Chapter 58 Revision Anterior Cruciate Ligament Reconstruction*

Introduction

Reconstruction of the anterior cruciate ligament (ACL) has become an increasingly common orthopaedic procedure. In the United Kingdom, approximately 5000 ACL reconstructions are performed per year ¹; in the United States, more than 100,000 procedures are currently performed annually.² This trend is likely to continue with the general population’s increasing pursuit of an active lifestyle. Although long-term functional stability and symptom relief after primary ACL reconstruction exceed 90% in some studies,^3,⁴ overall clinical failure rates of 10% to 25% have been documented.¹ It is currently estimated that between 3000 and 10,000 U.S. patients and approximately 1000 U.K. patients are candidates for revision ACL surgery annually.¹

Revision ACL surgery is recommended for patients who have instability or reduced activity with pathological laxity after a failed primary ACL reconstruction. The important stages in assessing a patient with a failed ACL reconstruction include a detailed history, patient selection, physical examination and appropriate investigations, choice of graft, surgical technique, and rehabilitation.⁵ Eliciting important relevant history from a patient who is usually apprehensive and has some knowledge of the problem (from general practitioners, physiotherapists, and the Internet) can be difficult. One should spend enough time trying to find out the details of the original injury (e.g., high-velocity trauma may suggest multiligament laxity) and also the patient’s experience of previous treatment as well as his or her knowledge of the problem. A full history of occupational and future recreational activities is mandatory. Often the patient’s expectations are not realistic, and therefore despite achieving knee stability, the revision surgery will not result in a contented patient. Instability and/or pain top the list of patient symptoms. It should be clarified with the patient preoperatively that a reduced activity level and/or excellent natural proprioception may result in a reduction or even an abolition in symptoms of instability without the need for surgery. Revision reconstruction should be offered to patients with symptoms of instability or those who wish to increase their activity level to include manoeuvres involving twisting or a sudden change in direction. In such cases symptoms of instability, if left untreated, will contribute to repeated meniscal and chondral damage, leading to an earlier progression of osteoarthritis (OA). At the same time, the patient should be made aware of the risk of a gradual progression of OA, irrespective of the method of treatment but especially if symptoms of instability are ignored. It should be carefully explained that symptoms of pain are likely to be caused by degenerative disease or a torn meniscus and that a revision ACL reconstruction alone is unlikely to be the answer to this problem. One should also alert the patient to the potential need for bone grafting and thus a staged reconstruction.

The most useful investigations are the plain x-ray series of an anteroposterior (AP) standing radiograph and a lateral x-ray in full extension, together with skyline and Rosenberg views (Fig. 58-1).¹ These will show the original tunnel placement and usually the fixation methods used, tunnel widening,^6,⁷ osteolysis, and the presence and extent of joint space narrowing. If possible, comparison with previous radiographs will help quantify bone loss (tunnel widening). It is our practice to obtain a magnetic resonance imaging (MRI) scan preoperatively, but only rarely has this provided additional information that has changed the course of management. If no reason for the primary failure can be elicited, vigilance for a missed or complex laxity should be exercised. Careful clinical examination and an examination under anesthesia, which may include fluoroscopic stress views, are useful in finding an additional laxity.

Fig. 58-1 Failed anterior cruciate ligament (ACL) reconstruction. Anteroposterior (A) and lateral (B) views.

Causes Of Failure of Primary Procedure

The causes of recurrent patholaxity after primary ACL reconstruction ⁶^–²⁶ can be broadly divided into four groups: technical errors, failure due to biological factors, failure due to significant trauma, and failure owing to laxity in the secondary restraints.¹⁷ By far the most common cause is error in the surgical technique, with 77% to 95% of all cases of ACL failure attributed to technical error.²⁷ This category includes poor graft selection or harvest, improper tensioning or fixation, and especially incorrect tunnel placement.^9,^17,¹⁸ More than 70% of technical failures, and thus more than 50% of all ACL failures, can be attributed to malpositioned tunnels.^8,¹⁷ Inappropriate positioning of either the tibial or the femoral tunnel results in excessive length changes in the graft as the knee moves through a range of motion, resulting in either a limited range of motion or excessive graft laxity.^8,¹⁸ Anterior placement of the femoral tunnel, a common mistake, will result in limited flexion and potential graft failure if full flexion is achieved. Tibial tunnel placement may be somewhat more forgiving, but anterior placement leads to impingement in extension and excessive tension in flexion, whereas posterior placement may cause laxity in flexion.¹⁷ Perhaps the most common error in surgical technique involves the anterior placement of femoral and/or tibial tunnels.¹⁶ Carson et al recently published their review of 90 failed ACL reconstructions and quoted 52% of the failures as being due to surgical technical errors.²⁸ Several studies have shown that a posterior and proximal placement of the intraarticular exit of the femoral tunnel is advisable and involves minimal lengthening of the ACL substitute toward extension.