The Effects of Plate Type, Angle of Ilial Osteotomy, and Degree of Axial Rotation on the Structural Anatomy of the Pelvis

Unilateral triple pelvic osteotomy was performed with three variations in technique on canine cadaver pelves. The following variables were studied: the angle of the ilial osteotomy (perpendicular to the long axis of the ilium and 10d?, 20d?, and 30d? off perpendicular); the degree of axial rotation (20d?, 30d?, and 45d?); and the type of fixation (canine pelvic osteotomy plate [CPOP] or a 2.7-mm dynamic compression plate [DCP]). Structural changes measured were the pelvic inlet and acetabular area, interischiatic tuberosity distance, and degree of acetabular version. Means and standard error of the means were determined for all pelvic measurements and were analyzed by three-way analysis of variance (P < .05). As the axial rotation increased from 20d? to 45d? an ilial osteotomy angled 10d?, 20d?, or 30d? resulted in a significantly greater decrease in the pelvic inlet area and significantly less deviation of the interischiatic tuberosity distance and degree of acetabular version from normal than an osteotomy directed perpendicular to the long axis of the ilium. Compared with the CPOP, as the axial rotation increased from 20d? to 45d?, the DCP resulted in a significantly greater decrease in the pelvic inlet area, an increase in the interischiatic tuberosity distance and degree of acetabular version, and less of an increase in the acetabular area. The results of this study suggest that to maximize dorsal acetabular coverage, while minimizing disruption of normal pelvic architecture, a CPOP and an ilial osteotomy angled 10d? to 30d? are preferred for all degrees of axial rotation.     

Effects of degree of acetabular rotation after triple pelvic osteotomy on the position of the femoral head in relationship to the acetabulum

OBJECTIVE: To assess the effect of rotating the acetabulum 20 degrees and 30 degrees on percent coverage (PC) of the femoral head by the acetabulum and Norberg angle (NA) after triple pelvic osteotomy (TPO). STUDY DESIGN: Retrospective study. ANIMAL POPULATION: Fifty-six client-owned dogs. METHODS: PC and NA were measured from preoperative, immediate postoperative, first recheck, and second recheck radiographs to compare the effects of 20 degrees and 30 degrees of rotation of the acetabulum after TPO for treatment of hip dysplasia. RESULTS: Within the 20 degrees rotation group, PC and NA values were significantly greater at each subsequent evaluation time starting at the preoperative measurement except for NA between the first and second recheck times. Within the 30 degrees rotation group, PC and NA values were significantly greater at each subsequent evaluation time starting at the preoperative measurement except for PC and NA between the first and second recheck times. No significant differences between the 20 degrees and 30 degrees rotation groups were found at any corresponding times for either PC or NA. CONCLUSIONS: Acetabular rotation of 20 degrees provided the same degree of improvement in acetabular femoral head coverage as 30 degrees of rotation after TPO at the immediate postoperative, first recheck, and second recheck evaluation times. CLINICAL RELEVANCE: Based on PC and NA, 20 degrees rotation of the acetabulum provides as much benefit as 30 degrees of acetabular rotation when performing a TPO.     

EFFECTS OF PELVIC POSITIONING AND SIMULATED DORSAL ACETABULAR RIM REMODELING ON THE RADIOGRAPHIC SHAPE OF THE DORSAL ACETABULAR EDGE

A radiographic study was conducted to evaluate the effect of pelvic rotation and of simulated dorsal acetabular rim (DAR) remodeling on the radiographic appearance of the dorsal acetabular edge (DAE). The DAE is the line connecting the cranial and caudal rims of the acetabulum when viewing a pelvic radiograph made with the dog in the ventrodorsal position with the hind limbs extended. In this study, it was hypothesized that the DAE would change with pelvic rotation and simulated DAR damage. Ventrodorsal radiographs of eight canine pelves were made at 0 degrees, 5 degrees, and 10 degrees of left and right pelvic rotation over its longitudinal axis. These radiographs were repeated following removal of 2, 4, and then 6 mm of bone from the right DAR of each pelvis. The ratio of acetabular width to maximum depth of the DAE was calculated. The area between the DAE and a straight line connecting the cranial and caudal acetabular rims was measured digitally. The DAE depth and area changed with pelvic rotation, and with increasing simulated DAR damage. A linear relationship between the obturator foramina width ratio and pelvic rotation allowed estimation of the degree and direction of pelvic rotation. Equations were developed from the data to assist with the estimation of the amount of DAR remodeling on a clinical radiograph.     

Definition and determination of acetabular component orientation in cemented total hip arthroplasty

OBJECTIVE: To describe the spatial orientation of the cemented acetabular component in cemented total hip arthroplasty, based on a ventrodorsal and lateral radiographic projection of the pelvis. METHODS: Equations were derived by using trigonometric relationships that describe the radiographic rotation about the longitudinal pelvic axis (alpha), transverse pelvic axis (beta), acetabular inclination (phi), acetabular inclination corrected for longitudinal pelvic rotation, version (phiC), acetabular version (theta), acetabular version corrected for longitudinal pelvic rotation (thetaC), acetabular inclination corrected for transverse pelvic rotation (phi(beta)), and acetabular version corrected for transverse pelvic rotation (theta(beta)) RESULTS: Alpha was calculated by using the equation alpha = sin(-1) (x/y) where x is the transverse distance between the dorsal spinous processes and the center of the pubis on a ventrodorsal radiograph and y is the distance from the pubis to the dorsal aspect of the first coccygeal vertebra perpendicular to the long axis of the pelvis on a lateral radiograph. Phi was calculated from the long axis (LA) and short axis (SA) of the ellipse formed by the radiopaque acetabular marker ring by using the equation phi = sin(-1) (SA/LA). phiC was calculated by using the equation phiC = phi +/- (alpha - tan(-1) (tan alpha cos thetaC)). Theta was determined as previously described. ThetaC was calculated by using the equation thetaC = tan(-1) (tan theta cos alpha). Theta(beta) and theta(beta) were calculated with the equations phi(beta) = tan(-1) (tan theta cos beta) and theta(beta) = theta - tan(-1) (sin beta), respectively. Beta could not be accurately determined from ventrodorsal and lateral pelvic radiographs. CONCLUSIONS AND CLINICAL RELEVANCE: These techniques allow for more accurate postoperative radiographic assessment of acetabular component positioning. This information can then be used in retrospective or prospective analyses examining that effects of implant positioning on clinical outcome.     

Effects of triple pelvic osteotomy on anatomic structures of the pelvic region in the dog

Triple pelvic osteotomy has been used in dogs to maintain normal form and anatomical function of the hip in canine hip dysplasia. Pelves subjected to triple pelvic osteotomy undergo several architectural changes of different magnitudes. The aim of this study was to determine the positional changes of the anatomical structure of the pelvis after unilateral triple pelvic osteotomy in five mongrel dogs. Atrophy of the middle gluteal muscle, reduction in tension of the external and internal obturator muscles, compression on the caudal gluteal vein and entrapment of the sciatic nerve at the level of the ilial body were the most remarkable findings in the study. From an anatomical standpoint, it is suggested that the lateral rotation of the acetabulum should be kept minimal to guarantee least alterations in the normal anatomic architecture of the pelvic region.     

Evaluation of the dorsal acetabular coverage obtained by a modified triple pelvic osteotomy (2.5 pelvic osteotomy). An ex vivo study on a cadaveric canine codel

Objectives: To evaluate the acetabular ventroversion obtained with a modified triple pelvic osteotomy (2.5 PO) compared with that resulting from standard double pelvic osteo-tomy (DPO). Study design: Ex vivo study. Animals: Seven pelves obtained from skeletally mature dogs with a total body weight ranging from 26-41 kg were used. Methods: Unilateral DPO technique and dorsal ischial mono-cortical osteotomy were performed on every right hemipelvis. Angular ventral rotation was measured by determining the relative orientation of two Kirschner wires placed in the ilial wing and in the dorsal acetabular rim. Results: The mean angle of ventroversion was 9.5 ± 5.2 degrees for the DPO group (range 2.1-18.1) and 10.9 ± 4.8 degrees for the 2.5 PO group (range 4.1-19.5). The mean difference between the 2.5 PO and DPO was 1.5 ± 0.6 degrees (range 0.5-2.1). Conclusions: The 2.5 PO technique increased acetabular ventroversion versus DPO.     

Pelvic osteotomy for axial rotation of the acetabular segment in dogs with hip dysplasia.

Pelvic osteotomy has provided normal function and activity to dogs with hip dysplasia. Physical and radiographic examination and palpation under anesthesia permit evaluation of the degenerative process and provide the specific amount of axial rotation of the pelvis necessary for each dog. The technique consists of an osteotomy of the pubis, ischium, and ilium to reestablish acetabular support of the femoral head.     

Evaluation of a method for experimental induction of osteoarthritis of the hip joints in dogs

OBJECTIVE: To evaluate a method for experimental induction of osteoarthritis in the hip joints of dogs. ANIMALS: 12 mixed-breed dogs. PROCEDURE: A unilateral triple pelvic osteotomy was performed. In 6 dogs, the iliac osteotomy was repaired with 45 degrees of internal rotation, reducing coverage of the femoral head by the acetabulum. In the other 6 dogs, the fragments were repaired in anatomic alignment. Radiography, force plate evaluations, and subjective lameness evaluations were performed before and after surgery. Dogs were euthanatized 7 months after surgery, and samples of cartilage and joint capsule were examined histologically. RESULTS: Subjective lameness scores, radiographic appearance of the hip joints, and Norberg angles were not significantly different between groups; however, force plate evaluations did reveal significant differences in vertical ground reaction forces. Femoral head coverage was significantly decreased with rotation of the acetabulum. Mild inflammatory changes were discernible in the joint capsule and articular cartilage of some dogs in both groups. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that 45 degrees internal rotation of the acetabulum does not consistently induce biologically important osteoarthritic changes in the hip joints of dogs.     

A technique for pelvic radiography in the standing horse

REASONS FOR PERFORMING STUDY: An alternative technique of radiographing the pelvis in the standing horse is required, to avoid the risks associated with general anaesthesia. HYPOTHESIS: That lateral oblique radiography in the standing horse would be a useful technique in the investigation of pelvic injury. OBJECTIVES: To describe the technique of lateral oblique pelvic radiography in the standing horse and demonstrate the feasibility and usefulness of this technique. METHODS: A technique for lateral oblique radiography in the standing horse was devised and retrospective review made of radiographic findings in 18 clinical cases. RESULTS: The caudal iliac shaft, greater trochanter of the femur, femoral head, acetabulum and coxofemoral articulation on the side under investigation were visualised consistently using this technique. Of the 18 cases, 3 iliac shaft fractures, 1 acetabular fracture, 2 coxofemoral luxations and 4 horses with new bone formation around the coxofemoral joint and/or proximal femur were identified. CONCLUSIONS: Lateral oblique radiography in the standing, conscious horse can be used to investigate conditions affecting the caudal iliac shaft, coxofemoral articulation and proximal femur in the horse. POTENTIAL RELEVANCE: The technique is straightforward, noninvasive and useful in the investigation of horses with suspected pelvic injury. However, not all pelvic injuries would be identified, and normal radiographic findings do not rule out injury or fractures elsewhere in the pelvis.     

Effects of pubic symphysiodesis in dysplastic puppies

OBJECTIVE--To determine the long-term effects of juvenile pubic symphysiodesis (JPS) in dysplastic puppies. STUDY DESIGN--Prospective, randomized, clinical trial. ANIMALS--Seven dysplastic Chesapeake Bay retrievers and 2 beagle-crosses (BX1 and 2). METHODS--Five puppies had JPS performed with electrocauterization at 12, 16, 20, 22, and 24 weeks of age, respectively. Two puppies served as controls. BX1 and BX2 were used to obtain biopsies of the symphysis. Hips were evaluated for: pelvic development (transverse computerized tomography for acetabular angle [AA] and dorsal acetabular rim angle [DARA]); laxity [hip extended and stress radiography [distraction index (DI)]); Ortolani maneuver with reduction angles; acetabular coverage (Norberg angles); and function (coxofemoral range of motion, hip pain, and gait analysis by force-plate technique at 44 and 137 weeks of age). RESULTS--The pubis fused prematurely in every puppy that was operated on with the JPS technique. Greater acetabular responses were related to younger ages at surgery. The final mean AA in dogs that had JPS was 25 degrees greater than preoperative values; 40% increased over control. The DARA final mean was 10 degrees, 52% less than preoperative values and 46% less than control. The final mean DI in dogs having JPS was 0.28, 47% improved over preoperative values and 58% better than control. Mean pelvic dimensions in dogs that had JPS were 18% less than control. Gait analyses were normal for all dogs at 137 weeks. No urinary or bowel complications occurred. CONCLUSIONS--Significant ventrolateral acetabular rotation, increased hip coverage, diminished hip laxity, normal pain-free gait, and insignificantly reduced pelvic size occurred after JPS. CLINICAL SIGNIFICANCE--Dysplastic hips in young dogs were significantly improved by JPS.     

Biomechanical Comparison of Two Plating Techniques for Fixation of Acetabular Osteotomies in Dogs

OBJECTIVE: To compare the failure properties of a 5-hole, 2.7-mm curved acetabular plate (AP) to a 5-hole, 3.5-mm reconstruction plate (RP) when applied to acetabular osteotomies. STUDY DESIGN: Cadaver study. ANIMALS OR SAMPLE POPULATION: Pelves of 8 mature, large-breed dogs. METHODS: A 5-hole, 2.7-mm AP and a 5-hole, 3.5-mm RP were contoured and applied to the dorsal acetabulum of each pelvis. A central acetabular fracture was simulated after plate application by a transverse osteotomy with a fine saw. Each acetabulum was loaded in a weight-bearing direction. A load-deformation curve was produced for each construct, and biomechanical properties of the AP and RP were compared with the Student's paired t-test. A P value of < .05 was considered significant. RESULTS: For the AP and RP composite respectively, the mean +/- SD maximum load to failure was 2,721 +/- 632 N and 2,488 +/- 800 N, the stiffness was 4.8 +/- 1.8 N/m and 5.3 +/- 1.9 N/m, and the energy absorbed was 15.1 +/- 5.2 Nm and 16.3 +/- 8.3 Nm. None of these differences was statistically significant. CONCLUSIONS: Both fixation techniques provided comparable strength, stiffness, and energy absorbed under the loading conditions of this study. CLINICAL RELEVANCE: Because of the relative ease of application, the 2.7-mm curved AP may be the practical choice for acetabular fracture repair in large dogs.     

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. PRACTICAL RELEVANCE: 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.     

Tension band stabilisation of acetabular physeal fractures in four kittens

The surgical repair of acetabular physeal fractures in four kittens using a screw and tension band technique is reported. This was an appropriate method for restoring articular congruency and improving pelvic alignment. All cases had an excellent outcome and full limb use following fracture repair. In kittens younger than 12 weeks, there is a possibility of premature fusion of the acetabular bone resulting in development of a deformed, shallow acetabulum and hip subluxation. However, surgery is still justified when there is pelvic canal narrowing to decrease the risk of future defecatory problems. Early implant removal in such young kittens may decrease the severity of deformity caused by premature physeal closure. In kittens of 16 weeks or older, the prognosis is good for normal acetabular development and implant removal is not necessary.     

Early detection and treatment of screw loosening in triple pelvic osteotomy

OBJECTIVE: To detect early screw loosening in triple pelvic osteotomy (TPO) and to evaluate the efficacy of retightening using fluoroscopic guidance and minimally invasive surgery to maintain acetabular alignment and achieve bone healing. STUDY DESIGN: Prospective clinical study. SAMPLE POPULATION: Sixteen dogs that had TPO. METHODS: Dogs (16) had TPO (21) by using pre-angled plates secured with 3.5 and 4.0 mm screws, with ischiatic or iliac cerclage, for osteosynthesis. In all but 1 TPO at least 1 screw was inserted into the sacral body (43 screws). The mean radiographic screw length inserted in the sacrum was 10.2 mm, and the mean percent sacral engagement was 22%. Dogs were examined clinically and radiographically immediately postoperatively, and at 10, 30, 60, and 90 days to evaluate screw position. Loose screws were retightened through stab incisions using fluoroscopy to locate the screw. RESULTS: TPO was performed without operative complications. At 10 days, 12 TPOs (57%; 11 dogs) had loose screws primarily located in the cranial aspect of the plate. This represented 20% (25) of the inserted screws. In 5 dogs, screw loosening resulted in medial rotation of the acetabular segment. All loose screws were retightened; 3 screws loosened again in 2 dogs and were detected at 60 days. However, the osteotomies healed with the planned acetabular rotation without further intervention. Screw tightening corrected the acetabular segment displacement. Screws correctly seated at 10 days did not subsequently loosen. Clinical and radiographic outcome was judged excellent in all dogs. CONCLUSION: Loose screws in TPO plates can be identified by 10 days postoperatively and retightened using fluoroscopic guidance to achieve acetabular realignment and healing without need for further surgery. CLINICAL RELEVANCE: Postoperative radiographic evaluation of screw position at 10 days after TPO is recommended to detect loose screws. Retightening loose screws should be considered as an alternative to TPO revision or confinement, especially in immature dogs.     

Acetabular ventroversion with double pelvic osteotomy versus triple pelvic osteotomy: a cadaveric study in dogs

Objective: To determine which of 3 different plate angles (20°, 25°, 30°) used in double pelvic osteotomy (DPO) would result in the most similar acetabular angle (AA) achieved with a 20° triple pelvic osteotomy (TPO) technique in dogs. Study Design: Experimental anatomic study. Animals: Cadaveric canine pelves (n=8). Methods: Transverse plane computed tomographic images of cadaveric pelves with intact sacroiliac joints, mounted in a custom jig, were made (baseline) and again after DPO (20°, 25°, 30°) and TPO (20°) and pelvic angles measured in 6 transverse planes. Pelvic angles of the 3 DPO techniques were compared with TPO using concordance correlation to determine which DPO angle resulted in an acetabular ventroversion angle closest to TPO. Results: Mean ± SD AAs were 32.89 ± 2.23 (baseline), 47.39 ± 4.39 (20° DPO), 51.43 ± 5.06 (25° DPO), 54.75 ± 4.38 (30° DPO), and 50.20 ± 5.76 (20° TPO). Concordance correlations for the AA compared with 20° TPO were 0.027 (baseline), 0.721 (20° DPO), 0.902 (25° DPO), and 0.593 (30° DPO). A concordance correlation of ≥0.8 indicates good correlation. Conclusions: A 25° DPO is most similar in acetabular ventroversion to 20° TPO (concordance correlation, 0.902).     

Two cases of dysuria as a complication of single-session bilateral triple pelvic osteotomy

Dysuria is a rare, but nevertheless severe postoperative complication associated with single-session bilateral triple pelvic osteotomy. Two cases are described in which contrast radiography of the lower urinary tract was used to diagnose urethral compression due to pelvic canal narrowing. Relief of the pressure on the urethra was achieved with an external fixation device, which distracted the acetabular fragments of the pelvis. In both cases the dysuria was resolved. The significance of this complication and its possible causes, especially regarding surgical technique, are discussed.     

Evaluation of ilial screw loosening after triple pelvic osteotomy in dogs: 227 cases (1991-1999)

OBJECTIVE: To investigate factors influencing screw loosening after triple pelvic osteotomy (TPO) and ischial wire stabilization of the acetabular segment. DESIGN: Retrospective case series. Animals-227 dogs with congenital hip dysplasia or subluxated hip joints. PROCEDURES: Medical records and radiographs of 227 dogs that underwent 332 TPO procedures were evaluated, and data pertaining to screw type, plate position, sacral screw engagement, use of ischial interfragmentary wires, and pelvic alignment were assessed for associations with screw loosening. RESULTS: Complications developed in 96 of the 332 (29%) procedures. Cancellous screws without sacral engagement were associated with the lowest frequency (6%) of loosening, compared with cancellous and cortical screws engaging the sacrum and cortical screws that did not engage the sacrum. Frequency of screw loosening increased when cortical or cancellous screws engaged the sacrum and when cortical screws were used. In dogs that had surgery bilaterally, the first limb on which TPO was performed had a higher frequency of screw loosening than the second limb. Pelvic alignment loss was greatest (5.4 degrees ) when the 3 most cranial screws were loosened. Loss of pelvic alignment was significantly different between dogs that underwent surgery and had complications and those that underwent surgery and did not have complications in association with loosening of 1, 2, and 3 screws. CONCLUSIONS AND CLINICAL RELEVANCE: TPO screw loosening was multifactorial and related to stability of the affected ilium, screw type, and screw position. Placing cancellous screws that do not engage the sacrum in pelvic osteotomy plate positions 1 through 3 may decrease the number of screws that loosen.     

Use of Reconstruction Plates for the Repair of Segmental llial Fractures Involving Acetabular Comminution in Four Dogs

Four dogs (27.3–31.8 kg) with ilial body fractures associated with various degrees of acetabular comminution were treated using internal fixation. Anatomic reduction and internal fixation were achieved using a long 2.7 mm reconstruction plate on the hemipelvis. Based on the patient's pelvic radiographs, the reconstruction plate was precontoured before surgery to precisely fit a bony pelvis of similar size and shape. Excellent anatomic reduction of the fractures was achieved in all four dogs. Three dogs recovered uneventfully and regained full function of the affected leg. In one dog with comminution of the acetabulum, reduction of the most caudally located fracture was not maintained. Severe osteoarthritis developed, and excision arthroplasty was performed.
Reconstruction plates offer greater versatility than dynamic compression plates in the treatment of complex pelvic fractures such as ilial body fractures with acetabular comminution. The technique of precontouring the reconstruction plate prior to surgery decreases intraoperative time and corrects minor discrepancies in reduction.     

A Biomechanical Comparison of Screw and Wire Fixation With and Without Polymethylmethacrylate Re-Enforcement for Acetabular Osteotomy Stabilization in Dogs

Objective— Compare the biomechanical characteristics of screw and wire fixation with and without polymethylmethacrylate (PMMA) re-enforcement for acetabular osteotomy stabilization in dogs. Animals— Pelves removed from 8 adult mixed breed dogs weighing between 25 and 30 kg. Procedure— The pubic symphysis of each pelvis was split and a central transverse acetabular osteotomy was performed. One hemipelvis from each dog was stabilized with the composite fixation (interfragmentary Kirschner wire, two screws and a figure-of-eight orthopedic wire with PMMA). The contralateral hemipelves was stabilized with an interfragmentary Kirschner wire, two screws, and a figure-of-eight orthopedic wire without PMMA. All hemipelves were tested in bending by using a materials testing machine at a cross head speed of 5 mm/min. An extensometer was placed on the dorsomedial surface of the hemipelves centered over acetabular osteotomy to record distraction of the osteotomy during loading. A load/deformation curve and a load/distraction curve was produced for each hemipelvis. The slope for the initial linear portion of the load/deformation curve and the load/distraction curve, yield load and maximum load sustained were compared between repair groups using a paired t-test with P < .05 considered significant. Results— The slope of the load/deformation curve was significantly greater (P= .001 ) for hemipelves stabilized with the composite fixation (mean ± SD: 69 ± 18 N/mm) compared with hemipelves stabilized without PMMA (mean ± SD: 39 ± 8 N/mm). There was no significant difference (P= .593 ) between repair groups in the slope of the load/distraction curves as measured on the extensometer. Yield load was significantly greater (P= .0002 ) for hemipelves stabilized with the composite fixation (mean ± SD: 184 ± 25 N) compared to hemipelves stabilized without PMMA (mean ± SD: 74 ± 12 N). Maximum load sustained was also significantly greater (P= .013 ) for hemipelves stabilized with the composite fixation (mean ± SD: 396 ± 71 N) compared to hemipelves stabilized without PMMA (mean ± SD: 265 ± 94 N). Failure of hemipelves stabilized with the composite fixation occurred primarily by ventrolateral bending of the cranial and caudal pelvic segments at the osteotomy site. Failure of hemipelves stabilized without PMMA occurred by ventrolateral bending of the cranial and caudal pelvic segments at the osteotomy site with pronounced concurrent ventrolateral rotation of the cranial pelvic segment. Conclusion— PMMA improves the mechanical characteristics of acetabular fracture fixation, at least in part by neutralization of rotational forces. The results of this study justify use of PMMA as a component of the composite fixation when repairing acetabular fractures.     

Effect of public symphysiodesis on pelvic development in the skeletally immature greyhound

OBJECTIVE: To evaluate the effect of pubic symphysiodesis (PS) on pelvic development in skeletally immature dogs. STUDY DESIGN: Prospective randomized clinical trial. ANIMALS: Eight 4 month-old, sexually intact female Greyhounds. METHODS: Initial PS was performed at 4 months of age using a powered stapling device. Because of failure of the initial surgery, a second PS was performed 1 month later by resecting the pubic symphysis with a rongeur followed by placement of handmade bone staples in four dogs. Sham PS was performed in four control dogs at 4 months of age. Pubic growth rate and pelvic development were evaluated using standard plane radiography and computed tomography. Specific measurements included acetabular ventroversion, Norberg angle, lateral center-edge angle, and pelvic inlet dimensions. Hip distraction indices were determined as well. RESULTS: PS at 4 months of age using a stapling device failed. Pubic symphysiodesis using hand made staples was successful at 5 months of age and did not result in any clinically significant intraoperative or postoperative complications. Pubic symphysiodesis markedly decreased pubic symphysis growth in the treatment group. Hip distraction indices and pelvic inlet circumference, area, and width significantly decreased in treated dogs compared to those in the control group. Acetabular ventroversion was significantly increased in treated dogs compared to those in the control group. CONCLUSIONS: PS decreases pelvic canal size, increases acetabular ventroversion, and does not appear to have any clinically significant complications. CLINICAL RELEVANCE: PS performed in skeletally immature dogs with hip dysplasia may provide an effect similar to a triple pelvic osteotomy and warrants further investigation.