A radiological study of the true anatomical position of the acetabulum in Japanese women

Computer simulation study of cementless cup placement for dysplastic hip osteoarthritis using subluxation percentage of Crowe classification

It is often difficult to achieve adequate bone coverage of the cup in total hip arthroplasty in cases of severe developmental dysplasia of the hip (DDH). This study aimed to evaluate the relationship between subluxation percentage of Crowe classification and cup center-edge (cup-CE) angle to investigate whether subluxation percentage according to the Crowe classification is a useful indicator for cementless cup placement. Cementless cup placement was simulated in 77 women with DDH in 91 hips (Crowe I, 35 hips; Crowe II, 35 hips; and Crowe III, 21 hips) using computed tomography-based computer simulation software. The cups were placed at the anatomic hip center (AHC) and 10-mm high hip center (HHC). The relationship between the subluxation percentage and cup-CE angle was evaluated using Spearman's rank correlation coefficient. In addition, the cutoff values for the subluxation percentage that satisfied a cup-CE angle ≥0° were determined using the receiving operating characteristic curve. The cup-CE angle was negatively correlated with the subluxation percentage in both AHC and 10-mm HHC (correlation coefficient ρ = -0.542 [p < 0.01] and -0.704 [p < 0.01], respectively). The cutoff values for subluxation percentage that satisfied a cup-CE angle ≥0° were 56.1% and 73.6% for AHC and 10-mm HHC, respectively. Cementless cup placement in AHC is difficult in cases with the subluxation percentage ≥56.1%, and HHC reconstruction or femoral structural autograft technique should be considered as an alternative. Moreover, placement at 10 mm above AHC is difficult in cases with subluxation percentage ≥73.6%.

Comparative Study of Highly Cross-Linked Polyethylene Liner Wear by Hip Center Location Using Elevated Hip Center Technique in Crowe I to III Hip Dysplasia: Outcomes for a Minimum of Eighteen Years of Follow-Up

BACKGROUND

The literature has reported that supero-lateralization of the femoral head increases the rates of aseptic loosening and prosthesis revision. However, there are few reports on the influence of different hip center positions on liner wear with more than a 15-year follow-up period.

METHODS

From April 2000 to August 2003, 91 patients underwent 108 total hip arthroplasties using a highly cross-linked polyethylene liner combined with zirconia femoral head and cup components. Pelvic radiographs were used to assess the vertical and horizontal distances to the center of the hip and the amount of liner wear. Mean patient age at the time of surgery was 54 years (range, 33 to 73), and mean follow-up duration was 19 years (range, 18 to 21).

RESULTS

Average liner wear was 0.221 mm, with average annual wear of 0.012 mm/year. Mean vertical and horizontal distances for the hip center were 24.9 and 31.8 mm, respectively. There was no difference in linear wear between patients who had different hip center heights (<20, 20 to 30, and >30 mm), and quadrant partitioning showed no differences across the 4 quadrant zones.

CONCLUSION

At a minimum of 18 years of follow-up in patients having developmental dysplasia of the hip who had different Crowe subtypes and different hip centers, elevated hip center and uncemented fixation techniques using a highly cross-linked polyethylene on ceramic components were associated with very low wear rates and excellent functional scores.

Femoral nerve status during the anterolateral approach for total hip arthroplasty: Motor-evoked potential analysis and an influencing factor

BACKGROUND

Femoral nerve palsy is an uncommon but serious complication during the anterolateral approach for total hip arthroplasty. One of the reported reasons for femoral nerve palsy is retractor-induced intraoperative damage after retractor placement on the anterior wall of the acetabulum. The present study aimed to clarify the femoral nerve status during anterolateral approach total hip arthroplasty using motor-evoked potential analysis and to identify risk factors influencing the nerve status.

METHODS

From June 2019 to September 2020, 32 hips in 31 patients underwent primary total hip arthroplasty via the anterolateral approach. The integrity of the femoral nerve was tested by the motor-evoked potential at three time points: preoperatively as a control (first period), immediately after retractor placement on the anterior wall of the acetabulum (second period), and after the procedure (third period). In the second period, the hips were divided into the following two groups: a <50% femoral nerve amplitude group and a ≥50% group. The iliopsoas muscle volume was evaluated by measuring the muscle cross-sectional area on preoperative computed tomography images, and compared between the two groups.

RESULTS

The mean amplitude of the femoral nerve was significantly reduced from 100% in the first period to 35% in the second period (p < 0.01), but then significantly recovered to 54% in the third period (p < 0.01). In 26 (81%) hips, the femoral nerve amplitude was <50% in the second period. The muscle cross-sectional area of the iliopsoas muscle in the <50% group was significantly smaller than that in the ≥50% group (p < 0.05).

CONCLUSIONS

The mean amplitude of the femoral nerve was significantly reduced to 35% in the second period, and the iliopsoas muscle volume was considered to influence this femoral nerve status.

Total hip arthroplasty after rotational acetabular osteotomy for developmental dysplasia of the hip: a retrospective observational study

Background

Total hip arthroplasty after osteotomy is more technically challenging than primary total hip arthroplasty, especially concerning cup placement. This is attributed to bone morphological abnormalities caused by acetabular bone loss and osteophyte formation. This study aimed to investigate the clinical and radiological outcomes of total hip arthroplasty after rotational acetabular osteotomy compared with those of primary total hip arthroplasty, focusing mainly on acetabular deformity and cup position.

Methods

The study included 22 hips that had undergone rotational acetabular osteotomy and 22 hips in an age- and sex-matched control group of patients who underwent total hip arthroplasties between 2005 and 2020. We analyzed cup abduction and anteversion; lateral, anterior, and posterior cup center–edge angle; hip joint center position; femoral anteversion angle; and presence of acetabular defect using postoperative radiography and computed tomography. Operative results and clinical evaluations were also analyzed.

Results

The clinical evaluation showed that the postoperative flexion range of motion was lower in total hip arthroplasty after rotational acetabular osteotomy than in primary total hip arthroplasty, although no significant difference was noted in the postoperative total Japanese Orthopedic Association hip score. The operative time was significantly longer in the rotational acetabular osteotomy group than in the control group, but there was no significant difference in blood loss. The lateral cup center–edge angle was significantly higher and the posterior cup center–edge angle was significantly lower in the total hip arthroplasty after rotational acetabular osteotomy, suggesting a posterior bone defect existed in the acetabulum. In total hip arthroplasty after rotational acetabular osteotomy, the hip joint center was located significantly superior and lateral to the primary total hip arthroplasty.

Conclusions

In total hip arthroplasty after rotational acetabular osteotomy, the cup tended to be placed in the superior and lateral positions, where there was more bone volume. The deformity of the acetabulum and the high hip center should be considered for treatment success because they may cause cup instability, limited range of motion, and impingement.

Wear of a Highly Cross-Linked Polyethylene Liner of the Acetabular Component Placed With Excessive Acetabular Inclination

Few studies have investigated the influence of excessive acetabular inclination during total hip arthroplasty (THA) on the wear of highly cross-linked polyethylene (HXLPE). The goal of this study was to determine whether excessive acetabular inclination during THA causes prominent wear of the HXLPE liner. We retrospectively evaluated 62 hips of 54 women and 8 men who underwent primary THA with an HXLPE liner between January 2006 and September 2011. Postoperative anteroposterior pelvic radiographs were used to measure acetabular inclination and analyze polyethylene wear. Patients were divided into the following groups: the excessive acetabular inclination group (acetabular inclination angle ≥50°; n=20) and the control group (acetabular inclination angle <50°; n=42). Clinical information and imaging findings were compared and examined between the 2 groups. Further, we evaluated the correlation between the acetabular inclination angle and the polyethylene wear rate. In all cases, mean follow-up duration was 6.3 years. The annual liner wear was 0.00446 and 0.0254 mm/y in the control and excessive acetabular inclination groups, respectively. The excessive acetabular inclination group had significantly higher polyethylene liner wear compared with the control group (P=.00991). A weak correlation was seen between acetabular inclination angle and polyethylene wear rate in all cases (Spearman's rank correlation, r=0.283, P=.0258). Excessive acetabular inclination may increase HXLPE liner wear in the long term. [Orthopedics. 2022;45(2):e96-e100.].

Is Ranawat triangle method accurate in estimating hip joint center in Japanese population?

BACKGROUND

Little information has been available regarding the usefulness of Ranawat triangle method in estimating anatomical hip joint center in the Japanese population. In this study, we aimed to determine the accuracy of the method in estimating hip joint center.

METHODS

Using digitally reconstructed radiographs of 123 normal hips (123 patients), we measured the hip joint center coordinates (Cx, Cy) with reference to the ipsilateral lowest point of the teardrop, the pelvic width, and the pelvic height. Using these measurement values, we performed the following analyses: (1) the relationship of hip joint center location with pelvic dimensions; (2) accuracy of Ranawat method in estimating hip joint center; (3) alternative methods to estimate hip joint center using pelvic height.

RESULTS

The mean Cx and Cy were 32 ± 3.0 mm and 13 ± 2.1 mm, respectively. Pelvic height was positively correlated with Cx (r = 0.51, p < 0.001) and Cy (r = 0.69, p < 0.001), but the correlations of pelvic width with Cx and Cy were negligible. The mean estimation error of the Ranawat method was -6.7 ± 2.6 mm in x-axis and 6.6 ± 1.9 mm in y-axis, respectively. The hip joint center was estimated within a 5 mm error in both axes in only 8 hips (6.5%). Thus, we developed two estimating methods using pelvic height, modified Ranawat method and pelvic height ratio method, and the estimation errors of these methods were within 5 mm in both axes in 118 hips (96%) and 116 hips (94%), respectively.

CONCLUSIONS

Ranawat method showed poor accuracy in estimating anatomical hip joint center and is not recommended for clinical use. Our alternative methods may be useful for surgeons planning the position of the acetabular component in total hip arthroplasty.

Satisfactory Outcomes in Patients Operated With Primary Total Hip Arthroplasty for Perthes-like Deformities: Results From a Surgical Technique Utilizing a Conical Stem, an Elevated Hip Center, and No Shortening Femoral Osteotomy

Background

Total hip arthroplasty (THA) performed on patients with Perthes-like deformities are technically challenging because of the patient's abnormal hip anatomy. Patients with Perthes-like deformities are at a higher risk of revision, aseptic loosening, nerve injury, and intraoperative fracture after THA, especially if shortening osteotomies are performed. This analysis sought to examine the clinical and radiographic outcomes of a patient cohort with Perthes-like deformities receiving THA with a conical stem, an elevated hip center, and no shortening femoral osteotomy.

Methods

Twenty-six patients (27 hips) received THA with MODULUS femoral stems, ceramic or metal femoral heads, and highly cross-linked polyethylene liners between April 2011 and March 2016. All patients were treated at a single center by 4 participating surgeons. Patients completed 2 questionnaires preoperatively and at the final follow-up visit (between 1 and 5 years postoperatively): Harris Hip Score and Japanese Orthopaedic Association Hip-Disease Evaluation Questionnaire. Differences in patient-reported outcome measures (PROM) scores were measured by paired t-tests. Preoperative and postoperative anteroposterior radiographs were analyzed to monitor patient outcomes.

Results

Significant clinical improvements were observed in all individual subcategories of the Harris Hip Score and of the Japanese Orthopaedic Association Hip-Disease Evaluation Questionnaire; the largest magnitude improvements were observed in the subcategory of pain relief for both questionnaires. No complications, including intraoperative and postoperative femoral fractures, nerve palsy, dislocations, or deep venous thrombosis, were observed.

Conclusion

This study found that patients treated with an elevated hip center and low stem-positioning technique using a conical, modular implant system had good clinical outcomes and did not suffer complications at the mean follow-up from surgery of 2.8 years (range: 1-5 years).

Computed Tomographic Osteolytic Analysis of a First-Generation Remelted Highly Cross-Linked Polyethylene in Total Hip Arthroplasty-At a Minimum of 15-Year Follow-Up

BACKGROUND

Low polyethylene wear rate and low incidence of osteolysis have been reported after total hip arthroplasty (THA) using first-generation remelted highly cross-linked polyethylene (HXLPE). However, osteolysis has not been evaluated in long-term studies of these patients (15 years or more). The present study assessed computed tomography (CT) images to determine the incidence of osteolysis associated with HXLPE in THA during at least 15 years of follow-up.

METHODS

We evaluated 105 primary THAs in 84 patients (77 women and 7 men). Mean follow-up was 15.9 years (range, 15-18 years). All THAs used a Longevity HXLPE liner and a 26-mm zirconia femoral head. Areas of osteolysis were identified from CT images using 3D and multiplanar reconstruction views.

RESULTS

CT 3D multiplanar reconstruction images at 15-year follow-up showed no obvious osteolysis in the acetabulum or femur of any patient. No patients developed cup loosening or liner breakage.

CONCLUSION

Our study indicates that first-generation remelted HXLPE liners do not increase the risk of osteolysis during 15-year follow-up and suggests that the wear particles from first-generation remelted HXLPE are less biologically active than those generated by conventional polyethylene devices.

Can the hip joint center be estimated from pelvic dimensions in dysplastic hips?

BACKGROUND

We aimed to determine correlations between the hip joint center position and pelvic dimensions and whether the three-dimensional position of the original hip joint center could be estimated from pelvic landmarks in dysplastic and normal hips.

METHODS

We reviewed the pelvic CT scans of 70 patients (70 hips) with hip dysplasia. Seventy-seven normal hips were used as controls. The hip joint center coordinates (Cx, Cy, and Cz) and pelvic dimensions were measured with reference to the anterior pelvic plane coordinate system. Multiple regression formulas were used to estimate the original hip joint center.

RESULTS

The hip center for both dysplastic and normal hip was highly correlated with the distance between the anterior superior iliac spine (ASIS) in the coronal plane (r = 0.76 and 0.84), the distance from the ASIS to the pubic tubercle in the sagittal plane (r = 0.81 and 0.76), and distance from the pubic tubercle to the most posterior point of the ischium on the transverse plane (r = 0.76 and 0.78). The hip joint center could be estimated within a 5-mm error for more than 80% of hips on their respective axes in both dysplastic and normal hips.

CONCLUSIONS

The three-dimensional position of the original hip joint center was correlated with pelvic dimensions, and can be estimated with substantial accuracy using pelvic landmarks as references. Although these results are preliminary, this estimation method may be useful for surgeons planning total hip arthroplasties.

Favorable Results of Primary Total Hip Arthroplasty With Acetabular Impaction Bone Grafting for Large Segmental Bone Defects in Dysplastic Hips

BACKGROUND

The aim of the present study was to assess midterm results after acetabular impaction bone grafting (IBG) in primary total hip arthroplasty (THA) for developmental dysplasia of the hip (DDH) with large acetabular segmental defect.

METHODS

Primary THA with IBG for DDH with large acetabular segmental defect was performed in 40 hips of 38 patients. The average age was 61.6 years (range: 33-82 years), and the average follow-up period was 7.5 years (range: 3-10.3 years). The Merle d'Aubigné and Postel hip score and complications were assessed. For radiological assessment, postoperative location of the hip rotation center, the socket inclination angle, and the socket center-edge angle were assessed. Kaplan-Meier survival analysis was performed with the end points of any type of reoperation and aseptic acetabular loosening.

RESULTS

The mean Merle d'Aubigné and Postel hip score improved from 10.4 points to 16.2 points at the final follow-up. Reoperation was performed in 1 case for acute infection without loosening. In 39 out of 40 hips (97.5%), the center of hip rotation was located beneath the "high hip center." The average socket inclination angle was 39.3° (range: 30°-54°), and the average socket center-edge angle was -11.8° (range: -23° to 9°). Survival rate of acetabular component at 8 years with the end point of any reoperation and of aseptic loosening was 96.6% (95% confidence interval: 89.9%-100%) and 100%, respectively.

CONCLUSION

Acetabular IBG represents one of the useful options for restoring a normal hip center and acetabular bone stock in primary THA for DDH with large acetabular defect.

Significantly Poor Outcomes of Total Hip Arthroplasty After Failed Periacetabular Osteotomy

BACKGROUND

Periacetabular osteotomy (PAO) is an effective treatment for preosteoarthritis and early osteoarthritis in young and active patients with hip dysplasia. However, conversion to total hip arthroplasty (THA) for failed PAO is difficult owing to morphologic changes. The objective of the present study was to investigate outcomes of patients who underwent THA for failed PAO.

METHODS

We performed a case-control study. The participants were 48 patients (52 hips) who underwent THA after PAO (the osteotomy group); type of PAO was eccentric rotational acetabular osteotomy in 36 hips and rotational acetabular osteotomy in 16 hips. These patients had a mean age at surgery of 56.5 years and underwent postoperative follow-up for a mean period of 5.4 years. For the control group, after matching age, gender, and time of surgery, we included 96 patients (104 joints) who underwent primary THA for hip dysplasia.

RESULTS

The 2 groups demonstrated no significant difference in the preoperative Harris Hip Score. However, the osteotomy group demonstrated a significantly poor Harris Hip Score at the last follow-up, with particularly low scores for gait and activity. The osteotomy group demonstrated significantly poor range of motion at the last follow-up. Although neither group had any cases of revision surgery, both groups had 1 case of postoperative dislocation. Considering socket placement in Lewinnek's safe zone, the osteotomy group had significantly poorer results compared to that obtained after primary THA.

CONCLUSION

The therapeutic outcomes and socket positioning for THA after PAO were poorer compared to those of primary THA.

Total hip arthroplasty after rotational acetabular osteotomy

In this study, we aimed to determine whether the outcomes of total hip arthroplasty (THA) after rotational acetabular osteotomy (RAO) are equal to those of primary THA, and to elucidate the characteristics of THA after RAO. The clinical and radiographic findings of THA after RAO (44 hips), with minimum 24 months of follow-up, were compared with a matched control group of 58 hips without prior RAO. We found that the outcomes in terms of functional scores and complication rates did not differ between THA after RAO and THA without previous pelvic osteotomy, indicating that the results of THA after RAO are equivalent to those of primary THA. Although THA after RAO requires technical considerations, similar clinical outcomes to primary THA can be expected.

Massive bone defect compromises postoperative cup survivorship of acetabular revision hip arthroplasty with impaction bone grafting

We evaluated 66 acetabular revision arthroplasties using cemented cup with impaction bone grafting (IBG) to detect the extent that bone defect affects the outcome. We defined the maximum acetabular defect distance (MADD), which indicates the greatest depth of the grafted layer. Cup survival analysis with aseptic loosening as the endpoint revealed that the "MADD≤20mm" group showed higher survivorship than the "MADD>20mm" group (95% vs. 74%, P=0.034), and that the simple-wall-defect group (none or one mesh used) showed higher survivorship than the complex-wall-defect group (two meshes used) (96% vs. 73%, P=0.044). A favorable indication for acetabular IBG reconstruction is cases in which those cups can be placed at≤20mm MADD with a simple wall defect.

How far above the true anatomic position can the acetabular cup be placed in total hip arthroplasty?

INTRODUCTION

There is controversy about which is more suitable for determining correct socket position in patients with severe bone deficiency of the acetabular roof because of developmental dysplasia of the hip (DDH): the anatomic centre of hip rotation or a high centre. 


METHOD

We evaluated the relationship, in 200 hips, between the centre of rotation and presence of the Trendelenburg sign to determine the upper limit of cup position from the standpoint of hip-abductor strength. 


RESULTS

Of the 200 hips, 20 (10%) showed a positive Trendelenburg sign. There were no statistically significant differences between parameters (the centre of rotation, femoral offset, abductor lever arm) regarding the presence of the Trendelenburg sign except for age at surgery. Patients with a positive Trendelenburg sign were significantly older (64.1 ± 9.4 years) than those with a negative Trendelenburg sign (58.8 ± 7.7 years) (P = 0.01).


CONCLUSIONS

Our findings indicate that a high centre of hip rotation of up to approximately 30 mm from the inter-teardrop line is a feasible option for patients with DDH from the standpoint of hip-abductor strength if stems are used that allow the restoration of femoral offset and the abductor lever arm.

The techniques of soft tissue release and true socket reconstruction in total hip arthroplasty for patients with severe developmental dysplasia of the hip

PURPOSE

Total hip arthroplasty (THA) is an effective procedure for developmental dysplasia of the hip (DDH); however, it is sometimes difficult to complete for severe cases because of femoral head dislocation, dysplasia of the acetabulum and the femur, disparity in limb length, soft tissue contraction, and muscular atrophy. We aimed at exploring the efficiency of the techniques of release and balance of soft tissues and reconstruction of true socket THA for patients with severe DDH.

METHODS

From January 2000 to January 2009, 46 adult patients with severe DDH (50 hips) were included in this study. According to the classification system, there were 26 type III and 24 type IV. Among them there were 32 women and 14 men, aged from 38 to 77 years. THA was performed via a lateral approach. All acetabular sockets were reconstructed at the original anatomical location following a meticulous technique of soft tissue release and balance around the hip to restore limb length, to strengthen the abductor and improve its function.

RESULTS

All patients had restoration of limb length (range, 2.5-5.5 cm; 30 limbs of more than 4 cm) without injury to the sciatic nerve. One postoperative dislocation occurred due to slight enlargement of the angle of abduction of the acetabulum. The follow-up ranged from 2.2 to 11.5 years (median 6.4 years) in 46 patients, and the Harris score increased from 40.2 preoperatively to 86.5 (P = 0.027). All hips were pain free with good function at the latest follow-up.

CONCLUSION

The meticulous techniques of soft tissue release and balance can be recommended to ensure anatomical reconstruction of the true acetabular socket and to improve abductor function during arthroplasty for DDH.