The total hip replacement (THR) is a common surgical procedure that can offer patients with severe hip joint problems a significant improvement in their quality of life. However, after the operation, there are numerous recommendations and restrictions that patients should follow to ensure a successful recovery. One of these recommendations is the so-called 90-degree rule, which states that patients should not bend their hip joint beyond an angle of 90 degrees. But is this rule still really necessary today? In this blog post, we will thoroughly investigate this question and discuss the medical background, postoperative guidelines, and new developments in hip arthroplasty.

Why the 90-degree rule after hip replacement surgery?

The 90-degree rule after hip replacement surgery is a preventive measure aimed at minimizing the risk of dislocation of the new hip joint. Dislocation occurs when the femoral head jumps out of the acetabulum, which is extremely painful and requires immediate medical attention. Orthopedic surgeons still advise adhering to this rule, particularly in the first few months after surgery, as the tissue around the new joint is still healing and is supposed to be stabilized.

Reducing the Risk of Dislocations after Hip Replacement Surgery

Hip dislocation is a serious complication that can occur in patients with a hip replacement. This occurs when the femoral head slips out of the acetabulum, which is extremely painful and often requires additional surgery. Adherence to the 90-degree rule significantly reduces this risk, as it prevents the joint from being positioned in a way that could favor dislocation.

Postoperative phase and rehabilitation

After total hip replacement, the postoperative phase is crucial for the success of the surgery. In the first days and weeks after the procedure, it is essential to avoid certain loads that could overload or destabilize the new joint. From the past, the recommendation to avoid excessive flexion of the hip joint continues to be a frequently formulated restriction. The 90-degree rule is intended to help prevent harmful movements and ensure safe healing.

Early Stage after Hip Replacement Surgery

In the immediate postoperative phase, rehabilitation measures often focus on pain management, prevention of thrombosis, and restoration of mobility. In addition, patients often receive specific instructions on movement sequences that they should avoid, including bending the hip joint beyond 90 degrees. Many physiotherapists still work with this rule to ensure that there is no dislocation.

Postoperative guidelines in the past

1. Movement restrictions: Avoid bending the hip beyond 90 degrees, crossing your legs, and rotating your leg inward or outward.
2. Sleeping position: Sleep on your back with a pillow between your legs to ensure proper alignment of the hip.
3. Sitting Habits: Use high chairs and avoid low seating furniture that may require deep hip flexion.

Techniques for everyday life in the past

In addition to targeted exercises, there are various techniques and aids that can help patients adhere to the 90-degree rule in everyday life. These include:

• Ergonomic seating: Chairs and armchairs with higher seat surfaces help to avoid excessive bending of the hip joint.
• Reaching aids: Devices that enable picking up objects from the floor without bending down.
• Dressing aids: Special aids that make it easier to put on socks and shoes without bending the hip.

Advances in recent years have often made the 90-degree rule unnecessary!

With advances in hip arthroplasty over the past 10 years, the conditions have changed markedly. In particular, the use of short stem prostheses and minimally invasive approaches (ALMIS and AMIS) can enable patients after total hip replacement to start rehabilitation today much more safely and in many cases without significant limitations.

Some recent studies and reports suggest that an individually adapted rehabilitation, not strictly bound by the 90-degree limit, can also lead to successful outcomes. This view is based on the assumption that modern surgical methods and improved prosthetic technologies allow for greater freedom of movement.

Critical voices on the necessity of the rule

Some experts and patients argue that the 90-degree rule may be overly cautious and not necessary in all cases. They suggest that rehabilitation should be more individualized to meet the needs and abilities of each patient.

• Prof. Kutzner, ENDOPROTHETICUM: "While the 90-degree rule is useful for many patients, we should also consider flexible approaches that take into account advances in prosthetics and individual healing processes."
• Patient: "I didn't follow the 90-degree rule very strictly, was able to perform almost all movements painlessly very quickly, and still had a successful recovery. My physiotherapist helped me create a rehabilitation plan tailored to me."

Scientific studies and research findings

There are some studies that question the necessity of the 90-degree rule. These studies show that patients with more modern prostheses and surgical methods may require less strict movement restrictions.

Effects of choosing short-stem prostheses on the 90-degree rule

(see also: "Luxation of the Hip Prosthesis - Short Stem Prostheses Offer More Security")

With advances in endoprosthetics, short-stem prostheses have become a popular choice, especially among younger and more active patients. These prostheses differ from traditional long-stem prostheses in their design and the way they are anchored in the femur. The question arises as to how the use of short-stem prostheses affects the postoperative rehabilitation phase, particularly with regard to the 90-degree rule.

What are short stem prostheses?

Short stem prostheses are hip implants that have a shorter stem that is inserted into the femur. These prostheses are less invasive and require less bone removal than conventional long stem prostheses. They are designed to better mimic the natural anatomy and biomechanics of the hip joint.

Benefits of short-stem prostheses:

1. Preservation of Bone Mass: Less bone removal means that more bone mass is preserved, which is particularly beneficial for future revisions.
2. Faster recovery: Patients often report faster recovery and less postoperative pain.
3. Better mobility: The natural biomechanics of the hip are better preserved, leading to greater freedom of movement.

Effects on the 90-degree rule

The choice of a short-stem prosthesis can have various effects on the adherence to and necessity of the 90-degree rule. These effects can be both positive and negative and depend heavily on the individual situation of the patient as well as the recommendations of the treating physician.

Potential benefits:

1. Lower risk of dislocation: Some studies suggest that short-stem prostheses have a lower risk of dislocation because they better preserve the natural anatomy and are more stable. This could mean that strict adherence to the 90-degree rule may be less critical.
2. Faster Rehabilitation: Due to the less invasive nature of the surgery and the faster recovery, patients may be able to resume normal activities earlier, allowing for a gradual relaxation of the 90-degree rule.

Challenges and Considerations:

1. Individual Adjustment: Although short-stem prostheses potentially offer greater freedom of movement, it is still important that rehabilitation is individually adjusted. Not every patient can or should immediately relax the 90-degree rule.
2. Long-term Stability: The long-term stability and functionality of the prosthesis must be considered. Even though the short stem prosthesis offers advantages, the 90-degree rule should be strictly followed in the first postoperative months to ensure safe healing.

Studies and expert opinions

Some scientific studies and expert opinions support the assumption that short-stem prostheses can facilitate rehabilitation and may require less strict adherence to the 90-degree rule.

• Study on Dislocation Rate: A study published in the Journal of Arthroplasty showed that patients with short stem prostheses had a lower dislocation rate compared to those with conventional long stem prostheses. This suggests that the biomechanical advantages of the short stem prosthesis contribute to a more stable hip.
• Expert opinion: Prof. Kutzner explains: "Short-stem prostheses offer significant advantages in terms of preserving bone structure and postoperative results. The importance of the 90-degree rule in the first weeks after surgery to ensure safe healing has decreased significantly. However, any relaxation of the rule should be done under close medical supervision and communication."

Conclusion and Recommendations

The use of short-stem prostheses can facilitate postoperative rehabilitation after hip replacement surgery and allow for a relaxation of the 90-degree rule. However, it is crucial that these adjustments are made individually, based on specific healing processes and under the guidance of the treating physician and physiotherapist.

Recommendations for patients with short-stem prostheses

1. Get individual advice: Talk to your orthopedic surgeon and physiotherapist about the specific benefits and risks associated with your short-stem prosthesis.
2. Gradual Relaxation: If your recovery is going well and your doctor agrees, you may be able to gradually relax the 90-degree rule early on. However, this should always be done under medical supervision and based on your individual progress.
3. Long-term Follow-up Care: Regular check-ups with your orthopedic surgeon are important to monitor the stability of the prosthesis and ensure that no complications arise.

Effects of choosing minimally invasive approaches on the 90-degree rule

(see also: "Comparison of minimally invasive (ALMIS and AMIS) and traditional hip approaches")

In hip arthroplasty, minimally invasive surgery (MIS) has established itself as a popular alternative to conventional surgical methods. This technique aims to reduce the access to the hip, minimize muscle and tissue damage, and enable faster recovery. The choice of a minimally invasive approach has significant implications for postoperative rehabilitation and the need for the 90-degree rule.

What are minimally invasive approaches (ALMIS and AMIS)?

Minimally invasive approaches to hip replacement surgery involve smaller incisions and less trauma to the surrounding muscles and soft tissues compared to traditional procedures. The most well-known minimally invasive approaches include the anterior (AMIS) and anterolateral (ALMIS) approaches.

Benefits of minimally invasive approaches:

1. Smaller incisions: Reduction of incision size to 8-10 cm, compared to 15-20 cm with conventional procedures.
2. Less muscle trauma: Preservation of the musculature by avoiding dissections or extensive pulling apart of the muscles.
3. Faster Recovery: Patients report less pain and a faster resumption of normal activities.

Effects on the 90-degree rule

The choice of a minimally invasive approach can have various positive effects on the postoperative phase and adherence to the 90-degree rule. These techniques can reduce the need for strict adherence to the rule in many cases, as they minimize the risk of dislocation and other complications.

Potential benefits:

1. Lower risk of dislocations: Due to the gentle surgical method and preservation of the musculature, the hip joint may be more stable, which can reduce the risk of dislocation.
2. Faster mobilization: Patients can be mobilized more quickly, which can enable an earlier return to normal movements, including a potential relaxation of the 90-degree rule.

Challenges and Considerations:

1. Individual Variability: Despite the advantages, the healing processes can vary individually, and it may be important to adhere to the 90-degree rule during the first weeks after surgery.
2. Gradual adjustment: Even with minimally invasive approaches, adjustments to the 90-degree rule should be made gradually and under professional guidance if in doubt.

Studies

Several studies have investigated the benefits of minimally invasive approaches and confirmed that these techniques can facilitate postoperative rehabilitation.

• Study on postoperative recovery: A study in the Journal of Bone and Joint Surgery found that patients who underwent surgery with a minimally invasive anterior approach experienced faster recovery and less postoperative pain. This led to a quicker resumption of normal activities.
• Expert Opinion: Prof. Kutzner explains: "Minimally invasive approaches offer significant advantages in terms of recovery. The 90-degree rule in the first weeks after surgery does not necessarily have to be strictly adhered to in many cases today. However, any relaxation of the rule should be communicated individually accordingly."

Conclusion and Recommendations

Minimally invasive approaches to hip arthroplasty offer many benefits, including faster recovery and a lower risk of dislocation. These benefits can help reduce the need for strict adherence to the 90-degree rule, especially after the first few weeks of rehabilitation. However, it is crucial that any adjustment to the rule is made under medical supervision to ensure safe and successful healing.

Recommendations for patients with minimally invasive approaches:

1. Consult your doctor: Discuss the specific benefits and potential risks of the minimally invasive approach with your surgeon.
2. Gradual relaxation: Work closely with your physiotherapist to gradually increase mobility while ensuring the joint remains stable.
3. Regular check-ups: Visit your doctor regularly to monitor the healing process and make adjustments to the rehabilitation measures.

Conclusion: Is the 90-degree rule really necessary?

The question of whether the 90-degree rule after hip replacement is really necessary cannot be answered in a general way. It depends on various factors, including individual healing, the type of prosthesis used, and the recommendations of the treating physician. It is important that patients follow the guidelines of their doctors and physiotherapists exactly and always seek professional advice in case of uncertainty. The strict communication of the 90-degree rule is, however, outdated today and should be done on an individual basis.

Conclusion

The 90-degree rule after hip replacement surgery played an important role in the past in preventing dislocations and supporting safe healing. While this rule is a valuable guideline for many patients, there are also arguments for a more individualized approach to rehabilitation. Ultimately, patients should work closely with their doctors and physiotherapists to develop the best rehabilitation plan for their specific needs.

Recommendations for patients

1. Follow your doctor's instructions: Your individual recommendations are based on your specific situation and should therefore be given priority.
2. Work with a physiotherapist: An experienced physiotherapist can help you learn appropriate exercises and techniques without rigidly adhering to the 90-degree rule.
3. Assistive devices: In many cases, assistive devices (ergonomic seating furniture, gripping aids, and other assistive devices) are no longer necessary after hip replacement today. Speak with your treating surgeon.
4. Stay active and patient: Regular movement and exercises are important for your recovery, but it's equally important to be patient and give your body the time it needs to heal.