The Supercapsular Percutaneously Assisted Total Hip Approach Does Not Provide Any Clinical Advantage Over the Conventional Posterior Approach for THA in a Randomized Clinical Trial.

BACKGROUND: The supercapsular percutaneously assisted total hip (SuperPATH) approach was designed to be a less-invasive surgical approach to THA. This approach may have advantages, including less pain, more rapid mobilization, and shorter hospital length of stay. However, few published studies have compared the SuperPATH technique to existing standard approaches in a randomized, controlled manner. QUESTIONS/PURPOSES: In this study, we asked: (1) Do patients with SuperPATH demonstrate improved early function, using the timed up and go (TUG) and timed stair climbing (TSC) tests as instruments for assessment during the first 100 days postoperatively? (2) Are patient-reported outcomes, in the form of Oxford Hip Scores, better for the SuperPATH group during the first 3 months postoperatively? (3) Are opioid consumption and pain score in the first month postoperatively different between patients undergoing SuperPATH and patients undergoing a standard posterior approach? (4) Are patients with SuperPATH able to discontinue using mobility aids and return to work more quickly? METHODS: Between February 2017 and May 2019, 46% (46 of 101) of patients were recruited among 101 patients who met our inclusion criteria. Those 46 patients were randomized into two groups on the day of surgery; 54% (25 of 46) were assigned to the study group (SuperPATH approach) and 46% (21 of 46) were assigned to the control group (posterior approach). The SuperPATH technique uses the plane between the gluteus medius and the external rotators while preserving the piriformis and the superior aspect of the capsule. A percutaneous accessory portal is required for acetabular reaming and cup insertion. The posterior approach involves releasing short rotators and partially releasing the quadratus femoris while retaining the gluteus maximus's insertion site. The two groups did not differ in BMI, gender, American Society of Anesthesiologists class, surgical side, or diagnosis. The length of stay, component position, and blood loss were similar between the groups, but the operative time was longer in the SuperPATH group than in the group with the posterior approach. One patient from the control group was lost to follow-up and was excluded. Three patients in the study group had complications. The TUG and TSC tests are timed tasks for the patient. In the TUG test, patients stand from sitting, walk 3 meters and turn, walk back, and sit down. The TSC test measures the time taken to ascend and descend 10 steps. Patients were followed for 24 months for any complications. RESULTS: The TUG time at 100 days was 8.9 ± 2.6 seconds in the SuperPATH group and 8.7 ± 2.2 seconds in the posterior group (mean difference -0.2 seconds [95% CI -1.8 to 1.4]; p = 0.98); results were similar at other timepoints. The TSC time at 100 days was 11.6 ± 4.7 seconds in the SuperPATH group and 10.8 ± 3.6 seconds in the posterior group (mean difference -0.7 seconds [95% CI -3.5 to 2.1]; p = 0.88), and there were no differences between the two groups at all timepoints. The Oxford Hip Score showed no difference at any point postoperatively. At 6 weeks, it was 36 ± 5.9 points in the SuperPATH group and 38 ± 8.6 in the posterior group (mean difference 1.7 points [95% CI -2.7 to 6.1]; p = 0.51). At 3 months, it was 42± 6.7 points in the SuperPATH group and 41 ± 10.2 points in the posterior group (mean difference 0.7 points [95% CI -6.2 to 4.9]; p = 0.34). Patients' pain scores did not show any differences at all tested timepoints (mean difference 1 [95% CI -0.2 to 2.2]; p = 0.102). Total opioid consumption in the posterior group was higher in the first 2 weeks than that in the SuperPATH group (mean difference 6 [95% CI 2.3 to 9.9]; p = 0.001), but there was no difference in either group by week 4 (mean difference 0.4 [95% CI -0.5 to 1.4]; p = 0.36). There was no difference in return to work between the SuperPATH group and the posterior approach group (mean difference 6 days [95% CI -29 to 41]; p = 0.74). Discontinuation of mobility aids was similar between the two groups (mean difference 0.9 days [95% CI -25 to 27]; p = 0.94). CONCLUSION: The SuperPATH approach had no clinical advantages over the posterior approach, resulted in more complications, and only showed a short-term reduction in pain. The results of our small randomized controlled trial can be used to calculate future sample sizes, but our data suggest that any differences favoring the SuperPATH approach are likely to be small and transient. This approach should not be used routinely in clinical practice until an adequately powered trial shows clinically important differences in patient-relevant endpoints. The improved postoperative recovery is likely multifactorial and not dependent on the invasiveness of the approach. LEVEL OF EVIDENCE: Level II, therapeutic study.

Adductor canal block with or without added magnesium sulfate following total knee arthroplasty: a multi-arm randomized controlled trial.

PURPOSE: Postoperative analgesia following total knee arthroplasty (TKA) often includes intrathecal opioids, periarticular injection (PAI) of local anesthetic, systemic multimodal analgesia, and/or peripheral nerve blockade. The adductor canal block (ACB) provides analgesia without muscle weakness and magnesium sulphate (MgSO4) may extend its duration. The purpose of this trial was to compare the duration and quality of early post-TKA analgesia in patients receiving postoperative ACB (± MgSO4) in addition to standard care. METHODS: Elective TKA patients were randomized to: 1) sham ACB, 2) ropivacaine ACB, or 3) ropivacaine ACB with added MgSO4. All received spinal anesthesia with intrathecal morphine, intraoperative PAI, and multimodal systemic analgesia. Patients and assessors remained blinded to allocation. Anesthesiologists knew whether patients had received sham or ACB but were blinded to MgSO4. The primary outcome was time to first analgesic (via patient-controlled analgesia [PCA] with iv morphine) following ACB. Secondary outcomes were morphine consumption, side effects, visual analogue scale pain scores, satisfaction until 24 hr postoperatively, and length of stay. RESULTS: Of 130 patients, 121 were included. Nine were excluded post randomization: four were protocol violations, three did not meet inclusion criteria, and two had severe pain requiring open label blockade. There were no differences in the median [interquartile range] time to first PCA request: sham, 310 min [165-550]; ropivacaine ACB, 298 min [120-776]; and ropivacaine ACB with MgSO4, 270 min [113-780] (P = 0.96). Similarly, we detected no differences in resting pain, opioid consumption, length of stay, or associated side effects until 24 hr postoperatively. CONCLUSION: We found no analgesic benefit of a postoperative ACB, with or without added MgSO4, in TKA patients undergoing spinal anesthesia and receiving intrathecal morphine, an intraoperative PAI, and multimodal systemic analgesia. TRIAL REGISTRATION: www.clinicaltrials.gov (NCT02581683); registered 21 October 2015.

RéSUMé: OBJECTIF: L'analgésie postopératoire suivant une arthroplastie totale du genou (ATG) inclut souvent des opioïdes intrathécaux, une injection périarticulaire (IPA) d'anesthésique local, une analgésie multimodale systémique, et/ou des blocs des nerfs périphériques. Le bloc du canal des adducteurs (BCA) permet une analgésie sans faiblesse musculaire et le sulfate de magnésium (MgSO4) pourrait prolonger sa durée. L'objectif de cette étude était de comparer la durée et la qualité de l'analgésie post-ATG précoce chez les patients recevant un BCA postopératoire (± MgSO4) en plus des soins standard. MéTHODE: Des patients devant subir une ATG non urgente ont été randomisés à recevoir : 1) un BCA placebo (groupe témoin), 2) un BCA avec ropivacaïne, ou 3) un BCA avec ropivacaïne et MgSO4. Tous ont reçu une rachianesthésie avec morphine intrathécale, une IPA peropératoire, et une analgésie multimodale systémique. L'allocation a été faite à l'insu des patients et des évaluateurs. Les anesthésiologistes savaient si les patients avaient reçu un placebo ou un BCA, mais n'étaient pas informés de l'ajout ou non de MgSO4. Le critère d'évaluation principal était le temps jusqu'à la première prise d'analgésique (via une analgésie contrôlée par le patient [ACP] avec de la morphine iv) après le BCA. Les critères secondaires comprenaient la consommation de morphine, les effets secondaires, les scores de douleur sur l'échelle visuelle analogue, la satisfaction jusqu'à 24 heures postopératoires, et la durée de séjour. RéSULTATS: Sur 130 patients, 121 ont été inclus. Neuf ont été exclus après la randomisation : quatre l'ont été en raison de violations du protocole, trois ne répondaient pas aux critères d'inclusion, et deux ont ressenti des douleurs graves nécessitant un bloc sans insu. Aucune différence n'a été observée dans le temps médian [écart interquartile] jusqu'à la première demande d'ACP : placebo, 310 min [165-550]; BCA ropivacaïne, 298 min [120-776]; et BCA ropivacaïne avec MgSO4, 270 min [113-780] (P = 0,96). De la même manière, nous n'avons détecté aucune différence dans la douleur au repos, la consommation d'opioïdes, la durée de séjour, ou les effets secondaires associés jusqu'à 24 heures postopératoires. CONCLUSION: Nous n'avons trouvé aucun avantage analgésique à un BCA postopératoire, avec ou sans ajout de MgSO4, chez les patients subissant une ATG sous rachianesthésie et recevant de la morphine intrathécale, une IPA peropératoire, et une analgésie multimodale systémique. ENREGISTREMENT DE L'éTUDE: www.clinicaltrials.gov (NCT02581683); enregistrée le 21 octobre 2015.

Short stay total joint arthroplasty program: patient factors predicting readmission

Background: The aim of this study was to evaluate the effectiveness of our short stay arthroplasty program as measured by 30-day readmission rate and the rate of transfer to inpatient care. Risk factors for readmission/transfer were also evaluated and contrasted with current patient screening criteria. Methods: We retrospectively reviewed 297 charts for all primary total joint arthroplasties completed in the short stay program during an 18-month period. Data included readmission and patient characteristics such as age, sex, comorbidities, the American Society of Anesthesiologists (ASA) physical classification grade, body mass index (BMI) and the number of preoperative medications. Results: The 30-day readmission rate was 2.6% (n = 8). With the inclusion of patients transferred to the inpatient hospital, the overall failure rate of our short stay program was 6.7% (n = 20). Multivariable modelling controlling for age, BMI and ASA suggested that those with an in-hospital complication were 11.4 times more likely to be readmitted or transferred to inpatient care (p < 0.001) with a trend for patients who were taking more medications (p = 0.09). Conclusion: The current readmission rate from this program is comparable to previously published data in the arthroplasty literature. However, several patients required transfer to inpatient care, which significantly impacted the effectiveness of the short stay program. Risk factors for readmission/transfer are not completely accounted for by current presurgical screening criteria. Further evaluation of the Blaylock Risk Assessment Screening Score is required to determine its value for predicting hospital readmission.

Contexte: Cette étude avait pour but d'évaluer l'efficacité de notre programme d'arthroplastie court séjour sur la base du taux de réadmission à 30 jours et du taux de conversion en hospitalisation. Les facteurs de risque de réadmission/conversion ont aussi été évalués et mis en parallèle avec les critères actuels de sélection des patients. Méthodes: Nous avons passé en revue de manière rétrospective les 297 dossiers d'arthroplasties totales primaires effectuées dans le cadre du programme court séjour sur une période de 18 mois. Les données incluaient les réadmissions et les caractéristiques des patients telles que âge, sexe, comorbidités, score ASA (classification de l'état de santé physique selon l'American Society of Anesthesiologists), indice de masse corporelle (IMC) et nombre de médicaments courants. Résultats: Le taux de réadmission à 30 jours a été de 2,6 % (n = 8). En incluant les cas de conversion en hospitalisation, le taux d'échec global de notre programme court séjour a été de 6,7 % (n = 20). Après ajustement selon un modèle multivarié tenant compte de l'âge, de l'IMC et de la classification de l'ASA, les patients ayant présenté une complication justifiant l'hospitalisation étaient 11,4 fois plus susceptibles d'être réadmis ou hospitalisés (p < 0,001), avec une tendance proportionnelle au nombre de médicaments courants avant l'intervention (p = 0,09). Conclusion: Le taux actuel de réadmission pour ce programme est comparable aux données publiées antérieurement dans la littérature sur l'arthroplastie. Toutefois, plusieurs patients ont eu besoin d'être hospitalisés, ce qui a eu un impact significatif sur l'efficacité du programme court séjour. Les facteurs de risque de réadmission/conversion ne sont pas entièrement expliqués par les critères de sélection préchirurgicaux actuels. Il faudra continuer d'évaluer le score Blaylock d'estimation des risques pour en déterminer l'utilité à prédire les réhospitalisations.

The aspherical human hip: implication for early osteoarthritis.

One marker for early-onset hip arthritis is femoral acetabular impingement. The current standard way of quantifying impingement is manual calculation of anatomical measures on plain radiographs, including the α-angle. Such measurements are user-dependent and prone to error. We provided a robust computational alternative and proposed using numerical fitting of geometrical shapes. We applied least-squares fitting of an ellipse to the femoral head contour and used the difference between the ellipse axes as a quantification method. The results showed a good correlation between the new measure and previous definitions of the α-angle.

Effect of Osteochondroplasty on Time to Reoperation After Arthroscopic Management of Femoroacetabular Impingement: Analysis of a Randomized Controlled Trial.

Background: A subset of patients with femoroacetabular impingement (FAI) fail arthroscopic management. It is not clear which patients will fail surgical management; however, several surgical and patient factors, such as type of procedure and age, are thought to be important predictors. Purpose: This time-to-event analysis with a 27-month follow-up analysis compared the effect of (1) arthroscopic osteochondroplasty with or without labral repair versus (2) arthroscopic lavage with or without labral repair on the time to reoperation in adults aged 18 to 50 years with FAI. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: Eligible participants had been randomized in a previous study trial to a treatment of arthroscopic osteochondroplasty or arthroscopic lavage with or without labral repair. Using the comprehensive data set from the Multinational Femoroacetabular Impingement Randomized controlled Trial, all reoperations until 27 months after surgery were identified. The analysis was conducted using a Cox proportional hazards model, with percentage of patients with a reoperation evaluated in a time-to-event analysis as the outcome. The independent variable was the procedure, with age and impingement subtype explored as potential covariates. The effects from the Cox model were expressed as the hazard ratio (HR). All tests were 2-sided, with an alpha level of .05. Results: A total of 108 patients in the osteochondroplasty group and 106 patients in the lavage group were included. The mean age of the patients included in the study was 36 ± 8.5 years. Overall, 27 incident reoperations were identified within the 27-month follow-up, with an incidence rate of 6 per 100 person-years. Within the osteochondroplasty group, 8 incident reoperations were identified (incidence rate, 3.4 per 100 person-years), while within the lavage group, 19 incident reoperations were identified (incidence rate, 8.7 per 100 person-years). The hazard of reoperation for patients undergoing osteochondroplasty was 40% of that of patients undergoing lavage (HR, 0.40 [95% CI, 0.17-0.91] P = .029). Conclusion: This study demonstrated that for adults between the ages of 18 and 50 years with FAI, arthroscopic osteochondroplasty was associated with a 2.5-fold decrease in the hazard of reoperation at any point in time compared with arthroscopic lavage. Registration: NCT01623843 (ClinicalTrials.gov identifier).

Locking compression plates for the treatment of periprosthetic femoral fractures around well-fixed total hip and knee implants.

There are currently few published studies examining the use of locking compression plates for the treatment of periprosthetic femoral fractures. Fifteen total hip or knee arthroplasty patients with 16 Vancouver type B1 and C fractures with an average age of 76 years were fixed and followed clinically and radiographically for 2 years. Fourteen patients achieved radiographic union by 6 months, and 13 patients were ambulatory by 6 months. There were no intraoperative complications. In summary, locking plates offer a viable treatment option for these difficult fractures. We advocate a minimum of 10 cortices of fixation (with unicortical or bicortical screws and cable combinations) above and below the fracture. Bone grafting should be used if the soft tissue envelope is violated with extensive dissection, and cortical struts should be considered in cases of failed hardware and revision fixation.

Do waiting list initiatives discriminate in favour of those in a higher socioeconomic group?

The UK has a publicly funded health care system with open access to all. In the past, demand for services overwhelmed the resources available. Recent government initiatives have attempted to address this. To achieve shorter waiting times (and guaranteed waiting times), access to additional services has been purchased from the private sector under short-term initiatives, often at sites firth of the home health board. There has been a suspicion that patients from higher socioeconomic groups have benefited differentially from this by rapid access to private health care facilities, due to ease of transport. The aim of this study was to analyse whether a patient's socioeconomic group influenced their access to, and place of, surgery. Patients undergoing a primary total hip or knee arthroplasty in a single health region over a three-year period were identified and their social group was determined by postcode address. Analysis of 3888 patients operated on in four different treatment centres comparing the distribution of patients according to their social group, revealed no bias in the provision of treatment. The study group was comparable to the control population in that health region. In conclusion, the introduction of health policies to reduce time to orthopaedic treatment within one health board area has not resulted in patient bias.

Registration stability of physical templates in hip surgery.

We tested the registration stability of individualized templates in a consecutive study with 80 patients undergoing hip-resurfacing surgery. These templates physically encode registration and navigation parameters but do not require a computer during the actual surgery. The surgical target was the placement of the femoral guidance pin during hip resurfacing, which is a difficult and highly variable task using conventional instruments. The drill trajectory for the guidance pin of the femoral component was planned on a 3D computer model of the femur derived from a preoperative computed tomography (CT) scan. A surface-matched drilling template was designed to perform mechanical registration on the bone surface and had a hole for the drill guide; the template was created using a rapid prototyping machine. Intraoperatively, the individualized template was positioned on the patient anatomy and the pin was drilled into the femoral neck. The final achieved pin orientation and position were measured using an optoelectronic CT-based navigation system. The measured mean deviation between planned and actual central pin alignment of 0.05° in valgus and 2.8° in anteversion shows that the proposed individualized templates for hip resurfacing have reliable registration.

Management of Mycobacterium tuberculosis Prosthetic Joint Infection: 2 Cases and Literature Review.

Prosthetic joint infection caused by Mycobacterium tuberculosis (TBPJI) is uncommon but can be encountered in immunocompromised patients or those from tuberculosis-endemic regions. A lack of clinical suspicion and experience with TBPJI often leads to a delay in diagnosis. We report 2 cases of TBPJI in a Hungarian-Canadian and Iranian-Canadian immigrant, respectively. Both were treated with concurrent surgical and medical therapy. We also performed a literature review on TBPJI case reports, outlining their diagnosis and management.

Osteochondroplasty and Labral Repair for the Treatment of Young Adults With Femoroacetabular Impingement: A Randomized Controlled Trial.

BACKGROUND: Femoroacetabular impingement (FAI) is a condition known to cause hip pain in young adults. PURPOSE: To evaluate the efficacy of the surgical correction of FAI via arthroscopic osteochondroplasty with or without labral repair compared with arthroscopic lavage of the hip joint with or without labral repair. STUDY DESIGN: Randomized controlled trial; Level of evidence, 1. METHODS: A total of 220 male and female participants aged 18 to 50 years with nonarthritic FAI suitable for surgical treatment were recruited for the trial at 10 clinical centers in Canada, Finland, and Denmark between October 2012 and November 2017, of whom 214 were included in the final analysis. In the osteochondroplasty group, cam- and/or pincer-type lesions were resected using fluoroscopic guidance. In the lavage group, the joint was washed out with 3 L of normal saline. Surgeons were instructed to repair the labrum in both groups if it was mechanically unstable once probed, showing visible displacement or chondrolabral separation. The primary outcome was patient-reported pain (using the 100-point visual analog scale [VAS]) at 12 months. Secondary outcomes included hip function (Hip Outcome Score [HOS] and International Hip Outcome Tool), physical and mental health (12-Item Short Form Health Survey), and health utility (EuroQol-5 Dimensions) at 12 months as well as any reoperations and other hip-related adverse events at 24 months. RESULTS: At 12 months, there was no difference in pain (VAS) between the groups (mean difference [MD], 0.11 [95% CI, -7.22 to 7.45]; P = .98). Also, 88.3% (189/214) of participants had a labral tear, of which 60.3% were repaired. For the secondary outcomes, there were no significant differences between treatment groups, with the exception of the HOS activities of daily living domain in which lavage showed significant improvement compared with osteochondroplasty (MD, -5.03 [95% CI, -10.40 to -0.03]; P = .049). By 24 months, there were significantly fewer reoperations reported in the osteochondroplasty group (8/105) than the lavage group (19/104) (odds ratio, 0.37 [95% CI, 0.15-0.89]; P = .026). The primary reasons for a reoperation included hip pain (15/27; 55.6%) and a reinjury of the labrum (11/27; 40.7%). CONCLUSION: Both the osteochondroplasty and the lavage groups with or without labral repair for FAI had significantly improved pain or function significantly at 1 year. By 2 years, the reoperation rate was significantly lower in the osteochondroplasty group. REGISTRATION: NCT01623843 (ClinicalTrials.gov identifier).

Effects of accelerated versus standard care surgery on the risk of acute kidney injury in patients with a hip fracture: a substudy protocol of the hip fracture Accelerated surgical TreaTment And Care tracK (HIP ATTACK) international randomised controlled trial.

INTRODUCTION: Inflammation, dehydration, hypotension and bleeding may all contribute to the development of acute kidney injury (AKI). Accelerated surgery after a hip fracture can decrease the exposure time to such contributors and may reduce the risk of AKI. METHODS AND ANALYSIS: Hip fracture Accelerated surgical TreaTment And Care tracK (HIP ATTACK) is a multicentre, international, parallel-group randomised controlled trial (RCT). Patients who suffer a hip fracture are randomly allocated to either accelerated medical assessment and surgical repair with a goal of surgery within 6 hours of diagnosis or standard care where a repair typically occurs 24 to 48 hours after diagnosis. The primary outcome of this substudy is the development of AKI within 7 days of randomisation. We anticipate at least 1998 patients will participate in this substudy. ETHICS AND DISSEMINATION: We obtained ethics approval for additional serum creatinine recordings in consecutive patients enrolled at 70 participating centres. All patients provide consent before randomisation. We anticipate reporting substudy results by 2021. TRIAL REGISTRATION NUMBER: NCT02027896; Pre-results.

Shared morphology of slipped capital femoral epiphysis and femoroacetabular impingement in early-onset arthritis.

A subclinical form of slipped capital femoral epiphysis (SCFE) can lead to subtle morphologic abnormalities, such as cam-type femoroacetabular impingement (FAI). Femoroacetabular impingement is a mechanical hip abnormality that typically affects young populations and leads to hip pain and premature osteoarthritis. Imaging is critical to diagnosis, whether by radiograph, magnetic resonance imaging, or computed tomography. The authors investigated the use of imaging to detect characteristics of subclinical SCFE and cam-type FAI in patients undergoing hip resurfacing. They retrospectively assessed computed tomography scans of 81 hips from 75 patients. Measurements were taken of the proximal femur and included the alpha angle, head-neck tilt, and anterior offset taken in both the conventional oblique axial plane and the radial plane. The cohort consisted of 68 men and 13 women with an average age of 52 years. Ninety percent of hips on the oblique axial view and 95% of hips on the radial view were found to have pathologically increased alpha angles. Negative correlations were found between the alpha angle and head-neck tilt and positive correlations between head-neck tilt and anterior offset ratio. Sixty percent and 68% of hips in the oblique axial and radial planes, respectively, were abnormal for the alpha angle, head-neck tilt, and anterior offset ratio, strongly suggesting SCFE morphology. This study's results show similarity in morphology between cam-type FAI and SCFE, known precursors to osteoarthritis, in an early arthritic patient population.

Articular surface remodeling of the hip after periacetabular osteotomy.

PURPOSE: Periacetabular osteotomies are a family of surgical procedures used to treat hip dysplasia. In a periacetabular osteotomy, the operating surgeon aims to increase acetabular coverage of the femoral head. The surgical correction has mechanical goals of increasing the stability of the joint and to improving the pressure distribution across the acetabulum. Although it is known that bone will remodel under changing load at the microstructural level, it is unclear whether there is any gross remodeling of the acetabulum or the femoral head in response to the change in loading following a periacetabular osteotomy. This observational study aims to quantify the shape of operative and contralateral hip joint surfaces pre and postoperatively to determine whether there are gross morphological changes in the shape of any of the bony articular surfaces of the joint. METHODS: Preoperative and postoperative computed tomography (CT) scans were segmented as triangulated meshes. The bony articular surfaces of these meshes were then isolated. The vertices of these surfaces were fit to spheres and to general ellipsoids and, in the case of the acetabulum, examined in anatomical coordinate frames to look for changes between pre and postoperative segmentations. RESULTS: Spherical fit results were consistent preoperatively and postoperatively, with small changes in the radii of the spheres of best fit for both operative and nonoperative hips. Ellipsoid fitting showed variations between preoperative and postoperative scans in both eccentricity and orientation. CONCLUSIONS: Because there is no clear evidence of gross articular surface remodeling, periacetabular osteotomy for an adult should be planned with the expectation that the patient's existing articular structure will be preserved.