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Abstract
Failure loads of suture anchors play a very important role during the rehabilitation programs. This study aims to find out the time-dependant variations in the loads to failure of bioabsorbable suture anchors and point of failure on a specific anchor type.Material and Method: 24 absorbable (polyglyconate) and 16 nonabsorbable wedge-type suture anchors (TAG®, Acufex) were implanted into the tibiae of 10 sheep, with 12 bioabsorbable anchors placed into the metaphysis, 12 into the diaphysis and 8 nonabsorbable anchors into the diaphysis, 8 into the metaphysis. 4 sheep, carrying 8 absorbable and 8 nonabsorbable wedges were sacrificed on the same day of implantation, 2 sheep with 8 absorbable wedges in the third week and 4 sheep with 8 absorbable and 8 nonabsorbable wedges on the sixth postoperative week. Bone blocks including the wedge anchors were prepared and buried into polymethylmetacrylate. Load to failure tests with forces applied in line with the axis of insertion were performed using an Instron machine. All implanted material were examined histologically following the tests in order to find out the point of failure at the anchor.Results: The first results taken on day zero showed suture breakage for all wedges, at an average force of 138.75±13.7 N for diaphyseal nonabsorbable wedges, at 129.75±10.1 N for diaphyseal absorbable, at 146.25±14.2 N for metaphyseal nonabsorbable and at 137.25±14.0 N for metaphyseal absorbable wedges. On the third week, suture cut-out occurred in all absorbable anchors, at an average force of 35±18.4 N for diaphyseal and at 32.5±11.6 N for metaphyseal wedges. On the 6th week, suture breakage occurred again in all nonabsorbable anchors, at an average force of 149.25±11.6 N for diaphyseal and at 126.75±18.5 N for metaphyseal wedges. Absorbable wedges placed on diaphyses exhibited however, suture cut-out at 22.5±5.0 N and those on the metaphyses at 24.0 ± 7.7 N. For the nonabsorbable anchors, there were no statistically significant differences neither between the results obtained on 0 and 6 weeks, nor between the metaphyseal or diaphyseal insertion sites. On the contrary, for absorbable anchors, the results on the third, and sixth weeks were significantly lower as compared to week 0, both for metaphyseal (p<0.05) and diaphyseal (p<0.05) groups. Comparison between the 3rd and 6th weeks and metaphyseal and diaphyseal groups however, did not show any significant differences.Macroscopic examination of the absorbable anchor specimens on the 3rd and 6th weeks revealed that the wedge was structurally intact except for a tear in the suture eyelet.Conclusion: These results show that wedge type absorbable anchor systems loose 75% of their ultimate strength within the first 3 weeks and 80% in 6 weeks, compared to their strength at insertion. The main reason for this is suture cut-out through the eyelet. It is concluded that absorbable anchors with an eyelet may not be appropriate for procedures requiring early active exercises of the operated joint.
Özet
24 emilebilir tipte ve 16 emilmeyen tipte wedge tipi TAG ankor (TAG ®, Acufex) 10 koyunun tibialarına yerleştirildi. 8 koyunun sağ tibialarına, diafize ve metafize birer adet emilmeyen, sol tarafta ise emilen ankorlar, diğer 2 koyunun her iki tarafına da aynı seviyelerde yalnızca emilebilen ankorlar koyuldu. Farklı tipte ankorlar yerleştirilen 8 denek herbirinde 4 koyun bulunun 2 gruba bölündü; 1. grup aynı gün, 2. grup 6. haftada sakrifiye edildi. Her iki tarafta aynı tipte ankor içeren 2 denek ise 3. haftada sakrifiye edildi. Ankorları içeren kemik blokları hazırlandı ve polimetilmetakrilata gömüldü. Ankorlar üzerindeki #2 Ethihond ile çekme deneyleri uygulandı. Çekme deneyi sonrasında implante edilen materyaller makroskopik olarak incelendiler. İlk gün yapılan çekme deneylerinde tüm ankorlarda sütürün koptuğu gözlendi. Kopma, diafizer emilmeyen grupta ortalama 138.75±13.7 N, diafizer emilen grupta 129.75±10.1 N, metafizer emilmeyen grupta 146.25±14.2 N ve metafizer emilen grupta 137.25±l4.0 N seviyesinde gerçekleşti. Üçüncü haftada tüm emilebilir ankorlarda sütür ankordan sıyrıldı. Sıyrılma diafizer grupta 35.l ±18.4 N ve metafizer grupta 32.5±11.6 N seviyesinde oldu. Altıncı haftada emilmeyen grupta tüm ankorlarda yine sütür koptu. Kopma diafizer grupsa ortalama 149.25±l1.6 N. metafizer grupta l26.75±18.5 N yük ile oldu. Metafizdeki emilebilir ankorlardan sütürler onalama 27.0±7.7 N ve diafizdekilerden 22.5 ±5.0 N ile sıyrıldılar. Emilmeyen grupta ilk gün değerleri ile 6. hafta değerleri arasında istatistiksel açıdan anlamlı farklılık saptanmadı. Emilebilen grupla 3. ve 6. haftalarda alınan sonuçların hem metafizer