Materials and methods
This retrospective study investigated a cohort of head and neck patients
who underwent oncologic resection and free tissue transfer between
January 2017 and July 2019 at a quaternary referral unit in Sydney,
Australia. Following institutional ethics approval
(HREC/X20-0337/LH20.074), patients were identified using the
prospectively maintained Sydney Head and Neck Institute (SHNCI) database
and included if they had undergone primary or secondary free flap
reconstruction. Patients were excluded if operative time was not
recorded. Operative time data was collected for each patient and was
defined as the time interval between entering and leaving the operating
room. Operative time was analyzed as a continuous variable (number of
hours) and dichotomized based on the mean.
Potential confounders assessed included patient
gender, age, American Society of
Anesthesiologists (ASA) classification, Charlson comorbidity index
(CCI), tumor site, elective tracheostomy, defect type (mucosal or
cutaneous), reconstruction type defined as fasciocutaneous (soft tissue)
or composite (osseo-cutaneous, myo-osseous, myo-cutaneous), osseous
resection (mandibulectomy, maxillectomy, craniectomy or temporal bone
resection), prior radiotherapy or head and neck surgery.
Outcomes of interest were complication rate, return to theatre
(operating room), and length of stay, defined as the number of inpatient
days including the day of surgery. Complications were divided into
medical and surgical. Medical complications included myocardial
infarction, pneumonia, pulmonary embolism, urinary tract infection,
stroke, deep vein thrombosis, sepsis, and renal insufficiency. Surgical
complications included both recipient site and donor site complications,
flap loss (partial or total), wound infection, wound dehiscence,
orocutaneous fistula, and hematoma as well as any event necessitating
return to theatre.
Statistical analysis was performed using Stata version 12.0 SE
(StataCorp LP, College Station, TX, USA). Complication rates and return
to theatre were analyzed using univariable and multivariable logistic
regression and presented as odds ratios (OR) and confidence intervals
(CI). Length of stay was analyzed as count data using a negative
binomial regression. Operative time was included in all multivariable
models as the intervention of interest. Covariates were selected based
on statistical significance on univariable analysis, however patient age
and comorbidity scale were included a priori . The choice of
comorbidity scale (ASA or CCI) was determined by statistical
significance. Continuous variables were transformed where required. A
p-value < 0.05 was considered statistically significant.