PURPOSE:Lateral unicompartmental knee arthroplasty (UKA) is an effective treatment for isolated lateral-compartment osteoarthritis, yet detailed evidence-based indication criteria remain poorly defined. Therefore, this study evaluated the association between preoperative medial-compartment osteophytes and reoperation-free survival, implant survivorship, medial-compartment disease progression requiring reoperation, and postoperative functional outcomes following lateral UKA. METHODS:A total of 900 lateral UKAs (830 patients) performed between 2016 and 2021 with a minimum follow-up of 2 years (mean 5.1 ± 1.8 years) were retrospectively analysed. Using the OARSI (Osteoarthritis Research Society International) atlas, knee radiographs were stratified into no medial osteophytes (n = 601), small osteophytes (n = 180) and moderate/severe osteophytes (n = 119). Kaplan-Meier survival analysis estimated 9-year survival for the endpoints reoperation, implant revision and disease progression requiring reoperation. Functional outcomes were assessed using the Oxford Knee Score (OKS) and University of California, Los Angeles (UCLA) Activity Score. RESULTS:Reoperation-free survival at 9 years was 94.2% (95% confidence interval [CI]: 91.6-96.8) for knees without osteophytes, 93.0% (95% CI: 88.5-97.5) for small osteophytes, and 91.8% (95% CI: 86.5-97.1) for moderate/severe osteophytes (p = 0.489). Implant survivorship was comparably high across groups (98.3%, 98.1% and 98.0%), respectively (p = 0.972). Medial-compartment disease progression was not associated with radiographic medial osteophyte status (97.6% [95% CI: 96.1-98.5], 98.7% [95% CI: 95.0-99.7] and 96.9% [95% CI: 93.4-98.5]; p = 0.616). Functional outcomes improved significantly across groups without differences between groups (OKS: p = 0.389; UCLA: p = 0.353). CONCLUSIONS:Clinically relevant medial-compartment disease progression requiring reoperation after lateral UKA is uncommon at mid-term follow-up and appears to be independent of the presence or severity of medial-compartment osteophytes. These findings suggest that medial-compartment osteophytes alone should not preclude appropriately selected patients from undergoing lateral UKA when indications are based on stress radiographs. LEVEL OF EVIDENCE:Level IV.

Patients with Parkinson’s disease (PD) are a vulnerable subgroup facing elevated risks of complications and functional decline following knee arthroplasty. However, data on the outcomes of minimally invasive unicompartmental knee arthroplasty (UKA) in this population are limited. This study´s purpose was to assess perioperative complications, implant revision-free and reoperation-free survivorship as well as functional outcome in PD patients following UKA. In this retrospective single-center study, 42 knees in 39 patients with PD who underwent medial or lateral UKA between 2016 and 2022 were analyzed. The mean age was 70.6 ± 9.1 years, and the mean BMI was 27.9 ± 5.2 kg/m². A total of 26 medial and 16 lateral UKAs were performed, with a minimum follow-up of two years (mean 5.0 ± 2.0). All medical complications were recorded. Implant survivorship (tibia and/or femur) and reoperation-free survival were evaluated using Kaplan-Meier analysis, allowing estimation of long-term survival beyond the mean follow-up duration. Functional outcomes were assessed using the Oxford Knee Score (OKS) and the UCLA Activity Score. Of the 42 knees, 6 (14.3

BACKGROUND:Isolated lateral-compartment knee osteoarthritis (OA) remains a condition challenging to treat. Lateral unicompartmental knee arthroplasty (UKA) may offer therapeutic advantages over total knee arthroplasty (TKA); however, it remains infrequently performed. This study determined implant survivorship and reoperation-free survival in a consecutive single-center series of primary lateral UKA. Furthermore, patient-reported outcome measures (PROMs) and radiological outcomes were assessed. METHODS:In this retrospective analysis, 1,015 knees in 927 patients (75% women) who had a mean follow-up of 5.1 years (range, 2.0 to 8.9) were included (mean age 70 years, range, 37 to 94; mean body mass index 27.5, range, 15 to 48). All patients were contacted via telephone to record implant survivorship, any reoperation, and the functional outcome (follow-up rate: 92%). Preoperative and postoperative radiographs were obtained following a standardized protocol. The Oxford Knee Score and the University of California, Los Angeles Activity Score were documented. Patients who had a previous ipsilateral medial UKA or patellofemoral arthroplasty and patients who declined consent were retrospectively excluded. Cumulative survival was calculated using Kaplan-Meier survival analysis. RESULTS:The cumulative 9-year survival rate was 97.6% (95% confidence interval: 96.6 to 98.6) with implant revision as the endpoint and 92.4% (95% confidence interval: 90.4 to 94.4) with reoperation for any reason as the end point. Medial-compartment OA progression was the most common reason for reoperation (2.8%), followed by medial osteonecrosis (1.1%) and infection (0.8%). The mean Oxford Knee Score improved from 23.9 ± 8.0 to 43.2 ± 6.4 (P < 0.001); the mean University of California, Los Angeles Activity Score improved from 4.5 ± 1.7 to 5.8 ± 1.6 (P < 0.001). The mean hip-knee-ankle angle was corrected from 7.4° ± 4.5 valgus to 2.4° ± 2.6 valgus (P < 0.001). CONCLUSIONS:This study demonstrated that primary lateral UKA is a highly successful procedure with excellent implant survival and favorable PROMs at a mean follow-up of five years. The low revision rates and promising functional outcomes strongly confirm its role as a viable alternative to TKA in appropriately selected patients who have isolated lateral-compartment OA. LEVEL OF EVIDENCE:IV, case series.

Der unikondyläre Gelenkersatz ist ein etabliertes Verfahren zur Therapie der anteromedialen Gonarthrose mit sehr guten funktionellen Ergebnissen und Prothesenstandzeiten. Die Grenzindikationen des Verfahrens erfordern im besonderen Maße eine differenzierte Indikationsstellung und Patientenselektion sowie genaue Kenntnisse über das verwendete Implantat. Der Teilgelenkersatz ist auch bei Grenzindikationen eine erfolgreiche Behandlungsoption, und sollte aufgrund der niedrigen perioperativen Morbidität und Mortalität und guten funktionellen Ergebnissen fester Bestandteil der individuellen Therapieentscheidung sein. Der unikondyläre Gelenkersatz (UKA) nach Umstellungsosteotomie ist technisch anspruchsvoll, bietet jedoch zahlreiche Vorteile gegenüber dem bikondylären Oberflächenersatz. Zementfreie Implantate können auch bei Osteonekrose verwendet werden, wenn eine sichere primäre Fixation gewährleistet ist. Die mediale Arthrose mit Läsionen des vorderen Kreuzbands (VKB) ohne klinische Instabilität stellt keine Kontraindikation für den medialen Schlitten dar. Meniskuswurzelläsionen ohne höhergradige Arthrose bleiben eine absolute Grenzindikation für die endoprothetische Versorgung.

PURPOSE:Disease progression in the untreated compartment is the leading cause for reoperation following unicompartmental knee arthroplasty (UKA). A less-invasive alternative to total knee arthroplasty (TKA) conversion is the addition of a second UKA. The study assessed survival, functional, and radiological outcomes after two-staged bicompartmental UKA. METHODS:A retrospective analysis was performed on 102 knees (98 patients, mean age 73.7 years) who received an additional medial (n = 29) or lateral UKA (n = 73) between 2016 and 2025 with a minimum follow-up of 1 year. Primary outcomes were cumulative revision rates for (1) any reoperation and (2) implant revision. Functional outcomes included the Oxford Knee Score (OKS) and UCLA (University of California, Los Angeles) Activity Score. Radiographic assessment included measurement of the hip-knee-ankle angle (HKAA). RESULTS:The mean follow-up was 4.0 years (SD 2.1). At 9 years, cumulative survival rate was 84.3% (95% CI: 0.763-0.923) for any reoperation and 89.3% (95% CI: 0.822-0.964) for implant revision. There were nine implant revisions (8.8%), most commonly due to medial mobile-bearing dislocation (44.4%). In 50%, implant revision to TKA was performed using primary non-modular components. Mean postoperative OKS and UCLA scores were 40.4 (SD 8.0) and 5.5 (SD 1.7), respectively. Medial osteonecrosis (ON) following primary lateral UKA accounted for 38% (11/29) of all indications for an additional medial UKA, and was associated with greater HKAA correction following prior lateral UKA. CONCLUSION:Two-staged bicompartmental UKA is a viable less-invasive alternative to TKA conversion for patients with disease progression or ON after primary UKA. This approach demonstrates excellent mid-term functional outcomes and satisfactory implant survivorship, providing valuable evidence to support its role as a contemporary revision option Fixed-bearing implants for additional medial UKA are advised to eliminate the risk of bearing dislocations. In the absence of major complications, conversion to non-modular TKA components is feasible. LEVEL OF EVIDENCE:Level IV.

BACKGROUND:Osteonecrosis (ON) of the knee commonly affects the medial femoral condyle, leading to secondary unicompartmental arthritis. While most studies on unicompartmental knee arthroplasty (UKA) in patients who have ON focus on cemented fixation, the outcomes of cementless UKA remain unknown. This study evaluated survival, functional and radiological outcomes, and assessed potential differences for cemented and cementless medial mobile-bearing UKA in patients who had ON. METHODS:This retrospective, single-center study analyzed 119 patients who underwent medial UKA for ON between 2020 and 2022, with a minimum follow-up of two years. Patients were stratified into cemented (n = 63, women/men 71/29%, mean age 70 ± nine years, BMI 29 ± 4) and cementless (n = 56, women/men 34/66%, mean age 72 ± eight years, BMI 28 ± 4) groups. Demographics were similar between groups, except for sex, with more men in the cementless UKA group (P < 0.001). Kaplan-Meier survival analysis compared survival rates for aseptic loosening, implant revision (exchange of the femoral or tibial component), and any reoperation. Functional outcomes were assessed using the Oxford Knee Score (OKS) and the UCLA (University of California, Los Angeles) Activity Score. RESULTS:At 50 months, cumulative survival rates showed no significant differences between cemented and cementless UKA for aseptic loosening (100 versus 97.7%; P = 0.35), implant revision (97.5 versus 93.3%; P = 0.36), or any reoperation (92.1 versus 87.0%; P = 0.35). There was one case of aseptic tibial subsidence that occurred in the cementless group in a patient who had femoral ON. Functional outcomes were excellent in both groups, with no significant differences in OKS (cemented/cementless: 42.6 ± 5.4 versus 43.5 ± 6.3; P = 0.12) or UCLA Activity Scores (6.1 ± 1.0 versus 6.1 ± 1.2; P = 0.57). CONCLUSIONS:Cementless medial mobile-bearing UKA is a safe treatment option for ON in the medial compartment, offering stable primary fixation and implant survival comparable to cemented fixation. However, future research with sex-balanced cohorts and extended follow-up is needed to confirm these findings.

PURPOSE:Limited evidence exists regarding the safety and efficacy of medial unicompartmental knee arthroplasty (UKA) in patients with end-stage medial arthritis following knee osteotomy. This study aims to evaluate survival, functional and radiological outcomes in patients undergoing medial UKA following knee osteotomy. METHODS:A retrospective analysis was conducted evaluating 63 knees (60 patients; 62% men, 38% women; mean age 61 ± 8 years; body mass index 28 ± 5 kg/m2) who underwent medial UKA (n = 47 mobile-bearing, n = 16 fixed-bearing) following knee osteotomy. Patients were considered suitable for medial UKA if they met the Oxford criteria and had a preoperative hip-knee-ankle angle (HKAA) < 5° valgus and a medial proximal tibial angle (MPTA) < 95°. Primary outcomes were cumulative revision rates for (1) conversion to total knee arthroplasty (TKA) and (2) any reoperation. Functional outcomes were assessed using the Oxford Knee Score (OKS) and the UCLA Activity Score. HKAA was measured to determine overall limb alignment pre- and post-operatively. RESULTS:The average time from osteotomy to UKA was 11 ± 8 years, and the mean follow-up after UKA was 5 ± 2 years. The cumulative 8-year implant survival rate was 96.3% (95% confidence interval [CI]: 0.912-1.0) for revision to TKA and 93.2% (95% CI: 0.899-0.965) for any reoperation. Two patients required revision to TKA due to overcorrection and infection. The mean OKS improved from 25.5 ± 5.9 preoperatively to 42.8 ± 6.0 post-operatively (p < 0.001). The mean preoperative HKAA of 2.4 ± 3.0° varus was corrected to 0.0 ± 3.1°. CONCLUSION:Medial UKA after knee osteotomy represents a viable treatment option, but it requires a strict preoperative alignment assessment. In the absence of excessive mechanical valgus alignment (HKAA < 3° valgus) and severe valgus deformities (MPTA < 95°) of the proximal tibia, medial UKA provides favourable midterm implant survivorship and excellent functional outcomes. In borderline cases, fixed-bearing implants should be considered to avoid valgus overcorrection. LEVEL OF EVIDENCE:Level IV.

PURPOSE:Patients with prior anterior cruciate ligament reconstruction (ACLR) are at increased risk of early medial osteoarthritis. Medial mobile-bearing (MB) unicompartmental knee arthroplasty (UKA) offers a minimal-invasive and joint-preserving alternative to total knee arthroplasty (TKA), yet evidence in ACLR patients remains limited. This study compared survivorship, reoperation causes and functional outcomes of medial MB UKA in ACLR patients versus matched controls. METHODS:This retrospective 1:2 matched case-control study included 106 medial MB UKAs after ACLR (mean age 61 ± 9 years; body mass index [BMI]: 29 ± 5 kg/m2; follow-up 5 ± 2 years) and 208 matched controls (n = 4 with only one match) with a minimum follow-up of 2 years. Kaplan-Meier analysis estimated 9-year survival for reoperation, implant revision (femur and/or tibia) and conversion to TKA. Reoperation causes and PROMs (Oxford Knee Score [OKS] and UCLA Activity Score) were compared. RESULTS:Cumulative 9-year reoperation-free survival was significantly lower (p = 0.026) in the ACLR group (81.2%; 95% confidence interval [CI]: 71.8-90.6) compared with matched controls (92.1%; 95% CI: 88.2-96.0). Cumulative 9-year implant revision-free survival was also significantly lower (p = 0.004) in the ACLR group (89.8%; 95% CI: 81.8-97.8) compared with matched controls (98.4%; 95% CI: 96.6-100.0). For conversion to TKA, survival rates were 92.7% (95% CI: 85.3-100.0) and 98.2% (95% CI: 96.2-100.0), respectively (p = 0.071). The risk for bearing dislocation was eightfold higher in the ACLR group compared with controls (3.8% vs. 0.5%; p = 0.046). The mean postoperative OKS in the ACLR group was 42.5 ± 6.2 and 42.3 ± 6.1 in controls; the UCLA Activity Score was 6.3 ± 1.2 and 6.1 ± 1.2, respectively. CONCLUSION:Despite excellent functional outcomes, ACLR patients undergoing MB UKA face a significantly higher risk for reoperation and inferior implant survival compared with matched controls. The increased risk for additional surgery in patients with prior ACLR, particularly for bearing dislocation, should be acknowledged when indicating medial UKA, and the usage of fixed-bearing implants reduces this risk. LEVEL OF EVIDENCE:Level III.

Background: Unicompartmental knee arthroplasty (UKA) is an established surgical treatment option for end-stage anteromedial osteoarthritis with excellent functional outcomes and implant survival. Routine preoperative varus and valgus stress views are crucial for the selection of patients for unicompartmental or total knee arthroplasty. Therapy: UKA is a soft-tissue based operation that aims to reconstruct the individual joint line and pre-arthritic alignment by restoring the physiological tension of the medial collateral and the cruciate ligaments. Results: Current data for medial UKA show excellent results for both mobile and fixed bearing implant designs with the correct indication and surgical technique. Cementless fixation offers potential advantages over cemented implants. Registry data demonstrate that institutions and surgeons specializing in partial knee replacement (> 30 cases/year per surgeon, > 100/year per institution) with a high percentage of UKA relative to the total number of knee implants (> 20%) have significantly lower revision rates.

Der unikondyläre Gelenkersatz (UKA) ist ein etabliertes Verfahren zur Therapie der anteromedialen Gonarthrose mit sehr guten funktionellen Ergebnissen und Prothesenstandzeiten. Eine differenzierte Indikationsstellung und Patientenselektion sind für den Erfolg des Teilgelenkersatzes essenziell. Hierbei haben routinemäßige Varus‑/Valgusstressaufnahmen einen hohen Stellenwert. Der unikondyläre Gelenkersatz ist eine wenig invasive und bandspannungsbasierte Operation mit dem Ziel, die patientenindividuelle präarthrotische Gelenklinie und Beinachse durch ein physiologisches Wiederanspannen des Innenbandes und der Kreuzbänder zu rekonstruieren. Aktuelle Daten für mediale UKA zeigen sowohl für mobile als auch „fixed bearing“ Implantate bei korrekter Indikation und Operationstechnik sehr gute Ergebnisse. Die zementfreie Verankerung bietet potenzielle Vorteile gegenüber der zementierten Versorgung. Registerdaten zeigen eindeutig, dass auf den Teilgelenkersatz spezialisierte Kliniken bzw. Operateure (Fallzahl > 30/Jahr pro Operateur, > 100/Jahr pro Klinik) mit einem hohen Anteil an UKA bezogen auf die Gesamtanzahl von Knieprothesen (> 20

Zementfreie Press-fit-Pfannen stellen heute den Goldstandard in der Primärendoprothetik der Hüfte dar. Über die letzten Jahrzehnte wurden das Implantatdesign, die Oberflächenstruktur, die Wandstärke, die Inlayoptionen mit hochmodernen Gleitpaarungen derart optimiert, dass grundsätzlich eine luxationssichere, primär stabile Implantation mit einer im Verlauf sicheren ossären Integration erzielt werden kann. Neben der hemisphärischen Pfannenform erlauben insbesondere polabgeflachte, bisphärische Pfannen mit optimaler Fräsenimplantabstimmung eine sichere Press-fit-Verankerung. Dünnwandige Titanlegierungen mit makro- und mikrostrukturierter Oberfläche stellen einen sicheren Kraftschluss am Implantatknocheninterface her und verhindern durch physiologische Krafteinleitung ein übermäßiges Stress-shielding. Heute sind alle technisch möglichen Inlayoptionen von Vitamin-E-versetzten, hochvernetzten Polyethylenen, über Keramikinlays mit konischer Klemmung bis hin zu tripolaren Designvarianten verfügbar und werden in der klinischen Routine eingesetzt. Die richtige Operations- und Implantationstechnik ermöglicht dabei einen dauerhaftes Implantatüberleben und eine sichere Funktion.

Die Datenlage für konventionell implantierte unikondyläre Knieprothesen zeigt anhand zahlreicher Langzeitergebnisse, dass sowohl der mediale als auch der laterale unikondyläre Kniegelenksersatz bei korrekter Indikationsstellung und gut ausgebildeten Operateuren als eine zuverlässige und erfolgreiche Behandlungsmethode der isolierten anteromedialen oder lateralen Gonarthrose gelten kann. Der Zusammenhang zwischen Operationsvolumen und Implantatstandzeit ist aus aktuellen Einzelstudien und Registerdaten eindeutig belegt. Der Einsatz neuer Technologien ermöglicht unter Berücksichtigung der aktuellen Datenlage potenziell eine Verbesserung der Genauigkeit der Implantatposition mit weniger Ausreißern, wobei evidenzbasierte Zielzonen für die jeweiligen Implantate nicht hinreichend etabliert sind. Für patientenindividuelle Instrumente und „Custom-made“-Implantate ist die aktuelle Datenlage unzureichend, sodass deren routinemäßiger Einsatz nicht zu rechtfertigen ist. Roboterassistierte Verfahren müssen als durchaus vielversprechender Ansatz für die Zukunft interpretiert werden. Bisher existiert jedoch ebenfalls keine ausreichende Datenlage, dass robotergestützte Operationstechniken die Implantatstandzeit verbessern oder zu einem besseren funktionellen Ergebnis aus Sicht des Patienten führen.

Background: The objectives of the present study were to (1) evaluate the accuracy and reliability of native acetabular offset (AO) measurements performed on conventional supine anterior-posterior (ap) pelvis radiographs with reference to computed tomography (CT) in patients with end-stage hip osteoarthritis (OA); (2) determine the minimum and maximum amount of medialization of the center of rotation (COR) simulating different reaming techniques; and (3) identify patients at increased risk of excessive medialization of the COR. Methods: A consecutive series of corresponding 131 CT scans and radiographs of patients with primary hip OA was evaluated using validated software for three-dimensional acetabular and femoral measurements. We simulated the implantation of a hemispherical press-fit cup comparing anatomic and conventional reaming techniques and assessed corresponding changes in AO. Results: Standardized ap pelvis radiographs allowed for an accurate and reliable assessment of AO compared with CT. Cup placement in the most lateral position (anatomic reaming technique) resulted in a mean implant-related medialization of 5.9 +/- 3.4 mm. Anatomic cup placement did not require reaming to the true floor in 64 hips (49%). With the conventional reaming technique, the total medialization of the COR (implant-related and reaming-related) was 6.8 +/- 2.9, with 34% of cases having a medialization >= 8 mm. Conclusion: The present study highlights the variability of acetabular anatomy in patients with primary OA. AO can be accurately and reliably determined on conventional radiographs and appears to be independent of femoral shape and geometry. Depending on the preferred reaming technique a substantial number of patients appear at risk for excessive cup medialization. (c) 2019 Elsevier Inc. All rights reserved.

The hypothesis of the present study was that degenerative fibro-ostosis (FO) of the ischial hamstring tendon insertion is a risk factor for heterotopic ossification (HO) following THA.

Background: We questioned whether there was a radiographic difference in hip geometry reconstruction and implant fixation between 3 different cementless stem design concepts in patients with primary end-stage hip osteoarthritis. Methods: We retrospectively evaluated the preoperative and postoperative radiographs by 2 independent and blinded reviewers in a series of 264 consecutive patients who had received either a straight double-tapered stem with 3 offset options (group A), a straight double-tapered stem with 2 shape options and modular necks (group B), and a bone-preserving curved tapered stem with 4 offset options (group C). The following parameters were assessed: acetabular, femoral and hip offset (HO), center of rotation height, leg length difference (LLD), and the endosteal fit of stem in the proximal femur (canal fill index). Group comparisons were performed using a one-way analysis of variance and subsequent pairwise comparisons (t-test). Results: Postoperatively, HO could be equally restored with all 3 stem designs (P = .079). The postoperative LLD was smaller in group C compared to group A (0.8 mm [standard deviation, 3.2] vs 2.6 mm [standard deviation, 4.5], P = .002). Best combined reconstruction of HO and LLD could be achieved with the short curved stem by junior and senior surgeons (HO: -2.0 and -2.1 mm; LLD: 1.9 and 0.7 mm, respectively). The proximal and mid-height canal fill indexes were higher in groups B and C compared to group A, indicating a better metaphyseal and diaphyseal fit in the proximal femur (both P < .001). Conclusion: All 3 cementless stem designs allowed for good hip geometry reconstruction. Multiple shape and offset options allowed for a better metaphyseal stem fit and offered minor clinical advantages for leg length reconstruction. Modular necks did not provide reconstructive advantages in patients with primary hip osteoarthritis. (c) 2017 Elsevier Inc. All rights reserved.

Bei Vorliegen einer isolierten Osteoarthrose im lateralen tibiofemoralen Gelenk stellt der unikompartimentelle Kniegelenkersatz eine sinnvolle Alternative zur Versorgung mit einer bikompartimentellen Oberflächenersatzprothese dar. Aufgrund anatomischer und biomechanischer Besonderheiten im lateralen femorotibialen Kompartiment bestehen wesentliche Unterschiede im Prothesendesign sowie in der Operationstechnik im Vergleich zum medialen Gelenkersatz. Prinzipiell werden Prothesen mit mobiler („mobile bearing“) und fixierter Inlaykomponente („fixed bearing“) unterschieden.

Advanced knee arthritis in young patients is a challenging problem that may necessitate surgical treatment. There are few published studies of mobile-bearing unicompartmental knee arthroplasty (UKA) in young patients, while indications have expanded to its use in this demanding patient group.

Background: Minimal invasive surgery (MIS) has gained growing popularity in total hip arthroplasty (THA) but concerns exist regarding component malpositioning. The aim of the present study was to evaluate femoral and acetabular component positioning in primary cementless THA comparing a lateral to a MIS anterolateral approach.Methods: We evaluated 6 week postoperative radiographs of 52 hips with a minimal invasive anterolateral approach compared to 54 hips with a standard lateral approach. All hips had received the same type of implant for primary cementless unilateral THA and had a healthy hip contralaterally.Results: Hip offset was equally restored comparing both approaches. No influence of the approach was observed with regard to reconstruction of acetabular offset, femoral offset, vertical placement of the center of rotation, stem alignment and leg length discrepancy. However, with the MIS approach, a significantly higher percentage of cups (38.5 %) was malpositioned compared to the standard approach (16.7 %) (p = 0.022).Conclusions: The MIS anterolateral approach allows for comparable reconstruction of stem position, offset and center of rotation compared to the lateral approach. However, surgeons must be aware of a higher risk of cup malpositioning for inclination and anteversion using the MIS anterolateral approach.

PURPOSE:Concerns have been raised in relation to metal-on-metal (MoM) articulations with catastrophic soft-tissue reactions due to metal debris. We reviewed how small head MoM articulations perform in primary uncemented total hip arthroplasty (THA) in young patients at a minimum of ten years.METHODS:We retrospectively evaluated the clinical and radiographic results of the first 100 consecutive primary cementless THAs using the 28-mm Metasul MoM articulation in 91 patients younger than 50 years of age at the time of surgery.RESULTS:After 13 years, survival for the endpoint revision due to any reason was 90.9 % and 98.9 % for revision due to aseptic implant loosening. The cumulative incidence of MoM related revisions was 1.2 %. Small proximal femoral osteolysis was found in 18 % of hips. No acetabular osteolysis or loosening was detected. Two hips showed signs of femoral neck impingement with severe damage to the neck.CONCLUSIONS:Early in the second decade, MoM-associated complications were rare using the 28-mm Metasul articulation, and aseptic loosening was not a major mode of failure in this cohort of young patients.LEVEL OF EVIDENCE:Therapeutic Level IV.