Dislocation after Total Hip Arthroplasty (THA) is a frequent cause of revision and patients with intrinsic risk factors have been identified. The use of dual mobility (DM) cup has shown great efficiency in preventing dislocation, with questions regarding selective or absolute use. The aim of this study was to compare the outcome of single mobility THA (SM-THA) and DM-THA, when used for selected patients.

This retrospective continuous cohort study evaluated 490 patients of whom 275 received SM-THA and 215 received DM-THA. There were 304 primary osteoarthritis (62%), 121 femoral neck fractures (24%) and 65 other indications (14%). The surgical approach was anterior (AA) in 79% and posterior (PA) in 21% of cases. In the DM-THA group, 189 patients (87%) presented at least one dislocation risk factor compared to 128 patients (46%) in the SM-THA group. The primary outcome was revision for all causes, with or without implant removal. Secondary outcomes included length of hospital stay.

There was no difference in all cause revision at two years follow up with 9 procedures (3.2%) in SM-THA group and 11 in DM-THA group (5.1%) (p=0.3). There were 3 dislocations in SM-THA group (3 AA) and 3 in DM-THA group (2 PA and 1 AA) (p=0.4).

The length of stay was significantly longer in DM-THA group with 7 days (2–12) compared to 4 days (1–7) in SM-THA group (p=0.001).

SM-THA and DM-THA are two complementary devices in the management of patients requiring primary THA. SM-THA is a safe option for patients without dislocation risk factors, especially when using AA. The identification of such factors is important to select patients requiring DM-THA and provide reproducible outcomes in a University Hospital practice including various levels of surgeon experience.

Dual mobility cups (DMC) reduce the risk of dislocation in femoral neck fractures (FNF). Direct anterior approach (DAA), historically promoted for better stability, has been developed in recent years for better functional results. The aim of this study was to compare the early functional results of DMC in FNF by DAA versus posterolateral approach (PLA).

A prospective study was conducted on a continuous series of patients who received DMC for FNF by DAA or PLA. The primary endpoint was Harris Hip Score and Parker score assessed at the first follow-up visit. Intraoperative complications were collected during hospitalization. One year clinical results and all cause revision rate were also collected. Radiographic data of cup positioning and limb length were evaluated.

Fifty-two patients were included in the DAA group and 54 in the PLA group. Two patients were lost to follow-up. The mean age was 72.8 years. There was no significant difference in HHS or Parker score at 3 and 12 months follow up (p=0.6, p= 0.75). DAA was associated with more intraoperative complications with 4 fractures and 1 femoral nerve deficit (p=0.018). There were 3 revisions in the DAA group (1 infection, 1 dislocation, 1 peri prosthetic fracture) and 1 in the PLA group (infection), which was not statistically significant (p=0.34). Cup anteversion was 6° greater and inclination 9° lesser in DAA group (p=0.028, p<0.01).

Results suggest that DAA does not provide any early functional benefit in THA-DMC for FNF compared to PLA. It could lead to more intraoperative complications and a higher revision rate. DAA requires an experienced surgeon and careful patient selection.

Aims

Two-stage exchange revision total hip arthroplasty (THA) performed in case of periprosthetic joint infection (PJI) has been considered for many years as being the gold standard for the treatment of chronic infection. However, over the past decade, there have been concerns about its safety and its effectiveness. The purposes of our study were to investigate our practice, collecting the overall spacer complications, and then to analyze their risk factors.

Two-stage exchange revision total hip arthroplasty performed in case of infection has been considered during many years the gold standard for treatment of chronic infection. Nevertheless, during the last decade, concerns have risen regarding its safety and its efficiency. The purpose of our study was to, first investigate the spacer complications, then to analyze their risks factors.

We retrospectively included 125 patients with chronic hip periprosthetic joint infection who underwent a two stage exchange revision arthroplasty performed between January 2013 and December 2019. All spacer complications were systematically collected and risk factors were analyzed. Statistical evaluation were performed using the Student and Mann-Whitney tests.

Our study confirms the hypothesis of a high-risk strategy with 42% of patients who had a mechanical spacer failure and a 20% recurrence of infection during the average two years period of follow-up. We found a high rate of spacer migration (23%) and a low rate of spacer fracture (8%) compared to literature.

The most important finding was that the majority of spacer complications and failures were found in a population with high medical comorbidities as highlighted by the ASA, Charlson and Lee score associations, as well as with the cardiac, pulmonary, kidney or hepatic chronic conditions.

This study showed that a two-stage hip exchange revision is a high-risk procedure regarding complications and mechanical failures of PMMA spacers.

In patients with high medical comorbidities, other strategies may be considered and interdisciplinary cooperation with other facilities are needed to identify and control each risk factor.

Treatment of osteoarthritis of the knee remains a challenging problem since the evolution of the disease may be different in each compartment of the knee, as well as the state of the ligaments. Total knee arthroplasty may provide a reliable long-lasting option but do not preserve the bone stock. In another hand, compartmental arthroplasty is a bone and ligament sparing solution to manage limited osteoarthritis of the knee affecting the medial, lateral or the patello-femoral compartment.1, 2, 3

Patient's selection and surgical indication are based on the physical examination and on the radiological analysis including full-length x-rays and stress x-rays. Clinical experience has shown the need for high flexion in patients who have both high flexibility and a desire to perform deep flexion.

Additionally the shape differences related to anatomy or the patient expectations after the surgery may also affect the surgeon decision. 4

The limited incision into the extensor mechanism allows a quicker recovery which represents a functional improvement for the patient additionally to the cosmetic result. A dedicated physiotherapy starting on the following day allowing weight bearing exercises protected by crutches and focusing on early mobilization and range of motion combined to a multimodal pain management approach is critical despite the type of individualized solution chosen for the patient knee. 5

Since bony landmarks may be different form a patient to another one as well as anatomical shapes, several tools have been developed in order to provide the surgeons an assisted tool during the surgery adapted to each knee, this include navigation, patient specific instrumentation and robotic surgery.

Improving the adaptation between the implant and the patient bone during total hip arthroplasty (THA) may improve the survival of the implant. This requires a perfect understanding of the tridimensional characteristics of the patient hip. The perfect evaluation of the tridimensional anatomy of the patient hip can be done pre-operatively using X-rays and CT-scan. All patients underwent a standard x-rays evaluation in the same center according to the same protocol. Pre-operatively, the frontal analysis of the hip geometry was performed and the optimal center of rotation, CCD angle, neck length and lever arm was analyzed to choose the optimal solution for proper balance of the hip in order to obtain adequate range of motion, appropriate leg length, and correct tension of the abductors muscles. Standard or lateralized monoblock stems can be valid or modular neck shape can be choosen among 9 available shape. These 9 frontal shapes are available in standard, anteverted or retroverted shapes, leading to 27 potential neck combinations. In case of important hip deformation, a custom implant can be used in order to balance the extra-medullar geometry without compromising the intra-medullary adaptation of the stem.

We prospectively included 209 hips treated in our institution with total hip arthroplasty performed using a supine Watson-Jones approach and the same anatomic stem. The mean patient age was 68 years and the mean BMI 26 Kg/m². Intra-operatively the sagittal anatomy of the hip was analyzed and standard, ante or retro modular necks were tested for the frontal shape defined pre-operatively.

According to the pre-operative frontal planning, non-standard necks were required in 24 % of the cases to restore the anatomy of the hip. Intra-operatively, a sagittal correction using anteverted neck was required in 5% of the cases and retroverted necks in 18% of the cases. Harris hip score improved from 56 to 95 points at min. 5 year follow-up. No leg length discrepancy greater than 1 cm was observed. Restoration of the lever arm (mean 39.3 mm, range 30 to 49 mm) and of the neck length (55.2, range 43 to 68 mm) was adapted for 95% compared to the non operate opposite side. Disturbed anatomy like in DDH or post-traumatic cases may require additional solutions to balance the hip such combined osteotomy or customized stem and neck.

Introduction:

Recent studies have concluded that gender influences hip morphology at the time of surgery as well as dysplastic development of the hip. This may lead to a particular choice of implant including stem design and/or neck modularity. In this study we hypothesized that not only gender but also morphotype and etiology (primary osteoarthritis versus aseptic osteonecrosis) may be a significant factor to predict the anatomy of the hip at the time of total hip arthroplasty (THA).

Unicompartmental knee arthroplasty (UKA) is a logic procedure when osteoarthritis or avascular necrosis is limitad to one femorotibial compartment. The indications for the procedure includes osteoarthrosis or osteonecrosis with full-thickness loss of articular cartilage limited to one of the tibiofemoral knee compartments. Physical examination should ensure full range of knee motion. Frontal and sagittal knee stability has to be tested. A particular attention should be given to the state of the anterior cruciate ligament. The status of the patellofemoral joint should be analysed by physical examination and patellofemoral view at 30, 60 and 90° of flexion. Preoperative anteroposterior varus and valgus stress radiographs should be done to confirm the complete loss of articular cartilage in the involved compartment, the full thickness cartilage in the opposite compartment and the possibility of full correction of the deformity to neutral.

The so-called minimally invasive surgery (MIS) procedure using a specific instrumentation is able to provide quicker recovery since the extensor mechanism disruption is eliminated. More importantly the radiological evaluation has shown that precise implantation of the components is possible with an MIS approach which is important for the long term results of the arthroplasty. The clinical results at ten years of follow-up of cemented metal-backed UKA performed through a conventional approach have shown results comparable to those obtained with total knee arthroplasty. The in vivo kinematic evaluation of patients implanted with UKA has shown that kinematics similar to the normal knee can be obtained, enhancing the importance of a functional anterior cruciate ligament.

Recent design improvements have increased the femorotibial area of contact to accommodate high flexion angles. Additionally our experience has demonstrated that modern UKA is a valid alternative for young and active patients with unicompartmental tibiofemoral noninflammatory disease, including both osteoarthritis and avascular necrosis. Compared to medial UKA lateral UKA represents in our experience only 5% of all UKA implantations.

However the long term results of lateral UKA compares at least equally with those reported for medial UKA.

Introduction and Method: For 16 years, now, we have been using custom made femoral stems (titanium stem, HA coated) based on preoperative patient CT scans in young patients presenting with symptomatic osteoarthritis of the hip. The aim was to provide optimum initial fit-and-fill of the stem in the femoral medullary canal, conferring the best chance of secondary osteoin-tegration. This, with a goal of long term survivorship. The custom stem also enables dialling-in correction of the (often abnormal) femoral neck version (in young patients presenting with arthritis) to a more normalised 15 degrees of anteversion.

Results: We present the long term results (5–16 year, mean of 10 years), clinical, survivorship and radiological, of 312 primary total hip arthroplasties in 280 patients, all of whom were under the age of 50 years of age (mean age 40).

At 10 years we have a survivorship, if femoral aseptic loosening is used as an end point, of 97.6%. There was a deep infection rate of 1.2%, and a dislocation rate of 1.9%. There were no cases of thigh pain, and no intra-operative femoral neck/shaft fractures.

Discussion: The under 50’s with hip arthritis requiring total hip arthroplasty are a highly challenging group, they are young, active and tend to have distorted anatomy. Our results are superior to those previously published using either cemented or standard uncemented stems. Thus, justifying the increased initial financial outlay on the custom-made stem.

Introduction: Due to the diversity of the prosthetic implants for hip arthroplasty, a better matching between the implant and the intra and extra-medullary characteristic of the patient anatomy is now possible. This adaptation however requires a perfect understanding of the tridimensional characteristics of the patient hip anatomy. Little data are available in the literature. We aimed to analyze the muscular and bony anatomy of the hip at the time of arthroplasty.

Material and Methods: data acquisition was performed according a standardized CT-scan in the same center for all patients within the standard workup before arthroplasty. Standardized measurements were obtained after automatic tridimensional bone reconstructions using dedicated software. 549 femurs in 469 patients including primitive coxarthrosis (COX), dysplasic development of the hip (DDH) and aseptic osteonecrosis (ONA) were analyzed. Mean age was 58 and 70% of the patients were women. Tridimensional reconstruction of the muscular anatomy of the hip was performed for 30 patients using manual contouring on dedicated software. Characteristics of the bony and muscular anatomy were then analyzed according to the etiology and correlations between bony and muscular anatomy were evaluated.

Results: Concerning the bone analysis, mean offset was 23.2 ±1.5mm in the DDH group, 40.5±1.2 mm in the COX group and 29.6± 0.9mm in the ONA group(p< 0.001). Neck-shaft angle was 132±25º in the DDH group, 130±0.5º in the COX group and 134±1º in the ONA group (p< 0.001). Mean anteversion was 33±3.5º in the DDH group, 25±3.8º in the COX group and 16±3.2º in the ONA group (p< 0.001). Concerning the muscular analysis, gluteus medius and minimus volumes were correlated with the body mass index and with the gender, but not with patient age (p: NS). Location of the muscular insertion of the gluteus medius and minimus on the greater trochanter were correlated with the femoral anteversion.

Discussion: The results of our study demonstrated that bony and muscular anatomical characteristics were correlated with the etiology of the degenerative joint disease, with the patient body mass index and gender. Surgeons should be aware of these characteristics to improve the patient anatomy reconstruction during the arthroplasty.

A clinical and radiographic study was conducted on 97 total hip arthroplasties (79 patients) performed for congenital hip dislocation using three-dimensional custom cementless stem. The mean age was 48 years (17 to 72). The mean follow up was 123 months (83 to 182).

According to Crowe, there were 37 class 1, 28 class 2, 13 class 3 and 19 class 4. The average lengthening was 25 mm (5 to 58 mm), the mean femoral anteversion 38.6° (2° to 86°) and the correction in the prosthetic neck −23.6° (71° to 13°). The average Harris hip score improved from 58 to 93 points. Six hips (6.2%) required a revision. The survival rate was 97.7% ± 0.3% at 13 years.

Custom cementless stem allows anatomical reconstruction and good functional results in a young and active population with disturbed anatomy, while avoiding a femoral osteotomy.

Purpose of the study: Malposition of the acetabular implant of a total hip arthroplasty can provoke dislocation, limited joint movement, and early wear. The purpose of this prospective randomized study was to assess the efficacy of a image-free navigation system to achieve correct acetabular position for total hip arthroplasty.

Material and methods: The navigation software for the acetabular component used intraoperative anatomic acquisition. The prospective randomized study included two groups of 20 patients. In the first group, the acetabular implant was inserted using the computer-assisted system and in the second using the conventional method. The same operator performed all procedures via an anterolateral approach and using the same non-cemented hemispheric cup. The postoperative assessment was performed by an independent investigator who noted the cup inclination on the standard ap view and cup anteversion on the computed tomography; then using a dedicated system for 3D reconstruction, the same values were determined one month after surgery.

Results: Each group included ten men and ten women, mean age 63 years and mean body mass index 24. For the computed-assisted group, mean additional operative time for navigation was 13 minutes (range 8–20 min). The intraopeartive concordance with the surgeons subjective impression was excellent for 12 patients and good for 8. Mean intraoperative values were for the computer-assisted group were: for operative mode: inclination 30° (25–46°), anteversion 14° (0–25°), radiographic mode: inclination 35° (25–47°), anteversion 13° (0–26°), anatomic mode: inclination 36°, anteversion 19° (0–27°). There was no significant difference between the intraoperative and postoperative values for the computer-assisted group. There was no significant difference between the average values between the computer-assisted and conventional groups but the standard deviation was smaller in the computer-assisted group.

Discussion and conclusion: The image-free navigation system enables reliable positioning of the prosthetic cup for total hip arthroplasty and increases the precision of acetabular implantation without increasing significantly operative time. This first step must be integrated into the computerized preoperative planning for total hip arthroplasty. The next step will be to use the navigation system for implanting the femoral component.

Purpose of the study: Acetabular dysplasia is a recognized cause of premature hip degeneration. With increasing use of arthroplasty, the role of conservative treatment can be debated. The purpose of this work was to describe technical advances achieved with Ganz triple periacetabular osteotomy and evaluate long-term results.

Material and methods: This study included 32 dysplastic hips in 28 patients treated by Ganz triple osteotomy and assessed a mean 12 years follow-up (range 2 – 20 years). Mean age was 32 years (range 18–47). There were 24 women and four men. Hip joint measurements were made on preoperaive standard x-rays with complementary recentered views if needed as well as computed tomography (CT) to better distinguish progressive degeneration. For early patients, the iniail osteotomy involved three cuts (ilioischial, iliopubic, ilial) starting close to the acetabulum and performed via three approaches: sub coxofemoral, intrapelvic, extrapelvic. The first technical change involved osteotomy of the anterosuperior iliac spine and an oblique iliac cut farther from the acetabulum.

Results: Mean preoperative angles were: 135° (121 to 150°) for CC’D, 23.2° (3 to 40°) for HTE, 8.4° (−14 to 22°) VCE, 11.3° (−26 to 32°) for VCA. The postoperative values were: 134.5° (121 to 150°) for CC’D, 9.5° (−9 to 20°) for HTE, 31.7° (14 to 60°) for VCE, 31.7° (10 to 48°) for VCA. Six patients required total hip arthroplasty on average four years later (range 2 – 9 years), including one patient with aseptic necrosis of the acetabulum.

Discussion and Conclusion: This study confirms the usefulness of triple periacetabular osteotomy for conservative treatment of acetabular dysplasia. In light of our results, the following changes have been instituted:

all three cuts are performed via a single intra-pelvic approach;

Purpose of the study: Compter-assisted surgery enables improved precision of prosthetic implantations, but the basis of data acquisition remains variable. The purpose of this study was to assess the radiological quality of a total knee arthroplasty (TKA) implanted with a computer-assisted surgical technique with or without pre-operative imaging.

Material and methods: This was a case-control study of a group of 40 patients who underwent TKA implanted with a navigation systm (N+) which was compared with a control group of patients who underwent the same procedure with a conventional technique (N-). The two groups were comparable for: age, gender, BMI, preoperative HKA. The same surgeon operated all patients using the same cemented posterior stabilized TKA. Outcome was analyzed by an independent operator. The same navigation system was used for all knees, with, for the first 20 knees, acquisition based on preoperative computed tomography and for the next 20 knee, intra-operative acquisition. Postoperatively, six radiographic parameters were studied for each knee on the ap and lateral views. An optimal interval was determined for each parameter and the number of optimal criteria was noted for each knee.

Results: The mean HKA was 177.5° in the N- group and 179.2° in the N+ group. The angle of implantation of the femoral piece was 90.3° in the N- group and 90° in the n+ group. The mean posterior tibial slope was 3.5° in the N+ group and 3.1° in the N- group. There was a significant difference for the tibial prosthetic angle in favor of the N+ group, i.e. 89° compared with 87.3° for the N- group. The overall quality of the implantation was considered optimal for 54.5% of knees in the N+ group and for 29.8% in the N- group. There was no significant difference between computed tomographic acquisition and intraoperative acquisition.

Discussion and conclusion: This study demonstrates that the results exhibit a distribution closer to the ideal values for the navigation group but that the difference is solely significant for the tibial implantation. This improvement requires a longer operative time of 18 minutes. The lack of any difference between the computed tomographic acquisition and the intraoperative acquisition suggests that intraoperative acquisition should be favored for reasons of cost and simplicity. Computed tomography imaging can still be useful for a precision of the biepicondylar line in certain complex situations such as revision arthroplasty.

Purpose of the study: Changes in prosthetic design to adapt to knee flexion greater than 120 degrees can modify the bone-prosthesis fixation and also displace the femorotibial contact. The purpose of this study was to analyze mid-term results in a consecutive series of 186 arthroplasties and to examine the femorotibial kinematics in vivo.

Material and methods: A posterior stabilized cemented prosthesis with a plateau with motion limited to rotation was used. Design changes concerned: lengthening of the posterior femoral condyle, scooping out the poly-ethylene anteriorly with reorientation and change in the height of the posterior stabilization stem. The same technique was used for all patients who followed the same rehabilitation protocol. Mean age was 69 years (range 22–87). All patients were evaluated clinically with the IKS score and radiologically on the anterioposterior and lateral images. An in vivo analysis of the femorotibial kinematics in the weight bearing condition was also performed in 20 patients under fluoroscopic control with automatic 3D modelization.

Results: Mean follow-up was 40 months (range 2–5 years). Mean IKS function score improved from 34 preoperatively to 96 at last follow-up. The knee score improved from 53 on average to 91 at last follow-up. The mean flexion was 115° (range 45–135°) preop-eratively and 120° (115–145°) at last follow-up. One implant was removed for infection and arthrolysis was performed for one case of stiff joint. Radiographically: the mean postoperative femorotibial alignment was 179° (178–181°), the mean tibial slope 3.8° (0–10°°, the mean patellar height (0.8° (0.56–1°), and the mean elevation of the joint space (4.5 mm. There were two cases of progressive lucent lines in the tibial zone which were stable at last follow-up. All patients analyzed showed a mean posterior displacement of the femorotibial point of contact of 9.7 mm at flexion.

Discussion and conclusion: Changes in prosthesis design to adapt to greater range of flexion do not appear to have a negative effect at mid-term on implant fixation. The clinical flexion ranges obtained were encourageing and the correlation with kinematic results show that the degree of preoperative flexion remains a determining factor for the postoperative outcome. Posterior displacement of the femoro-tibial point of contact, observed in all patients examined fluoroscopically, certainly contributed to the good postoperative flexion.

Purpose: Wrist fractures are often seen in elderly subjects who cannot generally tolerate aggressive fixation of unstable fractures. Percutaneous intra-focal pinning (Kapandji) is usually employed. The purpose of this study was to compare the classical treatment of unstable extra-articular fractures of the lower quarter of the radius with posterior displacement with a modified pinning technique.

Material and methods: This prospective radiological study concerned two groups of randomised patients aged 30 – 70 years who were hospitalised for surgical treatment of Pouteau-Colles fractures. In the first group, all patients were treated by the classical intra-focal technique using one or two dorsal pins and one lateral pin (group K). In the second group, all patients were treated by fixation with one or two infrafocal dorsal pins and a third pin inserted transfocally (group KM). Preoperative care, anaesthesia, and postoperative care (21 days immobilisation, pin removal at 45 days) were the same in both groups. The following anatomic measurements were made on the radiographs at day 1, 21, 45, and last follow-up: radial inclination on the lateral and AP views, bistyloid line.

Results: Group K included 49 patients, mean age 45 years. Group KM included 46 patients, mean age 54 years. There was no statistical difference between groups for age, gender, side, type of fracture. Radial inclination on the AP view was 19.2 (10–27 in group KM and 23.2 (19-30) in group. On the lateral view, radial inclination was 0 (−11 to 20) in group KM and −5.7 (−25 to 2) in group K. The proportion of bistyloid lines considered satisfactory was not different between groups.

Discussion: Infra-focal pinning can have limitations for maintaining reduction to bone healing. The Kapandji technique modified by use of a third transstyloid pin appears to provide better stabilisation of unstable fractures of the lower extremity of the radius, particularly in older subjects who cannot tolerate aggressive surgery. This preliminary study should be completed by a radio-clinical analysis in a larger number of patients to confirm these results.

Purpose: Most revisions of total knee arthroplasty (TKA) occur before the fifth year. The leading cause is prosthesis malalignment. Computer-assisted surgery is presented as a technique which improves implantation precision. The purpose of this study was to evaluate the radiographic quality of computer-assisted TKA implantation in comparison with conventional implantation.

Material and methods: A prospective randomised study was conducted with a total of 82 patients assigned randomly to conventional instrumentation (group 1) or computer-assisted implantation (group 2). The two groups were comparable for age, gender, body mass index, side, and preoperative femorotibial angle (HKA). The same surgeon operated all patients using the same cemented posterostabilised prosthesis. Radiographically, the HKA, the theta angle between the mechanical and anatomic femoral axis, the angle of the femoral and tibial implantations, and the posterior tibial slope were noted. All measures were taken by an independent operator who was unaware of the operative technique.

Results: There was no statistical difference in the HKA 177.5° in group 1 and 179.2° in group 2 (p=0.13); the theta angle was 6° in group 1 and 5.9° in group 2 (p=0.78); the femoral implantation angle was 90.3° in group 1 and 90° in group 2 (p=0.74); the posterior tibial slope was 3.5° in group 1 and 3.15° in group 2 (p=0.65). There was a statistical difference in the tibial angle, 87.3° in group 1 and 89° in group 2 (p=0.012).

Discussion: This study demonstrates a significant improvement in the navigation group for the position of the tibial implant and no difference for the femoral implant. This might be related to the cut guide which allowed more intra-operative adjustment for the tibia. Blood loss was equivalent in the two groups (503 mg) and operative time was longer in the navigation group (18 minutes).

Conclusion: It appears important to have specifically adapted cut guides for computer-assisted surgery and to reduce operative time.

Purpose: Implantation of a unicompartmental knee pros-thesis (UKP) via a short incisiosn was proposed to improve rapid postoperative recovery. But it is known that long-term survival is highly dependent on implantation quality. The purpose of this study was to evaluate the influence of implantation quality assessed radiographically and that of rapid recovery after unicompartmental arthroplasty using the conventional or minimally invasive approach.

Material and methods: A continuous series of the first 25 cases of UKP implanted using the minimally invasive approach (group 1) was compared with a homogeneous group of matched knees in a series of 145 UKP implanted with the same approach as used for total knee arthroplasty (group 2). The groups were comparable for age, gender, weight, and height. The same medial cemented UKP with a metallic tibial base plate was implanted in both groups. Postoperative radiographic measures included the overall mechanical axis, the femoral and tibial implantation orientations, and the posterior tibial slope.

Results: There was no significantly different between groups 1 and 2 for mechanical axis (3.6° and 4.7° respectively), tibial implantation angle (87° and 88°), or posterior tibial slope (2.6° and 2°). The femoral implantation angle was also comparable (2.3° and 2.9°) with the exception of one knee (9°) in group 1. Hospital stay, use of crutches and resumed activity were significantly shorter in group 1. Blood loss (222 and 244 ml respectively), postoperative pain (visual analogue scale), and full flexion at one year were comparable between the groups.

Discussion: The basic difference between the two approaches is the absence of patellar eversion and rupture of the extensor system with the minimally invasive method. This probably explains the more rapid recovery of function and activity in this group. The one case of significant femoral deviation noted in this group points out the need for greater care in positioning the specific guides for the short incision approach. To evaluate the long-term results of UKP implanted with the minimally invasive approach, the same criteria for patient selection and prosthetic implantation should be used.

Purpose: Impacted piecemeal allografts for nonce-mented hemispheric cups raises a problem of primary stability in the case of extensive bone defects. The high centre of rotation of the oversized cup further increases bone loss, requiring an extralong neck. The purpose of this study was to describe the use of impacted piecemeal grafts associated with a pressfit supporting ring with reposition of the centre of rotation.

Material and methods: The piecemeal grafts were impacted into the acetabulum to fill the defect. The hydroxyapatite coated ring was pressfit for primary stability then stabilised with axial screws in the upper paste. A distal hook on the obturator foramen repositioned the centre of rotation. The study group included 103 cases of acetabular reconstruction, including 34 for aseptic loosening and type 2 and 3 acetabular substance loss. Clinical and radiographic assessment was performed at 5 and 12 years.

Results: Mean patient age was 58 years, mean weight was 64kg. The Harris score improved from 53 points preoperatively to 88 points at last follow-up. Radiographically, there were no cases of cup migration according to the Massin classification, and the centre of rotation (Pierchon) was anatomic in 66% horizontally and in 44% vertically. There were two lucent lines in zone 2 and mean polyethylene wear was 0.015 mm per year. Graft integration (Conn) was identical to the host in 84% with disappearance of the interface in 67%. There were three dislocations treated without changing the implant and two revisions for infection.

Discussion: Several theoretical and clinical studies have shown that the high centre of rotation increases stress on the implants and decreased abductor force. The results obtained in this study with a maximum 12 year follow-up show that indications for this pressfit technique associating reposition of the centre of rotation, fixation for stability, and restoration of bone stock can be widened. Limitations are bone destructions with rupture of the pelvic girdle.

Purpose: Hip prosthesis for sequelar developmental dysplasia of the hip is a therapeutic challenge because of the anatomic deformity and the young age of the patients. The purpose of this work was to report results obtained using a non-cemented femoral stem with an intramedullar design and a prosthetic neck custom-made to match individual anatomy observed on preoperative computerised tomographic.

Material and methods: This study included 257 hips with a mean follow-up of 5.6 years. Mean age at implantation was 55 years (range 17–78). The computed tomography study assessed: dislocation according to Crowe, leg length discrepancy, and acetabular anteversion and diameter. The cup was not cemented and was inserted with an anchor hook in the obturator foramen for implantation in the paleoacetabulum. The medullary canal was prepared using a blunt reamer shaped like the definitive prosthesis. The prosthetic neck was designed individually to match the lever arm and anteverion.

Results: There were 174 cases of dysplasia and 83 dislocations (39% grade 1, 30% grade 2, 14% grade 3 and 17% grade 4). Mean lengthening was 39 mm. The mean ante-verion was 28±16° and the mean anteroposterior diameter of the acetabulum was 51 mm. The Harris clinical score improved from 58 points preoperatively to 93 points at last follow-up. The follow-up x-rays showed osteointegration in 88% of the cases with osteolysis in 5% and one stem impaction. The prosthesis had to be changed for six hips: two for infection, one for dislocation and two for nonfixation. The 11-year survival rate was 97%.

Discussion and conclusion: This study illustrates the anatomic sequelae observed in patients with developmental dysplasia of the hip and demonstrates a surgical solution for these problems. There is no correlation between dislocation and the degree of anteversion so it is difficult to assess the difficulty of inserting a non-cemented stem without preoperative computed tomography. The good 11-year survival is encouraging for this young and active population.