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To evaluate the clinical performance of the Dynamic Helical Hip System (DHHS) spiral blade relative to the Dynamic Hip Screw (DHS) lag screw. Randomized prospective study. One level-2 trauma center and one level-3 trauma center. Fifty-one consecutive patients were recruited into the trial. Inclusion criteria included patients over 50 years of age with AO/OTA 31A1 or 31A2 fracture. Surgeries were performed by one of 15 participating community orthopaedic surgeons. The patients were randomized to either a DHHS or DHS implant. Follow-up occurred at two weeks and six weeks and then at six-week intervals until healing occurred. Primary outcome variables included sliding of die implant on the final AP radiographs, failure by cut-out and implant failure. There were 24 patients in the DHS group and 27 in the DHHS group. There was no difference in age, gender, ASA score, fracture classification or in the quality of reduction measured on the immediate postoperative radiographs (p=0.28) between the two groups. The tip apex distance was 18.7 mm in the DHHS group and 18.5 mm in the DHS group (p=0.40). The DHHS group had average blade sliding of 7.4 mm while the DHS group had an average lag-screw sliding of 7.7 (p=0.45). The DHHS group had two failures by central protrusion of the blade through the femoral head without significant varus collapse or superior migration. One was revised to a DHS and healed, the other was revised to a proximal femoral locking plate, which also failed and eventually required revision to a total hip arthroplasty. Investigation of the implants post failure showed evidence of binding of the blade shaft in the barrel as a mechanism of failure in both cases. No DHS implants cut out in this series, although one patient was revised to a total hip arthroplasty for symptomatic segmental osteonecrosis. Both implants performed well in a majority of cases. The higher incidence of failure in the DHHS group is concerning, despite the low numbers. The mechanism of failure of the DHHS implant left adequate bone stock for attempts at revision fixation.


Paterson W.H.,University of Memphis | Throckmorton T.W.,University of Memphis | Koester M.,Slocum Center for Orthopedics and Sports Medicine | Azar F.M.,University of Memphis | Kuhn J.E.,Vanderbilt University
Journal of Bone and Joint Surgery - Series A | Year: 2010

Background: Immobilization after closed reduction has long been the standard treatment for primary anterior dislocation of the shoulder. To determine the optimum duration and position of immobilization to prevent recurrent dislocation, a systematic review of the relevant literature was conducted. Methods: Of 2083 published studies that were identified by means of a literature review, nine Level-I and Level-II studies were systematically reviewed. The outcome of interest was recurrent dislocation. Additional calculations were performed by pooling data to identify the ideal length and position (external or internal rotation) of immobilization. Results: Six studies (including five Level-I studies and one Level-II study) evaluated the use of immobilization in internal rotation for varying lengths of time. Pooled data analysis of patients younger than thirty years old demonstrated that the rate of recurrent instability was 41% (forty of ninety-seven) in patients who had been immobilized for one week or less and 37% (thirty-four of ninety-three) in patients who had been immobilized for three weeks or longer (p = 0.52). An age of less than thirty years at the time of the index dislocation was significantly predictive of recurrence in most studies. Three studies (including one Level-I and two Level-II studies) compared recurrence rates with immobilization in external and internal rotation. Analysis of the pooled data demonstrated that the rate of recurrence was 40% (twenty-five of sixty-three) for patients managed with conventional sling immobilization in internal rotation and 25% (twenty-two of eighty-eight) for those managed with bracing in external rotation (p = 0.07). Conclusions: Analysis of the best available evidence indicates there is no benefit of conventional sling immobilization for longer than one week for the treatment of primary anterior shoulder dislocation in younger patients. An age of less than thirty years at the time of injury is significantly predictive of recurrence. Bracing in external rotation may provide a clinically important benefit over traditional sling immobilization, but the difference in recurrence rates did not achieve significance with the numbers available. Level of Evidence: Therapeutic Level II. See Instructions to Authors for a complete description of levels of evidence. Copyright © 2010 by The Journal of Bone and Joint Surgery, Incorporated.


Tsai S.,Legacy Research and Technology Center | Fitzpatrick D.C.,Slocum Center for Orthopedics and Sports Medicine | Madey S.M.,Legacy Research and Technology Center | Bottlang M.,Legacy Research and Technology Center
Journal of Orthopaedic Research | Year: 2015

Axial dynamization of an osteosynthesis construct can promote fracture healing. This biomechanical study evaluated a novel dynamic locking plate that derives symmetric axial dynamization by elastic suspension of locking holes within the plate. Standard locked and dynamic plating constructs were tested in a diaphyseal bridge-plating model of the femoral diaphysis to determine the amount and symmetry of interfragmentary motion under axial loading, and to assess construct stiffness under axial loading, torsion, and bending. Subsequently, constructs were loaded until failure to determine construct strength and failure modes. Finally, strength tests were repeated in osteoporotic bone surrogates. One body-weight axial loading of standard locked constructs produced asymmetric interfragmentary motion that was over three times smaller at the near cortex (0.1±0.01) than at the far cortex (0.32±0.02). Compared to standard locked constructs, dynamic plating constructs enhanced motion by 0.32 at the near cortex and by 0.33 at the far cortex and yielded a 77% lower axial stiffness (p<0.001). Dynamic plating constructs were at least as strong as standard locked constructs under all test conditions. In conclusion, dynamic locking plates symmetrically enhance interfragmentary motion, deliver controlled axial dynamization, and are at least comparable in strength to standard locked constructs. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1218-1225, 2015.


Doornink J.,Legacy Research and Technology Center | Fitzpatrick D.C.,Slocum Center for Orthopedics and Sports Medicine | Madey S.M.,Legacy Research and Technology Center | Bottlang M.,Legacy Research and Technology Center
Journal of Orthopaedic Trauma | Year: 2011

The high stiffness of periarticular locked plating constructs can suppress callus formation and fracture healing. Replacing standard locking screws with far cortical locking (FCL) screws can decrease construct stiffness and can improve fracture healing in diaphyseal plating constructs. However, FCL function has not been tested in conjunction with periarticular plating constructs in which FCL screws are confined to the diaphyseal segment. This biomechanical study evaluated if diaphyseal fixation of a periarticular locking plate with FCL screws reduces construct stiffness and induces parallel interfragmentary motion without decreasing construct strength. Periarticular locking plates were applied to stabilize distal femur fractures in 22 paired femurs using either a standard locked plating approach (LP group) or FCL for diaphyseal fixation (FCL group) using MotionLoc screws (Zimmer, Warsaw, IN). Each specimen was evaluated under quasiphysiological loading to assess construct stiffness, construct durability under dynamic loading, and residual strength after dynamic loading. FCL constructs had an 81% lower initial stiffness than LP constructs. They induced nearly five times more interfragmentary motion than LP constructs under one body weight loading (P < 0.001). FCL constructs generated parallel interfragmentary motion, whereas LP constructs exhibited 48% less motion at the near cortex than at the far cortex (P = 0.002). Seven LP constructs and eight FCL constructs survived 100,000 loading cycles. The residual strength of surviving constructs was 4.9 ± 1.6 kN (LP group) and 5.3 ± 1.1 kN (FCL group, P = 0.73). In summary, FCL screws reduce stiffness, generate parallel interfragmentary motion, and retain the strength of a periarticular locked plating construct. Therefore, FCL fixation may be advisable for stiffness reduction of periarticular plating constructs to promote fracture healing by callus formation. Copyright © 2011 by Lippincott Williams & Wilkins.


Lujan T.J.,Legacy Research and Technology Center | Madey S.M.,Legacy Research and Technology Center | Fitzpatrick D.C.,Slocum Center for Orthopedics and Sports Medicine | Byrd G.D.,Legacy Research and Technology Center | And 2 more authors.
Journal of Biomechanics | Year: 2010

Callus formation occurs in the presence of secondary bone healing and has relevance to the fracture's mechanical environment. An objective image processing algorithm was developed to standardize the quantitative measurement of periosteal callus area in plain radiographs of long bone fractures. Algorithm accuracy and sensitivity were evaluated using surrogate models. For algorithm validation, callus formation on clinical radiographs was measured manually by orthopaedic surgeons and compared to non-clinicians using the algorithm. The algorithm measured the projected area of surrogate calluses with less than 5% error. However, error will increase when analyzing very small areas of callus and when using radiographs with low image resolution (i.e. 100 pixels per inch). The callus size extracted by the algorithm correlated well to the callus size outlined by the surgeons (R 2=0.94, p<0.001). Furthermore, compared to clinician results, the algorithm yielded results with five times less inter-observer variance. This computational technique provides a reliable and efficient method to quantify secondary bone healing response. © 2009 Elsevier Ltd.

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