Hip resurfacing arthroplasty (HRA) is being offered as a viable alternative to total hip arthroplasty (THA). For very young patients (under 30 years old), THA achieves fair results but with high revision and complication rates. This retrospective study was designed to evaluate the results of HRA performed in patients under 30 years old with a long follow-up.

During the inclusion period (2007–2021), we collected in a single operator database, all HRA performed in patients under 30 with a minimum follow up of 2 years.

103 HRA in 93 patients (77 male / 16 females; a mean age at operation 27.7 years (18 to 29.9)) were included. The two mean preoperative diagnoses were osteoarthritis in 54 HRA (52.5%) and DDH or hip dislocation in 19.4% (20 cases). No patient was lost to follow-up and 3 patients (5 HRA) deceased. There were 2 revisions (one for femoral aseptic loosening and one infection recurrence (pediatric osteoarthritis)). No dislocation and adverse wear-related failures were found. At a mean follow-up of 10.4 years (2–17.4), mean UCLA activity and Oxford Hip score improved respectively from 5.4 (1 to 7) and 39.9 (25–55) pre-operatively to 7.9 (3 to 10) and 15.8 (12–34) post-operatively (p<0.001). Mean Harris hip score increased from 41.6 (22–63) to 91.8 (72–100) (p<0.001). There were no radiological cases exhibiting lysis while two cases displayed limited partial radiolucency around the femoral stem. Kaplan-Meier survival analysis, with the endpoint revision for any reason, showed a 10.8-year survival rate of 98% (95% expected with NICE guidelines).

This cohort of HRA performed under 30 is the longest follow-up ever reported in the literature. Despite a challenging cohort of patients, HRA exceeds the stricter NICE survivorship criteria. HRA remains an effective treatment with excellent functional outcomes and a very low rate of complications.

The results of total hip arthroplasty (THA) revisions to correct leg length discrepancy (LLD) are not clear, with only two former limited series (< 25 patients). Therefore, we conducted a retrospective study of THA revisions for LLD to determine: 1) the change in LLD, 2) the function outcomes and whether obtaining equal leg lengths influenced function, 3) the complication and survival rates.

This multicenter study included 57 patients: 42 THA revisions for limb shortening and 15 revisions for limb lengthening. LLD was measured on conventional radiographs and EOS. The Oxford-12 and FJS outcome scores were collected and the number of patients achieving the Oxford-12 MCID.

The revisions were carried out a mean of 2.8 years after the index THA. The median LLD decreased from 7.5 mm (IQR: [5;12]) to 1 mm (IQR: [0.5;2.5]) at follow-up (p=0.0002). Overall, 55 of 57 patients (96%) had < 5 mm LLD at follow-up and 12 patients (21%) had equal leg lengths. The complication rate was 25%: 12 mechanical complications (8 periprosthetic femoral fractures, 2 stem loosening and 1 cup loosening, 1 dislocation) and 1 periprosthetic infection. The patient satisfaction was high with a median FJS of 79.2/100 and 77% of patients reached the Oxford-12 MCID. Lengthening procedures had significantly worst function than shortening (38% vs 91% of patients achieving the Oxford-12 MCID (p=0.0004)). Survivorship was 85% (95% CI: 77.9 – 92.5) at 2 years and 77% (95% CI: 66.3 – 87.1) at 4.6 years when using re-revision for any reason as the endpoint.

When LLD after THA does not respond to conservative management, revision THA should be considered. Although revision THA for LLD improved medium-term functional outcomes with a high patient satisfaction rate, especially for shortening procedures, the complication rate was high, particularly related to periprosthetic femoral fracture.

Aims

Mechanical impingement of the iliopsoas (IP) tendon accounts for 2% to 6% of persistent postoperative pain after total hip arthroplasty (THA). The most common initiator is anterior acetabular component protrusion, where the anterior margin is not covered by anterior acetabular wall. A CT scan can be used to identify and measure this overhang; however, no threshold exists for determining symptomatic anterior IP impingement due to overhang. A case-control study was conducted in which CT scan measurements were used to define a threshold that differentiates patients with IP impingement from asymptomatic patients after THA.

Mechanical irritation or impingement of the iliopsoas tendon accounts for 2–6% of persistent postoperative pain cases after total hip arthroplasty (THA). The most common trigger is anterior cup overhang. CT-scan can be used to identify and measure this overhang; however, no threshold exists for symptomatic anterior iliopsoas impingement. We conducted a case–control study in which CT-scan was used to define a threshold that differentiates patients with iliopsoas impingement from asymptomatic patients after THA.

We analyzed the CT-scans of 622 patients (758 CT-scans) between 2011 and 2020. Out of this population we identified 136 patients with symptoms suggestive of iliopsoas impingement. Among them, 6 were subsequently excluded: three because the diagnosis was reestablished intra-operatively (one metallosis, two anterior instability related to posterior prosthetic impingement) and three because they had another obvious cause of impingement (one protruding screw, one protruding cement plug, one stem collar), leaving 130 patients in the study (impingement) group. They were matched to a control group of 138 patients who were asymptomatic after THA. The anterior cup overhang (anterior margin of cup not covered by anterior wall) was measured by an observer (without knowledge of the clinical status) on an axial CT slice based on anatomical landmarks (orthogonal to pelvic axis).

The impingement group had a median overhang of 8 mm [IQR: 5 to 11] versus 0 mm [IQR: 0 to 4] for the control group (p<.001). Using ROC curves, an overhang threshold of 4 mm was best correlated with a diagnosis of impingement (sensitivity 79%, specificity 85%, PPV = 75%, NPV = 85%).

Pain after THA related to iliopsoas impingement can be reasonably linked to acetabular overhang if it exceeds 4 mm on a CT scan. Below this threshold, it seems logical to look for another cause of iliopsoas irritation or another reason for the pain after THA before concluding impingement is present.

The management of prosthetic joint infection (PJI) has been widely performed for total hip arthroplasties (THA), but none has compared it with hip resurfacing arthroplasty (RSA). We also carried out a retrospective case-control study comparing the surgical treatment of PJI by surgical debridement and implant retention between RSA and THA in order to clarify whether there was a difference in terms of (1) successful healing of PJI (2) functional scores after recovery (3) risk factors for recurrence of PJI. Our hypothesis was that simple debridement with prosthesis retention regardless of the timeframe allowed to obtain a higher success rate for RSA compared to THA.

From 2010 to 2018, a single-center case-control study based on 3056 RSA found 13 PJI were age-matched (based on the 139 THA PJI treated) with 15 THA PJI (mean age of 53 years old (47–58) for THA and 59 (45–66) for RSA (p=0.34)). We compared their survival (absence of infectious recurrence) and the means differences between the 2 groups (demographical, clinical and biological data).

There was no difference between the 2 groups concerning: age (p=0.3), BMI (p=0.4), initial diagnosis (p=0.4), operating time for primary surgery (p=0.3), the presence of a postoperative hematoma (p=0.4), the type of bacteria (p=0.5), the total duration of antibiotic therapy (p=0.9) and the type of antibiotic therapy (p=0.6). Early postoperative infections (less than 6 weeks) occurred in 7/13 RSA cases (54%) compared to 11/15 THA cases (73%). At the mean follow-up of 5 years (2–7), the success rate without recurrence was significantly higher in the RSA group 100% versus 66.7% (10/15) for the THA group (p=0.044). At the last follow-up, the Oxford Hip Score was higher in the RSA versus THA group's (14 versus 22 p=0.004).

Simple surgical debridement an RSA without changing implants after PJI can be done regardless of the time to onset of infection. This is secondary to the absence of metaphyseal bone invasion and the low content of joint fluid.

The hip-shelf procedure is less often indicated since the introduction of peri-acetabular osteotomy (PAO). Although this procedure does not modify pelvic shape, its influence on subsequent total hip arthroplasty (THA) is not known. We performed a case-control study comparing THA after hip-shelf surgery and THA in dysplastic hips to determine: 1) its influence on THA survival, 2) technical issues and complications related to the former procedure.

We performed a retrospective case-control study comparing 61 THA cases done after hip-shelf versus 63 THA in case-matched dysplastic hips (control group). The control group was matched according to sex, age, BMI, ASA and Charnley score, and bearing type. We compared survival and function (Harris, Oxford-12), complications at surgery, rate of bone graft at cup insertion, and post-operative complications.

The 13-year survival rates for any reason did not differ: 89% ± 3.2% in THA after hip shelf versus 83% ± 4.5% in the controls (p = 0.56). Functional scores were better in the control group (Harris 90 ± 10, Oxford 41/48) than in the hip-shelf group (Harris 84.7 ± 14.7, Oxford 39/48) (p = 0.01 and p = 0.04). Operative time, bleeding and rate of acetabular bone grafting (1.6 hip-shelf versus 9.5 control) were not different (p > 0.05). Postoperative complication rates did not differ: one transient fibular nerve palsy and two dislocations (3.2%) in the hip-shelf group versus four dislocations in the control group (6.3%).

The hip-shelf procedure does not compromise the results of a subsequent THA in dysplastic hips. This procedure is simple and may keep its indications versus PAO in severely subluxed hips or in case of severe femoral head deformity.

Cementless distally locked stems were introduced in revision hip arthroplasty (RTHA) in the late 1980s to deal with severe femoral bone loss. These implants have not been assessed over the long-term, particularly the influence of the design and porous coating. Therefore we performed a retrospective case-control study at a minimum 10-years' follow-up comparing the straight Ultime™ stem with 1/3 porous coating versus the anatomical Linea™ stem with 2/3 proximal coating with hydroxyapatite.

We performed a single-center case-control study measuring survival, function based the Harris and Oxford-12 scores, and rate of thigh pain. X-rays were done at regular intervals and at follow-up. No femoral bone graft was used at insertion.

The two groups were comparable in terms of age, sex and follow-up (mean 12.2 years in Ultime and 10.8 years in Linea cohorts); however they differed in the severity of bone loss therefore the results were adjusted according to this variable. Ten-year survival considering revision for any reason was 63.5% ± 5.4 for Ultime and 91.6% ± 2.7 for Linea (p < 0.001). Merle d'Aubigné scores and Oxford-12 were higher in the Linea group 82.9 ± 12.4 and 26.3/48, respectively, versus 69.5 ± 16 and 21/48 in the Ultime group (p < 0.001). Thigh pain was observed in 30% of Ultime cases versus 3% of Linea cases. Bone reconstruction measured via cortical thickness was better in the Linea group and correlated to metaphyseal filling at insertion.

This study confirms the benefits of using of locked stems in RTHA with severe bone loss. Better metaphyseal filling and optimized porous coating help to minimize thigh pain and the revision rate.

Introduction

In valgus knees, ligament balance remain difficult when implanting a total knee arthroplasty (TKA), this leads some authors to systematically propose the use of constrained devices. Others prefer reserving higher constraints to cases where it is not possible to obtain final satisfactory balance: less than 5 of residual frontal laxity in extension in each compartment, and a tibiofemoral gap difference not in excess to 3mm between flexion and extension. The goal of the study was to assess if is possible to establish preoperative criteria that can predict a constrained design prosthetic implantation at surgery.

Introduction

The prosthetic impingement occurs if the range of motion of the hip exceeds implant mobility or in case of component malorientation. This retrieval study was designed to assess the frequency and the risk factors of this phenomenon.

Purpose of the study: The purpose of this work was to compare the subjective and functional outcomes of patients with a large diameter total hip arthroplasty (LD-THA) or hip resurfacing (HR).

Material and methods: Forty-eight persons were assessed and double blind randomised to receive either LD-THA (n=24) or HR (n=24). The clinical and radiographic assessment and gait analysis were performed preoperatively and at three, six and 12 months postoperatively. Gait analysis was performed once in a third group of healthy adults (n=14) who served as controls.

Results: The two groups were comparable preoperatively regarding demongraphic and functional characteristics. Postoperatively, the two groups with prostheses exhibited very rapid recovery with normalization of test results compared with controls within three to six months. The clinical assessment, the analysis of postural balance, gait analysis and most of the specific tests were not different between the two groups with prostheses.

Conclusion: There was no remarkable difference in subjective or objective assessments between subjects with a LD-THA or HR. This suggests that the only potential advantage of HR is the preservation of femoral bone stock. Long-term HR implant survival will determine the reality of this benefit.

Purpose of the study: The objectives of this work were to assess the stability of outcome achieved after Duquennoy procedure to tighten the lateral capsule-ligament structures of the ankle joint. To do this, we reviewed the same series of patients at 3 and 25 years follow-up to analyse the very long-term stability, laxity, and stiffness of the ankle joint and any osteoarthritic degradation.

Material and methods: From 1975 to 1986, we performed 75 Duquennoy procedures on the lateral capsule and ligament structures of the ankle joint. At mean 25 years follow-up (2007) we were able to review 28 ankles (27 patients) with the same method as applied in 1980 (3 years follow-up). The function outcome was assessed with the Good, Karlsson, Duquennoy and Tegner scores. Clinically, other than joint range of motion, were noted varus laxity or anterior drawer. Static x-rays were obtained to search for signs of osteoarthritis and stress images to measure talocrural laxity, in comparison with the preoperative figures and the 1980 data.

Results: There were two early technique failures (one persistent talocrural instability, one subtalar instability). Good and Karlsson scores were good or excellent in 92% of cases. Patients were very satisfied with the operation and the VAS was 8.9/10. Pain and occasional instability were reported by 27% of patients. There was no talocrural no subtalar stiffness at last follow-up. Radiographic laxity declined significantly between the preoperative value and the last review. Only one patient presented a narrow talocrural space (less than 50% narrowing). Eight patients had osteophytes whose presence was not correlated with poor functional outcome. These osteophytes were also present on the controlateral side. Importantly, there was no significant difference in the mean function scores between 3 and 25 years follow-up (Duquennoy score). Similarly joint range of motion and radiographic laxity remained stable over time.

Discussion: The Duquennoy procedure to tighten the lateral capsule and ligament structures is a simple technique with rare complications which provides excellent results both in terms of ligament stability and in terms of preservation from degenerative osteoarthritis. These results remain stable over time. Conversely, the technique has no action on the subtalar joint and should not be proposed as treatment for associated subtalar laxity, if diagnosed.

Purpose of the study: A medial incision for implantation of a total knee arthroplasty (TKA) offers an excellent surgical exposure while minimising the length of the skin opening. This incision however implies section of the proximal portion of the infrapatellar branch of the medial saphenous nerve, potentially associated with lateral hypoesthesia and formation of a neuroma (painful scar). We hypothesised that an anterolateral skin incision would produce less hypoesthesia and postoperative discomfort.

Material and methods: We conducted a prospective randomised study to compare the degree of hypoesthesia after a medial or lateral skin incision for the implantation of a TKA. Fifty-knees in 43 patients, mean age 65.9±8.4 years were included; 26 knees for the lateral incision and 24 for the medial. All patients had the same type of implant. Clinical results were assessed with WOMAC, KOOS and SF36. Semme-Weinstein monofilaments were applied to measure sensitivity at 13 characteristic points. Patients were assessed at six weeks and six months. The zone of hypoesthesia was delimited and photographed for measurement with Mesurim Pro9^®. Satisfaction with the surgery and the scar was noted. Data were processed with Statview^®; p< 0.05 was considered significant.

Results: The two groups were comparable preoperatively regarding age, gender, body weight, height, body mass index, body surface area, aetiology, and clinical score. Operative time, blood loss, and number of complications were comparable. The functional outcomes (WOMAC, KOOS, SF36) were comparable at six weeks and six months. Active flexion was significantly greater at six months in the lateral incision group (p=0.03). The zone of hypoesthesia was significantly smaller in the lateral incision group at six weeks (p< 0.01) and at six months (p< 0.01), as were the number of points not perceived on the filament test (p< 0.01 in both cases) while the length of the incision was comparable (p> 0.05). This was associated subjectively, with less loss of sensitivity and less anterior pain reported by the patient at six months.

Discussion: Lateral and medial incisions enable comparable functional outcomes. The lateral incision produces less hypoesthesia and less anterior pain. This improves the immediate postoperative period and facilitates rehabilitation as is shown by the gain in flexion at six months.

Purpose of the study: For young active patients, implantation of metal backed socket with a metal-on-metal bearing is an attractive tribological alternative when a standard prosthesis cannot be implanted. Metal ion assays have not been reported in this type of population. The purpose of this work was to present the clinical, radiographic and metal ion results.

Material and methods: Between 1998 and 2003 23 total hip arthroplasties (THA) (six primary and 17 revision) were implanted with a cemented Metasul™ bearing in a Muller inlay. Mean follow-up was 6.1 years (5–10). None of the patients was lost to follow-up. The Harris and PMA scores were noted as were signs of implant loosening or migration. Metal ions were assayed in total blood (Cr and Co) by mass spectrometry and atomic emission spectrometry (Ti).

Results: At follow-up, the mean Harris and PMA scores were significantly increased, from 62.2 to 95.2 (p = 0.01) and from 12.9 to 17.4 (p = 0.02) respectively. No revisions were required for aseptic loosening or failure of fixation. The radiographs did not reveal any signs of osteolysis or lucency. The mean levels of Cr, Co and Ti were 1.85μg/l (0.8–3.2). 1.24μg/l (0.5–1.86) and 9.62μg/l (5–18) respectively. Ti > 10μg/l was noted in six patients; Ti > 10 μg/l and Cr > 2μg/l in five patients. There was no correlation of metal ion levels with size of the implants, activity level, gender, clinical scores or cup inclination.

Discussion: The mean Co and Cr levels observed in this series were similar to those reported in the literature for standard THA (cementless press fit cups). Ti levels have only been reported in rare studies so that comparison with other series is hazardous. The Ti level observed here appeared to depend on the femoral stem resurfacing (in our series, the porous surface of the stem was coated with a Ti-6Al-7nB alloy).

Conclusion: Cementing the metal-on-metal bearing in the supporting inlay appears to be a reliable and attractive technique for this young and active population. Levels of Cr and Co in blood were the same as reported for standard implants. These levels of metal ions should be followed to confirm the long-term results.

Purpose of the study: Tribology studies of total hip arthroplasty (THA) have demonstrated that large diameter head in metal-on-metal bearings produce fewer wear particles than small diameter heads. The other advantages of this option are better stability, less dislocation, and optimal joint range of motion. The purpose of this work was to compare blood levels of chromium, cobalt and titanium six months and one year after implantation of different models of large diameter metal-on-metal THA.

Material and methods: We conducted a retrospective comparative and randomised study including 110 patients who had been implanted with a larger diameter head THA/Zimmer? Smith and Nephez, Biomet or Depuy. The metal ion concentrations (Cr, Co, Ti) were measured in whole blood by an independent laboratory using high-resolution mass spectrometry (HR-ICP-MS). Blood samples were drawn preoperatively and postoperatively at six months and one year.

Results: At six months, the concentrations of metal ions in whole blood expressed as mean (range) for Cr (μg/L) Co (μg/L) and Ti (μg/L) were, respectively: Zimmer 1.3 (0.4/2.8) 1.7 (0.9/6.8) 2.5 (0.6/6.7); Smith and Nephew 2.0 (0.7/4.2) 2.1 (0.5/6.6) 1.1 (0.5/4.1); Biomet 1.2 (0.4/2.2) 0.9 (0.3/3.4) 1.4 (0.8/2.4); Depuy 1.7 (0.5/3.2) 1.9 (0.3/4.2) 1.3 (0.5/3.9). There was a significant difference between groups for Cr (p=0.006), Co (p=0.047) and Ti (p< 0.001). The Biomet implants presented the lowest concentrations for Cr and Co; the Zimmer implants gave the highest levels of Ti.

Discussion and Conclusion: Several implant-related factors affect blood concentrations of metal ions: contact surfaces leading to “active” abrasion but also wear in other parts of the implant giving rise to “passive” corrosion. Bearing wear is related to the diameter of the head, its roughness, its spherical shape, joint clearance, the manufacturing technique (forging, casting) and its carbon content. The Biomet head corresponds to a better compromise for these different factors. Passive corrosion can result from an exposed metal surface or from metal to metal contact. This explains the high level of Ti ions found for all implants tested since titanium is not present in the bearings.

Purpose of the study: Locked implants have yielded favourable results for femoral bone reconstruction for revision total hip arthroplasty, but defective integration has also been reported due to insufficient bioactive coating. The purpose of this work was to evaluate a locked pivot with a two-third proximal hydroxyapatite coating.

Material and methods: From 1996 to 2007, 158 femoral implants (Linea™) were implanted for hip arthroplasty revision. The 143 cases with more than one year follow-up were reviewed (14 deaths, 1 lost to follow-up); 83 revisions for aseptic loosening, 41 periprosthetic fractures, 19 revisions in an infected context. Patients were reviewed retrospectively by a non-operator observer. These were older patients (mean age 68 years, range 31–93) and 36 patients had complex situations requiring at least two prior prostheses; 25% had severe grade 3 or 4 (SOFCOT) bone lesions and 59% diaphyseal damage.

Results: Clinical improvement was significant, the Postel Merle d’Aubigné score improved from 7.7 + 4.3 (0–17) to 15.6 + 2.2 (8–18) at mean 50 months (14–131) (p< 0.001). At last follow-up, 14 patients (10%) reported thigh pain and only seven pivots (5%) had not achieved Engh osteointegration (five with thigh pain two without). There were no fractures. There was on non-union of the femorotomy. According to the Hoffman index, femoral bone regeneration was significant at the metaphyseal and diaphyseal levels. Eighteen of the 19 infections cured, all periprosthetic fractures healed. The implant survival was 88.9% at 91 months (65–96.7%). There were five pivot replacements for non integration and/or thigh pain which resolved in all cases; there were no other pivot replacements. The quality of the metaphyseal and diaphyseal filling was predictive of the quality of the bone fixation of the pivot (p< 0.01).

Discussion: Compared with older models of locked pivots, this implant reduced the rate of thigh pain while allowing constantly satisfactory bone reconstruction. The metaphyseal and diaphyseal filling index is the main factor predictive of clinical and radiological success by favouring osteointegration. Maximal filling, obtained with a full range of implant diameters and lengths, contributes to this good result.

Purpose of the study: Hip resurfacing (HR) is becoming popular again with the advent the the metal-on-metal bearing. This type of surgery is proposed for young, often very active, patients for whom restoration of optimal hip joint range of motion constitutes and important objective. The purpose of this work was to analyse anterior translation of the femoral component to optimise joint range of motion (particularly flexion).

Material and method: From September 2007 to May 2008, 68 hip resurfacing prostheses were implanted in 66 patients aged on average 45 years (range 19–61). All procedures were performed by the same operator using a posterorlateral approach and the same surgical technique. Anterior head-neck offset was a constant objective. The Postel-Merle-d’Aubigné and Harris scores as well as the Devane classification and the WOMAC and the SF-12 were noted. Joint range of motion was noted preoperatively and at last follow-up by and independent operator. Anterior head-neck offset was measured radiographically on the Dunn view using an original technique and calibrated by the Imagika software according to the known diameter of the implants.

Results: All clinical scores as well as the activity level and the subjective scores improved significantly. There were no revisions. The mean anterior head-neck offset was 4.5 mm (range 2–9). Significant correction was observed for gain in postoperative flexion and increased offset (p< 0.005). The group of patients who had an anterior offset considered to be significant (> 4 mm) exhibited significantly better flexion than the group of patients with a small anterior offset.

Discussion: Hip resurfacing has a poor head-neck ratio, depending on the patient’s anatomy, which compares unfavourable with conventional hip prostheses (THA). Nevertheless, the joint range of motion after resurfacing, as observed in our study and in the literature, does not show any decline compared with THA. The greater gain in flexion is an important factor to take into consideration, especially in a young active athletic subject. Each millimetre of gain in anterior offset produces a significant increase in flexion. This offset can be improved by the surgical technique (implanting the femoral component tangentially to the posterior cortical), but also by the design of the resurfacing prosthesis (thick femoral component, increased cement sheath). After hip resurfacing, anterior offset appears to be an essential biomechanical factor for restoration of joint motion.

Purpose of the study: Drilling along yields disappointing results for osteonecrosis of the femoral head due to the high failure rate despite prolonged rest and also because of the risk of fracture. To prevent these problems, we have developed a new drilling technique which was evaluated prospectively.

Material and methods: The procedure performed percutaneously uses a lateral cortical orifice measuring 5mm, non-concentrated autologous bone marrow was injected after drilling. Osteoinductive protein (BMP7) was associated in random fashion (groups BMP+ and BMP−). Ficat stage 1 and 2 necrosis was included. Outcome was the rate or revision for prosthesis.

Results: Forty hips (36 patients) were included and assessed at mean four years (range 2–6). The necrosis was related to: alcoholism (n=5), cortisone (n=25), barotraumas (n=2), metabolic disease (n=4), idiopathic condition (n=4). Group BMP- (drilling+bone marrow) included 24 hips and group BMP+ (drilling+bone marrow+BMP7) 16 hips. The groups were comparable regarding necrosis stage (15% stage 3, 65% stage 2, 20% stage 1) and mean Koo index (27 BMP+ vs 34 BMP-; NS). There were no infections and no fractures despite immediate and complete weight-bearing. The revision rate for prosthesis was higher in the BMP- group (67%) than in the BMP+ group (43%) but the difference did not reach significance (p=0.10). The failure rate was not affected by the severity of the necrosis in the BMP+ group: all stage 3 hips were revised in the BMP- group versus none in the BMP+ group. The only variable predictive of revision for prosthesis was the Koo index (p=0.02).

Discussion: Adjunction of BMP did not improve significantly the success rate of drilling with bone marrow adjunction but adding BMP appeared to limit the unfavourable impact of server necrosis observed in the BMP- group. To reach a statistical power of 80%, 40 cases would be needed in each arm. This threshold has not yet been reached. It can be noted however that the proposed method does ensures early weight bearing without the risk of complications. Similarly, since it is a percutaneous procedure, later arthroplasty is not compromised. The principle confounding factor, the richness of the bone marrow, was not assessed, motivating a new randomized trial with measurement of CFU-F.

Purpose of the study: Despite a survival rate to the order of 90–95% at ten years, implant malposition and particularly malrotation can cause an underestimation of failure after total knee arthroplasty (TKA). We report our experience with revision TKA for isolated malrotation.

Material and methods: Twelve patients underwent revision for isolated maltrotation of an implant. This series of three men and nine women, mean age 66 years, range 47–74 years at primary surgery, were reviewed retrospectively. During the follow-up, all patients complained of early onset anterior knee pain, which was generally noted severe, associated with moderate patellar instability in four cases, noted severe in 7 others and extreme in one (permanent patellar dislocation). Half of the patients also exhibited hyperlaxity was invalidating instability. Range of motion was generally preserved (2/5/100). In all cases, the rotational problems were confirmed on the computed tomography which revealed predominant tibial malrotation, measured at 23 mean internal rotation and a cumulative malrotation (femur+tibia) of 22 internal rotation.

Results: All patients except two required revision of both femoral and tibial implants. In one case, the tibial piece was alone changed and in another, isolated translation of the anterior tibial tuberosity was performed. For eight of eleven cases, the revision implants had a stem and femoral inserts were used to control the bone stock loss induced by the corrective cuts in six cases and requiring more or less extensive ligament balance procedures in six. At mean follow-up (30 months, range 12–60), there was a very significant improvement in the functional results; only one patients with a history of patellectomy complained of persistent anterior pain. None of the patients complained of patellar instability.

Discussion: Excessive cumulative internal rotation of the implants induces increased stress on the patella, causing early anterior pain, then subluxation and finally dislocation beyond −15 to −20° internal rotation. These position errors are concentrated on the tibia were care must be taken to respect the anatomic landmarks (bicondylar axis, anterior tibial tuberosity) to avoid early failure. In the event of major rotational disorders, revision may be required with procedures to correct the ligament balance.

Introduction: Metal on metal hip replacement using large diameter bearings can be used as part of a hip resurfacing (HR) system or with a large diameter head total hip arthroplasty (LDH-THA). Both types of implant release metal ion, but the amount of ion released after LDH-THA has not been studied. The aim of the present study was to assess whole blood metal ion release at one year following LDH-THA.

Material and Method: Pre and post operative Cr, Co and Ti concentrations in whole blood were measured using a high resolution mass spectrometer (HR-ICP-MS) in 29 patients with LDH-THA (Durom LDH, Zimmer). The results were compared to published ion levels on a HR system (Durom, Zimmer) possessing the same tribological characteristics, the only differences being the presence of a modular sleeve and opened femoral head design in LDH-THA.

Summary of results: Post operative Cr, Co and Ti mean levels of LDH-THA were 1.3, 2.0 and 2.8 μg/L at 6 months and 1.3, 2.2 and 2.7 μg/L at 12 months. In the LDH-THA, the opened femoral head design showed significantly higher Co ion concentrations than the closed femoral head design (3.0 vs 1.8 ug/L, p=0.037). Compared to previously published results after HR, Co levels were significantly higher at one year in the LDH THA (2.2 ug/L vs. 0.7 ug/L, p< 0.001).

Discussion: In order to reduce wear and ion release from metal-metal bearing, most manufacturers focus research on improvements at the bearing surfaces. This study has demonstrated that the addition of a sleeve with modular junctions and an open femoral head design of LDH-THA causes more Co release than bearing surface wear (157% and 67% respectively). Even if no pathological metal ion threshold level has been determined, efforts should be made to minimize their release. We recommend modification or abandonment of the modular junction and femoral head closed design for this specific LDH-THA system. The total amount of ion released from a metal-metal implant should be considered globally and newer implant design should be scientifically evaluated before their widespread clinical use.

Introduction: The prosthetic impingement occurs if the range of motion of the hip exceeds implant mobility or in case of component malorientation. This phenomenon is rarely studied in the literature and most data have come from sporadic cases. This study was designed to assess the frequency and the risk factors of this phenomenon.

Material: The frequency and the severity of the impingement were calculated from a continuous series of 413 cups retrievals. These cups were examined macroscopically twice by two independent observers. The cam effect was noted as: absent, grade 1 (visible at gross inspection but measuring < 1 mm), grade 2 (notch measuring 1–3 mm), grade 3 (notch measuring > 3 mm). The risk factors were analyzed for 298 retrievals that had complete clinical charts.

Results: Among the 413 cups explants, the frequency of impingement was 51.3 percent (grade 3 in 12% and grade 2 in 24%). The impingement was the reason for removal in only 1.7 percent (only for hard bearings), meaning that impingement was mainly an unexpected event (98.3 percent). The impingement was more frequent when revisions were performed because of instability (80 percent; odd-ratio 4.2 (1.1–16.2)) than for loosening (52%) osteolysis (59%) or infection (38%) (p =.002). Likewise, impingement was more frequent when the sum of hip motion exceeded 200 degrees (sum of motion in the 6 degrees of freedom of the hip) (66% versus 45% if the sum was below 200°). The other risk factors were: use of heads with skirts (78% versus 55%), liner with an elevated rim (73% versus 55%), and head-neck ratio below 2.

Discusssion and conclusion: This study underlines the impingement is common when assessing cup retrievals (over 50 percent). One should be aware of impingement when performing hip replacement in patients having a high range of motion. This situation may require prostheses with a high head-neck ratio, as well as use of computer-assisted surgery. One should avoid liners with elevated rim as well as heads with skirts to prevent dislocation, particularly when other risk factors are detected.