Review Article

Sports Medicine 9 (4); 229-243, 1990 OI12-1642/9O/0004-0229!S07.50/0 © ADIS Press Limited All rights reserved. SPOAT2281

Intensive Training in Young Athletes The Orthopaedic Surgeon's Viewpoint

Nicola Maffulli Institute of Child Health, Respiratory and Anaesthetic Unit, Sports Medicine Laboratory, and The Hospital for Sick Children, Department of Orthopaedics, London, England

Contents

Summary ..................................................................................................................................... 229 I. Acute Fractures .......................................................................................................................23 I 2. Stress Fractures .......................................................................................................................232 3. Epiphyseal Plate Fractures ..................................................................................................... 233 4. Soft Tissue Injuries ................................................................................................................ 234 5. Osteochondritis Dissecans ..................................................................................................... 236 6. Apophysitides ................................................................. ............................................ ............. 237 7. Lumbar Disc Lesions ............................................................ ................................................. 238 8. Conclusions ..................................................................................... ........................................239

Summary

A young athlete's musculoskeletal system is unique, in that it is not only growing, but is giving support to the growing soft tissues as well. With this in mind, it is easily understood that the fastest growing areas of children skeletal system are at greater risk of injury. No controlled longitudinal studies have yet been performed about the long term effects of injuries occurring in intensively trained young athletes. During the growth spurt, a dissociation between bone matrix formation and bone mineralisation occurs, thus leaving the child with the risks of chronic moderate-to-high overloading, sudden great overload, and diminished bone strength. This may account for both acute and overuse bone injuries in this age group. Epiphyseal plate injuries can have disastrous consequences. About 10% of all skeletal trauma in children involves the epiphysis, but few long-lasting effects have been reported. It is not clear whether intensively trained young athletes are at greater risk of injury than children engaged in free-play activities It is worrying, though, that about 20% of injuries in sports children require internal fixation. Few studies have addressed injuries to tendons, ligaments and the enthesis in young athletes. It seems that tendon injuries are mild, not requiring surgery, and with a low recurrence rate, but no prospective studies have been performed. Avulsion of the ligamentous insertion occurs more frequently than ligament ruptures in this age group, even though they seem on the increase. Osteochondritis dissecans affects weightbearing joints such as the hip, the knee and the ankle, but elbow lesions in gymnasts and throwers are also relatively frequent. If it occurs before epiphyseal fusion, long term effects are scarce. The centre of growth or ossification where a major tendon is attached may undergo

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chronic inflammation and avulsion of cartilage and bone, due to the stresses transmitted to it. Typical areas are the inferior pole of the patella, the tibial tubercle and the calcaneal apophysis. Sports activity contributes to the disease by excessive traction at the tendinous and fascial insertion, or as a result of direct pressure. The lumbar spine is subjected to enormous forces in some sports. The true incidence of lumbar disc lesions in sporting children is not known, but it seems that acute trauma may playa major role. With the increase of the intensity and duration of training programmes, degenerative changes may play an adjuvant role. In conclusion, a better knowledge of all aspects of training theory and of the biomechanical requirements of a given sport are required of all the professionals dealing with athletic children in order to avoid permanent damage to the skeletal system of these youngsters.

Sports activities impose forces of a higher intensity and frequency than those associated with normal life on the skeletal system. In the past decade, there has been an exercise explosion in the industrialised countries (Davidson & Taunton 1987), and competitive sport participation has become an established feature of Western children (Rowley 1986). The magnitude of the phenomenon is partly highlighted by the younger age of the athletes taking part in competition at international level in sports like tennis, gymnastics and swimming (Malina et al. 1982). In practice, children in their early teens may have already undergone intensive training and high level competition for several years (Maffulli & Helms 1988; Malina et al. 1982). This is due to the introduction of the 'catch them young' philosophy (Rowley 1986), and to the widespread belief that, in order to achieve international success at senior level, it is necessary to start intensive training before puberty (Maffulli & Helms 1988). The number of children taking part in organised competitive sports is so high that some medical bodies have felt the need to issue guidelines to govern participation (American Academy of Pediatrics 1981, 1982). Concern has been expressed over a potential epidemic of both acute and overuse sports injuries as children change from multivaried free play to the stereotyped demands dictated by the specialised pattern of movement imposed by a single sport at hight level (Micheli 1983; Stanitski 1985), although the true risk of injury in young athletes is, at present, unknown (Birrer & Levine 1987).

During the period of rapid growth, adolescents are particularly vulnerable to injuries, partially at least due to imbalance in strength and flexibility (Micheli 1983). This huge increase in participants and in the amount of time spent training and/or competing has meant that children seek treatment for injuries that were previously seen almost exclusively in adults (Hulkko & Orava 1987; K vist et al. 1989). There is good evidence that the skeletal system is extremely plastic, and shows pronounced adaptive changes to intensive sports training (Dalen & Olson 1974). The long term clinical effects of participating in intensive training during the period of growth and development are still obscure. Experimental studies have shown that low intensity training can stimulate bone length growth, while high intensity exercise can inhibit it (Booth & Gould 1975; Tipton et al. 1972). Intense training may accelerate bone maturation in mice, resulting in permanent suppression of growth in long bones (Kiiskinen 1987), and circumferential bone growth in chickens is suppressed with exercise at 8 and 12 weeks of age (Matsuda et al. 1986). No longitudinal studies have been performed in humans, but a hypertrophic response to long term overloading of bone has been reported in the upper limb of tennis players (Priest et al. 1977). Sports injuries may affect both growing bone and soft tissues (Williams 1981) and, due to the uniqueness of the young athlete's musculoskeletal system (Wilkins 1980), they could result in damage to the growth mechanisms, with consequent lifelong damage (Larson & McMahon 1966). The de-

Intensive Training in Young Athletes

gree of bone mineralisation increases with maturation. This implies changes in the mechanical properties of bone, because with increasing mineralisation bone stiffness increases and resistance to impact decreases (Buckwalter & Cooper 1987). This is why the pattern of bony injury in children is different from that in adults. When subjected to sudden overload, normal adult bone generally breaks, while children's bone may bow or buckle and may resume its original shape with time. While physiological repetitive loading is beneficial (Sedhom & Wright 1988), excessive cyclical efforts at an early age may result in serious alterations of the weightbearing joint surfaces (Sowinski et al. 1986). Some large epidemiological studies have shown that 3% to II % of school-aged children are injured each year taking part in some form of sports activity (Gallagher et al. 1984; Zaricznyj et al. 1980). Boys appear to be affected twice as much as girls (Crompton & Tubbs 1977; Zaricznyj et al. 1980) probably because they engage in higher risk sports and have a higher level of sports activity than girls. Physical characteristics can play a major role not only in the choice of a sport, but on the pattern of injuries as well (Beaty 1987). For example, joint laxity is associated with ligamentous injury, while tightness is strongly correlated with meniscal injuries and ankle, shoulder and wrist sprains (Marshall & Tischler 1981). Joint instability is associated with recurrent sprains and dislocations (Lysens et al. 1984). Other than the 'usual' injuries, children are said to sustain some bony injuries which are unique to the growing bone (Wilkins 1980): l. Acute violent injuries: (a) plastic deformation (no apparent fracture seen); (b) torus fracture (compression of the metaphyseal cortex); (c) greenstick fracture (the periosteum is intact); (d) epiphyseal plate injury; and (e) acute apophyseal avulsion. 2. Stress injuries: microtears of tendon-bone junction. In addition, there are several cases of exertion pain in adolescents when the load to joints increases whose only cause is the relative transient overloading. These are quite frequent but usually

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resolve in 6 months (Kujala et al. 1986) without any treatment. A musculoskeletal lesion is not just a local dis. order. Following nociceptor stimulation, muscles contract spasmodically, and, as part of a complex system in a finely tuned equilibrium, alter the load distribution on the surrounding structures, causing further disruption if appropriate therapy is not promptly started. This is complicated because a large proportion of patients may seek medical help several months after the onset of symptoms (Kannus 1988). This paper reviews various lesions typical of intense prolonged high standard sports activities in young athletes.

1. A.cute Fractures Bone is an extremely hard derivative of connective tissue. It is a very dynamic tissue which, under overloading, hypertrophies and reorganises its structure to bring mechanical strains to acceptable levels (Montoye et al. 1980). A cyclical load is necessary for bone formation (Lanyon 1984). If the overload is severe, and applied suddenly, a traumatic fracture results. A moderate load, applied often, can result in a stress fracture. The number of times a loading cycle is repeated and the maximum applicable stress will determine the ability of a bone to withstand a fracturing force (Cornwall 1984). A stress fracture can be produced by increased muscle loading at the bone-tendon junction (Altman 1985). When a muscle is tired, its capability to absorb shocks decreases, and abnormally high repetitive stresses are transmitted to the bone (Nordin & Frankel 1980). These stresses may interfere with the resorption-formation cycle. After the erosion of a lacuna, a layer of cement is deposited. Osteoblasts lay down osteoid, which then takes several weeks to be fully mineralised (Parfitt 1984). During this period, a bone is more prone to both traumatic and overuse fractures. This observation is of practical importance in children. A dissociation between bone matrix formation and mineralisation during the growth spurt may occur (Bailey et al. 1988). An intensively trained child is

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left with the disadvantages of chronic moderate overloading, risk of sudden relative great overload, and decreased 'relative bone strength. This may be the reason why at the age of peak height velocity there is a peak incidence of fractures of the distal radius (Bailey et al. 1988). Boys were affected nearly twice as often as girls, with a peak incidence occurring between the ages of 11.5 and 12.0 years in girls, and 14.0 and 14.5 years in boys. The respective peak height velocities occurred at ages 11.8 and 14.3 years. The age of peak fracture incidence did not correspond to the peak activity level in the same population. Several epidemiological studies have reported the occurrence of acute bone fracture in children involved in sports. The results vary greatly (table I). Most of the studies where several sports were considered agree that soccer is the sport accounting for the greatest number of injuries, including fractures (Jacobsson 1986; Kristiansen 1983; Tursz &

erost 1986; Zaricznyj et al. 1980). In the study by K vist et al. (1989), soccer came second after ice hockey, but this could be because soccer is not as widely practised in Finland.

2. Stress Fractures Any repetitive activity, no matter how innocuous it may seem, can be a cause of overuse injuries. 20 years ago, a study showed that 12% of young adults running at 70% of their maximal oxygen uptake for 40 minutes 4 times per week sustained injuries. 22% of those training at 85 to 90% of their maximal oxygen uptake for 15 minutes 3 times per week sustained injuries. Finally, 54% of those training at 85 to 90% of their maximal oxygen uptake for 45 minutes 3 times per week sustained injuries (Pollock et al. 1969). Stress fractures in children are rare, but their incidence is increasing (Micheli 1983). They are mostly associated with incorrect training (Micheli 1983). Most of them are preventable if proper at-

Table I. Fracture incidence Sport Soccer American football Various

Various Skiers

Incidence (%) 2 35 21 21 21 28 11.1

Total number

Age (years)

Reference

681 458 5128 203 114 248 173 25512 3534

6 to 17

Backous et al. (1988)

8 to 15 6 to 11

Goldberg et al. (1988) Tursz & Crost (1986)

boys girls boys boys girls boys girls

School children 3 to 19

Outdoor soccer

1

455 boys

Indoor soccer Various Various

6

366 295 772 352 931 341 551

Soccer Weight-training

23 24.6 30.1 2 0.9

12 to 15

8 to 15

boys

o to 19 boys girls boys girls boys

6 to 15

Jacobsson (1986) Kvist et al. (1989)

7 to 18

Sullivan et al. (1980)

Adolescents

Risser & Preston (1989)a Kersey & Rowan (1983) Snook (1982)b

Wrestling

31.2

353 boys

Collegiate students

Wrestling

69.8

129 boys

Collegiate students

a b

Fractures and dislocations were considered together. The wrestlers were followed for 5 years.

Zaricznyj et al. (1980) ~arrick & Requa (1979) Hoff & Martin (1986)

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Intensive Training in YQung Athletes

tention is paid to the rate and the intensity of training and its gradual progression (Maffulli & Helms 1988). Several other factors may contribute to a stress fracture, including tight muscle-tendon structure (Jackson et al. 1978; Wiklander & Lysholm 1987) and altered anatomic alignment (Kvist & Jarvinen 1982). Tibia, fibula and metatarsal stress fractures are the most common, but each sport shows a typical pattern of stress fractures (Devas 1975; Walter & Wolf 1977). Competitive running affects tibia and fibula (Hulko & Orava 1987); recreational running and race walking affect the tarsal bones (Matheson et al. 1985); jumping sports affect the pelvis, the femur and the tarsal navicular (Torg et al. 1982); basketball affects the patella, the calcaneum, the femur and the pubis (Devas 1975); gymnastics affects the whole of the upper body (Dzioba 1985; Snook 1979) and the hallux sesamoid bones (Van Hal et al. 1982); throwing affects the olecranon (Hulkko et al. 1986); ice-skating affects the fibula (Devas 1975); fencing affects the pelvis (ForcherMayr 1951); diving affects the tibia (Dowey & Moore 1984); volleyball affects the pisiform (Israeli et al. 1982); rowing affects the ribs (Holden & Jackson 1985). The pattern of stress fractures in young athletes is thought to be different from their older counterparts (Harvey 1982). In the juvenile form, usually cancellous bone is involved, with compressive stresses applied to trabecular bone. The mechanism of fracture would be microfracture of these trabeculae (Devas 1975). In older athletes a stress fracture is generally produced in a more cortical area (Devas 1975). There is some evidence that intensively-trained children may exhibit a pattern more similar to the adult type (Micheli 1983). Some athletes seem to be more prone to overuse injuries than others, even though those who train more have a significantly greater number of overuse injuries than those who train less (Orava & Saarela 1978). Most of the studies on stress fractures in young athletes were performed in track-and-field athletes. The whole of the lower limb in these athletes can be affected: 3 cases of stress fractures of the ante-

rior iliac apophysis in adolescent runners have been described (Clancy & Foltz 1976). Hulkko and Orava (1987) reported about 368 fractures occurring in 324 athletes. Of these, 32 (8.7%) occurred in children less than 16, and 117 (31.8%) in adolescents between 16 and 19. Only 9 athletes trained less than 3 times per week. Running accounted for 72% of the fractures, while all ball games combined showed an incidence of 6.5%. Athletes at international standard suffered from multiple fractures significantly more often than those at lower levels, probably reflecting the greater amount of intensive training they were undergoing. The diagnosis of stress fractures in young athletes relies on bone scanning (Rosen et al. 1982). Magnetic resonance imaging has a definite potential in diagnosing stress fractures in a safe way. Rest (Hulkko & Orava 1987; James et al. 1978) and nonweightbearing immobilisation (Torg et al. 1982) are the treatment forms most commonly used. Surgery is rarely indicated (Hulkko et al. 1985; Hulkko & Orava 1987; Torg et al. 1982).

3. Epiphyseal Plate Injuries Because of growth cartilage, and the process of growth itself, the bones and joints of young athletes are susceptible to specific injuries (Wilkins 1980). The epiphyseal plate is less resistant to shearing and tensile forces than the adjacent bone (Wilkins 1980). The epiphyseal area most susceptible to injuries is the zone of hypertrophy (Joki & Lynch 1985), where the matrix is weakened by the degeneration of the cartilage cells (Wilkins 1980). Approximately 10% of all skeletal trauma in children involves epiphyseal injuries (Pollen 1979), but only the absolute minority of these may produce subsequent long-lasting effects (Pappas 1983). The most commonly injured epiphysis is the distal radial epiphysis (Peterson & Peterson 1972). Most of the epiphyseal injuries associated with sports activity occur at about the onset of the adolescent growth spurt (Pappas 1983). The cortex of newly laid bone is thin, and less resistant to compressive stresses (Wilkins 1980). The injuries to the growth plate occurring dur-

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ing sports activity are the same as those incurred during other activities. The difference, and the factors determining the final result of a given injury, is the damage done to the cells in the reserve and proliferating zones of the growth plate (Jokl & Lynch 1985). If these cells or their blood supply (Wilkins 1980) are damaged irreversibly, growth disturbances may ensue (Brighton 1978), resulting in premature growth arrest and, at least theoretically, in limb length discrepancy and abnormal limb angulation (Pappas 1983; Williams 1981). Despite the marked increase in the participation of children in competitive sports, very few controlled clinical or biomechanical reports on the adverse effects of intensive training on the growth plate have been published (Albanese et al. 1989; Carter et al. 1988). Some authors believe that the presence of the open physis does not lead to a higher incidence of epiphyseal injuries (Garrick & Requa 1919). A study of 25 512 students during 1 year of sports participation did not show any deformities or crippling injuries, and only some permanent conditions (Zaricznyj et al. 1980). Larson and McMahon (1966) studied 1338 sports injuries, and reported an incidence of epiphyseal injuries of 6% in the 15 years and under age group. Adams (I 968} found that 96% of the Little League pitchers examined had had some form of injury to the medial epicondylar epiphysis. Other authors (Cahill et al. 1914; Lipscomb 1915; Rosegrant 1981) reported a lower incidence, and showed a decreasing trend, probably due to new regulations, tailor-made for young athletes. Tursz and Crost (1986) recently reported an incidence of sports-induced epiphyseal fractures in school children of 10%. Ofthese, 11% required internal fixation. Probably the most extensive analysis of acute injuries to the distal tibial epiphysis has been performed by MacNealy et al. (1982). 194 patients were reviewed, two-thirds of whom were boys. The most common fracture was the Salter-Harris type II (46.4%), followed by the Salter-Harris type III (25.2%), Salter-Harris type IV (l0.3%), the triplane fracture (9.8%) and Salter-Harris type I (5.1%), with

Sports Medicine 9 (4) 1990

excessive sudden external rotation accounting for 41.2% of the fractures. The growth plate may suffer from overuse injuries. Recently, 3 cases of premature growth plate closure of the distal radius in gymnasts were described (Albanese et al. 1989). Shortening of the radius and alteration of alignment of the distal radioulnar joint resulted. One patient underwent an ulna-shortening osteotomy. A repetitive compressive load was proposed as the aetiology ofthe condition. A Salter type I stress fracture of the distal end of the radius was described in 1 gymnasts and a roller skater (Carter et al. 1988). There was bilateral asymmetrical widening and irregularity of the epiphysis, with an ill-defined cystic appearance and flaring of the metaphysis. Rapid healing occurred with cessation of training. 21 young high performance gymnasts showed widening of the growth plate on both the radial and volar aspect of the epiphysis, associated with cystic changes, irregularities of the metaphyseal margin, and a beaked effect of the distal aspect of the epiphysis (Roy et al. 1985). These findings were consistent with a diagnosis of stress changes to the distal radial epiphysis. After a period of rest, no residual growth-related problems were observed. The olecranon epiphysis was affected in an adolescent baseball pitcher, and failed to unite promptly when operated on (Torg & Moyer 1911). In a 14-year-old break-dancer, the distal ulnar physis was affected, with displacement and widening, coupled with metaphyseal irregularities (Gerber et al. 1986). Rotational stresses were hypothesised to be the cause of the stress fracture of the proximal tibial epiphysis in a 15-year-old male crosscountry runner who had been running 40 to 50 miles (65 to 80km) per week for 2 months (Cahill 1911). Similar changes have been previously described by the same group in the proximal humeral epiphysis of Little League pitchers (Cahill et al. 1914).

4. Soft Tissue Injuries Soft tissue injuries may occur to tendons, ligaments and the enthesis. Several authors have studied tendons (Blanton & Biggs 1910; Barfred 1911)

Intensive Training in Ygung Athletes

and ligaments (Haut & Little 1969; Noyes et a1. 1974), but the relationship between their macroscopic behaviour and fine structure is still unclear (Elliot 1965). Furthermore, the properties of the collagenous structure are modified by exercise (Sommer 1987) and immobilisation (Noyes et a1. 1974). Tendons are constituted of collagenous tissue, arranged in parallel bundles to distribute muscular tensions equally to all parts of the insertions, at whatever position of the joint (Elliot 1965). The bundles lie in an amorphous matrix containing mucopolysaccarides (Jackson 1953). Developing tendons show a greater cellularity (Williams 1985) and a greater vascularity (Rothman & Slogoth 1967), than tendons taken from more mature animals. The diameter of the fibrils increases with age (Cetta et al. 1982). In young rats on an intensive running training regimen, tendons increase the total collagen quantity and decrease their ultimate tensile strength (Sommer 1987). In athletes, a tendon constitutes the weak link of the muscle-tendon-bone unit (Barfred 1971). In these cases, a rapid elongation of the muscle-tendon-bone unit with maximal muscle contraction may rupture a fully healthy tendon (Barfred 1971). Ligaments are composed of dense, regularly wavy collagen bundles (Amiel et a1. 1984). Compared with tendons, they show greater cellularity, with thin, spindle-shaped fibroblasts, less collagen and less mature collagen crosslinking pattern (Harper et a1. 1988). In practice, they are more stretchable and work in a purely passive way (Amis 1985). Ligaments may insert into bone either at a large angle, as the anterior cruciate ligament (Viidik 1966), or tangentially, as the medial collateralligament of the knee (Grood & Noyes 1976). In the first instance, the ligamentous fibres continue as Sharpey's fibres (Niepel & Sit'aj 1979; Viidik 1966). They gradually change from ligament to fibrocartilage to mineralised fibrocartilage to bone (Noyes et al. 1974), with the 2 fibrocartilagineous layers constituting an area of mechanical transition (Amis 1985). In case of tangential insertion, most of the fibres of the ligament insert over a large area of the fibrous periosteal layers (Laros et a1. 1971). No fi-

235

brocartilage zone is present, and the collagenous tissue lies directly on the bone (Noyes et a1. 1974). The relatively vascular fibrous tissue of the large angle insertion is then more prone to injury-mediated pathological changes (Amis 1985). The enthesis is the zone of insertion of tendons, ligaments and articular capsule into· bone (Niepel & Sit'aj 1979). All the elements of the skeletal system may be part of the enthesis (Niepel & Sit'aj 1979). At this region, the bone has an arrangement that allows it to withstand the traction forces applied to it through the ligament or the tendon (Heisler 1933). The peritenon, perichondrium and periosteum are highly vascular. Their supply comes from both bone and tendon (Moseley & Goldie 1963), and reflects their very active metabolism. During sports activities, the whole anatomical complex of the enthesis undergoes great dynamic loads (Niepel & Sit'aj 1979). Because the enthesis is metabolically active, local ischaemia can be an underlying cause for enthesopathies (Maffulli 1989). In this respect, heavy exercise may be a causative factor because most of the blood is taken up by the exercising muscle (Astrand & Rodahl 1986). The enthesis also undergoes high mechanical stresses, with possible traumatic inflammation, especially evident at the tendinous insertion of slow-reacting muscles (Niepel & Sit'aj 1979). As a result, there may be pathological enlargement of the tendinous insertion, with alteration of the bone profile and microcalcification (Maffulli et a1. 1987), or bursitis (Reilly & Nicholas 1987), with oedematous enlargement of the bursa and wall thickening (Ho & Tice 1979). In addition to bony injuries, tendons and ligaments can be injured in the intensively trained young athlete. In practice, very few controlled studies have addressed directly soft tissue injuries in intensively trained young athletes. The results obtained studying 'en passant' the incidence and severity of sports injuries in children and adolescents practising sports, but not intensively trained, can hardly be applied to young athletes undergoing training regimens of intensity and duration comparable with those of their adult counterparts. Probably the only study which has tackled this

236

problem is that of Orava and Saarela (1978). A total of 48 young track and field athletes in intensive training (mean age 13 years at the beginning of the study) were followed for 3 years. During the study period, 30 children had a total of 52 soft tissue exertion injuries. About one-third of these were various 'growth disorders', but the remaining twothirds were typical of intense athletic activity. The fact that the injuries were mild, not requiring surgery, and with a low recurrence rate is only relatively reassuring, as it is not known what the long term consequences can be. Because the resiliency and strength of the ligaments are greater than those of the physis and bone (Rang 1974), ligamentous lesions in children with open physes are regarded as rare (Clanton et al. 1979). In practice, avulsions of the ligamentous insertion into the bone occur much more frequently than ligamentous ruptures (Wilkins 1980), even though they are more common than previously noted (Kennedy 1979). Two studies have reported on knee ligament injuries in a total of 15 children aged 6 to 13.5 years (Bradley et al. 1979; Clanton et al. 1979). None of them had been injured during sports. A high incidence of tibial spine avulsion coupled with medial collateral ligament injury was noted (Clanton et al. 1979). Anterior cruciate ligamentous injuries were reviewed in 24 patients aged 12 to 15 years who underwent surgery (Lipscomb & Anderson 1981). 23 of them obtained good to excellent results at an average follow-up of 3 years after surgery. Acute insufficiency of the posterior cruciate ligaments has been described in 2 boys of 6 and 8 years (Sanders et al. 1980). It appears that in this age group failure to diagnose and repair a knee ligament injury will lead to late instability (Lipscomb & Anderson 1981). Appropriate surgical repair is the preferred treatment (Singer 1987). In any knee injury in the skeletally immature athlete, it is necessary to exclude an epiphyseal fracture as opposed to a collateral ligament injury (Shelton & Canale 1979). Orava and Saarela (1978) described some cases of Achilles tendon peritendonitis. peroneal tenosynovitis and patellar tendon pain in a group of

Sports Medicine 9 (4) 1990

young athletes, for an overall incidence of 17%. The most frequent knee injury in adolescent runners is patellofemoral stress, while posterior tibial tendonitis is the most frequent tendinopathy encountered (Paty & Swafford 1984). In our series of 47 runners, 6 of whom were adolescents between 14 and 18 years, the ultrasonographic findings in Achilles tendinopathy were not different from what was found in older runners (Maffulli et al. 1987). From a therapeutic view point, a period of 'relative rest' is necessary. In practice, the limb is used with a different stress pattern. The training programme should be adjusted so that the fitness state is maintained (Bishop et al. 1989; Moroz & Houston 1987). Eccentric contractions may be performed during the early healing phase of a tendonitis to promote healing (Stanish 1981).

5. Osteochondritis Dissecans Osteochondritis dissecans is a disorder of joint surfaces in which a segment of subchondral bone becomes avascular and, with the articular cartilage covering it, may separate from the surrounding bone forming a loose body (Aichroth 1971; Smillie 1960). The aetiopathogenesis of the condition remains uncertain (Barrie 1987). Intense physical activity and high level sport were frequently encountered and considered a causative factor in young patients suffering from osteochondritis dissecans of the knee (Aichroth 1971). Osteochondritis dissecans may produce degenerative changes because of loose body formation or the residual deformity of the joint surface. However, if osteochondritis dissecans occurred before epiphyseal fusion, the chances of degeneration are low (Linden 1977). The joints most commonly affected are the knee (lateral aspect of the medial femoral condyle), the hip (femoral head), the ankle (talus) and the elbow (humeral capitellum). Two groups of patients have been identified, one of children below 15, and one of adults up to 50 years of age (Clanton & DeLee 1982). Recently, the lesions of the femoral condyles seen in 5000 consecutive arthroscopies performed by one surgeon in II years were reviewed (Bradley

237

Intensive Training in Young Athletes

& Dandy 1989). The definition of osteochondritis dissecans was 'an expanding concentric lesion at the margin of an otherwise normal epiphysis' (Bradley & Dandy 1989). Osteocondritis dissecans was classified in 'developing' and 'late' (Bradley & Dandy 1989). The number of patients showing lesions meeting the criterion for developing osteochondritis dissecans was 16, of an average age of 13.6 years. The male: female ratio was 2 : 1 (Bradley & Dandy 1989). Osteochondritis dissecans of the elbow is unusual (Roberts & Hughes 1950; Woodward & Bianco 1975). It generally affects the humeral capitellum (Ellman 1967: Weisl 1967), although the radial head may be involved (Dennes 1953; Roberts & Hughes 1950). Six cases were reported by Adams (1965) in Little League pitchers. Pitching was identified as a cause of permanent joint damage. 12 children aged 13 to 17 years at surgery and followed-up from 1 to 7 years were reviewed (Tivnon et al. 1976). Two cases required further surgery with partial excision of the capitellum. The results were excellent only in 1 athlete. A recognised aetiological factor in young sportsmen is repetitive valgus stress, resulting in compression overuse injury of the lateral compartment of the elbow (Andrews 1985), potentially leading to permanent disability in inexperienced throwing athletes (DeHaven & Evarts 1973). Most reports have focused on throwing, but some athletes may develop osteochondritis dissecans of the elbow due to repetitive compressive stresses on the hands being transmitted to the elbow. This is the case in competitive diving (Kimball et al. 1985) and boxing (Hay 1950), and possibly in gymnastics and BMX riding (Fixsen & Maffulli 1989). The articular cartilage of a joint affected by osteochondritis dissecans may appear intact (Aichroth 1971, 1983) and, at times, given the length of time before the actual operation, cartilage healing could have taken place (Mitchell & Shepard 1980; Salter et al. 1980). Management of osteochondritis dissecans depends on the state of the lesion and on the age of the athlete (Stanitski 1988). In the appropriate joints, arthroscopy is the procedure of choice (Bradley & Dandy 1989). Nonoperative treatment

in skeletally immature young athletes may allow resolution in circumscribed stable lesions (Stanitski 1988). Surgical or arthroscopic removal of intra-articular loose bodies resulting from late osteochondritis dissecans is mandatory, so as to allow early return to the sport and avoid permanent disability in the young athlete.

6. Apophysitides Degeneration of the centre of growth or ossification where major tendons attach may lead to a chronic inflammation and avulsion of cartilage and bone from the developing area, with tendinous microtears and haemorrhages (Wilkins 1980). Common sites are the inferior pole of the patella (Sinding-Larsen-Johansson disease), the tibial tubercle (Osgood-Schlatter's disease) and the calcaneal apophysis where the Achilles tendon is inserted (Sever's disease). Sinding-Larsen-Johansson disease is a syndrome of tenderness and radiographic fragmentation at the inferior pole of the patella. The lesion is considered a calcification in an avulsed portion of the patellar tendon (Medlar & Lyne 1978), supporting its classification as a traction apophysitis (Rosenthal & Levine 1977). In a perspective study of 10 knees in 8 patients aged 10 to 13 years, one of whom was female, it was concluded that the condition is self-limiting (Medlar & Lyne 1978). All male patients were vigorous athletes. One of them had an associated bilateral Osgood-Schlatter disease, another had bilateral Sever's disease. A mature tibial tubercle forms from ossification centres in the epiphysis, and shows 4 stages of maturation from cartilage stage to closure of the growth plate (Ogden et al. 1975). The pulling action by the patellar tendon may cause inflammation by the above described mechanism. The apophysis of the tibial tuberosity shows adaptive changes to tensile stresses (Ogden et al. 1975), with direct correlation between the amount of fibrous tissue and the traction exerted on the tuberosity (Ogden et al. 1975). The lesion occurs between 8 and 13 years in girls, and 10 and 15 years in boys (Kulund 1982). Eh-

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renborg (1962) evaluated the results of conservative treatment of 218 knees in 170 children. In the plaster cast immobilisation group the disease lasted an average of 14.6 months, and in the nonimmobilised group it lasted an average of 27.8 months. In the first group, one-third of the patients showed considerable deformity of the tibial tuberosity or loose fragments compared with one-half of the nonimmobilised cases. Operative treatment for removal of loose fragments trying to achieve a more rapid relief of the symptoms has been reported (King & Blundell-Jones 1981). Osgood-Schlatter's disease was found to be the most frequent exertion injury in the knee of adolescent athletes, with 24 cases, 6 of which were bilateral, out of a total of 46 knee injuries (Orava & Puranen 1978), and a total of 20 cases in 157 athletic children (Kannus et al. 1988). In both these series boys were nearly twice as affected as girls. Recently, 68 athletes with Osgood-Schlatter's disease were reviewed (Kujala et al. 1985). The age of first occurrence was 13.1 years. The disease interfered with training for an average of 7.3 months. The incidence of OsgoodSchlatter's disease was significantly higher in siblings and in the patients who had also suffered from Sever's disease. Recently, high resolution ultrasonography was performed in 82 young patients in which a clinical diagnosis of Osgood-Schlatter's disease had been made. Their age ranged from 10 to 15 years (mean 13 years), and 71 patients were male. It was shown that there is not a single underlying pathology, and at least 4 ultrasonic pictures can account for the same symptomatology and clinical diagnosis (De Aaviis et al. 1989). In particular: 1. The ossification centre may be normal, but the cartilage is swollen and the subcutaneous tissues appear displaced forward. 2. In addition to the above mentioned changes, the nucleus is fragmented and hypoechoic. 3. The main pathology is patellar tendinitis, with or without involvement of the ossification centre 4. Infrapatellar bursitis is evident, with or without involvement of the ossification centre. An asymptomatic radiographic fragmentation

Sports Medicine 9 (4) 1990

of the proximal pole of the patella has been described in 6 boys aged 10 to 11 years (Batten & Menelaus 1985). Four of them had Osgood-Schlatter disease or Sinding-Larsen-Johansson disease in the same or contralateral knee. Radiographic findings returned to normal in a boy followed up for 2 years. The calcaneal apophysis serves as attachment for the Achilles tendon superiorly and for the plantar fascia and the short muscles of the sole of the foot inferiorly. Sever's disease consists of local tenderness in the posteroinferior or inferior surface of the heel and radiographic appearance of disordered ossification of the calcaneal apophysis (Katz 1981). It is the most common cause of heel pain in the growing athlete (Micheli 1983). The condition is easily treated with physical therapy and rest (McKenzie et al. 1981; Micheli & Ireland 1987). A series of 20 patients showed reduction of symptoms within 1 month from the diagnosis in 75% of the patients, and in 95% within 3 months (McKenzie et al. 1981). 85 children, for a total of 137 heels, were recently studied (Micheli & Ireland 1987). Threequarters of the patients were boys. The overall average age at presentation was 11 years 7 months. The sports which most often exacerbated the symptoms were soccer for boys and gymnastics for girls. All patients were treated with physiotherapy, and 98% of them were prescribed orthotics. All patients were able to return to their sport 2 months after the diagnosis. The condition recurred in 2 patients. Both these series reported a high incidence of foot malalignment. Weightbearing and sports activity may contribute to the symptoms either by excessive traction at the insertions of the tendon and fascia, or as a result of direct pressure (Katz 1981).

7. Lumbar Disc Lesions The association between some sports, namely gymnastics, dance, soccer, weightlifting and running (Dzioba 1985; Letts et al. 1986; Matheson et al. 1987; Teitz 1982; Wiltse et al. 1975) and spondylolisis and spondylolisthesis has been widely recognised. A much less frequent factor in low back

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pain in adolescent athletes is lumbar disc protrusion. The role of continuous bony microtrauma is not clear. In a recent study of 36 former competitive female gymnasts and 10 general female gymnasts, all examined at least 3 years after retiring from sports, more than half of them showed degenerative changes of the vertebral bodies and the intervertebral joints (Wismach & Krause 1988). In a study of 70 adolescents between the age of 9 and 19 undergoing surgery for lumbar disc herniation, 22 were injured during sports activities, and 26 were routinely participating in sports (Kurihara & Kataoka 1980). Not all the patients suffered back pain, but they all eventually developed sciatica. Recently, in a study of 87 adolescents aged 13 to 18 years treated for lumbar disc prolapse, contact sports accounted for 12 cases and gymnastics for 8 (Ghabrial & Tarrant 1989). Leg pain was absent in about half of the patients, but limited straight leg raising was present in 10 youngsters without any evidence of leg pain. Only one-third were operated on, and all were treated with bed rest and physiotherapy. A swollen disc with increased nuclear tension but no sequestration was always found. The true incidence of the lesion in sporting children is unknown, and no conclusion can be made. The role of acute trauma as an aetiological factor in the development of disc herniation in young and very young patients has been stressed (Epstein & Lavine 1974), but degenerative changes may playa leading role, with trauma acting just as a precipitating factor (Borgesen & Yang 1974). A single traumatic episode is probably not sufficient to produce a disc prolapse unless a degenerative condition is present. This could explain the infrequency of the lesion in children, and hence in intensively trained young athletes.

8. Conclusions The risk of injury is intrinsic to any sport, and the specific pattern of injuries of specific sports should be known by health professionals. Children are not just adults in miniature, and they should

not be assumed to be capable of the same amount and quality of exertion as adults. Probably, it is safe for the children to follow the' I 0% rule' (Micheli 1986), which states that the intensity of any training programme should not be progressed more that 10% per week. Preparation and performance standards should take into account the chronological and biological age of the participants, as well as their physical and psychological immaturity. All adults dealing with high standard athletic children should be willing not to exploit their own ego through the youngsters, but to maintain the well-being of the children under their care, while helping them to improve their athletic performance. A better insight of the different aspects of training theory, including duration, intensity, frequency and recovery, are needed to avoid serious damage to the skeletal system of athletic children. When planning a training programme for youngsters, it is important to consider the physiological maturation process to which children undergo. Time is needed for the growing child to incorporate his own body changes, and probably little room is left at this critical stage for developing speed, strength and resistance (Wojtys 1987).

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Author's address: Dr Nicola Ma.f]Ulli, Institute of Child Health, Respiratory and Anaesthetic Unit, Sports Medicine Laboratory, 30 Guilford Street, London WCI, England.