The in vivo biodynamic properties of the intact equine linea alba

Ex vivo comparison of the bursting strength of an equine ventral midline celiotomy covered by two standard abdominal bandages

OBJECTIVE

To determine the compressive effect of abdominal bandages after ventral midline celiotomy closure in horses.

STUDY DESIGN

Ex vivo, experimental study.

ANIMALS

Equine cadavers (n = 18), six per group.

METHODS

A 20-cm ventral midline celiotomy was created in each of 18 equine cadavers. A 200-L inflatable bladder was placed in the abdomen, and the linea alba was apposed. Horses were randomly assigned to no bandage (C), elastic (E), or Velcro inelastic (I) bandage groups for testing. Circumferential bandages were placed with a subbandage pressure monitoring system over the incision. The bladder was insufflated until construct failure, which was determined by a decrease in pressure reading. Bursting pressure, location of body wall or bandage failure, and subbandage pressures were recorded.

RESULTS

Maximum bursting pressure was different between groups E and C (P = .004), with no difference between groups E and I (P = .146) or I and C (P = .085). Group I achieved higher subbandage pressure compared with group E (P = .036). Abdominal compliance was not different between groups (P = .099). Location of failure differed between groups (P = .011), with failure at the diaphragm more common in group I (6/6, 100%) compared with groups E (3/6 [50%]) and C (1/6 [16.7%]).

CONCLUSION

Elastic abdominal bandages had higher abdominal bursting pressures compared with unbandaged incisions.

Ultrasonographic evaluation of the width, thickness, and length of the normal linea alba in standing and dorsal recumbent horses

OBJECTIVE

To determine the variability in length, width, and thickness of the equine linea alba (LA) and the effect of a standing vs dorsal recumbent position on these measurements.

STUDY DESIGN

Descriptive anatomical comparative study.

ANIMALS

Standing horses (N = 75; in 30 horses, measurements were obtained in dorsal recumbency first and repeated after horses were standing).

METHODS

Linea alba length was measured in standing position from xiphoid to umbilicus, and transverse ultrasonographic images were obtained at five reference points to measure LA width and thickness. In 30 horses, measurements were obtained in dorsal recumbency first and repeated after horses were standing.

RESULTS

There was wide variation in LA width and thickness between standing horses, with gradual increase from xiphoid (range, 0.14-0.64 cm) to umbilicus (range, 0.2-2.97 cm). Linea alba length in standing position was 51.09 ± 6.219 cm. Width was independent of the size of the horse; thickness and length were correlated at some reference points to height (r = 0.346-585, P < .05) and weight (r = 0.324-0.642, P < .05). Different LA shapes could be identified. In dorsal recumbency, the LA was smaller in width at all reference points (15%-23%, P < .05) and shorter (20%, P < .001) compared with standing.

CONCLUSION

In addition to the wide variability in LA measurements and shapes between horses, there was a significant decrease in LA width and length when horses changed from standing to dorsal recumbency.

CLINICAL SIGNIFICANCE

The difference in LA length and width between dorsal recumbency and when standing could increase tension on sutures after laparotomy and should be taken into account when surgeons are closing the abdomen.

Incisional infections associated with ventral midline celiotomy in horses

OBJECTIVE

To review the veterinary literature regarding healing and complications associated with equine celiotomy including anatomy and physiology, risk factors for incisional infection and hernia, and treatment.

ETIOLOGY

Celiotomy is the most common approach to treat horses with surgical colic. Incision through the linea alba provides exposure to most of the abdomen for exploration, exteriorization, and correction of surgical lesions. Incisional apposition relies on suture strength during anesthetic recovery and for the first 30 days postoperatively. Factors associated with the patient, surgical lesion and procedures, anesthesia, and recovery put the horse at risk for surgical site infection. Infection is the most important risk factor for incisional hernia formation.

DIAGNOSIS

A presumptive diagnosis of surgical site infection is made based on the presence of fever and incisional swelling, pain, and discharge. Ultrasonography can be used to identify areas of fluid accumulation prior to the appearance of incisional drainage. Definitive diagnosis is based on positive bacteriologic culture of the incisional discharge. Incisional hernia is diagnosed by palpation of the incision, usually 30-60 days after surgery. Ultrasound of the incision may aide in early diagnosis of incisional hernia if gaps along the incision in the linea alba are apparent.

THERAPY

No objective data exist to assess the efficacy of specific therapies for surgical site infections following celiotomy. Principles of treatment include the establishment of drainage, bandaging, antimicrobial therapy based on culture and sensitivity, and extended rest in an attempt to avoid incisional hernia or dehiscence. Treatment for incisional hernia includes prolonged circumferential bandaging, open or minimally invasive hernia repair, or no treatment.

PROGNOSIS

Incisional complications are associated with prolonged convalescence and diminished prognosis for return to athleticism. Limiting risk factors for surgical site infections, prompt treatment, and incisional support may optimize celiotomy healing and timely return to function. Horses compete in many disciplines with incisional hernias.

The Effect of Core Abdominal Muscle Rehabilitation Exercises on Return to Training and Performance in Horses After Colic Surgery

We conducted a retrospective cohort study to test the hypothesis that performing 4 weeks of core abdominal rehabilitation exercises (CARE) postoperatively would be safe and associated with faster return to training and improved performance after colic surgery. Performance horses that recovered from colic surgery performed by the same surgeon and survived ≥ 1 year from 2008 to 2017 were included. Data were obtained from a review of medical records. Information about the horses' rehabilitation and performance was obtained from owners/trainers. Data from horses that completed a 4-week CARE program after surgery were compared with control horses that did not do the exercises after colic surgery. Data were analyzed using univariate and multiple regression, P < .05. Eleven CARE horses and 51 controls between the ages of 3 and 18 years were included in the data analysis. All CARE horses completed the rehabilitation program with no reported complications, returned to work faster after surgery, P = .002, and to training faster, P = .0002. After colic surgery, 81% of CARE horses improved their performance level compared with 7.8% of controls, P < .001. Core abdominal rehabilitation exercises were safely performed by horses after colic surgery with no reported complications and may have facilitated faster convalescence and improved performance.

Bursting strength of surgeon's and self-locking knots for closure of ventral midline celiotomy in horses

OBJECTIVE

To compare the bursting strength and failure mode of ventral midline celiotomy closed with a simple continuous suture pattern with 1 of 2 knot combinations, a novel self-locking knot combination of a forwarder start with an Aberdeen end knot (F-A) and a traditional combination of a surgeon's start with a surgeon's end knot (S-S).

STUDY DESIGN

Ex vivo experimental.

SAMPLE POPULATION

Equine cadavers (n = 14).

METHODS

A 20-cm ventral midline celiotomy was created in 14 equine cadavers. Horses were assigned to celiotomy closure with an F-A or S-S knot combination. Prior to closure, a 200-L inflatable bladder was placed in the abdomen and then insufflated until failure of the celiotomy closure. The horses' signalment, weight, breed, and age, as well as knot combination type, mode of failure, closure time, and bursting strength (mm Hg) were recorded.

RESULTS

The median bursting strength was significantly greater when incisions were closed with the F-A knot combination (388 mm Hg) compared with the S-S knot combination (290 mm Hg) (P = .035). Most incisions failed along the fascia when closed with F-A combinations and at the knot when closed with S-S combinations.

CONCLUSION

The bursting strength of ventral midline incisions in equine cadavers was increased by an average of 25% when closed with the self-locking F-A knot combination.

CLINICAL SIGNIFICANCE

Closing ventral midline celiotomies with an F-A knot combination may provide a more secure closure than the traditional S-S knot combination. Additional in vivo investigation is required prior to recommending this closure in clinical cases.

Incisional complications following ventral median coeliotomy in horses. Does suturing of the peritoneum reduce the risk?

OBJECTIVE

Despite advances in surgical technique in abdominal surgery, incisional complications are frequently reported following ventral midline laparotomy in horses. The aim of this study was to determine the incidence of incisional complications at our clinic and to identify possible risk factors. Furthermore, we investigated whether suturing the peritoneum leads to a reduction of incisional complications.

MATERIAL AND METHODS

In this retrospective study, records of patients of the Large Animal Clinic for Surgery of the University of Leipzig from January 2010 to December 2015 were analysed. Horses with ventral midline laparotomy following colic were included in the study. Evaluated parameters comprised breed, sex, age of the horse, localisation of the colic disease, invasiveness of the surgical intervention, duration of general anaesthesia, suture pattern of the laparotomy wound and postoperative fever or leukopenia. Incisional complications included suture dehiscence, exudation from the wound and incisional hernia formation. Wound oedema formation was evaluated separately.

RESULTS

Incisional complications in the form of exudation and suture dehiscence occurred in 8.9% (18/202) of the horses. Postoperative hernia formation was observed in 5.2% (9/173) of patients. Breed, sex, localisation of the colic disease, invasiveness of the surgical intervention, duration of general anaesthesia and postoperative leukopenia did not influence the frequency of incisional complications. An increased risk of incisional complications was found in horses aged 20 years and older (odds ratio [OR] 17.90), in animals with postoperative fever (OR 7.48) and in horses with unsutured peritoneum (OR 7.68). Furthermore, patients with moderate and severe wound oedema displayed a significantly increased risk for the development of incisional complications.

CONCLUSION AND CLINICAL RELEVANCE

Suture pattern is the only risk factor that can be directly influenced by the surgeon. Because a peritoneal suture is associated with a decreased risk of incisional complications, it should be standard practice when closing a laparotomy wound in the horse.

Tissue strength and wound morphology of the equine linea alba after ventral median celiotomy

OBJECTIVE

To evaluate the tensile strength and wound morphology of the equine linea alba at intervals over 6 months after ventral median celiotomy.

STUDY DESIGN

Linea alba tensile strength and wound morphology were determined at 2, 4, 8, 16, and 24 weeks postoperatively. Linea alba samples from 3 unoperated horses were used as controls.

ANIMALS

Eighteen adult horses, weighing 400 to 500 kg, 4 to 15 years old.

METHODS

Tensile strength and thickness of incised linea alba samples collected at 2, 4, 8, 16, and 24 weeks after ventral median celiotomy were compared with control linea alba samples. Additional samples were subjectively evaluated for wound morphology, notably collagen morphology.

RESULTS

Control linea alba had a mean (+/-SEM) tensile strength of 484.9 +/- 58.3 N and was significantly (P < or = .05) stronger than at 2 weeks (87.7 +/- 61.4 N) after surgery. The tensile strength of 4-week (305.8 +/- 61.7 N), 8-week (465.4 +/- 56.5 N), and 16-week (477.8 +/- 57.2 N) samples were not significantly different from control linea alba. At 24 weeks, the tensile strength (721.0 +/- 57.9 N) was significantly stronger than control. The 2-, 4-, and 8-week samples were significantly thicker than controls, whereas the 16- and 24-week samples were not different from controls. On microscopy, control samples were characterized by dense mature collagen bundles. At 2 weeks, samples consisted primarily of granulation tissue, whereas at 4 weeks, samples had immature collagen fibers that were not formed into bundles, and at 8, 16, and 24 weeks, all samples had abundant mature collagen fibers formed into bundles.

CONCLUSIONS

At 8 weeks, incised and sutured equine linea alba had a tensile strength comparable with non-incised linea alba and was characterized by mature collagen.

CLINICAL RELEVANCE

Based on tensile strength and wound morphology, horses that have had an uncomplicated recovery after ventral median celiotomy should be able to return to controlled exercise as early as 60 days after surgery.

Comparison of incisional bursting strength of simple continuous and inverted cruciate suture patterns in the equine linea alba

OBJECTIVE

To determine the bursting strength of ventral median abdominal incisions closed by either simple continuous or inverted cruciate suture patterns.

STUDY DESIGN

Experimental.

ANIMAL OR SAMPLE POPULATION

Twelve equine cadavers.

METHODS

A 25 cm ventral median incision was made through the linea alba and a 200 L polyurethane bladder was placed within the abdomen. Either a simple continuous or an inverted cruciate pattern using 3 polyglactin 910 with a bite size and suture interval of 1.5 cm was used to close linea incisions. Closure time was recorded for each pattern. The bladder was inflated with air at 40 L/min, and the pressure at body wall failure recorded. The length of suture used for wound closure and the wound failure modes were recorded. Deviation from the linea (cm), total suture length (cm), suture length to wound length ratio (SL:WL), closure time (min), bursting pressure (mm Hg), and failure modes were compared between groups using Welch-Aspin t-tests. The effects of independent subject variables were assessed for possible effects on bursting strength using analysis of covariance.

RESULTS

Mean bursting pressure was significantly greater for the simple continuous pattern than for the inverted cruciate pattern (P = .01). Significantly less suture material (P = .0002) was required with the continuous pattern than with the inverted cruciate pattern. Mean closure time, SL:WL, deviation from the linea, and failure modes were not significantly different between groups. No significant effects were noted for independent variables in both groups on bursting strength.

CONCLUSIONS

In this model, a simple continuous closure pattern for ventral median abdominal incisions was stronger than an inverted cruciate pattern. A simple continuous pattern leaves less foreign material in the wound, which may be of benefit in reducing incisional complications.

CLINICAL RELEVANCE

Use of a continuous closure pattern for the linea alba may offer greater wound security during episodes of increased intra-abdominal pressure in horses.