Kenneth E Davis

Saint Francis Hospital, Tulsa, Oklahoma, United States

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Publications (31)88.14 Total impact

  • John B Meding · Merrill A Ritter · Kenneth E Davis · Maggie Hillery ·
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    ABSTRACT: Purpose: The purpose of this study was to evaluate the same femoral component after cemented and uncemented total hip arthroplasty. The results were compared in terms of hip scores, subsidence, and survivorship. Methods: Between 1986 and 1996, 1017 primary THAs were implanted in 882 patients using the same porous-coated, titanium-alloy, femoral component. 507 cemented stems (441 patients) and 510 uncemented stems (441 patients) were compared. The primary diagnosis was osteoarthritis in 866 hips (85%). 541 patients were female (61%). The clinical results were evaluated based on the Harris hip score. Radiographs were evaluated at each follow-up for stem subsidence and loosening. Kaplan-Meier survival analysis was used to determine stem survivorship. The average follow-up of the entire cohort was 13.2 years (range, 2-26 y). Results: The average Harris Hip Scores at 20 years follow-up was 87 points in the cemented group and 85 points in the uncemented group. Pain scores averaged 42 and 38 in the cemented and uncemented group, respectively, at 20 years. There were 6 loose stems identified in the cemented group (1.2%) and 2 loose stems in the uncemented group (0.4%). Cemented and uncemented stem survivorship at 20 years was 98.1% and 99.6%, respectively. There was no difference in cemented or uncemented stem survivorship at any time period. Conclusions: Although there were more cases of aseptic cemented femoral component loosening, there was no significant difference in stem survivorship out to 20 years whether this stem was implanted with or without cement.
    Hip international: the journal of clinical and experimental research on hip pathology and therapy 10/2015; DOI:10.5301/hipint.5000296 · 0.76 Impact Factor
  • Philip M. Faris · Merrill A. Ritter · Kenneth E. Davis · Hana M. Priscu ·
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    ABSTRACT: The development of a new total knee system as a successor prosthesis in total knee arthroplasty (TKA) requires clinical outcome improvement. 10,843 TKAs were performed of which 9169 utilized the Anatomical Graduated Component (AGC) and 1674 utilized the Vanguard prosthesis (both Biomet, Warsaw, IN). Survival rates at ten years postoperatively for the AGC and Vanguard were 98.7% and 98.4% (P=.4897) respectively. The top reasons for component failure were loosening (AGC: 0.33% (86.7% tibial); Vanguard: 0.36% (66.7% tibial)), polyethylene wear, and instability. These results reveal similar outcomes in both designs, with relatively few revisions and high survival rates at ten years postoperatively. This abstract offers data concerning the usefulness of the Vanguard Total Knee System as a successor to the Anatomical Graduated Component. Copyright © 2015 Elsevier Inc. All rights reserved.
    The Journal of Arthroplasty 05/2015; DOI:10.1016/j.arth.2015.04.042 · 2.67 Impact Factor

  • Open Journal of Orthopedics 01/2015; 05(06):151-156. DOI:10.4236/ojo.2015.56020
  • David M. Fang · Tatsuya Sueyoshi · Kenneth E. Davis · Merrill A. Ritter ·

    Open Journal of Orthopedics 01/2015; 05(07):175-178. DOI:10.4236/ojo.2015.57023

  • Open Journal of Orthopedics 01/2015; 05(08):245-252. DOI:10.4236/ojo.2015.58033
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    ABSTRACT: The purpose of this study was to investigate the use for screws and cement, and primary and revision specific prosthesis for revision TKR. Between July 1989 and February 2010, 839 consecutive revision TKAs were performed, with 609 knees meeting inclusion criteria. At 17 years followup, Kaplan-Meier survivorship was .9859 for revision specific prosthesis with screws and cement, .9848 for revision prosthesis with no screws, 0.9118 for primary prosthesis with screws, and .9424 for primary prosthesis with no screws. Revision TKRs using screws had greater defects (p < .0001). Use of revision prosthesis along with screws and cement to correct largely defective revision TKRs is highly recommended.
    The Journal of Arthroplasty 12/2014; 30(1). DOI:10.1016/j.arth.2014.07.027 · 2.67 Impact Factor
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    ABSTRACT: The orthopedic literature has not shown a universal and replicated difference, outside of flexion, in clinical results between posterior cruciate ligament retention and posterior cruciate ligament substitution in total knee arthroplasty.
    HSS Journal 07/2014; 10(2):107-15. DOI:10.1007/s11420-014-9389-5
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    ABSTRACT: The purpose of this study was to investigate screws and cement for large tibial bone defects during primary TKA. Of 14,686 consecutive primary TKAs performed between December 1988 and February 2010, 256 received screws and cement for tibial defects. Cox regression was used for the analysis. 20-year survival probability was 0.9897 (screws) and 0.9339 (no screws) (P=.4225 log-rank). Tibial bone condition was significantly worse in knees receiving screws (P<.0001) with 73.0% having defects in the screws group and 3.4% (P<.0001) for non-screws. Radiolucency appeared in 13.7% (screws) and 6.4% (no screws) postoperatively. Screws were $137 each, wedges $910 to $2240. Knees with tibial defects and screws performed similarly if not better than knees without defects at substantially lower cost than alternatives.
    The Journal of arthroplasty 12/2013; 29(6). DOI:10.1016/j.arth.2013.12.023 · 2.67 Impact Factor
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    ABSTRACT: Implant survival after total knee arthroplasty has historically been dependent on postoperative knee alignment, although failure may occur when alignment is correct. Preoperative knee alignment has not been thoroughly evaluated as a possible risk factor for implant failure after arthroplasty. The purpose of this study was to analyze the effect of preoperative knee alignment on implant survival after total knee arthroplasty. We performed a retrospective review of 5342 total knee arthroplasties performed with use of cemented Anatomic Graduated Component implants from 1983 to 2006. Each knee was independently measured preoperatively and postoperatively for overall coronal alignment. Neutral ranges for preoperative and postoperative alignment were defined by means of Cox proportional hazards regression. The overall failure rate was 1.0% (fifty-four of 5342 prostheses); failure was defined as aseptic loosening of the femoral and/or tibial component. The average preoperative anatomical alignment (and standard deviation) was 0.1° ± 7.7° of varus (range, 25° of varus to 35° of valgus), and the average postoperative anatomical alignment (and standard deviation) was 4.7° ± 2.5° of valgus (range, 12° of varus to 20° of valgus). The failure rate in knees in >8° of varus preoperatively (2.2%; p = 0.0005) or >11° of valgus preoperatively (2.4%; p = 0.0081) was elevated when compared with knees in neutral preoperatively (0.71%). Knees with preoperative deformities corrected to postoperative neutral alignment (2.5° through 7.4°) had a lower failure rate (1.9%) than undercorrected or overcorrected knees (3.0%) (p = 0.0103). Knees with postoperative neutral alignment, regardless of preoperative alignment, had a lower failure rate (0.74%) than knees with postoperative alignment of <2.5° or >7.4° of anatomic valgus (1.7%) (p < 0.0001). Patients with excessive preoperative alignment (>8° of varus or >11° of valgus) have a greater risk of failure (2.3%). Neutral postoperative alignment (2.5° through 7.4° of valgus) improves (1.9% for preoperatively deformed knees) but does not completely eliminate the risk of failure (0.5% for knees that were neutral both preoperatively and postoperatively). Careful attention should be paid to knee alignment during total knee arthroplasty, especially for patients with severe preoperative deformities. Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.
    The Journal of Bone and Joint Surgery 01/2013; 95(2):126-31. DOI:10.2106/JBJS.K.00607 · 5.28 Impact Factor
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    ABSTRACT: The purpose of this study was to determine the effect of tibiofemoral alignment, femoral and tibial component alignment, and body-mass index (BMI) on implant survival following total knee replacement. We retrospectively reviewed 6070 knees in 3992 patients with a minimum of two years of follow-up. Each knee was classified on the basis of postoperative alignment (overall tibiofemoral alignment and alignment of the tibial and the femoral component in the coronal plane). Failures (defined as revision for any reason other than infection) were analyzed with use of Cox regression; patient covariates included overall alignment, component alignments, and preoperative BMI. Failure was most likely to occur if the orientation of the tibial component was <90° relative to the tibial axis and the orientation of the femoral component was ≥8° of valgus (failure rate, 8.7%; p < 0.0001). In contrast, failure was least likely to occur if both the tibial and the femoral component were in a neutral orientation (≥90° and <8° of valgus, respectively) (failure rate, 0.2% [nine of 4633]; p < 0.0001). "Correction" of varus or valgus malalignment of the first implanted component by placement of the second component to attain neutral tibiofemoral alignment was associated with a failure rate of 3.2% (p = 0.4922) for varus tibial malalignment and 7.8% (p = 0.0082) for valgus femoral malalignment. A higher BMI was associated with an increased failure rate. Compared with patients with a BMI of 23 to 26 kg/m2, the failure rate in patients with a BMI of ≥41 kg/m2 increased from 0.7% to 2.6% (p = 0.0046) in well-aligned knees, from 1.6% to 2.9% (p = 0.0180) in varus knees, and from 1.0% to 7.1% (p = 0.0260) in valgus knees. Attaining neutrality in all three alignments is important in maximizing total knee implant survival. Substantial "correction" of the alignment of one component in order to compensate for malalignment of the other component and thus produce a neutrally aligned total knee replacement can increase the risk of failure (p = 0.0082). The use of conventional guides to align a total knee replacement provides acceptable alignment; however, the surgeon should be aware that the patient's size, as determined by the BMI, is also a major factor in total knee replacement failure.
    The Journal of Bone and Joint Surgery 09/2011; 93(17):1588-96. DOI:10.2106/JBJS.J.00772 · 5.28 Impact Factor
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    John B Meding · E Michael Keating · Kenneth E Davis ·
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    ABSTRACT: Polyethylene wear may be affected by the type of polyethylene resin, manufacturing technique, degree of thermal stabilization, and sterilization technique. We therefore compared femoral head penetration into the PE and cup survival using the same cup system with different PE resins, manufacturing, and sterilization techniques. Our study group consisted of 1912 THAs performed using the same uncemented cup and identical 28-mm cobalt-chrome heads. The polyethylene varied as follows: Group 1 (94 cups), GUR 4150 resin, ram-extruded, sterilized in air, no barrier packaging; Group 2 (74 cups), same as Group 1 but sterilized in argon; Group 3 (75 cups), Himont 1900 resin, compression-molded bar stock, sterilized in argon, no barrier packaging; Group 4 (620 cups), same as Group 3 except with barrier packing; Group 5 (711 cups), GUR 1050 resin, compression-molded bar stock, sterilized in argon gas with barrier packaging; and Group 6 (338 cups), GUR 1050 resin, compression-molded bar stock, sterilized in argon with barrier packaging, irradiated with 50 kGy, heated below melting temperature, machined, and finally placed in nonbarrier packaging with gas plasma sterilization. Minimum followup was 2 years (average, 7 years; range, 2-17 years). Femoral head penetration averaged 0.05 mm per year for Groups 5 and 6 and was substantially lower than for Groups 1 to 4. Cup survival was higher at seven years in Groups 3, 4, and 5, and at 10 years in group 4 when compared to groups 1, 2, and 3. We observed lower FHP rates and higher cup survival with polyethylene machined from direct compression-molded bar stock, sterilized in argon gas, with barrier packaging. Level III Therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
    Clinical Orthopaedics and Related Research 02/2011; 469(2):405-11. DOI:10.1007/s11999-010-1571-6 · 2.77 Impact Factor
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    David M Fang · Merrill A Ritter · Kenneth E Davis ·
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    ABSTRACT: A recent study has challenged the premise that well-aligned total knee arthroplasties (TKAs) have better survival than outliers. This study examines the importance of overall coronal alignment as a predictor for revision. Patients with primary TKAs were stratified into neutral, varus, and valgus alignment groups based on the postoperative tibiofemoral angle. In 6070 knees (3992 patients), there were 51 failures (0.84%): 21 (0.5%) in the neutral group, 18 (1.8%) in the varus group, and 12 (1.5%) in the valgus group. The best survival was for overall alignment between 2.4 degrees and 7.2 degrees of valgus. Varus knees failed primarily by medial tibia collapse, whereas valgus knees failed from ligament instability. Outliers in overall alignment have a higher rate of revision than well-aligned knees. The goal of TKA should be to restore alignment within 2.4 degrees to 7.2 degrees of valgus.
    The Journal of arthroplasty 07/2009; 24(6 Suppl):39-43. DOI:10.1016/j.arth.2009.04.034 · 2.67 Impact Factor
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    ABSTRACT: The study aims to delineate the deep infection rates and infection risk factors for primary total knee and total hip arthroplasty patients. A retrospective review was conducted on 6108 patients from 1991 to 2004. The deep infection cases were compared to the noninfected cohort whereby infection risk factors were identified. Of the 8494 joint arthroplasties, 43 (0.51%) developed a deep infection (30 total knee arthroplasties, 13 total hip arthroplasties). Patients with a body mass index greater than 50 had an increased odds ratio of infection of 21.3 (P < .0001). Diabetic patients were 3 times as likely to become infected compared to nondiabetic patients (P = .0027). Simultaneous bilateral total joint arthroplasties were found to have developed infection 3 times less frequently than those performed as unilateral procedures (P = .0024). The average age in our infection cohort was 64.3 and 68.4 in the noninfected cohort. In this retrospective review study, obesity, diabetes, and younger age were found to be risk factors for joint arthroplasty infection.
    The Journal of arthroplasty 07/2009; 24(6 Suppl):84-8. DOI:10.1016/j.arth.2009.05.016 · 2.67 Impact Factor

  • The Journal of Arthroplasty 02/2009; 24(2):e36. DOI:10.1016/j.arth.2008.11.050 · 2.67 Impact Factor
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    ABSTRACT: Range of motion is recognized as an important indicator of the success of a total knee replacement; however, an optimal range of motion has yet to be defined. This study was designed to determine the optimal range of motion for knee function after total knee arthroplasty with a posterior cruciate-retaining prosthesis. We retrospectively reviewed 5556 primary total knee arthroplasties performed with posterior cruciate-retaining prostheses between 1983 and 2003. The relationship between postoperative range of motion and pain, walking ability, stair-climbing ability, and knee function scores was examined at three to five years postoperatively. The relationship between a postoperative flexion contracture or hyperextension and knee function was also examined. Patients with 128 degrees to 132 degrees of motion obtained the highest scores for pain, walking, and knee function and the highest Knee Society scores. The outcomes became substantially compromised with motion of <118 degrees . Patients with 133 degrees to 150 degrees of motion had the highest scores for stair-climbing. A postoperative flexion contracture and hyperextension were associated with lower scores for pain, walking, stair-climbing, and knee function. The best functional results following total knee arthroplasty are achieved with 128 degrees to 132 degrees of motion. A postoperative flexion contracture and hyperextension of >or=10 degrees are associated with a poorer outcome except that stair-climbing is improved with more motion.
    The Journal of Bone and Joint Surgery 05/2008; 90(4):777-84. DOI:10.2106/JBJS.F.01022 · 5.28 Impact Factor
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    ABSTRACT: The purpose of this study was to quantify the effect of sex on the clinical outcome and survivorship of a total knee arthroplasty (TKA) with clinical and radiographic follow-up. Seven thousand three hundred twenty-six primary AGC (Biomet, Warsaw, Ind) cruciate-retaining TKAs were performed from 1987 to 2004. Of these, 59.5% were performed on women. We examined preoperative and postoperative Knee Society knee score, function scores, pain scores, walking ability, stair-climbing ability, flexion, and implant survivorship based on sex. Female sex was associated with lower overall preoperative clinical scores for all parameters (P < .01). Improvement in Knee Society knee score and flexion was greater for women (P = .006), and there were equal pain relief and walking improvements for both sexes (P < .32). Stair and function score improvements were greater for men (P = .002). Implant survival was 98% for women and men at 15 years (P = .4684). We conclude that improvement after TKA is similar for men and women, with few clinically significant differences. Sex-specific implants would appear to offer no clinical advantage.
    The Journal of Arthroplasty 04/2008; 23(3):331-6. DOI:10.1016/j.arth.2007.10.031 · 2.67 Impact Factor
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    ABSTRACT: This study examined the role that flexion contracture plays in postoperative outcomes after total knee arthroplasty using a retrospective database review. The relationships between preoperative and postoperative knee extension, walking ability, stair climbing ability, Knee Society scores, pain scores, and knee function scores were studied in 5,622 knees. A preoperative flexion contracture was associated with an increased incidence of a persistent postoperative flexion deformity. A postoperative flexion contracture was associated with poorer postoperative results. Furthermore, a postoperative hyperextension deformity of greater than 10 degrees was associated with an increased risk of suboptimal pain and Knee Society scores. Knee extension deformities play a substantial detrimental role in the functional outcome of primary total knee arthroplasty.
    The Journal of Arthroplasty 01/2008; 22(8):1092-6. DOI:10.1016/j.arth.2006.11.009 · 2.67 Impact Factor
  • Kenneth E Davis · Merrill A Ritter · Michael E Berend · John B Meding ·
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    ABSTRACT: Unlike the knee, range of motion has been of questionable value in evaluating clinical outcome after THA. We retrospectively analyzed the ranges of motion (flexion, abduction, adduction, external rotation, internal rotation, and flexion contracture) of 1383 patients (1517 hips) having primary THA. We recorded Harris hip score components for walking distance, stair climbing, socks and shoes, sitting, pain, presence of limp, and use of support devices. Postoperative hip motion was defined as high (115 degrees of flexion, 25 degrees of abduction, 20 degrees of external rotation, and less than 20 degrees of flexion contracture), average (90 degrees -114 degrees of flexion, 16 degrees -24 degrees of abduction, or 11 degrees -19 degrees of external rotation, and less than 20 degrees of flexion contracture), or low (less than 90 degrees of flexion, 15 degrees or less of abduction, 10 degrees or less of external rotation, or 20 degrees or more of flexion contracture) motion. We correlated this with high, average, or poor postoperative Harris hip scores. Hip motion was found to be correlated with postoperative hip function and may be more useful than previously thought in evaluating hip outcome.
    Clinical Orthopaedics and Related Research 01/2008; 465(465):180-4. DOI:10.1097/BLO.0b013e31815c5a64 · 2.77 Impact Factor
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    ABSTRACT: The effect of so-called stuffing of the patellofemoral compartment at the time of total knee arthroplasty (that is, increasing the anterior patellar displacement, the anteroposterior femoral size, or the combined anteroposterior patellofemoral size) has not been well studied. The purpose of the present study was to evaluate the effect of stuffing the patellofemoral compartment on the outcome of primary total knee arthroplasty. A retrospective review of 1100 primary total knee arthroplasties that had been performed in 1997 and 1998 was conducted. Eight hundred and thirty arthroplasties (75.5%) met the diagnostic and minimum two-year follow-up criteria for inclusion in this report. Radiographic measurements were made to determine preoperative and postoperative anterior patellar displacement, anteroposterior femoral size, combined anteroposterior patellofemoral size, anterior femoral offset, and posterior femoral offset. Regression analysis was performed to determine the effects of changes in these variables on the range of motion, the Knee Society Knee Score, the Knee Society Function Score, the Knee Society Pain Score, and the rate of lateral retinacular release. Preoperative to postoperative changes in anterior patellar displacement, anteroposterior femoral size, combined anteroposterior patellofemoral size, anterior femoral offset, and posterior femoral offset had no clinically meaningful effect on the range of motion of the knee or on any of the Knee Society scores. Increases in anterior patellar displacement were associated with a lower probability of the need for a lateral retinacular release. Increases in measured anteroposterior femoral size were associated with a higher probability of the need for lateral release. Even when combined, however, these relationships explained only 10.1% of the observed variance in the need for lateral retinacular release. Moreover, analyses indicated that patient gender, large as opposed to medium patellar size, and absolute femoral component size influenced the likelihood of lateral release more than did anterior patellar displacement and measured anteroposterior femoral size. Our findings do not support the widely held belief that stuffing of the patellofemoral joint results in adverse outcomes after total knee arthroplasty. Furthermore, the need for lateral release appears to be multifactorial and likely involves a more complex set of factors. Thus, without evidence of other identifiable causes of failure, we do not recommend revision for the treatment of pain of an overstuffed knee joint.
    The Journal of Bone and Joint Surgery 11/2007; 89(10):2195-203. DOI:10.2106/JBJS.E.01223 · 5.28 Impact Factor
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    ABSTRACT: In the past, total knee arthroplasty, although very successful, was only indicated for an elderly population. Recently though, several papers have been published confirming that total knee arthroplasty is effective in younger patients. This paper supports the results of those papers. In our study, 207 total knee arthroplasties were performed on patients 55 years old and younger using a posterior cruciate-retaining prosthesis. There was an overall survival rate of 97.6% with an average follow-up of 9.1 years. There were some minor variations in the outcome of the operation based on diagnosis (osteoarthritis vs. rheumatoid arthritis). The success also continued over time with an estimated survival rate of 94.8% at 12 years. Total knee arthroplasty is an effective operation in patients younger then 55 years old.
    The Knee 02/2007; 14(1):9-11. DOI:10.1016/j.knee.2006.10.010 · 1.94 Impact Factor