Diagnostic Test Performances for Identifying Periprosthetic Joint Infection in Hip Hemiarthroplasty

INTRODUCTION

Periprosthetic joint infection (PJI) is a devastating complication of hip hemiarthroplasty (HHA) that is not well-represented in the literature. Therefore, this study aimed to evaluate diagnostic markers for identifying PJI in patients after HHA and compare them with the most recent 2018 International Consensus Meeting on Musculoskeletal Infection criteria.

METHODS

A total of 98 patients (64 PJIs, 65.3%) were analyzed. Patients were identified by relevant Current Procedural Terminology and International Classification of Diseases-9/10 codes from 2000 to 2021 across a single healthcare system. Preoperative or intraoperative synovial fluid nucleated cell (NC) count, synovial polymorphonuclear (PMN) percentage, serum erythrocyte sedimentation rate (ESR), serum C-reactive protein (CRP), and serum white blood cell count were compared with Student t -test between aseptic and septic cohorts. Diagnostic utility and laboratory cutoff values were determined using receiver-operating characteristic curves and Youden index, respectively.

RESULTS

Mean values were significantly higher in the septic cohort for synovial NC count (120,992.2 versus 1,498.0 cells/μL, P < 0.001), synovial PMN percentage (91.3% versus 56.2%, P < 0.001), serum ESR (75.6 versus 36.3 mm/hr, P < 0.001), serum CRP (20.2 versus 125.8 mg/L, P < 0.001), and serum white blood cell count (8.5 versus 11.5 cells/μL, P < 0.001). Synovial NC count, synovial PMN percentage, and serum CRP had excellent PJI discriminatory ability with an area under the curve of 0.99, 0.90, and 0.93, respectively. Optimal cutoffs were 2,700 cells/μL for synovial NC count (100% sensitivity and 94% specificity), 81.0% for synovial PMN percentage (96% sensitivity and 89% specificity), 52.0 mm/hr for serum ESR (75% sensitivity and 80% specificity), and 40.0 mg/L for serum CRP (85% sensitivity and 92% specificity).

CONCLUSION

Our findings support the continued use of routine serum and synovial fluid tests for diagnosing PJI in HHA patients. Optimal cutoff values for both synovial fluid biomarkers were very close in alignment with the 2018 International Consensus Meeting criteria.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Deep-Learning Automation of Preoperative Radiographic Parameters Associated With Early Periprosthetic Femur Fracture After Total Hip Arthroplasty

BACKGROUND

The radiographic assessment of bone morphology impacts implant selection and fixation type in total hip arthroplasty (THA) and is important to minimize the risk of periprosthetic femur fracture (PFF). We utilized a deep-learning algorithm to automate femoral radiographic parameters and determined which automated parameters were associated with early PFF.

METHODS

Radiographs from a publicly available database and from patients undergoing primary cementless THA at a high-volume institution (2016 to 2020) were obtained. A U-Net algorithm was trained to segment femoral landmarks for bone morphology parameter automation. Automated parameters were compared against that of a fellowship-trained surgeon and compared in an independent cohort of 100 patients who underwent THA (50 with early PFF and 50 controls matched by femoral component, age, sex, body mass index, and surgical approach).

RESULTS

On the independent cohort, the algorithm generated 1,710 unique measurements for 95 images (5% lesser trochanter identification failure) in 22 minutes. Medullary canal width, femoral cortex width, canal flare index, morphological cortical index, canal bone ratio, and canal calcar ratio had good-to-excellent correlation with surgeon measurements (Pearson's correlation coefficient: 0.76 to 0.96). Canal calcar ratios (0.43 ± 0.08 versus 0.40 ± 0.07) and canal bone ratios (0.39 ± 0.06 versus 0.36 ± 0.06) were higher (P < .05) in the PFF cohort when comparing the automated parameters.

CONCLUSIONS

Deep-learning automated parameters demonstrated differences in patients who had and did not have early PFF after cementless primary THA. This algorithm has the potential to complement and improve patient-specific PFF risk-prediction tools.

Time to Achieve the Minimal Clinically Important Difference in Primary Total Hip Arthroplasty: Comparison of Anterior and Posterior Surgical Approaches

BACKGROUND

Controversy remains over outcomes between total hip arthroplasty (THA) approaches. This study aimed to compare the time to achieve the minimal clinically important difference (MCID) for the Hip Disability and Osteoarthritis Outcome Score-Physical Function Short Form (HOOS-PS) and the Patient-Reported Outcomes Measurement Information System (PROMIS) Global-Physical for patients who underwent anterior and posterior surgical approaches in primary THA.

METHODS

Patients from 2018 to 2021 with preoperative and postoperative HOOS-PS or PROMIS Global-Physical questionnaires were grouped by approach. Demographic and MCID achievement rates were compared, and survival curves with and without interval-censoring were used to assess the time to achieve the MCID by approach. Log-rank and weighted log-rank tests were used to compare groups, and Weibull regression analyses were performed to assess potential covariates.

RESULTS

A total of 2,725 patients (1,054 anterior and 1,671 posterior) were analyzed. There were no significant differences in median MCID achievement times for either the HOOS-PS (anterior: 5.9 months, 95% confidence interval (CI): 4.6 to 6.4; posterior: 4.4 months, 95% CI: 4.1 to 5.1, P = 0.65) or the PROMIS Global-Physical (anterior: 4.2 months, 95% CI: 3.5 to 5.3; posterior: 3.5 months, 95% CI: 3.4 to 3.8, P = 0.08) between approaches. Interval-censoring revealed earlier times of achieving the MCID for both the HOOS-PS (anterior: 1.509 to 1.511 months; posterior: 1.7 to 2.3 months, P = 0.87) and the PROMIS Global-Physical (anterior: 3.0 to 3.1 weeks; posterior: 2.7 to 3.3 weeks, P = 0.18) for both surgical approaches.

CONCLUSIONS

The time to achieve the MCID did not differ by surgical approach. Most patients will achieve clinically meaningful improvements in physical function much earlier than previously believed.

Mental Health Effects on the Minimal Clinically Important Difference in Total Joint Arthroplasty

INTRODUCTION

The effect of mental health on patient-reported outcome measures is not fully understood in total joint arthroplasty (TJA). Thus, we investigated the relationship between mental health diagnoses (MHDs) and the Minimal Clinically Important Difference for Improvement (MCID-I) and Worsening (MCID-W) in primary TJA and revision TJA (rTJA).

METHODS

Retrospective data were collected using relevant Current Procedural Terminology and MHDs International Classification of Diseases, 10th Revision, codes with completed Hip Disability and Osteoarthritis Outcome Score-Physical Function Short Form, Knee Injury and Osteoarthritis Outcome Score-Physical Function Short Form, Patient-reported Outcomes Measurement Information System (PROMIS)-Physical Function Short Form 10a, PROMIS Global-Mental, or PROMIS Global-Physical questionnaires. Logistic regressions and statistical analyses were used to determine the effect of a MHD on MCID-I/MCID-W rates.

RESULTS

Data included 4,562 patients (4,190 primary TJAs/372 rTJAs). In primary total hip arthroplasty (pTHA), MHD-affected outcomes for Hip Disability and Osteoarthritis Outcome Score-Physical Function Short Form (MCID-I: 81% versus 86%, P = 0.007; MCID-W: 6.0% versus 3.2%, P = 0.008), Physical Function Short Form 10a (MCID-I: 68% versus 77%, P < 0.001), PROMIS Global-Mental (MCID-I: 38% versus 44%, P = 0.009), and PROMIS Global-Physical (MCID-I: 61% versus 73%, P < 0.001; MCID-W: 14% versus 7.9%, P < 0.001) versus pTHA patients without MHD. A MHD led to lower rates of MCID-I for PROMIS Global-Physical (MCID-I: 56% versus 63%, P = 0.003) in primary total knee arthroplasty patients. No effects from a MHD were observed in rTJA patients.

DISCUSSION

The presence of a MHD had a prominent negative influence on pTHA patients. Patients who underwent rTJA had lower MCID-I rates, higher MCID-W rates, and lower patient-reported outcome measure scores despite less influence from a MHD.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Intersurgeon Variability of Minimal Clinically Important Difference for Worsening Achievement Rates After Total Joint Arthroplasty

BACKGROUND

Using the Patient-Reported Outcome Measurement Information System, we sought to evaluate surgeon performance variability via minimal clinically important difference for worsening (MCID-W) achievement rates in primary and revision total knee and hip arthroplasty.

METHODS

This retrospective study analyzed 3,496 primary total hip arthroplasty (THA), 4,622 primary total knee arthroplasty (TKA), 592 revision THA, and 569 revision TKA patients. Patient factors collected included demographics, comorbidities, and Patient-Reported Outcome Measurement Information System physical function short form 10a scores. Surgeon factors collected included caseload, years of experience, and fellowship training. The MCID-W rate was calculated as the percent of patients in each surgeon's cohort who achieved MCID-W. Distribution was presented via a histogram with associated average, standard deviation, range, and interquartile range (IQR). Linear regressions were performed to evaluate the potential correlation between surgeon- and patient-level factors with MCID-W rate.

RESULTS

The average MCID-W rates of the surgeons represented in the primary THA and TKA cohorts were 12.7 ± 9.2% (range, 0 to 35.3%; IQR, 6.7 to 15.5%) and 18.0 ± 8.2% (range, 0 to 36%; IQR, 14.3 to 22.0%). The average MCID-W rates among the revision THA and TKA surgeons were 36.0 ± 22.2% (range, 9.1 to 90%; IQR, 25.0 to 41.4%) and 21.2 ± 7.7% (range, 8.1 to 37.0%; IQR, 16.6 to 25.4%). Strong correlations were not found between patient- or surgeon-level factors and MCID-W rate of the surgeon.

CONCLUSION

We demonstrated variance in MCID-W achievement rates across surgeons in both primary and revision joint arthroplasty, independent of patient- or surgeon-level factors.

Postoperative Outcomes in Total Hip and Total Knee Arthroplasty for Patients Who Have Multiple Myeloma

BACKGROUND

Advancements in oncologic care have increased the longevity of patients who have multiple myeloma, although outcomes beyond the early postoperative period following total hip arthroplasty (THA) and total knee arthroplasty (TKA) remain unknown. This study investigated the influence of preoperative factors on implant survivorship following THA and TKA after a minimum 1-year interval for multiple myeloma patients.

METHODS

Using our institutional database, we identified 104 patients (78 THAs, 26 TKAs) from 2000 to 2021 diagnosed with multiple myeloma before their index arthroplasty by International Classification of Diseases, Ninth and Tenth Revisions (ICD-9 and ICD-10) codes 203.0× and C90.0× and corresponding Current Procedural Terminology (CPT) codes. Demographic data, oncologic treatments, and operative variables were collected. Multivariate logistic regressions assessed variables of interest, and Kaplan-Meier curves were used to estimate implant survival.

RESULTS

There were 9 (11.5%) patients who underwent revision THA after an average time of 1,312 days (range, 14 to 5,763), with infection (33.3%), periprosthetic fracture (22.2%), and instability (22.2%) being the most common indications. Of these patients, 3 (33.3%) underwent multiple revision surgeries. There was 1 (3.8%) patient who underwent revision TKA at 74 days postoperatively for infection. Patients treated with radiotherapy were more likely to require revision THA (odds Rratio (OR): 6.551, 95% confidence interval (CI): 1.148-53.365, P = .045), but no predictors of failure were identified for TKA patients.

CONCLUSION

Orthopaedic surgeons should know that multiple myeloma patients have a relatively high risk of revision, particularly following THA. Accordingly, patients who have risk factors for failure should be identified preoperatively to avoid poor outcomes.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

A Matched Comparison of the Rates of Achieving the Minimal Clinically Important Difference Following Conversion and Primary Total Hip Arthroplasty

BACKGROUND

Patient-reported outcome measures (PROMs) are often lower following conversion total hip arthroplasty (cTHA) compared to matched primary total hip arthroplasty (THA) controls. However, the minimal clinically important differences (MCIDs) for any PROMs are yet to be analyzed for cTHA. This study aimed to (1) determine if patients undergoing cTHA achieve primary THA-specific 1-year PROM MCIDs at comparable rates to matched controls undergoing primary THA and (2) establish 1-year MCID values for specific PROMs following cTHA.

METHODS

A retrospective case-control study was conducted using 148 cases of cTHA which were matched 1:2 to 296 primary THA patients. Previously defined anchor values for 2 PROM measures in primary THA were used to compare cTHA to primary THA, while novel cTHA-specific MCID values for 2 PROMs were calculated through a distribution method. Predictors of achieving the MCID of PROMs were analyzed through multivariate logistic regressions.

RESULTS

Conversion THA was associated with decreased odds of achieving the primary THA-specific 1-year Hip dysfunction and Osteoarthritis Outcome Score for Joint Replacement PROM (Odds Ratio: 0.319, 95% Confidence Interval: 0.182-0.560, P < .001) and Patient Reported Outcomes Measurement Information System Physical Function Short-Form-10a PROM (Odds Ratio: 0.531, 95% Confidence Interval: 0.313-0.900, P = .019) MCIDs in reference to matched primary THA patients. Less than 60% of cTHA patients achieved an MCID. The 1-year MCID of the Hip dysfunction and Osteoarthritis Outcome Score for Joint Replacement and Patient Reported Outcomes Measurement Information System Physical Function Short-Form-10a specific to cTHA were +10.71 and +4.68, respectively.

CONCLUSION

While cTHA is within the same diagnosis-related group as primary THA, patients undergoing cTHA have decreased odds of achieving 1-year MCIDs of primary THA-specific PROMs.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Sarcopenia is an independent risk factor for failure to achieve the 1-year MCID of the KOOS, JR and PROMIS PF-SF10a after TKA

BACKGROUND

Sarcopenia, which is a progressive and multifactorial condition of decreased muscle strength, has been identified as an independent predictor for falls, revision, infection, and readmissions following total knee arthroplasty (TKA), but its association to patient reported outcomes (PROMs) is less studied. The aim of this study is to determine if sarcopenia and other measures of body composition are correlated with ability to achieve the 1-year minimal clinically important difference (MCID) of the KOOS JR and PROMIS-PF-SF10a following primary TKA.

METHODS

A multicenter retrospective case-control study was performed. Inclusion criteria consisted of patients over the age of 18 undergoing primary TKA, body composition metrics determined by computed tomography (CT), and available pre- and post-operative PROM scores. Predictors of achievement of the 1-year MCID of the KOOS JR and PROMIS PF-SF-10a were determined through a multivariate linear regression.

RESULTS

140 primary TKAs met inclusion criteria. 74 (52.85%) patients achieved the 1-year KOOS, JR MCID and 108 (77.41%) patients achieved the 1-year MCID for the PROMIS PF-SF10a. Sarcopenia was independently associated with decreased odds of achieving the MCID of both the KOOS, JR (OR 0.31, 95%CI 0.10-0.97, p = 0.04) and the PROMIS-PF-SF10a (OR 0.32, 95%CI 0.12-0.85, p = 0.02) CONCLUSIONS: In our study, sarcopenia was independently associated with increased odds of failure to achieve the 1-year MCID of the KOOS, JR and PROMIS PF-SF10a after TKA. Early identification of sarcopenic patients may be beneficial for arthroplasty surgeons so that targeted nutritional counseling and exercises can be recommended prior to TKA.

Identifying Aseptic Revision Total Knee Arthroplasty Diagnoses That Achieve Minimal Clinically Important Difference and Patient Acceptable Symptom State

BACKGROUND

Minimal clinically important difference (MCID) defines a meaningful clinical change in patient-reported outcome measures. Patient acceptable symptom state (PASS) provides a patient-reported outcome measures threshold value to indicate a satisfactory clinical state. MCID and PASS for revision total knee arthroplasty (rTKA) are ill-defined. Moreover, it is unknown whether diagnosis influences the likelihood of achieving MCID or PASS. The purpose of this study was to calculate MCID for aseptic rTKA and compare the percentage of patients achieving MCID and PASS per diagnosis.

METHODS

An institutional registry of rTKA was used. First-time aseptic rTKA were included. Demographics, revision diagnosis, preoperative Knee Injury and Osteoarthritis Outcome Score, Jr (KOOS Jr), and 1-year postoperative KOOS Jr were recorded. The 1-year postoperative KOOS Jr PASS score was available. MCID was calculated using distribution-based methods. Three hundred fifty eight first-time aseptic rTKAs were analyzed. The 3 most common diagnoses were aseptic loosening (n = 156), instability (n = 109), and stiffness (n = 37).

RESULTS

The mean KOOS Jr 1-year postoperative MCID for rTKA was 10.3. Overall, 75.4% achieved MCID and 56.9% achieved PASS. The percentage of patients per diagnosis achieving MCID and PASS, respectively, were periprosthetic fracture (100, 44), aseptic loosening (94, 60), implant fracture (88, 63), stiffness (60, 38), instability (59, 61), polyethylene wear/osteolysis (57, 57), and metal allergy (44, 33).

CONCLUSION

Aseptic rTKA MCID is 10.3 for KOOS Jr at 1 year postoperatively. rTKA outcomes vary depending on preoperative diagnosis. Even in diagnoses with a high proportion of MCID achieved, less than 2/3 of patients achieved PASS, suggesting rTKA provides noticeable improvement but may not return patients to a satisfactory state.

Rates and Outcomes of Periprosthetic Joint Infection in Persons Who Inject Drugs

BACKGROUND

The risk of periprosthetic joint infection (PJI) is higher in persons who inject drugs (PWID) after total joint arthroplasty (TJA), though reported rates vary widely. This study was designed to assess outcomes of TJA in PWID and to describe factors associated with improved PJI outcomes among PWID.

METHODS

A retrospective matched cohort study was performed using a 1:4 match among those with and those without a history of injection drug use (IDU) undergoing TJA. Demographic, surgical, and outcome variables were compared in multivariate logistic regressions to determine PJI predictors. Kaplan-Meier analyses were constructed to characterize the difference in survival of patients who did not have PJI or undergo joint explantation between PWID and the matching cohort.

RESULTS

PWID had a 9-fold increased risk of PJI compared to the matched cohort (odds ratio 9.605, 95% CI 2.781-33.175, P < .001). Ten of 17 PWID whose last use was within 6 months (active use) of primary TJA had a PJI, while 7 of 41 PWID who did not have active use developed a PJI. Of PWID with PJI, treatment failure was seen in 15 of 17, while in patients who did not have an IDU history, 5 of 8 with PJI had treatment failure.

CONCLUSION

IDU is a significant risk factor for PJI following TJA. Future work investigating the effect of a multidisciplinary support team to assist in cessation of IDU and to provide social support may improve outcomes and reduce morbidity in this vulnerable population.

Minimal Clinically Important Difference (MCID) at One Year Postoperatively in Aseptic Revision Total Hip Arthroplasty

BACKGROUND

Outcomes after aseptic revision total hip arthroplasty (THA) are variable, and it is unknown whether the indication for aseptic revision THA influences postoperative clinical improvement. The minimal clinically important difference (MCID) assesses if changes in patient-reported outcome measure result in meaningful clinical benefit to patients. The purpose of this study was to quantify the 1-year postoperative MCID for aseptic revision THA and to assess the percentage of patients achieving the MCID for each revision diagnosis.

METHODS

A prospective, single-institution registry of revision total joint arthroplasties was used. Retrospective review of 413 first-time aseptic revision THAs was performed. Demographics, revision diagnosis, preoperative Hip Disability and Osteoarthritis Outcome Score, Joint Replacement (HOOS Jr.), and 1-year postoperative HOOS Jr. were recorded. The MCID for the HOOS Jr. at one year postoperatively was calculated for each revision diagnosis using a distribution-based method. The percentage of patients exceeding the MCID with each diagnosis was determined.

RESULTS

There were 9 aseptic revision diagnoses, all with n ≥ 5. The 3 most common revision diagnosis were aseptic loosening (n = 114), dislocation or instability (n = 103), and polyethylene wear or osteolysis (n = 73). The MCID for all the aseptic revision THAs was 10.9. Seven of the nine revision diagnoses achieved the MCID. The highest percentage of patients achieving the MCID was for aseptic loosening (84.2%) and implant fracture (81.3%), whereas lowest was for adverse local tissue reaction (35.3%) and implant recall (20.0%).

CONCLUSION

The one-year revision THA MCID is 10.9 for the HOOS Jr. There is variability in the percentage of patients achieving the MCID based on diagnosis. Our data can be used to counsel patients undergoing revision THA for noninfectious etiologies.

Femoral Component Undersizing and Alignment are Risk Factors for Early Periprosthetic Femur Fracture

BACKGROUND

Known risk factors for early periprosthetic femur fracture (PFF) following total hip arthroplasty (THA) include poor bone quality and the use of cementless implants. The association between femoral component size and alignment and the risk of early PFF is not well described. We evaluated radiographic parameters of femoral component sizing and alignment as risk factors for early PFF.

METHODS

From 16,065 primary cementless THAs, we identified 66 cases (0.41%) of early PFFs (<90 days from index THA) at a single institution between 2016 and 2020. Sixty early PFFs were (1:2) matched to 120 controls based on the femoral component model, offset, surgical approach, age, body mass index (BMI), and gender. Radiographic assessment of preoperative bone morphology and postoperative femoral component orientation included stem alignment, metaphyseal fill, and implant congruence with medial cortical bone. A multivariable logistic regression was built to identify radiographic risk factors associated with early PFF.

RESULTS

Markers of preoperative bone quality including canal calcar ratio (P = .003), canal flare index (P < .001), anteroposterior canal bone ratio (CBR) (P < .001), and lateral CBR (P < .001) were statistically associated with PFF. Distance between the medial cortical bone and implant was greater in cases of PFF (2.5 mm vs 1.4 mm) (P < .001). A multivariate analysis demonstrated that a larger lateral metaphyseal CBR (Odds Ratio [OR] 5), valgus implant alignment (OR 5), and medial implant-bone incongruity (OR 2) increased the risk of early PFF.

CONCLUSION

A larger lateral metaphyseal CBR, valgus component alignment, and implant incongruity with medial cortical bone posed the greatest radiographic risk for early PFF following cementless THA.

Immersive technologies for total knee arthroplasty surgical education

The need to adapt surgical curricula to meet the demands of an increasingly restrictive training environment is rising. Modern constraints of surgical trainees including work-hour restrictions and concerns surrounding patient safety have created an opportunity to supplement traditional teaching methods with developing immersive technologies including virtual and augmented reality. Virtual reality (VR) and augmented reality (AR) have been preliminarily investigated as it relates to total joint arthroplasty. The purpose of this article is to discuss VR and AR as it applies to modern total knee replacement (TKR) surgical education.

Rotating Hinge Revision Total Knee Arthroplasty for Severe Arthrofibrosis

Stiffness following total knee arthroplasty is a challenging complication for both the patient and surgeon, with an incidence that ranges from 1% to 13%1. There are several correctable mechanical causes for stiffness including malposition, malalignment, overstuffing, aseptic loosening, patella baja, and heterotopic ossification2. Idiopathic stiffness is often termed arthrofibrosis and is more difficult to treat1. Once patients have exhausted nonoperative options, including physical therapy and manipulation under anesthesia, revision surgery may be considered. Rotating hinge revision total knee arthroplasty has been shown to be an effective surgical treatment for severe arthrofibrosis.

Description

First, remove all soft-tissue and osseous sources of stiffness and adequately expose the knee, then remove all previous components. Create a stable and balanced extension gap, and, conversely, a relatively loose flexion gap, which allows for a substantial increase in range of motion. Then, in order to prevent instability in flexion, a rotating hinge prosthesis is utilized, which allows for appropriate kinematic motion despite gap imbalance. Additional steps to regain flexion include medial and lateral distal femoral partial condylectomies, as well as patellar component revision.

Alternatives

The first line of treatment for stiffness following total knee arthroplasty is nonoperative and is mainly focused on physical therapy3. Manipulation under anesthesia can also be performed within the first 12 weeks postoperatively3. Surgical treatments can include arthroscopic debridement as well as open debridement with possible polyethylene liner exchange. If there is a mechanical cause for stiffness, then this should also be addressed surgically. For cases of arthrofibrosis without a clear mechanical etiology or for cases in which the above treatment has failed, complete revision of the femoral and tibial components should be considered3. An alternative option to the technique proposed here is to utilize a varus-valgus constrained implant.

Rationale

Revision with a hinged implant allows for a more aggressive approach to regaining motion, as compared with all other surgical alternatives. By revising all components, the surgeon is able to remove all sources of stiffness and reconstruct the knee until as much range of motion as possible is achieved. Unfortunately, even with balanced extension and flexion gaps, refractory stiffness is common. A solution for this residual stiffness is to unbalance the gaps and create a loose flexion gap. By doing so, the surgeon is advised to switch to a hinged implant to create a kinematically balanced knee. Any other revision implant, such as a varus-valgus constrained implant, would risk flexion instability.

Expected Outcomes

Several studies have examined the use of revision total knee arthroplasty with a hinged implant for arthrofibrosis and have showed substantial improvements in knee range of motion. Bingham et al. showed that the rotating hinge group had a 20° improvement in range of motion (p = 0.048)1. Hermans et al. found a 35.8° flexion gain in the hinge group compared with a 14.2° flexion gain in the varus-valgus constrained group (p = 0.0002)4. van Rensch et al. found a median gain of 45° of range of motion5. Patients should be aware that this procedure involving the use of a hinged implant has similar risks to other revision total knee arthroplasty procedures; specifically, there is a risk of recurrent arthrofibrosis as well as mechanical complications1,5.

Important Tips

Achieve adequate exposure with a quadriceps snip.Perform a thorough synovectomy and debridement.Create a balanced extension gap with a relatively loose flexion gap.Distalize the joint line by resecting additional proximal tibia in cases of patella baja.Beware of refractory stiffness as a result of a scarred extensor mechanism.Consider revising the patellar component.Consider performing a partial condylectomy at the medial and lateral distal aspects of the femur.

Acronyms and Abbreviations

TKA = total knee arthroplastyAP = anteroposteriorCT = computed tomographyMRI = magnetic resonance imagingRHK = rotating hinge kneeNSAIDs = nonsteroidal anti-inflammatory drugs.

Hip Arthroscopy Versus Physical Therapy for the Treatment of Symptomatic Acetabular Labral Tears in Patients Older Than 40 Years: A Randomized Controlled Trial

BACKGROUND

Previous observational studies have suggested poor results of arthroscopic surgery for the treatment of acetabular labral tears in patients older than 40 years.

PURPOSE

To compare hip arthroscopy versus nonoperative management for symptomatic labral tears in patients older than 40 years who have limited radiographic osteoarthritis.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

In this single-surgeon, parallel randomized controlled trial, patients older than 40 years who had symptomatic, MRI-confirmed labral tears and limited radiographic osteoarthritis (Tönnis grades 0-2) were randomized 1:1 to arthroscopic surgery with postoperative physical therapy (SPT) or physical therapy alone (PTA) using an electronic randomization program. PTA patients who achieved unsatisfactory improvement were permitted to cross over to SPT after completing ≥14 weeks of physical therapy. The primary outcomes were International Hip Outcome Tool (iHOT-33) and modified Harris Hip Score (mHHS) at 12 months after randomization, and secondary outcomes included other patient-reported outcome measures and the visual analog scale. Outcomes were assessed at baseline and at 3, 6, and 12 months after randomization. Primary analysis was performed on an intention-to-treat basis using linear mixed-effect models. Sensitivity analyses included modified as-treated analysis and treatment-failure analysis. Due to infeasibility, patients and health care providers were both unblinded.

RESULTS

The study enrolled 90 patients (46 [51.1%] SPT; 44 [48.9%] PTA); of these, 81 patients (42 [51.9%] SPT; 39 (48.1%) PTA) completed 12-month follow-up. A total of 28 of the 44 PTA patients crossed over to SPT within the study period (63.6% crossover). Intention-to-treat analysis revealed significantly greater iHOT-33 scores (+12.11; P = .007) and mHHS scores (+6.99 points; P = .04) in the SPT group than the PTA group at 12 months. Modified as-treated analysis revealed that these differences exceeded the minimal clinically important difference of 10.0 points (SPT-PTA iHOT-33, +11.95) and 8.0 points (SPT-PTA mHHS, +9.76), respectively.

CONCLUSION

In patients older than 40 years with limited osteoarthritis, arthroscopic acetabular labral repair with postoperative physical therapy led to better outcomes than physical therapy alone. Thus, age over 40 years should not be considered a contraindication to arthroscopic acetabular labral repair.

REGISTRATION

NCT03909178 (ClinicalTrials.gov identifier).

The new dynamic isotonic manipulation examination (DIME) is a highly sensitive secondary screening tool for supraspinatus full-thickness tears

BACKGROUND

Traditional shoulder physical examination (PE) tests have suboptimal sensitivity for detection of supraspinatus full-thickness tears (FTTs). Therefore, clinicians may continue to suspect FTTs in some patients with negative rotator cuff PE tests and turn to magnetic resonance imaging (MRI) for definitive diagnosis. Consequently, there is a need for a secondary screening test that can accurately rule out FTTs in these patients to better inform clinicians which patients should undergo MRI. The purpose of this study was to assess the ability of 2 new dynamic PE tests to detect supraspinatus pathology in patients for whom traditional static PE tests failed to detect pathology.

METHODS

We prospectively enrolled 171 patients with suspected rotator cuff pathology with negative findings on traditional rotator cuff PE, who underwent 2 new dynamic PE tests: first, measurement of angle at which the patient first reports pain on unopposed active abduction and, second, the dynamic isotonic manipulation examination (DIME). Patients then underwent shoulder magnetic resonance arthrogram. Data from the new PE maneuvers were compared with outcomes collected from magnetic resonance arthrogram reports.

RESULTS

Pain during DIME testing had a sensitivity of 96.3% and 92.6% and a negative predictive value of 96.2% and 94.9% in the coronal and scapular planes, respectively. DIME strength ≤86.0 N had a sensitivity of 100% and 96.3% and a negative predictive value of 100% and 95.7% in the coronal and scapular planes, respectively. Pain at ≤90° on unopposed active abduction in the coronal plane had a specificity of 100% and a positive predictive value of 100% for supraspinatus pathology of any kind (ie, tendinopathy, "fraying," or tearing).

CONCLUSION

DIME is highly sensitive for supraspinatus FTTs in patients with negative traditional rotator cuff PE tests for whom there is still high clinical suspicion of FTTs. Thus, this test is an excellent secondary screening tool for supraspinatus FTTs in patients for whom clinicians suspect rotator cuff pathology despite negative traditional static PE tests. Given its high sensitivity, a negative DIME test rules out supraspinatus FTT well in these patients, and can therefore better inform clinicians which patients should undergo MRI. In addition, the angle at which patients first report pain on unopposed active shoulder abduction is highly specific for supraspinatus pathology.

Endoscopic Repair of Full-Thickness Gluteus Medius and Minimus Tears-Prospective Study With a Minimum 2-Year Follow-Up

PURPOSE

To evaluate the short-term outcomes of endoscopic repair of full-thickness gluteus medius and minimus tendon tears with a minimum of 2-year follow-up and add to the paucity of literature on abductor tendon tears.

METHODS

All patients who underwent endoscopic abductor tendon repair between December 2013 and August 2017 were prospectively evaluated. The inclusion criteria for this study were primary full-thickness gluteal tendon tears and at least 2-years of follow-up. Clinical outcome data consisted of visual analog scale (VAS) pain score, hip abduction strength, Trendelenburg sign, complications, and patient-reported outcome measures (PROMs): modified Harris Hip Score, Hip Outcome Score, Non-arthritic Hip Scale, International Hip Outcome Tool-33, and Lower Extremity Functional Scale.

RESULTS

A total of 15 hips, all full-thickness tears, met inclusion criteria with an average follow-up of 31.2 months, with no patients being excluded. On physical examination, there was a significant improvement in VAS pain score from 5.36 to 2.43 (P = .0243), hip abduction strength with 8 (53.3%) hips improving by at least 1 point (P = .02056), and resolution of Trendelenburg sign in all 15 hips at 2-years (P = .0019). The mean difference for all 6 PROMs was statistically significant, even after Bonferroni adjustment, with the majority of patient improvement exceeding the minimal clinically important difference (MCID) thresholds: modified Harris Hip Score: 86.67%, Hip Outcome Score-ADL: 86.67%, Hip Outcome Score-SSS: 66.67%, Non-arthritic Hip Scale: 93.33%, and International Hip Outcome Tool-33: 80%. Greater Goutallier grade was associated with a greater VAS pain score. There were no complications, including no retears.

CONCLUSIONS

In this study of 15 hips with full-thickness gluteal tendon tears managed endoscopically, we found excellent outcomes that exceeded the MCID thresholds in the majority of patients at an average of 31.2 months follow-up, while offering the potential advantages of less tissue violation, ambulatory day surgery, and fewer complications compared with open repair.

LEVEL OF EVIDENCE

Level 4, Case Series.

Translational relevance of the goat as a preclinical model of the human labrum and chondrolabral junction-histological study

The purpose of this study was to evaluate the histologic features of the caprine labrum, with emphasis on the chondrolabral junction, with the goal of informing the feasibility of the goat as an animal model. The left hip joint of six adolescent Spanish goats (Capra pyrenaica) was harvested and subjected to anatomical and histological assessments. Human acetabular and femoral head samples, collected during total hip arthroplasty, served as comparison samples. The caprine labrum was found to consist of mostly type I collagen with uniform crimp, with an average crimp length of 20.8 µm. Upon histological assessment, acetabular articular chondrocytes were found to express substance-P, especially near or in the chondrolabral junction. And the majority of nonvascular cells expressed α-smooth muscle actin (SMA), with no notable elastin and laminin expression. Human labrum demonstrated similar staining patterns. Overall, the goat hip was found to be homologous to the human hip, demonstrating potential as a useful animal model for future studies. This is the first report of a crimped collagen structure in the labrum. Crimped type I collagen at the chondrolabral junction imparts an extension-recovery property which allows for toleration of stress without permanent deformation, underlying the importance of its preservation during surgery. The high expression of substance-P reflects the degree to which the labrum is innervated. Finally, the expression of α-SMA with contractile characteristics could indicate the potential for chondrocyte (i.e., myochondrocytes) modeling of the extracellular matrix. Statement of Clinical Significance: Establishment of a large animal model and deeper knowledge of the histological composition of the hip joint will enhance our study of the acetabular labrum, including repair techniques. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:1070-1080, 2020.

A value-based care analysis of magnetic resonance imaging in patients with suspected rotator cuff tendinopathy and the implicated role of conservative management

BACKGROUND

Magnetic resonance imaging (MRI) is often used to evaluate the integrity of the rotator cuff in patients with suspected full-thickness rotator cuff tears or other cuff tendinopathies. The value of advanced imaging value comes into question when it is used as the initial musculoskeletal imaging test before a trial of conservative therapy in patients with atraumatic shoulder pain, minimal to no strength deficits on examination, and suspected cuff tendinopathy.

METHODS

A prospective study of a group of patients suspected to have cuff tendinopathy based on clinical findings was performed. Every patient underwent MRI and was offered an initial trial of conservative management. Patients had an average follow-up of 28.3 ± 5.3 months after imaging to determine whether surgery was performed.

RESULTS

A total of 51 patients were included in this study. Of this cohort, 46 (90.2%) patients did not go on to surgical intervention, whereas 5 (9.8%) patients did at an average 68.3 days after imaging. These results suggest that over 90.2% of patients (46 of 51) had premature MRI, posing an unnecessary economic burden of $181,619 in advanced imaging charges.

CONCLUSIONS

The use of MRI before a trial of conservative management in patients with atraumatic shoulder pain, minimal to no strength deficits on physical examination, and suspected cuff tendinopathy other than full-thickness tears provides negative value in the management of these patients, at both the individual and population level.

Improvement in Functional Outcome Scores Despite Persistent Pain With 1 Year of Nonsurgical Management for Acetabular Labral Tears With or Without Femoroacetabular Impingement

BACKGROUND

Acetabular labral tears are increasingly recognized as a source of hip pain in a younger active population. Given the significant focus on surgical intervention, there has been limited investigation on the nonsurgical management and natural history of such injuries.

HYPOTHESIS

Patients undergoing nonsurgical treatment for symptomatic acetabular labral tears experience functional improvement based on patient-reported outcome measures over the course of 1 year.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Seventy-one patients were identified who had acetabular labral injuries confirmed by magnetic resonance imaging or arthrography, received a minimum of 1 year of nonsurgical treatment, and completed baseline functional outcome questionnaires: modified Harris Hip Score (mHHS), Hip Outcome Score (HOS)-Activities of Daily Living, HOS-Sports, and iHOT-33 (International Hip Outcome Tool-33). Of these, 52 (73.2%) completed the minimum 1-year follow-up questionnaires. Chart review was conducted to obtain demographic information. Statistical significance ( P < .05) was determined by paired t test, independent samples t test, and chi-square test.

RESULTS

Twenty-two male and 30 female patients completed 1-year follow-up questionnaires. Mean ± SD follow-up time was 16.2 ± 3.1 months. The cohort had a mean age of 38.9 ± 9.3 years. Baseline radiographs demonstrated minimal arthritis (Tönnis grades 0-2). Mean alpha angle differed significantly between men and women at 52.9°± 8.6° and 46.3°± 8.5°, respectively. At 1-year follow-up, patients experienced a significant improvement in all 4 functional outcome measures (mHHS: 72.6 vs 81.8, HOS-Activities of Daily Living: 78.6 vs 86.4, HOS-Sports: 56.0 vs 71.1, iHOT-33: 47.5 vs 67.9). Patients with and without femoroacetabular impingement demonstrated a significant improvement in the mHHS. However, 48.1% reported no improvement in their pain; 69.2% were limited in their activities; and 40.4% were still considering surgery. Overall, 71.2% were satisfied with nonsurgical treatment.

CONCLUSION

Patients with symptomatic labral tears can experience functional improvement after a minimum 1 year of nonsurgical treatment in the presence and absence of femoroacetabular impingement. However, many report residual pain, alteration of their activities, and interest in surgery. This information is important when patients are counseled in the treatment options for this injury. Identifying the population that responds best to nonsurgical management and comparing outcomes with those undergoing surgical management should be the focus of future research. Longer-term follow-up may be necessary to reevaluate pain, function, and return to activities.

All-Arthroscopic Reconstruction of the Acetabular Labrum by Capsular Augmentation

The acetabular labrum plays an important role in hip joint stability and articular cartilage maintenance. As such, reconstitution of the labral complex is ideal. In cases in which the labrum is too degenerative to allow adequate reconstruction with current repair techniques, a capsular augmentation is a novel technique that can be used to restore the labral structure. Use of capsular augmentation enables preservation of the donor-tissue blood supply with local tissue transfer, without adding significant complexity to the procedure or significant donor-site morbidity.

Arthroscopic T-capsulotomy for excision of pigmented villonodular synovitis in the hip

Pigmented villonodular synovitis (PVNS) is a benign synovial tumor of unknown etiology with a predilection for the large joints of the appendicular skeleton. The poor prognosis for patients with hip disease is partially imparted by current surgical techniques. Recent advances in hip arthroscopy technique and instrumentation may enable arthroscopic treatment for PVNS in the hip. The authors report the first case where hip arthroscopy was used to surgically excise a biopsy-confirmed local PVNS lesion in the hip. Using selected capsular releases and accessory portals, the authors achieved adequate visualization and instrument mobilization to successfully excise the entire PVNS tumor with no identifiable complications.

Intra-articular Fluid Distension for Initial Portal Placement During Hip Arthroscopy: The "Femoral Head Drop" Technique

Iatrogenic injury is a known complication of initial portal placement during hip arthroscopy. The rate of labral puncture or damage to the articular surfaces with arthroscopic instruments is variable and may be associated with operator inexperience or complex anatomy. In addition, the amount of traction applied to achieve joint distraction may unnecessarily place patients at risk of neurapraxia. The purpose of this article is to describe the "femoral head drop" technique as a method to increase safe access to the central compartment and minimize the amount of traction needed to do so, especially in patients with challenging bony anatomy. This technique uses the application of intra-articular saline solution to cause inferior migration of the femoral head. Intra-articular fluid distension, or the femoral head drop technique, is simple, safe, and reproducible, making it appropriate for hip arthroscopists at any level of experience.

Endoscopic repair of full-thickness abductor tendon tears: surgical technique and outcome at minimum of 1-year follow-up

PURPOSE

The purpose of this study was to assess the surgical outcomes of endoscopically repaired full-thickness abductor tendon tears using validated outcome measures.

METHODS

After institutional review board approval was obtained, clinical outcome data were retrospectively collected from patients who underwent endoscopic gluteus medius and/or minimus repair by a single surgeon between August 2009 and September 2011. With a minimum follow-up of 1 year, patients were evaluated using the modified Harris Hip Score and the validated Hip Outcome Score (HOS). The HOS questionnaire included 2 subsections: HOS-Activities of Daily Living and HOS-Sports. Physical examination data were gathered during routine clinic visits, 1 year postoperatively. Statistical analysis was descriptive. The change in strength testing postoperatively was assessed with the Wilcoxon signed rank test, with significance set at P ≤ .05.

RESULTS

Twelve patients were identified, 1 of whom was excluded; 10 of 11 patients (91%) completed the study requirements. The mean patient age was 65.9 years (range, 60 to 74 years), 70% were women, and the mean follow-up period was 23 months (range, 13 to 38 months). The mean postoperative scores were 84.7 (SD, 14.5) for the modified Harris Hip Score and 89.1 (SD, 11.3) for the HOS-Activities of Daily Living, with 90% patient satisfaction. All patients had clinically and statistically improved abductor tendon strength (P = .004). Patients with good to excellent outcomes were younger (P < .001). There were no complications identified.

CONCLUSIONS

In our small series, endoscopic abductor tendon repair was an effective surgical intervention after failed conservative management at short-term follow-up. Patients had reliably good to excellent outcomes with improved strength during hip abduction, were at low risk of complications, and were satisfied with the outcome. In addition, younger patients achieved better outcomes.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Effect of radiofrequency use on hip arthroscopy irrigation fluid temperature

PURPOSE

The purpose of this study was to determine operating parameters for joint fluid lavage using radiofrequency (RF) in maintaining intra-articular temperatures ≤50°C in the hip joint and to then quantify the influence of flow rate on maintaining safe intra-articular temperatures.

METHODS

Fiberoptic intra-articular thermometers at radial distance intervals of 1, 2, 5, and 10 mm, spanning cross-sectional areas of 3.14, 12.56, 78.5, and 314.1 mm(2), respectively, from the RF probe were used in 3 human hip cadaveric specimens at room temperature, with 9 trials per variable, using a 3-portal technique with a capsule release. Using a new Dyonics RF System continuously at the superior capsulolabral junction for 90 seconds, continuous temperatures were recorded at 50 mm Hg inflow and variable outflow intervals: no flow and 5, 15, and 30 seconds. Lavages were 1 second in duration on suction. Statistical comparison was through multivariate regression analysis and a logistic model.

RESULTS

Temperatures reached ≥50°C at 5-mm radial distance from the probe in all but the 5-second pulse lavage group. Elevated temperatures were reached within 1 to 2 seconds locally (1- to 2-mm radial distance) and at a radial distance of 5 mm in the 15-, 30-, and 0-second lavage groups. Logistic regression revealed a reduction in the odds that temperatures ≥50°C will occur as flow frequency increases every 30 (odds ratio = 0.68, P = .086); 15 (odds ratio = -1.22, P = .0067); and 5 (odds ratio = -4.26, P < .0001) seconds.

CONCLUSIONS

Increasing-interval pulsed irrigation is effective in maintaining intra-articular temperature profiles below 50°C during use of continuous RF ablation. Five-second-interval pulsed lavage is the longest flow interval identified during which fluid 5 mm radially from the RF device never reached temperatures >50°C.

CLINICAL RELEVANCE

Clinical guidelines for using the RF ablation include: meticulous technique, intermittent use, good inflow and outflow, and pulsed lavage at frequent intervals.

Predictors of hip arthroscopy outcomes for labral tears at minimum 2-year follow-up: the influence of age and arthritis

PURPOSE

The purpose of this study was to perform a retrospective case-control outcome analysis at a minimum 2-year follow-up using a validated hip arthroscopy outcome measure to determine whether arthritis or age is predictive of outcomes after hip arthroscopy for labral pathology.

METHODS

We identified 176 consecutive patients undergoing hip arthroscopy for labral tears performed between 2001 and 2009 to complete the Modified Harris Hip Score (MHHS) and Hip Outcome Score questionnaires. Patients who underwent additional surgeries or reported an MHHS of less than 80 were compared with the control group of patients who achieved good to excellent surgical results on the MHHS (>80) to calculate odds ratios with 95% confidence intervals by use of the independent variables of patient age of 40 years or older and age below 40 years and the presence of grade 4 Outerbridge changes found at arthroscopy.

RESULTS

Of 176 patients, 125 (71%) were contacted: 27 patients had undergone additional surgery in the follow-up period, and 98 completed questionnaires. The mean patient age at surgery was 40.9 years (range, 17.3 to 62.8 years) at a mean follow-up of 4.3 years (range, 2 to 10.4 years). Of 98 respondents, 71 (72%) obtained a good to excellent surgical outcome, with 84% reporting satisfaction. The presence of osteoarthritic changes at the time of arthroscopy was predictive of worse outcome scores compared with the nonarthritic cohort (odds ratio, 2.5; 95% confidence interval, 1.2 to 5.3; P = .02). Youth (age <40 years) is predictive of good to excellent results (odds ratio, 7; 95% confidence interval, 2.9 to 16.9; P < .0001).

CONCLUSIONS

Of the 98 patients who completed the questionnaires in this study, 71 (72%) obtained good to excellent outcome scores. Overall satisfaction among patients undergoing hip arthroscopy was high (84%). Patients aged younger than 40 years did better than older patients, and arthroscopically identified arthritis was predictive of worse surgical outcomes.

LEVEL OF EVIDENCE

Level III, case-control study.

High affinity promotes more effective ADCC by anti-HER2/neu monoclonal antibodies

2538

Background: Although monoclonal antibodies have emerged as useful cancer therapeutics, the antibody structural features and biologic properties that maximize therapeutic benefit are not fully understood. Antibody-dependent cellular cytotoxicity (ADCC) is believed to be a major mechanism of some anti-cancer antibodies. Herein, we describe the relationship between antibody affinity and the biologic properties of ADCC. Methods: A series of human IgG1 antibodies was created from the anti-HER2/neu C6.5 scFv and its affinity mutants (affinity ranging from 10−7 to 10−11 M). The IgGs were tested for their ability to elicit ADCC using a standard 51Cr-release assay. The ability of these IgGs to inhibit tumor cell proliferation and to induce apoptosis was evaluated using a colorimetric cell proliferation assay and homogeneous caspase assay/Annexin-V-FLUOS assay, respectively. Three tumor cell lines with differing levels of HER2/neu expression were used as target cells, and unactivated human PBMC from healthy donors were the effector cells. Results: There was a clear influence of both intrinsic and functional affinity on ADCC, with higher levels of peak cytotoxicity as apparent affinity approached 10−11 M. Among the antibodies with apparent affinity of 10−11 M, antibodies with higher intrinsic affinities elicited more ADCC. There also was an affinity-dependent increase in cytotoxicity at lower antibody concentrations and lower effector: target ratios. These antibodies elicited more cytotoxicity against tumor cells expressing high levels of HER2/neu than against cells expressing lower amounts of HER2/neu. None of these IgGs inhibited tumor cell proliferation, or induced apoptosis. Conclusions: Additional studies are needed to determine why, at the same functional avidity, ADCC is improved in antibodies with higher intrinsic affinities. These findings justify the examination of high affinity antibodies for ADCC promotion, although the impaired tumor targeting associated with high affinity may be an important confounding factor in the design of unconjugated anti-tumor antibodies. A careful examination of antibody structure: function relationships is required to develop optimized therapeutic unconjugated antibodies.

No significant financial relationships to disclose.

Purification and characterization of the human ovarian LH/hCG receptor and comparison of the properties of mammalian LH/hCG receptors

Methods previously published by us [Wimalasena et al., J Biol Chem 260: 10689-10697, 1985; Wimalasena et al., J Biol Chem 261: 9416-9420, 1986] were utilized to solubilize the human corpus luteal leuteinizing hormone/human chorionic gonadotropin (LH/hCG) receptor with 3-[(3-cholamide-propyl)dimethylammonio]-1-propanesulfonate (CHAPS) and to purify the receptor by two steps of hCG-Sepharose affinity chromatography. The specific binding capacity (SBC) of the purified human receptor was 7510 pmol/mg protein, and KA = 2.2 x 10(9) M-1 when iodo hCG was competed by hCG; the yield was 4-7% of starting activity. When hLH was used in competition with hCG, specific binding capacity was 7900 pmol/mg protein and KA 1.0 x 10(9) M-1. Silver staining and autoradiography demonstrated a single protein of Mr 78,000 under reducing and Mr 58-62 x 10(3) under nonreducing conditions. Rat ovarian LH/hCG receptor was purified by similar methods and the KA of 3.5 x 10(10) M-1 for hCG was substantially different from the KA for hLH which was 2.1 x 10(9) M-1. Mr of the rat protein was 78-82 x 10(3) (reduced) and 58-62 x 10(3) (nonreduced) when analyzed by silver staining and autoradiography. For the first time, human LH/hCG receptor has been purified to apparent homogeneity, and its Mr of 78,000 was essentially identical to the Mr values of purified rat and porcine receptors.