Debridement, Antibiotics, and Implant Retention in Unicompartmental Knee Arthroplasty Infection

BACKGROUND

This multicenter study sought to further investigate the method and outcome of debridement, antibiotics, and implant retention (DAIR) for the management of unicompartmental knee periprosthetic joint infection (PJI).

METHODS

This retrospective study was performed on 52 patients who underwent DAIR for PJI of a unicompartmental knee arthroplasty (UKA) across 4 academic medical centers, all performed by fellowship-trained arthroplasty surgeons. Patient demographics, American Society of Anesthesiologists score, infecting organism, operative data, antibiotic data, and success in infection control at 1 year were collected.

RESULTS

The average time from index surgery to diagnosis of PJI was 11.1 weeks (range, 1.4 to 48). There was no correlation between time of diagnosis and success at 1 year (R = 0.09, P = .46). There was an association between surgical synovectomy and the eradication of infection (R = 0.28, P = .04). Overall, there was an 80.8% (42 of 52) infection-controlled success rate at 1 year from the DAIR procedure. All DAIR failures went on to require another procedure, either 1-stage (2 of 10) or 2-stage (8 of 10) revision to total knee arthroplasty (TKA). Of the DAIR successes, 6 (14.3%) went on to require conversion to TKA for progression of arthritis within 5 years.

CONCLUSIONS

This study demonstrates that DAIR is a safe and moderately effective procedure in the setting of acute PJI of UKA across institutions, with a success rate consistent with DAIR for TKA. The data suggest that a wide exposure and thorough synovectomy be incorporated during the DAIR UKA to improve the likelihood of successful eradication of PJI at the 1-year mark.

LEVEL OF EVIDENCE

Level III.

The CCJR® Charles A. Engh, Sr, MD. Excellence in Hip Research Award: The Evolution of Revision Hip Arthroplasty and Impact on the Trainee's Experience

BACKGROUND

Advances in total hip arthroplasty (THA) have resulted in evolving revision indications and intraoperative techniques, which can influence the exposure of trainees to complex cases. We report 3 decades of revision experience from a tertiary referral center that trains fellows, comparing the reasons for revision and the complexity of revisions over time.

METHODS

We retrospectively reviewed all revision THAs performed at our institution from 1990 to 2022. Revision diagnoses, components revised, types of revision implants used, and exposure techniques were collected. A "complex" revision was defined as a case that involved an extended trochanteric osteotomy, triflange and cup-cage construct, or acetabular augment.

RESULTS

A total of 3,556 THA revisions were identified (108 revisions/year). Aseptic loosening was the most common indication in 1990 to 1999 (45 per year), but decreased to 28.3/year in 2010 to 2019. From 1990 to 1999 and 2010 to 2019, fracture increased from 3.1 to 7.3 per year, infection from 2.9/year to 16.9/year, and metallosis from 0.1 to 13.2 per year. Both component revision were common from 1990 to 1994 (42.6 per year), while polyethylene exchange was most common in 2010 to 2019 (43.3 per year). A decrease was observed in "complex" cases over time: 14.8 extended trochanteric osteotomies/year in 2000 to 2004 compared to 5.4 per year in 2018 to 2022, 4.5 triflange and cup-cage constructs/year in 2004 to 2007 compared to 0.8 per year in 2018 to 2022, and 4 acetabular augments per year in 2009 to 2012 compared to 1 per year in 2018 to 2022.

CONCLUSIONS

Indications for revision have changed over the decades, while the number of "complex" revisions has gradually decreased, presumably due to advances in implants and materials. If this trend extends to other training institutions, the next generation of arthroplasty surgeons will have less exposure to complex revisions during their training.

Cementless Total Knee Arthroplasty: A Resurgence - Who, When, Where, and How?

BACKGROUND

Total knee arthroplasty (TKA) is one of the most common procedures in orthopaedics, but there is still debate over the optimal fixation method for long-term durability: cement versus cementless bone ingrowth. Recent improvements in implant materials and technology have offered the possibility of cementless TKA to change clinical practice with durable, stable biological fixation of the implants, improved operative efficiency, and optimal long-term results, particularly in younger and more active patients.

METHODS

This symposium evaluated the history of cementless TKA, the recent resurgence, and appropriate patient selection, as well as the historical and modern-generation outcomes of each implant (tibia, femur, and patella). Additionally, surgical technique pearls to assist in reliable, reproducible outcomes were detailed.

RESULTS

Historically, cemented fixation has been the gold standard for TKA. However, cementless fixation is increasing in prevalence in the United States and globally, with equivalent or improved results demonstrated in appropriately selected patients.

CONCLUSION

Cementless TKA provides durable biologic fixation and successful long-term results with improved operating room efficiency. Cementless TKA may be broadly utilized in appropriately selected patients, with intraoperative care taken to perform meticulous bone cuts to promote appropriate bony contact and biologic fixation.

Outcomes Following Intraoperative Calcar Fractures During Cementless Total Hip Arthroplasty

BACKGROUND

Intraoperative calcar fractures (IOCFs) are an established complication of cementless total hip arthroplasty (THA). Prompt recognition and management may prevent subsequent postoperative complications. This study aimed to evaluate the outcomes and revision rates of THAs with IOCFs identified and managed intraoperatively.

METHODS

There were 11,438 primary cementless THAs performed at a single institution from 2009 to 2022. Prospectively collected data on cases with an IOCF was compared to cases without the complication. The fracture group had a lower body mass index (26.9 versus 28.9 kg/m2; P = .01). Patient age, sex, and mean follow-up (3.2 (0 to 12.8) versus 3.5 years (0 to 14); P = .45) were similar between groups.

RESULTS

An IOCF occurred in 62 of 11,438 (0.54%) cases. The THAs done via a direct anterior approach experienced the lowest rate of fractures (31 of 7,505, 0.4%) compared to postero-lateral (27 of 3,759, 0.7%; P = .03) and lateral (4 of 165, 2.4%; P < .01) approaches. Of the IOCFs, 48 of 62 (77%) were managed with cerclage cabling, 4 of 62 (6.5%) with intraoperative stem design change and cabling, 4 of 62 (6.5%) with restricted weight-bearing, and 6 of 62 (9.7%) with no modification to the standard postoperative protocol. The IOCF group experienced one case of postoperative component subsidence. No subjects in the IOCF cohort required revision, and rates were similar between groups (0 of 62, 0% versus 215 of 11,376, 1.9%; P = .63). Postoperative Hip dysfunction and Osteoarthritis Outcome Score for Joint Replacement scores were comparable (85.7 versus 86.4; P = .80).

CONCLUSIONS

Cementless THA complicated by IOCF had similar postoperative revision rates and patient-reported outcome measures at early follow-up when compared to patients not experiencing this complication. Surgeons may use these data to provide postoperative counseling on expectations and outcomes following these rare intraoperative events.

Early Practice All-Cause Complications for Fellowship-Trained Anterior Hip Surgeons Are Not Increased When Compared to "Gold Standard" Experienced Posterior Approach Surgeons

BACKGROUND

Increased complication rates have been reported during the learning curve for direct anterior approach (DAA) total hip arthroplasty (THA). However, emerging literature suggests that complications associated with the learning curve may be substantially reduced with fellowship training.

METHODS

Our institutional database was queried to identify 2 groups: (1) 600 THAs comprised of the first 300 consecutive cases performed by 2 DAA fellowship-trained surgeons; and (2) 600 posterolateral approach (PA) THAs, including the most recent 300 primary cases performed by 2 experienced PA surgeons. All-cause complications, revision rates, reoperations, operative times, and transfusion rates were evaluated.

RESULTS

Comparing DAA and PA cases, there were no significant differences in rates of all-cause complications (DAA = 18, 3.0% versus PA = 23, 3.8%; P = .43), periprosthetic fractures (DAA = 5, 0.8% versus PA = 10, 1.7%; P = .19), wound complications (DAA = 7, 1.2% versus PA = 2, 0.3%; P = .09), dislocations (DAA = 2, 0.3% versus PA = 8, 1.3%, P = .06), or revisions (DAA = 2, 0.3% versus PL = 5, 0.8%; P = .45) at 120 days postoperatively. There were 4 patients who required reoperation for wound complications, all within the DAA group (DAA = 4, 0.67% versus PA = 0; P = .045). Operative times were shorter in the DAA group (DAA <1.5 hours = 93% versus PA <1.5 hours = 86%; P < .01). No blood transfusions were given in either group.

CONCLUSION

In this retrospective study, DAA THAs performed by fellowship-trained surgeons early in practice were not associated with higher complication rates compared to THAs performed by experienced PA surgeons. These results suggest that fellowship training may allow DAA surgeons to complete their learning curve period with complication rates similar to experienced PA surgeons.

Outpatient Total Knee Arthroplasty From a Stand-Alone Surgery Center: Safe as the Hospital?

BACKGROUND

Literature suggests that outpatient arthroplasty may result in low rates of complications and readmissions. There is, however, a dearth of information on the relative safety of total knee arthroplasty (TKA) performed at stand-alone ambulatory surgery centers (ASCs) versus hospital outpatient (HOP) settings. We aimed to compare safety profiles and 90-day adverse events of these 2 cohorts.

METHODS

Prospectively collected data were reviewed on all patients who underwent outpatient TKA from 2015 to 2022. The ASC and HOP groups were compared, and differences in demographics, complications, reoperations, revisions, readmissions, and emergency department (ED) visits within 90 days of surgery were analyzed. There were 4 surgeons who performed 4,307 TKAs during the study period, including 740 outpatient cases (ASC = 157; HOP = 583). The ASC patients were younger than HOP patients (ASC = 61 versus HOP = 65; P < .001). Body mass index and sex did not differ significantly between groups.

RESULTS

Within 90 days, 44 (6%) complications occurred. No differences were observed between groups in rates of 90-day complications (ASC = 9 of 157, 5.7% versus HOP = 35 of 583, 6.0%; P = .899), reoperations (ASC = 2 of 157, 1.3% versus HOP = 3 of 583, 0.5%; P = .303), revisions (ASC = 0 of 157 versus HOP = 3 of 583, 0.5%; P = 1), readmissions (ASC = 3 of 157, 1.9% versus HOP = 8 of 583, 1.4%; P = .625), and ED visits (ASC = 1 of 157, 0.6% versus HOP = 3 of 583, 0.5%; P = .853).

CONCLUSION

These results suggest that in appropriately selected patients, outpatient TKA can be safely performed in both ASC and HOP settings with similar low rates of 90-day complications, reoperations, revisions, readmissions, and ED visits.

Motor Nerve Palsy After Direct Anterior vs. Posterior Total Hip Arthroplasty: Incidence, Risk Factors, and Recovery

BACKGROUND

There is limited literature on motor nerve palsy in modern total hip arthroplasty (THA). The purpose of this study was to establish the incidence of nerve palsy following THA using the direct anterior (DA) and postero-lateral (PL) approaches, identify risk factors, and describe the extent of recovery.

METHODS

Using our institutional database we examined 10,047 primary THAs performed between 2009 and 2021 using the DA (6,592; 65.6%) or PL (3,455; 34.4%) approach. Postoperative femoral (FNP) and sciatic/peroneal (PNP) nerve palsies were identified. Incidence and time to recovery was calculated, and association between surgical and patient risk factors and nerve palsy were evaluated using Chi-square tests.

RESULTS

The overall rate of nerve palsy was 0.34% (34/10,047), and was lower with the DA approach (0.24%) than the PL approach (0.52%), P=0.02. The rate of FNPs in the DA group (0.20%) was 4.3-times higher than the rate of PNPs (0.05%), while in the PL group the rate of PNPs (0.46%) was 8-times higher than FNPs (0.06%). Higher rates of nerve palsy were observed with women, shorter patients, and non-osteoarthritis pre-operative diagnoses. Full recovery of motor strength occurred in 60% of cases with FNP and 58% of cases with PNP.

CONCLUSION

Nerve palsy is rare after contemporary THA through the PL and DA approaches. The PL approach was associated with a higher rate of PNP, whereas the DA approach was associated with a higher rate of FNP. Femoral and sciatic/peroneal palsies had similar rates of complete recovery.

Timing and Factors Associated with Revision for Infection after Primary Total Knee Arthroplasty Based on American Joint Replacement Registry Data

BACKGROUND

Infection following total knee arthroplasty (TKA) remains a challenging clinical problem. Using American Joint Replacement Registry (AJRR) data, this study examined factors related to the incidence and timing of infection.

METHODS

Primary TKAs performed from January 2012 through December 2018 among patients ≥65 years of age at surgery were queried from AJRR and merged with Medicare data to enhance capture of revisions for infection. Multivariate Cox regressions incorporating patient, surgical, and institutional factors were used to produce hazard ratios (HR) associated with revision for infection and mortality after revision for infection.

RESULTS

Among 525,887 TKAs, 2,821 (0.54%) were revised for infection. Men had an increased risk of revision for infection at all time intervals (≤90 days, HR=2.06, 95% confidence interval (CI): 1.75-2.43, P<0.0001; >90 days to 1 year, HR=1.90, 95% CI: 1.58-2.28, P<0.0001; >1 year, HR=1.57, 95% CI: 1.37-1.79, P<0.0001). TKAs performed for osteoarthritis had an increased risk of revision for infection at ≤90 days (HR=2.01, 95% CI: 1.45-2.78, P<0.0001), but not at later times. Mortality was more likely among patients who had a Charlson Comorbidity Index (CCI)≥5 compared to those who had a CCI≤2 (HR=3.21, 95% CI: 1.35-7.63, P=0.008). Mortality was also more likely among older patients (HR=1.61 for each decade, 95% CI: 1.04-2.49, P=0.03).

CONCLUSION

Based on primary TKAs performed in the United States, men were found to have a persistently higher risk of revision for infection, while a diagnosis of osteoarthritis was associated with a significantly higher risk only during the first 90 days after surgery.

Spinal Anesthesia for Primary Hip and Knee Arthroplasty: Comparative Rates of Transient Neurological Symptoms and Urinary Retention using Lidocaine, Mepivacaine, and Bupivacaine

BACKGROUND

Short-acting spinal anesthetics enable rapid recovery hip and knee arthroplasty, however concerns with transient neurological symptoms (TNS) cause some to avoid using lidocaine. Post-operative urinary retention (POUR) is also a concern with spinal anesthesia. We sought to study the comparative rates of TNS and POUR between lidocaine, mepivacaine, and bupivacaine in a high-volume hip and knee arthroplasty setting.

METHODS

Data for 1,217 primary THA, TKA, and UKA cases were reviewed and grouped by spinal anesthetic agent (Lidocaine, Mepivacaine, or Bupivacaine). Of the 1,217 cases, utilization was 523 Lidocaine, 573 Mepivacaine, and 121 Bupivacaine. The incidence of TNS and POUR requiring catheterization was measured both by clinical evaluation as well as a questionnaire sent to patients 14 days postoperatively.

RESULTS

The overall rate of TNS was 8%. With the numbers available, there was no difference in rates of TNS between groups (6.9% Lidocaine, 9.2% Mepivacaine, and 4.1% Bupivacaine; P=0.297). There was no difference in rates of TNS or POUR between THA and TKA/UKA. Bupivacaine had a significantly higher rate of urinary retention (9.1%; P<0.001) than mepivacaine (2.8%) or lidocaine (1.5%).

CONCLUSIONS

This study showed no difference in the rate of TNS between the 3 common agents used in spinal anesthesia. Short-acting spinal anesthetics such as lidocaine and mepivacaine can lower the rate of POUR requiring catheterization helping to enable rapid recovery hip and knee arthroplasty.

Early Results of a Randomized Controlled Trial of Partial Versus Total Knee Arthroplasty

BACKGROUND

Debate still exists regarding the benefits of unicompartmental (UKA) versus total knee arthroplasty (TKA) for the treatment of medial compartment osteoarthritis. The purpose of this randomized trial is to compare the early outcomes of UKA versus TKA.

METHODS

One-hundred and seven candidates for UKA were randomized at two centers; 57 candidates received UKA and 50 received TKA. Six-week and 6-month outcome measures including Knee Injury and Osteoarthritis Outcome Score, Joint Replacement (KOOS, JR), Knee Society Score (KSS), Forgotten Joint Score (FJS), and VR-12 global health scores were obtained. No demographic or baseline patient reported outcome (PRO) differences were present suggesting successful randomization (P > .05).

RESULTS

UKA demonstrated shorter operative times (UKA = 65 minutes, TKA = 74 minutes; P < .001) and length of stay (UKA = 0.7 nights, TKA = 1.2 nights; P < .01). At 6 weeks, there were no differences in KOOS, JR (P = .755), KSS (P = .754), FJS (P = .664), or PRO change from preoperative scores (P = .468). There were three surgical complications within 90 days in each group. The duration of opioid consumption (UKA = 33.8 days, TKA = 28.5 days; P = .290) and return to work (UKA = 57.1 days, TKA = 47.3 days; P = .346) did not differ between groups.

CONCLUSION

Data suggest no clinically significant differences between UKA and TKA in the early postoperative period in regards to patient-reported outcome measures, duration of opioid use, or return to work. Patients undergoing UKA can anticipate a shorter length of stay and greater early range of motion. All-cause short-term complications may be more prevalent with TKA.

Prior Anterior Cruciate Ligament Reconstruction Does Not Compromise the Functional Outcomes of Medial Unicompartmental Knee Arthroplasty Although Revision for Progressive Arthritis May Occur Earlier

BACKGROUND

Anterior cruciate ligament (ACL) deficiency is commonly considered a contraindication for unicompartmental knee arthroplasty (UKA). The purpose of this study is to compare the outcomes of UKA after prior ACL reconstruction (rACL cohort) to UKA with an intact native ACL (nACL cohort).

METHODS

Forty-five patients from 3 institutions who underwent medial UKA after prior rACL were matched by age, gender, preoperative function scores, and body mass index to 90 patients who underwent UKA with an intact nACL. Primary outcomes were Knee Injury and Osteoarthritis Outcome Score for Joint Replacement, Oxford Knee Scores, Knee Society Functional Scores, and Kellgren-Lawrence scores in the unresurfaced, lateral tibiofemoral compartment. Secondary outcomes were postoperative complications and the need for revision to TKA.

RESULTS

At a mean of 3.6 years, all PROMs improved significantly with no differences identified between groups. The incidence of revision TKA was similar between cohorts (P = 1.00); however, the mean time to revision for progressive osteoarthritis was 4.0 years in the nACL group and 2.2 years in the rACL group. Twenty percent of rACL patients had a postoperative complication compared to 8% in the nACL group. Despite presenting with a similar degree of lateral arthritis, a greater percentage of patients developed Kellgren-Lawrence scores of ≥3 in the rACL cohort (9%) than in the nACL cohort (0%).

CONCLUSION

A previously reconstructed ACL does not appear to compromise the short-term functional outcomes of UKA; however, there is a higher rate of minor complications and progression of lateral compartment arthritis, which should be considered with patients in the shared decision process.

Alignment in Medial Fixed-Bearing Unicompartmental Knee Arthroplasty: The Limb Has a Leg Up on the Component

BACKGROUND

To assess how implant alignment affects unicompartmental knee arthroplasty (UKA) outcome, we compared tibial component alignment of well-functioning UKAs against 2 groups of failed UKAs, revised for progression of lateral compartment arthritis ("Progression") and aseptic loosening ("Loosening").

METHODS

We identified 37 revisions for Progression and 61 revisions for Loosening from our prospective institutional database of 3351 medial fixed-bearing UKAs performed since 2000. Revision cohorts were matched on age, gender, body mass index, and postoperative range of motion with "Successful" unrevised UKAs with minimum 10-year follow-up and Knee Society Score ≥70. Tibial component coronal (TCA) and sagittal (TSA) plane alignment was measured on postoperative radiographs. Limb alignment was quantified by hip-knee-ankle (HKA) angle on long-leg radiographs. In addition to directly comparing groups, a multivariate logistic regression examined how limb and component alignments were associated with UKA revision.

RESULTS

In the Progression group, component alignment was similar to the matched successes (TCA 3.6° ± 3.5° varus vs 5.1° ± 3.5° varus, P = .07; TSA 8.4° ± 4.4° vs 8.8° ± 3.6°, P = .67), whereas HKA angle was significantly more valgus (0.3° ± 3.6° valgus vs 4.4° ± 2.6° varus, P < .001). Loosening group component alignment was also similar to the matched successes (TCA 6.1° ± 3.7° varus vs 5.9° ± 3.1° varus, P = .72; TSA 8.4° ± 4.6° vs 8.1° ± 3.9°, P = .68), and HKA was significantly more varus (6.1° ± 3.1° varus vs 4.0° ± 2.7° varus, P < .001). Using a multivariate logistic regression, HKA angle was the most significant factor associated with revision (P < .001).

CONCLUSION

In this population of revised UKAs and long-term successes, limb alignment was a more important determinant of outcome than tibial component alignment.

LEVEL OF EVIDENCE

Level III case-control study.

A lower threshold for revision of aseptic unicompartmental vs total knee arthroplasty

AIMS

It has been hypothesized that a unicompartmental knee arthroplasty (UKA) is more likely to be revised than a total knee arthroplasty (TKA) because conversion surgery to a primary TKA is a less complicated procedure. The purpose of this study was to determine if there is a lower threshold for revising a UKA compared with TKA based on Oxford Knee Scores (OKSs) and range of movement (ROM) at the time of revision.

METHODS

We retrospectively reviewed 619 aseptic revision cases performed between December 1998 and October 2018. This included 138 UKAs that underwent conversion to TKA and 481 initial TKA revisions. Age, body mass index (BMI), time in situ, OKS, and ROM were available for all patients.

RESULTS

There were no differences between the two groups based on demographics or time to revision. The top reasons for aseptic TKA revision were loosening in 212 (44%), instability in 88 (18%), and wear in 69 (14%). UKA revision diagnoses were primarily for loosening in 50 (36%), progression of osteoarthritis (OA) in 50 (36%), and wear in 17 (12%). Out of a maximum 48 points, the mean OKS of the UKAs before revision was 23 (SD 9.3), which was significantly higher than the TKAs at 19.2 (SD 9.8; p < 0.001). UKA patients scored statistically better on nine of the 12 individual OKS questions. The UKA cases also had a larger pre-revision mean ROM (114°, SD 14.3°) than TKAs (98°, SD 25°) ; p < 0.001).

CONCLUSION

At revision, the mean UKA OKSs and ROM were significantly better than those of TKA cases. This study suggests that at our institution there is a difference in preoperative OKS between UKA and TKA at the time of revision, demonstrating a revision bias. Cite this article: Bone Joint J 2020;102-B(6 Supple A):91-95.

The Impact of Coronal Alignment on Revision in Medial Fixed-Bearing Unicompartmental Knee Arthroplasty

BACKGROUND

To better define the optimal alignment target for medial fixed-bearing unicompartmental knee arthroplasty (UKA), this study compares the postoperative mechanical alignment of well-functioning UKAs against 2 groups of failed UKAs, including revisions for progression of lateral compartment osteoarthritis ("Progression") and revisions for aseptic loosening or subsidence ("Loosening").

METHODS

From our prospective institutional database of 3351 medial fixed-bearing UKAs performed since 2000, we identified 37 UKAs revised for Progression and 61 UKAs revised for Loosening. Each of these revision cohorts was matched based on age at surgery, gender, body mass index, and postoperative range of motion with unrevised UKAs that had at least 10 years of follow-up and a Knee Society Score of 70 or greater without subtracting points for alignment ("Success" groups). Postoperative alignment was quantified by the hip-knee-ankle (HKA) angle measured on long-leg alignment radiographs.

RESULTS

The mean HKA angle at 4-month follow-up for the Progression group was 0.3° ± 3.6° of valgus compared to 4.4° ± 2.6° of varus for the matched Success group (P < 0.001). For the Loosening group, the mean HKA angle was 6.1° ± 3.1° of varus versus 4.0° ± 2.7° of varus for the matched Success group (P < 0.001).

CONCLUSIONS

Patients with well-functioning UKAs at 10 years exhibited mild varus mechanical alignment of approximately 4°, whereas patients revised for progression of osteoarthritis averaged more valgus and those revised for loosening or subsidence averaged more varus. The optimal mechanical alignment for medial fixed-bearing UKA survival with contemporary polyethylene is likely slight varus.

To Cement or Not? Five-Year Results of a Prospective, Randomized Study Comparing Cemented vs Cementless Total Knee Arthroplasty

BACKGROUND

The optimal mode of fixation in total knee arthroplasty is a continuing subject of debate.

METHODS

Previously, we reported 2-year results for this prospective, randomized trial. Knee Society Scores, Oxford scores, and pain visual analog scales were collected pre-operatively and post-operatively. Minimum 5-year follow-up has been obtained with radiographic analysis for 85 patients.

RESULTS

Mean Knee Society Scores and Oxford scores and patient-reported outcomes were similar in both groups. Each group had 1 additional revision, but neither was related to implant fixation. Survivorship with revision as an endpoint was equivalent (95.9% and 95.3%, P = .98). There was no significant difference in radiolucencies observed between groups (P = .10), all were non-progressive.

CONCLUSION

Cementless and cemented total knee arthroplasty had equivalent patient-reported outcomes and survivorship at midterm follow-up. Updates are planned at 10 and 15-year intervals to observe long-term modes of failure between these 2 methods of fixation.

Is Outpatient Unicompartmental Knee Arthroplasty Safe to Perform at an Ambulatory Surgery Center? A Comparative Study of Early Post-Operative Complications

BACKGROUND

Unicompartmental knee arthroplasty (UKA) lends itself to the outpatient surgical setting. Prior literature has established a low rate of readmission and post-operative complications when performed in a hospital outpatient setting (HOP). To our knowledge, there have been no studies comparing complications of UKA performed at an ambulatory surgery center (ASC) and those in a HOP.

METHODS

We retrospectively reviewed all patients who underwent outpatient UKA by a single surgeon from 2012 to 2016. In all 569 outpatient UKAs were performed: 288 in the ASC group and 281 in the HOP group. We compared the groups with regard to all complications within the first 90 days after surgery.

RESULTS

Thirty minor and major complications occurred within 90 days (5.3%). There was no difference in the overall complication rate between groups (ASC 12, 4.2%; HOP 18, 6.4%) (P = .26). Day of surgery admission occurred once in the HOP group (0.4%) and did not occur in the ASC group (P = .49). There was 1 visit to the emergency department (ED) <24 hours from surgery in each group (ASC 0.3%, HOP 0.4%) (P = 1.0). ED visits occurred within 7 days in 3 ASC cases (1.0%) and 4 HOP cases (1.4%) (P = .72). Re-admissions in the first 90 days occurred in 5 ASC cases (1.7%) and 8 HOP cases (2.8%) (P = .41).

CONCLUSION

UKA at an ASC has a low early postoperative complication rate without increased risk of re-admission or ED evaluation when compared to UKAs performed at a HOP.

To Cement or Not? Two-Year Results of a Prospective, Randomized Study Comparing Cemented Vs. Cementless Total Knee Arthroplasty (TKA)

The optimal mode of fixation in total knee arthroplasty (TKA) is a subject of debate. We enrolled 100 TKA patients randomized to cemented or cementless fixation. Knee Society Scores (KSS), Oxford scores and pain visual analog scales (VAS) were collected pre-operatively and post-operatively. Two-year follow-up was obtained for 93 patients. The mean VAS trended higher for the cementless group at 4 months (P=0.06). At 2 years, the KSS functional scores, Oxford scores, and self-reported questions for satisfaction, less pain and better function were similar but the cemented group had higher KSS clinical scores (96.4 vs. 92.3, P=0.03). More radiolucencies were seen in cementless knees (P<0.001). The cementless group had one revision for instability and one cemented knee was revised for infection. Cementless TKA showed equivalent survivorship (revision for any reason as the endpoint) compared to cemented TKA at this early follow-up. Close monitoring of radiolucencies is important with continued follow-up.

Greater Trochanteric Fragmentation After Failed Metal-on-Metal Hip Arthroplasty

Adverse reaction to metal debris (ARMD) involving the hip joint has emerged as an important reason for failure and revision among patients with metal-on-metal (MOM) hip arthroplasty. To the authors' knowledge, there are no reports of adverse radiographic sequelae in the greater trochanter subsequent to revision for ARMD. The authors describe clinical and radiographic findings in 2 patients who developed greater trochanteric fragmentation 1 to 2 years after conversion of their failed MOM hips to polyethylene bearings. Both patients had solid pseudotumors with tissue necrosis. Several reports describe various clinical features of ARMD. Although poor outcomes have been demonstrated after some MOM revisions, to the authors' knowledge, no reports document greater trochanter fragmentation in ARMD. The current patients highlight the fact that tissue damage occurring with MOM bearing hips can involve bone in addition to soft tissue even after a pseudotumor has been removed and serum metal levels have decreased to normal levels after revision. Unlike the greater trochanteric fractures historically associated with polyethylene wear and osteolysis, no evidence of bone cysts or lesions was found prior to the fractures and neither fracture healed with conservative treatment. For these 2 patients, the authors believe the tissue necrosis included both soft tissue and bone. The necrotic bone resorbed gradually after removal of the MOM bearing, resulting in bone fragmentation with ongoing symptoms. These patients emphasize and remind us that damage is not only limited to soft tissues, but also includes bone. Surgeons should be aware of this radiographic finding and the associated clinical symptoms.

Mechanical thromboembolic prophylaxis with risk stratification in total knee arthroplasty

The purpose of this study was to determine the rate of thromboembolic and bleeding complications when using mechanical prophylaxis with preoperative risk stratification following total knee arthroplasty (TKA). Between 1994 and 2007, 4037 TKAs were performed on 3144 patients at our institution. Mechanical VTE prophylaxis was used for standard risk patients, which included AV impulse foot pumps, thigh high stockings, and early mobilization. Chemoprophylaxis was only given to patients who were at increased thromboembolic risk. The incidence of DVT identified by ultrasound following TKA was 2.1%. A retrospective review showed 1 patient had a fatal pulmonary embolism, and 5 patients had bleeding complications in the knee. We conclude that mechanical thromboembolic prophylaxis using risk stratification is safe and effective following TKA.

Do you have to remove a corroded femoral stem?

Corrosion at the head-neck taper has been recently identified as a cause of adverse local tissue reaction. There are no guidelines concerning removal of fixed femoral components when corrosion is present. The objective of this study is to report the survivorship when a new metal ball is placed on a corroded stem. We examined 86 retrieved femoral heads from metal-on-polyethylene THAs that underwent head and liner exchanges after a minimum 10 years in-vivo and evaluated the subsequent survivorship. There were 7 re-revisions (8.1%) but none were for corrosion-related diagnoses and there was no difference in the survivorship between the 32 THAs with high-grade head taper corrosion and the 54 THAs with low-grade corrosion. We do not currently recommend removing well-fixed femoral stems with corrosion.

Metal-on-metal local tissue reaction is associated with corrosion of the head taper junction

We evaluated taper corrosion in 36-mm diameter metal-on-metal (MOM) and metal-on-polyethylene (MOP) femoral heads from a single manufacturer retrieved for various reasons. Three reviewers visually graded taper corrosion with a 5-point scale on 19 MOM heads and 14 MOP heads. The MOM group had a higher corrosion score than the MOP group (mean, 3.5 vs 1.9; P < .001). There were 8 MOM heads (42%) and only 1 MOP head (7%) that demonstrated corrosion outside of the taper zone. Metal-on-metal patients revised secondary to adverse local tissue reactions (ALTRs) had greater scores than patients without ALTRs (mean, 4.36 vs 2.38; P < .01). Adverse local tissue reactions MOM patients were also likely to have corrosion outside of the taper junction. The corrosion score increased with implantation time, and at all time intervals, the corrosion score for the MOM group was greater. Because corrosion worsens with time, we are concerned that MOM ALTR failures will increase with longer follow-up.

Five Duraloc locking ring failures

We report on 5 cases that underwent revision for locking ring failure in the Duraloc product line (DePuy, Warsaw, Ind). All liner retrievals showed signs of posterior neck/liner impingement and superior edge loading or significant wear. In these cases, we believe superior head migration and neck/liner impingement due to cup anteversion contributed to these locking ring failures. More research is needed to determine the incidence of this complication. Patients with locking ring failures should be closely monitored. Full cup revision, face-changing liners, or cementing liners into well-fixed cups are all options to correct suboptimal cup positioning.

Survivorship of a low-stiffness extensively porous-coated femoral stem at 10 years

A novel low-stiffness extensively porous-coated total hip femoral component was designed to achieve stable skeletal fixation, structural durability, and reduced periprosthetic femoral stress shielding. In short- to intermediate-term clinical review, this implant achieved secure biologic fixation and preserved periprosthetic bone. We retrospectively reviewed all 102 prospectively followed patients (106 implants) with this implant to document the longer-term implant survivorship, clinical function, fixation quality, and periprosthetic bone preservation. Ninety-seven patients with 101 implants had current followup or were followed to patient death (range, 1-14 years; average, 10 years). Eighty-six living patients were followed for an average implant survivorship of 10 years. There were no known femoral implant removals. The average Harris hip score at 10-year followup was 98. Radiographs demonstrated secure implant fixation and maintenance of periprosthetic bone. These data suggest this implant design provided long-term function characterized by extensive fixation, structural durability, and radiographic appearance of maintained periprosthetic cortical thickness and density.

LEVEL OF EVIDENCE

Level I, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Constrained liners in revision total hip arthroplasty: an overuse syndrome: in the affirmative

Instability after primary and revision total hip arthroplasty continues to be problematic for the surgeon. The use of constrained liners, which use a locking mechanism to capture the femoral head, has increased to help manage this problem. Constrained liners, however, present problems with acetabular component loosening, dissociation of the liner/shell interface, failure by breakage, and excessive polyethylene wear. Rather than resort to constrained liners, our approach has been to restore joint stability with large-diameter femoral heads. The advantages are increased range of motion due to more favorable head/neck ratio, increased resistance to dislocation due to increased jump distance, and the avoidance of skirted femoral heads. With the addition of cross-linked polyethylene, the volumetric wear associated with large heads is much decreased and makes this a viable option today.

Biomechanical analysis of antegrade and retrograde flexible intramedullary nail fixation of pediatric femoral fractures using a synthetic bone model

Biomechanical testing was performed to evaluate the stability of simulated transverse and comminuted femoral fractures after retrograde and antegrade flexible titanium intramedullary nail fixation. Ten synthetic adolescent-sized femoral bone models were used. Five underwent retrograde fixation with two C-shaped nails inserted from medial and lateral entry portals. The other five underwent antegrade fixation using one C- and one S-shaped nail through lateral entry holes just inferior to the greater trochanter. Retrograde nail fixation demonstrated significantly less axial range of motion and greater torsional stiffness than antegrade fixation in both transverse and comminuted fracture patterns. However, there appeared to be a biomechanical trend of greater resistance to shortening for antegrade nails.

Utility of three-dimensional and multiplanar reformatted computed tomography for evaluation of pediatric congenital spine abnormalities

STUDY DESIGN

A retrospective radiographic review of 31 patients with congenital spine abnormalities who underwent conventional radiography and advanced imaging studies was conducted.

OBJECTIVE

To analyze the utility of three-dimensional computed tomography with multiplanar reformatted images for congenital spine anomalies, as compared with plain radiographs and axial two-dimensional computed tomography imaging.

SUMMARY OF BACKGROUND DATA

Conventional radiographic imaging for congenital spine disorders often are difficult to interpret because of the patient's small size, the complexity of the disorder, a deformity not in the plane of the radiographs, superimposed structures, and difficulty in forming a mental three-dimensional image. Multiplanar reformatted and three-dimensional computed tomographic imaging offers many potential advantages for defining congenital spine anomalies including visualization of the deformity in any plane, from any angle, with the overlying structures subtracted.

METHODS

The imaging studies of patients who had undergone a three-dimensional computed tomography for congenital deformities of the spine between 1992 and 1998 were reviewed (31 cases). All plain radiographs and axial two-dimensional computed tomography images performed before the three-dimensional computed tomography were reviewed and the findings documented. This was repeated for the three-dimensional reconstructions and, when available, the multiplanar reformatted images (15 cases). In each case, the utility of the advanced imaging was graded as one of the following: Grade A (substantial new information obtained), Grade B (confirmatory with improved visualization and understanding of the deformity), and Grade C (no added useful information obtained).

RESULTS

In 17 of 31 cases, the multiplanar reformatted and three-dimensional images allowed identification of unrecognized malformations. In nine additional cases, the advanced imaging was helpful in better visualizing and understanding previously identified deformities. In five cases, no new information was gained. The standard and curved multiplanar reformatted images were best for defining the occiput-C1-C2 anatomy and the extent of segmentation defects. The curved multiplanar reformatted images were especially helpful in keeping the spine from "coming in" and "going out" of the plane of the image when there was significant spine deformity in the sagittal or coronal plane. The three-dimensional reconstructions proved valuable in defining failures of formation.

CONCLUSIONS

Advanced computed tomography imaging (three-dimensional computed tomography and curved/standard multiplanar reformatted images) allows better definition of congenital spine anomalies. More than 50% of the cases showed additional abnormalities not appreciated on plain radiographs or axial two-dimensional computed tomography images. Curved multiplanar reformatted images allowed imaging in the coronal and sagittal planes of the entire deformity.

Asymmetrical flexible tethering of spine growth in an immature bovine model

STUDY DESIGN

A 12-week bovine survival study of tethering anterior spine growth that included untethered control subjects.

OBJECTIVE

To determine the effects that a flexible cable attached to the anterolateral aspect of the thoracic spine has on spine growth in rapidly growing calves.

SUMMARY OF BACKGROUND DATA

The search for a way to correct scoliosis without the use of an arthrodesis continues in an attempt to maintain normal spine mobility. Experience in the hemiepiphyseal stapling of long bones has provided a background rationale for attempting growth modulation in the spine. It is postulated that a mechanical tether to the anterior and lateral growth of the spine in a growing child with scoliosis may allow spontaneous correction of sagittal and coronal plane deformity obviating the need for an arthrodesis.

METHODS

Eight calves (age, 3-4 weeks; weight, 47 +/- 4.6 kg) underwent right-side thoracotomies exposing the thoracic spine. Laterally directed anterior vertebral body screws were placed into each body and two vertebrae, either T6 and T7 or T8 and T9, were tethered with a stainless steel cable. After 12 weeks, radiographs were obtained to evaluate the degree of deformity that had developed. In addition, biomechanical testing to determine the range of motion in the tethered and untethered segments was performed.

RESULTS

The calves increased their weight 153% during the 12-week postoperative period. The radiographic analysis demonstrated scoliosis of 11.6 degrees +/- 4.8 degrees in the tethered levels, as compared with 0.3 degrees +/- 1.7 degrees in the control segments (P < 0.0001). Similarly, kyphosis developed in the tethered segments (5.1 degrees +/- 5.8 degrees ), as compared with -1.8 degrees +/- 3.1 degrees at the control levels (P = 0.01). There was a significant wedging of the disc in the tethered (6.8 degrees +/- 1.6 degrees ) as compared with the untethered (0.7 degrees +/- 2 degrees ) segments (P < 0.0001). There was a trend toward lower height of the vertebrae on the tethered right side, as compared with the left side in the tethered segments (P = 0.075), whereas no side-to-side difference was noted in the control subjects (P = 0.48). Biomechanical analysis showed that the tether did not affect the range of motion in axial rotation or flexion-extension. However, the tether did restrict lateral bending as compared with that of the control subjects. When the tether was cut, the range of motion returned to levels matching that of the untethered control subjects.

CONCLUSIONS

Anterolateral tethering of the spine creates kyphosis and scoliosis in this rapidly growing bovine model. The spinal tether limited motion primarily in lateral flexion. However, total lateral bending motion returned to levels comparable with control motion segments after removal of the tether. This method of spine growth modulation may provide a possible treatment for the correction of spine deformities without arthrodesis in patients who are skeletally immature. The exact mechanisms of growth modulation and the effects of tethering on disc function and integrity are unknown and deserve further study.

Biomechanical analysis of anterior scoliosis instrumentation: differences between single and dual rod systems with and without interbody structural support

STUDY DESIGN

Nondestructive biomechanical testing was performed on bovine lumbar spines instrumented with multilevel scoliosis type anterior spine constructs.

OBJECTIVE

To determine the biomechanical effects from the number of anterior rods (1 vs 2) and the effects of interbody structural support on construct stiffness after anterior multisegmental instrumentation.

SUMMARY OF BACKGROUND DATA

Corrective surgery using anterior instrumentation for thoracolumbar and lumbar scoliosis has been performed with single rod and, more recently, with dual rod constructs. The biomechanical effect of one- or two-rod anterior instrumentation systems on construct stiffness and the addition or absence of interbody structural support have not been defined adequately in the literature.

METHODS

Eight bovine lumbar spines each underwent instrumentation using four different constructs: one rod without interbody support; one rod with titanium mesh interbody support at the L2-L3, L3-L4, and L4-L5 disc spaces; two rods alone; and two rods with interbody support. Nondestructive cyclic testing in flexion-extension (+/-5 Nm), lateral bending (+/-5 Nm), and torsion (+/-2 Nm) were performed. The construct stiffness (Nm/ degrees ) of the four implant configurations was compared.

RESULTS

With the addition of a second rod, the construct was significantly stiffer than a single rod construct in flexion (P = 0.006), extension (P = 0.02), and torsion (P = 0.01), but not in lateral bending. The addition of interbody structural support to the rod systems resulted in significantly stiffer constructs than those without cages in flexion (P = 0.03), but not in the other loading conditions (extension, lateral bending, torsion).

CONCLUSIONS

Dual rod constructs were stiffer in torsion and flexion-extension loading than single rod constructs. Neither the number of rods nor the use of structural mesh interbody support had any effect on lateral bending stiffness. However, in a single rod system, the addition of interbody support increased stiffness in flexion. The use of structural support in dual rod constructs may be helpful in "setting" the desired lordosis, but adds little to construct stiffness.

Spinal lordosis with marked opisthotonus secondary to dystonia musculorum deformans: case report with surgical management

STUDY DESIGN

A case report of severe spinal lordosis with marked opisthotonus and retrocollis secondary to dystonia musculorum deformans is presented.

OBJECTIVE

To describe a case of dystonia musculorum deformans with progressive spinal lordosis and its surgical treatment.

SUMMARY OF BACKGROUND DATA

Four patients with correction of coronal spinal deformity associated with dystonia musculorum deformans have been reported in the literature. No reports of sagittal spinal deformity treated with surgical instrumentation and fusion were found.

METHODS

A retrospective chart and radiographic review of a single case was conducted.

RESULTS

Orthotic management and pharmacologic therapy with botulinum toxin injections were unsuccessful in controlling the deformity. Severe spinal lordosis (170 degrees ) from occiput to sacrum was corrected surgically, allowing an upright posture.

CONCLUSION

Dystonia musculorum deformans is a rare condition resulting in coronal or sagittal plane deformities. When other treatment methods are unsuccessful, surgical instrumentation and arthrodesis may correct the deformity and improve function.