Contribution of surgical specialization to improved colorectal cancer survival.

BACKGROUND: Reorganization of colorectal cancer services has led to surgery being increasingly, but not exclusively, delivered by specialist surgeons. Outcomes from colorectal cancer surgery have improved, but the exact determinants remain unclear. This study explored the determinants of outcome after colorectal cancer surgery over time. METHODS: Postoperative mortality (within 30 days of surgery) and 5-year relative survival rates for patients in the West of Scotland undergoing surgery for colorectal cancer between 1991 and 1994 were compared with rates for those having surgery between 2001 and 2004. RESULTS: The 1823 patients who had surgery in 2001-2004 were more likely to have had stage I or III tumours, and to have undergone surgery with curative intent than the 1715 patients operated on in 1991-1994. The proportion of patients presenting electively who received surgery by a specialist surgeon increased over time (from 14·9 to 72·8 per cent; P < 0·001). Postoperative mortality increased among patients treated by non-specialists over time (from 7·4 to 10·3 per cent; P = 0·026). Non-specialist surgery was associated with an increased risk of postoperative death (adjusted odds ratio 1·72, 95 per cent confidence interval (c.i.) 1·17 to 2·55; P = 0·006) compared with specialist surgery. The 5-year relative survival rate increased over time and was higher among those treated by specialist compared with non-specialist surgeons (62·1 versus 53·0 per cent; P < 0·001). Compared with the earlier period, the adjusted relative excess risk ratio for the later period was 0·69 (95 per cent c.i. 0·61 to 0·79; P < 0·001). Increased surgical specialization accounted for 18·9 per cent of the observed survival improvement. CONCLUSION: Increased surgical specialization contributed significantly to the observed improvement in longer-term survival following colorectal cancer surgery.

Quality of care in rectal cancer surgery. Exploring influencing factors in the West of Scotland.

AIM: To assess variability in the proportions of types of major resection for rectal cancer throughout the west of Scotland (WoS) and ascertain factors explaining the variability. METHOD: Retrospective cohort study of a regional population clinical audit database. This was linked to cancer registrations and death certificates in order that outcome analyses could be derived. Univariate and multivariate binary logistic regression analyses were used to explore determinants of survival. RESULTS: A total of 1574 patients met the inclusion criteria. The age range was from 22 to 97 years. The mean age was 67, median age 68 and the standard deviation was 11.5. The majority of patients (61%) were male. Unlike previous series, male patients and those with poorer socioeconomic circumstances (SEC) were no more likely to receive an abdominoperineal excision (APE) procedure for rectal cancer. CONCLUSION: Variation exists in the west of Scotland regarding surgical treatment for rectal cancer. We found no difference in the type of procedure offered according to sex, intent of operation or socioeconomic circumstances with reference to APE and anterior resection (AR) for rectal cancer. We conclude therefore that our region provides an equitable service on grounds of sex and SEC. This demonstrates that an equitable surgical service has been provided for those suffering from rectal cancer. Circumferential margin positivity was four times more likely in an APE than an AR for rectal cancer. This is not explained by age, stage, sex, socioeconomic circumstances (SEC), volume of surgery, intent of operation, type of admission or year of incidence.

Mechanical bowel preparation does not influence outcomes following colonic cancer resection.

BACKGROUND: Meta-analyses have indicated that preoperative mechanical bowel preparation (MBP) confers no clear benefit and may indeed be harmful for patients with colorectal cancer. The effects of bowel preparation on longer-term outcomes have not been reported. The aim was to compare long-term survival and surgical complications in patients who did or did not receive MBP before surgery for colonic cancer. METHODS: This was a retrospective cohort study of all patients undergoing potentially curative surgery for colonic cancer after routine hospital admission in the West of Scotland between January 2000 and December 2005. Clinical audit data were linked to cancer registrations and death certificates. Kaplan-Meier and Cox proportional hazards models were used to explore determinants of survival. RESULTS: A total of 1730 patients underwent potentially curative surgery for colonic cancer, of whom 886 (51·2 per cent) were men. The mean(s.d.) age was 69·7(10·6) years. Some 1460 patients (84·4 per cent) received MBP. Median follow-up was 3·5 (range 0·1-6·7) years. There were no statistically significant differences in 30-day postoperative complication rates between groups. The unadjusted hazard ratio (HR) for death from all causes for patients treated with MBP (versus no MBP) was 0·72 (95 per cent confidence interval 0·57 to 0·91). Multivariable analysis with adjustment for age, sex, socioeconomic circumstances, disease stage and presentation for surgery showed that MBP had no independent effect on all-cause mortality (HR 0·85, 0·67 to 1·10). CONCLUSION: Neither postoperative complications nor long-term survival are improved by MBP before colonic cancer surgery.

C-reactive protein as a predictor of postoperative infective complications following elective colorectal resection.

AIM: C-reactive protein (CRP) may be useful in predicting postoperative complications [1]. We investigated the sensitivity and specificity of postoperative CRP for infective complications after elective colorectal surgery. METHOD: One hundred and sixty consecutive patients (72 years old; interquartile range, 63-79) undergoing elective resection for colorectal cancer treated between September 2003 and October 2006 were studied. Details of the postoperative course were prospectively entered into a database. Of the 160 patients, 10 had incomplete CRP data and were excluded from further analysis. RESULTS: Infective complications occurred in 21%, with an overall complication rate of 29%. Infective complications occurred as follows: respiratory (10), wound (9), urinary tract (2) and central line infection (1), anastomotic leakage (5), intra-abdominal abscess (3) and septicaemia of unknown origin (2). There were three postoperative deaths. The positive predictive value for infection of CRP > 145 mg/l on postoperative day 4 was 61%. The negative predictive value of CRP < 145 mg/l on postoperative day 4 for an infective complication was 96%. CONCLUSION: A CRP > 145 mg/l on day 4 has high specificity and sensitivity for infective complications following elective colorectal resection.

Perineum compression during EAUS enhances visualization of anterior anal sphincter defects.

OBJECTIVE: Endo-anal ultrasound (EAUS) can detect anal sphincter injuries. However, anterior external anal sphincter (EAS) defects can be difficult to define. We assessed different EAUS techniques to determine if any particular method improved defect identification. METHOD: Ninety females with faecal incontinence were prospectively studied. Wexner faecal incontinence scores were obtained. All patients underwent anorectal manometry and EAUS using three different techniques: standard, digit-assisted (gloved finger pressing on posterior vaginal wall) and balloon-assisted (standard balloon inflated into the vagina). The three techniques were assessed by comparing defect characteristics (detection, angle, edges and scar tissue), and perineal body thickness. All measurements were performed at the mid anal canal level. RESULTS: are expressed as medians (IQR). Results Standard EAUS (S-EAUS) identified a sphincter defect in 54 patients. Digit assisted EAUS (D-EAUS) and balloon-assisted EAUS (B-EAUS) ultrasound revealed a sphincter defect in additional 11 and 9 patients respectively compared to S-EAUS. Correlation of maximum squeeze pressure with EAUS findings improved on D-EAUS and B-EAUS. The defect angle was significantly wider with D-EAUS and B-EAUS [S-EAUS 90 degrees (63-97), D-EAUS 100 degrees (81-101.5), B-EAUS 100 degrees (80-105), P = 0.0005]. The perineal body was significantly thicker when measured with B-EAUS [D-EAUS 9 mm (7-10) vs B-EAUS 10 mm (8-11), P = 0.0005]. Inter-observer agreement was comparable [S-EAUS (K) = 0.677, D-EAUS (K) = 0.658, B-EAUS (K) = 0.601]. CONCLUSION: EAS anterior defect detection and definition on EAUS may be improved by the demarcation and gentle pressure on the posterior vaginal wall.

Nicorandil-induced colonic ulceration: a new cause of colonic ulceration. Report of four cases.

PURPOSE: Nicorandil is a widely used third-line treatment for ischemic heart disease. It can be associated with the development of stomatitis and oro-anal ulceration. The current report suggests an association between nicorandil and the development of colonic ulceration, both in isolation and in combination with anal ulceration. METHODS: This is a case report of four patients with new onset lower gastrointestinal symptoms. All had a history of ischemic heart disease and angina. All were taking several cardiac medications, including nicorandil. RESULTS: Four patients (3 men) were investigated. Colonoscopy revealed both solitary and multiple colonic ulcers. Pathology showed acute nonspecific inflammation. Two patients also displayed concomitant anal ulceration. Nicorandil therapy was stopped in all patients. No other active treatment was offered. All patients became asymptomatic within six weeks of cessation of nicorandil therapy with resolution of the anal and colonic ulceration. CONCLUSION: Nicorandil may induce colonic ulceration and should be considered in the differential diagnosis of idiopathic colonic ulceration in appropriate patients.

Anterior anal fissures are associated with occult sphincter injury and abnormal sphincter function.

OBJECTIVE: The pathogenesis of chronic anal fissure (CAF) remains incompletely understood but most are associated with a high resting anal pressure and reduced perfusion at the fissure site. To date, no major distinction has been made between anterior and posterior anal fissures and their aetiology and treatment. We compared anterior and posterior fissures in patients who have failed to respond to medical treatment with respect to their underlying aetiology, anal canal pressures and sphincter muscle integrity. METHOD: Seventy consecutive patients (54 female:16 male) with a symptomatic CAF and 39 normal controls (19 female:20 male) without evidence of significant ano-rectal pathology were prospectively assessed by manometry and anal endosonography. RESULTS: Anterior anal fissures were identified in a younger age group [33 years (IQR 26-37) vs 41 years (IQR 36-52)] and predominantly in women. Anterior fissure patients were significantly more likely to have underlying external anal sphincter defects compared with posterior fissures [OR 10.9 (95% CI 3.4-35.4)]. Maximum resting pressure was not significantly elevated for anterior fissures compared with controls (P = 0.316) but was significantly elevated in posterior fissures (P = 0.005). The maximum squeeze pressure was significantly lower in the anterior fissure group [167 cmH2O (IQR 126-196) vs 205 cmH2O (IQR 174-262), P = 0.004]. A history of obstetric trauma was significantly associated with anterior fissure location [OR 13.9 (95% CI 3.4-55.7)]. CONCLUSIONS: Anterior anal fissures are associated with occult external anal sphincter injury and impaired external anal sphincter function compared with posterior fissures. These findings have implications for treatment, especially if a definitive procedure, such as lateral internal sphincterotomy, is considered.

Correlation between anal manometry and endosonography in females with faecal incontinence.

OBJECTIVE: Female faecal incontinence (FI) is largely because of sphincter injury at childbirth. Sphincter assessment aims to identify surgically correctable defects. We aimed to identify endoanal ultrasonography (EAUS) parameters that correlate with sphincter function. METHOD: One hundred females with FI and 28 healthy asymptomatic females were prospectively assessed. Wexner FI score was recorded and all subjects underwent anorectal manometry and EAUS. Multiple EAUS parameters were assessed and correlated with external (EAS) and internal (IAS) anal sphincter function, determined by maximum squeeze pressure (MSP) and maximum resting pressure (MRP) respectively. Parameters included sphincter quality (echogenicity), thickness, perineal body thickness (PBT) and defect characteristics (angle, length). Results are expressed as medians and interquartile range (IQR). RESULTS: Median Wexner score was 14 (12-17). Maximum EAS thickness significantly correlated with MSP (P = 0.019). EAS defects were detected in 84 patients and seven controls (P < 0.0001). Full-length EAS defects were only detected in FI group and had significantly lower MSP [MSP mmHg: full length 85 (65-103) vs partial length 119 (75-155), P = 0.006]. FI patients were more likely to have a mixed echogenicity of EAS compared with controls. EAS ring quality, PBT and defect angle were not significant. IAS quality was significantly associated with MRP [MRP mmHg: uniform 62 (43-82) vs mixed 47 (30.5-57.5), P = 0.002]. CONCLUSION: Certain EAUS parameters can be predictive of anal sphincter function. These include the presence of an EAS defect and its length, EAS maximum thickness, IAS ring quality. Integration of these parameters can give better EAUS correlation with manometry for FI evaluation.

Prospective study of the diagnostic evaluation of faecal incontinence and leakage in male patients.

OBJECTIVE: Male faecal incontinence (FI) has received little attention. No consistent pathophysiological abnormality has been identified in those studies that have specifically assessed male patients with FI or faecal leakage (FL). This study was designed to re-examine the different theories relating to the pathophysiology of male incontinence and to assess if manometric and ultrasound assessment yields clinically relevant information that directs patient care. METHOD: This was a prospective study of all men referred to a Coloproctology clinic with incontinence. The Wexner Incontinence score was used to assess severity of symptoms. Specific investigations included anal manometry, rectal sensation and endo-anal ultrasound (EAUS). Results were compared with a group of 20 normal male controls. RESULTS: A total of 59 symptomatic male patients were investigated (36 FI, 23 FL). FL and control groups had similar maximum resting (MRP) and maximum squeeze pressure (MSP). The incontinence group had a significantly lower MRP & MSP compared with controls [MRP: FI 58 (42-75.5) vs control 85 (72-104)] (P < 0.0001), [MSP: FI 167 (125-215) vs control 248 (192-302)] (P < 0.0001). There was no significant difference in rectal sensation between the groups and the defecation index was also similar. EAUS detected only one external anal sphincter defect amongst the 23 male patients with FL. One external sphincter defect and three internal sphincter defects were identified amongst the 36 patients with incontinence. Of these five patients with sphincter defects, four had previously undergone anorectal surgery. [Results expressed as median (interquartile range): manometry expressed as mmHg]. CONCLUSION: Male patients presenting with faecal incontinence frequently show impaired sphincter function which may be associated with sphincter defects. In contrast, those presenting predominantly with FL have no morphological or physiological changes that might account for their symptoms. Investigating such patients with anorectal physiology and EAUS is usually unhelpful and can be omitted.

A computer model of the position of the combined component in the prevention of impingement in total hip replacement.

Dislocation remains a major concern after total hip replacement, and is often attributed to malposition of the components. The optimum position for placement of the components remains uncertain. We have attempted to identify a relatively safe zone in which movement of the hip will occur without impingement, even if one component is positioned incorrectly. A three-dimensional computer model was designed to simulate impingement and used to examine 125 combinations of positioning of the components in order to allow maximum movement without impingement. Increase in acetabular and/or femoral anteversion allowed greater internal rotation before impingement occurred, but decreases the amount of external rotation. A decrease in abduction of the acetabular components increased internal rotation while decreasing external rotation. Although some correction for malposition was allowable on the opposite side of the joint, extreme degrees could not be corrected because of bony impingement. We introduce the concept of combined component position, in which anteversion and abduction of the acetabular component, along with femoral anteversion, are all defined as critical elements for stability.

Laparoscopic colonic resection in fast-track patients does not enhance short-term recovery after elective surgery.

BACKGROUND: Laparoscopic colorectal surgery has been claimed to enhance recovery when compared with open surgery. The aim of our study was to investigate whether laparoscopic colorectal resection improved recovery with the use of a multimodal rehabilitation programme. METHOD: We carried out a prospective audit of 80 patients undergoing elective colorectal resection between November 2003 and March 2005. All patients underwent a fast-track protocol with early feeding, mobilization and a fluid and sodium restriction regime. Recovery was measured in terms of return of gastrointestinal function, hospital stay, complications and quality of life measures. RESULTS: Of the 80 patients in the study 22 underwent laparoscopic resection and 58 had open surgery. Patients were well matched for all baseline characteristics. The groups were not significantly different in terms of opioid or antiemetic use. They were also similar in median time to first flatus (69 h vs 69 h, P = 0.36) and median time to first bowel motion (127 h vs 101 h, P = 0.07). There was no difference in median hospital stay (5.8 days vs 5.9 days, P = 0.87) or complications (P = 0.46) between the laparoscopic and open group. There were no significant differences in Short Form 36 scores between the two groups for any of the components measured. CONCLUSION: Laparoscopic colorectal resection does not appear to reduce the duration of ileus or hospital stay with the use of a multimodal rehabilitation regime. Further large randomized trials are required to confirm these findings.

Prospective study on the role of C-reactive protein (CRP) in patients with an acute abdomen.

INTRODUCTION: C-reactive protein (CRP) is used routinely in many hospitals to evaluate patients with an acute abdomen. We assessed CRP levels in non-specific abdominal pain (NSAP) and surgical conditions requiring operative or non-operative intervention. The aim of this study was to identify a level of CRP that can be useful in differentiating these three groups. PATIENTS AND METHODS: All patients older than 25 years and admitted with acute abdominal pain other than those requiring emergency surgery were included. CRP within 24 h was assessed in all patients. Various cut-off values (< 6, > 6-50, > 50-100, > 100-150 and > 150 mg/l) were used to identify a useful diagnostic level of CRP in the 3 groups. RESULTS: A total of 211 patients were prospectively evaluated - 129 women and 82 men with a mean age of 62.4 years (range, 27-92 years). CRP was performed in 196 within 24 h of admission. Sixty had NSAP while 136 had a surgical condition, of whom 69 had an operation/intervention while the rest were treated non-operatively. The median and interquartile (IQ) range for the three groups were: NSAP, 16 mg/l and 7.75-85.75 mg/l; surgical non-operative group, 75 mg/l and 30.5-150 mg/l; and surgical-operative, 111 mg/l and 42-212 mg/l, respectively. These results were statistically significant (P = 0.001). NSAP was diagnosed in 61% of patients at levels < 6 mg/l compared to 39% of patients in the surgical groups. At levels > 150 mg/l, NSAP was diagnosed in 15% of patients compared to only 54% and 31% for the operative and non-operative groups, respectively. CONCLUSIONS: Despite statistically significant differences between the three groups, no useful level of CRP could be identified to differentiate between patients with NSAP and those requiring operative or non-operative management.

Randomized clinical trial of the effect of postoperative intravenous fluid restriction on recovery after elective colorectal surgery.

BACKGROUND: Use of intravenous fluids is an important part of perioperative management. The aim of this study was to compare outcome following administration of restricted or standard postoperative intravenous fluids and sodium in patients undergoing elective colorectal surgery. METHODS: Eighty patients were randomized to restricted fluids (less than 2 litres water and 77 mmol sodium for 24 h after surgery) or a standard postoperative fluid regimen (3 litres water and 154 mmol sodium per day for as long as necessary). The primary endpoint was hospital stay. RESULTS: The median (i.q.r.) total intravenous fluid intake in the restricted group was 4.50 (4.00-5.62) litres compared with 8.75 (8.00-9.80) litres in the standard group (P < 0.001). Intravenous sodium intake was also significantly less in the restricted group (229 (131-332) versus 560 (477-667) mmol; P < 0.001). There was no difference in median time to first flatus (2.9 versus 2.9 days; hazard ratio (HR) 0.85 (95 per cent confidence interval (c.i.) 0.54 to 1.32); P = 0.466) or first bowel motion (4.7 versus 4.9 days; HR 1.06 (95 per cent c.i. 0.68 to 1.65); P = 0.802) between the restricted and standard groups, or in median hospital stay (7.2 versus 7.2 days; HR 1.03 (95 per cent c.i. 0.66 to 1.61); P = 0.902). CONCLUSION: Restriction of postoperative intravenous fluid and sodium does not reduce hospital stay following elective colorectal surgery.

Is pre-operative radiotherapy necessary in T-T rectal cancer with TME?

OBJECTIVE: The indications for pre-operative radiotherapy in rectal cancer are still unclear with the exception of T4 tumours. The aim of this study was to assess local and overall recurrence in patients with T1-T3 rectal cancers undergoing total mesorectal excision (TME). METHODS: Prospective data was collected from 150 patients with rectal cancer treated in one surgical centre between July 1997 and July 2002. One hundred and twenty-nine primary resections were carried of which 102 were with curative intent. Seventy-nine patients with T1-T3 tumours were included in the analysis. Nine had local resections and 70 underwent TME; 19 of the 70 patients were node positive and 51 were node negative. RESULTS: At a median follow-up of 37 months (range 19-79 months) there were 3 (4.3%) isolated local recurrences. One node positive patient developed isolated local recurrence compared with 2 node negative patients. The node positive patient died from a myocardial infarction while the two node negative patients died as a consequence of local recurrence. Three (4.3%) of 70 patients developed systemic relapse all of whom were node positive. The cancer specific mortality rate over the same follow-up period was 3/19 for node positive patients and 2/51 for node negative patients. Of 9 patients who had local resections, none developed local recurrence or systemic relapse. CONCLUSIONS: With TME the rate of local recurrence in T1-T3 tumours is low. Our results do not support the use of pre-operative radiotherapy for these patients.

Prospective study on the management of patients with complicated diverticular disease.

INTRODUCTION: Diverticular disease is a common condition with high morbidity and mortality related to its complications. The aim of this study was to assess the predictive role of acute diverticulitis in the development of further complications from diverticular disease. PATIENTS AND METHODS: Prospective assessment of all patients with complicated diverticular disease over a 1-year period in a large teaching hospital was undertaken. All patients had documented evidence of their diagnosis by radiological, endoscopic or histopathological techniques when feasible. RESULTS: Seventy-seven patients with complicated diverticular disease were identified. There were 53 females and 24 males with a median age of 74 years (range 30-97 years). Complications included: acute diverticulitis (37), fistula (12), perforation (8), bleeding (7), abscess (7) and stricture (6). Only 8 had two or more previous documented episodes of diverticulitis. Twenty-five underwent surgery, 3 died (peritonitis 2, abscess1) and 5 had a complication (anastomotic dehiscence 1, adhesive obstruction 1, incisional hernia 2 and pneumonia 1). Three (5%) of 37 patients with acute diverticulitis had two or more admissions but none underwent surgery or developed further complications. CT was performed during acute admission in 14/37 patients with acute diverticulitis. The majority of patients with fistula (9/12), perforation 7/8, bleeding 6/7 and abscess 5/7 had no previous episode of diverticulitis while most patients with stricture (4/6) had previous documented episodes. CONCLUSION: In our patient population acute diverticulitis is not a good predictor of the development of further complications from diverticular disease as only a minority of patients with perforation, fistula, abscess and bleeding had previous documented episodes of diverticulitis.

Prospective study on the role of the CT scan in patients with an acute abdomen.

OBJECTIVES: Recent reports indicate that early CT scan (within 24 h) increases diagnostic accuracy, reduces hospital stay and mortality in patients with an acute abdomen. The aim of this study was to assess the surgeons' use of CT in patients with an acute abdomen and the impact of this on diagnostic accuracy and mortality. PATIENTS AND METHODS: Patients older than 25 years admitted as an emergency with acute abdominal pain were prospectively evaluated. RESULTS: Two hundred and eleven patients fulfilled the inclusion criteria including 129 women and 82 men with a mean age of 62.4 years (range 27-92 years). The correct diagnosis on admission was made in 99 (47%) patients. CT was performed in 81 (38%), including 24 who had the scan performed within 24 h of admission. The sensitivity, specificity and accuracy of CT were 86%, 79% and 84%. CT was considered to have changed clinical management in 40 patients. Fifteen patients died, and one death may have been prevented by an early CT. Five had a delay in diagnosis of a serious condition; all could have been prevented by early CT. CONCLUSION: Selective use of CT increases diagnostic accuracy and improves the management of patients with an acute abdomen. Clinical trials are necessary to assess outcome following selective vs routine use of CT in this group of patients.

A technically difficult endorectal ultrasound is more likely to be inaccurate.

OBJECTIVE: Endorectal ultrasound (ERUS) is well established as an accurate modality for local staging of rectal tumours. The aim of this study was to identify reasons for inaccurate staging of tumours, and to assess whether difficulties encountered during scanning are likely to influence accuracy. PATIENTS AND METHODS: ERUS was performed by a single operator using a 10 MHz rigid instrument. One hundred and seventeen patients that had both ERUS and surgery are included in this study (patients that had pre-operative radiotherapy were excluded). During ERUS, procedural conditions and limiting factors were recorded. Data was collected prospectively. RESULTS: In 78 (66.7%) patients no technical difficulty was encountered during ERUS. In this group accuracy was 80% for T-stage and 77% for N-stage. Specific reasons for inaccuracy identified in this group were: inflammatory lymph nodes (from a tumour associated abscess and a colovesical fistula) and deep biopsy causing a submucosal defect with intramural haemorrhage in benign lesions (2 cases). In the remaining 39 (33.3%), the following problems were encountered: stenotic lesions (23), patient discomfort (8), poor bowel preparation (6), and scarring from previous surgery (2). In 11 patients from this group, the scan was considered inconclusive and no stage could be determined. For the other 28, the accuracy for T-stage was 68% and for N-stage 67%. CONCLUSION: A technically difficult ERUS is likely to give an inconclusive or inaccurate result for both T-stage (P = 0.001) and N-stage (P = 0.003). In this situation a repeat scan may be considered (where appropriate). Alternatively, further assessment by MRI or flexible endoscopic ultrasound may be considered.

Synthesis, characterization and melt spinning of a block copolymer of L-lactide and epsilon-caprolactone for potential use as an absorbable monofilament surgical suture.

This paper describes the synthesis and characterization of a block copolymer of L-lactide (LL) and epsilon -caprolactone (CL) and its subsequent melt spinning into a monofilament fiber. The synthesis reaction was a two-step process. In the first step, an approximately 50:50 mol% random copolymer, P(LL-co-CL), was synthesized via bulk copolymerization of LL and CL. This first-step prepolymer then became the macroinitiator in the second-step reaction in which more LL monomer was added to form a block copolymer, PLL-b-P(LL-co-CL)-b-PLL. Both the prepolymer and block copolymer were characterized by a combination of analytical techniques comprising dilute-solution viscometry, GPC, 1H and 13C NMR, DSC and TG. The block copolymer was then processed into a monofilament fiber using a small-scale melt spinning apparatus. The fiber was spun with a minimum amount of chain orientation and crystallinity so that its semi-crystalline morphology could be constructed under more controlled conditions in subsequent off-line hot-drawing and annealing steps. In this way, the fiber's tensile properties and dimensional stability were developed, as indicated by the changes in its stress-strain curve. The final drawn and annealed fiber had a tensile strength (>400 MPa) approaching that of a commercial PDS II suture of similar size. It is considered that this type of block copolymer has the potential to be developed further as a lower-cost alternative to the current commercial monofilament surgical sutures.