Anterior cruciate ligament

Transcription

1 A Critical Analysis Review Brandon J. Erickson, MD Gregory L. Cvetanovich, MD Rachel M. Frank, MD Andrew J. Riff, MD Bernard R. Bach Jr., MD Investigation performed at Midwest Orthopaedics at Rush, Rush University Medical Center, Chicago, Illinois Abstract» There are multiple causes of failure following a primary anterior cruciate ligament (ACL) reconstruction. These include technical factors, patient sex, patient age, graft type, and others.» When performing a revision ACL reconstruction, the decision as to what graft to use should be made in conjunction with the patient, taking into consideration his or her activity level, sport of interest, and work or personal lifestyle.» In the setting of a revision ACL reconstruction, the risk of failure of an allograft is substantially higher than that of an autograft, especially in patients younger than 30 years of age.» The surgeon must determine whether to perform a single-stage or 2-stage revision when performing a revision ACL reconstruction. Twostage revisions are rarely performed, but are particularly useful in the setting of substantial tunnel widening.» One of the most debated issues following revision ACL reconstruction is timing of return to sport. To our knowledge, no high-level evidence exists to guide surgeons in setting a definitive return-to-sport timeline for athletes. Hence, surgeons should evaluate each patient on an individual basis to determine when he or she is ready to return to sport. Anterior cruciate ligament (ACL) tears are common among athletes of all levels 1. In young, active patients who sustain an ACL tear and wish to return to sport at the same level, the standard of treatment is an ACL reconstruction 2,3. As patients increasingly participate in higher-level activities later in their lives, the number of ACL reconstructions in the United States rose from 86,687 in 1994 to 129,836 in 2006 and continues to grow 1. Unfortunately, as the number of primary ACL reconstructions has increased, the number of revision ACL reconstructions has also increased. Failure rates among primary ACL reconstructions have been reported between 5% and 25%, with young patients participating in cutting, jumping, deceleration, and pivoting sports at a substantially increased risk 4-7. There are many different causes and patient-related factors that contribute to failed ACL reconstruction requiring revision reconstruction. These factors include sex, age, activity level, graft type, graft size, concomitant injuries, timing of return to sport, and surgical technique used In 1 study, when 78 patients with a mean age of 17.1 years who underwent primary ACL reconstruction were compared with 47 healthy controls with a mean age of 17.2 years, the overall incidence of a second ACL injury within 2 years was almost 6 times greater in the patients who had COPYRIGHT 2017 BY THE JOURNAL OF BONE AND JOINT SURGERY, INCORPORATED Disclosure: There was no source of external funding for this study. On the Disclosure of Potential Conflicts of Interest forms, which are provided with the online version of the article, one or more of the authors checked yes to indicate that the author had a relevant financial relationship in the biomedical arena outside the submitted work ( JBJS REVIEWS 2017;5(6):e1 1

2 undergone prior ACL reconstruction than that in healthy controls 15. These patients all participated in pivoting and cutting sports, which is considered the highest-risk activity for sustaining a retear. The results following revision ACL reconstruction have largely been less predictable than those following primary ACL reconstruction, with lower rates of return to sport and higher rates of graft rerupture, with rerupture rates reported between 3.5% and 33%, even when the revision is performed by experienced surgeons This range of revision rates speaks to the variable outcomes following revision ACL reconstruction, as well as the variability of study designs that have been conducted (retrospective single-surgeon reviews, database reviews, and so forth). There are many areas of controversy for revision ACL reconstruction including graft choice, timing of return to sport, and indications for single-stage revision compared with 2-stage revision. The purpose of this review was to critically analyze the literature as it relates to the risk of reinjury following primary ACL reconstruction leading to revision ACL reconstruction, the factors surrounding revision ACL reconstruction, the results following revision ACL reconstruction, and the timing of return to sport following revision ACL reconstruction. All publications regarding ACL reconstruction available in the English language were available for inclusion in this review. No systematic review was performed. Risk Factors Contributing to Primary Graft Failure Technical Errors Interestingly, atraumatic causes (feelings of knee instability without a new traumatic injury) account for 75% of ACL reconstruction failures, with only 25% of failures attributed to repeat trauma 19,20. There are several causes of atraumatic failure following ACL reconstruction, but the most common is a technical error during the surgical procedure, with the majority related to tunnel malposition 19. Diamantopoulos et al. reviewed 148 patients who underwent revision ACL reconstruction and found that 63.5% of these failures were due to inappropriate tunnel position 19. The most common error in tunnel positioning is anterior or vertical femoral tunnel placement. Anterior tunnel placement causes the graft to stretch when the knee flexes, thereby resulting in plastic deformation and graft incompetence 3,21. Additionally, vertical femoral tunnel placement, although more isometric, essentially creates an anteromedial-bundle-dominant ACL graft, which can result in posteroanterior plane stability (normal Lachman test) but does not control rotation (pathologic pivot shift phenomenon). Trojani et al. evaluated 293 patients who underwent revision ACL reconstruction to determine the initial cause of failure 21. The most common cause of failure in that cohort was femoral tunnel malposition, which occurred in 36% of cases. The tibial tunnel can also be malpositioned, especially with smaller tibial tunnel drill-holes used with hamstring grafts, as it is more difficult to accurately position the femoral tunnel, resulting in a more posteriorized tibial tunnel when using the transtibial technique. This issue is avoided with independent drilling. Issues with graft harvest, graft fixation, and improper graft tensioning can also increase the risk of failure following a primary ACL reconstruction 22,23. Patient Sex Female patients have a higher risk of sustaining an ACL tear than male patients, with studies citing between a twofold and eightfold greater risk of primary ACL tears in female patients 11,24. Interestingly, after undergoing a primary ACL reconstruction, female patients are at a higher risk of sustaining a contralateral ACL tear than a rerupture of a reconstructed ACL 15. When Paterno et al. compared patients who had undergone an ACL reconstruction with healthy controls, all of whom participated in cutting and pivoting sports, at a 2-year follow-up, they found that female patients within the ACL reconstruction group were twice as likely to sustain a contralateral injury than an ipsilateral retear 15. Salmon et al. found a similar risk of reinjury to the reconstructed ACL among male and female patients, and, similar to Paterno et al., a trend of higher risk of contralateral ACL injury in female patients than in male patients 11. Shelbourne et al. followed 1,415 patients for a minimum of 5 years and found that there was no significant difference in male patients between sustaining an ipsilateral reinjury (4.1%) and injuring the contralateral ACL (3.7%), but found that significantly more women sustained a contralateral injury (7.8%) than a reinjury (3.7%) (p, 0.001) 12. The senior author (B.R.B.) recently reviewed his 30-year outcome data following ACL reconstruction and found a substantial difference in revision rates between female patients (2.6%) and male patients (1.2%), especially in patients younger than 20 years of age. In his own personal data set, the senior author found that 5.3% of patients (111 patients, 56 of whom were female and 55 of whom were male) who underwent a primary ACL reconstruction subsequently underwent a contralateral ACL reconstruction. Furthermore, female patients were more likely to undergo contralateral reconstruction than male patients (6.4% for female patients compared with 4.4% for male patients; p ), and the contralateral ACL reconstruction was performed at a mean of 34 months following the primary ACL reconstruction in female patients compared with 48 months in male patients (p ). Therefore, the implication is that this is not a compensatory phenomenon. Patient Age Several studies have evaluated the impact of patient age on the risk of reinjury following ACL reconstruction The common thread among those studies was that failure rates following ACL reconstruction are much higher in younger patients than older 2 JUNE 2017 VOLUME 5, ISSUE 6 e1

3 patients 1,3,5,14,19,20, Maletis et al. found that the risk of reinjury drops by 7% for every year of increasing patient age 10. Shelbourne et al. found that patients younger than 18 years of age who had an ACL reconstruction using a bone-patellar tendon-bone (BTB) autograft had a higher risk of retearing the reconstructed ACL and of tearing the contralateral ACL than patients older than 18 years of age 12. Furthermore, patients younger than 18 years of age had an 8.7% risk of reinjuring the ACL and an 8.7% risk of sustaining a contralateral ACL injury. A dramatic decrease in reinjury rates was seen in patients between the ages of 18 and 25 years, with a 2.6% risk of retear and a 4.0% risk of a contralateral ACL tear. After the age of 25 years, patients had a 1.1% risk of a retear and a 2.8% rate of a contralateral ACL tear. Similarly, Webster et al. 36 found that patients younger than 20 years of age who underwent a primary ACL reconstruction had a 6 times higher risk of graft rupture than older patients, and Wasserstein et al. used the Canadian registry of 12,967 ACL reconstructions to show that patients in the 15 to 19-year age range had a 2.1 times higher risk of reinjury than older patients 14. Finally, of the 12,193 patients in the Danish registry who underwent ACL reconstruction, the revision rate for patients younger than 20 years of age was 8.7% compared with 2.8% for those 20 years of age and older 18. The senior author found a higher revision rate following primary ACL reconstruction among patients younger than 20 years of age (2.8%) compared with those older than 30 years of age (,1.0%). Graft Type The impact of primary ACL reconstruction graft type on the need for revision ACL reconstruction is a continued source of debate. As multiple graft choices exist, and surgeon preference may impact graft selection, it is difficult to make an unequivocal recommendation on graft choice. Although some surgeons may be technically more comfortable with a patellar tendon autograft but others prefer a hamstring autograft, a technically well-performed ACL reconstruction is likely more important than the specific graft used by the surgeon. One caveat is that allograft should be used very selectively in patients younger than 25 years of age, as there are convincing data suggesting a higher rate of failure with allograft in this cohort. Mohtadi et al. performed a Cochrane database review of 19 studies (1,597 patients) to determine the differences in rerupture rates and clinical outcomes for patients who underwent primary ACL reconstruction with either BTB autograft or hamstring autograft 34. The authors found no difference in clinical outcome scores or rerupture rates between groups, although BTB autografts more commonly resulted in stable knees with a higher prevalence of stiffness and anterior knee pain than hamstring autografts 34. Conversely, Reinhardt et al. performed a systematic review of Level-I studies and found a reinjury rate of 15.8% with hamstring autografts and only 7.2% with BTB autografts 37. The senior author found a substantial difference in revision rates between primary ACL reconstruction performed using BTB allograft (2.7%) and BTB autograft (1.3%) when evaluating his 30-year outcome data, with a more substantial difference noted in patients younger than 30 years of age. Using the Norwegian Cruciate Ligament Registry of 12,643 patients who underwent ACL reconstruction, Persson et al. reported a twofold higher failure rate with hamstring autografts compared with BTB autografts 38. Rahr-Wagner et al. used the Danish Knee Ligament Reconstruction Registry to show that the relative risk of revision surgical procedures in patients who underwent ACL reconstruction with a hamstring autograft compared with BTB autograft was Several other studies have corroborated the results that failure rates of hamstring autografts are higher than those of BTB autografts 10,39,40. When deciding on an autograft choice, one must take donor-site morbidity into consideration as well, as patients who routinely kneel for their job or religious beliefs may not tolerate the discomfort from a BTB autograft harvest as well as they would tolerate a hamstring harvest. Conversely, some surgeons may avoid hamstring autografts in athletes who compete in hamstring-dominant sports such as skiing and soccer, although there is little evidence to support this theory. This is just one part of the discussion that must be undertaken with patients prior to performing an ACL reconstruction. The comparison of autografts and allografts is more straightforward. A number of studies have found a higher retear rate and need for revision ACL reconstruction when patients undergo ACL reconstruction with allograft compared with autograft, especially among young athletes 10,14,30,41,42. Engelman et al. compared the use of hamstring autograft (35 patients) with that of soft-tissue allograft (38 patients) in adolescent male patients and found a 4.4 times higher risk of graft failure in the allograft group 30. The authors also noted that the failure risk in the softtissue allograft group continued to rise between 24 and 28 months postoperatively, but the failure risk in the hamstring autograft group remained constant 30. Similarly, Ellis et al. found a 15 times higher risk of retear in patients younger than 18 years of age who received a BTB allograft compared with a BTB autograft 29. Bottoni et al. compared 50 patients who underwent ACL reconstruction using hamstring autograft with 50 patients who underwent ACL reconstruction using tibialis posterior allograft and, at a minimum follow-up of 10 years, found 4 autograft failures (8.3%) and 13 allograft failures (26.5%) that required revision ACL reconstruction 41. Finally, a 5 times higher risk of graft rerupture was seen by the Multicenter Orthopaedic Outcomes Network (MOON) study group when comparing allograft reconstruction with autograft reconstruction in all patients 32. JUNE 2017 VOLUME 5, ISSUE 6 e1 3

4 Patient factors, such as graft morphology, particularly with hamstring autografts, also come into consideration, as these may impact outcomes. Although BTB grafts are routinely harvested with a 10-mm tendon width, the diameter of a hamstring autograft can, unfortunately, be variable on the basis of the patient s anatomy. Graft diameter of hamstring autografts has been shown to affect revision rates 43. Spragg et al. evaluated 491 patients who underwent ACL reconstruction using a hamstring autograft and separated the patients into those who had undergone a revision ACL reconstruction (124 patients) and those who had not (367 patients) during their study period. The authors found the likelihood of a patient requiring a revision ACL reconstruction was 0.82 times lower for every 0.5-mm increase in the graft diameter from 7.0 mm to 9.0 mm 43. Hence, although previous evidence suggested that a mean diameter of 8 mm is sufficient to decrease rerupture rates following ACL reconstruction using a hamstring graft, it appears that a graft diameter of,9 mm may place the patient at increased risk of requiring a revision ACL reconstruction when using a hamstring graft 44. Timing of Return to Sport One of the most controversial issues surrounding ACL reconstruction is timing of return to competitive sports participation. Allowing patients to return to sport too early risks reinjury, but restricting them for too long results in missed play and reduced rates of return to sport. To our knowledge, there has been no good literature to support a specific timetable for athletes to return to sport following ACL reconstruction to minimize the risk of revision ACL reconstruction, although earlier onset of osteoarthritis may plague those who return to sport too quickly. Petersen and Zantop surveyed 221 orthopaedic surgeons and found that only 5 surgeons (2.3%) recommended return to sport between 4 and 6 months; all other surgeons required a minimum of 6 months to allow return to sport, with the majority (35.3%) recommending 6 to 8 months of recovery before return to sport 45. Erickson et al. surveyed 137 team physicians for the National Football League (NFL) and National Collegiate Athletic Association (NCAA) Division-I Football and found that 55.8% recommended waiting at least 6 months before return to sport, but 12.3% recommended waiting at least 9 months to return to sport following ACL reconstruction in their elite-level football players 46. Interestingly, no physician in this survey recommended waiting at least 12 months to return to sport following ACL reconstruction. In contrast, Shelbourne et al. investigated the risk of sustaining a retear following return to sport longer than or shorter than 6 months after an ACL reconstruction using a BTB autograft and found no significant difference in rerupture rates 12. Conversely, in a study of 168 patients who underwent ACL reconstruction with a soft-tissue allograft, van Eck et al. found a significantly higher failure rate when patients were allowed to return to sport before 7 months compared with waiting at least 9 months 35. In the senior author s experience of personal revision and reoperation rates over 30 years in 2,275 primary ACL reconstructions using either BTB autograft or allograft, there have been only 3 patients who reinjured the knee in the first year following reconstruction using a 4.5 to 6-month return-to-sport protocol. Technical Considerations When Performing a Revision ACL Reconstruction Graft Choice Deciding on a particular graft choice when performing a revision ACL reconstruction is important, as the failure rate can be directly correlated with the graft that is used. There are many factors that may contribute to graft choice recommendation or selection for patients undergoing a revision ACL reconstruction. The Multicenter ACL Revision Study (MARS) group recently investigated the propensity score, defined as the conditional probability of the treatment choice, given the individual s covariates, on graft choice for revision ACL reconstruction 47. The authors found that surgeon, prior graft choice, and patient age each had substantial influence on which graft type was chosen for the revision ACL reconstruction. Of the factors, surgeon preference had the largest impact on the graft choice (approximately 5 times more influential than the second factor, which was the graft used for the index ACL reconstruction). Unfortunately, the risk of failure of an allograft in the setting of a revision ACL reconstruction is higher than that of an autograft. The MARS Group compared patients who underwent revision ACL reconstruction using autograft compared with allograft to determine the risk of failure and clinical outcomes 48. The study involved 1,205 patients (583 autograft, 590 allograft, and 32 both autograft and allograft) and found that patients who underwent revision ACL reconstruction with autograft were 2.78 times less likely to retear the revision ACL reconstruction than patients who had an allograft. The autograft group also had significantly better clinical outcome scores using the Knee injury and Osteoarthritis Outcome Score (KOOS), International Knee Documentation Committee (IKDC) score, and others (p, 0.001). However, patient age and activity level also come into play when deciding on graft choice for revision ACL reconstruction. Allografts may be well suited for recreational athletes older than 30 years of age, but autografts may be a better choice for younger athletes who wish to return to higher-level athletics. Interestingly, graft-processing methods seem to play a role in the success of allograft ACL reconstruction. Tejwani et al. recently used the Kaiser Permanente ACL Reconstruction Registry to evaluate 5,968 primary ACL reconstruction cases 49. The authors used aseptic failure as a primary outcome and found that the use of BioCleanse (RTI Surgical) and graft irradiation of JUNE 2017 VOLUME 5, ISSUE 6 e1

5 Mrad were associated with a higher risk of revision when compared with all other methods of processing. Many factors may impact allograft results: method of secondary sterilization, donor age, type of allograft (soft tissue, Achilles tendon, quadriceps tendon, BTB); one factor that has not been reported, to our knowledge, is whether a hemi-btb graft has inferior clinical results compared with a central one-third BTB allograft. Yanke et al. evaluated various types of BTB allografts (central portion of a whole bone tendon [BT] allograft, the medial 10 mm of a lateral hemi-btb allograft, and the lateral 10 mm of a medial hemi-btb allograft) to determine if differences existed in biomechanical properties 50. The authors found that the biomechanical failure properties, including maximum stress, stiffness, and load, of the central portion of a whole BTB allograft were superior to those of the lateral portion of a medial hemi-btb allograft and the medial portion of a lateral hemi-btb allograft. The best choice for autograft in the revision ACL reconstruction setting remains a topic of debate as BTB autograft (either ipsilateral or contralateral), hamstring autograft, and quadriceps tendon autograft are all viable options. Häner et al. compared 30 patients who underwent revision ACL reconstruction using contralateral hamstring autograft with 30 patients who underwent revision ACL reconstruction using ipsilateral quadriceps autograft 51. The authors found no difference in clinical outcomes or revision rates between the 2 groups. Similarly, to our knowledge, there has been only Level-IV evidence to show that either BTB autograft or hamstring autograft is a preferred graft option in the revision ACL reconstruction setting 52. Again, patient-specific factors including occupation, religious beliefs, and pain tolerance must come into play when deciding on a graft choice for a revision ACL reconstruction. An important consideration is the presence of bone tunnel expansion. If, for example, the primary graft was a BTB autograft or allograft, the previous tunnels might be larger than ones generally used for a hamstring graft. In the senior author s experience involving 225 revision procedures (41 personal and 184 referred), the personal repeat revision rate has been 3.5% for cases in which a BTB allograft was used (this accounted for 76% of the revision procedures). Hence, allograft was a source of failure compared with autograft in the senior author s results. The recommendations-for-care table (Table I) further elaborates on graft choice and other variables. One-Stage Compared with 2-Stage Revision Surgical Procedures One issue that must be considered when performing a revision ACL TABLE I Recommendations for Care in Recommendation Supporting Evidence Grade of Recommendation* Autograft is preferred because of lower retear rate and higher clinical outcome scores Soft-tissue autograft or BTB autograft may be used on the basis of graft availability and surgeon preference, with similar outcomes Advanced meniscal and chondral damage identified at time of revision ACL reconstruction is associated with inferior 2-year outcomes Two-stage revision ACL reconstruction should be performed in the presence of active infection, arthrofibrosis, or excessive tunnel widening Excessive tunnel widening of.15 mm should cause consideration of 2-stage revision ACL reconstruction For 2-stage revision ACL reconstruction, time from tunnel bone-grafting to revision ACL reconstruction should be 24 weeks Timing of return to sport after revision ACL reconstruction may be longer and rate of return to sport is lower than primary ACL reconstruction Two-stage revision should also be considered, depending on surgeon preference, for concomitant disease such as malalignment requiring osteotomy or cartilage restoration MARS Group 48 (Level II) MARS Group 48 (Level II); Balazs 52 (Level IV); Häner 51 (Level II) MARS Group 68 (Level II) Uchida 56 (Level IV); Franceschi 70 (Level IV); Thomas 57 (Level III) Anand 64 (Level IV); Shelbourne 65 (Level II) Dejour 54 (Level IV) B B B I I C B C *Grade A 5 Good evidence (Level-I studies with consistent findings) for or against recommending intervention. Grade B 5 Fair evidence (Level-II or III studies with consistent findings) for or against recommending intervention. Grade C 5 Conflicting or poor-quality evidence (Level-IV or V studies) not allowing a recommendation for or against intervention. Grade I 5 There is insufficient evidence to make a recommendation. JUNE 2017 VOLUME 5, ISSUE 6 e1 5

6 reconstruction is whether the procedure should be performed as a single operation or in a staged fashion. There are straightforward indications for performing a 2-stage revision ACL reconstruction including active infection and arthrofibrosis, as putting a new graft in a stiff or infected knee is likely to lead to suboptimal outcomes. An active infection should undergo irrigation and debridement and should be proven to be eradicated (normalized laboratory test results, negative aspiration) before a patient has a new graft and implant put in place. Similarly, a patient with substantial loss of knee range of motion should undergo a lysis of adhesions and manipulation under anesthesia followed by rehabilitation and then the second stage of the revision ACL reconstruction when the reconstruction is performed. Unfortunately, other situations that may require a 2-stage revision are not as straightforward. There is controversy as it relates to performing a 1 or 2-stage revision ACL reconstruction in patients with concomitant disease such as limb malalignment, meniscal deficiency, cartilage defects, and others. These factors are important to address as studies have shown increased failure rates when they are not properly treated, especially as they relate to lateral posterior tibial slope and meniscal deficiency 53. It has been shown that tibial dorsiflexion osteotomies performed concomitantly with revision ACL reconstruction in patients with excessive posterior tibial slope are protective of the revised ACL and decrease the risk of further injury 54. Unfortunately, there have been no high-level studies, to our knowledge, that have compared a single-stage with a 2-stage revision ACL reconstruction in these groups of patients, so it is difficult to make a definitive recommendation as to whether treatment of the concomitant disease can be performed at the same time as the revision ACL reconstruction, or should be performed in a staged manner. In the senior author s experience, the necessity to perform a staged tunnel grafting followed by definitive ACL reconstruction has been very unusual. One of the indications for performing a 2-stage revision ACL reconstruction is substantial tunnel widening on the tibial side, femoral side, or both. In the setting of clinically important tunnel widening, patients typically undergo bone-grafting primarily and then undergo revision ACL reconstruction in a staged fashion after the graft has incorporated into the tunnels. To perform a bone-grafting procedure, first any implanted material (screws, wires, and so forth) that is in the way must be removed and the previous tunnels must be debrided of any soft tissue and sclerotic bone using a shaver, burr, drill, rasp, and curet. All viable, good bone should be preserved. Bone graft, either in the form of iliac crest or tibial autograft or allograft, is then impacted into each tunnel. For autograft, the bone is harvested as dowels and then is impacted into the tunnels. For allograft, a single bone dowel approximately 1 mm larger than the diameter of the tunnel is used. It is inserted using a bone tamp for a press fit. The sterilization technique, risks, and cost information for these dowels have been previously described 55. Morselized bone graft inserted using an enlarged anteromedial arthroscopic portal directly into the bone defect is also an option for bone-grafting. A 3-mL syringe with the tip cut off will allow insertion of graft into the defect while minimizing extravasation of graft into the joint. The tibial tunnel is packed from outside the joint, ensuring that one does not breach the joint with the bone graft. At the conclusion of the case, the joint is examined arthroscopically to verify that no free pieces of bone graft are loose in the knee. A critical factor of this 2-stage revision that must be addressed is the amount of time that one should wait between the first stage, when the patient undergoes bone-grafting, and the second stage, which involves the ACL reconstruction. Uchida et al. reviewed 10 consecutive patients (4 female patients and 6 male patients, with a mean age of 28 years) who underwent bonegrafting with autogenous graft as the first stage of their 2-stage revision ACL reconstruction to determine the ideal time to perform the second stage of the revision 56. The authors performed computed tomography (CT) scans at 3, 12, and 24 weeks following bone-grafting to determine the occupying ratio, union ratio, bone mineral density of the grafted bone, and side-to-side bone mineral density ratio. The mean occupying ratios were 81% at 3 weeks, 85% at 12 weeks, and 94% at 24 weeks; the mean union ratios were 49% at 3 weeks, 75% at 12 weeks, and 89% at 24 weeks, with a significant increase seen between 3 and 12 weeks for the occupying ratio (p ) and union ratio (p, ) as well as between 12 and 24 weeks for the occupying ratio (p, ) and union ratio (p, ). The mean bone mineral density was 510 mg/cm 3 at 12 weeks and 571 mg/cm 3 at 24 weeks, which was a significant increase (p ), although the clinical importance is unknown. Considering prior evidence and the evidence put forth in this study, it appears that 12 to 24 weeks is a reasonable amount of time to wait to perform the second stage of a revision ACL reconstruction in which the first stage involved bonegrafting with autograft 57. This recommendation cannot be translated to allograft bone dowels, as the authors only evaluated autograft. Although no absolute value exists for the amount of tunnel widening that must be present to definitively dictate whether a patient must undergo a 2-stage revision ACL reconstruction, if more than 10 to 15 mm of tunnel widening is present, the best available evidence suggests that a patient should undergo a 2-stage revision ACL reconstruction 57,58. Overall, a 1-stage revision ACL reconstruction can be performed in patients who have adequate bone stock, properly positioned tunnels, and implant material that will not interfere with graft fixation or can be removed for graft fixation. Furthermore, if the original tunnels are extremely 6 JUNE 2017 VOLUME 5, ISSUE 6 e1

7 malpositioned and will not interfere with the revision ACL reconstruction tunnel placement in the proper anatomic location, a single-stage revision can also be performed while ignoring the old tunnels and implant 25. Timing of Return to Sport Following Many recent studies have demonstrated the overall success and ability to return to sport following a primary ACL reconstruction in both recreational and elite-level athletes across multiple sports 31, Unfortunately, although the return-to-sport rate following primary ACL reconstruction is encouraging, the return-to-sport rate following revision ACL reconstruction is lower. Studies have shown the return-to-sport rate in the revision ACL reconstruction setting to be 46% to 74% among athletes of all levels, with recreational athletes having the lowest return-tosport rate at 62% and high school and college athletes achieving a 74% return-to-sport rate 64,65.Unfortunately, there have been no data, to our knowledge, to support a specific timetable to allow patients to safely return to sport or a specific rehabilitation program that should be adhered to following revision ACL reconstruction. Many surgeons will prolong the time to return to sport in their patients who have undergone revision ACL reconstruction, particularly if these surgeons also performed the index ACL reconstruction. Legnani et al. compared 23 patients who underwent revision ACL reconstruction using contralateral hamstring autograft with 21 patients who underwent revision ACL reconstruction using either BTB or Achilles tendon allograft 66. Those authors did not find a difference in clinical outcome scores or return-to-sport rates between the groups, but did find a quicker mean time to return to sport in the hamstring autograft group (7.7 months) compared with the allograft group (9.8 months). The faster return-to-sport time in the hamstring autograft group could have had something to do with the tunnel sizes that were drilled or with the use of an all-soft-tissue graft, although both theories are speculative. Surgical Outcomes It has been well established in the literature that the results following revision ACL reconstruction are inferior to those of primary ACL reconstruction, with lower rates of return to sport and a prolonged time frame to return to sport 20,48,67. The MARS Group recently reported on 1,205 patients who underwent revision ACL reconstruction 68. No patients included in this study had concomitant ligamentous injuries. The authors found that prior injury and treatment of the medial and lateral menisci, as well as the presence of articular cartilage damage, were substantially associated with poorer outcomes at 2 years following revision ACL reconstruction. Patients who underwent a prior partial lateral meniscectomy had significantly poorer outcomes on the IKDC score, KOOS subscales, and all Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) subscales. Furthermore, patients with grade-3 to 4 trochlear cartilage damage had significantly worse outcomes in the IKDC as well as most KOOS and WOMAC subscales. This information is important to understand, as preoperative counseling of patients undergoing revision ACL reconstruction should be very different from that before a primary ACL reconstruction, and establishing appropriate goals and expectations preoperatively may prevent frustration postoperatively. However, it should be noted that these statistical differences do not always correlate with clinical meaningful differences, and surgeons should continue to scrutinize the results of their own patients in comparison with the literature before changing practice. Carson et al. reported the results of 43 patients who underwent a singlestage revision ACL reconstruction, the majority of whom (93%) required a concomitant procedure at the time of revision 69. At the 2-year follow-up, 86% of patients had a negative pivot shift and a grade-0 or 1 Lachman result, 63% of patients had good or excellent outcomes on the Hospital for Special Surgery (HSS) knee rating system, and 74% of patients returned to athletic activity at the preoperative level or with some limitations. Diamantopoulos et al. studied 107 patients who underwent revision ACL reconstructions 19. Six of these underwent a 2-stage revision. At 73 months following the surgical procedure, meaningful improvements were witnessed in Lysholm and Tegner scores. Unfortunately, the majority of patients did not return to their pre-injury activity level 19. The results of the 2-stage revisions were not differentiated from the single-stage revisions. Anand et al. reviewed 109 patients who underwent revision ACL reconstruction at a mean follow-up of 5 years after revision 64. All patients included in that study participated in high-impact sports that involved jumping, pivoting, and cutting before the index ACL reconstruction. Of the 109 patients, 105 had a single-stage revision ACL reconstruction and 4 had a 2-stage revision ACL reconstruction. After revision ACL reconstruction, 46% of patients returned to their pre-injury level of sport compared with 50% following their index ACL reconstruction. There were 7 professional athletes in this cohort; 5 were able to return to sport at the same level after their index ACL reconstruction, and 4 of these 5 were able to return to sport at the same level after their revision ACL reconstruction. In this cohort, patients younger than 25 years of age were more likely to return to sport at the same level than older patients. Interestingly, 13% of the patients who had a revision ACL reconstruction went on to rerupture their ACL, and the majority underwent a second revision ACL reconstruction. When reviewing his personal revision and rerevision rates for ACL reconstruction, the senior author found the revision rate following primary ACL reconstruction to be 1.8% JUNE 2017 VOLUME 5, ISSUE 6 e1 7

8 (40 of 2,225) and the rerevision rate of patients who had undergone revision ACL reconstruction procedure to be 3.5%. All failed revision cases were BTB allograft. To our knowledge, only 2 studies in the literature have shown results of 2-stage revision ACL reconstruction alone 57,70. Franceschi et al. reviewed 30 patients who underwent a 2-stage revision ACL reconstruction after a traumatic rerupture 70. The first stage included implant removal and filling of the tunnels with autograft bone from the tibia (mean tunnel size, 10.4 mm in diameter and 26.4 mm in length). At a minimum of 3 months following the bone-grafting procedure and after CT was obtained to demonstrate adequate fill of the tunnels, the second-stage ACL reconstruction was performed. The revision ACL reconstruction was performed using hamstring autograft through a transtibial drilling technique. At 5 years postoperatively, 86.7% of patients had full extension and 66.7% returned to their pre-injury level of sport. Thomas et al. reviewed 49 consecutive 2-stage revision ACL reconstruction procedures: stage I consisted of implant removal and bone-grafting of the tunnels, and stage II was the revision ACL reconstruction 57. They then compared the revision group with a group of patients who underwent only a primary ACL reconstruction. The authors found significantly more patients with meniscal and chondral disease in the revision ACL reconstruction group. At the 6-year follow-up, there was an improvement in the IKDC scores for both groups, but higher scores were seen in the primary ACL reconstruction group. Interestingly, no difference in objective laxity of the knee was seen between groups. Conclusions Revision ACL reconstruction presents a unique set of challenges to the treating surgeon. Patient factors, graft types, surgical technique, and timing of return to sport are all aspects of the treatment algorithm that can affect outcomes in this patient population. Setting realistic expectations with patients undergoing revision ACL reconstruction is of paramount importance as the clinical results for revision ACL reconstruction are inferior to primary ACL reconstruction. Brandon J. Erickson, MD 1, Gregory L. Cvetanovich, MD 1, Rachel M. Frank, MD 1, Andrew J. Riff, MD 1, Bernard R. Bach Jr., MD 1 1 Midwest Orthopaedics at Rush, Rush University Medical Center, Chicago, Illinois address for B.R. Bach Jr.: brbachmd1952@gmail.com References 1. Mall NA, Chalmers PN, Moric M, Tanaka MJ, Cole BJ, Bach BR Jr, Paletta GA Jr. Incidence and trends of anterior cruciate ligament reconstruction in the United States. Am J Sports Med Oct;42(10): Epub 2014 Aug Frank CB, Jackson DW. The science of reconstruction of the anterior cruciate ligament. J Bone Joint Surg Am Oct;79 (10): Marrale J, Morrissey MC, Haddad FS. A literature review of autograft and allograft anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc Jun;15(6): Epub 2007 Apr George MS, Dunn WR, Spindler KP. Current concepts review: revision anterior cruciate ligament reconstruction. Am J Sports Med Dec;34(12): Epub 2006 Nov Hettrich CM, Dunn WR, Reinke EK, Spindler KP; MOON Group. The rate of subsequent surgery and predictors after anterior cruciate ligament reconstruction: two- and 6-year follow-up results from a multicenter cohort. Am J Sports Med Jul;41(7): Epub 2013 May Leiter JR, Gourlay R, McRae S, de Korompay N, MacDonald PB. Long-term follow-up of ACL reconstruction with hamstring autograft. Knee Surg Sports Traumatol Arthrosc May;22 (5): Epub 2013 Apr Wright RW, Magnussen RA, Dunn WR, Spindler KP. Ipsilateral graft and contralateral ACL rupture at five years or more following ACL reconstruction: a systematic review. J Bone Joint Surg Am Jun 15;93(12): Borchers JR, Pedroza A, Kaeding C. Activity level and graft type as risk factors for anterior cruciate ligament graft failure: a case-control study. Am J Sports Med Dec;37(12): Epub 2009 Aug Leys T, Salmon L, Waller A, Linklater J, Pinczewski L. Clinical results and risk factors for reinjury 15 years after anterior cruciate ligament reconstruction: a prospective study of hamstring and patellar tendon grafts. Am J Sports Med Mar;40(3): Epub 2011 Dec Maletis GB, Inacio MC, Desmond JL, Funahashi TT. Reconstruction of the anterior cruciate ligament: association of graft choice with increased risk of early revision. Bone Joint J May;95-B(5): Salmon L, Russell V, Musgrove T, Pinczewski L, Refshauge K. Incidence and risk factors for graft rupture and contralateral rupture after anterior cruciate ligament reconstruction. Arthroscopy Aug;21(8): Shelbourne KD, Gray T, Haro M. Incidence of subsequent injury to either knee within 5 years after anterior cruciate ligament reconstruction with patellar tendon autograft. Am J Sports Med Feb;37(2): Epub 2008 Dec Swärd P, Kostogiannis I, Roos H. Risk factors for a contralateral anterior cruciate ligament injury. Knee Surg Sports Traumatol Arthrosc Mar;18(3): Wasserstein D, Khoshbin A, Dwyer T, Chahal J, Gandhi R, Mahomed N, Ogilvie-Harris D. Risk factors for recurrent anterior cruciate ligament reconstruction: a population study in Ontario, Canada, with 5-year follow-up. Am J Sports Med Sep;41(9): Epub 2013 Jul Paterno MV, Rauh MJ, Schmitt LC, Ford KR, Hewett TE. Incidence of second ACL injuries 2 years after primary ACL reconstruction and return to sport. Am J Sports Med Jul;42(7): Epub 2014 Apr Leroux T, Wasserstein D, Dwyer T, Ogilvie- Harris DJ, Marks PH, Bach BR Jr, Townley JB, Mahomed N, Chahal J. The epidemiology of revision anterior cruciate ligament reconstruction in Ontario, Canada. Am J Sports Med Nov;42(11): Epub 2014 Sep Lind M, Lund B, Faunø P, Said S, Miller LL, Christiansen SE. Medium to long-term followup after ACL revision. Knee Surg Sports Traumatol Arthrosc Jan;20(1): Epub 2011 Jul Lind M, Menhert F, Pedersen AB. Incidence and outcome after revision anterior cruciate ligament reconstruction: results from the Danish registry for knee ligament reconstructions. Am J Sports Med Jul;40 (7): Epub 2012 May Diamantopoulos AP, Lorbach O, Paessler HH. Anterior cruciate ligament revision reconstruction: results in 107 patients. Am J Sports Med May;36(5): Epub 2008 Feb Wang B, Lee KT. Results of revision anterior cruciate ligament reconstruction using a transportal technique. Acta Orthop Belg Dec;81(4): Trojani C, Sbihi A, Djian P, Potel JF, Hulet C, Jouve F, BussièreC, Ehkirch FP,BurdinG, Dubrana F, Beaufils P, Franceschi JP, Chassaing V, Colombet P, Neyret P. Causes for failure of ACL reconstruction and influence of meniscectomies after revision. Knee Surg Sports Traumatol Arthrosc Feb;19(2): Epub 2010 Jul Conner CS, Morris RP, Vallurupalli S, Buford WL Jr, Ivey FM. Tensioning of anterior cruciate ligament hamstring grafts: comparing equal tension versus equal stress. Arthroscopy Dec;24(12): Epub 2008 Aug Galdi B, Reyes A, Brabston EW, Levine WN. Autologous hamstring anterior cruciate 8 JUNE 2017 VOLUME 5, ISSUE 6 e1

9 ligament graft failure using the anteromedial portal technique with suspensory femoral fixation: a case series of 7 patients. Orthop J Sports Med Jan 22;3(1): Ponce BA, Cain EL Jr, Pflugner R, Fleisig GS, Young BL, Boohaker HA, Swain TA, Andrews JR, Dugas JR. Risk factors for revision anterior cruciate ligament reconstruction. J Knee Surg May;29(4): Epub 2015 Aug Allen CR, Giffin JR, Harner CD. Revision anterior cruciate ligament reconstruction. Orthop Clin North Am Jan;34(1): Morgan MD, Salmon LJ, Waller A, Roe JP, Pinczewski LA. Fifteen-year survival of endoscopic anterior cruciate ligament reconstruction in patients aged 18 years and younger. Am J Sports Med Feb;44(2): Epub 2016 Jan Andernord D, Desai N, Björnsson H, Ylander M, Karlsson J, Samuelsson K. Patient predictors of early revision surgery after anterior cruciate ligament reconstruction: a cohort study of 16,930 patients with 2-year follow-up. Am J Sports Med Jan;43(1): Epub 2014 Oct Barrett AM, Craft JA, Replogle WH, Hydrick JM, Barrett GR. Anterior cruciate ligament graft failure: a comparison of graft type based on age and Tegner activity level. Am J Sports Med Oct;39(10): Epub 2011 Jul Ellis HB, Matheny LM, Briggs KK, Pennock AT, Steadman JR. Outcomes and revision rate after bone-patellar tendon-bone allograft versus autograft anterior cruciate ligament reconstruction in patients aged 18 years or younger with closed physes. Arthroscopy Dec;28(12): Epub 2012 Oct Engelman GH, Carry PM, Hitt KG, Polousky JD, Vidal AF. Comparison of allograft versus autograft anterior cruciate ligament reconstruction graft survival in an active adolescent cohort. Am J Sports Med Oct; 42(10): Epub 2014 Jul Harris JD, Erickson BJ, Bach BR Jr, Abrams GD, Cvetanovich GL, Forsythe B, McCormick FM, Gupta AK, Cole BJ. Return-to-sport and performance after anterior cruciate ligament reconstruction in National Basketball Association players. Sports Health Nov;5 (6): Kaeding CC, Pedroza AD, Reinke EK, Huston LJ, Spindler KP; MOON Consortium. Risk factors and predictors of subsequent ACL injury in either knee after ACL reconstruction: prospective analysis of 2488 primary ACL reconstructions from the MOON cohort. Am J Sports Med Jul;43(7): Epub 2015 Apr Kamien PM, Hydrick JM, Replogle WH, Go LT, Barrett GR. Age, graft size, and Tegner activity level as predictors of failure in anterior cruciate ligament reconstruction with hamstring autograft. Am J Sports Med Aug;41(8): Epub 2013 Jun Mohtadi NG, Chan DS, Dainty KN, Whelan DB. Patellar tendon versus hamstring tendon autograft for anterior cruciate ligament rupture in adults. Cochrane Database Syst Rev Sep 7;9:CD van Eck CF, Schkrohowsky JG, Working ZM, Irrgang JJ, Fu FH. Prospective analysis of failure rate and predictors of failure after anatomic anterior cruciate ligament reconstruction with allograft. Am J Sports Med Apr;40(4): Epub 2012 Jan Webster KE, Feller JA, Leigh WB, Richmond AK. Younger patients are at increased risk for graft rupture and contralateral injury after anterior cruciate ligament reconstruction. Am J Sports Med Mar;42(3): Epub 2014 Jan Reinhardt KR, Hetsroni I, Marx RG. Graft selection for anterior cruciate ligament reconstruction: a level I systematic review comparing failure rates and functional outcomes. Orthop Clin North Am Apr;41 (2): Persson A, Fjeldsgaard K, Gjertsen JE, KjellsenAB, EngebretsenL, HoleRM, Fevang JM. Increased risk of revision with hamstring tendon grafts compared with patellar tendon grafts after anterior cruciate ligament reconstruction: a study of 12,643 patients from the Norwegian Cruciate Ligament Registry, Am J Sports Med Feb;42(2): Epub 2013 Dec Rahr-Wagner L, Thillemann TM, Pedersen AB, Lind M. Comparison of hamstring tendon and patellar tendon grafts in anterior cruciate ligament reconstruction in a nationwide population-based cohort study: results from the Danish registry of knee ligament reconstruction. Am J Sports Med Feb;42 (2): Epub 2013 Nov Pallis M, Svoboda SJ, Cameron KL, Owens BD. Survival comparison of allograft and autograft anterior cruciate ligament reconstruction at the United States Military Academy. Am J Sports Med Jun;40(6): Epub 2012 Apr Bottoni CR, Smith EL, Shaha J, Shaha SS, Raybin SG, Tokish JM, Rowles DJ. Autograft versus allograft anterior cruciate ligament reconstruction: a prospective, randomized clinical study with a minimum 10-year followup. Am J Sports Med Oct;43(10): Epub 2015 Aug Kraeutler MJ, Bravman JT, McCarty EC. Bone-patellar tendon-bone autograft versus allograft in outcomes of anterior cruciate ligament reconstruction: a meta-analysis of 5182 patients. Am J Sports Med Oct;41 (10): Epub 2013 Apr SpraggL, ChenJ, Mirzayan R, LoveR, Maletis G. The effect of autologous hamstring graft diameter on the likelihood for revision of anterior cruciate ligament reconstruction. Am J Sports Med Jun;44(6): Epub 2016 Mar Conte EJ, Hyatt AE, Gatt CJ Jr, Dhawan A. Hamstring autograft size can be predicted and is a potential risk factor for anterior cruciate ligament reconstruction failure. Arthroscopy Jul;30(7): Petersen W, Zantop T. Return to play following ACL reconstruction: survey among experienced arthroscopic surgeons (AGA instructors). Arch Orthop TraumaSurg Jul; 133(7): Epub 2013 Apr Erickson BJ, Harris JD, Fillingham YA, Frank RM, Bush-Joseph CA, Bach BR Jr, Cole BJ, Verma NN. Anterior cruciate ligament reconstruction practice patterns by NFL and NCAA football team physicians. Arthroscopy Jun;30(6): Epub 2014 Apr Group M. Factors influencing graft choice in revision anterior cruciate ligament reconstruction in the MARS Group. J Knee Surg Aug;29(6): Epub 2015 Nov MARS Group; MARS Group. Effect of graft choice on the outcome of revision anterior cruciate ligament reconstruction in the Multicenter ACL Revision Study (MARS) Cohort. Am J Sports Med Oct;42(10): Tejwani SG, Chen J, Funahashi TT, Love R, Maletis GB. Revision risk after allograft anterior cruciate ligament reconstruction: association with graft processing techniques, patient characteristics, and graft type. Am J Sports Med Nov;43(11): Epub 2015 Jun Yanke AB, Bell R, Lee AS, Shewman E, Wang VM, Bach BR Jr. Central-third bone-patellar tendon-bone allografts demonstrate superior biomechanical failure characteristics compared with hemi-patellar tendon grafts. Am J Sports Med Nov;41(11): Epub 2013 Sep Häner M, Bierke S, Petersen W. Anterior cruciate ligament revision surgery: ipsilateral quadriceps versus contralateral semitendinosus-gracilis autografts. Arthroscopy Nov;32(11): Epub 2016 May Balazs GC, Grimm PD, Donohue MA, Keblish DJ, Rue JP. Revision anterior cruciate ligament reconstruction in military personnel. J Knee Surg Aug;29(6): Epub 2015 Nov Christensen JJ, Krych AJ, Engasser WM, Vanhees MK, Collins MS, Dahm DL. Lateral tibial posterior slope is increased in patients with early graft failure after anterior cruciate ligament reconstruction. Am J Sports Med Oct;43(10): Epub 2015 Aug Dejour D, Saffarini M, Demey G, Baverel L. Tibial slope correction combined with second revision ACL produces good knee stability and prevents graft rupture. Knee Surg Sports Traumatol Arthrosc Oct;23(10): Epub 2015 Aug Battaglia TC, Miller MD. Management of bony deficiency in revision anterior cruciate ligament reconstruction using allograft bone dowels: surgical technique. Arthroscopy Jun;21(6): Uchida R, Toritsuka Y, Mae T, Kusano M, Ohzono K. Healing of tibial bone tunnels after bone grafting for staged revision anterior cruciate ligament surgery: a prospective computed tomography analysis. Knee Oct;23(5): Epub 2016 May Thomas NP, Kankate R, Wandless F, Pandit H. Revision anterior cruciate ligament reconstruction using a 2-stage technique with bone grafting of the tibial tunnel. Am J Sports Med Nov;33(11): Epub 2005 Aug Groves C, Chandramohan M, Chew C, Subedi N. Use of CT in the management of anterior cruciate ligament revision surgery. Clin Radiol Oct;68(10):e Epub 2013 Aug Erickson BJ, Harris JD, Cole BJ, Frank RM, Fillingham YA, Ellman MB, Verma NN, Bach BR Jr. Performance and return to sport after anterior cruciate ligament reconstruction in National Hockey League players. Orthop J Sports Med Sep 5;2(9): Erickson BJ, Harris JD, Cvetanovich GL, Bach BR, Bush-Joseph CA, Abrams GD, Gupta AK, McCormick FM, Cole BJ. Performance and return to sport after anterior cruciate ligament reconstruction in male Major League soccer players. Orthop J Sports Med Jul 11;1(2): Erickson BJ, Harris JD, Fillingham YA, Cvetanovich GL, Bhatia S, Bach BR Jr, JUNE 2017 VOLUME 5, ISSUE 6 e1 9