Introduction. Limb-length discrepancy (LLD) is a common postoperative complication after total hip arthroplasty (THA). This study focuses on the correlation between patients’ perception of LLD after THA and the anatomical and functional leg length, pelvic and knee alignments and foot height. Previous publications have explored this topic in patients without significant spinal pathology or previous spine or lower extremity surgery. The objective of this work is to verify if the results are the same in case of stiff or fused spine. Methods. 170 patients with stiff spine (less than 10° L1-S1 lordosis variation between standing and sitting) were evaluated minimum 1 year after unilateral primary THA implantation using EOS® images in standing position (46/170 had previous lumbar fusion). We excluded cases with previous lower limbs surgery or frontal and sagittal spinal imbalance. 3D measures were performed to evaluate femoral and tibial length, femoral offset, pelvic obliquity, hip-knee-ankle angle (HKA), knee flexion/hyperextension angle, tibial and femoral rotation. Axial pelvic rotation was measured as the angle between the line through the centers of the hips and the EOS x-ray beam source. The distance between middle of the tibial plafond and the ground was used to investigate the height of the foot. For data with normal distribution, paired Student's t-test and independent sample t-test were used for analysis. Univariate logistic regression was used to determine the correlation between the perception of limb length discrepancy and different variables. Multiple logistic regression was used to investigate the correlation between the patient perception of LLD and variables found significant in the univariate analysis. Significance level was set at 0.05. Results. Anatomical femoral length correlated with patients’ perception of LLD but other variables were significant (the height of the foot, sagittal and frontal knee alignment, pelvic obliquity and pelvic rotation more than 10°). Interestingly some factors induced an unexpected perception of LLD despite a non-significant femoral length discrepancy less than 1cm (pelvic rotation and obliquity, height of the foot). Conclusions. LLD is a multifactorial problem. This study showed that the anatomical femoral length as the factor that can be modified with THA technique or choice of prosthesis is not the only important factor. A comprehensive clinical and radiological evaluation is necessary preoperatively to investigate spinal stiffness, pelvic obliquity and rotation, sagittal and coronal knee alignment and foot deformity in these patients. Our study has limitations as we do not have preoperative EOS measurements for all patients. We cannot assess changes in leg length as a result of THA. We also did not investigate the degree of any foot deformities as flat foot deformity may potentially affect the patients perception of the leg length. Instead, we measured the distance between the medial malleolus and ground that can reflect the foot arch height. More cases must be included to evaluate the potential influence of pelvis anatomy and functional orientation (pelvic incidence, sacral slope and pelvic tilt) but this study points out that spinal stiffness significantly decreases the LLD tolerance previously reported in patients without degenerative stiffness or fusion

Introduction. Leg length discrepancy (LLD) in patients with unilateral developmental dysplasia of the hip (DDH) can be problematic for both patients and surgeons. Patients can acquire gait asymmetry, back pain, and arthritis. Surgical considerations include timing of correction and arthroplasty planning. This study audits standing long leg films performed at skeletal maturity in our patients. The aim of this study is to identify if surgical procedure or AVN type could predict the odds of needing an LLD Intervention (LLDI) and influence our surveillance. Materials and Methods. Hospital database was searched for all patients diagnosed with DDH. Inclusion criteria were patients with appropriately performed long leg films at skeletal maturity. Exclusion criteria were patients with non DDH pathology, skeletally immature and inadequate radiographs. All data was tabulated in excel and SPSS was used for analysis. Traumacad was used for measurements and AVN and radiologic outcome grades were independently classified in duplicate. Results. 110 patients were identified. The mean age of follow-up was 15 years with final average LLD of 1mm(±5mm). The DDH leg tended to be longer and length primarily in the femur. 31(28.2%) patients required an LLDI. 19 Patients had a final LLD >1.5cm. There was no statistical significant difference in the odds of needing an LLDI by type of surgical procedure or AVN. AVN type 4 was associated with greatest odds of intervention. The DDH leg was more likely to require ipsilateral epiphysiodesis or contralateral lengthening in Type 1 and 2 AVN. Conclusions. The DDH leg tends to be longer, leg lengths should be monitored, and leg length interventions are frequently required irrespective of previous DDH surgical procedure or the presence of AVN

Introduction. While THA is associated with positive results and long-term improvement in patient quality of life, outcomes are nonetheless associated with adverse events and post-procedural deficits related to discrepancies in leg length (LLD), offset and cup placement. Post-THA errors in these parameters are associated with gait alteration, low back pain and patient dissatisfaction. Such discrepancies often necessitate revision and increasingly lead to medical malpractice litigation. Maintaining accuracy in post-surgical leg length, offset and cup placement during THA is difficult and subject to error. The sensitivity of these factors is highlighted in studies that have shown that a change of as little as 5 degrees of flexion or abduction can induce alterations in leg length of up to several millimeters. Similarly, positioning of implants can alter global and femoral offset, affecting abductor strength, range of motion and overall physical function. Compounding the biochemical issues associated with inaccurate leg length are the costs associated with these deficits. Traditional freehand techniques of managing intra-operative parameters rely on surgeon experience and tissue tensioning to manually place components accurately. These methods, however, are only able to assess leg length and are subject to inaccuracies associated with patient movement or orientation changes during surgery. Mechanical methods of minimizing post-surgical discrepancies have been developed, such as outrigger or caliper devices, although these methods also address leg length only and provide poor feedback regarding offset and center of rotation, therefore providing insufficient data to accurately achieve appropriate post-surgical leg length. Computer-assisted navigation methods provide more data regarding leg length, offset and center of rotation, but are limited by their cumbersome nature and the large capital costs associated with the systems. The Intellijoint HIP. ®. surgical smart tool (Intellijoint Surgical, Inc., Waterloo, ON) is an intra-operative guidance tool that provides surgeons with real time data on leg length, offset and center of rotation, thereby allowing for confident selection of the correct implant in order to ensure appropriate post-surgical biomechanics. The early clinical results from an initial cohort of patients indicate that Intellijoint HIP. ®. is safe and effective. No adverse events were reported in the initial cohort, and the smart tool was able to measure surgical parameters to within 1mm when compared to radiographic measurements. With training cases removed, 100% of cases had a post-procedure leg length discrepancy of less than 5mm. This paper describes the indications, procedural technique and early clinical results of the Intellijoint HIP. ®. smart tool, which offers a safe, accurate and easy-to-use option for hip surgeons to manage leg length, offset and cup position intra-operatively

Objective. Open-wedge high tibial osteotomy (OWHTO) involves performing a corrective osteotomy of the proximal tibia and removing a wedge of bone to correct varus alignment. Although previous studies have investigated changes in leg length before and after OWHTO using X-rays, none has evaluated three-dimensional (3D) leg length changes after OWHTO. We therefore used 3D preoperative planning software to evaluate changes in leg length after OWHTO in three dimensions. Methods. The study subjects were 55 knees of 46 patients (10 men and 36 women of mean age 69.9 years) with medial osteoarthritis of the knee or osteonecrosis of the medial femoral condyle with a femorotibial angle of >185º and restricted range of motion (extension <–10º, flexion <130º), excluding those also suffering from patellofemoral arthritis or lateral osteoarthritis of the knee. OWHTO was simulated from computed tomography scans of the whole leg using ZedHTO 3D preoperative planning software. We analyzed the hip-knee-ankle angle (HKA), flexion contracture angle (FCA), mechanical medial proximal tibial angle (mMPTA), angle of correction, wedge length, 3D tibial length, 3D leg length, and 3D increase in leg length before and after OWHTO. We also performed univariate and multivariate analysis of factors affecting the change in leg length (preoperative and postoperative H-K-A angle, wedge length, and correction angle). Results. Mean HKA increased significantly from −4.7º ± 2.7º to 3.5º ± 1.3º, as did mean mMPTA from 83.7º ± 3.3º to 92.5º ± 3.0º (p <0.01). Mean FCA was 4.7º ± 3.6° preoperatively and 4.8º ± 3.3º postoperatively, a difference that was not significant (p = 0.725). The mean correction angle was 9.1º ± 2.8º and the mean wedge length was 9.4º ± 3.2º mm. Mean tibial length increased significantly by 4.7 ± 2.3 mm (p <0.01), and mean leg length by 5.6 ± 2.8 mm (p <0.01). The change in leg length was strongly correlated with wedge length (R = 0.846, adjusted R. 2. = 0.711, p <0.01). Discussion and Conclusion. Mean 3D leg length after OWHTO increased significantly by 5.4 ± 3.1 mm. A difference in leg length of >5 mm is believed to affect back pain and gait abnormalities, and changes in leg length must therefore be taken into consideration. The 3D dimensional change in leg length was strongly correlated with wedge length, and could be predicted by the formula (change in leg length in mm) = [(wedge length in mm) ×0.75) − 1.5]. For any figures or tables, please contact authors directly

Leg length inequality, both actual and functional, is the most important cause of disappointment for the surgeon and his patient. The reported incidence of leg length inequality of 1 cm has been reported to be between 23% and 50%, and half of these patients require a lift in their shoe. In the author’s opinion, there is a relationship between leg length and stability of the hip. Increase in leg length and offset improves soft tissue tension and reduces the dislocation rate. The goal at surgery is:. To restore the center of rotation for the hip. To restore offset, i.e. abductor moment arm. To restore hip center to lesser trochanter difference. The various tests for hip stability, soft tissue tension and contractures:. Assess component position. Assess for anterior impingement. Assess for tight anterior capsule. Assess for tight iliotibial band (Ober’s test). Assess for tight rectus, iliopsoas and adductors. Correct soft tissue balance. Leg length inequality is caused by:. Increase in anatomic leg length or offset or both. Tight anterolateral structures, which include:. IT band. Anterior and lateral capsule and gluteus maximus. Adduction contractures of the opposite hip. Spinal deformity causing pelvic tilt. Excessive trochanteric advancement causing abduction contracture

Typical devices to limit leg length changes rely on a fixed point in the ileum and femur in order to measure leg length changes intraoperatively. The aim of this study is to determine the ideal position for placement of these devices and to identify potential sources of error. Using saw bones the leg length device was attached at four different positions along the iliac crest extending from the ASIS to its midpoint. After marking the femur on the lateral edge of the Greater Trochanter, measurements were taken with gradually increasing leg length from each individual position on the ileum. This was also performed for different degrees of hip flexion. It was determined that when the hip was in an extended position the degree of error was small for all positions along the iliac crest, with a tendency for an increase error the closer the pin is to the ASIS. When the hip is flexed the error is increased with pin positions closer to the ASIS. With a lengthening of 10 mm, minimal leg length changes can be determined using the device. More than 20 mm resulted in significant change using the leg length device. Ideal iliac crest pin position is towards the midpoint of the iliac crest, which will minimise the potential error. Measuring the leg length while the hip is in a neutral position will limit the error and increase the accuracy—thus avoiding unwanted lengthening

Introduction. Leg length discrepancy is a significant concern after total hip replacement (THR). We hypothesised that the intra-operative use of a navigation system was able to accurately control the leg length during THR. Material. 50 cases have been prospectively analysed. There were 29 men and 21 women, with a mean age of 66.1 years (range, 50 to 80 years), all operated on for THR for end-stage hip osteoarthritis. Methods. All procedures were performed with a non-image based navigation system. The expected correction of the leg length was defined prior to the procedure. The leg length was recorded before any bone resection by the 3D-distance between the pelvic and the femoral navigation trackers when placing the operated leg in a position near the anatomic one. The THR was performed according to the indication of the navigation system. The vertical positioning of the femoral component and the length of the prosthetic neck were defined to achieve the expected planning; however a correction was allowed to compensate for excessive muscular tension or risk of prosthetic instability according to the surgeon's judgment. The final leg length was recorded with the same technique as previously, with an accurate control of the repositioning of the limb in the 3D space by the navigation system. The length variation before and after THR measured by the navigation system was compared to the planning and to a conventional radiographic measurement on plain, standing pelvic X-rays with a Wilcoxon test at a 5% level of significance. The linear correlation coefficient between the different techniques was calculated. The agreement between the different techniques was assessed according to Bland-Altman. Results. The mean planned leg length change was 7.1 ± 6.1 mm. The mean leg length variation was 9.7 ± 4.2 mm as measured by the navigation system, and 11.0 ± 9.2 mm as measured on plain X-rays. The expected goal was achieved within 5 mm for 45 patients (90%). There was no significant difference between paired navigated and radiographic measurements (p=0.46). There was no significant difference between the planning variation and the navigated measurements (p=0.15). There was a good correlation between the planning variation and the navigated measurements (R. 2. =0.59, p<0.001). There was a good coherence between the planning variation and the navigated measurements. Discussion. The hypothesis of the current study was confirmed. The navigation system used in the current study was able to control very accurately the leg length change during THR. This technique of measurements may be more accurate and more precise than any conventional technique of intra-operative leg length control. The incidence of changes in the implant size or position can be easily detected, and the best compromise may be chosen intra-operatively

Introduction: Leg length inequality (LLI) following arthroplasty, though often asymptomatic, can be cause for considerable morbidity and has increasing medicolegal consequences. There are various methods of quantifying leg length inequality on plain AP radiograph. The aim of this study is to review the established practice in the measurement of leg length inequality and compare it to two methods used locally. Methods: This is a retrospective study assessing the radiographs of 35 patients with a mix of native, unilateral and bilateral total hip arthroplasty. Two methods of measuring leg length inequality were prominent in the literature, the Woolson method and the Williamson method. A further two methods are used locally. Measurements for all four techniques were made by two senior consultant radiologist to on the trust PACS to assess inter and intra observer variability. Data analysis was performed using SPS 16 to produce intraclass correlation co-efficient (ICC) and Bland Altman plots. Results: ICC for all methods in the measurement of LLI is excellent (≥0.90). The repeatability ICC for the four methods is; Woolson 0.65, Williamson 0.87, Direct 0.96 and the Leeds method 0.95. Discussion: This study demonstrates that all four methods have excellent correlation; however the repeatability is better for the Direct and the Leeds methods than the two that are more widely used in the literature. While the Direct measurement is able to give an overall measurement for the leg length inequality, the Leeds method is able to distinguish between any inequality due to cup malpostion and stem malposition. It is therefore of particular value in the assessment of bilateral or revision arthroplasty and the audit of practice

Summary. The mathematical model has proven to be highly accurate in measuring leg length before and after surgery to determine how leg length effects hip joint mechanics. Introduction. Leg length discrepancy (LLD) has been proven to be one of the most concerning problems associated with total hip arthroplasty (THA). Long-term follow-up studies have documented the presence of LLD having direct correlation with patient dissatisfaction, dislocation, back pain, and early complications. Several researchers sought to minimize limb length discrepancy based on pre-operative radiological templating or intra-operative measurements. While often being a common occurrence in clinical practice to compensate for LLD intra-operatively, the center of rotation of the hip joint has often changes unintentionally due to excessive reaming. Therefore, the clinical importance of LLD is still difficult to solve and remains a concern for clinicians. Objective. The objective of this study is two-fold: (1) use a validated forward-solution hip model to theoretically analyze the effects of LLD, gaining better understanding of mechanisms leading to early complication of THA and poor patient satisfaction and (2) to investigate the effect of the altered center of rotation of the hip joint regardless LLD compensation. Methods. The theoretical mathematical model used in this study has been previously validated using fluoroscopic results from existing implant designs and telemetric devices. The model can be used to theoretically investigate various surgical alignments, approaches, and procedures. In this study, we analyzed LLD and the effects of the altered center of rotation regardless of LLD compensation surgeons made. The simulations were conducted in both swing and stance phase of gait. Results. During swing phase, leg shortening lead to loosening of the hip capsular ligaments and subsequently, variable kinematic patterns. The momentum of the lower leg increased to levels where the ligaments could not properly constrain the hip leading to the femoral head sliding from within the acetabular cup (Figure 1). This piston motion led to decreased contact area and increased contact stress within the cup. Leg lengthening did not yield femoral head sliding but increased joint tension and contact stress. A tight hip may be an influential factor leading to back pain and poor patient satisfaction. During stance phase, leg shortening caused femoral head sliding leading to decreased contact area and an increase in contact stress. Leg lengthening caused an increase in capsular ligaments tension leading to higher stress in the hip joint (Figure 2). Interestingly, when the acetabular cup was superiorized and the surgeon compensated for LLD, thus matching the pre-operative leg length by increasing the neck length of the femoral implant, the contact forces and stresses were marginally increased at heel strike (Figure 3). Conclusion and Discussion. Altering the leg length during surgery can lead to higher contact forces and contact stresses due to tightening the hip joint or increasing likelihood of hip joint separation. Leg shortening often lead to higher stress within the joint. Further assessment must be conducted to develop tools that surgeons can use to ensure post-operative leg length is similar to the pre-operative condition. For any figures or tables, please contact authors directly

Introduction:. High tibial osteotomy (HTO) is a common treatment for medial compartment arthritis of the knee in younger, more active patients. The HTO shifts load away from the degenerative medial compartment and into the lateral compartment. This change can be accomplished with either a lateral closing or a medial opening wedge HTO. An HTO also potentially affects leg length. Mathematical models predict that the osteotomy type (opening versus closing) and the magnitude of the correction determine the change in leg length, but no in vivo studies have been published. The purpose of this study is to quantify and compare leg length change following opening and closing wedge HTO. Study Design:. Retrospective cohort study – Level III evidence. Methods:. Thirty-two medial opening and 32 lateral closing HTO's were selected from patients treated at our institution between 2006 and 2009. Pre-operative and one-year post-operative full-length lower extremity radiographs were obtained along with operative reports. Pre- and post-operative coronal plane alignment and leg length were measured and surgical details were collected. Results:. The 64 osteotomies were performed in 62 patients (43 male, 19 female) at an average age of 57 years. The mean opening wedge was 9.3 mm (range: 5 to 17 mm) and the mean closing wedge was 8.0 mm (range: 6 to 10 mm). Knee alignment changed from a mean of 174 degrees pre-operatively to a mean of 183 degrees post-operatively in both groups. In the medial opening wedge group, total leg length was found to increase from 836.3 ± 63.5 mm pre-operatively to 841.8 ± 64.1 post-operatively, a change of 5.5 ± 4.4 mm (p < 0.0001). A significant correlation was found between the amount of correction and the increase in overall leg length (r. 2. = 0.21, p = 0.009). In the lateral closing wedge group, total leg length was found to decrease from 840.6 ± 51.5 mm pre-operatively to 837.9 ± 52.0 post-operatively, a decrease of 2.7 ± 4.0 mm (p = 0.0008). No correlation was found between the amount of correction and the change in overall leg length. The difference in mean leg length change between opening and closing wedge osteotomies was 8.2 ± 5.9 mm (p < 0.0001). Conclusions:. Medial opening wedge HTO can result in significant leg lengthening depending on the degree of opening. Leg length changes associated with lateral closing wedge HTO are generally smaller. Both techniques results in less leg length change than mathematical models predict. Pre-operative leg length discrepancy should be considered when choosing an osteotomy technique

Introduction. Leg length and offset are important considerations in total hip arthroplasty (THA). Navigation systems are capable of providing intra-operative measurements of leg length and offset, and high accuracy has been shown in experimental studies. Objective. This in-vivo study assesses the accuracy of an imageless navigation system, with a pin-less femoral array, in measuring offset and leg length changes. Method. A prospective, consecutive series of 24 patients undergoing navigated total hip arthroplasty were included in the study. Intra-operative measurements of leg length and offset were recorded using the navigation system. For each patient pre- and post-operative digital radiographs were scaled and analysed to provide radiographic measurements of change in leg length and offset. Results. Measurements of leg length change made by the navigation system showed a statistically significant correlation with the size of change measured radiographically (R=.77, P < 0.0001). The mean difference between the radiographic and navigational measurement was 0.4 ± 2.8 mm. The navigation system was accurate to within 1 mm of the radiographic measurement in 50% of cases, within 2 mm in 67% of cases, and within 5 mm in 96% of cases. Measurements of offset change by the navigation system also showed a statistically significant correlation with radiographic measurements, however the correlation was less pronounced (R=.47, P=0.02). The mean difference between navigational and radiographic measurements was 1.4 ± 6.4 mm. The navigation system was accurate to within 1 mm of the radiographic measurement in 8% of cases, within 2 mm in 25% of cases, and within 5 mm in 75% of cases. Conclusion. This study demonstrates in-vivo that an imageless, non-invasive navigation system is a reliable tool for intra-operative leg length and offset measurement

We have developed a technique with the underlying principle being that the difference in height between what is removed and what is inserted will determine the leg length correction (Figure 1). The height of the implant to be inserted is determined from the manufacturer's specifications. We have developed a Vertical Measurement Tool to accurately and reproducibly determine the height of the resected bone (Figure 2). Leg length correction = a−b−c+d. Vertical Measurement Tool validation was performed by 4 separate surgeons on 20 resected femoral heads in the laboratory. Inter and intra-observer error was assessed. Fifty patients were assessed clinically and radiologically, to assess if desired leg length correction was achieved. Statistical analysis showed the device to be accurate with high intra and inter observer reliability. Differences between the observers were tested using a general linear model in a repeated measure design. No main effect and interaction effects were found. Intra operatively the resected head was measured and the formula was applied. The range of desired correction was 0mm to 18mm. In all cases the post-operative correction was within 4mm of the pre-operative planned correction. Statistical analysis showed that a linear Regression with ‘Actual’ as dependent and ‘Lambda’ as independent variables resulted in R= 0.889. We believe that it is consistently possible to achieve a leg length correction to within 5 mm of the pre-operative plan using the Vertical Measurement System. The system is simple and reproducible even in the hands of relatively inexperienced surgeons. For any figures or tables, please contact the authors directly by clicking on ‘Info & Metrics’ above to access author contact details

Introduction. One of the more common complaints from patients in their post-operative total knee arthroplasty (TKA) is the perceived feeling of the operative leg feeling longer than the non-operative leg. Studies have shown that the leg length discrepancies may occur in up to 80% of patients following unilateral TKA patients. The purpose of this study was to determine the incidence of leg length discrepancy (LLD) after primary TKA as well as determine the correlation between deformity and incidence of LLD. Methods. We retrospectively reviewed 1108 patients who underwent a primary unilateral TKA at a single institution. 97 patients were excluded for lack of imaging, prior total hip replacement or body mass index greater than 40 kg/m2. Hip to ankle biplanar radiographs were obtained pre-operative and 6 weeks postoperatively for all patients. Two independent observers measures leg length, femur length, tibia length, overall alignment and deformity present for all radiographs. Results. 1,101 patients were included. Mean overall lengthening was 3.4 mm [Range −21 to 22.8mm; SD 7.4] with 81% of limbs lengthened. In our cohort, 9% of patients had LLD greater than 10 mm and 43% of patients had LLD of more than 5mm after TKA. Post-operative radiographic LLD was associated with increased pre-operative LLD (P<.001) and with female gender (p=0.03). Patients with pre-operative valgus deformity were more likely to have an increased lengthening of greater than 5mm compared to patients with varus deformity (OR:1.66). Conclusion. 43% of patients will have a LLD >5mm following correction of deformity and ligament balances in knee replacement surgery. Surgeons should be aware and this should be reviewed with patients as part of their expectations of surgery. For figures, tables, or references, please contact authors directly

Aims. There is no consensus about the best method of achieving equal leg lengths at total hip arthroplasty (THA) in patients with Crowe type-IV developmental dysplasia of the hip (DDH). We reviewed our experience of a consecutive series of patients who underwent THA for this indication. Patients and Methods. We retrospectively reviewed 78 patients (86 THAs) with Crowe type-IV DDH, including 64 women and 14 men, with a minimum follow-up of two years. The mean age at the time of surgery was 52.2 years (34 to 82). We subdivided Crowe type-IV DDH into two major types according to the number of dislocated hips, and further categorised them into three groups according to the occurrence of pelvic obliquity or spinal curvature. Leg length discrepancy (LLD) and functional scores were analysed. Results. Type-I included 53 patients with unilateral dislocation, in which 25 (category A) had no pelvic obliquity or spinal deformity, 19 (category B) had pelvic obliquity with a compensated spinal curvature and nine (category C) had pelvic obliquity and decompensated spinal degenerative changes. Type-II included 25 patients with one dislocated and one dysplastic hip, in which there were eight of category A, 15 of category B and two of category C. Pre-operatively, there were significant differences between the anatomical and functional LLD in type-IB (p = 0.005) and -IC (p < 0.001), but not in type-IA, -IIA or -IIB. Post-operatively, bony LLD increased significantly in types-IB, -IC and -IIB, whereas functional LLD decreased significantly in each type except for IIA. The mean functional LLD decreased from 30.7 mm (standard deviation (. sd. ) 18.5) pre-operatively to 6.2 mm (. sd. 4.4) post-operatively and the mean anatomical LLD improved from 35.8 mm (. sd. 19.7) pre-operatively to 12.4 mm (. sd. 8.3) post-operatively. Conclusion. Pelvic and spinal changes are common in patients with Crowe type-IV DDH and need to be taken into consideration when planning THA, in order to obtain equal leg lengths post-operatively. The principal subdivisions of Crowe type-IV DDH which we describe proved effective in achieving equal leg lengths and satisfactory outcomes. Cite this article: Bone Joint J 2017;99-B:872–9

Introduction: Modular prostheses were first developed for use in total hip arthroplasty (THA) in the 1980s as a potential solution to the problem of leg length inequality. There is much literature discussing the advantages and disadvantages of modularity in THA but there are few studies directly comparing modular and non-modular prostheses and their accuracy in restoring normal anatomy. Our aim was to assess whether modularity in THA improves the restoration of femoral offset and leg length. Methods: An analysis of post-operative radiographs of 76 patients who underwent THA - 38 using modular and 38 using non-modular prostheses was undertaken. The femoral offset and leg length of the operated and un-operated hip were measured for each patient. Inter-and intra-observer errors were reduced to a minimum. A two-tailed T test was then applied to the data. Results: Restoration of leg length (to within +/− 10mm of the un-operated hip) was achieved in 81.6% of patients in the non-modular group, compared to 78.9% in the modular group (p=0.60). On average, the modular system increases leg length of the operated hip by 0.64mm compared to the non-modular system, which reduces leg length by 3.76mm (p=0.016). The femoral offset is restored to within 5mm of the un-operated hip in 60.5% of modular THA and in 55.3% using a non-modular prosthesis (P=0.48). On average, modular prostheses increased offset by 0.85mm and non-modular prostheses by 0.15mm (P=0.64). Discussion: The modular and non-modular hip prostheses are equally successful in achieving restoration of leg length and femoral offset to the pre-pathological state

Introduction. Leg length and offset are important considerations in total hip arthroplasty (THA). Navigation systems are capable of providing intra-operative measurements, which help guide the surgeon in leg length and offset adjustment. Objective. This controlled study investigates whether the use of computer navigation leads to more accurate achievement of pre-operative leg length and offset targets in THA. Method. A total of 61 patients were included in the study. A prospective, consecutive series of 24 patients undergoing navigated total hip arthroplasty were compared to an historic, consecutive series of 37 patients who underwent total hip arthroplasty without the use of navigation. The changes made to leg length and femoral offset were measured from scaled pre- and post-operative digital radiographs. The target changes to leg length and femoral offset were recorded from pre-operative digital templating sessions. Results. No statistically significant differences in terms of age, sex and body mass index were found between the two groups. Femoral offset targets were more closely achieved in the navigated cohort compared with the non-navigated group (P < 0.05). The mean deviation from the pre-operative target offset change was 2.9 ± 2.7 mm in the navigated group, and 5.1 ± 4.6 mm in the non-navigated group. For leg length, no statistically significant difference was found between the navigated and non-navigated cohorts in the difference between planned targets and radiographic changes (P=0.78). The mean deviation from target leg length change was 3.9 ± 2.9 mm in the navigated group and 4.2 ± 3.4 mm in the non-navigated group. When the navigation system was employed, procedure time was longer by a mean of 6 minutes, however this finding was not statistically significant (P=0.084). Conclusion. The use of navigation helps the surgeon to achieve their pre-operative goals for offset change. The navigation system was not shown to impact leg length management

Background. Leg length discrepancy real or perceived remains an important source of patient dissatisfaction after a total hip replacement. Pre-operative templating and intra-operative measurement has to be used to ensure an accurate restoration of the normal centre of rotation of the hip as well as equal leg lengths. Theoretically more bone has to be resected from the femur to maintain the centre of the femoral head in the same location. This is due to a smaller size of the prosthetic femoral head compared to the native femoral head. It was postulated that this was an accurate predictor of leg length after a total hip replacement. Methods. 56 consecutive patients who underwent a total hip replacement (cemented, uncemented or hybrid) had intra-operative measurements documented of their femoral head-neck resection distance. This was compared with the measurement of the femoral prosthesis that was inserted. A telephonic survey of the patients perceived leg equality as well as a radiological measurement of their actual leg lengths on a standing AP X-ray at 6 weeks post-operatively was done. Results. Forty eight of the 56 patients (85%) reported subjectively equal leg lengths. Eight patients reported unequal leg lengths, 5 longer and 3 shorter. Of the 5 cases that reported longer leg lengths 4 had more prosthesis inserted than bone resected. The 3 shorter reported legs also had more prosthesis inserted than bone resected in 2 cases. Of the 8 patients who reported unequal leg lengths only 3 were unequal on X-ray measurement (2 longer and 1 shorter). There was good correlation between the amount of bone resected versus prosthesis inserted and the patient's subjective evaluation of leg length discrepancy, but poor correlation between subjective leg length discrepancy and objective radiological evaluation. NO DISCLOSURES

Background. Total hip arthroplasty for Crowe type IV developmental dysplasia of the hip is a technically demanding procedure. Restoration of the anatomical hip center frequently requires limb lengthening in excess of 4 cm and increases the risk of neurologic traction injury. However, it can be difficult to predict potential leg length change, especially in total hip arthroplasty for Crowe type IV developmental hip dysplasia. The purpose of the present study was to better define features that might aid in the preoperative prediction of leg length change in THAs with subtrochanteric femoral shortening osteotomy for Crowe type IV developmental dysplasia of the hip. Patients and Methods. Primary total hip arthroplasties with subtrochanteric femoral shortening osteotomy were performed in 70 hips for the treatment of Crowe type IV developmental hip dysplasia. The patients were subdivided into two groups with or without iliofemoral osteoarthritis. Leg length change after surgery was measured radiographically by subtracting the amount of resection of the femur from the amount of distraction of the greater trochanter. Preoperative passive hip motion was retrospectively reviewed from medical records and defined as either higher or lower motion groups. Results. The preoperative flexion of patients without iliofemoral osteoarthritis was significantly higher than for patients with iliofemoral osteoarthritis. All hips without iliofemoral OA had higher motion. The preoperative flexion in the higher motion group both with and without iliofemoral OA was significantly greater than in the lower group with iliofemoral OA (Figure 1). Leg length change in patients without iliofemoral osteoarthritis was significantly greater than with iliofemoral osteoarthritis (Figure 2), and the higher hip motion group had greater leg length change in THA than the lower motion group. No clinical evidence of postoperative neurologic injury was observed in patients with iliofemoral OA. Postoperative transient calf numbness in the distribution of the sciatic nerve was observed in 2 of 25 hips without iliofemoral OA (8.0%), however, no sensory and motor nerve deficit was observed. Discussion. The authors hypothesized that preoperative hip motion could affect soft tissue contractures, and our findings suggest that the soft tissues surrounding the hip joint with iliofemoral OA should be more contracted than the hip without OA. We also found leg length change in the higher motion group was greater than in the lower motion group. Previous studies reported limb lengthening in excess of 4 cm could increase the risk of nerve palsy. Transient calf numbness in the distribution of the sciatic nerve was observed in 2 hips without iliofemoral OA and their leg length change was not greater than 4 cm. Our findings suggest that hips without iliofemoral OA should be paid attention to protect the nerves from excessive elongation. The current study identifies several features that might help predict leg length change during the preoperative planning of total hip arthroplasty for Crowe type IV developmental hip dysplasia

Introduction Leg length inequalities (LLIs) are a common finding in every orthopaedic practice. They can be classified into anatomical and functional LLIs. LLIs can e.g. cause gait and balance disabilities, low back pain and functional scoliosis of the spine. In patients with a total hip replacement a higher rate of aseptic loosening of the prosthesis was found when LLIs were present (Gurney 2002). Until today LLIs are treated statically by wooden blocs, which are placed under the shorter extremity, until the pelvis is levelled. However, the correction of LLIs should also be evaluated dynamically to examine the influence of correction onto the spine and pelvis during gait. Therefore, we seek to evaluate in this pilot study the influence of simulated LLIs on spine and pelvis during gait. Methods A total of 30 healthy subjects (17 females & 13 males) with an average age of 24.4 years were measured in this study. First, LLIs (1 to 4 cm) were simulated with the subjects standing on a simulation platform, which height could be controlled, as previously described (Betsch 2012). In addition, a specially designed sandal with different insole heights (1 to 4 cm) was used to simulate LLIs under dynamic condition while subjects were walking on a treadmill. Changes in pelvic position and spinal posture caused by the LLIS were measured using a rasterstereographic system (Formetric 4D motion, Diers International GmbH, Germany). All data were checked for Gaussian distribution by the Chi square test. Student t-tests were used to check for differences between the LLIs. The level of significance was set at p