SummaryGuidelines for assessing total hip arthroplasty (THA) radiographs for femoral implant stability have not been published; therefore, often the determination is subjective. The aim of this study was to identify radiographic criteria for veterinary clinicians to use when evaluating radiographs for femoral implant stability. Specific objectives were to: identify radiographic features associated with canine THA femoral implant loosening, evaluate whether technical recommendations for human femoral component implantation apply to dogs, and evaluate the effectiveness of radiographs for identifying canine THA implant loosening. Post-operative, follow-up, and post-mortem contact radiographs of canine implanted femora retrieved postmortem and mechanically tested for implant stability were evaluated. Based on the results, radiographic evaluation is not an effective means of assessing canine femoral implant stability; however, certain radiographic findings including implant retroversion, cement mantle cracks, or the appearance of cementmetal interface radiolucencies, may be indicative of implant loosening. It was also found that femoral implants completely surrounded by cement mantle of any thickness were less likely to loosen than those with an area lacking cement between the implant and bone. There was also a trend suggesting an association between inferior cement mantle quality and femoral implant loosening. In order to improve cement mantle quality and ensure that implants are completely surrounded by cement mantle, the use of modern cementing techniques is recommended.

Objective-To evaluate owners' perceptions of the outcomes of dogs that have undergone total hip arthroplasty (THA).Design-Survey.Sample Population-Owners of 145 dogs that had undergone THA.Procedure-Surveys were mailed to owners of 353 dogs that underwent THA between 1982 and 1996. Owners were asked to answer multiple-choice questions and provide written comments.Results-The response rate was 41%. For owners who responded to the survey, time from surgery to completion of the questionnaire ranged from 6 months to 11 years. Overall, 122 respondents (84.1%) rated results of THA in their dog as excellent or good.Conclusions and Clinical Relevance-Results suggest that owners are generally satisfied with the results of THA in their dogs.

OBJECTIVE To evaluate the effect of knotting method on the mechanical properties of large diameter nonabsorbable monofilament suture materials. STUDY DESIGN In vitro mechanical evaluation. METHODS A conventional square knot was compared with the surgeon's knot, sliding half-hitch, and clamped square knot. Knotted suture loops were created in a uniform manner and acutely tensioned to failure (20 mm/min loading rate; n = 20 per knot type for each material). Stiffness, yield, and failure characteristics of USP #2 nylon, #2 polybutester, #2 polypropylene, 27 kg test monofilament nylon fishing line, and 27 kg nylon leader material were evaluated. RESULTS Compared with a conventional square knot, a surgeon's knot decreased stiffness for #2 polypropylene, 27 kg fishing line, and 27 kg leader (P < .05). A sliding half-hitch weakened all materials except 27 kg leader (P < .05). Clamping the first throw of a square knot increased the stiffness of 27 kg leader loops (P < .05). CONCLUSIONS Based on clinically relevant parameters (stiffness and yield), knotting method had no effect on #2 nylon and #2 polybutester. The surgeon's knot is not recommended for #2 polypropylene and 27 kg fishing line and leader material. A sliding half-hitch decreased the yield of leader material. Clamping the first throw of a square knot had no adverse effects on acute properties of tested materials; it increased the stiffness for leader material. CLINICAL RELEVANCE Knotting method does influence the structural properties of suture materials and should be considered when tying knots under tension.

The morphology of fracture healing depends on the mechanical environment afforded by external fixation and ranges between the extremes of direct bone healing and spontaneous hone healing. The mechanical environment at a fracture is affected by the stiffness of the fixator and the degree of load sharing of the fixator with the bone. As the stability of the fracture increases because of increased fixator rigidity, anatomic fracture reduction, or a combination of these factors, callus formation decreases. However, optimal rigidity may consist of early rigid immobilization followed by destabilization of the fixator to allow controlled loading of the fracture site. The biological Environment at the fracture also affects fracture healing with external fixation. Surgical techniques and implants, which compromise the surrounding soft tissue and interfere with the vasculature to the injured bone, will delay bone union. Fixation techniques for severely comminuted fractures using closed reduction and external skeletal fixation allow presentation of soft tissue. These biologically oriented techniques have been termed biological fracture fixation and feature realignment of the limb (i.e., joint surfaces) rather than anatomic reconstruction of the fracture; minimal to no sort tissue dissection; and optimal stability, resulting in moderate strain levels and allowing the progression of bone formation. Fractures treated in this manner seem to heal with endosteal bone formation and bone bridging between fragments rather than with periosteal callus.

Aseptic loosening of the femoral implant (ALFI) was diagnosed in 10 dogs that had undergone cemented total hip arthroplasty (THA). One dog had bilateral ALFI. Loosening developed at the stem-cement interface a mean of 30 months after THA. The most common clinical sign was intermittent subtle or non-weight-bearing lameness. On radiographs obtained after THA, the distal stem tip was in contact with the cortical endosteum in all dogs. Radiographic changes at the time of diagnosis of ALFI included asymmetric periosteal reaction along the femoral diaphysis (n = 11), radiolucent zone at the stem-cement interface (6), altered implant position (4), and femur fracture (1). Surgical revision resulted in a good or excellent outcome in 9 dogs. In 1 dog, the implant became infected. In another, aseptic loosening recurred. Aseptic loosening of the femoral implant was significantly more common when initial positioning of the implant resulted in contact between the distal tip of the implant and cortical endosteum than when there was no contact.

SummaryThis study investigated the effect of destabilizing initially rigid external fixation of transverse canine tibial osteotomies, compared to contralateral osteotomies continuously stabilized, with rigid fixators. Destabilization, by conversion of a type III configuration fixator to a type I configuration, after one to four weeks resulted in increased periosteal callus formation but decreased mechanical strength and histologically a preponderance of fibrous and cartilaginous tissues in the osteotomy when studied after nine weeks. Destabilization at six weeks did not result in an increase in periosteal callus formation, nor greater bending strength. Histologically there was a combination of woven and lamellar bone, with the appearance of more active remodelling of primary bone healing. Destabilization at 12 weeks did not result in any effect, when studied after 15 weeks. These findings suggest that increasing weight-bearing loading of a fracture, at the proper time, may enhance the remodelling and hypertrophy of primary bone healing. However, inappropriate timing of destabilization may not have any or even a deleterious effect.Effects of reducing initially rigid fixation of canine tibial osteotomies, after various periods of time, were studied. Destabilization after one to four weeks caused increased periosteal callus formation but decreased mechanical strength. Destabilization after six weeks resulted in increased mechanical strength but no increase in periosteal callus, and destabilization after 12 weeks had no effect compared to osteotomies continuously stabilized with rigid fixation.

External skeletal fixation is a very useful technique for managing many orthopedic problems in veterinary practice. The Kirschner apparatus has been the most widely used fixator for many years in veterinary orthopedics because of its versatility, simplicity, and economy in use. The medium-sized device has the widest indications and is easiest to begin with. The small size can be acquired later for use on cats and small dogs. The new "raised thread" fixation pin designs improve bone-pin integrity and can be used in combination with nonthreaded pins to decrease the incidence of postoperative complications and for economy. Acrylic-pin external fixators are particularly useful for treatment of mandibular fractures and transarticular application since they allow nonlinear placement of fixation pins in highly contoured bones. A commercial system, currently being developed, will have all the equipment and materials necessary for their application in a convenient kit. Circular fixators (Ilizarov design) use thin K wires placed under tension to replace rigid fixation pins. Their unique adjustability characteristics make them useful in the treatment of limb deformity and shortening. Many other human fixators can be used for veterinary application if the basic principles of fixators are followed. Instrumentation required for external fixator application include a pin driver, pin cutter, and wrenches. Although surgical versions of these materials are available, less expensive alternatives are available using gas sterilization instead of autoclaving. The use of selected orthopedic instrumentation such as a periosteal elevator, bone clamps, and curets will facilitate fracture management.

Full-thickness wall necrosis involving 90 to 95% of the urinary bladder was diagnosed in a 6-month-old Golden Retriever 2 days after ovariohysterectomy. An isolated, vascularized segment of ileum denuded of mucosa was used to reconstruct the urinary bladder. Serial excretory urography over 1 year indicated gradual enlargement of the bladder, with development of a smooth mucosal surface. At 6 months after reconstructive surgery, the dog was voiding urine 2 to 3 times/d and was continent. Results of renal function testing, urinalysis, and bacteriologic culture of urine were all considered normal on follow-up examinations. The cause of bladder wall necrosis was never determined. Ileocystoplasty as described herein appears to be an effective urinary bladder reconstructive procedure in dogs whenever the bladder neck, proximal portion of the urethra, and their neurovascular supply can be spared.

Type III configuration of external skeletal fixation was used as a means of fracture repair in 23 clinical fractures. Twenty-one of the fractures healed, and all cases ultimately returned to a complete or prefracture weight-bearing status. Radiographically the healing process was representative of rigid fracture site stabilization as indicated by minimal external callous formation. The most commonly encountered problems were those of pin tract drainage and loose pins. Overall results were excellent and complications minimal when type III external skeletal fixator was utilized as a method of fracture management.

An external fixation fracture model was created to determine the appropriate diameter acrylic necessary to provide mechanical strength comparable to 3/16-inch stainless steel when used as a connecting bar for external skeletal fixation. The 3/16-inch stainless steel connecting bar was compared to 1/2-inch, 3/4-inch, and 1-inch diameter acrylic when used on the external fixation fracture model. Type I, type II, and type III configurations were mechanically tested in axial compression, mediolateral bending, anterior-posterior bending, and torsion. Within the limits explored in this study, 3/4-inch diameter acrylic fixation models were stronger than the standard medium-size Kirschner apparatus. Larger diameter acrylic bars may be indicated if they will be subjected predominantly to compressive and tensile forces.

External fixation is an effective method of stabilizing many fractures in veterinary orthopedics, however, it is not foolproof. Although careful attention to the principles of fixator selection and application is the optimal way to minimize complications, they do still occur. Prompt recognition of these complications and appropriate treatment, however, will minimize their effects and result in the successful outcome of fracture healing and normal limb function.

SummaryA modification of the unilateral Type I external skeletal fixator was developed for use in repair of supracondylar femoral and humeral fractures. The application technique and the results of its use in five clinical cases are discussed. In comminuted supracondylar fractures with loss of cortical bone structure, the modified unilateral Type I external skeletal fixator appears to have advantages over other external skeletal fixator configurations and bone plating.A modification of the unilateral Type I external skeletal fixator (ESF) was developed for use in repair of supracondylar femoral and humeral fractures. In comminuted supracondylar fractures with loss of cortical bone structure, the modified Type IESF appears to have advantages over other ESF configurations and bone plating.

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)

Smooth and partially threaded 3.12 mm (1/8 inch) trochar‐tipped Steinmann pins were inserted transversely through both diaphyseal cortices of eight mature canine tibias using five methods. Angular velocity (revolutions per minute) during insertion and temperature elevation due to friction during penetration of the second cortex were recorded. The force required for extraction of the pins from the bone and the histologic appearance of the bone‐pin interface were determined for one‐half of the pins 2 days after insertion and for one‐half of the pins 56 days after insertion. The increase in temperature was similar for all methods of insertion except high speed power, which was significantly greater (p < 0.05). The force required for axial pin extraction was similar for pins inserted by hand chuck, predrilled, and low speed power methods after both 2 and 56 days. Pins inserted by high speed power and hand drill required force similar to the others for extraction after 2 days but significantly less force (p < 0.05) for extraction after 56 days. The partially threaded pins required significantly greater force (p < 0.01) extraction after both 2 and 56 days. Histologic examination revealed increased mechanical bone damage surrounding hand chuck inserted pins, increased bone necrosis surrounding high speed power inserted pins, and increased inflammatory changes surrounding hand drill inserted pins.

Both triceps tendons and the medial collateral ligaments of both stifles of 10 freshly euthanized dogs were sharply transected. One tendon and one ligament of each dog were sutured with a three loop pulley pattern, and the opposite tendons and ligaments were sutured with a locking loop pattern. The tendons and ligaments were harvested with their muscular and bony attachments. The anastomoses were slowly tested in tension until failure occurred. The amount of tensile load required to produce failure of the anastomosis, the amount of distraction of the sutured ends prior to failure, and the modes of failure were recorded. In both tendons and ligaments, the three loop pulley pattern provided significantly greater tensile strength (p < 0.01) and allowed significantly less distraction between the sutured ends (p < 0.01) than the locking loop pattern. In tendons, disruption of the suture material was the most common mode of failure with both patterns. In ligaments, both patterns failed most commonly by pulling free from the tissue.

Mechanical attributes and techniques of applying the type I biplanar (quadrilateral) configuration of external skeletal fixation are reported. The apparatus was used clinically on 9 dogs and 1 cat with long bone fractures. Bony union occurred in these animals, but was slightly delayed in one. Return to clinical function of the limb generally was good to excellent. The instances of delayed union and poor clinical results are discussed to emphasize the use of good techniques of application and case selection.

Seventeen dogs that had incurred Salter Type I or II injuries to the distal femoral physis were evaluated clinically and radiographically for evidence of altered growth of the femur or tibia. Some degree of femoral growth disturbance was found in 82.4% of the dogs; the mean extent of decreased growth was 6.7%. Obvious clinical lameness resulted from the leg length discrepancy in three dogs. Several factors were evaluated statistically as predictors of growth disturbance; the age of the animal at the time of injury appeared to have the most prognostic importance. Factors found not to be as significant were the adult size of the animal, the type of Salter fracture incurred, the displacement of the fracture, the time lag between injury and surgery, and the method of fracture fixation employed. Compensatory overgrowth of the tibia in response to decreased growth of the femur was a rare finding.