Criteria-Based Rehabilitation After Tibial Fracture Fixation: A Randomized Controlled Trial

### Detailed Intervention Prescription

Participants allocated to the intervention group will receive a structured criteria-based progressive loading and functional rehabilitation program for approximately 6-8 weeks, consisting of 2-3 supervised physiotherapy sessions per week in addition to an individualized home exercise program. Each supervised session will last approximately 45-60 minutes and will include an individualized combination of joint mobility, muscle strengthening, balance, gait, and functional training according to the participant's clinical status and stage of recovery.

The fundamental principle of the intervention is that progression will be determined by predefined clinical and functional criteria rather than postoperative time alone. All weight-bearing and loading activities will strictly follow the restrictions prescribed by the treating orthopedic or surgical team. The physiotherapist will not independently advance a participant beyond the medically permitted weight-bearing level.

Phase 1: Protection and Early Mobility

During the initial phase, rehabilitation will focus on protecting the surgical site, controlling symptoms, maintaining joint mobility, minimizing muscle weakness, and achieving safe basic mobility. Treatment will include patient education, appropriate positioning, pain and edema management, active or active-assisted knee and ankle range-of-motion exercises as clinically permitted, quadriceps activation, hamstring and gluteal exercises, ankle exercises, and straight-leg raising when appropriate. Muscle activation and mobility exercises will generally be performed for 2-3 sets of 10-15 repetitions according to the participant's tolerance.

Functional rehabilitation during this phase will include bed mobility, transfer training, sit-to-stand practice when appropriate, and instruction in the safe use of crutches or a walker according to the prescribed weight-bearing status. Participants will also receive an individualized home exercise program focusing primarily on mobility and muscle activation.

Progression from this phase will not occur simply because a predetermined number of postoperative weeks has elapsed. Progression will be considered when the participant demonstrates satisfactory wound and soft-tissue status, controlled pain and swelling, improving knee and ankle mobility, safe transfers, appropriate performance of the prescribed exercises, and adequate neuromuscular control.

Phase 2: Initial Loading and Gait Rehabilitation

This phase will begin once increased loading or weight-bearing has been medically permitted by the orthopedic or surgical team. Treatment will focus on gradually introducing the permitted load to the affected limb and restoring safe functional mobility.

Interventions will include controlled weight-shifting activities, weight-bearing practice within the prescribed limits, gait retraining using the appropriate walking aid, progressive lower-limb strengthening, sit-to-stand training, supported balance exercises, continued knee and ankle mobility exercises, and progressive walking practice. Strengthening exercises will generally be performed for 2-3 sets of approximately 8-15 repetitions, with resistance adjusted according to the participant's clinical status and ability to perform the movement with appropriate control.

Gait training will emphasize safe loading of the affected limb within the prescribed restriction, appropriate step pattern, correct use of the walking aid, balance, and progressive improvement in walking quality. Walking duration and distance will be increased gradually according to tolerance.

Progression will be considered when the participant can tolerate the currently prescribed loading level without clinically significant worsening of pain, swelling, or other symptoms; demonstrate controlled weight transfer; perform functional activities with satisfactory movement control; and walk safely using the prescribed assistive device. Advancement to a higher weight-bearing level will occur only when permitted by the treating orthopedic team.

Phase 3: Progressive Functional Loading

As greater weight-bearing is medically permitted, rehabilitation will progressively emphasize functional loading, lower-limb strength, balance, gait quality, and independence. Treatment will include progressive closed-chain exercises, functional strengthening, repeated sit-to-stand practice, step-up and step-down activities, balance and proprioceptive exercises, progressive walking, and gait-quality training.

Exercises will generally be prescribed for approximately 2-4 sets of 8-15 repetitions depending on the exercise, participant tolerance, and functional goal. The difficulty of exercises will be progressively increased by modifying resistance, repetitions, movement complexity, balance demands, walking distance, or the amount of upper-limb support rather than progressing according to time alone.

Reliance on crutches, a walker, or other upper-limb support will be reduced gradually when clinically appropriate and when consistent with the prescribed weight-bearing status. The participant must demonstrate adequate balance and safe gait before progressing to a less supportive walking aid.

Progression to advanced functional rehabilitation will require satisfactory tolerance of the current loading level, controlled symptoms, adequate movement quality, improving functional mobility and balance, safe ambulation, and medical permission for further loading.

Phase 4: Advanced Functional Rehabilitation

Once full weight-bearing is medically permitted, rehabilitation will focus on restoring independent mobility and preparing the participant for community, daily living, and occupational activities. Treatment will include independent gait training, stair negotiation, uneven-surface walking, functional squatting, advanced balance and proprioceptive exercises, progressive lower-limb strengthening, walking endurance training, community mobility activities, and activities of daily living.

Where relevant, rehabilitation will also include work-, household-, or activity-specific tasks based on the participant's individual functional requirements. Walking duration and distance will be progressively increased, and the participant will be encouraged to achieve safe mobility with the least restrictive walking aid or without an assistive device when appropriate.

Throughout all phases, the physiotherapist will assess pain, swelling, range of motion, functional performance, gait safety, exercise tolerance, and any adverse clinical response. Exercise intensity or loading will be reduced or temporarily withheld if the participant develops clinically significant worsening of pain or swelling, wound problems, loss of functional performance, or other signs requiring medical reassessment. Suspected fixation-related complications, wound complications, or other significant adverse events will be referred to the treating medical or surgical team.

The home exercise program will be individualized according to the participant's current rehabilitation phase. Mobility and muscle-activation exercises may be performed daily, while strengthening, balance, gait, and functional activities will be prescribed according to clinical tolerance and safety. Adherence to the home program and supervised physiotherapy sessions will be documented.

The main distinction between this intervention and usual physiotherapy is therefore not the individual exercises themselves. Participants receiving usual physiotherapy may also receive range-of-motion exercises, strengthening, gait training, balance exercises, walking-aid training, and functional exercises. In the intervention group, however, rehabilitation will follow a standardized criteria-based pathway in which advancement, regression, and functional progression are determined by predefined clinical and functional milestones while remaining within the weight-bearing restrictions established by the orthopedic team.