Pelvic Canal Diameter Research Articles

Stabilization of 82 sacroiliac luxations in 67 cats using two sacroiliac screws (2014-2023).

To describe sacroiliac luxation stabilization in cats using two screws and to report clinical and radiographic short-term outcomes. Retrospective clinical cohort study. Cats (n = 67) with sacroiliac luxation. Case records of cats presented for sacroiliac luxation stabilized using two screws per side affected, one lag and one positional, between 2014 and 2023 were reviewed. The percentage of sacral purchase (PoSP) for each screw, percentage of reduction (PoR), and pelvic canal width ratio (PCWR) were measured and calculated. Eighty-two sacroiliac luxations were stabilized. Two 2.0 mm screws were used in 69 cases; two 2.4-mm screws in nine cases, and one 2.4 mm with one 2.0 mm screw in four cases. The mean PoSPs for lag and positional screws were 46% ± 12 and 31% ± 11, respectively. The median PoR was 89% (41 to 100). The mean PCWR was 1.23 ± 0.11. Clinical follow up was available for 42 cats with 53 sacroiliac luxations at a median of 87 days (36 to 2503). The full function was noted in 34 patients (81%). Screw failure occurred in five sacroiliac joints (4.7%), including loosening (n = 3), and breakage (n = 2) of the positional screws (n = 1). Pelvic canal diameter was maintained in all cases. Excellent functional and radiographic outcomes were obtained for cats with sacroiliac luxation stabilized with two sacroiliac screws. Feline sacroiliac luxation can be stabilized using two sacroiliac screws.

Fluoroscopically-assisted closed reduction and percutaneous fixation of sacroiliac luxations in cats using 2.4 mm headless cannulated compression screws: Description, evaluation and clinical outcome.

To describe fluoroscopically-assisted closed reduction and percutaneous fixation of sacroiliac-luxation (SIL) in cats and report radiographic results and long-term functional outcomes. Retrospective clinical study. Eleven cats. Percutaneous fixation of 17 SILs in 11 cats was performed with 2.4 mm headless cannulated compression screws under fluoroscopic guidance. Luxation-reduction, screw placement and purchase within the sacral body, pelvic canal diameter ratio (PCDR) and hemipelvic canal width ratio (HCWR) were assessed on pre- and postoperative radiographs. Radiographic follow-up was performed to assess the same parameters when available. Long-term clinical outcome was evaluated with an owner questionnaire. Wilcoxon paired-test was performed for comparison. Mean age and bodyweight of the cats were 3.3 ± 2.6 years and 4.0 ± 0.82 kg, respectively. Nine cats presented with concurrent pelvic injuries. Median luxation-reduction was 94.1% (IQR = 13.9) and median screw-purchase within the sacral body was 73.3% (IQR = 17.0) immediately postoperatively. One screw exited the sacral body caudally. Upon 7-week radiographic follow-up, luxation-reduction (88.3%, IQR = 20.1) and screw-purchase (70.7%, IQR = 12.8) had decreased compared to immediately postoperatively (p = .008 and p = .013 respectively). Screw migration was not observed. PCDR and HCWR measured on postoperative radiographs indicated successful restoration of the pelvic canal width. Owners reported an excellent long-term functional outcome (mean postoperative time: 19 ± 5 months). Fluoroscopically-assisted closed reduction and fixation of feline SIL using 2.4 mm headless cannulated compression screws allowed good reduction and optimal screw purchase within the sacral body. An excellent functional outcome was reported. Minimally invasive reduction and fixation with headless compression screws should be considered in cats with SIL.

Evaluation of minimally invasive surgical reduction of sacroiliac luxation in toy breed dogs: a cadaver study

BackgroundMinimally invasive surgery (MIS) technique of sacroiliac luxation in toy breed dogs using cannulated screws has not been described.ObjectivesThe purpose of this study was to evaluate the effectiveness of pelvic canal recovery, the reproducibility of successful surgery outcomes, and the acceptable difficulty of the procedure in MIS of sacroiliac luxation in toy breed dogs.MethodsMIS using 2.3-mm cannulated screws was demonstrated in 12 toy breed dog cadavers with sacroiliac luxation artificially induced. Pre and postoperative radiographs were used to evaluate the pelvic canal diameter ratio (PCDR), hemipelvic canal width ratio (HCWR), and reduction rate. Dorsoventral angle (DVA) and craniocaudal angle (CCA) of the inserted screw were obtained postoperative computed tomographic scan.ResultsThe statistically significant difference between the mean pre and postoperative PCDR was found (1.10 ± 0.12 and 1.26 ± 0.11, respectively; p = 0.002), and the mean HCWR close to 1.0 meaning symmetric pelvis also was obtained (0.97 ± 0.07). The mean DVA and CCA were 2.26° ± 1.33° and 2.60° ± 1.86°, respectively.ConclusionsMIS of sacroiliac luxation using 2.3-mm cannulated screws is applicable to toy breed dogs with acceptable difficulty.

Evaluation of a screw insertion landmark for a minimally invasive repair technique in induced bilateral sacroiliac luxation in feline cadavers.

The aim of this study was to describe an alternative landmark for screw insertion into the body of the ilium with bilateral sacroiliac luxation in cats. Seven cat cadavers with artificially induced bilateral sacroiliac luxation were used. The screw insertion point was determined using the caudal iliac crest and cranial acetabular rim. These two points make the first guideline; a second guideline ran perpendicular to the caudal iliac crest point. The screw insertion point was halfway along the second guideline across the ilium body. Surgery was performed in a minimally invasive manner using fluoroscopy. Postoperative radiographs and CT were performed. In the postoperative evaluation, the sacroiliac joint reduction percentage was almost 90% and there was no significant difference in pelvic canal diameter ratio before and after surgery. Screw depth/sacral width was >60% in all cadavers. On CT, the angle between the screw and sacrum wing was within the normal range of 96.24° to the left and 98.65° to the right, except in one case. In previous studies, surgical repair was based on having an intact contralateral ilium. However, this method is not applicable to patients with bilateral sacroiliac luxation and is mostly performed using open reduction methods. The screw insertion point suggested in this study offers a potential alternative repair technique for patients with bilateral sacroiliac luxation.

Tibial plateau levelling osteotomy locking-compression plates for stabilisation of canine and feline ilial body fractures.

To evaluate the clinical and radiographic outcomes following surgical stabilisation of ilial fractures in dogs and cats using a laterally applied Synthes TPLO locking compression plate. Medical records and radiographs of seven dogs and two cats which had undergone surgical repair of an ilial body fracture with a TPLO locking compression plate were reviewed. Long-term clinical follow-up was obtained from an owner or referring veterinarian questionnaire. Fracture reduction was anatomic in six of nine ilia and near-anatomic in three of nine. All but one fracture achieved osseous union by 6 weeks after surgery. No screw loosening or implant-related complications occurred in any patient. There was pelvic canal narrowing in six of nine patients (median reduction in pelvic canal diameter was 4·9%). No intraoperative or postoperative complications were reported. Lateral plating of canine and feline ilial fractures with a Synthes TPLO locking compression plate was associated with a low complication rate and satisfactory radiographic and clinical outcomes in this small case series.

Bilateral sacroiliac luxation fixation using a single transiliosacral pin: surgical technique and clinical outcomes in eight cats.

A very limited safe anatomical window for transiliosacral implant placement exists in cats (<0·5 cm2 ). Lag screw fixation requires multiple bilateral implants thus increasing the risk of iatrogenic trauma and implant interference. We describe a safe and effective method for bilateral sacroiliac fixation in cats using a single implant to minimise inadvertent iatrogenic damage to local structures and restore pelvic canal diameter. Eight cats underwent surgical fixation for traumatic bilateral sacroiliac luxation using a single smooth intramedullary pin. The pin spanned both ilial wings and sacrum. Implants were applied using a Universal C-guide. Pre- and postsurgery pelvic canal diameter ratios were calculated. Short-term follow-up was performed at 10 to 14 days postoperatively. Long-term follow-up was performed using the Feline Musculoskeletal Pain Index Questionnaire. Long-term radiographic assessment was available in two cases. The technique achieved safe and accurate implant position with precise sacroiliac joint reduction. Pelvic canal diameter ratios were restored to normal in all cases. Rapid return to normal hind leg function and excellent long-term clinical outcomes were achieved. This technique offers a simple, safe, repeatable and affordable technique for treating bilateral sacroiliac luxations in the cat without the aid of fluoroscopy. The procedure can be performed using surgical tools and inventory readily available in general small animal practices.

Use of a locking plate “notched head T-plate®” for the fixation of an ilial body fracture in a dog

Several types of implants may be used to treat iliac fractures in dogs, of which osteosynthesis with plate is the most described and recommended in the literature. The type of plate and screw are major factors in osteosynthesis success. The use of locking plates has been advocated for this purpose, as they do not allow the plate-bone-screw unit to shift, providing angular stability and rigidity to the system. The present study aimed to describe the unprecedented use of a locking notched head T-plate in the treatment of a caudal body of ilium fracture. A two year old male mongrel dog was attended after falling from a third floor height, with two days of evolution. The animal was in standing position, and during orthopedic examination non-weight bearing lameness of the right hind limb, instability, and crepitus in the right body of ilium, with considerable swelling and pain. The radiographic examination allowed diagnosing a complete fracture of the caudal body of ilium with decrease of the pelvic canal diameter. The patient underwent surgery, and the fracture was stabilized with an LCP notched head T-plate. The patient evolved satisfactorily, with good weight-bearing of the affected limb within 24 hours of surgery, and complete recovery with medical discharge after 60 days of postoperative period, with consolidation of the fracture.

Subcolectomy and symphyseal distraction-osteotomy using a spacer of spirally fashioned orthopedic wire: a treatment option for cats with pelvic canal stenosis, megacolon and obstipation

ABSTRACT: The use of two cerclages with wire spirals as distractor spacers was evaluated for the correction of pelvic stenosis in felines. A three-year-old, mixed-breed, male feline was taken to the Veterinary Hospital of the UFRJ. It presented symptoms of constipation, dyschezia, hyporexia and mild apathy. On radiographic examination, a deformation of the pelvic bones and a narrowing of the pelvic canal were detected. The patient underwent pelvic stenosis correction surgery. Two spirals were made with cerclage wire and 2.0-mm diameter Steinmann pins; coupled to the chuck of a drill, the pins were wrapped with cerclage wire, running laps around the pin. Then, the coils were positioned in the space formed by separating the hemipelves and stabilized by keeping them separated to the desired opening. Effectiveness of the technique was evidenced by measurements made using new radiographic images in comparison with the images obtained before the surgical procedure. There were evident decreases in the sacro-ischium line and pubic line of 3.98 and 3.18, demonstrating an increase of approximately 21% in the pelvic canal diameter. The animal showed no apparent macroscopic or radiographic reaction. The preliminary clinical application of the adapted pelvic distraction technique is relevant for allowing the appropriate correction of a stenosis of the pelvic girdle and its consequences, representing a major technical and scientific innovation in the correction.

Pelvic Symphyseal Distraction Osteotomy for Constipation Management Secondary to Pelvic Stenosis

A 7-year-old neutered male Korean domestic short-haired cat was referred to our clinic to treat constipation which had persisted for 6 months. The rectal examination revealed narrowing of the right lateral portion of the pelvic canal. A reduced pelvic canal diameter by pelvic fracture malunion was revealed on radiography. The pelvic canal diameter ratio measured from preoperative was 0.68. Based on rectal and radiographic examinations, constipation caused by pelvic canal narrowing was confirmed. Pelvic symphyseal distraction-osteotomy and iliac wedge osteotomy were performed. An iliac osteotomy of the ilium was performed to ease the pelvic symphyseal distraction. After the symphysis was split longitudinally, pelvic symphyseal distraction was maintained by using a spacer made of poly-methylmethacrylate. The osteotomy of the ilium was fixed using a bone plate and screws. Increased pelvic canal diameter was confirmed on post-operative radiography and the postoperative pelvic canal diameter ratio was 0.91. The patient received antibiotics, NSAIDs, crystalloids and Lactulose for post-operative care. The cat recovered normal defecation abilities and did not have constipation at one week postoperatively. No episodes of constipation persisting longer than 6 months have been reported by owners in previous studies. Pelvic symphyseal distraction osteotomy and iliac wedge osteotomy may prove to be a useful surgical procedure to treat pelvic canal stenosis that is caused by pelvic fracture malunion.

Closed reduction and percutaneous fixation of sacroiliac luxations in cats using 2.4 mm cannulated screws – a cadaveric study

To describe fluoroscopically assisted percutaneous placement of 2.4 mm cannulated screws for fixation of artificially induced sacroiliac luxations in cats, and to evaluate the success of this technique in restoration of normal pelvic anatomy. Fluoroscopically assisted closed reduction and percutaneous fixation of sacro-iliac luxations using 2.4 mm cannulated screws was performed in cadavers of 12 cats. Pre- and postoperative radiographs and postoperative computed tomographic scans were used to evaluate screw placement, screw purchase within the sacral body, reduction of the sacroiliac joint, pelvic canal diameter ratio, and hemipelvic canal width ratio. Mean total surgical time was 6 minutes and 10 seconds ± 53 seconds and mean total time of fluoroscopic screening for each procedure was 44 seconds ± 6 seconds. Mean percent of reduction was 98.33% and mean screw purchase within the sacral body was 73%. Eleven out of 12 screws were placed in a satisfactory location in the sacral body. Pelvic canal diameter ratio and hemipelvic canal width ratio indicated successful restoration of the pelvic anatomy. Our results confirm that fluoroscopically assisted percutaneous placement of 2.4 mm cannulated screws is a feasible technique for fixation of sacroiliac luxations in cats. Mechanical properties of this fixation technique need to be evaluated before the use in clinical patients.

Composite fixation of comminuted ilial wing fractures in cats: three cases

CLINICAL SUMMARY: The surgical repair of comminuted ilial wing fractures (comprising a long oblique fracture with ventral multiple fragmentation) in three cats using composite internal fixation is reported. The technique comprised the use of pins, screws, wire and polymethylmethacrylate. All cases had an excellent outcome with uneventful bone healing. One case had a very mild reduction in pelvic canal diameter postoperatively. There was no evidence of implant loosening or migration in any cat on follow-up radiographs. This technique provided a quick and highly adaptable means of stabilising this fracture configuration, as well as restoring pelvic symmetry, when limited buttressing support and bone stock were available cranial and ventral to the acetabulum. This method of fixation may have biomechanical advantages over lateral or dorsal plating techniques for this particular type of fracture configuration.

Repair of a transverse ilial fracture in a cat using an intramedullary pin

This case report describes the novel use of an intramedullary pin in an eight-month-old cat to repair malunion of a right transverse ilial fracture that was causing pelvic canal diameter narrowing and constipation. A routine, right femoral head and neck ostectomy was performed due to the presence of a femoral head fracture with apparent femoral neck necrosis. Significant callus formation around the ilial fracture was removed in order to achieve satisfactory fracture reduction. A 2 mm Steinmann pin was passed in a retrograde fashion from the acetabular fracture towards the ischial tuberosity, and following removal of the trochar tip and reduction of the fracture, was driven normograde to end in the cranial ilial wing. The pin was bent at the ischium following cutting in an attempt to prevent cranial migration. Radiographic examination showed good fracture alignment and increased pelvic diameter by 31% The cat regained normal limb function and the constipation resolved. A transilial pin was utilised successfully in a cat to realign and stabilise a simple transverse ilial fracture following femoral head and neck ostectomy. This technique has the potential to be useful for stabilisation of feline caudal ilial body fractures, but should not be used where there is articular surface involvement unless the coxofemoral joint is not preserved. Further studies are required to assess this technique.

Evaluation of Closed Reduction and Screw Fixation in Lag Fashion of Sacroiliac Fracture‐Luxations

To evaluate outcome by radiographic assessment after closed reduction and percutaneous screw fixation in lag fashion of sacroiliac fracture-luxations in dogs. Retrospective study. Dogs (n=24) with sacroiliac fracture-luxations. Medical records (1999-2006) and radiographs of 24 dogs (29 fracture-luxations) that had stabilization of sacroiliac fracture-luxation by fluoroscopic-guided closed reduction and percutaneous screw fixation in lag fashion were reviewed. Signalment, body weight, number, and location of all concurrent injuries and implants used for repair were recorded. Radiographs were used to evaluate the accuracy of screw placement in the sacral body, screw depth/sacral width ratio, reduction of the sacroiliac joint, pelvic canal diameter, and hemipelvic canal width. Radiographic re-examination (range, 4 to >8 weeks postoperatively) was available for evaluation. Mean screw depth/sacral width ratio on immediate postoperative and re-examination radiographs was 64% and 61%, respectively. Mean percentage reduction of the sacroiliac joint on immediate postoperative and re-examination radiographs were 91% and 87%, respectively. Pelvic canal diameter ratio demonstrated successful restoration of the pelvic canal. Hemipelvic canal width ratio documented successful closed reduction repair independent of concurrent pelvic injuries. Successful repair of sacroiliac fracture-luxations, determined by radiographic assessment, can be achieved by fluoroscopic-guided closed reduction and percutaneous screw fixation in lag fashion. Fluoroscopic-guided closed reduction and percutaneous screw fixation in lag fashion of sacroiliac fracture-luxations is a minimally invasive technique that restores and maintains pelvic canal dimensions and should be considered as an alternative to open reduction or nonsurgical management of sacroiliac fracture-luxations.

Limited Open Reduction and Stabilization of Sacroiliac Fracture‐Luxations Using Fluoroscopically Assisted Placement of a Trans‐Iliosacral Rod in Five Dogs

To describe percutaneous fluoroscopically assisted placement of a trans-iliosacral rod to stabilize sacroiliac fracture-luxations after limited open reduction. Retrospective clinical case series. Dogs (n=5) with sacroiliac fracture-luxations. Medical records and radiographs were reviewed to evaluate implant placement, fracture reduction, pelvic canal diameter ratio, maintenance of reduction, implant stability, assessment of union, and to identify any complications. Owners were contacted to obtain long-term assessment of limb function. Dogs weighed between 6 and 31 kg. Trans-iliosacral rods were placed correctly traversing the sacral body. Mean (+/-SD) percent reduction of the sacroiliac joint was 92.9+/-6.6%. Pelvic canal diameter ratio did not differ significantly between time periods. With the exception of 1 dog, which died in the early postoperative period, all sacroiliac fracture-luxations healed without appreciable complications. Three dogs were sound and 1 dog had a subtle lameness at final physical and radiographic examination (mean+/-SD: 217+/-205 days). Owners assessed their dog's limb function (mean+/-SD: 355+/-205 days) as good or excellent. Trans-iliosacral rods can be accurately placed using intraoperative fluoroscopy after limited open reduction of sacroiliac fracture-luxations. Trans-iliosacral rods provided bilateral secure fixation, allowed early weight-bearing and dogs consistently had good long-term clinical results. Trans-iliosacral rods are suitable implants for the stabilization of sacroiliac fracture-luxations, particularly in dogs with bilateral fracture-luxations and/or concurrent musculoskeletal injuries.

A possible egg of the dromaeosaur Deinonychus antirrhopus: phylogenetic and biological implications

A unique find of a partial egg in contact with articulated gastralia from a known specimen of the dromaeosaurid Deinonychus antirrhopus (AMNH 3015) is described. Much of the original taphonomic context of the specimen was lost during the 1931 excavation and preparation, but enough information is preserved to provide strong evidence for a parental association between the adult skeleton and egg. The articulated nature of the gastralia suggests that the adult skeleton was at least partially articulated and had not suffered from either extensive subaerial exposure or postmortem transport, and the egg preservation also indicates in situ burial and postburial lithogenic crushing. Additional support stems from the presence of limey claystone matrix that indicates a low-energy depositional event. Phylogenetic characteristics of the eggshell microstructure are consistent with a theropod origin, and skeletochronological analysis suggests that AMNH 3015 was an adult and thus of breeding age bolstering the interpretation that the egg derives from the skeletal specimen. Physiological parameters of D. antirrhopus, such as estimated mass and pelvic canal diameter, as well as eggshell thickness, are very similar to the similar sized and closely related oviraptorid Citipati osmolskae. Closely related maniraptoran theropods of several species have been found brooding their nests with the gastralia close to or in contact with eggs, and such a scenario is consistent with the preservation of AMNH 3015. Alternative explanations to a parental association, such as random co-occurrence or feeding, are improbable given the taphonomic and biological data of the find. AMNH 3015, therefore, probably represents the first identifiable dromaeosaurid egg yet discovered. It shares derived characters such as two eggshell layers with other theropods. Within theropods, the AMNH 3015 eggshell shares derived characteristics with oviraptorids and differs from troodontid eggshell despite the fact that these taxa are often recovered as sister groups in analyses of skeletal characters, but this signal is weak.

Increased Sacral Screw Purchase Minimizes Screw Loosening in Canine Triple Pelvic Osteotomy

To determine if screw loosening in triple pelvic osteotomies (TPO) is minimized when screws cranial to the ilial osteotomy had maximal sacral purchase. Prospective study. Forty-six dogs with decreased acetabular coverage of the femoral head and minimal degenerative joint changes. TPOs were performed where screws cranial to the ilial osteotomy were inserted to maximally engage sacral bone. Data collected were: use of ilial and ischial cerclage wire, screw length, ventrodorsal radiographic sacral width (most caudal aspect), pelvic canal diameter, and sacral penetration of the 3 cranial screws. On all subsequent radiographs, changes in screw position, pelvic canal diameter, and sacral purchase were noted. For 69 TPOs, 414 screws were used. Mean radiographic cranial screw length was 34.54 mm. Combined sacral depth of all 3 screws was 93.3% of sacral width. All osteotomies healed uneventfully. Twenty-four screws (6%) loosened with 12 being in the most cranial positions. Use of ischial or ilial cerclage wires did not statistically influence screw loosening. Pelvic diameter decreased by a mean of 7.79% from postoperative radiographs to the last radiographic recheck. By sufficiently engaging the sacrum with screws cranial to the ilial osteotomy, implant failures can be avoided and screw loosening minimized when a 6-hole TPO plate is used. To minimize screw-loosening in TPO, screws inserted cranial to the ilial osteotomy should be inserted to maximum sacral depth without penetrating the vertebral canal.

Closed reduction and lag screw fixation of sacroiliac luxations and fractures.

To describe a technique for closed reduction and percutaneous insertion of a lag screw for fixation of sacroiliac fracture-luxations, and to report the success of this technique in stabilizing sacroiliac fracture-luxations. A retrospective clinical study. 13 consecutive client-owned dogs with sacroiliac fracture-luxations. Sacroiliac fracture-luxations were stabilized by using a closed reduction and percutaneous lag screw fixation technique. Preoperative, postoperative, and last re-examination radiographs were used to assess the location and number of pelvic injuries, other orthopedic injuries, percent reduction of the sacroiliac joint, percent sacral width screw depth, position of the screw, pelvic canal diameter ratio, hemipelvic canal width ratio, and complications. Information on signalment, weight, weight-bearing status, neurologic status, and complications was obtained from the medical record. Mean percent reduction of the sacroiliac joint was 92.33%. All screws were placed within the sacral body with a mean screw depth/sacral width of 79.03%. No screw loosening occurred. Mean pelvic canal diameter ratios were 0.99, 1.20, and 1.14 preoperatively, immediately postoperatively, and at the last re-examination, respectively. Nine of 13 dogs were willing to walk on the ipsilateral rear leg the day after surgery. Closed reduction and percutaneous insertion of a lag screw for stabilization of fracture-luxation of the sacroiliac joint is an acceptable method of repair. Sacroiliac fracture-luxations can be successfully reduced and stabilized using a minimally invasive technique.

Risk factors associated with development of pelvic canal stenosis secondary to sacroiliac separation: 84 cases (1985–1995)

Objective— To measure pelvic canal diameter in dogs from a ventrodorsal radiographic view of the pelvic region, to define a normal pelvic canal diameter, to evaluate risk factors associated with stenosis of the pelvic canal secondary to sacroiliac separation, and to determine clinical signs associated with pelvic canal stenosis. Design— Retrospective case series. Animals— 84 case-group and 46 control-group dogs. Procedure— Medical records and radiographs of dogs with conditions unrelated to pelvic fracture (control group) and dogs with sacroiliac separation (case group) in which radiographs were obtained before surgery, I after surgery, or after fracture healing were reviewed. Discriminant analysis was used to determine a normal pelvic canal diameter. An ANOVA and Dunnett's two-sided test were used to determine factors associated with pelvic canal stenosis. Results— Pelvic canal diameter ratio determined from control-group dogs was ≥ 1.1. Pelvic canal diameter ratios were significantly less for case-group dogs on radiographs obtained before surgery and after fracture healing than for control-group dogs, regardless of fracture type or treatment, except for dogs with ilial fractures treated conservatively. Pelvic canal diameter ratios did not differ for case-group dogs on radiographs obtained after surgery from those for control-group dogs, except when ilial fractures were surgically reduced. None of the dogs had clinical signs associated with pelvic canal stenosis. Clinical Implications— Pelvic canal diameter in dogs can be determined from a ventrodorsal radiographic view of the pelvic region. Dogs with pelvic fractures that have a normal pelvic canal diameter before surgery tend to have a normal pelvic canal diameter after fracture healing. (J Am Vet Med Assoc 1997; 211:75–78)

Reproductive Ecology of the Painted Turtle (Chrysemys picta) in the Nebraska Sandhills and across Its Range

Female painted turtles in western Nebraska matured after 5-6 activity seasons at 160-165 mm carapace length. Annual adult survivorship was at least 91.5%, and some females apparently survive beyond 30 yr of age. Nesting was recorded from 19 May to 17 July, and its onset was inversely related to March-May temperatures. Internesting interval averaged 16.4 days and decreased through the nesting season. Females usually produced two clutches per season, but many produced three clutches, and two may have produced four clutches. Average annual clutch frequency was estimated at 2.78 per female. Egg size was correlated with female size. When standardized for body size, egg size was negatively correlated with body size and clutch size and varied across estimated clutch number (early season clutches having larger, more elongate eggs than later ones) but not among years. Egg size was not constrained by pelvic canal width. Clutch size averaged 13.9, was positively correlated with body size, and varied across estimated clutch number (later clutches being smaller than earlier clutches) as well as across years. Clutch mass increased with body size but remained constant as a proportion of spent female body mass (=RCM). RCM varied across clutch number within years (higher in earlier clutches) and across years (with a trend for higher RCM in years following a warmer Oct.). Actual annual clutch output in triple-nesting females averaged 42 eggs or 30.9% of spent female body mass. Across populations of painted turtles, body size is positively correlated with latitude and elevation and negatively correlated with average frost-free days and mean annual temperature. Clutch frequency remains one of the most elusive traits but seems to be inversely related to latitude and age at maturity and positively related to frost-free days. Both egg size and clutch size tend to vary with body size within and among populations, with clutch size varying the most. Presumably because of its correlation with body size, clutch size also varied with latitude, elevation, the inverse of frost-free days, and the inverse of mean annual temperature. Populations of small turtles (at lower latitudes and/or warmer climates) apparently produce the largest eggs possible within the constraints of their pelvic canal diameter, whereas no such constraint exists for larger-bodied populations at high latitudes. Selection is probably more intense on egg size than clutch size, and clutch size seems to have a much greater environmental component.