Patellofemoral arthroplasty, where are we today?

Robotic-assisted patellofemoral arthroplasty provides excellent implant survivorship and high patient satisfaction at mid-term follow-up

PURPOSE

Robotic adoption in knee surgery has yielded several benefits, but its application in patellofemoral arthroplasty (PFA) remains barely reported. The purpose of this study was to determine implant survival, patient satisfaction, and functional outcomes after robotic-assisted PFA at an intermediate follow-up.

METHODS

This prospective analysis targeted 18 knees of 16 consecutive patients who underwent robot-aided PFA with three-year minimum follow-up (range, 3 to 6 years). Each patient was evaluated collecting pre-operative and post-operative medical record data, including range of motion, radiographic images, and multiple scores, such as VAS, APKS, and OKS.

RESULTS

At surgery, the mean age was 55.4 years ± 14.4 (range, 32 to 78 years), and the mean BMI was 26.8 kg/m² ±5.2 (range, 20 to 36). Etiologies of patellofemoral osteoarthritis included idiopathic degeneration (28%), post-traumatic (33%), and dysplasia (39%). Pre-implantation scores were VAS 7.9 ± 1.4, AKPS 34.6 ± 23.3, and OKS 17.3 ± 10.3. One implant was revised with primary total knee arthroplasty for osteoarthritis progression. Clinical and radiographic follow-up showed no signs of loosening or infection. The maximum flexion reached an average of 131.1°±10.5° (range, 110° to 145°), accompanied by significantly improved score results (P-value < 0.01): VAS 1.1 ± 1.4, AKPS 90.2 ± 8.6, and OKS 46.3 ± 1.8.

CONCLUSIONS

At 3 years after robotic assisted patellofemoral arthroplasty, excellent implant survival and patient satisfaction rates can be expected along with significantly improved functional and pain control outcomes. Although the limitations imposed by the restricted cohort, these findings indicate that robotic assistance in PFA is both safe and effective at intermediate follow-up.

Patello-femoral arthroplasty- indications and contraindications

Patellofemoral arthroplasty (PFA) is emerging as an attractive alternative to total knee arthroplasty (TKA) for isolated patellofemoral-osteoarthritis (PF-OA) for selected patients. The success of PFA is highly dependent on patient selection. This intervention is still burdened with a higher rate of revisions and a lower survival rate than TKA when the indications or the surgical technique are not optimal. We highlight the indications and contraindications of PFA to obtain satisfying functional outcomes and survivorship. Preoperative clinical and radiological assessment is critical to determine the presence of PFA indications, the absence of contraindications and the necessity of any associated procedures, particularly for the tibial tubercle. The typical indications are patients with isolated symptomatic PF-OA, with trochlear dysplasia, when bone-on-bone Iwano 4 osteoarthritis is observed, without significant malalignment and with the absence of risk factors for developing progressive tibiofemoral-OA. The three main causes of isolated PF-OA are primary OA, trochlear dysplasia and posttraumatic OA following patellar fracture. Trochlear dysplasia is the preferred indication for PFA. Lack of experience with arthroplasty or realignment of the extensor mechanism is a relative contraindication to performing PFA.

[Isolated Patellofemoral Osteoarthritis]

Isolated patellofemoral osteoarthritis is a complex pathology. It occurs frequently in women over 40 years and leads to a high degree of suffering. The causes of femoropatellar degeneration are manifold and require stage-specific therapy. This is very challenging for the treating physician. This article is intended to provide a structured overview of the symptoms, diagnostics and stage-specific therapy of patellofemoral osteoarthritis.

Internal Rotation, Varus, and Anterior Femoral Component Malalignments Adversely Affect Patellofemoral Joint Kinematics in Patellofemoral Arthroplasty

Background

Patellofemoral arthroplasty (PFA) is reported to provide nearly normal PF joint kinematics but only with adequate surgical techniques. This study evaluated the effects of various femoral component settings on patellar component biomechanics.

Methods

A dynamic musculoskeletal computer simulation analyzed normal knee and standard PFA models, as well as 8 femoral component malposition models: 5° internal or external rotation, 5° valgus or varus, 5° extension or flexion, and 3-mm or 5-mm anterior positioning. Mediolateral patellar translation, lateral patellar tilt, and contact force and stress at the PF joint were measured in each model during gait.

Results

The patella in the standard PFA model was shifted up to 5.0 mm laterally near heel off and was tilted up to 3.0° laterally at heel strike compared to the normal knee model. The patella in the external rotation model translated more laterally in the direction of the femoral component setting than in the standard model. However, in the internal rotation and varus alignment models, the patellar lateral shift occurred largely in the opposite direction of the femoral component setting. The patella in most models was tilted in the same direction as the femoral component setting. The PF contact force was increased, especially in the anterior femoral position models, by up to 30 MPa compared with 20 MPa in the standard model.

Conclusions

Internal rotation, varus, and anterior femoral component settings during PFA should be avoided to reduce postoperative complications, whereas external rotation might be appropriate only for cases with lateral patellar instability.

Complications and costs of patellofemoral arthroplasty versus total knee arthroplasty

BACKGROUND

Patellofemoral arthroplasty (PFA) is an alternative to total knee arthroplasty (TKA) for the treatment of patellofemoral arthritis. Although PFA may preserve native kinematics and accelerate recovery, it has been associated with higher revision rates. The purpose of this study is to compare complication rates and costs between PFA and TKA.

METHODS

Using the PearlDiver database, 6,179 patients with isolated patellofemoral arthritis treated with PFA or TKA from 2010-2015 were retrospectively reviewed with 5-year follow up. PFA and TKA patients were matched by age, sex, and Elixhauser Comorbidity Index via a 1:1 stepwise algorithm. Five-year costs and complications were compared between matched cohorts. The lifetime costs of PFA and TKA were evaluated with Markov decision modeling.

RESULTS

Compared to TKA, PFA was associated with fewer Emergency Department (ED) visits (6.1% vs 3.9%, p = 0.004) but a higher 5-year revision rate (9.9% vs 4.2%, p < 0.001). After multivariate regression, PFA was independently more likely to require revision (odds ratio 2.60, 95% confidence interval 1.32-4.71, p = 0.003). PFA was associated with lower total healthcare costs at every time point between 3 months ($18,014 vs $26,473, p < 0.001) and 5 years ($20,837 vs $27,942, p < 0.001). On average, the lifetime cost of PFA per patient was $5,235 less than for TKA ($26,343 vs $31,578).

CONCLUSIONS

PFA is a less expensive alternative to TKA with a similar risk of medical complications but is associated with a significantly higher 5-year revision rate. Future studies should examine the reasons for PFA failure and methods to mitigate this risk.

Better PROMs and higher return-to-sport rate after modular bicompartmental knee arthroplasty than after total knee arthroplasty for medial and patellofemoral compartment osteoarthritis

Background

Theoretical advantages of bicompartmental knee arthroplasty (BKA) over total knee arthroplasty (TKA) for bicompartmental (medial combined with patellofemoral) osteoarthritis (OA) are still unclear. This study aimed to compare patient-reported outcome measures (PROMs) and return-to-sport (RTS) rate between modular BKA and TKA in early follow-up.

Methods

Twenty-five consecutive modular BKA cases with a minimum 2-year follow-up were matched with 50 TKA cases at 1:2 ratio. Demographic data and preoperative functional scores, including the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Knee Society Scores (KSSs), were analyzed to ensure comparability. Postoperative WOMAC score, KSS, range of motion (ROM), Forgotten Joint Score-12 (FJS-12), and RTS rates were compared. Operative time and blood loss were also analyzed.

Results

Significant differences in the WOMAC-function (median 97.1 vs. 89.7, p < 0.001) and KSS-function (median 90.0 vs. 80.0, p = 0.003) scores were identified between the BKA and TKA groups. ROM was significantly greater in the BKA group than in the TKA group (median 125.0° vs. 120.0°, p = 0.004), in addition to the FJS-12 (median 89.6 vs. 53.1, p < 0.001). The overall RTS rate was significantly higher in the BKA group than in the TKA group (71.6% vs. 56.5%, p = 0.039). Operative time was significantly longer in the BKA group than in the TKA group (median 105.0 vs. 67.5 min, p < 0.001), but blood loss was similar (median 557.6 vs. 450.7 ml, p = 0.334).

Conclusion

Modular BKA demonstrated better functional recovery, better joint perception, and higher RTS rate than TKA; thus, modular BKA can be a good alternative for bicompartmental OA.

[When nothing else works: patellofemoral joint arthroplasty]

Patellofemoral joint replacement is the best treatment option available for isolated patellofemoral arthritis. Especially young patients should be operated on with bone-sparing techniques that also preserve the soft tissues, since these patients are very likely to be revised at some point in their lifetime. Correct patient selection is important for the success of surgery and should include a meticulous clinical examination and imaging. Special attention should be paid to additional pathologies that may also need to be addressed. For the trochlea, there are two different options for treatment with the inlay and onlay system. The retropatellar surface should be replaced. Patellofemoral joint replacement is still rarely performed, so treatment in specialised centres is recommended. National joint registry data show high revision rates, while data from centres show promising results.

Patient-related outcomes of patellofemoral arthroplasty: experience of a single center

Purpose

The purpose of this prospective study was to present the experience of a single center on patellofemoral arthroplasty, in terms of patient-related outcomes.

Method

From January 2005 to January 2016, 42 patients with isolated patellofemoral osteoarthritis were treated. The patients were assessed using the Oxford Knee Score preoperatively, and one, five, and eight year(s) after surgery. The data of the patients were analyzed using linear mixed effects models. A P value of 0.05 was considered statistically significant.

Results

Among 42 patients who underwent patellofemoral arthroplasty, only 25 patients (31 limbs involved) had records up to 5 years. There was a significant clinical improvement of Oxford Knee Score postoperatively (P < 0.05), lowering the score on average by 10.4 ± 1.5 one year after surgery and 8.9 ± 1.9 five years after surgery. This improvement was independent of the types of implants (P > 0.05), gender (P > 0.05), age (P < 0.05), and body mass index (BMI) (P < 0.05).

Conclusion

Patellofemoral arthroplasty can significantly improve the knee function, and this improvement is independent of the type of implant, gender, age, and BMI. However, further studies will need to assess the long-term outcomes of PFA.

Mid- to long-term follow-up of combined small implants

AIMS

In the last decade, interest in partial knee arthroplasties and bicruciate retaining total knee arthroplasties has increased. In addition, patient-related outcomes and functional results such as range of movement and ambulation may be more promising with less invasive procedures such as bicompartmental arthroplasty (BCA). The purpose of this study is to evaluate clinical and radiological outcomes after a third-generation patellofemoral arthroplasty (PFA) combined with a medial or lateral unicompartmental knee arthroplasty (UKA) at mid- to long-term follow-up.

METHODS

A total of 57 procedures were performed. In 45 cases, a PFA was associated with a medial UKA and, in 12, with a lateral UKA. Patients were followed with validated patient-reported outcome measures (Oxford Knee Score (OKS), EuroQol five-dimension questionnaire (EQ-5D), EuroQoL Visual Analogue Scale (EQ-VAS)), the Knee Society Score (KSS), the Forgotten Joint Score (FJS), and radiological analysis.

RESULTS

The mean follow-up was nine years (6 to 13). All scores significantly improved from preoperatively to final follow-up (mean and SD): OKS from 23.2 (8.1) to 42.5 (3.5), EQ-5D from 0.44 (0.25) to 0.815 (0.1), EQ-VAS from 46.7 (24.9) to 89.1 (9.8), KSS (Knee) from 51.4 (8.5) to 94.4 (4.2), and KSS (Function) from 48.7 (5.5) to 88.8 (5.2). The mean FJS at final follow-up was 79.2 (4.2). All failures involved the medial UKA + PFA group. Overall, survival rate was 91.5% for all the combined implants at ten years with 95% confidence intervals and 22 knees at risk.

CONCLUSION

Excellent clinical and radiological outcomes were achieved after a third-generation PFA combined with a medial or lateral UKA. BCA with unlinked partial knee prostheses showed a good survival rate at mid- to long-term follow-up. Cite this article: Bone Joint J 2021;103-B(5):840-845.

Tibial Osteolysis After Long-Term Isolated Polyethylene Patellar Resurfacing

Isolated patellar resurfacing served as an early treatment for patellofemoral arthritis but was abandoned because of erosion of the native femoral trochlear groove over time. We present the case of a large native tibial osteolytic lesion 20 years after isolated patellar resurfacing with a cemented polyethylene component. The patient had severe tricompartmental arthritic changes. The patellar component was very worn, and the resultant particle debris produced a large cavitary lesion in the proximal tibia. Osteolysis is a rare complication in patellofemoral arthroplasty, and, to our knowledge, this is the first reported case of native tibial osteolysis after isolated patellar resurfacing. The patient was treated with initial curettage and bone grafting of the lesion followed by total knee arthroplasty with a tibial cone and stemmed tibial fixation.

[Patellofemoral inlay implants-an innovation in patellofemoral joint arthroplasty?]

Isolated arthrosis of the patellofemoral joint is a rare and complex disease. After conservative therapy has been exhausted, the orthopedist has various soft-tissue and bone reconstructive procedures as well as cartilage regenerative procedures at his hands. In cases of failed or unsatisfactory therapy, patellofemoral arthroplasty continues to be controversially discussed as an alternative therapy. A closer look at these studies reveals promising results with the correct indication and patient selection. The different prosthesis designs provide good postoperative results while considering general and specific risks. The current generation of patellofemoral inlay prostheses shows high patient satisfaction with significant improvements in knee function and pain relief in mid-term outcomes. However, a relatively high revision rate must be considered.

Patellofemoral Arthroplasty: Short-Term Complications and Risk Factors

There is a paucity of literature regarding the short-term readmission, reoperation, and complication rates of patellofemoral arthroplasty (PFA). The purpose of this study is to determine the incidence and risk factors of 30-day postoperative complications in patients undergoing PFA. A retrospective cohort study of subjects who underwent PFA from 2010 to 2015 was performed using the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database. Perioperative outcomes and 30-day postoperative complications were ascertained, and patient demographics and comorbidities were analyzed using linear and binomial logistic regression analyses to determine risk factors for postoperative complications. Among the 1,069 patients identified in the NSQIP database, there was a 30-day readmission rate of 4.3% and a 30-day reoperation rate of 1.5%. The leading complications identified were bleeding requiring transfusion (11.7%), urinary tract infection (0.8%), and deep vein thrombosis (DVT) (0.8%). Younger age was a risk factor for superficial wound infection (p = 0.012). Older age was a significant risk factor for longer hospital stays, readmission, bleeding requiring transfusion, urinary tract infection, and pneumonia (p < 0.05 for all). Male sex was a risk factor for longer operation time and DVT (p = 0.001 and p = 0.017, respectively), while female sex was associated with greater incidence of bleeding requiring transfusion (p = 0.049). Elevated body mass index (BMI) was a risk factor for longer hospital stays, greater total operation time, and bleeding requiring transfusion (p < 0.001, p < 0.001, and p = 0.001, respectively). Nonwhite race was a significant risk factor for readmission (p = 0.008). This represents the largest study on early readmissions and the associated risk factors after PFA. PFA 30-day readmission and reoperation rates were <5%. Older age and elevated BMI were both identified as risk factors for adverse perioperative outcomes, including longer operation times, longer hospital stays, and bleeding requiring transfusion.

Smoking, unemployment, female sex, obesity, and medication use yield worse outcomes in patellofemoral arthroplasty

PURPOSE

The purpose of this study was to identify effects of psychosocial and demographic factors on patellofemoral arthroplasty (PFA) outcomes.

METHODS

Patients who underwent PFA by a single surgeon between 2002 and 2013 (min. 2 year follow-up) were included. Knee Society scores (KSS), UCLA, and Tegner Scores were prospectively collected in a designated arthroplasty registry. Patient records were retrospectively reviewed and univariate and multivariate statistical analyses were performed to assess the effect of psychosocial factors and demographic variables including patient sex, BMI, smoking and medication use, psychiatric history, and employment status on improvement between pre- and post-operative scores.

RESULTS

Seventy-four knees in 55 patients (88% female) with a mean age of 51.8 (SD 8.8) and mean follow-up of 46.5 (SD 26.9) months were included. Patients showed significant improvement in all functional outcomes (p < 0.001). Mean improvement in KSS-F scores and median improvement in Tegner scores was greater in males compared to females (37.8 vs 16.1, p = 0.007; 3.0 vs 2.0, p = 0.07, respectively). Smokers showed less improvement in KSS-P compared to non-smokers (17.2 vs 30.0, p = 0.028). Retired or employed patients had a greater mean improvement in KSS-F and median improvement in Tegner Scores compared to those were unemployed or on work disability (p = 0.022, p = 0.01). Patients who reported using opioids and/or anti-depressants pre-operatively showed less improvement in UCLA scores (p = 0.006). Obese patients showed less improvement in both KSS-F and Tegner score compared to non-obese patients (p = 0.009, p = 0.004).

CONCLUSION

Psychosocial factors influence the degree of improvement following PFA. Although patients showed overall improvement compared to their baseline scores, obese patients, smokers, unemployed/work disabled, and pre-operative use of opioids and/or anti-depressants were risk factors for decreased improvement… The consideration of psychosocial variables are clinically important when assessing a patient's candidacy for PFA and improve pre-operative patient selection and counselling.

LEVEL OF EVIDENCE

Level IV.

Short-term Revision Risk of Patellofemoral Arthroplasty Is High: An Analysis from Eight Large Arthroplasty Registries

BACKGROUND

Patellofemoral arthroplasty (PFA) is one option for the treatment of isolated patellofemoral osteoarthritis, but there are limited data regarding the procedure and results. Because isolated patellofemoral arthritis is relatively uncommon, available case series generally are small, and even within national registries, sample sizes are limited. Combining data from multiple registries may aid in assessing worldwide PFA usage and survivorship.

QUESTIONS/PURPOSES

We combined and compared data from multiple large arthroplasty registries worldwide to ask: (1) What proportion of patients undergoing primary knee arthroplasty have PFA? (2) What are the patient and prosthesis characteristics associated with PFA in common practice, as reflected in registries? (3) What is the survivorship free from revision of PFA and what are the reasons for and types of revisions?

METHODS

Data were provided by eight registries that are members of the International Society of Arthroplasty Registries (ISAR) who agreed to share aggregate data: Australia, New Zealand, Canada, Sweden, Finland, Norway, the Netherlands, and the United States. De-identified data were obtained for PFA performed from either the beginning of year 2000, or the earliest recorded implantation date after that in each individual registry when PFA data collection commenced, up to December 31, 2016. This included patient demographics, implant use, all-cause revision rate (determined by cumulative percent revision [CPR]), and reasons for and type of revision.

RESULTS

During the data collection period, 6784 PFAs were performed in the eight countries. PFAs comprised less than 1% of primary knee replacements in all registries. Patient demographics were comparable in all countries. Patients were generally more likely to be women than men, and the mean age ranged from 50 years to 60 years. All registries showed a high rate of revision for PFA. The 5-year CPR for any reason ranged from 8.0% (95% CI 4.5 to 11.5) in Norway to 18.1% (95% CI 15.5 to 20.7) in the Netherlands. The most common reason for revision across all countries was disease progression (42%, 434 of 1034). Most PFAs (83%, 810 of 980) were revised to a TKA.

CONCLUSIONS

The revision risk of PFA in all registries surveyed was more than three times higher than the reported revision risk of TKA at the same times. The survivorship of PFA is similar to that of the no-longer-used procedure of metal-on-metal conventional hip replacement. Although there may be potential functional benefits from PFA, these findings of consistent and alarmingly high rates of revision should create concern, particularly as this procedure is often used in younger patients.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Preoperative patellofemoral anatomy affects failure rate after isolated patellofemoral inlay arthroplasty

PURPOSE

To analyze whether preoperative patellofemoral anatomy is associated with clinical improvement and failure rate after isolated patellofemoral arthroplasty (PFA) using a modern inlay-type trochlear implant.

METHODS

Prospectively collected 24 months data of patients treated with isolated inlay PFA (HemiCAP^® Wave, Arthrosurface, Franklin, MA, USA) between 2009 and 2016, and available digitalized preoperative imaging (plain radiographs in three planes and MRI) were retrospectively analyzed. All patients were evaluated using the WOMAC score, Lysholm score, and VAS pain. Patients revised to TKA or not achieving the minimal clinically important difference (MCID) for the total WOMAC score or VAS pain were considered failures. Preoperative imaging was analyzed regarding the following aspects: Tibiofemoral OA, patellofemoral OA, trochlear dysplasia (Dejour classification), patellar height (Insall-Salvati index [ISI]; Patellotrochlear index [PTI]), and position of the tibial tuberosity (TT-TG and TT-PCL distance).

RESULTS

A total of 41 patients (61% female) with a mean age of 48 ± 13 years could be included. Fifteen patients (37%) were considered failures, with 5 patients (12%) revised to TKA and 10 patients (24%) not achieving MCID for WOMAC total or VAS pain. Failures had a significantly higher ISI, and a significantly lower PTI. Furthermore, the proportion of patients with a pathologic ISI (> 1.2), a pathologic PTI (< 0.28), and without trochlear dysplasia were significantly higher in failures. Significantly greater improvements in clinical outcome scores were observed in patients with a higher preoperative grade of patellofemoral OA, ISI ≤ 1.2, PTI ≥ 0.28, TT-PCL distance ≤ 21 mm, and a dysplastic trochlea.

CONCLUSION

Preoperative patellofemoral anatomy is significantly associated with clinical improvement and failure rate after isolated inlay PFA. Less improvement and a higher failure rate must be expected in patients with patella alta (ISI > 1.2 and PTI < 0.28), absence of trochlear dysplasia, and a lateralized position of the tibial tuberosity (TT-PCL distance > 21 mm). Concomitant procedures such as tibial tuberosity transfer may, therefore, be considered in such patients.

LEVEL OF EVIDENCE

Level III, retrospective analysis of prospectively collected data.

The Combination of Inlay Patellofemoral Arthroplasty and Medial Unicompartmental Knee Arthroplasty Versus Total Knee Arthroplasty for Mediopatellofemoral Osteoarthritis: A Comparison of Mid-Term Outcomes

BACKGROUND

To the best of our knowledge, there have been no studies in the literature related to the use of second-generation inlay patellofemoral arthroplasty and unicompartmental knee arthroplasty combination (inlay PFA/UKA) in the treatment of mediopatellofemoral osteoarthritis (MPFOA). The aim of this study is to evaluate the efficacy of inlay PFA/UKA in MPFOA.

METHODS

The study included 49 patients applied with inlay PFA/UKA because of MPFOA and 49 patients applied with TKA, matched one-to-one according to age, gender, body mass index, follow-up period, preoperative Knee Society Score, and range of motion. All the patients were evaluated clinically using the Knee Society Score, Knee Injury Osteoarthritis Outcome Score, and range of motion, and were also evaluated radiologically. Complication rates and length of hospital stay were compared.

RESULTS

The mean follow-up period was 54 ± 4 and 54.4 ± 3.9 months in inlay PFA/UKA and TKA groups, respectively. (P = .841). No statistically significant difference was determined between the 2 groups in respect of the mean clinical scores at the final follow-up examination (P ≥ .129). Total complications were fewer and length of hospital stay was shorter in the inlay PFA/UKA group than in the TKA group (P = .037 and P = .002). There was no radiographic evidence of progression of lateral compartment osteoarthritis according to Kellgren-Lawrence in any patient in the inlay PFA/UKA group.

CONCLUSION

In selected patient groups, inlay PFA/UKA is an alternative to TKA, with lower complication rates, shorter length of hospital stay, and clinical and functional results similar to those of TKA without osteoarthritis progression in the unresurfaced lateral compartment in the mid-term.

LEVEL OF EVIDENCE

III.

Foot Orthoses and Footwear for the Management of Patellofemoral Osteoarthritis: A Pilot Randomized Trial

OBJECTIVE

To determine the feasibility of a full-scale randomized controlled trial (RCT) comparing foot orthoses and footwear to footwear alone in individuals with patellofemoral (PF) osteoarthritis (OA).

METHODS

This 4-month, parallel, 2-arm pilot trial took place in Brisbane, Queensland and Hobart, Tasmania (August 2014 to October 2016). Forty-six individuals with PF OA were randomized by concealed allocation to foot orthoses plus prescribed footwear (n = 24) or prescribed footwear alone (n = 22). Study feasibility was the primary outcome (e.g., recruitment rate, adherence, adverse events, dropout rate). Secondary outcomes included patient-reported outcome measures of pain, function, and quality of life. Effect sizes with 95% confidence intervals were calculated at the 4-month primary end point (standardized mean differences for between-group effects; standardized response mean for within-group effects).

RESULTS

From 782 volunteers, 47 were eligible (6%), and 46 participated. One participant withdrew (2%), and 1 (2%) was lost to follow-up. Intervention adherence was high for both groups (9-10 hours of wear per day). No serious adverse events were reported. More than 80% of questionnaires were completed at 4 months. Between-group effect sizes for patient-reported outcome measures were typically small, while moderate-to-large within-group response effects were observed in both groups.

CONCLUSION

A full-scale RCT for PF OA is feasible with modifications to eligibility criteria. However, our observed small between-group effect sizes, combined with moderate-to-large within-group responses for both interventions, indicate that a full-scale trial is unlikely to find clinically meaningful differences. Secondary outcomes suggest that both interventions can be recommended for individuals with PF OA.

What Is the Risk of Repeat Revision When Patellofemoral Replacement Is Revised to TKA? An Analysis of 482 Cases From a Large National Arthroplasty Registry

BACKGROUND

Patellofemoral replacements (PFRs) have a higher rate of revision than unicompartmental knee arthroplasty or TKA. However, there is little information regarding why PFRs are revised, the components used for these revisions, or the outcome of the revision procedure. Some contend that PFR is a bridging procedure that can easily be revised to a TKA with similar results as a primary TKA; however, others dispute this suggestion.

QUESTIONS/PURPOSES

(1) In the setting of a large national registry, what were the reasons for revision of PFR to TKA and was the level of TKA constraint used in the revision associated with a subsequent risk of rerevision? (2) Is the risk of revision of the TKA used to revise a PFR greater than the risk of revision after a primary TKA and greater than the risk of rerevision after revision TKA?

METHODS

Data were obtained from the Australian Orthopaedic Association Joint Replacement Registry through December 31, 2016, for TKA revision procedures after PFR. Because revisions for infection may be staged procedures resulting in further planned operations, for the revision analyses, these were excluded. There were 3251 PFRs, 482 of which were revised to TKA during the 17-year study period. The risk of second revision was calculated using Kaplan-Meier estimates of survivorship for PFRs revised to TKAs, and that risk was compared with the risk of first revision after TKA and also with the risk of a second revision after revision TKA. Hazard ratios (HRs) from Cox proportional hazards models were used to compare second revision rates among the different levels of prosthesis constraint used in the index revision after PFR (specifically, cruciate-retaining versus cruciate-substituting).

RESULTS

The main reasons for revising a PFR to TKA were progression of disease (56%), loosening (17%), and pain (12%). With the numbers available for analysis, there was no difference in the risk of a second revision when a PFR was revised to a cruciate-retaining TKA than when it was revised to a cruciate-substituting TKA (HR, 1.24 [0.65-2.36]; p = 0.512). A total of 204 (42%) of the PFR revisions had the patella component revised when the PFR was converted to a TKA. There difference in rates of second revision when the patella component was revised or not revised (HR, 1.01 [0.55-1.85]; p = 0.964). When we eliminated the devices that ceased to be used before 2005 (older devices), we found no change in the overall risk of repeat revision. The risk of a PFR that was revised to a TKA undergoing a second revision was greater than the risk of TKA undergoing a first revision (HR, 2.39 [1.77-3.24]; p < 0.001), but it was less than the risk of a revision TKA undergoing a second revision (HR, 0.60 [0.43-0.81]; p = 0.001).

CONCLUSIONS

The risk of second revision when a PFR is revised is not altered if cruciate-retaining or posterior-stabilized TKA is used for the revision nor if the patella component is revised or not revised. The risk of repeat revision after revision of a PFR to a TKA was much higher than the risk of revision after a primary TKA, and these findings did not change when we analyzed only devices in use since 2005. When PFR is used for the management of isolated patellofemoral osteoarthritis, patients should be counselled not only about the high revision rate of the primary procedure, but also the revision rate after TKA. Further studies regarding the functional outcomes of these procedures may help clarify the value of PFRs and subsequent revisions.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Patella alta and patellar subluxation might lead to early failure with inlay patello-femoral joint arthroplasty

PURPOSE

With the growing interest in resurfacing procedures, several new implants have been recently introduced for isolated patello-femoral joint arthroplasty (PFA). However, not much data are available for these new techniques or about the right indications for each type of implant.

METHODS

Out of a retrospective cohort of 20 inlay PFA, 11 PFA with an elevated Insall-Salvati index and an increased patello-femoral congruence angle showed an initial satisfactory result, but presented thereafter with recurrent pain and "clunk" phenomena. They were all revised after a median time of 25 months (range 8-28 months) into an onlay technique PFA and analyzed for their failure mode and revision technique.

RESULTS

Clinical symptoms such as clunking, as well as abraded areas craniolateral of the inlay implant found intraoperatively, were the main observations of this study. The modified Insall-Salvati index (mISI) was significantly higher in the revised knees compared to the unrevised (median 1.8 versus 1.6; p = 0.041). VAS and KSS significantly improved after revision (median VAS reduction in pain of 4.0 points, median KSS improvement of 20.0 points; p < 0.05).

CONCLUSION

Patients with high-normal patellar height index or patella alta, as well as a craniolateral type of arthritis with additional lateralization, should be considered contra-indicated for an inlay technique PFA. They could be considered for a PFA system reaching further proximal into the distal femur. An onlay PFA can be an option for early revision of failed inlay implants. The clinical relevance of this study is that patella alta and patellar subluxation are more difficult to adjust for with an inlay PFJ component.

LEVEL OF EVIDENCE

Level IV.

Mid-Term Clinical, Functional, and Radiographic Outcomes of 105 Gender-Specific Patellofemoral Arthroplasties, With or Without the Association of Medial Unicompartmental Knee Arthroplasty

BACKGROUND

The purpose of this study is to evaluate clinical and radiographic outcomes after gender-specific patellofemoral arthroplasty (PFA) either isolated or combined with unicompartmental knee arthroplasty (UKA).

METHODS

A total of 105 PFAs in 85 patients were reviewed: 64 knees had isolated patellofemoral osteoarthritis and received an isolated PFA, and 41 knees with bicompartmental osteoarthritis were treated with medial UKA and PFA. Preoperative and postoperative clinical and functional assessment included knee range of motion, Knee Society Score, University of California Los Angeles Activity Score, Tegner Activity Level Scale, and visual analogue scale pain. Preoperative and postoperative radiographs were evaluated for patellofemoral and tibiofemoral compartment osteoarthritis, trochlear dysplasia, changes in patellar height, and signs of osteolysis.

RESULTS

At a mean follow-up of 5.5 ± 1.6 years, both groups showed improvement in knee joint range of motion (P < .001), clinical and functional Knee Society Score (P < .001), University of California Los Angeles Activity Score (P < .001 in the PFA group and P = .004 in the UKA + PFA group), and visual analogue scale pain (P < .001). There were no statistically significant postoperative differences between the 2 groups. No signs of osteolysis or subsidence were recorded. Survivorship of these 105 implants was 95.2%.

CONCLUSION

Excellent clinical and radiographic outcomes were achieved after PFA with a gender-specific implant both as isolated replacement and when combined with medial UKA. Bicompartmental replacement with small implants can be considered in patients with bicompartmental osteoarthritis and intact anterior cruciate ligament.

The need for secondary resurfacing is affected by trochlear height in total knee arthroplasty

PURPOSE

The purpose of the study was to compare the rate of secondary resurfacing in a consecutive series of five different total knee arthroplasty (TKA) systems. It was our hypothesis that different TKA design features such as sulcus angle or trochlear height influence the rate of secondary resurfacing.

METHODS

A retrospective study was performed on data from patients who underwent TKA without primary patellar resurfacing from 2004 to 2012 in an university-affiliated hospital. The study cohort included 784 TKA patients (m:f = 302:482, mean age at surgery ± SD 71 ± 10). Five different cruciate-retaining TKA systems were used consecutively (Group A, Triathlon, Stryker, Switzerland (n = 296), Group B, PFC Sigma, DepuySynthes, Switzerland (n = 215), Group C, LCS, DepuySynthes, Switzerland (n = 81), Group D, Balansys, Mathys, Switzerland (n = 128), Group E, Duracon, Stryker, Switzerland (n = 64)). Data were retrospectively obtained from hospital archives. Patients demographics, age at surgery, type of TKA were noted. In addition, TKA component position was assessed on radiographs with respect to "The knee society total knee arthroplasty roentgenographic evaluation and scoring system" (TKA-RESS). Pearson Chi-square test was used to compare differences between groups (p < 0.05). There were no significant differences between the groups in terms of age, gender, and radiological outcomes.

RESULTS

Twenty-six of 784 patients (3.3 %) underwent secondary resurfacing due to patellofemoral pain. In group A 4/296 patients (1.4 %), in group B 15/215 patients (7 %), in group C 5/81 patients (6.2 %), in group D 1/128 patients (0.8 %), in group E 1/64 patients (1.6 %) underwent secondary patellar resurfacing during follow-up. Significantly higher rates of secondary patellar resurfacing were seen in groups B and C when compared to the others (p < 0.001). It was found that the trochlear height in these TKA was higher than in the others.

CONCLUSIONS

Based on the findings of this study, trochlear height influences the need for secondary patellar resurfacing. The resurfacing rate ranged from 1 to 7 %, with the highest rate in the PFC Sigma TKA.

LEVEL OF EVIDENCE

Therapeutic study, Level III.

High mid-term revision rate after treatment of large, full-thickness cartilage lesions and OA in the patellofemoral joint using a large inlay resurfacing prosthesis: HemiCAP-Wave®

PURPOSE

The HemiCAP-Wave® implant for the patellofemoral resurfacing treatment of large cartilage lesions and osteoarthritis (OA) was introduced in 2009. The outcome of a prospective cohort study of 18 patients with large trochlea lesions or isolated OA treated with the HemiCAP-Wave® implant is presented with up to a 6-year survival rate, and hypothesised short-to mid-term reduced pain and improved function.

METHODS

Indication for treatment with the HemiCAP-Wave® implant was a symptomatic, large cartilage lesion in trochlea demonstrated by MRI or arthroscopy, which was ICRS grades 3-4 and larger than 4 cm². Patients were followed for 2 years with American Knee Society Subjective outcome Scores (AKSS), pain scores and radiographic evaluations and for up to 6 years with complications and reoperations.

RESULTS

At the 1- and 2-year follow-up mean AKSS clinical score, the mean AKSS function score and mean pain score improved significantly. Within 6 years, 28 % of the implants were revised to arthroplasty due to the progression of cartilage lesions, osteoarthritis or increased knee pain.

CONCLUSION

The present study demonstrated an improved short- to mid-term clinical outcome and reduced pain but high mid-term revision rate after patellofemoral inlay resurfacing using the HemiCAP-Wave® implant. Patellofemoral resurfacing implantation treatment with a large inlay prosthesis can offer temporary treatment for large isolated patellofemoral cartilage lesions or OA in younger patients with almost healthy cartilage in the other compartments who are not yet eligible for arthroplasty treatment.

LEVEL OF EVIDENCE

IV.

Patellofemoral arthroplasty conversion to total knee arthroplasty: Retrieval analysis and clinical correlation

BACKGROUND

Patellofemoral arthroplasty (PFA) can be a successful, bone-sparing treatment for isolated patellofemoral arthritis. However, progression of tibio-femoral arthritis or incorrect indications may predispose patients to early conversion to total knee arthroplasty (TKA). The purpose of this study was to review the clinical cases and perform retrieval analysis of PFA conversions to TKA at our institution.

METHODS

Twenty one patellofemoral arthroplasties in 18 patients that were converted to TKA were identified through our implant retrieval registry. Sixteen implants were available for review by biomechanical engineers, who recorded surface markings, wear patterns, and integrity of fixation. Patient charts were reviewed and time to conversion, tourniquet time, conversion implant, additional surgeries, infections, and Kellgren & Lawrence grade of the tibio-femoral joint on pre-operative radiographs were recorded.

RESULTS

PFAs converted to TKAs at our institution were implanted for an average of 2.7years. The most common reason for conversion was pain, but most patients had significant tibio-femoral arthritis, as indicated by an average Kellgren & Lawrence grade of 2.6. The average tourniquet time for these conversions was 67min. These patients underwent an average of one additional surgery per PFA converted, and the infection rate of these conversions was approximately 14%.

CONCLUSION

Success of PFA depends upon correct patient selection rather than implant failure or wear. Conversion of PFA to TKA is technically similar to primary TKA, with similar post-operative pain relief and range of motion. However, infection rates and complications requiring further surgery are more consistent with results seen in revision TKA.

LEVEL OF EVIDENCE

IV.

A matched-pair comparison of inlay and onlay trochlear designs for patellofemoral arthroplasty: no differences in clinical outcome but less progression of osteoarthritis with inlay designs

PURPOSE

To compare clinical and radiographic results after isolated patellofemoral arthroplasty (PFA) using either a second-generation inlay or onlay trochlear design. The hypothesis was that an inlay design will produce better clinical results and less progression of tibiofemoral osteoarthritis (OA) compared to an onlay design.

METHODS

Fifteen consecutive patients undergoing isolated PFA with an onlay design trochlear component (Journey™ PFJ, Smith & Nephew) were matched with 15 patients after isolated PFA with an inlay design trochlear component (HemiCAP^® Wave, Arthrosurface). Matching criteria were age, gender, body mass index, and follow-up period. An independent observer evaluated patients prospectively, whereas data were compared retrospectively. Clinical outcome was assessed using WOMAC, Lysholm score, and pain VAS. Kellgren-Lawrence grading was used to assess progression of tibiofemoral OA.

RESULTS

Conversion to total knee arthroplasty was necessary in one patient within each group, leaving 14 patients per group for final evaluation. The mean follow-up was 26 months in the inlay group and 25 months in the onlay group (n.s.). Both groups displayed significant improvements of all clinical scores (p < 0.05). No significant differences were found between the two groups with regard to the clinical outcome and reoperation rate. No significant progression of tibiofemoral OA was observed in the inlay group, whereas 53 % of the onlay group showed progression of medial and/or lateral tibiofemoral OA (p = 0.009).

CONCLUSION

Isolated PFA using either a second-generation inlay or onlay trochlear component significantly improves functional outcome scores and pain. The theoretical advantages of an inlay design did not result in better clinical outcome scores; however, progression of tibiofemoral OA was significantly less common in patients with an inlay trochlear component. This implant design may therefore improve long-term results and survival rates after isolated PFA.

LEVEL OF EVIDENCE

III.

PATELLOFEMORAL ARTHROPLASTY CHANGES THE TROCHLEAR GROOVE ANGLE

High early failure rates occur in the treatment of isolated symptomatic patellofemoral arthritis with commercially available patellofemoral arthroplasty (PFA) prostheses. We postulate that PFA changes the trochlear groove angle, thereby causing patellar maltracking, catching and pain. We examined the extent of this change in trochlear groove angle by virtually implanting five commercially available patellofemoral prostheses into two 3D reconstructed knees, one with a normal and the other with a dysplastic trochlea. The axial and coronal trochlear groove angles were measured pre- and post PFA for the five different prostheses in both the normal and the dysplastic knee. Post PFA, the trochlear groove angle changed from the original in both the axial and coronal planes for all the prostheses in both the normal and the dysplastic knee. The trochlear groove change is dependent on the design of the specific prosthesis. To avoid excessive changes post PFA, both the wide variation of changes between different generic PFA prostheses, as well as the wide variation in patient femoral anatomy should be considered.

[Patellofemoral arthroplasty]

OBJECTIVE

Isolated resurfacing of the trochlea using an inlay prosthesis without changing the complex kinematics of the patellofemoral joint.

INDICATIONS

Symptomatic, isolated patellofemoral osteoarthritis or isolated osteochondral lesions, failed conservative and cartilage regeneration procedures. No or concurrently corrected ligament instability, tibiofemoral and patellofemoral malalignment.

CONTRAINDICATIONS

Symptomatic patellofemoral osteoarthritis, inflammatory joint disease, chondrocalcinosis, chronic pain syndromes, active infections or knee ankylosis.

SURGICAL TECHNIQUE

Following a medial arthrotomy, coronal and sagittal curvatures of the trochlea are measured. Based on these measurements, corresponding surface reamers create an implant bed by removing damaged cartilage of the trochlea. A central fixation screw is placed to the desired depth and the inlay prosthesis is tapped carefully onto it. Final placement of the prosthesis is targeted slightly recessed to the surrounding joint surface.

POSTOPERATIVE MANAGEMENT

Free passive range of motion exercises of the knee joint are recommended starting on postoperative day 1. Depending on symptoms (e.g., pain and joint effusion), partial weight-bearing of 20 kg is allowed during postoperative weeks 1 and 2, which is increased by 20 kg/week thereafter.

RESULTS

In a prospective study of 29 patients (mean age: 42 years) treated with inlay arthroplasty, 2‑year follow-up results showed significant improvements (p < 0.05) in WOMAC, IKDC and VAS (pain) scores when compared to baseline. Compared to onlay PF arthroplasty modern inlay prosthetic placement showed a better preservation of the tibiofemoral joint without progression of tibiofemoral degeneration. This may be due to possible avoidance of patellofemoral overstuffing using a more physiological placement of the inlay prosthesis.

Management of Patellofemoral Arthritis: From Cartilage Restoration to Arthroplasty

The management of patellofemoral cartilage lesions is controversial and should begin with a comprehensive nonsurgical treatment plan. Patients with patellofemoral cartilage lesions in whom nonsurgical treatment fails may be candidates for surgical treatment. Surgical treatment strategies for the management of patellofemoral cartilage lesions are guided by the size, quality, and location of the defect. Recent advancements in cartilage restoration and arthroplasty techniques as well as appropriate patient selection and meticulous surgical technique have resulted in promising outcomes in patients with patellofemoral cartilage lesions who undergo surgical treatment.

Navigated "small implants" in knee reconstruction

PURPOSE

At the beginning of this century, unprecedented interest in the concept of using less invasive approaches for the treatment of knee degenerative diseases was ignited. Initial interest in this approach was about navigated and non-navigated knee reconstruction using small implants and conventional total knee arthroplasty.

METHODS

To this end, a review of the published literature relating to less invasive compartmental arthroplasty of the knee using computer-based alignment techniques and on soft tissue-dedicated small implants is presented. The authors present and compare their personal results using these techniques with those reported in the current literature. These involved the use of a shorter incision and an emphasis sparing. However, nowadays most surgeons look at compartmental knee resurfacing with the use of small implants as the new customized approach for younger and higher-demand patients. The aim of this paper is to stimulate further debate.

RESULTS

Since the beginning of 2000, computer-assisted surgery has been applied to total knee arthroplasty (TKA) and later to compartmental knee arthroplasty. Recent studies in the literature have reported better implant survivorship for younger patients using navigation in TKA at longer-term follow-up. Only one published report was identified showing superior clinical outcomes at short-term follow-up using computer-assisted technology compared with conventional alignment techniques in small implant surgery. No studies were found in the literature that demonstrated similar clinical advantages with navigated small implants at long-term follow-up. Two published meta-analyses were identified reporting better implant and limb alignment and no increase in complications using a navigated unicompartmental knee arthroplasty. However, neither meta-analysis showed superior clinical outcomes or survivorship with the navigated techniques.

CONCLUSION

In conclusion, we can assert that replacing just the damaged compartment and preserving the normal biomechanics will require not only new implant designs but also new technologies allowing the surgeon to make extremely precise adjustments to implant alignment and providing continuous feedback during surgery.

LEVEL OF EVIDENCE

IV.

Isolated patellofemoral arthroplasty reproduces natural patellofemoral joint kinematics when the patella is resurfaced

PURPOSE

The objectives of this in vitro project were to compare the dynamic three-dimensional patellofemoral kinematics, contact forces, contact areas and contact pressures of a contemporary patellofemoral prosthetic implant with those of the native knee and to measure the influence of patellar resurfacing and patellar thickness. The hypothesis was that these designs are capable to reproduce the natural kinematics but result in higher contact pressures.

METHODS

Six fresh-frozen specimens were tested on a custom-made mechanical knee rig before and after prosthetic trochlear resurfacing, without and with patellar resurfacing in three different patellar thicknesses. Full three-dimensional kinematics were analysed during three different motor tasks, using infrared motion capture cameras and retroflective markers. Patellar contact characteristics were registered using a pressure measuring device.

RESULTS

The patellofemoral kinematic behaviour of the patellofemoral arthroplasty was similar to that of the normal knee when the patella was resurfaced, showing only significant (p < 0.0001) changes in patellar flexion. Without patellar resurfacing, significant more patellar flexion, lateral tilt and lateral rotation was noticed. Compared to the normal knee, contact pressures were significantly elevated after isolated trochlear resurfacing. However, the values were more than doubled after patellar resurfacing. Changes in patellar thickness only influenced the antero-posterior patellar position. There was no other influence on the kinematics, and only a limited influence on the contact pressures in the low flexion angles.

CONCLUSION

The investigated design reproduced the normal patellofemoral kinematics acceptable well when the patella was resurfaced. From a kinematic point of view, patellar resurfacing may be advisable. However, the substantially elevated patellar contact pressures remain a point of concern in the decision whether or not to resurface the patella. This study therefore not only adds a new point in the discussion whether or not to resurface the patella, but also supports the claimed advantage that a patellofemoral arthroplasty is capable to reproduce the natural knee kinematics.

The Journey patellofemoral joint arthroplasty: A minimum 5year follow-up study

BACKGROUND

The Journey patellofemoral joint arthroplasty (PFA) was designed to improve patient outcomes following surgical management of patellofemoral joint osteoarthritis. It is based on the asymmetric trochlear geometry of the Genesis II total knee arthroplasty, with Oxinium components, to provide a reliable treatment option in an often young, high demand group of patients.

METHODS

We report the minimum five year functional outcome and survivorship of the Journey PFA performed at our institution between October 2005 and September 2009.

RESULTS

A total of 101 Journey PFAs were implanted in 83 patients, and we have complete outcomes for 90 implants (89%). There were 80 implants in female patients, and the mean age at time of surgery was 60years (26 to 86). The median Oxford Knee Score (0 to 48) improved from 18 to 30, and median Western Ontario and McMaster University Osteoarthritis Short Form Index (0 to 60) improved from 22 to 35. There were a total of 12 revisions, with mean time to revision 50months (10 to 99).

CONCLUSIONS

The Journey PFA gives a good medium-term functional outcome with 88% survivorship at a mean of seven years. This is the largest study of Journey PFA in the literature, and it provides a reliable option for patients with isolated patellofemoral joint osteoarthritis when arthroplasty is considered.

[Patellofemoral arthroplasty: indication, technique and results]

BACKGROUND

Although patellofemoral arthroplasty has been used for more than 30 years, it is still a challenging subject in orthopedics. The reason for this are the complex kinematics of the patellofemoral joint which are influenced by dynamic and static factors. New implant concepts that incorporate multiple coronal and sagittal curvatures and surface controlled inlay implantation show a positive direction in modern patellofemoral arthroplasty.

OBJECTIVES

The purpose of this work is the review of the literature on patellofemoral arthroplasty and the presentation of our own experience.

METHODS

We present indications and surgical techniques of patellofemoral arthroplasty as well as the most important aspects of preoperative evaluation. The patellofemoral joint can be reconstructed using either an inlay or an onlay prosthesis. Both arthroplasty concepts are discussed. Additional pathologies like chronic patellofemoral instabilities due to dysplasia, valgus/varus or rotational malalignment, and soft-tissue alterations are addressed with concomitant procedures.

RESULTS

Both inlay and onlay arthroplasty have demonstrated good functional outcome scores in patients with patellofemoral osteoarthritis. Patients with patellofemoral instability and/or trochlear dysplasia may benefit more from patellofemoral arthroplasty than patients with primary osteoarthritis because not only pain but also secondary pathologies are addressed.

CONCLUSION

Patellofemoral arthroplasty is an effective and safe procedure if the indication criteria are respected and the specific surgical technique is used. However, comparative results on current inlay and onlay prostheses have not been published in the literature to date.

Prospective evaluation of anatomic patellofemoral inlay resurfacing: clinical, radiographic, and sports-related results after 24 months

PURPOSE

To prospectively evaluate the clinical, radiographic, and sports-related outcomes at 24 months after isolated and combined patellofemoral inlay resurfacing (PFIR).

METHODS

Between 2009 and 2010, 29 consecutive patients with patellofemoral osteoarthritis (OA) were treated with the HemiCAP(®) Wave Patellofemoral Resurfacing System (Arthrosurface, Franklin, MA, USA). Based on preoperative findings, patients were divided into two groups: group I, isolated PFIR (n = 20); and group II, combined PFIR with concomitant procedures to address patellofemoral instability, patellofemoral malalignment, and tibiofemoral malalignment (n = 9). Patients were evaluated preoperatively and at 24 months postoperatively. Clinical outcomes included WOMAC, subjective IKDC, Pain VAS, Tegner activity score, and a self-designed sports questionnaire. Kellgren-Lawrence grading was used to assess progression of tibiofemoral OA. The Caton-Deschamps Index was used to assess differences in patellar height.

RESULTS

Twenty-seven patients (93 %) were available for 24-month follow-up. Eighty-one per cent of the patients were either satisfied or very satisfied with the overall outcome. Significant improvements in the WOMAC, subjective IKDC, and Pain VAS were seen in the overall patient cohort and in both subgroups. The median Tegner score and sports frequency showed a significant increase in the overall patient cohort and in group II. The number of sports disciplines increased significantly in both subgroups. No significant progression of tibiofemoral OA or changes in patellar height were observed.

CONCLUSION

Patellofemoral inlay resurfacing is an effective and safe procedure in patients with symptomatic patellofemoral OA. Significant improvements in functional scores and sports activity were found after both isolated and combined procedures.

LEVEL OF EVIDENCE

Prospective case series, Level III.

TROCHLEAR GROOVE ALIGNMENT MEASUREMENT METHOD FOR SURGICAL APPLICATIONS

In patellofemoral arthroplasty (PFA), rotational alignment is paramount for optimal patellofemoral function. Surgeons require a simple and effective measurement reference, through which the intact trochlear groove orientation can be quantified, to ensure good PFA alignment. We measured axial and coronal trochlear groove alignment in three-dimensional (3D) segmented computed tomography (CT) femurs relative to different references: The posterior condylar plane; the distal condylar plane, and the anatomical axis. The trochlear inclination angle (TIA) shows a better linear correlation with the axial groove angle when measured from the line perpendicular to the axial groove line as opposed to measurement from the posterior condylar plane. Similarly, a better linear correlation was achieved between the anatomical and the mechanical angles when measured from the coronal groove line as opposed to a line perpendicular to the distal condylar plane. Since axial and coronal groove alignment is quantifiable with respect to anatomical landmarks preoperatively, it may allow using the groove lines as a guideline for selection of the most appropriate patellofemoral prosthesis design. This may lead to the application of a PFA that better fits the patients' trochlear anatomy.

Evidence of trochlear dysplasia in patellofemoral arthroplasty designs

PURPOSE

The design of the trochlear compartment is crucial in patellofemoral arthroplasty (PFA), because 78% of patients with isolated patellofemoral arthritis present concomitant trochlear dysplasia with patellar maltracking and therefore remain predisposed to post-operative patellar subluxation and dislocation. The study investigated whether current PFA implants are designed with anatomic trochlear parameters such as the sulcus angle, lateral facet height and groove orientation.

METHODS

Five trochlear components of commercially available PFA implants were scanned, and the generated three-dimensional surfaces were measured using engineering design software. The mediolateral trochlear profiles were plotted at various flexion angles (0°, 15°, 30° and 45°) to deduce the following variables: sulcus angle, height of lateral facet and trochlear groove orientation.

RESULTS

Four specimens had sulcus angle>144° in the 45° of flexion, and all five specimens had sulcus angle>143° in 30° of flexion. Three specimens had a facet<5 mm high through the entire range of early flexion (0°-30°), and two specimens had a facet<5 mm high beyond early flexion (30°-45°). The trochlear groove was oriented laterally in all specimens (range 1.6°-13.5°).

CONCLUSION

Current PFA trochlear components are not always designed with anatomic parameters, and some models exhibit characteristics of trochlear dysplasia. Surgeons are therefore advised to implant components with a deep sulcus, particularly in patients with history of patellofemoral disorders, and to adapt the surgical technique and extensor mechanism if the component implanted has a shallow sulcus, to ensure normal patellar tracking.

LEVEL OF EVIDENCE

III.

Patellofemoral arthroplasty influences tibiofemoral kinematics: the effect of patellar thickness

PURPOSE

Although controversy still remains, isolated patellofemoral arthroplasty recently gained in popularity as a treatment option for patellofemoral osteoarthritis. It has compared to total knee arthroplasty the advantage of preserving the tibiofemoral articulation, which in theory would allow the preservation of natural tibiofemoral kinematics. Today, however, no data exist to support this assumption. This study was therefore performed in order to investigate the effect of isolated patellofemoral arthroplasty on the native three-dimensional tibiofemoral kinematic behaviour and whether a change in patellar thickness would have an influence.

METHODS

Six fresh-frozen cadavers were fixed on a custom-made mechanical knee rig. Full 3D kinematics was analysed during passive flexion-extension cycles, open chain extension, with and without mechanical resistance, as well as deep knee squats, using infrared motion capture cameras and retroflective markers. Measurements were taken for the native knee and after prosthetic trochlear resurfacing with and without patellar resurfacing in three different patellar thicknesses.

RESULTS

Compared to the natural knee, patellofemoral arthroplasty resulted in significant changes in tibiofemoral kinematics, which were most pronounced in the most loaded motor tasks. Increased internal tibial rotation was noted in the mid- and high flexion ranges, reaching at 120° of flexion a mean difference of 4.5°±4.3° (p<0.0001) during squat motion, over the whole flexion range during open chain motion and in deeper flexion beyond 50° (mean at 70°, 1.9°±3.7°) during resisted open chain. During squats, also, a more posterior translation of the lateral femoral condyle was observed. The effect was accentuated in case of patella overstuffing, whereas kinematics was closer to normal with patellar thinning.

CONCLUSION

Isolated patellofemoral arthroplasty alters natural tibiofemoral kinematics, and the effects become more pronounced in case of increased patellar thickness. Therefore, it might be recommended to aim for a slight over-resection of patellar bone if sufficient bone stock is available.

Femoral condylar contact points start and remain posterior in high flexing patients

This study compares kinematic patterns of 136 patients following total knee arthroplasty with high post-operative knee flexion (HighFlex) versus kinematics of 114 patients with limited knee flexion (LowFlex) using a blocked stratified random sampling study design to reduce confounding and bias. The kinematics was collected using fluoroscopy and 2D to 3D registration for a weight-bearing deep knee bend activity. Both the lateral and the medial condylar contact positions for the HighFlex subjects were significantly more posterior than the LowFlex subjects at full extension and remained that way at all flexion angles. The amount translation of the contact points, axial orientation angle and axial rotation were found to be similar for the two groups. Lift-off was significantly higher in the LowFlex indicating mid-flexion instability.

Surgical treatment of isolated patellofemoral osteoarthritis

BACKGROUND

Isolated patellofemoral (PF) osteoarthritis (OA) affects 9% of persons older than 40 years. Nonoperative treatment should be exhausted fully before surgical treatment.

QUESTIONS/PURPOSES

The purpose of this article is to review the literature after 2008 with the aim of answering the following question: Which of the following surgical procedures has the highest survival rate and the lowest revision rate in advanced isolated PF OA: patellofemoral arthroplasty (PFA), total knee arthroplasty (TKA) or lateral facetectomy.

METHODS

The search engine was MedLine. The keywords used were: PF OA and PFA. Three hundred and fifty-three articles were found between 2008 and 25 July 2013. Of those, only 23 were selected and reviewed because they were strictly focused on the topic and the question of this article.

RESULTS

The types of studies reported so far have a low level of evidence (levels III and IV). Most of them are prospective case series (level IV). Some are systematic reviews of level III studies. Reported survival rate of lateral facetectomy is 85% at 5 years, 67% at 10 years and 47% at 20 years. Reported failure rate of lateral facetectomy is 26% at 10 years and 16% at 12 years. The reported average time of reoperation is 8 years and 37% of such procedures fail. Survival rate of PFA has been reported to be 87.5% on average (range, 60-100%). The revision rate of PFA is 20%. Recent improvements in PFA design have resulted in improvements in short-and medium-term results, similar to those of TKA.

CONCLUSIONS

There is still no gold standard for the surgical treatment of isolated PF OA. However, PFA or TKA appear to be the most recommendable treatment in cases that do not respond to conservative treatment.

Patellofemoral arthroplasty

Patellofemoral arthroplasty remains controversial, primarily due to the high failure rates reported with early implants. Several case series have been published over the years, which describe the results with various first- and second-generation implants. The purpose of this work was to summarize results published up to now and identify common themes for implants, surgical techniques, and indications. First-generation resurfacing implants had relatively high failure rates in the medium term. Second-generation implants, with femoral cuts based on TKA designs, have yielded more promising medium-term results. The surgical indications are quite specific and must be chosen carefully to minimize poor results. Short-term complications are generally related to patellar maltracking, while long-term complications are generally related to progression of osteoarthritis in the tibiofemoral joint. Implant loosening and polyethylene wear are rare. Overall, recent improvements in implant design and surgical techniques have resulted in better short- and medium-term results. But more work is required to assess the long-term outcomes of modern implant designs.

Coronal alignment of patellofemoral arthroplasty

BACKGROUND

Patellofemoral arthroplasty (PFA) can yield successful results in appropriately selected patients. The varus-valgus position or coronal alignment of the trochlear implant is determined by how its transitional edges articulate with the condylar cartilage. Whilst variation in condylar anatomy will not influence the axis of the lower limb in PFA, it can impact on the Q-angle of the PF joint. The aim of this study was to analyze how the coronal alignment can be influenced by the choice of anatomical landmarks.

MATERIALS AND METHODS

Retrospective analysis of 57 PFAs with measurements of alignment from full leg radiographs.

RESULTS

Coronal alignment following anterior condylar anatomy leads to a mean (SD) proximal valgus alignment of 100° (9°). Aligning the component with Whiteside's line gives a better alignment with less variance 89° (3°).

DISCUSSION

A trochlear component with a higher Q-angle compensates for patellar maltracking if the condylar anatomy would tend to put the implant in a more proximal varus or neutral position. If the trochlear component is proximally aligned in valgus this may have the opposite effect. Aligning the trochlear component with the AP-axis in the coronal plane avoids maltracking and optimally utilizes the design features of the implant.

LEVEL OF EVIDENCE

Level III.

Patellofemoral joint replacement, an evolving concept

Isolated patellofemoral arthritis is a rare disease, whose management is challenging and controversial. Patellofemoral joint replacement can be an effective treatment for this condition. The very concept of a patellofemoral implant has evolved throughout the years, resulting in more anatomic designs and reproducible surgical techniques. The clinical outcomes of this procedure are strictly related to surgical indications, implant design and appropriate surgical technique.

Joint awareness in different types of knee arthroplasty evaluated with the Forgotten Joint score

The purpose of this study was to validate the 'Forgotten Joint' score (FJS-12), a 12-item questionnaire designed to analyze the patient's ability to forget the joint in everyday life, in French and to compare the results of this Patient Reported Outcome (PRO) score in patients who had other than total joint arthroplasties. The score was compared in 122 patients that had either medial unicompartmental (N=51), patellofemoral (N=21) or total knee arthroplasty (N=50). After having validated the FJS-12 in French, a similar PRO was observed in unicompartmental and postero-stabilized total knee arthroplasty. Patellofemoral resurfacing had a significantly lower score than the two other types of arthroplasty, which can be explained by a significantly younger and smaller patient group.

Bicompartmental knee arthroplasty of the patellofemoral and medial compartments

PURPOSE

Studies have shown that after total knee arthroplasty neither normal biomechanics nor function is obtained. Selective resurfacing of diseased compartments could be a solution. A narrative review of the available literature on bicompartmental arthroplasty is presented.

METHODS

A literature review of all peer reviewed published articles on bicompartmental arthroplasty of the knee was performed. Bicompartmental arthroplasty is by definition the replacement of the tibiofemoral and the patellofemoral joint. It can be performed with a modular unlinked or a monolithic femoral component.

RESULTS

Bicompartmental arthroplasty performed with modular components obtains good to excellent results at ± 10 years follow-up. Function and biomechanics are superior to total knee arthroplasty. Modern monolithic femoral components are reported to give early failure and high revision rates and should be avoided.

CONCLUSION

Modular bicompartmental arthroplasty is an excellent alternative to treat bicompartmental arthritis of the knee leading to good functional results and superior biomechanics in well-selected patients. Caution is needed since only a few peer reviewed articles with small series and old implant designs are available on this type of arthritis treatment. Survivorship in these studies is inferior to total knee arthroplasty.

Prospective clinical and radiological two-year results after patellofemoral arthroplasty using an implant with an asymmetric trochlea design

PURPOSE

The purpose was to prospectively evaluate the two-year results after implantation of the Journey PFJ(®) (Smith & Nephew, Andover, MA). The authors hypothesized that patellofemoral arthroplasty would result in improved outcomes after 24 months in patients treated with an isolated procedure as well as in patients demonstrating concomitant patellofemoral instability (PFI), which were treated with a combined surgical procedure.

METHODS

Patients were included between 02/2006 and 08/2008. According to the history and clinical findings, patients were grouped into group I with no history or clinical signs of PFI, and patients with concomitant PFI were assorted to group II. Patients were then treated with an isolated (group I) or a combined (group II) surgical procedure to additionally treat the PFI. Visual analogue scale (VAS), Lysholm score and WOMAC score were recorded preoperatively, 6, 12 and 24 months postoperatively. Patellar height was evaluated according to the index of Caton-Deschamps (CDI), and osteoarthritic changes were evaluated according to Kellgren and Lawrence.

RESULTS

A total of 25 patients were enrolled, of them three discontinued interventions and were excluded from final analysis. An isolated implantation of the Journey PFJ(®) was performed in 14 patients (group I) and a combined procedure in 8 (group II). Daily pain and clinical scores significantly improved at 6, 12 and 24 months compared to preoperative values (P < 0.05). Significant decrease (P = 0.02) of mean CDI could be noticed. Significant increase in tibiofemoral OA within the medial but not in the lateral tibiofemoral joint was assessed (P = 0.011; n.s.).

CONCLUSIONS

Patellofemoral arthroplasty using the Journey(®) PFJ for treatment of significant patellofemoral OA demonstrated improved clinical scores at the 2-year follow-up in both groups. Comparing the primary OA (I) and OA + instability (II) groups, patients with patellofemoral OA treated with a combined procedure for concomitant stabilization of patellofemoral instability may benefit more from such a combined procedure, than patients treated with an isolated procedure for treatment of isolated patellofemoral OA.

LEVEL OF EVIDENCE

Prospective case series, Level III.