Derek F Amanatullah

Stanford University, Palo Alto, California, United States

Are you Derek F Amanatullah?

Claim your profile

Publications (37)39.23 Total impact

  • Derek F Amanatullah, Robert T Trousdale, Rafael J Sierra
    [Show abstract] [Hide abstract]
    ABSTRACT: There are approximately 1.6 million lower extremity amputees in the United States. Lower extremity amputees are subject to increased physical demands proportional to their level of amputation. Lower extremity amputees have a 6-fold higher risk of developing radiographic osteoarthritis in the ipsilateral hip and a 2-fold risk of developing radiographic osteoarthritis in contralateral hip when compared with the non-amputee population. Additionally, there is a 3-fold increased risk of developing radiographic osteoarthritis in the ipsilateral hip after an above knee amputation when compared with a below knee amputation. The authors retrospectively reviewed 35 total hip arthroplasties after lower extremity amputation. The mean clinical follow-up was 5.3±4.0 years. The mean time from lower extremity amputation to total hip arthroplasty was 12.2±12.8 years after a contralateral amputation and 5.4±6.0 years after an ipsilateral amputation (P=.050). The mean time to total hip arthroplasty was 15.6±15.4 years after an above knee amputation and 6.4±6.1 years after a below knee amputation (P=.021). There was a statistically significant improvement in the mean Harris Hip Score from 35.9±21.8 to 76.8±12.8 with total hip arthroplasty after a contralateral amputation (P<.001). There also was a statistically significant improvement in the mean Harris Hip Score from 25.4±21.7 to 78.6±17.1 with total hip arthroplasty after an ispilateral amputation (P<.001). Three (17.7%) total hip arthroplasties after a contralateral amputation and 2 (11.1%) total hip arthroplasties after an ipsilateral amputation required revision total hip arthroplasty. Patients with an ipsilateral amputation or a below knee amputation progress to total hip arthroplasty faster than those with a contralateral amputation or an above knee amputation, respectively. Lower extremity amputees experience clinically significant improvements with total hip arthroplasty after lower extremity amputation. [Orthopedics. 2015; 38(5):e394-e400.]. Copyright 2015, SLACK Incorporated.
    Orthopedics 05/2015; 38(5):e394-400. DOI:10.3928/01477447-20150504-56
  • [Show abstract] [Hide abstract]
    ABSTRACT: EDUCATIONAL OBJECTIVES As a result of reading this article, physicians should be able to: 1. Identify the etiology of femoroacetabular impingement. 2. Assess femoroacetabular impingement on physical examination. 3. Recognize femoroacetabular impingement on imaging studies. 4. Discuss modern techniques to effectively treat femoroacetabular impingement, both open and arthroscopic. Femoroacetabular impingement (FAI) is a recently proposed concept describing abnormal anatomic relationships within the hip joint that may lead to articular damage. Impingement is caused by bony deformities or spatial malorientation of the femoral head-neck junction and/or the acetabulum. These abnormalities lead to pathologic contact and shearing forces at the acetabular labrum and cartilage during physiological hip motion. There is an increasing body of evidence that these forces lead to cartilage wear and eventual osteoarthritis. Treatment options for FAI are evolving rapidly. Although the gold standard remains open hip dislocation, arthroscopic techniques have shown significant promise. It is possible that early recognition and treatment of subtle deformity about the hip may reduce the rate of hip osteoarthritis in the future. [Orthopedics. 2015; 38(3):185-199.]. Copyright 2015, SLACK Incorporated.
    Orthopedics 03/2015; 38(3):185-99. DOI:10.3928/01477447-20150305-07
  • [Show abstract] [Hide abstract]
    ABSTRACT: Revision total hip arthroplasty (THA) is challenging when there is severe loss of bone in the proximal femur. The purpose of this study was to evaluate the clinical and radiographic outcomes of revision THA in patients with severe proximal femoral bone loss treated with a fluted, tapered, modular femoral component. Between January 1998 and December 2004, 92 revision THAs were performed in 92 patients using a single fluted, tapered, modular femoral stem design. Pre-operative diagnoses included aseptic loosening, infection and peri-prosthetic fracture. Bone loss was categorised pre-operatively as Paprosky types III-IV, or Vancouver B3 in patients with a peri-prosthetic fracture. The mean clinical follow-up was 6.4 years (2 to 12). A total of 47 patients had peri-operative complications, 27 of whom required further surgery. However, most of these further operations involved retention of a well-fixed femoral stem, and 88/92 femoral components (97%) remained in situ. Of the four components requiring revision, three were revised for infection and were well fixed at the time of revision; only one (1%) was revised for aseptic loosening. The most common complications were post-operative instability (17 hips, 19%) and intra-operative femoral fracture during insertion of the stem (11 hips, 12%). Diaphyseal stress shielding was noted in 20 hips (22%). There were no fractures of the femoral component. At the final follow-up 78% of patients had minimal or no pain. Revision THA in patients with extensive proximal femoral bone loss using the Link MP fluted, tapered, modular stem led to a high rate of osseointegration of the stem at mid-term follow-up. Cite this article: Bone Joint J 2015; 97-B:312-17. ©2015 The British Editorial Society of Bone & Joint Surgery.
    03/2015; 97-B(3):312-7. DOI:10.1302/0301-620X.97B3.34684
  • [Show abstract] [Hide abstract]
    ABSTRACT: Optimization of patient expectations in TKA requires understanding the risk profile of each patient and tailoring preoperative counseling appropriately. There are numerous postoperative thromboprophylaxis regimens, but aspirin has gained consensus approval from the Academy of Orthopaedic Surgeons and American College of Chest Physicians and may decrease the risk of bleeding when compared to other agents. Early mobilization or mechanical compression remain useful adjuncts to chemical thromboprophylaxis. Pre-emptive multimodal pain control is effective and minimizes narcotic-related side effects. Regional blockade and periarticular injection are effective strategies for site-specific pain control and avoid opioid induced side effects. Strategies for perioperative physical therapy vary widely and there are no well-defined guidelines for postoperative rehabilitation. Rehabilitation lacks durable clinical benefits long-term for the average patient. However, targeted utilization of perioperative rehabilitation to the most debilitated patients may be beneficial.
    Current Orthopaedic Practice 01/2015; 26(3):217-223. DOI:10.1097/BCO.0000000000000230
  • D F Amanatullah, S R Rachala, R T Trousdale, R J Sierra
    [Show abstract] [Hide abstract]
    ABSTRACT: Dysplasia of the hip, hypotonia, osteopenia, ligamentous laxity, and mental retardation increase the complexity of performing and managing patients with Down syndrome who require total hip replacement (THR). We identified 14 patients (six males, eight females, 21 hips) with Down syndrome and degenerative disease of the hip who underwent THR, with a minimum follow-up of two years from 1969 to 2009. In seven patients, bilateral THRs were performed while the rest had unilateral THRs. The mean clinical follow-up was 5.8 years (standard deviation (sd) 4.7; 2 to 17). The mean Harris hip score was 37.9 points (sd 7.8) pre-operatively and increased to 89.2 (sd 12.3) at final follow-up (p = 1x10(-9)). No patient suffered a post-operative dislocation. In three patients, four hips had revision THR for aseptic loosening at a mean follow-up of 7.7 years (sd 6.3; 3 to 17). This rate of revision THR was higher than expected. Our patients with Down syndrome benefitted clinically from THR at mid-term follow-up. Cite this article: Bone Joint J 2014;96-B:1455-8.
    11/2014; 96-B(11):1455-8. DOI:10.1302/0301-620X.96B11.34089
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Some patients opt to undergo conversion to a THA for continued pain or progression of hip arthritis after periacetabular osteotomy. Whether patients are at greater risk for postoperative complications, revision THA, poor clinical outcomes, or compromised radiographic results after periacetabular osteotomy is debatable.
    Clinical Orthopaedics and Related Research 10/2014; 473(2). DOI:10.1007/s11999-014-4026-7
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The utility of heterotopic ossification (HO) classification systems is debatable. The range of motion and Harris hip score (HHS) were calculated in 104 patients with known HO after total hip arthroplasty and 208 matched controls without HO. The patients with HO were radiographically divided into high and low grade HO groups. There was no statistically significant association of HHS with high or low grade HO. High grade HO had a statistically significant 6° loss of terminal hip flexion, 4° loss of abduction, and 6° loss of internal rotation at the hip. The small changes terminal hip range of motion and lack of an association with HHS may be the result of false radiographic continuity resulting in an overestimation of the disability in high grade HO.
    The Journal of Arthroplasty 10/2014; 30(3). DOI:10.1016/j.arth.2014.09.019
  • Derek F. Amanatullah, Robert T. Trousdale, Rafael J. Sierra
    [Show abstract] [Hide abstract]
    ABSTRACT: Below knee amputation protects the ipsilateral knee from osteoarthritis and overloads the contralateral knee predisposing it to symptomatic osteoarthritis. We retrospectively reviewed 13 primary TKA patients with a prior lower extremity amputation. Twelve TKAs were performed on the contralateral side of the amputated limb while only one TKA was performed on the ipsilateral side. The average clinical follow-up was 6.8 ± 4.8 years. Knee Society scores improved from 30.4 ± 11.8 to 88.5 ± 4.2 after TKA with a prior contralateral amputation. Three (23.1%) patients with TKA after contralateral amputation had aseptic loosening of the tibial component. Patients experience clinically significant improvement with TKA after lower extremity amputation. Augmentation of tibial fixation with a stem may be advisable during TKA after contralateral amputation.
    The Journal of Arthroplasty 10/2014; 29(8). DOI:10.1016/j.arth.2014.03.041
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Total femoral arthroplasty (TFA) is an option to amputation in the setting of excessive bones loss during revision total hip and knee arthroplasty. Twenty non-oncologic TFAs with a minimum of 2years follow-up were retrospectively reviewed. The average clinical follow-up was 73±49months. The incidence of new infection was 25% (5/20), while the overall infection rate was 35% (7/20). The incidence of primary hip instability was 10% (2/20), while the overall instability rate was 25% (5/20). Six patients (30%) required revision. The average pre-operative HHS was 30.2±13.1. The average post-operative HHS was 65.3±16.9. TFA is a viable alternative to amputation in non-oncologic patients with massive femoral bone deficiency. However, TFA performed poorly in the setting of infection and instability.
    The Journal of Arthroplasty 05/2014; 29(10). DOI:10.1016/j.arth.2014.05.012
  • [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. DOI:10.3928/01477447-20140225-51
  • [Show abstract] [Hide abstract]
    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. DOI:10.3928/01477447-20140124-08
  • Current Orthopaedic Practice 01/2014; 25(3):297-301. DOI:10.1097/BCO.0000000000000103
  • Source
    [Show abstract] [Hide abstract]
    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.
    12/2013; 2013:946745. DOI:10.1155/2013/946745
  • Source
    [Show abstract] [Hide abstract]
    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.
  • [Show abstract] [Hide abstract]
    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. DOI:10.1097/BTH.0b013e318295238b
  • [Show abstract] [Hide abstract]
    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; 28(6). DOI:10.1016/j.arth.2012.12.013
  • Source
    [Show abstract] [Hide abstract]
    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; 4(2). DOI:10.1177/1947603512472697
  • [Show abstract] [Hide abstract]
    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; 471(1). DOI:10.1007/s11999-012-2612-0
  • [Show abstract] [Hide abstract]
    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.
  • Source
    [Show abstract] [Hide abstract]
    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. DOI:10.1089/ten.TEA.2011.0497

Publication Stats

59 Citations
39.23 Total Impact Points

Institutions

  • 2014–2015
    • Stanford University
      • Department of Orthopaedic Surgery
      Palo Alto, California, United States
    • Mayo Clinic - Rochester
      Рочестер, Minnesota, United States
  • 2012–2013
    • California State University, Sacramento
      Sacramento, California, United States
  • 2010–2012
    • University of California, Davis
      • Department of Orthopaedic Surgery
      Davis, California, United States