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Biomedical subjects

M C Harper

Publications and source records attributed to M C Harper.

At least 19 recordsLinked to original sources
PubMed2001

Delayed reduction and stabilization of the tibiofibular syndesmosis.

Six patients with chronic widening and instability of the tibiofibular syndesmosis subsequent to pronation--external rotation ankle fractures were reviewed as regards diagnosis and treatment. An evaluation of the syndesmotic interval was best done by CT scans using axial cuts. Delayed reduction and stabilization using primarily large screw fixation resulted in maintenance of the reduction and satisfactory results in 5 of 6 cases. In one case, an arthrodesis of the tibiofibular interval was done because of significant incongruity.

Adult↗
PubMed1999

Talonavicular arthrodesis for the acquired flatfoot in the adult.

The acquired painful flatfoot in the adult is a syndrome that commonly is disabling and progressive. Patients should benefit from a surgical technique that can provide correction of the major deformities and lasting stability with limited surgical morbidity. Twenty-nine patients treated with a talonavicular arthrodesis for this disorder were followed up a minimum of 12 months and an average of 26 months. Twenty-five patients (86%) were satisfied with no or minor reservations and achieved good or excellent results. A talonavicular arthrodesis, by addressing the instability at its focal point, appears to achieve these goals with one surgical procedure.

Adult↗
PubMed1997

Congenital myasthenic syndromes due to heteroallelic nonsense/missense mutations in the acetylcholine receptor epsilon subunit gene: identification and functional characterization of six new mutations.

We describe and functionally characterize six mutations of the acetylcholine receptor (AChR) epsilon subunit gene in three congenital myasthenic syndrome patients. Endplate studies demonstrated severe endplate AChR deficiency, dispersed endplate regions and well preserved junctional folds in all three patients. Electrophysiologic studies were consistent with expression of the fetal gamma-AChR at the endplates in one patient, prolongation of some channel events in another and gamma-AChR expression as well as some shorter than normal channel events in still another. Genetic analysis revealed two recessive and heteroallelic epsilon subunit gene mutations in each patient. One mutation in each (epsilonC190T [epsilon R64X], epsilon 127ins5 and epsilon 553del 7) generates a nonsense codon that predicts truncation of the epsilon subunit in its N-terminal, extracellular domain; and one mutation in each generates a missense codon (epsilon R147L, epsilon P245L and epsilon R311W). None of the mutations was detected in 100 controls. Expression studies in HEK cells indicate that the three nonsense mutations are null mutations and that surface expression of AChRs harboring the missense mutations is significantly reduced. Kinetic analysis of AChRs harboring the missense mutations show that epsilon R147L is kinetically benign, epsilon P245L prolongs burst open duration 2-fold by slowing the rate of channel closing and epsilon R311W shortens burst duration 2-fold by slowing the rate of channel opening and speeding the rate of ACh dissociation. The modest changes in activation kinetics are probably overshadowed by reduced expression of the missense mutations. The consequences of the endplate AChR deficiency are mitigated by persistent expression of gamma-AChR, changes in the release of transmitter quanta and appearance of multiple endplate regions on the muscle fiber.

Acetylcholine↗
PubMed1996

Chronic plantar heel pain: treatment with a short leg walking cast.

The efficacy of a short leg walking cast in the treatment of chronic plantar heel pain was assessed for 32 patients with 37 involved extremities treated over a 2-year period. All patients had failed numerous other treatment modalities and had been symptomatic for an average of 1 year. Long-term follow-up for 24 patients with 28 involved extremities revealed complete resolution of pain for 7 extremities (25%), improvement for 17 (61%), and no improvement for 4 (14%). Ten (42%) patients were completely satisfied with cast treatment, 3 (12%) were satisfied with reservations, and 11 (46%) were dissatisfied. Casting appears to be a reasonable option for patients with recalcitrant heel pain and should be offered before surgical intervention.

Adult↗
PubMed1996

Talonavicular arthrodesis for the painful adult acquired flatfoot.

Twenty-seven consecutive patients with posterior tibial tendon insufficiency were treated with talonavicular arthrodesis as the primary stabilizing procedure. Twenty-six patients were followed a minimum of 12 and an average of 27 months. Twenty-four patients had either no pain or pain only after heavy usage. Eleven patients were completely satisfied with postoperative foot function, 13 were satisfied, with minor reservations, and 2 were satisfied, with major reservations. Results were rated as excellent in 10 patients, good in 14 patients, and fair in 2 patients. Successful arthrodesis was achieved in all patients, although one patient required two additional bone grafts. Progressive arthrosis in adjacent joints was noted in five patients, four of whom had arthrosis preoperatively. No deterioration of foot position was seen in any patient with follow-up as long as 5 years. An isolated talonavicular arthrodesis seems to offer patients with this disorder both reliable pain improvement and lasting stability.

Adult↗
PubMed1996

Operative treatment of fractures of the tibial plafond. A randomized, prospective study.

We performed a randomized, prospective study to compare the results of two methods for the operative fixation of fractures of the tibial plafond. Surgeons were assigned to a group on the basis of the operation that they preferred (randomized-surgeon design). In the first group, which consisted of eighteen patients, open reduction and internal fixation of both the tibia and the fibula was performed through two separate incisions. An additional patient, who had an intact fibula, had fixation of the tibia only through an anteromedial incision. The second group consisted of twenty patients who were managed with external fixation with or without limited internal fixation (a fibular plate or tibial interfragmentary screws). Ten (26 per cent) of the thirty-nine fractures were open, and seventeen (44 per cent) were type III according to the classification of Rüedi and Allgöwer. There were fifteen operative complications in seven patients who had been managed with open reduction and internal fixation and four complications in four patients who had been managed with external fixation. All but four of the complications were infection or dehiscence of the wound that had developed within four months after the initial operation. The complications after open reduction and internal fixation tended to be more severe, and amputation was eventually done in three patients in this group. At a minimum of two years postoperatively (average, thirty-nine months; range, twenty-five to fifty-one months), the average clinical score was lower for the patients who had had a type-II or III fracture, regardless of the type of treatment. With the numbers available, no significant difference was found between the average clinical scores for the two groups. All of the patients, in both groups, who had had a type-II or III fracture had some degree of osteoarthrosis on plain radiographs at the time of the latest follow-up. With the numbers available, there was no significant difference between the two groups with regard to the osteoarthrotic changes. We concluded that external fixation is a satisfactory method of treatment for fractures of the tibial plafond and is associated with fewer complications than internal fixation.

Adult↗
PubMed1995

The short oblique fracture of the distal fibula without medial injury: an assessment of displacement.

Eighteen patients with ankle injuries presenting as short oblique fractures of the distal fibula with no clinical or radiographic evidence of injury to the medial ankle were studied for fracture displacement. Plain radiographs and computed tomography were used for analysis. All fractures were clinically diagnosed as supination-external rotation stage 2 (SE-II) injuries under the Lauge-Hansen scheme. All exhibited slight displacement on plain radiographs and were treated nonoperatively. Computerized tomography using axial cuts across the fracture site and ankle mortise revealed normal positioning of the talus beneath the tibial plafond, as evidenced by no abnormality of the medial joint space in all patients. In the majority of patients, the relationship between the talus and distal fibula also appeared undisturbed, with fracture displacement being confined to a change in position of the proximal fibular fragment relative to the tibia as compared with the contralateral ankle. In a minority of cases, in addition to the above-described displacement of the proximal fibular fragment, the distal fibular fragment was noted to shift slightly laterally relative to the talus, with mild widening of the lateral joint space. Occult-associated avulsion fractures off the distal tibia were present in 39% of the cases.

Adult↗
PubMed1995

Closed reduction and percutaneous stabilization of tibial plateau fractures.

Twenty-eight patients with tibial plateau fractures treated by closed reduction using forceful traction and percutaneous stabilization with pins or screws were reviewed. For six bicondylar fractures, transfixion pins with an external fixation device were used. In six cases, an arthroscopic exam was also done. For 21 patients, external support was used postoperatively. Twenty-one patients were followed an average of 26 months. All fractures healed. Functional ratings were: 14 excellent, 6 good, and 1 poor. Radiographic ratings were: 11 excellent, 9 good, and 1 fair. For fractures with large fragments without excessive comminution or severe central depression, this technique yields good results with minimal surgical morbidity.

Adult↗
PubMed1993

An anatomic and radiographic investigation of the tibiofibular clear space.

The tibiofibular clear space, a commonly used parameter in assessing the reduction of the syndesmosis in the management of ankle injuries, its anatomic boundaries, and resultant diagnostic ramifications were evaluated. This interval is seen to reflect the posterior aspect of the distal tibiofibular relationship and to vary not only with direct lateral displacement of the distal fibula but also potentially with rotational abnormalities of the fibula.

Ankle Injuries↗
PubMed1992

Focal adhesion protein-tyrosine kinase phosphorylated in response to cell attachment to fibronectin.

A homology-based cDNA cloning approach was used to identify a widely expressed protein-tyrosine kinase designated as "focal adhesion kinase" (FadK). The entire mouse FadK amino acid sequence was deduced from cDNA clones, revealing a large (119-kDa) non-membrane-spanning protein-tyrosine kinase that lacks Src-homology SH2 and SH3 domains. Immunostaining of BALB/c 3T3 fibroblasts revealed that FadK is concentrated in focal adhesions. FadK is phosphorylated on tyrosine in growing cultures of BALB/c 3T3 cells but contains little or no phosphotyrosine in cells detached by trypsinization. The tyrosine-phosphorylated state is regained within minutes when the cells are replated onto fibronectin. Activation of FadK may be an important early step in intracellular signal transduction pathways triggered in response to cell interactions with the extracellular matrix.

Amino Acid Sequence↗
PubMed1992

Ankle fracture classification systems: a case for integration of the Lauge-Hansen and AO-Danis-Weber schemes.

The two dominant classification systems for ankle fractures in use are the Lauge-Hansen and AO-Danis-Weber schemes. Each has certain advantages and disadvantages. Because of basic similarities, integration of these systems into one scheme involving three basic patterns with appropriate staging appears to be reasonable. This integration is based upon combining the pronation-abduction and pronation-external rotation injuries in Lauge-Hansen's scheme into one pronation-abduction-external rotation pattern. The resultant system would appear attractive in terms of combining relative simplicity with completeness.

Ankle Injuries↗
PubMed1991

Polymyositis mediated by T lymphocytes that express the gamma/delta receptor.

BACKGROUND: The invasion and destruction of nonnecrotic muscle fibers by CD8+ cytotoxic T cells is considered a hallmark of polymyositis. In the cases of polymyositis reported so far, the autoinvasive CD8+ T cells expressed the common form of T-cell receptor for the recognition of antigen, the so-called alpha/beta T-cell receptor. We describe a 69-year-old man with polymyositis mediated by CD4-, CD8- T cells expressing the recently discovered, uncommon gamma/delta T-cell receptor. METHODS: We used immunofluorescence or immunoperoxidase techniques to study frozen sections of muscle from our patient, who had mild weakness of cervical and proximal limb muscles, and from control patients with polymyositis, inclusion-body myositis, dermatomyositis, or granulomatous myopathy with monoclonal antibodies against T-cell-related antigens (CD2, CD3, CD4, CD8, and gamma/delta T-cell receptor), B cells (CD22), major histocompatibility complex (MHC) and MHC-related antigens (MHC Class I, CD1a, CD1b, and CD1c), and the 65-kd heat-shock protein. The membrane contacts between the autoinvasive cells and the sarcolemma were investigated by electron microscopy. RESULTS: In the patient described here, but not in 28 others with inflammatory myopathies, myriad gamma/delta T cells surrounded and invaded nonnecrotic muscle fibers. All muscle fibers were highly reactive for MHC Class I antigen and the 65-kd heat-shock protein. Treatment with prednisone improved the clinical and histologic findings. CONCLUSIONS: Polymyositis can be mediated by gamma/delta T cells. This new form of polymyositis appears to be highly responsive to steroids.

Aged↗