Utilizing an antibiotic-eluting articulated cemented spacer in the two-stage management of infected total hip arthroplasty: a technical note.

Two-stage revision is generally preferred to eradicate chronic periprosthetic infections after total hip arthroplasty (THA) because of its good infection control and promising results. During two-stage revision, a temporary antibiotic-impregnated cement spacer was initially used for the local delivery of antibiotics, thereby reducing the risk of infection recurrence. Many researchers have reported various techniques for fabricating cemented spacers; however, there is no established standard technique. We share our cost-effective and easily reproducible technique for creating an articulated cemented spacer for managing infected THA.

Forte ceramic-on-delta ceramic cementless total hip arthroplasty: an 8- to 15-year follow-up study.

INTRODUCTION: Forte ceramic head on delta ceramic liner articulation showed satisfactory midterm results without ceramic-related complication. We aimed to investigate the clinical and radiological outcomes of cementless total hip arthroplasty (THA) with forte ceramic head on delta ceramic liner articulation. MATERIALS AND METHODS: Overall, 107 patients (57 men, 50 women; 138 hips) who underwent cementless THA with forte ceramic head on delta ceramic liner articulation were enrolled. The mean follow-up duration was 11.6 years. For the clinical assessments, Harris hip score (HHS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), presence of thigh pain, and presence of squeaking were evaluated. Radiographs were assessed to search for osteolysis, stem subsidence, loosening of implants. Kaplan-Meier survival curves were evaluated. RESULTS: The mean HHS and WOMAC improved from 57.1 and 28.1 preoperatively to 81.4 and 13.1 at the final follow-up, respectively. Nine revisions (6.5%) were performed; 5 hips for stem loosening, 1 hip for ceramic liner fracture, 2 hips for periprosthetic fracture, and 1 hip for progressive osteolysis around cup and stem. Thirty-two patients (37 hips) complained squeaking, in which 4 cases (2.9%) were identified as ceramic-related noises. After a mean follow-up period of 11.6 years, 91% (95% CI 87.8-94.2) were free from revision of both femoral and acetabular components due to any reason. CONCLUSIONS: Cementless THA with forte ceramic-on-delta ceramic articulation showed acceptable clinical and radiological results. Serial surveillance of these patients should be performed due to the possibility of cerami- related complications such as squeaking, osteolysis, and ceramic liner fracture.

The diagnostic value of SPECT/CT in predicting the occurrence of osteonecrosis following femoral neck fracture: a prospective cohort study.

BACKGROUNDS: One of the most significant complications after a femoral neck fracture is osteonecrosis of the femoral head (ONFH). The concomitant use of single-photon emission computed tomography (SPECT) with computed tomography (CT) increases the sensitivity for detecting the anatomic location and severity of ONFH. In this study, we evaluated the diagnostic value of SPECT/CT for the occurrence of ONFH by quantifying the perfusion status of the femoral head. METHODS: A total of 30 patients who had multiple pinnings for femur neck fractures were included in this study. We classified the perfusion status into three groups: normal perfusion, decreased perfusion, and avascular groups, and compared the occurrence of femoral head necrosis between them. For quantitative analysis, we evaluated the uptake ratio of both femur heads (head-to-head uptake ratio). If the patient's contralateral hip was incomparable, we measured the uptake ratio from the superior dome of the ipsilateral acetabulum (head-to-acetabulum uptake ratio). RESULTS: Twenty-four patients out of 30 achieved bone union, whereas the others developed ONFH. When the population was divided into intact and defective perfusion groups on scintigraphy, the sensitivity, specificity, and accuracy of the test were 83.3, 75.0, and 76.7%, respectively. The mean head-to-head uptake ratio value with a 95% confidence interval (CI) was 1.10 (95% CI: 0.85-1.36). In the osteonecrosis group, the mean value of the head-to-head uptake ratio was 0.33 (95% CI: 0.28-0.38). In contrast, the ratio was 1.30 (95% CI: 1.03-1.57) in the non-osteonecrosis group, demonstrating a significant difference in the uptake ratio (P < 0.001). When the cutoff value of the uptake ratio was set to 0.5, both the sensitivity and specificity were 100%. There was also a significant difference in the head-to-acetabulum uptake ratio between the two groups (P <  0.001). CONCLUSIONS: SPECT/CT was useful in evaluating the perfusion status of the femoral head, showing high accuracy in predicting the occurrence of avascular necrosis. To demonstrate the reliability and validity of SPECT/CT, further prospective studies on a larger scale are warranted.

Hip Arthroscopy for Femoroacetabular Impingement and Concomitant Labral Tears: A Minimum 2-Year Follow-Up Study.

PURPOSE: The present study investigated the minimum 2-year outcomes of hip arthroscopy for femoroacetabular impingement (FAI) and concomitant labral tears in Asian patients. METHODS: Patients who underwent hip arthroscopy for both FAI and concomitant labral tears between January 2012 and December 2017 were included. Patients with hip osteoarthritis of Tönnis grade ≥2, previous hip surgery, or followed for less than 2 years were excluded. Clinical assessments were performed using the modified Harris Hip Score, Western Ontario and McMaster Universities Osteoarthritis Index, and the rates of achieving threshold values of the minimal clinically important difference and patient acceptable symptomatic state at the latest follow-up. Plain radiographs were acquired pre- and postoperatively for radiologic assessments. RESULTS: A total of 73 patients (90 hips, 58 male, 15 female; mean age 34.4 years) who underwent hip arthroscopy for FAI and concomitant labral tears were enrolled. Forty-three hips (47.8%) had cam-type, 7 (7.8%) had pincer-type, and 40 (44.4%) had mixed-type FAI. The mean follow-up duration was 5.2 years. In cam- and mixed-type FAI hips, the mean α angle significantly decreased from 66.7 ± 8.28° preoperatively to 44.9 ± 3.78° postoperatively (95% confidence interval [CI] 19.6°-22.8°; P < .001). The mean modified Harris Hip Score and Western Ontario and McMaster Universities Osteoarthritis Index increased from 74.8 ± 13.2 and 75 ± 12.7 preoperatively to 93 ± 8.1 (95% CI 15.4-20.9; P = .001) and 89.4 ± 8.4 postoperatively (95% CI 11.8-17; P = .001), respectively. Seventy-four hips (82.2%) crossed the minimal clinically important difference, and 85 hips (94.4%) had achieved the patient acceptable symptomatic state. There were 2 cases of pudendal nerve palsy and 1 case of sciatic nerve palsy. No additional surgeries were required. CONCLUSIONS: Hip arthroscopy can be an effective treatment for FAI and concomitant labral tears in Asian patients as demonstrated in this study, with improved PRO scores and reoperation rates. Longer-term studies with larger cohorts are necessary. LEVEL OF EVIDENCE: Level IV, case series.

The Effect of Povidone-Iodine Lavage in Preventing Infection After Total Hip and Knee Arthroplasties: Systematic Review and Meta-Analysis.

BACKGROUND: Dilute povidone-iodine (PI) lavage, a simple disinfection method, could reduce postoperative infection risk. However, there is no clinical consensus regarding its efficacy in total joint arthroplasties (TJAs). This systematic review and meta-analysis evaluated PI lavage's efficacy in preventing infection after TJA. METHODS: MEDLINE, Embase, and the Cochrane Library were systematically searched for studies published before November 22, 2019, that compared postoperative infection rates in patients who underwent TJA with or without PI lavage before wound closure. Subgroup analyses were designed to identify the differences in infection site (overall or deep), type of surgery (total hip arthroplasty or total knee arthroplasty), time until diagnosis of infection (3 or 12 months postoperatively), and primary/aseptic revision arthroplasties. RESULTS: We included 7 studies with 31,213 TJA cases, comprising 8861 patients who received PI lavage and 22,352 who did not. Pooled odds ratio for overall infection rate for the PI and non-PI lavage groups was 0.67 (95% confidence interval, 0.38-1.19, P = .17) and for the deep infection rate was 0.90 (95% confidence interval, 0.27-2.98, P = .86). Subgroup analyses revealed no differences in postoperative infection rates between the PI and non-PI lavage groups in terms of total hip arthroplasty and total knee arthroplasty, diagnosis of infection at 3 and 12 months postoperatively, or primary and aseptic revision arthroplasties. CONCLUSION: We detected no differences in the overall postoperative infection rates between the PI and non-PI lavage groups before wound closure in TJA including all studies in the subgroup analyses.

Efficacy of total hip arthroplasty after operatively treated acetabular fracture.

INTRODUCTION: We evaluated the clinical and radiological outcomes of patients following total hip arthroplasty (THA) for acetabular fracture. MATERIALS AND METHODS: This was a retrospective cohort study in a single center. The medical records of patients who underwent THA from March 2002 to March 2017 were reviewed. Inclusion criteria were THA and a history of open reduction and internal fixation of acetabular fractures. Thirty-seven patients with a mean age of 56.2 years were enrolled. The Harris hip score (HHS), acetabular fracture classification, time interval between acetabular fracture and THA, cause of THA, surgical approach, implant type, complications, radiographic results, and Kaplan-Meier survival curves were analyzed. RESULTS: All patients were followed up for an average of 6.6 years. The mean preoperative HHS of 42.5 had improved to 83.5 at the final follow-up (p < 0.05). There were 29 cases of post-traumatic arthritis, 6 cases of avascular necrosis, and 4 cases of non-union. The average interval from injury to THA was 58 months (range 4-336 months). The re-admission rate was 18.9%. Patients who underwent conversion to THA due to post-traumatic arthritis combined with non-union acetabular fracture developed clinical failure more frequently than patients with post-traumatic arthritis (p = 0.037). At 12 years, 83.4% of patients were free from revision of femoral and acetabular components. CONCLUSION: THA secondary to an operatively treated acetabular fracture provides good symptomatic relief, but shows relatively inferior survival rates, and clinical failure was related to post-traumatic arthritis with acetabular non-union.

Multiple drilling and multiple matchstick-like bone allografts for large osteonecrotic lesions in the femoral head: an average 3-year follow-up study.

INTRODUCTION: We aimed to present the clinical outcomes of multiple drilling and multiple matchstick-like bone allograft for large osteonecrotic lesions of the femoral head as a joint-preserving surgery. MATERIALS AND METHODS: Between March 2014 and March 2018, 57 patients (77 hips) who underwent multiple drilling and multiple matchstick-like bone allograft for large lesions (≥ 30%) in osteonecrosis of the femoral head (ONFH) were included. Harris hip scores (HHS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were obtained preoperatively and at the latest follow-up. Plain radiographs were obtained every 3 months. Femoral head collapse ≥ 2 mm was defined as a radiological failure, and conversion to total hip arthroplasty (THA) was regarded as a clinical failure. RESULTS: After exclusion of 5 patients (5 hips) who lost to follow-up, 52 patients (34 men, 18 women; 72 hips) were finally enrolled. The mean follow-up period was 3.4 (range 2-4.5) years. Nineteen hips (28.4%) required conversion to THA at a mean of 21.6 (range 6-42) months postoperatively. In the remaining 53 hips (71.6%) with clinical success, the mean HHS and WOMAC improved from 63 and 31.3 preoperatively to 80.6 and 16.3 at the final follow-up, respectively (p < 0.001). Radiological failure occurred in four hips (6%). The overall failure rate was 31.9% (23/72 hips), and the mean survival duration until failure was 21.2 months (6-42 months). The lesion size, lesion location, and the use of corticosteroids as the cause of ONFH were associated with clinical failure. CONCLUSION: Multiple drilling and multiple matchstick-like bone allograft may be a useful treatment option for alleviating the symptoms in ONFH patients with large lesions who want to preserve their hips.

Serum Metal Ion Levels in Cementless Metal-On-Metal Total Hip Arthroplasty: Long-Term Follow-Up Trends.

BACKGROUND: Long-term trends in serum metal ion concentration after metal-on-metal (MoM) total hip arthroplasty (THA) are unclear. In most studies, serum metal ion levels increase initially and remain constant during follow-up. However, there are no previous studies that evaluate the metal ion level longitudinally at multiple intervals over the long term. Increasing metal ion levels during the long-term follow-up of patients who underwent cementless MoM THA has been seen, so this study investigated those trends. METHODS: Seventy-one patients were followed for a minimum of 10 years (range, 10.0-18.6 years). All underwent unilateral THA with MoM bearings. Serum cobalt (Co) and chromium (Cr) levels were measured preoperatively and annually after surgery. Trends and differences in serum levels based on sex, mean age, body mass index, cup inclination, and implant selection were analyzed. RESULTS: Within 5 years after the operation, the mean Co and Cr levels peaked postoperatively at 3-4 years (4.14 and 6.89 µg/L, respectively). Between 5 and 10 years postoperatively, the serum levels showed 2 tendencies. One group (62) showed a constant range, but a smaller group (9) showed increasing serum metal ion levels. The only factor which showed a difference between the 2 groups was body mass index (P = .030), which was lower in the increasing serum metal ion level group. CONCLUSION: At a medium-term to long-term follow-up period, serum Co and Cr levels are not always constant. This should be considered when seeing patients with MoM THA, and laboratory tests may be needed for long-term follow-up.

What is the Prevalence of Radiographic Hip Findings Associated With Femoroacetabular Impingement in Asymptomatic Asian Volunteers?

BACKGROUND: Morphologic features of the proximal femur reminiscent of those seen in patients with femoroacetabular impingement (FAI) have been reported among asymptomatic individuals in Western populations, but whether this is the case in Asian populations is unknown. QUESTIONS/PURPOSES: The purpose of this study was to determine the prevalence of radiographic findings in the proximal femur that are consistent with FAI in asymptomatic Korean volunteers. METHODS: Two hundred asymptomatic volunteers with no prior hip surgery or childhood hip problems underwent three-view plain radiographs (pelvis AP view, Sugioka view, and 45° Dunn view) of both hips. There were 146 hips from male volunteers and 254 hips from female volunteers in the study. The mean age of all participants was 34.7 years (range, 21-49 years). Cam-type morphologic features were defined as the presence of the following on one or more of the three views: pistol-grip morphologic features, an osseous bump at the femoral head-neck junction, flattening of the femoral head-neck offset, or alpha angle greater than 55°. Pincer-type morphologic features were determined by radiographic signs, including crossover sign, deficient posterior wall sign, or lateral center-edge angle greater than 40°. RESULTS: The prevalence of cam-type morphologic features seen on at least one radiograph was 38% (male, 57%; female, 26%). The prevalence of cam-type features (at least one positive cam-type feature) was 2.0% (male, 6%; female, 0%) on the pelvic AP view, 24% (male, 36%; female, 17%) on the Sugioka view, and 30% (male, 47%; female, 20%) on the 45° Dunn view. The prevalence of pincer-type morphologic features (at least one positive pincer-type feature) was 23% (male, 27%; female, 21%) on the pelvic AP view. CONCLUSION: The prevalence of FAI-related morphologic features in asymptomatic Asian populations was comparable to the prevalence in Western populations. Considering the high prevalence of radiographic hip findings reminiscent of FAI in asymptomatic Asian populations, it will be important to determine whether FAI-related morphologic features are a cause of hip pain when considering surgery in Asian patients.

Venous Thromboembolism Following Hip and Knee Replacement Arthroplasty in Korea: A Nationwide Study Based on Claims Registry.

The aim of this study was to examine the incidence and trends of clinically relevant venous thromboembolism (VTE) including deep vein thrombosis (DVT) and pulmonary embolism (PE) after hip and knee replacement arthroplasty (HKRA) in Korea. Between January 1 and December 31, 2010, 22,127 hip replacement arthroplasty (HRA) patients and 52,882 knee replacement arthroplasty (KRA) patients were enrolled in the analysis using the administrative claims database of the Health Insurance Review and Assessment Service (HIRA). All available parameters including procedure history and clinically relevant VTE during the 90 days after HKRA were identified based on diagnostic and electronic data interchange (EDI) codes. The overall incidence of VTE, DVT, and PE during the 90 days was 3.9% (n=853), 2.7% (n=597), and 1.5% (n=327) after HRA, while the incidence was 3.8% (n=1,990), 3.2% (n=1,699), and 0.7% (n=355) after KRA. The incidence of VTE after HKRA was significantly higher in patients who had previous VTE history (odds ratio [OR], 10.8 after HRA, OR, 8.5 after KRA), chronic heart failure (2.1, 1.3), arrhythmia (1.8, 1.7), and atrial fibrillation (3.4, 2.1) than in patients who did not. The VTE incidence in patients with chemoprophylaxis was higher than that in patients without chemoprophylaxis. The incidence of VTEs revealed in this retrospective review was not low compared with the results of the studies targeting other Asian or Caucasian populations. It may warrant routine prevention including employment of chemoprophylaxis. However, the limitation of the reviewed data mandates large scale prospective investigation to affirm this observation.

Subchondral insufficiency fracture of the femoral head in elderly people.

We evaluated the clinical course of subchondral insufficiency fracture of the femoral head (SIFFH) and its characteristic findings with special regard to joint space narrowing (JSN). Thirty-one cases of SIFFH of mean age 68.9 yr initially underwent limited weight-bearing conservative treatment. During the follow-up period, the patients with intractable pain underwent total hip arthroplasty (THA). For radiographic evaluation, lateral center-edge angle, JSN and femoral head collapse (FHC) were documented, and the extent of FHC was classified as mild (<2 mm), moderate (2-4 mm), and severe (>4 mm). The progression or new development of FHC more than 2 mm was evaluated on sequential plain radiographs. The relationship between radiographic parameters and clinical outcomes were evaluated. THAs were performed in 15 cases (48.4%). There was no significant correlation between clinical outcomes and the extent of initial FHC. However, a significantly larger proportion of patients that underwent THA showed JSN and FHC progression compared to the symptom improvement group. The risk factor significantly associated with failed conservative treatment was JSN (P=0.038; OR, 11.8; 95% CI, 1.15-122.26). Clinical results of conservative treatment for SIFFH in elderly patients are relatively poor. The patients with JSN are at higher risk of failed conservative treatment.

Epidemiology of hip replacements in Korea from 2007 to 2011.

We analyzed national data collected by the Health Insurance Review and Assessment Service in Korea from 2007 to 2011; 1) to document procedural numbers and procedural rate of bipolar hemiarthroplasty (BH), primary and revision total hip arthroplasties (THAs), 2) to stratify the prevalence of each procedure by age, gender, and hospital type, and quantified, 3) to estimate the revision burden and evaluate whether the burden is changed over time. Our final study population included 60,230 BHs, 40,760 primary THAs, and 10,341 revision THAs. From 2007 to 2011, both the number and the rate of BHs, primary THAs increased steadily, whereas there was no significant change in revision THAs. Over the 5 yr, the rate of BHs and primary THAs per 100,000 persons significantly increased by 33.2% and 21.4%, respectively. The number of revision THAs was consistent over time. The overall annual revision burden for THA decreased from 22.1% in 2007 to 18.9% in 2011. In contrast to western data, there were no changes in the number and rate of revision THAs, and the rates of primary and revision THAs were higher for men than those for women. Although 5 yr is a short time to determine a change in the revision burden, there have been significant decreases in some age groups.

The efficacy of Denosumab in the treatment of femoral head osteonecrosis: a retrospective comparative study.

The present study aimed to compare clinical and radiological differences of ONFH patients who were treated with denosumab, and a control group. A total of 178 patients (272 hips) with symptomatic, nontraumatic ONFH were divided into a denosumab group (98 patients, 146 hips) and a control group (80 patients, 126 hips). Patients in the denosumab group received a 60 mg subcutaneous dose of denosumab every 6 months. For the clinical assessments, Harris hip scores (HHS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were evaluated. Plain radiographs and MRI were performed before and a minimum of 1 year after administration of denosumab, which were evaluated for radiological results including femoral head collapse (≥ 2 mm) and volume change of necrotic lesion. Femoral head collapse occurred in 36 hips (24.7%) in the denosumab group, and 48 hips (38.1%) in the control group, which was statistically significant (P = 0.012). Twenty-three hips (15.8%) in the denosumab group and 29 hips (23%) in the control group required THA, which showed no significant difference (P = 0.086). At the final follow-up, 71.9% of hips in the denosumab group had a good or excellent HHS compared with 48.9% in the control group, showing a significant difference (P = 0.012). The denosumab group showed a significantly higher rate of necrotic lesion volume reductions compared with the control group (P < 0.001). Denosumab can significantly reduce the volume of necrotic lesions and prevent femoral head collapse in patients with ARCO stage I or II ONFH.

Comparative evaluation of in vivo osteogenic differentiation of fetal and adult mesenchymal stem cell in rat critical-sized femoral defect model.

Mesenchymal stem cells (MSCs) can be obtained from various sources. MSCs from different origins appear to have different preferences for differentiation. In this study, we have compared the in vivo osteogenic potential of adult MSCs from adipose tissue (AT) and bone marrow (BM) with fetal MSCs from umbilical cord (UC) and umbilical cord blood (UCB) by using a rat critical-sized femoral defect model. We have also sought to determine whether pretreatment with an osteogenic medium promotes osteogenesis in MSCs. Study groups were divided as follows: (1) defect only, (2) scaffold only, (3) AT MSCs in scaffolds, (4) BM MSCs in scaffolds, (5) UC MSCs in scaffolds and (6) UCB MSCs in scaffolds. Groups with MSCs were further divided with respect to their pretreatment. At 12 weeks after surgery, in vivo osteogenesis was measured radiographically and by micro-computed tomography (CT). Based on quantitative assessment by micro-CT, no significant difference of the mean bone volume fraction value (BV/TV) was seen between adult MSCs (AT and BM MSCs) and fetal MSCs (UC and UCB MSCs). The mean BV/TVs were significantly higher in non-pretreated BM MSC (14.2±1.4%) and UCB MSC (14.0±1.2%) and pretreated UC MSC (14.8±2.0%) than in those with the scaffold only (11.3±1.3%; P<0.05). In addition, AT (from 10.4±1.2% to 13.1±2.2%) and UC (from 10.3±0.7% to 14.8±2.0%) MSCs from solid tissues showed a significant increase in the mean BV/TV with pretreatment (P<0.05). In contrast, BM MSC (from 14.2±1.4% to 10.9±1.2%) and UCB MSC (from 14.0±1.2% to 11.6±1.0%) from non-solid tissues showed a significant decrease with pretreatment (P<0.05).

Revision total hip arthroplasty using an alumina-on-alumina bearing surface in patients with osteolysis.

We evaluated the outcomes of 64 consecutive revision total hip arthroplasties with an alumina-on-alumina bearing surface in 61 patients with osteolysis. No implants had been rerevised nor was osteolysis detected at a mean of 9.8 years (range, 7.0-13.1 years) postoperatively. There was 1 case of stem loosening but no cup loosening or alumina bearing fractures. Two surgical procedures were performed for an infection in 1 patient. Three dislocations occurred in 3 hips; all were treated with closed reduction and abduction bracing for 3 months. No further dislocations occurred. With any reoperation or radiographic evidence of osteolysis or loosening as the end point, the 7-year survival rate was 96.9% (95% confidence interval, 90.8%-100%). The alumina-on-alumina bearing surfaces used for revision total hip arthroplasty in patients with osteolysis were found to produce encouraging clinical results and implant survival rates at a minimum of 7 years postoperatively.

Medial placement of the acetabular component in an alumina-on-alumina total hip arthroplasty: a comparative study with propensity score matching.

PURPOSE: In an alumina-on-alumina total hip arthroplasty (THA), recommended with a small inclination angle <45°, the acetabular component (cup) may be positioned more medially to be covered almost completely by host bone. The purpose of this study was to identify the correlating factors and to evaluate the outcomes of medial placement of the cup in patients with alumina-on-alumina THAs. METHODS: Using the propensity score matching with age, gender, body mass index, initial diagnosis, and the length of follow-up as variables, 38 hips with a medialized cup and 38 hips with a non-medialized one were identified from 389 hips in 347 who patients underwent primary alumina-on-alumina THA and followed up for more than 7 years. Clinical and radiological outcomes were compared between the two groups. RESULTS: Preoperative acetabular medial wall thickness and the cup inclination angle were significantly smaller in the medialization group compared to the non-medialization group. Center edge angle, cup size, and coverage by host bone were not significantly different between the two groups. The hip center of rotation was significantly medialized in the medialization group. The Harris hip scores were not significantly different between the two groups. No component loosening or osteolysis was observed and no revision was required in either groups. CONCLUSIONS: Thin acetabular medial wall and a small inclination angle of the cup were the correlating factors of medial placement of the cup in patients who underwent an alumina-on-alumina THA. Medial placement did not lead to differences in the clinical or radiological outcomes.

Case report: multifocal subchondral stress fractures of the femoral heads and tibial condyles in a young military recruit.

BACKGROUND: Subchondral stress fractures of the femoral head may be either of the insufficiency-type with poor quality bone or the fatigue-type with normal quality bone but subject to high repetitive stresses. Unlike osteonecrosis, multiple site involvement rarely has been reported for subchondral stress fractures. We describe a case of multifocal subchondral stress fractures involving femoral heads and medial tibial condyles bilaterally within 2 weeks. CASE DESCRIPTION: A 27-year-old military recruit began having left knee pain after 2 weeks of basic training, without any injury. Subsequently, right knee, right hip, and left hip pain developed sequentially within 2 weeks. The diagnosis of multifocal subchondral stress fracture was confirmed by plain radiographs and MR images. Nonoperative treatment of the subchondral stress fractures of both medial tibial condyles and the left uncollapsed femoral head resulted in resolution of symptoms. The collapsed right femoral head was treated with a fibular strut allograft to restore congruity and healed without further collapse. LITERATURE REVIEW: There has been one case report in which an insufficiency-type subchondral stress fracture of the femoral head and medial femoral condyle occurred within a 2-year interval. CLINICAL RELEVANCE: Because the incidence of bilateral subchondral stress fractures of the femoral head is low and multifocal involvement has not been reported, multifocal subchondral stress fractures can be confused with multifocal osteonecrosis. Our case shows that subchondral stress fractures can occur in multiple sites almost simultaneously.

Malignant fibrous histiocytoma at the site of an alumina-on-alumina-bearing total hip arthroplasty mimicking infected trochanteric bursitis.

Although the incidence of malignant tumors in patients undergoing total hip arthroplasties (THAs) is known to be lower than the general population, there exist several reports on the development of malignant tumors at the site of THAs. We report another case of malignant fibrous histiocytoma at the site of a THA, which was developed in an older patient who presented a cystic mass around the total hip prosthesis using a ceramic-on-ceramic bearing system, even without evidence of osteolysis or loosening of implants. This is the second case associated with an aluminum oxide prosthesis in English literature.