The Impact of Regional Motor-sparing Blocks on Early Rehabilitation Following Primary Hip or Knee Arthroplasty

The planned study will be a prospective, randomized, controlled clinical trial with blinded outcome assessment, designed to evaluate the effect of a single preoperative ultrasound-guided peripheral nerve block on early functional independence in patients undergoing elective primary unilateral total hip arthroplasty (THA) or total knee arthroplasty (TKA) for osteoarthritis.

Adults scheduled for elective primary unilateral THA or TKA who are able to walk at least 10 meters with or without an assistive device before surgery will be eligible for inclusion. Patients will be randomly allocated to either an intervention group or a control group. The intervention will depend on the type of surgery: patients undergoing THA will receive a single preoperative pericapsular nerve group (PENG) block, whereas patients undergoing TKA will receive a single preoperative adductor canal block (ACB). Both procedures will be performed under ultrasound guidance, using a dose of ropivacaine predefined and limited by the study safety protocol.

Patients in the control group will undergo identical preparation and an ultrasound-guided procedure; however, the needle will not be advanced into the target compartment and no study drug will be administered into the target space. This approach is intended to maintain comparable procedural conditions and minimize the potential influence of patient and staff expectations on study outcomes. Both groups will receive standardized multimodal perioperative analgesia. In the TKA population, both groups will additionally receive identical intraoperative local infiltration analgesia (LIA).

Study Objective The primary objective of the study will be to determine whether a single preoperative PENG block in patients undergoing THA and an ACB in patients undergoing TKA improves early postoperative functional independence compared with the control intervention.

The primary endpoint will be the total score on the modified mILOA/mILAS scale, assessed 24 ± 3 hours after completion of surgery. The scale ranges from 0 to 36 points, with lower scores indicating greater functional independence. The assessment will be performed by a physiotherapist who is blinded to the patient's treatment allocation.

Secondary Outcomes

Key secondary outcomes will include:

hierarchical Timed Up and Go (TUG) outcome at 24 hours after surgery; time from completion of surgery to the first independent 10-meter walk; mILOA/mILAS score at 6 and 48 hours; TUG performance at hospital discharge; effectiveness and quality of the scheduled physiotherapy session; postoperative quadriceps muscle strength; pain intensity assessed using the numerical rating scale (NRS), particularly during movement; total postoperative opioid consumption; incidence and nature of adverse events related to the study intervention; time to readiness for hospital discharge. Follow-up Patient follow-up will begin at the preoperative visit and continue until postoperative day 90. The primary assessment of treatment efficacy will be performed at 24 ± 3 hours after completion of surgery. Additional functional assessments will be performed at predefined time points during the first 48 postoperative hours and at hospital discharge. During the 90-day follow-up period, data regarding postoperative recovery and clinically relevant postoperative events will be collected.

Statistical Analysis The primary efficacy analysis will follow the intention-to-treat principle and will include all randomized patients according to their assigned treatment group. The primary endpoint will be analyzed using a linear regression model with robust standard errors. The model will be adjusted for type of surgery (THA/TKA), study center, and baseline TUG performance.

The primary treatment effect measure will be the adjusted mean difference in the mILOA/mILAS score between the intervention and control groups, reported together with a 95% confidence interval. The direction of the effect will be interpreted according to the scale characteristics, whereby a lower mILOA/mILAS score indicates greater functional independence.

Sensitivity analyses will be performed to assess the robustness of the findings to the underlying analytical assumptions. These will include an ordinal regression model and an appropriate stratified test. Detailed procedures for handling missing data and any per-protocol analyses will be prespecified in the statistical analysis plan.

Clinical Relevance The study is designed to determine whether targeted single-shot peripheral nerve blocks administered before surgery can improve early functional recovery after THA and TKA without compromising safety or the patient's ability to participate effectively in postoperative rehabilitation. Particular emphasis will be placed on functional independence rather than pain control alone, as early restoration of mobility is a key component of contemporary postoperative care following joint arthroplasty.

The study design distinguishes the intervention according to the type of surgery: the PENG block will be evaluated in patients undergoing THA, whereas the ACB will be evaluated in patients undergoing TKA. Identical procedural preparation in the control group, blinded outcome assessment, and standardized analgesic management are intended to minimize the risk of systematic bias and improve the reliability of the assessment of the effects of the study interventions on early postoperative functional recovery.