clinical, biomechanical, and biological factors to achieve deep flexion in tka kazunori yasuda, md,...
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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
Knee lecture course, Prague 2007
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 gardeningPlaying 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
apparatusQuadriceps lengtheningTibial tubercle transferBone resectionSpecial prosthetic design
Each idea has their own set of serious complicationsThis remains unsolved at the present time
In these cases, surgeons cannot expect much improvement in the ROM after surgery
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
PCL contracture
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 perfec
t 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 posi
tion
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 tendonOnly the proximal part of the tibial att
achment 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, t
he 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 apparat
us
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
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1.2
1.4
1.6
1.8
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EM
MP
RIN
95 100 105 110 115 120 125 130 135Flexion (° )
(ng/
ml)
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.4
.6
.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
EM
MP
RIN
95 100 105 110 115 120 125 130 135Flexion (° )
(ng/
ml)
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