Study design
This is a prospective, dual-center, single-blind, randomized, single-blind, randomized, controlled study.
Ethical aspects and informed consent
The study was initiated after approval by an ethics committee in January 2019. It is registered with the University Hospital Medical Information Network with an ID of UMIN000035944. All patients who satisfy all of the inclusion criteria and do not meet any of the exclusion criteria will be briefed on this study. After sufficient explanation, consent to participation will be received from the patients themselves.
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 and randomization
Those with the fan type LFCN confirmed preoperatively by ultrasonography will be enrolled. The conventional approach and the medial approach will be performed in the order specified in the allocation table created in advance by our clinical trial center.
The trial flow chart is showed in Figure1.
The target number of patients is 40, and they will be randomly allocated to the conventional incision group (20 hips) and new incision group (20 hips) based on an allocation table using a permuted block randomization schedule with a fixed block size of 4 created prior to the start of the study.
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 by an orthopedic surgeon under general anesthesia before surgery in the operating room. All patients will be positioned supine and scanned on the affected side using the LOGIQ e Expert (GE health- care, Japan) with a 12-MHz linear array transducer. Ultrasonography will be performed following the method reported by Zhu et al (13). The ultrasound transducer is placed in the transverse position and first placed 1–2 cm distal to the lateral inguinal ligament. Initially, the tensor fascia latae muscle and the sartorius are imaged. The LFCN is located in the intermuscular space between the tensor fascia latae and the sartorius. After identifying the LFCN, the probe is moved from the proximal to distal hip joint along the region between the sartorius and tensor fascia latae muscle to confirm the LFCN distribution (Figure3-A). An oval or spindle-shaped high-echoic region (epi- and perineurium) with an inner low-echoic region (nerve bundle) present between the sartorius and tensor fasciae latae muscle corresponds to the LFCN or its branch (13). Following the definition made by Rudin et al. based on a cadaver study, several branches with a similar size present between the muscles are defined as the fan type (Figure3-B). The main root or major branch with surrounding thin branches is defined as the non-fan type (Figure3-C)(12).
Surgical procedures
THA will be performed using the DAA for all patients. Surgical procedures will be performed by 5 hip joint surgeons with experience performing no less than 50 THA procedures through the DAA(9, 14). THA will be performed under general anesthesia on all patients. Patients will be placed in the supine position and operated on using a traction bed and intraoperative fluoroscope (15). The skin incision will begin 2 cm lateral and distal to the anterior superior iliac spine, and proceed distally for 10 cm along a line angling toward the head of the fibula. The surgical field will be ensured and the implant will be placed in the same manner in 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 new approach, on the other hand, proceeds medially from the site of skin incision, and involves incision of the fascia at a site 2 cm medial 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
If a subject declines to participate in the study or withdraws his/her consent, or if unexpected postoperative complications develop, the subject will be withdrawn from the study.
Outcomes and measurements
Primary outcomes
The primary endpoint is the presence of LFCN injury. The presence of neuropathy will be investigated based on a patient-based questionnaire 3 months after surgery on an outpatient basis. Consistent with our previous report, LFCN injury is defined as the presence of the following symptoms over the lateral aspect of the thigh, excluding the surgical scar: numbness, dull sensation, tingling or jolt-like sensation, or pain (10).
Secondary outcomes
The secondary endpoints will be assessed based on patient-reported outcomes (PROs) at 3 months after surgery in an outpatient setting to examine the extent to which LFCN injury affects the QOL. PROs will be evaluated using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) (pain, stiffness, and function subscales), the Japanese Orthopaedic Association Hip-Disease Evaluation Questionnaire (JHEQ), and the Forgotten-Joint Score-12 (FJS-12).
The WOMAC, first reported by Bellamy and Buchanan in 1986, is used worldwide to evaluate the lower limbs, particularly the hip and knee joints, and has a total score range from 0 (best) to 96 (worst). The JHEQ is a validated self-administered questionnaire evaluating the QOL of Asian-lifestyle patients with hip disease; the total range is from 0 (worst) to 84 (best). The FJS-12, another self-administered questionnaire, is a specific and subjective PRO tool that assesses patients’ awareness of their knee or hip joint during activities of daily living. Its final score range is from 0 (worst) to 100 (best) (15).
The highest scores reflecting the best results for the WOMAC are 0 and 96, and JHEQ are 0 and 84, respectively. Therefore, the lowest and highest scores for each questionnaire are converted to 0 and 100, respectively.
Sample size
According to previous studies, the incidence of LFCN injury due to THA with the DAA is 90% in fan type patients (16). In total, 40 patients, 20 hips each operated on using the conventional approach and the new approach, are considered necessary assuming that the incidence of adverse events is reduced from 90% to 50% by employing the new approach using the chi-square test.
Statistical analysis
To assess the impact of LFCN injury on patient QOL, we will use Mann–Whitney U tests to compare differences in the PROs between patients reporting neuropraxia versus those with no symptoms, and p < 0.05 will be regarded as significant. All statistical analyses will be performed using SPSS 22 for Mac (SPSS Inc, Chicago, IL).
Data protection
When handling information related to the conduct of the study, such information will be managed using a study-specific ID that is not related to the personal information of the study subject, with consideration being given to the protection of confidentiality of the study subject. The principal investigator will store all documents related to the conduct of the study on a computer or at the Department of Orthopaedic Surgery in accordance with the Standard Operating Procedures for the Storage of Samples and Information Pertaining to Medical Research Involving Human Subjects until the day on which 5 years have elapsed from the discontinuation or completion of the study, and will dispose of them while paying attention to personal information.
Study quality assurance and control audits
The ethics committee of the hospital will review the study implementation status every year to determine whether it is appropriate to continue the study. Any changes to the documents used for the review at the time of application must be approved by the hospital ethics committee in advance. If a serious adverse event develops in the hospital, it should be reported promptly to the hospital director and reviewed by the hospital ethics committee to determine whether it is appropriate to continue the study.