The gluteus maximus musculocutaneous island flap: refinements in design and application

The gluteus maximus island musculocutaneous flap has been described using a variety of designs. We employ an island whose long axis is directed toward the pressure sore, minimizing tension in wound closure. Skin overlying the greater trochanter is avoided. Previously undermined skin can be included in the flap. Fifty patients with ischial or sacral pressure sores have been managed by this technique. Superficial dehiscence occurred in 13 percent of patients, and deep dehiscence occurred in 10 percent. The dehiscence closed spontaneously in all but one patient. Forty-nine of the 50 patients experienced complete wound healing at the pressure sore site. The patients have been observed for an average of 20 months (range 3 to 38 months), with one recurrent pressure sore seen at 28 months postoperatively. The gluteus maximus musculocutaneous island flap has proven to be both reliable in healing and durable over the observed interval.     

Triple coverage of ischial ulcers with adipofascial turnover and fasciocutaneous flaps

Despite a wide variety of flap options, ischial ulcers remain the most difficult pressure ulcers to treat. This article describes the authors' successful surgical procedure for coverage of ischial ulcers using adipofascial turnover flaps combined with a local fasciocutaneous flap. After debridement, the adipofascial flaps are harvested both cephalad and caudal to the defect. The flaps are then turned over to cover the exposed bone in a manner so as to overlap the two flaps. A local fasciocutaneous flap (Limberg flap) is applied to the raw surface of the turnover flaps. Twenty-two patients with ischial ulcers were treated using this surgical procedure. Overall, 86.4 percent of the flaps (19 of 22) healed primarily. Triple coverage with the combination of double adipofascial turnover flaps and a local fasciocutaneous flap allows for an easily performed and minimally invasive procedure, preservation of future flap options, and a soft-tissue supply sufficient for covering the prominence and bony prominence and filling dead space. This technique provides successful soft-tissue reconstruction for minor to moderate-size ischial pressure ulcers.     

The inferiorly based rectus abdominis myocutaneous flap for reconstruction of recurrent pressure sores.

Eight neurologically impaired patients underwent reconstruction of chronic perineal and ischial pressure sores utilizing an inferiorly based rectus abdominis myocutaneous flap. Other local and regional flap options had been previously used or were not feasible. In six patients, healing was uncomplicated. One patient required local debridement and flap readvancement. The second involved minor separation of a suture line and healed by secondary intention. All donor sites were closed directly and healed by primary intention. There was no evidence of hernia formation, and no functional deficit was detected from removal of the rectus muscle in any of the patients. In conclusion, it was felt that the inferiorly based rectus abdominis myocutaneous flap should be considered a reconstructive option in dealing with perineal and ischial pressure sores. Furthermore, for reasons discussed, we found distinct advantages to using this flap in spinal cord injury patients.     

Evolution of the ischial spine and of the pelvic floor in the Hominoidea

Study of the pelvis in 143 different mammals reveals that in quadrupeds the ischial spines are barely noticeable and are located posteriorly near the sacrum. In humans, the ischial spines are prominent and more anteriorly located. As a consequence of their position and size, the ischial spines in humans become an obstacle to parturition. Herein a theory is proposed to account for what appears to be an incongruous development and orientation of the ischial spines in humans. The pelvic diaphragm is a vertical pelvic "wall" in tailed mammals and is composed of muscles involved mostly with the motion of the tail. In humans, the muscles of the pelvic diaphragm have a very different anatomical orientation. They form a horizontal pelvic "floor," and their functions are first to support the abdominopelvic organs and resist intra-abdominal pressure that is exerted from above, and second, as levator ani, to control the anal sphincter. In humans the muscles and fascias of the pelvic diaphragm are inserted on the ischial spines either directly or indirectly through the sacrospinous ligament and the tendinous arch of the pelvic fascia. The result is a medial pull on the ischial spines to produce a more rigid and narrower pelvic floor. An inconstant ossification center for the ischial spines make them more prominent. The backward tilt of the sacrum placed the bispinal line in a diameter position. Pongids and even fossil hominids occupy an intermediate position between tailed mammals and Homo sapiens. The present form of the pelvis in Homo sapiens may be determined by a significant genetic component but may also be partly acquired during childhood and adolescence.     

Treatment of ischial pressure ulcers with a posteromedial thigh fasciocutaneous flap.

This study describes the use of the posteromedial thigh fasciocutaneous flap for the treatment of ischial pressure sores. The authors prefer this flap because it is the fasciocutaneous flap nearest to the ischial region, it is easy to raise, and it causes no donor-site morbidity. In this study, 11 ischial pressure sores in 10 paraplegic patients were closed using the posteromedial thigh fasciocutaneous flaps. All flaps survived, although two caused distal necrosis; after these same two flaps were readvanced, they survived. After an average follow-up time of 77 months, seven of the 10 patients have had no recurrence of ulcers.This fasciocutaneous flap was previously described by Wang et al. However, this study revealed that the arrangement of the vascular pedicle was different from that described by Wang et al. To reveal the vascular supply of this flap, anatomic dissections were conducted. The source of circulation to this flap was the suprafascial vascular plexus, in addition to the musculocutaneous perforator. The dominant pedicle was the musculocutaneous perforator from either the adductor magnus muscle or the gracilis muscle. The key to safe elevation of this flap was the accurate outlining of the skin island directly over the vascular pedicle and the preservation of the proximal fascial continuity. Of the 11 flaps, two viability problems occurred. These partial flap losses resulted from the failure to properly include the perforator. It is the authors' conclusion that the width of the flap should be greater than 5 cm. In addition, it is safe to make a flap within a 1:3 base-to-length ratio in a fatty, diabetic patient. This posteromedial thigh fasciocutaneous flap was found to be a valuable alternative for reconstruction of primary or recurrent ischial pressure ulcers.     

Ischial tuberosities and ischial callosities

Ischial callosities are specialised regions of skin and subdermal tissue in the form of fibro-fatty cushions with a tough, non-slip surface, firmly bound to the underlying ischial tuberosity. They occur in primates of the families Cercopithecidae and Hylobatidae. Ischial callosity usage helps animals to adopt stable sitting postures on the tops of branches, particularly during feeding, resting and sleeping. Callosity-like areas in pongids are mainly epidermal specialisations and differ in their development and usage from true callosities. They are similar to the para-callosity skin regions in some ground living cercopithecids. The ischial tuberosity in animals with true callosities has a flat surface which flares out from the lower end of the ischial body and which is devoid of muscle attachments. In animals without callosities the ischial tuberosity is not flared, has a curved surface, and acts as a site for muscle attachment. The ischial tuberosity is relatively broader in animals with callosities than in animals without callosities, although the absolute size of the specimens concerned must be taken into account. The combination of qualitative and quantitative features of fossil ischial tuberosities enables the presence or absence of callosities in these forms to be deduced. The recognition of these features in fossil material might be of use in the elucidation of the evolution of one type of primate arboreal adaptation.     

Multiple and repetitive uses of the extended hamstring V-Y myocutaneous flap

An extended hamstring V-Y myocutaneous advancement flap is described that may be used to cover unusually large defects in the ischial region. Technical points that allow a large amount of flap advancement are discussed. Because of its large size, the flap can be raised and used on repeated occasions to repair defects from recurrent ischial pressure sores. Two patients are presented in whom the same flap was used repeatedly on multiple occasions, demonstrating the potential for preservation of future options in such patients when this flap is used.     

Comparative assessment of the ischial morphology of Victoriapithecus macinnesi

An almost complete primate ischium was recovered from middle Miocene (ca. 15 ma) deposits of Maboko Island (Kenya) in 1987. The specimen shows numerous similarities to the ischial morphology of extant cercopithecids and is attributed to Victoriapithecus macinnesi (Von Koenigswald, 1969), the early Old World monkey best known from Maboko Island. The Victoriapithecus ischium provides the first evidence of early Old World monkey pelvic girdle anatomy. The ischium is characterized by an obliquely oriented and broadly flaring tuberosity, a relatively small acetabulum with little ventrally directed curvature of its caudal portion, a long ischial body and a flange-like ischial spine positioned caudal to the rim of the acetabulum. In these features, Victoriapithecus most closely resembles the vervet monkey, Cercopithecus aethiops. The fossil specimen indicates that Victoriapithecus possessed ischial callosities, a mobile tail and adaptations for (possibly cursorial) quadrupedalism with an adducted posture of the thigh. The occurrence of ischial callosities in Victoriapithecus extends the documented antiquity of this feature in catarrhines by more than 12 million years and shows that the distinctive “sitting-sleeping” adaptations of Old World monkeys (Washburn, 1957) originated prior to the divergence of Colobinae and Cercopithecinae. Differences of developmental sequence and tissue composition indicate that the ischial pads of cercopithecids, hylobatids, and pongids may have arisen independently, through parallel evolution. Contrary to Strasser and Delson (1987), discontinuity of ischial callosities was probably the primitive condition for male cercopithecids.     

Complications of total ischiectomy for the treatment of ischial pressure sores

Five patients are reported, 4 of whom had total ischiectomies and the other an extensive partial ischiectomy. In each, recurrent ulcers, extending into the perineum, developed subsequently. One patient had a urethrocutaneous fistula as a result of his perineal ulcer, and he had to undergo an ileal loop diversion. Following a unilateral ischiectomy, the pressure is shifted to the opposite ischium, and this favors the development of another ischial pressure sore on the opposite side. After bilateral ischiectomy there is much more pressure on the perineum, and these patients may go on to develop a perineal pressure sore--particularly if there is a dislocated hip. Recurrent pressure sores which extend into the perineum are difficult to treat, and usually they appear to be related to a previous extensive removal of the ischia.     

Muscle-splitting approach to superior and inferior gluteal vessels: versatile source of recipient vessels for free-tissue transfer to sacral, gluteal, and ischial regions

The superior gluteal vessel has been reported as a recipient in free-tissue transfer for the coverage of complex soft-tissue defects in the lumbosacral region, where a suitable recipient vessel is difficult to find. The characteristics of proximity, vessel caliber, and constancy make the superior gluteal vessel preferable to previously reported recipient vessels. However, there are technical difficulties in microsurgery (e.g., short pedicle length and deep location) and muscle injury (transection of the muscle) associated with use of the superior gluteal vessel. The purpose of this article is to present a modification of an approach to the gluteal vessel to alleviate technical difficulties and minimize muscle injury. From August of 1997 to January of 1999, six patients received microvascular transfer of the latissimus dorsi muscle or myocutaneous flap to the sacral (4) and ischial (2) regions. The causes of defects were tumor (1), trauma (1), and pressure sores (4). A muscle-splitting approach was used on the superior gluteal vessel and was later applied to the inferior gluteal vessel. The gluteus maximus muscle was split as needed in the direction of its fibers, and the perforators were dissected down to the superior or inferior gluteal artery and vein deep into the muscle. The follow-up period ranged from 6 to 22 months, and all of the flaps survived with complete recovery of the lesion. The major drawbacks of using the superior and inferior gluteal vessels can be overcome with the muscle-splitting approach, which provides increased accessibility and additional length to the vascular pedicle while causing minimal injury to the muscle itself. It also proves to be an easy, safe, and reliable method of dissection. When free-tissue transfer to sacral, gluteal, and ischial regions is indicated, the muscle-splitting approach to the superior and inferior gluteal vessels is a recommended option in the selection of a recipient vessel.     

Gluteal perforator flaps for coverage of pressure sores at various locations

Flap coverage is essential for successful treatment of pressure sores, and musculocutaneous flaps have been preferred universally. Development of perforator flaps supplied by musculocutaneous perforators has allowed reconstructive surgeons to harvest flaps without including muscles. Perforator flaps have enhanced the possibility of donor sites because a flap can be supplied by any musculocutaneous perforator, and donor-site morbidity is also reduced. Between November of 1998 and June of 2002, the authors used 35 gluteal perforator flaps in 32 consecutive patients for coverage of pressure sores located at sacral (n = 22), ischial (n = 7), and trochanteric (n = 6) regions. The mean age of the patients was 53.1 years (range, 5 to 87 years), and there were 16 male and 16 female patients. All flaps in this series were supplied by musculocutaneous arteries arising from gluteal muscles. Patients were followed up for a mean period of 13.6 months. Wound dehiscence was observed in two patients and treated by secondary closure. Three patients died during the follow-up period. All flaps survived except one that had undergone total necrosis, and only one recurrence was noted during the follow-up period. Gluteal perforator flaps are safe and reliable options for coverage of pressure sores located at different locations. Freedom in flap design and low donor-site morbidity make gluteal perforator flaps an excellent choice for pressure sore coverage.     

Regulation of the patellofemoral contact area: An essential mechanism in patellofemoral joint mechanics?

Although the relationship between contact area and pressure under physiological loading has been described in the feline patellofemoral joint, this interaction has only been examined under simplified loading conditions and/or considerably lower forces than those occurring during demanding activities in humans. We hypothesized that patellofemoral contact area increases non-linearly under an increasing joint reaction force to regulate patellofemoral pressure. Eight human cadaveric knees were ramp loaded with muscle forces representative of the stance phase of stair climbing at 30° knee flexion. Continuous pressure data were acquired with a pressure sensitive film that was positioned within the patellofemoral joint. While pressure was linearly dependent upon the resulting joint reaction force, contact area asymptotically approached a maximum value and reached 95% of this maximum at patellofemoral forces of 349–723 N (95% CI). Our findings indicate that the regulatory influence of increasing contact area to protect against high patellofemoral pressure is exhausted at relatively low loads.     

Dynamic forces over the interface between a seated human body and a rigid seat during vertical whole-body vibration

Biodynamic responses of the seated human body are usually measured and modelled assuming a single point of vibration excitation. With vertical vibration excitation, this study investigated how forces are distributed over the body-seat interface. Vertical and fore-and-aft forces were measured beneath the ischial tuberosities, middle thighs, and front thighs of 14 subjects sitting on a rigid flat seat in three postures with different thigh contact while exposed to random vertical vibration at three magnitudes. Measures of apparent mass were calculated from transfer functions between the vertical acceleration of the seat and the vertical or fore-and-aft forces measured at the three locations, and the sum of these forces. When sitting normally or sitting with a high footrest, vertical forces at the ischial tuberosities dominated the vertical apparent mass. With feet unsupported to give increased thigh contact, vertical forces at the front thighs were dominant around 8 Hz. Around 3–7 Hz, fore-and-aft forces at the middle thighs dominated the fore-and-aft cross-axis apparent mass. Around 8–10 Hz, fore-and-aft forces were dominant at the ischial tuberosities with feet supported but at the front thighs with feet unsupported. All apparent masses were nonlinear: as the vibration magnitude increased the resonance frequencies decreased. With feet unsupported, the nonlinearity in the apparent mass was greater at the front thighs than at the ischial tuberosities. It is concluded that when the thighs are supported on a seat it is not appropriate to assume the body has a single point of vibration excitation.     

A Flexible Restraint Chair for the Cynomolgus Monkey (Macaca fascicularis)1

We have found that commercial restraint chairs suitable for the rhesus monkey (Macaca mulatta) cause severe physical distress to many cynomolgus monkeys (Macaca fascicularis). A new restraint chair has therefore been designed specifically for the cynomolgus. The key features of the chair are an angled neck piece, a large opening to provide free movement for the tail, a soft waist restraint, and a level surface for both the heels and ischial pads. This new chair is not only suitable for the cynomolgus monkey but may also be more comfortable for the rhesus monkey than standard commercial chairs.     

The function of ischial callosities

Ischial callosities are generally related to the sitting positions of cercopithecoid monkeys, gibbons, and siamangs, but the selective advantage of ischial callosities to the sitting postures of these animals is uncertain. It is suggested that ischial callosities are adaptations that evolved for comfortable and stable sitting on thin branches during feeding in the peripheral branch zone. It is further suggested that prehensile tails in larger New World monkeys also developed as mechanisms for exploitation of food resources found among terminal branches. Small platyrrhine monkeys do not possess any structural adaptations to peripheral branch feeding because their body size permits them to efficiently exploit small or large branches for food. Pongids are in the process of losing their ischial callosities because their large body size precludes sitting on thin branches.     

Intermittent electrical stimulation redistributes pressure and promotes tissue oxygenation in loaded muscles of individuals with spinal cord injury

Deep tissue injury (DTI) is a severe form of pressure ulcer that originates at the bone-muscle interface. It results from mechanical damage and ischemic injury due to unrelieved pressure. Currently, there are no established clinical methods to detect the formation of DTI. Moreover, despite the many recommended methods for preventing pressure ulcers, none so far has significantly reduced the incidence of DTI. The goal of this study was to assess the effectiveness of a new electrical stimulation-based intervention, termed intermittent electrical stimulation (IES), in ameliorating the factors leading to DTI in individuals with compromised mobility and sensation. Specifically, we sought to determine whether IES-induced contractions in the gluteal muscles can 1) reduce pressure in tissue surrounding bony prominences susceptible to the development of DTI and 2) increase oxygenation in deep tissue. Experiments were conducted in individuals with spinal cord injury, and two paradigms of IES were utilized to induce contractions in the gluteus maximus muscles of the seated participants. Changes in surface pressure around the ischial tuberosities were assessed using a pressure-sensing mattress, and changes in deep tissue oxygenation were indirectly assessed using T?*-weighted magnetic resonance imaging (MRI) techniques. Both IES paradigms significantly reduced pressure around the bony prominences in the buttocks by an average of 10-26% (P < 0.05). Furthermore, both IES paradigms induced significant increases in T?* signal intensity (SI), indicating significant increases in tissue oxygenation, which were sustained for the duration of each 10-min trial (P < 0.05). Maximal increases in SI ranged from 2-3.3% (arbitrary units). Direct measurements of oxygenation in adult rats revealed that IES produces up to a 100% increase in tissue oxygenation. The results suggest that IES directly targets factors contributing to the development of DTI in people with reduced mobility and sensation and may therefore be an effective method for the prevention of deep pressure ulcers.     

Ratio of cut surface area to leaf sample volume for water potential measurements by thermocouple psychrometers

Evaporative losses from the cut edge of leaf samples are of considerable importance in measurements of leaf water potential using thermocouple psychrometers. The ratio of cut surface area to leaf sample volume (area to volume ratio) has been used to give an estimate of possible effects of evaporative loss in relation to sample size. A wide range of sample sizes with different area to volume ratios has been used. Our results using Glycine max L. Merr. cv Bragg indicate that leaf samples with area to volume values less than 0.2 square millimeter per cubic millimeter give psychrometric leaf water potential measurements that compare favorably with pressure chamber measurements.     

Functional aspects of primate pelvic structure: A multivariate approach

This study aims to clarify the relationship of primate bony pelvic structure to locomotor habit. As with most of the postcranial skeleton, the pelvic bones of species within the Ceboidea and the Cercopithecoidea are remarkably similar visually except for variations in size. Yet there are substantial differences in locomotor pattern between the species in these taxa. I performed canonical analyses on a sample of 17 pelvic variables describing 22 primate species of the Ceboidea, the Cercopithecoidea, and the Hominoidea to discover which variables were significant in separating them into groups. In both analyses there was good separation of major taxa and additional separation of groups that differed in locomotor habit. The separation of colobine from cercopithecine monkeys was particularly consistent. In the analysis, including all 22 species, the variables given particular weight by the canonical analysis were the same as those traditionally used by anatomists for the same purpose. Specifically, breadth of the ischial tuberosity (reflecting presence or absence of ischial callosities) separated the Old from the New World monkeys. Breadth of the iliac tuberosity, in which man and to some extent other hominoids differ from other primates, and ilium height, in which man differs from other primates, were significant. Sagittal diameter of the pelvis was also substantially weighted. Having established that the technique would select variables of anatomical significance, the same method was applied to a study of monkeys only where the characteristics that differ between groups are not well established. Breadth of the ischial tuberosity was again important in separating the Ceboidea from the Cercopithecoidea. Discrimination of locomotor groups within these large divisions was brought about mainly by ischial length and the sagittal diameter of the pelvis. In studying these variables and their relationship to size in greater detail, it was found that among cercopithecoid monkeys, the colobines showed relatively lower values than did cercopithecines for both these dimensions. Atelines showed low values for ischial length but high values for the sagittal pelvic diameter. Biomechanical explanations of these observations are suggested.     

Effect of a low-frequency magnetic field on systemic arterial pressure in spontaneously hypertensive rats

The effect of low-frequency magnetic field (MF) on systemic blood pressure has been studied in chronic experiments on 21 spontaneously hypertensive rats. The animals' kidney area was exposed to MF (induction value 30T). Direct blood pressure measurements have revealed an antihypertensive effect.