A pig model for investigation of muscle and myocutaneous flaps

Porcine training models for endoscopic and robotic reconstructive breast surgery: a preliminary study

Background

With recent advances in surgical techniques, minimally invasive methods for reconstructive breast surgery are being investigated. To enhance surgical proficiency through training and minimize predictable complications before human application, we conducted a preliminary experimental study of reconstructive breast surgery using a porcine model.

Methods

Between February and March 2019, four 3-month-old pigs underwent a bilateral mastectomy and immediate breast reconstruction with a latissimus dorsi (LD) flap or silicone implants. After performing the mastectomy by dissecting the pectoralis profundus in the subcutaneous plane, the pig was placed in the decubitus position, and ultrasound-guided marking was used to design the LD flap. The thoracodorsal artery was marked, and a 4-cm incision was made on the midaxillary line. An additional endoscopic incision was made in the inferior margin of the LD flap; a 2-hole approach was used for endoscopic LD flap elevation. In the silicone implant model, a silicone implant (Allergan, smooth, round type, 90 cc) was placed using a single incision (4-5 cm).

Results

Eight mastectomies followed by breast reconstruction with LD flap elevation or silicone implant models were performed on four pigs. Serious complications, such as active bleeding, did not occur. However, heat dispersion to the skin flap that became thinner by endoscopic dissection caused a second-degree burn in one pig.

Conclusions

This preliminary study of endoscopic or robot-assisted minimally invasive reconstructive breast surgery demonstrates that a porcine training model is a highly valuable experimental model for surface anatomy verification, incision plan selection, instrument selection, operator proficiency enhancement, and complication prevention.

Validation of an in vivo porcine simulation model of pedicled latissimus dorsi myocutaneous flap elevation

Background

In vivo and ex vivo simulation training workshops can contribute to surgical skill acquisition but require validation before becoming incorporated within curricula. Ideally, that validation should include the following: face, content, construct, concurrent, and predictive validity.

Methods

During two in vivo porcine surgical training workshops, 27 participants completed questionnaires relating to face and content validity of porcine in vivo flap elevation. Six participants’ performances raising a pedicled myocutaneous latissimus dorsi (LD) flap in the pig (2 experts and 4 trainees) were sequentially and objectively assessed for construct validity with hand motion analysis (HMA), a performance checklist, a blinded randomized procedure-specific rating scale of standardized video recordings, and flap viability by fluorescence imaging.

Results

Face and content validity were demonstrated straightforwardly. Construct validity was demonstrated for average procedure time by HMA between trainees and experts (p = 0.036). Skill acquisition was demonstrated by trainees’ HMA average number of hand movements (p = 0.046) and fluorescence flap viability (p = 0.034).

Conclusion

Face and content validity for in vivo porcine flap elevation simulation training were established. Construct validity was established for an in vivo porcine latissimus dorsi flap elevation simulation specifically. Predictive validity will prove more challenging to establish.

Level of evidence: Not ratable .

Latissimus Dorsi Myocutaneous Flap Procedure in a Swine Model

BACKGROUND

As surgical research expands in both breadth and scope, translational models become increasingly important. The accessibility, reproducibility, and clinical applicability of translational models is of vital importance to ensure adequate and accurate research. Though different flap models have been described, the literature lacks an in-depth, technical description of an easy large-animal preclinical model. We here describe the procedure for elevation of a latissimus dorsi flap in a swine. This flap contains muscle and skin that can be isolated on a vascular pedicle, transferred as a free flap, perfused, or innervated/denervated as dictated by the needs of the experiment.

METHODS

Five different latissimus dorsi flaps were elevated in miniature swine. Careful attention was paid to anatomical landmarks and optimal placement of incision, dissection, and retraction. Temporary ischemia with vascular clamping was performed along with serial digital and infrared imaging both intra- and postoperatively. In three of the flaps with induced ischemia, the animal was observed for a 30-day follow up with daily photodocumentation and intermittent biopsy.

RESULTS

A reproducible latissimus flap model was designed with optimized conditions. In the animals in which flaps were followed postoperatively, complete healing was seen within 30 days without evidence of procedure-related ischemia or loss of motor function.

CONCLUSION

We have identified and described a pre-clinical large animal flap model that can be easily reproduced for translational studies of multiple scientific areas including flap-based repair, ischemia, ischemia reperfusion, and operative technique. This provides an important model for ready replication in preclinical studies of many varieties.

Enhanced Peripheral Neovascularization of Musculocutaneous Flaps Following Pedicle Ligation in the Pig

HM Clarke, G Chen. Enhanced peripheral neovascularization of musculocutaneous flaps following pedicle ligation in the pig. Can J Plast Surg 1994:2(4): 159-163. The augmentation of blood flow from the periphery following dominant pedicle ligation was studied in island latissimus dorsi muscle and musculocutaneous flaps in the pig. In the first study, a musculocutaneous flap and a muscle flap covered with a skin graft were raised on two sides of the same pig (n=25). Silicone rubber sheeting inhibited revascularization from the base. From one to seven days later the dominant vascular pedicles were ligated and blood flow from neovascularization to the flap was assessed immediately using radiolabelled 15 μm microspheres. The peripheral neovascularization of muscle and musculocutaneous flaps was not different when assessed at the time of pedicle ligation. Comparison with a previous study of flap survival, however, revealed that increased blood flow was seen in flaps in which the pedicle had been ligated two days prior to rather than at the time of assessment. Therefore, in a second study, musculocutaneous flaps were raised bilaterally and from one to eight days later the pedicle was ligated on one side only (n=29). After two days of further neovascularization the blood flow to the components of the flaps was assessed using 15 μm microspheres. Significant enhancement of peripheral neovascularization was seen in all animals in which two days had elapsed between pedicle ligation and the assessment of neovascularization (P<0.05). In addition, the flows seen in the skin component of the flaps were substantially greater than normal, suggesting a delay-like phenomenon.

Peripheral neovascularisation of muscle and musculocutaneous flaps

The collateral vascularisation of muscle flaps covered by a skin graft and of musculocutaneous island flaps was studied in a pig model using the latissimus dorsi muscle. Vascular ingrowth from the underlying bed was stopped by using silastic sheeting. The time taken for peripheral vascularisation of flaps to render them independent of pedicle blood supply was studied. In addition microangiograms were performed at the time of sacrifice of the animals (4 weeks postop.) to give a visual conception of the sites and sizes of new vessel growth at the periphery of the flaps. Results showed significant delay, in muscle flaps with skin grafts reset onto a poor bed, in obtaining a blood supply independent of the pedicle supply.