Predicting the Timing and Cause of Microvascular Free Flap Failure: An Australian Study of 1569 Free Flaps.

BACKGROUND: The aim of the study is to assess the possible predictors of microvascular free flap failure and determine the critical postoperative timing of flap failure, thereby minimizing this adverse outcome. METHODS: This is a retrospective single-institutional review of 1569 free flap operations. All free flaps with outcome status recorded were analyzed for possible predictors in the development of microvascular compromise. Compromised cases were then analyzed for differences in time to compromise and time to theater takeback between salvaged versus failed free flaps. RESULTS: Of the assessable 1569 free flaps, 31 developed microvascular compromise (2.0%); the salvage rate was 20.0%, and overall failure rate was 1.5%. Osteocutaneous free flaps in head and neck had increased risk of developing free flap failure compared to other flaps (odds ratio = 3.8, 95% confidence interval: 1.2-12.7). Among breast patients, previous radiotherapy had a significant association with flap failure (P < 0.001). Free flap salvage rates dropped from 38.5% to 7.7% for compromises detected after 24 hours (P = 0.160), and from 57.1% to 11.1% for free flaps taken back to theater greater than 3 hours after compromise detection (P = 0.032). CONCLUSIONS: Delays in compromise detection and flap takeback to theater resulted in reduced salvage rates, with the critical timing of takeback being under 3 hours. Standardized flap monitoring protocols and incorporation of newer technologies could see faster detection and improved salvage rates. Additional care is required when reconstructing: osteocutaneous head and neck free flaps and previously irradiated breast patients.

The Effect of Sedation on Diagnostic Lumbar Medial Branch Blocks for Facetogenic Low Back Pain: An Observational Study.

BACKGROUND: Lumbar medial branch blocks (MBB) are some of the most commonly performed pain procedures in the United States. Diagnostic MBBs are performed to confirm if the generator of low back pain is the facet joint. However, with diagnostic injections, false positive blocks may occur. OBJECTIVES:   Our prospective observational study aims to investigate the effects of midazolam sedation on patients' perceived intensity of pain relief following lumbar MBB. STUDY DESIGN: This is a single-center multi-site prospective observational study registered on clinicaltrials.gov (NCT04453449). SETTING: The study was approved by the Henry Ford Health System Institutional Review Board (IRB) in June 2020 (IRB# 14010) and registered on clinicaltrials.gov in July 2020 (NCT04453449). This manuscript adheres to the applicable EQUATOR STROBE guidelines for an observational cohort study. METHODS: Patients that underwent MBB without sedation were compared to sedated patients. Patients were asked to complete the Numeric Rating Scale (NRS) at baseline, one day after their diagnostic blocks, as well as 4 weeks and 8 weeks after their lumbar radiofrequency ablation (RFA). The primary outcome is the difference between baseline NRS pain scores and the lowest reported score in the 8 hours following MBB. For patients who proceed to RFA, the frequency of false positive blocks was evaluated. A patient was considered to have a false positive block when they failed to achieve 50% pain relief from RFA after 2 successful sequential MBBs. RESULTS: There was no significant difference in the NRS pain score change between the sedated and non-sedated groups for diagnostic block one (P = 0.167) and diagnostic block 2 (P = 0.6145). There was no significant difference of false positive rates between non-sedation and sedation patients at 4-weeks post-RFA (P = 0.7178) and at 8-weeks post-RFA (P = 1.000). LIMITATIONS: Some of the limitations of this study include its nonrandomized design, patient self-reported pain scores, as well as the small variability in the injection technique of proceduralists and in the anatomical location of the injection site. CONCLUSIONS: This study showed that midazolam did not change patients' perceived intensity of pain following MBB, as well as false positive rates after RFA. Larger studies are required to draw definitive conclusions.

The thoracoacromial axis in salvage head and neck reconstructive surgery, a case series.

We present the surgical technique, relevant anatomy and a consecutive case series of salvage head and neck free flap reconstructions utilising the thoracoacromial axis. We demonstrated that the thoracoacromial axis is safe and reliable in salvage head and neck reconstruction with particular use in reconstruction of tracheoespophageal and pharyngolaryngectomy fistulae.

Validation of a risk prediction calculator in Australian patients undergoing head and neck microsurgery reconstruction.

BACKGROUND: The American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) surgical risk calculator (SRC) is an open access calculator predicting patients' risk of postoperative complications. This study aims to assess the validity of the SRC in patients undergoing microsurgical free flap reconstruction at an Australian tertiary referral centre. METHODS: This is a retrospective cohort study of 200 consecutive patients treated up to November 2020. SRC-predicted rates of postoperative complications and hospital length of stay (LOS) were compared to those observed for the ablative and reconstructive components of the procedure. The performance of the SRC was assessed using Brier scores, area under the receiver operating characteristic (ROC) curve (AUC), and the Hosmer-Lemeshow test. RESULTS: For both ablative and reconstructive components, the SRC discriminates well for pneumonia and urinary tract infection, and it is calibrated well for readmission and sepsis, but it does not discriminate and calibrate well for any single outcome. SRC-predicted hospital LOS and actual LOS did not correlate well for the reconstructive component, but they correlated strongly for the ablative component. CONCLUSIONS: The SRC is a poor predictor of postoperative complication rates and hospital LOS in patients undergoing head and neck microsurgical reconstruction.

Validated specialty-specific models for multi-disciplinary microsurgery training laboratories: a systematic review.

BACKGROUND: Laboratory simulation is increasingly important for teaching microsurgical skills. Training microsurgeons of different specialties within the same simulation laboratory increases efficiency of resource use. For maximal benefit, simulations should be available for trainees to practice specialty-specific, higher-order skills. Selection of appropriate simulations requires knowledge of the efficacy and validity of the numerous described laboratory models. Here we present a systematic review of validated training models that may serve as useful adjuncts to achieving competency in specialty elements of microsurgery, and appraise the evidence behind them. METHODS: In setting up a multi-disciplinary microsurgery training course, we performed a systematic review according to preferred reporting items for systematic reviews and meta-analyses guidelines. EMBASE, MEDLINE, Cochrane and PubMed databases were searched for studies describing validated, microscope-based, specialty-specific simulations, and awarded a level of evidence and level of recommendation based on a modified Oxford Centre for Evidence-Based Medicine classification. RESULTS: A total of 141 papers describing specialty-specific microsimulation models were identified, 49 of which included evidence of validation. Eleven were in the field of neurosurgery, 21 in otolaryngology/head and neck surgery, two in urology/gynaecology and 15 plastic and reconstructive surgery. These papers described synthetic models in 19 cases, cadaveric animals in 10 cases, live animals in 12 cases and human cadaveric material in 10 cases. CONCLUSION: Numerous specialty-specific models for use in the microscope laboratory are available, but the quality of evidence for them is poor. Provision of models that span numerous specialties may encourage use of a microscope lab whilst still enabling more specific skills training over a 'one-size-fits-all' approach.

Structural Failure Mechanisms of Common Flexor Tendon Repairs.

BACKGROUND: This study investigated the exact failure mechanisms of the most commonly used conventional tendon repair techniques. A new method, radiographing repair constructs in antero-posterior and lateral projections before and after tensioning was used. This allowed to precisely analyse failure mechanisms in regards to geometrical changes in all three dimensions. Additionally the biomechanical stability focusing on gapping was tested. METHODS: Sheep fore limb deep flexor tendons were harvested and divided in eight groups of ten tendons. Three common variants of the Kessler repair method and four common 4-strand repair techniques were tested. Additionally a new modification of the Adelaide repair was tested. RESULTS: Biomechanical testing showed no significant differences in gapping for the three tested 2-strand Kessler repair groups. Once a double Kessler or 4-strand Kessler repair was performed the stability of the repair improved significantly. Further significant improvements in biomechanical stability could be achieved by using cross locks in the repair like in the Adelaide repair method. Qualitative analysis using radiographs showed that all Kessler repair variants unfolded via rotations around the transverse suturing component, no matter which variant was used. CONCLUSIONS: Additional to the commonly described constriction of the repair construct, the rotating deformation is the main reason for repair site gapping in Kessler tendon repair methods. The term "locking" in a Kessler repair is misleading. The cruciate repairs tended to loose grip and drag (cheese-wire) through the tendon and therefore lead to gapping. The most stable repair constructs in all three dimensions were the Adelaide repair and its interlocking modification. This is due to the superior anchoring qualities of its cross locks and three dimensional stability.

The Interlocking Modification of the Cross Locked Cruciate Tendon Repair (Modified Adelaide Repair): A Static and Dynamic Biomechanical Assessment.

The 4-strand cross-locked cruciate flexor tendon repair technique (Adelaide technique) has been shown to have comparably high resistance to gap formation and ultimate tensile strength. This study aimed to determine whether an interlocking modification to the Adelaide repair would impart improved biomechanical characteristics. Twenty four sheep flexor tendons were harvested, transected and repaired using either standard or modified Adelaide techniques. Repaired tendons were cyclically loaded. Gap formation and ultimate tensile strength were measured. Additionally, suture exposure on the tendon surface was determined. There was a statistically significant increase in resistance to gap formation in the early phase of cyclic loading within the modified Adelaide group. In the later stages of testing no significant difference could be noted. The average final load to failure in the modified group was higher than the standard group but this did not achieve statistical significance. Interlocking suture techniques in four strand tendon repair constructs can improve gapping behavior in the early phase of cyclic loading.

Whip stitch versus grasping suture for tendon autograft.

PURPOSE: During tendon autograft harvest, either a grasping suture or traditional whip stitch can be used to grasp tendon prior to definitive bone fixation. Their grip strength has not, to our knowledge, been compared. This article compares a needle-free suture technique to a standard whip stitch by testing grip strength in vitro. METHODS: Twelve uniform ovine flexor tendons were prepared; six tendons with a standard, non-locking whip stitch and six tendons with a grasping suture. All the samples were tested to failure in uniaxial tension in a materials testing machine. Load/displacement curves were generated, and qualitatively assessed and peak loads were compared. RESULTS: There were no significant differences between the groups in tendon length or diameter. Modes of failure between the groups, as characterised by the load/displacement curves, were quite distinct. Peak load to failure was lower in the utility suture group (mean peak load at failure 121.28 N) than the whip stitch group (mean peak load to failure 188.82 N). All failures in the utility suture group occurred when the suture snapped. CONCLUSIONS: The grasping suture described here is weaker than a standard whip stitch but may be sufficiently strong to harvest and handle tendon autograft. A standard whip stitch remains the choice for definitive graft fixation.

A highly elastic and adhesive gelatin tissue sealant for gastrointestinal surgery and colon anastomosis.

BACKGROUND: We describe the development of a highly elastic and adhesive surgical tissue sealant, based on photochemically crosslinked gelatin, for sealing sutured incisions in the gastrointestinal (GI) tract in a rabbit surgical model and in a canine colon anastomosis study. METHODS: The study included in vitro assessment of mechanical parameters of the tissue sealant and in vivo analysis of burst strength and histology at 24 h, 3 days and 7 days post surgery, in a rabbit model, to assess progress of wound healing at the suture sites. Utility of this sealant to repair and seal a lower colonic resection and anastomosis procedure in a canine model was also investigated. RESULTS: We show that a photopolymerised gelatin tissue sealant provides effective sealing of GI incisions and facilitates wound healing with no evidence of inflammation up to 28 days post-surgery. Blending of derivatised gelatin with underivatised gelatin allowed tuning of elasticity and elastic modulus of the photopolymerised sealant to suit surgical applications. High tissue adhesive strength was maintained at all blend ratios and exceeded 100 kPa. CONCLUSIONS: This highly elastic and adhesive photopolymerised gelatin tissue sealant offers a number of advantages over currently available sealants suitable for GI surgical procedures.

Influence of locking stitch size in a four-strand cross-locked cruciate flexor tendon repair.

PURPOSE: The 4-strand cross-locked cruciate technique (Adelaide technique) for repairing flexor tendons in zone II is a favorable method in terms of strength and simplicity. The purpose of this study was to investigate the effects of varying the cross-lock stitch size in this repair technique. Outcomes measured were load to failure and gap formation. METHODS: We harvested 22 deep flexor tendons from adult pig forelimbs and randomly allocated them into 2 groups. After cutting the tendons at a standard point, we performed a 4-strand cross-locked cruciate repair using 3-0 braided polyester with either 2-mm cross-locks (n = 11) or 4-mm cross-locks (n = 11). All repairs were completed with a simple running peripheral suture using 6-0 polypropylene. Repaired tendons were loaded to failure and the mechanism of failure, load to failure, stiffness, and load to 2-mm gap formation were determined. RESULTS: All repairs failed by suture breakage; we noted no suture pullout. There was no difference in load to failure (71.7-71.1 N; p = .89) or stiffness (4.1-4.6 N/mm; p = .23) between the 2-mm cross-lock and the 4-mm cross-lock groups. There was a trend toward higher resistance to 2-mm gap formation with the 4-mm cross-locks (55-62.2 N; p = .07). CONCLUSIONS: Four-strand cross-locked cruciate repairs with cross-lock sizes of 2 and 4 mm provide high tensile strength and are resistant to pullout. Repairs with 4-mm cross-locks tend to provide a more central load distribution and better gapping resistance than repairs with 2-mm cross-locks.

The relationship between gap formation and grip-to-grip displacement during cyclic testing of repaired flexor tendons.

The assessment of repair site gap formation during cyclic loading of reconstructed flexor tendons provides important data on the performance of repair techniques in the early postoperative period. This study describes our cyclic testing protocol and evaluates the relationship between changes in optical gap and grip-to-grip displacement. Sixteen sheep hind limb deep flexor tendons were randomized into four repair groups (n=4 per group): a 2-strand repair (modified Kessler) and 4-strand repair (Adelaide), both with and without a simple running peripheral suture. Repaired tendons were cycled for 1000 cycles at appropriate rehabilitation loads for the reconstruction. Tendons were paused at 18 pre-determined cycle points to measure gap and displacement. A strong positively linear relationship between gap and displacement was demonstrated for all repair groups (R²>0.90). An initial non-linear region during the first 10 cycles was noted with some combined core and peripheral repairs. Although trends in displacement after 10 cycles can be used to reflect gapping behaviour, direct optical measurement of gap remains preferable. We hypothesized that the adjustment of suture strands and equilibration of forces within the reconstruction occurs mostly during the initial 10 cycles. Gap-cycle curves provide a good illustration of dynamic changes at the repair site, and should be added more frequently to cyclic testing studies.

Cross-sectional area and strength differences of fiberwire, prolene, and ticron sutures.

PURPOSE: Flexor tendons should be repaired with suture material strong enough to permit early motion and small enough for the resulting knot to allow unimpeded tendon glide and healing. This study sought to define differences in cross-sectional area and knotted tensile strength among Fiberwire, Prolene, and Ticron sutures. METHODS: Five strands, each of 3-0 and 4-0 Prolene, Ticron, and Fiberwire sutures, were embedded in polymethylmethacrylate and sectioned in a linear precision saw to obtain 10 cross-sections of each material and size. These were examined by scanning electron microscopy and digitally analyzed for cross-sectional areas. Ten strands of each suture material and size had a single throw knot placed, and they were loaded to failure in a micromechanical tester. RESULTS: Prolene and Ticron cross-sections were circular. Fiberwire was noncircular. The 3-0 Fiberwire sutures had greater cross-sectional area than the 3-0 Ticron sutures (p < .001), which in turn were larger than 3-0 Prolene (p < .05). The 4-0 Fiberwire cross-sectional area was also greater than that of 3-0 Ticron and Prolene (p < .05). After relating knotted tensile strength to cross-sectional area, Fiberwire was 10% stronger than Prolene, and 25% stronger than Ticron. CONCLUSIONS: Fiberwire is not only stronger, but also larger than other sutures in the same or even higher suture size category. Failure to meet the United States Pharmacopeia standards for suture diameter is declared in the product information sheet, although surgeons may not be aware of these size variations. Suture size definitions are currently based on diameter, a consistent measure for circular monofilament sutures, but not for braided or noncircular sutures.

A biomechanical assessment of repair versus nonrepair of sheep flexor tendons lacerated to 75 percent.

PURPOSE: The benefit of repairing a 75% partial flexor tendon laceration remains controversial. The purpose of this study was to assess the degree of gap formation with and without repair when the 75% lacerated tendon is subjected to cyclic loading. Repair with only a peripheral suture was compared to that using a core and peripheral repair technique. METHODS: Sixteen deep flexor tendons from sheep hind limbs were lacerated to 75% of the tendon diameter. The cut tendons were loaded for 100 cycles from 3 N up to 30 N and then back to 3 N, at a rate of 0.2 Hz. Gap formation was measured at 0 and 100 cycles. Tendons were then randomized into 2 repair groups of 8 each: group 1 was repaired with only a simple, running peripheral suture (6-0 polypropylene monofilament), whereas group 2 was repaired with a modified Kessler core suture (4-0 silicone-coated braided polyester) plus a peripheral suture (6-0 polypropylene monofilament). Repaired tendons were tested for 500 cycles, and the gap was measured at 0, 100, and 500 cycles. After cycling, gap was measured at 100 N load, and the peak loads were determined on static failure testing. RESULTS: The 75% partially lacerated tendons had >2 mm gap at 100 cycles. This gap was significantly reduced by peripheral or peripheral plus core repairs (p < .001). There was no difference in gap formation between tendons with peripheral repair only and those with both peripheral and core repairs. Gap formation in repaired tendons remained

Effectiveness of a new tunneled catheter in preventing catheter malfunction: a comparative study.

PURPOSE: To compare infection and malfunction rates of two different types of antimicrobial-eluting tunneled cuffed catheters (TCCs) for hemodialysis. MATERIALS AND METHODS: The HemoSplit TCC with BioBloc (silver sulfadiazine) coating (n = 100, control group) and the Tal Palindrome Ruby TCC, which has a novel silver antimicrobial sleeve and a spiral-z tip design (n = 100, study group), were compared in this case-controlled study. The main endpoints were TCC infection and malfunction. RESULTS: Primary-assisted TCC patency was significantly reduced with the BioBloc TCC (71% and 61% at 90 and 180 days, respectively) compared with the Palindrome Ruby TCC (94% at 90 and 180 days, P < .0001). Multivariate analysis identified only the BioBloc TCC and common femoral access site as independent predictors of worse patency. The unadjusted relative risk (95% confidence interval) for TCC dysfunction with the BioBloc compared with the Palindrome Ruby was 6.0 (2.33-15.53, P < .001), and the relative risk adjusted for access site was 3.2 (1.71-11.96, P = .002). The infection-free rates of the two TCC types were similar (P = .36). The reintervention-free rate for infection or malfunction was significantly better with the Palindrome Ruby TCC (76% and 58% at 90 and 180 days, respectively) than with the BioBloc TCC (60% and 45% at 90 and 180 days, respectively; P = .03). CONCLUSIONS: The results support the use of the Palindrome Ruby TCC on the basis of the significantly lower thrombosis and reintervention rate; randomized trials are justified to confirm this finding and to evaluate its role in the prevention of TCC infection.

Results of aggressive graft surveillance and endovascular treatment on secondary patency rates of Vectra Vascular Access Grafts.

OBJECTIVE: The aim of the present study was to determine the effect of an aggressive graft surveillance and endovascular treatment protocol on secondary patency rates of a polyetherurethaneurea vascular access graft, specially designed to provide early access and rapid hemostasis. METHODS: One hundred and ninety Vectra Vascular Access Grafts (C. R. Bard, Inc, Murray Hill, NJ) were placed in 176 patients (78 females and 98 males, mean age 61.7 years). There were 41 forearm grafts, 145 upper arm grafts and four thigh grafts. Graft surveillance was performed by using clinical and hemodialysis parameters to detect a failing/failed graft and followed by endovascular treatment, rheolytic thrombectomy (AngioJet, Possis Medical Inc, Minneapolis, Minn) and/or angioplasty +/- stenting of the anatomical lesion (arterial anastomosis, graft, venous outflow, draining or central veins). RESULTS: Hemodialysis started after a median of 15.5 days, as soon as from the day of the operation in some cases. Bleeding complications occurred in six patients (3.2%), venous hypertension in seven (3.7%), steal syndrome in two (1.1%), neurological complications in two (1.1%), while late infection (range 2.7-14.6 months) was seen in six patients (3.2%). Thrombectomy and angioplasty (median number of sessions 1, interquartile range 1-2) was performed in 43 grafts. Isolated angioplasty, not associated with thrombosis (median number of sessions 1, interquartile range 1-2), was performed in 50 grafts. These interventions increased primary assisted patency from 69% and 63% at 12 and 18 months, respectively to a secondary patency rate of 86%. Taking into account grafts removed for late infection, functional secondary patency rate dropped to 83% and 81%, at 12 and 18 months, respectively. Arterial anastomosis angioplasty was performed more frequently in thrombosed grafts (28.6%) than failing grafts (6.7%), P < .001 and had a significant negative predictive value on secondary patency rates at 12 and 18 months, which were 60.5% compared with 89% for grafts that had no interventions performed (P = .007) and 90.9% for grafts that had any intra-graft, venous outflow, or draining or central vein stenosis treated with angioplasty at any stage (P = .002). Multivariate analysis identified the presence of arterial anastomosis stenosis as the single predictor of secondary patency (relative risk 0.247, P = .002). CONCLUSIONS: Aggressive graft surveillance and endovascular treatment increases significantly secondary patency rates of Vectra Vascular Access Grafts. Longer follow-up will determine the effectiveness of this policy. The role of inflow stenosis on graft longevity and alternative treatment options warrant further investigation.