Excellent Long-Term Survival Rate of Polished, Tapered, Cemented Stems in Patients Aged 35 Years or Younger With Avascular Necrosis or Inflammatory Arthritis of the Hip.

BACKGROUND: Total hip arthroplasty (THA) for avascular necrosis (AVN) or inflammatory arthritis (IA) comes with a relatively high risk of aseptic stem loosening, especially in young patients. There are limited long-term data on the survivorship of polished, tapered, cemented stems in this population. We therefore performed a single-center retrospective study investigating the survival of this particular stem type in young patients with AVN or IA. METHODS: All patients aged ≤35 years who had received a THA for AVN or IA operated on by the senior author between 1990 and 2010 at the University Hospitals Leuven were identified. In total, 85 THAs in 62 patients were included. Primary endpoint was revision of the femoral component for aseptic loosening. Secondary endpoints were revision of the acetabular component for aseptic loosening, revision for other reasons, and the presence of radiolucencies around the components. RESULTS: The mean follow-up for the entire cohort was 18.0 ± 5.3 years (range 8.0-28.9). Taking revision for aseptic loosening as endpoint, the survival of cemented stems was 100% after 15 years and 95.1% after 20 years. Survival of uncemented cups (91.3%) was significantly better than survival of cemented cups (50.3%) after 20 years of follow-up for aseptic loosening. Taking revision for any reason as endpoint, the survival of THAs with uncemented and cemented cups was 90% and 43.1% at 20 years respectively. Radiolucencies developed in the cement mantles around 11 of the 81 nonrevised stems, mainly in zones 1 and 7. CONCLUSION: In this cohort of young patients with high-risk profiles for aseptic stem loosening, polished, tapered, cemented stems showed excellent long-term survival rates and they therefore remain a viable alternative to uncemented stem designs.

High rates of implant fracture of a generic polished tapered femoral stem.

OBJECTIVES: Cemented polished tapered stems have demonstrated excellent long-term outcomes. Based on this concept, many generic tapered stems have been released into the market. The aim of this study was to evaluate implant-related complications of 1 specific stem design. METHODS: Between 2010 and 2017, 315 total hip replacements were performed using a Fortress stem (Biotechni, La Ciotat, France). Patient records and radiology were retrospectively reviewed for implant-related complications. A failure analysis was performed on the failed Fortress stems in order to determine the cause of premature failure. RESULTS: 7 (2.2%) patients sustained a fracture of the neck of the implant after a mean of 5 years (range 50-81 months). All fractures were atraumatic, originating at the introducer inlet of the stem. All fractured occurred in obese patients (BMI >33 kg/m2) with a small sized prosthesis. Of these, there were 5 135° and 2 125° stems. Fracture risk was 23% (7/30) for patients with a small sized stem and a BMI >30 kg/m2. All cases were revised using a cement-in-cement technique or a cementless modular revision stem. Failure analysis on the retrieved stems revealed a stress riser at the bottom of the introducer inlet. CONCLUSIONS: An alarmingly high rate of early implant fractures was seen using this specific type of cemented stem, particularly when using smaller implant sizes in obese patients. Although based on a proven design, a specific modification led to a stress riser in the neck area, which resulted in a high incidence of implant failure. This series underlines the importance of a stepwise introduction into the market of new orthopaedic devices even when based on established concepts. Generic stems may not behave as the original stem upon which it was designed.

Degenerative changes of the hip following in situ fixation for slipped capital femoral epiphysis: a minimum 18-year follow-up study.

INTRODUCTION: In situ fixation (ISF) is currently still the 'gold standard' treatment for slipped capital femoral epiphysis (SCFE) and has shown acceptable results at mid-term follow-up. This study aims to evaluate functional, clinical and radiographic long-term outcomes after this procedure. METHODS: We reviewed 64 SCFE patients (76 SCFE hips) treated with ISF between 1983 and 1998. 82.9% were stable hips and 17.1% unstable according to Loder's definition. Initial radiographs demonstrated a mild slip in 50%, moderate in 41.3% and severe in 8.7% based on the Southwick angle. Long-term outcomes were assessed using the modified Harris Hip Score (mHHS), University of California at Los Angeles (UCLA) and Tegner activity scores, visual analogue scale (VAS) pain, VAS function, flexion-adduction-internal rotation (FADIR) test, extent of internal-rotation at 90° of hip flexion and Tönnis classification for hip osteoarthritis (OA). RESULTS: 10 (15.6%) SCFE hips were converted to a total hip replacement (THR) after a mean of 16 years. 38 (59.4%) patients underwent a clinical and radiographic examination after a mean follow-up of 23 (range 18-33) years. 12 (18.8%) patients were lost to follow-up. 74% of SCFE hips demonstrated degenerative change on radiography or were converted to THR (Tönnis 1: 33.3%, 2: 18.5%, 3 or THR: 22.2%). There were 3 cases of avascular necrosis (AVN) all in unstable hips. Mean mHHS was 86.8/100, UCLA activity score 7.5/10, Tegner activity score 3.8/10, VAS pain 1.7/10 and VAS function 1.5/10. 20% of SCFE hips were found to have a positive FADIR-test and a limited internal-rotation of 19.7° versus 36.1° (p < 0.001) in contralateral normal hips. DISCUSSION: This long-term follow-up study of ISF for SCFE shows that although complication rates in terms of AVN are low, a high number of patients become symptomatic and have a limited function. Degenerative changes are common with 22.2% of hips developing end-stage hip OA (Tönnis 3 or THR). It is important that patients and parents are informed about these risks.

Cup oversizing as a risk factor for postoperative groin pain in Total Hip Arthroplasty : a retrospective analysis of 437 hips.

The majority of patients are pain free after total hip replacement, but some experience anterior hip pain due to iliopsoas impingement. There is evidence that a prominent or malpositioned cup may cause iliopsoas tendonitis. The purpose of this study was to determine whether oversizing the cup is a risk factor for postoperative groin pain. We retrospectively investigated 437 total hip replacements in which the femoral head diameter had been measured for other research purposes. Data regarding the cup size and positioning was collected from implant identification labels and pelvis x-rays. Clinical data were recovered from the medical files. Native femoral head size, cup size, anteversion, inclination and DS (difference between native femoral head size and cup size) and type of pain (anterior hip pain or non-anterior hip pain) were analyzed and correlations were sought. There was a strong and significant correlation between native femoral head size and cup size. Mean DS was 5.5 mm in the no pain group, 6.9 mm in the anterior hip pain group and 5.9 mm in the non-anterior hip pain group. The difference in mean DS was significant (P=0.046) in patients experiencing anterior hip pain vs. those with no pain or non-anterior hip pain. As patients with anterior hip pain had a significant larger DS of 6.9 mm, it seems that a cup size of more than 6 mm above the native femoral head size should be avoided. We therefore recommend a systematic intraoperative head size measurement prior to definite cup choice.

Hip movement pathomechanics of patients with hip osteoarthritis aim at reducing hip joint loading on the osteoarthritic side.

This study aims at defining gait pathomechanics in patients with hip osteoarthritis (OA) and their effect on hip joint loading by combining analyses of hip kinematics, kinetics and contact forces during gait. Twenty patients with hip OA and 17 healthy volunteers matched for age and BMI performed three-dimensional gait analysis. Hip OA level was evaluated based on plane radiographs using the Tönnis classification. Hip joint kinematics, kinetics as well as hip contact forces were calculated. Waveforms were time normalized and compared between groups using statistical parametric mapping analysis. Patients walked with reduced hip adduction angle and reduced hip abduction and external rotation moments. The work generated by the hip abductors during the stance phase of gait was largely decreased. These changes resulted in a decrease and a more vertical and anterior orientation of the hip contact forces compared to healthy controls. This study documents alterations in hip kinematics and kinetics resulting in decreased hip loading in patients with hip OA. The results suggested that patients altered their gait to increase medio-lateral stability, thereby decreasing demand on the hip abductors. These findings support discharge of abductor muscles that may bear clinical relevance of tailored rehabilitation targeting hip abductor muscles strengthening and gait retraining.

Is there a place for conservative treatment of a Vancouver B2 fracture around a cemented polished tapered stem?

Revision of the unstable stem of a total hip replacement following a peri-prosthetic fracture of the femur is a complex procedure with a high complication rate. With this study we aim to describe the radiologic findings of a specific fracture around polished tapered cemented stems and we present the results of a two- stage treatment plan for non-displaced Vancouver type B2 fractures. Eight male patients with a cemented polished, tapered stem presented after a fall. Standard radiographs did not show any direct signs of a fracture. CT scans showed a complex burst fracture with cement mantle cracks in all cases. Partial weight bearing with 2 crutches was initiated for at least 6 weeks. A cement- in-cement revision was conducted at 3 months in case the patient was not pain free. After 3 months of weight bearing as tolerated, none of the fractures had displaced any further, neither had the stem further subsided. Five patients were pain free and did not require surgical intervention. One patient underwent a cement-in-cement stem revision because of persistent pain. Normal radiographs of a post-traumatic and painful polished tapered stem do not exclude a Vancouver type B2 fracture and should be followed by a CT-scan. Cement cracks, eccentric gaps and subsidence are highly suspicious signs for a non-displaced fracture pattern. Conservative treatment remains an option for these fractures and can be followed by a cement- in-cement stem revision after fracture healing, if this is still required.

Distal Extension of the Anterior Approach to the Hip Using the Femoral Interbundle Technique: Surgical Technique and Case Series.

BACKGROUND: The direct anterior approach (DAA) is becoming more popular as the standard surgical approach for primary total hip arthroplasty. However, it has been associated with an increased incidence of intraoperative femoral fractures in particular during the learning curve. Distal extension of the approach may be needed in case of intraoperative complications. The aim of the present study is to describe the distal extension of the DAA using the femoral interbundle technique. METHODS: A stepwise approach based on a cadaveric study to extend the DAA distally is presented. The interval between the neurovascular bundles running to the vastus lateralis is used to gain access to the femur. Clinical and electromyography results of 5 patients undergoing a revision of the femoral component through an extended anterior approach are reported. RESULTS: In 2 cases, the proximal bundle was exposed whereas in 3 cases the interval between the proximal and distal bundle was developed and cerclage wires were applied around the isthmus of the femur. All fractures had healed at 6 months of follow-up. Four cases had a normal electromyography, and 1 case demonstrated a neuropraxia of a branch to the vastus lateralis. All cases had a 5/5 extension power of the quadriceps muscle clinically. CONCLUSION: The interbundle technique is an alternative way to gain additional exposure of the femur during the DAA and is based on precise knowledge of the periarticular neurovascular structures. This approach can be helpful to safely deal with intraoperative complications such as fractures requiring proximal femoral cerclage wiring during the anterior approach.

Small interprosthetic gaps do not increase femoral peri-prosthetic fracture risk. An in vitro biomechanical analysis.

It has been hypothesized that the interprosthetic gap between ipsilateral hip and knee replacements acts as a stress riser affecting bone fracture behaviour. The aim of this study was to quantify femoral strength and fracture morphology for a wide range of interprosthetic gaps. Seven interprosthetic gaps (0-20cm) were created in artificial femora (N = 6-9/group). All specimens were loaded to failure following a compressive loading protocol. Fracture load and fracture morphology were recorded. Outcomes were compared to femora with a hip implant only (N = 6; reference group). Fracture load was highest for 0 cm gaps. All other interprosthetic gaps had fracture loads similar to that of the reference group. Fracture occurred most frequently with a medial butterfly fragment located at the tip of the hip stem.We conclude that small gaps do not act as stress risers. The specific fracture morphology may benefit from different treatment than peri-prosthetic hip fractures.

Distal Extension of the Direct Anterior Approach to the Hip: A Cadaveric Feasibility Study.

BACKGROUND: The direct anterior approach (DAA) is becoming more popular as the standard surgical approach for primary total hip arthroplasty. However, femoral complications of up to 2.8% have been reported. Therefore, it is important for surgeons to understand the periarticular neurovascular anatomy in order to safely deal with intraoperative complications. METHODS: Anatomic dissections were performed on 20 cadaveric hips. The neurovascular structures anterior to the femur and distal to the intertrochanteric line were dissected and its position was described in relation to anatomic landmarks easily identified through the DAA: anterior superior iliac spine (ASIS), the insertion of the gluteus minimus (GM), and the lesser trochanter (LT). RESULTS: Two clearly distinguishable neurovascular bundles running to the vastus lateralis were seen in 17 of 20 specimens. The average distances to the landmarks were as follows: ASIS-1st bundle = 12.3 cm (range, 9.7-14.5); GM-1st bundle = 3.2 cm (range, 2.2-4); LT-1st bundle = 1.6 cm (range, 0.7-2.8); 1st bundle-2nd bundle = 3.3 cm (range, 1.8-6.1). CONCLUSION: A consistent pattern of 2 clearly distinguishable neurovascular bundles was seen in 85% of the specimens. Knowledge of the position of these neurovascular bundles in relation to the anatomic landmarks makes distal femoral extension of the DAA feasible. Further clinical studies are needed to confirm the safety of the extensile anterior approach.

Subject-specific musculoskeletal modelling in patients before and after total hip arthroplasty.

The goal of this study was to define the effect on hip contact forces of including subject-specific moment generating capacity in the musculoskeletal model by scaling isometric muscle strength and by including geometrical information in control subjects, hip osteoarthritis and total hip arthroplasty patients. Scaling based on dynamometer measurements decreased the strength of all flexor and abductor muscles. This resulted in a model that lacked the capacity to generate joint moments required during functional activities. Scaling muscle forces based on functional activities and inclusion of MRI-based geometrical detail did not compromise the model strength and resulted in hip contact forces comparable to previously reported measured contact forces.

Sequential and compartmentalized action of Rabs, SNAREs, and MAL in the apical delivery of fusiform vesicles in urothelial umbrella cells.

Uroplakins (UPs) are major differentiation products of urothelial umbrella cells and play important roles in forming the permeability barrier and in the expansion/stabilization of the apical membrane. Further, UPIa serves as a uropathogenic Escherichia coli receptor. Although it is understood that UPs are delivered to the apical membrane via fusiform vesicles (FVs), the mechanisms that regulate this exocytic pathway remain poorly understood. Immunomicroscopy of normal and mutant mouse urothelia show that the UP-delivering FVs contained Rab8/11 and Rab27b/Slac2-a, which mediate apical transport along actin filaments. Subsequently a Rab27b/Slp2-a complex mediated FV-membrane anchorage before SNARE-mediated and MAL-facilitated apical fusion. We also show that keratin 20 (K20), which forms a chicken-wire network ∼200 nm below the apical membrane and has hole sizes allowing FV passage, defines a subapical compartment containing FVs primed and strategically located for fusion. Finally, we show that Rab8/11 and Rab27b function in the same pathway, Rab27b knockout leads to uroplakin and Slp2-a destabilization, and Rab27b works upstream from MAL. These data support a unifying model in which UP cargoes are targeted for apical insertion via sequential interactions with Rabs and their effectors, SNAREs and MAL, and in which K20 plays a key role in regulating vesicular trafficking.

Does surgical approach or prosthesis type affect hip joint loading one year after surgery?

Several approaches may be used for hip replacement surgery either in combination with conventional total hip arthroplasty (THA) or resurfacing hip arthroplasty (RHA). This study investigates the differences in hip loading during gait one year or more after surgery in three cohorts presenting different surgical procedures, more specific RHA placed using the direct lateral (RHA-DLA, n=8) and posterolateral (RHA-PLA, n=14) approach as well as THA placed using the direct anterior (THA-DAA, n=12) approach. For the DAA and control subjects, hip loading was also evaluated during stair ascent and descent to evaluate whether these motions can better discriminate between patients and controls compared to gait. Musculoskeletal modelling in OpenSim was used to calculate in vivo joint loading. Results showed that for all operated patients, regardless the surgical procedure, hip loading was decreased compared to control subjects, while no differences were found between patient groups. This indicates that THA via DAA results in similar hip loading as a RHA via DLA or PLA. Stair climbing did not result in more distinct differences in hip contact force magnitude between patients and controls, although differences in orientation were more distinct. However, patients after hip surgery did adjust their motion pattern to decrease the magnitude of loading on the hip joint compared to control subjects.

Gait alterations can reduce the risk of edge loading.

Following metal-on-metal hip arthroplasty, edge loading (i.e., loading near the edge of a prosthesis cup) can increase wear and lead to early revision. The position and coverage angle of the prosthesis cup influence the risk of edge loading. This study investigates the effect of altered gait patterns, more specific hip, and pelvis kinematics, on the orientation of hip contact force and the consequent risk of antero-superior edge loading using muscle driven simulations of gait. With a cup orientation of 25° anteversion and 50° inclination and a coverage angle of 168°, many gait patterns presented risk of edge loading. Specifically at terminal double support, 189 out of 405 gait patterns indicated a risk of edge loading. At this time instant, the high hip contact forces and the proximity of the hip contact force to the edge of the cup indicated the likelihood of the occurrence of edge loading. Although the cup position contributed most to edge loading, altering kinematics considerably influenced the risk of edge loading. Increased hip abduction, resulting in decreasing hip contact force magnitude, and decreased hip extension, resulting in decreased risk on edge loading, are gait strategies that could prevent edge loading. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1069-1076, 2016.

Evaluation of stair motion contributes to new insights into hip osteoarthritis-related motion pathomechanics.

Stair motion in the presence of hip osteoarthritis (OA) has received less attention than level walking. Its more strenuous aspect may shed the light on different locomotor strategies when compared to walking. We, therefore, aimed to define stair motion features associated to hip OA and to evaluate whether these specific features would differ from level walking and better characterize the hip pathological condition. Principal component and linear discriminant analyses were, respectively, used as data reduction and classification techniques. Our study highlighted that most of stair motion features associated to hip OA were similar to the ones of walking. Stair descent presented with the lowest misclassification error rate, ranging from 12% to 19% (estimated by cross-validation). But, features that may be considered as a mechanism to reduce demand on the hip abductors were found to be more important in the stair ascent condition. This was reflected by both, greater importance in the classification rule and variance compared with walking, that is, decreased hip internal rotation moment at mid-stance (72.50% vs. 57.63%) and increased trunk lateroflexion toward affected side (56.43% vs. 29.37%). This study emphasized the importance of investigating stair motion in hip osteoarthritic population by highlighting specific locomotor strategies.

Biomechanical gait features associated with hip osteoarthritis: Towards a better definition of clinical hallmarks.

Critical appraisal of the literature highlights that the discriminative power of gait-related features in patients with hip osteoarthritis (OA) has not been fully explored. We aimed to reduce the number of gait-related features and define the most discriminative ones comparing the three-dimensional gait analysis of 20 patients with hip osteoarthritis (OA) with those of 17 healthy peers. First, principal component analysis was used to reduce the high-dimensional gait data into a reduced set of interpretable variables for further analysis, including tests for group differences. These differences were indicative for the selection of the top 10 variables to be included into linear discriminant analysis models (LDA). Our findings demonstrated the successful data reduction of hip osteoarthritic-related gait features with a high discriminatory power. The combination of the top variables into LDA models clearly separated groups, with a maximum misclassification error rate of 19%, estimated by cross-validation. Decreased hip/knee extension, hip flexion and internal rotation moment were gait features with the highest discriminatory power. This study listed the most clinically relevant gait features characteristics of hip OA. Moreover, it will help clinicians and physiotherapists understand the movement pathomechanics related to hip OA useful in the management and design of rehabilitation intervention.

Gait alterations to effectively reduce hip contact forces.

Patients with hip pathology present alterations in gait which have an effect on joint moments and loading. In knee osteoarthritic patients, the relation between medial knee contact forces and the knee adduction moment are currently being exploited to define gait retraining strategies to effectively reduce pain and disease progression. However, the relation between hip contact forces and joint moments has not been clearly established. Therefore, this study aims to investigate the effect of changes in hip and pelvis kinematics during gait on internal hip moments and contact forces which is calculated using muscle driven simulations. The results showed that frontal plane kinetics have the largest effect on hip contact forces. Given the high correlation between the change in hip adduction moment and contact force at initial stance (R(2) = 0.87), this parameter can be used to alter kinematics and predict changes in contact force. At terminal stance the hip adduction and flexion moment can be used to predict changes in contact force (R(2) = 0.76). Therefore, gait training that focuses on decreasing hip adduction moments, a wide base gait pattern, has the largest potential to reduce hip contact forces.

SNX31: a novel sorting nexin associated with the uroplakin-degrading multivesicular bodies in terminally differentiated urothelial cells.

Uroplakins (UP), a group of integral membrane proteins, are major urothelial differentiation products that form 2D crystals of 16-nm particles (urothelial plaques) covering the apical surface of mammalian bladder urothelium. They contribute to the urothelial barrier function and, one of them, UPIa, serves as the receptor for uropathogenic Escherichia coli. It is therefore important to understand the mechanism by which these surface-associated uroplakins are degraded. While it is known that endocytosed uroplakin plaques are targeted to and line the multivesicular bodies (MVBs), it is unclear how these rigid-looking plaques can go to the highly curved membranes of intraluminal vesicles (ILVs). From a cDNA subtraction library, we identified a highly urothelium-specific sorting nexin, SNX31. SNX31 is expressed, like uroplakins, in terminally differentiated urothelial umbrella cells where it is predominantly associated with MVBs. Apical membrane proteins including uroplakins that are surface biotin-tagged are endocytosed and targeted to the SNX31-positive MVBs. EM localization demonstrated that SNX31 and uroplakins are both associated not only with the limiting membranes of MVBs containing uroplakin plaques, but also with ILVs. SNX31 can bind, on one hand, the PtdIns3P-enriched lipids via its N-terminal PX-domain, and, on the other hand, it binds uroplakins as demonstrated by co-immunoprecipitation and proximity ligation assay, and by its reduced membrane association in uroplakin II-deficient urothelium. The fact that in urothelial umbrella cells MVBs are the only major intracellular organelles enriched in both PtdIns3P and uroplakins may explain SNX31's MVB-specificity in these cells. However, in MDCK and other cultured cells transfected SNX31 can bind to early endosomes possibly via lipids. These data support a model in which SNX31 mediates the endocytic degradation of uroplakins by disassembling/collapsing the MVB-associated uroplakin plaques, thus enabling the uroplakin-containing (but 'softened') membranes to bud and form the ILVs for lysosomal degradation and/or exosome formation.

Test-retest reliability of innovated strength tests for hip muscles.

The burden of hip muscles weakness and its relation to other impairments has been well documented. It is therefore a pre-requisite to have a reliable method for clinical assessment of hip muscles function allowing the design and implementation of a proper strengthening program. Motor-driven dynamometry has been widely accepted as the gold-standard for lower limb muscle strength assessment but is mainly related to the knee joint. Studies focusing on the hip joint are less exhaustive and somewhat discrepant with regard to optimal participants position, consequently influencing outcome measures. Thus, we aimed to develop a standardized test setup for the assessment of hip muscles strength, i.e. flexors/extensors and abductors/adductors, with improved participant stability and to define its psychometric characteristics. Eighteen participants performed unilateral isokinetic and isometric contractions of the hip muscles in the sagittal and coronal plane at two separate occasions. Peak torque and normalized peak torque were measured for each contraction. Relative and absolute measures of reliability were calculated using the intraclass correlation coefficient and standard error of measurement, respectively. Results from this study revealed higher levels of between-day reliability of isokinetic/isometric hip abduction/flexion peak torque compared to existing literature. The least reliable measures were found for hip extension and adduction, which could be explained by a less efficient stabilization technique. Our study additionally provided a first set of reference normalized data which can be used in future research.

Radiographic analysis of a bone plug in 275 primary cemented total hip arthroplasties.

Various designs of cement restrictors for total hip arthroplasty have shown a variability in resistance to intramedullary pressure and migration. The performance of a conical bone plug was studied in 275 cemented total hip arthroplasties with a followup between 5 and 19 years. In a radiographic analysis the relation between the plug position and the cement mantle quality was investigated. The results were compared to the performance of other cement restrictors as reported in the literature. Good to excellent cement mantles were observed in 80% of the femurs. A significant correlation between the stability of the plug and the quality of the cement mantle was found. Forty-nine percent of the plugs were within 1 to 3 centimetres of the Exeter stem hollow centraliser. We also demonstrated that bone plugs performed almost always better than polyethylene or gelatine restrictors reported in other studies.

Removal of an intra-pelvic socket: description of a safe surgical algorithm.

Migration of an acetabular component beyond the ilio-ischial line is a rare but potentially lethal complication following a total hip arthroplasty, because the socket can become entrapped between the iliac vessels. Pre-operative assessment of the position of the socket relative to the intra-pelvic vascular structures is always mandatory to set up a staged procedure with a retroperitoneal exposure of the iliac vessels. This allows for a safe mobilization and looping of the vessels followed by extraction of the component either through the retroperitoneal or standard surgical approach to the hip joint. This strategy will minimize the risk of disruption of the vessels and of uncontrollable bleeding in case of vessel damage.