Clinical, biomechanical, and biological factors to achieve deep flexion in TKA

1. Knee lecture course, Prague 2007 Clinical, biomechanical, and biological factors to achieve deep flexion in TKA Kazunori Yasuda, MD, PhD Department of Sports Medicine & Joint Surgery Hokkaido University School of Medicine, Sapporo, Japan

2. ROM after TKA • Commonly limited to 100 to 110 degrees • Acceptable to perform Western daily activities • Patients in Asia and the Middle East hope for a deep flexion of 140 degrees or more after TKA • Needed to continue their usual life-style

3. Deep flexion after TKA • Recently, deep knee flexion is required increasingly for patients in Europe and North America • Frequently needed to pursue their quality of life, • Sitting on the floor • Squatting for gardening • Playing light sports • Thus, the issue of deep flexion after TKA has attracted much notice

4. The fundamental base-line in considering deep flexion • The 2 greatest effects of TKA should not be disturbed • Pain relief • Restoration of walking ability • Surgeons should not create unstable knees in order to obtain deep knee flexion • Knee instability disturbs walking ability

5. What degree is deep flexion for the knee with TKA? • The real deep flexion means 140 degrees or more • In my clinical practice • The average ROM after TKA: 125 degrees. • Very difficult to improve this value to 140 degrees hereafter • Many surgeons are worried about the average ROM of 100 degrees after TKA • Easier for the surgeons to improve the average ROM from 100 degrees to 120 degrees, using current knowledge and techniques

6. A focus on my talk • How should we do to obtain the average ROM of 120 degrees after TKA? • If it will be achieved, about 10 % of patients will perform the real deep flexion without any instability Postop. 4 wks

7. The fundamental principle to simultaneously obtain deep flexion and knee stability • In the normal knee • The beautiful matching between the shape of the 2 bone surfaces and the functions of the ligament and tendon tissues allows for deep flexion of the knee • In the knee that obtained deep flexion after TKA • We can find similarity between the 2 knees

8. To obtain deep flexion and knee stability after TKA • Surgeons should simultaneously restore the normal soft tissue functions and the anatomical joint surface • Ideal soft tissue release • Anatomical shaped prosthesis • This is difficult, but the only way

9. Examples • Previously, resection of the posterior condyle was recommended • To create a sufficient flexion-gap • Recently sufficient posterior condylar offset is recommended • To avoid the insert impingement • What should we learn from this history • A sufficient flexion-gap should not be created by bone resection, but by soft tissue release • Then, an anatomical design is essential for obtaining deep flexion

10. Factors disturbing deep flexion • Clinically, many factors may strongly disturb the restoration of the normal soft tissue functions and the anatomical joint surface • Preoperative factors • Intra-operative factors • Postoperative factors

11. The preoperative factors • Shortening of the extensor apparatus • Patella baja • Quadriceps contracture • Contracture of the ligaments and capsular tissues

12. Shortening of the extensor apparatus • Extremely difficult to be treated • Some surgical ideas have been proposed to lengthen the extensor apparatus • Quadriceps lengthening • Tibial tubercle transfer • Bone resection • Special prosthetic design • Each idea has their own set of serious complications • This remains unsolved at the present time • In these cases, surgeons cannot expect much improvement in the ROM after surgery

13. PCL contracture Soft-tissue contracture • Collateral contracture • Well treated during surgery with the tissue-release (Technique will be shown later) • PCL contracture • The most difficult to be treated with the tissue-release technique • In knees having severe contracture, a posterior-stabilizing prosthesis is recommended

14. Intra-operative factors • Various technical failures by surgeons • Insufficient release of the soft tissues having contracture • Incorrect bone resection • Mal-position of component • Mismatch of the component design to the original knee • Insufficient resection of the posterior bony spur • These are the most important for surgeons • Because these factors depend on surgeon’s skill

15. Possible technical failure: #1 • A case that the distal femur was resected too much • Ligament function is normal due to perfect tissue release • Note that the flexion gap is normal • If a surgeon choose an appropriate insert for the flexion gap • Significant instability in the extension position • Then, If the surgeon changes the insert to a thicker one to treat the instability • Significant loss of flexion

16. Possible technical failure: #2 • A case that the posterior capsule contracture was not sufficiently released • The knee is apparently stable in the full extension position because of the tight posterior capsule • But collateral ligs are relaxed • When the knee is flexed (the posterior capsule is relaxed) • Significant instability • Then, if the surgeon places a thicker insert to treat the instability • Loss of both extension and flexion

17. Take home message • Inappropriate bone resection cannot be compensated by soft tissue releasing • Insufficient soft tissue release cannot be compensated by bone resection • Recent trend • Precise bone resection can be easily navigated by specially designed instruments • However, soft tissue release remains the most critical in TKA • Several releasing techniques

18. My step-release procedure (For the CR-type prosthesis) • The first step • Release from the tibia • M and PM part of the menisco-tibial ligament • Deep layer of the MCL • Completely remove a tibial bone block after carefully releasing from the PCL • Check the ligament balance

19. My step-release procedure (For the CR-type prosthesis) • The second step • Release from the tibia • Semi-membranosus tendon • Only the proximal part of the tibial attachment of the PCL • Again check the ligament balance

20. My step-release procedure (For the CR-type prosthesis) • The third step (for the severe varus knees) • Release from the tibia • The proximal one-third of the superficial layer of the MCL, preserving the distal part

21. My step-release procedure (For the PS-type prosthesis) • Warning • If the PCL is finally resected after the collateral release, the knee frequently become unstable • For severe varus deformity or flexion contracture • Resect the PCL first • Then, gradually perform from the first step

22. “High-flexion” designs • Biomechanical factors affecting the postoperative ROM • Loss of roll-back movement of the femur • Tibial slope • Narrow flexion gap • Loss of the posterior condyle offset • Shortening of the extensor mechanism • Loss of internal rotation of the tibia • Prosthetic designs to improve each biomechanical factor • PCL-substitution • Insert/osteotomy with the tibial slope • Short posterior offset • Long posterior offset • Deep patellar groove • Mobile tibial insert

23. “High-flexion” designs? • No doubt that each improvement in the design is biomechanically important • Clinically, however, - - - • “Can surgeons significantly improve the average ROM by using a new design in their clinical practice?” • Commonly speaking, prospective randomized clinical trials have showed no significant differences between previous and new prosthetic designs • Aigner et al: JBJS-Am, 2004 • A-P griding mobile bearing vs. Conventional mobile • 113 degrees vs. 111 degrees (NS)

24. Do any “High-flexion” designs significantly improve the ROM? • It may be difficult for surgeons to easily achieve deep flexion by changing a prosthetic design • Commonly speaking, the degree of the design change is minimal. • The pre-, intra-, and post-operative factors strongly affect the postoperative ROM • Again, surgeons should make effort to restore the normal ligament functions and the anatomical joint shape, using surgeons’ skill

25. Post-operative factors • Using the soft release technique, we can obtain deep flexion during surgery in almost all cases • Except for cases with the extensor contracture • Nevertheless, these knees frequently fail to obtain deep flexion due to the following postoperative biological factors • Postoperative arthrofibrosis • Postoperative contracture of the extensor apparatus

26. Postoperative rehabilitation • Only a method to minimize effects of the postoperative biological factors at the present time • The effect of the standard rehabilitation varies among the individuals • The effect of aggressive rehabilitation commonly disappears over time

27. Postperative arthrofibrosis and contracture • The most critical factors to obtain deep flexion after TKA at the present time • Onodera, Yasuda, et al: TORS, 2006 • Expression of TGF-beta and EMMPRIN within the knee joint after TKA are significantly correlated with the postoperative ROM • In the future • We may have to clarify these biological mechanisms and to develop useful methods to control them • If we hope to obtain the real deep flexion in all cases

28. Conclusions • To obtain deep flexion in the artificial knee, we should simultaneously restore the normal ligament balance and the anatomical joint surface • Clinically, however, pre-, intra-, and post-operative factors may strongly disturb the restoration, resulting in loss of ROM • Both precise soft tissue release and bone resection are the most essential for surgeons • The postoperative arfthrofibrosis and contracture are the most critical to obtain deep flexion • In the future, we should develop useful methods to control these postoperative biological responses within the living body

29. Acknowledgement Thank you