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Dr Prodromos ACL blog March 2015

Dr Prodromos ACL blog March 2015

Each month there are roughly 50 – 75 new scientific journal articles in the world’s peer reviewed literature dealing with the human ACL which we collect and peruse. I will summarize the main point of those few that, in my opinion, say something genuinely new or particularly important in this monthly blog


Article 1:
describes instances of breakage of a bioabsorbable interference screw used in ACL reconstruction. (Although after replacement of an apparently faulty device inserter no further breakages occurred in the hands of these surgeons). The paper highlights the heterogeneity of absorbable interference screws and the problems some of them have had. The original interference screws were made of metal and have been essentially trouble free. However the introduction of the bioabsorbability feature has generally not delivered on its promise to have the screw replaced by bone.

Often the screw is replaced by “sludge.” Screw breakage, such as described in this paper, has also been a problem. Finally, inflammation secondary to reabsorption has been seen. Some bioabsorbable screws, such as the Milagro from DePuys-Synthes, have been generally well tolerated. The Collaxo from Smith and Nephew is an example of a different design that did not fare well and has been discontinued. Myriad other designs exist and full follow up data is not always available. The issue is further complicated by the presence of non-metallic screws that are radiolucent (as all the bioabsorbable screws are) but not bioabsorbable. It is challenging for Orthopaedic surgeons to keep track of the characteristics and clinical data from the various devices. Unfortunately new screws, initially introduced with positive fanfare, are invariably in clinical use for years before adverse clinical events are aggregated sufficiently to result in discontinuance of screws with significant problems. It should be noted too that bioabsorbable screws are also generally more expensive than metallic screws.



Both Articles 2 and 3
showed that increased time from ACL tear to reconstruction resulted in greater knee, cartilage injury. The point is that cartilage damage in the knee, which results in worse outcomes, is at least partially preventable by prompt ACL reconstruction after ACL tear. This is useful for both patients and surgeons to utilize in their surgical decision making. Not all papers have shown this result, but overall there is more evidence in favor of prompt repair than not.

ACL deficient knees have been clearly shown to get more meniscal tears than stable knees. And meniscal deficient knees have been clearly shown to get more arthritis than knees with intact menisci. For this reason alone it is clear that prompt repair is worthwhile. The definition of prompt is not completely clear but both papers would suggest that reconstruction within three months is worthwhile.


Article 4
showed worse outcomes in female pigs versus male after (suture) repair of a torn ACL. Some, studies on human ACL patients have shown worse outcomes in females. Others have shown equal results. For example in our large published series of ACL reconstructions we found no increased laxity in females after ACL reconstruction.

This study shows worse biomechanical outcome in females with a less stringent technique that uses bioabsorbable sutures, but no difference when non-bioabsorbable sutures were used. The best interpretation of this information is that there is probably less margin for error in ACL Reconstruction for females vs males.

Interestingly, this study in pigs establishes that gender differences in human females vs males is at least partly physiologic, and not cultural, in a way that no human study ever could.


Article 5
presents an important technique for revision ACL Reconstruction. Due to excessive tunnel widening or aberrantly placed tunnels that overlap ideal tunnel location, many ACL revisions require a bone grafting procedure first before definitive reconstruction is carried out months later. Iliac crest is the gold standard for bone grafting, but the harvesting of this graft is a painful procedure in itself. Allograft use is not painful, but allografts are less reliable as a bone graft. Thus the good results of this procedure using”local” femoral bone, a procedure that would not cause significantly increased post-operative pain, represents a real advance for revision ACL reconstruction.


ARTICLE 1: Bioabsorbable interference screw failure in anterior cruciate ligament reconstruction: A case series and review of the literature

Watson JN1, McQueen P2, Kim W3, Hutchinson MR4.

Author information

  • 1 University of Illinois at Chicago Department of Orthopaedic Surgery, Chicago, IL, United States. Electronic address:
  • 2 University of Illinois at Chicago Department of Orthopaedic Surgery, Chicago, IL, United States. Electronic address:
  • 3 University of Illinois at Chicago Department of Orthopaedic Surgery, Chicago, IL, United States. Electronic address:
  • 4 University of Illinois at Chicago Department of Orthopaedic Surgery, Chicago, IL, United States. Electronic address:

To report a case series of failures of bioabsorbable interference screws with possible identification of a novel failure mechanism.

A retrospective review of ACL reconstructions by the senior author utilizing BioComposite™ Interference Screws (Arthrex, Inc., Naples, FL) was performed. Complications related to screw placement, including fracture, breakage or bending were examined. Our rate and methods of failure were compared to those quoted in the current literature.

Eighty-seven patients of average age 23.8years met inclusion criteria. There were eight screw failures in six patients, with femoral failure in seven and tibial failure in one. The femoral screw fractured halfway between the tip and head in five, while the head of the screw broke in one and the screw bent in another. In the case of tibial interference screw fracture, failure occurred halfway between the tip and head. The insertion device that was used was replaced after recognition of material deformation and considered a potential contributor to the breakage risk as no further screw failures have occurred since.

We demonstrate a unique failure mechanism of bio-absorbable interference screws. In each case, the reconstruction was salvaged. Regular inspection of materials and implants can ensure optimal outcomes and decrease complications intra-operatively.
Copyright © 2015 Elsevier B.V. All rights reserved.

ACL reconstruction failure; Anterior cruciate ligament (ACL) reconstruction; Aperture fixation; Bioabsorbable interference screw; Interference screw breakage

PMID: 25795545 [PubMed - as supplied by publisher] CASE STUDY – ACLR HARDWARE COMPLIX

ARTICLE 2: Incidence of Secondary Intra-articular Injuries With Time to Anterior Cruciate Ligament Reconstruction.

Ralles S1, Agel J2, Obermeier M3, Tompkins M2.

Author information

  • 1TRIA Orthopaedic Center, Bloomington, Minnesota, USA Drexel University College of Medicine, Philadelphia, Pennsylvania, USA
  • 2TRIA Orthopaedic Center, Bloomington, Minnesota, USA Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, Minnesota, USA.
  • 3TRIA Orthopaedic Center, Bloomington, Minnesota, USA.

Precise locations of chondral and meniscal damage with increased time to anterior cruciate ligament reconstruction (ACLR) have not been well described.

The purpose of the study was to determine the relationship between delay in primary ACLR and incidence of secondary intra-articular injury. The hypothesis was that patients with increased time between initial injury and ACLR will exhibit greater incidence of secondary intra-articular injury when compared with those who receive surgical intervention promptly after injury. A second hypothesis was that patients with higher preinjury activity levels or older age will exhibit greater secondary injury when compared with those with minimal preinjury activity levels and younger age.

Cohort study; Level of evidence, 3.

A retrospective review was performed on 1434 patients with an anterior cruciate ligament deficiency who underwent primary ACLR at a single institution between 2009 and 2013. Patients were grouped according to time to surgery after initial injury: 0-3, 4-12, and >12 months. Operative notes were used to analyze 10 variables across time-to-surgery groups: cartilage damage in the patella, trochlea, medial femoral condyle, lateral femoral condyle, medial tibial plateau, and lateral tibial plateau; medial and lateral meniscal injury; and the incidence of procedures involving either the meniscus or cartilage. Patient age and preinjury activity level were also analyzed for the 10 variables based on time-to-surgery groups.

An association was noted between time to surgery and increased incidence of injury in the trochlea, lateral femoral condyle, medial tibial plateau, and medial meniscus (P < .001). Different significant findings within each age group were observed, but overall positive findings were seen in the same 4 locations described above. On the basis of preinjury activity level, the less active patients were most at risk for medial meniscal and trochlear injury, while the more active patients were most at risk for medial tibial plateau injury with increased time from injury to ACLR.

Increasing time from injury to ACLR was associated with increased incidence of secondary injury seen in the trochlea, lateral femoral condyle, medial tibial plateau, and medial meniscus. Separate analyses of patient age and preinjury activity level showed similar findings, thus supporting the primary analysis.
© 2015 The Author(s).

activity level; anterior cruciate ligament reconstruction; articular cartilage; injury; meniscus; time to surgery

PMID: 25767266 [PubMed - as supplied by publisher] TIMING

ARTICLE 3: Risk factors for knee instability after anterior cruciate ligament reconstruction.

Ahn JH1, Lee SH.


  • 1Department of Orthopedic Surgery, Dongguk University Ilsan Hospital, 814 Siksadong, Ilsandonggu, Goyangsi, Gyeonggido, 411-773, Korea,

The objective of this study was to estimate risk factors that influence postoperative instability after anterior cruciate ligament (ACL) reconstruction using multivariate logistic regression analysis.

A total of 152 consecutive patients with symptomatic ACL insufficiency underwent arthroscopic ACL reconstruction between 2005 and 2011. Loss to follow-up and previous ligament reconstruction were exclusion criteria, resulting in 131 patients remaining for this retrospective study. The median follow-up was 55 months (range 25-100 months). Patients were sorted into two groups by anterior translation on stress radiograph and pivot shift test grade and were analysed for the statistical significance of various risk factors including age at surgery, gender, body mass index, preoperative instability, time from injury to surgery, single-bundle reconstruction with preserved abundant remnant versus double-bundle reconstruction with scanty remnant, and concomitant ligament, meniscus, and articular cartilage injury with use of multivariate logistic regression analysis.

Time from injury to surgery over 12 weeks was found to be a significant risk factor for postoperative instability [p < 0.001, adjusted odds ratio (OR) 6.22; 95 % confidence interval (CI) 2.14-18.06)]. Grade 2 injury of medial collateral ligament (MCL) was also a risk factor (p = 0.02, adjusted OR 13.60; 95 % CI 1.24-148.25). The other variables were not found to be a significant risk factor.

Among the risk factor variables, concomitant grade 2 MCL injury and surgical delay of more than 12 weeks from injury were significant risk factors for postoperative knee instability after ACL reconstruction. The overall results suggest that surgery < 12 weeks from injury and meticulous attention to concomitant MCL injury should be considered.

Retrospective case-control study, Level III.

PMID: 25786822 [PubMed - as supplied by publisher] STABILITY

ARTICLE 4: Biomechanical Outcomes of Bridge-enhanced Anterior Cruciate Ligament Repair Are Influenced by Sex in a Preclinical Model

Kiapour AM1, Fleming BC, Murray MM.


  • 1Sports Medicine Research Laboratory, Department of Orthopaedic Surgery, Boston Children’s Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA, 02115, USA.

Despite the well-established role of sex on the anterior cruciate ligament (ACL) injury risk, its effects on ACL surgical outcomes remain controversial. This is particularly critical when developing novel surgical techniques to treat the injury because there are limited data existing on how these procedures will respond in each sex. One such approach is bridge-enhanced ACL repair, in which primary suture repair of the ACL is augmented with a bioactive scaffold saturated with autologous blood. It has shown comparable biomechanical outcomes to ACL reconstruction in preclinical models.

We asked (1) whether sex affects the biomechanical outcomes of bridge-enhanced ACL repair; and (2) if suture type (absorbable or nonabsorbable), used to repair the torn ACL, can minimize the potential sex discrepancies in outcomes after 15 weeks of healing in a large animal preclinical model.

Seventeen (eight males, nine females) Yorkshire pigs (Parson’s Farms, Hadley, MA, USA) underwent bilateral ACL transection and received bridge-enhanced ACL repair with an absorbable suture (n = 17) on one side and with a nonabsorbable suture (n = 17) on the other side. The leg receiving the absorbable suture was randomized within each animal. ACL structural properties and AP knee laxity for each knee were measured after 15 weeks of healing. Mixed linear models were used to compare the biomechanical outcomes between sexes and suture groups.

When treated with absorbable suture, females had a lower ACL linear stiffness (females, 11 N/mm [range, 8-42]; males, 31 N/mm [range, 12-56]; difference, 20 N/mm [95% confidence interval {CI}, 4-36]; p = 0.032), ACL yield (females, 121 N [range, 56-316]; males, 224 N [range, 55-538]; difference, 103 N [95% CI, 6-200]; p = 0.078), and maximum load (females, 128 N [range, 63-332]; males, 241 N [range, 82-538]; difference, 114 N [95% CI, 15-212]; p = 0.052) than males after 15 weeks of healing. Female knees treated with absorbable suture had a lower linear stiffness (absorbable, 11 N/mm [range, 8-42]; nonabsorbable, 25 N/mm [range, 8-64]; difference, 14 [95% CI, 2-26] N; p = 0.054), ACL yield (absorbable, 121 N [range, 56-316]; nonabsorbable, 230 N [range, 149-573]; difference, 109 N [95% CI, 56-162]; p = 0.002), and maximum load (absorbable, 128 N [range, 63-332]; nonabsorbable, 235 N [range, 151-593]; difference, 107 N [95% CI, 51-163]; p = 0.002) along with greater AP knee laxity at 30° (absorbable, 9 mm [range, 5-12]; nonabsorbable, 7 mm [range, 2-13]; difference, 2 mm [95% CI, 1-4]; p = 0.034) than females treated with nonabsorbable suture. When repaired using nonabsorbable suture, the biomechanical outcomes were similar between female and male knees (p > 0.10).

Females had significantly worse biomechanical outcomes than males when the repairs were performed using absorbable sutures. However, the use of nonabsorbable sutures ameliorated these differences between males and females.

The current findings highlight the critical role of sex on the biomechanical outcomes of bridge-enhanced ACL repair in a relevant large animal model. Better understanding of the mechanisms responsible for these observations using preclinical models and concomitant clinical studies in human patients may allow for additional development of sex-specific surgical and rehabilitative strategies with potentially improved outcomes in women.

PMID: 25742916 [PubMed - as supplied by publisher] REPAIR

ARTICLE 5: Femoral marrow cavity bone harvesting used for arthroscopic refilling of misplaced or enlarged bone tunnels in revision ACL surgery : An arthroscopically supported technique with antegrade intramedullary bone harvesting by a reamer-irrigator-aspirator (RIA) system.

Grote S1, Helfen T, Mück F, Regauer M, Prall WC.


  • 1Section of Arthroscopic Surgery, Department of Trauma Surgery, Ludwig-Maximilians-University Munich, Campus Innenstadt, Nußbaumstr. 20, 80336, Munich, Germany,

In anterior cruciate ligament (ACL) revision surgery, refilling of misplaced or enlarged tunnels frequently requires bone harvesting from the iliac crest. Unfortunately, donor-site pain displays a relevant complication. In order to optimize patients’ comfort, we developed a procedure combining minimally invasive intramedullary bone harvesting from the femur with arthroscopic tunnel refilling.

Patients with ACL reconstruction failure that were not eligible for one-step revision surgery but required tunnel refilling prior to the next ACL reconstruction were enrolled prospectively. Cancellous bone was harvested intramedullarily from the ipsilateral femur using the reamer-irrigator-aspirator system in a minimally invasive manner. Afterwards, the femoral and tibial tunnels were arthroscopically refilled using cones and push rods. Computer tomography (CT) analyses were carried out before and after the filling procedure. Pain levels were assessed during the entire follow-up. Patients undergoing iliac crest bone harvesting for other reasons served as a control group. Finally, the quality of the newly formed bone stock was evaluated in the subsequent ACL reconstruction procedure.

Five patients were included during a 6-month period. Prior to refilling, tunnel analysis revealed a mean tunnel volume of 7.9 cm(3) at the femur [SD ± 5.3 cm(3)] and of 6.7 cm(3) [SD ± 5.1 cm(3)] at the tibia. The CT analyses further revealed that graft failure was predominantly caused by tunnel misplacement. Post-operatively, pain levels due to intramedullary bone harvesting were significantly lower compared to iliac crest bone harvesting at every analysed time point. Three to five months after tunnel filling, CT analyses showed sufficiently incorporated bone stocks with filling rates of 75 % femoral and 94 % tibial. ACL revision surgery was performed 4-5 months after tunnel filling without any complication.

Intramedullary bone harvesting from the ipsilateral femur combined with arthroscopic refilling of the bone tunnels ensures a high-quality bone stock for further ACL reconstruction. The clinical relevance is shown by the feasibility of this technique and the significantly reduced pain levels during post-operative recovery.

LEVEL OF EVIDENCE: Therapeutic study, Level III.

PMID: 24682491 [PubMed - in process] REVISON

Credibility Logo

  • American Academy Regenerative Medicine
  • American Academy and Board of Regenerative Medicine
  • American Orthopaedic Society for Sports Medicine
  • isakos
  • Rush University Medical Center
  • American Association of Nurse Anesthetists
  • American Academy of Orthopaedic Surgeons
  • European Society of Sports Traumatology, Knee Surgery Academy
  • International Cartilage Repair Society