Abstract
Background
Revision anterior cruciate ligament (ACL) reconstruction has been documented to have worse outcomes compared with primary ACL reconstructions. The reasons why remain varied. The purpose of this study was to determine whether previous or current surgical factors noted at the time of revision ACL reconstruction are significant predictors towards activity level, sports function, and osteoarthritis (OA) symptoms at 2-year follow-up.
Hypothesis
Certain factors under the control of the surgeonat the time of revision surgery can both negatively and positively impact outcome.
Study Design
Cohort Study; Level of evidence, 2.
Methods
Revision ACL reconstruction patients were identified and prospectively enrolled between 2006 and 2011. Data collected included baseline demographics, intra-operative surgical technique and joint pathology, and a series of validated patient-reported outcome instruments (International Knee Documentation Committee [IKDC], Knee Injury and Osteoarthritis Outcome Score [KOOS], Western Ontario McMaster Universities Osteoarthritis Index [WOMAC], and Marx activity rating score) completed prior to surgery. Patients were followed up for 2 years, and asked to complete the identical set of outcome instruments.
Regression analysis was used to control for age, gender, body mass index (BMI), activity level, baseline outcome scores, revision number, time since last ACL reconstruction, and a variety of previous and current surgical variables, in order to assess the surgical risk factors for clinical outcomes 2 years after revision ACL reconstruction.
Results
A total of 1205 patients (697 [58%] males) met the inclusion criteria and were successfully enrolled. The median age was 26 years, and median time since their last ACL reconstruction was 3.4 years.
Two-year follow-up was obtained on 82% (989/1205). Both previous as well as current surgical factors were found to be significant contributors towards poorer clinical outcomes at 2 years. The most consistent surgical factors driving outcome in revision patients were prior surgical approach (arthrotomy vs. no arthrotomy), prior tibial tunnel position, femoral fixation at the time of revision, and having a notchplasty. Having a previous arthrotomy (non-arthroscopic open approach) for ACL reconstruction compared to the one-incision technique resulted in significantly poorer outcomes on 2-year IKDC (p=0.037; odds ratio[OR]=2.43; 95% CI, 1.05–5.88) and KOOS pain, sports/rec, and quality of life (QOL) subscales (p≤0.05; OR range=2.38–4.35; 95% CI, 1.03–10.0). Using a metal interference screw for current femoral fixation resulted in significantly better outcomes in 2-year KOOS symptoms, pain, and QOL subscales (p≤0.05; OR range=1.70–1.96; 95% CI, 1.00–3.33), as well as WOMAC stiffness (p=0.041; OR=1.75; 95% CI, 1.02–3.03). Not having a notchplasty at revision significantly improved 2-year outcomes of the IKDC (p=0.013; OR=1.47; 95% CI, 1.08–1.99), KOOS activities of daily living (ADL) and QOL subscales (p≤0.04; OR range=1.40–1.41; 95% CI, 1.03–1.93), and the WOMAC stiffness and ADL subscales (p≤0.04; OR range=1.41–1.49; 95% CI, 1.03–2.05).
Factors prior to revision ACL that increase risk of poorer clinical outcomes at two years include lower baseline outcome scores, lower Marx activity score at the time of revision, higher BMI, female gender, and shorter time since the patient's last ACL reconstruction.
Prior femoral fixation, prior femoral aperture position, and the knee flexion angle at the time of revision graft fixation were not found to affect2-year outcomes in this revision cohort.
Conclusions
There are certain surgical variables the physician can control at the time of an ACL revision that can modify clinical outcomes at 2 years. Whenever possible, opting for an anteromedial portal or transtibial surgical exposure, choosing a metal interference screw for femoral fixation, and not having a notchplasty are associated with a significantly better 2-year clinical outcome.
Clinical Relevance
Revision ACL reconstruction remains a challenging clinical situation with revisions resulting in worse outcomes than primary ACL reconstructions. This study adds to the growing body of evidence to improve revision results. Some surgical variables may be utilized to help improve outcome.
Keywords: anterior cruciate ligament, revision ACL reconstruction, outcomes, surgical factors, surgical approach, tunnel position, ACL fixation
What is known about the subject
Little was known prior to the analysis of this cohort regarding surgical options impacting outcome. Most previous studies have centered upon failure, patient-reported outcomes and graft choice surrounding revision reconstruction and have not had the ability to assess the impact of surgical options due to the relatively small clinical series.
Adds to existing knowledge
This study provides evidence from a large prospective ACL revision cohort that surgical factors can be significant contributors towards poorer clinical outcomes at 2 years.
INTRODUCTION
Revision anterior cruciate ligament (ACL) reconstruction has been documented to have worse outcomes compared with primary ACL reconstructions.1–3,8–10,15,20,22,23,25,26The Multicenter ACL Revision (MARS) group has identified several contributing factors for outcomes, including graft choice, previous lateral meniscectomy, and trochlear groove chondrosis.11,12Other factors remain unknown. Numerous factors remain beyond the control of the patient or the surgeon with regards to revision ACL reconstructions. Fortunately, some factors can be chosen by the surgeon when planning reconstruction.
ACL graft choice at the time of revision reconstruction has been shown to affect outcome.5,12,14In a previous study by the MARS group it was demonstrated that the use of an autograft (compared to an allograft) is associated with an improved return to sports and decreased risk of graft re-rupture by 2.78 times.12 Additional factors such as surgical approach (e.g., anteromedial portal, transtibial, 2 incision, arthrotomy), tunnel choice (new, old or “blended”, defined as the combination of old and new tunnels), bone grafting, and fixation choice may have the ability to offer options for the operating surgeon. The purpose of this study was to determine if either previous or current surgical factors noted at the time of ACL revision reconstruction predicted activity level, sports function, and osteoarthritis symptoms at 2-year follow-up. Our hypothesis is that surgical factors under the control of the surgeon (e.g., surgical approach, tunnel choice, notchplasty, bone grafting, fixation choice) can both negatively and positively impact revision ACL reconstruction outcome.
METHODS
Setting and Study Population
The MARS Group was assembled with the aim of determining what impacts outcome in an ACL revision setting, and to identify potentially modifiable factors that could improve these outcomes.6,13,24,27 This collaboration consists of a group of 83 sports medicine fellowship trained surgeons across 52 sites. Surgeons are a near equal mix of academic and private practitioners. After obtaining approval from respective institutional review boards (IRBs), this multicenter consortium began patient enrollment in 2006 and ended in 2011, during which time 1205 revision ACL reconstruction patients were enrolled in this prospective longitudinal cohort. The study enrolled patients undergoing revision of a previously failed ACL reconstruction (as identified by clinical exam, imaging, or arthroscopic confirmation) who agreed to participate, signed an informed consent, and completed a series of patient-reported outcome instruments. Indications for the revision ACL reconstruction included functional instability, abnormal laxity testing or an MRI indicating graft tear. Multi-ligament reconstructions were excluded. Ligament injuries not requiring reconstruction (i.e., MCL) were included. Surgeon inclusion criteria included maintenance of an active IRB approval, completion of a training session that integrated articular cartilage and meniscus agreement studies, review of the study design and patient inclusion criteria, and a review of the surgeon questionnaire.18Surgical technique was at the discretion of the treating surgeon.
Data Sources and Measurement
After obtaining informed consent, the patient filled out a 13-page questionnaire that included questions regarding demographics, sports participation, injury mechanism, comorbidities and knee injury history, as previously described.12,13 Within this questionnaire, each participant also completed a series of validated general and knee-specific outcome instruments, including the Knee Injury and Osteoarthritis Outcome Score (KOOS), the International Knee Documentation Committee Subjective form (IKDC) and the Marx activity rating scale. Contained within the KOOS was the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Surgeons filled out a 42-page questionnaire that included the impression of the etiology of the previous failure, physical exam findings, surgical technique utilized, the intra-articular findings and surgical management of meniscal and chondral damage.
Completed data forms were mailed from each participating site to the data coordinating center. Data from both the patient and surgeon questionnaires were scanned with Teleform™ software (Cardiff Software, Inc., Vista, CA) utilizing optical character recognition, and the scanned data was verified and exported to a master database. A series of logical error and quality control checks were subsequently performed prior to data analysis.
Patient Follow-up
Two-year patient follow-up was completed by mail with re-administration of the same questionnaire as the one they completed at baseline. Patients were also contacted by phone to determine whether any subsequent surgery had occurred to either knee since their initial revision ACL reconstruction. If so, operative reports were obtained, whenever possible, in order to verify pathology and treatment.
Statistical Analysis
To describe our patient sample, we summarized continuous variables as percentiles (i.e., 25th, 50th, and 75th), and categorical variables with frequencies and percentages. Multivariable regression analyses were constructed to examine which baseline risk factors were independently associated with each outcome variable. The primary outcome variables of interest were the 2-year outcome scores of the KOOS, IKDC, WOMAC and Marx activity level. These primary outcome variables were all treated as continuous, and as such, ordinal logistic regression models were used. All models controlled for age, gender, body mass index (BMI), activity level, baseline outcome scores, revision number, time from previous ACL reconstruction, and a variety of previous and current surgical variables (including graft choice, meniscal and chondral damage), in order to assess the surgical risk factors for clinical outcomes 2 years after revision surgery. Per number of levels, categorical variables were fit according to their degrees of freedom (i.e. n-1). To stay within the allowable degrees of freedom, each continuous variable was fit as a linear effect, as there was little or no evidence of a non-linear relationship with a p-value ≤ 0.05 for the non-linear test. Statistical analysis was performed using open source R statistical software (www.r-project.org; Version 3.0.3).
RESULTS
Study Population and Follow-up
A total of 1205 patients (697 [58%] males) met the inclusion criteria and were successfully enrolled. The median age was 26 years, and median time since the patients’ last ACL reconstruction was 3.4 years. Baseline characteristics of the cohort are summarized in Table 1. At 2 years, questionnaire follow-up was obtained on 82% (989/1205).
Table 1.
Baseline Characteristics of Cohort
| N (%) | |
|---|---|
| PATIENT DEMOGRAPHICS | |
|
| |
| Gender | |
| • Males | 697 (58%) |
| • Females | 508 (42%) |
| Age (years) | 20 26 35 |
| BMI | 22.6 25.1 28.5 |
| Baseline Activity Level (Marx) | 4 11 16 |
|
| |
| PREVIOUS SURGICAL INFORMATION | |
|
| |
| Time since last ACL reconstruction (years) | 1.4 3.4 8.3 |
| Revision number | |
| • 1 | 1055 (88%) |
| • 2 | 125 (10%) |
| • 3 or more | 25 (2%) |
| Surgeon’s opinion of failure | |
| • Traumatic | 405 (34%) |
| • Technical | 265 (22%) |
| • Biologic/other | 135 (11%) |
| • Combination | 398 (33%) |
| Cause of technical failure (Surgeon opinion) | |
| • Tunnel malposition | 532 (45%) |
| • Other | 76 (6%) |
| • Combination | 114 (10%) |
| • None | 452 (39%) |
| Surgeon’s revision his/her own failure | |
| • No | 859 (72%) |
| • Yes | 341 (28%) |
| Prior surgical technique | |
| • One-incision | 975 (81%) |
| • Two-incision | 203 (17%) |
| • Open Arthrotomy | 22 (2%) |
| Technique of prior femoral tunnel | |
| • Single tunnel | 1167 (98%) |
| • Double tunnel | 18 (2%) |
| Previous femoral fixation | |
| • Interference screw | 721 (60%) |
| • Endobutton | 205 (17%) |
| • Cross pin | 149 (12%) |
| • Other | 101 (8%) |
| • Combination | 25 (2%) |
| Prior femoral tunnel aperture position1 | |
| • Ideal | 386 (33%) |
| • Ideal (both position + size), but enlarged tunnels | 28 (2%) |
| • Compromised (position) | 689 (58%) |
| • Compromised (size) | 20 (2%) |
| • Compromised (position + size) | 60 (5%) |
| Prior tibial fixation | |
| • Interference screw | 857 (71%) |
| • Other | 241 (20%) |
| • Combination | 101 (8%) |
| Prior tibial tunnel aperture position1 | |
| • Ideal | 721 (60%) |
| • Ideal (both position + size), but enlarged tunnels | 72 (6%) |
| • Compromised (position) | 338 (28%) |
| • Compromised (size) | 35 (3%) |
| • Compromised (position + size) | 27 (2%) |
|
| |
| CURRENT SURGICAL INFORMATION | |
|
| |
| Surgical exposure/technique | |
| • Anteromedial portal | 556 (46%) |
| • Transtibial | 426 (36%) |
| • 2 Incision | 211 (18%) |
| • Open Arthrotomy | 6(1%) |
| Notchplasty | |
| • No | 277 (23%) |
| • Yes | 927 (77%) |
| Femoral tunnel aperture position | |
| • Optimum position | 324 (27%) |
| • Same tunnel – but compromised position | 23 (2%) |
| • Blended new/old tunnel | 220 (18%) |
| • Entirely new tunnel | 590 (49%) |
| • Added a 2nd tunnel | 45 (4%) |
| Femoral tunnel bone graft | |
| • None | 1082 (90%) |
| • Staged (prior) | 87 (7%) |
| • Yes (current) | 32 (3%) |
| Femoral fixation | |
| • Interference screw (metal) | 522 (43%) |
| • Interference screw (bioabsorbable) | 154 (13%) |
| • Suture + button/endobutton | 251 (21%) |
| • Cross pin | 144 (12%) |
| • Other | 55 (5%) |
| • Combination | 76 (6%) |
| Tibial tunnel aperture position | |
| • Optimum position | 692 (58%) |
| • Same tunnel – but compromised position | 23 (2%) |
| • Blended new tunnel | 248 (21%) |
| • Entirely new tunnel | 199 (17%) |
| • Added a 2nd tunnel | 41 (3%) |
| Tibial tunnel bone graft | |
| • None | 1076 (89%) |
| • Staged (prior) | 93(8%) |
| • Yes (current) | 34 (3%) |
| Tibial fixation | |
| • Interference screw (metal) | 386 (32%) |
| • Interference screw (bioabsorbable) | 297 (25%) |
| • Interference screw + suture | 41(3%) |
| • Intrafix | 107 (9%) |
| • Other | 124 (10%) |
| • Combination | 247 (21%) |
| Graft | |
| • Autograft – BTB | 336 (28%) |
| • Autograft – soft tissue | 244 (20%) |
| • Allograft – BTB | 287 (24%) |
| • Allograft – soft tissue | 298 (25%) |
| • Other (ie. autograft +allograft) | 39 (3%) |
| Biologic enhancement | |
| • No | 1103 (92%) |
| • Yes | 97 (8%) |
| Knee position at the time of graft fixation (degrees of flexion) | 0 10 20 |
| Knee position at the time of graft fixation (degrees of hyperextension) | 0 0 0 |
| Surgeon experience (years) | 8 13 18 |
Key: a b crepresents the lower quartile a, the median b, and the upper quartile c for continuous variables.
All tunnel determinations for position and size are individual surgeons’ determinations. BTB = bone-patellar tendon-bone
Influence of Surgical Factors on 2-Year Outcomes
A variety of surgeon-based surgical factors predicted outcome. Both previous as well as current surgical factors were found to be associated with poorer outcomes at 2 years (Table 2).
Table 2.
Significant Odds Ratios (95% CI) for Variables in the Model
| Reference value | Worse Outcome | Marx | Symptoms | Pain | KOOS ADL |
Sports/Rec | QOL | IKDC | Stiffness | WOMAC Pain |
ADL | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PATIENT DEMOGRAPHICS | ||||||||||||
| Age | older age | 1.04 (1.02–1.05) p<0.001 | ||||||||||
| Gender | males | females | 1.93 (1.50–2.49) p<0.001 | 1.30 (1.01–1.66) p=0.041 | 1.67 (1.30–2.13) p<0.001 | 1.36 (1.05–1.76) p=0.018 | 1.30 (1.01–1.66) p=0.041 | |||||
| Body Mass Index (BMI) | higher BMI | 1.04 (1.01–1.08) p=0.014 | 1.04 (1.01–1.08) p=0.008 | 1.06 (1.03–1.10) p<0.001 | 1.04 (1.01–1.08) p=0.003 | 1.04 (1.01–1.08) p=0.012 | 1.06 (1.03–1.09) p<0.001 | 1.05 (1.02–1.09) p=0.001 | 1.06 (1.03–1.10) p<0.001 | |||
| Baseline Activity Level (Marx score) | lower activity level | 1.15 (1.13–1.18) p<0.001 | 1.03 (1.01–1.06) p=0.004 | 1.03 (1.01–1.06) p=0.006 | 1.05 (1.02–1.07) p<0.001 | 1.05 (1.02–1.07) p<0.001 | 1.07 (1.04–1.09) p<0.001 | 1.03 (1.01–1.06) p=0.008 | 1.03 (1.01–1.06) p=0.006 | |||
| Baseline Outcome Scores | lower T0 (baseline) score | 1.15 (1.13–1.18) p<0.001 | 1.05 (1.04–1.05) p<0.001 | 1.05 (1.04–1.06) p<0.001 | 1.06 (1.05–1.06) p<0.001 | 1.03 (1.02–1.03) p<0.001 | 1.03 (1.02–1.04) p<0.001 | 1.05 (1.04–1.05) p<0.001 | 1.04 (1.03–1.05) p<0.001 | 1.05 (1.04–1.06) p<0.001 | 1.06 (1.05–1.06) p<0.001 | |
| SURGICAL INFORMATION | ||||||||||||
| Time since last ACLR (years) | shorter time since last ACLR | 1.05 (1.02–1.08) p<0.001 | 1.06 (1.03–1.09) p<0.001 | 1.07 (1.04–1.10) p<0.001 | 1.06 (1.03–1.09) p<0.001 | 1.05 (1.02–1.08) p<0.001 | 1.05 (1.02–1.08) p=0.002 | 1.07 (1.03–1.10) p<0.001 | 1.07 (1.03–1.10) p<0.001 | 1.07 (1.04–1.10) p<0.001 | ||
| Revision number | 1st | 2nd | 1.64 (1.10–2.44) p=0.014 | |||||||||
| Surgeon experience (years) | less years of experience | 1.03 (1.01–1.05) p=0.007 | ||||||||||
| Surgeon's revision his/her own failure | not surgeon's own failure | 1.52 (1.08–2.14) p=0.015 | ||||||||||
| SURGICAL APPROACH and TUNNEL POSITION | ||||||||||||
| Prior | ||||||||||||
| Surgical approach/exposure | one-incision | open arthrotomy | 2.38 (1.03–5.56) p=0.042 | 3.13 (1.25–7.69) p=0.015 | 4.35 (1.85–10.0) p=0.001 | 2.43 (1.05–5.88) p=0.037 | ||||||
| Femoral tunnel technique | single tunnel | double tunnel | 3.13 (1.14–8.33) p=0.027 | |||||||||
| Femoral tunnel aperture position | ||||||||||||
| Tibial tunnel aperture position | ideal vs. ideal (both position+size), but enlarged tunnels | ideal | 2.03 (1.20–3.42) p=0.008 | 1.88 (1.11–3.19) p=0.019 | 1.79 (1.06–3.02) p=0.030 | 2.06 (1.21–3.52) p=0.008 | 1.19 (1.14–3.22) p=0.014 | 2.68 (1.53–4.70) p=0.001 | 2.13 (1.22–3.70) p=0.008 | 1.88 (1.11–3.19) p=0.019 | ||
| Current | ||||||||||||
| Surgical approach/exposure | AM portal | two-incision | 1.54 (1.04–2.22) p=0.029 | 1.52 (1.04–2.22) p=0.028 | ||||||||
| Femoral tunnel aperture position | optimum position vs. entirely new tunnel | optimum position | 1.79 (1.08–2.94) p=0.025 | |||||||||
| Tibial tunnel aperture position | optimum position | adding a 2nd tunnel | 3.45 (1.16–10.0) p=0.026 | 3.45 (1.16–10.0) p=0.026 | ||||||||
| Notchplasty | no | yes | 1.41 (1.03–1.93) p=0.034 | 1.40 (1.03–1.89) p=0.031 | 1.47 (1.08–1.99) p=0.013 | 1.49 (1.08–2.05) p=0.015 | 1.41 (1.03–1.93) p=0.034 | |||||
| Knee position at time of graft fixation (degrees of flexion) | ||||||||||||
| FIXATION | ||||||||||||
| Current femoral fixation | interference screw (metal) | interference screw (bioabsorbable) | 1.96 (1.18–3.33) p=0.010 | 1.70 (1.00–2.86) p=0.051 | ||||||||
| interference screw (metal) | cross pin | 1.75 (1.02–3.03) p=0.041 | ||||||||||
| interference screw (metal) | combination | 1.92 (1.11–3.33) p=0.019 | ||||||||||
| Current tibial fixation | interference screw (metal) | combination | 1.67 (1.10–2.50) p=0.017 | 1.72 (1.12–2.63) p=0.013 | ||||||||
| BIOLOGY | ||||||||||||
| Femoral tunnel bone graft | none | yes (current) | 2.04 (1.00–4.17) p=0.048 | |||||||||
| Tibial tunnel bone graft | none vs. yes (current) | none | 1.95 (1.01–3.75) p=0.046 | 3.31 (1.47–7.44) p=0.004 | ||||||||
| Biologic enhancement | none | yes | 1.79 (1.08–2.94) p=0.025 |
Key: An empty cell indicates that the particular knee rating at the top of the column was not signficantly affected by the listed variable on the left column.
A. Surgical Approach and Tunnel Choice
A history of arthrotomy at the time of the previous reconstruction (compared to a one-incision technique) was associated with significantly poorer outcomes on 2-year IKDC (p=0.037; odds ratio [OR]=2.43; 95% CI, 1.05–5.88) and KOOS pain, sports/recreation, and quality of life (QOL) subscales (p≤0.05; OR range=2.38–4.35; 95% CI, 1.03–10.0). In particular, patients having a previous arthrotomy from their previous reconstruction were 4.35 times more likely to have a poorer KOOS QOL outcome at 2 years, compared with a patient who had a previous one-incision approach (p=0.001). Patients having a history of double femoral tunnels were 3.13 times more likely to have a poorer KOOS QOL outcome at 2 years, compared with patients who had a single femoral tunnel (p=0.027). A prior tibial tunnel aperture position defined as ‘ideal’ in position and size by the participating MARS surgeon at the time of the revision surgery was associated with significantly worse 2-year clinical outcomes in nearly all instruments (IKDC; KOOS symptoms, pain, ADL, sports/rec, QOL subscales; WOMAC stiffness, pain, ADL subscales), when compared to a tibial aperture position of “ideal in both position and size, but enlarged tunnels”.
At revision surgical exposure with a two-incision technique had worse Marx (p=0.029) and KOOS symptoms (p=0.028) scores compared with anteromedial portal femoral tunnel drilling. Transtibial vs. anteromedial approach was not associated with outcome. Choosing to utilize a previous femoral tunnel that was deemed to be in the optimum position versus drilling an entirely new tunnel was associated with worse KOOS QOL scores (p=0.025).
Choosing to drill a second tibial tunnel versus utilizing the previous tibial tunnel position was associated with a significantly worse KOOS ADL and WOMAC ADL outcome scores at 2 years (p=0.026). In particular, a patient needing a 2nd tibial tunnel drilled had a 3.45 times higher likelihood of having a poorer 2-year KOOS ADL and WOMAC ADL score, when compared to the tibial tunnel being in the optimum position at the time of the revision surgery.
Patients who had a notchplasty at the time of revision had worse IKDC, KOOS ADL and QOL, and WOMAC stiffness and ADL scores. Revisions without a notchplasty had significantly improved 2-year outcomes of the IKDC (p=0.013; OR=1.47; 95% CI, 1.08–1.99), KOOS ADL and QOL subscales (p≤0.04; OR range=1.40–1.41; 95% CI, 1.03–1.93), and the WOMAC stiffness and ADL subscales (p≤0.04; OR range = 1.41–1.49; 95% CI, 1.03–2.05).
B. Fixation Choice
Using a metal interference screw for current revision femoral fixation (compared with bioabsorbable interference screws, cross pins, or a combination of fixation devices) was associated with significantly better outcomes in 2-year KOOS symptoms, pain, and QOL subscales (p≤0.05; OR range=1.70–1.96; 95% CI, 1.00–3.33), as well as WOMAC stiffness (p=0.041; OR=1.75; 95% CI, 1.02–3.03). Similarly, using a metal interference screw for current revision tibial fixation (compared with using a combination of fixation devices) was associated with significantly better IKDC (p=0.017) and WOMAC stiffness (p=0.013) scores.
C. Biology
Femoral tunnel bone grafting, either single or two staged, was associated with worse Marx scores at 2 years (p=0.048; OR=2.04; 95% CI, 1.00–4.17). Conversely, patients who required tibial tunnel bone grafting (single or two staged) actually reported improved outcomes for KOOS pain (p=0.046) and WOMAC pain (p=0.004). Utilization of a biologic enhancement agent (i.e. platelet rich plasma, mesenchymal stem cells) was associated with worse Marx activity level scores at 2 years (p=0.025).
In summary, the most consistent surgical factors associated with better outcome in revision patients were prior surgical approach, prior tibial tunnel position, current femoral fixation, and not having a notchplasty. Conversely, prior femoral fixation, prior femoral aperture position, and the knee flexion angle at the time of graft fixation were not found to be associated with2-year outcomes in this revision cohort.
Influence of Patient Characteristics on 2-Year Outcomes
Lower baseline outcome scores predicted worse 2-year outcomes for Marx activity, all KOOS subscales, IKDC, and all WOMAC subscales (p<0.001). (Table 2) Lower baseline Marx activity scores predicted worse 2-year Marx activity, KOOS pain, ADL, sports/recreation, QOL, WOMAC pain and ADL subscales (p<0.01). Higher BMI predicted worse outcomes for all KOOS subscales, the IKDC and WOMAC pain and ADL subscales (p<0.01). Female gender predicted worse outcome for Marx, KOOS ADLs, IKDC, WOMAC pain and ADL subscales. Age (increased) predicted lower 2-year Marx activity level scores (p<0.001). A shorter time since the last ACL reconstruction predicted worse outcomes for all 5 KOOS subscales and all WOMAC subscales in addition to the IKDC (p≤0.002). A second revision or higher predicted a worse outcome for KOOS knee-related QOL (p=0.014). If the surgeon was revising a patient they had not previously reconstructed it predicted a worse Marx score at 2 years (p=0.015).
DISCUSSION
The goal of this study was to determine if surgeon modifiable factors could be identified that are associated with improved outcome. While there are a few findings that can be impacted by the surgeon, many are beyond the control or do not impact outcome enough to drive technique changes. Tunnel position, fixation, bone grafting and biologic agent usage are at least somewhat controlled by the surgeon and are associated with outcome.
Tunnel position has a variety of presentations in the revision setting and how to drill the new tunnel may be controllable for the surgeon. The pre-existing tunnel may be appropriately placed and utilized again, it may be so poorly positioned that an entirely new tunnel is drilled or it may be a combination which when drilled again results in a blended (blended = a combination old and new tunnel) tunnel that may have a wider aperture. It was feared that a blended tunnel with a wide aperture might result in worse outcomes or higher failure rates. Interestingly, a blended tunnel for the femur and tibia did not impact outcome. However, utilizing a previous tunnel did not result in outcomes as good as those obtained by a completely new tunnel. It may be surmised that at times using a previous tunnel was at some level a compromise of position, by not wanting a blended tunnel. Additionally, revision graft healing within a previously utilized tunnel may impact outcome at a level this current study is unable to detect or measure. There may be biological factors we are yet able to detect that compromise outcome despite correctly drilled tunnels and appropriately placed grafts. Additionally, some factors that predict outcome in this study may not actually be causative, but are surrogates for factors we have not yet identified with our research.
Transtibial drilling did not predict outcome despite some surgeons’ belief that anteromedial portal drilling allows independent and improved ability to localize the femoral tunnel. Previous clinical studies have corroborated this finding that anteromedial portal drilling while theoretically an improvement has not necessarily been verified in clinical findings in the primary ACL reconstruction setting.19,21Two-incision femoral tunnel drilling versus anteromedial drilling impacted outcome as measured by the KOOS Symptoms subscale (p=0.028, OR=1.52). A previous study has not corroborated this finding where both methods resulted in similar outcomes.16
Graft fixation surprisingly impacted outcome in this revision setting. Fixation has rarely been demonstrated to make a clinical difference in the primary setting, where most fixation methods appear adequate for both soft tissue autografts and allografts and patellar tendon autografts and allografts.4,7,17 In the current study, metal femoral fixation resulted in significantly improved KOOS pain, symptoms and QOL subscales. Additionally, use of a metal screw versus a combination of fixation for the tibia improved IKDC and WOMAC stiffness scores. It is not possible to determine the exact pathophysiological reason that this predicts outcome, but bone quality is often worse in the revision setting due to previous tunnels even if not enlarged and use of a metal fixation may overcome some of this challenge. Additionally, metal as an inert implant may offer less reactivity than bioabsorbable in the revision ACL reconstruction setting.
Bone grafting either single or two staged of dilated tunnels can be challenging for patients, resulting in additional surgery and time to ultimate revision if staged. Thus, it is important to determine if this impacts outcome. For dilated tibial tunnels requiring bone grafting it significantly improves patient outcomes as measured by KOOS and WOMAC pain scores. Unfortunately, femoral tunnel bone grafting predicted a worse Marx activity score at 2 years. This represents one of those findings that are challenging to incorporate in practice. Bone grafting a femoral tunnel too dilated should not be avoided to try to improve 2-year Marx scores. Also, utilization of biologic agents to enhance surgical results was not shown to improve outcome and in fact demonstrated worse 2-year MARX scores.
Other factors that were noted to impact outcome, but may not be modifiable include performance of a notchplasty, which resulted in worse KOOS ADL and QOL, IKDC and WOMAC stiffness and ADL scores. If a notchplasty is definitely needed as determined by the surgeon then there remains little choice in performing this step in reconstruction. Typically, in the revision setting this represents notch overgrowth and may be a surrogate indicator of degenerative processes occurring throughout the joint. Within the limits of our study it remains uncertain why a notchplasty would be associated with worse outcome, but our analysis technique controls for a variety of variables including chondral damage and thus it remains an independent predictor. Presence or absence of notchplasty is all that is recorded so size or amount of notchplasty may matter, but that is beyond the scope of our study. The presence of two femoral tunnels from previous surgery is associated with a worse outcome, but is not a surgically modifiable variable. A previous arthrotomy resulted in worse outcome, but is also not able to be modified.
Strengths of the study include the prospective data collection of validated patient-reported outcome measures with the largest prospective revision ACL reconstruction cohort collected to date. This allows multivariable analysis of a high number of factors. Weaknesses include no onsite follow-up, surgeon variation in tunnel drilling as to blended vs. previous tunnel usage, and inability to control indications for bone grafting, tunnel placement and fixation choice by surgeons.
CONCLUSIONS
A variety of surgical variables are represented in the revision ACL reconstruction setting. Some are modifiable, but unfortunately many remain beyond the individual surgeon’s control. The strongest predictor for revision surgery that is controlled by the surgeon is femoral fixation where a metal screw improved outcome. Additional factors that less strongly impacted outcome included drilling a new femoral tunnel vs. utilizing a previous tunnel, and bone grafting the tibia when indicated. Surgical approach for femoral drilling was not a large factor with no advantage of anteromedial versus transtibial, but some improvement of anteromedial over two-incision. Surgeons must balance a variety of these factors in revision ACL reconstruction outcomes along with graft choice, meniscal and articular cartilage findings and management to optimize outcome in these challenging clinical settings.
Acknowledgments
This study received funding from the AOSSM, Smith & Nephew, National Football League Charities, and Musculoskeletal Transplant Foundation. This project was partially funded by grant No. 5R01-AR060846 from the National Institutes of Health/National Institute of Arthritis and Musculoskeletal and Skin Diseases.
Contributor Information
Christina R. Allen, University of California, San Francisco, San Francisco, California USA.
Allen F. Anderson, Tennessee Orthopaedic Alliance, Nashville, TN USA.
Daniel E. Cooper, W.B. Carrell Memorial Clinic, Dallas, TX USA.
Thomas M. DeBerardino, The San Antonio Orthopaedic Group, San Antonio, TX USA.
Warren R. Dunn, Reedsburg Area Medical Center, Reedsburg, WI USA.
Amanda K. Haas, Washington University in St. Louis, St. Louis, MO USA.
Laura J. Huston, Vanderbilt University, Nashville, TN USA.
Brett (Brick) A. Lantz, Slocum Research and Education Foundation, Eugene, OR USA.
Barton Mann, AOSSM, Rosemont, IL USA.
Sam K Nwosu, Vanderbilt University, Nashville, TN, USA.
Kurt P. Spindler, Cleveland Clinic, Cleveland, OH USA.
Michael J. Stuart, Mayo Clinic, Rochester, MN USA.
Rick W. Wright, Washington University in St. Louis, St. Louis, MO USA.
John P. Albright, University of Iowa Hospitals and Clinics, Iowa City, IA USA.
Annunziato (Ned) Amendola, Duke University, Durham, NC USA.
Jack T. Andrish, Cleveland Clinic, Cleveland, OH USA.
Christopher C. Annunziata, Commonwealth Orthopaedics & Rehabilitation, Arlington, VA USA.
Robert A. Arciero, University of Connecticut Health Center, Farmington, CT USA.
Bernard R. Bach, Jr, Rush University Medical Center, Chicago, IL USA.
Champ L. Baker, III, The Hughston Clinic, Columbus, GA USA.
Arthur R. Bartolozzi, 3B Orthopaedics, University of Pennsylvania Health System, Philadelphia, PA USA.
Keith M. Baumgarten, Orthopedic Institute, Sioux Falls, SD USA.
Jeffery R. Bechler, University Orthopaedic Associates LLC, Princeton, NJ USA.
Jeffrey H. Berg, own Center Orthopaedic Associates, Reston, VA USA.
Geoffrey A. Bernas, State University of New York at Buffalo, Buffalo, NY.
Stephen F. Brockmeier, University of Virginia, Charlottesville, VA USA.
Robert H. Brophy, Washington University in St. Louis, St. Louis, MO USA.
Charles A. Bush-Joseph, Rush University Medical Center, Chicago, IL USA.
J. Brad Butler V, Orthopedic and Fracture Clinic, Portland, OR USA.
John D. Campbell, Bridger Orthopedic and Sports Medicine, Bozeman, MT USA.
James L. Carey, University of Pennsylvania, Philadelphia, PA USA.
James E. Carpenter, University of Michigan, Ann Arbor, MI USA.
Brian J. Cole, Rush University Medical Center, Chicago, IL USA.
Jonathan M. Cooper, HealthPartners Specialty Center, St. Paul, MN USA.
Charles L. Cox, Vanderbilt University, Nashville, TN USA.
R. Alexander Creighton, University of North Carolina Medical Center, Chapel Hill, NC USA.
Diane L. Dahm, Mayo Clinic, Rochester, MN USA.
Tal S. David, Synergy Specialists Medical Group, San Diego, CA USA.
David C. Flanigan, The Ohio State University, Columbus, OH USA.
Robert W. Frederick, The Rothman Institute/Thomas Jefferson University, Philadelphia, PA USA.
Theodore J. Ganley, Children’s Hospital of Philadelphia, Philadelphia, PA USA.
Elizabeth A. Garofoli, Washington University in St. Louis, St. Louis, MO USA
Charles J. Gatt, Jr, University Orthopaedic Associates LLC, Princeton, NJ USA.
Steven R. Gecha, Princeton Orthopaedic Associates, Princeton, NJ USA.
James Robert Giffin, Fowler Kennedy Sport Medicine Clinic, University of Western Ontario, London Ontario, Canada.
Sharon L. Hame, David Geffen School of Medicine at UCLA, Los Angeles, CA USA.
Jo A. Hannafin, Hospital for Special Surgery, New York, NY USA.
Christopher D. Harner, University of Texas Health Center, Houston, TX USA.
Norman Lindsay Harris, Jr, Grand River Health in Rifle, CO USA.
Keith S. Hechtman, UHZ Sports Medicine Institute, Coral Gables, FL USA.
Elliott B. Hershman, Lenox Hill Hospital, New York, NY USA.
Rudolf G. Hoellrich, Slocum Research and Education Foundation, Eugene, OR USA.
Timothy M. Hosea, University Orthopaedic Associates LLC, Princeton, NJ USA.
David C. Johnson, National Sports Medicine Institute, Leesburg, VA USA.
Timothy S. Johnson, National Sports Medicine Institute, Leesburg, VA USA.
Morgan H. Jones, Cleveland Clinic, Cleveland, OH USA.
Christopher C. Kaeding, The Ohio State University, Columbus, OH USA.
Ganesh V. Kamath, University of North Carolina Medical Center, Chapel Hill, NC USA.
Thomas E. Klootwyk, Methodist Sports Medicine, Indianapolis, IN USA.
Bruce A. Levy, Mayo Clinic Rochester, MN USA.
C. Benjamin Ma, University of California, San Francisco, CA USA.
G. Peter Maiers, II, Methodist Sports Medicine Center, Indianapolis, IN USA.
Robert G. Marx, Hospital for Special Surgery, New York, NY USA.
Matthew J. Matava, Washington University in St. Louis, St. Louis, MO USA.
Gregory M. Mathien, Knoxville Orthopaedic Clinic, Knoxville, TN USA.
David R. McAllister, David Geffen School of Medicine at UCLA, Los Angeles, CA USA.
Eric C. McCarty, University of Colorado Denver School of Medicine, Denver, CO USA.
Robert G. McCormack, University of British Columbia, New Westminster, BC Canada.
Bruce S. Miller, University of Michigan, Ann Arbor, MI USA.
Carl W. Nissen, Connecticut Children’s Medical Center, Hartford, CT USA.
Daniel F. O’Neill, Littleton Regional Healthcare, Littleton, NH USA.
Brett D. Owens, Warren Alpert Medical School, Brown University, Providence, RI USA.
Richard D. Parker, Cleveland Clinic, Cleveland, OH USA.
Mark L. Purnell, Orthopaedic Associates of Aspen & Glenwood, Aspen, CO USA.
Arun J. Ramappa, Beth Israel Deaconess Medical Center, Boston, MA USA.
Michael A. Rauh, State University of New York at Buffalo, Buffalo, NY USA.
Arthur C. Rettig, Methodist Sports Medicine, Indianapolis, IN USA.
Jon K. Sekiya, University of Michigan, Ann Arbor, MI USA.
Kevin G. Shea, Intermountain Orthopaedics, Boise, ID USA.
Orrin H. Sherman, NYU Hospital for Joint Diseases, New York, NY USA.
James R. Slauterbeck, Robert Larner College of Medicine, University of Vermont, Burlington, VT USA.
Matthew V. Smith, Washington University in St. Louis, St. Louis, MO USA.
Jeffrey T. Spang, University of North Carolina Medical Center, Chapel Hill, NC USA.
LTC Steven J. Svoboda, Keller Army Community Hospital, United States Military Academy, West Point, NY USA.
Timothy N. Taft, University of North Carolina Medical Center, Chapel Hill, NC USA.
Joachim J. Tenuta, Albany Medical Center, Albany, NY USA.
Edwin M. Tingstad, Inland Orthopaedic Surgery and Sports Medicine Clinic, Pullman, WA USA.
Armando F. Vidal, University of Colorado Denver School of Medicine, Denver, CO USA.
Darius G. Viskontas, Royal Columbian Hospital, New Westminster, BC Canada.
Richard A. White, St. Mary’s Audrain, Mexico, MO USA.
James S. Williams, Jr, Cleveland Clinic, Euclid, OH USA.
Michelle L. Wolcott, University of Colorado Denver School of Medicine, Denver, CO USA.
Brian R. Wolf, University of Iowa Hospitals and Clinics, Iowa City, IA USA.
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