There are a growing number of younger patients with developmental dysplasia of hip, proximal femoral deformity and osteonecrosis seeking surgical intervention to restore quality of life, and the advent of ISTCs has resulted in a greater proportion of such cases being referred to existing NHS departments. Bone-saving hip athroplasty is often advocated for younger active patients, as they are potential candidates for subsequent revision arthroplasty. If resurfacing is contraindicated, short bone-conserving stems may be an option. The rationale for short stems in cementless total hip arthroplasty is proximal load transfer and absence of distal fixation, resulting in preserved femoral bone stock and avoidance of thigh pain. We have carried out 17 short stem hip replacements (Mini-hip, Corin Medical, Cirencester, UK) using ceramic bearings in 16 patients since June 2010. There were 14 females and 2 males, with a mean age of 50.1 years (range 35–63 years) at the time of the surgery. The etiology was osteoarthritis in 11, developmental dysplasia in 4, and osteonecrosis of the femoral head in one patient. All operations were performed through a conservative anterolateral (Bauer) approach. These patients are being followed and evaluated clinically with the Harris and Oxford hip scores, with follow-up at 6 weeks, 3 months, and annually thereafter. Initital results have been encouraging in terms of pain relief, restoration of leg length (one of the objectives in cases of shortening) and rage of movement. Radiological assessment has shown restoration of hip biomechanics. Specific techniques are required to address varus, valgus and femoral deformity with leg length inequality. There are two main groups of short stems, those that are neck-preserving and those that do not preserve the femoral neck. The latter group requires traditional techniques for revision. Another feature that differentiates them is the availability of modularity. The device we employed is neck-preserving and available with different neck lengths and offsets, which help in restoration of hip biomechanics. The advantage of such short stems may be preservation of proximal femoral bone stock, decreased stress shielding and the ease of potential revision. Such devices may be a consideration for patients with malformations of the proximal femur. Long-term follow-up will be of value in determining if perceived benefits are realised in practice

Introduction. The objective of our study was to determine the extent to which the quality of the biomechanical reconstruction when performing hip replacement influences gait performances. We aimed to answer the following questions: 1) Does the quality of restoration of hip biomechanics after conventional THR influence gait outcomes? (question 1), and 2) Is HR more beneficial to gait outcomes when compared with THR? (question 2). Methods. we retrospectively reviewed 52 satisfied unilateral prosthetic hip patients (40 THRs and 12 HRs) who undertook objective gait assessment at a mean follow-up of 14 months. The quality of the prosthetic hip biomechanical restoration was assessed on standing pelvic radiograph by comparison to the healthy contralateral hip. Results. We were unable to detect any statistically significant correlation between the radiographical parameters and the gait data, for THR patients. In stress conditions (inclination or declination of the ramp), the gait was more symmetric in the HR group, compared to the THR group. Discussion/Conclusions. We found that slight variations in the quality of the hip biomechanical restoration had little effect on gait outcomes of THR patients, and HR generated a more physiological gait under stress conditions than well-functioning THR

The use of modular systems adds versatility to the implant system, better restoration of hip biomechanics and lower inventory to the hospital. There have been reports of high metal ions, ARMD reactions and high implant failure rates due to potential problems from taper failures. These are more common in metal-on-metal hip replacements, but are being also reported in other bearings. Between 2001 and 2010, we performed 383 consecutive metal-on-metal (MoM) THRs through a posterior approach, using a BHR cup and Birmingham modular head with one of three different stems, all with 12/14 tapers. The earliest 104 hips employed a cemented MS30 stem (Zimmer GmbH, Winterthur, Switzerland). Subsequent 256 were Synergy and then 23 Anthology (both uncemented and both Smith and Nephew Orthopaedics, Memphis TN USA). There was no significant difference in the average age at surgery (65.4 years cemented vs 65.6 uncemented, p = 0.69), gender ratio (1.68 vs 1.89, p = 0.64), or bearing diameter (46.7 vs 46.8, p = 0.31). The earlier 203 Synergy stems were monoblock heads, while the remaining uncemented stems included a tapered sleeve in addition. There were 3 deep infections and 11 debris-related failures (overall revision rate 4.9%). The revision rate from aseptic failures (ALTR, effusion, osteolysis or component loosening) is 2.87%. Kaplan-Meier analysis of the entire cohort showed a 10-year implant survival of 96.8% with revision for any reason as the end-point. Cemented stems had a 100% survival at 10 years and 98.6% at 12 years. The uncemented stems had a 93.8% survival at 10 years. Within the uncemented group, the monoblocks had a 5 and 10-year survival of 99.0% and 96.4% respectively while the sleeved had 98.7% (5 years) and 96.3% (7 years) and 82.5% at 8 years. Retreival analysis showed clear evidence of taper failure. Our experience suggests taper failure leading to ALTRs and its sequelae. Others have reported ALTR type reactions in metal on polyethylene and ceramic on polyethylene bearing types as well in bearing diameters ranging from 28mm to 40mm. There is a need to improve taper design especially for use with large heads, and in high demand patients

Introduction. Natural population variation in femoral morphology results in a large range of offsets, anteversion angles and lengths. During total hip arthroplasty, accurate restoration of hip biomechanics is essential to achieve good functional results. One option is to restore the anatomic hip rotation center. Alternatively, medializing the rotation center and compensating by increasing the femoral offset, reduces acetabular contact forces and increases the abductor lever arm. We investigated the ability of two cemented stem systems to restore hip biomechanics in an anatomic and medialized way. We compared an undersized “Exeter-type” of stem with three offset options and 18 sizes (CPT, Zimmer), to a line-to-line “Kerboul-type” of stem with proportional offset and 12 sizes (Centris, Mathys). Methods. Thirty CT scans of whole femora were segmented and the hip rotation center, proximal femoral axis and femoral length were determined with Mimics and 3-matic (Materialise). Using scripting functionality in the software, CAD design files of both stems were automatically sized and aligned along the proximal femoral axis to restore an anatomical and a 5 mm medialized hip rotation center. Stem size and position could be fine-tuned manually. The maximum distances between the prosthetic (PRC), the anatomic (ARC) and the medialized hip rotation center (MRC) were calculated (Fig. 1). Variations in femoral offset (ΔFO), anteroposterior (ΔAP) and proximodistal distance (ΔPD) were analyzed. Finally, the number of cases where the hip rotation center could be restored within 5 mm was reported. Results. Both implants allowed restoring the ARC accurately (mean distance PRC-ARC: CPT 0.97±0.88 mm, Centris 1.66±1.59 mm; mean difference ΔFO: CPT 0.09±0.19 mm, Centris 0.11±0.29 mm; mean difference ΔAP: CPT 0.12±1.22°, Centris 0.27±1.78 mm, mean difference ΔPD: CPT 0.04±0.44 mm, Centris 0.49±1.35 mm). The CPT stem allowed restoring the PRC within 5 mm of the ARC in all cases (max. 4.31 mm), whereas the Centris stem achieved this in only 28/30 hips (max. 6.72 mm) (Fig. 2). Aiming for a MRC was less satisfactory with both stems (mean distance PRC-MRC: CPT 1.38±1.63 mm, Centris 3.61±2.73 mm; mean difference ΔFO: CPT 0.09±0.10 mm, Centris 0.06±0.35 mm; mean difference ΔAP: CPT 0.17±2.02 mm, Centris 2.58±2.68 mm, mean difference ΔDP; CPT 0.28±0.67 mm, Centris 1.98±1.66 mm). The CPT stem allowed restoring the PRC within 5 mm of the MRC in 29/30 cases (max. 8.09 mm), whereas the Centris stem achieved this in only 25/30 cases (max. 11.15 mm) (Fig. 3). Discussion. Although both stem systems allowed restoring hip biomechanics accurately in most cases, the CPT system was superior to the Centris stem for achieving both ARC and MRC. This could be explained by more implant sizes (18 vs. 12) and undersized stems offering more freedom to correct version. Although medializing the hip rotation center offers biomechanical advantages, both stems had more difficulties achieving this. In some cases, differences between aimed and planned rotation centers were close to 1 cm which might negatively impact on clinical outcome. As such, to avoid suboptimal reconstructions with the available implants, templating is mandatory especially when aiming at a medialized reconstruction strategy

Introduction. Large diameter metal-on-metal hip arthroplasty (LDMMTHA) provides benefits of reduced dislocation rates and low wear. The use of modular systems allows better restoration of hip biomechanics. There have been reports of modular LDMMTHAs with tapered sleeves generating excessively high metal ions, due to possible mismatch between the titanium stem and the cobalt-chrome sleeve and the dual Morse tapers involved. We evaluated metal ion levels in LDMMTHA patients with and without a cobalt-chrome (CoCr) tapered sleeve. Methods. A cross-sectional series of 91 patients with proximal porous titanium alloy stem LDMMTHA with identical design CoCr bearings, attending a 1 to 2-year review were assessed with routine clinical and radiographic examinations, hip scores and metal ion analysis. Of these 65 had a single Morse taper between monoblock CoCr heads and the stems. Twentysix had a tapered cobalt-chrome sleeve in addition, with the resultant dual taper. Mean bearing diameter was 46 mm in both groups and mean age was 58 years in the monoblocks and 66 years in the tapered sleeve group. Results. Mean Oxford Hip score is worse in the tapered group (14.7) than in the monoblocks (12.6). All patients had well-functioning hips clinically and radiologically. Median blood cobalt and chromium are higher in the tapered sleeve (2.3μg/L and 1.8 μg/L) compared to the monoblocks (1.8 μg/L and 1.1 μg/L). Urine cobalt and chromium levels in the tapered sleeve (13.8 μg/24 hr and 5.3 μg/24 hr) also are higher than those in the monoblocks (12.2 μg/24 hr and 4.5 μg/24 hr respectively). Discussion and Conclusion. The limitation of this study is that it is a cross-sectional study. The results indicate that the use of a tapered sleeve in total hip arthroplasty does lead elevation of cobalt and chromium levels and the difference is statistically significant. However these levels are not as high as the levels reported with some other hip systems which have been withdrawn and the clinical significance of the elevated levels in the present study is unknown

Purpose. The ultimate goal in total hip arthroplasty is not only to relieve the pain but also to restore original hip joint biomechanics. The average femoral neck-shaft angle(FNSA) in Korean tend to have more varus pattern. Since most of conventional femoral stems have relatively high, single, fixed neck shaft angle, it's not easy to restore vertical and horizontal offset exactly especially in Korean people. This study demonstrates the advantages of dual offset(especially high-offset) stem for restoring original biomechanics of hip joint during the total hip arthroplasty in Korean. Materials and Methods. 180 hips of 155 patients who underwent total hip arthroplasty using one of the standard(132°) or extended(127°) offset Accolade cementless stems were evaluated retrospectively. Offset of stem was chosen according to the patient's own FNSA in preoperative templating. In a morphometric study, neck-shaft angle of proximal femur, vertical offset and horizontal offset, abductor moment arm were measured on preoperative and postoperative both hip AP radiographs and the differences and correlation of each parameters, between operated hip and original non-operated hip which had no deformity (preoperative ipsilateral or postoperative contralateral hip), were analyzed. Results. The standard stems were used in 34 hips and extended offset stems were used in 146 hips. The FNSA of non-operated hip was an average of 129.8°(127.2°□135.8°) in standard group and mean 125.4°(122.7°□129.9°) in extended offset group. The FNSA of operated hip was an average of 131.6° and 127.1° in each group. In the statistical analysis, there was no significant difference of mean horizontal and abductor moment arm between operated hip and non-operated hip in both groups and the restoration of horizontal offset and abductor moment arm showed(p=0.217, p=0.093) significant positive correlation(R=0.870, R=0.851) to the original value. However, vertical offset was increased an average of 1.4mm in operated hip and there was statistical significance. Restoration of vertical offset showed positive correlation to original value (R=0.845). Conclusion. Dual- or multi-offset stem, especially extended offset stem can provide easy restoration of hip biomechanics and soft tissue tension without significant alteration of leg length especially in Korean with more varus femoral neck compared to Caucacian. Precise radiographic measurements of original hip and application of proper-offset stem should be taken in order to restore ideal hip biomechanics successfully and easily. A use of a proper offset stem can afford to enhance joint stability and implant longevity by improving soft-tissue tension and reducing resultant force, and it will guarantee a successful results after total hip arthroplasty in the aspect of function and longevity

Introduction:. Restoration of normal hip biomechanics is vital for success of total hip arthroplasty (THA). This requires accurate placement of implants and restoration of limb length and offset. The purpose of this study was to assess the accuracy of computer navigation system in predicting cup placement and restoring limb length and offset. Material and Methods:. An analysis of 259 consecutive patients who had THA performed with imageless computer navigation system was carried out. Acetabular cup abduction and anteversion, medialisation or lateralisation of offset and limb length change were compared between navigation measurements and follow-up radiographs. Sensitivity, specificity, accuracy and PPV were calculated to assess navigation for cup orientation and student t-test used for evaluation of offset and limb length change. Results:. Mean cup abduction and anteversion was 40.35° (SD, 5.81) and 18.46° (SD, 6.79) in postop radiographs compared to 41° (SD, 5.03) and 14.76°(SD, 6.11) for navigation measurements. Intraoperative navigation measurements had high PPV and specificity for determining cup abduction and anteversion (PPV >95%, specificity >90%). Accuracy for determining cup abduction was 96.13% compared to 72.2% for cup anteversion. Change in limb length and offset was mean 6.46 mm (SD, 5.68) and −1.07 mm (SD, 5.75) on radiograph evaluation and 5.41 mm (SD, 5.11) and −2.24 mm (SD, 5.87) from navigation measurements respectively, the difference being not significant in both (p value >0.2). Radiograph and navigation had a mean difference of 1.01 mm (SD, 2.83) for offset measurements and a mean difference of 1.05 mm (SD, 4.37) for postop limb length assessment. Discussion:. To conclude, navigation can serve as an excellent tool for appropriate placement of implants and restoring limb length and offset in THA

Introduction. Hip Resurfacing Arthroplasty (HRA) has been performed in the United States for over 10 years and is an alternative to standard Total Hip Arthropastly (THA). It is appealing to younger patients with end stage osteoarthritis who seek to maintain active lifestyles. Benefits of HRA versus THR include a larger femoral ball size, potential to return to impact activities, decreased dislocation rates, and restoration of normal hip biomechanics. Patients ≤50 years old are a particularly challenging patient group to treat with THA because of their young age and high activity level, and as such, are well-suited for HRA. However, there are limited reports in the literature about clinical, radiographic and functional outcomes for this patient cohort. We present results of a clinical investigation at our institution for this patient cohort with minimum 5-year follow up, including long term survivorship and outcome scores. Methods. HRA, using the Birmingham Hip Resurfacing (BHR), was performed for 538 procedures between 2006–2009 by a single surgeon at a United States teaching hospital. After Institutional Review Board approval, medical and radiographic study records were retrospectively reviewed. Harris Hip Scores (HHS) were routinely collected. Patients who had not returned for follow-up examination were contacted by telephone for information pertaining to their status and implant, and a modified HHS was also administered. A Kaplan Meier survival curve was constructed to evaluate time to revision. Statistical analysis was performed (SAS version 9.3; SAS Institute, Cary, NC). Results. Of the 538 patients who underwent HRA from 2006–2009, 238 were aged ≤50 years (44%). Five-year follow up data was obtained from 209 of these patients (88%), using medical record documentation, and telephone survey as needed. The mean follow-up for all patients was 6 years (range 5–8 years). A total of 3% (8/238) were revised. Reasons included: (i) femoral loosening in 4, (ii) Iliopsoas impingement in 1, (iii) metallosis/adverse tissue reaction in 1, (iv) femoral neck fracture following motor vehicle accident in 1, and (v) unknown reasons in 1. Of the 238 patients, 55 (23%) were female, 2 (2/55; 3.6%) of whom have since undergone revision surgery for either metallosis/adverse tissue reaction, or unknown reasons. Of the 53 women who retained their BHR at 5-year follow up, the average HHS was 96.5. Of the 238 patients, 183 (77%) were male patients, 6 (6/183; 3.2%) of whom have since undergone revision surgery for femoral component loosening, iliopsoas impingement, or femoral neck fracture sustained in a motor vehicle accident. At 5-year follow-up, 177 male patients retained their implant and had an average Harris Hip Score of 98.8. The overall implant survival was 96.6% at approximately 5 years. Conclusion. In our cohort of patients aged ≤50 treated with BHR [Fig. 1], our results demonstrated 5-year survivorship of 96.6%, with average HHS of 98.8 in males and 96.5 in females. This study demonstrates HRA is a successful alternative to traditional THA in a challenging cohort of younger, active patients

Introduction. Restoration of normal hip biomechanics is vital for success of total hip arthroplasty (THA). This requires accurate placement of implants and restoration of limb length and offset. The purpose of this study was to assess the precision and accuracy of computer navigation system in predicting cup placement and restoring limb length and offset. Material and Methods. An analysis of 259 consecutive patients who had THA performed with imageless computer navigation system was carried out. All surgeries were done by single surgeon (KD) using similar technique. Acetabular cup abduction and anteversion, medialisation or lateralisation of offset and limb length change were compared between navigation measurements and follow-up radiographs. Precision, accuracy, sensitivity and specificity were calculated to assess navigation for cup orientation and student t-test used for evaluation of offset and limb length change. A p value of <0.05 was considered significant for evaluation. Results. Mean cup abduction and anteversion was 40.35° (SD, 5.81) and 18.46° (SD, 6.79) in postop radiographs compared to 41° (SD, 5.03) and 14.76° (SD, 6.11) for navigation measurements. Intraoperative navigation measurements had high precision and specificity for determining cup abduction and anteversion (precision >95%, specificity >90%). Accuracy for determining cup abduction was 96.13% compared to 72.2% for cup anteversion. Change in limb length and offset was mean 6.46mm (SD, 5.68) and −1.07mm (SD, 5.75) on radiograph evaluation and 5.41mm (SD, 5.11) and −2.24mm (SD, 5.87) from navigation measurements respectively, the difference being not significant in both (p value > 0.2). Radiograph and navigation had a mean difference of 1.01mm (SD, 2.83) for offset measurements and a mean difference of 1.05mm (SD, 4.37) for postop limb length assessment. Discussion. To the best of our knowledge this is the largest single surgeon study of navigated THA. We found that computer navigation assessment of acetabular cup abduction and anteversion and limb length and offset restoration has high probability of predicting correct placement of implants. To conclude, navigation can serve as an excellent tool for appropriate placement of implants and restoring limb length and offset in THA