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Biomedical subjects

W M Kuzon

Publications and source records attributed to W M Kuzon.

At least 19 recordsLinked to original sources
PubMed2000

Termino-lateral neurorrhaphy: the functional axonal anatomy.

The goal of this study was to determine the functional axonal anatomy of a termino-lateral neurorrhaphy (TLN). We hypothesize that axons populating a TLN must relinquish functional connections with their original targets prior to establishing new connections via the TLN. Two-month-old F344 rats underwent a TLN between the left peroneal nerve and a nerve graft tunneled to the contralateral hindlimb. Three months postoperatively, an end-to-end neurorrhaphy was performed between the nerve graft and the right peroneal nerve. Four months after the second operation, contractile properties and electromyographic (EMG) signals were measured in the bilateral hindlimbs. Left peroneal nerve stimulation proximal to the TLN site resulted in bilateral extensor digitorum longus (EDL) and tibialis anterior (TA) muscle contractions, with significantly lower forces on the side reinnervated by TLN. Evoked EMGs demonstrated that the right and left hindlimb musculature were electrically discontinuous following TLN. These data support our hypothesis that axons can form functional connections via a TLN, but they must first relinquish functional connections with their original targets.

Anastomosis, Surgical↗
PubMed2000

Skeletal muscle reinnervation by reduced axonal numbers results in whole muscle force deficits.

Patients sustaining a peripheral nerve injury will frequently experience residual muscle weakness after muscle reinnervation, even if the nerve repair is performed under optimal circumstances to allow rapid muscle reinnervation. The mechanisms responsible for this contractile dysfunction remain unclear. It is hypothesized that after peripheral nerve injury and repair, a reduced number of axons are available for skeletal muscle reinnervation that results in whole muscle force and specific force deficits. A rat model of peroneal nerve injury and repair was designed so that the number of axons available for reinnervation could be systematically reduced. In adult rats, the peroneal nerve to the extensor digitorum longus muscle was either left intact (sham group, n = 8) or divided and repaired with either 50 percent (R50 group, n = 7) or 100 percent (R100 group, n = 8) of the axons in the proximal stump included in the repair. Four months after surgery, maximal tetanic isometric force was measured and specific force was calculated for each animal. Mean tetanic isometric force for extensor digitorum longus muscles from R50 rats (2765.7 +/- 767.6 mN) was significantly lower than sham (4082.8 +/- 196.5 mN) and R100 (3729.0 +/-370.2 mN) rats (p < 0.003). Mean specific force calculations revealed significant deficits in both the R100 (242.1 +/- 30 kN/m2) and R50 (190.6 +/- 51.8 kN/m2) rats compared with the sham animals (295.9 +/- 14 kN/m2) (p < 0.0005). These data support our hypothesis that after peripheral nerve injury and repair, reinnervation of skeletal muscle by a reduced number of axons results in a reduction in tetanic isometric force and specific force. The greater relative reduction in specific force compared with absolute force production after partial nerve repair may indicate that a population of residual denervated muscle fibers is responsible for this deficit.

Animals↗
PubMed1999

The effect of reinnervation on force production and power output in skeletal muscle.

Failure to fully restore contractile function after denervation and reinnervation of skeletal muscle engenders significant disability in patients suffering peripheral nerve injuries. This work tested the hypothesis that skeletal muscle denervation and reinnervation result in a deficit in normalized power (W/kg), which exceeds the deficit in specific force (N/cm2), and that the mechanisms responsible for these deficits are independent. Adult Lewis rats underwent either transection and epineurial repair of the left peroneal nerve (denervation-reinnervation, n = 13) or SHAM exposure of the peroneal nerve (SHAM, n = 13). After a 4-month recovery period, isometric force, peak power, and maximum sustained power output were measured in the left extensor digitorum longus (EDL) muscle from each animal. Isometric force measurements revealed a specific force deficit of 14.3% in the reinnervated muscles. Power measurements during isovelocity shortening contractions demonstrated a normalized peak power deficit of 25.8% in the reinnervated muscles, which is accounted for by decreases in both optimal velocity (10.5%) and average force during shortening (13.7%). Maximum sustained power was similar in both groups. These data support our working hypothesis that both whole muscle force production and power output can be impaired in reinnervated muscle and that the relative deficits in power output exceed the deficits in force production. The mechanisms responsible for the deficits in force production appear to be independent of those that result in changes in peak power output. The measurement of muscle power output may represent a clinically relevant variable for studies of the recovery of mechanical function after motor nerve injury and repair.

Animals↗
PubMed1999

Plastic surgery.

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Animals↗
PubMed1999

Rat walking tracks do not reflect maximal muscle force capacity.

The relationship between walking-track measurements and maximum force generation in reinnervated rat hindlimb muscles was assessed. A rat model was designed to result in a broad range of recoveries of both muscle force and walking-track measurements after unilateral sciatic nerve injury and reconstruction. Three months following sciatic nerve injury, maximal force in the extensor digitorum longus (EDL) muscle ranged from 1325 to 3666 mN, and maximal specific forces ranged from 137.5 to 359.4 kNm(-2). In the same animals, functional intermediate toe spread factor (FIS) ranged from -0.03 to -0.78. Neither the correlation coefficient between EDL muscle maximal force and FIS (r = 0.4) nor that between EDL maximal specific force and FIS (r = -0.2) were statistically significant. The lack of correlation between muscle maximal force values and walking-track measurements suggests that these neuromuscular tests are assessing different factors.

Analysis of Variance↗
PubMed1999

Mechanical function of muscle reinnervated by end-to-side neurorrhaphy.

End-to-side neurorrhaphy is a surgical technique for peripheral nerve reconstruction when end-to-end neurorrhaphy is not an option. To define the effectiveness of end-to-side neurorrhaphy as a method of nerve repair, the authors tested the null hypothesis: there is no difference in the mechanical function of skeletal muscle denervated and reinnervated by end-to-side versus end-to-end neurorrhaphy. Adult Lewis rats underwent either transection and end-to-end epineurial repair of the left peroneal nerve (n = 9) or end-to-side repair of the distal stump of the peroneal nerve to the side of the tibial nerve (n = 8). After a 6-month recovery period, isometric force (Fo) was measured, and specific force (sFo) was calculated for the extensor digitorum longus muscle of each animal. Immunohistochemical staining for neural cell adhesion molecule (NCAM) was performed to identify populations of denervated muscle fibers. The mean extensor digitorum longus muscle mass in the end-to-end group (195 +/- 32 g) was significantly greater than that of the end-to-side group (146 +/- 55 g) (p < 0.05). A significantly greater percentage of denervated fibers was identified in the extensor digitorum longus muscles of animals in the end-to-side group (9.4 +/- 3.2 percent) than in those in the end-to-end group (3.8 +/- 1.0 percent) (p < 0.05). Despite a lower muscle mass and a higher percentage of denervated fibers, neither Fo nor sFo was significantly different in the two groups. These data support the null hypothesis that, under appropriate circumstances, there is no difference in the recovery of whole muscle force and specific force production in muscles reinnervated by end-to-side versus end-to-end neurorrhaphy.

Animals↗
PubMed1999

Intraocular and intraorbital compartment pressure changes following orbital bone grafting: a clinical and laboratory study.

Visual loss is an uncommon but catastrophic complication after intraorbital bone grafting for the reconstruction of acute traumatic defects or long-standing enophthalmos. Increased intraocular or intraorbital compartment pressure may be pathogenic in this setting. A two-part study was designed to test the null hypothesis that intraocular and intraorbital compartment pressure values remain constant despite orbital volume reduction with graft material. Laboratory study: Intraocular and intraorbital compartment pressures were measured during sequential orbital volume reduction in New Zealand White rabbits that had been randomized to one of three groups: intact orbits (n = 10), acute orbital wall defects (n = 8), and chronic (3 months) orbital wall defects (n = 11). Intraocular pressure was significantly (p<0.05) elevated in all three groups of orbits undergoing orbital volume reduction compared with control, nonoperated orbits. Intraorbital compartment pressure values did not change significantly from control levels throughout the grafting sequence. Although no significant differences existed between groups in the maximum levels of intraocular pressure attained, the chronic group demonstrated a greater rate of rise and slower rate of decline. Clinical study: Using applanation tonometry, intraocular pressure was measured before and serially after orbital floor exploration and intraorbital placement of split calvarial bone grafts in 19 patients who presented with orbital-zygomatic complex fractures that required surgery. A separate group of 16 patients with orbital-zygomatic complex fractures that required exploration of the orbital floor but not bone grafting was used for comparison. A significant (p<0.05) elevation of intraocular pressure was observed immediately after bone grafting compared with nongrafted orbits, but values returned to normal within 30 minutes and remained stable through the third postoperative day. There were no cases of visual impairment in any patients in either group as the result of surgical treatment. These data indicate that orbital volume reduction with graft material results in significant, temporary elevation of intraocular pressure. No significant elevations of intraorbital compartment pressure were detected in the rabbit orbits. Data from this study may have direct relevance in defining guidelines for "tolerable" changes in orbital tissue and globe pressures after surgery.

Adult↗
PubMed1998

Double free-flap reconstruction of massive defects involving the lip, chin, and mandible.

Two patients with massive, composite defects of the total lower lip, chin, and anterior mandible underwent double free-flap reconstruction. A fibular osteoseptocutaneous flap was used to reconstruct the mandible and floor of the mouth and a radial forearm fasciocutaneous composite flap, including the palmaris longus tendon, was used for total lower lip and chin reconstruction. Postoperatively, both patients had acceptable cosmesis, were orally competent, and recovered adequate mandibular function. Double free-flap reconstruction is indicated only in those circumstances in which composite tissue requirements or massive tissue defects preclude reconstruction with a single free-tissue transfer.

Adolescent↗
PubMed1998

Myosin heavy chain expression in skeletal muscle autografts under neural or aneural conditions.

BACKGROUND: Our purpose was to investigate (1) the heterogeneity of satellite cells derived from adult fast-twitch and slow-twitch skeletal muscles, (2) the influence of innervation on muscle regeneration, and (3) the differences between developmental myoblasts and satellite cells with regard to myosin heavy chain (MHC) expression. MATERIALS AND METHODS: Autografts under neural (nerve-intact graft; brief denervation interval) or aneural (aneural graft; prolonged denervation interval) conditions of the fast-twitch extensor digitorum longus (EDL) muscle or the slow-twitch soleus muscle were performed in adult rat hindlimbs. MHC expression during skeletal muscle regeneration was determined sequentially using immunocytochemistry. RESULTS: After grafting, most muscle fibers in the EDL and soleus underwent ischemic degeneration and regeneration; at the periphery of each muscle, a few adult fibers survived. All regenerating fibers initially expressed embryonic/fetal (developmental) MHC alone, and subsequently both developmental and fast MHC. During the first week, no expression of slow MHC was observed in regenerating fibers in either the EDL or the soleus. In nerve-intact grafts, regenerating fibers expressed slow MHC as early as the second week; under aneural conditions, no regenerating fibers expressed slow MHC even 4 weeks after grafting. On the other hand, some persisting fibers in aneural grafts could maintain expression of slow MHC 4 weeks after grafting; other fibers underwent MHC transformation induced by denervation. No significant difference in MHC expression during regeneration was observed for slow compared with fast muscles, under either neural or aneural condition. CONCLUSIONS: These data suggest that regenerating adult skeletal muscle fibers, derived only from satellite cells, cannot express slow MHC without motor innervation, and that persisting muscle fibers, derived from both myoblasts in fetal development and satellite cells, may be intrinsically distinct from regenerating fibers. Satellite cells derived from slow and from fast muscles may be a single, homogenous population and may be the same population as fetal (secondary) myoblasts with regard to MHC expression.

Animals↗
PubMed1997

The effect of duration of muscle denervation on functional recovery in the rat model.

The effect of long-term denervation on neuromuscular recovery was studied in a rat hind limb model. The posterior tibial nerve was transected and repaired immediately or after denervation periods of 2 weeks, or 1, 3, 6, 9, or 12 months. Six months following reconstruction excellent axonal regeneration was seen across all nerve repairs irrespective of periods of denervation. However, there was a precipitous and profound decrease in the recovery of both muscle mass and integrated motor function if the reconstruction was delayed for longer than 1 month. Rather than a progressive change proportional to the length of the denervation period, significant, more discrete changes occurred sometime after 1 month of denervation that precluded a full recovery of muscle mass. Integrated motor function quantified using walking track analysis was impaired even after immediate nerve repair.

Animals↗
PubMed1996

Deletion of individual muscles alters rat walking-track parameters.

Rat walking-track analysis has been employed extensively to quantify motor recovery in studies of hindlimb nerve injury and repair. In order to clarify the relationship between individual print measurements and the function of specific hindlimb muscles, 40 young adult rats were assigned to one of five groups (n = 8/group) in which specific deletions of motors were created as follows: Group 1--division of the tendon of insertion of the gastrocnemius, soleus, and plantaris muscles (GSP); Group 2--division of the extensor digitorum longus muscles tendons of insertion (EDL); Group 3--division of the extensor hallicus longus muscle tendon of insertion (EHL); Group 4--division of the tibialis anterior muscle tendon of insertion (TA); or Group 5--division of the tibial nerve at the ankle (TNA). Parameters for print length (PL), intermediate toe spread (IS), and total toe spread (TS) were calculated from walking tracks recorded before and again five days after deletion of the motors. Specific, predictable patterns of change in footprint parameters were observed for each group. It was concluded that triceps surae and tibialis anterior muscle function directly affects print length; EHL function directly influences total toe spread; and EDL function is directly related to intermediary toe spread. These data demonstrate a direct relationship between individual print measurements and the function of individual rat hindlimb muscles.

Animals↗
PubMed1996

Evaluations of aesthetic results in breast reconstruction: an analysis of reliability.

This study evaluated the reliability of three commonly used measures of aesthetic outcomes of breast surgery: a four-point ordinal scale of overall aesthetics, five four-point subscales, and a visual analogue scale. Fifty patients were randomly selected from women who underwent breast reconstruction surgery at University of Michigan hospitals between July 1989 and May 1993. Postoperative photographs of these patients were provided to three plastic surgeons, who were asked to rate the photographs using the three methods. The same process was repeated 4 weeks later. Intrarater and interrater reliability ranged from poor to good for the three methods, with the subscales showing the highest reliability. The lowest reliability occurred for those scales with the least-explicit rating criteria. Without explicit criteria, raters must develop and use their own criteria, which are likely to differ for each rater. Separating the various components of the aesthetic results of breast surgery into different subscales helps make the rating criteria more explicit. Scales with demonstrated reliability are critical for ensuring comparability of results across studies.

Breast↗
PubMed1996

Effect of electrosurgical technique on wound healing and early complication rate following abdominal dermolipectomy.

Thirty-eight patients with significant weight loss after vertical banded gastroplasty were studied prospectively while undergoing abdominal dermolipectomy to determine if the current intensity used during electrosurgical dissection influenced wound complication rates after this surgery. Patients were assigned randomly to one of two groups: (1) a HI group, in which the electrosurgical current intensity was set at a level that easily allowed coagulation of all vessels smaller than 0.5 mm in diameter or (2) a LO group, in which the current intensity was set at a much lower level that allowed dissection, but required that nearly all visible vessels be ligated separately. A standardized procedure was employed for all patients. The patients in the LO (N = 14) and HI (N = 24) groups were well matched for age, weight history, nutritional parameters, operative times, surgical blood loss, and postoperative hospital stay. The overall complication rates of 36% and 21%, and wound complication rates of 36% and 13% for the LO and HI groups, respectively, were not significantly different. These data indicate that using a relatively high electrosurgical current intensity for dissection during abdominal lipectomy does not result in a higher wound complication rate.

Abdomen↗
PubMed1996

The seven deadly sins of statistical analysis.

In a pedantic but playful way, we discuss some common errors in the use of 'statistical analysis' that are regularly observed in our professional plastic surgical literature. The seven errors we discuss are (1) the use of parametric analysis of ordinal data; (2) the inappropriate use of parametric analysis in general; (3) the failure to consider the possibility of committing type II statistical error; (4) the use of unmodified t-tests for multiple comparisons; (5) the failure to employ analysis of covariance, multivariate regression, nonlinear regression, and logistical regression when indicated; (6) the habit of reporting standard error instead of standard deviation; and (7) the underuse or overuse of statistical consultation. Confidence and common sense are advocated as a means to balance statistical significance with clinical importance.

Humans↗
PubMed1996

Mycobacterium avium infection in a patient with acquired immunodeficiency syndrome and a solid silicone buttock implant.

A 31-year-old female patient with both acquired immunodeficiency syndrome and a solid silicone buttock implant presented with fever. Using ultrasound-guided aspiration of the periprosthetic space, a diagnosis of Mycobacterium avium complex infection involving the implant was made. The implant was surgically removed and the patient had a resolution of her fevers while treated with ethambutol, rifabutin, ciprofloxacin, and clarithromycin.

Acquired Immunodeficiency Syndrome↗