Incidence of Total Knee Arthroplasty After Arthroscopic Surgery for Knee Osteoarthritis: A Secondary Analysis of a Randomized Clinical Trial.

Importance: It is unclear whether arthroscopic resection of degenerative knee tissues among patients with osteoarthritis (OA) of the knee delays or hastens total knee arthroplasty (TKA); opposite findings have been reported. Objective: To compare the long-term incidence of TKA in patients with OA of the knee after nonoperative management with or without additional arthroscopic surgery. Design, Setting, and Participants: In this ad hoc secondary analysis of a single-center, assessor-blinded randomized clinical trial performed from January 1, 1999, to August 31, 2007, 178 patients were followed up through March 31, 2019. Participants included adults diagnosed with OA of the knee referred for potential arthroscopic surgery in a tertiary care center specializing in orthopedics in London, Ontario, Canada. All participants from the original randomized clinical trial were included. Data were analyzed from June 1, 2021, to October 20, 2022. Exposures: Arthroscopic surgery (resection or debridement of degenerative tears of the menisci, fragments of articular cartilage, or chondral flaps and osteophytes that prevented full extension) plus nonoperative management (physical therapy plus medications as required) compared with nonoperative management only (control). Main Outcomes and Measures: Total knee arthroplasty was identified by linking the randomized trial data with prospectively collected Canadian health administrative datasets where participants were followed up for a maximum of 20 years. Multivariable Cox proportional hazards regression models were used to compare the incidence of TKA between intervention groups. Results: A total of 178 of 277 eligible patients (64.3%; 112 [62.9%] female; mean [SD] age, 59.0 [10.0] years) were included. The mean (SD) body mass index was 31.0 (6.5). With a median follow-up of 13.8 (IQR, 8.4-16.8) years, 31 of 92 patients (33.7%) in the arthroscopic surgery group vs 36 of 86 (41.9%) in the control group underwent TKA (adjusted hazard ratio [HR], 0.85 [95% CI, 0.52-1.40]). Results were similar when accounting for crossovers to arthroscopic surgery (13 of 86 [15.1%]) during follow-up (HR, 0.88 [95% CI, 0.53-1.44]). Within 5 years, the cumulative incidence was 10.2% vs 9.3% in the arthroscopic surgery group and control group, respectively (time-stratified HR for 0-5 years, 1.06 [95% CI, 0.41-2.75]); within 10 years, the cumulative incidence was 23.3% vs 21.4%, respectively (time-stratified HR for 5-10 years, 1.06 [95% CI, 0.45-2.51]). Sensitivity analyses yielded consistent results. Conclusions and Relevance: In this secondary analysis of a randomized clinical trial of arthroscopic surgery for patients with OA of the knee, a statistically significant association with delaying or hastening TKA was not identified. Approximately 80% of patients did not undergo TKA within 10 years of nonoperative management with or without additional knee arthroscopic surgery. Trial Registration: ClinicalTrials.gov Identifier: NCT00158431.

Total knee replacement after high tibial osteotomy: time-to-event analysis and predictors.

BACKGROUND: An important aim of high tibial osteotomy (HTO) is to prevent or delay the need for total knee replacement (TKR). We sought to estimate the frequency and timing of conversion from HTO to TKR and the factors associated with it. METHODS: We prospectively evaluated patients with osteoarthritis (OA) of the knee who underwent medial opening wedge HTO from 2002 to 2014 and analyzed the cumulative incidence of TKR in July 2019. The presence or absence of TKR on the HTO limb was identified from the orthopedic surgery reports and knee radiographs contained in the electronic medical records for each patient at London Health Sciences Centre. We used cumulative incidence curves to evaluate the primary outcome of time to TKR. We used multivariable Cox proportional hazards analysis to assess potential preoperative predictors including radiographic disease severity, malalignment, correction size, pain, sex, age, body mass index (BMI) and year of surgery. RESULTS: Among 556 patients who underwent 643 HTO procedures, the cumulative incidence of TKR was 5% (95% confidence interval [CI] 3%-7%) at 5 years and 21% (95% CI 17%-26%) at 10 years. With the Cox proportional hazards multivariable model, the following preoperative factors were significantly associated with an increased rate of conversion: radiographic OA severity (adjusted hazard ratio [HR] 1.96, 95% CI 1.12-3.45), pain (adjusted HR 0.85, 95% CI 0.75-0.96)], female sex (adjusted HR 1.67, 95% CI 1.08-2.58), age (adjusted HR 1.50 per 10 yr, 95% CI 1.17-1.93) and BMI (adjusted HR 1.31 per 5 kng/m2, 95% CI 1.12-1.53). INTERPRETATION: We found that 79% of knees did not undergo TKR within 10 years after undergoing medial opening wedge HTO. The strongest predictor of conversion to TKR is greater radiographic disease at the time of HTO.

The Impact of Resident Involvement on Surgical Outcomes following Anterior Cruciate Ligament Reconstruction.

Hands-on participation in the operating room (OR) is an integral component of surgical resident training. However, the implications of resident involvement in many orthopaedic procedures are not well defined. This study aims to assess the effect of resident involvement on short-term outcomes following anterior cruciate ligament reconstruction (ACLR). The National Surgical Quality Improvement Program (NSQIP) database was queried to identify all patients who underwent ACLR from 2005 to 2012. Demographic variables, resident participation, 30-day complications, and intraoperative time parameters were assessed for all cases. Resident and nonresident cases were matched using propensity scores. Outcomes were analyzed using univariate and multivariate regression analyses, as well as stratified by resident level of training. Univariate analysis of 1,222 resident and 1,188 nonresident cases demonstrated no difference in acute postoperative complication rates between groups. There was no significant difference in the incidence of overall complications based on resident level of training (p = 0.109). Operative time was significantly longer for cases in which a resident was involved (109.5 vs. 101.7 minutes; p < 0.001). Multivariate analysis identified no significant predictors of major postoperative complications, while patient history of chronic obstructive pulmonary disease was the only independent risk factor associated with minor complications. Resident involvement in ACLR was not associated with 30-day complications despite a slight increase in operative time. These findings provide reassurance that resident involvement in ACLR procedures is safe, although future investigations should focus on long-term postoperative outcomes.

Trends in knee arthroscopy utilization: a gap in knowledge translation.

PURPOSE: To evaluate the longitudinal trends in knee arthroscopy utilization in relation to published negative randomized controlled trials, focusing on annual rates, patient demographics and associated 30-day post-operative complications. METHODS: The American College of Surgeons National Surgical Quality Improvement Program database was queried using Current Procedural Terminology billing codes to identify arthroscopy cases between 2006 and 2016. 30-day post-operative complications were identified, and potential risk factors analysed using univariate and multivariate analyses. RESULTS: 68,346 patients underwent knee arthroscopy, of which 47,446 (69.5%) represented partial meniscectomies. The annual procedural rate, as a proportion of all reported cases, increased significantly from 2006 (0.3%) to 2016 (1.6%; p < 0.001), along with a significant increase in average patient age (44.3 ± 15.5 to 48.4 ± 14.5; p < 0.001). Specifically focusing on the meniscectomy cohort, average patient age significantly increased from 47.9 ± 15.1 to 50.7 ± 13.5 (p = 0.001). The overall incidence of complications was 2.0% (n = 1333), with major complications in 0.9% (n = 639) and minor complications in 1.0% (n = 701). Common complications included a return to the operating room (0.5%), deep vein thrombosis/thrombophlebitis (0.4%), and superficial infection (0.2%). Operating time > 90 min, diabetes, steroid use, ASA class 2+, and dialysis-dependency were the predictors of overall complication rates. CONCLUSION: Despite the publication of negative trials and new clinical practice guidelines, knee arthroscopy utilization and average patient age continue to increase. Given the high utilization, even low adverse event rates equate to substantial numbers of patients with minor and major complications. The NSQIP data show a gap in knowledge translation to clinical practice and highlight the need for improved clinical guidelines. LEVEL OF EVIDENCE: Cohort study; Level III.

Correction to: A case series of lateral opening wedge high tibial osteotomy for valgus malalignment.

Unfortunately, one of the co-author affiliation was incorrect in the original publication of this article. The correct affiliation is given below: Abdulaziz Z. Alomar, King Khalid University Hospital, College of Medicine, King Saud University, Riyadh, Saudi Arabia.

Radiographic landmarks for surgical reconstruction of the anterolateral ligament of the knee.

PURPOSE: To determine the radiographic landmarks of the anterolateral ligament (ALL) on the femur and tibia to assist in intraoperative graft placement during ALL reconstruction. METHODS: The footprints of the ALL, fibular collateral ligament (FCL), popliteus insertion, lateral gastrocnemius insertion, and Gerdy's tubercle were isolated and centrally marked with tantalum beads in thirteen fresh-frozen cadaveric knees. Measurements were taken from the true lateral fluoroscopic images. On the femur, the mean distances from the ALL origin to the FCL origin and from the ALL origin to the popliteus insertion were measured. On the tibia, the mean distances from the ALL insertion to Gerdy's tubercle and from the ALL insertion to the lateral tibial plateau were measured. Furthermore, radiographic descriptions of the ALL origin and insertion were developed. RESULTS: The ALL origin on the femur averaged 3.3 ± 1.5 mm anterior-distal to the FCL origin in one anatomical variant and 5.4 ± 1.4 mm posterior-proximal to the FCL origin in a second variant. The ALL origin was 9.9 ± 2.7 mm from the popliteus insertion. The ALL origin is described as overlying the posterior femoral cortical line, between Blumensaat's line and a line from the posterior condylar articular edge parallel to Blumensaat's line. The ALL insertion on the tibia averaged 24.7 ± 4.5 mm posterior to Gerdy's tubercle and 11.5 ± 2.9 mm distal to the lateral tibial plateau. The tibial ALL insertion is described between the posterior tibial cortical line and a parallel line drawn down from the apex of the tibial spine, and overlying a line drawn perpendicular to the posterior tibial cortical line starting from the apex of the posterior tibial condyles. CONCLUSIONS: Using direct lateral fluoroscopy, radiographic landmarks of the ALL origin and insertion have been described.

Biomechanics of complex shoulder instability.

Identification and treatment of the osseous lesions associated with complex shoulder instability remains challenging. Further biomechanical testing is required to delineate critical defect values and determine which treatments provide improved glenohumeral joint stability for the various defect sizes, while minimizing the associated complications.

A biomechanical assessment of superior shoulder translation after reconstruction of anterior glenoid bone defects: The Latarjet procedure versus allograft reconstruction.

BACKGROUND: The coracoacromial ligament (CAL) is an important restraint to superior shoulder translation. The effect of CAL release on superior stability following the Latarjet is unknown; therefore, our purpose was to compare the effect of two Latarjet techniques and allograft reconstruction on superior instability. MATERIALS AND METHODS: Eight cadaveric specimens were tested on a simulator. Superior translation was monitored following an axial force in various glenohumeral rotations (neutral, internal, and external) with and without muscle loading. Three intact CAL states were tested (intact specimen, 30% glenoid bone defect, and allograft reconstruction) and two CAL deficient states (classic Latarjet (classicLAT) and congruent-arc Latarjet (congruentLAT)). RESULTS: In neutral without muscle loading, a significant increase in superior translation occurred with the classicLAT as compared to 30% defect (P = 0.046) and allograft conditions (P = 0.041). With muscle loading, the classicLAT (P = 0.005, 0.002) and the congruentLAT (P = 0.018, 0.021) had significantly greater superior translation compared to intact and allograft, respectively. In internal rotation, only loaded tests produced significant results; specifically, classicLAT increased translation compared to all intact CAL states (P < 0.05). In external rotation, only unloaded tests produced significant results with classicLAT and congruentLAT allowing greater translations than intact (P ≤ 0.028). For all simulations, the allograft was not significantly different than intact (P > 0.05) and no differences (P = 1.0) were found between classicLAT and congruentLAT. DISCUSSION: In most simulations, CAL release with the Latarjet lead to increased superior humeral translation. CONCLUSION: The choice of technique for glenoid bone loss reconstruction has implications on the magnitude of superior humeral translation. This previously unknown effect requires further study to determine its clinical and kinematic outcomes.

A case series of lateral opening wedge high tibial osteotomy for valgus malalignment.

INTRODUCTION: Lateral opening wedge high tibial osteotomy is a rarely employed surgical technique used for the treatment of lateral knee pain and degeneration in the setting of genu valgum. There exists little evidence of the suitability of this procedure for patients requiring osteotomies with a small correction. MATERIALS AND METHODS: A case series of 23 patients (24 knees) undergoing lateral opening wedge high tibial osteotomy with a minimum follow-up of 2 years was performed between 2002 and 2008. A surgical technique avoiding the need for fibular osteotomy is described. Adverse events, patient-reported outcomes and radiographic measures of alignment were assessed at baseline, at 6 months postoperatively, and at time of final follow-up. A subgroup of 12 patients also underwent 3D gait analysis at the same time points. RESULTS: The mean follow-up was 52 months (±20.4). Statistically and clinically significant improvements were identified in the lower extremity functional scale [mean change (95%CI) = 10 (2.4, 17.6)], and in the knee injury and osteoarthritis outcome score [mean change (95%CI) = 10.9 (0.5, 21.4)]. Mechanical axis changed from 2.4 ± 2.4° valgus to 0 ± 2.6° varus (p<0.001), anatomical axis from 6.9 ± 2.8° to 4.7 ± 2.5° valgus (p < 0.001), with weight-bearing line offset changing from 60.2 ± 11.4% to 49.5 ± 12.4% (p < 0.001). Change in lateral tibial slope, from 6.5 ± 2.2° to 7.5 ± 2.3°, was very small and not statistically significant (n.s.). The peak knee adduction moment during gait significantly increased [mean change (95%CI) = 0.72%BW*Ht (0.42, 1.02), suggesting a medial shift in dynamic knee joint load. Two patients underwent total knee arthroplasty during the study period. CONCLUSIONS: Lateral opening wedge high tibial osteotomy is a viable surgical option for patients with lateral knee pain and valgus malalignment requiring small degrees of correction. LEVEL OF EVIDENCE: IV.

A prospective, randomized evaluation of acellular human dermal matrix augmentation for arthroscopic rotator cuff repair.

PURPOSE: To prospectively evaluate the safety and effectiveness of arthroscopic acellular human dermal matrix augmentation of large rotator cuff tear repairs. METHODS: A prospective, institutional review board-approved, multicenter series of patients undergoing arthroscopic repair of 2-tendon rotator cuff tears measuring greater than 3 cm were randomized by sealed envelopes opened at the time of surgery to arthroscopic single-row rotator cuff repair with GraftJacket acellular human dermal matrix (Wright Medical Technology, Arlington, TN) augmentation (group 1) or without augmentation (group 2). Preoperative and postoperative functional outcome assessments were obtained by use of the American Shoulder and Elbow Surgeons (ASES), Constant, and University of California, Los Angeles scales. Gadolinium-enhanced magnetic resonance imaging (MRI) evaluation of these repairs was obtained at a mean of 14.5 months (range, 12 to 24 months). Adverse events were recorded. RESULTS: There were 22 patients in group 1 and 20 in group 2 with a mean age of 56 years. The mean follow-up was 24 months (range, 12 to 38 months). The ASES score improved from 48.5 to 98.9 in group 1 and from 46.0 to 94.8 in group 2. The scores in group 1 were statistically better than those in group 2 (P = .035). The Constant score improved from 41.0 to 91.9 in group 1 and from 45.8 to 85.3 in group 2. The scores in group 1 were statistically better than those in group 2 (P = .008). The University of California, Los Angeles score improved from 13.3 to 28.2 in group 1 and from 15.9 to 28.3 in group 2 (P = .43). Gadolinium-enhanced MRI scans showed intact cuffs in 85% of repairs in group 1 and 40% in group 2 (P < .01). No adverse events were attributed to the presence of the matrix grafts. CONCLUSIONS: Acellular human dermal matrix augmentation of large (>3 cm) cuff tears involving 2 tendons showed better ASES and Constant scores and more frequent intact cuffs as determined by gadolinium-enhanced MRI. Intact repairs were found in 85% of the augmented group and 40% of the nonaugmented group (P < .01). No adverse events related to the acellular human dermal matrix were observed. LEVEL OF EVIDENCE: Level II, lesser-quality randomized controlled trial.

Cemented versus uncemented fixation of humeral components in total shoulder arthroplasty for osteoarthritis of the shoulder: a prospective, randomized, double-blind clinical trial-A JOINTs Canada Project.

BACKGROUND: Although cemented humeral fixation is recognized as the standard of care in total shoulder arthroplasty (TSA), uncemented fixation has the potential to provide stable fixation, decrease operative time, and simplify potential revision procedures. This prospective, randomized, double-blind clinical trial compared cemented and uncemented humeral fixation in TSA for primary shoulder osteoarthritis. METHODS: Patients with primary shoulder osteoarthritis requiring replacement were screened for eligibility. After providing informed consent, subjects received baseline clinical and radiologic assessments, computed tomography scans, and standardized TSA. After glenoid component insertion, patients were randomized to either a cemented or uncemented humeral component. The primary outcome was the WOOS (Western Ontario Arthritis of the Shoulder Index) score at 2 years. Other outcomes included the Short Form 12 score, American Shoulder and Elbow Surgeons score, McMaster-Toronto Arthritis Patient Preference Disability Questionnaire, operative time, complications, and revisions. Patients were assessed by a blinded evaluator at 2 and 6 weeks and 3, 6, 12, 18, and 24 months postoperatively. RESULTS: In total, 161 patients consented to be included and were randomized: 80 in the cemented group and 81 in the uncemented group. There were no significant differences in demographics or baseline evaluations between groups, except for gender. The 12-, 18-, and 24-month WOOS scores showed a significant difference in favor of the cemented group. The cemented group also had better strength and forward flexion. As expected, the operative time was significantly less for the uncemented group. CONCLUSIONS: These findings provide level I evidence that cemented fixation of the humeral component provides better quality of life, strength, and range of motion than uncemented fixation.

A randomized trial of arthroscopic surgery for osteoarthritis of the knee.

BACKGROUND: The efficacy of arthroscopic surgery for the treatment of osteoarthritis of the knee is unknown. METHODS: We conducted a single-center, randomized, controlled trial of arthroscopic surgery in patients with moderate-to-severe osteoarthritis of the knee. Patients were randomly assigned to surgical lavage and arthroscopic débridement together with optimized physical and medical therapy or to treatment with physical and medical therapy alone. The primary outcome was the total Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score (range, 0 to 2400; higher scores indicate more severe symptoms) at 2 years of follow-up. Secondary outcomes included the Short Form-36 (SF-36) Physical Component Summary score (range, 0 to 100; higher scores indicate better quality of life). RESULTS: Of the 92 patients assigned to surgery, 6 did not undergo surgery. Of the 86 patients assigned to control treatment, all received only physical and medical therapy. After 2 years, the mean (+/-SD) WOMAC score for the surgery group was 874+/-624, as compared with 897+/-583 for the control group (absolute difference [surgery-group score minus control-group score], -23+/-605; 95% confidence interval [CI], -208 to 161; P=0.22 after adjustment for baseline score and grade of severity). The SF-36 Physical Component Summary scores were 37.0+/-11.4 and 37.2+/-10.6, respectively (absolute difference, -0.2+/-11.1; 95% CI, -3.6 to 3.2; P=0.93). Analyses of WOMAC scores at interim visits and other secondary outcomes also failed to show superiority of surgery. CONCLUSIONS: Arthroscopic surgery for osteoarthritis of the knee provides no additional benefit to optimized physical and medical therapy. (ClinicalTrials.gov number, NCT00158431.)

A randomized controlled trial comparing the effectiveness of functional knee brace and neoprene sleeve use after anterior cruciate ligament reconstruction.

BACKGROUND: Despite a lack of evidence for their effectiveness, functional knee braces are commonly prescribed to patients after anterior cruciate ligament (ACL) reconstruction. PURPOSE: This trial was conducted to compare postoperative outcomes in patients using an ACL functional knee brace and patients using a neoprene knee sleeve. HYPOTHESIS: Patients using a brace will have superior outcomes than those using a sleeve. STUDY DESIGN: Randomized controlled clinical trial; Level of evidence, 1. METHODS: One hundred fifty patients were randomized to receive a brace (n = 76) or neoprene sleeve (n = 74) at their 6-week postoperative visit after primary ACL reconstruction with hamstring autograft. Patients were assessed preoperatively, then 6 weeks and 6, 12, and 24 months postoperatively. Outcome measures included disease-specific quality of life (Anterior Cruciate Ligament-Quality of Life [ACL-QOL] Questionnaire), anterior tibial translation (KT-1000 arthrometer side-to-side difference), the single-limb forward hop test (limb symmetry index), and Tegner Activity Scale. Outcomes at 1 and 2 years were compared after adjusting for baseline scores. Subjective ratings of how patients felt while using the brace/sleeve were also collected for descriptive purposes using a questionnaire. Four a priori directional subgroup hypotheses were evaluated using tests for interactions. RESULTS: There were no significant differences between brace (n = 62) and sleeve (n = 65) groups for any of the outcomes at 1- and 2-year follow-ups. Adjusted mean differences at 2 years were as follows: -0.94 (95% confidence interval [CI], -7.52 to 5.64) for the ACL-QOL Questionnaire, -0.10 mm (95% CI, -0.99 to 0.81) for KT-1000 arthrometer side-to-side difference, -0.87% (95% CI, -8.89 to 7.12) for hop limb symmetry index, and -0.05 (95% CI, -0.72 to 0.62) for the Tegner Activity Scale. Subjective ratings of confidence in the knee provided by the brace/sleeve were higher for the brace group than the sleeve group. Subgroup findings were minimal. Adverse events were few and similar between groups. CONCLUSIONS: A functional knee brace does not result in superior outcomes compared with a neoprene sleeve after ACL reconstruction. Current evidence does not support the recommendation of using an ACL functional knee brace after ACL reconstruction.

Quality-of-life outcome following hemiarthroplasty or total shoulder arthroplasty in patients with osteoarthritis. A prospective, randomized trial.

BACKGROUND: Both total shoulder arthroplasty and hemiarthroplasty have been used commonly to treat severe osteoarthritis of the shoulder; however, their effect on disease-specific quality-of-life outcome is unknown. The purpose of this study was to compare the quality-of-life outcome following hemiarthroplasty with that following total shoulder arthroplasty in patients with osteoarthritis of the shoulder. METHODS: Forty-two patients with a diagnosis of osteoarthritis of the shoulder were randomized to receive a hemiarthroplasty or a total shoulder arthroplasty. One patient died, and all others were evaluated preoperatively and at six weeks and three, six, twelve, eighteen, and twenty-four months postoperatively with use of a standardized format including a disease-specific quality-of-life measurement tool (Western Ontario Osteoarthritis of the Shoulder [WOOS] index), general shoulder rating scales (University of California at Los Angeles [UCLA] shoulder scale, Constant score, and American Shoulder and Elbow Surgeons [ASES] evaluation form), general pain scales (McGill pain score and visual analogue scale), and a global health measure (Short Form-36 [SF-36]). When a patient required revision of a hemiarthroplasty to a total shoulder arthroplasty, the last score before he or she "crossed over" was used for the analysis. RESULTS: Significant improvements in disease-specific quality of life were seen two years after both the total shoulder arthroplasties and the hemiarthroplasties. There were no significant differences in quality of life (WOOS score) between the group treated with total shoulder arthroplasty and that treated with hemiarthroplasty (90.6 +/- 13.2 and 81.5 +/- 24.1 points, respectively; p = 0.18). The other outcome measures demonstrated similar findings. Two patients in the hemiarthroplasty group crossed over to the other group by undergoing a revision to a total shoulder arthroplasty because of glenoid arthrosis. CONCLUSIONS: Both total shoulder arthroplasty and hemiarthroplasty improve disease-specific and general quality-of-life measurements. With the small number of patients in our study, we found no significant differences in these measurements between the two treatment groups. LEVEL OF EVIDENCE: Therapeutic Level I.

The use of the impingement test as a predictor of outcome following subacromial decompression for rotator cuff tendinosis.

PURPOSE: To evaluate the use of the impingement test as a predictor of outcome following subacromial decompression for patients with rotator cuff tendinosis. TYPE OF STUDY: Observational study. METHODS: An impingement test was administered to each patient immediately before surgery. Patients underwent a subacromial decompression and were assessed postoperatively at 3 and 6 months. The primary outcome measure was the Western Ontario Rotator Cuff Index (WORC). RESULTS: Thirty patients (mean age, 47.0 years; range, 29.4 to 71.2 years) took part in this study. There was no significant correlation between the classic impingement test (Neer's impingement sign before and after subacromial injection of local anesthetic) and the change in WORC score (r = -.174, P =.358). Similar results were obtained for the aggregate impingement test (pain at rest plus Neer's impingement sign plus Hawkins sign plus resisted abduction) before and after subacromial injection of local anesthetic (r = -.208, P =.270). When divided into categories of improvement following the classic impingement test (worse 0%-25%, 26%-50%, 51%-75%, 76%-100% better), there was no significant difference between groups for outcome as indicated by WORC score (P =.203). Results were similar for the aggregate impingement test (P =.271). CONCLUSIONS: The impingement test is a poor tool for predicting the success of subacromial decompression. There are 6 assumptions discussed that must hold true in order for the impingement test to be a useful predictor of outcome following subacromial decompression. If one or more of these assumptions are not met, or are only partially met, the impingement test would be rendered invalid as a predictor of outcome, as this study suggests.