Biodegradable screw presents as a loose intra-articular body after anterior cruciate ligament reconstruction

Bioabsorbable implants in forefoot surgery: a review of materials, possibilities and disadvantages

Bioabsorbable and biodegradable implants offer new possibilities in orthopaedic and trauma surgery. As soon as the initial stability of the degradable implants has reached the qualities of conventional materials, new devices may find usage in younger and more demanding patients. Residual conventional osteosynthetic material or the necessity to remove metal increasingly seems to be more of an adverse event than daily practice in forefoot surgery. Nevertheless, some drawbacks need to be discussed. Recent literature screened for the use of bioabsorbable and biodegradable materials in forefoot surgery, available implants and indications in forefoot surgery were analysed and summarized. Apart from common indications in forefoot surgery, points of interest were the type of biomaterial, the process of biodegradation and biointegration, and possible adverse events. Materials were comprehensively discussed for each indication based on the available literature. Polylactide, polyglycoside and polydioxanone are considered safe and sufficiently stable for use in forefoot surgery. Low complication rates (e.g. 0.7% for pin fixation in hallux deformities) are given. Magnesium implants suffered from an extensive corrosive process in the first generation but now seem to be safe in forefoot surgery and offer good options compared with conventional titanium screws, especially in procedures of the first ray. Allograft bone has proven feasibility in small case series, but still lacks larger or randomized clinical trials. The first results are promising. Bioresorbable and osseointegrating devices offer attractive new possibilities for surgeons and patients. Despite all the known advantages, the difficulties and possible complications must not be forgotten, such as soft tissue reactions, unwanted osteolysis and a lower primary mechanical load capacity.

Cite this article: EFORT Open Rev 2021;6:1132-1139. DOI: 10.1302/2058-5241.6.200157

Clinical outcomes after absorbable suture fixation of patellar osteochondral fracture following patellar dislocation

Background

Osteochondral fracture (OCF) is one of the severe complications following a patellar dislocation. The appropriate fixation method for patients with OCF remains controversial.

Methods

Eighteen patients who had undergone surgery after a patellar dislocation were recruited retrospectively. Patellar OCF was fixed with an absorbable suture in an unreported method. The medial patellofemoral ligament (MPFL) was repaired or reconstructed if necessary. The Lysholm and Kujala knee scoring systems were used to evaluate the knee function. Imaging examinations were used to confirm the fracture healing.

Results

The mean period of follow-up was 36 months. All patients recovered well postoperatively without symptomatic complications. The Lysholm score and the Kujala score improved significantly from 37.6 (SD =6.8) and 45.9 (SD =6.4) preoperatively to 80.9 (SD =7.4) and 89.4 (SD =6.8) postoperatively at the latest follow-up, respectively. Imaging evidence including X-ray and MRI revealed good healing of the OCFs.

Conclusions

This study showed satisfactory mid-term outcomes of OCF fixation using absorbable suture, which supports this method's potential to be a novel surgical method in the treatment of patellar OCF caused by a patellar dislocation.

Natural and Synthetic Polyesters for Musculoskeletal Tissue Repair: Experimental in Vitro and in Vivo Evaluations

Two natural Biopol™ polyesters, containing 8% (D400G) and 12% (D600G) of hydroxyvalerate component, and a synthetic polyester based on 1,4 cyclohexanediol [Poly(cyclohexyl-sebacate) - PCS] were studied to investigate their in vitro and in vivo behavior for application in musculoskeletal tissue repair. The polyesters were placed in direct contact with L929 fibroblasts and cell proliferation (WST-1), cytotoxic effect (LDH), synthetic activity (total proteins) and cytokine production (IL-1β, IL-6, TNFα) were assessed after an incubation period of 72 hours and 7 days. Then, 12 Sprague-Dawley rats underwent dorsal subcutaneous implants of tested polyesters under general anesthesia. After 1 and 4 weeks from surgery, the animals were pharmacologically euthanized and the implants retrieved with surrounding tissue for histologic and histomorphometric investigations. In vitro results showed that D600G behaved a little worse in comparison to other tested polyesters in terms of cell proliferation and TNFα at 7 days. PCS presented the lowest total protein value at 7 days. In vivo results indicated that PCS implants produced a higher (p < 0.01) extent of inflammatory tissue in comparison to D600G at 1 week and to D400G at 4 weeks, and the lowest vascular densities at both experimental times. D400G seems to be the most suitable material for biomedical application when tested in fibroblast cultures and in the subcutaneous tissue of rats.

The knee joint loose body as a source of viable autologous human chondrocytes

Loose bodies are fragments of cartilage or bone present in the synovial fluid. In the present study we assessed if loose bodies could be used as a source of autologous human chondrocytes for experimental purposes. Histochemical examination of loose bodies and differential enzymatic digestions were undertaken, the isolated cells were cultured in alginate bead microspheres and immunolocalisations were undertaken for chondrogenic markers such as aggrecan, and type II collagen. Isolated loose body cells had high viability (≥90% viable), expressed chondrogenic markers (aggrecan, type II collagen) but no type I collagen. Loose bodies may be a useful source of autologous chondrocytes of high viability.

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

BACKGROUND

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

METHODS

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.

RESULTS

Eighty-seven patients of average age 23.8 years 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.

CONCLUSIONS

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.

Migration of "bioabsorbable" screws in ACL repair. How much do we know? A systematic review

PURPOSE

Although bioabsorbable screws promise to degrade within months up to several years after implantation, often this does not happen. In fact, other problems such as screw breakage, tunnel enlargement, allergic or foreign body reactions, cyst or abscess formation, and delayed migration of "biodegradable" screws have been reported. This study aims to provide relevant basic science knowledge and recent insights concerning "biomaterials" currently used in fixation devices for anterior cruciate ligament (ACL) repair. A systematic review on the topic of screw "migration" is provided.

METHODS

A PubMed search combining all the key terms was done looking for complications related to late migration of "bioabsorbable" screws used in ACL reconstruction without inferior time limitation up to January 2012. Only clinical reports were included. Reference lists of reports were checked to detect others not identified by the original search. A pre-publication search was performed to identify the most recent relevant articles.

RESULTS

A total of ten articles referred to migration of "bioabsorbable" interference screws. Most cases reported on poly-L-lactic acid-based screws. Migration was noticed between 3 and 22 months postoperatively. It was noticed both in the tibia and the femur and with the application of several types of graft.

CONCLUSION

Migration is a possible complication of "bioabsorbable" interference screws. The information related to all clinical implications of the so-called "biodegradable screws" remains scarce and probably suffers from the phenomenon of publication bias. The complexity of possible reactions occurring in the human body is difficult to reproduce under controlled laboratory conditions.

Retrospective analysis of the survivability of absorbable versus nonabsorbable subtalar joint arthroereisis implants

Subtalar joint arthroereisis is a surgical modality that has been shown to be an effective procedure for flexible flatfoot in both pediatric and adult populations. Despite advances in understanding its mechanics and function, complication and implant removal rates remain as high as 30% to 40%. Analysis was performed to determine the survivability of 2 subtalar joint arthroereisis implants, absorbable and nonabsorbable, used alone and in combination with other procedures in both the adult and pediatric populations. The 95 total arthroereisis procedures were analyzed in several major categories: absorbable implants versus nonabsorbable implants and adult versus pediatric patients. Each major group was then further subdivided to create further subgroups: absorbable isolated procedures, absorbable combined procedures, nonabsorbable isolated procedures, and nonabsorbable combined procedures. The overall survival rates were 83% for absorbable implants and 81% for nonabsorbable implants. A total of 11 (17%) absorbable implants and 6 (19%) nonabsorbable implants were removed, respectively, at an average of 9 months and 23 months postoperatively. When used alone and in combination with other procedures, 36% and 13% of absorbable implants and 18% and 19% of nonabsorbable implants, respectively, were removed. When comparing adult versus pediatric populations, the overall survival rates of the absorbable and nonabsorbable implants were 81% for absorbable implants and 79% for nonabsorbable implants in the adult population and 85% for absorbable implants and 100% for nonabsorbable implants in the pediatric population.

Bone screws have advantages in repair of experimental osteochondral fragments

BACKGROUND

Cartilage defects are created on intraarticular osteochondral fragments at the entrance holes of fixation devices when these fragments are fixed to the original sites. Conventional fixation devices hinder repair of these defects and there is a latent risk of secondary osteoarthritis. We therefore developed a novel fixation device system consisting of bone screws made of cortical bone for osteochondral fragments to improve repair of these surface defects.

QUESTIONS/PURPOSES

We asked whether bone screws had advantages over poly-L-lactic acid (PLLA) screws in terms of (1) gross assessment of the surface, (2) volume and histologic quality of the repair tissue, and (3) biomechanical assessment of the tissue stiffness.

METHODS

We examined gross morphology, microCT, histology, and stiffness of the repaired tissue with PLLA (n = 32) and bone (n = 32) screws in a rabbit model of osteochondral fracture, compared with normal controls (n = 16).

RESULTS

Gross morphology and histology revealed better quality with bone screws than with PLLA screws. Mean repaired volumes in microCT were 70.6% ± 14% with bone screws and 50.3% ± 15% with PLLA screws. Average stiffness values for PLLA screws, bone screws, and normal cartilage were 1.67 ± 0.54 N/mm, 2.63 ± 0.42 N/mm, and 3.15 ± 0.49 N/mm, respectively.

CONCLUSIONS

Our results show better repaired tissue was observed for quality and quantity when chondral fractures were treated with bone screws than when treated with PLLA screws.

CLINICAL RELEVANCE

Bone screws made of cortical bone may have applications in clinical situations for the fixation of intraarticular osteochondral fragments.

In vitro and in vivo response to nanotopographically-modified surfaces of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and polycaprolactone

Colloidal lithography and embossing master are new techniques of producing nanotopography, which have been recently applied to improve tissue response to biomaterials by modifying the surface topography on a nano-scale dimension. A natural polyester (Biopol), 8% 3-hydroxyvalerate-component (D400G) and a conventional biodegradable polycaprolactone (PCL) were studied, both nanostructured and native forms, in vitro and in vivo. Nanopits (100-nm deep, 120-nm diameter) on the D400G surface were produced by the embossing master technique (Nano-D400G), while nanocylinders (160-nm height, 100-nm diameter) on the PCL surface were made by the colloidal lithography technique (Nano-PCL). L929 fibroblasts were seeded on polyesters, and cell proliferation, cytotoxic effect, synthetic and cytokine production were assessed after 72 h and 7 days. Then, under general anesthesia, 3 Sprague-Dawley rats received dorsal subcutaneous implants of nanostructured and native polyesters. At 1, 4 and 12 weeks the animals were pharmacologically euthanized and implants with surrounding tissue studied histologically and histomorphometrically. In vitro results showed significant differences between D400G and PCL in Interleukin-6 production at 72 h. At 7 days, significant (P < 0.05) differences were found in Interleukin-1beta and tumor necrosis factor-alpha release for Nano-PCL when compared to Nano-D400G, and for PCL in comparison with D400G. In vivo results indicated that Nano-D400G implants produced a greater extent of inflammatory tissue than Nano-PCL at 4 weeks. The highest vascular densities were observed for Nano-PCL at 4 and 12 weeks. Chemical and topographical factors seem to be responsible for the different behaviour, and from the obtained results a prevalence of chemistry on in vitro data and nanotopography on soft tissue response in vivo are hypothesized, although more detailed investigations are necessary in this field.

[Biodegradable screw versus a press-fit bone plug fixation for ACL reconstruction: a prospective randomized study]

BACKGROUND

Press-fit fixation of a tendon graft has been advocated in order to achieve tendon to bone healing.

HYPOTHESIS

Fixation of a tendon graft with a porous bone scaffold limits bone tunnel enlargement compared with a biodegradable interference screw fixation.

METHODS

Between 2005 and 2006, 20 patients (17 men, 3 women) were enrolled in this study for primary reconstruction of the ACL. Patients were randomized to either obtain graft fixation in the tibial tunnel by means of an interference screw (I) or a press-fit fixation with a porous bone cylinder (P). Three months after surgery, a CT scan of the knee was performed and tunnel enlargement was analysed in the coronal and sagittal planes for the proximal, middle and distal thirds of the tunnel. After 6 months, 1 and 2 years, International Knee Documentation Committee (IKDC), Tegner and Lysholm scores of both groups were compared.

RESULTS

The bone tunnel enlargement was 106.9±10.9% for group P and 121.9±9.0% for group I (P<0.02) in the AP plane and 102.8±15.2% vs 121.5±10.1% in the coronal plane (P<0.01). IKDC, Tegner, and Lysholm scores improved in both groups from pre- to postoperative assessment without significant differences between the two groups. There was a trend to higher knee stability in group P after 3 months (0.6±1.4 mm vs 1.81±.5 mm, P=0.08).

CONCLUSIONS

Both interference screw and a press-fit fixation lead to a high number of good or very good outcomes after ACL reconstruction. Tibial press-fit fixation decreases the amount of proximal bone tunnel enlargement. Press-fit fixation decreases the amount of proximal bone tunnel enlargement and improves bone to tendon contact.

MRI of broken bioabsorbable crosspin fixation in hamstring graft reconstruction of the anterior cruciate ligament

PURPOSE

To report seven cases of broken bioabsorbable femoral crosspins identified by MRI in evaluation of hamstring grafts of the anterior cruciate ligament.

METHODS

Seven cases of broken bioabsorbable crosspins utilized in femoral fixation of ACL hamstring grafts were identified prospectively and retrospectively from our PACs database during a period from 9/1/08 to 8/31/09. All imaging was performed using 1.5 or 3.0 Tesla MRI and were evaluated for T2 signal within and surrounding the crosspin, osteolysis surrounding the fragments, displacement of fragments, and graft integrity. Time from surgery was also recorded.

RESULTS

Seven cases of hamstring grafts with broken bioabsorbable crosspins were imaged 4 months to 3 years following grafting. There was osteolysis surrounding the crosspin in all but one case in which the graft was intact but a pin fragment was displaced into the joint. One graft failed due to aseptic foreign-body reaction to the fixation with aggressive osteolysis at 9 months post surgery. In the remaining five, the ACL graft was either completely torn, partially torn, lax, or degenerative and frayed. Of these, the crosspins were broken and angulated with osteolysis surrounding the apex of the angulated fragment or demonstrated lateral extrusion of the peripheral fragment.

CONCLUSIONS

Bioabsorbable crosspins utilized in femoral fixation of hamstring graft reconstruction of the ACL may become fractured. While the natural history of osteo-integration of these devices as demonstrated by MRI has not been defined, osteolysis surrounding the fragments, extrusion or displacement of the fragments, and graft laxity or failure would suggest that these are abnormal findings that should be reported.

Biodegradable screw versus a press-fit bone plug fixation for hamstring anterior cruciate ligament reconstruction: a prospective randomized study

BACKGROUND

Press-fit fixation of a tendon graft has been advocated to achieve tendon-to-bone healing.

HYPOTHESIS

Fixation of hamstring tendon grafts with a porous bone scaffold limits bone tunnel enlargement compared with a biodegradable interference screw fixation.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1. Methods Between 2005 and 2006, 20 patients (17 men, 3 women) with a primary reconstruction of the anterior cruciate ligament (ACL) were enrolled in this study. Patients were randomized to obtain graft fixation in the tibial tunnel either by means of an interference screw (I) or a press-fit fixation with a porous bone cylinder (P). At 3 months after surgery, a computed tomography (CT) scan of the knee was performed, and tunnel enlargement was analyzed in the coronal and sagittal planes for the proximal, middle, and distal thirds of the tunnel. After 6 months and 1 and 2 years, radiographs of the knee in the sagittal and coronal plane were analyzed for bone tunnel widening. The International Knee Documentation Committee (IKDC), Tegner, and Lysholm scores of both groups were compared after 1 and 2 years.

RESULTS

The bone tunnel enlargement determined by CT was 106.9% + or - 10.9% for group P and 121.9% + or - 9.0% for group I (P < .02) in the anteroposterior (AP) plane and 102.8% + or - 15.2% versus 121.5% + or - 10.1% in the coronal plane (P <.01). The IKDC, Tegner, and Lysholm scores improved in both groups from preoperatively to postoperatively without significant differences between the 2 groups. There was a trend to higher knee stability in group P after 3 months (0.6 + or - 1.4 mm vs 1.8 + or - 1.5 mm; P = .08).

CONCLUSION

Both interference screw and a press-fit fixation lead to a high number of good or very good outcomes after ACL reconstruction. Tibial press-fit fixation decreases the amount of proximal bone tunnel enlargement.

The unpredictable material properties of bioabsorbable PLC interference screws and their adverse effects in ACL reconstruction surgery

The aim of this study was to look at the clinical outcome of polylactide carbonate (PLC) interference screws in knee ligament reconstruction surgery. We prospectively followed up 59 patients who underwent primary hamstring anterior cruciate ligament (ACL) reconstructions using PLC (Calaxo screw; Smith and Nephew, Andover, MA) screws to secure the graft in the tibial tunnel. The average age was 34 years (range 17-55 years, SD 8.93). Twenty-three (39%) patients presented with complications [synovitis in 15% (nine) patients, prominent tibial swelling in 34% (20) patients and both in seven patients]. In comparison, similar complications were not seen in two groups of 59 age and sex matched patients in whom PLLA (Bio RCI; Smith and Nephew, Andover, MA) screws or Titanium (RCI; Smith and Nephew, Andover, MA) screws were used by the same surgeon. The problems encountered in the PLC screw group did not adversely affect knee stability. Six patients underwent exploration of the tibial tunnel site. A sterile white cheesy substance was removed, leaving an empty tibial tunnel. The ACL graft was found to be well attached to tibial tunnel in all cases. The PLC screw diameter, surface area or tibial tunnel diameter did not have any correlation to the occurrence of complications. Two patients required multiple washouts, one of whom developed a deep infection. The degradation of PLC screws does not follow the gradual and controlled pattern demonstrated in the ovine model. The unpredictable screw degradation, and the reaction to it can lead to serious clinical consequences.

A clinical review of bioabsorbable interference screws and their adverse effects in anterior cruciate ligament reconstruction surgery

Bioabsorbable material screws are widely used in various surgical specialties. One popular application is their use as interference screws in anterior cruciate ligament (ACL) reconstruction surgery. Despite their routine use, a major concern with bioabsorbable materials in surgery has been the incidence of adverse events. Various case reports, series reports and studies in the past years have reported complications specific to the use of bioabsorbable interference screws intra operatively and at different time periods post operatively. The aim of this literature review is to summarize the clinical studies where bioabsorbable screws have been used in ACL reconstruction surgery and in particular to highlight any specific complications and adverse effects related to the use of these materials.

Spontaneous locking of the knee after anterior cruciate ligament reconstruction as a result of a broken tibial fixation device

The Intrafix device (DePuy Mitek, Raynham, MA) is one of a number of recently developed products whose aim is to improve fixation of quadrupled hamstring grafts when used for anterior cruciate ligament reconstruction. We present a case of failure and intra-articular migration of the sleeve of an Intrafix device causing locking of the knee 10 weeks after anterior cruciate ligament reconstruction. We were unable to identify the cause of the failure or migration of the device. Rehabilitation had been progressing normally and without incident. The broken fragments were removed arthroscopically, and the reconstruction was found to be intact and healing well. Presumably, the device retained enough mechanical function to allow healing to progress, despite failure of the sleeve. This is, to our knowledge, the first reported case of such an event occurring with the new generation of hamstring graft fixation devices.

A pilot clinical evaluation comparing the Mitek bone-tendon-bone cross pin and bioabsorbable screw in anterior cruciate ligament reconstruction fixation, a randomized double blind controlled trial

PURPOSE

To compare the clinical efficacy of ACL reconstruction using the Mitek bone-tendon-bone cross pin (RIGIDfix) to the Linvatec Bioscrew (control device).

METHODS

Forty subjects were randomized into one of two groups: the RIGIDfix or control group. Eligible subjects were male and female, 18 years of age and older, with an ACL injury of at least 3 weeks duration and no evidence of ACL insufficiency on the contralateral side. Subjects were followed for 24-month post-operatively. Evaluations included the International Knee Documentation Committee (IKDC) Knee Ligament Standard Evaluation, Mohtadi's ACL Deficiency Quality of Life (ACL-QOL) questionnaire and the attainment of six rehabilitation milestones. Subjects and assessors were blinded to the surgical device used.

RESULTS

Four subjects in the RIGIDfix group and four controls were lost to follow-up. The change in final IKDC scores did not differ significantly between groups with the majority demonstrating an improvement of one to two grades. The change in ACL-QOL scores did not differ significantly between the RIGIDfix subjects (40.0+4.4) and controls (46.0+3.6). Furthermore, the number of weeks that the RIGIDfix subjects versus controls attained full active extension, functional range of motion, normal gait, stair climbing, running gait and sprinting did not differ significantly.

CONCLUSIONS

The RIGIDfix results in a similar post-operative course to the control device and is efficacious for the reconstruction of the ACL. No adverse events were associated with the use of the RIGIDfix. The results of this study should be considered preliminary due to the small sample size.

Delayed intra-articular inflammatory reaction due to poly-L-lactide bioabsorbable interference screw used in anterior cruciate ligament reconstruction

Bioabsorbable interference screws have replaced metal interference screws in anterior cruciate ligament reconstruction surgery because they have several advantages. Poly-L-lactide (PLLA) is one of the commonly used materials for bioabsorbable interference screws. PLLA produces a lower inflammatory reaction than polyglycolide as a result of its slower degradation rate and better biocompatibility. We describe a case of a delayed intra-articular inflammatory reaction caused by a PLLA bioabsorbable interference screw used in anterior cruciate ligament reconstruction.

Recurrent locking of knee joint caused by intraarticular migration of bioabsorbable tibial interference screw after arthroscopic ACL reconstruction

Two cases are reported in which, after ACL reconstruction with autologous hamstring grafts, tibial polylactide interference screws migrated into the knee joint. Clinically, both patients presented with recurrent locking of the joint. In one case, a broken 15 mm-long tip of the screw was found intra-articularly. In the other case, the whole screw had migrated into the joint cavity. The degradation process of polylactic acid, operative technique and bone quality are discussed as possible reasons for these complications.

The migration of a BioScrew as a differential diagnosis of knee pain, locking after ACL reconstruction: a report of two cases

INTRODUCTION

Problems with the initial fixation strength and widening of the femoral and tibial canal after ACL reconstruction using a triple or quadruple semitendinosus autograft have led to the introduction of the so-called Hybrid fixation with the additional use of interference screws. Pain and intraarticular migration have been reported with metal interference screws requiring implant removal (Am J Knee Surg 11:32-34, 2000, Arthroscopy 11:289-291, 1995) but not yet with bioabsorbable screws.

MATERIALS AND METHODS

We report on two cases were the intraarticular position of a bioabsorbable interference screw possibly due to migration in the early postoperative period lead to symptoms, the need for further surgery, and implant removal.

RESULTS

A preoperative MRI revealed the diagnosis. After removal of the tibial interference screw both knees were settling down, albeit with residual instability and only a moderate clinical result.

DISCUSSION

Despite the attractiveness of bioabsorbable screws due to the very fact that they are being reabsorbed over time, there is a slight risk of migration in the first month after the operation. In any suspicious case an MRI will easily clarify the diagnosis.

Broken Delta interference screw after ACL reconstruction: a report of two cases

We report two cases of an intra-articular dislocation of the proximal part of a broken biodegradable interference screw (Delta screw) used for tibial fixation of a semitendinosis gracilis graft in an unstable knee.

Intraarticular migration of a broken biodegradable interference screw after anterior cruciate ligament reconstruction

Poly-L: -lactic acid biodegradable screws have been used effectively for graft fixation in anterior cruciate ligament (ACL) reconstruction. The overall complication rate associated with the use of this implant is low, although some authors reported complications, such as osteolysis and aseptic effusion of the knee joint. We report a case of a 29-year-old female patient with a failure of a biodegradable interference screw at 22 months after ACL reconstruction using bone-patellar tendon-bone graft. In this illustrated case, the screw broke and migrated into the knee joint. In addition, we performed a detailed review of the medical literature from 1990-2005 to identify possible causes of biodegradable screw failures. We identified six published cases of bioabsorbable interference screw failure with migration into the knee joint. Several authors have reported small diameter of the screw, poor bone quality, bone resorption, and screw divergence as potential causes for intraarticular migration of metallic interference screws. With regard to bioscrews, no specific risk factors for screw breakage and intraarticular migration have been reported. ACL reconstruction with the use of bioabsorbable interference screws for fixation is considered to be reliable. However, we need to be aware of potential problems associated with the use of this implant. Early recognition of bioscrew failure may prevent associated morbidities, such as subsequent cartilage damage.

Prospective evaluation of patellar tendon graft fixation in anterior cruciate ligament reconstruction comparing composite bioabsorbable and allograft interference screws

PURPOSE

Bioabsorbable interference screws have proved to be biologically safe and to provide adequate graft fixation. Metallic interference screws have therefore been continuously replaced over the years. However, degradation times are highly variable, and bony replacement of the screw does not always occur in human beings. Composite interference screws have recently been introduced to enhance bony integration. We evaluated 2 different composite interference screws and compared them with an allograft interference screw over a 2-year period after anterior cruciate ligament (ACL) reconstruction with an autologous bone-patellar tendon-bone graft.

METHODS

Three groups of patients were prospectively evaluated. Poly-L-lactid acid/hydroxyapatite composite screws (BioRCI-HA; Smith & Nephew, Andover, MA) (group A), poly-L-lactid acid/beta-tricalcium phosphate composite screws (Bilok; Atlantech, Radevormwald, Germany) (group B), or allograft interference screws (CorlS; Regeneration Technologies, Alachua, FL) (group C) were used for tibial fixation of a patellar tendon autograft in ACL reconstruction. Each group consisted of 20 patients (mean age, 32.2 +/- 10.9 years in group A, 32.3 +/- 10.6 years in group B, and 31.1 +/- 6.6 years in group C) with no significant (P < .05) differences in age, sex, and time of follow-up. Subjective and clinical International Knee Documentation Committee parameters were evaluated preoperatively and at 3, 12, and 24 months postoperatively; computed tomography scans were obtained postoperatively and at 3, 12, and 24 months; and magnetic resonance imaging (MRI) scans were obtained at 3 and 24 months postoperatively.

RESULTS

Screw breakage during insertion occurred in 2 cases (1 in group A and 1 in group B). There was no significant (P < .05) difference in subjective and clinical results at any time of follow-up. No inflammatory response could be detected on MRI in any of the patients in all groups. Computed tomography scans documented complete bone block incorporation at 3 months in all groups. Both composite interference screws showed signs of degradation but were still clearly visible 24 months after ACL reconstruction. At 12 months, a sclerotic rim around the screw cavity could be outlined in group B only. No bony replacement had taken place up to 24 months postoperatively in group A or B. In group C the allograft bone screw was completely integrated and barely visible after 24 months.

CONCLUSIONS

All 3 screw types provided adequate graft fixation and were associated with excellent clinical results and no inflammatory response on MRI. Ultimately, a resorbable screw has to be replaced by bone to facilitate revision surgery. Formation of a sclerotic rim around the outline of the screw makes later bony replacement (group B) unlikely. After 24 months, complete bony integration had only taken place when allograft screws were used.

CLINICAL RELEVANCE

At 24 months, no advantage of composite screw materials over conventional bioabsorbable screws could be detected. If composite materials will be of any advantage with respect to bony replacement has to be observed with longer-term follow-up. The allograft bone screw was completely incorporated and replaced by cancellous bone after 24 months. Unfortunately, the screw's more complicated handling, higher cost, and limited availability impair the possibilities for its standard clinical use.

Biodegradable Materials in Arthroscopy

The use of biodegradable materials as implants has revolutionized the way medicine is practiced today. This review provides a general description of salient biodegradable polymeric materials currently used in arthroscopy. These materials include polyglycolic acid, self-reinforced polyglycolic acid, poly-L-lactic acid, self-reinforced polylactic-L-acid, poly-D-L-lactic acid, copolymer of poly-D-L-lactic acid polyglycolic acid, and polyglyconate. The mechanical strength, degradation properties, and widespread use of these materials, especially in the knee and shoulder, are discussed individually. Also discussed are the relatively few complications that are related to these materials' arthroscopic use. Future directions in biodegradable materials, including smart polymers, are also considered. In the future, novel techniques to identify the ideal polymer for a particular application will need to be developed to minimize the risk for implant complications.

Role of phase diagram of membrane formation system in controlling the crystallinity and degradation rate of PLLA membranes

In this work, the theoretical phase diagram of membrane formation system of ethanol, methylene chloride, and poly-L-lactide (PLLA) was studied. On the basis of the phase diagram, particulate and porous membranes, dominated by crystallization and liquid-liquid demixing, respectively, were prepared. Furthermore, degradation of PLLA membranes with particulate, porous, and dense morphologies was performed in phosphate buffered solution (PBS) at 37 degrees C for 168 days and was investigated by mass loss, scanning electron microscopy (SEM), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). Besides the membrane morphology, a close relationship between the phase behavior of the membrane formation system and the membrane crystallinity was found, which in turn influenced the degradation rate of these membranes significantly. In the case of dense membranes, it showed the lowest initial crystallinity and the greatest rate of mass loss and molecular weight decrease compared with particulate and porous membranes. In contrast, the particulate membranes had the highest crystallinity and the slowest degradation rate in this study. Therefore, the phase diagram of membrane formation system could not only anticipate membrane morphology, but could also control the membrane crystallinity and degradation rate simultaneously.

Magnetic resonance imaging evaluation of biodegradable transfemoral fixation used in anterior cruciate ligament reconstruction

PURPOSE

The study was designed to evaluate bioabsorbable transfemoral fixation in anterior cruciate ligament (ACL) reconstruction using hamstring tendon as graft. Magnetic resonance imaging (MRI) was used to assess the continuity of the bioabsorbable implant at different stages of the patients' rehabilitation.

TYPE OF STUDY

Retrospective case series.

METHODS

Forty-nine patients underwent ACL reconstruction performed by a single surgeon. The graft, a tensioned quadrupled semitendinosus tendon, was fixed proximally using a bioabsorbable TransFix implant (Arthrex, Naples, FL). The patients underwent an accelerated rehabilitation program and were assessed clinically at regular intervals postoperatively using MRI, with specific attention focused on the implant.

RESULTS

The average time from surgery to MRI was 28 weeks (range, 4 to 54 weeks). All implants were fully visible with no evidence of resorption. Five implants were fractured at an average of 20 weeks postoperatively (range, 9 to 47 weeks). Three implants showed deformation but no definite fracture at an average of 14 weeks (range, 12 to 17 weeks). This amounts to 16% of implants with fractures or deformation, many close to the period of theoretical graft incorporation. All patients were clinically stable with no symptoms or signs or instability on clinical review and all had returned to preinjury sporting activities.

CONCLUSIONS

Transfemoral biodegradable implants have the potential to fracture or deform during their postoperative course in tensioned hamstring tendon ACL reconstruction. Although no apparent detrimental effect was found in our series, further research is needed on this device before it can be recommended for ACL reconstruction. We also question the idea that rigid fixation for the ACL graft for the entire healing process is required.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Tissue restoration after resorption of polyglycolide and poly-laevo-lactic acid screws

Despite worldwide clinical use of bio-absorbable devices for internal fixation in orthopaedic surgery, the degradation behaviour and tissue replacement of these implants are not fully understood. In a long-term experimental study, we have determined the patterns of tissue restoration 36 and 54 months after implantation of polyglycolic acid and poly-laevo-lactic acid screws in the distal femur of the rabbit. After 36 months in the polyglycolic acid group the specimens showed no remaining polymer and loose connective tissue occupied 80% of the screw track. Tissue restoration remained poor at 54 months, the amounts of trabecular bone and haematopoietic elements being significantly lower than those in the intact control group. The amount of trabecular bone within the screw track at 54 months in the polyglycolic acid group was less than in the empty drill holes (p = 0.04). In the poly-laevo-lactic acid group, polymeric material was present in abundance after 54 months, occupying 60% of the cross-section of the core area of the screw track. When using absorbable internal fixation implants we should recognise that the degradation of the devices will probably not be accompanied by the restoration of normal trabecular bone.

Poly-D,L-lactide interference screws for anterior cruciate ligament reconstruction

PURPOSE

Biodegradable interference fixation screws are widely used for anterior cruciate ligament surgery. This study evaluated 2 issues: the clinical effectiveness of a poly-D,L-lactide interference screw and the radiographic response.

TYPE OF STUDY

Prospective case series.

METHODS

A prospective series of anterior cruciate ligament reconstructions fixed with poly-D(2%),L(98%)-lactide screws were evaluated at annual intervals. Inclusion criteria were unilateral knee instability, positive Lachman and pivot-shift tests, minimum age of 16 years, and adequate bone density. Exclusionary criteria included posterior cruciate ligament tears and previous ligament surgery on the same knee. Tegner, Lysholm, International Knee Documentation Committee (IKDC) activity scores, Lachman and pivot-shift tests, and radiographs were obtained. Postoperative KT-2000 examinations were performed.

RESULTS

Sixty-one patients with 63 knees met these criteria (39 male, 22 female), at an average follow-up of 24 months (range, 12 to 42 months). The average postoperative Cincinnati score was 86 (45 preoperative), median Tegner score was 6 (2 preoperative), average Lysholm score was 89 (53 preoperative), and average IKDC activity score was 3.3 out of 4 (1.5 preoperative). Two patients had positive postoperative Lachman tests (+1) with no positive pivot-shift tests. The average KT-2000 manual-maximum difference was 0.7 mm. Only 1 KT-2000 value was greater than 3 mm (4 mm). No adverse events were encountered during screw insertion and postoperative radiographs showed bone plug consolidation and tunnel obliteration with bone in-growth increasingly apparent at 2 and 3 years (significantly earlier than published reports using pure poly-L-lactide screws).

CONCLUSIONS

This is the first clinical report of a poly-D(2%),L(98%)-lactide interference fixation screw. This copolymer is zinc catalyzed, instead of the conventional tin, making the polymer more hydrophilic. The "D" isomer speeds the degradation process. These screws worked well with no adverse events. Graft tunnel obliteration was observed at 2 and 3 years.

LEVEL OF EVIDENCE

Level 4, no or historical control.

Loose intra-articular body following anterior cruciate ligament reconstruction

We report a case of intra-articular fracture of a bioabsorbable fixation device from the femoral tunnel in an anterior cruciate ligament reconstruction using a bone-tendon-bone graft. Thirteen months after successful reconstruction surgery, the patient experienced episodes of locking and medial joint pain. There was no history of trauma and no symptoms of instability or swelling. On revision arthroscopy, a fractured tip of a bioabsorbable RIGIDfix cross pin (Mitek, Westwood, MA) was identified in the medial compartment of the knee. There was a broad area of chondral erosion affecting the medial femoral condyle and a small defect to the medial tibial plateau where the loose body had been lodged. The bone-tendon-bone graft was intact without disruption. After arthroscopy, the patient was symptom free for 3 weeks but then developed further symptoms of locking. Magnetic resonance imaging showed another loose body within the knee. A repeat arthroscopy was performed 6 weeks after the earlier procedure and another piece of the polylactic acid RIGIDfix cross pin was removed, this time from the lateral gutter. This case raises concern about the potential for breakage and resultant loose body formation that may occur after bioabsorbable cross-pin fixation and, particularly, the associated chondral damage that can occur if early intervention is not conducted.