Revision for adverse local tissue reaction following metal-on-polyethylene total hip arthroplasty is associated with a high risk of early major complications.

Aims: Fretting and corrosion at the modular head/neck junction, known as trunnionosis, in total hip arthroplasty (THA) is a cause of adverse reaction to metal debris (ARMD). We describe the outcome of revision of metal-on-polyethylene (MoP) THA for ARMD due to trunnionosis with emphasis on the risk of major complications. Patients and Methods: A total of 36 patients with a MoP THA who underwent revision for ARMD due to trunnionosis were identified. Three were excluded as their revision had been to another metal head. The remaining 33 were revised to a ceramic head with a titanium sleeve. We describe the presentation, revision findings, and risk of complications in these patients. Results: The patients presented with pain, swelling, stiffness, or instability and an inflammatory mass was confirmed radiologically. Macroscopic material deposition on the trunnion was seen in all patients, associated with ARMD. Following revision, six (18.2%) dislocated, requiring further revision in four. Three (9.1%) developed a deep infection and six (18.2%) had significant persistent pain without an obvious cause. One developed a femoral artery thrombosis after excision of an iliofemoral pseudotumor, requiring a thrombectomy. Conclusion: The risk of serious complications following revision MoP THA for ARMD associated with trunnionosis is high. In the presence of extensive tissue damage, a constrained liner or dual mobility construct is recommended in these patients. Cite this article: Bone Joint J 2018;100-B:720-4.

Delayed dislocation following metal-on-polyethylene arthroplasty of the hip due to 'silent' trunnion corrosion.

AIMS: We present a case series of ten metal-on-polyethylene total hip arthroplasties (MoP THAs) with delayed dislocation associated with unrecognised adverse local tissue reaction due to corrosion at the trunnion and pseudotumour formation. METHODS: The diagnosis was not suspected in nine of the ten patients (six female/four male; mean age 66 years), despite treatment in a specialist unit (mean time from index surgery to revision was 58 months, 36 to 84). It was identified at revision surgery and subsequently confirmed by histological examination of resected tissue. Pre-operative assessment and culture results ruled out infection. A variety of treatment strategies were used, including resection of the pseudotumour and efforts to avoid recurrent dislocation. RESULTS: The rate of complications was high and included three deep infections, two patients with recurrent dislocation, and one recurrent pseudotumour. CONCLUSION: This series (mean follow-up of 76 months following index procedure and 19 months following revision THA) demonstrates that pseudotumour is an infrequent but important contributor to delayed instability following MoP THA. It is easy to overlook in the differential diagnosis, especially if the alignment of the components is less than optimal, leading to an assumption that malalignment is the cause of the dislocation. The instability is likely to be multifactorial and the revision surgery is complex. TAKE HOME MESSAGE: Due to the high complication rate associated with revision in this cohort, the diagnosis should be borne in mind when counselling patients regarding the risks of revision surgery.

Adverse local tissue reactions in metal-on-polyethylene total hip arthroplasty due to trunnion corrosion: the risk of misdiagnosis.

Adverse reaction to wear and corrosion debris is a cause for concern in total hip arthroplasty (THA). Modular junctions are a potential source of such wear products and are associated with secondary pseudotumour formation. We present a consecutive series of 17 patients treated at our unit for this complication following metal-on-highly cross-linked polyethylene (MoP) THA. We emphasise the risk of misdiagnosis as infection, and present the aggregate laboratory results and pathological findings in this series. The clinical presentation was pain, swelling or instability. Solid, cystic and mixed soft-tissue lesions were noted on imaging and confirmed intra-operatively. Corrosion at the head-neck junction was noted in all cases. No bacteria were isolated on multiple pre- and intra-operative samples yet the mean erythrocyte sedimentation rate was 49 (9 to 100) and C-reactive protein 32 (0.6 to 106) and stromal polymorphonuclear cell counts were noted in nine cases. Adverse soft-tissue reactions can occur in MoP THA owing to corrosion products released from the head-neck junction. The diagnosis should be carefully considered when investigating pain after THA. This may avoid the misdiagnosis of periprosthetic infection with an unidentified organism and mitigate the unnecessary management of these cases with complete single- or two-stage exchange.

Development of a population-based microsimulation model of osteoarthritis in Canada.

OBJECTIVES: The purpose of the study was to develop a population-based simulation model of osteoarthritis (OA) in Canada that can be used to quantify the future health and economic burden of OA under a range of scenarios for changes in the OA risk factors and treatments. In this article we describe the overall structure of the model, sources of data, derivation of key input parameters for the epidemiological component of the model, and preliminary validation studies. DESIGN: We used the Population Health Model (POHEM) platform to develop a stochastic continuous-time microsimulation model of physician-diagnosed OA. Incidence rates were calibrated to agree with administrative data for the province of British Columbia, Canada. The effect of obesity on OA incidence and the impact of OA on health-related quality of life (HRQL) were modeled using Canadian national surveys. RESULTS: Incidence rates of OA in the model increase approximately linearly with age in both sexes between the ages of 50 and 80 and plateau in the very old. In those aged 50+, the rates are substantially higher in women. At baseline, the prevalence of OA is 11.5%, 13.6% in women and 9.3% in men. The OA hazard ratios for obesity are 2.0 in women and 1.7 in men. The effect of OA diagnosis on HRQL, as measured by the Health Utilities Index Mark 3 (HUI3), is to reduce it by 0.10 in women and 0.14 in men. CONCLUSIONS: We describe the development of the first population-based microsimulation model of OA. Strengths of this model include the use of large population databases to derive the key parameters and the application of modern microsimulation technology. Limitations of the model reflect the limitations of administrative and survey data and gaps in the epidemiological and HRQL literature.

Finding and defining the ideal patellar resection plane in total knee arthroplasty.

Asymmetric resection of the patella during total knee arthroplasty (TKA) correlates with anterior knee pain, bony impingement and patellar maltracking. Despite this, there is no consensus regarding the desired landmarks; the cut is often done freehand; and there has been no quantitative comparison of proposed resection planes. The objectives of this study were to: determine the intra- and inter-surgeon repeatability of two radiographic resection definitions (medial-divot, MD, and medial-lateral extents, MLE); calculate two additional definitions from the radiographic patellar circumferences (parallel to the anterior surface, ANT, and perpendicular to the anteroposterior tangent points, PERP); compare the clinical resection line to the previous four definitions before and after introducing the MD method clinically; and identify distinguishing features of patellae with better vs. worse resection angles. We hypothesized that the MD method would improve repeatability both radiographically and clinically, that the different radiographic definitions would produce comparable angles, and that we could identify distinguishing features. For the radiographic study, three surgeons drew lines on 40 preoperative X-rays plus 9 interspersed repetitions of 3 of these X-rays. For the clinical study, we compared the patellar resection angle for 20 patients immediately before and after implementing the new method. Given that the clinical goal is to have equal distances from the resection surface to the anterior surface, we compared all results to the ANT definition as the theoretically ideal definition. Confirming the first hypothesis, intra-surgeon repeatability (10 repetitions of 3 X-rays) and inter-surgeon repeatability (3 surgeons x 40 X-rays) were both significantly better using the new MD method compared to the MLE method (p<0.001). Contrary to the second hypothesis, clinical use of the MD method did not improve resection symmetry. Contrary to the third hypothesis, the PERP definition was significantly different from the other three definitions. In agreement with the fourth hypothesis, female patellae and more deformed patella had significantly greater asymmetry (p<0.001). Given the inherent variability shown in drawing the 'patellar horizon', we encourage researchers to draw the line several times and average the results when comparing tilt or the resection angle to this horizon. Based on the distinguishing characteristics of asymmetrically resurfaced patellae in our series, we recommend that clinicians be particularly careful when resecting laterally deformed patellae and the patellae of female patients.

Porous tantalum uncemented acetabular shells in revision total hip replacement: two to four year clinical and radiographic results.

In cementless revision total hip arthroplasty (THA), achieving initial implant stability and maximising host bone contact is key to the success of reconstruction. Porous tantalum acetabular shells may represent an improvement from conventional porous coated uncemented cups in revision acetabular reconstruction associated with severe acetabular bone defects. We reviewed the results of 46 acetabular revisions with Paprosky 2 and 3 acetabular bone defects done with a hemispheric, tantalum acetabular shell and multiple supplementary screws. At a mean follow-up of 40 (24-51) months, one acetabular shell had been revised in a patient with a Paprosky 3B defect. Cementless acetabular revision with the tantalum acetabular shell demonstrated excellent early clinical and radiographic results and warrants further evaluation in revision acetabular reconstruction associated with severe acetabular bone defects.

Determinants of patellar tracking in total knee arthroplasty.

BACKGROUND: Optimizing patellar tracking in total knee arthroplasty is a surgical priority. Despite this, a comparison of the effects of different component placements on patellar tracking is not available; the biomechanical impact of the patellar resection angle has not been studied; and the similarity between intraoperative and postoperative effects, fundamental to improving patellar tracking, is unknown. Our objective was to compare the impact of the major controllable femoral, tibial and patellar component positions on patellar kinematics during both passive and loaded flexion. METHODS: We tested eight cadaveric knee specimens in two rigs, simulating intraoperative and weightbearing flexion. Optoelectronic marker arrays were attached to the femur, tibia and patella to record kinematics throughout the range of motion. We modified posterior-stabilized fixed-bearing knee components to allow for five types of variations in component placement in addition to the neutral position: femoral component rotation, tibial component rotation, patellar resection angle, patellar component medialization and additional patellar thickness, for a total of 11 individual variations. FINDINGS: The major determinants of patellar tilt and shift were patellar component medialization, patellar resection angle and femoral component rotation. The relative order of these variables depended on the structure (bone or component), kinematic parameter (tilt or shift) and flexion angle (early or late flexion). Effects of component changes were consistent between the intraoperative and weightbearing rigs. INTERPRETATION: To improve patellar tracking, and thereby the clinical outcome, surgeons should focus on patellar component medialization, patellar resection angle and femoral component rotation. These have been linked with anterior knee pain as well. Neither tibial component rotation nor patellar thickness should be adjusted to improve patellar tracking.

Intraoperative vs. weightbearing patellar kinematics in total knee arthroplasty: a cadaveric study.

BACKGROUND: During knee replacement surgery, surgeons optimize intraoperative patellar tracking with the aim of optimizing postoperative tracking. This link has not been investigated to date. Our research questions were: (1) How well do patellar kinematics correlate between passive and weightbearing flexion across numerous changes in component placement? (2) How do the kinematics differ between the two loading configurations? METHODS: Eight cadaveric knee joints with modified knee components that allowed 11 different femoral, tibial and patellar placements were tested in two experimental rigs simulating intraoperative and weightbearing dynamic flexion. Baseline placement had all components in neutral position. Pearson correlation coefficients were calculated for absolute baseline kinematics and for relative kinematics due to changes in component position (i.e., the 10 altered positions vs. baseline). FINDINGS: Correlations between intraoperative and weightbearing rigs for absolute baseline kinematics were unpredictable, ranging from poor to excellent (mean 0.56 for tilt and mean 0.50 for shift). Correlations between rigs for changes in tilt and shift, i.e. relative kinematics, were strong (>0.8) or very strong (>0.9), with the exception of shift in early flexion (0.54). Differences in relative kinematics, which averaged 2.2 degrees in tilt (standard deviation 1.8 degrees ) and 1.6mm in shift (standard deviation 1.7mm), were notably smaller and less variable than differences in absolute kinematics, which averaged 4.2 degrees in tilt (standard deviation 3.6 degrees ) and 4.3mm in shift (standard deviation 3.9mm). INTERPRETATION: The results of this study suggest that, while absolute kinematics may differ between conditions, if a surgeon adjusts a component position to improve patellar kinematics intraoperatively, the effects of such a geometric change will likely carry through to the postoperative joint.

Predictors of quality of life outcomes after revision total hip replacement.

A prospective cohort of 222 patients who underwent revision hip replacement between April 2001 and March 2004 was evaluated to determine predictors of function, pain and activity level between one and two years post-operatively, and to define quality of life outcomes using validated patient reported outcome tools. Predictive models were developed and proportional odds regression analyses were performed to identify factors that predict quality of life outcomes at one and two years post-operatively. The dependent outcome variables were the Western Ontario and McMaster Osteoarthritis Index (WOMAC) function and pain scores, and University of California Los Angeles activity scores. The independent variables included patient demographics, operative factors, and objective quality of life parameters, including pre-operative WOMAC, and the Short Form-12 mental component score. There was a significant improvement (t-test, p < 0.001) in all patient quality of life scores. In the predictive model, factors predictive of improved function (original regression analyses, p < 0.05) included a higher pre-operative WOMAC function score (p < 0.001), age between 60 and 70 years (p < 0.037), male gender (p = 0.017), lower Charnley class (p < 0.001) and aseptic loosening being the indication for revision (p < 0.003). Using the WOMAC pain score as an outcome variable, factors predictive of improvement included the pre-operative WOMAC function score (p = 0.001), age between 60 and 70 years (p = 0.004), male gender (p = 0.005), lower Charnley class (p = 0.001) and no previous revision procedure (p = 0.023). The pre-operative WOMAC function score (p = 0.001), the indication for the operation (p = 0.007), and the operating surgeon (p = 0.008) were significant predictors of the activity assessment at follow-up. Predictors of quality of life outcomes after revision hip replacement were established. Although some patient-specific and surgery-specific variables were important, age, gender, Charnley class and pre-operative WOMAC function score had the most robust associations with outcome.

Comparative repeatability of guide-pin axis positioning in computer-assisted and manual femoral head resurfacing arthroplasty.

The orientation of the femoral component in hip resurfacing arthroplasty affects the likelihood of loosening and fracture. Computer-assisted surgery has been shown to improve significantly the surgeon's ability to achieve a desired position and orientation; nevertheless, both bias and variability in positioning remain and can potentially be improved. The authors recently developed a computer-assisted surgical (CAS) technique to guide the placement of the pin used in femoral head resurfacing arthroplasty and showed that it produced significantly less variation than a typical manual technique in varus/valgus placement relative to a preoperatively determined surgical plan while taking a comparable amount of time. In the present study, the repeatability of both the CAS and manual techniques is evaluated in order to estimate the relative contributions to overall variability of surgical technique (CAS versus manual), surgeon experience (novice versus experienced), and other sources of variability (e.g. across specimens and across surgeons). This will enable further improvements in the accuracy of CAS techniques. Three residents/fellows new to femoral head resurfacing and three experienced hip arthroplasty surgeons performed 20-30 repetitions of each of the CAS and manual techniques on at least one of four cadaveric femur specimens. The CAS system had markedly better repeatability (1.2 degrees) in varus/valgus placement relative to the manual technique (2.8 degrees), slightly worse repeatability in version (4.4 degrees versus 3.2 degrees), markedly better repeatability in mid-neck placement (0.7 mm versus 2.5 mm), no significant dependence on surgeon skill level (in contrast to the manual technique), and took significantly less time (50 s versus 123 s). Proposed improvements to the version measurement process showed potential for reducing the standard deviation by almost two thirds. This study supports the use of CAS for femoral head resurfacing as it is quicker than the manual technique, independent of surgeon experience, and demonstrates improved repeatability.

The extensile rectus snip exposure in revision of total knee arthroplasty.

Revision of a total knee arthroplasty may require an extensile approach to permit a satisfactory exposure without compromising the attachment of the patellar tendon. It has been assumed that a rectus snip is a relatively benign form of release, but the effect of using this approach on function, pain and patient satisfaction is not known. From January 1997 to December 1999, 107 patients who underwent revision of total knee arthroplasty were followed up at a minimum of two years (mean 40.5 months) and assessed by the Oxford Hip Score, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), the Short-Form (SF)-12 and patient satisfaction. Co-morbidity, surgical exposure, the Hospital for Special Surgery (HSS) knee scores and the range of movement were also used. A standard medial parapatellar approach was used in 57 patients and the rectus snip in 50. The two groups were equivalent for age, sex and co-morbidity scores. The WOMAC function, pain, stiffness and satisfaction scores demonstrated no statistical difference. The use of a rectus snip as an extensile procedure has no effect on outcome.

Removal of well-fixed, cementless, acetabular components in revision hip arthroplasty.

Removal of well-fixed, cementless, acetabular components during revision arthroplasty remains a challenging problem. Further damage to host bone may limit options for reconstruction and compromise the long-term result of the revision operation. We report the results of 31 hips with well-fixed, cementless sockets which were removed using a new cup extraction system. In all hips the socket was removed without difficulty and with minimal further bone loss.

Treatment of hip instability.

Instability after total hip arthroplasty is a major source of patient morbidity, second only to aseptic loosening. Certain patient groups have been identified as having a greater risk of instability, including patients undergoing revision arthroplasty as early or late treatment for proximal femoral fractures.

Extensively coated cementless femoral components in revision hip arthroplasty.

A septic loosening and osteolysis can compromise the available host bone in patients requiring revision hip arthroplasty. Secure fixation of revision femoral components may not be possible if reliant only on proximal femoral bone for biologic fixation or cement interdigitation. The challenge for the revision arthroplasty surgeon is to find the best method to secure the implant in a femur with deficient bone proximally that will provide stability for load bearing and motion. In addition to providing stability, the implant must be durable and maintain long-term fixation. With over 16 years of experience with fully porous coated femoral revision implants, we have found that maximizing prosthetic-bone fit in the proximal femoral diaphyseal bone provides reliable long-term fixation in the majority of femoral revision cases.

Minimum 10-year-results of extensively porous-coated stems in revision hip arthroplasty.

Obtaining predictable, stable fixation of revision femoral implants is important for the long-term success of revision hip arthroplasty. The authors report on minimum 10 years clinical and radiographic followup of 170 patients with extensively coated cementless revision femoral components. With a range of followup of 10 to 16 years and a mean of 13.2 years, a survivorship of greater than 95% was reported. Clinically, the average Postel-D'Aubigne pain and walking score improved from a preoperative score of 5.4 points to 10.8 points postoperatively. Eighty-two percent of the hips had radiographic evidence of a bone-ingrown prosthesis and 13.9% had evidence of stable fibrous fixation. Four percent of stems were unstable as seen on radiographs. Six stems were revised to larger extensively coated stems and one stem is causing pain and is unstable but has yet to be revised. The overall mechanical failure rate was 4.1%. Stress shielding was greatest in patients with stems larger than 16.5 mm and in osteoporotic bone (Dorr Type C). Nine percent of patients had significant thigh pain including all of the patients with unstable stems. In the presence of bone loss in the proximal metaphyseal region of the femur, fixation of the femoral component is predictable when optimizing prosthetic-bone fit in the diaphyseal region of the femur using an extensively coated femoral component.

High rate of failure of allograft reconstruction of the extensor mechanism after total knee arthroplasty.

BACKGROUND: Disruption of the extensor mechanism is an uncommon but devastating complication of total knee arthroplasty. Several techniques for reconstruction of the extensor mechanism after total knee arthroplasty have been reported, but we do not know of any study in which the results of one group's method were corroborated by a second group using the same technique. In the present series, we evaluated the results of reconstruction of the extensor mechanism with use of allograft according to the method described by Emerson et al. METHODS: Seven reconstructions of the extensor mechanism with use of a bone-tendon-bone allograft were performed with the technique of Emerson et al. in six patients. The patients were evaluated before and after the operation. The knee score according to the system of The Hospital for Special Surgery, evidence of an extensor lag, use of walking aids, and the ambulatory status of each patient were recorded. The patients were also asked about, and the medical records were reviewed for, episodes of falling related to weakness of the quadriceps after the reconstruction. The mean duration of follow-up was thirty-nine months (range, six to 115 months). As these reconstructions often fail early, the minimum duration of follow-up was six months. RESULTS: All seven reconstructions were rated as clinical failures on the basis of a persistent or recurrent extensor lag of more than 30 degrees. All but one patient needed an assistive device full time for walking, and four patients (five knees) had at least one documented episode of falling that was due to giving-way of the affected knee. Four of the reconstructions were revised; one revision was performed with use of another extensor mechanism allograft and three were performed with use of a medial gastrocnemius rotation flap. The other three clinical failures had not been revised at the time of writing. At the time of the most recent follow-up (or at the time of revision of the extensor reconstruction), the mean extensor lag was 59 degrees and the mean knee score was 52 points (a poor result). CONCLUSIONS: Undertensioning of the allograft reconstruction at the time of the operation and attenuation of the allograft both may have played a role in the inability of the patients to regain active extension of the knee postoperatively. Alternative techniques for reconstruction of the extensor mechanism or modifications of this technique should be considered in the treatment of this difficult problem.

A comparison of the innervation characteristics of the lateral spinal ligaments between normal subjects and patients with adolescent idiopathic scoliosis.

Evidence is rapidly accumulating to suggest that general proprioceptive dysfunction might be a major contributing factor in the development of adolescent idiopathic scoliosis (AIS). The innervation of appropriate ligaments which has been shown to be involved in proprioceptive feedback mechanisms, has also been suggested to play a part in this sensory dysfunction. Accordingly, this study compared the innervation characteristics of lateral spinal ligaments from patients with AIS to similar measurements from control subjects. Using an antibody to neurofilament protein, Ruffini corpuscles, small and large nerve bundles, and free nerve endings were identified and their numbers and distribution patterns compared. In the control group, the innervation was found to be symmetrical between left and right sides but was more concentrated in the ventral portion of each ligament. No apparent morphological defect of the innervation was found in the lateral spinal ligaments of the scoliosis patients but the innervation densities of Ruffini corpuscles, single nerve fibres and total neural elements were significantly lower (p<0.01) than those found in normal subjects. These results suggest a possible mechanism for the production of AIS and warrant further study.

The spatiotemporal development of innervation in spinal ligaments of chickens.

The development of the innervation of both central and lateral (intertransverse) spinal ligaments was investigated in chickens between the time of hatching and 13 wk of age. A total of 36 White Leghorn chickens in 4 groups of 9 at ages 0, 2, 7, and 13 wk were used. The spinal ligaments were dissected, serially sectioned and labelled with a monoclonal antibody against neurofilament protein and observed using either conventional fluorescence or confocal microscopy. Only a few nerve elements were found in the ligaments at hatching and these consisted simply of single nerve fibres and small nerve bundles. The number of nerve elements increased rapidly up to 7 wk of age when large nerve bundles and Ruffini corpuscles were also found. The number of nerve elements decreased between 7 and 13 wk birds when the ligaments had begun to ossify and the amount of collagenous ligamentous tissue was significantly reduced. The fluctuation in numbers of neural elements was due to changes in numbers of single nerve fibres and small nerve bundles rather than large nerve bundles and Ruffini corpuscles which remained constant. In contrast to this significant increase in numbers of nerve elements, the innervation density of the ligaments decreased because of the overwhelming increase of the ligament volume due to growth. There were no differences between ligaments on the left and right sides of the body, but there was an unequal distribution of the neural elements within the ligaments; most were found in the cranial third of the intertransverse ligaments. These results show that significant changes in innervation of spinal ligaments occur during development and reflect the possibility that damage to the ligaments during this time could produce significant and permanent damage, especially in relation to the maintenance of an erect spine.