Clinical biomechanical and biological factors to achieve deep flexion in tka
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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. ROM after TKA.

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

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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


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


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


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


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


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


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


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


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


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


The preoperative factors

  • Shortening of the extensor apparatus

    • Patella baja

    • Quadriceps contracture

  • Contracture of the ligaments and capsular tissues


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


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


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


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


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


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


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


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


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


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


“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


“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)


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


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


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


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


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


Acknowledgement

Thank you


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