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A 44-year-old woman with right knee pain
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A 44-year-old woman with a history of hypothyroidism and dyslipidemia presented to our office with right knee pain and instability. She reported a history of an ACL tear 4 years prior to presentation, which was managed with an ACL reconstruction using hamstring autograft at an outside hospital. She did well after ACL reconstruction for approximately 1 year, at which time she noticed a sensation of looseness and instability within the knee. She underwent an MRI at that time, which was relatively unremarkable and showed an intact ACL graft.
Approximately 2 years later, she slipped and re-injured her knee, resulting in a new tear of her previously reconstructed ACL. She subsequently underwent revision ACL reconstruction with tibialis anterior allograft, as well as a partial posterior horn medial meniscectomy.
Since that surgery, she stated that her knee never felt stable, with intermittent episodes of “giving way,” as well as intermittent effusions. She was able to return to work as a medical technician, but reported difficulty with attempting to change directions or twist.
Physical examination revealed no effusion, well-preserved range of motion and a normal neurovascular exam. She had tenderness to palpation along the medial joint line and in the pes anserine bursa. She had a Grade 3 Lachman test, as well as a positive pivot shift maneuver. She was otherwise ligamentously stable to varus and valgus stressing, as well as to posterior drawer testing. In office KT-1000 testing revealed 7 mm, 9 mm and 15 mm, compared with 3 mm, 4 mm and 7 mm in the unaffected knee. Plain radiographs (Figure 1) were reviewed, revealing tunnel dilation to approximately 18 mm in both the femoral and tibial tunnels.
Images: Bush-Joseph, CA
What is your diagnosis?
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Atraumatic ACLR failure in the setting of significant bone tunnel dilation
This patient has experienced an atraumatic ACL reconstruction, or ACLR, failure following two prior ACLR surgeries. Her situation was complicated by both femoral and tibial bone tunnel widening, possibly indicative of an adverse reaction to the allograft utilized in her second ACLR (first revision).
Overall, ACLR is a highly successful procedure, with most patients experiencing pain relief and return to sport. Nevertheless, various authors have reported failure rates and recurrent instability rates as high as 15% following ACLR, with worse outcomes following revision ACLR. The most common etiology of failure has historically been considered iatrogenic as a result poor tunnel placement; however, traumatic re-rupture and biologic failures are also common. Other etiologies that must be considered include unrecognized concomitant ligamentous injuries and/or malalignment. A variety of factors must be considered when evaluating the patient with an atraumatic ACLR failure, particularly in patients with recurrent failures, including graft(s) previously utilized, graft tensioning, graft positioning, tunnel positioning and tunnel status (i.e., bone quality).
Tunnel widening following ACLR has been analyzed extensively by a variety of authors, and has been attributed to graft choice, fixation type (i.e., device) and graft placement, as well as synovial fluid infiltration. Given the variety of potential etiologies of tunnel widening, in addition to its ability to present both asymptomatically as an incidental radiographic finding, tunnel widening remains a challenging diagnosis to treat.
When associated with symptomatic laxity, the presence of tunnel widening becomes a major factor in surgical decision-making. In particular, the clinician must decide if the revision ACLR procedure needs to be staged in order to allow for an index bone-grafting procedure or if it can be performed without prior grafting. In patients with adequate bone stock, tunnel bone grafting is not needed, and revision ACLR can be performed immediately using either divergent tunnels (i.e., funnel technique) if the prior tunnels were anatomic or anatomic tunnels if the prior tunnels were non-anatomic. The divergent tunnel technique should only be used in cases in which the index tunnels are anatomic, so that the aperture of the new tunnel remains the same while the direction and angle of the new tunnel is divergent.
Especially difficult are cases in which there is less than 100% tunnel widening, but without adequate bone stock for an immediate revision procedure. In these cases, the widened tunnel can be filled with an additional screw (stacking screw technique) or can undergo bulk allograft grafting, in which allograft bone is shaped either into a large “bullet” or multiple “matchsticks,” which are inserted into the widened tunnel, followed by insertion of the bone plug of the new allograft and fixation with an interference screw.
In patients with 100% or greater tunnel widening, a staged reconstruction strategy is beneficial, first with bone grafting, followed 3 months to 4 months later by revision ACLR. Bone grafting can be performed with a variety of different materials, including iliac crest autograft, allograft bone chips and/or bone substitutes, including demineralized bone matrix, calcium sulfate and calcium phosphate. Once the bone tunnels are deemed adequate, revision ACLR can be performed. In this setting, we prefer to utilize a bone-patella-tendon-bone (BPTB) allograft, as the bone plugs will allow for bone-to-bone healing within the new tunnels. Furthermore, due to the association of bioabsorbable screws with tunnel widening, we prefer to use metallic interference screws for fixation, with supplemental suspensory fixation on the femoral side, particularly if the widening impacts the posterior femoral cortex.
Intraoperative arthroscopic image during the revision ACLR, demonstrating execellent placement of the BPTB allograft.
Treatment of our patient
In this case, the patient underwent further diagnostic work-up with a CT scan in order to more accurately quantify the degree of bone tunnel dilation. The CT revealed the femoral tunnel to be 22 mm in width and the tibial tunnel to be 23 mm in width (Figure 2). Given these findings, the decision was made to perform revision-ACLR in a staged fashion: 1) bone grafting of both tunnels (Figure 3); and 2) revision ACLR with BPTB allograft.
On examination under anesthesia at the time of the first stage, our patient was noted to have a gross pivot shift with a Grade III Lachman test. Arthroscopic evaluation revealed an intact, but ineffectual allograft, which was debrided, followed by debridement and grafting of both bone tunnels. The tunnels were grafted with a combination of cancellous allograft bone chips and a calcium sulfate-calcium phosphate composite graft (Pro-Dense, Wright Medical). Approximately 4 months following grafting, the patient underwent arthroscopic revision ACLR with BPTB allograft (Figure 4).
At her 1-year follow-up, the patient was noted to be doing well. Her physical examination was notable for a Grade I pivot slide and a Grade I Lachman test with a firm endpoint. Radiographs showed evidence of ossification of the areas of prior bone grafting (Figure 5). Despite her mild residual laxity, she was completely asymptomatic and pleased with her recovery, and subsequently was released to full activity without restrictions.
- References:
- Bach BR Jr. Arthroscopy. 2003; doi:10.1016/j.arthro.2003.09.044.
- Frank RM, et al. J Knee Surg. 2012;25(2):143-149.
- Maak TG, et al. J Am Acad Orthop Surg. 2010;18(11):695-706.
- Weber AE, et al. Am J Sports Med. 2015;doi: 10.1177/0363546515570461.
- Wilde J, et al. Sports Health. 2014;doi: 10.1177/1941738113500910.
- For more information:
- Rachel M. Frank, MD; Nicholas Brown, MD; and Charles A. Bush-Joseph, MD, can be reached at Rush University Medical Center, 1611 W. Harrison, Ste. 300, Chicago, IL 60612; Frank’s email: rmfrank3@gmail.com; Brown’s email: nmb2116@gmail.com; Bush-Joseph’s email: cbj@rushortho.com.
Disclosures: Frank and Brown report no relevant financial disclosures. Bush-Joseph reports he is an unpaid consultant to The Foundry and receives institutional research support from Smith & Nephew, Arthrex, Ossur and DePuy Mitek.