Translation and Cross-Cultural Adaptation into French of the Harris Hip Score and the Modified Harris Hip Score.

Purpose: The objective of this study was to develop a cross-cultural adaptation and translation into French of the original Harris Hip Score (HHS) and the modified Harris Hip Score (mHHS). Patients and Methods: The translation and cultural-adaptation of the questionnaire were performed following a 10-step process as recommended by the International Society for Pharmacoeconomics and Outcomes Research (ISPOR). During the cognitive debriefing, each item of the questionnaire has been rated between 1 and 10 according to the comprehension level of 8 patients who underwent total hip arthroplasty. Results: The cross-cultural adaptation process required the modification of the walking distance item by converting the number of blocks into meters but also in walking time (minutes). All the different steps have been performed without any other important changes on the translated questionnaire which has been found highly understandable by interviewed patients (9.6 ± 1.1). Conclusion: This study successfully reports the French version development of the original HHS (HHS-Fr) and its modified patient-reported version (mHHS-Fr), thereby providing to clinicians a standardised version for the evaluation of French-speaking patients suffering from hip osteoarthritis.

Hip Arthroscopy Followed by 6-Month Rehabilitation Leads to Improved Periarticular Muscle Strength, Except for Abductors and External Rotators.

Purpose: To evaluate the variations in hip muscles strength following arthroscopy and 6-month rehabilitation in patients treated for femoroacetabular impingement (FAI). Methods: A retrospective analysis was carried out on a series of patients who were arthroscopically treated for FAI at La Tour Hospital between 2020 and 2022. Bilateral isometric strengths of 8 hip-related muscles (abductors, adductors, hamstrings, quadriceps, extensors, flexors, internal and external rotators) were assessed using a handheld dynamometer before surgery and postoperatively after 6 months of rehabilitation in terms of relative strength changes between time points. Results: A total of 29 patients (aged 26.9 ± 7.1 years, 86% of women) were included. Except for the abductors, which remained of comparable strength than before surgery, a statistically significant (P < .05) increase in hip muscle strength on the operated side could be noted at 6 postoperative months for hamstrings (9% ± 17%, P = .041), quadriceps (11% ± 27%, P = .045), extensors (17% ± 32%, P = .006), flexors (17% ± 29%, P = .003), adductors (18% ± 23%, P < .001), and internal rotators (32% ± 36%, P < .001). The proportion of patients who reached a strength level above their preoperative status ranged from 62% (quadriceps) to 86% (adductors and flexors), depending on the muscle studied. The external rotators were the only muscles that remained significantly weakened at 6 months on both operated (-13% ± 26%, P = .002) and nonoperated (-17% ± 25%, P < .001) sides, with a decrease beyond 15% in almost half of the patients (45% and 48%, respectively). Conclusions: Arthroscopic treatment followed by 6-month rehabilitation granted to most FAI patients a higher strength level for several hip muscles, except for abductors and external rotators, which remained comparable and weakened, respectively. Level of Evidence: Level IV, therapeutic case series.

Evolution of Hip Muscles Strength in Femoroacetabular Impingement Patients Treated by Arthroscopy or Surgical Hip Dislocation: A Retrospective Exploratory Study.

Hip arthroscopy and surgical hip dislocation (SHD) can be adequate surgical options for patients suffering from femoroacetabular impingement (FAI) syndrome, but there is to date no published data on their impact on hip muscles strength. The purpose of this retrospective study was, therefore, to evaluate it on a consecutive series of 50 FAI patients treated either by arthroscopy (n = 29, aged 27.4 ± 7.5 years, 76% of women) or SHD (n = 21, aged 25.9 ± 6.5 years, 38% of women) at La Tour Hospital between 2020 and 2021. The bilateral isometric strengths of eight hip-related muscles were evaluated before and three months after surgery (halfway through the rehabilitation program). For arthroscopy, a statistically significant (p < 0.05) reduction in hip muscles strength could be noted on the operated hamstrings (1.49 ± 0.43 vs. 1.39 ± 0.38 Nm/kg), flexors (1.88 ± 0.46 vs. 1.73 ± 0.41 Nm/kg), abductors (1.97 ± 0.42 vs. 1.72 ± 0.40 Nm/kg) and external rotators (1.17 ± 0.40 vs. 1.04 ± 0.37 Nm/kg). The abductors were the most affected muscles, with 45% of the patients suffering from a strength reduction ≥15%. The non-operated external rotators were also affected but to a lesser extent (1.21 ± 0.38 vs. 1.10 ± 0.36 Nm/kg). For SHD, a statistically significant strength reduction could be noted on the operated extensors (2.28 ± 0.84 vs. 2.05 ± 0.70 Nm/kg), abductors (1.87 ± 0.49 vs. 1.65 ± 0.41 Nm/kg), quadriceps (2.96 ± 0.92 vs. 2.44 ± 0.89 Nm/kg), external rotators (1.16 ± 0.42 vs. 0.93 ± 0.36 Nm/kg) and internal rotators (1.26 ± 0.38 vs. 0.96 ± 0.30 Nm/kg). The internal rotators were the most affected muscles, with 75% of the patients suffering from a strength reduction ≥15%. To conclude, particular attention should be paid to operated abductors for patients treated by arthroscopy as well as operated internal/external rotators, abductors and quadriceps for those treated by surgical hip dislocation. It reinforces that a rehabilitation method based on isolated muscle reinforcement and functional exercises that goes beyond three postoperative months is needed.

Gluteus maximus tendon transfer for chronic abductor insufficiency: the Geneva technique.

INTRODUCTION: The treatment options of chronic abductor insufficiency in the setting of muscle degeneration, are limited and technically demanding. We present the outcomes of a salvage technique for unreconstructable, chronic abductor tears performed by a single surgeon. METHODS: We retrospectively evaluated 38 patients who were surgically managed for chronic abductor insufficiency. Patients without hip implants and patients following primary or revision total hip arthroplasty (THA) were involved. All patients had a Trendelenburg gait, impaired muscle strength of abduction (⩽M4) and fatty degeneration of muscles (Goutallier ⩾3). They underwent transfer of a flap of the anterior third of gluteus maximus to the greater trochanter that was sutured under the slightly mobilised vastus lateralis. The level of pain, functional scores, muscle strength and Trendelenburg gait were re-evaluated at 12 postoperative months. RESULTS: The mean age of patients was 70.2 years. 10 patients received the tendon transfer on a native hip, 6 following primary THA and 22 after revision THA. The mean pain level (3.2 vs. 7, p < 0.001) and Harris Hip Score (80.2 vs. 41.6, p < 0.001) and the median abductor strength (4 vs. 3, p < 0.001) was significantly improved compared to the preoperative scores. 26 patients demonstrated negative and 12 positive Trendelenburg sign at 12 postoperative months. No serious complications were reported. CONCLUSIONS: This salvage technique improved the strength of abduction and functional results and reduced the level of pain in 80% of patients with chronic abductor tears. The short-term outcomes of the procedure were favourable; however, further evaluation is needed.

Short-term outcomes following mini-open repair of chronic gluteus medius tendon tears using a double-row technique.

Gluteal tendon tears represent a common but underreported cause of lateral hip pain and dysfunction. In case of conservative management failure, a surgical procedure must be performed to relieve patient symptoms. Current operative treatments, either open or endoscopic, have been however associated with different drawbacks which led to the introduction of the mini-open technique. The aim of this study was to evaluate and report the short-term outcomes of patients operated through the aforementioned surgical technique for gluteus medius (GM) chronic tears. We retrospectively analysed the records of 14 consecutive patients operated at the La Tour hospital by mini-open repair using a double-row technique for full-thickness GM chronic tears. Intra- and post-operative complications were recorded. The pre- and post-operative pain on visual analogue scale (pVAS), modified Harris Hip score (mHHS), abduction strength and gait dysfunction were assessed for all patients. Pre- and post-operative values were compared to evaluate whether improvements were statistically significant and clinically relevant. The study cohort comprised 13 women (93%) and 1 man (3%) aged 62.4 ± 18.0 at index surgery. No intra- or post-operative complications were noted. Compared to pre-operative values, patients reported a significant improvement in mHHS (59.1 ± 7.1 vs 92.7 ± 4.6) and pVAS (7.4 ± 1.0 vs 1.3 ± 1.3) at last follow-up. Patients exhibited a perfect improvement in muscle strength (3.6 ± 0.5 vs 5.0 ± 0.0), and the proportion of patients with a positive Trendelenburg sign decreased from 71% to 0%. Mini-open repair of chronic GM tendon tears using a double-row technique demonstrated excellent clinical and functional outcomes at short follow-up. Level of Evidence: IV.

A roadmap to develop clinical guidelines for open surgery of acute and chronic tears of hip abductor tendons.

PURPOSE: Abductor tendon tears are increasingly recognised as a common cause of lateral hip pain. Surgical treatment of these tears has been recommended, but the indications and types of open surgery have not been precisely elucidated yet. This manuscript aimed to critically review the literature concerning all open treatment options for this condition while identifying knowledge gaps and introducing a treatment algorithm. METHODS: Literature search was conducted, including PubMed, Cochrane library, ScienceDirect and Ovid MEDLINE from 2000 to May 2020. Inclusion criteria were set as: (i) clinical studies reporting outcomes following open surgical treatment of acute or chronic hip abductor tendon tears, (ii) studies reporting an open direct or augmented suturing or muscle transfer procedure, (iii) acute or chronic tears found in native or prosthetic hips. RESULTS: A total of 34 studies published between 2004 and 2020 were included. The vast majority of studies were uncontrolled case series of a single treatment method. A total of 970 patients (76% women) with an age range between 48 and 76 years were involved. Women between 60 and 75 years old were most commonly treated. Preoperative evaluation of patients and reporting of open surgical technique and outcomes are inconsistent. All studies reported variable improvement of pain, functional outcomes and gait of patients. Overall, complication rates ranged from 0 to 31.2%. CONCLUSION: The current literature on this topic is highly heterogeneous, and the overall level of the available evidence is low. A roadmap to develop practical guidelines for open surgery of acute and chronic tears of abductor tendons is provided. The anatomy and chronicity of the lesion, the extent of fatty infiltration and neurologic integrity of hip abductor muscles may influence both treatment choice and outcome. Further high-quality studies with standardisation of preoperative evaluation of patients and reporting of outcomes will help delineate best treatments. LEVEL OF EVIDENCE: IV.

Quality of the femoral cement mantle in total hip arthroplasty using the direct anterior hip approach.

BACKGROUND: Limited literature exists concerning the femoral cement mantle quality that can be achieved through an anterior approach in total hip arthroplasty (THA). We radiologically evaluated the quality and thickness of the femoral cement mantle in patients undergoing THA utilizing the direct anterior approach (DAA). METHODS: Immediate postoperative anteroposterior and lateral radiographs of 116 consecutive patients who underwent hybrid or fully cemented THA using the DAA and cemented Quadra-C stem (Medacta, International, SA, Switzerland) were assessed by 2 arthroplasty surgeons blinded to the study. Surgical indications were hip osteoarthritis or subcapital hip fracture. The cement mantle and stem alignment were evaluated using the Barrack classification and Khalily methods, respectively. After calibration of radiographs, the thinnest part of the cement mantle per Gruen zone was recorded. Parameters were compared between obese and nonobese patients. RESULTS: Agreement between raters was substantial for the cement quality in anteroposterior (k = 0.707, P ≤ .001) and moderate for lateral radiographs (k = 0.574, P ≤ 001). The cement mantle was graded A in 39.25%, B in 53.0%, and C in 7.75% of anteroposterior radiographs and similarly for lateral radiographs (40.1% A, 51.75% B, 9.5% C). 93% of stems had neutral alignment. The mean thinnest cement mantle (P = .237) and incidence of inadequate cement mantle (<2 mm) per zone (P = .431) were comparable between Gruen zones. The cement mantle quality (P = .174) and inadequacy (P > .05) and stem alignment (P = .652) were comparable between obese and nonobese patients. CONCLUSIONS: DAA enables correct implantation and effective cementation of straight femoral stems. A high-quality cement mantle can be achieved using DAA even in obese patients.

Lesions of the abductors in the hip.

Abductor tendon lesions and insertional tendinopathy are the most common causes of lateral thigh pain. Gluteal tendon pathology is more prevalent in women and frequency increases with age.Chronic atraumatic tears result in altered lower limb biomechanics. The chief complaint is lateral thigh pain. Clinical examination should include evaluation of muscle strength, lumbar spine, hip and fascia lata pathology. The hip lag sign and 30-second single leg stance tests are useful in diagnosing abductor insufficiency.Magnetic resonance imaging (MRI) is the gold-standard investigation to identify abductor tendon tears and evaluate the extent of muscle fatty infiltration that has predictive value on the outcome of abductor repair.Abductor tendinosis treatment is mainly conservative, including non-steroidal anti-inflammatory medications, activity modification, local corticosteroid injections, plasma-rich protein, physical and radial shockwave therapy. The limited number of available high-quality studies on treatment outcomes and limited evidence between tendinosis and partial ruptures make it difficult to provide definite conclusions regarding the best management of gluteal tendinopathy.Surgical management is indicated in complete and partial gluteal tendon tears that are unresponsive to conservative treatment.There are various open and arthroscopic surgical procedures for direct repair of abductor tendon tears. There is limited evidence concerning surgical management outcomes. Prerequisites for effective tendon suturing are neurologic integrity and limited muscle fatty infiltration. Chronic irreparable tears with limited muscle atrophy and limited fatty infiltration can be augmented with grafts. Gluteus maximus or/vastus lateralis muscle transfers are salvage reconstruction procedures for the management of chronic end-stage abductor tears with significant tendon insufficiency or gluteal atrophy. Cite this article: EFORT Open Rev 2020;5:464-476. DOI: 10.1302/2058-5241.5.190094.

Total hip arthroplasty in sickle cell disease: a systematic review.

Total hip arthroplasty (THA) in sickle cell disease (SCD) patients can be a challenging procedure.This systematic review evaluated the revision rate, functional outcomes and complications of THA in sicklers.A systematic search was conducted according to the PRISMA guidelines, using four search engines from inception to May 2019.Fifteen studies with 971 THAs were included. There were 437 cemented and 520 uncemented THAs.There were 164 revision THAs (16.8%); 52 uncemented and 105 cemented THAs.Forty-two infections were recorded; 16 infections for cemented and 23 for uncemented THAs.Fifty-seven cups, 26 stems, eight cup/stem with aseptic loosening that were more frequently cemented were reported. The 28 unspecified aseptic loosening cases were more frequently uncemented THAs.All studies demonstrated the functional improvement of patients.There were 109 medical complications (14.3%). Sickle cell crises (SCC) and transfusion reactions were most usually recorded.Forty-six intraoperative complications (4.7%) were reported; 18 femoral fractures, four acetabular and 18 femoral perforations. Seventeen femoral fractures occurred during uncemented THA.THA in SCD is still related to a high risk of complications. The outcomes in properly selected sicklers have been improved. Perioperative adequate hydration, warming, oxygen supply and transfusion protocols are mandated to prevent SCC and transfusion reactions. The surgeon must be prepared to deal with a high rate of intraoperative fractures and have different implant options readily available. No definite conclusion can be made regarding the best fixation mode. Cemented implants demonstrated a higher revision rate and uncemented implants a higher risk for intraoperative complications. Cite this article: EFORT Open Rev 2020;5:180-188. DOI: 10.1302/2058-5241.5.190038.

Genetic Predisposition to Developmental Dysplasia of the Hip.

BACKGROUND: The etiopathogenesis of developmental dysplasia of the hip (DDH) has not been clarified. This systematic review evaluated current literature concerning all known chromosomes, loci, genes, and their polymorphisms that have been associated or not with the prevalence and severity of DDH. METHODS: Following the established methodology of Meta-analysis of Observational Studies in Epidemiology guidelines, MEDLINE, EMBASE, and Cochrane Register of Controlled Trials were systematically searched from inception to January 2019. RESULTS: Forty-five studies were finally included. The majority of genetic studies were candidate gene association studies assessing Chinese populations with moderate methodological quality. Among the most frequently studied are the first, third, 12th,17th, and 20th chromosomes. No gene was firmly associated with DDH phenotype. Studies from different populations often report conflicting results on the same single-nucleotide polymorphism (SNP). The SNP rs143384 of GDF5 gene on chromosome 20 demonstrated the most robust relationship with DDH phenotype in association studies. The highest odds of coinheritance in linkage studies have been reported for regions of chromosome 3 and 13. Five SNPs have been associated with the severity of DDH. Animal model studies validating previous human findings provided suggestive evidence of an inducing role of mutations of the GDF5, CX3CR1, and TENM3 genes in DDH etiopathogenesis. CONCLUSION: DDH is a complex disorder with environmental and genetic causes. However, no firm correlation between genotype and DDH phenotype currently exists. Systematic genome evaluation in studies with larger sample size, better methodological quality, and assessment of DDH patients is necessary to clarify the DDH heredity. The role of next-generation sequencing techniques is promising.

Total hip arthroplasty through an anterior approach: The pros and cons.

Total hip arthroplasty through an anterior approach has been increasing in popularity amongst surgeons and patients.Anterior approach hip arthroplasty seems to offer improved early outcomes in terms of pain, rehabilitation and length of stay.No difference in long-term outcomes has been shown between anterior and posterior or lateral approaches.Proper formal training, utilization of fluoroscopy and adequate experience can mitigate risks of complications and improve early and medium-term outcomes. Cite this article: EFORT Open Rev 2018;3:574-583. DOI: 10.1302/2058-5241.3.180023.

Important patient characteristics differ prior to total knee arthroplasty and total hip arthroplasty between Switzerland and the United States.

BACKGROUND: Outcomes after total knee (TKA) and hip (THA) arthroplasty are often generalized internationally. Patient-dependent factors and preoperative symptom levels may differ across countries. We compared preoperative patient and clinical characteristics from two large cohorts, one in Switzerland, the other in the US. METHODS: Patient characteristics were collected prospectively on all elective primary TKAs and THAs performed at a large Swiss hospital and in a US national sample. Data included age, sex, education level, BMI, diagnosis, medical co-morbidities, PROMs (WOMAC pain/function), global health (SF-12). RESULTS: Six thousand six hundred eighty primary TKAs (US) and 823 TKAs (Swiss) were evaluated. US vs. Switzerland TKA patients were younger (mean age 67 vs. 72 years.), more obese (BMI ≥30 55% vs. 43%), had higher levels of education, more cardiac disease. Swiss patients had lower preoperative WOMAC pain scores (41 vs. 52) but pre-operative physical disability were comparable. 4,647 primary THAs (US) and 1,023 THAs (Swiss) were evaluated. US vs. Switzerland patients were younger (65 vs. 68 years.), more obese (BMI ≥30: 38% vs. 24%), had higher levels of education, more diabetes. Swiss patients had lower preoperative WOMAC pain scores (40 vs. 48 points). Physical disability was reported comparable, but Swiss patients indicated lower mental health scores. CONCLUSION: We found substantial differences between US and Swiss cohorts in pre-operative patient characteristics and pain levels, which has potentially important implications for cross-cultural comparison of TKA/THA outcomes. Reports from national registries lack detailed patient information while these data suggest the need for adequate risk adjustment of patient factors.

Comparison of dual-mobility cup and unipolar cup for prevention of dislocation after revision total hip arthroplasty.

Background and purpose - Revision total hip arthroplasty (THA) is associated with higher dislocation rates than primary THA. We compared the risk of dislocation within 6 months and all-cause re-revision during the whole study period using either the dual-mobility cup or the unipolar cup. Methods - We used a prospective hospital registry-based cohort including all total and cup-only revision THAs performed between 2003 and 2013. The cups used were either dual-mobility or unipolar; the choice was made according to the preference of the surgeon. 316 revision THAs were included. The mean age of the cohort was 69 (25-98) years and 160 THAs (51%) were performed in women. The dual-mobility group (group 1) included 150 THAs (48%) and the mean length of follow-up was 31 (0-128) months. The unipolar group (group 2) included 166 THAs (53%) and the mean length of follow-up was 52 (0-136) months. Results - The incidence of dislocation within 6 months was significantly lower with the dual-mobility cup than with the unipolar cup (2.7% vs. 7.8%). The unadjusted risk ratio (RR) was 0.34 (95% CI: 0.11-1.02) and the adjusted RR was 0.28 (95% CI: 0.09-0.87). The number of patients needed to treat with a dual-mobility cup in order to prevent 1 case of dislocation was 19. The unadjusted incidence rate ratio for all-cause re-revision in the dual-mobility group compared to the unipolar group was 0.6 (95% CI: 0.3-1.4). Interpretation - Use of a dual-mobility rather than a unipolar cup in revision THA reduced the risk of dislocation within 6 months.

Rivaroxaban for Thromboprophylaxis After Nonelective Orthopedic Trauma Surgery in Switzerland.

This study investigated the effectiveness and the outcomes of rivaroxaban vs the standard of care for venous thromboembolic prophylaxis in patients undergoing fracture-related surgery. A total of 413 patients undergoing fracture-related surgery from 9 Swiss orthopedic and trauma centers were enrolled. The authors selected the type of venous thromboembolic prophylaxis according to standardized medical practice at the participating centers before the inclusion of patients: 208 patients received rivaroxaban and 205 received the standard of care. Data on symptomatic thromboembolic and bleeding events, surgery-related complications, death, adverse events, time to mobilization, and hospital discharge were collected. Symptomatic thromboembolic events were reported in 1 patient (0.5%) and 2 patients (1.0%) and treatment-emergent major bleeding events were reported in 1 patient (0.5%) and 2 patients (1.0%) receiving rivaroxaban and the standard of care, respectively. The durations of hospital stay and venous thromboembolic prophylaxis were similar in the 2 groups. In both groups, adverse events related to venous thromboembolic prophylaxis were reported in 12 patients. The proportion of patients with minor and major fracture surgery was 74.3% and 25.7%, respectively. In patients undergoing minor fracture surgery receiving rivaroxaban (n=167) and the standard of care (n=140), no symptomatic thromboembolic events and no major bleeding events were reported. Outcomes of this study indicate that rivaroxaban might be an appropriate oral alternative for venous thromboembolic prophylaxis in routine medical care after fracture-related major and minor surgery. Reported results were comparable to those from other large-scale, noninterventional and randomized controlled studies. [Orthopedics. 2017; 40(2):109-116.].

Nerve injuries in total hip arthroplasty with a mini invasive anterior approach.

PURPOSE: Minimal invasive techniques in total hip arthroplasty (THA) have become increasingly popular during recent years. Despite much debate over the outcome of several minimal invasive techniques, complications arising from the use of anterior minimally invasive surgery (AMIS) for THA on a traction table are not well documented. Our study aims to focus on nerve damage during the AMIS procedure and the possible explanations of these injuries. METHODS: We reviewed all primary THAs performed with the AMIS technique using a traction table, over 5 years and recorded all intraoperative and postoperative complications up to the latest follow-up. We focused on nerve injuries and nerve function impairment following the aforementioned technique. RESULTS: Our study included 1,512 THAs performed with the AMIS technique in 2 major hip reconstruction centres (KAT General Hospital, Athens, Greece and University Hospital of Geneva, Switzerland), on 1,238 patients (985 women, 253 men; mean age 65.24 years). Mean follow-up was 29.4 months. We observed 51 cases of transient lateral femoral cutaneous nerve neuropraxia (3.37%), 4 cases of femoral nerve paralysis (3 permanent, 1 transient [0.26%]) and 1 case of permanent sciatic nerve paralysis (0.06%). No case of obturator or pudendal nerve injury was noticed. Mean age of these cases was 68.97 years. Sciatic and femoral nerve injuries were confirmed by electromyography, showing axonotmesis of the damaged nerve. CONCLUSIONS: Neurological injuries are a rare but distinct complication of THAs using the AMIS technique. Possible explanations for such referred nerve injuries are direct nerve injury, extreme traction, hyperextension, extreme external rotation of the leg, use of retractors and coexisting spinal deformities. Controlled use of traction in hip extension, cautious use of retractors and potential use of dynamometers may be useful, so that neurological damage can be avoided. Further studies are needed to fully elucidate the role of the above factors in AMIS neurological complications.

Body mass and weight thresholds for increased prosthetic joint infection rates after primary total joint arthroplasty.

BACKGROUND AND PURPOSE: Obesity increases the risk of deep infection after total joint arthroplasty (TJA). Our objective was to determine whether there may be body mass index (BMI) and weight thresholds indicating a higher prosthetic joint infection rate. PATIENTS AND METHODS: We included all 9,061 primary hip and knee arthroplasties (mean age 70 years, 61% women) performed between March 1996 and December 2013 where the patient had received intravenous cefuroxime (1.5 g) perioperatively. The main exposures of interest were BMI (5 categories: < 24.9, 25-29.9, 30-34.9, 35-39.9, and ≥ 40) and weight (5 categories: < 60, 60-79, 80-99, 100-119, and ≥ 120 kg). Numbers of TJAs according to BMI categories (lowest to highest) were as follows: 2,956, 3,350, 1,908, 633, and 214, respectively. The main outcome was prosthetic joint infection. The mean follow-up time was 6.5 years (0.5-18 years). RESULTS: 111 prosthetic joint infections were observed: 68 postoperative, 16 hematogenous, and 27 of undetermined cause. Incidence rates were similar in the first 3 BMI categories (< 35), but they were twice as high with BMI 35-39.9 (adjusted HR = 2.1, 95% CI: 1.1-4.3) and 4 times higher with BMI ≥ 40 (adjusted HR = 4.2, 95% CI: 1.8-9.7). Weight ≥ 100 kg was identified as threshold for a significant increase in infection from the early postoperative period onward (adjusted HR = 2.1, 95% CI: 1.3-3.6). INTERPRETATION: BMI ≥ 35 or weight ≥ 100 kg may serve as a cutoff for higher perioperative dosage of antibiotics.