Leg length discrepancy after total hip arthroplasty: comparison of 3 intraoperative measurement methods

Integrated Acetabular Prosthesis Versus Bone Grafting in Total Hip Arthroplasty for Crowe Type II and III Hip Dysplasia: A Retrospective Case-Control Study

OBJECTIVE

Many methods of acetabular reconstruction with total hip arthroplasty (THA) for Crowe type II and III adult developmental dysplasia of the hip (DDH) acetabular bone defect have been implemented clinically. However, there was no study comparing the results of integrated acetabular prosthesis (IAP) with bone grafting (BG). This study aims to investigate the efficacy of IAP and BG for acetabular reconstruction in Crowe type II and III DDH.

METHODS

The clinical data of 45 patients with unilateral Crowe type II and III DDH who underwent THA from January 2020 to January 2023 were retrospectively analyzed. The patients were divided into two groups: 25 patients using 3D-printed IAP (IAP group) and 20 patients using BG (BG group). The operation time and intraoperative blood loss were recorded. The clinical outcomes were assessed by Harris Hip Score (HHS) and full weight-bearing time. The radiological outcomes were evaluated by the radiological examination. Accordingly, intraoperative and postoperative complications were observed as well. The data between the two groups were compared by independent sample t-tests and the Mann-Whitney U rank sum test.

RESULTS

There were no significant differences between the two groups in Harris Hip Score (HHS) (preoperative, 6 months postoperative, and the last follow-up), leg length discrepancy (LLD), cup inclination, cup anteversion, vertical center of rotation (V-COR), horizontal center of rotation (H-COR) (p > 0.05). The mean HHS in the IAP group was higher than in the BG group at 1 and 3 months postoperative (p < 0.001). The mean surgical time and blood loss in the IAP group were less than in the BG group (p < 0.001). The mean full weight-bearing time in the IAP group was shorter than in the BG group (p < 0.01). No complications were observed in either group during the follow-up period.

CONCLUSION

IAP and BG have similar radiographic outcomes and long-term clinical efficacy in THA for Crowe type II and III DDH, but the IAP technique has higher surgical safety and facilitates the recovery of hip joint function, which is worthy of clinical promotion.

A Novel Approach for Correcting Limb Length Discrepancy in Total Hip Arthroplasty

INTRODUCTION

This study aimed to evaluate the accuracy of the suture technique, along with the utilization of a spirit-level device which is an instrument designed to indicate whether a surface is horizontal or vertical, in comparison to the conventional supraacetabular pin method and caliper measurement for correcting leg length discrepancy (LLD) during total hip arthroplasty (THA). Materials and methods: Consecutive patients who underwent unilateral primary THA between January 2021 and March 2023 were included in the study. The exclusion criteria were severe flexion and adduction contracture that could affect the accuracy of measurements, a history of lower extremity surgery, the presence of lower extremity deformity, and the absence of postoperative full-length radiographs. Patients were allocated into two groups based on the technique employed for correcting LLD during THA. Group 1 (n=62) consisted of patients evaluated using the suture technique with a spirit-level device, while group 2 (n=75) comprised patients who underwent the supraacetabular pin method with caliper measurement. The distance between the inter-teardrop line and the tip of the lesser trochanter was measured for both hips to assess LLD.

RESULTS

The mean preoperative LLD was similar between groups, which was 11.6 ± 9.1 mm in group 1 and 9.5 ± 9.8 mm in group 2 (p=0.191). Postoperatively, group 1 had a significantly lower LLD compared to group 2 (p<0.001).

CONCLUSION

According to the results obtained from this study, the use of a suture technique in conjunction with a spirit-level device to achieve a consistent leg position is an effective method for correcting LLD during THA.

Minimal pre-operative leg length discrepancy as a risk factor of post-operative leg length discrepancy after total hip arthroplasty: a retrospective study of patients with non-traumatic osteonecrosis of the femoral head

BACKGROUND

Leg length discrepancy (LLD) is one of the troublesome complications of total hip arthroplasty (THA). Previously, several risk factors have been suggested, but they were subjected to their inherent limitations. By controlling confounding variables, we hypothesized that known risk factors be re-evaluated and novel ones be discovered. This study aimed to analyze the independent risk factors for LLD after primary THA in patients with non-traumatic osteonecrosis of the femoral head (ONFH).

METHODS

We retrospectively reviewed patients with non-traumatic ONFH who underwent unilateral THA between 2014 and 2021. All patients were operated by one senior surgeon using a single implant. Demographic data, surgical parameters, and radiological findings (pre-operative LLD, Dorr classification, and femoral neck resection) were analyzed to identify the risk factors of ≥ 5 mm post-operative LLD based on radiological measurement and to calculate odds ratios by logistic regression analysis. Post hoc power analysis demonstrated that the number of analyzed patients was sufficient with 80% power.

RESULTS

One hundred and eighty-six patients were analyzed, including 96 females, with a mean age of 58.8 years at the time of initial THA. The average post-operative LLD was 1.2 ± 2.9 mm in the control group and 9.7 ± 3.2 mm in the LLD group, respectively. The LLD group tended to have minimal pre-operative LLD than the control group (-3.2 ± 5.1 mm vs. -7.9 ± 5.8 mm p = 2.38 × 10- 8). No significant difference was found between the groups in age, gender, body mass index, femoral cortical index, and implant size.

CONCLUSION

Mild pre-operative LLD is associated with an increased risk of post-operative LLD after primary THA in patients with ONFH. Thus, surgeons should recognize pre-operative LLD to achieve an optimal outcome and must inform patients about the risk of developing LLD.

Selective THA-approach use amongst junior surgeons improves safety of introducing the anterior approach: a prospective, multi-surgeon, comparative, study

BACKGROUND

Learning curves associated with independent practice and anterior approach total hip arthroplasty (AA-THA) has been associated with inferior outcome. This study compared outcome of junior, fellowship-trained, surgeons who perform THA through both anterior and posterior (PA) approach, with senior surgeons who perform either AA or PA, to determine whether: 1. Fellowship training and selective practice allows for safe introduction of AA into practice; and 2. Whether selective approach-use influences outcome.

METHODS

This is a prospective, consecutive study comparing the first 800 THAs of two junior, dual-approach, surgeons (AA/PA: 455/345), with 400 THAs cases of two senior, single-approach, surgeons (AA/PA: 200/200), between 2018 and 2020. Most patients were female (54.4%), mean age was 65 years-old (range 19-96) and mean BMI was 29 kg/m2 (range 16-66). Outcome included radiologic measurements (inclination/anteversion and leg-length), complication- and revision rates, and patient-reported outcomes including Oxford Hip Score (OHS).

RESULTS

At 3.1 years (range 2.0-6.8) follow-up, there were 43 complications (3.6%), including 27 re-operations (2.3%); with no difference between junior and senior surgeons for AA-THA (Junior: 8/455 vs. Senior: 3/200; p = 0.355) or PA-THA (Junior: 11/345 vs. Senior: 5/200; p = 0.400). Amongst juniors, there was no difference in complications (AA:8/455 vs. PA:11/345; p = 0.140) and in ΔOHS (AA:20.5 ± 7.7 vs. PA:20.5 ± 8.0; p = 0.581) between approaches.

CONCLUSION

Contemporary training and selective approach-use minimizes the learning curve, allowing junior staff to have equivalent outcome to established, senior surgeons in both AA and PA. We would advocate for selective approach use amongst junior arthroplasty surgeons when introducing the AA into independent practice.

Does the use of intraoperative measurement reduce limb length discrepancies after total hip arthroplasty?

PURPOSE

Postoperative limb length discrepancy (LLD) is a common complication of total hip arthroplasty, and several methods exist to prevent LLD, but each has its benefits and drawbacks. The study investigates the application of intraoperative lower limb length measurement in preventing postoperative LLD.

METHODS

This study retrospectively analyzed 70 patients who underwent total hip arthroplasty from October 2018 to July 2022. The length of the lower limb on the operated side was measured intraoperatively using a sterilized paper ruler after the fitting of the trial mould and compared with the healthy side. Then the prosthesis size, depth and neck length were adjusted accordingly.

RESULTS

The absolute value of postoperative LLD was found to be 6.68 ± 4.48 mm, of which 53 cases (75.7%) were less than or equal to 10 mm, while 30 patients (42.9%) were less than or equal to 5 mm.

CONCLUSION

The use of intraoperative measurement is effective in reducing LLD after total hip arthroplasty.

The effectiveness and influencing factors of the "Y" line technique in reducing the leg length discrepancy after total hip arthroplasty

Objective

To introduce a surgical technique (the "Y" line technique) that will control leg length discrepancy (LLD) after total hip arthroplasty and to observe its effectiveness and influencing factors.

Methods

According to the inclusion and exclusion criteria, a total of 350 patients were selected in this study; 134 patients in whom used the "Y" line technique was used to control lower limb length were included in Group A and 166 patients treated with freehand methods to control lower limb length were included in Group B. A total of 50 patients in whom the standard anteroposterior x-ray of bilateral hips was taken preoperatively and in whom the "Y" line technique was used during the operation were included in Group C.

Results

The postoperative LLD of Group A was 4.74 mm (3.93), that of Group B was 5.85 mm (4.60), and that of Group C was 2 mm (1.00)-the difference was statistically significant (p < 0.001). There were significant statistical differences when comparisons were made between any two groups (p < 0.01). The distribution of postoperative LLD in Group A was better than that in Group B, and this factor was better in Group C than in Group A-the difference was statistically significant (p < 0.001). Severe unequal length rates of the lower extremities (LLD > 10 mm) were 5.97% (8/134) in Group A, 14.3% (24/166) in Group B, and 0% (0/50) in Group C-the difference was statistically significant (p < 0.001). There were significant differences between Group A and Group B and between Group B and Group C (p < 0.05), but there was no significant difference between Group A and Group C (p = 0.078).

Conclusion

The "Y" line technique, which does not increase the operating time and patient cost, can effectively reduce postoperative LLD. Insufficient internal rotation of the healthy lower extremity and the low projection position in the preoperative anteroposterior x-ray of the bilateral hips were important factors affecting the accuracy of the "Y" line technique.

[A new measurement method of offset in total hip arthroplasty]

OBJECTIVE

To report a new offset parameter for total hip arthroplasty (THA)-greater trochanter offset (GTO), and analyze the effectiveness and feasibility of this parameter based on clinical data.

METHODS

The 47 patients who met the selection criteria and admitted between January 2016 and May 2020 were selected as the research object. The global offset (GO) was used as the offset parameter in preoperative design. Firstly, the test-retest reliability and inter-rater reliability of GTO were analyzed based on pelvic X-ray films. The GTO reconstruction was defined as the difference between the operative side and the healthy side within ±5 mm, and 47 patients were divided into the reconstruction group and the non-reconstruction group. General data (age, gender, type and side of fracture, the interval between injury and operation), visual analogue scale (VAS) score, Harris score, gait score, and leg length discrepancy (LLD) were recorded and compared between two groups. Then, the GTO was used as the offset parameter in preoperative design of 21 patients (GTO group) admitted between June 2020 and December 2020. The pre- and post-operative clinical data were compared between GTO group and GO group to explore the feasibility of GTO for THA.

RESULTS

Statistical analysis showed that GTO had good test-retest reliability (P<0.001) and inter-rater reliability (P<0.001). There was no significant difference in gender, age, type and side of fracture, the interval between injury and operation, preoperative VAS score, and LLD at 1 year after operation between the GTO reconstruction group and the non-reconstruction group, as well as between the GO and GTO groups (P>0.05). The Harris score and gait score at 1 year after operation, and difference of VAS score between pre- and post- operation in the reconstruction group and GTO group were significantly better than those in the non-reconstruction group and GO group, respectively (P<0.05). There were 23 cases (48.9%) in the GO group and 19 cases (90.5%) in the GTO group with GTO reconstruction, and the difference was significant (χ²=10.606, P=0.001). There were 25 cases (53.2%) in the GO group and 13 cases (61.9%) in the GTO group with GO reconstruction, and the difference was not significant (χ²=0.447, P=0.504). There were 34 cases (72.3%) in the GO group and 19 cases (90.5%) in the GTO group with LLD reconstruction, and the difference was not significant (χ²=2.777, P=0.096).

CONCLUSION

GTO has reliable test-retest reliability and inter-rater reliability. GTO as a parameter of preoperative offset reconstruction plan of THA can obtain good reconstruction of offset and limb length, and obtain a good effectiveness.

Accuracy of the Horizontal Calibrator in Correcting Leg Length and Restoring Femoral Offset in Total Hip Arthroplasty

Background

Limb length discrepancy (LLD) is one of the most common postoperative complications and can cause serious consequences. Poor recovery of femoral offset (OD) will result in weakness of the patient's external rotator muscles and affect the patient's postoperative function. The study is aimed to present a simple approach that compensates for the shortcomings of previous measuring devices and combines the advantages of different measuring devices to provide more accurate limb length and femoral offset restoration in total hip arthroplasty (THA).

Methods

This study was a prospective controlled trial involving 89 patients with THA. Group I (n = 44) was used for intraoperative measurement of THA with our self-designed horizontal calibrator. Group II (n = 45) was measured by a traditional freehand technique. The main outcome indicators were measured on the Neusoft PACS, including LLD, femoral offset deviation, and operative time. IBM SPSS 23.0 was used for data analysis.

Results

The independent sample t-test was performed for all the data. The operative time, preoperative radiographic LLD, and OD of Group I and Group II had no statistical significance. Postoperative LLD of Group I and Group II were 2.5 ± 2.1 mm (range −5.7 to 8.3 mm) and 6.2 ± 4.3 mm (range −18.0 to 15.2 mm), and the independent sample t-test data of both (P < 0.001; 95% CI = −5.1, −2.2) showed statistical significance. In Group I, there were 38 THAs with LLD <5 mm, accounting for 86% and there were 44 THAs with LLD <10 mm, accounting for 100%. In Group II, there were 20 THAs with LLD <5 mm, accounting for 44%. There were 36 THAs with LLD <10 mm, covering for 80%. There was no significant difference in postoperative femoral offset and OD.

Conclusion

The horizontal calibrator can provide more accurate limb length and femoral offset recovery in THA. It is a simple surgical technique that does not add additionally surgical costs and does not significantly increase operative time, providing a new solution for surgeons to resolve postoperative LLD and restore femoral offset.

Does robotic-assisted computer navigation improve acetabular cup positioning in total hip arthroplasty for Crowe III/IV hip dysplasia? A propensity score case-match analysis

AIMS

Total hip arthroplasty (THA) in patients with hip-dislocation dysplasia remains challenging. This study aims to evaluate whether these patients may benefit from robotic-assisted techniques.

METHODS

We reviewed 135 THAs (108 conventional THAs and 27 robotic-assisted THAs) for Crowe type III or IV from January 2017 to August 2019 in our institution. Robotic-assisted THAs were matched with conventional THAs at a 1:1 ratio (27 hips each group) using propensity score matching. The accuracy of cup positioning and clinical outcomes were compared between groups.

RESULTS

The inclination of the cup for conventional THAs and robotic THAs was 42.1 ± 5.7 and 41.3 ± 4.6 (p = 0.574), respectively. The anteversion of the cup for conventional THAs was significantly greater than that of robotic THAs (29.5 ± 8.1 and 18.0 ± 4.6; p < 0.001), respectively. The ratio of the acetabular cup in the Lewinnek safe zone was 37% (10/27) in conventional THAs and 96.3% (26/27) in robotic THAs (p < 0.001). Robotic THAs did not achieve better leg length discrepancy than that of conventional THAs (- 0.4 ± 10.9 mm vs. 0.4 ± 8.8 mm, p = 0.774). There was no difference in Harris Hip Score and WOMAC Osteoarthritis index between groups at the 2-year follow-up. No dislocation occurred in all cases at the final follow-up.

CONCLUSION

Robotic-assisted THA for patients with high dislocation improves the accuracy of the implantation of the acetabular component with respect to safe zone.

Use of Surgical Approach Is Not Associated With Instability After Primary Total Hip Arthroplasty: A Meta-analysis Comparing Direct Anterior and Posterolateral Approaches

INTRODUCTION

Posterolateral approach (PA) has been historically associated with an increased risk of dislocation after primary total hip arthroplasty (THA), especially when compared with the direct anterior approach (DAA). However, current evidence is inconsistent regarding the risk of dislocation with either approach. The purpose of this study is to determine whether surgical approach influences joint stability.

METHODS

A systematic search in PubMed, MEDLINE, and Embase databases was performed. Randomized controlled trials (RCTs) and non-RCTs comparing DAA with PA in primary THA were included. Pooled effect measure of risk differences, relative risk and mean differences for postoperative dislocation, acetabular implant positioning, and leg length discrepancy were calculated.

RESULTS

Twenty-five studies (5 RCTs and 20 non-RCTs) of 7,172 THAs were assessed. There were no significant differences in dislocation rates between approaches (risk difference = -0.00, 95% confidence interval: -0.01 to 0.00; P = 0.92; I2 = 0%). Results were similar in the subgroup analysis of RCTs (P = 0.98), posterior soft-tissue repair (P = 0.50), and learning curve (P = 0.77). The acetabular implant was better positioned within the safe zone in the DAA group (relative risk = 1.17; 95% confidence interval: 1.03 to 1.33; P = 0.01), but no significant differences were found in cup inclination (P = 0.8), anteversion (P = 0.10), and leg length discrepancy (P = 0.54).

CONCLUSION

Dislocation rates after THA are not different between DAA and PA. Furthermore, no differences in the rate of dislocation were associated with cup positioning or surgical factors related with hip instability. Therefore, the surgical approach has little influence in prosthesis instability after primary THA.

LEVEL OF EVIDENCE

Level III.

[Measurement and analysis of leg length in adults with unilateral developmental dysplasia of the hip]

OBJECTIVE

To measure and analyze the radiographic characteristics of the leg length discrepancy in adult patients with unilateral developmental dysplasia of the hip (DDH).

METHODS

The clinical data of 112 patients with unilateral DDH who met the selection criteria between January 2016 and June 2018 were retrospectively analyzed. There were 16 males and 96 females with an age of 20-76 years (mean, 42.9 years). According to the Crowe classification, there were 25 hips of type Ⅰ, 26 hips of type Ⅱ, 15 hips of type Ⅲ, and 46 hips of type Ⅳ (26 hips of type ⅣA without secondary acetabular formation, and 20 hips of type ⅣB with secondary acetabular formation). Full-length X-ray films of the lower limbs in the standing position were used to measure the following parameters: greater trochanter leg length (GTLL), greater trochanter femoral length (GTFL), lesser trochanter leg length (LTLL), lesser trochanter femoral length (LTFL), tibial length (TL), and intertrochanteric distance (ITD). The above parameters on the healthy and affected sides were compared and the difference of each parameter between the healthy and affected sides was calculated. Taking the difference of 5 mm between the healthy side and the affected side as the threshold value, the number of cases with the healthy side was greater than 5 mm and the affected side was greater than 5 mm were counted respectively. The difference of the imaging parameters between the healthy side and the affected side were compared between different Crowe types and between type ⅣA and type ⅣB.

RESULTS

There was no significant difference in GTLL and LTFL between healthy and affected sides ( P>0.05); LTLL and TL of affected side were longer than healthy side, GTFL and ITD were shorter than healthy side, and the differences were significant ( P<0.05). The constituent ratio of long cases on the affected side of TL and LTLL was greater than the constituent ratio of long cases on the healthy side, while the constituent ratio of long cases on the healthy side of GTFL and ITD was greater than the constituent ratio of long cases on the affected side; there was no obvious difference in the constituent ratio of long cases on the healthy side or the affected side of GTLL and LTFL. The comparison between different Crowe types showed that only the difference in TL between type Ⅰ and type Ⅳ was significant ( P<0.05), the difference of each imaging parameter among the other types showing no significant difference ( P>0.05). Compared with type ⅣB, the differences of GTLL, TL, and ITD of type ⅣA were bigger, and the differences were significant ( P<0.05); the differences of other parameters between type ⅣA and type ⅣB were not significant ( P>0.05).

CONCLUSION

In adult unilateral DDH patients, the leg length on the healthy side and the affected side is different, and the difference mainly comes from the TL and ITD, which should be paid attention to in preoperative planning.

Anatomical Mapping of the External Obturator Footprint: A Study In Cadavers with Implications for Direct Anterior THA

BACKGROUND

The external obturator footprint in the trochanteric fossa has been suggested as a potential landmark for stem depth in direct anterior THA. Its upper border can be visualized during surgical exposure of the femur. A recent study reported that the height of the tendon has little variability (6.4 ± 1.4 mm) as measured on CT scans and that the trochanteric fossa is consistently visible on conventional pelvic radiographs. However, it is unclear where exactly the footprint of this tendon should be templated during preoperative planning so that it can be useful intraoperatively.

QUESTIONS/PURPOSES

In this study, we sought: (1) to provide instructions on exactly where to template the external obturator footprint on a preoperative planning radiograph, and (2) to confirm the small variability in height of the external obturator footprint found on CT scans in a cadaver study.

METHODS

Two-dimensional (2-D) and three-dimensional (3-D) imaging was used to map the anatomy of the external obturator footprint. This dual approach was chosen because of their complementarity; conventional 2-D radiographs translate to clinical practice but 3-D navigation-based digitalization combined with CT allows for a better understanding of the cortical lines that comprise the outline of the trochanteric fossa. In 12 (four males, mean age 80 years, range 69 to 88) formalin-treated cadaveric lower extremities including the pelvis, the external obturator tendon was dissected, and the top and bottom end of its footprint marked with two small needles, and calibrated radiographs were taken. For another five (three males, mean age 75.7 years, range 61 to 91) fresh-frozen cadaveric lower extremities, including femoral reflective marker frames, CT scans were obtained and the exact location of the external obturator footprint was recorded using 3-D navigation-based digitalization. Qualitative analysis of both imaging modalities was used to develop instructions on where the external obturator footprint should be templated on a preoperative planning radiograph. Quantitative analysis of the dimensions of the external obturator footprint was performed.

RESULTS

The lowest point of the external obturator footprint was consistently found (± 1 mm) at the intersection of the vertical line comprised of the lateral wall of the trochanteric fossa and the oblique line formed by the intertrochanteric crest and therefore allows templating of this structure on the preoperative planning radiograph. The median (range) height of the footprint measured 6.4 mm and demonstrated small variability (4.7 to 7.6).

CONCLUSIONS

We suggest templating a 6.4-mm circle with its bottom on the intersection described above.

CLINICAL RELEVANCE

The distance between the templated shoulder of the stem and the top of the circle can be used intraoperatively for guidance. Discrepancy should lead to re-evaluation of stem depth and leg length. Future work will investigate the usability, validity, and reliability of the proposed methodology in daily clinical practice.

Cementless femoral stem fixation and leg-length discrepancy after total hip arthroplasty in different proximal femoral morphological types

PURPOSE

Leg-length changes at total hip arthroplasty (THA) may result from too proximal position of the femoral component, i.e. not being sunk deep enough into the femoral canal due to the size and shape of both medullary canal and implant. Some femoral implants are designed to achieve such fixation in the mediolateral dimension, while others also engage the bone anteroposteriorly. Our aim was to examine the relationship between proximal femoral morphology, osseointegration and leg-length equalization at THA. We asked whether the Dorr classification, femoral cortical index and canal flare index on preoperative radiographs had significant impact on THA aseptic loosening rates and post-operative leg-length discrepancy (LLD).

METHODS

Literature review included original articles on proximal femoral morphology with post-operative LLD and other clinical outcomes of THA, published in the last decade. Case reports and biomechanical studies without clinical data were excluded.

RESULTS

Higher femoral cortical index and/or canal flare index (corresponding to the Dorr type A) increases the risk of leg lengthening at THA. This is particularly notable in femoral stems with metaphyseal fixation, where high canal flare index has also been linked to osseointegration failure and implant loosening. On the other hand, lower canal flare index (corresponding to the Dorr type C) is more prevalent in the elderly population and increases late periprosthetic fracture rates and stress shielding. Even the most commonly used cementless femoral stems cannot offer optimal fit to intra-/extramedullary geometry or offset restoration in up to 30% of clinical cases.

CONCLUSIONS

Femoral morphology can have significant impact on post-operative LLD and osseointegration of cementless THA. Quantitative measurements of the proximal femoral canal may improve the choice of a particular implant and fixation method.

A low-volume surgeon is an independent risk factor for leg length discrepancy after primary total hip arthroplasty: a case-control study

PURPOSE

Leg length discrepancy (LLD) is one of the bothersome complications that reduce patient satisfaction after total hip arthroplasty (THA). This study aimed to investigate the independent risk factors of LLD after primary THA.

METHODS

This is a case-control study of 163 THAs for 163 patients at our institution between April 2015 and March 2018. The relevant data about the general characteristics of the patients (age, sex, body mass index, and diagnosis), surgery (surgical approach, type of femoral stem fixation, and surgeon volume), and radiological findings (Dorr classification and pre-operative LLD) were reviewed to identify the risk factors of ≥ 5 mm post-operative LLD according to radiological measurement and to calculate odds ratios (OR) via logistic regression analysis.

RESULTS

The median (interquartile) absolute value of post-operative LLD was 3.9 (2.3-7.4) mm, and 57 (35.0%) patients had LLD of ≥ 5 mm. After controlling for possible confounders, a low-volume surgeon was considered the only independent risk factor of post-operative LLD (adjusted OR: 8.26; 95% confidence interval: 3.48, 19.60; P < 0.001). Among the 103 patients performed by high-volume surgeons, 82 (79.6%) had LLD of < 5 mm, whereas among the 60 patients performed by low-volume surgeons, only 24 (40.0%) achieved LLD of < 5 mm (P < 0.001).

CONCLUSION

A low-volume surgeon is associated with an increased risk of a post-operative LLD after primary THA, and the importance of measurements should be recognized to prevent post-operative LLD and achieve optimal outcomes. Moreover, surgeons must inform patients about the risk of developing LLD pre-operatively.

Improvements to a method for determining leg length following total hip arthroplasty

Discrepancy in leg length does frequently occur as a side effect of total hip arthroplasty and may lead to reduced patient satisfaction as well as injury in the sequalae. It is consequently important to reduce leg length discrepancy where-ever technically possible. This may be achieved by recording precise intraoperative measurements and using different sized implanted components. The aim of the given study was to improve the accuracy of a previously validated optic measurement system (OMS) to reduce leg length discrepancy. This pre-existing OMS was first trialled and based on these preliminary findings developed further. Using this improved system, measurements were taken in models and cadavers. Inter observer reliability of the improved OMS was assessed. The system is introduced in the given technical feasibility study. Its accuracy was greater in the model setup (swivel joint: 772.7 ± 1.5 mm; ball joint: 770.0 ± 3.7 mm; reference: 772 mm) compared to the trial using cadaveric tissues (588.8 ± 5.7 mm; reference: 586 mm). Results of two examiners were similar. The third one measured significantly shorter values (p=.011). The results of the measurements with the OMS indicate that a significant increase in accuracy (p = 2.076×¹⁰-⁶) has been achieved compared to the previously reported system, however, a further improvement to measurement accuracy is necessary for this to be applied clinically.

A simple method to minimize leg length discrepancy in hip hemiarthroplasty

Purpose

We developed a simple method to minimize leg length discrepancy (LLD) during hip arthroplasty. The purpose of this study is to evaluate the accuracy of the method.

Patients and methods

A total of 47 patients who suffered from unilateral femoral neck fracture and underwent hip hemiarthroplasty between 2015 and 2018 were enrolled in this study. We measured the diameter of the contralateral femoral head (D) and the distance (L) between the center of the femoral head and the top of lesser trochanter in the antero-posterior pelvic X-ray view before the operation, the ratio (R) of D to L was calculated. During the operation, the diameter of the femoral head (d) was measured using a Vernier caliper. Then, the distance should be obtained from the center of the femoral head prosthesis to the lesser trochanter was calculated according to the contralateral ratio R.

Results

The mean LLD was 4.4±3.2 mm (−4.0 to 11.1 mm), 80.9% of the patients had LLD <6 mm, 93.6% of the patients with LLD <10 mm, only 6.4% ≥10 mm LLD.

Conclusion

This method is a simple, cost-effective, fast and accurate way to reduce the postoperative leg length discrepancy.