Femoral Pinless Length and Offset Measurements During Computer-Assisted,Minimally Invasive Total Hip Arthroplasty

We asked whether the intraoperative assessment of leg length (LL) and offset (OS) change would be accurate using a novel pinless femoral reference system during unilateral minimally invasive THA in 50 patients with a mean age of 60 years (48–79). LL and OS change measured at surgery was compared with LL/OS change as measured on magnification-corrected preoperative and postoperative radiographs by two blinded examiners. The radiographic evaluation showed a high inter-rater reliability (r > 0.80 for all assessments). The mean differences (± 95% limits of agreement) between navigation and radiographic measurements on the treated side were + 0.4 mm (± 3.6) for LL and − 1.0 mm (± 3.9) for OS. Femoral pinless navigation technology represents a feasible assistance in THA.     

Effect of Femoral Offset on Pain and Function After Total Hip Arthroplasty

The effects of altering patients’ femoral offset (FO) during total hip arthroplasty on postoperative pain and function have not been well described. This study compared clinical outcomes as assessed by the Short Form 12 Health Survey and Western Ontario and McMaster University Osteoarthritis Index between patients who had their FOs restored to varying degrees (compared to the contralateral normal hip [CL]). We retrospectively measured postoperative FOs on standard anteroposterior pelvis radiographs and compared to the CL. Patients were categorized into one of 3 groups: decreased offset (< − 5 mm compared to CL), normal offset (between − 5 and + 5 mm), and increased offset (> + 5 mm). The decreased offset group exhibited Western Ontario and McMaster University Osteoarthritis Index Physical Function scores that were less than those of the normal offset and increased offset groups (72.03, 82.23, and 79.51, respectively [P = .019]). In conclusion, reducing a patients’ native FO led to inferior functional outcome scores.     

Determining and Achieving Target Limb Length and Offset in Total Hip Arthroplasty Using Intraoperative Digital Radiography

BackgroundAchieving appropriate limb length and offset in total hip arthroplasty (THA) is challenging. Target limb length and offset may not always mean equal radiographic measurements bilaterally. The goal of this study is to introduce a method for determining as well as achieving target limb length and offset using digital radiographic measurements.MethodsOne hundred and two consecutive patients with unilateral hip osteoarthritis undergoing primary THA in the lateral decubitus position were included. Limb length and offset were measured on anterior-posterior pelvic radiographs preoperatively, intraoperatively, and postoperatively. Offset was defined as the length of a line parallel to the inter-teardrop line, extending from the edge of the ischium, at about the lower border of the ipsilateral obturator foramen, to the edge of the femoral cortex, usually at, or just below, the neck resection level. Target limb length was determined for each patient based on patient perception and severity of disease. Target offset equaled the contralateral limb. Using intraoperative digital radiography, adjustments were made until targets were achieved and the hip was stable. Patients were followed for an average of 4.2 years postoperatively.ResultsLimb length was within 5 mm of target measurements in 100% of patients and offset was within 5 mm of targets in 97.1%. Target measurements differed by >5 mm from the contralateral side in 2.0% of limb length and 2.9% of offset measurements. There were no significant differences between intraoperative and postoperative limb length (P = .261) or offset (P = .747) measurements. At final follow-up, there were no dislocations or reoperations and average Hip disability and Osteoarthritis Outcome Score for Joint Replacement was 95.78.ConclusionTarget limb length and offset goals can be determined for most patients undergoing THA. Targets are not always equal to the contralateral side. Intraoperative digital radiography can allow surgeons to accurately achieve target limb length and offset to within 5 mm in a homogenous cohort of patients with unilateral hip osteoarthritis with excellent clinical outcomes.     

Anatomic placement of the acetabular implant in cementless total hip arthroplasty does not adversely affect the implant survival and patient satisfaction

ObjectiveThis study aimed to evaluate if the acetabulum's conservative reaming with preservation of the medial acetabular bone and anatomic placement of the acetabular implant in cementless total hip arthroplasty (THA) has any adverse effect on the radiological outcome, long term implant survival and patient satisfaction.Methods106 consecutive patients were identified from a single surgeon practice who underwent cementless THA from 2005 to 2010. Twenty-one were lost to follow up, and five patients died unrelated to THA. Eighty patients were available for the study. The mean follow-up was 8.6 years (range 5.7–11.6). The mean age was 61.9 years. Immediate pre- and postoperative radiographs were reviewed to calculate combined offset (Acetabular offset – AO, plus Femoral offset – FO). Implant failure, aseptic loosening, revision surgery, patient satisfaction and complications were assessed on long-term follow-up.ResultsAcetabular component survival was 100% with no aseptic failure. None of the patients had revision surgery for any cause. The mean difference in the acetabular offset and combined offset postoperatively was within 3 mm. One patient had a dislocation, and one had a prosthetic joint infection (PJI). 95% of the patients in this series would recommend the hip replacement procedure to others, with a mean satisfaction score of 8.7 (range; 1–10).ConclusionConservative acetabular reaming with preservation of medial acetabulum bone with the anatomic placement of the acetabular implant in cementless THA is safe with no adverse effects on implant survival and patient satisfaction. It offers the advantage of preserving the patient's bone stock, which would potentially be of significant advantage to the patient and the surgeon in case of revision arthroplasty.     

Leg Length and Offset Measures with a Pinless Femoral Reference Array during THA

The bony fixation of reference marker arrays used for computer-assisted navigation during total hip arthroplasty (THA) theoretically involves the risk of fracture, infection, and/or pin loosening. We asked whether intraoperative assessment of leg length (LL) and offset (OS) changes would be accurate using a novel pinless femoral reference system in conjunction with an imageless measurement algorithm based on specific realignment of the relationship between a dynamic femoral and pelvis reference array. LL/OS measurements were recorded during THA in 17 cadaver specimen hips. Preoperatively and postoperatively, specimens were scanned using CT. Linear radiographic LL/OS changes were determined by two investigators using visible fiducial landmarks and image processing software. We found a high correlation of repeated measurements within and between (both 0.95 or greater) the two examiners who did the CT assessments. Pinless LL/OS values showed mean differences less than 1 mm and correlations when compared with CT measurements.     

Direct plain radiographic methods versus EBRA-Digital for measuring implant migration after total hip arthroplasty

We aimed to determine whether the precision and sensitivity of migration measurements after total hip arthroplasty (THA) using direct plain radiographic techniques could be made comparable to those of digital methods (EBRA-Digital; University of Innsbruck, Innsbruck, Austria) by careful control of radiographic technique and use of modern measuring tools. Precision was examined by analysis of consecutive radiographs taken after repositioning in 20 patients after hybrid THA. The precision (95% confidence interval) of measurements for cup migration using direct methods was +/-1.11 to 3.07 mm (x-axis) and +/-1.28 to 1.92 mm (y-axis). The precision of EBRA for cup measurements was +/-1.00 mm (x-axis) and +/-0.82 mm (y-axis). The precision of stem y-axis migration measurements was +/-1.12 to 6.91 mm using direct methods and +/-0.80 mm using EBRA. Migration of the stem (1.53 mm subsidence; P<.01) and the cup (0.53 mm cranial migration, P<.05) was detected using EBRA in 10 patients followed for 6 months after hybrid THA, but significant migration was not detectable using the most precise of the direct methods. Careful measures to standardize plain radiographs improve precision of direct radiographic measurements; however, their long-term sensitivity remains inferior to methods that employ quality control and measurement algorithms to measure migration from digitized radiographs.     

Reliability and Validity of Standing Lateral Radiograph Method for Measuring Acetabular Component Version: A Modified Cross‐table Lateral Radiograph Method

ObjectivesTo investigate the effect of the X‐ray incidence angle on cup version measurements and the reliability and validity of standing lateral (SL) radiography for measuring cup versions.MethodsCup versions under different X‐ray incidence angles were investigated by the 3D simulation analysis. Ninety‐three patients, who underwent primary total hip arthroplasty (THA) with postoperative SL radiographs and CT scans between April 2020 and December 2021, were retrospectively analyzed. SL radiography was taken under naturally standing position, correcting for the measurement error of pelvic tilt in cross‐table lateral (CL) radiography. Cup versions were measured on SL radiographs and CT images by two qualified orthopedic physicians. The intra‐ and inter‐observer reliabilities were assessed by intra‐class correlation coefficient. The consistency between radiographic and CT measurements was evaluated using Pearson correlation coefficient.ResultsNo significant differences in cup version measurements were observed between groups of different X‐ray incidence angles (P = 0.663) in the 3D simulation analysis. All measurements had excellent intra‐ and inter‐observer reliabilities, with an intraclass correlation coefficient of >0.95. Mean cup version measurements from SL radiographs correlated well with those from CT scans (r = 0.853, P < 0.001). The mean difference between radiographic and CT measurements was −0.49° (range −12.62° to 10.37°, SD 3.95°), and the majority of differences were within the 95% limits of agreement.ConclusionThe cup versions measured with SL radiography were close to the CT measurements. SL radiograph method is reliable and valid for measuring acetabular component version after THA.     

Large Diameter Metal on Metal Articulations. Comparison of Total Hip Arthroplasty and Hip Resurfacing Arthroplasty

The use of large diameter metal bearing total hip arthroplasty (THA) and hip resurfacing arthroplasty (HRA) increased in popularity in the last decade. More recent literature has highlighted the effect of head size in patient outcomes. Data was obtained from the Australian Orthopaedic Association National Joint Replacement Registry (AOA-NJRR) to evaluate the Birmingham (MoM) bearing surface when used with THA and HRA. There is no difference in the overall rate of revision between the THA and HRA but head size has a significant effect on revision rate. The data show that small diameter metal bearings in HRA (below 50 mm) have a higher rate of revision than large diameter metal bearings in HRA (equal to and above 50 mm) (P < .001). Conversely the large diameter metal bearings in THA have a higher rate of revision than the small diameter metal bearings in THA (P = .027). The revision rate for large diameter HRA compared to small diameter THA is not significantly different P = .670. We recommend caution when choosing either a large diameter (≥ 50 mm) metal on metal THA or small diameter (< 50 mm) HRA.     

Errors in femoral anteversion,femoral offset,and vertical offset following robot‐assisted total hip arthroplasty

The objectives were to determine errors in femoral anteversion (FA), femoral offset (FO), and vertical offset (VO) with robot‐assisted total hip arthroplasty (THA) and how consistently these errors are within clinically desirable limits of ±5° and ±5 mm. After preoperative planning, robot‐assisted THAs were performed on twelve cadaveric specimens. The error between achieved and planned component placements was used to determine bias (mean error) and precision (SD of error). The percent of the population within clinically desirable limits was determined. Bias of 1.5° and 2.7 mm occurred for FA and VO, respectively. Precision was 1.2° for FA and better than 1.5 mm for FO and VO. The percent of population within clinically desirable limits was at least 95% for FA and at least 99% for FO. With limits of ±7 mm, at least 95% of the population was within these limits for VO. Robot‐assisted THA may improve clinical outcomes.     

Effect of Price Capitation on Implant Selection for Primary Total Hip and Knee Arthroplasty

While price capitation strategies may help to control total hip (THA) and knee arthroplasty (TKA) implant costs, its effect on premium implant selection is unclear. Primary THA and TKA cases 6 months before and after capitated pricing implementation were retrospectively identified. After exclusions, 716 THA and 981 TKA from a large academic hospital and 2 midsize private practice community hospitals were reviewed. Academic hospital surgeons increased premium THA implant usage (66.5% to 70.6%; P = 0.28), while community surgeons selected fewer premium implants (36.4%) compared to academic surgeons, with no practice change (P = 0.95). Conversely, premium TKA implant usage significantly increased (73.4% to 89.4%; P < 0.001) for academic surgeons. Community surgeons used premium TKA implants at greater rates in both periods, with all cases having ≥ 1 premium criterion.     

Oversized Cups as a Major Risk Factor of Postoperative Pain After Total Hip Arthroplasty

After total hip arthroplasty (THA) some patients have persistent postoperative pain (POP). Some of these POP are anterior and are caused by an anterior iliopsoas impingement (AIPI). We have hypothesized that oversized implanted cups could be responsible for POP and especially AIPI. We screened 237 patients who had a primary THA and compared the size difference (ΔS) between the native femoral head and the implanted cup, in patients with and without POP. Median ΔS was 2 mm [− 6; 11 mm] and patients with POP had a significantly increased ΔS (P < 0.0001). The threshold above which pain was significantly more frequent was ΔS ≥ 6 mm. Odds ratio was 14.4 for POP and 26 for AIPI pain when ΔS ≥ 6 mm.     

A New Method to Make 2-D Wear Measurements Less Sensitive to Projection Differences of Cemented THAs

Wear curves from individual patients often show unexplained irregular wear curves or impossible values (negative wear). We postulated errors of two-dimensional wear measurements are mainly the result of radiographic projection differences. We tested a new method that makes two-dimensional wear measurements less sensitive for radiograph projection differences of cemented THAs. The measurement errors that occur when radiographically projecting a three-dimensional THA were modeled. Based on the model, we developed a method to reduce the errors, thus approximating three-dimensional linear wear values, which are less sensitive for projection differences. An error analysis was performed by virtually simulating 144 wear measurements under varying conditions with and without application of the correction: the mean absolute error was reduced from 1.8 mm (range, 0-4.51 mm) to 0.11 mm (range, 0-0.27 mm). For clinical validation, radiostereometric analysis was performed on 47 patients to determine the true wear at 1, 2, and 5 years. Subsequently, wear was measured on conventional radiographs with and without the correction: the overall occurrence of errors greater than 0.2 mm was reduced from 35% to 15%. Wear measurements are less sensitive to differences in two-dimensional projection of the THA when using the correction method.     

The Impact of Leg Length Discrepancy on Patient Satisfaction and Functional Outcome Following Total Hip Arthroplasty

A series of 191 patients undergoing THA with a standardised stem were studied. The effect of leg length discrepancy (LLD) on patient function (Oxford Hip Score), health measures (Short Form 12) and satisfaction (Self-Administered Patient Satisfaction Scale) at a mean 3.8 years of follow up (range 3.3 to 4.9) is reported. 8.9% of cases had shortening, 0.5% no LLD and 90.6% had lengthening. In 21.5% the LLD was more than 10 mm, in 37.1% 5–10 mm, and in 40.9% 0–5 mm. There was no significant difference in patient reported outcome measures (PROMs) according to LLD. Correlation of recorded measurements between multiple observers was excellent (0.93). LLD following total hip arthroplasty remains common but in this series, was not correlated with PROMs.     

Pubic Symphysis to Sacrococcygeal Joint: A Poor Correlate to Other Spinopelvic Measurements

BackgroundThe hip-spine relationship is increasingly recognized as critical for optimizing stability following total hip arthroplasty (THA). However, these measurements are not routinely obtained during THA workup. It has been suggested that insight can be gained from supine antero-posterior pelvis radiograph, measuring the distance from the superior border of the pubic symphysis to the sacro-coccygeal joint (PSCD). This study assessed the correlation between PSCD and lateral lumbar radiographic metrics in a cohort of preoperative THA patients.MethodsWe retrospectively evaluated 250 consecutive patients who underwent THA with preoperative supine antero-posterior pelvis and lateral lumbar radiographs. The mean age was 68 years (range, 42 to 89), 61% were women, and the mean body mass index was 30 kg/m² (range, 19 to 52). Two reviewers measured PSCD, pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI), and lumbar lordosis (LL). Inter-observer reliability was calculated for all measurements, and correlation coefficients were calculated for PSCD with respect to PT, SS, PI, and LL.ResultsCorrelations between PSCD and lumbar radiographic metrics were all statistically significant, except for PI in men but graded as “weak” or “very weak” for men and women, respectively, as follows: PT = −0.30 (P < .01) and −0.46 (P < .01); SS = 0.27 (P < .01) and 0.22 (P < .01); PI = −0.04 (P = .70) and −0.19 (P = .02); and LL = 0.45 (P < .01) and 0.30 (P < .01). Inter-observer reliability was graded as “strong” for every metric.ConclusionThe PSCD was weakly correlated with all evaluated lateral lumbar radiographic metrics in both sexes, despite strong inter-observer reliability. Therefore, PSCD cannot reliably serve as a proxy for evaluating the hip-spine relationship.     

India ink artifact on Dixon out-of-phase images can be used as a landmark to measure joint space width at MRI

PurposeThe purpose of this study was to test the feasibility of joint space width (JSW) measurement on Dixon MR images with the “India ink” artifact between cartilage and bone marrow as a landmark for the subchondral plate and to correlate it with radiographic JSW.Materials and methodsBoth hands of six volunteers (three women, three men; mean age, 36.7 ± 10.4 [SD] years) and 24 patients with early rheumatoid arthritis (16 women, 8 men; mean age, 45.7 ± 14.5 [SD] years) were imaged with MRI Dixon sequences and radiographs. Two radiologists (R1, R2) separately measured JSW in 11 joints per hand on all Dixon images in volunteers, on contrast-enhanced T1-weighted out-of-phase images in patients and on radiographs in both groups. Inter-technique, intra-observer and inter-observer agreements were assessed using intraclass correlation coefficient (ICC) and Bland Altman analysis.ResultsIn volunteers, agreement between JSW measurements on MRI and radiographs was the highest with T1-weighted Dixon out-of-phase images (mean ICC ranging from 0.69 to 0.76 for R1 and 0.65 to 0.74 for R2). In patients, median bias between JSW measurements at first and second readings was not statistically significantly different from 0 on T1-weighted Dixon out-of-phase images (mean bias of 0.00 and + 0.01 mm) and radiographs (mean bias of 0.00 and +0.01 mm). Median bias of the difference between measurements of R1 and R2 was statistically significantly different from 0 on T1-weighted Dixon out-of-phase images (mean bias of -0.11 and -0.09 mm; P < 0.039) and radiographs (mean bias of -0.24 and -0.20 mm; P < 0.035).ConclusionMeasurement of hand JSW on T1-weighted Dixon out-of-phase images using India ink artifact as a landmark for the subchondral plate is repeatable and reproducible.     

Excellent Results and Minimal Complications of Total Hip Arthroplasty in Sickle Cell Hemoglobinopathy at Mid-Term Follow-Up Using Cementless Prosthetic Components

The purpose of this study was to compare the outcomes of cementless primary total hip arthroplasty (THA) in sickle cell patients compared to the remaining cohort of osteonecrosis patients who did not have this disease. Thirty-two sickle cell patients (42 hips) who had a mean age of 37 years and mean follow-up of 7.5 years (range, 5–11 years) were compared to 87 non-sickle cell osteonecrosis patients (102 hips) who had mean age of 43 years and mean follow-up of 7 years (range, 3–10.5 years). Outcomes evaluated included implant survivorship, Harris hip scores, complication rates, radiographic outcomes, and Short Form-(SF-36) health questionnaire. There were no significant differences in aseptic implant survivorship (95 vs. 97%), Harris hip scores (87 vs. 88 points), SF-36 score, or radiographic findings between the two patient cohorts. In light of these findings, we believe that the outcomes of THA improved in sickle cell patients with optimized medical management and the use of cementless prosthetic devices.     

Spinopelvic alignment does not change after bilateral total hip arthroplasty in patients with bilateral Crowe type-IV developmental dysplasia of the hip

ObjectiveThis prospective study aimed to evaluate the changes in the sagittal alignment after total hip arthroplasty (THA) in patients with hip osteoarthritis (OA) secondary to Crowe type-IV developmental dysplasia of the hip (DDH) and whether THA would contribute to the relief of low-back pain (LBP).MethodsA total of 27 patients (2 men and 25 women) with bilateral hip OA secondary to Crowe type-IV DDH were enrolled in this study. Their mean age at the time of surgery was 40,36±12,35. All patients underwent simultaneous, bilateral THA between January 2015 and December 2016. Clinical assessment included Oswestry disability index (ODI) score and Harris hip score (HHS), and pelvic incidence (PI), sacral slope (SS), lumbar lordosis (LL), and pelvic tilt (PT) were measured from radiographs.ResultsPreoperatively, all the patients had hip and low-back pain. Preoperative and final follow-up ODI scores were 48.3 and 3.9 (p=0.000), respectively. HHS changed from 43.54 to 92.68 (p=0.000). PT and PI significantly changed from −20.4°±20.4° to 3.2°±16.7° (p=0.001) and from 26.6°±35.1° to 47.4°±17.9° (p=0.001), respectively. There were no significant differences regarding the SS and LL measurements. Age or limb-length discrepancy was not significantly associated with the spinopelvic alignment measurements.ConclusionRestoring the function of the hip with THA is shown to improve hip-associated LBP, but the accompanying hyperlordosis does not change. THA in patients with bilateral Crowe type-IV hips relieves hip pain as well as associated LBP. Hyperlordosis of the lumbar vertebra does not change after surgery, but PI and PT changes are observed; this improvement might have a role in the relief of LBP.Level of EvidenceLevel IV, Therapeutic study     

A Novel Method for Accurate and Reproducible Functional Cup Positioning in Total Hip Arthroplasty

Cup positioning is an important variable for short and long term function, stability, and durability of total hip arthroplasty (THA). This novel method utilizes internal and external bony landmarks, and the transverse acetabular ligament for positioning the acetabular component. The cup is placed parallel and superior to the transverse ligament and inside the anterior wall notch of the true acetabulum, then adjusted for femoral version and pelvic tilt and obliquity based on weight bearing radiographs. In 78 consecutive THAs, the mean functional anteversion and abduction angles were 17.9 ° ± 4.7 ° and 41.7 ° ± 3.8 °, respectively. 96% of the functional anteversion measurements and 100% of the functional abduction angles were within the safe zone. This technique is an easy, reproducible, and accurate method for functional cup placement.     

Activity,Sleep and Cognition After Fast-Track Hip or Knee Arthroplasty

Optimized perioperative care after total hip and knee arthroplasty (THA/TKA) has decreased length of stay (LOS) but data on activity, sleep and cognition after discharge are limited. We included 20 patients ≥ 60 years undergoing THA/TKA, monitoring them for 3 days preoperatively and 9 days postoperatively with actigraphs for sleep and activity assessment. Pain scores were recorded daily. Cognition was evaluated by 2 cognitive tests. Results showed a mean age was 70.5 years and mean LOS was 2.6 days. Actigraphs showed increased daytime sleep and decreased motor activity postoperatively. Early postoperatively cognitive decline and increased pain returned to preoperative levels by postoperative day (POD) 5–9. Despite the small sample size the study illustrated that post-discharge activity is decreased and daytime sleep is increased after fast-track THA/TKA, while cognition and pain return to preoperative levels by POD 9. Objective assessment of these recovery parameters may be valuable in future interventional studies to enhance recovery after THA/TKA.     

The Utility of Routine Postoperative Radiographs in the Asymptomatic Total Hip Arthroplasty Patient

BackgroundTotal hip arthroplasty (THA) patients often receive routine radiographs in the year following their index surgery. This study sought to investigate the clinical and economic value of obtaining routine postoperative hip radiographs for asymptomatic patients following primary elective THA.MethodsA retrospective cohort study of consecutive patients who underwent primary elective THA from 2016 to 2019 was conducted. Patients undergoing nonelective or revision THA, radiographic follow-up <10 months, and patients aged <18 years were excluded. All radiographs were reviewed for abnormalities in the first postoperative year by an arthroplasty fellowship-trained orthopaedic surgeon, blinded to the symptoms of the patient.ResultsOf the 327 patients (351 hips) included, 57.2% were women and 68.2% were White, with an average age of 65 years (range, 22-97 years) and average body mass index of 29.1 kg/m² (range, 16.2-49.8 kg/m²). Only four (0.4%) radiographic series revealed abnormalities with the potential to alter postoperative management. One patient experienced a change in management directly related to their abnormal finding (closed reduction for dislocation at 10.2 months postoperatively). The remaining three abnormal radiographic findings included femoral stem subsidence, progressive radiolucencies around an acetabular component, and cement mantle fracture. The average cost for each radiographic series was $155.27, resulting in total direct charges of $167,691.60.ConclusionRoutine postoperative radiographs may be of limited utility in the asymptomatic patient in the first year following elective primary THA. Consideration should be given to limit postoperative radiographs following standard elective THA, while reserving postoperative radiographic evaluation for patients who are symptomatic.Level of EvidenceLevel III.