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Biomedical subjects

C Parker Gibbs

Publications and source records attributed to C Parker Gibbs.

10 recordsLinked to original sources
PubMed2006

Deficit in human muscle strength with cast immobilization: contribution of inorganic phosphate.

Metabolic factors have been proposed to explain strength deficits observed in skeletal muscle with immobilization that are not completely accounted for by changes in muscle cross-sectional area (CSA) and neural adaptations. The aim of this study was to quantify changes in the resting inorganic phosphate (Pi) concentration from the medial gastrocnemius muscle during immobilization, reloading and rehabilitation. Additionally, we assessed the contributions of CSA, muscle activation and Pi concentration to plantar flexor torque during rehabilitation following immobilization. Eight persons with a surgically stabilized ankle fracture participated. Subjects were immobilized for 6-8 weeks and subsequently participated in 10 weeks of rehabilitation. Localized (31)P-Magnetic resonance spectroscopy, magnetic resonance imaging, isometric torque and activation testing were performed on the immobilized and uninvolved limbs. At 6 weeks of immobilization, significant differences were noted between the immobilized and uninvolved limbs for the Pi concentration and the Pi/PCr ratio (P < 0.05). From 6 weeks of immobilization to 3-5 days of reloading, the increase in Pi concentration (15%, P = 0.26) and Pi/PCr (20%, P = 0.29) was not significant. During rehabilitation, the relative contributions of CSA, muscle activation and Pi concentration to plantarflexor torque were 32, 44 and 40%, respectively. Together, CSA, muscle activation and Pi concentration accounted for 76% of the variance in torque (P < 0.01). In summary, our findings suggest that immobilization, independent of reloading, leads to a significant increase in the resting Pi concentration of human skeletal muscle. Additionally, alterations in resting Pi concentration may contribute to strength deficits with immobilization not accounted for by changes in muscle CSA or neural adaptations.

Adult↗
PubMed2006

Relative contributions of muscle activation and muscle size to plantarflexor torque during rehabilitation after immobilization.

Muscle atrophy is clearly related to a loss of muscle torque, but the reduction in muscle size cannot entirely account for the decrease in muscle torque. Reduced neural input to muscle has been proposed to account for much of the remaining torque deficits after disuse or immobilization. The purpose of this investigation was to assess the relative contributions of voluntary muscle activation failure and muscle atrophy to loss of plantarflexor muscle torque after immobilization. Nine subjects (ages 19-23) years with unilateral ankle malleolar fractures were treated by open reduction-internal fixation and 7 weeks of cast immobilization. Subjects participated in 10 weeks of rehabilitation that focused on both strength and endurance of the plantarflexors. Magnetic resonance imaging, isometric plantarflexor muscle torque and activation (interpolated twitch technique) measurements were performed at 0, 5, and 10 weeks of rehabilitation. Following immobilization, voluntary muscle activation (56.8 +/- 16.3%), maximal cross-sectional area (CSA) (35.3 +/- 7.6 cm(2)), and peak torque (26.2 +/- 12.7 N-m) were all significantly decreased ( p < 0.0056) compared to the uninvolved limb (98.0 +/- 2.3%, 48.0 +/- 6.8 cm(2), and 105.2 +/- 27.0 N-m, respectively). During 10 weeks of rehabilitation, muscle activation alone accounted for 56.1% of the variance in torque ( p < 0.01) and muscle CSA alone accounted for 35.5% of the variance in torque ( p < 0.01). Together, CSA and muscle activation accounted for 61.5% of the variance in torque ( p < 0.01). The greatest gains in muscle activation were made during the first 5 weeks of rehabilitation. Both increases in voluntary muscle activation and muscle hypertrophy contributed to the recovery in muscle strength following immobilization, with large gains in activation during the first 5 weeks of rehabilitation. In contrast, muscle CSA showed fairly comparable gains throughout both the early and later phase of rehabilitation.

Adult↗
PubMed2006

Giant cell tumor of bone.

OBJECTIVE: To discuss the treatment and outcomes for giant cell tumor (GCT) of bone. MATERIALS AND METHODS: Review of the pertinent literature. RESULTS: GCT is a rare benign bone lesion most often found in the extremities of women in the third and fourth decades of life. Surgery is the mainstay of treatment and usually consists of intralesional curettage; local control rates range from 80% to 90% after this procedure. Patients with extensive, recurrent, and/or biologically more aggressive tumors may require wide excision. A small subset of patients with incompletely resectable GCTs or with lesions that are surgically inaccessible may be treated with moderate-dose radiotherapy (45-50 Gy) and have a 65% to 80% likelihood of being locally controlled. CONCLUSION: The majority of patients with GCTs are effectively treated with intralesional curettage. Wide excision or radiotherapy is necessary to cure a relatively limited subset of patients with extensive, aggressive, and/or incompletely resectable GCTs.

Bone Neoplasms↗
PubMed2006

Aneurysmal bone cyst.

OBJECTIVES: The purpose of this article is to discuss the natural history, treatment, and outcomes for patients with aneurysmal bone cysts (ABC). METHODS: Review of the pertinent literature. RESULTS: ABCs account for 1% to 2% of all primary bone tumors, usually present in the first 2 decades of life, and exhibit a slight female preponderance. The majority of patients are treated with curettage with local control rates ranging from approximately 70% to 90%. Almost all patients with recurrences are salvaged by one or more additional operations. A small subset of patients is treated with marginal or wide excision and almost all are locally controlled. A few patients with incompletely resectable, aggressive, and/or recurrent ABCs are treated with low-dose (26-30 Gy) radiotherapy (RT) and are locally controlled in approximately 90% of cases. CONCLUSIONS: The mainstay of treatment is surgery and most patients are cured with one or more operations. A small subset of patients with incompletely resectable, aggressive, and/or recurrent ABCs may be cured with low-dose RT.

Bone Cysts, Aneurysmal↗
PubMed2006

Pigmented villonodular synovitis.

Pigmented villonodular synovitis (PVNS) is a rare proliferative disorder that affects the synovium in young and middle-aged adults. Although most believe that it is an inflammatory process, some believe that it is a benign neoplasm. The optimal treatment is surgery. The local recurrence rate after marginal excision for localized PVNS is low. In contrast, the local recurrence rate after open synovectomy for diffuse PVNS is relatively high. The intra-articular instillation of radioactive isotopes or external beam radiotherapy (approximately 35 Gy in 14-15 fractions over 3 weeks) may significantly improve the likelihood of local control and long-term function in patients with incompletely resected diffuse PVNS. The probability of complications after moderate-dose radiotherapy (RT) is low.

Brachytherapy↗
PubMed2005

Stem-like cells in bone sarcomas: implications for tumorigenesis.

Bone sarcomas are a clinically and molecularly heterogeneous group of malignancies characterized by varying degrees of mesenchymal differentiation. Despite advances in medical and surgical management, survival rates for high-grade tumors have remained static at 50% to 70%. Tumor stem cells have been recently implicated in the pathogenesis of other heterogeneous, highly malignant tumors. We demonstrate here the existence of a small subpopulation of self-renewing bone sarcoma cells that are capable of forming suspended spherical, clonal colonies, also called "sarcospheres," in anchorage-independent, serum-starved conditions. These bone sarcoma cells as well as tissue specimens express activated STAT3 and the marker genes of pluripotent embryonic stem (ES) cells, Oct 3/4 and Nanog. Expression levels of Oct 3/4 and Nanog are greater in sarcospheres than in adherent cultures. A subset of bone sarcoma cells displays several surface markers of mesenchymal stem cells (Stro-1, CD105, and CD44) as well as attributes of mesodermal, ectodermal, and endodermal differentiation. Although previously documented in brain and breast tumors, our results support the extension of the cancer stem cell hypothesis to include tumors of mesenchymal lineage. Furthermore, they suggest the participation of ES cell homeobox proteins in non-germ cell tumorigenesis.

Bone Neoplasms↗
PubMed2005

Beyond bone grafting: techniques in the surgical management of benign bone tumors.

The traditional surgical treatment of benign bone tumors has been curettage and autologous bone graft or marginal resection of expendable bones. These procedures are associated with good results in most patients and should be considered the standard against which newer treatments are compared. Recently, however, surgeons have been evaluating the results of treatments using limited surgical approaches, including percutaneous treatments, alternatives to autograft bone, and thermal or cytotoxic adjuvant therapies. The goal has been to improve patient outcomes by decreasing perioperative morbidity and enhancing surgical efficiency. This process has been facilitated by the availability of multiple bone grafting materials and substitutes, the use of cross-sectional imaging, and technology such as that used with radiofrequency ablation. Techniques using these therapies in two benign bone tumor models are described. The use of percutaneous radiofrequency ablation, now used for both benign and malignant disease, is reviewed as a surgical alternative for osteoid osteoma. The role of adjuvant therapies such as liquid nitrogen and phenol, as well as the indications for resection, are described in the management of giant cell tumors of bone.

Bone Neoplasms↗
PubMed2004

Changes in inorganic phosphate and force production in human skeletal muscle after cast immobilization.

Cast immobilization is associated with decreases in muscle contractile area, specific force, and functional ability. The pathophysiological processes underlying the loss of specific force production as well as the role of metabolic alterations are not well understood. The aim of this study was to quantify changes in the resting energy-rich phosphate content and specific force production after immobilization. (31)P-magnetic resonance spectroscopy, three-dimensional magnetic resonance imaging, and isometric strength testing were performed in healthy subjects and patients with an ankle fracture after 7 wk of immobilization and during rehabilitation. Muscle biopsies were obtained in a subset of patients. After immobilization, there was a significant decrease in the specific plantar flexor torque and a significant increase in the inorganic phosphate (P(i)) concentration (P < 0.001) and the P(i)-to-phosphocreatine (PCr) ratio (P < 0.001). No significant change in the PCr content or basal pH was noted. During rehabilitation, both the P(i) content and the P(i)-to-PCr ratio decreased and specific torque increased, approaching control values after 10 wk of rehabilitation. Regression analysis showed an inverse relationship between the in vivo P(i) concentration and specific torque (r = 0.65, P < 0.01). In vitro force mechanics performed on skinned human muscle fibers demonstrated that varying the P(i) levels within the ranges observed across individuals in vivo (4-10 mM) changed force production by approximately 16%. In summary, our findings clearly depict a change in the resting energy-rich phosphate content of skeletal muscle with immobilization, which may negatively impact its force generation.

Ankle Injuries↗
PubMed2004

Muscle adaptations with immobilization and rehabilitation after ankle fracture.

UNLABELLED: INTRODUCTION/ PURPOSE: The widespread occurrence of muscular atrophy during immobilization and its reversal presents an important challenge to rehabilitation medicine. We used 3D-magnetic resonance imaging (MRI) in patients with surgically-stabilized ankle mortise fractures to quantify changes in plantarflexor and dorsiflexor muscle size during immobilization and rehabilitation, as well as to evaluate changes in force generating capacity (specific torque). METHODS: Twenty-individuals participated in a 10 wk rehabilitation program after 7 wk of immobilization. MRIs were acquired at baseline, 2, and 7 wk of immobilization, and at 5 and 10 wk of rehabilitation. Isometric plantarflexor muscle strength testing was performed at 0, 5, and 10 wk of rehabilitation. RESULTS: Dorsiflexors and plantarflexors atrophied 18.9% and 24.4% respectively, the majority of which occurred during the first 2 wk of immobilization (dorsiflexors: 9.6%; plantarflexors: 14.1%). Likewise, more than 50% of hypertrophy during rehabilitation occurred within the first 5 wk of rehabilitation for both the dorsiflexors (12.9%) and plantarflexors (13.2%), when compared to the total amount of hypertrophy over 10 wk of rehabilitation (dorsiflexors: 17.6%, plantarflexors: 22.5%). There were no significant differences in hypertrophy or atrophy of the dorsiflexor or plantarflexor muscles, despite a rehabilitation emphasis on the plantarflexors. Patients had significantly lower plantarflexor specific torque (torque/CSA) than healthy, control subjects immediately after cast immobilization, which did not return to normal after 10 wk of rehabilitation (P < 0.05). CONCLUSION: Our investigation of the consequences of limb immobilization on rehabilitation outcomes in patients can be applied directly to optimizing rehabilitation programs. Although muscle hypertrophy occurred early during rehabilitation, plantarflexor muscle function (specific torque) should remain the focus of rehabilitation programs because although CSA recovered quickly, specific torque still lagged behind that of control subjects.

Adaptation, Physiological↗