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					Mechanisms of Injury and
Repair

  Classification of injury.
  The repair process.
  Ligament healing.
  Functional knee brace.
Classifications of injury

                According to
                 mechanism:
                  primary vs secondary.
                According to tissues:
                  soft tissues vs hard
                   tissues. (Oakes 1992)
Primary injuries (1)

               direct/extrinsic:
                usually high forces,
                result in severe
                injuries.
               indirect/intrinsic:
                eccentric overload of
                musculotendinous
                units.
Primary injuries (2)

               Overuse injury:
                repetitive friction
                leads to
                tenosynovitis.
               Chronic repetitive
                microfatigue: stress #
                or Osgood-Schlatter’s
                disease.
Secondary injuries

Short term: previous mismanaged injury
 e.g. resolving phase of inflammation when
 pain is down.
Long term: e.g. secondary O.A. knee due
 to ACLD.
The repair process (1)

Three phases of
 tissue repair in
 general.
Inflammation phase.
Repair phase.
Remodelling phase.
The repair process (2)

Acute inflammation at initial 72 hours.
New blood vessels to the wound.
Healing: wound must be clean and blood
 must be available.
Little inflammation, healing is slow;
 excessive inflammation, over scarring.
The repair process (3)

Matrix and cellular proliferation phase 72
 hours to 6 weeks.
Active synthesis of collagen/proteoglycan
 matrix forming granulation tissue.
Induce epithelialization and wound
 contraction.
Neovascularization probably controlled by
 growth factors.
The repair process (4)

New collagen is mainly type III.
Collagen fibrils are small and not oriented.
Poor material properties of the scar
 tissue.
Remodelling and maturation: 6 weeks to
 several months.
Loading, movements determine collagen
 maturation and alignment.
Ligament healing 1

Proximity of rupture
 ends.
Availability of repair
 cells.
Synovial fluid (the
 hostile environment).
Load during
 remodelling.
Ligament healing 2

Complete sectioning of the PLB of goat
 ACL (Ng et al 1996 AJSM).
No surgical repair.
Free activities in a farm.
Ligament healing 3

Mechanical testing at 12 wk (n=3), 24 wk
 (N=3), 52 wk (N=3) and 3 yr (N=2).
Laxity testing.
Instron material testing for UTS, stiffness,
 Young’s modulus and load relaxation.
Ligament healing 4

Evidence of healing at 12 weeks with
 translucent fibrous tissue.
Repair tissues appeared normal at 1 year.
Indistinguishable repair tissue from
 normal tissue surrounding the repair at 3
 years.
The whole ligament bundle has grown in
 size.
Ligament healing 5

No significant difference in laxity among
 all groups.
The intact amb provided the restrain?
Not enough drawer force to test the
 ligament?
Ligament healing 6

General increase in normalised UTS with
 time.
Significantly higher UTS at 3 years than
 12 weeks.
Control UTS: 1167 N; UTS 3 years: 1493N
Ligament failure at 12 and 24 weeks, but
 bony avulsion at 3 years.
           1500
                                                     Control n=11
UTS (N)




           1000                                      12 wk n=3

            500                                      24 wk n=3

              0                                      1 yr n=3
                  Contro 12 wk 24 wk   1 yr   3 yr
                                                     3 yr n=2
          UTS (N) 1167 419.7 669.7 828.3 1494
Ligament healing 7

General increase in stiffness with time.
Significantly higher stiffness at 3 years
 than 12 weeks.
Control stiffness: 258 N/mm; 12 weeks:
 146 N/mm; 1 year: 198 N/mm; 3 years:
 250 N/mm.
        300


        200                                       Control n=11

                                                  12 wk n=3
        100                                       24 wk n=3

                                                  1 yr n=3
          0
              Control 12 wk 24 wk   1 yr   3 yr   3 yr n=2

Stiffness N/mm 258.7 146.4 196.5 197.8 249.8
Ligament healing 8

General increase in Young’s modulus with
 time.
Control modulus: 487 MPa; 12 weeks:
 257 MPa; 1 year: 408 MPa; 3 year: 351
 MPa.
Why is stiffness different from Young’s
 modulus?
Clinical implication.
              600
              500
Modulus MPa
                                                      Control n=11
              400
              300                                     12 wk n=3

              200                                     24 wk n=3
              100                                     1 yr n=3
                0
                    Contr 12 wk 24 wk   1 yr   3 yr   3 yr n=2
                     ol    n=3   n=3    n=3    n=2
 Modulus 487.3 257.3 332.1 408.7               351
 MPa
Ligament healing 9

 No general trend in load relaxation
 pattern with time.
Frank (1985) found scar would load relax
 quicker than normal tissues.
This could result in overloading to the
 secondary restraints.
                                        Load relax

                 40                                                      Control n=11
  Load relax %




                                                                         12 wk n=3
                 20                                                      24 wk n=3
                                                                         1 yr n=3
                  0                                                      3 yr n=2
                      Control   12 wk     24 wk      1 yr n=3 3 yr n=2
Load relax             16.6     15.7        19         18       25.5
Functional knee brace (1)

    Three functions:
      biomechanical
      physiological
      proprioceptive
Functional knee brace (2)

Little mechanical protection
 (Bagger, 1992; Beynnon,
 1992; Warming & Jorgensen,
 1998).
Increase energy consumption
 (Highgenboten, 1991).
increasing relaxation
 pressure of muscles (Styf,
 1994).
Functional knee brace (3)

Improve proprioception and AP body sway
 (Kuster, 1999).
Improve cutaneous sensation (Beynnon,
 1999; Birmingham, 1998).
Controversies among studies on knee brace.
Mechanical vs. non-mechanical components
 of the braces.
Tests to simulate sports activities.
Study objectives      (Wu, Ng, Mak 2001a
& b)


       To compare:
         (1) no brace,
         (2) Donjoy legend
           functional brace,
         (3) mechanical
           placebo brace.
Parameters measured

    Running and turning.
    Jumping and landing.
    Isokinetic performance.
    Joint sense.
Methods

Subjects
   31 subjects aged 15-40 with single
    limb injury.
   Arthroscopic ACL reconstruction with
    semitendinosus by the same surgeon.
   At least 5 months post-operation.
Running and Turning Test

Subjects ran on
 a “figure-of-
 eight” runway of
 22 m long for 10
 laps.
Time of running
 and turning on
 each side
 recorded.
Jumping and landing Test

Subject ran on a
 semicircular path.
Jumped and turned
 internally with the
 affected leg.
Landed on a floor
 marker (20Cm X 28Cm).
Accuracy of landing and
 time to complete the
 run/jump task recorded.
Isokinetic Test


60o/s & 180o/s.
0 - 60o of knee flexion.
Peak torque and total work recorded.
Copying of knee joint angle

Five pre-set angles
 by passive
 positioning.
Subjects indicated
 the perceived angle
 on a knee model
  (Attfield et al 1996).

Mean Difference in
 the angles recorded.
 Result 1
                            Turning time in different conditions


                                   4
Time (second)




                                   3
                                   2
                                   1
                                   0
                                       No brace         Donjoy         Placebo

                Affected p=0.006          1.6            1.744         1.731
                Unaffected p=0.008       1.691           1.758         1.731

                                         Affected p=0.006    Unaffected p=0.008
Result 2
                                    Total running time


                            200
Time (second)




                            150

                            100
                             50

                              0
                                     No brace         Donjoy         Placebo

                Total time p=0.00      92.6              96.9         95.5

                                           No brace      Donjoy   Placebo
Result 3
                                  Landing accuracy


                          150
Accuracy (%)




                          100


                           50


                            0
                                  No brace            Donjoy        Placebo

               Landing accuracy     93.5               92             93.8
               p=0.248

                                           No brace    Donjoy   Placebo
 Result 4
                                Best run-jump time

                          6
Time (second)




                          4

                          2

                          0
                                 No brace            Donjoy         Placebo

                Run-jump time      2.26               2.31           2.27
                p=0.483

                                          No brace    Donjoy   Placebo
  Result 5
                                   Peak torque at 60 deg/s


                            200
Peak torque (Nm)




                            150

                            100

                             50

                              0
                                    No brace           Donjoy           Placebo

                   Hams p=0.350       98.4              95.5             97.7
                   Quads p=0.107      138.1             144              139.2

                                          Hams p=0.350         Quads p=0.107
           Result 6
                            Total work at 180 deg/ s

                     150
Work (J)




                     100

                      50


                       0
                                No brace       Donjoy           Placebo

            H ams p=0.402        50.2           49.1             50.1
            Quads p=0.793        74.8           73.1             72.9

                                     H ams p=0.402     Quads p=0.793
             Result 7
                                    Difference in angles


                         14
                         12
Angle (degree)




                         10
                          8
                          6
                          4
                          2
                          0
                                No brace              Donjoy          Placebo

                 Angle p=0.00     8.65                 6.59               7.12

                                           No brace    Donjoy   Placebo
Conclusion 1

Subjects ran 3.2 % - 4.6 % slower in
 both bracing conditions than no
 brace.

Similar to the report of increase
 energy expenditure values (Highgenboten
 1991).
Conclusion 2

Bracing enhanced the static knee
 joint sense.
Improvement was not due to
 mechanical restraint of the brace.
Conclusion 3
Bracing had
 slowed down
 running/turning.
Bracing did not
 improve isokinetic
 and jumping
 performance.

				
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posted:11/1/2011
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