Radiologic and gross anatomic evaluation of bone healing in the dog.

Bone healing associated with 3 techniques of midshaft femoral fracture fixation in 36 young adult Beagle-type dogs was evaluated in radiographic and gross pathoanatomic studies. A serrated transverse fracture was surgically and aseptically created on the midshaft of either the left or the right femur of each dog. The fixation devices used were intramedullary (IM) pin, IM pin and 1/2 Kirschner device, and tension bone plates. The radiographic evaluation was done in series. The first radiographs were taken during surgery. Radiographs were then taken immediately after surgery, to record the status of reduction, alignment, and fixation. Radiographs were taken at the 4th and 10th postoperative weeks, to monitor healing. All dogs were euthanatized at the 10th week. Both the normal femur and the healing femur were removed from all dogs, all soft tissue was removed from the bone, and each femur was examined grossly. Each type of fixation was associated with a distinct mode of osteogenesis. Bony union and clinical union (that stage in the healing process when fixation can be removed) were defined as a successful conclusion to each case. Malunion and nonunion were defined as unsuccessful conclusions. Delayed union was defined as neither successful nor unsuccessful. The IM pin cases had a 64.2% success rate and a 14.2% failure rate. The IM pin and 1/2 Kirschner cases had a 100% success rate. The bone plate cases were 91% successful, with 0% failure. A problem identified with IM pinning was axial rotation (6 of 14 or 42% of the cases). It was concluded that IM pins should not be used alone for the fixation of femoral fractures in adult dogs.     

Two techniques for supplementing interlocking nail repair of fractures of the humerus, femur, and tibia: results in 12 dogs and cats

OBJECTIVE: To describe 2 devices for improving stabilization of inadequately stabilized interlocking nail (ILN) repairs of the humerus, tibia, and femur in dogs and cats. STUDY DESIGN: Prospective study. ANIMALS: Twelve client-owned dogs and cats. METHODS: Two devices to further stabilize ILN repair of inadequately stabilized diaphyseal fractures were developed. Device 1 was an axial extension for the ILN that was connected to a conventional type I external skeletal fixator (ESF) with a short connecting bar. Device 2 had hybrid ILN bolt/ESF pins that were used to lock the ILN and serve as the pins for a type I ESF. Devices were used at the initial surgery when the stability of ILN repair was considered inadequate based on palpable fracture segment movement, insufficient medullary canal filling of the ILN at the fracture site, or when the ILN was used in a buttress mode. Outcome was obtained by recheck examinations, radiography, and telephone interview. RESULTS: Device 1 was applicable to fractures of the humerus and femur, but was not used for fractures of the tibia because the ILN extension would have interfered with the stifle. No gross loosening of the ILN/ESF extension connection to the ILN occurred. Device 2 was easily placed and used in the humerus, femur, and tibia. Device 2 allowed removal of the ILN interlock to one or both main fracture segments non-invasively. Clinically, both devices added stability compared with ILN repair alone. Both devices facilitated controlled destabilization of the fracture repair as healing progressed. Complications of pin tract infection, and premature hybrid bolt/ESF pin loosening resulting in premature ESF removal each occurred in 1 patient. Four of 28 hybrid ILN/ESF pins were grossly loose at 4- or 6-week postoperative recheck examinations. Outcomes were excellent (9), good (1), fair (1), and poor (1). CONCLUSIONS: Inadequately stabilized ILN repair of fractures can be stabilized by use of either device, both of which also permit controlled destabilization of the repair during healing. Device 2 can be used when non-invasive removal of the ILN interlock is desired during healing. CLINICAL RELEVANCE: These 2 devices should be considered as alternative methods for stabilization of inadequately stabilized ILN repairs in dogs and cats, or when controlled destabilization of an ILN fracture repair is desired.     

Management of fractures of the long bones of eight cats using external skeletal fixation and a tied-in intra-medullary pin with a resin-acrylic bar

CASE HISTORY AND CLINICAL FINDINGS: Eight feline patients with fractures of the femur, tibia or humerus were presented non-weight-bearing, with varying degrees of soft tissue and concurrent injury. Five fractures were comminuted, two were open fractures and there was one malunion. TREATMENT: Fracture repair was performed in each case using a low-cost resin-acrylic external skeletal fixator (ESF). An open, limited open, or 'open but do not touch' (OBDNT) approach allowed intra-medullary (IM) pinning of the major fragments, establishing axial alignment and countering bending stress. Application of a unilateral, uniplanar (Type IA) ESF using small diameter half-pins provided stabilisation against rotational and compressive forces. The half-pins and IM pin (tied-in) were incorporated into a composite bar with the resin-acrylic. The single humeral construct incorporated a transcondylar pin into a Type I-II design. RESULTS: Seven cats, including all five comminuted fractures, had uncomplicated fracture healing. Median time to complete removal of the construct was 7 (range 5-12) weeks. In the eighth cat, an open fracture developed into a non-union, which required revision with a plate and bone graft. This cat and six others available for follow-up (median 6 months) were reported by their owners to enjoy normal activity. Two had a mild, intermittent lameness, one had a mild but persistent lameness, and four were sound. Six out of seven owners rated the appearance of their pet's limb as normal. CLINICAL RELEVANCE: The resin-acrylic ESF/tied-in IM pin construct was versatile and lightweight and allowed even highly comminuted non-load-sharing fracture configurations to be stabilised successfully using a biological strategy. Failure of the pin/acrylic interface did not occur and the frames provided sufficient strength as evidenced by healing without failure of the bar in these cases. A resin-acrylic ESF construct is inexpensive and affords the occasional orthopaedist the means to provide rotational stability when IM pinning has been used as the primary mode of fracture repair for short-oblique and transverse fractures. An extensive and costly clamp/bar inventory is not required, and there is greater flexibility for the orientation and placement of fixation pins than allowed by traditional linear bar systems.     

Long-term results of transarticular pinning for surgical stabilisation of coxofemoral luxation in 20 cats

O bjectives : The objective of this study was to describe initial and long-term results of open reduction and transarticular pinning for treatment of coxofemoral luxations in cats.
M ethods : Cats were treated by open reduction and transarticular pinning for coxofemoral luxation over a five year period at two institutions. Follow-up assessment included orthopaedic examination, radiography and owner questionnaires.
R esults : Twenty cats were included in the study (14 males and six females). One cat was affected bilaterally. Mean time to follow-up was 21 months. Seventeen joints were stabilised with a 1·6 mm pin, three with 2·0 mm pins and a 1·2 mm pin was used in the remaining joint. An Ehmer sling was not utilised in any case. All transarticular pins except one were removed (mean 3·5 weeks), with all hips still in reduction The overall success rate was 77 per cent, with two reluxations and one resorbed femoral head noted on radiographs of 13 joints followed long term. All 20 owners reported good to excellent long-term functional outcome for their cats.
C linical S ignificance : Results from this study indicate that transarticular pinning for stabilisation of coxofemoral luxation in cats can provide a good long-term outcome without sacrificing the integrity of the coxofemoral joint.     

Internal Skeletal Fixation Using a Kirschner Apparatus for Stabilization of Fracture/Luxations of the Lumbosacral Joint in Six Dogs: A Modification of the Transilial Pin Technique

A technique using a modification of the transilial pin technique for stabilization of fracture/ luxations of the lumbosacral joint was performed in six dogs. This technique used an internal skeletal fixator composed of two transilial pins secured with two double fixator clamps. Collapse (shortening) of the seventh lumbar vertebra (L7) was observed in five dogs without compromise of the vertebral canal. Kirschner wires placed across the articular facets as supplemental fixation devices migrated to the subcutaneous tissues in two dogs and were easily removed. Migration of the internal fixators was not observed during healing; vertebral canal dimensions were maintained in all cases, and the internal fixators were not removed after resolution of fracture healing. All fractures were healed within 6 to 12 weeks of surgery without evidence of pain, neurologic impairment, or long-term complications.     

Repair of a proximal diaphyseal femoral fracture in a calf, using intramedullary pinning, cerclage wiring, and external fixation.

Repair of a comminuted, spiral oblique, proximal diaphyseal femoral fracture in a 7-day-old calf was achieved by use of an intramedullary pin, cerclage wires, and external fixator. Six stainless steel wires were used for full cerclage to secure a long butterfly fragment and multiple incomplete and complete nondisplaced fragments to the femur in order to create 2 principal fragments. Axial alignment and resistance to bending was provided by a round, double-pointed, end-threaded intramedullary pin (6.35 mm in diameter), which was inserted in a retrograde fashion. A type-1, double-connecting-bar external fixator, using 4 round pins (4.8 mm in diameter), was used to provide supplemental stabilization against shear and torsional forces. At 45 days after surgery, healing at the fracture site was seen on radiography of the limb, and the external fixator was removed. Eight months after surgery, the calf had a normal gait.     

Dynamic intramedullary crosspinning technique for repair of distal femoral fractures in dogs and cats: 71 cases (1981-1985)

Dynamic intramedullary crosspinning was used in the surgical treatment of supracondylar and distal physeal fractures of the femur in 129 dogs and cats over a 5-year period; the records of the 44 dogs and 27 cats with follow-up information up to time of bony union were evaluated. The results were good or excellent in 66 of 71 animals (93%). The mean follow-up period was 22 months. Distal pin migration was the major complication (10 animals; 14%). The pin migrated before bony union in 2 animals because of instability and collapse at the fracture site. The pin migrated in 8 animals after bony union and was associated with intermittent lameness. In 5 of these, pin removal was performed and the lameness resolved.     

Treatment of tibial fractures with plates using minimally invasive percutaneous osteosynthesis in dogs and cats

OBJECTIVES: The aim of the here described case series was to develop and evaluate the minimally invasive percutaneous osteosynthesis for the plate fixation of tibial fractures in dogs and cats. METHODS: Six dogs and four cats with shaft fractures of the tibia were treated using minimally invasive percutaneous osteosynthesis. Follow-up radiographs four to six weeks after fracture fixation were evaluated for fracture healing. For the long-term follow-up (minimum 2.4 years), owners were contacted by phone to complete a questionnaire. RESULTS: All fractures healed without the need for a second procedure. Follow-up radiographs obtained after four to six weeks in seven cases showed advanced bony healing with callus formation and filling of the fracture gaps with calcified tissue in all seven. All the patients had a good to excellent long-term result with full limb function. The time needed for regaining full limb use was two to three months. CLINICAL SIGNIFICANCE: Minimally invasive percutaneous osteosynthesis seems to be a useful technique for the treatment of tibial shaft fractures in dogs and cats.     

Comparison of the Strength and Holding Power of 4 Pin Designs for Use with Half Pin (Type I) External Skeletal Fixation

The strength and holding power of four pin designs for use with half pin (type I) external skeletal fixation were evaluated. Pins that were tested were fully threaded, nonthreaded, two cortices partially threaded, and one cortex partially threaded. The study involved three parts: (1) resistance of the pins to axial extraction immediately after insertion; (2) resistance of the pins to axial extraction 8 weeks after being inserted into the tibiae of live dogs; and (3) resistance of the pins to bending load. Pins with threads engaging two cortices were more resistant to axial extraction than nonthreaded pins in both the acute (p less than 0.0001) and chronic (p less than 0.0001) studies. Nonthreaded pins were more resistant to bending than fully threaded and two cortices partially threaded pins (p less than 0.0005). One cortex partially threaded pins possessed similar bending strength to nonthreaded pins (p = 0.21) and had 5.3 times more resistance to axial extraction in the acute study (p less than 0.0001) and 6.9 times more in the chronic study (p less than 0.0001). Though one cortex partially threaded pins were not as resistant to axial extraction as pins with threads engaging two cortices (p less than 0.0001), they were more resistant to bending loads (p less than 0.0005). Loss of holding power and pin failure are two of the most serious problems associated with fracture stabilization using external skeletal fixation. The results of this study suggest that one cortex partially threaded pins are better at maintaining holding power and resisting bending and breaking than nonthreaded pins.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intramedullary pinning of femoral diaphyseal fractures in neonatal calves: 12 cases (1980-1990).

Medical records of 12 calves less than or equal to 1 month old, with fracture of the femoral diaphysis, were reviewed. Ten calves were within 1 week of birth at the time of diagnosis. Open reduction was accomplished by use of a lateral approach. Retrograde intramedullary pinning was accomplished in all calves, using 2 (n = 4 calves) or 3 (n = 8 calves) pins. Cerclage wire was used to supplement fixation in 7 calves. A closed continuous suction drain was placed along the lateral aspect of the femur in every calf. Postsurgical complications included seroma formation over the middle gluteal musculature (n = 5 calves), pin migration (n = 6 calves), and osteomyelitis (n = 1 calf). Pin migration was observed in 4 calves that had been treated with nonthreaded trochar point pins. Fractures in 10 of 12 calves (83%) were considered to have healed satisfactorily. One calf was euthanatized because of septic osteomyelitis of the femur. One calf was euthanatized because of persistent lameness and pin migration. Pins were removed in 8 of 12 calves (67%) between the 13th and 90th postoperative days. Results of this study indicate that application of intramedullary pins may be a useful solution for management of femoral diaphyseal fracture in young calves.     

Ellis Pin Complications in Seven Dogs

Complications developed with the clinical use of Ellis pins in external skeletal fixation in seven dogs weighing 11 to 24 kg. Pins broke at the threaded-nonthreaded shaft junction in six dogs, and there was radiographic evidence of pin loosening six dogs. One pin pulled out causing loss of fixation in one dog. These complications with the recently introduced Ellis pin emphasize a need for further evaluation of its proper use.     

Use of veterinary interlocking nails for diaphyseal fractures in dogs and cats: 121 cases

OBJECTIVE: To report clinical outcome after use of an interlocking nail (veterinary interlocking nail [VIN]) for stabilization of diaphyseal fractures in dogs and cats. STUDY DESIGN: Retrospective study. Animals: Seventy-eight dogs and 43 cats with diaphyseal fractures of the femur (n = 96), tibia (n = 14), or humerus (n = 11). METHODS: Interlocking nails (4 mm diameter [n = 72], 6 mm [n = 25] or 8 mm [n = 24]), were used in static (n = 106) or dynamic (n = 15) fixation mode. Cerclage wires also were used in 63 (52%) cases. Data about the patient (species, breed, weight, age), characteristics of the fracture, and details of the surgery and perioperative complications were recorded. The surgeon evaluated functional outcome, and fracture healing was quantified 6 weeks (W6) and 3 months (M3) after surgery with a radiographic index. RESULTS: Twelve cases had been unsuccessfully treated by another technique. Of 106 comminuted fractures, 60 were classified as unstable. Only 112 animals were evaluated at W6; 86 (77%) healed without complication and had a functional outcome considered excellent (n = 80, 93%), good (n = 5, 4%), or fair (n = 1). Twenty-six complications were noted: 16 (14%) patients did not require additional surgery and had a good or excellent outcome, whereas 10 (8%) patients needed surgical intervention to CONCLUSIONS: VINs can be used to repair diaphyseal fractures of the femur, tibia, and humerus in dogs and cats provided the implants are appropriately sized for the fractured bone. The high healing rate (even with unstable fractures), associated with a functional outcome, and low complication rate support the use of VINs for these fracture types. However, a period of training and the application of basic principles are necessary to ensure successful results. CLINICAL RELEVANCE: VINs should be considered as alternative technique for management of selected diaphyseal fractures of the femur, tibia, and humerus in dogs and cats.     

Comparison of Holding Power of Three Different Pin Designs for External Skeletal Fixation in Avian Bone: A Study in Common Buzzard (Buteo buteo)

Objective— (1) To evaluate resistance to axial extraction of 3 pin designs in avian humerus and tibiotarsus; (2) to assess the effect of pin location within the bone on holding power; and (3) to assess the influence of thread pitch on holding power. Study Design— Resistance of pins to axial extraction was measured immediately after insertion. Animals— Adult common buzzards (Buteo buteo; n=9). Methods— Different pin designs (1 smooth; 2 threaded pins, differing in pitch) were inserted into the proximal and distal metaphysis and the proximal, middle, and distal diaphysis of the humerus and tibiotarsus. Maximum force required for axial extraction of pins was recorded. Results— Smooth pins had the lowest extraction force (P<.05). Pins inserted into the diaphysis (proximal, middle and distal) of the humerus and the distal metaphysis of the tibiotarsus had a greater pullout strength than pins in other locations. Pins with a smaller pitch inserted into the proximal diaphysis and distal metaphysis of the humerus, and the proximal metaphysis of the tibiotarsus had significantly greater holding power than pins with a larger pitch (P<.05). Conclusions— Pins inserted into the diaphysis of humerus and the distal metaphysis of the tibiotarsus are better at resisting extraction. Pins with a smaller pitch possess greater holding power than pins with a larger pitch in avian humerus and tibiotarsus. Clinical Relevance— Consideration should be given to pin location and thread pitch, when choosing external skeletal fixation to repair an avian humeral or tibiotarsal fracture.     

Use of a four pin and methylmethacrylate fixation in L7 and the iliac body to stabilize lumbosacral fracture-luxations: a clinical and anatomic study

Objectives— To describe the clinical outcome of a 4 pin lumbosacral fixation technique for lumbosacral fracture–luxations, and to refine placement technique for iliac pins based on canine cadaver studies.
Study Design— Retrospective and anatomic study.
Sample Population— Dogs (n=5) with lumbosacral fracture-luxations and 8 cadaveric canine pelvi.
Methods— Lumbosacral fracture–luxations were stabilized with a 4 pin (positive-profile threaded) and bone cement fixation. Caudal pins were inserted in the iliac body and cranial pins were inserted into the L7 or L6 pedicle and body. Follow-up examinations and radiographs were performed to assess patient outcome. Intramedullary pins were inserted into the iliac bodies of 8 cadaver pelvi. Radiographs were taken to measure pin insertion angles and define ideal insertion angles that would maximize pin purchase in the ilium.
Results— Follow-up neurologic examination was normal in 4 dogs. Radiographic healing of the fracture was evident in 5 dogs. One implant failure occurred but did not require re-operation. For cadaver iliac pins, mean craniocaudal insertion angle was 29° and mean lateromedial insertion angle was 20°.
Conclusions— Four pin and bone cement fixation effectively stabilizes lumbosacral fracture luxations. The iliac body provides ample bone stock, which can be maximized using an average craniocaudal pin trajectory of 29° and an average lateromedial pin trajectory of 20°.
Clinical Relevance— Lumbosacral fracture–luxations can be stabilized with 4 pin and bone cement fixation in the lumbar vertebrae and iliac body, using 29 and 20° as guidelines for the craniocaudal and lateromedial pin insertion angles in the ilium.     

Occurrence and pattern of long bone fractures in growing dogs with normal and osteopenic bones

A retrospective study was undertaken to record the occurrence and pattern of long bone fractures, and the efficacy of Intramedullary (IM) Steinmann pin fixing in growing dogs. All the records of growing dogs during a 10-year-period were screened to record the cause of trauma, the age and sex of the animal, the bone involved, the type and location of the fracture, the status of fixation, alignment, maintenance of fixation and fracture healing. The results were analysed and comparisons were made between growing dogs with normal and osteopenic bones. Among the 310 cases of fractures recorded, the bones were osteopenic in 91 cases (29%). Minor trauma was the principal cause of fracture in dogs with osteopenia (25%), and indigenous breeds were most commonly affected (38%). Fractures in dogs with osteopenic bones were most commonly recorded in the age group of 2-4 months (53%), whereas fractures in normal dogs were almost equally distributed between 2 and 8 months of age. Male dogs were affected significantly more often in both groups. In osteopenic bones, most fractures were recorded in the femur (56%), and they were distributed equally along the length of the bone. Whereas in normal bones, fractures were almost equally distributed in radius/ulna, femur and tibia, and were more often recorded at the middle and distal third of long bones. Oblique fractures were most common in both groups; however, comminuted fractures were more frequent in normal bones, whereas incomplete fractures were more common in osteopenic bones. Ninety-nine fracture cases treated with IM pinning (66 normal, 33 osteopenic) were evaluated for the status of fracture reduction and healing. In a majority of the cases (61%) with osteopenic bones, the diameter of the pin was relatively smaller than the diameter of the medullary cavity (<70-75%), whereas in 68% of the cases in normal bones the pin diameter was optimum. The status of fracture fixing was satisfactory to good in significantly more osteonormal (59%) than osteopenic dogs (42%). Fracture healing, however, was satisfactory in significantly more cases with osteopenic than normal bones. The appearance of callus was relatively early and the amount of bridging callus was relatively large in greater number of osteopenic bone fractures. Mal-union and non-union were recorded more often in osteopenic cases than in normal cases. However, the incidence of bone shortening and osteomyelitis was significantly higher in normal bones than in osteopenic bones.     

Ex Vivo Biomechanical Comparison of Pin Fixation Techniques for Canine Distal Femoral Physeal Fractures

Objective— To compare the biomechanical properties of five intramedullary (IM) pin fixation techniques for Salter-Harris type I fractures of the distal femur in dogs.
Study Design— Randomized, one-way factorial design composed of five treatment groups: (1) single IM pin, (2) dynamic IM crossed pins, (3) paired convergent pins, (4) crossed pins, and (5) crossed polyglycolic acid (PGA) rods.
Sample Population— Forty pairs of cadaver canine femurs.
Materials— One femur of each pair was manually fractured and subsequently repaired; the contralateral intact femur served as its control. Each femur was loaded in torsion until failure occurred and load-deformation curves were generated.
Results— The crossed-pin technique sustained the greatest load to failure (116.8%) followed by the paired convergent pins (104.8%), dynamic IM pins (90.6%), single IM pin (72.1%), and crossed PGA rods (71.9%). Statistically significant differences in strength at failure were detected between the crossed-pin and single IM pin and the crossed-pin and crossed PGA rod techniques. All fixation techniques underwent greater deformation (1.5 times as much) and had a lower stiffness (66% to 75%) compared with the intact controls; however, there was no significant difference between techniques. Failure in the paired convergent and crossed-pin techniques occurred by fracture of the bone; failure in the other techniques occurred by distraction at the fracture site.
Conclusion— The rotational stability of any of the fixation techniques appears to be primarily determined by the ability to prevent distraction and maintain interdigitation of the physis.
Clinical Relevance— When choosing a particular fixation technique for repair of a distal femoral physeal fracture, consideration should be given to the technique's relative biomechanical merits.     

Radial and Tibial Fracture Repair with External Skeletal Fixation: Effects of Fracture Type, Reduction, and Complications on Healing

Twenty-eight consecutive fractures of the canine radius and tibia were treated with external skeletal fixation as the primary method of stabilization. The time of fixation removal (T1) and the time to unsupported weight-bearing (T2) were correlated with: (1) bone involved; (2) communication of the fracture with the external environment; (3) severity of the fracture; (4) proximity of the fracture to the nutrient artery; (5) method of reduction; (6) diaphyseal displacement after reduction; and (7) gap between cortical fragments after reduction. The Kruskal-Wallis one-way analysis of variance was used to test the correlation with p less than .05 set as the criterion for significance. The median T1 was 10 weeks and the median T2 was 11 weeks. None of the variables correlated significantly with either of the healing times; however, there was a strong trend toward longer healing times associated with open fractures and shorter healing times associated with closed reduction. Periosteal and endosteal callus uniting the fragments were observed radiographically in comminuted fractures, with primary bone union observed in six fractures in which anatomic reduction was achieved. Complications observed in the treatment of these fractures included: bone lysis around pins (27 fractures), pin track drainage (27 fractures), pin track hemorrhage (1 fracture), periosteal reaction around pins (27 fractures), radiographic signs consistent with osteomyelitis (12 fractures), degenerative joint disease (2 dogs), and nonunion (1 fracture). Valgus or rotational malalignment resulted in 16 malunions of fractures. One external fixation device was replaced and four loose pins were removed before the fractures healed. One dog was treated with antibiotics during the postoperative period because clinical signs of osteomyelitis appeared.(ABSTRACT TRUNCATED AT 250 WORDS)     

Transarticular pinning for repair of hip dislocation in the dog: a retrospective study of 40 cases

Transarticular pinning was used for the repair of hip dislocation in 40 dogs. The mean follow-up period was 18.4 months. Satisfactory results were achieved in 80% of the cases. Body weight, ipsilateral femoral head fracture, and hip dysplasia appeared to affect long-term prognosis. The most frequent complication was pin breakage, but this did not affect final outcome and could be avoided by using pins of larger diameter. Osteonecrosis was observed in two cases.     

Evaluation of a tapered-sleeve transcortical pin to reduce stress at the bone-pin interface in metacarpal bones obtained from horses

OBJECTIVE: To evaluate stiffness and bone-pin interface stress for a transcortical tapered-sleeve pin (TSP) that incorporates bilateral tapered sleeves over a transcortical pin. SAMPLE POPULATION: 14 third metacarpal bones (MCIII) collected from adult horses of various breeds. PROCEDURE: Each MCIII was cut in half to provide 2 test specimens. Pins (conventional and TSP) of 3 diameters (6.35, 7.94, and 9.50 mm) were inserted in specimens (3 specimens for each diameter and each type of pin). The test fixture simulated a typical sidebar-span skeletal fixation device for horses. Single cycle load-deflection tests were performed. Cyclic fatigue tests of TSP were performed to evaluate fatigue characteristics and stress conditions at the bone-pin interface. Maximum stress and strain were calculated, and results were compared with existing data on fatigue characteristics of bone. RESULTS: Significant increases in stiffness (load-deflection) and higher loads at yield point were detected for the TSP (stiffness for conventional 9.50mm pins, 4,500 N/mm; stiffness for TSP, 19,988 N/mm). Results of cyclic tests revealed a close correlation with existing data on fatigue characteristics. CONCLUSIONS AND CLINICAL RELEVANCE: The TSP described here is stiffer than conventional transcortical pins, and stress across the bone-pin interface is more evenly distributed. Use of this TSP should minimize major problems encountered during external fixation associated with the transcortical pin and bone-pin interface (ie, bone necrosis, infection of the pin track, pin loosening, and bone failure).     

An unusual sequel to intra-medullary pinning

Extract

The use of an intra-medullary pin for repair of a midshaft fracture of the dog's femur is usually followed by excellent bone healing. Untoward sequelae may follow poor technique, or the use of pins in cases in which other techniques are indicated. This communication records an unusual sequel to intra-medullary pinning which the writer has not observed previously.