ABSTRACT

Corresponding Author:
Dr. Avinash Prabhu,
Associate Professor,
Department of Plastic Surgery,
SDM College of Medical & Hospital,
Sattur, Dharwad-580009.
E-mail: dravinashprabhu@gmail.com

ABSTRACT

BACKGROUND

Reverse sural artery flap is a fasciocutaneous flap which is still a workhorse in covering distal third of leg defects when the option of free tissue transfer is not practical.

To know the association between the successful outcome of the flap and the selected factors.

MATERIALS AND METHODS

Our retrospective study included 40 patients who had soft tissue defect in the distal third of the leg, heel, ankle and dorsum of the foot. Detailed history was obtained, thorough clinical examination performed, necessary preoperative investigations done and reverse sural artery fasciocutaneous flap cover performed.

STATISTICAL ANALYSIS USED- IBM-SPSS-STATISTICS-VERSION 20.

RESULTS

All the patients selected in the study group underwent reverse sural artery flap cover in a satisfactory way. Majority of the patients were discharged with no complications and a minor group of them with minimal complications.

CONCLUSION

Reverse sural artery flap is a versatile and reliable flap for the coverage of soft tissue defects of distal lower extremity. The leading independent factors which contribute to the success of the flap are trauma as the aetiology, distal third of the leg, and dorsum of the foot being the site of the defect and flap size of 24 sq. cm in comparison to the rest of the factors in the study.

KEYWORDS

Reverse Sural Artery Flap, Defects in Distal Third of Leg, Fasciocutaneous Flap Cover.

INTRODUCTION

Soft tissue cover for distal lower limb defects, where vascular support for tissue is critical has been a continuous challenge for orthopaedic and plastic surgeon for many years. Exposed bone, fracture segments, tendons should be closed as early as possible to reduce the rate of infection.^1-6 As the subcutaneous tissue in distal third of lower limb is thin, the tendons, bones and implants are frequently exposed following trauma to this anatomical zone.⁷ Although few flaps exist for soft tissue cover of distal third of lower limb, many of them were not popular and not practised due to surgical difficulties in raising the flap,

limited arch of rotation and high degree of unreliability.^8-16 Fasciocutaneous flaps have significantly helped to solve the problems involved with distal third of leg, ankle and hind foot.¹⁷Free flap is currently the treatment of choice for large

TABLE 2: SUMMARY OF LOGISTIC REGRESSION ANALYSIS

2c) The Wald Criterion demonstrated the significance of the following independent factors.

1. Trauma as the aetiology.
2. Distal 1/3^rd of the leg and dorsum of the foot as site of the defect.
3. A flap size of 24 sq. cm.

Fig. 1: Post-traumatic Defect  in a Diabetic Patient

Fig. 2: Postoperative Photograph with  the Defect Covered in a Diabetic Patient

Fig. 3: Unstable Scar over Achilles Tendon

Fig. 4: Postoperative Cover of Achilles Tendon.

DISCUSSION

Reconstruction of distal third of the leg and foot continues to be one of the challenging tasks for the reconstructive surgeon.¹⁹ This has stimulated a continued research and modification in obtaining an ideal method of reconstruction for such defects. In recent years, fasciocutaneous flap and free flap have become the workhorses for reconstruction of distal third of the leg.

Various fasciocutaneous flaps have been described to solve this problem; each has its own indications, limitations, advantages and disadvantages.²⁰ Although innovations in microsurgery have solved many problems, not all cases are best suited for microsurgical procedure. There are some situations in which microsurgical procedure may not be feasible due to technical or patient related factors. Easy dissection, single surgeon operating, no sacrifice of any major vessel and large arc of rotation, all of these things have made reverse sural artery flap more popular. Distal based sural artery flap has stood the test of time in being a reliable and effective method in reconstruction of distal leg, ankle and foot.²¹

In our study, four were children. Three were having defect over the dorsum of foot and one child had exposed ankle joint. The mean size of the flap was 6 x 7 cm. Complete flap survival was observed in all four children which implies that reverse sural artery flap is equally applicable and is safe in paediatric patients. Trauma constituted 70% and was the main aetiological factor in our study. This is similar to other studies reported in the literature, where trauma was the aetiological factor in 70-90% of the cases.^7,20,22 Three patients with diabetic ulcer were treated successfully. This has also been observed in other studies which state flap can be safely performed in diabetic and medically compromised patients.²³ Patients with occlusion of anterior and posterior tibial arteries occlusion and varicose veins are not considered absolute contraindication to the use of this flap.^18,24

Our complication rate was 15%. Two patients (5%) who had epidermal loss were treated conservatively by regular wound dressings. Two patients (5%) who had partial flap necrosis (Figure 10) underwent wound debridement, underneath tissue was found healthy and treated conservatively by regular wound dressings. Yet, another two patients (5%) who had complete flap necrosis (Figure 11) were posted for secondary procedure, necrosed flap excised, negative pressure wound therapy by vacuum assisted closure done and later skin graft was performed once the healthy granulation tissue appeared. Our complication rate is comparable with previous similar studies conducted by Samira Ajmal et al²⁵ which reports 20% complication rate.

Probable cause for complete flap necrosis was thick subcutaneous fat in flap donor area in one patient and poor compliance of the patient to maintain the lower limb postoperatively in another patient respectively. One of the studies signifies the importance of thickness of subcutaneous fat of the flap rather than its surface area. Further, the same study quotes peroneal artery perforator may not support a flap with large volume.²⁰

The major issues which we should make a note of in determining the survival of reverse sural artery flap are–reverse arterial and venous flow to be established through axial vessels and no kinking of the pedicle of the flap following inset. Venous congestion which is the predominant factor for flap failure is prevented by including short saphenous vein and lower limb elevation in postoperative period. Apart from all these, there may be some other factor which can influence in better outcome of the flap. This has to be answered comprehensively.

Although extensive anatomical studies have been carried out earlier, with respect to the safe extension of reverse sural artery flap and its exact dimension there is no definitive answer for the same till date. Few of the previous studies have been performed to know the association between success of reverse sural artery flap and individual factors like diabetes mellitus,²³ venous ulcer,²⁴ smoking, etc. In our study, random independent factors like age of the patient, aetiology of the defect, site of the defect, smoking habit of the patient and diabetes mellitus as a chronic disease in patient were selected by us and these factors were assessed to know if any association existed between the former and the successful outcome of the reverse sural artery flap which was statistically tested. We did not come across any earlier studies which included all the above-mentioned factors and its relation to the successful outcome of reverse sural artery flap.

A logistic regression analysis was conducted to predict the outcome in 40 patients who underwent reverse sural artery flap surgery using the surgical and baseline parameters as predictors. A test of the full model against a constant only model was statistically significant, indicating that the predictors as a set reliably distinguished between Absence of complications and Occurrence of complications as outcomes (The final omnibus tests of model coefficients showing a Deviance Chi-square= 30.195, p= 0.305 with df=27 improving to 27.326, p= 0.446 demonstrating a good fit prediction model).

Similarly, the -2 log likelihood model also showed the initial value decreasing from -2LLnull = 33.817 to -2LLk = 6.491 from Step 0 to Step 1.

Nagelkerke’s R² of .867 indicated a strong 86.7% relationship between prediction and grouping. Prediction success overall was 97.5% (100% for absence of complications and 83.3% for the outcome of complications). Hosmer and Lemeshow Test of significance of the goodness of fit also returned a value of 1.000, for df=7 thereby indicating a good fit of the model (Table 2).

The Wald criterion demonstrated that 1) Trauma as the aetiology, 2) Distal 1/3^rd of the Leg and dorsum of the foot as the site of the defect, and 3) A Flap size of 24 sq. cm. were leading independent factors which contributed to the absence of complications in comparison to the rest of the factors. Exp (B) values are not reported because none of these probable factors were significant as Odds Ratios predicting the good outcome of surgery. The probable reason is that a minimum of 50 samples for each independent variable is recommended and desired in logistic regression analysis. However, this study is useful as a pointer for further studies to model the factors associated with good outcome of plastic surgery of reverse sural artery flaps.