instability after total hip arthroplasty.pptx

Instability following total hip arthroplasty (THA) is an unfortunately frequent and serious problem that requires thorough evaluation and preoperative planning before surgical intervention. Prevention through optimal index surgery is of great importance, as the management of an unstable THA is challenging even for an experienced joints surgeon. However, even after well-planned surgery, a significant incidence of recurrent instability still exists. Non-operative management is often successful if the components are well-fixed and correctly positioned in the absence of neurocognitive disorders. If conservative management fails, surgical options include revision of malpositioned components; exchange of modular components such as the femoral head and acetabular liner; bipolar arthroplasty; tripolar arthroplasty; use of a larger femoral head; use of a constrained liner; soft tissue reinforcement and advancement of the greater trochanter.Instability following THA is an unfortunately frequent and serious problem that requires thorough evaluation and preoperative planning before surgical intervention. Prevention through optimal index surgery is of great importance, as the management of an unstable THA is challenging even for an experienced joints surgeon. However, even after well-planned surgery, a significant incidence of recurrent instability still exists. Non-operative management is often successful if the components are well-fixed and correctly positioned in the absence of neurocognitive disorders. If conservative management fails, surgical options include revision of malpositioned components; exchange of modular components such as the femoral head and acetabular liner; bipolar arthroplasty; tripolar arthroplasty; use of a larger femoral head; use of a constrained liner; soft tissue reinforcement and advancement of the greater trochanter. In cases of recurrent instability after appropriate revision surgery, salvage procedures may become necessary. Patients who fail to respond to any measures may be candidates for end stage revision to a resection arthroplasty.

1. Instability after Total Hip Arthroplasty RD Presenter-Dr Rajesh Dhanasekar Moderator- Dr Sunil Rajan HOD Orthopedics Apollo Indore.

2. Incidence of Dislocation 3.2% Primary THA Dislocation rate in over 10,000 primary THAs reported by Woo and Morrey in 1982 28% Revision THA Highest reported dislocation rate for revision THAs in literature 0.3-10% Range Reported range of dislocation rates for primary THAs in various studies The wide range of reported dislocation rates highlights the variability in patient populations, surgical techniques, and implant designs across different studies.

3. Timing of Dislocations 1 Early Postoperative Period 50%-70% of dislocations occur within the first 5 weeks to 3 months after surgery 2 First Year More than three-fourths of dislocations occur within the first year following surgery 3 Long-term Risk Cumulative risk of dislocation increases over time due to factors like trauma, polyethylene wear, and muscle weakness

4. Patient-Related Risk Factors Gender Women dislocate approximately twice as frequently as men, possibly due to differences in muscle mass, strength, and soft tissue elasticity Age Advanced age (>80 years) may increase risk due to frailty, muscle weakness, and cognitive issues Neuromuscular Disorders Conditions like cerebral palsy, muscular dystrophies, and Parkinson's disease increase dislocation risk Prior Hip Surgery Previous hip surgeries double the risk of dislocation due to scarring and soft tissue issues

5. Cognitive and Neuromuscular Disorders Cognitive Disorders Dementia Psychoses Alcoholism These conditions increase dislocation risk due to inability to comply with post-operative restrictions Neuromuscular Disorders Cerebral palsy Muscular dystrophies Parkinson's disease Multiple sclerosis These conditions lead to muscle weakness, particularly in abductors, increasing instability

6. Surgical Approach and Dislocation Risk 1 Posterior Approach Historically highest risk: 5.8% 2 Anterolateral Approach Moderate risk: 2.3% 3 Direct Lateral Approach Lowest risk: 0.55% A meta-analysis of 13,203 primary THAs found varying dislocation rates based on surgical approach. However, meticulous posterior capsular repair can significantly reduce dislocation rates in the posterior approach.

7. Impact of Posterior Capsular Repair Without Repair Dislocation rates of 2.8% to 4.8% With Repair Reduced rates of 0.6% to 0.7% Optimal Outcome Pellicci et al. reported 0.0% dislocation rate with repair

8. Soft Tissue Tension and Stability Joint Capsule Reconstruction of the posterior capsule after a posterior approach significantly reduces dislocation rate Short External Rotators Repair of short external rotators contributes to improved stability Gluteal Muscles Proper tensioning of gluteal muscles, especially abductors, is crucial for stability Femoral Offset Restoring or increasing femoral offset can improve soft tissue tension and reduce dislocation risk

9. Implant-Related Factors: Femoral Head Size Increased Head Size Larger femoral heads increase the jump distance, reducing dislocation risk Study Results Berry et al. found significantly decreased dislocation rates with larger femoral heads across all surgical approaches Trade-offs Larger heads may require thinner polyethylene liners, potentially affecting long-term wear

10. Component Positioning 1 Most Common Cause Component malposition is the leading cause of instability following THA 2 Acetabular Component Excessive anteversion or retroversion can lead to anterior or posterior dislocation 3 Safe Zone Cup anteversion should be 20° ± 5° and abduction 40° ± 10° 4 Femoral Component Proper version is crucial but challenging to standardize and measure

11. Evaluation of Unstable THA: History Mechanism of Dislocation Understand how the current dislocation occurred and the position of the affected limb Previous Episodes Inquire about any other potential previous episodes of instability or dislocation Infectious Symptoms Ask about fevers, chills, antecedent pain, or night sweats Surgical History Review previous documentation, including operative notes, approach used, and implant details

12. Evaluation of Unstable THA: Physical Examination Lower Extremity Assessment Gait evaluation Range of motion Strength testing (focus on abductors) Neurovascular status Specific Observations Leg length discrepancy Previous incision locations Leg position on presentation Stable range of motion post-reduction

13. Radiographic Evaluation Standard Views Anteroposterior pelvis and true lateral radiograph of the affected hip Femoral Component Assessment Evaluate head-to-neck ratio, loosening, neck length, offset, angulation, and subsidence Acetabular Component Assessment Assess orientation, though challenging on plain radiographs Advanced Imaging Consider CT scans for more accurate measurement of component version

14. Initial Management of Dislocation Closed Reduction Attempt closed reduction as the first step in management Assess Stability Evaluate the stable range of motion after reduction Post-Reduction Imaging Obtain radiographs to confirm reduction and assess component position Treatment Decision Choose between non-operative and operative management based on findings

15. Non-Operative Management: Bracing Indications First-time dislocation with acceptable component position and stable range of motion Stable Range of Motion > 90 degrees of flexion and at least 45 degrees of internal rotation Success Rate Estimated that two-thirds of patients can be successfully managed with closed reduction and bracing Challenges Braces can be inconvenient and cumbersome, affecting patient compliance

16. Surgical Indications Recurrent Dislocation Consider surgery for patients with secondary or multiple dislocations Failed Conservative Management Surgical intervention if non-operative treatment is unsuccessful Component Malalignment Surgery indicated when obvious component malalignment is noted on radiographs Abductor Deficiency Surgical management may be necessary for patients with significant abductor weakness

17. Preoperative Considerations Surgical Approach Consider using the previous approach, but be open to alternatives if needed. Incorporate previous incisions to avoid vascular compromise of bridging skin. Component Retention vs. Revision Evaluate whether to retain well-fixed components. Generally, malpositioned components should be replaced, even if well-fixed. Be aware that subtle malpositioning can cause significant instability.

18. Modular Component Exchange Indications Patients without gross component malpositioning or significant abductor weakness Procedure Exchange and elevation of polyethylene acetabular liner and upsizing of femoral head Options Increase femoral head size, increase neck length, or use various liner options Success Rate Studies show 69%-96% success in reducing instability

19. Bipolar Arthroplasty Mechanism Small femoral head inside polyethylene shell, covered by larger femoral head Outcomes Parvizi et al: 81% gained stability, 7% single episode, 11% recurrent instability Concerns Potential for medial or superior migration, groin pain

20. Large Femoral Heads Mechanism Increased head size improves head-neck ratio and increases jump distance Size Definition Femoral heads greater than 36 mm are considered large Study Results Kung et al: 36 mm heads reduced dislocation rate from 12.7% to 0% in 230 patients Limitations May require thinner polyethylene liners, potentially affecting long-term wear

21. Constrained Liners Design Physically resist dislocation by locking the femoral head into the acetabular cup Indications Abductor deficiency Recurrent dislocation of undetermined etiology Multiple dislocations due to neurological impairment

22. Constrained Liners: Outcomes 71% Early Success Anderson et al: 71% of 21 patients had no further dislocations at 2-year follow-up 94% Mid-term Results Callaghan et al: 94% of 31 hips were failure-free at average 4-year follow-up 90%+ Recent Studies More recent series show significant improvements in dislocation rates, often exceeding 90% success

23. Soft Tissue Reinforcement: Achilles Tendon Allograft Technique Achilles tendon allograft placed between greater trochanter and ischium Purpose Reduce range of internal rotation and enhance stability Outcomes Lavigne et al: 6/10 patients had complete elimination of instability at 3-year follow-up

24. Soft Tissue Reinforcement: Other Techniques Synthetic Ligament Barbosa et al: 4/4 patients with no recurrent dislocation at 2-year follow-up Fascia Lata Stromsoe et al: 16/18 patients achieved stability with fascia lata augmentation Advantages Option for patients who are poor candidates for other techniques Challenges Technically demanding and may fail if components are malpositioned

25. Greater Trochanter Advancement 1 Historical Technique Used to increase abductor tension and stability 2 Success Rate Improved hip stability in 81%-90% of cases 3 Modern Application Limited use due to modular implants allowing increased femoral neck length 4 Current Indication Used when there is proximal migration of an ununited trochanter after osteotomy

26. Case Study 1: Anterior Dislocation

27. Case 2

28. Case Study 3 : Revision for Instability

29. Case 4

30. CASE 5

31. Prevention Strategies: Component Positioning Acetabular Component Aim for 20° ± 5° anteversion and 40° ± 10° abduction Femoral Component Ensure proper anteversion, though standardization is challenging Combined Anteversion Consider the relationship between acetabular and femoral anteversion Intraoperative Assessment Use of navigation or robotic assistance can improve accuracy

32. Prevention Strategies: Soft Tissue Handling Posterior Approach Meticulous posterior capsular repair Reattachment of short external rotators Consider capsular plication Anterolateral Approach Careful repair of abductor mechanism Avoid excessive release of anterior capsule Consider anterior capsular repair

33. Prevention Strategies: Implant Selection Head Size Consider larger femoral heads (>36mm) to increase stability Neck Design Optimize head-neck ratio to improve range of motion before impingement Offset Restore or slightly increase femoral offset to improve soft tissue tension

34. Prevention Strategies: Patient Education Preoperative Counseling Educate patients on their individual risk factors for dislocation Postoperative Instructions Provide clear guidelines on safe movements and positions to avoid Activity Modifications Teach patients how to perform daily activities safely during recovery Red Flags Instruct patients on signs and symptoms that should prompt medical attention

35. Future Directions: Advanced Imaging 3D Planning Utilization of 3D CT scans for more accurate preoperative planning and component positioning Patient-Specific Instrumentation Development of custom guides based on patient anatomy to improve component placement accuracy

36. Future Directions: Navigation and Robotics Computer Navigation Improved accuracy in component positioning Robotic-Assisted Surgery Enhanced precision in bone preparation and implant placement Real-Time Feedback Intraoperative assessment of component position and stability Machine Learning Predictive models for identifying high-risk patients

37. Future Directions: Implant Technology Smart Implants Development of implants with sensors to detect early signs of instability Advanced Materials Research into new materials that allow for larger heads without compromising wear resistance Dual Mobility Designs Refinement of dual mobility cups to provide stability without increasing complexity Personalized Implants 3D-printed custom implants tailored to individual patient anatomy

38. Conclusion: Key Points Multifactorial Etiology Instability after THA results from a combination of patient, surgical, and implant-related factors Thorough Evaluation Comprehensive assessment including history, physical examination, and imaging is crucial Tailored Treatment Management should be individualized based on the specific cause(s) of instability Prevention Focus Emphasis on proper component positioning, soft tissue handling, and patient education

39. Conclusion: Management Algorithm Initial Dislocation Attempt closed reduction and assess stability Conservative Management Consider bracing for first-time dislocations with good component position Surgical Intervention Indicated for recurrent dislocations or obvious component malposition Revision Options Range from modular exchanges to complete component revision based on etiology