In small animals, FHNE is commonly performed to alleviate pain and salvage limb function when irreparable damage to the hip joint exists.1 Indications for FHNE include chronic or recurrent hip luxations, comminuted intra-articular fractures not amenable to surgical fixation, and degenerative joint disease secondary to aseptic necrosis of the femoral head and neck (ie, Legg-Calvé-Perthes disease) or hip dysplasia.2 Good to excellent clinical results have been found for dogs weighing < 20 kg; however, results are less consistent in larger dogs (> 20 kg).2–7 Factors reported to influence limb function following FHNE include temperament,8 body weight,2–7 concurrent orthopedic disorders,2 chronicity of lameness prior to surgery,2,3 preexisting muscle atrophy,2,3 surgically induced trauma,2,3,9 completeness of excision,2,3,9,10 bone-on-bone contact2,3,5,7,9,10–14 and postoperative activity and physical rehabilitation.2,8 In larger dogs, bone-on-bone contact from inadequate surgical resection of the distal portion of the femoral neck has been implicated as one of the most important factors leading to less satisfactory results caused by a greater body mass driving the femur against the acetabular rim.2,3,5,7,9–14
Clinical evaluation of the adequacy of excision currently includes intraoperative postexcision examination of the hip joint via range of motion for detection of bone-on-bone contact and postoperative radiographs of the pelvis for evidence of inadequate femoral neck resection. The reliability of palpation to predict postoperative outcome in dogs with bone-on-bone contact after FHNE has been questioned. In 1 study,4 25% of dogs with bone-on-bone contact during manipulation of the hip joint had associated pain and lameness in the early postoperative period. In another study,15 bone-on-bone contact was not associated with pain or discomfort.
Postoperative radiographic assessment of FHNE includes standard lateromedial and ventrodorsal radiographic views of the pelvis. Ventrodorsal radiographic views16 obtained with the femurs positioned parallel to the table and stifle joints rotated inward may obscure the medial distal aspect of the femoral neck (a common site of inadequate resection)9,17 as a result of the x-ray beam not being tangential to the excised surface. We hypothesized that craniocaudal radiographic views obtained with the femur in extension with external rotation would improve the ability to detect inadequate resection of the medial distal aspect of the femoral neck. Goals of the study reported here were to demonstrate the effects of femur position on radiographic assessment of completeness of FHNE and to obtain accurate, repeatable qualitative data to assess completeness of excision from evaluation of nonstandard radiographic views.
Materials and Methods
Specimen preparation—Ten femurs were harvested from mixed-breed dogs (> 20 kg) euthanatized for reasons unrelated to this study. Signalment and history were unavailable as a result of the source of the specimens. Eight specimens were skeletally mature as evidenced by complete closure of the growth plates on radiographs, and 2 specimens were skeletally immature with lack of physeal closure. Soft tissues were dissected from the femurs, and specimens were placed in freezer bags for storage at -80°C. Specimens were thawed to room temperature (approx 20° to 22°C) prior to use. Complete excision was performed on 5 femurs and incomplete excision on the remaining 5 femurs. In the completely excised femurs, the osteotomy was performed at an angle such that complete FHNE just proximal to the lesser trochanter was achieved. In the incompletely excised femurs, the osteotomy was performed at an angle such that complete excision of the femoral head with inadequate excision of the medial distal aspect of the femoral neck (leaving a lip of bone proximal to the lesser trochanter) was achieved. All excisions were performed by 2 investigators (AV and SCK).
Specimen positioning and imaging—Each femur was mounted in an orthogonal plexiglass frame by use of a modified technique of transverse plane leveling.18,19 Transverse plane leveling was achieved by elevating the medial aspect of the lesser trochanter and the medial aspect of the lateral supracondylar tubercle equidistant above the x-z plane (Figure 1). Positioning in the x-y plane was standardized by placing Kirschner wires or Steinmann pins (1.6 to 2.4 mm) in the x-axis through the condyles and in the y-axis perpendicular to the long axis of the femur (z-axis) and the x-axis. Craniocaudal radiographic views of the femur positioned in external and internal rotation were obtained in the x-y plane about the z-axis. All radiographs were made at a focal-film distance of 34 cm with the x-z plane of the frame elevated 10 cm above the table to achieve uniform magnification in all femurs. Standard lateromedial and craniocaudal radiographic views (50 kV and 2.5 mA) of each femur were made with the beam centered in the mid-diaphyseal region while the femur was mounted in the orthogonal frame. Craniocaudal radiographic views of the femur positioned in rotation were obtained by rotating the femurs in the frame to simulate 15°, 30°, and 45° of external rotation and 15°, 30°, and 45° of internal rotation. For each angle of internal and external rotation, the degree of rotation was confirmed prior to radiography by measurement with a protractor and goniometer in the x-y plane. Angles of external and internal rotation were similar to those that have been used in experimental and clinical evaluation of femoral implant position in total hip arthroplasty in dogs.20
Oblique photographic view of a femur with an FHNE placed in a frame for orthogonal positioning, observing the principles of transverse plane leveling. X, Y, and Z denote the x-, y-, and z-axes.
Citation: American Journal of Veterinary Research 67, 1; 10.2460/ajvr.67.1.64
Radiography and positioning of the femurs in the frame were performed by 1 investigator (AV). The entire sequence of 8 radiographic views (standard lateromedial; standard craniocaudal; craniocaudal with 15°, 30°, and 45° of external rotation; and craniocaudal with 15°, 30°, and 45° of internal rotation) from 2 randomly selected femurs (femurs A and D) was radiographed on 3 occasions by 1 investigator (AV) to ensure repeatability and consistency in angle measurement and positioning. Superimposition of the 3 images for each angle was used for verification of positioning.
Evaluator training and image evaluation—The 10 femurs (5 with complete FHNEs and 5 with incomplete FHNEs) were randomly assigned letters A through J. The radiograph packet for each femur (A through J) contained 8 radiographic views (standard lateromedial; standard craniocaudal; craniocaudal with 15°, 30°, and 45° of external rotation; and, craniocaudal with 15°, 30°, and 45° of internal rotation) randomly assigned numbers 1 through 8 with no lead markers denoting the type of radiographic view. All randomization was performed by use of a random number table.21 An evaluator training session consisted of reviewing labeled radiographic images of 1 completely excised and 1 incompletely excised femur. The training session was provided for 3 evaluators (SCK, LEP, and WDM) by 1 investigator (AV; Figure 2). Following the training session, the 3 evaluators, blinded to the randomization process, evaluated packets for each femur with no prior knowledge of the adequacy of the excision (Figure 3). Randomized radiographs in each packet were placed on the view box one at a time, and evaluators were provided with a questionnaire to assess the completeness of excision (complete, incomplete, or unable to assess) based on each radiograph. They were subsequently asked to make an overall assessment of completeness of excision based on the entire radiographic sequence. Evaluators were instructed to select “unable to assess” if they could not evaluate the medial distal aspect of the femoral neck on a particular radiographic view. Evaluators ranked the completeness of excision on a scale of 1 to 5, with 1 being the most incomplete and 5 being the most complete excision. Evaluators were also asked to choose 3 radiographs from each packet that most helped them make their assessment and rank those radiographic views on a scale of 1 to 3, from first to third most helpful. To assess consistency in evaluation, the investigators, still blinded to the randomization process and adequacy of excision, reevaluated complete radiographic sequences from 2 randomly chosen femurs (femurs B and D) 1 week after initial evaluation.
Comparison of craniocaudal radiographic views of femurs in 30° of external rotations about the long axis with a completely excised (A) and incompletely excised (B) femoral neck. A radiopaque marker highlights the medial cortex of the excised femoral neck in both radiographic views. Notice the presence of the residual medial distal aspect of the femoral neck cortex in the incompletely excised femur (arrows).
Citation: American Journal of Veterinary Research 67, 1; 10.2460/ajvr.67.1.64
Radiographic sequence of a femur with complete excision of the femoral neck as follows: standard craniocaudal view (A), craniocaudal view with 15° of external rotation of the femur about the long axis (B), craniocaudal view with 30° of external rotation (C), craniocaudal view with 45° of external rotation (D), craniocaudal view with 15° of internal rotation (E), craniocaudal view with 30° of internal rotation (F), craniocaudal view with 45° of internal rotation (G), and standard lateromedial view (H).
Citation: American Journal of Veterinary Research 67, 1; 10.2460/ajvr.67.1.64
Statistical analysis—For each radiographic view assessed, SE, SP, PPV, NPV, and accuracy of assessment were calculated. For the purposes of this study, SE was defined as the probability that a completely excised femur was evaluated as a complete excision and SP was defined as the probability that an incompletely excised femur was evaluated as an incomplete excision. The PPV was defined as the probability that an excision determined to be complete from a particular radiographic view was truly a complete excision. The NPV was defined as the probability that an excision determined to be incomplete was truly an incomplete excision. Thus, the PPV is related to SE, and NPV is related to SP. Accuracy is an indication of the extent to which assessment of a radiographic view confirms the truth about the completeness of the excision.
The SE was calculated as 1–false-negative rate and SP was calculated as 1–false-positive rate, assuming a complete excision to be the gold standard positive result and an incomplete excision to be the gold standard negative result. Accuracy of assessment was estimated as 1 - overall false rate. Ninety-five percent CIs were calculated for estimates of accuracy, assuming a binomial distribution, and type I error of 0.05 was used for statistical testing.
Consistency of assessment of individual radiographic views by evaluators of initial and follow-up evaluation of 2 femurs (femurs B and D) was estimated by calculating kappa statistics and 95% CIs. Overall agreement between these 2 assessments was estimated by use of a kappa statistic. Differences in scores (1 to 5) assigned by evaluators as to adequacy of excision, including initial versus follow-up evaluation, were compared by use of paired t tests. Values of P < 0.05 were considered significant.
Results
Standard lateromedial radiographic view of the femur—Of the 8 radiographic views, lateromedial radiographic views for completely and incompletely excised femurs yielded the highest percentage (100%) of unsure responses (Table 1). Thus, the SE, SP, PPV, NPV, and accuracy of assessment for this radiographic view were not calculated.
Evaluator responses from assessment of 8 radiographic views for 5 completely excised and 5 incompletely excised femurs following femoral head and neck excision.
| Radiographic view of femur | Evaluator responses | Complete excision* | Incomplete excision* | Unsure responses (%) |
|---|---|---|---|---|
| Craniocaudal, standard | Complete | 5 | 3 | NA |
| Unsure | 5 | 1 | 20 | |
| Incomplete | 5 | 11 | NA | |
| External rotation | ||||
| Craniocaudal, 15° | Complete | 10 | 2 | NA |
| Unsure | 0 | 1 | 3 | |
| Incomplete | 5 | 12 | NA | |
| Craniocaudal, 30° | Complete | 12 | 1 | NA |
| Unsure | 1 | 1 | 7 | |
| Incomplete | 2 | 13 | NA | |
| Craniocaudal, 45° | Complete | 12 | 1 | NA |
| Unsure | 1 | 3 | 13 | |
| Incomplete | 2 | 11 | NA | |
| Internal rotation | ||||
| Craniocaudal, 15° | Complete | 0 | 1 | NA |
| Unsure | 13 | 12 | 83 | |
| Incomplete | 2 | 2 | NA | |
| Craniocaudal, 30° | Complete | 0 | 0 | NA |
| Unsure | 15 | 13 | 93 | |
| Incomplete | 0 | 2 | NA | |
| Craniocaudal, 45° | Complete | 1 | 0 | NA |
| Unsure | 14 | 13 | 90 | |
| Incomplete | 0 | 2 | NA | |
| Lateromedial, standard | Complete | 0 | 0 | NA |
| Unsure | 15 | 15 | 100 | |
| Incomplete | 0 | 0 | NA | |
With 3 evaluators assessing 5 completely excised and 5 incompletely excised femurs, there are thus a total of 15 responses for completely excised femurs and 15 responses for incompletely excised femurs for each radiographic view.
NA = Not applicable.
Craniocaudal radiographic view of the femur in internal rotation (15°, 30°, and 45°)—Compared with lateromedial radiographic views, craniocaudal radiographic views of the femur positioned in internal rotation of 15°, 30°, and 45° had the second highest percentage of unsure responses (83% to 93%) with the percentage of unsure responses increasing with increasing degrees of internal rotation (Table 1). As for lateromedial radiographic views, SE, SP, PPV, NPV, and accuracy of assessment for this radiographic view were not calculated because of the inherent inaccuracy associated with the calculations.
Standard craniocaudal radiographic view of the femur—The percentage of unsure responses (20%) was lower for standard craniocaudal radiographic views than for craniocaudal radiographic views of the femur positioned in internal rotation and for lateromedial radiographic views (Table 1). The accuracy of assessment of the standard craniocaudal radiographic view for predicting the true nature of excision was 67% (95% CI, 45% to 84%), and the ability to predict incompleteness of excision (SP, 79%) was greater than the ability to predict completeness of excision (SE, 50%; Table 2).
Sensitivity, SP, PPV, NPV, and accuracy of assessment of femoral neck excision of a standard craniocaudal radiographic view of the femur and craniocaudal radiographic views of the femur in external rotation about the long axis.
| Radiographic view of femur | SE | SP | PPV | NPV | Accuracy (95% CI) |
|---|---|---|---|---|---|
| Craniocaudal, standard | 50% | 79% | 63% | 69% | 67% (45–84) |
| External rotation | |||||
| Craniocaudal, 15° | 67% | 86% | 83% | 71% | 76% (56–89) |
| Craniocaudal, 30° | 86% | 93% | 92% | 87% | 89% (71–97) |
| Craniocaudal, 45° | 86% | 92% | 92% | 85% | 88% (69–97) |
Craniocaudal radiographic view of the femur positioned in external rotation (15°, 30°, and 45°)— Craniocaudal radiographic views with the femur in external rotation had the highest SE, SP, and accuracy of assessment (SE, 67% to 86%; SP, 86% to 92%; and accuracy, 76% to 88%) in predicting adequacy of excision of the various radiographic views obtained (Table 2; Figure 4). Assessment was more accurate for radiographic views of the femur in 30° and 45° (89% and 88%, respectively) of external rotation than for 15° of external rotation (76%), but the differences were not significant. External rotation of 15° resulted in the fewest (3%) unsure responses in our study (Table 1).
Radiographic sequence of a femur with incomplete excision of the femoral neck as follows: craniocaudal view with 15° of external rotation of the femur about the long axis (A), craniocaudal view with 30° of external rotation (B), and craniocaudal view with 45° of external rotation (C). Notice the residual medial distal aspect of the femoral neck from inadequate excision (arrows).
Citation: American Journal of Veterinary Research 67, 1; 10.2460/ajvr.67.1.64
Most useful radiographic views—The single most useful view as ranked by the 3 evaluators was the craniocaudal radiographic view of the femur in 45° of external rotation; 2 evaluators ranked it as the most useful radiographic view for evaluation of incomplete FHNE on 9 of 15 and 7 of 15 selected radiographs, respectively. Craniocaudal radiographic views of the femur in 15° and 30° of external rotation were ranked as 1 of the 3 most useful radiographic views on 14 of 45 (31%) and 15 of 45 (33%) selected radiographs, respectively.
Evaluator consistency—Overall, there was only fair agreement (kappa, 0.31; 95% CI, 0.10 to 0.52) between assessments of the same femurs (ie, femurs B and D) by the evaluators initially and 1 week later. Although agreement ranged from 0.17 to 0.48 for the 3 evaluators, no significant difference between kappa estimates was detected. Overall and for each evaluator, no significant (P = 0.63) difference was detected between the rank assessing completeness (1 to 5) assigned initially and 1 week later.
Discussion
Although FHNE is a commonly performed salvage procedure for irreparable conditions of the hip joint, up to 37.1% of dogs have been reported to have residual lameness postoperatively.3 Grossly inadequate resection may be palpable intraoperatively, necessitating further resection; however, subtle inadequacy may not be detected. Our goal was to demonstrate the ability of nonstandard radiographic views to assess the completeness of femoral neck excision with accurate, repeatable, qualitative data. We hypothesized that positioning femurs in extension with external rotation would improve the ability to detect inadequate resection of the medial distal aspect of the femoral neck.
Results of our study indicate that an assessment of adequacy of excision could not be made based on evaluation of lateromedial radiographs, a standard view used in general assessment of the pelvis. Similarly, evaluators were unable to assess adequacy of excision on most of the craniocaudal radiographic views of the femur in 15°, 30°, and 45° of internal rotation. Lateromedial positioning of the femur causes summation and superimposition of the medial distal aspect of the femoral neck on the greater trochanter and the intertrochanteric fossa. Similarly, internal rotation of the femurs causes superimposition of the medial distal aspect of the femoral neck on the intertrochanteric fossa. In other words, the x-ray beam was not tangential to the excised surface; thus, inadequate resection was not observed. This was evidenced by the percentage of unsure responses increasing as the degree of internal rotation increased from 15° to 30° or 45°. The SE, SP, PPV, NPV, and accuracy of assessment were not calculated for these radiographic views because of the inherent inaccuracy associated with calculating these values given the high percentage of unsure responses.
Standard craniocaudal radiographic views in this study are similar to standard ventrodorsal radiographic views used clinically. Evaluators were more confident of their evaluations with this radiographic view than they were with the lateromedial radiographic view and craniocaudal radiographic views of the femur in internal rotation, as indicated by their percentage of unsure responses. The assessment of the standard craniocaudal radiographic view confirmed the true nature of excision in 67% of the cases, leaving a 33% inaccurate interpretation with this radiographic view. Evaluators also were more likely to judge an incomplete excision as incomplete from the standard craniocaudal radiographic view than to judge a complete excision as complete as evidenced by a higher SP and NPV, compared with SE and PPV.
Assessment of craniocaudal radiographic views of the femur in external rotation confirmed the true nature of excision in 76% to 88% of the cases. Craniocaudal radiographic views of the femur in 15° of external rotation had the lowest percentage of unsure responses of all radiographic views with SE, SP, PPV, NPV, and accuracy of assessment being considerably higher than for standard craniocaudal radiographic views. However, craniocaudal radiographic views of the femur in 30° and 45° of external rotation were especially accurate in predicting completeness of excision. The craniocaudal radiographic view of the femur in 45° of external rotation was ranked the single most useful view, and craniocaudal radiographic views of the femur in 15° and 30° of external rotation were ranked the most useful radiographic views overall on the basis of evaluator assessments. External rotation of the femur accentuates the medial cortex of the excised neck; thus, inadequate excision was detected. With excessive external rotation, the x-ray beam may no longer be tangential to the excised surface. This may be why external rotation from 30° to 45° did not significantly improve the SE, SP, PPV, NPV, and accuracy of assessment.
Assessment of radiographic sequences on 2 randomly chosen femurs (femur B, complete; femur D, incomplete) was repeated 1 week later to assess evaluator consistency. The kappa statistic provided a method to assess agreements within the observer (intraobserver) from 1 evaluation to the next. The kappa statistic indicated only fair agreement between evaluations in our study. Complete excision was consistently evaluated as being complete; however, evaluation of the incomplete excision varied between unsure and incomplete.
Fair agreements in kappa statistics when assessing intraobserver consistency during radiographic interpretation are not uncommon. Inconsistent kappa agreements have been reported in both human and veterinary medicine. A review of human orthopedic literature over the last 10 years indicates good to excellent kappa agreements in some studies,22–26 fair to poor agreements in others,27–30 and mixed results (good, fair, and poor agreements in kappa statistics) within the same study when evaluating different radiographic aspects.31 Similarly, results from a recent veterinary orthopedic study32 by use of kappa statistics to assess intraobserver variability indicated mixed results within the same study. In our study, one explanation for this discrepancy is that the evaluators received a training session prior to the first evaluation and received none prior to the second evaluation. The effect of a training session prior to both evaluations was not examined. Given the use of nonstandard radiographic views, results may suggest a need for more than 1 training session. Access to radiographic sequences of complete and incomplete excisions with a radiopaque marker denoting the medial cortex during evaluations may have improved consistency and accuracy by having a source for comparison available.
All angles were confirmed once the femurs were positioned in the orthogonal frame by use of a goniometer and protractor. Despite these precautions, potential sources of errors include femur positioning and angle measurement. The x-ray beam in all radiographic views in our study was centered on the midshaft of the femur to include the femoral condyles (important in evaluator assessment of internal vs external rotation) on the film. We did not examine the effect of centering the beam on the hip joint on SE, SP, PPV, NPV, and accuracy of assessment.
One consideration when performing traditional ventrodorsal radiographic views16 on dogs after FHNE is that internal rotation of the stifle joints may obscure the medial distal aspect of the femoral neck cortex as a result of superimposition and summation on the intertrochanteric fossa as the x-ray beam is no longer tangential to the excised surface. Degenerative changes in dogs with hip dysplasia, aseptic necrosis of the femoral head, and chronic hip fractures may impede the ability to extend the hind limbs fully such that they are parallel to the cassette and may also restrict the ability to externally rotate the femur.
In our study, we were able to demonstrate that assessment of craniocaudal radiographic views of the femur in external rotation increased SE, SP, PPV, NPV, and accuracy of assessment relative to assessment of standard radiographic views. Results of our study indicate that use of nonstandard radiographic views of femurs with external rotation for dogs with FHNE may result in an improvement in the ability of the evaluator to assess adequacy of excision. The focus of our study was to study medium- to large-breed dogs (> 20 kg); similar studies in small dogs (< 20 kg) and cats are necessary. From the results of our study, a follow-up study will include clinical evaluation of dogs with FHNE by use of craniocaudal radiographic views of the pelvis with the femurs placed in a range of 15° to 45° of external rotation.
| FHNE | Femoral head and neck excision |
| SE | Sensitivity |
| SP | Specificity |
| PPV | Positive predictive value |
| NPV | Negative predictive value |
| CI | Confidence interval |
References
- 1↑
Hauptman J. The hip joint. In: Slatter DH, ed. Textbook of small animal surgery. Vol 2. Philadelphia: WB Saunders Co, 1985; 2153–2179.
- 2↑
Vasseur PB. Femoral head and neck ostectomy. In: Bojrab MJ, ed. Current techniques in small animal surgery. 3rd ed. Philadelphia: Lea &Febiger, 1990; 674–683.
- 3↑
Gendreau CCawley AJ. Excision of the femoral head and neck: the long-term results of 35 operations. J Am Anim Hosp Assoc 1977; 13: 605–608.
- 4↑
Duff RCampbell JR. Long-term results of excision arthroplasty of the canine hip. Vet Rec 1977; 101: 181–184.
- 5
Lippincott CL. Improvement of excision arthroplasty of the femoral head and neck utilizing a biceps femoris muscle sling. J Am Anim Hosp Assoc 1981; 17: 668–672.
- 6
Tarvin GLippincott CL. Excision arthroplasty for the treatment of canine hip dysplasia using the biceps femoris muscle sling: an evaluation of 92 cases. Semin Vet Med Surg (Small Anim) 1987; 2: 158–160.
- 7
Lippincott CL. Excision arthroplasty of the femoral head and neck utilizing a biceps femoris muscle sling. Part II: the caudal pass. J Am Anim Hosp Assoc 1984; 20: 377–384.
- 8↑
Olsson SEFigarola FSuzuki K. Femoral head excision arthroplasty. A salvage operation in severe hip dysplasia in dogs. Clin Orthop Relat Res 1969; 62: 104–112.
- 9
Berzon JLHoward PECovell SJ, et al.A retrospective study of the efficacy of femoral head and neck excisions in 94 dogs and cats. Vet Surg 1980; 9: 88–92.
- 10
Duff RCampbell JR. Radiographic appearance of clinical progress after incision arthroplasty of the canine hip. J Small Anim Pract 1978; 19: 439–449.
- 11
Lewis DDBellah JRMcGavin MD, et al.Postoperative examination of biceps femoris muscle sling used in the excision of the femoral head and neck in dogs. Vet Surg 1988; 17: 269–277.
- 12
Remedios AMClayton HMSkuba E. Femoral head excision arthroplasty using the vascularized rectus femoris muscle sling. Vet Comp Orthop Trauma 1994; 7: 82–87.
- 13
Montgomery RDMilton JLHorne RD, et al.A retrospective comparison of three techniques for femoral head and neck excision in the dog. Vet Surg 1987; 16: 423–426.
- 14
Bjorling DEChambers JN. The biceps femoris flap and femoral head and neck excision in dogs. Compend Contin Educ Pract Vet 1986; 8: 359–364.
- 15↑
Plante JDupuis JBeauregard G, et al.Long-term results of conservative treatment, excision arthroplasty and triple pelvic osteotomy for the treatment of hip dysplasia in the immature dog. Part I: radiographic and physical results. Vet Comp Orthop Trauma 1997; 10: 101–110.
- 16↑
Allan G. Radiographic signs of joint disease. In: Thrall DE, ed. Textbook of veterinary diagnostic radiology. 4th ed. Philadelphia: WB Saunders Co, 2002; 190–196.
- 17
Lippincott CL. Femoral head and neck excision in the management of canine hip dysplasia. Vet Clin North Am Small Anim Pract 1992; 22: 721–737.
- 18
Schulz KSVasseur PBStover SM, et al.Transverse plane evaluation of the effects of surgical technique on stem positioning and geometry of reconstruction in canine total hip replacement. Am J Vet Res 1998; 59: 1071–1079.
- 19
Ruff CBHayes WC. Cross-sectional geometry of Pecos Pueblo femora and tibiae—a biomechanical investigation: I. Method and general patterns of variation. Am J Phys Anthropol 1983; 60: 359–381.
- 20↑
Jehn CTBergh MSManley PA. Orthogonal view analysis for evaluating the femoral component position of total hip implants in dogs using postoperative radiographs. Vet Surg 2003; 32: 134–141.
- 21↑
Cannon RMRoe RT. Livestock disease surveys: a field manual for veterinarians. Canberra, Australia: Australian Government Publishing Service, 1982; 27–29.
- 22
Herring JAKim HTBrowne R. Legg-Calve-Perthes disease. Part I: classification of radiographs with use of the modified lateral pillar and Stulberg classifications. J Bone Joint Surg Am 2004; 86A: 2103–2120.
- 23
Beaule PEDorey FJMatta JM. Letournel classification for acetabular fractures. Assessment of interobserver and intraobserver reliability. J Bone Joint Surg Am 2003; 85A: 1704–1709.
- 24
Omeroglu HAgus HBicimoglu A, et al.Analysis of a radiographic method of acetabular cover in developmental dysplasia of the hip. Arch Orthop Trauma Surg 2002; 122: 334–337.
- 25
Ali AMAngliss RFuji G, et al.Reliability of the Severin classification in the assessment of developmental dysplasia of the hip. J Pediatr Orthop 2001; 10: 293–297.
- 26
Nelitz MGuenther KPGunkel S, et al.Reliability of radiological measurements in the assessment of hip dysplasia in adults. Br J Radiol 1999; 72: 331–334.
- 27
Schmidt GLAltman GTDougherty JT, et al.Reproducibility and reliability of the anatomic axis of the lower extremity. J Knee Surg 2004; 17: 141–143.
- 28
Pervez HParker MJPryor GA, et al.Classification of trochanteric fracture of the proximal femur: a study of the reliability of current systems. Injury 2002; 33: 713–715.
- 29
Remy FChantelot CFontaine C, et al.Inter-and intraobserver reproducibility in radiographic diagnosis and classification of femoral trochlear dysplasia. Surg Radiol Anat 1998; 20: 285–289.
- 30
McCaskie AWBrown ARThompson JR, et al.Radiological evaluation of the interfaces after cemented total hip replacement. Interobserver and intraobserver agreement. J Bone Joint Surg Br 1996; 78B: 191–194.
- 31↑
Schipper IBSteyerberg EWCastelein RM, et al.Reliability of the AO/ASIF classification for pertrochanteric femoral fractures. Acta Orthop Scand 2001; 72: 36–41.
- 32↑
Innes JFCostello MBarr FJ, et al.Radiographic progression of osteoarthritis of the canine stifle joint: a prospective study. Vet Radiol Ultrasound 2004; 45: 143–148.
