2019 John Charnley Award: Increased risk of prosthetic joint infection following primary total knee and hip arthroplasty with the use of alternative antibiotics to cefazolin: the value of allergy testing for antibiotic prophylaxis.

AIMS: The aims of this study were to characterize antibiotic choices for perioperative total knee arthroplasty (TKA) and total hip arthroplasty (THA) prophylaxis, assess antibiotic allergy testing efficacy, and determine rates of prosthetic joint infection (PJI) based on perioperative antibiotic regimen. PATIENTS AND METHODS: We evaluated all patients undergoing primary TKA or THA at a single academic institution between January 2004 and May 2017, yielding 29 695 arthroplasties (22 705 patients), with 3411 arthroplasties in 2576 patients (11.5%) having undergone preoperative allergy testing. A series of institutional databases were combined to identify allergy consultation outcomes, perioperative antibiotic regimen, and infection-free survivorship until final follow-up. RESULTS: Among 2576 allergy-tested patients, 2493 patients (97%) were cleared to use cephalosporins. For the entire cohort, 28 174 arthroplasties (94.9%) received cefazolin and 1521 (5.1%) received non-cefazolin antibiotics. Infection-free survivorship was significantly higher among arthroplasties receiving cefazolin compared with non-cefazolin antibiotics, with 0.06% higher survival free of infection at one month, 0.56% at two months, 0.61% at one year, and 1.19% at ten years (p < 0.001). Overall, the risk of PJI was 32% lower in patients treated with cefazolin after adjusting for the American Society of Anesthesiologists (ASA) classification, joint arthroplasty (TKA or THA), and body mass index (BMI; p < 0.001). The number needed to treat with cefazolin to prevent one PJI was 164 patients at one year and 84 patients at ten years. Therefore, potentially 6098 PJIs could be prevented by one year and 11 905 by ten years in a cohort of 1 000 000 primary TKA and THA patients. CONCLUSION: PJI rates are significantly higher when non-cefazolin antibiotics are used for perioperative TKA and THA prophylaxis, highlighting the positive impact of preoperative antibiotic allergy testing to increase cefazolin usage. Given the low rate of true penicillin allergy positivity, and the readily modifiable risk factor that antibiotic choice provides, we recommend perioperative testing and clearance for all patients presenting with penicillin and cephalosporin allergies. Cite this article: Bone Joint J 2019;101-B(6 Supple B):9-15.

Total hip arthroplasty in patients affected by poliomyelitis.

Aims: The aims of this study were to determine the clinical and radiographic outcomes, implant survivorship, and complications of patients with a history of poliomyelitis undergoing total hip arthroplasty (THA) in affected limbs and unaffected limbs of this same population. Patients and Methods: A retrospective review identified 51 patients (27 male and 24 female, 59 hips) with a mean age of 66 years (38 to 88) and with the history of poliomyelitis who underwent THA for degenerative arthritis between 1970 and 2012. Immigrant status, clinical outcomes, radiographic results, implant survival, and complications were recorded. Results: In all, 32 THAs (63%) were performed on an affected limb, while 27 (37%) were performed on an unaffected limb. The overall ten-year survivorship free from aseptic loosening, any revision, or any reoperation were 91% (95% CI 0.76 to 0.99), 91% (95% CI 0.64 to 0.97) and 87% (95% CI 0.61 to 0.95), respectively. There were no revisions for prosthetic joint infection. There were no significant differences in any of the above parameters if THA was on the affected or unaffected control limbs. Conclusion: Patients with a history of poliomyelitis who undergo THA on the affected or unaffected limbs have similar results with overall survivorship and complication rates to those reported results in patients undergoing THA for osteoarthritis. At long-term follow-up, previous clinical concerns about increased hip instability due to post-polio abductor weakness were not observed. Cite this article: Bone Joint J 2018;100-B:733-9.

Reconstruction of the hip after resection of periacetabular oncological lesions: a systematic review.

AIMS: Reconstruction of the acetabulum after resection of a periacetabular malignancy is technically challenging and many different techniques have been used with varying success. Our aim was to prepare a systematic review of the literature dealing with these techniques in order to clarify the management, the rate of complications and the outcomes. PATIENTS AND METHODS: A search of PubMed and MEDLINE was conducted for English language articles published between January 1990 and February 2017 with combinations of key search terms to identify studies dealing with periacetabular resection with reconstruction in patients with a malignancy. Studies in English that reported radiographic or clinical outcomes were included. Data collected from each study included: the number and type of reconstructions, the pathological diagnosis of the lesions, the mean age and follow-up, gender distribution, implant survivorship, complications, functional outcome, and mortality. The results from individual studies were combined for the general analysis, and then grouped according to the type of reconstruction. RESULTS: A total of 57 studies met the inclusion criteria and included 1700 patients. Most lesions were metastatic (41%), followed by chondrosarcoma (29%), osteosarcoma (10%), Ewing's sarcoma (7%), and multiple myeloma (2%). The techniques of reconstruction were divided into seven types for analysis: those involving a Harrington reconstruction, a saddle prosthesis, an allograft and allograft prosthesis composite, a pasteurised autograft, a porous tantalum implant, a custom-made prosthesis and a modular hemipelvic reconstruction. The rate of complications was 50%, with infection (14%) and instability (8%) being the most common. Mortality data were available for 1427 patients (84%); 50% had died of disease progression, 23% were alive with disease, and 27% had no evidence of disease at a mean follow-up of 3.4 years (0 to 34). CONCLUSION: Both the rate of complications and mortality are high following resection of oncological periacetabular lesions and reconstruction. Many types of reconstruction have been used with unique challenges and complications for each technique. Newer prostheses, including custom-made prostheses and porous tantalum implants and augments, have shown promising early functional and radiographic outcomes. Cite this article: Bone Joint J 2018;100-B(1 Supple A):22-30.

Prior bariatric surgery may decrease the rate of re-operation and revision following total hip arthroplasty.

AIMS: We compared the outcome of total hip arthroplasty (THA) in obese patients who previously underwent bariatric surgery and those who did not, in a matched cohort study. PATIENTS AND METHODS: There were 47 THAs in the bariatric group (42 patients), and 94 THAs in the comparison group (92 patients). The mean age of the patients was 57 years in both groups (24 to 79) and 57% of the patients in both groups were women. The mean time between bariatric surgery and THA was five years (four months to 12 years) in the bariatric group. The mean follow-up after THA was three years (2 to 9). RESULTS: The mean BMI improved from 49.7 kg/m(2) (35 to 75) prior to bariatric surgery to 35.3 kg/m(2) (21 to 49) at the time of THA (p < 0.001). Patients in the comparison group had an increased risk of re-operation (Hazard Ratio (HR) 3.2; 95% confidence intervals (CI) 1.3 to 9.5, p = 0.01) and revision (HR 5.4; 95% CI 1.5 to 34.5, p = 0.01) when compared with the bariatric group. CONCLUSION: Patients had a dramatic improvement in BMI after bariatric surgery and those with prior bariatric surgery had a lower risk of re-operation and revision in the short- and mid-term after a subsequent THA. Larger prospective studies are required before it can be concluded that this extra surgery should be advised in these patients. Cite this article: Bone Joint J 2016;98-B:1180-4.

Epidemiology of periprosthetic femoral fractures in 5417 revision total hip arthroplasties: a 40-year experience.

AIMS: The goals of this study were to define the risk factors, characteristics, and chronology of fractures in 5417 revision total hip arthroplasties (THAs). PATIENTS AND METHODS: From our hospital's prospectively collected database we identified all patients who had undergone a revision THA between 1969 and 2011 which involved the femoral stem. The patients' medical records and radiographs were examined and the relevant data extracted. Post-operative periprosthetic fractures were classified using the Vancouver system. A total of 5417 revision THAs were identified. RESULTS: There were 668 intra-operative fractures, giving an incidence of 12%. Fractures were three times more common with uncemented stems (19%) than with cemented stems (6%) (p < 0.001). The incidence of intra-operative femoral fracture varied by uncemented stem type: fully-coated (20%); proximally-coated (19%); modular fluted tapered (16%) (p < 0.05). Most fractures occurred during the insertion of the femoral component (35%). One-third involved the diaphysis and 26% were of the calcar: 69% were undisplaced. There were 281 post-operative fractures of the femur (20-year probability = 11%). There was no difference in risk for cemented and uncemented stems. Post-operative fractures were more common in men < 70 years (p = 0.02). Periprosthetic fractures occurred earlier after uncemented revision of the femoral component, but later after a cemented revision. The most common fracture type was a Vancouver B1 (31%). Of all post-operative fractures, 24% underwent open reduction and internal fixation and 15% revision arthroplasty. CONCLUSION: In revision THA, intra-operative fractures occurred three times more often with an uncemented stem. Many were undisplaced diaphyseal fractures treated with cerclage fixation. While the risk of post-operative fracture is similar between uncemented and cemented components, they occur at notably different times depending on the type of stem fixation. TAKE HOME MESSAGE: In revision THA, intra-operative periprosthetic femoral fractures occur three times more often with uncemented stems. Many are non-displaced diaphyseal fractures treated with cerclage fixation. While postoperative fracture risks are equivalent between uncemented and cemented components, they occur at notably different time periods based on stem fixation type.

Epidemiology of periprosthetic fracture of the femur in 32 644 primary total hip arthroplasties: a 40-year experience.

AIM AND METHODS: The goals of this study were to define the risk factors, nature, chronology, and treatment strategies adopted for periprosthetic femoral fractures in 32 644 primary total hip arthroplasties (THAs). RESULTS: There were 564 intra-operative fractures (1.7%); 529 during uncemented stem placement (3.0%) and 35 during cemented stem placement (0.23%). Intra-operative fractures were more common in females and patients over 65 years (p < 0.001). The majority occurred during placement of the femoral component (60%), and involved the calcar (69%). There were 557 post-operative fractures (20-year probability: 3.5%; 95% confidence interval (CI) 3.2 to 3.9); 335 fractures after placement of an uncemented stem (20-year probability: 7.7%; 95% CI 6.2 to 9.1) and 222 after placement of a cemented stem (20-year probability: 2.1%; 95% CI 1.8 to 2.5). The probability of a post-operative fracture within 30 days after an uncemented stem was ten times higher than a cemented stem. The most common post-operative fracture type was a Vancouver AG (32%; n = 135), with 67% occurring after a fall. In all, 36% (n = 152) were treated with revision arthroplasty. CONCLUSION: In summary, intra-operative fractures occur 14 times more often with uncemented stems. Female patients over 65 years of age are at highest risk. Post-operative fractures are also most common with uncemented stems, but are independent of age or gender. Cumulative risk of post-operative periprosthetic femur fracture was 3.5% at 20 years. TAKE HOME MESSAGE: Intra-operative fractures occur 14 times more often with uncemented stems, particularly with female patients over 65 years of age, while post-operative fracture risk is independent of age or gender, but still increased with uncemented stems.

The management of bone loss in revision total knee arthroplasty: rebuild, reinforce, and augment.

The treatment of bone loss in revision total knee arthroplasty has evolved over the past decade. While the management of small to moderate sized defects has demonstrated good results with a variety of traditional techniques (cement and screws, small metal augments, impaction bone grafting or modular stems), the treatment of severe defects continues to be problematic. The use of a structural allograft has declined in recent years due to an increased failure rate with long-term follow-up and with the introduction of highly porous metal augments that emphasise biological metaphyseal fixation. Recently published mid-term results on the use of tantalum cones in patients with severe bone loss has reaffirmed the success of this treatment strategy.

Clinically important body weight gain following total hip arthroplasty: a cohort study with 5-year follow-up.

OBJECTIVE: Literature examining the effects of total hip arthroplasty (THA) on subsequent body weight gain is inconclusive. Determining the extent to which clinically relevant weight gain occurs following THA has important public health implications. DESIGN: We used multi-variable logistic regression to compare data from one of the largest US-based THA registries to a population-based control sample from the same geographic region. We also identified factors that increased risk of clinically important weight gain specifically among persons undergoing THA. The outcome measure of interest was weight gain of ≥5% of body weight up to 5 years following surgery. RESULTS: The multi-variable adjusted [age, sex, body mass index (BMI), education, comorbidity and pre-surgical weight change] odds ratio for important weight gain was 1.7 [95% confidence interval (CI), 1.06, 2.6] for a person with THA as compared to the control sample. Additional arthroplasty procedures during the 5-year follow-up further increased odds for important weight gain (OR = 2.0, 95% CI, 1.4, 2.7) relative to the control sample. A patient with THA had increased risk of important post-surgical weight gain of 12% (OR = 1.12, 95% CI, 1.08, 1.16) for every kilogram of pre-operative weight loss. CONCLUSIONS: While findings should be interpreted with caution because of missing follow-up weight data, patients with THA appear to be at increased risk of clinically important weight gain following surgery as compared to peers. Patients less than 60 years and who have lost a substantial amount of weight prior to surgery appear to be at particularly high risk of important post-surgical weight gain.

Pessimistic explanatory style: a psychological risk factor for poor pain and functional outcomes two years after knee replacement.

Seligman's theory of causal attribution predicts that patients with a pessimistic explanatory style will have less favourable health outcomes. We identified 702 patients who had undergone 894 primary total knee replacements between 1993 and 2005, who responded to follow-up surveys at two (n = 783 knee replacements) and/or five years (n = 443 knee replacements) and had also completed the Minnesota Multiphasic Personality Inventory long before the joint replacement (median = 16.6 and 14.5 years for two- and five-year cohorts, respectively). Scores from the Minnesota Multiphasic Personality Inventory Optimism-Pessimism scale were used to categorise patients as pessimistic (t-score > 60) or non-pessimistic (t-score < or = 60). Multivariate logistic regression models assessing the effect of pessimistic explanatory style on pain or improvement in knee function were adjusted for gender, age, distance from the place of treatment and depression score. Pessimists reported (a) significantly more moderate or severe pain at two years with odds ratio 2.21 (95% confidence interval (CI) 1.12 to 4.35; p = 0.02), but not at five years when the odds ratio was 1.21 (95% CI 0.51 to 2.83; p = 0.67); and (b) less improvement in knee function at two years when the odds ratio was 0.53 (95% CI 0.30 to 0.96; p = 0.04), but not at five years when the odds ratio was 1.26 (95% CI 0.57 to 2.77; p = 0.57). No significant associations with moderate or severe limitation of activity were seen at two or five years. We conclude that a pessimistic explanatory style is associated with worse pain and functional outcomes two years after total knee replacement.

The kinematic rotating hinge prosthesis for complex knee arthroplasty.

Fifty-eight patients (69 knees) treated with the Kinematic Rotating Hinged knee prosthesis for complex primary and salvage revision total knee arthroplasty were followed up for an average of 75.2 months (range, 24-199 months). The indications for use of the Kinematic Rotating Hinged knee prosthesis included severe bone loss combined with ligamentous instability (30 knees), nonunion of a periprosthetic fracture (10 knees), an acute periprosthetic fracture (nine knees), severe collateral ligamentous instability (five knees), reimplantation for infection (six knees), nonunion of a supracondylar femoral fracture (four knees), congenital dislocation of the knee (three knees), and treatment of a severely comminuted distal femur (two knees). At the time of surgery, the average patient age was 72 years (range, 46-92 years). Preoperatively, knee extension averaged 4.94 degrees (range, 0 degrees-40 degrees) and flexion averaged 81 degrees (range, 15 degrees-125 degrees). At final followup, knee extension averaged 1.25 degrees (range, -5 degrees-25 degrees) and flexion averaged 94.2 degrees (range, 5 degrees-125 degrees). The preoperative Knee Society Knee score averaged 40.3 points (range, 2-93 points) and improved to 77 points (range, 33-99 points) at final followup. Complications were numerous: 23 (32%) patients experienced at least one complication and 12 (17%) patients had two or more complications. Deep periprosthetic infection was the most common complication (14.5%), followed by patellar complications (13%), and prosthetic component breakage (10%). During the period of this study, there were 15,798 primary and 2673 revision total knee arthroplasties done at the authors' institution. The patients receiving a Kinematic Rotating Hinged knee prosthesis represent a highly complex and small subset (0.37%) of the overall population having knee arthroplasty. Although the use of the Kinematic Rotating Hinged knee prosthesis for these limited indications has been useful for the authors, the incidence of complications and the poor outcome of these complications is disconcerting. Hinged total knee arthroplasty should be reserved for the final salvage option of the treatment options available when doing complex primary and salvage revision knee arthroplasties.

Thirty-day mortality after elective total hip arthroplasty.

BACKGROUND: Previous reports on perioperative mortality associated with hip arthroplasty have not documented, to our knowledge, patient characteristics and surgical factors that increase the likelihood of death. The purpose of this study was to determine the prevalence of and associated risk factors for perioperative death after elective hip arthroplasty. METHODS: The records of 30,714 consecutive patients who had undergone elective hip arthroplasty at our institution from 1969 to 1997 were retrospectively reviewed to identify patients who had died within thirty days after the procedure. Mortality rates were determined according to age, gender, diagnosis, implant type, and fixation mode. RESULTS: Ninety deaths occurred within thirty days after elective total hip arthroplasty, for an overall mortality rate of 0.29% (ninety of 30,714). The thirty-day mortality rate was significantly higher for patients with preexisting cardiovascular disease (p < 0.0001), male patients (p < 0.0001), and patients who were seventy years of age or older (p < 0.0002). The mortality rate was slightly, but not significantly, higher for patients with an underlying diagnosis of rheumatoid arthritis (p < 0.36) and those receiving cemented implants (p < 0.57). There was no difference in the thirty-day mortality rate for revision as compared with primary hip arthroplasty (p < 0.92). CONCLUSIONS: Factors that are associated with an increased risk of mortality within thirty days after elective hip arthroplasty include an older age, male gender, and a history of cardiorespiratory disease. There has been a significant decline in the thirty-day mortality rate after elective hip arthroplasty in the last decade (p < 0.0002); during the 1990s, the overall rate at our institution was 0.15% (twenty-three of 14,989).

Vertebral osteomyelitis and prosthetic joint infection due to Staphylococcus simulans.

Staphylococcus simulans, a coagulase-negative staphylococcus, is a common animal pathogen that is rarely encountered in human infections. We describe a 70-year-old man who developed multifocal vertebral osteomyelitis and late prosthetic joint infection caused by this pathogen. The patient was a farmer who had daily contact with cows and drank unpasteurized milk, although the portal of the pathogen's entry remains speculative. Culture of the vertebral disk biopsy specimen and cultures during resection arthroplasty yielded S. simulans. A review of the literature suggests that S. simulans may be more virulent than other species of coagulase-negative staphylococci. Accurate identification of S. simulans isolates would facilitate studies to further define its pathogenic role in human infections.

Thirty-day mortality after total knee arthroplasty.

BACKGROUND: There have been sporadic reports on perioperative mortality associated with total knee arthroplasty. The purpose of this study was to determine risk factors for such mortality. METHODS: A computer-assisted review of the records of 22,540 consecutive patients who had undergone total knee arthroplasty between 1969 and 1997 was performed to identify all patients who had died within thirty days after the procedure. A detailed analysis of the medical, surgical, anesthetic, and pathological records of the patients was performed, and the mortality was determined according to age, gender, diagnosis, and fixation method. RESULTS: The rate of mortality within thirty days after the operation was 0.21% (forty-seven of 22,540). All deaths occurred in the group of 18,810 patients who had received a cemented implant, and no deaths occurred among the 3730 patients who had received an uncemented implant (p < 0.0001). The mortality rate was 0.24% (forty-three of 18,165) after primary arthroplasty and 0.09% (four of 4375) after revision arthroplasty (p < 0.0003). Three patients (0.01%) died during the operation. Forty-three of the forty-seven patients who died had a history of preexisting cardiovascular and/or pulmonary disease. Simultaneous bilateral total knee arthroplasty was associated with a significantly higher rate of perioperative mortality (p < 0.002). CONCLUSIONS: Factors that were associated with a significantly increased mortality after total knee arthroplasty included an age of more than seventy years, primary (as compared with revision) knee surgery, use of a cemented prosthesis, preexisting cardiopulmonary disease, and simultaneous bilateral arthroplasty.

The Frank Stinchfield Award. Sudden death during primary hip arthroplasty.

The records of 23 patients who died intraoperatively during hip arthroplasty at the authors' institution were reviewed. Of the 38,488 hip arthroplasties in 29,431 patients performed between 1969 and 1997, there were 23 deaths during surgery. There were 15 women and eight men with a mean age of 80.9 years. Preoperative diagnoses were acute hip fracture (13 patients), pathologic fracture (four patients), femoral neck nonunion (one patient), osteoarthritis (four patients), and rheumatoid arthritis (one patient). Eleven patients undergoing cemented total hip arthroplasty died and 12 patients undergoing cemented hemiarthroplasty died. All deaths occurred because of irreversible cardiorespiratory disturbances that were initiated during cementing. There were no deaths among 12,551 patients receiving 15,411 uncemented hip arthroplasties during the 28-year period under review. Autopsy was performed in 13 patients. Bone marrow microemboli were seen in the lungs of 11 of 13 patients in whom an autopsy was performed and methylmethacrylate particles were seen in the lungs of three of 13 patients. These data suggest that elderly patients with preexisting cardiovascular conditions undergoing cemented arthroplasty, especially for fracture diagnosis, are at increased risk for intraoperative death compared with patients undergoing elective hip arthroplasty. In the latter years of the current study, modifications of the operative techniques designed to minimize intramedullary hypertension were associated with a reduction greater than three-fold in overall intraoperative mortality rate. These changes in surgical technique should be considered when cement fixation is used in patients thought to be at risk for having cardiopulmonary disturbances develop from venous embolization of marrow contents.

Hip arthroplasty in patients with Paget's disease.

In individuals with Paget's disease, the pelvis and upper femur are the areas of the skeleton most frequently involved. Associated deformities and alterations in bone quality can complicate total hip arthroplasty when required for degenerative joint changes, and can compromise outcome. A review of reported series shows that patients with Paget's disease may present unique problems during the preoperative assessment, intraoperative treatment, and postoperative followup. Preoperative determination of disease activity and assessment of the cause of hip symptoms is important. Intraoperatively, deformity such as coxa vara, femoral bowing, acetabular protrusio, and bony enlargement may cause alterations in implant choice or fixation method used and the patient may even require corrective osteotomy. Excessive bleeding and bone quality changes may complicate these efforts additionally. Postoperative problems include heterotopic bone formation, and in those patients in whom the underlying disease is highly active or poorly controlled, rapid postoperative bone resorption is possible. Results of cemented arthroplasty in patients with Paget's disease have been reported as comparable with but slightly worse than the results reported for unselected patients who underwent hip arthroplasty. The long-term results of uncemented implants in patients with Paget's disease remains to be established.

Pelvic discontinuity in revision total hip arthroplasty.

BACKGROUND: Pelvic discontinuity is a distinct form of bone loss, occurring in association with total hip arthroplasty, in which the superior aspect of the pelvis is separated from the inferior aspect because of bone loss or a fracture through the acetabulum. The purpose of this study was to describe the population of patients who are at risk for this condition, to identify the characteristic radiographic features associated with it, and to report the results of revision total hip arthroplasty for the treatment of pelvic discontinuity. METHODS: The cases of all twenty-seven patients (thirty-one hips) who were identified as having a pelvic discontinuity at the time of a reoperation for a failed hip arthroplasty at one institution were reviewed retrospectively, and demographic information was collected. The preoperative radiographs and the operative notes were reviewed, and the postoperative results and complications were recorded. RESULTS: Pelvic discontinuity was identified in association with thirty-one (0.9 percent) of 3505 acetabular revisions. The mean age of the patients was sixty-one years (range, thirty-eight to eighty years). Twenty-eight hips were in women, and three were in men. Women (p < 0.001) and patients who had rheumatoid arthritis (p = 0.003) had a significantly increased risk of pelvic discontinuity. The radiographic findings included a visible fracture line through the anterior and posterior columns, medial translation of the inferior aspect of the hemipelvis relative to the superior aspect (seen as a break in Kohler's line), and rotation of the inferior aspect of the hemipelvis relative to the superior aspect (seen as asymmetry of the obturator rings) on a true anteroposterior radiograph. Two patients died within two years after the revision, and two had a resection arthroplasty for the treatment of the pelvic discontinuity; thus, twenty-seven hips were reconstructed and were eligible for follow-up at least two years after the operation. A number of different methods were used for reconstruction, but the results were best in patients who did not have severe segmental acetabular bone loss (type IVa [a satisfactory result in three of three hips]) and poorer in those who had severe segmental or combined segmental and cavitary bone loss (type IVb [a satisfactory result in ten of nineteen hips]) and in those who previously had been treated with irradiation to the pelvis (type IVc [a satisfactory result in three of five hips]). Nine of the twenty-seven hips needed another operation: four, because of aseptic loosening of the acetabular component; four, because of recurrent dislocation; and one, because of deep infection. Excluding three hips that were revised early because of infection or dislocation, a mechanically stable construct (that is, a stable socket and a possibly or definitely healed discontinuity) was obtained in seventeen of twenty-four hips. CONCLUSIONS: Pelvic discontinuity is uncommon, and treatment is associated with a high rate of complications. For hips with type-IVa bone loss and selected hips with type-IVb defects, in which a socket inserted without cement can be satisfactorily supported by native bone, we prefer to use a posterior column plate to stabilize the pelvis and a porous-coated socket inserted without cement. For most hips with type-IVb and type-IVc bone loss, we prefer to use particulate bone graft or a single structural bone graft protected with an antiprotrusion cage.

Nonunion after periprosthetic femoral fracture associated with total hip arthroplasty.

BACKGROUND: Nonunion after a periprosthetic femoral fracture associated with total hip arthroplasty occurs rarely. There is little information, to our knowledge, regarding the prevalence of this complication, its treatment, and the functional outcomes of treatment. The purpose of this study was to identify the patterns and frequency of nonunions of femoral fractures around total hip prostheses and to evaluate the results and problems associated with treatment of this complication in a consecutive series of patients. METHODS: The study included twenty-three nonunions of periprosthetic femoral fractures in twenty-three patients with an average age of fifty-five years (range, twenty-two to eighty-five years) at the time of the initiation of treatment of the nonunion. Thirteen of the fractures occurred during or after a primary total hip arthroplasty, and ten occurred during or after a revision total hip arthroplasty. According to the classification system of Duncan and Masri, there were six B1 fractures (associated with a well fixed prosthesis), seven B2 fractures (associated with a loose stem), and ten B3 fractures (associated with very poor proximal bone). Ten patients were managed with revision to a long-stem prosthesis. Six patients had revision to a proximal femoral replacement prosthesis. A two-stage technique consisting of removal of the prosthesis and open reduction and internal fixation of the nonunion followed by reimplantation of the prosthesis was used in two patients. Two patients were managed initially with bone-grafting alone, and two patients were managed nonoperatively. One patient who had an infection at the site of the nonunion was managed definitively with resection arthroplasty. RESULTS: The duration of clinical follow-up averaged 8.3 years (range, three months to twenty-three years), and that of radiographic surveillance averaged 7.0 years (range, eight months to seventeen years). Of the thirteen patients in whom an attempt to achieve union was made and for whom radiographs were available, nine eventually had bone-healing. Five of the twenty-three femora became infected and were treated with resection arthroplasty. Of the seventeen patients who had not had a resection arthroplasty for infection and for whom radiographs were available at the time of the most recent follow-up, eleven had a stable and well fixed implant and six had a loose implant as seen radiographically or had had a revision because of aseptic loosening. Seventeen patients had no or mild pain at the time of the most recent follow-up, but ten required two-handed support to walk. The overall complication rate was 52 percent (twelve of twenty-three patients). CONCLUSIONS: Nonunion of a femoral fracture associated with a total hip prosthesis is an infrequent problem. Treatment is difficult, with a high rate of complications and relatively poor functional outcomes. The data from this series must be interpreted with caution, as patients were managed over a period of three decades and many did not have the advantage of modern techniques of revision hip arthroplasty. Prevention of nonunion by optimum treatment of the initial fracture is most important. Treatment of a femoral nonunion about a total hip implant should be implemented on the basis of the status of the fixation of the prosthesis and the quality of the surrounding bone.

Low-intensity ultrasound stimulates proteoglycan synthesis in rat chondrocytes by increasing aggrecan gene expression.

We evaluated the effect of low intensity-pulsed ultrasound stimulation on rat chondrocytes in vitro using two different 1.0-MHz ultrasound signals with spatial and temporal average intensities of 50 or 120 mW/cm2. The pulses had a duration of 200 microseconds and were repeated every millisecond, with corresponding average peak-pressure amplitudes of 230 or 360 kPa, respectively. Cells were stimulated one, three, or five times for 10 minutes each day starting the third day after plating. One group of cells was exposed to sham ultrasound as a control. The cultures were evaluated for cell proliferation (by [3H]thymidine incorporation and DNA measurement), steady-state mRNA levels of alpha1(I) and alpha1(II) procollagens and aggrecan (by Northern blotting), and proteoglycan synthesis (by [35S]sulfate incorporation). The results revealed that ultrasound causes increases in the level of aggrecan mRNA (p < 0.05) and in proteoglycan synthesis (p < 0.03) after three and five treatments. Expression of mRNA for alpha1(II) procollagen increased over time, but ultrasound had no stimulatory effect. Expression of mRNA for alpha1(I) procollagen was initially low and remained unchanged with time. Although cell proliferation increased with time in both groups, there was no statistically significant difference between the cultures treated with ultrasound and the controls (p = 0.1). The in vitro results support our previous in vivo findings that low-intensity ultrasound stimulates aggrecan mRNA expression and proteoglycan synthesis by chondrocytes, which may explain the role of ultrasound in advancing endochondral ossification, increasing the mechanical strength of fractures, and facilitating fracture repair.