PDS (poly-p-diaxanon) Pins as Fixation in Distal Chevron Osteotomies of the First Ray.Steven G. Tillett, D.P.M., John L. Mozena, D.P.M.ABSTRACT
The Chevron osteotomy has become a prevalent procedure utilized to address hallux valgus deformities. Since Corless first described the Chevron osteotomy in 1976, various forms of fixation have been reported, in attempts to further stabilize the distal first ray Chevron osteotomy. This study was undertaken to further evaluate the use of the poly-p-diaxanone (OrthoSorb) absorbable pin as a form of fixation for the distal first ray Chevron type of osteotomies, for the correction of hallux valgus.
Fifty distal first ray osteotomies were evaluated on 38 patients. Each osteotomy was fixated with two points of fixation (1.3mm PDS pins), in a crossing fashion. These patients were randomly selected from procedures performed on patients between 1995 to 2000 by the senior author. The patient population had an average age of 43 years (range 19 -76 years). The average follow up was 11.19 months (range 2 – 40 months). No osteotomy displacement, osteonecrosis, nor sterile sinus formation was noted in this patient population. No adverse clinical reactions were observed in response to the use of the OrthoSorb pins.
The intrinsic stability of the Chevron osteotomy for distal first metatarsal procedures, has made it a very popular procedure for the treatment of Hallux valgus since its description by Corless in 1976. Austin then popularized this procedure in the early eighties.
The concern for further stability has popularized internal fixation as an adjunct to insure stability of the osteotomy. Small et al, in 95 reported an 8% incidence of displacement at the osteotomy site for distal chevron osteotomies without fixation . The utilization of fixation has had its own inherent risks and inconveniences. Percutaneous kirschner wires have an inherent risk of pin tract infections. The use of permanent screws or wires may sometimes cause pain in the patient postoperatively due to positioning or location of the device, and lead to subsequent surgical removal. The utilization of bio-absorbable implants has become more popular in order to reduce the risk and inconvenience of infection or need for eventual removal of hardware associated other forms of fixation.
There have been several studies evaluating absorbable implant devices and their relationship with complications such as osteolytic changes in bone. Despite the formation of a sterile sinus in 3 of 59 procedures, Burns concluded that Biofix absorbable rods were an effective and reliable mode of fixation . Pelto Vasenius et al relate osteolytic changes with the degradation with PGA (polyglycolic acid) implants however conclude that the osteolytic changes did not correlate with any loss of Hallux Valgus correction but more importantly with infection or osteoarthritic changes . Lowell et al., highlighted the fact that when osteolysis with a draining sinus has been observed it has been associated with the polyglycolic acid implants but not the poly-p-diaxanone materials. They also compared the outcome and complications of the PDS with the kirschner wire fixation and found that there were no differences between the two groups: “notably the prevalence of osteolysis was quite similar between the treatment groups.; none of the feet that had fixation with bio-absorbable pins had formation of sinus with sterile discharge.” 
The synthetic absorbable materials have gone through some changes since the 1960’s when they became available. One class the alpha-hydroxy polyester family consisted of the poly-glycolic acid (PGA) was originally used to create the biofix absorbable pin however in 1994; the manufacturer changed the material to poly-L-lactic acid (PLLA) and renamed their product to Biofix SR PLLA. The pins are now sold as Smart pin SR PLLA, which replaced the biofix pin in 1996. The PLLA is characterized by a considerably longer half-life (~ 6 months) with respect to PGA and PDS (~ 2 months).
The second class of the synthetic polymers is the poly-p-diaxanon (PDS). PDS suture and ABSOLOK [ABSOLOCK, Ethicon Inc,. Somerville, NJ.] (a ligating clip) are both a product of poly-p-dioxanone. The PDS pins are marketed as OrthoSorb absorbable pins.
The purpose of this study is to evaluate the reliability of the PDS pin as a form of fixation in the distal first ray chevron osteotomy.
MATERIALS AND METHODS
Thirty-eight patients, who had underwent a distal first metatarsal osteotomy fixated with a PDS pin, were randomly selected from the senior author’s patient list. These patients were selected from procedures performed on patients between 1995 to 2000. A total of 50 distal first metatarsal were evaluated, of patients who underwent unilateral or bilateral distal chevron-type osteotomies or combined Chevron-Akin osteotomies for the correction of hallux valgus deformity. The apex of the cut is from slightly medial dorsal to plantar lateral to prevent sub 2nd capsulitis or neuroma caused by elevation of the head from the shortening due to the bone cut – which by definition elevates on a 15 degree declined metatarsal. All of these procedures were performed either by or under the supervision of the senior author. The average age of the patient was 43 years (range 19 -76 years). The average follow up was 11.19 months (range 2 – 40 months). The indication for the procedure was a painful hallux valgus deformity, which was recalcitrant to non-operative care.
Each of the chevron osteotomies were internally fixated utilizing one or two 1.3mm PDS pins. Two points of fixation, across the osteotomy site, were utilized in every case. Frequently, a single PDS pin was sectioned and utilized for both points of fixation. Any osteotomy which appears to have any motion, after the PDS pins are placed, should be either re-fixated or a BK cast should be applied.
A total of 38 patients (5 males, 33 females) underwent a distal first metatarsal osteotomy with two-point Orthosorb pin fixation. Twenty-three bunionectomies were performed on the right foot and twenty-seven on the left side. Eleven patients received bunionectomies on the contra-lateral foot on a later date. None of the bilateral bunionectomies were performed concurrently. Eighty-seven percent of the patients operated on were female, which compares closely to the ninety percent reported by Brunetti, et al. .
Radiographic and clinical evaluation was performed on all patients for a duration of at least 3 months. The result of this evaluation revealed no evidence of sterile sinus formation, no osteotomy displacement, no avascular necrosis, no painful range of motion, no joint crepitus, with normal range of motion noted in all patients. All patients had clinical improvement of the first metatarsophalangeal joint position. One patient did develop a stress fracture in the second metatarsal of the operative foot during the post-operative. Two patients had evidence of superficial erythema that was successfully treated with a short (14 day) course of oral antibiotics.
Evaluation revealed no incidence of displacement of the capital fragment, no instances of aseptic necrosis, allergic reaction to the PDS, nor apparent failure of the Orthosorb pin documented.
The community standard for a distal chevron type of osteotomy in the first metatarsal has evolved to include some sort of fixation, despite the fact that Austin and Leventin originally described it without fixation . There has been an on going discussion regarding the reliability of absorbable pins utilized as fixation for selected distal first metatarsal osteotomies.
This study was performed as a retrospective analysis of such osteotomies fixated with a poly-p-diaxanon (Orthosorb) pin over a six-year period of time. The results of this study showed no clinical or radiographic evidence of fixation failure, or complications related to the method of fixation. The results of this study are consistent with previous studies of PDS absorbable pin fixation in distal first metatarsal osteotomies [2,3,4,8,10,11]
The PDS pins are a reliable form of fixation for distal Chevron osteotomies of the first ray. The use of absorbable forms of fixation has advantages over the metallic fixation devices. The PDS (poly-p-diaxanon) pins appear to have advantages over other forms of absorbable fixation. In this study PDS was evaluated for it’s reliability as a form of fixation. No adverse clinical outcomes were noted in this patient population, and the author’s feel OrthoSorb pins offer a very patient friendly form of fixation.
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