Comparison of Direct Surgical Costs for Proximal Row Carpectomy and Four-Corner Arthrodesis

Proximal row carpectomy versus four-corner arthrodesis: a retrospective comparative study

BACKGROUND

Four-corner arthrodesis with scaphoid excision (FCA) and proximal row carpal resection (PRC) are frequently performed in wrists with post-traumatic Scaphoid Non- Union Advanced Collapse (SNAC)/Scapho-Lunate Advanced Collapse (SLAC) osteoarthritis. The aim of this study was to compare the clinical outcomes of these two procedures.

METHODS

This single-center, retrospective cohort study included all patients who had PRC or FCA between January 1st, 2009 and January 1st, 2019 and who were followed up. Follow-up included: mobility (radial deviation, ulnar deviation, flexion, extension), strength (grip test, pinch test), function (QuickDash, patient-rated wrist evaluation [PRWE]), subjective mobility, and global satisfaction scores.

RESULTS

Among 25 patients included, 11 had PRC and 14 had FCA with a mean follow-up of 69.5 months [12-132]. Radial deviation was 18° versus 14° (p = 0.7), ulnar deviation was 21° versus 22° (p = 0.15), flexion was 39° versus 30° (p = 0.32), extension was 32.5° versus 29.5° (p = 0.09), grip test compared to the controlateral side was 72% versus 62% (p = 0.53), Quick Dash score was 12.5 versus 17.6 (p = 0.84), PRWE was 18.7 versus 17.6 (p = 0.38), subjective mobility was 7.8 versus 7.5 (p = 0.23), and satisfaction score was 8.7 versus 9 (p = 0.76), respectively, in the FCA group and the PRC group. Re-operation rates were 14% patients in the FCA group and 0% in the PRC group.

CONCLUSION

This study found no significant difference between FCA and PRC on strength, mobility, and function in patients with post-traumatic SLAC or SNAC stage II wrist arthritis. Both FCA and PRC seem to be reliable surgical techniques with good outcomes with more revision in the FCA group.

Proximal Row Carpectomy Modifications for Capitate Arthritis: A Systematic Review

Introduction  Proximal row carpectomy (PRC) is a motion-sparing procedure for radiocarpal arthritis with reliable results. Traditionally, proximal capitate arthritis is a contraindication to PRC; however, PRC with modifications are proposed to circumvent this contraindication. PRC modifications can be broadly grouped into capitate resurfacing (CR) and capsular interposition (CI) procedures which could expand PRC indications. Our primary question was to characterize the outcomes achievable with various PRC modifications. Our secondary question was to determine which PRC modification was the optimal procedure when capitate arthritis was present. Methods  A systematic review was conducted to examine the outcomes of modified PRC procedures. Independent reviewers appraised multiple databases for PRC studies with modifications for capitate arthritis in adult patients (age >18 years) with a minimum of three cases and extractable outcomes. Modified PRC procedures included capsular/allograft interposition, resurfacing capitate pyrocarbon implants, and osteochondral grafting. Pertinent outcomes included patient demographics, range-of-motion, grip strength, patient-reported outcomes, and complications, including salvage rates. Results  Overall, 18 studies met the inclusion criteria-10 studies ( n  = 147) on CI and 8 studies on CR ( n  = 136). PRC with CI had the greatest flexion-extension arc and grip strength. Complications were marginally higher in the CR group (4%), while the CI group had a higher conversion to total wrist arthrodesis (10%). Conclusion  Techniques to address capitate arthritis center around resurfacing or soft tissue interposition. PRC modifications with CI produces better range-of-motion and grip strength but higher conversion to total wrist arthrodesis. Higher conversion rates may be attributable to longer follow-up periods in studies examining CI compared with CR. Level of Evidence  This is a Level III study.

Proximal row carpectomy generates better mid- to long-term outcomes than four-corner arthrodesis for post-traumatic wrist arthritis: A meta-analysis

INTRODUCTION

In posttraumatic wrist arthritis of intermediate severity, two main palliative procedures are used to preserve some mobility in the wrist: proximal row carpectomy (PRC) and scaphoid excision followed by four corner arthrodesis (4CA). Despite satisfactory overall results, the debate continues about which one provides the best results and long-term outcomes, particularly prevention of arthritis progression. Recent comparative studies now provide us with information about mid- and long-term results. The aim of this study was to compare the clinical results, complications, conversion rate to total wrist arthrodesis and progression to osteoarthritis of PRC versus 4CA in the medium and long term.

HYPOTHESIS

The null hypothesis was that there is no significant difference between PRC and 4CA in the clinical results, complications, conversion to total wrist arthrodesis and arthritis progression.

MATERIALS AND METHODS

A systematic literature review was carried out by following the PRISMA guidelines. Included were studies comparing 4CA and PRC for the treatment of post-traumatic wrist arthritis secondary to scapholunate dissociation (SLAC) and scaphoid nonunion (SNAC) with a mean follow-up of 5 years. A search was performed of the MEDLINE, EMBASE and Cochrane databases that identified 831 articles. After removing 230 duplicates and excluding 595 articles based on their title and/or abstract, and then adding 1 article manually, 7 articles were included in our analysis. Parameters analyzed were range of motion (ROM), pain, grip strength, functional scores, complications, conversion to total wrist arthrodesis, and arthritis progression.

RESULTS

In the 7 articles, 1059 wrists - 582 PRC and 477 4CA - were analyzed with follow-up ranging from 5.2 to 18 years. PRC produced significantly better ROM in flexion (weighted mean difference [WMD]=10.0°; p<0.01) and in ulnar deviation (WMD=8.7°; p<0.01) along with significantly lower complication rates (OR=0.3; p<0.01) and reoperation rates (OR=0.1; p<0.01). There was no significant difference in the conversion rate, grip strength, extension, radial deviation, pain, DASH and PRWE scores. The progression of osteoarthritis could not be analyzed due to lack of data.

DISCUSSION

This meta-analysis was the first to include recently published mid- and long-term studies comparing PRC and 4CA. The main finding is that PRC is superior overall with better ROM and a lower complication rate. Another important finding was the absence of differences in grip strength and the conversion rate to total wrist arthrodesis. Unfortunately, the lack of systematic studies on arthritis progression leaves this question unanswered. Our findings must be interpreted cautiously because it was impossible to stratify the cases by etiology and osteoarthritis stage.

LEVEL OF EVIDENCE

III; systematic review and meta-analysis.

Surgical management of osteoarthritis of the hand and wrist

Osteoarthritis of the hand and wrist is common; varying disease manifestations and a spectrum of symptoms make it imperative to approach treatment strategies in an individualized fashion. In this review, attention is focused upon site specific diagnoses and indications for various surgical treatment strategies.

Two-Corner Fusion or Four-Corner Fusion of the Wrist for Midcarpal Osteoarthritis? A Multicenter Prospective Comparative Cohort Study

BACKGROUND

Midcarpal osteoarthritis is a debilitating wrist pain, and a mainstay treatment is midcarpal fusion. The accepted standard for midcarpal fusion is four-corner fusion, but lately, two-corner fusion (i.e., capitolunate fusion) has gained popularity. This is the first prospective, multicenter, cohort study comparing capitolunate fusion with four-corner fusion for midcarpal osteoarthritis.

METHODS

Patients with scaphoid nonunion advanced collapse or scapholunate advanced collapse wrist of grade 2 to 3 undergoing capitolunate fusion or four-corner fusion between 2013 and 2019 were included. Sixty-three patients (34 with capitolunate fusion, 29 with four-corner fusion) were included. Patient demographics were similar between groups. Patient-Rated Wrist Hand Evaluation questionnaire score, visual analog scale pain score, grip strength, range of motion, and complications were measured at baseline and 3 months and 12 months postoperatively. Complications (i.e., nonunion, hardware migration, conversion to wrist arthrodesis, or arthroplasty) were determined.

RESULTS

A significant difference in Patient-Rated Wrist Hand Evaluation or visual analog scale pain score at 3 and 12 months postoperatively between the capitolunate fusion and four-corner fusion groups was not found. There were no differences in grip strength between patient groups preoperatively or 12 months postoperatively. At 12 months postoperatively, capitolunate fusion patients had better flexion compared with that in the four-corner fusion group (p = 0.002); there were no differences in complications and reoperation rates between groups.

CONCLUSIONS

Capitolunate fusion and four-corner fusion were comparable in terms of functional scores (i.e., Patient-Rated Wrist Hand Evaluation and visual analog scale pain scores) and complication scores. Capitolunate fusion showed favorable wrist mobility compared with four-corner fusion in treatment of midcarpal osteoarthritis. Capitolunate fusion advantages include use of less material, less need for bone-graft harvesting, and easier reduction of the lunate during fixation.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, II.

Cost Assessment of Plating Versus Tension Band Wiring Constructs for Treating Mayo Type 2A Olecranon Fractures

PURPOSE

Tension band wiring (TBW) or plating may be used for fixation with similar clinical outcomes for adults with displaced Mayo 2A olecranon fractures. The primary hypothesis is that total direct costs (TDCs) for surgery are lower for TBW than plating. Our secondary hypothesis is that combined surgical TDCs are lower for TBW even with a 100% rate of subsequent tension band hardware removal and a 0% rate of plate removal.

METHODS

Patients who underwent TBW or plating of an isolated unilateral Mayo 2A olecranon fracture between July 2011 and January 2020 at a single academic medical center were identified. Then, TDC for each surgery on plate fixation, TBW, and hardware removal was obtained and converted to 2020 US dollars using information technology cost tools provided by our institution. Finally, relative TDCs were compared between plate fixation and TBW groups using univariate and multivariable generalized estimating equations with log-link.

RESULTS

Of the 97 included patients, the mean age was 50 ± 21 years, and 48% were female. Tension band wiring and plate fixation were performed on 18% (17/97) and 82% (80/97) of male and female patients, respectively. Demographics were similar between groups, although the finding that plate fixation cost 2.6 times that of TBW within the index surgery was significant in the multivariable model, independent of potential confounders (coefficient 2.55, 95% confidence interval: 2.09-3.10). Additionally, mean TDC remained significantly greater for plate fixation even under the hypothetical situation where 100% TBW were removed, and the plate removal rate was 0% (cost difference 181%).

CONCLUSIONS

Using TBW relative to plate fixation may improve the cost of care for operative Mayo 2A olecranon fractures. Furthermore, this finding was robust to the rate of hardware removal.

TYPE OF STUDY/LEVEL OF EVIDENCE

Economic and Decision Analyses III.

Methodologic and Reporting Quality of Economic Evaluations in Hand and Wrist Surgery: A Systematic Review

BACKGROUND

Economic evaluations can inform decision-making; however, previous publications have identified poor quality of economic evaluations in surgical specialties.

METHODS

Study periods were from January 1, 2006, to April 20, 2020 (methodologic quality) and January 1, 2014, to April 20, 2020 (reporting quality). Primary outcomes were methodologic quality [Guidelines for Authors and Peer Reviewers of Economic Submissions to The BMJ (Drummond's checklist), 33 points; Quality of Health Economic Studies (QHES), 100 points; Consensus on Health Economic Criteria (CHEC), 19 points] and reporting quality (Consolidated Health Economic Evaluation Standards (CHEERS) statement, 24 points).

RESULTS

Forty-seven hand economic evaluations were included. Partial economic analyses (i.e., cost analysis) were the most common (n = 34; 72 percent). Average scores of full economic evaluations (i.e., cost-utility analysis and cost-effectiveness analysis) were: Drummond's checklist, 27.08 of 33 (82.05 percent); QHES, 79.76 of 100 (79.76 percent); CHEC, 15.54 of 19 (81.78 percent); and CHEERS, 20.25 of 24 (84.38 percent). Cost utility analyses had the highest methodologic and reporting quality scores: Drummond's checklist, 28.89 of 35 (82.54 percent); QHES, 86.56 of 100 (86.56 percent); CHEC, 16.78 of 19 (88.30 percent); and CHEERS, 20.8 of 24 (86.67 percent). The association (multiple R) between CHEC and CHEERS was strongest: CHEC, 0.953; Drummond's checklist, 0.907; and QHES, 0.909.

CONCLUSIONS

Partial economic evaluations in hand surgery are prevalent but not very useful. The Consensus on Health Economic Criteria and Consolidated Health Economic Evaluation Standards should be used in tandem when undertaking and evaluating economic evaluation in hand surgery.

A Failed 4-Corner Arthrodesis Using a Polyether-Ether-Ketone Implant: A Case Report

CASE

A 59-year-old man underwent scaphoidectomy and 4-corner arthrodesis with a polyether-ether-ketone (PEEK) circular plate for scapholunate advanced collapse of the wrist. Five years later, he presented with a symptomatic nonunion and radiocarpal arthritis. Total wrist arthrodesis with a dorsal plate was performed. During revision surgery, considerable synovitis was encountered. Histological evaluation revealed a foreign body response likely secondary to PEEK particles.

CONCLUSION

Use of PEEK implants can result in an adverse local tissue reaction if particles are generated. This is a rare biomaterial-related complication, and surgeons should be aware of this adverse tissue response when using this or other PEEK implants.

Comparison of direct surgical cost for humeral shaft fracture fixation: open reduction internal fixation versus intramedullary nailing

Background and/or Hypothesis

Prior literature has supported similar complication rates and outcomes for humeral shaft fractures treated with open reduction internal fixation (ORIF) with a plate/screw construct versus intramedullary nailing (IMN). The purpose of this study is to determine whether surgical encounter total direct costs (SETDCs) differ between ORIF and IMN for these fractures.

Methods

Adult patients (≥ 18 years) treated for isolated humeral shaft fractures by ORIF or IMN between June 18, 2014 and June 17, 2019 at a single tertiary academic center were available for inclusion. SETDCs for ORIF and IMN groups, obtained through our institution's information technology value tool, were adjusted to 2019 US dollars and converted to relative costs per institutional policy. SETDCs for ORIF and IMN were compared using the Wilcoxon rank-sum test.

Results

Demographic factors did not differ between ORIF and IMN cohorts with the exception of age (mean of 18.6 years older for IMN; P < .001) and American Society of Anesthesiologist class (higher for IMN; P = .029). Substantial cost variation was observed among the 39 included ORIF and 21 IMN cases. Costs pertaining to operating room utilization (P = .77), implants (P = .64), and the recovery room (P = .27) were similar for ORIF and IMN, whereas supply costs were significantly greater for IMN with a median (interquartile range) of 0.21 (0.17 ∼ 0.28), more than twice the supply costs of ORIF (0.09 [0.05 ∼ 0.13], P < .001). The SETDC of IMN was significantly greater than that of ORIF (median [interquartile range]:1.00 [0.9 to 1.13] vs. 0.83 [0.71∼1.05], respectively; P = .047).

Discussion and/or Conclusion

Our study found that the SETDC for humeral shaft fracture fixation was greater for IMN than for ORIF, although patient cohorts differed significantly with respect to age and the American Society of Anesthesiologist class. Surgeons should take these findings into consideration when consenting patients with humeral shaft fractures for the appropriate fixation type.

Evaluation of factors driving cost variation for distal humerus open reduction internal fixation

Background

Distal humerus fracture open reduction and internal fixation (ORIF) represents a substantial cost burden to the health care system. The purpose of this study was to describe surgical encounter cost variation for distal humerus ORIF, and to determine demographic-, injury-, and treatment-specific factors that influence cost.

Methods

We retrospectively identified adult patients (≥18 years) treated for isolated distal humerus fractures between July 2014 and July 2019 at a single tertiary academic referral center. For each case, surgical encounter total direct costs (SETDCs) were obtained via our institution's information technology value tools, which prospectively record granular direct cost data for every health care encounter. Costs were converted to 2019 dollars using the personal consumption expenditure indices for health and summarized with descriptive statistics. Univariate and multivariate linear regression models were used to identify factors influencing SETDC.

Results

Surgical costs varied widely for the 47 included patients, with a standard deviation (SD) of 33% and interquartile range of 76%-124% relative to the mean SETDC. Implant and facility costs were responsible for 46.2% and 32.6% of the SETDC, respectively. Implant costs also varied considerably, with an SD of 21% and range from 13%-36% relative to the mean SETDC. Multivariate analysis demonstrated that SETDC increased 24% (P < .001) on performing an olecranon osteotomy, and by 15% for each additional 1 hour of surgical time (P < .001). These findings were independent of age, sex, body mass index, open fracture, need for an additional small plate construct as a reduction aid, and fracture pattern (all insignificant in the multivariate analysis, with P >.05 for each factor).

Conclusion

Substantial variations in surgical encounter total direct costs for distal humerus ORIF exist, as do wide variations in associated implant costs that comprise nearly half of the entire surgical cost. Performing an olecranon osteotomy, and increased surgical time, significantly increased surgical costs. Although use of an olecranon osteotomy may not be a completely controllable factor as it is confounded by fracture severity and operative time, this may suggest that surgeons should try to use an olecranon osteotomy judiciously. Although complexity of the fracture pattern was statistically insignificant, it is confounded by the need for an olecranon osteotomy and increased surgical time and likely is a clinically relevant and nonmodifiable driver of surgical cost. These findings highlight opportunities to reduce cost variation, and potentially improve the value of care, for distal humerus ORIF patients.

Cost Implications of Varying the Surgical Setting and Anesthesia Type for De Quervain Release Surgery

Background  First extensor compartment release is a common surgical procedure that represents a financial burden to the health care system. Questions/Purposes  Study questions included (1) whether surgical encounter costs differ based upon surgical setting (operating room [OR] vs. procedure room [PR]) or (2) based upon anesthesia choice (local only, Bier's block [BB], monitored anesthesia care [MAC], or general [GA]) for De Quervain release (DQR). Patients and Methods  Consecutive adult patients undergoing isolated unilateral DQR at a single academic medical center were identified retrospectively by Current Procedural Terminology code (25000). Using our institution's information technology value tools, we calculated total direct costs for each surgical encounter. Costs were adjusted to January 2016 dollars using the Consumer Price Index, normalized using each participant's surgical encounter cost divided by the median cost in the PR group, then compared across each group using Kruskal-Wallis and Nemenyi's post hoc pair-wise tests. Multivariable gamma regression analysis with a log link was performed to identify factors associated with surgical costs. QuickDASH (disabilities of the arm, shoulder, and the hand) scores were compared using a t -test at final follow-up. Results  Among 58 included patients, 29% (17/58) were treated in the PR and 71% (41/58) in the OR. Compared with local only in the PR, all other groups were significantly more costly. Multivariable gamma regression indicated that use of OR/BB, OR/MAC, or OR/GA independently led to 211, 222, and 357% greater surgical costs as compared with the PR with local only while controlling for provider and patient age. Furthermore, QuickDASH scores were similar between PR and OR groups at final follow-up. Conclusion  Performing DQR in the PR setting under local only anesthesia yields greater value than the OR, as patient-reported outcomes are similar despite significantly lower surgical costs. Level of Evidence This is a Level III, cost analysis study.

Cost-Effectiveness Analysis Comparing Proximal Row Carpectomy and Four-Corner Arthrodesis

Background:

The optimal surgical treatment for scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC) remains unclear. To inform clinical decision-makers, we conducted a cost-effectiveness analysis comparing proximal row carpectomy (PRC) and four-corner arthrodesis (FCA).

Methods:

A Markov microsimulation model was used to compare clinical outcomes, costs, and health utilities between PRC and FCA. The model used a 10-year time horizon and a 1-month cycle length, and it was evaluated from the societal perspective. Utilities and clinical parameters including transition probabilities for debridement for infection, removal of implants, conversion to total wrist arthrodesis, revision FCA, and revision total wrist arthrodesis were obtained from published literature. Timing of complications was estimated from the literature. Direct medical costs were derived from Medicare ambulatory surgical cost data, and indirect costs for missed work due to surgical procedures and complications were included. The effectiveness outcome was quality-adjusted life years (QALYs). Probabilistic sensitivity analysis and 1-way threshold analysis for utilities were performed.

Results:

In the base-case model, PRC dominated FCA (i.e., PRC had lower cost and greater effectiveness). The mean (and standard deviation) for the total cost and QALYs per patient were $30,970 ± $5,931 and 8.24 ± 1.28, respectively, for PRC and $44,526 ± $11,205 and 8.23 ± 1.26, respectively, for FCA. In the probabilistic sensitivity analysis, PRC dominated FCA in 57% of the 1 million iterations. The cost-effectiveness acceptability curve indicated that PRC is the most cost-effective strategy regardless of the willingness-to-pay threshold up to $100,000/QALY.

Conclusions:

PRC dominated FCA in the base-case analysis and in the probabilistic sensitivity analysis. These results suggest that PRC is the optimal strategy for Stage-I or II SLAC and for SNAC in patients ≥55 years of age.

Level of Evidence:

Economic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Evaluation of factors influencing surgical treatment costs for distal biceps rupture

BACKGROUND

Given the similar outcomes of various fixation constructs for single-incision distal biceps repair, a critical evaluation of the factors that drive the cost of the procedure is the key to optimizing treatment value. The purpose of this study was to quantify variation in costs for surgical treatment of complete distal biceps ruptures, as well as identify factors affecting costs.

METHODS

We retrospectively identified adult patients consecutively treated surgically for complete distal biceps ruptures between July 2011 and January 2018 at a single academic medical center. Using our institution's information technology value tool, we recorded the surgical encounter total direct costs (SETDCs) for each patient. Univariate and multivariate gamma regression models were used to determine factors affecting SETDCs.

RESULTS

Of 121 included patients, 102 (86%), 7 (6%), and 12 (10%) underwent primary repair, revision, and reconstruction. SETDCs varied widely, with a standard deviation of 40% and a range of 58% to 276% of the average SETDC. The main contributors to SETDCs were facility utilization costs (53%) and implant costs (29%). Implant costs also varied, with a standard deviation of 16%, ranging up to 121% of the mean SETDC. Multivariate analysis demonstrated that reconstructions were 72% more costly than primary repairs (P < .001). No significant cost differences were found between cortical button and dual-suture anchor fixation (P = .058). American Society of Anesthesiologists class, body mass index, revision surgery, time to surgery, location, administration of postoperative block, and surgeon performing the procedure did not significantly affect the SETDC.

CONCLUSION

Surgical encounter and implant costs vary widely for distal biceps rupture treatment. However, no significant difference in SETDC was identified between repair with a cortical button vs. dual-suture anchor repair. The greater costs associated with reconstruction surgery should be taken into consideration.

Functional outcomes after salvage procedures for the destroyed wrist: an overview

The most widely used procedures for salvaging a destroyed wrist are four-corner arthrodesis, radiocarpal arthrodesis, proximal row carpectomy, total wrist arthrodesis, and total wrist replacement or resurfacing. The purpose of this article is to give an overview of the functional results obtained with the various salvage procedures and of the common methods for assessing the surgical outcomes. The outcomes are assessed by clinical measurements and scoring methods, but the actual functional status and well-being of the patients should be presented together with patient-reported outcomes. No salvage procedure can restore entirely full wrist function. Understanding indications, risks, and the outcomes of these procedures would favour a better decision for surgery and help choose the proper treatment from among the surgical options discussed with patients.

Functional Outcomes After Salvage Procedures for Wrist Trauma and Arthritis (Four-Corner Fusion, Proximal Row Carpectomy, Total Wrist Arthroplasty, Total Wrist Fusion, Wrist Denervation): A Review of Literature

Background:

Several salvage procedures for the arthritically destroyed wrist exist. Each of these has advantages as well as disadvantages.

Aims:

The aim of this article is to give practical insights for the clinician on: (1) biomechanical and clinical fundamentals of normal and impaired wrist motion; (2) difficulties in assessment of postoperative outcome between measured motion by the surgeon and self-reported outcome by the patient; (3) indications for each procedure; and (4) differences in functional outcome between partial and complete motion-preserving as well as complete motion-restricting salvage procedures.

Methods:

In trend, Proximal Row Carpectomy (PRC) is slightly superior over four-corner fusion (4CF) in terms of functional outcome, but the methodology-related postoperative motion is decreased for both procedures. Furthermore, PRC is easier to perform, needs lower costs, and has fewer complications than 4CF. Total Wrist Arthroplasty (TWA) has the advantage compared to PRC and 4CF that the preoperative motion values are preserved, but it is limited by decreased load-bearing capacity for the wrist. Total Wrist Fusion (TWF) is associated with a higher load-bearing capacity for the wrist than TWA, but it is limited for carrying out essential activities of daily living. Both PRC and 4CF can be combined primarily by wrist denervation. Wrist denervation alone does not impair the movement of the wrist.

Results and Conclusion:

Salvage procedures for the arthritically destroyed wrist should be detected regarding patients age- and gender-related claims in work and leisure. Not all of them can be successfully re-employed in their original occupations associated with high load-bearing conditions.