Hamstring injuries are common in athletic populations and can affect all levels of athletes. From 1989 to 1998, the National Football League surveillance systems identified 1716 hamstring strains amongst all players, with range of 132-210 injuries per year. This accounts for an overall injury rate of 0.77 per 1000 athlete-exposures and a reinjury rate of 16.5%. This is consistent with the rate of muscle strain in high school (12-24%) and collegiate football (18.9-22.2%).
Hamstring injuries can range from musculotendinous strains (partial tears) to avulsion injuries (complete tears). By definition a strain is a partial or complete disruption of the musculotendinous unit. A complete tear or avulsion, in contrast, is a discontinuity of the tendon bone unit (where it tears off the bone). Most hamstring strains do not require surgery and resolve with a variety of treatment including physical therapy and rest. The most important point in evaluating these injuries is to differentiate the complete or partial tears from the muscle strain subgroup, because patients with a complete tear can suffer from more significant disabilities and inability to return to their prior activity levels.
Anatomy of the Hamstrings
With the exception of the short head of the biceps femoris, the hamstring complex begins at the ischial tuberosity (sit bone) and end below the knee on the inside part of the leg bone. The proximal (beginning part) of the hamstring complex has a strong bony attachment on the ischial tuberosity (sit bone) (Figure 1).
Their footprint on the ischium is made up of the semitendinosus and the long head of biceps femoris beginning as a common proximal tendon and footprint, and a separate semimembranosus footprint.
Problems After a Hamstring Injury
The history of an acute injury usually involves a traumatic event with forced hip flexion and knee in extension, as is classically observed in waterskiing. However, the injury can result from a wide variety of sporting activities that require rapid acceleration and deceleration (starts and stops).
Proximal hamstring injuries can be categorized as complete tendinous avulsions, partial tendinous avulsions, apophyseal avulsions, and degenerative (tendinosis) avulsions. Degenerative tears of the hamstring origin can occur more slowly and are commonly seen as an overuse injury in middle- and long-distance runners. Repetitive irritation of the inner part of the hamstring tendon (typically along the lateral aspect of the tuberosity, where the bursa resides) can ultimately cause a tear of the tendon as well as chronic pain on sitting.
Commonly, athletes with proximal hamstring tendon tears can describe a popping or tearing sensation with associated pain and bruising over the back of the hip. They may also find themselves to have weakness with bending the knee or giving out in the hip. Some patients may also complain of a pins and needle sensation over the back of the leg and thigh, much like sciatica. This may be due to acute compression of bleeding from the injury in the area of the sciatic nerve or may happen with scar tissue and tethering of the tendon to the nerve.
Symptoms of ischial bursitis include buttock pain or hip pain, and localized tenderness overlying the ischial tuberosity. Additional symptoms of chronic ischial bursitis may include tingling into the buttock that spreads down the leg. This is presumably from local inflammation and swelling in the area of the sciatic nerve. The symptoms usually worsen while sitting. Most of the people affected tend to sit with the painful buttock elevated off their seat.
Examination in the Doctor’s Office
A physical examination is typically performed with the patient in the prone (belly down) position. Examination with the knee slightly flexed will limit muscle spasms and make examination more comfortable in acute ruptures. There may be a lot of muscle spasm and bruising may also be seen. The entire back of the thigh may be very tender to the touch. In the acute injuries there is typically focal tenderness and swelling. However, with after a few days to one week, there is more likely to be diffuse swelling and tenderness in the whole thigh. Low-grade strains typically have limited swelling and tenderness, while in the more severe strain a defect may be felt in the area of tearing.
MRI and Xrays
After the history and physical examination have been completed by your doctor, and there is a high level of suspicion of hamstring injury x-rays of the pelvis may be performed to rule out any breaks in the bone. If a fracture is identified, a CT scan may assist in the assessment of displacement and fracture configuration for a possible surgical procedure. More commonly, no fractures are identified and an MRI is ordered to look at the area of a possible tear.
In some cases a hamstring injury can be evaluated with ultrasound (U/S) in the office. While U/S can be extremely user specific it can also be highly accurate to evaluate partial tears and partial tears. It can help the physician make a decision on how to approach the treatment.
Partial hamstring injuries are most commonly treated without surgery. Initial treatment consists of active rest, oral non-steroidal anti-inflammatory medications (such as Ibuprofen) and a physical therapy program, consisting of a gentle hamstring stretching and a strengthening program. As the initial symptoms go away, exercises can be added in association with a more aggressive hamstring injury prevention program. Full return to sports and activities are allowed when you are asymptomatic. This can take four to six weeks.
If you are unable to progress with this program, an U/S guided corticosteroid injection may be used and has been shown to provide initial relief in up to 50% of patients at one month following a partial tear. A platelet rich plasma (PRP) injection may be suggested by your doctor, instead of a cortisone injection. Failure of nonoperative treatment of partial tears may benefit from surgical clean-up and repair, similar to other commonly seen partial tendon tears in other areas of the body (patella, quadriceps, and biceps).
Nonoperative treatment of complete ruptures of the proximal hamstring is less frequently recommended since surgical repair has been more recognized and has had successful results in several studies. This is especially important in those patients that are highly active. One study identified 12 water skiers with hamstring avulsion injuries, which he treated initially with nonoperative means. It was found that 83% of the patients had persistent cramping or pulling sensation with vigorous activity. Seven patients returned to sports activities but at a lower level. Five patients were only able to do limited activities. Overall, these patients had 61% of hamstring strength deficit and 23% quadriceps deficit. Two of these patients were persistently dissatisfied with their function, eventually leading to delayed surgical repairs.
After developing experience in the open management of these injuries, I have developed an endoscopic technique that allows a safe approach to the area of damage in most tears. It is expected that the benefits of a more direct approach, without a large incision should be easier to recover from as well as cause less pain. With the use of endoscopic magnification to protect the sciatic nerve, this treatment also improves the management of these injuries and reduces the problems associated with an open approach.
The technique positions the patient on their belly after being put under anesthesia. The back part of the hip is then sterilized assuring that the leg and thigh are free so that the leg and hip can be re-positioned during surgery.
Two or three incisions are then made as shown in the picture above. Using the arthroscopic equipment that is commonly used for arthroscopy of many other joints, including the hip and shoulder, the area of the hamstring tendon tearing is found. In addition, the sciatic nerve is identified and protected during the case to assure that no damage is done to the area of the nerve.
With the nerve identified and protected tendon edges are cleared of any torn and devitalized tissue and a repair of the tendon is then done using suture material that is anchored to the bone. In some cases, there is ischial bursitis that also has to be removed. In those cases, the bursa will reform after about three months with no residual problems, in most patients.
Following this type of surgery, the patient is fitted with a knee brace that is fixed at 90º of flexion for four weeks in order to limit not only weight bearing, but also to restrict movement of the hamstring tendons and protect the repair. At four weeks, the knee is gradually extended by about 30º per week in order to allow full weight bearing by six to eight weeks, while maintaining the use of crutches. Physical therapy is instituted at this point, with the initial phase focused on hip and knee range of motion. Hamstring strengthening is begun at about ten to twelve weeks. Dry land training and sport specific training are initiated at 12 weeks with return to full sports participation between 5 to 8 months.
Problems After Surgery (Complications)
It is important when considering surgical repair of proximal hamstring injuries to not only consider the benefits but the risks as well. There are complications associated with proximal hamstring ruptures even prior to surgical treatment, related to the type of injury and they can be early or delayed. The early complications most commonly involve a neuropraxia (injury to the sciatic nerve) as a result of a stretch injury. Depending on the mechanism and force of the injury the sciatic nerve can be damaged leading to burning symptoms radiating down the leg and weakness of the foot. This is critical to determine during the initial examination to document and ensure that there is no additional injury at the time of surgery. Fortunately however, a neuropraxia injury most commonly goes over time, despite being troubling initially. The problem can last several weeks. Delayed problems from nonoperative treatment of proximal hamstring ruptures have been include weakness in bending the knee and hip extension weakness, difficulty sitting, hamstring deformity, and the potential development of symptoms associated with scar tissue to the sciatic nerve. Pain may worsen with stretching and during exercises such as sprinting, hurdling, kicking.
Surgical for proximal hamstring ruptures also has its inherent risks. Superficial as well as deep wound infections can occur similar to any other surgeries, however, the location of the incision can potentially increase this risk due to the proximity of the incision to urination and bowel movements. Additionally there are three main nervous structures at risk and they are the posterior femoral cutaneous (PFC), inferior gluteal nerve, and sciatic nerves. The PFC nerve runs down the back of the thigh and provides sensation to the back surface of the thigh and leg as well as to the skin of the groin. It can be injured during the surgical approach for repair if it is not protected. The inferior gluteal nerve is the principal extensor as it allows the gluteus maximus (butt muscle) to function. It can be injured with retraction of the gluteus during the surgical approach.
The sciatic nerve is the longest and widest single nerve in the human body. The sciatic provides sensation of the skin of the leg and makes the muscles of the back of the thigh calf and foot work. The nerve is close to the ischial tuberosity as can be seen in the figures above.
Other potential complications associated with proximal hamstring repair include rerupture, weakness, and sitting pain. In the number of reports on hamstring repair, reruptures are rare. In one study, three of 41 patients were found to have failure of surgical repair. Several studies have tested postoperative hamstring strength after repair. One study found that mean postoperative strength was 84% as compared to the other side; however other studies have shown a return of strength ranging from 60-90% following repair.
In summary, proximal hamstring ruptures can be treated endoscopically. This allows early treatment with surgical repair and a faster recovery as a result of the limited scarring and incision that are necessary. With proper treatment, good functional results can be achieved in most patients. It is important to realize that some patients may not be candidates for this procedure as a result of several factors including a larger tear, prior surgery and many other factors. It is important to discuss these things with your doctor.