Does Artificial Intelligence Outperform Humans Using Fluoroscopic-Assisted Computer Navigation for Total Hip Arthroplasty?

Background: Successful total hip arthroplasty (THA) relies on the correct implant position. THA accuracy can be improved with the use of intraoperative fluoroscopic-assisted computer navigation. Artificial intelligence (AI) software may enhance fluoroscopic navigation; however, the accuracy of the AI compared to human-controlled software in assessing acetabular component position and leg length discrepancy (LLD) has not been studied. Methods: We analyzed 420 consecutive primary THAs performed by a single surgeon using fluoroscopic-assisted computer navigation software. The first cohort of 211 patients required inputs from a human technician (manual), while the second cohort of 209 patients used an automated version of the software controlled by AI. The intraoperative acetabular component placement (inclination and anteversion) and LLD were recorded and compared to the 2-week postoperative standing anterior-posterior pelvis radiograph. Results: Ninety-four percent (199/211) of cups in the manual cohort and 95% (198/209) of cups in the AI cohort were within the Lewinnek "safe-zone" (P = 1.0). In the manual cohort, 69% (146/211) of THAs had a final LLD within ±2 mm of the intraoperatively navigated LLD (ie, ΔLLD ≤2 mm). In the AI cohort, 66% (137/209) of THAs had a final LLD within ±2 mm of the intraoperatively navigated LLD (P = .47). Ninety-nine percent (209/211) of hips in the manual cohort and 98% (205/209) of hips in the AI cohort had a final LLD within ±5 mm of the intraoperatively navigated LLD (P = .45). Conclusions: Both AI and human-controlled versions of the same navigation platform were similarly accurate for navigating cup position within the Lewinnek "safe zone" and LLD accuracy.

Fluoroscopy-Assisted Computer Navigation Accurately Determines Cup Position and Leg Length for Anterior Hip Arthroplasty.

BACKGROUND: Recently, fluoroscopy-assisted computer navigation has been developed to assess intraoperative cup inclination/anteversion and leg-length discrepancy (LLD) in the operating room. However, there is a relative dearth of studies investigating the accuracy of this software compared with postoperative radiographs. MATERIALS AND METHODS: We prospectively enrolled 211 navigated anterior total hip arthroplasties using fluoroscopy-assisted computer navigation software. Intraoperative navigated measurements were compared with postoperative anteroposterior radiographs to assess accuracy of cup inclination/anteversion and LLD. Continuous variables were analyzed using the Student's t test, and categorical variables were analyzed using Fisher's exact test. RESULTS: On postoperative radiographs, 94.3% of cups (199 of 211) were positioned within the Lewinnek "safe zone," compared with 99.1% navigated intraoperatively (P=.01). Eighty-two percent of hips (174 of 211) were navigated intraoperatively to LLDs within ±2 mm; on postoperative radiographs, 65% of hips (138 of 211) had LLDs within ±2 mm (P=.0001). Intraoperatively, 100% of hips (211 of 211) were navigated to LLDs within ±5 mm; similarly, on postoperative radiographs, 98% of hips (207 of 211) had LLDs within ±5 mm (P=.12). CONCLUSION: A novel fluoroscopy-assisted computer navigation platform accurately assessed intraoperative cup position and LLD during anterior total hip arthroplasty. Careful attention to fluoroscopic technique, positioning of radiographic landmarks, and knowledge of the limitations of fluoroscopy, including parallax effect, are important concepts that surgeons should incorporate into their decision algorithm. [Orthopedics. 2024;47(4):e174-e180.].

Handheld Navigation Improves Accuracy in Direct Anterior Total Hip Replacement.

Background: This study sought to determine the accuracy in placing the acetabular component, estimation of leg length, offset, radiation time and dose, and operative time using a handheld navigation device compared to conventional anterior total hip arthroplasty (THA). It also examined the learning curve of the handheld navigation device. Methods: Data were prospectively collected for a consecutive series of 159 THAs; 99 THAs with handheld navigation and 60 conventional THAs. Thresholds of <5°, ≥5° to <10°, and ≥10° for acetabular inclination and version and thresholds of <5 mm, ≥5 mm to <10 mm, and ≥10 mm for leg-length and combined offset discrepancy were used to assess accuracy. Fluoroscopy time and exposure, operative time, and complications were compared. Learning curve was determined using operative time. Statistical analysis was performed for the different accuracy thresholds with P values set a <0.05 for significance. Results: The handheld navigation device demonstrated a mean accuracy of 3.2° and 1.8° for version and inclination, respectively. The handheld navigation group had significantly fewer outliers in version (P < .001), inclination (P < .001), leg-length discrepancy (P < .001), and offset discrepancy (P < .001). Fluoroscopic dose and time (P < .001) were lower in the handheld navigation cohort. The learning curve for handheld navigation was 31-35 cases. The mean operative time after the learning curve was similar to that in the conventional fluoroscopy group (P = .113). Conclusions: Handheld navigation technology provided more accurate results while mitigating radiation exposure to the surgeon and patient. There were fewer outliers in the handheld navigation group. After the learning curve, all metrics improved in accuracy, and operative time was similar to that of the conventional technique.

Erratum to 'Adverse Reaction to Zirconia in a Modern Total Hip Arthroplasty With Ceramic Head' [Arthroplasty Today 6 (2020) 612-616].

[This corrects the article DOI: 10.1016/j.artd.2020.03.009.].

No Effect of Surgical Approach on Discharge Outcomes in Outpatient Total Hip Arthroplasty.

Background: The interest in ambulatory total hip arthroplasty (THA) has increased recently due to a national focus on value-based care and improved rapid recovery protocols. Purpose: We sought to determine if surgical approach had an effect on discharge outcomes in outpatient THA. Methods: We performed a retrospective cohort study examining patients who underwent unilateral THA at a single institution using a standardized perioperative care pathway who were discharged home within 24 hours. In total, we compared 106 patients who underwent THA using the direct anterior approach (ATHA) and 90 patients who underwent THA using the posterior approach (PTHA). Univariate and multivariable analyses were used to compare time to ambulation, length of surgery, readmissions, and 90-day complications. Results:Time to ambulation in the ATHA and PTHA groups was 3.9 hours and 4.1 hours, respectively, and time to discharge was 5.9 hours and 6.0 hours, respectively. Length of surgery was shorter in the ATHA group than in the PTHA group (78 minutes vs 86 minutes, respectively). Complications occurred in 3 patients (3%) in the ATHA group vs 4 patients (4%) in PTHA group. In both groups, early ambulation (within 5 hours) predicted earlier time to discharge. Surgical approach was not associated with time to ambulation or time to discharge on multivariable analysis. Conclusion: In this retrospective study, outpatient THA was feasible in a well-selected population of patients undergoing anterior or posterior approaches. Further study is warranted.

Favorable Radiographic and Early Postoperative Results with the Inguinal Crease Direct Anterior Total Hip Arthroplasty.

We report the results, scar appearance, and patient satisfaction of a direct anterior approach total hip arthroplasty performed through an oblique inguinal incision. Patients were separated into direct anterior THA (n = 29) or an oblique inguinal incision anterior approach (n = 41). Clinical and radiographic data was compared, scar appearance was assessed by the Vancouver Scar Scale (VSS), and satisfaction was assessed by a simple questionnaire. Harris Hip Scores significantly improved in each group (1.8×10-8) and improved similarly between groups (p ≥ 0.35). The VSS score was lower in the inguinal incision versus the standard incision group (0.68 [range 0-3] vs. 1.56 [range 0-4], p = 0.015). Scar satisfaction was higher in the inguinal incision group with 87% compared to only 32% in the standard approach. The inguinal incision approach was safe, offered similar postoperative results, and resulted in improved patient scar satisfaction compared to the standard anterior approach by using an incision that more closely resembled normal anatomy. (Journal of Surgical Orthopaedic Advances 31(1):056-060, 2022).

Comparison of Self-reported Versus Actual Height and Weight in the Orthopaedic Population.

The purpose of our study was to determine the accuracy of orthopaedic patient's reported height, weight, and body mass index (BMI). We hypothesized that patient's age, sex and/or BMI may affect their accuracy. We performed a prospective, observational study in the setting of our orthopaedic clinic. Differences between self-reported and actual values were calculated. Patients were categorized based on their age (< 65 vs. ≥ 65), sex, and actual BMI (<30 vs. >30). Student t-test and chi-square test were used to compare groups. Our study included 329 patients. Patients were more likely to underestimate weight (p < 0.001) and overestimate height (p = 0.007). Comparing patients with a BMI < 30 and > 30, height overestimation (0cm vs. 1.14cm, p = 0.004) and weight underestimation (0.09kg vs. 1.29kg, p = 0.02) discrepancies were greater in the BMI > 30 group. Patients, particularly with a BMI >30 kg/m2, over-estimate their height and under-estimate their weight. (Journal of Surgical Orthopaedic Advances 30(3):176-180, 2021).

Is Dislocation Risk due to Posterior Pelvic Tilt Reduced With Direct Anterior Approach Total Hip Arthroplasty?

BACKGROUND: Pelvic tilt affects acetabular anteversion, and thus total hip arthroplasty (THA) dislocation risk. The pubic symphysis-sacrococcygeal distance (PSCD) is an indicator of pelvic tilt, and a PSCD < 0 mm (ie, excessive posterior pelvic tilt) is associated with a 3.7-fold increase in postoperative dislocation rate. However, it is not known if the direct anterior (DA) approach might reduce this dislocation rate, specifically in high-risk populations such as negative PSCD. METHODS: Standing anteroposterior radiographs were reviewed for 510 consecutive DA THAs to determine PSCD. Patients were separated into 2 groups: (1) PSCD > 0 mm (PSCD[+]) and (2) PSCD < 0 mm (PSCD[-]). Incidence of dislocation was determined. We recorded if patients had spinal deformity or lumbar fusion. Continuous variables were analyzed using Student's t-test, categorical variables were analyzed using Fisher's exact test, and a sample size calculation was performed. RESULTS: Three hundred fifty-eight hips (70.2%) were PSCD[+], while 152 hips (29.8%) were PSCD[-]. Three dislocations (3/510 hips, 0.6%) occurred. Two dislocators were in the PSCD[-] group (2/152 hips, 1.3%) and 1 dislocator was in the PSCD[+] group (1/358 hips, 0.3%) (P = .21). Twenty-four patients had degenerative scoliosis (24/510, 4.7%), of which 1 had a dislocation (1/24, 4.2%); 2 dislocations occurred in nonscoliosis patients (2/486, 0.4%) (P = .134). Twenty-seven patients had lumbar spinal fusion (27/510, 5.3%), of which there were no dislocations (0/27, 0.0%); all dislocations were in nonfusion patients (3/483, 0.6%) (P = 1.0). CONCLUSION: We demonstrate no increased risk for THA dislocation in patients with a PSCD < 0 mm who have undergone a DA approach. These data would suggest a protective effect of the DA approach against dislocation, even in historically high-risk populations.

Can robotic technology mitigate the learning curve of total hip arthroplasty?

AIMS: Traditionally, acetabular component insertion during total hip arthroplasty (THA) is visually assisted in the posterior approach and fluoroscopically assisted in the anterior approach. The present study examined the accuracy of a new surgeon during anterior (NSA) and posterior (NSP) THA using robotic arm-assisted technology compared to two experienced surgeons using traditional methods. METHODS: Prospectively collected data was reviewed for 120 patients at two institutions. Data were collected on the first 30 anterior approach and the first 30 posterior approach surgeries performed by a newly graduated arthroplasty surgeon (all using robotic arm-assisted technology) and was compared to standard THA by an experienced anterior (SSA) and posterior surgeon (SSP). Acetabular component inclination, version, and leg length were calculated postoperatively and differences calculated based on postoperative film measurement. RESULTS: Demographic data were similar between groups with the exception of BMI being lower in the NSA group (27.98 vs 25.2; p = 0.005). Operating time and total time in operating room (TTOR) was lower in the SSA (p < 0.001) and TTOR was higher in the NSP group (p = 0.014). Planned versus postoperative leg length discrepancy were similar among both anterior and posterior surgeries (p > 0.104). Planned versus postoperative abduction and anteversion were similar among the NSA and SSA (p > 0.425), whereas planned versus postoperative abduction and anteversion were lower in the NSP (p < 0.001). Outliers > 10 mm from planned leg length were present in one case of the SSP and NSP, with none in the anterior groups. There were no outliers > 10° in anterior or posterior for abduction in all surgeons. The SSP had six outliers > 10° in anteversion while the NSP had none (p = 0.004); the SSA had no outliers for anteversion while the NSA had one (p = 0.500). CONCLUSION: Robotic arm-assisted technology allowed a newly trained surgeon to produce similarly accurate results and outcomes as experienced surgeons in anterior and posterior hip arthroplasty. Cite this article: Bone Jt Open 2021;2(6):365-370.

Genicular Artery Embolization for Refractory Hemarthrosis following Total Knee Arthroplasty: Technique, Safety, Efficacy, and Patient-Reported Outcomes.

PURPOSE: To investigate the safety and efficacy of genicular artery embolization for treatment of refractory hemarthrosis following total knee arthroplasty. MATERIAL AND METHODS: Patients who underwent genicular artery embolization with spherical embolics between January 2010 and March 2020 at a single institution were included if they had undergone total knee arthroplasty and subsequently experienced recurrent hemarthrosis. Technical success was defined as the significant reduction or elimination of the hyperemic blush. Clinical success was defined as the absence of clinical evidence of further hemarthrosis. Clinical follow-up was performed 7-14 days after the procedure and at 3-month intervals thereafter via a telephone interview. A total of 117 embolizations, comprising 82 initial, 28 first repeat, and 7 second repeat, were performed. RESULTS: An average of 2.5 arteries was treated per procedure. The superior lateral genicular artery was the most frequently embolized. The most utilized embolic size was 100-300 µm. Follow-up was available for all patients, with a median duration of 21.5 months. 65.9%, 25.6%, and 8.5% of patients underwent 1, 2, and 3 treatments, respectively. Complications occurred following 12.8% of treatments, of which the most common was transient cutaneous ischemia. Technical success was achieved in all cases. Clinical success was achieved in 56%, 79%, and 85% of patients following the first, second, and third treatment, respectively. 83% of patients reported being either satisfied or very satisfied with the overall result. CONCLUSIONS: Targeted genicular artery embolization with spherical embolics is an effective treatment for recurrent hemarthrosis with infrequent serious complications. Repeat embolization should be considered in cases of recurrence following initial therapy.

Adverse Reaction to Zirconia in a Modern Total Hip Arthroplasty with Ceramic Head.

Hypersensitivity reactions to zirconia (ZrO2) or similar ceramics is highly unusual. Owing to the stable oxide formed between the base metal and oxygen, ceramics are considered relatively biologically inert. We report the case of an otherwise healthy 50-year-old woman with a 5-year history of progressively worsening right hip pain who underwent a ceramic-on-polyethylene total hip replacement and subsequently developed hypersensitivity reaction. After metal allergy testing showed her to be highly reactive to zirconium, the femoral head was revised to a custom titanium implant and her symptoms resolved.

Prospective Evaluation of a Noninvasive Hemoglobin Measurement System in Total Joint Arthroplasty.

We sought to prospectively determine the efficacy of a noninvasive hemoglobin measurement system compared to a traditional blood draw in patients undergoing total joint arthroplasty. One hundred consecutive patients had their hemoglobin level measured by blood draw and the noninvasive device, simultaneously. Results were analyzed for the entire group and further stratified based on race and perfusion index measured by the device. The financial implications and patient satisfaction were compared. Hemoglobin measurements in the entire group and the two sub-groups were similar between the noninvasive device and the traditional blood draw. The noninvasive system was preferred by 100% of patients. Additionally, cost savings per patient using the noninvasive system was $16.50. This correlated to an 86% savings per case over the standard blood draw. The noninvasive hemoglobin monitoring system offers comparable measurements to a standard blood draw, while improving patient satisfaction and lowering costs. (Journal of Surgical Orthopaedic Advances 29(2):94-98, 2020).

Insulin-Dependent Diabetic Patients are at Increased Risk of Postoperative Hyperglycemia When Undergoing Total Joint Arthroplasty.

BACKGROUND: Diabetic patients are at an increased risk of prosthetic joint infection (PJI) after total joint arthroplasty (TJA). The relationship between insulin-dependence and PJI has not been investigated. We aimed at evaluating whether insulin-dependent diabetes mellitus (IDDM) patients were more susceptible to postoperative hyperglycemia and PJI than their non-insulin-dependent diabetes mellitus (NIDDM) counterparts. METHODS: A retrospective review was conducted of diabetic patients undergoing TJA (hip or knee) from January 2011 to December 2016. Preoperative hemoglobin A1c (A1c) and postoperative glucose measurements were observed. Patients were stratified as IDDM or NIDDM. The A1c values that predicted hyperglycemia >200 mg/dL for each group were calculated. Primary end point was postoperative hyperglycemia >200 mg/dL and secondary end point was PJI. RESULTS: There were 773 patients meeting inclusion criteria. The IDDM cohort had a higher preoperative A1c (6.97% vs 6.28%, P < .0001) and postoperative glucose (235.2 vs 163.5, P < .0001). IDDM patients were more likely to have postoperative hyperglycemia (63.84% vs 20.83%, P < .0001; odds ratio, 5.2; 95% confidence interval, 3.66-7.4). Overall, an A1c of >7.45% predicted postoperative hyperglycemia >200 mg/mL (odds ratio, 6.94; 95% confidence interval, 4.32-11.45). When separating our 2 cohorts, an A1c of >6.59% in IDDM, and >6.60% in NIDDM, was associated with an increased risk of postoperative hyperglycemia (P < .0001). PJI was similar between the 2 cohorts (2.52% vs 2.38%, P = .9034). CONCLUSION: IDDM patients undergoing TJA are 5.2 times more likely to have postoperative hyperglycemia >200 mg/dL than their NIDDM counterparts, although increased risk of PJI was not found in this study. Despite the higher A1c and postoperative hyperglycemia in IDDM patients, there was found to be no clinical difference between A1c cutoff values for postoperative hyperglycemia between IDDM and NIDDM patients.

Anesthesia and Analgesia Practices in Total Joint Arthroplasty: A Survey of the American Association of Hip and Knee Surgeons Membership.

BACKGROUND: The purpose of this study is to survey the current analgesia and anesthesia practices used by total joint arthroplasty surgeon members of the American Association of Hip and Knee Surgeons (AAHKS). METHODS: A survey of 28 questions was created and approved by the AAHKS Research Committee. The survey was distributed to all 2208 board-certified adult reconstruction surgeon members of AAHKS in November 2018. RESULTS: There were 622 responses (28.2%) to the survey. A majority of respondents (93.2%, n = 576) use preemptive analgesia prior to total joint arthroplasty. Most respondents use a spinal for total knee arthroplasty (TKA) (74.4%) and total hip arthroplasty (THA) (72.6%). A peripheral nerve block is routinely used by 68.7% of respondents in primary TKA. Periarticular injection or local infiltration anesthesia is routinely used by 80.3% of respondents for both TKA and THA patients. The average number of opioid pills prescribed postoperatively after TKA is 49 pills (range 0-200) and after THA is 44 pills (range 0-200). Most surgeons (58%) expect that this prescription should last for 2 weeks. A majority of respondents (74.0%) use multimodal analgesics in addition to opioids. CONCLUSION: There is no consensus regarding the optimal multimodal anesthetic and analgesic regimen for total joint arthroplasty among surveyed board-certified arthroplasty surgeon members of AAHKS. Understanding current practice patterns in anesthesia, analgesia, and opioid prescribing may serve as a platform for future work aimed at establishing best clinical practices of maximizing effective postoperative pain control and minimizing the risks associated with prescribing opioids.

Web-based patient portal access in an orthopedic adult reconstruction patient population.

BACKGROUND: We surveyed patients in an adult reconstruction practice as to their use of the Web-based portal provided by our electronic health record, seeking to reveal patterns of use and helpfulness. METHODS: A total of 150 completed surveys were received. The survey queried demographics, the number of clinic visits, Internet access, portal activation, portal use frequency, and portal information questions and how patients answered them. Helpfulness was rated from 1 (not helpful) to 5 (very helpful). Statistical analysis included bivariate analysis and logistic regression, with odds ratio (OR) and 95% confidence interval (CI) reported. RESULTS: The mean age was 67.6 years. Most were females (n = 97, 65.1%). Most (68.7%) patients used the portal. Younger age (OR, 0.94; CI, 0.90-0.99) and access to Internet (OR, 31.8; CI, 8.5-119.4) predicted portal use (P < .005), whereas gender and number of clinic visits did not (P > .373). Of all, 47.5% of patients were unclear about online chart information. Older age indicated being unclear of portal information (68.5 vs 66, P = .0002). Of those who clarified doubts regarding information (n = 67), 23 used the Internet (34.3%), 32 (47.7%) called the physician, and 12 (17.9%) asked a friend and/or family member. Most (90.3%) patients felt the portal was helpful in gathering health information. CONCLUSIONS: Age and Internet access affected portal usage; ability to understand chart information decreased with age. Most patients used the Internet or a family member to clarify doubts regarding portal information. The use of portal data resulted in 32 extra communications to the physician.

Have large femoral heads reduced prosthetic impingement in total hip arthroplasty?

BACKGROUND:: Prosthetic impingement is implicated in dislocation after total hip arthroplasty (THA). While use of larger diameter femoral heads reduces the incidence of dislocation, the effect of larger heads upon impingement rate is unknown. We assessed retrieved THA components for evidence of impingement to determine if large femoral heads reduced the rate of impingement in primary THA and what factors might influence impingement. METHODS:: Liners from 97 primary THAs retrieved at revision arthroplasty were scored for evidence of impingement, defined as wear or deformation on the rim of the component. Component inclination and version were measured from anteroposterior and cross-table lateral radiographs. RESULTS:: Independent of revision diagnosis, 77% of liners demonstrated evidence of impingement. Impingement was less prevalent and less severe as head size increased. Severe impingement was observed in 50% of the liners with 28-mm heads, 15% of liners with 32-mm heads, and 21% of liners with 36-mm heads. Regardless of head size, 76% of liners revised for instability demonstrated impingement. Decreased head-neck ratio, use of an elevated liner, increased length of implantation, and increased version were associated with increased severity of impingement. DISCUSSION:: We showed that larger head sizes are associated with decreased incidence of impingement on retrieved acetabular liners when compared to smaller head sizes. Larger heads have reduced but not eliminated impingement, which remains a potential source of instability.

Preoperative Glycemic Control Predicts Perioperative Serum Glucose Levels in Patients Undergoing Total Joint Arthroplasty.

BACKGROUND: Diabetic patients undergoing total joint arthroplasty (TJA) with postoperative hyperglycemia >200 mg/dL have increased the risk of prosthetic joint infection (PJI). We investigated the correlation between preoperative hemoglobin A1c (A1c) and postoperative hyperglycemia in diabetic patients undergoing TJA. METHODS: A retrospective review of 773 diabetic patients undergoing TJA was conducted. A Youden's J computational analysis determined the A1c where postoperative glucose levels >200 mg/dL were statistically more likely. Patients were then stratified into 3 groups: A1c <7%, A1c 7.0-8.0%, and A1c >8.0%. Outcomes included the highest postoperative in-hospital serum glucose level and PJI. RESULTS: We determined an A1c >7.45% resulted in a greater chance of postoperative hyperglycemia >200 mg/dL. Average postoperative serum glucose increased with A1c (A1c < 7 = 167 mg/dL, A1c 7.0-8.0 = 240 mg/dL, and A1c > 8 = 276 mg/dL, P < .0001). PJI did not statistically increase with A1c (2.25%, 1.99%, and 4.55%, respectively, P = .4319). CONCLUSION: Preoperative hemoglobin A1c levels correlate with postoperative glucose levels. We recommend using an A1c cutoff of 7.45% for patients undergoing TJA and suggest that caution should be exercised in patients with elevated A1c levels undergoing TJA.

Early intraprosthetic dislocation in dual-mobility implants: a systematic review.

BACKGROUND: Dual mobility implants are subject to a specific implant-related complication, intraprosthetic dislocation (IPD), in which the polyethylene liner dissociates from the femoral head. For older generation designs, IPD was attributable to late polyethylene wear and subsequent failure of the head capture mechanism. However, early IPDs have been reportedly affecting contemporary designs. METHODS: A systematic review of the literature according to the preferred reporting items for systematic reviews and meta-analyses guidelines was performed. A comprehensive search of PubMed, MEDLINE, Embase, and Google Scholar was conducted for English articles between January 1974 and August 2016 using various combinations of the keywords "intraprosthetic dislocation," "dual mobility," "dual-mobility," "tripolar," "double mobility," "double-mobility," "hip," "cup," "socket," and "dislocation." RESULTS: In all, 16 articles met our inclusion criteria. Fourteen were case reports and 2 were retrospective case series. These included a total of 19 total hip arthroplasties, which were divided into 2 groups: studies dealing with early IPD after attempted closed reduction and those dealing with early IPD with no history of previous attempted closed reduction. Early IPD was reported in 15 patients after a mean follow-up of 3.2 months (2.9 SD) in the first group and in 4 patients after a mean follow-up of 15.1 months (9.9 SD) in the second group. CONCLUSIONS: Based on the current data, most cases have been preceded by an attempted closed reduction in the setting of outer, large articulation dislocation, perhaps indicating an iatrogenic etiology for early IPD. Recognition of this possible failure mode is essential to its prevention and treatment.