Cranial deformation in craniosynostosis. A new explanation.

Skull growth after premature fusion of a single suture was described by Virchow in 1851. He observed that growth was restricted in a plane perpendicular to a fused suture. However, he failed to predict the compensatory growth patterns that produce many of the deformities recognized as features of individual craniosynostosis syndromes. The deformities resulting from premature closure of a coronal, sagittal, metopic, or lambdoid suture can be predicted by the following observations: (1) cranial vault bones that are prematurely fused act as a single bone plate with decreased growth potential; (2) asymmetrical bone deposition occurs mainly at perimeter sutures, with increased bone deposition directed away from the bone plate; (3) sutures adjacent to the stenotic suture compensate in growth more than those sutures not contiguous with the closed suture; and (4) enhanced bone deposition occurs along both sides of a nonperimeter suture that is a continuation of the prematurely closed suture. These four rules were derived by critically examining the clinical deformities observed with each form of craniosynostosis. These rules assume that cranial sutures have the capacity to compensate by depositing bone asymmetrically along their edges. Unequal growth patterns have been demonstrated in the frontonasal suture of rabbits by Selman and Sarnat. In addition, unequal bone deposition has also been demonstrated along the parieto-interparietal suture in albino rats by Baer. Human studies to determine if asymmetrical bone deposition actively occurs along cranial vault sutures in response to a stenotic suture have not been performed, however. It is also unclear whether these four guidelines apply to cranial base abnormalities observed with craniosynostosis. As new radiologic techniques develop to define the configuration of the skull in intricate detail, a skull pattern of growth explaining the pathogenesis of all deformities created by premature fusion of a cranial vault suture may become apparent.     

兔颅骨双侧冠状缝早闭后颅面骨的生长变化

为从骨生长量和生长方向两个方面探讨兔双侧冠状缝早闭后对颅骨骨生长发育的影响，用牙科釉质和剂固定２周龄幼兔双侧冠状缝，于冠状缝，鼻额缝和人字缝前后置入金属标记物，观察双侧冠状缝早闭后各骨缝及颅面长度，颅穹窿高度，长度和鼻骨长度变化情况，结果表明兔颅骨缝扩张性生长高峰期在２～８周龄，双侧冠状缝固定后，骨缝生长停止，鼻额缝补偿生长加快，４周解除固定带后，冠状缝在８周前出现补偿性生长高峰期，８周解除固定带     

兔颅骨双侧冠状缝早闭后颅面骨的生长变化

为从骨生长量和生长方向两个方面探讨兔双侧冠状缝早闭后对颅面骨生长发育的影响，用牙科釉质粘和剂固定２周龄幼兔双侧冠状缝，于冠状缝、鼻额缝和人字缝前后置入金属标记物，观察双侧冠状缝早闭后各骨缝及颅面长度、颅穹窿高度、长度和鼻骨长度变化情况。结果表明兔颅骨缝扩张性生长高峰期在２～８周龄。双侧冠状缝固定后，骨缝生长停止，鼻额缝补偿性生长加快。４周解除固定带后，冠状缝在８周前出现补偿性生长高峰期，８周解除固定带无补偿性生长高峰出现。另外鼻骨长度增加并向下移位，颅穹隆长度和颅面长度缩短。提示临床手术矫正颅骨畸形时，除考虑到手术年龄的安全性外，必须强调早期手术的必要性。     

兔颅骨双侧冠状缝早闭后颅面骨的生长变化

为从骨生长量和生长方向两个方面探讨免双侧冠状缝早闭后对颅面骨生长发育的影响,用牙科釉质粘和剂固定2周龄幼免双侧冠状缝,于冠状缝、鼻额缝和人字缝前后置入金属标记物,观察双侧冠状缝早闭后各骨缝及颅面长度、颅穹窿高度、长度和鼻骨长度变化情况。结果表明兔颅骨缝扩张性生长高峰期在2～8周龄。双侧冠状缝固定后,骨缝生长停止,鼻额缝补偿性生长加快。4周解除固定带后,冠状缝在8周前出现补偿性生长高峰期,8周解除固定带无补偿性生长高峰出现。另外鼻骨长度增加并向下移位,颅穹隆长度和颅面长度缩短。提示临床手术矫正颅骨畸形时,除考虑到手术年龄的安全性外,必须强调早期手术的必要性。     

A Pro253Arg mutation in fibroblast growth factor receptor 2 (Fgfr2) causes skeleton malformation mimicking human Apert syndrome by affecting both chondrogenesis and osteogenesis

Apert syndrome is one of the most severe craniosynostosis that is mainly caused by either a Ser252Trp(S252W) or Pro253Arg(P253R) mutation in fibroblast growth factor receptor 2 (FGFR2). As an autosomal dominant disorder, Apert syndrome is mainly characterized by skull malformation resulting from premature fusion of craniofacial sutures, as well as syndactyly, etc. A P253R mutation of FGFR2 results in nearly one-thirds of the cases of Apert syndrome. The pathogenesis of Apert syndrome resulting from P253R mutation of FGFR2 is still not fully understood. Here we reported a knock-in mouse model carrying P253R mutation in Fgfr2. The mutant mice exhibit smaller body size and brachycephaly. Analysis of the mutant skulls and long bones revealed premature fusion of coronal suture, shortened cranial base and growth plates of long bones. In vitro organ culture studies further revealed that, compared with wild-type littermates, the mutant mice have prematurely fused coronal sutures and retarded long bone growth. Treatment of the cultured calvaria and femur with PD98059, an Erk1/2 inhibitor, resulted in partially alleviated coronal suture fusion and growth retardation of femur respectively. Our data indicated that the P253R mutation in Fgfr2 directly affect intramembranous and endochondral ossification, which resulted in the premature closure of coronal sutures and growth retardation of long bones and cranial base. And the Erk1/2 signaling pathway partially mediated the effects of P253R mutation of Fgfr2 on cranial sutures and long bones.     

Water-tight knee arthrotomy closure: comparison of a novel single bidirectional barbed self-retaining running suture versus conventional interrupted sutures

Standard medial parapatellar arthrotomies of 10 cadaveric knees were closed with either conventional interrupted absorbable sutures (control group, mean of 19.4 sutures) or a single running knotless bidirectional barbed absorbable suture (experimental group). Water-tightness of the arthrotomy closure was compared by simulating a tense hemarthrosis and measuring arthrotomy leakage over 3 minutes. Mean total leakage was 356 mL and 89 mL in the control and experimental groups, respectively (p = 0.027). Using 8 of the 10 knees (4 closed with control sutures, 4 closed with an experimental suture), a tense hemarthrosis was again created, and iatrogenic suture rupture was performed: a proximal suture was cut at 1 minute; a distal suture was cut at 2 minutes. The impact of suture rupture was compared by measuring total arthrotomy leakage over 3 minutes. Mean total leakage was 601 mL and 174 mL in the control and experimental groups, respectively (p = 0.3). In summary, using a cadaveric model, arthrotomies closed with a single bidirectional barbed running suture were statistically significantly more water-tight than those closed using a standard interrupted technique. The sample size was insufficient to determine whether the two closure techniques differed in leakage volume after suture rupture.     

Influence of suture material and suture technique on collagen fibril diameters in midline laparotomies

BACKGROUND: Although laparotomy closure is associated with a cumulative 15% failure rate, the effect of different suture techniques and materials on the ultrastructural composition of the healing incision has not been investigated. METHOD: in 40 Wistar rats the collagen fibril diameters and the regenerative tissue were compared using electron microscopy 14 and 28 days after midline laparotomy. Wounds were closed with single and running sutures using either polypropylene or polyglactin 910. RESULTS: Closure with polypropylene led to significantly larger mean fibril diameters than closure with polyglactin. Regardless of time and suture material, running closure resulted in significantly smaller mean collagen fibril diameters than single sutures. Four weeks after laparotomy, inflammatory reactions, disorganization of collagen and irregularities of the vascular architecture were found after closure with absorbable suture material but not after closure with nonabsorbable material. CONCLUSION: Suture material and suture method significantly influence the ultrastructural composition of the healing incision. Persisting mechanical irritation around the suture threads after single sutures and severe persisting inflammatory reactions after the use of absorbable suture material are important influencing factors.     

Influence of laparotomy closure technique on collagen synthesis in the incisional region

Background: Variations of suture technique have an influence on the mechanical strength of laparotomy wounds. To investigate whether these differences in biomechanical properties influence collagen synthesis in the incisional region, an animal experiment on laparotomy closure was performed. Material: In 100 rats median laparotomies were closed with polypropylene. Continuous and single sutures were applied with variations of suture length to wound length (SLWL) ratio and suture tension. Methods: Tissue samples from the incisional region after 2 and 4 weeks were analysed spectro-photometrically for the concentration of collagen protein and by digital image analysis for the percentage of collagen type III. Results: Running closure with an SLWL ratio ≥4:1 resulted in a significantly higher concentration of collagen protein than single sutures with the same SLWL ratio. In contrast, single closure with an SLWL ratio <4:1 led to in a higher collagen protein concentration than running closure with the same SLWL ratio. With an SLWL ratio ≥4:1 running sutures resulted in a significant reduction of the percentage of collagen type III after 4 weeks compared to single sutures. Closure with high suture tension led to a significant reduction of collagen protein between the 2nd and 4th week but left the percentage of collagen type III mostly unaffected. Conclusion: Suture technique, SLWL ratio, and suture tension have an effect on the ultrastructural composition of the regenerating tissue. This influence outlasts the period of tissue restructuring during which the presence of sutures in the incisional edges is absolutely required. Running sutures with an SLWL ratio ≥4:1 and low suture tension promote a favourable collagen composition of the incisional region. Electronic Publication     

Influence of suture technique on laparotomy wound healing: an experimental study in the rat

A suture length to wound length ratio (SLWL ratio) of 4:1 for laparotomy closure has proven in clinical studies to reduce incisional hernia incidence. The effect of different SLWL ratios on the mechanical qualities of the healing incision has not been examined experimentally. In 50 rats, the musculo-fascial layer of median laparotomies was closed with polypropylene sutures using SLWL ratios of 8:1, 4:1, 2:1 and 1.7:1. Single and running sutures, different tissue bites and different suture tensions were applied. Five rats served as controls. After 14 days, the horizontal strength of the incision was tested in a digitised tensiometer. The SLWL ratio, suture tension and suture technique proved to have significant influences on the mechanical strength of the incision. Running sutures and especially closures with a ratio of between 4:1 and 8:1 proved significantly stronger than wounds closed with single sutures. When small tissue bites were applied, the positive influence of running sutures was equalised in the early phase of wound healing. High suture tension led to significantly weaker scars independent of the applied suture technique. In accordance with clinical data, it could be proven experimentally that running closure of midline laparotomies with a SLWL ratio above 4:1 avoiding high suture tension exerts a significantly positive effect on the mechanical strength of the incision. Further studies are needed to allow measurement and better control of suture tension.     

Microfocal CT: a method for evaluating murine cranial sutures in situ

INTRODUCTION: The murine model is a well-established surrogate for studying human cranial suture biology. In mice, all sutures with the exception of the posterior frontal (PF) suture remain patent throughout life. Histology is regarded as the gold standard for analyzing sutures. On this basis, PF suture fusion begins on day of life 25 and is complete by day 45. Cranial suture histology, however, requires sacrifice of the animal to obtain tissue for analysis. As a result, knowledge of the kinetics of cranial suture fusion is based on a patchwork analysis of many sutures from many different animals. The behavior of a single suture through time is unknown. Our goal is to develop a noninvasive means to repeatedly image mouse cranial sutures in vivo. As a first step, the present study was performed to evaluate microfocal computer tomography (micro-CT) technology for the use of capturing images of a mouse cranium in situ. METHODS: The micro-CT system consists of a microfocal X-ray source and a large format CCD camera optically coupled to a high-resolution X-ray image intensifier, digitally linked to a computer. The PF and sagittal sutures lie in continuity along the midline of the skull. Holes were drilled in the calvaria on both sides of the PF and sagittal sutures of a 45-day-old euthanized mouse. A micro-CT scan of this animal was performed and hundreds of cross-sectional images were generated for the cranium. These images were used to reconstruct three-dimensional volumetric images of the entire cranium. Comparisons were made between (1). the gross specimen and the three dimensional reconstructions; (2). two-dimensional coronal images obtained by micro-CT and those obtained by histology. RESULTS: Analysis of PF and sagittal sutures demonstrated the following: (1). The drilled holes were accurately rendered by micro-CT, when compared to both the gross specimen and the histology. (2). The sagittal suture was found to be patent by both micro-CT and histology. (3). The PF suture is fused by histology, but unexpectedly, the PF suture appears incompletely fused by micro-CT. By micro-CT, however, the anterior and endocranial regions appear more extensively fused than the remainder of the PF suture, a finding consistent with published histologic analysis. CONCLUSIONS: We successfully imaged 45-day-old mouse cranial sutures in situ using micro-CT technology. Precise correlation between histologic sections and radiologic images is difficult, but convincing similarities exist between the gross specimen and images from micro-CT and histology. PF suture fusion in a 45-day-old animal appears different by micro-CT than by histology. One possible explanation for this apparent discrepancy is that suture fusion in histology is determined based on the appearance of bone morphology and not tissue density, as the specimens are necessarily decalcified to section the bone. Micro-CT, on the other hand, distinguishes tissues on the basis of density. Newly forming bone may require bone matrix formation prior to complete calcification; PF suture in 45-day-old mice may be morphologically complete but incompletely ossified. Studies correlating histologic and micro-CT assessment of suture development are underway. Micro-CT appears to be a promising method for noninvasive imaging of mouse cranial suture.     

Raman spectroscopic evidence for octacalcium phosphate and other transient mineral species deposited during intramembranous mineralization

To understand early mineralization events, we studied living murine calvarial tissue by Raman spectroscopy using fibroblast growth factor 2 (FGF2)-soaked porous beads. We detected increased levels of a transient phase resembling octacalcium phosphate in sutures undergoing premature suture closure. INTRODUCTION: Several calcium phosphates have been postulated as the earliest inorganic precursors to bone mineral. They are unstable and have not been previously detected in tissue specimens. Whether the same intermediates are formed in sutures undergoing premature closure is also unknown. METHODS: Six coronal suture tissue specimens from fetal day 18.5 B6CBA F1/J wild-type mice were studied. Three sutures specimens were treated with FGF2-soaked heparin acrylic beads to induce accelerated mineralization and premature suture closure. Three control specimens were treated with empty heparin acrylic beads. All sutures were maintained as organ cultures to permit repeated spectral analyses at 12-24 h intervals over a 72-h period. RESULTS: During the first 24 h, the spectra contained bands of octacalcium phosphate (OCP) or an OCP-like mineral. The main phosphorus-oxygen stretch was at 955 cm(-1), instead of the 957-959 cm(-1) seen in bone mineral, and there was an additional band at 1010-1014 cm(-1), as expected for OCP. A broad band was found at 945 cm(-1), characteristic of a highly disordered or amorphous calcium phosphate. An increased amount of mineral was observed in FGF2-treated sutures, but no qualitative differences in Raman spectra were observed between experimental and control specimens. CONCLUSIONS: Inorganic mineral deposition proceeds through transient intermediates, including an OCP-like phase. Although this transient phase has been observed in purely inorganic model systems, this study is the first to report OCP or an OCP-like intermediate in living tissue. Raman microspectroscopy allows observation of this transient mineral and may allow observation of other precursors as well.     

培养软骨移植修复兔生长板缺损

目的 将体外培养软骨移植修复兔生长板缺损,防止生长板缺损早闭造成的肢体发育畸形。方法 分离收集1月龄兔关节软骨细胞,经离心管内培养形成软骨。将培养2周软骨植入6周龄兔胫骨上端生长板缺损区,于4、16周时对术肢行X线摄片、组织学及免疫组织化学等检查。结果 兔胫骨上端生长板缺损区移植培养软骨4周时,胫骨无明显畸形发生,组织学检查显示生长板缺损由软骨充填,Ⅱ型胶原免疫组织化学染色阳性。16周时移植侧胫骨仍无明显畸形,组织学检查显示生长板已近闭合。而对照侧胫骨发生严重畸形,生长板闭合。结论 培养软骨异体植入兔生长板缺损,可替代缺损的生长板软骨组织,维持肢体正常生长,防止肢体发育畸形。     

Suspension Sutures Aid Facial Reconstruction

Background.  Suspension, pexing or tacking sutures, which have a long history of use in facial cosmetic surgery, have only recently begun use in reconstruction.
Objective.  In this study, the suspension suture was used to fix the closure line at the junction of cosmetic units, to prevent distortion of free margins secondary to wound contraction, eg, ectropion or eclabium, to prevent tenting across concavities, and to prevent scar spreading of wounds closed under tension. The acute complications and long-term effectiveness of this suturing technique in achieving the 4 desired results were evaluated.
Methods.  During a 10-year period, 136 cases of surgical defects of the face created by the removal of nonmelanoma skin cancer by Mohs micrographic surgery were repaired using absorbable suspension sutures. The wounds were evaluated initially for acute complications of hemorrhage, infection, dehiscence, and necrosis; and later over 3 years for chronic sequela of hypertrophic scar, spread scar, contraction deformities such as distortion of free margins, and pigmentary changes.
Results.  Suspension sutures were used in 60 cases of primary layered closure and 76 flaps of the face. Suspension sutures allowed primary closure of defects that would have required flaps in 72% of the cases and prevented distortion of free margins. There were more acute and long-term complications related to excess tension with primary closure than with flaps. Suspension sutures fixed the closure line at the junction of cosmetic units, prevented tenting across concavities, and both features were maintained over the duration of the study.
Conclusion.  Suspension sutures aided in obtaining linear closures, prevented distortion of free margins, prevented tenting across concavities, and fixed the closure line at the junction of cosmetic units; however, they did not prevent spread scars.     

Octylcyanoacrylate skin closure in laparoscopy.

OBJECTIVES: Octylcyanoacrylate (Dermabond) is a dermal bond useful in closing surgical skin incisions. We compared skin octylcyanoacrylate with subcuticular skin sutures to close laparoscopic trocar sites. METHODS: A randomized, double-armed, prospective study was performed with 59 patients, in whom 228 trocar sites were closed. Twenty-nine patients underwent subcuticular closure of laparoscopic incisions, and 30 patients received closure with octylcyanoacrylate. Sutured trocar sites were closed with subcuticular 4-0 absorable suture. Octylcyanoacrylate wounds received closure in accordance with the recommendations of the manufacturer (Ethicon, Somerville, NJ). The number of sutures or vials of octylcyanoacrylate used, closure times, and postoperative wound problems were recorded. Wounds were assessed 2 weeks postoperatively for healing complications. Closure costs were estimated using published operating room time per hour plus the cost of octylcyanoacrylate or suture. The Student paired t test was used for statistical analysis. RESULTS: The overall mean time for skin closure using octylcyanoacrylate and suture was 3.7 minutes and 14 minutes, respectively (P<0.00001). An average of 2.2 packets of suture were used to close all port sites, while those closed with octylcyanoacrylate required an average of 3.4 vials per patient. Wound complications consisted of subcuticular seroma with skin separation. No difference was noted in complication rates between the 2 groups. Overall average cost per closure using octylcyanoacrylate was 198 dollars while cost for closure using suture was 497 dollars (P<0.00001). CONCLUSIONS: Laparoscopic port-site skin closure with octylcyanoacrylate is rapid and effective. Closure with octylcyanoacrylate yields cost savings and a decrease in operative time of more than 9 minutes per case.     

Abdominal wound closure comparing the proximate stapler with sutures

Proximate staple closure of transverse and vertical abdominal wounds is compared with suture closure in a prospective, blind, randomized trial. Fifty-seven wounds were randomly allocated to 3/0 Prolene or Proximate staple closure. Each wound was photographed after removal of staples or sutures and again in the sixth postoperative week. The photographic slides were independently assessed by eight observers, who graded the cosmetic result of each wound on a scale from 1 to 10. The cosmetic score in transverse wounds closed with sub-cuticular sutures was better than with staples. Cosmetic scores in vertical wounds were almost equal for staples and sutures. Staple closure was faster than suture closure. Proximate staple closure is considered a suitable and faster method for vertical abdominal wounds.     

The use of sterile adhesive tape in the closure of arthroscopic puncture wounds: a comparison with a single layer nylon closure.

A prospective trial was undertaken comparing the wound healing and infection rates in arthroscopic arthrotomy wounds closed by sterile adhesive tapes on interrupted Nylon skin sutures. Two hundred and thirty consecutive arthroscopic procedures had arthrotomy wounds closed by a single layer skin closure of either interrupted Nylon (n = 62) or sterile adhesive tapes (n = 168). All wounds healed by primary intention. Only one wound developed a superficial infection around a Nylon suture and no patient developed a synovial herniation. It is concluded that closure of arthroscopic puncture wounds with sterile adhesive tape is effective and convenient for wound management.     

A revolutionary advance in skin closure compared to current methods

Six pigs were used to evaluate the influence of three separate modalities on contaminated wounds. Full-thickness skin wounds on the abdomen were contaminated with 10(4) or 10(5) Staphylococcus aureus and then closed with one of three methods. The three closure modalities included (1) a new absorbable staple (Insorb) placed in the subcuticular tissue, (2) a braided Vicryl suture, and (3) percutaneous metal staples. Any foreign body material implanted in tissue increases the risk of infection at that site. Wound closure always involves the use of a foreign body. Historically, sutures have been the primary material used to close tissue. The newer synthetic sutures are significangly more biodegradable and cause less infection than sutures composed of protein, such as silk and catgut. Metal staples are also associated with a low risk of infection. Recently, Incisive Surgical, Inc. (Plymouth, Minnesota) has developed an absorbable polymer staple specifically for subcuticular skin closure. The purpose of this study was to compare the new Insorb staple to both an absorbable polymer suture and a metal staple. Wound infection was assessed 7 days after closure by clinical signs and quantitative bacterial swabs. The results demonstrated that wounds closed with Insorb staples had the lowest incidence (33%) of infection, followed by percutaneous metal staples (44%). All wounds (100%) closed with Vicryl suture became infected. The incidence of wound infection directly correlated with the level of quantitative bacterial count at analysis. The Insorb staple was associated with significantly reduced closure time, less inflammation and infection, and better aesthetic result compared to Vicryl. Compared to metal staples, the Insorb subcuticular staplers demonstrated comparable closure time without the need for later staple removal. In conclusion, the closure of contaminated wounds with the Insorb staples is a superior choice to Vicryl suture because they have a significantly (p = 0.009) lower incidence of infection. The Insorb staple is a revolutionary advance in subcuticular skin stapling.     

Dermotaxis v/s loop suture technique for closure of fasciotomy wounds: a study of 50 cases

Fasciotomy incisions lead to large, unsightly, chronic wounds after surgical intervention. Classic management was to use split-thickness skin grafts, but this leads to insensate skin with reports that as many as 23% of patients are dissatisfied by the appearance of the wound. Since no skin loss has occurred with the fasciotomy incision, utilizing the dermal properties of creep, stress relaxation and load cycling, closure can be achieved in a better way. We describe using dermotaxis for skin edge approximation that is done using inexpensive equipment available readily in any standard operating room. Twenty-five patients had fasciotomy wounds closed either by dermotaxis or a loop suture technique with the inclusion criteria being closed fractures, no concomitant skin loss, fracture-related compartment syndrome and fasciotomy performed within 36 h. The fasciotomy incision was closed in a single stage by loop suture technique or gradually by dermotaxis once the oedema had settled between 3 and 5 days. Results were graded as excellent if approximation could be achieved, good if sutures had to be applied for protective care and poor if wounds needed to be skin-grafted. In the dermotaxis group, results were excellent in 15, good in 8 and poor in 2 cases. In the loop suture technique group, results were excellent in 20, good in 4 and poor in 1 case. Dermal apposition using inexpensive, readily available equipment is an alternative method for closure of fasciotomy wounds. If limb oedema has settled sufficiently, closure using a loop suture can be done in a single stage. If the limb remains oedematous, gradual closure can be done using dermotaxis.     

Experimental studies in swine for measurement of suture extrusion

The purpose of this scientific investigation was to identify the determinants of suture extrusion following subcuticular skin closure of dermal skin wounds. Miniature swine were used to develop a model for studying suture extrusion. Standard, full-thickness skin incisions were made on each leg and the abdomen. The wounds were closed with size 4/0 POLYSORB* or COATED VICRYL* sutures. Each incision was closed with five interrupted, subcuticular, vertical loops secured with a surgeon's knot. The loops were secured with 3-throw knots in one pig, 4-throw knots in the second pig, and 5-throw knots in the third pig. The swine model reproduced the human clinical experience and suture extrusion, wound dehiscence, stitch abscess, and granuloma formation were all observed. The cumulative incidence of suture extrusion over 5 weeks ranged from 10 to 33%. COATED VICRYL* sutures had a higher mean cumulative incidence of suture extrusion than that of POLYSORB* sutures (31% vs. 19%).With POLYSORB* sutures, the 5-throw surgeon's knots had a higher cumulative incidence of suture extrusion than the 3-throw or 4-throw surgeon's knot square, 30% vs. 17% and 10%, respectively. This swine model offers an opportunity to study the parameters that influence suture extrusion. Because the volume of suture material in the wound is obviously a critical determinant of suture extrusion, it is imperative that the surgeon construct a knot that fails by breakage, rather than by slippage with the least number of throws. Because both braided absorbable suture materials are constructed with a secure surgical knot that fails only by breakage rather than slippage with a 3-throw surgeon's knot square (2 = 1 = 1), the construction of additional throws with these sutures does not enhance the suture holding capacity but plays a key factor in precipitating suture extrusion. Finally, it is important to emphasize that the surgeon must always construct symmetrical surgical knots for dermal subcuticular skin closure in which the constructed knot is always positioned perpendicular to the linear wound incision. Asymmetrical knot construction for dermal wound closure becomes an obvious invitation for suture extrusion.