The "true" 1-year incidence of dislocation after primary total hip arthroplasty: validation of an algorithm identifying dislocations in the Danish National Patient Register based on 5,415 patients from the Danish Hip Arthroplasty Register.

BACKGROUND AND PURPOSE: Dislocations continue to be a serious complication after primary total hip arthroplasty (THA). Our primary aim was to report the "true" incidence of dislocations in Denmark and secondarily to validate a previously developed algorithm designed to identify THA dislocations in the updated version of the Danish National Patient Register (DNPR), based on data from the Danish Hip Arthroplasty Register (DHR). METHODS: We included 5,415 primary THAs from the DHR performed from July 1 to December 31, 2019. Version 3 of the DNPR was launched in February 2019, and a combination of data from the DNPR and a comprehensive national review of 1,762 hospital contacts enabled us to identify every dislocation occurring during the 1st year after THA to determine the "true" 1-year incidence of dislocation. The results were presented as proportions with 95% confidence intervals (CI), and validation was performed by calculating sensitivity and predictive values. RESULTS: The "true" 1-year incidence of dislocation was 2.8% (CI 2.4-3.3). Of these, 37% suffered recurrent dislocations during the follow-up period. Between-hospital variation ranged from 0.0% to 9.6%. The algorithm demonstrated a sensitivity close to 95%, while maintaining a positive predictive value of above 94%. CONCLUSION:  The "true" 1-year incidence of dislocation of 2.8% is comparable to earlier findings, and large variation among hospitals continues to be evident. We have proven the algorithm to be valid in the latest DNPR (version 3), enabling it to be employed as a new quality indicator in future annual DHR reports.

Large hospital variation in the risk of dislocation after primary total hip arthroplasty for primary osteoarthritis: 31,105 patients in 59 hospitals from the Danish Hip Arthroplasty Register.

BACKGROUND AND PURPOSE: The risk of dislocation after primary total hip arthroplasty (THA) is affected by several factors, which increases the possibility of substantial differences among hospitals. We compared cumulative incidences of dislocation between regions and hospitals after primary THA surgery in osteoarthritis (OA) patients. PATIENTS AND METHODS: From the Danish Hip Arthroplasty Register, we included 31,105 THAs performed from 2010 to 2014 with 2 years' follow-up. Dislocations treated by closed reduction were identified in the Danish National Patient Register combined with patient file review. The results are presented as 2-year cumulative incidence on national, regional, and hospital level as proportions with 95% confidence intervals (CI) and as adjusted odds ratios (OR) analyzed by multiple logistic regression. RESULTS: 1,861 dislocations in 1,079 THAs were identified from 59 orthopedic departments. The 2-year cumulative incidence ranged from 2.2% to 4.3% between the 5 regions in Denmark. Hospital variation was 0-12%. For hospitals with a 5-year volume of more than 100 procedures, the incidence was 0.9-7.4%. Using the highest volume hospital as the reference, ORs for dislocation for the remaining hospitals were between 0.3 (CI 0.1-0.6) and 2.7 (1.9-4.0) after adjusting for age, sex, head size, and fixation method. Low-volume hospitals showed a higher dislocation risk than high-volume units with an adjusted OR of 1.2 (1.1-1.4). INTERPRETATION: We found substantial variation in the incidence of dislocation between hospitals within Denmark, which can be explained by a combination of patient-, component-, and surgery-related factors. There is a need for continuous monitoring of THA dislocation on regional and hospital levels to reduce overall and local dislocation risk for future patients.

Patient-reported outcome after dislocation of primary total hip arthroplasties: a cross-sectional study derived from the Danish Hip Arthroplasty Register.

Background and purpose - Knowledge regarding patient-reported outcomes (PROs) after dislocation and closed reduction is lacking. We report health- and hip-related quality of life (QoL) after dislocation, following primary total hip arthroplasty (THA). Patients and methods - We conducted a crosssectional study with patients registered in the Danish Hip Arthroplasty Register from 2010 to 2014. Dislocations were captured based on diagnosis/procedure codes and patient file reviews. Patients with dislocation were matched 1:2, according to age, sex, date, and hospital of primary surgery, to patients without dislocation. 2 PRO questionnaires were applied (EQ-5D, HOOS). Results - We identified 1,010 living patients with dislocation. Mean follow-up was 7.2 years from index surgery and 4.9 years (range 0.6-9.7) from the latest dislocation. Patients without dislocation reported a higher EQ VAS score of 76 (95% CI 75-77) compared with 68 (CI 66-70) for the dislocation group. The EQ-5D-5L mean index score was 0.89 (CI 0.88-0.90) for the control group, compared with 0.78 (CI 0.76-0.80) for the cases with dislocation without revision. Patients with dislocation reported a lower HOOSQoL domain score of 63 (CI 60-65), compared with 83 (CI 82-84) for the control group. Even 5 years after the latest dislocation, the HOOS-QoL score remained low, at 66 (CI 62-69). The other HOOS domains were consistently 8-10 points worse after dislocation. Interpretation - Both health- and hip-related QoL were markedly and persistently reduced among dislocation patients compared with those in controls, for several years. Therefore, the avoidance of the initial dislocation episode is important because the THA does not appear to achieve the full relieving potential.

Development of a diagnostic algorithm identifying cases of dislocation after primary total hip arthroplasty-based on 31,762 patients from the Danish Hip Arthroplasty Register.

Background and purpose - Dislocation of total hip arthroplasties (THA) is often treated with closed reduction and traditionally not registered in orthopedic registers. This study aimed to create an algorithm designed to identify cases of dislocations of THAs with high sensitivity, specificity, and positive predictive value (PPV) based on codes from the Danish National Patient Register (DNPR).Patients and methods - All patients (n = 31,762) with primary osteoarthritis undergoing THA from January 1, 2010 to December 31, 2014 were included from the Danish Hip Arthroplasty Register (DHR). We extracted available data for every hospital contact in the DNPR during a 2-year follow-up period, then conducted a comprehensive nationwide review of 5,096 patient files to register all dislocations and applied codes.Results - We identified 1,890 hip dislocations among 1,094 of the included 31,762 THAs. More than 70 different diagnoses and 55 procedural codes were coupled to the hospital contacts with dislocation. A combination of the correct codes produced a sensitivity of 63% and a PPV of 98%. Adding alternative and often applied codes increased the sensitivity to 91%, while the PPV was maintained at 93%. Additional steps increased sensitivity to 95% but at the expense of an unacceptable decrease in the PPV to 82%. Specificity was, in all steps, greater than 99%.Interpretation - The developed algorithm achieved high and acceptable values for sensitivity, specificity, and predictive values. We found that surgeons in most cases coded correctly. However, the codes were not always transferred to the discharge summary. In perspective, this kind of algorithm may be used in Danish quality registers.

Risk Factors for Dislocation and Re-revision After First-Time Revision Total Hip Arthroplasty due to Recurrent Dislocation - A Study From the Danish Hip Arthroplasty Register.

BACKGROUND: Persistent instability after hip revision is a serious problem. Our aim was to analyze surgical and patient-related risk factors for both a new dislocation and re-revision after first-time hip revision due to dislocation. METHODS: We included patients with a primary THA due to osteoarthritis and a first-time revision due to dislocation registered in the Danish Hip Arthroplasty Register (DHR) from 1996 to 2016. We identified dislocations in the Danish National Patient Register and re-revisions in the DHR. Risk factors were analyzed by a multivariable regression analysis adjusting for the competing risk of death. Results are presented as subdistribution hazard ratios (sHR). RESULTS: We identified 1678 first-time revisions due to dislocation. Of these, 22.4% had a new dislocation. 19.8% were re-revised for any reason. With new dislocations treated by closed reduction as the endpoint, the sHR was 0.36 (95% CI, 0.27-0.48) for those who had a constrained liner (CL) during revision and 0.21 (0.08-0.58) for dual mobility cups (DMC), thereby lowering the risk of dislocation compared to regular liners. Changing only the head/liner increased the risk of dislocation (sHR = 2.65; 2.05-3.42) compared to full cup revisions. The protective effect of CLs and DMCs on dislocations vanished when re-revisions became the endpoint. The head/liner exchange was still found inferior compared to cup revision (sHR = 1.73; 1.34-2.23). CONCLUSION: Patients revised with DMCs and CLs were associated with a lower risk of dislocation after a first-time revision but not re-revision, whereas only changing the head/liner was associated with a higher risk of dislocation and re-revision of any cause compared to cup revision.

"True" Cumulative Incidence of and Risk Factors for Hip Dislocation within 2 Years After Primary Total Hip Arthroplasty Due to Osteoarthritis: A Nationwide Population-Based Study from the Danish Hip Arthroplasty Register.

BACKGROUND: Hip dislocation is one of the leading indications for revision of total hip arthroplasty (THA) implants, and the extent of this complication is often measured by the number of revisions. The exact incidence of dislocation can be difficult to establish as closed reductions may not be captured in available registers. The purpose of this study was to identify the "true" cumulative incidence of hip dislocation (revisions and closed reductions) after primary THA, and the secondary aim was to identify risk factors for dislocation. METHODS: From the Danish Hip Arthroplasty Register, we identified 31,105 primary THAs indicated by primary osteoarthritis that had been performed from 2010 to 2014 and had 2 years of follow-up. Dislocations were identified through extraction from the Danish National Patient Register. Matching diagnosis and procedure codes were deemed correct while non-matching codes were reviewed through a comprehensive, nationwide review of patient files. Risk factors were analyzed with multiple logistic regression analysis and presented as odds ratios (ORs) with 95% confidence intervals (CIs). RESULTS: Our review of patient files identified 1,861 dislocations in 1,079 THAs, which corresponds to a 2-year cumulative incidence of 3.5% (CI = 3.3% to 3.7%). This was a 50% increase compared with the correctly coded dislocations captured by administrative register data only. Patients who were <65 years of age had a lower dislocation risk (OR = 0.70; CI = 0.59 to 0.83) and those who were >75 years of age had a higher risk (OR = 1.32; CI = 1.14 to 1.52) compared with those who were 65 to 75. Male sex (OR = 0.86; CI = 0.75 to 0.98), cemented fixation (OR = 0.71; CI = 0.58 to 0.87), and lateral approach (OR = 0.28; CI = 0.16 to 0.49) were all associated with a lower risk. A head size of 32 mm was associated with a higher risk of dislocation (OR = 1.27; CI = 1.10 to 1.46) than 36-mm heads, whereas dual-mobility cups had a reduced risk (OR = 0.13; CI = 0.05 to 0.36). CONCLUSIONS: We found the "true" cumulative incidence of dislocations within 2 years after primary THAs performed between 2010 and 2014 in Denmark to be 3.5%. Age, sex, American Society of Anesthesiologists (ASA) score, head size and type, fixation method, and surgical approach were independent significant factors for dislocation. Comprehensive search algorithms are needed in order to identify all dislocations so that this complication can be accurately reported in national registers.

Bifocal osseous avulsion of the patellar tendon from the distal patella and tibial tuberosity in a child.

This case report describes a 12-year-old boy, who suffered an injury to the right knee in a skateboard accident. Radiographs and surgery confirmed the extremely rare bifocal avulsion fracture including the distal patellar pole and tibial tuberosity. Open reduction and internal fixation was accomplished, and 4-month follow-up demonstrated a good outcome.

Incorporation of raloxifene-impregnated allograft around orthopedic titanium implants impairs early fixation but improves new bone formation.

BACKGROUND: The anti-osteoporotic drug raloxifene reduces the risk of vertebral fractures by increasing bone mass density. We investigated whether raloxifene offers any benefits in augmenting early fixation of orthopedic implants in the setting of impaction bone grafting. METHODS: 24 non-weight-bearing grafted gap implants were inserted bilaterally into the tibia of 12 dogs. The 2.5-mm peri-implant gap was filled with either raloxifene-impregnated or untreated bone allograft. Implants were harvested after 28 days. Implant fixation was assessed by mechanical testing and histomorphometric evaluation. RESULTS: Raloxifene-treated allograft reduced early implant fixation compared to untreated allograft, as measured by inferior maximum shear strength (p < 0.001) and apparent shear stiffness (p = 0.001). We found that the raloxifene group had more newly formed bone in the gap around the implant (p = 0.02), but also less allograft (p = 0.03). INTERPRETATION: The accelerated allograft resorption in the raloxifene group explained the impaired early fixation, despite its stimulation of new bone formation. Our results with local and possible high-dose treatment are not consistent with current theory regarding the mechanism of how systemic raloxifene administration counteracts the decrease in BMD in postmenopausal women. Instead of being solely anti-resorptive as generally held, our results indicate a possible anabolic side of raloxifene.