Journal of Applied Physiology August 15, 2012; Vol. 113; No. 4, pp. 532-540 Daniel WH Mang, Gunter P Siegmund, J Timothy Inglis, JS Blouin KEY POINTS FROM THIS STUDY: 1) During whiplash collisions, initially relaxed occupants exhibit brisk,stereotypical muscle responses consisting of postural and startle responses thatmay contribute to the injury. 2) The neck neuromuscular response to a rear-end impact consists of a posturalresponse and a startle response elicited by a multisensory stimulus(somatosensory, acoustic, and vestibular) associated with the vehicle impact. 3) During a rear-end collision, afferents from the somatosensory, acoustic, andvestibular systems are activated and trigger a startle response in the neckmuscles. 4) These authors sought to determine if the startle response elicited during arear-end collision contributes to head stabilization or represents a potentiallyharmful, overreaction of the body. In the context of a rear-end collision, it is notclear whether these reflex actions are protective and thus beneficial or potentially injurious and therefore harmful. 5) Three experiments were performed using 33 different subjects. The analysisincluded the use of surface electromyography, and head accelerations weremeasured using an accelerometer array. 6) The startle response represents an overreaction that increases the kinematicsin a way that potentially increases the forces and strains in the neck tissues. [Key] 7) Neck muscle activity begins about 50 – 100 ms after vehicle accelerationonset, early enough to influence peak head and neck kinematics. There is evidencethat neck muscles are a contributor to other neck tissue injuries during whiplashmechanism. 8) The time period over which the neck muscles are active overlaps the timeperiod during which peak acceleration and displacement of the head and neckoccur. This overlap suggests that muscle-induced strains and motion-inducedstrains in the posterior neck tissues potentially coincide and cause more severewhiplash injury and related symptoms following a rear-end collision. 9) In experimental rear-end collisions, subjects who reported temporary neckpain exhibited larger startle responses in their posterior neck muscles than didsubjects who did not report neck symptoms. 10) Based on prior studies, injuries sustained during a rear-end car collisioncould be exacerbated by a startle response that increases neck muscle activityduring a time when the posterior neck tissues may be vulnerable. 11) During whiplash, the startle response inhibits muscle tone; therefore, thestartle response is potentially harmful and ill-adapted for whiplash collisionexposures. 12) The startle response during a rear-end collision decreased the whiplash-evokedneck muscle response by 16 – 29%. [Muscles protect joints. Jointinjuries (facet/disc) are primarily responsible for chronic whiplash pain.Startle reduces muscle protection of joints, increasing whiplash injury andchronicity]. 13) These kinematic differences suggest that the startle response evoked by arear-end collision may be more harmful than protective. 14) Our findings suggest that the startle response evoked by a rear-end collisionmay increase the risk of certain whiplash injuries. 15) The cervical facet joints are a source of neck pain in 40 – 68% of patients withchronic whiplash injuries, and excess strain in the facet joint capsule can occurduring whiplash exposures. The neck multifidus muscles insert directly onto the[facet] capsule. 16) Posterior neck muscle activity, and multifidus muscle activity in particular,elicited by the collision may exacerbate cervical facet capsular ligament strain at amoment when the ligament is already being strained by the collision-inducedintervertebral motion. 17) Our results provide additional support for the potential role of the startleresponse in exacerbating certain whiplash-related neck injuries. 18) Although startle responses are generalized body reactions to intense stimuliand are generally thought to protect the body from potential injury by drawing inthe limbs and stiffening the body, during whiplash they tend to inhibit cervicalmuscle tone and increase cervical spine injury. COMMENTS FROM DAN MURPHY This article may help explain why some patients can be injured in very low impactscenarios; they are injured as a consequence of the startle response, caused by acervical neuromuscular multisensory response from somatosensory, acoustic, andvestibular afferents associated with the vehicle impact.

Sports Medicine Arthroscopic Review September 2005; Vol. 13; No. 3; pp. 136 – 144 Kevin A. Hildebrand, MD, Corrie L. Gallant-Behm, BSc, Alison S. Kydd, BSc, andDavid A. Hart, PhD: From the University of Calgary, Alberta, Canada. KEY POINTS FROM THIS ARTICLE: 1) Wound healing following overt injury to a tissue follows general rulesirrespective of the tissue involved. 2) Wound healing and repair of injured tissues follows several steps in thehealthy individual. The process is initiated by the inflammatory response andsubsequent steps are based on this initial response. 3) Whereas wound healing generally leads to a repair of the injured site, it doesnot lead to tissue regeneration. This difference between repair and regeneration hasinfluence on tissues such as ligaments and tendons that function in a mechanicallyactive environment. 4) The dynamic interface between mechanics and biology influence theeffectiveness of the healing response. [Important] 5) Factors that impact the outcome of the healing response include the biologyof the host, such as: A)) Age B)) Sex C)) Genetics D)) Tissue history (prior injuries, scar tissue, and disease states) 6) The repair process can lead to a loss of function, primarily from scar tissue,and this can occur in both musculoskeletal and visceral tissue (heart, lung, kidney,liver). 7) Recent investigations have detailed the healing response of many connectivetissues (ligaments, tendons, menisci, joint capsules) that function in mechanicallydiverse environments. 8) The functional outcome of the healing process depends on the extent ofrepair versus regeneration. 9) The basic steps in the repair or healing of a tissue following overt injury are: A)) Hemostasis and a rapid inflammatory phase B)) A phase of cell proliferation and matrix deposition 2 C)) A slow remodeling phase, which may take months to years A)) The Inflammatory Phase *Following acute injury there is bleeding into the area of injury and pain. *Hemostasis is restored by the formation of a fibrin clot, which prevents furtherbleeding and serves as a provisional matrix for migrating cells. *This clotting cascade results in the release of inflammatory molecules andinflammatory cytokines from cells such as platelets. *There is an influx of fibroblasts, which sets the stage for the second phase (B) ofthe repair process. B)) The Matrix Deposition Phase *Deposition of matrix molecules [fibroblasts] produce collagen proteins that bridgethe damaged area with the residual endogenous ligament tissue. *If the matrix deposited early during the healing or repair process is alteredcompared with normal, the organization of the repair tissue is also likely to bealtered. [Important: early best treatment is critical for ultimate quality of healing] *The organization of the matrix deposited early following injury is disorganizedcompared with normal tissue. [The Fibrosis Of Repair] *The tissue deposited early after injury appears to be an attempt to bridge thedamaged area without regard to what was present before injury. *Not only does this provisional matrix have a different structural and cellularcomposition as compared with normal tissue, but in the case of ligament injury, thistissue is not necessarily even localized to the injury gap but also may extend tosurround the entire remaining ligament midsubstance. *This somewhat amorphous material, resulting from the initiation of an overtinflammatory response and subsequent events is compromised at both theorganizational and functional levels, independent of whether it is a ligament,tendon, or skin. C)) The Remodeling Phase *The remodeling phase is a slow process and is accompanied by alterations notonly in matrix remodeling, but also gene expression, cellularity, vascularity, andinnervation. *The scar tissue in a ligament undergos a protracted process where the initiallydeposited material seems to be turning over and the organization of collagen fibrilsbecome more oriented along the long axis of the ligament. *Because the remodeling phase occurs slowly, and may take months (i.e., skin) oryears (i.e., tendon and ligament). [Important] *A number of variables seem to influence the rate of remodeling and the finaloutcome, and it is not always possible to assign potential cause and effectrelationships. *Even after protracted time post-injury, the mechanical properties of a scar tissuein a ligament … is still compromised compared with normal. *The scar tissue may be functional for most activities even though it is notnormal. [Fails during high demand activities] 10) Normal tissues are organized with respect to collagen alignment and collagenfibril assembly, whereas collagen expressed early following injury is not aligned andheterogeneous with regard to orientation in the tissue. Because the latter is criticalfor function in a mechanically active environment such as a ligament, it is notsurprising that the mechanical properties of the healing ligament are severelycompromised compared with normal tissue. [The Fibrosis Of Repair] 11) The scar cells in the healing ligament are different from normal cells andtherefore the scar is intrinsically different. [Key Point] 12) Tissues that do not have an influx of new microvasculature, like the disc andmeniscus, do not heal well. [Very Important] 13) Not all ligaments heal to the same degree, and healing of ligament injuriesseems to be influenced by various factors including location (i.e. extra-articular vs.intra-articular), intrinsic aspects (which are largely unknown), mechanicalenvironment, as well as factors discussed in more detail in the following sections. 14) The large scar tissue mass gradually remodels, likely under the influence ofthe mechanical environment. [Very Important: supports the contention thatthe mechanics of the chiropractic adjustment can enhance the timing andquality of scar remodeling] 15) Scar-like tissue is functionally ineffective. 16) Maturation of the scar tissue requires mechanical loading to continue theremodeling phase of healing. [Very Important] 17) Normal connective tissues that function in a mechanically active environment(actually most tissues) subscribe to the use it or lose it paradigm of tissue integrity. Increased loading leads to adaptation, whereas decreased loadingbelow a threshold leads to atrophy. The same principle likely also holds for scartissue and immobilization beyond the initial phases of healing could have adetrimental impact on outcome. [Very Important] 18) Too much loading of a scar at too early a time point may have a detrimentalimpact on the maturation of the scar. 19) Post healing joint instability and the loss of function leads to increasedexpression of inflammatory mediators, likely caused by microinjuries to the scartissue, and resulted in a protracted healing response. There is a delicate balancebetween biology and mechanical environment when it comes to optimizing the basichealing response in tissues such as ligaments, tendons, or skin. 20) Some tendon and ligament injuries lead to formation of scar tissue that ispartially functional, but to regain as much function as possible requiresphysiotherapy to facilitate the return to function after the scar tissue has formed.[Very Important] 21) The inflammatory response associated with overt injury or surgery can lead toformation of adhesions, where the ligament/tendon scar tissue is bonded to thesurrounding tissue and thus, such restrictions compromise function in situationswhere movement is required. [Adhesions, Fibrosis Of Repair] 22) This emphasizes the need to minimize the induction of a vigorousinflammatory response in some environments to assist in the repair process withoutside effects such as adhesions. [Very Important: the resolution ofinflammation is fibrosis; reducing inflammation reduces the fibrosis] 23) It is clear that the outcome is repair and not regeneration in all softconnective tissues, except for muscle and of course the hard tissue, bone.[Most Important: ligaments and tendons repair (with scar tissue) ratherthan regenerate (heal with normal pre-injury tissue)]. 24) Writings from ships captains from the 17th to 19th centuries whose mensuffered from scurvy noted: Under conditions of vitamin C deficiency, scars on menthat had formed greater than 20 years prior seemed to dissolve before normal skinwas affected, leaving gaping wounds where once there were scars. Thus, even aftermany years, scar tissue is more ascorbate dependent than normal skin formaintenance of integrity in humans. [Both acute injury and the long-termintegrity of healed tissues are Vitamin C dependent]. 25) The healing process is influenced by age. 26) It is known that the biomechanical properties of ligaments and tendonschange with age (become stiffer) because of accumulated stresses and theincidence of injuries, and degenerative processes in many of these tissues increasewith age (aside from those associated with athletics). [Very Important] 27) The authors present evidence that indicates that different tissues anddifferent individual [animals] have phenotypes that allow them to genetically healbetter or worse. Apparently, genetics in part, determines if the healing occurs by regeneration or by scar tissue, which is linked to the severity and extent of theinflammatory response. [Very Important] 28) Women tend to have a more vigorous inflammatory response than males,[and therefore more fibrotic and mechanical (scar) healing residuals]. This responseis probably linked to estrogen levels. 29) Normal ligament and joint function (laxity) can be influenced by themenstrual cycle in some women. 30) Pregnancy is associated with changes in several hormones qualitatively andquantitatively, impairing the metabolism of cells in the healing ligament, and alsoaffecting the functioning of the normal ligament (i.e. laxity). 31) Genetic factors play a role in some pathologic scarring or wound healing suchas keloid formation. 32) It is apparent from talking with orthopedic surgeons that there is a body ofanecdotal information that has implicated genetics in wound healing followingligament injuries and surgical interventions. 33) The quality of the tissue prior to overt injury may play a role in the woundhealing process and the final outcome, and therefore should be considered. Thepresence of previous injury, either overt or subclinical, could also impact thehealing outcome. The healing outcome following re-injury could impact both thequality of the outcome and the functioning of the healed tissue.[Very Important] 34) Mechanobiology is likely important in the healing outcome in tissues such asligaments, tendons, and related tissues. That is, depriving healing ligaments ofmechanical loading likely has a detrimental impact on healing outcome.[Very Important: improved with chiropractic adjustments] 35) Ligaments and tendons adapt to increases in mechanical loading within aphysiologic window; therefore, decreased loading decreases function. [Important] 36) When loading is consistently decreased, the quality of the tissue is decreased;this may influence the ability of these injuries to heal and their functional residuals. 37) Aging influences healing outcomes. [Very Important] 38) Re-injury of an acutely healing ligament increases inflammatory molecules,which could worsen the long-term consequence of the mechanical properties of thetissue. [Very Important] 39) Because not all injuries to a tissue are overt, it is possible that theaccumulated cycles of injury and repair to a tissue could impact the startingmaterial following an overt injury. If one extends this to the situation of a secondacute injury, the starting material following a second injury is really scar tissuerather than normal tissue. This could impact the functional outcome in at least ways; first, the quality of the scar may be compromised compared with the originalscar tissue; and second, the size of the scar may be increased and thus couldimpact the functional outcome. [Very Important] 40) The size of the wound and the resulting scar tissue has a dramatic impact onthe biomechanical outcome. 41) Diabetes can impact the healing outcome. 42) Many patients with diabetes have a compromised wound healing responsedue in part to an impaired inflammatory response and elaboration of growthfactors. 43) In conditions such as diabetes, the disease could affect the quality of theconnective tissue directly via derivatization of the tissues and formation ofadvanced glycation endproducts [AGEs] by carbohydrates. 44) Many individuals with diabetes exhibit impaired wound healing and candevelop chronic wounds that do not readily heal. 45) In animals, a single local glucocorticoid treatment of a healing ligamentresulted in reduced biomechanical properties of the scar, possibly because of adelay in the maturation/remodeling of the healing tissue. 46) It is readily apparent that wound healing in the adult under the most optimalconditions should be considered tissue repair not regeneration. For tissues like aligament or tendon, the mechanical outcome may be less than ideal, depending onthe expectations of tissue use post-injury and the occurrence of side-effects such asadhesions. [Very Important] 47) Improved understanding and application of the regulation of the inflammatoryresponse may improve the subsequent healing processes improving thefunctionality of the reparative outcome. [Lasers, Omega-3, Antioxidant Status, etc.] 48) Regulation of the interface between biology and biomechanics (i.e.mechanobiology) may also affect the functionality of the reparative outcome.[Chiropractically Very Important] 7 COMMENTS FROM DAN MURPHY This article reiterates that ligaments are important sources of proprioception. This isimportant because proprioceptive afferents control joint muscle tone; there isappreciative evidence from other sources that indicate that joint proprioceptioninfluences sympathetic autonomic tone and immunology. This article reiterates that soft tissue healing occurs over a period of 12 months ormore. Ligaments and tendons heal with scar tissue (repair) as a rule, and not with normalpre-injury tissue (regeneration). This scar tissue causes permanent loss of function. Scar tissue is mechanically and neurologically functionally inferior to normal tissue. Its inherent weakness makes the tissue prone to failure at previously normal loadlevels, and subsequent new trauma to scarred tissue will result in greater injury. Scar tissue (fibrosis) is linked to the intensity of the initial inflammatory response. Consequently, early inflammation control could improve the timing and quality ofhealing. Scar tissue, to varying degrees, is remodelable with the application of controlledmotion, which I believe includes and even requires chiropractic adjustment. Mechanical loading is critical for scar tissue remodeling and maturation. Lack of symptoms is not synonymous with full healing and functional recovery. There are definitive reasons as to why some patients heal slowly or incompletelywith functional residuals. These reasons include: A)) Age B)) Female Sex C)) Genetics D)) Tissue history (prior injuries, scar tissue, and disease states) E)) Diabetes F)) Disc injuries heal poorly, primarily as a consequence of poor blood supply G)) Pregnancy H)) Vitamin C levels I)) Menstrual cycle hormonal changes J)) Any reason that deprives the healing tissues from mechanical loading K)) Re-injury of a prior injury or prior tissue that has sustained repetitive stress L)) Excess carbohydrates that increase glycation (AGEs) [Hb-A1c] M)) Any treatment with corticosteroids N)) Anything that exaggerates the inflammatory response[omega-6/omega-3 or AA/EPA ratio]

Sports Medicine Arthroscopic Review September 2005; Vol. 13; No. 3; pp. 136 – 144 Kevin A. Hildebrand, MD, Corrie L. Gallant-Behm, BSc, Alison S. Kydd, BSc, andDavid A. Hart, PhD: From the University of Calgary, Alberta, Canada. KEY POINTS FROM THIS ARTICLE: 1) Wound healing following overt injury to a tissue follows general rulesirrespective of the tissue involved. 2) Wound healing and repair of injured tissues follows several steps in thehealthy individual. The process is initiated by the inflammatory response andsubsequent steps are based on this initial response. 3) Whereas wound healing generally leads to a repair of the injured site, it doesnot lead to tissue regeneration. This difference between repair and regeneration hasinfluence on tissues such as ligaments and tendons that function in a mechanicallyactive environment. 4) The dynamic interface between mechanics and biology influence theeffectiveness of the healing response. [Important] 5) Factors that impact the outcome of the healing response include the biologyof the host, such as: A)) Age B)) Sex C)) Genetics D)) Tissue history (prior injuries, scar tissue, and disease states) 6) The repair process can lead to a loss of function, primarily from scar tissue,and this can occur in both musculoskeletal and visceral tissue (heart, lung, kidney,liver). 7) Recent investigations have detailed the healing response of many connectivetissues (ligaments, tendons, menisci, joint capsules) that function in mechanicallydiverse environments. 8) The functional outcome of the healing process depends on the extent ofrepair versus regeneration. 9) The basic steps in the repair or healing of a tissue following overt injury are: A)) Hemostasis and a rapid inflammatory phase B)) A phase of cell proliferation and matrix deposition 2 C)) A slow remodeling phase, which may take months to years A)) The Inflammatory Phase *Following acute injury there is bleeding into the area of injury and pain. *Hemostasis is restored by the formation of a fibrin clot, which prevents furtherbleeding and serves as a provisional matrix for migrating cells. *This clotting cascade results in the release of inflammatory molecules andinflammatory cytokines from cells such as platelets. *There is an influx of fibroblasts, which sets the stage for the second phase (B) ofthe repair process. B)) The Matrix Deposition Phase *Deposition of matrix molecules [fibroblasts] produce collagen proteins that bridgethe damaged area with the residual endogenous ligament tissue. *If the matrix deposited early during the healing or repair process is alteredcompared with normal, the organization of the repair tissue is also likely to bealtered. [Important: early best treatment is critical for ultimate quality of healing] *The organization of the matrix deposited early following injury is disorganizedcompared with normal tissue. [The Fibrosis Of Repair] *The tissue deposited early after injury appears to be an attempt to bridge thedamaged area without regard to what was present before injury. *Not only does this provisional matrix have a different structural and cellularcomposition as compared with normal tissue, but in the case of ligament injury, thistissue is not necessarily even localized to the injury gap but also may extend tosurround the entire remaining ligament midsubstance. *This somewhat amorphous material, resulting from the initiation of an overtinflammatory response and subsequent events is compromised at both theorganizational and functional levels, independent of whether it is a ligament,tendon, or skin. C)) The Remodeling Phase *The remodeling phase is a slow process and is accompanied by alterations notonly in matrix remodeling, but also gene expression, cellularity, vascularity, andinnervation. *The scar tissue in a ligament undergos a protracted process where the initiallydeposited material seems to be turning over and the organization of collagen fibrilsbecome more oriented along the long axis of the ligament. *Because the remodeling phase occurs slowly, and may take months (i.e., skin) oryears (i.e., tendon and ligament). [Important] *A number of variables seem to influence the rate of remodeling and the finaloutcome, and it is not always possible to assign potential cause and effectrelationships. *Even after protracted time post-injury, the mechanical properties of a scar tissuein a ligament … is still compromised compared with normal. *The scar tissue may be functional for most activities even though it is notnormal. [Fails during high demand activities] 10) Normal tissues are organized with respect to collagen alignment and collagenfibril assembly, whereas collagen expressed early following injury is not aligned andheterogeneous with regard to orientation in the tissue. Because the latter is criticalfor function in a mechanically active environment such as a ligament, it is notsurprising that the mechanical properties of the healing ligament are severelycompromised compared with normal tissue. [The Fibrosis Of Repair] 11) The scar cells in the healing ligament are different from normal cells andtherefore the scar is intrinsically different. [Key Point] 12) Tissues that do not have an influx of new microvasculature, like the disc andmeniscus, do not heal well. [Very Important] 13) Not all ligaments heal to the same degree, and healing of ligament injuriesseems to be influenced by various factors including location (i.e. extra-articular vs.intra-articular), intrinsic aspects (which are largely unknown), mechanicalenvironment, as well as factors discussed in more detail in the following sections. 14) The large scar tissue mass gradually remodels, likely under the influence ofthe mechanical environment. [Very Important: supports the contention thatthe mechanics of the chiropractic adjustment can enhance the timing andquality of scar remodeling] 15) Scar-like tissue is functionally ineffective. 16) Maturation of the scar tissue requires mechanical loading to continue theremodeling phase of healing. [Very Important] 17) Normal connective tissues that function in a mechanically active environment(actually most tissues) subscribe to the use it or lose it paradigm of tissue integrity. Increased loading leads to adaptation, whereas decreased loadingbelow a threshold leads to atrophy. The same principle likely also holds for scartissue and immobilization beyond the initial phases of healing could have adetrimental impact on outcome. [Very Important] 18) Too much loading of a scar at too early a time point may have a detrimentalimpact on the maturation of the scar. 19) Post healing joint instability and the loss of function leads to increasedexpression of inflammatory mediators, likely caused by microinjuries to the scartissue, and resulted in a protracted healing response. There is a delicate balancebetween biology and mechanical environment when it comes to optimizing the basichealing response in tissues such as ligaments, tendons, or skin. 20) Some tendon and ligament injuries lead to formation of scar tissue that ispartially functional, but to regain as much function as possible requiresphysiotherapy to facilitate the return to function after the scar tissue has formed.[Very Important] 21) The inflammatory response associated with overt injury or surgery can lead toformation of adhesions, where the ligament/tendon scar tissue is bonded to thesurrounding tissue and thus, such restrictions compromise function in situationswhere movement is required. [Adhesions, Fibrosis Of Repair] 22) This emphasizes the need to minimize the induction of a vigorousinflammatory response in some environments to assist in the repair process withoutside effects such as adhesions. [Very Important: the resolution ofinflammation is fibrosis; reducing inflammation reduces the fibrosis] 23) It is clear that the outcome is repair and not regeneration in all softconnective tissues, except for muscle and of course the hard tissue, bone.[Most Important: ligaments and tendons repair (with scar tissue) ratherthan regenerate (heal with normal pre-injury tissue)]. 24) Writings from ships captains from the 17th to 19th centuries whose mensuffered from scurvy noted: Under conditions of vitamin C deficiency, scars on menthat had formed greater than 20 years prior seemed to dissolve before normal skinwas affected, leaving gaping wounds where once there were scars. Thus, even aftermany years, scar tissue is more ascorbate dependent than normal skin formaintenance of integrity in humans. [Both acute injury and the long-termintegrity of healed tissues are Vitamin C dependent]. 25) The healing process is influenced by age. 26) It is known that the biomechanical properties of ligaments and tendonschange with age (become stiffer) because of accumulated stresses and theincidence of injuries, and degenerative processes in many of these tissues increasewith age (aside from those associated with athletics). [Very Important] 27) The authors present evidence that indicates that different tissues anddifferent individual [animals] have phenotypes that allow them to genetically healbetter or worse. Apparently, genetics in part, determines if the healing occurs by regeneration or by scar tissue, which is linked to the severity and extent of theinflammatory response. [Very Important] 28) Women tend to have a more vigorous inflammatory response than males,[and therefore more fibrotic and mechanical (scar) healing residuals]. This responseis probably linked to estrogen levels. 29) Normal ligament and joint function (laxity) can be influenced by themenstrual cycle in some women. 30) Pregnancy is associated with changes in several hormones qualitatively andquantitatively, impairing the metabolism of cells in the healing ligament, and alsoaffecting the functioning of the normal ligament (i.e. laxity). 31) Genetic factors play a role in some pathologic scarring or wound healing suchas keloid formation. 32) It is apparent from talking with orthopedic surgeons that there is a body ofanecdotal information that has implicated genetics in wound healing followingligament injuries and surgical interventions. 33) The quality of the tissue prior to overt injury may play a role in the woundhealing process and the final outcome, and therefore should be considered. Thepresence of previous injury, either overt or subclinical, could also impact thehealing outcome. The healing outcome following re-injury could impact both thequality of the outcome and the functioning of the healed tissue.[Very Important] 34) Mechanobiology is likely important in the healing outcome in tissues such asligaments, tendons, and related tissues. That is, depriving healing ligaments ofmechanical loading likely has a detrimental impact on healing outcome.[Very Important: improved with chiropractic adjustments] 35) Ligaments and tendons adapt to increases in mechanical loading within aphysiologic window; therefore, decreased loading decreases function. [Important] 36) When loading is consistently decreased, the quality of the tissue is decreased;this may influence the ability of these injuries to heal and their functional residuals. 37) Aging influences healing outcomes. [Very Important] 38) Re-injury of an acutely healing ligament increases inflammatory molecules,which could worsen the long-term consequence of the mechanical properties of thetissue. [Very Important] 39) Because not all injuries to a tissue are overt, it is possible that theaccumulated cycles of injury and repair to a tissue could impact the startingmaterial following an overt injury. If one extends this to the situation of a secondacute injury, the starting material following a second injury is really scar tissuerather than normal tissue. This could impact the functional outcome in at least ways; first, the quality of the scar may be compromised compared with the originalscar tissue; and second, the size of the scar may be increased and thus couldimpact the functional outcome. [Very Important] 40) The size of the wound and the resulting scar tissue has a dramatic impact onthe biomechanical outcome. 41) Diabetes can impact the healing outcome. 42) Many patients with diabetes have a compromised wound healing responsedue in part to an impaired inflammatory response and elaboration of growthfactors. 43) In conditions such as diabetes, the disease could affect the quality of theconnective tissue directly via derivatization of the tissues and formation ofadvanced glycation endproducts [AGEs] by carbohydrates. 44) Many individuals with diabetes exhibit impaired wound healing and candevelop chronic wounds that do not readily heal. 45) In animals, a single local glucocorticoid treatment of a healing ligamentresulted in reduced biomechanical properties of the scar, possibly because of adelay in the maturation/remodeling of the healing tissue. 46) It is readily apparent that wound healing in the adult under the most optimalconditions should be considered tissue repair not regeneration. For tissues like aligament or tendon, the mechanical outcome may be less than ideal, depending onthe expectations of tissue use post-injury and the occurrence of side-effects such asadhesions. [Very Important] 47) Improved understanding and application of the regulation of the inflammatoryresponse may improve the subsequent healing processes improving thefunctionality of the reparative outcome. [Lasers, Omega-3, Antioxidant Status, etc.] 48) Regulation of the interface between biology and biomechanics (i.e.mechanobiology) may also affect the functionality of the reparative outcome.[Chiropractically Very Important] 7 COMMENTS FROM DAN MURPHY This article reiterates that ligaments are important sources of proprioception. This isimportant because proprioceptive afferents control joint muscle tone; there isappreciative evidence from other sources that indicate that joint proprioceptioninfluences sympathetic autonomic tone and immunology. This article reiterates that soft tissue healing occurs over a period of 12 months ormore. Ligaments and tendons heal with scar tissue (repair) as a rule, and not with normalpre-injury tissue (regeneration). This scar tissue causes permanent loss of function. Scar tissue is mechanically and neurologically functionally inferior to normal tissue. Its inherent weakness makes the tissue prone to failure at previously normal loadlevels, and subsequent new trauma to scarred tissue will result in greater injury. Scar tissue (fibrosis) is linked to the intensity of the initial inflammatory response. Consequently, early inflammation control could improve the timing and quality ofhealing. Scar tissue, to varying degrees, is remodelable with the application of controlledmotion, which I believe includes and even requires chiropractic adjustment. Mechanical loading is critical for scar tissue remodeling and maturation. Lack of symptoms is not synonymous with full healing and functional recovery. There are definitive reasons as to why some patients heal slowly or incompletelywith functional residuals. These reasons include: A)) Age B)) Female Sex C)) Genetics D)) Tissue history (prior injuries, scar tissue, and disease states) E)) Diabetes F)) Disc injuries heal poorly, primarily as a consequence of poor blood supply G)) Pregnancy H)) Vitamin C levels I)) Menstrual cycle hormonal changes J)) Any reason that deprives the healing tissues from mechanical loading K)) Re-injury of a prior injury or prior tissue that has sustained repetitive stress L)) Excess carbohydrates that increase glycation (AGEs) [Hb-A1c] M)) Any treatment with corticosteroids N)) Anything that exaggerates the inflammatory response[omega-6/omega-3 or AA/EPA ratio]

Canadian Journal of Surgery December 1998; Vol. 41; No. 6; pp. 425-429 Kevin Hildebrand, MD and Cyril Frank, MD KEY POINTS FROM THIS ARTICLE 1) Ligaments are fibrous connective tissues that provide stability to joints. 2) Ligaments have a vascular network with an accompanying nerve supply. 3) Ligaments also participate in joint proprioception. [Key Point] 4) Injuries to ligaments induce a healing response that is characterized by theformation of a scar. This scar tissue is weaker. [Key Points] 5) Ligament healing is characterized by the formation and remodeling of scartissue that is weaker than normal ligament owing to alterations in biochemicalcomposition and structural organization. The scars have a greater amount ofinferior strength tissue compared with that of normal ligaments. 6) Ligaments are composed of: 70% water25% collagen protein 05% other matrix components 7) Ligament collagen fibers are arranged longitudinally but not in parallel. 8) When forces to the ligament are increased more fibers are recruited, allowingthe ligament to accommodate greater physiologic forces. If forces beyond thisrange are applied, progressive sequential failure of fibers occur, leading to completedisruption of the ligament. 9) Ligaments and ligament scars have the ability to biomechanically adapt tochanges in length or force (viscoelastic behavior, creep). [Adjustment?] 10) Ligaments are dynamic participants in joint function, helping to balancecompressive and tensile forces. 11) Ligaments are part of a neurophysiological mechanism involved with jointfunction. They contain specialized neurological receptors that play a role in aproprioceptive ligamentomuscular reflex loop. [Subluxation] 12) There is evidence that autonomic nerves control blood flow in normal andhealing ligaments. Regulation of blood flow could be an important mechanism forinflammation or repair in ligaments and periarticular tissues. [Key Point] 13) Ligament healing culminates in the formation of a scar that bridges the tornends. Ligament healing follows these steps: A)) A fibrin clot is formed within minutes. B)) An inflammatory response ensues over the next 3-5 days, removing debrisand attracting fibroblasts. C)) For the next 6 weeks, the fibroblasts produce a collagen matrix. D)) The healing tissue is remodeled over the next several months and yearsleading to better collagen alignment. 14) The structural strength and stiffness, stress and tissue quality continue toimprove up to 12 months after injury, but after that time only relatively smallincreases are made. However, the material properties of the ligament scar do notreturn to normal even after 2 years. 15) Residual scar tissue behaves with abnormal biomechanical, biochemical andultrastructural properties. 16) The return of joint function after injury does not mean that the ligament hashealed. [Very Important] 17) Motion in stable joints improves the biomechanical properties of healingligaments compared with immobilization of joints. The mechanism presumablyinvolves the application of controlled forces; too little or too much force isdetrimental. [Very Important] [Adjustment?] 18) Clinically, it can be difficult to accurately classify ligament injuries as stableor unstable. 19) Biomechanically, ligament scars are weaker because of inferior materialquality. 20) Ligament healing in what may be considered to be the best case scenario ischaracterized by a scar material with inferior tissue quality, with changes inbiochemical and histologic properties, that does not regenerate a normal ligamenteven after 2 years of healing. 21) The ligament scar affects the associated joint function. [Key Point] COMMENTS FROM DAN MURPHY These concepts on ligament repair have important applications for chiropractorsthat treat spinal trauma patients: * Even healed ligament injury leaves residual weakness and altered proprioception. * The altered proprioception function of injured and healed ligaments not onlyalters joint protective reflex muscle tone, but also alters the autonomic control ofblood flow, which further impairs the ligament healing. [Not to mention that alters the autonomic control of blood flow has the potential to adversely affect systemichealth including immunology]. * Controlled motion [chiropractic adjustment] is the best approach to enhancethe quality of ligament healing, especially in the remodeling phase.