The majority of hamstring injuries are simple muscle strains, and these can be treated conservatively. A true hamstring avulsion, a much less common but more serious injury, requires surgical intervention to prevent chronic pain and disability. Characteristically, a patient with a true hamstring avulsion will recall feeling the tendon rupture and there will be extensive bruising on the posterior aspect of the thigh (Fig. 1). Clinical examination may demonstrate a palpable defect in the hamstring tendon if there has been sufficient retraction, and considerable weakness is found when the involved side is compared with the contralateral side. Magnetic resonance imaging is recommended in all cases to confirm the nature of the avulsion and to assess the path of the sciatic nerve and the position of the gluteus maximus muscle belly in relation to the ischial tuberosity.
Long-term sequelae of a neglected hamstring avulsion include pain, weakness, poor endurance, and sciatica due to tethering of the retracted muscle to the sciatic nerve. In order to prevent these unpleasant problems and to enable a return to sports activity, we developed a method for the reattachment of the avulsed tendon to restore power to the detached muscle.
Position
The patient is fully anesthetized and is positioned prone on the operating table. The affected side is draped free in such a manner as to allow access to the surgical site and unrestricted flexion of the knee. Preparation and draping of the patient is greatly facilitated by the use of a fixed suspension device designed to hold the limb elevated (Figs. 2 and 3).
Exposure
The defect is often palpable, which assists in accurate placement of the incision (Fig. 4). A 5 to 7-cm incision is extended vertically and distally from the ischial tuberosity in line with the tendons. The incision is lengthened as necessary to identify the retracted muscles, which may lie up to 10 cm distal to the tuberosity, and, in chronic cases, the dissection may need to be extended substantially farther to allow mobilization of the retracted muscle. A vertical incision is used to provide the necessary flexibility of the exposure. A horizontal incision results in a more cosmetically acceptable scar but substantially increases the difficulty of the procedure.
The inferior free edge of the gluteus maximus is defined (Figs. 5-A and 5-B) and is retracted proximally. In some cases, the gluteus maximus extends a substantial distance below the ischial tuberosity. If it does, the lower fibers are divided to improve access to the hamstrings and exposure. The deep fascia of the thigh is then incised in line with the skin incision.
Once the dissection has been carried through the deep fascia, the ischial tuberosity is palpated in the proximal extent of the wound under the gluteus maximus muscle belly. A Hohmann retractor is placed on either side of the tuberosity, and the fibrous tissue is cleared from its inferior and lateral surfaces with use of a periosteal elevator.
The retracted tendons are then identified. In acute cases, they may be bound in a pseudo-capsule formed by the hematoma. In more chronic cases, they may be bound down by scar tissue but they remain as a prominent lump in the wound.
The sciatic nerve passes deep and lateral to the proximal hamstring origin, lying alongside or deep to the hamstring muscle bellies. The proximity of the sciatic nerve to the muscles and tendons means that it is advisable to identify the nerve prior to mobilization and fixation of the tendons (Fig. 6). In chronic cases, or when there are symptoms of sciatica, the nerve may become tightly bound in the scar tissue and require formal neurolysis to prevent iatrogenic injury. This can be a time-consuming and demanding procedure; nerve stimulators and magnification devices such as surgical loupes are of great assistance. In acute cases, the avulsed hamstring tendons may be identified within a hematoma and the sciatic nerve remains separate.
Once the hamstring tendons have been identified and mobilized, the inferior and lateral aspects of the ischial tuberosity are exposed and scar tissue is excised to obtain a fresh bed for reattachment. Three suture anchors with additional number-5 braided nonabsorbable sutures threaded through them are inserted into the exposed tuberosity. The sutures are passed through the tendon ends with use of a modified Mason-Allen technique, and they are tied when the avulsed structures are reapproximated snugly to the ischial tuberosity (Figs. 7-A, 7-B, and7-C).
Meticulous hemostasis is achieved to prevent hematoma formation and sciatic nerve compression postoperatively. Wound closure is performed in layers with a subcuticular skin closure. The patient is placed in the lateral position to prevent any undue pressure on the nerve during recovery from the anesthesia.
In chronic cases, a degree of knee flexion may be required to relieve tension on the surgical repair. If this is the case, a hinged knee brace is applied with restriction of knee extension. The initial degree of extension that is allowed is determined by the tension within the hamstrings, and it is gradually increased over the four to eight weeks following surgery.
The wound is checked at twelve days postoperatively. Although each case is treated individually on the basis of the repair tension and the chronicity of the rupture, the basic rehabilitation protocol remains the same. Patients walk with crutches for two weeks, but active knee flexion against gravity is not started until six weeks postoperatively. Resistance activity is gradually introduced at three months, and the patient is allowed to return to sports activity at six months.
INDICATIONS:
In an acute case, repair of the proximal hamstring origin is indicated for:avulsion of the ischial apophysis in the immature skeletonavulsion of the tendon from the ischial tuberosity, with or without an osseous fragmentmidtendinous rupture of the proximal hamstring origin
avulsion of the ischial apophysis in the immature skeleton
avulsion of the tendon from the ischial tuberosity, with or without an osseous fragment
midtendinous rupture of the proximal hamstring origin
In a chronic case, repair is merited where there is:persistent power loss despite rehabilitationpainsciatic nerve involvement indicating that the avulsed tendon is attached to the nerve
persistent power loss despite rehabilitation
pain
sciatic nerve involvement indicating that the avulsed tendon is attached to the nerve
CONTRAINDICATIONS:
Repair of the proximal hamstring origin is not indicated for:intramuscular injurieschronic injuries with no functional deficit
intramuscular injuries
chronic injuries with no functional deficit
Magnetic resonance imaging is essential for identifying the nature and level of the injury.
PITFALLS:
Timing of Surgery
Early surgery is substantially easier than delayed surgery. In our experience, operations performed at three to four weeks postinjury are the most straightforward. If the operation is performed too soon after the injury, then the tissues are edematous and friable, resulting in a difficult repair. Delaying intervention for more than five weeks may allow the tendon to become attached to the sciatic nerve by scar tissue.
Sciatic Nerve Involvement
Any suggestion of sciatica during the preoperative assessment should alert the surgeon to the possibility that the avulsed tendon may be adherent to the sciatic nerve. When this is the case, the operation becomes far more challenging, as the nerve requires formal mobilization from the scar. This is aided by the use of magnification (loupes) and a nerve stimulator. The difficulty of this situation should not be underestimated. The sciatic nerve may become bound in scar tissue extremely soon after the injury. We have identified this phenomenon as early as five weeks after the injury. In all cases, the function of the sciatic nerve must be assessed in the recovery suite. Any suggestion that function has become impaired is an indication for an immediate return to the operating room. Of our 155 patients treated with this procedure, two have had early reexploration because of lower-limb weakness. One patient had to return to the operating room within one hour; nerve kinking due to the scar tissue pulling the nerve proximally after the repair was identified. In the second patient, a reexploration for hematoma formation was performed eighteen hours after the surgery because of marked weakness that did not become clinically apparent until twelve hours following the surgery; the neurological function had been entirely normal in the recovery room after the index operation.
While there is obviously a theoretical risk that the nerve could be caught in a suture, we have not observed this complication. However, the risk must be borne in mind when any postoperative sciatic nerve impairment is identified.
Hematoma Formation
Meticulous hemostasis throughout the procedure is essential to prevent the development of a hematoma that can induce a subsequent iatrogenic nerve injury. The neurovascular status of the limb must be carefully monitored for the initial twenty-four hours, and any impairment that develops and does not resolve when the patient lies prone is an indication for emergent decompression.
Chronically Retracted Tendon
In this situation, it may be difficult to maintain a tension-free repair with the knee extended. The use of a hinged knee brace may be helpful. The brace is utilized as an extension block. Initially, extension is limited to 90° with unlimited flexion. Further extension is allowed gradually as dictated by the clinical progression of the patient.
AUTHOR UPDATE:
It is now our routine practice to formally identify the sciatic nerve and perform a neurolysis in every case. This is due to the occasional case of early dramatic adhesion between the sciatic nerve and scar tissue, possibly as a result of an unrecognized prior injury.