The Journal of HAND SURGERY
Buchler, McCollam, Oppikofer
33. Freeland A, Jabaley M, Burkhalter W, Chaves A. Delayed primary bone grafting in the hand and wrist after
28. Stuchin S, Kummer F. Stiffness of small-bone external fixation methods: an experimental study. J HAND SURG 1984;9A:7 18-24.
traumatic bone loss. J HAND SURC 1984;9A:22-7.
34. Lacroix H, Dunki Jacobs PB, Keeman JN. Operative
29. Chapman M. The use of immediate internal fixation in open fractures.
treatment of unstable distal radius fractures. Neth J Surg 1987;39(2):59-64. 35. Ruedi T, Allgower M. The operative treatment of intraarticular fractures of the lower end of the tibia. Clin Orthop 1979;138:105-10. 36. Mast J, Jakob R, Ganz R. Preoperative planning of fracture reduction. New York: Springer-Verlag, 1988.
Orthop Clin North Am 1980; 11579-91.
30. Ruedi T, Burri C, Pfeiffer K. Stable internal fixation of fractures of the hand. J Trauma 1971;11:381-8.
31. Bone L. Fractures of the Tibia1 Plafond. Orthop Clin North Am 1987;18:95-104.
32. Chaix 0, Herman S, Cohen P, LeBalc’h T, Lamare JP. Osteosynthese par plaque epiphysaier dans les fractures des plateaux tibiaux. Rev Chir Orthop 1982;68:189-7.
External fixator pin insertion techniques: Biomechanical
analysis and clinical relevance
A series of identically matched pairs of fresh-frozen canine femora (approximating in size and dimension) predrilled,
self-tapping,
were used to mechanically
half-pins and 4 mm self-drilling,
like cutting flutes. A second biomechanical differences
compare
and videotape
human radii
pull-out strength between 4 mm
self-tapping analysis
half-pins with drill bitwas done comparing
the
of pin insertion by power versus hand drilling. Results indicated a mean 22% re-
duction in bone purchase of self-drilling,
self-tapping pins compared with that of predrilled pins
and a marked increase in depth of insertion required of the self-drilling pins for comparable
pin
purchase (10 mm). It was also observed that a visible “wobble factor” exists, which tends to weaken
the pin-bone
interface
when hand drilling is performed.
(J HAND SURG 1991316A:
560-3.)
H. Seitz, Jr., MD, Avrum I. Froimson, MD, Dennis B. Brooks, MD, Paul Postak, BS, Gordie Polando, BS, and A. Seth Greenwald, D. Phil (Oxon), Cleveland, Ohio William
S
ignificant advances in the use of external fixation of unstable distal radius fractures have been developed over the past few years.‘” These advances
From the Department of Orthopaedic Surgery. The Mt. Sinai Medical Center, Cleveland.
Ohio.
Received for publication Feb. 16, 1990. Presented at the American Washington. September
Nov. 16, 1989; accepted
in revised form
Society for Surgery of the Hand, Seattle, I3- 16, 1989.
No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: William H. Setiz, Jr., MD, Head of Hand and Upper Extremity Surgery Clinics, Department of Orthopaedic Surgery. The Mt. Sinai Medical Center, One Mt. Sinai Dr., Cleveland, OH 44106. 3/l I21044
560
THE JOURNALOF HANDSURGERY
have included improved fracture management,4. 5 simplification of surgical technique,‘j and reduction in treatment-related complications.’ One concept that continues to arise in the attempt to simplify surgical technique is the elimination of “predrilling” through the use of self-drilling, self-tapping pins.8 Proponents of such pins with new “drill-bit-like” cutting tips claim, “equal mechanical purchase; no increase in heat generation (when ‘hand inserted’)“; and shorter insertion time when compared with the predrilled self-tapping pins. This concept raises questions concerning the potential hazards of eliminating the step of predrilling for the sake of saving a small amount of time. Recently we reported a marked reduction in treatment-related complications when external fixation is used to manage unstable distal radius fractures by
Vol. 16A, No. 3 May 1991
Seitz et al.
561
initial vertical starting point was then recorded on videotape and measured.
Results
Fig. 1. A drill bit-tipped 4 mm half-pin is seen above a standard 4 mm half-pin below. Note the almost complete absence of threads on the distal 10 mm of the drill bit-tipped pin.
identifying those factors likely to contribute to complications and carefully avoiding them.7 The technique of fixator pin insertion, although only one of many factors influencing the outcome of this surgical procedure, is nonetheless a critical one. The fixator pin is, after all, the link between the fixation device and the fracture, between the establishment and maintenance of a good reduction. For these reasons we have critically evaluated the technique of fixator pin insertion.
Comparative pull-out strength of 4 mm half-pins inserted by predrilling and self-drilling demonstrated a mean pull-out strength of 390 pounds for the predrilled group, with a range from 270 to 540 pounds and a standard deviation of 73 pounds. The self-drilled group demonstrated a mean pull-out strength of 3 10 pounds, with a range from 160 to 610 pounds with a standard deviation of 120 pounds. This represented a mean decrease of 22% in the pull-out strength of the self-drilled pins compared with the predrilled pins (Fig. 2). For comparable pull-out strength to be achieved, the self-drilling pin required insertion completely beyond the cutting flutes of its tip, with 10 mm of the pin tip protruding out of the far cortex. The videotape analysis demonstrated a “wobble factor” of up to 1.2 cm in all planes at the proximal end of the drill bit when hand drilling was performed. Power drilling demonstrated a deviation of at most, 2 mm from the vertical during drilling.
Discussion Materials and methods Because of the appearance of new drill bit tipped pins recommended for direct insertion under hand drilling, a biomechanical analysis compared insertion of 4 mm pins by predrilling with 3.2 mm power-driven drill bit and hand insertion of 4.0 mm self-tapping threaded half-pins, and hand-driven insertion of selfdrilling, self-tapping 4 mm half-pins. Fourteen identically matched pairs of fresh-frozen canine femora (approximating human radii in size and dimension) were used to mechanically compare pull-out strength between 4 mm predrilled, self-tapping half-pins and 4 mm self-drilling, self-tapping half-pins with drill-bitlike cutting flutes (Fig. 1). Pins were placed under direct vision at identical locations in the canine bones. They were placed to identical depths with 1.0 mm of the pin protruding from the far side of the bone. The bone-pin unit was then placed in a protected mount on the Instron Unit and a tensile force was applied to the pin at a rate of 2 inches per minute through the point of pull-out failure, and all values were recorded. A videotape analysis was then done comparing power drilling versus hand drilling. A 1 cm grid was placed directly behind a mounted canine long bone and experienced surgeons were asked to drill a 3.2 mm hole with a small power drill at 1100 rpm and with a handdriven drill system. The degree of deviation from the
The rationale for applying a drill bit to the tip of a fixator pin is to eliminate the additional step of predrilling. The designers of this pin recognized that such a pin would not permit power insertion and have recommended implantation by a hand driven technique.* To justify this they have voiced concern over the heat generated by a pin inserted by power. However, this drilltipped pin has almost no thread along its distal 10 mm. Inserting this pin in a radius or metacarpal, therefore markedly diminishes the total amount of thread/ bone contact and therefore its “bone-holding” capacity. Laboratory tests confirmed a significant (p < 0.005) reduction in bone-holding capacity of 22% when these pins were inserted to standard clinical depths and pullout strength was compared with self-tapping pins threaded to the tip and inserted into predrilled holes. To achieve a comparable degree of holding power, drilltipped pins required insertion to the point of thread engagement of both cortices. This, however, required 10 mm of pin to protrude through the far cortex (Fig. 3, A). When applied to the clinical settings of unstable distal radius fractures, the decrease in pull-out strength correlates to a greater potential for pin loosening and secondary pin tract infection, fracture through the enlarged pinhole, loss of fixation, and loss of fracture reduction .‘, 9 Deeper insertion with 10 mm of pin protruding from
562
The Journal of HAND SURGERY
External jixator pin insertion techniques
Comparative Pullout Strength of 4mm Half-pins Strenoth
Data
Fig. 2. Bar graph demonstrating canine femora.
tlbl
from 14 matched fresh canine long bone6
individual pull out test results in 14 identically matched pairs of
Fig. 3. Comparable pull-out strength requires deep insertion of the drill bit-tipped pin to engage threads at both cortices. These models depict the degree of violation this causes of the interosseous spaces of the distal forearm (A) and the hand (B).
Vol. 16A, No. 3 May 1991
the far cortex can cause damage to deep, soft tissue structures, impair pronation and supination range of motion in the forearm, and create violation, scarring, and contracture of the interossei. The lack of fine control of the drill bit during hand drilling can create an “out-of-round” hole. The visible wobble noted in our videotape recordings would tend to create such an “out-of-round” hole with microfractures that could cause additional pin loosening in the clinical setting. Certainly, this added risk does not seem justified, even in an attempt to prevent heat generation and bone damage. In fact, it has been demonstrated that the factors leading to thermal damage are drill sharpness, pressure applied, lack of adequate irrigation, and nor drill speed ,I0 and that the best way to avoid thermal damage when inserting a fixator pin is to predrill. ” The rationale for using a “drill-bit-tipped” fixator pin inserted by hand drilling for the external fixation of distal radius fractures is unfounded and, in fact, potentially hazardous. The “drill-bit-tipped” pin has minimal thread over its distal 10 mm causing significantly diminished pull-out strength or requiring deep insertion that violates the interosseous space. The wobble factor present in hand drilling generates poor drill control, an out-of-round hole, and cortical fragmentation leading to potential progressive pin loosening. With careful attention to details in the surgical application of the external fixation device we are close to solving the heretofore “unsolved problem” of the unstable distal radius fracture by providing stability, while reducing complications.‘, I2 This study demonstrates: (1) that the insignificant time saved in avoiding the step of predrilling is not worth the potential morbidity; (2) that power should be employed for drilling; and (3) that pins threaded to the distal tip should be used. REFERENCES 1. Andrianne Y, Donkerwolcke M, Kinsenkamp M, et al. Hoffman external fixation of fractures of the radius and
Seitz et al.
2.
3.
4. 5.
6.
563
ulna. A prospective study of 53 patients. Orthopaedics 1984;7:845. Jupiter JB, Knirk JL. Intra-articular fractures of the distal end of the radius in young adults. J Bone Joint Surg 1986;68(5):647-59. Kongsholm J, Olerud C. Plaster cast versus external fixation for unstable intra-articular Colles’ fractures. Clin Orthop Philadelphia: JB Lippincott, 1989:57-65. Melone CP. Articular fractures of the distal radius. Clin Orthop North Am 1984;15:217. Seitz WH, Flatow EL, Putnam MD, Dick HM. The treatment of unstable distal radius fractures by a technique of external fixation utilizing a limited open approach. Orthop Trans 1986;10(3):575. Seitz WH, Putnam MD, Flatow EL, Dick MD. The limited open surgical approach for external fixations of unstable distal radius fractures. American Academy of Orthopaedic Surgeons Videotape No. 202, 1985. J HAND SURC 1990;15A:288-93.
7.
8.
9.
10.
11.
12.
Seitz WH, Froimson AI. Reduction of treatment-related complications in the external fixation of unstable distal radius fractures. Presented at the American Orthopaedic Associational Annual Meeting. Colorado Springs. Colorado. June 1989. Andrianne Y, Wagenknecht M, Donkerwolcke M, Zurbuchen C, Bumy F. External fixation pin: An in vitro general investigation. Othopaedics 1987;10( 1 I): 150716. Seitz WH, Froimson AI, Brooks DB, Greenwald AS D, Phil (Oxon), et al. Biomechanical analysis of pin placement and pin size for external fixation of distal radius fractures. Orthop Trans 1987;11(3):470. Mathews LS, Hirsch C. Temperatures measured in human cortical bone when drilling. J Bone Joint Surg 1972;54A:297-308. Matthews LS, Green CA, Goldstein. The thermal effects of skeletal fixation-pin insertion in bone. J Bone Joint Surg 1984;7(66A): 1077-83. Weber SC, Szabo RM. The severely comminuted distal radius fractures as an unsolved problem: complications associated with external fixation and pins-and-plaster technique. J HAND SURG 1986;11:157-65.
Buchler, McCollam, Oppikofer
33. Freeland A, Jabaley M, Burkhalter W, Chaves A. Delayed primary bone grafting in the hand and wrist after
28. Stuchin S, Kummer F. Stiffness of small-bone external fixation methods: an experimental study. J HAND SURG 1984;9A:7 18-24.
traumatic bone loss. J HAND SURC 1984;9A:22-7.
34. Lacroix H, Dunki Jacobs PB, Keeman JN. Operative
29. Chapman M. The use of immediate internal fixation in open fractures.
treatment of unstable distal radius fractures. Neth J Surg 1987;39(2):59-64. 35. Ruedi T, Allgower M. The operative treatment of intraarticular fractures of the lower end of the tibia. Clin Orthop 1979;138:105-10. 36. Mast J, Jakob R, Ganz R. Preoperative planning of fracture reduction. New York: Springer-Verlag, 1988.
Orthop Clin North Am 1980; 11579-91.
30. Ruedi T, Burri C, Pfeiffer K. Stable internal fixation of fractures of the hand. J Trauma 1971;11:381-8.
31. Bone L. Fractures of the Tibia1 Plafond. Orthop Clin North Am 1987;18:95-104.
32. Chaix 0, Herman S, Cohen P, LeBalc’h T, Lamare JP. Osteosynthese par plaque epiphysaier dans les fractures des plateaux tibiaux. Rev Chir Orthop 1982;68:189-7.
External fixator pin insertion techniques: Biomechanical
analysis and clinical relevance
A series of identically matched pairs of fresh-frozen canine femora (approximating in size and dimension) predrilled,
self-tapping,
were used to mechanically
half-pins and 4 mm self-drilling,
like cutting flutes. A second biomechanical differences
compare
and videotape
human radii
pull-out strength between 4 mm
self-tapping analysis
half-pins with drill bitwas done comparing
the
of pin insertion by power versus hand drilling. Results indicated a mean 22% re-
duction in bone purchase of self-drilling,
self-tapping pins compared with that of predrilled pins
and a marked increase in depth of insertion required of the self-drilling pins for comparable
pin
purchase (10 mm). It was also observed that a visible “wobble factor” exists, which tends to weaken
the pin-bone
interface
when hand drilling is performed.
(J HAND SURG 1991316A:
560-3.)
H. Seitz, Jr., MD, Avrum I. Froimson, MD, Dennis B. Brooks, MD, Paul Postak, BS, Gordie Polando, BS, and A. Seth Greenwald, D. Phil (Oxon), Cleveland, Ohio William
S
ignificant advances in the use of external fixation of unstable distal radius fractures have been developed over the past few years.‘” These advances
From the Department of Orthopaedic Surgery. The Mt. Sinai Medical Center, Cleveland.
Ohio.
Received for publication Feb. 16, 1990. Presented at the American Washington. September
Nov. 16, 1989; accepted
in revised form
Society for Surgery of the Hand, Seattle, I3- 16, 1989.
No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: William H. Setiz, Jr., MD, Head of Hand and Upper Extremity Surgery Clinics, Department of Orthopaedic Surgery. The Mt. Sinai Medical Center, One Mt. Sinai Dr., Cleveland, OH 44106. 3/l I21044
560
THE JOURNALOF HANDSURGERY
have included improved fracture management,4. 5 simplification of surgical technique,‘j and reduction in treatment-related complications.’ One concept that continues to arise in the attempt to simplify surgical technique is the elimination of “predrilling” through the use of self-drilling, self-tapping pins.8 Proponents of such pins with new “drill-bit-like” cutting tips claim, “equal mechanical purchase; no increase in heat generation (when ‘hand inserted’)“; and shorter insertion time when compared with the predrilled self-tapping pins. This concept raises questions concerning the potential hazards of eliminating the step of predrilling for the sake of saving a small amount of time. Recently we reported a marked reduction in treatment-related complications when external fixation is used to manage unstable distal radius fractures by
Vol. 16A, No. 3 May 1991
Seitz et al.
561
initial vertical starting point was then recorded on videotape and measured.
Results
Fig. 1. A drill bit-tipped 4 mm half-pin is seen above a standard 4 mm half-pin below. Note the almost complete absence of threads on the distal 10 mm of the drill bit-tipped pin.
identifying those factors likely to contribute to complications and carefully avoiding them.7 The technique of fixator pin insertion, although only one of many factors influencing the outcome of this surgical procedure, is nonetheless a critical one. The fixator pin is, after all, the link between the fixation device and the fracture, between the establishment and maintenance of a good reduction. For these reasons we have critically evaluated the technique of fixator pin insertion.
Comparative pull-out strength of 4 mm half-pins inserted by predrilling and self-drilling demonstrated a mean pull-out strength of 390 pounds for the predrilled group, with a range from 270 to 540 pounds and a standard deviation of 73 pounds. The self-drilled group demonstrated a mean pull-out strength of 3 10 pounds, with a range from 160 to 610 pounds with a standard deviation of 120 pounds. This represented a mean decrease of 22% in the pull-out strength of the self-drilled pins compared with the predrilled pins (Fig. 2). For comparable pull-out strength to be achieved, the self-drilling pin required insertion completely beyond the cutting flutes of its tip, with 10 mm of the pin tip protruding out of the far cortex. The videotape analysis demonstrated a “wobble factor” of up to 1.2 cm in all planes at the proximal end of the drill bit when hand drilling was performed. Power drilling demonstrated a deviation of at most, 2 mm from the vertical during drilling.
Discussion Materials and methods Because of the appearance of new drill bit tipped pins recommended for direct insertion under hand drilling, a biomechanical analysis compared insertion of 4 mm pins by predrilling with 3.2 mm power-driven drill bit and hand insertion of 4.0 mm self-tapping threaded half-pins, and hand-driven insertion of selfdrilling, self-tapping 4 mm half-pins. Fourteen identically matched pairs of fresh-frozen canine femora (approximating human radii in size and dimension) were used to mechanically compare pull-out strength between 4 mm predrilled, self-tapping half-pins and 4 mm self-drilling, self-tapping half-pins with drill-bitlike cutting flutes (Fig. 1). Pins were placed under direct vision at identical locations in the canine bones. They were placed to identical depths with 1.0 mm of the pin protruding from the far side of the bone. The bone-pin unit was then placed in a protected mount on the Instron Unit and a tensile force was applied to the pin at a rate of 2 inches per minute through the point of pull-out failure, and all values were recorded. A videotape analysis was then done comparing power drilling versus hand drilling. A 1 cm grid was placed directly behind a mounted canine long bone and experienced surgeons were asked to drill a 3.2 mm hole with a small power drill at 1100 rpm and with a handdriven drill system. The degree of deviation from the
The rationale for applying a drill bit to the tip of a fixator pin is to eliminate the additional step of predrilling. The designers of this pin recognized that such a pin would not permit power insertion and have recommended implantation by a hand driven technique.* To justify this they have voiced concern over the heat generated by a pin inserted by power. However, this drilltipped pin has almost no thread along its distal 10 mm. Inserting this pin in a radius or metacarpal, therefore markedly diminishes the total amount of thread/ bone contact and therefore its “bone-holding” capacity. Laboratory tests confirmed a significant (p < 0.005) reduction in bone-holding capacity of 22% when these pins were inserted to standard clinical depths and pullout strength was compared with self-tapping pins threaded to the tip and inserted into predrilled holes. To achieve a comparable degree of holding power, drilltipped pins required insertion to the point of thread engagement of both cortices. This, however, required 10 mm of pin to protrude through the far cortex (Fig. 3, A). When applied to the clinical settings of unstable distal radius fractures, the decrease in pull-out strength correlates to a greater potential for pin loosening and secondary pin tract infection, fracture through the enlarged pinhole, loss of fixation, and loss of fracture reduction .‘, 9 Deeper insertion with 10 mm of pin protruding from
562
The Journal of HAND SURGERY
External jixator pin insertion techniques
Comparative Pullout Strength of 4mm Half-pins Strenoth
Data
Fig. 2. Bar graph demonstrating canine femora.
tlbl
from 14 matched fresh canine long bone6
individual pull out test results in 14 identically matched pairs of
Fig. 3. Comparable pull-out strength requires deep insertion of the drill bit-tipped pin to engage threads at both cortices. These models depict the degree of violation this causes of the interosseous spaces of the distal forearm (A) and the hand (B).
Vol. 16A, No. 3 May 1991
the far cortex can cause damage to deep, soft tissue structures, impair pronation and supination range of motion in the forearm, and create violation, scarring, and contracture of the interossei. The lack of fine control of the drill bit during hand drilling can create an “out-of-round” hole. The visible wobble noted in our videotape recordings would tend to create such an “out-of-round” hole with microfractures that could cause additional pin loosening in the clinical setting. Certainly, this added risk does not seem justified, even in an attempt to prevent heat generation and bone damage. In fact, it has been demonstrated that the factors leading to thermal damage are drill sharpness, pressure applied, lack of adequate irrigation, and nor drill speed ,I0 and that the best way to avoid thermal damage when inserting a fixator pin is to predrill. ” The rationale for using a “drill-bit-tipped” fixator pin inserted by hand drilling for the external fixation of distal radius fractures is unfounded and, in fact, potentially hazardous. The “drill-bit-tipped” pin has minimal thread over its distal 10 mm causing significantly diminished pull-out strength or requiring deep insertion that violates the interosseous space. The wobble factor present in hand drilling generates poor drill control, an out-of-round hole, and cortical fragmentation leading to potential progressive pin loosening. With careful attention to details in the surgical application of the external fixation device we are close to solving the heretofore “unsolved problem” of the unstable distal radius fracture by providing stability, while reducing complications.‘, I2 This study demonstrates: (1) that the insignificant time saved in avoiding the step of predrilling is not worth the potential morbidity; (2) that power should be employed for drilling; and (3) that pins threaded to the distal tip should be used. REFERENCES 1. Andrianne Y, Donkerwolcke M, Kinsenkamp M, et al. Hoffman external fixation of fractures of the radius and
Seitz et al.
2.
3.
4. 5.
6.
563
ulna. A prospective study of 53 patients. Orthopaedics 1984;7:845. Jupiter JB, Knirk JL. Intra-articular fractures of the distal end of the radius in young adults. J Bone Joint Surg 1986;68(5):647-59. Kongsholm J, Olerud C. Plaster cast versus external fixation for unstable intra-articular Colles’ fractures. Clin Orthop Philadelphia: JB Lippincott, 1989:57-65. Melone CP. Articular fractures of the distal radius. Clin Orthop North Am 1984;15:217. Seitz WH, Flatow EL, Putnam MD, Dick HM. The treatment of unstable distal radius fractures by a technique of external fixation utilizing a limited open approach. Orthop Trans 1986;10(3):575. Seitz WH, Putnam MD, Flatow EL, Dick MD. The limited open surgical approach for external fixations of unstable distal radius fractures. American Academy of Orthopaedic Surgeons Videotape No. 202, 1985. J HAND SURC 1990;15A:288-93.
7.
8.
9.
10.
11.
12.
Seitz WH, Froimson AI. Reduction of treatment-related complications in the external fixation of unstable distal radius fractures. Presented at the American Orthopaedic Associational Annual Meeting. Colorado Springs. Colorado. June 1989. Andrianne Y, Wagenknecht M, Donkerwolcke M, Zurbuchen C, Bumy F. External fixation pin: An in vitro general investigation. Othopaedics 1987;10( 1 I): 150716. Seitz WH, Froimson AI, Brooks DB, Greenwald AS D, Phil (Oxon), et al. Biomechanical analysis of pin placement and pin size for external fixation of distal radius fractures. Orthop Trans 1987;11(3):470. Mathews LS, Hirsch C. Temperatures measured in human cortical bone when drilling. J Bone Joint Surg 1972;54A:297-308. Matthews LS, Green CA, Goldstein. The thermal effects of skeletal fixation-pin insertion in bone. J Bone Joint Surg 1984;7(66A): 1077-83. Weber SC, Szabo RM. The severely comminuted distal radius fractures as an unsolved problem: complications associated with external fixation and pins-and-plaster technique. J HAND SURG 1986;11:157-65.
