Bioabsorbable Versus Metal Interference Screws: Adverse Events and Clinical Results

One of the most essential success factors in anterior cruciate ligament (ACL) reconstruction is the advent of the interference screw for securing the graft tissue inside the bone tunnel. During the early era, screws were primarily metallic, which was appropriate for grafts with bony ends such as bone–patellar tendon–bone (BPTB) composites. Later, when grafts with soft tissue ends such as medial hamstring (semitendinosus and gracilis) tendons (MHT) were popularized, development of the nonmetallic screw provided an alternate choice.

The key revolution of the bioabsorbable screw (BS) is the use of synthetic materials expected to overcome many disadvantages posed by the metal screw (MS). These include graft or suture damage while applying the screw, ferromagnetic artifacts shown in magnetic resonance imaging (MRI), concerns about reoperation to remove the hardware, and management of the resulting socket defect in revision surgery. BSs are supplied in many polymeric forms of alpha-polyesters or poly-(alpha-hydroxy) acids. Primary industrial products are made of poly- L -lactic acid (PLLA), later by polyglycolic acid (PGA), copolymers of PGA/polylactic acid (PLA), stereoisomers of PLA such as poly-D-lactic acid, poly- DL -lactic acid (PDLLA), poly- L – D -lactic acid, and so on. Current BSs are available in different formulas and might be combined with osteoconductive ceramic constituents such as β-tricalcium phosphate (β-TCP) or hydroxyapatite in the form of biocomposite screws.

Theoretically, these biomaterials could be engineered to optimize their biomechanical properties, biocompatibility, biodegradation characteristics, osteoconductivity, potential toxicity, and histologic effects. In addition, being a nonmetallic material lessens distortion in cases in which MRI is required for postoperative assessment.

Systematic reviews and meta-analyses have been reported to date by including similar sets of randomized clinical trials comparing both types of screws used in various ACL reconstruction techniques. Adverse events and clinical results are quite analogous in these reviews.

To date, many case reports or case series have described various adverse events after the use of BSs ( Table 75.1 ), while similar effects are rarely stated for the counterpart metallic implants.

TABLE 75.1

Selected Articles Describing Common Adverse Events After Using Bioabsorbable Screws Made of Different Materials in Anterior Cruciate Ligament Reconstruction

First Author(s)	Publication Year	Publication Type ^∗	Screw Material ^∗∗	Common Complications
First Author(s)	Publication Year	Publication Type ^∗	Screw Material ^∗∗	Breakage	Migration	Cyst Formation	Prolonged Effusion/Synovitis	Delayed Bone Ingrowth	Tunnel Widening	Remark ^∗∗∗ (The Proportion Annotates Number of Events per Studied Population and the Time Indicates Postoperative Period)
Barber	1995	RCT	PLLA	x						• 6/85 intraoperative screw breakages that occurred only with 7-mm screws
Marti	1997	Retrospective	PLLA	x						• 3/31 intraoperative femoral screw breakages
Stahelin	1997	Case report	PLLA				x	x		• Broken screw fragments still present at 20 months
Stahelin	1997	Case report	PDLLA/PGA		x					• Spontaneous screw extrusion from tibial tunnel at 3 weeks
Lajtai and Humer	1999	Case series	PDLLG	x			x			• 2/32 intraoperative screw breakages • 17/32 effusions from 4 to 16 weeks
Lajtai and Noszian	1999	Case series	PDLLG			x			x	• Fluid collection at femoral tunnel greatest at 6 months • Tunnel widening greatest after 6 months
Martinek	1999	Case report	PDLLA			x				• Osteolytic pretibial cyst formed at 8 months
McGuire	1999	RCT	PLLA	x			x			• 12/103 screws broke on insertion • 4/103 effusions at 30 months (compared with 1/100 in MS)
Benedetto	2000	RCT	PGA/TMC			x	x			• 3/67 effusions at 1 year • 1/67 fluid-filled pretibial cyst at 6 months
Bottoni	2000	Case report	PLLA		x					• Intra-articular migration of tibial screw mimicking meniscal tear at 7 months
Buelow	2000	Prospective	PLLA				x		x	• 3/101 prolonged effusions after 6 months • Tunnel widening, 6.6% femoral and 1.7% tibial • 1% infection
Martinek	2001	Case report	PLLA					x		• Incomplete resorption after 2.5 years
Bach	2002	Prospective	PGA/TMC				x	x	x	• No MRI evidence of new bone formation at 2 years • 18/20 with 40% mean bone tunnel enlargement after 6 months • 6/20 effusions seen at 6 months, disappeared by 2 years • 18/20 synovial reaction at intercondylar notch by MRI
Malhan	2002	Case report	PLLA/TCP			x				• Painful pretibial cyst at 12 months
Werner	2002	Case report	PLLA	x					x	• Symptomatic broken tibial screw at 5 months • Tunnel widening allowing fragment migration
MacDonald	2003	Case report	PLLA	x						• Symptomatic broken screw at 11 months
Sassmannshausen	2003	Case report	PLLA		x			x	x	• Transcutaneous migration of tibial screw at 12 months • Tunnel widening and no resorption at 12 months
Kaeding	2005	RCT	PLLA				x			• 6/48 prolonged effusions (compared with 4/49 in MS)
Lembeck	2005	Case report	PLLA	x						• Broken screw with cartilage damage at 12 months
Radford	2005	Case series	PLLA			x		x		• MRI showed no screw resorption by 4 years • 1/8 developed small cyst at tibia
Laxdal	2006	RCT	PLLA						x	• Significantly larger mean tunnel diameter in BS than MS at 6 and 24 months
Baums	2006	Case report	PLLA	x	x					• Intra-articular migration of broken screw at 22 months
Tecklenburg	2006	Prospective	PLLA/HA, PLLA/TCP	x				x		• 1/20 intraoperative screw breakages in each screw type • No bony replacement by 24 months
Thaunat	2006	Case report	PGA/TMC					x	x	• Tibial plateau fracture resulted from tibial tunnel widening and no bone ingrowth at 4 years
Appelt	2007	Case report	PLLA	x	x		x			• Recurrent knee locking from intra-articular migration of broken screw piece (at 1 year) or whole screw (at 3 months) with effusion and graft loosening
Busfield	2007	Case report	PLLA			x				• Sterile pretibial abscess at 18 months and 3 years
Maletis	2007	RCT	PLLA	x						• 2/99 intraoperative screw breakages using BPTB
Thaunat	2007	Case report	PLLA			x		x		• Pretibial ganglion cyst and no full bone ingrowth at 5 years
Dujardin	2008	Case report	PLC			x				• Sterile pretibial cysts in double-bundle tunnels with intra-articular granuloma formation at 5 months
Moisala	2008	RCT	PDLLA/TMC			x		x	x	• Significant mean femoral tunnel widening and higher graft failure rate using BS than MS at 2 years • 14/20 BS still partly visible in femur and 17/20 in tibia • 3/20 fluid collection in tibial tunnel
Myers	2008	RCT	PLLA/HA	x					x	• 1/50 intraoperative screw breakages • Femoral tunnel (middle part) widening up to 2 years
Sharma	2008	Case report	PLLA		x					• Extra-articular, extraosseous screw migration
Warden	2008	Prospective	PLLA					x		• 19/20 BS not absorbed at 2 years • Intraosseous fluid collection at tibia (6/6) and femur (4/6) at 10 years
Gawęda	2009	Comparative	PLLA			x	x	x		• 14/20 prolonged knee pain, 2/20 required screw removal at 16 and 20 months • 6/20 large cyst formation with delayed screw resorption assessed between 16 and 30 months
Hall	2009	Case report	PLLA/PGA	x	x					• Intra-articular loose body from screw breakage with chondral injury at 4 months
Umar	2009	Case report	PLLA			x				• Pretibial swelling by foreign body reaction at 30 months
Foldager	2010	Case series	PLC					x	x	• No bone ingrowth by CT scanning at 1 year • 78% and 128% mean tunnel widening observed at 2 weeks and 1 year, respectively
Sadat-Ali	2010	Case report	PLLA/DLA			x				• Pretibial swelling from fibroxanthoma formed in the tibial tunnel at 3 years
Bourke	2013	RCT	PDLLG/C			x		x	x	• 88% tibial cyst formation • 12% incomplete resorption at 1 year without new bone formation • Tunnel widening up to 24 months, most at 6 months
Bourke	2013	RCT	PLG/TCP			x		x	x	• 7% tibial cyst formation • 100% incomplete resorption at 1 year without new bone formation • Tunnel widening up to 24 months, most at 12 months
Pereira	2013	Systematic review	PLLA based		x					• Ten articles reviewed reporting BS migration • Migration was noticed between 3 and 22 months
Shen	2013	Case report	PLLA	x		x				• Painful pretibial cyst formed at 2 years • BS fragments detected with nodular granulomatous foreign body reaction
Ramsingh	2014	Case series	PLLA/TCP			x				• 14/273 pretibial pain and swelling at 26 months
Watson	2015	Retrospective	PDLLA/BCP	x						• 6/87 cases with eight intraoperative screw failures