Study design
This is a prospective, dual-center, single-blind, randomized, single-blind, randomized, controlled study.
Ethics
The study was approved by the research ethics board of Juntendo University Hospital in January 2019 and was subsequently registered in the University Hospital Medical Information Network (UMIN) clinical trials registry on February 20, 2019 (ID: UMIN000035945). The study team will explain about the study in writing and verbally, and voluntary written consent will be received from the study subjects.
Informed consent
The informed consent form was approved by the hospital’s research ethics board. The consent form will be provided to study subjects, and the study team will explain about the study in writing and verbally. Voluntary consent will be received from study subjects in a written form. Study subjects will be informed immediately if any new information that may affect consent is obtained or if any changes to the study protocol that may affect consent is to be implemented. Study subjects will then have the opportunity to decide whether they wish to continue participating in the study. We will also revise the consent form, and upon approval from the hospital’s research ethics board, we will provide the revised form to study subjects to receive consent.
Study setting
This study will be conducted in the Juntendo University Hospital and the Juntendo Tokyo Koto Geriatric Medical Center.
Eligibility criteria
Inclusion criteria
Prior to enrollment, patients must comply with all of the following:
・Age 20-90 years
・Primary THA via DAA
・Patients who provide written consent for participation after receiving sufficient explanation and understanding the study content.
Exclusion criteria
Patients are excluded if presenting any of the following:
・Trauma
・A history of hip surgery
・Purulent coxitis
・failure to follow instructions of physicians
・Neurological disorder
・BMI of 35 or greater
・Patients deemed unsuitable for inclusion in the study by the principal investigator
Recruitment
After explaining about the study, consent will be received from study subjects that meet all of the inclusion and exclusion criteria. Study subjects will undergo preoperative ultrasound, and those with non-fan type LFCN will be registered for the study. We aim to recruit a total of 130 subjects, with 65 in each group (conventional and lateral fasciotomy). The flow chart of the study is shown in Figure 1. After consent, the study subjects will participate for 4 months, including 1 month of preoperative monitoring and 3 months of postoperative follow-up.
The trial flow chart is showed in Figure1.
Randomization
An assignment sheet will be created by the hospital’s clinical trial center prior to the start of the study. According to the assignment sheet, subjects will be randomized to undergo either the conventional approach or the lateral approach using a fixed block size of 4.
Study timeline and data collection
After providing consent, study subjects will participate in the study for a total of 4 months, consisting of a 1-month pre-observation period and a 3-month post-observation period. The timeline for the assessment and date collection regarding primary and secondary outcomes is shown in Figure 2.
Ultrasonography of LFCN
Ultrasonography will be performed in the supine position using LOGIQ e Expert (GE health-care, Japan) with a 12-MHz linear array transducer according to the protocol developed by Zhu et al..
First, the transducer will be placed perpendicular to the body axis and 1-2 cm away from the outer edge of the inguinal ligament. At this location, images of the sartorius and tensor fasciae latae muscles will be collected, and LFCN in between the muscles will be identified. While keeping the LFCN in the imaging field, the probe will be moved distally between the sartorius and tensor fasciae latae muscles (Figure3-A). The LFCN will be defined as a structure in between the sartorius and tensor fasciae latae muscles that is characterized by low signal intensity (nerve bundle) surrounded by oval or spindle-shaped high signal intensity (perineurium)(24). Fan type and non-fan type LFCN will be defined based on the pathological findings reported by Rudin et al. Specifically, non-fan type LFCN will be defined as a structure with one main nerve surrounded by multiple smaller branches(Figure 3-B), and fan type LFCN will be defined as a structure with three or more branches of similar size or two or more nerves branching out from one main nerve(Figure 3-C).(15).
Surgical procedures of THA
In all cases, THA will be performed under general anesthesia by one of 5 experienced (>50 cases) hip surgeons(10, 25). Study subjects will be placed in the supine position, and the procedures will be performed with traction beds and intraoperative fluoroscopy(26). The skin incision will be made 2 cm distally from the superior anterior iliac spine; specifically, the incision will begin 2 cm away from the superior anterior iliac spine and in parallel to the line that connects the superior anterior iliac spine with the head of the fibula. The total length of the incision will be 10 cm. The same techniques will be used to set up the surgical field and place the implants for both groups. The same implant will be used for both groups.
Interventions
The conventional approach involves incision of the skin, followed by incision of the fascia just below the site of skin incision. The lateral approach, on the other hand, proceeds outside from the site of skin incision, and involves incision of the fascia at a site 2 cm lateral from the conventional site of incision. Incision of the fascia will be performed to the extent that both approaches can be viewed in the surgical field.
Withdrawal criteria
Study subjects will be withdrawn from the study if the principle investigator and the study team decide that it is impossible to continue the study activities under the following criteria. If this applies, the subject will be given the explanation for their withdrawal. Subjects will continue to receive the standard of care that they need after study withdrawal.
- If withdrawal from the study is requested or if the consent is withdrawn by a study subject,
- If a subject develops any unexpected postoperative complication,
- If the study is terminated, or
- If the principle investigator decides that the study should be terminated for reasons other than those listed above.