Item-reduced Forgotten Joint Score provides adequate psychometric properties in ACLR patients.

Purpose: The purpose of this study was to evaluate content validity, test-retest reliability, internal consistency, construct validity, responsiveness and floor/ceiling effects of Forgotten Joint Score (FJS) for assessing functions in activities of daily living (ADL) following anterior cruciate ligament reconstruction (ACLR) and perform an item reduction of FJS. Methods: Swedish-speaking ACLR patients in one surgical clinic were eligible. Content validity was evaluated through patient responses and patient and expert clinician relevance ratings, omitting items with low relevance. Principal component factor analysis, Cronbach's ⍺, paired t test, correlations between FJS and Knee Injury and Osteoarthritis Outcome Score (KOOS), Cohen's d effect sizes (ESs) and standardized response mean (SRM) were used to evaluate internal consistency, test-retest reliability, construct validity and responsiveness. Floor/ceiling effects were calculated. FJS was expected to reveal one dominant factor, a Cronbach's ⍺ between 0.70 and 0.95, correlations >0.50 to all KOOS subscores, highest for ADL, moderate ES and SRM, floor/ceiling effects <15%. Results: One hundred and seventy-six participants (103 for assessing internal consistency, construct validity, responsiveness and floor/ceiling effects; 73 for assessing test-retest reliability and content validity) were included. Item reduction yielded a nine-item FJS (FJS-9). FJS-12 and FJS-9 demonstrated sufficient content validity (95% confidence interval [CI], 2.5-3.1, respectively, 2.9-3.3). FJS-9 was found unidimensional, and FJS-12 was multidimensional. Cronbach's ⍺ was 0.94 for FJS, and the intraclass correlation coefficient > 0.90. FJS showed significant correlations >0.65 to all KOOS subscales, moderate ES and SRM > 0.50. No floor/ceiling effects were found. Conclusion: FJS-9 demonstrated adequate validity for the evaluation of joint awareness in ACLR patients and can be a valuable tool to assess ADL and joint awareness. Level of Eidence: Level III.

Reliability and responsiveness of the Swedish short Hip-RSI.

Purpose: The aim of this study was to examine test-retest reliability and responsiveness of the short version (6-item) Hip Return to Sport after Injury (Hip-RSI) scale in patients following hip arthroscopy. Methods: The study included 100 hip arthroscopy patients responding to a digital survey including the short version (6-item) Hip-RSI, International Hip Outcome Tool (short version) (iHOT-12) and RTS status 3, 6 and 9 months following surgery. The Hip-RSI was administered twice at 3-month follow-up. Test-retest reliability was evaluated using intraclass correlation coefficients. Responsiveness was tested by correlations between changes in Hip-RSI and iHOT-12 scores and by comparing change in Hip-RSI scores of patients who progressed on the return to sport (RTS) continuum (from return to any sport to return to performance) to patients who did not, using independent samples t-tests. Results: Hip-RSI was found to have excellent test-retest reliability on the individual (intraclass correlation coefficient, ICC [95% confidence interval, CI]: 0.90 [0.83-0.94]) and group level (ICC [95% CI]: 0.95 [0.91-0.97]) with a standard error of measurement of 5.53 and smallest detectable change of 15.3 on the individual and 2.2 on the group level. Hip-RSI was found responsive to change through positive correlations of changes in scores with changes in iHOT-12 scores from 3 to 6 months (r [95% CI]: 0.51 [0.35-0.65]; p < 0.001) and from 3 to 9 months following arthroscopy (r [95% CI]: 0.61 [0.57-0.79); p < 0.001). Further responsiveness was shown by significant mean changes in scores among patients that progressed on the RTS-continuum (3-6 months: 8.6 [95% CI: 3.8- 13.5); 3-9 months: 12.6 [5.6-19.7]). Conclusion: The short version (6-item) Hip-RSI demonstrated excellent test-retest reliability and responsiveness to change in the evaluation of psychological readiness to RTS following hip arthroscopy. Level of Evidence: Level II.

Ultralong transients enhance sensitivity and resolution in Orbitrap-based single-ion mass spectrometry.

Orbitrap-based charge detection mass spectrometry utilizes single-molecule sensitivity to enable mass analysis of even highly heterogeneous, high-mass macromolecular assemblies. For contemporary Orbitrap instruments, the accessible ion detection (recording) times are maximally ~1-2 s. Here by modifying a data acquisition method on an Orbitrap ultrahigh mass range mass spectrometer, we trapped and monitored individual (single) ions for up to 25 s, resulting in a corresponding and huge improvement in signal-to-noise ratio (×5 compared with 1 s), mass resolution (×25) and accuracy in charge and mass determination of Orbitrap-based charge detection mass spectrometry.

Expanding Differential Ion Mobility Separations into the MegaDalton Range.

Along with mass spectrometry (MS), ion mobility separations (IMS) are advancing to ever larger biomolecules. The emergence of electrospray ionization (ESI) and native MS enabled the IMS/MS analyses of proteins up to ∼100 kDa in the 1990s and whole protein complexes and viruses up to ∼10 MDa since the 2000s. Differential IMS (FAIMS) is substantially orthogonal to linear IMS based on absolute mobility K and offers exceptional resolution, unique selectivity, and steady filtering readily compatible with slower analytical methods such as electron capture or transfer dissociation (ECD/ETD). However, the associated MS stages had limited FAIMS to ions with m/z < 8000 and masses under ∼300 kDa. Here, we integrate high-definition FAIMS with the Q-Exactive Orbitrap UHMR mass spectrometer that can handle m/z up to 80,000 and MDa-size ions in the native ESI regime. In the initial evaluation, the oligomers of monoclonal antibody adalimumab (148 kDa) are size-selected up to at least the nonamers (1.34 MDa) with m/z values up to ∼17,000. This demonstrates the survival and efficient separation of noncovalent MDa assemblies in the FAIMS process, opening the door to novel analyses of the heaviest macromolecules.

Same game, different worlds? General conditions, perceived stress, and associations between stress and past season injuries in elite female and male ice hockey players.

BACKGROUND: Ice hockey is played by women and men but the arena they play in may differ substantially. Potential differences in general conditions to play the sport may be associated to perceived stress, which has shown to be related to athletic injury in other sports. Therefore, this study aimed to describe and compare general conditions for playing ice hockey, stress levels, and the association between perceived stress and injury occurrence among elite female and male players. METHODS: Prior to the 2022-2023 season all female and male players from the top ice hockey leagues in Sweden were invited to an online survey. Players provided information about their general conditions for playing ice hockey and reported perceived stress during the previous season on the Perceived Stress Scale (PSS-10; sum score range 0-40) and current stress on the Single Item Stress Question (SISQ; scale range 1-5). Injuries during the previous season were self-reported on a modified version of the Oslo Sports Trauma Research Center - Overuse Injury Questionnaire. RESULTS: We received responses from 360 players (170 females and 190 males). Female players more frequently reported additional occupations besides ice hockey and less medical support during games and practices than male players (p < .001). General stress levels were significantly higher among female players (mean PSS score [SD]: 17.4 [5.6] vs 14.1 [5.6], p < 0.001; SISQ median [IQR]: 3 [2-3] vs 2 [1-3], p < 0.001). There was a statistically significant but weak correlation between past season injury and perceived stress (PSS score: rho 0.29; SISQ: rho 0.24). This correlation was stronger among males than females (PSS score: 0.38 vs 0.162; SISQ: 0.29 vs 0.16, p's < 0.05). Players with substantial injuries during previous season had higher previous and current stress levels than players without injury, a difference that was largest and statistically significant only among male players. CONCLUSIONS: General conditions for playing elite ice hockey are inequal for female and male athletes. Stress levels of elite ice hockey players were comparable to the general population. Experience of severe injuries during the previous season was associated to higher levels of perceived stress. This association is stronger among male players, which may be due to greater economic dependency.

Weaker Quadriceps Muscle Strength With a Quadriceps Tendon Graft Compared With a Patellar or Hamstring Tendon Graft at 7 Months After Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Impaired quadriceps muscle strength after anterior cruciate ligament reconstruction (ACLR) is associated with worse clinical outcomes and a risk of reinjuries. Yet, we know little about quadriceps muscle strength in patients reconstructed with a quadriceps tendon (QT) graft, which is increasing in popularity worldwide. PURPOSE: To describe and compare isokinetic quadriceps strength in patients undergoing ACLR with a QT, hamstring tendon (HT), or bone-patellar tendon-bone (BPTB) autograft. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: We included patients with QT grafts (n = 104) and matched them to patients with HT (n = 104) and BPTB (n = 104) grafts based on age, sex, and associated meniscal surgery. Data were collected through clinical strength testing at a mean of 7 ± 1 months postoperatively. Isokinetic strength was measured at 90 deg/s, and quadriceps strength was expressed as the limb symmetry index (LSI) for peak torque, total work, torque at 30° of knee flexion, and time to peak torque. RESULTS: Patients with QT grafts had the most impaired isokinetic quadriceps strength, with the LSI ranging between 67.5% and 75.1%, followed by those with BPTB grafts (74.4%-81.5%) and HT grafts (84.0%-89.0%). Patients with QT grafts had a significantly lower LSI for all variables compared with patients with HT grafts (mean difference: peak torque: -17.4% [95% CI, -21.7 to -13.2], P < .001; total work: -15.9% [95% CI, -20.6 to -11.1], P < .001; torque at 30° of knee flexion: -8.8% [95% CI, -14.7 to -2.9], P = .001; time to peak torque: -17.7% [95% CI, -25.8 to -9.6], P < .001). Compared with patients with BPTB grafts, patients with QT grafts had a significantly lower LSI for all variables (mean difference: peak torque: -6.9% [95% CI, -11.2 to -2.7], P < .001; total work: -7.7% [95% CI, -12.4 to -2.9], P < .001; torque at 30° of knee flexion: -6.3% [95% CI, -12.2 to -0.5], P = .03; time to peak torque: -8.8% [95% CI, -16.9 to -0.7], P = .03). None of the graft groups reached a mean LSI of >90% for peak torque (QT: 67.5% [95% CI, 64.8-70.1]; HT: 84.9% [95% CI, 82.4-87.4]; BPTB: 74.4% [95% CI, 72.0-76.9]). CONCLUSION: At 7 months after ACLR, patients with QT grafts had significantly worse isokinetic quadriceps strength than patients with HT and BPTB grafts. None of the 3 graft groups reached a mean LSI of >90% in quadriceps strength.

Injury patterns in Swedish elite female and male ice hockey - A cross-sectional comparison of past-season's injuries.

OBJECTIVES: To describe and compare seasonal prevalence, anatomical location, severity, and onset of injuries between female and male elite ice hockey players. DESIGN: Cross-sectional survey study. SETTING: Elite ice hockey. PARTICIPANTS: Swedish elite ice hockey players (170 females & 190 males). MAIN OUTCOME MEASURES: Past season injuries reported on a modified version of the Oslo Sports Trauma Research Center overuse injury questionnaire. Proportions of players who experienced any and substantial problems, as well as respective injury severity scores were presented and compared between sexes. RESULTS: Highest seasonal prevalence was reported for hip/groin [31.1% (n = 112)], lower back [24.2% (n = 87)], and shoulder injuries [23.6% (n = 85)]. Prevalence of injuries was approximately similar between sexes. Substantial injuries were most prevalent in the hip/groin (13.3% [n = 48]) and knee (18.6% [n = 67]) region. Females reported a higher proportion of substantial hip/groin injuries. Most reported injuries were acute except for hip/groin and lower back injuries (74.4% and 81.8% due to overuse). CONCLUSION: Seasonal prevalence of injuries in elite ice hockey players were comparable between sexes. Acute injuries were most common but hip/groin as well as lower back injuries were predominantly due to overuse. The highest reported prevalence was found for hip and groin-, lower back-, and shoulder injuries.

Changes in pain and disability in patients with shoulder pain after three months of digitally delivered exercise and patient education.

OBJECTIVE: To describe and examine potential predictors of changes in pain and disability in patients with shoulder pain who have completed 3 months of digitally delivered treatment comprising exercise and patient education. DESIGN: Retrospective cohort study (clinicaltrials.org Nr: NCT05402514). SUBJECTS: Patients with shoulder pain who completed treatment (n = 682). METHODS: Primary outcome was change in shoulder pain (numerical rating scale 0-10; minimal clinical important change: at least 2 points). Pain and disability were reported on the Shoulder Pain and Disability Index. Changes in outcomes were analysed with paired sample t-tests. Association with potential predictors (sex, age, education, body mass index, physical activity, symptom duration, baseline pain/function, and treatment adherence) were explored with linear regression models Results: Statistically significant improvements were found for all treatment outcomes. Minimal clinically important change in pain was reached by 54.5% (n = 372). Higher baseline level of symptoms, short symptom duration, and high treatment adherence were associated with greater changes. CONCLUSION: Patients with shoulder pain reported significant reductions in pain and disability following treatment, but the clinical relevance of the improvements has not been confirmed. Satisfactory treatment adherence, higher baseline pain and shorter symptom duration predicted larger improvements. A control group is needed to evaluate the actual effect of the treatment.

Frequency chasing of individual megadalton ions in an Orbitrap analyser improves precision of analysis in single-molecule mass spectrometry.

To enhance the performance of charge-detection mass spectrometry, we investigated the behaviour of macromolecular single ions on their paths towards and within the Orbitrap analyser. Ions with a mass beyond one megadalton reach a plateau of stability and can be successfully trapped for seconds, travelling a path length of multiple kilometres, thereby enabling precise mass analysis with an effective resolution of greater than 100,000 at a mass-to-charge ratio of 35,000. Through monitoring the frequency of individual ions, we show that these high-mass ions, rather than being lost from the trap, can gradually lose residual solvent molecules and, in rare cases, a single elementary charge. We also demonstrate that the frequency drift of single ions due to desolvation and charge stripping can be corrected, which improves the effective ion sampling 23-fold and gives a twofold improvement in mass precision and resolution.

Assessment of genome packaging in AAVs using Orbitrap-based charge-detection mass spectrometry.

Adeno-associated viruses (AAVs) represent important gene therapy vectors with several approved clinical applications and numerous more in clinical trials. Genome packaging is an essential step in the bioprocessing of AAVs and needs to be tightly monitored to ensure the proper delivery of transgenes and the production of effective drugs. Current methods to monitor genome packaging have limited sensitivity, a high demand on labor, and struggle to distinguish between packaging of the intended genome or unwanted side-products. Here we show that Orbitrap-based charge-detection mass spectrometry allows the very sensitive quantification of all these different AAV bioprocessing products. A protocol is presented that allows the quantification of genome-packed AAV preparations in under half an hour, requiring only micro-liter quantities of typical AAV preparations with ∼1013 viral capsids per milliliter. The method quickly assesses the integrity and amount of genome packed AAV particles to support AAV bioprocessing and characterization of this rapidly emerging class of advanced drug therapies.

Incidence, Prevalence, and Severity of and Risk Factors for Hip and Groin Problems in Swedish Male Ice Hockey Players: A 1-Season Prospective Cohort Study.

CONTEXT: The epidemiologic focus on time loss may underestimate the true magnitude of hip and groin problems in male ice hockey players. OBJECTIVE: To describe the prevalence, incidence, and severity of hip and groin problems (time loss and non-time loss) in Swedish ice hockey players over the course of a season and explore potential preseason risk factors for these conditions. DESIGN: Prospective 1-season cohort study. SETTING: Professional and semiprofessional Swedish ice hockey players. PATIENTS OR OTHER PARTICIPANTS: A total of 12 professional and semiprofessional male ice hockey teams were invited to participate. Of those, 9 teams agreed, and 163 players were included in the analyses. MAIN OUTCOME MEASURE(S): Hip and groin problems in the previous season (time loss, non-time loss), isometric adduction and abduction strength, and 5-second squeeze test results were recorded before the season and served as independent variables in the risk factor analysis. Main outcome measures were cumulative incidence of hip and groin problems, average prevalence, and odds ratios (ORs) for groin problems in season. RESULTS: Cumulative incidence was 45.4% (95% CI = 37.6%, 53.4%) for all problems and 19% (95% CI = 13.3%, 25.9%) for substantial problems. Average prevalence was 14.1% (95% CI = 10.8%, 17.5%) for all and 5.7% (95% CI = 4.3%, 7.2%) for substantial problems. Among reported problems, 69.2% had a gradual onset, and only 17% led to time loss. Players with non-time-loss problems in the previous season had higher odds for new problems (all: OR = 3.3 [95% CI = 1.7, 6.3]; substantial: OR = 3.6 [95% CI = 1.8, 8.4]). Preseason strength was not significantly associated with the odds for subsequent problems. CONCLUSION: Hip and groin problems are common in ice hockey players and may lead to substantial impairments in performance. Only 1 in 5 problems led to time loss, and 7 in 10 had a gradual onset. Non-time-loss problems in the previous season were a significant risk factor for new problems, whereas decreased preseason hip-adduction and -abduction strength was not.

The Perceived Demands of Ice Hockey Goaltending Movements on the Hip and Groin Region: An Elite Coach and Player Perspective.

BACKGROUND: Many ice hockey goaltending techniques force hip joints and groin muscles into extreme ranges of motion, which may increase the risk of hip and groin problems. PURPOSE: To explore how elite goaltenders and goaltending coaches perceive the demands of common goaltending techniques on the hip and groin region. We further explored differences in perception between goaltenders and their coaches as well as between junior (age <20 years) and senior (age ≥20 years) goaltenders. STUDY DESIGN: Cross-sectional survey. METHODS: We developed a model to categorize common ice hockey goaltending techniques into quantifiable units and invited elite goaltenders and coaches in Sweden to complete an online survey. Participants were asked to rate the perceived demands of each technique on the hip and groin using a Likert scale (not at all, slightly, somewhat, very, or extremely demanding). Using the chi-square test, the proportion of participants perceiving each technique as very or extremely demanding were compared between goaltenders and coaches as well as between senior and junior goaltenders. RESULTS: We received responses from 132 goaltenders and 43 coaches. The stances most frequently perceived as very or extremely demanding were the reverse vertical horizontal post-play (40%) and the butterfly save (25%). Among transitions, movements into the post were most frequently rated as very or extremely demanding (11%-40%). Several techniques were perceived as demanding by a larger share of coaches than goaltenders (difference, 13%-46%; P < .001-.028) and a larger share of senior versus junior goaltenders (difference, 12%-20%; P = .13-.18). CONCLUSION: The post-play and the butterfly were the goaltending techniques most frequently perceived as demanding, and more coaches than goaltenders percieved these techniques demanding. The results of this study may inform injury prevention efforts for ice hockey goaltending.

Hip and groin function and strength in male ice hockey players with and without hip and groin problems in the previous season- a prospective cohort study.

OBJECTIVE: To describe and compare hip and groin strength and function of male ice hockey players over one season in players with and without hip and groin problems in the previous season. DESIGN: Prospective cohort study. SETTING: Swedish male ice hockey. PARTICIPANTS: We followed 193 players from 10 teams during the 2017/2018 season. MAIN OUTCOME MEASURES: Hip adduction and abduction strength, 5 s squeeze test (5SST), and self-reported hip and groin function (Hip and Groin Outcome Score). Changes over the season and differences between players with and without problems in the previous season were analyzed by linear mixed models. RESULTS: Adduction strength decreased slightly from pre-to mid-season and abduction strength increased slightly over the full season. However, self-reported function or pain did not change. Players with hip and groin problems in the previous season had significantly worse self-reported function, and more groin pain during the 5SST compared to players without. Strength measurments did not differ between groups. CONCLUSIONS: Hip muscle strength, groin pain, and self-reported function appear to remain stable throughout the season in male ice hockey players. Remaining impairments in players with problems in the previous season suggest that function does not recover by ice hockey participation alone.

Rapid decline of yearly number of hip arthroscopies in Sweden: a retrospective time series of 6,105 hip arthroscopies based on a national patient data register.

Background and purpose - Hip arthroscopies (HAs) have increased exponentially worldwide and are expected to continue rising. We describe time trends in HA procedures in Sweden (10 million inhabitants) between 2006 and 2018 with a focus on procedure rates, surgical procedures, and patient demographics such as age and sex distribution.Patients and methods - We retrospectively collected data from the Swedish National Patient Register (NPR) for all surgeries including surgical treatment codes considered relevant for HA from 2006 to 2018. Surgical codes were validated through a multiple-step procedure and classified into femoroacetabular impingement syndrome (FAIS) related or non-FAIS related procedure. Frequencies, sex differences, and time trends of surgical procedures and patient demographics are presented.Results - After validation of HA codes, 6,105 individual procedures, performed in 4,924 patients (mean age 34 years [SD 12]) were confirmed HAs and included in the analysis. Yearly HA procedure rates increased from 15 in 2006 to 884 in 2014, after which a steady decline was observed with 469 procedures in 2018. The majority (65%) of HAs was performed in males. Male patients were younger, and surgeries on males more frequently included an FAIS-related procedure.Interpretation - Similar to previous studies in other parts of the world, we found dramatic increases in HA procedures in Sweden between 2006 and 2014. Contrary to existing predictions, HA rates declined steadily after 2014, which may be explained by more restrictive patient selection based on refined surgical indications, increasing evidence, and clinical experience with the procedure.

Improvements After Arthroscopic Treatment for Femoroacetabular Impingement Syndrome in High-Level Ice Hockey Players: 2-Year Outcomes by Player Position.

BACKGROUND: Ice hockey players often undergo arthroscopic treatment for femoroacetabular impingement syndrome (FAIS); however, only a few studies have reported postoperative patient-reported outcomes. It has been debated whether player position is related to FAIS. PURPOSE: To evaluate the change in patient-reported outcome measures (PROMs) in high-level ice hockey players from presurgery to 2 years after arthroscopic treatment for FAIS. The secondary aim was to evaluate differences in outcomes among player positions and whether stick handedness is related to the side of the symptomatic hip. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Ice hockey players undergoing treatment for FAIS between 2011 and 2019 were prospectively included. Preoperative and 2-year follow-up scores were collected for the following PROMs: HAGOS (Copenhagen Hip and Groin Outcome Score), iHOT-12 (12-item International Hip Outcome Tool), EQ-5D (EuroQol-5 Dimensions) and EQ-VAS (EuroQol-Visual Analog Scale), Hip Sports Activity Scale, and visual analog scale for overall hip function. Player position and stick handedness were collected from public sources. Preoperative and follow-up outcomes were compared for the entire cohort and among player positions. RESULTS: The cohort included 172 ice hockey players with a mean age of 28 years, a mean body mass index of 25.6, and a mean symptom duration of 46.3 months. In the 120 players with 2-year follow-up data, there was significant improvement in all PROMs as compared with presurgery: HAGOS subscales (symptoms, 47.5 vs 68.0; pain, 57.0 vs 75.8; activities of daily living, 62.5 vs 81.0; sports, 40.0 vs 64.7; physical activity, 30.9 vs 57.2; quality of life, 32.5 vs 57.8), iHOT-12 (45.2 vs 66.7), EQ-5D (0.59 vs 0.75), EQ-VAS (68.3 vs 73.2), and visual analog scale for overall hip function (49.6 vs 69.2) (P < .0001 for all). At 2-year follow-up, 83% reported satisfaction with the procedure. There was no difference in the improvement in PROMs among player positions. Further, there was no significant relationship between stick handedness and side of symptomatic hip; however, because of the number of bilateral procedures and large number of left-handed shooters, no conclusions could be drawn. CONCLUSION: High-level ice hockey players undergoing arthroscopic treatment for FAIS reported improvements in PROMs 2 years after surgery, regardless of player position.

Adeno-associated virus capsid assembly is divergent and stochastic.

Adeno-associated viruses (AAVs) are increasingly used as gene therapy vectors. AAVs package their genome in a non-enveloped T = 1 icosahedral capsid of ~3.8 megaDalton, consisting of 60 subunits of 3 distinct viral proteins (VPs), which vary only in their N-terminus. While all three VPs play a role in cell-entry and transduction, their precise stoichiometry and structural organization in the capsid has remained elusive. Here we investigate the composition of several AAV serotypes by high-resolution native mass spectrometry. Our data reveal that the capsids assemble stochastically, leading to a highly heterogeneous population of capsids of variable composition, whereby even the single-most abundant VP stoichiometry represents only a small percentage of the total AAV population. We estimate that virtually every AAV capsid in a particular preparation has a unique composition. The systematic scoring of the simulations against experimental native MS data offers a sensitive new method to characterize these therapeutically important heterogeneous capsids.

Complete and cooperative in vitro assembly of computationally designed self-assembling protein nanomaterials.

Recent advances in computational methods have enabled the predictive design of self-assembling protein nanomaterials with atomic-level accuracy. These design strategies focus exclusively on a single target structure, without consideration of the mechanism or dynamics of assembly. However, understanding the assembly process, and in particular its robustness to perturbation, will be critical for translating this class of materials into useful technologies. Here we investigate the assembly of two computationally designed, 120-subunit icosahedral complexes in detail using several complementary biochemical methods. We found that assembly of each material from its two constituent protein building blocks was highly cooperative and yielded exclusively complete, 120-subunit complexes except in one non-stoichiometric regime for one of the materials. Our results suggest that in vitro assembly provides a robust and controllable route for the manufacture of designed protein nanomaterials and confirm that cooperative assembly can be an intrinsic, rather than evolved, feature of hierarchically structured protein complexes.