Strength deficit as a residual disability at the functional unstable ankle.

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Ankle injuries in sport accounts from 10 to 30% off all sport related injuries (3, 7), while is estimated ankle injury rates to occur to 1 per 10,000 people per day (3, 13) in the USA over 25,000 ankle injuries occur daily (28, 29, 30), and the UK, 5,000 ankle injuries per day (30). The 85% of all ankle injuries concern the lateral complex of the ankle. Is reported that 40% to 73% of the individual that suffers from LAS develops residual symptoms from week six up to 18 months post injury (6, 7, 13, 21). The residual problems are described as pain, swelling, stiffness, weakness and instability (6 12,13).

Repetitive lateral ankle injury leads to chronic ankle instability (CAI) that is caused either by mechanical instability or functional instability or a combination of those attributes (13, 27). Mechanical ankle instability (MAI) is defined as ankle movement beyond the physiologic limit of the ankle’s range of motion (26). Mechanical instability is a broad term that includes pathological laxity, altered arthrokinematics, degenerative and synovial changes (13). Great concern is raised when mechanically stable ankles present with FAI symptoms and eventually lead to mechanical ankle deficits (12, 13). The feeling of “giving away” at the ankle was first described by (13) by Freeman et al (1965) where he stated that the subjective feeling of “giving away” to be product of motor in-coordination due to articular de-afferentiation. Hertel (2000^a; 2002^b) provided a modified definition for FAI which has been accepted by others (26, 29) and states that functional instability is the occurrence of recurrent ankle instability and the sensation of joint instability due to the contributions of proprioceptive and neuromuscular insufficiencies. The elements of FAI have been distinguished to affect postural control, proprioception, strength and altered neuromuscular function (5, 12, 13).

Strength deficits as residual disability has been reported even before Freemans coined worked by Bonnin (1950 cited at Kaminski^a, Hartsell 2002 pg 399). Bonnin (1950) suggested that if a lever is created due to a rotational translation away from the midline may overstress the ligaments resulting to frequent sprains (cited at Kaminski^a, Hartsell 2002). Bosein and colleagues (1955) followed 113 subjects and found peroneal weakness in 29 patients (22%), examined by manual muscle testing. In addition at 23 (66%) of the 35 cases reporting residual changes and ankle symptoms showed peroneals weakness, attributing their findings overstretching of the peroneal muscles. Authors (Bosien, Staples, Russell 1955) suggested eversion resistance exercises should the treatment of choice for patients with residual symptoms after ankle sprain.

Joint stability is attributed to be succeeded by the static and dynamic elements of a joint (24). Strength belongs to the dynamic restraints contributing by cocontraction of the muscle during activities to minimize forces between the ground and ankle foot complex (16). A literature review to investigate the presence of strength deficits at the functional unstable ankle and determine the muscles that are affected how could be approach to diminish the residual disability and provide prevention for reoccurrence of lateral ankle sprain.

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Methods:

I searched using electronic search engines Pubmed, the university’s online resources and through cross referencing between 1998 and 2008 using the words: functional ankle instability, peroneals strength weakness/ deficits, ankle strength weakness/deficits and ankle injury.

Results:

Ryan (1994) in his study investigated the strength of the ankle evertors and invertors at 45 subjects with a Cybex II isokinetic dynamometer (CID2). Author (Ryan 1994) tested at speeds 30^o.s^-1 and 120^o.s^-1 and found significant differences for the invertor muscle groups and none for the evertors. Ryan’s (1994) study contested previous findings (Bosein et al 1955) though Bosein et al (1955) used manual muscle testing which the use of such testing in research has been questioned (Kaminski^a, Hartsell 2002). Author (Ryan 1994) reasonable the unexpected invertor weakness at selective inhibition that prevents motions that may produce further injury, his speculation was later supported by others (11, 12, 16, 21, 31).

Lentell et al (1995) investigated for peak torque deficits of the evertors at 42 subjects, suffering from unilateral CAI, with a CID2 at high speeds (30 ^o.s^-1,90 ^o.s^-1, 150 ^o.s^-1, 210 ^o.s^-1). Authors did not find evertors weakness at their subjects supporting Ryan’s (1994) findings.

Wilkerson, Pinerola and Caturano (1997) investigated the evertors and invertors muscles isokinetic strength performance at 15 subjects with CAI and 15 subjects who had sustained a grade II LAS. Authors used Biodex 2 dynamometer at 30^o.s^-1 and 120^o.s^-1 and the results showed small differences at eversion comparing affected and unaffected sides. Inversion results showed greater discrepancy between sides and authors agreed with Ryan’s (1994) findings and suggestion of reflexive inhibition. They further suggested that during a closed kinetic chain (CKC) activity the invertors E^cc control lateral displacement from the centre of gravity (COG) thus preventing the lateral border to act as fulcrum that will result in an unexpected inversion (11,12, 31).

Konradsen^b, Olesen and Hansen (1998) investigated maximal isometric eversion strength at 44 subjects that had sustained a grade II and III and with no previous history at either ankle. Subjects were designated to perform the test at week one, at three weeks, at six weeks and 12 weeks post injury though 38 subjects were able to perform the test at the third week post injury and the rest at week six. Results of the investigation showed a significant decrease in strength, though mean values increased from week 6 and onward without great differences when compared to health contralateral ankle.

Kaminski, Perrin and Gansneder (1999) compared E^cc and C^on eversion isokinetic and isometric ankle strength between 21 subjects with unilateral FAI and 21 health subjects. They used a Kin Com 125 AP isokinetic dynamometer, at speeds 30^o.s^-1 60^o.s^-1, 90^o.s^-1, 120^o.s^-1, 150^o.s^-1 and 180^o.s^-1 and were unable as Bernier et al (1997) to find strength deficits at evertors muscle group and suggested more research of the E^cc invertor group.

Hartsell and Spaulding (1999) conducted a similar investigation, also included the invertors muscle group, tested 24 subjects, ten of which served as control. Authors in that study used a Biodex dynamometer at speeds 60^o.s^-1, 120^o.s^-1, 180^o.s^-1, 240^o.s^-1 and they found weakness at their CAI group for both movements at E^cc and C^on ankle strength supporting the findings of previous studies (25, 31). Hartsell and Spaulding (1999) observed that maximal E^cc strength showed deficits of both inversion and eversion at high speeds that is functional relevant to the muscles representation of daily living activities. They also suggested that deficits may had occurred because of the repeated testing and because E^cc contractions fatigue a muscle faster.

A study by Willems et al 2002 investigated the invertor and evertors E^cc and concentric strength with a Biodex 3 isokinetic dynamometer in subjects with CAI and history of ankle sprain and compared them with a control group. A total of 174 ankles (87 volunteers) was divided into 4 groups: a symptom-free control group, subjects with chronic ankle instability, subjects who had sustained an ankle sprain in the last 2 years without instability, and subjects who sustained an ankle sprain 3 to 5 years earlier without instability. Willem et al (2002) did not find inversion deficits contrasting the findings for inversion strength deficits supporting that there is a relationship of the peroneals muscle weakness.

Munn et al (2003) contrasted that peroneals weakness is associated to FAI. Munn et al (2003) investigated E^cc strength of the invertors and evertors with a Biodex dynamometer. Authors used as control the uninjured ankle at 16 subjects at 60^o.s^-1 and 120^o.s^-1 speeds and empowered the findings of previous work (10,25,31).

Fox et al (2008) investigated strength deficits for inversion and eversion as well for dorsiflexion and plantarflexion at 20 subjects with FAI and 20 that served as control. In that study they tested at 90^o.s^-1 with Kin Com III isokinetic dynamometer suggesting that speed is optimal for eversion deficits. The results of that study showed only platar-flexion E^cc strength deficits refuting the existence deficits at other motions at FAI. Fox et al (2008) suggested that similar studies should be carried out, since limited literature exists with similar procedure. Authors suggested for future investigation for testing the eccentric strength should be accompanied with the aid of an electromyographic analysis during the isokinetic testing.

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Discussion:

Strength deficits in the functional unstable ankle literature shown that may be impaired. The papers presented some supported (Bonnin 1950 cited at 16, 17, 32) the theory of peroneal muscle weakness were others refute it (18, 21, 25, 31) and presented invertor muscle group with impairments. One study (9) observed impairments for both evertors and invertors while another (8) showed impairment to the plantarflexor.

Comparing and contrasting the papers shows great differences in the speed tested for each direction, forceplates models, data sampling, isokinetic dynamometers, testing mode, sample size, FAI inclusion criteria, and comparison between unaffected side and use of control group. Kaminski and Hartsell (2002) in their review concluded that strength training programmes may be pointless to be carry out if no actual strength deficit exists. It is also observed that despite that the method section was imported in journals articles with propose to present the material and how was the investigation conducted so it can be “copy-pasted” to allow support or debate is something that we do not see in peer reviewed articles.

It also seems that a new confusion is developing to add up in the sequel of FAI. Referring to strength deficits it should be questioned the fact for which muscle group are we suggesting that is affected. By far the most cited muscle group for muscle weakness is advocated to the peroneal longus and brevis. Though based on three published articles (4, 10, 24) reporting gluteal weakness/dysfunction after LAS, no article, as far as concerned this research, was found to contrast such findings. Therefore it should be consider during an examination and rehabilitation regime and eliminate possible compensatory adaptations that may lead at a cumulative injury cycle. Gluteus medius during isotonic contractions is responsible to produce with the anterior fibres medial rotation and flexion of the hip while the posterior a lateral rotation and extension to the hip joint. Isometric contraction of the contributes preventing the opposite side of the pelvis from dropping during the stance phase providing frontal stability for the entire pelvis during walking and other functional activities (23).

Strength is defined as the integrated result of several force producing muscles to perform isometrically or dynamically for a given task (14). Further force generation is depended on motor unit activation (1). Adaptations to strength and conditioning have been theorized to be due to neural adaptations. Neural adaptations is a broad term that includes selective motor units activation, synchronisation, selective muscle activation, ballistic contractions, increased motor unit recruitment, increased rate of coding or frequency, increased reflex potential and increased co-contractions of the antagonists (2, 14). It also appears that untrained individuals benefit the most from strength and conditioning while highly trained may shown 2% improvements after a prolonged program (1). It is also found that maximal force develement is depended on the number of motor unit recruitment it has been found that trained athletes have faster nerve mobility and sensitivity resulting in higher rate of coding reaching the 100Hz in contrast with the 1-60Hz that are suggested to be normal fire frequencies. Clearly the latter two are properties of power training that further include stretch shortening cycle and coordination of movement pattern and skill (1). Therefore these variables should also taken in consideration when addressing strength deficits.

From the latter sounds logical that an integrated strength rehabilitation regime may have a more sound foundation and resolve strength residual problem in the ankle. Additional strength programs during rehabilitation appear to have no logical sequence or progressions for strength, hypertrophy or power. Hence someone can speculate that if the ankle rehabilitation follows an intergraded periodized strength and conditioning rehabilitation program it may resolve residual problems, but unfortunately the answer to that will remain unresolved till an investigation of these aspects is carried out.

Further it should be consider from future researchers and or from medical or allied health professionals and/or students for their thesis to investigate those effects. It is strongly speculated that if logical evidence based analytical approach to the strength rehabilitation is accomplished with critical appraised Level I investigation is carried out it may provide a better understanding to strength deficits. An recent review of Loudon et al (2008), demonstrate that most of the published articles concerning the FAI were nonrandomized designs (Level 3). Investigations concerning proprioceptive improvements in that review received a C+ recommendation while strength investigation received B. It appears that the lack of Level 1 evidence and follow ups causes inability to generalise the data (19). The question raising here would have been is it possible to carry out Level 1 investigations? Theoretical it can happen though in action it is questionable due to time and funding expensive or to facts such as that 55% of the individuals do not seek any medical attention (20).

Limitations:

Limitations of the current work are many as no actual inclusion criteria were set. The level of evidence of current work was also apparently not included. Analytical discussion and presentation of the current available journals was also poor. Another limitation of the current study is that is not peer reviewed.

Conclusions:

Surgical interventions at the functional unstable ankle appear to have a great success. It appears that the rehabilitation part is not including a proximal to distal approach neither a basic evidence based approach to meet the demands of the athlete or the untrained individual. Return to the basics fundamentals of rehabilitation and strength and conditioning and investigate their effects on residual problems of the unstable ankle and repeat existed published literature at Level I or II will provide a better understanding to the problem. Common terminology also appears to affect data expression. FAI inclusion criteria till today remain to under the personal choice of the authors without some accepting the findings of others.

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References:

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