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Mechanisms of Injury and Repair Classification of injury. The repair process. Ligament healing. Functional knee brace.

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Presentation on theme: "Mechanisms of Injury and Repair Classification of injury. The repair process. Ligament healing. Functional knee brace."— Presentation transcript:

1 Mechanisms of Injury and Repair Classification of injury. The repair process. Ligament healing. Functional knee brace.

2 Classifications of injury z According to mechanism: yprimary vs secondary. z According to tissues: ysoft tissues vs hard tissues. (Oakes 1992)

3 Primary injuries (1) z direct/extrinsic: usually high forces, result in severe injuries. z indirect/intrinsic: eccentric overload of musculotendinous units.

4 Primary injuries (2) z Overuse injury: repetitive friction leads to tenosynovitis. z Chronic repetitive microfatigue: stress # or Osgood-Schlatter’s disease.

5 Secondary injuries zShort term: previous mismanaged injury e.g. resolving phase of inflammation when pain is down. zLong term: e.g. secondary O.A. knee due to ACLD.

6 The repair process (1) zThree phases of tissue repair in general. zInflammation phase. zRepair phase. zRemodelling phase.


8 The repair process (2) zAcute inflammation at initial 72 hours. zNew blood vessels to the wound. zHealing: wound must be clean and blood must be available. zLittle inflammation, healing is slow; excessive inflammation, over scarring.

9 The repair process (3) zMatrix and cellular proliferation phase 72 hours to 6 weeks. zActive synthesis of collagen/proteoglycan matrix forming granulation tissue. zInduce epithelialization and wound contraction. zNeovascularization probably controlled by growth factors.

10 The repair process (4) zNew collagen is mainly type III. zCollagen fibrils are small and not oriented. zPoor material properties of the scar tissue. zRemodelling and maturation: 6 weeks to several months. zLoading, movements determine collagen maturation and alignment.

11 Ligament healing 1 zProximity of rupture ends. zAvailability of repair cells. zSynovial fluid (the hostile environment). zLoad during remodelling.

12 Ligament healing 2 zComplete sectioning of the PLB of goat ACL (Ng et al 1996 AJSM). zNo surgical repair. zFree activities in a farm.

13 Ligament healing 3 zMechanical testing at 12 wk (n=3), 24 wk (N=3), 52 wk (N=3) and 3 yr (N=2). zLaxity testing. zInstron material testing for UTS, stiffness, Young’s modulus and load relaxation.

14 Ligament healing 4 zEvidence of healing at 12 weeks with translucent fibrous tissue. zRepair tissues appeared normal at 1 year. zIndistinguishable repair tissue from normal tissue surrounding the repair at 3 years. zThe whole ligament bundle has grown in size.

15 Ligament healing 5 zNo significant difference in laxity among all groups. zThe intact amb provided the restrain? zNot enough drawer force to test the ligament?

16 Ligament healing 6 zGeneral increase in normalised UTS with time. zSignificantly higher UTS at 3 years than 12 weeks. zControl UTS: 1167 N; UTS 3 years: 1493N zLigament failure at 12 and 24 weeks, but bony avulsion at 3 years.


18 Ligament healing 7 zGeneral increase in stiffness with time. zSignificantly higher stiffness at 3 years than 12 weeks. zControl stiffness: 258 N/mm; 12 weeks: 146 N/mm; 1 year: 198 N/mm; 3 years: 250 N/mm.


20 Ligament healing 8 zGeneral increase in Young’s modulus with time. zControl modulus: 487 MPa; 12 weeks: 257 MPa; 1 year: 408 MPa; 3 year: 351 MPa. zWhy is stiffness different from Young’s modulus? zClinical implication.


22 Ligament healing 9 z No general trend in load relaxation pattern with time. zFrank (1985) found scar would load relax quicker than normal tissues. zThis could result in overloading to the secondary restraints.


24 Functional knee brace (1) zThree functions:  biomechanical  physiological  proprioceptive

25 Functional knee brace (2) zLittle mechanical protection (Bagger, 1992; Beynnon, 1992; Warming & Jorgensen, 1998). zIncrease energy consumption (Highgenboten, 1991). zincreasing relaxation pressure of muscles (Styf, 1994).

26 Functional knee brace (3) zImprove proprioception and AP body sway (Kuster, 1999). zImprove cutaneous sensation (Beynnon, 1999; Birmingham, 1998). zControversies among studies on knee brace. zMechanical vs. non-mechanical components of the braces. zTests to simulate sports activities.

27 Study objectives (Wu, Ng, Mak 2001a & b) z To compare: (1) no brace, (2) Donjoy legend functional brace, (3) mechanical placebo brace.

28 Parameters measured Ô Running and turning. Ô Jumping and landing. Ô Isokinetic performance. Ô Joint sense.

29 Methods zSubjects x31 subjects aged with single limb injury. xArthroscopic ACL reconstruction with semitendinosus by the same surgeon. xAt least 5 months post-operation.

30 Running and Turning Test zSubjects ran on a “figure-of- eight” runway of 22 m long for 10 laps. zTime of running and turning on each side recorded.

31 Jumping and landing Test zSubject ran on a semicircular path. zJumped and turned internally with the affected leg. zLanded on a floor marker (20Cm X 28Cm). zAccuracy of landing and time to complete the run/jump task recorded.

32 Isokinetic Test z60 o /s & 180 o /s. z o of knee flexion. zPeak torque and total work recorded.

33 Copying of knee joint angle zFive pre-set angles by passive positioning. zSubjects indicated the perceived angle on a knee model (Attfield et al 1996). zMean Difference in the angles recorded.

34 Result 1

35 Result 2

36 Result 3

37 Result 4

38 Result 5

39 Result 6

40 Result 7

41 Conclusion 1 zSubjects ran 3.2 % % slower in both bracing conditions than no brace. zSimilar to the report of increase energy expenditure values (Highgenboten 1991).

42 Conclusion 2 zBracing enhanced the static knee joint sense. zImprovement was not due to mechanical restraint of the brace.

43 Conclusion 3 zBracing had slowed down running/turning. zBracing did not improve isokinetic and jumping performance.

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