Critical Evaluation Of Biodegradable Implants In Intraarticular Fracture Fixation: A Recent Experience In India

Sushil Rangdal, Kanniraj M, Narendra Joshi, Rakesh Bhargava, Daljit Singh.

Department of Orthopaedics, PGIMER,
Chandigarh

Address for Correspondence:
Sushil Rangdal,
Registrar,
Department of Orthopaedics,
PGIMER, Sector 12,
Chandigarh 160012.

Abstract:

Background: Biodegradable implants after their successful worldwide usage have recently entered Indian orthopaedics. Since then there are only handful comments on their utilisation for  fracture fixation in this developing country. This study has evaluated results of biodegradable implant fixation in commonly occuring intraarticular fractures around elbow and ankle joint.

Materials and Methods: A prospective study was undertaken to evaluate functional outcomes and complications of fractures stabilized with biodegradable (PLLA) implants in Indian set up. Thirty two patients including twenty childrens (< 14 yrs) and twelve adults of closed intraarticular fractures around elbow and ankle undergone fixation with biodegradable implants. Results were evaluated after a minimum follow up period of six months. Mayo’s scoring system was used for elbow cases and Olerude-Molander scoring was used for ankle cases. Functional outcome and complications were noted.

Results: Fracture union and functional outcome at six months was satisfactory among all cases. Two elbow cases showed inflammatory swelling at operative site at fourteenth week followup. Two showed extraosseous calcification and one had malunion. Five patients suffered stiffness of elbow joint for some time during their followup. One patient of ankle fracture had displacement and infection. Other four cases had stiffness. No any child among cases followed more than thirtytwo weeks showed growth disturbance or abnormal carrying angle.  No patient of either elbow or ankle suffered sterile abscess or sinus.

Conclusion: Biodegradable implants could be advantageous in properly selected intraarticular fractures around elbow joint, especialy in children. They are no better than metal implants for fractures around ankle joint because of delayed mobilization and associated stiffness.

J.Orthopaedics 2010;7(4)e7

Keywords:

Biodegradable Implant; Intraaritcular Fixation; PLLA.

Introduction:

The internal fixation devices used in fracture repair serve to hold the fractures in proper alignment and apposition till the fracture unites, after which they do not serve any function. Although protocol for removal of  these hardware varies greatly among different institutes, from regular removal to only from those with symptoms and complications. These retained metallic devices proved to have some adverse effects, the most important of which are osteopenia of cortical bone induced by stress protection¹, others include corrosion and sensitisation  reactions with some alloys^2,3. These seem to be of minor importance when fractures are confined to cancellous bone and modern biologically inert implants (Titanium) are used. However, there are always patients who request removal of  implant because of chronic irritation of the surrounding soft tissues by prominent hardware⁴. This removal surgery besides being an economic burden, pushes the patient through same physical and psychological stresses of that of initial surgery. In this scenario bioabsorbable (PLLA) implant is a logical way to proceed for fracture fixation.

Displaced malleolar fractures are common injuries, and the functional results are strongly correlated with anatomical reduction and internal fixation²⁴. Fractures of the lateral condyle of the humerus are common in childrens and usually treated by open reduction and internal fixation to ensure proper union and normal growth²³. These were the reasons to include these fractures in this study.

Many studies from developed world in previous four decades proved the efficacy of these devices as  similar as that of metal implants^{4,5,6,9,12,14,19,21,22}. Varying opinions had come up among their users in trauma surgery in relevance to advantages over conventional metal implants^{4, 5,6,8,9}. Now these implants have been introduced in the Indian orthopaedics¹⁸.

Little has been published about this topic in orthopaedic literature in India ^7,18. Very few  Indian studies till date, as per our knowledge has evaluated these implants for intraarticular fracture fixation. This study reports thirtytwo patients of commonly occurring intraarticular fractures around ankle and elbow, fixed with biodegradable implants  in Indian setup is unique in its kind.

Materials and Methods:

Materials & Methods

Study Design

A prospective trial was carried out for Biodegradable i.e. Poly-L-Lactic Acid (PLLA) implant  [INION, Finland]  in the internal fixation of intra articular fractures around elbow and ankle joints after approval by Hospital ethics committee. During the study period (July 2006 to November 2009) thirty eight patients with intraarticular fractures of elbow and ankle were enrolled in this trial. The patients were explained about the advantages, known risks and cost factors associated with biodegradable implants. Four patients could not afford for this implant and two patients didn’t  returned for first followup also, so excluded from final evaluation. This left with thirty two patients including twenty childrens (<14 years of age) and twelve adults.

Table. 1 : Patient Particulars

 Informed consent was given by the parents in case of minor patients and by patients in case of adults to be included in this study. Mandatory minimum follow up period was 6 months.

Patients having closed intraaritcular fractures around elbow or ankle joints with displacement of one millimeter or more needing open reduction and internal fixation were included in this study. Medically unfit, chronic alcoholics, psychiatric and uncooperative patients were excluded.

Table. 2: Fracture Patterns

Operative Technique

Under general or regional anesthesia, fractures were exposed using standard approaches. Procedures were performed in bloodless field under control of tourniquet. Procedure for placement of biodegradable screw is essentially same as that of its metal counterpart (i.e. making drill hole, tapping and placing the screw) except that the screw driver used for PLLA screws  are star tipped and torque-limiting, to avoid damage to screw head. (Fig.1)

Fig.1: Star tipped Torque Limiting screw driver used for Biodegrdable Screw

For lateral condyle of humerus, Kocher’s lateral approach was used, each fracture was reduced and held with bone clamps. Fine Kirschner wires were also used whenever necessary to provide temporary fixation. In initial two cases of lateral condyle fracture of humerus, PLLA pins were used but as the stability was not adequate, additional metallic K-wire in one case and PLLA screw in another case was used to supplement the fixation. In remaining all lateral condyle and capitulum fracture cases  PLLA screw was used.

In ankle fractures, medial malleolus was fixed with a 4.5mm biodegradable (PLLA) screw and fibula was fixed with a biodegradable plate. Technique of application of biodegradable malleolar screw and fibular plate was same as that of routinely used metal implants, except that PLLA fibular plate is malleable at specific temparature and can be contoured by molding it after heating in thermo water bath at 75^oC (Fig:2).

 Figure.2: Thermo-water bath Used to heat fibular plate to make it malleable

Patients  were followed post operatively at 2 wks, 6 wks, 3 months and 6 months. Patients were given appropriate supportive slabs until suture removal after 2wks of surgery.  Assisted active mobilization of elbow cases was allowed after suture removal. Ankle cases given further four weeks of splintage. Partial weight bearing  was allowed after six weeks in ankle cases. Full weight bearing was allowed after three months.  During this period patients were evaluated  clinically, subjectively and radiologicaly for functional outcome. Standard scoring systems i.e. Mayo’s scoring system for elbow joint and Olerud –Molander’s scoring for ankle joint were used. Any complications that were encountered were noted.

Results :

In the elbow fractures, the strength of fixation achieved at surgery was satisfactory. The wounds healed normally in all patients. Twelve patients (50%) of twenty four elbow cases showed excellent functional score (Fig.3), eight patients (33.3%) had good functional score, three patients (12.5%) had fair score and one patient showed poor result. Mayo’s elbow score was used to evaluate functional outcome.

Fig.3 : A  Case of fracture lateral condyle humerus with dislocation elbow

     a)PreOp X ray                 b) At 18 months Follw-up   

c) Range of motion at 18 months

One child  required a second surgery. This patient was experiencing swelling and pain at the operative site after 14^th week of follow up. During exploration, protruded screw head was found lying beneath the skin (Fig.4a).The symptoms subsided post operatively following removal of the protruding screw head. Tissue biopsy from the operative site showed nonspecific inflammatory changes. Symptoms were probably due to mechanical irritation by screw head which initiated inflammation and consequent swelling. This complication also occurred in another lateral condyle humerus case, but in lesser degree and patient was able to manage with anti inflammatory and analgesic drugs (Fig.4b).

Fig.4 : Complications – Inflammatory Swelling

a.The patient needed exploration & removal of screw head(arrow)

b) This patient resolved with anti-inflammatory drugs

Discussion :

Two patients had asymptomatic extra- osseous calcification in radiographs (Fig.5a). Reduction was maintained till healing in all children.

There was no evidence of infection or loss of fracture fixation in any of the children but five  patients suffered stiff elbow for some time during their follow up period. A case of fracture lateral condyle humerus had malunion (Fig.5b). Six months review showed that all patients had full elbow movement and normal function. Out of twenty childrens the thirteen casese  were followed for more than 32 months. None of these cases showed any evidence of abnormality in physeal growth or carrying angle.

Fig.5 : Complications – Extraosseous Calcification & Malunion

a.Two different patients showing Extraosseous calcification( Arrow)

b. A case of Malunion Lateral condyle Humerus

Clinical results among ankle cases operated with these implants were not as encouraging as that of elbow. Two out of eight ankle cases showed excellent result, one case showed good result, four showed fair results and one showed poor result. Four out of eight ankle patients had stiffnes. A patient of trimalleolar fracture operated initially in this series got displacement of fragments, may be due to over reliance on stability of fixation with these implants and partial weight bearing at six weeks. Same patient suffered infection also which further deferred mobilisation.  So in later ankle cases we have extended splintage up to six weeks.

No patient in this series suffered frank sterile abscess or sinus, which was common occurrence with first generation of biodegradable implants. There was no periprosthetic osteolysis and deep infection observed. Although occurrence of inflammatory swelling at operative site in two lateral condyle humerus  patients needs further investigation. This complication is not  common with Poly - L – Lactic acid implants.  

Discussion

Research for use of bioabsorbable implants in the repair of bone tissue began in the late 1970’s; the initial studies were performed in the field of maxillofacial and mandibular surgery ^28,29,30. Initial implant material was poor in strength which was not sufficient for orthopaedic application. After introduction of self reinforcing technique in manufacturing of theses materials, their use expanded to be included in orthopaedics ⁴ . Since then, they have been reported to be used in internal fixation of fractures of the ankle (Bostmann et al l989, 1990)^8,10, elbow (Hirvensalo et al 1988b)²⁶ and distal radius (Hoffmann et al 1989)^27, and to secure osteotomies of metatarsals (Hirvensalo et al l988a)²⁵ . In these strengthened first

generation implants, PGA (Polyglycolic acid) was the main constitute. Later this material found to have  rapid degradation rate leading to premature decrease in fracture stability and formation of typical sterile abscess and sinus.

Presently in use second generation biodegradable implants are copolymers  made up of PLA(Poly Lactic Acid) as their main core element, with initial molecular weight of 1,80,000 to 5,30,000 and melting point of 174^oC . Particularly its levo isomer (PLLA) has long degradation time i.e. two to five years, providing enough strength and stability for enough period ⁷.

P. G. Hope et al⁶    in their series of twenty-four patients compared biodegradable implants with metallic Kirschner wires in displaced fractures about elbow. Fracture union with full function occurred in all cases within six months. Kirschner wires caused problems including infection, soft-tissue ossification and  required removal under general anaesthesia.  Results of present study are also not different from this study except that biodegradable screws were used rather than pins. In initial two cases stability provided by pins was not adequate for complete reliance and required supplementation with metal implants. Advantage of avoidance of second surgery for removal proved definitely a major factor for their use in children with fracture lateral condyle humerus in whom general anaesthesia is necessary. In addition, lesser total days of hospital stay (including hospitalisation during implant removal surgery) should also be taken as a positive factor in favor of biodegradable implants.

O Bostman et al in his series of fifty six patients of displaced malleolar fractures ⁸ and in their series of 102 patients of unimalleolar or bimalleolar fracture¹¹, found no change in the ability to participate in sports and other physical activities at one year follow-up.

Ankle cases however in present study did not perform according to their elbow counterparts. This comparison although is irrational keeping in mind different anatomical and biomechanical properties of bones at these two different sites. Moreover difference in age group of occurrence of fractures, (i.e. lateral condyle humerus fracture  mainly occcurs in children and ankle fracture is the fracture of adults) is another major factor for varied  results among performance of this implant at these two different sites. The results showed ankle patients needed prolonged immobilization and developed subsequent stiffness. The worst part of present series was a case of Cotton’s fracture treated with biodegradable implant, which underwent implant displacement and infection after six weeks. Although the number of ankle cases was limited to draw any firm conclusion, but  facts were not in favor of use of biodegradable implants in this weight bearing joint.

Regular use of biodegradable implant in developing countries has its own limitations. First and foremost is the cost of implant, which is at eight times more than that of Indian made stainless steel implants. Next is the availability of implants. Only a few of big cities in India have access to these devices. Familiarity and confidence of surgeons with these devices is also an issue yet to be solved. As biomechanical properties of these implants differ with that of metal, and a different instrumentation kit is provided with the set of implants, operating with these devices has a learning curve.  All of four senior surgeons of our institute having experience of operating with these implants didn’t find themselves comfortable with biodegrdable pins in regard to purchase of bone and strength of stability provided by these devices. So to take advantage of properties of these devices in, they should be used for proper indications and in hands of experienced person who are well versed with their use. Despite these limitations, , patients are turning up to opt for these implants, may be due to psychological impact of the fact that, these implants dissolves in body and doesn’t need another surgery merely to remove it. But their cost effectiveness over metal implants in established indications is a matter of research. To study their efficacy and feasibility in India,  further long-term follow up and a larger study design is required.

Conclusion:

This study has shown that biodegradable implants are a promising modality of treatment for intraarticular fractures around elbow joint, especially in children in whom general anaesthesia is often required for removal of metal implants. Their use in intraarticular ankle fractures is not as encouraging and advantageous as conventionally used metal implants. So this study doesn’t recommend their use in this weight bearing joint. Cost, availability and familiarity with these implants are other issues associated with these devices that need further evaluation.

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This is a peer reviewed paper 

Please cite as: Sushil Rangdal: Critical evaluation of biodegradable implants in intraarticular fracture fixation: a recent experience in India.

J.Orthopaedics 2010;7(4)e7

URL: http://www.jortho.org/2010/7/4/e7

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