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Case Report
Rapid prototyping to design a customized locking plate for pancarpal arthrodesis in a giant breed dog M. Petazzoni1; T. Nicetto2 Milano Sud, Peschiera Borromeo (Mi), Italy; 2Diagnostica Piccoli Animali, Zugliano (Vi), Italy
Keywords Rapid prototyping, custom plate, pancarpal arthrodesis, locking plate, dog
Summary This report describes the treatment of traumatic carpal hyperextension in a giant breed dog by pancarpal arthrodesis using a custom-made Fixin locking plate, created with the aid of a three-dimensional plastic model of the bones of the antebrachium produced by rapid prototyping technology. A three-year-old 104 kg male Mastiff dog was admitted for treatment of carpal hyperextension injury. After diagnosis of carpal
Correspondence to: Massimo Petazzoni Clinica Veterinaria Milano Sud Via della Liberazione 26 20068 Peschiera Borromeo (Mi) Italy Phone: +39 02 55 30 55 68 Fax: +39 02 55 30 62 88 E-mail: [email protected]
Introduction In cases where it is not possible to restore the functionality of a joint, the surgical salvage procedure of arthrodesis is often used as an alternative to amputation (1). Arthrodesis of the carpus may be indicated in cases of osteoarthritis, articular fracture, chronic luxation, ligament lesions, hyperextension, and also developmental abnormalities of the antebrachiocarpal, middle carpal and carpal-metacarpal joints (1–8). Fusion of the middle carpal and carpal© Schattauer 2014
instability, surgery was recommended. Computed tomography images were used to create a life-size three-dimensional plastic model of the forelimb. The model was used as the basis for constructing a customized 12-hole Fixin locking plate. The plate was used to attain successful pancarpal arthrodesis in the animal. Radiographic examination after 74 and 140 days revealed signs of osseous union of the arthrodesis. Further clinical and radiographic follow-up examination three years later did not reveal any changes in implant position or complications.
Vet Comp Orthop Traumatol 2014; 27: 85–89 doi:10.3415/VCOT-13-04-0055 Received: April 29, 2013 Accepted: November 3, 2013 Pre-published online: December 9, 2013
metacarpal joints alone is possible if only these joints are affected, while pancarpal arthrodesis is generally performed if the antebrachiocarpal joint is involved (2). Osteosynthesis techniques described for these types of surgery include application of a bone plate to the dorsal, medial, or palmar aspects of the carpus; cross-pinning; and transarticular linear or circular external skeletal fixation (1–3, 9–13). For large breed dogs, a dorsal plate with 3.5 mm screws is suggested (2). Double implants on the dorsal surface of the carpus may be
necessary to achieve effective and stable arthrodesis in giant breed dogs (3). Biomodels have been successfully used since the 1990s to help diagnose, plan and rehearse medical procedures on human patients (14). More recently three-dimensional models, created by rapid prototyping techniques, have been used for the preoperative planning of surgery to correct angular deformities in the limbs of dogs (14–15). The present report describes the use of three-dimensional computer tomographic (CT) imaging and rapid prototype modelling to guide the manufacture of a custom plate with locking screws to achieve pancarpal arthrodesis in a giant breed dog (16).
Case report A three-year-old 104 kg male Mastiff dog was admitted for the complaint of severe (grade 3/4) right forelimb lameness. Twelve weeks previously the animal had fallen from a grooming table and had been severely lame since. On examination, hyperextension of the right carpus was evident (▶ Figure 1); signs of pain were elicited on passive flexion and extension of the carpus. Orthogonal radiographs revealed signs of osteoarthritic changes on the dorsal surface of the base of the metacarpal bones (▶ Figure 2). From mediolateral radiographic images in hyperflexion and hyperextension (▶ Figure 2 B) we determined that the maximum angles of flexion and extension of the carpus were 164° and 230° respectively. We diagnosed carpal hyperextension at the carpal-metacarpal joint and severe antebrachio-carpal instability. Pancarpal arthrodesis was recommended. Vet Comp Orthop Traumatol 1/2014
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M. Petazzoni, T. Nicetto: Arthrodesis in a giant breed dog
Figure 2 A) Preoperative craniocaudal view of the right antebrachium. B) Preoperative mediolateral view of right antebrachium in hyperextension.
Figure 1 Preoperative photograph of the right forelimb showing carpal hyperextension.
On the same day, the dog was premedicated with methadonea (0.2 mg/kg) and acepromazineb (10 µg/kg). Anaesthesia was induced with propofolc (3 mg/kg) and maintained with isofluoraned (1.5%) in oxygen for CT using a helical CT scanner in single-slice modee. The dog was positioned in sternal recumbency with the right forelimb extended cranially allowing the radius, the carpal joint and the metacarpal bones to lie in neutral position. Transverse 1 mm slices were obtained beginning at the elbow joint and including the metacarpalphalangeal joints. Images were obtained at zero degrees gantry tilt. Using the CT files (DICOM format), a rapid prototyping centref produced a three-dimensional model of the bones of the right antebrachium (▶ Figure 3). Screw positions were planned on the model (▶ Figure 3). A Fixin locking plateg was then designed and produced based on the model and the positions of the screw holes (▶ Figure 3) (16). The plate, 23 cm long and 3 mm thick, was made of AISI
a b c d e
Eptadone: L. Molteni & C., Firenze, Italy Prequillan: Fatro, Bologna, Italy Propofol Kabi: Fresenius Kabi, Verona, Italy Isoflurane-Vet: Merial, Milano, Italy Toshiba XPRESS/GX TSX-002A: Toshiba Corporation, Shimoishigami, Otawara-Shi, Japan f 3Dfast S.r.l., Padova (PD), Italy g Traumavet S.r.l., Rivoli (To), Italy
Vet Comp Orthop Traumatol 1/2014
type 316 LVM stainless steel; it had 12 threaded holes to accommodate 12 titanium-alloy screw-in bushings which in turn accepted 3 or 3.5 mm diameter selftapping titanium alloy screws. The tapered head of each screw precisely fitted the in-
Figure 3 Representation of the life-size threedimensional model of the right antebrachium of the patient as produced by rapid prototyping technology from computed tomographic images. The model was used to guide production of a customized Fixin locking plate, and in particular to determine the precise positions of screw holes.
ternal tapered surface of each bushing, thereby locking the screw to the plate as it was screwed into the bone (16).
Surgery Surgery was conducted under general anaesthesia with the patient in the sternal recumbency. A standard dorsal midline surgical approach from the mid-radius to the distal-metacarpal level was made, and the bones were exposed after a tourniquet had been applied (2, 17). The articular cartilage of the antebrachiocarpal, middle carpal, carpometacarpal and intercarpal joints was debrided using a high speed bur. Cancellous bone, harvested from the ipsilateral proximal humerus, was packed into all joint spaces. Ten 3.5 mm screwsg and two 3 mm screwsg were used to fix the plate. Six 3.5 mm screws were used to fix the plate to the radius, the other six to attach the plate to the third and fourth metacarpal bones (▶ Figure 4). The distal screws were fixed first to centre the plate holes over the third and fourth metacarpals. The two 3 mm screws were used in two plate holes as the surgeon noticed that the hole axes did not align perfectly with the centre of the underlying metacarpal bone. Cefazolin sodiumh (30 mg/Kg IV) was administered thirty minutes before surgery and then every hour till the end of the procedure. The wound was closed routinely. h Cefamezin: Pfizer, Latina, Italy
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Figure 4 Immediate postoperative (A) craniocaudal and (B) mediolateral radiographic images of the right antebrachium.
Postoperative management and outcome Orthogonal radiographs were obtained immediately after surgery (▶ Figure 4) to verify plate and screw position. The plate covered 55% of the length of the radius and 68% of the length of the third and fourth metacarpal bones. The administration of amoxicillin with clavulanic acidi (20 mg/ kg, orally, twice daily for 10 days), carprofenj (2 mg/kg orally, twice daily for three weeks) and tramadol hydrochloridek (2 mg/kg orally, twice daily for three weeks) was prescribed. A Robert Jones bandage was applied for three days to minimize postoperative swelling. The limb was not splinted during the postoperative period. The owner was instructed to confine the dog until radiographic signs of bone healing were evident. Confinement in a cage was suggested for eight weeks and in-door confinement for a further four weeks with 15 minute leash walks four times a day.
Results The patient was examined at 15 (when the sutures were removed), 30, 74, and 140 days, as well as at one, two, and three years after surgery. Fifteen and 30 days after surgery, lameness was difficult to observe and was not consistently apparent, and deep palpation of the carpal and metacarpal regions did not evoke a pain response. By 74 days, limping was absent, and palpation of the carpal and metacarpal region evoked no pain response; radiographs showed adequate radiographic healing (▶ Figure 5 A, B). Clinical and radiographic findings at 140 days were closely similar to those at 74 days (▶ Figure 5C). Clinical examinations one, two and three years after surgery showed no limping and no signs of pain on profound palpation of the forelimb, carpus and metacarpals. Three years after surgery, the mediolateral radiographic view (▶ Figure 6) showed signs of bone sclerosis around the most proximal screw of the radius, and exostosis on the dorsal surface of the distal end of the metacarpal bones. The owner declined further radiographic examinations.
would provide the greatest likelihood of achieving effective arthrodesis. The plate was designed with the aid of a full-scale model of the bones of the affected limb produced by rapid prototyping technology from CT images. The plate thus produced proved to be a perfect fit requiring no
Discussion i Synulox: Pfizer, Latina, Italy j Rimadyl: Pfizer, Latina, Italy k Altadol: Formevet, Milano, Italy
© Schattauer 2014
In view of the patient’s weight we considered that the use of a custom-made plate
Figure 6 Mediolateral radiographic image of the right antebrachium three years after surgery.
Vet Comp Orthop Traumatol 1/2014
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Figure 5 A) Mediolateral and (B) craniocaudal radiographic images of the right antebrachium 74 days after the operation. C) Mediolateral radiographic image of the right antebrachium 140 days after the operation.
M. Petazzoni, T. Nicetto: Arthrodesis in a giant breed dog
intraoperative modification. Furthermore, flattening the flare of the distal radius slightly by removing a small portion of bone to avoid the need to double bend the pate was unnecessary in our case because the custom-made plate fitted the bone perfectly (2). The angle between the distal and proximal parts of the plate – defining the angle of arthrodesis – was approximately six degrees, in line with the suggestion of Whitelock and colleagues, but less than the 10° suggested by other authors (2, 18). Whitelock and colleagues hypothesized that the smaller angle might reduce stress risers at the distal end of the plate by reducing the moment of weight-bearing forces at this point (18). The radial carpal bone was not used as a fixation point for the plate so that a plate hole in this location would not weaken the plate at the point where it was bent and bending forces were most concentrated. We used a locking plate that is not pressed tightly against the bone surface when the screws are tightened and is not required to be perfectly contoured to the bone surfaces, but relies on purchase between the screws and the bone to achieve stability (16, 19, 20). The minimal contact of the plate against the bone surface reduces insult to the periosteum and its vascularization (19–24). However, the locked screws enter the bone at predetermined angles which cannot be changed intraoperatively unless the plate is twisted. The risk of fracture is increased if a screw is inserted into the metacarpal bone peripherally rather than centrally (18). Since two plate holes did not align perfectly with the centre of the underlying metacarpal bone, we used two smaller diameter screws to minimize the risk of a fracture. Apart from these, we were able to use 3.5 mm screws in the metacarpals, as they did not exceed 30% of bone diameter as advised (2, 16, 20). The pre-planning of screw positions and angles on the model can help overcome this limitation (▶ Figure 3). In our opinion, currently available commercial plates are not of adequate size and strength to provide sufficient stability for achieving effective arthrodesis in giant
Vet Comp Orthop Traumatol 1/2014
breed dogs. We could have used double implants on the dorsal surface of the carpus, which affords more strength and stability than a single plate. Another option was to use a broad pancarpal arthrodesis plate (CastLess platel) with staggered distal plate holes that allow the screws to engage both the third and fourth metacarpal bones (25). However the largest available CastLess plate is 140 mm long, of which 77 mm covers the radius, 28 mm the carpus, and 35 mm the metacarpals. Such a plate would have covered only 35% of the radius and 36% of the metacarpals in the present patient. In view of the extraordinary weight of our patient, we considered that such minimal coverage would have resulted in an unacceptably high risk of metacarpal bone fracture. It was recommended that a plate should cover over 50% of the metacarpal bones to ensure low risk of fracture (18). The self-compressing load position of the screws in conventional plates allows the screws in the radius and metacarpals to compress all the joint levels. In our case, the locked position of the screws into the plate negated screw angulation and compression between bone fragments, thus interfragmentary bone compression was not achievable. Nevertheless the arthrodesis healed within the expected timing, probably due to good stability provided by the custom implant with locked technology (26). Use of a short moulded palmar splint or cylinder cast has been recommended to protect the plate during healing (2, 5, 8, 10). Cast-associated soft-tissue injuries occurred in 63% of the patients in one recent retrospective study (27). However, the Fixin implant system provided sufficient support to allow healing of the pancarpal arthrodesis in this giant breed dog without additional external coaptation. It has been proposed that the metacarpal bones are flexible enough to bend slightly during weight bearing, which may result in loosening of the distal screws since the plate is more rigid (2). The plate eventually may have to be removed because of screw loosening or irritation (2, 8). Three l
CastLess PCA Plate: Orthomed, Edgerton, UK
years after surgery, our patient did not show radiographic signs of screw loosening, and did not show clinical signs of soft tissue irritation. The locked plate we used may therefore have avoided or at least delayed screw loosening and soft tissue irritation, in part because it covered most of the length of the metacarpals and over half the length of the radius. Nevertheless, the bone sclerosis observed around some screws of the radius, and exostosis found on the dorsal surface of the distal extremities of the metacarpals, are indicative of force concentrations at these points. Lack of limping and signs of pain on palpation at one, two, and three-year check-ups suggested bone sclerosis and exostosis were not a clinical problem.
Conclusions Use of rapid prototyping technology appears as a useful means of producing life-size three-dimensional plastic models of affected skeletal structures that in turn serve as precise templates for the manufacture of custom-made plates to achieve osteosynthesis. No postoperative screw loosening, plate failure or metacarpal fractures occurred, which probably reflects the adequacy of the biomechanics of this custom-made construct and its locking-plate technology. Although the custom-made plate was very effective in the present application, the higher cost of custom-made implants may preclude their use in some cases. Acknowledgements
The authors would like to acknowledge Ing. Piero Costa for his technical assistance and Dr Giuliano Pedrani for his assistance in the postoperative management. Conflicts of interest
Massimo Petazzoni is a partner of and a consultant for the company Traumavet, which owns patents on, produces, and sells the Fixin system. Tommaso Nicetto is also a consultant for Traumavet.
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References 1. Lesser AL. Arthrodesis. In: Slatter D., editor. Textbook of Small Animal Surgery. 3rd ed. Philadelphia: Saunders; 2003. pg. 2171–2173. 2. Piermattei DL, Flo GL, DeCamp C. Fractures and other Orthopaedic Conditions of the Carpus, Metacarpus, and Phalanges. In: Brinker, Piermattei and Flo’s Handbook of Small Animal Orthopedics and Fracture Repair. 4th ed. Saint Luis, Missouri: Saunders Elsevier; 2006. pg. 382–412. 3. Turner TM, Lipowitz AJ. Endstage procedures – Arthrodesis. In: Bojrab JM, Ellison GW, Slocum B, editors. Current Techniques in Small Animal Surgery. 4th ed. Baltimore, MD: Williams & Watkins; 1998. pg. 1275–1279. 4. Comerford EJ, Doran IC, Owen MR. Carpal derangement and associated carpal valgus in a dog. Vet Comp Orthop Traumatol 2006; 19: 113–116. 5. Parker RB, Brown SG, Wind AP. Pancarpal arthrodesis in the dog: A review of forty-five cases. Vet Surg 1981; 10: 35–43 6. Keller WG, Chambers JN. Antebrachial metacarpal arthrodesis for fusion of deranged carpal joints in two dogs. J Am Vet Med Assoc 1989; 195: 1382–1384. 7. Willer RL, Johnson KA, Turner TM, et al. Partial carpal arthrodesis for third degree carpal sprains. A review of 45 carpi. Vet Surg 1990; 19: 334–340. 8. Denny HR, Barr AR. Partial carpal and pancarpal arthrodesis in the dog: a review of 50 cases. J Small Anim Pract 1991; 32: 329–334. 9. Li A, Gigson N, Carmichael S, et al. Thirteen pancarpal arthrodeses using 2.7/3.5 mm hybrid dy-
10. 11.
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namic compression plates. Vet Comp Orthop Traumatol 1999; 12: 102–107. Guerrero TG, Montavon PM. Medial plating for carpal panarthrodesis. Vet Surg 2005; 34: 153–158. Lewis DD, Radasch RM, Beale BS, et al. Initial clinical experience with the IMEXTM circular external skeletal fixation system. Vet Comp Orthop Traumatol 1999; 12: 108–117. Lotsikas PJ, Radasch RM. A clinical evaluation of pancarpal arthrodesis in nine dogs using circular external skeletal fixation. Vet Surg 2006; 35: 480–485. Arnott JL, Bailey R, Shields A et al. An in vitro comparison of a 2.7/3.5 mm hybrid plate alone and combined with crossed K-wires for canine pancarpal arthrodesis. Vet Comp Orthop Traumatol 2008; 21: 307–311. Harrysson OLA, Cormier DR, Marcellin-Little DJ, et al. Rapid prototyping for treatment of canine limb deformities. Rapid Prototyping Journal 2003; 9: 37–42. Crosse KR, Worth AJ. Computer-assisted surgical correction of an antebrachial deformity in a dog. Vet Comp Orthop Traumatol 2010; 23: 354–361. Petazzoni M, Urizzi A, Verdonck B, et al. Fixin internal fixator: Concept and technique. Vet Comp Orthop Traumatol 2010; 23: 250–253. Piermattei DL, Johnson KA. Approach to the Distal Radius and Carpus Through a Dorsal Incision. In: An Atlas of Surgical Approaches to the Bones and Joints of the Dog and Cat. 4th ed. Philadelphia, Pennsylvania: Saunders Elsevier; 2004. pg. 254–255. Whitelock RG, Dyce J, Houlton JEF. Metacarpal fractures associated with pancarpal arthrodesis in dogs. Vet Surg 1999; 28: 25–30.
19. Larson AN, Rizzo M. Locking plate technology and its applications in upper extremity fracture care. Hand Clin 2007; 23: 269–278. 20. Nicetto T, Petazzoni M, Urizzi A, et al. Experiences using the Fixin locking plate system for the stabilization of appendicular fractures in dogs. Vet Comp Orthop Traumatol 2013; 26: 61–68. 21. Wagner M. General principles for the clinical use of the LCP. Injury 2003; 34: S-B31-S-B42. 22. Perren SM. Evolution of the internal fixation of long bone fractures. The scientific basis of biological internal fixation: choosing a new balance between stability and biology. J Bone Joint Surg Br 2002; 84-B: 1093–1110. 23. Cronier P, Pietu G, Dujardin C, et al. The concept of locking plates. Orthop Traumatol Surg Res 2010; 96S: S17-S36. 24. Klaue K, Fengels I, Perren SM. Long-term effects of plate osteosynthesis: comparison of four different plates. Injury 2000; 31 (Suppl. 2): S-B51-S-B62. 25. Clarke SP, Ferguson JF, Miller A. Clinical evaluation of pancarpal arthrodesis using a CastLess plate in 11 dogs. Vet Surg 2009; 38: 852–860. 26. Johnson KA. A radiographic study of the effects of autologous cancellous bone grafts on bone healing after carpal arthrodesis in the dog. Vet Radiol 1981; 22: 177–183. 27. Meeson RL, Davidson C, Arthurs GI. Soft-tissue injuries associated with cast application for distal limb orthopaedic conditions. A retrospective study of sixty dogs and cats. Vet Comp Orthop Traumatol 2011; 24: 126–131.
Erratum to: Computer based gait analysis of dogs: Evaluation of kinetic and kinematic parameters after cemented and cementless total hip replacement by S. Drüen et al. (Vet Comp Orthop Traumatol 2012; 25: 375–384) Recently it was revealed that the surgical responsibilities for the carried out procedures were not described in sufficient detail within the manuscript. The authors for this paper would like to clarify this matter: Within the manuscript it is described that one surgeon carried out the cementless total hip replacements (THRs) and the other surgeon the cemented THRs. This description is correct for the dogs finally analyzed by computer-based gait analysis (9 cemented, 9 cementless THRs). However, in the initial phase of the study, both surgeons performed cemented as
© Schattauer 2014
well as cementless THRs. After the first dogs had been implanted, it became evident that one surgeon had increased severe complications in the cases of dogs implanted with cementless THRs. All these dogs had to be excluded from the final gait analysis study (4 dogs). From that point on, it was decided to continue the study with one surgeon carrying out the cemented and the other one the cementless THRs. The authors apologize for this oversight. Vet Comp Orthop Traumatol 2014; 27: 89 doi:10.3415/VCOT-10-02-0026e
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M. Petazzoni, T. Nicetto: Arthrodesis in a giant breed dog
Case Report
Rapid prototyping to design a customized locking plate for pancarpal arthrodesis in a giant breed dog M. Petazzoni1; T. Nicetto2 Milano Sud, Peschiera Borromeo (Mi), Italy; 2Diagnostica Piccoli Animali, Zugliano (Vi), Italy
Keywords Rapid prototyping, custom plate, pancarpal arthrodesis, locking plate, dog
Summary This report describes the treatment of traumatic carpal hyperextension in a giant breed dog by pancarpal arthrodesis using a custom-made Fixin locking plate, created with the aid of a three-dimensional plastic model of the bones of the antebrachium produced by rapid prototyping technology. A three-year-old 104 kg male Mastiff dog was admitted for treatment of carpal hyperextension injury. After diagnosis of carpal
Correspondence to: Massimo Petazzoni Clinica Veterinaria Milano Sud Via della Liberazione 26 20068 Peschiera Borromeo (Mi) Italy Phone: +39 02 55 30 55 68 Fax: +39 02 55 30 62 88 E-mail: [email protected]
Introduction In cases where it is not possible to restore the functionality of a joint, the surgical salvage procedure of arthrodesis is often used as an alternative to amputation (1). Arthrodesis of the carpus may be indicated in cases of osteoarthritis, articular fracture, chronic luxation, ligament lesions, hyperextension, and also developmental abnormalities of the antebrachiocarpal, middle carpal and carpal-metacarpal joints (1–8). Fusion of the middle carpal and carpal© Schattauer 2014
instability, surgery was recommended. Computed tomography images were used to create a life-size three-dimensional plastic model of the forelimb. The model was used as the basis for constructing a customized 12-hole Fixin locking plate. The plate was used to attain successful pancarpal arthrodesis in the animal. Radiographic examination after 74 and 140 days revealed signs of osseous union of the arthrodesis. Further clinical and radiographic follow-up examination three years later did not reveal any changes in implant position or complications.
Vet Comp Orthop Traumatol 2014; 27: 85–89 doi:10.3415/VCOT-13-04-0055 Received: April 29, 2013 Accepted: November 3, 2013 Pre-published online: December 9, 2013
metacarpal joints alone is possible if only these joints are affected, while pancarpal arthrodesis is generally performed if the antebrachiocarpal joint is involved (2). Osteosynthesis techniques described for these types of surgery include application of a bone plate to the dorsal, medial, or palmar aspects of the carpus; cross-pinning; and transarticular linear or circular external skeletal fixation (1–3, 9–13). For large breed dogs, a dorsal plate with 3.5 mm screws is suggested (2). Double implants on the dorsal surface of the carpus may be
necessary to achieve effective and stable arthrodesis in giant breed dogs (3). Biomodels have been successfully used since the 1990s to help diagnose, plan and rehearse medical procedures on human patients (14). More recently three-dimensional models, created by rapid prototyping techniques, have been used for the preoperative planning of surgery to correct angular deformities in the limbs of dogs (14–15). The present report describes the use of three-dimensional computer tomographic (CT) imaging and rapid prototype modelling to guide the manufacture of a custom plate with locking screws to achieve pancarpal arthrodesis in a giant breed dog (16).
Case report A three-year-old 104 kg male Mastiff dog was admitted for the complaint of severe (grade 3/4) right forelimb lameness. Twelve weeks previously the animal had fallen from a grooming table and had been severely lame since. On examination, hyperextension of the right carpus was evident (▶ Figure 1); signs of pain were elicited on passive flexion and extension of the carpus. Orthogonal radiographs revealed signs of osteoarthritic changes on the dorsal surface of the base of the metacarpal bones (▶ Figure 2). From mediolateral radiographic images in hyperflexion and hyperextension (▶ Figure 2 B) we determined that the maximum angles of flexion and extension of the carpus were 164° and 230° respectively. We diagnosed carpal hyperextension at the carpal-metacarpal joint and severe antebrachio-carpal instability. Pancarpal arthrodesis was recommended. Vet Comp Orthop Traumatol 1/2014
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M. Petazzoni, T. Nicetto: Arthrodesis in a giant breed dog
Figure 2 A) Preoperative craniocaudal view of the right antebrachium. B) Preoperative mediolateral view of right antebrachium in hyperextension.
Figure 1 Preoperative photograph of the right forelimb showing carpal hyperextension.
On the same day, the dog was premedicated with methadonea (0.2 mg/kg) and acepromazineb (10 µg/kg). Anaesthesia was induced with propofolc (3 mg/kg) and maintained with isofluoraned (1.5%) in oxygen for CT using a helical CT scanner in single-slice modee. The dog was positioned in sternal recumbency with the right forelimb extended cranially allowing the radius, the carpal joint and the metacarpal bones to lie in neutral position. Transverse 1 mm slices were obtained beginning at the elbow joint and including the metacarpalphalangeal joints. Images were obtained at zero degrees gantry tilt. Using the CT files (DICOM format), a rapid prototyping centref produced a three-dimensional model of the bones of the right antebrachium (▶ Figure 3). Screw positions were planned on the model (▶ Figure 3). A Fixin locking plateg was then designed and produced based on the model and the positions of the screw holes (▶ Figure 3) (16). The plate, 23 cm long and 3 mm thick, was made of AISI
a b c d e
Eptadone: L. Molteni & C., Firenze, Italy Prequillan: Fatro, Bologna, Italy Propofol Kabi: Fresenius Kabi, Verona, Italy Isoflurane-Vet: Merial, Milano, Italy Toshiba XPRESS/GX TSX-002A: Toshiba Corporation, Shimoishigami, Otawara-Shi, Japan f 3Dfast S.r.l., Padova (PD), Italy g Traumavet S.r.l., Rivoli (To), Italy
Vet Comp Orthop Traumatol 1/2014
type 316 LVM stainless steel; it had 12 threaded holes to accommodate 12 titanium-alloy screw-in bushings which in turn accepted 3 or 3.5 mm diameter selftapping titanium alloy screws. The tapered head of each screw precisely fitted the in-
Figure 3 Representation of the life-size threedimensional model of the right antebrachium of the patient as produced by rapid prototyping technology from computed tomographic images. The model was used to guide production of a customized Fixin locking plate, and in particular to determine the precise positions of screw holes.
ternal tapered surface of each bushing, thereby locking the screw to the plate as it was screwed into the bone (16).
Surgery Surgery was conducted under general anaesthesia with the patient in the sternal recumbency. A standard dorsal midline surgical approach from the mid-radius to the distal-metacarpal level was made, and the bones were exposed after a tourniquet had been applied (2, 17). The articular cartilage of the antebrachiocarpal, middle carpal, carpometacarpal and intercarpal joints was debrided using a high speed bur. Cancellous bone, harvested from the ipsilateral proximal humerus, was packed into all joint spaces. Ten 3.5 mm screwsg and two 3 mm screwsg were used to fix the plate. Six 3.5 mm screws were used to fix the plate to the radius, the other six to attach the plate to the third and fourth metacarpal bones (▶ Figure 4). The distal screws were fixed first to centre the plate holes over the third and fourth metacarpals. The two 3 mm screws were used in two plate holes as the surgeon noticed that the hole axes did not align perfectly with the centre of the underlying metacarpal bone. Cefazolin sodiumh (30 mg/Kg IV) was administered thirty minutes before surgery and then every hour till the end of the procedure. The wound was closed routinely. h Cefamezin: Pfizer, Latina, Italy
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Figure 4 Immediate postoperative (A) craniocaudal and (B) mediolateral radiographic images of the right antebrachium.
Postoperative management and outcome Orthogonal radiographs were obtained immediately after surgery (▶ Figure 4) to verify plate and screw position. The plate covered 55% of the length of the radius and 68% of the length of the third and fourth metacarpal bones. The administration of amoxicillin with clavulanic acidi (20 mg/ kg, orally, twice daily for 10 days), carprofenj (2 mg/kg orally, twice daily for three weeks) and tramadol hydrochloridek (2 mg/kg orally, twice daily for three weeks) was prescribed. A Robert Jones bandage was applied for three days to minimize postoperative swelling. The limb was not splinted during the postoperative period. The owner was instructed to confine the dog until radiographic signs of bone healing were evident. Confinement in a cage was suggested for eight weeks and in-door confinement for a further four weeks with 15 minute leash walks four times a day.
Results The patient was examined at 15 (when the sutures were removed), 30, 74, and 140 days, as well as at one, two, and three years after surgery. Fifteen and 30 days after surgery, lameness was difficult to observe and was not consistently apparent, and deep palpation of the carpal and metacarpal regions did not evoke a pain response. By 74 days, limping was absent, and palpation of the carpal and metacarpal region evoked no pain response; radiographs showed adequate radiographic healing (▶ Figure 5 A, B). Clinical and radiographic findings at 140 days were closely similar to those at 74 days (▶ Figure 5C). Clinical examinations one, two and three years after surgery showed no limping and no signs of pain on profound palpation of the forelimb, carpus and metacarpals. Three years after surgery, the mediolateral radiographic view (▶ Figure 6) showed signs of bone sclerosis around the most proximal screw of the radius, and exostosis on the dorsal surface of the distal end of the metacarpal bones. The owner declined further radiographic examinations.
would provide the greatest likelihood of achieving effective arthrodesis. The plate was designed with the aid of a full-scale model of the bones of the affected limb produced by rapid prototyping technology from CT images. The plate thus produced proved to be a perfect fit requiring no
Discussion i Synulox: Pfizer, Latina, Italy j Rimadyl: Pfizer, Latina, Italy k Altadol: Formevet, Milano, Italy
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In view of the patient’s weight we considered that the use of a custom-made plate
Figure 6 Mediolateral radiographic image of the right antebrachium three years after surgery.
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Figure 5 A) Mediolateral and (B) craniocaudal radiographic images of the right antebrachium 74 days after the operation. C) Mediolateral radiographic image of the right antebrachium 140 days after the operation.
M. Petazzoni, T. Nicetto: Arthrodesis in a giant breed dog
intraoperative modification. Furthermore, flattening the flare of the distal radius slightly by removing a small portion of bone to avoid the need to double bend the pate was unnecessary in our case because the custom-made plate fitted the bone perfectly (2). The angle between the distal and proximal parts of the plate – defining the angle of arthrodesis – was approximately six degrees, in line with the suggestion of Whitelock and colleagues, but less than the 10° suggested by other authors (2, 18). Whitelock and colleagues hypothesized that the smaller angle might reduce stress risers at the distal end of the plate by reducing the moment of weight-bearing forces at this point (18). The radial carpal bone was not used as a fixation point for the plate so that a plate hole in this location would not weaken the plate at the point where it was bent and bending forces were most concentrated. We used a locking plate that is not pressed tightly against the bone surface when the screws are tightened and is not required to be perfectly contoured to the bone surfaces, but relies on purchase between the screws and the bone to achieve stability (16, 19, 20). The minimal contact of the plate against the bone surface reduces insult to the periosteum and its vascularization (19–24). However, the locked screws enter the bone at predetermined angles which cannot be changed intraoperatively unless the plate is twisted. The risk of fracture is increased if a screw is inserted into the metacarpal bone peripherally rather than centrally (18). Since two plate holes did not align perfectly with the centre of the underlying metacarpal bone, we used two smaller diameter screws to minimize the risk of a fracture. Apart from these, we were able to use 3.5 mm screws in the metacarpals, as they did not exceed 30% of bone diameter as advised (2, 16, 20). The pre-planning of screw positions and angles on the model can help overcome this limitation (▶ Figure 3). In our opinion, currently available commercial plates are not of adequate size and strength to provide sufficient stability for achieving effective arthrodesis in giant
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breed dogs. We could have used double implants on the dorsal surface of the carpus, which affords more strength and stability than a single plate. Another option was to use a broad pancarpal arthrodesis plate (CastLess platel) with staggered distal plate holes that allow the screws to engage both the third and fourth metacarpal bones (25). However the largest available CastLess plate is 140 mm long, of which 77 mm covers the radius, 28 mm the carpus, and 35 mm the metacarpals. Such a plate would have covered only 35% of the radius and 36% of the metacarpals in the present patient. In view of the extraordinary weight of our patient, we considered that such minimal coverage would have resulted in an unacceptably high risk of metacarpal bone fracture. It was recommended that a plate should cover over 50% of the metacarpal bones to ensure low risk of fracture (18). The self-compressing load position of the screws in conventional plates allows the screws in the radius and metacarpals to compress all the joint levels. In our case, the locked position of the screws into the plate negated screw angulation and compression between bone fragments, thus interfragmentary bone compression was not achievable. Nevertheless the arthrodesis healed within the expected timing, probably due to good stability provided by the custom implant with locked technology (26). Use of a short moulded palmar splint or cylinder cast has been recommended to protect the plate during healing (2, 5, 8, 10). Cast-associated soft-tissue injuries occurred in 63% of the patients in one recent retrospective study (27). However, the Fixin implant system provided sufficient support to allow healing of the pancarpal arthrodesis in this giant breed dog without additional external coaptation. It has been proposed that the metacarpal bones are flexible enough to bend slightly during weight bearing, which may result in loosening of the distal screws since the plate is more rigid (2). The plate eventually may have to be removed because of screw loosening or irritation (2, 8). Three l
CastLess PCA Plate: Orthomed, Edgerton, UK
years after surgery, our patient did not show radiographic signs of screw loosening, and did not show clinical signs of soft tissue irritation. The locked plate we used may therefore have avoided or at least delayed screw loosening and soft tissue irritation, in part because it covered most of the length of the metacarpals and over half the length of the radius. Nevertheless, the bone sclerosis observed around some screws of the radius, and exostosis found on the dorsal surface of the distal extremities of the metacarpals, are indicative of force concentrations at these points. Lack of limping and signs of pain on palpation at one, two, and three-year check-ups suggested bone sclerosis and exostosis were not a clinical problem.
Conclusions Use of rapid prototyping technology appears as a useful means of producing life-size three-dimensional plastic models of affected skeletal structures that in turn serve as precise templates for the manufacture of custom-made plates to achieve osteosynthesis. No postoperative screw loosening, plate failure or metacarpal fractures occurred, which probably reflects the adequacy of the biomechanics of this custom-made construct and its locking-plate technology. Although the custom-made plate was very effective in the present application, the higher cost of custom-made implants may preclude their use in some cases. Acknowledgements
The authors would like to acknowledge Ing. Piero Costa for his technical assistance and Dr Giuliano Pedrani for his assistance in the postoperative management. Conflicts of interest
Massimo Petazzoni is a partner of and a consultant for the company Traumavet, which owns patents on, produces, and sells the Fixin system. Tommaso Nicetto is also a consultant for Traumavet.
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Erratum to: Computer based gait analysis of dogs: Evaluation of kinetic and kinematic parameters after cemented and cementless total hip replacement by S. Drüen et al. (Vet Comp Orthop Traumatol 2012; 25: 375–384) Recently it was revealed that the surgical responsibilities for the carried out procedures were not described in sufficient detail within the manuscript. The authors for this paper would like to clarify this matter: Within the manuscript it is described that one surgeon carried out the cementless total hip replacements (THRs) and the other surgeon the cemented THRs. This description is correct for the dogs finally analyzed by computer-based gait analysis (9 cemented, 9 cementless THRs). However, in the initial phase of the study, both surgeons performed cemented as
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well as cementless THRs. After the first dogs had been implanted, it became evident that one surgeon had increased severe complications in the cases of dogs implanted with cementless THRs. All these dogs had to be excluded from the final gait analysis study (4 dogs). From that point on, it was decided to continue the study with one surgeon carrying out the cemented and the other one the cementless THRs. The authors apologize for this oversight. Vet Comp Orthop Traumatol 2014; 27: 89 doi:10.3415/VCOT-10-02-0026e
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