellofemoral joint, theoretically reducing patellar polyethylene wear and increasing implant longevity. This article describes the case of a 47-year-old obese woman who presented with pain and loss of extension after a low-contact stress, high-congruity, mobile-bearing patellofemoral joint arthroplasty. Radiographs revealed dislocation (ie, spinout) of the patellar polyethylene. Patellar polyethylene spinout is a rare complication of metal-backed, mobile-bearing patellar resurfacing. Theoretically, patellar polyethylene spinout in low-contact stress, high-congruity, mobile-bearing patellofemoral arthroplasty is related to implant design and the placement of the metal base plate. Ultimately, the articulation of low-contact stress, high-congruity, mobile-bearing patellofemoral arthroplasty may be too congruent to resist the forces of the patellofemoral joint, particularly in patients who are obese, and the patellar rotation allowed by this articulation may not be sufficient for all patients. Should patellar spinout occur, replacement of the polyethylene is not sufficient to correct the problem; hence, revision of the patellar and trochlear components is required because it remains unclear whether failure is secondary to patellar or trochlear design deficiencies.
    Orthopedics 01/2012; 35(2):e272-6. · 1.05 Impact Factor
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    ABSTRACT: The present case report highlights the diagnosis and modern surgical techniques involved when treating an aggressive benign bone tumour in a skeletally mature patient. It also stresses the importance of a broad differential when examining a patient. An increase in circulating growth hormones during pregnancy could play a role in the rapid growth of particular tumours. For example, certain transforming growth factor (TGF)-β receptors have been identified in cells of aneurysmal bone cysts and a rat model has demonstrated that TGF-β isoforms are regulated differently in pregnancy, and also could have an important role in apoptosis and cell survival. The occurrence of aneurysmal bone cysts during pregnancy suggests a possible link between the pregnancy and tumour growth.
    Shoulder & Elbow 01/2012; 4(1).
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    ABSTRACT: Tibio-Fibular Fusion (Langenskild Procedure) after Fibular Harvest in Children Purpose: Harvest of a vascularized free fibula graft may result in ankle instability and donor site pain. In skeletally immature patients, progressive valgus can occur as well. Fusion of the remaining distal fibula to the tibia (Langenskild procedure) has been suggested to minimize the risk of these problems. This case series reports clinical and radiographic data collected prospectively for seven patients who underwent the Langenskild procedure after free fibula grafting. Methods: Seven patients underwent fusion of the distal fibula to the tibia after harvest of a fibular graft; six were vascularized grafts, and one non-vascularized. Underlying diagnoses included neurofibromatosis (4), aneurysmal bone cyst (1), desmoid tumor of the ulna (1), and osteomyelitis (1). Two patients underwent delayed Langenskild procedures after progressive ankle valgus occurred; these patients also underwent concomitant medial malleolar screw hemiephysiodesis. The other five patients underwent tibiofibular arthrodesis concomitant with fibular graft harvest. Age at time of the Langenskild procedure was mean 7+3 (range 1 to 11). Follow-up averaged 5+2 years (range 1 to 7 years). Age at latest follow up was mean 12+1 (range 5 to 16; 3 skeletally mature). Results: Six of the seven patients had no pain or functional limitations in the affected limb. None of the six had progression of valgus, and one corrected from 20o to 3o with medial hemiepiphysiodesis (Figure 1). One with neurofibromatosis developed a new gradual tibial bow precipitating some overall increased valgus (9o) despite initial correction of the ankle valgus with a medial malleolar screw, and had foot discomfort relieved with an ankle foot orthosis. The one patient with a non-vascularized graft reconstituted the fibula; the others with vascularized grafts did not. Conclusion: Fusion of the distal fibula to the tibia after harvest of fibula grafts in children is associated with good clinical and radiographic outcomes, either when performed at the same time as the index procedure or, if necessary, at a later date. Figure 1: Seven year old patient with tibial pseudoarthrosis as a result of neurofibromatosis treated with free fibula transfer at one year of age with 20 of ankle valgus (A) corrected to 3 of ankle valgus (B) with medial hemiepiphysiodesis and Langenskild procedure.
    2011 American Academy of Pediatrics National Conference and Exhibition; 10/2011
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    Derek F Amanatullah, Eric J Strauss, Paul E Di Cesare
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    ABSTRACT: Osteonecrosis of the femoral head is a multifactorial disease that can result in significant clinical morbidity and affects patients of any age, including young and active patients. Late sequelae of femoral head osteonecrosis include femoral head collapse and subsequent degeneration of the hip joint. A high index of suspicion and improved radiographic evaluation allow orthopedic surgeons to identify this disease at an earlier stage. Current management options for hip osteonecrosis have results that vary according to patient population and disease stage. Modifications of older techniques, as well as emerging technologies, have led to the development of management strategies that may be able to alter the course of femoral head osteonecrosis.
    American journal of orthopedics (Belle Mead, N.J.) 10/2011; 40(10):E216-25.
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    ABSTRACT: Osteoid osteoma is the most common bone-producing tumor that typically presents with "throbbing night pain" and that improves dramatically with use of low-dose salicylates. Few cases of pelvic osteoid osteoma have been reported, and most have involved patients younger than age 30. Surgical excision classically has been the treatment of choice, but, recently, less invasive modalities, including radiofrequency ablation, have begun to supplant surgical management of osteoid osteoma, resulting in a decrease in the need for definitive surgical diagnosis and treatment. We present a rare case of osteoid osteoma in the pelvis of a woman older than age 30.
    American journal of orthopedics (Belle Mead, N.J.) 09/2011; 40(9):476-8.
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    Derek F Amanatullah, Eric J Strauss, Paul E Di Cesare
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    ABSTRACT: Osteonecrosis of the femoral head is a multifactorial disease that can result in significant clinical morbidity and affects patients of any age, including young and active patients. Late sequelae of femoral head osteonecrosis include femoral head collapse and subsequent degeneration of the hip joint. A high index of suspicion and improved radiographic evaluation allow orthopedic surgeons to identify this disease at an earlier stage. Current management options for hip osteonecrosis have results that vary according to patient population and disease stage. Modifications of older techniques, as well as emerging technologies, have led to the development of management strategies that may be able to alter the course of femoral head osteonecrosis.
    American journal of orthopedics (Belle Mead, N.J.) 09/2011; 40(9):E186-92.
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    ABSTRACT: Appropriate implant alignment is a major goal of total joint arthroplasty. Obtaining appropriate alignment typically involves making intraoperative decisions in response to visual and tactile feedback. Integrated computer-based systems provide the option of continuous real-time feedback and offer the potential to decrease intraoperative errors while enhancing the surgical learning experience. Computer-assisted orthopedic surgery helps the surgeon perform both intraoperative and postoperative technical audits of implant alignment. Improving implant alignment can be correlated with improved long-term clinical outcomes. However, despite emerging data, many surgeons remain wary of computer-assisted orthopedic surgery.
    American journal of orthopedics (Belle Mead, N.J.) 08/2011; 40(8):419-26.

Publication Stats

34 Citations
25.05 Total Impact Points

Institutions

  • 2013
    • California State University, Sacramento
      Sacramento, California, United States
  • 2012
    • CSU Mentor
      Long Beach, California, United States
  • 2010–2012
    • University of California, Davis
      • Department of Orthopaedic Surgery
      Davis, CA, United States