Predicting the external formation of callus tissues in oblique bone fractures: idealised and clinical case studies.

It is proposed that the external asymmetric formation of callus tissues that forms naturally about an oblique bone fracture can be predicted computationally. We present an analysis of callus formation for two cases of bone fracture healing: idealised and subject-specific oblique bone fractures. Plane strain finite element (FE) models of the oblique fractures were generated to calculate the compressive strain field experienced by the immature callus tissues due to interfragmentary motion. The external formations of the calluses were phenomenologically simulated using an optimisation style algorithm that iteratively removes tissue that experiences low strains from a large domain. The resultant simulated spatial formation of the healing tissues for the two bone fracture cases showed that the calluses tended to form at an angle equivalent to the angle of the oblique fracture line. The computational results qualitatively correlated with the callus formations found in vivo. Consequently, the proposed methods show potential as a means of predicting callus formation in pre-clinical testing.

Predicting the external formation of a bone fracture callus: an optimisation approach.

The formation of a fracture callus in vivo tends to form in a structurally efficient manner distributing tissues where mechanical stimulus persists. Therefore, it is proposed that the formation of a fracture callus can be modelled in silico by way of an optimisation algorithm. This was tested by generating a finite element model of a transversal bone fracture embedded in a large tissue domain which was subjected to axial, bending and torsional loads. It was found that the relative fragment motion induced a compressive strain field in the early callus tissue which could be utilised to simulate the formation of external callus structures through an iterative optimisation process of tissue maintenance and removal. The phenomenological results showed a high level of congruence with in vivo healing patterns found in the literature. Consequently, the proposed strategy shows potential as a means of predicting spatial bone healing phenomena for pre-clinical testing.

The role of interfragmentary strain on the rate of bone healing-a new interpretation and mathematical model.

It is postulated that there is a causal relationship between mechanical stimulus and the rate of bone healing post fracture. However, despite numerous experimental studies in the literature, no quantifiable relationship has been proposed. It is hypothesized in the present study that the temporal rate of bone fracture healing, measured in terms of callus stiffening per week, can be described mathematically based on the relative motions between bone fragments at the initial stage of the healing process. To test this, a comparative reanalysis of experimental data found in the literature was conducted. These individual data sets described a relationship between an initial intermittently applied peak interfragmentary strain and the change in interfragmentary motion or the increase in callus stiffness over time. The data were converted into a relative increase in stiffness, which normalised the results and reduced inter-study variability. The rates of healing for the various initial strains were compared, and based on this a mathematical phenomenological model was derived. Error analyses were then performed, which showed a high level of congruence between the in-vivo and simulated rates of healing. The results of the comparative analysis revealed that there is a positive correlation between the rate of callus stiffening and interfragmentary strain. Finally, the proposed model has shown for the first time that a quantifiable cause-and-effect relationship exists between the rate of bone healing and mechanical stimulus.

Repair of thirty-six fractures in dogs using the Mennen clamp-on plate: preliminary results.

OBJECTIVE: To report the use of a human fixation device, the Mennen clamp-on plate (MCOP), for fracture repair in dogs as the sole method of fixation, or in combination with another fixation method such as an intramedullary pin. METHODS: The study, which was performed to evaluate the use of the MCOP in fracture repair in dogs, included 36 cases that were selected between 2004 and 2008. The selected cases were all closed diaphyseal fractures, in which sufficient plate prongs could engage the bone on either side of the fracture. RESULTS: Of the 36 cases, 32 had excellent outcomes, and four had complications; these were two cases of fixation failure, one case of osteomyelitis, and one with mild sciatic nerve deficits. DISCUSSION: The MCOP is a promising method for fracture repair on its own for young puppies (six months or less), and in conjunction with other fixation methods in older dogs. It is quick to apply, as no screw holes are created and it achieved a successful outcome in 95% of the cases, provided the cases were appropriately selected for this method. CONCLUSIONS: Using the MCOP has produced promising preliminary results in this study and warrants further evaluation.

Limb lengthening in three dogs using distraction rates without a latency period. Radius/ulna, tibia, femur.

OBJECTIVE: To report three clinical cases suffering from limb shortening secondary to monostotic physeal closure, in which distraction osteogenesis had been performed without a latency period and with high distraction rates. METHODS: Three dogs had limb lengthening performed, using an Ilizarov ring fixator in two dogs and a linear dynamic fixator in the other dog. Bone lengthening achieved for a radius/ulna was 27 mm at 2 mm per day , a tibia was 78 mm at 3 mm per day, and a femur of 45 mm was 3 mm per day . RESULTS: Complications related to pin loosening occurred in each case, thus requiring surgical corrective procedures, but these did not affect the final outcome. Lateral bowing of the bar and bone and some musculo-cutendinous contracture occurred in the femur. Fixation frames were on for 12 weeks in Case 1, eight weeks in Case 2 and nine weeks in Case 3. All three of the cases had a good functional outcome. DISCUSSION: The faster rates of lengthening were not associated with any long-term deleterious soft tissue complications, but they were associated with pin loosening and bending of the bar. In each case there was excellent osteogenesis. CONCLUSIONS: From the results achieved in these three cases it can be concluded that a latency period prior to distraction osteogenesis may not be necessary. Also, distraction rates up to 3 mm per day can be used to shorten the time needed to achieve lengthening; however further studies are needed to investigate the high level of complications.

Muscle separation approach to scapular neck fractures in eight dogs.

OBJECTIVES: To report on a new surgical approach to scapular neck fractures. METHODS: A combined prospective and retrospective study of eight dogs that had sustained a fracture of the scapular neck between 1992 and 2005 was performed. All eight dogs had an internal fixation using a T plate through a muscle separation approach. Retraction of the supraspinatus from the deltoideus and infraspinatus allows an adequate surgical window to enable plating of the scapular neck. RESULTS: Sixty-two percent had an excellent outcome without any lameness or stiffness detected. The remaining cases experienced infrequent bouts of stiffness, or, in one case lameness. CLINICAL SIGNIFICANCE: The current literature recommends that the surgical approach to the scapular neck is by osteotomy of the acromion process, which is unnecessary in the authors' opinion as it increases surgical trauma, operating time and the number of implants required.

Fixation of humeral intercondylar fractures using a lateral plate in 14 dogs supported by finite element analysis of repair.

Fourteen Spaniels that presented with an intercondylar fracture of the distal humerus were managed using a lateral plate and an additional pin in twelve cases. Fixation of the fracture was achieved using a plate applied laterally which incorporated the transcondylar lag screw in the most distal hole. Of the 14 cases, two had poor results, one of which was a bilateral case, whilst the remaining 12 cases had good or very good results with only occasional stiffness or lameness. Finite element (FE) modelling of a distal humerus was generated, and loading of fracture repairs using a lateral plate and caudal plate was completed in a comparative study to determine which fixation method resisted micro-motion most effectively. Finite element analysis revealed that the lateral plate fixation provided significantly more resistance to micro movement at the fracture site that the caudal plate fixation, with 40% more micro-motion in the latter.

Comparison of recovery times and complication rates between a modified slanted slot and the standard ventral slot for the treatment of cervical disc disease in 20 dogs.

OBJECTIVES: To compare the recovery times and complication rates between the standard ventral slot and the modified slanted ventral slot for the treatment of cervical disc disease in dogs with the same neurological grade. METHODS: A retrospective analysis of an equal number of cervical disc cases for each procedure was carried out specifically to determine the recovery times and complication rates. To allow for meaningful comparison only dogs that had the same neurological grade were selected. Outcomes were determined by time to recover and the resolution of symptoms and complications were graded in terms of severity. RESULTS: The standard ventral slot cases had a higher complication rate than the modified slanted slot cases with one case dying in the postoperative period. However, the modified slanted slot cases on average had a marginally slower recovery time than standard ventral slot cases. CLINICAL SIGNIFICANCE: Ventral decompression using the modified slanted slot instead of the standard ventral slot will allow for spinal decompression with potentially less destabilisation, and incur a similar incidence of complications and rate of recovery.

Use of transilial pinning for the treatment of sacroiliac separation in 25 dogs and finite element analysis of repair methods.

A retrospective study of 25 cases of sacroiliac separation showed that transilial pinning is an effective method of repair for sacroiliac separations. Only 8% of cases of sacroiliac separation had transilial pinning as the sole surgical intervention as other concomitant minor injuries, such as fractured ischium or pubis, did not require surgery. Even though pin loosening and migration along with local soft tissue irritation occurred in all cases, 92% of the cases had 'good' or 'excellent' outcomes. Sacroiliac separation heals by fibrosis, not directly by bone healing, and therefore can heal sufficiently in four weeks to allow pain free weight bearing in four weeks. Additionally, finite element modelling was undertaken to analyse micro-movement of repaired sacroiliac separations. The micro-motion analysis showed that the lag screw fixation method was more stable than the transilial fixation method since the relative motion between the two indicated that the latter allowed more unsupported iliac movement.

Proton pump inhibitors reduce gallbladder function.

BACKGROUND: In the authors' previous study of gallbladder function before and after fundoplication, 58% of the patients demonstrated preoperative gallbladder motor dysfunction, and 86% of those retested after operation and cessation of proton pump inhibitors (PPIs) normalized. Because no study has directly assessed the impact of antisecretory agents on gallbladder function, this study measured gallbladder ejection fraction (GBEF) in healthy volunteers before and after initiation of PPIs. METHODS: A total of 19 subjects completed the study, which included baseline determination of GBEF by cholecystokinin-stimulated hepatobiliary acid scan, 30 days of antisecretory therapy with omeprazole (40 mg daily), and repeat GBEF on day 30. Subjects were surveyed regarding compliance and symptoms. RESULTS: For 15 of 19 subjects, PPI therapy was associated with reduced gallbladder motility. Evolution of symptoms consistent with a biliary etiology was reported by 26.7% of these subjects. CONCLUSIONS: Short-term PPI therapy reduces gallbladder motility in healthy volunteers. Chronic PPI therapy may pose a risk for long-term gallbladder dysfunction and biliary complications.

Hepatobiliary scan showing type II choledochal cyst.

Nuclear medicine hepatobiliary scintigraphy is well established for the evaluation of right upper quadrant pain in cases of possible acute cholecystitis. The authors present a case of type II choledochal cyst shown on a hepatobiliary scan in a patient with possible acute cholecystitis.

Talar neck fractures in five cats.

Five cats with fracture of the talar neck were treated using external skeletal fixation (ESF). In four of the cases, ESF was the only fixation technique used and this was applied in a closed manner coupled with traction. In the remaining cat, ESF was used in combination with a lag screw. All the fractures eventually healed, demonstrating that ESF provided a simple and effective method of treatment for these cases.