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Biomedical subjects

C E Nichols

Publications and source records attributed to C E Nichols.

At least 37 records · Page 2Linked to original sources
PubMed1998

Kinematics of the glenohumeral joint with Bankart lesion and repair.

A Bankart repair is performed to reduce abnormal translations of the humeral head on the glenoid due to a Bankart lesion, a separation of the capsulolabral complex from the glenoid rim. However, this is often accompanied by a loss of rotational range of motion that may lead to decreased function and osteoarthritis. This loss of rotation, coupled to the goal of reducing humeral translations, may be a result of the amount of imbrication of the capsule during repair. To determine the effects of capsular imbrication, we investigated how two Bankart repairs (2.5 and 5.0 mm of capsular imbrication) and a Bankart lesion altered the translations and rotations of the human glenohumeral joint in vitro. Coupled moments were applied to the unconstrained humerus in abduction-adduction, in flexion-extension, and to simulate the cocked phase of throwing. Motion was measured with an electromagnetic system. There were no differences in the kinematics between the intact specimens and those with a Bankart lesion or between normal specimens and the first (2.5 mm) Bankart repair. The first repair significantly reduced external rotation for the cocked phase of throwing compared with the Bankart lesion: from 46.8 +/- 23.6 degrees to 32.4 +/- 14.2 degrees (+/-SD). The second (5.0 mm) Bankart repair produced significantly different posterior translation (-4.7 +/- 3.9 mm) of the humeral head relative to the glenoid compared with normal (5.1 +/- 4.7 mm anterior) and the first repair (6.1 +/- 8.3 mm anterior), as the humerus moved from full flexion to full extension. Differences were also found for all rotations in the cocked phase of throwing. For the second repair, the humerus extended 24.3 degrees and externally rotated 18.6 degrees less than normal and was abducted 15.4 degrees more. These results indicate that both Bankart repairs do little to affect humeral translations with unconstrained moment loading but that rotations are affected during the cocked phase of throwing, with significant losses of external and extension rotations.

Biomechanical Phenomena↗
PubMed1994

Determination of a zero strain reference for the anteromedial band of the anterior cruciate ligament.

The objective of this study was to verify a method previously used to determine a reference length for calculations of anterior cruciate ligament strain. In nine knee specimens, an arthroscopic force probe and a Hall effect transducer were placed in the anteromedial band of the ligament. Anteroposterior-directed shear loads then were applied to the knee joint with the knee flexed to 30 degrees. From the sigmoidal curve for shear load versus displacement of the anterior cruciate ligament midsubstance, the length of the transducer at the inflection point was determined graphically by two independent examiners. Previous studies suggested that the inflection point corresponds to the slack-taut transition of the anteromedial band. The force probe was used to determine the actual length of the transducer when the anteromedial band became load bearing. No significant differences were found between the reference lengths determined by the inflection point method and the force probe. The force probe demonstrated that the anterior cruciate ligament became load bearing when an anterior shear load of 8.8 N was applied to the tibia with the knee at 30 degrees of flexion. Furthermore, multiple cycles of anteroposterior shear loading did not influence these values. The force probe verified that the inflection method provides a reasonable estimate of the absolute strain reference (within 0.7% strain).

Adult↗
PubMed1994

An in vivo comparison between intraoperative isometric measurement and local elongation of the graft after reconstruction of the anterior cruciate ligament.

This study was designed to determine if isometric measurement can be used to predict the pattern of elongation (the change in length) of a bone-patellar ligament-bone graft during passive flexion-extension of the knee at the time of reconstruction of the anterior cruciate ligament in vivo. A standard operative reconstruction technique was performed on nine patients. The tunnel sites for the grafts were selected, and the change in the distance between these sites was measured, with use of a CA-5000 drill-guide isometer as the knee was subjected to passive flexion-extension. After the reconstruction was completed, a Hall-effect transducer was implanted in the graft to measure the local displacement in the mid-substance of the graft that was produced by passive flexion-extension of the knee. For comparison, the isometric measurements and the values for local displacement of the graft were normalized by calculation of the percentage change in the length. With the knee in 10 to 30 degrees of flexion, the average isometric measurements and the measurements of local displacement demonstrated a decrease in length; however, the two techniques of measurement deviated at angles of flexion of 40 degrees and more. On the average, the isometric measurement of elongation between the trial insertion sites predicted that the graft would increase in length in flexion relative to extension, in contrast to the response of the graft after fixation. There was no significant correlation between the isometric measurements and the local elongation of the graft (r2 = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

The measurement of elongation of anterior cruciate-ligament grafts in vivo.

Many investigators who have studied the mechanical behavior of anterior cruciate-ligament grafts have attributed the increase in anterior translation of the tibia relative to the femur (an increase in the anterior laxity of the knee joint) to the temporal changes in the material behavior (strength and elastic properties) of the graft that occur throughout the process of remodeling. However, with the onset of motion of the joint, it is unclear whether the repeatable mechanical behavior of the graft remains unchanged immediately after fixation, if the fixation slips, or if the length of the graft changes and produces an increase in anterior translation of the tibia relative to the femur. It is also unknown if procedures performed by different surgeons, using similar graft material and similar operative techniques, can produce similar mechanical behavior of the graft, or if the behavior of the graft is similar to that of the normal anterior cruciate ligament. In an effort to address these questions, two surgeons performed a reconstruction of the anterior cruciate ligament on ten patients each (groups 1 and 2) with use of a bone-patellar ligament-bone graft. Immediately after fixation of the graft, a Hall-effect transducer was implanted to measure the changes in the length of the mid-substance of the graft while the knee was moved through twenty cycles of passive flexion-extension. Unlike the length pattern of the normal anterior cruciate ligament, the length pattern of the graft changed during the initial cycles of passive motion of the knee. We defined this phenomenon as the cyclic response of the graft and characterized it by calculation of the changes in the length of the graft at fixed positions of the knee across the multiple cycles of passive motion. In some patients, the length of the graft increased through the initial passive-motion cycles, while in others, it decreased. With the knee nearly extended, the predicted increase in anterior translation of the tibia relative to the femur, resulting from the increase in the length of the graft, was a maximum of 1.0 millimeter. This indicates that increases in anterior translation of the tibia relative to the femur can occur immediately after reconstruction of the anterior cruciate ligament and that changes in the length of the graft occur after fixation at loads that are less than the ultimate failure load of the graft or of the fixation.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1993

Morphometry of the semitendinosus and gracilis tendons with application to anterior cruciate ligament reconstruction.

The length and cross-sectional area of human semitendinosus and gracilis tendons were measured in both single- and multi-strand configurations for the purpose of anterior cruciate ligament graft preparation. The average lengths of the semitendinosus and the gracilis tendons were 235 +/- 20 mm (mean +/- SD) and 200 +/- 17 mm, respectively. The cross-sectional area of a doubled semi-tendinosus tendon (two strands) was significantly less than that of a 10-mm-wide patellar tendon graft (P < 0.001). The cross-sectional area of the tripled semitendinosus tendon (three strands) and the 10-mm-wide patellar tendon were similar. Doubling of the combined semitendinosus and gracilis tendons (four strands) and tripling of this combination (six strands) resulted in a significantly greater cross-sectional area in comparison to the 10-mm-wide patellar tendon (P < 0.05, four strands; P < 0.001 six strands). This investigation demonstrates that anterior cruciate ligament grafts fashioned using multiple-strand combinations of the semitendinosus and gracilis tendons result in a cross-sectional area that is comparable to the bone-patellar tendon-bone graft. This is an important finding since cross-sectional area reflects the intra-articular volume of collagenous tissue. This information should be helpful to surgeons considering using the hamstring tendons as an anterior cruciate ligament graft.

Aged↗
PubMed1993

An in vivo comparison of anterior tibial translation and strain in the anteromedial band of the anterior cruciate ligament.

The objective of this in vivo study was to determine if strain in the anteromedial band (AMB) of the anterior cruciate ligament (ACL) may be predicted by an external measurement of anterior tibial-femoral translation. A Hall effect strain transducer was implanted on the AMB of five human subjects with normal intact ACLs. AMB strain was then measured during anterior shear loading of the tibia relative to the femur, with the knee flexed to 30 and 90 degrees, simulating the loads applied in the Lachman and anterior drawer tests, respectively. The Knee Signature System, a commercially available arthrometer, was used to simultaneously measure anterior tibial translation relative to the femur. The resulting AMB strains and translations during anterior shear loading of the tibia with respect to the femur at 30 and 90 degrees were compared using a regression analysis to determine if AMB strain could be predicted from a measure of anterior tibiofemoral translation at either flexion angle. AMB strain at 150 N anterior shear load at 30 degrees flexion (3.0%) was significantly greater than that at 150 N anterior shear load at 90 degrees flexion (0.9%). During anterior shear loading at 30 degrees flexion, AMB strain correlated with anterior tibial translation (r2 = 0.59). However, there was no significant correlation between AMB strain and anterior tibial translation for anterior shear loading at 90 degrees flexion (r2 = 0.002). Therefore, AMB strain was not accurately predicted from an external measurement of tibial displacement at 90 degrees in this experiment.

Adult↗
PubMed1993

An MseI RFLP in the 5' flanking region of the factor IX gene: its use for haemophilia B carrier detection in Caucasian and Thai populations.

We have identified an MseI restriction fragment length polymorphism (RFLP) in the 5' flanking region of the factor IX gene. RFLPs in the factor IX locus are routinely used as linkage markers to track defective factor IX genes through affected pedigrees, allowing diagnosis of the haemophilia B carrier state in female members of the kindred. Currently, seven intragenic polymorphic loci have been characterized allowing carrier diagnosis in 89% of cases in the Caucasian population. Additional screening with the MseI RFLP reported in this publication increases this figure to 94% of cases. In Asian populations only one of these RFLPs (HhaI) is present at any significant frequency. Hence, carrier detection rates are much reduced in comparison to the corresponding figure of 89% in Caucasians. We report that this MseI RFLP is also present in the Thai population. Indeed, when used in combination with the HhaI polymorphism, the MseI RFLP should significantly improve the carrier detection rate in the Thai population from 11% to 40% of cases.

Alleles↗
PubMed1992

Patellar tendon injuries.

Patellar tendon injury secondary to overuse represents a failure of soft tissue healing that can lead to chronic symptoms. Clinical staging of this process is helpful in the initial management. Diagnostic imaging can help define the character of the injury as well as localized pathology. Initial treatment of clinical stages I, II, and III is conservative.

Athletic Injuries↗
PubMed1992

The effect of functional knee-braces on strain on the anterior cruciate ligament in vivo.

Functional knee-braces are widely used to protect injured or reconstructed anterior cruciate ligaments, despite the fact that few scientific data support their efficacy. We studied seven functional braces, representative of both the typical custom-fit and off-the-shelf designs. The braces were tested on subjects who had a normal anterior cruciate ligament and were scheduled for arthroscopic meniscectomy or exploration of the knee under local anesthesia. After the operative procedure, a Hall-effect strain-transducer was applied to the anterior cruciate ligament. Under low anterior shear loads, two braces provided some protective strain-shielding effect compared with no brace, but this strain-shielding effect did not occur at the higher anterior shear loads expected during the high-stress activities common to athletic events. The DonJoy, Townsend, C.Ti., and Lenox Hill braces demonstrated a strain-shielding effect on the anterior cruciate ligament with an internal torque of five newton-meters applied to the tibia. None of the braces had any effect on strain on the anterior cruciate ligament during active range of motion of the knee from 10 to 120 degrees or during isometric contraction of the quadriceps. Wearing of a brace did not produce an increase in the value for strain on the anterior cruciate ligament. For the activities that were evaluated in this study, none of the braces produced adverse effects on the anterior cruciate ligament, and there were no significant differences in the strain on the anterior cruciate ligament between the use of a custom-fit or an off-the-shelf brace design. There were no apparent advantages of the more expensive custom-made braces compared with the off-the-shelf designs.

Adult↗
PubMed1991

ACL reconstruction: in vivo measurement of patellar tendon graft elongation.

The implantation of a free autogenous patellar tendon graft is the surgical technique that currently offers the best results in anterior cruciate ligament reconstruction. However, numerous aspects regarding both technique and postoperative rehabilitation can still be improved. The aim of this study was to measure the elongation of the patellar tendon in vivo in the operating room after reconstructive surgery, subjecting the knee to normal strain such as passive mobilization or anterior displacement of the tibia. Three volunteers were studied. Our results were different from those reported in a previous study conducted in vivo on a normal anterior cruciate ligament (ACL). In spite of the isometric position of the tendon, passive mobilization provoked a progressive increase in the elongation of the graft within each cycle of flexion-extension and between one cycle and the next. This also occurred during the Lachman test. These findings suggest that the graft undergoes a process of tensile adjustment when it is first put under strain. Continued elongation once this process appears stabilized raises doubts as to the reliability of isometric measuring devices.

Adult↗
PubMed1990

Absorption kinetics of regular, isophane, and protamine zinc insulin in normal cats.

Absorption kinetics of regular, isophane (NPH), and protamine zinc (PZI) insulin were evaluated in seven clinically normal domestic shorthair cats by measurement of serial serum concentrations of insulin after subcutaneous administration of each insulin preparation. These results were compared to measurements of serial serum insulin concentrations after similar dosages of regular insulin were administered intravenously. Regular insulin administered subcutaneously was better absorbed than NPH and PZI insulins (mean bioavailability index 45.4% vs. 33.0% for NPH and 27.3% for PZI), and resulted in a significantly greater maximal increase in mean circulating insulin concentrations above baseline values (3529 pM vs. 1044 pM for NPH and 344 pM for PZI, P less than 0.05). The mean time interval between insulin administration and time to reach peak concentrations was significantly shorter for regular insulin than for NPH or PZI insulin (0.5 hr vs. 1.6 hr for NPH and 4.1 hr for PZI, P less than 0.05). There was also a significant difference (P less than 0.05) in the mean time interval between insulin injection and return of serum insulin concentrations to baseline values between regular insulin (5.6 hr) and NPH (7.7 hr) or PZI (13.1 hr) insulins. When compared with PZI, NPH insulin showed a significantly (P less than 0.05) greater maximal increase in mean serum insulin concentrations over baseline values. In addition, the interval between insulin administration and time to reach peak concentrations, as well as the time between insulin injection and return of serum insulin concentrations to baseline values, were also significantly shorter with NPH insulin than with PZI. These results suggest that NPH and PZI insulins administered subcutaneously to cats may require a short time to reach peak serum insulin concentrations as well as a relatively short time for circulating insulin concentrations to return to baseline values. If the absorption kinetics are similar to that in this study, most cats with diabetes mellitus would need twice daily injection of NPH or PZI insulin to adequately control the diabetic state.

Absorption↗
PubMed1990

Arthroscopic strain gauge measurement of the normal anterior cruciate ligament.

This article describes a new arthroscopic technique to study the anterior cruciate ligament (ACL) in vivo. A Hall effect strain transducer (HEST) is inserted arthroscopically into the anterior medial band (AMB) of the ACL. The strain is calculated from HEST displacement data. This method determines a reference length of the AMB when it becomes taut and load bearing. Data from HEST implantation in five patients with normal ACLs are reported. The HEST was implanted in the AMB with patients under local anesthesia. Strain was calculated during anterior-posterior shear testing and isometric quadriceps contractions at 30 and 90 degrees of knee flexion. The results demonstrate that this technique is safe and reliable. Lachman testing (anterior shear testing at 30 degrees) caused significantly higher strain in comparison to the drawer tests (anterior shear testing at 90 degrees). A significant increase in strain occurred during isometric quadriceps contraction when the knee was flexed at 30 degrees. No significant change in strain was measured, however, during isometric quadriceps contraction at 90 degrees of flexion. These results confirm previous studies showing that the Lachman test is a more sensitive clinical method for evaluating the AMB. They suggest that isometric quadriceps activity at 90 degrees of knee flexion can be prescribed for rehabilitation without risk of increased strain of the AMB.

Adult↗
PubMed1985

Amelioration of oxygen-induced osteoporosis in the in vitro fetal rat tibia with a capacitively coupled electrical field.

Near-term fetal rat tibiae were grown in M.E.M. Eagle/NCTC 135/15% newborn calf serum in 5% carbon dioxide and 5, 10, 21, 35, 60, and 90% oxygen for 3, 7, 10, and 14 days. Linear growth of the explants, as measured from macrophotographs of the explants at day zero and each of the days above, was greatest in the lower oxygen concentrations and least in the higher oxygen concentrations. Breaking strengths of the tibial diaphyses were significantly reduced in those explants grown in 60 and 90% oxygen. When the fetal rat tibiae were grown in 60% oxygen for 7 days and were subjected to a capacitively coupled electrical signal (sine wave, 60 kHz, 10 V peak-to-peak output signal; current density and field in the culture dish calculated to be 5.2 microA/cm2 and 0.32 mV/cm, respectively), the breaking strengths and middiaphyseal widths were statistically significantly greater than control tibiae grown in 60% oxygen alone. It is concluded that an appropriate capacitively coupled electrical field can inhibit an oxygen-induced osteoporosis in an in vitro mammalian long bone model.

Animals↗
PubMed1985

Prevention and treatment of sciatic denervation disuse osteoporosis in the rat tibia with capacitively coupled electrical stimulation.

Osteoporosis in the sciatic-denervated rat tibia was both prevented and reversed with a capacitively coupled electrical field. In both the prevention of the development of osteoporosis and the reversal of a previously established osteoporosis, a statistically significant enhancement of wet weight, dry weight, ashed weight, ultimate strength, cortical area, cortical thickness, and a concomitant decrease in cortical porosity occurred in the stimulated, denervated tibiae of the experimental animals compared with the nonstimulated, denervated tibiae of the control animals. These effects exhibited dose-response characteristics. A 60 kHz symmetrical sinewave signal was effective in preventing osteoporosis at a range of 5-10 peak-to-peak, and it was effective in reversing osteoporosis at 10 V peak-to-peak. Reversal of a well-established osteoporosis in laboratory animals has not been reported previously. Continued investigation into the use of a capacitively coupled electrical field in the prevention and treatment of osteoporosis seems warranted from these studies.

Animals↗
PubMed1985

Ascites, renal abnormalities, and electrolyte and acid-base disorders associated with liver disease.

Ascites and renal dysfunction are often associated with decreased liver function and reflect the complex abnormalities of water, protein, electrolyte, and acid-base metabolism that may complicate severe liver disease. This article discusses the pathophysiology and management of ascites, polydipsia and polyuria, decreased renal function, and acid-base and electrolyte alterations that can complicate liver disease.

Acid-Base Imbalance↗