Surgical technique: Computer-assisted sliding medial condylar osteotomy to achieve gap balance in varus knees during TKA

Role and Results of Constrained Insert in Computer-Assisted Primary Total Knee Arthroplasty: A Propensity-Matched Study

Purpose

Mild ligament imbalance is often encountered in the mediolateral plane during complex primary total knee arthroplasty. A constrained (CP) polyethylene insert compatible with the primary femur is useful to manage these cases without the need to fall back on revision implants. The aim of the study was to define the correct indications of the use of a CP insert based on objective data from computer assisted surgery and to compare the early results of a CP insert with a standard posterior stabilized (PS) insert through one-to-one propensity score matching.

Methods

This is a retrospective case study from a prospectively collected database. One-to-one matching without replacement was used with a caliper width of 0.2 to match the scores between CP (N = 64) and PS groups (N = 1624), resulting in equal covariate matching of PS (N = 64) and CP (N = 64) cohorts. Patients were assessed radiographically and functionally at a minimum follow-up of 3 years.

Result

Average coronal and sagittal plane deformities were similar in both the group CP (varus 13.1 ± 5.2 valgus 13 ± 7.9) and the group PS (varus 13.4 ± 4.6 valgus 10.9 ± 8.6). The average residual medial lateral gap difference was significantly higher in group CP (3.8 ± 1.8) in comparison to group PS (1.3 ± 1) (P < .05). A CP insert was chosen where mild ligament imbalance of 3-5 mm persisted after medial soft tissue releases in a varus knee and in cases with residual medial collateral ligament laxity in valgus knees.

Conclusions

Constrained insert used with the primary femoral component is a valuable option to handle mild ligamentous instability in complex primary total knee arthroplasty after mechanical alignment is achieved with computer navigation.

Level of Evidence

III.

Complete Release of the Superficial Medial Collateral Ligament in Total Knee Arthroplasty

Background

Proper soft-tissue balance was essential in total knee arthroplasty (TKA). Superficial medial collateral ligament (sMCL) release has been recommended in correction of severe varus knee. However, it has concerns of overcorrection. This study aimed to analyze coronal plane laxity in sMCL-released TKA patients.

Methods

We prospectively collected data from TKA patients who were operated from January 2015 to November 2018. All patients went through the same surgical steps; however, sMCL was left intact in mild-to-moderate deformity (sMCL-intact), while it was completely released in patients with severe deformity (sMCL-released). All patients went through the same postoperative protocol. We used stress radiograph with 90 N force to evaluate coronal plane laxity and recorded modified Western Ontario and McMaster Universities Osteoarthritis Index score at 3- to 6-year postoperative appointments.

Results

There were 46 patients (59 knees) included with an average follow-up time of 48.3 months. The sMCL-intact group consisted of 14 patients (16 knees) with average preoperative mechanical axis (MA) varus of 4.84 degrees exhibited 1.64 mm (0.6-3.6 mm) laxity on medial side and 1.01 mm (0-3.1 mm) on lateral side. The sMCL-released group consisted of 32 patients (43 knees) with average preoperative MA varus of 14.74 degree exhibited 1.96 mm (0.4-4.8 mm) laxity on medial side and 1.57 mm (0.1-5.9 mm) on lateral side. At the time of follow-up, the mean modified Western Ontario and McMaster Universities Osteoarthritis Index in the sMCL-intact and sMCL-released groups were 14.8 and 13.5 (P value .79), respectively. There was no clinical laxity or reoperation of any causes in either groups.

Conclusions

Complete release of sMCL in severe varus knee does not result in overcorrection after TKA at the midterm follow-up period. Thus, sMCL release technique could be an effective and safe option for correction of severe varus deformity.

Predictive Factors for Lateral Hinge Fracture in Medial Closing Wedge Distal Femoral Osteotomy

BACKGROUND

Recent studies have reported that lateral hinge fracture (LHF) has a negative effect on bone healing at the osteotomy site after medial closing wedge distal femoral osteotomy (MCDFO). However, limited evidence exists in the literature regarding the predictive factors for LHF in MCDFO.

HYPOTHESIS

A large medial closing gap and a lateral hinge position in the supracondylar area would increase plain radiography-based and/or computed tomography (CT)-based LHF in MCDFO.

STUDY DESIGN

Case control study; Level of evidence, 3.

METHODS

We retrospectively evaluated 67 knees of 53 patients (mean age, 37.4 ± 16.9 years) who underwent MCDFO between May 2009 and June 2021. The surgical indications for MCDFO were genu valgum deformity combined with either lateral compartment osteoarthritis or recurrent patellar dislocation. The presence of LHF was evaluated based on immediate postoperative plain radiography and CT scans. The predictive factors for LHF in MCDFO were investigated using multivariate logistic regression analysis.

RESULTS

LHFs were identified in 21 knees (31.3%) through plain radiography and in 40 knees (59.7%) through CT. Multivariate logistic regression analysis showed that the medial closing gap and lateral hinge position were predictive factors for plain radiography- and CT-based LHF after MCDFO. Controlling for other variables, we found that an increase in the medial opening gap by 1 mm increased the likelihood of plain radiography-based LHF by a factor of 1.805 (95% CI, 1.291-2.525; P = .001) and CT-based LHF by 1.333 (95% CI, 1.003-1.772; P = .048). Moreover, a lateral hinge position in the supracondylar area increased the likelihood of plain radiography-based LHF by a factor of 9.870 (95% CI, 2.179-44.720; P = .003) and CT-based LHF by 5.686 (95% CI, 1.124-28.754; P = .036).

CONCLUSION

A large medial closing gap and lateral hinge position in the supracondylar area are associated with LHF in MCDFO. Care should be taken to prevent LHF in MCDFO with a large medial closing gap. Moreover, a lateral hinge position in the supracondylar area should be avoided to decrease the incidence of LHF in MCDFO.

Seven phenotypes of varus osteoarthritic knees can be identified in the coronal plane

PURPOSE

Recommendations for resecting distal femur and proximal tibia in mechanical and anatomical alignment techniques are standardized. Kinematic alignment propagates individualizing resection planes. Whether significant variation exists, to warrant departure from standardized resection planes, has not been shown thus far in a large cohort of knees and with a wide range of varus deformity. The null hypothesis of this study was that there was no phenotypic variation in varus osteoarthritic knees. The aim of this paper was to determine whether distinct phenotypes could be identified, based on variations in coronal femoral and tibial morphology, which could aid in surgical planning and categorizing varus knees for future studies.

METHODS

2129 full-leg weightbearing radiographs were analyzed (1704 preoperative; 425 of contralateral arthritic knee). Measurements made were of HKA (hip-knee-ankle angle), VCA (valgus correction angle), mLDFA (lateral mechanical distal femoral angle), aLDFA (lateral anatomical distal femoral angle), MPTA (medial proximal tibial angle), MNSA (medial neck shaft angle), TAMA (angle between tibial mechanical and anatomical axes), and TPDR (percentage length of tibia proximal to extra-articular deformity).

RESULTS

Seven distinct types were identified covering 2021 knees, reducible to 4 broad phenotypes: 11% were Type 1 'Neutral' knees showing values close to reported normal knees (mean VCA 5.5°, mLDFA 87°, aLDFA 81°). 38% were Type 2 'Intra-articular varus' with medial intra-articular bone loss (mean mLDFA 90.9°, MPTA 85.4°, VCA of 5.7°). 41% were Type 3 'Extra-articular varus' with extra-articular deformity (EAD). Type 3a had proximal tibial EAD; Type 3b had tibial diaphyseal EAD; Type 3c had femoral EAD (mean VCA 8.7°, HKA 166°), and severe medial bone loss (mean mLDFA 92°, MPTA 83°). 9% were Type 4 'Valgoid type' with features of valgus knees: Type 4a had medial femoral bowing (mean VCA 2.9°); Type 4b had significant distal femoral valgus (mean mLDFA 85.3°, aLDFA 78.6°).

CONCLUSIONS

The null hypothesis that there was no phenotypic variation in varus osteoarthritic knees was rejected as considerable variation was found in coronal morphology of femur and tibia. Four broad phenotypic groups could be identified. Plane of the knee joint articular surface was quite variable. This has relevance to planning and performance of corrective osteotomies, unicompartmental and total knee arthroplasty.

LEVEL OF EVIDENCE

III, retrospective cohort study.

Measurement for gap balancing technique in patients undergoing total knee arthroplasty: a large retrospective observational study

Background

Many traditional methods are available to prevent unbalance of extension and flexion gap during total knee arthroplasty (TKA), but there are no reports on the use of measurement and positioning method before tibial osteotomy with self-made tools. We designed a self-made tool measuring the location before tibial osteotomy and determined the clinical effect.

Methods

The retrospective study included patients who received TKA at our hospital, between January 1, 2012 and December 31, 2015. A new method, named as the measurement and localization before osteotomy with self-made tools, was developed to measure the osteotomy position of the posterior femoral condyle during TKA. They were divided into two groups, one that received the new method (Group I), and the other that received the traditional method as a control (Group I I). HSS score, Oxford score, VAS score and knee joint activity were evaluated in two groups.

Results

One hundred and eighty-seven of 210 eligible patients were included. The function of knee joint in all patients was improved and the pain was obviously relieved. Significant differences were found in the HSS score, Oxford score, VAS score, knee joint activity between two groups at 5-year follow-up (p < 0.05).

Conclusions

The biomet knee prosthesis was selected for all intraoperative implants. All operations were completed by the same senior surgeon. The use of self-made tools may contribute to improve the balance between flexion and extension gaps as well as the balance between internal and external gaps during TKA, and overcome knee flexion instability.

Is Static Alignment a Good Predictor of Dynamic Alignment after Total Knee Arthroplasty?

Background: Total knee arthroplasty (TKA) is the only effective treatment of end-stage knee osteoarthritis (OA). Lower limb neutral alignment has been a criterion to predict prosthesis life; however, there has been recent controversy over this. Some researchers believe that lower limb static alignment does not significantly affect prosthesis life and some researchers have found that dynamic mechanical alignment may affect prosthesis life, which needs to be further studied. Methods: Eighty-seven patients with knee OA were evaluated by a three-dimensional (3D) gait analysis system before TKA and six months after TKA, dynamic mechanical alignment and basic gait parameters were then calculated. Based on the static alignment of the lower limb on the postoperative X-radiographs, they were divided into a neutral alignment group (58 cases), varus alignment group (20 cases), and valgus alignment group (9 cases). Simple linear regression was used to assess the correlation between static and dynamic alignment. One-way analysis of variance (ANOVA) was used to compare the differences in gait parameters between and within groups. Results: Eighty-seven patients were followed up for an average of six months after the operation. There was no significant difference in all gait parameters among the three groups after TKA. There was no correlation found between static alignment and dynamic alignment/knee adduction moment (KAM) after TKA, although patients showed a significant linear correlation before operation. There was a significant linear correlation between dynamic alignment and KAM before and after the operation. Conclusions: Static alignment has no significant effect on postoperative gait function. Static alignment is no longer an effective predictor of the dynamic alignment or KAM six months after TKA, although they are correlated before TKA. The dynamic alignment allows for better prediction of KAM, which may be a risk factor for the life of the prosthesis.

Navigation and robotics improved alignment compared with PSI and conventional instrument, while clinical outcomes were similar in TKA: a network meta-analysis

PURPOSE

To achieve the desired alignment more accurately and improve postoperative outcomes, new techniques such as computer navigation (Navigation), patient-specific instruments (PSI) and surgical robots (Robot) are applied in Total Knee Arthroplasty (TKA). This network meta-analysis aims to compare the radiological and clinical outcomes among the above-mentioned techniques and conventional instruments (CON).

METHODS

A PRISMA network meta-analysis was conducted and study protocol was published online at INPLASY (INPLASY202060018). Three databases (PubMed, EMBASE and Cochrane) were searched up to June 1, 2020. Randomised controlled trials (RCTs) comparing any two of the four techniques were included. A Bayesian network meta-analysis was performed focusing on radiological and clinical outcomes. The odds ratio (OR) or mean difference (MD) in various outcomes were calculated, and the interventions were ranked by the surface under the cumulative ranking area (SUCRA) value.

RESULTS

Seventy-three RCTs were included, with a total of 4209 TKAs. Navigation and Robot could significantly reduce the occurrence of malalignment and malposition compared with PSI and CON, and Navigation could obtain higher medium-and-long-term KSS knee scores than CON. Robot had the greatest advantage in achieving the desired alignment accurately, followed by Navigation; Navigation had the greatest advantage in the KSS score.

CONCLUSION

Navigation and Robot did improve the accuracy of alignment compared with PSI and conventional instrument in TKA, but the above four techniques showed no clinical significance in postoperative outcomes.

LEVEL OF EVIDENCE

I.

Custom TKA enables adequate realignment with minimal ligament release and grants satisfactory outcomes in knees that had prior osteotomies or extra-articular fracture sequelae

PURPOSE

To report the early clinical and radiographic outcomes of custom total knee arthroplasty (TKA) in knees that had prior osteotomies and/or extra-articular fracture sequelae.

METHODS

The authors retrospectively analysed a consecutive series of 444 knees that received custom TKA between 2016 and 2019 and identified 41 knees that had prior extra-articular events (osteotomies or fracture sequelae). Patients responded to pre- and post-operative (> 12 months) questionnaires, including Knee Society Score (KSS), Oxford Knee Score (OKS), Forgotten Joint Score (FJS) and Knee injury and Osteoarthritis Outcome Score (KOOS). Net improvements were calculated by subtracting pre- from post-operative scores. In addition to a preoperative CT scan, pre- and post-operative long-leg weight-bearing radiographs were obtained, on which the hip-knee-ankle (HKA) angle, femoral mechanical angle (FMA, between femoral mechanical axis and joint line) and tibial mechanical angle (TMA, between tibial mechanical axis and joint line) angles were measured, and alignment was planned within a 'target zone' of FMA and TMA within 85°-95° and HKA angle within 175°-183°. Agreements between preoperative, planned and post-operative angles were calculated using intra-class correlation coefficients (ICC).

RESULTS

From the initial 41 knees, 3 had incomplete post-operative data and 1 was revised for painful stiffness due to uncorrected rotational malunion, leaving 37 knees for analysis. Twenty had prior osteotomies (tibia, n = 18, femur, n = 2), 8 had isolated fractures (tibial, n = 3; femoral, n = 5), and 9 had both osteotomies and fractures. Postoperative coronal alignments were 90.4° ± 2.4° for FMA, 89.3° ± 2.6° for TMA and 179.9° ± 3.0° for HKA angle. Agreements between planned and achieved alignments were fair to excellent, and 29 (78%) knees were within the 'target zone'. At a mean follow-up of 15 ± 5 months, all clinical scores had improved significantly (p < 0.001).

CONCLUSIONS

Custom TKA granted satisfactory clinical outcomes and a low complication rate in knees that had prior osteotomies and/or extra-articular fracture sequelae. Using custom implants and strategies for coronal alignment, 29 (78%) of the 37 knees were successfully aligned within the 'target zone', and 35 (95%) of the 41 knees did not require ligament release.

LEVEL OF EVIDENCE

IV.

Influence of Intraoperative Medial Collateral Ligament Bony Avulsion Injury on the Outcome of Primary Total Knee Arthroplasty

BACKGROUND

The purpose of this study is (1) to find the clinical and radiological outcome of intraoperative bony avulsion of medial collateral ligament (MCL) treated with screw and washer construct and (2) to predict the preoperative factors which may contribute to the avulsion-type MCL injury during primary total knee arthroplasty (TKA).

METHODS

Intraoperative MCL avulsion injury occurred in 46 (0.8%) of the 4916 consecutive primary TKA from January 2011 to December 2015. After exclusion, the 41 knees were matched 1:2 with controls without MCL injury and compared for the various clinical, radiological, and functional parameters. The clinical parameters analyzed were age, gender, body mass index, preoperative diagnosis like osteoarthritis or rheumatoid arthritis, range of motion, sagittal deformity, and vitamin D levels. The radiological parameters calculated were coronal deformity, proximal tibial varus angle, distal femur valgus angle, joint line congruence angle, posterior tibial slope, "cup and saucer" morphology, presence or absence of knee subluxation, tibia vara, and femoral bowing. The preoperative and postoperative Knee Society Score and Knee Society Functional Score were analyzed. Complications or revisions, if any, were noted during the follow-up. Multivariate logistic regression analysis was used to predict the preoperative risk factors for MCL avulsion injury.

RESULTS

At a mean follow-up of 58.4 ± 19.3 months, there were no radiological or physical examination findings of instability. Compared to the preoperative disability, there was a statistically significant improvement in clinical scores (Knee Society Score and Knee Society Functional Score) in the final follow-up (P < .001) in both cases and the control group. The mean preoperative coronal deformity was 170.6 ± 6.96 in the study group and 167.7 ± 4.3 in the control group (P = .021). The mean preoperative tibial slope was 10.5 ± 4.9 in the study group and 7.91 ± 4.15 in the control group (P = .003). The preoperative knee subluxation was present in 48.8% knees (P < .001) and "cup and saucer" morphology in 68.3 knees (P < .001) in the study group. The adjusted odds of MCL avulsion injury were greater for severe varus deformity (odds ratio [OR] 1.462, 95% confidence interval [CI] 1.15-1.86), knee subluxation (OR 39.78, 95% CI 3.78-418.86), and "cup and saucer" morphology (OR 33.11, 95% CI 5.69-192.66).

CONCLUSION

Intraoperative MCL bony avulsion injury can be managed successfully with screw and washer construct without the need for increased prosthetic constraint in primary TKA. The presence of severe varus deformity, knee subluxation, and "cup and saucer" morphology tend to have an increased chance of MCL avulsion injury.

Primary Results of Medial Epicondylar Osteotomy in Patients with Severe Bilateral Varus Knee Candidate for Total Knee Replacement

Total knee arthroplasty is a challenging task in patients with severe varus deformity. In most of these patients, an extensive medial release is needed that may lead to instability. Medial epicondylar osteotomy may be a better substitute for complete medial collateral release. Fourteen patients with bilateral knee osteoarthritis and severe varus deformity were enrolled in this study. In one side, the patients underwent medial epicondylar osteotomy for mediolateral imbalance if the only option was superficial medial collateral ligament (MCL) release. In contralateral side, the extensive medial release was performed and MCL was released either by pie-crusting technique or by subperiosteally release. The results of the two sides were compared. Patients were followed up for 12 months after the operation. Physical examination, clinical questionnaires, and radiography findings were recorded. Union of the osteotomies fragment and complications was evaluated. The mean varus angle before surgery was 21.6 ± 4.7 degrees, which was corrected to 8.6 ± 2.9 degrees after operation with an extensive medial release. The mean varus angle of contralateral side was 22.6 ± 1.7 degrees, which was corrected to 7.5 ± 2.3 degrees following medial femoral epicondyle osteotomy. There was no significant difference in varus correction (p = 0.1). Medial joint line opening in valgus stress test was 2.7 ± 0.4 mm in the osteotomized side and 3.5 ± 0.9 mm in contralateral side. Mean range of motion for the osteotomized side was 97.8 ± 4.3 degrees and 100.7 ± 2.7 degrees for contralateral side (p = 0.6). Nonunion occurred in a case in the osteotomized side and no medial instability was observed in medial release or osteotomies sides. No statistical difference was recorded based on clinical questionnaires (Oxford and WOMAC [Western Ontario and McMaster Universities Osteoarthritis Index] scores). Medial epicondylar osteotomy is a safe technique with the well-controlled medial extensive release in the patients with severe varus deformity during total knee arthroplasty.

Medial femoral epicondyle upsliding osteotomy with posterior stabilized arthroplasty provided good clinical outcomes such as constrained arthroplasty in primary total knee arthroplasty with severe valgus deformity

PURPOSE

A modified technique referred to as a medial femoral epicondyle upsliding osteotomy was proposed to address severe valgus deformity with unconstrained posterior stabilized (PS) arthroplasty. The study compared the effectiveness of the technique and PS arthroplasty with constrained arthroplasty during primary total knee arthroplasty (TKA).

METHODS

Fifty-three patients presenting with valgus knees with a mean valgus angle (VA) greater than 30° were prospectively randomized and divided into two groups, and both groups received primary TKA. Upsliding osteotomy with PS arthroplasty was performed on the knees of 27 patients (group A), while the remaining 26 patients (group B) received a constrained arthroplasty. The Knee Society function score (KSF), Hospital for Special Surgery knee score (HSS), range of motion (ROM), mediolateral stability and hospitalization expenses were recorded. The hip-knee-ankle angle (HKA), femorotibial angle (FTA) and VA were analysed. Complications were also recorded.

RESULTS

The patients received follow-up care for more than 50 months. The postoperative KSF, HSS and ROM showed marked improvement in both groups (p < 0.05). Radiological assessments showed that HKA, FTA and VA for group A were restored to (179.9 ± 3.0)°, (173.0 ± 2.4)° and (7.0 ± 2.4)°, respectively. For group B, the HKA, FTA and VA were restored to (181.5 ± 2.3)°, (172.5 ± 2.3)° and (7.5 ± 2.3)°, respectively. Only two patients from group A demonstrated mild medial laxity in their knees, and the remaining patients from both groups were stable medially and laterally. However, the total hospitalization expenses and material expenses of group A were less than those of group B because of the more expensive constrained prosthesis and stems. No late-onset loosening or recurrent valgus deformity was displayed.

CONCLUSIONS

Both medial femoral epicondyle upsliding osteotomy with PS arthroplasty and constrained arthroplasty showed good outcomes for the restoration of neutral limb alignment and soft tissue balance, which are demonstrated to be safe and effective techniques for correcting severely valgus knees. Therefore, the clinically important finding of this study is that medial femoral epicondyle upsliding osteotomy with PS arthroplasty can be an alternative method for correcting severe valgus knees.

LEVEL OF EVIDENCE

II.

Predictive Factors for and Detection of Lateral Hinge Fractures Following Open Wedge High Tibial Osteotomy: Plain Radiography Versus Computed Tomography

PURPOSE

To compare the accuracy of plain radiography and computed tomography (CT) in detecting lateral hinge fractures and to identify predictive factors of the lateral hinge fractures after open wedge high tibial osteotomy (HTO).

METHODS

This study included patients who underwent isolated primary open wedge HTO for medial compartment degenerative arthritis from 2015 to 2016 and were evaluated by postoperative CT scans and followed for a minimum of 1 year. This study involved 48 patients (48 knees) undergoing open wedge HTO for primary medial osteoarthritis. Lateral hinge fractures were evaluated on immediate plain radiographs and CT scans according to the Takeuchi classification. Predictive factors of plain radiograph-based hinge fracture and CT-based hinge fracture were investigated.

RESULTS

The detection rate of lateral hinge fracture was significantly higher on CT scans than on plain radiographs (50% vs 14.6%; P < .001). Seven knees (14.6%) showed lateral hinge fractures on postoperative plain radiographs, including 6 with type I and 1 with type III fractures; 24 (50.0%) showed lateral hinge fractures on postoperative CT scans, including 20 with type I, 2 with type II, and 2 with type III fractures. CT scans detected 14 type I, 2 type II, and 1 type III hinge fractures not detected by plain radiographs. The medial opening gap width was the only predictor of lateral hinge fracture on CT scans (adjusted odds ratio, 1.565; P =.034).

CONCLUSIONS

The incidence of lateral hinge fracture of the knee after open wedge HTO was higher on CT scans than on plain radiographs. The medial opening gap width was the only predictor of lateral hinge fractures, suggesting a need for care when spreading the gap to avoid lateral hinge fractures.

LEVEL OF EVIDENCE

Level III, cross-sectional study.

Deformity correction with total knee arthroplasty for severe knee osteoarthritis accompanying extra-articular femoral deformity: the results are promising

PURPOSE

This study aimed to evaluate patients with severe degenerative osteoarthritis of the knee and extra-articular femoral deformities treated with total knee arthroplasty (TKA) and acute deformity correction.

METHODS

Ten patients with severe degenerative osteoarthritis of the knee and extra-articular femoral deformities were included, and the median age was 63 years (range 38-67). The etiology was post-traumatic malunion in four patients, rickets sequelae in four patients, and surgical sequelae due to multiple epiphyseal dysplasia in two patients. The severity of degenerative osteoarthritis and deformity analyses were assessed according to the Kellgren-Lawrence and Paley criteria, respectively. The median number of previous operations the patients had undergone was two (range 0-3), and the median Oxford Knee Society score was 9 (range 5-13) before treatment. All patients were treated with primary TKA and deformity correction in the same surgery. The TKA was completed first, followed by an osteotomy at the apex of the deformity. Finally, a retrograde intramedullary nail was inserted.

RESULTS

The median follow-up period was 44 (31-60) months. A stable and functional knee joint, a physiological mechanical axis, and solid osseous union were achieved in all patients. Late prosthetic failure was seen in one patient due to deep infection. The median Oxford Knee Society score was 42 (range 37-47) at the final follow-up.

CONCLUSIONS

Combining several procedures in single setting for the treatment of severe knee osteoarthritis accompanied by extra-articular deformity may eliminate the need for multiple surgeries. Furthermore, a proper physiological mechanical axis can be obtained without causing substantial bone loss.

LEVEL OF EVIDENCE

IV.

Total knee arthroplasty in the varus knee: tips and tricks

Varus knee deformity is very common, and it can be classified according to the severity and reducibility of the deformity. Pre-operative planning is mandatory to obtain a good result. Both clinical and radiological planning should be carefully performed, particularly focused on collateral ligament deficiency. In most of the cases, a postero-stabilized implant is necessary, but in the presence of a varus thrust, a midlevel constrained (MLC) implant may be necessary. Rarely, if a severe extra-articular deformity is present, a femoral osteotomy and a high constrain implant may be necessary. In most of the cases, a standard midline approach can be performed. Soft tissue balancing is crucial, avoiding excessive releases of the medial collateral ligament (MCL). In the presence of severe deformity, more aggressive procedure such as tibial reduction osteotomy or sliding medial epicondyle osteotomy can be performed. In literature, good outcomes are reported for total knee arthroplasty (TKA) in varus deformity. In this manuscript, the available literature on TKA in varus deformity is analyzed, and the preferred surgical techniques of the authors are described.

Using a Tibial Short Extension Stem Reduces Tibial Component Loosening After Primary Total Knee Arthroplasty in Severely Varus Knees: Long-term Survival Analysis With Propensity Score Matching

BACKGROUND

Patients with severe preoperative varus deformity have been reported to have high rates of loosening after total knee arthroplasty (TKA), primarily on the tibial side. This study investigated whether a short extension stem for the tibial component in severely varus knees would reduce the failure rate due to loosening on the tibial side.

METHODS

Patients who underwent TKA, performed by a single surgeon using a single implant between November 1998 and January 2009, were retrospectively evaluated. Patients diagnosed with primary osteoarthritis, having a hip-knee-ankle axis greater than varus 8° on preoperative long-film radiographs, and postoperatively followed up for more than 2 years were included. Patients were divided into "stem" and "nonstem" groups, followed by 1:1 propensity score matching according to age, gender, body mass index, preoperative mechanical axis, and postoperative alignment. Tibial loosening rates in the 2 groups were compared.

RESULTS

The study cohort included 602 patients, divided into "stem" and "nonstem" groups. Propensity score matching yielded 88 pairs of patients. Mean follow-up duration was similar in the stem and nonstem groups (109.22 vs 103.81 months, P = .451). None of the patients in the stem group, compared with 5 in the nonstem group, experienced aseptic loosening. The overall implant survival rate was significantly higher in the stem group than in the nonstem group (P = .0201).

CONCLUSION

Using a short extension stem for the tibial component in primary TKA in patients with severe varus deformity greater than 8° may reduce the rate of loosening of the tibial side and increase the longevity of the implant.

LEVEL OF EVIDENCE

Level III.

Varus femoral and tibial coronal alignments result in different kinematics and kinetics after total knee arthroplasty

PURPOSE

Abnormal knee motion under various conditions has been described after total knee arthroplasty (TKA). However, differences in kinematics and kinetics of knees with varus femoral versus varus tibial alignment have not been evaluated. It was hypothesized that varus femoral and tibial alignments have the same impact on knee motion.

METHODS

A musculoskeletal computer simulation was used. Femoral and tibial alignment in the coronal plane was each varied from neutral to 5° of varus in 1° increments. Lift-off, defined as an intercomponent distance of >2 mm, and tibiofemoral contact forces were evaluated during gait up to 60° of knee flexion. Knee kinematics and contact stresses were also examined during squat, with up to 130° of knee flexion.

RESULTS

During gait, lift-off occurred readily with more than 3° of varus tibial alignment and slight lateral joint laxity. In contrast, lift-off did not occur with varus femoral or tibial alignment of up to 5° during squat. Peak medial contact forces with varus femoral alignment were approximately twice those observed with varus tibial alignment. The lowest points of the femoral condyles moved internally with varus femoral alignment, contrary to the kinematics with neutral or varus tibial alignment. On the other hand, there was femoral medial sliding and edge loading against the tibia in mid-flexion with varus tibial alignment.

CONCLUSION

Varus femoral alignment affects the non-physiological rotational movement of the tibiofemoral joint, whereas varus tibial alignment causes medial-lateral instability during mid-flexion. Varus femoral and tibial alignments might lead to post-TKA discomfort and unreliability.

Results with eight and a half years average follow-up on two hundred and eight e-Motion FP® knee prostheses, fitted using computer navigation for knee osteoarthritis in patients with over ten degrees genu varum

PURPOSE

The aim of this study was to analyse the clinical and radiographic results of 208 e-Motion® posterior cruciate-retaining, mobile bearing prostheses (BBraun-Aesculap, Tuttlingen, Germany) fitted using computer navigation, for knee osteoarthritis with a genu varum greater than 10°.

METHODS

One hundred ninety-two patients were operated on with 208 e-Motion® prostheses fitted, between January 2006 and December 2011, using the OrthoPilot® computer navigation system. Average pre-operative IKS score was 70 ± 27 points (6-143) with a function score of 38 ± 20.5 (0-90) and a knee score of 32.5 ± 13 (0-63). Average flexion was 116.5° ± 13° (65-140°). Average pre-operative HKA angle was 166° ± 3° (154-169°).

RESULTS

2Results are available for 134 patients, with a total of 150 knees operated on (38 lost to follow-up and 20 deceased). Average follow-up was 104.5 months (60-116 months). On last follow-up, the average IKS was 180 ± 22 points (95-200) with 86.5 ± 16 points (25-100) for the function score and 93.5 ± 8 points (55-100) for the knee score. Knee flexion was 116° ± 10.5° (80-135°) and average HKA angle was 179° ± 2° (175-184°). The pre-operative objective was achieved in 90.5% of knees.

CONCLUSION

The e-Motion® mobile bearing posterior cruciate-retaining prosthesis, fitted using computer navigation, offers excellent results after an average of 8.5 years follow-up. These results are at least equivalent, even superior, to those of the posterior-stabilised prostheses usually used for this type of deformity.

What Factors Are Associated With Femoral Component Internal Rotation in TKA Using the Gap Balancing Technique?

BACKGROUND

When using the gap-balancing technique for TKA, excessive medial release and varus proximal tibial resection can be associated with internal rotation of the femoral component. Previous studies have evaluated the causes of femoral component rotational alignment with a separate factor analysis using unadjusted statistical methods, which might result in treatment effects being attributed to confounding variables.

QUESTIONS/PURPOSES

(1) What pre- and intraoperative factors are associated with internal rotation of the femoral component in TKA using the gap balancing technique? (2) To what degree does femoral component rotation as defined by the navigation system differ from rotation as measured by postoperative CT?

METHODS

Three hundred seventy-seven knees that underwent computer-assisted primary TKA attributable to degenerative osteoarthritis with varus or mild valgus alignment in which medial soft tissue release was performed, and those with preoperative radiographs including preoperative CT between October 2007 and June 2014 were included in the study. To achieve a balanced mediolateral gap, the structures released during each medial release step were as follows: Step 1, deep medial collateral ligament (MCL); Step 2, superficial MCL (proximal, above the pes anserine tendon) and semimembranosus tendon; and Step 3, the superficial MCL (distal, below the pes anserine tendon). Knees with internal rotation of the femoral component, which was directed by navigation, to achieve a rectangular mediolateral flexion gap were considered cases, and knees without internally rotated femoral components were considered controls. Univariable analysis of the variables (age, sex, BMI, operated side, preoperative hip-knee-ankle angle, preoperative medial proximal tibial angle, preoperative rotation degree of the clinical transepicondylar axis [TEA] relative to the posterior condylar axis [PCA], coronal angle of resected tibia, resection of the posterior cruciate ligament, type of prosthesis, and extent of medial release) of cases and controls was performed, followed by a multivariable logistic regression analysis on those factors where p equals 0.15 or less. For an evaluation of navigation error, 88 knees that underwent postoperative CT were analyzed. Postoperative CT scans were obtained for patients with unexplained pain or stiffness after the operations. Using the paired t-test and Pearson's correlation analysis, the postoperative TEA-PCA measured with postoperative CT was compared with theoretical TEA-PCA, which was calculated with preoperative TEA-PCA and actual femoral component rotation checked by the navigation system.

RESULTS

After controlling for a relevant confounding variable such as postoperative hip-knee-ankle angle, we found that the extent of medial release (Step 1 as reference; Step 2: odds ratio [OR], 5.7, [95% CI, 2.2-15]; Step 3: OR, 22, [95% CI, 7.8-62], p < 0.001) was the only factor we identified that was associated with internal rotation of the femoral component. With the numbers available, we found no difference between the mean theoretical postoperative TEA-PCA and the postoperative TEA-PCA measured using postoperative CT (4.8° ± 2.7º versus 5.0° ± 2.3º; mean difference, 0.2° ± 1.5º; p = 0.160).

CONCLUSIONS

Extent of medial release was the only factor we identified that was associated with internal rotation of the femoral component in gap-balancing TKA. To avoid internal rotation of the femoral component, we recommend a carefully subdivided medial-releasing technique, especially for the superficial MCL because once the superficial MCL has been completely released it cannot easily be restored.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Correcting Severe Varus Deformity Using Trial Components During Total Knee Arthroplasty

BACKGROUND

Extensive medial soft tissue release may be necessary to correct severe varus deformity during total knee arthroplasty (TKA). However, this procedure may result in instability. Here, we describe a novel soft tissue balancing technique, which can minimize medial release in severe varus deformity during TKA.

METHODS

Fifty knees (40 patients) with hip-knee-ankle angle of more than 20° of varus were corrected using this technique (group 1). After achieving flexion gap balancing by needle puncturing and spreading of the superficial medial collateral ligament, extension gap balancing was obtained by gradual extension with the trial components in place. After group 1 was set, a one-to-one patient-matched control group who had mild varus deformity was selected by propensity score matching (50 knees, 48 patients, group 2). At postoperative 1 year, mediolateral laxity was compared between the 2 groups using the stress radiographs. Clinical outcomes were also compared using the Knee Society Score and Western Ontario and McMaster Universities Osteoarthritis Index score.

RESULTS

There were no differences in mean medial and lateral laxities between groups 1 and 2 at 1 year after the operation (medial laxity: 2.3° ± 1.4° and 2.7° ± 1.3°, respectively, P = .310) (lateral laxity: 3.6° ± 1.7° and 3.2° ± 2.0°, respectively, P = .459). There were no significant differences in postoperative clinical scores and knee alignment.

CONCLUSION

Our technique of obtaining extension gap balancing using trial components led to safe and effective balancing by avoiding unnecessary extensive release in severe varus deformity during TKA.

Lateral epicondylar osteotomy for severe varus deformity during total knee arthroplasty

In most cases of arthritic varus knees, stepwise osteophytes removal and medial soft tissue release could achieve satisfactory soft tissue balance during total knee arthroplasty. However, in some severe cases, conventional balancing techniques are not enough, necessitating other procedures like epicondylar osteotomy. To the best of our knowledge, no published article has reported the application of lateral epicondylar osteotomy in a severe varus knee. Here we reported a case of successful correction of a severe varus knee following lateral epicondylar osteotomy, and described its underlying rationale.

No condylar lift-off occurs because of excessive lateral soft tissue laxity in neutrally aligned total knee arthroplasty: a computer simulation study

PURPOSE

Condylar lift-off can induce excessive polyethylene wear after total knee arthroplasty (TKA). A computer simulation was used to evaluate the influence of femoral varus alignment and lateral collateral ligament (LCL) laxity on lift-off after single-design TKA. It was hypothesised that proper ligament balancing and coronal alignment would prevent lift-off.

METHODS

The computer model in this study is a dynamic musculoskeletal program that simulates gait up to 60° of knee flexion. The lift-off phenomenon was defined as positive with an intercomponent distance of >2 mm. In neutrally aligned components in the coronal plane, the femoral and tibial components were set perpendicular to the femoral and tibial mechanical axis, respectively. The femoral coronal alignment was changed from neutral to 5° varus in 1° increments. Simultaneously, the LCL length was elongated from 0 to 5 mm in 1-mm increments to provide a model of pathological slack.

RESULTS

Within 2° of femoral varus alignment, lift-off did not occur even if the LCL was elongated by up to 5 mm. However, lift-off occurred easily in the stance phase in femoral varus alignments of >3° with slight LCL slack. The contact forces of the tibiofemoral joint were influenced more by femoral varus alignment than by LCL laxity.

CONCLUSIONS

Aiming for neutral alignment in severely varus knees makes it difficult to achieve appropriate ligament balance. Our study suggests that no lift-off occurs with excessive LCL laxity alone in a neutrally aligned TKA and therefore that varus alignment should be avoided to decrease lift-off after TKA.

LEVEL OF EVIDENCE

Case series, Level IV.

Assessing coronal laxity in extension and flexion at a minimum of 10 years after primary total knee arthroplasty

PURPOSE

Favourable long-term results after total knee arthroplasty (TKA) require appropriate soft tissue balance. However, the relationships between long-term results after TKA surgery and mediolateral laxities at extension and at 90° flexion remain unknown. This study therefore quantitatively assessed ligament balance at extension and at 90° knee flexion at least 10 years after primary TKA, as well as clarifying the relationships between long-term outcomes and mediolateral laxities.

METHODS

This study included 49 knees (19 CR type and 30 PS type) of 33 patients followed up for at least 10 years after TKA at our hospital. Plain radiographs were obtained with about 150 N of varus or valgus stress using a Telos arthrometer at extension. At 90° flexion, epicondylar views were obtained under a 1.5-kg load and with about 10 kg of varus or valgus stress.

RESULTS

Lateral laxity of about 5° was observed in both extension and flexion, with total laxities of varus and valgus stress each less than 10°. Postoperative clinical outcomes were good, with significant improvements in extension angle, femorotibial angle, and KSS, and no loosening in any knee.

CONCLUSIONS

Good long-term results of TKA can be obtained with a lateral laxity of about 5°, equivalent to that of healthy knees.

LEVEL OF EVIDENCE

III.

A Novel Medial Soft Tissue Release Method for Varus Deformity during Total Knee Arthroplasty: Femoral Origin Release of the Medial Collateral Ligament

Introduction

Numerous methods of medial soft tissue release for severe varus deformity during total knee arthroplasty (TKA) have been reported. These include tibial stripping of the superficial medial collateral ligament (MCL), pie-crusting technique, and medial epicondylar osteotomy. However, there are inherent disadvantages in these techniques. Authors hereby present a novel quantitative method: femoral origin release of the medial collateral ligament (FORM).

Surgical Technique

For medial tightness remaining even after the release of the deep MCL and semimembranosus, the FORM is initiated with identification of the femoral insertion area of the MCL with the knee in flexion. Starting from the most posterior part of the femoral insertion, one third of the MCL femoral insertion is released from its attachment. If necessary, further sequential medial release is performed.

Materials and Methods

Seventeen knees that underwent the FORM were evaluated for radiological and clinical outcomes.

Results

Regardless of the extent of the FORM, no knees showed residual valgus instability at 24 weeks after surgery.

Conclusions

As the FORM is performed in a stepwise manner, fine adjustment during medial release might be beneficial to prevent inadvertent over-release of the medial structures of the knee.

Individualised distal femoral cut improves femoral component placement and limb alignment during total knee replacement in knees with moderate and severe varus deformity

AIM

Our aim was to determine the variation in valgus correction angle and the influence of individualised distal femoral cut on femoral component placement and limb alignment during total knee replacement (TKR) in knees with varus deformity.

MATERIALS AND METHODS

The study was done prospectively in two stages. In the first stage, the valgus correction angle (VCA) was calculated in long-limb radiographs of 227 patients and correlated with pre-operative parameters of femoral bowing, neck-shaft angle and hip-knee-ankle angle. In the second part comprising of 240 knees with varus deformity, 140 (group 1) had the distal femoral cut individualised according to the calculated VCA, while the remaining 100 knees (group 1) were operated with a fixed distal femoral cut of 5°. The outcome of surgery was studied by grouping the knees as varus <10°, 10-15° and >15°.

RESULTS

Of the 227 limbs analysed in stage I, 70 knees (31 %) had a VCA angle outside 5-7°. Coronal bowing (p < 0.001), neck-shaft angle (p < 0.001) and preoperative deformity (p < 0.001) significantly influenced VCA. Results of the second phase of the study showed a significant improvement in both femoral component placement and postoperative alignment when VCA was individualised in the groups of knees with varus 10-15° (p 0.002) and varus >15° (p 0.002).

CONCLUSION

Valgus correction angle is highly variable and is influenced by femoral bowing, neck-shaft angle and pre-operative deformity. Individualisation of VCA is preferable in patients with moderate and severe varus deformity.

LEVEL OF EVIDENCE

Level 2.

Correcting deformity in total knee arthroplasty

Collateral ligament release is advocated in total knee arthroplasty (TKA) to deal with significant coronal plane deformities, but is also associated with significant disadvantages.

We describe steps to avoid release of the collateral (superficial medial and lateral collateral) ligaments during TKA in severely deformed knees, while correcting deformity and balancing the knee.

Cite this article: Bone Joint J 2016;98-B(1 Suppl A):101–4.

Correction of varus deformity during TKA with reduction osteotomy

BACKGROUND

Reduction osteotomy (removing the posteromedial tibial bony flare) is one step to aid in achieving deformity correction in varus arthritic knees during TKA. However, the amount of deformity correction achieved with reduction osteotomy during TKA is unclear.

QUESTIONS/PURPOSES

We therefore addressed the following questions: (1) What is the amount of deformity correction achieved with reduction osteotomy during TKA in varus knees? (2) What is the correlation of amount of deformity correction achieved to the amount of bone osteotomized and the degree of varus deformity?

METHODS

We prospectively collected and analyzed intraoperative data on the degree of varus deformity before and after reduction osteotomy (using computer navigation) and the amount of reduction osteotomy performed (using a measuring scale) in 71 primary, computer-assisted TKAs.

RESULTS

For a mean reduction osteotomy of 7.5 ± 2 mm, a mean correction of 3.5° ± 1° was achieved; a mean osteotomy of 2 mm was required (confidence interval, 1.7-2.6 mm) for every 1° correction of varus deformity. Degree of varus correction achieved correlated positively with the amount of osteotomy performed, especially in knees with preoperative varus deformity of < 15° (r = 0.77, p < 0.001) and the preosteotomy residual varus deformity correlated positively with the amount of correction achieved (r = 0.81, p < 0.001).

CONCLUSIONS

Reduction osteotomy can achieve deformity correction in a predictable 2 mm for 1° in most varus arthritic knees during TKA. Further studies are required to ascertain its effectiveness as a soft tissue-sparing step when performed early on during TKA to achieve deformity correction.