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Biomedical subjects

M D McKee

Publications and source records attributed to M D McKee.

At least 55 records · Page 3Linked to original sources
PubMed1999

Complications of intramedullary nailing for fractures of the humeral shaft: a review.

OBJECTIVES: The purpose of the present review is to document the complications associated with the use of locking humeral nails and to discuss the prevention and management of these complications. DATA SOURCES: Clinical and research experience supported by a Medline review of the English-language literature from 1985 to 1998. STUDY SELECTION: The majority of (clinical) information available was contained in retrospective reviews; only three prospective or randomized studies were identified (all in abstract form). Anatomical research regarding locking humeral nailing was also identified and included. DATA EXTRACTION: Because there were so few prospective studies available, a formal meta-analysis of data was not performed. This review focuses on a descriptive assessment of available information on specific complication-related topics. CONCLUSIONS: The attractive theoretical advantages of locking humeral nails have not been borne out in clinical studies. Complications such as shoulder pain, delayed union or nonunion, fracture about the implant, iatrogenic fracture comminution, and the difficulty in the reconstruction of failures have diminished their usefulness. The precise role of locking nails in the treatment of humeral shaft fractures has yet to be defined. At present, open reduction and compression plating remain the treatment of choice for humeral shaft fractures that require operative intervention.

Bone Plates↗
PubMed1999

Early detection of arterial bleeding in acute pelvic trauma.

OBJECTIVE: To determine the accuracy of intravenous contrast-enhanced computerized tomography (CECT) in the detection of potentially life-threatening retroperitoneal hemorrhage in patients sustaining pelvic fractures, acetabular fractures or both. DESIGN: Retrospective review of sequential patients identified over a 1-year period by using a prospectively collected trauma database at two Level I trauma centers. MATERIALS AND METHODS: A group of patients admitted to one of two Level I trauma centers with pelvic or acetabular injuries between September 1, 1995, and September 30, 1996, was identified by using a prospectively collected trauma database. From this cohort, we selected those individuals who had undergone intravenous CECT scanning within 24 hours after admission and who had an Abbreviated Injury Score more than 3 because of their pelvic injury. Those individuals who required arterial embolization for uncontrolled hemodynamic shock were categorized as having "significant arterial bleeding" attributable to their pelvic injury. Individuals who regained hemodynamic ,stability without embolization were categorized as having "no significant arterial bleeding." Two observers who were blinded to clinical information and the results of angiography reviewed all injury radiographs and computed tomographic scans. The presence or absence of contrast extravasation on intravenous CECT was recorded. Each case was then categorized into a 2 x 2 table depending on the presence of contrast extravasation on CECT and the need for arterial embolization to determine the accuracy of the "contrast extravasation sign." RESULTS: Of the 192 eligible patients, 111 met the inclusion criteria. Eleven patients required an angiogram for ongoing hemodynamic instability. The sensitivity of extravasation on contrast enhanced computed tomography representing a significant arterial bleeding was 80%, and the specificity was 98%. The predictive value of a positive contrast "extravasation sign" was 80%, whereas the predictive value of a negative test was 98%. The likelihood ratio of a positive test was 40.4, and the likelihood ratio of a negative test was 0.204. CONCLUSION: The finding of contrast extravasation on CECT is highly suggestive of significant arterial bleeding that requires early angiographic embolization to restore hemodynamic stability.

Abbreviated Injury Scale↗
PubMed1999

Mature full-thickness articular cartilage explants attached to bone are physiologically stable over long-term culture in serum-free media.

Mature tissue explants containing the entire depth of articular cartilage, calcified and uncalcified, attached to a thin layer of subchondral bone were isolated from bovine humeral heads of 1-2-year-old steers. These explants were placed in defined serum-free culture medium for a period of 3 weeks to investigate their biological and mechanical stability and thus to determine their potential utility in studies of cartilage physiology. Tissue mass remained constant over the culture period and no evident tissue swelling or distortion was observed. Chondrocytes were viable in all zones at the time of tissue isolation and throughout the culture period, with the exception of a thin layer of cells at the articular surface and the cut radial edge of the disks. Proteoglycan metabolism attained a steady state after 5 days of culture when the rate of loss of proteoglycan to culture media was compensated by new synthesis to maintain a stable proteoglycan content. Collagen metabolism was also stable with a constant content of type II collagen and a constant content of denatured collagen II throughout culture; the content of the C-propeptide of type II procollagen as a measure of procollagen synthesis, dropped slightly during the first week to attain a steady state after that time. Dynamic and equilibrium mechanical properties of these explant disks were also stable confirming maintenance of these tissue properties during long-term culture. In addition, the disk geometry of the system, with the cut surface in the bone parallel to the intact articular surface, is well-suited to study tissue regulation by mechanical load. Taken together, the stability of these indicators of tissue physiology indicates the maintenance in serum-free conditions of normal metabolism for organ cultures containing full-depth mature articular cartilage attached to bone.

Animals↗
PubMed1999

Treatment of osteonecrosis of the femoral head by free vascularized fibular grafting: an analysis of surgical outcome and patient health status.

OBJECTIVE: To evaluate the limb-specific outcome and general health status of patients with osteonecrosis of the femoral head treated with vascularized fibular grafting. DESIGN: A retrospective review. SETTING: A single tertiary care centre. PATIENTS: Fifty-five consecutive patients with osteonecrosis of the femoral head who underwent fibular grafting (8 bilaterally). INTERVENTION: Vascularized fibular grafting. OUTCOME MEASURES: Limb-specific scores (Harris Hip Score, St. Michael's Hospital Hip Score), general health status (Nottingham Health Profile, SF-36 health status survey) and radiographic outcome measures (Steinberg stage). RESULTS: Patients were young (mean age 34 years, range from 18 to 52 years) and 80% had advanced osteonecrosis (Steinberg stages IV and V). Fifty-nine hips were followed up for an average of 50 months (range from 24 to 117 months) after vascularized fibular grafting. Sixteen hips (27%) were converted to total hip arthroplasty (THA). To date, 73% of hips treated with vascularized fibular grafting have required no further surgery. Preoperative and postoperative Harris Hip Scores were 57.3 and 83.6 respectively (p < 0.001). As measured by patient-oriented health status questionnaires (SF-36, Nottingham Health Profile) and compared with population controls, patients had normal mental health scores and only slight decreases in physical component scores. CONCLUSIONS: Free vascularized fibular grafting for osteonecrosis of the femoral head provides satisfactory pain relief, functional improvement and general health status and halts the progression of symptomatic disease.

Adolescent↗
PubMed1999

Antibiotic use for the treatment of upper respiratory infections in a diverse community.

BACKGROUND: Previous studies have not addressed whether cultural factors influence beliefs and practices related to the treatment of upper respiratory infections (URIs). The purpose of our project was to assess beliefs, care-seeking behavior, use of antibiotics, and means of obtaining antibiotics for the treatment of URIs among different ethnic groups in an urban community. METHODS: A total of 192 adults completed a self-administered questionnaire indicating their likelihood of seeking care, the perceived effectiveness of treatment methods, and their usual use of treatment regimens for 2 scenarios consistent with uncomplicated URIs. Respondents were also asked about their use of antibiotics not prescribed by a physician for a URI. RESULTS: A majority of subjects reported a belief in the effectiveness of antibiotics for URIs and indicated they are likely to seek care for URIs. Many (26%) had obtained antibiotics from sources other than a physician's prescription (e.g., directly from pharmacists or a supplier outside the United States). Many (31%) believed that antibiotics should be available over the counter. Individuals who reported using antibiotics for a URI were more likely than those who did not to obtain them without a prescription (35% vs. 11%, P = .001). Subjects with a cultural background from countries where antibiotics are available over the counter are more likely to use antibiotics not prescribed by a physician than those from countries with variably enforced regulations or the United States (40%, 30%, and 20%, respectively, P = .049). CONCLUSIONS: Members of an ethnically diverse community believe antibiotics are effective for colds, are very likely to seek care for colds, and often obtain antibiotics without a prescription. The ease of antibiotic access worldwide may influence their use in some communities in the United States.

Adult↗
PubMed1998

Developmental appearance and distribution of bone sialoprotein and osteopontin in human and rat cementum.

BACKGROUND: Bone sialoprotein (BSP) and osteopontin (OPN), two major noncollagenous proteins (NCPs) in collagen-based mineralized tissues, have been implicated in mineral deposition and cell- and matrix-matrix interactions during root development. However, their role in cementogenesis is still a subject of debate. Since distribution of proteins is indicative of function, we have analyzed their temporo-spatial appearance in relation to that of cementum collagen. METHODS: Human premolars and rat molars at various stages of root development characterized by differing rates of formation were fixed in aldehyde and embedded in epoxy and LR White resin. Sections were processed for ultrastructural analysis and postembedding colloidal gold (immuno)cytochemistry. RESULTS: Incubations with antibodies against BSP and OPN and with lectins recognizing prominent sugars in these proteins generally revealed similar labeling patterns in both human and rat teeth, with gold particles accumulating mainly in the interfibrillar spaces. The lectin Helix pomatia, specific for N-acetyl-D-galactosamine, was distinctive in that it consistently reacted with human cementum, but only sporadically labeled rat cementum. Regardless of both the species and the stage of root development, mineralization initiated in mantle predentin in association with distinct foci immunoreactive for BSP and OPN. In human teeth, the deposition of cementum collagen began before the start of dentin mineralization and thus prior to any detectable labeling for BSP and OPN. However, at early stages of root formation in the rat, cementum collagen appeared after BSP and OPN accumulated on the root surface, whereas at advanced stages the deposition of cementum collagen, BSP and OPN coincided. CONCLUSIONS: The temporo-spatial differences in the appearance of BSP and OPN relative to cementum collagen correlate well with known differences in the speed of root elongation and explain the variable appearance of the dentino-cemental junction. The data reveal no causal relationship between BSP and OPN and the differentiation of cementoprogenitor cells and indicate that the distribution of collagen fibrils ultimately determines the amount and pattern of accumulation of these NCPs. There also is no consistent planar accumulation of BSP and OPN between dentin and cementum such as the cement lines found between "old" and "new" bone. It is concluded that the interlacement of collagen fibrils at the dentino-cemental junction, across which mineralization spreads, represents the primary attachment mechanism between cementum and dentin.

Adolescent↗
PubMed1998

Morphological and immunocytochemical characterization of primary osteogenic cell cultures derived from fetal rat cranial tissue.

Enzymatic digestion of bone tissue potentially releases a mixture of precursor, differentiating, and mature cells. Conceptually, early fetal osteogenic tissue should provide a more uniform population of cells than late embryonic or newborn bone in which cells have already differentiated. In this context, we have applied sequential enzymatic digestion to obtain and culture cells from 15-16-day fetal rat cranial tissue, a developmental age where deposition of bone matrix has not yet started at this site. These cultures were compared with those of osteogenic cells isolated from newborn rat calvariae and grown under similar conditions. Matrix production and composition were examined by colloidal gold immunocytochemistry using antibodies to bone sialoprotein (BSP), osteocalcin (OC), and osteopontin (OPN). The plated cells formed mineralized nodules by day 14. The presence of mineral was determined by von Kossa staining and backscattered electron imaging (BEI), and the accumulation of calcium and phosphorus within the nodules was demonstrated by X-ray microanalysis and elemental mapping. At early time intervals, cells were generally cuboidal in shape and showed a well-developed Golgi apparatus, which occasionally was immunoreactive for OPN. Labeling for BSP and OPN was found over mineralization foci and electron-dense material within, and at the periphery, of larger mineralized masses and over accumulations of afibrillar matrix at the dish surface. Osteocalcin immunoreactivity was also associated with electron-dense portions of the bone-like matrix. These data demonstrate the potential of presumptive fetal rat calvarial cells to form a bone-like matrix in vitro and suggest that the assembly and mineralization pattern show similarities to the process of intramembranous ossification. Such a culture system is of interest not only for studying cellular and matrix events of bone formation, but also factors which influence mesenchymal cells in committing themselves to the osteogenic pathway.

Animals↗
PubMed1998

Chemical modification of titanium surfaces for covalent attachment of biological molecules.

The surface of implantable biomaterials is in direct contact with the host tissue and plays a critical role in determining biocompatibility. In order to improve the integration of implants, it is desirable to control interfacial reactions such that nonspecific adsorption of proteins is minimized and tissue-healing phenomena can be controlled. In this regard, our goal has been do develop a method to functionalize oxidized titanium surfaces by the covalent immobilization of bioactive organic molecules. Titanium first was chemically treated with a mixture of sulfuric acid and hydrogen peroxide to eliminate surface contaminants and to produce a consistent and reproducible titanium oxide surface layer. An intermediary aminoalkylsilane spacer molecule was then covalently linked to the oxide layer, followed by the covalent binding of either alkaline phosphatase or albumin to the free terminal NH2 groups using glutaraldehyde as a coupling agent. Surface analyses following coating procedures consisted of X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Enzymatic activity of coupled alkaline phosphatase was assayed colorimetrically, and surface coverage by bound albumin was evaluated by SEM visualization of colloidal gold immunolabeling. Our results indicate that the linkage of the aminoalkylsilane to the oxidized surface is stable and that bound proteins such alkaline phosphatase and albumin retain their enzymatic activity and antigenicity, respectively. The density of immunolabeling for albumin suggests that the binding and surface coverage obtained is in excess of what would be expected for inducing biological activity. In conclusion, this method offers the possibility of covalently linking selected molecules with known biological activity to oxidized titanium surfaces in order to guide and promote the tissue healing that occurs during implant integration in bone and soft tissues.

Biological Factors↗
PubMed1998

Donor site morbidity following vascularized fibular grafting.

We examined donor site morbidity in thirty-nine patients with avascular necrosis of the femoral head treated by curettage and transplantation of a free ipsilateral fibular graft. Utilising our donor site morbidity questionnaire, scar, functional loss, wound healing, complications, and pain were analysed. Subjective complaints and objective findings were evaluated and compared. Subjective complaints were common and included a sense of instability in 42% and a sense of weakness in 37%. However, objective findings were limited. No clinical instability could be elicited and only great toe flexion (29%) and extension (43%) were found to be mildly weak. Only one patient required reoperation for a donor site problem (2%). Eighty-nine percent were pain free at time of follow-up, and 93% felt the scar was good. Range of motion of the knee and ankle of the donor site leg was not different from the nonoperated leg. Donor site morbidity for avascular necrosis of the femoral head is low.

Adult↗
PubMed1998

Irreducible fracture-dislocation of the hip: a severe injury with a poor prognosis.

OBJECTIVE: To determine the outcome of and prognostic factors associated with irreducible fracture-dislocations of the hip. DESIGN: Retrospective review of a prospectively gathered trauma database. METHODS: Using a prospectively gathered trauma database, we identified twenty-five patients with fracture-dislocations of the hip that were irreducible with closed means under a general anaesthetic. All were victims of high-energy trauma with severe injuries (mean Injury Severity Score = 25, range 9 to 54). Eighteen patients had multiple fractures, fifteen had associated systemic injury, and only four sustained the hip injury in an isolated fashion. There were seven associated sciatic nerve injuries (28 percent) and nine associated femoral head or neck fractures (36 percent). The mean time from injury to open reduction was 15.3 hours (range 3 to 58 hours). RESULTS: Twenty-three patients (92 percent) were followed to definitive outcome. Despite accurate reduction, only six patients had satisfactory results (Thompson-Epstein = good or excellent). Poor results were associated with delay in reduction and an associated femoral head or neck fracture. Reasons for the poor results include avascular necrosis, posttraumatic arthritis or chondrolysis, persisting sciatic nerve injury, and heterotopic ossification. CONCLUSIONS: An irreducible fracture-dislocation of the hip is a severe injury with a poor prognosis and a high incidence of associated injuries. Outcome is best in patients who do not have an associated femoral head or neck fracture and those whose dislocation is promptly reduced.

Adolescent↗
PubMed1998

Primary external fixation of rotationally unstable pelvic fractures in obese patients.

BACKGROUND: Patients with obesity who undergo surgery have an increased risk for perioperative complications. The purpose of this study was to determine the perioperative outcome of rotationally unstable pelvic fractures treated with initial external fixation in obese patients. METHODS: Review of clinical data and radiographs of 42 patients identified from a prospectively entered trauma database who had rotationally unstable fractures of the pelvis treated with initial pelvic external fixation. RESULTS: Inability of an anterior uniplanar external fixator to maintain adequate reduction of the pelvic ring disruption occurred with a greater frequency in obese patients compared with nonobese patients (p < 0.005). The anterior frame was unable to provide sufficient stabilization of the pelvic ring disruption in all obese patients with pure open-book-type fractures. For these patients, stabilization of the pelvic ring was achieved with early symphyseal plating. CONCLUSION: We report a significantly higher incidence of inability to obtain or maintain reduction of open-book pelvic fractures in obese patients using primary anterior uniplanar external fixation. Early symphyseal plating allowed early patient mobilization and maintained acceptable reduction throughout the follow-up period.

Adolescent↗
PubMed1998

Outcome of ulnar neurolysis during post-traumatic reconstruction of the elbow.

We performed ulnar nerve neurolysis and transposition during reconstructive operations on 20 consecutive patients (21 elbows) with neuropathy after the failure of primary treatment of elbow fractures. There were 11 men and nine women with a mean age of 48.3 years. Preoperatively, four elbows were in McGowan stage I, seven in stage II and ten in stage III and the mean Gabel and Amadio ulnar nerve score was 3.2. At a mean follow-up of 32.1 months (24 to 67) we performed comprehensive neurological, functional, electrophysiological and outcome assessments. Patient satisfaction was high with good pain relief and restoration of hand strength and dexterity. The mean Gabel and Amadio score had improved to 6.5, an improvement of 3.3. There were one excellent, 16 good, 2 fair and 2 poor results; both of the last were due to failure of the underlying elbow reconstruction. Even for advanced stage-II and stage-III lesions we achieved good function, return of intrinsic power, and a high rate of patient satisfaction.

Adult↗
PubMed1998

Health status after Ilizarov reconstruction of post-traumatic lower-limb deformity.

Previous studies of the Ilizarov procedure have concentrated on musculoskeletal assessments rather than the opinions of patients. In a prospective trial of 25 consecutive patients, we evaluated the effect of Ilizarov reconstruction of post-traumatic deformity on general health status using the SF36 and Nottingham Health Profile (NHP). The patients had very low preoperative scores, which remained low during treatment and correction, but increased postoperatively. The mean overall SF36 score improved from 36 +/- 3 to 58 +/- 7 (p = 0.031) and the NHP score from 39 +/- 11 to 67 +/- 10 (p = 0.002). The improvements in scores were not limited to the physical components and were equal or better than the improvements reported for other orthopaedic procedures, including total joint arthroplasty. Ilizarov-type reconstruction of deformity of the lower limb not only restores bony configuration, but also produces a large improvement in the general health status of patients.

Activities of Daily Living↗
PubMed1998

Management of recurrent, complex instability of the elbow with a hinged external fixator.

We have treated 16 patients with recurrent complex elbow instability using a hinged external fixator. All patients had instability, dislocation or subluxation of the ulnohumeral joint. The injuries were open in eight patients and were associated with 20 other fractures and five peripheral nerve injuries. Two patients had received initial treatment from us; 14 had previously had a mean of 2.1 unsuccessful surgical procedures (1 to 6). The fixator was applied at a mean of 4.8 weeks (0 to 9) after the injury and remained on the elbow for a mean of 8.5 weeks (6 to 11). After treatment we found the mean range of flexion-extension to be 105 degrees (65 to 140). At a final follow-up of 23 months (14 to 40), the mean Morrey score was 84 (49 to 96): this translated into one poor, three fair, ten good and two excellent results. Complications included one fractured humeral pin, one temporary palsy of the radial nerve, one recurrent instability, one wound infection, one severe pin-track infection and one patient with reflex sympathetic dystrophy. Although technically demanding, the use of the fixator is an important advance in the management of recurrent complex elbow instability after failure of conventional treatment.

Adult↗
PubMed1998

Mice lacking osteopontin show normal development and bone structure but display altered osteoclast formation in vitro.

We have used homologous recombination in embryonic stem cells to generate mice with a targeted disruption of the osteopontin (Opn, or Spp1, for secreted phosphoprotein 1) gene. Mice homozygous for this disruption fail to express osteopontin (OPN) as assessed at both the mRNA and protein level, although an N-terminal fragment of OPN is detectable at extremely low levels in the bones of -/- animals. The Opn -/- mice are fertile, their litter size is normal, and they develop normally. The bones and teeth of animals not expressing OPN are morphologically normal at the level of light and electron microscopy, and the skeletal structure of young animals is normal as assessed by radiography. Ultrastructurally, proteinaceous structures normally rich in OPN, such as cement lines, persist in the bones of the Opn-/- animals. Osteoclastogenesis was assessed in vitro in cocultures with a feeder layer of calvarial osteoblast cells from wild-type mice. Spleen cells from Opn-/- mice cells formed osteoclasts 3- to 13-fold more frequently than did control Opn+/+ cells, while the extent of osteoclast development from Opn -/- bone marrow cells was about 2- to 4-fold more than from the corresponding wild-type cells. Osteoclast development occurred when Opn-/- spleen cells were differentiated in the presence of Opn-/-osteoblasts, indicating that endogenous OPN is not required for this process. These results suggest that OPN is not essential for normal mouse development and osteogenesis, but can modulate osteoclast differentiation.

Animals↗
PubMed1998

Quality of student learning and preceptor productivity in urban community health centers.

BACKGROUND AND OBJECTIVES: Clinicians in community health centers find it difficult to balance the demands of increased productivity and effective teaching. We hypothesized that precepting third-year students would decrease clinical productivity and that many elements related to the quality of the learning experience (e.g., amount of patient contact, student autonomy) would be adversely affected by pressure to see increasing numbers of patients. METHODS: Students and preceptors in a 6-week family medicine clerkship completed daily surveys that measured the presence of quantifiable elements of the ambulatory teaching experience. They also rated the overall quality of learning during each session. RESULTS: For 62 sessions for which both students and preceptors completed evaluations, students rated the overall quality of learning more highly than preceptors. For students, the elements most positively associated with quality of learning were total teaching time and the frequency with which family issues were raised. For preceptors, the elements that predicted quality of learning were the number of patients that students saw independently and total teaching time. The clinical productivity of preceptors did not differ for sessions with and without a student. CONCLUSIONS: Preceptors can be effective teachers who encourage student autonomy and who model behaviors central to family practice, without decreasing productivity.

Clinical Clerkship↗
PubMed1998

Molecular determinants of arterial calcification.

Calcification of extracellular matrix (ECM) can be either physiological or pathological. Physiological calcification (or mineralization) of ECM is restricted to bones, teeth and, to a lesser extent, growth plate cartilages. Pathological calcification appears often in the ECM of arteries where it is a frequent complication of atherosclerosis. However, calcification of the ECM of arteries is not restricted to atherosclerosis. Indeed, human diseases have been described that are characterized by calcification of the aortic media in the absence of any atherosclerotic lesions. The existence of these rare diseases, along with several mouse models recently generated and discussed below, indicates that the formation of atherosclerotic lesions and the calcification of the artery ECM are controlled by different genetic pathways. This emerging knowledge has implications for our understanding of ECM calcification beyond atherosclerosis.

Animals↗