Clinical results of periacetabular osteotomy with structural bone allograft for the treatment of severe hip dysplasia.

Aims: To clarify the mid-term results of transposition osteotomy of the acetabulum (TOA), a type of spherical periacetabular osteotomy, combined with structural allograft bone grafting for severe hip dysplasia. Methods: We reviewed patients with severe hip dysplasia, defined as Severin IVb or V (lateral centre-edge angle (LCEA) < 0°), who underwent TOA with a structural bone allograft between 1998 and 2019. A medical chart review was conducted to extract demographic data, complications related to the osteotomy, and modified Harris Hip Score (mHHS). Radiological parameters of hip dysplasia were measured on pre- and postoperative radiographs. The cumulative probability of TOA failure (progression to Tönnis grade 3 or conversion to total hip arthroplasty) was estimated using the Kaplan-Meier product-limited method, and a multivariate Cox proportional hazard model was used to identify predictors for failure. Results: A total of 64 patients (76 hips) were included in this study. The median follow-up period was ten years (interquartile range (IQR) five to 14). The median mHHS improved from 67 (IQR 56 to 80) preoperatively to 96 (IQR 85 to 97) at the latest follow-up (p < 0.001). The radiological parameters improved postoperatively (p < 0.001), with the resulting parameters falling within the normal range in 42% to 95% of hips. The survival rate was 95% at ten years and 80% at 15 years. Preoperative Tönnis grade 2 was an independent risk factor for TOA failure. Conclusion: Our findings suggest that TOA with structural bone allografting is a viable surgical option for correcting severely dysplastic acetabulum in adolescents and young adults without advanced osteoarthritis, with favourable mid-term outcomes.

Joint awareness following periacetabular osteotomy in patients with hip dysplasia.

Aims: The aims of this study were to validate the Forgotten Joint Score-12 (FJS-12) in the postoperative evaluation of periacetabular osteotomy (PAO), identify factors associated with joint awareness after PAO, and determine the FJS-12 threshold for patient-acceptable symptom state (PASS). Methods: Data from 686 patients (882 hips) with hip dysplasia who underwent transposition osteotomy of the acetabulum, a type of PAO, between 1998 and 2019 were reviewed. After screening the study included 442 patients (582 hips; response rate, 78%). Patients who completed a study questionnaire consisting of the visual analogue scale (VAS) for pain and satisfaction, FJS-12, and Hip disability and Osteoarthritis Outcome Score (HOOS) were included. The ceiling effects, internal consistency, convergent validity, and PASS thresholds of FJS-12 were investigated. Results: The median follow-up was 12 years (interquartile range 7 to 16). The ceiling effect of FJS-12 was 7.2%, the lowest of all the measures examined. FJS-12 correlated with all HOOS subscales (ρ = 0.72 to 0.77, p < 0.001) and pain and satisfaction-VAS (ρ = -0.63 and 0.56, p < 0.001), suggesting good convergent validity. Cronbach's α was 0.95 for the FJS-12, which indicated excellent internal consistency. The median FJS-12 score for preoperative Tönnis grade 0 hips (60 points) was higher than that for grade 1 (51 points) or 2 (46 points). When PASS was defined as pain-VAS < 21 and satisfaction-VAS ≥ 77, the FJS-12 threshold that maximized the sensitivity and specificity for detecting PASS was 50 points (area under the curve (AUC) = 0.85). Conclusion: Our results suggest that FJS-12 is a valid and reliable assessment tool for patients undergoing PAO, and the threshold of 50 points may be useful to determine patient satisfaction following PAO in clinical settings. Further investigation of the factors influencing postoperative joint awareness may enable improved prediction of treatment efficacy and informed decision-making regarding the indication of PAO.

Fragility fracture following total hip arthroplasty.

BACKGROUND: While periprosthetic fractures following total hip arthroplasty (THA) are a well-known phenomenon for orthopedic surgeons, fragility fractures following THA are also a significant, though less studied, concern. Furthermore, patients who have undergone THA have several additional risk factors for fragility fractures, including motor weakness, bone atrophy, and limping. The aims of this study were to evaluate the incidence of fragility fractures following THA and to clarify the characteristics of these fractures. METHODS: This study included 5678 primary THA procedures in 4589 female patients. This study evaluated body morphology data, disease type leading to THA, Japanese Orthopaedic Association hip score, range of motion of the hip joint, and medical history. Distal radius and patella fractures were defined as fragility fractures. Risk factors for fragility fractures after THA were calculated by comparing the fragility fracture group with the non-fracture group. RESULTS: Fifty-three fragility fractures were confirmed in 53 patients (distal radius fracture: 32 fractures in 32 patients, patella fracture: 21 fractures in 21 patients). In the univariate analysis, the following eight risk factors for fragility fractures were significantly different between the groups: height, weight, follow-up period, developmental dysplasia of the hip, primary osteoarthritis, abduction before THA, internal rotation before THA, and external rotation before THA. Medical histories were not significantly different between the groups. There was no difference in any study factor and in the time of occurrence between the radius fractures and patella fractures analyzed as fragility fractures. CONCLUSIONS: This study revealed that there are significant preoperative factors of fragility fractures following THA. These factors will serve as useful data for THA treatment strategies, preoperative explanations, and future studies.

Conventional cementless total hip arthroplasty in patients with dwarfism with height less than 140 cm and minimum 10-year follow up: A clinical study.

BACKGROUND: Orthopedic complications can cause issues and severe disability in patients with dwarfism. Thus, these individuals frequently undergo total hip arthroplasty to mitigate decline in daily functioning. Although studies have reported on the difficulties of orthopedic surgery in patients with dwarfism, many do not clearly define dwarfism and have a short follow-up period. We aimed to retrospectively investigate the clinical and radiographic results of total hip arthroplasty for patients with dwarfism. METHODS: A total of 68 hips of 49 patients with height <140 cm and at least 10-year follow-up periods were enrolled. All patients had conventional cementless implants. All hips were evaluated using the Japanese Orthopaedic Association hip score. RESULTS: The main hip disease etiologies were primary hip osteoarthritis (58%) and secondary osteoarthritis due to developmental dysplasia (31%). Rheumatoid arthritis, rapidly destructive coxarthrosis, spondyloepiphyseal dysplasia, childhood infection, and femoral head aseptic necrosis were also causative pathologies. Hip scores significantly improved from 44 to 82 out of 100. Overall implant-associated survival rate after 10 years was 94.1%. Cup loosening was observed in 2 hips, and subsidence >5 mm was observed in 9 hips. Presence of Crowe IV in hips was a significant risk factor for total hip arthroplasty in patients with dwarfism (p < 0.05); leg lengthening had a weak but significant correlation (r = 0.253, p < 0.05). CONCLUSIONS: Total hip arthroplasty using conventional cementless implants for patients with dwarfism shows good clinical and radiological outcomes and has a relatively low perioperative risk.

Total hip arthroplasty using hydroxyapatite-coated cementless cup for rapidly destructive coxarthrosis: Minimum 10-year follow-up.

BACKGROUND: Performing total hip arthroplasty (THA) as early as possible is recommended for rapidly destructive coxarthrosis (RDC) as it causes pain that becomes progressively more severe. However, acetabular bone loss remains an issue in THA. Special devices, such as a Kerboull-type plate, may be used for acetabular bone defects, but the procedure is highly invasive and often the patients are elderly, further complicating matters. We retrospectively investigated the clinical and radiographic results of THA using conventional hydroxyapatite-coated cementless cup in RDC. METHODS: A total of 32 patients (35 hips) with RDC were enrolled in the study with a minimum 10-year follow-up. All THAs were performed using conventional hydroxyapatite-coated cementless cup. All patients were evaluated clinically according to the Harris hip score (HHS). Acetabular bone deficiency was classified according to the American Academy of Orthopaedic Surgeons (AAOS) classification. RESULTS: Eleven hips (31%) were AAOS type III, and none were type IV. Total HHS significantly improved from 36.5 to 79.4 (p < 0.01). Two cups exhibited loosening. The overall implant-associated survival rate after 10 years was 91.4%. CONCLUSIONS: Clinical results of THA using conventional cementless implants for patients with RDC were acceptable. Thus, THA using conventional cementless implant is an effective and safe surgery for patients with RDC, minimizing surgical stress.

First experience with a thermal-sprayed silver oxide-containing hydroxyapatite coating implant in two-stage total hip arthroplasty for the treatment of septic arthritis with hip osteoarthritis: A case report.

INTRODUCTION: Septic arthritis of the hip joint in adults is a rare and potentially devasting disease. To the best of our knowledge, there have been no reports of two-stage total hip arthroplasty (THA) for the treatment of septic arthritis of the hip joint with a cementless hip implant that has antibacterial properties. PRESENTATION OF CASE: We present a case of two-stage THA with a thermal-sprayed silver oxide-containing hydroxyapatite coating (Ag-HA) implant to treat septic arthritis of the hip joint with hip osteoarthritis in an 80-year-old woman. There was no complication or recurrence at 28 months follow-up after 2nd-stage operation. DISCUSSION: Ag-HA implants were found to have antibacterial activity within the subcutaneous tissues and bone, osteoconductive properties, and no adverse reactions in vivo. Moreover, no adverse events due to silver were reported in a clinical or radiographic study. CONCLUSION: To further reduce infection after two-staged THA for septic arthritis of the hip joint, antibacterial implants, such as an Ag-HA implant, may be used.

Investigation of the priority among the roentgenogram measurements in acetabular dysplasia.

PURPOSE: There are many radiographic parameters to evaluate developmental dysplasia of the hip joint (DDH); however, the priority between the parameters is unclear. We evaluated the priority of radiographic parameters in DDH. METHODS: We retrospectively reviewed the radiographs of 82 consecutive patients aged above 85 years without hip osteoarthritis (OA; no osteoarthritis (NO) group), and 28 patients with early stage hip OA were set as the control group (OA group). We used the linear discriminant analysis (LDA) to consider the priority of the following parameters: acetabular roof obliquity (ARO), center-edge (CE) angle, Sharp angle, acetabular head index (AHI), and acetabular depth ratio (ADR). RESULTS: The LDA of five different parameters revealed that the NO and OA groups could be almost distinguished with 83.6% accuracy (p < 0.0001, Wilks' lambda test). The standardized scoring coefficients were as follows: ARO, -0.23; CE, -0.43; Sharp, -0.29; AHI, 0.97; and ADR, 0.11. The AHI was particularly noticeable in the NO group. CONCLUSION: Dissociation of the AHI in the OA group was significantly higher than that of the other parameters in the OA group compared to the parameters in the NO group. A small AHI may be a risk parameter for hip OA due to DDH.

Hip-Spine Syndrome: The Coronal Alignment of the Lumbar Spine and Pelvis in Patients with Ankylosed Hips.

INTRODUCTION: Fixed abduction and/or adduction deformities of the hip joint may cause pelvic obliquity with subsequent development of secondary lumbar scoliosis. However, the relationships between the magnitude of a fixed angle (either abduction or adduction) of the hip and the direction of pelvic tilt and lumbar scoliosis remain unclear. The purpose of this study was to investigate the coronal alignment of the lumbar spine and pelvis in patients with ankylosed hips. METHODS: A total of 56 patients were analyzed, including 17 males and 39 females, with an average age of 65 years (range: 45 to 80 years). Regarding the coronal spinopelvic alignment, the following parameters were measured: the degree of lumbar scoliosis (LS; Cobb angle), pelvic obliquity (PO), and ankylosed hip angle (AHA). The PO and AHA were defined as the angle between the inter-teardrop line and a horizontal line, respectively, and the long axis of the femur on the side of the ankylosed hip. For each parameter, correlations between the parameters were evaluated using a regression analysis. A P value of <0.05 was considered significant. RESULTS: Positive linear correlations were observed between the AHA and direction of the PO angles (r = 0.831, p<0.01), the AHA and direction of the LS angles (r = 0.770, p<0.01), and the directions of the PO and LS angles (r = 0.832, p<0.01). CONCLUSIONS: This study provides evidence to suggest that, in patients with ankylosed hips, the abduction position is positively correlated with the downward PO and the convexity of the LS toward the AH side. In contrast, the adduction position is positively correlated with these results on the opposite side.

Reduction of Postoperative Pain by Addition of Intravenous Acetaminophen after Total Hip Arthroplasty: A Retrospective Cohort Study.

We evaluated the analgesic effects of multimodal pain control in which intravenous acetaminophen (IV APAP) was added to the standard protocol for Japanese patients who had undergone a total hip arthroplasty (THA). We performed a retrospective cohort study of 180 patients aged 66.4±10.5 years (30% male) who had undergone a THA (Oct. 2014 to Feb. 2015) at our hospital. The control patients were administered the standard analgesic protocol: flurbiprofen axetil as a continuous intravenous infusion and oral celecoxib (NAPAP; n=109). The patients in the new analgesic protocol group received IV APAP in addition to the standard analgesic protocol (APAP; n=71). The primary outcome was the maximum value of postoperative pain the patients reported on a numerical rating scale (NRS) during the first 24 h post-surgery. A univariate analysis and multivariate analyses adjusted for age, sex, the stage of hip osteoarthritis, preoperative pain, and surgical time showed that the maximum postoperative pain NRS scores during the first 24 h after surgery was significantly lower when the APAP protocol was used. The addition of IV APAP to the current standard multimodal analgesia protocol for Japanese patients who have undergone a THA may decrease the patients' postoperative pain.

Bone ongrowth of a cementless silver oxide-containing hydroxyapatite-coated antibacterial acetabular socket.

BACKGROUND: The silver oxide-containing hydroxyapatite-coated socket (KYOCERA, Osaka, Japan) is a cementless antibacterial implant that has both the osteoconductivity of the HA and the antibacterial activity of silver. The silver oxide-containing hydroxyapatite coating was shown to have good osteoconductivity and new bone formation in vitro and in vivo. However, the histological bone ongrowth of this implant has not been proven in a clinical study. METHODS: We analyzed bone ongrowth using two silver oxide-containing hydroxyapatite-coated sockets that were removed in revision total hip arthroplasty for recurrent dislocation. A histomorphometric analysis was performed using a scanning electron microscope (SEM) connected to a CCD camera and an elemental analysis was performed by energy-dispersive elemental spectrometry (EDS). RESULT: A white structure thought to be osseous tissue was attached to the retrieved socket surface macroscopically, and histological bone ongrowth of the silver oxide-containing hydroxyapatite coating of the socket was confirmed by SEM. In addition, the presence of silver in the silver oxide-containing hydroxyapatite coating was confirmed in an elemental analysis by EDS. CONCLUSION: Histologically, the silver oxide-containing hydroxyapatite-coated socket presented bone ongrowth in this clinical study.

Risk Factors of Neuropathic Pain after Total Hip Arthroplasty.

PURPOSE: Pain caused by osteoarthritis is primarily nociceptive pain; however, it is considered that a component of this pain is due to neuropathic pain (NP). We investigated the effects of total hip arthroplasty (THA) in patients with NP diagnosed by the PainDETECT questionnaire. MATERIALS AND METHODS: One hundred sixty-three hips (161 patients) were evaluated. All patients were asked to complete the PainDETECT questionnaire based on their experience with NP, and clinical scores were evaluated using the Japanese Orthopaedic Association (JOA) Hip Score before and after THA. RESULTS: The patients of 24.5% reported NP before THA; 5.5% reported NP 2 months after THA. Prior to THA, there was no significant correlation between the PainDETECT score and the radiographic severity; however, there was a significant correlation between the PainDETECT score and JOA score. NP at 2 months after THA was not significantly correlated with pain scores at 1 week after THA; however, a significant correlation was observed between the preoperative pain score and NP at 2 months after THA. CONCLUSION: THA was useful for relieving nociceptive pain and for relieving NP in patients with hip osteoarthritis. Preoperative pain was a risk factor for NP after THA. Controlling preoperative pain may be effective for reducing postoperative NP.

Comparison of Total Hip Arthroplasty Outcomes after Failed Femoral Wedge or Curved Varus Osteotomy.

BACKGROUND: Differences in clinical and radiographic results following total hip arthroplasty between failed wedge and curved varus osteotomy are unclear. OBJECTIVE: To investigate differences in clinical and radiographic results following total hip arthroplasty in patients who exhibited failed wedge or curved varus osteotomy. METHOD: We performed 18 total hip arthroplasties after failed femoral varus osteotomy. Hips were divided into two groups: 14 had failed wedge varus osteotomy and four had failed curved varus osteotomy. Average ages at osteotomy and total hip arthroplasty were 27 years old (range, 10-46 years old) and 56 years old (range, 25-74 years old), respectively. The average duration of follow-up monitoring was 72.2 months (range, 54-91 months). Clinical and radiographic evaluations were completed for each group. RESULTS: The Japanese Orthopaedic Association hip score of total hip arthroplasty after failed varus osteotomy significantly improved at the last follow-up in both groups. However, hip score at the last follow-up was significantly higher after failed curved varus osteotomy than after failed wedge varus osteotomy (p<0.01). Four hips that failed wedge varus osteotomy underwent subtrochanteric corrective osteotomy with total hip arthroplasty. Radiographic evaluation showed that three stems for total hip arthroplasty after failed wedge varus osteotomy were inserted in malposition, and all stems in total hip arthroplasty after failed curved varus osteotomy were inserted in the normal position. CONCLUSION: Surgeons performing femoral varus osteotomy should consider possible future conversion to total hip arthroplasty. Curved varus osteotomy is more suitable than wedge varus osteotomy for future conversion to total hip arthroplasty.

Risk Factors for the Development of Nerve Palsy Following Primary Total Hip Arthroplasty.

BACKGROUND: Nerve palsy following total hip arthroplasty (THA) is a complication that worsens the functional prognosis. The present study analyzed the risk factors of nerve palsy following THA. METHODS: The subjects of this study included 6,123 cases in which primary THA was performed under spinal anesthesia with cementless implants used in the posterolateral approach. RESULTS: Fourteen cases (0.22%) developed nerve palsy following THA, all of which involved palsy of the entire peroneal nerve region. The diagnoses included osteoarthritis due to subluxation (n=6), complete hip dislocation (n=3), osteonecrosis of the femoral head (n=2), primary osteoarthritis (n=1), osteoarthritis due to trauma (n=1), and multiple osteochondromatosis (n=1). Recovery from nerve palsy was confirmed in 10 cases; the longest recovery period was three years. A univariate analysis revealed significant differences in the osteoarthritis due to subluxation, osteonecrosis of the femoral head, complete hip dislocation, body weight and body mass index. However, none of the factors remained significant in multivariate analysis. Peroneal (ischiadic) nerve palsy following THA occurred in patients with osteonecrosis of the femoral head, complete hip dislocation, low body weight and a low body mass index. However, there were no cases of nerve palsy after the introduction of THA combined with shortening osteotomy of the femur for complete hip dislocation. patients. CONCLUSION: It is necessary to pay attention to direct pressure in cases of lower body weight and lower BMI because compression of the sciatic nerve during surgery and compression of the fibular head are considered to be risk factors.

Total Hip Arthroplasty for Patients with Residual Poliomyelitis at a Mean Eight Years of Follow-up.

In patients with poliomyelitis, degenerative arthritis of the hip may be encountered in the paralytic or normal contralateral limb because of leg length discrepancy, pelvic obliquity, or severe deformities of the affected hip. Although total hip arthroplasty (THA) is one of the most common orthopedic procedures, there are few reports of THA in adult patients with residual poliomyelitis. From March 2001 to January 2011, 5 patients with residual poliomyelitis (6 hips) underwent THA using uncemented implants at our hospital. We retrospectively evaluated the Japanese Orthopaedic Association (JOA) hip score, complications, and radiographs. All five patients' follow-up information was available: 4.5 years minimum, 8.4 years average, range 4.5-15 years. Surgery was done at the same side of the paralytic limb in 2 hips and contralateral to the paralytic limb in four hips. All patients had pain relief and improvement in function; JOA hip score improved significantly from the mean of 42.8 preoperatively to 78.8 at the last follow-up (p=0.028). There was no loosening or osteolysis in this series, and no cases of dislocation, infection or nerve palsy. These findings can contribute to decisions regarding treatment for arthritic hips in adults with residual poliomyelitis.

Total Hip Arthroplasty for Patients with Residual Poliomyelitis at a Mean Eight Years of Follow-up.

In patients with poliomyelitis, degenerative arthritis of the hip may be encountered in the paralytic or normal contralateral limb because of leg length discrepancy, pelvic obliquity, or severe deformities of the affected hip. Although total hip arthroplasty (THA) is one of the most common orthopedic procedures, there are few reports of THA in adult patients with residual poliomyelitis. From March 2001 to January 2011, 5 patients with residual poliomyelitis (6 hips) underwent THA using uncemented implants at our hospital. We retrospectively evaluated the Japanese Orthopedic Association (JOA) hip rating score, complications, and radiographs. All five patients' follow-up information was available: 4.5 years minimum, 8.4 years average, range 4.5-15 years. Surgery was done at the same side of the paralytic limb in 2 hips and contralateral to the paralytic limb in four hips. All patients had pain relief and improvement in function; JOA hip rating score improved significantly from the mean of 45 preoperatively to 78 at the last follow-up (p=0.0313). There was no loosening or osteolysis in this series, and no cases of dislocation, infection or nerve palsy. These findings can contribute to decisions regarding treatment for arthritic hips in adults with residual poliomyelitis.

Total hip arthroplasty following Girdlestone arthroplasty.

BACKGROUND: Complications associated with re-implantation of total hip arthroplasty (THA) after resection arthroplasty for the treatment of primary septic hip arthritis or infected THA and bipolar hemiarthroplasty (BHA) are not well-documented. Furthermore, no comparison has been made between septic arthritis (SA) and infected THA and BHA. We divided subjects into two groups for evaluation: a SA group and an infected THA or BHA group. METHODS: Nineteen hips in 19 patients (12 in the SA group, 7 in the infected THA or BHA group) with an average of 77 months of follow-up from the time of re-implantation THA were retrospectively evaluated. RESULTS: The average Japanese Orthopaedic Association hip score improved from 50 points (range, 30 to 73 points) preoperatively to 80 points (range: 64 to 96 points) at the time of the final follow-up (p < 0.01). Intra- and postoperative complications occurred in 11 cases, including intraoperative fracture in 1 hip, deep infection in 6 hips, dislocation in 7 hips, and septic loosening of acetabular component in 2 hips. Following re-implantation, further surgical revision was required in four cases. Two revisions were performed for recurrent infection: one patient had recurrent dislocation of one hip, and one patient had recurrent infection and dislocation. The number of hips with relapsed infection in the infected THA or BHA group (5 hips) was significantly higher than that in the SA group (1 hip) (p < 0.05). CONCLUSIONS: Re-implantation after septic hip arthritis or infected THA or BHA was an effective treatment for improving the activity of daily life, especially the gait function. Furthermore, 94.7% of patients were free of infection at the latest follow-up. However, the rate of recurrence of infection was 31.6%, and re-implantation after resection arthroplasty following infected THA or BHA led to a lower rate of infection control than that after primary SA.

Sagittal spino-pelvic alignment in rapidly destructive coxarthrosis.

PURPOSE: To investigate the sagittal spino-pelvic alignment (SSPA) in patients with rapidly destructive coxarthrosis (RDC). METHODS: SSPA was investigated in 44 patients with RDC and 70 patients with hip osteoarthritis (HOA). The study included only female patients over the age of 70 years because epidemiological reports indicate that RDC most commonly occurs in this group of patients. The SSPA parameters that were analyzed included lumbar lordosis (LL), lumbar range of motion (ΔLL), sacral slope (SS), pelvic incidence (PI), and pelvic tilt (PT). The pelvic inclination angle (PIA) in the supine position and the change in the PIA from the supine to the standing position (ΔPIA) were measured using anteroposterior pelvic radiographs. The values of these parameters were compared between the two groups. The levels of the SRS-Schwab classification modifiers were used to investigate the degree of sagittal malalignment. RESULTS: The RDC group showed significant lower LL, ΔLL and SS values, and significantly higher PT and ΔPIA values than the HOA group (P < 0.01). With regard to the sagittal modifiers in the SRS-Schwab classifications of the patients, the PI-LL and PT levels of the RDC group were significantly worse than those in the HOA group (P < 0.01). CONCLUSIONS: The present study suggests that the static factors of a reduction in the lumbar lordotic angle and greater posterior pelvic tilt, the dynamic factors of small ΔLL values and large ΔPIA values and the complex interaction of these two types of factors, may play important roles in the development of RDC.

Wear of XLPE liner against zirconium heads in cementless total hip arthroplasty for patients under 40 years of age.

INTRODUCTION: Total hip arthroplasty (THA) in the young is challenging. The purpose of this study was to retrospectively determine the clinical, radiographic, and polyethylene wear rate of relatively young patients. METHODS: We evaluated the outcome of consecutive patients receiving primary THA who were under 40 years of age with a minimum 10-year follow-up. Indications for THA in these patients were osteoarthritis due to developmental dysplasia of the hip joint (9 hips), osteonecrosis of the femoral head (7 hips), juvenile idiopathic arthritis (2 hips), and osteoarthritis due to Perthes disease (1 hip). All THA were performed with a cross-linked ultra-high-molecular-weight polyethylene (XLPE) liner against zirconium heads with cementless implants. RESULTS: The average Japanese Orthopaedic Association hip score significantly improved from 42 to 93 points at the latest follow-up. The mean steady wear was 0.015 mm/year (maximum 0.033 mm/year), and the mean creep wear was 0.111 mm (maximum 0.4 mm). Osteolysis was observed around 1 acetabular component and 2 stems. 1 femoral component had subsidence over 5 mm. All of the femoral components achieved fixation with an optimal interface with spot welds at the latest follow-up. Stress shielding was observed in all hips. CONCLUSIONS: THA using an XLPE liner against zirconium heads appeared to have improved THA longevity. However, the imaging findings in some cases were suggestive of wear debris. A rigorous continual follow-up is required for relatively young patients undergoing THA.