The fate of the hip in spondylo-epi-metaphyseal dysplasia: clinical and radiological evaluation of adults with SEMD Handigodu type

Purpose

This study was undertaken to document the fate of the hip with reference to its structure and function in patients with spondylo-epi-metaphyseal dysplasia tarda Handigodu type (SEMD_HG).

Material and methods

Radiographs of 271 adult patients with SEMD_HG were studied to identify the pattern of long-term sequelae in the hips. Several measurements of the proximal femur and acetabulum were made to quantify morphological alterations in the hip. Fifty-four adult patients were examined and administered a questionnaire to evaluate the extent of disability attributable to the hips.

Results

Three patterns of changes in the hips were noted: 35% had acetabular protrusio, 33% had subluxation of the hip, and 32% had no protrusio or subluxation. Distinctly different anthropometric measurements and dimensional alterations around the hip were noted in these three patterns. Patients with protrusio were relatively tall while those with subluxation were the shortest. All the patients had developed degenerative arthritis of the hips by the fourth decade of life irrespective of the pattern of hip involvement. The reduction in the range of hip motion and fixed deformities were most severe in patients with protrusio. All the patients had significant disability and very low functional hip scores.

Conclusion

Degenerative arthritis of the hip develops in the majority of patients with SEMD_HG; the symptoms are severe enough to warrant reconstructive surgery by the fourth decade of life. Protrusio or subluxation develops in a third of the patients each; both these complications will influence the surgical approach if total hip arthroplasty is planned.     

Femoral anteversion is correlated with acetabular version and coverage in Asian women with anterior and global deficient subgroups of hip dysplasia: a CT study

Objective

Morphological correlation between the acetabulum and femur at the hip joint is still controversial. We tested the hypothesis that femoral anteversion correlates with acetabular version and coverage in patients with developmental dysplasia of the hip (DDH).

Materials and methods

Using pelvic computed tomography (CT) images of 79 hips in 49 Asian women with DDH and 49 normal hips, we measured femoral anteversion, the axial and vertical acetabular version and the acetabular sector angle (ASA) to demarcate femoral head coverage. Depending on the location of the acetabular bone defect, dysplastic hips were divided into three subgroups: the anterior, global and posterior deficiency groups. We performed a comparative analysis between dysplastic and normal hips using the Wilcoxon rank sum test, and a relative analysis between femoral anteversion and acetabular measurements in dysplastic hips using Pearson’s correlation coefficient.

Results

The amount of femoral anteversion in dysplastic hips was greater and more variable than in normal hips (p?p?=?0.0277 respectively). Femoral anteversion in dysplastic hips correlated significantly with acetabular anteversion in the groups with anterior and global deficiency subgroups (p?p?Conclusions Our results showed significantly greater and more variable femoral anteversion in DDH, and a significant correlation between femoral anteversion and acetabular version and coverage in DDH with anterior and global acetabular bone deficiency.     

Reliability of radiographic parameters in adults with hip dysplasia

Objective

To assess the reliability of radiographic measurements in adults previously treated for developmental dysplasia of the hip (DDH) and to clarify whether these parameters differ according to position of the patient (supine versus standing).

Materials and methods

Fifty-one patients (41 females and 10 males) with 63 affected hips were included in the study. The mean follow-up period was 45 (44–49) years in the patients who had not undergone total hip replacement (THR). Anteroposterior radiographs of the pelvis were taken with the patient in the supine and in the standing position. Measurements used for residual hip dysplasia were center-edge (CE) angle and migration percentage (MP). The joint space width (JSW) was measured at three or four locations of the upper, weight-bearing part of the joint, and the shortest distance was termed the minimum joint space width (minJSW). One radiologist and one orthopaedic surgeon, each with more than 30?years of experience, independently measured the radiographic parameters.

Results

The limits of agreement (LOA) of the CE angle (mean interobserver difference ± 2SD) were within the range ?8 to 7°. The LOA of the MP were in the range ?8 to 8% and of the minJSW ?0.6 to 1.1?mm. The mean differences in CE angle between supine and standing radiographs (supine ? standing) ranged from ?1.1 to 0.0° and the mean differences in MP between supine and standing positions were below 1%. The mean positional differences in minJSW were below 0.1?mm and were not statistically significant.

Conclusion

The interobserver variations with regard to CE angle, MP, and minJSW were moderate, indicating that these are reliable measurements in clinical practice. Femoral head coverage and JSW did not significantly differ between supine and weight-bearing positions.     

Significant effect of the posterior tibial slope and medial/lateral ligament balance on knee flexion in total knee arthroplasty

Purpose

The intra-operative femorotibial joint gap and ligament balance, the predictors affecting these gaps and their balances, as well as the postoperative knee flexion, were examined. These factors were assessed radiographically after a posterior cruciate-retaining total knee arthroplasty (TKA). The posterior condylar offset and posterior tibial slope have been reported as the most important intra-operative factors affecting cruciate-retaining-type TKAs. The joint gap and balance have not been investigated in assessments of the posterior condylar offset and the posterior tibial slope.

Methods

The femorotibial gap and medial/lateral ligament balance were measured with an offset-type tensor. The femorotibial gaps were measured at 0°, 45°, 90° and 135° of knee flexion, and various gap changes were calculated at 0°–90° and 0°–135°. Cruciate-retaining-type arthroplasties were performed in 98 knees with varus osteoarthritis.

Results

The 0°–90° femorotibial gap change was strongly affected by the posterior condylar offset value (postoperative posterior condylar offset subtracted by the preoperative posterior condylar offset). The 0°–135° femorotibial gap change was significantly correlated with the posterior tibial slope and the 135° medial/lateral ligament balance. The postoperative flexion angle was positively correlated with the preoperative flexion angle, γ angle and the posterior tibial slope. Multiple-regression analysis demonstrated that the preoperative flexion angle, γ angle, posterior tibial slope and 90° medial/lateral ligament balance were significant independent factors for the postoperative knee flexion angle. The flexion angle change (postoperative flexion angle subtracted by the preoperative flexion angle) was also strongly correlated with the preoperative flexion angle, posterior tibial slope and 90° medial/lateral ligament balance.

Conclusion

The postoperative flexion angle is affected by multiple factors, especially in cruciate-retaining-type TKAs. However, it is important to pay attention not only to the posterior tibial slope, but also to the flexion medial/lateral ligament balance during surgery. A cruciate-retaining-type TKA has the potential to achieve both stability and a wide range of motion and to improve the patients’ activities of daily living.     

The effect of distal femur bony morphology on in vivo knee translational and rotational kinematics

Purpose

Tibio-femoral kinematics are clearly influenced by the bony morphology of the femur. Previous morphological studies have not directly evaluated relationships between morphology and knee kinematics. Therefore, the purpose of this study was to examine the relationship between distal femur bony morphology and in vivo knee kinematics during running. It was hypothesized that the posterior offset of the transcondylar axis would be related to the magnitude of anterior/posterior tibio-femoral translation and that the rotational angle of the transcondylar axis would be related to the magnitude of internal/external knee rotation.

Methods

Seventeen contralateral (uninjured) knees of ACL-reconstructed patients were used. Distal femoral geometry was analyzed from 3D-CT data by determining the anteroposterior location (condyle offset ratio—COR) and rotational angle (condylar twist angle—CTA) of the femoral transcondylar axis. Six degree-of-freedom knee kinematics were obtained during running using a dynamic stereo radiograph system. Knee kinematics were correlated with the femoral morphologic measures (COR and CTA) to investigate the influence of femoral geometry on dynamic knee function.

Results

Significant correlations were identified between distal femur morphology and knee kinematics. Anterior tibial translation was positively correlated with the condyle offset ratio (R ²?=?0.41, P?R ²?=?0.48, P?Conclusions Correlations between knee kinematics and morphologic measures describing the position and orientation of the femoral transcondylar axis suggest that these specific measures are valuable for characterizing the influence of femur shape on dynamic knee function.

Level of evidence

III.     

The patellofemoral kinematics in patients with untreated developmental dislocation of the hip suffering from patellofemoral pain

Purpose

This study reviews the dynamic patellofemoral CT results of 39 patients with untreated developmental dislocation of the hip who are suffering from knee pain.

Method

The mean age of the patients with unilateral developmental dislocation of the hip was 33.3 (±7.9), for bilateral patients 36.2 (±11.3), and for the control group, it was 31.5 (±8.5). While 14 of them were bilateral, 25 were unilateral. The CT results of 24 asymptomatic adult knees served as the control group. The patellofemoral parameters of patients with unilateral and bilateral developmental dislocation of the hip, the control group’s parameters and the effect of femoral anteversion, limb length discrepancy, severity of dislocation, the mechanical axis deviation on patellofemoral parameters were analyzed.

Results

In patients with unilateral untreated developmental dislocation of the hip, although the patella was located more laterally at initial flexion degrees, it was located more medially at 30° and 60° flexion with respect to the control group. For the involved extremity, the PTA angles at 15°, 30°, and 60° flexion were significantly higher than in the control group corresponding to medial patellar tilt. In patients with bilateral developmental dislocation of the hip, the course of the patella during tracking in terms of patellar shift was similar to that of the unilateral patients. The amount of leg length discrepancy and the severity of dislocation, as well as the mechanical axis deviation, did not affect the patellofemoral parameters.

Conclusion

The patients with untreated developmental dislocation of the hip and suffering from knee pain should be analyzed not only for tibiofemoral abnormalities but also for patellofemoral malalignment.

Level of evidence

Case–control study, Level III.     

Pubo-femoral distance: an easy sonographic screening test to avoid late diagnosis of developmental dysplasia of the hip

Objectives

To propose an easy and reproducible sonographic screening test able to avoid late presentation of developmental dysplasia of the hip (DDH).

Methods

The pubo-femoral distance (PFD) cut-off point was determined on 980 infants who underwent ultrasonography of the hips in comparison with the final diagnosis, based on clinical, ultrasound data and follow-up. PFD reproducibility was tested on 52 hips by both an experienced and an inexperienced radiologist. After teaching this screening method to general radiologists, its impact was evaluated by analysing the rate of late diagnosis in an entire administrative area.

Results

An abnormal PFD threshold above 6 mm gave a sensitivity of 97.4 % for the diagnosis of DDH (271 hips) and a specificity of 84 %. Sensitivity increased to 100 % when taking into consideration children of 1 month or older. The PFD measurement stayed reproducible even in inexperienced hands (k?=?0.795). For 3 years, following the extension of screening to all female infants, there was no late diagnosis of DDH in girls in amongst a catchment area of 1 million inhabitants.

Conclusions

PFD measurement with a threshold for abnormality of 6 mm at the age of 1 month, without asymmetry above 1.5 mm, could eradicate DDH late diagnosis.

Key Points

? Late diagnosis of developmental dysplasia of the hip (DDH) should be avoidable ? Pubofemoral distance (PFD) is a reproducible measurement of hip instability ? PFD > 6 mm or a difference > 1.5 mm should lead to expert referral ? Universal screening using PFD at 1 month could eradicate DDH late diagnosis     

Normal values of Wiberg’s lateral center-edge angle and Lequesne’s acetabular index–a coxometric update

Background

The historical pathological cut-off values for Wiberg’s lateral center-edge (LCE) angle and Lequesne’s acetabular index (AI) are below 20° and above 12° for the LCE and AI, respectively. The aim of this study was to reassess these two angles more than 50?years after their introduction using a standardized conventional radiological measurement method, considering changing social habits and their associated physiological changes.

Methods

A total of 1,226 anteroposterior radiographs of the pelvis (2,452 hips) were obtained according to a strict standardized radiographic technique allowing reliable measurements of the LCE angle and the AI.

Results

Distributions of the LCE and AI were pronouncedly Gaussian, with mean values of 33.6° for the LCE and 4.4° for the AI. The 2.5th and 97.5th empirical percentiles were 18.1 and 48.0° for the LCE and ?6.9 and 14.9° for the AI. These intervals contained 95?% of the data in our large sample. Small but statistically significant differences between the sexes and right and left hips have been demonstrated. Correlation between age and coxometric indices was low.

Conclusion

The above findings do not conflict with the historical benchmarks. Statistical differences between sexes and between right and left hips were not clinically relevant. No conclusion can be drawn about coxometric indices and clinical manifestations of hip dysplasia.     

Toe-out angle changes after total knee arthroplasty in patients with varus knee osteoarthritis

Purpose

Toeing-out is a commonly proposed kinematic variable that has been suggested to reduce external knee adduction moment. Analyses of the toe-out angle after total knee arthroplasty (TKA) are useful for obtaining a proper understanding of the abnormal gait caused by varus knee osteoarthritis (OA), as well as performing rehabilitation after arthroplasty. Changes in the toe-out angle after arthroplasty have not yet been defined or analysed.

Methods

The study population consisted of 32 knees in 32 patients with varus knee OA who underwent TKA. The femorotibial angle was evaluated on standing anteroposterior radiographs before and after arthroplasty. The subjects underwent three-dimensional motion capture analyses to measure gait parameters (walking speed, cadence, stride length, step length, step width and the relative length of the single-limb support (SLS) percentage of one gait cycle) and the maximal hip adduction angle in the stance phase, the trunk lean angle in the coronal plane and the toe-out angle before and 4 weeks after arthroplasty.

Results

The femorotibial angle on the side of arthroplasty improved after surgery. Among the measured gait parameters, only the SLS percentage increased significantly. The hip adduction angle and toe-out angle on the side of arthroplasty increased significantly after surgery.

Conclusions

The knee alignment and hip adduction angle in the coronal plane and SLS phase were normalized after arthroplasty. The increase in the toe-out angle after arthroplasty may be attributable to the restoration of a normal knee alignment. These findings contribute to obtaining a proper understanding of the abnormal gait caused by varus knee OA and are useful for orthopaedic surgeons and rehabilitation therapists when treating patients after arthroplasty.

Level of evidence

Prospective study, Level II.     

CT measurements prior to computer-assisted total knee arthroplasty do not improve rotational placement of the femoral component

Purpose

The aim of this study is to determine whether computer-assisted surgery (CAS) can gain more precision by utilizing information from pre-operative computed tomography (CT).

Methods

Sixty-five patients undergoing total knee arthroplasty in 2008 were included. On pre- and post-operative CT, epicondylar and posterior condylar lines were drawn and the posterior condylar angle between these two lines measured. During the surgery, epicondylar and posterior condylar lines were also registered before and after CAS-guided cuts were made. CAS was used to fix the orientation of the cutting guide on the distal femur at 3° of external rotation from the posterior condylar line.

Results

There was no correlation between CT measurements and CAS measurements. All orientations of the lines (relative to the horizontal) and angles measured using CT were significantly different (p?<?0.05).

Conclusion

No relationship was found between pre-operative CT measurements and peri-operative CAS measurements used to orient the femoral component. Data obtained from CT cannot be used peri-operatively with CAS to improve rotational setting of the femoral component.

Level of evidence

Therapeutic study, Level II.     

Long-term survival analysis of posterior cruciate-retaining total knee arthroplasty

Purpose

Clinical factors related to cruciate-retaining knee arthroplasty failure in a long-term follow-up are yet unclear. The study was designed to evaluate the long-term survival rate of cruciate-retaining arthroplasty and clinical factors that may contribute to its failure.

Methods

A total of 162 patients (188 knees) who received cruciate-retaining press-fit condylar arthroplasty from June 1993 to May 1994 were followed up. All patients were assessed clinically and radiographically. Revision for any reason was regarded as failure of arthroplasty.

Results

A total of 120 patients (138 knees) were successfully followed up. Survivorship over 17?years was 92.5%. Fourteen knees were revised. Tibial varus angle of the operated knee in the unrevised patient group was greater than in revised group. There was statistical difference between these two groups (P?Conclusion Long-term survivorship of cruciate-retaining arthroplasty was fair. Varus and valgus deformity of the unoperated contralateral knee and tibial varus deformity of the operated knee could be important factors related to arthroplasty failure.

Clinical relevance

This long-term follow-up result of Press-Fit Condylar cruciate-retaining arthroplasty was good considering it was an old design. The alignment of the operated knee and deformity of the unoperated contralateral knee are important clinical factors that should be paid attention to avoid unexpected arthroplasty failure.

Level of evidence

IV.     

Decreased femoral head–neck offset: a possible risk factor for ACL injury

Purpose

Reduction in anterior cruciate ligament (ACL) injuries in young, active individuals continues to be a major goal in sports medicine. The purpose of this study was to determine the head–neck offset, as measured by AP pelvis alpha angles, in patients presenting to a single surgeon with isolated ACL and non-ACL knee injuries.

Methods

In a group of 48 patients with complete, primary ACL rupture and 42 controls with non-ACL injury (i.e., meniscus tear, cartilage defect), a single surgeon, blinded to the diagnosis, took radiographic measures of the AP alpha angle of both hips and the weight-bearing line at both knees. All knee pathology was confirmed with knee arthroscopy. Inclusion criteria included no previous hip or knee surgery, and long-leg standing alignment radiographic series completed at index visit.

Results

There was no difference in gender distribution, height, BMI or age between groups. ACL-injured patients had a significantly higher alpha angle (mean = 84, SD = 14) on the injured side than the controls (mean = 59, SD = 7, p < 0.0001). Ninety-four percent of the ACL-injured group had alpha angles over 60°, while only 35% of the non-ACL-injured group had alpha angles over 60° (p = 0.001). Those patients with alpha angle over 60° were 27 times more likely (95% CI 6.4–131) to be in the ACL injury group than those patients with alpha angle 60° or less (p = 0.001).

Conclusion

Our findings establish an important preliminary correlation between ACL injury and diminished femoral head–neck offset, as characterized by abnormal, elevated alpha angles.

Level of evidence

Prognostic study, Level III.     

Significance of asymmetrical posteromedial and posterolateral femoral condylar chamfer cuts in total knee arthroplasty

Purpose

Orthopedic surgeons remove more bone from the posteromedial femoral condyle than the posterolateral condyle to achieve the desired femoral component rotation. Here, the correlation between the asymmetry of chamfer cuts and femoral component rotation in total knee arthroplasty was determined.

Methods

A model was built to simulate anterior chamfer cuts performed during total knee arthroplasty to measure posterior condylar offset. Right knee axial magnetic resonance imaging slices were examined from 280 consecutive patients (142 men, 138 women; mean age 31.4 ± 6.6 years). The anatomic and surgical transepicondylar axes, as well as the posterior condylar joint line, were drawn. Differences in the posteromedial and posterolateral offsets and the femoral rotation angles relative to the posterior joint line were measured.

Results

The mean surgical femoral rotation angle was 4.8° ± 1.2°, and the mean posterior condylar offset difference was 4.4 ± 1 mm, with a strong correlation (p < 0.0001; r = 0.803). There was no statistically significant difference between genders. Linear regression analyses revealed that a 0.8-mm difference between the anteroposterior dimensions of the medial and lateral posterior condylar offsets corresponded to 1° of femoral external rotation (p < 0.0001, R ² = 0.645).

Conclusion

The accuracy of the applied technique intra-operatively can be verified by correlating the asymmetry of posterior chamfer cuts with the achieved femoral component rotation, as determined by measuring the thicknesses of posterior chamfer cuts with a caliper. Technical errors can also be minimized by confirming the association between the femoral component rotation—as predicted by the posterior condylar offset difference—and the preoperatively measured femoral rotation angle.

Level of evidence

II.     

Periprosthetic supracondylar femoral fractures above total knee arthroplasty: comparison of the locking and non-locking plating methods

Purpose

The purpose of this study was to compare the results and complications of periprosthetic supracondylar femoral fracture treatment using locking or non-locking plates.

Methods

A locking compression plate was used in 14 patients, and a non-locking condylar buttress plate was used in 19 patients. There were no significant differences in the demographic data between the two groups. The primary healing rate and bone union time were compared. The Knee Society knee score and range of motion (ROM) were reviewed. The femorotibial angle and α and γ angles were measured using the Knee Society radiological evaluation method. The clinical and radiographic results, complications, and additional surgeries were compared between the two groups.

Results

Thirteen of 14 locking plating patients and 11 of 19 non-locking plating patients healed without any additional surgeries. There were no differences in the average bone union time, knee score, or ROM between the two groups. The alignment and position of the implants were better without a loss in the reduction angle of >3° in the locking plating group compared with the non-locking plating group. Locking plate fixation reduced the incidence of overall complications, non-union, malunion, loss of reduction, and additional surgeries compared with non-locking plate fixation.

Conclusion

Fixation of periprosthetic supracondylar femoral fractures with a locking plate provided satisfactory results with a low risk of complications and additional surgeries compared with fixation with a non-locking plate.

Level of evidence

III.     

Analysis of mandibular condylar and glenoid fossa fractures with computed tomography

Objectives

The purpose of this study was to investigate the prevalence of glenoid fossa and condylar fractures in patients with mandibular fractures using multidetector computed tomography (MDCT).

Methods

A prospective study was performed in 227 patients with mandibular fractures who underwent 64-MDCT. Mandibular fractures were classified into four types: median, paramedian, angle and condylar. Statistical analysis of the relationship between prevalence of condylar fractures and mandibular fracture locations was performed using χ² test with Fisher’s exact test. A P value less than 0.05 was considered statistically significant.

Results

The prevalence of condylar fracture was 64.8 % of all patients with mandibular fractures, 66.7 % of median type (P?=?0.667), 45.5 % of paramedian type (P?=?0.001) and 12.3 % of angle type (P?=?0.000), respectively. Furthermore, glenoid fossa fracture was seen in 1.4 % of patients with condylar fractures.

Conclusions

The results of the presented study suggest focusing also on incidental findings such as glenoid fossa fractures.

Key Points

? The prevalence of condylar fracture was 64.8 % in patients with mandibular fractures. ? Glenoid fossa fracture was seen in 1.4 % of patients with condylar fractures. ? The study suggests a focus on incidental findings such as glenoid fossa fractures.     

Mid-term clinical results of alumina medial pivot total knee arthroplasty

Purpose

The medial pivot total knee prosthesis has been designed to reproduce physiological knee kinematics. It has been reported that alumina ceramic femoral components reduce polyethylene wear. Thus, medial pivot total knee prostheses with alumina ceramic femoral components were introduced. The purpose of this study was to evaluate the clinical results of patients who underwent newly introduced alumina medial pivot total knee arthroplasties (TKA).

Methods

We evaluated the clinical results of 107 alumina medial pivot TKAs in 80 consecutive patients with a mean follow-up period of 5?years.

Results

Alumina medial pivot TKAs provided significant improvements in the patients’ Knee Society knee scores, function scores and post-operative ranges of motion compared with their pre-operative statuses (each, P?Conclusions This study demonstrates satisfactory mid-term clinical results for patients receiving the alumina medial pivot prosthesis.

Level of evidence

Therapeutic study, Level IV.     

Radiological findings for hip dysplasia at skeletal maturity. Validation of digital and manual measurement techniques

Objective

To report on intra-observer, inter-observer, and inter-method reliability and agreement for radiological measurements used in the diagnosis of hip dysplasia at skeletal maturity, as obtained by a manual and a digital measurement technique.

Materials and methods

Pelvic radiographs from 95 participants (56 females) in a follow-up hip study of 18- to 19-year-old patients were included. Eleven radiological measurements relevant for hip dysplasia (Sharp’s, Wiberg’s, and Ogata’s angles; acetabular roof angle of T?nnis; articulo-trochanteric distance; acetabular depth-width ratio; femoral head extrusion index; maximum teardrop width; and the joint space width in three different locations) were validated. Three observers measured the radiographs using both a digital measurement program and manually in AgfaWeb1000. Inter-method and inter- and intra-observer agreement were analyzed using the mean differences between the readings/readers, establishing the 95% limits of agreement. We also calculated the minimum detectable change and the intra-class correlation coefficient.

Results

Large variations among different radiological measurements were demonstrated. However, the variation was not related to the use of either the manual or digital measurement technique. For measurements with greater absolute values (Sharp’s angle, femoral head extrusion index, and acetabular depth-width ratio) the inter- and intra-observer and inter-method agreements were better as compared to measurements with lower absolute values (acetabular roof angle, teardrop and joint space width).

Conclusion

The inter- and intra-observer variation differs notably across different radiological measurements relevant for hip dysplasia at skeletal maturity, a fact that should be taken into account in clinical practice. The agreement between the manual and digital methods is good.     

A biomechanical analysis of the soft tissue and osseous constraints of the hip joint

Purpose

The goal of this study was to determine the role of soft tissue and osseous constraints in hip biomechanics using a unique robotic testing apparatus.

Methods

Four fresh-frozen human cadaveric hemi-pelvises without degenerative changes or dysplasia were stripped of all soft tissue except the ligamentous capsule and the intra-articular structures. All hips were tested using a robotic manipulator/universal force-moment sensor testing system to measure and compare end-range of motion (ROM) and kinematic translations in “capsule vented” (a small hole in the capsule) and “capsule separated” (capsular ligaments separated from each other) states. Then, the “capsule vented” state was compared to the condition in which the capsule and labrum were removed to calculate bone and soft tissue forces with 40 N of load applied in six different directions along three axes.

Results

There were no significant differences in end-ROM or kinematic translations between the “capsule vented” and “capsule separated” states. Bone forces significantly increased with loads applied in the anterior, posterior and superior directions. Soft tissue forces increased significantly with loads applied in the medial, lateral and inferior directions.

Conclusion

The individual hip capsular ligaments act independently of each other to resist end-ROM. Both osseous and soft tissue constraints are important to hip biomechanics depending upon the direction of applied force. The clinical relevance is that surgical management for hip disorders should preserve the soft tissue constraints in the hip when possible to maintain normal hip biomechanics.     

Quantifying the contribution of pincer deformity to femoro-acetabular impingement using 3D computerised tomography

Objective

To provide a simple, reliable method for the three-dimensional quantification of pincer-type hip deformity.

Materials and methods

Computerised tomography scans of 16 normal female hips and 15 female hips with clinical femoro-acetabular impingement (FAI) and radiographic signs of pincer secondary to acetabular protrusio were analysed. After orientating the pelvis in the anterior pelvic plane, the acetabular centre was determined, and the ratios of its coordinates to the corresponding pelvic dimensions were calculated. Acetabular coverage of the femoral head and centre-edge angles were also measured for the two groups.

Results

In hips with a pincer, the hip was medialised by 37?% (p?=?0.03), more proximal by 5?% (p?=?0.05) and more posterior by 9?% (p?=?0.03) compared with the normal hips. Coverage of the femoral head in protrusio hips was significantly greater than normal (average 71?% vs 82?%, p?=?0.0001). Both the lateral centre-edge angle and the combined anterior–posterior centre-edge angle were greater in protrusio hips than in the normal ones (48° vs 37 °, p?p?Conclusion Displacement in acetabular protrusio occurs in all planes. This CT-based method allows for the accurate and standardised quantification of the extent of displacement, as well as 3D measurement of femoral head coverage. In the adult female population, a combined centre-edge angle of over 190° suggests an acetabulum that is too deep and a potential cause of symptoms of femoro-acetabular impingement. Conversely, an acetabulum that has a combined centre-edge angle of less than 190° may be considered to be of normal depth, and therefore not contributing a pincer to FAI should it occur.     

Less femoral lift-off and better femoral alignment in TKA using computer-assisted surgery

Purpose

A comparison has been made between navigation-assisted and conventional measured resection total knee arthroplasty (TKA), under the hypothesis that navigation assistance would improve the precision and consistency of component alignment and femoral component rotation.

Methods

The following radiographic parameters were measured: mechanical femorotibial angle, coronal and sagittal component angle, and femoral component rotation. Femoral condylar lift-off was checked by axial radiographs, and thresholds for outliers were set at 1.0 mm.

Results

Clinical results obtained using Knee Society and Hospital for Special Surgery systems were not statistically different. The mean mechanical femorotibial angle was 2.2° (SD: 0.9) in the conventional group and 1.7° (SD: 0.7) in navigation group (p = 0.001). The mean coronal femoral component angle was 89.2° (SD: 2.2) in conventional group and 90.4° (SD: 1.8) in navigation group (p = 0.006). The mean transepicondylar-posterior condylar axis angle was 1.7° (SD: 0.9) in conventional group and 1.2° (SD: 0.5) in navigation group (p = 0.008). Femoral condylar lift-off greater than 1 mm occurred more frequently (p = 0.000) in conventional group.

Conclusion

Coronal plane stability and precision of femoral component rotation were impacted by navigation system. The use of a navigation system with measured resection TKA can help optimize coronal stability and parallel component position.

Level of evidence

Retrospective case control study, Level IV.