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Biomedical subjects

Michael Leunig

Publications and source records attributed to Michael Leunig.

31 records · Page 2Linked to original sources
PubMed2004

Anterior femoroacetabular impingement: part I. Techniques of joint preserving surgery.

The exact pathomechanism responsible for osteoarthritis (OA) of the nondysplastic hip has remained unknown for many years. There is, however, emerging clinical evidence implicating femoroacetabular impingement as an etiologic factor for having early OA of the hip develop. Femoroacetabular impingement is an abutment conflict occurring between the proximal femur and the acetabular rim arising from morphologic abnormalities affecting the acetabulum or the proximal femur, or both. The repetitive mechanical conflict occurring during motion, particularly flexion and internal rotation, can lead to lesions of acetabular labrum and, even more serious, the adjacent acetabular cartilage. Surgical treatment of femoroacetabular impingement focuses on improving the clearance for hip motion and alleviation of femoral abutment against the acetabular rim. We will describe the rationale for the treatment of this condition, and discuss the technique of joint-preserving surgery.

Acetabulum↗
PubMed2004

Anterior femoroacetabular impingement: part II. Midterm results of surgical treatment.

Femoroacetabular impingement has been shown to cause labral and chondral lesions and leads to osteoarthrosis of the hip. With the elimination of the pathogenic cause we hope to prevent or delay additional degeneration of the hip. Fourteen men and five women with a mean age of 36 years (range, 21-52 years) were treated with a surgical dislocation and offset creation of the hip. The followup averaged 4.7 years (range, 4-5.2 years). Using the Merle d'Aubigné hip score, 13 hips were rated excellent to good, with the pain score improving from 2.9 points to 5.1 points at the latest followup. There was no avascular necrosis of the femoral head. Five of the 19 patients, two with Grade 2 osteoarthrosis, two with Grade 1 osteoarthrosis but severe acetabular cartilage damage, and one with untreated ossified labrum had subsequent total hip arthroplasty (THA). In the stable hips without subluxation of the head into the acetabular cartilage defect, no additional joint space narrowing occurred. Surgical dislocation with correction of femoroacetabular impingement yields good results in patients with early degenerative changes not exceeding Grade 1 osteoarthrosis. This procedure is not suitable for patients with advanced degenerative changes and extensive articular cartilage damage.

Acetabulum↗
PubMed2003

Traumatic labral avulsion from the stable rim: a constant pathology in displaced transverse acetabular fractures.

INTRODUCTION: During the treatment of a malunited transverse acetabular fracture, a hitherto undescribed extended avulsion of the labrum from the stable acetabular fragment was found. Based on the labral pathomorphology present in this case, the hypothesis was put forward that traumatic acetabular labral avulsions are a constant phenomenon in transverse acetabular fractures. PATIENTS AND METHODS: Fourteen patients underwent capsulotomy and/or surgical dislocation of the involved hip to facilitate open reduction and internal fixation of transverse acetabular fractures. RESULTS: In all cases, the labrum was partially or completely detached from the superior acetabular rim. In eight cases with bucket-handle tears of the labrum from the stable superior fragment, the injured portion was resected back to normal margins. In one case the labrum was avulsed with an attached piece of bone and was repaired by screw fixation. Small separations of the labrum from the underlying acetabular rim occurred at the level of the fractures in five cases with minor displacement and received no treatment. CONCLUSION: With displaced transverse acetabular fractures, consideration should be given to opening the joint at the time of open reduction and internal fixation to look for associated intracapsular injuries. An avulsed portion of the labrum should be left if stable and undamaged. If unstable and damaged, it is probably better resected and if unstable but intact and/or attached to a bony fragment, it should be repaired.

Acetabulum↗
PubMed2003

Improved oxygenation in ischemic hamster flap tissue is correlated with increasing hemodilution with Hb vesicles and their O2 affinity.

The aim of this study was to test the influence of oxygen affinity of Hb vesicles (HbVs) and level of blood exchange on the oxygenation in collateralized, ischemic, and hypoxic hamster flap tissue during normovolemic hemodilution. Microhemodynamics were investigated with intravital microscopy. Tissue Po2 was measured with Clark-type microprobes. HbVs with a P50 of 15 mmHg (HbV15) and 30 mmHg (HbV30) were suspended in 6% Dextran 70 (Dx70). The Hb concentration of the solutions was 7.5 g/dl. A stepwise replacement of 15%, 30%, and 50% of total blood volume was performed, which resulted in a gradual decrease in total Hb concentration. In the ischemic tissue, hemodilution led to an increase in microvascular blood flow to maximally 141-166% of baseline in all groups (median; P < 0.01 vs. baseline, not significant between groups). Oxygen tension was transiently raised to 121 +/- 17% after the 30% blood exchange with Dx70 (P < 0.05), whereas it was increased after each step of hemodilution with HbV15-Dx70 and HbV30-Dx70, reaching 217 +/- 67% (P < 0.01) and 164 +/- 33% (P < 0.01 vs. baseline and other groups), respectively, after the 50% blood exchange. We conclude that despite a decrease in total Hb concentration, the oxygenation in the ischemic, hypoxic tissue could be improved with increasing blood exchange with HbV solutions. Furthermore, better oxygenation was obtained with the left-shifted HbVs.

Animals↗
PubMed2003

Normovolemic hemodilution with Hb vesicle solution attenuates hypoxia in ischemic hamster flap tissue.

The aim of this study was to test whether oxygenation in acutely ischemic, collateralized tissue may be improved by normovolemic hemodilution with a solution containing liposome-encapsulated human Hb (HbV). A skin flap model in anesthetized hamsters was used, which consisted of two parts receiving either anatomic or collateral perfusion. Microhemodynamics were investigated with intravital microscopy. Partial tissue oxygen tension was measured with a Clark-type microprobe. Hemodilution was obtained by exchanging 50% of the total blood volume with HbV suspended in 8% human serum albumin (HSA8) or 6% Dextran 70 (Dx70). The size of the vesicles was 276 nm, the P(50) was 22 mmHg, and the Hb concentration of the solutions was 7.5 g/dl. Colloid osmotic pressure and viscosity were 49.9 mmHg and 8.7 cP for HbV-Dx70 and 40.0 mmHg and 2.9 cP for HbV-HSA8, respectively. Hemodilution with HbV-Dx70 led to an increase in microvascular blood flow in the ischemic microvessels to maximally 158% (median, P < 0.01), whereas blood flow remained virtually unchanged after hemodilution with HbV-HSA8. In the ischemic tissue, oxygen tension was improved from 11.9 to 17.0 mmHg (P < 0.01) after hemodilution with HbV-Dx70 but remained virtually unchanged after hemodilution with HbV-HSA8. Our study suggests that the oxygenation in acutely ischemic, collateralized tissue may be improved by normovolemic hemodilution with HbV suspended in Dx70. The effect was achieved by an increase in microcirculatory blood flow related to the rheological properties of the suspending medium.

Animals↗
PubMed2003

Acetabular blood flow during Bernese periacetabular osteotomy: an intraoperative study using laser Doppler flowmetry.

BACKGROUND: The blood flow to the acetabular fragment is of some concern in juxtaarticular pelvic osteotomies used for the treatment of hip dysplasia. No direct measurements have determined the effect of the Bernese periacetabular osteotomy (PAO) on acetabular perfusion. METHODS: Acetabular perfusion was measured by means of laser Doppler flowmetry in 10 patients undergoing a PAO for symptomatic acetabular dysplasia. During the surgical procedure, the intraosseous high energy laser Doppler reliably depicts dynamic changes of small vessel blood flow. Measurements were performed after defined surgical steps to obtain sequential information on the blood perfusion of the acetabular fragment. RESULTS: After complete separation of the acetabular fragment, nine out of 10 patients had pulsatile signals, but the blood flow (BF) significantly decreased by 77%. Corrective positioning of the fragment induced no further drop of the BF signal but a loss of pulsatility in six patients. After a recovery period of about 30 min following preliminary fixation of the fragment, reestablishment of the pulsatile signal and an increase of the BF signal was seen. At termination of the surgical procedure, five out of eight patients, who could be followed throughout the whole procedure, showed a clear pulsatile signal in the supraacetabular area. Bleeding of the supraacetabular cancellous surface could be observed in all acetabula. CONCLUSION: Despite careful preservation of soft tissues during the surgical procedure, a significant reduction of the blood flow in the supraacetabular region has been observed. Nevertheless, a pulsatile signal in more than 60% of the fragments after fragment correction and an increasing signal during the recovery period showed ongoing blood perfusion indicating reversible changes in the measured supraacetabular area. All osteotomies healed within eight weeks without showing signs of necrosis during a minimum follow up of 1 year.

Acetabulum↗
PubMed2003

Reperfusion injury in free bone grafts after tourniquet-induced ischemia.

For successful revascularization, incorporation, and survival of fracture fragments or free nonpedicled bone grafts, the first days after surgery seem to be most critical. Using intravital fluorescence microscopy, the effects of 3 hours of tourniquet-induced ischemia were assessed on newly formed angiogenic microvessels 4, 8, and 12 days after isogeneic transplantation of metatarsal bones into dorsal skin fold chambers of adult inbred C57BL/6 mice. The microvascular perfusion index of newly formed microvessels was quantified 30 and 120 minutes after initiation of reperfusion. Four days after transplantation, a complete breakdown of the perfusion of all grafts was found accompanied by hemorrhage as a sign of microvascular damage. In contrast, at 8 and 12 days after transplantation a complete breakdown of graft perfusion rarely occurred. Therefore, the tourniquet-induced ischemia was most pronounced in early stages of development of angiogenic microvessels. These experimental data provide rationale for critical application of tourniquets in revision surgery shortly after initiation of fracture treatment or transplantation of free nonpedicled grafts so as not to compromise angiogenesis-induced tissue revascularization.

Animals↗
PubMed2003

Acetabular rim degeneration: a constant finding in the aged hip.

During recent years the acetabular labrum has gained increased interest because its degeneration frequently is found in association with early osteoarthritis of the hip. To determine spatial distribution of labral degeneration in the aged hip and to identify the pathologic features triggering this event, an anatomic postmortem and an intraoperative in vivo study were done in 30 cadavers (range, 60-90 years) and in 18 elderly patients (range, 69-97 years) who had hemiarthroplasty for displaced femoral neck fractures. In both groups, no gross anatomic or radiographic abnormalities suggesting advanced osteoarthritis were present. All cadaveric acetabuli (30 of 30) revealed labrum and cartilage damage. Labrum damage (17 of 18) and cartilage lesions (16 of 18) occurred less frequently and were smaller in the elderly patients. Peripheral joint degeneration was most frequent at the superior acetabular rim close to the anterior inferior iliac spine. More centrally localized cartilage lesions were present in 47% of cadavers and in 28% of patients. The majority of femurs (cadavers) (80%) showed reduced narrowing at the anteromedial femoral head-neck junction causing impingement against the corresponding acetabular rim or squeezing of this area into the joint during flexion, whereas the femoral head cartilage appeared normal in all but one hip. Acetabular rim degeneration is a constant finding in the aged hip, which seems to be triggered by femoroacetabular impingement.

Acetabulum↗
PubMed2003

Femoroacetabular impingement: a cause for osteoarthritis of the hip.

A multitude of factors including biochemical, genetic, and acquired abnormalities may contribute to osteoarthritis of the hip. Although the pathomechanism of degenerative process affecting the dysplastic hip is well understood, the exact pathogenesis for idiopathic osteoarthritis has not been established. Based on clinical experience, with more than 600 surgical dislocations of the hip, allowing in situ inspection of the damage pattern and the dynamic proof of its origin, we propose femoroacetabular impingement as a mechanism for the development of early osteoarthritis for most nondysplastic hips. The concept focuses more on motion than on axial loading of the hip. Distinct clinical, radiographic, and intraoperative parameters can be used to confirm the diagnosis of this entity with timely delivery of treatment. Surgical treatment of femoroacetabular impingement focuses on improving the clearance for hip motion and alleviation of femoral abutment against the acetabular rim. It is proposed that early surgical intervention for treatment of femoroacetabular impingement, besides providing relief of symptoms, may decelerate the progression of the degenerative process for this group of young patients.

Acetabulum↗
PubMed2003

Hemorrhage secondary to pelvic fracture: coil embolization of an aberrant obturator artery.

PURPOSE: To describe the anatomical variations of the corona mortis, a vascular anomaly that may lead to dangerous hemorrhage and possible death. CASE REPORT: A 46-year-old male cyclist was involved in a collision with a car, during which he sustained fractures to the left ribs and pelvic ring. Abdominal ultrasound imaging demonstrated a large (12x6x7 cm) nonhomogeneous mass ventral to the bladder, suggestive of a hematoma, which was confirmed on computed tomography. During angiography, 2 branches of the internal iliac artery were identified as sources of the bleeding; these were successfully embolized with microcoils, but the bleeding continued. Examination of the external iliac system found a lacerated aberrant obturator artery arising from the inferior epigastric branch of the external iliac artery, a condition known as the corona mortis. Additional embolization quelled the hemorrhage. CONCLUSIONS: Coil embolization of the internal iliac artery branches is very effective in managing hemorrhage due to pelvic fractures, but variations in the origin of the obturator artery from the internal or external iliac artery may be additional sources of bleeding.

Embolization, Therapeutic↗
PubMed2002

Fatal retroperitoneal hemorrhage caused by perforation of a guidewire pin for proximal femur fixation.

A 77-year-old woman with a slightly displaced intertrochanteric two-fragment fracture of the left hip was treated by internal fixation using a screw-nail device (gamma nail). After the operation she became hemodynamically unstable, and ultrasound revealed a large retroperitoneal fluid accumulation in the left lower abdomen. A contrast computed tomogram revealed active hemorrhage next to the quadrilateral surface of the left acetabulum. Selective angiography and embolization were immediately initiated and stopped the bleeding. However, despite the successful treatment of the retroperitoneal hemorrhage, the patient developed an oligosymptomatic myocardial infarction associated with clinical evidence of a cerebrovascular insult and pulmonary decompensation and died 2 weeks after her accident. The hemorrhage in this patient was most likely caused by surgical damage to the obturator artery during placement of the guidewire pin (with threaded tip) to position the screw of the implant.

Aged↗
PubMed2002

Cryopreservation of osteochondral allografts: dimethyl sulfoxide promotes angiogenesis and immune tolerance in mice.

BACKGROUND: Although transplantation of cryopreserved bone allografts has become a routine procedure in orthopaedic surgery, biological and immunological impairment remains an unsolved problem that causes clinical failures. Experimental and clinical evidence has indicated that bone grafts that are revascularized early remain viable and contribute to union at the recipient site. Unprotected cryopreservation, used in most bone banks to reduce graft antigenicity, is associated with complete loss of graft viability, potentially contributing to graft failure. The differences in the survival of various cell types during cryopreservation with use of dimethyl sulfoxide, particularly the increased sensitivity of leukocytes to fast freezing, has resulted in a new approach to modulate immunogenicity. On the basis of this concept, it was proposed that a reduction in the immune response and enhanced revascularization of osteochondral allografts could be achieved by rapid cryopreservation with dimethyl sulfoxide. To test this hypothesis, angiogenesis and immune tolerance were quantified in a murine model with use of intravital microscopy. METHODS: Fresh osteochondral tissue and osteochondral tissue that had been cryopreserved with and without dimethyl sulfoxide was transplanted into dorsal skinfold chambers as isografts and as allografts in presensitized and nonsensitized recipient mice. To quantify angiogenesis, the onset of hemorrhages in the vicinity of the grafts and the revascularization of the grafts were determined by means of intravital fluorescence microscopy. To determine the recipient's intravascular immune response to the grafts, the leukocyte-endothelium interaction was assessed on the twelfth day after transplantation. RESULTS: Nine of nine fresh isografts were revascularized at a mean (and standard deviation) of 57 +/- 33 hours, eight of nine isografts that had been cryopreserved with dimethyl sulfoxide were revascularized at 98 +/- 50 hours, and zero of nine isografts that had been cryopreserved without dimethyl sulfoxide were revascularized. Seven of seven fresh allografts were revascularized at 53 +/- 6 hours, and ten of ten allografts that had been cryopreserved with dimethyl sulfoxide were revascularized at 82 +/- 29 hours. However, signs of revascularization faded in four of the seven fresh allografts whereas reperfusion was maintained in the majority (seven) of the ten grafts frozen in the presence of dimethyl sulfoxide. Similar to the findings associated with unprotected frozen isografts, zero of ten unprotected frozen allografts were revascularized. None of the allografts that had been transplanted into presensitized recipients were revascularized, regardless of whether they had been implanted fresh (nine grafts) or had been implanted after protected (eight grafts) or unprotected (nine grafts) freezing. Quantification of the leukocyte-endothelium interaction revealed a reduction in the intravascular immune response to frozen allografts (both protected and unprotected) compared with fresh allografts. CONCLUSION: Osteochondral allografts that had been pretreated by cryopreservation with dimethyl sulfoxide demonstrated improved angiogenesis induction and enhanced immune tolerance compared with unprotected frozen grafts. A selective reduction in donor passenger leukocytes is the proposed mechanism underlying this phenomenon. CLINICAL RELEVANCE: In the absence of presensitization, cryopreservation with dimethyl sulfoxide appears to reduce the immune response to allografts and to enhance their revascularization; in the presence of presensitization, alternatives to allograft transplantation should be considered since the allografts will be exposed to a deleterious immune response.

Animals↗