Leg Length Adjustment Research Articles

The Value of Computed Tomography Scan in Three-dimensional Planning and Intraoperative Navigation in Primary Total Hip Arthroplasty.

Total hip arthroplasty (THA) is a frequently performed procedure; the objective is restoration of native hip biomechanics and achieving functional range of motion (ROM) through precise positioning of the prosthetic components. Advanced three-dimensional (3D) imaging and computed tomography (CT)-based navigation are valuable tools in both the preoperative planning and intraoperative execution. The aim of this study is to provide a thorough overview on the applications of CT scans in both the preoperative and intraoperative settings of primary THA. Preoperative planning using CT-based 3D imaging enables greater accuracy in prediction of implant sizes, leading to enhancement of surgical workflow with optimization of implant inventory. Surgeons can perform a more thorough assessment of posterior and anterior acetabular wall coverage, acetabular osteophytes, anatomical landmarks, and thus achieve more functional implant positioning. Intraoperative CT-based navigation can facilitate precise execution of the preoperative plan, to attain optimal positioning of the prosthetic components to avoid impingement. Medial reaming can be minimized preserving native bone stock, which can enable restoration of femoral, acetabular, and combined offsets. In addition, it is associated with greater accuracy in leg length adjustment, a critical factor in patients' postoperative satisfaction. Despite the higher costs and radiation exposure, which currently limits its widespread adoption, it offers many benefits, and the increasing interest in robotic surgery has facilitated its integration into routine practice. Conducting additional research on ultra-low-dose CT scans and examining the potential for translation of 3D imaging into improved clinical outcomes will be necessary to warrant its expanded application.

Validity of leg length measurement in the supine and standing position compared with pelvic survey X-ray after total hip arthroplasty

IntroductionThe correct adjustment of leg length is a major goal in the implantation of total hip replacements (THRs). Differences in leg length can lead to functional impairment and patient dissatisfaction. By determining leg length at an early stage, before the patient is discharged from hospital, compensatory measures such as the production of special insoles or orthopaedic footwear can be initiated promptly if there is a difference in leg length. Due to shortening of the period of time spent in hospital, the traditional measurement of leg length in a standing position may be increasingly subject to error. A protective posture immediately after surgery or the presence of a twisted pelvis, for example, due to scoliotic spinal misalignments, falsifies the measurement result in the standing position. Here, the measurement of leg length in the supine position may prove to be accurate immediately postoperatively, regardless of potential sources of error, and is to be compared with measurement in the standing position versus radiological measurement on the AP pelvic survey.Material and methodsThe present retrospective study included 190 patients who had undergone primary total hip arthroplasty. The leg length difference (LLD) of the patients was determined pre- and postoperatively both in the supine and standing position and compared with the postoperative radiological pelvic survey image.ResultsPostoperatively, it was shown that the mean length measured was 0.35 mm too long in the supine position and 0.68 mm too short in the standing position (p value < 0.001). Determination of the average absolute measurement error produces a deviation of 4.06 mm in the standing and 4.51 mm in the supine position (p value 0.126).ConclusionsIt is shown that the postoperative measurement of LLD in the supine and standing position is equally valid and sufficiently accurate, compared with the gold standard of measurement on a radiograph.

Crowe Type IV Hip Dysplasia Treated by THA Comebined with Osteotomy to Balance Functional Leg Length Discrepancy: A Prospective Observational Study.

ObjectiveTo measure the factors that affect functional leg length of Crowe type IV Developmental dysplasia of the hip (DDH) patients and to review our own methods to balance leg length discrepancy (LLD) in Crowe type IV DDH patients.MethodsThis was a prospective observational study which started in June 2017 and ended in August 2019. Inclusion criteria included: (i) Crowe type I or Crowe type IV hip dysplasia patients who underwent total hip arthroplasty (THA) in the Department of Orthopaedics at our institution between July 2017 and June 2018; (ii) the patients were treated with our specific leg length balance strategy; and (iii) the related outcomes of patients were completely recorded. Finally, 18 consecutive Crowe type I patients (20 hips) and 14 consecutive Crowe type IV patients (18 hips) were selected and divided into two groups according to Crowe types. All patients received THA, and patients with a longer affected side and inferior anatomical acetabular positions in Crowe type IV group also received subtrochanteric osteotomy. During operation and after hip reduction, leg lengths were compared while two legs were in an extended position and the operative leg was on top of the non‐operative one. Additional leg length adjustment was applied when leg length was considered to be unequal. Prior to surgery, subluxation height of the femoral head on the affected side, functional LLD, bony length of lower limbs, and distance from teardrops to the lowest point line of the sacroiliac joint were recorded. After surgery, cup sizes, functional LLD, and height of hip rotational centers were measured. Clinical evaluations, such as Harris Hip Score (HHS) and SF‐12 scale, were also obtained before and after surgery for all patients.ResultsAt the last follow‐up, functional LLD and clinical measurements of both Crowe type IV group and Crowe type I group were significantly improved. Compared with Crowe type I patients, Crowe type IV patients had a significantly lower MCS, a significantly longer leg lengthening length and a significantly lower hip center height after surgery. Significant differences of tibia length, leg length, and teardrop position were found between affected side and healthy side of Crowe type IV patients. Only three of 14 Crowe type IV patients remained under 1 cm functional LLD. Five patients in the Crowe type IV group developed lower limb numbness immediately following surgery, and they all recovered within 6 months. The average follow‐up period for either group was 14 months, and all patients were followed‐up at 1, 3, 6, and 12 months then yearly after surgery until the final follow‐up.ConclusionAfter detailed leg length balance process, THA combined with transverse sub‐trochanter osteotomy could be an effective method to achieve equal function leg length with most Crowe type IV patients.

Necessity of Leg Length Adjustment When Measuring the Knee Extensor Strength Using Hand-held Dynamometers

Necessity of Leg Length Adjustment When Measuring the Knee Extensor Strength Using Hand-held Dynamometers

Accuracy of Component Orientation and Leg Length Adjustment in Total Hip Arthroplasty Using Image-free Navigation

Purpose:The purpose of this study was to examine the accuracy of implant orientation and leg length in total hip arthroplasty (THA) with an image-free navigation system based on a comparison of the intraoperative navigation and postoperative CT evaluations.Material and Methods:A consecutive series of 111 patients (118 hips) who underwent THA using the current version of the image-free navigation system constituted the basic study population. Subsequently, a total of 101 patients (108 hips) meeting the inclusion and exclusion criteria were selected as study subjects for the analysis. THA was performed using an image-free navigation system that was capable of adjusting both the prosthetic position and leg length. Postoperative CT examination was performed for all study subjects, and the prosthetic position and leg length were measured on CT images using the image analysis software. Subsequently, the intraoperative navigation results and the corresponding values obtained from the postoperative CT measurements were compared to test the accuracy of the navigation system.Results:The average discrepancies between the intra- and postoperative assessments were 6.8°, 3.7°, and 5.7° for cup anteversion, cup inclination, and stem anteversion, respectively. The corresponding value in leg length averaged 4.1 mm.Conclusion:Average discrepancies between the intra- and postoperative measurements were less than 10° in all prosthetic alignment parameters and less than 5 mm in leg length. Intraoperative assessments with the use of the image-free navigation in THA could afford satisfactory result.

Head-neck taper corrosion in hip arthroplasty.

Modularity at the head-neck junction of the femoral component in THA became popular as a design feature with advantages of decreasing implant inventory and allowing adjustment of leg length, offset, and soft tissue balancing through different head options. The introduction of a new modular interface to femoral stems that were previously monoblock, or nonmodular, comes with the potential for corrosion at the taper junction through mechanically assisted crevice corrosion. The incidence of revision hip arthroplasty is on the rise and along with improved wear properties of polyethylene and ceramic, use of larger femoral head sizes is becoming increasingly popular. Taper corrosion appears to be related to all of its geometric parameters, material combinations, and femoral head size. This review article discusses the pathogenesis, risk factors, clinical assessment, and management of taper corrosion at the head-neck junction.

Structural-Parameter-Based Jumping-Height-and-Distance Adjustment and Obstacle Sensing of a Bio-Inspired Jumping Robot

Jumping-height-and-distance (JHD) active adjustment capability is important for jumping robots to overcome different sizes of obstacle. This paper proposes a new structural-parameter-based JHD active adjustment approach for our previous jumping robot. First, the JHD adjustments, modifying the lengths of different legs of the robot, are modelled and simulated. Then, three mechanisms for leg-length adjustment are proposed and compared, and the screw-and-nut mechanism is selected. And for adjusting of different structural-parameters using this mechanism, the one with the best JHD adjusting performance and the lowest mechanical complexity is adopted. Thirdly, an obstacle-distance-and-height (ODH) detection method using only one infrared sensor is designed. Finally, the performances of the proposed methods are tested. Experimental results show that the jumping-height-and-distance adjustable ranges are 0.11 m and 0.96 m, respectively, which validates the effectiveness of the proposed JHD adjustment method.

A novel non-invasive mechanical technique of cup and stem placement and leg length adjustment in total hip arthroplasty for dysplastic hips.

This study assessed the accuracy of cup and stem positioning and limb length adjustment for developmental dysplasia of the hip (DDH) using our new mechanical technique compared with imageless navigation or a computed tomography (CT)-based navigation system. One hundred thirteen primary total hip arthroplasties (THAs) for DDH were evaluated. At pre-operative positioning, patients were placed in a precise lateral decubitus position by tilting the surgical table using simple ready-made devices (two shot pipe, metal chain, level gauge and goniometer). During surgery, cups were intentionally placed at 45° inclination and 15° anteversion on radiograph by using a level gauge and goniometer. Cup inclination was 44.2° ± 3.4° (range, 32.0-51.2°), cup anteversion was 19.6° ± 6.1° (range, 3.0-33.1°), stem alignment was 0.04° ± 0.8° valgus (range, 2.1° varus to 1.9° valgus), and leg length discrepancy was -0.37 ± 3.7 mm (range, -12.8 to 8.8 mm) in postoperative radiographs. Outliers (outside ±10° from intentional position) occurred in 15 cases (13.3 %) in inclination or anteversion. Postoperative dislocation did not occur in any cases. Cup and stem positioning in THAs with our new mechanical technique yielded satisfactory results compared with previously reported imageless navigation or CT-based navigation. Our results were superior with regard to being non-invasive and low cost and involving minimum radiation exposure.

Proximal component modularity in THA--at what cost? An implant retrieval study.

While modular femoral heads have been used in THA for decades, a recent innovation is a second neck-stem taper junction. Clinical advantages include intraoperative adjustment of leg length, femoral anteversion, and easier revision, all providing flexibility to the surgeon; however, there have been reports of catastrophic fracture, cold welding, and corrosion and fretting of the modular junction. We asked whether (1) the neck-stem junction showed the same degradation mechanisms, if any, as the head-neck junction, (2) the junction contributed to THA revision, (3) the alloy affected the degree of degradation, and (4) the trunion machine finish affected the degradation mechanisms. We compared 57 retrievals from seven total hip modular designs, three cobalt-chromium-molybdenum and four titanium based: Bionik(®) (four), GMRS(®) (four), Margron(®) (22), Apex(®) (five), M-series(®) (five), ZMR(®) (two), and S-ROM(®) (15). Macroscopic inspection, microscopy, and micro-CT were conducted to determine the effects of materials and design. The cobalt-chromium-molybdenum components showed crevice corrosion and fretting of the neck-stem taper, whereas the titanium components had less corrosion; however, there were several cases of cold welding where disassembly could not be achieved in theater. Even with modern taper designs and corrosion-resistant materials, corrosion, fretting, and particulate debris were observed to a greater extent in the second neck-stem junction. Titanium-based modular arthroplasty may lessen the degree of degradation, but cold welding of the components may occur. Degradation of the second junction contributed to 8 cases of metallosis and two cases of aseptic lymphocyte-laminated vascular-associated lesions contributing to revision.

Adjustment of leg length using imageless navigation THA software without a femoral tracker

BackgroundAdjustment of leg length discrepancy is an important factor influencing the outcome of total hip arthroplasty (THA). However, leg length discrepancy after THA has been reported to be associated with inferior clinical outcome in previous studies. A new version of the imageless navigation software “OrthoPilot THAplus” has been developed to assess the leg length adjustment and offset value. The clear advantage of this system is the elimination of the need for femoral pin insertion, which is associated with potential complications and additional surgical invasion. MethodsIn this study, the accuracy of this newly developed system was evaluated in 50 consecutive hips implanted with primary THA. The operative results of these 50 patients were compared with those of another 50 consecutive primary THA patients operated on with the previous navigation system that was not equipped with the leg length adjustment system. ResultsAfter surgery, the average leg length discrepancy in the THA plus group was 0.9 mm (range –5 to 5 mm), while the corresponding value in the other group with the older software was 2.9 mm (range –13 to 20 mm), showing a significant difference. ConclusionThe accuracy and reproducibility of new software added to the imageless THA navigation system in achieving equalization of leg length were assessed. Comparison of the surgical results as compared with the control group performed with the conventional navigation system showed the advantage of this system over the previous system.

Evaluation of the Accuracy of Computed Tomography–Based Navigation for Femoral Stem Orientation and Leg Length Discrepancy

Although there is a great deal in the literature about the clinical accuracy of computed tomography (CT)–based navigation systems for acetabular cup orientation and leg length discrepancy in total hip arthroplasty, there is little analysis of femoral stem orientation. Thirty total hip arthroplasties in which CT-based navigation system had been used had their anteversion, valgus angle of stem, and leg length discrepancy measured on postoperative CT data. Differences in postoperative measurements from intraoperative records were −0.6° ± 4.8° (range, −11° to 10°) for stem anteversion, −0.2° ± 1.8° (range, −4° to 3°) for valgus angle of stem, and 1.3 ± 4.1 mm (range, −6 to 10 mm) for leg length. Although this system may need further improvement for stem orientation, it was helpful for intraoperative leg length adjustment.

A modular femoral neck and head system works well in cementless total hip replacement for patients with developmental dysplasia of the hip

We compared a modular neck system with a non-modular system in a cementless anatomical total hip replacement (THR). Each group consisted of 74 hips with developmental hip dysplasia. Both groups had the same cementless acetabular component and the same articulation, which consisted of a conventional polyethylene liner and a 28 mm alumina head. The mean follow-up was 14.5 years (13 to 15), at which point there were significant differences in the mean total Harris hip score (modular/non-modular: 98.6 (64 to 100)/93.8 (68 to 100)), the mean range of abduction (32 degrees (15 degrees to 40 degrees )/28 (0 degrees to 40 degrees )), use of a 10 degrees elevated liner (31%/100%), the incidence of osteolysis (27%/79.7%) and the incidence of equal leg lengths (> or = 6 mm, 92%/61%). There was no disassociation or fracture of the modular neck. The modular system reduces the need for an elevated liner, thereby reducing the incidence of osteolysis. It gives a better range of movement and allows the surgeon to make an accurate adjustment of leg length.

Corrosion of a Hip Stem With a Modular Neck Taper Junction: A Retrieval Study of 16 Cases

Since the early 1990s, there has been a dramatic increase in modular total hip designs ranging from a stem with a proximal taper and modular head, to a distal stem, double taper proximal neck, and modular head. Clinical advantages of the modular neck include intraoperative adjustment of leg length via the neck-head taper and femoral anteversion via the neck-stem taper. Sixteen cases of a double tapered cone, Margron hip prosthesis, were presented for retrieval analysis. Macroscopic inspection, corrosion testing, light microscopy, and scanning electron microscopy were conducted to elucidate mechanisms of failure. In this regard, 6 neck components showed significant fretting, and crevice corrosion of the neck-stem taper with an average implantation time of 39 months compared with the remaining retrievals, which showed no corrosion with and average time in situ of 2.7 months. This retrieval study demonstrates that even with a modern taper design and corrosion-resistant materials, increased modularity can lead to fretting and crevice corrosion, metal ion generation, and particulate debris that may contribute to periprosthetic osteolysis and loosening.

Management of Significant Femoral Bone Loss with Use of Modular Stems

Significant femoral bone loss can be encountered in the multiply revised patient. Deficient proximal bone requires either a bulk allograft or a femoral component that allows stable distal fixation. Extensively coated stems have shown excellent results for many revisions but have shown higher rates of failure among patients with femoral remodeling in retroversion, an enlarged endosteal diameter, or an ectatic canal. A modular tapered stem is an alternative in this subset of patients. A modular tapered implant provides axial and rotational stability through the use of distal splines while the proximal body segments can allow independent adjustment of leg length, offset, and anteversion. We previously reported the 1- to 4-year (average 2 years) results of modular tapered femoral prosthesis in cementless femoral revisions. In the previous study there were 16 patients all with Type IIIB or IV Paprosky femurs. This is a follow-up of that article reporting on 24 patients, all with Type IIIB or IV Paprosky femurs with a follow-up of 2 to 5 years (average 3 years). We revised one component for subsidence, one component was revised for fracture at the modular junction, and one component was revised for sepsis.

A Case of Disassociation of a Modular Femoral Neck Trunion After Total Hip Arthroplasty

Modular femoral heads offer the advantages of increased intraoperative flexibility through the adjustment of leg length and offset, whereas a modular femoral neck can also allow independent adjustment of femoral anteversion. Despite the potential advantages of hip systems using increased modularity, these component designs also offer a greater number of junctions through which problems may occur. This case demonstrates the potential for dissociation of a Morse taper between a modular femoral neck and stem.

Femoral Fixation in the Face of Considerable Bone Loss

Considerable femoral bone loss can be encountered in the multiply revised total hip arthroplasty patient. Deficient proximal bone requires either a bulk allograft or a femoral component that allows stable distal fixation. Extensively coated stems have shown excellent results for many revisions but have shown higher rates of failure among patients with femoral remodeling in retroversion, an enlarged endosteal diameter, or an ectatic canal. A modular tapered stem is an alternative in this subset of patients. A modular tapered implant provides axial and rotational stability through the use of distal splines, and the proximal body segments can allow independent adjustment of leg length, offset, and anteversion.

3M integral bipolar cup system for dysplastic osteoarthritis

Between 1995 and 1997 we undertook 40 bipolar hip arthroplasties in 35 patients with dysplastic osteoarthritis. The steep and shallow acetabulum was excavated and the bipolar socket was placed high with an adjustment of leg-length. At follow-up of between five and seven years, there were 19 excellent, 16 good and five fair results according to the scoring system of Merle d'Aubigné and Postel. The mean radiographic superior migration of the bipolar socket was 2.1 mm (0 to 10). Osteolysis was noted in three hips within three years of the operation. Abduction on weight-bearing was recorded in 24 hips and the bipolar system was found to be functioning predominantly between the inner bearing and the metal femoral head in 20.

Custom and Modular Components in Primary Total Hip Replacement

Cementless custom implants attempted to enhance fit and fill of variable hip geometry. Fabrication of custom implants in referenced from a computed tomography scan, thus allowing three dimensional specifications of femoral anatomy. However, the aggregate charge of manufacturing the implant and obtaining the computed tomography scan is prohibitive in today's healthcare climate. Clinical studies have not shown that customized implants incrementally improve clinical success or implant longevity. Modular prostheses allow the surgeon intraoperative versatility, allowing adjustment of leg length, offset, neck length, anteversion, and fixation. This is particularly helpful in developmental dysplasia of the hip and posttraumatic arthritis. Other advantages of modularity include decreased implant inventory and the ability to remove the femoral head at revision surgery to improve exposure or change head size without component removal. Subsequent clinical experience has witnessed significant drawbacks associated with modularity. These include corrosion, especially with mixed metals, fretting, dissociation, implant fracture below the head and neck taper joint, and reduced range of motion. In addition, thin acetabular polyethylene contributes to higher were rates, earlier failure, local or distal debris particles, and osteolysis. Finally, the cost of modular implants is generally higher than a comparable monolithic prosthesis. In primary hip arthroplasty, use of custom or modular implants should be judicious. Modularity beyond the head and neck junction should be reserved for those cases where a comparable monolithic implant would not suffice.