Epidemiologic analysis of 8000 acute vertebral fractures: evolution of treatment and complications at 10-year follow-up.

STUDY DESIGN: This is a retrospective cohort study. OBJECTIVES: This study aims to determine the proportional incidence, clinical characteristics, treatment patterns with complications and changes in treatment of vertebral fractures over 10 years at a Swiss university hospital. METHODS: A retrospective cohort study was performed. All patients with an acute vertebral fracture were included in this study. The extracted anonymized data from the medical records were manually assessed. Demographic data, exact location, etiology, type of treatment and complications related to the treatment were obtained. RESULTS: Of 330,225 treated patients, 4772 presented with at least one vertebral fracture. In total 8307 vertebral fractures were identified, leading to a proportional incidence of 25 vertebral fractures in 1000 patients. Fractures were equally distributed between genders. Male patients were significantly younger and more likely to sustain a traumatic fracture, while female patients more commonly presented with osteoporotic fractures. The thoracolumbar junction (Th11-L2) was the most frequent fracture site in all etiologies. More than two-thirds of vertebral fractures were treated surgically (68.6%). Out of 4622 performed surgeries, we found 290 complications (6.3%). The odds for surgical treatment in osteoporotic fractures were two times higher before 2010 compared to 2010 and after (odds ratio: 2.1, 95% CI 1.5-2.9, p < 0.001). CONCLUSION: Twenty-five out of 1000 patients presented with a vertebral fracture. More than 4000 patients with over 8307 vertebral body fractures were treated in 10 years. Over two-thirds of all fractures were treated surgically with 6.3% complications. There was a substantial decrease in surgeries for osteoporotic fractures after 2009.

Navigation-Assisted Posterior Open Reduction and Internal Fixation in a C-CLAMP Fashion for an Isolated C1 Fracture.

C1 fractures with an intact transverse ligament are usually treated conservatively. Patients who present with a progressive diastasis of bone fragments and a progressive articular subluxation mainly attributed to progressive lengthening of the transverse ligament (TAL) fibers can be treated with a C1 "C-clamp" fusion. A 75-year-old male who sustained a motor vehicle accident was neurologically intact. A computed tomography (CT) imaging demonstrated a Jefferson's type-C1 fracture with a slight lateral displacement of the C1 left lateral mass (LM) and a rotatory subluxation on the right. MRI showed an intact TAL and demonstrated an isolated rupture of the left alar ligament. Conservative treatment was chosen. Radiographic follow-up showed, at 3 months, progressive lateral mass displacement, most likely due to elongation of the TAL fibers; this was also associated with a persistent mechanical neck pain. For this reason, we performed a posterior reduction and internal fixation in a C-clamp fashion by placement of C1 lateral mass screws and posterior compression sparing the C1-2 joint. Using navigation, a 3.5-mm screw was inserted into the LM bilaterally. The screw heads were then connected with a rod and compression was applied before tightening. Postoperative CT scan demonstrated a satisfying reduction and further imaging will be made during the follow-up. The patient had a considerable relief of neck pain. Simple lateral mass fixation with C-clamp technique is a reasonable option in case of isolated C1 fractures in patients who have failed conservative management while preserving the range of motion (ROM) at the atlanto-axial joint. The link to the video can be found at: https://youtu.be/x8bsVwzCt_M .

One-year follow-up for type II odontoid process fractures in octogenarians: Is there a place for surgical management?

BACKGROUND: Type II odontoid fractures are becoming one of the most common injuries among elderly patients and are associated with increased morbidity rates. Here, we compared the safety/efficacy of conservative versus surgical treatment for type II C2 fractures and, in particular, evaluated the complications, hospital lengths of stay, and mortality rates for patients over 80 years of age. METHODS: We retrospectively reviewed the records of 63 nonsurgically versus 18 surgically treated C2 fractures in patients over 80 years of age (2003-2018). Cervical computed tomography images, X-rays, and magnetic resonance images were reviewed by both a neurosurgeon and a neuroradiologist. The following patient data were included in the analysis; Glasgow Coma Scale score, injury severity score, the abbreviated injury scale scores, their comorbidities (e.g., utilizing the Charlson comorbidity index), their primary outcomes, and mortality rates (e.g., at 6 weeks and 1 year after treatment). RESULTS: Eighty-one patients were included in the study; 63 were treated conservatively and 18 underwent surgical management of type II C2 fractures. Patients averaged 87.0 ± 5.0 years of age, and their combined mortality rates were 13.6% at 6 weeks and 25.9% at 1 year. Notably, at 1 year, the mortality rates were not statistically different between the two groups: 18 (30.0%) patients from the conservatively treated group versus 3 (16.7%) patients from the surgically managed patients died indicating (e.g., using the Kaplan-Meier analysis) no survival advantage for either treatment strategy. CONCLUSION: Surgical versus conservative management of type II odontoid fractures were associated with comparable high mortality rates at 1 year.

Return to Sport and Patient Satisfaction at 5-Year Follow-up After Nonoperative Treatment for Acute Achilles Tendon Rupture.

BACKGROUND: There is controversy whether nonoperative or operative treatment for Achilles tendon rupture is superior. It is unknown if patients with acute Achilles tendon rupture return to previous sports activity. The purpose of this study was to assess 5-year return to sport and subjective satisfaction, minimum 1-year functional outcomes, and complications in patients following nonoperative treatment of Achilles tendon rupture with early weightbearing rehabilitation. METHODS: An institutional review board-approved, retrospective observational study involving 89 patients was performed. Out of 114 consecutive patients, 89 (78%) responded to questionnaires for sports activity. Nonoperative treatment consisted of an equinus cast and rehabilitation boot that enabled early weightbearing. Sports activity at 1-year and 5-year follow-up was compared to the prerupture status. Based on the prerupture Tegner Activity Scale (TAS), patients were divided into low-level (<6) and high-level (≥6) activity groups. Clinical assessment at minimum 1-year follow-up was performed with the Thermann score. Mean clinical follow-up was 34 ± 23 months. RESULTS: Overall, >70% of the patients returned to their previous sports activity level after a nonoperative early weightbearing treatment. Return-to-sport rate was significantly (P = .029) higher for patients in the low-level activity group (91%) compared to patients (67%) in the high-level activity group at 5-year follow-up. Subjective satisfaction with treatment was good in both groups (93% and 96%, respectively). The mean Thermann score did not differ between the 2 groups at 1-year follow-up. There were 11 reruptures, 5 deep venous thromboses, and 1 case of complex regional pain syndrome. CONCLUSION: Nonoperative treatment for Achilles tendon rupture yielded good functional outcome and high patient satisfaction. For patients with a high preinjury activity level, return to previous sporting level (assessed by TAS) was possible in 67% of the patients compared to >90% of patients with low preinjury activity level. LEVEL OF EVIDENCE: Level III, retrospective comparative series.

[Vertebroplasty: the new CHUV consensus]. / Fracture vertébrale ostéoporotique aiguë et douloureuse - Proposition d'un algorithme décisionnel pour la cimentoplastie au CHUV.

Should we continue to treat patients suffering from an acute osteoporotic vertebral fracture with vertebroplasty ? What is the potential benefit ? What are its indications ? What are its risks ? Which way to perform it ? How to manage the osteoporosis evaluation and therapy ? In 2009 we published the «â€…CHUV consensus ¼ on the management of vertebral osteoporotic fractures by vertebroplasty. We here propose an update including recent knowledge on the management of vertebral fractures by bone insufficiency by percutaneous cementoplasty.

Doit-on continuer à traiter les patients souffrant d'une fracture vertébrale aiguë ostéoporotique par cimentoplastie ? Quel est le bénéfice potentiel ? Quelles sont ses indications ? Quels sont ses risques ? À qui les adresser ? Quand faire le bilan et le traitement de la maladie ostéoporotique ? En 2009, nous avions publié le consensus du CHUV de prise en charge par vertébroplastie des fractures vertébrales ostéoporotiques. Nous proposons une mise à jour incluant les connaissances récentes sur la prise en charge des fractures vertébrales par insuffisance osseuse par technique de cimentoplastie percutanée.

Spinal angiolipomas in pregnancy: Natural history and surgical treatment.

Spinal angiolipomas (SALs) are rare extradural tumors frequently located at the level of the thoracic spine and they are associated with spinal cord compromise that might result in severe myelopathy. While the first macroscopic description dates 1890, histologically these tumors where not described as angiolipomas until 1986 by Haddad et al. Occurrence in pregnancy is even more infrequent. Since their first macroscopic description, spinal angiolipomas were reported anecdotally in pregnant women. We present a case of spinal angiolipoma in pregnancy with confirmed histologic diagnosis. In the present paper, we reviewed the literature regarding spinal angiolipomas in order to characterize their clinical manifestation, natural history, radiologic and histologic appearance. We add also a further case of spinal angiolipoma in a pregnant woman. Finally, we provide suggestions for the management of such rare tumors in pregnancy.

Augmented marker tracking for peri-acetabular osteotomy surgery.

OBJECTIVE: To develop a hybrid augmented marker-based navigation system for acetabular reorientation during peri-acetabular osteotomy (PAO). METHODS: The system consists of a tracking unit attached to the patient's pelvis, augmented marker attached to the acetabular fragment and a host computer to do all the computations and visualization. The augmented marker is comprised of an external planar Aruco marker facing toward the tracking unit and an internal inertial measurement unit (IMU) to measure its orientation. The orientation output from the IMU is sent to the host computer. The tracking unit streams a live video of the augmented marker to the host computer, where the planar marker is detected and its pose is estimated. A Kalman filter-based sensor fusion combines the output from marker tracking and the IMU. We validated the proposed system using a plastic bone study and a cadaver study. Every time, we compared the inclination and anteversion values measured by the proposed system to those from a previously developed optical tracking-based navigation system. RESULTS: Mean absolute differences for inclination and anteversion were 1.34 ([Formula: see text]) and 1.21 ([Formula: see text])[Formula: see text], respectively, for the cadaver study. Mean absolute differences were 1.63 ([Formula: see text]) and 1.55 ([Formula: see text])[Formula: see text] for inclination and anteversion for the plastic bone study. In both validation studies, very strong correlations were observed. CONCLUSION: We successfully demonstrated the feasibility of our system to measure the acetabular orientation during PAO.

Augmented marker tracking for peri-acetabular osteotomy surgery.

We developed and validated a small, easy to use and cost-effective augmented marker-based hybrid navigation system for peri-acetabular osteotomy (PAO) surgery. The hybrid system consists of a tracking unit directly placed on the patient's pelvis, an augmented marker with an integrated inertial measurement unit ('MU) attached to the patient's acetabular fragment and the host computer. The tracking unit sends a live video stream of the marker to the host computer where the marker's pose is estimated. The augmented marker with the 'MU sends its pose estimate to the host computer where we apply sensor fusion to compute the final marker pose estimate. The host computer then tracks the orientation of the acetabular fragment during peri-acetabular osteotomy surgery. Anatomy registration is done using a previously developed registration device. A Kalman filter-based sensor fusion was added to complete the system. A plastic bone study was performed for validation between an optical tracking-based navigation system and our proposed system. Mean absolute difference for inclination and anteversion was 1.63 degrees and 1.55 degrees, respectively. The results show that our system is able to accurately measure the orientation of the acetabular fragment.

Short Posterior Stabilization in Combination With Cement Augmentation for the Treatment of Thoracolumbar Fractures and the Effects of Implant Removal.

STUDY DESIGN: Retrospective case series. OBJECTIVE: Short posterior stabilization with vertebroplasty is one treatment option for thoracolumbar burst fractures (AO A3). Whether it avoids progression in segmental kyphosis, especially after implant removal, is unclear. In a retrospective case-control study, its stability and the effect on intervertebral discs with and without implant removal was studied. METHODS: Fifty-nine consecutive patients were treated with bisegmental short posterior instrumentation and additional vertebroplasty of the fractured vertebra. Twenty-nine patients (male/female 17/12; age: 41.7 ± 15.4 years) underwent implant removal. Changes of segmental kyphosis and disc heights between both groups (with and without implant removal) were compared on lateral X-rays preoperative, postoperative, after 1 year and after implant removal. Risk factors for loss of reduction were analyzed. RESULTS: Kyphosis increased up to 12 months after implant removal. The loss of bisegmental correction was 6.0 ± 4.2 (range 0° to 16°) 12 months after implant removal. Risk factors for loss of reduction are younger patient age, fractures of the thoracolumbar junction (Th12), and degree of traumatic kyphosis. Intervertebral discs traversed by the stabilization lose height and don't recover within 1 year after implant removal. Without implant removal, disc height of the lower adjacent level is reduced after 24 months. CONCLUSIONS: Short posterior stabilization in combination with vertebroplasty is a treatment alternative for thoracic and lumbar AO A3 fractures. After implant removal kyphosis increases, predominantly in the segment above the augmented vertebra. Risk factors for loss of reduction include younger age, fractures of the thoracolumbar junction (T12), and higher fracture kyphosis.

Evaluation of Constant Thickness Cartilage Models vs. Patient Specific Cartilage Models for an Optimized Computer-Assisted Planning of Periacetabular Osteotomy.

Modern computerized planning tools for periacetabular osteotomy (PAO) use either morphology-based or biomechanics-based methods. The latter relies on estimation of peak contact pressures and contact areas using either patient specific or constant thickness cartilage models. We performed a finite element analysis investigating the optimal reorientation of the acetabulum in PAO surgery based on simulated joint contact pressures and contact areas using patient specific cartilage model. Furthermore we investigated the influences of using patient specific cartilage model or constant thickness cartilage model on the biomechanical simulation results. Ten specimens with hip dysplasia were used in this study. Image data were available from CT arthrography studies. Bone models were reconstructed. Mesh models for the patient specific cartilage were defined and subsequently loaded under previously reported boundary and loading conditions. Peak contact pressures and contact areas were estimated in the original position. Afterwards we used a validated preoperative planning software to change the acetabular inclination by an increment of 5° and measured the lateral center edge angle (LCE) at each reorientation position. The position with the largest contact area and the lowest peak contact pressure was defined as the optimal position. In order to investigate the influence of using patient specific cartilage model or constant thickness cartilage model on the biomechanical simulation results, the same procedure was repeated with the same bone models but with a cartilage mesh of constant thickness. Comparison of the peak contact pressures and the contact areas between these two different cartilage models showed that good correlation between these two cartilage models for peak contact pressures (r = 0.634 ∈ [0.6, 0.8], p < 0.001) and contact areas (r = 0.872 > 0.8, p < 0.001). For both cartilage models, the largest contact areas and the lowest peak pressures were found at the same position. Our study is the first study comparing peak contact pressures and contact areas between patient specific and constant thickness cartilage models during PAO planning. Good correlation for these two models was detected. Computer assisted planning with FE modeling using constant thickness cartilage models might be a promising PAO planning tool when a conventional CT is available.

Prospective Use of a Standardized Nonoperative Early Weightbearing Protocol for Achilles Tendon Rupture: 17 Years of Experience.

BACKGROUND: Acute traumatic rupture of the Achilles tendon can be treated operatively or nonoperatively. Throughout the literature, there is no consensus regarding the optimal treatment protocol. PURPOSE: To report on 17 years of experience with treating this injury with a standardized nonoperative treatment protocol. STUDY DESIGN: Case Series; Level of evidence, 4. METHODS: The treatment protocol was based on a combination of an equinus cast and rehabilitation boot, which promoted immediate full weightbearing and early functional rehabilitation. A total of 171 patients were consecutively treated and prospectively followed from 1996 to 2013. Assessed were subjective parameters such as pain, loss of strength, return to previous activity level, meteosensitivity, and general satisfaction with the treatment outcome. Clinical assessment included testing of plantar flexion strength and endurance, calf circumference, and tendon length. Subjective and clinical parameters were then used to calculate a modified Thermann score. The correlation between tendon lengthening and function was calculated using the Pearson correlation coefficient. RESULTS: A total of 114 patients were followed for a minimum of 12 months (mean, 27 ± 20 months; range, 12-88 months). The mean Thermann score was 82 ± 13 (range, 41-100), and subjective satisfaction was rated "very good" and "good" in 90%. An inverse correlation was found between tendon length and muscle strength (R = -0.3). There were 11 reruptures (8 with and 3 without an adequate trauma). General complications were 5 deep venous thromboses, 1 complex regional pain syndrome, and minor problems such as transient heel pain (n = 3), heel numbness (n = 1), and cast-associated skin abrasions (n = 4). CONCLUSION: Seventeen years of experience with a nonoperative treatment protocol for acute rupture of the Achilles tendon confirmed good functional outcome and patient satisfaction. Reruptures mostly occurred with new traumatic events in the vulnerable phase from 6 to 12 weeks after the initial injury. Muscle strength correlated to tendon length, making its assessment a crucial follow-up parameter. The protective equinus cast and boot can protect against excessive tendon lengthening during the healing process.

Lavage prior to vertebral augmentation reduces the risk for cement leakage.

PURPOSE: This study aimed at assessing the cement leakage rate and the filling pattern in patients treated with vertebroplasty, kyphoplasty and stentoplasty with and without a newly developed lavage technique. STUDY DESIGN: Retrospective clinical case-control study. METHODS: A newly developed bipedicular lavage technique prior to cement application was applied in 64 patients (45.1 %) with 116 vertebrae, ("lavage" group). A conventional bipedicular cement injection technique was used in 78 patients (54.9 %) with 99 levels ("controls"). The outcome measures were filling patterns and leakage rates. RESULTS: The overall leakage rate (venous, cortical defect, intradiscal) was 37.9 % in the lavage and 83.8 % in the control group (p < 0.001). Venous leakage (lavage 12.9 % vs. controls 31.3 %; p = 0.001) and cortical defect leakage (lavage 17.2 % vs. controls 63.3 %; p < 0.001) were significantly lower in the lavage group compared to "controls," whereas intradiscal leakages were similar in both groups (lavage 12.1 % vs. controls 15.2 %; p = 0.51). For venous leakage multivariate logistic regression analysis showed lavage to be the only independent predictor. Lavage was associated with 0.33-times (95 % CI 0.16-0.65; p = 0.001) lower likelihood for leakage in compared to controls. CONCLUSIONS: Vertebral body lavage prior to cement augmentation is a safe technique to reduce cement leakage in a clinical setting and has the potential to prevent pulmonary fat embolism. Moreover, a better filling pattern can be achieved.

A cost-effective surgical navigation solution for periacetabular osteotomy (PAO) surgery.

PURPOSE: To evaluate a low-cost, inertial sensor-based surgical navigation solution for periacetabular osteotomy (PAO) surgery without the line-of-sight impediment. METHODS: Two commercial inertial measurement units (IMU, Xsens Technologies, The Netherlands), are attached to a patient's pelvis and to the acetabular fragment, respectively. Registration of the patient with a pre-operatively acquired computer model is done by recording the orientation of the patient's anterior pelvic plane (APP) using one IMU. A custom-designed device is used to record the orientation of the APP in the reference coordinate system of the IMU. After registration, the two sensors are mounted to the patient's pelvis and acetabular fragment, respectively. Once the initial position is recorded, the orientation is measured and displayed on a computer screen. A patient-specific computer model generated from a pre-operatively acquired computed tomography scan is used to visualize the updated orientation of the acetabular fragment. RESULTS: Experiments with plastic bones (eight hip joints) performed in an operating room comparing a previously developed optical navigation system with our inertial-based navigation system showed no statistically significant difference on the measurement of acetabular component reorientation. In all eight hip joints the mean absolute difference was below four degrees. CONCLUSION: Using two commercially available inertial measurement units we show that it is possible to accurately measure the orientation (inclination and anteversion) of the acetabular fragment during PAO surgery and therefore to successfully eliminate the line-of-sight impediment that optical navigation systems have.

Periacetabular osteotomy through the pararectus approach: technical feasibility and control of fragment mobility by a validated surgical navigation system in a cadaver experiment.

PURPOSE: The pararectus approach has been validated for managing acetabular fractures. We hypothesised it might be an alternative approach for performing periacetabular osteotomy (PAO). METHODS: Using four cadaver specimens, we randomly performed PAO through either the pararectus or a modified Smith-Petersen (SP) approach. We assessed technical feasibility and safety. Furthermore, we controlled fragment mobility using a surgical navigation system and compared mobility between approaches. The navigation system's accuracy was tested by cross-examination with validated preoperative planning software. RESULTS: The pararectus approach is technically feasible, allowing for adequate exposure, safe osteotomies and excellent control of structures at risk. Fragment mobility is equal to that achieved through the SP approach. Validation of these measurements yielded a mean difference of less <1 mm without statistical significance. CONCLUSION: Experimental data suggests the pararectus approach might be an alternative approach for performing PAO. Clinical validation is necessary to confirm these promising preliminary results.

Computer assisted planning and navigation of periacetabular osteotomy with range of motion optimization.

Femoroacetabular impingement (FAI) before or after Periacetabular Osteotomy (PAO) is surprisingly frequent and surgeons need to be aware of the risk preoperatively and be able to avoid it intraoperatively. In this paper we present a novel computer assisted planning and navigation system for PAO with impingement analysis and range of motion (ROM) optimization. Our system starts with a fully automatic detection of the acetabular rim, which allows for quantifying the acetabular morphology with parameters such as acetabular version, inclination and femoral head coverage ratio for a computer assisted diagnosis and planning. The planned situation was optimized with impingement simulation by balancing acetabuar coverage with ROM. Intra-operatively navigation was conducted until the optimized planning situation was achieved. Our experimental results demonstrated: 1) The fully automated acetabular rim detection was validated with accuracy 1.1 ± 0.7mm; 2) The optimized PAO planning improved ROM significantly compared to that without ROM optimization; 3) By comparing the pre-operatively planned situation and the intra-operatively achieved situation, sub-degree accuracy was achieved for all directions.

LCPD: reduced range of motion resulting from extra- and intraarticular impingement.

BACKGROUND: Legg-Calvé-Perthes disease (LCPD) often results in a deformity that can be considered as a complex form of femoroacetabular impingement (FAI). Improved preoperative characterization of the FAI problem based on a noninvasive three-dimensional computer analysis may help to plan the appropriate operative treatment. QUESTIONS/PURPOSES: We asked whether the location of impingement zones, the presence of additional extraarticular impingement, and the resulting ROM differ between hips with LCPD and normal hips or hips with FAI. METHODS: We used a CT-based virtual dynamic motion analysis based on a motion algorithm to simulate the individual motion for 13 hips with LCPD, 22 hips with FAI, and 27 normal hips. We then determined the motion and impingement pattern of each hip for the anterior (flexion, adduction, internal rotation) and the posterior impingement tests (extension, adduction, external rotation). RESULTS: The location of impingement zones in hips with LCPD differed compared with the FAI/normal groups. Intra- and extraarticular impingement was more frequent in LCPD (79% and 86%, respectively) compared with normal (15%, 15%) and FAI hips (36%, 14%). Hips with LCPD had decreased amplitude for all hip motions (flexion, extension, abduction, adduction, internal and external rotation) compared with FAI or normal. CONCLUSIONS: Hips with LCPD show a decreased ROM as a result of a higher prevalence of intra- and extraarticular FAI. Noninvasive assessment of impingement characteristics in hips with LCPD may be helpful in the future for establishment of a surgical plan.

Computer-assisted femoral head-neck osteochondroplasty using a surgical milling device an in vitro accuracy study.

Surgical navigation might increase the safety of osteochondroplasty procedures in patients with femoroacetabular impingement. Feasibility and accuracy of navigation of a surgical reaming device were assessed. Three-dimensional models of 18 identical sawbone femora and 5 cadaver hips were created. Custom software was used to plan and perform repeated computer-assisted osteochondroplasty procedures using a navigated burr. Postoperative 3-dimensional models were created and compared with the preoperative models. A Bland-Altmann analysis assessing α angle and offset ratio accuracy showed even distribution along the zero line with narrow confidence intervals. No differences in α angle and offset ratio accuracy (P = 0.486 and P = 0.2) were detected between both observers. Planning and conduction of navigated osteochondroplasty using a surgical reaming device is feasible and accurate.

Automated detection of the osseous acetabular rim using three-dimensional models of the pelvis.

An automated algorithm for detection of the acetabular rim was developed. Accuracy of the algorithm was validated in a sawbone study and compared against manually conducted digitization attempts, which were established as the ground truth. The latter proved to be reliable and reproducible, demonstrated by almost perfect intra- and interobserver reliability. Validation of the automated algorithm showed no significant difference compared to the manually acquired data in terms of detected version and inclination. Automated detection of the acetabular rim contour and the spatial orientation of the acetabular opening plane can be accurately achieved with this algorithm.

The Equidistant Method - a novel hip joint simulation algorithm for detection of femoroacetabular impingement.

INTRODUCTION: A novel computerized algorithm for hip joint motion simulation and collision detection, called the Equidistant Method, has been developed. This was compared to three pre-existing methods having different properties regarding definition of the hip joint center and behavior after collision detection. It was proposed that the Equidistant Method would be most accurate in detecting the location and extent of femoroacetabular impingement. MATERIALS AND METHODS: Five plastic pelves and ten plastic femora with modified acetabula and head-neck junctions, allowing for 50 different morphologic combinations, were examined, along with six cadaver hips. First, motions along anatomically relevant paths were performed. These motions were tracked by a navigation system and impingement locations were digitized with a pointer. Subsequently, previously generated 3D models of all the specimens, together with the recorded anatomic motion paths, were applied to all four simulation algorithms implemented in a diagnostic computer application. Collisions were detected within the motion paths, and the linear and angular differences regarding the location as well as the size of the detected impingement areas were compared and analyzed. RESULTS: The Equidistant Method detected impingement with significantly higher linear and angular accuracy compared to the other methods (p < 0.05). The size of the detected impingement area was smaller than that detected with the other methods, but this difference was not statistically significant. CONCLUSIONS: The increased accuracy of the Equidistant Method is achieved by implementing a dynamic hip joint center, more closely resembling the natural characteristics of the hip joint. Clinical application of this algorithm might serve as a diagnostic adjunct and support in the planning of joint-preserving surgery in patients with femoroacetabular impingement.

Factors affecting bony impingement in hip arthroplasty.

Computer modeling of 10 patients' computed tomographic scans was used to study the variables affecting hip arthroplasty range of motion before bony impingement (ROMBI) including acetabular offset and height, femoral offset, height and anteversion, and osteophyte removal. The ROMBI was compared with the ROM before component impingement and the native hip ROM. The ROMBI decreased with decreased total offset and limb shortening. Acetabular offset and height had a greater effect on ROMBI than femoral offset and height. The ROMBI lost with decreased acetabular offset was not fully recoverable with an increase in femoral offset or osteophyte removal. Bony impingement increased and component impingement decreased with decreased acetabular offset and increased head diameter.