**7. Hamstring muscle**

The hamstring is one of the muscle groups most affected by injuries in athletes. They often suffer strains localized in the muscle-tendon junction due to an eccentric contraction. The lesions may occur in different areas: proximal or distal muscle-tendon junction, muscle belly, the proximal and distal tendon insertion [29].

Usually hamstring injurues are treated conservatively with rest, ice, physical therapy, NSAIDs and a gradual return to sport. Rarely a lesion in this anatomical site requires surgical treatment.

One of the rare occasions when the patient may have to undergo surgery is when the hamstring is detached from the ischial tuberosity. This injury is rare but its incidence is increasing, especially in middle-aged patients who continue to be physically active [30]. The triggering mechanism of injury is a sudden flexion of the hip and extension of the knee that causes a contraction of the hamstring. The patient reports feeling a shot in the rear thigh and walks with his leg straight (stiff-legged gait) avoiding flexing hip and knee in order to relieve the pain.

The hamstring avulsion from the ischial tuberosity is not always treated surgically. Presently there is no commonly accepted classification, or any guidelines to be followed for treatment [29]. The current literature recommends conservative treatment if the injury affects only one tendon and the retraction does not exceed 1 - 2 cm. The single damaged tendon tends to heal by adhering to intact neighboring tendons and even professional athletes will be able to return to competitive activity within about 6 weeks from injury.

muscles should be encouraged to reduce muscle atrophy as well as ankle pumps to prevent

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The results of surgical treatment reported in literature appear to be satisfactory with 62 -90% of patients satisfied with return to sporting activity levels the same as before the injury [33, 34, 35, 36]. A recent review of the literature [37] shows that early surgical treatment guarantees a better performance in terms of rate of return to sports, patient subjective satisfaction, recovery of strength and performance compared to conservative treatment. Unfortunately the results presented in literature are not easy to interpret because the techniques used are varied and,

The results of the operation depend on many factors. The timing of surgery seems crucial as after 14 days from injury there is a higher risk of adhesions between the lesion and the sciatic nerve [38] so surgery should be performed before this limit. If surgery is performed after five weeks, the post-operative cast must be worn for a longer perid of time [39]. It is not clear how the retraction of the tendon influences the treatment decisions : while in children retraction is an important factor in avulsion fractures, in skeletally mature subjects the importance of retraction has not yet been demonstrated. It has been shown how the level of retraction changes if observed on MRI or intra-operatively and it is closely related to hip and knee flexion and

Another rare lesion that can take place to the hamstring is a lesion to the distal insertion. In literature this injury is briefly described and the need for surgery is indicated although no more than 10 case reports and one case series with only a few patients enrolled, have been published. The most common in the distal region is the avulsion of the biceps femoris associated with a multiligamentous lesion of the knee with a trauma in varus and hyperextension [40]. This muscle is an important and strong flexor and an active stabilizer of the knee and its injury can cause weakness and instability of the knee, especially in athletes [41]. Moreover, in the case of partial tears, the haphazard rearrangement of scar tissue and the formation of adhesions may jeopardize competitive sport activity because it causes pain. From an analysis of the 19 cases present in literature [41], it can be concluded that this type of injury, both complete and incomplete, allows the return to competition and that sometimes conservative treatment of

The semimembranosus muscle has a role in flexion and internal rotation of the tibia. An injury to its distal portion determines a worse prognosis for players than the biceps femoris. There are fewer reports in literature (6 cases) [41], and it seems that the early reconstruction of total lesions lead to good results (2 cases). However, in the case of partial lesions, despite late reconstruction (4 cases), the subjects were unable to return to the same level of sporting activity as performed before previous to the injury. Biopsies performed on the unhealed muscles showed a severe denervation of muscle fibers. We can therefore suppose that a partial tear of the distal myotendinous junction of this muscle can cause serious nerve damage and determine

The semitendinosus muscle contributes to flexion strength at high degrees of knee flexion and intrarotation of the tibia. The tendon of this muscle is often harvested for use as a graft for

partial tears may eventually require surgery to stop the painful symptoms.

deep vein thrombosis [30].

muscle activation [29].

a worse prognosis [41].

being a rather rare lesion, the cases analyzed are few.

The rupture of three tendons usually causes a major retraction of the stumps (greater than 5 cm) and in this case surgical treatment is recommended.

When two tendons are completely damaged, the regimen is not clear and depends on the physician's personal experience. Surgery is generally recommended if the patient is less than 50 years old, active and participating in athletic activities. Furthermore, the retraction of the stumps for more than 2 cm may be the indirect sign of injury to the third muscle at the muscletendon junction or in the muscle belly; that has gone unseen at diagnosis, making surgery absolutely necessary [30]. It should be remembered that the MRI is difficult to interpret with certainty when multiple tendons are damaged in this region.

Conservative treatment lead to a reduction of strength in the knee flexion and extension of the hip; also a superabundant scar could entrap the sciatic nerve, which runs nearby, giving rise to a "hamstring syndrome". The cause of neurological symptoms in the sciatic nerve is not well defined and remains ambiguous: it is possible that the fibrotic scar tissue generated from the lesion could lead to adhesions with the nerve, it is possible that the detached bone of the tuberosity forms a callus which compresses the nerve, or that the hamstrings during retraction cause the sciatic nerve or one of its branches to stretch [31].

Surgical treatment provides for an incision (longitudinal or transverse) on the posterior side of the proximal thigh, once tendons are isolated, the surface of the ischial tuberosity is debrided, the injured tendons are reinserted with bone anchors and if necessary, the neurolysis of the sciatic nerve is performed to free it from any adhesions.

There is no "one and only" postoperative care in literature; some authors recommend to avoiding using a cast; at least one suggests keeping the knee flexed at 30 ° [29], others recommend a splint at 90 ° for 2 weeks followed by a gradual lengthening of the knee [31], others advise protecting the affected hip with a cast to be worn for 6 weeks that allows only movements between 15 ° and 30 ° of flexion [30]. This is followed by a a gradual recovery of the joint's ROM and muscle strength during which time it is important to avoid too much tension on the insertion of the proximal hamstring in the first post-operative period. In particular, passive aggressive stretching should be avoided in the first 3 months post-op [29]. The return to sports-specific conditioning is expected between 6-9 months after surgery. It should be kept in mind that the full recovery of muscle strength requires a long time; often more than a year is needed to obtain an equal force in both legs. Residual muscle atrophy is common, especially in the long head of the biceps which results in a compensa‐ tory hypertrophy of the short head [32].

In the preoperative period hamstring stretching exercises should be avoided to prevent further distancing of the ends of the lesion; instead isometric contractions of the quadriceps and gluteal muscles should be encouraged to reduce muscle atrophy as well as ankle pumps to prevent deep vein thrombosis [30].

The hamstring avulsion from the ischial tuberosity is not always treated surgically. Presently there is no commonly accepted classification, or any guidelines to be followed for treatment [29]. The current literature recommends conservative treatment if the injury affects only one tendon and the retraction does not exceed 1 - 2 cm. The single damaged tendon tends to heal by adhering to intact neighboring tendons and even professional athletes will be able to return

The rupture of three tendons usually causes a major retraction of the stumps (greater than 5

When two tendons are completely damaged, the regimen is not clear and depends on the physician's personal experience. Surgery is generally recommended if the patient is less than 50 years old, active and participating in athletic activities. Furthermore, the retraction of the stumps for more than 2 cm may be the indirect sign of injury to the third muscle at the muscletendon junction or in the muscle belly; that has gone unseen at diagnosis, making surgery absolutely necessary [30]. It should be remembered that the MRI is difficult to interpret with

Conservative treatment lead to a reduction of strength in the knee flexion and extension of the hip; also a superabundant scar could entrap the sciatic nerve, which runs nearby, giving rise to a "hamstring syndrome". The cause of neurological symptoms in the sciatic nerve is not well defined and remains ambiguous: it is possible that the fibrotic scar tissue generated from the lesion could lead to adhesions with the nerve, it is possible that the detached bone of the tuberosity forms a callus which compresses the nerve, or that the hamstrings during retraction

Surgical treatment provides for an incision (longitudinal or transverse) on the posterior side of the proximal thigh, once tendons are isolated, the surface of the ischial tuberosity is debrided, the injured tendons are reinserted with bone anchors and if necessary, the neurolysis

There is no "one and only" postoperative care in literature; some authors recommend to avoiding using a cast; at least one suggests keeping the knee flexed at 30 ° [29], others recommend a splint at 90 ° for 2 weeks followed by a gradual lengthening of the knee [31], others advise protecting the affected hip with a cast to be worn for 6 weeks that allows only movements between 15 ° and 30 ° of flexion [30]. This is followed by a a gradual recovery of the joint's ROM and muscle strength during which time it is important to avoid too much tension on the insertion of the proximal hamstring in the first post-operative period. In particular, passive aggressive stretching should be avoided in the first 3 months post-op [29]. The return to sports-specific conditioning is expected between 6-9 months after surgery. It should be kept in mind that the full recovery of muscle strength requires a long time; often more than a year is needed to obtain an equal force in both legs. Residual muscle atrophy is common, especially in the long head of the biceps which results in a compensa‐

In the preoperative period hamstring stretching exercises should be avoided to prevent further distancing of the ends of the lesion; instead isometric contractions of the quadriceps and gluteal

to competitive activity within about 6 weeks from injury.

228 Muscle Injuries in Sport Medicine

cm) and in this case surgical treatment is recommended.

certainty when multiple tendons are damaged in this region.

cause the sciatic nerve or one of its branches to stretch [31].

of the sciatic nerve is performed to free it from any adhesions.

tory hypertrophy of the short head [32].

The results of surgical treatment reported in literature appear to be satisfactory with 62 -90% of patients satisfied with return to sporting activity levels the same as before the injury [33, 34, 35, 36]. A recent review of the literature [37] shows that early surgical treatment guarantees a better performance in terms of rate of return to sports, patient subjective satisfaction, recovery of strength and performance compared to conservative treatment. Unfortunately the results presented in literature are not easy to interpret because the techniques used are varied and, being a rather rare lesion, the cases analyzed are few.

The results of the operation depend on many factors. The timing of surgery seems crucial as after 14 days from injury there is a higher risk of adhesions between the lesion and the sciatic nerve [38] so surgery should be performed before this limit. If surgery is performed after five weeks, the post-operative cast must be worn for a longer perid of time [39]. It is not clear how the retraction of the tendon influences the treatment decisions : while in children retraction is an important factor in avulsion fractures, in skeletally mature subjects the importance of retraction has not yet been demonstrated. It has been shown how the level of retraction changes if observed on MRI or intra-operatively and it is closely related to hip and knee flexion and muscle activation [29].

Another rare lesion that can take place to the hamstring is a lesion to the distal insertion. In literature this injury is briefly described and the need for surgery is indicated although no more than 10 case reports and one case series with only a few patients enrolled, have been published.

The most common in the distal region is the avulsion of the biceps femoris associated with a multiligamentous lesion of the knee with a trauma in varus and hyperextension [40]. This muscle is an important and strong flexor and an active stabilizer of the knee and its injury can cause weakness and instability of the knee, especially in athletes [41]. Moreover, in the case of partial tears, the haphazard rearrangement of scar tissue and the formation of adhesions may jeopardize competitive sport activity because it causes pain. From an analysis of the 19 cases present in literature [41], it can be concluded that this type of injury, both complete and incomplete, allows the return to competition and that sometimes conservative treatment of partial tears may eventually require surgery to stop the painful symptoms.

The semimembranosus muscle has a role in flexion and internal rotation of the tibia. An injury to its distal portion determines a worse prognosis for players than the biceps femoris. There are fewer reports in literature (6 cases) [41], and it seems that the early reconstruction of total lesions lead to good results (2 cases). However, in the case of partial lesions, despite late reconstruction (4 cases), the subjects were unable to return to the same level of sporting activity as performed before previous to the injury. Biopsies performed on the unhealed muscles showed a severe denervation of muscle fibers. We can therefore suppose that a partial tear of the distal myotendinous junction of this muscle can cause serious nerve damage and determine a worse prognosis [41].

The semitendinosus muscle contributes to flexion strength at high degrees of knee flexion and intrarotation of the tibia. The tendon of this muscle is often harvested for use as a graft for reconstruction of the anterior cruciate ligament, so in theory it is an "expendable" tendon. Indeed it has been shown that athletes who have had removed their semitendinosus tendon were able to return to the previous level of activity without the harvest causing an important deficit in the competitive performance [42]. A traumatic injury of this region, however, can result in a partial or total lesion that causes pain, and interferes with the physical activity of the patient. Also in this case few articles are available in literature and it is not clear when it is advisable to choose conservative treatment and when to opt for surgical treatment. From our literature search we found 25 cases described [40, 41, 43, 44], 14 patients had been treated conservatively and 11 surgically. The surgery in all cases was a tenotomy with eventual release of adhesions, in no case was a suture performed to restore the damaged anatomical structure. In 5 of the 14 cases (35%) treated conservatively there was a treatment failure and the patient needed surgery that subsequently gave good results. Of the 11 patients treated surgically al returned to their previous level of athletic activities.

structures is not essential for a high athletic performance and electromyographical studies support the idea that the abductor muscles do not play a key role in sprinting and cutting

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The most recent study with the largest series includes 19 players of the American National Football League (NFL) [49], 14 were treated conservatively and 5 surgically. The authors conclude that although all the players returned to play in the top league, those who received conservative treatment returned to the field sooner (6.1 + / - 3.1 weeks) than those treated surgically (12.0 + / - 2.5 weeks). Moreover, besides the risk of complications with surgery, the operation is not easy to perform if the lesion is at the level of the muscle-tendon junction [45]. The information available in the literature on this subject is scarce, with a low level of evidence and often conflicting. Some authors recommend surgery to suture / reinsert in the case of acute injuries occurring in athletes and excision / tenotomy in the case of inveterate injuries; other authors do not recommend surgery because it extends recovery time and does not guarantee better results than conservative treatment, considering also the non fundamental function of this muscle group in sport activities. Much still needs to be understood in this regards and future studies should be conducted with better methods and possibly with a larger number of

Few studies in the literature have compared muscle suture and immobilization. Animal studies, usually in the Sprague-Dawley rat, have shown that lesions performed for experi‐ mental purposes heal better if sutured. Almekinders [52] has shown that the benefits obtained by suturing muscles are significant at one week after injury, while at two weeks surgical treatment or treatment with simple immobilization bring the same results in terms of maxi‐ mum failure load, active force generation as well as from the histological point of view. Menetrey [3] instead found significant improvements with suturing muscle in respect to not suturing and immobilization; in fact one month after the injury the sutured muscle produced 81% of the tetanus strength misured in the intact muscle, while the non sutured muscle produced 35% and the immobilized muscle 18%. It is evident how the overabundance of connective tissue in the scar tissue inhibits the formation of myofibers at 12 weeks [1] whereas the suture prevents the formation of scar tissue in depth; it restricts the formation of hematoma by decreasing the gap of the lesion and the infiltration of mononuclear cells is limited to the surface region only. Desmin's detection has proved that the greatest number of regenerating myofibers is in the sutured muscle already at 2 days after injury, this is not because it limits the inflammatory phase or cellular necrosis (that occurs anyway) but probably because it produces a microenvironment favorable to repair, keeping the muscle stumps together [3]. Clearly the results of the animal tests should be interpreted with caution for several reasons: the lesion that is created is a surgical one, metabolism and healing of the lesion are different between humans and rats. In humans, the only studies comparing surgery and conservative treatment are about lesions of the biceps brachii [25, 53] where the best results are had in

movements [50, 51].

patients.

**9. Suture versus immobilization**

The study with the largest case series [40] emphasized that early surgical treatment (within 4 weeks from injury) leads to a much earlier return to sports: with conservative treatment (7 cases) return to sport occurs at an average of 18.4 weeks, with surgery (5 cases) at 6.8 weeks, while if conservative treatment fails and surgery is needed (5 cases), return to the field is much later, at 29.6 weeks on average. Unfortunately, however, the results are not statistically significant because of the small sample number.
