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ACL Reconstruction and the Curse of Evidence-Based Medicine

Raffy Mirzayan, MD Keck School of Medicine  

The anterior cruciate ligament (ACL) is one of the most widely studied ligaments in the body. It is estimated that 100,000 ACL reconstructions are performed each year in the United States. There are over 600 22322p1515w 0 published reports in the peer-reviewed literature with regard to the anatomy, histology, biomechanical function, surgical reconstruction, and rehabilitation of the ACL. Recently, there has been a strong push in medicine to practice evidence-based medicine (EBM). EBM has been defined as "the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients. The practice of evidence based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research " Despite the thousands of published reports on ACL surgery, relatively few studies are of sufficient quality to be used as EBM. Prospective, randomized clinical trials (PRCTs) that are aimed at answering a specific question are the best studies to gain valuable information from.

Little Consensus on Grafts

One of the controversies in ACL surgery is the type of graft to use to reconstruct the ligament. Autologous bone-patella tendon bone and hamstring (HS) tendons are the two most popular grafts. At the American Academy of Orthopaedic Surgeons (AAOS) 2006 Annual Meeting, March 22-26, Chicago, Illinois, D. Whelan, MD, and coworkers^[ quantitatively synthesized the outcomes of recently published RCTs comparing quadruple strand HS and patellar tendon (PT) autografts. Their objective was to evaluate trials with respect to anterior-posterior (AP) laxity, graft rerupture, incidence of anterior knee pain, and patient function to improve the precision of outcome estimates. Specific inclusion criteria were established prior to initiating an extensive literature search. They used electronic databases (PubMed and Medline) for searching appropriate keywords. Limits included human RCTs published in the English language with a minimum of 24 months follow-up. Articles meeting these criteria were reviewed for final eligibility, and citations were examined for additional potentially eligible studies. Six investigations were included in the final analysis. A fixed effects model was used, with odds ratios (ORs) and associated 95% confidence intervals (CIs) reported. Statistical pooling across studies was appropriate given the similarity of point estimates, widely overlapping CIs, and nonsignificant tests of heterogeneity. Large variations in trial quality were noted. None of the investigations were adequately powered on post hoc analysis. An increased risk for anterior knee pain (OR, 2.06 [1.05, 4.05]) and kneeling pain (OR, 6.19 [2.78, 13.77]) was associated with PT reconstruction. Arthrometer data suggested a trend toward increased significance of a weighted mean side-to-side difference in AP laxity of 0.6 mm (95% CI [0.08, 1.13]) at 89 N and 0.47 mm (95% CI [-0.01, 0.96]) at 134 N is uncertain. The incidence of graft rupture was not found to be significantly different between the groups, nor was functional outcome as measured by IKDC, Cincinnati, and Lysholm knee scores. The current investigation, which includes only Level 1 evidence pooled from PRCTs, suggests that insufficient data remain to conclude differences in patient function or graft rerupture rates. All included trials are insufficiently powered. Inconsistent and inadequate reporting of validated outcome measures in the current sample of trials limited the analysis.

Emergent Clinical Trials Data at AAOS

Three PRCTs investigated the ACL. The first trial by G.B. Maletis, MD, and colleagues^[ was entitled "A PRCT of ACL Reconstruction Using Patellar or Hamstring Tendons Fixed with Bio-interference Screws." The study authors evaluated the differences in outcomes after ACL reconstruction with either autologous PT or HS grafts fixed with bioabsorbable interference screws. Ninety-nine patients were prospectively randomized to either the PT or HS reconstruction group. All surgeries were performed by a single surgeon with a single-incision endoscopic technique; the only difference was the graft. All grafts were secured with biointerference screws for femoral and tibial fixation. Rehabilitation was standardized for all patients. An examiner other than the surgeon evaluated patients at 2-year follow-up with IKDC, Tegner, Lysholm, KT 1000, ROM, Biodex strength testing, and patient self-assessment outcomes. Ninety-four patients were available at 2-year follow-up (45 PT and 49 HS). There were no differences in final IKDC grade, KT1000, ROM, Tegner, or Lysholm. The results revealed that flexion strength was better in the PT group at 180°/second (PT 104% vs HS 90%; P < .0001), and extension strength was better in the HS group at 60°/second (PT 85.7% vs HS 93.1%; P < .03). Extension strength did not reach the contralateral leg strength in either group. No differences were seen in internal rotation strength. Anterior knee sensory deficits were greater in the PT group (P < .0001), but there was no difference noted in kneeling pain. This finding is in contrast to several studies, including the one presented above by Whelan and colleagues in which there is a significant higher risk for anterior knee pain and kneeling pain associated with bone-tendon-bone autograft use. Self-assessment ratings were equal with each group rating their knee at 93%. Similarly, good outcomes were obtained in patients undergoing ACL reconstruction with autologous PT or HS grafts fixed with biointerference screws. The study authors did note greater flexion strength in the PT group and better extension strength in the HS group.

Autograft vs Allograft

Another PRCT was highlighted by T.M. Husain, MD, and coworkers^[ entitled "Autograft versus Allograft ACL Reconstructions: A Prospective, Randomized Clinical Study." The objective of the study was to assess the clinical outcome of primary ACL with fresh frozen tibialis posterior allograft and quadrupled HS autografts in a PRCT. One hundred patients with isolated ACL injuries were prospectively randomized equally to endoscopic reconstruction with either an autograft HS or allograft tibialis posterior tendon. The allograft used was provided by Musculoskeletal Tissue Foundation (MTF). All grafts were fixed the same way in both groups. The Arthrex (Naples, Florida) Crosspin femoral fixation was used along with a tibial screw backed up by a post (screw and washer). The patients in both groups underwent similar postoperative rehabilitation programs. KT-1000 measurements were obtained pre- and postoperatively. Standard outcome measurements, including SANE, Lysholm, IKDC, and Tegner scores, were obtained. With 94% follow-up at a median of 25 months (average, 24; range, 5-37 months), there were 7 (14%) failures in the allograft group and 3 (6%) failures in the autograft group. This difference was not statistically significant. The average KT 1000 measurements were 0.87 mm (range, -2 to +5 mm) for the autograft group and 0.85 mm (-1 to +6 mm) for the allograft group. There was no significance between the 2 groups. The average SANE, Lysholm, and Tegner scores were 83, 82, and 5.7, respectively, for the autograft group, and 84, 82, and 5.5 for the allograft group. All scores were improved from the preoperative scores (P < .0001). There was no statistically significant difference between the 2 groups with regard to age, sex (number of males and females in each group), clinical scores (SANE, Lysholm, Tegner), meniscal pathology, chondral pathology, and tourniquet time. The study authors concluded that the use of fresh frozen tibialis posterior allografts for primary ACL reconstruction is a successful procedure for stabilizing an ACL-deficient knee.

Double-Bundle Reconstruction

Recently, double-bundle ACL reconstruction has become popular in the United States. An anatomic reconstruction that aims to reproduce both anteromedial (AM) and posterolateral (PL) bundles has theoretical biomechanical advantages in controlling rotational stability over the single-bundle (traditional) ACL reconstruction procedure. In vivo studies have not completely supported this theoretical advantage. A PCRT by Masayoshi, MD, and colleagues entitled "Prospective Randomized Comparison of Single AM, PL and Anatomical ACL Reconstruction" compared the outcomes of ACL reconstruction with 3 different techniques -- single-bundle AM, single-bundle PL, and anatomic (double-bundle) ACL reconstruction to test the validity of this assumption. Sixty consecutive patients were randomly divided into 3 groups: single AM reconstruction, single PL reconstruction, and anatomic ACL reconstruction. In all ACL reconstructive procedures, the HS tendon graft was used, and grafts were fixed with Endobutton (Smith & Nephew, Andover, Massachusetts) and post screw. Follow-up examinations at 1 year were performed with the IKDC score. Stability of the knee joint was examined with a KT-1000 arthrometer and the pivot shift test under general anesthesia. To record the kinematics and velocity between the femur and tibia during the pivot shift test, 3-dimensional electromagnetic sensors were used. The IKDC score and KT evaluation revealed no difference among the 3 groups. However, in the quantitative evaluation of the pivot shift test, the single-bundle AM and PL reconstruction showed larger velocity values in the femorotibial motion compared with anatomic ACL reconstruction. Anatomic ACL reconstruction provides excellent knee stability without any complications. The pivot shift test showed that anatomic ACL reconstruction provides better control of dynamic stability than single-bundle AM and PL reconstruction in vivo.

HS Tendon Reconstruction

A retrospective study by Gobbi and Francisco^[ entitled "Hamstring Tendon ACLR: Advantages and Disadvantages of Using ST Versus STG" reviewed results with ACL reconstruction with the semitendinosus tendon (ST) alone vs the combined semitendinosus and gracilis (STG) to determine whether there were any differences in the clinical outcome. The study authors performed 4-stranded HS tendon ACL reconstruction with the ST alone as a quadrupled graft in 50 patients and a doubled semitendinosus and doubled gracilis tendon (STG) in combination in another 50 patients. The average age in the ST group was 31, with 31 males and 19 females, whereas the average age in the STG group was 28.8 with 26 males and 24 females. At an average follow-up of 36 months (range, 24-70 months), the 2 groups were compared in terms of clinical assessment, knee laxity, standard knee scores, and isokinetic and functional strength tests. In the ST group, the average knee scores were Tegner, 7.4; Lysholm, 95; Noyes, 85; and subjective score, 89%. In the STG group, the average scores were Tegner, 6.5; Lysholm, 94; Noyes, 82; and subjective score, 87%. In the ST group, 84% had normal or nearly normal knees by IKDC score, with 7 abnormal knees. In the STG group, 86% were classified as normal or nearly normal by the IKDC score, with 6 abnormal and 1 severely abnormal. There was less than a 3-mm side-to-side difference in 90% of patients in both groups. There were no significant differences in isokinetic strength deficits of the hamstrings and quadriceps in both groups. HS tendon ACL reconstruction with only 1 tendon (semitendinosus) has comparable results to reconstruction with 2 tendons (semitendinosus and gracilis). The study authors recommend using only the ST for HS ACL reconstruction because there is no additional benefit from concurrent harvest of the gracilis tendon. This may also reduce donor-site morbidity.

References

Sackett D, Rosenberg WM, Gray JA, Haynes RB, Richardson WS. Evidence based medicine: what it is and what it isn't. BMJ. 1996;312:71-72.

Whelan D, Schemitsch EH, Fowler PJ, Dainty K, Bhandari M. Graft choice for ACL reconstruction: a meta-analysis of level 1 evidence. Program and abstracts of the American Academy of Orthopaedic Surgeons 2006 Annual Meeting; March 22-26, 2006; Chicago, Illinois. Paper 021.

Maletis GB, Cameron SL, Tengan J, Burchette R. A PRCT of ACL reconstruction using patellar or hamstring tendons fixed with bio-interference screws. Program and abstracts of the American Academy of Orthopaedic Surgeons 2006 Annual Meeting; March 22-26, 2006; Chicago, Illinois. Paper 018.

Husain TM, Bottoni CR, Smith EL, Ipsen DF, Afra R. Autograft versus allograft ACL reconstructions: a prospective, randomized clinical study. Program and abstracts of the American Academy of Orthopaedic Surgeons 2006 Annual Meeting; March 22-26, 2006; Chicago, Illinois. Paper 016.

Masayoshi Y, Kuroda R, Mizuno K, Muratsu H, Yoshiya S, Kurosaka M. Prospective randomized comparison of single AM, PL and anatomical ACL reconstruction. Program and abstracts of the American Academy of Orthopaedic Surgeons 2006 Annual Meeting; March 22-26, 2006; Chicago, Illinois. Paper 017.

Gobbi A, Francisco RA. Hamstring tendon ACL reconstruction: advantages & disadvantages of using semitendinosus versus semitendinosus and gracilis. Program and abstracts of the American Academy of Orthopaedic Surgeons 2006 Annual Meeting; March 22-26, 2006; Chicago, Illinois. Paper 020.