Minimizing tip-apex distance has been shown to reduce clinical failure of sliding hip screws used to fix peritro-chanteric fractures. The purpose of this study was to determine if such a relationship exists for the position of the lag screw in the femoral head using a cephalomedullary device.
Superior (N=6), Inferior (N=6), Anterior (N=6), Posterior (N=6), Central (N=6). Mechanical tests were repeated for axial, lateral and torsional stiffness. All specimens were radiographed in the anterioposterior and lateral planes and tip-apex (TAD) distance was calculated. A calcar referenced tip-apex distance (CalTAD) was also calculated. ANOVA was used to compare means of the five treatment groups. Linear regression analysis was used to compare axial, lateral and torsional stiffness (dependant variables) to both TAD and CalTAD (independent variables).
The use of metal on polyethylene articulations was a key development in establishing total hip arthroplasty as a successful and reproducible treatment for end stage osteoarthritis. In order to ensure implant durability in relatively younger populations, there is a need for alternative, wear resistant bearing surfaces. Oxidized Zirconium (Oxinium, Smith &
Nephew, Inc., Memphis, TN) is a relatively new material that features an oxidized ceramic surface chemically bonded to a tough metallic substrate. This material has demonstrated the reduced polyethylene wear characteristics of a ceramic, without the increased risk of implant fracture. The purpose of the current investigation was to assess early clinical outcomes following primary total hip arthroplasty with Oxinium versus Cobalt Chrome femoral heads. One-hundred primary THA procedures were prospectively performed in 100 patients. There were 52 males and 48 females. Using a process of sealed envelope randomization, patients were divided into 2 groups. Group 1 consisted of fifty patients, each receiving primary THA implants with an Oxinium femoral head (OX). The mean age of each patient was 51 years (SD 10.8, Range 22–74) with 26 males and 24 females. Group 2 also consisted of 50 patients. Within this group again each patient received primary THA implants however with a cobalt-chrome femoral head (CC). Demographics were similar with mean age 51 years (SD 11.0, Range 19–76) and again 26 males and 24 females. The current study reports clinical outcome measures for both the OX and CC groups at a minimum follow-up of 2 years postoperatively. At the time of latest follow-up, stem survival for both groups was 98%. There was a significant improvement in all clinical outcome scores between preoperative and 2 year postoperative time periods for both bearing groups (p<
0.003). There were no significant differences between bearing groups for any of the clinical outcome scores at final follow-up (p>
0.159). Mean Harris Hip Scores at 2 years postoperatively were 92 and 92.5 for OX and CC, respectively (range; 65–100 OX, 60–100 CC). For SF-12, both the Physical Component Summary Scale (PCS) and the Mental Component Summary Scale (MCS) are reported. Mean PCS scores at final follow-up were 45.2 and 49.21 for OX and CC (range; 27.1–56.7 OX, 26.3–61.8 CC). Mean MCS scores were 53.8 and 52.57 for OX and CC (range; 39.2–65.5 OX, 34.3–64 CC). Mean final WOMAC scores are reported as 84.9 and 87 for OX and CC, respectively. The current data suggest that total hip arthroplasty utilizing Oxinium femoral heads is safe and effective. Additional follow-up of the current cohort will be performed in order to fully assess mid- to long-term clinical outcomes.
Total hip replacement in the young active patient remains one of the major challenges in orthopaedics today. The use of ultra high molecular weight (UHMW) polyethylene acetabular liners is known to cause polyethylene wear related osteolysis, the major limiting factor in its use in the younger active patient. Modern alumina ceramic articulations have been developed in order to reduce wear and avoid polyethylene debris. This prospective randomized long-term study aims to compare the outcome between an alumina ceramic-on-ceramic (CC) articulation with a ceramic on UHMW polyethylene articulation (CP). In the younger active patient, is one option superior to the other with regard to patient satisfaction, osteolysis and implant longevity? 56 hips in 55 patients with mean age 42.2 (range 19–56) each received uncemented components (Wright Medical) and a 28mm alumina head with acetabular liner selected via sealed envelope randomization following anesthetic induction. Subsequent regular clinical and radiologic follow up measured patient outcome scores and noted any radiological changes. 26 CP hips and 30 CC hips were evaluated. One failure required revision in each group. Mean St Michael’s outcome score for each group with up to 10 years follow-up (median 8 years, range 1–10) was 22.8 and 22.9 respectively (p=0.057). Radiographs with a minimum 5 years post-operative follow-up were analyzed in 42 hips (23 CC and 19 CP). Radiolucency of all 3 acetabular zones was identified in one of the CP hips. There was no evidence of osteolysis or loosening identified in the remaining hips. The mean time of wear measurement for the CC group was 8.3 years (SD 1.3, Range 4.8–10.1 years) and for the CP group was 8.1 years (SD 0.9, Range 6.1–9.2 years)(p=0.471). Wear was identified in all but one of the CP replacements but only 12 of 23 CC articulations. The mean wear for the CC group was 0.14 mm (SD 0.16, Range 0–0.48 mm) and for the CP group was 0.89 mm (SD 0.6, Range 0–2.43 mm)(p<
0.001). Extrapolating the annual wear rate from these figures, the respective wear is 0.02mm for the CC group compared to 0.11mm per year for the CP group. To our knowledge this is the first long term randomized trial comparing in vivo ceramic-on-ceramic with ceramic-on-conventional polyethylene hip articulations. Other than significantly greater wear in the polyethylene group there was no significant difference in long-term outcome scores between the two groups with up to 10 years of follow-up. The use of a ceramic-on-ceramic bearing is a safe and durable option in the young patient avoiding the concerns of active metal ions and osteolytic polyethylene debris. These patients remain under review.
The effect of cup geometry in uncemented Total Hip Arthroplasty has not been investigated. We reviewed the radiological and clinical results of 527 primary total hip arthroplasties. We assessed the bone ingrowth potential of two geometric variations of an uncemented cup and compared hydroxyappetite and porous coated shells. Patients undergoing primary hip arthroplasty between 1997 and 2004 were prospectively entered into an arthroplasty database. Patients were reviewed at 1,2,4,5,8 and 10 years post surgery. Three acetabular shell types were used. These included hemispherical cups with porous or hydroxyapatite coating, and cups with peripheral expansion with porous coating. Radiographs with minimum 1-year follow-up were examined in 542 cases, using digital templating software. Radiographs were assessed for signs of bone in-growth, lucent lines, migration and polyethylene wear. Survivorship analysis was performed using Kaplan-Meier analysis with 95% confidence intervals. Radiological findings and cup type were analysed using Fishers exact test. Radiological evidence of bone ingrowth was seen in 82% of hemispherical cups, compared with 59% of peripherally expanded cups, which was significant (p,0.05). Bone ingrowth was not affected by the presence of HA coating. The most common diagnoses were osteoarthritis (67%) and avascular necrosis (12%). The mean age was 56 years. Survivorship with revision or impending revision for aseptic loosening was 95.6% at 7 years (95%CI 1.0134-0.8987). The 3 revisions and 1 impending revision for loosening were in patients with avascular necrosis (3) or previous acetabular and femoral osteotomies for DDH (1), with a mean age of 44 years. Hemispherical shells have improved radiographic outcome in comparison with peripherally expanded components. At 7 years, clinical results are similar for both components.
In perfroming hip resurfacing arthroplasty, concern has been expressed as to the proximity of the femoral neurovascular bundle during the anterior capsulotomy and the risk of damage during this maneuver. We therefore aimed to identify the proximity of the femoral nerve, artery and vein during an anterior capsulotomy done during a hip resurfacing procedure using the posterior approach. A standard posterior approach was performed in 5 fresh frozen cadavic limbs. An anterior incision was then used to measure the distance of the femoral neurovascular structures to the anterior capsule. Measurements from the most posterior aspect of the vessels and nerves to the most anterior aspect of the anterior capsule were taken prior to hip dislocation. The femoral head was then dislocated, and measurements were made with the hip in both flexion and extension. In a separate group of eleven patients that underwent routine MR imaging of the hip, measurements were taken to assess the proximity of the anterior joint capsule to the femoral neurovascular bundle, by a specialist musculoskeletal radiologist who had no prior knowledge of the results obtained during the cadaveric dissection All 5 cadaveric limbs were utilised. 3 were male and 2 were female. The average age was 72.4 years (range 56–84). The patients whom underwent routine MR imaging incorporated 6 males and 5 females with a mean age of 43.7 years (age range 18–64 years). There was no significant difference between the mean distances to the nerve (p=0.21), artery (p=0.21) or vein (p=0.65) between the MR and cadaveric groups. Prior to dislocation the femoral artery and vein were closest to the anterior capsule (mean distance of 21mm) and the femoral nerve was the furthest away (mean distance 25mm). Following dislocation there was a significant increase (25mm to 31mm) in mean distance to the femoral nerve when the superior capsule was cut with the hip in a flexed position (p=0.01) and to the femoral artery in flexion (increase mean distance from 21mm to 35mm) (p<
0.0001) and in extension(increase mean distance from 21mm to 31mm) (p=0.005). When the inferior capsule was cut, there was a significant increase (25mm to 31mm) in mean distance to the femoral nerve and femoral artery when the hip was dislocated and the capsule cut with the hip in flexion (increase mean distance from 21mm to 27mm) (p=0.019) and in extension(increase mean distance from 21mm to 28mm) (p=0.015). This study suggests that the neurovascular structures are relatively well protected during an anterior capsulotomy performed during hip resurfacing. The procedure may be safer if the capsulotomy is performed with the hip dislocated and the hip in a flexed position while cutting the antero-superior aspect and in an extended position while cutting the antero-inferior aspect.
The purpose of this study was to assess the accuracy of clinical assessment compared to imageless computer navigation in determining the amount of fixed flexion during knee arthroplasty. In fourteen cadaver knees, a medial para-patella approach was performed and the navigation anatomy registration process performed. The knees were held in various degrees of flexion with two crossed pins. The degree of flexion was first recorded on the computer and then on lateral radiographs. The cadaver knees were draped as for a knee arthroplasty and nine examiners (three arthroplasty surgeons, three fellows, and three residents) were asked to clinically assess the amount of fixed flexion. Three examiners repeated the process one week later. The mean error from the radiograph in the navigation group was 2.18 degrees (95%CI 2.18+/−0.917) compared to 5.57 degrees (CI 5.57+/− 0.715) in the observer group. The navigation was more consistent with a range of error of only 5.5 degrees (standard deviation 1.59). The observers had a range of error of 18.5 degrees (S.D. = 4.06). When analysing the observers’ error with respect to flexion (+) and extension (−), they tended to under-estimate the amount of knee flexion (median error=−4) whereas the navigation was more evenly distributed (median error=0). The highest correlation was found between navigation and the radiograph r=0.96. The highest observer correlation with the radiograph was a consultant surgeon (r=0.91) and the worst was from a resident (r=0.74). The intra-class correlation coefficient was 0.88 for the three surgeons who repeated the measurements; their mean error was 3.5 degrees with a range of fifteen degrees. The use of computer navigation appears to be more accurate in assessing the degree of knee flexion, with a reduced range of error when compared to clinical assessment. It is therefore less likely to leave the patient with residual fixed flexion after knee arthroplasty.
The purpose of this study was to evaluate the effect of previous femoral osteotomy on the outcome of total hip replacement performed for degenerative arthritis secondary to developmental dysplasia of the hip. Eighty three primary total hip arthroplasties were performed in sixty-nine patients with osteoarthritis secondary to developmental hip dysplasia (DDH) with a minimum three year follow up. Twenty six hips had undergone previous femoral osteotomy (eleven hips, femoral osteotomy alone (FO); fifteen hips, combined femoral and pelvic osteotomy and fifty-seven hips, no previous surgery. The non operative patients with DDH served as an age and sex matched control group (control). Cementless arthroplasty was performed in seventy-eight hips. The mean duration from femoral osteotomy to primary THA was 22.9 years. The mean follow up was 7.6 years (FO) and 7.2 years (control). The overall revision rate was 15.4 % (FO) and 21.1 % in the Control group (p>
0.05). Twenty-one hips had one or more complications during or after surgery. The FO group had a higher femoral fracture rate (23.1%) compared to controls (10.5%) (p<
0.05). At latest mean follow-up (7.4 yrs (range, two to sixteen)), the mean Harris hip score was eighty-five (FO) and eighty-five (control group) (p>
0.05). The function and pain scores in the femoral osteotomy group were similar to the controls (p>
0.05). The requirement for bone grafting was similar and operative time significantly greater (FO) compared to controls. The frequency of radiolucent lines around the femoral component in the FO group (36%) was significantly higher than the control group (12.2%) (p<
0.05). Survival analysis was performed with the Kaplan-Meier method. At ten years, the survival of the acetabular component was 84.6%/73.6% and for the femoral component 92.2%/96% in the FO/control group. Patients with a prior femoral osteotomy have no significant difference in functional outcome, overall complication rate or revision rate compared to controls. However, there is a significant increase in femoral fracture and operative time. Previous femoral osteotomy does not compromise the functional outcome of subsequent total hip arthroplasty.
To assess the accuracy of plain digitised radiographic images for measurement of neck-shaft and stem-shaft angles in hip resurfacing arthroplasty. Fifteen patients having undergone hip resurfacing arthroplasty with the Birmingham Hip Resurfacing (BHR) were selected at random. Digital radiographs were analyzed by three observers. Each observer measured the femoral neck-shaft angles (NSA) of the pre-operative and stem-shaft angles (SSA) of the postoperative radiographs on two separate occasions spanning one week. The effect of femur position on SSA measured by digital radiographs was also analyzed. A BHR prosthesis was cemented into a third generation Sawbone composite femur. Radiographs were taken with the synthetic specimen positioned in varying angles of both flexion and external rotation in increments of 10° ranging from 0° to 90°. The mean intraobserver difference in measured angle was 3.13° (SD 2.37°, 95% CI +/−4.64°) for the NSA group and 1.49° (SD 2.28°, 95% CI +/−4.47°) for the SSA group. The intraclass correlation coefficient for the NSA group was 0.616 and for the SSA group was 0.855. Flexion of the synthetic femur of twenty degrees resulted in a five degree discrepancy in measured SSA and flexion of forty degrees resulted in a thirteen degree discrepancy. External rotation of the synthetic specimen of twenty and forty degrees resulted in a three and nine degree discrepancy in measured SSA, respectively. Patient malposition during radiographic imaging can contribute to erroneous NSA and SSA results. Significant intra- and inter-observer variation was noted in the measurement of neck shaft angle however, variation was less marked for measurement of stem shaft angle.
The purpose of this study was to evaluate functional outcome following supracondylar femur fractures using patient-based outcome measures. Patients having sustained supracondylar femur fractures between 1990 and 2004 were identified from the fracture databases of two level-one trauma centres. Three patient-based outcome measures, the Short Form-36 (SF-36) Version two, the Short Musculoskeletal Functional Scale (SMFA), and the Lower Extremity Functional Scale (LEFS) were used to evaluate functional outcome. Each patient’s medical record was also reviewed to obtain information regarding potential predictors of outcome, including age, gender, fracture type (AO classification), presence of comorbidities, smoking status, open vs. closed fracture, and occurrence of complications. Univariate and multivariate models were then used to identify significant predictors of outcome, as reflected in the SMFA bother and dysfunction scores. Sixty-one patients (thirty-five males and twenty-six females) with an average age (at time of injury) of 53 ± 18 years consented to participate. The average length of follow-up was 64 ± 34 months from the time of injury. Mean SF-36 V2 scores were lower than Canadian population norms indicating decreased function or greater pain, while mean SMFA scores were higher than published population norms indicating greater impairment and bother. The mean LEFS score was 40.78 ± 15.90 out of a maximum score of eighty. At the univariate level, the presence of complications was a significant predictor of both the SMFA bother (p=0.002) and dysfunction scores (p=0.015), while positive smoking status was a significant predictor of the bother score (p=0.002). Based on a multivariate linear regression model, the presence of complications (p=0.013) and positive smoking status (p=0.011) were both significant predictors of a higher SMFA bother score. In the multivariate model for SMFA dysfunction score, the presence of complications (p=0.014) and the presence of comorbidities (p=0.017) were significant predictors of a higher score. Comparing SF-36 and SMFA scores with published population norms, supracondylar femur fractures were associated with residual impact. Based on our analysis, smoking, the presence of medical comorbidities at the time of fracture, and the occurrence of complications following fracture repair were the main predictors of poorer patient outcomes following supracondylar femur fracture.
We aimed to establish if radiological parameters, dual energy x-ray absorbtiometry (DEXA) and quantitative CT (qCT) could predict the risk of sustaining a femoral neck fracture following hip resurfacing. Twenty-one unilateral fresh frozen femurs were used. Each femur had a plain AP radiograph, DEXA scan and quantitative CT scan. Femurs were then prepared for a Birmingham Hip Resurfacing femoral component with the stem shaft angle equal to the native neck shaft angle. The femoral component was then cemented onto the prepared femoral head. No notching of the femoral neck occurred in any specimens. A repeat radiograph was performed to confirm the stem shaft angle. The femurs were then potted in a position of single leg stance and tested in the axial direction to failure using an Instron mechanical tester. The load to failure was then analysed with the radiological, DEXA and qCT parameters using multiple regression. The strongest correlation with the load to failure values was the total mineral content of the femoral neck at the head/neck junction using qCT r= 0.74 (p<
0.001). This improved to r=0.76 (p<
0.001) when neck width was included in the analysis. The total bone mineral density measurement from the DEXA scan showed a correlation with the load to failure of r=0.69 (p<
0.001). Radiological parameters only moderately correlated with the load to failure values; neck width (r=0.55), head diameter (r= 0.49) and femoral off-set (r=0.3). This study suggests that a patient’s risk of femoral neck fracture following hip resurfacing is most strongly correlated with total mineral content at the head/neck junction and bone mineral density. This biomechanical data suggests that the risk of post-operative femoral neck fracture may be most accurately identified with a pre-operative quantitative CT scan through the head/neck junction combined with the femoral neck width.
We aimed to identify whether patients in lower socioeconomic groups had worse function prior to total knee arthroplasty and to establish whether these patients had worse post-operative outcome following total knee arthroplasty. Data was obtained from the Kinemax outcome study, this was a prospective observational study of 974 patients undergoing primary total knee arthroplasty for osteoarthritis. The study was undertaken in thirteen centers, four in the United States, six in the United Kingdom, two in Australia and one in Canada. Pre-operative data was collected within six weeks of surgery and patients were followed for two years post-operatively. Pre-operative details of the patient’s demographics, socioeconomic status (education and income), height, weight and co-morbid conditions were obtained. The WOMAC and SF-36 scores were also obtained. Multivariate regression was utilised to analyse the association between socioeconomic status and the patient’s pre-operative scores and post-operative outcome. During the analysis, we were able to control for variables that have previously been shown to effect pre-operative scores and post-operative outcome. Patients with a lower income had a significantly worse pre-operative WOMAC pain (p=0.021) and function score (p=0.039) than those with higher incomes. However, income did not have a significant impact on outcome except for WOMAC Pain at 12-months (p=0.014). At all the other post-operative assessment times, there was no correlation between income and WOMAC Pain and WOMAC Function. Level of education did not correlate with pre-operative scores or with outcome at any time during follow-up. This study demonstrates that across all four countries, patients with lower incomes appear to have a greater need for total knee arthroplasty. However, level of income and educational status did not appear to effect the final outcome following total knee arthroplasty. Patients with lower incomes appear able to compensate for their worse pre-operative score and obtain similar outcomes post-operatively.
Alignment of the femoral component during hip resurfacing has been implicated in the early failure of this device. Techniques to facilitate a more accurate placement of the femoral component may help prevent these early failures. We aim to establish whether the use of imageless computer navigation can improve the accuracy in alignment of the femoral component during hip resurfacing. 6 pairs of cadaveric limbs were randomized to the use of computer navigation or standard instrumentation. All hips had radiographs taken prior to the procedure to facilitate accurate templating. All femoral components were planned to be implanted with a stem shaft angle of 135 degrees. The initial guide wire was placed using either the standard jig with a pin placed in the lateral cortex or with the use of an imageless computer navigation system. The femoral head was then prepared in the same fashion for both groups. Following the procedure radiographs were taken to assess the alignment of the femoral component. The mean stem shaft angle in the computer navigation group was 133.3 degrees compared to 127.7 degrees in the standard instrumentation group (p=0.03). The standard instrumentation group had a range of error of 15 degrees with a standard deviation of 4.2 degrees. The computer navigated group had a range of error of only 8 degrees with a standard deviation of 2.9 degrees. Our results demonstrated that the use of standard alignment instrumentation consistently placed the femoral component in a more varus position when compared to the computer navigation group. The computer navigation was also more consistent in its placement of the femoral component when compared to standard instrumentation. We suggest that imageless computer navigation appears to improve the accuracy of alignment of the femoral component during hip resurfacing.
Ten out of 32 hips required revision; 9 acetabular components were revised because of aseptic loosening (3), osteolysis/excessive wear (4), instability (1) and infection (1) with a total revision rate of 28%. Eight patients needed acetabular revision alone, one femoral revision alone and one revision of both components. There was no significant difference in bone grafting, heterotopic bone formation, revision rate, operative time and blood loss between the two groups (p>
0.05).
We aimed to establish if radiological parameters, dual energy x-ray absorbtiometry (DEXA) and quantitative CT (qCT) could predict the risk of sustaining a femoral neck fracture following hip resurfacing. 21 unilateral fresh frozen femurs were used. Each femur had a plain AP radiograph, DEXA scan and quantitative CT scan. Femurs were then prepared for a Birmingham Hip Resurfacing femoral component with the stem shaft angle equal to the native neck shaft angle. The femoral component was then cemented onto the prepared femoral head. No notching of the femoral neck occurred in any specimens. A repeat radiograph was performed to confirm the stem shaft angle. The femurs were then potted in a position of single leg stance and tested in the axial direction to failure using an Instron mechanical tester. The load to failure was then analysed with the radiological, DEXA and qCT parameters using multiple regression. The strongest correlation with the load to failure values was the total mineral content of the femoral neck at the head/neck junction using qCT r= 0.74 (p<
0.001). This improved to r=0.76 (p<
0.001) when neck width was included in the analysis. The total bone mineral density measurement from the DEXA scan showed a correlation with the load to failure of r=0.69 (p<
0.001). Radiological parameters only moderately correlated with the load to failure values; neck width (r=0.55), head diameter (r= 0.49) and femoral off-set (r=0.3). This study suggests that a patient’s risk of femoral neck fracture following hip resurfacing is most strongly correlated with total mineral content at the head/neck junction and bone mineral density. This biomechanical data suggests that the risk of post-operative femoral neck fracture may be most accurately identified with a pre-operative quantitative CT scan through the head/neck junction combined with the femoral neck width.
A three dimensional femoral finite element model was constructed and molded with a femoral component constructed from the dimensions of a Birmingham Hip Resurfacing. The model was created with a superior femoral neck notch of increasing depths.