Profit-Influencing Factors in Orthopedic Surgery: An Analysis of Costs and Reimbursements.

The aging population and the associated demand for orthopedic surgeries are increasing health costs. Although the Diagnostic Related Groups (DRG) system was introduced to offer incentives for hospitals, concerns remain that reimbursements for older and frail patients do not cover all hospital expenses. We investigated further: (1) Does age influence net financial results in orthopedic surgery? (2) Are there patient or surgical factors that influence results? This retrospective, monocentric study compares costs and reimbursements for orthopedic patients in a tertiary care hospital in Switzerland between 2015 and 2017. The data of 1230 patients were analyzed. Overall, the net results for the hospital were positive, despite 19.5% of patients being treated at a loss. We did not find any correlation between age and profitability (p = 0.61). Patient-related factors associated with financial losses were female sex (p < 0.001) and diabetes (p = 0.013). Patients free of serious comorbidities (p = 0.012) or with a higher cost weight (p < 0.001) were more often profitable. A longer length of stay was associated with higher losses (p < 0.001). This is the first study to address the Swiss DRG reimbursement system in a broad orthopedic population, while also analyzing specific patient and surgical factors. Overall, the reimbursement system is fair, but could better account for certain interventions.

Short proximal components in modular revision stems carry a higher risk for stem fractures.

INTRODUCTION: Fractures of modular hip revision stems are not uncommon. The current study examined implant-related factors on stem fracture. We hypothesised that in a modular stem the fracture risk is increased with the use of a short proximal implant component. MATERIALS AND METHODS: Anonymised data of all 32 patients in Switzerland with a Revitan modular hip system who had a stem fracture were obtained from the manufacturer. Implant and patient data were compared with all components implanted in Switzerland during the same time interval. RESULTS: Between 2002 and 2017, 4834 Revitan stems were implanted, of which 32 fractured. A smaller size of the proximal stem component was significantly associated with a higher fracture risk (p < 0.001). Compared with the control group, the proportion of male patients was higher among the fracture cases, patients were younger, and they had a higher body weight (p < 0.001, respectively). CONCLUSIONS: The present study suggests that small proximal stem components increase the load at the modular junction due to size and lack of bony support. Surgeons should therefore avoid short proximal components so that the mid-stem junction lies as distally as possible and the risk of fracture is minimised.

A Treatment Pathway Variation for Chronic Prosthesis-Associated Infections.

Periprosthetic joint infections (PJIs) are relatively rare but are on the rise because of the increasing total number of implantations performed. Treatment of PJI remains individualized and involves both surgical and medical treatment, with variations depending on the time of implantation, the duration and severity of the infection, tissue damage, and the underlying microorganism. In this case series study, we investigated clinical and functional outcomes of a variation of the Liestal algorithm in patients with PJI following total hip arthroplasty. METHODS: This study included 32 patients (33 cases) who were treated for chronic PJI with 2-stage exchange using a cement spacer during the period of 2003 to 2014. In contrast to other treatment pathways, antibiotic therapy was targeted to the causative microorganism as early as possible despite the presence of a cement spacer. Second-look surgery was performed 4 days after removal of the primary implant and a 4-week antibiotic-free window was interposed before definitive reimplantation. Thereafter, antibiotic treatment continued for approximately 6 weeks. All patients were followed for a minimum of 2 years. Parameters investigated were the duration of infection-free survival, functional outcome, and epidemiological data. RESULTS: At 2 years of follow-up and at the most recent follow-up (on average, 7 years after reimplantation), 100% of the patients were free of signs of infection, and the mean Harris hip score (HHS) was 89 at the latest follow-up. CONCLUSIONS: A meticulously performed 2-stage exchange for PJI with early targeted antibiotic treatment, second-look surgery, an antibiotic-free window before reimplantation, and antibiotic treatment post-reimplantation of medium duration is associated with excellent infection-related and good functional outcome after ≥2 years of follow-up even in cases of chronic PJI. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Does Preoperative Decolonization Reduce Surgical Site Infections in Elective Orthopaedic Surgery? A Prospective Randomized Controlled Trial.

BACKGROUND: Surgical site infections (SSIs) after elective orthopaedic surgery are very stressful for patients due to frequent rehospitalizations with reoperations and poorer functional outcomes. Prevention of such events is therefore crucial. Although an evidence-based consensus is still lacking, preoperative decolonization could decrease SSI. Specifically, more information is needed about the effect of a preoperative decolonization procedure on SSI proportions in both Staphylococcus aureus carriers and non-S. aureus carriers after general orthopaedic surgery. QUESTIONS/PURPOSES: Our study addressed the following questions: (1) Does preoperative decolonization reduce the risk of SSI after general elective orthopaedic surgery in patients colonized with S. aureus? (2) Does preoperative decolonization reduce the risk of SSI among patients who are not colonized with S. aureus? METHODS: In this prospective, randomized, single-blinded trial, we recruited patients undergoing general elective orthopaedic surgery in one tertiary care center in Switzerland. Between November 2014 and September 2017, 1318 of 1897 screened patients were enrolled. Patients were allocated into either the S. aureus carrier group (35%, 465 of 1318 patients) or the noncarrier group (65%, 853 of 1318 patients) according to screening culture results. In the S. aureus group, 232 patients were allocated to the intervention arm and 233 were allocated to the control arm. Intervention was 5 days of daily chlorhexidine showers and mupirocin nasal ointment twice a day. Of the 853 noncarriers, 426 were allocated to the intervention arm and 427 were allocated to the control arm. All patients in both groups were analyzed in an intention-to-treat manner. The primary endpoint was SSI occurrence at 90 days postoperative and the secondary endpoint was SSI occurrence at 30 days postoperative.The initial sample size calculation was made for the S. aureus carrier group. Based on the literature review, a 4% proportion of SSI was expected in the control group. Thus, 726 carriers would have been needed to detect a relative risk reduction of 80% with a power of 80% at a two-sided α-error of 0.048 (adjusted for interim analysis). Assuming carrier prevalence of 27%, 2690 patients would have been needed in total. An interim analysis was performed after including half of the targeted S. aureus carriers (363 of 726). Based on the low infection rate in the control group (one of 179), a new sample size of 15,000 patients would have been needed. This was deemed not feasible and the trial was stopped prematurely. RESULTS: Among carriers, there was no difference in the risk of SSI between the intervention and control arms (decolonized SSI risk: 0.4% [one of 232], control SSI risk: 0.4% [one of 233], risk difference: 0.0% [95% CI -1.2% to 1.2%], stratified for randomization stratification factors; p > 0.999). For noncarriers, there was no difference in risk between the intervention and control arms (decolonized SSI risk: 0.2% [one of 426], control SSI risk: 0.2% [one of 247], stratified risk difference: -0.0% [95% CI -0.7 to 0.6]; p = 0.973). CONCLUSIONS: We found no difference in the risk of SSI between the decolonization and control groups, both in S. aureus carriers and noncarriers. Because of the low event numbers, no definite conclusion about efficacy of routine preoperative decolonization can be drawn. The results, however, may be helpful in future meta-analyses. LEVEL OF EVIDENCE: Level II, therapeutic study.

No regeneration of the human acetabular labrum after excision to bone.

BACKGROUND: Treatment options for a symptomatic, torn, irreparable, or completely ossified acetabular labrum are limited to either excision and/or reconstruction with grafts. In a previous animal model, regeneration of the acetabular labrum after excision to the bony rim has been shown. In humans, less is known about the potential of regeneration of the labrum. Recent studies seem to confirm labral regrowth, but it is still unclear if wide excision might be a surgical option in cases where repair is not possible. QUESTIONS/PURPOSES: The purposes of this study were (1) to determine the extent of acetabular labrum regeneration after excision to the bony rim; and (2) to determine whether this procedure results in higher hip scores. METHODS: We reviewed all patients treated with surgical dislocation for symptomatic femoroacetabular impingement by a single surgeon at one institution between 2003 and 2008, of whom 14 underwent wide labral excision (of at least 60°) down to bone; we used this approach when there was an absence of reparable tissue. Of these 14, nine were available for voluntary reexamination. The mean age at surgery was 38 ± 9 SD years and the mean followup was 4 ± 1 SD years. All patients consented to a physical examination and an MRI arthrogram, which was evaluated for evidence of new tissue formation by four observers. A modified Harris hip score and the UCLA were recorded. RESULTS: Regrowth of a structure equivalent to normal labrum was not observed on the MRI arthrograms. Six of nine hips had segmental defects, bone formation was found in five, and the capsule was confluent with the new tissue in six. The mean Harris hip score at latest followup was 83 ± 14, and the mean UCLA score was 6 ± 2. CONCLUSIONS: Resection of a nonreparable acetabular labrum down to a bleeding bony surface does not stimulate regrowth of tissue that appears to be capable of normal function by MR arthrography, and patients who underwent this procedure had lower hip scores at midterm than previously reported from the same institution for patients undergoing labral repair or sparse débridement. Based on these results, we believe that future studies should evaluate alternatives to reconstructing the labrum, perhaps using ligamentum teres, because resection seems neither to result in regrowth nor the restoration of consistently high hip scores.

Sports and Activity Levels After Open Surgical Treatment of Femoroacetabular Impingement.

BACKGROUND: Several studies indicate that professional athletes can successfully return to competition after surgical treatment of femoroacetabular impingement (FAI). However, little is known about sports and activity levels after FAI surgery in the general patient population. HYPOTHESIS/PURPOSE: The purpose was to determine the sports behavior, satisfaction with sports ability, and activity levels in a consecutive cohort of patients with FAI who were treated by surgical hip dislocation. The hypothesis was that the majority of patients (>75%) would be active in sports at follow-up. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: This retrospective study included 153 patients (mean age, 30.0 years; 40.5% female) with 192 hips treated. Sports behavior and satisfaction were determined at a mean follow-up of 59.4 months with the use of a questionnaire. Activity levels at follow-up were assessed by the Hip Sports Activity Scale (HSAS) and the University of California, Los Angeles (UCLA) activity scale. RESULTS: Of 126 patients who were regularly active in sports before surgery, 107 (85%) were so at follow-up. Nineteen patients (12.4%) stopped participating in regular sports, and 8 (5.2%) commenced with sports after the operation. The most popular activities before surgery were skiing (22%), cycling (22%), jogging (20%), and soccer (13%). At follow-up, most patients were engaged in cycling (23%), fitness/weight training (20%), skiing (18%), and jogging (11%). Of all patients, 75% were satisfied with their sports ability, and 25% were not. Moreover, 60.3% stated that their sports ability had improved after surgery, 20.5% declared no change, and 19.2% were subjectively deteriorated. The mean pain level during sports was rated to be 2.1 according to the visual analog scale. The mean HSAS score was 3.5 (range, 0-8), and the mean UCLA score was 7.7 (range, 3-10); male patients reported significantly higher scores than did female patients on the HSAS (4.1 vs 2.7, respectively) and UCLA scale (8.2 vs 7.0, respectively). CONCLUSION: The vast majority of patients with FAI who are treated by surgical hip dislocation return to sports activities, and most patients are satisfied with their sports ability at midterm follow-up. Activity levels are significantly higher in male patients, but this does not yield higher satisfaction rates.

Extracortical plate fixation with new plate inserts and cerclage wires for the treatment of periprosthetic hip fractures.

PURPOSE: Fixation of periprosthetic hip fractures with intracortical anchorage might not be feasible in cases with bulky implants and/or poor bone stock. METHODS: Rotational stability of new plate inserts with extracortical anchorage for cerclage fixation was measured and compared to the stability found using a standard technique in a biomechanical setup using a torsion testing machine. In a synthetic PUR bone model, transverse fractures were fixed distally using screws and proximally by wire cerclages attached to the plates using "new" (extracortical anchorage) or "standard" (intracortical anchorage) plate inserts. Time to fracture consolidation and complications were assessed in a consecutive series of 18 patients (18 female; mean age 81 years, range 55-92) with periprosthetic hip fractures (ten type B1, eight type C-Vancouver) treated with the new device between July 2003 and July 2010. RESULTS: The "new" device showed a higher rotational stability than the "standard" technique (p < 0.001). Fractures showed radiographic consolidation after 14 ± 5 weeks (mean ± SD) postoperatively in patients. Revision surgery was necessary in four patients, unrelated to the new technique. CONCLUSION: In periprosthetic hip fractures in which fixation with intracortical anchorage using conventional means might be difficult due to bulky revision stems and/or poor bone stock, the new device may be an addition to the range of existing implants.

Five-year results of the uncemented RM pressfit cup clinical evaluation and migration measurements by EBRA.

This was a prospective consecutive, study of 50 patients (mean age 72 years, 56% males) treated unilaterally for primary osteoarthrosis using the uncemented, isoelastic, monoblock RM Pressfit Cup. Migration and wear were assessed using the EBRA (Ein-Bild-Röntgen-Analyse) software (201 radiographs from 36 patients). Mean migration was 0.82 mm after 2 years and 1.25 mm after 5 years. A decreasing migration rate over the period was observed. The mean annual wear rate was 0.09 mm/y. Five years after surgery, 84% of patients reached good or excellent Harris hip score values. No revisions related to the acetabular component were necessary. All cups appeared to have high primary stability.

Midterm results of surgical hip dislocation for the treatment of femoroacetabular impingement.

BACKGROUND: Surgical treatment of femoroacetabular impingement (FAI) includes both open and arthroscopic procedures. Encouraging results have been reported for the majority of patients after surgical hip dislocation; however, most of these reports were short term and included only small cohorts. PURPOSE: To determine the results of surgical hip dislocation in a large cohort of FAI patients at a midterm follow-up. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: A retrospective study including 185 consecutive patients (mean age, 30 years; 40% female) with 233 hips treated was conducted. We determined clinical outcomes in terms of range of motion and analyzed radiographs for several criteria including the alpha angle preoperatively and at 1 year postoperatively. At latest follow-up, on average 61 months postoperatively, patient satisfaction, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Hip Outcome Score, SF-12, and University of California, Los Angeles (UCLA) activity scale scores were determined. All revisions and conversions to total hip arthroplasty (THA) were recorded. RESULTS: Both hip flexion and internal rotation improved from preoperatively to postoperatively. Alpha angles decreased from 65.1° ± 14.2° to 42.4° ± 4.9°. At 5 years, 82% of the patients were satisfied or very satisfied with the results of surgery, and 81% would undergo the same surgery again. There were 83% who rated their overall hip function as normal or nearly normal. Mean scores for the WOMAC pain, stiffness, and function subscales were 10.3 ± 15.8, 15.9 ± 17.4, and 9.6 ± 13.0 points; for Hip Outcome Score activities of daily living and sport subscales were 89.0 ± 13.1 and 75.6 ± 23.0 points; and for the SF-12 Physical Component Scale and Mental Component Scale were 47.4 ± 6.3 and 52.3 ± 7.4 points, respectively. The mean UCLA activity level was 7.7 ± 1.9. Conversion to THA was performed in 7 hips (3%). Seven hips (3%) underwent other major revisions, and 11 (4.7%) underwent minor revisions. Female patients had a significantly increased risk for conversion to THA (odds ratio, 13.3; 95% confidence interval [CI], 1.3-92.6) and major revision (odds ratio, 19.2; 95% CI, 2.4-152.9). The mean body mass index was significantly lower in those patients who underwent conversion to THA. The need for microfracture because of residual full-thickness cartilage defects after rim trimming was a significant (P = .04) predictor of subjective dissatisfaction. CONCLUSION: This study demonstrates that surgical hip dislocation is a successful procedure for the treatment of FAI. A majority of patients were satisfied with the results of surgery at a midterm follow-up. Older and slim female patients were at an increased risk for a less successful outcome in terms of conversion to THA and revision surgery.

Surgical hip dislocation for the treatment of femoroacetabular impingement in high-level athletes.

BACKGROUND: Midterm outcome studies show that symptomatic femoroacetabular impingement (FAI) can be successfully treated by addressing the underlying pathomorphology with open or arthroscopic surgery. Although athletes may be vulnerable to hip injury from impingement, limited information is available regarding the results of open surgery in this group. HYPOTHESIS: High-level athletes with FAI can resume their sports after surgical hip dislocation and continue professional careers for a significant period. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Twenty-two professional male athletes (19.7 ± 2.2 years) were evaluated by postal survey at a mean of 45.1 months (range, 12 to 79) after treatment by surgical hip dislocation (30 hips, cam- or mixed-type FAI; mean α angle, 69.3°; 14 ice hockey players). Evaluation included types and level of sports, subjective ratings, and CLINICAL OUTCOMES: Hip Outcome Score, SF-12, UCLA (University of California, Los Angeles) activity scale, Hip Sports Activity Scale, visual analog scale for pain. The primary outcome variable was return to professional sports; the clinical result was the secondary outcome variable. RESULTS: At follow-up, 21 of 22 patients (96%) were still competing professionally: 19 at their previous level and 2 in minor leagues. Eighteen (82%) were satisfied with their hip surgery and 19 (86%) with their sports ability. Mean activity levels were 9.8 per the UCLA scale and 7.6 per the Hip Sports Activity Scale. Mean scores of the Hip Outcome Score-Activities of Daily Living and Sport subscales were 94.5 and 89.1. Mean scores of the SF-12 physical and mental component summaries were 51.1 and 54.3. Pain levels during sports were 1.8 per the visual analog scale. CONCLUSION: Surgical hip dislocation for the treatment of FAI allows athletes to resume sports and continue professional careers at the same level for several years. Clinical outcomes in terms of subjective ratings and scores were favorable.

Late repair of abductor avulsion after the transgluteal approach for hip arthroplasty.

The abductor release sometimes does not heal after a transgluteal approach for hip arthroplasty. Factors influencing the success of subsequent repair are unclear. We used magnetic resonance imaging (MRI) to compare the condition of the gluteus medius with clinical outcome after late repair of abductor dehiscence in 12 total hip patients. Evaluation included a pain rating, gait evaluation, Trendelenburg test, strength grading, and Harris Hip Score. Most had both prerepair and postrepair MRI studies to assess the repair and to grade abductor muscle fatty degeneration. Two repairs without MRI were explored surgically. Although average pain, limp, and strength scores improved significantly, rerupture occurred in 4 subjects and fatty degeneration in the gluteus medius did not improve, even with intact repair. Nine patients were satisfied; 7 of these had an intact repair. Magnetic resonance imaging and operative observations suggest that chronic degeneration in the abductor mechanism is the major impediment to successful repair.

Stepped osteotomy of the trochanter for stable, anatomic refixation.

Refixation of a trochanteric osteotomy carries a high complication rate. To enhance stability and facilitate anatomic reduction of the trochanteric fragment, we have introduced a stepped osteotomy. Between April 2006 and June 2007, we performed surgical hip dislocations using the modified trochanteric osteotomy combined with a relatively aggressive rehabilitation program. Full weightbearing was allowed at a mean of 42 days (range, 33-54 days). The minimum followup was 8 months (median, 13 months; range, 8-24 months). Postoperative radiographs were assessed prospectively for consolidation or the appearance of malreduction/nonunion/malunion of the osteotomy and heterotopic ossification. In 110 of 113 hips, the trochanteric osteotomy healed in the anatomic position. Two patients had a trochanteric delayed union with loss of anatomic position, and one additional patient underwent revision surgery for a pseudarthrosis and cranial migration of the trochanteric fragment. All three complications related to healing occurred in the first 60 patients when the step height was 3 to 4 mm. After increasing the step heights to 6 mm, we observed no healing complications. Despite more aggressive postoperative mobilization, the incidence of malunion or nonunion related to the new stepped osteotomy is low and approaches zero for steps of 6 mm. It is now our technique of choice.

Femoroacetabular impingement in professional ice hockey players: a case series of 5 athletes after open surgical decompression of the hip.

BACKGROUND: Femoroacetabular impingement of the hip joint has been identified as a major cause for hip pain in athletes. Surgical open decompression of the hip has historically been proposed as the first treatment of choice. Functional outcomes in athletes after this procedure are unknown. PURPOSE: To describe the functional and sport-related outcome 2 years after open surgical hip decompression in a group of young professional ice hockey players suffering from cam femoroacetabular impingement. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Five young professional ice hockey players (mean age, 21.4 y at follow-up) who suffered from cam femoroacetabular impingement were treated with open surgical decompression of the hip. The operation was performed by the same surgeon, and all athletes followed the same rehabilitation guidelines. Mean follow-up time was 2.7 years. Outcome measures were recorded as time to regain symmetrical hip rotation, regain preoperative core/hip muscle strength, return to team practice, and play at competitive level. RESULTS: Hip rotation range of motion was regained by a mean 10.3 weeks. Core and hip strength values reached preoperative levels by a mean 7.8 months. Return to unrestricted team practice with the ice hockey team was achieved by a mean 6.7 months, and athletes were able to play their first competitive game after a mean 9.6 months. Three athletes were able to perform again at the highest level and in international competitions. Two athletes had to return to minor league ice hockey. CONCLUSION: Return to high-level ice hockey after open surgical decompression of the hip was possible in this series of 5 consecutive cases.

Correlation between internal rotation and bony anatomy in the hip.

Femoroacetabular impingement has been implicated as a risk factor for degenerative arthritis in young people with normally concentric hips. On presentation, patients with impingement have groin pain, limited internal rotation in 90 degrees flexion, and focal articular lesions. We hypothesized that the amount of internal rotation is dictated primarily by the underlying bony anatomy and not secondary to contractures. We compared 23 consecutive patients (32 hips) with 40 asymptomatic control subjects using positional magnetic resonance imaging, physical examination, and a questionnaire regarding symptoms and their commencement. There was a strong correlation between internal rotation in 90 degrees flexion and the measurable free space between the relevant bony contours on magnetic resonance imaging (r = 0.97) in the patient group and the control subjects. The range of internal rotation is closely related to skeletal anatomy, and internal rotation can be used as a noninvasive tool to predict the risk of impingement.

Reduction of vertebral blood flow by segmental vessel occlusion: an intraoperative study using laser Doppler flowmetry.

STUDY DESIGN: During anterior spinal surgery, vertebral perfusion was assessed by laser Doppler flowmetry. Blood flow changes were assessed after unilateral ligation and contralateral compression of the segmental vessels. OBJECTIVE: To assess the influence of unilateral and bilateral segmental vessel occlusion on vertebral blood flow. SUMMARY OF BACKGROUND DATA: During anterior spinal surgery, segmental vessels are frequently being ligated. The reduced blood supply to the vertebrae may impair intervertebral fusion, and the decreased spinal cord perfusion may lead to ischemic myelopathy. To our knowledge, this is the first in vivo study to investigate vertebral blood flow. METHODS.: There were 10 patients who underwent anterior release for adult idiopathic scoliosis (n = 6), Scheuermann disease (n = 3), and posttraumatic kyphosis (n = 1). A high-power laser Doppler flowmeter was used to assess vertebral blood flow. Measurements were performed in 19 thoracic and 4 lumbar vertebrae (n = 23) after unilateral segmental vessel ligation and additional temporary digital compression of the contralateral vessels. RESULTS: Initial mean blood flow was 49.1 +/- 27.6 arbitrary units, and all signals were pulsatile. The blood flow decreased by a mean of 8% after unilateral ligation of the segmental vessels. With additional compression of the contralateral vessels, the signal heights decreased significantly by 54% (mean 18.3 +/- 7.8 arbitrary units, P = 0.00003), and a loss of the pulsatile pattern was observed in 75% of the vertebrae. On release of digital compression, the signal height as well as the pulsatility promptly returned. CONCLUSIONS: Unilateral ligation of segmental vessels led only to a slight decrease of the vertebral blood flow. Future studies may show whether sparing the segmental vessels during anterior fusion enhances bone graft incorporation, thus decreasing the rate of pseudarthrosis. According to clinical data, the risk of neurologic injury through unilateral ligation is negligible. Bilateral segmental vessel occlusion markedly reduced vertebral bloodflow. Therefore, when treating patients with a higher neurologic risk or in revision cases, the surgeon should always consider sparing the segmental vessels.

Submillimeter measurement of cup migration in clinical standard radiographs.

Assessing the displacement of bony implants is an important topic in arthroplasty, particularly in total hip replacement (THR). The observation of the migration is supposed to provide an insight into the fixation of the implant. Diagnostic standard radiographs of the pelvis are an advantageous data source for this purpose. The previous methods based on these images, however, lack of a thorough consideration of their projective nature. They do, hence, not reach the desired precision, which should lie in the submillimeter range to allow a detection of migration in the first one or two years after implantation. The aim of the work presented here was, therefore, a method for measuring the distance of the artificial hip socket to the bone with an error of less than 0.5 mm. The approach has been on the one hand to define the bone-cup distance measured in the radiograph so that the variability of the intrinsic and extrinsic parameters at exposure has a minimal impact. On the other, specialized matching techniques are applied in order to optimize the localization of the necessary bony landmarks and the cup in the X-ray image. The coordinates of the bony landmarks are determined by means of a template matching algorithm. The position of the implant is estimated by intensity-based registration using the cup's CAD-model. The method was validated theoretically, experimentally, and clinically. In the clinical radiographs, the standard deviation of the migration measurements resulted to be 0.28 mm when using only natural bony landmarks. The implantation of a bony marker was found to increase the precision to a standard deviation of 0.20 mm. The interobserver variability in the two cases was estimated to be 0.11 mm and 0.04 mm.

Abductor tendons and muscles assessed at MR imaging after total hip arthroplasty in asymptomatic and symptomatic patients.

PURPOSE: To prospectively evaluate magnetic resonance (MR) imaging findings of abductor tendons and muscles in asymptomatic and symptomatic patients after lateral transgluteal total hip arthroplasty (THA). MATERIALS AND METHODS: The institutional review board approved the study, and all patients provided informed consent. Two musculoskeletal radiologists blinded to clinical information analyzed triplanar MR images of the greater trochanter obtained in 25 patients without and 39 patients with trochanteric pain and abductor weakness after THA. Tendon defects, diameter, signal intensity, and ossification; fatty atrophy; and bursal fluid collections were assessed. In 14 symptomatic patients, MR imaging and surgical findings were correlated. Differences in the frequencies of findings between the two groups were tested for significance by using chi2 analysis. RESULTS: Tendon defects were uncommon in asymptomatic patients and significantly more frequent in symptomatic patients: Two asymptomatic versus 22 symptomatic patients had gluteus minimus defects (P < .001); four asymptomatic versus 24 symptomatic patients, lateral gluteus medius defects (P < .001); and no asymptomatic versus seven symptomatic patients, posterior gluteus medius defects (P = .025). In both patient groups, tendon signal intensity changes were frequent, with the exception of those in the posterior gluteus medius tendon, which demonstrated these changes more frequently in symptomatic patients (in 23 vs five asymptomatic patients, P = .002). Tendon diameter changes were frequent in both groups but significantly (P = .001 to P = .009) more frequent in symptomatic patients (all tendon parts). Fatty atrophy was evident in the anterior two-thirds of the gluteus minimus muscle in both groups, without significant differences. In the posterosuperior third of the gluteus minimus muscle, however, differences in fatty atrophy between the two groups were significant (P = .026). Fatty atrophy of the gluteus medius muscle was present in symptomatic patients only, with significant differences among all muscle parts. Bursal fluid collections were more frequent in symptomatic patients (n = 24) than in asymptomatic patients (n = 8, P = .021). The MR imaging-based diagnosis was confirmed in all 14 patients who underwent revision surgery. CONCLUSION: Abductor tendon defects and fatty atrophy of the gluteus medius muscle and the posterior part of the gluteus minimus muscle are uncommon in asymptomatic patients after THA.

Increased intraarticular pressure reduces blood flow to the femoral head.

Hemarthrosis leading to increased intracapsular pressure after an undisplaced femoral neck fracture is suspected to impair blood flow to the femoral head and may lead to osteonecrosis. We hypothesized that an increase of intraarticular pressure would reversibly decrease the blood flow to the femoral head. Eleven patients having surgical dislocations for treatment of femoroacetabular impingement were included in this study. Saline was injected into the intact intracapsular space while the blood flow to the femoral head was recorded using laser Doppler flowmetry. Injection of saline resulted in an increase in the intracapsular pressure. The injected volume of normal saline until disappearance of the pulsatile signal was on average 20 mL (range, 10-35 mL) with an average intraarticular pressure of 58 mm Hg (range, 25-88 mm Hg). Aspiration of the joint resulted in a return of the pulsatile flow. Hemarthrosis after undisplaced intracapsular fractures of the femoral neck are likely to cause an increase in intracapsular pressure. Decompression of the hematoma to reduce the intracapsular pressure is strongly advocated to optimize blood flow to the femoral head in acute fractures.

FDG PET for differentiation of infection and aseptic loosening in total hip replacements: comparison with conventional radiography and three-phase bone scintigraphy.

PURPOSE: To compare the diagnostic efficacy of fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) with that of conventional radiography and three-phase bone scintigraphy in patients suspected of having infection in their total hip replacements. MATERIALS AND METHODS: Thirty-five patients with painful total hip replacements and possible septic prosthetic loosening were examined with FDG PET, conventional radiography, and three-phase bone scintigraphy. PET, radiographic, and scintigraphic images were each evaluated by two independent observers in a blinded fashion. For 32 of 35 patients, serial conventional radiographs were available. Results of microbiologic examinations of surgical specimens represented the standard of reference in 26 patients, and results of joint aspiration plus clinical follow-up of at least 6 months represented the standard of reference in the remaining nine patients. Sensitivity, specificity, accuracy, and interobserver variability (kappa) values were calculated. The imaging modalities were compared in terms of diagnostic confidence by using the sign test. RESULTS: Nine patients had septic and 21 patients had aseptic loosening. In five patients, neither loosening nor infection was confirmed. For diagnosing infection with FDG PET, conventional radiography, and bone scintigraphy, respectively, sensitivity values for reader 1 and reader 2 were 33% and 22%, 89% and 78%, and 56% and 44%, while specificity values were 81% and 85%, 50% and 65%, and 88% and 92% and accuracy values were 69% for both readers, 60% and 69%, and 80% for both readers. PET was significantly more specific (P =.035) but less sensitive (P =.016) than conventional radiography for the diagnosis of infection. CONCLUSION: In a study population of patients suspected of having infected total hip replacements, FDG PET performed similarly to three-phase bone scintigraphy. FDG PET was more specific but less sensitive than conventional radiography for the diagnosis of infection.