Functional Safe Zone Is Superior to the Lewinnek Safe Zone for Total Hip Arthroplasty: Why the Lewinnek Safe Zone Is Not Always Predictive of Stability

Tezuka, T.; Heckmann, Nathanael; Bodner, Russell J.; Dorr, Lawrence D.

doi:10.1016/j.arth.2018.10.034

Cited by 206 publications

(185 citation statements)

References 24 publications

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“…It has been considered for several decades that the cup should be oriented within a safe zone defined as 15° ± 10° of anteversion and 40° ± 10° of inclination according to the anterior pelvic plane (APP) . Some authors mentioned that this safe zone is not suitable because of the extreme interindividual variation of the pelvic kinematics . During daily activities such as in the sitting, standing, and supine positions, the pelvic tilt varies substantially to modify the functional orientation of the acetabulum and to adjust the range of motion of the hip according to these different positions.…”

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confidence: 99%

“…5 Some authors mentioned that this safe zone is not suitable because of the extreme interindividual variation of the pelvic kinematics. [9][10][11][12] During daily activities such as in the sitting, standing, and supine positions, the pelvic tilt varies substantially to modify the functional orientation of the acetabulum and to adjust the range of motion of the hip according to these different positions. When the pelvis posteriorly tilts, as, for instance, in the sitting position, the acetabular anteversion is increased to enable higher flexion but reducing extension at the same time.…”

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confidence: 99%

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Accuracy and Precision of an Ultrasound‐Based Device to Measure the Pelvic Tilt in Several Positions

Dardenne

Pluchon

Letissier

et al. 2019

J of Ultrasound Medicine

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Objectives A new ultrasound‐based device is proposed to measure the patient‐specific pelvic tilt in different daily positions. The aim of this study was to assess the accuracy of this device as well as the intraobserver and interobserver precisions. Methods The accuracy was assessed by performing several tilt measurements with the device on a testing mechanical bench. The error was defined as the difference between the tilt measured with the device and the tilt provided by this test bench. Three physicians, a novice, an intermediate, and an expert user, were also asked to perform 10 measurements on 3 healthy volunteers with low, medium, and high body mass indices to analyze the intraobserver and interobserver precisions. These 10 measurements were performed in the standing, sitting, and supine positions. Results The mean accuracy of the device ± SD was 1.1° ± 0.7° (range, 0°–4.0°). The interobserver and intraobserver precisions were excellent whatever the body mass index and good to excellent according to the positions. There was no learning curve, and the time required to complete the measurements was approximately 5 minutes. Conclusions This study presents an accurate and precise noninvasive device for measurement of the pelvic tilt in different positions.

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confidence: 99%

mentioning

confidence: 99%

Accuracy and Precision of an Ultrasound‐Based Device to Measure the Pelvic Tilt in Several Positions

Dardenne

Pluchon

Letissier

et al. 2019

J of Ultrasound Medicine

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“…According to the Lewinnek safe zone (anteversion angle of 15°±10° and abduction angle of 40°±10°) [32] , we estimated the radiographic outcomes of the DAA and PA. Five studies [18-20, 28, 31] with a total of 503 patients were included in the comparison of the radiographic outcomes between the DAA and PA in primary THA. There was no significant difference between the two groups in the postoperative anteversion angle (MD=-0.01, 95% CI -4.21 to 4.20, p = 1.00, I 2 =96%, Fig.…”

Section: Radiographic Outcomesmentioning

confidence: 99%

Clinical, Functional and Radiographic Outcomes of Primary Total Hip Arthroplasty between Direct Anterior Approach and Posterior Approach: a Systematic Review and Meta-analysis

Peng

Zeng

et al. 2020

Preprint

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Background: The purpose of this systematic review and meta-analysis was to compare the direct anterior approach and posterior approach for primary total hip arthroplasty in terms of the clinical, functional and radiographic outcomes. Methods: We searched the PubMed and EMBASE databases and Cochrane Library from their inception to November 1, 2019. We searched for previously published articles and meta-analyses of randomized controlled trials. Results: A total of 7 randomized controlled trials with 600 participants met the inclusion criteria. Among these patients, 301 and 299 were included in the DAA and PA groups, respectively. The DAA was associated with a longer surgery by a mean duration of 13.74 min (95% CI 6.88 to 20.61, p < 0.0001, I 2 =93%). The postoperative early functional outcomes were significantly better in the DAA group than in the PA group, such as the Visual Analogue Scale (VAS) score at 1 day postoperatively (MD=-0.65, 95% CI -0.91 to -0.38, p < 0.00001, I 2 =0%), VAS score at 2 days postoperatively (MD=-0.67, 95% CI -1.34 to -0.01, p =0.05, I 2 =88%) and Harris Hip Score (HHS) at 6 weeks postoperatively (MD=6.05, 95% CI 1.14 to 10.95, p =0.02, I 2 =52%). There was no significant difference between the DAA and PA groups in the length of the incision, hospital length of stay (LOS), blood loss, transfusion rates or complication rates. We found no significant difference between the two groups regarding late functional outcomes, such as the VAS score at 12 months postoperatively or the HHS scores at 3, 6, and 12 months postoperatively. A significant difference in the radiographic outcomes was not detected. Conclusions: The DAA requires a longer surgery time than does the PA in primary total hip arthroplasty. The DAA yields better early functional recovery than does the PA. There was no significant difference between the two groups in terms of other clinical, complication-related, late functional or radiographic outcomes. The evidence on the superiority of the DAA is insufficient and needs to be studied further.

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“…[14][15][16] Originally, Elkins and colleagues 14 proposed narrowing the coronal safe zone inclination and anteversion from 37 o -46 0 and 12 o -22 0 , respectively. Tezuka et al 16 reported that using this method resulted in fewer hips implanted into the narrow safe zone but no change in the number of hips in the functional safe zone. As a result, the authors believe that the size and shape of coronal safe zones are not predictive of safety.…”

Section: Discussionmentioning

confidence: 99%

“…Esposito and colleagues 18 described a dislocation rate of 2.1% in 7,040 patients with 57% of dislocated hips positioned in the LSZ. More recently, Tezuka et al 16 used computer navigation to determine whether implanting cups within the LSZ resulted in cup placement within their defined functional safe zone. They found that 85.8% of acetabular cups implanted within the previously described LSZ were within the functional safe zone, meaning 14.2% of cups within the LSZ were not within the functional safe zone.…”

Section: Figure 1: Planned Ops Cups In Comparison To Lewinnek Safe Zonementioning

confidence: 99%

Patient-Specific “Safe Zones” Reduce the Rate of Dislocation after Total Hip Arthroplasty

Vigdorchik¹,

Cizmic²,

Novikov³

et al.

EPiC Series in Health Sciences

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INTRODUCTION: Most dislocations have been shown to occur within Lewinnek’s proposed safe zone (LSZ) for cup inclination (40°±10°) and anteversion (15°±10°). Using a functional and dynamic simulation that accounts for individual patient anatomy and variations in pelvic tilt, we created a patient-specific target orientation for the acetabular cup. The purposes of this study were to: (1) compare pre-operative acetabular cup parameters using this novel dynamic imaging sequence to the LSZ, and (2) describe rates of dislocation in patients whose pre-operative acetabular cup parameters were determined using dynamic imaging sequences.METHODS: We retrospectively reviewed 1,500 consecutive, primary THAs that underwent dynamic sitting and standing pre-operative acetabular cup planning. Using these inputs, we modeled an optimal cup position for each patient. Inclination, anteversion, pelvic tilt, pelvic incidence, lumbar flexion angles, and rates of dislocation were analyzed.RESULTS: Mean age of patients was 63 years. Mean pelvic tilt was 4.7o when supine, -0.3o when standing, and -0.7o when flex-seated. Mean pelvic incidence was 54o and mean lumbar flexion was 43o. Mean inclination was 40° and mean anteversion was 24°. Only 56% of the dynamically planned cups were within the LSZ (p<0.05). Mean inclination and anteversion difference between dynamic and LSZ was 1.3o and 8.9o, respectively. Only 0.5% of dynamically planned cups dislocated post-operatively, all were within LSZ.DISCUSSION: Acetabular cup positioning in patient-specific safe zones reduces the rate of dislocation after THA. Historical target parameters for cup inclination and anteversion significantly differ to target values obtained with the use of functional imaging.

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Functional Safe Zone Is Superior to the Lewinnek Safe Zone for Total Hip Arthroplasty: Why the Lewinnek Safe Zone Is Not Always Predictive of Stability

Cited by 206 publications

References 24 publications

Accuracy and Precision of an Ultrasound‐Based Device to Measure the Pelvic Tilt in Several Positions

Accuracy and Precision of an Ultrasound‐Based Device to Measure the Pelvic Tilt in Several Positions

Clinical, Functional and Radiographic Outcomes of Primary Total Hip Arthroplasty between Direct Anterior Approach and Posterior Approach: a Systematic Review and Meta-analysis

Patient-Specific “Safe Zones” Reduce the Rate of Dislocation after Total Hip Arthroplasty

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