Loose intra-articular body following anterior cruciate ligament reconstruction

Case Report

Loose Intra-articular Body Following Anterior Cruciate Ligament Reconstruction A. J. Cossey, M.B.B.S., F.R.C.S., and R. S. Paterson, M.B.B.S., F.R.A.C.S., F.A.Orth.A.

Abstract: We report a case of intra-articular fracture of a bioabsorbable fixation device from the femoral tunnel in an anterior cruciate ligament reconstruction using a bone-tendon-bone graft. Thirteen months after successful reconstruction surgery, the patient experienced episodes of locking and medial joint pain. There was no history of trauma and no symptoms of instability or swelling. On revision arthroscopy, a fractured tip of a bioabsorbable RIGIDfix cross pin (Mitek, Westwood, MA) was identified in the medial compartment of the knee. There was a broad area of chondral erosion affecting the medial femoral condyle and a small defect to the medial tibial plateau where the loose body had been lodged. The bone-tendon-bone graft was intact without disruption. After arthroscopy, the patient was symptom free for 3 weeks but then developed further symptoms of locking. Magnetic resonance imaging showed another loose body within the knee. A repeat arthroscopy was performed 6 weeks after the earlier procedure and another piece of the polylactic acid RIGIDfix cross pin was removed, this time from the lateral gutter. This case raises concern about the potential for breakage and resultant loose body formation that may occur after bioabsorbable cross-pin fixation and, particularly, the associated chondral damage that can occur if early intervention is not conducted. Key Words: Loose body—ACL reconstruction—Bioabsorbable fixation.

A

common form of fixation in bone-tendon-bone grafts in anterior cruciate ligament (ACL) reconstruction is the bioabsorbable (polylactic acid) cross pin. This system has many theoretical advantages including 360° bone-to-graft contact at the graft tunnel interface, decreased incidence of graft damage during fixation, and decreased interference if magnetic resonance imaging is required postoperatively. Disadvantages of this form of fixation include inflammatory reactions to the synthetic material and component fracture. We report a case of fracture of a RIGIDfix ACL

From SportsMed SA, Adelaide, South Australia, Australia. Address correspondence and reprint requests to A. J. Cossey, M.B.B.S., F.R.C.S., SportsMed SA, 32 Payneham Rd, Stepney 5069, South Australia, Australia. E-mail: cosseyboy@ btopenworld.com © 2005 by the Arthroscopy Association of North America 0749-8063/05/2103-4169$30.00/0 doi:10.1016/j.arthro.2004.11.010

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cross pin (Mitek, Westwood, MA) used in femoral fixation of the graft. This case illustrates the possibility of fixation breakage with associated intra-articular migration of the device and the associated chondral damage that can occur. CASE REPORT A 23-year-old man initially underwent ACL reconstruction in April 2002. The ACL reconstruction was performed using bone-tendon-bone graft, the graft being fixed with polylactic acid bioabsorbable RIGIDfix cross pins to secure the graft in both the femoral and tibial tunnels. After surgery, the patient underwent a routine rehabilitation regimen under the guidance of the physiotherapists. This was uneventful and he was discharged from clinical follow-up having resumed competitive sports 7 months postoperatively. However, 13 months after his reconstruction, the patient experienced pain on the inner aspect of his knee as well as intermittent episodes of locking. He

Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 21, No 3 (March), 2005: pp 348-350

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FIGURE 1. The RIGIDfix cross pin within the medial compartment of the knee found at the first arthroscopy.

FIGURE 3. A piece of the fractured RIGIDfix cross pin found at the second arthroscopy.

disclosed no symptoms of instability or swelling. An initial diagnosis of synovial impingement secondary to postoperative fibrosis was made and he was treated with a course of nonsteroidal anti-inflammatory drugs and an intra-articular injection of local anesthetic and steroid. The subject was reviewed in clinic having gained no therapeutic response to the conservative management. Arthroscopy was performed 1 month after his representation and a loose body consistent with a fragment of the RIGIDfix cross pin used for femoral graft fixation was found in the medial compartment of the knee (Fig 1). The cross pin was embedded in the medial tibial plateau causing a broad area of chondral erosion on the medial femoral condyle (Fig 2). The loose body was easily removed using arthro-

scopic instrumentation. A minimal chondroplasty was performed on both the medial femoral condyle and the medial tibial plateau. A thorough arthroscopic assessment including the ACL graft, patellofemoral joint, and lateral compartment was conducted and all were found to be normal. No other loose body was identified. Following arthroscopy, the patient was symptom free for a period of 3 weeks. At this stage, he started to experience symptoms of locking. A magnetic resonance imaging scan was requested and it showed another loose body within the knee joint. Repeat arthroscopy was performed 6 weeks following the earlier procedure. Because of the translucency of the RIGIDfix loose body, difficulties arose locating it, but another piece of RIGIDfix was removed, this time from the lateral gutter (Figs 3 and 4).

FIGURE 2. Chondral damage on the medial femoral condyle caused by the RIGIDfix cross pin.

FIGURE 4.

Photograph of the fractured RIGIDfix.

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A. J. COSSEY AND R. S. PATERSON DISCUSSION

REFERENCES

Bioabsorbable fixation of grafts in ACL surgery has become popular in recent times. Studies have shown this form of fixation to be comparable to metal in terms of fixation strength and pullout strength.1-5 Bioabsorbable materials also offer advantages in terms of less damage to the graft on its insertion and less distortion with the use of magnetic resonance imaging postoperatively. The Mitek RIGIDfix system uses bioabsorbable polylactic acid cross pins for the fixation of the graft in the femoral tunnel. This allows 360° of bone-to-graft contact, allowing 100% circumferential in growth at 12 weeks postoperatively6 and less damage to the graft on fixation. Complications of bioabsorbable fixation have been reported in the literature, although they are rare. Component breakage with the formation of an intra-articular loose body has been reported,7-10 but we are unaware of any previous report of cross-pin fracture creating a loose body. We recommend a high index of suspicion if patients represent with mechanical symptoms following reconstructive surgery using RIGIDfix. Prompt arthroscopic intervention is recommended to prevent the potential for extensive chondral damage secondary to intraarticular loose bodies arising from fracture of the fixation device.

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