Biodegradable Vs Metallic Screws for ACL Reconstruction

Reviewed by – Dr. Satish Reddy

Many considering an ACL surgery have questions on what type of screws, biodegradable screws or metallic screws, would give the best outcome. There are many factors to be considered before choosing one. Let’s see the details about choosing the biodegradable screws or metallic screws for ACL Surgery.

What Is An ACL Surgery?

An ACL reconstruction surgery involves the replacement of anterior cruciate ligament by a tissue graft. A new ligament grows on the tissue graft approximately six months after the procedure.

Tissue grafts can be obtained from a patient’s own body (autograft), such as from patellar tendon or hamstrings tendon; or from other sources (allograft).

During the surgery, a tissue graft is secured by interference screws which help in securing the tendon into bones (tibia and femur).

Read More: Best Treatment For ACL Injury

Type Of Screws For ACL Surgery

Initially, titanium was the material of choice for interference screws, used in ACL reconstruction surgeries owing to its biocompatibility. Lately, biodegradable screws are widely used.

A bioabsorbable or biodegradable screw automatically resorbs or disintegrates in our body, unlike a metallic (titanium) screw.

An anterior cruciate ligament reconstruction surgery is minimally invasive and requires small incisions. Post-surgical rehabilitation is an important determinant to a successful recovery.1

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Read More – How to decide you need an ACL Surgery

How To Decide On The Type Of Screw And Graft? 

Biodegradable Screws VS Metallic Screws for ACL surgeryUsually, a surgeon decides on the type of tissue graft to be used, but you will be asked to choose between biodegradable or metallic screws, prior to surgery. The total cost of surgery varies with the type of screw chosen since biodegradable screws cost higher than their titanium counterparts.

An ACL reconstruction surgery costs between 75,000 and 1.5 lac rupees in India. Sometimes, patients also choose metallic screws in the case of a budget constraint.

Read More: How Does A Tendon Graft Grow Into An ACL?

Biodegradable Or Metallic Screws For ACL Reconstruction?

Recently, biodegradable interference screws have been widely used in ACL reconstructions. Apart from being more expensive, biodegradable implants have other major drawbacks such as foreign body reaction, incomplete bone formation (after implant/screw resorption), and a slower rate of graft tissue formation.

Titanium screws, though biocompatible may result in an increased risk for infection if retained; hence a second surgery is required for removal of the screw. Additionally, these implants interfere with diagnostic imaging; make revision surgery difficult, and may induce stresses in the surrounding bone causing a reduction in bone density.

Now the question is, which of these interference screws will provide you with better long-term results?

In 2014, British Medical Bulletin reviewed the outcomes of different materials for fixation screws in ACL reconstruction. It was observed that both biodegradable screws and metallic screws had similar results with regard to the clinical scores, evaluation, and imaging assessment of patients. Biodegradable screws were considered superior due to their property of osteointegration (integration with the surrounding bone). However, higher costs of these screws could not be justified, since the long-term results of metallic screws were equivalent.2

In 2015, The Journal of Arthroscopic and Related Surgery published a study which showed that biodegradable screws caused prolonged fluid accumulation around the joint (fluid effusion), increased femoral tunnel widening (widening of the bone surrounding the screw), and screw breakage. Here, functional comparisons between the two types of screws did not show significant differences.3

Another interesting study in 2015 conducted a 5-year follow-up post-surgery, comparing metallic screws to PLLA-HA (L-lactic acid with hydroxyapatite) screws – a type of biodegradable screw. It was shown that unlike metallic screws, PLLA-HA screws were not associated with femoral tunnel widening or increased cyst formation. Although these screws showed incomplete ossification of the surrounding bone after screw resorption, no adverse effects were noted over 5 years.4

A recent study in 2016, searched medical databases to compare the functional outcomes of ACL surgeries with bio-degradable screws and metallic screws, in 944 patients. Patients from both groups (with biodegradable screws and metallic screws) reported similar knee functions, one, two and five or more years post-surgery. Furthermore, the levels of activity of patients with either screw-type did not show any differences.

However, biodegradable screws were associated with more treatment failures, like screw breakage during placement and graft rupture.5

Read More: ACL Surgery Post Care Instructions

So let us summarize the advantages and disadvantages of biodegradable screws and metallic screws used in ACL reconstruction surgeries.

Biodegradable Screws – Advantages and Disadvantage 6,8 

Advantages Disadvantage
MRI imaging is possible post-surgery.Do not necessarily resorb at defined rates – i.e., they vary in their rates of degradation.
No long-term interference with surrounding tissues.Slower rates of biological tissue (new ligament) regeneration.
The need for a second operation for screw removal is eradicated.May cause inflammatory or foreign body reactions leading to osteolysis or cyst formation.
Reduced risk of infection.Require precise technique due to inadequate stiffness and a higher rate of breakage.
No osteoporosis (brittle bone disease) or stress in tissues surrounding the screw.May result in incomplete ossification (bone formation) and tunnel widening in the surrounding bone.
Have rapid loss of implant (screw) strength leading to higher fracture rates.
Cause fluid-effusion – collection of fluid around the joint.

Titanium Screws – Advantages and Disadvantages 7,9

Advantages Disadvantages
No foreign-body reaction.Do not resorb over time – causing distortion of diagnostic images and making visualization of surrounding tissues difficult.
No tunnel widening of the surrounding bone.MRI imaging cannot be done post-surgery.
Faster biological tissue (new ligament) regeneration.Interfere with revision surgeries as they are difficult to remove.
Easier placement.Second surgery is required for screw removal.
No fluid effusion.May cause metal sensitivity or localized irritation and pose a risk of infection if retained.
No osteolysis (bone depletion) or cyst formation.Cause stress shielding or reduction in bone density in the surrounding area.

Read More: ACL Surgery Cost In India

Do You Need A Specialist?

An ACL reconstruction surgery is a technique sensitive procedure, hence it will be performed by an experienced orthopedic surgeon. If you are choosing to go for a biodegradable screw, you must find out whether the surgeon performs such procedures often.

Biodegradable screws require more precision during placement. If your surgeon has experience in similar surgeries, chances of the procedure being a success, increases.

You could ask your physician or family members if they know of an experienced orthopedic surgeon. Patient reviews may also help to a certain extent, in this aspect.

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Since most of the medical research findings suggest that long-term outcomes of both biodegradable screws and metallic screws are similar and satisfactory, main criteria for selection depend on the patient’s age and budget.

If you are young, you may require revision surgery at a later stage, hence the best option for you would be to choose a biodegradable screw.

Whereas, if your doctor does not anticipate a need for revision surgery in your case or if your activity aspirations after recovery are limited and you have a limited budget, a metallic screw would be a good choice for an ACL reconstruction surgery.

Ultimately, it is important to know that although a biodegradable screw costs more, its superiority over metallic screws with respect to outcome and function has not been proven on long-term analysis. Your orthopedic surgeon can be your best guide in deciding on the type of interference screw best suited for your joint, based on your medical condition and the pros and cons of ACL reconstructions with biodegradable screws and metallic screws.

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References

  1. http://orthoinfo.aaos.org/topic.cfm?topic=a00549
  2. https://academic.oup.com/bmb/article/109/1/19/292514/Metallic-or-bioabsorbable-interference-screw-for
  3. http://www.briancolemd.com/wp-content/themes/ypo-theme/pdf/bioabsorbable-vs-metallic-screws-acl-reconstruction-2014.pdf
  4. http://researchonline.nd.edu.au/cgi/viewcontent.cgi?article=1711&context=med_article
  5. http://www.cochrane.org/CD009772/MUSKINJ_bioabsorbable-versus-metal-screw-graft-fixation-surgical-treatment-anterior-cruciate-ligament-injury
  6. http://researchonline.nd.edu.au/cgi/viewcontent.cgi?article=1711&context=med_article
  7. http://www.ijoonline.com/article.asp?issn=0019-5413;year=2006;volume=40;issue=4;spage=205;epage=209;aulast=Dhillon
  8. http://homepages.cae.wisc.edu/~bme200/hydrogel_templates_fall05/reports/Final
  9. http://www.staehelin.ch/pt/bscrewe.html
  10. http://www.wheelessonline.com/ortho/anatomy_of_acl

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Biodegradable Vs Metallic Screws for ACL Reconstruction
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