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ORIGINAL ARTICLE

Treatment of Ankle Fractures Using New High-Strength, Bioactive, Bioresorbable Forged Composites of Unsintered Hydroxyapatite/poly-L-lactide (F-u-HA/PLLA) Implants

TakadaN, Suzuki H, Yamada K, Otsuka T

Department of Orthopaedic Surgery
Nagoya City University

Address for Correspondence:
Naoya Takada
2024 Lakefront Drive Apt201, Collierville, TN 38017.

Phone : 901-289-7906
Fax     :
901-861-0809
E-mail :
kotakada17@yahoo.co.jp
 

Abstract:

Introduction: The purpose of this study was to retrospectively evaluate the clinical outcomes of ankle fractures treated with F-u-HA/PLLA implants.
Patients and Methods:
From June 2004 to September 2008, 75 closed ankle fractures were treated with F-u-HA/PLLA implants.  Forty-seven patients could be followed for 6 months or more (average 13.4 months), and their clinical outcomes were evaluated.   F-u-HA/PLLA screws and/or pins were used for fixation of medial and/or posterior malleolar fractures.  An F-u-HA/PLLA screw was used as the lag screw for fixation of lateral malleolar fractures.  Radiographic and clinical outcomes and postoperative complications were evaluated. 
Results: Bone union was achieved in all fractures.  The average ranges of dorsiflexion and plantarflexion of the ankle were 17 degrees (range, 5-20) and 40 degrees (range, 30-45), respectively.  No patients had loss of reduction, implant failure, deep infection, aseptic bone necrosis, or complications involving the subcutaneous tissue and skin postoperatively.
Conclusions: F-u-HA/PLLA implants have several advantages over other bioresorbable implants: 1) higher bending strength than human cortical bone, 2) osteoconductivity, which promotes bone bonding and total replacement with bone, 3) stable initial fixation obtained by binding with surrounding bone, 4) good biocompatibility throughout the bioresorption processes, and 5) radio-opacity, which allows postoperative observation on radiographs.

J.Orthopaedics 2010;7(2)e5

Keywords:

ankle fracture; bioresorbable implant; HA/PLLA

Introduction:
Bioresorbable implants have been used for the fixation of foot and ankle fractures since the early 1980s1).  The original implants were made primarily of polyglycolic acid (PGA) and polylactic acid (PLA).   Since 1995, we have been using poly-L-lactic acid (PLLA) implants for the treatment of ankle fractures and have obtained good clinical outcomes, as reported previously1).  However, the following problems have been encountered: 1) implants do not combine with bone directly, but combine with bone via soft tissue, 2) absorption of the implant and bone replacement take a long time, possibly resulting in bone canal development, 3) implants cannot be seen on radiographs during surgery or at postoperative follow-up because of their radiolucency. 

In 1995, forged composites of unsintered hydro- xyapatite/poly-L-lactide (F-u-HA/PLLA) implants were developed by Takiron Co. Ltd, Japan, in an effort to resolve these problems Since 2004, we have been using F-u-HA/PLLA implants for fixation of ankle fractures.  The purpose of this study was to retrospectively evaluate the clinical outcomes of ankle fractures treated with F-u-HA/PLLA implants.

Materials and Methods:

Between June 2004 and September 2008, 75 closed ankle fractures were treated with F-u-HA/PLLA implants. Follow-up of 6 months or more was available for 47 patients, 26 males and 21 females.  According to the AO/OTA fracture classification system, 12 patients were 43B1, 1 43B2, 2 44A3, 6 44B1, 4 44-B2, 16 44B3, 2 44C1 and 4 44C2. The average age at surgery was 49 years (range, 16-77 years).

Treatment protocol

Two F-u-HA/PLLA screws (diameter, 4.5 mm) were used for medial malleolar fractures.  If the distal fragment was small, a screw and a pin were used for fracture fixation.  From June 2004 to October 2007, solid screws were used.  Since October of 2007, cannulated screws have been used for this procedure (Fig. 1).  In patients with a posterior tuberosity fracture, one or two screws were used for fracture fixation.  For lateral malleolar fractures, a titanium plate and screws (SPS Fibula Plate, Stryker, Mahwah) were used and an F-u-HA/PLLA screw (diameter, 3.5 mm) was used as the lag screw (Fig. 2).  If an anterior tibiofibular ligament rupture was present, a stainless steel staple (S -type staple, Mizuho, Japan) was used for fixation of the syndesmosis.  Postoperative cast immobilization lasted 2 to 3 weeks.  Partial weightbearing was started at 3 to 6 weeks, and full weightbearing was allowed at 6 to 10 weeks after surgery.

Figure 1: Two F-u-HA/PLLA cannulated screws were used for medial malleoral fracture.

Figure 2: An F-u-HA/PLLA screw was used as the lag screw for lateral malleoral fracture.

Evaluation

The average follow-up was 13.4 months (range, 6-55 months).  Bone union was evaluated radiographically and was defined as three cortices of bony bridging.  Range of motion was evaluated clinically.  Any postoperative complications were recorded.

 

Results :

Bone union was achieved in all fractures.  The average ranges of dorsiflexion and plantarflexion of the ankle were 17 degrees (range, 5-20 degrees) and 40 degrees (range, 30-45 degrees), respectively.  No patient had loss of reduction, implant failure, deep infection, aseptic bone necrosis, or complications involving the subcutaneous tissue and skin postoperatively.  All 47 patients returned to pre-injury activity of daily living.

Representative case

A 61-year-old male sustained a type AO 43-B1 medial malleolar fracture.  Two solid F-u-HA/PLLA screws (diameter, 4.5 mm) were used for fixation of the fracture.  Bone union was achieved, and there were no postoperative complications.  The ranges of dorsiflexion and plantarflexion of the ankle were 20 degrees and 40 degrees, respectively.  On radiographs, shadows of the screws were clearly identifiable 1 month after surgery, but they were less visible 4 years after the surgery, suggesting that the process of absorption and decomposition had progressed.  There were no osteolytic findings in the bone around the screws (Fig. 3).  On CT obtained 4.5 years after surgery, shadows of the screws were barely visible and there were no gaps around them (Fig. 4).

Figure 3: A 61-year-old male sustained a type AO 43-B1 medial malleolar fracture.

Figure 4: CT obtained at 4.5 years after the surgery.

Discussion :

Advantages of bioresorbable implants used for fracture fixation include avoidance of a second procedure for removal of the implants, potentially reducing the economic and social burdens on patients, and the elasticity of the implants, possibly preventing osteoporotic changes in the bone. 

F-u-HA/PLLA is a composite structure consisting of cubes of unsintered hydroxyapatite (u-HA) particles.  A thin PLLA film between the u-HA particles provides an interface with invading water molecules, which allows homogeneous hydrolysis and steady degradation of the PLLA.  The strength of F-u-HA/PLLA implants is higher than that of PLLA-only implants, and their degradation and absorption times are shorter than those of PLLA-only implants2)3) Other advantages of F-u-HA/PLLA implants over PLLA-only implants include higher bending strength than human cortical bone; osteoconductivity, which promotes bone bonding and total replacement with bone; strong initial fixation obtained by binding with surrounding bone; good biocompatibility throughout the bioresorption processes; and radio-opacity that allows postoperative observation on radiographs.

In 2000, we4) reported good clinical outcomes in 60 patients with ankle fractures treated with PLLA implants.  In 2005, Jainandunsing et al. 5) examined numerous randomized controlled trials and quasi-randomized trials comparing bioresorbable osteosynthesis with metal osteosynthesis and found no significant differences between the bioresorbable and other implants with respect to functional outcomes, infections, and other complications, and re-operation rates were lower in some of the groups treated with bioresorbable implants.  They concluded that in a select group of compliant patients the use of bioresorbable fixation devices might be advantageous. 

Postoperative complications also have been reported with the use of bioresorbable implants.  In 1996, Rokkanen et al. 6) reported the use of bioresorbable implants for bone or ligament fixation in 2,500 patients over 10 years. Noninfectious foreign-body reactions were observed at 2 to 3 months postoperatively in 2.3% of patients with PGA implants but in none of the patients with PLA implants.   In 1998, Böstman et al. 7) reported that of 1223 patients with malleolar fractures of the ankle treated with absorbable implants 74 (6.1%) had obvious inflammatory foreign-body reactions to the implants, and 10 of these 74 patients later developed osteoarthritis of the ankle.  All 10 had been treated with PGA implants, and no articular damage was found in those who had PLA implants. 

The degradation and absorption of PLA implants are very gradual, and the implants are degraded by uniform hydrolysis from the surface and/or the center.  Postoperative complications such as osteolysis and skin ulcers are uncommon with the use of PLA implants, in contrast to PGA devices which dissolve rapidly. 

In 2005, Shikinami et al. 3) described complete bioresorption and bone replacement of F-u-HA/PLLA rods implanted in the femoral medullary cavities of rabbits. Nearly all of the u-HA particles were replaced with natural bone after 5.5 years, with no significant foreign-body reaction or inflammation.  In our study, on CT images obtained 4.5 years after the surgery, shadows of the F-u-HA/PLLA screws were barely visible and there were no gaps around them, suggesting that the processes of degradation and absorption of the screws had been progressing.  CT scanning also showed direct contact of the HA and the surrounding bone, without inflammatory reaction.

Furukawa et al. 8) described direct binding between F-u-HA/PLLA rods implanted in the distal femurs of rabbits and surrounding bone, as demonstrated by contact microradiograms obtained at 25 weeks after implantation.  The osteoconductivity of the implants and their direct binding to the surrounding bone are advantageous for initial fixation of the fracture.  These properties decrease postoperative complications such as loss of reduction and re-fracture. There was no loss of reduction or implant failure in our 47 patients.

A number of late foreign-body reactions have been described after the use of bioresorbable implants. Yoshino et al. 9) reported delayed aseptic swelling 15 months after fixation of a talar neck fracture with a biodegradable poly-L-lactide rod, Böstman et al. 10) reported a late foreign-body reaction 4 years after placement of an intraosseous bioresorbable PLA screw, and LaClair 11) reported an intraosseous bioresorbable PLLA screw presenting as a late foreign-body reaction 30 months after surgery. In 1999, one of our patients had a late foreign-body reaction around a PLLA-only screw head that had degraded and subsequently migrated into the subcutaneous tissue.  Further long-term follow-up is necessary to determine if late foreign-body reactions will occur in any of our patients.

The radio-opacity of the F-u-HA/PLLA implants is a major advantage in checking the positions of implants.  Shadows of the F-u-HA/PLLA implants can be seen on radiographs during surgery and at postoperative follow- up.  Implants made of PGA or PLLA-only cannot be seen on radiographs.

Fractures of the medial malleolus and posterior tuberosity can be fixed with bioresorbable screws and/or pins, but currently no bioresorbable plate has been developed for lateral malleolar fractures.  In our patients with lateral malleolar fractures, a titanium plate and screws were used, with a bioresorbable screw used only as the lag screw.  For hardware removal, the titanium plate and screws can be removed through two small skin incisions without wide exposure around the lag screw or damage to the subcutaneous tissue and periosteum.  This is one of the advantages of using a bioresorbable screw as the lag screw.   

The higher strength and shorter degradation and absorption times of F-u-HA/PLLA implants compared to PLLA-only implants make these devices very useful for the treatment of ankle fractures.  At short-term follow-up, there were no postoperative complications and bone union with acceptable range of ankle motion was obtained in all patients; further long-term follow-up is necessary to confirm continued good results.

Reference :

  1. Rokkanen P, Vainionpää S, Törmälä P, Kilpikari J, Böstman O, Vihtonen K et al. Biodegradable implants in fracture fixation: early results of treatment of fractures of the ankle. Lancet 1985; 1: 1422-1424

  2. Shikinami Y, Okuno M. Bioresorbable devices made of forged composites of hydroxyapatite (HA) particles and poly-L-lactide (PLLA): Part I. Basic characteristics. Biomaterials 1999; 20: 859-877

  3. Shikinami Y, Matsusue Y, Nakamura T. The complete process of bioresorption and bone replacement using devices made of forged composites of raw hydroxyapatite particles/poly L-lactide(F-u-HA/PLLA). Biomaterials 2005; 26: 5542-5551

  4. Takada N, Imaizumi T, Uemura M. Yamada K. Treatment of ankle fractures using bioabsorbable implants. Journal of Tohkai Orthopaedic Society of Traumatology 13: 96~98, 2000. (in Japanese)

  5. Jainandunsing JS, van der Elst M, van der Werken CC. Bioresorbable fixation devices for musculoskeletal injuries in adults. The Cochrane Database of Systematic Reviews Issue 4, 2005.

  6. Rokkanen P, Bӧstman OM, Vainionpää S, Makela EA, Hirvensalo E, Partio EK, et al. Absorbable Devices in the Fixation of Fractures. The Journal of Trauma 1996; 40: S123-127

  7. Bӧstman OM. Osteoarthritis of the ankle after foreign-body reaction to absorbable pins and screws. Journal of Bone and Joint Surgery 1998; 80B: 333~338

  8. Furukawa T, Matsusue Y, Yasunaga T, Nakagawa Y, Okada Y, Shikinami Y, et al. Histomorphometric study on high-strength hydroxyapatite/poly(L-lactide) composite rods for internal fixation of bone fractures. Journal of Biomedical Materials Research 2000; 50: 410-419

  9. Yoshino N, Takai S, Watanabe Y, Kamata K, Hirasawa Y. Delayed Aseptic Swelling after Fixation of Talar Neck Fracture with a Biodegradable Poly-L-Lactide Rod: Case Reports. Foot and Ankle International 1998; 19: 634-637

  10. Bӧstman OM, Pihlajamäki HK. Late Foreign-Body Reaction to an Intraosseous Bioabsorbable Polylactic Acid Screw. Journal of Bone and Joint Surgery 19998; 80A: 17911794

  11. Mosier-LaClair S, Pike H, Pomeroy G. Intraosseous Bioabsorbable Poly-L-Lactic Acid Screw Presenting as a Late Foreign-Body Reaction: A Case Report. Foot and Ankle International 2001; 22: 247251

 

This is a peer reviewed paper 

Please cite as: Naoya Takada: Treatment of Ankle Fractures Using New High-Strength, Bioactive, Bioresorbable Forged Composites of Unsintered Hydroxyapatite/poly-L-lactide (F-u-HA/PLLA) Implants

J.Orthopaedics 2010;7(2)e5

URL: http://www.jortho.org/2010/7/2/e5

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