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Internal screw fixation: Retentive strength and the effect of repetitive screw hole use in pre-tapped and self-tapped screws
Abstract
Wolfe, S.A. and Berkowitz, S.: The use of cranial bone grafts in the closure of alveolar and anterior palatal clefts. Plast Reconstr Surg 12:659-666, 1983 Funding
source not applicable
Internal Screw Fixation: Retentive Strength and the Eflect of Repetitive Screw Hole Use in Pre- Tapped and Self - Tapped Screws DMD, School of Dentistry, CB 27599-7450 (Frost, D.E. Merck Sharp & Dohme William
L. Foley,
Univ. of North Carolina, #7450, Chapel Hill, NC Tucker, M.R.) Resident Award winner
Background: The use of internal screw fixation (ISF) has gained wide acceptance in fracture management, reconstructive and orthognathic surgery in recent years. Several different systems for ISF have been developed differing in screw diameter, material and design. Screws can be broadly classified as pre-tapped or self-tapped. Pre-tapped screws offer the theoretical advantage of multiple insertions into the same hole without loss of retentive strength. This is an advantage in compression plate adaptation and reconstruction plate placement. Purpose: This study compares the retentive (uniaxial pull-out) strength of 5 commonly used fixation systems. These systems vary as to screw size, material, thread design and placement technique. This study also evaluates the effect of removing and replacing pre-tapped and self-tapped screws in the same hole one, two and three times on retentive strength. Materials and Methods: Rib bone from a freshly killed pig was used to evaluate the uniaxial pull-out strength of 5 groups of bone screws. The screws varied as to size (2.0 mm, 2.7 mm, 3.5 mm) and placement technique (pretapped and seIf-tapped). An instron machine was used to subject the screws to uniaxial tension loading to the point of failure. The effect of repetitive screw hole use was evaluated by placing screws, removing them and replacing them in the same hole one, two and three times prior to pull-out testing. Failure point for pull-out testing was recorded in kg of tension applied. Results: Results of uniaxial pull-out tests revealed that in all cases failure occurred at the metal bone interface with bone splintering around the screw threads. Analysis of variance and Tukey pairwise comparisons with level of significance set at .05 revealed no difference (P>.O5) in pull-out strength of pre-tapped or self-tapped screws of equal diameter. Increased external screw diameter produced increased pull-out strength. 2.7 mm and 3.5 mm screws demonstrated significantly greater retentive strength than 2.0 mm screws (Pc.05). Results of multiple screw insertions prior to pull-out testing were analyzed using repeated measures analysis of variance. No significant difference (P= .7) in pull-out strength after insertion AAOMS
l
1989
Session V: Reconstruction
into the same hole one, two or three times prior to pull-out testing was noted. Conclusions: No significant difference in pull-out strength exists between pre-tapped and self-tapped screws of equal diameter. Increased screw diameter produced increased pull-out strength. Removing and replacing both pre-tapped and self-tapped screws in the same hole prior to pull-out testing did not alter retentive strength.
References Foley, W.L., Frost, D.E., Paulin, W.B. and Tucker, M.R.: Uniaxial pull-out evaluation of internal screw fixation. .I Oral Maxillofac Surg, 671221, 1989 Schatzker, J., Sanderson, R., Murnaghan, J.P.: The holding power of orthognathic screws in vivo. Clin Orthop and Related Res. 108:l IS, 1975 Funding
provided by Univ. of North Carolina
and NIDR Grant
Nasal Reconstruction with Full-thickness Cranial Bone Grafts and Rigid Internal Skeletal Fixation Through a Coronal Incision Jeffrey C. Posnick, DMD, MD, The Hospital for Sick Children, 555 University Ave., Room 5430, Toronto, Ontario, M5G 1X8 (Seagle, M.B. Armstrong, D.) The effectiveness of nasal augmentation with fullthickness cranial bone grafts crafted and stabilized with rigid fixation through a coronal incision was studied from a prospective patient registry. Over a 2-year period, 26 patients (aged 2.5 to 30 years) requiring major nasal augmentation were studied prospectively. Indications for reconstruction included congenital defect ( 14), tumor resection defect (4), and late trauma (8). Patients had undergone 0 to 6 (mean, 2) previous bone or cartilage grafts for nasal augmentation. Sixteen patients underwent simultaneous craniofacial procedures ( 10 intracranial, 6 extracranial), including monobloc osteotomy, LeFort III osteotomy, orbital osteotomy, onlay bone grafting to other regions, and cranial vault reshaping. Postoperative follow-up was at least 1 year. Full-thickness calvarium was harvested through a craniotomy. In 14 patients, two mirror-image grafts corresponding to the left and right nasal bones were shaped. The grafts were placed through exposure provided by a coronal flap, obviating both midline vertical-forehead and intranasal incisions. If mirror-image grafts were required for total bony reconstruction, two miniplates were used for stabilization to the frontal bones. If only one full-thickness graft was required (12 patients), bicortical screws or a T-shaped miniplate was used. No major complications occurred at either the donor or recipient sites. There was no infection, wound dehiscence, graft erosion through the soft tissue, or injury to the brain, eyes or facial nerve. tlospit.alization ranged105
Wolfe, S.A. and Berkowitz, S.: The use of cranial bone grafts in the closure of alveolar and anterior palatal clefts. Plast Reconstr Surg 12:659-666, 1983 Funding
source not applicable
Internal Screw Fixation: Retentive Strength and the Eflect of Repetitive Screw Hole Use in Pre- Tapped and Self - Tapped Screws DMD, School of Dentistry, CB 27599-7450 (Frost, D.E. Merck Sharp & Dohme William
L. Foley,
Univ. of North Carolina, #7450, Chapel Hill, NC Tucker, M.R.) Resident Award winner
Background: The use of internal screw fixation (ISF) has gained wide acceptance in fracture management, reconstructive and orthognathic surgery in recent years. Several different systems for ISF have been developed differing in screw diameter, material and design. Screws can be broadly classified as pre-tapped or self-tapped. Pre-tapped screws offer the theoretical advantage of multiple insertions into the same hole without loss of retentive strength. This is an advantage in compression plate adaptation and reconstruction plate placement. Purpose: This study compares the retentive (uniaxial pull-out) strength of 5 commonly used fixation systems. These systems vary as to screw size, material, thread design and placement technique. This study also evaluates the effect of removing and replacing pre-tapped and self-tapped screws in the same hole one, two and three times on retentive strength. Materials and Methods: Rib bone from a freshly killed pig was used to evaluate the uniaxial pull-out strength of 5 groups of bone screws. The screws varied as to size (2.0 mm, 2.7 mm, 3.5 mm) and placement technique (pretapped and seIf-tapped). An instron machine was used to subject the screws to uniaxial tension loading to the point of failure. The effect of repetitive screw hole use was evaluated by placing screws, removing them and replacing them in the same hole one, two and three times prior to pull-out testing. Failure point for pull-out testing was recorded in kg of tension applied. Results: Results of uniaxial pull-out tests revealed that in all cases failure occurred at the metal bone interface with bone splintering around the screw threads. Analysis of variance and Tukey pairwise comparisons with level of significance set at .05 revealed no difference (P>.O5) in pull-out strength of pre-tapped or self-tapped screws of equal diameter. Increased external screw diameter produced increased pull-out strength. 2.7 mm and 3.5 mm screws demonstrated significantly greater retentive strength than 2.0 mm screws (Pc.05). Results of multiple screw insertions prior to pull-out testing were analyzed using repeated measures analysis of variance. No significant difference (P= .7) in pull-out strength after insertion AAOMS
l
1989
Session V: Reconstruction
into the same hole one, two or three times prior to pull-out testing was noted. Conclusions: No significant difference in pull-out strength exists between pre-tapped and self-tapped screws of equal diameter. Increased screw diameter produced increased pull-out strength. Removing and replacing both pre-tapped and self-tapped screws in the same hole prior to pull-out testing did not alter retentive strength.
References Foley, W.L., Frost, D.E., Paulin, W.B. and Tucker, M.R.: Uniaxial pull-out evaluation of internal screw fixation. .I Oral Maxillofac Surg, 671221, 1989 Schatzker, J., Sanderson, R., Murnaghan, J.P.: The holding power of orthognathic screws in vivo. Clin Orthop and Related Res. 108:l IS, 1975 Funding
provided by Univ. of North Carolina
and NIDR Grant
Nasal Reconstruction with Full-thickness Cranial Bone Grafts and Rigid Internal Skeletal Fixation Through a Coronal Incision Jeffrey C. Posnick, DMD, MD, The Hospital for Sick Children, 555 University Ave., Room 5430, Toronto, Ontario, M5G 1X8 (Seagle, M.B. Armstrong, D.) The effectiveness of nasal augmentation with fullthickness cranial bone grafts crafted and stabilized with rigid fixation through a coronal incision was studied from a prospective patient registry. Over a 2-year period, 26 patients (aged 2.5 to 30 years) requiring major nasal augmentation were studied prospectively. Indications for reconstruction included congenital defect ( 14), tumor resection defect (4), and late trauma (8). Patients had undergone 0 to 6 (mean, 2) previous bone or cartilage grafts for nasal augmentation. Sixteen patients underwent simultaneous craniofacial procedures ( 10 intracranial, 6 extracranial), including monobloc osteotomy, LeFort III osteotomy, orbital osteotomy, onlay bone grafting to other regions, and cranial vault reshaping. Postoperative follow-up was at least 1 year. Full-thickness calvarium was harvested through a craniotomy. In 14 patients, two mirror-image grafts corresponding to the left and right nasal bones were shaped. The grafts were placed through exposure provided by a coronal flap, obviating both midline vertical-forehead and intranasal incisions. If mirror-image grafts were required for total bony reconstruction, two miniplates were used for stabilization to the frontal bones. If only one full-thickness graft was required (12 patients), bicortical screws or a T-shaped miniplate was used. No major complications occurred at either the donor or recipient sites. There was no infection, wound dehiscence, graft erosion through the soft tissue, or injury to the brain, eyes or facial nerve. tlospit.alization ranged105