Reliability, validity, and responsiveness of the lower extremity measure for patients with a hip fracture.

BACKGROUND: The purpose of this study was to determine whether currently published outcome measures of physical function would be suitable for use for older adults with a hip fracture. The measures that were considered were the Musculoskeletal Function Assessment (MFA) Instrument, the Older Americans' Resources and Services (OARS) Multidimensional Functional Assessment Questionnaire physical function subscale, the Toronto Extremity Salvage Score (TESS), and the Short Form-36 (SF-36). Following suggestions by an expert panel and patient interviews, the MFA was not tested further. The TESS was modified and renamed the Lower Extremity Measure (LEM). METHODS: Forty-three community-dwelling patients with a hip fracture completed the LEM, OARS, and SF-36 in the hospital so that the prefracture status could be obtained; they were then followed prospectively at six weeks and at six months. All patients were interviewed twice in the hospital to assess the reliability of the LEM (intraclass correlation coefficient = 0.85). To establish criterion validity, the measures were compared with the Timed Up and Go (TUG) test at six weeks. We tested a number of hypotheses to determine construct validity. RESULTS: Only the LEM scores were significantly correlated with the TUG scores (r = -0.53, p = 0.03). The LEM scores were significantly correlated with the SF-36 subscale scores and the OARS scores. Patients with at least one comorbidity had a lower mean prefracture LEM score (90.0 +/- 9.7) than patients with no comorbidity (96.9 +/- 8.1) (p = 0.02). Patients who had used no walking aids before the fracture had a higher mean prefracture LEM score than those who had used a cane (95.5 +/- 5.8 compared with 85.5 +/- 12.7; p = 0.0007). Both the LEM and the SF-36 scores changed significantly between all of the time-periods (p < 0.05). Measures of responsiveness indicated that the LEM was the best measure for detecting changes in physical function. CONCLUSIONS: The LEM can detect clinically important changes in physical function over time in patients with a hip fracture and would be most useful for clinical trials or cohort studies. Orthopaedists who are currently utilizing the SF-36 can be reassured that the physical function subscale is a valid measure for patients with a hip fracture.

Acetabular revision. The role of rings and cages.

This study reports on the successful long-term use of the acetabular roof ring and the antiprotrusio cage in acetabular reconstruction in which the hip center and acetabular biomechanics are normalized and bone stock is restored through the use of morselized allograft. The failure rate of the acetabular roof ring used in 57 patients who were followed up for a mean of 8.3 years was 12.5%. The failure rate of the antiprotrusio cage used in 38 patients who were followed up for a mean of 6.6 years was 5.4%. The higher failure rate of the acetabular roof ring resulted from its inappropriate use in patients with medial wall deficiency and protrusio. The acetabular roof ring is indicated for patients with isolated peripheral segmental or cavitatory defects. The antiprotrusio cage is indicated for patients with extensive combined segmental and cavitatory defects but particularly for those patients with protrusio and medial segmental bone loss. Both methods have given a high degree of success for evaluation of implant specific, patient subjective, and global health status instruments such as the Short Form-36.

Economic evaluations in the hip arthroplasty literature: lessons to be learned.

Readers are increasingly encountering articles dealing with health economic evaluations that compare various surgical strategies, leaving orthopaedists with the challenge of determining which program is cost-efficient and truly pertains to their setting. This study carries out a systematic review of the literature to appraise the quality, quantity, and type of economic evaluation as it pertains to the hip arthroplasty literature. To identify all relevant articles, we conducted a comprehensive computerized bibliographic search of Medline from 1966 to 1996. This search produced 1,611 abstracts that were screened. Studies that were incorporated met the following inclusion criteria: i) formal economic analysis, ii) an intervention specific to hip arthroplasty, and iii) the perspective of the study was evident (ie, patient, provider, society). These studies were appraised with regards to methodologic soundness based on 8 established economic principles. Only 68 articles from the 138 retrieved met the study criteria. Only 2 of the 68 articles met all 8 criteria of a comprehensive economic evaluation. The hip arthroplasty literature is deficient in methodologically sound economic evaluations. Several guidelines are introduced to aid orthopaedists in appraising the various economic studies, and recommendations are made to improve the quality of these studies in the orthopaedic literature. We suggest that the generation of such information should rank high on the priority list of the orthopaedic profession, granting agencies, and governments.

Understanding economic evaluations: a review of the knee arthroplasty literature.

The study reviewed the literature to appraise the quality, quantity, and type of economic evaluation as it pertains to the knee arthroplasty literature. A computerized bibliographic search of MEDLINE from 1966-1996 was conducted, revealing a total of 43,178 articles dealing with cost analysis, of which 1611 were orthopedic. Of the economic orthopedic studies, only 63 dealt with the topic of knee arthroplasty. These studies were retrieved, of which only 40 papers met the inclusion criteria. These 40 studies were evaluated for methodological soundness based on established economic principles. None of the 40 studies met the established criteria to form a comprehensive economic evaluation. These results indicate that the orthopedic literature is lacking in economically sound evaluations, and guidelines are offered to aid orthopedists in appraising and improving the quality of economic studies.

Predictors of early failure of fixation in the treatment of displaced subcapital hip fractures.

OBJECTIVE: To examine predictors of fixation failure in the treatment of displaced subcapital hip fractures. DESIGN: Retrospective study. METHODS: All patients aged sixty-five years and older discharged from a large teaching hospital after treatment for displaced subcapital fracture between April 1, 1989 and February 29, 1995 were identified (n = 344). Of these, 108 patients treated with internal fixation became the study group. Clinical information included demographics, implant, comorbidity, complications, mortality, surgeon' s assessment of reduction, and need for revision. Preoperative x-ray information: Garden grade, Singh Index, Pauwel's angle, medial neck and femoral shaft cortex width, and displacement of fracture fragments. Postoperative: Quality of reduction, a visible gap or step, evidence of union, fracture collapse, and failure. RESULTS: The failure rate was 31 percent. The two most important predictors were varus reduction and perceived difficulty in achieving reduction. If the patient had a varus reduction or the surgeon had difficulty achieving a satisfactory reduction, fixation was 4.3 times more likely to fail (p = 0.007). If the patient had a varus reduction and reduction was difficult, fixation was 13.6 times more likely to fail (p = 0.04). Under this latter scenario, 75 percent of the fixations failed. CONCLUSION: In a fracture of the neck of the femur, if difficulty is encountered in obtaining a closed reduction or there is residual varus angulation, the chance of subsequent fixation failure is high. Hemiarthroplasty may be considered in these cases.

Fractures of the distal femur revisited.

The treatment of supracondylar fractures is presented, including the most recent developments. The author uses the comprehensive classification of these fractures and explains the method of this classification scheme as a guide to treatment. New surgical approaches and a discussion of the surgical anatomy are presented in detail. The traditional and contemporary methods of reduction and fixation are discussed, and how the need to preserve the blood supply to the soft tissues and bone has led to the development of the modern methods. The biologic and biomechanical reasons for absolutely stable fixation for simple fractures and splinting with bridging plates, the so called bridge plating of multifragmentary fractures are explained as are the technical details of fixation. Discussed in detail are specific variations in treatment methods for the particularly difficult problem of open fractures, fractures above total knee arthroplasty, and fractures in osteoporotic bone.

Temporal trends and geographic variations in surgical treatment of femoral neck fractures.

BACKGROUND: The objectives of this study were to examine temporal trends in treatment of femoral neck fractures, factors associated with treatment, and variations in practice patterns among counties and hospitals in Ontario, Canada. METHODS: Hospital discharge data were analyzed. Cases were defined as age > 50 years with a surgically treated femoral neck fracture between 1981 and 1992 (n = 29,391). RESULTS: The age-adjusted and sex-adjusted proportion of patients treated with hemiarthroplasty (HA) increased from 45% in 1981 to 61% in 1992 (p < 0.0001). HA is more likely to be performed among women, older patients, and nursing home patients. Among counties there was a 38-fold variation for total hip arthroplasty (0.5-38%) and a 9-fold variation in use of HA (9-83%). The degree of variation in treatment was mainly the result of individual hospitals. CONCLUSION: The wide regional variations in treatment of femoral neck fractures reflect a lack of consensus in Ontario.

An orthopedic surgeon survey on the treatment of displaced femoral neck fracture: opposing views.

OBJECTIVE: To examine the reasons for practice variation in the treatment of displaced femoral neck fractures. DESIGN: A survey, asking surgeons to choose either hemiarthroplasty or internal fixation for 2 different female patients with a displaced femoral neck fracture. SETTING: The Canadian Orthopaedic Association Meeting, Halifax, May 1995. PATIENTS: The scenario in the first patient was of an independent 70-year-old woman with no pre-existing medical conditions. The scenario in the second patient was of a housebound 84-year-old woman with co-morbidity. MAIN OUTCOME MEASURES: Proportion of surgeons choosing either hemiarthroplasty or internal fixation for each case scenario. Distribution of reasons to explain the treatment decision. RESULTS: Ninety-nine surgeons responded. For the case of the 70-year-old woman, 47% chose hemiarthroplasty and 53% chose internal fixation (p = 0.60), and for the 84-year-old woman, 96% chose hemiarthroplasty. These findings were consistent within the subgroups of teaching surgeons and community practice surgeons. Surgeons with 10 years or less of practice tended to favour hemiarthroplasty whereas those with more than 15 years' practice favoured internal fixation. Important reasons for treatment choice were avoidance of reoperation in the hemiarthroplasty group (85%) and better hip function in the fixation group (83%), durability (83%) and ease of revision (77%). CONCLUSION: The surgeon's interpretation of the importance of reoperation and function underlies the differences in treatment decision regarding the management of femoral neck fractures in elderly patients.

Appropriateness of primary total hip and knee replacements in regions of Ontario with high and low utilization rates.

OBJECTIVE: To compare the appropriateness of case selection for primary hip and knee replacements between two regions in Ontario: one with a high population-based utilization rate and one with a low rate. DESIGN: Random audit of medical records sampled from hospital discharge abstracts, with subsequent implicit and explicit criteria-based assessments of the appropriateness of surgery. STUDY POPULATION: People aged 60 years or over who underwent elective, single-joint, non-fracture-related, primary hip or knee replacement between Apr. 1, 1992, and Mar. 31, 1993, at one of seven hospitals in a high-rate region (comprising Brant, Huron and Oxford countries) or one of eight hospitals in a low-rate region (comprising the cities of Scarborough and Toronto). INTERVENTIONS: Structured review of hospital medical records, with additional review of information from surgeons and family physicians' office charts if necessary. Three physicians reviewed patient data and rated the preoperative pain level and functional status of patients, with agreement among at least two reviewers. The proportion of inappropriate cases was then assessed according to explicit criteria defined by a multidisciplinary panel using the delphi process. Profiles of each case were also subjected to independent implicit review by two rheumatologists and two orthopedic surgeons. OUTCOME MEASURES: Proportion of joint replacements deemed inappropriate in the high- and low-rate regions according to either the explicit criteria or the implicit review, as well as preoperative pain levels and functional status of patients in the high- and low-rate regions. RESULTS: Hip replacements were more common among patients sampled in the low-rate region than among those in the high-rate region (57.3% v. 39.3%; p < 0.002), although the patients' baseline characteristics, including severity of preoperative pain and dysfunction, were otherwise similar between the regions. Inappropriate surgery, determined by explicit criteria, was equally uncommon in the two regions (6.4% and 6.1%). On implicit review, the two rheumatologists rated fewer cases as appropriate than did the two orthopedic surgeons (63.0% v. 80.0%; p < 0.001); however, the proportion of cases rated as inappropriate by the subspecialists was similar in the high- and low-rate regions (11.4% and 11.0%, respectively, by the rheumatologists, and 6.3% and 10.4%, respectively, by the orthopedic surgeons). CONCLUSIONS: Patients selected for primary hip or knee replacement are similar in the high- and low-rate regions of Ontario. Inappropriate use of this procedure does not account for the high rate of surgery in some areas. Further studies will be required to determine which other factors account for the regional variations in the utilization rates and whether there is underservicing in low-rate areas.

The impact and consequences of hip fracture in Ontario.

OBJECTIVES: To assess the magnitude and the burden of hip fracture on the health care system, including time trends in hip fracture rates, in-hospital death rates, length of hospital stay (LHS) and discharge destination. DESIGN: A retrospective study of discharge abstracts. SETTING: The Province of Ontario. PATIENTS: All patients (n = 93,660) over the age of 50 years and with a diagnosis of hip fracture discharged from hospital between 1981 and 1992 (excluding transfers). MAIN OUTCOME MEASURES: Age-sex standardized hip fracture rates per 1000 population, in-hospital death rates and age-adjusted mean LHS. RESULTS: The overall hip fracture rate was 3.3 per 1000 persons (1.7 per 1000 men and 4.6 per 1000 women). There was no change in rates between 1981 and 1992 (p = 0.089), but there have been increases in the numbers of hip fractures. There was no change in the in-hospital death rate over time (p = 0.78). The age-adjusted mean LHS in 1981 was 28.6 days compared with 22.2 days in 1992. The numbers of hip fractures will increase from 8490 in 1990 to 16 963 in 2010. CONCLUSIONS: Despite stable age-adjusted rates of hip fractures, the doubling of the number of hip fractures by the year 2010 due to an aging population will become an increasing burden on the health care system.

Sample size estimates for the use of human bone in the experimental study of cancellous screw extraction mechanics.

Cancellous bone screw extraction strengths are determined in four matched anatomical locations in five pairs of unembalmed human distal femora. The results are used to calculate sample size estimates for the experimental detection of differences in screw extraction mechanics. While unmatched designs require prohibitively large numbers of bone specimens, matched designs require between 71.6 and 88.5% fewer, depending on the correlation between matched observations and the homogeneity of sample variances.

Radiographic appearance and structural properties of proximal femoral bone in total hip arthroplasty patients.

The relationship between the morphology of the proximal femur and the physical properties of intertrochanteric trabecular bone was assessed in 26 patients undergoing total hip arthroplasty. Significant correlations were found between ash density and (1) Singh index, (2) "calcar-to-canal isthmus ratio," and (3) a modified "morphologic cortical index." Despite this, these radiographic indices accounted for only 30% of the variability in bone density and are therefore of limited predictive value in this context. Two indices of cortical morphology were at least as effective as the Singh index in predicting cancellous bone density. Surgeons using these indices to quantify the morphology and structure of proximal femoral bone should be aware of their limitations when selecting patients for cementless arthroplasty.

The strength of plate fixation in relation to the number and spacing of bone screws.

Our purpose was to study the relationship between the number of plate holes filled and the spacing between the screws and the resultant strength of plated constructs. Broad regular DC plates were anchored with 4.5-mm cortical screws to blocks of polyurethane foam. Six constructs were tested: (a) screws in holes 1, 2, and 3; (b) screws in holes 1 and 3; (c) screws in holes 1 and 4; (d) screws in holes 1 and 5; (e) screws in holes 1 and 6; (f) screws in holes 1, 3, and 5. The strength was quantified using a material-testing system. In cantilever and four-point bending, the constructs were loaded in both gap-closing and gap-opening modes. Screws in holes 1, 2, and 3 were tested against other constructs. For cantilever bending (gap opening and gap closing), construct (a) was stronger than construct (b), as strong as construct (c), but weaker than the constructs with more widely spaced screws (p < 0.0001). In terms of four-point bending, for gap opening, the standard fixation (construct (a) was stronger than construct (b) but weaker than the more widely spaced constructs. For gap closing, construct (a) was stronger than constructs (b) and (c) but weaker than the rest. Regardless of the spacing of screws and the plate length, strength in torsion was dependent on the number of screws securing the plate. In a laboratory fracture model of plate-bone constructs tested to failure by screw pullout, wider spacing of bone screws increases the bending strength of screw-plate fixation and can be more effective than increasing the number of screws. Torsional strength is independent of screw placement in plates of a given width and depends on the number of screws used.

Ceramic head failure.

A case of abrupt failure of the ceramic head component of a total hip arthroplasty is reported. The prosthesis had been inserted more than 5 years previously and had functioned well until its abrupt failure. At revision, the metal femoral and acetabular components were intact and well fixed. The broken ceramic head was replaced with a metal component, and the polyethylene liner replaced with a new one.

Osseointegration of metal.

The healing response of bone to the injury of implant insertion is similar to its response to fracture. If there is absolute stability between the bone and the implant, the injury to the bone will result in bone formation, the bone growing and conforming to the surface configuration of the implant. There is first appositional bone growth and subsequently bone ingrowth into the interstices of the surface. The newly formed bone is not an uninterrupted layer of bone. It is mixed with well-differentiated fibrous tissue; only 13% to 20% of the bone is in contact with the implant. If the implant is relatively stable after insertion the healing response results in the implant becoming enveloped by dense organized fibrous tissue with occasional areas of fibrocartilage, without any areas of resorption in the surrounding bone. If the implant is unstable after insertion the healing response causes the implant to become surrounded by loosely organized fibrous tissue with active bone resorption occurring in the surrounding bone.

Rapidly destructive arthropathy followed by heterotopic ossification. A case report and literature review.

This is the first reported case of heterotopic ossification following total hip replacement for bilateral, rapidly destructive arthropathy of the hip. The aetiological theories of this rare condition are discussed, particularly with reference to this complication.

A case of fracture of a ceramic head in total hip arthroplasty.

We report a case of fracture of a ceramic femoral head, which spontaneously occurred 4 years after implantation of an uncemented total hip replacement in a 48-year-old male patient with avascular necrosis of the hip. At revision surgery, the fractured ceramic head was replaced with a 32-mm metallic femoral head.

Biomechanical analysis of a distally interlocked press-fit femoral total hip prosthesis.

This study was undertaken to compare the stability of a distally interlocked femoral prosthesis to a standard press-fit implant (Cementless Spotorno, Protek Co., Toronto, Canada). Five human femora were studied with each acting as its own control. All were tested in the locked mode followed by unlocked testing modes. The MTS 858 Biomaterials Testing System was used to test the implanted femoral stems under both pure torsional and pure axial loading. Distal interlocking increased the torsional stability by 320% (locked 4.05 Nm/degree; unlocked 1.25 Nm/degree) (P < .01) and the axial stability by 230% (locked 1,236.26 N/mm; unlocked 527.44 N/mm) (P < .01). the use of temporary distal interlock in cases where the initial stability of a press-fit implant is suboptimal should allow for improved biological fixation by minimizing micromotion at the stem-bone interface.

Extraction strength of cannulated cancellous bone screws.

The purpose of this study was to determine whether the alterations in the relative dimensions of thread and core diameter that accompany cannulation of cancellous bone screws affect their holding strength. The screws were inserted in bovine femoral cancellous bone and mounted in the load train of a materials testing system. They were then extracted under servo-hydraulic displacement control. The tests were repeated in synthetic cancellous material. From the corresponding load-displacement histories, the maximum force values attained were determined as the screws' holding strengths. The results of tests from 17 matched pairs of bovine femora, and of 15 tests of each screw in synthetic material, were recorded. No significant differences in extraction strength between 7.0-mm cannulated and 6.5-mm standard cancellous bone screws were found. Based on tests in the bovine femur and synthetic cancellous material, this study showed that the extraction strength of cancellous bone screws is not altered by the changes in thread-to-core ratio accommodating cannulation.