Accuracy of Preoperative 3D vs 2D Digital Templating for Cementless Total Hip Arthroplasty Using a Direct Anterior Approach.

Background: An important aspect of preoperative planning for total hip arthroplasty is templating. Although two-dimensional (2D) templating remains the gold standard, computerized tomography (CT)-based three-dimensional (3D) templating is a novel preoperative planning technique. This study aims to compare the accuracy of a 2D and 3D plan using an anterior approach for the placement of the same uncemented prosthesis. Methods: Two consecutive cohorts of 100 patients each were retrospectively analyzed. We analyzed the accuracy of the size of the implant (stem, cup, head), the length of head, and offset. As a secondary criterion, we analyzed the rates of stems with more than 3° of varus, fracture, and/or subsidence at 3 months postoperatively. Results: Within the exact size, the accuracy of the stem and cup size with the 2D plan was 69% and 56%, respectively. With the 3D plan accuracy being 88% (P = .0046) and 96% (P < .0001), respectively. Regarding size and length of the implant head, accuracy was 86% and 82% with the 2D plan and 100% (P < .0001) and 94% (P = .016), respectively, with the 3D plan. The offset of the implants increased beyond 3 mm in 23% of patients in the 2D group and in 5% of patients in the 3D group (P = .0003). The rate of varus stems was 10% in the 2D group and 2% in the 3D group (P = .03). Two fractures and one case of subsidence occurred in the 2D group. None were identified in the 3D cohort. Conclusions: A CT-based 3D plan is more accurate for implant size selection, allows better prosthetic offset, and reduces the rate of varus stems.

Revision total hip arthroplasty by a ceramic bearing surface after a third- and fourth-generation ceramic head or liner fracture.

PURPOSE: Although rare, fractures of ceramic components are difficult to revise, mainly due to the presence of residual ceramic debris that can cause catastrophic wear of the replacement components. Modern ceramic-on-ceramic bearings are suggested to improve outcomes of revision total hip arthroplasty (THA) for ceramic fractures. However, there are few published reports of mid-term outcomes of revision THA using ceramic-on-ceramic bearings. We evaluated clinical and radiographic outcomes of 10 patients who received ceramic-on-ceramic bearings during revision THA for ceramic fractures. METHODS: All patients but one received fourth-generation Biolox Delta bearings. Clinical evaluation was performed using the Harris hip score at latest follow-up, and all patients received a radiographic evaluation to analyze the fixation of the acetabular cup and of the femoral stem. Osteolytic lesions and the presence of ceramic debris were noted. RESULTS: After a mean follow-up of 8.0 years, there were no complications or implant failures, and all patients reported satisfaction with their implant. The average Harris hip score was 90.6. There was neither osteolysis nor loosening, but despite our extensive synovial debridement, ceramic debris was noted in the radiographs of five patients (50%). CONCLUSION: We report excellent mid-term outcomes, with no implant failures after eight years despite ceramic debris being found in a significant proportion of patients. We conclude that modern ceramic-on-ceramic bearings are an advantageous option for the revision of THA due to the fracture of initial ceramic components.

Doctor, what does my ceramic-on-ceramic hip arthroplasty weigh?

BACKGROUND: While total hip arthroplasty (THA) is generally very successful, certain patients remain dissatisfied. A common concern, especially in younger and more active patients, is the weight the implant will add to the hip. However, there is very little data available to help guide surgeons in addressing this concern. The goal of this study was therefore to compare the weight of the total hip arthroplasty implants to that of tissue removed. HYPOTHESIS: That the weight of the total hip arthroplasty implants would exceed that removed tissue. PATIENTS AND METHODS: A prospective study was conducted in 104 patients, without interfering with surgical plans. To account for different implant designs, especially relating to stem fixation, we included both cementless (n=51) and cemented (n=53) femoral stems. During the procedure, the removed bone and soft tissues, as well as the post-implantation cement were collected and weighed. The weight of the implants was provided by the manufacturer. RESULTS: Both cemented and cementless THA implants proved significantly heavier than the removed bone and soft tissues. The median weight gained was 145g [IQR: 123-168] with the cementless implant and 241g [221-364] with the cemented implant (p<0.001). Multivariable regression analysis of patient- or implant factors influencing weight gain after THA revealed that weight gain decreased with patient BMI (ß=-1.0, 95% CI: -2.0--0.1 (p=0.034)). In contrast, weight gain increased slightly with total implant weight (ß=0.7, 95% CI: 0.6-0.8 (p≤0.001)). Further, weight gain was greater for women (ß=19.0, 95% CI: 9.1-29.0 (p≤0.001) (men 150g [135-219], women 211g [157-250] (p=0.010)) and patients who received the cemented stem (ß=40.0, 95% CI, 19.4-46.5, p≤0.001). DISCUSSION: Current models cause a two- to three-fold gain of weight at the hip joint after THA. While it is not clear whether this weight increase has any clinical repercussions, this finding can be helpful when a patient raises questions on this topic during the preoperative counseling. More research is necessary to determine whether lighter implants may be beneficial for patients. LEVEL OF EVIDENCE: III, case control study.

Risk Factors Associated With Femorotomy or Fracture During Cementless Stem Removal and Generation of an Individual Predictive Risk Score.

BACKGROUND: Femorotomy is a commonly used technique during cementless stem removal but should be preferred in selective revision cases to prevent intraoperative femoral fracture associated with deteriorated clinical outcome. Our aim was to assess the risk factors for fracture or femorotomy and develop a predictive risk stratification score. METHODS: A monocentric retrospective cohort including 202 patients was analyzed. Thirty six candidate prognostic factors were assessed. RESULTS: The following independent predictors of fracture or femorotomy were identified: presence of a "bracket sign" (Odds Ratio [OR]: 10.857; 95% Confidence interval [CI]: 2.613-45.115; P = .001) defined as a distal spot weld between the surface of the implant and closest endosteum, bone contact in zone 2 (OR: 4.700; 95% CI: 1.827-12.089; P = .001), 6 (OR: 4.966; 95% CI: 1.823-13.530; P = .002), 12 (OR: 9.660; 95% CI: 3.715-25.116; P < .0001), 13 (OR: 2.958; 95% CI: 1.009-8.021; P = .033), and global hypertrophy (OR: 0.170; 95% CI: 0.036-0.806; P = .026). The prognostic score, named Femorotomy INcidence Numeric scoring system, had good performance and discriminability; the area under the curve of the model was 0.924 (95% CI: 0.878-0.969). CONCLUSION: The only independent risk factors were those assessed on X-ray (eg, bracket sign, bone contact in zones 2, 6, 12, and 13), while global hypertrophy was protective. We noticed the importance of differentiating pedestals and "bracket signs"; the latter is an indicator of fixation of the stem. We developed a risk prediction score (Femorotomy INcidence Numeric score) of fracture or femorotomy that can be used as a companion tool to assess the risk for doing an early osteotomy of the femur.

One-Stage Exchange Arthroplasty for Fistulizing Periprosthetic Joint Infection of the Hip: An Effective Strategy.

Background: Prosthetic hip infection (PHI) is a disastrous scenario after an arthroplasty. International guidelines contraindicate one-stage exchange arthroplasty for fistulizing chronic prosthetic hip infection (FCPHI), nevertheless few surgical teams, mostly from Europe, support one stage procedure for this indication. Questions/Purposes: Analysis of infection recurrence and implant failure of a series of FCPHIs treated with one stage arthroplasty. Patients and Methods: Sixty-six FCPHIs treated with one-stage exchange arthroplasty were prospectively followed up at least 2 years. Clinical, radiological and bacteriological signs suggestive of reinfection were sought, as well as implant failures and PHI related deaths. Results: Thirty-four females and thirty-two males with median age of 69.5 years [61-77] and BMI of 26 kg/m2 [22-31] were included. Fistulae were productive in 50 patients (76%). Staphylococcus was responsible for 45% of PHI and 21% were polymicrobial. Twenty-nine patients (44%) received preoperative antibiotic therapy. After a median 60-month follow-up [35-82], 3 patients (4.5%) presented reinfection (two new infections, one relapse) and 3 patients experienced implant failure (1 femoral fracture, 1 stem breakage, 1 recurrent dislocation). One death was related to PHI. After a minimum of 2 years, the infection control rate was of 95.3% (±0.02). Conclusion: One-stage exchange arthroplasty for FCPHIs showed a good infection control rate similar to that of non-fistulizing PHI. Systematic preoperative microbiological documentation with joint aspiration and, in some specific cases, the use of preoperative antibiotic therapy are among the optimizations accounting for the success of the one-stage arthroplasty. In light of these results, and those of other studies, international recommendations could evolve. Level of Evidence: Descriptive therapeutic prospective cohort study. Level of evidence: IV.

Haematogenous prosthetic knee infections: Prospective cohort study of 58 patients.

BACKGROUND: Prosthetic joint infection (PJI) is a rare (incidence, 0.15% to 0.9%) but serious complication of knee arthroplasty. Haematogenous PJI of the knee (KhPJI) which accounts for 10% of cases, has been less studied than PJI due to other mechanisms. The primary objective of this study in patients with KhPJI of the knee was to determine the 2-year infection eradication failure rate after either exchange arthroplasty or arthrotomy/synovectomy/irrigation (ASI), combined with prolonged peri-operative antibiotic therapy, at a referral centre for complex osteo-articular infections. HYPOTHESIS: ASI within 2 weeks after symptom onset and one-stage exchange arthroplasty produce similar 2-year success rates in patients with KhPJI of the knee. MATERIAL AND METHODS: A prospective observational cohort study was performed in patients managed for PJI of the knee between 2003 and 2015. The primary outcome measure was the occurrence of a septic event or of KhPJI -related death during a minimum follow-up of 2 years. RESULTS: Of 265 patients with PJI after total knee arthroplasty, 58 (22.1%) had KhPJI with onset more than 3 months after the last arthroplasty procedure and were included in the study. Among them, one-third had immune deficiencies. The most common causative organisms were streptococci (n=25, 43%) and Staphylococcusaureus (n=20, 34%). The primary focus of infection was identified in only 64% of patients and was most often cutaneous (n=19, 33%) or dental (n=11, 19%). A septic event or KhPJI-related death occurred in 5/34 (15%) patients after one-stage exchange arthroplasty and 6/19 (32%) patients after ASI within 15 days after symptom onset (p=0.03). Patient characteristics, type of prosthesis, and causative organism were not significantly associated with failure to eradicate the infection. CONCLUSION: ASI carried a high failure rate despite being performed within 15 days after symptom onset. One-stage exchange arthroplasty seems to be the best surgical option, particularly as the exact time of symptom onset may be difficult to determine. Identifying and eradicating the primary focus of infection is crucial. LEVEL OF EVIDENCE: II, low-powered prospective cohort study.

Curative treatment of prosthetic joint infection in patients younger than 80 vs. 80 or older.

OBJECTIVE: Prosthetic joint infection (PJI) is a serious complication of joint replacement surgery. The major pharmacological and surgical treatments required by PJI increase the risk of peri-operative complications in elderly patients. The increase in life expectancy combined with procedural advances make these treatments possible even in the oldest patients. Here, our objective was to compare the characteristics and outcomes of curative PJI treatment in patients < 80 years vs. ≥ 80 years. METHODS: A prospective single-center design was used to compare the characteristics and outcomes of curative treatment for hip or knee PJI in patients < 80 years and ≥ 80 years admitted in 2004-2014. RESULTS: Of 765 patients admitted for PJI, 590 were < 80 years and 124 were ≥ 80 years. Medical history and comorbidities were similar in the two groups. The older group had a significantly higher proportion of patients with American Society of Anesthesiologists Scores ≥ 3 and with streptococcal infection (20% vs. 13%, P < 0.05). After complete surgical excision and prolonged antibiotic therapy, the only event whose frequency differed significantly between the two groups was PJI-related death, which was more common in the older patients (6.5% vs. 0.8%, P < 0.05). The 2-year survival rate after one-stage exchange arthroplasty was > 90% in the ≥80 year group. CONCLUSION: Patients aged 80 years or older are eligible for the same curative pharmacological and surgical PJI treatments used in their younger counterparts. Before surgery, the risk/benefit ratio of the major surgical procedure required to treat PJI must be assessed on a case-by-case basis.

Prosthetic joint infections due to Mycobacterium tuberculosis: A retrospective study.

OBJECTIVE: Tuberculous prosthetic joint infection (PJI) is uncommon and often diagnosed late. The objective here is to describe the management of tuberculous PJI at an osteoarticular infection referral center. METHODS: A single-center retrospective study of patients managed between 1987 and 2016 was performed. RESULTS: We identified 9 patients with a median age of 80 years. The hip was involved in all 9 patients. A known history of tuberculosis was noted in 2 patients and tuberculosis was present at other sites in 4 patients (lung, n = 3; urinary tract and scrotum, n = 1; and spine, n = 1). The diagnosis was established by routine intra-operative microbiological sampling, during (n = 4) or at a distance from (n = 5) hip arthroplasty. In the 8 patients with available follow-up data, mean antibiotic therapy duration was 16 months (range, 12-18 months). None of the 4 patients in whom the infection was diagnosed during arthroplasty required surgical revision because of the infection. Of the other 5 patients, 3 were managed by exchange arthroplasty and 1 by excision of the hip without subsequent prosthesis implantation; the remaining patient did not undergo revision surgery. The infection was eradicated in all 9 patients, after 15 months to 10 years. CONCLUSION: Tuberculous PJI is uncommon. The prognosis is good with prolonged antibiotic therapy, although the optimal duration remains unclear. The surgical strategy should be discussed on a case-by-case basis. The prosthesis can be retained if the tuberculous infection is an unexpected finding during arthroplasty.

Concomitant Multiple Joint Arthroplasty Infections: Report on 16 Cases.

BACKGROUND: Concomitant infections of several prostheses are very rare, serious events that pose particular medical and surgical therapeutic challenges. This study was undertaken to describe epidemiologic, clinical, and microbiological characteristics of concomitant multiple joint arthroplasty infections, their treatments, and outcomes. METHODS: Retrospective (January 2000 and January 2014), single-center, cohort study in a referral center for bone and joint infections. All patients with at least 2 concomitant, microbiologically documented, prosthetic joint infections, that is, during the same septic episode, were included. RESULTS: Sixteen patients were included. Median (range) age was 78 years (46-93 years), gender ratio was 1, and median (range) body mass index was 27 (21-42). Multiple joint arthroplasties (bilateral hip in 8 patients; bilateral knee in 3 patients; hip and knee in 1 patient; and 2 knees and 1 hip in 1 patient) were contaminated hematogenously in all patients, 2 after early postoperative infections. Eight Staphylococcus aureus, 1 Staphylococcus epidermidis, 6 Streptococcus, and 1 Escherichia coli strains were isolated. A curative strategy was applied to 11 patients: 3 underwent bilateral synovectomies, 6 had successive 1-stage exchange arthroplasties, and 2 were treated with other strategies. After 37 months (range, 24-132 months) of follow-up, reinfection occurred in 1 patient. The 5 other patients received prolonged suppressive antibiotic therapy. CONCLUSION: These complex infections occur during staphylococcal or streptococcal bacteremia. Treatment strategies should be discussed by a multidisciplinary team on a case-by-case basis.

Crystal-induced arthritis after arthroplasty: 7 cases.

OBJECTIVES: To describe the occurrence in prosthetic joints of crystal-induced arthritis (CIA) defined as the deposition within the synovial membrane and/or joint cavity of calcium pyrophosphate dehydrate (CPPD) (chondrocalcinosis), sodium urate (gout), or hydroxyapatite. METHODS: We retrospectively reviewed the 7 cases of prosthetic-joint CIA seen between 1993 and 2013 at a medical-surgical center specialized in the management of osteoarticular infections. RESULTS: The 4 females and 3 males ranged in age from 67 to 79 years. Acute CIA occurred at the knee in 6 patients (5 with total knee arthroplasty and 1 with unicompartmental knee arthroplasty) and at the hip in 1 patient (with total hip arthroplasty). Time from arthroplasty to CIA varied from 7 days to 9 years. An abrupt onset was a consistent feature, with pain, complete loss of function, and local evidence of inflammation. A single patient had a fever and 6 patients had laboratory evidence of systemic inflammation. Joint aspiration showed hemarthrosis in 3 patients and inflammatory joint fluid with 20,000 to 79,000neutrophils/mm(3) in 6 patients. Joint fluid cultures were negative in 6 patients. CPPD crystals were evidenced in 5 patients, including 1 who also had hydroxyapatite crystals detected by electron microscopy after alizarin red staining. Monosodium urate crystals were found in 1 patient. The remaining patient had both CPPD crystals and positive cultures for Campylobacter fetus. In 5 patients, treatment with colchicine or a nonsteroidal antiinflammatory drug ensured prompt control of the symptoms and systemic inflammation. The patient with total hip arthroplasty underwent joint aspiration for hemarthrosis. In 1 patient, an intraarticular injection of triamcinolone hexacetonide improved the symptoms and systemic inflammation. The patient with Campylobacter fetus infection was treated with antibiotics, excision of the abscess, and synovectomy. CONCLUSION: CIA may occur after arthroplasty, within synovial membrane remains or neosynovium developed around the prosthetic joint. CIA is a manifestation of a metabolic disease that persists and can reactivate after surgery. Routine testing for crystals is rarely performed in patients with sterile arthritis of a prosthetic joint, and crystals are difficult to detect in joints with hemarthrosis; consequently, the frequency of prosthetic-joint CIA may be underestimated. Although rare, CIA should be considered routinely when symptoms suggesting septic arthritis develop in a prosthetic joint, in order to avoid unnecessary prolonged antibiotic therapy and, in some cases, surgery. The treatment is usually simple.

One-stage exchange arthroplasty for chronic periprosthetic hip infection: results of a large prospective cohort study.

BACKGROUND: Exchange arthroplasty of one or two stages is required for the treatment of chronic periprosthetic joint infections. Two-stage exchange is costly and has high morbidity with limited patient mobility between procedures. One-stage exchange has been promoted by several European teams as the preferred alternative. The aim of this study was to prospectively analyze the outcome of patients with a periprosthetic hip infection treated with one-stage exchange arthroplasty. METHODS: We performed a prospective cohort study in a French referral center for osteoarticular infections including all periprosthetic hip infections treated with one-stage exchange arthroplasty from November 2002 to March 2010. Direct exchange was performed in chronic periprosthetic hip infection with no or minor bone loss and preoperative identification of a microorganism from joint fluid aspirate. No antibiotic-loaded bone cement was used. Antibiotic therapy was administered for twelve weeks: intravenously for four to six weeks, followed by an oral regimen for six to eight weeks. Follow-up was a minimum of two years. The following events were noted: relapse, new infection, joint revision for mechanical reasons, and periprosthetic hip infection-related and unrelated deaths. RESULTS: One hundred and fifty-seven patients with periprosthetic hip infections with a median infection duration of 258 days (interquartile range, 120 to 551 days) prior to our index surgical procedure for infection were included. Periprosthetic hip infection occurred in ninety-nine cases of primary hip arthroplasty, twenty-seven cases of revision arthroplasty, and thirty-one cases in which the periprosthetic hip infection had been treated previously. A difficult-to-treat organism was isolated in fifty-nine cases (38%). After a median follow-up of 41.6 months (interquartile range, 28.1 to 66.9 months), two relapses, six new infections, nine revisions for mechanical reasons, two related deaths, and nineteen unrelated deaths occurred. CONCLUSIONS: One-stage exchange arthroplasty is an effective surgical procedure in patients with periprosthetic hip infection who have good bone quality. Precise identification of the microorganism(s) and prolonged administration of appropriate intravenous antibiotic therapy are key factors for successful treatment.

Campylobacter infection after prosthetic joint surgery.

Few cases of Campylobacter prosthetic joint infection (PJI) have been reported so far. We describe the demographic characteristics, underlying conditions, clinical features, treatment, and outcome of 8 patients with Campylobacter PJI in our hospital. All strains were confirmed at the French National Reference Center for Campylobacter and Helicobacter. Seven patients were infected with C. fetus and 1 with C. jejuni. Most patients were elderly and immunocompromised. Four had bacteremia, one of these with a pacemaker endocarditis. All the patients received at least 3 months of antibiotic treatment and 6 were treated surgically. The outcome was favorable at 2 years of follow-up in all except for 1 patient. Campylobacter PJI cases are rare but likely to become more frequent. C. fetus bacteremia should motivate physicians to look for a secondary localization such as a Campylobacter PJI.

Monitoring the one year postoperative infection rate after primary total hip replacement.

PURPOSE: Infection of a total hip replacement is potentially a devastating complication. Statistical process control methods have been generating interest as a means of improving the quality of healthcare, and we report our experience with the implementation of such a method to monitor the one year infection rate after primary total hip replacement. METHOD: Infection was defined as the growth of the same organism in cultures of at least two aspirates or intra-operative specimens, or growth of one pathogen in a patient with local signs of infection such as erythema, abscess or draining sinus tract. The cumulative summation test (CUSUM test) was used to continuously monitor the one year postoperative infection rate. The target performance was 0.5% and the test was set to detect twice that rate. RESULTS: Over the three year study period, 2006 primary total hip replacements were performed. Infection developed within one year after surgery in eight (0.4%) hips. The CUSUM test generated no alarms during the study period, indicating that there was no evidence that the process was out of control. CONCLUSION: The one year infection rate after primary total hip replacement was in control. The CUSUM test is a useful method to continuously ensure that performance is maintained at an adequate level.

Group B streptococcal prosthetic joint infections: a retrospective study of 30 cases.

OBJECTIVE: To describe the epidemiological, clinical, and laboratory characteristics of patients with group B streptococcal (GBS) prosthetic joint infections, their diagnoses, treatment, and long-term outcomes. METHODS: We conducted a retrospective cohort study including all patients hospitalized from January 1994 through May 2006 for a GBS prosthetic joint infection. RESULTS: The study included 30 patients, aged 35-87 (median 74) years with prosthetic hip (24) or knee (6) infections, 20 with at least one underlying disease. The route of infection was presumed to be hematogenous in 27 patients, and a portal of entry was identified in 9 (genitourinary tract 4, skin 2, gastrointestinal tract 2, oropharynx 1). All patients underwent surgery (6 debridement-synovectomy, 9 1-stage exchange arthroplasty, 8 2-stage exchange arthroplasty, 6 hip resection arthroplasty, and 1 knee arthrodesis) and received prolonged intravenous antibiotics. Four patients relapsed. One patient developed 2 other infections on her knee prosthesis. Two deaths were infection-related, and one was treatment-related. Nineteen patients followed for >/=2 years were cured. One patient was lost to follow-up and 3 died of causes unrelated to infection or treatment within 2 years. CONCLUSION: GBS prosthetic joint infections are mostly acute hematogenous infections that require prompt management for satisfactory outcome. Despite high antibiotic susceptibility, treatment failure is frequent because of the severity of the infection and patients' advanced age, underlying diseases, and relapses.

Continuous cefazolin infusion to treat bone and joint infections: clinical efficacy, feasibility, safety, and serum and bone concentrations.

Cefazolin has been used for many years to treat bone and joint infections. Because of its time-dependent antimicrobial activity, continuous infusion would potentially be beneficial. We report on the feasibility, safety, and efficacy of prolonged continuous intravenous cefazolin therapy in a cohort of 100 patients, their serum cefazolin levels, and the concomitant bone cefazolin concentrations in 8 of them. This retrospective cohort study included all the patients treated for bone or joint infection with a continuous cefazolin infusion administered over a 12-h period twice daily for >or=2 weeks. Drug monitoring was performed at least twice for all the patients. Serum and bone cefazolin concentrations were determined by standardized disk diffusion microbiological assays. The absence of clinical, biological, and radiological signs of infection after 2 years of follow-up and the same criteria after 1 year of follow-up defined cures and probable cures, respectively. The median treatment duration was 42 days, and the median daily cefazolin dose was 6 g. Half of the patients received parenteral antibiotic therapy on an outpatient basis. Two moderate-grade adverse events were observed. The median serum cefazolin concentrations were 63 microg/ml (range, 13 to 203 microg/ml) and 57 microg/ml (range, 29 to 128 microg/ml) on days 2 to 10 and days 11 to 21, respectively. The median bone cefazolin concentration reached 13.5 microg/g (range, 3.5 to 29 microg/g). The median bone concentration/serum concentration ratio was 0.25 (range, 0.06 to 0.41). Among 88 patients with a median follow-up of 25 months (range, 12 to 53 months), 52 were considered cured and 29 were considered probably cured. Thus, the treatment of bone and joint infections with a prolonged continuous intravenous cefazolin infusion was feasible, effective, well-tolerated, safe, and convenient, making it a strong candidate for home therapy.

Contribution of routine joint aspiration to the diagnosis of infection before hip revision surgery.

OBJECTIVES: To define the sensitivity and specificity of routine preoperative hip aspiration for diagnosing hip prosthesis infection (HPI) and to separately analyze subgroups with and without a clinical suspicion of HPI before aspiration. METHODS: From June 1994 to June 1997, all patients scheduled for hip revision surgery underwent aspiration of the hip under image intensifier guidance. Microbiological results were compared between these preoperative specimens and the intraoperative specimens. The reason for surgery was either a clinical suspicion of HPI or pain suggesting loosening. RESULTS: The study patients had had multiple surgical procedures. HPI was suspected clinically in 39.4% of cases. Of the 109 patients who underwent aspiration, 54 had true-negative results, nine had false-negative results, and 44 had true-positive results (there were no false-positive results), yielding a sensitivity of 83% and a specificity of 100%. Diagnostic efficiency was 91.6%, positive predictive value was 100%, and negative predictive value was 85.7%. In the subset of 43 patients with a clinical suspicion of HPI, aspiration identified all the causative organisms in 60.5% of cases. Of the 66 patients with no clinical suspicion of HPI, 12 had HPI, and aspiration provided the diagnosis preoperatively in seven of these patients, radically changing their management plans. Restricting routine aspiration to patients whose prosthesis had been implanted within the last 5 years or whose erythrocyte sedimentation rate (ESR) was above 30 mm/h would not have modified our findings. CONCLUSIONS: Hip aspiration before revision surgery for pain is effective in detecting HPI, which can simulate aseptic loosening. However, this investigation may be noncontributive in patients who have had their prosthesis for more than 5 years and whose ESR is less than 30 mm/h.

Synovial cysts of the proximal tibiofibular joint: three case reports.

Synovial cysts are fluid-filled masses lined with synovium and located within or about joints. The main symptoms are pain and/or neurological deficits. They can be intraneural or extraneural or develop between or within muscles. Synovial cysts that arise at a distance from a joint raise diagnostic challenges. We report three cases of synovial cysts of the proximal tibiofibular joint, including an intramuscular cyst responsible for paralysis of the anterolateral leg muscles. Tibiofibular synovial cysts are less common than popliteal cysts, and their pathophysiology is poorly understood. Pressure on the common peroneal nerve is the main complication and requires careful surgical excision of the cyst. Injection of a glucocorticoid into the cyst can be used as the first-line treatment in patients without common peroneal nerve symptoms.