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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EM

MP

RIN

95 100 105 110 115 120 125 130 135Flexion (° )

（ng/

ml）

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.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

Thank youThank you

Acknowledgement