Trunnions and Modularity in Total Hip Arthroplasty: A Historical Review With Current Clinical Implications.

Trunnion in total hip arthroplasty refers to the interface between the neck of a femoral stem and the femoral head. Clinical complications arising from damage to this junction, whether it be due to mechanical wear, corrosion, or a combination, are referred to as mechanically assisted crevice corrosion (MACC), also commonly known as trunnionosis. With the use of modular hip prostheses, which help customize offset and leg length to an individual patient's anatomy, the incidence of MACC and revision due to MACC has increased in recent years. Although the cause of MACC is multifactorial, with patient factors and technique factors contributing to this condition, taper design and geometry, metallurgical properties of implants, and size mismatch of the bearing couple are some of the implant factors that have also been implicated in this clinical phenomenon. Understanding the history of taper design and geometry, the track record of older implants, and the rationale behind the development of current prostheses can help surgeons choose the right implants for their patients and accurately assess the pros and cons of new implants being introduced to the market each year.

National Decline in Knee Fusions Performed for Salvage of Chronic Periprosthetic Total Knee Infections.

The primary purpose of this study was to study and compare rates of two salvage operations for patients with chronically infected total knee arthroplasties: (1) knee arthrodesis and (2) above knee amputation (AKA). An analysis was performed comparing the inpatient hospital characteristics and complications between the two procedures. Secondarily, we presented rates of all surgically treated periprosthetic total knee infections over a 6-year period. Using the Nationwide Inpatient Sample, we identified all patients with a periprosthetic infection (International Classification of Diseases, Ninth Revision [ICD-9] 996.66) from 2009 to 2014. Subsequently, we identified surgically treated total knee infections through the following ICD-9 codes: 00.80 (all component revision), 00.84 (liner exchange), 80.06 (removal of prosthesis), 84.17 (AKA), and 81.22 (knee fusion). From 2009 to 2014, the annual incidence of surgically treated total knee periprosthetic infections increased by 34.9% nationally, while the annual incidence of primary total knees increased by only 13.9%. Salvage operations (AKA and knee fusion) represented 5.8% of all surgically treated infections. The rate of knee fusions decreased from 1.9% of surgically treated infections in 2009 to 1.4% in 2014 (p < 0.05), while the rate of AKA stayed steady at 4.5% of cases over the 6-year period. Length of stay was significantly shorter in the knee fusion group (7.9 vs. 10.8 days, p < 0.05), but total hospital costs were higher (33,016 vs. 24,933, p < 0.05). In the multivariable adjusted model, patients undergoing knee fusion had significantly decreased odds of being discharged to skilled nursing facility (odds ratio: 0.42, 95% confidence interval: 0.31-0.58). The annual incidence of surgically treated periprosthetic total knee infections is increasing. The rate of knee arthrodesis for chronic periprosthetic total knee infections is decreasing. Reasons for this downward trend in knee fusions should be evaluated carefully as knee fusions have shown to have the potential advantage of improved mobility and decreased patient morbidity for chronic PJI. The level of evidence is III.

Nuclear Medicine Scans in Total Joint Replacement.

¼: A 3-phase bone scan is a potential first-line nuclear medicine study for pain after total joint arthroplasty (TJA) when there is concern for periprosthetic joint infection or aseptic loosening. ¼: In patients who have a positive bone scintigraphy result and suspected infection of the joint, but where aspiration or other studies are inconclusive, labeled leukocyte scintigraphy with bone marrow imaging may be of benefit. ¼: Magnetic resonance imaging (MRI), while not a nuclear medicine study, also shows promise and has the advantage of providing information about the soft tissues around a total joint replacement. ¼: Radiotracer uptake patterns in scintigraphy are affected by the prosthesis (total knee arthroplasty [TKA] versus total hip arthroplasty [THA]) and the use of cement. ¼: Nuclear medicine scans may be ordered 1 year postoperatively but may have positive findings that are due to normal physiologic bone remodeling. Nuclear studies may be falsely positive for up to 2 years after TJA. ¼: Single-photon emission computed tomography (SPECT) combined with computed tomography (CT) (SPECT/CT), fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/CT, and MRI show promise; however, more studies are needed to better define their role in the diagnostic workup of pain after TJA.

Trends of Prosthetic Joint Infection Organisms and Recurrence for a Single High-Volume Arthroplasty Surgeon Over 20 Years.

BACKGROUND: Prosthetic joint infection (PJI) is a morbid complication following total joint arthroplasty (TJA). PJI diagnosis and treatment has changed over time, and patient co-management with a high-volume musculoskeletal infectious disease (MSK ID) specialist has been implemented at our institution in the last decade. METHODS: We retrospectively evaluated all consecutive TJA patients treated for PJI between 1995 and 2018 by a single high-volume revision TJA surgeon. Microbial identities, antibiotic resistance, prior PJI, and MSK ID consultation were investigated. RESULTS: In total, 261 PJI patients (median age 66 years, interquartile range 57-75) were treated. One-year and 5-year reinfection rates were 15.8% (95% confidence interval [CI] 11.6-20.7) and 22.1% (95% CI 17.0-27.7), respectively. Microbial identities and antibiotic resistances did not change significantly over time. Despite seeing more prior PJI patients (53.3% vs 37.6%, P = .012), MSK ID-managed patients had similar infection rates as non-MSK ID-managed patients (hazard ratio [HR] 1.02, 95% CI 0.6-1.75, P = .93). Prior PJI was associated with higher reinfection risk (HR 2.39, 95% CI 1.39-4.12, P = .002) overall and in patients without MSK ID consultation, specifically (HR 2.78, 95% CI 1.37-5.65, P = .005). This risk was somewhat lower and did not reach significance in prior PJI patients with MSK ID consultation (HR 1.97, 95% CI 0.87-4.48, P = .106). CONCLUSION: We noted minimal differences in microbial/antibiotic resistances for PJI over 20 years in a single institution, suggesting current standards of PJI treatment remain encouragingly valid in most cases. MSK ID involvement was not associated with lower reinfection risk overall; however, in patients with prior PJI, the risk of reinfection appeared to be somewhat lower with MSK ID involvement. LEVEL OF EVIDENCE: Level IV-Case Series.

Knee Arthrodesis Is a Durable Option for the Salvage of Infected Total Knee Arthroplasty.

BACKGROUND: Knee arthrodesis (KA) and above-knee amputation (AKA) have been used for salvage of failed total knee arthroplasty (TKA) after periprosthetic joint infection (PJI). However, few studies have assessed the outcomes of KA after TKA PJI, as it remains an uncommon procedure. We investigated rates of AKA, control of infection, and ambulatory status after KA for TKA PJI treatment. METHODS: This was a retrospective and single-surgeon series of 51 failed TKAs due to PJI treated with two-stage KA between 2000 and 2016 with a minimum of 2-year follow-up. Patient demographics, comorbidities, surgical history, radiographic data, and outcomes of KA treatment were recorded. RESULTS: Infection was successfully controlled in 48 of 51 patients (94.1%); of these, 24 knees (50.0%) required no reoperation subsequent to the index KA, whereas the remaining 24 (50.0%) patients required a median of 1 additional operation. Nonunion, malunion, or delayed union was noted in 10 patients (19.6%). Of the 48 patients who were successfully treated with KA, 41 patients (85.4%) remained ambulatory after KA and 9 of these patients (18.8%) did not require assistive devices. Three of 51 patients (5.9%) progressed to AKA after KA. CONCLUSION: Patients undergoing KA for TKA PJI had high rates of infection control and preservation of ambulatory status, with low rates of progression to AKA in our study. LEVEL OF EVIDENCE: Level IV-case series.

An unexpected pathogen causing prosthetic joint infection following screening colonoscopy.

A 61-year-old woman with a right total knee arthroplasty presented with 1 week of atraumatic right knee swelling, pain, and fevers 2 weeks following a routine screening colonoscopy. Aspiration was concerning for prosthetic joint infection and she underwent definitive treatment with irrigation and debridement with polyethylene exchange followed by a 6-week course of oral metronidazole. Cultures speciated as Bacteroides fragilis with the presumed source being the colonoscopy causing transient bacteremia and subsequent seeding of the right knee. This case highlights the need for consideration of guidelines regarding prophylactic antibiotics to prevent prosthetic joint infection after endoscopic procedures.

The Double-Cup Construct: A Novel Treatment Strategy for the Management of Paprosky IIIA and IIIB Acetabular Defects.

BACKGROUND: Treatment of massive acetabular bone loss in revision total hip arthroplasty is complex, and various treatment strategies have been described. We describe a novel technique of using a Trabecular Metal Revision Shell as a buttress augment creating a "double-cup" construct rather than the use of custom triflanges or cup-cage constructs for Paprosky types IIIA and IIIB acetabular defects. METHODS: We retrospectively reviewed 20 double-cup cases at a mean of 2.4 years follow-up at a single institution between 2005 and 2014. We evaluated postoperative radiographic evidence of acetabular loosening and complication rates, restoration of hip center of rotation, preoperative and postoperative modified Harris Hip Score, and Merle d'Aubigne-Postel pain and walking scores. RESULTS: There were no revisions for acetabular loosening and no cases of aseptic loosening. We observed a 25% dislocation rate, which was the most common complication. Most dislocations occurred within the first year after surgery and most were acetabulum only revisions. Hip center of rotation was restored to an average of 22.5 mm within the interteardrop line. Average Harris Hip Score improved from 28.2 to 68.7 (P < .001) and Merle d'Aubigne-Postel pain and walking scores improved from 2.7 to 5.1 and 2.4 to 4, respectively (P < .001). CONCLUSION: The double-cup construct is a reliable option for reconstruction of Paprosky type IIIA and IIIB acetabular defects with no cases of acetabular loosening both clinically and radiographically at a mean of 2 years follow-up. The most common complication was dislocation in the acetabulum-only revisions, and clinical outcome measures were reliably improved in surviving cases.

Treatment failure among infected periprosthetic total hip arthroplasty patients.

Two-stage revision has been shown to be the most successful treatment in eradicating deep infection following total hiparthroplasty. We identified 62 patients treated by a two-stage revision. We defined "successful revision" as negative intraoperative cultures and no further infection-related procedure. We defined "eradication of infection" on the basis of negative cultures and clinical diagnosis at least one year after 2(nd) stage procedure. After a mean follow up of 2.7 years, eradication of the infection was documented in 91.1%, and a successful two-stage revision in 85.7% of patients. We observed no association between higher pre-reimplantation levels of ESR and C-reactive protein and lower likelihood of successful two-stage revision. We found an association between a history of another previous infected prosthetic joint and a failed 2(nd) stage procedure. Failure to achieve eradication of infection and successful two-stage revision occurs infrequently. Patients with prior history of a previous prosthetic joint infection are at higher risk of failure.

Inflammatory cytokines induce a unique mineralizing phenotype in mesenchymal stem cells derived from human bone marrow.

Bone marrow contains mesenchymal stem cells (MSCs) that can differentiate along multiple mesenchymal lineages. In this capacity they are thought to be important in the intrinsic turnover and repair of connective tissues while also serving as a basis for tissue engineering and regenerative medicine. However, little is known of the biological responses of human MSCs to inflammatory conditions. When cultured with IL-1ß, marrow-derived MSCs from 8 of 10 human subjects deposited copious hydroxyapatite, in which authenticity was confirmed by Fourier transform infrared spectroscopy. Transmission electron microscopy revealed the production of fine needles of hydroxyapatite in conjunction with matrix vesicles. Alkaline phosphatase activity did not increase in response to inflammatory mediators, but PPi production fell, reflecting lower ectonucleotide pyrophosphatase activity in cells and matrix vesicles. Because PPi is the major physiological inhibitor of mineralization, its decline generated permissive conditions for hydroxyapatite formation. This is in contrast to MSCs treated with dexamethasone, where PPi levels did not fall and mineralization was fuelled by a large and rapid increase in alkaline phosphatase activity. Bone sialoprotein was the only osteoblast marker strongly induced by IL-1ß; thus these cells do not become osteoblasts despite depositing abundant mineral. RT-PCR did not detect transcripts indicative of alternative mesenchymal lineages, including chondrocytes, myoblasts, adipocytes, ligament, tendon, or vascular smooth muscle cells. IL-1ß phosphorylated multiple MAPKs and activated nuclear factor-κB (NF-κB). Certain inhibitors of MAPK and PI3K, but not NF-κB, prevented mineralization. The findings are of importance to soft tissue mineralization, tissue engineering, and regenerative medicine.

Treatment Failure Among Infected Periprosthetic Patients at a Highly Specialized Revision TKA Referral Practice.

Deep infection is a serious and costly complication of total knee arthroplasty (TKA), which can increase patient morbidity and compromise functional outcome and satisfaction. Two-stage revision with an interval of parental antibiotics has been shown to be the most successful treatment in eradicating deep infection following TKA. We report a large series by a single surgeon with a highly specialized revision TKA referral practice. We identified 84 patients treated by a two-stage revision. We defined "successful two-stage revision" as negative intraoperative cultures and no further infection-related procedure. We defined "eradication of infection" on the basis of negative cultures and clinical diagnosis. After a mean follow up of 25 months, eradication of the infection was documented in 90.5% of the patients; some had undergone further surgical intervention after the index two-stage procedure. Successful two-stage revision (e.g. no I&D, fusion, amputation) was documented only in 63.5% of the patients. We also observed a trend between presence of resistant staphylococcus (MRSA) (p=0.05) as well as pre-revision surgical procedures (p=0.08) and a lower likelihood of successfully two-stage revision. Factors affecting the high failure rate included multiple surgeries prior to the two-stage revision done at our institution, and high prevalence of MRSA present among failed cases. The relatively high rate of failure to achieve a successful two-stage revision observed in our series may be attributed to the highly specialized referral practice. Thus increasing the prevalence of patients with previous failed attempts at infection eradication and delayed care as well as more fragile and immune compromised hosts.

Revision hip arthroplasty with a modular cementless stem: mid-term follow up.

Despite the increasing volume of revision total hip arthroplasty (THA) being performed in the United States, there are few studies reporting mid-term clinical and radiographic outcomes of modular fully porous-coated femoral stems. We retrospectively studied a consecutive series of patients who underwent revision THA with a modular extensively porous-coated femoral component at a single institution and by a single surgeon. The final study group included 54 hips (52 patients) followed for an average of 84 months. Ten-year survival rates with revision for any reason and revision for femoral loosening as endpoints were 94% and 100%, respectively. No complications regarding the modular junction were encountered. Of the 50 hips with adequate radiographs, all showed proximal ingrowth and 42 (84%) had both proximal and distal ingrowth. The modular, fully porous-coated femoral stem studied demonstrated excellent survivorship and bone ingrowth at mid-term follow up.

Autologous bone grafting on steroids: preliminary clinical results. A novel treatment for nonunions and segmental bone defects.

Clinical management of delayed healing or nonunion of long bone fractures and segmental bone defects poses a substantial orthopaedic challenge. Surgical advances and bone tissue engineering are providing new avenues to stimulate bone growth in cases of bone loss and nonunion. The reamer-irrigator-aspirator (RIA) device allows surgeons to aspirate the medullary contents of long bones and use the progenitor-rich "flow-through" fraction in autologous bone grafting. Dexamethasone (DEX) is a synthetic steroid that has been shown to induce osteoblastic differentiation. A series of 13 patients treated with RIA bone grafting enhanced with DEX for nonunion or segmental defect was examined retrospectively to assess the quality of bony union and clinical outcomes. Despite the initial poor prognoses, promising results were achieved using this technique; and given the complexity of these cases the observed success is of great value and warrants controlled study into both standardisation of the procedure and concentration of the grafting material.

Incidence of sciatic nerve palsy after revision hip arthroplasty through a posterior approach.

Sciatic nerve palsy after revision hip arthroplasty is rare, but can have substantial impacts. The purpose of this study is to report the safety and reliability of limited sciatic nerve exposure during revision surgery. A retrospective case series of 350 revision hip surgeries performed by a single surgeon underwent sciatic nerve identification. In each case, the sciatic nerve was identified and tagged loosely with a Penrose drain. Three hundred forty-eight of 350 patients (99.4%) underwent successful revision hip arthroplasty. One patient developed a transient sensory palsy; and another patient, a delayed palsy. Both nerve palsies recovered by the 1-year visit. We advocate visual nerve identification and tagging in revision hip surgery as 1 possible method to potentially reduce the risks of sciatic nerve injury.

Do commonly reported outcome measures reflect patient satisfaction after revision hip arthroplasty?

The purpose of this study was to determine which commonly reported outcome measures best correlated with patient satisfaction after revision hip arthroplasty and to identify factors unrelated to hip status that may also play a role. From our institutional database, we identified 78 patients (80 hips) who underwent revision total hip arthroplasty and collected follow-up data. Patients with moderate or severe pain and those with limited walking ability reported significantly lower satisfaction scores. Harris hip score and patient-rated general health status were independently associated with patient satisfaction. Patient-rated anxiety and depression correlated inversely with satisfaction. Commonly reported outcome measures do reflect patient satisfaction after revision hip arthroplasty. However, satisfaction also appears to be influenced by psychologic factors.

Interprosthetic fractures of the femur: treatment with a single-locked plate.

Interprosthetic fractures of the femur, those between an ipsilateral hip and knee arthroplasty, are challenging to treat secondary to limited bone available for fixation, osteopenic bone, a compromised intramedullary blood supply, and an often elderly patient population. From 2002 to 2006, 22 consecutive patients with an interprosthetic femur fracture were treated with a single-locking plate. Follow-up averaged 17.7 months, with fracture union achieved an average of 13.8 weeks postoperatively. All patients regained their preoperative ambulatory status and subjectively reported unchanged function of their hip and knee arthroplasties. Single-locked plating is an effective method of treatment of interprosthetic fractures of the femur. Emphasis on preservation of the soft tissue envelope and sufficient cortical purchase both above and below the fracture is of paramount importance.

Dislocation rate after conversion from hip hemiarthroplasty to total hip arthroplasty.

BACKGROUND: Revision hip arthroplasty is associated with a dislocation rate that is three to five times greater than the rate following primary hip replacement. Conversion of a hip hemiarthroplasty to a total hip replacement is a revision arthroplasty, but it differs from revisions of total hip arthroplasties because a native acetabulum is replaced and the subsequent prosthetic femoral head is smaller. It was our purpose to determine whether the risk of dislocation following conversion surgery is the same as or greater than that following revision total hip replacement. METHODS: From 1994 to 2005, eighty-nine hemiarthroplasties were converted to a total hip arthroplasty in seventy-seven patients, and the results were compared with those of 115 first-time revision total hip replacements following a primary total hip replacement in 111 patients. A retrospective chart review was performed, and radiographic measurements were obtained. The patient demographics were similar between the two groups. The percentages of patients who had undergone revision of only the acetabular component as compared with both components as well as the percentages of those who had received a modular femoral stem as compared with a nonmodular stem were also similar between the two groups. RESULTS: Postoperatively, the femoral head size and the positioning of the acetabular component were similar between the two groups. The acetabular components were significantly larger (p < 0.001) in the group in which a total hip arthroplasty had been revised because they required additional acetabular reaming for placement of a new component. There were significantly more dislocations after the conversion procedures (22%) than after the revisions of the total hip arthroplasties (10%) (p < 0.018). Within both groups, the size of the acetabular component, the intraoperative range of motion, and the positioning of the acetabular component were similar between the hips that dislocated and those that did not. However, smaller femoral head components were at greater risk for dislocation after conversion surgery than after revision of a total hip arthroplasty. CONCLUSIONS: A substantial reduction of the size of the prosthetic femoral head is unique to conversion arthroplasty and appears to play a role in instability after the revision surgery. While the smallest heads dislocated in the conversion group, a larger femoral head did not ensure stability. The increased dislocation risk with conversion surgery requires emphasis on soft-tissue balance and avoidance of excessive downsizing of the femoral head in an attempt to maximize hip stability.

Mortality after periprosthetic fracture of the femur.

BACKGROUND: Management of periprosthetic femoral fractures is often complex, and few studies have documented its associated mortality. METHODS: We retrospectively identified from our trauma and surgical registries 106 patients who underwent surgery for a periprosthetic femoral fracture. We then identified a contemporaneous age and sex-matched control cohort of 309 patients who had a hip fracture (femoral neck or intertrochanteric) and 311 patients who underwent primary hip or knee replacement. Mortality at one year was identified with use of the Social Security database. RESULTS: Twelve (11%) of 106 patients died within one year following surgical treatment of a periprosthetic fracture. During the same follow-up period, fifty-one (16.5%) of 309 patients died following surgery for a hip fracture and nine (2.9%) of 311 patients died following primary joint replacement. The mortality rate after a periprosthetic femoral fracture was significantly higher (p < 0.0001) compared with that for matched patients who had undergone primary joint replacement, and it was similar to the mortality rate after a hip fracture. For periprosthetic fractures, a delay of greater than two days from admission to the time of surgery was associated with an increased mortality rate at one year (p < 0.0007). Forty-nine patients underwent revision arthroplasty for the treatment of a Vancouver type-B periprosthetic fracture, and six (12%) died. In contrast, twenty-four patients with a Vancouver type-B periprosthetic fracture were treated with open reduction and internal fixation and eight (33%) died. The difference was significant (p < 0.03). CONCLUSIONS: The mortality rate within one year following surgical treatment of periprosthetic femoral fractures is high and is similar to that after treatment for hip fractures. Because revision arthroplasty for the treatment of type-B periprosthetic fractures was associated with a one-year mortality rate that was significantly less than that after surgical treatment with open reduction and internal fixation, in instances when either treatment option is feasible, revision arthroplasty may be the preferred option.

Comparison of hip simulator wear of 2 different highly cross-linked ultra high molecular weight polyethylene acetabular components using both 32- and 38-mm femoral heads.

Much evidence suggests that ultra high molecular weight polyethylene (UHMWP) irradiated to 9.5 Mrad has lower wear than UHMWP given 5 Mrad. Curiously, highly cross-linked polyethylenes gain weight during hip simulator testing. We postulated that (a) UHMWP irradiated to 9.5 Mrad would wear less than UHMWP irradiated to 5 Mrad UHMWP, (b) articulation against 38-mm heads would accentuate this difference, and (c) weight gain of highly cross-linked material reflects the inadequacy of load soak controls. We compared 9.5 versus 5 Mrad polyethylene in hip simulator wear tests, with both load soak corrections and with novel "motion soak" corrections. The 9.5-Mrad material wore less than 5-Mrad material for 32- and 38-mm heads. Motion soak corrections were more accurate than load soak corrections.

Contact stress assessment of conventional and highly crosslinked ultra high molecular weight polyethylene acetabular liners with finite element analysis and pressure sensitive film.

Stress magnitude and distribution of both conventional polyethylene versus a crosslinked polyethylene in the liner of a total hip replacement (THR) were examined using finite element analysis and pressure sensitive film. Both types of polyethylene were assessed against head sizes of 22 and 28 mm with 5-mm thick polyethylene liners and head sizes of 28, 38, and 46 mm with 3-mm thick polyethylene liners. Liners with 5-mm conventional polyethylene represented successful combinations with long track records. Our hypothesis was that although the combination of the large head and the lower modulus of the highly crosslinked polyethylene would lead to lower stresses, the stresses would be excessive if the liner was extremely thin at 3 mm. Von Mises stresses at the articulating surface of the highly crosslinked liners were lower, when compared to conventional polyethylene, in every THR size examined. Specifically, however, the 38- and 46-mm inner diameter (ID) highly crosslinked polyethylene even at the extreme of only 3-mm thick had lower stresses than the 22-mm ID conventional liner of 5-mm thickness. These data indicate that the use of a large head against highly crosslinked material even at 3-mm thickness results in lower stresses than in an existing conventional 22-mm head and 5-mm thick combination. Obviously, other considerations will influence the minimum thickness to be recommended.

Comparison of femoral head penetration using RSA and the Martell method.

UNLABELLED: Radiostereometry has high precision and accuracy measuring polyethylene wear in total hip arthroplasty but requires a specialized setup. The Martell method is simpler and can be used on larger populations. The hypothesis that the radiostereometry analysis and the Martell analysis would yield comparable wear data from the same group of patients having total hip arthroplasty was tested. A group of twenty-five total hip arthroplasty patients who had both radiostereometry and standard anterior-posterior pelvic and cross-table lateral radiographs of sufficient quality for analysis were identified. The films were taken at postoperative periods of 6 weeks, 1 year, 2 years, and 5 years. Femoral head penetration was measured by both methods at each time point. The median penetration rates measured by each method decreased over time. Penetration results were affected by method of analysis, time, and dimension, with greater penetration for Martell compared with radiostereometry at each time point, greater penetration with increasing time for each method, and larger three-dimensional magnitude compared with two-dimensional analysis. LEVEL OF EVIDENCE: Case series Level IV. See Guidelines for Authors for a complete description of levels of evidence.