Total Hip Arthroplasty (THA), commonly known as total hip replacement, is a highly successful surgical procedure designed to alleviate chronic pain and restore mobility. The surgery involves removing damaged bone and cartilage, replacing them with artificial implants. While immediate recovery focuses on healing, the long-term success of the replacement depends on maintaining specific precautions. These post-operative rules transition into permanent lifestyle adjustments, protecting the new joint for decades.
Understanding the Risk: Why Precautions Are Necessary
The primary reason for permanent restrictions is to prevent the prosthetic joint from dislocating. Dislocation occurs when the ball component separates completely from the artificial socket. This mechanical failure is often triggered when the hip is forced into an extreme position that exceeds the safe range of motion.
The risk of dislocation for a primary THA is estimated to be between 2% and 3%. While dislocations are most common in the first few months post-surgery, the risk remains a lifelong consideration during unusual movements. Noncompliance with recommended hip positioning is a significant factor contributing to instability.
The Core Lifelong Movement Restrictions
The traditional, most widely applied permanent restrictions are associated with the posterior surgical approach. These restrictions aim to prevent movements that place maximum strain on the joint capsule and soft tissues. Patients should commit to avoiding these motions permanently to maintain the implant’s integrity.
The first rule is to avoid hip flexion past 90 degrees. This means not bending the hip too far, such as when leaning over to tie shoes or sitting in a low chair. The 90-degree angle is a mechanical threshold where the pressure inside the joint increases significantly, risking posterior dislocation.
Patients must also avoid crossing the operated leg across the midline of the body, known as adduction. This includes crossing the legs at the knees or ankles while sitting and lying down. Keeping a pillow between the legs while sleeping helps maintain the necessary separation.
The third restriction involves avoiding internal rotation, which is pivoting the foot and knee inward. This twisting motion, especially when combined with flexion, torques the hip into a vulnerable position. Patients are advised to turn their entire body when changing direction rather than twisting at the hip.
How Surgical Approach Impacts Permanent Rules
The specific permanent rules a patient must follow are heavily influenced by the surgical technique used to access the hip joint. The traditional set of three lifelong restrictions is most strictly applied following the posterior approach.
The posterior approach requires cutting or detaching some muscles and tendons at the back of the hip. Although these structures are repaired, the initial disruption means the hip is inherently less stable backward. This necessitates strict, permanent avoidance of the three movements that cause posterior dislocation.
In contrast, the direct anterior approach is often referred to as a muscle-sparing technique. The surgeon accesses the joint by working between muscle planes rather than cutting major muscles. This preservation of muscles generally results in greater immediate stability. For many patients who undergo an anterior THA, the surgeon may lift or eliminate the traditional permanent restrictions. Every patient must confirm their specific, lifelong restrictions directly with their orthopedic surgeon, as the individual approach is the determining factor.
Adapting Daily Life and Recreation
Translating movement restrictions into daily habits is necessary for protecting the new joint over the long term. Maintaining the 90-degree flexion rule requires practical adjustments to common furniture and activities. Using elevated toilet seats, firm cushions, and high-seated chairs ensures that the knees remain lower than the hips when seated, preventing excessive flexion.
Driving requires modifications to both technique and seating posture to avoid high-risk movements. Patients should adjust the car seat back to allow for a more open hip angle and use safe techniques for entering and exiting the vehicle to prevent twisting and deep bending. Assistive devices, such as long-handled reachers and shoehorns, should be used permanently to avoid the temptation to bend down to pick up items or put on footwear.
Regarding physical activity, a permanent shift to low-impact exercises is generally recommended to maximize the lifespan of the implant. Activities like swimming, cycling, and walking are highly encouraged because they strengthen the surrounding muscles without subjecting the joint to excessive force. High-impact sports that involve running, jumping, or rapid changes in direction, such as basketball or racquetball, should be avoided permanently because they can accelerate the wear of the prosthetic components and increase the risk of periprosthetic fracture. Maintaining a healthy body weight is also a lifelong precaution that significantly reduces stress on the implant and contributes to its durability.