Introduction of ROSA robotic-arm system for total knee arthroplasty is associated with a minimal learning curve for operative time.

PURPOSE: The introduction of robotics for total knee arthroplasty (TKA) into the operating theatre is often associated with a learning curve and is potentially associated with additional complications. The purpose of this study was to determine the learning curve of robotic-assisted (RA) TKA within a multi-surgeon team. METHODS: This prospective cohort study included 83 consecutive conventional jig-based TKAs compared with 53 RA TKAs using the Robotic Surgical Assistant (ROSA) system (Zimmer Biomet, Warsaw, Indiana, USA) for knee osteoarthritis performed by three high-volume (> 100 TKA per year) orthopaedic surgeons. Baseline characteristics including age, BMI, sex and pre-operative Kellgren-Lawrence graded and Hip-Knee-Ankle Axis were well-matched between the conventional and RA TKA groups. Cumulative summation (CUSUM) analysis was used to assess learning curves for operative times for each surgeon. Peri-operative and delayed complications (infection, periprosthetic fracture, thromboembolism, and compromised wound healing) and revisions were reviewed. RESULTS: The CUSUM analysis for operative time demonstrated an inflexion point after 5, 6 and 15 cases for each of the three surgeons, or 8.7 cases on average. There were no significant differences (p = 0.53) in operative times between the RA TKA learning (before inflexion point) and proficiency (after inflexion point) phases. Similarly, the operative times of the RA TKA group did not differ significantly (p = 0.92) from the conventional TKA group. There was no discernible learning curve for the accuracy of component planning using the RA TKA system. The average length of post-operative follow-up was 21.3 ± 9.0 months. There was one revision for instability in the conventional TKA group and none in the RA TKA group. There were no significant difference (p > 0.99) in post-operative complication rates between the conventional TKA and RA TKA groups. CONCLUSIONS: The introduction of the RA TKA system was associated with a learning curve for operative time of 8.7 cases. Operative times between the RA TKA and conventional TKA group were similar. The short learning curve implies this RA TKA system can be adopted relatively quickly into a surgical team with minimal risks to patients.

Getting it right first time (GIRFT): A closed loop study of hip arthroplasty documentation in a trauma and orthopaedic department.

INTRODUCTION: The objectives of this study conducted in the University Hospital of North Tees, UK were to: (i) Identify if the current hip arthroplasty documentation met good compliance with the Getting It Right First Time (GIRFT) hip arthroplasty guidance (ii) Improve current documentation with a transition from hand-written notes to an online typed personalised operative hip arthroplasty template (iii) Improve the quality of documentation and adherence to GIRFT guidance in hip arthroplasty. METHODS: We led a team of 7 doctors to review University Hospital of North Tees compliance against 24 criteria laid out by GIRFT. After examining 20 operative records retrospectively at random from a spread of orthopaedic consultants in the department, it was shown that there was poor compliance against GIRFT guidelines. We proposed a pragmatic solution of incorporating a pre-populated hip arthroplasty online template adhering to GIRFT guidance into our local 'Trackcare' system. Following that, we closed the audit loop by prospectively reviewing 20 operative notes. RESULTS: Our initial results showed that poor compliance ranging 0%-100% over the 24 criteria. The findings of the 24 criteria with the online hip arthroplasty template in place showed a significant improvement between 80 and 100% compliance over the 24 criteria. CONCLUSION: The majority of the issues identified are modifiable risks factors which were amenable to some simple pragmatic solutions. A review of a single surgeon template has shown that it is simple to use, has excellent compliance (has pre-populated 24 criteria), takes 6-7 min to complete the operative notes, easily auditable and thus appears promising in minimising medico-legal claims for surgeons and the Trust.

Early to medium term outcomes of osteochondral lesions of the talus treated by autologous matrix induced chondrogenesis (AMIC).

BACKGROUND: The primary aim of the study is to evaluate the functional outcome following AMIC procedure in patients with osteochondral injury of the talus. The secondary aim is to evaluate if size of the lesion and patient's age influence outcome. MATERIALS AND METHODS: This is a retrospective study of 25 patients who underwent AMIC procedure of the talus treated by a single surgeon. Functional outcomes were evaluated using pre and post operative AOFAS and VAS scores. RESULTS: The mean lesion size was 1.74 cms with 88% of lesions in the study more than 1.4 cms. There was a significant improvement in AOFAS score with mean improvement of 49.40 (p < 0.05) and VAS score of 5.36 (p < 0.05). We could not find any correlation between either age or lesion size with functional outcome for AMIC procedure. CONCLUSION: AMIC procedure seems to be a reliable treatment method for larger diameter osteochondral lesions of the talus up to 2.5 cms in diameter.

A comparative surface topographical analysis of explanted total knee replacement prostheses: Oxidised zirconium vs cobalt chromium femoral components.

It has been proposed that an increased surface roughness of the femoral components of Total Knee Replacements (TKRs) may be a contributing factor to the accelerated wear of the polyethylene (PE) bearing and ultimately prosthesis failure. Oxidised Zirconium was introduced to the orthopaedic market in an attempt to reduce PE wear associated failures and increase the longevity of the prosthesis. In this study, non-contacting profilometry was used to measure the surface roughness of the femoral components of 6 retrieved TKRs (3 Oxidised Zirconium (OxZr) and 3 Cobalt Chromium alloy (CoCr) femoral components) and 2 as-manufactured femoral components (1 OxZr and 1 CoCr). A semi-quantitative method was used to analyse the damage on the retrieved PE components. The Sa values for the retrieved OxZr femoral components (Sa = 0.093 µm ± 0.014) and for the retrieved CoCr femoral components (Sa = 0.065 µm ± 0.005) were significantly greater (p < .05) than the roughness values for the as-manufactured femoral components (OxZr Sa = 0.061 µm ± 0.004 and CoCr Sa = 0.042 µm ± 0.003). No significant difference was seen between the surface roughness parameters of the retrieved OxZr and retrieved CoCr femoral components. There was no difference between the PE component damage scores for the retrieved OxZr TKRs compared to the retrieved CoCr TKRs. These results agree with other studies that both OxZr and CoCr femoral components roughen during time in vivo but the lack of difference between the surface roughness measurements of the two materials is in contrast to previous topographical reports. Further analysis of retrieved OxZr TKRs is recommended so that a fuller appreciation of their benefits and limitations be obtained.

Investigation of Taper Failure in a Contemporary Metal-on-Metal Hip Arthroplasty System Through Examination of Unused and Explanted Prostheses.

BACKGROUND: Large-diameter (≥36-mm) metal-on-metal (MoM) total hip replacements have been shown to fail at an unacceptably high rate. Globally, the DePuy Pinnacle prosthesis was the most widely used device of this type. There is evidence to suggest that one of the main reasons for the poor clinical performance of large-diameter MoM prostheses is the metal debris released from the head-stem taper junction-i.e., taper junction failure. The aim of this study was to investigate variation in the as-manufactured finish of the female taper surface and to determine its influence on material loss. We hypothesized that rougher surfaces with higher relative material peaks would be significantly associated with greater taper wear rates. METHODS: We analyzed 93 Articul/eze femoral head tapers with a 36-mm bearing diameter that had been used in combination with a Corail titanium uncemented stem. The influence of the surface topography of the as-manufactured female taper surface on taper wear was examined by means of a multiple regression model, taking into account other known variables. RESULTS: We identified great variation in the as-manufactured surface finish of the female taper surface, with a range of measured Ra values from 0.14 to 4.20 µm. The roughness of the female taper surface appeared to be the most important variable associated with taper wear (p < 0.001). The best-fitting regression model, including duration in vivo, head offset, reduced peak height (Rpk) value, stem shaft angle, and bearing surface wear rate, explained approximately 44% of the variation in taper wear rates. CONCLUSIONS: We concluded that the roughness of the female taper surface appears to be a significant factor in metal debris release from head-stem taper junctions. CLINICAL RELEVANCE: This study shows evidence that previously unappreciated variations in manufacturing processes may have a major impact on the clinical outcomes of patients.

Retrospective cohort study of the performance of the Pinnacle metal on metal (MoM) total hip replacement: a single-centre investigation in combination with the findings of a national retrieval centre.

OBJECTIVES: To determine risk factors for revision in patients implanted with a commonly used metal on metal (MoM) hip replacement. DESIGN: Retrospective cohort study in combination with a prospective national retrieval study (Northern Retrieval Registry (NRR)). SETTING: Combined orthopaedic unit in combination with the NRR. PARTICIPANTS: All patients implanted with a DePuy Pinnacle MoM hip prostheses by the 2 senior authors were invited to attend for a review which included clinical examination, blood metal ion measurements, radiographs and targeted imaging. Explanted components underwent wear analysis using validated methodology and these results were compared with those obtained from the NRR. RESULTS: 489 MoM Pinnacle hips were implanted into 434 patients (243 females and 191 males). Of these, 352 patients attended the MoM recall clinics. 64 patients had died during the study period. For the purposes of survival analysis, non-attendees were assumed to have well-functioning prostheses. The mean follow-up of the cohort as a whole was 89 months. 71 hips were revised. Prosthetic survival for the whole cohort was 83.6% (79.9-87.3) at 9 years. The majority of explanted devices exhibited signs of taper junction failure. Risk factors for revision were bilateral MoM prostheses, smaller Pinnacle liners, and implantation in 2006 and later years. A significant number of devices were found to be manufactured out of their specifications. This was confirmed with analysis of the wider data set from the NRR. CONCLUSIONS: This device was found to have an unacceptably high revision rate. Bilateral prostheses, those implanted into female patients and devices implanted in later years were found to be at greater risk. A significant number of explanted components were found to be manufactured with bearing diameters outside of the manufacturer's stated tolerances. Our findings highlight the clinical importance of hitherto unrecognised variations in device production.

Shorter, rough trunnion surfaces are associated with higher taper wear rates than longer, smooth trunnion surfaces in a contemporary large head metal-on-metal total hip arthroplasty system.

Taper wear at the head-neck junction is a possible cause of early failure in large head metal-on-metal (LH-MoM) hip replacements. We hypothesized that: (i) taper wear may be more pronounced in certain product designs; and (ii) an increased abductor moment arm may be protective. The tapers of 104 explanted LH-MoM hip replacements revised for adverse reaction to metal debris (ARMD) from a single manufacturer were analyzed for linear and volumetric wear using a co-ordinate measuring machine. The mated stem was a shorter 12/14, threaded trunnion (n=72) or a longer, smooth 11/13 trunnion (n=32). The abductor moment arm was calculated from pre-revision radiographs. Independent predictors of linear and volumetric wear included taper angle, stem type, and the horizontal moment arm. Tapers mated with the threaded 12/14 trunnion had significantly higher rates of volumetric wear (0.402 mm3/yr vs. 0.123 mm3/yr [t=-2.145, p=0.035]). There was a trend to larger abductor moment arms being protective (p=0.055). Design variation appears to play an important role in taper-trunnion junction failure. We recommend that surgeons bear these findings in mind when considering the use of a short, threaded trunnion with a cobalt-chromium head.

Determining material loss from the femoral stem trunnion in hip arthroplasty using a coordinate measuring machine.

In contrast to the articulating and taper surfaces of failed total hip replacements, volumetric wear analysis of trunnions is not routinely performed. Metal wear particles from the trunnion may contribute not only to the failures of metal-on-metal total hip replacements but also to all hip replacements utilising metal trunnions. A validation study was performed with the material removed in stages from the trunnions of an Exeter V40 stem, a Corail stem and an Accolade stem to simulate different magnitudes of wear. The material loss from the trunnions was measured both volumetrically with a coordinate measuring machine and gravimetrically with a high-precision balance. A cohort of 28 ex vivo trunnions was also measured using the coordinate measuring machine. The maximum error between the two methods was found to be 0.13 mm(3). This result was comparable with the coordinate measuring machine method for the taper surface (0.2 mm(3)). The ex vivo trunnions had a median wear volume of 0.14mm(3) (range: 0.04-0.28 mm(3)). This is the first study to determine the accuracy of volumetric wear measurements of trunnions by comparing against gravimetric measurements. Volumetric wear analysis of trunnions may provide additional insights into failures of modular total hip prostheses and will be performed routinely at our centre.

The clinical implications of elevated blood metal ion concentrations in asymptomatic patients with MoM hip resurfacings: a cohort study.

OBJECTIVE: To determine whether elevated blood cobalt (Co) concentrations are associated with early failure of metal-on-metal (MoM) hip resurfacings secondary to adverse reaction to metal debris (ARMD). DESIGN: Cohort study. SETTING: Single centre orthopaedic unit. PARTICIPANTS: Following the identification of complications potentially related to metal wear debris, a blood metal ion screening programme was instigated at our unit in 2007 for all patients with Articular Surface Replacement (ASR) and Birmingham MoM hip resurfacings. Patients were followed annually unless symptoms presented earlier. Symptomatic patients were investigated with ultrasound scan and joint aspiration. The clinical course of all 278 patients with 'no pain' or 'slight/occasional' pain and a Harris Hip Score greater than or equal to 95 at the time of venesection were documented. A retrospective analysis was subsequently conducted using mixed effect modelling to investigate the temporal pattern of blood Co levels in the patients and survival analysis to investigate the potential role of case demographics and blood Co levels as risk factors for subsequent failure secondary to ARMD. RESULTS: Blood Co concentration was a positive and significant risk factor (z=8.44, p=2×10(-16)) for joint failure, as was the device, where the Birmingham Hip Resurfacing posed a significantly reduced risk for revision by 89% (z=-3.445, p=0.00005 (95% CI on risk 62 to 97)). Analysis using Cox-proportional hazards models indicated that men had a 66% lower risk of joint failure than women (z=-2.29419, p=0.0218, (95% CI on risk reduction 23 to 89)). CONCLUSIONS: The results suggest that elevated blood metal ion concentrations are associated with early failure of MoM devices secondary to adverse reactions to metal debris. Co concentrations greater than 20 µg/l are frequently associated with metal staining of tissues and the development of osteolysis. Development of soft tissue damage appears to be more complex with females and patients with ASR devices seemingly more at risk when exposed to equivalent doses of metal debris.

Dynamic condylar screw as a solution to operative dilemma in early sub-trochanteric fracture following cannulated screw fixation for slipped capital femoral epiphysis: a case report.

A 14-year-old boy presented with a 2-month history of left groin pain and a limp on the left side. Radiographs confirmed slipped capital femoral epiphysis (SCFE) of the left hip. The surgical procedure he received used a single, 8-mm, partially threaded, cannulated screw. Postoperatively he was advised to remain strictly non-weight bearing on the affected lower limb until physeal closure was achieved. Unfortunately, he fell down 4 weeks postoperatively and sustained a subtrochanteric fracture on the same hip, with the cannulated screw still in place. This injury was surgically treated using a dynamic condylar screw and a side plate.

Adverse reactions to metal debris: histopathological features of periprosthetic soft tissue reactions seen in association with failed metal on metal hip arthroplasties.

AIM: To describe the histopathology of localised adverse reactions to metal debris (ARMD) seen in association with failed metal on metal (MoM) hip arthroplasties. The nature of aseptic lymphocytic vasculitis associated lesion (ALVAL) is investigated. METHODS: Periprosthetic soft tissues biopsied at time of revision from failed MoM hip arthroplasties from January 2007 to March 2011 were analysed. The inflammatory cell response was categorised into perivascular lymphocytic cuffing (ALVAL), lymphoid aggregate formation with or without germinal centres, metallosis characterised by sheets of macrophages with intracytoplasmic metallic debris and well-defined granulomas. RESULTS: 123 patient samples were analysed, 36 males (29.2%) and 87 females (70.8%). Three cases showing complete tissue necrosis were excluded. Patients were reviewed between 3.27 to 69.6 months postarthroplasty, with an average of 30.92 months. 103 cases (85.8%) showed ALVAL, 18 cases also showed well-defined granulomas. Of the 103 cases with ALVAL, 60 cases also showed a diffuse chronic lymphocytic synovitis, and 40 cases showed lymphoid aggregates with germinal centres. 17 cases (14.2%) showed pure metallosis. Small vessels showing ALVAL expressed peripheral node addressin. CONCLUSIONS: ARMD is a spectrum of changes comprising of pure metallosis, ALVAL and granulomatous inflammation. ALVAL, a distinctive inflammatory response seen in ARMD, is a precursor of lymphoid neogenesis. Lymphoid neogenesis documented in a variety of chronic inflammatory conditions most probably contributes to tissue necrosis and prosthetic failure seen in MoM hip arthroplasties. The role of vascular changes in contributing to necrosis is unclear at this stage.

Hip pain and pseudo-lengthening of the leg due to iliopsoas haematoma following implantation of an uncemented component in acetabular cotyloplasty technique.

We report early symptomatic (groin pain and apparent limb lengthening) findings in our 12 consecutive patients who underwent total hip replacements using a cementless acetabular cotyloplasty technique. This report is the first in the literature to mention such an early complication in a large number of patients and also to describe early detection and treatment in these cases. During the period of January 2007 to December 2010, 12 patients (seven female, five male) with dysplastic hip underwent total hip arthroplasty. The mean age of the patients was 57 years (range 52-61 years) and the mean follow-up time was 18 months (12-36 months). A cotyloplasty technique was performed and uncemented acetabular and femoral components were implanted in all these 12 patients. All patients were reviewed postoperatively for clinical and radiographic assessment at six weeks, three months, six months, and one year, and then annually thereafter. During the first one to two months (mean time 22 ± 16 days), all patients complained of a constant pain in the groin that started in the early postoperative period. A pseudo lengthening of the operated hip and pelvic tilt was found on clinical examination at the three-month follow-up. The True length did not reveal a significant leg length discrepancy. Hip pain, pseudo lengthening, and pelvic tilt resolved within 123 ± 17 days post-op. A cotyloplasty technique using an uncemented acetabular implant can cause an intrapelvic hematoma of the iliopsoas muscle giving rise to temporary groin pain, pseudo lengthening on the operated side, and gait disturbances to the patient in the early postoperative period. Symptoms resolved completely in all of our cases. Iliopsoas physiotherapy could be useful and should be encouraged during the symptomatic period. Patients have to be informed during consenting and reassured about this symptomatology. Awareness of this likely complication would help surgeons to detect the problem and initiate treatment early.