The main causes of total hip arthroplasty (THA) revisions are loosening and instability. Use of a dual mobility cup cemented in a acetabular reconstruction cage device limits the risk of instability and does not hinder the acetabular fixation during THA revisions. The objective of this study was to analyse a retrospective series of 123 THA revisions with antiprotusio cage and dual mobility socket.

Patients and methods: At a mean follow-up of 10 years, we analysed a continuous series of 123 revisions using a reconstruction device (87 Kerboull cross-plates, 12 Burch-Schneider antiprotrusio cages, 24 custom-fit Novae ARM cages associated in all cases with a Novae Stick dual mobility cup cemented into the cage). There were 80 women and 43 males. The mean age at the surgery was 69.2 years old.

PMA score increased from 9.6 +/− 3.06 preoperatively to 14.2 +/− 2. at the follow-up. 9 early dislocations occurred and one late dislocation. At the last follow-up, the X-rays showed nine hardware failures, including one cross-plate fracture, one hook fracture, and one flange fracture. Analysis of the radiological position of the cup showed a mean lowering of 13 mm and a 7 mm lateralisation compared to the preoperative position. 2 revisions for aseptic loosening and 3 for septic loosening were performed.

This study confirms the advantage of dual mobility cups during acetabular reconstruction cemented in antiprotrusio cages as a way to limit, without eliminating, the risk of dislocation. Therefore cemented fixation of dual mobility cups in cages appears to be a reliable short-term option.

Aims

The purpose of this study was to analyse the biomechanics of walking, through the ground reaction forces (GRF) measured, after first metatarsal osteotomy or metatarsophalangeal joint (MTP) arthrodesis.

Dual mobility significantly reduces the risk of prosthetic instability. This mechanical complication occurs when the prosthetic head moves out from the retentive polyethylene liner, such phenomenon called intra-prosthetic dislocation reports a ten-year incidence of 2% in the literature.

We prospectively analysed all intra-prosthetic dislocations having occurred since 1985 in our department in order to investigate patient- and implant-related risk factors.

91 intra-prosthetic dislocations occurred with NOVAE (SERF) cups in 85 patients of mean age 50.7 years. Intra-prosthetic dislocation occurred after a mean period of 8.8 years.

A PRO (SERF) stem was implanted in 56 cases and a PF (SERF) stem in 35. The stems were different from one another in their neck diameter and material: 13 mm titanium neck and 16 mm stainless steel neck respectively.

When taking both prosthetic features into account, no significant difference could be established regarding the time between implantation and dislocation.

Comparison between these two prosthetic features was performed by means of two continuous homogeneous series which included 240 patients implanted with PF stems and 382 patients with PRO stems. At a mean 15-year follow-up, the two series reported a non-statistically different intra-prosthetic dislocation rate of 4%.

In both series, young age and large diameter cups were considered predisposing factors for intra-prosthetic dislocation.

Therefore, unlike suggested by several authors, prosthetic neck material and diameter do not appear as the main predictors for intra-prosthetic dislocation which is highly promoted by patient-related features.

The concept of stainless steel dual mobility cups in total hip arthroplasty has demonstrated very low long-term instability rates and a 98% survival rate after 12 years. We systematically implanted titanium alloy acetabular cups during a one year period. The purpose of our retrospective study was to report the 18-year clinical outcome data in a homogeneous and continuous series of 103 primary total hip replacements after implantation of a cementless titanium cup.

All patients were implanted with NOVAE Ti (SERF) cups made of titanium alloy combined with a retentive polyethylene liner and a 22.2 mm cobalt chrome prosthetic head. Mean patient age at the time of surgery was 53 years. All patients were clinically and radiographically evaluated.

The overall 18-year actuarial cup survival rate with a 95% confidence interval was 87.4%. At last follow-up, there was no evidence of implant instability whereas acetabular aseptic loosening was reported in one case and high wear of the retentive liner in 9.

The results of this investigation confirmed the long-term stability of dual-mobility implants. The main limitation of this system was early wear of the polyethylene liner in contact with the titanium metal back and reaction with third body along with loss of liner retentivity. In our study, titanium demonstrated favourable osteointegration properties but poor tribologic characteristics, therefore suggesting its interest at the bone-cup interface only.

Purpose of the study: The pertinence of locking for major femoral revision remains a controversial issue. We conducted a retrospective multicentric study to assess the benefit and potential clinical and radiographic complications after using a long locked stem entirely coated with hydroxyapatite.

Material and methods: Our series included 77 patients (42 women, 35 men), mean age 71 years (range 34–90) reviewed at minimum one year. A modular implant was used; the long curved stem allowed total integration. Screws guaranteed distal locking. There were 71 revision THA on trochanteric-shaft fractures, three shaft nonunions, 34 aseptic loosenings, 9 septic loosening, 21 fractures on prosthesis, 6 implant failures and one instability. Seventy percent of patients had stage 3 and 4 bone lesions. Mean follow-up was 60 months.

Results: At last follow-up, 90% of patients were satisfied or very satisfied. The mean Harris function score improved from 32 to 83 and the PMA from 7 to 15. Sixty-four patients were pain free and 22% had pain solely under stress. There were 15 bone complications: dislocation (n=3), early infection (n=3 including 2 recurrences), implant failure (n=2), secondary femur fracture (n=5). Stem survival was 94% at nine years. Radiographically, total stem stability was noted in 73 patients (95%); instability was noted in four cases of fracture. Undeniable metaphyseal improvement was noted in 20% of cases, more modest improvement in 32%; the situation was considered unchanged in 31%. Locking was successful in all cases; cortical bone in contact with the locking screw was unchanged in 59 cases, slightly thickened in 16, including one case with a context of septic recurrence. The locking was dismantled in two cases (one empirically and one for pain), but the stem remained stable.

Discussion: Major damage to the femur can compromise stabilisation of the proximal or diaphyseal implants. Distal locking contributes to the initial mechanical stability, indispensable for secondary osteointegration of the implant. However, with total hydroxyapatite coating, rapid fixation in healthy zones is also crucial. Reconstruction of metaphyseal bone is not easy to quantify, but the absence of bone absorption is noteworthy.

Purpose of the study: Revision ligamentoplasty can improve function and laxity control but with a less satisfactory result than obtained after primary reconstruction. The purpose of this study was to report management practices and results of revision ACL reconstructions and to assess the course of meniscocartilage damage and determine causes of failures.

Material and method: This was a consecutive series of ten patients, mean age 30 years (range 17–48) who underwent arthroscopic reconstruction. The review was retrospective. Criteria for failure were redevelopment of instability and/or pain, objective laxity, and a KT-100 differential greater than 5 mm. The IKDC protocol was used for the clinical and radiographic assessment. Goniometry, arthroscan and MRI were also performed. The position of the tunnels was analysed according to the Aglietti criteria. The type of surgery, transplant used and status of the menisci and cartilage were analysed.

Results: Mean follow-up of the second revision was 38 months. At last follow-up, seven patients had a global IKDC score of A or B. Two patients had resumed regular sports activities at the same level as before the first tear, four at a lower level. Four had interrupted their sports activities. At the second revision, two patients exhibited medial femorotibial narrowing measured at less than 50%, three had a remodelled medial femorotibial compartment and one a remodelled lateral compartment. All had a partial homolateral meniscectomy and seven had cartilage injuries (3 ICRS III and 1 ICRS IV). At the successive interventions, the number of meniscal lesions, meniscetomies, and cartilage lesions increased (p=0.016, 00098 and 0.0197 respectively). ICRS grade II and IV cartilage lesions were associated with an overall C or D IKCD (p=0.0472). The cartilage lesions were more frequent in knees with meniscal lesions and meniscectomies. The causes of failure of the primary ligamentoplasty and of the first revision (six and seven patients respectively) were poor position of the tunnels (respectively 4 and 1 patients).

Discussion: In 70% of the patients outcome after repeated revision was good or excellent, although the quality declined with increasing number of revisions, in relation to the development of meniscal and cartilaginous lesions. These latter were more frequent and more severe, related to recurrent laxity. Failures were mainly due to recurrent trauma followed by technical errors.

Purpose of the study: In 1975, Bousquet and Rambert invented the concept of dual mobility to reduce the risk of dislocation by changing the fixed insert on a Charnley implant to a mobile liner within a metal back shell held onto the femoral head by a retaining collar. This enabled implant recipients to maintain their intense activities without restriction after a first-intention procedure and to overcome muscle deficits after revisions. The screw-on PF stem was introduced in 1985. The purpose of our study was to demonstrate the long-term advantages and failures of this combination.

Material and method: This series included 240 hips with a PF stem and a Novae metal back cup. This was a retrospective analysis of a homogenous group of consecutive patients who underwent surgery from 1985 to 1990 (mean follow-up 22 years). Mean age at implantation was 56.7 years. This is the largest series, with the longest follow-up reported to date with dual mobile cups. The main indication was degenerative joint disease (79%) then osteonecrosis (11%). The implant was made of 316 L stainless steel. The PF was composed of the stem, a 22 mm diameter monobloc modular base and a 16 mm diameter neck. The tripodal Novae metal back cup was alumina coated. Preop, intraoperative and postop data were analysed. Clinical and radiographic follow-up (lucent lines, implant position) were noted at last follow-up. The Charnley, PMA, Devane and Sedel scores were noted.

Results: The preoperative PMA was 10.8, reaching 16.9 at last follow-up. The Devane score remained unchanged at 3. The mean Brooker score was 1.2. There were no cases with crural pain. Survival at last follow-up was 80%. There were no cases of dislocation, 18 intraprosthetic dislocations (4% at 9.25 years), four revisions of implant wear (1.7% at 19 years), five femoral revisions (2%), two infections (0.8%), nine patients lost to follow-up (4%) and 100 deaths.

Conclusion: The PF stem has a remarkable survival. The overall survival is comparable with series having an equivalent follow-up. The dislocation rate was zero, demonstrating the superiority of the dual mobility concept. There were several intraprosthetic displacements which came later than with Profil stems (role of the neck on the lip). The main complication was acetabular loosening, attributed to insufficient secondary fixation, improved later by adjunction of hydroxyapatite. Wear of the dual mobility cup should be modelised to define the role of osetolysis in these failures.

Purpose of the study: From a biomechanical view, the medial force stabilising the patella is assured for 50 to 60% by the medial patellofemoral ligament (MPFL). The purpose of this cadaver study was to present a precise description of the anatomic features of the MPFL concerning its femoral insertion, its relations with the oblique vastus medialis (OVM) and its relation with the medial collateral ligament (MCL) in order to optimise surgical reconstruction.

Material and methods: This cadaver study was performed on 23 knees from fresh cadavers. All measures were made knee flexed 30° by the same operator. Insertions of the OVM on the MPFL, when present, were identified. The length of the zone of reflexion was recorded. For these measurements, a orthonormal landmark centred on the femoral insertion of the MPFL was established. This landmark was used to position the medial epicondyle and the adductor tubercle for each knee.

Results: The MPFL was found in all 23 knees (100%); the length of the MPFL was 57.7±5.8 mm; its femoral insertion measured 12.2±2.6 mm (8–136); its patellar insertion measured 24.4±4.8 mm. A junction between the OVM and the MPFL was found for all 23 knees (100%). This zone appeared to be a veritable reflexion zone with the OVM fibres arching over the MPFL fibres for a length of 25.7±6 mm.

Discussion: Our study confirms the constant presence of the MPFL, observed in 100% of the knees studied. During the reconstruction of the MPFL, the key point is the position of the femoral insertion of the ligament, in order to restore the native femoral insertion of the MPFL surgically and thus attempt to recreate perfect isometry of the graft. The graft must be positions 10 mm posteriorly to the medial epicondyle and 10 mm distally to the adductor tubercle. In our cadaver the MPFL, the main medial stabilising force of the patella was a constant finding, always located in the second thickness of the medial plane of the knee.

Conclusion: We detailed the native femoral insertion of the MPFL and described its relations with the medial femoral epicondyle and the adductor tubercle using an orthonormal landmark. Long-term function of the graft depends on proper positioning.

Introduction: The double-hindfoot arthrodesis (subtalar and midtarsal joints) is traditionally performed through a lateral surgical approach associated or not with a medial approach. The main goal of this procedure is to correct severe deformities of the hindfoot in varus or in valgus. In this study we report a series of 19 double-hin-foot arthrodeses through a single medial approach.

Methods and Materials: 19 double arthrodeses (subtalar and talonavicular joint) were performed on 16 patients, 8 males and 8 females with a mean age at surgery of 58.3 years (range 27–72). The indications were: 12 pes planovalgus and 7 cavus foot. 9 deformities were fixed (3 in valgus and 6 in varus).

The chosen surgical technique was always identical using a medial approach and performed by a single dedicated orthopaedic foot and ankle surgeon (JLB), followed by an osteotomy of the insertion of the Tibialis posterior muscle to the Navicular bone, distraction and avivement of the articular surface done without bone resection, reduction of the talus on the calcaneus, fixation of the talonavicular joint with titanium staples (Pareos®) and of the subtalar joint with two 6.5 mm canulated cancellous screws (Unima®). On five occasions (in 3 pes planovalgus and in 2 cavus foot) arthrodesis of the calcaneocuboid joint was carried out through a mini lateral approach due to painful arthritic lesions.

Results: The average follow up was 16.5 months (range 6–40). Consolidation was always achieved.

In the subgroup with pes planovalgus: the mean Kitaoka score increased from 44 to 75, the axis of the hind-foot decreased from 21° to 11° in valgus, Djian’s angle decreased from 142° to 134.4°, the slope of the calcaneus increased from 17° to 19.4°. Two failures of the associated medial ligament reparation have led to a secondary complementary arthrodesis of the talo-crural joint.

In the subgroup with cavus foot: the mean Kitaoka score increased from 16 to 67. The axis of the hindfoot decreased from 13° in varus to 0.6° in valgus. Djians’s angle increased from 117° to 127.4°, the slope of the calcaneus ranges from 21.3° to 21.5°.

Discussion: The double-hindfoot arthrodesis via a medial approach permits the fusion without developing nonunion (in comparison with 20% non-union of triple arthrodesis reported in the literature).

Double arthrodesis via a medial approach provide a significant correction of the fixed deformities without resorting to bone grafts. Not classically used in cavus foot, it has permitted the correction of the cavo varus deformity without complications of the surgical wound and by extending the approach, a double elevating osteotomy of the metatarsal bases was performed when necessary.

Introduction: Achilles tendon (AT) rupture is a common sports injury. However, about 10% to 25% of the complete AT ruptures are not diagnosed. The management of neglected or chronic AT ruptures is usually different from that of acute rupture as the tendon ends were retracted and atrophied with short fibrous distal stumps. In the current series, we reported the mid- to long-term outcome of 10 patients with neglected or chronic AT rupture managed by a modified Flexor Hallucis Longus (FHL) transfer.

Materials and Methods: Between April 2002 and December 2003, 10 patients (6 males, 4 females) were operated on for a neglected or chronic AT rupture with a FHL transfer. The age at surgery averaged 44.1 years (range, 27–70). Five patients presented with a neglected AT rupture, 3 with a chronic AT rupture associated with Achilles tendinosis and 2 with an AT re-rupture. The AT defect after fibrosis debridement averaged 7.4 cm (range, 2.5–10). Beside FHL transfer, we performed a transfer augmentation with the 2 remaining Achilles fibrosis flaps. If no residual fibrosis after debridement was found, a Bosworth augmentation was performed to strengthen the transfer.

Functional assessment was performed using Kitaoka score. Postoperative complications were analyzed. Delay of work and sports recovery was noticed. Isokinetic evaluation was performed using Con-Trex^® dynamometer.

Statistical analysis was performed using Student’s t-test and Wilcoxon test (level of significance, p < 0.05).

Results: The mean follow-up was 61 months (range, 40–73). Functional outcome was excellent with a significant improvement of the average Kitaoka score at latest follow-up (98/100 (range, 90–100)). Average delay of work and sports recovery was 5 months (range, 2–12) and 10 months (range, 6–18) respectively. All patients returned to a sports activity within minor limitations. No re-rupture has been described. No major complication was observed particularly on wound healing. All patients presented with a loss of active range of motion of the hallux interphallangeal joint without subsequent hyperextension. However, no patient presented with functional weakness of the hallux during athletic or daily life activities. Isokinetic testing at 30 deg/sec and 120 deg/sec revealed a significant average decrease of 28±11% and 36±4.1% respectively, in the plantar flexion peak torque of the involved ankle compared with the non-involved ankle.

Discussion: Although strength deficit persisted at latest follow-up, functional improvement was significant. Morbidity due to FHL harvesting was clinically in significant at latest follow-up. For patients with neglected or chronic Achilles tendon rupture with a rupture gap of at least 5 centimeters, surgical repair using FHL transfer with fibrous AT stumps reinforcement achieved excellent outcome at our latest follow-up.

Background: Implant instability is a major complication of total hip arthroplasty. The concept of dual articulation invented by Prof. Bousquet in 1974 is now increasingly recognized in Europe. This concept has proved to provide high stability after total hip arthroplasty revision, and to successfully address chronic instability after total hip arthroplasty. The aim of our study was to evaluate the incidence of prosthetic instability in a consecutive homogeneous series of three hundred and eighty four hips primary cases with a mean follow-up of fifteen years.

Methods: Three hundred and eighty four hips have been implanted with a dual articulation acetabular cup system. This system consists of a cementless acetabular shell, and a polyethylene liner which freely rotates within the shell and positively captures the prosthetic head. It was a consecutive and homogeneous series of cases. Only primary cases were included in the study. A final evaluation was performed at the last follow-up. Implant survival was evaluated using the Kaplan-Meier method (p< 0.05), with surgical revision for aseptic loosening as the endpoint for failure. We have evaluated the incidence of instability by prospectively listing all the episodes of implant instability.

Results: At the last follow-up, 6 patients could not be located and 92 were deceased.

Mean follow-up was 15.3 years. The mean Merle d’Aubigner hip score was 16.3±1.8 at the latest follow-up. There was no early or late instability. Radiologically, there were 31% of severe granuloma formation extending beyond zones I and VII. However, granuloma remained asymptomatic in all of the cases and did not require surgical revision of the femoral component. On the acetabular side, late complications occurred: aseptic loosening (3.3%), intra-prosthetic dislocation (3.6%), polyethylene wear that required replacement of the liner (1.8%). Survival of dual-articulation acetabular system with surgical revision for aseptic loosening as the end-point for failure was 96.4% at 15 years and 94.9% at 18 years postoperatively (p< 0.05).

Conclusion: Our consecutive homogeneous series proves the good long-term behaviour of dual-articulation acetabular components in primary arthroplasty. Their excellent survivorship rate at 18 years increases our confidence in this concept. Considering the absence of episodes of prosthetic instability in our series, we can rightly claim that the goal of decreasing instability has been achieved.

Introduction: Many publications have already shown the great interest of dual-mobility concept which significantly reduces the rate of prosthetic dislocation and thus find its place for patients at high risk of post operative instability. The aim of our study is to evaluate the prevalence of prosthetic instability in revision total hip arthroplasty using a dualmobility cup.

Materials and Methods: Our multicentric series consists of 163 revision total hip arthroplasties performed between may 1999 and may 2004. The mean age at revision was 70 years and the mean follow-up period was 56 months.

The primary etiology necessitating revision is aseptic loosening.

According to the SOFCOT classification, the acetabular deficiency was grade IV 9 times, grade III 47 times, grade I or II 107 times.

All the implanted acetabular components are SERF dual-mobility implants. This system consists of a metal back which can be HA-coated and Press Fit or cemented in a Kerboull cross or in a Novae Arm. The mobile-bearing insert which allows a dual articulation between the head and the metal back is of polyethylene.

We implanted 119 HA-coated press-fit cups and cemented 44 dual-mobility cups in a support ring or in a Kerboull cross.

Results: The mean Merle d’Aubigné and Postel score is 14,1 at the last follow-up and 4,2 in the preoperative period.

We reported 8 complications: 6 early dislocations and 2 acetabular revisions for secondary mobilisation of the cup.

Discussion: According to Huten’s 1996 SOFCOT teaching conference, this rate ranges between 2 and 5% and we have already published a series of 106 dual-mobility with no dislocation at a 10 year follow-up period.

With 4% dislocations at a mean follow-up of 56 months, the dual-mobility cup seems to provide high stability in revision hip surgery when other factors such as muscular deficiency, extended synovectomies, difficult implant placement, encourage an uncertain postoperative prosthetic stability.

These results have to be compared to those of other systems such as constrained acetabular cups or tripolar cups.

Conclusion: This is why dual-mobility remains an efficient and reliable choice to avoid prosthetic dislocation in revision surgery. Moreover, we encourage the use of dual-mobility cup in any high risk situation in terms of post-operative instability such as for old or neurological patients.

Introduction: In the last years, the use of second generation cementless anatomical stems has generated an increasing interest in primary total hip arthroplasty. They are believed to offer long term stability through appropriate stress transfer and bone remodelling in the proximal femur. We conducted a monocentric prospective study on a homogeneous series of total hip replacements performed with a cementless anatomic, hydroxyapatite-coated stem. The purpose of the study was to evaluate the contribution of this implant in terms of clinical and radiological results at a minimum 5-year follow-up.

Material and Methods: The continuous homogeneous series included 176 THA performed between September 1997 and December 1998 by a single surgeon with the same implant system (SPS femoral stem and Hilock acetabular cup, Symbios Orthopédie SA). Indications were restricted to primary or secondary degenerative hip diseases. Revisions were excluded. Patients were reviewed for clinical performance (Harris hip score), satisfaction, and radiological outcome. The radiological analysis (implant migration, Ara and Engh scores, Brooker classification) was performed by an independent surgeon unaware of the clinical performance outcome. The survival curve was determined with the Kaplan-Meier method at 95% confidence interval, using exclusively implant revision as the criteria for failure.

Results: The follow-up rate in the series was 93.2%. The five-year implant survival was 98.8%. Two revisions were recorded: one for early instability due to excessive joint laxity after surgery, one due to recurrent dislocation following improper cup positioning during surgery. The clinical improvement was obvious, as the Harris hip score improved significantly (p< 0.0001) from 32.9±1.2 preoperatively to 93.1±0.8 at five years follow-up. Pain was the item exhibiting the largest improvement with only 10.2% of patients complaining of mild pain at last follow-up. The radiological analysis revealed a high stability of the femoral implant with Ara and Engh scores reaching 5.0±0.2 and 20.7±0.5 respectively. The migration remained low at 2.4 mm ±0.3 (p=0.02) and had no incidence on the clinical outcome. Heterotopic ossifications at various grades were observed in a large proportion of patients (65.1%). The polyethylene wear rate was 0.075 mm/yr in the series, below most values commonly reported for Ø28mm PE inserts.

Discussion: The survival rate of the SPS stem is comparable with that of other published series at same follow-up. Both the stem and cup implants used provided good clinical and radiological results at five years. The objectives of good integration and stability of the cementless anatomical stem appeared to be met, despite a significant rate of heterotopic ossifications. The excellent clinical and radiological results recorded at five years should be confirmed at longer follow-up.

Purpose of the study: The double-mobility concept was introduced for clinical applications for total hip arthroplasty in 1976. The concept preserves joint range of motion while increasing stability. In this study we evaluated the consequences of these advantages in terms of polyethylene wear, measuring wear both on the concave and convex surfaces and volumetrically.

Material and methods: Forty polyethylene inserts were explanted and analyzed. Explantation had been performed for mechanical or septic failure after eight years implantation on average. Mean age of patients at implantation was 46 years. After examining the gross aspect of the insert, surface analysis was performed with direct measurement of changes in the curvature using a BHN 706 position sensor for the inner concave surface and lateral projection for the outer convex surface. Estimated measurement error was ±5μm for each method; the manufacturer's tolerance for production of the inserts was 50μm. Volumetric wear was determined by reference to the manufacturer’s data. Student’s t test for paired series was applied.

Results: At gross inspection, all inserts had lost the strips originally present on the convex surface; 40% presented visible wear of the retaining ring. Mean annual wear (± standard deviation, SD) obtained with the measuring system was 9±9 μm/yr) for the convex surface and 73 ± 69 μm/yr for the concave surface. Total annual wear, the sum of inner and outer surface wear, was 82±72 μm/yr. The mean volumetric wear was 28±28 mm3/year for the convex surface and 25±23 mm3/year for the concave surface and 53.4±40 mm3/year for total wear.

Discussion: Total wear for these 40 double-mobility inserts which had functioned in vivo was not greater than the values reported for the metal-polyethylene bearing with 22.2 mm femoral heads. The double mobility is not associated with greater wear. While there was no significant difference between the wear volume of the convex versus the concave surfaces, the differentials wear were widespread, which can be considered to result from functional differences.

Purpose of the study: Double mobility prostheses are increasingly popular. Evidence in the literature demonstrates greater efficacy for the treatment and prevention of prosthesis instability. Ten-year survival is to the order of 95% (Aubriot, Philippot). One of the drawbacks is the risk of prosthetic head displacement outside the retaining polyethylene ring, i.e. intraprosthetic dislocation. We searched for factors causing this complication.

Material and methods: We reviewed retrospectively 67 files concerning intraprosthetic dislocation among a series of Novae cups (Serf) implanted from 1982. Head diameter was 22.2 mm for 59 cases, with a Pro stem (Serf) for 31 cases and a PF stem (Serf) for 36. Each type of stem has a specific neck design. All patients underwent revision surgery; the retaining function of the explanted pieces was analyzed.

Results: Mean time to the complication was 91 months; mean patient age at implantation was 54 years. Early cases exhibited macroscopically intact retaining capacity. Intermediary and late cases exhibited macroscopic wear with an oval shaped retaining ring. For three cases, intraprosthetic dislocation followed an episode of dislocation reduced under sedation. The cups measured 53 mm on average. The rate of calcification was high in this population (15 cases of Brooker grade 3 or 4). Mean survival was significantly different between the Pro and PF stems.

Discussion: Early dislocations were related to insufficient retaining capacity of the initially inserted ring. After a corrective measure by the manufacturer, this type of early complication has disappeared. Late dislocations resulted from impingement wear. Dislocation of a prosthesis with a double-mobility cup increases the risk of intraprosthetic dislocation after reduction; reduction procedures should thus be performed under general anesthesia with curare treatment. We analyzed the different parameters involved: head-neck relation, activity, periprosthetic calcification, cup diameter, resurfacing of the prosthetic neck. Observations were compared with data in the literature.

Purpose of the study: The iliopsoas bursa lies immediately anteriorly to the hip joint capsule and in certain cases there exists a natural communication between a hip prosthesis and the iliopsoas bursa, enabling formation of an inguinal mass by distension of the bursa.

Material and methods: We report six cases of a pseudo-tumoral mass which developed in the femoral scarpa triangle revealing a complication of total hip arthroplasty. These six patients, aged 66–79 years had their prosthesis for 11.5 years on average (range 4–20 years). Three had a history of acetabular dysplasia. All complained of pain. Five patients presented a palpable mass in the inguinal region. Two patients underwent emergency surgery, one for suspected strangulation of a crural herniation and the second for septic inguinal adenopathy. In two patients the clinical presentation was related to the local effect of the mass: lower limb edema with recurrent phlebitis due to venous and lymphatic compression, and femoralgia due to compression of the femoral nerve. The underlying prosthetic complications were: aseptic loosening (n=4), polyethylene wear (n=2), infection (n=1). All patients underwent revision surgery to change the prosthesis. The cystic formation was drained without resection. Symptoms resolved after replacement surgery in all patients.

Discussion: Palpation of an inguinal mass with signs of local compression in a patient with a painful total hip arthroplasty is a sign of a prosthetic complication (infection, loosening, wear). The diagnostic work-up should include bacteriology and plain x-rays of the hip joint. Bone scintigraphy may be contributive. Arthrography can demonstrate presence of a communication. Computed tomography provides the best visualization of the mass and its relations with neighboring organs. A duplex-Doppler is needed in all cases to search for thromboembolic complications prior to surgery. We chose not to resect the cystic formation in our patients, preferring treatment of the intra-articular cause. The fact that the mass and local its effects resolved in all cases with no recurrence at last follow-up leads us to recommend this attitude for typical presentations.