John L Masonis

The University of Western Ontario, London, Ontario, Canada

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Publications (6)15.67 Total impact

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    ABSTRACT: Zirconia femoral heads provide increased fracture strength, but 343 zirconia head failures have been documented since 2000. Retrieval analysis of 6 fractured heads, 4 suspect heads, 4 control zirconia heads, and 2 failed alumina heads was performed. Zirconia failures have been isolated to heads sintered in a "tunnel" furnace introduced in 1998. The monoclinic composition at the taper surface of fractured and nonfractured heads was significantly elevated (21% to 68%) compared to that of control zirconia heads (less than 5%). Electron microscopy identified circular fracture footprints unique to the zirconia heads produced in the tunnel furnace. Cobalt chrome heads were used in the urgent revision setting due to Morse taper damage. Partial capsulectomy was performed in an effort to reduce future third body wear. Monoclinic phase transformation following implantation remains a potential mechanism of ceramic head failure. We recommend that patients with recalled zirconia heads be advised of a potential fracture risk.
    The Journal of Arthroplasty 11/2004; 19(7):898-905. DOI:10.1016/j.arth.2004.02.045 · 2.37 Impact Factor
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    ABSTRACT: We report the five- to-ten year results of Anderson Orthopaedic Research Institute type-2 bone defects treated with modular metal augments in revision knee surgery. A total of 102 revision knee arthroplasties in patients with type-2 defects treated with augments and stems were prospectively studied. Seven patients (seven knees) had incomplete follow-up and 15 patients (16 knees) died with the arthroplasty in situ. The mean follow-up of the 79 remaining knees was 7 +/- 2 years (5 to 11). The presence of non-progressive radiolucent lines around the augment in 14% of knees was not associated with poorer knee scores, the range of movement, survival of the component or the type of insert which was used (p > 0.05). The survival of the components was 92 +/- 0.03% at 11 years (95% CI, 10.3 to 11.2). We recommend the use of modular augmentation devices to treat type-2 defects in revision knee surgery.
    The Bone & Joint Journal 04/2004; 86(2):195-9. DOI:10.1302/0301-620X.86B2.13564 · 2.80 Impact Factor
  • Robert B Bourne, John Masonis, Mary Anthony
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    ABSTRACT: Rotating-platform, mobile-bearing total knee replacements have been developed to improve knee kinematics, lower contact stresses on the polyethylene tibial component, minimize constraint, and allow implant self-alignment. The purpose of the current study was to examine some of these parameters. Gait studies during normal gait showed that the stance phase was associated with knee flexion between 8 degrees and 15 degrees. Contact area studies have shown two types of rotating-platform total knee replacements, namely gait congruous (congruous only during the stance phase of gait) and totally congruous (congruous up to 90 degrees knee flexion) implants. Knee simulator studies have shown increased gravimetric wear with rotating-platform total knee replacements compared with their fixed-bearing counterparts. Rotate-only implants had less gravimetric wear than rotate and translate rotating-platform total knee replacements. Clinical studies show similar outcomes (knee scores, range of motion, and complications) when rotating-platform and fixed-bearing total knee replacements are compared. Although attractive, the benefits of rotating-platform total knee replacements still need to be proven.
    Clinical Orthopaedics and Related Research 06/2003; DOI:10.1097/01.blo.0000063562.90853.6a · 2.88 Impact Factor
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    ABSTRACT: Twenty-one primary hip arthroplasties were performed in Crowe grade 3 or 4 hip dysplasia using a subtrochanteric shortening osteotomy. Average patient age was 48.2 years. Average follow-up was 5.8 years (minimum, 2 years). Femoral fixation was cemented in 10 hips and uncemented in 11 hips. All acetabular components were uncemented, with 33% requiring structural autograft. Ninety-one percent of femoral osteotomies healed without complication. Two osteotomy nonunions required revision. Two acetabular revisions were performed for malposition and polyethylene failure. Three patients experienced postoperative dislocation. One cemented femoral component was revised for loosening. However, no neurologic deficiencies were identified. Harris hip score improved from 32.5 to 73.6. Limp improved in 60% of patients and dependence on assistive walking device improved in 40% of patients. Subtrochanteric shortening osteotomy is a safe and predictable method of restoring the anatomic hip center in high developmental hip dislocation. However, the complication rate in these patients is higher than primary hip arthroplasty for osteoarthritis.
    The Journal of Arthroplasty 05/2003; 18(3 Suppl 1):68-73. DOI:10.1054/arth.2003.50104 · 2.37 Impact Factor
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    ABSTRACT: We report 5-year minimum results of cementless over-sized cups used in revision hip arthroplasty, with significant associated bone defects. Forty-three porous-coated jumbo cups were used to treat acetabular defects in revision hip arthroplasty in 42 patients with a mean age of 63 (range, 25-86). Morsellized allograft only was used in 27 hips, and bulk allograft was used in 8 cases. Two patients were lost to follow-up, and 5 died after a mean 7 years' follow-up, with retention of their prostheses. In the remaining 36 cases, the mean follow-up was 10 years (range, 6-14 years). Two acetabular components were revised for aseptic loosening and graft resorption. Two cases were complicated by dislocation. A satisfactory 92% Kaplan Meier shell survival rate was seen at 14 years.
    The Journal of Arthroplasty 03/2003; 18(2):129-33. DOI:10.1054/arth.2003.50038 · 2.37 Impact Factor
  • John L Masonis, Robert B Bourne
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    ABSTRACT: Dislocation is a leading early complication of total hip arthroplasty. The effect of surgical approach on instability and abductor function is a controversial topic. A comprehensive literature review was done to evaluate the correlation of surgical approach and primary total hip arthroplasty dislocation. Two hundred sixty clinical studies were identified between 1970 and 2001. Four prospective studies were identified but individually they contained insufficient power or control groups to reach statistical significance regarding surgical approach and dislocation. Fourteen studies involving 13,203 primary total hip arthroplasties met the inclusion criteria based on variables previously shown to affect stability. These studies were evaluated with respect to surgical approach and dislocation. The combined dislocation rate for these studies was 1.27% for the transtrochanteric approach, 3.23% for the posterior approach (3.95% without posterior repair and 2.03% with posterior repair), 2.18% for the anterolateral approach, and 0.55% for the direct lateral approach. Eight studies involving 2455 primary total hip arthroplasties evaluated postoperative limp. The incidence of postoperative limp was 4% to 20% for patients who had the lateral approach and 0% to 16% for patients who had the posterior approach. The quality of the literature regarding surgical approach, dislocation rates, and abductor function is limited. Larger controlled prospective studies are needed to investigate the potential benefits of the posterior approach in lieu of a dislocation rate six times higher than the direct lateral approach for primary total hip arthroplasty.
    Clinical Orthopaedics and Related Research 01/2003; DOI:10.1097/00003086-200212000-00006 · 2.88 Impact Factor

Publication Stats

279 Citations
15.67 Total Impact Points

Institutions

  • 2004
    • The University of Western Ontario
      • Division of Orthopaedic Surgery
      London, Ontario, Canada