Biomedical subjects
M D Miller
Publications and source records attributed to M D Miller.
Health care insurance for retired employees.
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Uterine response to nerve stimulation; relation to hormonal status and catecholamines.
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Today's problems in voluntary financing mechanisms.
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Ideal tibial tunnel length for endoscopic anterior cruciate ligament reconstruction.
A successful single-incision endoscopic anterior cruciate ligament reconstruction using bone-patellar tendon-bone autograft requires attention to many technical details. The emphasis of placing the femoral bone plug flush with the opening of the femoral tunnel results in distal shift of the graft. Longer tibial tunnels are required to prevent excessive graft extrusion. The purpose of this study is to compare four direct and indirect measurement methods of tibial tunnel preparation to determine which method can be used to create consistently reproducible tibial tunnels that prevent excessive extrusion or recession of the graft within the tunnel. Tunnels placed at the empiric angles of 40 degrees, 50 degrees, and 60 degrees to the tibial plateau resulted in the incidence of acceptable tibial tunnel lengths of 44%, 83%, and 39%, respectively. Tunnels placed at an angle determined by the formula "N + 7" where 7 degrees is added to the patellar tendon length (N) resulted in acceptable tunnels 89% of the time. Direct measurement methods using the formulas "graft - 50 mm" and "N + 2 mm" resulted in acceptable tibial tunnels of 44% and 100%, respectively. We recommend using the "N + 7" in conjunction with the "N + 2 mm" formula to obtain the advantages of both indirect and direct measurement methods.
Revision cruciate ligament surgery with retention of femoral interference screws.
As the popularity of cruciate ligament reconstruction continues to escalate, the need for revision surgery has also increased. Revision cruciate ligament surgery is often associated with difficult technical challenges including removing previously placed femoral interference screws. Not only can this hardware be difficult to remove, interference screw extraction often creates a large bony defect immediately adjacent to the revised femoral tunnel that can jeopardize the fixation of the new cruciate ligament graft. It is often possible to perform revision cruciate ligament reconstruction without removing femoral interference screws. This technical note provides several examples of this technique. Routine removal of femoral interference screws during revision cruciate ligament surgery is often not necessary.
Comparison of knowledge-based and distance geometry approaches for generation of molecular conformations.
A knowledge-based approach for generating conformations of molecules has been developed. The method described here provides a good sampling of the molecule's conformational space by restricting the generated conformations to those consistent with the reference database. The present approach, internally named et for enumerate torsions, differs from previous database-mining approaches by employing a library of much larger substructures while treating open chains, rings, and combinations of chains and rings in the same manner. In addition to knowledge in the form of observed torsion angles, some knowledge from the medicinal chemist is captured in the form of which substructures are identified. The knowledge-based approach is compared to Blaney et al.'s distance geometry (DG) algorithm for sampling the conformational space of molecules. The structures of 113 protein-bound molecules, determined by X-ray crystallography, were used to compare the methods. The present knowledge-based approach (i) generates conformations closer to the experimentally determined conformation, (ii) generates them sooner, and (iii) is significantly faster than the DG method.
Tenofovir (PMPA) is less susceptible to pyrophosphorolysis and nucleotide-dependent chain-terminator removal than zidovudine or stavudine.
Pyrophosphorolysis, the removal of nucleoside chain-terminators by a pyrophosphate (PPi) acceptor molecule, and a similar mechanism (nucleotide-dependent chain-terminator removal) which uses ATP as an acceptor molecule have been proposed as mechanisms of zidovudine (AZT) resistance. Recombinant HIV-1 wild-type reverse transcriptase (RT) and a mutant RT enzyme containing the AZT/thymidine analog resistance mutations D67N/K70R/T215Y were analyzed for pyrophosphorolysis and nucleotide-dependent chain-terminator removal activities. Our results confirm that pyrophosphorolysis and nucleotide-dependent chain-terminator removal are potential mechanisms of AZT and d4T resistance. However, tenofovir is less efficiently removed by pyrophosphorolysis and by nucleotide-dependent mechanisms. These results are consistent with the minor changes in susceptibility to tenofovir of the AZT/thymidine analog-resistant HIV RT mutants and the corresponding resistance of these mutants to AZT. The inability to remove tenofovir efficiently by these mechanisms may contribute to the durability of the HIV RNA response observed in patients treated with the oral prodrug, tenofovir disoproxil fumarate.
Antiviral activity of tenofovir (PMPA) against nucleoside-resistant clinical HIV samples.
The presence of the lamivudine-associated M184V RT mutation increases tenofovir susceptibility in multiple HIV genotypes. Tenofovir is uniquely active against multinucleoside-resistant HIV expressing the Q151M mutation, but shows reduced susceptibility to the T69S insertion mutations. HIV with common forms of zidovudine and lamivudine resistance are susceptible to tenofovir, corroborating phase II clinical results demonstrating the activity of tenofovir DF in treatment-experienced patients.
Medial patellofemoral ligament injury following acute transient dislocation of the patella: MR findings with surgical correlation in 14 patients.
PURPOSE: The purpose of this study was to determine the accuracy of MRI in determining both the extent and the location of injury to the medial patellofemoral ligament (MPFL). METHOD: MR findings were compared to the surgical results of 14 consecutive patients who experienced transient patellar dislocation. Two musculoskeletal radiologists, blinded to the surgical results, retrospectively reviewed the MR studies, and a consensus reading was obtained. RESULTS: Surgery demonstrated complete disruption of the MPFL in 7 of 14 patients (50%), with stretching or partial tearing of the MPFL in the remaining 7 (50%) patients. MRI was 85% sensitive and 70% accurate in detecting MPFL disruption. Vastus medialis obliquus muscle elevation was present in 12 of 14 (85%). CONCLUSION: MRI accurately depicts both the extent and the location of MPFL injury following transient patellar dislocation and can therefore play a significant role in directing surgical management of these patients.
Evaluation and need of education programs for community hospital nurses providing neonatal care.
Phase I: Of 204 RN's providing neonatal care in community hospitals in east Georgia and who were examined using a standardized test, those from large hospitals (greater than 1,000 live births/year) performed significantly better than those from medium or small hospitals (P less than .05). Also, there was negative correlation between test scores and years of experience in areas of the hospital other than the nursery and percent of employment time currently spent in areas of the hospital other than the nursery. Phase II: An educational program in neonatal nursing was then provided to 48 RN's by the authors and to 12 RN's by peer-instructors. At the end of the course of instruction a posttest was given. Thirteen RN's who received no formal instruction served as a control group. On the posttest, both experimental groups performed significantly better than the control group (P less than .01), but the group taught by the authors scored significantly higher than the group taught by peers (P less than .05). Educational programs taught by RN's from the community hospital staff are not as effective in regional educational programs as instruction by course by developers.
Preparing librarians to meet the challenges of today's health care environment.
OBJECTIVE: Refine the understanding of the desirable skills for health sciences librarians as a basis for developing a training program model that reflects the fundamental changes in health care delivery and information technology. DESIGN: A four-step needs assessment process: focus groups developed lists of desirable skills; the research team organized candidate skills into a taxonomy; a survey of a random sample of librarians and library users assessed perception of importance of individual skills; and the research team framed, as a unifying hypothesis, a training model. SURVEY METHODS: The survey was distributed to random samples of 150 librarians, stratified by type of library, and 150 library users, stratified by type of use. A non-randomized sample was obtained by mounting the survey on a World Wide Web server. The survey instrument included 96 distinct skills organized into 13 categories. Respondents rated the importance of each skill on a Likert scale and provided a separate ranking by identifying the ten most important skills for the profession. RESULTS: Among the participants, 51% of librarians and 36% of library users responded to the survey. All categories of skills were rated above the midpoint of priority on the Likert scale. All groups rated personality characteristics and skills as most important, with an understanding of the health sciences, education, and research being rated comparably to technical skills. CONCLUSIONS: Health sciences librarians need a new educational model that provides them with broad-based tools to discover new roles and new resources for acquiring individual skills as the need arises. A unifying training model would involve trainees in developing their learning plan in a way that promotes proactive inquiry and self-directed learning, and it would rotate the trainees through projects to provide skills and an understanding of end-user work processes.
Imaging techniques for the evaluation of glenohumeral instability.
The ability to image lesions associated with glenohumeral instability has evolved significantly over the past 2 decades. In the past, several imaging techniques ranging from conventional radiography to computerized axial arthrography and, most recently, to magnetic resonance imaging have been used to depict various labral abnormalities. In most instances, conventional radiography remains the initial imaging study for evaluating the patient with persistent shoulder pain and instability. Recently, however, magnetic resonance arthrography has been firmly established as the imaging modality of choice for demonstrating specific soft tissue abnormalities associated with glenohumeral instability. This article will review the role of various imaging modalities including conventional radiography, conventional arthrography, computerized axial arthrography, magnetic resonance imaging, and magnetic resonance arthrography. Emphasis will be placed on the role of magnetic resonance arthrography as it pertains to the lesions associated with glenohumeral instability. A thorough discussion of the appearance of normal anatomic structures, anatomic variations that mimic abnormality, and the various lesions associated with glenohumeral instability will be provided.
Rupture of the pectoralis major muscle in a collegiate football player. Use of magnetic resonance imaging in early diagnosis.
We have reported an unusual case of pectoralis major muscle rupture and repair. There were three interesting aspects of this case. First, the injury occurred in a football player with an unusual mechanism of injury. Second, MRI using special techniques was valuable in confirming the diagnosis acutely and in planning treatment. Finally, we reported on the use of suture anchors to secure the avulsed tendon. We recommend the early use of MRI for diagnosis and in planning treatment of suspected pectoralis major muscle ruptures.
Meniscal repair. An experimental study in the goat.
To evaluate the healing potential of the meniscus, we created a longitudinal medial meniscal tear in both knees of 24 adult goats (48 knees). In all goats, the meniscus was repaired in one knee and left unrepaired in the other. The goats were placed into one of three groups based on the location of the tear and the status of the anterior cruciate ligament. At 6 months' followup, an arthrogram was obtained and the menisci were examined. In knees with an intact anterior cruciate ligament, tears in the peripheral 20% to 25% of the meniscus healed in six of seven repaired menisci, but in only one of seven of the unrepaired menisci. Tears in the peripheral 40% to 50% healed in only one of the eight repaired menisci and in none of the unrepaired menisci. When the anterior cruciate ligament was incised, tears in the peripheral 20% to 25% of the meniscus healed in only 1 of 8 repaired menisci and in none of the unrepaired menisci; the rest developed into complex tears. Arthrography was 92% accurate in predicting the status of meniscal repair. This study supports current clinical practices in meniscal repair and emphasizes the importance of tear location and knee stability in successful meniscal repair.
Posterior tibial tunnel placement to avoid anterior cruciate ligament graft impingement by the intercondylar roof. An in vitro and in vivo study.
Recent recommendations to "customize" tibial tunnel placement based on the slope of the intercondylar roof and the amount knee hyperextension were derived from a series of cases with graft impingement by the intercondylar roof. We believe that this impingement is caused by anterior placement of the graft and not by variations of notch anatomy among individual patients. In Phase 1 of this study, we drilled tibial tunnels in the posteromedial aspect of the anterior cruciate ligament "footprint" after the ligament was excised in cadaveric knees. We then passed an impingement rod into the back of the knee joint. Lateral radiographs with the knee in hyperextension were taken of each specimen, and the distance between the superior border of the rod and intercondylar roof was measured. In Phase 2, we prospectively obtained lateral hyperextension radiographs of 75 consecutive knees with anterior cruciate ligament reconstructions and evaluated them for graft impingement based on recently published guidelines. In Phase 1, we found no cases of impingement and an average roof clearance of 8.3 mm. In Phase 2, we noted no cases of severe impingement, 3 cases of moderate impingement (4%), and 72 cases (96%) with no impingement. We conclude that posteromedial tibial tunnel placement alone is adequate to avoid graft impingement in almost all patients. Individualized tibial tunnel placement with specialized tibial guidance systems is not necessary.
The natural history of bone bruises. A prospective study of magnetic resonance imaging-detected trabecular microfractures in patients with isolated medial collateral ligament injuries.
We conducted a prospective study to evaluate bone bruises, or trabecular microfractures, associated with isolated medial collateral ligament injuries. Magnetic resonance imaging was performed on 65 patients with isolated medial collateral ligament injuries determined by physical examination and imaging studies. Of these 65 patients, 29 (45%) had associated trabecular microfractures. Follow-up images were completed at various intervals on 24 of these 29 patients (83%). Complete resolution of these lesions was observed in all cases. This process appears to occur as a result of gradual diffusion over a period of 2 to 4 months. Bone bruises associated with medial collateral ligament injuries are approximately one-half as common as bone bruises associated with anterior cruciate ligament injuries. However, medial collateral ligament-associated trabecular microfractures may be a better natural history model because these injuries are treated nonoperatively.
Meniscal repair in the goat model. The use of healing adjuncts on central tears and the role of magnetic resonance arthrography in repair evaluation.
We evaluated the effect of adjunctive healing measures on central tears of the adult goat medial meniscus and the role of magnetic resonance arthrography in the assessment of menisci that have undergone a repair. Peripheral tears were made unilaterally in the medial menisci of seven goats in Group I and repaired with nonabsorbable suture. Six Group II goats had central medial meniscal tears repaired as in Group I plus an exogenous fibrin clot. Eight Group III goats had central tears plus abrasion of the parameniscal synovium and tear edges. Six months after surgery, a magnetic resonance imaging scan and a magnetic resonance arthrogram were obtained and the menisci were examined grossly. Group I goats showed healing in all seven knees. Central tears repaired with a fibrin clot (Group II) showed healing in one of six knees (17%). Central tears repaired with abrasion (Group III) showed healing in seven of eight knees (87.5%). Magnetic resonance arthrography was 100% accurate in detecting the presence or absence of complete residual tears. This study supports the current trend of using adjunctive measures for repair of central tears. Furthermore, abrasion of the parameniscal synovium and the tear edges appears to be more effective than the use of an exogenous fibrin clot. Magnetic resonance arthrography is useful in the evaluation of menisci that have undergone repair.