Primary single suture anchor re-fixation of anterior cruciate ligament proximal avulsion tears leads to good functional mid-term results: a preliminary study in 12 patients

The patient was placed in supine position, and the leg was prepared in standard fashion. A high anterolateral portal was created, and diagnostic arthroscopy was performed routinely. After creating an additional anteromedial portal, the ligament was assessed by probing under direct vision. Concomitant injuries were treated first. After diagnosis of a proximal avulsion tear Sherman type 1 [4] with excellent tissue quality, a number 2 Fiber Wire® (Arthrex, Naples, FL, USA) was passed twice through the anteromedial bundle of the ACL using a Scorpion suture passer in 40° knee flexion through the anteromedial portal. No cannulas were used. The first suture was placed in the middle third of the ligament. The second stich was placed in the proximal third of the ligament remnant. Afterwards, the procedure was repeated using a number 0 Fiber Wire® at the proximal and middle third of the posterolateral bundle (Fig. 1). Special care was taken to rule out soft tissue interposition at the anteromedial portal or a miss-link between the two sutures. The suture tails were threaded through the eyelet of a 2.9-mm push lock anchor. With the knee flexed to 90°, a 2.9 × 20 mm hole was drilled into the origin of the ACL footprint under direct visualization. While the anchor was put into the drill hole, the wire limbs were released when the first rim of the anchor was covered by bony cortex. The anchor was forwarded into the socked to the second laser line. After removing the driver, the free ends were cut with an open-end suture cutter (Arthrex, Naples, FL, USA). Tension and stiffness were tested with a probe in 60° of knee flexion. Impingement was ruled out arthroscopically. Two to three microperforation holes were put into the cortex of the lateral femoral condyle with an awl surrounding the ACL. No drainage was utilized.

Postoperative care included partial weight bearing for 2 weeks, a knee brace with full extension and flexion limitation to 90° for 6 weeks, control of swelling, and early gain of range of motion. In case of meniscal repair, flexion was limited to 60° for 4 weeks and to 90° for additional 2 weeks. For the time of inpatient treatment, continuous passive motion (CPM) was implemented. After 6 weeks, the patients weaned off the brace and started muscle strengthening according to a standard ACL rehabilitation protocol.

However, three patients (25%) reported lasting impairment of knee function including instability in two cases and one early re-tear during clinical examination. One must assume that the ACL did not heal properly in those three cases.

The patient with the early re-tear during clinical examination was the very first patient who underwent ACL re-fixation in our department. The re-tear happened with a pop sensation during clinical investigation 8 weeks after the index procedure. The load on the ACL was inadequate which suggests the absence of healing of the ACL. However, early re-tears also occur in recent studies published by Achtnich et al. and DiFelice et al. [3, 5] Both, Achtnich and DiFelice traced their failures back to noncompliant patients with refusal of adequate postoperative treatment, no sticking to the rehabilitation protocol, or too early return to sports. In contrast, our patient stuck to the postoperative rehabilitation protocol.

One other patient suffered from severe knee distortion with a concomitant patellar tendon tear. This patient underwent revision surgery 2 years after primary surgery due to a persisting feeling of instability. The surgical report described a complete loss of the ACL fibers. The patient’s subjective knee function did not improve after ACL single bundle reconstruction. Due to persistent pain, he had to quit sports completely and still requires sporadic pain medication. Simultaneous traumatic patellar tendon rupture and ACL rupture is an uncommon injury and is rarely reported in literature [8]. No clear treatment regime has been established yet. Nevertheless, there is an agreement that immediate repair of the patellar tendon is recommended [9, 10]. Two-staged surgical treatment is preferred by a few authors [11, 12], but also one-staged procedures are reported to lead to satisfying functional results [10, 13, 14]. In this case, a one-staged surgical approach with primary suture anchor repair of the ACL and suture of the patellar tendon competes with a single repair of the patellar tendon and ACL reconstruction in a second step. Although in our case the ACL did not heal, there were no signs for intraoperative problems caused by the enclosed push lock anchor in the surgical report of ACL reconstruction. In contrary to preceding studies, in our case, no extravasation of fluid during arthroscopy occurred. In the described patient, not stiffness or arthrofibrosis [10, 13], but recurrent instability and lasting pain were attributed to be the main problem. Retrospectively, severe damage to the knee extensor structures seemed to impede adequate healing of the ACL fibers.

The surgical technique of ACL re-fixation is still subject of controversial discussion. However, based on current literature reports, there is no clinical evidence for supremacy of one or another technique. Achtnich et al. introduced a single-bundle re-fixation whereas DiFelice et al. and Weninger et al. performed a double-bundle re-fixation with two anchors [3, 5, 15]. Achtnich et al. combined a direct suture anchor re-fixation with the healing response technique and reported early re-tear in one case and recurrent instability in two cases [5]. DiFelice reported one clinical failure with early re-tear after 3 months [3]. We believe that one advantage of a single anchor re-fixation, in addition to a reduced amount of suture material placed in the ACL, might be reduced foreign material in the femur. In case of revision surgery, the anchors are supposed to be over drilled to create an adequate bony socket. Parts of the anchors might get spread through the joint by drilling, and osseous defects of the femoral insertion zone might occur. However, no intraoperative problems associated with the enclosed anchors have been reported in the described studies, which underlines, that ACL reconstruction after primary suture anchor repair is comparable with primary reconstruction.

The abandonment of ACL primary suture anchor repair can be traced back to the landmark studies of Feagin et al. and Taylor et al. reporting open suture repair of ruptured ACL via arthrotomy [1, 7]. In their studies of West Point Cadets, Feagin et al. reported an instability rate of 94%, pain and stiffness rate of 71%, and swelling rate of 66% at a 5-year follow-up despite initially promising short-term results.

In our investigation, we could not find any delayed deterioration of knee function. All cases which had considered to be failures demonstrated unsatisfying knee function from the beginning. The one incident of atraumatic re-tear occurred 8 weeks after surgery, and the instability in two other cases appeared immediately after the index procedure. Taylor et al. reported in their long-term follow-up after 30 years that 64% of their patients had at least one more knee surgery, in 28% due to instability. Fifty percent of those patients recovered well. In our cohort, one patient needed revision surgery, and one patient rejected revision surgery despite instability. In addition, Taylor et al. reported that the 5-year results were supposed to be a good predictor of the subjective results after more than 30 years. This generates expectations that even mid-term results following primary suture anchor repair remain good or excellent. In addition, follow-up MRI scans or second look arthroscopies could highlight the status of the ACL remnant also in clinically asymptomatic patients (Fig. 4).

In addition to the small size of our study cohort, the limitations of this study include the variety of age of patients, of patients’ preoperative activity level (Tegner activity score preoperatively 4–8 points), and the relatively heterogeneous nature of the cohort group. Furthermore, we report on surgical results of two different senior surgeons which may have influenced the results.