Functionally aligned total knee arthroplasty: A lateral flexion laxity up to 6 mm is safe!

PURPOSE: Loose flexion gaps are associated with poor functional outcomes and instability in total knee arthroplasty (TKA). The effect of a trapezoidal flexion gap in a functionally aligned TKA remains unknown. The aim of this study was to investigate the effect of a larger lateral flexion gap in a robotic-assisted (RA), functionally aligned (FA) and cruciate-retaining (CR) TKA on clinical outcomes. METHODS: Data from 527 TKA in 478 patients from 2018 to 2020 were collected. All patients underwent an RA (MAKO, Stryker), FA and CR TKA. Gap measurements were collected intraoperatively. Patient-reported outcome measures (PROMs), pain Visual analogue score (VAS) and range of motion were collected postoperatively. Patients were also asked about the ease of stair ascent and descent and kneeling on a 5-point scale. The minimum follow-up was 2 years. Patients were stratified into three groups based on lateral flexion laxity. RESULTS: At 2 years postoperatively, the group with a looser gap (3-6 mm) had higher mean PROMs when compared with the group with a gap of 2-3 mm. There were no differences detected in any other outcomes at 2 years. A total of 70.9% of patients in the group with a 3-6 mm gap reported being able to walk down a flight of stairs 'easily', compared with 56.7% in the 2-3 mm group and 54% in the <2 mm group (p = 0.04). CONCLUSION: The study shows that a loose lateral flexion gap in functionally aligned CR TKA does not adversely affect outcomes in the short term. LEVEL OF EVIDENCE: Level III, retrospective cohort study.

Maintaining Joint Line Obliquity Optimizes Outcomes of Functional Alignment in Total Knee Arthroplasty in Patients With Constitutionally Varus Knees.

BACKGROUND: Functional alignment (FA) strives to balance the knee soft-tissue envelope during total knee arthroplasty (TKA) using implant alignment adjustments rather than soft-tissue releases. There is a debate on how best to achieve FA. We compared minimum two-year outcomes between FA with a mechanical alignment plan [FA(m)] and FA with a kinematic alignment plan [FA(k)]. The null hypothesis was that there would be no difference in outcomes between FA(m) and FA(k). METHODS: Prospective data was collected from 300 consecutive robotic-assisted FA TKAs [135 FA(m) and 165 FA(k)]. Patient reported outcomes were obtained preoperatively and 2 years postoperatively. The coronal plane alignment of the knee classification was used to classify knee alignment phenotypes. RESULTS: Overall limb alignment was equivalent between groups. Final implant alignment was different between FA(m) and FA(k) groups, with FA(k) TKAs having higher tibial varus (P < .01), higher femoral valgus (P < .01), and higher joint line obliquity (P < .01). Patients reported higher Forgotten Joint Score-12 scores with FA(k) TKAs (79.4 versus 71.6, P = .018) and greater range of motion (125 versus 121°; P = .003). Patients who had constitutional varus reported the greatest improvement with FA(k) technique (Forgotten Joint Score at minimum 2 years of 89 versus 65; P < .001). CONCLUSION: Utilizing an individualized alignment plan [FA(k)] led to a final implant position with greater joint line obliquity, yet the same overall limb alignment. This was associated with improved outcomes at 2 years post-TKA in patients who had constitutional varus. Three-dimensional component position and joint line obliquity affect the outcomes following TKA independently of coronal limb alignment.

Two-Year Prospective RSA Measured Migration of a Third-Generation Taper Wedge Cementless Femoral Stem.

INTRODUCTION: Implant migration is a concern with newly designed cementless femoral stems for total hip arthroplasty. Radiostereometric analysis (RSA) is the most accurate technique available to measure implant migration following total hip arthroplasty (THA). The objective of this study was to establish the migration pattern of a cementless tapered wedge stem during the first two years after implantation using RSA as well as assess clinical results. MATERIALS AND METHODS: Thirty patients underwent a primary THA with a morphometrically designed cementless stem. RSA was completed immediately after surgery and at three-, six-, 12- and 24-month intervals. Subsidence after two years was compared to the migration thresholds, and survivorship and clinical outcome scores were obtained. RESULTS: After two years, the mean subsidence (distal migration) of the stem within the canal was 0.08mm (standard deviation [SD] 0.036mm), the mean retroversion was 0.301mm (SD 0.362), and the maximal total point motion was 0.764mm (SD 0.195). All stems demonstrated stable motion patterns beyond six months (p=0.99). Patient outcome data highlighted a statistical and clinically significant improvement (p<0.05) after hip arthroplasty at six months, and then there were modest changes at subsequent follow ups. CONCLUSION: The femoral stem tested in this study was designed to provide adequate implant stability in total hip arthroplasty patients in the short term. We found stable fixation of the third-generation tapered wedge stem two years postoperatively and clinical improvements in patient-reported outcomes.

Clinical results and patient-reported outcomes following robotic-assisted primary total knee arthroplasty : a multicentre study.

AIMS: The aim of this study was to report patient and clinical outcomes following robotic-assisted total knee arthroplasty (RA-TKA) at multiple institutions with a minimum two-year follow-up. METHODS: This was a multicentre registry study from October 2016 to June 2021 that included 861 primary RA-TKA patients who completed at least one pre- and postoperative patient-reported outcome measure (PROM) questionnaire, including Forgotten Joint Score (FJS), Knee Injury and Osteoarthritis Outcomes Score for Joint Replacement (KOOS JR), and pain out of 100 points. The mean age was 67 years (35 to 86), 452 were male (53%), mean BMI was 31.5 kg/m2 (19 to 58), and 553 (64%) cemented and 308 (36%) cementless implants. RESULTS: There were significant improvements in PROMs over time between preoperative, one- to two-year, and > two-year follow-up, with a mean FJS of 17.5 (SD 18.2), 70.2 (SD 27.8), and 76.7 (SD 25.8; p < 0.001); mean KOOS JR of 51.6 (SD 11.5), 85.1 (SD 13.8), and 87.9 (SD 13.0; p < 0.001); and mean pain scores of 65.7 (SD 20.4), 13.0 (SD 19.1), and 11.3 (SD 19.9; p < 0.001), respectively. There were eight superficial infections (0.9%) and four revisions (0.5%). CONCLUSION: RA-TKA demonstrated consistent clinical results across multiple institutions with excellent PROMs that continued to improve over time. With the ability to achieve target alignment in the coronal, axial, and sagittal planes and provide intraoperative real-time data to obtain balanced gaps, RA-TKA demonstrated excellent clinical outcomes and PROMs in this patient population.Cite this article: Bone Jt Open 2022;3(7):589-595.

A prospective randomised control trial comparing functional with mechanical axis alignment in total knee arthroplasty: study protocol for an investigator initiated trial.

BACKGROUND: A drive to improve functional outcomes for patients undergoing total knee arthroplasty (TKA) has led to alternative alignment being used. Functional alignment (FA) uses intraoperative soft tissue tension to determine the optimal position of the prosthesis within the patient's soft tissue envelope. Angular limits for bone resections are followed to prevent long-term prosthesis failure. This study will use the aid of robotic assistance to plan and implement the final prosthesis position. This method has yet to be compared to the traditional mechanically aligned (MA) knee in a randomised trial. METHODS: A blinded randomised control trial with 100 patients will be undertaken via Perth Hip and Knee Clinic. Fifty patients will undergo a MA TKA and fifty will undergo a FA TKA. Both alignment techniques will be balanced via computer-assisted navigation to assess prosthetic gaps, being achieved via the initial bony resection and further soft tissue releases as required to achieve satisfactory balance. The primary outcome will be the Forgotten Joint Score (FJS) 2 years after surgery, with secondary outcomes being other patient-reported outcome measures, clinical functional assessment, radiographic position and complications. Other data that will be collected will be patient demography (sex, age, level of activity) and medical information (grade of knee injury, any other relevant medical information). The linear statistical model will be fitted to the response (FJS), including all the other variables as covariates. DISCUSSION: Many surgeons are utilising alternative alignment techniques with a goal of achieving better functional outcomes for their patients. Currently, MA TKA remains the gold standard with good outcomes and excellent longevity. There is no published RCTs comparing FA to MA yet and only two registered studies are planned or currently in progress. This study utilises a FA technique which differs from the two studies. This study will help determine if FA TKA has superior functional results for patients. TRIAL REGISTRATION: This trial has been registered with the Australian New Zealand Clinical Trials Registry (ANZCTR) http://www.anzctr.org.au : U1111-1257-2291, registered 25th Jan 2021. It is also listed on www.clinicaltrials.gov : NCT04748510.

A progressive scholarly acceptance analysis of robot-assisted arthroplasty: a review of the literature and prediction of future research trends.

Robot-assisted arthroplasty (RAA) is increasingly practised in orthopaedic surgery. The aim of this study was to perform a bibliometric analysis of all published primary research into RAA and to apply the Progressive Scholarly Acceptance (PSA) model to evaluate its acceptance as an orthopaedic surgical technique. A literature search was performed that included all peer-reviewed, primary, English language publications on RAA from its introduction in 1992 up to 2019. RAA was defined as robot-assisted hip or knee arthroplasty. A bibliometric analysis was performed to categorise articles by type of study and level of evidence. Studies were also categorised as initial investigations (II) or refining studies (RS). A PSA analysis was performed, with the end-point being defined as the point in time when the number of RS exceeded the number of II. Of the 199 studies originating from 19 countries and 101 institutions, only 16 (8.04%) were randomised-controlled trials. Fifty-one percent of studies had been published since 2015. Using PSA analysis, 161 (80.9%) studies were categorised as II and 38 (19.1%) were categorised as RS. This demonstrates that RAA has not yet reached the point of scholarly acceptance. Scholarly acceptance of RAA as an orthopaedic surgical technique has yet to be reached. However, there has been an exponential increase in the number of publications on RAA in the last 5 years, reflecting renewed interest this technique. We predict that, for the next 5 years, RAA will remain in the experimental phase due to the rapid development of new technology in this field.

Taper Corrosion and Adverse Local Tissue Reactions in Patients with a Modular Knee Prosthesis.

BACKGROUND: Corrosion has been documented in modular knee implants, but it has not been related to negative patient outcomes. We performed an observational retrieval investigation of 13 Stryker Triathlon TS modular knee implants, 3 of which were revised because of osteolysis and adverse local tissue reactions secondary to fretting corrosion at the modular junctions. METHODS: Modular surfaces were examined for the presence and severity of corrosion, and factors that may influence the development of corrosion were investigated. Scanning electron microscopy and energy-dispersive x-ray spectroscopy were performed to evaluate implants with severe corrosion, and tissue samples were sent for histopathological analysis. RESULTS: Mild to severe corrosion was present in association with 62% of modular tibial components and 75% of modular femoral components. Although tibial corrosion was less prevalent than femoral corrosion, it occurred earlier and with greater severity. Scanning electron microscopy and energy-dispersive x-ray spectroscopy demonstrated the appearances of fretting and corrosion of the modular junctions. Histopathological analysis of specimens from the 3 patients with adverse local tissue reactions demonstrated severe reactions to metal debris, including 1 reaction that was consistent with an aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL). CONCLUSIONS: To our knowledge, ALVAL and pseudotumors have not previously been reported secondary to corrosion of modular knee replacements. The threaded taper design and the release of cobalt-chromium ions and/or debris are implicated in the occurrence of the adverse local tissue reactions, osteolysis, and soft-tissue damage that we observed in our investigation. Clinicians should be aware of this possible complication associated with modular knee implants. CLINICAL RELEVANCE: This article should raise clinician awareness of adverse local tissue reactions secondary to corrosion, potentially resulting in earlier recognition of this complication.

Incidence and clinical relevance of heterotopic ossification after internal fixation of acetabular fractures: retrospective cohort and case control study.

OBJECTIVE: The aim of the study was to evaluate predictors and clinical relevance of heterotopic ossification (HO) in patients treated for acetabular fractures in a tertiary referral centre. PATIENTS AND METHODS: The study is a retrospective cohort study with a nested case-control study. All patients treated with internal fixation of acetabular fractures from January 2004 to October 2013. Ninety patients had postoperative imaging available at 6 and 12 months postoperatively and received no prophylaxis. Plain radiographs were used to grade HO. The Hip disability and Osteoarthritis Outcome Score (HOOS) was used to compare outcomes between patients suffering from HO with patients who did not. RESULTS: Sixteen patients (17.7%) suffered from HO. According to the Brooker classification, 5 had class I, 4 class II, 3 class III and 4 class IV HO. Traumatic brain injury (TBI) was the only significant risk factor for developing HO (odds ratio (OR) 8.6, 95% confidence interval (CI) (1.693-43.753), p = 0.014). The HO rate in patients with an anterior (ilioinguinal) or posterior (Kocher-Langenbeck) surgical approach was 20% and 21% respectively, and the HO rate in patients with a combined approach was much lower at 11%. Neither fracture type nor gender nor age increased the risk of HO significantly. The outcome measured by HOOS was not significantly different between patients with HO and patients in the control group. Patients with HO Brooker class II-IV had slightly lower (effect estimate +4.25, 95% CI (-10.2 to +12.10), p = 0.220) HOOS compared to the majority of the control group. CONCLUSION: A very low rate of HO was found compared to the HO rates described in other studies with similar patient cohorts who received prophylaxis. Based on our findings and the current literature, we do not recommend giving prophylaxis against HO to patients after internal fixation of acetabular fractures.

Development and verification of a cementless novel tapered wedge stem for total hip arthroplasty.

Most current tapered wedge hip stems were designed based upon the original Mueller straight stem design introduced in 1977. These stems were designed to have a single medial curvature and grew laterally to accommodate different sizes. In this preclinical study, the design and verification of a tapered wedge stem using computed tomography scans of 556 patients are presented. The computer simulation demonstrated that the novel stem, designed for proximal engagement, allowed for reduced distal fixation, particularly in the 40-60 year male population. Moreover, the physical micromotion testing and finite element analysis demonstrated that the novel stem allowed for reduced micromotion. In summary, preclinical data suggest that the computed tomography based stem design described here may offer enhanced implant fit and reduced micromotion.

Alignment for total knee replacement: a comparison of kinematic axis versus mechanical axis techniques. A cadaver study.

PURPOSE: Standard instrumentation tries to reproduce mechanical axes based on mechanical alignment (MA) guides. A kinematic alignment (KA) technique derives its plan from pre-operative MRI-measurements. This matched-pair cadaveric study compared the resulting postoperative alignments. METHODS: A prospective series of 12 torsos were acquired for a total of 24 limb specimens including intact pelvises, femoral heads, knees, and ankles.The cadavers received MRI scans to manufacture the kinematic alignment cutting guides. Two investigating surgeons performed total knee arthroplasties on randomly chosen sides using MA instruments. On the contralateral sides, KA cutting guides were used. A navigation system was used to measure final alignment. RESULTS: The overall alignment showed no significant differences between the systems. In the MA group the differences between the planned and the final implantation regarding overall limb alignment ranged between 0.2° and 6.2°. In the KA group the differences between the planned and final implantation regarding overall limb alignment ranged between 0.3° and 9.1°. The differences of the deviation from plan for overall limb alignment showed no significant differences between the methods. CONCLUSIONS: The different alignment strategies resulted in variations of the combinations of the three-dimensional component position on the femur and the tibia. However, the legs were aligned within comparable range for both chosen techniques.

Patellar resurfacing in total knee arthroplasty: a prospective, randomized trial.

BACKGROUND: The management of the patella in total knee arthroplasty is still problematic. We aimed to identify differences in the clinical outcome of total knee arthroplasty according to whether or not patellar resurfacing had been performed in a prospective, randomized study of 220 osteoarthritic knees. METHODS: Two hundred and twenty total knee arthroplasties in 201 patients were randomly assigned to be performed with either resurfacing or retention of the patella, and the results were followed for a mean of forty-eight months (range, thirty-six to seventy-nine months) in a double-blind (both patient and clinical evaluator blinded), prospective study. Evaluation was performed annually by an independent observer and consisted of assessment with the Knee Society clinical rating system, specific evaluation of anterior knee pain, a stair-climbing test, and radiographic examination. RESULTS: Fifteen (12%) of the 128 knees without patellar resurfacing and nine (10%) of the ninety-two knees with patellar resurfacing underwent a revision or another type of reoperation related to the patellofemoral articulation. This difference was not significant (chi square with one degree of freedom = 0.206, p = 0.650). At the time of the latest follow-up, there was a significantly higher incidence of anterior pain (chi square with one degree of freedom = 5.757, p = 0.016) in the knees that had not had patellar resurfacing. CONCLUSIONS: Patients who underwent patellar resurfacing had superior clinical results in terms of anterior knee pain and stair descent. However, anterior knee pain still occurred in patients with patellar resurfacing, and nine (10%) of the ninety-two patients in that group underwent a revision or another type of reoperation involving the patellofemoral joint. Weight but not body mass index was associated with the development of anterior knee pain in the patients without patellar resurfacing, a finding that suggests that patellofemoral dysfunction may be a function of joint loading rather than obesity.