The spinopelvic alignment is often assessed via the Pelvic Incidence-Lumbar Lordosis (PI-LL) mismatch. Here we describe and validate a simplified method to evaluating the spinopelvic alignment through the L1-Pelvis angle (L1P). This method is set to reduce the operator error and make the on-film measurement more practicable. 126 standing lateral radiographs of patients presenting for Total Hip Arthroplasty were examined. Three operators were recruited to label 6 landmarks. One operator repeated the landmark selection for intra-operator analysis. We compare PI-LL mismatch obtained via the conventional method, and our simplified method where we estimate this mismatch using PI-LL = L1P - 90°. We also assess the method's reliability and repeatability. We found no significant difference ( Results indicate an equivalence in PI-LL measurement between the methods. Reproducibility of the measurements and reliability between operators were improved. Using the L1P angle, the classification of the sagittal spinal deformity found in the literature translates to:
Human error is usually evaluated using statistical descriptions during radiographic annotation. The technological advances popularized the “non-human” landmarking techniques, such as deep learning, in which the error is presented in a confidence format that is not comparable to that of the human method. The region-based landmark definition makes an arbitrary “ground truth” point impossible. The differences in patients’ anatomies, radiograph qualities, and scales make the horizontal comparison difficult. There is a demand to quantify the manual landmarking error in a probability format. Taking the measurement of pelvic tilt (PT) as an example, this study recruited 115 sagittal pelvic radiographs for the measurement of two PTs. We proposed a method to unify the scale of images that allows horizontal comparisons of landmarks and calculated the maximum possible error using a density vector. Traditional descriptive statistics were also applied. All measurements showed excellent reliabilities (intraclass correlation coefficients > 0.9). Eighty-four measurements (6.09%) were qualified as wrong landmarks that failed to label the correct locations. Directional bias (systematic error) was identified due to cognitive differences between observers. By removing wrong labels and rotated pelves, the analysis quantified the error density as a “good doctor” performance and found 6.77°-11.76° maximum PT disagreement with 95% data points. The landmarks with excellent reliability still have a chance (at least 6.09% in our case) of making wrong landmark decisions. Identifying skeletal contours is at least 24.64% more accurate than estimating landmark locations. The landmark at a clear skeletal contour is more likely to generate systematic errors. Due to landmark ambiguity, a very careful surgeon measuring PT could make a maximum 11.76° random difference in 95% of cases, serving as a “good doctor benchmark” to qualify good landmarking techniques.
Pelvic tilt (PT) is always described as the pelvic orientation along the transverse axis, yet four PT definitions were established based on different radiographic landmarks: anterior pelvic plane (PTa), the centres of femoral heads and sacral plate (PTm), pelvic outlet (PTh), and sacral slope (SS). These landmarks quantify a similar concept, yet understanding of their relationships is lacking. Some studies referred to the words “pelvic tilt” for horizontal comparisons, but their PT definitions might differ. There is a demand for understanding their correlations and differences for education and research purposes. This study recruited 105 sagittal pelvic radiographs (68 males and 37 females) from a single clinic awaiting their hip surgeries. Hip hardware and spine pathologies were examined for sub-group analysis. Two observers annotated four PTs in a gender-dependent manner and repeated it after six months. The linear regression model and intraclass correlation coefficient (ICC) were applied with a 95% significance interval. The SS showed significant gender differences and the lowest correlations to the other parameters in the male group (−0.3< r <0.2). The correlations of SS in scoliosis (n = 7) and hip implant (female, n = 18) groups were statistically different, yet the sample sizes were too small. PTm demonstrated very strong correlation to PTh (r > 0.9) under the linear model PTm = 0.951 × PTh - 68.284. The PTm and PTh are interchangeable under a simple linear regression model, which enables study comparisons between them. In the male group, SS is more of a personalised spinal landmark independent of the pelvic anatomy. Female patients with hip implant may have more static spinopelvic relationships following a certain pattern, yet a deeper study using a larger dataset is required. The understanding of different PTs improves anatomical education.
Accurate measurement of pelvic tilt (PT) is critical in diagnosing hip and spine pathologies. Yet a sagittal pelvic radiograph with good quality is not always available. Studies explored the correlation between PT and sacro-femoral-pubic (SFP) angle from anteroposterior (AP) radiographs yet demonstrated conflicting conclusions about its feasibilities. This study aims to perform a cohort-controlled meta-analysis to examine the correlation between the SFP angle and PT and proposes an application range of the method. This study searched PubMed, Embase, Cochrane, and Web of Science databases for studies that evaluated the correlation between SFP angle and PT. The Pearson's correlation coefficient r from studies were tabulated and compared. Pooled r for overall and gender/age (teenage or adult) controlled subgroup were reported using Fisher's Z transformation. Heterogeneity and publication bias were evaluated using Egger's regression test for the funnel plot asymmetry. Eleven studies were recruited, with nine reported r (totalling 1,247 patients). The overall pooled r was 0.61 with high inter-study heterogeneity (I2 = 75.95%). Subgroup analysis showed that the adult group had a higher r than the teenage group (0.70 versus 0.56, p < 0.001). Although statistically insignificant (p = 0.062), the female group showed a higher r than the male group (0.72 versus 0.65). The SFP method must be used with caution and should not be used in the male teenage group. The current studies did not demonstrate that the SFP method was superior to other AP landmarks correlating to PT. Identical heterogeneity was observed among studies, indicating that more ethnicity-segregated and gender-specific subgroup studies might be necessary. More data input analysing the errors will be useful.
Navigation in total hip arthroplasty has been shown to improve acetabular positioning and can decrease the incidence of mal-positioned acetabular components. The aim of this study was to assess two surgical guidance systems by comparing intra-operative measurements of acetabular component inclination and anteversion with a post-operative CT scan. We prospectively collected intra-operative navigation data from 102 hips receiving conventional THA or hip resurfacing arthroplasty through either a direct anterior or posterior approach. Two guidance systems were used simultaneously: an inertial navigation system (INS) and optical navigation system (ONS). Acetabular component anteversion and inclination was measured on a post-operative CT. The average age of the patients was 64 years (range: 24-92) and average BMI was 27 kg/m2 (range 19-38). 52% had hip surgery through an anterior approach. 98% of the INS measurements and 88% of the ONS measurements were within 10° of the CT measurements. The mean (and standard deviation) of the absolute difference between the post-operative CT and the intra-operative measurements for inclination and anteversion were 3.0° (2.8) and 4.5° (3.2) respectively for the ONS, along with 2.1° (2.3) and 2.4° (2.1) respectively for the INS. There was significantly lower mean absolute difference to CT for the INS when compared to ONS in both anteversion (p<0.001) and inclination (p=0.02). Both types of navigation produced reliable and reproducible acetabular cup positioning. It is important that patient-specific planning and navigation are used together to ensure that surgeons are targeting the optimal acetabular cup position. This assistance with cup positioning can provide benefits over free-hand techniques, especially in patients with an altered acetabular structure or extensive acetabular bone loss. In conclusion, both ONS and INS allowed for adequate acetabular positioning as measured on postoperative CT, and thus provide reliable intraoperative feedback for optimal acetabular component placement.
Hip resurfacing arthroplasty (HRA) is a bone conserving alternative to total hip arthroplasty. We present the early 1 and 2-year clinical and radiographical follow-up of a novel ceramic-on-ceramic (CoC) HRA in a multi-centric Australian cohort. Patient undergoing HRA between September 2018 and April 2021 were prospectively included. Patient-reported outcome measures (PROMS) in the form of the Forgotten Joint Score (FJS), HOOS Jr, WOMAC, Oxford Hip Score (OHS) and UCLA Activity Score were collected preoperatively and at 1- and 2-years post-operation. Serial radiographs were assessed for migration, component alignment, evidence of osteolysis/loosening and heterotopic ossification formation. 209 patients were identified of which 106 reached 2-year follow-up. Of these, 187 completed PROMS at 1 year and 90 at 2 years. There was significant improvement in HOOS (p< 0.001) and OHS (p< 0.001) between the pre-operative, 1-year and 2-years outcomes. Patients also reported improved pain (p<0.001), function (p<0.001) and reduced stiffness (p<0.001) as measured by the WOMAC score. Patients had improved activity scores on the UCLA Active Score (p<0.001) with 53% reporting return to impact activity at 2 years. FJS at 1 and 2-years were not significantly different (p=0.38). There was no migration, osteolysis or loosening of any of the implants. The mean acetabular cup inclination angle was 41.3° and the femoral component shaft angle was 137°. No fractures were reported over the 2-year follow-up with only 1 patient reporting a sciatic nerve palsy. There was early return to impact activities in more than half our patients at 2 years with no early clinical or radiological complications related to the implant. Longer term follow-up with increased patient numbers are required to restore surgeon confidence in HRA and expand the use of this novel product. In conclusion, CoC resurfacing at 2-years post-operation demonstrate promising results with satisfactory outcomes in all recorded PROMS.
Imageless computer navigation systems have the potential to improve acetabular cup position in total hip arthroplasty (THA), thereby reducing the risk of revision surgery. This study aimed to evaluate the accuracy of three alternate registration planes in the supine surgical position generated using imageless navigation for patients undergoing THA via the direct anterior approach (DAA). Fifty-one participants who underwent a primary THA for osteoarthritis were assessed in the supine position using both optical and inertial sensor imageless navigation systems. Three registration planes were recorded: the anterior pelvic plane (APP) method, the anterior superior iliac spines (ASIS) functional method, and the Table Tilt (TT) functional method. Post-operative acetabular cup position was assessed using CT scans and converted to radiographic inclination and anteversion. Two repeated measures analysis of variance (ANOVA) and Bland-Altman plots were used to assess errors and agreement of the final cup position. For inclination, the mean absolute error was lower using the TT functional method (2.4°±1.7°) than the ASIS functional method (2.8°±1.7°, A functional registration plane is preferable to an anatomic reference plane to measure intra-operative acetabular cup inclination and anteversion accurately. Accuracy may be further improved by registering patient location using their position on the operating table rather than anatomic landmarks, particularly if a tighter target window of ± 5° is desired.
Imageless computer navigation systems in total hip arthroplasty (THA) improve acetabular cup position, thereby reducing the risk of revision surgery for all causes as well as dislocation. We aimed to evaluate the registration accuracy of 3 alternate registration planes. A prospective, observational study was conducted with 45 THA in the supine position using two imageless navigation systems and 3 registration planes. Patient position was registered sequentially using an optical system (Stryker OrthoMap) and an inertial sensor-based system (Navbit Sprint) with 3 planes of reference: (Plane 1) an anatomical plane using the anterior superior iliac spines (ASISs) and the pubic symphysis; (Plane 2) a functional plane parallel to the line between the ASISs and the table plane; and, (Plane 3) a functional plane that was perpendicular to the gravity vector and aligned with the longitudinal axis of the patient. The 3 measurements of acetabular cup inclination and anteversion were compared with the measurements from postoperative computed tomography (CT) scans. For inclination, the mean absolute error was significantly lower for Plane 3 (1.80°) than for Plane 2 (2.74°), p = .038 and was lower for both functional planes than for the anatomical plane (3.75°), p < .001. For anteversion, the mean absolute error was significantly lower for Plane 3 (2.00°) than for Plane 2 (3.69°), p = .004 and was lower for both functional planes than for the anatomical plane (8.58°), p < .001. Patient registration using functional planes more accurately measured the acetabular cup position than registration using anatomic planes.
In total knee arthroplasty, the aim is to relieve pain and provide a stable, functional knee. Sagittal stability is crucial in enabling a patient to return to functional activities. Knee implants with a medial pivot (MP) design are thought to more accurately reproduce the mechanics of the native joint, and potentially confer greater antero-posterior stability through the range of flexion than some other implant designs. This study aims to compare the sagittal stability of four different total knee arthroplasty implant designs. Method Comparison was made between four different implant designs: medial pivot (MP), two different types of cruciate retaining (CR1 and CR 2) and deep dish (DD). A cohort of 30 Medial Pivot (MP) knees were compared with matched patients from each of the other designs, 10 in each group. Patients were matched for age, body mass index and time to follow up. Clinical examination was carried out by an orthopaedic surgeon blinded to implant type, and sagittal stability was tested using a KT1000 knee arthrometer, applying 67N of force at 30˚ and 90˚.Introduction
Aim
Component positioning is of great importance in total hip arthroplasty (THA) and navigation systems can help guide surgeons in the optimal placement of the implants. We report on a newly developed navigation system which employs an inertial measurement unit (IMU) to measure acetabular cup inclination and anteversion. To assess the accuracy of the IMU when used for acetabular cup placement and compare this with an established optical navigation system (ONS).Introduction
Aims
Accurate implant positioning is of supreme importance in total knee replacement (TKR). The rotational profile of the femoral and tibial components can affect outcomes, and the aim is to achieve coronal conformity with parallelism between the medio-lateral axes of the femur and tibia. The aim of this study is to determine the accuracy of implant rotation in total knee replacement.Background
Aims
Kinematics post-TKA are complex; component alignment, component geometry and the patient specific musculoskeletal environment contribute towards the kinematic and kinetic outcomes of TKA. Tibial rotation in particular is largely uncontrolled during TKA and affects both tibiofemoral and patellofemoral kinematics. Given the complex nature of post- TKA kinematics, this study sought to characterize the contribution of tibial tray rotation to kinematic outcome variability across three separate knee geometries in a simulated framework. Five 50th percentile knees were selected from a database of planned TKAs produced as part of a pre-operative dynamic planning system. Virtual surgery was performed using Stryker (Kalamazoo, MI) Triathlon CR and PS and MatOrtho (Leatherhead, UK) SAIPH knee medially stabilised (MS) components. All components were initially planned in mechanical alignment, with the femoral component neutral to the surgical TEA. Each knee was simulated through a deep knee bend, and the kinematics extracted. The tibial tray rotational alignment was then rotated internally and externally by 5° & 10°. The computational model simulates a patient specific deep knee bend and has been validated against a cadaveric Oxford Knee Rig. Preoperative CT imaging was obtained, landmarking to identify all patient specific axes and ligament attachment sites was performed by pairs of trained biomedical engineers. Ethics for this study is covered by Bellberry Human Research Ethics Committee application number 2012-03-710.Introduction
Method
We present a technique of single posterior longitudinal slot femorotomy. This technique allows the expansion of the metaphyseal-diaphyseal region of the proximal femur facilitating extraction of proximally coated uncemented femoral components while leaving the metaphysis and diaphysis intact. Since 1996 we have performed this technique in 18 revision total hip arthroplasties in 15 patients who had x-ray appearance of bony in-growth/on-growth and where found to have solidly ingrown stems at revision surgery. All were revised to a metaphyseal-fitting uncemented stem. At mean follow-up of 122.4 months, there were significant improvements in both pain and function. All revised stems achieved stable bony fixation. There were no complications due to this technique. No patient developed a limp or thigh pain post-operatively. There have been no re-revisions of the stem. With appropriate patient selection, this simple, reliable, and extensile technique is useful to assist in the extraction of uncemented proximally coated femoral components whether hydroxyapatite-coated or not.
Ceramic-on-ceramic bearings provide a solution to the osteolysis seen with traditional metal-on-polyethylene bearings. Sporadic reports of ceramic breakage and squeaking concern some surgeons and this bearing combination can show in vivo signs of edge loading wear which was not predicted from in vitro studies. Taper damage or debris in the taper between the ceramic and metal may lead to breakage of either a ceramic head or insert. Fastidious surgical technique may help to minimise the risk of ceramic breakage. Squeaking is usually a benign complication, most frequently occurring when the hip is fully flexed. Rarely, it can occur with each step of walking when it can be sufficiently troublesome to require revision surgery. The etiology of squeaking is multifactorial in origin. Taller, heavier and younger patients with higher activity levels are more prone to hips that squeak. Cup version and inclination are also relevant factors. Osteolysis following metal-on-UHMW polyethylene Total Hip Arthroplasty (THA) is well reported. Earlier generation ceramic-on-ceramic bearings did produce some osteolysis, but in flawed implants. As third and now fourth generation ceramic THAs come into mid- and long-term service, the orthopaedic community has begun to see reports of high survival rates and very low incidence of osteolysis in these bearings. The technique used by radiologists for identifying the nature of lesions on Computed Tomography (CT) scan is the Hounsfield score which will identify the density of the tissue within the lucent area. Commonly the radiologist will have no access to previous imaging, especially pre-operative imaging if a long time has elapsed. With such a low incidence of osteolysis in this patient group, what, then, should a surgeon do on receiving a CT report on a ceramic-on-ceramic THA, which states there is osteolysis? This retrospective review aims to determine the accuracy of CT in identifying true osteolysis in a cohort of long-term third generation ceramic-on-ceramic uncemented hip arthroplasties in our department. Pelvic CT scans were performed on the first 27 patients from a cohort of 301 patients undergoing 15-year review with third generation alumina-alumina cementless THAs. The average follow-up was 15 years (15–17). The CT scans were reviewed against pre-operative and post-operative radiographs and reviewed by a second musculoskeletal specialist radiologist. Eleven of the CT scans were reported to show acetabular osteolysis, two reported osteolysis or a possible pre-existing cyst and one reported a definitive pre-existing cyst. After review of previous imaging including pre-operative radiographs, eleven of the thirteen patients initially reported to have osteolysis were found to have pre-existing cysts or geodes in the same size and position as the reported osteolysis, and a further patient had spot-welds with stress-shielding. One patient with evidence of true osteolysis awaits aspiration or biopsy to determine if he has evidence of ceramic wear or metallosis. Reports of osteolysis on CT should be interpreted with care in modern ceramic-on-ceramic THA to prevent unnecessary revision. Further imaging and investigations may be necessary to exclude other conditions such as geodes, or stress shielding which are frequently confused with osteolysis on CT scans.
Medial ball and socket knee designs have a long history but are not yet widely used. The Saiph medial ball and socket knee passed preclinical testing before an introductory cohort of 20 patients were studied in detail for 2 years. Subsequently a multicenter study was undertaken by the developing surgeons. We report the minimum 5-year follow-up of the first 102 Saiph knee replacements implanted in Australia as part of a step-wise or phased introduction of this device to the market. These 102 consecutive patients were recruited to the study at two centers in Australia. Revisions, complications and adverse events were collected. Patient reported scores including EQ-5D, Oxford Knee Score (OKS), Knee Injury and Osteoarthritis Outcome Score (KOOS) and Kujala and range of motion satisfaction and forgotten joint score were collected. Data were collected pre-operatively and at one to two years post-operatively and at a minimum of five years.INTRODUCTION
METHODS
The pelvis is known to undergo significant movement during Total Hip Replacement (THR). We developed a 4D-tracking device employing an inertial measurement unit (IMU) to track changes in pelvic orientation during THR. The IMU was mounted on the iliac crest in 39 cases with tracking initiated at the commencement of surgery and digital logging of significant intra-operative milestones (i.e. acetabular impaction). The system was validated by videoing a select number of cases and the 4D model linked in real-time. Data were processed using a custom Java-based infrastructure to calculate roll (left/right) and tilt (flexion/extension). 19 patients underwent direct anterior approach (DAA) and 20 posterior approach (PA). Comparing DAA to PA, at acetabular impaction there was mean pelvic roll seen of 3.7°(range 0.5–10.1°) in the DAA group, and 5.6°(range 0.1–16.2°) in the PA group. Mean tilt in the DAA group was 3.7°(range: 0.2–7.1°) and in the PA group was 1.7°(range: 0.2–4.3°). Mean BMI in the DAA group was 25.2(range: 18.4–34.2) and 29.1(range: 21.5–42.4). There was no direct correlation between BMI and the amount of roll or tilt recorded for individual patients. The IMU tracking device provided a useful and real-time method of assessing pelvic orientation during THR via both the DAA and posterior approach. Specific variations in tilt and roll are consistent with previous literature. Significant variation in the pattern of pelvic movement was noted to be dependent on the approach and the position of the patient on the operating table.
Since the development of modern total hip replacement (THR) more than 50 years ago, thousands of devices have been developed in attempt to improve patient outcomes and prolong implant survival. Modern THR devices are often broadly classified according to their method of fixation; cemented, uncemented or hybrid (typically an uncemented acetabular component with a cemented stem). Due to early failures of THR in young active patients, the concept of hip resurfacing was revisited in the 1990's and numerous prostheses were developed to serve this patient cohort, some with excellent clinical results. Experience with metal-on-metal (MoM) bearing related issues particularly involving the ASR (DePuy Synthes, Warsaw, Indiana) precipitated a fall in the use of hip resurfacing (HR) prostheses in Australia from a peak of 30.2% in 2004 to 4.3% in 2015. The effects of poorly performing prostheses and what is now recognised as suboptimal patient selection are reflected in the AOANJRR cumulative percent revision (CPR) data which demonstrates 13.2% revision at 15 years for all resurfacing hip replacements combined; with 11 different types of hip resurfacing prostheses recorded for patients less than 55 years of age and a primary diagnosis of OA. When this data is restricted to only those prostheses currently used in Australia (BHR; Smith and Nephew, Birmingham, UK & ADEPT; MatOrtho Ltd, Surrey, UK) there is a CPR of 9.5% at 15 years for all patients. Despite these CPR results, recognition is emerging of the important distinction between MoM THR and resurfacing. Furthermore, in light of current consensus for patient selection and the surgical indications for resurfacing, a gender analysis demonstrates a CPR for females of 14.5% at 10 years compared to 3.7% for males. Similar difference for head size >50mm with 6% CPR at 10 years compared to 17.6% for head size <50mm (HR=2.15; 1.76, 2.63; p<0.001). Leading to renewed interest in resurfacing particularly in the young, active male. In addition to registry based CPR data, several studies have concluded that a true difference in mortality rates between HR and other forms of THR exists independent of age, sex or other confounding factors. We hypothesised that a difference in adjusted mortality rates between HR and other forms of THR may also be present in the Australian population. We undertook an ad hoc data report request to the AOANJRR. The data set provided was deidentified for patient, surgeon and institution and included all HR and conventional THR procedures performed for the diagnosis of primary osteoarthritis recorded in the Registry since inception in 1999. We requested mortality and yearly cumulative percent survival (CPS) of patients for primary HR and THR with sub-group analysis by the mode of fixation. There were 12,910 hip resurfacings (79% male) compared to 234,484 conventional THR (46.8% male) over the study period. When adjusted for age and gender over the 15 years of available data, there was a statistically significant difference in cumulative percent survival (CPS) between conventional THR and hip resurfacing (HR 1.66 (1.52, 1.82; p<0.001)) and between cemented THR and hip resurfacing (HR 1.96 (1.78, 2.43; p<0.001)); between uncemented THR and hip resurfacing (HR 1.58 (1.45, 1.73; p<0.001)); and between hybrid THR and hip resurfacing (HR 1.82 (1.66, 1.99; p<0.001)). When adjusted for age, gender and ASA over the 3 years data available, there was no statistically significant difference in CPS between hip resurfacing and any individual fixation type of THR. The results demonstrate a statistically significant adjusted survival advantage for hip resurfacing compared to conventional THR and between fixation methods for THR. These findings are consistent with previous studies. While a difference in adjusted mortality rate appears to exist, we are yet to definitively determine the complex interplay of causative factors that may contribute to it.Background
Discussion
Ceramic-on-ceramic bearings provide a solution to the osteolysis seen with traditional metal-on-polyethylene bearings. Sporadic reports of ceramic breakage and squeaking concern some surgeons and this bearing combination can show in vivo signs of edge loading wear which was not predicted from in vitro studies. Taper damage or debris in the taper between the ceramic and metal may lead to breakage of either a ceramic head or insert. Fastidious surgical technique may help to minimise the risk of ceramic breakage. Squeaking is usually a benign complication, most frequently occurring when the hip is fully flexed. Rarely, it can occur with each step of walking when it can be sufficiently troublesome to require revision surgery. The etiology of squeaking is multifactorial origin. Taller, heavier and younger patients with higher activity levels are more prone to hips that squeak. Cup version and inclination are also relevant factors. Fifty-five ceramic bearings revised at our center were collected over 12 years. Median time to revision was 2.7 years. Forty-six (84%) cases had edge loading wear. The median femoral head wear volume overall was 0.2mm3/yr, for anterosuperior edge loading was 2.0mm3/yr, and the median volumetric wear rate for posterior edge loading was 0.15mm3/yr (p=0.005). Osteolysis following metal-on-polyethylene total hip arthroplasty (THA) is well reported. Earlier generation ceramic-on-ceramic bearings did produce some osteolysis, but in flawed implants. As 3rd and now 4th generation ceramic THAs come into mid- and long-term service, the orthopaedic community has begun to see reports of high survival rates and very low incidence of osteolysis in these bearings. The technique used by radiologists for identifying the nature of lesions on Computed Tomography (CT) scan is the Hounsfield score which will identify the density of the tissue within the lucent area. Commonly the radiologist will have no access to previous imaging, especially pre-operative imaging if a long time has elapsed. With such a low incidence of osteolysis in this patient group, what, then, should a surgeon do on receiving a CT report on a ceramic-on-ceramic THA, which states there is osteolysis? This retrospective review aims to determine the accuracy of CT in identifying true osteolysis in a cohort of long-term 3rd generation ceramic-on-ceramic uncemented hip arthroplasties in our department. Pelvic CT scans were performed on the first 27 patients from a cohort of 301 patients undergoing 15-year review with 3rd generation alumina-alumina cementless THAs. The average follow-up was 15 years (15–17). The CT scans were reviewed against pre-operative and post-operative radiographs and reviewed by a second musculoskeletal specialist radiologist. Eleven of the CT scans were reported to show acetabular osteolysis, two reported osteolysis or possible pre-existing cyst and one reported a definitive pre-existing cyst. After review of previous imaging including pre-operative radiographs, eleven of the thirteen patients initially reported to have osteolysis were found to have pre-existing cysts or geodes in the same size and position as the reported osteolysis, and a further patient had spot-welds with stress-shielding. One patient with evidence of true osteolysis awaits aspiration or biopsy to determine if he has evidence of ceramic wear or metallosis.Methods
Results
The continued improvement of ceramic materials for total hip arthroplasty led to the development of Zirconia and Zirconia toughened Alumina materials such as BIOLOX® Twenty-six retrieved BIOLOX® Raman spectra were collected using a confocal Raman spectrometer (WITec Gmbh, Germany) a laser wavelength of 532nm, a 50× objective and a 100μm pinhole. Twenty-five measurements were made on each retrieval at random locations outside any visible wear scars and inside visible wear scars. The average monoclinic content was calculated based on the method of Clarke and Adar [1]. For comparison 5 new BIOLOX® Introduction
Methods
Dislocation is one of the leading causes of revision after primary total hip arthroplasty (THA). Polyethylene wear is one of the risk factors for late dislocations (>2 years). It can induce an inflammatory response resulting in distension and thinning of the pseudocapsule, predisposing the hip to dislocation. Alternatively, eccentric seating of the femoral head in a worn out socket may result in an asymmetric excursion arc predisposing the hip to impingement, levering out and dislocation. Highly cross linked polyethylene has a significantly lower wear rate as compared to conventional polyethylene. Incidence of late dislocations has been shown to be significantly greater with conventional polyethylene bearings as compared to ceramic bearings. However, there is no literature comparing the risk of dislocation between ceramic- on- ceramic (CoC) bearings with metal/ceramic- on- cross linked polyethylene (M/CoP) bearings and this was the aim our study Data regarding revision for dislocation after primary THA for osteoarthritis (OA) between September 1999 and December 2013 was obtained from the Australian Orthopaedic Association National Joint Replacement Registry (AOA NJRR). Revision risk for dislocation was compared between CoC, CoP, and MoP bearings. Only those THAs with 28 mm, 32 mm, or 36 mm heads were included in the study.Introduction
Methods
Osteloysis following metal-on-UHMW polyethylene Total Hip Arthroplasty (THA) is well reported, as is lack of osteolysis following Ceramic-on-Ceramic (CoC)THA. Early ceramic failures did report some osteolysis, but in flawed implants. As 3rd and now 4th generation ceramic THAs come into mid- and long-term use, the orthopaedic community has begun to see reports of high survival rates and very low incidence of osteolysis in these bearings. Osteolysis reported after 3rd generation CoC THA often included metallosis due to neck rim impingement. In our department we have revised only 2 hips in over 6000 CoC THAs for osteolysis. Both had evidence of metallosis as well as ceramic wear. The technique used by Radiologists for identifying the nature of lesions on CT is the Hounsfield score which will identify the density of the tissue within the lucent area. It is common for radiologist to have no access to previous imaging, especially pre-operative imaging if a long time has elapsed. With such a low incidence of osteolysis in this patient group, what, then, should a surgeon do on receiving a CT report on a ceramic-on-ceramic THA which states there is osteolysis? Revision of such implants in elderly patients has a high risk of morbidity and mortality. This retrospective review aims to determine the accuracy of CT in identifying true osteolysis in a cohort of long-term third generation ceramic-on-ceramic uncemented hip arthroplasties in our department.Introduction
Objectives
The possibility of corrosion at the taper junction of hip replacements was initially identified as a concern of generating adverse reactions in the late 1980s. Common clinical findings of failure are pain, clicking, swelling, fluid collections, soft tissue masses, and gluteal muscle necrosis identified intra operatively. The joint replacement surgery was performed utilizing a posterior approach to the hip joint. The data from all surgical, clinical and radiological examinations was prospectively collected and stored in a database. Patients were separated into two groups based on bearing material, where group 1 had a CoC bearing and ABG modular stem whilst group 2 had a MoM bearing and SROM stem, with each group having 13 cases. Pre-operative revision surgery and post-operative blood serum metal ion levels we collected. Cup inclination and anteversion was measured using the Ein-Bild-Roentgen-Analyse (EBRA) software. A range of 2–5 tissue sections was examined per case. 2 independent observers that were blinded to the clinical patient findings scored all cases. The tissue grading for the H&E tissue sections were graded based on the presence of fibrin exudates, necrosis, inflammatory cells, metallic deposits, and corrosion products. The corrosion products were identified into 3 groups based on visible observation and graded based on abundance. A scanning electron microscope (SEM) Hitachi S3400 was used to allow for topographic and compositional surface imaging. Unstained tissue sections were used for imaging and elemental analysis. X-Ray diffraction was the analytical technique used for the taper debris that provided identification on the atomic and molecular structure of a crystal.Introduction
Methodology
Sagittal stability of the knee is believed to be of significant importance following total knee arthroplasty. We examine four different knee designs at a minimum of twenty-four months postoperatively. Sagittal stability was measured at four degrees of flexion: 0°; 30°; 60°; and 90°, to examine the effect of design on mid-flexion stability. The knee designs included were: the rotating platform LCS design (DePuy); the cruciate sparing Triathlon system (Stryker); SAIPH system (Matortho, UK); and the medial rotating knee design, MRK (Matortho, UK). Following ethical approval, 64 cases were enrolled into the study, 22 male and 42 female. Inclusion criteria included: a minimum of 18 months from surgery; ability to flex beyond 90 degrees; and have no postoperative complications. 18 LCS, 18 MRK, 14 SAIPH and 14 Triathlon knee designs were analysed. Sagittal stability was measured using the KT1000 device. Active range of movement was measured using a hand held goniometer and recorded as was Oxford knee score, WOMAC knee score, SF12 and Kujala patellofemoral knee score. Mean follow-up was 33.7 months postoperative, with a mean age of 72 years. Mean weight was 82.7kgs and height 164cms. There was no significant difference in preoperative demographics between the groups. Mean active post-operative range of motion of the knee was from 2–113° with no significant difference between groups. Sagittal stability was similar in all four groups in full extension; however the MRK and SAIPH designs showed improved stability in the mid-range of flexion (30–90°). Patient satisfaction also showed a similar trend with MRK achieving better patient reported functional outcomes and satisfaction than that of the SAIPH, LCS and Triathlon systems. All four knee designs demonstrated good post-operative range of movement with comparative improvement of patient scores to other reported studies. The MRK and SAIPH knee design showed an improved mid-flexion sagittal stability with better patient reported satisfaction and functional scores.
Total Hip Arthroplasty (THA) using the Direct Anterior Approach (DAA) is a muscle sparing approach which promotes early mobilisation of patients. It is a technically challenging approach shown to have a high rate of complications, especially during the learning curve. Here we present the results of 157 cases of THA via a DAA on a standard theatre table, with a minimum of 6 months follow-up. The authors conducted a prospective study on a group of 149 consecutive patients undergoing 157 cementless primary THAs for coxarthrosis, 8 bilateral. The same surgical technique was used in all patients, performed by the senior author WLW at a single centre. The average age of the patients at time of surgery was 69 years, 78% were female and 57% were right sided. All implants were uncemented, with bearings being ceramic on ceramic or Ceramic on highly cross-linked polyethylene. Patients were assessed clinically and radiographically pre- and post-operatively at 6 weeks, 6 months, 1 and 2 years. Intra-operatively, navigation was used to guide cup position and assess offset and leg length.Background
Materials & Methods
The 21st Century has seen ceramic bearings become an increasingly popular choice in total hip arthroplasty due to their high wear resistance and inert wear debris without osteolysis promising a long term bearing solution. Early ceramic bearings were hindered by fracture but improved manufacturing processes and materials subsequently produced stronger ceramics. These third generation ceramics showed greatly reduced fracture rates but there is limited evidence in the literature reporting their long term survival and wear characteristics. The purpose of this study was to determine osteolysis and survival rates of Alumina ceramic bearings in cementless total hip arthroplasties with a minimum follow-up of 15 years. We analyzed a series of 301 third-generation alumina-on-alumina cementless primary total hip replacements in 283 patients. The average age of the patients at the time of the arthroplasty was fifty-eight years, 51% were in women and 54% were right sided. All procedures were performed using the same surgical technique and the same implant at a single centre. Patients were followed up at six weeks, one, two, five, ten and 15 years. At 15 years postoperatively 46 patients (17%) had died of unrelated causes and 31 (10.2%) were lost to follow-up. Patients were assessed clinically and radiographically. Retrieved bearings were analyzed for wear.Introduction and Aims
Methods
The aim of this study is to describe the influence of sitting and standing posture on sagittal pelvic inclination in preoperative total hip replacement patients to assist with correct acetabular component positioning. Lateral radiographs of the pelvis and lumbar spine in sitting and standing of preoperative hip arthroplasty patients with primary hip osteoarthritis were extracted. Pelvic tilt was measured using the vertical inclination of a line from the ASIS to pubic tubercle. Sacral inclination was measured as the angle between the anterior surface of the sacrum and a horizontal reference. Figure one is a representation of the pelvic tilt angle and sacrel inclination angle taken during standing. The Cobb angle of the lumbar spine was recorded represented for a sitting patient in figure 2. Hip flexion was recorded (figure 2).Purpose
Methods
Squeaking is a potential problem of all hard on hard bearings yet it has been less frequently reported in metal-on-metal hips. We compared a cohort of 11 squeaking metal-on-metal hip resurfacings to individually matched controls, assessing cup inclination and anteversion between the groups to look for any differences. We retrospectively reviewed the patient records of 332 patients (387 hip resurfacings) who underwent hip resurfacing between December 1999 and Dec 2012. 11 hips in 11 patients were reported to squeak postoperatively. Each of these patients, except one, were matched by age, sex, BMI and implant to 3 controls. The final patient only had one control due to his high BMI. The latest post-operative radiographs of the squeaking group and controls were analysed using EBRA (Einzel-Bild-Roentgen-Analysis, University of Innsbruck, Austria) software to evaluate cup inclination and anteversion.Introduction
Methods
The accuracy of cup position in total hip arthroplasty is essential for a satisfactory result as malpositioning increases the risk of complications including dislocation, high wear rate, loosening, squeaking, edge loading, impingement and ultimately failure. We studied 173 patients in a single surgeon series of matched cohorts of patients who underwent total hip arthroplasty. Four separate groups were identified comprising of posterior approach +/− navigation and direct anterior approach +/− navigation. We found a significant difference between the direct anterior navigated group and the posterior non-navigated group for both anteversion (p < 0.05, CI −3.86 to −1.73) and inclination (p < 0.05, CI −3.08 to −1.08). 72% of anterior navigated patients fell within 5° of the navigation software set target cup position of 45° inclination and 20° anteversion and 100% were within 10°. Only 30% of posterior non-navigated were within 5° of both anteversion and inclination and 73% were within 10°. There was also a significant difference between the direct anterior navigated and non-navigated group with respect to anteversion only (p < 0.05, CI 1.50 to 1.30). There were no other significant differences between approaches +/− navigation. The direct anterior approach allows ease of access to both anterior-superior iliac spines for navigation and a supine patient allows anteversion and inclination to be measured in the frontal plane. We conclude that the direct anterior approach with navigation improves accuracy of cup position compared to the conventional posterior approach without navigation.
The design of the femoral prosthesis in cementless total hip arthroplasty is known to affect the initial strains in the cortex during implantation and in the early postoperative time period. High strains have a direct influence on periprosthetic fracture. This study compares the existing ABGII stem, which is proximally coated with a grit blasted titanium surface with hydroxyapatite coating with a prototype that has a rougher titanium plasma spray proximal coating. The Australian National Joint registry results 2011 reported the ABG2 femoral component cumulative percent revision (CPR) of 6.5 (93.5% survival), which compares favourably with equivalent stems with 10 year CPR data such as the Taperloc 6.6 and Corail 7.3. Six pairs of fresh-frozen cadaveric femurs were mounted in blocks according to ISO guidelines in single leg stance setup. Five strain gauges were attached around the neck of the femur and then prepared according to routine operative techniques to accept the femoral prosthesis. Cortical strains were measured during insertion of the prosthesis with an instrumented mallet attached to an accelerometer. Subsequently, force-displacement readings were taken during cyclical loading on a servo-hydraulic machine and finally the stems were tested to failure. Our results showed significantly less strain during cyclical loading of the stem with increased surface roughness (p < 0.05). They also showed no significant differences loads/strains during impaction (p = 0.159), no significant difference in micromotion (p = 0.148) and no significant difference in load-to-failure (p = 0.37).
The success of total hip arthroplasty has meant its indications have been extended to the younger more active patient. Due to the higher activity levels and increased demands of these patients, revision rates have been traditionally higher than when compared to older patients [1]. Ceramic on ceramic bearings may offer a viable long term solution as manufacturing methods have evolved resulting in improved mechanical properties, particularly of third and fourth generation ceramics. We report the outcome of primary cementless, alumina-on-alumina hip arthroplasty with a minimum 10 year follow up in 110 patients under the age of 55 years of age at time of surgery. A series of 120 consecutive total hip arthroplasties in 110 patients were performed between June 1997 and February 1999 by the two senior authors. All patients had an Osteonics ABC acetabular component and SecurFit or SecurFit Plus femoral component (Stryker Orthopaedics, Mahwah, NJ) with an alumina C-taper ceramic head (Biolox Forte, Ceramtec, Plochingen, Germany).Introduction
Methods
Sagittal stability of the knee is believed to be of significant importance following a total knee arthroplasty. We examine three different knee designs at a minimum of twenty-four months postoperatively. Sagittal stability was measured at four degrees of flexion; 0°, 30°, 60° and 90° to examine the effect of design on mid-flexion stability. The knee designs included the rotating platform LCS design, the cruciate sparing Triathlon system and the medial rotating knee design, MRK. Following ethical approval 50 cases were enrolled into the study, 15 male and 35 female. Eighteen LCS, 18 MRK and 14 Triathlon knee designs were analysed. Sagittal stability was measured using the KT1000 device. Active range of movement was measured using a hand held goniometer and recorded as was Oxford knee score, WOMAC knee score, SF12 and Kujala patellofemoral knee score. Mean follow-up was 37 months postoperative with a mean age of 73 years. Mean weight was 82.7 kgs and height 164 cms. There was no significant difference in preoperative demographics between the groups. Mean active post-operative range of motion of the knee was from 2–113° with no significant difference between groups. Sagittal stability was similar in all three groups in full extension; however the MRK design showed improved stability in the mid-range of flexion (30–90°). Patient satisfaction also showed a similar trend with MRK achieving slightly better patient reported outcomes than that of the LCS and Triathlon systems, although this was not statistically significant. All three knee designs demonstrated good post-operative range of movement with comparative improvement of patient scores to other reported studies. The MRK knee design showed an improved mid-flexion sagittal stability.
The purpose of this study was to prospectively measure serum cobalt and chromium ion levels in patients who had MITCH Resurfacing (Stryker) and to correlate these with acetabular component orientation (anteversion and inclination). Twenty-seven patients were enrolled in the study. Serum ion levels were measured pre-operatively, six weeks, six months, twelve months and twenty-four months post-operatively. Axial CT scans of the pelvis were used to measure cup anteversion and plain radiographs used to measure cup inclination. The median serum cobalt and chromium levels at one year were 14.5 nmol/l (range, 6 nmol/l to 59 nmol/l) and 36 nmol/l (range, 17nmol/l to 63 nmol/l) respectively. The median serum cobalt and chromium levels at two years were 16.5 nmol/l (range, 6 nmol/l to 75 nmol/l) and 37.5 nmol/l (range, 13 nmol/l to 109 nmol/l) respectively. The mean cup inclination was 43° (range, 30° to 60°). The mean cup anteversion was 19° (range, 1° to 47°). There was no clear correlation with cup position and serum ion levels. There was one outlier with slightly elevated chromium (109 nmol/l) in a female with a small head size. All patients at all time points showed serum cobalt and chromium levels below the level indicating a high-risk implant (7 parts per billion or chromium >134 nmol/l and cobalt > 119 nmol/l). Our results show no clear relationship between cup position and serum metal ions in this group of patients with relatively well-positioned components
Edge loading commonly occurs in all bearings in hip arthroplasty. The aim of this study compares metal bearings with edge loading to alumina bearings with edge loading and to metal bearings without edge loading. Seventeen failed large diameter metal-on-metal hip bearings (8 total hips, 9 resurfacings) were compared to 55 failed alumina-on-alumina bearings collected from 1998 to 2010. The surface topography of the femoral heads was measured using a chromatically encoded confocal measurement machine (Artificial Hip Profiler, RedLux Ltd.). The median time to revision for the metal hip bearings and the alumina hip bearings was 2.7 years. Forty-six out of 55 (84%) alumina bearings and 9 out 17 (53%) metal bearings had edge loading wear (p<0.01). The average volumetric wear rate for metal femoral heads was 7.87 mm3/yr (median 0.25 mm3/yr) and for alumina heads was 0.78 mm3/yr (median 0.18 mm3/yr) (p=0.02). The average volumetric wear rate for metal heads with edge loading was 16.51 mm3/yr (median 1.77 mm3/yr) and for metal heads without edge loading was 0.19 mm3/yr (median 0 mm3/yr) (p=0.1). There was a significant difference in gender, with a higher ratio of females in the alumina group than the metal group (p=0.02). Large diameter metal femoral heads with edge loading have a higher wear rate than smaller alumina heads with edge loading. Metal-on-metal bearings have low wear when edge loading does not occur.
Alumina ceramic on ceramic bearings in total hip arthroplasty (THA) may reduce the prevalence of osteolysis due to its properties of low wear and chemical inertness. This is critical in the younger patient population as they place increased demands over a longer period. This study reports on the clinical and radiographic outcomes of a series of modern cementless ceramic on ceramic THA at a minimum of 10 years in this younger group. A series of 120 consecutive third generation ceramic cementless THA were performed at a single centre in 110 patients from 1997 to 1999. The average age of the patients at the time of surgery was 45 years (20 to 55 years). All procedures were carried out via the posterior approach using the same implant by the two senior authors.Aim
Method
Two types of ceramic materials currently used in total hip replacements are third generation hot isostatic pressed (HIPed) alumina ceramic (commercially known as BIOLOX®forte, CeramTec) and an alumina matrix composite material consisting of 75% alumina, 24% zirconia, and 1% mixed oxides (BIOLOX®delta, CeramTec). The aim of this study is to compare BIOLOX delta femoral heads to BIOLOX forte femoral heads revised within 2 years in vivo. Ceramic bearings revised at one center from 1998 to 2010 were collected (61 bearings). BIOLOX delta heads (n=11) revised between 1–33 months were compared to BIOLOX forte femoral heads with less than 24 months in vivo (n=20). The surface topography of the femoral heads was measured using a chromatically encoded confocal measurement machine (Artificial Hip Profiler, RedLux Ltd.). The median time to revision for BIOLOX delta femoral heads was 12 months, compared to 13 months for BIOLOX forte femoral heads. Sixteen out of 20 BIOLOX forte femoral heads and 6 out of 11 BIOLOX delta femoral heads had edge loading wear. The average volumetric wear rate for BIOLOX forte was 0.96 mm3/yr (median 0.13 mm3/yr), and 0.06 mm3/yr (median 0.01 mm3/yr) for BIOLOX delta (p=0.03). There was no significant difference (p>0.05) in age, gender, time to revision or femoral head diameter between the two groups. Early results suggest less volumetric wear with BIOLOX delta femoral heads in comparison to BIOLOX forte femoral heads.
Pseudotumours have been associated with metal-on-metal (MoM) hip replacements. We define it as a solid mass which may have cystic components that is neither neoplastic nor infectious in aetiology. The cause of a pseudotumour is not fully understood but could be due to excessive wear, metal hypersensitivity or due to an as-yet unknown cause. We present the retrieval analysis of early failure MoM hips revised for pain, loosening or a symptomatic mass. Tissues and implants were examined for the possible causes of failure and pseudotumour formation. Corrosion as a potential new cause for pseudotumour formation will be presented.Background
Aim
Squeaking ceramics bearing surfaces have been recently recognised as a problem in total hip arthroplasty. The position of the acetabular cup has been alluded to as a potential cause of the squeaking, along with particular combinations of primary stems and acetabular cups. This study has used the finite element method to investigate the propensity of a new large diameter preassembled ceramic acetabular cup to squeaking due to malpositioning. A verified three-dimensional FE model of a cadaveric human pelvis was developed which had been CT scanned, and the geometry reconstructed; this was to be used to determine the behaviour of large diameter acetabular cup system with a thin delta ceramic liner in the acetabulum. The model was generated using ABAQUS CAE pre-processing software. The bone model incorporated both the geometry and the materials properties of the bone throughout based on the CT scan. Finite element analysis and bone material assignment was performed using ABAQUS software and a FORTRAN user subroutine. The loading applied simulated edge loading for rising from a chair, heel-strike, toe off and stumbling. All results of the analysis were used to determine if the liner separated from the shell and if the liner was toggling out of the shell. The results were also examined to see if there was a propensity for the liner to demobilise and vibrate causing a squeaking sound under the prescribed loading regime. This study indicates that there is a reduction in contact area between the ceramic liner and titanium shell if a patient happens to trip or stumble. However, since the contact between the liner and the shell is not completely lost the propensity for it to squeak is highly unlikely.
Reasons for failure of hip resurfacing arthroplasty include femoral neck fracture, loosening, femoral head osteonecrosis, metal sensitivity or toxicity and component malpositioning. Patient factors that influence the outcome include prior surgery, body mass index, age and gender, with female patients having two and a half times greater risk of revision by 5 years than males We explore the relationship between component size and the factors that may influence the survivorship of this procedure, resulting in higher revision rates with smaller components. These include femoral neck loading, edge loading, wear debris production and the effects of metal ions, cement penetration, component orientation, and femoral head vascularity. In particular the way the components are scaled from the large sizes down to the smaller sizes results in some marked changes in interactions between the implant and the patient. Wall thickness of the acetabular and femoral component does not change between the large and small sizes in most devices. This results in a relative excessively thick component in the small sizes. This may cause more acetabular and femoral bone loss, increased risk of femoral neck notching and relative undersizing of the component where acetabular bone is a limiting factor. Stem thickness does not change throughout the size range in many of the devices leading to relatively more femoral bone loss and a greater stiffness mismatch between the femoral stem and the bone. Relatively stiffness between the femoral stem and the bone is up to six times greater in the small size compared to the large size in some designs. The angle subtended by the articular surface (the articular arc) ranges from 170° down to as low as 144° in the small sizes of some devices. A smaller articular arc increases the risk of edge loading, especially if there is any acetabular component malpositioning. Acetabular inclination has been related to metal ion levels 5 and to the early development of pseudotumour An acetabular component with a radiographic inclination of 45° will have an effective inclination anywhere from 50° to 64° depending on the type and size of the component. This corresponds to a centre-edge angle from 40° down to 26°. The effective anteversion is similarly influenced by design. The result of a smaller articular arc is to reduce the size of the ‘safe window’ which is the target for orthopaedic surgeons.
Previously ankylosed or surgically arthrodesed hip joints can be converted successfully to a total hip replacement (THR) in order to improve patient mobility and function. We present a long term prospective cohort study of cementless revisions of previously ankylosed hips. Sixteen hips (15 patients) with a mean age of 52 years (range 16 to 75) had ankylosed hips for a mean of 36 years (range 3.5 to 65 years). They all received a cementless THR between August 1988 and January 2003 and were prospectively followed-up for a mean of 11 years (range 5.0 to 19 years). Two patients died during the study period of unrelated causes and none were lost to follow-up. All patients showed improved mobility and function following the conversion of their ankylosed hips. The Harris Hip Score improved from a pre-operative mean value of 70 (Standard Error of Mean (SEM) 3.4) to a post-operative value of 83 (SEM 4.4) at the latest review, which was statistically significant (p <
0.05). There was one acetabular cup revision at 5 years post implantation for aseptic loosening. At a mean of 11 years post THR, all other femoral and acetabular components remained clinically and radiographically well fixed. One patient with systemic ankylosing spondylitis and spontaneous bilateral bony hip ankylosis developed the unusual complication of Paget’s disease of the left hemipelvis and proximal femur two years after successful bilateral THR surgery. His symptoms resolved following medical therapy for Paget’s disease. We conclude that a previously ankylosed hip can be effectively converted to a cementless total hip replacement with good long term results.
There is a relative risk of 3.0 of dislocation in cups with ≤15 degrees of anteversion compared with >
15 degrees of anteversion. This difference in dislocation is statistically significant (p<
0.01). Increased femoral offset compared with the normal contralateral hip is statistically significantly associated with an increased risk of dislocation (p=0.03). Change in leg length is not associated with dislocation risk.
The increase in femoral offset in the prosthetic hip compared with the normal contralateral hip and its association with dislocation may be due to intraoperative attempts to compensate for an unstable hip by increasing offset. These results indicate that a surgeon should be cautious when increasing femoral offset alone to try and compensate for a potentially unstable hip. Other factors, for example acetabular version should be addressed, with readjustment of cup position intra-operatively if required.
Previously ankylosed or surgically arthrodesed hip joints can be converted successfully to a Total Hip Replacement (THR) in order to improve patient mobility and function. We present a long term prospective cohort study of cementless revisions of previously ankylosed hips. Sixteen hips (15 patients) with a mean age of 52 years (range 16 to 75) had ankylosed hips for a mean of 36 years (range 3.5 to 65 years). They all received a cement-less THR between August 1988 and January 2003 and were prospectively followed-up for a mean of 11 years (range 5.0 to 19 years). Two patients died during the study period of unrelated causes and none were lost to follow-up. All patients showed improved mobility and function following the conversion of their ankylosed hips. The Harris Hip Score improved from a pre-operative mean value of 70 (Standard Error of Mean (SEM) 3.4) to a post-operative value of 83 (SEM 4.4) at the latest review, which was statistically significant (p <
0.05). There was one acetabular cup revision at 5 years post implantation for aseptic loosening. At a mean of 11 years post THR, all other femoral and acetabular components remained clinically and radiographically well fixed. One patient with systemic ankylosing spondylitis and spontaneous bilateral bony hip ankylosis developed the unusual complication of Paget’s disease of the Left hemipelvis and proximal femur two years after successful bilateral THR surgery. His symptoms resolved following medical therapy for Paget’s disease. We conclude that a previously ankylosed hip can be effectively converted to a cementless total hip replacement with good long term results.
Dislocation remains a common complication following total hip arthroplasty, second only to aseptic loosening as a cause of revision. Factors thought to play a role in dislocation include cup and stem alignment, soft tissue tension, surgical approach, patient factors, and design features of the prosthesis, including femoral head size. We analysed all consecutive total hip replacements at one institution over a 17 year period. Criteria for study inclusion were hips replaced due to primary osteoarthritis with no previous surgery, femoral head sizes of 28mm and 32mm only, and at least one year from date of surgery. 3682 hips fulfilled these criteria. All procedures were carried out using a posterolateral approach with enhanced posterior repair, and a standard method of intraoperative soft tissue balance assessment. The rate of dislocation was 1.6%. 32mm femoral head size was associated with a statistically significant lower rate of dislocation. However, after controlling for different follow-up times between 28mm and 32mm heads, this difference was no longer observed. Older age at time of surgery and decreased cup anteversion were shown to be significantly associated with an increased risk of dislocation. Ceramic on ceramic bearing surface was significantly associated with a decreased risk of dislocation, after controlling for age, bearing wear and time from surgery. Cup inclination, gender, BMI, and preoperative hip score were not related to dislocation risk. Our dislocation rate may reflect current dislocation rates of surgeons using the posterolateral approach with posterior capsule and external rotator repair. The risk factors identified and excluded in this study are likely to be relevant to all surgeons who utilise this approach in total hip arthroplasty.
Dislocation remains a common complication following total hip arthroplasty, second only to aseptic loosening as a cause of revision. Factors thought to play a role in dislocation include cup and stem alignment, soft tissue tension, surgical approach, patient factors, and design features of the prosthesis, including femoral head size. We analysed all consecutive total hip replacements at one institution over a 17 year period. Criteria for study inclusion were hips replaced due to primary osteoarthritis with no previous surgery, femoral head sizes of 28mm and 32mm only, and at least one year from date of surgery. 3682 hips fulfilled these criteria. All procedures were carried out using a posterolateral approach with enhanced posterior repair, and a standard method of intraoperative soft tissue balance assessment. The rate of dislocation was 1.6%. 32mm femoral head size was associated with a statistically significant lower rate of dislocation. However, after controlling for different follow-up times between 28mm and 32mm heads, this difference was no longer observed. Older age at time of surgery and decreased cup anteversion were shown to be significantly associated with an increased risk of dislocation. Ceramic on ceramic bearing surface was significantly associated with a decreased risk of dislocation, after controlling for age, bearing wear and time from surgery. Cup inclination, gender, BMI, and preoperative hip score were not related to dislocation risk. Our dislocation rate may reflect current dislocation rates of surgeons using the posterolateral approach with posterior capsule and external rotator repair. The risk factors identified and excluded in this study are likely to be relevant to all surgeons who utilise this approach in total hip arthroplasty.
Squeaking is a rare complication of hard-on-hard hip bearings. Occasionally the noise is troublesome enough to warrant revision surgery. The purpose of this study is to contribute to the understanding of the mechanism(s) underlying squeaking. We analyzed 10 alumina ceramic-on-ceramic bearings from squeaking hips collected at revision surgery. The reason for revision was given as squeaking (6 cases) or squeaking and pain (4 cases). Six of the 10 patients were male, average patient age was 48. Bearings were retrieved after an average of 23 months in service (11 to 61 months). There were 4 different designs of acetabular component from 2 different manufacturers. Nine have an elevated metal rim which is proud of the ceramic and one does not. Two bearings were 36mm in diameter, 6 were 32mm and 2 were 28mm. All 10 bearings showed evidence of edge loading wear. Mean dimensions of the wear patch were 37mm by 12mm on the acetabular component and 32mm by 13mm on the femoral heads. Wear dimension was not related to bearing diameter. Seven of the 10 implants also had evidence of impingement of the femoral neck against the elevated metallic rim or the ceramic insert or both. There was no chipping or fracture of any of the ceramic components. Squeaking is a recently recognized complication of hard on hard bearing surface. This retrieval study is the first of its kind, to our knowledge attempting to unravel the mechanism of this undesirable complication. Although impingement seems to be present in majority of cases, the latter does not seem to be necessary. Edge loading wear was the common factor in all cases and this may prove to be a critical mechanism.
1152 ABG I primary hip arthroplasties were performed in 1037 patients from 1991–1997. Osteoarthritis was diagnosed in 93% of cases. The average age was 65 years; there were 536 females and 501 males. Mean follow-up was 79.6 months.
The average age of the fracture group was 73 years, compared to 65 years for the whole series (p<
0.0001). The incidence of periprosthetic fracture increased with age. The relative risk for patients over 70 years for peri-prosthetic fracture is 4.7 greater (95% CI 2.14–10.21). Distinct fractures patterns were related to time from initial surgery. Four fractures occurred within three months of surgery; these early fractures exhibited a particular pattern. The remaining 24 occurred between four and 114 months after surgery. These late fractures exhibited a different but consistent fracture pattern. Two fractures in the early group were identified immediately post-operatively. All others presented after minor low energy trauma. The mean cortical index in the fracture group was 47% and in the matched group 51%. If the pre-operative cortical index is below 50%, the risk of periprosthetic fracture is 4.75 greater (odds ratio 4.75 CI 1.5–15.00). All fractures were adequately classified and managed by guidelines in the Vancouver classification.
In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.
A cannula was placed through the capsule into the hip joint and another was placed through the periosteum and bone of the ilium into the osteolytic lesion above the ingrown cup. The continuity of these two spaces through the holes in the cup was confirmed by the injection of methylene blue. Pressure transducers were then connected to both cannulae. Measurements were taken while applying compression and distraction forces across the artificial hip joint.
The average time from primary procedure to revision was 72 months. The osteolytic group was younger than the overall group at the time of index surgery (53 years vs 63 years, p<
0.0001). There were 16 females and 7 males (p = 0.06). The osteolytic group were also less likely to have an initial diagnosis of primary osteoarthritis than the control group (p=0.05). Other diagnoses in the osteolytic group included dysplasia, previous trauma and inflammatory arthropathy. Acetabular liner thickness was assessed for all patients. The osteolytic group had a significantly higher proportion of cases with polyethylene thickness of less than 7mm (p <
0.005), and less than 6mm (p <
0.0001). There was no difference in the mean height and weight of the two groups.
There were 78 Crowe I &
II, and 18 Crowe III &
IV hips. The more dysplastic hips required the versatility of the SROM stems to avoid excessive lengthening or femoral osteotomy. These cases also had significantly more inferior reconstruction of the hip centre, and medialisation of the hip centre. Complications occurred in 8/106 (8%) of cases, the mean time to occurrence being 25 months. The majority were dislocations 7 (7%). There were no sciatic nerve palsies. Revision was required for 5 cups and 1 stem. Clinical evaluation showed all patients were living at home and 85% had no activity restrictions. Mean Harris Hip Score was 92/100. None or mild thigh pain only was reported in 90% of cases. In 98% of cases patients were satisfied with their outcome. Radiographic evaluation showed stem ingrowth occurred in all cases. Minor osteolysis was apparent in 6% of cases. Spot welds were identified in 76% of cases. One case demonstrated pedestal formation.