Termičko oštećenje kosti tijekom bušenja dvostupnjevanim svrdlom i svrdlom s protočnim hlađenjem [Thermal osteonecrosis during drilling with two-step drills and internally cooled drills]

Augustin, Goran (2011) Termičko oštećenje kosti tijekom bušenja dvostupnjevanim svrdlom i svrdlom s protočnim hlađenjem [Thermal osteonecrosis during drilling with two-step drills and internally cooled drills]. PhD thesis, Sveučilište u Zagrebu.

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Abstract

Objective. Bone drilling causes increase in bone temperature and the level above 47oC is critical and causes thermal bone necrosis. Thermal osteonecrosis is common with drill of ≥ 4.5 mm without cooling. The aim of this study is determine the influence of various drilling parameters and their interactions on bone drilling temperature with the use of newly contructed (two-step and internally cooled) drills. ----- Materials and methods. Experiment was made accoring to central composite design. Internally cooled drill (3.4 mm i 4.5 mm) and two-step drill (2.5/3.4 i 3.4/4.5 mm) were used in combination with feed (0.02, 0.04, 0.10, 0.16 i 0.18 mm/rev) and cutting speed (1.18, 10.68, 33.61, 56.55, 66.05 m/min) with and without cooling with water of 24oC. Bone temperatures are measured with thermocouple with reaction time <0.1 s and accuracy of 0.1oC. Drilling were conducted on pig bones with 3-axis mini milling machine Flexmatic FA 530 S. ----- Results. Bone temperatures of all analysed combinations of parameters with internal cooling were below critical 47oC (p=0.05). Cooling fluid flow was low (0.1 dcl/min = 0.16cm3/s) and did not cause damage to bone and surrounding soft tissue. Highest temperatures were detected using 4.5 mm drill (40.5oC). Statistical influence on bone temperature was detected. Statistically significant effect other than cooling was detected with the drill diameter and feed. Drill diameter of 3.4 mm with internal cooling developed maximum temperature of 38.5oC and without cooling 46.3oC. For the same conditions drill with diameter of 4.5 mm obtained temperatures 40.5oC and 55.7oC respectively. Effect of feed is inversely proportional to the increase in bone temperature. With the feed rate 0.16 mm/rev temperature exceeded critical even using the drill diameter of 4.5 mm (46.4oC, p=0.05). Using the drill diameter of 3.4 mm, all temperatures were below critical (46.2oC, p=0.05). Two-step drill compared to standard drill with the same diameter did not show statistical differences in mean and maximal bone temperatures with all combinations of parameters (p=0.005). ----- Conclusion. Two-step drill does not have any advantages over standard drill of the same diameter. Internally cooled drill causes significantly smaller increase of mean and maximal bone temperatures during drilling with water of 24oC. Internally cooled drill is ideal drill in tramatology/orthopedics because it produces the smallest increase in bone drilling temperature- If internal cooling is used the regulation of other drilling parameters is not neccessary.

Abstract in Croatian

Svrha rada. Bušenje kosti uzrokuje porast temperature, a temperatura iznad kritične od 47oC dovodi do termičke nekroze kosti. Temperature iznad kritične izražene su uporabom svrdla promjera ≥ 4.5 mm bez hlađenja. Cilj istraživanja je ispitati utjecaj različitih parametara, kao i njihovih interakcija, na porast temperature kosti korištenjem novokontruiranih svrdla (dvostupnjevanog svrdla i svrdla sa protočnim hlađenjem). ----- Materijali i metode. Plan pokusa napravljen je prema centralno kompozitnom planu pokusa. Svrdla sa protočnim hlađenjem (3.4 mm i 4.5 mm) i dvostupnjevana svrdla (2.5/3.4 i 3.4/4.5 mm) korištena su u kombinacijama sa posmakom (0.02, 0.04, 0.10, 0.16 i 0.18 mm/okr) i brzinom rezanja (1.18, 10.68, 33.61, 56.55, 66.05 m/min). Mjerenja su provedena sa i bez protočnog hlađenja vodom temperature 24oC. Temperature kosti tijekom bušenja mjerena su termoparom s vremenom reagiranja <0.1 s i točnosti od 0.1oC. Bušenja su vršena na svinskoj kosti korištenjem tro-osne portalna glodalica Flexmatic FA 530 S. ----- Rezultati. Za sve kombinacije ispitivanih parametara sa protočnim hlađenjem temperature kosti nisu prelazile kritičnu (p=0.05). Protok rashladne tekućine je nizak (0.1 dcl/min = 0.16cm3/s). i nije uzrokovao oštećenja kosti i okolnog tkiva tijekom bušenja. Najviša temperatura dobivena je uporabom svrdla promjera 4.5 mm i iznosila je 40.5oC. Statistički značajan utjecaj osim hlađenja pokazuje i promjer svrdla i posmak. Svrdlom promjera 3.4 mm najviša temperatura uz hlađenje iznosila je 38.5oC, a bez hlađenja 46.3oC. Za iste uvjete svrdlom promjera 4.5 mm dobivene su temperature 40.5oC i 55.7oC. Utjecaj posmaka je obrnuto proporcionalan s porastom temperature kosti. Uz posmak 0.16 mm/okr temperatura kosti nije prešla kritičnu čak ni uporabom svrdla promjera 4.5 mm (46.4oC, p=0.05). Korištenjem svrdla promjera 3.4 mm, temperature ispod kritične dobivene su za sve vrijednosti posmaka (46.2oC, p=0.05). Dvostupnjevano svrdlo u usporedbi sa standardnim svrdlom istog promjera ne pokazuje razlike u porastu temperature kosti tijekom bušenja kod svih kombinacija parametara (p=0.005) bez hlađenja. ----- Zaključak. Dvostupnjevano spiralno svrdlo nema prednosti u odnosu na standardno spiralno svrdlo jednakog promjera. Svrdlo sa protočnim hlađenjem značajno snizuje srednju i maksimalnu temperaturu kosti korištenjem rashladne tekućine od 24oC. Njegovom primjenom u traumatologiji/ortopediji nije potrebno regulirati ostale parametre koji utjeću na porast temperature kosti. Primjena svrdla sa protočnim hlađenjem predstavlja trenutno idealno svrdlo za bušenje kosti čijom primjenom bi se mogao potpuno izbjeći nastanak termičke nekroze kosti.

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