Prolonged Conservative Management in Total Joint Arthroplasty: Harming the Patient?

BACKGROUND: It is important to understand the long-term consequences of postponing total joint arthroplasty until the onset of severe functional impairment. Therefore, the purpose of this investigation was to determine and compare the midterm to long-term postoperative outcomes of patients who underwent total joint arthroplasty with severe vs less severe preoperative functional impairment. METHODS: A total of 105 primary unilateral total hip/knee arthroplasty patients were studied. Patients were divided into 2 groups-severely functionally impaired (preoperative Western Ontario and McMaster Osteoarthritis Index function ≥51 points) and functionally impaired (preoperative Western Ontario and McMaster Osteoarthritis Index function <51 points). RESULTS: At an average of 11.2 years postoperatively, the patients who were severely functionally impaired preoperatively had worse outcomes than did the patients with less severe preoperative functional impairment. CONCLUSION: Our data suggest that, after surgery, it is unlikely that patients who are severely functionally impaired preoperatively will ever catch up to patients who have the surgery with less severe functional impairment.

Preoperative Glycemic Control on Total Joint Arthroplasty Patient-Perceived Outcomes and Hospital Costs.

BACKGROUND: The purpose of this study was to determine the influence of preoperative glycemic control in diabetic patients undergoing a primary total hip or knee arthroplasty. We wanted to study patient-perceived outcomes in the medium term, the length of stay, hospital costs, and rate of short-term postoperative complications. METHODS: One hundred twenty consecutive primary total joint arthroplasties (TJAs) performed in type 2 diabetic patients were stratified into 2 groups representing optimal and suboptimal preoperative glycemic control, based on serum levels of glycated hemoglobin (HbA1c), and those groups compared. RESULTS: The mean follow-up time was 5.9 years (range, 2.1-10.7 years). Both groups demonstrated improvement in all patient-perceived outcome measures after TJA, with no significant difference detected in any change of a measure between the groups. No significant difference was detected in the length of stay, hospital costs, or rate of short-term postoperative complications between the groups. CONCLUSION: Preoperative glycemic control in type 2 diabetic patients undergoing TJA did not affect patient-perceived outcomes in the medium term. Optimal vs suboptimal glycemic control in these patients also had no effect on the length of stay, hospital costs, or rate of short-term postoperative complications.

THA Retrievals: The Need to Mark the Anatomic Orientation of the Femoral Head.

The hypothesis of this study was that the rotational orientation of femoral head damage would greatly affect the volumetric wear rate of the opposing polyethylene (PE) liner. Damage on twenty retrieved cobalt-chromium femoral heads was simulated in a validated damage-feature-based finite element model. For each individual retrieval, the anatomic orientation of the femoral head about the femoral neck axis was systematically varied, in 30° increments. The PE wear rate differential between the maximum- versus minimum-wear orientations was often sizable, as high as 7-fold. Knowing the correct femoral head anatomic orientation is therefore important when analyzing the effects of femoral head damage on PE liner wear. Surgeons retrieving modular femoral heads should routinely mark the anatomic orientation of those components.

Modeling polyethylene wear acceleration due to femoral head dislocation damage.

Scratching, scraping, and metal transfer to femoral heads commonly accompany acetabular shell contact during dislocation and closed reduction maneuvers. While head damage conceptually leads to accelerated wear, reports on this subject are mainly anecdotal, and differ widely on the potency of such effect. Towards better understanding this relationship, a physically validated finite element (FE) model was used to compute polyethylene wear acceleration propensity of specific head damage patterns on thirteen retrievals. These FE models estimated wear increases averaging half an order of magnitude when compared to simulations for undamaged heads. There was no correlation between the number of dislocations sustained and wear acceleration. These results underscore the importance of implant-gentle closed reduction, and heightened wear monitoring of successfully reduced dislocation patients.

Enhancing damage visibility on metallic bearing surfaces: a simple technique for photography and viewing.

Damage to metallic bearing surfaces typically involves scratches, scrapes, metal transfer, and organic deposits. This damage can cause accelerated wear of the opposing surface and subsequent implant failure. Photography and viewing of metallic bearing surfaces, for documenting this damage, are hindered by optical reflectivity. This note demonstrates a simple, practical technique for metallic bearing surface photography and viewing that minimizes this reflectivity problem, that does not involve any modification of the bearing surface, and that allows for improved observation and documentation of overall damage. When the metallic bearing surface is placed within a tube of translucent material, the appearance of damage on that bearing surface is dramatically enhanced, showing up against a smooth, even background with excellent contrast and with fine detail achievable.

Cementing acetabular liners into secure cementless shells for polyethylene wear provides durable mid-term fixation.

BACKGROUND: In a previous experiment studying cementation of liners into cementless acetabular shells, placing grooves in the liner in a spider-web configuration created the greatest construct strength. Scoring shells without screw holes or other texturing helped prevent failure at the shell-cement interface. However, it was unclear whether these practices caused durable constructs in patients. QUESTIONS/PURPOSES: We therefore determined (1) rerevision rates; (2) functional scores (Harris hip scores, WOMAC, and SF-36); (3) acetabular loosening rates; and (4) acetabular osteolysis rates in patients in whom we cemented nonconstrained liners into well-fixed and well-positioned acetabular shells. METHODS: We prospectively followed 30 patients with 31 total hip arthroplasties in which a worn acetabular liner was revised by cementing a new liner into the existing shell that was stable and well positioned. Acetabular liners were prepared as determined by our previous study. Twenty-seven of the 30 patients (28 hips) were evaluated clinically. We recorded revisions and determined radiographic loosening and osteolysis. The minimum clinical followup was 2 years (mean, 5.3 years; range, 2-10 years). Twenty-six hips (87%) had minimum 2-year radiographic followup with an average length of 4.8 years. RESULTS: No hip required rerevision during the followup interval. Two hips (6%) dislocated once, both treated nonoperatively. Harris hip scores, WOMAC, and SF-36 scores increased over preoperatively at last followup. All acetabular shells and liners were radiographically stable without evidence of loosening or progressive acetabular osteolysis. CONCLUSIONS: Cementation of a liner into a well-fixed cementless shell after scoring in a spider-web configuration provided secure fixation with no failures of the construct at average 5.3 years followup. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Scratching vulnerability of conventional vs highly cross-linked polyethylene liners because of large embedded third-body particles.

The hypothesis of this study was that acetabular liner vulnerability to scratching from femoral heads, roughened by third bodies embedded in the liner, is not significantly lower for highly cross-linked polyethylene (HXPE) than for conventional polyethylene (CPE). Six CPE and 6 HXPE acetabular liners were each reproducibly embedded with 5 cobalt-chromium-molybdenum (CoCrMo) beads then run for 10,000 cycles in a joint simulator. By visual rank ordering, there was low association between liner scratch severity and polyethylene type. The CPE and HXPE liner scratches were not significantly different in scratch peak-valley height or width or in liner roughness in the vicinity of the embedded beads. This model indicated that high cross-linking of polyethylene does not offer appreciable protection against severe scratching induced by large embedded third-body particles.

Methodology for measuring the in vitro seating and unseating forces of prefabricated attachment systems used to retain implant overdentures.

PURPOSE: The purpose of this in vitro investigation was to measure the forces generated during the continuous seating and unseating of prefabricated attachment systems used to retain implant overdentures. MATERIALS AND METHODS: An experimental design consisting of interchangeable fixture mounts, a radially indexable fixture holder, and a materials testing systems (MTS) machine was used to measure forces generated during the insertion and removal of spherical stud attachments (Straumann, Inc, Waltham, WA). Three separate experiments were conducted measuring the seating and unseating forces of a vertically aligned patrix/matrix assembly, a 20 degrees angled patrix opposing a vertically positioned matrix, and a vertically positioned patrix opposing a 20 degrees angled matrix. For each patrix/matrix combination, three specimens were tested. Measurements were continuously recorded under reproducible conditions in the presence of artificial saliva. All specimens were subjected to 10,000 seating/unseating cycles. Statistical analysis was performed with rank analysis of variance (ANOVA) for a group comparison (alpha= 0.05). RESULTS: Results showed variability in the initial insertion and removal forces among experimental groups and among specimens within each experiment. A marked increase in the seating and unseating forces was recorded for all specimens during the first 300 cycles, followed by a gradual decrease in these forces. The exact p-values for the Kruskal-Wallis test showed no significant difference between the initial and final seating/unseating forces (p > 0.1) nor in the maximum seating/unseating forces (p > 0.6) among the three experimental groups. CONCLUSIONS: Spherical stud attachments exhibited consistent seating and unseating forces over 10,000 cycles. A 20 degrees angle between the patrix and matrix had no effect on the overall seating and unseating force values.

Outcomes of posterior cervical fusion and decompression: a systematic review and meta-analysis.

BACKGROUND CONTEXT: Posterior cervical fusion (PCF) with decompression is a treatment option for patients with conditions such as spondylosis, spinal stenosis, and degenerative disc disorders that result in myelopathy or radiculopathy. The annual rate, number, and cost of PCF in the United States has increased. Far fewer studies have been published on PCF outcomes than on anterior cervical fusion (ACF) outcomes, most likely because far fewer PCFs than ACFs are performed. PURPOSE: To evaluate the patient-reported and clinical outcomes of adult patients who underwent subaxial posterior cervical fusion with decompression. STUDY DESIGN/SETTING: Systematic review and meta-analysis. PATIENT SAMPLE: The total number of patients in the 31 articles reviewed and included in the meta-analysis was 1,238 (range 7-166). OUTCOME MEASURES: Preoperative to postoperative change in patient-reported outcomes (visual analog scales for arm pain and neck pain, Neck Disability Index, Japanese Orthopaedic Association [JOA] score, modified JOA score, and Nurick pain scale) and rates of fusion, revision, and complications or adverse events. METHODS: This study was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and a preapproved protocol. PubMed and Embase databases were searched for articles published from January 2001 through July 2018. Statistical analyses for patient-reported outcomes were performed on the outcomes' raw mean differences, calculated as postoperative value minus preoperative value from each study. Pooled rates of successful fusion, revision surgery, and complications or adverse events, and their 95% confidence intervals, were also calculated. Two subgroup analyses were performed: one for studies in which only myelopathy or radiculopathy (or both) were stated as surgical indications and the other for studies in which only myelopathy or ossification of the posterior longitudinal ligament (or both) were stated as surgical indications. This study was funded by Providence Medical Technology, Inc. ($32,000). RESULTS: Thirty-three articles were included in the systematic review, and 31 articles were included in the meta-analysis. For all surgical indications and for the 2 subgroup analyses, every cumulative change in patient-reported outcome improved. Many of the reported changes in patient-reported outcome also exceeded the minimal clinically important differences. Pooled outcome rates with all surgical indications were 98.25% for successful fusion, 1.09% for revision, and 9.02% for complications or adverse events. Commonly reported complications or adverse events were axial pain, C5 palsy, transient neurological worsening, and wound infection. CONCLUSIONS: Posterior cervical fusion with decompression resulted in significant clinical improvement, as indicated by the changes in patient-reported outcomes. Additionally, high fusion rates and low rates of revision and of complications and adverse events were found.

Structural properties of fourth-generation composite femurs and tibias.

The purpose of this study was to measure the structural properties of the latest design (fourth-generation) of composite femurs and tibias from Pacific Research Laboratories, Inc. Fourth-generation composite bones have the same geometries as the third-generation bones, but the cortical bone analogue material was changed to one with increased fracture and fatigue resistance, tensile and compressive properties, thermal stability, and moisture resistance. The stiffnesses of the femurs and tibias were tested under bending, axial, and torsional loading, and the longitudinal strain distribution along the proximal-medial diaphysis of the femur was also determined. The fourth-generation composite bones had average stiffnesses and strains that were for the most part closer to corresponding values measured for natural bones, than was the case for third-generation composite bones; all measurements were taken by the same investigator in separate studies using identical methodology. For the stiffness tests, variability between the specimens was less than 10% for all cases, and setup variability was less than 6%.

Effects of episodic subluxation events on third body ingress and embedment in the THA bearing surface.

In total joint arthroplasty, third body particle access to the articulating surfaces results in accelerated wear. Hip joint subluxation is an under-recognized means by which third body particles could potentially enter the otherwise closely conforming articular bearing space. The present study was designed to test the hypothesis that, other factors being equal, even occasional events of femoral head subluxation greatly increase the number of third body particles that enter the bearing space and become embedded in the acetabular liner, as compared to level-walking cycles alone. Ten metal-on-polyethylene hip joint head-liner pairs were tested in a multi-axis joint motion simulator, with CoCrMo third body particles added to the synovial fluid analog. All component pairs were tested for 2h of level walking; half were also subjected to 20 intermittent subluxation events. The number and location of embedded particles on the acetabular liners were then determined. Subluxation dramatically increased the number of third body particles embedded in the acetabular liners, and it considerably increased the amount of scratch damage on the femoral heads. Since both third body particles and subluxation frequently occur in contemporary total hip arthroplasty, their potent synergy needs to be factored prominently into strategies to minimize wear.

Stability differentials for proximal vs distal fusion of total hip arthroplasty femoral impaction grafts.

In impaction grafting for revision joint arthroplasty, the morselized cancellous bone ideally remodels into a new contiguous lattice. However, the use of biologically active factors may sometimes be indicated to enhance fusion. The purpose of this study was to determine the stability of femoral impaction-graft constructs for which either only the proximal or distal half of the morselized cancellous bone volume was modeled as fused. Fusing the proximal half of the impaction-graft volume resulted in a higher femoral stem stability than did fusing the distal half. This proximal graft fusion also resulted in a stem stability that was similar to that of fusing the entire graft. These results emphasize the importance of proximal fixation of an impaction-grafted femoral stem.

Stability of fused versus nonfused THA femoral impaction grafts.

Impaction grafting for THA involves compacting morselized cancellous bone (MCB) into a cavitary defect to build up bone stock. Ideally, the MCB subsequently remodels into a new contiguous cancellous lattice. A recent laboratory model of MCB fusion allows simulating an impaction graft construct in this ideal eventual clinical state. The purpose of the present study was to determine the relative stability of femoral impaction graft constructs in which the MCB has fused versus that for MCB in the freshly impacted nonfused condition. Cemented femoral impaction graft constructs were created in composite femurs. For fused constructs, the MCB was mixed with an amine epoxy that causes the MCB to set up into a contiguous structure biomechanically comparable to intact cancellous bone in compression. The constructs were loaded with 500,000 physiologic gait cycles. Three-dimensional motion was measured between the femur and the stem. The fused femoral impaction grafts were much more stable than the nonfused grafts at the proximal stem location, but MCB fusion had only a modest effect on distal stem stability. These results indicate that most of the opportunity to reduce femoral stem micromotion and migration lies proximal, and that steps to enhance impaction graft remodeling and fusion are most effectively focused proximally.

In vivo measurement of translational stiffness of rabbit knees.

This paper describes the design, evaluation, and preliminary results of a specialized testing device and surgical protocol to determine translational stiffness of a rabbit knee, replicating the clinical anterior drawer test. Coronal-plane transverse pins are inserted through the rabbit leg, two in the tibia and one in the distal femur, to hold and reproducibly position the leg in the device for tests at multiple time points. A linear stepper motor draws the tibia upward then returns to the home position, and a load cell measures the resisting force; force-displacement knee stiffness is then calculated. Initial evaluation of this testing device determined the effects of preconditioning, intra-operator repeatability, rabbit-to-rabbit variability, knee flexion angle (90 degrees vs. 135 degrees ), and anterior cruciate ligament (ACL) sectioning (0%, 25%, 50%, 75%, 100%). Knee stiffness generally decreased as ACL sectioning increased. This testing device and surgical protocol provide an objective and efficient method of determining translational rabbit knee stiffness in vivo, and are being used in an ongoing study to evaluate the effect of knee instability (via partial to complete ACL sectioning) on the development of post-traumatic osteoarthritis.

A laboratory simulation for morselized bone graft fusion: apparent modulus under operatively based femoral impaction kinetics.

The purpose of this study was to determine the apparent modulus changes accompanying a novel procedure for simulating in situ fusion of morselized cancellous bone femoral impaction grafts. An experienced surgeon's habitual intra-operative impaction grafting protocol was first quantified in human cadaver femurs, using a customized impulse force hammer. A corresponding standardized impaction procedure was then defined, and was used to prepare impaction grafts in axisymmetric metallic fixturing designed to replicate the nominal geometry of femoral canal confinement. Impaction graft fusion was simulated by mixing morselized cancellous bone with an amine-based epoxy adhesive before the impaction, then allowing the mixture to fuse after the impaction (J. Biomech. 34 (2001) 811). Force/deflection behavior of the unfused and fused impaction grafts was measured for both the (tapered) proximal and (untapered) distal portions of the grafts. Apparent modulus was then calculated from force/deflection stiffness. The impaction graft fusion simulation increased apparent modulus by an order of magnitude over the unfused state, for mixture parameters appropriate to have the fused graft apparent modulus be comparable to the compressive modulus of intact femoral cancellous bone.

Protrusio After Medial Acetabular Wall Breach in Total Hip Arthroplasty.

BACKGROUND: Medial protrusio is a recognized complication of total hip arthroplasty, but it is not known if a medial wall breach during cup implantation increases the risk. We thus investigated the effect of up to a 2 cm defect in the medial acetabular wall in a cadaveric model. Separately, we investigated the ability of acetabular screws to rescue the construct. METHODS: Nine human fresh-frozen hemipelves were reamed medially to create the defect, implanted with acetabular cups, and then loaded to failure. The nine contralateral hemipelves were reamed in a standard fashion and served as controls. Separately, nine hemipelves with a medial defect were augmented with two acetabular screws each, then loaded to failure, with the contralateral side as a control. Load-to-failure, stiffness, and energy were recorded. FINDINGS: The presence of a medial wall defect decreased the load-to-failure by a mean of 26% (5710 v. 4221 N, p=0.024). The addition of two acetabular screws did not rescue the construct (mean 27% decrease, 4082 v. 2985 N, p=0.024). The majority of specimens failed in a supra-physiologic range of force. Bone density correlated with failure loads (R(2) range of 0.54-0.78), and osteoporotic specimens were more likely to fail at a physiologic range, consistent with forces experienced during minor stumbles or falls. INTERPRETATION: Osteoporotic patients with a medial wall defect after hip arthroplasty may be susceptible to fracture during activities of daily living. Protected weight bearing with an assistive device may be reasonable in order to minimize fall risk until cup ingrowth is achieved.

Bearing-Foreign Material Deposition on Retrieved Co-Cr Femoral Heads: Composition and Morphology.

Bearing-foreign material deposition onto a femoral head can occur from contact with an acetabular shell due to dislocation, reduction, or subluxation. The purpose of this study was to comprehensively characterize deposit regions on retrieved cobalt-chrome femoral heads from metal-on-polyethylene total hip arthroplasties that had experienced such adverse events. The morphology, topography, and composition of deposition regions were characterized using macrophotography, optical profilometry, scanning electron microscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy. The deposit areas were relatively large, they were much rougher than the surrounding undamaged clean areas, and they displayed several distinct morphologies. Titanium alloy elements were the predominant constituents. Calcium and phosphorous were also detected within the deposit areas, in a composition that could nucleate abrasive hydroxyapatite. In addition, tungsten-rich particles, likely present as tungsten carbide, were observed on top of the titanium deposits. The increased roughness associated with these deposition features would be expected to accelerate damage and wear of the opposing liner and hence accelerate the development of osteolysis.

Reliability of detecting prosthesis/cement interface radiolucencies in total hip arthroplasty.

A laboratory study assessed the reliability of detecting radiolucencies at the prosthesis/cement interface in femoral components for total hip replacement. Radiolucencies (thicknesses = 0.1, 0.3, 0.5 and 0.7 mm) were created by randomly masking non-tip Gruen zones (six per stem) in a group of 72 matte-finish femoral components. Only half of all Gruen zones were masked. The femoral components were reproducibly implanted in composite fiberglass replicate femurs. Anteroposterior and lateral radiographs taken using conventional techniques were then presented to 10 experienced readers, who scored each of 432 non-tip Gruen zones for radiolucency presence or absence. The series-average radiolucency detection rate was 47.1%, with a breakdown of 9.8%, 20.7%, 69.8% and 88.0, for radiolucency thicknesses of 0.1, 0.3, 0.5 and 0.7 mm, respectively. The false positive rate was 7.5%. The findings argue strongly that in many or most instances, initial cement-prosthesis debonding is not reliably detected from conventional plain film radiographs. Radiolucencies of at least 0.7 mm width are necessary to be accurately detectable by most viewers.

A biomechanical analysis of polyethylene liner cementation into a fixed metal acetabular shell.

BACKGROUND: A common clinical scenario encountered by an orthopaedic surgeon is a patient with a secure cementless acetabular shell and a failed polyethylene liner. One treatment option is to cement a new liner into the fixed shell. The purpose of this study was to evaluate technical variables to improve the mechanical strength of such cemented liner constructs. METHODS: The contributions of shell texturing, liner texturing, and cement mantle thickness (between the liner and the shell) were evaluated by comparing torsional strength (among nine groups of constructs) and lever-out strength (among eight groups of constructs). RESULTS: Failure almost always occurred at the cement-liner interface. The two exceptions (failure at the shell-cement interface) occurred with a polished, untextured shell with no screw-holes. This finding indicates that if a shell has existing texturing (such as holes), further intraoperative scoring of the shell is unnecessary, but some sort of texturing is necessary to avoid construct failure at the shell-cement interface. Textured liners had significantly (a = 0.05) greater torsional and lever-out strength than untextured liners. The greatest construct strength occurred when liner grooves were oriented so as to oppose the applied loading. A 4-mm-thick cement mantle resulted in slightly greater torsional strength than a 2-mm-thick cement mantle, and a 2-mm-thick cement mantle resulted in considerably greater lever-out strength than a 4-mm-thick cement mantle, but these differences were not significant. CONCLUSIONS: When cementing a liner into a well-fixed shell, a surgeon should ensure that both the shell and the liner are textured, as interdigitation of the cement with the shell and the liner is crucial to the mechanical strength of this construct.

Fracture of a BIOLOX Delta Ceramic Femoral Head Articulating Against a Polyethylene Liner: A Case Report.

CASE: A forty-five-year-old woman underwent primary total hip arthroplasty with a 36-mm BIOLOX delta ceramic femoral head articulating against a polyethylene liner. She presented with hip pain at eighteen months postoperatively, two months after being in a bicycle accident; fracture of the femoral head was diagnosed. CONCLUSION: The possibility of a ceramic femoral head fracture should be decreased with use of the latest generation of ceramic material, a ceramic-on-polyethylene articulation rather than a ceramic-on-ceramic articulation, and a larger head size, all of which applied to this case. Taper-trunnion compatibility and correct intraoperative handling of the components are also essential.