Postoperative Changes in Soft Tissue Balance


Author

Year of publication

Type of implant

Preoperative knee alignment

Method of stress

Degree of knee flexion

Stress direction

Angles between the femoral and tibial components (degrees)

Intraoperative

3 weeks

1 month

3 months

6 months

1 year

2 years

Ishii [24]

2003

Mobile CR TKA(N:20)

ΝΑ

Tebs

150 N

0–20°

Varus

Valgus

4.4 ± 2.8

2.9 ± 1.8
   
3.6 ± l.5

3.0 ± 1.2
  
Mobile PS

TKA (N:20)

NA

Tebs

150 N

0–20°

Varus

Valgus

4.6 ± 3.8

3.8 ± 1.4
   
4.0 ± 1.7

3.5 ± 0.9
  
Chkawa [7]

2007

Fixed PS

TKA(N:131)

NA

Tebs

150 N


Varus

Valgus
 
6.0 ± 3.7

5.5 ± 3.2
  
5.5 ± 1.7

4.5 ± l.7

4.7 ± 3.3

5.5 ± 2.7
 
Sekiya [18]

2009

Fixed PS

TKA(N:71)

15.9°± 6.5°

varus

Tebs

70 N

15°

Varus

Valgus

8.6 ± 3.2

3.6 ± l.7
  
5.1 ± 22

4.3 ± 22

4.5 ± 2.4

4.2 ± 2.1

4.8 ± 2.2

3.9 ± 1.8
 
Takeda [23]

2011

Mobile CR

TKA (N:30)

NA

Tebs

150 N

20°

Varus

Valgus
    
3.7 ± l.2

3.5 ± 1.3

4.0 ± 1.3

3.5 ± 1.3

4.1 ± 1.7

3.5 ± 1.1

Mobile PS

TKA (N:30)

NA

Tebs

150 N

20°

Varus

Valgus
    
4.3 ± 1.9

3.7 ± 1.3

4.3 ± 1.9

3.4 ± 1.3

4.3 ± 1.8

3.5 ± 1.1

Sekiya [22]

2011

Fixed PS

TKA(N:37)

12.8°± 1.6° valgus

Tebs

70N

15°

Varus

Valgus

5.5 ± 2.3

5.0 ± 2.3
  
4.1 ± 2.2

4.8 ± 2.6

4.2 ± 1.8

4.1 ± 2.1

3.9 ± 1.9

4.2 ± 1.5
 


A428787_1_En_15_Fig1_HTML.gif


Fig. 15.1
Postoperative values of lateral laxity (=varus laxity) and medial laxity (=valgus laxity) after TKA in varus-deformed knees. The error bars represent one standard deviation. The lateral laxity is greater immediately after surgery than at 3, 6, and 12 months postoperatively


On the other hand, Ishii et al. reported no significant postoperative change in coronal laxity between under anesthesia and 6 months after surgery in both mobile cruciate ligament-retaining TKA and rotating-type cruciate-sacrificing TKA in knees with osteoarthritis (Table 15.1) [24]. Their mean lateral ligamentous laxity under anesthesia was 4.4° in cruciate-retaining TKA and 4.4° in cruciate-sacrificing TKA. These values were smaller than our values of 8.6° in posterior-stabilized TKA. However, due to the lack of data on preoperative deformity and detail regarding soft tissue balancing in Ishii et al.’s report, the reason for the difference in the values cannot be determined.

Why was the large lateral laxity that was observed immediately after surgery in the present study dramatically decreased 3 months after surgery? A change in alignment due to TKA from varus to valgus would decrease the tension on the soft tissues at the lateral side of the knee. Yamamoto et al. reported approximately 10% shortening of the length of the patellar tendon in rabbits 2 weeks after stress shielding of the tendon [26]. Decreased tension at the lateral side of the knee in TKA may cause the shortening of the soft tissue observed by Yamamoto et al.



15.7 Postoperative Change in Soft Tissue Balance in Valgus-Deformed Knees


To the best of our knowledge, there have been no reports dealing with the postoperative change in the soft tissue balance in TKA for valgus-deformed knees in the English literature. We now present our original study written in Japanese [22]. We evaluated the changes in coronal laxity after TKA in 37 valgus-deformed knees (4 osteoarthritis, 33 rheumatoid arthritis, all females). Posterior-stabilized TKA (Scorpio NRG) was used in all cases. Lateral soft tissues including the iliotibial band were properly released to adjust the soft tissue balance using a Tensor device. Postoperative alignment of the knee was 1.4 ± 1.6° varus. We measured coronal valgus or varus ligamentous laxity by stress X-ray using the same method as the previous study [18] immediately after surgery and 3, 6, and 12 months thereafter. Lateral laxity decreased significantly during these periods, and medial laxity tended to decrease during these periods (Table 15.1 , Fig. 15.2 ). Furthermore, we divided the cases into three groups according to the value of coronal laxity immediately after TKA: 3° or less, over 3° and less than 7°, and 7° or greater. The coronal laxity in the “3° or less” group had a tendency to increase over follow-up, and that in the “7° or greater” group had decreased (Figs. 15.3 and 15.4). Regardless of the size of the laxity immediately after surgery, medial and lateral laxity had converged to approximately 4° at 12 months after TKA. In the case of a valgus deformity with a narrow joint gap at the medial side, we released the soft tissues until the medial and lateral gaps were equal at least in extension. However, in the case of valgus deformity with a wide medial gap preoperatively, to equalize the gap at the medial and lateral sides, we had to release extensively at the lateral side. This extensive lateral release may result in failure with elevation of the joint line and being too loose at the lateral side in flexion. To prevent such a failure, we aimed for 1–2° of varus alignment from neutral at TKA, allowing a small amount of medial laxity.

A428787_1_En_15_Fig2_HTML.gif


Fig. 15.2
Postoperative values of lateral laxity (=varus laxity) and medial laxity (=valgus laxity) after TKA in valgus-deformed knees. The error bars represent one standard deviation. The lateral laxity is greater immediately after surgery than at 3, 6, and 12 months postoperatively


A428787_1_En_15_Fig3_HTML.gif


Fig. 15.3
Postoperative values of lateral laxity (=varus laxity) after TKA in valgus-deformed knees. Knees were divided by the values of laxity into three groups: 3° or less, over 3° and less than 7°, and 7° or greater. The values of the group of 7°or greater at 3, 6, and 12 months are smaller than the value immediately after surgery


A428787_1_En_15_Fig4_HTML.gif


Fig. 15.4
Postoperative values of medial laxity (=valgus laxity) after TKA in valgus-deformed knees. Knees were divided by the values of laxity into three groups: 3° or less, over 3° and less than 7°, and 7° or greater. The values of the group of 7° or greater at 6 and 12 months are smaller than the value immediately after surgery


15.8 Postoperative Change in Soft Tissue Balance in Flexion


Although flexion instability after TKA is a major reason for revision surgery [27], only a few studies reported flexion laxity objectively after TKA. Oh et al. [28] first reported flexion laxity at 90° after TKA. Patients were asked to sit on a radiolucent wooden chair, and radiographic examinations were performed with the knee joint flexed to 90°. Under varus and valgus loads with a force of 50 N, varus and valgus stress X-rays were taken. Mean lateral laxity, mean medial laxity, and total laxity were 4.7° ± 2.4°, 4.1 ± 2.1°, and 8.8° ± 3.5° in 61 TKAs at a mean 26.1 months after surgery. Yoshihara et al. [29] measured varus and valgus laxities at 90° under a 1.5-kg external force in 49 TKAs at a minimum of 10 years after surgery. They reported laxity of 6° ± 4° (0–20°) in varus, 4° ± 3° (0–9°) in valgus, and 10° ± 5° (0–21°) in total laxity. To the best of our knowledge, there have been no reports about the postoperative change in flexion laxity in TKA. If flexion laxity during TKA was lax laterally and tight medially, as has been reported [20, 30], flexion laxity would be spontaneously adjusted in the postoperative period, similar to the phenomenon found in extension [18]. Further studies are needed to clarify the postoperative change in flexion after TKA.

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Sep 6, 2017 | Posted by in ORTHOPEDIC | Comments Off on Postoperative Changes in Soft Tissue Balance

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