Does high hip centre affect dislocation after total hip arthroplasty for developmental dysplasia of the hip?

Retrospective Review of Outcomes of Total Hip Arthroplasty in Developmental Dysplasia of the Hip in Adults

BACKGROUND

Developmental dysplasia of the hip (DDH) is a major cause of hip arthritis in young adults. Total hip arthroplasty (THA) is an effective treatment for DDH, but few studies have examined mid- (5 to 10 years) to long-term (> 10 years) outcomes. This study reports the long-term survivorship, clinical, and radiographic outcomes of THA in DDH patients.

METHODS

A total of 255 patients were included from our retrospective review of THAs from January 2004 to January 2022. Among these cases, 214 (83.9%) were women; the mean age at the time of surgery was 46 years (range, 18 to 87), and the mean follow-up was 8.3 (range, 0.05 to 21.1) years. Kaplan-Meier survivorship analysis was conducted with failure defined as revision surgery for any reason.

RESULTS

Kaplan-Meier survivorship for patients who underwent THA to treat DDH due to all-cause failure was 93.4% (95% confidence interval (CI): 90.3 to 96.5) at 5 years, 92.5% (95% CI: 89.0 to 95.6) at 10 years, and 90.9% (95% CI: 86.2 to 94.0) at 15 years. The overall rate of revision of the index surgery was 18 of 255 (7.1%). These complications included pain (seven), dislocation (four), aseptic loosening of the cup (three), periprosthetic fracture (two), complete foot drop (one), and infection (one). Kaplan-Meier all-cause survivorship for Hartofilakidis A, B, and C was also conducted and showed no significant differences. The mean femoral offset improved from a preoperative value of 12.2 cm (SD 1.4) to a postoperative value of 11.7 cm (SD 1.1) (P < 0.001). The rate of femoral nerve palsy was 0.78%.

CONCLUSIONS

Our study suggests THA for DDH is a viable treatment, providing excellent mid-term to long-term survivorship, clinical, and radiographic outcomes with a low complication rate. Future research should evaluate patient-reported outcomes and long-term follow-up in larger cohorts.

Preoperative digital design in artificial total hip arthroplasty for patients with Crowe type III and IV developmental dysplasia of the hip: A case series

Successful complete artificial total hip arthroplasty for patients with Crowe type III or IV developmental dysplasia of the hip is challenging in clinical practice. This study aimed to explore the accuracy and effectiveness of preoperative digital design for patients with Crowe type III or IV developmental dysplasia of the hip. This case series study included patients with osteoarthritis secondary to developmental dysplasia of the hip who did not respond to conservative treatment and subsequently required total hip arthroplasty in Tianjin Third Central Hospital between January 2018 and February 2020. A total of 20 patients (5 males and 15 females) were enrolled, of whom 12 presented with Crowe type III and 8 with Crowe type IV developmental dysplasia of the hip. Total hip arthroplasty for each patient was successful. The implanted acetabular cups were one size (2 mm) smaller than the preoperatively designed size in four patients, and the implanted femoral stem prosthesis was one size (1 mm) larger than the preoperatively designed size in four patients with type IV DDH. The Harris scores differed significantly between preoperative and postoperative measurements (58.6 vs. 94.4; P = 0.016). No infection or joint dislocation was observed. Preoperative digital modeling may be used to predict the size of prosthesis required and location for implantation in patients undergoing total hip arthroplasty.

Trendelenburg gait after total hip arthroplasty due to reduced muscle contraction of the hip abductors and extensors

Background

Despite experiencing pain relief and improved activities of daily living after total hip arthroplasty (THA) for osteoarthritis of the hip, a Trendelenburg gait may be observed in some patients. The concentric and eccentric contraction patterns of hip muscles in a Trendelenburg gait are not well understood.

Methods

This study included 89 patients (28 males and 61 females, mean age 66.5 ± 8.4 years, mean postoperative period 1.3 ± 0.4 years) after unilateral THA without functional impairment on the contralateral side. Gait analysis utilized a three-dimensional motion capture system to assess pelvis and hip angles, hip moment, and hip power. A Trendelenburg gait was defined as positive when nonoperative pelvic descent occurred at 30 % of the gait cycle, equivalent to mid-stance. Patients were classified into Trendelenburg gait-positive and -negative groups for statistical analysis. Unpaired t-test and chi-square test were used to compare the two groups. Multiple regression analysis was conducted to identify factors associated with the presence of a Trendelenburg gait.

Results

A Trendelenburg gait was observed in 24 patients (27 %). Multiple regression analysis indicated that abduction (p < 0.01) and extension (p = 0.03) of hip joint power were significant determining of a Trendelenburg gait. Patients with a Trendelenburg gait exhibited reduced eccentric contraction of the hip abductor muscles and decreased concentric contraction of hip extensor muscles during early to mid-stance of their gait.

Conclusion

Centrifugal contraction of hip abductor muscles and diminished eccentric contractility of hip extensor muscles appear crucial for hip stabilization mechanisms during gait after THA.

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%.

Measurement accuracy of the acetabular cup position using an inertial portable hip navigation system with patients in the lateral decubitus position

Accurate cup placement is critical to ensure satisfactory outcomes after total hip arthroplasty. Portable hip navigation systems are novel intraoperative guidance tools that achieve accurate cup placement in the supine position; however, accuracy in the lateral decubitus position is under debate. A new inertial portable navigation system has recently become available. The present study investigated the accuracy of measurements of the cup position in 54 patients in the lateral decubitus position using this system and compared it with that by a goniometer. After cup placement, cup abduction and anteversion were measured using the system and by the goniometer, and were then compared with postoperatively measured angles. Absolute measurement errors with the system were 2.8° ± 2.6° for cup abduction and 3.9° ± 2.9° for anteversion. The system achieved 98 and 96% measurement accuracies within 10° for cup abduction and anteversion, respectively. The system was more accurate than the goniometer for cup anteversion (p < 0.001), but not for abduction (p = 0.537). The system uses a new registration method of the pelvic reference plane and corrects intraoperative pelvic motion errors, which may affect measurement accuracy. In the present study, reliable and reproducible intraoperative measurements of the cup position were obtained using the inertial portable navigation system.

Direct Anterior Approach in Total Hip Arthroplasty for Severe Crowe IV Dysplasia: Retrospective Clinical and Radiological Study

Background and Objectives: total hip arthroplasty (THA) for Crowe IV hip dysplasia poses challenges due to severe leg shortening, muscle retraction and bone stock issues, leading to an increased neurological complication, and revision rate. The direct anterior approach (DAA) is used for minimally invasive THA but its role in Crowe IV dysplasia is unclear. This retrospective study examines if DAA effectively restores hip biomechanics in Crowe IV dysplasia patients with <4 cm leg length discrepancy, managing soft tissue and yielding functional improvement, limb length correction, and limited complications. Materials and Methods: 19 patients with unilateral Crowe IV hip osteoarthritis and <4 cm leg length discrepancy undergoing DAA THA were reviewed. Surgery involved gradual soft tissue release, precise acetabular cup positioning, and stem placement without femoral osteotomy. Results: results were evaluated clinically and radiographically, with complications recorded. Follow-up revealed significant Harris Hip Score and limb length discrepancy improvements. Abductor muscle insufficiency was present in 21%. The acetabular component was accurately placed, centralizing the prosthetic joint's rotation. Complications occurred in 16% of cases, including fractures, nerve issues, and infection. DAA in THA showcased positive outcomes for hip function, limb length, and biomechanics in Crowe IV dysplasia. Conclusions: the technique enabled accurate cup positioning and rotation center adjustment. Complications were managed well without implant revisions. DAA is a viable option for Crowe IV dysplasia, restoring hip function, biomechanics, and reducing limb length discrepancy. Larger, longer studies are needed for validation.

Risk Factors for Dislocation following Total Hip Arthroplasty in Developmental Dysplasia of the Hip: A Systematic Review and Meta-Analysis

PURPOSE

This systematic review and meta-analysis aimed to identify risk factors of dislocation after total hip arthroplasty (THA) in patients with developmental dysplasia of the hip (DDH).

METHODS

A systematic literature review was performed on 18th August 2022 using Medline, Embase, Scopus, Web of Science electronic databases, and a manual search. The study was conducted according to the PRISMA guidelines and registered with PROSPERO. Statistical analysis includes assessment of heterogeneity and data synthesis using RevMan 5.4.

RESULTS

Review of five studies including 2865 patients and 116 dislocated hips found that lower body mass index (BMI) (SMD = 0.22, p = 0.04, I2 = 0%), Crowe classification type IV versus I, II, and III (OR = 2.70, p = 0.004, I2 = 51%), higher cup inclination (SMD = 0.39 p = 0.0007, I2 = 0%), femoral head size < 28 mm (OR = 5.07, p = 0.003, I2 = 71%), lateral surgical approach (OR = 1.96, p = 0.02, I2 = 0%), and postoperative infection (OR = 6.26, p < 0.0001, I2 = 0%) were significant risk factors. However, age, gender, cup anteversion, femoral osteotomy, vertical (V-COR) centre of rotation, intraoperative fracture, preoperative and postoperative leg length discrepancy (LLD) and previous hip surgery were not found to be significant risk factors.

CONCLUSION

This study underscores importance of these risk factors in THA planning for DDH patients to reduce dislocation risk. Further research needed to understand mechanisms.

Total Hip Arthroplasty in Patients with Crowe III/IV Developmental Dysplasia of the Hip: Acetabular Morphology and Reconstruction Techniques

The severe anatomic deformities render acetabular reconstruction as one of the greatest challenges in total hip arthroplasty (THA) for patients with Crowe III/IV developmental dysplasia of the hip (DDH). Thorough understanding of acetabular morphology and bone defect is the basis of acetabular reconstruction techniques. Researchers have proposed either true acetabulum position reconstruction or high hip center (HHC) position reconstruction. The former can obtain the optimal hip biomechanics, including bulk femoral head autograft, acetabular medial wall displacement osteotomy, and acetabular component medialization, while the latter is relatively easy for hip reduction, as it can avoid neurovascular lesions and obtain more bone coverage; however, it cannot achieve good hip biomechanics. Both techniques have their own advantages and disadvantages. Although there is no consensus on which approach is better, most researchers suggest the true acetabulum position reconstruction. Based on the various acetabular deformities in DDH patients, evaluation of acetabular morphology, bone defect, and bone stock using the 3D image and acetabular component simulation techniques, as well as the soft tissue tension around the hip joint, individualized acetabular reconstruction plans can be formulated and appropriate techniques can be selected to acquire desired clinical outcomes.

Comparison of re-revision rate and radiological outcomes between Kerboull-type plate and metal mesh with impaction bone grafting for revision total hip arthroplasty

BACKGROUND

This study compared the re-revision rate and radiographic outcomes of revision total hip arthroplasty (THA) using a Kerboull-type acetabular reinforcement device (KT plate) with bulk structural allograft and metal mesh with impaction bone grafting (IBG).

METHODS

Ninety-one hips of 81 patients underwent revision THA for American Academy of Orthopedic Surgeons (AAOS) classification type III defects from 2008 to 2018. Of these, seven hips of five patients and 15 hips of 13 patients were excluded due to insufficient follow-up information (< 24 months) and large bone defects with a vertical defect height ≥ 60 mm, respectively. The current study compared the survival and radiographic parameters of 45 hips of 41 patients using a KT plate (KT group) and 24 hips of 24 patients using a metal mesh with IBG (mesh group).

RESULTS

Eleven hips (24.4%) in the KT group and 1 hip (4.2%) in the mesh group exhibited radiological failure. Moreover, 8 hips in the KT group (17.0%) required a re-revision THA, while none of the patients in the mesh group required a re-revision. The survival rate with radiographic failure as the endpoint in the mesh group was significantly higher than that in the KT group (100% vs 86.7% at 1-year and 95.8% vs 80.0% at 5-years, respectively; p = 0.032). On multivariable analysis evaluating factors associated with radiographic failure, there were no significant associations with any radiographic measurement. Of the 11 hips with radiographic failure, 1 (11.1%), 3 (12.5%), and 7 (58.3%) hips were of Kawanabe classification stages 2, 3, and 4, respectively.

CONCLUSIONS

The findings of this study suggest that revision THA using KT plates with bulk structure allografts could provide poorer clinical outcomes than revision THA using a metal mesh with IBG. Although revision THA using KT plates with bulk structural allografts could set the true hip center, there is no association between a high hip center and clinical outcomes. The relationship between the position of the KT plate and the host bone might be considered more carefully.

Mid-term outcomes after total hip arthroplasty in 106 Crowe II/III hips: different hip center positions

BACKGROUND

Under the obvious acetabular superolateral bone defect of Crowe II/III hips, this study aimed to investigate the difference in surgical technique of different hip center positions from the surgical data and clinical outcomes.

METHODS

From July 2007 to December 2016, 87 patients (106 Crowe II/III hips) consecutively received total hip arthroplasty (THA). The minimum follow-up time was 5 years. The mean limb length discrepancy was 1.97 ± 1.81 cm. Twenty-four hips had surgical histories. The patients were divided into three groups according to the acetabular prosthesis positions, depending on the Crowe classification, respectively, group 1 (Crowe I), group 2 (Crowe II) and group 3 (Crowe III). The surgical data and clinical results were used to evaluate the outcome of different surgical techniques of different hip center positions, including surgical time, blood loss, blood transfusion, number of osteotomy hips, osteotomy length, the distribution of prothesis, postoperative inpatient days, Harris hip scores, Visual Analogue Scale (VAS), Back Pain Function Scale (BPFS) and complications.

RESULTS

The mean follow-up time was 8.93 ± 2.55 years. Nineteen hips performed intraoperative osteotomy. From group 1 to group 3, the mean osteotomy length were 0.53 ± 1.11 cm, 0.05 ± 0.22 cm, and 0.00 ± 0.00 cm, respectively (p = 0.083); the surgical time were 142.57 ± 57.94 min, 118.4 ± 41.22 min, and 120.00 ± 84.85 min, respectively (p = 0.324); the blood loss were 498.21 ± 368.53 mL, 333.33 ± 167.62 mL, and 350.00 ± 212.13 mL, respectively (p = 0.255); the blood transfusion were 288.48 ± 381.68 mL, 128.00 ± 235.17 mL, and 385.00 ± 219.20 mL, respectively (p = 0.199); the postoperative inpatient days were 7.95 ± 4.42 d, 7.47 ± 4.29 d, and 6.50 ± 0.71 d, respectively (p = 0.831). Among the groups, the distribution of acetabular prosthesis, acetabular liner, acetabular prosthesis sizes, femoral head sizes and femoral prothesis distal sizes were not significantly different (p > 0.05). Only the distribution of femoral prosthesis was significantly different (p = 0.046); the Harris, VAS, BPFS, and the distribution of complications were not significantly different (p > 0.05).

CONCLUSIONS

We provided a framework to guide decision-making in Crowe II/III hips for surgeons: the surgical technique of different hip center positions was stable and had good outcomes, but the acetabular prothesis position and femoral prothesis should be determined according to the intraoperative situation.

LEVEL OF EVIDENCE

Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Risk factor investigation for hip dislocation after periacetabular tumour resection and endoprosthetic reconstruction via thin-slice CT-based 3D model

AIMS

Dislocation of the hip remains a major complication after periacetabular tumour resection and endoprosthetic reconstruction. The position of the acetabular component is an important modifiable factor for surgeons in determining the risk of postoperative dislocation. We investigated the significance of horizontal, vertical, and sagittal displacement of the hip centre of rotation (COR) on postoperative dislocation using a CT-based 3D model, as well as other potential risk factors for dislocation.

METHODS

A total of 122 patients who underwent reconstruction following resection of periacetabular tumour between January 2011 and January 2020 were studied. The risk factors for dislocation were investigated with univariate and multivariate logistic regression analysis on patient-specific, resection-specific, and reconstruction-specific variables.

RESULTS

The dislocation rate was 13.9% (n = 17). The hip COR was found to be significantly shifted anteriorly and inferiorly in most patients in the dislocation group compared with the non-dislocation group. Three independent risk factors were found to be related to dislocation: resection of gluteus medius (odds ratio (OR) 3.68 (95% confidence interval (CI) 1.24 to 19.70); p = 0.039), vertical shift of COR > 18 mm (OR 24.8 (95% CI 6.23 to 128.00); p = 0.001), and sagittal shift of COR > 20 mm (OR 6.22 (95% CI 1.33 to 32.2); p = 0.026).

CONCLUSION

Among the 17 patients who dislocated, 70.3% (n = 12) were anterior dislocations. Three independent risk factors were identified, suggesting the importance of proper restoration of the COR and the role of the gluteus medius in maintaining hip joint stability.Cite this article: Bone Joint J 2022;104-B(10):1180-1188.

Comparing the effect of cup placement between true and false acetabula in total hip arthroplasty in patients with Crowe type 3 dysplastic hip: A randomized clinical trial

BACKGROUND

Hip dysplasia is one of the most widespread hip disorders. Total hip arthroplasty (THA) is the preferred treatment in patients with cup placement choices in true or false acetabulum. The objective of this research was to compare the effectiveness of the two mentioned procedures.

MATERIALS AND METHODS

This study was a randomized, open-label, parallel-group clinical trial, in which 46 patients/51 hips with Crowe type 3 dysplastic hip having THA were assigned to two groups: Group 1 - patients who had cup placement in the true acetabulum and Group 2 - patients who underwent cup placement in the false acetabulum. The variables that were evaluated and analyzed included severity of pain using the visual analog scale (VAS), range of motion (ROM), gait ability, the need for repeated joint replacement, and the Harris Hip Score (HHS).

RESULTS

Forty-six patients/51 hips were included in the present study. The patients who were evaluated included 30 (65.2%) males and 16 (34.8%) females. The mean age in the population under study was 71.0 ± 10.22, and the mean body mass index of participants was 26.34 ± 2.22 kg/m². The basic parameters in the two research groups were similar (P > 0.05). There were no significant differences between the two groups in terms of the mean values of VAS and ROM (P > 0.05); however, the mean HHS was significantly higher in the true acetabulum group, 57.90 ± 18.47 versus 48.29 ± 13.80 (P = 0.04).

CONCLUSION

The effectiveness of cup placements both in the true and false acetabula was similar in all of the evaluated variables in terms of clinical outcomes except for HHS which was higher in the true acetabulum group. To further support the results of this research, it is recommended that more research be done on a greater population.

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.

Preliminary application of 3D-printed individualised guiding templates for total hip arthroplasty in Crowe type IV developmental dysplasia of the hip

OBJECTIVE

To evaluate the feasibility and accuracy of three-dimensional (3D)-printed individualised guiding templates in total hip arthroplasty (THA) for the treatment of developmental dysplasia of the hip (DDH).

METHODS

12 hips in 12 patients with Crowe type IV DDH were treated with THA. A 3D digital model of the pelvis and lower limbs was reconstructed using the computed tomography data of the patients. Preoperative surgical simulations were performed to determine the most suitable surgical planning, including femoral osteotomy and prosthesis placement. Based on the ideal surgical planning, individualised guiding templates were designed by software, manufactured using a 3D printer, and used in acetabulum reconstruction and femoral osteotomy during surgery.

RESULTS

12 patients were followed up for an average of 72.42 months (range 38-135 months). During surgery, the guiding template for each case was matched to the bony markers of the acetabulum and proximal femur. Preoperative and follow-up Harris Hip Scores were 34.2 ± 3.7 and 85.2 ± 4.2; leg-length discrepancy, 51.5 ± 6.5 mm and 10.2 ± 1.5 mm; and visual analogue scale scores, 6.2 ± 0.8 and 1.3 ± 0.3, respectively, with statistical difference. Shortened deformity and claudication of the affected limb were obviously improved after surgery. However, 1 patient had artificial hip dislocation 2 weeks after surgery, and another patient had sciatic nerve traction injury, both of whom recovered after physical treatment.

CONCLUSIONS

Preoperative surgical simulation and 3D-printed individualised guiding templates can fulfil surgeon-specific requirements for the treatment of Crowe type IV DDH. Accurate THA can be achieved using 3D-printed individualised templates, which provide a new personalised surgical plan for the precise positioning and orientation of acetabular reconstruction and femoral osteotomy.

Risk factors of dislocation after total hip arthroplasty in patients with developmental dysplasia of the hip

PURPOSE

Dislocation following total hip arthroplasty (THA) is a well-known complication. However, there is little data on its rate and predictors in patients with developmental dysplasia of the hip (DDH). The current study is aimed to determine the rate and specific risk factors of dislocation following THA in DDH patients.

METHODS

All the medico-surgical records of primary THAs from January 2014 to January 2019 were retrospectively reviewed. They were categorized into three main groups: primary OA, DDH, and others. Pre-operative and post-operative radiographs, past medical and surgical history, and surgical notes were reviewed in DDH cases.

RESULTS

In a total of 171 patients with DDH, 21 suffered from dislocation after THA (12%) which was significantly more frequent than those with primary OA. In univariate analysis, higher grade of dysplasia, smaller head size, intra-operative fracture, Wagner Cone stem, failure of offset restoration, and implanting the cup outside the Lewinnek's safe zone were identified as predictors of dislocation. In multiple regression analysis, however, only higher Crowe grade, intra-operative fracture, and post-operative acetabular offset less than 16 mm were independent predictors of dislocation.

CONCLUSION

Dysplastic hips can be more prone to post-THA dislocation than those with primary OA. Higher grades of dysplasia, failure of offset restoration, and intra-operative fracture can increase the rate of dislocation in this group of patients.

Does total hip arthroplasty with high hip centre in dysplasia compromise acetabular bone stock?

BACKGROUND

The placement of uncemented acetabular components during total hip arthroplasty (THA) in Crowe II and Crowe III dysplasia can be at the anatomic or high hip centre position.

PURPOSES

Using computerised tomography data, we simulated acetabular cup placement at the anatomic hip centre and the high hip centre positions to assess whether there is a difference between the 2 in terms of bone loss from acetabular reaming and in acetabular coverage by host bone.

METHODS

The study population included a consecutive cohort of 19 patients (22 hips) with Crowe II or III dysplasia. 3-dimensional models of the pelvis were created for each patient and digital templating was used to determine the anatomic and high hip centre positions. The coordinates of the digitally templated cup positions were fed into an image processing software to estimate the amount of bone reamed, the cup coverage by host bone and the elevation from tear drop.

RESULTS

The mean volume of bone reamed was greater in the high hip centre position as compared to the anatomic position (27.3 ± 11. 4 cm³ vs. 19.4 ± 12.2 cm³, p < 0.0001). The coverage of the acetabular cup by host bone was greater in the high hip centre position (87.3 ± 5.9% vs. 68.3 ± 10%). The mean elevation in the high hip centre group was 13 mm with 3 hips having a breach of the medial wall.

CONCLUSIONS

In Crowe II and III dysplasia, placement of acetabular cups at the anatomic hip centre better preserves bone stock as compared to high hip centre placement and should be preferred in young patients requiring THA.

Robotic-arm assisted THA can achieve precise cup positioning in developmental dysplasia of the hip : a case control study

AIMS

This study aimed to evaluate the accuracy of implant placement with robotic-arm assisted total hip arthroplasty (THA) in patients with developmental dysplasia of the hip (DDH).

METHODS

The study analyzed a consecutive series of 69 patients who underwent robotic-arm assisted THA between September 2018 and December 2019. Of these, 30 patients had DDH and were classified according to the Crowe type. Acetabular component alignment and 3D positions were measured using pre- and postoperative CT data. The absolute differences of cup alignment and 3D position were compared between DDH and non-DDH patients. Moreover, these differences were analyzed in relation to the severity of DDH. The discrepancy of leg length and combined offset compared with contralateral hip were measured.

RESULTS

The mean values of absolute differences (postoperative CT-preoperative plan) were 1.7° (standard deviation (SD) 2.0) (inclination) and 2.5° (SD 2.1°) (anteversion) in DDH patients, and no significant differences were found between non-DDH and DDH patients. The mean absolute differences for 3D cup position were 1.1 mm (SD 1.0) (coronal plane) and 1.2 mm (SD 2.1) (axial plane) in DDH patients, and no significant differences were found between two groups. No significant difference was found either in cup alignment between postoperative CT and navigation record after cup screws or in the severity of DDH. Excellent restoration of leg length and combined offset were achieved in both groups.

CONCLUSION

We demonstrated that robotic-assisted THA may achieve precise cup positioning in DDH patients, and may be useful in those with severe DDH. Cite this article: Bone Joint Res 2021;10(10):629-638.

Total hip arthroplasty after periacetabular osteotomy versus primary total hip arthroplasty: a propensity-matched cohort study

BACKGROUND

Controversy still exist regarding the outcomes of total hip arthroplasty (THA) after periacetabular osteotomy (PAO). The purpose of this study was to compare the clinical and radiologic outcomes of THA after PAO with primary THA based on balanced baseline characteristics with propensity score matching.

METHODS

Using propensity score matching, 1:2 matched cohort to facilitate comparison between patients who underwent primary cementless THA with or without previous PAO. Then, we compared the operative time, blood loss, complications, postoperative clinical score, cup size, position, and alignment of acetabular cup, and degree of bony coverage on cup between the two groups.

RESULTS

Thirty-five patients with 37 hips who underwent THA after PAO were successfully matched to 70 patients with 74 hips who underwent primary THA. The operative time and blood loss in THA after PAO were significantly longer and larger than those in primary THA (P < 0.001 and = 0.0067, respectively). Clinical score showed no difference between the groups (P > 0.05). For THA after PAO, the cup size and bony coverage were larger (P = 0.0014 and < 0.001, respectively), and the hip center was significantly higher and laterally (P < 0.001 and < 0.001, respectively) comparing primary THA.

CONCLUSION

This study demonstrated longer operative time and larger blood loss without difference in the postoperative clinical score or complications between THA after PAO and primary THA. Furthermore, THA after PAO provided larger cup size and superolaterally positioned cup center without difference in the cup inclination or anteversion comparing primary THA.

Instability After Total Hip Arthroplasty and the Role of Advanced and Robotic Technology

Instability remains the leading cause of reoperation following total hip arthroplasty (THA). In this article, the risk factors for instability after THA are reviewed, including patient-related characteristics, surgical techniques, positioning of implants, and the role of advanced technology and robotics as a platform that may reduce the incidence of instability.

Does Cup Position at the High Hip Center or Anatomic Hip Center in THA for Developmental Dysplasia of the Hip Result in Better Harris Hip Scores and Revision Incidence? A Systematic Review

BACKGROUND

One goal of THA is to restore the anatomic hip center, which can be achieved in hips with developmental dysplasia by placing cups at the level of the native acetabulum. However, this might require adjuvant procedures such as femoral shortening osteotomy. Another option is to place the cup at the high hip center, potentially reducing surgical complexity. Currently, no clear consensus exists regarding which of these cup positions might offer better functional outcomes or long-term survival.

QUESTION/PURPOSE

We performed a systematic review to determine whether (1) functional outcomes as measured by the Harris hip score, (2) revision incidence, and (3) complications that do not result in revision differ based on the position of the acetabular cup (high hip center versus anatomic hip center) in patients undergoing THA for developmental dysplasia of the hip (DDH).

METHODS

We performed a systematic review using Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines, including studies comparing the functional outcomes, revision incidence, and complications of primary THA in dysplastic hips with acetabular cups placed at the high hip center versus those placed at the anatomic hip center, over any time frame. The review protocol was registered with PROSPERO (registration number CRD42020168183) before commencement. Of 238 records, eight comparative, retrospective nonrandomized studies of interventions were eligible for our systematic review, reporting on 207 hips with cups placed at the high hip center and 268 hips with cups at the anatomic hip center. Risk of bias within eligible studies was assessed using the Risk Of Bias In Non-randomized Studies of Interventions tool. Due to low comparability between studies, data could not be pooled, so these studies were assessed without summary effects.

RESULTS

Six studies compared Harris hip scores, two of which favored high hip center cup placement and three of which favored anatomic hip center cup placement, although none of the differences between cohorts met the minimum clinically important difference. Five studies reliably compared revision incidence, which ranged from 2% to 9% for high hip center at 7 to 15 years and 0% to 5.9% for anatomic hip center at 6 to 16 years. Five studies reported intra- and postoperative complications, with the high hip center being associated with higher incidence of dislocation and lower incidence of neurological complications. No clear difference was observed in intraoperative complications between the high hip center and anatomic hip center.

CONCLUSION

No obvious differences could be observed in Harris hip score or revision incidence after THA for osteoarthritis secondary to DDH between cups placed at the anatomic hip center and those placed at the high hip center. Placement of the acetabular cup in the high hip center may lead to higher risk of dislocation but lower risk of neurologic complications, although no difference in intraoperative complications was observed. Surgeons should be able to achieve satisfactory functional scores and revision incidence using either technique, although they should be aware of how their choice influences hip biomechanics and the need for adjunct procedures and associated risks and operative time. These recommendations should be considered with respect to the several limitations in the studies reviewed, including the presence of serious confounding factors and selection biases, inconsistent definitions of the high hip center, variations in dysplasia severity, small sample sizes, and follow-up periods. These weaknesses should be addressed in well-designed future studies.

LEVEL OF EVIDENCE

Level III, therapeutic study.

[What are the benefits of patient-specific reconstruction in total hip replacement?]

BACKGROUND

The success of primary total hip replacement (THR) is predominately determined by the primary stability of the implant and the restoration of the patient-specific joint biomechanics. The three-dimensional (patho-) anatomy, size, geometry, and shape of the acetabulum and proximal femur is highly variable in patients with advanced hip osteoarthritis. Accurate preoperative planning is an essential prerequisite for all replacement procedures.

CURRENT SITUATION

Current data demonstrates clinical advantages for patient-specific reconstruction of functional joint geometry via surrogate parameters (offset and leg length). Frequently cited "target zones" for the positioning and orientation of the cup are increasingly in the focus of scientific discussion, as individually adjusted target zones for implant positioning allow for a potential reduction of impingement risk. Patients with spinal fusions or pathologic spinopelvic alignment require that particular attention be paid to patient-specific preoperative preparation, the surgical technique, and implant selection in order to reduce the risk of postoperative instability.

Mid-Term Outcomes of Cementless Total Hip Arthroplasty in Adult Patients with Childhood Hip Infection

BACKGROUND Patients with hip joint infections in childhood often have many aftereffects of different degrees, regardless of the kind of treatment or natural course. Total hip arthroplasty is currently the most effective treatment for sequelae of childhood hip septic or tuberculous infection. This is a mid-term follow-up study of treatment results of patients who had undergone total hip arthroplasty (THA) with cementless prostheses. MATERIAL AND METHODS We retrospectively analyzed and followed 45 patients (45 hips) who underwent THA with cementless prostheses between 2010 and 2017. There were 45 patients, including 17 men and 28 women. The average age of the patients was 46 years (range, 18-67 years). All hip infections occurred in early childhood or adolescence, and the mean interval between initial infection and THA was 38.2 years (range, 15-60 years). The mean follow-up was 6.1 years (range, 2.7-9.5 years). RESULTS Two patients underwent revision surgery because of loosening of the prosthesis, and 1 patient underwent revision surgery because of a new infection with no relationship with childhood infection during the follow-up. The average Harris hip scores significantly increased from 43.1 to 86.4 (P<0.01), and the average visual analog scale significantly increased from 4.6 to 1.7 (P<0.01). The hip dysfunction and osteoarthritis outcome scores were also significantly changed (P<0.01) at the final follow-up. There were 2 cases of transient sciatic nerve palsy and intraoperative periprosthetic fractures in 3 cases. During follow-up, single revision was performed after 6 years of primary arthroplasty because of aseptic loosening in 2 cases and prosthesis infection in 1 case, which was not related to childhood pathogens. CONCLUSIONS THA for patients with sequelae of hip joint infection has a satisfactory effect that can effectively relieve joint pain and improve hip function. The recurrence rate of infection after either pyogenic infection or tuberculous is very low. The mid-term outcomes of THA in this setting were satisfactory, with high prosthesis survivorship and hip function scores.

Risk factors for early dislocation of the hip after periacetabular tumour resection and endoprosthetic reconstruction of the hemipelvis

AIMS

There is an increased risk of dislocation of the hip after the resection of a periacetabular tumour and endoprosthetic reconstruction of the defect in the hemipelvis. The aim of this study was to determine the rate and timing of dislocation and to identify its risk factors.

METHODS

To determine the dislocation rate, we conducted a retrospective single-institution study of 441 patients with a periacetabular tumour who had undergone a standard modular hemipelvic endoprosthetic reconstruction between 2003 and 2019. After excluding ineligible patients, 420 patients were enrolled. Patient-specific, resection-specific, and reconstruction-specific variables were studied using univariate and multivariate analyses.

RESULTS

The dislocation rate was 9.3% (n = 41). Dislocation was most likely to occur in the first three months after surgery. Four independent risk factors were found, one of which was older age at operation (p = 0.039). The odds ratios (ORs) of those aged ≥ 60 years and 30 to 60 years were 8.50 and 4.64, respectively, compared with those aged < 30 years. The other three risk factors were resection of gluteus maximus (p = 0.010, OR = 5.8), vertical shift of the centre of rotation (COR) of the hip by ≥ 20 mm (p = 0.008, OR = 3.60), and a type I+II+III pelvic resection (p = 0.014, OR = 3.04).

CONCLUSION

Hemipelvic endoprosthetic reconstruction after resection of a periacetabular tumour has a dislocation rate of 9.3% (n = 41). Patients are most likely to dislocate in the first three months after surgery. The risk is increased for older patients (especially those aged > 60 years) and for those with gluteus maximus resection, vertical shift of the COR ≥ 20 mm, and a type I+II+III pelvic resection. Cite this article: Bone Joint J 2021;103-B(2):382-390.

Evaluation of Dislocation Risk Factors With Total Hip Arthroplasty in Developmental Hip Dysplasia Patients: A Multivariate Analysis

BACKGROUND

This study aimed to investigate the risk factors for dislocation in patients diagnosed with developmental dysplasia of the hip (DDH) who underwent total hip arthroplasty.

METHODS

We retrospectively reviewed 40 patients who developed dislocation and compared them with 400 patients in the control group without hip instability. Patients-, surgery-, and implant-related factors were investigated. Risk factors were evaluated using multivariate logistic regression.

RESULTS

The mean follow-up period was 32.3 months. The mean time to dislocation was 4.4 months. There were 7 men (17.5%) and 33 women (82.5%) in the dislocation group and 83 men (20.7%) and 317 women (79.3%) in the control group (P = .627). Diabetes mellitus (DM; P = .032) and history of previous hip surgery for DDH were associated with dislocation (P < .001). The subtrochanteric shortening osteotomy (P = .001), acetabular inclination (P = .037), acetabular anteversion (P < .001), femoral head size (P < .001), and postoperative infection (P = .003) were associated with dislocation. Major predictors of hip dislocation after total hip arthroplasty in patients with DDH were previous hip surgery (odds ratio [OR], 6.76; 95% confidence interval [CI], 1.86-24.6; P = .004), high hip center (OR, 2.90; 95% CI, 1.31-6.38; P = .008), DM (OR, 2.68; 95% CI, 1.06-6.80; P = .037), and acetabular inclination (OR, 2.62; 95% CI, 1.09-6.26; P = .03).

CONCLUSION

Patients with DM and previous hip surgery should be informed about increased dislocation rates. Using a larger head diameter and restoration of the true hip rotation center are essential to prevent hip dislocation in these patients. Furthermore, accurate positioning of the acetabular inclination and anteversion are also important.

Mid-term results of total hip arthroplasty with modified trochanteric osteotomy in Crowe type IV developmental dysplasia of the hip

Background

This study aimed to explore mid-term clinical results of cementless total hip arthroplasty (THA) with modified trochanteric osteotomy in Crowe type IV developmental dysplasia of the hip (DDH).

Methods

Thirteen patients (13 hips) with Crowe type IV DDH who underwent THA with modified trochanteric osteotomy between May 2013 and October 2015 were retrospectively analyzed. The mean follow-up duration was 5.2 years (range, 4.9–6.1 years).

Results

The mean Harris Hip Score (HHS) significantly (p < 0.05) improved from 30.7 (range, 22–38) to 87.5 (range, 83–93). The mean leg length discrepancy (LLD) was 53.4 mm (range, 42.1–68.5 mm) preoperatively. The final LLD was 5.6 mm (range, 2.4–9.1 mm; p < 0.05). The mean leg length after surgery was 47.4 mm (range, 33.6–67.2 mm) and the femur shortening distance was 43.8 mm (range, 31.2–53.4 mm). The average duration of bone union for the greater trochanter (GT) was 2.5 months (range, 1.5–3.6 months). There was no infection, GT non-union, or loosening (septic or aseptic) of the stem or cup in any case.

Conclusions

THA with modified trochanteric osteotomy with a cementless cup is an effective treatment for Crowe type IV DDH. It can rebuild complex biomechanics and biology of hip dysplasia without increasing complications.

Diagnosis, preoperative evaluation, classification and total hip arthroplasty in patients with long-term unreduced hip joint dislocation, secondary osteoarthritis and pseudoarthrosis

BACKGROUND

Neglected long-term unreduced hip joint dislocation with secondary osteoarthritis and pseudoarthrosis poses a great challenge to hip surgeons. However, as this is an uncommon injury, few studies have systematically investigated these patients.

METHODS

We retrospectively reviewed 16 patients from 2010 to 2017. The diagnostic values of three different types of common radiological examinations were evaluated. We evaluated the bone conditions of the original acetabulum and classified the patients into three types (four subtypes). The surgical procedures and prognosis of the patients were also investigated.

RESULTS

With the combined application of X-ray, CT scans and 3D reconstruction, 93.8% of these patients (sensitivity = 93.8%, Youden's index = 0.93, intraclass correlation coefficient = 0.95) could be diagnosed correctly. There were 6/16 (37.5%) type A patients, 4/16 (25.0%) type B1 patients, 5/16 (31.3%) type B2 patients and 1/16 (6.3%) type C patient. For patients with type A injury, the surgical procedures for total hip arthroplasty were similar to "standard" total hip arthroplasty. For patients with type B injury, due to atrophy or partial bone deficiency of the original acetabulum, the surgical procedure for total hip arthroplasty was probably similar to those for patients with developmental dysplasia of the hip. For patients with type C injury, the situation was similar to that of revision surgery. The average Harris hip score postoperatively was 89.94 ± 5.78 points (range: 79-98 points).

CONCLUSIONS

The new classification system could help surgeons estimate potential difficulties during total hip arthroplasty. The prognosis of most patients after total hip arthroplasty is expected to be excellent or good.

Subtrochanteric femoral shortening for hip centre restoration in complex total hip arthroplasty with functional outcome

Aims

Complex total hip arthroplasty (THA) with subtrochanteric shortening osteotomy is necessary in conditions other than developmental dysplasia of the hip (DDH) and septic arthritis sequelae with significant proximal femur migration. Our aim was to evaluate the hip centre restoration with THAs in these hips.

Methods

In all, 27 THAs in 25 patients requiring THA with femoral shortening between 2012 and 2019 were assessed. Bilateral shortening was required in two patients. Subtrochanteric shortening was required in 14 out of 27 hips (51.9%) with aetiology other than DDH or septic arthritis. Vertical centre of rotation (VCOR), horizontal centre of rotation, offset, and functional outcome was calculated. The mean followup was 24.4 months (5 to 92 months).

Results

The mean VCOR was 17.43 mm (9.5 to 27 mm) and horizontal centre of rotation (HCOR) was 24.79 mm (17.2 to 37.6 mm). Dislocation at three months following acetabulum reconstruction required femoral shortening for offset correction and hip centre restoration in one hip. Mean horizontal offset was 39.72 (32.7 to 48.2 mm) compared to 42.89 (26.7 to 50.6 mm) on the normal side. Mean Harris Hip Score (HHS) of 22.64 (14 to 35) improved to 79.43 (68 to 92). Mean pre-operative shortening was 3.95 cm (2 to 8 cm). Residual limb length discrepancy was 1.5 cm (0 to 2 cm). Sciatic neuropraxia in two patients recovered by six months, and femoral neuropraxia in one hip recovered by 12 months. Mean Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) was 13.92 (9 to 19). Mean 12-item short form survey (SF-12) physical scores of 50.6 and mental of 60.12 were obtained.

Conclusion

THA with subtrochanteric shortening is valuable in complex hips with high dislocation. The restoration of the hip centre of rotation and offset is important in these hips.

Level of evidence IV

Femoral shortening useful in conditions other than DDH and septic sequelae. Restoration of hip centre combined with offset to be planned and ensured.

Subtrochanteric femoral shortening for hip centre restoration in complex total hip arthroplasty with functional outcome

AIMS

Complex total hip arthroplasty (THA) with subtrochanteric shortening osteotomy is necessary in conditions other than developmental dysplasia of the hip (DDH) and septic arthritis sequelae with significant proximal femur migration. Our aim was to evaluate the hip centre restoration with THAs in these hips.

METHODS

In all, 27 THAs in 25 patients requiring THA with femoral shortening between 2012 and 2019 were assessed. Bilateral shortening was required in two patients. Subtrochanteric shortening was required in 14 out of 27 hips (51.9%) with aetiology other than DDH or septic arthritis. Vertical centre of rotation (VCOR), horizontal centre of rotation, offset, and functional outcome was calculated. The mean followup was 24.4 months (5 to 92 months).

RESULTS

The mean VCOR was 17.43 mm (9.5 to 27 mm) and horizontal centre of rotation (HCOR) was 24.79 mm (17.2 to 37.6 mm). Dislocation at three months following acetabulum reconstruction required femoral shortening for offset correction and hip centre restoration in one hip. Mean horizontal offset was 39.72 (32.7 to 48.2 mm) compared to 42.89 (26.7 to 50.6 mm) on the normal side. Mean Harris Hip Score (HHS) of 22.64 (14 to 35) improved to 79.43 (68 to 92). Mean pre-operative shortening was 3.95 cm (2 to 8 cm). Residual limb length discrepancy was 1.5 cm (0 to 2 cm). Sciatic neuropraxia in two patients recovered by six months, and femoral neuropraxia in one hip recovered by 12 months. Mean Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) was 13.92 (9 to 19). Mean 12-item short form survey (SF-12) physical scores of 50.6 and mental of 60.12 were obtained.

CONCLUSION

THA with subtrochanteric shortening is valuable in complex hips with high dislocation. The restoration of the hip centre of rotation and offset is important in these hips.

LEVEL OF EVIDENCE IV

Femoral shortening useful in conditions other than DDH and septic sequelae.Restoration of hip centre combined with offset to be planned and ensured.

Risk of Dislocation After Total Hip Arthroplasty in Patients with Crowe Type IV Developmental Dysplasia of the Hip

Objective

To investigate whether the risk of dislocation after total hip arthroplasty (THA) in patients with Crowe type IV developmental dysplasia of the hip (DDH) is high and to further identify the risk factors for postoperative dislocation in these patients.

Methods

This retrospective cohort study reviewed Crowe type IV DDH patients undergoing THA between January 2009 and December 2017 in our institution. Each Crowe type IV DDH patient was matched with three Crowe type I, II, or III DDH patients according to gender, side and date of operation. The primary outcome of this study was postoperative dislocation after THA. Occurrence, rate, classification, treatment and outcome of dislocation were documented in detail for all patients. The dislocation rates were compared between Crowe type IV DDH patients and Crowe type I, II, or III DDH patients. Demographic data, implant factors, and surgical factors were compared between the dislocation and no dislocation groups. Multiple logistic regression analysis was used to determine the independent risk factors for dislocation in Crowe type IV hips.

Results

A total of 131 Crowe type IV hips were followed up for a mean of 76.5 ± 28.1 months. Three hundred and ninety‐three Crowe type I, II and III hips, including 261 type I hips, 94 type II hips, and 38 type III hips, were identified as controls and followed up for a mean of 76.4 ± 28.2 months. No significant difference was observed in follow‐up time between two groups (P = 0.804). One or more dislocations occurred in 22 of the 524 dysplasia hips (4.20%). Of the 22 dislocated hips, 20 hips (90.9%) were successfully managed with non‐operative treatment. Two patients (9.1%, one Crowe type I and one Crowe type IV) experienced recurrent dislocation and required revision surgery. Crowe type IV hips had a significantly higher postoperative dislocation rate than type I, II, and III hips (11.45% vs 1.78%, P < 0.001). The use of a 22‐mm femoral head (odds ratio [OR] = 23.55, 95% confidence interval [CI] = 1.901–291.788, P = 0.014), older age (OR = 1.128, 95% CI = 1.037–1.275, P = 0.031), and absence of false acetabulum (OR = 12.425, 95% CI = 1.982–77.879, P = 0.007) were identified as independent risk factors for dislocation in Crowe type IV hips.

Conclusions

Crowe type IV DDH patients were at a high risk of dislocation after THA, and using large femoral heads and improving abductor muscle strength may help decrease the rate of postoperative dislocation in such patients.

Optimizing leg length correction in total hip arthroplasty

PURPOSE

Residual feeling of leg length discrepancy (LLD) is a common cause of patient dissatisfaction following total hip arthroplasty (THA). The purpose of this study is to propose a method for determining an optimal leg length correction goal in THA.

METHODS

We conducted a retrospective study of 132 patients to examine the radiographic LLD (R-LLD), perceived LLD (P-LLD), and whether or not the patient has an uncomfortable feeling about the leg length after THA.

RESULTS

The residual discomfort rate in all patients was 9.1% (12/132 patients), and ten of these 12 patients felt uncomfortable due to a longer leg length. When R-LLD was within 7 mm, the rate was 6.8% (8/118 patients), which is nearly equal to the rate of 7.8% (5/64 patients) in cases in which R-LLD was within 2 mm. On the other hand, when R-LLD was 8 mm or more, the rate was 57.1% (4/7 patients).

CONCLUSIONS

The results of our study show that 7 mm may be a reasonable threshold for reducing the residual discomfort. However, even with little or no R-LLD, some patients will continue to experience discomfort. We think that this is because of pre-operative differences between R-LLD and P-LLD in such cases. If the patient has a pelvic declination on the affected hip side and a lumbar scoliosis angle that is convex toward the affected hip side before surgery, the ideal length may be a little shorter than the radiographic isometry, since such patients are likely to feel a longer leg length than that shown radiographically.

Best bone of acetabulum for cup component placement in Crowe types I to III dysplastic hips: a computer simulation study

BACKGROUND

During cup implantation, vertical height of the cup center (V-HCC) should be precisely controlled to achieve sufficient bone-cup coverage (BCC). Our study aimed to investigate the acetabular bone stock and the quantitative relationship between V-HCC and BCC in Crowe types I to III hips.

METHODS

From November 2013 to March 2016, pelvic models of 51 patients (61 hips) with hip dysplasia were retrospectively reconstructed using a computer software. Acetabular height and doom thickness were measured on the mid-acetabular coronal cross section. V-HCC was defined as the vertical distance of cup rotational center to the interteardrop line (ITL). In the cup implantation simulation, the cup was placed at the initial preset position, with a V-HCC of 15 mm, and moved proximally by 3-mm increments. At each level, the BCC was automatically calculated by computer. Analysis of variance and Kruskal-Wallis test were used to compare the differences between groups.

RESULTS

There were no significant between-group differences in maximum thickness of the acetabular doom; however, peak bone stock values were obtained at heights of 41.63 ± 5.14 mm (Crowe type I), 47.58 ± 4.10 mm (Crowe type II), and 55.78 ± 3.64 mm (Crowe type III) above the ITL. At 15 mm of V-HCC, median BCC was 78% (75-83%) (Crowe type I), 74% (66-71%) (Crowe type II), and 61% (57-68%) (Crowe type III). To achieve 80% of the BCC, the median V-HCC was 16.27 (15.00-16.93) mm, 18.19 (15.01-21.53) mm, and 24.13 (21.02-28.70) mm for Crowe types I, II, and III hips, respectively.

CONCLUSION

During acetabular reconstruction, slightly superior placement with V-HCC <25 mm retained sufficient bone coverage in Crowe I to III hips.

Total Hip Arthroplasty for Crowe Type IV Hip Dysplasia: Surgical Techniques and Postoperative Complications

Total hip arthroplasty (THA) of Crowe type IV developmental dysplasia of the hip (DDH) is challenging. Although traditional (lateral, posterolateral, and posterior) THA approaches have been used with great anatomic success, they damage periarticular muscles, which are already quite weak in type IV DDH. The recently developed direct anterior approach (DAA) can provide an inter‐nerve and inter‐muscle approach for THA of type IV dysplasia hips. However, femur exposure with the DAA could be difficult during surgery and it is hard to apply femoral shortening osteotomy. THA techniques used for type IV DDH include anatomic hip center techniques (true acetabular reconstruction) and high hip center techniques, wherein an acetabulum is reconstructed above the original one. Although anatomic construction of the hip center is considered “the gold standard” treatment, it is impossible if the anatomical acetabular is too small and shallow. Procedures used to support type IV DDH reduction with anatomic hip center techniques include greater trochanter osteotomy, lesser trochanter osteotomy, and subtrochanteric osteotomy. However, these techniques have yet to be standardized, and it is unclear which is best for type IV DDH. One‐state and two‐state non‐osteotomy reduction techniques have also been introduced to treat type IV DDH. Potential complications of THA performed in patients with type IV DDH include leg length discrepancy (LLD), peri‐operative femur fracture, nonunion of the osteotomy site, and nerve injury. It is worth noting that nowadays an increasing number of Crowe type IV DDH patients are more sensitive to postoperative LLD.

Effect of changing femoral head diameter on bony and prosthetic jumping angles

BACKGROUND

In THA, using a larger femoral head can increase the oscillation angle and jumping distance. However, there have been no reports which indicate precisely how increasing the jumping distance leads to an increase in the angle from impingement to dislocation (jumping angle). In this study, we clarified the jumping angle of various head diameters and its relationship with pelvic morphology.

METHODS

Using a three-dimensional templating system, virtual THA and ROM simulations were performed in 82 patients. We investigated the distance between bony and prosthetic impingement points and the head centre and calculated the jumping angle for various head diameters. We measured various pelvic shapes and length to clarify the relationship between pelvic morphology and impingement distance.

RESULTS

Jumping angles were 7.7° ± 3.2°, 12.1° ± 1.6°, 15.4° ± 2.5° and 10.0° ± 3.0° with flexion, internal rotation with 90° flexion (IR), extension and external rotation (ER), respectively, when we used a 22-mm head diameter. Bony jumping angle increased about 0.5°, 0.8°, 1.0° and 0.7° per 2-mm increase in head diameter with flexion, IR, extension and ER. On the other hand, prosthetic jumping angle remained almost stable at about 31°. Impingement distance was related to pelvic morphology in all directions. Bony jumping angles differed with ROM; the biggest was seen with extension, followed by IR, ER and flexion. On the other hand, bony jumping angle was less than prosthetic jumping angle in all cases.

CONCLUSION

Bony jumping angles differed with ROM; the biggest was seen with extension, followed by IR, ER and flexion. Prosthetic impingement angles were stable. In addition, the bony jumping angle was less than the prosthetic jumping angle in all cases.