All-Arthroscopic Refixation of an Osteochondral Femoral Avulsion of the Anterior Cruciate Ligament with a Laxity-Minimizing Suture

Introduction

Insufficient anterior cruciate ligaments (ACL) in skeletally immature patients are rare. The incidence of this injury is 1–3.4%.¹ Whereas the literature presents a number of studies on tibial insertional avulsions, reports on the uncommon femoral fracture site are seldom.^2–5 Operative techniques vary from arthrotomy with suture refixation⁶ to arthroscopic retrograde K-wire fixation.⁷ Furthermore, some of these case reports lack in precise illustration of surgical technique options.

This case report presents an all-arthroscopic refixation of an osteochondral femoral avulsion of the anterior cruciate ligament with a laxity-minimizing suture to prevent secondary elongation.

Case Presentation

A seven-year-old girl had a trauma with twisting her left knee. She had pain, swelling and instability. The patient used crutches. The knee had an extension deficit of 15° with flexion up to 70°. Knee examination revealed a grade two Lachman and anterior drawer test with a soft endpoint. No valgus- or varus-instability was examined. Initial anteroposterior and lateral radiographs were inconspicuous. Magnetic resonance imaging (MRI) revealed a displaced femoral avulsion fracture of the ACL (Figure 1). The physes presented unfused.

Figure 1 MRI, coronal (a) and sagittal (b) plane; the black arrow marks the femoral avulsion.

The patient and parents were consented for an arthroscopic procedure with refixation of the avulsion with or without meniscal repair. Surgery was performed 18 days after trauma.

Examination under anesthesia confirmed a grade two positive Lachman and anterior drawer test with a soft endpoint as well.

Setup: The patient was positioned supine with the leg placed in a static leg holder flexed to 90°. A tourniquet of 150 mm Hg was used after exsanguinating the leg.

Portals: An anterolateral viewing portal, an anteromedial working portal and a far medial drilling portal were created in vertical direction.

Diagnostic arthroscopy: Diagnostic arthroscopy was performed. An unstable vertical longitudinal tear of the lateral meniscus in the posterior horn was detected. The ACL was proved to be lax with the expected femoral avulsion (Figures 2 and 3). The medial meniscus as well as the posterior cruciate ligament (PCL) was intact. No cartilage defect was observed.

Figure 2 Arthroscopy, notch; ACL tear.

Figure 3 Arthroscopy, notch; ACL avulsion.

Lateral meniscus repair: An all-inside meniscal repair system (Truespan^TM, DePuy Mitek Inc., Raynham, USA) was used for fixation of the lateral meniscus.

ACL avulsion refixation: The femoral ACL insertion site was debrided using a 4.0 curved shaver (Arthrex, Naples, FL, USA). Using a 5.5 mm offset drilling guide, a beath pin was inserted at the anatomic femoral insertion site of the ACL via the anteromedial portal (Figure 4). Fluoroscopy was used to ensure appropriate positioning of the transphyseal pin.⁸ Using an arthroscopic lasso, 2 strands of No. 2 Dynacord^TM (DePuy Mitek, Raynham, MA, USA) non-absorbable sutures were shuttled through the proximal part of the ACL stump (Figure 5). The strands were passed through the beath pin tunnel. A 3 cm longitudinal incision was performed at the distal lateral femur, the iliotibial band was split longitudinally, and the suture strands were retrieved. The knee was placed into 20° of flexion, and the sutures were then tied over a suture button (Arthrex, Naples, FL, USA) under direct arthroscopic visualization of the ACL stump. At this point, subtle manipulation of the avulsed osteochondral fragment was performed with a probe and arthroscopic forceps to ensure anatomic reduction of the fragment into its original site (Figures 6 and 7). No redon drainage was used.

Figure 4 Arthroscopy, notch; femoral avulsion site.

Figure 5 Arthroscopy, notch; ACL avulsion looped with DynacordTM suture.

Figure 6 Arthroscopy, notch; anatomically reducted ACL.

Figure 7 Postoperative x-ray, coronal (a) and sagittal (b) plane.

No intra- or postoperative complications occurred. The patient was mobilized with partial weight bearing using crutches and a hinged knee brace. Range of motion limitation was set to 0° extension for three days postoperatively and then 0°/0°/80° (extension/flexion) until the second postoperative week. Between the third and sixth postoperative week we recommended 0°/0°/90° limitation in the hinged brace. Partial weight-bearing recommendations were: sole contact for the first week, half a body weight for the second week and pain adapted full body weight-bearing for the third and fourth week.

At the first follow-up exam at eight weeks postoperatively, the patient had a stable knee with a negative Lachman and negative anterior drawer test. Range of motion showed 120° of flexion with full extension.

The seven months follow up MRI scan shows complete healing of the avulsion and the meniscal tear. The growth plates proof to be intact. No further bone marrow enhancement is evident.

Discussion

Avulsion fractures of the anterior cruciate ligament are rare injuries, accounting for about 7% in children and adolescents.⁹ Literature about surgical techniques and outcomes is sparse. A variety of surgical techniques have been proposed, starting from extensive arthrotomy approaches^3,4,6,10,11 over to arthroscopic techniques^2,7,12,13 (Table 1).

Table 1 Literature on Surgical Techniques and Outcomes

The long-term outcome of the described techniques remains unknown. In particular, secondary elongation due to early loosening of the utilized suture materials persists a matter of concern. In ACL reconstruction, secondary elongation resulting in graft failure is a common problem.^14–17 In addition, growth disturbance with the used technique cannot yet be predicted. Nevertheless, our technique including transphyseal drilling is supported by the current literature.⁸

The ideal suture for refixation remains a matter of debate. The Dynacord^TM suture (DePuy Mitek, Raynham, MA, USA) was launched in 2018 with the initial goal to improve fixation strength in rotator cuff repair. It was developed when a failure of repair was observed in about 20% of the cases due to a loss of suture tension, causing gap formation and precluding the soft tissue from healing to the bony insertion site.¹⁸

In an in vivo ovine shoulder model, gap formation with this laxity-minimizing suture was half of the size of the standard suture. In addition, no local tissue damage (cut-through) was observed.¹⁹

Arthroscopy provides excellent visualization of the injury, while at the same time allowing for thorough exam of the joint for accompanying injuries. In this particular case, a vertical tear of the posterior horn of the lateral meniscus was detected and repaired with an all-inside suture device (Truespan^TM, DePuy Mitek, Raynham, MA, USA).

The technique described here offers the advantages of an all-arthroscopic procedure and a sustainable femoral fixation using high-strength laxity-minimizing sutures.

Conclusion

All-arthroscopic refixation of femoral avulsion injury of the ACL has the potential to restore anatomic joint kinematics and to yield excellent clinical results. Transosseous refixation with extra-epiphyseal button fixation minimizes the risk for growth disturbance. The use of a dynamically shortening suture might be helpful to prevent early gap formation, which might lead to clinical failure.

Clinical Message

This case report illustrates precisely an all-arthroscopic refixation of an osteochondral femoral avulsion of the anterior cruciate ligament with a laxity-minimizing suture to prevent secondary elongation.