Acetabular centre-edge angles revisited: applications and limitations in patients with acetabular dysplasia undergoing periacetabular osteotomy

This study evaluates the application and limitations of the acetabular centre-edge angles as described by Wiberg (LCE) and Lequesne (VCA) in a group of adult patients with acetabular dysplasia that were treated with periacetabular osteotomy. Fifty hips in patients with a mean age of 30 years (range, 17-45) were identified and a number of radiographic indices were compared pre and post osteotomy. The potential for measurement variation in both the LCE and VCA angle was evaluated and relationships between the centre-edge angles and other radiographic indices were determined. While all hips displayed some degree of lateral deficiency only 19 (40%) of these cases displayed a ''classic'' lateral and anterior deficiency while 12 (20%) were in fact retroverted. The mean VCA in hips with primarily anterior and lateral deficiency (-6.712.5) was significantly lower (p<0.01) than those with uniform deficiency (5.18.3) or those with retroverted acetabuli (8.913.3). Overall the mean VCA angle of 2.3 (SD12.7) and LCE angle of 3.4 (SD9.3) was corrected to 25.8 (SD11.6) and 28.6 (SD8.7) following osteotomy. The VCA and LCE angles were not correlated (r=0.35) and the LCE angle showed no significant correlation to other lateral coverage indices (Tnnis, Sharp). No correlation was seen either in the post osteotomy values, or in the absolute degree of correction. An alternate VCA (aVCA), identifying the most anterior aspect of the acetabular margin as the reference point, was significantly larger (p<0.001) but did correlate (r=0.77) with the traditional VCA. Potential sources of error in measurement were identified and are reviewed.

Hip morphology influences the pattern of damage to the acetabular cartilage: femoroacetabular impingement as a cause of early osteoarthritis of the hip

Recently, femoroacetabular impingement has been recognised as a cause of early osteoarthritis. There are two mechanisms of impingement: 1) cam impingement caused by a non-spherical head and 2) pincer impingement caused by excessive acetabular cover. We hypothesised that both mechanisms result in different patterns of articular damage. Of 302 analysed hips only 26 had an isolated cam and 16 an isolated pincer impingement. Cam impingement caused damage to the anterosuperior acetabular cartilage with separation between the labrum and cartilage. During flexion, the cartilage was sheared off the bone by the non-spherical femoral head while the labrum remained untouched. In pincer impingement, the cartilage damage was located circumferentially and included only a narrow strip. During movement the labrum is crushed between the acetabular rim and the femoral neck causing degeneration and ossification. Both cam and pincer impingement lead to osteoarthritis of the hip. Labral damage indicates ongoing impingement and rarely occurs alone.

Femoroacetabul�res Impingement

The exact cause of the idiopathic osteoarthritis of the hip has not been identified, although the cause of hip degeneration in developmental dysplasia can clearly be attributed to an excessive axial loading. Based on the development of a surgical technique for the safe surgical dislocation of the hip and the associated possibility of intraoperative joint evaluation, we have found motion-induced joint damage in many of these hips. This begins peripherally at the acetabular rim, progressing centrally. This so-called "femoroacetabular impingement" (FAI), leads, by an increased acetabular coverage and/or a missing sphericity of the femoral head, to an abutment of the femoral head/neck junction against the acetabular rim, or even entering of the non-spherical femoral head into the hip. It initiates damage to the labrum and/or acetabular cartilage. Frequently, this becomes symptomatic in the second or third decade of life in patients with increased sport activity. Based on the predominance of the acetabular or femoral pathology, two different types of FAI, the pincer and the cam can be differentiated. Apart from these morphological alterations, supraphysiological mobility and overuse can contribute to FAI. The impingement concept has led to a new type of mainly intracapsular hip surgery.

Predictors of humeral head ischemia after intracapsular fracture of the proximal humerus

The purpose of this study was to evaluate predictors of fracture-induced humeral head ischemia. Between February 1998 and December 2001, 100 intracapsular fractures of the proximal humerus, treated by open surgery, were included in a prospective surgical evaluation protocol (mean age, 60 years; minimum, 21 years; maximum, 88 years; 45 men; 57 right shoulders). Fracture morphology was assessed following a structured questionnaire and based on radiographic and intraoperative findings. Perfusion was assessed intraoperatively by observation of backflow after a borehole was drilled into the central part of the head in all shoulders and by intraosseous laser Doppler flowmetry in 46. Good predictors of ischemia were the length of the metaphyseal head extension (accuracy, 0.84 for calcar segments <8 mm), the integrity of the medial hinge (accuracy, 0.79 for disrupted hinge), and the basic fracture pattern (accuracy, 0.7 for combined types 2, 9, 10, 11, and 12). Moderate and poor predictors of ischemia were fractures consisting of four fragments (accuracy, 0.67), angular displacement of the head (accuracy, 0.62 for angulations over 45 degrees ), the amount of displacement of the tuberosities (accuracy, 0.61 for displacement over 10 mm), glenohumeral dislocation (accuracy, 0.49), head-split components (accuracy, 0.49), and fractures consisting of three fragments (accuracy, 0.38). When the above criteria (anatomic neck, short calcar, disrupted hinge) were combined, positive predictive values of up to 97% could be obtained. The most relevant predictors of ischemia were the length of the dorsomedial metaphyseal extension, the integrity of the medial hinge, and the basic fracture type determined with the binary description system.

Abnormal extension of the femoral head epiphysis as a cause of cam impingement

The etiology of an insufficient femoral head-neck offset has not been identified yet. It was investigated whether a decreased head-neck offset might be correlated with an unusual orientation of the physeal capital scar. Therefore, the femoral head-neck offset and the extension of the physeal scar onto the femoral neck were measured with specific magnetic resonance imaging arthrography. The measurements were done in 15 patients with anterior femoroacetabular impingement attributable to a nonspherical head and were compared with 15 age- and gender-matched control subjects. Eight serial magnetic resonance imaging sections perpendicular to the femoral neck axis were used in each hip to measure the head-neck offset and the epiphyseal extension toward the femoral neck at 16 measurement points. In both groups there was an inverse correlation between the amount of head-neck offset and the relative extension of the capital physeal scar in the cranial hemisphere of the head. Within the anterosuperior head quadrant, there was statistically significant different decrease of the head-neck offset and increase of the lateral epiphyseal extension in the patients compared with the control subjects. These findings suggest a growth abnormality of the capital physis as one probable underlying cause for a nonspherical head.

The acetabular blood supply: implications for periacetabular osteotomies

As the popularity of juxta-acetabular osteotomies in adults increases, concern arises that such a procedure will potentially cause avascular necrosis of the acetabular fragment. In order to verify the remaining vascularization after a Bernese periacetabular osteotomy, an injection study with colored latex was performed. The vascularity of the outside of the periacetabular bone was studied in 16 hips after injection of colored latex into the abdominal aorta and the inside in four hips. To confirm the conclusions drawn from the anatomic study, a Bernese periacetabular osteotomy was performed in two additional hips after latex injection. This study demonstrated that through a modified Smith-Peterson approach and with execution of the osteotomies from the inside of the pelvis the acetabular fragment remains vascularized by the supra-acetabular and acetabular branches of the superior gluteal artery, the obturator artery and the inferior gluteal artery. Some uncertainty remains about how much correction is tolerated by the smaller blood vessels.

Cryopreservation with dimethyl sulfoxide sustains partially the biological function of osteochondral tissue

The clinical routine use of bone allograft transplants dates back to the discovery that grafts devitalized by freezing bear a reduced antigenicity. Graft failures, caused by a host versus graft reaction, however, remain a clinical problem. Previous investigations on pancreatic islet allografts revealed improved survival and biological function when fast cryopreservation (-70 degrees C/min) was performed in the presence of dimethyl sulfoxide (DMSO). The aim of this study was to determine the effect of fast freezing using DMSO on the biological function of osteochondral tissues. Organ culture was performed with neonatal femora of mice, untreated, rapidly frozen (-70 degrees C/min) with DMSO, or frozen without DMSO. After the culture, tissue morphology, cellular proliferation, osteoblast function, osteoclasts, and the presence of antigen-presenting cells were investigated. In untreated control femora histology appeared normal and proliferating and collagen-synthesizing osteoblasts, osteoclasts, and B-cells and macrophages were present. In frozen femora (with and without DMSO) a disintegration of the periosteum and the epiphyseal growth plate were observed and no active osteoblasts could be detected. Osteoclasts were partially detached from the bone surface. Cell proliferation was fully blocked in femora frozen in the absence of DMSO, while freezing in the presence of DMSO preserved cell proliferation in the medullary canal. The proliferating cells do not express epitopes present on the cells of the B-cell or macrophage lineages. Although the biological function of osteoblasts and osteoclasts was lost upon freezing of osteochondral tissue, DMSO included in freezing protocols preserves some residual cell viability which may be of importance for early graft revascularization as has been previously demonstrated by our group.

[Early damage to the acetabular cartilage in slipped capital femoral epiphysis. Therapeutic consequences]

Epiphyseolysis capitis femoris represents the most common disorder of the adolescent hip, which is followed by a significant rate of early osteoarthrosis. Based on intraoperative findings during the surgical management of 23 hips with epiphyseolysis, early acetabular cartilage abrasion by a cam effect and acetabular rim impingement elicited by the prominent femoral metaphysis have been identified. Both phenomena cause direct damage to the hip joint, especially during flexion and flexion/internal rotation of the hip. As evidenced during surgery, the prominent and sometimes sharp-edged anterior neck metaphysis leveling or exceeding the femoral head showed marks of contusion and the labrum revealed erosions, scars, or tears. Moreover, adjacent acetabular cartilage damage was present ranging from superficial abrasions to a full thickness cartilage loss propagating into the weight-bearing area. In all patients the femoral head cartilage was intact; no avascular necrosis was present. These findings suggest that osteoarthrosis is triggered by direct mechanical damage in the epiphysiolysis hip already during the process of slipping and that chondrolysis appears to represent just the most severe form of this cartilage damage. Consequently, we propose that treatment should not only address the avoidance of a further slippage but also the prevention of impingement and cam leading to early acetabular cartilage damage.

Early lesions of the labrum and acetabular cartilage in osteonecrosis of the femoral head

Osteonecrosis of the femoral head can be caused by a variety of disorders and affects the relatively young patient. Most studies have concentrated on the femoral changes; the sites of early lesions of the labrum and acetabular cartilage have not been recorded. We studied 17 hips with osteonecrosis and a wide congruent joint space on radiographs and by direct inspection of the femoral head, labrum and acetabular cartilage during surgery. All of the femoral heads had some anterosuperior flattening which reduced the head-neck ratio in this area. A consistent pattern of damage to the labrum and the acetabular cartilage was seen in all hips. Intraoperatively, impingement and the cam-effect with its spatial correlation with lesions of the labrum and acetabular cartilage were observed. These findings could be helpful when undertaking conservative surgery for osteonecrosis, since the recognition of early radiologically undetectable acetabular lesions may require modification of the surgical technique.

Early lesions of the labrum and acetabular cartilage in osteonecrosis of the femoral head

Osteonecrosis of the femoral head can be caused by a variety of disorders and affects the relatively young patient. Most studies have concentrated on the femoral changes; the sites of early lesions of the labrum and acetabular cartilage have not been recorded. We studied 17 hips with osteonecrosis and a wide congruent joint space on radiographs and by direct inspection of the femoral head, labrum and acetabular cartilage during surgery. All of the femoral heads had some anterosuperior flattening which reduced the head-neck ratio in this area. A consistent pattern of damage to the labrum and the acetabular cartilage was seen in all hips. Intraoperatively, impingement and the cam-effect with its spatial correlation with lesions of the labrum and acetabular cartilage were observed. These findings could be helpful when undertaking conservative surgery for osteonecrosis, since the recognition of early radiologically undetectable acetabular lesions may require modification of the surgical technique.

[MR-Arthrography with radial sequences for visualization of early hip pathology not visible on plain radiographs]

AIM

We wanted to improve MRI visualization of early hip pathology invisible on plain radiographs.

METHOD

An MR arthrography of the hip with radial sequences is described. The standard MR technique is improved by 1) using a small flexible surface coil to show selectively the hip joint to be examined, 2) application of gadolinium intra-articularly and 3) by radial imaging sequences perpendicular to the true plane of the acetabulum.

CONCLUSION

By this technique it is possible to achieve an undistorted image of each aspect of the acetabular rim. Regions of special interest can be defined and their pathologies possibly related to morphologies of the proximal end of the femur.

Surgical landmarks to determine humeral head retrotorsion for hemiarthroplasty in fractures

Malrotation has been suggested as a cause of failure of hemiarthroplasty of the proximal humerus. Placing a shoulder prosthesis in relationship to the bicipital groove might reproduce individual anatomy more reliably than using a standardized retrotorsion. The purpose of this study was to determine criteria for accurate adjustment of retrotorsion even when the proximal bicipital groove is destroyed, as is the case in fractures. The distance of the humeral head equatorial plane to the center of the bicipital groove was measured by high-resolution computed tomography at 4 levels (proximal and distal with 2 intermediate levels). The distal distance was considered to correspond to available references in fracture cases. The mean proximal distance was 8.0 mm (10th percentile, 6.2 mm; 90th percentile, 9.8 mm), and the mean distal distance was 8.5 mm (10th percentile, 7.1 mm; 90th percentile, 9.9 mm). As to the clinical relevance, there was no statistically significant difference between distances. For practical purposes in fracture indications, it is adequate to adjust the retrotorsion of the prosthetic component to the distal bicipital groove.

Entry point soft tissue damage in antegrade femoral nailing: a cadaver study

INTRODUCTION

Little attention is paid to insertion site morbidity associated with antegrade femoral nailing. However, residual peritrochanteric pain after nailing is not uncommon. Additionally, the end branches of the medial femoral circumflex artery (m.f.c.a.) supplying the femoral head are in close proximity to the insertion site of the nail, and the occurrence of avascular necrosis of the femoral epiphysis after nailing in adolescents is rather frequent.

OBJECTIVE

The aim of this study was to assess iatrogenic soft tissue injuries at the site of nail insertion.

MATERIALS AND METHODS

Nailing with a reamed AO universal femoral nail was performed on sixteen adult cadavers followed by dissection of the proximal part of the femur to assess possible damage to the soft tissues. Three entry portals were defined. (A) entry portal lateral to the junction of the neck and the greater trochanter; (B) entry portal at the base of the greater trochanter anterior to a line along the longitudinal axis of the femoral neck; and (C) entry portal at the base of the greater trochanter posterior to a line along the axis of the femoral neck (at the piriformis fossa).

RESULTS

In Group A, partial avulsion of the piriformis and the obturator internus tendon were present in four and in one of five specimens, respectively. Group B showed injuries to the piriformis tendon in two and to the gluteus minimus tendon in one of four cases. In Group C, partial avulsion of the piriformis, obturator internus, and obturator externus tendon were encountered in five, six, and two of seven specimens, respectively. Anterior branches of the ramus profundus of the m.f.c.a. within the synovial fold were damaged in all of these cases.

CONCLUSION

To select the best nail entry portal, the ease of nail insertion must be weighed against the resulting soft tissue damage at the site of insertion. The nail entry portal at the piriformis fossa, although geometrically ideal and most recommended, causes the most significant damage to muscle and tendons as well as to the blood supply to the femoral head. Therefore, even if reported only once, the occurrence of avascular necrosis of the femoral head after nailing in adults is a possible complication of this nail entry portal. The authors therefore prefer to avoid this entry portal in every case. The nail entry portal anterior to the longitudinal axis of the femoral neck, as in group B, although better with respect to the soft tissue damage, has the worst geometric and biomechanical disadvantages. The results of the current study favor the nail entry portal lateral at the greater trochanter as in Group A, which is equal to the entry portal B with respect to the soft tissue damage but allows introduction of the nail into the medullar cavity without difficulties.

Femoroacetabular impingement and the cam-effect. A MRI-based quantitative anatomical study of the femoral head-neck offset

We have observed damage to the labrum as a result of repetitive acetabular impingement in non-dysplastic hips, in which the femoral neck appears to abut against the acetabular labrum and a non-spherical femoral head to press against the labrum and adjacent cartilage. In both mechanisms anatomical variations of the proximal femur may be a factor. We have measured the orientation of the femoral neck and the offset of the head at various circumferential positions, using MRI data from volunteers with no osteoarthritic changes on standard radiographs. Compared with the control subjects, paired for gender and age, patients showed a significant reduction in mean femoral anteversion and mean head-neck offset on the anterior aspect of the neck. This was consistent with the site of symptomatic impingement in flexion and internal rotation, and with lesions of the adjacent rim. Furthermore, when stratified for gender and age, and compared with the control group, the mean femoral head-neck offset was significantly reduced in the lateral-to-anterior aspect of the neck for young men, and in the anterolateral-to-anterior aspect of the neck for older women. For patients suspected of having impingement of the rim, anatomical variations in the proximal femur should be considered as a possible cause.

Femoroacetabular impingement and the cam-effect. A MRI-based quantitative anatomical study of the femoral head-neck offset

We have observed damage to the labrum as a result of repetitive acetabular impingement in non-dysplastic hips, in which the femoral neck appears to abut against the acetabular labrum and a non-spherical femoral head to press against the labrum and adjacent cartilage. In both mechanisms anatomical variations of the proximal femur may be a factor. We have measured the orientation of the femoral neck and the offset of the head at various circumferential positions, using MRI data from volunteers with no osteoarthritic changes on standard radiographs. Compared with the control subjects, paired for gender and age, patients showed a significant reduction in mean femoral anteversion and mean head-neck offset on the anterior aspect of the neck. This was consistent with the site of symptomatic impingement in flexion and internal rotation, and with lesions of the adjacent rim. Furthermore, when stratified for gender and age, and compared with the control group, the mean femoral head-neck offset was significantly reduced in the lateral-to-anterior aspect of the neck for young men, and in the anterolateral-to-anterior aspect of the neck for older women. For patients suspected of having impingement of the rim, anatomical variations in the proximal femur should be considered as a possible cause.

Gluteus minimus-induced femoral head deformation in dysplasia of the hip

Lateral notching of the femoral head is considered pathognomonic for spastic subluxation of the hip. Less frequently, flattening is seen with extrusion of the femoral head in nonspastic hip dysplasia. The aim of this study was to throw light on its underlying pathomechanism. On the radiographs of 297 hips with developmental dysplasia, lateral flattening of the femoral head was seen in 18 hips (6%), but notching was present in only 1. Of 7 dysplasias due to cerebral palsy, 6 showed lateral notching. The gluteus minimus was felt to be responsible for the lateral femoral head changes as the muscle counteracts lateral migration of the femoral head. Intraoperative dissection of 3 hips supported this view. 1 hip with developmental dysplasia and lateral notching was subjected to a periacetabular osteotomy. At surgery, the tendon of the gluteus minimus was found to fit tightly into the notch. Of 2 hips with spastic dysplasia, 1 presented with and the other without lateral notching. In the hip with lateral notching, the gluteus minimus had a normal appearance and it lay in the defect of the femoral head. In the hip without notching, the gluteus minimus was atrophied with signs of fatty degeneration. We therefore believe that lateral notching is a sign of hypertonicity of the gluteus minimus muscle.

Cross-Table Lateral Radiographs for Screening of Anterior Femoral Head-Neck Offset in Patients with Femoro-Acetabular Impingement

One theory for the aetiology of osteoarthrosis of the hip is the impingement of the anterior femoral neck against the acetabulum in flexion. The reduced femoral head-neck offset not visible on AP-radiography is implicated in this impingement. The anterior part of the head-neck region is well visualised on cross table lateral radiographs. A retrospective analysis of the offset using cross table lateral radiographs was therefore performed on twelve symptomatic and ten asymptomatic hips. The anterior offset (AOS) was defined as the difference in radius between the anterior femoral head and the anterior femoral neck. The offset ratio (OSR) was defined as the AOS divided by the femoral head diameter. The AOS was 11.6 ± 0.7 mm in the asymptomatic group and 7.2 ± 0.7 mm in the symptomatic group, which was statistically significantly different (p=0.0006). The OSR was 0.21 ± 0.03 in the asymptomatic group and 0.13 ± 0.05 in the symptomatic group, which was also statistically significantly different (p=0.0004). Cross-table lateral radiographs of the hip are useful for screening patients complaining of anterior femoro-acetabular impingement symptoms, as their anterior femoral head-neck offset may be smaller.

Development of transplanted fetal bones: differences between isografts and allografts in mice

Allogeneic bone from bone banks frequently is used when large skeletal defects have to be bridged in orthopaedic surgery. Beside immunologic rejection of the graft, the loss in osteogenic potential caused by bone banking procedures may be a major reason for limited clinical success. Similar problems as described for bone have occurred with cartilage and osteochondral transplants. Improving the properties of allogenic bone so that its biologic activity becomes comparable to autologous bone could be substantially beneficial for the outcome of allograft transplantation. To dissect the steps involved in the integration of a fetal osteochondral graft as it matures to bone, the current study compared the development and biologic function of metatarsals from 18-day-old fetal mice freshly transplanted in three different immunologic settings. Morphologic assessment of (1) isografts and (2) allografts in nonsensitized hosts 12 days after transplantation revealed that the grafts bear an intrinsic potential to develop after transplantation. In allografts in nonsensitized hosts, however, a slight alteration in biologic activity as compared with isografts could be detected already in this early phase after transplantation by in situ hybridization for messenger ribonucleic acids encoding extracellular matrix proteins. (3) In contrast to isografts and allografts in nonsensitized hosts, morphologic features and biologic function of allografts transplanted to presensitized hosts were altered severely.

[Inadequate detectability of early stages of coxarthrosis with conventional roentgen images]

AIM

The study was undertaken to determine the value of standard radiographs in the early stages of osteoarthritis.

METHODS

Standard radiographs and arthro-MRI's from thirty hips operated on for early arthrosis (age 25-57 years) were independently analyzed by two orthopaedic surgeons and one radiologist blinded from the intra-operative findings. The radiographs were read on two occasions two months apart. The radiographic findings were then compared to the intra-operative findings.

RESULTS

Intra-operatively, all cases had a labral lesion and, in all but three of the cases, there was a major acetabular cartilage lesion. Each investigator diagnosed all of the labral and/or cartilage lesions on the arthro-MRI. However, on average, the investigators judged 20% (10-35%) of the hips to be normal on the standard radiographs. The probability of detecting an abnormal hip joint was statistically significantly better with arthro-MRI in four of six readings (p < 0.05) and there was a trend in favor of the arthro-MRI in the other two readings (p < 0.1). Intra-observer agreement when using the Tönnis classification of arthrosis on standard radiographs was 0.26 (-0.1-0.62), 0.69 (0.42-0.96) and 0.83 (0.53-1) [kappa-statistic, (95% confidence interval)]. The interobserver agreement was 0.24 (-0.07-0.55).

CONCLUSION

Plain radiographs in the early stages of osteoarthrosis of the hip are neither reliable nor valid to diagnose the onset of disease. Therefore, in the case of a normal radiograph and clinical suspicion of arthrosis, a "normal" radiograph does not exclude the diagnosis and an artho-MRI should be obtained for further evaluation.

Rationale of periacetabular osteotomy and background work

The Bernese periacetabular osteotomy is a joint-preserving procedure used after growth plate closure to correct acetabular coverage and stabilize the femoral head. The polygonal, juxta-articular osteotomy respects the vascular blood supply to the acetabular fragment and facilitates an extensive acetabular reorientation. It achieves improvement of the insufficient coverage of the femoral head, reduction of mediolateral displacement, and correction of the version of the fragment. All osteotomies are performed through the modified Smith-Petersen approach, which also allows for an anterior capsulotomy. Joint inspection not only provides information on lesions of the rim but also facilitates the control of an impingement-free range of motion after the correction. The posterior column remains partially intact, allowing minimal internal fixation of the acetabular fragment and early mobilization similar to that after an intertrochanteric osteotomy. Because the majority of this patient population consists of young women, it is important to note that the dimensions of the true pelvis and thus the potential for future vaginal delivery are preserved.

Free nerve endings in the ligamentum capitis femoris

We report the presence of free nerve endings (FNE) in the ligamentum capitis femoris (LCF). Qualitative and quantitative measurements on the incidence of FNE, as assessed by immuno-histochemistry for the S-100 protein, were obtained from 18 patients undergoing hip surgery. We found FNE in all LCF, with no association to age. The presence of FNE in the LCF suggests a role in noci-/proprioception of the hip.

The effect of pedicle artery vasospasm on microhemodynamics in anatomically perfused and extended skin flap tissue

The aim of this study was to evaluate quantitatively the influence of pedicle artery vasospasm on the microcirculation in skin flaps, particularly in the jeopardized extended portions. For this purpose, the hamster island skin flap model was used, which allowed for simultaneous assessment of hemodynamics in both the pedicle artery and the microvasculature of the flap by intravital microscopy. Vasospasm was induced by applying a V3 microvascular clamp for 30 seconds. Clamping resulted in a severe vasospasm, with the artery exhibiting a diameter of 7% +/- 2% (mean +/- standard error) of its original diameter (n = 10; p < 0.01), and with a reduction of total blood flow to the flap of 11% +/- 2% (p < 0.01). Diameter and blood flow recovered gradually to baseline levels after 25 and 15 minutes respectively. During recovery from severe pedicle artery vasospasm (moderate to mild vasospasm), the arterioles in the anatomically perfused flap tissue (n = 38) showed reactive vasodilation (p < 0.01), which was absent in the extended tissue (n = 49; p < 0.01 vs. anatomic). At a pedicle artery vasospasm of 50% of the original diameter, blood flow was restored to normal levels in the anatomically perfused arterioles, but remained below baseline in the extended part (partly p < 0.05 vs. baseline and anatomic). The findings suggest that the development of ischemic necrosis in extended flap portions may be promoted by prolonged, moderate vasospasm, which is well tolerated in the anatomically perfused tissue because of its high capacity for implementing compensatory local regulatory mechanisms.

Slipped capital femoral epiphysis: early mechanical damage to the acetabular cartilage by a prominent femoral metaphysis

On the basis of intraoperative observations in 13 consecutive adolescents (14 hips) with slipped capital femoral epiphysis (SCFE), we found that when the anterior femoral metaphysis was level with or extended past the epiphysis, it caused labrum and cartilage damage. As a result of an impingement between the metaphysis and the superomedial acetabular rim, the labrum revealed erosions, scars or tears. Further jamming of the metaphysis into the joint damaged the adjacent acetabular cartilage, varying from a partial- to a full-thickness cartilage loss. In all patients, the femoral head cartilage was intact; no avascular necrosis was present. Our findings suggest that arthrosis in SCFE can be triggered by early mechanical damage of the acetabular cartilage.

The evolution of indirect reduction techniques for the treatment of fractures

During the last decade, classic AO/ASIF techniques for internal fixation shifted from direct reduction and rigid fixation to biologic internal fixation using indirect reduction techniques. Biologic internal fixation is characterized by the preservation of bone and soft tissue vascularity and relative rather than absolute mechanical stability. Reduction is achieved by using soft tissue traction while obtaining axial and rotational alignment and the correct length. Stabilization is performed when possible by compression plating for load sharing or by bridge plating in comminuted fractures. Advancements of these techniques and the development of newer implants that minimize vascular damage have contributed to the development of biologic internal fixation. By using indirect reduction, by using longer plates to improve the mechanical leverage, and by applying fewer screws to avoid unnecessary damage to the bone, fracture union rates were high. There also was a decreased need for supplemental bone grafting. All of these factors provided stable fixation and allowed early motion.