T R Yoon

Publications (5)17.04 Total impact

• Article: Strut-autografting with and without osteogenic protein-1 : a preliminary study of a canine femoral head defect model.

  M A Mont, L C Jones, J J Elias, N Inoue, T R Yoon, E Y Chao, D S Hungerford
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  ABSTRACT: Osteonecrosis of the femoral head frequently leads to collapse of the articular cartilage and to disabling osteoarthritis, which ultimately may necessitate joint arthroplasty. One treatment method that has had moderate success is the so-called trapdoor approach, which involves excavation of diseased (necrotic) bone followed by bone-grafting. Augmentation of this procedure with various growth and differentiation factors may improve the outcome. We developed a canine model that mimics the clinical situation with trapdoor bone-grafting. The objective of this study was to evaluate the effect of the addition of osteogenic protein-1 on healing following the trapdoor procedure with strut-autografting. Thirty-four skeletally mature dogs were used in the experiment. After capsulotomy, a trapdoor was created in the anterolateral surface of the femoral head and a 2-cm-diameter subchondral area of bone was removed. In the phase-I experiments, seven dogs had no treatment of the defect (Group I) and nine dogs were treated with strut-grafting (Group II). In phase II, the procedure was modified by collapsing the trapdoor into the created defect intraoperatively in eighteen dogs, which were divided into three equal groups: six untreated defects were left collapsed (Group III), six were treated with bone graft (Group IV), and six were treated with bone graft augmented with osteogenic protein-1 (Group V). Three of the seven femoral heads in Group I (untreated defect) and one of the nine heads in Group II (grafting without collapsing of the trapdoor) had evidence of cartilage collapse. Inspection of sagittal slices and radiographs revealed an unfilled residual defect in all Group-I heads, whereas all Group-II heads were well healed. The mean normalized stiffness value was significantly larger in Group II than it was in Group I. On visual inspection, depression was noted in all of the femoral heads in Group III (untreated defect; trapdoor left collapsed). In both Group IV and Group V (grafting without and with osteogenic protein-1), the trapdoor cartilage appeared to be essentially normal. Groups IV and V had more radiographic healing than did Group III. The defects in Group V (grafting with osteogenic protein-1) healed faster radiographically than did those in Group IV (grafting without osteogenic protein-1). Moderate-to-excellent healing was seen both radiographically and biomechanically by four months in the groups treated with grafting, with and without osteogenic protein-1, whereas untreated defects did not heal. Clinical Relevance: Symptomatic osteonecrosis of the femoral head is a clinical challenge. The animal model in the current study is a useful tool for the evaluation of methods to treat osteonecrosis of the femoral head. Studies investigating additional time-periods between implantation of osteogenic protein-1 and assessment of results as well as different doses of osteogenic protein-1 are warranted.
  The Journal of Bone and Joint Surgery 08/2001; 83-A(7):1013-22. · 3.27 Impact Factor
• Article: Femoral head osteonecrosis: detection and grading by using a rapid MR imaging protocol.

  A J Khanna, T R Yoon, M A Mont, D S Hungerford, D A Bluemke
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  ABSTRACT: To design and evaluate a limited magnetic resonance (MR) imaging examination that can be performed rapidly and potentially inexpensively in patients with clinical suspicion of osteonecrosis. Both a limited and a full hip MR examination were performed prospectively in 179 hips in 92 patients with clinical suspicion of femoral head osteonecrosis. The presence of osteonecrosis was determined by two radiologists. The percentage of involvement of the femoral head weight-bearing surface was evaluated subsequently for osteonecrosis-positive hips on both sets of images. Both examinations were performed successfully in all cases. Agreement between the limited and full examinations for presence of osteonecrosis was 98.9% (177 of 179 cases; kappa, 0.97). Forty-six (92%) of 50 patients with femoral head osteonecrosis at both examinations were placed in the appropriate quartile of percentage of femoral head weight-bearing surface involvement by both readers (weighted kappa, 0.94). Incidental findings were made at the full examination that could not be made or were difficult to make at the limited examination. There was excellent agreement between the full and screening MR examinations for both detection of and determining the extent of osteonecrosis. The time and potential cost reduction achieved with a limited examination may allow introduction of MR imaging earlier in the diagnosis of femoral head osteonecrosis, as well as its more widespread use in patient care.
  Radiology 11/2000; 217(1):188-92. · 5.73 Impact Factor
• Article: Clinical experience with a proximally porous-coated second-generation cementless total hip prosthesis: minimum 5-year follow-up.

  M A Mont, T R Yoon, K A Krackow, D S Hungerford
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  ABSTRACT: This study reports the minimum 5-year follow-up of our experience with the Porous-Coated Anatomic E (PCA-E) series femoral stem and the modular acetabular cup. A total of 115 consecutive total hip replacements using PCA-E series (Howmedica, Rutherford, NJ) were performed in 108 patients. Six patients whose hips were performing well clinically died before 5-year follow-up and were excluded from the final evaluation. The remaining 109 hips (102 patients) were assessed at a mean follow-up of 72 months (range, 60-84 months). The hip diagnoses were osteoarthritis in 73, osteonecrosis in 31, rheumatoid arthritis in 2, and hip dysplasia in 3. The mean age was 56 years (range, 24-83 years). Three hips were revised: 1 because of late hematogenous infection, 1 because of aseptic loosening of the femoral component, and 1 because of postoperative loosening of an acetabular component. The Harris hip scores improved from a mean of 50 points (range, 20-66 points) preoperatively to a mean of 92 points (range, 64-100 points) at final follow-up. The score differed in each Charnley functional class, with a mean of 93 points (range, 72-100 points) in 57 hips of class A (no other joint involvement); 90 points (range, 58-100 points) in 26 hips of class B (opposite hip involvement); and 85 points (range, 37-100 points) in 26 hips of class C (multiple joint involvement or severe systemic disease). Out of 106 hips that had a full radiographic evaluation performed, 103 femoral components revealed stable bony ingrowth, 2 revealed stable fibrous ingrowth, and 1 showed migration with progressive loosening. This patient with radiographic loosening has minimal symptoms and has not required or been offered further surgery (Harris hip score of 86 points). The low aseptic loosening rate (2%) at minimum 5-year follow-up compares favorably with any cemented or cementless series. The osteolysis that was seen was focal and localized. The short follow-up does not allow determination of progression. There were no cases of distal osteolysis. We attribute the improved results from reported first-generation experience to multiple factors, including increased number of sizes (9 vs 6), increased proportional metaphyseal size, improved polyethylene manufacture (ram extruded vs machined), improved acetabular locking mechanism, and change to 26-mm from 32-mm femoral heads.
  The Journal of Arthroplasty 12/1999; 14(8):930-9. · 2.38 Impact Factor
• Article: Eliminating patellofemoral complications in total knee arthroplasty: clinical and radiographic results of 121 consecutive cases using the Duracon system.

  M A Mont, T R Yoon, K A Krackow, D S Hungerford
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  ABSTRACT: This study reports the minimum 5-year follow-up of our experience with the Duracon Total Knee Arthroplasty System. A total of 121 consecutive total knee replacements using the Duracon system (Howmedica, Rutherford, NJ) were performed in 104 patients. Three patients died before the 5-year follow-up and were excluded from the final evaluation. The remaining 118 knees (101 patients) were assessed at a mean follow-up of 65 months (range, 60-80 months). The knee diagnoses were osteoarthritis in 97 patients, rheumatoid arthritis in 2 patients, osteonecrosis in 1 patient, and pigmented villonodular synovitis in 1 patient. The mean age was 70 years (range, 28-85 years). There were no reoperations for aseptic loosening, and there have been no reoperations for patellofemoral problems. At final follow-up evaluation, 112 knees (96%) had good or excellent results, and 6 knees (4%) had poor clinical results or went on to revision. For the surviving knees, the preoperative Knee Society objective score improved from a mean of 52 points (range, 20-72 points) to a final follow-up mean of 94 points (range, 66-100 points). Five knees needed reoperations: 2 knees in 1 patient because of acute hematogenous infection at 12 months, 1 knee because of a supracondylar femur fracture, 1 because of a patellar tendon rupture, and 1 to increase polyethylene thickness because of instability. The lack of aseptic loosening at the minimum 5-year follow-up compares favorably with any cemented or cementless series of knee replacement. The almost complete absence of patellofemoral complications in this series also indicates that the design changes, with particular attention to the trochlea design and patellofemoral contact throughout full flexion, have achieved their intended purpose. The results are encouraging at midterm, awaiting true long-term (15-20 years) follow-up.
  The Journal of Arthroplasty 07/1999; 14(4):446-55. · 2.38 Impact Factor
• Article: Atraumatic osteonecrosis of the talus.

  R E Delanois, M A Mont, T R Yoon, M Mizell, D S Hungerford
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  ABSTRACT: Thirty-seven ankles in twenty-four patients were treated at our institution between July 1, 1974, and December 31, 1996, for atraumatic osteonecrosis of the talus. This group represents 2 per cent of the 1056 patients who were managed for osteonecrosis during this period. There were twenty-one women and three men, and their mean age was forty years (range, twenty-six to sixty-two years) at the time of the diagnosis. Thirteen (54 per cent) of the twenty-four patients had bilateral involvement. Sixteen patients (67 per cent) had a disease that affects the immune system, including systemic lupus erythematosus (thirteen patients), scleroderma (one), insulin-dependent diabetes mellitus (one), and multiple sclerosis (one). Four patients had a history of regular alcohol use, and four patients had a history of moderate smoking. One patient had a protein-S deficiency, one patient had had a renal transplant, and one patient had a history of asthma. Two patients had no identifiable risk factors for osteonecrosis [corrected]. Fifteen patients (63 per cent) had involvement of other large joints. The mean duration of symptoms before the patients were seen was 5.4 months (range, two months to two years). The mean ankle score at the time of presentation was 34 points (range, 2 to 75 points), according to the system of Mazur et al. A radiographic review revealed that, according to the system of Ficat and Arlet, eight ankles had stage-III or IV disease of the talus at presentation. The remaining twenty-nine ankles had stage-II disease. The osteonecrosis was seen in the posterolateral aspect of the talar dome (zones III and IV on the sagittal images and zones II, III, and IV on the coronal images) in twenty-two of the twenty-three ankles for which magnetic resonance images were available. The osteonecrosis was seen in the anteromedial aspect of the talar dome (zones I and II on the sagittal images and zone I on the coronal images) in the remaining ankle. Bone scans, which were available for eleven ankles, revealed increased uptake in the talus. All patients were initially managed non-operatively with restricted weight-bearing, an ankle-foot orthosis, and use of analgesics; two ankles responded to this regimen. Thirty-two ankles that remained severely symptomatic were treated with core decompression, which was useful in the treatment of precollapse (stage-II) disease. Twenty-nine of these ankles had a fair-to-excellent clinical outcome a mean of seven years (range, two to fifteen years) postoperatively; the remaining three ankles had an arthrodesis after the core decompression failed. Three ankles were treated initially with an arthrodesis for postcollapse (stage-III or IV) disease. All six of the ankles that had an arthrodesis fused, at a mean of seven months (range, five to nine months) postoperatively. When patients who have a history of osteonecrosis are seen because of pain in the ankle, the diagnosis of osteonecrosis of the talus should be considered. Early detection may allow the ankle to be treated non-operatively or with core decompression and thus reduce the need for arthrodesis. We also believe that when a patient has osteonecrosis of the talus, the hips should be screened with use of standard radiography or magnetic resonance imaging, or both.
  The Journal of Bone and Joint Surgery 05/1998; 80(4):529-36. · 3.27 Impact Factor